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BIOFILTER FOR ODOUR CONTROL

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INTRODUCTION H2S is highly toxic, odorous and poisonous

It is produced from Petroleum refiningWaste water treatmentPaper and pupl manufacturingFood processing

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H2S removal is crucial in every odour abatement.

Several chemical and physical process are used for removal. They are less effective and more expensive

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Why Biofilter ?????It uses microorganisms to remove undesirable

components.Low operation cost.Low maintenance requirement.Low energy requirement.No secondary pollution.

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LITERATURE REVIEW“Performance of Biofilter for the Removal of Hydrogen

Sulphide Odour”; Rehman, Z. U , Farooqi I. H and Ayub S

In this paper laboratory scale experiments were performed to evaluate the

feasibility of biofilters for the removal of H2S from wastewater treatment plant

waste air. Compost was used as media in biofilter. Carried out in six different

phases, by increasing H2S concentrations gradually. It was concluded that the

biofilter, used in the study, was more efficient for low contaminant

concentrations .

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“Biofiltration: An Innovative Air Pollution Control

Technology For VOC Emissions”; Gero Leson and Arthur

M. Winer

  This paper views the history and current status of

biofiltration, outlines its underlying scientific and

engineering principles, and discusses the

applicability of biofilters for a wide range of

specific emission sources .

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“Microbial biofiltration technology for odour abatement”;

Sonil Nanda, Prakash Kumar Sarangi and Jayanthi Abraham

This report describes the generation of odorants from different

sources and their possible degradation by suitable microbial

cultures. In addition, comparisons among physiochemical and

biological methods for odour abatement have been discussed.

Nevertheless, the type of biofilter, its packing material and other

reaction conditions for an effective biofiltration have also been

considered.

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OBJECTIVETo design a biofilter and determine

operational parameters necessary to optimize the performance

Also to study the effect of operational parameters on H2 S removal efficiency.

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METHODOLOGY

Schematic representation of an open single-bed biofilter system

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A typical biofilter configuration

Water sprinkler system to apply moisture directly to

the filter media surface.

The typical depth of biofilter media is 1 m

Many different media types include soil, compost,

sand, shredded bark, peat, heather, volcanic ash, and

a mixture of these components .

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The growth and activities of the microorganisms is

dependent on

• absence of toxic materials

• ample inorganic nutrients

• optimum moisture conditions,

• appropriate temperatures

• neutral pH range.

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MECHANISM As odorous gas passes through biofilter 2

processes occur simultaneously.

Sorption ( Adsorption & Absorption)Bio conversion

Organic Pollutant + O2 ─> CO2 + H2O + Biomass

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DESIGN PARAMETERS

The depending factors in the biofilter design are :

Volumetric flow rate of air to be treated.Specific air contaminants and their concentration.Media characteristicsBiofilter sizeMoisture controlMaintainenceCost

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AIR FLOW RATE

Literature values for biofilter airflows range from 0.005 to 0.0025m/s and are typically 0.015 to 0.02 m/s

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MEDIA CHARACTERISTICSCritical properties of media material

include:PorosityMoisture holding capacityNutrient contentSlow decomposition

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MEDIA CHARACTERISTICS

Organic mixture for odour removal

biofilters ranges from approximately

30:70 to 50:50 ratio by weight of compost

to wood chips

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BIOFILTER SIZE

The depth of filter med is kept as 1 meter. Excessive depth results in excessive

pressure drop lesser depth will dry out

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EMPTY BED RESIDENCE TIME( EBRT)

Time that the air is in contact with biofilter media.

Taken as 7-23 seconds .Beyond 23 seconds there is no apparent effect. EBCT= Volume of media/Airflow rate. The actual contact time is usually less than

EBRT

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MOISTURE CONTENTInadequate moisture Allow the media to dry outDeactivate the microbes Create cracks and channelling of air

Results in reduction of filter efficiency.

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MOISTURE CONTENTToo much moisture cause Channelling Limit oxygen flow

Thus create anaerobic zones in the biofilm.

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MOISTURE CONTENT Recommended moisture content for

biofilters range from 40-65% wet basis.

Optimal moisture content is 50-65%.

Moisture content (%) = (mass of water)/(mass of water + mass of dry packing) x 100

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TEMPERATURE

Microorganisms tolerate a temperature range of 70-90F

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CONTROL OF pHThe pH in compost filters is typically

between7 and 8.

In some cases the biodegradation of air pollutants can generate acidic by-products

Reduces filter’s removal efficiency

Hence add buffers like lime.

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MAINTAINENCEDifferent areas that require maintenance are Moisture contentWeedsRodentsAssessment of pressure drop

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COSTS

Cost for installation of fans, media ductwork ,plenum and labour to construct.

 Maintenance costOperation cost

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DESIGN STEPSFor given airflow rate and EBRTMedia Volume (Vm ) = [Air flow rate

(Q) x EBRT ] / 60

If area is not limited select a suitable depth Dm

Unit Air flow rate = Q / Am

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DESIGN STEPSUnit Pressure Drop

(UPD) = 8.82 x ( % of Voids ) x Unit air flow rate

Total Pressure Drop = UPD x Dm

Expected Total pressure drop and Air flow rate can be used to select exhaust fan.

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REFERENCES1. “Performance of Biofilter for the Removal of Hydrogen

Sulphide Odour”; Rehman, Z. U , Farooqi I. H and Ayub

S, Int. J. En viron. Res., 3(4):537-544, Autumn 2009

ISSN: 1735-6865

2. “Microbial biofiltration technology for odour abatement”;

Sonil Nanda, Prakash Kumar Sarangi and Jayanthi

Abraham, Journal of Soil Science and Environmental

Management Vol. 3(2), pp. 28-35, February 2012

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3.  “Biofiltration: An Innovative Air Pollution Control

Technology For VOC Emissions”; Gero Leson

and Arthur M. Winer, Journal of the Air and

Waste Management Association, Vol 41 no 8,

August 1991. 

4. “Biofiltration : An Emerging Technology”;

Carlos.R.Soccel , Indian Journal of

Biotechnology ,Vol 2, July 2003,pp 396-410