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Com m ission of the European C om m unit ies

ODOUR PREVENTIONAND CONTROL OF

ORGANIC SLUDGE AND

LIVESTOCK FARMING

ELSEVIER APPLIED SCIENCE PUBLISHERS



ODOUR PREVENTION AND CONTROL OFORGANIC SLUDGE AND LIVESTOCK FARMING



Proceedings of a seminar held in Silsoe, United Kingdom, 15-19 April 1985

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ODOUR PREVENTIONA N D C O N T R O L OFORGANIC SLUDGE

AND LIVESTOCK FA R M IN G

Edited by

V. C. NIELSEN

Ministry of Agriculture, Fisheries and Food, Reading, UK

J. H. VOORBURG

Rijks Agrarische Afvalwater Dienst, Arnhem, The Netherlands

and

P. L'HERMITECommission of the European Com munities, B russels, Belgium

P A R I E U R O P . B ib J io th .

C I . T V

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British Library Cataloguing in Publication DataOdour prevention and control of organic

sludge and livestock farmingI. Agriculture—odor controlI. Nielsen, V. C. II. Vo orbu rg, J. H.III. L'Hermite, P.630 S494.5.03

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PREFACE

An important aspect of the treatment of sludges and slurries is the emission

of odour. International cooperation in odour control and odour measure

ment is only possible if the results are comparable. For this reason,

W orking Party I of the CO ST Project 681 established a sub-group to study

the international development of odour measurement techniques. The

inventory m ade by this sub -grou p resulted in a prop osa l for a w ork sho p on

olfactometric measurement in order (1) to exchange experiences with

different olfactometers, and (2) to consider the possibilities of moreharm onised m easurem ent. As od ou r m easurem ent is not a goal in itself bu t

a step on the way to od ou r con trol, it was decided to com bine this wo rks ho p

with a w orksho p of the FA O Sub-network 2 devoted to reduction of odou r

in animal farming. Although odour control and odour measurement were

mainly discussed in parallel sessions, the combination of these two

workshops contributed to the success of the meeting. There was an

intensive exchange of information between the parallel sessions and lively

contact between the participants. The excellent organisation and the good

accommodation of the National Institute of Agricultural Engineering in

Silsoe made this possible.

The results of the sessions on odour control are summarised by the

organiser of the joint workshop, V. C. Nielsen.

The sessions on odour measurement were followed by a meeting of a

small grou p of experts in the Rosew arne Ho use. D uring this meeting there

was agreement on a num ber of con ditions to be met to mak e the results ofolfactometric measurement more consistent and more comparable. These

'Recommendations on olfactometric measurement' are a useful result of

the sessions on odour measurement.

J. H. VOORBURG



V ll

C O N T E N T S

Preface.

General Scientific Papers

A review of CO ST Project 681 T re at m en t and use of organic sludges

and liquid agricultura l w astes' 2

A. M. BRUCE {Water Research Centre, Stevenage, UK)

A review of work of the FA O Su b-network 2: the reduction of od ou rs

in anim al pro duc tion 8

V. C. NIELSEN (Farm W aste Unit, M inistry of Agriculture,

Fisheries and Food, Reading, UK)

O do ur problem s related to waste water and sludge treatm ent . 12A. S. EIKUM and R. STORHAUG (Aquateam-Norwegian Water

Technology Centre, Oslo, Norway)

Ag ricultural problem s related to od ou r prevention and con trol . 21

D. C. H A R D W I C K (Ministry of Agriculture, Fisheries and Food,

London, UK)

O do ur research and am m onia volatilisation 27

J. H. VOORBURG (Government Agricultural Wastewater Service,

Arnhem, The Netherlands)

A m m onia loss from grassland systems 33

J. C. RYDEN (Animal and Grassland Research Institute, Hurley,

Maidenhead, UK)



Vl l l

Session I: Olfactometry EEC-Group

Sam pling of od oro us air for olfactom etric m easurem ent . . 44

J. H A R T U N G (Institute for Animal Hygiene of the Hannover

School of Veterinary Medicine, Federal Republic of Germany)

Standardization of olfactom etric m easurem ents . . . . 52



Selection and treatment of panelists for determination of odor

thresholds 55

M . HANGARTNER (Department of Hygiene and Applied Physiology,

Swiss Federa l Institute of Technology, Zurich, Switzerland)

VDI guidelines on od ou r problem s 61

V. THIELE (Landesanstaltfur Immissionsschutz des Landes NRW ,

Essen, Federal Republic of Germany)

An established system for od ou r detection threshold m easurem ents 63

R. L. Moss (Warren Spring Laboratory, Stevenage, Herts, UK)

Guideline for olfactometric measurements in The Netherlands:

com parison with W estern European guidelines . . . . 69

H. L. J. M. WIJNEN (Ministry of Housing, Physical Planning

and Environm ent, Air Directorate, Division of Air Quality,Leidschendam, The Netherlands)

French Tentative Standard X-43-101: Method of measurements of

the odour of a gaseous effluent. Comments on interpretations made

by M essrs H artung , V oorburg and H angartner . . . . 78

M. F . THAL (Comm issariat a FEnergie Atomique, IPSN/DPT/

SPIN, Fontenay-aux-Roses, France)

Experiences with olfactometric measurements in Norway . . 8 1

P. HOLMVANG (Centre for Industrial Research, Oslo, Norw ay)

Limitations imposed on olfactometric measurements by the human

factor 86

E. P. KOSTER (Psychological Laboratory, Utrecht University,

The Netherlands)



IX

Experiences with transportable olfactom eters . . . . 94

H . MANNEBECK (Institut fur Landwirtschaftliche Verfahrens-technik der Universitdt Kiel, Federal Republic of Germany)

Dispersion models for em issions from ag ricu ltura l sources . 99

G.-J. M E J E R and K.-H. K R A U S E (Institut fur Landtechnische

Grundlagenforschung der Bundesforschungsanstalt fur Landwirt-

schaft, Braunschweig, Federal Republic of Germany)

Experiences with olfactom eters 113

J. V. KLARENBEEK (Institute of Agricultural Engineering , I M AG ,

Wageningen, The Netherlands)

Physical calibration of olfactometric measurem ents . . . 1 2 0

A. G. WILLIAMS {National Institute of Agricultural Engineering,

Silsoe, UK)

Developments in the assessment of odo urs from sludges . . 1 3 1

S. J. TOOGOOD (Water Research Centre, Stevenage, UK) and

J. D IA P E R (School of Environmental Science, University of

Bradford, UK)

O dou r concentration and od our annoyan ce 146

P. H . PUNTER, E. P. KOSTER (Psychological Laboratory, Utrecht

University, The Netherlands), J. SCHAEFER (Divisionfor Nutritionand Food Research, TNO Zeist, The Netherlands) and K. D.

MAIWALD (Hydraulics Laboratory, Delft, The Netherlands)

Comparison of olfactometric odour measurement and chemical

odo ur mea surement 153

N. S C H A M P and H. VAN LANGENHOVE (Laboratory of Organic

Chemistry, Faculty of Agricultural Sciences, State University of

Ghent, Belgium)

Session II: Odour Control FAO-Group

Treatment of livestock manure: air drying and composting poultry

manure 166

W. KROODSMA (Institute of Agricultural Engineering, I M AG ,




Th e effect of insu lating broiler house floors on od ou r emission . 175

E. N. J. V A N O U W E R K E R K and J. A. M. VOERMANS (Institute ofAgricultural Engineering, I M AG, W ageningen, The Netherlands)

Use of peat as litter for milking cows 181

I. PELTOLA (Work E fficiency Association, Rajam dki, Finland)

Covering m anure storing tanks to control odour . . . . 1 8 8

H . M A N N E B E C K (Institut fur Landwirtschaftliche Verfahrens-technik der Universitdt Kiel, Federal Republic of Germany)

M ach inery spread ing : soil injection as a barrie r to od ou r dispersion 194

J. E. HALL (Water Research Centre, M edmenham Laboratory,

UK)

Swedish experiences with soil injection 207

O. NOREN (Swedish Institute of Agricultural Engineering, Uppsala,

Sweden)

Separation as a method of m anure han dling and o dou rs reduction in

pig buildings 213

W . KROODSMA (Institute of Agricultural Engineering, I M AG ,


Measurements of the olfactometric efficiency of various odour

co ntrol devices in rend ering plants 222

G.-J. MEJER (Institut fur Landtechnische Grundlagenforschung

der Bundesforschungsanstalt fur Landwirtschaft, Braunschweig,

Federal Republic of Germany)

The effects of weather on odour dispersion from livestock buildingsand from fields 227

M. L. WILLIAMS (Warren Spring Laboratory, Stevenage, UK)

and N. THOMPSON (Meteorological O ffice, Bracknell, UK )

Design and use of biofilters for livestock build ings . . . 234

O . NOREN (Swedish Institute of Agricultural Engineering, Uppsala,

Sweden)



XI

Experience in the use of biofilters 238

M. A. VAN GEELEN (Institute of Agricultural Engineering, 1MAG,Wageningen, The Netherlands)

Design and experience obtained with bioscrubbers . 2 4 1

S. SCHIRZ (Kuratorium fur Technik und Bauwesen in der Land-

wirtschaft (KTB L), Darmstadt, Federa l Repub lic of Germany)

Aeration of pig slurry to control odours and to reduc e nitrogen levels 251M . C O P E L L I , S. DE ANGELIS and G. BONAZZI (Centro Ricerche

Produzioni Animali, Reggio Emilia, Italy)

Oxygen requirements for controlling odours from pig slurry by

aeration 258

A. G. WILLIAMS, M. S H A W , C. M. SELVIAH and R. J. C U M B Y

(National Institute of Agricultural Engineering, Silsoe, UK)

Aeration and odour control by heterotrophic and autotrophic

microorganisms 273

M. R. EVANS and S. BAINES (West of Scotland Agricultural

College, Auchincruive, Ayr, Scotland, UK)

Joint Session: Other Aspects of Measuring Odours

Identification of volatile components in headspace from animal

slurries 284

E. M. O D A M , J. M. J. PAGE, M. G. T O W N S E N D and J. P. G.

W IL K IN S (Agricultural Science Service, M inistry of Agriculture,

Fisheries and Food, Tolworth Laboratory, UK)

Odours at water reclamation works 296G . L. JOHNSON (Regional Laboratory, Severn-Tren t W ater

Authority, Finham, UK)

B O D 5 , TOA and odour offensiveness 307

F. E. T H A C K E R and M. R. EVANS (Microbiology Department,

West of Scotland Agricultural College, Auchincruive, Ayr,

Scotland, UK)



X ll

Du st in livestock buildings as a carrier of od ou rs . . . . 3 2 1

J.H A R T U N G

(Institute for Animal Hygiene of the HannoverSchool of Veterinary Medicine, Federal Republic of Germany)

Du st con cen tratio ns in pig buildings 333

G. A. CARPENTER and L. J. MOULSLEY (National Institute of

Agricultural Engineering, Silsoe, UK )

Large-scale biogas plants in Hu nga ry 336

G . MESZAROS and L. M A T Y A S (National Institute of AgriculturalEngineering, Godollo, Hungary)

A naero bic digestion to con trol od ours 343

P. ESTEBAN TU R Z O , J . GUTT IEREZ SALGUERO and A. M OR E

HERRERO

The bio-gas project in Em ilia-Rom agna (Italy) . . . . 347

G. B O N A Z Z I , L. CORTELLINI , S. PICCININI (Centro RicercheProduzioni Animali, Reggio Emilia, Italy) and A. TILCHE

(ENEA, Roma, Italy)

The bio-gas project in Emilia-Romagna (Italy): first results of five full

scale plan ts 353

L. CORTELLINI , S. PICCININI (Centro Richerche Produzioni

Animali, Reggio Emilia, Italy) and A. T IL C H E (ENEA, Bologna,

Italy)

Farm experiments of anaerobic digestion to control odours from

slurry 358

J. A. M. VOERMANS (Institute of Agricultural Engineering,

I M AG, W ageningen, The Netherlands)

Use of methanogenic fermentation to upgrade farm animal and

slaugh terhous e wastes 366I. KLlNGERand U. MARCHAIM (Kimron Veterinary Institute, Beit

Dagan and M igal Galilee Technological Centre, Kiryat Shmona,

Israel)

Latest chemical slurry hand ling m etho ds 372

I. BOLONI and Gy. MESZAROS (National Institute of Agricultural

Engineering, Godollo, Hungary)



X l l l

Conclusions and Recommendations

Rec om m endation s on olfactometric m easurem ents . . . 378



The conclusions and rec om me ndation s for further w ork arising from

the FA O EEC joint wo rkshop on odou r prevention and control of

organic sludges and livestock farming 382

V. C. NIELSEN (Co-ordinator of the workshop for the FAO Subnetworks 2 and 3, Farm W aste Unit, M inistry of Agriculture,

Fisheries and Food, Reading, UK)

List of Participants 387

Index of Authors 391



GENERAL SCIENTIFIC PAPERS

A review of cost project 681 "Treatment and useof organic sludges and liquid agriculturalwastes"

A review of work of the FAO sub-network 2. Thereduction of odours in animal production

Odour problems related to waste water and sludgetreatment

Agricultural problems related to odourprevention and control

Odour research and ammonia volatilisation

Ammonia loss from grassland systems



A REVIEW OF COST PROJECT 681 TREATM ENT AND USE OF ORGAHIC SLUDGES

AND LIQUID AGRICULTURAL WASTES"A. H. Bruce

Water Research Centre, Stevenage, Herts

Smmarv

Co-ordination and co-operation among EEC and other countries in thefield of research on sewage sludge has been active since 1972 under the

auspices of a 'COST' Project sponsored by the Commission of the EuropeanCommunities. The most recent stage of this co-operation - COST 681 -has seen a widening of scope to include research on animal manures.There is interest in both the processing of sludges and manures and intheir effects when used in agriculture. Five Working Parties areestablished.

Odour nuisance is a particular problem associated with handling anddisposal of organic sludges and manures. Recently COST 681 established asub-group (as part of Working Party 1) to review the methods used forodour measurement in various countries with the aim of promoting greaterharmonisation. Involvement in this Workshop is part of the activity.

The sub-group is also preparing an inventory of Europeanorganisations and scientists actively involved in research onenvironmental odour measurement and control. A bibliography of recentpublications in this field will also be prepared for a COST 681 Symposiumto be held in Rome in October 1985.

INTRODUCTIONIn 1972, the Commission of the European Communities initiated COST

Project 68 "Sewage Sludge Processing". COST is an acronym for'Co-operation £cientifique et Technique1 - the main object of COST 68, aswith all COST projects, being to promote co-operation, co-ordination andinformation-exchange among people involved in publicly-funded research inthe EEC Member States - in this case on ' sewage sludge processing'.Several countries outside the EEC also accepted an invitation toparticipate in this scientific and technical co-operation.

Taking Europe as a whole, around 120 million wet tonnes of sewagesludge are produced each year and production will probably rise to closeto 200 million tonnes per year by the end of the century. There is,therefore, an interest in all countries in research to improve ways of

dealing with sewage sludge and thus most countries support some researchin this area. The establishment of 'COST 68' was a formal recognitionthat the problems related to sewage sludge are shared to a greater orlesser extent by all European countries.

The COST Project 68 lasted for 2 years and was considered "fruitfulfor scientific progress in the field"; there were seen to be also"considerable advantages to the 13 individual countries in sharingresearch in this project"(D. It was not surprising therefore when adecision was made by the European Commission in 1976 to continue thistype of co-operation in the form of a 'Concerted Action' designated 'COST68 bis'.



COST 68 bis was more extensive in scope than the initial projectsince it covered both treatment and use of sewage sludge. This meant

that the topics included both the engineering and economics aspects ofsludge processing at sewage works and the environmental aspects of sludgedisposal particularly in regard to its utilisation as a fertilizer inagriculture. The use of sewage sludge in this way is important in mostcountries and it was recognised that co-ordinated research was desirableinto both the possible adverse environmental effects of heavy metals andpathogens in sludges and the beneficial effects of plant nutrients insludge. The problem of odour nuisance arising from the handling andspreading of sewage sludge was also recognised as an importantsubject-area for research.

Under COST 68 bis, five Working Parties were established to

co-ordinate the various areas of research. As a 'Concerted Action', nodirect funding was available from the European Commission to financeresearch projects on sewage sludge, each country being expected tocontribute its own publicly-funded projects to the common 'pool'.

COST 68 bis ran from 1977 to 1980(2) and was followed by anextension programme - COST 68 ter - which ran from 1981 to 1983(3). In1983, it was decided to further extend this Concerted Action but to widenthe range of research topics in the scientific programme to includeanimal manures. The renewed programme was designated COST Project 681'Treatment and Use of Organic Sludges and Liquid Agricultural Wastes'.

It is obvious that sewage sludges and farm manures have many aspects

in common particularly with regard to handling and treatment techniquesand to the environmental impact (e.g. odour) which can occur from theirutilisation on land. On the other hand, from the administrative point ofview, sewage sludge and farm manures are in two different 'worlds'.Sewage sludge is the general responsibility of public authorities whileresponsibility for disposing of animal manures belong mainly to theprivate farming sector. Funding for research on the two types of waste,even if from Government sources, is usually from different Departmentsand there is little cross-involvement of research scientists in the twosectors. Nonetheless, the COST 681 activity is attempting to promoteseme co-ordination of effort between the two research areas and,

hopefully, this will result in mutual benefit to both those authoritiesresponsible for sewage sludge treatment and those concerned with farmmanures and their disposal.

This joint Workshop on 'odours' is a good example of the type ofco-operation, and sharing of information on a common problem, which canbe of great mutual benefit to both sectors.

PARTICIPATING COUNTRIESThe countries participating in the current COST 681 activity are:-

£ E £ Other European CountriesBelgium AustriaDenmark FinlandFrance NorwayFR Germany + Sweden + CanadaGreece SwitzerlandIrelandItalyNetherlandsUnited Kingdom



The non-EEC European countr ies have to ma ke a financial contributionto the Europ ean Commissio n in respect of the COST 681 activ ity and this

is a sure indication that they consider their involvem ent to be of va lue.Canada has the more informal status of an invited participant in seme ofthe technical meetings. There are also links with relevant internationalorga nisati ons such as the FAO - as is evidenced by this joint Works hop.

ORGANISATION OF COST 681 A C T I V m E SAs indicated earlier, COST 681 is organised into 5 Working Parties

under the general guidance of a Management Committee of NationalDelega tes (Current President: H. H. Scheltinga of the Nethe rl an ds) . TheWorking Parties and their respective areas of responsibilities are :-

Wor kin g Party 1. Sludge ProcessingNew sludge/manure processing techniques; sludge and manure handling;economics; odour measurement and control; sludge chara cterisation.

Wo rk in g Party 2 ; ChwnlraJ Pollnt-jonAnalytical methods for heavy metals and organic contaminants in

sludges. Costs of Analyses.

Working Party 3. Hvgenic AspectsEnumeration of sludge pathogens and parasites; efficiency of

disinfection methods; indicator organisms; epidemiological aspects of

sludge utilisati on. Fate of pathogens on land.

Working Party 4. Agricultural ValueAvailability to crops of sludge N and P; effects of sludge organic

matter on soil fertility.

Working Party 5. Environmental EffectsPhytotoxic and zootoxic effects of heavy metals in sludge.

Guidelines for disposal to farmland.

Each Working Party organises workshops and seminars on relevant

topics and the proceedings of these are published by the EuropeanCommission. Over 10 of these publications are now availa ble. Inter-laboratory compa risons of analytical methods are also organised among theparticipa ting countries. The mai n emphasis is still on sewage sludgesince many of the scientists involved are based in the 'water industry'and receive support largely, if not entirely, from that industry.

RESEARCH ON ODOURSThe topic of 'odours' and odour measurement has been on the

programm e of the COST 68 activity since the early day s. Initially, underCOST 68, seme studies were made of methods of assessing sludgestability^) and these included odour assessment but little furtherco-ordinated wo rk wa s done until the establishment in 1981 of a sub-groupon 'odours' as part of the a ctivity of Working Party 1 of COST 681.

The problem of odour nuisance arising from the handling and land-spreading of sewage sludge is wel l known in the water industry. Indeedthe main purpose of subjecting sludges to stabilisation treatment (e.g.diges tion) at sewage wor ks is to control odour nuisance. The problem isshared in all countries but it is usually not possible to quantify itprecisely in relation to other problems associated with sewage sludge.In the UK, however, a recent survey s h o w e d ^ (Table 1) that most of the



complaints or pr oblems relating to disposal of sewage sludge to land wer erelated to odour nuisa nce.

Table 1. Summary of complaints or problem s relating todisposal of sewage sludge to land in the UK (1980 d a t a ) C)

Type of problem

Environmental nuisance

Transport

Water Pollution

Agricultural

Metals

Veterinary

Planning consent

(smell)

Per cent occurrence

60

19

10

5

4

1

1

100

It is clear from this that odour nuisance is an important problemand it follows that standard methods of scientifically measuring odoursare desirable.

ACTIVITY OF COST 681 SUB-GROUP 'ODOURS'This sub group was established in 1984 as part of the activity of

Working Party 1 but drawing on experts from outside the Worki ng Party.The Chairman is Mr J H Voorburg of the Netherlands and other experts inodours include Dr M Hanga rtner (CH) , Dr J Hartung (D ), Dr A Eikum (No)and Mr V C Nielsen (U K) . Mr H M Scheltinga (NL) and A M Bru ce (UK) arealso members of the group.

The sub-group is hoping to complete its tasks quickly, the main onesbeing(a) To deve lop proposals for a harmonised and standardised odour

measurement technique

(b) To exchange information about research on odour measurement andcontrol.

On (a) good progress has been mad e in collecting informa tion on the

existing guidelines in different countries for sampling andtransportation of samples for odour measurement, for dilution techniquesand for panel selection etc. The question of acceptable levels of odourintensity is not being considered. All these ma tter s will be discussedat this joint Workshop and it is hoped that clear recommendations willemerge from the experts so that a formal report can be presented fordiscussion at the COST 681 4th Symposium to be held in Rome in October1985.

In regard to objective ( b) , one of the majo r tasks of the sub-grou phas been to compile an inventory of organisations and scientists inEurope who a re actively involved in research on the mea surem ent and/or



control of environmental odours. Additionally, the sub-group ispreparing a bibliography of European reports and papers on odour

measurement and control which have been published in the last 5 years.This inventory will also be made available at the COST 681 Rome Symposiumin October 1985.

So far, the enquiries for the inventory of research organisationshas indicated a considerable variation in research activity on odoursamong the European countries (Table 2 ) . In most cases, there is semeGovernment funding for this research. Overall, it is hoped that thisaspect of the sub-group's work will promote an improved inter-change ofinformation and co-operation between organisations and scientists in thisfield.

Table 2. Preliminary information concerning research on themeasurement and control of environmental odours in

European countries

Country No of Research Government

organisations involved Funding

v/

x/v/

X

/X

Other countries 0* ?

• Information to date;The final report will contain full details of the organisationsand their personnel.

OTHER COST 681 ACTIVITIES RELATING TO O DOURSOther activities related to odours are directed mainly at odour

control techniques - particularly methods of sludge and slurrystabilisation. There is continuing research and development relating toanaerobic digestion as a process for odour control; a COST 681 Workshopon new developments in anerobic digestion was held in 1984(5). There arealso developments in aerobic thermophilic digestion which have beenconsidered by COST 681 Working Party No 1. A review of chemical andbiological methods of odour control has been prepared for a COST 681series of Review papers^).

CONCLUSIONSOdour measurement and control is just one of the many aspects of the

treatment and use of organic sludges and liquid animal wastes consideredwithin the COST 681 co-ordination activity. But it is a very importantaspect and one which is receiving particular attention during the currentphase of the scientific programme.

BelgiumFranceFR GermanyNetherlands

NorwaySwedenSwitzerlandUnited Kingdom

25156

2128



REFERENCES

(1) Commission of the European Communi ties. COST Project 68 . SewageSludge Processing. Final Report of the Managem ent Committee. 1975.

(2) Commissio n of the European Communi ties. COST Project 68 bis .Treatment and Use of Sewage Sludge. Final Reports of the Community- COST Concertation Committee.

(3) Commission of the European Communities. COST project 68 ter. FinalReports of the Community COST Concertation Committee. 1983.

(1) Department of the Environm ent/National Wat er Council Standing

Committee on the Disposal of Sewage Sludge. Sewage Sludge Survey1980 Dat a. Department of the Environment 1983.

(5) Anaerobic digestion of Sewage Sludge and Organi c Agricultural Was te.Proceedings of a COST 681 Work shop held in Athens Hay 1984. (In thePress).

(6) EIKUM, A.S., and BERG, N. Odour characterisa tion and removal ofodours from facilities receiving septage. To be published in ReviewPapers on Sewage Sludge Processing, 1985. Commission of theEuropean Communities, Brussels.



A REVIEW OF WORK 0 ? THE FAO SUB-NET.VORK 2THE REDUCTION OF ODOURS IN ANIMAL PRODUCTION

V. C. NIELSENHead of t h e Farm ,Vaste U n i t , ADAS

M i n i s t r y of A g r i c u l t u r e , F i s h e r i e s an d Food

Summary

Sub-networ k 2, the r eduction of odour s in a nim a l pr oductio n, for m s pa r t oft h e c o n s ul t a t i v e i n f o r m a t i o n n e t w o r k o n A n i m a l W a s t e U t i l i s a t i o n . Th econcept of inter n a tiona l cooper a tion a nd the excha nge of scientific infor ma tion wa s esta blished by the Food a nd Agr icultu r a l Or ga nisa tion (F.A.O.)of the United Na tions in 19 73 . Ther e a r e ten eur opea n consulta tiv ei n f o r m a t i o n n e t w o r k s in o p e r a t i o n . Th e An i m a l W a s t e U t i l i s a t i o n n e t w o r kis coor dina ted by Mr P. E. Lohm in Sweden. This networ k is br oken downinto fiv e sub-networ ks whic h cov er the effect of liv estock wa stes on :a nim a l a nd hum a n hea lth, odour r eduction, building a nd m a chiner y design ,sta nda r disa tion of m ethods of sa m pling a nd a na l ysis, a nd the effect ofloa ding r a tes on soil fer tility. Sub-networ k 2, a ctiv ities ov er the pasteight yea r s ha v e been to esta blish the excha nge of infor m a tion a t m eetings

a r r a nged a t r esea r ch institut es, to define r esea r ch pr ior iti es for futur ew o r k a n d to e s t a b l i s h s ta n da r d t e c h n i q u e s o f m o n i t o r i n g a n d a n a l y s i s . A Hthe sub—networ ks m eet ev er y thr ee yea r s to r ev iew pr ogr ess a nd a r r a ngef u t u r e p r o g r a m m e s . Th e ob j e c ti v e t o e v e n tu a l l y p r o d u c e a n e a s i l y u n d e r stood set of guidelines for fa r m e r s a nd pr ov ide techni ca l a dv ioe a nda s s i s t a nc e t o d e v e l o p in g c o u n t r i e s .

1. INTRODUCTIONThe sub—networ k on the r eduction of odour s in a nim a l pr oducti on, wa sset up a s a r esult of a consulta tiv e m eeting of inter ested Eur ope a n sta tesorganised by the Swedish Governm ent on beha lf of FAO in 1976« The conceptof a consulta tiv e in for m a tion networ k wa s a lr e a dy well esta blished by FAOby its Euro pea n System of Co-oper ati ve Research Networ ks (ESCORENA) whichcom m enced in 19 73 . ESCORENA ha s sponsor ed a nd esta blished ten netwo r ks,these r a nge in inter est fr om oliv e pr odu ction, pesticid e im pa ct on thee n v i r o n m e n t , m a i z e p r o d u c t i o n t o a n im a l w a s t e u t i l i s a t i o n .

The ba sic pr inoiple on whic h a ll the networ ks oper a te is tha t, nosingle countr y ha s the r esour ces to ca r r y out a ll the technologica l a nd

s c i e nt i f i c r e s e a r c h n e c e s sa r y t o m a i n t a i n p r o g r e s s i n a ny s u b j e c t . T h e r efor e, a well defined inter n a tiona l co-oper a tiv e r esea r ch a nd dev elopm entpr ogr a m m e which encour a ges the sha r ing of infor m a tion a nd a v oids theunnecessa r y duplica tion of wor k a nd r esour ces would be of benefit to a llthose inv olv ed. Also enshr ined in this idea l is the concept tha t theinfor m a tion ga ther ed should be m a de fr eely a v a ila ble to a ll dev elopingcountr ies thr oughout the wor ld. The Bteps necessa r y to a chiev e theseo b j ec t i v es a r e : -

1. the dev elopm ent of integr a ted inter n a tiona l r esea r ch a nd dev elopm entpr ogr a m m es or ga nised thr ough the consulta tiv e system .



2 . the collection and ev a lua tion of scientific data and t e c h n i c a linfor m a tion by the co-oper a ting institutions, co-or dina ted by the

s u b - n e t w o r k s .3 . the pr oduction of t e c h n i c a l and scientific r epor ts by m e a ns of

sem ina r s, wor kshops and sym posia .4 . the dev elopm ent of b a s i c s y s t e m s .

5. fina lly the pr oduction of ea sily under stood guidelines for f a r m e r s .

The consulta tiv e infor m a tion net wor k on A n i m a l w a s t e U t i l i s a t i o n is m a i n tained by the co-or dina tor of the networ k, Mr p E Lohm, he r uns theco-or dina tion centr e at the Swedish Boa r d of Ag r i c u l t u r e , J o n k o p i n g .

At the initia l consulta tiv e m eeting held at Solna Sweden in 1 9 7 6 , itwa s a gr eed that a gr i cultur a l wa stes was such a la r ge and w i d e r a n g i n gsubject area, that it could not be cov e r ed entir ely by the n e t w o r k . Af t e rdiscussion fiv e im por t a nt subject a r ea s wer e selected for deta iled a ttention as s u b - ne t w o r k s t h e s e w e r e : -

1 . The influence of m a nu r e ha ndling and utilisa tion system s on a n i m a l andh u m a n h e a l t h .

The oo-or dina tor is Pr ofessor I Ekesbo, Depa r t m ent of An i m a l H y g i e n eSwedish Univ er sit y of Ag r i c u l t u r a l S c i e n c e s .

2 . The Reduction of Odour s in Anim a l Pr oductionThe co-or dina tor Mr V C Niels en Farm Waste Unit ADAS Reading UK.

3. Differ ent m a nur e ha ndling m ethods and their inter a ction with buildingconstr uction and e n v i r on m e n t al h a z a r d s .Co-ordinator Dr I Boloni, In s t i t u t e of Ag ri cul tu ral Engineering,

Godollo, Hungary.

4 . The oo ll ec t io n and eva luati on of di f fer en t li qu id manure sampling

and anal y t i ca l methods t o ob tain comparable r e s u l t s .

Co-or dinator Mr J Kar li nger , Department of Plant Pr o te ct ion and

Ag r ic ul tu ral Chemistry, Minist ry of Ag ri cu lt ur e and Food, Budapest,

Hungary.

5 . The So i ls capaci ty for animal wastes

Co-ordinator Professor B7 Ve t t e r , Uni ve rsi ty, Oldenburg, F R Germany.

2 . SUB-NETWORK 2, THE REDUCTION OF ODOURS IK ANIMAL PRODUCTION

The following ob ject ive s are th e oasi s of i t s co-ope rati ve programme:

1 . The dev elopm ent of m ethods to m e a sur e odour s and odour disper sion. Todeter m ine a ccepta ble concentr a tions of odor a nts and a ccepta bledista nces between pr iv a te houses and l i v e s t o c k b u i l d i n g s .

2 . The contr ol of odour s fr om m a nur e spr ea d on fields and f r o m m a n u r es t o r e s . To ev a lua te existing contr ol m ethods in t e r m s of costs ande f f e c t i v e n e s s .

3 . To e v a l u a t e the treatment of liquid m a nur e by a e r obic and a n a e r obic

b i o l o g i c a l s y s t e m s . To deter m ine the p a r a m e t e r s w h i c h c o n t r o ltreatment and its efficiency in contr olling odour s and the costs of

t r e a t m e n t .4 . To dev elop and ev a lua te contr ol system s for the t r e a t m e n t of odour

e m issions fr om the v e n t i l a t i o n s y s t em s in l i v e s t o c k b u i l d i n g s .

The sub-networ k oper a tes by a g r eeing a pr ogr a m m e of w o r k w h i c h is put

for w a r d for a p p r o v a l at the tr i a nnua l consulta tion m eeting of the entir en e t w o r k . A r e v iew of the oper a tion of the sub-networ k is carried out at

m eetings held at co-oper a ting scientific insti tute s. These usua lly



10

ooour halfway between the major consultation meetings. The sub-networkmeetings consist of the presentation of technical reports by Bombers and

a review of progres s. These meetings may make fundamental changes inthe programme depending on how the work is progressing.

Hone of the research and development work is funded by FAO and all ofthe participation by co-operating institutes and their staff is entirelyvoluntary. It therefore requires a certain amount of adjustment byparticipants to link up their research and development work funded byinternational and national agencies with the co-operative programm e.

It is UB ual during sub-network meetings to visit sites where researchand development is being carried out and to observe the introduction ofnew techniques on far ms.

During the eight years that the sub-network has functioned consulta

tion meetings have been held at N yon , Switzerland 1 9 7 8, Wageningen,Netherlands 19 80 , and Budapest, Hungary 19 83 . Sub-network meetingshave been held at Wageningen, Netherlands 19 79 and at Hanover , F R Germany1982. At the sub-network meeting held at Wageningen in 197 9 papers werepresented on the following topics.

1. Odour measurement techniques in use in the Netherlands and in Sweden.2. The use of gaschromatography to determine the presence of odorous

compounds in the air in pig buildings and poultry houses.3 . Methods of collecting and evaluating odorous air from land spreading

operations.

k- Odour dispersion studies around farm buildi ngs.5. Information on odour control and prevention.

Papers were presented at the consultative meeting held at Wageningen1980 as follows:-

Sampling of odorous compounds in animal house air by paperabsorption for gaschromatographic analyses J Hartung

The control of odours in animal production A A Jongebreur

Papers were presented at the Sub-network meeting held at HannoverF R Germany in 1 982 were as follows:-

Odour measurement techniques under trial with ADASin the UK V C Nielsen

Investigation of the effect of pig fattening house

dust on some odorous compounds J Hartung

Odour measurements in Dutch Agriculture J V Klarenbeek

Latest state of the Olfactometer and guidelines

for its use G T Meyer

Odour control of pig housing and land spreading 0 Noren

Odour control problems in the U K , some case

histories V C Nielsen

Dust filters to reduce odour from broiler houses M Van Geelen

Legislation in France, some case histories J F David

Emission control problems and experiences withthe VD 1 Guidelines 3471 in Germany Mr Huffmeyer



11

A paper was presented to the consultation meeting held in Budapest,Hungary 19 83 .

Odour complaints caused by agricultural enterprisesin the U K and some control procedures. V C Nielsen

At the last consultation meeting held in Budapest 19 83 , the sub-networksoutline programme for the next three years agreed to hold a workshop atSilsoe U K . At that meeting Professor A A Jongebreur gave up theco-ordination of the sub-network which he had held since 197 7 and it wasagreed that V C Nielsen should take over.

The content of the programme of the workshop was as follows:-

1. To agree to standardise odour measurement techniques to enable

quantitative measurements of emission rates of odour from differentlivestock production systems.

2. To quantify odour reduction by aerobic and anaerobic treatment ofliquid manures.

3 . To evaluate odour reduction from livestock buildings by the use ofbiofliters.

if. To evaluate and describe livestock production systems which have lowlevels of odour emission and which have low energy demands and improvethe welfare of livestock.

5. To evaluate the role of dust in livestock buildings and its effect onthe transmission of odour and disease.

The consultative meeting suggested that the topics set out in the workshop programme had an interest and an input from Snb—network 3 and thatboth groups should combine their interests.

As the programme for the workshop developed there was an overlap ofinterest with the Cost 681 ESC programme of work on the "Treatment andUse of Organic Sludge and Liquid Agricultural Was tes ", in particular withthe work of the expert group on Odours. It was agreed by this groupthat a combined workshop would be of advantage to both the FAO and EECworking part ies. Formal arrangements were made for a combined workshopat a meeting held at the University of Hannover in November 19 84 .

It is expected that the proceedings of the workshop will be publishedby the E E C . The drawing together of all the information will then beused as a basis on which to commence work on guidelines for farmers.



12

ODOUR P ROBLEMS RELATED TO WASTE WATER AND SLUDGE TREATMENT

A.S. EIKUMR. STORHAUG

Aquateam-Norwegian W ater Technology Centre A/S

Summary

Odour problems are closely connected to sewage collection, treatmentand sludge disposal. There are many reasons for this, like improper

operation and design of the facilities.Different methods are in use for avoiding the generation ofodourous gases in sewage treatment systems. One of the most effectivemeans are new operational routines like sewer cleaning programs, andodour reduction equipment at treatment plants.

Collection and treatment of the odourous air have proved to bevery effective. Different methods are in use for reducing the odourousgases. A chemical scrubber or combustion effectively eliminatesodours. The use of activated carbon filters will reduce odours, butfilter media get saturated and require a total change or regeneration.Biological methods, for exemple a soil filter, for odour reduction

have come into use in the last few years; mainly due to a simple andinexpensive design. The soil filter effectively reduces the odour andseems to have a relatively long lifespan. Iron oxide filters have alsoproven to reduce odours. Experience is limited with these filters, butso far they seem to be inexpensive and effective.

1. INTRODUCTION

Collection and handling of wastewater have caused odour problems for

many years. New treatment plants are built close to populated areas and oldplants have been gradually surrounded by new dwellings. Many countries haveregulations for the minimum distance between treatment plant and dwellingareas. Even though the treatment plant meets the minimum distancerequirement, still odour can become a large nuisance in the neighbourhood.Today, public is more aware of odour problems and no longer accepts strongodour emissions from sewage and sludge treatment facilities.

2. ODOUR PRODUCTIONFresh wastewater has a characteristic musty scent. The wastewater is

named "fresh" when disolved oxygen is present. If microbiological decay is

occuring in the absence of molecular oxygen and nitrates, the wastewater iscalled "septic".

The odour-causing substances usually arise as a result of biologicalactivity in the sewerage system or at the treatment plant. Hydrogensulfide (H S ) and ammonia (NH ) are the principal inorganic gases, thatcauses odour problems. Mercaptans, indoles, skatoles and various othernitrogen and sulfur-bearing organics are the most important organicsubstances. In some cases the odour is not produced in the wastewater, butis added from industrial or other sources. The most common cause of odoursin wastewater collection and treatment is hydrogen sulfide (H S ) . This gashas a smell often described as "rotten eggs".



13

3. ODOUR IN THE SEWAGE COLLECTION SYSTEM The anaerobic conditions occur when the disolved oxygen (DO) of the

sewage is

absent.

The

anaerobic

bacteria

has

a longer

generation

time

than

their aerobic counter parts. As a result of this a sufficient detention time in the collection system is necessary before the production of H S can start. The sulfides are produced in the slimes of the submerged surface of the sewer or from settled sludge in the sewer. Odour problems from the collection system (man-holes and pumping stations) occure normally only in flat areas where the sewage has a long detention time in the pipeline. The odour effect in the collection system is usually most prevalent during warm weather conditions (20°C and higher) (1). As a result of this, odour from the collection system is not a large problem in the northern part of Europe.

4. ODOUR IN THE SEWAGE TREATMENT PROCESS The treatment of municipal sewage can be devided into four different

groups. • Primary treatment: Removal of settable particles " Secondary treatment: Removal of organic matter. ■ Tertiary treatment: Removal of phosphorus. • Sludge treatment: Different processes, stabilisation, dewatering,

desinfection. Figure 1 shows a flow-sheet where the four different groups of treatment are put together.

| PRIMARY TREATMENT | SECONDARY TREATMENT | TERTIARY TREATMENT |

Bar Grit t cmn clumber Flocculatlon

^H~

Rotating biological contactor*

SLUDGE TREATMENT

Figure 1■ The most common processes in municipal sewage treatment



14

The odour arise from many different sources within the plant. The mostimportant sources are:

Odours fron raw sewageRaw sewage entering the plant may have already developed odours in thecollection system. These gases will quickly be released when enteringthe plant.

Screenings and grit removalMaterial removed by the bar-screen and in the grit chamber can causeodours if not disposed off quickly after removal. However, screeningsand grit are not a major source of odours at municipal plants.

The outlet weirs from the sedimentation tanks.Water that drops down a foot or two from the outlet weir can cause theemission of odourous gases from the sewage. This is usually a problemonly after primary sedimentation.

Accumulated grease and sludge on surfacesUnless the plant operation is proper, grease and sludge willaccumulate on different surfaces and cause odour.

Accumulated sludge in the settling tanks.If the sludge in the settling tanks are not removed on regularly, the

accumulated sludge can cause odour problems.

Secondary treatment unitsIf the secondary treatment step is overloaded, the DO-consentrationwill be depleted and odours will develope.

Sludge treatment processesBoth thickening, digestion and sludge dewatering very often causeodour problems.

Receiving facilities for septage

Discharging of septage from tanker vehicles is on one of the mostcommon sources of odour problems.

Figure 1 shows a conventional treatment plant. Oxidation-ponds serving asindependent treatment units are mainly used in rural areas. These ponds canbe the source of a variety of different odours. Algaes are probably themain problem with regard to odour production at these plants. (1)

5. METH ODS FOR ODOUR PREVEN TION OR REMOVALIn general there are four different areas of odour control in sewerage

systems.

• Changes in operational routines.• Chemical treatment of the sewage.• The use of new and less odour-producing methods in the sewagetreatment.

• Covering the treatment units and treatment of the odourous air.Changes in present operation routines are in many cases of the mosteffective and inexpensive means of odour control. Sewer cleaning programsare examples of that kind of odour control. Chlorine has been found to bethe most popular chemical for inhibiting the anaerobic bacteria causing H Sgeneration. But the use of chemicals to prevent odour generation in tne



15

sewer system or at the treatment plant is usually a temporary method in thecase of odour problems. Covering the odour-generating processes and

treatment 'of the collected air is a common method of odour control. InScandinavia nearly all of the treatment plants are built indoor. Usuallythe different tanks are also covered. The air is collected under the coverand blown through odour removal equipment. On outdoor plants domes andenclosures are frequently used to cover the different tanks.

6. AN OVERVIEW OF ODOUR-REMOVAL EQUIP MEN T

Chemical scrubbers

Chemical scrubbers utilize hypochlorite as oxidizing agent. Thescrubbers are either single- or two/three-stage scrubbers. Generally it can

be concluded that the installation and use of the scrubbers have been quitesuccessful. On Figure 2 a two-stage scrubber, type Steuler, is shown. Thefirst stage is an alkaline oxidation (NaOH+ NaOCL) and the second stage isan acidic wash using H SO..

Mitt alimiiMtot

Figure 2. Chemical scrubber, type Steuler.

The results from total odour strength measurements of differentchemical scrubbers, show odour reduction efficiencies between 95 per cent

and 98 per cent. ED of the cleaned air has been found to be between 50and 100, and the air has been characterized as "free from sewage odours,but it smells like chemicals". It seems as if a chemical scrubber alwaysgives this "scrubber odour".

Cost for operating the chemical scrubbers can be devided into chemicalcost and cost of energy. Energy will always contribute most to the totalcost of operation.



16

Activated carbon filtersUse of carbon filter odour reduction is quite common at municipal

wastewater treatment plants. The odour compounds are not destroyed in thefilter, but only retained until the carbon becomes saturated. When thefilter is saturated the carbon is changed or regenerated.

Odour strength measurements at different sewage treatment plants inNorway have shown that no rule can be made as to when the change of filtershas to take place. During a cold winter longer intervals are possiblecompared to the warmer seasons.

In Figure 3 an activated carbon filter used for cleaning exhaust airfrom a dewatering process is shown. Together with the carbon, the equipmentincludes a grease-filter and a condensation unit.

Odour strength measurements in Norway have indicated reduction

efficiensies up to 83 per cent when a completely new filter was used. Anold filter, which had been used twice as long as the manufacturer hadrecommended, shewed, however, reduction efficiencies of 72 per cent.

Cleaned air

Activated carbon filter

Grease filter Condensing unit

Exhaust air

Condensing water

Figure 3. Carbon filter for odour reduction.

The cleaned air from the activated carbon unit had a wastewater smell.Evidently not all odour components were destroyed in the filter. When thefilter becomes saturated, the components leave the filter as new odourousair reaches the filter.

Combustion

The principle of burning odour components to highly oxidized productswith little or no odour, is very old. If the temperature and contact timeof the gases in the combustion chamber are sufficient, combustion of odourfrom a sewage treatment plant, without doubt, is the best odour reductionmethod. Contact time up to 3 seconds and temperatures of about 850 °C havebeen reported as sufficient.(4)(5)

Catalytic oxidation makes it possible to destroy odourous gases attemperatures lower than without catalysts. Low concentrations of odourouscompounds and sulfuric odour compounds reduce the effect of the catalystand thus limit the application of catalytic oxidation for control of odours



17

at wastewater treatment plants.Another problem with combustion of odourous gases is the rising fuel

costs. A special incinerator just to take care of the odours from atreatment plant would not be economical compared to the use of chemicalscrubbers. If, however, sludge gas from a digester is available, the fuelcosts can be reduced.

The City of Oslo has the only treatment plant in Norway usingcombustion to reduce odour. The plant has digesters and therefore low fuelcosts. The efficiencies measured show a very good odour reduction, up to98-99 per cent. No wastewater odour was recognized in the cleaned air, onlya faint "burnt odour".

Soil filters

Extensive work has been carried out in the US regarding the use ofsoil filters for odour reduction. (6) It was shown that the filterperformance depended on filter loading, type of soil, soil moisture,temperature and concentration of odourous components. The US study alsoconcluded that both chemical and biological processes were responsible forthe odour reduction.

At TAU Treatment Plant in Tensberg, Norway, a full-scale soil filterwas put into operation in the Summer 1981. (3) The filter treats odoursfrom the receiving facility for septage only. This facility handles14.000 m] of septic tank pumpings annually. The filter consists of 35 m' offilter area, 0.5 m thick. The air is distributed through a diffusor system

with a 40 0 mm header pipe with twelve mm laterals. The pipes are located inthe gravel layer. The air flow through the filter is 2.000 m3 /h underconstant operation. When a tank truck empties septage at the plant, thescreen automatically goes into operation, and the fan speed increases to acapacity of 3.000 m 3/h. When the screen stops, the fan capacity is againreduced to 2.000 m 3 /h. The filter loading therefore varies between57 m 3/ m!

. h and 86 m 3/ m !. h. The filter design is shown in Figure 4.

Regarding longterm performance it is too early to draw any conclusions.

Tau/Vallø Soil Filter

Scratn/lan control

Stptagt

Chlmnay

Xw

"p f^w^^^m-Soil (50 cm)

- » 100 mm pipe

Storage tank (clo«d>

Figure 4. Full-scale soil filter at TAU Treatment Plant, Tonsberg, Norway.



Iron oxide filters

Only limited information is available regarding the design and use of

iron oxide filters for odour reduction, although Cormack et al. describethe filters in their work. (7)

Based on a study by Eikum ( 8) , the City of Oslo built an iron oxidefilter at Festningen Treatment Plant. The untreated air is taken from aclosed compartment above a sludge storage basin. The filter was designedfor a maximum capacity of 90 m 3/ m 2 .h, but the actual loading can varybetween 20 and 90 m3 /m2 .h. The total filter area is 9 m2 and the mediaconsists of 90 0 kg Fe 0 mixed with 4 m3 wood chips. The design of thefilter is shown in Figure 5.

The ED was tested through a 4-month period. Prior to this testingperiod the iilter had been in operation for four months. The removalefficiency varied between 61 and 89 per cent (9) . No offensive odour wasdetected out of the filter; only the "wood chips odor" from the filtermedia.

Cleaned air

Mixture of wood chips and iron oxide

Dense top

Drainage ' Exhaust air

Figure 5. Iron oxide filter design at Festningen Treatment Plant, Oslo,

Norway.

In Tonsberg, Norway, an iron oxide filter was constructed to reduceodours from a pumping station close to the municipal treatment plant. Thefilter is shown in Figure 6. The filter treats odours caused by evacuationof air from a pressure main. The air enters the filter through a perforatedpipe at the bottom and flows through the filter media into the atmosphere.The filter has been in operation since the Summer of 1978. Tests of thefilter performance have been carried out regularly since then.



19

/ J t - f r om

pumping station

Perforated pipe

Pipe to open in case of

fi lter media treating

Figure 6. Iron oxide filter in Tansberg, Norway.

The pumping station is located in a residential district, and beforethe iron oxide filter was installed, there were frequent complaints fromresidents in the area. After the filter was installed, the complaintsceased completely.

Ozone

Ozone has been used successfully to treat odourous air on wastewatertreatment plants. Due to its relatively high generation costs and highreactivity, the addition of ozone to a large flow is not practical.However, ozone can be applied economically to odours that are collected bycovered facilities. Ozon will ox idize sulfides and amines to nonodoursgases. Figure 7 shows ozone odour-removal equipment installed at atreatment plant that receives septage.



20

'o1— O

1

Figure 7. Ozone odour-removal equipment.

In (1C) the investment costs for a system treating 1.500 m 3 air/hourare estimated to about £10 .00 0.

REFERENCES

(1) CHE REM ISI NOF, P.N. and YOUNG , R.A. (1975). Industrial Odor TechnologyAssessment. Ann Arbour S cience Publishers I nc.

(2) DAGUE, R.R. (1972). Fundamentals of Odor Control. Journal of WaterPollution Control Federation Vol. 44 , No. 4 , 583-59 4 .

(3) EIKUM, A.S. (1982). Treatment of Septage, VA-rapport 11/82, NorwegianInstitute of Water R esearch.

(4) PETTIT, C.G. (1959), Twenty Years of Sewage Sludge Burning atBarberton, Ohio. Journ. San. Eng. D iv. Proc. Amer. Soc. Civil E ngr. 85SA 6, p. 17 .

(5) LAB00N, J.F., (1961), Construction and Operation of the PittsburghProject. Jour. Water Poll. Control Fed. 3 3 , p. 758

(6) CARL SON, D.A. and LEIS ER, C.P., (1966), Soil Beds for the Control ofSewage Odors. Jour. Water Poll. Control Fed. 3 4 , pp. 829-840.

(7) C0R MACK , J.W. et al., (1974), Odor Control Facilities at the ClaveyRoad Sewage Treatment Plant. The 47th Annual Conference WaterPollution Control Federation, Denver, Colorado, Sept.

(8) EIKUM, A.S., (1976), Reduksjon av lukt fra mottakeranlegg forseptikslam. P roceedings N IF-kurs, Fagernes, Norway.

(9) BERG, N., (1979), Reduksjon av lukt ved kloakkrenseanlegg. NTNF'sUtvalg for drift av renseanlegg, HPF 24/76, Oslo, N orway.

(10) J0HAN SE N, O.J., (1982). Luktfjerning ved bruk av ozon. Drift 2/82,

NTNF's Utvalg for drift av renseanlegg; 10-12.



21

AOTICULTURAL PROBLEMS RELATED TO O DO UR PREVENTION AND CONTROL

D. C. HardwickPollution S cientist, Ministry of Agriculture, Fisheries and Food,

England and Wales

Summary

The paper provides a general background to the need for odourresearch. The origin of the problem includes the changing attitude to

agriculture and the changes in agricultural practice.Complaints about smells can be reduced either by reducing the strengthand/or offensiveness of the smell or by reducing the adverse reactionof human beings to the smell.The majority of complaints are caused by pig farming in the UK andslurry spreading from pigs and cattle account for half the sources ofcomplaint. Buildings and storage are less significant, this indicatesthat the greatest need for control is for slurry as spread, althoughtreatment in storage may help both storage and spreading problems.The basis for providing cordon sanitaire around offensive smellsources involves estimations of the distances travelled by smells. The

vagaries of weather create difficulties here and precise measurementat one time can give misleading information. What is perhaps needed isrough estimates much more frequently. Short term peaks of odour maygive rise to complaints without being easily recorded.There are also important social factors in assessing people'sreactions to smells.It is unlikely that any one approach alone will solve the problems ofsmell. The application of a battery of remedies as part of a totalsystems approach seems to offer the best possibility.

IntroductionThis paper attemps to analyse the problems of agricultural odour in

order to assess the potential contribution of the various approaches toreducing complaints. The paper refers mainly to the UK situation but thediscussion should be valid more generally.

Origins of the ProblemA number of industries are traditionally associated with the

production of unpleasant smells, e.g. leatherworks, fat rendering plants,cement works, soap works and glue works. But these are generally associatedwith urban environments and many living close to them depend on theindustry for their livelihood. Similarly, those traditionallly living inthe country depended on agriculture for their income and acceptedunpleasant smells as part of the situation. Excursions into the countrygave most city people the idea that the agricultural environment smeltpleasantly of hay, field beans and, at worse, a brief whiff of cow manure.

Nowadays, people are increasingly moving their homes from the town(where they still work) into the country and these are often the richer

people. They find that the impression of a fine summer's day in the country



22

is not sustained on more permanent acquaintance. Their expectation was fartoo often disappointed. They have no financial interest in the agricultural

industry because they can get a supply of cheap food from elsewhere. Theytherefore have no incentive and no wish to put up with the unpleasant factsof country life.

Parallel to this move into the country, the keeping of animals,particularly pigs, in large numbers has provided economic benefits. Butthis has involved methods of handling excreta based on slurry rather thanon solid farmyard manure and this increases the intensity and offensivenessof animal operations. Silage and oilseed rape add to the unpleasantness ofcountry air.

The UK Royal Commission on Environmental Pollution, in its report onAgriculture and Pollution, said :

"It is clear that the smells associated with intensive animalproduction give the most offence to, and cause most complaint by, thepublic at large. It is also the most difficult problem to define. Thereaction to smells and the assessment of their intensity are highlysubjective matters. However, refined measurement is unnecessary toestablish that the smell created by intensivelive stock units can be veryobjectionable. We are talking here of smells that are far removed from the"good country smell" of farmyard manure. The smell of pig slurry, as weexperienced when visiting Humberside with its many pig units, is highlyoffensive and penetrating. Those people unfortunate enough to be living orworking downwind when pig slurry is being spread on the land may well find

the smell intolerable. In broiler and veal calf units the smell problem isintensified for a week or two at the end of the creatures' brief lifecycle,when the accumulated excreta and dropped feedstuff in the bedding encourageextensive fungal and bacterial growth and an extremely strong ammoniacalsmell is produced. This smell builds up and is then vented outside of thebuilding.

The problems of smell nuisance are mainly associated with intensiveanimal production and are more acute when intensive units are close tosettlements or when the units need to export excreta for disposal on otherfarms that are so sited. Much can be done to minimise the smell nuisance byadhering to good management practice both in the rearing process and whenthe excreta are stored or spread on the land. If slurry can be spread onthe land within one or two days of its production, that is, beforeanaerobic decomposition starts, much of the smell problem is avoided. Therisk of smell nuisance is also affected by the technique used for slurryapplication, being reduced by the use of slurry tankers having a lowtrajectory discharge or fitted with low-level dribble bars, or by directinjection into the soil. For a number of reasons, however, such as theavoidance of water pollution, the weather conditions, the farmers croppingprogramme or the soil type, it is not usually possible to spread slurry sosoon after its production, or at regular intervals. Thus the slurry has tobe stored, perhaps for the duration of the winter, and it may then be

necessary to consider some form of treatment to facilitate storage and toavoid the risk of pollution and smell."

Unfortunately, animals - and their excreta - smell and there is noprospect that such smell can be totally eliminated. Do not let us forgetthat humans smell too, but we become habituated to those smells. Threefactors conspire together to make the problem very difficult : -a. the production of smells is very variable;b. the transport of smells to sensitive human noses is very variable;c. human response to odours, their offensiveness, strength and duration, is

very variable.



23

It is particularly difficult to remove the cause of complaint oncepeople become sensitised to a situation. Even if the smell is reduced towhat would originally have been acceptable, people will often continue to

complain, perhaps fearing peaks of smell as great as they earlierexperienced.

Possible Approaches to Reducing C omplaintsThere are two major areas of study implied in this analysis of the

problem. First, how can we reduce the smell at source or restrict theproduction of odour to acceptable levels and defined period. Experiencehere suggests that reductions would have to be by at least an order ofmagnitude to cure a problem, although smaller reductions may help toprevent complaints in the first place.

Secondly, there is the much less scientific but equally important and

very complex question of how to reduce the adverse reactions of humanbeings to unpleasant smells. There are many problems here of attitudesurveys, of definition of strength and offensiveness of smells and theirduration which need to be considered. But our discussions so often centrearound the physical smell and ignore the human reaction which is an equallyimportant factor in the situation. Changes in attitude have been asimportant as changes in agriculture in highlighting the problem and shouldbe part of the way we attempt to reduce it.

Sources of ComplaintAB explained below, administration of the law on nuisance from odour

is in the hands of our local authorities - those in charge of cities orrural districts. These are the only source of statistics on the occurrenceof odour nuisance generally and, in recent yea rs, we have been developing auseful basis on which such figures can be collected and reported. We cannotyet say what the trend is because we have no run of comparable figures overthe years. Table 1 gives the number of premises reported as causingcomplaints in 1982 - in earlier years the number of complaints wassometimes recorded and it appears (although we cannot be certain) that, onaverage, there are two or three complaints for every odour source.

Table 1. Number of premises caualng .justifiable complaints - 1982

Odour Source

Buildings

SlurryStorage

Slurry

Spreading

Animal FeedProduction

SilageClamps

Total

%

PigsNo |

2241

1691

5261

841

101

10131

X

22

17

52

8

1

100

561

Ca tNo

65

98

122

4

68

3 5 7

20

ti eX

18

28

34

1

19

100

PoultryNo | X

163| 36

781 17

190| 4 2

111 3

8| 2

4 5 0 | 100

2 4|

To tNo

452

345

838

99

86

1820

,1X

25

19

46

5

5

1001



24

For England and Wales , pigs predominate with over half the number ofpremises. For pigs t cattle and poultry together, manure spreadingpredominates although poultry buildings are almost as important. Buildings

and storage each provide about a fifth of the complaints, rather more forcattle. For cattle, too , silage is an important odour source. Of course therelative balance of such figures will vary from country to countrydepending on the balance in agricultural activities, but I think that thegeneral sort of distribution would be similar.

These figures are useful in indicating where major effort is required.For ex ample, eliminating odour from buildings alone would not diminish thecomplaints overall by a big factor, although such work could be importantin individual cases. The most important problem is reducing odour producedby spreading and its importance probably reflects the difficulties ofsolving it at a cost acceptable to the farmer. Reducing that problem couldalso help in some measure with reducing smell during storage.

At present, the sort of options include reverting to earlier systemsbased on straw. In this country, welfare considerations demand some strawfor housed livestock and this may cause problems in some modern slurrysystems. Whether there will be a move back to traditional systems becauseof welfare considerations is not yet clear. Treatment of the exhaust airfrom buildings or distributing it sufficiently high that it does not reachnoses at 2m above the ground are options to be costed. Treatment of slurryduring storage either aerobically or anaerobically affects smell and couldhelp both storage and preading problems. And finally, methods of spreadingsuch as injection or immediate incorporation have a limited utility.

Another approach to treatment is to mask the odour with another oneand this depends crucially on the attitude of people to different smells.Not everyone finds a continual smell of violets pleasant. Nevertheless,such an approach has had some success.

Because no one method seems likely to be effective enough,combinations of approaches will often be necessary and this suggests thatmore work could well be done on total systems approaches rather than onlooking at individual factors. Such research work is costly, and the extentto which it is supported will depend on the extent to which the problem ofodours is given priority over some other subjects.

Distances Over Which C omplaints OccurIn the UK, we have also started to get information on the distances

over which offensive smells travel. The data are, as y et , in a preliminaryform and no well-founded conclusions can be drawn from them. But theimpression so far is that relatively few complaints are more than 500m fromthe source. This may, of course, be related to the increasing difficulty ofidentifying a source at a distance - or even identifying the nature of atransient, unpleasant smell. On the other hand, it would appear that pigodours can, on occasion, cause complaints at 5 km or more. This againemphasises the predominance of pigs as a source of unacceptable smells.

The question of distance is important legally in deciding whether tospecify distances between odour sources and housing, hospitals, schoolsetc. The rules operated in Germany, the Netherlands and Australia are ofgreat interest and it may be significant that Australia, which has muchmore space and lower concentrations of humans than Europe, allows largerdistances between source and human nose than does Europe.

The UK Legal Situation

It might be helpful if here I describe something of the UK law onodour about which I shall be speaking later in the Conference. Odour



25

offences are included under the Public Health Act (1936) although a reportrecently of a Working P arty on the Supression of Odour from Offensive andSelective Trades said " Farm odours have no known effect on the health of

the individual but reactions to these are undoubtedly real and can causedistress and, above all , negation of leisure in the accepted Englishsense."

The Act, however, probably reflects the ancient view that disease canbe carried by smell. Essentially, the Act provides two approaches. Thefirst concentrates on the cause of the nuisance and how to remedy thenuisance. Here the defendant can claim that he is using best practicablemeans to abate the smell or that such means will be used in future. Thesecond deals with the loss of amenity suffered by the complainant; here thenuisance must be removed completely.

Currently in the UK, most complaints are upheld. This may reflect thefact that only the worst cases get as far as a court, but it also createsthe feeling that the defending farmer has little to defend himself with.This is therefore another important area for study which is particularlydifficult. How can we provide an adequate evaluation of whether a situationwould be acceptable or not to "the average man", and how can we evaluatemeasures to reduce a cause of complaint ? Much work has been done on oneaspect, the intensity of smell, but the offensiveness is also a factor. N omeasure of either of these is independent of the other. Currently, themethodology is based on panels of human beings but, because this is a veryexpensive way of doing things, we are in the U K looking at the possibility

of correlating such observations with chemical measures. If the correlationis sufficiently good, chemical methods could be an acceptable subsitute butthat possibility is still a long way off.

There is, too , an important aspect which adds to the problems we face.Human reaction is often to transient smells, perhaps lasting less than aminute. Indeed, variation may often create more complaint than a steadylevel of smell. But it is difficult to collect enough samples over such ashort time to allow measurement by a panel or even by chemical means. Andit is equally difficult to be ready to sample when the problems of smellare being experienced.

Social FactorsFinally, I wish to touch on the broader area of psychological and

social approaches. We have instances where farmers have no complaints whenthey maintain slurry spreaders in a clean condition, and people do not,presumably, identify what is happening with smell. Equally , people havebecome so sensitised that they complain when water is put onto fields froma slurry Bpreader. More broadly, people will be more likely to complainabout someone they dislike and tolerate unpleasant smells caused by someonewho is generally liked, although at the physical level farmers should doall they can to keep smells down to a minimum, we know how intractable theproblem is at that level at present. Let us not ignore other ways of

helping farmers deal with the problem, even if these ways ar not veryscientific.

ConclusionI have tried to provide a broad view of the agricultural problem, how

it has developed and the areas which merit study. Inevitably, we shall beconcerned here with ways of reducing smell more effectively and morecheaply. But we should be aware that, in difficult situations, only largereductions may reduce complaints. Alongside this area of study, the vaguerarea of reaction to odour and the related social situations also requires



26

work because greater knowledge there could contribute to the overallsolution. In England, we have a saying "What can't be cured must beendured" and, short of a complete cure , we must learn how to help people toendure. And finally, we must establish the basis for a more equitable legalregime based, inevitably, on the average man's response. This should alsoprovide us with better, more widely acceptable means of evaluatingsituations objectively so that laws can be effectively administered.



27

ODOUR RESEARCH AND AMMONIA VOLATILISATION

J.H. VOORBURGGovernment Agricultural Waste Water Service (R.A.A.D.)

Arnhem, The Netherlands

Summary

One of the volatile compounds in animal m anure is amm onia. It isnot supposed to give an important contribution to the odour pro ble ms. However it is sometimes used to estimate the concentration or the volume of odour emissions.Recent publications lead to the conclusion that ammonia contributes to the effects of acid precipitatio n. The main source ofammonia is animal pr oduction and regions with a high animal density are expected to have a high emission of a mmonia . Because itis a volatile compound research worker s in the field of odourmeasurement and odour control have the best knowledge and the

best tools to study ammonia emissions . A proposal is made forthe main goals of a research progra m.

1. INTRODUCTIONLiquid ma nure contains quite a lot of volat ile comp ounds. Each

of them can contribute to the odour emission. Sometimes this contribution can be neglected as is the case with acetic acid.

A volatile compound which deserves more attention is ammonia.Sometimes it is considered to be important as a factor in odourmeasurement techniques.

In this paper attention is paid to the ammonia emission fromslurry as such. There are more and more indications that this emis«sions cause considerable damage to the environment, being possiblymore important than the nuisance of bad sm ells.

2. AMMONIA AND ODOUR MEASUREMENTDuring the CEC-seminar in Bad Zwischena hn, Kowalewsky (1) con

cluded that NH-i is suita ble for use a s a ma in component . He defined a

main component as a compound whose concentration correlates with thesensory evaluation of odour intensity.

He found a correlation coefficient of r = 0.85 and concludedthat only four NH, determina tions are necessary to determine the odourlevel with a confidence of 90 percent.

In the Netherla nds Logtenberg (2) found in the air from pighouses a correlation between the odour concentration in odour units andthe concentration of p-cresal of r = 0.71. The correlation with theNH, concentration was 0.3 so it was concluded that in any way the NH,concentration is not a suitable estimate of the odour concentration.



28

A Becond case of the use of ammonia for odour measurement is reported by van Harreveld (3)-

Van Harreveld measured the odour emission of a composting plant.AS it was a composting plant with a surface of k ha it was impossibleto measure the flowrate. He solved this problem in measuring the ratio mg NH-i/m^: odour unit6/m3 in the air leewards of the plant.

As it was known from other experiments that the NH-z losses perton of compost produced were 2,1 kg, he could calculate the emissionin odour unit/s from this composting plant.

3. AMMONIA IS NOT A TRACER BUT A SEVERE PR OBLEMAn important topic of this workshop is: "Odour measurement". The

two cases I described in which ammonia was just an aid in odour mea

surement are an illustration of the fact that usually ammonia is considered as just one of the volatile compounds in the air from stables,but not as a severe problem. Recent publications have shown that ammonia emissions from stables and from manure are a problem as seriousas the odour emissions.

The first mention of this problem is done by Breemen etal C O .In analysing canopy throughfall and stemflow in woodland areas in theNetherlands he found unexpected high concentrations of ammonia sulphate. This concentration was two to five times higher than in therainwater that did not come in contact with the leaves or stem.

In the soil under this woods he found a low pH and N in the formof N Oj~ . From this he concluded that the N Hj after nitrification iscontributing to the acidification caused by the acid rain. He estimates the nitrogen inputs from throughfall and stemflow in the locations under observation to be 64 and 63 kg per ha per year.

After this publication much work is done to check this conclusions.

This leads more and more to the conviction that ammonia plays animportant part in the problem of acid precipitation.

The main part is deposed in a dry form. This in combination withsulphate. There are discussions between agriculture and industry if

ammonia is stimulating the dry deposition of sulphates or that thesulphates increase the deposition of ammonia. The main source of ammonia emissions is animal production.

As this are ground - level sources the dispersion and depositionis over much shorter distances than the emissions from the industryejected from high chimneys. Buijsman (5), calculated the ammonia emission in the Netherlands. He estimates the total emission into the atmosphere to be 130000 ton per year of which 110000 tons from animalmanure.

k. ANIMAL PRODUCTION AND ACID PRECIP ITATIONBuijsman based his calculation on the manure production per animal and the N content of this manure. He assumed that in cattle andpig manure 50# of the N is in mineral from and in poulty manure 70$.

The volatilisation of ammonia was estimated as follows.• Emission from stables: no reliable data available and thereforeneglected.

• Emission from manure storage: 7% of total N.• Emission from land spreading:a) arable land and grassland are receiving the same volume per ha.



29

b) half of the cattle ma nure is produced in the stable the otherhalf during gra zing.

- arable land: 20 % of mineral N.

- gra sslan d: gr azing peri od: 40J6 of tota l N in urine and 3% of totalN in fae ces.land spreading: Summer (1/3 of the are a) 50# of mineralN. Best of the year 32% of mineral N.

In a special study, made in charge of the Dutch government ayearly deposition of acids and a cidifying compounds was calculated assummarised in table I.

Table I. Deposition of acid and acidifying compounds 1) in molequiva -

lents per ha per year in the Netherlands in the period round1980.

wet deposition

dry deposition

Total

in %

so2

890

i860

2750

46

NOX

420

890

1310

22

NH + N H ^

790

1150

1940

32

Total

2100

3900

6000

100

1) Supposed is that all compounds are converted into acid s.

This table shows that one third of the acid s is coining from a m

moni a. That means mainly from anim al produ ction. Of the total deposition one third is wet and two thirds are dry deposition.

5. NOT JUST A DUTCH PROBLEMIt is well known that a nimal production in the Nether lands has a

high stocking ra te. So it is not a surpr ise that the problems relatedwith high ammonia emissions get m uch attention in our country.

Ammonia is evaporated from a nimal ma nure in the stable, in thestorage and during and a fter landspreading. The amount of ammonialost from the manure depends on many factors a s:

- NH-i concent rat ion in the ma nu re .- P r- dry matter content.- temperature.- storage time.- contact surface between manure and the air .

This last factor explains why the main losses ocaur after land-spreading.

After spreading on arable land this losses can be r estricted byploughing as soon as possible or by injection.



30

Qn grassland this is not possible, moreover during the grazingseason the droppings are exposed many days to high temperatures.

One can estimate that there is a fair good correlation between N

produced in animal manure and the ammonia emission. As the production of cattle slurry is linked with grassland and in many regionsthe main part of the manure from pigs and poultry is spread on arableland, there is a risk for underestimating the ammonia emissions fromcattle slurry. In table II an estimate is made of the total production of mineral N in animal manure in the Netherlands.

Table I I . Amount of mineral N in tons/year produced in animal manurein the Netherlands in 198a.

Cattle

Veal Calfs

Sows

Pigs

Layers

Broilers

Manure Product

1000 tons y

67000

17700

6000

8600

3000 1 )

280 2)

ion

ear

N contant

kg/ton

4.4

3.0

3-9

5-5

9.2

26

Mi eral N

%

50

80

50

50

70

70

Mineral N

tons year

147400

4080

11700

23650

1 9 3 2 0

5076

211226

1) Supposed is that all the manure from layers is produced as a slur

ry with + 14# dry matter.

2) A solid manure with + 60$ dry matter.

From this table it can be concluded that even in the Netherlands,with a relative high stocking rate for pigs and poultry, more thantwo thirds of the mineral N is produced by cattle.

Moreover the volatilisation of ammonia from grassland is suppo

sed to be higher than from arable land.In report N r. 4 8 in the CEC series "Information on Agriculture"(6) the stocking-rate in different regions of the EC is calculated.From the maps in this report the regions with a possibly high ammoniavolatilization can be indicated.

It stands to reason that the highest risks ocour in regions where a high cattle density coincides with a large number of pigs andpoultry. In a region with 3 cows/ha the N production in manure is i250 kg/ha. If half of the mineral N is lost this means an emission of60 kg N/ha. This is equal to the deposition in woodlands reported by



31

van Breemen.

6. WHY A COMBINATION OF ODOUR - MEASUREMENT AND MEASUREM ENT OF AMMO

NIA VOLATILIZATION?Most information on ammonia losses is coming from fertilizer experiments. In calculating N-balances,losses of N can be considered ascaused by volatilization of ammonia or by denitrification.

This method for determination of ammonia losses is inaccurateand gives no information on the factors playing a role in this proces.Specialists in odour measurement techniques have the tools for a muchmore accurate measurement. In determining the losses over short periods they can look for correlations with the circumstances. This isthe first step in controling this ammonia losses.

In general I should like to plead for an integration of researchon ammonia volatilization and odour research. In many cases odourcontrol can be combined with reduction of ammonia losses. This is forinstance the case with storage systems, ventilation systems, bio-filters or air scrubbers and injection of slurry. This double effectgives more possibilities to make the cost of control paying.

On the other hand there is sometimes the risk that odour reduction increases the volatilization of ammonia. This can be the casewith under cage drying of poultry manure or with anaerobic digestionof liquid manure.

In this situations we should balance the positive effects of

odour control against the negative effects of ammonia emissions.

7. AIMS OF THE MEASUREM ENT OF AMMONIA VOLATILIZATIONa)Inventory of ammonia losses from animal production.

The inventory made by Buijsman in the Netherlands should be caracte-rised as a quite rough estimate. This is demonstrated by the assumptions on which he based his calculations. For instance he neglectedthe emission from stables for laek of reliable data. If the Government wants to reduce the acid precipitation, there will be paid attention to ammonia. As it is released from ground level sources re

duction of ammonia emission has more effect on acid deposition in theregion than in the case with' S O, and NO .To take efficient measures reliable information about the main

sources should be available.

b) Determination of the correlation between ammonia losses andcircumstances on the farm.

There are theoretical models, which describe the influence ofthe main factors on ammonia evaporation.

However little is known about the relevant conditions in thestable or the storage pit and in the field. To give good advise tothe farmer about his means to reduce ammonia emission this knowledgeis necessary. For instance what is the effect of covering the manurepit and what are the losses after landspreading on a frozen field.

c) Measurement of the effects of new techniques on ammonia losses.'

I gave some examples of a positive effect of odour control onammonia losses. There are more activities that can have an influencelike housing system, manure treatment or grazing system.



32

In future in developing this techniques, ammonia losses shouldbe taken into consideration.

d) Studying the spreading and deposition of ammonia.High concentrations of ammonia in the air may cause direct damage to crops. In the Netherlands different cases of damage to horticulture crops or treenurseries are reported. This form of damageoccurs at distances of maximal 300 m. If a livestock farm is situatedin an agricultural region the part of the ammonia deposed in this region does not do any harm. It has the effect of a fertilizer and theacidification i6 easaly corrected by liming.

Little is known however at what distance of the sources deposition of ammonia may be expected.

There excist models describing the dispersion of airpollutants,but this models neglect deposition of the pollutant. Moreover theredo not excist models predicting the deposition to be expected from acertain emission. In other words we do not know in how far it is possible to protect area's by reducing the emission from neighbouringsources.

REFERENCES

(1) KOWALEWSK Y, H.H., R. SC HEU and H. VETTER. I98O. Measurement ofodour emissions and im-missions. In: J.K.R. GASSER (editor). Ef

fluents from livestock. Apple. Sc. Publ.(2) L OGTENBERG , M. Th. 1975- Het ontwikkelen van meetmethoden voor

het bepalen van de stank van ventilatielucht van varkensBtallen.CTI - TNO Apeldoorn N L. ref. no - 75 - 05^62.

(3 ) HARREVELD, A. P h. van. 1981. Rapportage geurverspreidingsonder-zoek bij het compostbedrijf van de Cooperatieve Nederlandse Cham-pignonkwekersvereniging B.V. te Ottersum. I.M.A.G. rapport no. 30.

C O BREE MEN, N . van. 1982. Soil acidification from atmospheric ammonium sulphate in forest canopy throughfall. Nature Volume 299,October 1982.

(5) BUI JSMAN , E. 1983. Ammoniak-emissie in Nederland. Instituut voorMeteorologie en Oceanografie Rijksuniversiteit - Utrecht. RapportV - 83 - 3.

(6) Commission of the European Communities. 19 78. The spreading ofanimal excrement on utilized agricultural areas of the Community.Report Nr. h& Aug. 1978.



33

AMMOHIA LOSS FROM GRASSLAND SYSTEMS

J. C. RYDE N

The Animal and Grassland Research Institute,Hurley, Maidenhead, SL6 5LR , U.K.

Summary

A large proportion of the input of nitrogen (N ) that remainsunaccounted for during livestock production (up to 90$ in grasslandsystems) is lost through volatilisation of ammonia (N H3 ) to theatmosphere. Such loss of N has important economic and environmentalimplications. Particular problems are presented when measuring NH 3loss due to the reactivity of the gas and the dependence of loss onenvironmental conditions. Unequivocal measurements are obtainedonly when a micrometeorological method is used. However, recentstudies have shown that enclosures suited to experiments using smallplots can be designed and operated to have negligible effects on NH3loss. These enclosures may also be useful in studies of odouremission, a process dependent on factors similar to those affectingNH3 loss. Findings in recent studies of NH3 loss from grasslandsystems are discussed. These reveal losses of 20 to 3 0$ of the Ninput during grazing or following land application of slurry.

Significant losses of N H3 from winter-housed cattle have also beenmeasured. Methods of reducing NH 3 loss, including injection ofslurry and the role of zeolites, are discussed.

1. INTRODUCTIONConsideration of the nitrogen (N) balance during livestock

production reveals a large difference between the input of N and its

output in animal products (1,2). For ex ample, ruminants ex crete between75 and 95$ of the N ingested ( 3 ) . Much of the N not accounted for ininput-output relationships of this type is lost from the soil-plant-animal system, particularly when intensively managed. Loss of ammonia(NH3 ) through volatilisation to the atmosphere is expected to be a majo r,if not the most important pathway of N loss during livestock production.

Apart from the economic significance of such loss there are potentially adverse effects on the environment arising from acidification ofrain and soil. Ammonia may react with hydroxyl radicals in the atmosphere to produce N 0 X contributing to the acidification of rain (U). Wetand dry deposition of NH3/NHi,+ inevitably contributes to soil acidifi

cation through their subsequent nitrification. This effect can beaccentuated in woodland by absorption of aerosols containing N H ^ withinthe canopy followed by transport to the soil in stem flow ( 5 ) . In moreextreme ca ses, NH3 emission from feedlots, pig and poultry units maycontribute to eutrophication of surface waters in the locality ( 6) .

There is some evidence to suggest that NH 3 is a useful marker forodour emission ( 7 ) . This is to be expected as odourous components arein many cases water miscible volatiles that are released under conditions



34

similar to those favouring NH3 loss. Although odours cause immediateenvironmental proble ms, I concur with Voorburg (8) that longer term andmore damaging environmental effects may be associated with NH 3 loss.

The purpose of this paper is to outline the types of methods suitedto studies of NH 3 loss (and possibly odour emission). Findings in recentstudies of N H3 loss at The Animal and Grassland Research Institute,Hurley, will be discussed as will possible methods to reduce such loss.

2. METH ODS FOR MEASUR ING L OSSES OF AMMONIA THROUG H VOLATILISATIONMethods suitable for field studies of ammonia loss fall into two

basic categories:(i) Those in which the loss is calculated from changes in NH3 concentration within covers or enclosures placed over the surface of interest(e.g. refs 9 ,1 0).

(ii) Those in which the loss is determined from micrometeorologicalmeasurements and concentrations of ammonia in air above the land surface.

Although the use of enclosures is conceptually the simplest approach ,some particular problems arise in their use in studies of NH3 loss.These are associated with the chemical reactivity of the gas, particularly its reactivity with water, and to the strong influence of environmental factors on the volatilization process ( 11) . Matching conditionswithin the enclosure to those prevailing outside is a difficult task andmuch of the data obtained using enclosures is open to question. However,the problems associated with enclosures can be overcome if the air speedthrough the enclosure is controllable to within the same range as that ofwind speed at the experimental site (9,12).

Methods based on micrometeorological measurements are to be preferredin principle. They do not disturb the environmental parameters orprocesses which influence gas exchange. Furthermore, they allow continuous measurement and integrate the flux over a large ar ea, therebyfacilitating studies in grazed swards in which NH3 loss arises from aheterogeneous distribution of dung- and urine-affected areas. Thedifficulties of many micrometeorological techniques lie in the requirement of a large experimental area, thermal stability and in some casesrapid measurements of small gas concentrations. The recently proposedmass balance method (13 ,lU) overcomes many of these difficulties and forthe first time permits routine measurement of N H3 loss within the contextof a nitrogen balance study (15,16).

Methods used in studies of NH3 loss at A G R I , Hurley, involve themicrometeorological mass balance method for studies in grazed swards anda system of wind tunnels for small field plots to which specific treatments have been applied (e.g., slurry or urine). In the mass balancemeth od, NH 3 loss is calculated from measurements of (i) wind speed to aheight of 3 m (ii) wind direction and (iii) the NH 3 concentration profilein air windward and leeward of a treated area. The method has beensuccessfully applied in studies in which the distance between the wind

ward and leeward sampling positions has been as little as 10 m and thesampling time as great as 2k h ( 17 ) . In the system of wind tunnels ,each consists of a transparent polycarbonate sheet, bent to form thetunnel per se and pinned to the ground to cover an area of 0.5 x 2 mwith a max imum height of 1(5 cm ( 9 ) . A high capacity fan and van anemometer are mounted in steel ducting connected to one end of the tunnel. Thefan and anemometer allows air to be drawn through the tunnel at continuously recorded speeds up to 1(.5 ms~l, i.e. in the same range as wind



35

speeds prevailing at the site. The concentrations of NH3 in airentering and leaving the tunnel are determined and used in the calculation of NH 3 loss.

In preliminary studies, the reliability of measurements of NH 3 lossprovided by the tunnels was assessed by comparing the measured rates ofNH 3 loss with those observed using the mass balance method. A circularplot (10 m radius) was established on a ryegrass sward to which ureafertilizer was applied at a rate of 200 kg N ha~l . The equipment forthe mass balance method was erected at the centre of the plot therebyproviding a fetch of 10 m regardless of wind direction. The tunnelswere positioned on the windward edge of the p lot, their axes aligned onits radius thereby ensuring that air drawn through the tunnels had notpassed over the area treated with urea.

When the air speed through the tunnels was matched as closely as

possible with the prevailing wind speed outside, rates of N H3 lossprovided by the two methods were not significantly different (Fig. 1 ) .Regimes of temperature and relative humidity inside the tunnels werealso similar to those outside (9,12). When the air speed through thetunnels deviated by more than about ± 20i( from the prevailing wind speed,rates of NH3 loss determined using the two methods differed substantially even though regimes of temperature and relative humidity remainedlargely unaffected.

The data in Fig. I indicate that enclosures can be designed andoperated to have minimal effects on the emission of volatiles such asNH 3 from the land surface. The tunnels may also represent a useful and

Bimple experimental approach to the assessment of odour emission undercontrolled and replicated conditions.

3. LOSS OF AMMONIA DURI NG LIVESTOCK PRODUC TIONAmmonia may be lost from excreta either during grazing or during

collection, storage and land application of slurry and manure. Approx imately 80 % of the N excreted by cattle is contained in uri ne, most ofwhich is present as urea and results in the deposition of N at ratesequivalent to 3 00 to 1000 kg N h a - 1 in urine-affected areas of pasture.Nitrogen in dung is present as organic compounds less readily hydroly-able than urea and mainly of bacterial origin. Although some NH 3 may belost from dung, it is urine that affords the greatest potential for loss.Nitrogen in urine is subject to almost immediate loss as NH3 which isproduced in the high pH environment generated during the hydrolysis ofurea. In slurry and manure, N is present largely as NHlj and morestable organic compounds derived from dung. Ammonia loss from slurryand manure probably arises from the decomposition of ammonium carbonatesand bicarbonates as the land surface dries following application.3.1. Losses of ammonia during grazing

In studies of the fate of N in urine-treated areas of pasture inNew Zealand, 66 % of the N applied (30 to 60 g urine-N m -^ ) was lost

during warm dry conditions ( 15 ) . Losses were lower (6 to 16%) duringcooler or wetter conditions. In Queensland, Vallis et al. (10) reporteda loss of lU to 28U of the N applied in urine depending on the season.A similar range in NH 3 loss (12-25/f) has been reported by Sherlock andGoh (18) following application of urine (50 g N m~2) to a ryegrass-cloversward. Recent work at Hurley (19 ) using the system of wind tunnelsdescribed above indicated a total NH 3 loss of 17 g N m~^ during 17 daysfrom I42 g urine-N m - ^ applied to a ryegrass sward; within seven days,92.5/t of the total loss had occurred.



36

2 5 0 i

I

E

o

£

CD

Ea>cc

CO

CO

o

coEEa»*-o

CD

CO

D C

2 0 0

1 5 0

1 0 0

5 0 -

5 0 1 0 0 1 5 0 2 0 0

Rate o f ammonia loss (mass ba lance method) , mgNm- 2 ! ! - 1

Fig. I. Relationship 'between concurrent measurements of the rate ofammonia loss made using the wind tunnel and micrometeorological

mass balance methods during an experiment in which the meanair speed through the tunnels was adjusted to maintain a valuewithin 20!f of the mean ambient wind speed. Rates of lossmeasured using the wind tunnels are the means of fourreplicates, the tars around each point indicating the 953Sconfidence limits (reproduced from ref. 1 2 ) .



37

There are few data for NH3 loss from whole grazed fields. Denmeadet al. (20) reported rates of NH 3 loss of between 0.2 and 0.7 kg Nha-lday~l from lucerne grazed by sheep (50 ewes per ha) in Australia.

They estimated that the annual loss of NH3 from this pasture which fixedapproximately 20 0 kg N ha~lyr~l was about 100 kg N ha--1-. In a laterstudy ( 21 ) , it was shown that although as much as O.O56 kg NH 3-N ha h r - 1

may be produced at the base of a sward, a large proportion was re-absorbedwithin the standing canopy (U0 to 50 c m ) . This observation has obviousimplications to the effect of continuous as opposed to rotationalgrazing on NH 3 loss and to the cycling of N in grass-clover swards.

Recent work in the U.K. (15 ,19 ,22) has shown that mean daily ratesof NH3 loss are frequently close to or in excess of 1 kg N ha'^-day -^ inthe period during and immediately following grazing within a rotationalsystem involving yearling steers (Fig. I I ) . The highest rates of NH 3

loss were associated with high stocking densities while changes in therate of loss following the removal of animals depended on weatherconditions. For ex ample, following the grazing period 2l*~30 M ay , themean rate of NH3 loss decreased as the soil surface dried (evapotrans-piration greatly exceed precipitation) . However, in the third weekfollowing the removal of ani mals , the rate of NH 3 loss increased to0.8 kg N h a - 1d a y _ 1 in response to the wetting and drying cycles imposedby increased rainfall. A similar effect was probably important duringthe period 21-27 June and in the week following the grazing between2-9 August. The dependence of high rates of NH 3 loss on cyclical wettingand drying is in agreement with findings in laboratory studies. More

NH3 was lost from urea applied to wet soil as it dried than when the soilwas maintained at a constant water content ( 23 ) .

The use of mean values in Fig. II masks the day to day change in therate of NH3 loss, particularly as it was affected by specific rainfallevents. For example, during the period 2U to 26 June in which 39 mm rainwere recorded, the rate of NH3 loss decreased from k.2 to 0.05 kg Nha-1day~-1-. Within two days, however, the rate of loss had increased to1.3 kg N ha'^ -day-1. The importance of drying in promoting further NH 3loss after rainfall is illustrated by the pattern of loss observed duringSeptember/October. During this period, rainfall exceeded potentialevapotranspiration by 123 mm and rate of NH 3 loss never exceeded 0.2 kg

N ha- 1

day-

l. Ammonia loss ceased in the third week after grazingfollowing further rainfall.

The pattern of NH3 loss from a urine-treated sward (15, 19) ismarkedly different to that from a grazed field (Fig. I I ) . Loss of NH 3was largely complete within seven days of urine application. In contrast ,losses from the grazed plot continued at rates in excess of 0.2 kg Nha'-May--1- for two to three weeks following the removal of animals. Asmuch as 16 to 1)7 per cent of the loss during each It-week period occurredduring weeks 3 and It. This pattern of loss suggests that sources otherthan urine contributed to the loss of N from the grazed sward. Theorigin of this loss is as yet unexplained, but it is possibly associated

with dung-affected areas of the sward.3.2. Losses of ammonia associated with winter-housed stock

Ammonia may be produced and lost between deposition and collectionof excreta in winter housing, during its storage and following landapplication. The treatment of excreta from winter-housed stock as awaste disposal problem rather than a fertilizer resource results insubstantial loss of N as N H 3 .



38

Fig. I I . Mean values during weekly intervals of the rate of ammonialoss from a grazed ryegrass sward receiving 1*20 kg N ha yrand the corresponding values for accumulated rainfall andpotential evapotranspiration. The swards were grazed byyearling steers within a 28-day rotation. The numberedbars indicate each grazing period and the actual stockingrate (steers per ha) during that period.



39

Loss of NH 3 from housed dairy cows has been estimated from measurements of N content in fresh excreta and that in the material scrapedfrom the alleys (2k). The results of this study indicated that N losses

were in the range 1 to 5$ when the average daily air temperature wasbelow 5°C . When air temperatures were in the range 15 to 25 °C , lossesincreased to between 15 and 50 $. Recently , NH 3 loss from the winter-housed dairy herd at Hurley has been estimated by direct measurement ofthe air flow into and NH3 concentrations in air within the cubical housethe alleys of which are scraped on average once every three hours.Daily losses of NH3 ranged from 0.3 to 2.6 kg N during January andFebruary, 1985 . Losses were greatest on windy days when the house waswell ventilated; losses were also greater when air temperatures exceeded5°C. The losses of N as NH 3 were equivalent to 1.1* to 11.8!* of the dailyinput of N in feed or 1.6 to ll*.l$ of the N estimated to have been

excreted by the cows.Little is known about the importance of NH3 loss during storage of

slurry and manur e. Estimates place this loss at 10 to 20$ of the Nentering the store ( 25 ) . Losses are almost certain to be greater fromstores with a large surface area to volume ratio. Mixing is alsoexpected to increase loss.

Loss of N H3 associated with land application of slurry has beenassessed from measurements of the content of inorganic N in soil beforeand following the application of slurry (e.g., ref. 26 ) . Losses between20 and 60 % of the N applied have been inferred. There are few directmeasurements of NH 3 loss from slurry. Beauchamp et al. (27) havemeasured a NH 3 loss equivalent to 20 $ of the N applied during the weekfollowing a surface application of dairy-shed slurry (325 kg N ha--*-) tofallow soil in eastern Canada. The total loss of NH 3 was probablysubstantially higher as it was continuing at rates between 0.3 and 0.7 kgN ha~lhr~l when measurements were terminated. Rates of loss as high as2.9 kg N ha -lhr~l were observed during warm dry periods. More significant, however, was the fact that NH 3 continued to be lost at rates up to0.3 kg N ha~^hr~l in cold wet weather, conditions that are usuallyassumed to minimise NH 3 loss. N evertheless, the generally higherefficiency of slurry N following application in late winter and earlyspring can probably be attributed to reduced NH3 loss particularly when

application occurs during periods of frequent rain.

In recent work at Hurley ( 28 ) , N H3 loss was measured after surfaceapplication or injection of cattle slurry during warm dry weather inlate spring. Following the surface application, NH3 loss amounted to17)1 of the total N applied (100 kg h a " M or approx imately 1*5$ of theinorganic N content of the slurry. More than 95 $ of the total lossoccurred within two days of application. A loss of < 2$ was observedfor the injected treatment.

A similar loss of N (approximately 30$ of that applied) has beenobserved following surface application of slurry containing 220 kg N

h a- 1

in cool moist weather in December when the soil was at fieldcapacity. Although lower daily rates of NH 3 loss were observed at thistime, loss extended over a longer period following application.Observations in the field suggest that the more extended period of NH3loss arose from restricted infiltration of slurry following the winterapplication.



40

It. CONTROL OF AMMONI A L OSSControl of HH 3 loss during grassland production presents many

problems. The most readily manipulated loss is that arising from landapplication of slurry. Injection effectively eliminates NH3 loss, asdiscussed above, and is sometimes reflected in increased efficiency ofutilisation of the N applied ( 29 ) . On grass/arable farms , applicationof slurry prior to ploughing or cultivation also increases N recoveryby the following crop. However, the speed with which NH 3 loss can occurrequires that cultivation takes place almost immediately after application (2 9) .

Reduction of N H3 loss from grazed swards presents more dauntingproblems. In rotational systems, swards could be irrigated followingeach grazing to wash urea and ammonium-N into the base of the swardthereby increasing contact with the surface soil. More N is likely tobe retained as wet soil restricts NH 3 loss and there will be increasedcontact between ammonium ions and sites of cation exchange ( 11 ) .Furthermore, subsequent loss of N H3 as the soil dries may be attenuatedby re-absorption in the plant canopy ( 21) . Re-absorption of NH 3 withinthe canopy may also be important in reducing NH3 loss from continuouslyas opposed to rotationally grazed swards in which the height of thecanopy is reduced to no more than a few centimeters during each grazinginterval. The latter is also expected to accelerate N H3 loss bydecreasing the height of the boundary layer thereby increasing exchangenear the base of the sward where N H3 is produced.

Control of NH 3 loss arising from winter-housed stock presentssimilarly difficult problems. Increased frequency of scraping andreduced ventilation are expected to restrict such loss. The use ofchopped straw or other carbonaceous bedding may also reduce loss byincreasing immobilisation of NH!j+ as it forms. Losses of NH 3 from slurrystores will be minimiz ed when the surface area to volume ratio is low.Covering the store may also assist in reducing loss.

A novel and potentially effective strategy to reduce NH 3 loss is byintroducing natural or synthetic zeolites into the production system.Zeolites have a high cation-exchange capacity and readily absorb ammoniumions. In a laboratory study, addition of the zeolite clinoptilorite to

soil at a rate equivalent to 10 t ha

-

-'- reduced N H3 loss by 70 to 80?following application of a urea solution ( 3 0 ) . Similar results havebeen obtained in field studies. Zeolites have been similarly effectivein removing NH1,+ from sewage effluents, absorbing NH 3 during gasificationof coal and in removing NH3 from air in battery houses ( 3 1) . Zeoliteswould be most effectively introduced by their addition to winter feed andby incorporation into bedding. In this wa y, NH3 will be mineral bound toa greater or lesser ex tent throughout the production, storage and landapplication of slurry. In the longer term, accumulation of zeolite inthe surface soil will increase its cation-exchange capacity and mayreduce NH3 loss from urine-affected areas of grazed swards.



41

REFERENCES

(1) BLAXTER , K. (1980). Soils plants and animals Macaulay Institutefor Soil Research, Annual Report No . 5 0 , 197 9-80 , 138-157.

(2) VAN DER MEER , H. G. (1983). Effective use of nitrogen on grasslandfarms. In: Corrall, A. J. (ed.) Efficient G rassland Farming.Proceedings of 9th General Meeting of European GrasslandFederation (Reading), 61-68. Hurley, The B ritish Grassland S ociety.

(3) HEN ZELL, E. F. and RO SS, P. J. (1973). The nitrogen cycle ofpasture ecosystems. In: Butler, G. W. and Bailey, R. W. (eds).Chemistry and Biochemistry of Herbage , Volume 2, 227-2U 6. L ondon,Academic Press.

(U) GALB ALLY, I. E. and ROY , C. R.(l983). The fate of nitrogencompounds in the atmosphere. In: Freney, J. R. and Simpson , J. R.(eds). Gaseous Losses of Nitrogen from Plant-Soil S ystems, 265-28U .The H ague, Martinus Nijhoff/Dr Junk.

(5) VAN BREE MAN, N. , BURROUGH, P. A., VELTHORST, E. J., et al. (1982).Soil acidification from atmospheric ammonium sulphate in forestcanopy through fall. N ature, 29 9 , 5>»8-550.

(6) HUTCH IN SON, G. L. and VIE TS, F. G.(l969). Nitrogen enrichment ofsurface water by absorption of ammonia volatilized from cattlefeedlots. Science 16 6, 51I1-515.

(7) KOWALEWSKY, H. H., SCHEU, R. andVET TER , H. (1980). Measurementof odour emissions and imissions. In: Gasser, J. K. R. (ed.).

Effluents from Livestock, 609 -626. Lo ndon, Applied SciencePublishers.

(8) V00RBU RG, J. H. (1985). Odour research and ammonia volatilisation.This volume.

(9) LOCKYER , D. R. (I98U). A system for the measurement of fieldlosses of ammonia through volatilisation. Journal of the S cienceof Food and Agriculture 3 5 , 83T-8U8.

(10) VALLIS , I., HARPER, L. A., CATCHPOOLE, V. R., and WE IER , K. L.(1982). Volatilisation of ammonia from urine patches in a subtropical pasture. Australian Journal Agricultural Research 3 3 ,97-107.

(11) FREN EY, J. R., SIM PSON , J. R. and DENM EAD , 0. T. (1983).Volatilisation of ammonia. In: Freney, J. R. and Simpson, J. R.(eds), Gaseous Loss of Nitrogen from Soil-Plant Systems , 1-32.The H ague, Martinus Nijhoff/Dr W. Junk.

(12) RYDE N, J. C. and LOCKYER , D. R. (1985). Evaluation of a system ofwind tunnels for field studies of ammonia loss from grasslandthrough volatilisation. Journal of the Science of Food andAgriculture 36 (in press).

(13) DE NM EAD, 0. T., SI MPS ON, J. R. and FREN EY, J. R. (1977). Directfield measurement of ammonia emission after injection of anhydrousammonia. Soil Science Society of America Journal Ul , 100 1-100 U.

(lU) DENMEAD, 0. T. (1983). Micrometeorological methods for measuringgaseous losses of nitrogen in the field. In: Frney, J. R. andSimpson, J. R. (eds). Gaseous loss of nitrogen from soil-plantsystems, 133 -157 , The H ague, Martinus Nijhoff/Dr Junk.



42

(15) BALL , P. R. and RYD E N, J. C. (1984). Nitrogen relationships in

intensively managed temperate grassland. Plant and Soil 76,23-33.

(16) RYD EN , J. C. (198U). The flow of nitrogen in grassland.Proceedings of the Fertiliser Society, London, No. 229, PP- kk.

(17) RYDEN, J. C. and McNEILL, J. E. (1984). Application of the micro-

meoro logical mass balance method t o th e determinat ion of ammonia

loss from a grazed sward. Journal of the Science of Food and

Agriculture 35, 1297-1310.

(18) SHERLOCK , R. R. and G O H , K. M. (198^). Dynamics of ammoniavolatilisation from simulated urine patches and aqueous ureaapplied to pasture. I. Field experiments. Fertilizer Research 5,

181-196.

(19) RYDEN , J. C , LOCKYER, D. R. and BRISTOW, A. W. (1984). Circulationof mineral elements within the environment of forage plants.Nitrogen. Annual Report 1983-1981*, Hurley, The Grassland ResearchInstitute.

(20) DEN MEAD, 0. T. , S I M P SON, J. R. (1971*). Ammonia flux into theatmosphere from a grazed pasture. Scienc e, 185> 609-6IO.

(21) DENME AD, 0. T., FRE NEY, J. R. and SIMPSON, J. R. (19T6). A closedammonia cycle within a plant canopy. Soil Biology and Biochemistry,8, l6l-l61t.

(22) RYDEN , J. C , LOCKYER, D. R. and BRISTOW, A. W. (1983). Circulationof mineral elements within the environment of forage plants. Gaseous

nitrogen losses from grassland soils. Annual Report 19 82 , 25

_

3 2,Hurley, The Grassland Research Institute.

(23) ERN ST, J. W. and MAS S EY, H. F. (i960). The effects of severalfactors on volatilisation of ammonia formed from urea in the soil.Soil Science Society of America P roceedings 2k, 87-90.

(2k) MUCK, R. E. and RICHARDS, B. K. (1983). Losses of manurial nit rogen

in f r e e -s t al l bar ns. Ag ri cul tu ra l Wastes 7, 65-79-

(25) GOSTICK, K. G. (1982). Recommendations to farmers on manure

disposal and rec yc li ng . Phi los ophical Transacti ons of th e Royal

Society, London B296, 329-332.

(26) LAUER, D. A., BOULDIN, D. R. and KLAUSNER, S. D. (1976). Ammonia

vo la t i l i s at i o n from dair y manure spread on th e so i l su rf ace .Journal of Environmental Quality 5, 134-1

41.

(27) BEAUCHAMP, E. G., KIDD, G. E. and THURTELL, G. (1982). Ammonia

vo l at i li s at i o n from li qu id dairy ca t t le manure in the fi el d.

Canadian Journal of Soil Science 62, 11-19.

(28) RYD EN , J. C. and LOCKYER, D. R. (1985). Fate of nitrogen followingland application of slurry. Annual Report 1981t-85, Hurley, TheGrassland Research Institute (in press).

(29) KOLENBRANDE R, G. J. (1981). Effect of injection of animal wasteon ammonia losses by volatilisation on arable land and grassland.In: Brogen, J. C. (ed.) Nitrogen Losses and Surface Run-off from

Land Spreading of Manures, 425-43 0. The Ha gue, Martinus N ijhoff/Dr Junk.

(30) RYDEN , J. C. (1984). Fertilisers for grassland. Chemistry and

Industry (1984), 652-657-(31) SAND , L. B. and MUMPTON, F. A. (eds). (1977). Natural Zeolites:

Occurrences, Properties and Us e. Oxford:Pergamon Press.



SESSION I : OLFACTOMETRY EEC - GROUP

Sampling of odourous air for olfactometricmeasurement

Standardization of olfactometric measurements

Selection and treatment of panelists fordetermination of odor thresholds

VDI guidelines on odour problems

An established system for odour detectionthreshold measurements

Guideline for olfactometric measurements in theNetherlands. Comparison with Western Europeanguidelines

French tentative standard X-43-10 1 : method ofmeasurements of the odour of a gaseous effluent.Comments on interpretations made by MessrsHARTUNG, VOORBURG and HANGARTNER

Experiences with olfactometric measurements inNorway

Limitations imposed on olfactometricmeasurements by the human factor

Experiences with transportable olfactometers

Dispersion models for emissions fromagricultural sources

Experiences with olfactometers

Physical calibration of olfactometricmeasurements

Developments in the assessment of odours fromsludges

Odour concentration and odour annoyance

Comparison of olfactometric odour measurementand chemical odour measurement



44

SAMPLING OF ODOUROUS AIR FOR OLFACTOMETRIC MEASUREMENT

J. HARTUNGInstitute for Animal Hygiene of the Hannover School

of Veterinary Medicine, Bunteweg 17p, 3000 Hannover 71, FRG

Summary

Both static and dynamic sampling procedures are used for

olfactometric measurements. Care must be taken inorder toobtain a representative sample and to minimize samplelosses due to condensation, adsorption and permeation,when using static sampling methods, particularly. Teflonor Tedlar bags and inert tubing materials help to diminishadsorption and desorption problems. Condensation can beavoided by heating the sampling tubes or by predilutingthe sample with pure, odour-free air. Within the EEC guidelines exist for odour measurement in The Netherlands,France, Germany and the United Kingdom. The usefulness ofdynamic sampling is agreed on. The opinions differ as far

as static sampling is concerned. It seems that both sampling methods can be applied successfully for olfactometr y measurements. However, it is necessary to define thedetails of the procedures aiming at a standardization ofsampling which might be the first step for a harmonization of olfactometric measurements in the laboratoriesof the different countries.

1. INTRODUCTIONThe method of measuring odour sensorily in general can be

devided into the following basic steps ( 1) :- sample collection- sample dilution and presentation- indication of response- interpretation of response

Due to the fact that many different testing proceduresexist in the different laboratories, results can only be com

pared when knowing exactly- the conditions and procedures for s a m p l i n g of the air to bei nvesti gated,

- the design and function of the o l f a c t o m e t r i c a p p a r a t u s , and- the physiological and physical status of the p a n e l .

The olfactometric apparatus and the panel are in closeconnection with each other as shown in Table I whereas the sampling procedure is more or less apart from the apparatus andthe panel and affects the olfactometric inlet, only. However,sample collection is the first step and can influence the results considerably; thus, valid sampling is the base for valid



45

measurements.This paper is confined to the different forms of sampling

odourous gases for olfactometric measurements and the problemsinvolved. It refers to existing guidelines for olfactometricmeasurements in the countries of the EEC, as well.

2 . TYPES OF SAMPLINGSamples of odourous gas may be collected in unconcentrated

or concentrated form. Concentrated sampling is usually necessary when gas chromatography or other chemical analytical methods are to be used. Unconcentrated sampling is provided if o-dour threshold concentrations are required (2).

Depending on the type of olfactometer used dynamic sampling or static sampling are provided. The principle of dynamic sampling is shown in Figure 1. It requires a part-flow ofthe odourous gas to be continoulsy extracted from the sourceand subsequently directed to the olfactometer. This samplingmethod implies that the measurements are carried out close tothe source. An advantage of the method is that there is thepossibility of controlling a process, directly, and in case ofthe break-down of the process this can be noticed right away.A disadvantage of the dynamic method is that odour sourcesthat are not readily accessible require a relatively great effort in order to install the olfactometer and suitable sampling pipes which often should be insulated or heated to avoid

adsorption or condensation (3).When static sampling is used a partial stream of the o-

dourous air is collected in a sampling vessel. Samples aretaken from this vessel or bag to dilute the odourous air forthe olfactometer using syringes or on-line tubings. When usingthis method odour measurement with the panel can be carriedout at any arbitrary location, if the vessel is a transportable one. An example for static sampling is given in Figure 2.

3. PROBLEMS OF SAMPLING

The main problems encountered when sampling odourous airderive from surface effects of the sampling tubes and vessels,namely by- adsorption,- desorption, and- condensation.This depends mainly on the material of the tube, the vessel orthe bag (adsorption) or on the nature of the gas, whether itis hot and/or containes a high amount of humidity (condensat i o n ) . On the other hand the sample can be altered by tracecomponents bleeding from the material of the walls of the ves

sel or the tube (desorption).The following factors are to be observed for valid staticsampling.a^_Choi_c\e of_inateri aj_

For tTTe sampling of odourous gases glas vessels, stainless steel tanks (4 ) and flexible plastic bags (5) were tested.The initial concentrations of the test gases decrease considerably with storage time in glass and steel vessels. In recentyears bags made of Polyethylene(6), Teflon (3) and Tedlar ( 7 ) ,(8) were usually used. Figure 3 shows a graph from SCHUETZLE



46

et al. (8) indicating the good properties of Tedlar. ROOS etal . (3 ) point out that when Tedlar bags are used decreases inconcentration up to 60 and 70% are observed with aromatic compounds. These authors prefer Teflon FEP-bags and report on comparable results between dynamic sampling and static Teflon FEP-bag sampling, as shown in Table II.

Assuming that adsorption and desorption effects are minimized by the choice of material, reactions between compoundsin the gas phase can not be excluded,b. The prevention of conde n s a tion

ContTensatTon can Fe avoTded by the predilution of the sample by dry, odour-free air. It is important to know in whichratio the sample is diluted for odour unit or odour thresholddetermi nation,c. 0ther factors of importance

wKen performing vesseT/Fag sampling:- permeability of the vessel/bag (% of losses), ( 9 ) ,- sampling time (moment value, or time integral),- transport and storage time,- sampling volume (sufficient for repeated measurements),- preflushing (to minimiz e the self-odour of the bag, (6),and- the dust problem (heated dustfilter), (10 ).

Recently WAUTERS et al. (9) used a large handpump in con

nection with Rilsan and Tedlar bags. This set-up allows thesampling of one liter per second. This method is very suitablefor sampling in the field, independent from any power supply.They found diffusions from the bags to be about 2% in 24 h.Thediffusion from the Tedlar bag was slightly lower than from theRilsan bag. The humidity in the bags remained unchanged over along period of time. Changing the humidity in all previoustests from 70% to 100% had no effect to the results.

Testing the storage stability of 25 compounds in differentstorage conditions (clear place resp. dark place at room temperature, cool dark place) it was shown that the greatest de

crease in concentration took place during the first 24 h. Tedlar bags seemed to show higher recovery rates than Rilsan bags.The compound concentrations in these experiments were determined by gas chromatography, (9).

Using dynamic sampling short and inert sampling tubesmade from glas or teflon snould be provided to prevent surfaceeffects. Insulating and/or heating of the sampling tubes or diluting the gas sample with dry, odour-free air will avoid condensation .

The use of the dynamic or static sampling procedure depends not only on the type of the olfactometer used (mobile orstationary) but also on the field of application, and on theexpenses ( 11) . In industry dynamic sampling and mobile olfactometers are preferred ( 10 ) . However, practical limitations oftenmean that the analysis will be conductedin a laboratory whichimplies static sampling ( 12) . In agriculture mobile "sniff-cars" and large panels are usually too expensive. Thereforesimple measuring devices like the Mannebeck-01factometer TO 4were introduced (13).



47

4 . R E C O M M E N D A T I O N S FO R S A M P L I N G A S D E S C R I B E D B Y G U I D E L I N E SFour guidelines exist in th e states of the E E C concerning

odour:- The Netherland- France:

- Germany:- U . K . :

Only1 i ne

agreeand hdry otionhaveshoulbe prdust.

G e r m acertathe r

encesthe sportanarydilutforms

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ngs , U . K . , a nd t h e V D I - G u i d e -s of th e sampling procedure.s t a t i c s a m p l i n g there is ancondensation B y insulating

by prediluting t h e sample withssel sampling is used. Desorp-preflushing. Inert materials

e time of th e sample in bagsf required dust filters c anation of th e olfactometer by

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is used tocollapsed

NAL REMARKSBoth dynamic and static sampling procedures are suitable

for taking samples for olfactometric measurements ( 15 ) , ( 16 ) .If the olfactometer and the panel are available close to thesource dynamic sampling may be preferred. The equipment forpreventing condensation in the sampling pipe and contaminationof the sampling pipe and the olfactometer by dust should be

provi ded.Static sampling may be used at sources of odour that are

not readily accessible or where the odour concentrations arechanging quickly or because of ex pense s. When using staticsampling the most important requirements are to avoid losses ofsample-born compounds by adsorption and condensation and thecontamination of the sample by impurities desorbing from thesampling and storing divice. Interaction of the compounds inthe sample during storage can be minimized by keeping the time



48

o f s t o r a g e as s h o r t as p o s s i b l e , o n l y ; 24 h s h o u l d n o t be e x c e e d e d . T a b le I I I c o m p r i s e s t h e m os t i m p o r t a n t c r i t e r i a f o rv a l i d s t a t i c and d yn am ic s a m p l i n g .

I t s eem s t h a t b o t h t h e g u i d e o f W a r r e n S p r i n g s , U . K . a ndt h e V D I - G u i d e l i n e m i g h t be a u s e f u l b as e t o d e s c r i b e c o mm o nlya c c e p t e d s a m p l i n g p r o c e d u r e s a i m i n g a t a s t a n d a r d i z a t i o n o fs a m p l i n g w h i c h m i g h t be a f i r s t s t e p f o r a h a r m o n i z a t i o n o fo l f a c t o m e t r i c m ea su re me nts i n t h e d i f f e r e n t l a b o r a t o r i e s andc o u n t r i e s .

REFERENCES

(1) BULLEY, N.R. and D. PHILLIPS (19 80 ). Sensory e va lu at io n of a g r i c u l tu ra l odours: A c r i t i c a l rev iew . Can. A gr ic . Eng. 22 , 107 - 112 .(2) HENRY, J.G . and R. GEHR (19 80 ). Odour c o n t r o l : An o p e ra to r' s gu id e .

Journ a l WPCF 52, 2523 - 2 537 .(3) ROOS, C , J. A . DON and J . SCHAEFER (1 9 84 ). C h a ra c te ri z a ti o n o f od ou r-

po l l u te d a i r . I n : P roc . In t .Sy m p. , Soc . Be ige de F i l t r . ( e ds . ) , 25 -27A p ri l 1984, Louvain-La-Neuve, Belgium , pp. 3 - 22.

(4) BAKER, A.R. and R.C. DOERR (1959). Methods of sampling and storage ofa i r co n ta in ing vapors and gases. In t . J . A i r P o l l . 2, 142 - 158.

(5) SCHUETTE, F .J . (19 67 ). P la s t i c bags fo r c o l l e c t i o n of gas samples.Atmosph.Environm. 1, 515 - 519.

(6) SCHODDER, F. (1977T. Messen von G e ru ch s st o ff ko n z en tr a tio n e n , Erfa sse nvon Geruch. G run dl. La ndtechnik 27, 73 - 82 .(7 ) CORMACK, D ., T .A . DORLING and B.W7J. LYNCH (1 974 ). C omparison o f t e c h

n iques fo r o rga no le p t ic od ou r - in ten s i ty assessment. Chem.Ind . (London) no. 2, 857 - 861.

(8 ) SCHUETZLE, D ., T . J . PRATER and S. RUDDELL (1 975 ). Sam pling and a n a l y s is of emiss ions f rom st at io na ry so urces. I . Odour and to ta l hydro ca rbo ns . APCA Jo urn al 25 , 925 - 93 2.

(9 ) WAUTERS, E . , E. WALRAVOS, E. MUYLLE and G. VERDUYN (1 983 ). An e v a lu a t i on o f a fa s t sampling procedure fo r the t rac e ana lys is o f v o l a t i l eor ga ni c compounds i n ambient a i r . E nvironm.Manitor.Assessm. 3 , 151-16 0.

(10) LACHENMAYER, U. and H. KOHLER (1984). Untersuchungen zur Neuentwick-lung e ines Ol faktometers. Staub - Reinhal t . Luf t 44, 359 - 362.

(11) BERNARD, F. (1 98 4) . S i m p li f ie d methods of odour measurement: I nd us t r i a l a p p l i c a t i o n and i n t e r e s t f o r a d m i n i s t r a t iv e c o n t r o l . P ro c. I n t .Symp., Soc. Beige de F i l t r . (e d s . ) , 25 - 27 A p r i l 1984, Louva in-La-Neuve, Belgium, pp. 139 - 150.

(12) GILLARD, F. (1984). Measurement of odours by dynamic olfactometry.Ap p l i ca t i on to the s tee l and ca rbo n iza t ion ind u s t r i e s . P roc . In t .Sym p. ,Soc. Beige de F i l t r . (e d s . ) , 25 - 27 A p r i l 1984, Louvain-La-Neuve,Belgium, pp. 53 - 86.

(13) MANNEBECK, H. (19 75 ). Tragba re O lfa k to m e te r. V D I-B e ric h t 226 , 103-1 05.

(14) BEDBOROUGH, D.R. (1 9 80 ). Sensory measurement of o dours . I n : OdourCo ntro l - a concise gu ide , F.H.H. Va len t in and A.A. Nor th (e d s . ) ,Warren Spr ings L ab or ato r ie s, Stevenage, He r t fo rd s h ire , U.K. , pp. 17-30.

(15) THIELE, V. (19 84) . Ol fa kto m etr ie an e in er E miss ions quel le - E rgebn is-se des VD I-Rin gve rg le ichs . Staub - R ein ha l t . Lu f t 4 4, 342 - 35 1.

(16) DUFFEE, R .A ., J .P . WAHL, W. MARRONE and J .S . NAD ERT1973). D e f in in gand measuring ob jec t ion ab le odo rs . I n te rn a t . P o l lu t io n Eng. Congress ,Phi ladelphia, paper no 25a, pp. 192 - 201.



4 9

G u i d e l i n e s - T h e N e t h e r l a n d s : G e u r n o r m e r i n g - O d o u r s t a n d a r d ( 1 9 8 3 ) . M i n i s t e r i e v a n

V o l k s h u i s v e s t i n g , R u i m t e l i j k e O r d e n i n g en M i l i e u b e h e e r , d i r e c t i e L u c h t ,

P o s t b u s 4 5 0 , 2 2 6 0 MB L e i d s c h e n d a m . - F r a n c e : N o r m e e x p e r i m e n t a l e - O d o u r s t a n d a r d , 1 s t d r a f t ( 1 9 8 2 ) . P o l -

l u t i o n a t m o s p h e r i c , m e t h o d e de m e s u r a g e de l ' o d e u r d ' u n e f f l u e n t g a z e u x , d e t e r m i n a t i o n du f a c t e u r de d i l u t i o n au s e u i l de p e r c e p t i o n - X 4 3 - 1 0 1 . A F N O R , T o u r E u r o p e C e d e x 7 , 9 2 0 8 0 P a r i s .

- G e r m a n y : V D I - R i c h t l i n i e 3 8 8 1 - V D I - G u i d e l i n e 3 8 8 1 , p a r t 2 , draft ( 1 9 8 4 ) . O l f a c t o m e t r i c m e t h o d of o d o u r t h r e s h o l d d e t e r m i n a t i o n . S a m p l i n g f o r o d o u r t h r e s h o l d d e t e r m i n a t i o n w i t h o l f a c t o m e t e r s . V D I - K o m m i s s i o n R e i n h a l t u n g d e r L u f t . B e u t h - V e r l a g G m b h , B u r g g r a f e n s t r a ß e 4 - 1 4 , 1 0 0 0 B e r l i n 3 0 .

- U n i t e d K i n g d o m : O d o u r C o n t r o l - a c o n c i s e g u i d e ( 1 9 8 0 ) . F . H . H . V a l e n t i n a n d A . A . N o r t h ( e d s . ) , W a r r e n S p r i n g L a b o r a t o r y , G u n n e l s W o o d R o a d , S t e v e n a g e - , H e r t f o r d s h i r e S G I 2 B X .

Table!: General methodology of sensory odour measurement

■ample collection -■ .. r J sampling

collection dilution presentation

response criteria indication interpretation

olfactometric apparatus

panel

Comparison of s t a t i c sampling and dynamic sampling on th e base of odour c o n c e n t r a t i o n ( o . u . / m

1) from

d i f f e r e n t sources ( f rom R00S e t a l . 1984 ( 3 ) . D -average of 2 measurements, 2 ) * average of 3 measurements, 3 ) * average of 6 measurements, 4 ) - average of 8 measurements.

Sample

Waste gas rendering plant 1 Waste gas rendering plant 11

Waste gas cattle-fodder factory Q030mg ethyl butyrate/m

1

72 mg butanol/m1

Odour concentration (au./m1)

Static sampling

71.600" 28.900

5030 3 0 0 ° 9 1 0 "

Dynamic sampling

75.000°

20,040

5,195 3 3 5 "

7 2 0 "

Ratio

105 0.69

1.03 1.12 0.79

Table IIl:Important criteria of

static sampling dynamic sampling

Inert material of the sampling device (bags, tu bes.valves), n o losses by diffusion

Pret lushing

Prediction equipment

Volume of the sample

Sampling time,pump speed

Storage time(<24h)

Inert tube material (PTFE, stainless steel, glass)

Preflushing

Predllullon equipment

Heated probe

Dust filters ] ■ required



I f

50

1 -tf-

Figure 1 : Example for a dynamic sampling device

(VDI - Guideline 3881, part 2, draft, 1984)

♦ 5

1 Sampling tube, inserted

2 Dust filter

3 Air inlet for predilution 4 Sample pipe

5 Excess gas exhaust 6 Pipe to the olfactometer

if required

1. 2. 3. 4. 5.

Metal drum Tedlar bag

Teflon valve Teflon tube

Flexible tube

6. 7. 8. 9.

10.

Flow meter

Air pump Battery

Hygrometer Thermometer

Figure 2 : Static sampling in bags (from

GILLARD 1984 (12) )

~6 40 80 120 K 0 200 R««id«nc* l inwin b a g , m i n u t M

Figure 3 : The effect of bag materials on ethyl-benzene recovery (from SCHUETZLE et al. 1975 (8) )



51

bag holder

evacuated

active pumpingi

prtdiUftionwith dry air

r O -

( ^

Figure 4 : Forms of static sampling (fromVDI-Guideline 3881, part 2, draft, 1984)1. Sampling tube2. Valve3. Bag

4. Bag holder5. Pump6. Active carbon filter7. Flow meter

PTFE Valve

Silicone Bum

1/2"PTFE-Connector

PTFE Backing-Nut

[1 / P T F E T u b e ( 1 / 2 " o . d )

\ f -Metal Tube(1A"i.d.)

' i | <

=c,PVC Nut

Two PTFEWashers

2 To Pump

•-PVF Bag

•601 Carboy

H

Macuum Release toPrevent PVF BagBursting

Figure 5 : Odour sampling apparatus (from WARRENSPRING, U.K. guide)



52

STANDARDIZATION OF OLFACTOMETRY MEASUREMENTS

J.H. VOORBURGGovernment Agricultural Wastewater Service

Arnhera Netherlands

Summary

Four different standards or guidelines for olfactometric measurement are compared and an inventory is made of the diffencesbetween the olfactometers.

1. INTRODUCTIONThree experimental standards for olfactometric measurement were

available and are compared in this review namely from France, theF.R.G. and the Netherlands. Moreover the guide for odour measurement

from the Warren Spring Laboratory is considered as a guideline.Some of the guidelines give very detailed informations (France

and F.R.G.).In the Netherlands only a number of boundary conditions are pu

blished. Therefore it is not possible to compare all the details.This is also beyond the goal of this review. We want to ask attentionfor the need of further international standardization or harmonisa-of odour measurement techniques in order to enable exchange of knowledge and experiences.

This review concentrates on the olfactometer: The sampling pro

cedures are reviewed by J. Hartung and the selection of panelist byM. Hangartner.

2 . THE OLFACTOMETER

The olfactometer is a device which dilutes odourou6 air withodour free air. This dilutions are offered to a panel in order to determine the odour threshold. There can be distinguished between static and dynamic dilution.

Static olfactometers dilute by mixing known volume of two gasesin the same vessel. In France they are considered as abandoned since- the consumption of considerable quantities of gas

- the time needed for changes in concentrationsIn Germany and U.K. no choice is made between statically and dy

namically diluting systems.In Japan a triangular odour bag method is used ( 1) . This con

sists of three bags with non-smelling air. Odour is poured into oneof the bags until a prescribed rate of dilution is achieved.

Dynamic olfactometers dilute the gas by mixing known flow ratesof two gases at the same outlet. The dilution factor is calculatedfrom the flow rates.



54

5. RANGE OF CONCENTRATIONSIn the German guidelines in the series of concentrations offered

two adjacent concentration point should differ by a maximum of a fac

tor two (or 0.3 on the log scale). A minimum of five concentrationsshould be plotted symmetrically around the probable threshold. Some20# of blank samples should be included at random in the series.

In France the olfactometer must be adjust from a dilution factorof 10 up to 10.000 in at least two stages without a factor of morethan 100 between one stage and the next.

In the Netherlands no more is said than:"Dilution stages with a factor of 2 should be possible" and "at least5 dilutions should be offered".

6. CALIBRATIONAs it should be taken for sure that the olfactometer gives thedilution which it is supposed to realize, it is surprising that solittle is said about calibration (method and frequency).

Warren Spring describes calibration with methane as a tracergas. The same holds for cleaning the device. In France it is proposedto clean with superheated steam, followed by a test if every trace ofodour is eliminated.

REFERENCES

1. ANON YMUS 1982. On target values for odour control by sensory testmethod. Japan environment summary. Vol. 10 , no: 9-



55

SELECTION AND TREATMENT OF PANELISTS FOR D ETERMINATION

OF ODOR THRESHOLDS

M. HangartnerSwiss Federal Institute of Technology,

Department of Hygiene and Applied Physiology

Summary

In order to harmonize an odor measurement technique, national guidelines or recommendations from Germany, France, the Netherlands andthe United Kingdom are compared with respect to selection and treatment of panelists. Different methods of mathematical treatment ofthreshold data are also presented.

1. IOTR0D0CTIONThe task of the working group "odours" in working party one of the

COST 681 prograime on processing and use of sewage sludge is to give a

contribution to harmonize an odor measurement technique. For this purposethe national guidelines or recommendations from Germany, France, theNetherlands and the United Kingdom are compared. The emphasis of thispaper lies on selection and treatment of panelists for odor thresholddetermination.

It is well known that sensitivity of men to odorants varies withina large range. By selecting the panelists at one extreme of the sensitivity distribution, the result can be falsified. However, by chosing alarge number of panelists, this effect can be minimized, but this isoften not suitable in practise. In the following the different recommen

dations are presented.Another source of variation of threshold values is the treatment of

panelists, that means comfort, motivation, interaction with panelleader,adaptation etc. These effects can be reduced using a proper detectionmethod. Finally, different methods for threshold data treatment may produce different threshold values.

For comparison, the following guidelines are reviewed:Germany- VDI Guideline 3881: Olfactcmetric method of odor threshold determina

tion, Fundamentals (Nov., 1983)

France- AFNOR Standard: Air pollution - Msthod of measuring odors from gaseous

effluents determination of the dilution factor of the threshold of perception (1982)

Netherlands- Odor standard, Ministerie van Volkshuisevesting (1983)United Kingdom- Odor control - a concise guide prepared on behalf of the Department of

the Environment Warren Spring Laboratory (1980)



56

2. GENERAL CONDITIONS OF ODOR THRESHOLD DETERMINATION2.1 Requirements for the test area

Olfactcmetric measurement should be undertaken In a room or areawhich is kept free from odors. There should be an atmosphere of comfortand relaxation in the test chamber, which will encourage panel members toconcentrate on the testing task and not to be distracted by external stimuli. The test should be carried out at room temperature and normal humidity.2.2 General conditions for test procedure

Odor measurements must be carried out with the help of a team leader,who instructs the panelists and operates the measuring equipment. Communication between the team leader and the panel has to be kept to an absolute minimum. Because of fatigue, the duration of a test series as well

as the time of the whole session should be limited. Breaks of at leastthe same duration as the proceeding test period should be provided.

Panel leader

duration oftest series

duration ofbreaks

time of a testperiod

Germany

yes

15-30 min

15-30 min

300 tests/day

France

yes

20 min

20 min

2 testseries of20 tests

Netherlands

yes

"9 - 5 min

UnitedKingdom

yes

15 min

30 min

2 hours

Table 1: General conditions

3. DETECTION METHODS3.1 Presentation of odor stimulus3.1.1 Method of limits

The most used method for establishing an absolute threshold in environmental studies is the Method of Limits. In its classical form, thestimuli are presented in alternating ascending and descending series,starting at different points to avoid having the subject fall into a routine. During this procedure there is a chance that adaptation phenomenamay develop. An effort to minimize these effects is for example to useonly an ascending series of stimuli. The threshold value for each separate test series is defined as a point in-between the last undetectedand the first detected point in the stimulus continuum.

A modification of the method of limits is the "up and down" method.A stimulus is presented: if the response is positive, the next lower stimulus is presented, if it is negative, the next higher is presented andso on. The primary advantage is, that it automatically concentrates nearthe mean and a considerable number of observations can be saved.



57

3.1.2 Method of constant stimuli (Method of frequency)By the Method of Frequency the stimulus range is selected in discrete

intervals so that the frequency of positive answers is distributed overthe range between 1% and 99%. In general, the frequency of positive responses either for an individual or for a group, is cumulatively normallydistributed over a geometric intensity continuum. The absolute odor threshold can then be defined as the effective dose corresponding to an arbitrarily selected frequency of positive responses, ordinarily 50% : ED..:Effective dose at the 50% level.3.1.3 Signal detection

The Signal Detection principle is a determination of the relationship between hits and false alarms. In determining signal detectability,a stimulus or a few stimuli are presented in random order, alternatingwith noise. Since sensory Impressions resulting from the presentation ofstimulus versus noise are assumed to be normally distributed over thesame intensity continuum and to have the same dispersion, the index ofdetectability d' for p (hits) minus p (false) indicates the extent towhich the two distributions overlap.3.2 Indication of response3.2.1 "Yes" or "no" response

In the classical evaluation yes-no answers are dependent on the subjects' honesty and motivation among other factors. However, yes-no answers may be evaluated if they are presented a sufficiently large number

of times alternating with blanks.3.2.2 forced choice technique

One method of controlling response perseveration and other anticipation factors is to use a forced choice response indication based ontwo or more response categories. In the measurement of odors the panelisthas to report the temporal position of positive stimuli in a series ofrandom blanks. If the concentration is below the threshold, the test subjects will guess. As the odorant concentration will increase, the relative cumulative frequency for identification of the correct sample willbe greater. In order to determine the relative odor recognition a cor

rection must be made.3.3 Size of stimulus Intervals3.3.1 Concentration intervals

In selecting the stimulus continuum in threshold determination, therelation between just noticeable difference in relation to the intensityof stimuli is of interest. In accordance with Weber's law this quotientis assumed to be a constant. Therefore it would appear best to determineabsolute thresholds on an intensity continuum in the form of a geometricprogression.3.2.2 Time intervals

Because of adaptation processes the exposure time until reaching adecision should be limited. Also the interval between two stimuli mustbe observed.



58

detection method

indication ofresponse

dilution steps

exposure tine

stimulus interval

Germany

limitrandom/ascend.

yes/no

1.5-2

<15 sec

15 sec

France

limitup & down

forced ch.

3

10 sec

3 min

Netherlands

limitascend.

forced ch.

S 2

<15 sec

1 min

UnitedKinqdom

limitrandom

yes/no

1.6

20 sec

1 min

Table 2:Detection method, indication of response and size of stimulusintervals.

4. EVALUATION OF THRESHOLD VALUES4.1 Definition of odor threshold

By convention the individual odor threshold is that concentrationwhich is just perceived by the subject in 50% of the cases in which itis presented to him. The group threshold is the concentration that isjust perceived by 50% of the panel members.4.2 Evaluation using the geometric mean

The point of change is determined for every series of dilution evaluated. It is defined as the geometric mean of the dilution of the lastnegative and the first positive answer. The arithmetical mean and itsstandard deviation are calculated from the logarithms of the points ofchange.4.3 Graphical evaluation

The characteristic curve of the odor threshold is used. The relative cumulative frequency of positive answers is calculated for each

odorant concentration and graphically plotted, while for odor concentration a logarithmic scale is used. The odor threshold can be obtainedfrom the resulting curve as the 50-percentile and so can the associated16- and 84-percentiles.4.4 Probit analysis

If the odor sensitivity is normally distributed over the logarithmof the odor concentration, the characteristic curve of the odor thresholdis a gaussian curve. This curve is converted into a straight line usingthe probit transformation. The analyses can be carried out graphicallyon probability paper or by transformation of the relative cumulative fre

quency by using a table function and calculating the regression lines.The odor threshold and the 16- and 84-percentiles can be determined fromthe results.



60

The physical condition is checked by the panel leader using a questionnaire or simply by asking the test persons according to the guidelines of

Germany and the United Kingdom. Only the German guideline tests reliability of panel members by repeated measurements with the same odorant.Problems of honesty are minimized by forced choice technique (France,

Netherlands). In the German guideline persons with more than 20% of errorsin more than three test series are excluded.5.2 Panel size

The extent to which a panel constitutes a representative sample of thepopulation depends directly on the numbers of panel members. For practicalreasons a compromise must be sought between costs and the representativeness of the result, and this depends on the question to be answered: basic

measurement e.g. emission standards or only comparative measurements, e.g.odor abatement efficiency.

basic measurements

comparativemeasurements

Germany

8-15

> 4

France

10

Netherlands

6-8

UnitedKingdom

6-8

Table 5: Panel size.

OCNCLUSICNSThere is more or less agreement in all guidelines about general background conditions.The limit method is proposed as detection method in all guidelines. Theindication of response is either yes/no or correct/incorrect. Thelatter, forced choice technique, may certainly give lower odor thresholds.

The mathematical treatment of data will produce only slight differencesin the threshold values.For the panel size different members are given. 8 people appears theright size for the panel.Selection of panelists is the most difficult question and large variations of threshold data are expected due to this problem. No generallyaccepted procedure exists and only vague recommendations are given inthe guidelines. A possible solution will be the evaluation of the sensitivity distribution of a large panel (> 25) of the actual odor to betested, and screening the panel members according to their position in

the distribution. However, this procedure might not be suitable inpractice.



61

VDI GUIDELINES ON ODOUR PROBLEMS

Dr. V. ThieleLandesanstalt fUr Immissionsschutz

des Landes NRWD-4300 Essen, FR Germany

Three working groups of VDI are mainly engaged in problems of odour determination and odour assessment. Theworking groups are titled:

-"Odorous Substances"

-"Application of Olfactometric Methods and PerformanceCharacteristics"

-"Dispersion and Odour Concentration in Ambient Air".

The titles characterize the subjects which are treated inthese working groups. At present the groups establish guidelines to solve odour problems. The guidelines are in different states of development.

3881-1: Olfactometry - Odour Threshold Determination -Fundamentals

-2: Olfactometry - Odour Threshold Determination -Sampling

-3: Olfactometry - Odour Threshold Determination -Olfactometers Types 1158 and TO-4

-4 : Olfactometry - Odour Threshold Determination -

Instruction for Application and PerformanceCharacteristics

3882 : Assessment and Effects of Odours - Intensity andHedonic Tone

3883 : Assessment and Effects of Odours - Measurement ofAnnoyance by Means of Interviews

394 0 : Odour Determination in Ambient Air by InspectionPanels

3781 : Odour Dispersion and Odour Concentration in AmbientAir

In the following some aspects of the guidelines are given indetail. Guideline VDI 3881 consists of four parts. The draftsof parts 1, 2, and 3 were published in the VDI handbook. Part4 is in preparation. The draft of part 1 was already revised.The new version will be published in a few months. The mostimportant result of the revision is the definition of odourconcentration expressed as odour units per cubic meter



62

(GE/m**3). According to this definition one odour unit is theamount of odorants in one cubic meter of air at odour threshold level. The new definition is a real concentration andgives a better form of input parameter for dispersion models.

On the basis of guideline VDI 3881 parts 1, 2, and 3ringtests were carried out with different odorants. Theresults can be summerized as follows:

-The dispersion of results varies and depends on the composition of the participants and on problems of sampling andpreparation of odorous sample. Lower dispersion is obtainedwhen results with obvious errors in application of guidelines or with large deviations from mean value are excluded.

-Participants of the Netherlands get systematically lowerthreshold values than the others. The reason has to beinvestigated.

-All findings of the ringtests lead to the conclusion that itis possible to determine odour thresholds which do not differby more than factor 10. At present another ringtest is inpreparation. This test will be carried out in summer 1985.The French collegues will also participate in this test.Experience of all ringtests will be reported in part 4 of

guideline VDI 3881.Guideline VDI 3882 deals with the determination of odour

intensity and hedonic tone. The members of the working group"odorous substances" assume that odour threshold and odourconcentration are insufficient for the characterization ofodorous perception. They recommend to judge the odour intensity and the hedonic tone by category estimation. Moreover,it is their opinion that the odour determination with olfactometers is not suitable to assess odour in ambient air. Therefore they are preparing two guidelines dealing with these

problems. Guideline VDI 3883 gives instructions on the registration of nuisance by interviews with nearby residents ofemitting plants or inhabitants of industrial areas. Additionally guideline VDI 3940 describes the determination of odourin ambient air by inspection panels based on the followingidea: During constant conditions as to the class of weather,wind speed, and wind direction each local point is characterized by a frequency of odour perception representing theprobability to perceive an odour. The situation at a localpoint will be have to determine the portion of a year with afrequency of odorous perception greater than 5 % in a randomtest. Both guidelines, VDI 3882 and 3940, should give corresponding results.

Guideline VDI 3781 part 5 completes the complex of odourdetermination and judgement with the calculation of dispersion models. The calculation methode and odour determinationby panelists should give comparable results.

The following summery can be given. Odour measurementswith olfactometers is only a small part of the whole field ofodour determination in ambient air and the measurement ofodour nuisance must be approached in the near future withappropriate urgency.



65

has control throughout , attempts to elicit all positive respons esinitially (to reduce panellist an xie ty) and then all negati veresponse s (thereby fixing approximately the range of diluti ons

i n v o l v e d ) . 'Blanks' are used, but sparingly and ma inly to test fora ppa r ently biased or er r a tic beha v iour by a pa nellist.

The sampling equipment and procedure have also been described ( 1 ) . Atno time, either during sampling or storage of the sample, do the odorousgases come in contact with glass or metal surfaces nor with pump or valvelubr ica nts. The samples are taken in 40-50 litre capacity bags, fabricatedfrom 50 (im thick polyv inyl fluorid e film ('Tedlar', Dupo nt) a nd fitted witha PTFE valv e. The PVF bag is placed in a rigid-walled polythene carboy (60litres capacity) and, by evacuating the space between the bag and carboy,the odour sample is drawn into the bag through a PTFE sample line . The bagmay be partia lly pre-filled with dry air to avoid cond ensation w hen

sampling warm moist ga se s. It should be noted that each sample bag is onlyused once and then discarded; no attempt is made to re-use the bag for morethan one sample.

4 . SOURCES OF ERRORObv iously ev er y effor t should be m a de to obta in r epr esenta tiv e

samp les, giving careful considera tion to the location of sampling poin ts.Errors due to the loss of odorants in sample lines and on storage areminimised by using approp riate materia ls as discussed ab ove . The extent ofthese errors is not easily quantified but it has been suggested that theyare much less than the uncertainty arising from the varia nce b etweenpanellis ts and the varia nce of an individual panellist . The vari ancebetween panellists can be reduced by increasing the severity of screeningthe potential panel list s. The size of the dilution steps (differencesbetween adjacent dilution va lues ) affects the consistency of the individualpa nellists; v er y la r ge dilution steps giv e a fa lse im pr ession ofcons isten cy. Finally the standard error is reduced by increasing thenumber of replicate samples and by increasing the number of pan ell ists .

Table I indicates the 95Z confidence limits determined with a WSLhigh-flow r a te olfa ctom eter (1) a nd suggests v a r ious options (under lined)wit h respect to panel screening, panel size, number of replicate samples

and dilution steps:(i) The optimum number of replicates was 2, having regard to the costs

of sampling and assessment,(ii ) Panels larger than 8, i.e. 12 or 16 produced similar confidence

limits whet her screened or unscreened but WSL believes thatscr eening is a lso a v a lua ble m ea ns of instr ucting the pa nellists ,

(il l) Based on duplicate sampling, a screened panel of 8 achieved almostthe same confidence limits with 60Z dilution steps as 6 screenedpa nellists or 8 unscr eened pa nellists when the olfa ctom eter isoperated with 30Z dilution steps,

(lv) A screened panel of 8, using 301 diluti on steps (and duplic ate

sam ple s) was a further improvement but on balance WSL prefers 60Zdiluti on steps in order to reduce the time needed for thea s s e s s m e n t .

Present practice is to screen potential panellists using hydrogensulphide from a cylinder (25 vpm in nit rog en) to eliminate those with apoor sense of smell (or with erra tic J u d g m e n t ) . Pr ev ious wor k with pur esubstanc es (Including hydrogen sulp hide) has shown (2) that the frequencydistri bution curve for threshold concentra tions is usually skewed . Theconfidence limits are improved by selecting the most sensitive 80Z ofpotential panellists who might be viewed as having a 'more Gaussian'



66

Table I Alternative Choices for Panel Type, Panel Sizeand Sample Replication

(95 2 Confidence Limits for Dilution Values , %)

Unscreened Panel; 3 0 % Dilution Steps

Panel Size 4 6 8 12 16

One sampleTwo samplesThree samples

Panel Size


Panel Size


Panel Size


-

464443

+

867875

Unscreened

4

-

534845

+

1129283

Panel Selected

4

-

443635

+

785653

Panel Selected

4

-

484239

+

947264

-

413837

1 Panel;

6

-

464239

for Top

6

-

383129

for Top

6

-

423633

+

686259

60%

+

877265

80%;

+

624641

80%;

+

735650

-

373433

+ +

59 34 465150

Dilution Steps

8

-

423836

+

736056

3 0 % Dilution Steps

8

-

352826

12

+ - +

54 32 463836

60 % Dilution Steps

8

-

393330

+

644943

+

31 43

16

+

31 43

distribution of sensitivities.

In summary, WSL uses 8 screened panellists, 60% dilution steps and,where possible, takes duplicate samples; it is indicated that the corresponding 95 % confidence limits are -3 3 % to +4 9 %. It should, of course, beremembered when comparing dilution values determined by the same set ofpanellists (e.g. to evaluate the % efficiency of odour control equipment ona particular day) that the standard error is somewhat reduced because theperson to person variance need not be considered.

5. THE APPLIC ATION OF DETECTION THRESHOLD MEASUR EMEN TSThe intention here is to list and comment very briefly on the range of



67

tasks to which the WSL Transportable olfactometer has been applied, asbackground to the views expressed in section 6 on possible standardisation.

Often the number of dilutions to detection threshold, D (dimension-

less) is combined with the rate, F (m 3 s _ 1 ) at which malodorous air isdischarged or escapes from the building or process plant to derive theodour emission rate, E (m3 s _ 1) where E = DF. Information on the odourstrength in terms of D or the odour emission rate, E , can be used invarious ways:

(i) Different process operations can be investigated to determine whichcontribute most to the total odour emission rate, with the objectiveof possible process changes which might reduce or eliminate odournuisance problems,

(ii) Where abatement equipment has been installed, measurements of odourstrength on inlet and outlet samples show the efficiency of odour

removal ( 3 ) .(iii) Similarly in laboratory or field studies of abatement techniques,

odour strength measurements can be used in conjunction withanalytical measurements, e.g. in studies of catalytic after-burning( 4 ) , chemical scrubbing ( 5 ) , adsorption on activated charcoal ( 6) ,bio-filtration etc.

(iv) An examination of odour complaints in relation to the odour emissionrate (2) has produced a most useful empirical formula for calculating the likely maximum distance from an odour source at whichcomplaints are likely to arise* This can be used in dealing withboth current disputes and in considering requests for planningpermission. It must be emphasised, however, that the formularelates only to values of odour strength measured by a WS L olfactometer,

(v) It may well also be necessary to calculate chimney heights for theadequate dispersion of residual odours from abatement equipment orfor process odours released without treatment. Again the calculations and examples published by Warren Spring Laboratory (7) assumethat the odour strengths were determined by the WSL olfactometer.

A great variety of processes and operations have been investigatedusing WSL olfactometers including a number of farming and sewage disposalproblems. Some examples specific to the present conference are: odourstrengths in broiler (poultry) houses in relation to weeks of growth; theeffect of filters/washers on pig house ventilation air; the treatment ofpoultry manure dryer emissions; head-space odours from agriculture andsewage wastes and odour assessment of the unit operations at sewagetreatment works.

6. SOME VIEWS ON POSSIBL E STANDARDISATIONIt is known that odour detection thresholds measured by different

types of olfactometer can vary substantially. Not unreasonably, there arewell-intentioned calls for 'standardisation of odour measurements' ,

possibly as the basis for odour emission regulations, and so it might beuseful to express some cautionary views.(I ) Detection threshold values need to be combined with other informa

tion to have any utility in assessing nuisance potential. Todetermine odour emission rates, the rate at which malodorous air isbeing discharged must be known and often can only be roughlyestimated where odour is escaping from a building or from equipmentoutside a building. Further, odour emission rate is only onedeterminant of potential odour nuisance which also depends on theperceived intensity, character and hedonic tone of the odour, the



68

frequency and duration of exposure, the height and location of thedischarge, the distance between the odour source and potentialcom pla ina nts a nd fina lly pr ev a iling m eteor ologica l conditions.

(ii) Wher e detection thr eshold v a lues ar e used com pa r a ti v ely, forexa mpl e, to assess the efficienc y of abatement e quipmen t, then thecase for standardisation is reduced and considerations of speed andconv enience becom e, possibly, m or e im por t a nt. Undoubtedly som e pa ststudies on odour control would have been improved if more odoursamples could have been assessed.

(ii i) It is not really understoo d why different types of olfactomete rp r oduce such differ ent odour detection thr eshold v a l ues. Thereas ons may includ e inadequate design (e.g. inadvertent di lution atthe sniffing ports or adsor ption l o s s e s ) , physical effects (e.g.m a ss-tr a nsfer of odor a nts in the n o s e ) , physiological effects (e.g.length of stimulus/rest inte rva ls) and panel behaviour (e.g. effectsarising from the mode of presentation or type of response r e q u i r e d ) .In these cir cum sta nces, sim ple guidelines for sta nda r disa tion m a ynot ac hieve their objective beca use a real variable is notcont roll ed. For example, standardis ing the volume flow rate of airfrom the sniffing port does not standardise air velocity into thenose unless the design of the ports and how the panellists used thema r e a lso contr olled.

(lv ) It may be impossible to correlate odour strengths determined with anew olfa ctom eter oper a ting to suggested guidelines with odour

str engths deter m ined by som e existing olfa ctom ete r s. It ha s beenobserved (2) that the relationship between two existing olfa ctomete rs appeared to depend on the nature and conce ntratio n of theodor a nts . In this situa tion, a ny pr oposed guidelines which r esultedin the loss of an established body of knowledge would not bea ccep ta bl e. For exa m ple, the WSL Tr a nspor t a ble olfa ctom eter ha sproduced a coherent set of dilution values over some years , which isthe basis for predicting odour nuisance, calculating chimney heightsetc and WSL would not readily abandon their well established systemfor odour detection thr eshold m ea sur e m ents.

REFERENCES

(1) BEDBOROUGH, D.R. ( 1 9 8 0 ) . Odour Control - A Concise Guide (Editors,F.H.H. Valentin and A.A. N o r t h ) , Wa r r en Spr ing La bor a tor y, Stev ena ge,1 7 - 2 9 . *

(2 ) BEDBOROUGH, D.R. and TROTT, P.E. ( 1 9 7 9 ) . The Sensory Measurement ofOdour s by Dynamic Dilu tion , Warr en Spring Laboratory Report, LR 299(AP).

(3) MOSS, R.L. Deve lopm ents in the Measurem ent and Control of ProcessO d o u r s , ( 1 9 8 3 ) . 50th Annual Conference, National Society for Clean

Air , Tor qua y.(4) IRWIN, J.G., DORLING, T.A. and MOSS, R.L. ( 1 9 7 9 ) . Atm ospher ic

En v i r o n m e n t , V o l . 1 3 , 1 5 6 9 - 15 7 9 .(5 ) POPE, D, DAVIS, B.J. and MOSS, R.L. ( 1 9 8 1 ) . Atm ospher ic Env ir onm ent,

V o l . 15, 251-2 62.(6) DORLING, T.A. ( 1 9 7 8 ) . Activated Carbon in Odour Contro l, Warre n

Spring Laborato ry Report, LR 293 (AP) .(7) KEDDIE, A.W.C. ( 1 9 8 0 ) . Odour Control - A Concise Guide (Editors,

F.H.H. Valentin and A.A. N o r t h ) , Wa r r en Spr ing La bor a tor y, Stev ena ge,9 3 - 1 0 7 .



70

1. The possibilit y of a for ced-choi ce detection m ethod on at least twosniffing por ts.

2 . A sample flow rate of at least 16 1/min.

3. Exclusion of "too good" a nd "too ba d" pa nellis ts.4. A pa nel size between 6 and 8 pa nell ists .5 . O d o u r - f r e e s u r r o u n d i n g s .6. Dilution steps with a m a xim u m fa ctor of t wo.7 . Pr esenta tion of a t lea st 5 dilution steps with a scending concentr a tion

i.e. descending d ilut ion.8. Pa nellists should not be influenced by ea ch o ther , by noises , by the

pa nel le a der , by the position of v a lv es a nd sniffing por ts e tc.

3. COMMENTS ON WESTERN EUROPEAN GUIDELINESThr ee Wester n Eur opea n Guidelines for olfa ctom etr ic m ea sur e m e nts a r e

discussed and compared with the Dutch guideline namely the VDI Richtlinie(10), the AFNOR Norme exper imen tale (1) and the Warren Spring Laboratory(WSL) guideli ne (2, 6 ) .

3.1 SamplingAlthough no pres crip tions on sampling odours are included in the

Dutch gui deli ne, som e r ecom m enda tions will be included in the AirPollution Contr ol Ma nua l .

Beca use the influence of concentr a ting a n odor ous sa m ple on theper ception ha s nev er been inv estiga ted thor oughly, only non-concentr a tedsa m pling m ethods a r e a v a ila ble for sensor y m ea sur e m ents.

When a dsor ption a nd condensa tion ca n be a v oided, both dyna m ic a ndstatic sampling metho ds can be used . Often rinsing the sampling appar atusor ev en the whole olfa ctom eter with odor ous a ir is necessa r y to r educea dsor ption. Befor e using the sta tic m ethod a com pa r a ti v e study should beca r r ied out if poss ible. On the other ha nd extr e m e fluctua ting em issionsca n only be sa mpled sta tica lly.

The Netherla nds Organ izatio n of Applied Scientific Research (TNO)ca r r ied out a com pa r a ti v e study with Teflon- FEP-ba gs. Ra tios between thedynam ic and static method ranged from 0.7 to 1.1 after a storag e time of24 hour s (7 ). These Teflon-ba gs ca n be used sev er a l tim e s. Nor m a l ly the

sample size is 50 to 100 litres but for ambient air samples of 1600litr es a r e som etim es necessa r y.

3.2 ApparatusIn The Nether l a nds dyna m ic dilution dev ices a r e, with one exceptio n,

a lwa ys used by r esea r ch in stitutes , pr ov incia l a uthor ities a nd industr y.However these devices differ g rea tly in design and in method ofa pplica tion. In ta ble I the pr incipa l da ta of four olfa ctom eter s a r esum m a r ised. These wer e built by the r esea r ch institutes t hem selv es.

In gener a l, r esea r ch on the design of a n olfa ct om eter , especia lly onthe dilution com pa r t m ent, the m a ter i a l used in constr uction a nd the

necessa r y odour less a ir for dilution, is either not ca r r ied out or nev erpublishe d. Beca use of this, r ecom m a nd a tions on these a bov e points a r e notyet included in the Dutch gui del in e.

In contr a st to this, sa m ple pr esenta tion is thor oughlyinves tiga ted. On behalf of the Ministry of Hou sing , Physical Planning andEnviro nmen t, TNO investigated the influence of flow rate in relation to



71

dilution factor, both analytically and sensorically. The flow rate varied from 6 to 35 1/min. Propane concentrations were measured at the back of the nose of an artificial head through which 20 1/min. was sucked continuously. Sensory measurements were carried out with butanol and ethylbutyrate. The results are summarized in figure 1. Based on this research 16 1/min. was recommended as the minimal sample flow rate.

dilution f t c to r

10 ■

-

\ °

A i i i

o butanol

A ethylbutyrate sensoric measurements

x propane FID measurements

= ^ = - = = ^ A — - 7 t r f ^ = r r-oxo A

A A I I I I .

10

Fig. 1 Dilution factor as

15 20 25 30 35 40

air-flow Cl/mln.)

a function of sample flow rate

Lack of data prohibited a recommendation on the design of the sample nose interface. According to TNO a sniffing port with a diameter between 4 and 7 cm will guarantee a perceptible but not too strong air stream and a port big enough for the nose. The velocity of the air stream varies from

9 to

27

cm/s

with

a flow

rate

of

20

1/min.

AFNOR

recommends

a diameter of 10 cm. With 30-60 1/min. this means a velocity of 6-13 cm/s.

WSL prescribes a tremendously high velocity of 200 cm/s with a flow rate of 60-190 1/min. The diameter of the sniffing ports must therefore be between 1.5 and 4.5 cm.

To minimise the influence of variables that are inherent to sensory evaluation, such as anticipation, decision criteria, doubt and adaption, the yes/no detection method is strongly rejected in the Netherlands and a forced-choice method recommended. The Psychological Laboratory of the State University of Utrecht investigated what influence differing numbers of sniffing ports in a forced-choice detection method had on the results

(9) .

Because negligible differences were found no specific number of sniffing ports has been recommended.

3.3 Panel Although panels can never be standardized so precisely as the other

items, prescriptions on the size, number of replicates, selection criteria and training can guarantee a rather good reproducibility.



73

detection threshold values are namely withdrawn from the literature without checking these thoroughly by an apparatus built according to the

French guideline. Training panellists is only mentioned as desirable by the WSL guideline. In the Netherlands a panel is sometimes tested every day, thus verifying the dilution apparatus itself. Sometimes trained panellists are used (see Table 1).

Table 1 Principal data of four olfactometers in the Netherlands

Sampling ncthod

Apparatus Dilution range (excl. predilutlon) Sample flow rat* Sanple detection ■ethod

Panel Size Selection

Training

Procedure Panel leader Number simultaneous evaluations Pactor dilution step Number of dilution steps Replicates Blanks/sample Number tests/sample Sniffing time Stimulus interval Duration sample evaluatlon(testserie Break Samples/day Concentration presentation

Calculation Calculation method

MT-TNO1

static or dynamic

1-16,000

20 1/mln.

forc.ch. triangle

8 anosmia and heavy

testserle/panel

yes 8

2 5-6

4 8

25-30 15 sec. 45 sec. 30 min.

15-30 min. 6

ascend

probitanalysls

CIVO-TNO2

static

1.2-250,000

16 1/min.

forc.ch. triangle

8 smokers rejected

testserie/day

yes 1

ca. 2 5

2 2

12 10-15 sec.

3 min. 60 min.

15 min. 5

ascend

arcsin transform.

IHAG3

static

2-100,000

20 1/mln.

forc.ch. duotest

10 permanent panel

-

yes 1

(1.25-2) 5-7

3 3

18-24 5 sec. 2 min.

90 min.

30 min. 3

at random

z-score transform

DCMR*

static

4-2250

IS 1/min.

forc.ch. triangle

4 permanent group of 20 panellist

-

yes 4

ca. 3 S

3-4 2-3

20-25 20-25 sec. 1 min.

30 min.

t,i 6

ascend

arcsin transform.

1. Division of Technology for the Society - TNO, Apeldoorn 2. Central Institute for Food Research - TNO, Zeist 3. Institute of Agricultural Engineering, Wageningen

4. Central Environmental Control Agency Rijnmond, Schiedam 5. For every sample a new panel is chosen.

3.4 Procedure General Perception of odour concentrations around the threshold value is

strongly effected by the presence of other odours. Results can be influenced very negatively if tests are carried out in the neighbourhood of odour sources. Measuring in odour-free surroundings is particularly important for mobile or transportable olfactometers. Also for



74

la bor a tor y m ea sur e m ents this is str ongly r ecom m ended in the Nether l a nds.AFNOR also pre scri bes it and the VDI in a minor way . The WSL, on the

other ha nd, does not pr escr ibe odour -fr ee sur r oundings for theirt r a n s p or t a b l e o l f a c t o m e t e r .

Another important feature for prec ise sensorica l mea sure ment s is thenecessa r y uninfluenced r esponse of the pa nelli sts. This is r ecom m ended bythe Netherlands, the VDI and the WSL. The olfactometer of WSL differsfro m the other s by not seper a ting pa nellists dur ing testing.

PresentationAdsorption and desorption can be avoided much better and adaptation

m inim ised when concentr a tions a r e pr esented with a scending concentr a tionlev els . A series of at least 5 dilution steps is recommended in theNetherla nds starting two or three steps under the expected threshold

v a lue with a m a xim u m fa ctor of two between the steps . The sa m e fa ctor a ndnumber of dilut ion steps are recommended by the VD I. The dilution ra ngecovered then extends to a factor of 16.

The Fr ench guidelin e pr escr ibes 6 to 9 dilutions steps with a fa ctorof 10 (= ca . 3 ) . This m ea ns a r a tio between the highest and lowestpr esented dilution is 300 to 10.0 00. On the contr a r y the r a tio pr escr ibedby the WSL ranges onl y from 6.3 (8 diluti on steps with a factor of 1.3)to 10.5 (6 dilut ion steps with a factor of 1. 6) .

The presented dilu tion s should at least cover the range from 10 to90% per cepti on. Consider ing the per ception c ur v es published in thelitera ture , this means a factor betw een 10 to 35 . Although 300 seems

m uch too high, the pr esented r a nge in the Nether l a nds a nd that pr escr ibedby the VDI, seem s r a ther sm a ll.

Regarding the number of times r equired for test replic ation the WSLguideline is explic it. The WSL dem a nd thr ee r epeti tions. In theNether l a nds two to four r epetitions a r e usua l.

Dur a tionThe dur a tion of a sa m ple a ssessm ent depends on sniffing tim e,

stim ulus inter v a l, pa nel size, sim ulta neous ev a lua tion, num ber ofdilution steps, num ber of bla nks a nd num ber of r epl ica te s. Accor ding tothe VDI Richtlinie a sample can be assessed once in 15 to 30 minutes.This a ssesm ent ta kes pla ce without sim ulta neous ev a lua tion a nd is arather short period of time due to the inadequate stimulus interval of 15seco nds. WSL assesse s a sample with the much longer interval of 1m in ute . Beca use they use sim ulta neous ev a lua tion with 3 or 4 pa nellistsa ssessm ents ca n ta ke pla ce once in ev er y 15 m in ute s. The r ecomm endedthr ee r eplica tes br ing the tota l test dur a tion up to 45 m in utes .

The French guidel ine is not clear at all on this po int . First of allnothing is sa id a bout sim ulta neous ev a lua tion a nd num ber of r eplica tes.If each panellist should evaluate 6 to 9 stimuli with an interval of 3m inutes befor e the next pa nellist m a y sta r t, the whole pr ocedur e with 20pa nellists will la st 7 to 9 hour s (1 ). Howev e r the pr escr ibed sequence ofstim uli m a kes it a lmost im possible to shor ten the pr ocedur e.

Nothing is prescrib ed yet in The Netherla nds regarding sniffingtim e, stim ulus inter v a l, sim ulta neous ev a lua tion a nd num ber of bla nks.Mostly a test ser ies ta kes 30 to 90 m inutes (see ta ble I ) . Sim ulta neousev a lua tion in pa r ticula r will shor ten the dur a tion of a test ser ies.

Com pa r a bilityOnly the VDI -Richtli nie giv es cr iter i a fr om which it is possible to

com p a r e sensor ica l m ea sur e m ent m ethods with ea ch othe r . Results ta ken



75

from the VDI-ringte st ace the base for this comp ar ison . However someolfactometers in this ringtest did not conform to the VDI Richtlinie.Ma ybe beca use of this the r a nge between the highest a llowa ble thr eshold

value for hydrogen sulf ide and the lowest is great (namely from 0.4 to 8u g / m 3 (fa ctor 2 0) ).

3.5 CalculationsIn contrast to the other guide line s a specific calcula tion metho d is

not recommended in the Nether lan ds. The results va ry less due todiffer ent ca lcula tion m ethods tha n beca use of other fa ctor s. In acom p a r a ti v e study with four olfa ctom eter s thr eshold v a lues wer eca lcula ted in thr ee differ ent wa y s: a r csin tr a nsfor m a tion, pr obita n a lysisa nd z-tr a nsfor m a tion. The a v er a ge of the r a tios between differ entcalculate d result s was max ima l 1.15 (± 0.16) (8 ).

4. STANDARDIZATION OF OLFACTOMETRIC MEASUREMENTS IN THE NETHERLANDSAlthough some r esearch institutes started a lread y in the midd le of

the sev enties to m ea sur e sensor ica lly odour e m issi ons, it wa s not until1980 before 4 different o lfa ctom eter s were compared with each other forthe first tim e. Great differ ences were found ra nging from a factor of 3to 40. A rela tionshi p betwee n the differing compo unds tested and thefactor number was also noticed. The differences between the two TNOolfa ctom eter s a lm ost disa ppea r ed a fter setting both on the sa m e flow r a teof 16 1/min. ( 7 ) .

In 1983, TNO thor oughly investigated the influence of the flow rate(see figure 2 ) . For the Ministry of Hous ing, Physical Planning andEnvironment three olfactometers with a flow rate of at least 16 1/min.

wer e then com pa r ed with ea ch other . The pr elim ina r y r esults of thiscomparative study are summarized in table II.

Table II Threshold valu es (ug/m 3) - Com pa r ison of thr ee olfa ctom eter s.

compound

n-butanolethylbutyr a tehydr ogen sulfide

MT-TNO 1

770,030

0,43

CIVO-TNO 1

1010,060

0,85

IMAG1

1360,090

1,05

1. See ta ble I

Although the results are not yet analys ed it can be concluded thatthe thr eshold v a lues a gr ee. Results of this study will a lso beincorporated in the defini tive v ersion of the chapter on odours in theAir Pollution Contr ol Ma nua l. The dr a ft is cur r e ntly with the pr inter a nd

will be released soon (4) . In com ing yea r s a r ingtest will pr oba bly beor g a nised under super v ision of the Nether l a nds Sta nda r ds Institute. Ev er yr esea r ch institute, pr ov incia l a uthor ity a nd industr y will be inv ited topa r ticipa te in this r ingtest.

The need to sta nda r dize olfa ctom etr ic m ea sur e m ents is gr owing in theNether la nds . In 1984 .interim limit valu es on odour con centr atio ns we republished in the Indicative Multi-year Program me to combat Air Pollution



77

12. Olfa ctom etr ic m ea sur e m ent m ethods m ust be r ejected when thr esholdv a lues of a t lea st thr ee substa nces ca n not be a ssessed within afa ctor of 2 to pr ev ious ly gener a lly a ccepted v a lu es.

REFERENCES(1) AFNOR (1982), Methode de m esur a ge de l'odeur d'un effluent ga zeux,

Deter m ina tion du fa cteur de dilution a u seuil de per ception. Nor eexper i m enta le X43-101.

(2) BEDBOROOGH D.R. and Trott , P.E. ( 1 9 7 9 ) , The Sensor y Mea sur e m ent ofOdour by Dyna m ic Di lution , Wa r r en Spr ing La bor a tor y , Stev e na ge , LR299 (AP) .

(3) Geurnormering (1983), Publica tier eeks Lucht n r . 11, Ministr y ofHousing, Physica l Pla nning a nd Env ir onm ent, Sta a tsuitgev e r ij's-Gravenhage, (in D u t c h ) .

(4) HML (Handboek Model voor schr iften Lucht ve ro ntr ein igi ng) , (AirPollution Contr ol Ma nua l) (1985), dr a ft cha pter on odo ur s ,Staatsuitge verij 's-Graven hage , (in Dutch) (in p r e s s ) .

(5) IMP, Indicative Multi-year Programme to combat Air Pollutio n1985-1989 (1984), Ministry of Housing, Physical Planning andEnv ir onm ent, Sta a tsuitgev e r ij 's-Gr a v enha ge, (in D u t c h ) .

(6) Odour Control (1980), a concise gu ide, Wa r r en Spr ing La bor a t or y,S t e v e n a g e .

(7) ROOS C , J.A. Don and J. Schaeffer j (1984) Characte riza tion ofodour -polluted a ir . Pr oceedings of a sym posium on "cha r a cter iza tiona nd contr ol of odor ifer ou s polluta nts in pr ocess industr i es",

Louv a in-la -Neuv e.(8) SCHAEFFER J. et.al. (1981), Ver gelijking v a n olfa ctom et er s v oor

stan konde rzoek , CIVO-TNO ra pport n r. A 81.170/ 1700 52, Zeist (inDutch) .

(9) SLUYTER T.G.M. and Punter P.H., (1982) Valid iteits onder zoekOlfa ctom eter s Phychologica l La bor a tor y, Rijksuniv e r siteit, Utr echt(in Dutc h) .

(10) VDI Richtlini e 3881 blatt 1-3, (1984) VDI-Han dbu ch Reinhalt ung derLuft band 1 (d raft).



81

EXPERIENCES WITH OLFACTOMETRY MEASUREMENTS IN HORWAY

P. HolmvangCenter for Industrial Research

Oslo

fimiary

Some experiences with olfactoaetric measu rements in connection withodour abatement pr ocesses, mainly in sewage sludge and waste water

treatment plants and in the fish meal industry, are presented. Studieshave been carried out to calculate the efficiency of var ious odourreducing met hods. The additional informa tion provided by the measu rements was of practical use for the mana gement of the process to im proveodour reducing efficiency.

1. INTRODUCTIONOdorous emissions from industrial and other plants have become of

greater concern also in Norway the last deca des.In order to assist the industry in establishing suitable odour

reducing processes, odour measurements are performed at our institute.Olfactometry is useful for objective evalua tion of odour levels and forcharacterization of certain odours, often in combination with gas chromatography .

Some of our experience connected to the applicat ion of olfactometr ic

studies is described in this paper.2. DESCRIPTION OF THE OLFACTOMETER

Among the several olfactom eters a vailable on the mar ket, our institutein 1976 ordered an olfactometer developed by Dr. Dravniek at IIT, Chicago( 1 ) , based upon the dynamic forced triangle princ iple.

The olfactometer supplies 6 dilution lev els. At each dilution level 3samples ("triangle") are presented to the panelist from a set of glasssniffing port3, two presenting the test room air (blanks). The third is theodorous gas sample diluted with test room a ir. The panelist is instructedthat one of the three ports at each dilution level exhibits an odour, and

that his task is to smell the effluents from the ports and decide whichport, in his opinion, delivers an odorous sample. If the panelist can smellno difference he has to guess ("forced triangle"). This is included in thestatistical ba sis for calculation of the total odour str ength.

The test panel consists of 7-10 tested and motiva ted persons, usuallypeople from our laboratory staff.

The test is carried out with one panelist at the time, starting withthe most diluted sample and pr oceeding towards higher concentr ations of thesample. The choice at each level is signalled by depressing a buttoncorresponding to the port thought to be odorou s. This choice is observed by



82

the panel leader on a panel of light in a separa te signal box.The panel leader records the judgements and ca lculates by aeans of a

statistical procedure, the averaged panel value termed ED . This termdenotes Effective Qosage a t the 50 percent level, i.e. that dilution levelat which 50 percent of the panel would and 50 percent would not detectodour of the diluted sa mple. The dilution is denoted by the dilutionfactor . For instance: ED = 1000 mea ns that one litre of the odorous airmust be diluted with 1000 litres of non-dodrous air to reach the panelthreshold termed ED . With the olfactometer in use it is possible tomea sure dilutions between approximately 10x up to approxim ately 30.000x.

3. APPLICATIONSIn general the ma in sources of odour emission in Norway a re fish meal

plants, pulp and paper mills, and plants for the treatment of sewage sludgeand waste wate r. Investigations ha ve been carried out in these and otherbranches of the industry, i.e. the food industry.

Each case may provide features which influence the olfactometricmeasurements, often demanding special sampling techniques and interpreta tions. In the following som e of the problems and exper iences will bepointed out by means of examples from sewage treatment and fish mealplants, showing the use of olfactometr y for obtaining satisfactory odourreducing results.

A couple of years ago an investigation was carried out to evaluate theefficiency of odour reducing processes based on different principles, such

as chemical scr ubbers, soil bed filters, activated car bon filters, ironoxide filters, and combustion.Samples for the olfactometric mea surements were taken in different

positions in the installations and the odour reducing efficiency wascalculated as the ratio between the recorded ED value at the outlet andinlet of the purifica tion steps:

( ED5o ' o u t l e t " (EDso'inlet

filter (ED )l t U5 0 Joutlet

The investigation provided a large amount of olfactometric data . Itbecame, however , obvious that the results could not be used for directcomparison of the effect of the different odour reducing meth ods. This wasdue to the fact that each plant handled a variety of gas quantities andqua lities . In addition, flow rates and degrees of humidity at the outletmade comparison ir relevant.

On the other hand, the set of data turned out to be a useful tool forcalculating the limitations of each odour reducing method under defini teconditions. The results also allowed precautions for appropriate processmanagement under conditions causing high levels of odorous compounds.

As examples can be mentione d:The odour emission da ta for chemical scrubbers can be used for

optimization of the odour reducing process. Several chemical scrubbershave been investigated. Most commonly used in Norway a re scrubber sutilizing sodium hypochlor ite as agent for the oxidation of odorouscompoun ds. Generally, the installation and effect of such scrubbers seemsto be quite successful , with very high odour r educing efficiency. If thescrubber, however , is operated incorr ectly, the odour of the scrubberitself nay be the predominant source of nuisance. When measuring thereducing efficiency of chemical scrubbers we always ask our panelists aboutthe odour impression of the sample at the less diluted level. The



83

information prov ided by the description of the odour is indispensable inthe evaluation of the purification effect. When operated incorrectly the

odour of the sample will be described a s "chemicals, faint chlor ine' orworse, 'typical chlori ne'. Quite often such informations a re used as abasis for adjustments and optimizing in chemical scrubber management.

Measure of odour reducing efficiency in iron oxide filters is anotheresample of how olfactometry may contribute to the optimization of an odourreducing method.

In some Norwegian sewage sludge and wastewater treatment plants ironoxide filters hav e been installed with succes s. The filter consists ofmixed wood chips and iron oxide, and the odorous compounds ar e oxidizedin the filter. The total odour strength was measured in such a filter wherethe air from sludge tanks providing an offensive odour was finely dispersed

at the 3 m bottom of the filter box (total filter volum e: 3 m , containing300 kg iron oxide).

It was observed that the purifying efficiency was str ictly dependenton the gas flow in the filter, and that relatively high flow rates gave thehighest efficien cies. This is indicated in the curve below.

1 1 ^50 100 150 200 250

Gas flow(m 3/h)

Figure 1. Odour r eduction ef ficiency in iron oxide filterexpressed as a function of the gas flow throughthe filter.

At a low flow rate the odour was described as "wooden*, a smelloriginating from the filter m ass . At higher flow ra tes the odour got afaint smell of sewage slu dge.

What is then the explanation to the high efficiency at high flowrates? Probably the odour of the filter mass ma kes a great part of thetotal odour at low flow rates. At higher flow rates this odour is dilutedto some extent, while the oxidation of odorous com pounds in the sludge tank

air is still effective, r esulting in a high total odour reducingefficiency.

It should be mentioned that the iron oxide filter at the right flowrate has functioned well for 3-4 yea rs with a good odour reducingefficiency and impressing capacity.

Development of a 'new' odour reducing method:This is an example of how present processes can be combined to obtain

a better odour abatement system, and how olfactometric measurements areuseful by evaluation of the efforts made to improve the odour reducing



89

N S + N

/ ' \

y i \\ : \

i v \1

"V ^3 *-|

SENSATION

Figure 1. Distr ibutio n of the sensation strengt hs caused by Noise (N) andSignal plus Noise (S+N) accor ding to Signal Det ection Theor y. Threehypothetica l r esponse cr iter i aindica ted.

(C, and C,) set by the subject are

a wr ong im pr ession of the subjects tr ue sensitiv ity. In signa l detectiontheory an elegant solution for determ ining the true sensitivity has beendev eloped, but this ca n only be done a t the cost of extensiv e m ea sur e m ent

pr ocedur es inv olv ing v er y m a ny pr esenta tions of both odour stim uli a ndb l a n k s . Such a pr ocedur e is im pr a ctica l in ev er yda y a pplied r esea r ch .Forced choice procedur es do force the subject to use a very libe ralcr iter ion. Ev en if he is a bsolutely uncer t a in , he m ust still giv e his bestg u e s s . With such a procedure the subject r eally use s all of his resourcesa nd a s a r esult the thr esholds found with this pr ocedur e a r e usua lly lowerthan with a single yes-no method -However, it should be remembered that in using forced choice, thepercentages correct choices obtained should be corrected for guessingusing the following formula:

Pobs - Pchanc ePcor r - x 100.

100 - Pchance

in which Pcorr - Percentage corrected, Pob6 - Percentage observed andPchange is the Percent age that would be obtained by me re gu essi ng.If, in conclusion, for ced choice m ethods giv e a better im pr ession of thetr ue sensitiv ity of the subject tha n yes-no m et hod s, olfa ctom eter s shouldbe equipped to make their use possibl e. This mea ns that the subject should

ha v e a ccess to a t lea st two sniffing por ts , one of which deliv e r s theodor ous a ir , wher e a s the other ( s) do giv e pur e a ir only.Another m ethodologica l consequence ca n be infer r ed fr om signa l detectiontheor y a s well .In signa l detection exper i m ents it ha s been dem onstr a ted, tha t thecr iter ion the subject chooses is influenced by his expecta tions a bout theoccurr ence of a sign al. If the signal is expected to occur freq uently, hewill be inclined to sa y yes m or e often (liber a l c r iter ion) tha n in theca se he expects the signa l to occur only r a r ely.



90

In signa l detection exper i m ents it ha s been dem onstr a ted, tha t thecriterion the subject chooses is influenced by his expectations about the

occur r ence of a sig na l. If the signa l is expected to occur fr equently, hewill be inclined to sa y yes m or e often (liber a l cr ite r ion) tha n in theca se he expects the signa l to occur only r a r ely.In deter m ining thr esholds with the yes-no m ethod such expecta tions m a ypla y a n im por t a nt r ol e.Va r ying the pr opor tion of singna ls ond bla nks in successiv e exper i m entsm a y lea d to v a r i a tion in the thr esholds found.If theyes- no method is used, it is Important to keep the overa ll odourstim ulus to bla nk r a tio consta nt in a ll expe r i m e nts, in or der to keep thesubjects' signa l expecta ncy a s consta nt a s possi ble.

4. PANEL REQUIREMENTSThe la st set of r equir e m ents in olfa ctom etr y is concer ned with thediffer en ces between pa nel m em ber s. People v a r y widely in theirsensitiv ity. A fa ctor of a 100 between the thr esholds of two subjects forthe sa m e substa nce is not uncom m on. For a num ber of substa nc es, specifica nosm i a 's or specific hyposm i a 's a r e found. In such ca ses a per son ha s nosensitiv ity a t a ll or a v er y high thr eshold for the giv en substa nce, butnor m a l sensitiv ity to other substa nces ( 1 ) . This is a n illustr a tion of thefa ct that sensitiv ity to odour s is specific r a ther tha n gener a l. This isa lso dem onstr a ted by Punter ( 2,3) who deter m ined the thr esholds of 69odor ous substa nces for the sa m e gr oup of subjects a nd ca lcula ted the

c o r r e l a t i o ns b e t w e en t h es e t h r e s h o l d s ( s e e f i g u r e 2 ) .

C O R R E L A T I O N C O E F F I C I E N T S

N-2348 88 ODORS

7 _ . 2 1 8

Figur e 2 . Histogr a m of the cor r ela tion coef ficients between the thr esholdsfor 69 differ ent odor ous substa nces obta ined fr om the sa m e gr oup ofsubjects (P.H. Pu n t e r ) .



91

The cor r ela tion coefficients cha nged fr om -.90 to 1.00 with a m ea n of.216. Ev en if specific gr oups of substa nces like the hom ologous ser ies ofthe fa tty-a cids or a gr oup of a r om a tics wer e singled out, the m ea n of the

cor r ela tion coeffi cients r ose only to .219 and .280 r espectiv ely.Ther efor e, it ca n be concluded tha t sensitiv ity to one odour or to a giv engr oup of odour s does not pr edict the subjects ' sensitiv ity to otherodour s. This m ea ns tha t selection of pa nelm e m ber s on the ba sis of theirsensitiv ity to a num ber of sta nda r d odour s is only v a lid in a s fa r a s ithelps to elim ina te gener a l a nosm ics (people suffer ing fr om com plete lossof sm ell) or gener a l hyp osm i cs. Fur ther m o r e, it will be clea r tha t r a therl a r ge gr oups of subjects a r e needed to obta in v a lid concentr a tion v a lue s.For the deter m i na tion of a r epr esenta tiv e thr eshold a t lea st 20 subjectsa r e needed. If on the other ha nd, one m er ely wa nts to m a ke r ela tiv eJudgem ents, a s in the ca se wher e one m a kes pr e- a nd posttests to m ea su r e

the effect of insta lling wa sher s or a fter bur n er s, a tr a ined pa nel of 8subjects or per ha ps ev en 6 m a y suffice, pr ov ided the sam e subjects a r eused thr oughout the m ea sur e m en ts.

In v iew of the intr a indiv idua l v a r i a tion in olfa ctor y sensitiv ity, whi chm a y be quite consider a ble, a pa nel of six subjects would be the a bsolutem i n i m u m .Intr a indiv idua l v a r i a tion in sensitiv ity m a y be due to the followings o u r c e s :A. Whea ther conditio ns:The da y a fter a depr ession subjects in Holla nd a r e m or e sensitiv e tha n theda ys bef or e . This m a y be due to the a ccom p a nying cha nge in hum idity.B . Illness:Com m on colds ca n influence sensitiv ity consider a bly a s we a ll know, butother illnesses which a r e a ccom p a nied with a cha nge of body tem per atur em a y a ct In this r espect a s wel l. Since the nose ha s a v er y gener ousbloodsupply, cha nges in this supply m a y influence olfa ction a lso.C. Hor m ona l cha nges :Wom en a r e usua lly m or e senstiv e tha n m en . They do a cquir e this super ior ityin part during the hormonal ch anges wh ich take place around pub erty. Atthe sa m e tim e wom en sta r t v a r ying in sensitiv ity in r ela tion to theirm enstr u a l cycle, being v er y sensitiv e a t ov ula tion a nd less sensitiv e atm e n s t r u a t i o n .

D . Ada pta tion:As pointed out ea r lier , a da pta tion or loss of sensitiv ity due to pr ev iousstimulation, is strong in the sense of smell and its effects are quitelongla sting. If a per son who liv es in a polluted a r ea com es ba ck fr omholida ys he or she m a y be m uch m or e sensitiv e to the sur r ounding odour s a sbefor e, but he or she will soon loose this sensitiv ity a ga in.E. H a b i t u a t i o n :Ha bitua tion or loss of inter est in m onotonou s stim ula tion m a y a lso be a nim por t a nt fa ctor . The intensity of m onotonous stim ula tion is usua llyestimated to be lower than that of single instances of the same physical

intensity-F. Novelt y:When, a fter a ser ies of a m onotonous stim uli , a nother stim ulus ispr esented the intensity of such a nov el stim ulus is usua llyo v e r e s t i m a t e d .G. Contrast:The perceived intensity of a stimulus is often determined by the contextin which it a ppea r s.



REFERENCES

93

(1) AMOORE, T.E., VENSTROM, D. and DAVIS, A.R. ( 196 8) Mea sur eme nt of

specific a nosm i a . Per cept. Motor Skills, 26, 1968, 143-164(2) PUNTER, P.H., r eported in: KBSTER, E.P. ( 197 8) Onder zoe k van de

r eukwa a r ne m ing.(3) PUNTER, P.H. (1983 ) Measur ement of human o lfact ory thres holds for

sev e r a l gr oups of str uctur a lly r ela ted com po unds. Chem ica lSenses, v ol 7, nr 3/4, 215-235.

(4 ) FRIJTERS, J.E.R. (197 8) A cr itica l a na lysis of the odour num ber a ndits use. Chem ica l Senses a nd Fla v our , v ol 3, nr 2, 227-23 3.



94

EXPERIENCES WITH TRANSPORTABLE OLFACTOMETERS

H. MANNEBECKInstitut fur Landwirtschaftliche Verfahrenstechnik der Universitat Kiel

Summary

Some experiences with development and application of portable andtransportable olfactometers are presented. Investigations have beencarried out to find differences in odour production of differentstall compartments in pig breeding and fattening units. For getting

more dates and decreasing the costs per measured sample it is necessary to increase the speed of measurement.

1.INTRODUCTIONIn the early 70's the increase of stock caused increasing problems

with odour immissions from livestock farming. For a practicable researchwork in this field, a portable olfactometer was required to get objectiveresults direct from the different odour emitting sources. Since that timeportable and transportable types of olfactometers have been developed.Some of our experience concerning the application of portable and transportable olfactometers is presented in this paper.

2. PORTABLE AND TRANSPORTABLE OLFACTOMETERS; DEVELOPMENT AND EXPERIEN CE

2.1 THE EARLY OLFACTOMETER TYPE TO 4In the beginning, a portable olfactometer operated only by one person

was required to measure odour direct at the odour emitting sources in andaround livestock house s. The early type TO 4 fulfilled both requirements.

It is basically a respirator supplied with oxygen from commercialsteel flasks or with 300 bar respirator air. A gas jet pump is driven bythe oxygen from the flask via a pressure reducing valve. This pump sucksthe odour loaded air via adjustable butterfly valves and flow meters andmixes it with the odourless oxygen. The mixture passes through a short pipeto the respirator mask. The flow of odourous air can be interrupted by aquickclosing handle to switch over from odourless oxygen to the adjusteddilution. The first years we used bigger masks covering nose and mouth. Theuser worked as panel leader and as panelist at the same time. Outdoors inan odourless area he had to start with the TO 4 connected to his nose,breathing only odourless oxygen. Then he entered the stall or the testingarea for measurement. The mask could never be held completely tight, sothis principal didn't deliver satisfying results. A smaller mask justcovering the nose was fit to the TO 4 type and the equipment was used in anodourless athmosphere only. Suction pipes were used for direct measurementand sample bags in case of greater distances. The.iresults were much moresatisfying than before.

The TO 4 type has been in use for years and it was made commercially.Totally more than 15 0 olfactometers TO 4 were manufactured. Concerning theuse of oxygen, pressed or synthetic air in flasks and gasjet pumps all further TO-types are based on this early TO 4 type.



97

3. APPLICATIONS

3.1 ODOUR FROM PIG KEEPINGOne of the main problems with intensive livestock keeping in villages

and near to dwelling houses are the odour emissions. Especially for working out guidelines like VDI 34 71 "E mission control, livestock management -pigs" knowledges about odour production from different species of animal,different stall types and different types of kepping areas in a stall arevery important.

In the last time, investigations have been carried out by using thecaravan with the olfactometer TO 6 type as described before. The main question was, whether pig breeding would produce less odour emissions per livestock unit than pig fattening. Pig breeding units normally are devided into different compartments: farrowing compartments, single ranging for sows,service station and flat deck batteries for piglets. Fattening housesmostly are devided into initial fattening and fishing. For olfactometricmeasurement samples from different compartments must be collected. Thesample collecting procedure is an important factor for getting comparableresults.

3.2 SAMPLE COLLECTING PROCEDUREThe samples normally should be collected at the ventilation shaft, but

sometimes it is impossible, because there are very high ridges. In thiscase the samples must be collected directly in the stall compartment whereclothes will become very odourous. Therefore nobody of the team is permit

ted to collect samples in the stall. Using the sampling device has to bevery easy, because each farmer must be able to do sampling without anyroutine.

The sampling device in use is a 50 litre cylindrical container with atransparent cover. An empty 30 litre sample bag with a stainless steel pipewill be put into the container. The pipe is pushed through the cover. APTFE tube will be fixed to the pipe to collect samples from differentpoints. On the transparent cover a battery operated vacuum cleaner and abattery are mounted. Only by pressing a push button the sample is filledin about 10 seconds. By using this sampling device sampling doesn' t makeany problems.

Tests with sampling pipes for dynamic sampling showed no significantdifferences to the used sampling system, because the time between samplingand measurement is very short.

3.3 MEASUREMENT AND RESULTSUp to now odour production of different pig house compartments has

been measured on 15 farms under winter conditions.The most important dates to get comparable results are: odour inten

sity as dilution level Z50 (1)> ventilation air flow rate V and number oflivestock units LU. The comparable emission level per livestock unit ELfrom each stall compartment will be:

vi - Z 5 0 x V

LU

Fig.3 shows the results of the measurement under winter conditions.

It was demonstrated with high significance that pig breeding in theaverage produces half as much odour as pig fattening.



99

D I S P E R S I O N M O D E L S F O R E M I S S I O N S F R O M A G R I C U L T U R A L S O U R C E S

G . - J . M E J E R a n d K . - H . K R A U S EI n s t i t u t f u r l a n d t e c h n i s c h e G r u n d l a g e n f o r s c h u n g d e r

B u n d e s f o r s c h u n g s a n s t a l t flir L a n d w i r t s c h a f t

S u m m a r y

T h e a i m o f d i s p e r s i o n m o d e l s is t h e p r e d i c t i o n o f a t m o s p h e r i c d i l u t i o no f p o l l u t a n t s in o r d e r to p r e v e n t o r a v o i d n u i s a n c e . E s t a b l i s h e d

d i s p e r s i o n m o d e l s , d e s i g n e d f o r t h e l a r g e s c a l e o f i n d u s t r i a l a i r p o l l u t i o n h a v e to be m o d i f i e d to t h e s m a l l s c a l e o f a g r i c u l t u r a l p o l l u t i o n s . An e x p e r i m e n t a l s e t u p is d e s c r i b e d to m e a s u r e a t m o s p h e r i cd i l u t i o n of t r a c e r g a s u n d e r a g r i c u l t u r a l c o n d i t i o n s . T h e e x p e r i m e n t a lr e s u l t s d e l i v e r t h e d a t a b a s e to i d e n t i f y t h e p a r a m e t e r s of t h e m o d e l s .F o r u n d i s t u r b e d a i r f l o w m o d i f i e d G a u s s i a n m o d e l s a r e a p p l i c a b l e . Fort h e c o n s i d e r a t i o n of o b s t a c l e s m o r e s o p h i s t i c a t e d m o d e l s a r e n e c e s s a r y .

1 . I N T R O D U C T I O NT h e a i m of d i s p e r s i o n m o d e l s is to d e v e l o p r e l i a b l e m e t h o d s f o r c a l c u

l a t i n g t h e a t m o s p h e r i c d i l u t i o n o f a i r b o r n e p o l l u t a n t s u n d e r p r a c t i c a lc o n d i t i o n s . O n e a p p l i c a t i o n in a g r i c u l t u r e is t h e d e t e r m i n a t i o n of t h a td i s t a n c e , a t w h i c h i . g . o d o u r i f e r o u s p o l l u t a n t s o f an a n i m a l f a r m a r ed i l u t e d in t h e a t m o s p h e r e to a c o n c e n t r a t i o n b e l o w a c e r t a i n t h r e s h o l d , ino r d e r to a l l o w t h e f a r m e r a p r o f i t a b l e p r o d u c t i o n a n d l i k e w i s e to p r e v e n to d o u r n u i s a n c e f r o m t h e n e i g h b o u r h o o d .

A n o t h e r a p p l i c a t i o n is t h e p r e d i c t i o n o f t h e e f f e c t i v e n e s s of c h a n g e si n t h e e m i s s i o n s o u r c e c o n f i g u r a t i o n , in o r d e r to r e d u c e t h e o d o u r n u i s a n c e

i n t h e e x i s t e n t v i c i n i t y . T h a t c o u l d h e l p to a v o i d e x p e n s i v e m i s i n v e s t m e n t s .In a i r p o l l u t i o n c o n t r o l it is u s e f u l l to s u b d i v i d e t h i s l a r g e p r o b l e m

i n t o t h r e e m a i n d i v i s i o n s /!/, f i g . 1:

EmissionQuelle

L u f t -

bewegungTransmission

VerdunnungImmissionBelastigung

F i g ^ 1 . E m i s s i o n - T r a n s m i s s i o n - I m m i s s i o n o f a i r b o r n p o l l u t a n t s .Q u e l l e = s o u r c e , L u f t b e w e g u n g = a t m o s p h e r i c f l o w , V e r d u n n u n gd i l u t i o n , B e l a s t i g u n g = n u i s a n c e .



100

- t h e e m i s s i o n ; t h i s i s t h e e n t r a n c e o f t h e a i r b o r n e p o l l u t a n t s i n t o t h eo p e n a t m o s p h e r e . T h e l o c a l p o s i t i o n o f t h i s e n t r a n c e i s t h e e m i s s i o ns o u r c e ,

- t h e t r a n s m i s s i o n , i n c l u d i n g a l l p h e n o m e n a o f t r a n s p o r t , d i s p e r s i o n a n dd i l u t i o n i n t h e o p e n a t m o s p h e r e ,

- t h e i m m i s s i o n ; t h i s i s t h e e n t r a n c e o f t h e p o l l u t a n t i n t o a n a c c e p t o r .

A s w e a r e r e g a r d i n g o d o r i f e r o u s p o l l u t a n t s , t h e i m m i s s o n i s t h e i re n t r a n c e i n t o a h u m a n n o s e .

A b o u t a i r p o l l u t i o n f r o m i n d u s t r i a l e m i s s i o n s o u r c e s , i . g. S 0 2 f r o mp o w e r p l a n t s , a w i d e k n o w l e d g e i s a v a i l a b l e , i n c l u d i n g s o p h i s t i c a t e dm e t h o d s o f e m i s s i o n m e a s u r e m e n t , a t m o s p h e r i c d i f f u s i o n c a l c u l a t i o n a n dm e a s u r e m e n t o f i m m i s s i o n c o n c e n t r a t i o n i n t h e a m b i e n t a i r . I n m o s t c o u n t r i e sw e h a v e c o m p l e t e n a t i o n a l l e g a l r e g u l a t i o n s , c o n c e r n i n g l i m i t a t i o n o f a i r

c o n t a m i n e n t e m i s s i o n s , c a l c u l a t i o n o f s t a c k h e i g h t a n d a t l e a s t e v a l u a t i o na n d d e t e r m i n a t i o n o f m a x i m u m i m m i s s i o n v a l u e s . W i t h i n t h i s s i t u a t i o n t h eq u e s t i o n a r i s e s , w h e t h e r t h e s e w e l l p r o v e d m e t h o d s a n d d e v i c e s a r e s u i t a b l ef o r a g r i c u l t u r a l o d o u r e m i s s i o n s f r o m a g r i c u l t u r a l s o u r c e s t o o .

I t i s w e l l k n o w n t h a t al l c a l c u l a t i o n s a n d v a l u e s , e s t a b l i s h e d i n a i rp o l l u t i o n c o n t r o l , a r e b a s e d o n l a r g e s e t s o f d a t a , o b t a i n e d b y am u l t i t u d e o f e x p e r i m e n t s a n d o b s e r v a t i o n s .

T h e a t t e m p t t o a p p l y t h e s e e s t a b l i s h e d d i s p e r s i o n m o d e l s t o a g r i c u l t u r a le m i s s i o n s o u r c e s , l e a d s t o u n r e a s o n a b l e r e s u l t s . A c o m p a r i s o n i n t a b l e 1s h o w s t h a t t h e l a r g e s c a l e v a l u e s o f i n d u s t r i a l a i r p o l l u t i o n s , o n w h i c ht h e e s t a b l i s h e d d i s p e r s i o n m o d e l s a r e b a s e d , a r e t o o d i f f e r e n t f r o m t h o s e

i n a g r i c u l t u r e . In o r d e r t o m o d i f y t h e e x i s t i n g d i s p e r s i o n m o d e l s o r t od e s i g n o t h e r t y p e s o f m o d e l s , w e n e e d t h e c o r r e s p o n d i n g s e t s o f o bs er va t i on sa n d o f e x p e r i m e n t a l d a t a , a d e q u a t e t o t h e t y p i c a l a g r i c u l t u r a l c o n d i t i o n s .T h e r e a r e a l r e a d y a l o t o f i n v e s t i g a t i o n s t o m e a s u r e o d o u r a t t h e s o u r c ea n d i n t h e a m b i e n t a i r . B u t w e a l l k n o w a b o u t t h e r e l i a b i l i t y o f t h o s em e a s u r e m e n t s a n d a b o u t t h e d i f f i c u l t i e s t o q u a n t i f y t h e s e r e s u l t s a d e q u a t et o a c o m p u t e r m o d e l c a l c u l a t i n g t h e r e l a t i o n b e t w e e n e m i s s i o n a n d i m m i s i o nd e p e n d i n g o n v a r i o u s i n f l u e n c e s a n d p a r a m e t e r s . S o w e d e c i d e d t o s u p p l e m e n tt h e o d o u r m e a s u r e m e n t s b y t r a c e r g a s m e a s u r e m e n t s e a s y t o r e a l i s e w i t h h i g ha c c u r a c y . T h e a i m i s t o g e t t h e n e c e s s a r y s e t s o f e x p e r i m e n t a l d a t a f o r t h em o d i f i c a t i o n o f e x i s t i n g d i s p e r s i o n m o d e l s f o r a g r i c u l t u r a l c o n d i t i o n s .

2 . I N S T R U M E N T A L

2 . 1 E M I S S I O NT h e p u b l i s h e d g u i d e l i n e V D I 3 88 1 / 2 - 4 / d e s c r i b e s , h o w t o m e a s u r e o d o u r

e m i s s i o n s f o r a p p l i c a t i o n i n d i s p e r s i o n m o d e l s . R e s u l t s o b t a i n e d b y t h i sm e t h o d h a v e t o b e c o m p l e t e d w i t h p h y s i c a l d a t a l i k e f l o w r a t e s e t c . A so l f a c t o m e t r i c o d o u r t h r e s h o l d d e t e r m i n a t i o n i s r a t h e r e x p e n s i v e , i t i ss u p p l e m e n t e d w i t h t r a c e r g a s e m i s s i o n s , e a s y t o q u a n t i f y . In t h e m o b i l et r a c e r g a s e m i s s i o n s o u r c e , f i g . 2 , u p t o 5 0 k g p r o p a n e p e r h o u r a r ed i l u t e d w i t h u p t o 1 0 0 0 m 3 a i r p e r h o u r . T h i s b l e n d i s b l o w n i n t o t h e o p e n

a t m o s p h e r e . T h e d i l u t i o n d e v i c e , i n c l u d i n g t h e f a n , c a n b e s e p e r a t e d f r o mt h e t r a i l e r a n d m o u n t e d a t a n y p l a c e , e . g . o n t o p o f a r o o f t o s i m u l a t e t h ee x a u s t o f a p i g h o u s e o r i n t h e m i d d l e o f a f i e l d t o s i m u l a t e u n d i s t u r b e da i r f l o w .

2 . 2 T R A N S M I S S I O NF o r s a f e t y r e a s o n s , p r o p a n e c o n c e n t r a t i o n a t t h e s o u r c e i s a l w a y s b e l o w

t h e l o w e r i g n i t i o n c o n c e n t r a t i o n o f 2, 1 % . A s t h e s p e c i f i c g r a v i t y o f t h i se m i t t e d p r o p a n e - a i r - b l e n d i s v e r y c l o s e t o t h a t o f p u r e a i r ( d i f f e r e n c e lesst h a n 0 , 2 % ) a n d a s f l o w p a r a m e t e r s c a n b e c h o s e n i n a w i d e r a n g e , w e a s s u m e



1 0 2

t h a t t h e a t m o s p h e r i c d i f f u s i o n o f t h i s b l e n d i s e q u a l t o t h a t o f o d o u r -p o l l u t e d a i r f r o m a g r i c u l t u r a l e m i s s i o n s o u r c e s .

I n a f i r s t s t e p t h e d i s p e r s i o n i n a n u n d i s t u r b e d a t m o s p h e r i c f l o w w a sm e a s u r e d . In a s e c o n d s t e p t h e d i s p e r s i o n i n a n a t m o s p h e r i c f l o w w i t ho b s t a c l e s i s d e s i g n a t e d . In a t h i r d s t e p t h e d i s p e r s i o n i n t h e n e i g h b o u r h o o do f r e al f a r m b u i l d i n g s i s i n t e n d e d .

2 . 3 I M M I S S I O N

2 .3 .1 S P A T I A L D I S T R I B U T I O N O F T R A C E R G A S C O N C E N T R A T I O NT o o b t a i n m u l t i p l e s e t s o f e x p e r i m e n t a l d i s p e r s i o n d a t a , i n e a c h

e x p e r i m e n t 5 0 s a m p l e s o f t r a c e r - p o l l u t e d a m b i e n t a i r d o w n w i n d i n t h e p l u m eo f t h e p r o p a n e e m i s s i o n s o u r c e a r e t a k e n b y 1 0 s a m p l e u n i t s , d i s t r i b u t e d i nt h e f i e l d , s e e f i g . 3 . E a c h u n i t c a r r i e s f i v e g l a s s c y l i n d e r s , f i l l e d w i t h

rtL^J /

\

F i g . 3 . E x p e r i m e n t a l s e t u p f o r f i e l d m e a s u r e m e n t s w i t h o u to b s t a c l e s .

w a t e r a n d c o n n e c t e d w i t h s m a l l t u b e s t o t h e d i f f e r e n t i m m i s s i o n s a m p l eh e i g h t s , s e e f i g . 4 . P a s s i n g a t h r o t t l e a n d a s o l e n o i d v a l v e , t h e w a t e rf l o w s d o w n b y t h e f o r c e o f g r a v i t y i n t o a t a n k , t h u s s u c k i n g t h e s a m p l ea i r i n t o t h e g l a s s c y l i n d e r s . A t t h e e n d o f e a c h e x p e r i m e n t , t h e s e a i rs a m p l e s a r e a n a l y s e d in a f l a m e i o n i s a t i o n d e t e c t o r ( F I D ) . T h e F I D r e s p o n s es i g n a l i s n o t s e l e c t i v e t o p r o p a n e b u t t o a ll h y d r o c a r b o n s . F o r c o m p e n s a t i o no f t h e a c t u a l a m b i e n t b a c k g r o u n d H C - c o n c e n t r a t i o n o n e s a m p l e u n i t i s p l a c e di n a p o s i t i o n ( c ) , u n p o l l u t e d b y t h e p r o p a n e s o u r c e ( a ) .

A s t h e s a m p l e t i m e i s s e t t o 2 - 1 0 m i n u t e s b y a d j u s t m e n t o f t h e w a t e rf l o w t h r o t t l e , t h i s e x p e r i m e n t a l s e t u p d e l i v e r s t i m e m e a n v a l u e s , a s u s u a li n i m m i s s i o n m o n i t o r i n g a s w e l l a s i n e s t a b l i s h e d d i s p e r s i o n m o d e l s .

2 . 3 . 2 T E M P O R A L F L U C T U A T I O N O F T R A C E R G A S C O N C E N T R A T I O NO b s e r v a t i o n s o f s m o k e p l u m e s , f i r s t b r i e f t e s t s a n d s o m e p a p e r s / 5 , 6 /

s u g g e s t t h a t t h e i m m i s s i o n c o n c e n t r a t i o n i s f l u c t u a t i n g in a w i d e r a n g en e a r t h e s o u r c e . H u m a n n o s e i s m o r e s e n s i t i v e t o o d o u r c o n c e n t r a t i o nf l u c t u a t i o n t h a n , d u e t o a d a p t i o n , t o c o n s t a n t o d o u r c o n c e n t r a t i o n . In f i g . 5i t i s s h o w n q u a l i t a t i v l y t h a t o d o u r p e r c e p t i o n m a y o c c u r d u e t o c o n c e n t r a -t i o n f l u c t u a t i o n s a l t h o u g h t h e m e a n v a l u e i s f a r b e l o w t h e o d o u r t h r e s h o l d .In t a b l e 1 i t is i n d i c a t e d t h a t t h e d i s t a n c e b e t w e e n a g r i c u l t u r a l e m i s s i o ns o u r c e s a n d r e c e p t o r i s r e l a t i v e l y s m a l l i n r e l a t i o n s h i p t o i n d u s t r i a l



104

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F i g . 6. E x p e r i m e n t a l s e t u p to m e a s u r e and r e c o r dc o n c e n t r a t i o n f l u c t u a t i o n ,w a h l w e i s e = o p t i o n a l

t h r o u g h t h e F I D a n d p r o p a n e p o l l u t i o n is o n - l i n e a n a l y s e d a n d d i g i t a l l yr e c o r d e d . T h e r e s p o n s e t i m e o f t h e F I D is a b o u t o n e s e c o n d , c o m p a r a b l e tot h e r e s p o n s e t i m e o f t h e h u m a n n o s e .

F r o m t h i s e x p e r i m e n t a l s e t u p , w e e x p e c t d e t a i l e d i n f o r m a t i o n h o w t h ei n f l u e n c e of f l u c t u a t i o n h a s to be e v a l u a t e d , h o w i m p o r t a n t it is u n d e rd i f f e r e n t d i f f u s i o n c o n d i t i o n s a nd h o w it c a n be t a k e n i n t o c o n s i d e r a t i o ni n d i s p e r s i o n m o d e l s .

3 . T H E O R E T I C A L B A C K R O U N D F O R P O L L U T I O N P R E D I C T I O NT h e t h r e e - d i m e n s i o n a l t r a n s p o r t e q u a t i o n f o r i n e r t p o l l u t a n t d i s p e r

s i o n r e s u l t s f r o m t i m e - s m o o t h i n g t h e e q u a t i o n of c o n t i n u i t y of t h e e m i t t e ds u b s t a n c e . In C a r t e s i a n c o o r d i n a t e s t h e d i s t r i b u t i o n o f a p u l l u t a n t isg i v e n by t h e p a r t i a l d i f f e r e n t i a l e q u a t i o n of s e c o n d o r d e r f o r t h e c o n c e n t r a t i o n C ( x , y , z , t ) PI:

M + U ^ x + V3 y

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3z uz 5z ; (3.1)

x , y , z a r e c o o r d i n a t e s , t is t i m e . It is a s s u m e d t h a t an e l e v a t e d c o n t i n u o u s p o i n t s o u r c e at h e i g h t H is e m i t t i n g i n t o a s e m i - i n f i n i t e a t m o s p h e r ea b o v e t h e g r o u n d , d i s c r i b e d by t h e x - y - p l a n e at z = 0 . T h e z-axis e x t e n d sv e r t i c a l l y to t h e g r o u n d . T h e o r i g i n o f t h e c o o r d i n a t e s y s t e m is at theg r o u n d l e v e l b e n e a t h t h e s o u r c e l o c a t i o n . T h e w i n d h a s c o m p o n e n t s U, V a n dw p a r a l l e l to t h e x - , y - a n d z - a x i s . K x , K y a n d K z a r e t h e e d d y d i f f u s i v i -t i e s in t h e c o r r e s p o n d i n g d i r e c t i o n s . D a t a on t h e w i n d f i e l d a n d on thed i f f u s i o n a r e t h e m e t e o r o l o g i c a l i n p u t s r e q u i r e d by an a t m o s p h e r i c t r a n s p o r t m o d e l .

I n o r d e r to m a k e t h e t r a n s p o r t m o d e l a d a p t a b l e to m e a s u r e m e n t r e s u l t ss o m e s i m p l i f i c a t i o n s a r e u s e d . V e r t i c a l and l a t e r a l c o m p o n e n t s o f w i n d a r en e g l i b l e , t h e m e a n t r a n s p o r t v e l o c i t y U in x - d i r e c t i o n is s t e a d y ; t h e p o l l u t a n t t r a n s f e r by a d v e c t i o n in t h e d r i f t d i r e c t i o n is g r e a t e r t h a n by



106

AK

IIII I I - 1III-2IVV

F

1,2940,8010,6400,6590,8761,503

f

0,7180,7540,7840,8070,8230,833

G

0,2410,2640,2150,1650,1270,151

g

0,6620,7740,8850,9961,1081,219

m

0,4190,3690,2820,2230,2050,089

Ak

5432

F

0,251.190,820,94

Fo

194354198168

f

0,720,670,740,76

G

0,690,600,090,08

Go

48421212

9

0,590,741,111,28

m

0,400,280,220,11

T a b l e 2 . C o e f f i c i e n t s o f d i f f u s i v i t y d e p e n d e n t on s t a b i l i t yc l a s s e s a f t e r K l u g and T u r n e r ; m s t a n d s for thee x p o n e n t in the p o w e r law of w i n d v e l o c i t y .

H o w e v e r , w e m u s t k e e p in m i n d the l i m i t a t i o n s of t h i s a p p r o a c h ,e s p e c i a l l y the t r a n s f e r of c o n s i s t e n t s e t s o f d i s p e r s i o n p a r a m e t e r s to thep r o p a g a t i o n of air p o l l u t i o n in the v i c i n i t y o f a s o u r c e . Th e G a u s s i a np l u m e f o r m u l a s h o u l d be u s e d o n l y for t h o s e d o w n w i n d d i s t a n c e s for w h i c ht h e e m p i r i c a l d i f f u s i o n c o e f f i c i e n t s h a v e b e e n d e t e r m i n e d by s t a n d a r dd i f f u s i o n e x p e r i m e n t s . B e c a u s e w e are i n t e r e s t e d in e m i s s i o n s n e a r g r o u n dl e v e l and i m m i s s i o n s n e a r b y the s o u r c e , w e use t h o s e d i f f u s i o n p a r a m e t e r sw h i c h are b a s e d on the c l a s s i f i c a t i o n o f K l u g / 1 2 / and T u r n e r / 1 3 / . Thep a r a m e t e r s a re e x p r e s s i b l e as p o w e r f u n c t i o n s ,

o y ( x ) = F x f and o z ( x ) = G x 9 a f t e r K l u g ( 3 . 6 a , b ) ,

c ( x ) = (FQ + F x ) f and a z ( x ) = (GQ + G x ) g a f t e r T u r n e r ( 3 . 7 a , b ) .

T h e p a r a m e t e r c l a s s i f i c a t i o n a f t e r K l ug is d e t e r m i n e d by six s t a b i l i t yc l a s s e s ( w i t h the G e r m a n a b b r e v i a t i o n AK for A u s b r e i t u n g s k l a s s e ) , r e a c h i n gf r o m e x t r e m e s t a b l e (AK I) to e x t r e m e l a b i l e TAK V ) . In the T u r n e rs t a b i l i t y s c h e m e AK 5 d e n o t e s e x t r e m e s t a b l e , AK 2 e x t r e m e l a b i l e , seet a b l e 2 . An e s t i m a t e o f the s t a b i l i t y can be m a d e f r o m s y n o p t i c a l o b s e r v a t i o n s o f s o l a r r a d i a t i o n , c l o u d c o v e r and w i n d v e l o c i t y / 1 4 / . W i t h thep a r a m e t e r s a f t e r K l u g e q u a t i o n ( 3 . 4 ) b e c o m e s

C (x ,y ,z ) = a x ' ^ e x p C - b x " ^ ) [e x p (-d 0 x_ 2 g

) + e x p ( - d 1 x "29 ) ]

wherein

Co

V

2TT UFG ' = £ p - .( z - H ) '

2G<(z+H)

2

( 3 . 8 ) ,

( 3 . 9 a , b , c , d ) .



107

I n t h e m e a n d i r e c t i o n , y = 0 , t h e f i r s t e x p o n e n t i a l e x p r e s s i o n g i v e s

( e x p ( - x "

2 f

) )

b

= 1 f o r b = 0 a n d a l l x > 0.E q u a t i o n ( 3 . 8 ) i s r e d u c e d t o

C ( x . y , z ) = a x "( f

* 9J

[ e x p ( - d 0 x "2 g

) + e x p ( - d l X "2 g

) ] ( 3 . 1 0 ) .

T h e e s s e n t i a l b e h a v i o u r o f t h e t r a n s p o r t m o d e l i n t h e v i c i n i t y o f t h es o u r c e c a n b e d i s c u s s e d b y t h e e q u a t i o n ( 3 . 1 0 ) , s e a r c h i n g f o r t h e m a x i m u mc o n c e n t r a ti o n in d i r e c ti o n o f t h e c e n t e r l i n e , d C / d x = 0 . F r o m e q u a t i o n( 3 . 1 1 ) t he d i s t a n c e x > 0 i s c o m p u t a b le a t w h i c h m a x i m u m c o n c e n t r a t i o no c c u r s :

2 gd „ d , d - d . „ d - d ,

T?f [ 1 X e x p ( i 2 g ) ] - ^ P + ^ P t - ^ g 1 ) ] <3.11).

A t g r o u n d l e v e l , z = 0 a n d d Q = d 1 = ̂ - , x m a x b e c o m e s

H2

x m a x = " Z G r( 3 . 1 3 ) .

E s t a b l i s h i n g t h e v a l u e s a t th e e m i s s i o n l ev el z = H , d = 0 a n d d . = H 2 / G Z ,xm a x

c a n be c a l c u l a t e d f r o m t n ef o l l o w i n g r e l a t i o n s h i p

exp (- - J L - )2 g H *

b xm a x 2g ,, ...

TTV 1 + exp (. f f_} =xmax (3.14)

G ! x ' 9

m a x

b y i t e r a t i o n m e t h o d s . If it i s a s s u m e d t h a t t h e e x p o n e n t i a l e x p r e s s i o n is< 1 , e q u a t i o n ( 3 . 1 4 ) r e d u c e s t o

"max " k^W exP(- T l V ^ <

3-

1 5 );

m a xt h a t m e a n s

1xm a x

( z = H ) " xm a x

( z = 0 ) P e x P ( XT } ^ <3. 1 6 ) .

m a x m a x G ' x 2 ^ ( z = H )F o r t h e r a t i o o f c o n c e n t r a t i o n a t t h e g r o u n d t o t h a t a t t h e p l u m e

c e n t e r l i n e a t e m i s s i o n - l e v e l t h e r e l a t i o n s h i p

c ( x , y 0 . z * 0 ).

Z e x p ( - ^ f f i )

clx.y-U.z-HJ " , exp(. f | a , <3'

1 7>

c a n b e o b t a i n e d . A t t h e d i s t a n c e o f m a x i m u m g r o u n d - l e v el c o n c e n t r a t i o n t h ec o n c e n t r a t i o n a t z = H is a b o u t o n e - h a l f g r e a t e r t h a n t h e c o n c e n t r a t i on a tg r o u n d , w h e n A K = I I i s c h o s e n .

4 . R E S U L T S A N D D I S C U S S I O NF r o m s ev e ra l f i e l d e x p e r i m e n t s o f m e a s u r i n g t h e c o n c e n t r a t i o n d i s t r i

b u t i o n in th e v i c i n i t y o f a n e m i s s i o n s o u r c e o n e e x a m p l e i s s e l e c t e d f o r



110

In t h e s p e c i a l c a s e s h o w n h e r e , t h e G a u s s i a n p l u m e m o d e l d o e s n o t p r e d i c tt h e l o c a t i o n o f t h e m a x i m u m c o n c e n t r a t i o n i n a g r e e m e n t w i t h t h e e x p e r i m e n t ,b u t i t i s a p p r o p r i a t e t o d e t e r m i n e t h e c o n c e n t r a t i o n d e c a y i n d o w n w i n dd i r e c t i o n . T h a t w h a t h a p p e n s b e t w e e n t h e p o i n t s o u r c e l o c a t i o n a n d t h em a x i m u m l o c a t i o n i s o f a c c a d e m i c i n t e r e s t o n l y . A q u e s t i o n f o r p r a c t i c a lp u r p o s e i s h o w w e c a n g e t i n f o r m a t i o n a b o u t t h e m a x i m u m l o c a t i o n , w h e r ef r o m t h e m o d e l i s r e a l i s t i c .

F r o m e q u a t i o n ( 3 . 1 3 ) w e c a n d e d u c t a r o u g h a p p r o x i m a t i o n o f t h el o c a t i o n w h e r e m a x i m u m g r o u n d - l e v e l c o n c e n t r a t i o n o c c u r s . It i s a r g u e dt h a t t h e t u r b u l e n t d i f f u s i o n a c t s m o r e a n d m o r e on t h e e m i t t e d s u b s t a n c e s ,w h e n t h e d i s t a n c e f r o m t h e p o i n t s o u r c e i n c r e a s e s : t h e r e f o r e t h e d o w n w i n dd i s t a n c e d e p e n d e n c y o f t h e d i f f u s i o n c o e f f i c i e n t s i s d o n e a f t e r w a r d s . I fw e d r o p t h i s d e p e n d e n c y , e q u a t i o n ( 3 . 1 3 ) l e a d s t o X m a X = 3 4 , 4 m f o r A K = I

( c u r v e a ) a n d x m a x = 8 7 , 7 m f o r A K = V ( c u r v e b ) , w h a t i s d e m o n s t r a t e d i nf i g . 1 1 . T h e i n t e r p o l a t e d r a n g e s o f m e a s u r e d v a l u e s a r e l i n e d i n . C u r v e ao v e r e s t i m a t e s t h e n o n d i m e n s i o n a l c o n c e n t r a t i o n m a x i m u m , b u t i t s l o c a t i o ns e e m s t o b e c o r r e c t . In t h e c a s e o f c u r v e b t h e s i t u a t i o n i s i n v e r t e d .C u r v e c i s c a l c u l a t e d w i t h t h e d a t a o f A K = I I . T h e d e c a y o f t h e n o n d i m e n s i o na l c o n c e n t r a t i o n i s p r e d i c t e d w e l l b e h i n d t h e m a x i m u m . C u r v e d i sp r o d u c e d w i t h F = 1 2 , 1 , f = 0 , 0 6 9 , G = 0 , 0 4 a n d g = 1 , 0 8 8 . T h e a s c e n t o fc o n c e n t r a t i o n i s a c c e p t a b l e , b u t t h a t i s a l l , b e c a u s e t h e r e i s n o e x p l a n a t i o n o f p l a u s i b i l i t y h o w t o a l t e r t h e d i f f u s i v i t y p a r a m e t e r s . T h e r e f o r e i tm u s t b e o u r a i m to f i n d a s u i t a b l e c o r r e c t i o n i n c o n n e c t i o n w i t h t h em e t e o r o l o g i c a l i n p u t d a t a .

75

i? 5

25

Wc

/ /

u /L

- . ^ ^ a

1 ^

b

d ^ ~ ~ ~ ~ ~

25 50 7 5 m 1 00

F i g . 1 1 . C a l c u l a t e d C / C 0 - d i s t r i b u t i o n s f o r d i f f e r e n t d i f f u s i v i t y p a r a m e t e r s ,

c u r v e a ) F = 1 , 2 9 4 , G = 0 , 2 4 1 , f = 0 , 5 0 0 , g = 0,500c u r v e b ) F = 1 , 5 0 3, G = 0 , 1 5 1 , f = 0 , 5 0 0 , g = 0,500c u r v e c ) F = 0 , 8 0 1 , G = 0 , 2 6 4 , f = 0 , 7 5 4 , g = 0,774c u r v e d ) F = 1 2 , 1 0 , G = 0 , 0 4 0 , f = 0 , 0 6 9 , g = 1 , 0 8 8 .

O n e w a y m a y b e t h a t w e d o n o t n e g l e c t d i f f u s i v i t y K x i n x - d i r e c t i o n .E q u a t i o n ( 3 . 2 ) m u s t b e e x t e n d e d b y K x 3

2 C / 3 x 2 o n t h e r i g h t s i d e . T u r b u l e n td i f f u s i v i t y i s n o p r o p e r t y o f m a t e r i a l , i t i s a f u n c t i o n o f t h e w i n d f i e l d .T h e r e f o r e w e m u s t m a k e u s e o f al l i n f o r m a t i o n w e c a n g e t a b o u t t h e w i n df i e l d . T h e m e a n w i n d s p e e d i s o n e c h a r a c t e r i s t i c m e a s u r e o f t h e a t m o s p h e r i c



I l l v e l o c i t y f i e l d ; a n o t h e r o n e i s g i v e n b y t h e f l u c t u a t i o n u

1 i n f o r m o f t h e t u r b u l e n c e d e g r e e T u = / u '

2/ U . F o r y = 0 a n d z = 0 t h e c o n c e n t r a t i o n

r e l a t i o n s h i p i s m o d i f i e d , C o V H * a x H *

H e r e i n w e h a v e a s s u m e d

° x H *

irzw<i < 4 - 2 > -a x m a y b e r e l a t e d t o t h e t u r b u l e n c e d e g r e e T u ; i n t h e u s e d e x a m p l e T u = 0 , 2 4 3 . B y o x t h e c o n c e n t r a t i o n o f e q u a t i o n ( 4 . 1 ) i s r e d u c e d . W e w i l l s e e

i f t h e r e e x i s t s a n y u s a b l e f o r m o x = f ( T u , x ) .

5 . C O N C L U S I O N S F i e l d m e a s u r e m e n t s w e r e m a d e t o g e t i n f o r m a t i o n a b o u t t h e c o n c e n t r a -

t i o n d i s t r i b u t i o n n e a r b y e m i s s i o n s o u r c e s . I n c o n t r a s t t o i n d u s t r i a l e m i s s i o n s t h e s o u r c e h e i g h t i s g i v e n b y f e w m e t e r s o n l y i n a g r i c u l t u r e . I n a c c o r d a n c e t o i n d u s t r i a l e x p e r i e n c e s p r e d i c t i o n m o d e l s h o l d f o r p o i n t s o u r c e s o f l o w h e i g h t , t o o , e s p e c i a l l y t h e G a u s s i a n p l u m e m o d e l a p p l i e d h e r e . B u t i t i s n e c e s s a r y t o g e t m e t e o r o l o g i c a l d a t a w i t h r e g a r d t o t h e d e t e r m i n a t i o n o f t h e c o n c e n t r a t i o n m a x i m u m a t d i f f e r e n t l e v e l s . T h i s c a n b e d o n e b y t h e p r e s e n t e d w a y o f c o n c e n t r a t i o n m e a s u r e m e n t . T h e r e i s a l a c k o f

e x p e r i m e n t a l d a t a t o g i v e a n a c c u r a t e c o r r e c t i o n o f t h e d i f f u s i v i t y p a r a m e t e r s .

F u r t h e r m o r e w e h a v e t o p r o v e t h e i n f l u e n c e o f o b s t a c l e s n e a r b y t h e e m i s s i o n s o u r c e . S u c h o b s t a c l e s w i l l i n d u c e m e c h a n i c a l t u r b u l e n c e t o t h e w i n d t u r b u l e n c e . I n l a r g e s c a l e s i m u l a t i o n s u c h e f f e c t s a r e p a r a m e t e r i z e d ; t h e t u r b u l e n c e i n f l u e n c e i s c o l l e c t e d i n g e n e r a l d i f f u s i o n c o e f f i c i e n t s . In t h e s m a l l s c a l e o f t h e s o u r c e v i c i n i t y t h i s m e t h o d i s s t i l l q u e s t i o n a b l e .

I t i s i n d u b i t a b l e t h a t i n m e c h a n i c a l l y u n d i s t u r b e d w i n d f l o w t h e e x -p a n s i o n m e c h a n i s m i s a l w a y s t h e s a m e , " m e r e l y " t h e b o u n d a r y c o n d i t i o n s a t g r o u n d l e v e l a r e m o r e o b v i o u s f o r t h e t e s t e d e m i s s i o n h e i g h t s . T h e d i l u t i o n f a c t o r a f t e r 6 0 m i s a b o u t 2 ■ 10"* a t a w i n d s p e e d o f 2 , 5 m / s .

R E F E R E N C E S

( 1 ) V D I 2 4 5 0 B l a t t 1 : M e s s e n v o n E m i s s i o n , T r a n s m i s s i o n u n d I m m i s s i o n l u f t v e r u n r e i n i g e n d e r S t o f f e , B e g r i f f e , D e f i n i t i o n e n , E r l a u t e r u n g e n . S e p t . 1 9 7 7 .

( 2 ) V D I 3 8 8 1 B l a t t 1 E n t w u r f : O l f a k t o m e t r i s c h e T e c h n i k d e r G e r u c h s s c h w e l -l e n b e s t i m m u n g , G r u n d l a g e n . N o v e m b e r 1 9 8 3 .

( 3 ) V D I 3 8 8 1 B l a t t 2 E n t w u r f : P r o b e n a h m e für d i e G e r u c h s s c h w e l l e n b e s t i m -m u n g m i t d e m O l f a k t o m e t e r .

( 4 ) V D I 3 8 8 1 B l a t t 3 E n t w u r f : M e s s e n d e r G e r u c h s s c h w e l l e m i t d e n O l f a k t o -m e t e r n M o d e l 1 1 1 5 8 u n d T 0 4 .

( 5 ) K E D D I E , A . W . C . : P r e d i c t i o n o f o d o u r n u i s a n c e . C h e m . a n d I n d . L o n d . ( 1 9 8 4 ) 9 , S . 3 2 3 - 3 2 6 .

( 6 ) M E D R O W , w . a n d C . J O R G E N S : D i e S i m u l a t i o n d e r G e r u c h s a u s b r e i t u n g . S t a u b - R e i n h a l t . L u f t 4 4 ( 1 9 8 4 ) S . 4 7 5 - 4 7 9 .

( 7 ) P A S Q U I L L , F . : A t m o s p h e r i c d i f f u s i o n . N e w Y o r k : J . W i l e y 1 9 7 4 . ( 8 ) S H I R , C . C . , L . J . S H I E H : A g e n e r a l i z e d u r b a n a i r p o l l u t i o n m o d e l a n d

i t s a p p l i c a t i o n t o t h e s t u d y o f S O 2 d i s t r i b u t i o n s i n t h e S t . L o u i s m e t r o p o l i t a n a r e a . J . A p p l . M e t e o r o l o g y 1 3 ( 1 9 7 4 ) , S . 1 8 5 - 2 0 4 .



112

( 9 ) H E I N E S , T . S . , L . K . P E T E R S : A n a n a l y t i c a l i n v e s t i g a t i o n o f e f f e c t o fa f i r s t o r d e r c h e m i c a l r e a c t i o n o n t h e d i s p e r s i o n o f p o l l u t a n t s i nt h e a t m o s p h e r e . A t m o s p h e r i c E n v i r o n m e n t 7 ( 1 9 7 2 ) S . 1 5 3 - 1 6 2 .

( 1 0 ) C A R S L A W , H . S . , J . C . J A E G E R : C o n d u c t i o n o f h e a t i n s o l i d s . O x f o r d :C l a r e d o n P r e s s 1 9 5 9 .

( 1 1 ) S C H Ö N B U C H E R , A . , V . S C H E L L E R : A u s b r e i t u n g v o n A b g a s f a h n e n . C h e m . - I n g .T e c h n . 5 3 ( 1 9 8 1 ) N r . 5 , S . 3 2 0 - 3 3 4 .

( 1 2 ) K L U G , W . : E i n V e r f a h r e n z u r B e s t i m m u n g d e r A u s b r e i t u n g s b e d i n g u n g e na u s s y n o p t i s c h e n B e o b a c h t u n g e n . S t a u b - R e i n h a l t . L u f t 2 9 ( 1 9 6 6 ) N r . 4 ,S . 1 4 3 - 1 4 7 .

( 1 3 ) T U R N E R , D . B . : W o r k b o o k o f a t m o s p h e r i c d i s p e r s i o n e s t i m a t e s . P u b l i cH e a l t h S e r v i c e P u b l i c a t i o n N o . 9 9 9 - A P - 2 6 . W a s h i n g t o n : D e p a r t m e n t o fH e a l t h , E d u c a t i o n a n d W e l f a r e 1 9 6 9 .

( 1 4 ) R d E r l . d . M i n i s t e r s für A r b e i t , G e s u n d h e i t u n d S o z i a l e s v o m1 4 . 4 . 1 9 7 5 , V e r w a l t u n g s v o r s c h r i f t e n z u m G e n e h m i g u n q s v e r f a h r e n n a c h§ § 6 , 15 - B u n d e s - I m m i s s i o n s s c h u t z g e s e t z ( B I m S c h G ) für M i n e r a l ö r a f f i -n e r i e n un d p e t r o c h e m i s c h e A n l a g e n z u r K o h l e n w a s s e r s t o f f h e r s t e l l u n g( R a f f i n e r i e - R i c h t l i n i e ) M i n i s t e r i a l b l a t t f u r d a s L a n d N o r d r h e i n -W e s t f a l e n , J a h r g a n g 1 9 7 5 , N r . 6 5 , S . 9 9 6 - 1 0 0 7 .



114

framework of a research comparing the emission of three housing systems.All panel members were employed by the Institute of Poultry Research at

Beekbergen. Due to the limited dimensions of experimentation room, panelmembers were asked to smell one at the time. Prior to experimentation,the olfactometer was modified so that panel members could not read theflowmeters or see its operation by the experimenter (fig. 1 ) . Theolfactometer can be classified as a variable flow type. Average flowratewas 3 1/min. Dilution air was obtained from a cylinder filled with withmedical grade compressed air. Research result using criterion freemethods as well as threshold methods are descriped by respectivelyFrijters et al. (2) and Klarenbeek et al . ( 5 ) .

Although applied procedures and results were satisfactory, it wasfelt after completion of the research programm that a double sniffing

port olfactometer should be used for further experimentation. Thisenables the use of paired comparison tests. Futhermore, the observersuncertainty is well defined. As a result of these views a second singlesniffing port olfactometer was purchased and installed next to theexisting one. The resulting distance between the two sniffing ports wasapprox . 25 centimetres. With the "new" olfactometer a research programwas carried out concerning odour emissions of six different pig housingsystems. As with the previous research, five observers and compresseddiluting air medical grade were used. Due to the fact that pig housesare more odorous than poultry houses more dilution air was needed toreach detection levels. Average flowrate was therefore 5 1/min. The

observations continued for over a year. The research results show adifference in odour emission which can be related to the slotted floorarea ( 5 ) .

As the pig house odour research continued, it became clear that theone observer procedure is time consuming. Only two odour measurementsper day were possible. Futhermore, panel members observed a stress whichwas caused by the noise of the olfactometers. Therefore it was decidedto order a set of three double sniffing port low noise olfacometers atthe University of Utrecht. The Psychological Laboratory of thisuniversity had some experience in the construction of olfactometers. Theflowrate was set at 10 1/min arbitrary.

After a considerable construction time the olfactometers becameavailable for use. With these olfactometers and a recently createdsniffing room at the IMAG premises, the poultry house odour research wasrepeated with a panel of eight observers. The necessary diluting air wasobtained from a rotary vane compressor. Filtration of the compressed airwas applied. The experimental procedures made it possible to use allpanel members at the time. As a result, two experimenters were able tocomplete four odour measurements per day.

Since more observers are brought together in the same room,possibility excists of obtaining non verbal information on the decisionsmade by others. However, it was felt that this was no serious drawback.

Usefull information can only be obtained when the performance ofpreceding panel members is reveiled instantly. This was not the case.The relative odour levels of the investigated housing systems (6) showssimular results as in the first research program. However, absoluteodour levels were higher. This was explained by the higher flowrates ofthe present olfactometer.

As mentioned three olfactometers were ordered. Unfortunately spareparts were not included. As it turned out spares became necessarry soon.



116

carried out. With treated air from the rotary vane compressor as astandard it was found that compressed air of medical grade reachesthreshold levels at 8-12 dilutions. The results of these experimentsemphasise the need of well cleaned diluting air for use witholfactometers.

The third experience gained concerns effects from differences inflowrate of olfactometers.Besides the two olfactometers used by IM AG , a third olfactometer ownedby the organisation of applied physical research in the Netherlands(TN O) participated in the experiments. The flowrate of this olfactometeramounts to 20 1/min. Flowrate experiments carried out by TNO show adistinct difference of inhaled concentration. This affirms the resultsobtained by Dravnieks ( 1 ) . Using the TNO results a difference of 2.4 may

be expected between the results of an olfactometer with a flowrate of 51/min and one with a flowrate of 20 1/min. These values represent thelowest and highest flowrates of olfactometers used in the comparativeodour research. The observed factor based upon the pooled data was 2.41.

The phenomena of flowrate effects on olfactometer results may beexplained by the following. During the process of sniffing, air isinhaled from the direct surroundings of the nose. Each respiration uses0.5-0.8 1 of breathing air. With approx . 18 respiration per minute thetotal air consumption amounts to 9-14.5 litres.

In case of an odour measurement the inhaled air is supposed to be equalto the air delivered by the olfactometer. However if flowrates of the

olfactometer are not equal to the respiration level, additional air fromthe experimental room will be used (see figure 2 ) . Since it is a goodpractice to keep an experimental room free from odour contamination theadditional air can be considered as diluting air. In that case the finaldilution of the odour sample is higher than calculated. The result maybe negative response in cases where a positive response should occur. Anincrease of the olfactometer flowrate will replace unaccounted dilutingair by accounted air thus making the final dilution is closer to thedesired dilution.

The desired dilution in case of a dynamic dilution system iscalculated by the formula:

odorous airflow + diluting airflowdilution =

odorous airflow

Whenever flowrates of the olfactometer and human respiration levels donot match, the dilution formula should be extended to:

odorous airflow + diluting airflow + complementary airflowdilution =

odorous airflow

Complementary airflows can be calculated by distracting the odorous anddiluting airflow from nasal airflows. Although some notion on themagnitude of the nasal airflow can be derived from medical litterature(10) .it should be realized that humans are unique. Therefore a generalfigure on the complementary airflow and the resulting olfactometerflowrate cannot be given. In order to obtain some idea on effects ofsub-respirational flowrates of olfactometers a simple computer program



CALCULATED D ILUT IONREAL DILUTION

V 1 0 0

1007„

507,

o

R-10 R-20

1

R=A0

10 15 20 25 30 35 40

AIRFLOW OLFACTOMETER. L/MIN

Figure 3 : Relation between res piration level and dilution.



121

n o t n e c e s s a r i l y t y p i c a l of o t h e r c o p i e s of t h e s e o l f a c t om e t e r s . The t ype o f p s y c h o p h y s i c a l p r o c e d u r e , eg s u p r a t h r e s h o l d o r t h r e s h o l d mea su r emen t s i s n o t i n c l u d e d i n t h i s p ap e r .

2. THE PROSSER OLFACTOMETER

The P r o s s e r o l f a c t om e t e r i s a c omme r c i a l l y - p r o d u c e d v e r s i o n of t h e p o r t a b l e o l f a c t om e t e r deve l oped by t h e Warren Sp r i n g Lab o r a t o r y (WSL) (2 ) . The o l f a c t om e t e r ( F i g s . 1,2) c o n t a i n s two f a n s , which draw i n amb i e n t a i r t h r o ugh an a c t i v a t e d ca rbon f i l t e r t o remove e x t r a n e o u s odou r s and t h e n mix t h i s o d o u r - f r e e a i r w i t h an odo rou s a i r s amp l e b e f o r e e x p e l l i n g t h e m i x t u r e t h r o ugh e i t h e r a samp l e p o r t ( fan 1) o r an e x h a u s t p o r t ( f a n 2 ) a t 240 l / m i n .

An odo rou s a i r s amp l e i s drawn t h r o ugh a PTFE f low c o n t r o l v a l v e (V1) and t h e f low i s d e t e c t e d by a h o t bead anemome t e r b e f o r e b e i n g mixed w i t h o d o u r - f r e e a i r a t t h e i n l e t of fan 1. The s i g n a l from t h e anemome t e r i s sw i t c h e d by t h e o p e r a t o r t o one of 11 p o t e n t i om e t e r s and when t h e d e s i r e d s am p l e f l ow r a t e i s o b t a i n e d by a d j u s t i n g v a l v e V1 , t h e r e a d i n g on a c e n t r e - z e r o g a l v a n o m e t e r i s z e r o ( T a b l e I ) . Ea c h p o t e n t i o m e t e r i s c a l i b r a t e d by t h e m a n u f a c t u r e r t o g i v e a n u l l r e a d i n g w i t h a known f l ow r a t e of 0 .096 t o 9.6 l / m i n , i n c r e a s i n g i n s t e p s by a f a c t o r o f 1.58. The s am p l e a i r i s t h u s d i l u t e d by f a c t o r s o f 25 t o 2 500 ( T a b l e I ) i n n o r m a l u se w i t h a o n e - s t a g e d i l u t i o n .

A t r a n s f e r v a l v e (V3 and V4) i n t r o d u c e s a s e c o n d d i l u t i o n s t a g e ,

wh i c h f u r t h e r d i l u t e s t h e s a m p l e by a f a c t o r of 100 . Wi t h t h e t r a n s f e r v a l v e i n t h e " l ow " p o s i t i o n , s am p l e a i r p a s s e s d i r e c t l y f rom t h e anemomete r t o fan 1, wh i l e i n t h e "h igh" p o s i t i o n , s amp l e a i r p a s s e s i n t o f a n 2 , wh e r e i t i s d i l u t e d w i t h o d o u r - f r e e a i r . The t r a n s f e r f l ow f rom f a n 2 i s a d j u s t e d t o 2.4 l / m i n by v a l v e V4 and i t p a s s e s t o f a n 1 , wh e r e i t i s d i l u t e d 100 t i m e s . The s u r p l u s m i x t u r e f rom f a n 2 i s v e n t e d t o exh au s t . I n t h e "h igh" p o s i t i o n , d i l u t i o n f a c t o r s of 2 500 t o 250 000 a r e p o s s i b l e .

Sample flow rates and dilution

Table I

factors percentage deviation when galvanometer

Switch settin,

1

2 3 4 5 6 7 8 9 10 11

Sample flow

grate l/min

9.6

6.0 3.8 2.4 1.52 0.96 0.60 0.38

0.24 0.152 0.096

Dilution factor

25

40 63 100 158 250 400 630

1000 1580 2500

when olfact reads full

ometer runs correctly and scale deflection

% deviation when galvanome' reads full-■scale

Full left

+13

+55 +95 +77

+126

+73 +73

+105

+79 +100 +200

ter deflection

Full right

-26

-29 -26 -40 -36 -39 -25 -44 -43 -39 -48



122

Nose -p i e c e s

?

>

fan 1

BCentre-zero

galvanometer

V2

-fc cj

Surplus flow

-ti<P

V3">L<Fan

from Fan 2

vented to

exhaust

Activated carbon filter

Fig. 1. Air flow equipment in the Prosser olfactometer

Valve V1 controls the sample flow rate

Valves V2 and V3 are in the same housing and switch flowsbetween the low (L) and high (H) ranges. In the highrange, fan 2 provides a second-stage dilution of 100X,which is controlled by valve V4

Fig. 2. Laminar flow meter connected to sample inlet port ofProsser olfactometer



123

2.1 Cal ibra t ionThe Prosser was c a l i b r a t e d by measuring the air f lows using a laminar

f low meter (^% a c c u r a c y ) for the odorous sample and a p i t o t tu b e w i t h a

micromanomete r for the fan-b lown ai r (3). The p i t o t p r e s s u r e s w e r econverted to air v e l o c i t i e s (4) and hence, from the c ross sec t iona l a reaof the tube , to volu m etric flow r a te s . Since f low near the tube wal l wasslower than the c e n t r e , the tube was t r ave rsed by the pitot head and thea v e r a g e v a l u e c a l c u l a t e d . A r o t a m e t e r was a l s o t r i e d but i t induced aback-pressure of 250 N/m and, as the manufac turer s ta tes tha t the maximumpermissible back-pressure is 60 N/m for c a l i b r a t i o n to be accura te , i t suse was not pursued.

Before measurement s of sample f low ra t e s were made , the air f l owst h r ough the fans were set to 240 *_ 10 1/min. The p o t e n t i o m e t e r s t h a tadjust motor speeds were too coarse to perm it more acc ura te adjustmen t .The sample flows were set to the f low ra tes spec i f ied and galvanometer wass e t to zero by ad jus t ing the re l evan t po ten t iomete r in t u rn . The t r a n s f e rf l o w e n t e r i n g fan 1 from fan 2 for t w o - s t a g e d i l u t i o n was set to2.4 1/min.

2.2 Resul t sDur ing oper a tion, it was difficult to obta in stea dy null r ea dings on

t h e g a l v a n o m e t e r , p a r t i cu l a r l y w h e n the s a m p l e f l o w r a t e s w e r e s m a l l . In

s o m e p o s i t i o n s , s m a l l m o v e m e n t s of the contr ol v a lv e ca used a full sca ledeflection (FSD) of the g a l v a n o m e t e r w h i l e in o t h er a r e a s , m o v e m e n t of the

v a l v ein the

s a m e d i r e c t i o n c a u s e dthe

f l o wto

i n c r e a s eand

d e c r e a s ealternately. Fig. 3 s h o w s the v a r i a t i o n of flow r a te with v a lv e position,w i t h i n the 5.2 r ot a tions of the valve that covered the full r a nge of f l o wrates. It shows tha t the sa m ple flow r a te of 0.24 1/min (switch position9 ) was deliv e r ed with the v a l v e in 11 positions. This pa r tly expla ins why

it was d i f f i c u l t to get c o n s i s t e n t n u l l r e a d i n g s w h e n o p e r a t i n g the

instr u m ent.P r osser do not indica te wha t or der of d e v i a t i o n can be expected when

t he g a l v a n o m e t e r d o e s not g i v e an e x a c t n u l l r e a d i n g . As it was o f t e ndifficult to obtain a null reading, the s a m p l e f l o w r a t e s w e r e m e a s u r e dw h e n the g a l v a n o m e t e r p r o d u c e d r e a d i n g s j u st at FSD, to b o t h l e f t and

r i g h t . The c o n s e q u e n t d e v i a t i o n s in d i l u t i o n f a c t o n ( T a b l e I) w e r eb e t w e e n 13 and 200?, depending on the switch position, and the dev i a tiongener a lly incr e a sed as the sa m ple flow ra te incr ea sed. Ta ble I thus showsthe im por t a nce of obta ining an a ccur a te null r ea ding on the g a l v a n o m e t e rbut experience suggested that the tim e ta ken to a chiev e this is likely to

exceed tha t a v a ila ble dur ing odour m ea sur e m ent sessions.

2.3 D i s c u s s i o nSome of the d i f f i c u l t i e s e n c ou n te re d when u s i n g the P r o s s e r

olfactometer were explained by making careful measurements of the samplef l ow r a t e s w i t h the c e n t r e - z e r o g a l v a n o m e t e r in the z e r o and FSD

p o s i t i o n s . T h i s a l s o s h o w e d t h a t i t was n e c e s s a r y to o b t a i n a good zeroreading to be confident about the delivered di lut ion. Measurement of thep r e s s u r e in the fan o u t l e t s s h o w e d t h a t a r o t a m e t e r , a commonly-usedinst rument of airflow measurement, was unsu i t ab le for t h i s a pp l i c a t i on .These findings emphasize the importance of understanding the working of ano l f a c t om e t e r . W i t hou t m e a su r i ng the back-pressure , ca l ibra t ion based ont he r o t a m e t e r r e a d i ngs wou l d ha ve be e n e r r one ous . The o r i g i n a l WSLpor tab le o l fac tomete r had i nbu i l t r o t a m e t e r s in by-pass tubes to monitorthe fan-blown flows, but by being in s i t u and c a l i b r a t e d e x t e r na l l y , thep r f o r m a n c e of the f a n s c o u l d be m o n i t o r e d c o n t i n u o u s l y w i t h o u t



124

120 240

Angle of rotation of sample control valve knob

Variation in the sample flow rate with the angle ofrotation of the sample control valve. The integerswithin the graph refer to the number of rotations.The y axis is shown on a log scale. The parallel,dashed lines, show the eleven flow rates correspondingto the eleven dilutions



127

diluting ga s : odor ous a ir a ga inst r ot a m et er r ea dings. These r a tios wer ec o n v e r t e d t o d i l u t i o n f a c t o r s , i n l i n e w i t h t h e v a l u e s u s e d w i t h t h ePr osser , by the der iv a tion s hown below :

Volum etr ic r a tio of diluting ga s : odor ous a ir = C : AConcentr a tion of odor ous ga s a fter m ixing with diluting ga s = A/(C+A)Dilution factor of odorous gas = (C+A)/AIf A-1 , the n the dil uti on fac tor is (C+1 )/1 - C+1

Th i s h a s a n e g l i g i b l e ef f e ct a t t h e m a x i m u m v o l u m e t r i c r a t io o f 7 0 0 ,but the m i nim u m r a tio of 0.43 is incr ea sed by m or e tha n 200 ^ to 1.43.

T h e a c t u a l d i l u t i o n f a c t o r s w e r e a l w a y s l e s s t h a n t h e t h e o r e t i c a lones (Fig. 6) a nd the dev ia tion with both r ota m eter s wa s a lwa ys la r ger a tlower flow r a tes. The dev ia tion of the la r ger r ota m et er wa s a lwa ys less

t h a n o f t h e s m a l l e r on e . D e v i a t i o n f r o m t h e t h e o r e t i c a l v a l u e s w e r eg e n e r a l l y i n c r e a s e d w h e n t he 1 0 t i m e s p r e - d i l u t e r w a s a t t a c h e d t o t h es m a l l r o t a m e t e r . Th e p r e - d i l u t i o n f a c t o r i n c r e a s e d w i t h f l o w r a t e a n doxygen pr essur e^ only r ea ching a 10 tim es dilution a t the higher pr essur eso f 4 a n d 6 x 1 0 5 H / m 2 (F i g . 7 ) .

3-2.3 Effect of or ie nt a t io nThe T04 olfa c tom et er wa s designed to be ha nd-held by a n oper a tor w hen

used in the field. When fixed 5° off-v e r tica l, the dilution fa ctor s w er eup to 30? lowe r than those obtained wh en it was ver tica l (Fig. 8) and thusis not ideally suited for portable use.

3-4 Discuss ionTh e s e i n v e s t i g a t i o n s s h o w e d t ha t t h e T0 4 o l f a c t o m e t e r c a n d e l i v e r

r epea t a ble dilutions, but tha t a n a bsolute ca libr a tion wa s needed befor eu s e . Th e m a i n p r o b l e m s a r i s e f r om t h e f l o w r a t e s m e a s u r e d i n t h e l o w e rr a n g e s o f t h e r o t a m e t e r s c a l e s , w h i c h a r e l e s s a c c u r a t e t h a n th e u p p e rranges. If the upper ranges only are used, then consistent results shouldbe obta ina ble. The olfa ctom eter should be used in the sa m e or ienta tion a swhen ca libr a ted.

4. GENERAL DISCUSSION OF CALIBRATION METH OD S

The m ethod of ca libr a tion used w ill v a r y a ccor ding to olfa ctom etertype. The COj dilutio n method could not have been used wit h the Prosser,since the a m bient a ir dr a wn in by fa ns conta ins COj, while it wa s suita blefor the use wi th a n olfa ct om ete r like the T04 in which the diluting ga s isbottled. It is thus impor tant to check the diluti ng gas for the presenceof a ny tr a cer befor e use. Metha n e ha s been used (2) a nd ha s the a dv a nta getha t, like other or ga nic ga ses, it ca n be detected by a fla m e ioniza tiondetector . A fla m e ioniza tion detector ha s a linea r r esponse tha t cov er sconcentr a tions r a nging ov er sev er a l or der s of m a gnitude.

This contr a sts with physica l m e a sur e m en t of flow r a te, in whic h them ea sur ed r esponse is often pr opor tiona l to the squa r e r oot of flow r a te,e.g. p r e s s u r e d r o p a c r o s s a n o r i f i c e p l a t e . T h u s s o m e f l o w m e a s u r e m e n tdev ices a r e only suita ble for m ea sur in g a na r r ow ba nd of flow r a tes.

The physica l pr oper ties of a tr a cer ga s m us t a lso be consider ed sincec o n t r o l a nd m e a s u r i n g d e v i c e s u s u a l l y r e s p o n d t o m a s s f l o w r a t e s ort h e r m a l c o n d u c t i v i t y . T h u s , t h e r e s p o n s e t o p u r e CO o o r m e t h a n e w o u l ddiffer substa ntia lly fr om a ir , a lthough cor r ection fa ctor s ca n often beca lcula ted.



128

0.8

0.4

Fig.6 Actual/theoretical dilution factors versus flow rate of odorous air (rotameter reading) with carrier gas pressures of 1,2,4 and 6 x 105 N/ta2

1 x 10 B N /m 2 2 x 10 5 N /m 2

• • • • * • «

|

i 0 . 8 - 4 x 105 N/m

2 6 x 10

5 N/m

2

5 u

< 0.4 . • • *

• 1 * » t * * Z . .

0 2 4 6 8 10 0 2 4 6 8 10 Rotameter reading

■ Large rotameter

• Small rotameter

* Small rotameter with 10 x pro-dilution



130

5. CONCLUSIONS

1. The accurate dilution of odorous gas is a prerequisite for odourmeasurement using an olfactometer.2. The methods of flow regulation and control are particularly critical.3* A thorough calibration and understanding of the operation of theolfactometer is needed before it is used with observers. Do not accept apurchased olfactometer at face value.

4. Flow measurement devices should preferably be fitted in situ, be non-interfering and always observable by the operator.5. The calibration method should be chosen with care.

ACKNOWLEDGEMENTS

T he a u t h o r w i s h e s t o t h a n k D r J . H . R a n d a l l a n d Mr H . J . H . H e s s e r f o rt h e i r h e l p a nd a d v i c e i n t h e p r e p a r a t i o n o f t h i s p a p e r .

REFERENCES

1 . DUFFEE, R .A . a n d CHA, S . S. ( 1 9 8 0 ) C o n s i d e r a t i o n o f p h y s i c a l f a c t o r si n d y na m ic o l f a c t o m e t r y . J . A i r P o l l . C o n t r o l A s s o c . 3 0 (1 2 ) , 1 2 94 -12 9 52 . BEDBOROUGH, D.R. and TROTT, P.E. (1979) The sensory measurement of

odou rs by dynamic d i l u t i o n . R epor t No. LR299, Warren Sp r in g Lab ora to r y :S t e v e n a g e3 . W ILLIAM S, A.G. ( 1 9 8 3 ) A s s e s s m e n t o f t h e P r o s s e r o l f a c t o m e t e r . D i v .N o te DN 1 1 7 5 , n e t . I n s t , a g r i c . E n g n g, S i l s o e . ( u n p u b l . )4 . IHVE ( 1 9 7 1 ) G u i d e B oo k C. L o n d o n : I n s t i t u t i o n o f H e a t i n g a ndV e n t i l a t i o n E n g i n e e r s5. MANNEBECK, H. (1974) A p r a c t i c a l p o r t a b le method of od our m ea sur em en t .In : P ro c . 1974 C or ne l l Ag r i c . Was te Management Conf., 291-2946. FR IJ T E R S, J .E .R ., BEUMER, S.C .C ., KLARENBEEK, J. V . a n d JONGEBREUR,A.A. (1 97 9) P s y c h o p h y s i c a l m e t h o d o l o g y i n o d o u r p o l l u t i o n r e s e a r c h : t h em e a s u r e m e n t o f p o u l t r y h o us e o do ur d e t e c t a b l i t y an d in t e n s l ty . C h e m .

Sen ses and F l av ou r 4 (4 ) , 327-3407 . W ILL IA MS, A.G. ( 1 9 8 3 ) C a l i b r a t i o n o f a M a n n e b ec k O l f a c t o m e t e r . D i v .N o t e DN 1 1 4 7 , n a t . I n s t , a g r i c . E n g ng , S i l s o e . ( u n p u b l . )



131

DEVELOPMENTS IN THE ASSESSMENT OF ODOURS FROM SLUDOES

S. J. ToogoodWater Research Centre, Stevenageand

J. Diaper,School of Environmental Science, University of Bradford

SlIMMAMThe remarkable sensitivity of the human nose to detect a large

nunber of chemicals by smell means that traditional odour monitoringmetho ds are costly either in capital (chemical a nalysis) or labour

(olfactometry). Not least among the problems in achieving worthwhileresults is the difficulty in representativ e sampling. This difficulty isgreatly magnified in sewage treatment and agriculture by the diffusenature of the odour sources.

A method is proposed to assess the 'Odour Potential 1 of slurries andsludges by sampling in the liquid phase, followed by extraction ofodorous components under reproducible conditions. The approa ch hasinherent advantages in providing speedy and less costly information forthe prediction of odour nuisance, scheduling land disposal, and forcomparing methods of sludge treatment and stabilisation.

1. INTRODUCTIONIn the assessment of odour production and nuisance from industrial

processes the techniques are by now reasonably well established, andtheir accuracy and consistency are in principle known. There are majo rdifferences however between say a rendering plant on the one hand and asewage treatment work s on the other. One difference is psychological; tomany people an odour problem is necessarily concomitant to the existence

of a sewage wor ks. There have been instances of a well-operated sewageworks built next to a tannery, where the sewage works has been almostuniversally blamed by irate local residents for a problem to which it hascontributed in only a minor way. To this extent, for seme people theonly way to convince them that there is no odour nuisance would be toshut the wor ks completely, and even then it is known that complaints cancontinue for some time afterwards.

1.1. Odou rs From Non-Point Source sThe maj or difference however is that industrial processes are

normally ca rried out in enclosed v essels, wher eas open tanks are the ruleat a sewage work s for storage and for much of the processing This me ansthat instead of an emission of odour from a chimney whose flow rate canbe measured and quality analysed, the odour diffuses from the surface oftanks and ch annels, in a way that is profoundly a ffected by geographicallocation and wind speed. This problem is magnified in agricultur e, whenanimal slurries or sewage sludges are spread onto land. It is clear thatthis makes an odour problem difficult to assess and harder to control,but it also increases the cost of treatment measures at a sewagetreatment works by the addition of covers or buildings to collect theodour before treatment can be contemplated.



134

Table I. Strength (Dilutions to Threshold) of odour samplesfrom Knostrop sludge tanks

Sample point

20 mm above sludge level

1 m above sludge level

4 m above sludge level

6 m above sludge leveland 20 m from tank

Wind

0.4

80

80

63

80

velocity (m/s)

1.8 3.6

195 80

128 63

80 40

100 46

producing odours, and to calibrate this to real applications byexperience.

A method which estimates the odour potential from a sludge or slurrycould be used to develop empirical relationships with complaints receivedduring e.g. spreading. Additionally such a method can be used toevaluate treatment processes.

A further advantage of this approach is that it deals well with thelogistics of sampling and measurement. Taking voluminous odour samples

from the vicinity of a liquid surface over an open tank requiresexperience and time if a representative sample is to be obtained, sincethe act of sampling disturbs the air being sampled unless the sample flowrate is infinitely slow. Not only this, but it is not unusual for thesite being assessed to be a considerable distance from the place wherethe olfactometry or chemical analysis is to be carried out. Storage ofsamples in transit results in a somewnat unpredictable change in theodour measurement. Results reported by Gillard(1) show attenuationsbetween 4 0 and 5 5% for seme samples over a 24 h storage period, and moreremarkably, an augmentation of 139J for one sample after 8 days storage.Though sewage sludge does change with storage, the effect is minor if the

sample is refrigerated. The odour sample can then be extracted at theplace of analysis, and used directly.

3. THE CONCEPT AND MEASUREME NT OF 'ODOUR POTENTIAL'In order to make the approach practicable it is necessary to

introduce the concept of 'odour potential'. By this we mean thepropensity of a liquid or slurry to release odorous substances to anatmosphere; in other words, a measure of the amount of potential odouravailable for future release.

Knowledge of the Odour Potential may be regarded as a 'worst case 1

assessment of the problems that can be anticipated from the handling and

processing of a liquid, sludge or slurry, and it is thus an importantparameter in the process design of a treatment works incorporating odourabatement methods, and of the design of operating procedures for existingor projected plants.

3.1. Develocment of a Standard Method for Assessing the Odour Potentialof a Sludge

To enable odour potential of different sludges to be compared in thelaboratory, a method was required which could be carried out understandard conditions. An initial method was to pass nitrogen (or air)



138

through tubing and fittings made of PTFE. Analysis was undertaken by theWarren Spring Laboratory of the Department of Trade and Industry,

according to the method described by Bailey and Bedborough^).The results are shown in Table IV. and plotted in Fig. 3. and 4.

Table IV. Variation of odour strength of extracted samples withvolume of eluted air

Volume of airpassing throughsludge beforesampling (1/1)

011.1

22.2

55.6

111

Strength of odour samples(dilutions)

Raw sludge Digested sludge

154 00 0

53 000

30 600

15 500

8 200

9 900

350

270

190

160

It is clear from these results that there is considerable die-off ofodour strength with time, and that, as would be expected, the anaerobicdigestion of sludge can reduce the odour potential by at least one order

of magnitude.To illustrate the importance of this die-off effect, the resultshave been re-plotted in Fig. 5. in a cumulative form; that is to say ascumulative percentage of the eventual colour release against volume ofair. In the case of the raw sewage sludge, 38X of the ultimate odour wascarried in the first odour sample, and 90J of the odour had beenextracted by the passage of about 200 1. In the case of theanaerobically digested sludge, the same effect is much more marked; 72%of the ultimate odour was carried by the first sample, and thereafter thestrength of the odour fell off very rapidly.

There are two possible explanations for this. First, it can be

postulated that as it is known that many of the important odorouschemical species are highly volatile, they may be only physically trappedin the sludge, and need little encouragement to transfer to theatmosphere.

An alternative explanation concerns the existence of two equilibria.As the vapour/liquid equilibrium is disturbed by the passage of air, theconcentration of dissolved compounds in the liquid phase falls,disturbing the 'solid'/liquid equilibrium. The kinetics of transferacross this latter phase boundary are much slower than for theliquid/vapour transfer, so that the extraction of odour becomes limitedby the rate of diffusion into the liquid phase.

Two observations may be cited as evidence for this latter view.First, when sludge is applied to land, there is a rapid tail-off of odournuisance after spreading. The incidence of rain after a dry period isknown to result in an increased evolution of odour.

Second, in earlier experiments samples of sludge were centrifuged,and the supernatant liquor discarded and replaced by tap water, beforebeing used in the standard odour potential test. Some re-extraction ofodour from the samples was rapidly found.

In practice, both postulated mechanisms are probably at work,especially if the concept of 'solid/liquid equilibrium1 be extended to



F i g . 4. V a r i a t i o n of o d o u r p o t e n t i a l w i t h v o l u m e of air p a s s e dt h r o u g h the s a m p l e - r e s u l t s fo r a n a e r o b i c a l l y d i g e s t e ds e w a g e s l u d g e

*.-^

— I —131-00

VOLUME OF AIR PASSED THROUGH SAMPLE (I)



147

Smell car eful ly. Do you smell anything now?

NO / YES

Is the smell that you perc eive ?:

1. not annoying2. a little bit a nnoying3. a nnoying4. str ongly a nnoying5. extr em ely a nnoying

They were Instructed to go to a place outside their home every tuesdaynight between 7 a nd 8 p.m ., sm ell, enter their Judgem ent on the postca r dand post the prepaid card as soon as possi ble . If they had any idea aboutthe nature of the odour or its or igin, they were asked to write theircom m ents on the ba ck of the postca r d.The pa nels wer e ca r efully selected on the ba sis of a ge, sex, socioeconom ic sta tus, schooling, num ber of yea r s they liv ed in the loca tion,a nd a ttitudes towa r ds env ir onm enta l m a tte r s . On m ost of these v a r i a bles,ther e wer e no significa nt differ ences between the pa nels of the differ entloca t ions. The pa nels wer e instr ucted both in wr iting a nd dur ing a specia lm eeti ng. Much a ttention wa s dev oted to keeping the pa nel m em ber s well

motiva ted during the one and a half year of the expe rim ent. They receiveda special Jour na l with gener a l infor m a tion a bout olfa ction, ta ste a ndenv i r onm enta l m a tte r s. They r eceiv ed a specia l pr esent a t Chr istm a s a ndbefor e the sum m er holida y . Mor e im po r t a nt, they a lwa ys r eceiv ed a n a nswerto questions and remarks which they wrote on the back of the postcard.Thu s , if someone informed us that he or she would be unable to participat edur ing thr ee weeks beca use he or she ha d to go to hospita l, the ca r dswould be witheld and a short well wishing letter and flowers would be sendto the hospita l .Due to all this , the panels functioned very well for the full period withan a ver age res pon se rat e of 805!.

On the basis of these responses a weekly Odour Annoyance Index wascalculated for each of the four locati ons . This index (described elsewherein deta il (2) r a nges fr om 0 to 100, if nobody sm ells a nything the indexha s the v a lue 0, if ev er ybody sm ells a extr em ely a nnoying odour it ha s thev a l u e 1 0 0 .Dur ing som e of the weeks, in Hoogv liet a ir sa m ples wer e collected in or derto m a ke a dir ect com pa r ison between im m ission concentr a tion a ndexper ienced a nnoya nce. The sa m pling wa s done by the Div ision for Nutr itionand Food Research TNO Zeist. The samples were collected by a mobi le unitof this institute during the same hour in whic h the panels mad e theirm e a sur e m ents. Four ty teflon ba gs of 40 liter s ea ch wer e filled a t thr ee

loca tions in such a wa y tha t a ll ba gs conta ined equa l a m ounts fr om a llthr ee loca tio ns. The next da y the odour concentr a tion (num ber of odourunits/ or ) wa s deter m ined in the la bor a tor y of the institute with a tr a inedpa nel. The samples we re diluted in an olfact omete r with pure air untilthey became Just barely detecta ble in 50% of the case s they were presentedto the pa nel m em ber s .In this paper, we will compar e the data obtained in these immissionm e a sur e m ents with the da ta on per ceiv ed a nnoya nce in Hoogv liet. We willa lso show som e da ta on im m ission m ea sur e m ents on sa m ples ta ken a t v a r iouspla ces in the v illa ge of Zeist, our contr ol loca t ion.



154

concentrations of odorous compounds with annoyance have still to be improved. At this moment the knowledge in this field is far inferior to the

knowledge for the sense of view and the sense of hearing. But there is noreason why we would not acquire the same understanding.

Although knowledge on the correlation of odorous compounds concentration and odour impression is still limited, it is used in all typesof olfactometry. Indeed diluting this concentration by adding pure airis a general practice. Also many investigations were performed where chemicals are added to air and used in psychophysical experiments. Many speakers in this workshop will present data in this field. Here only chemicalanalysis will be dealt with.

2. PKDCIPES

The goal of chemical analysis of odorous compounds in air is to determine all substances, which interact with odour perception cells in ournose, both qualitatively and quantitatively. However, with a few exceptions all compounds with certain vapor pressure have an odour, meaningthat their volatilized molecules react with the membrane of odour receptor cells. As will be shown, always hundreds of compounds are presentin air; this means that the analysis would be very complex. However as wassaid before, our sense of smell is selective : for some products it is verysensitive for other compounds it is much less sensitive.

Table I : Odour threshold values (ppb) of some organics

„ -, Odour „ -, OdourCompounds ^ ^ a Compound ^ ^ 1 *

butanebutanebutanol

butanalbutanethiol

1.3 10 6

500300

150.8

acetic acidpropionic acidbutyric acid

valeric acidhexanoic acid

4019038

842

Several extensive lists of threshold values, i.e. the minimum concentrationin air, that is detected by 50% of the population, have been published (1,2,3,4). However published threshold values for a particular compound canvary over a number of orders of magnitude, so they have to be treated withscepticism.

This selectivity makes chemical analysis of odour easier : many compounds, although present in ambient air, and although they have an odour in

pure form, are not contributing to the odour, while their concentration isfar inferior to the threshold value. On the other hand the sensitivity ishigh for a range of compounds, higher than any chemical analysis can copewith directly. These compounds have to be concentrated from the odorousair, so that higher amounts are available for the analytical technique. Ifthis concentrating could be done with the same selectivity of odour receptor cells, there would not be much of a problem. However the actual knowledge of this interaction is far too limited - in fact it is inexisting -to speculate on an analytical application. With all of the biochemical developments, it is not excluded that at a certain moment it becomes feasible,but right now the only way is to use crude physicochemical methods, such as



155

freezing out, adsorption and absorption. After concentrating, separationis achieved by classical methods such as gas chromatography (QC) or high

pressure liquid chromatography (HPLC). Identification is based mainly onmass spectrometry, infra-red spectrometry and chromatographic data.

3. RESULTS

The primary goal of these methods is to concentrate all volatile compounds, mainly volatile organic compounds or VOCs, present. This mixtureof VOCs, containing odorous compounds, next to a large majority of unodo-rous substance, then is analysed. This chemical analysis is based an theseparation of these hundreds of compounds by gas chromatography, is hampered by large amounts of water, which is always present in air, and which

is also freezed out or adsorbed. The only way to escape more or lessthis difficulty is to use a rather apolar adsorbant, in casu Tenax QC orsimilar materials (e.g. Chromosorb 102) (5). A second limitation is thefact that no material will ever be capable of adsorbing all odorous compounds completely, and permit to desorb them afterwards completely. Forcompounds with very low boiling point, e.g. hydrogen sulphide, strong ad-sorbants are necessary, while for odorants with high boiling point, e.g.skatol or the sesquiterpenes, thermal desorption is difficult with strongadsorbants. So a compromise has to be accepted, or several complementary adsorbants have to be used. At this moment this compromise far concentrating all odorous substances is found in the adsorbant mentioned, kno

wing that the most volatile compounds might escape partly. Many systemshave been described and even commercialised, but we use a home-built system, which is schematically represented in figure 1 (6). On an cuterside wall of the gas chromatograph (GC) an oven in which the Tenax-adsorp-tian-sampling tubes fit is constructed. Connections with pressurized helium (transfer gas) is provided and their is a connection with a high temperature resistant sixway valve, which replaces the normal QC-injector.During thermal desorption (position 1 in figure 1) the transfer gas, carrying desorbed volatiles, passes the sixway valve, a cold trap (stainlesssteel loop cold with liquid air) and enters the ambient air. The heliumcarrier gas is connected to the GC-column via the sixway valve. After thedesorption stage which usually takes about 45 minutes, with a desorptionoven temperature of 220°C for 30 minutes at least, the sixway valve isswitched (position 2 in figure 1 ) . At that moment transfer gas flowsthrough the sixway valve directly into the ambient whereas the carrier gaspasses the cold trap before entering the QC-column. The liquid air isremoved from the cold trap and the latter is quickly heated by a high intensity fload light. In this way condensed compounds are flash-evaporatedand injected into the GC-system.

Concentrating odorants by adsorption-desorption techniques producesa terribly complex mixture of TC s, which is separated by gas chromato

graphy. Fortunately this technique allows formidable separation power,but still then the result is not always sufficient far a clear-cut odouranalysis. In figure 2 the GC-analysis is shown of an air sample in theneighbourhood of a rendering plant, showing a great number of VOCs; howeveralmost all of them are hydrocarbons produced by cars and heating systemsand some other products, which do not contribute to the odour. Very smallpeaks of odorants are detected, which shows the difficult task of odour analysis with a general concentrating technique. Of course this analysis isfar more relevant if emission gases are examined as is demonstrated in figure 3 (7). Part of these difficulties can be overcome if the odorants can



156

be detected specifically, which is possible for scene groups of odorants(thiols or mercaptans, sulphides, amines) with specific GC-detectors. Sper

cific detectors are available for haloganted compounds, sulphur-, phosphor-and nitrogen compounds. Figure 4 shows the analysis of the sulphur-compoundsproduced by the acidic decomposition of phosphate-rock and causing the typical smell of fertilizer plants.

Another approach is to aim at selective concentration methods. Indeedodour problems are caused by a limited number of compounds, on rather a limited number of classes of compounds, mentioned in figure 5.

For most odour nuisance problems, chemical plants, refineries, livestock production, food processing, rendering, water purification plants etc.,the compounds responsible for the odour are known. So chemical analysis ofthe odour can be limited to these odorants, and selective concentrating

techniques can be used. Selective concentrating methods are based on specific absorption techniques, using particular chemical reactions of odorantclasses. Sometimes several absorption methods have to be used in order todescribe the odour problem, thus increasing the labor cost of the analysis.On the other hand absorption methods allow better quantitative results. Selective absorption of odorants from air produces a far less complex mixture.We developed or are developing several of these methods for aldehydes,amines, acids, thiols etc.

Carbonyl compounds for instance can be trapped by absorption in a reagent solution containing 2,4-dinitrophenylhydrazine and hydrogen chloride.Details of this method are extensively described elsewhere (8). The principle of the method is that the carbonyl compounds, in case of renderingplant emission the aldehydes, react with the 2,4-dinitrophenylhydrazine andform 2,4-dinitrophenylhydrazones (2,4-DNPH's) according to the scheme.

R . N 0 2 N 0 2 R

\ = 0 + N 0 2 -/ O \ _ N H - N H Z — N 0 2- / 0 Y - N H - N - / + H 20

R2 R2

These 2,4-dinitrcphenylhydrazones have some interesting properties. Itare cristalline compounds so that after extract of the 2,4-DNPH's from thereagens, they can be concentrated by evaporation of the solvent withoutlosing product. Besides these compounds shown intense absorption of UV-light Ojnax 356 nm) and so they can easily be detected with an UV-detec-tor. These properties make the 2,4-DNPH's particularly suitable for HPLC-analyse. This methods is used since some time. A chromatogram is givenin figure 6 and results of the quantitative determination of carbonyl compounds in different situations are given in table 2.

For amines absorption in an acid solution, or preferably adsorption

onto an acid ion exchange column (acidified divinylbenzene-styrenesulfo-nic acid copolymer) is used. 10-50 1 of ambient air is sent over'a wet100 mm x 3 mm I.D. column; the ion exchange polymer is put into a vial,made alkaline and the water solution is analysed on packed Carbowax-KDHGC-column with a thermionic selective detector (TSD), which is specificfor nitrogen- and phosphorus-compounds. Trimethylamine is detected easily at 1 ppb.

Acids can be absorbed specifically in an alkaline impringer, whichis extracted with ether after acidification to pH 2. This method wasused for rendering plant emissions, showing a series of linear and branched



'"•AJLjJl Aukw

FIGURE 2

CHROMATOGRAM OF THE GC-MS ANALYSES OF AMBIENT AIR, SAMPLED IN THE NEIGHBOURHOOD OF A RENDE

RING PLANT



169

From Table 1 it is found that the distance over which heating uptakes place at a stall temperature of 22 °C is mainly influenced by the

outside temperature and much less by tube cross-section and relativehumidity of the air in the stall. Moreover, it is evident that the air hasto travel a long distance to reach 10 °C. Faster warming-up is possible byincreasing the area of the heat-exchanging surface. This can be achieved byusing a number of smaller tubes instead of one large one. A practicalobjection to this set-up is , however, the space in the stalls, which is toorestricted for installation of a large number of tubes. Where more heatingis needed, a compact heat exchanger or additional heating equipment has tobe installed.

In the batteries using this drying system the space between cagefloor and manure belt has been increased so that the manure can collect

there for about 7 days. This is important in order to get a favourableratio between the amount of fresh manure and the amount of drier manure.Compared to belt batteries using liquid manure, the time required forcleaning out the manure is reduced by half. After drying, the manure with adry-matter content of about 4 5 % is removed from the belts and transferredby transport belts to a covered storage place.

2.2. Postdrying in a covered store by spontaneous internal heatingSuch storage is required in the system to ensure the obtaining of

homogeneously dry manure. Manure with a dry-matter content of about 4 5 % isunsuitable for transport and storage in the open air. Anaerobic processes

readily take place in such manure, the result being a sticky, malodorousmanure which is difficult to process. Spontaneous internal heating startsquickly in the stored manure. In the top layer in particular, hightemperatures (> 60°C) have been measured, those in the layers below varyingbetween 30 and 50°C. The drying is promoted by the fact that a new layer ofmanure is dropped on to the heating pile every week. The thinner the layer,the faster the manure dries. For that reason, in addition to the advantageof greater manure storage, a swivelling conveyor is to be recommended.

During the composting process much moisture is evaporated and aslight smell of ammonia is perceptible. After a successful spontaneousheating process has taken place, manure is obtained with a dry-matter

content of at least 55 %. This manure is suitable for transport and storagein the open air and can be easily applied by means of conventional manurespreaders. The minimum manure-storage requirement is not less than a 6weeks1 capacity, a hardened floor and a roof.

In such storage the water vapour is quickly removed by the wind andattack by rain is prevented. In more closed storage places, adequateventilation must be provided via walls and roof-ridge, while large doorsbeing required for removal of the manure.

3. PRACTICAL RE SULTS

3.1 Drying and power consumption

Manure drying in 5 stalls, each with a population of about 25,000hens kept in 3- and 4-tier batteries, was investigated over the period ofone year. Although the drying system evinces differences in matters ofdetail, the ventilation output is based on at least 0.4 . m /hen/h at abackpressure of more than 30 0 Pa at the end of the duct. In all cases theventilation capacity can be reduced, particularly to prevent lowtemperatures at night and in the winter. In a number of different weeks,after 5-7 days drying, samples of fresh and belt-dried manure werecollected for determination of dry-matter content and the kWh consumptionwas ascertained. In Table 2 a survey is given of the measured data.



170

Table 2 Survey of average dry matter contents (in %) and kWh-consumption(in kWh/hen/year)

October 1983

Dry matter content

Fresh belt-driedmanure manure

December 1983

kWh Dry matter content kWh

Fresh belt-driedmanure manure

Average 21 , - 43 ,1 1,05 21,3 44 ,5 1,15

Spread 19,4 -22,4 39,9 -45,4 0,83-1,30 19,2-22,8 40,2-48,8 0,93-1,84

March 1984

Dry matter content kWh

freshmanure

belt-driedmanure

May 1984

Dry matter content

freshmanure

belt-driedmanure

kWh

Average 20, 2 4 0, 2 1,05 21,3 46, 3 1,27

Spread 19,1-21,7 36,4 -45, 4 0,89-1,22 19,5-22,7 4 3, 48,6 0,94-1,60

From Table 2 it is found that, on average, the dry-matter content ofthe belt-dried manure amounts to 4 0 - 4 5%. Moreover, the power consumptionwas found to be more than lkWh/hen/ h. To ensure that the internalspontaneous heating is successful, a dry-matter content of 4 5 % isrecommended.

The dry-matter contents are affected by various things :- the dry-matter content of fresh manure;- the drying properties of the air; in general the drying conditions are

better in sunmer than in winter;- the ventilation capacity. In winter, in particular, in stalls with

insufficient isolation and in stalls with poorly closing inlets theventilation is reduced to prevent the stall temperature from going down;

- cutting down on the use of energy; trying to save too much can lead topoor drying results;

- blocking up of the perforated ducts; blocking has been found to occur inwinter at the beginning of the ducts. In such cases condensation hasformed on the ducts, leading eddying dust to adhere to them and blockingup the holes.

3.2 Composition of the manureAs experience with in-house manure-drying systems has shown, about

5 0 % of the organic matter and nitrogen can be lost during prolonguedstorage in the stall. Particularly when the ventilation is restricted,there is a perceptible smell of NH in such stalls. On the other hand, installs having the manure-belt battery system, the stall climate is good,even in the winter period. During the heating-up process some nitrogenousmatter does escape from the store in the form of ammonia.

In Table 3 the fertilizing value is mentioned of a number of samplesof fresh manure, belt-dried manure and belt-dried heated manure.



174

Fig. 3 Roofed-over manure storage where further drying takes placeby means of spontaneous heating

Fig. 4 House with manure drying and roofed-over manure storage



177

4. THE EXPERIME NTOn one farm with two identical broiler houses the floor of one house

was insulated by lining the floor with polystyrene slabs 0.05 m thickcovered with plastic film (0.15 mm ) . Chopped straw was then spread on thefloors of both houses.

The dry matter content of the straw was measured during one spring andone summer fattening period. The straw on the insulated floor was found tobe appreciably drier (Fig. 1 ) . During the summer fattening period theconcentration and emission of NH where also measured, because it wasexpected that there would be less heating in the drier straw and hence lessproduction of NH This was in fact confirmed (Fig. 2 and Fig. 3 ) . Weeklysamples of air were taken and tested by an odour panel of 10 persons,giving the results illustrated in Fig. 4.

At the end of the summer fattening period the broilers wereslaughtered and evaluated according to the criteria "wrong legs" and"blistered briskets" (Table 1 ) . At the same time, the litter was subjectedto chemical analysis (Table 2 ) . A small difference in pH value resulted ina higher nitrogen content in the litter from the insulated floor - aphenomenon already described by Elliot et al.

5. THE PRELIMIN ARY RESULTSAlthough we realize that the two experiments do not provide an

adequate basis for significant results, the findings should be of interest.First of all, it is evident that insulation of the floor in broiler

houses is advisable if the ground water level is one metre or less belowthe surface. If the ground water level is lower, the soil package acts asinsulation.

- Dry matter content of the litter.The litter on the insulated floor was dryer in both experiments, thedifference being 15 % in spring and 10 % in summer. The smaller differencein summer may be due to a lower ground water level, but a dry mattercontent of 70 % is very acceptable. If this litter is to be burnt for heatproduction, the higher dry matter content is of benefit as regardsefficiency and smoke production.

- Ammonia and odour.

The dryer litter on the insulated floor has a lower emission of ammonia.The difference becomes evident from the third week and subsequentlyincreases. This reduction is beneficial from the point of view of acidrain.

The assessment of odour on the basis of the samples of air leaves somequestions open, particularly as regards the sample taken from the broilerhouse with the insulated floor at seven weeks. This was the only one withhigher odour emission and cannot be explained, since the other values werelower. Assuming that most odour is produced by the litter, it is reasonableto suggest that the drier litter has a lower emission level. The relativehumidity in the broiler house with the insulated floor was slightly lower

from the third week onwards, at 68.3 % compared with 70.9 %.- The quality of the broilers.

The quality of the broilers was assessed in the slaughterhouse, withspecial attention being paid to the presence of blistered briskets andwrong legs. Both criteria give better results for the broilers from thehouse with the insulated floor. However, better quality is not rewarded byhigher prices, so that insulation does not yield any direct extra profits.Economically, therefore, there is no incentive to insulate the floors, andmore information is needed on this subject.



181

USE OF PEAT AS Ll'lTEK FOR MILKING OOWS

I. PeltolaWork Efficiency Association, Finland

This study compared the advandages and disadvantages of peat,straw and sawdust for use as litter. The way in which peat isused, the amounts used and the effect of the litter on thestructural parts of the tying-stall shed and on the labourrequirement were investigated, and the quality of milk, theincidents of mastitis and the value of the manure werestudied. The results show that peat absorbs urine and binds

ammonia better than the other litters tested. Peat manurecontains more than the average amounts of nitrogen andmagnesium, and the nutriens are in the form that is morereadily utilised by plants. The ammonia contents of thecowshed air were slightly lower with peat litter than witheither straw or sawdust. The difficulty in peat was inhandling it. There were no significant differences betweenthe three litters in terms of the labour required. On theother hand, peat was more difficult to store during the coldwinter because it tended to freeze. Urine separation systemswere easily blocked by peat. The dust content of the cowshed

air rose when peat was used. The litter had no affect on thestate of health of the animals or on the quality of the milk.These factors are affected more by conditions on the farm inquestion. Peat was found to be suitable for use as litter.Flexible use of peat requires storage, spreading method andmanure removal be designed specifically for peat. Thesefactors are being studied in the final part of the work,which is still in progress.

1. INTRODUCTION

The aim of this three year joint study was to investigate theadvantages and disadvantages of peat, straw and sawdust for litter ascomprehensively as possible. In Finland straw is used on 67% of farms,sawdust on 25% and peat on 3% of dairy farms. Only about 3% of farmsuse no litter at all.

The use of peat as litter was compared with sawdust and straw on15 dairy farms during the indoor feeding period of 1983- 84 . For thefirst 3 months 5 farms used straw as litter, 5 used sawdust and 5

peat. At the end of this period all the farms changed over to peatlitter. All the cowsheds had tying-stalls, from which the manure wasremoved in solid form.

The use of peat as litter was studied in Finland in the 1930s and40s. Today, peat is harvested mechanically by means of a millingcutter, which creates fine particle peat. Cowsheds have also changedwith respect to the use of peat with the mechanisation of manureremoval. At the same time workers are now demanding better workingconditions.



182

2. PROPERTIES OF Ll'lThK PEAT

Litter peat is the surface peat removed fran the bog beforecutting of fuel peat. As fuel peat production increases, so the amountsurface peat removed also grows. Around 1 million m3 of surface peatis lifted every year in Finland, and the figure is expected to rise to2-3 million m3 a year by the 1990 (1). Surface peat is used mainly farhorticultural purposes.

The properties of the peat vary, depending on the place in thebog frcm were it ccmes. The surface layer provides the best litterpeat. Lifting peat from deeper in the bog results in the inclusion oflayers of more highly decomposed peat, which is not as good for use aslitter.

Freshly cut peat usually contains 40-60% water. Litter peat,however, must not contain more than 40% water, since its absorptioncapacity and storability both decrease with increasing water content.

Good quality litter peat should be Sphagnum fuscum peat. Asuitable degree of decomposition is 2-3. Raw Sphagnum peat is acidic,with a pH of 3.0-4.5. Its total nitrogen content 1.0-1.5% of drymatter.

3. AMMONIA-BINDING CAPACITY

Because its acidic character, peat binds ammonia well. Theammonia-binding capacities of the different litters were measured inthe laboratory. Aqueous ammonia solution was applied to the peat,which was then dried under reduced pressure. The results showed thatpeat can bind up to 2.5% of its dry weight of ammonia (Fig. 1 ) . Theammonia is so strongly bound that it does not evaporate even when thepeat dries. The binding capacity of straw and sawdust is less than 1%(2).

From the point of view of the binding of ammonia, it is importantthat the peat is Sphagnum fuscum peat. Earlier studies (3) have shownthat other varieties of peat bind only 0.26-0.86% of their dry weight

of ammonia.



183

100-

90-

80

70

60

50-

40-

30-

20-

10-

0

fSaw dust, cutter s ha vings

/-—^_____y====^ ~ "

[ (\

\

Straw 1

I Peat

11

11 1 1 1 i i 11 2 3 4 5

Ammonia content , %of litter dry ma tter

Figure 1. Ammonia-binding capacity of the three litters underlaboratory conditions.

4. LIQUID-BINDING CAPACITY

The absorption capacity of the litter determines the amount used,and also affects the functioning of hydraulic manure presses. Theabsorption capacity of litter depends on its initial moisture content.In the laboratory tests , peat had a much greater absorption capacitythan other litters.

Peat absorbed a maximum of 4.5 times its own weight of liquid,straw 3.5 times, cutter shavings 3.6 times and sawdust 1.5 times ( 4 ) .The litters used in the tests had an initial moisture content of 20 %,with the exception of peat, which contained 4 0 % moisture. Thesemoisture contents represent the working values for good-qualitylitters.

Peat was far superior in terms of absoption capacity to the otherlitters. Litter should retain its absorption capacity even when underpressure, for example in a hydraulic manure press.

The ability of litters to withstand pressure was tested by firstallowing them to absorb either water or urine. The litters were thencompressed in a hydraulic press for one hour as the pressure wasincreased stepwise from 20 N/cm2 to 50 N/cm2. The pressure exerted byhydraulic manure presses in practice is around 40-60 N/cm2. All theretained urine better than water. Sawdust was found to have thegreatest resistance to pressure, retaining about 7 5 % of the absorbed



184

l i q u id . C utte r shavings re tai ne d 40% of water and 52% of th e u ri n e,wh ile chopped straw re tai ne d 46-50% of i t s absorbed l i q u id . Peat

showed th e lowest re te n t i o n of l i q u id , keeping only 19% of the waterand 33% of t h e uri n e (F ig. 2 ) .

Water binding coefficientbefore pressing

Peat 4.4B

Cutter 3.64

shavings

Straw 2.89

Sawdust 1.52

Water binding coefficientafter pressing

1.47 Cutter shavings1.34 Straw1.14 Sawdust.96 Peat

Pressure20 N /cm

2

t = 20min

Pressure3SN/cm

2

t=20min

Pressure50/V/cm 2

t=20min

Figure Effect oflitters.

pressure on water-binding capacity of

The results indicate that special attention should be given tothe efficiency of urine separation on farms using peat. Manure pressesshould be fitted with seme means of urine separation so that urinepressed from the litter can be led out of the press chute. This isessential for the smooth operation of the manure press. The urineseparation system in the troughs, perforated plates or scale platesmay become blocked when peat is used. Provision should be made forflushing out the urine separation pipes in the case of a blockage.Various types of perforated plate are currently being studied withrespect to their susceptibility to blocking.

5. NUTRIENT-BINDING CAPACITY

Samples of manure were collected from the farms during bothexperimental periods. The samples were used for nutrient contentdeterminations and for a pot experiment in which Italian rye grass wascultivated. The nutrient contents obtained were compared with the



185

values for the farm in question during the use of different litters, and with the grouped means for the different litter manures.

Peat manures

contained

statistically

significantly

more

total

nitrogen, magnesium and dry matter. The lowest nutrient contents were found in the sawdust manures.

The pot experiment showed the same differences. The rye grass was cut four times. The greatest differences in the increase in dry matter yield were obtained with the second crop. As all pots received the same basic phosphorus, potassium and magnesium fertilizer, the differences in yield were due to the amount of available nitrogen contained in the litter manures (Fig. 3 ) . In addition 31% of the total nitrogen in the peat manure was comparable with the nitrogen present in commercial fertilizer, compared with only 19% in the case

of straw manure and sawdust manure (2).

30'

o

tfc

U j

I Q

-yield increase with straw manure

yield increase

with sawdust manure increase

with peat manure

yield without fertilizer

■ •yield with

n

fft l l f f l f t l izi -'■?'Jr-C'-

Cut F - value

I U

II 7.7

m 8.8

IY 12.1

TOTAL 8.4

Figure 3. Effect of litter on fertilizer value of manure in pot experiment.

6. EFFECT OF PEAT ON COWSHED AIR

6.1. Dust content of air

The dust content of the air in the cowsheds was measured in connection with routine care of the cattle. Measurements were made



189

The dista nce dia gr a m shows the possible liv estock uni ts, ta ble 1.

distance

115 m in or to

a vi l lage

or

230 m to a

resident ial

area

points in

VDI-3471

100

85

60

(50)

livestock

LU

100

72

45

(38)

number of

fattening pigs

770

554

345

(292)

type of

coveringt ightcoverings

permanentcrust

none

none, newguideline

Ta ble 1. Pr a ctica ble liv estock r ela tiv e to a fixed dis ta nce.

On the sa m e conditions it is possible to keep m or e tha n twice a s m uchliv estock units only by cov er ing the stor ing t a nk s. Ther efor e ther e m ustbe str ict r ule s a t the v a lua tion of differ ent types of cov er ing the m a nur estor ing t a nks. So it m ostly won't be possible to a ccept m a keshift solutions. In case of poultry keeping - guidelin e VDI 3472 (2 ) - a similarv a lu a tion will be found.

3. CLASSIFICATION AND DESCRIPTION OF COVERING D EVICESThe differ ent types of cov er ing dev ices m a inly dev ide up into thr ee

gr oups:- na tur a l floa ting cr usts- a r tificia l floa ting cov er s

set up of pour ingsset up of m a ts or ta r p a ulin

- close cov er ing dev ices a nd light constr uction r oofs

3.1 NATURAL FLOATING CRUSTSNa tur a l floa ting cr usts a r ise pr eponder a ntly on ca ttle m a nur e. The

coa r se solids for m her e a v er y tight a nd str ong floa ting cr ust . On pig a nd

poultr y m a nur e nor m a lly floa ting cr usts a r ise only for a tim e or not a ta l l . On a m ixtur e of ca ttle a nd pig m a nur e ther e is the a r ising of a n effi cient per m a nent floa ting cr ust sur e, if ther e is a t lea st a contents of50 I ca ttle m a n ur e . Ther efor e this solution is only possible for a fewf a r m s . Befor e the ta nk is being em ptied, the floa ting cr ust m ust be destroyed by stiring and hom ogeni zing. It takes a few week s until a newfloa ting cr ust will a ppea r .

3.2 ARTIFICIALLY SET UP FLOATING CRUSTS SET UP OF POURINGSIt is also possible to set up floating cru sts consisti ng of chopped

str a w, pla stic foa m pellets or a com bina tion of str a w a nd pellet s.

The floa ting str a w cr ust a r ises m ost r elia bly by a ddition of str a w into the mixing pit. It will be destroyed by homoge nizing and so it has to a-r ise a ga in a fter ea ch single la nd spr ea ding.

A floa ting cr ust consisting of pla stic foa m pellets shows sm a ll eff i-cience, is very relia ble to wind and there will be lost mat eria l by windinfluence or at the land spreading.

Mor e efficient a nd a lso sa fer is a floa ting cr ust consisting of onela yer of str a w with a la yer of pla stic foa m pellets below a s a floa t. It isinsensible to weather inf luen ces. An even width of the la yers of for ex ample 15 cm straw and 5 cm pell ets below can hardly be rea lized .



190

There will be a loss of straw and plastic foam pellets, because thisfloating crust is easily being damaged by stiring. The production andmaintenance requires a great expenditure of work.

3.3 ARTIFICIAL FLOATING COVERS SE T UP OF MATS AND TARPAULINA floating cover of plastic texture with an about 15 mm thick layer

of plastic foam pellets is insensitive to weather influences and rainwater is able to pass it. Homogenizing the tank contents doesn't make anyproblems.

Floating covers set up of tarpaulin consist of reinforced tarpaulinlike it is used as lorry tilts. The tarpaulin is stretched by an in-drawnring-shaped PVC tube. It is also working as a float, so it is impossiblethat manure gets from the border onto the surf ace of the tarpaulin. Adjusting devices of jet mixers and inlet tubes pass it through conical sockets.

3.4 TIG HT COVERIN GS AND LI GHT CONSTRUCTION ROOFSFor a tight covering of the tanks especially tarpaulins, however they

have supporting constructions or not, are very useful.

3.41 COVERINGS WITHOUT SUPPORTING CONSTRUCTIONSSelf-supporting tarpaulins, which are attached to the tank border are

only suitable for small tanks.

'plastic cover (tarpaulinT - ^ _infla ted ' ^ ^ / ^ -

PT.O dnvenmixer

FiR.l. Inflatable truncated cone shaped tarpaulin as a tight covering

Especially for tanks with a great diameter and for steel and wooden

tanks truncated cone shaped tarpaulins are very useful, because they do notburden the tank wall very much. If the tank is empty, the tarpaulin musttouch the center of the tank bottom in order to support bigger water orsnow loads. With increasing contents the tarpaulin starts floating on themanure surface, fig.l.

On steel tanks the tarpaulin which has been reinforced at the borderwith a rope is fastened by an additional fixing rim.The mounting is difficult and demands a great expenditure of work.



191

On wooden or on concrete tanks the tarpaulin has to be fit out withloops at the border. The tank border is pasted with felt , so that the tarpaulin can be stretched over the tank border and is fixed on hooks in the

tank wall.The tanks are nearly tight now. To ex clude damaging the covering by

homogenizing with an impeller mixer, the tarpaulin can be inflated beforemixing. This is dispensible if it is used a hydraulic mixing system.

3.2 COVERIN GS WITH SUPPORTING CONSTRUCTIONSSo far self-supporting light construction roofs are only used for

tanks up to a diameter of 12 m. Onto a supporting construction set up ofsteel or wooden trusses a roofing set up of corrugated material or timberis mounted. These roofs are quite expending, but they mostly cannot be accepted as a tight covering. More advantageous is a roofing set up of re

inforced tarpaulin. It is stretched onto the tank with a bracing rope anda system of loops and hooks.

plastic cover(tarpaulin)

stainless steel rope

. - supp orting post

f f < *T S f / t * t s / , / zl g » > ' -" "- "^^ '<ssmFig.2. Truncated cone shaped tarpaulin on a central supporting post

Truncated cone shaped tarpaulins on a central supporting post are alsosuitable for tanks with a great diameter. At the top of the supporting postthere is a big ring or a mushroom-shaped head in order to avoid stressingthe tarpaulin punctiformly. The central supporting post is tightened to thetank border with ropes, fig.2.

—o ooourliM air

^ » odcur loadtd air

^ » clcantd air

Fig.3. Light construction roof and biofilter on an aerobic treatment plant



192

In case of aerobic treatment or storing tanks located extremely neardwelling houses it can be necessary to treat the exhaust air. A biofilter(size 2 to 4 m5 operated with a small fan and filled up with moist peat

moss is able to avoid odour problems, fig.3.

4. ODOUR REDUC TION EFFICIEN CY OF DIFFEREN T TYPES OF COVERIN GS AND THEIRVALUATION ACCORDING TO THE GUIDELINE VDI 3471

According to the strict rules , as confirmed before, 25 points onlyshould be accepted with at least 60 %, and 4 0 points with at least 85 %odour reduction efficiency.

The odour reduction efficiency can be measured by using an olfactometer and additional equipment. A constant air stream is passing througha hood, adjusted to the slurry surface, crust or cover. One part of theexhausted odour loaded air is fed into the olfactometer.

The different types of coverings have got different modes of operation. They show clear differences in their efficiency and must be valuedaccording to the guidelines VDI 3 47 1 and 3 4 72.

From nearly tight coverings and roofs only a very small flow rate ofproduced gases can be emitted. The emission by air exchanging is set tozero. Therefore the odour reduction efficiency of those coverings comparedwith an uncovered open manure surface is 95 to 100 %. 4 0 points can beaccepted, fig.4.

40(50)

25(30)

Fig.4. Odour reduction efficiency of different types of coverings

Roofs can only get 4 0 points, if they are nearly tight. Corrugated materialwithout a packing in the tank border doesn't fulfill the requisitions andonly 25 points can be accepted, because the efficiency is less 85 %.

Floating tarpaulins don't keep close to the wall. An open gap is unavoidable. The odour reduction efficiency is mostly not more than 80 %.Only 25 points can be accepted.



193

The impermeable floating mat shows nearly the same efficiency as apermeable tarpaulin and is much better than all tested artificial floating crusts. Among these only the combination of straw and plastic foam

pellets shows an odour reduction of more than 60 %, and 25 points can beaccepted.

Natural floating crusts in a tank containing at least 50 % cattlemanure get 60 to 85 % efficiency and 25 points can be accepted.

Floating crusts set up just of straw or plastic foam pellets andmakeshift solutions cannot be accepted. Their odour reduction is mostlyless 60 %.

5. UTILITZATION PE RIOD AND COSTS OF DI FFERENT TYPES OF COVERINGSThe actual utilization period and the real costs of the different ty

pes of coverings are not exactly known up to now. The existing dates andestimates are shown in table 2.

type of cover

straw

plastic foam pellets

straw.plastic foam pell

floating mat

floating tarpaulin

truncated cone tarpaulin

light weight roof

concrete cover

est imated

ut i l i za t ion

period (years)

0.5

2.0

2 0

10 0

1 0 0

15.0

15.0

20.0

price of the

mater ia l

(DM/m2)

0 5

3 0

2.5

25.0

30.0

40.0

6 0 0

80-120

expenditure

DM/fattening pig

0.25

0 20

0.15

0.30

0.35

0.35

0.50

0.60 - 0.75

Table 2. Estimated costs of different types of coverings.

The better the odour reduction efficiency of the covering the higher

the investment. Regarding the utilization period the costs per cubic meterliquid manure (and with that also per fattening pig) are about

- 0,3 DM per m 1 for a 25-point-covering and- 0,5 DM per m 1 for a 40-point-covering.

Regarding the higher requirement of working hours for education and maintenance the floating crust set up of the combination of straw and plasticfoam pellets costs about 0,3 DM per m'.

Totally the discussed coverings are useful possibilities to controlimmissions. For a lot of farms located in villages or in a short distanceto residential quarters an effective covering on the liquid manure storingtanks is the only convenient possibility to get restocking permitted.

REFERENCES

(1) VDI 34 71: Emission control, livestock management - pigs 19 77 , 1984(2) VDI 3472: Emission control, livestock management - poultry farming 1982(3 ) MAN NE BE CK , H ., Abdeckung von Fliissigmistbehaltern zur G eruchsminderung.

Vortrage zur Hochschultagung, S chriftenreihe der Agrarwissenschaft-lichen Fakultat der Universitat Kiel, Heft 61 (1980)



194

MACHINERY SPRE ADING: SOIL INJECTION AS A BARRIER TO ODOUR

DISPERSION

J. E HALLWater Research Centre, Medmenham L aboratory, UK

Summary

The dispersal of odours during and after surface spreading of farmslurries and sewage sludges is to the public the most significantcause of complaint in manure handling and disposal. Whilst goodtanker design and cultivation after spreading can limit the problemto some extent, soil injection is the only technique which canpotentially eliminate the problem entirely. Apart from odourcontrol there are a number of other important environmental andagronomic advantages such as the control of surface run-off,improvements in pasture hygiene and better nutrient management bypreventing ammonia volatilisation. However, soil injection is nota panacea as there are constraints such as higher operating costs,the difficulties of certain soil types and the extra weatherdependency. Nevertheless, the costs of injection must beconsidered not only in the light of the potential benefits and itsflexibility of operation but also with regard to the costs ofalternative means of treatment and disposal to achieve the samestandard of environmental acceptability.

1. INTRODUCTIONUnlike the variable and diffuse odours associated with animalhousing, slurry storage and sewage treatment, the surface spreading ofanimal slurries and sewage sludges on farm land has a discrete pointsource which potentially can be eliminated by soil injection. The controlof aerial pollution is perhaps the most valued benefit of soil injectionand, although there are a number of other important agronomicconsiderations, there are also some constraints on the technique. Theseconstraints are mitigated by the costs of alternative means of treatmentand disposal to reach the same level of environmental acceptability. Thislast point is of particular concern to the water industry as the proposed

EC directive on the use of sewage sludge in agriculture would prohibit thespreading of unstabilised sludges unless immediately incorporated orinjected ( 1) . In the UK about one third of the sludge spread on land isunstabilised.

2. THE ODOUR PROBLEMHalf of the farm-related odour complaints in the UK are concerned

with the spreading of manures on the land. The problem has two phases;firstly the action of spreading which, although of short duration, cangive rise to aerosols and odours that can drift several kilometers.



195

Secondly, there is the longer term problem of slurry lying exposed overlarge areas of ground which can generate odours as well as attract fliesand vermin for some time.

The degree of nuisance during and after spreading depends a greatdeal on the prevailing weather conditions. Odours are dispersed mostrapidly by strong winds and bright sunshine however, these conditions alsoencourage rapid ammonia volatilisation. Such losses of ammonia can belarge (eg 2,3) with consequent and unpredictable reductions in thefertiliser value of slurry as well as possible deleterious effects ofatmospheric ammonia on the environment (1 ) .

3. SLURRY SPREADING EQUIPMENTTable 1 summarises the features of equipment design which influence

the risks of odour problems arising from surface spreading. There arenumerous combinations of these features to be found in slurry tankershowever, tanker design is often directed more to productivity in terms ofspeed of operating and area of ground covered rather than to minimisingodour and aerosol production.

Table 1Equipment design and relative risks of odour and aerosol production

Means ofDischarge

Droplet Trajectory DistributionSize Device

ODOURRISK

Vacuum

Pump

Auger

Gravity

Small

Large

High

Low

Gun

Splash Plate

Dribble Bar

Injector

High

Low

Vacuum tankers which distribute slurry through high trajectory guns

are the worst combination of features as these produce small droplet sizesand frequently cause aerosol clouds particularly when the tank empties.Such aerosols have been detected eight kilometers downwind duringspreading operations. Low slurry trajectory and large droplet size areless likely to cause such intense odour problems at spreading thereforecareful selection of equipment is important. (There are approximately 280tanker models from 10 manufacturers available in the UK (5).) Gravitydischarge through a dribble bar or curtain minimises the problems duringspreading as far as possible but such equipment is much slower than thevacuum tanker with gun and moreover, the odour problems after spreadingare likely to be the same following either type of tanker.

Soil injection is the only technique which potentially eliminates theaerial pollution problem entirely and with the new generation of equipmentavailable now, the speed of injection operations can be similar to surfacespreading.



197

200

160 -

Q

o>

120

80 -

40 -

simple

T

100 150 200 250

DEPTH OF INJECTION (mm)

300 350

Figure 1 Volum es of slurry injected at diffe ren t depths bywinged and simple injection tines.

simple

T

100 150 200 250

DEPTH OF INJECTION (mm)

Figure 2 Draught force required by winged and simple injectiontines operated at different depths.



199

land within urban areas is generally nearer to the sewage treatment works. Sludges and slurries which have been stabilised, particularly by

anaerobic digestion, have no offensive smell, but injection may still be

desirable to prevent aerosol production during spreading and for visual and aesthetic reasons.

1.2.2 Surface Run-off

Pollution of watercourses generally results from excessive rates of application of slurry and from heavy rainfall following surface spreading resulting in run-off. The slope of the ground is also a critical factor. The risks of surface run-off can be significantly reduced by injection provided that there is sufficient soil cover to contain the slurry. The risks to groundwater are probably no more or less than for surface spreading provided injection is limited to the rooting zone. Injection into dry cracked soils is inadvisable due to the possible risk of slurry running directly into land drains and watercourses.

Ross et al (11) in monitoring run-off quality for a range of pollution parameters from grass and cultivated contour plots which had received cow slurry to the surface or injected, found that injection 'essentially eliminated any pollutant yield in the r u n - o f f .

Slurries with low dry solids contents will be much more susceptible to surface run-off than thick slurries. Vetter and Steffens (12) showed that on a slope of 9-13%, rotary cultivation prevented the run-off of slurry. Injection along the contour can effectively prevent run-off however this is not always possible and on gradients of over 10%, normal practice is to inject down the slope. The concern here is that the injection slot may act as a drain and Godwin and Warner (9) have shown that application rates should be decreased for sewage sludges less than 5% ds as the slope increases. Above 5% ds, slope had no effect on sludge movement where winged tines were used (Figure 3 ) .

Figure 3. Effect of slope upon the maximum application rate

■z 150r

o M

>5% ds.

6 9 12

SLOPE ( d e g r e e s )

< 5 7 o ds .

15



200

1.2.3 Implication s for livest ocka) Crop taint

It is well known that cattle do not relish grazing wher e their ownslurry ha s been su rface spread previou sly and can result in reducedintakes of her ba ge. Pain and Broom showed that soil injection can avoidthis pr oblem (1 3) . They com pa r ed gr a zing beha v iour of da ir y cows onpa ddocks sur fa ce spr ea d or injected with cow slur r y a t 25 t/ha a ndnitr ogen fer tiliser a pplied a t the equiv a lent nitr ogen r a te of the slur r yof 60 kg N/ha . The ca ttle on the sur fa ce slur r y tr ea t m ent consum ed a bout3 0 % less her ba ge dr y m a tter tha n those on the other two tr ea t m ents (Ta ble3 ) . Gr a zing beha v iour in ter m s of tim e spent wa lking, size of bite etcwa s less effected on the injection tr ea t m ent tha n the sur fa ce a pplied.

Table 3Amounts of herbag e av aila ble and removed by cows (kg DM per cow per day)Fr om r efer ence 13.

H e r ba g e a v a i l a b l e

Her b a ge r em o v ed

Her b a ge r em o v ed a s% a v a i l a b l e

Fertiliser

2t.1

12-3

51

Injected

19.9

11.3

58

SlurrySurfaceApplied

21.1

8.1

to

b) Pa thogensThe pa thogenic content of slur r y depends la r gely on the hea lth of the

a nim a ls on the fa r m , but with sewa ge sludge, a pa r t fr om the gener a l hea lthof the popula tion, a dditiona l sour ces of potentia l infection com e fr oma b a tto ir s, hospita l s, m ea t pr ocessing fa ctor ies, ta nner ies etc. Theor ga nism s of pr inciple concer n in sewa ge sludges a r e sa lm onella a nd ta enias a gina t a the hum a n beef ta pe wor m . UK na tiona l guidelines (11) specify a

thr ee week 'no gr a zing' per iod following the sur fa ce spr ea ding of digestedsludge on gr a ssla nd a s a pr eca ution a ga inst sa lm onella infection, but withundigest ed slud ge, the 'no graz ing' period is extended to six month s topr e v ent the com pletion of the life cycle of the beef ta pe wor m . Witha nim a l slur r y, ther e is no contr ol on the r etur n of gr a zing a nim a ls topa stur e but fa r m e r s a r e a dv ised to wa it a t least one m onth befor er e t u r n i ng s t o c k ( 1 5 ) .

If com plete bur ia l of slur r y ca n be gua r a nteed then the r etur n ofgr a zing a nim a ls to injected pa stur e would be contr olled m or e by the sta teof the swa r d r a ther tha n the potentia l pa thogen content of the slur r y.Andrews et al (16) and Dickson and Tribe (17) have confi rmed that the soil

cov e r ov er injected sludge is a n effectiv e ba r r ier to infection a nd tha tnum ber s of or ga nism s fa ll r a pidly following injection.

Good farm ing p ract ice would require slurry to be injected afterg r a zing or m owing but befor e gr a ss r egr owth a nd then to a llow a t leastthr ee weeks befor e r etur ning stock to la nd. This a llows sufficient tim efor the liquid to dissipa te, for the injection pathway to seal therebypr e v enting a ccess by stock a nd for the gr a ss to r espond to the nutr ien ts.This suggest s that a 'no gra zing 1 period of three weeks for all sludges



201

a nd slur r ies would be a ppr opr i a te pr ov ided injection is sa tisfa ctor y. Ifdeemed to be unsa tisfa ctor y beca use ther e is som e m a ter i a l on the sur fa c e,

then the 'no gra zing

1

per iod for sur fa ce a pplica tions should be a dher edt o . This is a n im por t a nt a spect of injection pa r ticula r ly in the light ofthe pr oposed EC dir ectiv e on the use of sewa ge sludge in a gr icultur ewhich, if im plem ented would pr ohibit the sur fa ce spr ea ding of unsta bilisedsludges unless they wer e im m edia tely cultiv a ted in or injected a nd wouldr equir e 6 weeks no gr a zing for sta bilised slu dges.

c) Conta m ina ntsSlur r ies a nd sludges conta in conta m ina nts which if a llowed to

a ccum ula te to excessiv e concentr a tions could pr esent a hea lth ha za r d toa n i m a l s . These a r e pr im a r ily hea v y m eta ls such a s copper a nd zinc in

slur r y der iv ed fr om feedstuff a dditiv e s, a nd in sewa ge sludge a m uch widerr a nge of m eta ls a r e found depending on the type a nd concentr a tion ofindustr y in the ca tchm ent a r ea of the sewa ge tr ea t m ent wor k s. Thepotentia l pr oblem is one of dir ect ingestion of soil by gr a zi ng a nim a lswher e the r esidues of r epea ted a pplica tions of slur r y or sludge ov er anum ber of yea r s m a y a ccum ula te in the soil sur fa ce of per m a nent pa stur e.Injection ensur es that ther e is m ixing in the soil a nd henc e dilution ofa ny m eta ls pr esent. Kir kha m (18) found that m eta l concentr a tions in whea twere lower when sewage sludge was injected as opposed to surfacea pplica tion.

An a dditiona l benefit of injection in this context is wher e slur r y is

sur f a ce a pplied to pa stur e ov er a per iod of tim e r esulting in theundesir a ble concentr a tion of or ga nic m a ter i a l a t the soil sur fa ce. Thisis of pa r ticula r concer n in a r ea s of per m a nent gr a ssla nd wher e ther e is asur plus of slur r y. Ploughing a nd r eseeding is a costly m ea ns of tr ea t m entwher e a s injection will help pr ev ent such pr oblem s a r ising .

Fur ther m o r e, injection pr ev ents the tr a nsitor y pr oblem of sur fa cea pplica tions sm other ing the gr a ss which ca n r esult in ba r e pa tchesfor m ing, pa r ticula r wher e thick slur r ies a r e a pplied under dr yingc o n d i t i o n s .

14.2.1 Cultiv ati on effe cts

Injection tines per for m a soil loosening function a s this is thenecessa r y a ction to cr ea te the v oids to a bsor b slur r y. The extent ofloosening depends on soil conditions a nd the design of the injector .

In gr a ssla nd, injection ca n pr ov ide a useful soil loosening function,pa r ticula r ly in per m a nent pa stur e wher e the com pa ction fr om the hoov es ofgr a zing a nim a ls a nd fr om v ehicles ca n ca use pr oblem s thr ough poor dr a ina gea nd r estr icted gr a ss r oot gr owth . The constr a int on the a m ount ofloosening achi evab le is that the injected sur face must be left clean andlev el. In a r a ble soils, this constr a int does not a pply a s subsequentcultiv a tions will r em o v e a ny unev enness ca used by the injection tines.The tine spa cing ca n ther efor e be a lter ed to a chiev e m a xim u m soil

distur b a nce a nd so could per for m pr im a r y cultiv a tions pa r ticula r ly wher estubble is injected in m inim a l cultiv a tion sy stem s .

1.2.5 Nutrient Manag ementApart from the theoretical b enefi ts of placin g the nutr ient s in the

r oot zone, a n im por ta nt fea tur e of injection is in the potentia l contr olof a m m onia loss by v ola tilis a tion. Both a nim a l slur r ies a nd digestedsewa ge sludge conta in significa nt qua ntities of a m m onia a nd the concer n is



202

that the immediate nitrogen fertiliser value can be greatly reduced when these materials are spread, particularly under drying conditions. The

loss of ammonia can be very large and the difficulty for the farmer is that it is not readily accountable in his fertiliser budget with the consequent problem of under fertilisation. Predictive models are available but these are not really practicable propositions for the farmer (eg 19).

Losses of up to 60% in seven days following spreading have been recorded from digested sludge applied under adverse drying conditions in Canada (2) for example, and in Ireland, loss of 10 - 80% were measured from pig slurry over a similar period (20). With cow slurry, losses of 2.7 kg N ha" h~ were found under warm dry conditions but significantly, under cold wet weather the losses were up to 0.3 kg N ha" h~ , conditions

which are conventionally assumed to minimise ammonia losses (3). The control of ammonia loss by injection has been measured directly

and indirectly through crop yields. Hoff et al (21) measured the proportion of applied NH^ -N lost as NH -N from pig manure over a 3-5 day ■■~ "--- * J Losses were 1t.0, T2.2 and 11.2% from 90, 135 and

Only 2.5% was lost from 90 and sampling period 180 m /ha surface spread respectively 180 m^/ha injected.

Kolenbrander and De La Lande Cremer (22) found that air temperature at the time of slurry application influenced greatly the nitrogen efficiency of slurry surface applied but not injected (Figure t ) . Safley et al (23) showed that pig slurry injected into maize produced equal

yields as the equivalent rate of fertiliser but surface applications were only 80%. Similarly an average annual increase in maize yield of 2.13 t/ha was observed by Sutton et al (2t) by injecting pig slurry compared with surface dressings. Beauchamp (25) has shown that cattle slurry injected both before and after sowing maize was 60% as effective as surface applications. Dam Kofoed (26) has found similar yield advantages for injection in trials with wheat, fodder beet and grass on loam and sandy soils.

Figure 4. Effect of air temperature on the N efficiency of slurry injected ( ) or surface spread ( )

100

80

60

40

20

0

0

arable land 10 cm depth

grassland 1-2 cm depth

x grassland

10 20 o U air temperature ( C)



203

With gr a ssla nd, this a dv a nta ge for injection is not a lwa ys soobvi ous. Whilst Dam Kofoed (26) and Luten et al (27) attribut ed higherg r a ss yields following injection of slur r y to losses of a m m onia fr omsur f a ce a pplica tions, Kondo (28) found no a dv a nta ge either wa y a ndKolenbr a nder (29) repor ted incr e a sing yield depr ession incr ea sing withdepth of inje ction . In fact, much depends on the soil and swardconditi ons and the time of year o f injection and is largely related toloca lised swa r d da m a ge a r ound the injection tine. Much a lso depends oninjector tine configur a tion (see Ta ble 2 ) . Godwin a nd Wa r ner (12) ha v eshown that t he yield fo llowing injectio n may be 10-20 % less than fromsur f a ce spr ea ding a ttr ibuta ble to tine losses but this m a y be com pensa tedfor in a la ter sea son when gr owth is r e-esta blished a long the injectionslot with gr ea ter utilisa tion of the r em a ining nutr ients .

1.3 CONSTRAINTS ON INJECTION

1.3.1 Soil Condit ion sSoil m oistu r e condition offer s the m ost significa nt constr a int on

injection. On a r a ble soils this is gener a lly not a pr oblem a s la nda v a il a bility for injection is usua lly r estr icted to stubble when gr oundconditions a r e good a nd qua lity of finish is unim por t a nt. Gr a ssla nd ispotentia lly a v a ila ble thr oughout the yea r a pa r t fr om conser v a tion a ndgr a zing per iods, but for the full benefits of injection to be r ea lised,a d v e r se conditions when significa nt swa r d a nd soil da m a ge ca n occur , need

to be r ecognised a nd a v o ided.On v er y wet soils, ther e a r e the ea sily r ecognisa ble pr oblem s ofexcessiv e sinka ge and wheelslip. Swa r d da m a ge m a y occur ea r lier whencom p ar ed with sur fa ce spr ea ding of slur r ies under such conditions thr oughthe extr a dr a ught r equir e m ents of the injector s but this ca n be a llev i a tedto som e extent by fitting flota tion tyr es . A fur ther constr a int on hea v ysoils when wet, is tha t a na e r obic conditions could pr ev a il in the slur r ycha nnel dela ying r oot gr owth (9) a nd hence cr op r esponse a nd will pr oba blyr esult in significa nt denitr ifica tion losses . Oper a tiona lly this m ea nsa v oiding injecting into soils a bov e field ca pa city m oistur e content orwhen hea v y r a in is for eca st.

The m or e difficult pr oblem is in ha r d, dr y conditions whentraffica bility is not a problem but injection can result in dama ge tosoil-r oot conta ct a nd ca use excessiv e soil hea v e. This is m ost likely tooccur when the soil enter s a dryin g phase in early summer and the soilm oistur e deficit exceeds 10 r a m (1.5 inches) a lthou gh m uch depends onpr e v a iling wea ther a nd swa rd conditi ons a nd soil type ( 9) . Much highersoil moistu re deficits can be tolerated when injecti ng in the autumn assur f a ce conditions a r e gener a lly m oist a nd ther e is the gr ea terp r oba bility of r a infa ll.

A furthe r co nstrai nt is found in stony soils. This will result inincreased wear of the injector tines and whilst injection into stony

a r a ble soils is success ful, when injecting into gr a ssla nd stones m a y bebrought to the surface and could present a hazard to mow ing equipment ifnot rolled in. In soils with very large ston es, the injector s arepr otected fr om da m a ge by shea r bolts or a utom a tic spr ing r elea sem echa nism s but this will r esult in disr upted tur f a nd slur r y a ppea r ing onthe sur fa ce when a ct iv a ted.



204

1.3.2 Power Requirem entsAs shown in Figure 2 and Table 1, the draught requir ement of inject or

tines incr eases with depth and that winged tines opera ting at 150 mm arem o r e efficient tha n sim ple tines a t gr ea ter de pth. It is clea r fr om Ta ble1 tha t soil type gr ea tly influen ces dr a ught r equir e m ent a nd dr a ught for cesof 2 to 6 kN per tine ha v e been obser v ed with winged tines oper a ting a t15 0 m m ( 7 ) .

Power r equir e m ent is a constr a int in so far a s it a ffects the choiceof injector to suit existing tr a ctor s on the fa r m , or it r equir es thepur cha se of a higher power ed tr a ctor . The r a nge of power r equir e m entsquoted by injection equipm ent m a nufa ctur e r s is 80 to 120 hp for atr a ctor -ta nker -injector com bina tion (5 ), a nd four wheel dr iv e isdesir a ble. Although m a ny fa r m s now ha v e tr a ctor s in this r a nge, tr a ctor s

with lower hp ca n be used by m ounting the injection equipm ent dir ectly tothe tr a ctor with slur r y being supplied by a slur r y ta nker dr a wn a longsideor indeed by pipe fr om the hea dla nd.

Table 1Dr a ught for ce r equir e m ents (kN) of a winged injector tine.Fr om r efer ences 7 a nd 9

Depth (mm) Loose sand Clay loam Sandy loam Clay loam

100 1.7 2.5 2.3 2.5

150 2.5 5.0 5.0 6.5

200 1.0 8.0 7.1 9.8

1.3.3 CostsThe costs of injectio n must be considered not only in the light of

the potentia l benefits of the technique in m inim is ing env ir onm enta lim p a ct, but a lso of the costs of a lter n a tiv e tr ea t m ent a nd disposa l r outesto a chiev e equa l env ir onm enta l a ccepta bility.

The benefits a r e incr e a singly a ppr ecia ted by the sewa ge sludge

disposa l a uthor ities a s it offer s r educed tr a nspor t costs wher e landba r r ed to sur fa ce spr ea ding is m a de a v a ila b le, a nd r educed tr ea t m ent costsa s in som e insta nces the tr a nspor t a nd injection of liquid sewa ge sludgeis chea per tha n dewa ter ing, tr a nspor ting a nd spr ea ding ca ke sludge a ndindeed injection of r a w sludges m a y be a chea per optio n to sta bilisingsludge pr ior to disposa l under cer ta in cir cum sta nces.

F a r m e r s ha v e not ta ken up soil injection to a ny gr ea t extent pr oba blybeca use of its a ppa r ent com plexity a nd ca pita l cost a lthough low costequipm ent is now a v a ila b le. Howev e r with incr ea sing env ir onm enta lpr essur es pa r ticula r ly on a er ia l pollution, fa r m e r s m a y yet find tha tinjection could be a n econom ic a nd a ccepta b le solution to (at lea st pa r t)

of their slur r y pr oblem .

5. CONCLUSIONSSoil injection of fa r m slur r ies a nd sewa ge sludges elim ina tes the

odour a nd v isua l pr oblem a ssocia ted with sur fa ce spr ea ding, it ca n contr olsur f a ce r un-off a nd help pr ev ent wa ter cour se pol lution. It ca n a v oid cr opta int a nd pa thogen tr a nsfer on pa stur es a nd ca n pr ov ide soil looseningw i t h b e tt e r n u t r i e nt m a n a g e m e n t .



205

Aga inst these benefits m ust be put the extr a wea ther dependency ofinjection, the constr a int of cer ta in soil types a nd tha t in gr a ssla ndther e m a y be a n unev en r esponse a nd sm a ll r eductions in yield com pa r edwith sur fa ce spr ea ding. Ther e is a lso the issue of incr ea sed oper a tiona lcom plexity a nd the ca pita l cost of equipm ent. Although it is clea r thatinjection is a m or e env ir onm enta lly a ccepta ble m ethod of spr ea ding liquidm a nur es , it should not be v iewed a s a pa na cea but pr im a r ily a s a m ea ns ofincr e a sing the flexibility of slur r y a nd sludge spr ea ding ope r a t ions .

REFERENCES

(1) COMMISSION OF THE EUROPEAN COMMUNITIES ( 1 9 8 2 ) . Proposal for aCouncil Dir ectiv e on the Use of Sewa ge Sludge in Agr icult ur e.

(2) BEAUCHAMP, E G., KIDD, G E and THURTELL, G. ( 1 9 7 8 ) . Ammoniav ola tilisa tion fr om sewa ge sludge a pplied in the field. J Env Qua l,7, 111-116.

(3) B EAUCHAMP, E G., K IDD, G E and THURTELL, G. ( 1 9 8 2 ) . Ammoniav ola tilisa tion fr om liquid da ir y ca ttle m a nur e in the field. Ca n JSoil Sci, 62 , 11-19.

(I) VAN BREEMAN, N., BU RROUGH, P A., VELTHORST, E J. et al . ( 1 9 8 2 ) . Soila cidifica tion fr om a tm ospher ic a m m onium sulpha te in for est ca nopythr ough fa ll. Na tur e, 299, 5 1t8-550.

(5) WATER RESEARCH CENTRE. ( 1 9 8 1 ) . Application of sewage sludge to land.A dir ector y of equipm ent. Av a ila ble fr om WRc Env ir onm ent, Henley

Roa d, Medm enha m , Ma r low, Buc ks.(6) GODWIN, R J and SPOOR, G. ( 1 9 7 7 ) . Soil fa ilur e with na r r ow tines . J

Agr ic Engng Res, 22, 213-228.(7) NEGI, S C , McK YES, E., GODWIN, R J and OGILVIE, J R. ( 1 9 7 8 ) . Design

a nd per for m a nce of a liquid m a nur e injector . Tr a ns Am Soc Agr icEngnr s. 2\_, 9 6 3 - 9 6 6 .

(8) SPOOR, G and GODWIN, R J. ( 1 9 7 8 ) . An exper i m enta l inv estiga tion intothe deep loosening of soil by rigid tin es. J Agric Engng Res. 23,2 1 3 - 2 5 8 .

(9) GODWIN, R J and WARNER, N. ( 1 9 8 4 ) . Soil injection of sewa ge slu dge.Contract report to WRc.

(10) SMITH, K A. (1981). Unpublished data from Muck '83, NationalAgr icultur a l Centr e, UK.

(II) ROSS, I J., SIZEMO RE, S., B OWD EN, J P an d HAAN, C T. ( 1 9 7 9 ) . Qua lityof r un-off fr om la nd r eceiv ing sur fa ce a pplica tion a nd injection ofliquid da ir y m a nur e. Tr a ns Am Soc Agr ic Engnr s. 22, 1058-1062.

(12) VETTER, H a nd STEFFENS, G. ( 1 9 8 0 ) . Sur fa ce r un-o ff. In Nitr ogenlosses a nd sur fa ce r un-off fr om la ndspr e a ding of m a nur es. Br oga n,JC-(ed).Nijhoff/Junk, The Ha gue, 1981 70-7 5.

(13) PAIN, B F and BROOM, D M . ( 1 9 7 8 ) . The effects of injected andsur f a ce-spr e a d slur r y on the inta ke a nd gr a z ing beha v iour of da ir yc o w s . Anim Prod. 26, 75-8 3.

(11 ) DEPARTMENT OF THE ENVIRONM ENT/NATIONAL W ATER CO UNCIL. ( 1 9 8 1 ) . Reportof the sub-com m ittee on the disposa l of sewa ge sludge s. DoE/NWCSta nding Technica l Com m ittee Repor t 20.

(15) MINISTRY OF AGRICULTURE, FISHERIES AND FOO D. ( 1 9 8 2 ) . Pr ofita bleutilisa tion of liv estock m a n ur e s. Booklet 2081.

(16) ANDREWS, D A., MAWER, S L and MATTHEWS, P J. ( 1 9 8 3 ) . Sur v iv a l ofsa l m onella e in sewa ge sludge injected into soil . Effluent a nd Wa terTr ea t m ent J, Febr ua r y 1983, 72-7 1.



206

(17) DICKS ON, P H and TRI BE, H T. (1981). A note on the fate ofsalmonellae, presumptive coliforns and faecal streptococci in rawsewage sludge buried in soils. Unpublished.

(18) KIRK HAM, M B. (1980). Characteristics of wheat grown with sewagesludge placed at different soil depths. J Env Qual. 9 0 ) , 13-18.

(19) ENG LIS H, C J., M IND ER, J R and KOELLIK ER, J K. (1980). Volatileammonia losses from surface applied sludge. J Water Poll ControlFed. 52(9), 2310-2350.

(20) SHERW OOD, M. (1981). Fate of nitrogen applied to grassland in animalwastes. In Proc XIV Int Grassland Congress, Lex ington, US A. Smith,J A and Hays, V W (eds) Westview Press, USA, 1983.

(21) HOFF, J D., N ELS ON, D W and SUTTON, A L. (1981). Ammoniavolatilisation from liquid swine manure applied to cropland. J Env

Qual.J £ ( 1 ) ,

90-95.(22) KOLEN BRAND ER, G J and LANDE C REM ER, L C N DE LA. (1967). Stalmest engier, waarde en mogelijkheden. Veenman, Wageningen, pp 188.

(23) SAFLEY, L M. , LESSM AN, G M., W0 LT, J D and SMITH, M C. (1981).Comparison of corn yields between broadcast and injected applicationsof swine-manure slurry. In Livestock waste: a renewable resource.Am Soc Agric Engnrs, 178-180.

(24) SUTTON, A L., NELS ON, D W., HOFF, J D and MAYR0SE, V B. (1982).Effects of injection and surface applications of liquid swine manureon corn yield and soil composition. J Env Qual. JJ_(3), 468-472.

(25) BEAUCHAMP, E G. (1983). Response of corn to nitrogen in preplant and

sidedress applications of liquid dairy cattle manure. Can J SoilSci. 63(2), 377-386.(26) DAM K0 F0ED, A. (1980). Water pollution caused by run-off of manure

and fertiliser. In Nitrogen losses and surface run-off fromlandspreading of manures. Brogan, J C (ed) Nijhoff/ Junk, The Hague,1981 70-75.

(27) LUTEN, W., GEUR INK , J H and W0LDRIN G, J J. (1983). Yield responseand nitrate accumulation of herbage by injection of cattle slurry ingrassland. In Efficient Grassland Farming. Corrall, A J ( ed ) .British Grassland Society, 185-191.

(28) K 0 N D 0 , H and HARAMAKI, 0. (1983). The effects of application of cow

slurry to mixed swards in Hokkaido. Res Bull Hokkaido Nat Agric Ex pStn. 138, 31-19.

(29) KOLENBRANDER , G J. (1980). Effect of injection of animal waste onammonia losses by volatilisation on arable and grassland. InNitrogen losses and surface run-off from landspreading manures.Brogan, J C (e d) . Nijhoff/Junk, The Hague, 1981, 4 25-130.



207

SWEDISH EXPERIENC ES WITH SOIL INJECTION

OLLE NORENSwedish Institute of Agricultural Engineering

Summary

Odours released during the spreading of manure are experienced by manyof the local population as very annoying. C onsequently, reduction of theodour emissions in connection with spreading of manure is a very important measure. In this respect, incorporation of the manure into thesoil is a good solution. Studies made in Sweden (2) show that incorporation of the manure largely reduced the emission of odour fromthe field. This mainly concerns the injection techniques, which insome cases reduced the odour to the background level.

Increased interest has been shown with regard to the plantnutrient content of slurry and experiments both in Sweden and elsewhere have demonstrated that a better utilization of the manure'snitrogen effect is obtained if the slurry is incorporated than if

spread conventionally. In a time study made when the distance betweenthe field and the manure pit was ca 800 m total spreading capacitydecreased by ca 10 % when the method was changed from conventionalspreading to spreading using an injector.

1. IN TRODUCTION

In conventional spreading of slurry inconveniences caused by malodours

may easily occur if the spreading is done close to built-up areas. Thesemalodours may cause considerable irritation and lead to discomfort anddiscord. Odours released during the spreading of manure are experienced,namely, by many of the local population as more annoying than odour fromthe livestock building itself. This is clearly shown by an investigationconducted by the Swedish Institute of Agricultural Engineering (Jordbruks-tekniska I nstitutet, JTI) and the Environmental Hygiene D ept ., KarolinskaInstitute, and the Swedish Environment Protection Board (KI).

An enquiry was made among more than 2000 homes in the neighbourhood often pig barns with more than 1000 pigs in each concerning how differentenvironmental factors were experienced. The neighbours were divided into

three groups namely; permanent non-farmer population, farmers and week-endpopulation. It was found that ca 19-33 % of the people living within 1 kmfrom the pig barn considered that manure spreading was an annoying environmental disturbance, Fig. 1. Within a radius of 2 km this figure was 8-11 %

and within 3 km it was 2-6 %. Odours from the ventilated air, from manurepits, etc ., annoyed fewer of the people living in the neighbourhood or ,expressed in figures, 13-27, 3-8 and 1-2 3! within 1, 2 and 3 km radius,respectively, Fig. 2. Consequently, reduction of the odour emissions inconnection with spreading manure is a very important measure. In thisrespect, incorporation of the manure into the soil is a good solution.



0-1 km

Permanent non- farmerpopulat ion

Farmers

Week-end populat ion

l-2km 2-3 km

Fig. 1. Percentage of population who were considerably annoyed by malodourfrom manure spreading.

^ Permanent non- farmerpopulat ion

Farmers

^ Week-end populat ion

0-1 km I-2 km 2-3km

Fig. 2. Percentage of population who were considerably annoyed by malodourfrom pig barns.

2. ODOUR REDUCTION

Comprehensive studies of this technique have been made at JTI and K I .In one of these studies comparisons were carried out between differentspreading and burial methods for pig manure. The odour determinations weremade in a mobile laboratory especially constructed for sensory measurements ofair pollutants ( 1) . The laboratory mainly consists of an airconditioned



209

test-r oom with thr ee exposur e hoods . Fig. 3 shows a gener a l outline of them obile la bor a tor y with the sa m pling equipm ent.

Fig. 3. Gener a l outline of the m obi le odour la bor a tor y. 1 Air conditioninga nd clea ning unit. 2 Wa iting r oom . 3 Test cha m ber with exposur e hood s.4 La bor a tor y for ga s dilution, chem ica l a na lyses a nd exper i m enta l contr ol.

5 Air intake ho od. 6 Fan s. 7 Field.

In table 1 some results from this study (2) of odour reduc tion arepr esented. The thr esholds a r e m ea n v a lu es expr essed a s log dilution fa cto r s.Sta ndar d dev ia tions a r e ca lcula ted on the a v er a ges of doubled ED-50 v a lue s,ea ch v a lue ba sed on the r epor ts of six obser v e r s a t a tim e. As ca n be seen,incorporation of the ma nur e largely reduced the emission of odour from thefield. This m a inly concer ns the injection techniqu es, which in som e ca sesr educed the odour to the ba ckgr ound l ev el . Conv entiona l tilla ge im plem entssuch as a plow or a disc ha r r ow a lso r educed the odour em ission consider a bly.

The effect of im m edia te injection in com pa r ison with conv entiona l sur

fa ce spr ea ding wa s a lso studied in la r ge-sca le field exper i m ent s. Oneobjective was to study the dependence of the odour strength on the distancefrom the manu red field and on the length of time that had elapsed since thespr e a ding took pla c e.

The str ength of the odour wa s estim a ted by a num ber of outdoor obser v e r s,who com pa red the odour with a sta nda r d r efer ence of pyr idi ne, a nd byobser v e r s sitting in the KI's m obil e la bor a tor y who m ea sur ed the odour inthe a m bient a ir . The obser v e r s m a de the deter m ina tions a t dista nces r a ngingfr om 50 to 400 m etr es downwind of the m a nur ed field. Fig. 4.



210

Table 1. Odour threshold values for untreated swine manure spread and buriedin different ways. Odour threshold ED -50 (from Lindvall , T. et al. 197 2)

Fallow inspring

Fallow inautumn

Grassland inautumn

Surface spread

Buried withplow

harrow

disc harrow

injector

Unmanured soil surface

3 .4 5 ± 0 .2 3

2 .30 ± 0 .40

2 .12 ± 0 .33

1 .5 0 ± 0 .4 0

1 .71 ± 0 .56

3 .4 5 ± 0 .4 0

2 .9 7 ± 0 .3 3

1 .94 ± 0 .39

2 .0 4 ± 0 .7 9

3 .7 5 ± 0 .6 1

2.73 i 0.762.36 i 0.69

Mobile

olfactometer

Wind direktion

Manuredarea

Fig. 4. Layout of field experiments withobservers determining the odour intensityon different distances from the manured

field.

The results are given in Fig. 5 a-b. Diagram a gives the strength ofthe odour emanating from the spreading alternatives as a function of thetime at the observation points 100 m to the leeward of the manured areas.The percentage value gives the odour strength as experienced by the observers in relation to the referent. According to the diagram, after surface spreading the odour in the ambient air was considerably stronger thanafter the injection method had been used; initially there was a five-fold

difference. The odour following the injection of manure held a fairlyconstant level, but the odour following surface spreading decreased sharplyafter about one hour. Towards the end of the 2-hour observation period, thegap between the odours from the two methods had decreased but a certaindifference still remained.

Diagram b gives the odour expressed as a function of the distance fromthe manured area. It can be seen that there was a considerable differencebetween the two met hod s. At 100 m the surface spreading resulted in (onaverage) about a 10 times stronger odour than when the slurry was injected.After slurry injection the level stabilised at 200 m , while with surface



211

40

.30

20.c

bo

I 10

/ s7*v-TT

tli« .

\

• Sur

o So/l

Pceveo

nety%

D O

O

O

face

injet

sprea

ztion

\\

\

ding

\

\\

\

40 80

Time. min.

120 200

Distance, m

400

Fig. 5. a. Perceived odour intensity as a function of time for two spr e a dinga lter n a tiv es; subsur f a ce injection and spr e a ding on the sur f a ce,b . Perceived odour intensity as a function of dista nce for two spr e a dinga lter n a tiv es; subsur f a ce injection and spr e a ding on the s u r f a c e .

spr e a ding the odour at 400 m was 5-10 tim es str onger tha n a fter injectionat the s a me d i s t a n c e . The odour at 200 m a fter injection was down to the

lev el wher e it could not be distinguished fr om other ba ckgr ound odou r s.Consequently it is clea r that bur ia l of the m a nu r e effectiv ely r educes theo d o u r .

3. UTILIZATION OF NITROGENOn fa r m s wher e a la r ge pr opor tion of the a r e a consists of long

dur a tion leys it may be essential to utilize som e of this area as a pla ceupon which slur r y can be s p r e a d ( 3 ) . As the spr e a ding of slurry on leys orpa stur es in the conv entiona l way is not suita ble fr om feed hygiene a spec ts,the spreading of slurry by m e a n s of injection would be a way of utilizingthese a r ea s .

Increased interest has been shown with r ega r d to the pla nt nutr ient

content of slur r y, and exper i m ents both in Sweden and elsewher e ha v e dem onstrated that a better utiliza tion of the m a nu r e's nitr ogen effect is

obtained if the slurry is incorporated than if spr e a d conv entiona lly.Finnish exper i m ents dem onstr a te tha t incor por a tion giv es v er y high yieldincr e a ses, pa r ticula r ly under dry condit ions. Com pa r isons in tr i a ls betweenincor por a tion and surface spreading of the sa m e a m ounts of slur r y ha v eresulted in almost 1000 kg higher gr a in yield per h e c t a r e or a 30-45 % yieldincr e a se a fter incor por a tion. Exper im ents with incor por a tion of slurry in

leys have also given good results and pa r ticula r ly as r eg a r ds the effect ofthe slurry in the following yea r . An important effect of incor por a tion on



212

leys is, in addition, that the risk of deteriorated seed quality is considerably less than if the slurry is spread on the surface.

Swedish experiments have resulted in yield increases in grain of 5-1OZ

when the slurry was incorporated instead of being spread on the surface.

4 . SPREADING CAPACITYTime studies were conducted at JTI during the spreading of slurry both

using an injector and when spread conventionally. When using the injectorthere is a strong reduction in the effective working width and in generalit is not practically possible to increase the driving speed so much thatthe same discharge rate from the tanker can be retained. This implies thatthe time needed to unload a tanker equipped with an injector is abouttwice as long as if conventional spreading was used. However, the differencebetween the two methods should be calculated using the total time forfilling, transport to the field, spreading, transport back from the fieldas well as any stationary periods, etc. In a time study made when thedistance between the field and the manure pit was ca 800 m the totalspreading capacity decreased by ca 10 % when the method was changed fromconventional spreading to spreading using an injector.

REFERENCES

(1) LI N DVALL , T. 19 70 . On sensory evaluation of odorous air pollutant

intensities. Nordisk H ygienisk Tidskrift, Supplementum 2:1-181,Stockholm.(2) LI ND VALL, T., NOR EN , 0. & THYSE LI US , L. 1972. Luktreducerande atgarder

vid flytgodselhantering. S pecialmeddelande 22 , Swedish Institute ofAgricultural Engineering, Uppsala.

(3) NO RE N , 0. & THYS EL IU S, L. 1982. Battre effekter uppnas med myllning.Lantbruks-Nytt 1982 nr 4 , Malmo.



213

SEPARATION AS A METHOD OF MANURE HANDLING

AND ODOURS REDUCTION IN PIG BUILDINGS

Ing. W. KroodsmaInstitute of Agricultural EngineeringMansholtlaan 10-12, Wageningen, The Netherlands

Summary

This paper discusses the development and performanceof a combined system for the separation and removal ofdung and liquid in piggeries. The system separates thefaeces and urine, directly after production, by a filternet situated under the slats. The filter net with thefaeces is removed from the pens daily. If the pigs eatwet feod, without drinking nippels,about 35% of thetotal production of faeces and urine is separated as asolid.Together with some wasted straw from the lyingarea the faeces are stackable. The strawmanure has ahigh fertilizer value.The remaining liquid flows continuously to a pitoutside the house and" is pumped in a silo. The fertilizervalue is low. Daily removal of faeces and urine promotesas well a better house climate as a lower odour emission incomparison with piggeries with underslat slurry storage.Installing this filtersystem in partly slatted floorhouses straw can be used to improve animal comfort, andto reduce heating costs.

The investment for the filter net system, is related tothe number of pigs and lay-out of the piggery. Theinvestment in mechanial components can be partly offsetby shallower, less expensive channels and by notinstalling a heating system.

1. INTRODUCTION

Till about 1970 pigs were kept in houses with slattedfloors. Straw was provided on the floor of the pens. The faecestogether with wasted straw were removed out of the house dailyand stacked and handled as farmyard manure. The liquid drainedto a pit continuously.

This manure handling system is replaced in the course ofthe years by the slurry system. This system is based on partlyor totally slatted floors with underslat slurry storage. Thismanure handling system is labour saving and together withdevelopments in technology and management the size of the



214

piggeries increased. In that time limits to farm size wereseldom determined by farm waste disposal and air polution.

At present there are local regions where is a surplusof slurry. Due to the low value as a fertilizer transportto other regions is too expensive and in some cases overmanuring will exceed.

Separation of slurry offers the possibility of obtainingsolid manure with a high fertilizer value and a liquid with alow value. On this way it becomes more worthwhile to transportthe solid manure over longer distances, so it reduces overmanuring. However slurry separation with a high efficiency iscostly about £4,-/pigplace by adding flocculants and expensivecomplicated separations (1).

Underslat slurry storage also influences environnement aswell inside as outside the piggery because gases are releasedfrom the slurry. On the other hand anaerobic digestionprocesses will be avoid by daily removal and separate storageof faeces and urine.

That factors were for IMAG a motive to develop a reliablecombined manure filter and removal system for piggeries.

2. SEPARATION EFFICIEN CY

In a preliminary investigation the separation efficiencyof different separation techniques under slatted floors wasdefined. Separation efficiency means which part of the totalcomponents in faeces and urine remains in the faeces. Thisresearch was carried out in a pen with 8 pigs. The pigs weregiven wet feed without drinkwaterprovisions.

In Fig.l the separation result is mentioned for a filternet of meshsize 0.78x0.78 mm. From Fig.l it is apparent thatabout 3 5% of the total faeces and urine is removed as a solidand that about 90% of the total dry matter is in the faeces.Also for a number of minerals, P?0,-, CaO, MgO and Cu, it

amounts to more than 90%. Nitrogen and potassium wereseparated in smaller amounts, about 60 % and 4 0% respectively,being retained in the solid.

On basis of this result and after comparative researchwith concern for filtering, clogging and cleaning the abovementioned filternet is now being used for the final mechanizedfilter and removal system.

3. THE MECHANIZED FILTER INSTALLATION

A combined filter and manure system must be completelyreliable, since it is not easy to make repairs under the slats.After 2-3 years of experience a system which works well hasbeen developed.(2,3,4 ) In Fig.2 a schematic diagram of thefilter system is shown under the slatted floor. In the channelunder the slats two angle sections (1) are attached one abovethe other and fixed over the whole length to both walls. Theseare covered from above with protective plates (2) Joinedunderneath the slats. The filter net (3) is provided with



215

□ aeces urine S j ( % )

10 0

9 0

8 0

70

6 0

50

4 0

30

20

10

i-«-kg dm. crude N-KJ NH4 - P 2 0 5 K20 CaO MgO Cu BOD 5 COD

ash N

Fig. 1 : Separation efficiency (in faeces) for net of mesh size 0.78 x 0.78 mm.

^

y y y

V/

y y y

y 4 '/,

'/,

y

y y y

y y y 6 y

y y y y

•0

c

2

y

y y

y

y y

y

y

r~ r

y y

y

y y

y y y y

y y

77

y

y

y y y

y

y

/ /

y

y

y y

tw* I ' j = T

J^^s:.vis.fcg!^

: /

Fig. 2 : Schematic diagram of the filter system 1 - Angle section 2 - Protective plates 3 - Filter net with steel strips 4 - Front roller 5 - Driving unit 6 - Wire cable 7 - Transport belt 8 - Brush roller



216

Fig. 3 : Plan of the piggery with the filter system~ and outside storage of dung and liquid

1 - storage for farmyard manure and liquid2 - dung gutter

3 - liquid gutter

Fig. 4 : Piggery with the filter| system. The straw manure

is removed by belts to

the manure spreader.



217

steel strips across the net at 1.0 m intervals and extendingfrom the net on both sides. During the day both ends of thesteel strips lie on the upper angle section. In this positionthe faeces, which have fallen through the slats remain on thenet, while the urine is filtered through. During the muckingout process, the filter net is drawn at a speed of about10 m/min over a roller (4 ) situated at the front of thepighouse. During mucking-out the strips slide from the upperangle section over the front roller to the bottom anglesection. A brush roller (8) assists removal of the faecesfrom the filter net. The combination of the angle sectionson the walls of the channel and the steel strips in the filternet ensure for a reliable mucking out. Two types of driving

units (5) are being investigated. In the first two motors of0.75 kW are placed at the back end of the pighouse and arejoined to the net via a stainless steel wire (6) When switchedon, one draws the net (3) over the front roller(4 ) back intothe pen. During the operation the faeces fall from the net onto the transport belt (7) which carries the faeces outside.At the end the first motor switches off automatically and thesecond switches on and draws the filter net back to itsoriginal position.

In the second case a 0.75 kW motor with a pre-setspringloaded tension apparatus is installed. The stainless

steel wire (6) is wound 4-5 times around a drum. When themotor is switched on, the wire tightens and the filter net (3)is drawn backwards and forwards over the front roller ( 4 ) .

Although the filter net has been cleaned by the brushroller during mucking-out some of the faeces block graduallythe net by puddling and drying-out. For this reason the nethas to be thoroughly cleaned periodically by a high-pressurehose while the net is drawn backwards and forwards. Thisturn-out depends on the consistency of the faeces and variesbetween 8-12 weeks.

4. LAY-OUT OF THE PIGGERY

The experiments were done in an old stall for 160 pigsand partly slatted floors. Fig.3 shows the piggery which wasrenewed and adapted to the filtersystem. The faeces mixed withthe wasted straw of the lying area were removed every day by atransport belt (2) in the dung gutter and stacked on top of thecovered pit ( 1). The urine flows through the liquid gutter (3)into the underground storage pit (1).

5. RESULTS

5 .1. Composition_of_faeces_and_urine

In Table 1 the average composition is recorded from twosamples of faeces and urine for the net with a mesh size of0.78x0.78 mm installed on the above mentioned piggery.



218

Table 1: Average composition of faeces and urine afterseparation by a filter net (0.78x0.78)

Dry matter

Crude

N-Kj

NH.-N4

P 2 ° 5K 2 0

CaO

MgO

C u

pH

ash

(%)

(%)

(%)

(%)(%)

(%)

(%)Wppm

of dry matter

Faeces

32.50

25.70

1.24

0.34

1.64

0.85

1.45

0.48

197

-

Urine

1.92

63.10

0.34

0.35

0.05

0.62

0.04

0.02

2.50

9.1

From Table 1 it is evident that the percentages of theminerals in the faeces are high. In the urine the percentagesare much lower except potassium.

By manuring grassland potassium is the limiting factor,while an arable land the quantity of nitrogen needs to betaken into account. In applying solid manure to cropland theCu-content needs to be taken into account. Depending on theCu-status of the soil, 0-6 kg Cu/ha is advised. By fertilizingwith 10 t/ha of solid manure about 3 kg Cu/ha is administeredBecause only a small amount of copper is taken up by plantgrowth and lost through drainage, the application of solidmanure needs to be spread out over a few years if Cu is not toaccumulate in the soil.

5.2 Odour emissions

It can be concluded that separation and removal of urineand faeces from piggery result in a reduced formation of odourcomponents ( 5 ) . This might result in a decrease of theprecieved odour as compared with a housing system withunderslat slurry storage.

In order to obtain a reliable figure for the actual odourreduction, measurements have been carried out. Samples ofventilation air from a pighouse with underslat slurry storage

as well as a pighouse with filter nets were taken on a numberof different occasions. All samples were collected in bagsmade from FEP-Teflon. Odour experiments were performed thefollowing day using a dilution apparatus (olfactometer) and agroup of observers (panel). Since the establishment of theodour intensity is a time consuming affair, it has becomepractice in Dutch agricultural odour research to concentrateon the establishment of the odour treshold ( 6) . The odourtreshold is defined as that dilution of odorous air which



219

cannot be distinguished from odourless air by 5 0 % of thepanel members ( D T 5 0 ) . This implies that the threshold is abarely detectable odour. The number of times a sample has tobe diluted to reach threshold levels is a measure for therelative strength of the odour. The relative odour strengthtimes the ventilation rate of the building results in theodour emission. This can be regarded as the total odour loadper unit of time leaving the building. Finally the odouremission can be used in atmospheric dispersion models in orderto calculate the odour threshold distance.

Table 2 shows the results of the experiments as well asthe relevant data of the pighouses at the time of sampling.During the measurements the ventilation rate between the

pighouses varied. The difference are due to differentventilation rates and due to sampling in the morning or inthe afternoon at different ambient temperatures.

Table 2: Odour measurements

158Average liveweight (kg2> _. 75

Ventilation rate (m 3kg h ) 0.61

Pighouse with separation

Data of sampling 24.5 .83 31.5 .83 14.9 .83 28.10.83Numb er of pigs 158 158 158 157

80 45 75

0.93 0.89 0.47Dilutions to threshold

(DT50) 77 0 1008 817 1634Total odour emission

( D T 5 0 / h.l 0 3) 559 5 11902 5195 9103Odour emission/pig

(DT50/ h) 354 10 75326 32877 57980Em ission reduction/pig (%) 49 5 0 50 59

Pighouse with underslat slurry storage

Data of sampling 24.5 .83 31.5 .83 14.9 .83 28.10.83Number of pigs 30 0 275 279 279Average liveweight ( kg}. _. 80 9 0 4 5 85Ventilation rate (m 3kg h ) 0.21 0.54 0.52 0.57Dilutions to threshold

(DT50 ) 4133 3068 2820 2903Total odour emission

( D T 5 0 / h.l 0 3) 20632 4 1234 18409 39205Odour emission/pig

(DT50 /h) 68773 14994 2 65982 140520E mission reduction / pig (%) n.a. n.a . n.a. n.a.

n.a.= not applicable

It can be concluded from Table 2 that the installation offilter nets reduced the odour emission per pig byapproximately 50%



220

6. ECONOMIC ASPECTS

6.1. Investment

In Fig. 3 the lay-out of the piggery is mentioned. Thestall is renewed and instead of the normal depth of 1.50 m byunderslat slurry storage the channels have a depth of 0.50 m.These shallow channels are as a matter of course cheaper buton the other hand facilities for storage of dung and liquidmust be build outside the building. In front of the stall adung and liquid gutter has been build, where thetransportbelts are installed. The investments for the filtersystem of this piggery are given in Table 3.

Table 3: Survey of extra capital investment of the filtersystem, in comparison with the slurry system(£/pigplace)

Filter system in both channels 3750Dung and liquid gutter 1250Transportbelts 2500Dung and liquid storage 2500

10000Estimated reduction by shallow channels 2500

Extra capital investment 7500

Extra capital investment/pigplace 46.90

This price is relatively high on account of the smallnumber of pigs. Other calculations show that the investmentcosts are lower in comparable stalls with a capacity for480 and 960 pigs. These stalls are more common, the costs arerespectively £ 18 and £ 11/pigplace.

Calculations confirm also the expectations that stalls

with long channels in longitudinal design are more favourablefor this filter system than stalls with short channels intransverse style.

6.2. Annual_cqsts

The costs depend first on the capital costs and secondlyon the costs of straw. On the other hand savings are possibleon building structures and heating system. Besides thesefactors other savings are possible because some disadvantagesof the slurry system can be removed by the filter system; for

example costs for fuelexpenditure and slurry disposal.A calculation for a standard plan for 480 and 960 pigs

shows that in a comparable stall as in Fig. 3 the extra annualcosts for the filter system are slightly higher than for theslurry system; respectively £ 1.11 and £ 0.08 /pigplace. Thecosts for stalls with transverse and short channels are muchhigher and vary between £ 3.70 - £ 3.40 /pigplace. Comparedwith the costs for slurry separation in a slurry disposalcentre the costs for the filter system in stalls with long



221

channels are lower and the costs in stalls with short channelsare nearly identical.

REFERENCES

(1) STUURGROEP Mestproblematiek, N.C.B. - Kostenramlng vanmestscheiding in een centraal mestverwerkingsbedrijf(1981) (Calculations of slurry separation in a slurrydisposal centre).

(2) KROODSMA, W. (1980) - Separation of Pig Faeces fromUrine using synthetic Netting under a slatted floor.The Proceedings of the 4th International Symposium on

Livestock Wastes 1980, 419-4 22. Livestock Waste: Arenewable resource.(3) KROODSMA, W. - Trennung von Fakalien und Harn in einem

Schweinestall mit Spaltenboden (Separation of faeces andurine in a piggery with slatted floors).Bericht Uber die 7. Arbeitstagung "Fragen der Gullerei",1981, III. Band, 761-771.

(4) KROODSMA, W. and POELMA, H.R. - Mestscheiding(Separation of pig and cow slurry)IMAG-publikatie 209 (in preparation).

(5) SPOELSTRA, S.F. - Microbial aspects of the formation of

malodorous compounds in anaerobically stored piggerywastes. Proefschrift - Agricultural University -Wageningen.

(6) KLARENBEEK, J.V. - Odour measurements in Dutchagriculture: current results and techniques.R.R. 82-2 Institute of Agricultural Engineering,Wageningen.



2 2 2

M E A S U R E M E N T S O F T H E O L F A C T O M E T R I C E F F I C I E N C Y O F V A R I O U S O D O U R C O N T R O LD E V I C E S IN R E N D E R I N G P L A N T ?

G . - J . M E J E RI n s t i t u t f u r l a n d t e c h n i s c h e G r u n d l a g e n f o r s c h u n g d e r

B u n d e s f o r s c h u n g s a n s t a l t f u r L a n d w i r t s c h a f t

S u m m a r y

A s t h e r a w m a t e r i a l o f r e n d e r i n g p l a n t s p r o d u c e s v e r y o d o r i f e r o u s

s u b s t a n c e s , a i r c l e a n i n g s y s t e m s a r e u s u a l . F i v e s u c h a i r c l e a n e r s inn o r m a l p e r f o r m a n c e w e r e m e a s u r e d o l f a c t o m e t r i c a l l y . T h e o l f a c t o m e t r i ce f f i c i e n c y o f b i o f i l t e r s p r o v e d t o b e b e t t e r t h a n t h a t o f c h e m i c a ls c r u b b e r s . A l a r g e d i f f e r e n c e b e t w e e n t h e r e l a t i v e o d o u r c o n c e n t r a t i o ni n t h e c l e a n e d a i r a n d a s s e r t e d l i m i t v a l u e s , b a s e d o n o l d e r o l f a c t o m e t r i c m e t h o d s c o n f i r m t h e n e c e s s i t y o f a s t a n d a r d i s a t i o n o f o l f a c t o m e t r i c m e a s u r e m e n t m e t h o d s .

1 . I N T R O D U a i O NF o r e p i d e m i c p r e v e n t i o n a n d p u b l i c h e a l t h , r e n d e r i n g p l a n t s a r e b o u n d

b y l a w t o a c c e p t a l l p e r i s h e d a n i m a l s a n d p a r t s o f a n i m a l s i n a n y s t a g e o fd e c o m p o s i t i o n . D u e t o t h e n a t u r e o f t h i s r a w m a t e r i a l , c o n t a i n i n g f a t a n dp r o t e i n , i ts b i o l o g i c a l d e c o m p o s i t i o n i n c r e a s e s w i t h t i m e a n d t e m p e r a t u r eo f s t o r a g e , a n d v e r y o d o r i f e r o u s c o m p o u n d s a r e p r o d u c e d .

A s s t o r i n g t e m p e r a t u r e a n d t i m e o u t s i d e t h e p l a n t a r e o f t e n o u t o f t h ei n f l u e n c e o f t h e p l a n t m a n a g e m e n t , a t l e a s t in s u m m e r t i m e t h e h a n d l i n g o ft h i s v e r y o d o r i f e r o u s m a t e r i a l i s a n o r m a l p r o c e d u r e . In o r d e r t o p r e v e n ta n e s c a p e o f t h e o d o r i f e r o u s c o m p o u n d s i n t o t h e a t m o s p h e r e , i n m o d e r n

p l a n t s a l l d e v i c e s a n d a ll m a c h i n e r y a r e c a p s u l a t e d a s c l o s e a s p o s s i b l ea n d a l l o d o r i f e r o u s g a s e s a n d a l l p o l l u t e d a i r a r e c o l l e c t e d a n d e x h a u s t e di n t o a n a p p r o p r i a t e a i r c l e a n i n g s y s t e m , w h e r e a ll o d o r i f e r o u s c o m p o u n d ss h o u l d b e r e m o v e d a n d / o r d e s i n t e g r a t e d t o o d o u r l e s s s u b s t a n c e s , b e f o r e t h ec l e a n e d a i r i s r e l e a s e d i n t o t h e o p e n a t m o s p h e r e .

I n f o r m e r t i m e s , r e n d e r i n g p l a n t s , w e ll k n o w n f o r t h e i r o d o u r p o l l u t i o n s , w e r e b a n i s h e d t o a s i t e f a r a w a y f r o m h u m a n h o u s i n g s , in o r d e r t op r e v e n t o d o u r n u i s a n c e . B u t i n o u r t i m e , v a r i o u s g r o u p s i n s i s t t h a t m o d e r nr e n d e r i n g p l a n t s c a n b e r u n w i t h o u t o d o u r n u i s a n c e o f t h e n e i g h b o u r h o o d/ V .

S o a u t h o r i t i e s a l l o w e d t h e s e t t l e m e n t c l o s e r t o t h e r e n d e r i n g p l a n t s ,b u t c o m p l a i n t s o f t h e i n h a b i t a n t s i n t h e v i c i n i t i e s b e c a m e c o m m o n .

I n t h e r e n d e r i n g p l a n t g u i d e l i n e p r o p o s a l V DI 2 5 9 0 E / 2 / , p u b l i s h e d i n1 9 7 9 , i t w a s c l a i m e d a s s t a t e o f t h e a r t t h a t t h e r e l a t i v e o d o u r c o n c e n t r a t i o n in t h e c l e a n e d e x h a u s t a i r s h o u l d b e l e s s t h a n 1 0 0 o d o u r u n i t s . Itm u s t b e s u p p o s e d t h a t t h e d a t a b a s e o f t h i s l i m i t v a l u e h a s b e e n a c h i e v e db y o l d e r m e a s u r i n g m e t h o d s , d i f f e r e n t f r o m t h a t d e s c r i b e d in t h e g u i d e l i n e/ 3 - 5 / .

T o p r o v e t h e r e al e f f i c i e n c y o f w o r k i n g a i r c l e a n i n g s y s t e m s i n t h ef i e l d a n d t o p r o v e o u r o d o u r m e a s u r e m e n t m e t h o d a n d d e v i c e t h a t a g r e e d w i t ht h e a l r e a d y p a r t i a l l y o u t l i n e d b u t n o t y e t p u b l i s h e d g u i d e l i n e V D I 3 8 8 1 E



223

/ 3 - 5 / , a s e r i e s of o l f a c t o m e t r i c m e a s u r e m e n t s in w o r k i n g r e n d e r i n g p l a n t sw e r e c a r r i e d o u t . F u r t h e r m o r e , the r e s u l t s s h o u l d h e l p to p r e v e n t m i s-p l a n i n g and m i s i n v e s t m e n t s due to m i s u n d e r s t a n d i n g o d o u r l i m i t v a l u e s .

2 . E X P E R I M E N T A L

2 . 1 R E N D E R I N G P L A N T S AND AIR C L E A N I N G S Y S T E M SI n G e r m a n y a p p r o x i m a t e l y 80 r e n d e r i n g p l a n t s , s p r e a d all o v e r the

l a n d , p r o c e s s m o r e t h a n 8 0 0 0 0 0 t of raw m a t e r i a l per y e a r . F i v e p l a n t s inn o r t h e r n G e r m a n y w e r e c h o s e n w i t h d i f f e r e n t s i z e and d i f f e r e n t air c l e a n i n gs y s t e m s , t a b l e 1. T h e s e c h o s e n air c l e a n e r s are of the c o m m o n t y p e s inr e n d e r i n g p l a n t s . The a t t e m p t to i n c l u d e a l s o a b i o s c r u b b e r and ana c t i v a t e d c a r b o n f i l t e r f a i l e d due to f r e q u e n t b r e a k d o w n s .

A l l air c l e a n e r s w o r k e d a l r e a d y for s e v e r a l y e a r s and w e r e o p e r a t e d in

u su a l m a n n e r w i t h o u t any v a r i a t i o n s or m a k e up e s p e c i a l l y for the m e a s u r e m e n t s . T h e s e w e r e c a r r i e d out in a m o d e r a t e w e a t h e r p e r i o d w i t h a m b i e n tt e m p e r a t u r e s of 16-21 °C. The s a m p l e s w e r e t a k e n d u r i n g n o r m a l c o n t i n u o u sp l a n t p e r f o r m a n c e , t h a t m e a n s w i t h c l o s e d c o o k e r . In a d d i t i o n , in p l a n t As a m p l e s w e r e t a k e n in p e a k l o a d p e r f o r m a n c e , w h e n the c o o k e r was o p e n e d .

Plant

raw material

capacitydistance tonext housing

air cleaningsystem

reagents

air flow

meanretentiontime

working time

t/hm

m 3 / h

s

years

A

animals/parts

5900

countercurrentscrubber

H 2 0 ,

H

2 °2

40000

3,6

3

B

animals/parts

121500

crosscurrentscrubber

H 2 0 ,

H 2S0 4 ,

NaOH,

NaOCl

60000

3

3

C

bones

1 ime-stonetower

H 2 0 .

c i 2 ,

CaCO,

60000

54

5

D

animals/parts

b i o -filter

carbagecompost

H 20

38000

54

6

E

blood

10800

b i o -filter

carbagecompost

H 20

37000

39

6renewed 1

T a b l e 1. S o m e d a t a of the m e a s u r e d r e n d e r i n g p l a n t s and of the airc l e a n i n g s y s t e m s .

2 .2 O D O U R T H R E S H O L D D E T E R M I N A T I O NA l t h o u g h the g u i d e l i n e VDI 3 8 8 1 E / 3 - 5 / was not yet p u b l i s h e d , it was ,

a s m e n t i o n e d a l r e a d y , p a r t i a l l y o u t l i n e d by the VDI w o r k i n g g r o u p s" O d o r i f e r o u s S u b s t a n c e s " . As a m e m b e r of t h i s g r o u p , the m e t h o d was a p p l i e da s d e s c r i b e d in t h a t g u i d e l i n e , w i t h two s l i g h t d i f f e r e n c e s .



2 2 4

In the v i c i n i t y o f a r e n d e r i n g p l a n t it is v e r y d i f f i c u l t to f i n d ar e a l l y u n p o l l u t e d p l a c e for the o l f a c t o m e t r i c m e a s u r e m e n t s . A l t h o u g h them o s t u n p o l l u t e d s i t e l u f f o f t h e p l a n t w a s c h o s e n , a n o t h e r p r e c a u t i o n wast a k e n . As a d a p t i o n o f t h e p a n e l i s t s to the p l a n t o d o u r c o u l d c a u s e one oft h e g r e a t e s t e r r o r s , s o m e m i n u t e s b e f o r e and d u r i n g t h e m e a s u r e m e n t thep a n e l i s t s i n h a l e s o l e l y o d o u r l e s s air f r o m t h e o l f a c t o m e t e r . To p r e v e n td i s c o m f o r t by i n h a l i n g c o m p l e t e l y dry a i r , the o l f a c t o m e t e r M o d e l l 1 1 5 8 iss u p p l i e d w i t h a m o i s t e n i n g d e v i c e , f i g . 1.

- t * H

Olfaktometer

Model 1158

F i g . 1. M o i s t e n i n g d e v i c e .

In a s t a n d a r d i m p i n g e r , f i l l e d w i t h d e s t i l l a t e d w a t e r , air ism o i s t e n e d c l o s e to s a t u r a t i o n . An e q u a l f l o w o f m o i s t e n e d air is m i x e d tot h e o l f a c t o m e t e r o u t l e t , t h u s d e l i v e r i n g to the p a n e l i s t a r e l . m o i s t u r ec o n t e n t o f n e a r l y 50 % . Th e p a n e l c o n s i s t e d o f 4 p e r s o n s .

T h e s a m p l e s a r e p r e d i l u t e d t a k e n i n t o p l a s t i c b a g s , s i m u l t a n e o u s l y a tt h e i n l e t ( r a w a i r ) and a t the o u t l e t ( c l e a n e d a i r ) o f t h e air c l e a n e r s .T o r e c e i v e an u n f a l s i f i e d s a m p l e f r o m the o u t l e t of the b i o f i l t e r s ,

u n d i l u t e d by a m b i e n t a i r , a " t e n t " o f p l a s t i c f o i l , f i g . 2 , is p l a c e d ont h e f i l t e r s u r f a c e . Th e c l e a n e d air b l o w s u p t h e t e n t and e s c a p e s t h r o u g ht h e s a m p l e h o l e , l a r g e e n o u g h to p r e v e n t a s i g n i f i c a n t i n c r e a s e of p r e s s u r e .T h e f o r m o f the u p b l o w n t e n t i n d i c a t e s , w e t h e r a s a m p l e a r e a w i t h n o r m a la i r f l o w is c h o s e n , and o v e r t h e s p a c e of the c o v e r e d f i l t e r a r e a of 6 , 2 5 m 2

a n a v e r a g e s a m p l e is r e c e i v e d .

sample hole

F i g . 2 . D e v i c e for c l e a n e d air s a m p l e s f r o m b i o f i l t e r o u t l e t .



225

3 . R E S U L T S AND D I S C U S S I O NT h e o l f a c t o m e t e r r e a d i n g s of the m e a s u r e m e n t s are s t a t i s t i c a l l y

t r e a t e d as d e s c r i b e d in / 3 / . The r e s u l t s for the p l a n t s and air c l e a n i n g

s y s t e m s , d e s c r i b e d in t a b l e 1, are g i v e n in t a b l e 2.

system

plant

r e l . odourconcentration

Z5 0

/odour units/olfactometricefficiency n

raw air

cleaned air

chemical

A

65200

48300

2 6 %

B

14200

7360

48 *

C

26800

29500

- 9 %

biological

D

41400

7930

8 1 %

E

95100

5100

95 *

T a b l e 2. R e s u l t s of m e a s u r e m e n t s , o b t a i n e d d u r i n g n o r m a l p e r f o r m a n c e ,c o o k e r c l o s e d .

T a k i n g the i n d e x R for raw air at the c l e a n e r i n l e t and the i n d e x Cf o r c l e a n e d air at the c l e a n e r o u t l e t , the o l f a c t o m e t r i c e f f i c i e n c y of thec l e a n e r is d e f i n e d a c c o r d i n g to /6/ :

L 5 0 R - Z,50C1 0 0 %

"-50R1.

I n the r e g a r d e d air c l e a n i n g s y s t e m s , the o d o r i f e r o u s p o l l u t a n t s aref i r s t s e p e r a t e d f r o m the raw air by s o r p t i o n and t h e n d e c o m p o s e d byc h e m i c a l s or by m i c r o - o r g a n i s m s . As l o n g as t h i s d e c o m p o s i t i o n is not y etc o m p l e t e d , the p o l l u t a n t s may d e s o r b and r e p o l l u t e the air , w h e n s o r p t i o nc o n d i t i o n s , i.g. the raw gas c o n c e n t r a t i o n , c h a n g e .

B y the r e l a t i o n of the d i f f e r e n c e in r aw and c l e a n e d gas c o n c e n t r a t i o nt o the a c t u a l raw gas c o n c e n t r a t i o n , a n e g a t i v e e f f i c i e n c y may be c a l c u l a t e d by e q u a t i o n 1, i.g. w h e n a low raw air c o n c e n t r a t i o n is p r e c e d e d by ah i gh o n e . T a b l e 3 s h o w s p e a k c o n c e n t r a t i o n s and i n c r e a s i n g o l f a c t o m e t r i ce f f i c i e n c y , w h e n ~ " i n p l a n t A the c o o k e r is o p e n e d .

r e l . odour concentration

ZJ-Q /odour units/

olfactometric efficiency n

raw air 627000

cleaned air 240800

6 2 %

T a b l e 3. R e s u l t s of m e a s u r e m e n t s , o b t a i n e d in p e a k l o a d p e r f o r m a n c e w h e n

c o o k e r is o p e n e d .A l t h o u g h the n u m b e r of m e a s u r e m e n t s is too s m a l l for g e n e r a l

a s s e r t i o n s , s o m e d e d u c t i o n s can be d r a w n :T h e r e s u l t s c o n f i r m the s u p e r i o r i t y of the b i o f i l t e r s . And in f a c t ,

t h e n u m b e r of b i o f i l t e r s in r e n d e r i n g p l a n t s i n c r e a s e s .C o n c e r n i n g the r e l . o d o u r c o n c e n t r a t i o n in the c l e a n e d air, a l a r g e

d i f f e r e n c e is e v i d e n t b e t w e e n the p r e s e n t e d r e s u l t s and the a s s e r t i o n t h a ta l i m i t v a l u e of 100 o d o u r u n i t s can be a c h i e v e d . Two i n t e r p r e t a t i o n s canb e o f f e r e d :



2 2 6

1 . A r e n d e r i n g p l a n t m a n a g e r i s o v e r c h a r g e d b y t h e c o r r e c t m a i n t e n a n c e a n dt h e c o r r e c t c o n t r o l o f a c h e m i c a l s c r u b b e r a c c o r d i n g t o t h e c h a n g i n g

c o n d i t i o n s o f h i s p l a n t . T h e p o l l u t i o n i s b lo w n i n t o t h e s k y an d h e h a sn o r e l i a b l e s i g n al t o s u r v e y c l e a n i n g e f f i c i e n c y . S o he s e t s t h e c h e m i c a l s d o s a g e a s r e c o m m e n d e d a n d t r u s t s i n t h e g u a r a n t e e o f t h e m a n u f a c t u r e r o f t h e c l e a n e r . A n d a s h e h a s p a y e d a l o t o f m o n e y f o r i t , h e i sc e r t a i n h e h as d o n e h i s b e s t .

B i o f i l t e r s a d a p t t h e m s e l v e s , a n d d u e t o t h e g r o u n d l e v e l o u t l e t a f a i l u r e i s e a s i e r p e r c e p t a b l e .

2 . T h e l i m i t v a l u e m e n t i o n e d a b o v e a n d l i k e w i s e g u a r a n t e e d b y m a n u f a c t u r e r so f a i r c l e a n e r s i s b a s e d o n m e a s u r i n g m e t h o d s d i f f e r e n t f r o m t h o s ea p p l i e d h e r e a n d d e s c r i b e d i n t h e g u i d e l i n e s / 3 - 5 / . R e s u l t s o f m e a s u r e m e n t s , a c h i e v e d b y d i f f e r e n t m e t h o d s a r e n o t c o m p a r a b l e . T h e l a r g e d i f

f e r e n c e o f t h e v a l u e s i s a d i s t i n c t i n d i c a t i o n o f d i f f e r e n c e s i n e x i s t i n g m e t h o d s .

4 . C O N C L U S I O NT h e n e c e s s i t y o f a h a r m o n i s a t i o n a n d s t a n d a r d i s a t i o n o f t h e c o m p l e t e

m e t h o d o f o l f a c t o m e t r i c m e a s u r e m e n t s i s e v i d e n t , i n o r d e r t o a c h i e v e c o m p a r a b l e r e s u l t s .

A b a s i c r e q u i r e m e n t f o r t h e e s t a b l i s h m e n t o f a n y o d o u r l i m i t v a l u e i st h a t s u c h a m e t h o d i s e s t a b l i s h e d a n d g e n e r a l l y a c c e p t e d , a n d t h a t a llm e a s u r e m e n t r e s u l t s o n w h i c h a n o d o u r l i m i t v a l u e i s b a s e d a r e a l s o a c h i e v e d b y e x a c t t h i s m e t h o d .

R E F E R E N C E S

( 1 ) Q U E L L M A L Z , E . , T i e r k o r p e r b e s e i t i g u n g o h n e G er u c hs be l ' a ' s ti g u ng . V D I -K o l l o q u i u m " M i n d e r u n g v o n G e r u c h s s t o f f e m i s s i o n e n " , W i e s b a d e n , M a i 1 9 8 1 .

( 2 ) V D I 2 5 9 0 E n t w u r f : A u s w u r f b e g r e n z u n g , A n l a g e n z u r T i e r k b r p e r b e s e i t i n g u g .A u g u s t 1 9 7 9 .

( 3 ) V D I 3 88 1 B l a t t 1 E n t w u r f : O l f a k t o m e t r i s c h e T e c h n i k d e r G e r u c h s s c h w e l -l e n b e s t i m m u n g , G r u n d l a g e n , N o v e m b e r 1 9 8 3 .

( 4 ) V D I 3 8 8 1 B l a t t 2 E n t w u r f : P r o b e n a h m e fiir d i e G e r u c h s s c h w e l l e n b e s t i m -

m u n g m i t d e m O l f a k t o m e t e r .( 5 ) V D I 3 8 8 1 3 B l a t t E n t w u r f : M e s s e n d e r G e r u c h s s c h w e l l e m i t d e n O l f a k t o -

m e t e r n M o d e l 1 1 1 5 8 u n d T 0 4 .( 6 ) V D I 3 4 7 7 : B i l o g i s c h e A b l u f t r e i n i g u n g . B i o f i l t e r , D e c . 1 9 8 4 .

S p e c i a l t h a n k s t o t h e o w n e r s a n d m a n a g e r s o f t h e p l a n t s f o r t h es p a n t a n e o u s p e r m i s s i o n t o c a r r y o u t t h e m e a s u r e m e n t s , a n d l i k e w i s e t o M r .E . G A R R E L T S f o r h i s c o m p e t e n t c o u n s e l a n d a n d a n g a g e m e n t i n t h i s w o r k .



227

THE EFFECTS OF WEATHER ON ODOUR DISPERSION FROM LIVESTOCKBUILDINGS AND FROM FIELDS

M .L. WILLIAMSWa r r e n Spr ing La bor a tor y, Stev ena ge , Her tfor dshir e , UK

and N. THOMPSONM e t e o r o lo g i c a l O f f i c e , B r a c k n e l l , U K

Summary

A br ief outline of the a pplica tion of disper sion m odelling to theestim a tion of odour nuisa nce is giv en. This is followed by som ea ppr oxim a te m ethods of estim a ting concentr a tions a r ising downwind ofbuildings and fields . These m ethods a r e intended to pr ov ide bestestim a tes of concentr a tions a nd nuisa nce a r ising fr om odor ouscompounds rather than to provide a rigorous discussion of the fluidm echa nics Inv olv ed. By com pa r ison with em pir ica l for m ula e r ela tingdista nce of com pla int to odour em ission obta ined fr om a la r ge num berof exper i m enta l studies, the disper sion m odelling a ppr o a ch is shownto pr ov ide r ea sona bly a ccur a te r esults.

1. INTRODUCTIONThe pr ediction of the effects of m eteor ology on odour disper sion

ev en in the a bsence of buildings or fields is a com plex pr oblem , chieflybeca use of the v er y shor t tlm esca les ov er which odor ous com poundsinteract with the human sensory syste m. This has the consequ ence thatconv enient a v er a ging ov er m a ny r e a lisa tions of tur bulent ev ents in the

a tm os pher e, sm oothing out shor t per iod fluctua tions to giv e a v er a ges ov erper iods of sa y ~10 m inutes of the v a r ious pa r a m eter s a ffecting thedisper sion of the polluta nt is not a ppr opr i a te. This a v er a ging pr ocess,which is used in dea ling with the pr ediction of the disper sion of othera i r polluta nts such a s sulphur dio xide , is a conv enient m ea ns of r educingthe er r o r in estim a ted conce ntr a tions. Assum ing for exa m ple tha t asingle sour ce em ission r a te is known exa ctly, it is r ela tiv ely str a ightfor wa r d using sta nda rd disper sion m odels to pr edict a n a nnua l a v er a geconcentr a tion a t a downwind loca tion to within a n a ccur a cy of sa y ±25-30Z, while the likely er r o r in pr edicting a 1 hour a v er a ge concentr a tionwould be of the order of a factor of 2 to 3. Odorous stimuli act

typically over tlmescales of the order of seconds, so that the errors inconcentr a tions ca lcula ted using disper sion m odels ca n be v er y la r ge ,unless som e for m of em pir ica l pa r a m eter isa tion is use d. This will bed i s c u s s e d b e l o w . An i l l u s t r a t i o n of t he d i f f e r e n c e b e t w e e n a n"insta nta neous" plum e pr ofile typica l of a n odour - r ela ted situa tion a ndan averaged pr ofile is given in Figure 1. The instanta neous profilea r ises fr om the stocha stic tur bulence pr ocesses a nd consequently is v er ydifficult to pr edict a b initio. The a v er a ged plum e pr ofile howev e r isless subject to er r o r a nd exper i m enta l a nd/or theor etica l da ta ca n beu s e d t o d e s c r i b e t he h o r i z on t a l an d v e r t i c a l p lu m e d i m e n si o n s ( O L a nd o )



228

for giv en m eteor ologica l conditions ( 1 ) . In such ca ses, sta nda rd Ga ussia ndisper si on equa tions such a s equa tion ( 1) ca n be used to estim a te downwind

gr ound lev el concentr a tions, C, a ppr opr i a te to the a v er a ging tim es used todeterm ine a- (and to a lesser extent o z ) :

C ^ - e x p (-0.5 ( y/ tt j 2) exp (-0.5 (H /a .) 2) ( 1 )ita 2a y U y z

wher e Q is the m a ss em ission r a te (g s - 1 ) , U is the wind speed (m 8 - ' ) , His the effectiv e emis sion height (m) and y is the crosswind dista nce fromthe plum e centr e line to the point a t which C is ev a lu a ted. Suchequa tions ca n be suita bly a v er a ged to ca lcula te long-ter m (a nnua l a v er a geconcentr a tions) or ca n be a pplied to a long-ter m ser ies of m eteor ologica l

conditions to inv estiga te the fr equency of exceedence of a pa r ticula rconcentr a tion, a s a function of tim e of yea r , wind speed a nd dir e ction.An example of such an exerci se is shown in Figure 2 where the frequency ofexceedence of fr a ctions of the m a xim u m a xia l concentr a tion is shown a s afunction of wind dir ection for a site in Exeter .

2 . ODO UR DISPERSIONThis subject ha s been tr ea ted pr ev iously in r efer ences 1 a nd 2 to

whic h the r ea der is r efer r ed for a fuller descr iption of the ba sicp r i n c i p l e s .

In dealing with the problem of odour dispersion it is convenient to

r e-define ter m s in the ba sic equa tion ( 1 ) . The "odour em ission" Eequiv a lent to a m a ss em ission r a te Q (g s - 1 ) is defined a s:

E - DF (m 3 s - 1 )

wher e F is the gas volume flow rate of the emissio n and D is the number ofdiluti ons to detecti on thr esho ld. E is thus equivalent to Q/Cg where Q isthe m a ss em ission r a te of the odor ous polluta nt (g s _ 1 ) and C 0 is thedetection thr eshold concentr a tion (g m - 3 ) .

If we consider downwind gr ound lev el concentr a tions on the plum ecentr eline (y - 0) for a gr ound lev el sour ce (H - 0) equa tion (1) becom es :

t O yC(2)

For a n elev a ted sour ce

2 C n DF ,o-_,

c- " 7 ±^ <$

(3)

U s i n g e q u a t i o n s ( 1 ) , ( 2 ) o r ( 3 ) w i t h v a l u e s o f c(̂ a nd o z obtained

fr o m the liter a tur e would in gener a l giv e unde r p r edictions of shor t per iod(~secs) odo ur related concen trat ions since most aver aging times of a„ ando z reported In the literature are at the least ~3-10 minu tes ( 3 ) . (The CL,v a lu es quoted by Sm ith a nd Ha y (4 ) a r e a n exception a nd r efer toeffectiv ely insta nta neous v a l ues. ) If C r epr esents the insta nta neous orpea k concentr a tion then the under p r ediction ca n be wr itten:

C = RC

Sim ila r l y, com pla ints do not a r ise when the odour is just detected, but a tthe r ecognition or a nnoya nce thr eshold which is la r ger tha n the detection



229

FIG.1 INSTANTANEOUS AND AVERAGE CONCENTRATION PROFILES

Instantaneous Top View

of Plume

Y

SOURCE x„

MEAN WIND>

<?

Instantaneous

Concentration

Profile at X=x„

Y

1 Hour Average

Concentration

Profile at X=x0

-s-C

FIG. 2 ODOUR CONCENTRATION FREQUENCIES

(AS % WITHIN EACH 10° WIND SECTOR)

( a l ALL CONCENTRATION , (b ) C > C 0 / 1 6 , (c ) C > C 0 / 4 ,

I d ) C > C 0 / 2 , | C 0 = MAX. AX IA L ODOUR STRENGTH I

116845]



230

thr eshold by a fa ctor S. Hence fr om (2) concentr a tions a t which nuisa nceor com pla ints a r e likely to occur is giv en by

C - -) ° „ (4)S tQyOjj U

As a workin g rule of thum b, WSL has used va lues of R ~ 10 and S ~ 5 asbr o a dly a dequa te, a ccepting tha t the pr ediction of shor t ter m pea ks isnecessa r ily ina ccur a te, a nd tha t som e centr a l estim a te of pr a ctica l use isr equi r ed. A discussion of shor t per iod tur bulent fluctua tions ha s beeng i v en b y H a nn a ( 5 ) .

3. EFFECTS OF LIVESTOCK B UILDINGS ON DISPERSION

In broad terms it is reasonable to assume that any plumes escapingfr o m liv estock buildings either thr ough chim neys or a dv entitiously thr oughc r a c k s , wind ows , etc will be entr a ined in the building wa ke . Exceptionswould be those cases where the chimney height was >2.5 times the buildingheight or wher e the efflux v elocity wa s ^4 tim es the wind speed. Theeffects of the building ca n be inv estiga ted in the nea r - a nd fa r -field,a nd a discussion ha s been giv en in r efer ence ( 6 ) .

3.1 FAR-FIELDThis would be defined typica lly a s a dista nce gr ea ter tha n -10-15

building heights downwind. In such ca ses it is a r ea sona ble a ppr oxim a tion

to assume that the effect of the building is to give what would otherwi sebe r epr esented by a point sour ce a n initia l non-zer o size r epr esented byp l u m e w i d t h s a° and a° , such that o* ~ H/3 and <£ ~ W/3 wher e H a nd W a r ethe height a nd width of the building r e spectiv ely. One can then define a" v i r t u a l s o u r c e " a d i s t a n c e x u p w i n d o f t he b u i l d i n g an d u s i n g i nequa tion (2) new plum e widths a' such that

° z ( x ) " °y ( x + x v z )

w h e r e o z(o ) « H/3 a nd with a sim ila r expr ession for CL.

3.2 NEAR-FIELDFlows within the wa ke r egion of buildings a r e extr e m ely com plex a nd

gener a lly a pplica ble equa tions a r e difficult to der iv e . In pr a cti ce, theestim a tion of nea r -field concentr a tions in com plex flows a r ound buildingsis best under t a ken in a wind t unnel . Howev e r this m a y not be possible inm a ny situa tions a nd r ela tiv ely sim ple num er ica l estim a tes m a y be r equir ed.The following discussion outlines a pr ocedur e which is necessa r ily v er ya ppr oxim a te but which could be used a s a n initia l scr eening estim a te forconcentr a tions which should be a ccur a te to a bout a fa ctor of 3.

For buildings whose widt h W is la r ge com par ed wit h their height H,i.e. with W/H = 4-6, which would include m ost liv estock buildings the flow

in the wa ke is a ppr oxim a tely two-dim ension a l. Tha t is, a t a ny pointdownwind of the building in the wa ke r egion, the flow is br oa dly the sa m e,see Figure 3 . In such a cas e, the concen trat ion C in the wake region isgiv en a ppr oxim a tely by

K QC - ^ (5)

U H 2

wher e K is a consta nt = 2-3, Q is the m a ss em ission r a te a nd U the windspeed. For pea k (~1 sec) concentr a tions for odour nuisa nce to occur ,



231

,R, K Q

S U H 2(6)

wher e a v a lue of R of ~2-5 m a y be m or e a ppr opr i a te tha n the v a lue of 10quoted In the non-wa ke ca lcula tion In Section 2 a bo v e.

For buildings of a sm a ller a spect r a tio, in the a bsence of a m or er elia ble for m ula , equa tions (5) a nd (6) could be used, with a likelya ccur a cy of a bout a fa ctor of thr ee.

4. DISPERSION FROM FIELDSIn the same way that in the far-field the effect of a building w as

consider ed to spr ea d out wha t wa s other wise a point em issi on, so a fieldm a y a lso be consider ed a s a sour ce of extended d im ens ions, cr osswind a nd

upwind, a nd m a y be tr ea ted m a th em a tic a lly in a sim ila r m a nner to thatdescribed in Section 3.1. If W is the widt h of the field then we cana g a in use equa tion (2) in the sa m e wa y a s descr ibed in Section 3.1 with av a l u e o f o a t x - 0 ( t h e f i e l d d o w n w i n d e d g e ) g i v e n a p p r ox i m a te l y b y~W/3, a nd with the a na logous upwind v ir tua l sour ce ca lcula tion.

5 . A PRACTICAL ILLUSTRATION OF THE APPLICATION OF DISPERSION FORMU LAE TOODOUR PROBLEMSWa r r en Spr ing La bor a tor y ha s m ea sur ed the odour em issions fr om a

consider a ble num ber of pr ocesses a nd sour ces a nd colla ting the em issionswith da ta on the spa tia l extent of odour com pla ints, ha s der iv ed em pir ica l

f o r m u l a e r e l a t i n g t h e d i s t a n c e d m a x f r o m t h e s o u r c e w i t h i n w h i c hcom pla ints a r e likely to the odour em ission E a s follows ( 1 ) :

d m a x " ( 2 . 2 E ) 0 - 6 ( 7 )

with a n estim a ted r a nge of uncer t a inty of ( 0 . 7 E ) ° * 6 - ( 7 E ) 0 , 6 . Similarly ane m p i r i c a l l y d e r i v e d c hi m ne y h ei gh t H e r equir ed for a dequa te disper s a l ofa n odor ous em ission E is giv en by

H e - ( 0 . 1 E ) 0 , 5

Some examp les of odour emi ssions a re shown in Table 1.

TABLE I. OD OU R EMISSIONS FROM UNABATED PROCESSES

Process

Chicken HousePig PensMaggot FarmPrinting (Web Offset)Fermenter SterilisingFlshmeal (White80Z Oily Fish

Fish)

OdourStr ength,

D

6004-600

5,000

40,000715,000150,000400,000

Volum eFlowrate( m 3 s " 1)

4.2

-61.50.757.97.9

OdourE m ission( m 3 s-1)

2,520

-30,00060,000

536,0001 . 1 9 x l 0 6

3 . 1 6 x l 0 6

(Fr om this it ca n be seen tha t com pa r ed with som e pr oce sses, odoure m ission r a tes fr om liv estock buildings a r e likely in gener a l to be low.)

The equa tion (4) ca n be r ea r r a nged to yield a theor etica l a na logue of



232

F I G . 3 2 - 0 F L O W A R O U N D A C U B I C A L B U I L D I N G

X IS T Y P I C A L L Y ~ 1 0 - 1 5 H b

| | 6 B 4 6 |

FI G .I WS L EMPIRICAL FORMULA [71 vs CALCULATIONS FOR B.D AND F

ST AB IL IT Y USING EQUATION <M

O B STABILITY

a D STABILITY

O F STABILITY

10,000

|l6«47|



233

(7) since a and a are, for given meteorological conditions, simply functions of the downwind distance x. Rearranging (4) then gives, for

distances less than which complaints might be expected ,R, DF

°v°z < H — <8> ' z S itU

Using l i t e r a t u r e values of a and a z for three typical atmospheric stabilities (Pasquill classes B, D and F or unstable/convective, neutral and stable conditions) and typical wind speeds of 2, 5, and 2 m s - 1

respectively the points shown in Figure 4 can be calculated. The values of R " 10 and S ■ 5 were used. The lines in Figure 4 are equation (7) with the range of uncertainties plotted. The points for B and D

stabilities fall within the empirical envelope suggesting that the dispersion formulae are reasonably adequate in such situations. However in the stable F conditions, for a given odour emission the distance of complaints is markedly overpredicted. This suggests that in such conditions the peak/mean ratio R is probably much lower than the value 10 used in the analysis. This is not unreasonabe since in such atmospheric conditions, turbulence is considerably damped and one would qualitatively at least expect the turbulent fluctuations to be small, leading to smaller values of instantaneous to time averaged (~3-10 minute) concentrations. Indeed, the Figure suggests that a value of R ~ 1-2 is more reasonable in F conditions.

ACKNOWLEDGEMENTS The authors would like to acknowledge the work of many colleagues at

WSL involved in odour assessment and in dispersion modelling, in particular to Dr R.L. Moss, Messrs D. Pope and H.R. Gibbens and to Dr A.W.C. Keddie and Dr D.J. Hall.

REFERENCES

(1) Odour Control - A Concise Guide, eds F.H.H. Valentin and A.A. North, Stevenage: Warren Spring Laboratory, 1980.

(2) KEDDIE, A.W.C. Prediction of Odour Nuisance, Chemistry and Industry, pp 323-326, May 1984. (3) TURNER, D.B. Workbook of Atmospheric Dispersion Estimates, Public

Health Service Publication No. 999-AP-26, Washington: US Dept of Health, Education and Welfare, 1969.

(4) SMITH, F.B. and HAY, J.S. The expansion of clusters of particles in the atmosphere, Quart. J. Royal Met. S o c , 87^, 82-101, 1961.

(5) HANNA, S.R. The exponential probability density function and concentration fluctuations in smoke plumes, Boundary Layer Met., 29, 361-375, 1984.

(6) Models to Allow for the Effects of Coastal Sites, Plume Rise, and

Buildings on Dispersion of Radionuclides and Guidance on the Value of Deposition Velocity and Washout Coefficients, Fifth Report of a Working Group on Atmospheric Dispersion, National Radiological Protection Board, NRPB-R157, 1983.



234

DESIGN AND USE OF BIOFILTERS FOR LIVESTOCK BUILDINGS

OLLE NORENSwedish Institute of Agr icultur a l Engineer ing

Summary

The v entila ted a ir fr om liv estock buildings com pr ises a potentia l

sour ce of com pla ints fr om people liv ing in the v ici nity. In or der toa v oid the com pla ints it m a y be necessa r y to r educe the odour in thev entila ted a ir . This m a y be a chiev ed using biofi lter s. Ver y com pr ehensiv e dev elopm ent a nd ev a lua t ion of such filter s ha v e been m a de byZe i si g ( 2, 3 ) .

The v enti la tio n a ir fr om the ba r n is extr a cted by fa ns whichblow the air into a duc t. From this duct the air is released bene atha sla tted floor upon whic h a ca 50 cm thick la yer of pea t h a s ' beenpla ced. Dur ing the pa ssa ge of the a ir thr ough the la yer of pea t theodour s a r e a bsor bed a nd conv er ted by m icr oor g a nism s to odourless subs t a n c e s .

The filter m a ter i a l should consist of pea t m ixed with hea ther inorder to keep the air res istanc e low. If the peat filter is to givem a xim u m odour r educt ion the pea t m ust be m oist.

Inv estiga tion concer ning the effect of biofilter s (4) showed thatthe concentr a tions of ga ses such a s a m m onia a nd hydr ogen sulphidedecr e a sed by a n a v er a ge 50 %. At a n optim u m lev el the r eduction wa s80 %.

The investment cost for a biofilt er was about 100 DM per pig inSouth Germa ny. As regar ds a Swedis h filter the investment cost wasc a 5 0 D M pe r p i g .

1 . I N T R O D U C T I O N

The v entila ted a ir fr om liv estock buildings com pr ises a potentia lsour ce of com pla ints fr om people liv ing in the v icin ity. Ma ny com pla intsa bout a nnoying odour s occur in built-up a r ea s wher e the dista nce betweenliv estock buildings a nd dwelling-houses is not or ca nnot be sufficientlyla r ge.

Em ission of odour s in the v entila ted a ir fr om a liv estock building isfr equently v er y la r ge. In a n inv estiga tion conducted by the SwedishInstitute of Agr icultur a l Engineer ing (Jor dbr ukstekniska Institutet, JTI)a nd the Env ir onm enta l Hygiene Dept., Ka r ol inska Institute (KI) a nd theSwedish Env ir onm ent Pr otection Boa r d (1) it wa s found, e.g., tha t the odourthr eshold wa s a bout 10^.° in two pig ba r n s, ea ch with ca 550 pig s. In oneba r n the m a n ur e system consisted of scr a pes a nd in the other of a sluicega te system . The odour em i ssion s, i.e., the pr oduct of odour str ength a nda i r flow, a r e a ll in the m a gnit ude 10^ m ^ per hour which im plies that ifthe odour s a r e diluted do wn to a n odour lesB lev el the flow wil l be ca100 m illion m 3 / h .



235

In order to avoid the complaints it may be necessary to reduce the odour in the ventilated air as much as possible. This may be achieved using biofilters.

Cleaning

of

discharged

air

is

commonly

used

in

industry

and

the

principles used are therefore well-known. The differences between applica-tion in industry and in agriculture are, however, very large. In industrial processes the air volume is usually relatively small and the concentration of odour substances large. As regards livestock buildings, there are large volumes of ventilated air but with a comparatively low concentration of odours in comparison with industry. Consequently, comprehensive work has been done with regard to developing biofilters suitable for livestock buildings.

The use of peat filters for reducing odours has been known for many years. Very comprehensive development and evaluations of peat filters have

been made by Zeisig (2, 3 ) . At present there are many filters being used in South Germany, a few in Holland and one in Sweden. My account will now mainly be based on experiences made by Zeisig but will be supplemented with our own experiences from the peat filter plant built in Sweden.

2. MODE OF OPERATION OF A BIOFILTER Figure I illustrates the construction and mode of operation of a bio-

filter. The ventilation air from the barn is extracted by fans which blow the air into a duct. From this duct the air is released beneath a slatted floor upon which a ca 50 cm thick layer of peat has been placed. During the passage of the air through the layer of peat the odours are adsorbed and

converted by microorganisms to odourless substances.

Dust filter

Peat mixed with heather

;-.V.-". \^ t! VJ-jvCi*-*t:":>,> ■:" ii'ii-:•'■'* •.'.' ■■ I '■ >

331

syivUv -• --—• ML ~ML

-~^-~ Q J -..

Fig.1.Principle of biofilter for odour reduction in the ventilation air according to Zeisig, H.D. et al 1982.

In order to keep the operating costs as low as possible the filter is dimensioned

in

such

a way

that

the

air

resistance

will

be

low.

Naturally,

the flow resistance is highly dependent on the filter material and the air speed through the filter. According to Zeisig, the filter area should be 25 m^ per 100 pigs. The filter material should consist of peat mixed with heather. A suitable mixture is considered to be ca 50 % peat and 50 X

heather calculated by volume. The flow resistance should then be below 15 mm water column. However, the fan should be capable of giving maximum air volume at 15 mm water column static pressure.

The slatted floor should be made of wooden slats. The spacing between two slats should be 30 mm. Large quantities of dust accompany the ventila-tion air and thus dust filters should be placed in the main duct in order



236

to prevent the dust from becoming deposited in the slatted floor and in the

peat, thereby gradually clogging the filter. The dust filters are cleaned

at intervals by being shaken. Zeisig considers suitable dust filter material to be Enkamort Type 7 0 2 0 .

If the peat filter is to give maximum odour reduction the peat must

be moist. Consequently, watering equipment of one kind or another must be

available.

3. EXAMPLES OF A BIOFILTER-PLANT

The Swedish farm where the biofilter has been built has a barn for

700 pigs. It is divided into two sections by a longitudinal wall. The

filter has been placed as far away as possible from existing dwelling-

houses. As is illustrated by Fig. 2, this implies that the ventilated air

is discharged at one end of the building, where a fan room containing6 ventilation fans has been built. The ventilated air is then blown through

a main duct to the filter. This consists of a slatted floor on both sides

of the main duct. In order to prevent condensation and possibly formation

of ice in the main duct during the winter, it has been insulated with

10 cm Frigolit.

;";^fg2j - ^

S S K ^ - » ~"S8 3 * * ^ - '

"̂ J ^ ' 4/7?

Fig. 2. View of biofilter plant in Sweden for 700 pigs.

Fig. 3 illustrates in detail how the filter has been constructed. The

filter is placed on a floor of merolit. The slatted floor is built of

32 x 50 mm slats. The distance between two adjacent slats is 30 cm and theslatted floor is at a height of 30 cm above the merolit floor.

Before filling the filter with the peat-heather mixture, measurements

of flow resistance were made with two different mixtures. The first mixture

consisted of 5.5 % by weight of heather and 94.5 % by weight of peat with

moisture contents of 54 and 82 Z respectively. With a filter depth of 50 cm

the flow resistance was 18 mm water column. The other mixture consisted of

10.4 % by weight of heather and 89.6 Z by weight of peat, the flow resist

ance here being 9 mm water column at a filter depth of 50 cm. The filter

was then filled with a mixture containing a slightly higher proportion of

heather than in test 2.



Corrugated

plate

Slatted floor

T Merolit floor

Dust fi lter

Pea t ' hea therreat .nearner 30mm

wdmmSni i i i r

500 m m

300 m m

Fig. 3. Cr oss-section of biofilter a ccor ding to Fig. 2.

4. EFFECT OF BIOFILTERSThe effect of biofilter s ha s been studied by Kowa lewsky (4 ). In these

studies he used both "DrSger rö r " a s well a s photom etr ic a nd ga s chr o m a togr a phic m ea sur e m ents to study the r eduction of cer ta in odour s such a sa m m onia a nd hydr o gen sulphide. The m ea sur e m e nts showed tha t the concentr ation of the ga ses studied decr ea sed by, on a v e r a ge, 50 %. W h e n t he m o i s t u r econtent of the filter wa s a t a n optim u m lev el the r eduction wa s 80 X.

The Swedish filter ha s not yet been ev a lua ted wit h r ega r d to odourr eduction. The filter wa s com pleted dur ing Decem ber 1984 and the exce ptiona lly cold winter ha s dela yed the ev a lua ti on. Howev e r , m ea s ur e m ents of odourthr esholds will be m a d e dur ing both winter a nd sum m e r condit ions.

5. COSTS

The investment costs for a biofil ter in Germany with 160 pigs wer ea bout 100 DM per pig (4 ). The oper a ting cost, i.e., electr icity, m a intena nc ea nd r epa i r s, is r epor ted to be 3 DM per m a r keted pig. As r ega r ds the Swedishfilter , the investments amount to slightly more than 60 DM per pig but

details of operatio nal costs are not yet av aila ble.

REFERENCES

(1) Grennfel t, P., Lindv all, T., Noren, 0. Rosen, G. and Thyse liu s, L.,1975. Luktutsläpp och luktspridn ing frin svinstall ar. JTI-ra pport 13.Swedish Institute of Agr icultur a l Engineer ing, Uppsa l a .

(2) Zeisig, H.D., Kr eitm eier , J. a nd Fr a nzspeck, J., 1977. Unter suchungeniiber Erdfilter zur Verringe rung der Geruchsb eias tigun g aus Tie r-ha ltung en. Schr iftenr eihe der La ndtechnik , Weihen stepha n, Fr eising-

W e i h e n s t e p h a n .

(3) Zeisig, H.D. und Kr eitm eier , J. 1982. Er dfilter a nla gen - Ba n- undBetr iebsa nleitung - Er ga nzun gsbla tter : Sta nd Dezem ber 19 82.Ba yer isches Sta a tsm inister ium fur La ndesentwicklung und Um weltfr a gen.W e i h e n s t e p h a n .

(4) Kowa lewsky, H-H. 1981. Ver m inder ung v on Ger uchsem issionen dur chEr dfilter . La ndtechnik 1. Ja nua r 1981.



238

EXPERIENCE IN THE USE OF BIOFILTERS

M. A. va n GEELENInstitute of Agr icultur a l Engineer ing, M A G

Wa genin gen, The Nether l a nds

After the m eeting of the FAO Eur opea n networ k on Anim a l Wa s te Util ization, a pr il 1983 in Buda pest, Hunga r y, wher e I descr ibed a biobed nea r a

r ender ing pla nt, we ha v e till now not succeeded to insta ll a biobed nea r a nintensiv e liv estock sta ll. Although we ha v e in design a biobed nea r a pigfa ttening sta ll a nd a v ea l ca lf s ta ll . He ha d a pilot biobed nea r a v ea lca lf sta ll to define the odour r eduction with help of a v ibr ous pea t filter .The odour r eduction is m ea sur ed by olfa ctom etr y. We defined the followingfigur es for the r edu ction:

sampling airr ate filling odourrea ding (DT) odour redu ction (%)d a t e m 3 / m2 / h h e i g h t

(m ) befor e a fter

8/5/84 390 0,5 651 170 7416/5/84 300 0,5 655 267 59

I ha v e a fter this figur es the intension to insta ll a biobed by a v ea lca lf sta ll with a n a ir r a te of 300 m 3 / m2/ h a nd 0,5 m hi gh. When the r eduction is not sa tisfying to put som e v ibr ous pea t-hea ther m ixtur e on the top,to give a longer contact time . It is a pity that we hav e not taken thea m m onia lev els befor e a nd a fter a s a m m onia is im por t a nt in conjunction witha cid r a in.

Mr Kr oo dsm a fr om IMAG dev eloped a system to dr y the m a n ur e under the

ca ges in sta lls for la ying h ens. After r em o v ing once a wee k, the m a nur e ispiled up in a stor age . This ra ther dry man ure (453! D.M.) is com postinga fter piling a nd ca uses except odour a lso a not slight a m m onia em ission.

For this two r ea sons we exper i m ented wi th a biologica l a ir w a sher a nda pilot biobed by this m a nur e stor a ge to r educe a m m onia a nd odour ; in thefir st pl a ce a m m onia for ther e ha s been da m a ge to cr ops fr om this stor a ge.

We got the following odour r eductio n figur es with the pilot biobed:

sa m pling a ir r a te filling odour r e a dings (DT) a m m onia (Kjelda hl) m g/m ^d a t e m 3 / m 2 / h h e i g ht

(m ) m a nu r e a fter

stor a ge biobed

18/06/8419/06/8420/06/8421/06/84

164164164164

1,001,001,001,00

5791728871

1198

434255121408

iction

Z

25858566

befor e a fter

24,36 1,8736,13 9,0033,93 10,635,71 3,96

r eduction

X

92756988

With the biologica l cr oss cur r ent a ir scr ubber we got the followingr e d u c t i on f i g u r e s :



samplingdate

airratem 3/ m2/ h

239

odourreadings (DT) ammonia mg/m 3 (Kjeldahl)

manu re after reduction before after reduction

storage biobed Z Z

18/06/8419/06/8420/06/8421/06/84

2278206819502380

57917298711198

499617256224

14647181

24,3636,1333,9335,71

22,5311,5711,9911,57

7,5676458

In spring 1984 w e designed a biobed for an insectnursery. The maggotbreeder installed a biobed of 200 m3 for 15.000 m 3 / h ventilation air. Thebed is 0,8 m high. On the top of the maggot production, in august 1984,we have taken samples from the air before and after the biobed.

The diluti on to threshold w a s before 3604 a nd after 232, reduction94Z. Th e ammonia w a s before 5 ppm and after 0,3 ppm , reduction 9 4 % ,measured with Draeger tubes. Th e pressure drop over the biobed of themixture of vibrous peat and heather w a s 5 m m WK. In the tube between thebreeding house and the biobed there is a sackfilter installed to removesawdust, that otherwise should clog the under layer of the be d.

The same problem w a s with the biobed on the rendering plant. Thebottom of the biobed, just above the slatted floor, w a s polluted by fattymaterial. The pressure drop over the biobed came lower after mixing thepeat-heather materia l and installation of an airscrubber to remove solids

and fatty part s.

AIR OUTLET INON POLLUTED!

SAMPLMC PONT

VMHOUS PEAT

JQ40M

VWflOUS PEAT

'rX T T r v r m T i T i i T r m Y n v r r v y r

AH CHA MB ER

Fig. 1 : Pilot Biobed



240

_ A IR C H AN NE L ( v . 6 M ' / s )1 5 0 0 0 M Y h

fcr— BAG FILTER

DIVING PUMP FOR WATER SPRINKLING

FA N

..PLASTIC FLAPS .VIBROUS PEAT/HEATER MIXTUR E

SLOPE 2%

L G R I D

AIR CHAMBER

Fig. 2 : Design biobed for a maggot farm



241

D E S I G N A N D E X P E R I E N C E O B T A I N E D W I T H B I O S C R U B B E R S

S t e p h a n S c h i r z

K u r a t o r i u m fiir T e c h n i k u n d B a u w e s e n i n d e r L a n d w i r t s c h a f t ( K T B L )

F e d . R e p . o f G e r m a n y , 6 1 0 0 D a r m s t a d t 1 2 , B a r t n i n g s t r a B e 4 9

S u m m a r y

A ll o d o u r a n t s s u s c e p t i b l e o f b e i n g s c r u b b e d a n d c o n v e r t e d b i o l o g i c a l l y c a n

b e t r e a t e d w i t h b i o s c r u b b e r s . T h e r e a r e t w o d i f f e r e n t t r e a t m e n t t e c h n i q u e s :

- S c r u b b e r w a t e r i s o n o c u l a t e d w i t h a c t i v a t e d s l u d g e , i . e . s p e c i a l m i c r o o r g a n i s m s ;

- o n l a r g e - s u r f a c e s c r u b b e r s t h e s o - c a l l e d " b i o l o g i c a l m a t " d e v e l o p s .

In b o t h t e c h n i q u e s t h e m o c r o o r g a n i s m s c h a n g e t h e o d o u r c h a r a c t e r i s t i c s o f

t h e e m i t t e d w a s t e a i r t o s u c h a n e x t e n t t h a t o d o u r n u i s a n c e w i l l n o l o n g e ro c c o u r i n t h e m o r e o r l e s s d i s t a n t v i c i n i t y . B i o s c r u b b e r s w o r k i n g o n t h e

p r i n c i p l e o f t h e a c t i v a t e d s l u d g e t e c h n i q u e i n v o l v e h i g h i n p u t in d e s i g n

a n d c o n t r o l . T h e r e f o r e i t i s o n l y t h e m o r e s i m p l e d e s i g n e d p e r c o l a t o rs c r u b b e r t h a t h a s b e e n u s e d f o r t h e c a s e s o f a p p l i c a t i o n r e f e r r e d t o i nt h i s p a p e r . C o u n t e r c u r r e n t o r c r o s s c u r r e n t s c r u b b e r s t h e c o n s t r u c t i o n o f

w h i c h c o n f o r m s e x c l u s i v e l y t o t h e c a s e o f a p p l i c a t i o n a r e s h o w n b y t h e a i d

o f d i f f e r e n t e x a m p l e s .

T h e p r i n c i p l e o f s c r u b b i n g n o x i u o u s o r o d o u r - i n t e n s i v e s u b s t a n c e s o f t h e

p r o c e s s w a s t e a i r h a s b e e n a p p l i e d i n i n d u s t r y f o r m a n y y e a r s . I t r e f e r s t o

r e l a t i v e l y l a r g e d e v i c e s i n w h i c h t h e a i r i s s c r u b b e d . A f t e r t h a t t h es c r u b b e d s u b s t a n c e s a r e g e n e r a l l y n e u t r a l i z e d b y c h e m i c a l s .

In t h e a r e a o f a g r i c u l t u r e a n d f o o d i n d u s t r y a s w e l l a s t h e p u b l i c s e w a g e

p l a n t s t h e r e a r e i n c r e a s i n g l y p r o b l e m s b e c a u s e o f o d o u r n u i s a n c e i n t h en e i g h b o u r h o o d . T h e s u b s t a n c e s e m i t t e d f r o m t h e d i f f e r e n t p r o c e s s e s a r e

s e l d o m n o x i o u s . T h e y a r e m a n y i n d i v i d u a l c o m p o n e n t s o f v e r y l o w c o n c e n t r a

t i o n w h i c h t o g e t h e r r e s u l t i n a s p e c i f i c o d o u r o u s m i x t u r e . A n d t h i s i s f e l tt o b e p e n e t r a t i n g a n d i n t o l e r a b l e . T h i s r e f e r s i n p a r t i c u l a r t o o d o u r s f r o m- r e n d e r i n g p l a n t s

- c a s i n g s a n d g l u e b o i l i n g- s l a u g h t e r h o u s e s , p a r t i c u l a r l y f r o m b l o o d s t o r a g e t a n k s , b r i s t l e s d i s p o s a l- d u n g a nd c a l f s t o m a c h d r y i n g p l a n t s

- p u b l i c s e w a g e p l a n t s

- f e e d m i l l i n g a n d m i x i n g p l a n t s

- s t a r c h d r y i n g p l a n t s- m a l t - h o u s e s a n d b r e w e r y

- p i g a n d c h i c k e n m a n a g e m e n t .



2 4 2

A l l t h e s e p r o c e s s e s d e v e l o p o r g a n i c c o m p o u n d s w h i c h a r e e a s i l y w a t e r s o l u b l e .

S i n c e t h e y al l a r e a l s o s u s c e p t i b l e o f b i o l o g i c a l d e g r a d a t i o n , t h e i d e a

s u g g e s t e d i t s e l f t o c o n s t r u c t s e w a g e p l a n t s o c c u p y i n g a m i n u t e s p a c e , i . e .b i o l o g i c a l s c r u b b e r s . T h e s e a r e d e s c r i b e d i n t h e V D I g u i d e l i n e 3 4 7 8 " B i o l o

g i c a l W a s t e A i r P u r i f i c a t i o n - B i o s c r u b b e r s " .

I w o u l d l i k e t o d e s c r i b e t w o t y p i c a l d e s i g n s a s f o l l o w s :

1 . T w o - s t a g e b i o s c r u b b e r f o r r e n d e r i n g . p l a n t s ( F i g . 1.)

T h e w a s t e g a s , c h a r g e d w i t h o d o u r - i n t e n s i v e s u b s t a n c e s ( r o o m w a s t e a i r

a n d p r o c e s s w a s t e a i r ) i s p u r i f i e d i n a t w o - s t a g e c o u n t e r - f l o w s c r u b b e r

( 1 ) . T h e s c r u b b i n g f l u i d f o r t h e f i r s t s t a g e i s w e a k l y a c i d i c ( A ) a n d

f o r t h e s e c o n d s t a g e , w e a k l y a l k a l i n e ( B ) . B o t h s c r u b b i n g f l u i d s c o n t a i na c t i v a t e d s l u d g e w h i c h i s a d a p t e d t o t h e m e d i u m c o n c e r n e d .

T h i s r e f e r s t o t h e a c t i v a t e d s l u d g e t e c h n i q u e .

T h e o d o u r o u s s u b s t a n c e s s c r u b b e d o u t o f t h e a i r a r e u s e d b y a e r o b i c m i c r o

o r g a n i s m s a s a s u b s t r a t e a n d a r e t h u s r e m o v e d f r o m t h e w a t e r .

T h e s e m i c r o - o r g a n i s m s , f l o a t i n g f r e e l y i n t h e w a t e r , f o r m t h e a c t i v a t e ds l u d g e t o g e t h e r w i t h i n d i s s o l v e d p o l l u t a n t s u b s t a n c e s . A s n o t a ll m i c r o

o r g a n i s m s a r e a b l e t o d e g r a d e c e r t a i n a t m o s p h e r i c p o l l u t a n t s , a n a t u r a l

s e l e c t i o n p r o c e s s t a k e s p l a c e i n t h e s c r u b b i n g p r o c e s s . A c e r t a i n p e r i o do f a d a p t a t i o n i s n e c e s s a r y i n t h i s r e s p e c t . E s s e n t i a l c h a n g e s i n t h ec o m p o s i t i o n o f t h e c r u d e g a s m a y r e q u i r e a n o t h e r a d a p t a t i o n .

I t i s p o s s i b l e t o c h e c k t h e a c t i v i t y o f t h e s e m i c r o - o r g a n i s m s b y d e t e r

m i n i n g t h e i r o x y g e n c o n s u m p t i o n ( r e s p i r a t o r y a c t i v i t y ) . A s t h e r e a c t i o n

s p e e d o f t h e b i o l o g i c a l d e g r a d a t i o n p r o c e s s i s r e l a t i v e l y l o w , c o r r e s p o n d i n g l y l a r g e a c i v a t e d s l u d g e t a n k s m u s t b e p r o v i d e d ( 2 ) . T h e s e t a n k s

m u s t b e a e r a t e d i f t h e y a r e l a r g e o r i f t h e i n s t a l l a t i o n i s s h u t d o w n fo r

a p r o t r a c t e d l e n g t h o f t i m e .

T h e a c t i v a t e d s l u d g e t a n k s ( 2 ) a r e f e d b y t h e a c i d i c t a n k ( 4 ) a n d t h e

a l k a l i n e t a n k ( 5 ) .

In o r d e r t o r e p l a c e e v a p o r a t i o n l o s s e s a n d a l s o t o p r e v e n t s a l t f o r m a t i o n

i n t h e s c r u b b i n g f l u i d , a s m a l l q u a n t i t y o f f r e s h w a t e r r u n s c o n t i n u o u s l yi n t o t h e t a n k ( 7 ) .

S m a l l q u a n t i t i e s o f f l u i d a r e c o n t i n u o u s l y r e m o v e d f r o m t h e t w o s c r u b b i n g

s t a g e s a n d t h e n c l a r i f i e d i n s e d i m e n t a t i o n t a n k s ( 8 ) . T h e r e s u l t a n t a c t i

v a t e d s l u d g e i s r e c i r c u l a t e d t o t h e s c r u b b e r .A s t h e w a s t e g a s c o n t a i n s p h o s p h a t e o n l y i n t r a c e s , a s m a l l q u a n t i t y o f

p h o s p h a t e i s c o n t i n u o u s l y a d d e d t o t h e s c r u b b i n g f l u i d s ( 6 ) .

W h e n p r o d u c t i o n s t o p s , t h e w a s t e g a s o n l y c o n t a i n s v e r y s m a l l q u a n t i t i e so f o r g a n i c c o m p o u n d s . In o r d e r t o k e e p t h e t w o b i o c e n o s i s s t a g e s a c t i v e ,

v a p o u r s a r e p u m p e d f r o m t h e v a p o u r c o n d e n s a t e t a n k i n t o t h e t a n k a s a

n u t r i e n t s o l u t i o n d u r i n g t h e s e p e r i o d s ( 3 ) .

T h e p h o t o g r a p h ( F i g . 2 ) s h o w s t h e w a y t h e s c r u b b e r i s i n s t a l l e d i n t h eb u i l d i n g o f t h e r e n d e r i n g p l a n t . It i s a v e r y l a r g e s c r u b b e r w i t h

a v e n t i l a t i o n c a p a c i t y o f 4 0 0 0 0 m 3 / h . T h e e f f l u e n t s c r u b b i n g w a t e r i s s o

c l e a n t h a t i t c an b e l e d i n t o a t r o u t p o o l .



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2 . O n e - s t a g e b i o s c r u b b e r f o r p i g g e r i e s ( F i g . 3 )

T h e w a s t e g a s a nd s c r u b b i n g l i q u i d c a n b e p u t i n t o c o n t a c t a c c o r d i n g t ot h e c o u n t e r - f l o w o r c r o s s - f l o w p r i n c i p l e . A c o u n t e r - f l o w s c r u b b e r , a si n d i c a t e d i n F i g . 3 , is a s t a n d a r d i s e d , c o m p a c t u n i t f o r t h e p u r i f i c a t i o no f c e r t a i n q u a n t i t i e s o f w a s t e a i r w h i c h a r e a d a p t e d t o t h e a n i m a l n u m b e r s a n d w e i t h t s i n t h e p e n , i n a c c o r d a n c e w i t h D I N 1 8 9 1 0 . T h e t o ta lw e i g h t o f t h e s e s c r u b b e r s i s r e l a t i v e l y s m a l l s o t h a t t h e y c a n b e s u s p e n d e d f r o m t h e w a l l o r c e i l i n g o f t h e pe n w i t h o u t t a k i n g u p v a l u a b l eb o x s p a c e .

C o n s e q u e n t l y , t h e y a r e s u i t a b l e f o r i n s t a l l a t i o n a t a l a t e r d a t e .T h e c e n t r a l e l e m e n t i s a p a c k e d s e c t i o n w h i c h i s p r o v i d e d w i t h d i f f e r e n t

t y p e s o f f i l l and i s a l s o d i f f e r e n t l y d i m e n s i o n e d a c c o r d i n g t o r e q u i r e m e n t s( d e g r e e s o f e f f i c i e n c y r e q u i r e d ) . A w a t e r c e l l e c t i n g t r o u g h , w i t h ac a p a c i t y o f a p p r o x i m a t e l y 3 0 0 1 , i s l o c a t e d b e l o w t h e p a c k e d s e c t i o n .T h e p u m p s u m p w i t h t h e c i r c u l a t i n g p u m p a n d t h e w a t e r o v e r f l o w a n d s up pl ya r e a l s o l o c a t e d t h e r e . T h e p e n a i r i s d r a w n u n i f o r m l y b e t w e e n p a c k e ds e c t i o n a n d w a t e r t r o u g h .

T h i s o n e - s t a g e s c r u b b e r w o r k e d o n t h e p r i n c i p l e o f t h e p e r c o l a t i n g f il te rt e c h n i q u e .

I f t h e m i c r o - o r g a n i s m s h a v e p e r m e n e n t l y c o l o n i s e d t h e i n t e r n a l s o r p a c k in go f t h e s c r u b b e r , t h e n t h i s i s r e f e r r e d t o a s a b i o l o g i c a l m a t . T h es c r u b b i n g w a t e r ( a b s o r b e n t ) f l o w i n g a c r o s s t h i s m a t s u p p l i e s t h e m i c r o o r g a n i s m s w i t h o x y g e n a n d s u b s t r a t e . T h e s c r u b b i n g w a t e r i s t h e n r e g e n e r a t e d .

P e r c o l a t i n g f i l t e r i n s t a l l a t i o n s c o n s i s t o f i n s t a l l a t i o n s w i t h a l a r g es p e c i f i c s u r f a c e o v e r w h i c h t h e s c r u b b i n g w a t e r t o b e p u r i f i e d i s d i s t r i

b u t e d . T h e e f f i c i e n c y o f t h e p e r c o l a t i n g f i l t e r d e p e n d s o n t h e s i z e o f

t h e b i o l o g i c a l m a t a n i s e x p r e s s e d i n m 2 a r e a p e r m 3 o f i n s t a l l a t i o n

v o l u m e .

U n i f o r m w e t t i n g o f t h e i n s t a l l a t i o n i s p a r t i c u l a r l y i m p o r t a n t i n o r d e r t oa v o i d d r y a r e a s a n d c l o g g i n g . T h e w e t t i n g r a t e o n l y p l a y s a p a r t i n

c o n n e c t i o n w i t h t h e t r a n s f e r o f o d o u r o u s s u b s t a n c e s t o t h e s c r u b b i n g w a t e r

b u t n o t f o r t h e b i o l o g i c a l d e g r a d a t i o n p r o c e s s .

A f t e r c o m m i s s i o n i n g , a l e a d - i n p e r i o d o f 1 t o 2 w e e k s i s r e q u i r e d b e f o r e

t h e b i o l o g i c a l m a t h a s f o r m e d i n t h e p a c k i n g . T h e s c r u b b e r m u s t n o t b e

a l l o w e d t o r u n d r y , i . e . t h e w a t e r c i r c u l a t i n g s y s t e m m u s t c o n t i n u e t o

o p e r a t e a f t e r t h e f a n s h a v e b e e n s w i t c h e d o f f .

T h e p h o t o g r a p h ( F i g . 4 ) s h o w s a s c r u b b e r i n a p i g g e r y f o r 1 0 0 a n i m a l s

r e s p . 8 0 0 0 m 3 / h . It w a s i n s t a l l e d s u b s e q u e n t l y .



245

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F i g . 3: O n e - s t a g e b i o s c r u b b e r f o r p i g g e r i e s

F i g . 4: B i o s c r u b b e r f o r 1 0 0 f a t t e n i n g p i g s , i n s t a l l e d s u b s e q u e n t l y



2 4 6

T h e f a n w h i c h m u s t b e d e s i g n e d i n s u c h a w a y t h a t i t c a n c o p e w i t h t h e

n e c e s s a r y a i r v o l u m e a n d a l s o t h e p r e s s u r e d i f f e r e n c e i n t h e s c r u b b e r ,

i s l o c a t e d i n t h e l i d o f t h e s c r u b b e r . T h e w a t e r d i s t r i b u t o r w h i c h m u s tb e a b l e t o o p e r a t e w i t h o u t r e s t r i c t i o n f r o m s k i n , h a i r a n d s u c h p a r t i c l e s

i n t h e s c r u b b i n g l i q u i d , i s l o c a t e d a t t h e l o w e r e d g e o f t h e l i d .

D u r i n g o p e r a t i o n , t h e p H - v a l u e o f t h e s c r u b b i n g l i q u i d m u s t b e c h e c k e d

w i t h t h e a i d o f i n d i c a t o r p a p e r , f o r e x a m p l e ; i t s h o u l d b e b e t w e e n 6 .2a n d 6 . 7 . I f t h i s v a l u e i n c r e a s e s , t h e n e i t h e r m o r e w a t e r m u s t b e d r a i n e d

o f f a n d t h e s u p p l y o f f r e s h w a t e r i n c r e a s e d o r s p e c i a l p r e p a r a t i o n s s u c h

a s p h o s p h o r i c a c i d s , m i l d , e t c . m u s t b e a d d e d ( F i g . 5 ) . T h i s p r o c e s s c a n

b e a u t o m a t e d b y t h e a i d o f a m e a s u r i n g d e v i c e .

T h e s c r u b b e r d e s i g n i m p l i e s t h a t t h e e x c e s s s l u d g e b e r e g u l a r l y r e m o v e df r o m t h e p a c k e d s e c t i o n . T h i s s l u d g e settles i n t h e l o w e r z o n e a n d r e d u c e s

t h e a i r t h r o u g h p u t . F o r c l e a n i n g , t h e b l o c k s o f t h e p a c k e d t o w e r a r e

r e m o v e d ( F i g . 6 ) , f l u s h e d o u t o r d r i e d a n d k n o c k e d o u t . T h e c l e a n i n g

m u s t t a k e p l a c e e v e r y 3 m o n t h s a n d 2 t o 3 h o u r s .

In b o t h t e c h n i q u e s t h e m i c r o - o r g a n i s m s c h a n g e t h e o d o u r c h a r a c t e r i s t i c s

o f t h e e m i t t e d w a s t e a i r t o s u c h a n e x t e n t t h a t o d o u r n u i s a n c e w i l l n o

l o n g e r o c c u r i n t h e m o r e o r l e s s d i s t a n t v i c i n i t y .

B i o s c r u b b e r s w o r k i n g o n t h e p r i n c i p l e o f t h e a c t i v a t e d s l u d g e t e c h n i q u e

i n v o l v e h i g h i n p u t i n d e s i g n a n d c o n t r o l . T h e r e f o r e i t is o n l y t h e m o r e

s i m p l y d e s i g n e d p e r c o l a t o r s c r u b b e r t h a t h a s b e e n u s e d f o r t h e p r a c t i c a l

e x a m p l e s o f i n s t a l l a t i o n s h o w n i n t h e f o l l o w i n g .

T h e p h o t o g r a p h ( F i g . 7 ) s h o w s a b i o s c r u b b e r a d a p t e d t o t h e m i l l i n g a n dm i x i n g p l a n t i n a f e e d i n g s t u f f f a c t o r y . T h e s u b s e q u e n t i n s t a l l a t i o n w a sp a r t i c u l a r l y d i f f i c u l t . T h e r e w a s l i t t l e r o o m f o r t h e s c r u b b e r w h i c hc o u l d o n l y b e i n s t a l l e d i n t h e a t t i c . In a d d i t i o n , t h e f i r m e n t e r e d r e s e r v a t i o n s a g a i n s t 5 0 0 1 o f w a t e r i n t h e s c r u b b e r a n d 1 0 0 0 1 i n a c o m p e n s a t i o n t a n k a b o v e al l d r y p r o d u c t s .

T h e s c r u b b e r h a s a g a s f l o w r a t e o f 5 0 0 0 m 3 / h a n d c o m b i n e s 3 a i r f l o w s :

- t h e w a s t e a i r o f t h e h a m m e r m i l l i n t h e c e l l a r- t h e a s p i r a t i o n a i r o f al l t h e m a c h i n e s- t h e d r y i n g o f t h e p e l l e t e d f e e d .

T h e s c r u b b e r c a u s e s a l o w p r e s s u r e i n t h e b u i l d i n g . T h e r e f o r e , n o o d o u r -

l a d e n w a s t e a i r g e t s t h r o u g h a n y g a r r e t w i n d o w s o r w i n d o w s . T h e p u r i f i e d

a i r f l o w i s d i r e c t e d t o e x h a u s t a b o v e t h e r o o f .

N o w a d a y s , p u b l i c s e w a g e p l a n t s a r e i n c r e a s i n g l y u s i n g s l u d g e s t a b i l i z a t i o n p l a n t s . I t i s a b o u t a t h e r m i c c o n d i t i o n i n g i n t w o t a n k s a n d o n e t a n ka s t h i c k e n e r . A s t h e s u b s t r a t e i s h e a t e d u p t o 8 0 ° C , e v i l - s m e l l i n g g a s e s ,m a i n l y a m m o n i a i n t h e r a n g e o f 4 0 0 p p m t o 6 0 0 p p m , w i l l d e v e l o p . T h et a n k s a r e c o v e r e d , b u t d u e t o t h e g a s p r e s s u r e t h e o d o u r s t o r e a c h t h ev i n c i n i t y .



247

F i g . 5 : T h e f e e d i n g o f t h e m i c r o - o r g a n i s m s w i t h p h o s p h o r u s

F i g . 6 : T h e c l e a n i n g o f t h e p a c k i n g b l o c k s



2 4 8

T h e p h o t o g r a p h ( F i g . 8 ) s h o w s a b i o s c r u b b e r n e x t t o t h e s e t a n k s . T h es c r u b b e r i s a s t a n d a r d v e r s i o n a s i t i s b e i n g u s e d i n p i g g e r i e s . A t t h e

b o t t o m , t h e w a t e r - c o l l e c t i n g t r o u g h a n d w a t e r p u m p , o n t o p o f i t t h ep a c k i n g . T h e f a n , i n t h i s c a s e d e m e n s i o n e d f o r 5 0 0 m 3 / h f o r e a c h t a n k -t o g e t h e r 1 5 0 0 m 3 / h , i s l o c a t e d a b o v e t h e w a t e r d i s t r i b u t i o n . T h e p u r if i e dg a s i s d r a i n e d o f f t h r o u g h a v e r t i c a l c h i m n e y i n t o t h e o p e n . T h e g a s f r o mt h e t a n k s i s c o l l e c t e d i n a d r a i n w h i c h p r o d u c e s a l o w p r e s s u r e . T h ep a c k i n g s c o n s i s t o f p o l e s l o o k i n g l i k e l a r g e c u r l e r s ( F i g . 9 ) . T h e s ep o l e s a r e f i l l e d i n d r a w e r s a n d a r e e a s y t o r e m o v e a n d c l e a n . T h e t i m eo f c l e a n i n g i s i n d i c a t e d b y a s i m p l e s h u t t l e f l a p . I f t h e p a c k i n g s a r ec l e a n , a l o w p r e s s u r e w i l l p r e v a i l i n t h e d r a i n a n d t h e f l a p b e d o w n . I ft h e p a c k i n g s a r e c l o g g e d , t h e f l a p g e t s u p . A n p o i n t e r f i x e d e x t e r n a l l y

s h o w s t h e d i r e c t i o n o f t h e f l a p .

A n o t h e r p o s s i b i l i t y t o c l e a n t h e w a s t e g a s e s o f t h e t a n k s c o n s i s t s i np l a c i n g a s m a ll s c r u b b e r w i t h 5 0 0 m 3 / h o n e a c h t a n k ( F i g . 1 0 ) . T h i si m p l e m e n t i s c o m p a c t a n d t h e a i r c o n c e n t r a t i o n i s l e f t o u t . A s f a r a sc o s t s a r e c o n c e r n e d , t h e r e i s n o d i f f e r e n c e a s a l l u n i t s , s u c h a s w a t e rp u m p , f a n a n d c o n t r o l , m u s t b e p r o v i d e d f o r t h r e e t i m e s .

T h e r e i s n o t m u c h t o s a y a b o u t t h e c o s t s o f s u c h i m p l e m e n t s a s t h e y a r ei n e a c h p r a c i t i c a l e x a m p l e i n d i v i d u a l c o n s t r u c t i o n s .

In p r i n c i p l e , i t c a n b e s t a t e d t h a t f o r p r o c e s s e s i n v o l v i n g w a s t e g a s e sw h i c h d o n o t h a v e t o o s t r o n g o d o u r c o n c e n t r a t i o n , t h e p e r c o l a t o r s c r u b b e r sa r e t h e m o s t f a v o u r a b l e s o l u t i o n . T h e y a r e s m a l l , c o m p a c t , e f f i c i e n t a n dt h u s m o r e e c o n o m y - p r i c e d t h a n t h e a c t i v a t e d s l u d g e s c r u b b e r s .

R e f e r e n c e s

V D I 3 4 7 8 B i o l o g i s c h e A b l u f t r e i n i g u n g - B i o w a s c h e r ( 1 9 8 5 )

G u s t , M . , F . S p o r e n b e r g u . E . S c h i p p e r t : G r u n d l a g e n d e r b i o l o g i s c h e n A b l u f t r e i n i g u n g . T e i l IV A b g a s r e i n i g u n g d u r c h M i k r o o r g a n i s m e n m i t H i l f e v o nB i o w a ' s c h e r n . S t a u b - R e i n h a l t u n g d e r L u f t ( 1 9 7 9 ) , H . 9 , S . 3 0 8 - 3 1 4

S c h i r z , S t . : A b l u f t r e i n i g u n g s v e r f a h r e n f n d e r I n t e n s i v t i e r h a l t u n g .K T B L - S c h r i f t 2 0 0 . D a r m s t a d t ( 1 9 7 4 )



249

F i g . 7 :

B i o s c r u b b e r s i n a f e e d i n g s t u f f

f a c t o r y

F i g . 8 : B i o s c r u b b e r s f o r t h e s l u d g e s t a b i l i z a t i o n o f a s e w a g e p l a n t

- c e n t r a l v e r s i o n



250

F i g . 9 : P o l e p a c k i n g s i n d r a w e r s

F i g . 1 0 :

B i o s c r u b b e r s f o r t h e s l u d g e

s t a b i l i z a t i o n o f a s e w a g e p l a n t

- i n d i v i d u a l v e r s i o n



251

AERATION OF PIG SLURRY TO CONTROL ODOURS AND TO REDUCE NITROGEN LEVELS

M. COPELLI, S. D E ANGELIS and G. BONAZZICentro Ricerche Produzioni Animali

Via Crispi, 3 - Reggio Emilia, Italy

SummaryIn areas where swine production is highly concentrated, land spreading is problematic, due to the excess of manure in relation tocrop-farming requirement, the emission of undesirable odours andrisks of transmitting disease. Emilia-Romagna, a Northern Italian region with a high number of swine raising enterprises and head of

stock, is a case in point. The regional Authorities have financedresearch into a system of treating pig manure to lower its Nitrogenlevel, deodorize it and sanitate it at a price accessible to thefarmer. The trial system is composed of 4 storage tanks in which theslurry is subjected to various types of treatment. The tests arestill in process, the first results, however, appear to indicatethat the desired objectives can be attained with intermittent aeration treatment. Indeed with this method partial sanitation, almosttotal deodorisation and a considerable reduction in the nitrogen level are obtained.

1 . INTRODUCTION

Emilia-Romagna, a region which represents a twentieth of the totalland area of Italy, contains 2,300,000 head, a quarter of the nationalpig population. This population is not distributed uniformally within theregion, but is concentrated in the area where Parmesan cheese is produced. Swine rearing in this area is an age-old tradition since it is linked to the production of whey, which has always been used as a feedingstuff.

The great increase in the number of swine reared in the area in thelast 20 years is due to the increases in national pork consumption and tothe presence, in this same area, of the country's largest butchering andpork processing industries.

The average size of the farms is 600 head, 48% of the pig populationis contained in farms with more than 1000 head, the vast size of whichalong with the dense concentration of these farms in the area heightenthe problem of manure disposal.

Land spreading is problematic as there is a surplus of pig manure inrelation to crop-farming needs. By far the most prevalent type of cultiva

tion is lucerne (taking up about 45% of cultivated land); this is followed by vine and fruit growing (15%) for which pig manure is unsuitable.This leaves about 15 meadow land and 25% arable land (sugar beets and cereals) where land spreading can be pratctised, too small a percentage, ifwe consider that in this area there are also cattle (about 0,8 tons liveweight per hectare) which provide farmers with manure they prefer.

A further difficulty derives from the presence of housing and residential centres in the area, since land spreading gives rise to complaints from residents about undesirable smells and provokes worry aboutsanitary risks.

In this kind of environmental situation then, pig manure can only be



252

successfully put to agricultural use if it can be treated, with the following results:

- acceptable decdorisation;- sufficient loss of nitrogen by volatilization to eliminate the excessin relation to crop-farming requirements;

- reduction in the pathogenic bacteria count;- limitation of treatment costs to under 15 lira/Kg of meat produced.

As a primary measure in this direction the Authorities of the EmiliaRomagna Region have passed a law whereby the volume of manure farmersstore must correspond to production over a 90 day period. The law aims atavoiding spreading in winter months and reducing, in part, the pathogenicbacterial count.

To test the potential in pursuing these objectives, the Administra

tion Authorities for the Bmilia-Romagna Region financed experiments, bothon aerobic treatment and anaerobic digestion. In this paper, we reportthe first results obtained in experiments on aerobic treatment.

2. MATERIALS AND METHODSExperimentation was carried out on a farm where a trial installation

was set up, consisting of 4 storage tanks made of reinforced concrete,each with a utilizable volume of 100 m (Fig. 1 ) . One tank was providedwith a surface aerator (4 Kw) and a second with a mixer (1.3 K w) .

Pumps for loading and unloading the tanks and devices for mechanically de-watering the slurry were also added to the experimental installa

tion.

2.1 Method of experimentationThe experimental tanks are gradually filled, over a period of 60

days, with slurry taken from the farm's reception pit. One of the tanksis loaded with clarified slurry after separation from the solid fraction.No treatment is effected at this stage.

Once the maximum level catered for has been reached, loading is suspended in all the tanks and a new period of 60 days starts, where the fqllowing experimental conditions are realised:- tank with untreated raw slurry: the slurry remains undisturbed until

unloading. This represents a reference situation to which the resultsobtained in the other 3 tanks can be compared;

- tank with clarified slurry: in farms of the Emilia-Romagna area, thisrepresents the most coniron storing condition. The clarified slurry remains undisturbed until unloading takes place; ,

- tank with aeration treatment: (power requirement 40 W/m for 6 hoursper day). The aim here, is to establish the effect of deodorisation andsanitation of the slurry, when provoked by intermittent aeration. Thetests also aimed at estimating the extent of the loss of Nitrogen in ammoniacal form at various periods in the year.This effect is considered positive in Emilia-Romagna, for the reasons

explained in the foreword. ,- tank with agitation treatment: (power requirement: 16 W/m for 15 mins.per hour). The test aims to evaluate changes in slurry when subjectedto anaerobic treatment and slow agitation, whithout heating.

Bacterial activity is, in theory, assumed to be encouraged by theagitation, as the bacteria present on the solid fraction are dispersed inthe entire slurry mass.

The length of these tests was planned at 120 days (60 days to fillthe tanks and 60 days for the treatment), since this period correspondsto an average retention time (of the slurry in the tanks) of 90 days, in



±

HIXEE

253

zHIXEE

-B&X/ s u j e e y -

3 .

AAKPA

aEBSBSTCIE

Fig. 1 - Trial installation for manure treatment.Tank 1. Raw slurry subjected to aeration treatment.Tank 2. Untreated, clarified slurry.Tank 3. Raw slurry subjected to homogenisation, before being

transferred to the other tanks.Tank 4. Untreated, raw slurry.Tank 5. Raw slurry subjected to agitation treatment.



254

accordance wi th the Region 's lega l requi rements .

2.2 Methods of SamplingIn order to reduce sampling errors, during the preliminary tests, inthe sampling process, the slurry was sampled with a device, consisting ofa rigid tube, 3 cm in diameter and 3 m in height, into which a plastic-coated steel cable was placed, to which a rubber sphere, 6 cm in diameterwas anchored. The sphere closes the lower end of the tube itself.

The whole column, apart from a small portion of the sediment, is sampled in this way.

The chemical checks were carried out every 15 days, determining: pH ,Conductivity, C.O.D., Ammoniacal Nitrogen, Orthophosphate Phosphorus;and, furthermore, each month: Total phosphorus, Total Kjeldahl Nitrogen,

Total Solids and Volatile Solids. The methods utilized are those indicated in the Standard Methods (A.P.H.A., 1980). The amount of matter particles sedimented in the tanks was estimated with the use of appropriatesampling devices located at the bottom of the tanks and withdrawn after avariable permanence of 40 to 60 days.

3. FIRST RESULTSSeveral preliminary tests have been carried out to date. These have

been used to set up the experimental system, the plan of analytical determinations and method of sampling. They were followed by two complete cycles of tests, one in the Feb. - May period and the other in the Jul. -

Oct. period of the same year. A third cycle is currently under way.

3.1. Reduction of the Organic Load and NutrientsThe data collected so far are currently being processed; it is never

theless possible to pick out certain indicative values, bearing in mindthat these may be modified somewhat in the final analysis. Table I reports the range of variations of some of the characteristics of the slurry, determined during loading. As the table shows, the slurry is greatlydiluted and indeed it was taken from a farm of growing-finishing pigs,raised on whey-based liquid feeding, where a certain amount of water isalso used for cleaning the boxes.

Tank filling (to 260 cm) was completed after 60 days. At this pointthe characteristics of the slurry in each of the 4 tanks was recorded.

Reduction in the various parameters was revealed, which, dependingon the time of year, varies from 20 and 30% for the V.S., from 10 to 15%for the Total Nitrogen, from 25 to 40% for the C.O.D., from 30 to 50%for the B.O.D.5 (table I ) .

Once filling was completed, the aeration and agitation treatment wasstarted in the 2 purpose-built tanks, while in the other 2 tanks the slurry was left undisturbed.

PARAMETERS

TOTAL SOLIDS

VOLATILE SOLIDS

TOTAL NITROGEN

NH4-N

C . O . D .

B . O . D g

CHARACTERISTICS

TH E

OF

LOADED SLURRYg / i

2 0 - 2 5

1 3 - 1 7

2 . 0 - 2 . 2

1 .5-1 .8

2 2 - 2 8

1 5 - 1 8

REDUCTION PERCENTAGES

DURING FILLING%1 0 - 2 0

2 0 - 3 0

1 0 - 1 5

5 - 1 5

2 5 - 4 0

3 0 - 5 0

Table I. The main characteristics of slurry used in the tests an percentages revealed when tank filling was complete.



255

The analytical data concerning this second period are, at presentbeing processed. At a first, brief examination, however, considerable differences in final characteristics (at the end of the tests), already emer

ge, in response to the kind of storage method adopted.Since the processes concerned here are predminantly biological, dif

ferences between the various storage conditions are as, predicted,more accentuated in the hot season.

In the test period Feb. - April '84 , in which the temperature of theslurry in the tanks was lower than 7°C, during the first 2 months (it increased to 17° - 18° C only during the final phase), changes in the parameters under observation were less marked, except in the tank where aeration had been carried out. In this predominantly wintery testing period,further reductions in the various parameters were observed after thetanks had been filled. The C.O.D. for example was reduced by 20% in the

tank without treatment; by 30% in the one with agitation and by 50% inthe aerated tank.

The Total Nitrogen was brought down by 30-35% in the aerated tankand by less than 20% in the other types of storage tanks.

In the test carried out in the period July-Oct. '84, in which thetemperature of the slurry remained between 16° and 24°C for the entire period, more marked reductions were brought about in all the storage conditions: the organic substance (expressed as C.O.D.) was reduced by 25-30%in the tanks without treatment, by 30-40% in the tank with agitation andby 70-80% in the tank with aeration.

Total Nitrogen was reduced by 20-30% in the tanks without treatmentand in the one with agitation, and by more than 80% in the tank with aeration. In the latter case a marked nitrification process was also noted:7% of the Total Nitrogen, initially present, was nitrified.

3.2 Odour ReductionOdour was determined in accordance with Standard Methods (A.P.H.A.

180). Table II shows how almost total deodorization is obtained when aeration treatment is practised. With the other types of treatment, too, there is a reduction in odour, most marked in the second period of tests(Jul. - Oct.), when temperatures are higher. In this period odour reduction is already considerable after 60 days.

3.3 Microbiological IndicesLiterature on the microbiological aspects regarding techniques of

treating and stabilising faeces is scarse and, to a certain extent, contradictory. This is not so for farmyard manure, where as we know, pathogenic micro-organisms originally present disappear over a period of about10 days and in any case before maturation is complete. Little is knownabout the destiny of pathogenic agents in diluted slurry, particularly inrelation to storage times and methods.

Since direct studies and calculations of the survival rate of the

specific pathogenic agents and viruses is complex and excessively laborious, we evaluated the possibility of risks to hygiene by means of indices of fecal contamination (streptococci and coliforms).

In raw slurry left untreated and in the single test tanks at the endof treatment, the microbiological indices reported in table III were determined according to the official methodology (Standard Methods, '80).

The results obtained show how the most efficient treatment in reducing the microbiological count is aeration, followed by agitation, as faras reduction of fecal coliforms is concerned, and also show that there isa direct link with seasonal conditions, i.e. temperature.



256

PERIOD

FEB-MAY

beginningtest

after 120days

JUL-OCT

beginningtest

after 60days

after 85days

after 100days

after 120days

of

of

UNTREATEDRAW SLURRY

120

40

120

24

20

15

10

AERATEDRAW SLURRY

120

1.5

120

20

10

2

2

AGITATEDRAW SLURRY

120

25

120

24

16

15

10

UNTREATEDCLARIFIED SLURRY

120

25

120

20

16

8

5

Table II. Threshold Odour Numbers determined at 25°C at various stages

of slurry storage.

TYPE OF TREATMENT TOTALCOLIFORMSM.P.N/100 ml

FECALCOLIFORMSM.P.N/100 ml

FECALSTREPTOCOCCIM.P.N/100 ml

FRESH SLURRYBeginning of 1st cycle 12.10' 14.10^Beginning of 2nd cycle 21.10 40.10

11.10'46.lo'

AERATED SLURRYEnd of 1st cycleEnd of 2nd cycle

4.10'93.10

<10900

11.10,46.10J

AGITATED SLURRYEnd of 1st cycleEnd of 2nd cycle

43.10,4.10

4.10J

<1011.10,43.10 J

UNTREATED CLARIFIED SLURRYEnd of 1st cycle 11.10, 11.10End of 2nd cycle 9.10 <10

21.10,43.10J

UNTREATED RAW SLURRYEnd of 1st cycle 93.10:;End of 2nd cycle 4.10

15.10-*<10

24.10'46.10

Table III. Microbiological indices determined in the slurry during thetwo cycles of tests.



257

4. CONCLUSIONS

The experiments are not yet complete and the data collected so farneed further processing. The data seem to indicate, however, that aeration treatment is the type that best responds to the needs of areas whichaccommodate high concentrations of swine, where quantities of manureexceed crop-farming requirements.

In addition, modest sanitation, good deodorization, often discussedin literature on the subject (1,2,3) and a marked reduction in nitrogenlevels can be achieved, at low energy costs (10-15 lira/kg meat produced)within the farmer's financial possibilities.

Confirmation of these affirmations, may be supplied by the 3rd cycleof tests, which are currently being carried out.

REFERENCES(1) - GIN NI VAN, M.J. ( 1 9 8 3 ) . The effects of aeration rate on odour and so

lids of pig slurry - Agric. Wastes, 7:197-207.(2) - JONGEBREUR, A.A. ( 1 9 8 1 ) . Odour control in Animal production - Inf.

Bull, from the FAO European netarork on Animal Waste Utilization.(3) - MIN ER , J.R. ( 1 9 8 0 ) . Controlling Odors from Livestock Production

facilities: State of the Art. Proceedings 4th Int. Symp. onLivestock Waste - ASAE.



258

OXYGEN REQUIREMENTS FOR CONTROLLING ODOURS FROM PIG SLURRY BY AERATION

A.G.WILLIAMS, M.SHAW, C.M.SELVIAH, R.J.CUMBYNational Institute of Agricultural Engineering, Silsoe, U.K.

Summary

P i l o t s c a l e c o n t i n u o u s - c u l t u r e e x p e ri m e n t s a r e d e s c r i b e d , w hic hde t e r m i ne t he oxyge n r e q u i r e m e n t s f o r c o n t r o l l i n g odour from p i gslurry . Odour cont rol and the s tabi l i ty of the t rea ted s lurr ies werem e a su r ed u s i n g v o l a t i l e f a t t y a c i d s (VFA) a s i n d i c a t o r s o f odou ro ff en si v en es s . Oxygen consu mp t ion was measured by the changes in

chemical oxygen demand (COD), N02~ and N0*~. Biodegradation wasmeasured by the changes in to ta l s o l id s , v o la t i le so l id s , b iochemicaloxygen demand (BOD ), VFA and COD. In c reas in g th e re s id ence tim e from1 to 4 .8 d s i g n i f i c a n t l y (P=0.001 ) inc rea sed biodegradat ion, oxygenconsumption and the s ta b i l i t y of the t rea ted s lu rry . Increasing thea e ra ti o n le v e l from a redox p o t e n ti a l of +50 mV Eh to +200 mV Eh andfu rth er to 0.5-2.0 mg/1 diss olv ed oxygen had no si g n if ic an t eff ec t onc a r b o n a c e o u s ox yg en c o n s u m p t i o n o r s o l i d s d e s t r u c t i o n , b u tn i t r i f i c a t i o n w as i n h i b i t e d w hen r ed o x c o t r o l was u se d and t h eresidual B0Dw of the t rea ted s lu rr ie s were higher . The s ta b i l i t y oft h e t r e a t e d s l u r r y w as r e l a t e d to t h e c o n t e n t o f r e s i d u a l

biodegradable COD, when an allowance was made for N02~ and N0*~. Theenergy requirements for t reat ing slurry from a standard fat tening pigranged from 110-225 Wh/d to obtain s t a b i l i t i e s af te r t reatm ent of18-56 days.

1. INTRODUCTION

Intensive pig production is the major cause of complaints aboutagricultural odours in the U.K.(1 ) . 56? of such complaints received bylocal authorities in 1982 concerned pig farms and 69? of these were aboutthe storage and spreading of manure, which is usually handled as slurry.The numbers of prosecutions against farmers are increasing and the publicare becoming increasingly intolerant of odours from livestock units. Theeffective control of odours from pig slurry is thus important.

The odours normally released from untreated slurries can becontrolled by biological treatment. Aerobic treatment is the mosteffective method , but energy is required to operate aerators. The cost of

aerobic treatment can be reduced principally by two methods; increasingthe efficiency of aerators and defining the minimum quantities of oxygenneeded to effect odour control. The latter is the subject of this paper.

Two oxygen requirements can be defined, firstly the oxygen requiredto eliminate odours and secondly the oxygen required to stabilize theslurry during any subsequent storage. After short-term aeration, somesubstrates remain, which may be degraded during subsequent anaerobicstorage to produce malodorous compounds (2). In order to design treatmentsystems to deal with the needs of a wide variety of farmers, it must beknown how stable a slurry will be after a particular treatment.

Workers elsewhere have investigated the batch and continuous-culture



259

t r e a t m e n t o f s l u r r i e s a t 1 5 - 5 0 °C u s i n g l a b o r a t o r y - s c a l e r e a c t o r s ( 3 ,4 ) .E va ns e t a l ( 3 , 4 ) p r o d u ce d e x p r e s s i o n s , b a s e d on M onod k i n e t i c s ( 5 )de s c r i b i ng the de s t r uc t i o n o f s o l i d s , o xy ge n c o nsum pt i on and c o n c e nt r a t i o n

o f r e s i d u a l b i o c h e m i c a l o x y g en d em an d (BOD) i n t h e t r e a t e d s l u r r i e s .W i l li a m s (6 ) show ed tha t the o do ur o f f e n s i v e n e s s o f t r e a te d s l u r r i e s w asr e l a t e d t o s o l u b l e BOD. By c o m b i n i n g t h e e x p r e s s i o n s p r o d u c e d b y t h e s ew o r k e r s , i t w as s u g g e s t e d t h a t t h e m in im um a e r o b i c t r e a t m e n t f o rc o n t r o l l i n g o d o ur s w o u ld r e q u i r e a t w o d ay r e s i d e n c e t i m e ( 7 ) . T h e s es t u d i e s d i d n o t , h ow e v e r, i n d i c a t e t h e e x p e c t e d s t a b i l i t y o f t r e a t e ds l u r r i e s . The s t a b i l i t y o f s l u r r i e s f o l l o w i n g b a tc h a e r a t i o n was l a t e rs ho w n t o b e a f u n c t i o n o f t h e s l u r r y c o n c e n t r a t i o n an d o f t h e e x t e n t o ft r e a tm e nt be fo r e s to r a g e ( 2 ) .

T h i s p a p e r d e s c r i b e s t h e m e a s u re m e n t o f t h e o x y g e n c o n s u m p t i o n o fs l u r r i e s d u r i n g c o n t i n u o u s - c u l t u r e t r e a t m e n t and t h e i r s u b s e q u e n ts t a b i l i t y . C o n t i n u o u s -c u l t u r e t r e at m e n t w as e v a lu a t e d a s i t i s l i k e l y t ob e m ore e f f i c i e n t i n t h e u s e o f o x y g en t h a n b a t c h t r e a t m e n t . T h i s i sb e c a u s e i n b a t c h t r e a t m e n t t h e o x y g e n d em an d c h a n g e s m o re t h a n 1 0 - f o l dw i t h i n a few day s (8 ) , w h i l e i n a c o n t i nu o u s -c u l tur e t r e a tm e nt i n s t e a dys ta te the demand fo r oxygen i s con stan t . Furthermore , a s t a b le b ac te r i a lpo p u l a t i o n i s a b l e t o grow dur ing c o n t i nu o us -c u l tur e t r e a tm e nt , w h i l e thepo p u l a t i o n c o n s ta nt l y c ha nge s i n a ba tc h c u l tu r e .

2 . MATERIALS AND METHODS

2 .1 S lurry

T he s l u r r y u s e d w a s p r o d u c e d b y f a t t e n i n g p i g s o f 1 5 - 4 0 k gl i v e w e i g h t , f ed on a p e l l e t e d r a t i o n c o n t a i n i n g 1 8^ c ru d e p r o t e i n , w i t had l ib i tu m ac ce ss to water . S lu rry was c o l l e c t ed week ly from the channe lu n de rn ea th th e p a r t i a l l y - s l a t t e d f l o o r of t h e j e t - v e n t i l a t e d h o us e. I t w asr e m o v e d a f t e r r e c i r c u l t i o n i n the 1 6 m ? channe l for a t l e a s t one hour wi tha 3*1 kW c e n t r i f u g a l p um p. The s l u r r y wa s t h e n m e c h a n i c a l l y s e p a r a t e dw i t h a b r u s h e d - s c r e e n , r o l l e r - p r e s s s e p a r a t o r c o n t a i n i n g a 1.6 mm d i ape r fo r a te d s c r e e n . T he s e pa r a te d s l ur r y w as c o l l e c t e d i n a 10 m ? h o l d i n gtank and the s o l i d s w ere disc ard ed. The sep ara ted s lu rr y was mixed in th eho ld ing tank by a 1 kW ce n tr i f u g al pump fo r at l e a s t 1 h and was an alys edf o r t o t a l s o l i d s (T S ). N e xt d a y, i t w a s d i l u t e d , i f a p p r o p r i a t e , t o anominal 30 g/1 TS.

2 .2 Chemica l ana lysesThe fo l l o w i n g c h a r a c te r i s t i c s w e re a na l y s e d by s tanda r d m ethods (9 ) :

TS, v o l a t i l e so l i d s (VS), chem ical oxygen demand (COD), K jelda hl ni tr og en(Kj-N) and amm oniacal n it ro ge n (NH^-N). The b io ch em ic al oxygen demand ofw h o l e s l u r r y ( B 0 D w) w a s a n a l y s e d by a d i l u t i o n m eth od ( 1 0 ) . V o l a t i l ef a t t y a c i d s (VFA) w e r e a n a l y s e d b y g a s c h r o m a t o g r a p h y ( 2 ) . N i t r a t e an dn i t r i t e n i tr oge n (NO-j-N, NO2-N) were ana lysed w i th in d ica to r s t r ip s .

2 .3 Treatment apparatus

The trea tm ent a pparatu s (F ig 1) co n si st ed of a feed tank and two 500l i t r e w o r k ing v olum e r e a c to r s . They had g l a s s r e i n f o r c e d p l a s t i c w a l l s andw e re i n s u l a t e d e x t e r n a l l y w i t h 50 mm e xp a nd ed p o l y s t y r e n e . T h ey w er ed e si gn e d f o r s e m i - co n t in u o u s f e e d in g , w i t h r e s i d e n c e t i m e , t e m p e r a t u r e ,foaming and ae ra t io n ra te be ing con tr o l l ed . The trea tm ent co nd i t io ns o fd i ss o lv ed oxygen con cen tra t ion (DO), res id en ce t im e , redox p ot en t i a l , pHand tem peratu re were recorded on a data log ge r .

R e s i de nc e ti m e w as c o n tr o l l e d by f i x i n g the r a t e o f f e e d i ng untr e a te d



260

Fig. 1 Pilot scale reactors for the aerobic treatment ofpig slurry



261

s l u r r y a u c h t h a t p r e d e t e r m i n e d d o s e s o f 5 t o 2 0 k g w e r e p um pe d I n e v e r yo ne o r t w o h o u r s . T h i s w a s a c h i e v e d b y w e i g h i n g e a c h r e a c t o r c o n t i n u o u s l y ,u s i n g a l o a d c e l l , an d c o n t r o l l i n g t h e p um p in g o p e r a t i o n s w i t h a p r o c e s s

t i m e r . W i t h i n a f e e d i n g c y c l e , a d i s c h a r g e pum p e m p t i e d s l u r r y do wn t o ap r e s e t r e a c t o r m a s s , t h e n , a f t e r a 10 m i n u t e w a i t , f e e d s l u r r y wa s pum pedi n u n t i l a s e c o n d p re s e t m a s s w a s r e a c h e d .

As e a ch r e a c t o r w as i n s u l a t e d , t h e h e a t l i b e r a t e d d u r in g t r e a t m e n tw as s u f f i c i e n t t o r a i s e t h e r e a c t o r t e m p e r a t u r e a bo ve 2 8° C. S u r p l u s h e a tw as r em o v ed i n r e s p o n s e t o a c o n t r o l l e r b y a h e a t e x c h a n g e r , s u p p l i e d w i t ht a p w a t e r , a t a c o n s t a n t p r e s s u r e -

F o am in g w as c o n t r o l l e d by s i t u a t i n g an i m p e l l e r , w h i ch w as d r i v e n a t140 0 r e v / m i n , u n d e r a s q u a r e - s e c t i o n p y r a m i d a l d r a f t t u b e . T he i m p e l l e rs u c k ed h e a d s p a c e a i r a nd foam i n t o t h e t r e a t e d s l u r r y . As fo am b u i l t u pi t f l o w e d dow n t h e t u b e a nd w a s r e c y c l e d b y t h e i m p e l l e r . No o t h e r

m e c h a n i c a l d e v i c e w as n e e de d t o c o n t ro l f o a m .A e r a t i o n w as c o n t r o l l e d a t on e o f t h r e e r a t e s b y c o n n e c t i n g e i t h e r a

d i s s o l v e d ox yg en (DO) o r r e d o x e l e c t r o d e , a s a p p r o p r i a t e (S e c t i o n 2 .4 ) , t oa m e t e r c o n t a i n i n g a t r i p a m p l i f i e r . The t r i p a m p l i f i e r o p e r a t e d a t t w os e t p o i n t s an d s w i t c h e d t w o s o l e n o i d v a l v e s t o a l l o w t h e e n t r y o f a i r a t ah i g h o r lo w f l o w r a t e t h ro u g h a p i p e t h a t e m e rg ed u n d e r t h e i m p e l l e r .

2 .4 E x p e r i m e n t a l d e s i g nT w e lv e t r e a t m e n t s w e r e i n v e s t i g a t e d ( T a b l e I ) i n w h i ch t h e r e s i d e n c e

t i m e s w e r e n o m i n a l l y 1 , 2 ,3 a nd 4 d a y s . A t e a c h r e s i d e n c e t i m e , t h ea e r a t i o n r a t e w a s c o n t r o l l e d a t l o w , m ed iu m o r h i g h r a t e s ( ru n s 1L -4 L , 1M -4M an d 1H-4H r e s p e c t i v e l y ) . T h e l o w e s t t w o a e r a t i o n r a t e s c o n t r o l l e d t h em i x ed l i q u o r r e d o x p o t e n t i a l i n t h e r a n g e 0 t o + 10 0 mV Eh o r + 1 00 t o+200 mV E h . D i s s o l v e d o x y g e n (DO) w a s n o t n o r m a l l y d e t e c t a b l e a t e i t h e rr e d ox v a l u e , b u t c o n d i t i o n s w e re a e r o b i c ( 11 ) an d t r e a t m e n t a t t h e s e r e d o xv a l u e s h ad b e e n f ou n d e f f e c t i v e on a l a b o r a t o r y s c a l e ( 7 ) . T he h i g ha e r a t i o n r a t e m a i n t a i n e d DO b e t w e e n 0.5 a nd 2 m g / 1 s o a s n o t t o i n h i b i t

T a b l e I . M ean v a l u e s o f r e d ox p o t e n t i a l , t e m p e r a t u r e , r e s i d e n c e t i m e , pHan d DO i n t h e t w e l v e t r e a t m e n t s ( s t a n d a r d d e v i a t i o n s a r e s ho w n i np a r e n t h e s e s ) .

Run number

Redox.mV E h

Temp,°Cr e s . t i m e . dpH

Run number

Redox,mV E h

Temp,°Cr e s . t i m e , dpH

Run number

DO,mg/1Temp,°Cr e s . t i m e , dpH

1L

51 (17)3 3 - 3 ( 0 . 8 )

1 .0 (0 .1 )7 . 9 5 ( 0 . 0 6 )

1M

114 (51)

3 3 . 7 ( 0 . 4 )1 .1 (0 .1 )7 . 4 3 ( 0 . 0 6 )

1H

0 . 5 ( 0 . 3 )3 3 . 1 ( 4 . 7 )

1 .1 (0 .1 )8 . 0 4 ( 0 . 3 5 )

2L

78 (37)3 1 . 8 ( 3 . 8 )

2 . 3 ( 0 . 2 )7 . 8 5 ( 0 . 1 4 )

2M

181 (69)

3 1 . 5 ( 3 . 6 )2 . 1 ( 0 . 3 )7 . 9 8 ( 0 . 1 4 )

2H

1 . 0 ( 0 . 1 )3 2 . 7 ( 0 . 5 )

2 . 1 ( 0 . 3 )7 .6 7 ( 0 . 5 3 )

3L

13 (50)3 3 . 2 ( 2 . 0 )

3 . 6 ( 0 . 4 )7 . 6 2 ( 0 . 1 2 )

3H

162 (37)

3 3 . 8 ( 0 . 4 )3 . 8 ( 0 . 7 )8 . 4 7 ( 0 . 1 2 )

3H

1 . 3 ( 0 . 1 )3 3 . 8 ( 0 . 8 )

3 . 6 ( 0 . 4 )7 . 4 5 ( 0 . 1 6 )

4L

83 (11)3 4 . 7 ( 0 . 4 )

4 . 4 ( 0 . 7 )8 .01 ( 0 . 0 5 )

4M

186 (102)

3 1 . 2 ( 1 . 8 )4 . 8 ( 1 . 0 )8 .26 ( 0 . 0 5 )

4H

0 . 8 ( 0 . 1 )2 7 . 8 ( 1 . 1 )

4 . 1 ( 0 . 5 )7 .0 4 ( 0 . 0 8 )



262

m i c r o b i a l a c t i v i t y . The u s e o f r e d o x p o t e n t i a l a s a c o n t r o l p a r a m e t e ra l l o w s a e r o b i c c o n d i t i o n s t o b e m a i n t a i n e d , w h i l e i n h i b i t i n g n i t r i f i c a t i o n( t h e b i o l o g i c a l o x i d a t i o n o f NH^ t o N O j" an d N 0*~) a nd p o s s i b l y i n h i b i t i n gt h e d e s t r u c t i o n o f so me c a r b o n a c e o u s s u b s t r a t e s , b u t n o t s o a s t o p r e v e n tt h e d e s t r u c t i o n of t h e s o l u b l e co m po un ds r e s p o n s i b l e f o r c a u s i n g t h eo f f e n s i v e o d o u r s o f s l u r r y . F u r t h e r m o r e , by m a i n t a i n i n g DO a t z e r o t h ed i f f u s i o n g r a d i e n t o f o xy ge n from t h e a t m o s p h e re t o s l u r ry i s m a x i m i s e d .T he t e m p e r a t u r e r a n g e , 2 8 - 5 5 ° C , w a s i n t h e m e s o p h i l i c r a n g e o f b a c t e r i a la c t i v i t y .

T he r a n g e s o f r e d o x p o t e n t i a l b e t w e e n t h e lo w a nd h i g h r e d o x r u n sw e r e s i g n i f i c a n t l y d i f f e r e n t , b o t h w hen g ro u pe d t o g e t h e r and a s i n d i v i d u a lr u n s (P =0 .0 01 ) . S i m i l a r l y , DO w a s s i g n i f i c a n t l y h i g h e r (P =0 .0 01 ) i n t h eh igh DO ru ns t ha n any o f t h e redo x ru ns .

I n e a c h t r e a t m e n t , a p p r o x i m a t e l y s t e a d y s t a t e c o n d i t i o n s (12) w erea s su m e d t o p r e v a i l a f t e r o p e r a t i o n f o r 3 r e s i d e n c e t i m e s w i t h o u tm e c h a n i c a l f a i l u r e . E ac h t r e a t m e n t wa s t h e n r u n f o r 2 0 d a ys d u r i n g w h ic ha n a l y s e s w e r e m ade d a i l y a n d, i n a d d i t i o n , t r e a t e d s l u r r y w a s a c c u m u l a t e di n 10 l i t r e , c l o s e d c o n t a i n e r s , i n n o m i n a l 0 .5 l i t r e d a i l y b a t c h e s . T heq u a n t i t y o f t r e a t e d s l u r r y a dd ed d a i l y w as a d j u s t e d t o c o m p e n s at e f o r t h ev o l u m e r e m o v e d d u r i n g s a m p l i n g , s o t h a t t h e m e an v o l u m e o f e a c h d a i l yi n c r e m e n t a f t e r 20 d a y s w a s 0 .5 l i t r e . Th e c o n t a i n e r s w e r e k e p t a t 1 0°Can d t h e c o n t e n t s s a m p le d t w i c e w e e k l y t o a s s e s s t h e s t a b i l i t y o f t h et r e a t e d s l u r r y . VFA w e r e u s e d a s i n d i c a t o r s o f o d o u r o f f e n s i v e n e s s ( 2 , 6 ) .S t a b i l i t y w as m e a su r ed a s t h e t i m e t a k e n t o r e a c h tw o c o n c e n t r a t i o n s o fVFA, 0 .2 3 an d 0 .6 5 g / 1 . S l u r r i e s c o n t a i n i n g u p t o 0 .2 3 g / 1 VFA w e r ec o n s i d e r e d a c c e p t a b l e by a n o d o ur p a n e l ( 6 ) , w h i l e a t h r e s h o l d o fu n e q u i v o c a l u n a c c e p t a b i l i t y w as r e a c h e d a t 0 .6 5 g / 1 VFA. T h u s , s l u r r i e ss t o r e d u n t i l t h e VFA c o n c e n t r a t i o n r e a c h e s 0 .2 3 g / 1 s h o u l d n o t c a u s e o d o u rp r o b l e m s , w h i l e t h o s e c o n t a i n i n g a b ov e 0 .6 5 g / 1 s h o u l d r e l e a s e o f f e n s i v eodo urs . The consu mp t ion o f oxygen was measured c he m ic a l ly by changes inCOD, N 0 2 " and N0 5 " .

T he e x p e r i m e n t s w e r e c a r r i e d o u t b e t w e e n N o ve m b er 1 98 2 a nd A p r i l1 984 , i n a rando mise d o r de r .

3 . RESULTS AND DISCUSSION

3.1 F ee d s l u r r yT he a v e r a g e c o m p o s i t i o n o f t h e fe e d s l u r r y u s e d i n t h e t r e a t m e n t s i s

s h o w n i n T a b l e 2 . T h e c o m p o s i t i o n o f T S , VS a n d COD d i d n o t v a rys i g n i f i c a n t l y b e t w e e n r u n s . T h e re w as s i g n i f i c a n t v a r i a t i o n (P =0 .0 01 ) i nB 0D w , VFA a n d NH-z-N, w h i c h w a s r e l a t e d t o t h e t i m e o f y e a r . T h e s ec h a r a c t e r i s t i c s g e n e r a l l y i n c r e a s e d w i t h r e s p e c t t o TS i n su mm er w henh i g h e r a m b i e n t t e m p e r a t u r e s p r om o t ed m i c r o b i a l a c t i v i t y . T he a v e r a g ec h e m i c a l c o m p o s i t i o n w as v e r y s i m i l a r t o t h a t of s l u r r i e s u s ed e l s e w h e r ei n l a b o r a t o r y s c a l e t r e a t m e n t e x p e r i m e n t s ( 3 , 4 ,7 , 1 3 ) .

3-2 C h e m i c a l c h a n g e s w i t h t r e a t m e n t

3 . 2 . 1 C a rb on ac eo us c h a r a c t e r i s t i c sT he d e s t r u c t i o n o f c a rb o n a ce o u s s u b s t r a t e s d u r i n g t r e a t m e n t r e s u l t e d

i n s i g n i f i c a n t ( P= 0.0 01 ) d e c r e a s e s o f T S, V S, B 0D w , VFA (T a b l e I I I ) a n dCOD (F ig 2 ) i n e ve r y run . The d e s t r u c t i o n o f VS and TS were ve ry s i m i l a ri n e a c h ru n b e i n g i n t h e r a n g e 2 -2 0 ? . COD d e s t ru c t i o n w a s h i g h e r , 2 1 -3 8 ? ,whi le B0Dw r e m o v a l w as 4 6 -8 5 ? . D e s t r u c t i o n o f VFA w a s n e a r l y t o t a l a t 9 8 -1 0 0 ? . E t h a n o i c a c i d w a s u s u a l l y t h e o n l y i n d i v i d u a l VFA f ou nd i n t h et r e a t e d s l u r r i e s . T h i s w as t a k e n t o b e t h e " r e s i d u a l e t h a n o i c a c i d " ( 6 ) ,



263

0.8

COD out/in

0.7

0.6

<_

• T

2 3 Residence t ime, days

Fig. 2 Destruction of COD with respect to residence t ime.

Low ( • ) , medium ( T ) and high ( ■ ) aeration rates and the

curve of Evans et al ( — ) .

4.0 , -

Predicted

mixed liquor

BODw

g/l

2 2.5 3.0 3.5

BOD w in treated slurry g/ l .

Fig. 3 Measured BOD w in treated slurry and values predicted from expression.

(Iv) fo r low ( • ) and medium (▼ ) aeration rates and expression (Mi) for the high ( ■ ) aeration rate.



264

w h i c h i s a n o t h e r , u n k n o w n , c om p ou nd t h a t s o m e t im e s c a u s e s i n t e r f e r e n c ed u r i n g t h e g a s c h r o m a t o g r a p h i c a n a l y s i s o f t r e a t e d s l u r r i e s . A p a r t from

VFA, d e s t r u c t i o n g e n e r a l l y i n c r e a s e d w i t h r e s i d e n c e t i m e , T h i s w ass i g n i f i c a n t a t P - 0 . 0 0 1 , w hen t h e d a t a fro m a l l t h r e e a e r a t i o n r a t e s w e r ec o m b i ne d . T he o n l y s i g n i f i c a n t e f f e c t o f a e r a t i o n r a t e , h o w e v e r , w a s onB0D w. B0Dw c o n c e n t r a t i o n s i n t h e s l u r r i e s f o l l o w i n g t r e a t m e n t a t h i g h DOw e r e s i g n i f i c a n t l y ( P- 0.0 01 ) l o w e r t h a n t h o s e t r e a t e d a t e i t h e r r e d o xp o t e n t i a l , b e tw e e n w h ic h t h e r e w as no s i g n i f i c a n t d i f f e r e n c e ( T ab le I I I ) .

T a bl e I I .

TSVSAshTSSCODB0Dw

BODsVFAHH,-NKj-N

Average

Mean

g / 1

2 9 . 02 0 . 9

8 .12 3 . 83 9 . 91 0 . 7

4 . 5 64 . 4 32 . 7 23 . 5 3

In d i v i d u a l V F A

E t h a n o i cP r o p a n o i c

2 - m e t h y l p r o p a n o i cn - b u t a n o i c2 - m e t h y l b u t a n o i c l5 - m e t h y l b u t a n o i c jn - p e n t a n o i c

c o m p o s i t i o n

sd

2 . 22 .11.13-15 .13 .21 .21.2

.4 7• 55

( a c e t i c )( p r o p i o n i c )

( i s o - b u t y r i c( n - b u t y r i c )( i s o - v a l e r i c

o f f ee d s l u r r y

n

174171171174172144155146174

39

)

) )( 3 - m e t h y l b u t y r i c ) J

( n - v a l e r i c )

% of TS(» /w)

722882

137371615

912

% of t o t a l VFA(w/w)

6420

29

4

1

T a b l e I I I . M ean c o m p o s i t i o n o f t h e t r e a t e d s l u r r i e s . T he p e r c e n t a g e o fe a c h c o m p o n en t c o m pa re d w i t h i t s r e s p e c t i v e f e e d s l u r r y i s sh ow n i np a r e n t h e s e s .

Run TS VS BOD VFA

g / 1 —NH5-N N0,-N N0,-N

1L2L3L4L

1H

2H3M4K

2 6 .9 (9 3 )2 6 .6 (9 3 )2 6 .2 (8 7 )2 3 .6 (8 6 )

2 7 .0 (9 2 )2 7 .0 (9 3 )2 5 .8 (8 9 )24 .1 (86 )

18 .8 (94 ) 3 .8 4 (43 ) 0 .04 (1 ) 2 .1 4 (87 ) 0 018 .4 (92 ) 3 .42 (54 ) 0 .00 (0 ) 2 .02 (88 ) 0 01 7. 7 (84 ) 1 .79 (26 ) 0 .01 (1) 1 .87 (76) 0 017 .7 (87) 3-9 3 (29) 0 . 00 (0) 1 .71 (91) 0 0

18 .2 (97) 3 .61 (46 ) 0 . 08 (2) 2 .01 (81) 0 019 .9 (92) 3 . 85 (22) 0 .01 (1) 1-50 (89 ) 0 017 .2 (86 ) 3 .4 3 (18 ) 0 .0 8 (2 ) 2 .36 (89 ) 0 017 .6 (83) 2 .42 (27 ) 0 .06 (2) 1 .62 (96) 0 0

1H 27 .4 (93 )2H 24 .4 (81 )3H 2 5 . 1 ( 9 1 )4H 2 5. 3 (84 )

19 .0 (92 ) 2 .2 7 (39 ) 0 .06 (2 )16 .3 (80 ) 2 .57 (15 ) 0 .04 (1 )17 .7 (87 ) 2 .9 3 (22 ) 0 .0 0 (0 )19 .0 (83 ) 2 .0 9 (21 ) 0 .01 (1 )

1.55 (66 ) 0 01 .20 (63 ) 0 .30 0 .200 .4 4 (2 3 ) 0 .4 0 0 .4 80 .2 4 (10 ) 0 .56 1 .12



265

3 .2 .2 Ni t r o g en t r an s f o rma t i on s N i t r i f i c a t i o n occurred only i n th e high DO runs w i t h r e s i d enc e t im e s

o f 2 da y s and abov e (Tab l e I I I ) ; t h i s was a l s o o b s e r v e d i n l a b o r a t o r y -s c a l e s t u d i e s a t 35 °C by Evans e t a l ( 1 3 ) . As t h e r e s i d e n c e t i m e i n c r e a s e d , th e percentage of Kj-N o x i d i s e d i n c r e a s ed from 9* a t 2 days t o 31 % a t 3 days and 4 8 * a t 4.1 d a y s . The s e a r e o f t h e same o r d e r a s t h o s e found by Evans e t a l (13) w i t h i n th e range of 2 -8 days .

The degree of n i t r i f i c a t i o n did not i n c r e a s e l i n e a r l y w i t h r e s i d e n c e t i m e , bu t was more o f a s t e p c hang e . The a c c um u l a t i o n o f " n i t r i f i e d oxygen" (H 0 2~ + NO^") was d e s c r i b e d by a l o g i s t i c g r ow t h c u r v e ( 2 0 ) , i n the range o f r e s i d e n c e t im e s 2.1 to 4.1 days:

n i t r i f i e d oxygen - 1 .46 ♦ ^ . ^ ^ . a s ) ) ' ^

where R i s th e r e s i d e n c e t ime in da y s .

3-3 Comparison w i t h th e r e s u l t s o f Evans e t a l (4) The e f f e c t s o f t r ea tment a t 15-50 " C o n some o f th e c h a r a c t e r i s t i c s

were s tud i ed by Evans e t a l (4 ) us i ng l a bo ra t o r y r e a c t o r s . These were fed s em i - c o n t i nuou s l y , wi th feed i n t e r v a l s of 5-20 min, and DO was mainta ined a t about 20* o f s a t u r a t i o n . The t r e a tmen t c o nd i t i o n s were thus s i m i l a r t o th e high DO t r e a tmen t s used i n th e pr e s en t s tudy , but th e main d i f f e r e n c e

was t h a t Evans e t a l ' s 3 and 15 l i t r e r e a c t o r s we r e s m a l l e r t han t h o s e u s e d i n t h e p r e s e n t s t u d y by f a c t o r s o f 167 and 33 r e s p e c t i v e l y . Evans e t a l ' s e x p r e s s i o n fo r TS and COD take the form:

TS or COD i n - 1 A + C

J (TS or COD i n f e e d s l u r r y ) , ( i i )

t r e a t ed s l u r r y ' ' +

(R K

d^ •

where K^ i s s p e c i f i c decay r a t e , C i s th e non-b i odegradab l e f r a c t i o n , R i s r e s i d e n c e t ime and A i s a c o n s t a n t , de f ined be l ow .

3.3.1 T5 and VS

For TS, Evans e t a l us ed t h e v a l u e s o f 0 . 2 6 2 , 0 . 4 , 0 .744 f o r A, K^ and C r e s p e c t i v e l y . The i r e xpr e s s i on was app l i e d to data from th e pr e s en t e x p e r i m e n t s and t h e c hang e s i n TS so p r e d i c t e d a g r e e d w e l l w i t h t h e observed changes a t a l l a e r a t i o n r a t e s . The va r i anc e accounted fo r (VAC) was 95*.

Evans e t a l did not model VS, however , th e TS e x p r e s s i o n f i t t e d the d a t a f a i r l y w e l l ( 8 8 * VAC). The s i g n i f i c a n c e o f t h e f i t o f e i t h e r c u r v e was not improved by a l t e r i n g th e v a l u e s of th e c o e f f i c i e n t s .

3 .3 .2 COD

The changes of COD predicted from the expression of Evans et al

agreed well with the changes observed at all aeration rates (96.7* VAC). The values of A, Kd and C were 0.33, 0.4 and 0.535 respectively.

3.3.3 BOD The BOD^ expression of Evans et al (ii) did not need to include a

term for endogenous decay. Thus, B 0 D w in treated slurry becomes a function of residence time and feed BOD only. Evans's expression was:

11.57 + 0.15| (feed BOD ) . (iii)



266

This expression fitted the present high DO data fairly well, but not the redox data, as expected because of the significant (P-0.0O1) effect of

aeration rate on B0D y. The fit was greatly improved (VAC increased from 89-4? to 97.9?) for the combined redox data by fitting new coefficients (Fig 3) so that expression (iii) becomes:

11.30 + 0.231 (feed B0D w) . (iv)

The increase of the non-biodegradable coefficient (C) shows that some restriction in treatment was evident in the redox runs, thus leaving a larger residual B0D w, which could be expected, as the oxygen supply was restricted. This does, however, appear to contradict the fact that the

changes in TS, VS and COD were independent of aeration rate, but may be explained by the fact that B0D w is partly renewable (2). Recalcitrant substrates that are not immediately available in untreated slurry may subsequently become available following the action of hydrolytic enzymes and mechanical attack by the impeller during aeration, thus producing "new" BODw. Thus, even with the same overall oxygen consumption (from the COD changes) it is possible that the residual BOD concentrations could differ. Precisely what substrates are involved, however, remains obscure.

3.4 Odour control and stability of treated slurries The treatments would all successfully control odours, since the total

VFA concentrations in all slurries at the start of storage were below 0.23 g/1 (ie within the "acceptable" concentration range). The stability of the treated slurries during subsequent anaerobic storage increased significantly (P=0.001) with residence time (Figs 4 and 5). The time taken to reach 0.23 g/1 increased linearly with residence time. The slurries from the high DO runs were significantly (FO.001) more stable than those from the redox controlled runs. Stability was not significantly affected by the redox potential during treatment. The data were described by the following expressions, where R is residence time, in days for the high DO treatment:

days to reach 0.23 g/1 = 3-9 R + 14 , (95.1* VAC)

and for the redox treatment:

days to reach 0.23 g/1 ■ 4.6 5 + 4.6 , (98.3? VAC).

The time taken to reach the "unacceptable" concentration of 0.65 g/1 VFA was an average of 1.6 times longer than the time taken to reach 0.23 g/1. One notable feature was the great stability of the treated slurry from run 4H. This probably resulted primarily from the high nitrified oxygen concentration. The nitrified oxygen can, like oxygen itself, act as an electron acceptor (15), thus permitting "aerobic" activity even in the absence of DO. Furthermore, once this source of oxygen is used, rapid anaerobic detruction of VFA can proceed because the NH^-N concentration has been lowered so minimising the inhibition of methanogenic anaerobic activity (2). The redox data were described by the following expression:

days to reach 0.65 g/1 = 3.2 R + 17 , (96.8? VAC).



267

60 r

Days to

reach

0.65 g/l ^

VFA

W

20

2 3 Residence t ime, d

50 p

Days to

reach

0.23 g/l

VFA

2 3 Residence t ime, days

Fig. 4 and 5 Time taken fo r VFA to reach 0.65 and 0.23 g/l during storage

after treatment against treatment residence t ime. Low ( • ) , medium (▼), and high ( ■ ) aeration rates



268

The high DO data, including the nitrifying runs, did not follow alinear relationship, probably because the non-linear relationship of

nitrification and residence time [expression (i)].The ma in factors that determ ines stability is the a mount of substrateavailable during anaerobic storage and whether a methanogenic populationdevelops that can degrade odorous compo unds to metha ne and COp- Theavaila ble substrate was estimated previously (2) by calculating theresidual biodegradable COD content (COD^), which is effectively the sam eas ultimate B0D w. COD^ was also a good measure of stability in the presentstudy, although it wa s calculated in a different way, by using expression(ii) for COD des tructio n. The coefficient of 0.535 (secti ons 3.3, 3.3.2)represents the non-biodegra dable fraction of COD; thus the degradablefraction in a treated slurry can be calculated as

(f8edC0D) |l +(£,)[

COD^ correlated wel l with the stability of slurries treated underredox control, but less wel l w ith those treated with high DO, probablybecause of the presence of nitrified oxygen in the latter case. Thepresence of nitrified oxygen, when nitrifica tion occurred, in effectreduced the concent ra tion of CODb, as less CODb rema ined in the slurryonce the nitrified oxygen w as used. Assuming 100? utilisation of thenitrified oxygen, CODb was corrected by subtracting the amount of

nitrified oxygen from it. The fit of the DO data wa s consequently greatlyimproved (Figs 6 and 7) . The relationships were described by theexpressions:

days to reach0.23 g/1 VFA = -2.685 (C0Db - nitrified oxygen) + 36 , (94.7* VAC),

days to reach0.65 g/1 VPA =-3- 03 7 (C0Db - nitrified oxyg en) + 48 , (87.1* VAC).

The allo wance for nitrified oxygen still did not fully account for

great stability of the treated slurry from run 4H, which probably partlyresulted also from the low NH^-N content. More experimental data is neededto derive a satisfactory term for the inhibitory effect of NHj-N onmethanogenesis.

3.6 Oxygen requirements and energy consumptionThe oxygen consumed during aerobic treatment can be calculated from

the expr essions for COD destruction and nitrifica tion (i and ii). Theoxygen consumed thus calculated correlated well with the stabilityachieved, wi th 97.5* and 96.3* VAC for the tim e taken to reach 0.23 and0.65 g/1 VFA r espectively . The energy required to supply this oxygen canbe calculated, assuming an aerator efficiency of 1 kg 0, / kWh energyconsumed . If one fattening pig pr oduces 0.6 kg COD / d, then afterseparation, with 20 * solids remova l, the slurry production is equivalentto 12 1 at 3* TS. The energy required, in Wh, per pig pla ce each day wa sdescribed by the following expressions (Figs 8 and 9) :days to reach0.23 g/1 VFA = 0.182 aeration energy - 8.10 , (96.6* VAC) ,

days to reach0.65 g/1 VFA - 0.243 aeration energy - 7.75 , (95-9* VAC) .



269

60 p

50 -

40 -ays to

reach

0.65 g /l

VFA 3 °

20

10

0

C O D . - n i t r i f i e d o x y g e n , g /l 10

o u

40 Days to reach 0.23 g/l 3° VFA

20

10

0

- """-

-

•

" i

" ^ C •"^

■

▼

_ l 1 8 10 2 4 6

C O D ^ - n i t r i f i e d o x y g e n , g /l

F i g . 6 and 7 T i m e taken f o r V F A t o reach 0.65 and 0.23 g /l d u r i n g storage af ter t r e a tm e n t against residual biodegradable C O D ( C O D b ) m i n u s

n i t r i f i e d o x y g e n L ow ( • ) , m e d i u m (▼ ) and h i g h ( ■ ) aera t ion rates



270

60 r

Days to

reach

0.65 g/l 40

VFA

20

J l_ 100

_l I 150

J L. 200

Aerator energy Wh pig place" d

50

Days to reach

0.23 g/ l 3 0

VFA

10

100 150 200

Aerator energy Wh pig place'1 d '

1

Figs. 8 and 9 Time taken fo r VFA to reach 0.65 and 0.23 g/l during storage

after treatment against aeration energy, assuming an aerator

efficiency of 1 kg 0 2 / kWh . Low ( • ) , medium ( T ) and high ( ■ ) aeration rates.



271

T h e g r a p h s s h o w t h a t t h e s t a b i l i t y i s m o r e t h a n d o u b l e d f o r adoubling of ener gy input a nd tha t the m i ni m u m ener gy consum ption, withoutextr a pola tion is 110 Wh pig pla c e" da y . The expr essions a bov e a r e ba sed

o n s l u r r y c o n t a i n i n g 3 0 g / 1 TS. It s h o u l d b e e m p h a s i s e d t h a t t h ec o n c e n t r a t i o n o f t he s l u r r y h a s a m a j o r e f f e c t o n s t a b i l i t y , w i t hs t a b i l i t y d e c r e a s i n g a s TS i n c r e a s e s . E x t r a p o l a t i o n f r o m p r e v i o u s w o r kw i t h b a t c h t r e a t m e n t a n d s t o r a g e ( 2) s u g g e s t s t h a t s l u r r y c o n t a i n i n g43 g/1 would be less sta ble tha n slur r y conta ining 30 g/1 by a bout 10 and3 0 ? a f t e r t r e a t m e n t w i t h r e s i d e n c e t i m e s o f 3 a n d 4 d a y s r e s p e c t i v e l y .F u r t h e r m o r e , a d i l u t e s l u r r y , c o n t a i n i n g l e s s t h a n 1 5 g /1 TS c o u l d b eexpected to be fully sta bilised for a yea r follow ing such tr ea t m e nts.

4. CONCLUSIONS

1. Th e o f f e n s i v e o d o u r s o f u n t r e a t e d , s e p a r a t e d p i g s l u r r y w e r econtr olled by a er obic tr ea t m ent, a t 28 to 35°C with r esidence tim es of1 to 4.8 d a nd w i t h a n a e r a t i o n r a t e t h a t m a i n t a i n e d r e d o x p o t e n t i a l a t13 mV Eh and above.2. Th e s t a b i l i t y of t h e t r e a t e d s l u r r i e s d u r i n g s u b s e q u e n t a n a e r o b i cstor a ge incr ea sed fr om 10 to 56 da ys a s both the tr ea t m ent r esidence tim eand the aera tion rate incr eased.3. Th e s t a b i l i t y o f th e t r e a t e d s l u r r i e s w a s d i r e c t l y r e l a t e d t o t h er esidua l biodegr a d a bl e COD content, with a n a llowa n ce for nitr ified oxygenbeing m a de whe n nitr ifica tion occur r ed in the DO contr olled r uns.4. Th e s t a b i l i t y o f t h e t r e a t e d s l u r r i e s w a s l i n e a r l y r e l a t e d t o t h eo x y g e n c o n s u m e d d u r i n g t r e a t m e n t , w h i c h c o u l d b e c a l c u l a t e d u s i n g a nexpression for nitrification derived in the present study and one for CODcha nges pr oduced by Ev a na et a l (4) fr om la bor a tor y sca le e xper i m ents.5. An e x p r e s s i o n p r e d i c t i n g t r e a t e d s l u r r y B 0 D w d u r i n g t r e a t m e n t w i t hredox control is presented.6. The m i nim u m ener gy r equir e m ent for tr ea ting sepa r a ted pig slur r y tocontr ol odour wa s 110 Wh pig pla ce" da y" , a ssu m ing a n a er a tor efficiencyof 1kg 02/kWh input.7. Ther e w a s no significa nt effect of a er a tion r a te on the destr uction ofTS, V S , V FA o r C O D , t h u s t h e o n l y s a v i n g i n o x y g e n c o n s u m p t i o n o f u s i n g

r e d o x c o n t r o l r a t h e r t h a n DO c o n t r o l w a s i n t h e i n h i b i t i o n o fnitr ifica tion.

ACKNOWLEDGEMENTS

The a uthor wishes to expr ess his tha nks to Sue Dim m ock, Ros Nicol a ndHa ndy Lee for their a na lytica l w or k a nd to Dr Roger Phillips a nd Dr JohnRa nda ll for their help a nd a dv ice in the pr epa r a tion of this pa per .

REFERENCES

1. INSTITUTION OF ENVIRONMENTAL HEALTH OFFICERS (1982) App en di x to ann ua lrepor t. London : IEHO2. WILLIAMS, A.G., SH AW , H. a nd AD AM S, S.J. ( 1 9 8 4 ) . T h e b i o l o g i c a lsta bility of a er obica lly-tr e a ted pigger y slur r y dur ing stor a ge. J. a gr ic.Engng Res. 29 , 231 -2393. EVANS, M.R., H ISSE TT, R., SM ITH , M.P.W., ELLAM , D.F., B AINE S, S. an d



272

WOODS, L . (1979)- E f f ec t o f m ic roo rgan i sm re s i de nc e t im e on ae ro b i ct r e a t m e n t o f p i g g e ry w a s t e . A g r i c . W a s t e s 1 (1 ) , 6 7 -8 54 . EVANS, M .R., DEANS, E .A ., H ISS ET T, R. , SM ITH, M.P.W ., SVOBODA, I . ? ,and THACKER, F .E. (1983) . The e f fe c t of te m p er at u re and re s i d e n ce t im e ona e r o b i c t r e a t m e n t o f p i g g e r y s l u r r y - d e g r a d a t i o n o f c a r b o n a c eo u scompounds . A gr i c . Was tes 5 , 25 -565 . MONOD, J . ( 1 9 4 9 ) . T h e g r o w t h o f b a c t e r i a l c u l t u r e s . A nn . R e v .M i c r o b i o l . 3 , 5 7 1 - 3 946 . WILLIAMS, A . S . Q 9 8 4 ) . I n d i c a t o r s o f p i g g e r y s l u r r y o d o u ro f f e n s i v e n e s s . A g r i c . W a s t e s 1 0 ( 1 ) , 1 5 -3 67 . WILLIAMS, A .G. (1981) . The b io lo g ic a l c o n t r o l o f odo urs em ana t ing f romp i g g e r y s l u r r y . PhD t h e s i s : U n i v e r s i t y o f G la sg ow8 . HISSETT, R., DEANS, E.A. and EVANS, M.R. ( 1 9 8 2 ) . Ox ygen c o n s u m p ti o nd u r i n g b a t c h a e r a t i o n o f p i g g e r y s l u r r y a t t e m p e r a t u r e s b e tw e e n 5 a nd50i!C. A gr ic . W astes 4 , 477-4879 . APHA. (1971) S ta nd ard m e thods fo r t he exa m ina t io n o f w a t e r s and w as te w a t e r s (1 3 t h E d .) . New Y ork : A m e r ic a n P u b l i c H e a l t h A s s o c i a t i o n1 0 . W ILLIAMS, A .G . (1 9 8 3 ) . O rg a n i c a c i d s , b i o c h e m i c a l o x y g e n d e m a n d a n dc h e m i c a l o xy ge n dem and i n t h e s o l u b l e f r a c t i o n o f p i g g e r y s l u r r y . J . S c i .Food A gr i c . 34 , 212-2201 1 . HEWITT, L .F . ( 1 9 50 ) . O x i d a t i o n - r e d u c t i o n p o t e n t i a l s i n b a c t e r i o l o g ya nd b i o c h e m i s t ry (6 t h E d . ). E d i n b u rg h : L i v i n g s t o n e1 2 . SMITH, M.P.W. and EVANS, M.R. (1 98 2 ) . The e f f e c t s o f l ow d i s s o l v e do xy ge n t e n s i o n d u r i n g t h e a e r o b i c t r e a t m e n t of p i g g e r y s l u r r y i n

c o m p l e t e l y m ix ed r e a c t o r s . J . a p p l . B a c t . 5 3 , 1 1 7- 12 61 3 . EVANS, M.R., SVOBODA, I .F . and BAINES, S. (1 98 2) . He at from a e r o b i ct r e a t m e n t o f p i g g e r y s l u r r y . J . a g r i c . E ngng R e s . 2 7 , 4 5 - 5 0~H. ROSS, G .J .S . ( 1 98 0 ) M a xim u m l i k e l i h o o d p r o g r a m . H a r p e n d e n :R o t ha m s te d E x p e r i m e n t a l S t a t i o n15 ROSE, A.H. (1968) Chem ical m ic ro bi o l og y. London : B ut te rw or th



273

AERATION AND ODOUR CONTROL BY HETEROTROPHIC

AND AUTOTROPHIC MICROORGANISMS

M.R. EVANS and S. BAI NESThe West of Scotland Agricultural College,

Auchincruive, Ayr, KA6.5HW, Scotland, U.K.

Summary

The control of odour from piggery slurry by continuousculture aerobic treatment systems is affected by treatmenttime, tem per atu re and dissolv ed ox ygen level. Thetechniques of monitoring these treatment systems for initial

and residual odour, odour stability during storage, oxygendemand by heterotrophic and auto trophi c bacte ria arediscussed. The selection of the appropriate treatmenttime, treatment temperature and rate of aeration can bedetermined from a series of equations and, together withspecifications of the aerator and insulation factors of thereactor, permit the design of an aerobic treatment system tomeet defined objectives in terms of odour control andstability.

1. INTRODUCTIONThe characteristic odours of slurries of animal wastes

are largely due to the release of volatile organic compoundsfrom the fermentative degradation of faecal residues.These compounds are the normal end products of catabolism byanaerobic bacteria. Odours create problems when theyhave nuis ance value giving rise to co mp la in ts . Thenuisance value is a function of both odour intensity andoffensiveness. Whereas, most odours create nuisance athigh intensity, at low intensity, nuisance is mostfrequently associated with offensiveness. The totalelimination of odour from slurry may be neither feasible ornecessary, and therefore, several workers (1, 2, 3, 4 , 5)have favoured the subjective assessment of offensivenessrather than objective tests of intensity. However, thefrequent use of odour panels for offensiveness testing inthe routine monitoring of the performance of a treatment



274

s y s t e m i s g e n e r a l l y r e g a r d e d a s c u m b e rs o m e , t i m e - c o n s u m i n ga n d e x p e n s i v e .

N u m e ro u s a u t h o r s ( 6 , 7 , 8 , 9) h a v e t r i e d t o c o r r e l a t et h e c o n c e n t r a t i o n s o f s p e c i f i c c om p ou nd s w i t h o d o u r b u t n on eh a v e b e e n r e a l l y s a t i s f a c t o r y . T h e p r e s e n c e o f s p e c i f i cc o m p o u n d s m ay i n d i c a t e a p o t e n t i a l n u i s a n c e , b u t t h e i ra b s e n c e d o e s n o t im p l y t h e a b s e n c e o f a l t e r n a t i v e o d o r a n t s .

W i l l i a m s (10) d e m o n s t r a t e d a g oo d c o r r e l a t i o n b e t w e e nt h e s u p e r n a t a n t BODc ( g / 1 ) o f p i g g e r y s l u r r y a nd i t s o d o u ro f f e n s i v e n e s s . T h i s r e g r e s s i o n w as l a t e r a m e n de d u s i n gd a t a o f a w i d e r r a n g e o f o f f e n s i v e n e s s v a l u e s ( 1 1 ) .

A l a r g e c o m p o n e n t o f s u p e r n a t a n t BODc i s c o m p r i s e d o fo r g a n i c a c i d s and s i m i l a r c o r r e l a t i o n s e x i s t b e t w e e n t o t a l

o r g a n i c a c i d s c o n c e n t r a t i o n (TOA) a n d o d o u r o f f e n s i v e n e s s .T he c o r r e l a t i o n i s n o t a s g o od a s t h a t o f s o l u b l e BOD5 b u tt h e e s t i m a t i o n o f TOA i s a m uch q u i c k e r p r o c e d u r e .

When a b a t c h o f s l u r r y i s a e r a t e d , i t s o f f e n s i v e o d o urs oo n d i s a p p e a r s l a r g e l y d u e t o b i o d e g r a d a t i o n . I n b a t c ha e r a t i o n , t h e m i c r o b i a l r e s p i r a t i o n r a t e r i s e s r a p i d l yd u r i n g t h e f i r s t 1 2h a n d t h e n f a i l s e q u a l l y r a p i d l y t o am uch l o w e r l e v e l ( 1 2 ) . T h us i t i s d i f f i c u l t a nd e x p e n s i v et o d e s i g n a b a t c h t r e a t m e n t r e a c t o r w h i c h i s e f f i c i e n t i nt e r m s o f u s e o f a e r a t i o n e n e r g y . I t r e q u i r e s an a e r a t i o nr a t e w h i ch c o n t i n u a l l y v a r i e s i n p r o p o r t i o n t o t h e c h a n g in g

r e s p i r a t i o n r a t e .C o n t i n u o u s c u l t u r e s y s t e m s o f a e r o b i c t r e a t m e n t a r e

l i k e l y t o b e m o re c o s t e f f e c t i v e s i n c e i n s t e a d y s t a t ec o n d i t i o n s t h e r e s p i r a t i o n r a t e a n d h e n c e o x y g e nr e q u i r e m e n t , r e m a i n c o n s t a n t . T h i s r e p o r t d e s c r i b e s t h ee f f e c t s o f m ean t r e a t m e n t t i m e , t r e a t m e n t t e m p e r a t u r e a n dd i s s o l v e d o xy gen l e v e l in a e r o b i c c o n t i n u o u s c u l t u r e s y s t e m son t h e r e m o v a l o f o d o r a n t s f ro m p i g g e r y s l u r r y a nd on t h eh e t e r o t r o p h i c o xy gen dem and d u r i n g t r e a t m e n t .

2 . MONITORING A TREATMENT SYSTEM

The p e r f o r m a n c e o f many e x i s t i n g t r e a t m e n t s y s t e m s onf a r m s c a n n o t b e e x p l a i n e d b e c a u s e o f i n a d e q u a t e m o n i t o r i n g .I n t h e l a b o r a t o r y n u m e r o u s p a r a m e t e r s c o n c e r n e d w i t h t h ef u n c t i o n i n g o f a r e a c t o r c a n b e m o n i t o r e d . On a f a rm o n l ya m ore r e s t r i c t e d m o n i t o r i n g p ro g ra m m e i s p o s s i b l e , b u t t h ep ro gr am m e m u st i n c l u d e e s s e n t i a l i n f o r m a t i o n t o a s s e s s t h ee f f i c i e n c y o f p e r f o r m a n c e . F o r a u n i t d e s i g n e ds p e c i f i c a l l y f o r o d o u r c o n t r o l t h e r e s i d u a l o d o u r a n d t h ep o t e n t i a l f o r o d o u r r e g e n e r a t i o n i n t h e s l u r r y a f t e rt r e a t m e n t m u s t b e m o n i t o r e d . I n a d d i t i o n , i t i s i m p o r t a n tt o m o n i t o r t h e o x y g e n c o n s u m p t i o n , d i s s o l v e d o x y g e n (DO)

l e v e l i n t h e r e a c t o r a n d n i t r a t e c o n c e n t r a t i o n i fn i t r i f i c a t i o n i s r e q u i r e d .

R e s i d u a l o d o u rT he o d o u r o f f e n s i v e n e s s i s b e s t a s s e s s e d by a n o d o u r

p a n e l b u t t h e i r f r e q u e n t u s e i s o f t e n i m p r a c t i c a l . R o u t i n em o n i t o r i n g m u s t r e l y o n a n i n d i c a t o r s y s t e m . T hes u p e r n a t a n t BODc w a s u s e d a s an i n d i c a t o r by W i l l i a m s ( 1 0 ) .B o th s u p e r n a t a n t BOD5 a nd TOA p r o v i d e i n d i c a t o r s (11) u s i n g



275

equations 1 and 2.

Odour offensiveness = 1.453LOG(sup.BOD 5) + 2.32 (1)

Odour offensiveness = 2.387LOG(TOA) + 2.327 (2)

Where odour offensiveness is described by a five pointscale:0 I n o f f e n s i v e ; 1 v e r y f a i n t l y o f f e n s i v e ; 2 f a i n t l yoffensive; 3 definitely offensive; 4 strongly offensive;and 5 very strongly offensive.

Odour StabilityOdour wi l l ret urn in t reat ed s lu r ry as a r e su l t of post

t re atment fe rmentati on. The conce ntr at ion of readi lyfe rmentable s ubs t r at e s , measured as BOD5, provide anindicator of th is problem. In continuous cult ure withoutoxygen l imi t at i on the BOD5 can be described by a modelderived from the Monod (13) model of microbial growth (14).The supernatant BODg (g/1) from treatment at 15 to 45°C, wasdescr ibed by equat ion 3 and the whole BOD5 by equations 4and 5 (15).

Sup. BOD5 (15-45) = .11/R (3)

Whole BO D 5 (15) = 2.694/R + 0.202BODf (4)

Whole BO D 5 (25-50) = 1.568/R + 0.152BODf (5)

W h e r e R is the m e a n t r e a t m e n t t i m e and BODf the B O D E(g/1) of the raw slurry. The r e a c ti o n t e m p e r a t u r e s (°C)are given in brackets.

Nitrate can be used to delay a return to f e r m e n t a t i o naf t er t re at m e n t . In this case the n i t rat e c o n c e n t rat i o nneeds to be m e a s u r e d . It is i mp o rt an t to realise that

n i t rat e can be l o s t t h ro u g h d e n i t ri f i c at i o n w i t h i n 20minutes of removing the sample from the reactor.

Oxygen DemandThe oxygen demand of the heterotrophic microbes can be

m e a s u r e d as the loss of COD. In the ab s e n c e of oxygenl i mi t at i o n t h i s was also described by e q u at i o n s (6, 7 & 8)developed from Monod kinetics (15).

Hetero.Oxygen Demand (15) = [ .621-.547/(1+.14R)]CODf (6)

Hetero.Oxygen Demand (25-45) = [.465-.333/(1+.40R)]CODf (7)

Hetero.Oxygen Demand (50) = [.555-.429/(1+.70R)]CODf (8)

Where R is the mean treatm ent time, CODf the COD (g/1)of the raw slurry and the r e a c ti o n t e m p e r a t u r e s (°C) areshown in brackets.

Wh e n n i t ri f i c at i o n o c c u rs 4.57 g ram o x y g e n are usedp er g ram of a m mo n i a n i t ro g e n o x i d i s e d. Thu s the t o t al



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oxygen d ema nd is then the sum of the autotr ophic andheterotrophic respiration rates.

3. DESIGN OF A TREATMENT SYSTEMThe des i g n s of mo s t f arm t re at m e n t s y s t e m s h ave n ot

fully utilised knowledge of the microbiology of continuousc u l t u re s . In re l at i on t o an i m al w as t e t re at m e n t t h re ema jor factor s affect the quality of the treated slurry.Th e y are a) t he me an t re at m e n t t i m e , b ) the re ac t i ontem per at ur e and c) the level of dissolved oxygen in therea ctor. The dilution factor of the excreta and therequired qualit y of treated slurry then fix the vo lum e ofthe reactor and the degre e of heat conserv atio n within the

s y s t e m t o c o n t ro l t h e re ac t i o n t e mp e r at u r e . The si ze o fthe aerator is then determ ined from the oxygen demand of theautotrophic and/or heterotrophic micr obes, together with thee f f i c i e n c y o f o x y g e n t r a n s f e r i n t o t h e s l u r r y b y t h emachine.

a) Choice of Mean Treatment TimeWithout oxygen lim itat ion in the reactor the oxygen

d e ma n d and t he c h ar ac t e r i s t i c s o f th e t re at e d s l urry ,including its odour of fensiv eness and its potentia l tore g e n e rat e o d o ra n t s du ri ng s u b s e qu e n t s t o rag e are l arg e l y

d e t e rm i n e d b y th e me an t re a t me n t t i m e . The re l at i o n s h ipb e t w e e n m e an t r e at m e n t t i me and t h e h e t e ro t ro p h i c o x y ge ndemand is described by equations 6-8 above.

O d o ur o f f e n s i v e n e s s , m o n i t o r e d b y t h e i n d i c a t o rs u p e r n a t a n t B O D5 (16, 1 1 ) , f a l l s r a p i d l y a s t h e m e a nt re a t me n t t i m e is ex t e n de d . Fro m t h e e q u at i o n s f or t h er e l a t i o n s h i p s b e t w e e n s u p e r n a t a n t B ODc a nd o do uro f f e n s i v e n e s s ( eq ua t i on 1) a nd m e a n t r e a t m e n t t i m e ,(equation 3) the effect of mean trea tment tim e (R, days) onodour offensiveness can be described (equation 9 ) .

Odour offensiveness = 0.927 - 1.453LOG(R) (9)If it is necessa ry to lower odour to a level below very

faintly offensive (rating 1) then the minim um treatment timeat psychrophilic and mesophilic temperatures will be 1 day.Wi ll ia m s (16) suggested that in many ca ss an odour levelbelow faintly offens ive (rating 2) should be accep table.Th i s w o u l d re q u i re a mi n i m u m t re at m e n t t i m e o f onl y 0.2days.

Thermophilic treatment at 50°C left a higher residualsupernatant BODc than that from similar mean tr eatment times

but lower reaction tem peratur es (15). However , odour panelassessments of samples from a thermophilic reactor showed asimilar relationship between odour and mean treatment timeto that provided by equation 9, despite the slightly highers u p e r n a t a n t B O D 5 ( u n p u b l i s h e d ) . Th i s a p p a r e n tcontradiction is probably due to the logar ithmic nature oft h e re l at i o n s h i p an d t h e s mal l n u mb e r o f s amp l e s f ro mthermophilic treatment, compared with the number from lowertemperature treatment.



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I f t h e s l u r r y i s t o b e s t o r e d a f t e r t r e a t m e n t t h er e s i d u a l , r e a d i l y - f e r m e n t a b l e s u b s t r a t e r e q u i r e sc o n s i d e r a t i o n . As t r e a t m e n t t i m e i s e x t e n d e d t h e t o t a l BOD5

f a l l s t o a m i n im u m v a l u e o f a b o u t 20% o f i t s v a l u e i n r a ws l u r r y a f t e r t r e a t m e n t a t 1 5 °C , o r 15% a f t e r t r e a t m e n t a th i g h e r t e m p e r a t u r e s , e q u a t i o n s 4 a nd 5 . I t may b e p o s t u l a t e dt h a t t h e d i f f e r e n c e b e t w e e n t h e a c t u a l r e s i d u a l t o t a l BODca nd i t s m i n i m a l v a l u e w i l l p r o v i d e a m ore a c c u r a t e m e a s u r eo f t h e r e s i d u a l , r e a d i l y - f e r m e n t a b l e s u b s t r a t e and h e nc e ani n d i c a t i o n o f t h e p o t e n t i a l f o r o do u r r e g e n e r a t i o n .

A f t e r m e s o p h i l i c t r e a t m e n t o f p i g g e r y s l u r r y , i n i t i a l l yd i l u t e d t o 1 0 g / l t o t a l BOD 5 t h i s r e s i d u a l , r e a d i l yf e r m e n t a b l e s u b s t r a t e p o r t i o n w o u ld b e 7 .8 a nd 1.6 g / 1 fro mt h e 0.2 a n d 1 d a y m ean t r e a t m e n t t i m e s ( e q u a t i o n 5 ) s ho w n t o

b e t h e m inim um t i m e s f o r o d ou r r e m o v a l t o a c c e p t a b l e l e v e l s .S u ch v a l u e s a r e h o w e v e r , u n a c c e p t a b l y h i g h . O w ens e t a l(17) d e m o n s t r a t e d t h a t w i t h a r e s i d u a l , r e a d i l y - f e r m e n t a b l es u b s t r a t e p o r t i o n o f BOD5 o f a b o u t 1.4g/ l t h e s u p e r n a t a n tBOD2 a nd t h e o d o u r i n c r e a s e d r a p i d l y d u r i n g t h e f i r s t 10d a y s o f p o s t t r e a t m e n t s t o r a g e . H o w e ve r , e x p e r i m e n t s t os t u d y t h e r a t e o f o d o u r r e g e n e r a t i o n h a v e s ho w n t h a t w i t hr e s i d u a l , r e a d i l y - f e r m e n t a b l e s u b s t r a t e l e v e l s o f 0 . 2 g / l( i . e . 7d t r e a t m e n t ) o d o u r r e g e n e r a t i o n t a k e s s e v e r a l d a y s( u n p u b l i s h e d ) .

O d ou r r e g e n e r a t i o n m ay b e d e l a y e d b y t h e p r e s e n c e o fn i t r a t e , w h ic h p r o v i d e s a r e s e r v o i r o f o xy ge n t h a t s e v e r a lh e t e r o t r o p h i c b a c t e r i a ca n u s e f o r o x i d a t i v e r e s p i r a t i o n i np r e f e r e n c e t o f e r m e n t a t i o n . N i t r a t e w i l l o n l y b e p r e s e n ti f a n a u t o t r o p h i c n i t r i f y i n g p o p u l a t i o n i s e s t a b l i s h e d i nt h e r e a c t o r . A t 1 5 ° C t h e d o u b l i n g t i m e o fN i t r o b a c t e r s p . . t h e s l o w e s t g r o w i n g o f t h e t w o g e n e r a o fb a c t e r i a i n v o l v e d i n n i t r i f i c a t i o n (18) i s a b o u t 3 d a y s , b u tt h i s f a l l s t o a b o u t 2 d a y s a t m e s o p h i l i c t e m p e r a t u r e s .H o w e v e r , t h e e s t a b l i s h m e n t o f a p o p u l a t i o n a n d i t s g r o w t hr a t e a r e a l s o a f f e c t e d by t h e r e a c t i o n t e m p e r a t u r e , pH v a l u ea nd d i s s o l v e d o xy ge n l e v e l a s d e s c r i b e d b e l o w .

b) C h o i c e o f r e a c t i o n t e m p e r a t u r e

A e r o b i c r e s p i r a t i o n i s h i g h l y e x o t h e r m i c . T h us l i t t l ei n s u l a t i o n i s n e c e s s a r y t o a l l o w t h e t e m p e r a t u r e i n t h er e a c t o r t o e n t e r t h e m e s o p h i l i c r a n g e . L a b o r a t o r ye x p e r i m e n t s ( 14 , 15) h av e sh ow n t h a t t h e r e i s a s u b s t a n t i a lb e n e f i t fr o m a l l o w i n g t h e r e a c t i o n t o s e l f - h e a t a n d r e a c he q u i l i b r i u m w i t h i n t h e m e s o p h i l i c r a n g e , c o m p a r e d t ot r e a t m e n t a t p s y c h r o p h i l i c t e m p e r a t u r e s . T h e r m o p h i l i c

t r e a t m e n t i n c r e a s e s t h e d e g r e e o f d e g r a d a t i o n o f c e l l u l o s i cr e s i d u e s an d s h o u l d e n s u r e p a t h o g e n k i l l b u t t h e a d v a n t a g e st o t h e f a r m e r a r e p r o b a b l y n e g a t e d b y t h e i n c r e a s e dt r e a t m e n t c o s t s b e c a u s e o f t h e n e e d f o r b e t t e r i n s u l a t i o na n d t h e h i g h e r o x y g e n d e m a n d .

c ) C h o i c e o f a e r a t i o n r a t e

T he a c t u a l l e v e l o f DO c o n t i n u o u s l y m a i n t a i n e d i n t h e



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reactor has a ma rked effect on both the autotr ophic andheterotrophic populations.

Autotrop hic activity. Because of the low C:N ratioa nd i ts d e c l i n i n g v a l u e a s c a r b o n a c e o u s r e s i d u e s a r ed e g rad e d t h e re is s u b s t an t i al am mo n i f i c a t i o n . Wi t h al lme an t re at me n t t i me s g re at e r t h an t h e d o u b l i n g t i me o fNitroba cter sp. nitr ifica tion will occur provided thatoxygen is not lim iti ng. Smith and Eva ns (19) found thatw i t h DO le ve l s ab o ve 15% of s at u ra t i o n , n i t ri f i c at i o ncontinued until the cultur e wa s lim ited by a fall in pHlevel. Up to 40% of the slurry am mon ia was oxidised. Theautotrophic activity never achieved steady state and cycledb e t w e e n p e ri o d s o f ac t i vi t y w h e n t h e pH va l u e w as ab o veabout 5.5 and period s of ina ctivity when the pH value fellb e l o w 5.5. Co mp l e t e n i t ri f i c a t i o n o f al l am mo n i a o n lyoccurred if the pH va lue w as contr olled at about 7 by theaddition of alka li. When the DO level was held withinthe range of 1 to 15% of saturation a system of sim ulta neousn i t ri f i c at i o n and d e n i t ri f i c at i o n w as e s t ab l i s h e d . Thereduction of nitrate allowed the pH value to remain above 6and nitr ifica tion to continu e. Thus mo re than 70% of theam mon ia wa s oxidised. If the DO level was held below 0.1%of saturation, nitrification was inhibited (unpublished).

Au t o t ro p h i c ac t i vi t y c l e arl y h as a ve ry i mp o rt an teffect on the residual ma nuria l value of treated slurry, itsodour stability and the costs of aeration. Denitrificationc an l os e up to 70% of th e amm o n i a c al n i t ro g e n t h ro u g hnitrification and denitrification. High aeration rates andshort mean treatment times can encourage similar losses asgaseous am mon ia. Nitrification can account for up to 31%of th e t o tal o x y g e n c o n s u me d d e p e n d in g on me an t re at m e n tt i m e w i t h DO le ve l s h el d ab o ve 15% s at u ra t i o n . Wi t h DOlevels held betwe en 1 and 15% of satur ation, about 62.5% ofthe oxygen consumed by nitrification is subsequently used bythe heter otro phic denitrifying bacteria (20). Thus thetotal oxygen consum ption is only slightly higher than thecarbonaceous oxygen dema nd in high DO system s.

Heter otr ophic activity. With the DO held above 1%saturation the degree of carbonaceous degradation is largelyd e t e r m i n e d by t he m e a n t r e a t m e n t t i m e a nd r e a c t i o ntemperature as described above. With lower aeration ratesthe DO falls to som e v alue between 0 and 1% of saturation.

It has not been p ossibl e to m onitor the DO at theselevels but its control can be achieved indirectly from

mea sur ing the redox pote ntia l. At 1% of satur ation theredox potentia l re ma ins about 0 to 50 mV Ecal (pH 7.8).There is an exponential fall in redox potential as DO fallsto zero at about -400 to -450 mV Ecal (pH 7.8).

W i t h i n t h i s r a n g e of r e d o x p o t e n t i a l a e r o b i cre s p i rat i o n c o n t i n u e s and f e rme n t at i o n is re s tri c t ed e vent h o u g h m i c r o b i a l a c t i v i t y is c l e a r l y o x yg e n l i m i t e d(unpublished). The expe ri me nta l results show that for ag i ve n me an t re a t me n t t i m e and fi xe d re ac t i o n t e mp e r at u r e



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t h e r e a r e v e r y h i g h l y s i g n i f i c a n t c o r r e l a t i o n s ( P > .0 01 andc o r r e l a t i o n c o e f f i c i e n t s > 0 . 9 ) b e t w e e n t h e r e s i d u a ls u p e r n a t a n t B O D5 and r ed o x p o t e n t i a l . A f t e r t r e a t m e n t a t

1 5 °C f o r 2 d a y s a nd 7 d a y s , 3 5 ° C f o r 2 d a y s a n d 5 0 ° C f o r 7d a y s , t h e r e s i d u a l o d ou r w a s i n o f f e n s i v e (0 t o 0 .5 r a t i n g )w i t h t h e DO a t 0.1% o f s a t u r a t i o n and r e d ox p o t e n t i a l a b o u t0 mV E c a l (pH 7 . 8 ) . I t i n c r e a s e d t o v e r y f a i n t l y o f f e n s i v e( r a t i n g 1) w i t h t h e r e d o x p o t e n t i a l h e l d a t a b o u t - 1 0 0 t o -1 50 mV an d t o f a i n t l y o f f e n s i v e ( r a t i n g 2 ) a t a b o u t - 3 0 0 mV.

T he r e s i d u a l , r e a d i l y - f e r m e n t a b l e s u b s t r a t e c o n t e n tp o s t u l a t e d a b o ve a s t h e d i f f e r e n c e b e t w e e n t h e a c t u a l BOD5

and i t s m i n i m a l v a l u e a f t e r p r o l o n g e d t r e a t m e n t , i s a l s oa f f e c t e d b y o x y g e n l i m i t a t i o n . A g a in v e r y h i g h l ys i g n i f i c a n t c o r r e l a t i o n s ( c o r r e l a t i o n c o e f f i c i e n t s > 0 .8 )

w e r e o b t a i n e d i n t h e f o u r s e r i e s o f l o w r e d ox e x p e r i m e n t s .When o x yg en w as l i m i t i n g t h e r e s i d u a l , r e a d i l y - f e r m e n t a b l es u b s t r a t e c o n c e n t r a t i o n i n c r e a s e d fro m t h e v a l u e s e x p e c t e df o r e a c h t r e a t m e n t t i m e an d t e m p e r a t u r e wh en o x y g e n w a su n l i m i t e d ( e q u a t i o n s 4 a n d 5 ) , t o a b o u t 9 .0 g / 1 a t-500 mV.

4 . CONCLUSIONSThe o p tim u m d e s i g n p a r a m e t e r s f o r a e r o b i c t r e a t m e n t

m u st b e t h o s e w h i c h s e l e c t f o r t h e m o s t d e s i r a b l e m i x t u r e o fm i c r o b e s and m e t a b o l i c a c t i v i t y t h a t b r i n g s a b ou t a d e g r e eo f d e g r a d a t i o n s o t h a t t h e t r e a t e d s l u r r y c h a r a c t e r i s t i c sm e et t h e t r e a t m e n t o b j e c t i v e s .

The s e l e c t i o n o f t h e m o s t a p p r o p r i a t e m ean t r e a t m e n tt i m e , r e a c t i o n te m p e r a t u r e and d i s s o l v e d o x yg en l e v e l t o b em a i n t a i n e d i n t h e a e r a t e d m i x ed l i q u o r r e q u i r e s a c l e a rd e f i n i t i o n o f t h e t r e a tm e n t o b j e c t i v e s f o r e ac h p a r t i c u l a rfa rm e n t e r p r i s e . T h e s e a r e t h e m axim um a c c e p t a b l e r e s i d u a ls u p e r n a t a n t B O D 5 , t o i n d i c a t e p o t e n t i a l o d o u ro f f e n s i v e n e s s , an d t h e m a x im u m a c c e p t a b l e r e s i d u a l ,r e a d i l y - f e r m e n t a b l e s u b s t r a t e , t o i n d i c a t e t h e p o t e n t i a l f o r

o do ur r e g e n e r a t i o n . I t m u s t b e d e c i d e d w h e t h e r o r n o tn i t r a t e i s d e s i r a b l e in t h e t r e a t e d s l u r r y t o f u r t h e r d e l a yo do ur r e g e n e r a t i o n . I n so m e c a s e s l o w e r c o n c e n t r a t i o n s o fBOD5 may b e r e q u i r e d b e c a u s e o f w a t e r c o n t r o l o b j e c t i v e s .M a n u r i a l v a l u e o f s l u r r y n i t r o g e n m a y a l s o n e e dc o n s i d e r a t i o n .

T he e q u a t i o n s , de v e l o p e d f ro m t h e m o de l ba se d o n H onodk i n e t i c s and t h e a d d i t i o n a l e q u a t i o n s , d e v e l op e d e m p i r i c a l l yt o d e s c r i b e t h e e f f e c t s o f o x y g e n l i m i t a t i o n on a e r o b i ct r e a t m e n t o f p i g g e r y s l u r r y , w i l l p r o v i d e t h i s i n f o r m a t i o na s t h e m o s t s u i t a b l e m ea n t r e a t m e n t t i m e , r e a c t i o n

t e m p e r a t u r e , an d DO l e v e l .S e l e c t i o n o f t h e m o st a p p r o p r i a t e s e t o f e q u a t i o n s andt h e i r s o l u t i o n c an b e v e r y l a b o r i o u s b u t l e n d s i t s e l f t oc o m p u t e r p ro gr am m e d s e l e c t i o n . A p r og ra m u s i n g t h eo r i g i n a l m o d e l (2 1 ) t o d e s i g n a s y s t e m w i t h a m a j o ro b j e c t i v e o f h e a t r e c o v e r y h a s b e en d e v e l o p e d . I t c o n s i s t so f a q u e s t i o n a i r e t o d e f i n e t h e t r e a t m e n t o b j e c t i v e s , t h ea p p r o p r i a t e e q u a t i o n s fr o m t h e m o d e l a r e t h e n s e l e c t e d b yt h e p r o g r a m , c a l c u l a t e d an d b o t h a g r a p h i c a l and t a b u l a r



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p r i n t o u t o f s u i t a b l e c o n d i t i o n s p r e s e n t e d . I t i s h o p e dt h a t a n e x p a n d e d p r o g r a m w i l l b e w r i t t e n w h i c h i n c o r p o r a t e sa l l t h e a d d i t i o n a l e q u a t i o n s .

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( 1 ) B EL L, R .G . ( 1 9 7 0 ) . F a t t y a c i d c o n t e n t a s a m e a s u r e o ft h e o d o u r p o t e n t i a l o f s t o r e d l i q u i d p o u l t r y m a n u r e .P o u l t r y S c i e n c e 4 9 , 1 1 2 6 - 1 1 2 9 .

(2 ) SOBEL, A .T . ( 1 9 7 2 ) . O l f a c t o r y m e a s u r e m e n t s o f a n i m a lm a nu r e o d o r s . T r a n s a c t i o n s o f t h e A m e r i c a n S o c i e t y o f

A g r i c u l t u r a l E n g i n e e r s 1 5 ( 4 ) , 6 9 6 - 6 9 9 .( 3) HASHIMOTO, A .G . ( 1 9 7 4 ) . A e r a t i o n o f p o u l t r y w a s t e f o ro d o r a n d n i t r o g e n c o n t r o l . T r a n s a c t i o n o f t h eA m e r i c a n S o c i e t y o f A g r i c u l t u r a l E n g i n e e r s , 1 7 , 9 7 8 -9 8 2 .

(4 ) COLE, C .A . , BAR TLETT, H .D . , BUCKNER, D .H . & YOUNKIN,D . E . ( 1 9 7 6 ) . E f f i c a c y o f c e r t a i n c h e m i c a l a n db i o l o g i c a l c o m p o u n d s f o r c o n t r o l o f o d o r f ro m a n a e r o b i cs w i n e m a n u r e . J o u r n a l o f A n i m a l S c i e n c e 4 2 , 1 - 7 .

(5 ) W E L SH, F . W . , SC HU L T E , D . D . , KR OE KE R, E . J . & L A P P , H .M.( 1 9 7 7 ) . T he e f f e c t o f a n a e r o b i c d i g e s t i o n up o n s w i n e

m a nu r e o d o u r s . C a n a d ia n A g r i c u l t u r a l E n g i n e e r i n g 1 9 ,1 2 2 - 1 2 6 .

( 6 ) B AR TH , C . L . , H I L L , D . T . & P O LK O W S K I, L . B . ( 1 9 7 4 ) .C o r r e l a t i n g o d o r i n t e n s i t y i n d e x a n d o d o r o u s c o m p o n e n t si n s t o r e d d a i r y m a n u r e . T r a n s a c t i o n o f t h e A m e r i c a nS o c i e t y o f A g r i c u l t u r a l E n g i n e e r s 1 7 ( 4 ) , 7 4 2 - 7 4 4 .

( 7 ) SH AEFER , J . ( 1 9 7 7 ) . S a m p l i n g , c h a r a c t e r i z a t i o n a n da n a l y s i s o f m a l o d o u r s . A g r i c u l t u r e a n d E n v i r o n m e n t 3 ,1 2 1 - 1 2 8 .

( 8) SPOELSTRA, S . F . ( 1 9 7 7 ) . S i m p l e p h e n o l s a n d i n d o l e s i na n a e r o b i c a l l y s t o r e d p i g g e r y w a s t e s . J o u r n a l o f t h e

S c i e n c e o f F oo d a n d A g r i c u l t u r e 2 8 , 4 1 5 - 4 2 3 .( 9 ) K OW A LE W SK Y, H . H . , S C H E V , R . & V E T T E R , H . ( 1 9 8 0 ) .

M e a s u r e m e n t o f o d o u r e m i s s i o n s a n d i m m i s s i o n s .E f f l u e n t s f r o m L i v e s t o c k , A p p l i e d S c i e n c e P u b l i s h e r s6 0 9 - 6 2 6 .

( 1 0 ) W IL L IA M S, A .G . ( 1 9 8 4 ) . I n d i c a t o r s o f p i g g e r y s l u r r yo d o u r o f f e n s i v e n e s s . A g r i c u l t u r a l W a s t e s 1 0 , 1 5 - 3 6 .

( 1 1 ) T HA CK ER , F . E . & E V A N S , M .R . ( 1 9 8 5 ) . B O D 5 , TOA ando d o u r o f f e n s i v e n e s s . W o r k s h o p ' O d o u r p r e v e n t i o n a n do d o u r c o n t r o l o f o r g a n i c s l u d g e s a n d l i v e s t o c kf a r m i n g ' . E E C /FA O , S i l s o e , U . K . , 1 5 - 1 9 A p r i l , 1 9 8 5 .

( 1 2 ) H I S S E T T , R . , EV A NS , M .R . & B A I N E S , S . ( 1 9 7 5 ) . T h e u s eo f r e s p i r o m e t r i c m e t h o d s f o r a s s e s s i n g t h eb i o d e g r a d a b i 1 i t y o f d i f f e r e n t c o m p o n e n t s o fa g r i c u l t u r a l w a s t e s . P r o g r e s s i n W a t e r T e c h n o l o g y ,V o l . 7 , N o . 2 , 1 3 - 2 1 .

( 1 3 ) MONOD, J . ( 1 9 4 9 ) . T h e g r o w t h o f b a c t e r i a l c u l t u r e s .Am. R e v . M i c r o b i o l o g y 3 , 3 7 1 - 3 9 4 .

( 1 4 ) E V A N S , M . R . , H I S S E T T , R . , S M I T H , M . P . W . , E LL AM , D . F .B A I N E S , S . & W O O D S , J . L . ( 1 9 7 9 ) . E f f e c t o f



281

m i c r o o r g a n i s m r e s i d e n c e t i m e on a e r o b i c t r e a t m e n t o fp i g g e r y w a s t e . A g r i c . W a s te s 1 , 6 7 - 8 5 .

(15) EVANS, H.R., DEANS, E.A., HISSETT, R., SMITH, M.P.W.,

SVOBODA, I .F . & THACKER, F.E . ( 1 9 8 3 ) . The e f f e c t o ft e m p e r a t u r e and r e s i d e n c e t i m e on a e r o b i c t r e a t m e n t o fp i g g e r y s l u r r y - d e g r a d a t i o n o f c a r b o n a c e o u s c o m po un d s.A g r i c . W a s te s 5 , 2 5 - 3 6 .

( 16 ) W ILLIAM S, A .G . ( 1 9 8 1 ) . T he b i o l o g i c a l c o n t r o l o fo d o u r s e m a n a t i n g fro m p i g g e r y s l u r r y . P h.D . t h e s i s ,U n i v e r s i t y o f G l a sg o w .

(1 7 ) OWENS, J . D . , EVANS, M.R., THACKER, F .E . , HIS SE TT , R. &BA IN ES, S . ( 1 9 7 3 ) . A e r o b i c t r e a t m e n t o f p i g g e r yw a s t e . W ater R e s e a r c h , 7 , 1 7 4 5 - 1 7 6 6 .

(1 8 ) DOWNING, A .L ., PAINTER, H.A. & KNOWLES, G. ( 1 9 6 4 ) .

N i t r i f i c a t i o n i n t h e a c t i v a t e d - s l u d g e p r o c e s s . J .P r o c . I n s t . S e w . Purif. P a r t 1 3 0 , 1 3 0 - 1 5 3 .

(19) SMITH, M.P.W. & EVANS, M.R. ( 1 9 8 2 ) . The e f f e c t s o fl o w d i s s o l v e d o x y g e n t e n s i o n d u r i n g t h e a e r o b i ct r e a t m e n t o f p i g g e r y s l u r r y i n c o m p l e t e l y m i x e dr e a c t o r s . J o u r n a l o f A p p l i e d B a c t e r i o l o g y 5 3 , 1 1 7 -1 2 6 .

(20) JOHNSTONE, D.W.M. (1 98 4 ). Oxygen r e q u ir e m e n ts , en er g yc o n s u m p t io n and s l u d g e p r o d u c t i o n i n e x t en d e d a e r a t i o np l a n t s . W ater P o l l u t . C o n t r o l 8 3 , 1 0 0 - 1 1 5 .

(2 1) EVANS, M.R., SVOBODA, I .F . & BAINES, S. (1 9 8 2 ) . H ea tfr o m a e r o b i c t r e a t m e n t o f p i g g e r y s l u r r y . J . A g r i c .E n g n g . R e s . 2 7 , 4 5 - 5 0 .



JO INT SESSION : OTHER ASPECTS OFMEASURING OD OURS

Identification of volatile components inheadspace from animal slurries

Odours at water reclamation works

BOD,., TOA and odour offensiveness

Dust in livestock buildings as a carrier ofodours

Dust concentrations in pig buildings

Large-scale biogas plants in Hungary

Anaerobic digestion to control odours

The bio-gas project in Emilia-Romagna (Italy)

The bio-gas project in Emilia-Romagna (Italy)firBt results of five full scale plants

Farm experiments of anaerobic digestion tocontrol odours from slurry

Use of methanogenic fermentation to upgrade farm

animal and slaughterhouse wastes

Latest chemical slurry handling methods



284

IDEN TIFICATION OF VOLATILE COMPONENTS IN HEADSPACE FROM ANIM AL SLUR RIES

E . M. Odam, Jane M. J. Page, M. G. Townsend and J. P . G. W ilkinsAgricultural Science Service, Tolworth L aboratory

Ministry of Agriculture, fisheries and Food

Summary

The Ministry of Agriculture, Fisheries and Food is involved inassessing a range of techniques for the measurement of odours arisingfrom agricultural practices. W e report here analytical resultsobtained from the collection of headspace slurries using TenaxG C. Samples were thermally desorbed and analysed by capillarycolumn gas chromatography using a range of detectors. Identificationof some of the components has been achieved using gas chromatography-mass spectrometry and the most abundant odorous compounds wereshown to contain sulphur. Quantitative techniques for themeasurement of the odorous components are being established andwill be applied to a range of air and slurry samples.

INTRODUCTIONThe increase in the number of complaints in the UK resulting from

agricultural odours has coincided with both changes to intensive animalhusbandry methods, and increased urbanisation. Legislation in thisfield is likely to result in stricter controls, and thus the role ofthe agricultural advisory service in relation to reducing odour nuisancewill become more important to the agricultural industry. In order tocarry out this role effectively there will be a need to have availablemethods to monitor the changes and to be able to quantify t he improvementsin air quality.

Methods have been developed to characterise odours according tostrength ( l) and offensiveness (2) using experienced panellists. Measuresof offensiveness are necessarily subjective and odour strength (thresholddilution) will depend upon the odour threshold value as well as theconcentration. For routine assessment these methods incur the costof panel time and the problems inherent in the transport and storageof samples.

A measure of the total organic material present in slurries canbe obtained by determining chemical oxygen demand (COD) or biologicaloxygen demand (B OD) ( 3) and the latter measure is used by WaterAuthorities in relation to the pollution of water courses where oxygentension in the water is a prime concern. In studies to evaluate aerobicdigestion as a means of odour reduction, the dissolved volatile fattyacids are a useful measure of the potential odour nuisance ( 2 ) .



285

c• • • * > - « » <

IK

F

^ x

• • • • • • • • • • • •• • • • • • • • • • • •> • • - • • • • • • • • • <

• • • • • • • • • • • • • • • • • • • I

• • • • • • • • > • • • • • • • • • • • •• • • • • • • • • • • • • • • • • • • I

Fig 1. Apparatus for collection of headspa ce volat iles from slurr

A Large O-rlng tap. B Small O-ring tap.C Olasa funnel. D Tenax tube.E Reduction joint. F p r F E s c r e w c a p

G 2L Pyrex glass screw top bottle containing 1L slurry.



286

Fig 2. App arat u s f o r t h e de ao rp t i o n o f vo l at i l e e f rom Ten a x .

A Spl i tt e r val veC Toggle valv eE $"-1/16" Reduction unionG TenaxI Septum holderK 0.2 mm l.d. trans fer lineU 0.3 mm l.d. capillar y N 0.2 mm l.d capillary0 1/16" low dead volume union tee p Glass InsertQ Helium

B Sep t u m p u rg e val veD Cold trapF Tenax tubeH D e s o rp t i o n h e at e rJ Septum

GC injector



287

The response of vertebrates to olfactory stimulation is affectedby previous experience but behaviour can be specifically affected byodours (pheromones) (k). The olfactory system has been shown to detect

specific components within complex mixtures and analytical chemistrytechniques have been used to identify these active components ( 5 ) - W ehave assessed the application of these methods to the problems ofagricultural odours in an attempt to develop techniques applicable toboth slurries and air samples. The identification of the odorouscomponents might allow specific treatment methods to be developed. I naddition, the designation of a range of indicator compounds might beuseful in practice for monitoring abatement of odour nuisances.

2. METHODSCollection of S lurry

During the study, samples of slurry were obtained from severalsources. Both pig and cow slurry samples were collected from holdingtankB and on-line at units operating anaerobic digestion systems forbio-gas production. In addition samples have been obtained from coresof slurry taken from a collection pit under a pig fattening unit. I nall cases, a 10 litre bulked sample was divided into 1 litre aliquotsin 2 litre glass bottles fitted with screwcaps and PTFE sealing discs(Corning L td., S tone, Staffs, U K ) for transport to the laboratory.

Collection of VolatilesThe screw caps on the bottles of slurry were replaced by purpose

made PTFE sampling heads (Production Techniques Ltd. Fleet, Hants.)fitted with two glass/PTFE valves ( J T Young L td, London W 3 ) (Figure1) and the samples maintained at l6°C. The Tenax (0.3 g ) used to collectthe volatiles was packed in a 6 mm (o.d.) glass tube containing a plugof quartz wool. These units were pre-conditioned at 2°0°C with a flowof nitrogen for l6 h Immediately prior to use and could be re-used severaltimes. Headspace volatiles (500 ml ) wer e collected by drawing gas witha constant flow (approximately 100 ml min -^ ) sampling pump (DuPont modelS200) through the Tenax whilst at the same time replacing it with anequal volume of water from the reservoir.

Thermal desorptionThe Tenax adsorption tube was put into the desorption oven, connected

to the cold trap through the injection port of the gas chromatograph(Figure 2) and thence to the analytical column via a T-connector. Withthe GC at ambient temperature and the valves (C ^ , C 2) open the systemwas back-flushed with helium (9 ml min-^-) to remove air and water fromthe Tenax and maintain a flow of helium (1 ml min"^) through theanalytical column. Valves Ci and Cg were closed and valves C3 and C4were opened to provide a gas flow of 6 ml min~l through the Tenax andthe cold trap which consists of a coil of approx imately U0 cm deactivated,but uncoated, flexible silica capillary (0.3 mm, i.d.). The desorptionoven was constructed from a central brass core and the electrical heatingcontrolled by a calibrated variable transformer. A temperature of 270 °Cwas obtained in 10 minutes and this was maintained for a further 35minutes. Following desorption the valves C3 and CI4. wer e closed, C ^was opened and after stabilisation of the gas flow through the analyticalcolumn the dewar flask of liquid nitrogen was removed.



Peak heigh t

M J M y d L L i ^ ^30 40

— I-

50

— I-

60

\ X J 4 J L _ A J L W ^ A I ~ ^ > * ^ * ^ "

50 600 40

Time (mint)

Fig 3 GC pr of i le of v ola t l le s fr on A) undigested and B) digested slu rry analysed on a polar coluwi withFID.



289

Gas Chromatography

During these studies the component profiles were obtained usingtwo analytical GC systems in conjunction with two types of detectors.

1. Erba model 416O (Erba Science ( UK) Ltd, Swindon, Wilts) with asub-ambient attachment was fitted with a 25m BP1 flexible silicacapillary column (SGE Ltd, Milton Keynes, Bucks.). Following 10minutes at 10°C the column oven was temperature programmed at 3°Cmin" 1 up to 150°C .

2. Erba model U200 was fitted with a 25m BP20 flexible silica capillarycolumn (SGE Ltd). Following 10 minutes at 50°C the column ovenwas temperature programmed at 3°C min - 1 up to 200 °C.

In both systems the flow of helium carrier gas through the columnswas 0.7-0.8 ml min~l, with a septum purge of 0.5 ml min~l and asplit valve flow of U-U.5 ml min - 1. The injection ports weremaintained at 260°C and the detector ovens at 2l»0 oC. The detectoremployed was either a flame ionisation or a nitrogen-specific NPD-kO thermionic detector (Erba Science (U K) Ltd) and the output wasrecorded on a HP 33 90 integrator (Hewlett Packard Ltd, Wokingham,U K ) .

Studies involving mass spectral identifications were carried outusing a VG 703 5 coupled to a Dani gas chromatograph (VG Analytical,Manchester). Modifications were made to the analytical system as thehigh vacuum of the mass spectrometer was incompatible with the air ventsystem normally employed between the cold trap and the analytical column.Consequently, the flow of gas through the Tenax during thermal desorptionwas reduced to 3 m l mi n -^ .

3. RESULTSDuring initial studies in which pig slurry samples were collected

in plastic bottles and nylon tubing was used to transfer the volatilesonto Tenax, it was found that blanks were variable due to contamination

of the analytical system and that there was a loss of Borne polar compounds(p-cresol, indole, skatole). The development of the collection system(Figure 1) and the use of Chromsep' tI,1 red septa (Chrompack UK L td, London)together with septum purge (Figure 2) has eliminated these problems.When a second Tenax tube was connected in series during the collectionof 1 litre of headspace, the only material recovered from the secondtube had a very short GC retention time. I n comparison with the totalsample this was a relatively small amount of material and 0.3 g Tenaxis considered sufficient for the routine recovery of the material from500 ml headspace.

Capillary gas chromatography allows the analysis of complex mixturesof compounds to be carried out. However, the analysis time per sampleis inherently long in order to obtain high resolution of the components,and this limits the throughput of samples. Slurry samples are bioticand therefore subject to continuing changes which are reflected byalteration in the composition of the headspace volatiles, especiallyin regard to the ratio of the components. In addition, the concentrationof this complex mixture by adsorption onto Tenax and the subsequentthermal desorption may lead to artefacts. It is therefore difficult



Peak height

[JJL_J -u jJ iLJ- r -

10 20 30

JJUj^. rJ^

10T -20

-f-30

Time (minj)

iliJL_40 to

o

" X -

40

Fig 4. GC p ro f i le o f vol at l le s from undigested slu rry analysed on a non-po lar column wit hA) FID and B) NPD.



291

I* hJ5 20

Tim* (mini)

100-

J8 0 -

4 0 -

20 -

J. J U A LJ0

Fig S.

30 35

Tim* (tnin)

TIC tract of headspace voletlles obtained froa undigestedslurry analysed on a non-polar column.

carbon dioxide bcarbon d1sulph ide e2-aathylpentane hhexene kdl w th yl dlsulphlde nsi l icone qundecene t

methanethloldimethyl sulphide2-butanonebenzenetolueneoclmenedodecane

pentane2-ppopanethiol

cf1 hexane1 heptaneo octaner dimethyl trls ulp hld eu a li p h at ic hydrocarbon



292

to obtain replicate samples in order to assess the reproducibility ofthe analytical method. In practice differences in the GC profiles,

of either the slurry stored at -20°C or headspace volatiles adsorbedon Tenax and stored in a sealed tube at ambient temperature for 2 daysor at -20°C for up to 2 months , vere acceptable.

Examination of the effect of temperature (220°C-270°C) and thetotal heating time (20-1*5 minutes) on the thermal desorption processled us to adopt 270°C for 1»5 minutes as the optimum conditions for furtherstudies. Assessment of the commercially available desorption systemsin which there is "flash heating" of the sample, have shown thatsignificant losses of some important compounds (p-cresol, indole) occuron the surfaces of the metal connectors and sample transfer lines. It

was to overcome these problems that the all silica system (Figure 2)was developed.

Odour assessment (2) indicated the odour from an undigested sampleof cow slurry was greater than that of an equivalent sample subjectedto anaerobic digestion. The GC profiles ( Figure 3 ) obtained fromcomparable samples using FID were complex and some of the componentsoverloaded the analytical system. The reduction in odour followingdigestion should be paralleled by significant changes in some componentsof the headspace volatiles. The digested sample contained more componentswith retention time (Ej) less than Ik minutes. The total area of the

peaks between 6 and 8 minutes and that at 13.5 minutes were greaterin the digested slurry but the components at 15.1 and 30.9 minutes weresmaller. Wi th the non-polar column the undigested sample appeared tocontain more of the less retained components (ftp < 10 minutes ) but thesewere overloaded and difficult to quantify. Four peaks with Rrp 11 .1 ,15.1*, 23.4 and Ul.3 minutes did show a decrease in the digested slurryand need to be identified and their contribution to the odour determined.

The complexity of the profiles was reduced (Figure h) when theresponse of a specific nitrogen detector was compared with that of aflame ionisation detector using samples analysed under the same

chromatographic conditions. It was apparent that there was a markeddecrease in the number of peaks detected and their peak heights werealso greatly reduced. I f these compounds had been nitrogen containing,then the peak size should have increased when the HPD-UO was used asthe detector. It would appear that there are few nitrogen-containingcompounds in the mix ture and the components with ftp of lk.2 and 16.1minutes are the only ones thought to contain nitrogen. The NPD-1*0detector will react to organic molecules other than those containingnitrogen, if the concentration is high enough, and this would accountfor the response at Rp 31.6, 35-8 and 40.9 minutes where the equivalentFID trace indicates column overloading for two of these components.

A similar situation was found when the polar column was used for thecomparison and in this case the only nitrogen response occurred witha component at ftp 5^.5 minutes, which was probably skatole.

I n order to characterise the components further, mass spectralanalysis was carried out. Wh en head space volatiles from undigestedcow slurry were analysed on a non-polar column the results (Figure 5)demonstrated the presence of several sulphur containing compounds -methanethiol, carbon disulphide, dimethyl sulphide, 2-propanethiol,



ii

100

80

60

40

20-

10 20 30 40 50

h h h

60

F1g 6.

30

Time (mln)

TIC trace of headspace vo la tl le s from pig s lu rry analysed on a polar column.

a carbon d1sulphide b benzened 3-methylth1ophen e 3-octanoneg dimethyl trl sulphlde h sil icone3 methyl naphthalene k phenolm p-ethylcresol n skatole

c toluenef 1-methylethenylbenzene1 octanol1 p-cresolo phthalate



Peak height

n

r

-1 ^

10— r-

20

— r -

30 40— i —

50 60

Fig 7 .

Time (min)

Trace of sulphur containing v ol at lle s 1n pig slu rry headspace.

a hydrogen sulph idec dimethyl sulphide

b carbon dlsu lphld ed dimethyl disulphide



295

d i m e t h y l d i s u l p h l d e a nd d i m e t h y l t r i s u l p h i d e : a l l o f t h e s e c om poundsa r e h i g h l y o d o r o u s . A n a l y s i s o f a s i m i l a r s am p l e u s i n g t h e p o l a r co lu mn( F i g u r e 3 ) sh o v ed t h a t t h e r e v a s p o o r r e s o l u t i o n o f t h e c om p o ne nt s e l u t e d

d u r i n g t h e f i r s t 10 m i n u te s a nd t h e m ass s p e c t r a l s t u d i e s I n d i c a t e dt h e s u l p h u r c o n t a i n i n g c om p on en ts t o h e p r e s e n t I n t h i s f r a c t i o n . P h e n o l ,e t h y l p h e n o l , p - c r e s o l , i n d o l e and s k a t o l e c o u l d o n l y h e i d e n t i f i e da t t h e low c o n c e n t r a t i o n s p r e s e n t b y o b t a i n i n g a r e c o n s t r u c t e d i o nc hr om a to g ra m from t h e f u l l - s c a n a c q u i s i t i o n d a t a . A s i m i l a r st u d y v i t hp i g s l u r r y u s i n g a n o n - p o l a r co lu mn show ed a d d i t i o n a l s u l p h u r c o n t a i n i n gc om p on en ts 2 - m e t h y l t h i o p r o p a n e , m e t h y l t h l o c y c l o p e n t a n e ( o r

m e t h y l t h i o h u t a n e ) , 1 - m e t h y l th i o p e n t a n e ( o r 3 - h e x a n e t h i o l ) d i m e t h y lt e t r a s u l p h i d e a nd a n i n d i c a t i o n o f t h e p r e s e n c e o f d i m e t h y l h e x a s u l p h l d e .A l t h o u g h a n a l y s i s w i t h t h e p o l a r c olu m n a g a i n r e s u l t e d i n a l a r g e n um bero f co mp ou nd s b e i n g e l u t e d w i t h i n t h e f i r s t 10 m i n u t e s ( F i g u r e 6 ) ,e x a m i n a t i o n o f t h e com pounds r e t a i n e d b y t h e c olu m n i d e n t i f i e d t h ep r e s e n c e o f 3 - m e t h y l th i o p h e n an d p h e n o l , p - c r e s o l , p - e t h y l p h e n o l a nds k a t o l e : i n d o l e w as d e t e c t e d f ro m t h e r e c o n s t r u c t e d i o n c h r o m a to g ra m .

A nu mber o f h y d r o c a r b o n s w e r e i d e n t i f i e d a n d t h e s i l i c o n e s a n d p h t h a l a t ep r o b a b l y a r o s e a s c o n t a m i n a n t s .

A r e c e n t r e p o r t ( 6 ) rec om m en ded t h e u s e o f T e n a x / m o l e c u l a r s i e v ef o r t h e c o l l e c t i o n o f v o l a t i l e s u l p h u r c om p ou nd s. T h i s t e c h n i q u e h a sb e e n a p p l i e d t o he ad s p ac e v o l a t i l e s f ro m p i g s l u r r y u s i n g a p a c ke dc olu m n (S u p e l p a k S ) a nd a T ra c o r f l a m e p h o t o m e t r i c s u l p h u r d e t e c t o r

( F i g u r e 7 ) . S i g n i f i c a n t a m ou nts o f h y d r o ge n s u l p h i d e a n d d i m e t h y ls u l p h i d e w e r e f ou nd an d t h i s m eth od w i l l b e a p p l i e d t o f u r t h e r s a m p l e so f h e a d s p a c e v o l a t i l e s a nd a i r i n a n a t t e m p t t o q u a n t i f y co mp ou nd sc o n t r i b u t i n g s i g n i f i c a n t l y t o o do ur p r o b le m s .

REFERENCES

1 . BEDBOROUGH, D. R. (1 98 0) . Odour C o n tr o l - A C on ci se Gu ide ( E d i t o r s ,F . H . H . V a l e n t i n a n d A . A . N o r t h ) , W a r ren S p r i n g L a b o ra t o ry ,S t e v e n a g e , 1 7 - 2 9 -

2 . WILLIAMS, A . G. (1 9 8 4 ) . I n d i c a t o r s o f p i g g e r y s l u r r y o d o u ro f f e n s l v e n e s s , A g r i c u l t u r a l W a s te s 10 : 1 5 - 3 6 .

3 . WILLIAMS, A. G. (1 98 3) . Org anic a c i d s , b io c h em ic a l oxygen demanda n d c h e m i c a l o xy ge n dem and i n t h e s o l u b l e f r a c t i o n o f p i g g e r y s l u r r y .J . S c i . F o o d A g r i c . 3k : 2 1 2 -2 2 0 .

k. ALB0NE, E . S . (19 81* ). M am malian S e m i o c h e m l s t ry - t h e i n v e s t i g a t i o n

of che m ica l s ig n a l s be tween mammals . John W i ley and Sons L td .

5 . BAILEY, S . , BUNYAN, P . J . and PAGE, J . M. J . ( 1 9 8 0 ) . V a r i a t i o n

i n t h e l e v e l s o f som e c om p on en ts o f t h e v o l a t i l e f r a c t i o n o f u r i n eo f c a p t i v e r e d fo x (V u lp es v u l p e s ) a nd i t s r e l a t i o n s h i p t o t h es t a t e o f t h e a n i m a l s . C h em i ca l S i g n a l s : V e r t e b r a t e s a nd A q u a t i cI n v e r t e b r a t e s ( e d . D . M i l ; l le r - S c h w a r z e a nd R . M. S i l v e r s t e i n ) P le nu mP r e s s , New York , 391-U03 .

6 . STEUDLER, P . A ., and KIJOWSKI, W. (1981*). D e te rm in a t i o n of re du ce ds u l p h u r g a s e s i n a i r b y s o l i d a d s o r b e n t p r e c o n c e n t r a t i o n a n d g a schro ma tograp hy . Ana l .Chem. 56 : 1^32- lU36 .



296

ODOURS AT WATER RECL AMATION W ORKS

G.L. JOHNSONRegional Laboratory

Severn-Trent W ater Authority

SUMMARY

The procedure used within the Severn-Trent Water Authority for theanalysis of odorous emissions is discussed. This method is basedon the sampling of malodorous air on Carbotrap D-l a graphitisedcarbon black adsorbent followed by solvent extraction of theenriched organic compounds. Interfering non-odorous hydrocarbonsalso present in the atmosphere are removed by adsorption columnchromatography with silica g el . Identification of the enriched odour-intensive compounds relies on high resolution gas chromatography -mass spectroscopy in the electron impact mode. The use of gaschromatography in conjunction with odour port detection is discussedas a valuable aid to this identification and interpretation of thefindings. Results obtained with the procedure are presented andareas requiring further attention are noted.

INTRODUCTION

Water R eclamation Works by their very nature can , at times be thesource of unpleasant odorous emission. The odour-intensive compounds(osmogenes) which make up these emissions are believed to arise mainlyas the decomposition products of carbohydrates and proteins. Thebreakdown of this waste material proceeds by aerobic and anaerobic

processes at various stages of the treatment plant. Atmospheric pollutionof this nature frequently results in complaints from members of thepublic either resident, or perhaps employed in the vicinity of suchworks. In order to confirm or deny that a reclamation works isresponsible for a particular nuisance and, if possible to identify thecausal agents it was decided that the Authority should have thecapability of analysing for odorous and other polluting constituents ofthe atmosphere. This paper describes the progress made towards thisobjective and summarises the ex perience gained with a procedure in use.There are two principle approaches available for the analyticalclassification of odorous emissions:-

1. Olfactometric or sensory methods which provide informationrelating to the human response to odours.

2. Physico-chemical methods , the ultimate aim of which is todetermine the ex act qualitative and quantitative compositionof an odorous emission.

Both of these techniques yield valuable information about odouremissions but neither can be considered perfect.



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OLFACTOMETRIC METHODSFr om a ha r dwa r e or ienta ted v iewpoint the olfa ctom etr ic or sensor y

m ethods ha v e the consider a ble a dv a nta ge tha t the detection system being

utilised, the hum a n nose, is both extr em ely sensitiv e a nd selectiv e forosm o genes . Cer ta in odour -intensiv e com pounds ca n be detected a nd ev enidentified by the hum a n sense of odour per ception a t c oncentr a tions whichwould be difficult if not im possible to m a tch with physico-chem i ca ldetec tor s . Fur ther m o r e, this detection/indent ifica tion of tr a ce lev elosm ogenes ca n ta ke pla ce ev en in the pr esence of a la r ge excess of anonodor ous com pound, a condition which would cr ea te ser ious pr oblem s forthe m ost sophistica ted a na lytica l instr u m enta tio n. The m a j or disa d v a nt a geof these sensor y techniques a r ise beca us e the detection of osm ogenes byodour per ception is a n extr em ely subjectiv e sensa tion which v a r ies withthe indiv id ua l, A r ev iew of a ppr opr i a te liter a tur e r ev e a ls for exa m ple

tha t v a lues quoted for odour per ception thr esholds of pur e substa nces a r enot exa ct a nd in m a ny ca ses v a r y cons ider a b ly. (1) In a sim ila r fa shiona ny indiv idua l m a y find difficulty in r ea ching a gr eem ent with other s onthe descr iption of odour sensa tions inv oked by specific com p ounds. Thesea r e a s of disa gr eem e nt a nd uncer t a inty a r e com pounded by the r a therr estr ictiv e a nd subjectiv e v oca bula r y used for the descr ipti on of odo ur s .Thus, to obta in useful da ta fr om olfa ctom etr ic m ethod s it is essentia l toutilise the ser v ices of either highly skilled a nd exper ienced per sonne lsuch a s in the ca se of per fum e r s o r pa nels of judges of sufficientnum ber s to ensur e their collectiv e opinions a r e sta tistica lly v a li d.

PHYSICO-CHEMICAL METHODSIn contr a st to olfa ctom etr ic m ethods this a ppr o a ch a ttem pts to

identify a nd qua ntita te th e constituent osm ogenes pr esent in a n odor ousem ission r a ther tha n dir ectly a ssess the qua lity or intensity of theem ission itse lf. Odour s of na tur a l or igin a r e com m only com plex m ixtur e sof these osm ogenes pr esen t a t v er y low concentr a tio n. Ana lysis of suchem ission by instr u m enta l techniques ther efor e necessita tes a concentr a tionstep a nd a highly efficient sepa r a tion a s pr er equisites to identific a tion.Ev en befor e consider ing the deta ils of such a n a na lytica l m ethod it isa ppa r ent tha t it is unlikely to be sim ple or str a ightfor w a r d in

a pplica t ion. It is ther efor e expedient to a sk wha t pa r ticul a r a dv a nta gessuch infor m a tion would pr ov i de to justify the effor t inv o lv ed. Theobjectiv es of using these techniques, a s a lr e a dy sta ted, a r e to deter m inethe com position of the odor ous em ission with r espect to the odour -intensiv e specie s, the osm o gene s. Once these key com ponents ca n beidentified a nd qua ntified it should be possible to obta in r epr oduciblea nd objectiv e, r a ther tha n subjectiv e, a ssessm ent of odour qua lity a ndintensity. Fur ther m o r e the effect of a ny m odifica tion to pla nt ope r a tionca n be m onitor ed a nd m ea ningful conclusions ca n be der iv ed a s to ther esult, if a ny, these cha nges m a y ha v e on the concentr a tion of the keyosm ogenes which m a ke up the odor ous em ission. This wa s sum m a r ised

succinctly by Ha genguth et a l in sta ting tha t "Infor m a tion on the typea nd for m a tion of odour -intensiv e substa nces in the cour se of oper a tionof a pur ifica tion pla nt is v ita l befor e a ny pur poseful a tta ck on odour sa nd a ny sta tem ent a bout its effectiv eness is possible". (2)Physico-chem ica l techniques which a im to pr ov ide this infor m a tion a r enot, howev e r , fr ee fr om som e inher ent disa d v a nt a ges in a ddition to a nytechnica l difficulties which m a y a r ise in their im plem enta tion. In or derto r ecognise these dr a wba cks it is essentia l to consider first them ethodology inv olv ed.



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METHODThe development of an analytical method for determining the

composition of malodorous emissions was initiated within Severn Trentin 19 7 9 . At this time three separate, but complementary tasks wereidentified as requiring development to achieve this goal:-

1. The sampling and concentration of organic compounds inthe atmosphere.

2. The transfer of the concentrated sample to analyticalinstrumentation and its subsequent separations.

3. The detection and identification of the separated components.

The method chosen for sampling and enrichment of the organiccompounds which make up an odorous emission is based on the use of solidadsorbents. Although the choice of adsorbent used has changed and isstill periodically reviewed the basic sampling technique remains thesame. The advantages and disadvantages of this approach compared forexample, with cryogenic trapping are reviewed extensively in theliterature. Our own earliest attempts at analysing odorous emissionswere based to some extent on the work of Baley fi V i n e y . O ) This utilisedTenax G C as the adsorbent material with thermal desorption of theenriched organic compounds. In our own case the eluted sample was

transferred directly to the injection port of a gas chromatographequipped with a high resolution glass capillary column and was coupledto a mass spectrometer-data system.

This inital work in conjunction with other research carried outin parallel which involved subjecting a variety of pure standards tothe same methodology, allowed the following conclusions to be derived.

1. Modification of the conditions used for thermal desorption,including a change of adsorbent, were unable to fully resolvethe problems of artifact formation and either adsorptive orcatalytic loss of thermo-labile species at trace levels.

2. The only odour-intensive species conclusively identified in theodorous emission of water reclamation works were dimethyl-disulphide, -trisulphide and -tetrasulphide.

3. In addition to any osmogenes present in the sampled emission thereexists a complex mixture of non-polar, mainly aliphatic andaromatic hydrocarbon compound which make u p the bulk of thesample. Even when utilising high resolution glass capillarycolumns the chromatographic separation is incomplete. Thisinvariably results in the odour-intensive species co-eluting withmore abundant non-odorous hydrocarbons and effectively preventsmass-spectroscopic identification of the osmogenes.

Subsequent work indicated that the sulphur containing species thathad been identified and in particular dimethyl trisulphide were importantcontributors to the odour under investigation. However, the results takenas a whole were considered to be less than satisfactory. In addition tothe possibility of sample corruption, the utilisation of thermaldesorption made the problem of interferences from non-odorous



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hydr oca r bons difficult to ov er com e. The difficulties a s socia ted withther m a l desor ption techniques ha v e been solv ed by pur suing with som em inor m odifica tion the m eth ods dev eloped by Ha nga r tner a nd the wor k

ca r r ied out subsequently by Ha genguth, Teichm a nn, Zem a n a nd Koch( 4 , 2 , 5 , 6 ) . This a ppr o a ch is ba sed on the solv ent extr a ction of the solida dsor bent followed by fr a ctiona tion of the extr a ct using a dsor ptioncolum n chr om a togr a phy with silica ge l. The logic under lying thispr ocedur e is ba sed on the following a ssu m ptio ns. If a com pound ha s thepr oper ty we r efer to a s odour then it is pr oba ble tha t som e functiona lgr oup or gr oups within the m olecula r str uctur e confer this pr oper tyeither dir ectly or indir ectly. It is a lso pr oba ble tha t the pr esence ofthese functiona l gr oups within the m olecula r str uctur e m a y im pa r t to thecom pound a degr ee of pola r ity whic h ca n be exploited by the pr ocedu r eoutlined. Elution of the a dsor ption colum n with a non-pola r solv ent such

a s penta ne r em o v es the bulk of the inter fer ing hydr oca r bons a ndsubsequent elution with a m or e pola r solv ent such a s diethyl ether yieldthe odour intensiv e com pounds. Following a concentr a tion step thea na lysis of this pola r elua te using com puter a ssisted high r esolution ga schr o m a togr a phy- m a ss spectr oscopy (GC-MS) a llows identifica tion a ndqua ntita tion of the enr iched osm og enes . Va lua ble infor m a tion ca n a lso beobta ined using high r esolution ga s chr om a togr a phy in conjunction withselectiv e detector s for sulphur a nd nitr ogen conta ining com pou nds.Alter na tiv ely, a m m onia - chem ica l ionisa tion - m a s s spectr oscopy ispr oposed by Zem a n a nd Koch to pr ov i de pr ofiles for pola r com poundsconta ining sulphur , nitr ogen or oxygen .(6) These a uxilia r y t echniques

ha v e the benefit tha t due to their inher ent selectiv ity they ca n oper a teon the unfr a ctiona ted solv ent extr a ct. This infor m a tion ca n be utilisedfor r outine m onitor in g, qua ntita ti on or a s a power ful a id to the electr onim p act m a ss - spectr oscopic identifica tion of odour - intensiv e spe cies .

INTERPRETATION OF RESULTS AND DISADVANTAGES O F PHY SICO- CHEMICAL METHO DSThe pr oblem s encounter ed using ther m a l desor ption techniques

indica te m or e funda m enta l disa d v a nt a ges inher ent in the physico-chem ica lm ethods descr ibed. In the conclusions der iv ed fr om our initia l wor k itwa s sta ted tha t due to inter fer ing hydr oca r bon it wa s im possible to

identify, using GC-MS the odour -intensiv e spec ies. In r ea lity thesitua tion is m or e com plex in tha t no infor m a tion obta ined b y GC-MS a tthis tim e could ev en indica te whether osm ogenes wer e pr esen t. Ev en usingthe im pr o v ed m ethodology descr ibed it is im por t a nt to a ppr ecia t e tha tneither m a ss-spectr oscopy or a ny of the a uxilia r y techniques outlineda bov e a ctua lly deter m ine od our s. Com puter a ssisted GC-MS is r ecogniseda s an extr em ely power ful technique for the identifica tion of or g a niccom pound s. Howev e r , a ny conclusions concer ning the odour pr oper ti es ofthe identified species r elies on a da ta -ba se of sepa r a te infor m a tion.These da ta m a y be in the for m of the exper ience of the wor ker s inv olv ed,a v a il a ble liter a tur e or in pr inciple a t lea st a n integr a ted com puter

b a sed system .To der iv e m ea ningful conclusion concer ning a m a lodo r ous em ission

using these physico-chem ica l techniques it is necessa r y to em ploy a nev a lua tion pr ocedur e a t lea st sim ila r to the fol lowing:-

1. The odour -intens iv e species which m a k e up the em ission underinv estiga tion m ust be identifi ed. The r esulting ta ble of osm ogenesshould be a s com plete a s poss ible . It is, of cour se v ita l tha tno im por t a nt osm ogenes a r e ov er looked a t this sta g e.



300

2. The identified osmogenes must be quantified, at leastapproximately to determine their relative abundance within thecomplex mixtu re.

3. For each of the identified osmogenes the relationship betweenthe compounds actual abundance in the mixture and theconcentration that represents the odour perception threshold mustbe evaluated. This is essential to give some indication of theosmogenes perceived intensity and assist in pinpointing whichof the odour-intensive species are most significant.

4 . Finally the odour sensation invoked by the original emission iscompared to those obtained for the pure compounds identified or

mixtures of these substances.

Obviously this procedure involves a lengthy and complex follow-upto the original analysis. Furthermore it is important to note thatalthough the analytical results are objective measurements, the appraisalof their effectiveness in describing the emission, ultimately relies onsubjective comparisons of odour sensation. This final observation couldbe interpreted as a weakness in the method in having to resort tosubjective odour comparisons. An alternative viewpoint however is thatthe most effective information can be derived by utilising a combinationof olfactometric and physico-chemical techniques.

ALTERNATIVE APPROACHWithin Severn Trent a modified version of this procedure is utilised

for the analysis of malodorous emissions. The most significant differencein this approach compared to those already discussed is the use of highresolution gas chromatography in combination with olfactory detection.This method also combines physico-chemical and olfactometric or sensorytechniques but in an alternative manner. Utilisation of gaschromatography combined with odour detection is not a new concept and hasbeen employed fairly commonly for the analysis of food aromas, essentialoils and other fragrances. The technique is equally applicable to

environmental problems and is used frequently in this laboratory for theanalysis of atmospheric emissions and taste and odours in wate r. Threeimportant benefits accrue from this approach in the context of odouremission analysis.

1. It provides a detection system for gas chromatography which isboth sensitive and selective for odour intensive compounds.

2. The use of retention data in combination with odour detectionprovides a valuable aid to the computer assisted GC-M S analysisof osmogenes. Ex perience in use of the technique frequently allowsquite accurate predictions to be made on sample composition basedon retention data and odour quality.

3. Not all odour-intensive species present in a sample willnecessarily be perceived at the odour port. This is for theobvious reason that positive odour detection is dependent on theosmogene being present in the mixture at concentrations in excessof the threshold for odour perception. Thus without any definiteinformation on identity, abundance, or odour threshold



301

concentrations, the technique offers an empirical system for thedetection of the most significant osmogenes.

As stated earlier the procedure for this analysis is based largelyon the methods developed by H angartner.(4 ) Figure 1 outlines the schemeutilised for sample processing and analysis. In addition to the detectionsystem already discussed the only other significant difference in thiswork is the choice of adsorbent which is C arbotrap D-l a graphitisedcarbon black (GCB). The use of GCB 's in environmental analysis is welldocumented in the literature both as column materials and adsorbants.(7 ,8)Initial work within Severn Trent confirmed the claimed superiority ofGC B' s compared with adsorbents based on porous polymers such as Tenax GC .No evaluation of the relative merits of GC B' s and activated carbons havebeen made at this laboratory but tests with the latter are likely in the

future.

ANALYTICAL PROCEDURE

Sampling and Extraction;-Sampling is accomplished by drawing malodorous air (0.5 - 2m )

through glass tubes (150mm x 4mm I.D) packed with 250mg Carbotrap D - l(Supelco I nc) using oil free vacuum pump s. Sample tubes are prepared foruse by thermal desorption at 320°C in a stream of purified helium.Desorption of the enriched organic compounds is by micro-Sox hletextraction with diethyl ether. Ex tracts are concentrated to 1ml by

micro-Kuderna concentrator. All further concentration of extracts oreluate fractions is by means of gradual evaporation at room temperaturefrom blood sedimentation tubes. These glass tubes are 10cm long,graduated in mm , approximately 2.6 - 2.7mm I.D, 0.55ml volume.

ADSORPTION COLUMN CHROMATOGRAPHYThis procedure utilises a glass column (130mm x 5 mn) wet packed

with approximately 2gm of Silica Gel (Merck 7754 BDH Chemicals) preparedby heating to 50 0°C ± 20°C for two hours, cooled and deactivated to1.0% w/w wat er. Solvents are n-pentane (glass distilled, RathburnChemicals Ltd) and diethyl ether (D istol, Fisons).

GAS CHROMATOGRAPHIC CONDITIONSFlame ionisation. Flame Photometric and Thermionic Detection use

a Perkin - Elmer Sigma 1 gas chromatograph, equipped with an S.G.E on-column injector. The column used was a 25 metre x 0.31mm I.D. fusedsilica WC OT capillary coated with B P-1 (S.G.E), a methyl silicone.

Olfactometric detection was originally carried out using the samegas chromatograph with a splitting device based on the design byEtzweiler and Neuner-Jehle attached to a locally produced odour port.( 9)This approach has been superseded with a Hewlett-Packard 5890 Achromatograph equipped with flame ionisation and a low volume (3.5mm )thermal conductivity detector, an ex tension of which allows odourperception.

GC-M S analysis used a Finnigan 4 00 0 quadrupole E I/ CI massspectrometer. Electron Impact spectra were recorded continually using anIncos Nova 4 data system. Ion source temperature was 250 °C and theionisation energy 70 eV.

All gas chromatography was carried out with pressure regulatedhelium carrier gas and the following temperature programme 15°C for 2mins and then 5°C to 250°C.



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RESULTS AND DISCUSSIONThe r esults obta ined with this pr ocedur e a r e sim ila r to those

pr e v iously r ep or ted in the liter a tur e by Ha nga r tner , Ha genguth et a l a nd

Zem a n et a l ( 4 , 2 , 5 , 6 ) . The m a jor exception, being the com plete la ck ofa l k y l a te d p y r a z i n e s a n d a l k y l a t e d t h i o p h e n e s . Th e s e o d o u r - i n t e n si v ecom pounds a r is e fr om the ther m a l decom position of pr oteins a nd sulphurconta ining a m ino a ci ds. They a lso dev elop in the ther m a lly inducedr e a ction of pr otei ns with ca r bohydr a tes (Ma illa r d r e a c t i o n ) . The a uthor sindica ted a bov e ha v e dem onstr a te d tha t these com pounds a r e inv a r i a blypr oduced dur ing the ther m a l tr ea t m ent of sludge, a pr ocess which is notused in this Author ity.

Ther e a ppea r s to be little point in pr esenting a long list of thev a r io us odour -intensiv e com pounds identified by this pr oc edur e. Such a na ppr o a ch would sim ply duplica t e, to a la r ge extent, the findings of other

wor ker s. The a dv a nta ges cla im ed for this technique which utilises highr esolution ga s chr o m a togr a ph y with olfa ctor y detection is tha t it offer sa n identifica tion a id a nd a n indica tion of the m ost significa nt osm ogenesidentified . It is ther efor e intended to pr esent the r esults obta ined fr oma v a r iety of sa m pling loca tions within the Sev er n-T r ent Wa ter Author it y.In ea ch ca se the odour em ission under inv estiga tion w a s judged to be a ni n t e n s e s o u r c e f o r t h a t p a r t i c u l a r w a t e r r e c l a m a t i o n w o r k s . Th e c o m p ou n d ssubsequently identified a r e believ ed to be the key com ponents pr esent int h a t p a r t i c u l a r e m i s s i o n .

Case 1

Sa m ple Loca tion: Downwind of ta nks used for stor ing sur plusa c t i v a t ed s l u d g e .

Odour Sensa tion: Intense, sha r p, choking, per spir a t ion lik e.

Pr oblem Identified: Excessiv e r etention tim e.

Osm ogenes detec ted by G.C/odour por t a nd identified by GC-MS.

1. Pr opa noic a cid2. 2-Methyl pr opa noic a cid3. Buta noic a cid4 . 3-Methyl buta noic a cid5. 2-m ethyl buta noic a cid6. Penta noic a cid7 . Methyl Phenol (cr esol)

Other com pounds identified by GC-MS - not detecta ble a t odour p or t.

1. Dim ethyl disulph ide

2. D i m e t h y l t r i s u l p h i d e3 . V a r i o u s h i g h e r f a t t y a c i d s

The m a lodo r ous em ission in this ca se a ppea r s to be dom ina ted by v ola tilefa tty a cids a nd cr eso l. It is inter esting t o note in pa ssing tha t cr esolis one of the few odour -intensiv e species found in a lm ost a ll odor ousem ission so fa r encounte r ed. This osm ogene is usua lly pr esent insufficient qua ntities to be clea r ly detecta ble of the odour por t. Cr esola nd phenol (only found occa siona lly) is r epor ted to be for m ed by thedecom position of lignin.



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Case 2

Sample Location: Double filtration unit treating dairy waste

(exclusively)

Odour Sensation: Strong, earthy, musty, "potato-bin"

Problem Identified: Probably due to excessive bacterial/algal filmon media surface

Osmogenes detected by GC /odour port and identified by GC- MS.

1. Methoxy benzene (Anisole)2. 2-Isopropyl-3-methoxy pyrazine

3. Phenol4 . Bicyclo ( 2.2.1) Heptan-2-one, l,7,7 ,trimethyl (C amphor)5. Bicyclo (2.2.1) Heptan-2-one, l,3,3 ,trimethyl (Fenchone)6. Methyl benzonitrile7. Bicyclo (2.2.1) Heptan-2-ol, 1,2,7,7 tetramethyl (2-methyl

isoborneol)8. Dichloro-methyl anisole9. Trichloroanisole

10. Trans-l,10-dimethyl-tran8-9-Decalol (Geosmin)

This sample is included because it is an interesting departure from the

odorous emissions more commonly associated with water reclamation works .Aqueous dairy waste sampled at this time and subsequently analysed by thesame techniques demonstrated that none of the listed osmogenes werepresent. The odorous emission was thus a function of the filtration unitand its mode of operation rather than directly originating from theeffluent being treated. The key osmogenes are believed to be: -

1. 2-isopropyl methox y pyraz ine - "potato-bin" odour2. 2-methyl isoborneol - earthy3. Trichloroanisole - musty4 . Geosmin - earthy

Of secondary importance as judged by gas chromatography with olfactorydetection are:-

1. Anisole - pungent2. Fenchone - slighty earthy3. Methyl benzonitrile - almonds4 . Dichloro methyl anisole - musty

Geosmin, 2-Methyl isoborneol (MI B) and 2-isopropyl methoxy pyrazine are

known to be produced by various types of actinomycete cultures (10-15).Geosmin and MI B are saturated tertiary alcohols and resist oxidation.The steric configuration of the hydroxyl and methyl groups in bothcompounds are believed to interact with receptors in the nose, impartingtheir characteristic earthy odour ( 16 ) . The four compounds itemised asthe key osmogenes in this odorous emission have extremely low odourthreshold concentrations. Their occasional occurence in drinking watercan lead to widespread complaints and are routinely monitored for withinthis Authority.



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Case 3

Sample Location: Press House - processing undigested sludge afterpolyelectrolyte conditioning

Odour Sensation: Unpleasant faecal , rotting cabbage

Problem Identified: Lack of digestion facilities, design

Osmogenes detected by G.C/ odour port and identified by GC- MS.

1. Dimethyl disulphide

2. Dimethyl trisulphide3. Dimethyl tetrasulphide4 . Methyl phenol (cresol)5. Indole6. Methyl Indole (probably skatole)7. 3-cyclohexene-l-methanol, a,a, 4 -Trimethyl(s)

(a-Terpineol) *

Other compounds detected only by GC-MS

1. Butanoic acid2. 3-Methyl butanoic acid3. 2-Methyl butanoic acid4 . Pentanoic acid5. Hex anoic acid6. Octanoic acid

7. Decanoic acid

* This compound and a variety of less abundant but similar species are

believed to arise due to essential oils present in the polyelectolyteconditioner.

In this case the key osmogenes appear to be the polymeric sulphides.Dimethyltrisulphide alone is judged to be very similar to the odoursensation perceived on-site. Significant contributions are also madeby cresol and indole which are usually found in such malodorousemissions. Methyl indole was detected on this occasion thoughsurprisingly this is an exception rather than typical of such analyses.

CONCLUSIONSA variety of compounds have been identified as key contributers

to certain malodorous emissions originating from water reclamationworks. The most important are considered to be polymeric sulphides ,volatile fatty acids, indole and cresol. The utilisation of highresolution gas chromatography in conjuction with olfactory detectionis identified as a valuable aid to the analytical procedure.



305

The only disadvantage inherent in the technique is that it takes noaccount of possible synergistic interaction between the osmogenes thatconstitute an odorous emission. Technical limitations which may be

improved upon are thought to be :~

1.2.

Sampling of the malodorous airSubsequent sample processing

) loss of volatile) components

The opinions expressed are those ofthe author and not necessarily thoseof the Severn-Trent Water Authority.

Malodorous emissionsampled on

solid adsorbent

Solvent extractionwithDiethyl Ether orDichloromethane

Con cen trat ion

Con cen trated extrac tOsmogenes + Interfer ing

Hydrocarbons

Pentane e luateI n t e r f e r e n c e s

GC-NitrogenGC-SulphurD e t e c t i o n

F i g u r e 1 . A n a l y t i c a l P r o c e d u r e



306

REFERENCES(1) National Institute for Water Supply, Netherlands.

Compilation of odour threshold values in air and water;

Central I nstitute for Nutrition and Food Research TNO N etherlandsJune 1977 .

(2) HAGEN GUTH, H., TEICHM ANN , H., ZEMAN, A., Geruchsmessungen inkommunalen Klaranlagen, Massenspektrometrische Identifizierunggeruchsaktiver Verbindungen.

(3) BAI LE Y, J.C., and VIN EY, N.J., The Analysis of Process Gases forMalodorous Compounds. Warren S pring Laboratory, Department ofIndustry, Stevenage.

(4) HANG ARTNE R, M., S ampling and Analysis of Odorous Compounds in WaterTreatment Plants. Institute of Hygiene and E rgonomics, Swiss FederalInstitute of Technology, 8092 Zurich, Switzerland.

(5) ZEMAN , A., and HAGE NG UTH , H., (1980) Identification of OdorousCompounds in Emissions from Municipal S ewage Plants by GC- MS.German Armed Forces University, Munich, West Germany.

(6) ZEMAN , A., and KOC H, K., (1981) Determination of Odorous Volatilesin Air using Chromatographic P rofiles, German Armed ForcesUniversity, Munich, D-8014 Neubiberg (G.F.R.)

(7) BRONE R, F., CI CC IOL I, P., and DI NARD O, F., Use of GraphitizedCarbon Black in Environmental Analysis. Laboratoriosull'Inquinamento Atmosferico del C.N.R. Via Montorio Romano,3600131 Rome (Italy).

(8) CICC IOLI, P., BERTONI , G., BR ANCALEONI, E., FRATARCANGELI, R., andBRUNER, F., Evaluation of Organic Pollutants in the Open Air andAtmospheres in Industrial S ites using Graphitized C arbon Black Trapsand Gas Chromatographic-Mass Spectrometric Analysis with SpecificDetectors. Laboratorio sull' Inquinamento Atmosferico del C.N.R.

ViaMontorio Romano, 36-00131 Rome (Italy).

(9) ETZWEILER and NE UN ER-JEH LE: Chromatographia 6, 1973, 50 3.

(10) GER BE R, N. N ., and LE CH EVALI ER, H.A., "Geosmin, an Earthy-SmellingSubstance Isolated from Actinomycetes", Appl.Microbiol 13:935(1965).

(11) SAFFERM AN, R.S ., ROS EN , A.A., "Earthy-Smelling Substance from aBlue-Green Algae"Environ, S ci, Technol. Ii429 (1967).

(12) MED SK ER, L.L ., JENK IN S, D., "Odorous Compounds in Natural Waters.An Earthy-Smelling Compound Associated with Blue-Green Algae andActinomycetes". Environ, S ci. Technol 2(6)t461-464 (1968).

(13) ROS EN , A. A., MA SH N I, C.I ., "Recent Development in the Chemistryof Odour in Watert The Cause of Earthy/Musty O dour", Water Treat.Exam 19(2):106-119 (1970).

(14) MED SK ER, L . L., JEN KI NS , D., "Odorous Compounds in Natural Waters.2-exo-Hydroxy-2-methylbornane,the Major Odorous Compound Producedby Several Actinomycetes". Environ. Sci Technol 3 (5) :47 6-477 (1969).

(15) GE RB ER , N. N., "Three Highly Odorous Metabolites from anActinomycete. 2-Isopropyl-3-methoxypyrazine, Methylisoborneol, and

Geosmin", J Chem Ecol 3:475 (1977).(16) TSU CH IYA, Y., "The Basic Research on the Causes of Odours in Wa ter.

Studies on Odorous Materials in the Water of the Pond of Tairo atMiyakejima", Tokyo Toritsu Eisei Kenkyusho Kenkyu Nempo 25:44 5(1974).



307

BOD^. TOA a n d o d o u r o f f e n s i v e n e s s

F .E . TH A C K E R a n d H . R . E V A N S .

M i c r o b i o l o g y D e p a r t m e n t r T h e W e s t o f S c o t l a n d A g r i c u l t u r a lC o l l e g e , A u c h i n c r u i v e , A y r KA6 5 H W , S c o t la n d , U K

ABSTRACT

S u p e r n a t a n t BODc a n d TOA c o n c e n t r a t i o n s o f p i g g e r y s l u r r yp r o v i d e u s e f u l i n d i c a t o r s o f p o t e n t i a l o d o u r n u i s a n c e . T h e yh a v e v e r y h i g h l y s i g n i f i c a n t l o g a r i t h m i c r e l a t i o n s h i p s w i t ht h e o d o u r o f f e n s i v e n e s s a s a s s e s s e d b y a p a n e l o f p e o p l e .S p e c i f i c o d o r a n t s i n c l u d i n g V F A , i n d o l e s a n d p h e n o l s a r es h o w n t o b e s i g n i f i c a n t l y l e s s r e l i a b l e .

INTRODUCTION

P u b l i c a w a r e n e s s o f a g r i c u l t u r a l o d o u r s a n d r e s u l t i n gc o m p l a i n t s h a v e i n c r e a s e d i n r e c e n t y e a r s ( 1 , 2 , 3 , 4 , 5 & 6 ) .M o s t c o m p l a i n t s a r e a s s o c i a t e d w i t h i n t e n s i v e a n i m a l h o u s i n ga n d t h e i r a s s o c i a t e d s l u r r y m a n a g e m e n t s y s t e m s .

T h e l a r g e s t n u m b e r o f c o m p l a i n t s a r i s e f r o m a n i m a l w a s t e sm a n a g e d i n s l u r r y s y s t e m s , a n d o f t h e s e c o m p l a i n t s , m o s to c c u r d u r i n g s l u r r y s p r e a d i n g o p e r a t i o n s . S l u r r y s y s t e m si n v o l v e t h e c o l l e c t i o n o f f a e c e s an d u r i n e w i t h a d d e d w a t e ri n v a r y i n g q u a n t i t i e s a n d s u b s e q u e n t s t o r a g e . T h e s l u r r yr e m a i n s a n a e r o b i c t h r o u g h o u t s t o r a g e u n d e r s l a t s a n d i n

o u t s i d e s t o r e s . A n a e r o b i c b a c t e r i a b r e a k d o w n m u c h o f t h eo r i g i n a l o r g a n i c m a t e r i a l t o s o l u b l e a n d v o l a t i l e c o m p o u n d sa n d s o t h e a c c u m u l a t i o n o f l a r g e a m o u n t s o f o f f e n s i v e o d o u rc o m p o u n d s o c c u r s . T h e s e a r e r e l e a s e d i f t h e s l u r r y i sa g i t a t e d o r s p r e a d o n t o l a n d ( 3 & 7 ) .

O d o ur n u i s a n c e i s a c o m b i n a t i o n o f o d o u r i n t e n s i t y a n d o d o u rq u a l i t y . O d o u r i n t e n s i t y i s a f u n c t i o n o f t h e n u m b e r o ft i m e s o d o u r o u s a i r m u s t b e d i l u t e d w i t h o d o u r - f r e e a i r ( i . e .a d i l u t i o n f a c t o r ) f o r 50% o f a n o d o u r p a n e l t o j u s t d e t e c tt h e o d o u r (8 & 9 ) . I t c a n a l s o b e m e a s u r e d b y u s i n g a

p a n e l o f p e o p l e a n d a s c a l e o f i n t e n s i t y o n w h i c h t h es t r e n g t h o f t h e o d o u r i s i n d i c a t e d ( 1 6 ) . L a r g e p a n e l s o fp e o p l e a r e n e e d e d f o r t h e s e m e a s u r e m e n t s , s i n c e d i f f e r e n c e si n s e n s i t i v i t y o f i n d i v i d u a l s a r e k no w n t o b e l a r g e ( 1 0 , 1 1 &1 2 ) .

T h e c o n c e n t r a t i o n s o f s e v e r a l s p e c i f i c o d o r a n t s f o u n d i np i g g e r y s l u r r y , i n p a r t i c u l a r v o l a t i l e f a t t y a c i d s , h y d r o g e ns u l p h i d e , a m m o n i a a n d p - c r e s o l , h a v e b e e n c o r r e l a t e d w i t ho d o u r i n t e n s i t y ( 1 3 , 1 4 , 1 5 & 1 6 ) .



308

O dour q u a l i t y d e p e n d s n o t o n l y on t h e s e n s i t i v i t y o f t h ehum an n o s e b u t a l s o on t h e s u b j e c t i v i t y o f t h e hum an

lan gu ag e t o be a b l e t o d e s c r ib e t h e odour (17 ) . Somechem ica l c h a r a c t e r i s t i c s of s l u r r y have been com pared t o t h es l u r r y o d ou r. A r e l a t i o n s h i p b etw ee n v o l a t i l e f a t t y a c i d s(VFA) a nd o d o u r o f f e n s i v e n e s s o f p o u l t r y m a n u r e w asd e sc r i b e d by B e l l ( 18 ) . Sobe l (19 ) u sed a p an e l o f pe op let o a s s e s s t h e o d ou r o f f e n s i v e n e s s of p o u l t r y m a n ure andfound a c o r r e l a t i o n b e tw e en t o t a l s o l i d s and o f f e n s i v e n e s s .

W i l l i a m s ( 5 ) f o u n d t h a t o d o u r i n t e n s i t y m e a s u r e m e n t s b yl i qu id d i l u t i o n of p igge ry s l u r r y w e re no t su cc es s fu l , andconc luded th a t t he o f f e ns iv ene s s of odou rs r a the r than t h e i r

i n t e n s i t y w as t h e b e s t i n d i c a t o r of o do ur n u is a n c e .O d o u rof fen s iv en ess i s a su pr a - th re sh o l d asse ssm ent and depends onth e human sen se of sm el l . S ince co m pla int s r e s u l t from th ed e t e c t i o n of o f f e n s iv e com pounds by t h e hum an nose andb e c a u s e o f t h e p r o b l e m s of q u a n t i f y i n g a l l t h e o d o u rcom pounds i n s l u r r y by a n a ly t i c a l m e thods, i t i s d e s i r ab l eto use th e human nose for odour of fe ns iv en es s mea suremen ts .T h i s p r e s e n t s p r o b le m s , s i n c e t h e r e i s a l a r g e v a r i a t i o n o fs e n s i t i v i t y t o o d o r a n t s a nd som e p e o p l e a r e a no s m i c (10 &2 0 ) . T he w e l l b e i n g of a p e r s o n a l s o a f f e c t s t h e i rr e s p o n s e t o o d o u r s ( 2 ) . O dour o f f e n s i v e n e s s i s a

s u b j e c t i v e d e t e r m i n a t i o n and r e q u i r e s a s many p e o p l e a sp o s s i b l e t o a s s e s s an o do ur and m i n i m i s e v a r i a t i o n s i ns e n s i t i v i t y . The p r o b le m s of r o u t i n e o l f a c t o r y o do urassessments a re tha t they a re no t on ly ve ry t ime consuming ,b u t a l s o v e r y s u b j e c t i v e .

S p o e l s t r a (21) l i s t e d c r i t e r i a fo r p o t e n t i a l l y s u i t a b l eo d ou r i n d i c a t o r s a nd c o n c l u d e d t h a t VFA an d p - c r e s o l w e rethe be s t odou r i nd i ca to r s o f p igge ry s lu r ry .

W i l l i a m s (5) e x am i n ed t h e s u p e r n a t a n t 5 d ay b i o c h e m i c a l

oxygen demand (BOD 5), t o t a l o r g a n ic a c id s (TOA), VFA andt o t a l i n d o l e s and p h e n o l s (T IP ) a s i n d i c a t o r s of t h ep o te n t i a l o f fe ns i ve ne ss o f odours emana t ing from samples o fraw and ae ro b i c a l l y t r e a t e d s l u r r y o f p ig ex c r e t a . I t w asf ou nd t h a t t h e s u p e r n a t a n t BODc c o u l d p r o v i d e a u s e f u li n d i c a t o r . I t e x h i b i te d a h i g h ly s i g n i f i c a n t c o r r e l a t i o n( c o r r e l a t i o n c o e f f i c i e n t = 0.86) w i t h o do ur o f f e n s i v e n e s s( E qu a ti on 1 ) . I t a l s o l a r g e l y f u l f i l l e d t h e c r i t e r i a fo ran in d ic a to r o f odour no ted by Sp oe ls t ra (21).

Odour o ff en si v en es s = 0.947 LogS upern atant BOD5 + 3.16 (1)

VFA and T IP a l s o c o r r e l a t e d w i t h o d o ur o f f e n s i v e n e s s , b u tt h e i r c o n c e n t r a t i o n s a t t h e l o w e s t o f f e n s i v e n e s s r a t i n g sw e r e t o o s c a t t e r e d f o r t h e c o r r e l a t i n g e q u a t i o n s t o p r o v i d es u f f i c i e n t l y r e l i a b l e i n d i c a t o r s .

T h i s r e p o r t i n c l u d e s d a t a w h ic h c o v e r s a w i d e r r a n g e ofs l u r r y t r e a t m e n t s g i v i n g a m ore even d i s t r i b u t i o n of s am p l esover the o f fens iveness sca le than those used by Wi l l i ams(5) .



309

An improved model using supernatant BODE and a similar modelusing TOA as indicators of potential odour offensiveness ispresented.

METHODS

The Slurry

Raw slu rry was collected and prepared by di lu ting freshexcreta from fattening pigs with tap water to a standardconcentration of t o tal solids (TS) 30 g/1 and chemical

oxygen demand (COD) 38 g / 1 . The methods of excretaco llect ion, the animal di e ts , and the slurry compositionwere described previously (22 & 23).

Treated Slurry

Samples of treated slurry were obtained from laboratory-scale continuous culture reactors (3 & 15 l i t re s ) during aseries of treatments studying the effects on residual slurryquali ty of mean treatment time, reaction temperature,dissolved oxygen level and pH value (27). Some were also

collected from a 2.4m3

pilot plant which was operating at35°C and 7 day residence time and with dissolved oxygensaturat ion of 0 to 40%. The pilot plant was treat ingseparated stored piggery slurry (TS 21 g/1; COD 26 g/1).

Measurement S_f B i o c h e m i c a l O x y g e n D e m a n d (BOD)

Supernatant BODg was measured by the standard method of theAmerican Public Health Association (24), but using the EILdissolved oxygen probe model no. 8012 to measure oxygen

concentration (Electronic Instruments Ltd., Richmond,Surrey,UK.)

To ensure that a suitable variety of microorganisms werepresent in the BOD bottles a seed was considered necessary.The seed was prepared from a daily-fed continuous culture,previously commissioned to steady s tat e conditions. Theculture was ini tiated with a 500 ml mixture of garden soil,mixed liquor from one of the laboratory treatment reactorsand tap water in a one l i t r e f las k . The cu ltu re wascontinually aerated and agitated at 20°C through a sintered

glass tube . Any water lo s s , from the cu l t u r e , byevaporation was made good by additiion of tap water. Seedwas prepared by diluting a sample of culture with an equalvolume of water and allowing it to s e t t le for 5 minutes. 2ml of the top liquor were then added to each l i t r e of BODdilution water.



310

Samples of raw and treated slurry were centrifuged at10,00 0g for 20 minutes at 10°C , as described by Hissett etal (25), to prepare the supernatants for the measurement ofBOD.

Determination of Total Organic Acids (TOA)

TOA wer e de te rm in ed, in the superna tant prepa red asdescribed by Hissett et al (25), by the method of Montgomeryet al (26) . The organic acids were esterified withacidified ethylene glycol. The esters were then reactedwith hydroxylamine and the hydroxamic acids thus formed wereconverted to their ferric complexes and their concentrationswere determined by optical density measurements at 500u.

Gas-liquid Chromatography of VFA and TIP

A Pye series 104 gas-liquid chromatograph (Pye UnicamLtd.,Cambridge,UK.) and a Packard model 439 gas-liquidchromatograph (Packard Instrument Ltd.,Reading,UK.) with aHewlett Packard HP 3390A reporting integrator (HewlettPackard Ltd.,Cheshire,UK.) were used. Determination of VFAwere by direct injection of acidified supernatant samplesinto a 2.15 m long by 4mm ID packed column of 5% FFAP on

Cnromosorb G.AW.DMCS 80/ 100 mesh. Determination of TIPwere by direct injection of solvent extracts, of wholesamples (30 ), into a 25 m long by 0.23 mm ID capillarycolumn of WCOT fused Silica with liquid phase CP sil 5CB(United Technologies Packard,Reading,UK.).

Odour Assessment

The odour panel consisted of 21 College Staff who hadprevious odour panel experience (5) and 5 staff who werelater recruited and whose performances at slurry odour

assessments were judged to be similar to those of theoriginal panellists.

The method of assessment of odour offensiveness was based onthat of Sobel (19). 20 ml samples of slurry were tranferredto 60 ml black glass bottles as described by Williams (5).These were handed to panellists in their own offices orlaboratories where they were already accustomed to thebackground odour and were least hindered by interruption.The panellists were shown a copy of Table I and asked toassign the odour offensiveness of each sample to a value

between 0 and 5. They were specifically requested not toconsider the samples relative strength compared with theother samples.



311

RESULTS

O d o u r o f f e n s i v e n e s s . Su p e r n a t a n t B O D ^ a n d TOA

T h i r t y s e v e n s a m p l e s o f r a w p i g g e r y s l u r r y (TS 2 9 g / 1 ,s t a n d a r d d e v i a t i o n 3 g / 1 ; CO D 3 7 g / 1 , s t a n d a r d d e v i a t i o n 3g / 1) w e r e a s s a y e d o v e r a p e r i o d o f 3 y e a r s . T h e s e h a do f f e n s i v e n e s s v a l u e s o f b e t w e e n 2.3 a nd 3.5 w i t h a m e a nv a l u e o f 2 . 9( d ef i n it e l y o f f e n s i v e ) a n d a s t a n d a r d d e v i a t i o nof 0.41.

Fi f t y s a m p l e s of a e r o b i c a l l y - t r e a t e d p i g g e r y s l u r r y w e r ea s s a y e d d u r i n g t h e s a m e p e r i o d o f t i m e . Th e o f f e n s i v e n e s s

v a l u e s r a n g e d f r o m 0 t o 2 . 7 ( i n o f f e n s i v e t o d e f i n i t e l yo f f e n s i v e ) . T h e a c t u a l v a l u e w a s i n f l u e n c e d b y t h e m e a nt r e a t m e n t t i m e , r e a c t i o n t e m p e r a t u r e a n d a e r a t i o n r a t e ( 2 7) .

Th e d a t a w e r e a n a l y s e d , b y r e g r e s s i o n a n a l y s i s f or o d o u ro f f e n s i v e n e s s w i t h s u p e r n a t a n t B OD c a n d T OA c o n c e n t r a t i o n so f t h e s a m p l e s o f r a w a n d t r e a t e d s l u r r y . T h e r e w e r e v e r yh i g h l y s i g n i f i c a n t ( P=0 .0 01 ) l o g a r i t h m i c r e l a t i o n s h i p sb e t w e e n o d o u r o f f e n s i v e n e s s a n d s u p e r n a t a n t B O D rc o n c e n t r a t i o n (Equ a t io n 2) an d od o u r o f f e n s i v e n e s s a n d T OAc o n c e n t r a t i o n ( Eq u a ti o n 3 ) . T h e r e g r e s s i o n e q u a t i o n s f or

o d o u r o f f e n s i v e n e s s d e v e l o p e d f r o m 7 6 s a m p l e s w i t hs u p e r n a t a n t B OD c a nd 61 s a m p l e s w i t h TO A h a v e c o r r e l a t i o nc o e f f i c i e n t s o f 0.96 a n d 0.93 r e s p e c t i v e l y . S c a t t e rd i a g r a m s a nd t h e r e g r e s s i o n l i n e s a r e s h o w n in Fi g u r e s 1 a n d2 .

O d o u r o f f e n s i v e n e s s = 1.453 L o g S u p e r n a t a n t B O D 5 + 2.320 (2)

Odo ur of fe ns iv en es s = 2.378 LogTOA + 2.327 (3)

S u p e r n a t a n t BOD,- a n d TO A c o n c e n t r a t i o n s a r e e x p r e s s e d a s

g / 1 . T h e m e a n v a r i a n c e o f t h e o f f e n s i v e n e s s f r o m t h er e g r e s s i o n l i n e a n d t h e s t a n d a r d e r r o r o f t h e s u p e r n a t a n tB O D 5 r e l a t i o n s h i p a r e 0.325 a n d 0.050 a n d f o r t h e T OAr e l a t i o n s h i p a r e 0.399 a n d 0.119 re s p e c t i v e l y .

O d o u r O f f e n s i v e n e s s . VFA a n d TIP

T h e a v e r a g e c o n c e n t r a t i o n s o f i n d i v i d u a l a n d t o t a l VFA a ndo f TIP in s a m p l e s o f r a w p i g g e r y s l u r r y a r e p r e s e n t e d inT a b l e I I.

D u r i n g c o n t i n u o u s c u l t u r e t r e a t m e n t VF A an d T IP a r e o x i d i s e d( 2 7 ). In t h e a b s e n c e o f V F A t h e o d o u r o f f e n s i v e n e s s o f t h es l u r r y v a r i e d b e t w e e n 0 a n d 2 . 4 ( i n o f f e n s i v e t o f a i n t l yo f f e n s i v e ) .

R e g r e s s i o n a n a l y s i s o f o d o u r o f f e n s i v e n e s s w i t h VFA (64s a m p l e s ) a n d T IP (41 s a m p l e s ) o f t h e s a m p l e s o f r a w a n dt r e a t e d s l u r r y g a v e c o r r e l a t i o n c o e f f i c i e n t s of o n l y 0.60



312

a nd 0 .5 0 r e s p e c t i v e l y . S c a t t e r d i a g r a m s o f VFA ( F i g u r e 3)a n d T I P ( F i g u r e 4 ) c o n c e n t r a t i o n s a g a i n s t o d o u ro f f e n s i v e n e s s o f s l u r r y a r e i l l u s t r a t e d . The r e l a t i o n s h i po f VFA c o n c e n t r a t i o n t o o d o u r o f f e n s i v e n e s s o f s l u r r y w a so n l y s l i g h t l y i m p r o v e d b y s u b t r a c t i o n o f t h e a c e t i c a c i dc o n c e n t r a t i o n f r o m t h e t o t a l V F A .

S u p e r n a t a n t BOD -̂ and TOA

T h e a v e r a g e s u p e r n a t a n t BODr o f ra w p i g g e r y s l u r r y w a s 2 .3 4 9g / 1 ( s t a n d a r d d e v i a t i o n 0 .4 7 0) a nd t h a t o f TOA w a s 1 .5 33 g / 1( s t a n d a r d d e v i a t i o n 0 . 2 1 3 ) . T he m ean r a t i o o f TOA t os u p e r n a t a n t B O D5 w as 0 .6 66 ( s t a n d a r d d e v i a t i o n 0 . 1 0 5 ) .

D u r i n g c o n t i n u o u s c u l t u r e t r e a t m e n t s u p e r n a t a n t BODj a nd TOAw e r e o x i d i s e d . T h e r a t i o of TOA t o s u p e r n a t a n t BODg o f t h er a w p i g g e r y s l u r r y i s r e v e r s e d a s t h e d e g r e e o f a e r o b i ct r e a t m e n t i n c r e a s e s . T h i s i s d ue t o a r e s i d u a l of o r g a n i ca c i d s w h i c h a r e n o t o x i d i s e d i n t h e s u p e r n a t a n t BODe t e s ta n d a l s o d o n o t h a v e a n o f f e n s i v e o d o u r . A s t h es u p e r n a t a n t BOD5 t e n d s t o w a r d z e r o t h e TOA c o n c e n t r a t i o nt e n d s t o w a r d 0 . 2 1 6 g / 1 .

T h e d a t a w e r e a n a l y s e d b y r e g r e s s i o n a n a l y s i s , f o r

s u p e r n a t a n t BOD5 c o n c e n t r a t i o n w i t h TOA c o n c e n t r a t i o n o f t h es a m p l e s o f ra w a n d t r e a t e d s l u r r y . T h e r e w a s a v e r y h i g h l ys i g n f i c a n t (p = 0 . 0 0 1 ) l i n e a r r e l a t i o n s h i p b e t w e e ns u p e r n a t a n t BOD5 a nd TOA ( F i g u r e 6 ) . T he r e g r e s s i o ne q u a t i o n f o r s u p e r n a t a n t BOD5 w i t h T O A ( E q u a t i o n 4 )d e v e l o p e d f ro m 70 s a m p l e s h ad a c o r r e l a t i o n c o e f f i c i e n t o f0 . 9 7 .

TOA = 0 . 6 31 S u pe r n a t a n t BOD5 + 0.216 (4)

B o th TOA a n d s u p e r n a t a n t BOD? c o n c e n t r a t i o n s a r e e x p r e s s e d

a s g / 1 . T he m ean v a r i a n c e o f t h e TOA c o n c e n t r a t i o n f ro mt h e r e g r e s s i o n l i n e i s 0 .2 08 a nd t h e s t a n d a r d e r r o r o f t h es l o p e 0 . 0 2 0 .

DISCUSSION

S u p e r n a t a n t B O D5 o f p i g g e r y s l u r r y f u l f i l l s m o s t o f t h ec r i t e r i a n o t e d b y S p o e l s t r a ( 2 1 ) , f o r a n o d o u r i n d i c a t o r . l tc an b e u s ed t o a s s e s s t h e e f f e c t i v e n e s s o f a e r o b i c t r e a t m e n tf o r o d o u r c o n t r o l ( 2 7 ) . T he a d v a n t a g e o f t h e s u p e r n a t a n t

BODr a s a n i n d i c a t o r o f o d o u r o f f e n s i v e n e s s i s t h a t i ti n c l u d e s a m e a s u r e o f m o s t , i f n o t a l l , o f t h e o r g a n i co d o r a n t s s u ch a s t h e v o l a t i l e f a t t y a c i d s , i n d o l e s , p h e n o l s ,m e r c a p t a n s e t c , a l t h o u g h t h e s e c om p ou nd s o n l y c o m p r i s e as m a l l p r o p o r t i o n o f t h e o x i d i s a b l e m a t e r i a l . T h e o t h e rc om p o un d s o x i d i s e d i n t h e BOD t e s t a r e r e a d i l y f e r m e n t a b l ea nd h e n c e m any a r e l i k e l y t o g i v e r i s e t o o d o r a n t s i na n a e r o b i c c o n d i t i o n s . T h e r e f o r e , t h e s u p e r n a t a n t BOD5p r o v i d e s a r e l i a b l e i n d i c a t o r o f b o t h t h e a c t u a l o d o u r



313

o f f e n s i v e n e s s of t h e s l u r r y and i t s p o t e n t i a l t o i n c r e a s e i nodour nu i sance dur ing s to rage (Equa t ion 2 ) .

T he u se o f t h e BOD5 t e s t t o p ro v id e an i n d i c a t o r o f t h ep o t e n t i a l o do ur o f f e n s i v e n e s s o f a s l u r r y i s s u b j e c t t os i m il a r prob lem s as tho se en co un tere d when th e BOD5 i s useda s an i n d i c a t o r of w a t e r p o l l u t i o n . The t e s t r e q u i r e s 5d ay s i n c u b a t i o n . T he r e p r o d u c i b i l i t y d ep en ds on a c o n s i s t e n tr e s p i r a t i o n r a t e w i t h a g iv e n m i x t u r e of s u b s t r a t e s , d e s p i t ea v a r i a t i o n in t h e v a r i e t y of s p e c i e s , t h e i r r e l a t i v ep r o p o r t i o n s and n um bers of a c t i v e m i c r o b i a l c e l l s p r e s e n t .The s u p e r n a t a n t BODc, h o w e v e r , i s l e s s s u b j e c t t o d i l u t i o ne r r o r s t h a n t h e BOD5 o f t h e w h o l e s u s p e n s i o n of s l u r r y .T h e s e p r o b l e m s o f a n a l y t i c a l e r r o r a r e l e s s e n e d b y t h el o g a r i t h m i c r e l a t i o n s h i p w i t h o do ur o f f e n s i v e n e s s . T h us ,o f f e n s i v e s l u r r i e s w i t h o do ur r a t i n g s a bo ve 2 .5 e x h i b i t as u p e r n a t a n t B O D5 i n t h e r a n g e o f 1 t o 8 g / 1 . W i th f a i n t l yof fe ns iv e s l u r r i e s ( ra t in g 2) the su pe rn a ta n t BOD5 i s about600 m g / 1 . T h i s v a l u e f a l l s t o b e l o w 50 m g / 1 a s t h eo f f en s iven es s f a l l s below 0 .5 .

T he TOA t e s t d e t e r m i n e s o r g a n i c a c i d s w h i c h a r e a m a j org r o u p of f e r m e n t a b l e c o m p o u n d s , many o f w h i c h a l s ocon t r i bu t e t o t he supe rna t an t BO D5. Thus , d es p i t e the mores p e c i f i c n a t u r e of t h e TOA d e t e r m i n a t i o n a nd t h a t i t d o e sno t i n c lu d e any m easu re of some o f t h e m os t o f f e n s iv eo d o r a n t s s uc h a s p h e n o l s , i n d o l e s , m e r c a p t a n s , e t c . , i ts t i l l p r o v i d e s a u s e f u l i n d i c a t o r of o do ur o f f e n s i v e n e s s .T he d i s a d v a n t a g e of a s l i g h t l y l e s s good c o r r e l a t i o n( E q u a t i o n 3 ) t h a n t h e s u p e r n a t a n t B O D5 c o r r e l a t i o n i scompensated by th e fa c t th a t th e TOA d et er m in at io n o ff e rs ad i s t i nc t advan tage o f speed , s i nce t he t e s t on ly t akes abou to ne h o u r . A few r e c a l c i t r a n t co m po un ds e . g . h u m ic a c i d s ,a r e a l s o m e a s u r e d i n t h e TOA d e t e r m i n a t i o n . T h u s , w hens l u r r y i s a e r a t e d t h e r e i s a r a p i d f a l l i n TOA s i m i l a r t ot h a t of t h e s u p e rn a t a n t BODc, bu t t h e r e i s a m in im umc o n c e n t r a t i o n o f a b o u t 0 .2 1 3 g / 1 TOA w h i c h r e m a i n sunox id i sed .T he re i s som e sugge s t i on t h a t t h i s va lue v a r i e sfrom f ar m t o f ar m ( 3 1 ) . N e v e r t h e l e s s , t h i s c l o s e

c o r re la t i o n between TOA and su pe rn at an t BOD5 co nc en tr a t io nm eans t h a t a s i m i l a r l y v e ry h i g h ly s i g n i f i c a n t c o r r e l a t i o ne x i s t s be tween TOA and odour o ff en si ve ne ss .

Specif ic odorants such as VFA, TIP or individual compoundsc an be u se d t o i n d i c a t e o d ou r o f f e n s i v e n e s s b u t t h e i rabsence does no t g ive any in fo rm a t ion abou t t he p o s s ib l i t y

of o t h e r o d o r a n t s b e i n g p r e s e n t . The o f f e n s i v e o d o u r s oft r e a te d s lu r r y , which d id no t co n ta in th e 6 VFA, 3 ph en ols ,2 indoles or ammonia, were due to compounds not determinedi n t h e s e e x p e r i m e n t s . T h e r e a r e a l a r g e n um b er of o t h e ro d o r a n t s c i t e d w i t h v e r y low t h r e s h o l d l e v e l s (28 & 29)w h ic h c o u l d b e r e s p o n s i b l e f o r t h i s o do ur o f f e n s i v e n e s s .S i n c e t h e o d ou r o f f e n s i v e n e s s t e s t i s so s u b j e c t i v e anyi n d i c a t o r m u st h ave a v e r y h i g h l y s i g n i f i c a n t r e l a t i o n s h i pin o rde r t o p rov ide a u se fu l i n d i ca to r o f o f f en s ive odour s .



314

The relationship of VFA and TIP concentrations with odouroffensiveness showed that at the lower offensiveness ratings

the concentrations were too scattered to provide sufficientreliable indicators of odour offensiveness. This was alsoshown by Williams (5).

REFERENCES

1 JONES, K.B.C. 1977 U.K. problems and Legislation relatingto odour control. Agriculture and Environment 3 (2,3)245-258.

2PEAKIN, F.H. 1979 Odours in agricultural practice,prevention and control. Agricultural Research Council,London.

3B AIN ES , S., McLARTY, R. & MI LL S, P. 1980 Odour inagriculture. The Scottish Agricultural Collegespublication No 57, May 1980.

4 BATTERSBY, S.A. Institute of Environmental Health OfficesAgricultural Odour Survey. April 1980 - March 1981.MAFF Farm Odour Group paper FOG/14 (unpublished).

5WILLIAMS, A.G. 1981 The biological control of odoursemanating from piggery slurry. PhD Thesis, University ofGlasgow, 1981.

6WIL LI AMS , A.G. 1984 Indicators of piggery slurry odouroffensiveness. Agricultural Wastes ^0_, 15-36.

7SKARP, S.U. 1975 Manure gases and air currents in livestock, housing. In managing livestock wastes. Proc 3rdIns. Symp. Livestock Wastes. Am. Soc. Agric. Engrs.,

St. Joseph, Michigan.8MANNEBECK , H. 1974 A practical portable method of odour

measurement in processing and management of Agriculturalwaste. Proceedings 1974 Cornell Agr. Waste ManagementConference 291-294. Rouchester, N.Y.

9K LARENBEEK , J.V. 1982 Odour measurements in Dutchagriculture; Reduction of odours in animal production.Presented at the meeting of FAO held at Department ofAnimal Hygiene, Hannover-D, May 11-12 1982.

10MONCRIEFF, R.W. 1967 The chemical senses p. 14 2, LeonardHill, London.

11DRAVNIEK S, A. & JAKE, F. 1980 Odour threshold measurementsby dynamic olfactometry; significant operational variables.J. Air Poll. Control Assoc. 30 (12) 1284-1289.



315

12 BEDBOROUGH , D.R. & TROTT, P.E. 1979 The sensorymeasurement of odours by dynamic dilution. Report NoLR 299 (AP) . Warren Springs Laboratories, Stevenage.

13 BARTH, C.L., HI LL , D.T. & POLKOWSK I, L.B. 1974 Correlatingodour intensity index and odorous components in storeddairy manure. Transactions of the American Society ofAgricultural Engineers 17(4), 742-4, 747.

14 SCHAEFER, J. 1977 Sampling, characterisation and analysisof malodours. Agriculture and Environment, 3(2,3),121-128.

15 SCHAEFER, J. 1980 Development of instrumental methods formeasuring odour levels in intensive livestock buildings.In: Effluents from Livestock (Gasser, J.K.R. (Ed.)).Applied Science Publishers, London pp 513-535.

16 KOWALEWSKY, H.H., SCHEV, R. & VETTER, H. 1980 Measurementof odour emissions and immissions. In: Effluents fromLivestock (Gasser, J.K.R. (Ed)), Applied SciencePublishers, London pp 609-626.

17 HARPER, R., BATESMITH, E.C. & LAND, D.G. 1968 Odourdescription and odour classification. J & A ChurchillLtd., London.

18 BELL, R.G. 1970 Fatty acid content as a measure of theodour potential of stored liquid poultry manure.Poultry Science, 4 9, 1126-9.

19 SOBEL, A.T. 1972 Olfactory measurement of animal manureodours. Transactions of the American Society ofAgricultural Engineers. 15(4), 696-699 and 703.

20 AMOORE, J.E., VENSTROM, D. & DAVIS , A.R. 1968 Measurementof specific anosmia perceptual and motor skills 26,143-164.

21 SPOELSTRA, S.F. (1980) Origin of objectionable odorouscomponents in piggery wastes and the possibility ofapplying indicator components for studying odourdevelopment. Agriculture and Environments( 3 ) , 241-260.

22 OWEN S, J.D., EVANS, M.R., THACKER, F.E., H ISSETT, R. &BAINES S. 1973 Aerobic treatment of piggery waste.

Water Research 7 1745-66.23 EVANS, M.R., HIS SETT, R., SMITH, M.P.W., THACKER, F.E. &

WI LL IAMS, A.G. (1980) Aerobic treatment of beef cattleand poultry waste compared with piggery waste. Agric.Wastes 2, 93-101.



316

24 APHA 1971 Standard methods for the examination of waterand waste water 13th Edition. American Public Health

Association Inc., New York.25 HISSETT, R., EVANS, M.R. & BAIN ES, S. 1975 The use of

respirometric methods for assessing the biodegradabilityof different components of agricultural wastes. Progressin Water Technology 7(2) 13-21.

26 MONTGOMERY, H.A.C., DYMOCK , J.F. & THOM, N.S. 1962 Therapid colourimetric determination of organic acids andtheir salts in sewage sludge liquor. Analyst 87 , 94 9-955.

27 BAIN ES, S. & EVAN S, M.R. 1985 Aeration and odour controlby heterotrophic and autotrophic aerobes. EEC/FAO,Silsoe, U.K. 15-19 April 1985.

28 SPOELSTRA, S.F. 1977 Simple phenols and indoles inanaerobically stored piggery wastes. Journal of theScience of Food and Agriculture 2j[, 415-4 23.

29 SPOELSTRA, S.F. 1979 Volatile fatty acids in anaerobicallystored piggery wastes. Netherlands Journal of

Agricultural Science 2_7, 60-66.

30 Her Majesty's Stationery Office 1981 Phenols in waters andeffluents.

31 Personal Communication with A.G. Williams, Farm BuildingsDivision, N.I.A.E., Silsoe, Bedford, U.K.



Odour offenslveness ratings

0 Inoffensive

1 Very faintly offensive

2 Faintly offensive

3 Definitely offensive

4 Strongly offensive

5 Very strongly offensive

317

TABLE I

The average concentrations of individual and total VFA and TIP in raw

piggery slurry.

VFA

Acetic acid

Propionic acid

Iso-butyric acid

Butyric acid

Iso-valeric acids

Valeric acid

Total VFA

0.761

0.209

0.023

0.116

0.061

0.042

1.212

(.243)

(.063)

(.017)

(.045)

(.028)

(.015)

(.319)

TIP

Phenol 0.006

p-cresol 0.049

p-ethyl phenol 0.010

Indole 0.002

Skatole 0.011

Total TIP 0.078

(.006)

(.054)

(.013)

(.002)

(.014)

(0.072)

concentration expressed as g

litre standard deviation in

brackets.



318

Fig. I Scatt er dia gra m and regr essi on line of supe rna tan t B00_ and

o d o u r o f f e n s i v e n e s s r a t i n g .

.02 .Oil

Super na ta nt BOD . g litr e

Fig. 2 Scatter diagr am and reg ress ion line of TOA and odou r

of fensi vene ss rat ing.

TOA g litre



319

F i g 3 S c a t t e r d i a g r a m of UFA and o d o u r o f f e n s i v e n e s s r a t i n g .

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320

Fig. 5 Sc a t t e r d i a g r a m a n d r egr ession line o f s u p e r n a t a n t B 0 D _ a n d TOA

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S u p e r n a t a n t B0D_ g l i t r e



321

DU ST IN LIV ESTO CK B U ILD INGS AS A CARRI ER OF O D O U RS

J. HARTUNGI n s t i t u t e f o r A n i m a l H y g i e n e o f t h e H a n n o v e r Sc h o o l

of V e t e r i n a r y M e d i c i n e , B u n t e w e g 1 7 p , 3 0 0 0 H a n n o v e r 7 1 , FRG

S u m m a r y

T h e d u s t o f a n i m a l h o u s e s o r i g i n( 8 0 - 9 0 % ) , t h e b e d d i n g m a t e r i a l ,

a n i m a l s ( 2 - 1 2 % ) t h e m s e l v e s . It co r g a n i c m a t t e r . Th e f a c t o r s d e t ein c o n f i n e m e n t s i n c l u d e a n i m a l aa t i v e h u m i d i t y , v e n t i l a t i o n r a t ev o l u m e t r i c a i r - s p a c e pe r a n i m a l ,t u r e o f t h e f e e d . T h i s d u s t o r i gs o u r c e s c a n c a r r y g a s e s , v a p o u r so f d u s t - b o r n e t r a c e g a s e s is us ut r a c t i o n f o l l o w e d by g a s c h r o m a tp o u n d s b e l o n g i n g t o d i f f e r e n t c hd e n t i f i e d i n t h e d u s t f r o m a n i m a

a c i d s a nd p h e n o l i c / i n d o l i c c o m p ot r i b u t e m o s t l y t o t h e s t r o n g , tyh o u s e s . M a i n c o m p o n e n t s i n t h e s ea nd p - c r e s o l , r e s p e c t i v e l y . In tq u a l i t a t i v e l y a nd q u a n t i t a t i v e l yf a t t y a c i d s a n d p h e n o l s a r e f o u nt h e s l u r r y . O n e m 3 o f t h e e x h a u sf a t t e n i n g u n i t c a n c o n t a i n d u s t -f a t t y a c i d s a n d 2 . 7 6 p g p h e n o l i cc o n c e n t r a t i o n o f o d o u r s on t h e dm u c h g r e a t e r t h a n i n a n e q u a l v od u s t f r o m t h e e x h a u s t a i r c a n r ef r o m a n i m a l h o u s e s u p t o 6 5 % . And u s t - b o r n e o d o u r e m i s s i o n is t oi n t h e a n i m a l h o u s e b y w e t f e e d is h o w e r i ng .

a t e s m a i n l yt h e m a n u r e (

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1. INTRODUCTION

D u st in a n i m a l h o u s e s is an a t m o s p h e r i c c o n t a m i n a n t o ft h e e n v i r o n m e n t o f t h e a n i m a l s ( 1 ) . It i s a n i m p o r t a n t c a r r i e ro f m i c r o o r g a n i s m s ( 2 ) , ( 3 ) , ( 4 ) , a nd ca n i n f l u e n c e t h e p e r f o r m a n c e a nd h e a l t h o f a n i m a l ( 5 ) , ( 6 ) , ( 7 ) , a n d m a n ( 8 ) , ( 9 ) , ( 1 0 ) .In a d d i t i o n t h e d u s t of a n i m a l h o u s e s w a s s u p p o s e d t o p l a y a ne s s e n t i a l r o l e in t h e t r a n s p o r t o f t r a c e g a s a nd o d o u r i n s i d ea nd in s p r e a d i n g o f o d o r o u s g a s e s o u t s i d e of t h e a n i m a l h o u s e( 1 1 ) , ( 1 2 ) , ( 1 3 ) , ( 1 4 ) .

Th i s p a p e r r e p o r t s on t h e a s p e c t s of d u s t f o r m a t i o n inl i v e s t o c k b u i l d i n g s , t h e m a t e r i a l c o m p o s i t i o n o f t h e d u s t , t h e



322

e m i s s i o n o f d u s t - b o r n e o d o u r a n t s l i ke v o l a t i l e f a t t y a c i d s( V F A ) a n d s i m p l e p h e n o l s a n d i n d o l e s f r o m p i g g e r i e s , t h e i m p o r

t a n c e o f p a r t i c l e - b o r n e o d o u r s , a n d t h e p o s s i b i l i t i e s o f c o n t r o l l i n g d u s t - b o r n e o d o u r s .

2 . O RIG IN, NATU RE AND RELEASE OF THE D USTIt i~i e s t i m a t e d t h a t t h e d u s t Tn a n i m a l h o u s e s o r i g i n a t e s

m a i n l y f r o m t h e f e e d ( 1 5 ) , ( 1 6 ) , ( 1 7 ) , t h e b e d d i n g m a t e r i a l ( 1 8 ) ,( 1 9 ) , t h e m a n u r e ( 2 0 ) a nd t h e a n i m a l s t h e m s e l v e s ( 2 1 ) , ( 2 2 ) .R e l e v a n t v a l u e s a r e r a r e . T a b l e I s h o w s t h a t f e e d a n d b e d d i n g ,w h e n u s e d , a r e t h e p r e d o m i n a n t s o u r c e s of d u s t in p i g a n d h e nh o u s e s .

D u s t f r o m a n i m a l h o u s e s c on s i s t s m a i n l y of o r g a n i c m a t t e r

( 2 3 ) . Th e p r e f e r r e d t e c h n i q u e f o r i n v e s t i g a t i n g b o t h t h e m a t e r i a l c o m p o s i t i o n o f t h e d u s t a n d f e e d s t u f f is t h e WEEND ER Ana l y s i s T e c h n i q u e ( 2 4 ) . T a b l e II s h o w s t h e c o m p o s i t i o n o f d u s tf r o m p ig a n d h e n h o u s e s c o m p a r e d t o t h e f e e d f e d . T he d i f f e r e n c e s i n t h e p r o t e i n c o n t e n t b e t w e e n d u s t a n d f e e d s u p p o r t t h eo p i n i o n t h a t a n i m p o r t a n t p a r t o f t h e d u s t o r i g i n a t e s f r o mf e a t h e r s , h a i r s , a n d s k in c e l l s of t h e a n i m a l s .

T h e r e l e a s e o f t h e d u s t is c a u s e d b y t h e a c t i v i t y o f a n i m a l s or m a n or t h e f u n c t i o n o f t e c h n i c a l e q u i p m e n t s in t h e a n i ma l h o u s e . F e e d i n g , p a r t i c u l a r l y d r y f e e d i n g ( 2 5 ) , a s w e ll a sb e d d i n g a nd c l e a n i n g a c t i v i t i e s , t h e u s e o f d i f f e r e n t s y s t e m s

o f f e e d d i s t r i b u t i o n , m a n u r e r e m o v a l a n d v e n t i l a t i o n ( 2 6 ) c a ni n c r e a s e t h e d u s t l e v e l i n t h e a i r o f a n i m a l h o u s e s c o n s i d e r a b l y ( 2 7 ) . F i g u r e 1 g i v e s an e x a m p l e o f t h e r e l a t i o n b e t w e e nt h e a m o u n t o f d u s t in t h e a i r a nd d i f f e r e n t a c t i v i t i e s b a s e do n v a l u e s a s r e p o r t e d b y CERMAK a n d ROSS ( 2 7 ) f o r p o u l t r yh o u s e s .

In t h e c o u r s e o f a d a y t h e d u s t l e v e l i n a n i m a l h o u s e sv a r i e s c o n s i d e r a b l y . M o s t l y f e e d i n g i n c r e a s e s t h e d u st c o n c e n t r a t i o n i n t h e a i r a s d e m o n s t r a t e d in F i g u r e 2 ( 2 2 ) . H o w e v e r ,w i t h i n 3 0 t o 1 2 0 m i n t h e " n o r m a l " b a c k g r o u n d l e v e l is r e a c h e da g a i n ( 1 6 ) , ( 2 2 ) . T h e f i g u r e s h o w s t h a t e v e n b e f o r e t h e f e e d i s

d i s t r i b u t e d , t h e a c t i v i t y of t h e a n i m a l s i n c r e a s e s t he d u s tc o n c e n t r a t i o n in t h e a ir c o n s i d e r a b l y .

T a b l e III s h o w s t h e i n f l u e n c e o f r e l . h u m i d i t y , p e n v o l u m e , f e e d i n g s y s t e m a n d a i r f l o w o n t h e n u m b e r o f d u s t p a r t i c l e s a n d w e i g h t o f s e t t l e d d u s t in a n e x p e r i m e n t a l p i g g e r y . T h ee s s e n t i a l i n f l u e n c e o f a n i m a l a c t i v i t y o n t h e f o r m a t i o n o f dusti s s h o w n by t h e f a c t t h a t s e l f - f e e d i n g r e s u l t s in s i g n i f i c a n t ly g r e a t e r a t m o s p h e r i c d u s t c o n c e n t r a t i o n ( p a r t i c l e s / v o l u m e ofa i r ) t h a n d o e s f l o o r - f e e d i n g . H o w e v e r , a s i g n i f i c a n t l y g r e a t e ra m o u n t of s e t t l e d d u s t i s a s s o c i a t e d w i t h f l o o r f e e d i n g . P r o b a b l y , t h e s e l f - f e d p i g s s p e n d m u c h m o r e t i m e e a t i n g t h a n t h e

f l o o r - f e d p i g s . T h e i n t e n s e a c t i v i t y o f t h e p i g s d u r i n g f l o o rf e e d i n g r e s u l t s i n a g r e a t d ea l o f v i s i b l e d u s t f o r o n l y a p e r i o d o f t i m e , w h i l e t h e s e l f - f e d p i g s m a y p l a y w i t h t h e e x c e s sf e e d ( 2 8 ) , ( 1 7 ) . T h e s e s t u d i e s i n d i c a t e t h a t t h e f a c t o r s d e t e r m i n i n g t h e a m o u n t of d u s t in c o n f i n e m e n t s i n c l u d e a n i m a l a c t i v i t y , t e m p e r a t u r e , r e l a t i v e h u m i d i t y , v e n t i l a t i o n r a t e , s t o c k i ng d e n s i t y a nd v o l u m e t r i c a i r - s p a c e p e r a n i m a l , f e e d i n g m et hod ,a n d n a t u r e o f f e e d . T h i s d u s t o r i g i n a t i n g f r o m v a r i o u s s o u r c e sc a n c a r r y g a s e s , v a p o u r s a nd o d o u r s ( 7 ) .



3 2 3

3 . D U S T - B O R N E T R A C E G A S E S A N D O D O R A N T ST h e a n a l y s i s o f d u s t - b o r n e t r a c e g a s e s r e q u i r e s t h e i r 1 -

s o l a t i o n f r o m t h e d u s t p a r t i c l e s . P r o c e d u r e s f o r t h e i s o l a t i o n

a n d c h a r a c t e r i z a t i o n o f t r a c e g a s e s a n d o d o r a n t s i n t h e d u s tf r o m p i g h o u s e s a r e g i v e n b y S C H A E F E R e t a l . ( 2 9 ) , H A M M O N D e ta l . ( 3 0 ) a n d T R A V I S a n d E L L I O T T ( 3 1 ) . A l c o h o l i c s o l v e n t s w e r ef o u n d t o b e e f f e c t i v e f o r t h e e x t r a c t i o n o f v o l a t i l e f a t t y a c i d s a n d p h e n o l s f r o m t h e d u s t o f h e n ( 3 2 ) a n d p i g h o u s e s ( 3 3 ) ,( 3 4 ) . T o d a y , g a s c h r o m a t o g r a p h y i s u s u a l l y u s e d f o r t h e s e p a r a t i o n a n d i d e n t i f i c a t i o n o f t h e t r a c e g a s e s . T a b l e l V g i v e s al i t e r a t u r e r e v i e w o f c o m p o u n d s i d e n t i f i e d i n t h e d u s t o f p i gh o u s e s . T h e r e a r e o n l y v e r y f e w r e p o r t s o n i n v e s t i g a t i o n s o nt h e d u s t f r o m h e n h o u s e s ( 3 2 ) .

M o s t o f t h e o d o u r s c o m i n g f r o m l i v e s t o c k p r o d u c t i o n u n i t s

a r e a s s o c i a t e d w i t h t h e b i o l o g i c a l d e g r a d a t i o n o f t h e a n i m a lw a s t e s ( 3 5 ) , t h e f e e d a n d t h e b o d y o d o u r o f t h e a n i m a l s ( 1 ) .V o l a t i l e f a t t y a c i d s a n d p h e n o l i c c o m p o u n d s w e r e f o u n d t o c o n t r i b u t e m o s t l y t o t h e s t r o n g , t y p i c a l o d o u r o f a n i m a l h o u s e sb y t h e h e l p o f s e n s o r y e v a l u a t i o n s p a r a l l e l t o t h e c h e m i c a la n a l y s i s ( 2 9 ) , ( 3 0 ) .

T a b l e V g i v e s q u a n t i t a t i v e v a l u e s o f v o l a t i l e f a t t y a c i d sa n d p h e n o l i c / i n d o l i c c o m p o u n d s f o u n d i n t h e a e r o s o l p h a s e a n di n s e t t l e d d u s t o f p i g g e r i e s , r e s p e c t i v e l y . T h e r e s u l t s f r o mt h e a e r o s o l p h a s e c o i n c i d e , p a r t i c u l a r l y a s f a r a s a c e t i c a c i di s c o n c e r n e d . F o r t h e i n v e s t i g a t i o n s o f t h e s e t t l e d d u s t t h e

c o e f f i c i e n t s o f v a r i a t i o n ( C V ) a n d t h e r e l a t i v e v a l u e s { % )c h a r a c t e r i z i n g t h e p e r c e n t a g e o f t h e s i n g l e c o m p o u n d s a s p a r to f t h e t o t a l a m o u n t a r e q u o t e d . T h e v a l u e s a r e c o r r e c t e d w i t ht h e d r y m a t t e r c o n t e n t o f t h e d u s t . M a i n c o m p o n e n t s a r e a c e t i ca c i d a n d p - c r e s o l , r e s p e c t i v e l y .

T a b l e V I c o m p a r e s r e s u l t s f r o m a i r , d u s t a n d s l u r r y i n v e s t i g a t i o n s o n V F A a n d p h e n o l i c / i n d o l i c c o m p o u n d s i n p i g g e r i e s .R e l a t i v e v a l u e s a r e u s e d . W h e n c o m p a r i n g t h e r e s u l t s d e r i v e df r o m i n v e s t i g a t i o n s o n d u s t , a i r o r s l u r r y i t i s n e c e s s a r y t ou s e r e l a t i v e v a l u e s b e c a u s e o f t h e d i f f e r e n t d i m e n s i o n s , f o re x p e r i e n c e s h o w s t h a t i n s p i t e o f l a r g e q u a n t i t a t i v e d i f f e r

e n c e s b e t w e e n t w o s a m p l e s w i t h i n t h e g r o u p o f c a r b o x y l i c a c i d sa n d w i t h i n t h e g r o u p o f p h e n o l i c / i n d o l i c c o m p o u n d s t h e p r o p o r t i o n s o f t h e c o m p o n e n t s r e m a i n r a t h e r s t a b l e ( 3 6 ) . I n t h eg r o u p o f V F A a c e t i c a c i d i s t h e m a i n c o m p o n e n t i n a i r , d u s t ,a n d s l u r r y f o l l o w e d b y p r o p i o n i c a n d b u t y r i c a c i d . T h e o t h e rt h r e e a c i d s a m o u n t t o l e s s t h a n 2 5 % . I n t h e g r o u p o f p h e n o l s /i n d o l e s p - c r e s o l i s t h e m a i n c o m p o n e n t i n t h e f o u r c i t e d i n v e s t i g a t i o n s . H o w e v e r , i t s e e m s t h a t s t r a w b e d d i n g c a n r e d u c et h e p - c r e s o l c o n t e n t ; i n t h i s c a s e p h e n o l i s t h e m a i n c o m p o n e n t , i n s t e a d ( 3 7 ) .

4 . E M I S S I O N O F D U S T - B O R N E V F A A N D P H E N O L S / I N D O L E S F R O M P I G G E R I E ST h e i n v e s t i g a t i o n s o f d u s t f r o m p i g g e r i e s s h o w t h a t b o t h

V F A a n d p h e n o l s / i n d o l e s a r e p r e s e n t i n a c o n s i d e r a b l e a m o u n t .H o w e v e r , c o m p a r e d t o t h e a i r - b o r n e e m i s s i o n s c a l c u l a t e d o n t h eb a s e o f t h e r e s u l t s o f L O G T E N B E R G a n d S T O R K ( 3 8 ) l e s s t h a n t h et e n t h p a r t ( 1 / 1 0 ) o f p h e n o l s / i n d o l e s a n d a b o u t t h e h u n d r e d t hp a r t ( 1 / 1 0 0 ) o f V F A a r e e m i t t e d b y t h e d u s t , o n l y . T a b l e V I Ic o m p a r e s t h e d u s t - b o r n e a n d a i r - b o r n e e m i s s i o n s o f V F A a n d



3 2 4

p h e n o l s f r o m p i g g e r i e s . T h e t o t a l a m o u n t s a r e g i v e n i n a d d i t i o nt o t h e a m o u n t s o f b u t y r i c a c i d a n d p - c r e s o l w h i c h a r e b o t hk n o w n a s i n t e n s i v e l y s m e l l i n g c o m p o u n d s . T h e r e c o g n i t i o n o d o u rt h r e s h o l d v a l u e s o f t h e s e t w o c o m p o n e n t s a r e i n c l u d e d , a s w e l l .U n d e r t h e a s s u m p t i o n o f a d u s t c o n c e n t r a t i o n o f 1 0 m g / m 3 ( 7 )o n e c u b i c m e t e r o f a i r f r o m a p i g h o u s e c o n t a i n s 6 . 2 7 u g d u s t -b o r n e V F A a n d 2 . 7 6 u g d u s t - b o r n e p h e n o l i c / i n d o l i c c o m p o u n d s ;6 2 . 7 m g V F A a n d 2 7 . 6 m g p h e n o l i c / i n d o l i c c o m p o u n d s a r e e m i t t e d f r o m a 5 0 0p i g f a t t e n i n g u n i t p e r h o u r a t a m e d i u m v e n t i l a t i o n r a t e o f 2 0 m 3 / 7 0 k g p i g - h .

W h e n c o m p a r i n g t h e d u s t - b o r n e c o n c e n t r a t i o n s o f b u t y r i ca c i d a n d p - c r e s o l w i t h t h e o d o u r t h r e s h o l d s i t s e e m s t h a t t h ec o n c e n t r a t i o n s a r e t o o s m a l l t o b e r e l e v a n t f o r a n o d o u r n u i s a n c e . H o w e v e r , i f t h e d u s t i s r e m o v e d f r o m t h e g a s p h a s e o ft h e a i r f r o m a n i m a l h o u s e s t h e o d o u r d i s a p p e a r s ( 3 9 ) , ( 4 0 ) , ( 1 4 ) .T h i s s u p p o r t s t h e o p i n i o n o f H A M M O N D e t a l . ( 4 0 ) t h a t t h e o d o ri s c o n c e n t r a t e d o n t h e d u s t p a r t i c l e s . T h e a u t h o r s c o n c l u d ef r o m t h e i r d a t a t h a t t h e c o n c e n t r a t i o n , o f t h e t w o o d o r a n t s b u t y r i c a c i d a n d p - c r e s o l i s a b o u t 4 • 1 0 g r e a t e r o n a n a e r o s o lp a r t i c l e t h a n i t i s i n a n e q u a l v o l u m e o f a i r . T h u s , a n a e r o s o l p a r t i c l e d e p o s i t e d o n t h e o l f a c t o r y o r g a n c a r r i e s o d o u re q u i v a l e n t t o a m u c h g r e a t e r v o l u m e o f a i r ( 4 0 ) . T h e s e c o n s i d e r a t i o n s i n d i c a t e t h a t d u s t f r o m a n i m a l h o u s e s s h o u l d b e t a k e ni n t o a c c o u n t i n c o n n e c t i o n w i t h o d o u r e m i s s i o n / i m m i s s i o n m e a s u r e m e n t s n o t o n l y b y c h e m i c a l a n a l y s i s b u t b y s e n s o r y e v a l u a t i o n s u s i n g o l f a c t o m e t e r s w i t h o u t d u s t f i 1 t e r s , a s w e l l .

5 . C O N T R O L O F D U S T - B O R N E O D O U R ST h e r e a r e b a s i c a l l y t w o w a y s o f c o n t r o l l i n g d u s t - b o r n e

o d o u r s . A n e f f e c t i v e w a y s e e m s t o b e t h e f i l t r a t i o n o f t h e a i rt o r e m o v e t h e d u s t ( 4 1 ) . V A N G E E L E N ( 1 4 ) r e p o r t s o n t h e r e d u c t i o n o f t h e o d o u r e m i s s i o n f r o m a b r o i l e r h o u s e w i t h 1 5 . 0 0 0a n i m a l s o f 6 5 % b y m e a n s o f f i l t e r b a g s w h e n f i l t e r i n g t h e e x h a u s t a i r . H o w e v e r , t h e i n v e s t m e n t s a n d r u n n i n g c o s t s a m o u n t e dt o a b o u t D M 4 . 0 0 p e r 1 0 0 b i r d s p e r y e a r .

T h e s e c o n d w a y i s t o a v o i d t h e d u s t r e l e a s e i n t h e a n i m a l

h o u s e a s f a r a s p o s s i b l e . T h e f o l l o w i n g p o s s i b i l i t i e s a r er e c o m m e n d e d :- f e e d i n g i n t e r v a l s , n o s e l f - f e e d i n g ( 1 7 )- p e l l e t s i n s t e a d o f m e a l f e e d- w e t f e e d i n g i n s t e a d o f d r y f e e d i n g ( 2 5 )- v a c u u m c l e a n i n g , f o g g i n g a n d s h o w e r i n g ( 2 2 )

A r e d u c t i o n o f t h e d u s t c o n t e n t i n t h e a i r o f a n i m a l c o n f i n e m e n t s b a r e n o t o n l y t h e c h a n c e t o d i m i n i s h t h e o d o u r e m i s s i o n f r o m t h e a n i m a l h o u s e s b u t c a n h a v e a p o s i t i v e i n f l u e n c eo n t h e a n i m a l s ' h e a l t h a n d p e r f o r m a n c e , a s w e l l .

A c k n o w l e d g e m e n tT h e a u t h o r w a n t s t o e x p r e s s h i s t h a n k s t o D r . W . H e i d m a n n , C h e m -m i c a l I n s t i t u t e f o r h i s h e l p i n p r e p a r i n g T a b l e I V , D r . G . K l i n k -m a n n f o r r e v i s i n g t h e E n g l i s h t e x t , M r . K . H . L i n k e r t f o r d o i n gt h e d r a w i n g , a n d M r s . U . A r z t f o r t y p i n g t h e m a n u s c r i p t .



325

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HONEY, L.F. and J.B. McQUITTY (1976). Dust in the animal environment.

Research Bulletin 76-2, 1-66.ACKEMANN, H.H. (1980). Quant itat ive Untersuc hungen liber den bakt eri -ellen Keimgehalt des Absetzstaubes in zwei Schweinemaststallen. DtschTierarztl. Wschr. 87 , 335-338.LANGE, A., G. MEHLWRN, W. METHLING and V. NEUPARTH (1983). Dynamikder bakter iellen Kontam ination des Staubes in Abferkelstall en. In:5. Int. Leipziger Tierhyg. Symp., Leipzig, Sammelbd. d. Vortr. S.137-142.HILLIGER, H.G. (1984). Zur Bilanzierung der Bakterienflora in derStalluft. Zbl. Vet. Med. B,31, 493-504.MARTIN, H. and R.A. WILLOUGHEY (1972). Organic dust, sulfur dioxide,

and the respirat ory tract of swine . Arch . Envir on. Health 2 5, 158-165.OWEN, J.E. (1982a). Dust - the problem and pos sibi liti es. Farm Bldg.Progress 67, 3-6.CURTIS, ETC. (1983). Environmental mana gement in animal agri culture.Iowa State Unive rsity Press, Ames , Iowa.PEPYS, I., P.A. IEMKINS, G.M. FESTENSTEIN, P.H. GREGORY, M.E. LASEYand F.A. SKINNER (1963). Farmer's lung: Thermophilic actinomycetes asa source of "farmer's lung hay" antigen. Lancet, 607-611.BiiTIKOFFER, E. and A.L. de K ECK (1969) .Hlihnerzuchterlunge. Dtsch.med. Wochenschr. 94, 2627-2631.KOSTERS, J. (19 8177 Stallsta ub kann gefa'hrlich w er de n. DGS 33 , 29 2-293.DAY, D.L., W .L. HENSEN and S. ANDERSON (1965). Gases and odors inconfinement buildings. Trans. ASAE 8, 118-121.BURNETT, W.E. (1969). Odor transport by particulate matter in highdensity poultry houses. Poultry Sci. 48, 182-185.WEURMAN, C. (1975). Verg leich zweier Met hod en flir die Messung von Ge-ruchen. VDI-Bericht 226, 135-139. VDI-Verlag GmbH Dusseldorf.VAN GEELEN, M. (198377~Stankproblemen bij slachtkuikenhok zijn even-tueel op te lossen. Pluimveehouderij 13, 12-13.

CURTIS, S.E., J.G. DRUMMOND, D.J. GRURUOH, P.B. LYNCH and A.H. JENSEN(1975). Relative and quantitative aspects of aerial bacteria and dustin swine house s. J. Animal Sci. 41, 1512-1520.BRESK, B. and J. STOLPE (1975). Eer EinfluB des Staubes in industrie-maBigen Schweineproduktionsanlagen auf die Leistung und Gesundheitder Tiere. Monatsh. Veterinarmed. 30, 572-576.HONEY, L.F. and J.B. McQUITTY (197 97. Some physical fac tor s af fecting dust concentrations in a pig facility. Can. Agric. Engineering21, 9-13.EOlLO, C.A. et al. (1969). Dust production of poultry litter materials. Auburn Un iv. Agr. Exp. Sta. Cir c. 169.

MATTHES, H. (1979). Art und Zusammensetzung der Luftverunreinigungenin der Nutztierhaltung und ihre Wirkung in der Stallumgebung. Dtsch.Tierarztl. Wochenschr. 86, 262-265.MAN, C..L. CERNEA and T. BUHATEL (1971). Examenal calitativ pulberi-lor din aerul adapstur ilor pentru pa sa ri . Lucrari stiinti fice, seriamedicina veterinar a 27 , 321-329.KOON, J., J.R. HOWESTW. GRUB and C.A. ROLLO (1963). Poultry dust:Origin and com position. Agr. Eng. 44, 608-609.



326

(22 ) NILSSON, C. (1982). Dust investigations in pig houses. Swedish University of Agricultural Sciences, Department of Farm Build ings, Di-

vison of Farm Building Constructions, Lund. Rapport 25, pp 93.(23 ) HILLIGER, H.G. (1966). Grav imetrische Stau bm es su ng en Tn Sta'llen. Zbl.

Vet. Med. B, 13, 698-708.(24) PALOHEIMO, L . T 1 9 6 9 ) . Weend er Anal ys e. In: W. LEMKEIT, K. BREIREM

and E. GRASSMANN (Hrsg.). Handbuch der Tierernahrung, Bd. 1, S.164-171, Verlag Parey, Berlin, Hamburg.

(25) H ELEN, M. (1984). Einige Ursachen fur die Variationen der Staubkon-zentrati on im Mast schw eine sta ll. In: Symposium der International enGesellschaft fur Tierhygiene, Hrsg.: Deutsche VeterinarmedizinischeGesellschaft, 28-30.

(26) NAKAUE, H.S., J.K. KOELLIKER, D.R. BUHLER and G.H. ARSCOTT (1981).

Distribution of inorganic elements in poultry house dust. PoultrySci. 60, 1386-1391.

(27 ) CERMAK, J.P. and P.A. ROSS (1978). Airborne dust concentrations associated with animal housing ta sks . Farm Buildg . Progr. 51^, 11-1 5.

(28) BUNDY, D.S. and E.T. HAZEN (1975). Dust levels in swine confinementsystems associated with different feeding met hods . Tra ns. Amer. Soc.Agric. Eng. 18, 137-139.

(29 ) SCHAEFER, J., J.M.H. BEMELMANS and M. C. Ten NOEVER DE BRAUW (1974).Onderzoek naar de voor de stank van varkensmesterijen verantwoordi-lijke componenten. Landbouwkund. Tijdschr., pt 86-9, 228-232.

(30) HAMMOND, E.G., C. FEDLER and G. JUNK (1979). Identification of dust-

borne odor s in swine con finement fa cil iti es. Tran s. ASAE 22, No. 5,1186-1189 & 1192.

(31) TRAVIS, T.A. and L.F. ELLIOTT (1977). Quantitation of indole andscatole in a housed swine unit. J. Env iro n. Qual . 6, 407-41 0.

(32) HARTUNG, J. (1983). Spurengase im Huhnerstall staub. In: 15. Kongressd. Dtsch. Veterinar med. Ges., Bad Nauheim, Ber. S.246-250 (Fortschr.Veterinarmed. 37 ).

(33) AENGST, C. (1984). Zur Zusammensetzung des Staubes in einem Schweine-maststall. Hannover, Tierarztl. Hochsch., Diss.

(34) HARTUNG, J. (1985). Gas chromatogra phic investigations of swinehouse dust on odorous compounds. Environmental Technology Letters 6,21-30.

(35) SPOELSTRA, S.F. (1978). Microbial aspects of the formation of mal odorous compounds in anaerobically stored piggery was tes. Wagenin gen,Landbouwho geschool, Diss., pp. 91.

(36) SCHAEFER, J. (1977). Sampling, chara cterization and analysis of ma l-odours. Agric. Environm. 3, 121-127.

(37) HARTUNG, J. and E. ROKICKT (1984). Zum Vorkommen phenolartiger Ver-bindungen im Staub von Schweine- und Huhne rsta ll. Zbl. Bakt. Hyg.,I. Abt. Orig. B , 179, 431 -43 9.

(38) LOGTENBERG, M.Th . and B. STORK (1976). Het ontwikkelen van meetm e-

thoden voor het bepalen van de stank van ventilatielucht van mest-va rke nssta llen.Rapp ort de Centraal Technisch Instituut TNO, Zeist/Holland. Ref.no: 76-06 054, Dossier: 01-4-40130.

(39) WILLSON, G.B. (1971). Control of odours from poultry hous es. ASAESymp. Livestock Waste Ma nagement, Columbus/Ohio, 19.-22.4.1971.

(40 ) HAMMOND, E.G., C. FEDLER and R.J. SMITH (1981). Analysis of par ticle-borne swine house odou rs. Agri c. and Environment 6, 395-399.

(41) OWEN, J.E. (1982b). Dust - Filtration solution s and their cost . FarmBuilding Progress 6 8, 19-23.



3 2 7

( 4 2 ) C O R M A C K , D . , T . A . D O R L I N G a n d B . W . J . L Y N C H ( 1 9 7 4 ) . C o m p a r i s o n o ft e c h n i q u e s f o r o r g a n o l e p t i c o d o u r i n t e n s i t y a s s e s s m e n t . C h e m . I n d .( L o n d o n ) n o . 2 , 8 5 7 - 8 6 1 .

( 4 3 ) L E O N A R D O S , G . , D . K E N D A L L a nd N . B A R N A R D ( 1 9 6 9 ) . O d o r t h r e s h o l d d e t e r m i n a t i o n o f 5 3 o d o r a n t c h e m i c a l s . J . A i r P o l l . C o n t r . A s s o c . 1 9 ,9 1 - 9 5 . —

mg/m3

6 0 -

5 0 -

4 0 -

3 0 -

2 0 -

1 0 -

i

m

*

B

r h

c i

±

E

r +

F

F i g u r e 1 : A m o u n t s o f d u s t ( m g / m 3 ) i n t h e a i r o f p o u l t r yh o u s e s d u r i n g d i f f e r e n t a c t i v i t i e s f r o m C E R H A K

a nd R O S S ( 2 7 ) . A = b a c k g r o u n d d u s t l e v e l , B =m e a l f e e d i n g ( t r o l l e y ) , C = m e al f e e d i n g( h o p p e r s ) , D = e g g c o l l e c t i n g , E = m u c k r e m o v a l ( b e l t ) , F = c l e a n i n g o p e r a t i o n s .



328

♦

I ■ I ' I ■ I ■ I — ■ — I — ■— I-

1 0 12 I t 16 IB 1 0 22 K h

F i g u r e 2 : D u s t c o n c e n t r a t i o n ( m g / m3) , v e n t i l a t i o n r a t e ( m 3/

p i g h ) , t e m p e r a t u r e ( ° C ) , and r e l a t i v e h u m i d i t y (%) d u r i n g 24 h in a pig f a t t e n i n g h o u s e f r o m N I L S S O N ( 2 2 ) . The a r r o w s (f) i n d i c a t e t i m e of f e e d i n g .

T a b l e I: P r e d o m i n a n t s o u r c e s of the d u s t in pig and hen h o u s e s f r o m 1)= H O N E Y and M c Q U I T T Y ( 1 7 ) and 2 ) = MAN et a l . ( 2 0 ) . n . r . = not r e p o r t e d .

dust originating

from

feed

bedding

animals

manure

P i g "

without bedding

8 0 - 9 0

-

5 - 1 1

rtr.

h battery

80-90

-

4 - 1 2

2 - 8

e n2 1

bedding

nr.

55 - 68

2 - 1 2

2 - 8



329

T a b l e II : M a t e r i a l c o m p o s i t i o n o f d u s t a n d f e e d s t u f f f r o mp i g a n d h e n h o u s e s . R e s u l t s f r o m 1 ) = A E N G S T ( 3 3 ) ,

2 ) = H A R T U N G ( 3 4 ) , 3 ) = K O O N e t a l . ( 2 1 ) , 4 ) = H A R -T U N G ( 3 2 ) . n . r . = n o t r e p o r t e d .

c o m p o n e n t s

d r y m a t t e r

c rude pro te in

fa t

c r u d e f i b r e

a s h

pig hoi

d u s t "

7 .

87

24

4

3

15

jse (no

d u s t2'

87

24

5

5

n.r.

bedding)

feed1'

88

19

4

5

5

h e n h o u s e ( b a t t e r y )

d u s t3' d u s t * ' f e e d "

•/ . V. 7.

92

60

9

4

ar.

89

50

10

nr.

nr.

92

17

15

2

4

T a b l e I I I : N u m b e r o f p a r t i c l e s c o l l e c t e d b y t h e A n d e r s e nS a m p l e r a n d w e i g h t o f s e t t l e d d u s t i n a n e x p e r i m e n t a l p i g g e r y a t d i f f e r e n t c o n d i t i o n s f r o mH O N E Y a n d M c Q U I T T Y ( 1 7 )

t r e a t m e n t

r e l h u m i d i t y ( l o w )

r e l h u m i d i t y ( h i g h )

p e n v o l u m e 2 2 . 1 rr?

p e n v o l u m e 11.1 m3

f l o o r f e e d i n g

s e l f f e e d i n g

a i r f l o w 5 9 5 r r ? / ha i r f l o w 2 9 7 r r ? / h

a v e r a g e

number of part

par t i c le

7-16j jm

5 1 3 7 0

3 2 4 5 0

3 8 2 0 0

4 5 6 3 0

42 770

4 1 0 5 0

3 8 6 5 04 5 1 7 0

4 1 9 0 0

cles / 0.028 rn

> s ize

< 5 , u m

1 1 9 9 2 0

8 5 2 3 0

8 6 4 2 0

118 730

8 8 3 9 0

1 1 6 7 6 0

9 3 8 2 01 1 1 3 3 0

1 0 2 5 8 0

set t led dust

g/rrfday

1 3 4 2

10.03

12.38

11.08

15.85

7.62

12.0811.37

11.37



330

Table IV: Volatile compounds identified i n th e dust of swine confinementunits

Hydrocarbons

Hexane•i- P i nenLimonen3 , 7 , 7 - T r i m e t h y l -

b i c y c l o ( 3 , 1 , 1 ) -2-Hepten

BenzeneToluene

Alcoho ls

1-Pentanol

i-Heptanol

4 - Me t h y l c y c l o -hexanol

2-Ethylhexanol

Phenols

Phenolp-Cresol

o-Cresolp-Ethylphenol

o-Ethylphenol

m-Ethylphenol

Indoles

Indo leSkato le

Aldehydes

Butanal2-ButenalPentanal2-Pentenal

Hexanal

2-HexenalHeptanal2-Heptenal

2,4-HeptadienalNonanal2-Nonenal

2,4-NonadienalDecanal2,4-DecadienalBenzaldehyde

1)1)1)

1)

1)1)

1)1)

1)1)

1)3)6)3)4)6)1)3)6)4)4)

2)6)2)3)6)

4)4)4)4)1)3)4)

4)1)3)4)3)4)3)3)3)4)4)3)4)1)4)

Ketones

Ac

Mi

1)

2)3)

4)

5)

6)

AcetoneButanonePentanoneOctanonel-0ctene-3-one

id s

Ace t i cProp ion ici -Butyric

Bu t y r i ci -Valeric

Va l e r i cHexanoicHeptanoicOctanoicNonanoicDecanoicUndecanoicDodecanoicLaur ieTr idecano icTetradecanoicBenzoicPhenyl acet ic3-Phenylpropionic

Hydrocinnamic

scellaneous Compounds

2-Pentylfuran

V a n i l l i n

= WEURMAN (13)

= TRAVIS and ELLIOTT= HAMMOND e t a l . (3 0)

= HAMMOND e t a l . (4 0)

= AENGST (33)

= HARTUNG (34)

4)4)4)4)4)

4 )5 )6 )4)5)6)1)5)6)4)5)6)5)6)4)5)6)4)5)4)4)4)4)4)4)3)4)4)4)3)4)3)4)

3)3)

(31)



331

T able V : A m o un ts o f o d o u r o u s c o n s t i t u e n t s i n t h e a e r o s o l p h as e( u g / g ) and i n t h e s e t t l e d d u s t ( u g / g ) o f s w i n e h o u se

a i r f r o m 1) = HAMMOND et a l . (4 0 ), 2) = AENGST ( 3 3 ) , and 3) =HARTUNG ( 3 4 ) . - i n d i c a t e s n o t r e p o r t e d .

compounds

acetic acid

propionic acid

i so -bu ty r i c ac id

buty r ic ac idiso-valer ic ac id

valer ic acid

cap ro ic ac id

p h e n o lp- cresol

p-ethylphenol

o-ethylphenol

m-ethylphenol

indoleska to le

quant i tat i

i n ng / l

D

1838.5

-65

-21

--1.5

-1.7

0,2

--

re results

aeroso l

2)

159

1.60 4

0.603

0.2

0.2

-----

--

quantitat

i n j j g / g

3)

267U O

4 7

7 362

38

-92

1A5

13

--

1115

ve results

sett led dustCV

818282

80 5

A 22ASA

1073

-455

47.157.8

--

48843.8

relativevalues

426223

7.5

11.69.9

6.1

-333

52.64.7

--

405.4

Table V I : C o m p a ris o n o f r e s u l t s f ro m i n v e s t i g a t i o n s o f a i r , s l u r r y ,an d d u s t s am p l e s f r o m p i g g e r i e s as s t a t e d i n t h e l i t e r

a t u r e . 1 )= LOGTENBERG an d STORK ( 3 8 ) , 2 ) = SPOELSTRA ( 3 5 ) ,3 )= HAMMOND e t a l . ( 4 0 ) , 4 ) = HARTUNG (3 4 ). n .r .= not re p o rt e d .

c o mp o u n d s

acetic acid

propionic acidiso-butyric acid

butyric acidisovaleric acid

valeric acid

phenolp-cresol

p-ethylphenol

indoles k a t o l e

air1'

40.1

2157.6

221

45

3.8

312

662

ar.

1.21.4

a n a e r o b i c

s lu r ry

r e l a t i v e

582

23.93.4

7.73.4

3A

7.1

71.38.5

09122

dus t3 1

values 7.

51.7

24.1

ar.

ISAnr.

5£

n.r.

5 t t

a r.a r.ar.

d u s t "

426

223

7.5

11.4

9.9

6.1

333

526

47

40

54



332

T a b l e V I I : A m o u n t s o f v o l a t i l e f a t t y a c i d s a n d p h e n o l i c / i n d o l i cc o m p o u n d s e m i t t e d f r o m p i g g e r i e s by d u s t a n d a i r ,r e s p e c t i v e l y . T h e r e c o g n i t i o n o d o u r t h r e s h o l d s f o rb u t y r i c a c i d a n d p - c r e s o l a r e i n c l u d e d . 1 ) = H A R T U N G( 3 4 ) , 2 ) = L O G T E N B E R G a n d S T O R K ( 3 8 ) , 3 ) = C O R M A C K e ta l . ( 4 2 ) , 4 ) = L E O N A R D O S e t a l . ( 4 3 ) .

components

volatile fatty acids

tota l

butyric acids

phenolics / indolicstotalp-cresol

emitted

dust-borne air-borne

pglnf n pg/m

3

2)

627

0.73

2.761.45

613

220

3524

odourthreshold

pg/rr?

4 "

4A*>



333

DOST CONCENTRATIONS IN PIG BUILDINGSG.A. Carpe nter and L.J. Mouls ley

N a tiona l Institute of Agr icultur a l Engineer ing

SummaryThe o r i g i n s , c o n s t i t u e n t s , e f f e c t s and p o s s i b l e b e n e f i t s from t h er em o v al o f dus t i n l i v e s to c k b u i l d i ng s a r e g i v e n . R e duc t i o ns i n dus tm a s s , a i r b o r n e b a c t e r i a and p a r t i c l e c o u n t s o f a t l e a s t 50% w e r er e po r ted us i ng a f i l t e r s y s t e m i n w ea ner p i g ho us e s .

1 . INTRODUCTION

1.1 Why du st occ ur sTh e h i g h c o n c e n t r a t i o n s of d u s t f r e q u e n t l y e n c o u n t e r e d i n s i d e

liv estock buildings a r e a n inev ita ble r esult of the high stocking densitiesused in intensiv e syst em s of husba ndr y. The situa tion is a ggr a v a ted by ther ela tiv ely low v entila tion r a tes to conser v e m eta bolic hea t of the stockf or t he m a i n t a i n a n c e o f o p t i m u m e n v i r o n m e n t a l t e m p e r a t u r e s .

Concentr a tions of dust a r e thus highest in cold wea t her (which m ea n s

m ost nights a s wel l a s in w i n t e r ) , w h e r e a s i n w a r m w e a t h e r h i g h v e n t i l a t i onrates tend to reduce dust levels. They are increase d by activ ity of stocka nd s t o c k m a n a t t i m e s o f f e e d i n g or s t o c k w e i g h i n g a nd m o v e m e n t . F o rg r o w i n g s t oc k , d u s t c o n c e n t r a t i o n s i n c r e a s e w i t h a g e a nd a r e a l s oinfluenced by the dustiness of the feed. The dust concentr a tion v a r ies inspa ce a nd tim e a nd deposited dust r e-suspended fr equently by a ir cur r ents,a r ising fr om conv ection, stock m ov e m en t or v entila tion.

1 . 2 C o ns t i tu e nt s o f dus tS o u r c e s o f d u s t a r e m o s t l y o r g a n i c , f o r ex a m p l e s k i n and f e a t h e r s ,

f e e d , l i t t e r and dr i e d fa e c e s . P a r t i c l e s i z e o f s uspe nde d dus t r a nge s fro m

0.1 t o 10 jim . On a v e r a g e , o ne p a r t i c l e i n s i x , m o s t l y l a r g e p a r t i c l e s i nthe range 3 to 10 jim has a l i v e bac ter ium a t t ach ed t o i t . Other p a r t i c l e sha ve v i r us e s o r fung a l s po r e s a t ta c he d . P a r t i c l e s tha t hav e l i v i n g m i c r o o r g a n i sm s a t t a c h e d to them a r e c a l l e d v i a b l e p a r t i c l e s . Som e v i a b l ep a r t i c l e s c o n s i s t o f u n a t t a c h e d s p o r e s o f f u n g i o r b a c t e r i a . V i a b l e andn o n - v i a b l e p a r t i c l e s c an b e c o u n t e d i n n u m b er s p e r m o f a i r e i t h e r a s at o t a l or in d i f fe re n t s i z e ranges . Many odorous compounds are a l so car r i edon dus t p a r t i c l e s . Gr a v i m e tr i c c o n c e ntr a t i o n o f dus t i s u s ua l l y g i v e n a smg per m

5and can be 10 to 80 t imes greater in animal houses than outdoors .

1.2 Possible effects of dust

Dust may a f f ec t the hea l th and per formance o f l i v es to c k i n four ways:a s a p h y s i c a l i r r i t a n t o f t h e r e s p i r a t o r y t r a c t , a s a c a r r i e r of t o x i cche m ica l s and odours , a s a ca rr i er o f pa th ogenic m icro -organi sm s and as aca rr i e r o f commensa l, non-pa thogen ic ba c t er ia . Dust may a l so a f f ec t theh e a l t h o f t h e st o c k m a n s i n c e f o r b o t h l i v e s t o c k an d h u m a n s, t h e ra n g e o fp a r t i c l e s i z e s th a t i s p o t e n t i a l l y dam a ging to l ung s i s be lo w 7 Jim w hi chc o r r e s p o n d s t o t h a t i n s u s p e n s i o n i n l i v e s t o c k b u i l d i n g s . A l th o u gh th ethr esh o ld l i m i t va lu e for in er t m inera l dust i s 10 mg/m , t o t a l and 5 mg/nr

3

r e s p i r a b l e ( i . e . s m a l l e r t h an 7 .0 u m ), t h e r e i s no o v e r a l l v a l u e f o ro r g a n i c dus t a s i t s na tur e i s s o v a r i a b l e .



334

1.4 The purp ose of removing du st

R em ov al o f d u s t i n r e l a t i o n t o i n t e n s i v e l i v e s t o c k b u i l d i n g s i s

u s u a l l y a c h i e v e d by u s e o f d ry a i r f i l t e r s , t h i s m eth od b e i n g c h o s e nb e c a u s e of e a s e o f m a i n t e n a n c e and l ow c a p i t a l c o s t . F ou r r e a s o n s e x i s tf o r re m ov in g d u s t i n c o n n e c t io n w i t h i n t e n s i v e b u i l d i n g s :

1 . To p r e v e n t i n f e c t i o n o f s p e c i a l d i s e a s e f r e e h e r d s o rf l o c k s , a i r e n t e r i n g t h e b u i l d i n g i s s o m e ti m e s f i l t e r e d .

2 . To r e d uc e nu i s a n c e f r o m o do ur s and du s t ar o und t heb u i l d i n g o r r e d u c e t h e c h a n c e s o f c r o s s - i n f e c t i o n t ol i v e s t o c k i n n ea rb y b u i l d i n g s , a i r l e a v i n g t h e b u i l d i n gi s s om e t im e s f i l t e r e d .

3- To p r e v e n t h e a t r e c o v e r y o r h e a t i n g and c o o l i n gequipment from be ing fouled by dust accum ula t ion .

4* To r e d u c e n u i s a n c e a nd h a z a r d s f r om d u s t i n s i d e t h el i v e s t o c k b u i l d i n g i t s e l f . B e c a u s e t h e d u s t i sp r a c t i c a l l y a l l g e n e r a t e d i n t h e b u i l d i n g , o n l yf i l t r a t i o n o f i n t e r n a l l y r e c i r c u l a t e d a i r c a ne f f e c t i v e l y r ed u ce t h e c o n c e n t r a t i o n o f d u s t i n s i d e t h eb u i l d i n g .

2 . THE NIAE INTERNAL AIR FILTERThe f i l t e r u n i t was l o c a t e d e n t i r e l y i n s i d e t h e r e s p e c t i v e b u i l d i n g s

and w a s i n d e p e n d e n t o f t h e v e n t i l a t i o n s y s t e m . The u n i t c o n s i s t e d o f as u c t i o n b ox ( u s u a l l y f l o o r s t a n d i n g ) t o w h i ch t h e f i l t e r m a t e r i a l w asa t t a c h e d u s u a l l y a s a f l a t v e r t i c a l s u r f a c e o f an a r e a t o g i v e a f a c ev e lo c i t y o f about 0 .75 m/s . Bust c o l l e c t e d on t h i s su r fa ce and was removedw i th a vacuum c l ea ne r . C leaned a i r was d i re c t ed in to an overhead di sch argeduc t w i th a pe r m e ab l e l o w e r s ur f a c e . The c a p a c i ty o f the fa n i n the f i l t e ru n i t w as m ad e t h e s am e o r d e r a s t h a t o f t h e m a i n v e n t i l a t i n g f a n . T heo v e r h e a d d u c t w a s l o c a t e d a b o v e an d a s n e a r t o t h e s t o c k a s p o s s i b l e s ot h a t t h e c l e a n a i r f l o w e d d ow n w ar d s t o w a r d s t h e s t o c k . T h i s a i r d i d n o t

c a u s e a d r a u g h t b e c a u s e i t w a s d i s c h a r g e d a t a l o w s p e e d ( 0 . 3 m / s ) an d a si t was re c i rc u la te d i t was a t the same temperature as the a i r in the room.

1.5 The effects of inter n a l a ir filtr a tionThe e f f e c t s o n l i v e s t o c k a r e l i k e l y t o d ep en d p a r t l y on t h e d i s e a s e

s t a t u s o f the s toc k . Those w i th resp ira to ry d i s ea se s such as pneumonia andr h i n i t i s a r e m ore l i k e l y t o b e n e f i t t h a n t h o s e t h a t a r e e n t i r e l y f r e e o fd i s e a s e .

E x pe r im e nt s w i th v e a l c a l v e s ha ve show n tha t f i l t r a t i o n r e duc e s theinc ide nc e and se v e r i t y o f v i ru s pneumonia . Exper iments w i th ear ly -we anedp i g s i n a r h i n i t i s - i n f e c t e d h er d h a ve sh ow n a 23% g r e a t e r g r ow t h r a t e

between 3 and 7 weeks o f age . Further expe r ime nts w i t h ear ly -wean ed pig si n d i c a te a s i g n i f i c a n t im pr ov em e nt i n da ys to s l a u g h te r i n the s ubse que ntf a t t e n i n g s t a g e . F u r t h e r e x p e r i m e n t s a r e n e ed e d t o e s t a b l i s h th e c o s te f f e c t i v e n e s s o f a i r f i l t r a t i o n .

1 .6 A ir sampl ingThere are thr ee common ways o f a s se ss in g the p ar t i cu la te c onte nt o f

a i r . One measures dust mass expr essed as mg/nr . Another coun ts p a r t i c l e se x p r e s s e d a s n u m be r/m ^ . A t h i r d m e a s u r e s b a c t e r i a l c o l o n y - f o r m i n gpartic les (BCFP) expressed a lso as number/m^.



335

3. SOME RESULTS OB TAINED

3.1 Measu reme nt of duet massA i r w a s d r a w n t h r o u g h a p r e - w e i g h e d f i l t e r p a p e r b y m e a ns o f an

e x h a u s t i n g p um p. F o r o u t d o o r o r c l e a n a i r , a f l o w r a t e o f a b o u t 3 0 1 / m i nf o r 3 h w as r e q u i r e d t o o b t a i n a d e p o s i t of s u f f i c i e n t w e i g h t . F o r t h e a i ri n s i d e l i v e s t o c k b u i l d i n g s , 1 0 1 /m i n f o r 3 h w a s s u f f i c i e n t . Some m e a s ur e da v e r a g e v a l u e s i n " f l a t - d e c k " p i g h o u s e s w i t h e a r ly - w e a n e d p i g s m e as ur edn e a r t h e p i g s a r e a s f o l l o w s ( m g / m ' ) :

Farm A Farm B Farm CAge o f p i g C o n t r o l F i l t e r e d C o n t r o l F i l t e r e d C o n t r o l F i l t e r e d4 weeks 3 1 7 4 0 .5 0 .36 weeks 5 2 14 7 5. 0 2 .0T he ' C o n t r o l ' was f o r a s t a n d a r d ro om a nd ' f i l t e r e d ' w as w hen a n i n t e r n a l

r e c i r c u l a t i n g f i l t e r was f i t t e d . T y p i c a l o u t d o o r v a l u e s on t h e f a rm s w e re0.1 - 0.2 mg/m*.

3 -2 A i r b o r n e b a c t e r i aUs ing an Andersen sam ple r , t o t a l cou n t s o f a i rb o rn e BCFP ranged from 3

to 7 (xlC*5) c l o s e t o p i g s . I n g e n e r a l , v a l u e s i n c r e a s e d 3 - f o l d a s t h e p i g s

g r ew f ro m 3 w e e k s t o 7 w e e k s o l d an d h a l v e d w he n i n t e r n a l f i l t e r s w e r ei n s t a l l e d .

3.3 Particle countsUsing a n optica l instr u m ent, typica l counts wer e a s fol lows :

Total p articl es large r than 0.5 Jim, near to pigs, standar d room,24 x 10° per m 3; filtered room 11 x 10° per m*Expressed as % in each size range,

Size ran ge (pi ) 0.5-1 1-2Standar d room 49 23Filtered room 66 24

3.4 Com pa r ison of dust m a ss and pa r ticle num ber sA s a n a p p r o x i m a t i o n , t h e s i z e r a n g e >2 jim c o n t a i n s 9 5 ^ o f t h e d u s t

m a s s b u t o n l y 3 0 ? o f th e p a r t i c l e s w h e r e a s t h e s i z e r a n g e <2 urn c o n t a i n s

only 5% of the dust ma ss but 10 % of the pa r ticles.

4. SOME CONCLUSIONS

2 -384

>520

6

1 . A s i m p l e f i l t e r i n g u n i t r e d u c e d t h e d u s t m a s sc o n c e n t r a t i o n s fou nd i n w e a n e r h o u s e s b y a b o u t a half.

2 . The r e d u c t i o n s i n t h e b a c t e r i a l and p a r t i c l e c o u n t s w e res i m i l a r .

3* R e m o v a l o f m o s t o f t h e d u s t m a s s a c c o u n t e d f o r o n l y am i n o r i t y o f t h e p a r t i c l e s .



336

LARGE-SCALE BIOGAS PLANTS IN HUNGARY

G. MESZAROS and L. M ATYASNational Institute of Agricultural Engineering

Hungary

Summary

On large-scale animal breeding farms in Hungary a large amount of

slurry is produced, its disposal is problematic on account of thehazard on environmental pollution. Governmental decisions were madeto establish biogas plants with central subsidy for processing a partof the slurry and other wastage of organic origin, such as communalwastage. Following this governmental programme two large-scale biogasplants were constructed and in this paper we would like to give areview about the results of our investigations.

At one of the biogas plants the appr. daily amount of 60 m slurrycoming from a dairy farm with 750 cows is processed in continuousoperation by the technology based on the Austrian BIMA licence. Theother plant operating periodically produces biogas in digesters of

650 cb.m volume by digesting mainly cattle litter and manure, andother communal wastage, sewage, etc.

1. BIMA SYSTEM BI OGAS PLANTThe plant was established between the specialized cattle breeding

farm and the broiler plant of the agricultural cooperative "I I . RakocziFerenc" at Szecseny. The adaptation project was prepared by the NationalInstitute of Agricultural Engineering and by AGROB ER . The daily 60 m totalslurry with 10 p.c. dry matter from the cattle farm is processed in thedigester of continuous operation in mezofil (30-35 °C) temperature range bydigestion for 30 days. The biogas plant of continuous operation can be runautomatically. During the operation only the temperature and the rechargingof the manure must be secured.

The main parts of the plant are the following : thecollecting-homogeniz ing pit with the pit for the digested slurry, digesterwith heat exchanger, the gas holder and the digested slurry storage(fig.l.).

The slurry is delivered by a bulldozer board into the sewer of the

dairy farm from where it flows into the collecting-homogenizing pit bygravitation. There is possibility here to mix poultry manure as well.After homogenization with the home-made screw mixer the raw slurry

gets through a CSN-600 slurry pump 5-6 times daily into the digesterthrough a counterflow heat exchanger. In the heat exchanger the alreadydigested slurry preheats the delivered "cold" raw slurry. The mixing of theslurry in the digester and the freshly fed one takes place without anymechanical mechanism, by gravitation, partly during the feeding of theslurry, partly during the pressure equalization of the main and secondarydigesters.

The base coarse and the inner division of the cylindrical reinforced



337

steel digester is heated by hot water. The heating temperature is ensuredby burning a part of the produced gas in a cast iron boiler. The producedbiogas and the digested slurry with the same mass as the conveyed raw

slurry is then delivered into gas holders. Here occurs some after,digestion. The gas holders are cylindrical reinforced concrete tanks withswimming plastic gas-dome. The digested slurry flows from here into anintermediary collecting pit, from where the already mentioned slurry pumpconveys it into the liquid phase silo and from there it will be deliveredby tanklorries onto the field.

The utilizable part of the biogas will be burnt in the BO-130 boilerswith gas burners of the poultry houses.

TECHNICAL DATA

Volume of the collecting-homogenizing pitVolume of the digesterVolume of slurry in the gas holder

in summer operationVolume of stored gas in summerPressure

Volume of slurry storageType of boiler heating the digesterTemperature of input heating water

Temperature of output waterPressure required for the gas-burners

200 m"1800 m

830 nu690 m

13-15 mbar(130-150 mm W .c)

1600 m 3

K0MF0RT K-II . V/o.60 °C

45 °C8 mbar

(80 mm W.C .)

TEST RESULTS

The planned and measured operation characteristics, as well as themain test results at the biogas plant of the agricultural co-operative "II.Rakoczi Ferenc" at SzS csSny are the following (Table 1., Fig. 2.)

Table 1.

Daily amount of slurrySingle amount of fed-in slurryDry matter contentOrganic matter contentTotal gas yieldGas amount for self-sustainmentUtilizable gas amountSpecific gas yield

Efficiency of dry matterdecomposition

COD reduction

TEST RESULTS

Unit

m 3/ dmp.c.t/dN.nu/dN.nu/dN.nu/dN.m /tdry matter

p.c.p.c.

Value

planned

538.8104.24

1658180

1478

-

46

measured

61.610.3105.15

1842308

1548335

62.246.0



338

In the summer period of 1984 the specific gas yield developed asexpected. The total gas yield projected to the organic matter has been 33 5

N.m^ per ton. This corresponds both the literature data and the results ofprevious test results.

According to the inner characteristics it has been succeeded to securethe 10 p.c. dry matter content for an average longer period. But duringrainy weather the cattle slurry will be deluted to such an extent that itcannot be delivered directly into the digester. This results in a slightshift of the feeding cycles, further in the development of less biogas withlower quality.

The CH content of the developed biogas in average corresponds 55 % ,

its heating value of 19-20 MJ/N .m equals to 0.45-0.48 kg fuel oil. Thedegree of digestion was advantageous. The dry matter content of the

digested slurry is 4 5 p.c. of the original amount, its organic mattercontent is 3 8 p. c. of the same.

The chemical reaction of the digested slurry becomes slightly alkalineaccording to the digesting processes taking place. The C/N ratio will bereduced by 4 5 p. c. during digestion. The NPK -content of the slurry slightlychanges during digestion, and the characteristics of the digested slurrycan be considered as equal in practice. The reduction of the digestedslurry's COD amounts to 4 6 p.c.

As a consequence of the simple construction and mode of operation ofthe biogas plant, it is not required to employ an operating staff withspecialized knowledge.

The biogas plant of BIMA-system realized on basis of the test resultsfulfils the projected parameteTs, it is suitable for producing biogas bydigesting litterless cattle slurry. A basic precondition of the profitableoperation is the total utilization of the biogas produced.

2. SEMI-DRY BIOGAS PLANT WITH PERIODIC OPERATIONThe GATE-DOMSOD biogas plant is the common process of the University

of Agricultural Sciences at GbdbllS and the Agricultural Cooperative"Dozsa" at Dbmsbd. It utilizes cattle slurry and litter, pig manure andcommunal sewage water in periodical processing, partly in mezofil, partlyin thermofil temperature zones.

The main parts of the plant are the following : bucket elevator, feedscrew conveyor, 4 digester towers, unloader screw for the digested slurry,liquid phase silo, digested slurry conveyor with storage, gas holder,collecting pits, excess liquid collection pit, boiler house (Fig.3.).

The cattle manure with about 25 p.c. dry matter content and the litteris transported by trailer to the reception hopper for manure and solidorganic wastes. From here manure will be delivered by a bucket elevator,with the help of feed screw conveyor into the digester tower made ofanticorrosive steel. The slurry and the sewage water mixed with faeces willbe pumped into the digester.

After aeration for 3-5 days, flooding with heated excess liquid thecharge will be heated to 55-60°C. The feeding orifice then willhermetically be closed and the anaerob digestion lasting 3-4 weeks will bestarted. During this process the temperature of the biomass will be reduceddaily by 1-1 °C, while at the end of digestion it will reach 30-3 5°C.

The developed biogas is pressed through a gasmeter attached to the topof the digesters into a steel gas holder and stored at 0.6 baroverpressure.

A part of the stored gas will be utilized for heating the digesterwhile the net gas production utilized in industrial plants.



339

The digested biomass will be delivered by a screw arranged under thedigesters, further by bucket conveyor into storage tank and then removed itwill be stacked or directly delivered onto the field. Since the operational

test of the biogas plant is still in the phase of fulfilment, only someproject data can be described.

PROJECTED OPERATIONAL CHARACTERISTICS

Composition of the substance for processing- litter manure with 25 p.c. dry matter content, 33 .3 m

per day 58 p.c.- pig slurry with 6 p.c. dry matter content,

9 m per day 16 p.c.- sewage with faeces with 8 p.c. dry matter

content, 15 m per day 26 pVolume of digester towers 4 x 670 n'Aerob digesting period 21 daysDaily produced amount of gas 30 14 N.mUtilizable gas amount per day 2153 N.mMethane-content of biogas 55 -60 p.c.Oil equivalent of the utilizable biogas 37 0-4 00 t/year

The realization of the planned parameters and the economic characteristicsmust be determined on the basis of the current operation and of the test.

3



rcsft?

o

/?/W SLURRY

DIGESTED SLURRY

BIOGAS

Fig. 1 FLOW DIAGRAM OF THE "BIMA" SYSTEM

1./ Dairy farm2. / Elevating pit3./ Heat exchanger4 ./ Digester5./ Digested slurry collection pit6./ Gas holder

7./ Digested slurry storage8./ Broiler plant



BIOGASPRODUCTION

TOTAL AVERAGE BIOGAS

PRODUCTION [1841,98 Nnt i

NET AVERAGE BIOGAS PRODUC TION ~

11548,28 A b f /

BIOGAS FOR HEATING

AVERAGE OF THE BIOGAS

PRODUCTION FOR HEATING

[293,70 Nrff]

1984. 10- 11.

MARCH

13. 14. 15.

APRIL

17. 18. 19.

MAY

20. 21. 22. 23. 24. 25. TIME/WEEK/

JUNE

Fig. 2 Biogas production



! '!< /J iJi i

L,^I

76/

Fig. 3 Flow diagram of the Bemi-dry digestion system

56789

1011121314

151617 ,

./ Reception hopper for manureand solid organic wastes

./ Bucket-conveyer

./ Reception bin for slurryeffluent and domestic sewage

./ Liquid was te feed pump

./ Feed screw conveyer

./ Digester

./ Liquid pha se silo

./ Liquid pha se feed pump

./ Bucket conveyer

./ Digested slurry Btorage, / Compressor/ Gas holder/ Hot water boiler/ Excess liquid collection pit

/ Excess liquid feed pump/ Unloader screw/ Aerator unit



343

ANAEROB IC D IGESTION TO CONTROL OD OU RS

P. ESTEBAN TURZO, J. GUTIERREZ SALGUERO an d A. MORE H ERRERO

Summary

The paper sets out Che result s obtained from the treatment of anim alwa ste pr oducts by a na er obic digestion. An initia l study wa s a lso m a deof the pr oduction of a m m onia com pounds in the wa ste pr oducts bya na e r obic digestion.In our opinion the a na e r obic pr ocess is not being optim ised for a nim a lwa s tes, a nd optim u m digestion should be ba sed on new technologies whichr educe the r etention tim e.The com bined effect of m ixing the wa ste pr oducts fr om differ ent speciesof a nim a ls is r epor ted.The effect of dehydr a ting the digested wa ste using sola r ener gy isinvestigated with respect to the stability of the ammonia compounds andthe r eduction of odour with the a im of pr oducing a n a gr icultur a llyv a l u a b l e p r o d u c t .

INTRODUCTION

Ana er obic digestion sta bilises a nim a l wa stes by r educing the com plexor g a nic com pounds to pr incipa lly ca r bon dioxide a nd m et ha n e. Althougha n a e r obic digestion r educes the odour , the tr ea ted wa ste is not com pletelyi n o f f e n s i v e .

Ana er obica lly digested wa stes ca n be v a r iously tr ea ted to pr oduce a na ccepta bly sta ble pr oduct with the r ecov e r y of useful co m pounds.

Tr ea t m ent using physico-che m ica l pr oces ses a r e fea sible but costl y.Bea r ing in m ind the a bov e , a ser ies of la bor a tor y studies wer e

under t a ken with the a im of m a xim ising tr ea t m ent using a na e r obic digestion,together with a seconda r y chem ica l tr ea t m ent of the digested r e sidue.

The first part of the study looked at the effect of retention time andthe effect of m ixing the wa ste pr oducts of v a r ious a nim a l species on m etha nepr oduction a nd tr ea t m ent efficiency.

The digested wa stes conta in a ppr oxim a tely 20Z or ga nic m a te r i a l togetherwith the fertilizer c ompounds N, P and K. The lev els of bacteri a ar e alsohigh with sim ila r lev els to undigested wa s tes . The ba cter i a ca n pr oduceodour s a nd ca use ba cter i a l conta m ina tion by colifor m s a nd str eptocci e tc.

The second part of the study aimed to assess the effect of dehydrationon the a na e r obica lly digested a nd chem ica lly tr ea ted a na e r obica lly digestedw a s t e s .

ANAEROBIC DIGESTION

Ma ter i a l studied: a nim a l wa ste pr oducts fr om ca ttle, pigs a nd poultr y.Retention Tim es: 10, 20 a nd 30 da ys .W a s t e m i x e s : p i g , c a tt l e a nd p i g , p o u l t r y .Dur a tion of tests: 1 a nd 2 m onthsTem per a tur e: 35"C



O p e r a t i o n :

An a l y t i c m e t h o d s :

Results:

DEHYDRATION

344

Continuous da ily a ddition of the wa ste v olum e cor r esponding to each R.T. or the volume established in the mixed

w a s t e s t u d i e s .Substr a tum : Tota l solids, Vola tile solids, Tota l N, NH,pH Vb i o g a s : C H 4 , C0 2 > H 2S , 0 2

The produ ctivi ty is expressed in CH, 1/kg VS digested andCH, m 3/ l i t r e o f s u b s t r a t e .

The a im of this system wa s to r em ov e a la r ge v olum e of wa ter by sola rener gy. To r educe losses of nitr ogen dur ing dr ying, a m m onia wa s r ea cted with

phosphor ic a cid to pr oduce less v ola tile com poun ds.The study was carried out using 14 x 7 L tray s. The pH in 7 trays was

m e a sur ed a s pH 5.4. The pH in the r em a ining tr a ys wa s not m ea sur ed. Thetr a ys wer e pla ced in a pla stic tunnel for 15 da ys a nd the tem per a tur e r a ngedfrom 15 to 45°C.

The r esults show the a v er a ge v a lues obta ined.

RESULTS

ANAEROBIC DIGESTIONMetha ne pr oduction (lCH,/kg VS)

pigca ttlepoultr y

Pigca ttlepoultr y

Retention

Mixed

pig & poultr ypig & ca ttle

Times

w a s t e s

30 Day199.1173.4281.0

144.6166.2130.1186.0196.5

20 Day

131.5169.1295.8

10 Day

127.5155.0309.6

Treatment efficiency

Pigca ttlepoultr y

Pigcattle

poultr y

Retention Tim es

M i x e d w a s t e s

pig & poultr ypig & cattle

30VS

66.269.853.6

DayCOD

60.169.759.6VS

55.758.8

59.258.965.0

:OVS

53,58,57,

.8

.0

.0

DayCOD

52.568.460.1CO D65.865.1

59.062.672.0

10 DayVS COD

54.2 63.540.0 50.751.1 59.6



345

REDUCING NITROGEN LOSSES

Befor e dr ying

Vol (1)NH (g/1)Total N (g/1)

After dryingVol (1)

N H . ( g / DTotal N(g/1)

Per centa ge of e

With phosphor icUntr e a ted

DISCUSSION

limination

acid

Untr e a tedZ-2.84.6

-13.4533.90

Vol93.689.3

Tota l7

196322

0.4560.60

153 00

NH,5.169.1

w i t h

Z-2.84.6

-25.838.9

N13?152.3

phosphor ic

acid Total7

196322

0.72186.0280.1

ANAEROBIC DIGESTIONRetention time

Except in ca se of the a na e r obic digestion of poultr y wa st e, m etha nepr oduction decr ea ses a s r etention tim e is r educed. This is a r esult of thesubstr a te being exposed for less tim e to the a ction of a na er obic ba cter i a .With the poultr y wa st e, it wa s noted tha t m etha ne pr oduction incr ea sed a s

the r etention tim e wa s r educed. Also the m etha ne pr oduction in the thr eer etention tim es studies wa s m uch higher tha n that r ea ched in the m ixedwa stes study when the r etention tim e wa s gr ea ter tha n 30 da y s.

The m a in differ ence is in the com position of the substr a te:In the r etention tim e study, the v ola tile solids v a lue v a r ied between 3, 5a nd 7 while in the m ixed wa ste s study it v a r ied between 3, 6 a nd 4,2.

The following ta bles show the a m ounts of v ola tile solids a dded a nddigested.

Volatil e Solids added to theRetention time

da ys302010

Mixed wa stes

Volatile Solids digestedRetention time

days

302010

Mixed wa stes

digesterVola tile solids

g1491.51901.82959.81085.9

Vola tile solids

g799.5

1084.71525.3624.4

The per centa ge of m etha ne in the bioga s wa s 60.1Z for a r etention timeof 30 da ys and 56.8Z for a sim ila r r etention tim e in the m ixed wa ste study.

We believ e tha t the concentr a tion of v ola tile solids in the digestedsubstrat e is fundamenta l and that an optimum (to be determ ined ) exists forea ch a nim a l species .



346

The a im of the next study will be to deter m ine the optim u mconcentr a tion in poultr y wa st e.

Mixed wa stesMetha ne pr oduct ion is higher when the a na e r obic digestion is ca r r ied

out with wa ste fr om a m ixtu r e of differ ent specie s, incr ea sing the v a lue by4 0 % in pig/poultr y m ix es a nd by 30Z in pig/ca ttle m i xes .

The expla n a tion m a inly com es fr om the fa ct tha t the m ixtur e is r icheri n m e t h a n o g e n i c b a c t e r i a c u l t u r e s .

DEHYDRATION

The r esults show a n optim u m ev a por a tion a long with a good for m a tion ofa m m onica l nitr ogen> which for m s a m m onium sa lts on r ea ction with the

p h o s p ho r i c a c i d .The a cidified r esidue r eta ined 94.9Z of a m m onia a nd 86.91 of tota l

nitr ogen , com pa r ed to 30.9% and 47.5% r espectiv ely in the untr ea ted r e sidue.Recent studies, not r epor ted h er e, ha v e shown that the optim um pH for

the conv e r sion of a m m onia to a m m ium sa lts using phosphor ic a cid isa ppr oxim a tely pH 4.

CONCLUSIONS

ANAEROBIC DIGESTIONRetention tim e.

The r eduction of r etention tim e r educes the conv er sion of v ola tiles o l id s t o m e t h a n e .

At shor t r etention tim es m or e m etha ne is pr oduced per unit of tim e .An optim u m r etention tim e r equir es the dev elopm ent of technologies

which pr ov ide the optim u m conditions for the ba cter i a popula tions to a tta ckthe substr a te.

Hom ogenisa tion of the wa ste is consider ed indispensible, to a v oid gr ea tv a r i a tions in the concentr a tion of a ntibiotics a nd the loss of undigestedfood, etc.

Mixed Wa stes

When m ixing a nim a l wa stes it is necessa r y to deter m ine the optim u mconcentr a tion of or ga nic m a ter i a l with the a im of r ea ching a n optim u md i g e s t io n p r o c e s s .

DEHYDRATION

The r esults show tha t the pr ocess is suita ble for countr ies with atem per a te clim a te.

The cost of the pr oces s, in r ea gents, is a ppr oxim a tely 5/m s tr e a ted.The fina l pr oduct conta ins significa nt qua ntities of the fer tilizer

nutr ient s N, P and K. The nitro gen content is close to 4Z and the phos phorusa nd or ga nic m a t er i a l contents a r e high, m a king a n a gr icultur a lly usefulo r g a n i c p r o d u c t .

The deter m ina tion of the optim u m pH is consider ed a pr ior ity in or derto esta blish the econom ic v ia bility of the pr o cess .

Futur e studies a r e gea r ed towa r ds deter m ining the optim u m , pH, ther ecov e r y of the ev a por a ted wa ter a nd the ev a lua tion of the pr ocess ina gr icultur e a long with the dev elopm ent of technology to im pr o v e per for m a nce.

The r eduction of odour r ea ched by a cidifica tion is good.



347

THE BIO- GAS PROJECT IN EMILIA-ROMAGNA (Ita ly )

BO NAZZI G.*, CO RTELLINI L.*, PICCININI S.*, TILCHE A.*** Centr o Ricer che Pr oduzioni Anim a li - Via Cr ispi , 3 - 42 100 Reggio Em ilia** ENEA - Di p. FARE - c.p. 240 0 - OO10 0 ROMA A.D . (Italy)

ABSTRACTThe r unning of fiv e full sca le pla nt s in br eed ing fa r m s is a na lized

her e in r ela tion to their yield. The digester s wer e oper a t ed a t HRT between10 a nd 40 da ys with pig, pi g a nd ca ttle a nd ca ttle wa s te,The digester s fedby pig wa ste ga v e a bio ga s yield between 0.28 a nd 0.50 m .kg vSo.d" , a t HRT

of_10 - 15 da ys , a t a n a v e r a ge or ga nic loa ding r a te of 0.84 - 2.55 kg VS.m.d , a nd a t a tem per a tur e of digestion of 28 - 40°C. One of the pla nts fedby m ixed_wa ste a nd oper a ted a t a n or ga nic loa ding r a te of 0.65 - 1.95 kgVS.m .d gav e a bio ga s yiel d of 0.39 - 0.48 m .kg" VSo.d " , at a HRT of20 - 35 da ys a nd a t a d igestion tem per a tur e of 30° - 34°C. Plug flow pla ntoper a ting on ca ttle wa s te ga v e a bioga s yield of 0.25 - 0.40 m .kg VSo.da t a HRT of 24 - 40 da ys, a t a n or ga nic loa ding r a te of 2.7 - 4.6 kg VS.m ".d a nd a t a digestion tem per a tur e a bov e 35°C. The or ga nic loa ding r a te a ndthe bioga s pr oduction wer e lower tha n expected due to pr ob lem s of the settling of solids in the pigge r ie s, to a difficult flow in the sewa ge a nd to a na nim a l liv e weight lower tha n tha t of design da ta .

INTRODUCTIONIn Em ilia -Rom a gna , a Region tha t r epr esents one twenti eth o f the Ita lia n

la nd sur fa ce, one four th of the na tiona l pig popul a tion is concentr a ted. Thea v e r a ge fa r m dim ension is 600 hea d s; 48% of pig popu la ti on is in fa r m s la rger tha n 1.000 hea ds. Ther efor e, on one ha nd m a ny fa r m s ha v e la r ge ener gyn e e d s , b u t o n t h e o th e r h a n d t h ey h a v e t h e a v a i l a b i l i t y o f a h i g h e n er g y p otentia l in the wa s tes . Ana er obic digestion is the technology tha t r ecov e r sener gy fr om such wa s tes . The Em ilia -Rom a gna Author ity fina nced the r ea lization of 5 dem onstr a ti v e full sca le pla nt s in or der to v er ify: 1) the effi

ciency of the a na e r obic di gestion pr oce ss; 2) the techni ca l r elia bility ofthe pla nt s sold by industr y; 3) their econom ic conv enien ce; 4) the fa r m e rc a p a ci t y t o m a n a g e a d i g e s t e r . T h re e p l a n t s a r e f e d b y p i g w a s t e , o n e b yboth pig a nd ca ttle wa ste a nd one by ca ttle wa s te. The pla nt s r a nge in sizefr o m 260 to 1.700 m , a ll of them a r e high-r a te, m esop hil ic, com pletelym i x e d d i g e s t e r s . Th e p l a n t s h a v e d i f f e r e nt s y s t e m s o f b i o g a s u t i l i z a t i o n :c o m bu s ti o n f o r h e a t p r o d u c t i o n , s t e am p r o d u c t i o n f o r c h e e s e m a n u f a c t u r i n g ,com bustion for for a ge dr ying, com bined hea t a nd power pr o duc tio n. The 5pla nt s ha v e been oper a ting since the beginning o f 198 3. The initia l r esultsof the efficiency of the digestion pr ocess a r e pr esente d her e. The bioga spr oduction (m ,d ) is com pa r ed to the or ga nic loa ding (kg VS.d ) a nd tothe tem per a tur es (°C) of the pr oc ess.

MATERIALS AND METHODSThe m a in cha r a cter istics of the fa r m s a r e r epor ted in ta ble 1 a nd the

m a in cha r a cter istics of th e pla nt s a r e r epor ted in ta ble 2. In the fir sts t a ge o f t h e r e s e a r c h , s t i l l u n d e r w a y , d i g e s t i o n c o n d i t i o n s a n d b i o g a s y i e l d(m bioga s kg VSo.d ) wer e deter m ined . Sa m pling wa s ca r r ied out differ e ntly a ccor ding to the cha r a cter is tics of ea ch fa r m a nd its pl a n t: da ily sa mpling of feed wa s ca r r ie d out a t the fa r m s 2 a nd 3, spot sa m pling twice a

week a t the fa r m s 4 a nd 5 a nd sa m pling thr o ughout th e da y for a few da ys a



348

month at farm 1. The content of Total Solids (TS) , Volatile Solids (VS) ,Total Kjeldahl N itrogen (TKN) , Ammonia (NH - N) , Chemical Oxigen Demand

(COD), Volatil Acids (VFA), pH and Total Alcalinity (TA) in feed, in digestionand in effluent were measured. Analyses for TS , VS , COD , TK N, N H -N were carried out according to Standard Methods (APHA, 1975); VA were determined bysteam distillation and titration , TA by titration at pH 3.8. The biogas methane and CO content were measured by IR and CO absorption. Furthermore theplants are equipped with a computerized system for the continuous recordingof data relating to the temperatures (T) of waste, gas and water in differentpoints, the biogas production and consumption, the production and consumptionof electric power and hot water, the CO and CH percentage in biogas. Thesecollected data will allow us to determine the energy flow of the plants andto evaluate the efficiency of the different heating and mixing systems.

TABLE 1MAIN C HARACTERISTICS OF THE FARMS

farm type ofbreeding

live weight(tons)

raw waste( m J.d _1)

waste disposal

1 TESTA2 S. MATTEO3 PERUGINA

4 PELLERANO

5 I.C.S.A.

Full cycle pigsFattening pigsFattening pigsand beef cattledairy cattle

100 30-40180 22-2530 0 (pigs) 60-85390(beef cattle)72 2.5-4

piglet production 4 10 140-160

depollutionland spreadingland spreading

land spreading

depollution

TABLE 2MAIN CH ARACTERISTICS OF THE PLANTS

farm

1

2

3

4

type ofplant

single stage with

slurry recirculationsingle stage without slurry recirculation

single stage withrecirculation ofslurry from thepost digester

plug-flow

digesterworkingvolume(m3)

220

350

1260

65

mixingsystem

auger

andpumpexternal gaslifter

internal gaslifter

heatingsystem

external

heatingexchangersexternalheatingexchangerin the gaslifter

perifericexchangers

internal

gasstoragevolume<m J)

50

200

450+600

40serpentines

biogas

use

combined heat

and powerunitssteamproduction

foragedrying

hot waterproduction and

single stage with 1500out slurry recirculation

inter- internal 200nal gas exchangerlifter in the gas

lifter

forage dryingcontinued heatand power unit



349

RESULTS AND DISCUSSION

Fig. 1: Organic loading (kg VS.d ) , biogas production (m .d ) and tempera

ture (°C) of digestion in the plant 1.Biogas(nrkl)

200.

150.

100.

50.

Digester Temperature

Biogas production

1

Organic loading

TFC)

.40

.35

.30

(Kg/d)JB00

J 0 0

.400

.300

N/82 D J/83 F M A M J J A S OFig. 2: Organic loading (kg VS.d ) , biogas production (m .d ) and tempera

ture (°C) of digestion in the plant 2.

B i o g a s( m t o )

J/84



350

PLANT 1 (Fig. 1)The wa stes a r e loa ded to the digester a fte r settli ng. In this pla n t the

settling ta n k is a lso the cla r ifier with the m ixing of feed a nd effl uent.The bio ga s yiel d vari ed from 0.28 to 0.33 m .kg VSo.d , at an HRT betw een11 (Nov em ber, Decem ber ) a nd,14.6 da y s (fr om Ma r ch to O c t o b e r ) , a t a loa dingrate of 1.7 - 2.55 kg VS.m .d" , and at a T ranging from 30 to 4 0°C.-Thea v e r a ge bioga s pr oduction r a te per unit v olum e of digestion wa s 0.6 m .m. d" (60 - 6 5% C H J .

4

PLANT 2 (Fig. 2) 3

The bioga s yield r a nged between 0.45 a nd 0.60 m kg VSo.d a t HRTof 15 da ys a nd a t a T of digestion of 33°C. The low pr oduction r a te pe r unitv o lum e, 0.62 m .m .d (65 - 70% CH K ca n be expla ined with the low a v er a ge

or g a ni c loa ding r a t e: 1.18 kg VS m .d (m a xim um v a lue s: 1.7 - 1.9 kg VS.m .d ) . The v a r i a tio ns of or ga nic loa ding in Febr a r y a nd in Ma r ch wer e duet o t h e u s e o f w a s t e f o r d i f fe r e n t p u r p o u s e s .

Fig. 3: Or ga nic loa ding (kg VS.d ) , biog a s pr oducti on (m .d ) a nd tem per a t u r e C O o f d i g e s t io n i n t h e p l a n t 3 .

T ( ° C )B i o g a s(m%)

J/84



351

_ 1 V S o . d - 1PLANT 3 (Fig. 3)

The bio ga s yield r a nged between 0.39 a nd 0.48 nT.kg " VSo.d a t a HRTof 20 - 35 da ys in the dige ster a nd a t a T of digestion of 30° - 34°C.

highest yield w a s obser v ed a t a n or ga nic loa ding r a te of 0.62 kg VS.sa nd at a T a bov e 32°C. The pla nt, due to r epea ted r epa i r s to the sewa ge system ,wa s under loa ded with r espect tp design da t a : a v er a ge 0.93 kg VS.m .d (design da ta : 3 - 3.5 kg VS.m .d ) . The a v er a ge bioga s pr od uctio n r a te per unitv olum e wa s ther ef or e 0.4 m ,m .d (60 - 62% CH . ) .

4

1 3 ^ 1.a

Fig. 4: Or ga nic loa ding (kg VS.d ) , bioga s pr oducti ont u r e C O o f d i g e s t i o n i n t h e p l a n t 4 .

(m .d ) and tempera -

Biogas

100.

,-iLANT 4 (Fig. 4)

The bi og as yiel d range d betwe en 0.24 and 0.4 m .kg VSo.d at a HRT of24 - 40 day s and at a loading ra te of 2.7 - 4.6 kg VS.m .d . The highestbioga s yield s wer e obs er v ed a t a n HRT of 40 da ys a nd a t a n or ga nic loa dingr a te of 2.7 - 3.4 kg VS.m .d . The bioga s pr od uctio n r a te per unit v olum e

(50 - 55% CH,) ran ged bet wee n 1 and 1.44 m .m . d

PLANT 5 (Fig. 5)The pla nt wa s op er a ted a t a n a v er a ge or ga nic loa ding r a te of 0.84 kg SV.

m .d a nd at a HRT of 10 - 15 da y s. The biog a s yield r a nged between 0.33and 0.49 m .kg VSo.d . The lowest val ues are rela ted to a HRT of 10d a y s . At a HRT of 15 day s bio ga s yield of 0.4 - 0.5 m .kg VS.d was obser v ed inspite of digestion tem per a tur e belo w 30°C. The a v er a ge bioga s pr oductionr a te per unit v olum e (60 - 65% CH ) wa s 0.36 m ,m .d



3 5 2

F i g . 5: Organic loading (kg VS.d ) , biogas production (m .d ) and tempera-

B i o g a s ( n r f t l )

ture (°C) o f digestion in the plant 5.

Digester Temperature

7 0 0 .

6 0 0 .

5 0 0 .

4 0 0 .

3 0 0 .

2 0 0 .

100.

Biogas production

Organic loading

T(°C) .35

.30

.25 ■ <

VS (Kg/d)

2000

.1500

.1000

. 500

J/84

CONCLUSIONS The bio ga s yield o f 5 full scale plants w a s determined; values range

between 0.28 and 0.50 m .kg VSo.d at a temperature ranging from 28 and 40°C and a t a HRT o f 28 - 40 days. In plants 1-2-3-5 the average biogas pro-duction rate p e r unit o f volume w a s of 0.36 - 0.62 m . m .d due to organic loading rate lower than expected. The modifications to barnes and sewage systems and future increase in animal live weight w il l p e r m it higher biogas production.



353

THE BIO-GAS PROJECT IN EMILI A-ROMAGNA (Italy) :FIRST RESULTS OF FIVE FULL SCALE PLANTS

* * **CORTELLINI L. , PICCINI NI S. , TILCH E A.

*Centro Ricerche Produzioni Animali - Via Crispi, 3 - 42100 Reggio Emilia (Italy)ENEA - Dip. FARE - TER COM IBI - Via Mazzini, 2 - 40138 BOLOGNA

SUMMARY

The operation and performance of five full scale plants installedin breeding farms are analyzed in this paper. The digesters wereoperated at an HR T from 10 to 40 days with pig, pig and cattle andcattle waste. The digesters/ fed by pig waste, gave an average bio-gas yield of between 0.30 and 0.55 m . K g VSo.d" , 0.80 and 1.20m .Kg VS .d at an HR T of 10-15 days, at an average organic loading rate of 0.84 - 1.95 Kg VS.m .d , and at a digestion temperature of 28-40 °C; TS , VS , COD removal was respectively 30-47%, 4 6-57%, 42-59%. One of the plants fed by mixed waste and operated atan organic loading rate of 0.60 - 1.78 Kg VS.m .d gave an average biogas yield of 0.46 m .Kg VSo.d , at an HR T of 20-35 days

and at a digestion temperature of 30 -34 °C; TS , VS , COD removal wasrespectively 3 5 %, 46 %, 5 0 %. The experimental plug flow plant operating on cattle waste gave a biogas yield of 0.24 - 0.41 m .KgVSo.d at an HR T of 24 - 40 days, at an organic loading rate of2.7 - 4.5 Kg VS.m .d and at a digestion temperature of 33 -37 °C.

INTRODUCTIONOne fourth of the entire national pig population is concentrated

in Emilia-R omagna, a R egion that represents one twentieth of the I talianland surface. The average farm size is 600 heads; 4 8% of pig population

is on farms larger than 1,000 heads. Therefore, on the one hand manyfarms have large energy needs, while on the other they have the availability of high energy potential in the waste water. Anaerobic digestion isthe technology that recovers energy from such wastes. The Emilia-RomagnaAuthorities have financed the realization of 4 demonstration full-scaleplants in order to monitor: 1) the efficiency of the anaerobic digestionprocess; 2) the technical reliability of the plants sold by industry; 3)their economic convenience; 4 ) the farmer's capacity to manage a digester.

The plants have been installed in farms which differ in size, typeof animals bred and management; they are of C.S.T.R. type with differentmixing and heating systems. They have been in operation since early1983. An experimental plug-flow plant on a dairy farm has been broughtout and used within the programme.

The results given below concern:1) the efficiency of the digestion process;2) energy contribution of the plant towards the energy needs of the farm;3) the electric and thermic consumption of the plant;4 ) problems relating to the introduction of the plant on a farm, and so

lutions relating to this.



354

2. MATERIALS AND METHODSThe m a i n cha r a cter istics of the fa r m s a r e r epor ted in ta ble I a nd

the m a in cha r a cter is tics of the pla nts a r e r epor ted in ta ble II.

TABLE I - Ma in cha r a cter istics of the fa r m s

Fa r m type ofb r e e d i n g

l i v e w e i g h t(tons)

r a w,wa ste wa ste disposa l(m 3.d )

1 TESTA Full cyc le pi gs

2 S. MATTEO Da iry wi thf a t t e n i n g p i g s

3 PERUGINA Fatteni ng pi gs

a n d b e e f c a t t l e

4 PELLERANO dairy cattle5 I.C.S.A. p i g l e t p r o d u c t i o n 4 1 0

100

180

300

390

72410

(pigs)

(beffca ttle)

30-40

22-25

60-85

2.5-4140-160

pollutiontr e a t m entland spreading

land spreading

land spreadingpollutiontr e a t m ent

TABLE II - Ma in c ha r a cter i stics of the pla nt s

Farm

1

2

3

4

5

t y p e o fp l a n t

s i n g l e s t a g e w i t hslur r y r ecycling

s i n g l e s t a g e w i t ho u t s l u r ry r e c i r cula tion

s i n g l e s t a g e w i t hr e c i r c u l a t i o n o fslur r y fr om thep o s t d i g e s t e r

p l u g - f l o w

s i n g l e s t a g e w i t ho u t s l u r r y r e c i r

c u l a t i o n

d i g e s t e rw o r k i n g

v o l u m e( m 3)

220

350

1260

65

1500

m i x i n gsystem

a u g e randpum p

e x t e r n a l g a slifter

i n t e r n a l g a slifter

i n t e r n a l g a s

lifter

hea tingsystem

exter n a lhea tingexcha nger s

exter n a lhea tingexcha nger

in the ga slifterper ifer icexcha nger s

inter n a lcoils

inter n a lexcha nger

in the gaslifter

gasstorage

v olum e(m 3)

50

200

450+600

40

200

b i o g a suse

combinedhea t a ndp o w e ru n i t s

stea m pr oduction inthe da ir y

b o i l e r

for a gedr ying

hot wa terp r oduction

combinedhea t a nd

p o w e r u n it

The content of Tota l Solids (TS), Vola tile Solids (VS), Tota l Kjelda hlNitr ogen (TKN), Am m onia (NH - N ) , Chem ica l Oxygen Dem a nd (COD), V o l a t i le Acids (VFA), pH and Total Alcali nity (TA) in feed, in digesti on andin effluent wer e m ea sur ed. Ana ly ses for TS, VS, COD, TKN, NH - N wer eca r r ied out in a ccor d a nce to Sta nda r d Methods (APHA, 1975); VA wer e de ter m ined by stea m distil la tio n a nd titr a tion, TA by titr a tion a t pH3.8. The biog a s m et ha n e a nd CO content wer e m ea sur ed by IR a nd COa bsor ption. Fur ther m o r e the pla nts a r e equipped with a com puter ized sy_



355

stem for the continuous r ecor ding of da ta r ela ting to the tem pe r a tur eso f w a s t e , g a s a nd w a t e r in d i f f e r e n t p o i n t s , t h e b i o g a s p r o d u c t i o n a n dconsum ption, the pr oduct ion a nd consum p tion of electr ic power a nd hot wa

ter , a nd the CO a nd CH per c enta ge in bi og a s . The da ta obta ined willena ble us to deter m ine the ener gy flow of the pla nts a nd to ev a lua te theefficiency of the differ ent hea ting a nd m ix ing system s.

3. RESULTS AND DISCUSSIONTh e b i o g a s yi e l d a nd o r g a n i c l o a d i n g r a t e o f t h e p l a n t s a r e r e p o r

ted in table III.

TABLE III B i o g a s y i e l d s , o r g a n i c l o a d i ng r a t e , HRT , d i g e st i o n t e m p e r a tur e of the pla n ts

Plant

1

2

3

4

5

(m . Kg"

a v e r a ge

0.30

0.55

0.46

0.37

0.45

Bioga s

\ s .d"1)o

r a n g e

0.28-0.33

0.45-0.60

0.39-0.53

0.24-0.41

0.33-0.50

y i e l d

/ 3 " 3 j " 1 ,

(m .m . d ]

a v e r a g e

0.60

0.62

0.40

1.22

0.36

Or ga nic loa ding

1 (Kg V S

a v e r a g e

1.95

1.13

0.79

3.60

0.84

.m .d )

r a nge

1.70-2.55

0.66-1.69

0.60-1.78

2.70-4.50

0.55-1.12

HRT(days)

11-15

14-16

20-35

24-40

10-15

T e m p e r a t u r eC C )

3 0 - 4 0

3 2 - 3 4

3 0 - 3 4

3 3 - 3 7

28-35

B i o g a s y i e l d a s r e p o r t e d i n t h e o p e r a t i n g c o n d it i o n s g i v e n a b o v e ,shows a r a ther high lev el. The lower yield obser v ed in fa r m 1 is due tothe la y-out of the pla nt. In fa ct the wa ste s a r e loa ded into the dig ester a fter settling a nd in this pla nt the settling ta nk ser v es a lso a s acla r ifer with the m ixing of feed a nd efflu ent. The highest yield ha sbeen obser v ed in fa r m 2 with fa ttening pig s fed on whey a nd house d onslotted floor s. Dur ing the fir st yea r of oper a tion, pla nts 2, 3 a nd 5wer e fed with a specific or ga ni c loa ding r a te lower tha n the expected

o n e : t h e r e fo r e t h e v o l u m e o f b i o g a s p r o d u c e d i s l o we r t h a n t h a t p r e d i cted in r ela tion to the num ber of a nim a ls pr e sent . The low or ga nic loa dfed into the pla nt is m a in ly due to sta gna tion of solids in the pita nd in the collection system , to the diluti on of m a nur e with clea ninga nd gr ound wa t er . In or der to r ectify these dr a wba cks differ ent solu tions ha v e been studied together with the fa r m e r s. The influence of thev a r i a tions in tem per a tur e in the m esop hilic r a nge is in ev idence inp l a n t s 3 a nd 4 t ha t t r e a t c a t t l e w a s t e . In p l a n t 4 it h a s b e e n o b s e r v e dtha t a pr ocess tem per a tur e lower tha n 35°C deter m ine s a m uch lowe r specifie bioga s yield. In pla nts 1, 2 a nd 5 fed with pig wa ste no influenc eo f t e m p er a t u r e o n b i o g a s y ie l d h a s b e e n o b s e r v e d w h e n k ep t i n t h e m e s o

philic r a nge. The a v er a ge V S, TS a nd COD r em ov a l of the pla nts is r epor ted in ta ble IV. The low or ga nic r em o v a l of VS, TS a nd COD a s shown onpla nt 3 is due in pa r t to the oper a tion of the post-d igeste r : thesludge fr om the bottom ha s not been r em o v ed consistently a nd syst em a tica lly. In two of the fiv e fa r m s, a na e r obic digestion constitutes thefir st sta ge in the pollution tr ea t m en t. The system is com posed bydigester followed by a er a ted la goons (fa r m 1) or by solid/liquidsepa r a tion of the effluent a nd a m m onia str ipping (fa rm 5 ) .



356

TABL E IV - VS , TS and COD removal of the plants

Plant

1

2

3

4

5

VS removal(%)

4 6 ( a ) - 6 1 ( b )

57

4 6 ( C>

40

49

TS

3 0 ( a

removal(%)

L> . 5 5 ( b)

47

3 5 ( c )

32

44

COD

42 (a!

removal<%)

1 - 6 1 ( b )

59

50<C>

~56

Note: a - digester onlyb - digester plus settling tankc - primary digester plu s post digester

On Testa farm biogas in used in two Fiat Totem combined heat and power units. The performance o f the Totem is reported in table V.

TAB LE V - The performances of Totem units

Electic power (Kw) 11.27

Thermal power(Kcal .h , ) . . .

30095Biogas consumption (Nm . h ) 8.94CH biogas content (%) 62

In the period November 82 - October 83 the average Totem electricenergy production was 154 Kwh.d representing 81% of the total electricenergy requirement (plant and breeding). Heat was used for heatingdigester.

On S. Matteo farm net biogas production is used for the dairy'ssteam generator. In the period October 83 - June 84 the average biogasproduction is 210 m .d with 5 8% used to satisfy the digester heat

requirement and 36% used for the dairy's steam generator.On Perugina farm net biogas production is used for drying forage

and cereals. The drying machine came into operation in June 84 , and hasbeen used up till now in the months of Jun e, July, September and October84 . In the period January-N ovember 84 the average biogas production is50 6 m .d and the average biogas used for the digester heat requirements is 277 m .d . The plant' s average electric consumption for plants1,2 and 3 is respectively: 206 wh.m digester.d , 34 1 wh.m digester,d , 148 wh.m digester.d

4 . PLUG-FLOW EXPERIMENTAL PLANT

Interesting data were obtained about the heat exchange capacitiesof the two coils immersed in the still manure, that range from 23 to 46W.m . °C for this experiment. The iron coil showed a lower heat exchange capacity in respect to the polyethylene one. This means that in suchconditions the exchange material is relatively less important, becausethe resistance of the manure to heating is very high. The relativelylower coefficient found for the iron pipe can be explained by the factthat the iron coil is in the first part of the reactor where the densityof the manure is higher and the bubbling of biogas is lower. The overallefficiency of the heating system is between 80 and 85 %. The biogas con



357

sum ption used in m a inta i ning a consta nt tem per a tur e r a nges fr om 25 to65% of the bioga s pr oduced, de pending on the loa ding r a te a nd the tem p er a tur e of the env ir onm ent. As fa r a s the needs in electr ic ener gy a r e

concer ned, they a r e v er y low, only a b out 21 kwh/d; 50% a r e used for thechopping a nd for the discha r ge p um ps . The concentr a tion of tota l soli ds,v ola tile solids a nd v ola til e a cids decr ea ses r egula r ly fr om the beg inning to the end of the r ea ct or , showing good plug-flow beha v iour of thepla nt, pr oba bly due to the pr ese nce o f thr ee inter n a l ba ff les tha t for cet h e d i g e st i n g w a s t e t o p a s s o v e r o r u n d e r t h em .

5. CONCLUSIONSThe m onitor i ng schem e ca r r ied out on 5 full-sca le pla nts , 4 dem o n

str a tiv e ones a nd a n exper i m enta l o ne , shows high bioga s yield (m .KgVS .d ) . The a na er obic digestion pr o ces s is shown to be sta bl e, ev en

when ther e a r e fa lls in digestion tem per a tur e, or br ea ks in the m ixin ga nd feeding pr o cess. Consider a ble pr obl em s wer e noted, howev e r , in them a nu r e collection system : sta gna tion lea ding to pa r tia l digestion of theor g a nic substa nce, a nd dilution of the wa ste by gr ound or clea ningwa t er . Sev er a l m ethods ha v e been studied to r ectfy this a nd in pa r t putinto pr a ctice in or der to im pr o v e wor king conditions. Im pr ov e m enttechniques a r e a lso needed in or der to m a ke full use of the ene r gy.

REFERENCES

- APHA - Ameri can Public Healt h Associat ion (1975) : "Sta nda r d Methodsfor exa m ina tion of wa ter a nd wa s te wa te r ", 14th edition, APHA, N.Y.

- B onaz zi G., Cortelli ni L., Picc ini ni S., Tilche A., (1984): "The Bi ogas Project in Emilia-Romagna (Italy)", p a p e r pr e s e n t e d t o t h e B i o -Ener gy 84 Confer ence, June 18-21, Gotebor g, Sweden.

- Chiumenti R. , De Poli F., Gabb i P., Moz zi A. and Tilche A. (1983): "Ada ta a cquisition system for the m onit or in g of a na er obic digeste r s: design a nd a pplica tion", in Pr oceeding s of the Ana er obic Wa ste Wa terTr ea t m ent Sym posium , Noor dw ijker out, 23-25 Nov em ber , 559-5 72.

- Tilche A., De Poli F., Ercol i L., Tesini 0., Cortellini L., Picci nini

S.: "An im pr o v ed plug-flow de sign for the a na e r obic digestion of da ir yca ttle wa st e" pa per pr esent ed to the Inter na tiona l Confer ence" Sta teof the a r t on b ioga s technology tr a nsfer a nd d iffusion", Ca ir o,November 1 7 - 2 4 , 1 9 8 4 .

- Regione Em ilia -Rom a gna , Dipa r tim ento Attiv ita Pr oduttiv e Agr icol tur a eAlim enta zione (1983): "Pr ogr a m m a di r icer c a per la pr oduzione e utilizza zione di ener gie integr a tiv e in zootecnia ".

- Regione Em ilia -Rom a gna Dipa r tim ento Attiv ita Pr oduttiv e Agr icoltur a eAlim enta zione (1983): "Risulta ti d i due a nni di contr ollo su cinque impia nt i di Bioga s in Rom a gna ".

- Tilche A., De Poli F., Erco li L., Tesini 0., Cortellini L., Picci niniS. (1984): "Un im pia nto sem plifica to di bioga s tipo "plug-flow" per liqua m i bo v in i", Regione Em ilia - Rom a g na - ENEA, Bologna , 23 pp.



358

FARM EXPERIMENTS OF ANAEROBIC DIGESTION TO CONTROL ODOURS FROM SLURRY

J.A.M. VOERMANSInstitute of Agricultural Engineering, IMAG

Wa geningen, the Nether l a nds

Summary

Ev er y fa r m e r in the Nether l a nds needs a per m is sion, a ccor ding to the

nuisa nce a ct, befor e oper a ting . It is possible tha t this per m issionincludes lim ita tions a nd conditions a ccor ding to a r estr icted em issionof m a l odou r s. Tha t conta ins tr ea t m ent of a ir a nd/or slur r y. For thistr e a t m ent ther e a r e sev er a l technics a v a i la ble. All the possibilitiesincr e a se the pr oductio n cost without a ny effect on sa le pr ice s. In thepa per a ttention is pa id to the question a bout the position of thea na e r obic di gestion between the other technics. Most of the m a lodor ouscom pounds disa ppea r by a na e r obic d igestion . To pr ev ent a m a lod our ofthe v entila tion a ir a fr equent clea ning of the a nim a l house is nec essa r y. Ba sed on ca lcula tions in m a ny situa tions a na e r obic digestionwill be the chea pest wa y to m eet the conditions of the per m issio n.

P r a ctica l exper iences pr ov e this.

1. INTRODUCTIONEnv ir onm enta l polluti on is the subject of m a ny p olitica l a nd socia l

discussions in the Nether l a nds. This is m a inly ca used by the concentr a tionof the a nim a l husba ndr y fa r m s close to the v illa ges a nd cities. Ther e a r etechnica l tr ea t m ents of a ir a nd slur r y to decr ea se the odour of it. Ana er o

bic digestion is one of these. This technology is known fr om biog a spr o duc-tion. Most countr ies in the wester n wor ld ha v e studied this possibility forr enewa ble ener gy. A lot of technica l pr oblem s a r e solv ed but on m ost pla cesit is not possible to pr oduce bioga s fr om fa r m wa ste to a com petitiv e pr ice.Wha t is the fea sibility for bioga s pr oduction if ther e is a need for r edu ction of the odour emission on the farm?

2. THE SITUATION IN THE NETHERLANDSSince 1984 there is a polit ical and social discu ssion about the surplus

of or ga nic/a nim a l m a nur e a nd the a ir polluti on, specia l the acid r a in . Ita r e the m iner a ls in the fa r m wa ste a nd the NH3 in the v entil a tion a ir , which

a r e in discussion.Calculation s (11) based on figures from 1982 show that in the Nethe r

la nds ther e a r e 10J m illi on pig s, 87 m ill ion poultr y a nd 5.2 m illio n ofca ttle . These a nim a ls pr oduce a tota l a m ount of 86.5 m illio n tons of slur r y.About 30 mil lio n tons of this amount is produced in the fields by thegr a zing ca ttle. So 56.5 m ill ion tons a r e stor ed for a cer ta in per iod. Nea r ly40 m ill ion tons ca n be used in the fa r m s wher e the slur r y is pr oduced whenther e a r e a gr icultur a l lim its to the gifts per a r ea . Such lim its a r e ba sedon a positiv e r ea ction of the cr ops to this gift. On this ba sis a bout 18m illio n tons should be tr a nspor ted to other fa r m s . Tha t m ea ns a bout 2000loads of 40 tons per work ing da y if it is transported by road . Nearly all



359

this slurry must be stored bec ause of the limited period for sprea ding.This im plies em ission of odour s dur ing s tor a ge, tr a nspor t a tion a nd

spr e a ding. In a high densitiv e popula ted countr y a s the Nether l a nds it

m ea ns that ther e a r e m a n y situa tions a nd per iods in which these odour sa nnoyed the people. In the Nether l a nds ea ch fa r m m ust ha v e a per m ission,a ccor ding to the nuisa nce a ct, to be in oper a tion. In this per m issionther e a r e lim ita tions a nd conditions a ccor ding to the unique loca tion ofthe farm. The presence of neighbour s is of significant influ ence. So itca n be pr edicted tha t specia l inv estm ents ha v e to be r ea lized for r eduction of m a lodour s fr om the slur r y. To the fa r m e r this ca n m ea n a choicebetween to be or not to be. Reduction of odour s r esults in extr a costsa nd by this wa y a lso a r eduction of the pr ofita bility.

Ther e a r e sev er a l technics a v a ila ble to r educe the em ission of

m a l odou r s. These technics ca n be div ided into the following gr oups.1. Tr ea tm ent of the v enti la tio n a ir

- wa shing - a ir -wa sher s- filter - biobeds

2. Treatment of the slurry- a er a tion- a na e r obic digestion- sepa r a tion com bined with a n (a n)a e r obic follow-up

In this paper attent ion is paid to the question about the positionof the a na e r obic digestio n between these technics.

3. ODOURS FROM SLURRYSlur r y is a m ixtur e of fa eces, ur ine a nd wa ter , som etim es with som e

feedr ests a nd/or bedding m a t er i a l. About the com position of the fa ecesa nd the ur ine a lot of infor m a tion is a v a i la ble. The m ost im por t a nt odor ouscom pounds a r e phenol (C6H5OH), pa r a -c r esol (CH3-C6H4-OH), 4 ethylphenol(C2H5-C6H4OH), indole (C8H7N) and skatole (CH3-C8H.6N). Also the v ola tilefa tty a cids ha v e a n offensiv e sm el l, specia lly the butyr ic a ci d(C3H7COOH).The m icr obia l br ea kdown of pr oteins in a n a na e r obic stor ed slur r y r esultsin the pr esence of the a r om a tic com pounds (Sp o e l s t r a ) .

The attempts at increasing the efficiency of labour and capital haveled to intensiv e system s for a nim a l husba ndr y. Sla tted floor s with thestor a ge of slur r y under it a r e v er y com m on. This is specia l tr ue for pigsa nd ca ttle. Poultr y is differ ent. Br oiler s liv e on a la yer of wood sha v ingswhich will be m ixed up with the dr oppings a nd wa ste wa ter dur ing thegr owing per iod. Most la ying hens a r e housed in ca ges. The dr oppings ca n bepr ocessed in differ ent wa ys. Dr ying in deeppit houses or on a belt justunder the ca ges a r e possibilities to r educe the tota l a m ount a nd the sm ell.On the other hand the..: are also wet storag e sy stem s.

All these dev elopm ents in the technology of a nim a l housing r esult instor a ge of the m a n ur e in such a wa y tha t it pollutes the a ir m or e or less.

4. REDUCTION TECHNICSIn cha pter 2 a sur v ey is giv en of the technics which ca n r educe the

em ission of m a lod or ous com pound s.

4.1. Tr ea tm ent of the v entil a tion a irAir tr ea t m ent m ea ns destr oying the effects of the pr esence of slur r y

in the sa m e spa ce wher e the a nim a ls liv e. The ca use of the pr esence of them a lodo ur s is not touched a t a ll. With both the a ir -wa sher a nd the biobedr eductions of 95-99U a r e r ea ched. These figur es a r e ba sed on the subjectiv e



360

p e r c e p t i o n o f pa n e l m e m be r s ( o l f a c t o m e t r y ) .The costs for these technics are high and most ly expressed as an

inv estm ent/m ^ a ir .h. Beside the ca pita l costs ther e a r e a lso r unning costs.Mecha nic a l v enti la tion is a necessity a nd extr a ener gy is used to pr ess thea i r thr ough the wa sher or the biobed. For this pur pose ther e is not m uchdiffer ence betwe en both technic s. For a 500-fa ttening pighous e the inv estm ent is a bout Dfl. 100.000,-. The a nnua l ca pita l a nd r unning costs a r ea b ou t D f l . 2 0 . 0 0 0 , - o r D f l . 4 0 , - p e r p i g p l a c e .

For these technics ther e a r e nea r ly no econom ics of sca le beca use thea m ount of v entila t ion a ir is dir ectly connected to the num ber of a nim a ls.Both the a ir -wa sher a nd the biobed ha v e a m a xim u m loa d.

4.2. Treatment of the slurry

Reduction of the emission of odours by treatment of the slurry is adir ect wa y . On one ha nd this ca n pa r tly be done by sepa r a te stor a ge of thefa eces a nd the ur i ne. On the other ha nd by a er obic or a na e r obic tr ea t m ent.

Aer obic_tr ea t m entWith the oxigen from the air the C from the organic material is

bur ned.

C6 H12°6 + 602 —» 6C02 + 6 H 2 ° + energySo there is a posi tiv e energy res ult, but it costs energy to mix the airthr ough the slur r y. In som e Da nish r esea r ch wor k they ha v e tr ied tor ecov e r this ener gy for hea ting the fa r m house. Nor m a lly the a er obictreatment is just used for destroying the mal odor ous compounds in theslur r y.

Ther e is a need for a ba sin outdoor s a nd no stor a ge of slur r y inside.The slurry is washed to the basin by the treated was te . The extra investmentfor 500 pigs is Dfl. 25.000,-. For la r ger units it is r ela tiv e ch ea per .The total annual costs (investment and runni ng) are for a 500-pig unitD f l . 20,-/pig p la ce. For a 1000-pig unit the total costs go down to aboutD f l . 1 1 , - p e r p i g p l a c e (Po e l ma , 8 ) .

Anaerob ic treatment

Since m or e tha n 10 yea r s m uch r esea r ch is done on the a na e r obicdigestion fr om slur r y. This r esea r ch is m a inly stim ula ted by the option ofthe r enewa ble ener gy: biog a s. But ther e is a lso a n effect on the pr esenceof the m a lodo r ous com pound s. In the next cha pter m or e deta ils a r e pr esented.

Separated storage of faeces and urine

Kroo dsma (6) studied the use of a filter to separate the urine and thef a e c e s . The ma in target is to transport the mix tur e of faeces and somestr a w to a r a ble fa r m e r s a nd spr ea d the ur ine on own fa r m l a nd. But a sideeffect of dir ect sepa r a tion is a r eduction of the em ission of odour s.This sepa r a tion system is r ela tiv e expensiv e, especia lly in m oder n pighouses

with tr a nsv e r se cha nne ls. For a 500-pig unit the extr a inv estm ent is a tlea st Dfl. 7 0, - per pig pla ce. The total a nnua l costs a r e Dfl. 5,- per pigpla ce. In a pigh ouse with channels in length this system is cheaper and thisdiffer ence incr e a ses when the house is longer .

5. ANAEROBIC DIGESTIONDuring the last 10 year s there is published an enormous amount of

r epor ts on a na er obic digestion. This pa per does not ha v e the intention tox )

According to V.d . Hoek (1) the aeration re quires at least an input of36 kWh per pig pla ce per ye a r .



361

sum m a r ize a ll this li ter a tur e. Just the pr inciples a r e im por t a nt. Undera n a e r obic conditions differ ent types of m icr o bes tr a nspor ted the v ola tile

fatty acids and the arom atic compounds to CH4 , C02, H2O and NH4OH . There

is also some H2S produced from the digestion of several protein a cids(cysteine and m e t h i o n i n e ) . All these endpr oducts together , known asbioga s, ha v e a typica l odour , m a inly ca used by H2S a nd NH3. Beca use of thebr e a kdown of the m a lod or ous com pounds the slur r y ha s lost its typica lsm ell.

5.1. Biogas yi eldsBioga s pla nts a r e designed a nd m a na ged to optim ize the bioga s yield.

Popula r a r e the fully m ixed system s which oper a te a t a tem per a tur e of30-35 °C. Depending from the type of slurry (dairy, pigs or poult ry) thedetenti on time change s. But fully mixed includes that it comes to an

a v e r a ge. So som e m a lodor ous com pounds will still be found in the effluent.But in the storage after that there wil l be a further break down at a lowspeed.

Econom ic ca lcula tions for bioga s pla nts a r e ba sed on a ll the costsbut for the yield ther e is only a n ev a lua tion for the bio ga s . Most pla ntsoper a te with a n econom ic loss. This loss depends m a inly on:. the investment for the total plant, including s torage digested slurry,

b o i l e r s , CPH-unit, piping, electr icity con nections.. the quali ty of the pro ces se s; the amount of CHA/nr* of dig est er/ day .. the use of the biogas. the price of the replaced ener gyCalculatio ns (7, 1982) resulted in losses for both dairy and pig un it s.T a ble I giv es som e com pr ehensiv e r esult s.

Table 1 Some result s for differe nt farm types

a nim a lsizea nnua llossesfrom thebiogas plant(Dfl.)

a v e r a geper pla ce

da90

7.000

9.000

90

iry150

1.500

5.000

20

fa ttening pigs500 2.500

6.500 1.400

7.500 1.600

14 0.6

br eeding

1 0 0 / 6 0 0 x )

3.500

3.600

5

and fattening

150/900

700

1.000

0.8

x)sows/pigs

5.2. Odour r eduction

The r eduction of the typica l sm ell of slur r y by a na er obic di gestionis the r esult of the br ea kdown of phenol , p-cr esol, 4-ethylphenol, indole,ska tole a nd the v ola tile fa tty a ci ds.

Va n Velsen (10) concludes tha t for pigger y wa ste the optim u m detent iontime, with r espect to the r eduction of the m a nur e odou r , is a ppr ox. 15 da ys .He did his experim ents with fully mixed systems at 30 °C. In practic alplants the detenti on time is at least 15-18 days . The exper iences inpr a ctice a gr ee with these r esults. This r eduction on its own is not e nough,because after digestio n the slurry will be stored till the mom ent that itca n be spr ea d on the la nd. Va n Velsen (10) ha s pr ov ed tha t the co ncentr ation of v ola tile fa tty a cids a nd the a r om a tic com pounds decr e a se dur ing the



362

stor a ge a fter diges tion. This ha ppens both in winter a nd sum m e r . Within1 m on th the concentr a tions a r e a lr e a dy a t a consta nt low lev el. The a cetic

acid is eliminate d quicker at 20 °C related to 4 °C. There are no si milarfigur es for da ir y slur r y a v a ila ble, but ther e seem s no r ea son to expecta nother r ea ction.

5.3. Effects during and after spreadingOlfacto ry resea rch was done by IMAG (Harreveld (2 )) . The result of

such resea rch is the numb er of the air dilu tion after whi ch 5031 of thepa nel m em ber s is not a ble to distinguish the fr esh clea n a ir fr om thepolluted a ir . This num er is ca lled the odour thr eshold . Ta ble 2 giv es ther esults of the thr esholds of fr esh a nd digested pigger y wa ste dur ing a nda fter spr ea ding.

T a ble 2 The thr eshold-v a lues for fr esh a nd digested pigger y wa ste a tdiffer ent per iods (h) a fter spr ea ding

per iod a fterspr e a ding (h)

04812

1620244872

- spr ea ding

thr esholdsfr esh

1000

760570430

320240180336

fordigested

3201204516

620--

These r esults show a clea r effect of digesti on. The sm ell a fter spr ea dingdigested slur r y ca n be inconv enient for just a shor t per iod.

Another str iking exper ience is the gr a zing ha bit of da ir y cows on agr a ssfield , pa r tly spr ea d with fr esh a nd pa r tly with digested slur r y. Ther eis a significa nt pr efer ence dur ing the fir st da ys for the digested slur r y.These exper i m ents did not pr ov e a differ ence in m ilkyi eld.

As a r esult of the m a int a ining a ccepta bility of the gr a ss by the cowsone da ir y fa r m e r uses nea r ly no a r tificia l nitr oge n on his la nd a ny m o r e .In early spring he gives a dosis of about 20-30 ton/ha and during thegr owing sea son a fter ea ch cut or gr a zing a sm a ller gift. He is quitesa tisfied.

6. BIOGAS PLANTS BASED ON ENVIRONMENTAL LIMITATION

On m a ny pla ces the possibilities for a nim a l husba ndr y fa r m s a r er estr icted beca use of the em ission of odour s. In such situa tions a bioga s

pla nt m a y r esult in a per m ission for continuing or incr e a sing the num ber ofa nim a ls. Fr om the Nether l a nds ther e a r e som e exa m ple s.

6.1. Fa r m Ver m eltfoor t a t Heeswijk-DintherThis fa r m is now situa ted between bunga lows a nd beside a footba ll

pla ygr oun d. On the fa r m ther e a r e 400 v ea lca l v es , 20 beefca l v es a nd 40.000guinea fow ls. The layout of the farm is given in figure I. The farmer hadto r educe the odour em ission on pena lty of closing. He ha d to decide betwee na e r obic or a na e r obic tr ea t m ent of the slur r y of the v ea lca l v es. He built a250 m 3 di gester . The influent in a m ixt ur e of the slurr y a nd the litter fr omthe guinea f owls. The bioga s is used dir ectly in boiler s to hea t the houses



363

of the fowls a nd the wa ter for the v ea lca l v es. Ther e is a lso a 20 kW CPH-unit in oper atio n. Hoeksma (3) calculated that the economi c result of thispla nt wa s nega ti v e. The differ ence is a lso the pr ice for the odour r educ

tion. The cost of biogas wa s D fl . 0,09 per m-3 higher than the va lue , basedon ener gy pr ice s. Tha t is one of the best econom ic r e sults.

6.2. Farm Rijkers at Nistelrod e (figure 2)This farm with /0.0UU laying hens and 500 fattening pigs decided to

incr e a se the poultr y br a nch. But they did not get per m i ssion beca use of theem ission of ba d odo ur s. A 950 nw bioga s pla nt offer s the oppor tunity tobuild a new poultr y hous e. All the pr oduced bioga s is used in a 75 kUCatterpilla r CPH-unit. At the mome nt a large part of the electr icity isdelivered to the grid. The heat is used for warmin g the offic e and coll ection room for the egg s. But there is too muc h h eat . For that rea son thefa r m e r bought a pr ess to pr ocess the dr y dr oppings of one poultr y ho use.The fa r m just sta r ted so ther e is still no econom ic ca lcula tion or ev a l uation.

7. ECONOMICS OF ODOUR REDUCTION

Ther e a r e sev er a l wa ys to r educe the em ission of odo ur s. Jongebr eur(4) giv es in ta ble 3 a sur v ey of the effects of the differ ent technologies .

Table 3 The effects of different method s for odour reduct ion

m ethod effect onv entila tion a ir slur ry stor a ge slur r y spr ea ding

a i r wa sher + -biobed + -separation of faeces and

urin e + + +fr equently r em o v a l of

slurry + -aerobic treatment + + +a na er obic digestion - + +frequent removal combinedwith a na e r obic digestion + + +

If there is a need for odour reduct ion on an animal husban dry farma n a e r obic diges tion is one of the r ea l possib ilitie s. The inv estm ent a ndr unning costs of the m et hod s, m entioned in ta ble 3, a r e indica ted inpr e v ious cha pter s. An econom ic ca lcula tion for the fea sibility of a n a na er obic digestion is open for discussion. For our pur pose we m ust v a lua tethe nett output of bioga s.

Table 1 showed that for a 500-pig unit the annual losses a re aboutD f l . 7.000,-. These losses a r e ca lcula ted (7) under optim a l co nditions .When odour r eduction is the fir st goa l, losses ca n be higher . Suppose tha t50Z of the produced b iogas is not used. The extra losses are 5000 m3 aD f l . 0,52 - Dfl . 2.600,- higher . So tota l losses incr ea se to Df l. 9.600,-.Per pigpla ce a r e the costs for odour r eduction nea r ly Dfl. 20, -.

For a 2000-pig fa r m ther e wa s ca lcula ted a pr ofit with bioga s pr odu ction of Dfl . 4.000,- a nnu a l. But if her e 50% of the bioga s is not pr oducedor used the r esult will be a loss of Dfl. 60 00,-. Odour r eduction costs inthis ca se Dfl. 3,- per pigpla ce a nnua l.

If there is a need for clea n vent ilat ion air the slurry must beremoved out of the house frequently. In existing buildings with storage



364

capacity under a slatted floor the removal of the slurry can be a problem.Keeping the amount of slurry at a low level is to realize without extra

cost. For new buildings there are solutions with scrapers in shallowcanals. The extra investment is not so high because of the cheaper canals.

8. CONCLUSION

On an increasing number of animal husbandry farms there are troubleswith pollution by ventilation air and slurry. The typical odour is causedby the slurry. In some situations it is sufficient to treat the ventilationair. In other cases there is also a penalty on the emission of odoursduring spreading the slurry on the field. For these problems there areseveral solutions. Anaerobic digestion is one of these. Interest inanaerobic digestion is mainly based on biogas production. All the countries

in the western world with the import of oil started research in this field.Nowadays the conclusion is that biogas production is not economicallyattractive on most of the animal husbandry farms. Biogas production is areal option if there is a need for the reduction of pollution. The totalbalance is not known exactly but the emission of odours can be reducedtill 9 0 %. It is necessary to have no storage of undigested slurry in thehouse. In many situations anaerobic digestion can be a technical andeconomical possibility to reduce the typical farm smell.

LITERATURE

(1) GE EL EN , M.A. van en K.W. v.d. HOE K. Stankbestrijdingstechnieken voorstallen in de intensieve veehouderij. Imag publ. 167(1982).

(2) HAR RE VEL D, A.Ph. van, De geuremissie tijdens en na het verspreiden vanvarkensmengmest. Imag rapport 37(1981).

(3) HOE KS MA, P. Biogaswinning en -benutting op veebedrijven. Imag publ.199(1984).

(4) JONGE BR EU R, A.A. en M.A. van GE EL EN , Mogelijkheden voor de preventieen bestrijding van stank. Colloquium Luchtreiniging m.b.v. biologischefilters. VROM (1983) Utrecht.

(5) KL ARE NB EE K , J.V. e.a. Geuremissie bij mestvarkensstallen. Imag rapport

48(1982).(6) KR OODS MA, W. en H.R. POEL MA. Mestscheiding. Imag publ. 209(1985).(7) N N . Biogas op veebedrijven , Toepassingsmogelijkheden en Perspectieven.

Imag publ. 176(1982).(8) POE LM A, H.R. I nvestment and cost of aerobic treatment. Personal

communication.(9) SP OEL STR A, S.F. Microbial aspects of the formation of malodorous

compounds in anaerobically stored piggery waste.(10) VEL SE N , A.F.M. van. Anaerobic digestion of piggery waste. Thesis L H ,

Wageningen (1981).(11) WIJNAN DS, J.H.M. and H.H. LUESINK. Een economische analyse van trans

port en verwerking van mestoverschotten in Nederland. LE I-onderz oek-verslag 12(1984).



365

F i g l : Ve rme l t fo o r t f a rm

Gemeente Heeswi jk-Din ther

Fig 2 : Ri jkers farm

Gemeente Nistelrode /



366

USE OF METHANOGENIC FERMENTATION TO UPGRADEFARM ANIMAL AND SLAUGHTERHOUSE WASTES

I. KLINGER and U. MARCHAIMKimron Veterinary Institute Beit Dagan and

Migal Gallilee Technological CenterIsrael

Summary

Anaerobic thermophilic digestion of farm animal and slaughterhousewastes were compared to each other especially from the bacteriological point of view.The process is recommended either as a solution for the ecologicalproblems involved with accumulation of animal wastes as well asprofitable recycling of this waste.

1. INTRODUCTIONThe concentration of a large number of farm animals in a limited

space as is common in modern farming results in the accumulation oforganic waste in big quantities over and above the neutralizationcapacity of the immediate environment. This problem is magnified inslaughterhouses in urban areas without access to agricultural land thatcan act as a depot for this material. Slaughterhouses are also theultimate place for disposal of animals carrying infectious agents whichlimit the utilization of slaughterhouse wastes. It contains also highlevels of solids with more than 80 % decomposable organic matter with veryhigh BOD levels.

This waste contains enough nutrients to allow multiplication of theoriginal heavy load of microorganisms.This situation creates thus the need to find novel methods for

neutralization of such hazardous material accumulating each day (10).

2. ANAEROBIC THERMOPHILIC DIGESTIONAnaerobic digestion of organic material has been implemented for many

years as a practical method for disposal combined with energy recoveryfrom the digested material (1, 2). Anaerobic fermentation is a processwherein complex organic materials are broken down resulting in the formation of biogas (consisting of methane and carbon dioxide). The speed of

the reaction can be increased by elevation of the temperature (3). Fromthe bacteriological point of view, this increase means a change in theactive population from mesophilic bacteria (4) (optimal temperature30-40°C) into thermophilic bacteria (optimum 50-60°C). This digestion ishighly influenced by the activation temperature and other factors such aspH-value, presence of nutrients, presence of oxygen and presence ofsubstances toxic to methane producing bacteria (6).

3. ADVANTAGES OF THE BIOLOGICAL FERMENTATION OF WASTEThe b e n e f i t s e xp ec t ed from th e An aero b ic Th erm oph i l i c D ig es t io n (ATD)

o f a n i m a l w a s t e a r e a s fo l l o w s :



367

1. Reduction of odour s r esulting fr om concentr a tion of a nim a ls .2. Reduction of or ga nic loa d fr om the env ir onm ent.(including sewa ge )3. Recycling of the v ola tile pha se a s bioga s for ener gy pur p oses.

4. Recycling of the solid pha se a s pea t substitute.5. Recycling of pa thogen-fr ee wa ste wa ter .6. Ina ctiv a tion of the infectiv e a gents pr esent in the wa s te.

Utiliza tion of the solid pha se o f the fer m ented m a ter i a l ha s la tely becom ethe main benefit o f ATD since intens ive digestion results in only thelignocellulose por tion of the or ga nic m a ter i a l r em a ining in the sludge.Following dehydr a tion the dr y m a ter i a l n ow known a s "Ca butz" is used a spea t-m oss substitute in gr eenhouses a nd m ushr oom gr owing. It wa s a doptedfor this pur pose pr oba bly beca use of its content of gr owth pr om otingfa ctor s, its por osity which a llows good a ir penetr a tion, a nd its goodwa te r holding ca pa city (5, 7, 8 ) .

4. BACTERIOLOGICAL ASPECTSATD is com m only under stood to occur in two sta ges: a cid for m a tion a nd

m etha n ogenesis, which is sum m a r ised a lso in the following da ta (tables1 and 2) . The nor m a l intestina l ba cter i a a r e r educed by 6-7 loga r ithm sfr om a lev el of 10' pr io r to the digestion into a lev el o f 10^ a nd lowerther e a fter . Am ong the com ponents of the intestina l flor a colifor m s,la ctoba cilli a nd enter ococci a r e r educed whilst Clostr idium welchii r emains at its initial le vel. The reaso n for this change in bacte rialpopula tion is pr oba bly due to the com bina tion of unfa v o r a ble tem per a tur ea nd for m a tion of fa tty a cids in the ingested m a ter i a l.

Sa lm onella e wer e fr equently isola ted fr om r a w m a ter i a l pr ior to theATD pr ocess but none fr om the digested sludge. It is howev e r o f pa r ticu la r inter est to follow the elim ina tion o f Sa lm onella e fr om the digestedm a ter i a l. For this r ea son a sepa r a te exper im ent including a r tificia linocula tion with sev er a l Sa lm onella ser otypes wa s per for m ed.

The inocula tion with Sa lm onella wa s a t m uch high er lev els tha n tha toccur r ing under field conditions r esulting in a n elim ina tion o f Sa lm onella e within 24 hour s. This wa s connected with the a mount of fr ee fattya cids r elea sed dur ing the ATD pr ocess (3, 6 ) .

5. SLAUGHTERHOUSE WASTESla ughter house wa ste is a m ixtur e of a nim a l excr eta deposited in theesta blishm ent a nd wa ste fr om the sla ughter ing pr ocess such a s intestina lcontent s, sluice wa ter which a lso include v a r ious body fluids such a sblood, ur ine , m ilk. Due to the high solid content which include 80% orm o r e putr escible or ga nic m a tt er a nd a high BOD lev el, ATD does notfunction sim ila r ly to fa rm a nim a l wa stes. In a ddition ther e a r e highv a r i a tions in the biolo gica l, m icr obiologica l a nd chem ica l com position ofintestina l content of v a r ious a nim a ls br ought to sla ughter . Som e of thesediffer ences fr om the ba cter iologica l point of v iew a r e sum m a r ized intable 3.

Adjustm ent of the ATD pr ocess to digestion of sla ughter house w a steseem s to be m or e com plica ted tha n a nim a l wa ste a lone. Howev e r this ca nbe solv ed by the a ddition o f a nim a l wa ste to the digestor s in a r a tio ofat least 40% animal was te. It mea ns also that adaption of ATD to solvethe sla ughter house wa s te needs a consta nt supply of r a w m a ter i a l fedinto the system.

6. DECONTAMINATION OF WASTEIn cer ta in cir cum sta nces a nd especia lly since sla ughter house wa ste is

digested, ther e is a need to disinfect to pr ev ent spr ea d of infectious



368

agents ( 4 ) . From the economical point of view it is much easier to disinfect prior to the ATD, however the decontamination procedures have to

fulfill several requirements in order to be suitable for ATD .a. As we deal with anaerobic digestion there is no possibility o f

utilization o f decontamination by ox idation.b. Because of the large amounts of material handled the price of the

decontamination process is of considerable importance.c. The decontamination process should not interfere with the ATD

process.d. Materials used should not have any corrosive effect on metals

used.Considering these points, the most beneficial method for decontaminationseems to be one of the fatty acids released during the ATD proces s, after

examination with and without organic material and in mesophilic or thermophilic temperatures, formic acid was found most effective even in concentration of less than 0.5%.

REFERENCES

(1) BU SW EL L, A.M. In: L. A. Underkofler and R. J. Hickey [Editors),Industrial Fermentations, Vol. w, Chemical Publishing C o., New York,518, 1949.

(2) HOBS ON, P.N., BOUSFIELD , S. and SUM MER S, R. CRC Crit, Rev. Environ.

Control, 4: 2, 1974.(3) KI MC HI E, S. High-rate anaerobic digestion of agricultural wastes.

Ph. D. Thesis, submitted to the Haifa Technion, Israel, 1984 .(4) KL IN GER , I. et. al. NE FAH annual reports (In Hebrew). Kibbutz

Industries Association, 1 9 82, 1983.(5) LEVANON, D.C., DOSORE TZ, B., M0T R0, and KAH N, I. Recycling

agricultural waste for mushroom casing. Mushroom J., 13 3 , 13 , 1984 .(6) MAR CH AIM , U., and CR ID EN , J. Research and development in the utili

zation of agricultural wastes in Israel for energy, feedstock fodder,and industrial products. In: D. L. Wise ( E d) , "Fuel Gas Productionfrom B iomass", Vol. 1, CRC Press Inc. Boca Raton, Florida, pp. 95-

120, 1981.(7) MA RC HA IM , U. Anaerobic digestion of agricultural wastes. The eco

nomic lie in the effluent uses. Int. Symposium.on Anaerobic Digestion 83. Boston M a. , 1983 .

(8) MAR CH AIM , U., PE RAC H, Z., and KI MC HI E, S. An integrated approach tothe anaerobic digestion process. In: D. L. Wise (Ed.) "Fuel GasSystems", CRC Press I nc., Boca Raton, Florida, 14 1, 1984.

(9) MC CARTY, P.L. Public Works, 95 : 12, 1964.(10) WE NTK ORTH, R.L., ASH ARE , E ., and WI SE , D.L. Fuel gas production from

animal residue, part 1. Res. Rec. and Conservation, 3, 3 4 3, 1979.



Table 1: Changes in bacterial population during and after Anaerobic Thermophilic Digestion of cattle waste

in a pilot plant

Type of bacteria

T. A. M.

T. A. T.

T. An. M.

Coliforms

Enterococci

Lactobacilli

S. Red CI.

Start

9.8 - 0.9*

7.0 - 0.6

8.1 - 0.7

7.4 - 0.7

6.1 - 0.7

5.7 - 0.4

3.3 - 0.5

batch

for 12

7.6 ;

7.1 i

6.0 :

2.1 i

2.5 I

1.7 i

3.5 i

days

0.5

0.3

0.6

0.6

0.7

0.6

0.3

Start

6.7 - 0.4

7.0 - 0.4

5.4 - 0.5

1.4 - 0.5

1.6 - 0.5

1.4 - 0.6

3.3 - 0.4

Plug flow method

Middle

6.6 - 1.0

6.9 i 0.6

5.7 - 0.7

1.2 - 0.4

1.3 - 0.5

1.3 - 0.6

3.3 - 0.4

End

7 . i ;

6.9 i

6.0 i

i . 6 :

i . 7 i

i . 5 :

3.4 i

0.7

0.4

0.6

0.5

0.7

0.5

0.4

as

T. A. M. = Total Aerobic Mesophilic bacteriaT. A. T. = Total Aerobic Thermophilic bacteriaT. An. M. = Total Anaerobic Mesophilic bacteriaColiforms = Total Coliform bacteriaS. Red. CI . = Sulphite Reducing Clostridia - Clostridium welchii

* = Decimal logarithms of counts



Table 2: Changes in bacterial population after Anaerobic Thermophilic Digestion in a full scale plant

Type of bacteriaLogarithms of bacterial count

Start Stage 1 Stage 2

T. A. T. 9.6 - 1.2* 7.4 - 0.3 7.4 - 0.3

T. A. M. 8.9 - 1.0 7.4 - 0.4 7.4 - 0.4

T. An. M. 8.8 - 0.5 6.9 - 0.5 6.9 - 0.4 ©

C. Conforms 8.7 - 0.7 3.5 - 1.1 2.8 - 1.0

Enterococci 7.9 t 0.8 4.4 - 1.1 3.8 - 1.0

Lactobacilli 6.7 - 0.6 1.6 - 1.1 1.7 - 1.0

S. Red. CI . 4,8 - 0.4 5.0 - 0.6 5.0 - 0.5

Decimal logarithms of counts



Table 3: Bacterial counts of rumen content collected in slaughterhouses

T. A. M.

T. A. T.

T. An. M.

Coliforms

Enterococci

Lactobacilli

S. Red. CI.

pH

upper

10.0*

8.0

9.0

6.8

9.0

7.0

2.8

8.7

Cows

lower

6.4

3.7

6.6

3.7

4.3

2.3

1.3

5.8

7.8

5.S

7.5

4.9

6.5

4.6

2.0

7.5

X

+

+

+

+

+

+

+

+

2.0

2.3

1.5

0.9

2.3

1.2

0.7

1.4

upper

8.4

7.0

8.1

6.2

7.2

6.4

2.5

7.9

Calves

lower

7.1

3.2

6.4

3.8

4.7

4.6

1.7

6.5

X

7.7 - 0.7

5.4 - 2.0

7.3 - 0.7

5.2 - 1.2

6.0 - 1.2

o.ssi 0.9

2.0 - 0.2

7.0 * 0,6

-J

Decimal logarithms o f bacterial counts



372

LATEST CHEMICAL SLURRY HANDLING METHODS

Dr. I. BOLON I and Gy. M E S Z X R O S

National Institute of Agricultural EngineeringHungary

Summary

An overwhelming majority of large-scale stock breeding farms built atthe end of the sixties, beginning of the seventies in Hungary wasoperating by gravitational manure removal. Characteristic for thegreat amount of water usage is that on a pig farm of 10 000 head a

daily amount of 150 -200 m slurry was produced with a very low, 0.4-3p.c. dry matter content.The handling, disposal of the slurry was not solved, it was stored fora long time generally in large ground basins. During the storageparasites were rapidly breeding, the groundwater polluted and theenvironment loaded by a strong smell. For the reduction ofenvironmental pollution the following experimental slurry handlingprocess has been developed resulting in a powerful phasedecomposition. The liquid phase a transparent, clear, practicallyodourless liquid can be used for irrigation without blocking off thesoil pores. The precipitated, filtered solids can be utilized as

organic manure containing suitable nutrients, by the traditionaltechnology.

1. THE DESCR IPTION OF THE PR OCESSThe essence of the first phase of the process is that homogenized,

rich in dissolved organic matter slurry coming from the pig farm will bechemically and mechanically handled in order to separate the solids and toreduce its polluting effect. Separating the colloid particles precipitatedin floccules against the effect of chemicals it will be delivered into

filter-containers where it will be sedimented for 3 weeks. The dry mattercontent of the sedimented solids increases to about 25 per cent. The liquidphase flowing through the filter-wall of the container will be led back tothe system.

The filtered, solid phase can be utilized :- as organic manure by using in the field,- after drying and adding fertilizers to it by marketing in trade.The liquid phase will be desinfected by formaldehyde, then led into a

transitory storage, from where it can be sprinkled onto the plant cultureswhen required or be reused for the flushing of the manure gutter.

The chemical treatment is carried out in the following way :

- adding hydrate of lime the reaction of the slurry is increased toover pH 12 , hereby ensuring a significant pre-desinfection. Thehydrate core of the colloid particles will open, that enablesgravitational settling. At the same time the unsoluble Ca and Mgsalts and phosphates are settled and precipitated.

- adding polyelectrolite (P raestol) and ferric sulfate ( I I ) . Itpromotes further flocculation and separation of sediments. Thereaction will be restored to pH 7-8. The liquid phase coming out ofthe settling tanks is a very clear transparent fluid.

- adding formaldehyde the desinfection of the liquid phase ispromoted.



373

The experimental plant consists of two technological lines of equalpurpose and construction.

From the central collecting pit of the pig farm slurry is conveyed by

a plunger pump into the homogenized basin of 130 0 m volume. For thefiltering of the coarse foreign matters in the slurry a steel grid ismounted onto the inner wall of the basin. The pump situated in the machinehouse beside the basin performs the homogenization of the slurry anddelivers it to the treating lines. These equipments were establishedparallel with the construction of the pig farm.

The slurry flows first into the liming reactors set up in line andthen into the settling tanks. Over the steel tanks there is a treatmentfootway made of steel plates where the feeding units for ferric sulfate andpolyelectrolite are situated. The solid phase collecting at the lower partof the settling tanks will be discharged by a screw pump into

filtering-settling containers. The liquid phase flowing away from the upperpart of the tank will be desinfected by formaldehyde and delivered into acontainer by plunger pump.

For the filtering of the settled solid phase filter containers areused. The frame of the containers was made of rolled section steel, itssides covered with sleazy plastic sackcloth. The containers stand onconcrete floor, their top is open. The volume of each container is 10 m .After filtering, the side walls of the containers will be demounted, set upat a new place and restart their repeated fill-up.

The flow diagram of the technology is illustrated in Fig. 1.



11 15

r^12 E r -

13

7y

1 . / Pig farm2. / Elevating pit3./ Slurry tank for homogenization and

feeding4 ./ Screw pump5./ C lear water pump6./ Storage tank for purified liquid phase1.1 Liming reactor8./ R ecycle pump9./ Chemical feeder

10./ Polyelectrolyte recirculation pump11./ Polyelectrolyte storage12./ Vacuum pump for feeding ferric sulfate

13./ Ferric sulfate storage14./ Chemical feed pump15./ Compressor unit16./ Clarifier17./ Sludge container18./ Sludge pump19./ Flocculator20./ Sludge filter containers21./ Formaldehyde feeding22./ Effluent elevating pit23./ Excess liquid collection pit24./ Excess liquid feed pump

Fig. 1 : Flow diagram of the chemical slurry handling



375

2. TECHNI CAL DATAVolume of the collecting-homogenizing basinVolume of the lime-hydrate reactors

Volume of the clarifierVolume of the ferric sulfateVolume of the polyelectrolite storage binVolume of the storage tank for the purified

liquid phaseVolume of the flocculatorVolume of the sludge filter containers, each

121300

and 28

1231

3001.610

m.m.

m.m.m

m .m,m

3. TEST RE SULTSDuring the tests the inner characteristics of the raw slurry, the

purified liquid and solid phases were determined and the performance intakeof the technological equipment was measured. The biological effect of thepurified substance has been controlled by germinating trials.

The test results of the inner characteristics are shown in Table 1.

Table 1

INNER CHARACTERISTICS

Characteristics Unit Measured value

Untreatedslurry

Treatedliquid ph.

Treatedsolid phase

Treated slurry per daypHDry matter contentOrganic matter content

NPKAerob bacteriaColoform germ numberFungiCCD

147

kg/m7.9

40.62.14

0.700.110.26

5.3x101.1x10

1.2x10^6.3x10

6.22.260.76

0.380.004

0.131.6x10^1.2xl0g6.7x10

4.4x10

10.525-5015.10

1.300.950.26

28.2x10.3.8x10!5.7x10!31x10'

Beside the 61 kW total performance, the specific performance projectedto the amount of treated slurry amounts to 0.41 kW per m . The specific

electric energy consumption per cubic meter : 2.14 kWh.For the purification of 1 m raw slurry during the purification

process the following chemicals were used :6 kg hydrate of lime (CaO)1 kg formaldehyde

0.5 kg ferric sulfate4 0 g polyelectrolite (Preastol)



376

For the operation of the plant 2 workers per shift are needed. In caseof continuous operation the employment of 5 persons is. required. On the

basis of the above mentioned facts the treatment of 1 m slurry requires0.12 man hours.

During the germination trials 400-400 pieces of tomato seeds wereapplied. As nutrient liquid raw slurry, purified liquid phase diluted withwater in ratio of 1:5 and tap water as control has been used. On the sixthday of treatment 34 % of the total seed germinated on the filterpapermoistured with raw slurry, 95 % on the filterpaper moistured with purifiedliquid phase, while in the control sample with tap water 68 per cent.

On the basis of aforesaid it can be stated that seed germination hasbeen more advantageously influenced by the purified liquid phase as by theother two.

The results of the hygienic tests are advantageous. Only a minimalquantity of coliform bacteria, no enterococci and a minimal quantity offungi can be found in the purified liquid phase. Salmonella could berevealed neither in the untreated, nor in the purified liquid phase as wellas in the filtered solid phase. At the same time the COD value of thepurified liquid phase amounted to 4-5000 mg/lit is high and thereforecannot be discharged into live water. From the results of the germinationtests one could draw the conclusion that the liquid phase does not containany inhibitor and thus can be used for irrigation of field plants and as aconsequence of its advantageous biological condition can be re-used forflushing the manure gutter.

The described process of the experimental chemical treatment of slurryrequires a significant investment. During our economic analysis it wasdetermined that the process can be applied only with high operating costsas a consequence of the high amortization cost and continuous expenditure.For the sake of comparison a relative cost factor is submitted, accordingto which the treatment of 1 m raw slurry by the said process requires thereturn of nearly 2 kg produced pork. For the reduction of such a high costdemand the return from sales of the solid phase could serve, but againrequires a suitable market and additional investment and therefore thepropagation of the process cannot be taken into consideration under thepresent conditions.



CONCLUSIONS AND RECOM MENDATIONS

Recommendations on olfactometric measurements

The conclusions and recommendations for furtherwork arising from the FAO/EEC joint workshop onodour prevention and control of organic sludges

and livestock farming



378

RECOMMENDATIONS ON OLFACTOMETRIC MEASUREMENTS

J.H. VoorburgGovernment Agricultural Wastewater Service Arnhera

1. INTRODUCTIONIn the working party on sludge treatment the emission of odours

is one of the problems being studied. In order to pay more attention

to odour measurement a subgroup was formed. This subgroup made aninventory of the excisting guidelines and prescriptions for olfacto-metric odour measurement. The results of this inventory are reportedin the papers by J. Hartung, M.Hangartner and J.H. Voorburg.

During the sessions devoted to odour measurement the experiencesof experts ware discussed and evaluated. As a follow-up of the discussions a small group of experts, meeting under the name "the Rose-warnegroup" agreed with these recommandations. The members of thisRosewarnegroup areA.M. Bruce, Water Research Centre Stevenage (U K ) .M. Hangartner, Institut fur Hygiene und Arbeitsphysiologie, Zurich(Sw).J. Hartung, Institut fur Tierhygiene, Hannover (F.R.G.).P.L'H ermite, C.E.C., Brussels.E.P. Koster, Vakgroep Psychische Funktieleer, Utrecht ( N L ) .R.L. Moss, Warren Spring Laboratory, Hertfordshire ( U K ) .M. Paduch, Verein Deutscher Ingenieure, Dusseldorf (F.R.G.)H.M.J. Scheltinga, Staatstoezicht op de Volksgezondheid, Arnhem ( N L ) .M.F. Thai, Commissariat a l'Energie Atomique, Fontenay aux Roses ( F) .V. Thiele, Landesanstalt fur Immissionsschutz, Essen (F.R.G.).J.H. Voorburg, R.A.A.D., Arnhem (N L) ,( Chairman).H. Wijnen, D.G.M.H.-L., Leidschendam ( N L ) .

These recommendations are produced to formulate minimum conditionsfor research workers,organisations and industries, who wish to haveconsistent results and measurements which can be compared with odourmeasurements in other laboratories and other countries. Also laboratories beginning with odour measurements are advised to start atleast at this level.

Improving an olfactometer into a more consistent and more sensitive one means that the results of earlier measurements are loosing apart of their value.

In all research work, the set-up of the experiments, the sampling

technique and the analytical methods ask for careful considerationand much common sense. This holds especially for olfactometric measurements.

Olfactometers are used to assess the concentration of odouremissions. An olfactometer is a device which dilutes the odorous airto be tested,with odour-free air. These dilutions are offered to apanel in order to determine the odour threshold. So the human nose isthe sensor and this means that many limitations are imposed by thehuman factor.In this connection a warning is given against measurement of samplescontaining harmful substances.



379

Even with a rather accurate olfactometer one should realise that measuring one compound with the same person over some days may give avariation with a factor 3-

2. SOME DEFINITIONSOdour concentration expressed in odour units per cubic meter

(O.U ."m~3 )is the number of dilutions to the detection threshold.(Theodour concentration of the undiluted sample being at threshold levelis 1 O. n / m ' OThe individual odour threshold is that concentration which is justperceived by the subject in 50% of the cases in which it is presentedto him.

The group threshold is the concentration that is just preceived

by 50 $ of the panel members.

3. SAMPLINGThe materials to be used should be inert. This means absorption

and desorption should be avoided. There should be no reaction withthe sample, and the material should not change the odour. Some examples of materials to be used for the probe, the tubes and the valvesare:

- PTFE (polytetrafluorethylene),- stainless steel,

- glass.Preflushing during half an hour is recommended, especially inthe case of long tubes.

Predilution should be provided in order to prevent condensation.The sample should be representative taking into account whether

it is a fluctuating or a constant source. In the case of static sampling, at least two samples should be taken.

Sampling by concentration on an absorbent is not recommended unless further research proves it to be reliable.

In the case of static sampling, the material of the bag shouldhave the same properties as given before and, moreover, should suffer

no sample losses by diffusion. Good experiences have so far been madewith PFTE, TEDLAR and Polyamid bags.

One should be careful with the re-use of the bags.The volume of the sample will be determined by the air delivery

rate to the olfactometer, the number of presentations and the concentration of the sample.

Transport and storage time should be as short as possible with amaximum of 2k hours. The bag should be kept in the dark at a temperature sufficient to prevent condensation.

In case of new types of odour emissions, the reliability of the

bag should be tested. The same holds for new bag materials.If a dust filter is required, it should be in front of the

olfactometer and not in front of the sampler. Experiments should becarried out to demonstrate that the properties of the odour have notbeen changed by the filter. Glass fibre filters are in use in Germany(LIS, Essen) and in the Netherlands (MT/TNO, Apeldoorn).



380

4 . OLFACTOMETER

Only dynamic systems should be used. The materials to be applied

should have the same properties as given under "sampling". Theconstruction should prevent losses of odorants and uncontrolledintake of clean air due leakage.

The clean air should be odour-free as judged by each member ofthe panel. We recommend synthetic air or ambient air filtered withcharcoal followed by a dust filter, to remove charcoal particles.

The tubes or sniffing ports in use have various designs. Themain condition is that the panelist should be supplied with the minimum breathing volume flow and that he should not inhale air from outside the sniffing port. In present practice,,there are volume flows

between 16 and 170 1. mnn~ (0.96 - 10 m . h~ ) .Forced-choice techniques (two or more tubes, one containing theodour and the others only odourless air) and yes/no techniques (onetube) are used. The forced-choice technique is the more sensitive one.The results obtained should be corrected for guessing following standard procedures:- Pobs - Pchance .__

Pcorr = „ _ =—r x 100100 - Pchance

in which Pcorr = Pcorrected.Pchance= the percentage correct observations obtained

by mere guessing (5 0$ in the case of 2 tubes)

Pobs = Percentage observed.Calibration of the volume flows in the olfactometer should be

done regulary. The frequency depends on:-construction of the olfactometer,-frequency of olfactometer transport,-degree of pollution of the sampled air,-working situations (dirt, humidity, etc.).Calibration can be done with a tracer gas, e.g. methane. Once a

year, a standard experiment should be carried out with a large paneland H S as well as n-butanol as odorants.

Cleaning is done with warm air, steam or, if possible, bywashing after dismantling. Special attention should be paid to cleaning after working under dirty conditions.5. PANEL

The following background conditions are important:-The test area should be odour-free.-The room should be well ventilated (at least 6 times per hour).-The test should be carried out at room temperature and with

normal humidity (40 to 7 0 &) .There should be comfortable surroundings with no external stimu

li such as smoke, noise, perfume, etc. No tests should be carried outwithin half an hour after a meal.

The test procedure:There should be an independent panel leader. During the actual

assessment there should be no communication among the panel members,and the communication between leader and panel should be very restricted.

The panelists should be motivated (interested in the job) . Information about the performance of the panelist should only be givenafterwards.



381

Fatigue should be prevented. In every hour, the panelist shouldalways have a rest of at least 15 minutes.

The presentation can be at random or in ascending steps. Descen-

dingseries should not be used (risk of adaptation).The size of the dilution steps, i.e. the ratio between two adja

cent dilutions, should be between 1.5 and 3-The utmost exposure time to the stimulus is 15 seconds.The interstiinulus interval should be sufficient to avoid adapta

tion of the panelist to the odour and sufficient to allow the olfactometer to provide the new stimulus. This can be attained with a cycletime of 1 minute (cycle time = exposition time plus interval).

The number of presentations (dilution steps) per panelist andseries should be at least 5- The steps should be located around the

threshold expected and overlap the range between less than 16$ andmore than 8h% detection of presented stimuli.The number of test series should be at least two (one replicateXThe group threshold should be calculated .as the geometric mean

of the observations or by graphical evaluation. Standard mathematicalprocedures should be followed.

Geometric means: the dilution at which the response changes fromno perception to perception has to be determined for each test series.After that the geometric means of the so defined dilution has to becalculated.

Graphical evaluation: the distribution of the frequency of perceptions as a function of dilution has to be determined. The evaluation can be performed using frequencies before or after probit transformation.

The size of the panel:The following minimum numbers of the panelists are required:a)*16 panelists to measure a representative threshold,b ) * 8 panelists for all practical measurements,c ) * k panelists in case of comparative judgements.Selection of panelistsPanelists should be screened and trained. They should be familiar with

the test procedure. This means that at least one series with H S should becarried out. If possible, more extended tests with more components arerecommended.

Only individuals between 16 and 50 years of age who have a normal senseof smell and can follow simple instructions should be included in the panel.Persons with an erratic judgement have to be excluded from the panel.



382

THE CONCLUSIONS AND RECOMMENDATIONS FOR FURTHER WORK ARISING FROM THE

FAQ/EEC JOINT WORKSHOP ON ODOUR PREVENTION AND CONTROL OF ORGANICSLUDGES AND LIVESTOCK FARMING

V.C. NIELSENCo-ordinat or of the wor kshop for the FAO sub-n etwor ks 2 and 3, Farm

Waste Unit, ADAS, MAFF Reading.

Summary

The workshop studied three aspects of odour nuisance ar ising fromthe agricultural use of organic sludge s and livestock farming.These were odour mea surem ent, prevention and control systems. TheEEC expert group on Odours, organised the sessions on odourmeasurement by olfactometry, their report is given separately.The FAO sub-ne tworks organised the sessions on other odourmea surem ents, prevention and control syste ms. The topics coveredby FAO included measurements of odour offensiveness, biochemicaland chemica l tests, odour prevention systems in livestock buildings,treatment of odorous air emissions from liv estock buildings bybiofilters, control systems for liquid agricultural manures byaeration and anaerobic digestion, odour prevention and control ofstored man ures and during land spreading opera tions. The effectof dust on odour concentr ations from liv estock buildings was alsoreported on.

Recommendations for further research and development workcovered all the topics mentioned above.

The workshop agr eed that enough information wa s available todraw up recommenda tions from which guidelines could be made forspecific aspects of odour prevention and control.

The Objectives of the Workshop we re :a. To agree guidelines and standa rds for odour measur ement techniques,

to enable quantitive measurements of odour emission concentrationsby Olfactometry and other methods for offensiveness and markercompounds.

b. To evaluate and describe liv estock production systems , which havelow lev els of odour emission and which have low energy dema nds,while improving livestock welfare.

c. To develop meth ods for quantifying odour reduction by aerobic andana erobic treatment of liquid ma nure s. Also to describe the

most successful systems available.d. To evalua te odour reduction from livestock buildings by the use of

biological air filters.e. To evaluate the role of dust in liv estock buildin gs and its effect

on the transmission of odours and pathogenic micro-organisms.

Conclusions - Odour Mea surem entsThe EEC expert group on Odou rs to gether with m embe rs o f the FAO

sub-network discussed standardisation of olfactometric mea surements.There was agreement on the general principles involved on the: -



383

a. The collection of samples, and the volume collected.b. The storage of samples, r e length of time, tempera ture, etc.c. The organisa tion of the odour pane ls, selection of member s, length

of time and number of samples offered. Choice of odourconcentrations.

d. Methods of testing the accuracy of the Olfactometer .e. Handling of results and statistical analysis.f. Degree of accuracy required and use of the resul ts.

The recommendations of this group will be published as a guidelineon Olfactometry.

The joint session of both groups discussed the use of instrum entalmethod s for evaluating odours, it was agreed that these methods couldhave adva ntages in terms of cost and labour input. In some cases

identification of the odorous com pounds was necessary to ensure thatthe correct treatment system is used. Cross reference to olfactometricmeas urem ents is necessary to ensure a good correlationship between theinstrumental results, offensiveness ratings and odour concentration bypanels.

The use of simple, cheap tests to obtain the supernatant B0D5 andtotal organic acids of slurries were shown to provide useful indicatorsof potential odour nuisance. These tests were particular ly a pplicableto assess the offensiveness of slurries before and after aerobictreatm ent. The tests can therefore be used to indicate how successfultreatment has been.

Odour Prevention Systems in Livestock BuildingsAir drying of poultry m anure on the collection belt s in the

building reduced the moisture content of the manur e to 45 per cent.Drying also reduced odour concentration significsntly. The driedmanur e required less storage spsce and composted natural ly. When themanur e is stored under cover composting reduced the moisture contentto 35 per cent snd sgsin reduced the volum e to be hand led. Furtherdevelopment work will be carried out on warm ing the inlet air in coldweather and on controlling composting odours.

A study on the effects of insulating broiler house floors to

reduce odour emission levels and improve broiler carcass qualityindicated that there was an improvement to the concentration of odouremissions for four weeks , then a decline to odorous emissions . Carcassquality was much improved by insulating floors . The study will continueto develop a floor which can be used on far ms.

Increased interest in animal welfa re has drawn attention for theneed for improved bedding in livestock pens and houses. A studycomparing peat with straw and other materia ls for bedding dairy cowshas shown that it has advantagea over straw in that it absor bs ammoniaand can absorb large volumes of wster . Development of better peatharvesting methods to reduce dust concentrations and handling problems

in buildings is required.The separation of faecea and urine beneath slatted floors in pig

buildings by mechanically operated mesh belts ha s been shown to reduceodour emissions in the building and from the ventilation outl ets. Thesystem has other adva ntages in that the collection cha nnels are muchshallower than conventional channels and that welfar e straw can begiven to the pigs without blocking the slurry system. The system isnow in use on farm s.



384

Odour control by covering slurry stores can be successfully usedin situat ions where stores are close to neighbouring ho uses. There

are a range of covers ava ilable from very cheap plastic sheetinglasting one winter to well made cover s costing more but lasting up toten year s.

Treatment of Liquid Manures (Slurries)1. Aerobic Treatment

Papers on the treatment of pig slurr ies indicated that aer ationwas successful in removing odour s. A range of treatments weredescribed including:-a. treatment after storage to remove odour and nitrogen compounds .

This operated as a batch system, treatment being carr ied outimmediately before land spreading.

b. Continuous treatment systems with variable retention timesdepending on whether the slurry wa s to be immediately spread orstored before spreading were also described.Research is continuing to develop low energy, low oxygen system swith a range of retention times . The objective to reduce thecost of treatment and give the operator a range of options tosuit his cropping programme.

2. Anaerobic Digestion

Papers indicated that efficiently run systems could control odours.The most efficient utilisation of biogas was as a fuel for domesticand industrial hot wat er. The economic s of the system were dependenton the size of the plan t. Experience in the Netherlands indicatedthat small pla nts run at a loss as far as returns from bioga s areconcerned. Utilisation of the biogas to obtain maximum benefit isdifficult to achieve on most livestock farms.

There is a need for far greater control of the process under farmconditi ons, for better inform ation on the choice of plant, itsmana gement and for simple instrumentation or tests to indicate tousers how the plant is operating. Guidelines and information on the

most econom ic method of utilising biogas on individual farms isrequired.

Odour Control Land SpreadingInjection of liquid manure s (slurries) and sewage sludges

significantly reduces odour emis sions. Research on the injectorshas reduced seepage and improved utilisa tion of plant nutr ientswithout major damage to grass swar ds. Other work has demonstratedthat there is very good contro l of odours both during and after spreading and only a 10 to 1585 incre ase in spreadin g time per load.

Improvem ents in wheel design and weight distribution have

allowed ma chines to be used on land which is just below ca pacity.The method is becoming more po pular .

BiofiltersThe full potential use of biofilters for cleaning air from

livestock buildings, treatment plants and emissions from chemicalindustry have yet to be exploited. The paper s presented producedproof of the efficiency of these filters to remove odour emissionsfrom odorous air str eam s. Research and Development work is requiredto reduce the costs of construction and to find materi als to which will



385

not deteriora te quickly. Work is required to reduce the large surfaceareas required at present.

DustThe papers presented quantified and characterised dust from pig

and poultry buildings . They also described the hazar ds to livestockand workers health due to the carriage of micr o-org anis ms, smell andreactive chemical agents.

So far there has been little research and development wor k on dustcollection systems which are self cleaning and can be cheaplyinstalled in livestock buildings. The papers suggest that improvedlivestock environment by dust removal can have an economic advantagein terms of earlier marketing of pigs.

The effect of welfare bedding on dust concentr ations in livestockbuildings has not yet been quanti fied.

The information ava ilable in the papers presented at the workshopcan now be used to make reco mmenda tions on odour prevention and controlwhich can be used as a basis for guidelines for fa rmer s. Therecomm endations will be drawn up and circulated for comment by theparticipants of the workshop.

Recommendations for further research and development1. Inhouse poultry manure drying to improve drying during very cold

weather.2. Improve odour control during composting process of air dried

poultry manure.3. Continuing developme nt of farm scale cheap insulation of broiler

house floors to reduce odours and improve broiler welfa re andcarcass quality.

4. Continue development work using new mat eria ls to obtain cheap andeffective co vers for both slurry and solid manur e store s, whichwill contain odour s and prevent r ainwater runoff and avoid waterpollution.

5. Aerobic treatment, develop low energy, low oxygen input system s.

Develop systems which prevent odour regeneration after treatmentto allow storage for optimum use by crops.

6. Anaerobic digestion develop cheap simple system s, to operate morereliably with improved gas yield s. To develop better methods ofutilisation of both the biogas and treated manur e while mai ntaining odour contr ol.

7. Develop injection systems which have a lower power requirementwhile effectively controlling odour . To develop better surfacemanure and slurry spreaders which have a low trajectory whilemaintaining evenness of spread.

8. Develop cheaper construction ma teria ls for biofilt ers, to developfilters which require less land area . To find cheap, simple,self cleaning dust filters for biofilter s.

9. To develop inhouse dust control systems for livestock to improvethe welfare of worker s and livestock and r educe dust emission frombuildings.



387

LIST OF PARTICIPANTS

BONAZZI, G.

Centro Ricerche Produzioni AnimaliVia Crispi 3I - 42100 - REGIO EMILIA

BRUCE, A.M.Water Research CentreElder WayUK - SGI 1TH - STEVENAGE HERTS

CLARKSON, C.Ministry of Agriculture,Fisheries and FoodFarm Waste Unit79-81 Basingstoke RoadUK - RG6 OEF - READING - BER KS

DIAPER, J.School of Environmental ScienceUniversity of BradfordUK - BD 7 1DP - BRADFORD - West Yorks

DOBBELAERE, A.Rijksstation voor LandbouwtechniekVan Gansberghelaan 115B - 9220 - MEREL BEKE

HARDWICK, D.C.Ministry of Agriculture,Fisheries and FoodGreat Westminster HouseHorse Ferry RoadUK - SW1P 2AE - LONDON

HARTUNG, J.Institut fur TierhygieneBunteweg 17P

D - 3000 - HANNOVER 61

HOLMVANG, P.Central Institute for IndustrialResearchForskningsveien 1BlindernN - 037 1 - OSLO 3

HOMANS, W.J.Institut fur Siedlungswasserbau

Abteilung BiologieUniversitat StuttgartBandtale 1D - 7000 - STUTTGART

EVANS, M.R.West of Scotland Agricultural CollegeDepartment of MicrobiologyAuchincruiveUK - KA6 5HW - AYR, SCOTLAND

FRIMAN, R.M.Ministry of Agriculture,Fisheries and FoodFarm Waste Unit79-81 Basingstoke RoadUK - RG6 OEF - READING - BER KS

HALL, J.E.Water Research CentreMedmenham LaboratoryHenley RoadMedmenhamP.O. Box 16UK - SL7 2HD - MARLOW, B UCKS

HUME, I.H.Ministry of Agriculture,Fisheries and FoodFarm Waste Unit79-81 Basingstoke RoadUK -RG6 OEF - READING - BERKS

JOHNSON, G.L.Finham Regional LaboratorySevern Trent Water AuthoritySt Martin's RoadFinhamUK - COVENTRY WARWICK S

KLARENBEEKI.M.A.G.

Postbus 4 3NL - 6700 AA

J.V.

WAGENINGEN

HANGARTNER, M.I n s t i t u t f li r H y g ie n e u ndArbeitsphysiologieClausius Str. 21CH - 8092 - ZURICH

KLINGER, I.Migal G alilee Technological CentreSouth Industrial AreaIL - 10200 - KIR YAT SHMONA



388

KOSTER, E.P.Vakgroup Psychische FunktieleerRUVVarkensmarkt 2NL - 3511 BZ - UTRECHT

MOSS, R.L.Warren Spring LaboratoryGunnels Wood RoadStevenageUK - SGI 1TH - H ERTFORDSHIR E

KROODSMA, W.Building Division IMAGInstitute of Agricultural EngineeringMansholtlaan 10-12NL - 6708 PA - WAGEN INGE N

LANG, J.Ministry of Agriculture,Fisheries and FoodGreat Westminster HouseHorse Ferry RoadUK - SW1P 2AE - LOND ON

LE ROUX, N.Warren Spring Laboratory

Gunnels Wood RoadStevenageUK - SGI 1TH - HE RTFORDSHIR E

L'HERMITE, P.Commission of the EuropeanCommunities200 rue de la LoiB - 1049 - BRUSSELS

MANNEBECK, H.

Institut fur Landw. Verfahrenstechnikder Universitat KielOlshausenstr. 4 0-60D - 2300 - KIEL

MEJER, G.J.Institut f. landtechnischeGrundlagenforschung der F.A.L.Bundesallee 50D - 3300 - BRAUNSCHWEIG

MESZAROS, G.National Institute of AgriculturalEngineeringPostafioi 103Tessedik SUTCA 14H - 2101 - G0D 0LL0

MOULSLEY, L.National Institute of AgriculturalEngineeringWrest ParkSilsoe

UK - MK4 5 4H5 - BEDFORD

NIELSEN, V.C.Ministry of Agriculture,Fisheries and FoodFarm Waste Unit79 - 81 Basingstoke RoadUK - RG6 OEF - READING - BERK S

NILSSON, N.C.Dept. of Farm B uildingsUniversity of AgricultureP.O.B. 625S - 22006 - LUND

NOREN, 0.Swedish Institute of AgriculturalEngineering

Box 7033S - 750 07 - UPPSALA

PADUCH, M.Verein Deutscher IngenieurePostfach 1139D - 4000 - DUSSELDORF 1

PELTOLA, I.

TyStehoseuraSF - 05200 - RAJAMAKI

RYDEN, J.Grassland Research InstituteHurley, MaidenheadUK - SL6 5LR - BERKSHIRE



389

SCHAMP, N.Laboratory of Organic ChemistryFaculty of Agricultural Sciences

Coupure Links 533B - 9000 - GENT

THIELE, V.Landesanstalt f. ImmissionsschutzWallneyer S tr. 6

D - 4300 - 2SSEN 1

SCHELTINGA, H.M.J.

Staatstoezicht op de VolksgezondheidPels Rijckenstraat 1P.O. Box 9013NL - 6800 DR - ARNHEM

SCHIRZ, S.KTBLBartningstrasse 49D - 6100 - DARMSTADT

THOMPSON, N .Meteorological OfficeBracknellUK - BERKSHIRE

T00G00D, S.Water Research CentreElder WayStevenageUK - SGI 1TH - HERTFORDSHIR E

STORHAUG, R.AQUATEAMNorwegian Water Technology C entre ASP . O . Box 6593 - RodeleSkkaTrondheimsvelen 84-86N - 050 1 - OSLO 5

STUART, I.National Institute forAgricultural EngineeringWrest ParkSilsoeUK - MK45 4 H5 - BEDFORD

TERMONIA, M.Instituut voor Scheikundig Onderzoek

MiniBterie van Landbouw5 MuseumlaanB - 1980 - TERVUREN

THACKER, F.E.West of Scotland Agricultural CollegeDepartment of M icrobiolgyAuchincruiveUK - KA6 5HW - AYR, SCOTLAND

THAL, F.Commissariat a l'Energie AtomiqueInstitut de Protection et SQreteNucleaireB.P. 6F - 92260 - FONTENAY AUX ROSES

TOWNSEN D, M.G.Ministry of Agriculture,Fisheries and FoodWild Life BiologyToby Jug SiteTolworth

UK - SURREY

VAN G EELEN, M.Building Division IMAGInstitute of AgriculturalEngineeringMansholtlaan 10-12NL - 6708 PA - WAGENIN GEN

VAN ZUIDAM, D.M.Ministerie van VROMAir Directorate, Div. Air QualityPostbus 450NL - 2260 MB - LEIDSCHE NDAM

VOERMANS, J.A.M.

Building Division IMAGInstitute of AgriculturalEngineering

Mansholtlaan 10-12NL - 6708 PA - WAGENING EN

VOORBUR G, J.H.Rijks Agrarische Afvalwater DienstKemperbergerweg 67NL - 6816 RM - ARNHEM



390

WIJNEN, H.Ministerie van VROM

Air Directorate, D iv. Air QualityPostbus 450NL - 2260 MB - LEIDSC HENDAM

WILLIAMS, A.G.Farm Building DivisionNational Institute of AgriculturalEngineeringWrest ParkSilsoe

UK - MK45 4H5 - BEDFORD

WILLIAMS, M.LWarren spring LaboratoryGunnels Wood RoadStevenageUK - SGI 1TH HERTS



391

INDEX OF AUTHORS

BAINES, S., 273BOLONI, I., 372BONAZZI, G., 251, 347BRUCE, A.M., 2

NIELSEN, V.C., 8, 382NOREN, 0., 207, 234

ODAM, E.M. 284

CARPENTER, G.A., 333COPELLI, M., 251CORTELLINI, L., 3 47 , 353CUMBY, R.J., 258

PAGE, J.M.J., 284PELTOLA, I., 181PICCININI, S., 34 7, 353PUNTER, P.H., 146

DE ANGELIS, S., 251DIAPER, J., 131

EIKUM, A.S., 12ESTEBAN TURZO, P., 343EVANS, M.R., 273 , 307

RYDEN, J.C., 33

SCHAEFER, J.,146

SCHAMP, N., 153SCHI RZ, S., 241SELVIAH, C M . , 258SHAW, M., 258STORHAUG, R., 12

GUTTIEREZ SALGUERO, J., 343

HALL, J.E., 194HANGARTNER, M., 55HARDWICK, D.C., 21

HARTUNG, J., 44, 321HOLMVANG, P., 81

THACKER, F.E., 307THAL, M.F., 78THIEL E, V., 61THOMPSON, N., 227TILCHE, A., 34 7, 353TOOGOOD, S.J., 131TOWNSEND, M.G., 284

JOHNSON, G.L., 296

KLARENBEEK, J.V., 113KLINGER, I., 366KOSTER, E.P., 86, 146KRAUSE, K.-H., 99KROODSMA, W., 166, 213

MAIWALD, K.D., 146MANNEBECK, H., 94 , 188MARCHAIM, U., 366MATYAS, L., 336MEJER, G.-J., 99 , 222MESZAROS, G., 336, 372MORE HERRERO, A., 343MOSS, R.L., 63MOULSLEY, L.J., 333

VAN GEELEN, M.A., 238VAN LANGENHOVE, H., 153VAN OUWERKERK, E.N.J., 17 5VOERMANS, J.A.M., 175, 358VOORBURG, J.H., 27 , 52, 378

WIJNEN, H.L.J.M., 69WILKINS, J.P.G., 284WILLIAMS, A.G., 120, 258WILLI AMS, M.L., 227

odour prevention

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