ecological effects of joint non-phosphate detergent builders ilr'l( · · 2013-05-10joint...

I ECOLOGICAL EFFECTS OF NON-PHOSPHATE DETERGENT BUILDERS : JOINT

ilr'l( FINAL REPORT ON NTA

REPORT TO THE

OF THE INTERNATIONAL JOINT COMMISSION

ON THE

ECOLOGICAL EFFECTS OF NON-PHOSPHATE DETERGENT BUILDERS:

FINAL REPORT ON NTA

FROM THE

TASKFORCEON ECOLOGICAL EFFECTS OF NON-PHOSPHATE DETERGENT BUILDERS

The Research Advisory Board effective November 22,1978 became $he Science ~dvisory Board. DECEMBER, 1978

NOTICE

1

Statements and views presented in this report are those of the Task Force members and do not necessarily reflect the views and policies of the International Joint Commission or the Great Lakes Research Advisory Board.

INTERNATIONAL JOINT COMMISSION

GREAT LAKES SCIENCE ADVISORY BOARD

December 1978

Great Lakes Science Advisory Board

I n t e r n a t i o n a l J o i n t Commission

Canada and t h e United S t a t e s

Members of t h e Board:

The Task Force on Ecological E f f e c t s of Non-Phosphate Detergent Builders i n p a r t i a l f u l f i l l m e n t o f ' i t s r e s p o n s i b i l i t i e s f o r meeting i ts Terms of Reference, hereby submits i t s f i n a l r e p o r t on NTA. The r e p o r t is a documenta- t i o n of t h e f ind ings presented i n t h e Research Advisory Board's 1977 'Annual Report t o t h e I n t e r n a t i o n a l J o i n t Commission. Reports on o the r de tergent b u i l d e r s c u r r e n t l y i n use o r proposed f o r use w i l l be presented a t a l a t e r da te .

Respect fu l ly submit ted,

-1 1 Joseph s h i p i r o (Chairman)

P e t e r J. Chapman /

Richard I. Dick

PA Pe te r J. Di l lon

& /e 0°4?A Charles R; OIMelia

uiii-3/? c?. CI. .,

Anne S8acie

ACKNOWLEDGEMENTS

The Task Force is indebted to the Soap and Detergent Associations of ~anada and the United States for their assistance in providing a mechanism through which companies interested in NTA could coordinate their efforts to provide information to the Task Force; and to the governments of Canada and the United States for the assistance of their research personnel.

Particular thanks are due to D. R. Rosenberger of the International Joint Commission's Great Lakes Regional Office; F. A. Brownridge of Procter and Gamble Co. of Canada Limited; F. Kennedy of Continental Oil Company; W. E. Lowe and K. Kaiser of the Department of Fisheries and Environment; and to W. Lacy, W. Fairless and J. Welch of the Environmental Protection Agency.

Appreciation is expressed to the Procter and Gamble Company and the Monsanto Company for their major assistance in preparing technical reviews and responding to the many queries of the Task Force; also to those members of the industry, government and academic community listed in the appendices who contributed through presentations and discussions of relevant information. A special note of thanks is also extended to those persons who provided a critical technical review of the draft report. These are: A. F. Beeton, J. M. Tiedje, F. M. Morel, H. E. Allen, J. W. Arthur, F. Huber, and L. F. Centofanti.

TABLE OF CONTENTS

Page No . ........................................................... INTRODUCTION 1

CONCLUSIONS AND RECOMMENDATIONS ...................................... 3

CHAPTER 1 - THE CHEMISTRY OF NTA IN WATER ............................ 7

CHAPTER 2 - MICROBIOLOGY AND BIOCHEMISTRY OF NTA DEGRADATION ......... 15

CHAPTER 3 . NTA AND MUNICIPAL WASTEWATER MANAGEMENT .................. 27

CHAPTER 4 . DEGRADATION OF NTA IN THE ENVIRONMENT ...................... 41 ................................. CHAPTER 5 . BIOLOGICAL EFFECTS OF NTA 51

..................................... . CHAPTER 6 EUTROPHICATION BY NTA 61

CHAPTER 7 . MODELLING OF NTA CONCENTRATIONS IN WATER .................. 69

CHAPTER 8 . ENVIRONMENTAL LEVELS OF NTA ............................... 73

APPENDIX ' .

......................................... NTA Meeting Participants 83

............................................... Terms of Reference 89

Membership List .................................................. 91

INTRODUCTION

This r e p o r t of t h e Research Advisory Board's Task Force on Ecological E f f e c t s of Non-Phosphate Detergent Bui lders p re sen t s t h e Task Force 's f i nd ings on NTA.

During t h e l a s t two decades i t has become c l e a r t h a t phosphorus contained i n domestic wastewater is one of t h e p r i n c i p a l con t r ibu to r s t o t h e i nc reas ing ly r ap id process of eu t roph ica t ion observed i n many inland waters , including t h e Great Lakes. In recogni t ion o f . t h i s , t h e 1972 Great Lakes Water Q u a l i t y Agreement between Canada and t h e United S t a t e s c a l l e d f o r t h e development and implementation of programs and o t h e r measures t o reduce i npu t s of phosphorus from municipal sewage. Phosphate-based de t e rgen t s were i d e n t i f i e d a s one of t h e main sources of c o n t r o l l a b l e wastewater phosphorus. R e s t r i c t i o n on de te rgent phosphate would i nc rease t h e use and r e l e a s e of a l t e r n a t i v e m a t e r i a l s developed and being developed by t h e de te rgent manufacturers. Therefore, t h e I n t e r n a t i o n a l J o i n t Commission's Great Lakes Research Advisory Board c r ea t ed a Task Force i n 1977 t o i n v e s t i g a t e t h e p o t e n t i a l e co log ica l e f f e c t s of t he se non-phosphate de te rgent bu i lde r s . The Task Force was d i r ec t ed t o examine t h e a v a i l a b l e information on t h e eco log ica l e f f e c t s of c u r r e n t l y e x i s t i n g o r proposed a l t e r n a t i v e s t o phosphate and t o r epo r t on t he eco log ica l a c c e p t a b i l i t y of t h e s e bu i lde r s . The terms of r e f e r ence given t o t h e Task Force by t h e Board a r e appended.

The Task Force was c o n s t i t u t e d of s c i e n t i s t s s e l e c t e d from those t e c h n i c a l a r e a s t h a t address known a n d p o t e n t i a l environmental e f f e c t s t h a t might be an t i c ipa t ed . These t echn ica l a r ea s a r e aqua t i c chemistry, microbia l degradat ion, wastewater management, b i o l o g i c a l e f f e c t s , eu t rophica t ion , and environmental modelling. Furt ,her, t o f a c i l i t a t e improved awareness of unpublished d a t a and ongoing research being conducted by indus t ry and governments, l i a i s o n members

' were s o l i c i t e d Erom t h e United S t a t e s and Canadian Soap and Detergent Associat ions and appropr ia te f e d e r a l agencies w i th in Canada and t h e United S t a t e s . The Task Force and l i a i s o n members a r e l i s t e d i n t h e appendix.

Seven ma te r i a l s were chosen f o r examination by t h e Task Force. These a r e a s fol lows: t h e organic polycarboxylate bu i lde r s - c i t r a t e , carboxymethyloxy- succ ina t e (CMOS), carboxymethyl tar t ronate (Bui lder M ) , and n i t r i l o t r i a c e t a t e (NTA); and t h e inorganic b u i l d e r s - carbonate , s i l i c a t e , and a l i m i n o s i l i c a t e ( z e o l i t e ) .

NTA was of p a r t i c u l a r i n t e r e s t t o t h e Task Force. This ma te r i a l was ' i n l i m i t e d use i n t h e USA and Canada i n 1970. Its use expanded when Canada began on a n a t i o n a l s c a l e - t o l i m i t t h e phosphorus conten t of de te rgents . I n December of 1970, t h e Surgeon General of t h e United S t a t e s Publ ic Health Service expressed

concern regarding possible health aspects of NTA, and requested that the major detergent manufacturers in the United States voluntarily discontinue its use pending further evaluation. The Canadian Government continued to allow its use as a detergent builder. Because of this and because another Task Force'of the Research Advisory Board was completing an investigation of the health aspects of NTA, this Task Force decided to consider and evaluate the ecological effects of NTA first and separately from the other builders.

The procedure followed by the Task Force in its evaluation of NTA was to request liaison members to arrange presentations by industry and government representatives. Following these presentations, scientists who had conducted NTA research or represented pertinent research disciplines were invited to discuss specific aspects of the properties of NTA. In addition, available literature was examined by the Task Force. Members were assigned sections to write, based on areas of expertise. -Sections of the report in draft form were circulated to Task Force members for review and comment. Outside technical review was obtained from government and industry and from selected experts. Those who participated in the discussions are listed in the appendix.

The findings of the Task Force on NTA are presented in the following chapters.

CONCLUSIONS AND RECOMMENDATIONS

The Task Force concludes that the extensive literature and Canadian experience indicates that the use of NTA does not constitute an obvious environmental hazard, however, a number of important questions remain. The Task Force feels that more work should be done to resolve these questions.

Based on this conclusion, the Task Force recommends that NTA should not be prohibited from use as a detergent builder. The Task Force further recommends that its use be accompanied by studies to address the following questions:

(1) Under aerobic-biological wastewater treatment regimesand in most circumstances in fresh water systems NTA ordinarily degrades rapidly. However, the Canadian monitoring experience did reveal that low concentrations of NTA may be found in the aquatic environment. The Task Force feels that the reasons for which NTA exists at these low concentrations should be investigated.

Whenever any new organic compound is released to the environment, there is concern over its persistence. By recommending that the persistence of NTA be investigated, we are in no way comparing the properties of NTA to such materials as halogenated hydrocarbons. On the contrary, we recognize the clear difference between NTA and such substances. But from the Canadian experience, NTA does appear to persist at low levels and it is important to know whether this is because of the kinetics of microbial activity or because of the presence of non-degradable chelates. For example, low temperatures slow the degradation of NTA preferentially and the acclimation time to attain NTA degradation is greater than for more readily biodegradable wastewater constituents.

(2) Although NTA degrades rapidly in most aerobic environments, studies on its ability to degrade during anaerobic waste treatment or under anaerobic environmental conditions are inconclusive. The Task Force feels the question needs further study.

Some controversy exists on the ability of NTA to degrade under "anaerobic conditions". Some of this controversy may rest on the question of whether certain systems were indeed anaerobic, but in other cases anaerobic degradation apparently has occurred. -Furthermore, it has occurred where the concentration of nitrate was probably too low to s'erve as an electron acceptor. The situation requires clarification.

(3) No investigations have been conducted to determine the concentrations of NTA in anaerobically digested sludges. Canadian studies have shown that about one-third of the NTA appears to be lost from solution during 'primary treatment. Because it may have settled out in the sludge and because sludge is frequently deposited in the sea and on land, investigation is necessary.

Because anaerobic degradation of NTA remains i n quest ion, it cannot be counted on and the re fo re NTA is l i k e l y t o show up i n s ludges where some, bu t not n e c e s s a r i l y a l l , w i l l be degraded aerobica l ly . The ex ten t t o which i t thus p e r s i s t s and comes i n contac t wi th land p l a n t s and aqua t i c organisms needs study.

( 4 ) Although NTA does degrade i n aerobic waste t reatment , t h e Task Force f e e l s t h a t i t s behavior i n physical-chemical t reatment processes needs e luc ida t ion .

L i t t l e , i f any information, is a v a i l a b l e on the removal of NTA by such pro- ce s ses a s alum coagulat ion, l ime coagulat ion, i r o n coagulat ion, carbon adsorpt ion, e t c . Although such processes a r e l i k e l y t o fol low aerobic wastewater t reatment , t h e i r e f f e c t s on NTA should be known.

(5) NTA degradat ion has been s tudied a t intermediate pH va lues ( 5 - 9 ) and a t temperatures i n t h e low t o moderate range. The behavior of NTA a t low and h igh environmental pH va lues and a t temperatures expected i n thermopbilic waste t reatment processes should be evaluated. .

Many eut rophic sof twater l akes , p a r t i c u l a r l y those rece iv ing wastewater e f f l u e n t s , maintain pH values we l l in excess of 9 f o r long periods of t ime, y e t most s t u d i e s of degradation have been done a t pH va lues below 9. S imi la r ly , a n increas ingly l a r g e number of streams and l akes a r e developing low pH values below 5, no t only from ac id mine drainage i n a r eas such a s West Vi rg in ia , bu t i n t h e no r theas t United S t a t e s , a s we l l a s i n southern Scandinavia, from ac id r a i n .

( 6 ) Degradation of NTA i n marine and e s tua r ine systems appears t o be very slow. The Task Force f e e l s t h a t because of t h e v e r s a t i l i t y of microorganisms i t i s l i k e l y t h a t NTA w i l l no t remain i n such systems. Further

. study is requi red , however.

Degradation of NTA by marine organisms has been demonstrated, bu t i n e s t u a r i n e systems t h e r e apparent ly is i n h i b i t i o n of t h e degradation by f reshwater organisms. The p o s s i b i l i t y of accumulation of NTA in such systems should b e f u r t h e r examined.

(7) NTA does not a o l u b i l i z e and t r anspor t heavy metals t o an apprec iab le ex t en t under most circumstances. However, t h e Task Force f e e l s t h a t i ts behavior i n systems of high inorganic t u r b i d i t y and/or high metal content needs inves t iga t ion .

There a r e s p e c i f i c systems where r eac t ion of NTA wi th heavy metals and subsequent t r anspor t of t h e metals might be e spec i a l ly important. Among these a r e waters rece iv ing drainage from mining operat ions. Such systems have not been examined.

(8) Available information i n d i c a t e s t h a t acu te t o x i c i t y t o aqua t i c organisms r e s u l t i n g from environmental concentrat ions of NTA is unl ike ly . Similar s t u d i e s on chronic t o x i c i t y suggest the' same. Eluc ida t ion of t h e mode of t o x i c i t y would al low a b e t t e r eva lua t ion of t h e l i ke l ihood of chronic t o x i c i t y t o organisms not s p e c i f i c a l l y t e s t e d under var ious environmental condi t ions.

It i s evident t h a t no t a l l aqua t i c organisms can be t e s t e d f o r t h e i r s u s c e p t i b i l i t y t o NTA. S imi la r ly , a l l t he environmental condi t ions can not be t e s t ed . Thus i t is important t o develop p r i n c i p l e s t o a s s i s t i n p red ic t ion of t o x i c i t y , chronic o r acute , bu t e spec i a l ly t h e f o p e r . Without such information, we a r e forced t o r e l y on empir ical observat ions.

(9) NTA is no t expected t o increase eu t rophicpt ion by providing n u t r i e n t s from i ts decomposition. Furthermore, most experiments .with simple systems i n d i c a t e t h a t i t does not s t imu la t e a l g a l growth. However, long term s t u d i e s using whole ecosystems have not been performed t o t he ex t en t of s a t i s f y i n g t h e Task Force t h a t NTA w i l l no t cause s i g n i f i c a n t changes i n aqua t i c community s t r u c t u r e . Such experiments a r e necessary.

One of t h e l e a s t s a t i s f y i n g aspec ts of t h e t e s t i n g of de te rgent b u i l d e r s has been t h a t on t h e aqua t i c community. Too o f t e n s t u d i e s have been done using s i n g l e spec i e s of a lgae , and when community s t u d i e s were done they were e i t h e r u n r e a l i s t i c , too s h o r t , i n s u f f i c i e n t l y s tudied , o r omitted important a spec t s of t h e community. S tudies of t h e r e s u l t s t o da t e do not r a i s e any se r ious concerns, bu t t h e . f i n a l answer is not y e t i n .

THE CHEMISTRY OF NTA IN WATER

A N A L Y T I C A L CHEMISTRY OF N T A

A t l e a s t two d i f f e r e n t methods have been used f o r t h e determinat ion of NTA i n de tergents , wastewaters, and n a t u r a l waters. One method, used extens ive ly a t t h e Canada Centre f o r Inland Waters'(CCIW), i s based on t h e formation of a bismuth-NTA complex a t low pH and ana lys i s by d i f f e r e n t i a l cathode-ray polarography a f t e r t he method of Afghan and Goulden (1971). The de tec t ion l i m i t i s 10 pg/R. I ron ( I I1 ) i n t e r f e r e s by forming complexes wi th NTA a t low pH. A second procedure, employed i n t h e . P r o c t e r and Gamble Company, i s based on a method developed by Warren and Malec (1972) and modified by Aue e t a l . (1972). NTA i s converted t o t h e t r i b u t y l e s t e r f o r determination by -- gas .chromatography. Warren and Malec i n d i c a t e a de t ec t ioq l i m i t of 25 pglR; modif icat ions by Aue -- e t a l . have lowered t h i s t o about 1 pglR.

An in t e r l abora to ry comparison of t hese two methods was performed by CCIW and Proc ter and Gamble. The r e s u l t s a s reported by Matheson (1977) a r e no t i n good agreement e s p e c i a l l y a t low concentrat ions on t h e order of 10 ppb and l e s s . A t l e v e l s above 10 ppb var ious s t a t i s t i c a l analyses confirmed t h a t t h e Procter and Gamble va lues a r e s i g n i f i c a n t l y higher. The two could be predic ted from each o ther by regress ion ana lys i s , however. Poss ib le causes inc lude :

(1) acc iden ta l contamination of samples; (2) t h e methods do no t respond t o t h e same spec ies o r have d i f f e r e n t i n t e r -

f erences ; (3) changes during s torage.

Perry (1977) of P roc te r and Gamble has a l s o performed a use fu l s t a t i s t i c a l ana lys i s of t h e r e s u l t s from both l abora to r i e s . Based on a t - t e s t of samples i n which both l a b o r a t o r i e s reported values > 1b pg/R, t h e Procter and Gamble d a t a were higher on t h e average than t h e CCTW values. The a s soc ia t ion between t h e two values was s t a t i s t i c a l l y s i g n i f i c a n t ; t h e c o r r e l a t i o n c o e f f i c i e n t was about 0.7. However, t h e d i f f e rences between t h e measurements can be considerable . Using regress ion ana lys i s , Per ry notes , f o r example, t h a t i f Proc ter and Gamble were t o measure 50 pg/R i n a sample, t h e predic ted CCIW value would be 39 pg/R. The 95% confidence i n t e r v a l f o r t h e t r u e CCIW average would be 33 t o 47 pg/R, and t h e 95% i n t e r v a l f o r an indiv idual measurement by CCIW would be 10 t o 148 pg/R.

CHEMICAL E Q U I L I B R I A

SOLUTION CHEMISTRY

The aqueous chemistry of NTA is dominated by its reactions with metals including the proton. Calculating the equilibrium state of a water containing'metals, NTA, and other ligands can be complex, so that numerical methods are frequently used..' Important examples include Childs (1971), Lerman and Childs (1973), and Winters (1977a).

Childs (1971) performed calculations using a model lake water with major ion chemistry (calcium, magnesium, inorganic carbon, sulfate) similar to the Great Lakes. At pH 8 and for NTA concentrations less than moles/%, most of the NTA is calculated to be complexed with Cu(I1). Some complexation of Pb also occurs. At concentrations of NTA from 2 x lo-' to 2 x 10 moles/%, the NTA is complexed primarily with calcium because there is insufficient copper present to react with it. Althou h not stated by the author, all of the copper present in the water (2 x lo-' moles/$) is presumably complexed with NTA at these higher NTA concentrations. Calculations for pH 6 indicate that Cu is again complexed with NTA at lower NTA concentration,-but "free" NTA (i.e. HNTA~ NTA complexed with one proton) predominates at higher concentrations (2 x moles/$). Similar results are reported by Winters (1977a) for a water with similar major ion chemistry. In addition to Cu and Pb, some complexation of Ni by NTA at low concentration moles/%) is also indicated. Of additional interest are the concentrations of free aquomet 1 ions in these

2q solutions. For example, Winters (1977b) calculates that [Cu ] decreases from to 1 0 " ~ ~ ~ moles/% as total NTA increases from lo-' to moles/R. This spectrum covers the range from the detection limit to concentrations in domestic wastewater.

Possible effects of complexation on degradation have been examined conceptually by Lerman and Childs (1973). A natural water will _contain a mixture of NTA-metal complexes such as HNTA-2, C~NTA-, and CuNTA . These different chemical species may degrade at different rates. Lerman and Childs consider the case when equilibrium is attained among the metal ions and NTA as degradation of NTA progresses, and also degradation of individual species without the reestablishment of equilibrium as decay occurs. Decay with .

reestablishment of equilibrium is predicted to occur faster. However, it is possible that degradation of NTA at l.ow concentrations (say moles/R total NTA) may still be slow if some metal-NTA complexes (such as CUNTA-) are slowly degradable, because these predominate and the concentrations of other, more biodegradable NTA complexes are very low.

These results suggest cautious interpretation of results in at least three areas. First, estimates of metal-NTA complexation cannot be made solely on the basis of the equilibrium between the metal and NTA. For example, the iron (111)-NTA complex has a very large thermodynamic formation constant, but does not exist in appreciable concentration in natural waters at pH 8 because hydroxide has an even stronger affinity for Fe(II1) than NTA. Speciation depends on the interaction among all metals and ligands in the system. Second, some laboratory studies of NTA degradation of specific metal-NTA complexes may have erred in assuming that a metal-NTA complex added

t o a growth medium w i l l remain i n i ts o r i g i n a l form. Rather, t h e metal and t h e NTA w i l l r e e s t a b l i s h equi l ibr ium with the l igands and metals i n rhe growth medium. These unknown spec ies formed i n the growth medium a r e those t h a t a r e a c t u a l l y s tudied. F ina l ly , NTA concentrat ions observed a t t h e l e v e l of moles/ll i n Canadian waters a r e very l i k e l y complexes wi th such metals a s Cu, N i , and Pb, and may be very slowly degradable under those circumstances.

EFFECTS OF SOLIDS

Sol ids , whether suspended i n t h e water column o r s e t t l e d i n sediments, s e rve a s poss ib le sources of metals t o s o l u t i o n and a s poss ib le s i n k s f o r NTA and NTA-metal complexes by adsorption. For example, Chau and Shiomi (1972) added NTA t o polyethylene tubes suspended i n Hamilton Harbor and observed t h a t Zn and Fe were re leased from t h e underlying sediments. A s t h e NTA was / degraded, t h e metal concentrat ions a l s o decreased. Laboratory experiments using l ake water and sediments showed increased concentrat ions of Cu, Fe, N i , and Zn. NTA dosages were i n t h e order of 50 pmoles/ll; increases i n metal concentrat ion were about 1 pmole/ll o r l e s s . It is probable t h a t Cu, N i , and Pb were mobilized a s so luble NTA-metal complexes. For i ron , t h i s is l e s s l i k e l y unless t he i r o n was present a s Fe(I1) . A l t e rna t ive ly , t h e NTA may have peptized c o l l o i d a l f e r r i c oxides. I n any event , t h e e f f e c t was small and r eve r s ib l e a s degradation of NTA occurred i n t hese oxidized environments.

Mobil izat ion under reduced environments can be d i f f e r e n t . Dunlap e t a l . (1971) ' i nves t iga t ed the e f f e c t s of passing NTA through d i f f e r e n t s o E s - under oxic and anoxic condit ions. Rapid and complete degradation occurred i n unsaturated o r ox ic s o i l s . Under s a tu ra t ed (anoxic) condi t ions , degradation of NTA was n e g l i g i b l e and s i g n i f i c a n t mobil izat ion of metals occurred under some condit ions. When the s o i l s contained metals a s s o l i d s u l f i d e s , mobiliza- t i o n was not g r e a t even under anoxic condit ions. Apparently s u l f i d e was a b l e t o compete with NTA f o r t h e metals and maintained them i n s o l i d phases. How- ever , when t h e s o i l s contained metals from organic s ludges, ex tens ive mobiliza t ion occurred. Su l f ide , then, is another important l igand t o be considered i n metal mobil izat ion.

Studies of t h e adsorpt ion of NTA on s o l i d s a r e d i f f i c u l t t o eva lua te , a s i n most cases t h e s o l i d s and t h e adsorbing NTA spec ies have not been we l l def ined. One exception is a s tudy by Huang and Ho (1977). These i n v e s t i g a t o r s s tud ied the adsorpt ion of uncomplexed NTA on s i L i c a , calcium carbonate , alumina, and k a o l i n i t e . Adsorption occurred on a l l so l id s . Adsorption depended on pH and s o l i d type, and genera l ly d id not exceed about 30%.

Dunlap -- e t a l . (1971) noted adsorpt ion of NTA on loam and loam-clay s o i l s . This adsorpt ion l e d t o enhanced degradat ion under oxic condit ions. Neither t he NTA spec ies nor t h e chemical composition of t h e s o l i d s were reported.

Resul ts of monitoring NTA removal i n wastewater t reatment p l a n t s i n Canada (Brownridge, 1977) i n d i c a t e s u b s t a n t i a l removal of NTA i n primary treatment and thereby suggest adsorpt ion of NTA on sewage p a r t i c u l a t e s . Bouveng -- e t a l . (1968) r epo r t adsorpt ion of NTA on ac t iva t ed sludge; t h e ex ten t of adsorpt ion was about 30%. Gledh i l l (1977) mixed primary and

activated .sludges with "c-labelled NTA and observed only very small amounts of adsorption. All of these results are difficult to interpret, as the NTA species, the solution composition, and the organic particulates were not characterized. It seems plausible, however, that adsorption of NTA can occur on organic particulates in some cases. The specific conditions (pH, metal composition, type of organic particulate, other soluble organics, etc.) are not known.

APPLICATIONS TO AQUATIC SYSTEMS

Measurements and models both indicate that the effects of NTA on aquatic systems will be influenced by other chemical constituents in these systems. Important factors include pH, major cations, trace cations, inorganic ligands, other organic ligands, redox conditions, and the presence of inorganic and organic particulates. The effects of NTA on fresh, moderately hard, somewhat alkaline, oxic waters containing low concentrations of humic and other organics have been documented in Canadian surface waters. Somewhat persistent low concentrations of NTA are indicated, possibly due to the formation of trace metal-NTA complexes that are slowly degradable. Extrapolation of these results to other conditions should be made with some caution, examples follow:

1. Hardvs. Soft Water

Hardness does not affect NTA speciation at low NTA concentrations (lom6 moles/ll).- At high NTA concentrations hard waters will produce c~NTA- and MgNTA complexes while soft waters, sukh as those in eastern U.S.A. will produce protonated NTA complexes such as HNTA-2. It is probable that this does not exert major effects on the fate of NTA and trace metals in aquatic systems.

2. Oxic vs Anoxic Waters

Anoxic conditions produce direct effects on several metals and ligands in water, and these changes can exert effects on NTA. For example, metals such as iron, manganese, and chromium are reduced. Iron and manganese become more soluble; chromium is less soluble. Effects of this type change metal concentrations in the water and hence should change NTA speciation. Sulfate is reduced to sulfide under anoxic conditions; sulfide in turn precipitates metals such as iron(I1) and lead. Phosphate may increase as organic matter is decomposed, and then form complexes and precipitates with metals. NTA is not readily degraded under anoxic conditions, so that it may accumulate. No systematic study of such,anoxic effects has been made; it is very likely that they will be significant.

3. Soluble Organics

Other organics in water, both those introduced by man and those produced naturally, can form soluble complexes with metals and may effectively compete with NTA to form metal complexes. Colored soft waters containing high concentrations of humic substances may respond differently to NTA than those Canadian surface waters which are low in such materials. It

, .

i s poss ib le t h a t organics i n sewage may prevent t h e formation of NTA- t r a c e metal complexes; removal of t h e sewage organics i n b i o l o g i c a l wastewater t reatment p l a n t s might then al low such complexes t o form between any NTA and t r a c e metals t h a t pass through t h e p lan t . No s t u d i e s of such e f f e c t s appear t o have been made.

4. Fresh v s Sa l ine Waters

The spec i a t ion of many substances i n e s tua r ine and oceanic waters i s impossible t o measure d i r e c t l y , although i n some cases i t can be calcu- l a t ed . It . i s l i k e l y t h a t NTA spec ia t ion is a f f ec t ed s i g n i f i c a n t l y , bu t no s t u d i e s , e i t h e r experimental o r conceptual, have been made.

5. Acidic Waters

Some l akes and r i v e r s develop low pH (4 o r l e s s ) from atmospheric input of ac id r a i n , o r input of acid mine drainage. A t low pH t h e NTA molecule becomes protonated, and does not i n t e r a c t a s s t rong ly wi th ca t ions . One except ion is Fe( I I1) . The s t a b i l i t y constant f o r t h e Fe(II1)-NTA complex i s very la rge . Hydroxide prevents formation of t h i s complex a t n e u t r a l pH, but i t can form a t pH 4. Acidic waters w i l l t hus contain Fe(II1)- NTA complexes, and no others .

6. Turbid Waters

The Colorado and Miss i s s ipp i Rivers and many r i v e r s i n t h e southeas te rn U.S.A. conta in s u b s t a n t i a l concentrat ions of suspended p a r t i c u l a t e s . The e f f e c t s of such suspended matter on t h e f a t e of NTA, and t h e e f f e c t s of NTA on t h e metals assoc ia ted with these p a r t i c u l a t e s , a r e no t known. Present knowledge of adsorpt ion and mobi l iza t ion phenomena suggests t h a t t hese a r e not important, but i t is poss ib l e t h a t they may be.

7. High Toxic Metal Concentrations

Waters containing high concent ra t ions of metals such a s Cu, N i , and Pb can form correspondingly l a r g e concent ra t ions of t h e metal-NTA complexes i f NTA i s added. It i s poss ib le t h a t t hese may p e r s i s t i n t h e environment. Actual spec i a t ion w i l l depend on o the r f a c t o r s , such a s t h e o the r organics i n t h e system. A s tudy of such a system would be usefu l .

PHOTOCHEMISTRY

The photochemical degradat ion of Fe(II1)-NTA complexes has been s tud ied by T r o t t -- et a l . (1972). Extensive degradation occurred over t h e pH range 4 t o 8. Ef f ic iency decl ined with increas ing pH. .Degradation products included iminodiacet ic ac id (IDA), formaldehyde, and C02. These au thors consider t h a t t h e photochemical r eac t ion o r i g i n a t e s from a charge t r a n s f e r exc i ted s t a t e complex. Langford -- e t a l . (1973) repor ted t h e r e s u l t s of s imi l a r s t u d i e s o f . ~ ~ ( 1 1 ) - N T A complexes. Photo-decomposition of NTA was observed. ~ l f i c i e n c ~ decreased wi th increas ing pH over t h e range 2 t o 12, and a l s o decreased wi th increas ing NTA concentrat ion. The r e s u l t s provide add i t i ona l support f o r t h e chazge t r a n s e r r eac t ion , and the re fo re suggest t h a t complexes of NTA wi th f ca2 and M~~ w i l l no t r e a c t with sunl ight .

Sto lzberg and Hume (1975) have a l s o s t u d i e d t h e photochemical degrada- t i o n of Fe(II1)-NTA s o l u t i o n s . Rapid degrada t ion of Fe(II1)-NTA complexes occurred; t h e h a l f l i f e was about 1 . 5 hours a t pH 5.2 t o 5.8. The p r i n c i p a l product w a s IDA. Very slow degrada t ion of Fe(II1)-IDA was observed, presum- a b l y because of t h e much lower s t a b i l i t y c o n s t a n t of t h e Fe(II1)-IDA complex. No photodegradat ion of Pb( I1) and Cd(I1) NTA complexes was noted. A margin- a l l y s ign i ' f i can t r e d u c t i o n was observed f o r C r ( I I I ) , and a 70 percen t reduc- t i o n of a 1 0 ppm NTA s o l u t i o n was observed i n a week wi th a s o l u t i o n con ta in - i n g a 40-fold excess of Cu(I1).

These r e s u l t s suggest t h a t t h e photochemical degrada t ion of Fe(II1)-NTA complexes t o I D A may be s i g n i f i c a n t i n a c i d i c wa te r s . A slow photochemical d e g r a d a t i o n of Cu(I1)-NTA complexes i n n e u t r a l wa te r s is a l s o p l a u s i b l e . The I D A t h a t i s produced i s probably b i o l o g i c a l l y degradable , a t l e a s t i n n e u t r a l wa te r s . The f a t e of I D A produced i n a c i d i c wa te r s should be cons idered .

CHLORINATION OF NTA

Warren (1976) has s t u d i e d t h e e f f e c t s of ammonia, meta l i o n s , pH, and s u n l i g h t on t h e r e a c t i o n s of NTA, I D A , and g l y c i n e w i t h c h l o r i n e . I n t h e absence of complexing metal i o n s and ammonia, c h l o r i n a t i o n of NTA was r a p i d , producing I D A , N-chloro I D A , and g lyc ine . These p roduc t s d i d n o t accumulate, s i n c e t h e i r r e a c t i o n s w i t h c h l o r i n e were even more r a p i d than NTA. Ammonia impaired t h e r e a c t i o n by forming chloramines t h a t d i d n o t r e a c t w i t h NTA. Diva len t m e t a l i o n s r e t a r d e d t h e r e a c t i o n by forming metal-NTA complexes, c o o r d i n a t i n g t h e n i t r o g e n atom of NTA t h a t apparen t ly is t h e i n i t i a l r e a c t i o n s i t e f o r f r e e c h l o r i n e . These r e s u l t s suggest t h a t NTA w i l l n o t be ox id ized by c h l o r i n e i n wastewater e f f l u e n t s because of t h e p resence of ammonia, o r i n p o t a b l e wa te r s u p p l i e s because of t h e e x i s t e n c e of metal-NTA complexes.

REFERENCES

Afghan, B. K . , and P. D. Goulden, 1971. Determination of Trace Q u a n t i t i e s of N i t r i l o t r i a c e t i c Acid by D i f f e r e n t i a l Cathode-Ray Polarography, Env. S c i . and Technol. , 5: 601-606.

Aue, A . , C. R. Has t ings , K. 0. Gerhardt , J. 0. P i e r c e , H. H. H i l l , and R. F. Moseman, 1972. The Determinat ion of pa r t -Per -Bi l l ion Levels of C i t r i c and N i t r i l o t r i a c e t i c Acids i n Tap Water and Sewage E f f l u e n t . J . of Chromatog 72: 259-267. -

Bouveng, H. O . , G. Davisson, and E. S te inberg , 1968. NTA i n Sewage Treatment. Va t ten , 22: 348-359.

Brownridge, F. A . , 1977. Concen t ra t ions of NTA i n Canadian Waters. I n : P r e s e n t a t i o n s Prepared by Monsanto and P r o c t e r and Gamble Companies f o r t h e I J C Task Force on Eco log ica l E f f e c t s of Non-Phosphate Detergent B u i l d e r s .

Chau, Y. K . , and M. T. Shiomi, 1972. Complexing P r o p e r t i e s of N i t r i l o t r i - a c e t i c Acid i n t h e Lake Environment; Water, A i r , and S o i l P o l l u t i o n . 1: - 149-164.

Childs , C. W . , 1971, Chemical Equilibrium Models f o r Lake Water Which Contains N i t r i l o t r i a c e t a t e and f o r "Normal" Lake Water. Proc. 14 th Conf. on Great Lakes Research; 198-210.

Dunlap, J . , R. L. Cosby, J. F. McNabb, B. E. Bledsoe, and M. R. Sca l f , 1971. Inves t i ga t ion Concerning Probable Impact of N i t r i l o t r i a c e t i c Acid on Ground Waters. Environmental P ro t ec t i on Agency, Water Po l lu t i on Research S e r i e s i/ 16060 GHR.

G l e d h i l l , W. E. 1977. NTA Adsorption t o Primary Sludge and Act ivated Sludge. Monsanto Company I n t e r n a l Report.

Huang, C. P . , and A. Ho, 1977. Adsorption C h a r a c t e r i s t i c s of N i t r i l o t r i a c e t a t e (NTA) a t Sol id Solu t ion I n t e r f a c e s , submitted t o Journa l of Col loid and I n t e r f a c e Science.

Langford, H. , M. Wingham, and V. S. S a s t r i , 1973. Ligand Photooxidation i n Copper(I1) Complexes of N i t r i l o t r i a c e t i c Acid: Impl ica t ions f o r Natural Waters. Env. Sc i . and Technol., 1: 820-822.

Lerman, A., and C. W. Childs, 1973. Metal-Organic Complexes i n Natural Waters: Control o f , D i s t r i b u t i o n by Thermodynamic, Kine t ic , and Phys ica l Fac tors . I n : "Trace Metals and Metal-Organic I n t e r a c t i o n s i n Natural Waters", ed i ted by P. C. Singer , Ann Arbor Science, 201-235.

I

Matheson, D. W . , 1977. N i t r i l o t r i a c e t i c Acid (NTA) i n the Canadian Environ- ment. S c i e n t i f i c S e r i e s No. 74, Environment Canada.

Perry, L., 1977, Communication t o I J C Task Force on Ecological E f f ec t s of Non-Phosphate Detergent Bui lders .

S to lzberg , R. J . , and D. M. Hume, 1975. Rapid Formation of Iminodiacetate from Photochemical Degradation of Fe( I I1) N i t r i l o t r i a c e t a t e Solut ion. Env. Sc i . and Technol., - 9: 654-656.

T r o t t , T., R. W. Henwood, and C. H. Langford, 1972. Sunl ight Photochemistry of F e r r i c N i t r i l o t r i a c e t a t e Complexes. Env. Sc i . and Technol., - 6: 367-368.

' .

Warren, C. B . , 1976. Chlorine Oxidation of N i t r i l o t r i a c e t a t e (NTA) and Related Imino and Amino Acids, Monsanto I n t e r n a l Report.

Warren, C. B. and E. J. Malec, 1972. Biodegradation of N i t r i l o t r i a c e t i c Acid and Related Imino and Amino Acids i n River Water. Sc i . , 176: 277-279.

Winters, R. E . , 1977a.. Chemistry of NTA. In: P re sen t a t i on Prepared by Monsanto and P roc t e r and Gamble Companies f o r t h e I J C Task Force on Ecological E f f e c t s of Non-Phosphate Detergent Bui lders .

Winters, R. E., 1977b. Communication t o I J C Task Force on Ecological E f f e c t s of Non-Phosphate Detergent Bui lders .

MICROBIOLOGY AND BIOCHEMISTRY OF NTA DEGRADATION

. . .

YICROBIOLOGY OF NTA-DEGRADING ORGANISMS

The p r i n c i p a l b i o l o g i c a l agents respons ib le f o r t h e complete degradat ion of the major i ty of organic compounds i n t he environment, both of n a t u r a l occurrence and of s y n t h e t i c o r i g i n , a r e recognized a s b a c t e r i a and fungi. It is wi th in these groups of microorganisms t h a t t h e r e q u i s i t e gene t i c p o t e n t i a l f o r t he e l abo ra t i on of degradat ive enzymes r e s i d e s , s i n c e such organisms f requent ly accomplish complete degradat ion a s a means of s a t i s f y i n g t h e i r requirements f o r carbon, n i t rogen and energy.

Aerobic degrada t ion of organic compounds by microorganisms can thereby r e s u l t i n complete ox ida t ion t o water, carbon d ioxide , inorganic forms of n i t rogen , and conversion of t h e remainder t o microbial biomass. That t h i s i s t h e case , f o r some i f no t a l l NTA-degrading microorganisms presen t i n oxygen r i c h s i t u a t i o n s where NTA is known t o occur, can be documented by re fe rence t o numerous l i t e r a t u r e r e p o r t s of t h e i s o l a t i o n of pure c u l t u r e s of aerobic b a c t e r i a growing a t t he expense of NTA (Forsberg & .L indqu i s t , 1967a, 1967b; Focht and Joseph, 1971; Wong e t a l . , 1972; Cripps & Noble, 1973; Enfors & Molin, 1973a; Parks & Sturus , 1973; T ied j e -- e t a l . , 1973).

Since a l l t h e organisms thus f a r descr ibed have been i s o l a t e d by procedures which d e l i b e r a t e l y s e l e c t f o r those which u t i l i z e NTA f o r growth, i t is not pos s ib l e t o s t a t e a t t h i s time whether o the r organisms may be found which possess t h e capac i ty merely t o modify o r a l t e r t h e s t r u c t u r e of t h e NTA molecule without de r iv ing any ene rge t i c o r n u t r i t i v e b e n e f i t from t h e process. This would appear l i k e l y , however. Pickaver (1976) has repor ted t h e i s o l a t i o n of Pseudomonas, and B a c i l l u s and yeas t s t r a i n s a b l e t o use NTA and iminodiace t ic ac id as t h e i r s o l e carbon source bu t no t a s t h e i r s o l e carbon and n i t rogen source, suggest ing t h a t they accumulate a ni t rogenous product (g lyc ine? ) . Of t h e var ious ae rob ic microorganisms i s o l a t e d and charac te r ized from sources such a s s o i l , mud, n a t u r a l waters , and sewage, a l l a r e b a c t e r i a o r yeas t s ; no examples of fungi , a lgae o r protozoa u t i l i z i n g o r modifying NTA have been reported. Notably where t he se b a c t e r i a l i s o l a t e s have been f u r t h e r c l a s s i f i e d , a high proport ion a r e found t o f a l l i n t h e genus Pseudomonas, a group of Gram negat ive, ae robic , mot i le , rods, long recognized a s organisms v e r s a t i l e i n t h e degradat ion of organic compounds ( S t a n i e r e t a l . , 1966). Because of t h e i r r ap id d i v i s i o n r a t e s with a wide v a r i e t y of organic compounds a s s o l e carbon source; t he se b a c t e r i a a r e f requent ly t h e p r i n c i p a l organisms found by t r a d i t i o n a l enrichment c u l t u r e methods. \ I t should be s t r e s s e d he re t h a t a l t e r n a t i v e i s o l a t i o n methods may y i e l d r ep re sen t a t i ve s of o the r b a c t e r i a l genera.

The n u t r i t i o n a l requirements f o r members of t he genus Pseudomonas a r e simple; they do no t r equ i r e cofac tors , amino ac ids , o r vi tamins f o r growth, and grow r e a d i l y i n simple, chemically def ined, mineral s a l t s media. Evidently b a c t e r i a capable of NTA degradat ion a r e present i n s o i l s , f r e s h water and sewage. Experience with NTA a s a chemical u se fu l f o r maintaining t r a c e metal '

s o l u b i l i t y i n bac t e r io log ica l growth media i n d i c a t e s t h a t t h e number of s tock b a c t e r i a l c u l t u r e s ab l e t o use NTA i s low. S imi la r ly i n populat ions of b a c t e r i a taken from sewage t h e occurrence of NTA-utilizers i s inf requent no doubt con t r ibu t ing t o t h e v a r i a t i o n s repor ted f o r t h e ease with which NTA- degrading microf lora a r e e s t ab l i shed i n ac t iva t ed sludge and o the r t reatment processes.

The c u r r e n t l y accepted pathway f o r t h e degradat ion of NTA by aerobic b a c t e r i a is t h a t based on biochemical s t u d i e s with pure c u l t u r e s of d i f f e r e n t s t r a i n s of Pseudomonas (Focht & Joseph, 1971; Tied je -- e t a l . , 1973; Cripps & Noble, 1973); F i r e s tone and T ied je , 1978). It should be emphasized t h a t a r e a l p o s s i b i l i t y e x i s t s t h a t a l t e r n a t i v e pathways f o r NTA degradat ion may opera te i n o ther b a c t e r i a l genera and t h a t only by a systematic microbiologi- c a l and biochemical s tudy would such a l t e r n a t i v e s be revealed. Numerous examples of a l t e r n a t i v e ca t abo l i c pathways used by d i f f e r e n t b a c t e r i a l genera f o r a given growth s u b s t r a t e can be found i n t h e l i t e r a t u r e of microbia l metabolism. It is poss ib le , t he re fo re , t h a t o the r NTA metabol i tes might be recognized from such s tudies .

The i s o l a t i o n of pure b a c t e r i a l c u i t u r e s capable of anaerobic growth wi th NTA i s documented i n only one r epor t (Enfors & Molin, 1973a). The organisms i s o l a t e d were capable both of aerobic growth wi th NTA a s s o l e carbon and n i t rogen source and of anaerobic growth only wi th n i t r a t e provided a s an a l t e r n a t i v e t o oxygen a s e l e c t r o n acceptor . The b a c t e r i a were not charac te r ized beyond t h e i r desc r ip t ion a s gram negat ive , mot i le rods.

BIOCHEMISTRY OF NTA-DEGRADATION

UPTAKE OF NTA BY MICROORGANISMS

Studies wi th organisms a b l e t o grow with NTA have provided evidence t h a t i t s permeation i n t o b a c t e r i a l c e l l s i s energy dependent s i n c e r e s p i r a t o r y i n h i b i t o r s (cyanide and azide) d r a s t i c a l l y reduce t h e r a t e and l e v e l of i t s uptake (Wong -- e t a l . , 1973). I f a c t i v e t r anspor t i s involved, b a c t e r i a may be a b l e t o concent ra te NTA from an environment where i ts concentrat ion i s low. Measurements of t h e r a t e s of ox ida t ign of N T A ' ~ ~ a Pseudomonas a s a func t ion of NTA concent ra t ion show t h a t a t 30 C half-maximal r a t e s ( s f o r i n t a c t c e l l s ) a r e found a t 18 W NTA (3.4 ppm) where t h e maximum r a t e of ox ida t ion i s 2.93 pmole 02 per h r pe r mg dry w t . (66 p l i t e r s O~/hr/mg c e l l d ry wt.) (F i res tone & Tiedje , 1975). This r a t e i s notably l a r g e r than t h a t found with a Pseudomonas mutant s e l ec t ed f o r i t s a b i l i t y t o grow rap id ly wAth high concent ra t ions (2.5%) of NTA (34 p l i t e r s 02/hr/rng dry w t . a t 25 C) ( ~ i u - e t al . , 1973). These au thors have repor ted a s f o r NTA uptake by i n t a k e - c e l l s of 82 pg/R (0.43 o r 82 ppb) a va lue s i g n i f i c a n t l y d i f f e r e n t from t h e va lue repor ted by F i r e s tone & Tiedje (1975) and revea l ing a remarkable capac i ty of t hese c e l l s t o transp= NTA a t very low concentrat ions (For E. c o l i a c t i v e t r anspor t of l a c t o s e is ha l f maximal a t an e x t e r n a l concent ra t ion of 70 W. Hence NTA i s concentrated by t h i s Pseudomonas about 200x more e f f i c i e n t l y ) .

For compounds such as glycine, glycolate and acetate Wright (1975) reports % values for cells of freshwater bacteria in the range established by Wong et al. (1973) for NTA. -

AEROBIC DEGRADATION; PATHWAYS AND ENZYMES

Based on preliminary studies with intact cells of NTA-grown Pseudomonas strains, and a variety of chemically feasible intermediates, the research groups of Focht (~ocht & Joseph, 1971) and Tiedje (Tiedje et al., 1973) both inferred that the degrative pathway involved inimodiacetic acid as the first intermediate, and that decarboxylation of NTA to such compounds as N- methyl inimodiacetic acid and sarcosine did not occur. Cells grown in the absence of NTA oxidized this compound only after a lag period suggesting that induction of the necessary enzymes was necessary (Tiedje -- et al., 1973; Cripps & Noble, 1973).

Confirmation that the reaction pathway involved two sequential cleavages of the C-N bonds of NTA was obtained from studies with enzymes present in cell extracts of NTA-grown cells (Cripps & Noble, 1973; Tiedje et al., 1973); Firestone and Tiedje, 1978; glyoxylate was identified as the cleavage product in the first reaction leading to formation of iminodiacetic acid (IDA). An analogous reaction follows which yields a second molecule of glyoxylate from iminodiacetic acid with glycine as the other product. Both glycine and glyoxylate are naturally-occurring compounds and their utilization by bacterial cells is well established (Callely et al., 1961).

NTA gx Glyoxylate +Cells,

C02 + H20 NADH2 NAD NADH2 +

Glyoxylate Gl yoxyla te

Earlier demonstration ofan.oxygen requirement by enzymes in cell extracts acting on NTA (Cripps & Noble, 1973) has been followed up by studies of purified enzymes in Tiedje's laboratory (Tiedje, 1977; Firestone et al., 1978).

The enzyme which accomplishes NTA oxidation has been partially purified and shown to be a manganese ion-dependent flavoprotein catalyzing an NADH- dependent mono-oxygenation of NTA (see scheme 1). It behaves as a typical flavoprotein monooxygenase and may be thought of as catalyzing the oxidation of a methylene group in NTA to a hydroxymethylene giving an unstable product which then yields glyoxylate and IDA. No evidence for the participation of NTA-N-oxide in this reactionhas.&en obtaisd. The NTA monooxygenase also acts on IDA and,again requires Mn (or Mg , . .for Cripps and Noble's organism)

for this reaction which yields glycine plus glyoxylate. Its requirements for molecular oxygen as a substrate in both the first and second reactions of NTA degradation demonstrate the importance of adequately aerobic conditions for NTA breakdown by these 'organisms.

Studies with the purified enzyme have yielded information about its relative affinities for NTA ( = 32 pM), IDA (% = 500-800 pM) and Mn

= 30 m) suggesting that e mechanism of concentration of NTA by act cells (% = 18 W) is one of active transport and not rate limiting.

There is no evidence to show that decarboxylation of NTA or its metabolites can occur to give such products as N-methyl iminodiacetic acid, dimethylglycine or N-methylglycine (sarcosine); this is significant in view of the fact that N-nitroso-sarcosine is recognized as a carcinogen (Druckrey -- et al., 1963).

DEGRADqTION OF STRUCTURALLY RELATED COMPOUNDS

Consideration of the biochemical mechanisms utilized by bacteria for the degradation of secondary and tertiary amines other than IDA and NTA reveals that both monooxygenase and dehydrogenase reactions are known (Large, 1971). Such examples can provide useful analogies for chemically and biologically feasible alternatives for NTA degradation. Clearly such alternatives must exist if biodegradation of NTA is to proceed under anaerobic conditions where oxygen dependent reactions of the type elucidated by Tiedje cannot apply. ,

Reactions of the monooxygenase type are known for dimethylamine oxidation by Pseudomonas AM1 (Colby & Zatman, 1971) and Pseudomonas aminovorans (Eady -- et al., 1971) and are catalyzed by flavin-containing, non-heme iron proteins requiring NADH or NADPH as electron donors. Formaldehyde is formed together with methylamine. These enzymes also appear to contain a haem prosthetic group as shown by their spectra and carbon monoxide inhibition. For trimethylamine different monooxygenases have been demonstrated in a Bacillus sp. and in Pseudomonas aminovorans both of which form trimethylamine-N-oxide by an NADPH-dependent reaction; demethylation of the product can then occur- to give formaldehyde and dimethylamine (Large et 'al. , 1972; Myers & Zatman, 1971) . The N-oxygenation reaction has been most carefully characterized in a hog liver microsomal system by studies with ''02 (Baker and Chaykin, 1962).

The above examples illustrate close analogies with the steps of aerobic degradation of NTA. There are, however, examples of secondary and tertiary amine metabolism where oxygen does not play a role as a substrate. Thus in a non-motile gram-negative bacterium, trimethylamine is demethylated by a tertiary amine dehydrogenase using artificial electron acceptors (Colby & Zatman, 1971). Similar dehydrogenases have been described for the secondary amines, spermidine (Tabor & Kellogg, 1970) and sarcosine (~risell, 1971; Hall, Simpson & Crosbie, 1971) and the tertiary amine, N, N-dimethylglycine (Hall, Simpson & Crosbie, 1971). In view of the existence of such dehydrogenases which effect C-N bond cleavage by generating hydrolyzable imines and ultimately yielding

aldehydes and t h e correspondly l e s s subs t i t u t ed amines, one can propose chemically f e a s i b l e rou te s f o r t he anaerobic degradat ion of NTA. I n l i n e with cur ren t views of t he ways i n which b a c t e r i a evolve new da tabo l i c enzymes and pathways by r e c r u i t i n g old enzymes, i t is no t unreasonable t o specula te t h a t t h e c u r r e n t l y accepted pathyay of aerobic degradat ion of NTA may have evolved from enzymes which had a s t h e i r 'normal s u b s t r a t e s ' compounds such a s dimethylglycine o r trimethylamine.

ANAEROBIC DEGRADATION; A SPECULATION ON PATHWAYS INVOLVED

A s mentioned e a r l i e r very l i t t l e is known of t h e anaerobic degradat ion of NTA by pure c u l t u r e s of b a c t e r i a (Enfors & Molin, 1973a, 1973b). I n t hese s t u d i e s f a c u l t a t i v e l y anaerobic b a c t e r i a were shown t o be capable of growing with NTA under anaerobic condit ions provided n i t r a t e was present a s an e l ec t ron

,' acceptor . From t h e foregoing considerat ions of r eac t ions by which t e r t i a r y amines can be d i s s imi l a t ed without r equ i r ing molecular oxygen, i t would appear t h a t such r eac t ions may be respons ib le f o r NTA degradat ion anaerobical ly . Unfortunately t h e above au thors have presented no evidence t o show what biochemical r eac t ions may be involved i n NTA degradat ion, e i t h e r ae rob ica l ly o r anaerobica l ly by t h e i r b a c t e r i a l s t r a i n s .

Since a number of l i t e r a t u r e r e p o r t s document t h e anaerobic degradat ion of NTA i n s o i l s (Tabatabai & Bremner, 1975); i n sewage systems (Claesson, 1971, Moore & Barth, 1976); and s e p t i c tanks (Klein, 1974, Thompson & Jones, 1971), environments where t h e concentrat ion of n i t r a t e would not appear t o be normally s u f f i c i e n t f o r nitrate-dependent anaerobic r e s p i r a t i o n , t h e r e a r e apparent ly o ther anaerobic mechanisms opera t ive (anaerobic r e s p i r a t i o n wi th HCO-a, c0a2-, ~ 0 ~ ~ - and fermentat ion) . Once converted t o g lyc ine and glyoxylate NTA could t h e o r e t i c a l l y support anaerobic growth, and dehydrogenases a c t i n g on NTA and I D A could e f f e c t t h a t conversion (Sagers & Gunsalus, 1961).

\ U n t i l s t u d i e s of t h e metabolic s t e p s involved i n t h e anaerobic biodegrada-

t i o n of NTA a r e undertaken one can only specula te about intermediates o r r e f e r t o appropr ia te analogues.,

PHYSICAL AND CHEMICAL FACTORS AFFECTING DEGRADATI'ON I

HYDROGEN I O N CONCENTRATION AND pH

Pure c u l t u r e s of NTA-utilizing b a c t e r i a a r e capable of growth over pH ranges normally encountered i n t he environment. The Pseudomonas s t r a i n i s o l a t e d by Focht and Joseph (1971) w i l l grow wi th NTA i n t h e pH range 6.5- 8.5; t h a t of Wong -- e t a l . (1972) t o l e r a t e s a pH range of 5 t o 9 f o r NTA growth with optimal growth a t pH 7.0.

SALINITY

The degradat ion of NTA by marine organisms i n marine environments has been reported (Erickson e t a l . , 1970), y e t under e s t u a r i n e condi t ions PPTA degradat ion i s apparent ly i n s i g n i f i c a n t (Gledhi l l 6 McDonald, 1976; Bourquin & Przybyszewski, 1977). Since freshwater b a c t e r i a capable of NTA degradat ion were apparent ly much l e s s e f f e c t i v e i n degrading t h i s compound i n s a l i n e

environments it would appear that an effect of salinity on NTA-degrading enzymes was responsible. Currently studies by Tiedje's group (Tiedje, personal communication) suggest that mono-oxygenase acting on NTA is subject to inhibition at high ionic strength, Firestone et g.., 1978. Anion inhibition of NADP dependent mono-oxygenases has been reported by others (Kamin, 1971; Steenis -- et al., 1973).

OXYGEN CONCENTRATION

With the demonstration that the degradation of NTA involves two oxygen- consuming reactions (at least in the organisms studied by Cripps & Noble; 1973, and that by Firestone, 1975) an absolute dependence on oxygen is to be expected for NTA metabolism in these strains. No determinations of % values for oxygen with intact cells or enzyme preparations have been reported. Experiments with soil microflora show that oxygen does not limit degradation when it is perfused at concentrations as low as 1% (Tiedje & Mason, 1974). At 0.1% 02 degradation rates are slowed suggesting that the microflora acclimated in the first 8-10 days under air uses an oxygen dependent route of degradation.

CONCENTRATION OF NTA

Bacteria able to utilize concentrations of NTA as high as 2.5% have been described (Wong -- et al., 1972). More usually pure cultures have been isolated which grow with NTA at 0.2% (Focht & Joseph, 1971), or 1.0% (Tiedje -- et al., 1973). While such high concentrations are unlikely to be encountered by more widespread use of NTA as a detergent builder, clearly high NTA concentrations present no problem to pure cultures selected for that ability. The question of how effectively low concentrations of NTA (0-1 mglliter) may be removed has not been addressed in pure culture studies other than those reported by Wong -- et al., 1973. Since the organism chosen for their work was selected for utilization of high concentrations of NTA it may not be typical of strains capable of growth with low concentrations. Additional studies of the utilization of NTA, and indeed other organic compounds, at low nutrient concentrations are required to determine whether organisms with a greater potential to concentrate nutrients can remove the low concentrations of NTA in water

\ leaving treatment facilities. In the absence of such organisms the rates of degradation of NTA will be seen to decrease linearly with decreasing concentration below comparatively high threshholds. Such is the case apparently in laboratory investigations of NTA degradation by aquatic communities (Patrick et a1 1976). At 0.02 mg1R NTA its degradati~n was 250 times slower than at - A, 20 mg/R. Without a more detailed examination of the kinetics of this process the threshold concentration of NTA remains indeterminate. One value of % for bacterial oxidation of NTA by cells is given as 18 pM (4.3 mg1R) (Firestone & Tiedje, 1975).

DEGRADATION OF NTA-CHELATES

NTA is considered a useful alternative to phosphate-containing detergent builders because it is a good chelating agent for divalent metals, yet it is precisely this property which prompts questions about its ability to mobilize metals from sediments and soils with environmental and health consequences. Concerns have also been expressed about the effect of metals on the biodegrad- ability of NTA.

Warren (1974) has reviewed the l i t e r a t u r e on microbial degradat ion of metal che l a t e s of NTA poin t ing out t h e importance of understanding more f u l l y t h e na tu re of NTA uptake by c e l l s and t h e p a r t i c i p a t i o n of d i f f e r e n t metal complexes. Since t h e enzymes of NTA oxida t ion i n a Pseudomonas a r e loca ted i n t h e so lub le f r a c t i o n wi th in the c e l l (Cripps & Noble, 1973; Tied je -- e t a l . , 1973) i t follows t h a t f o r degradation of var ious NTA c h e l a t e ~ they must e i t h e r be t ranspor ted and at tacked a t s imi l a r r a t e s o r exchange processes must occur outs ide t h e c e l l membrznce such t h a t NTA always reaches t h e i n t e r - n a l enzymes i n t h e same form. The l a t t e r process appears t o apply i n t h e Pseudomonas s tudied by T ied je ' s group. A t concentrat ions of c h e l a t e s low enough ( 2 x lo-' M) t o prevent t o x i c i t y , t h e NTA complexes of Ca, Mn, ~ g ; Cu, Zn, Cd, and Fe were degraded a t very s imi l a r r a t e s . The N i complex was no t degraded a t t h i s concentration. A t higher concentrat ions ( ~ o - ~ M ) the Cu, Cd and Zn complexes were metabolized more slowly than t h e t r isodium s a l t of NTA and t h e add i t i on of s o i l increased these r a t e s by d i f f e r i n g degrees. Evidence t h a t NTA does no t f a c i l i t a t e uptake of metals by c e l l s was a l s o obtained, support ing the concept of a NTA-binding p r o t e i n a t t h e membrane su r f ace which d e s t a b i l i z e s t he metal-NTA complex.

The e f f e c t of s o i l on s t imula t ing t h e metabolism of c e r t a i n metal che l a t e s was a t t r i b u t e d t o i ts binding of t ox ic ca t ions . Previous s t u d i e s (Tiedje & P

Mason, 1974) had shown t h a t a v a r i e t y of metal-NTA complexes were metabolized by s o i l s although t h e Cd- and Hg-chelates required longer l a g perzods and were degraded more slowly than others .

Generally t h e complexes of NTA wi th Cu, Zn, N i , and Cd a r e those which show lowered o r even n e g l i g i b l e r a t e s of ox ida t ion under d i f f e r e n t condi t ions. This may be a t t r i b u t e d t o t h e a b i l i t y of Cu, N i , Zn and Cd ions t o form s t rong t e t r a d e n t a t e complexes with NTA a t pH 7.0; l og K v a r i e s from 7-11 a s compared t o t h e weaker t r i d e n t a t e complexes ( log K from 2-6) formed by Fe, Ca and Mn ions whose complexes a r e more r e a d i l y degraded. On the o the r hand, t h e e f f e c t may be a s f o r mercury where t h e slow degradat ion of t h e Hg+~omplex i s apparent ly due no t t o i ts s t a b i l i t y bu t t o t h e tox ic e f f e c t s of Hg on c e l l metabolic processes.

The add i t i on of s o i l , sediments, ac t iva t ed s ludge, or! Ca and Mg ions can improve the b a c t e r i a l degradat ion of the less r e a d i l y at tacked NTA che la t e s by metal ion t r a n s f e r o r by l igand exchange o r perhaps even by i n a c t i v a t i o n of t he tox ic ions by adsorption. The f i r s t process allows f o r t h e che l a t ion of some f r a c t i o n of NTA wi th another ion t o give a complex which is more r e a d i l y degradable. This was r ea l i zed by Huber & Popp (1972) who added Ca ions t o sewage and thereby f a c i l i t a t e d t h e degradation of NTA o r i g i n a l l y present a s i t s Cd che la te . Ligand exchange involves a process i n which metal ions a r e r e d i s t r i b u t e d i n t h e system between NTA and o the r l igands. A v a r i e t y of organic and inorganic l igands i n s o i l s , sediments and ac t iva t ed s ludge can compete wi th NTA f o r var ious ca t ions and thereby render t h e p e r s i s t e n t complexes more degradable. Degradation of NTA-complexes w i l l t he re fo re be more complete i n var ious environments where l igand exchange and metal ion exchange can occur.

PRODUCTS AND R E S I D U E S FROM N T A

Apart from NTA, iminodiacet ic ac id is t h e only o ther compound found i n i t s degradation by pure b a c t e r i a l c u l t u r e s , which i s unknown a s a n a t u r a l

product. It has been i d e n t i f i e d a s t h e f i r s t nitrogen-containing metabol i te of NTA formed by aerobes (see A i i ) and is a pred ic ted in te rmedia te i f a dehydrogenase type a t t a c k on NTA occurs anaerobica l ly ( s ee C). Concern about t h e p o s s i b i l i t y t h a t t h i s secondary amine may form, under c e r t a i n environmental condi t ions a N-nitroso-derivative with p o t e n t i a l carcinogenic p rope r t i e s , was - f i r s t expressed by Epstein (1972). Numerous at tempts t o demonstrate i ts accumulation, t r a n s i e n t o r otherwise, from NTA i n pure c u l t u r e s and n a t u r a l environments have been unsuccessful, probably because I D A i s metabolized a t l e a s t a s r ap id ly a s NTA wi th in c e l l s (Focht & Joseph, 1971; Tied je -- e t a l . , 1973; Cripps & Noble, 1973; Warren & Malec, 1972; Tied je & Mason, 1974; Wong e t a 1 1973). - .,

Pickaver (1974, 1976) has repor ted t h e p e r s i s t e n t accumulation of N- n i t roso-iminodiacet ic ac id (-50 pg/mR) i n s o i l pe rco la to r s perfused with NTA and n i t r a t e , o r from I D A p lus n i t r i t e a t l e v e l s of 100-200 mg/R of each. Pure c u l t u r e s of f i v e d i f f e r e n t organisms were i s o l a t e d with t h e a b i l i t y t o form N-nitroso-IDA from n i t r i t e and I D A whereas appropr ia te ly pa i red b a c t e r i a l c u l t u r e s were necessary before N-nitroso-IDA formation occurred from n i t r a t e p lus NTA. The a b i l i t y t o form N-nitroso-IDA was present i n t h e c e l l e x t r a c t s of only one of t h e pa r tne r s and a second s t r a i n was apparent ly requi red t o - fu rn i sh some low molecular weight compound, poss ib ly NO2 o r I D A , before syn thes i s took place. While G ledh i l l and McDonald (1971) a l s o observed N- nitroso-IDA formation from n i t r i t e and I D A i n s imi l a r pe rco la to r s , t he n i t r o s a t e d product was subsequently biodegraded. No s i g n i f i c a n t formation of t h e n i t r o s o product from NTA and n i t r a t e was observed. Apparently t h e d i s t r i b u t i o n of microorganisms a b l e t o convert NTA and n i t r a t e t o N-nitroso-IDA, and of those ab le t o degrade t h i s compound i s not uniform. Nonetheless i t i s evident t h a t although N-nitroso-IDA can be formed by c e r t a i n microflora o the r b a c t e r i a l populat ions e x i s t t o e f f e c t i t s biodegradation.

I n pure c u l t u r e s of NTA-utilizers t h e u l t imate products of i t s degradation a r e carbon d ioxide , water, ammonia and c e l l cons t i t uen t s (Focht & Joseph, 1971; Tied je -- e t a l . , 1973). The n i t rogen t o carbon r a t i o of NTA (1:6) would suggest t h a t a l l of t h e n i t rogen would be ass imi la ted i n t o ce l l cons t i t uen t s bu t t h e f a c t t h a t much of t h e carbon is a l ready a t a high oxida t ion l e v e l means t h a t a considerable f r a c t i o n i s l o s t a s carbon d ioxide , a s i g n i f i c a n t product of glyoxylate metabolism ( see Scheme 1, IIIB) (Cal le ly -- e t a l . , 1961). Accordingly an equation t o show Con forxriation based on t h e

+ 3 pyruvates + 2NH4,

es tab l i shed pathway r evea l s t h a t -1 N per pyruvate (N:C = 1:4.5) i s a v a i l a b l e even before ex tens ive c e l l u l a r ox ida t ion has taken place. Accumulation of N a s NH4+ i s , the re fo re , not surpr i s ing .

Reports of t h e conversion of NTA n i t rogen t o small q u a n t i t i e s of n i t r i t e i n pure c u l t u r e s (Focht & Joseph, 1971) and t o n i t r a t e i n aerobic s o i l s (Tabatabai & Bremner, 1975), and aerobic c u l t u r e s of sewage organisms (Thompson & Duthie, 1968), a r e undoubtedly a t t r i b u t a b l e t o t h e a c t i o n of aerobic hetero- t roph ic and au to t rophic n i t r i f y i n g organisms a c t i n g on ammonia formed a s t h e immediate product of NTA degradation. When s o i l s a r e maintained under anaerobic condi t ions , ammonia r a t h e r than n i t r a t e accumulates (Tabatabai & Bremner,

1975). As for levels of NTA remaining in' soil and water beyond the point where NTA removal by vigorous microbial activity has occurred, monitoring studies (Matheson, 1977) show that concentrations from 0-l.mg/liter are found in waters below sewage treatment plants with most samples in the range 0-100 pglliter. In drinking waters values from 0-60 pglliter have been observed with most samples showing a range ofoO-25 pglliter. While these values are all below the KM for NTA oxidation at 30 C (3.4 mglliter) shown for Pseudomonas cells (Firestone & Tiedje, 1975) a second strain of Pseudomonas, obtained by mutagenesis, shows a KM for NTA uptake of 82 pglliter at 250C (Wong et al., 1973).

Thus the efficiency of NTA uptake mechanisms can vary from strain to strain and the potential for evolving bacterial strains with improved uptake appears to be a very real one. Concern has been expressed, however, (Dale Toetz, personal communication) that in natural environments having a low density of NTA-degrading organisms NTA will persist at low concentrations because of low degradation rates. Similar arguments apply to all organic materials whether natural or synthetic, hence the importance of such low level persistence must be carefully evaluated in the light of established effects or human health and aquatic environments.

I

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Tiedje, J. M., B. B. Mason, C. B. Warren, & E. J. Malec 1973. Metabolism of N i t r i l o t r i a c e t a t e by C e l l s of a Pseudomonas Species. Appl. Microbial. - 25: 811-818.

Warren, C. B. 1974. Biodegradation of N i t r i l o t r i a c e t a t e Acid and NTA Metal Ion Complexes: The Chemo-biological L i f e Cycle of a Detergent Builder. Survival i n Toxic Environments. Academic Press , N.Y. pp 473-496.

Warren, C. B. & E. J. Malec 1972. Biodegradation of N i t r i l o t r i a c e t i c Acid and Related Imino and Amino Acids i n River Water. Science 176: 277-279.

Wong, P. T. S., D. Liu, & B. J. Dutka 1972. Rapid Biodegradation of NTA by a Novel Bac te r i a l Mutant. Water Res. - 6: 1577-1584.

Wong, P. T. S. , D. Liu, & D. J. McGirr 1973. Mechanism of NTA Degradation by a Bac te r i a l Mutant. Water Res. - 7: 1367-1374.

Wright, R. 1975. S tudies on Glycolic Acid Metabolism By freshwater Bacter ia . Limnol. Oceanogr. - 20: 626-633.

NTA AND MUNICIPAL WASTEWATER MANAGEMENT

REMOVAL OF NTA I N WASTEWATER TREATMENT

EFFECTIVENESS OF REMOVAL . ,

Some r e p o r t s of t h e e f f i c i e n c y of a v a r i e t y of municipal wastewater t reatment processes i n removing NTA a r e summarized i n Table I. Data on t h e f a t e of NTA i n s e p t i c tank systems and i n one sludge management process , anaerobic d iges t ion , a l s o a r e included. Table I i s intended t o concise ly i l l u s t r a t e t h e na tu re of reported r e s u l t s . It i s no t an exhaust ive summary-- add i t i ona l r e p o r t s have been summarized i n reviews prepared by Thom (1971), Prakash (1976), Thayer and Kensler (1973) and Toetz (1977).

I n general , t he r e s u l t s tabula ted i n d i c a t e t h a t , under favourable con- d i t i o n s , acclimated aerobic b i o l o g i c a l wastewater t reatment systems a r e capable of high degrees ( say , 90 percent o r more) of NTA removal. Low degrees of NTA removal a r e assoc ia ted pr imar i ly with anaerobic condi t ions and low temperatures . '

Anaerobic waste t reatment processes included i n Table I a r e t h e s e p t i c tanks , anaerobic s ludge d i g e s t e r s , anaerobic s e p t i c tank t i l e systems and anaerobic s o i l systems. With a s i n g l e exception, t h e d a t a f o r t hese i n d i c a t e inappreciable NTA removal. The exception was r ecen t ly reported by Moore and Barth (1976). They found t h a t , while no NTA removal occurred i n anaerobic d iges t ion of primary sewage s ludge, good removal occurred when equal volumes of primary sludge and waste ac t iva t ed sludge containing NTA-acclimated organisms were anaerobica l ly digested. While Moore and Barth 's f i nd ings need t o be expanded, ava i l ab l e d a t a i n d i c a t e t h a t NTA should be considered t o move essen- t i a l l y unaffected through s e p t i c tanks, anaerobic sludge s t a b i l i z a t i o n processes , anaerobic s o i l s and any anaerobic systems adopted f o r t reatment of municipal wastewaters (Young and McCarty, 1969).

Data on NTA removal i n wastewater t reatment systems a r e cons i s t en t i n showing t h a t removal e f f i c i e n c i e s diminish a s temperatures decrease. Closely cont ro l led labora tory experiments with ac t iva t ed sludge, reported by Eden et a l . (1972), sgowed NTA removal e f f i c i e n c i e s above 90 percent when temperatures - were above 10 C , but a t ~ O C , e s s e n t i a l l y go NTA removal occurred. Although t h e l a t e r conclusion i s suspect because t h e 5 C sygtem may no t have acclimated during t h e 40 days, an acclimated system a t 20 C , removing >98% of t h e added NTA, d id drop i n e f f i c i e n c y t o 66 and 82% removal a t 7 . 5 ' ~ f o r 20 mg/R and 5 rngk6of NTA respec t ive ly . BOD removed was unaffected by t h e temperature change. Other experiences reported i n Table I a r e compatible with these f indings. Because wastewater.temperature i s not a cont ro l led v a r i a b l e i n wastewater t reatment , reduced NTA removal e f f i c i e n c i e s from aerobic b io log ica l treatment

p lan t s would be ant ic ipa ted during eo'ld seasons. S igni f icant temperature reductions can occur i n wastewater treatment processes such a s s t a b i l i z a t i o n ponds, extended ae ra t ion p lan t s , aerated lagoons, and t r i c k l i n g f i l t e r s , and such processes would be p a r t i c u l a r l y suscept ib le t o reduced NTA removal e f f i c - iency during cold weather.

Data on NTA removal from physical-chemical treatment processes such a s adsorpt ion and chemical p rec ip i t a t ion and coagulation a r e absent from Table I. Extensive s tud ies of NTA removal in physical-chemical treatment a r e not known, but i n view of t h e purpose of NTA i n detergent formulations, exceptional ly high removal e f f i c i e n c i e s would not be ant ic ipa ted . Indeed, an OECD Committee (1973) i n d i ~ a t e d ~ t h a t NTA is not removed by chemical p r e c i p i t a t i o n o r adsorption on ac t iva ted carbon.

Another process f o r which no da ta a r e included i n Table I is e f f luen t chlorinat ion. Speci f ic s tud ies of the e f f e c t s of wastewater chlor ina t ion p rac t i ces on NTA a r e not known. Reactions of NTA and chlor ine a r e reviewed elsewhere i n t h i s repor t . (Section 2)

MECHANISMS OF REMOVAL

Reductions i n NTA concentrat ions which occur a s wastewater flows through treatment p l an t s a r e o rd ina r i ly assumed t o be a t t r i b u t a b l e t o b io log ica l degradation. However, comprehensive s t u d i e s of t h e exact removal mechanisms a r e not known. Elaboration of removal mechanisms is of concern because, i f some removal involves incorporation of NTA i n t o wastewater sludges, then the f a t e of t h e NTA i n sludge becomes of concern. The question becomes part icu- l a r l y pe r t inen t when it i s considered t h a t the most common type of sludge s t a b i l i z a t i o n involves anaerobic treatment i n which NTA biodegradation would not be expected. Furthermore, appl ica t ion of wastewater and s t a b i l i z e d sludge on a g r i c u l t u r a l land i s a common p rac t i ce , and questions concerning the e f f e c t s of NTA i n sludge and wastewater on heavy metals i n s o i l s would a r i s e .

Swisher, -- e t a l . (1967) a r e commonly a t t r i b u t e d with having demonstrated t h a t NTA does not adsorb t o ac t iva ted sludge. Their r e s u l t s , however, merely indica ted t h a t the weight of NTA removed during a 30-day period exceeded t h e weight of sludge remaining i n the system, and would not seem t o preclude the p o s s i b i l i t y of associa t ion of NTA with sludge surfaces followed by biodegrada- t i o n o r removal from the process with sludge so l ids . I n con t ra s t with these f indings Bouveng, e t a l . , (1968), who conducted*specific t e s t s t o determine the amount of NTA adsorbed t o ac t iva ted sludge s o l i d s , found t h a t an equil ibr ium was es tabl i shed between f r e e and adsorbed NTA i n ac t iva ted sludge systems. A t t h e beginning of batch feeding experiments, 25 and 36 percent of the NTA was reported t o be adsorbed t o sludge surfaces when 2 and 10 mg/k of NTA?ere added respect ive ly .

Reported r e s u l t s of s i g n i f i c a n t NTA removal i n primary wastewater t reatment a r e - d i f f i c u l t t o explain by b io log ica l mechanisms. I n add i t ion t o t h e da ta on removal i n primary sedimentation shown i n Table I, Shumate, e t a l . -- (1970) found 8 percent NTA removal in primary sedimentation but a t t r i b u t e d it t o f a u l t y sampling procedures. Biological oxidation seems unl ike ly because of the anoxic condit ions which o rd ina r i ly p reva i l i n primary sedimentation tanks and because of t h e l ack of opportunity f o r developing an acclimated cu l tu re ,

(except perhaps, a s a r e s u l t of wastage of ac t iva t ed sludge t o primary sedimentation tanks).

I

Dunlap, -- e t a l . (1971) repor ted r e s u l t s of so rp t ion s t u d i e s with NTA and a v a r i e t y of s o i l s . They concluded t h a t r e l a t i v e l y weak s o r p t i v e fo rces were exhib i ted by these s o i l s toward NTA but t h a t t h e fo rces "cannot, however, be completely discounted i n considering t h e movement of NTA i n t o and through ground water". S tudies of adsorpt ion of NTA onto calcium carbonates , aluminum oxide, s i l i c a and k a o l i n i t e were reported by Huang and Ho (1977). They reported 11 s i g n i f i c a n t adsorpt ion of an ionic NTA spec ie s ... even f o r sur faces t h a t a r e nega t ive ly o r n e u t r a l l y charged". Prel iminary s t u d i e s of NTA adsorpt ion onto primary s ludge and ac t iva t ed s ludge ca r r i ed out e s p e c i a l l y f o r t h i s r epo r t by

, Gledh i l l (1977) showed only small amounts of NTA adsorpt ion t o t h e s ludges a t t h e end of a 30-min.-contact period. With an i n i t i a l NTA concentrat ion of about 10 mg/ll, maximum amounts of adsorpt ion on ac t iva t ed sludge were about 0.24 mg/kg while t h e maximum amount on primary sludge was only about 0.008 mg/kg. Some adsorpt ion s t u d i e s with copper and n i cke l NTA che la t e s a l s o were conducted with only small amounts of adsorpt ion being reported dur ing a 30-min. period.

To summarize, t h e r e remains a degree of unce r t a in ty regarding t h e f a t e of NTA i n wastewater t reatment f a c i l i t i e s . While i t i s commonly presumed t h a t NTA does no t reach anaerobic d i g e s t e r s i n amounts g r e a t e r than t h a t contained i n t h e l i q u i d phase of t h e s ludge, a c t u a l amounts of NTA i n anaerobic d i g e s t e r s (and on poss ib le subsequent a g r i c u l t u r a l land d isposa l s i t e s ) a r e apparent ly no t known.

REMOVAL OF NTA COMPLEXES

Biodegradation of NTA/metal complexes i s considered i n more d e t a i l e l s e - where i n t h i s r epo r t and only a few r e p o r t s s p e c i f i c t o wastewater treatment a r e mentioned here. In such s tud ie s , a quest ion would seem t o e x i s t a s t o whether o r no t t h e NTA a c t u a l l y ex i s t ed i n t h e complexed form a t t h e time

. , .

experimental observat ions were made.

Swisher, -- e t a l . (1967) found no d i f f e rence i n t h e r a t e of biodegradat ion of NTA and a NTA-iron complex i n labora tory ac t iva t ed sludge systems. Tiedje and Mason (1974), working i n aerobic s o i l systems, found cadmium and mercury complexes of NTA t o degrade more slowly than non-complexed NTA and, s i m i l a r l y , Shannon (1975) found t h a t complexes with mercury, cadmium and n i c k e l were r e s i s t e n t t o degradation. Walker (1975) emphasized t h e need f o r considering a l l mul t iva len t ca t ions i n t h e system. While NTA biodegradation was inh ib i t ed by copper o r cadmium i n his ,experiments t h e i n h i b i t o r y e f f e c t s were reduced by i ron . Furthermore, increased hardness improved t h e biodegradation of t h e NTA i n the presence of copper.

RELIABILITY OF NTA REMOVAL

While e f f i c i e n t NTA removal has been demonstrated i n c l o s e l y cont ro l led acclimated aerobic b io log ica l wastewater t reatment systems, i t i s prudent t o consider t h e ex t en t t o which p r a c t i c a l complications i n r e a l wastewater t r e a t - ment systems would d e t r a c t from t h a t performance.

Appreciable periods of acclimation have commonly been reported to be required to achieve biological degradation of NTA. Thus, Swisher -- et al. (1967) found 2 to 3 weeks of acclimation to be required in laboratory activated sludge systems and Cleasby -- et al. (1974) needed 2 to 4 weeks to acclimate trickling filters to NTA., Klein found 5 to 7 weeks to be required in septic tank percolation fields. Renn (1974) tried in vain for a three-month period to acclimate an activated sludge system to NTA.

If NTA were adopted as a prevalent builder in detergent products, then its occurrence in most wastewaters would be continuous. Available data suggest that once acclimation was achieved, sustaining the acclimated condition would not be difficult unless overloading occurred. Pfeil and Lee (1968), for example, found that an acclimated culture recovered following two days without exposure to NTA, and Tiedje and Mason .(1974) found that temporary exposure to anaerobic conditions did not severely harm an acclimated culture. Additionally, Cleasby -- et al. (1974) found that variations in NTA loading did not require an additional period of acclimation. However, when wastewater or sludge are applied to soil, application might be infrequent. Under such conditions acclimation to NTA might not be maintained.

The terms "refractory" or "biodegradable" as applied to biological wastewater treatment systems are relative terms. That is, a substance which is refractory at one mean cell residence time in a biological wastewater treatment process may be biodegradable at a longer mean cell residence time. Regrettably, insufficient kinetic data on NTA biodegradation appear to be available to permit estimation of loading conditions in biological wastewater treatment processes at which "washout" of organisms responsible for NTA biodegradation would occur. The fact that Bouveng -- et al. (1970) indicated that NTA biodegradation "dropped more than would be expected when the treatment plant was overloaded" suggests that there could be a reason for concern about the possibility that, during periods of overload, NTA degradation could be reduced more than that of other materials.

The adverse effect of low temperatures on NTA removal in biological wastewater treatment plants was reviewed in a previous section. It must be concluded with Eden -- et al. (1972) "that while NTA is almost completely removable under favorable conditions of sewage treatment, removal becomes incomplete under winter conditions". Eden et al., (1972) elaborated further in emphasizing that their results were based on idealized laboratory conditions and that "it is probable that under actual working conditions at sewage works the removal during winter would be even lower".

As suggested by Eden -- et al., it must be assumed that the practical problems of overloading, power failures, etc. which.prevented Renn (1974) from achieving acclimation in a three-month period are not restricted to experimental studies, and that operational efficiencies below reported laboratory removal levels might be anticipated. Cleasby -- et al. (1974) felt that observed variability in NTA removal was caused by susceptibility of NTA-consuming species to random environmental changes, such as pH changes orathe presence of toxic materials. In commenting on the removal of NTA under unfavorable circumstances in biological wastewater treatment plants, Bouveng -- et al. (1968) noted that "it seems justified to characterize it as a less preferred substrate".

The repor ted Canadian experience wi th NTA removal i n f u l l - s c a l e f a c i l i t i e s provides some measure of t h e ex t en t t o which p r a c t i c a l cons ide ra t i ons i n r e a l f u l l - s c a l e t reatment p l a n t opera t ion can r e s u l t i n reduc t ion of NTA removal e f f i c i e n c i e s . Data summarized by Thayer and Kensler (1973) on repor ted exper- i ences a t a v a r i e t y of Canadian wastewater t reatment p l a n t s ( included i n Table I ) a r e averages of monthly d a t a f o r a six-month per iod te rmina t ing i n May. During t h a t per iod , seven d i f f e r e n t a c t i v a t e d sludge p l a n t s averaged 72 percent removal of NTA, wi th one p l a n t i n d i c a t i n g an average removal e f f i c i e n c y of only 22 percent , and another 5 1 percent. The two t r i c k l i n g f i l t e r i n s t a l l a t i o n s included i n t h e t abu la t i on ind i ca t ed average NTA removals of only 34 percent .

Thus, i t is apparent t h a t i f NTA i s t o be used a s a de te rgent b u i l d e r , i t should be wi th t h e r e a l i z a t i o n t h a t e f f i c i e n t removal i n presen t municipal wastewater t reatment systems may not occur c o n s i s t e n t l y . ~ I n acclimated ae rob ic b i o l o g i c a l t reatment p l a n t s , e f f e c t i v e removal under i d e a l condi t ions can t ake - p lace , bu t those condi t ions may no t always e x i s t . Reduced e f f i c i e n c y of NTA removal is t o be a n t i c i p a t e d when low temperatures p reva i l . Avai lab le d a t a from f u l l - s c a l e Canadian p l a n t s , and repor ted d i f f i c u l t i e s i n achieving acclima- t i o n i n wastewater t rea tment p l a n t s , suggest t h a t p r a c t i c a l problems of load v a r i a t i o n , equipment maintenance, waste q u a l i t y v a r i a t i o n , e t c . would cause f u r t h e r reduct ion i n NTA removal e f f i c i ency .

EFFECTS OF NTA ON WASTEWATER MANAGEMENT

EFFECTS ON GENERAL PLANT PERFORMANCE

Municipal wastewaters conta in a heterogeneous mixture of chemical compounds. It is unusual f o r a s i n g l e compound' t o be a s preva len t i n wastewaters a s NTA would be i f i t were used a s a bu i lde r i n de te rgents . I n ca se s i n which p a r t i c u l a r substances have been preva len t i n municipal wastewaters ( a s , f o r example, when a p a r t i c u l a r i n d u s t r i a l wastewater comprises a s i g n i f i c a n t f rac- t i o n of a t o t a l load on a t reatment f a c i l i t y ) , changes i n t reatment p l a n t performance a t t r i b u t a b l e t o those substances have n o t been unusual. Thus, i t is appropr ia te t o i n q u i r e a s t o t h e probable in f luence of NTA i n wastewaters on f a c t o r s such a s s ludge s e t t l e a b i l i t y , removal of carbonaceous and ni t rogenous oxygen-demanding ma te r i a l s , phosphorus removal, and methane production.

A common e f f e c t of p reva len t , unusual, c o n s t i t u e n t s i n wastewaters is t o a l t e r t h e s e t t l e a b i l i t y of b i o l o g i c a l sludges. Swisher -- e t a l . (1967) repor ted t h a t NTA concent ra t ions up t o 200 mg/!L d id no t a l t e r a c t i v a t e d s ludge settle- a b i l i t y . S imi l a r ly , Thompson and Duthie (1968) found no d e l e t e r i o u s e f f e c t s of NTA on a c t i v a t e d s ludge s e t t l e a b i l i t y . Thompson and Duthie a l s o repor ted no e f f e c t s on s e t t l e a b i l i t y of primary sludges. Cleasby -- et a l . (1974) repor ted t h a t , a s measured by e f f l u e n t suspended s o l i d concent ra t ions , NTA displayed no adverse e f f e c t s on t h e s e t t l e a b i l i t y of t r i c k l i n g f i l t e r humus. No inves t iga- t i o n s on t h e e f f e c t s of NTA, o r of organisms s h t h e s i z e d i n removal of NTA, on another important phys i ca l property of s ludges, dewa te rab i l i t y , a r e known. However, i n t h e absence of e f f e c t s on s e t t l e a b i l i t y , s i g n i f i c a n t i n t e r f e r e n c e wi th dewa te rab i l i t y would no t be expected.

No e f f e c t s of NTA on removal of oxygen demanding m a t e r i a l s i n a c t i v a t e d s ludge systems were noted by Shannon (1975) o r by Swisher e t a l . (1967).

Simi l a r ly , Cleasby e t a l . (1974) repor ted no e f f e c t s on removal of BOD, COD or TOC i n t r i c k l i n g f i l t e r s , and Kle in (1974) repor ted t h a t t he .p re sence of NTA had no no t i ceab le e f f e c t on t h e ' performance of s e p t i c tank pe rco l a t i on f i e l d s o r ox ida t ion ponds.

Because of t h e quest ion of increased metal ion t o x i c i t y i n anaerobic d iges t i on , i t is of i n t e r e s t t h a t Moore and Bar th (1976), Thompson and Duthie (1968), and Kle in (1974) a l l reported t h a t NTA had no e f f ec t s ' on t h i s process.

The r e l a t i o n s h i p between t h e presence of NTA and n i t r i f i c a t i o n i n a t r i c k l i n g f i l t e r p l a n t were i nves t i ga t ed by Cleasby -- e t a l . (1974). No adverse e f f e c t s on n i t r i f i c a t i o n were found.

No e f f e c t of NTA on b i o l o g i c a l removal of phosphate . in an a c t i v a t e d s ludge wastewater t reatment p l a n t was recorded by Shannon (1975), b u t t h e average NTA concent ra t ion i n t h e t reatment p,lant i n f l u e n t was only 2.2 mg/R. No s i g n i f i c a n t changes i n phosphate removal when t h e concent ra t ion of NTA i n t h e feed t o a t r i c k l i n g f i l t e r was va r i ed were repor ted by Cleasby -- et a l . (1974).

Shannon (1975) repor ted t h a t t h e reduc t ion i n wastewater phosphorus concent ra t ion brought about by s u b s t i t u t i o n of NTA f o r a phosphate b u i l d e r , more than compensated f o r any inc rease i n dosage of alum o r f e r r i c ch lo r ide f o r phosphorus removal caused by the NTA. That is, lower dosages of alum and f e r r i c ch lo r ide were requi red when NTA was used i n p lace of a phosphorus- conta in ing de te rgent . Because of t h e dependence of phosphorus removal by lime on pH, a comparable sav ings i n l i m e dosage f o r phosphorus was no t r ea l i zed . Toetz (1977) c i t e d work by Manning and Ramanoothy (1972) i n d i c a t i n g t h a t NTA may complex wi th calcium phosphate compounds and reduce t h e e f f e c t i v e n e s s of phosphorus p r e c i p i t a t i o n by l i m e . Bouveng -- et a l . (1968) concluded t h a t t h e che l a t i on of aluminum by NTA i n alum p r e c i p i t a t i o n of phosphorus was "of small p r a c t i c a l s ign i f icance" . TRANSPORT OF HEAVY METALS THROUGH WASTEWATER TREATMENT PLANT

Because of t h e a b i l i t y of NTA t o c h e l a t e heavy meta l s , t h e p o s s i b i l i t y of i nc reases i n heavy metal d i scharges from wastewater t rea tment p l a n t s a s a r e s u l t of NTA usage warran ts i nves t i ga t ion . I n s t u d i e s wi th t r i c k l i n g f i l t e r s , Cleasby e t a l . (1974), found no s i g n i f i c a n t metal t r anspo r t a s a r e s u l t of t h e

1 -- presence of NTA, except f o r manganese under low temperature condi t ions . Shannon (1975), however, found t h a t wi th an inf,luent NTA concent ra t ion of only 2.2 mg/R, z inc , aluminum, and copper t r anspo r t through an a c t i v a t e d s ludge t reatment p l a n t increased under low temperature condi t ions. S imi l a r ly , Renn (1974) found t h a t t r a n s p o r t of z inc and i r o n through an a c t i v a t e d s ludge t r e a t - ment p l a n t increased a s a r e s u l t of NTA addi t ion . When acc l imat ion occurred, and NTA was removed i n t h e t reatment p l a n t , t h e z inc concent ra t ion i n t h e e f f l u e n t decreased. S imi l a r ly , Nilsson (1971) i nd i ca t ed t h a t heavy meta l s might b e expected t o be discharged from b i o l o g i c a l wastewater t rea tment p l a n t s i n which NTA removal i s incomplete because of overloading o r low temperatures . Nilsson a l s o c i t e d work i n d i c a t i n g t h a t copper-NTA complexes and nickel-NTA complexes a r e n o t b i o l o g i c a l l y degraded even under favorab le condi t ions and w i l l be discharged wi th b i o l o g i c a l wastewater t reatment p l a n t e f f l u e n t s .

In an evaluation of the effects of NTA on heavy metal removal in physicall chemical wastewater treatment plants, Argaman and Weddle (1974) concluded that "the data strongly indicate that NTA interferes significantly with the precipitation of specific heavy metals". Interference of NTA with precipitation of copper and cobalt with lime were particularly noted. Nilsson (1971) also indicated interference of NTA with heavy metal removal in chemical treatment processes, but indicated that the adverse effect was prevalent at pH values below 9.

EFFECTS ON LAND APPLICATION SYSTEMS

At least 20 percent of the sludge produced at wastewater treatment plants in the United States currently is applied to agricultural land, and increased application of sludge to land is anticipated in the future (Farrrll, 1974). Such sludge is commonly subjected to anaerobic digestion prior to land application, but available data would indicate that NTA in the liquid phase of the sludge would not be completely degraded dur5ng digestion. As indicated in the previous section, the prevalence of NTA in the solid stage of the sludge is unknown. Additionally, application of wastewaters to land could be a source of NTA in soil systems. The amount of NTA applied in such cases would be dependent upon the type of and efficiency of wastewater treatment provided before land application. Because of the heavy metal chelation properties of NTA, the effects of these land application practices on heavy metal concentrations in ground water and on heavy metal introduction intolhe food chain through crop production requires analysis. As noted above the periodic use of land application is likely to make maintenance of an acclimated microbial population difficult.

OCEAN DISPOSAL

Another possible means for introduction of NTA into the environment from wastewater treatment processes is ocean disposal of wastewaters and sludges. Currently, 15 percent of the sludges produced in'the United States are discharged to oceans (Farrell, 1974). Such sludges are commonly subjected to anaerobic digestion which would not be expected to eliminate whatever NTA might be present. Additionally, ocean discharges of wastewaters which had not been exposed to efficient aerobic biological treatment might still contain significant quantities of NTA.

Discharge of NTA to oceans is of potential concern because of the question (discussed elsewhere, in this report) of biodegradation of NTA in certain marine environments. In the absence of such biodegradation, questions concerning the introduction of heavy metals into the marine food chain-become pertinent.

EFFECTS OF NTA ON COSTS OF WASTEWATER MANAGWNT

Analyses of the economic implications of NTA on the capital and operating costs for wastewater management are not known. Degradation of NTA in aerobic biological wastewater treatment processes would require oxygen and result in synthesis of microorganisms which would be wasted as sludge. The incremental costs of wastewater management attributable to the oxygen consumed and sludge produced in the course of NTA degradation depends on the relative amounts of NTA and biodegradable materials from other sources in wastewaters. For esti- mating purposes, it may be noted that the theoretical oxygen demand of NTA is 0.77 mg oxygenlmg NTA. It must be emphasized that builders which are alternatives to NTA also influence the cost of wastewater treatment.

REFERENCES

Argaman, Y. and C. L. Weddle, 1974. Fa t e of Heavy Metals i n Physical- Chemical Treatment Processes. Water-1973. AIChE Symposium S e r i e s , %: 136, 400-414.

Bouveng, H. O . , G. Davisson, and E. S te inberg , 1968. NTA i n Sewage Treatment, 24: 348-359.

Bouveng, H. O . , P. Solyom and J. Werner, 1970. NTA i n Sewage Treatment, Pa r t 2. Degradation of NTA i n a T r i ck l ing F i l t e r and an Oxidation Pond. Vat ten, - 24: 389-402. ,

Cleasby, J. L., D. W. Hubly, T. A. Ladd and E. A. Schon, 1974. T r i ck l ing F i l t r a t i o n of a Waste Containing NTA. Jour. Water Po l l . Contr. Fed., 46: 1873-1887. - Dunlap, W. J . , R. L. Cosby, J. F. McNabb, B. E. Bledsoe, and M. R. Sca l f , 1971. Inves t i ga t ion Concerning Probable Impact of N i t r i l o t r i a c e t i c Acid on Ground Waters. Environmental Water Po l lu t i on Control Research S e r i e s 16060 GHR 11/71, U.S. Environmental P ro t ec t i on Agency, Washington, D. C . , 51 pp.

Duthie, J. R. , 1970. Trisodium ~ i t r i l o t r i a c e t a t e (NTA) Environmental Safe ty Review. P roc t e r and Gamble Company, I n t e r n a l Report.

Eden, G. E . , G. E. Cul ley and R. C. Rootham, 1972. E f f ec t of Temperature on t h e Removal of NTA ( N i t r i l o t r i a c e t i c Acid) During Sewage Treatment. Water Research 6 : 877-883.

~ a r r e l l , J. B . , 1974. Overview of Sludge Handling and Disposal. Proceedings Nat ional Conference on Municipal Sludge Management, P i t t sburgh , Pennsylvania, June 11-13, 1974. Information Transfer , Incorporated, Washington, D. C . , 5-10.

G ledh i l l , W. E . , 1977. NTA Adsorption t o primary Sludge and Act ivated Sludge. Monsanto Company, ' I n t e r n a l Report, 5 pp.

Huang, C. P. and A. Ho, 1977. Adsorption C h a r a c t e r i s t i c s of N i t r i l o t r i - a c e t a t e (N>TA) a t So l id Solu t ion In t e r f aces . Manuscript submitted t o Journa l of CoUoid and I n t e r f a c e Science, 16 pp.

,' . . ,

Klein, S. A. , 1974'. NTA Removal i n S e p t i c Tank and Oxidation Pond Systems. Jour. Water Po l l . Contr. Fed., 46: 78-88.

Manning, P. G. and S. Ramanoothy, 1972. for ma ti^ and St i&il i ty of Mixed-Ligand (NTA) and Phosphate Complexes of Ca and Cu . Inorganic Nuclear Chemistry L e t t e r s , 8: 653-658.

Moore, L. and E. F. Barth, 1976. Degradation of NTA During Anaerobic Digest ion, Jour. Water Pol l . Contr. Fed., 48: 2406-2409.

Nilsson, R . , 1971. Removal of Metals by.Chemica1 Treatment of Municipal Waste Water. Water Research, 5: 51-60.

Organizat ion f o r Economic Cooperation and Development, 1973. Report of t he Expert Group on Detergents , OECD, P a r i s , 40 pp.

P f e i l , B. H. and G. F. Lee, 1968. Biodegradation of N i t r i l o t r i a c e t i c Acid i n Aerobic Systems, Env. Sci. Tech. ,lz: 543-546.

Prakash, A . , 1976. NTA ( N i t r i l o t r i a c e t i c Acid) - An Ecological Appraisal. Environment Canada Water Po l lu t i on Control Di rec tora te . Economic and Technical Review Report, EPS-3-WP-76-8.

Renn, C. E . , 1974. Biodegradation of NTA,Detergents i n a Wastewater Treatment System. Jour . Water Pol l . Contr. Fed., 46: 2363-2371.

I

Rudd, J. W. M . , B. E. Townsend and R. D. Hamilton, 1973. Discharge of N i t r i l o t r i a c e t a t e (NTA) from Two Sewage T r e a t m e n t ' F a c i l i t i e s Located i n a Midcontinental Climate. Jour. Fish. Res. Bd. Canada, - 30: 1026-1030.

Shannon, E. E . , 1975. E f f e c t of Detergent Formulation on Wastewater C h a r a c t e r i s t i c s and Treatment. Jour. Water Po l l . Contr. Fed., c: 2371-2383.

Shumate, K. S. , J. E. Thompson, J. D. Boakhart, and C. L. Dean, 1970. NTA Removal by Act ivated Sludge-Field Study. Jour. Water Pol l . Contr. Fed., - 42: 631-640.

Swisher, R. D . , M. R. Cru tchf ie ld and D. W. Caldwell , 1967. Biodegradation of NTA i n Act ivated Sludge, Env. Sci . and Technol, - 1: 820-927..

Thayer, P. S. and C. J. Kensler, 1973. Current s t G u s of t h e Environmental and Human Safe ty Aspects of N i t r i l o t r i a c e t i c Acid (NTA). CRC C r i t i c a l Reviews i n Environmental Control - 3: 375-404.

4

Thom, N.S., 1971. , N i t r i l o t r i a c e t i c Acid: A L i t e r a t u r e Survey. Water Research, 5: 391-399.

Thompson, J. E. and J . R. Duthie, 1968. The Biodegradabi l i ty and T r e a t a b i l i t y of NTA. Jour. Water Po l l . Contr. Fed., 40: 306-319. ..

Tied je , J. M..and B. B. Mason, 1974. Biodegradation of N i t r i l o t r i a c e t a t e (NTA) i n S o i l s . S o i l Sci . Soc. Amer. Proc. , 38: 278-282.

Toetz, D. W . , 1977. Fa t e , Transport and E f f e c t s of NTA i n t he Aquatic Environment, Draf t Report. U.S. Environmental P ro t ec t i on Agency, Environ- mental Research Laboratory, Athens, Georgia, 72 pp. .

Young, J. C. and P. L. McCarty, 1969. The Anaerobic F i l t e r f o r Waste Treatment, Jour. Water Po l l . Contr. Fed., Res. Suppl. , 41: R160-R173.

Walker, A. P . , 1975. Ult imate Biodegradation of N i t r i l o t r i a c e t a t e i n - t h e Presence of Heavy Metals , Progress i n Water Technology, 1: 555-560.

TABLE I

REPORTED EFFICIENCIES OF NTA REMOVAL I N MUNICIPAL WASTEWATER TREATMENT FACILITIES

Waste Treatment I n f l u e n t NTA NTA Removal Processes Concentration, Eff ic iency

(mg/R) (percent)

Notes Reference

\

Primary Sedimentation

3 0 Average f o r 6-month per iod from Thayer and Kensler, 1973 Canadian Ci ty

58 Average f o r 6-month per iod from Thayer and Kensler, 1973 Canadian Ci ty

11 Average f o r 6-month period from, Thayer and Kensler, 1973 Canadian Ci ty

I W, Activated Sludge 2 0 9 2 Laboratory continuous flow u n i t s Swisher -- et a l . , 1967

I

5 and 20 3 * Laboratory Studies a t 5 ' ~ Eden e t a l . , 1972

5 and 20 66-82 Laboratory Studies a t 7 . 5 ' ~ Eden et a l . , 1972

5 and 20 9 8 Laboratory Studies a t 2 0 ' ~ Eden -- et a l . , 1972

High F u l l sca le -e f f luent < 0.5 mg Rudd, -- et a l . , 1973 NTA/R i n win te r and summer

10 90 Laboratory Scale Thompson and Duthie, 1968

.2.2 61 F u l l Scale , a t 1 4 ' ~

5 t o 45 65 t o 98 F u l l Scale

Shannon, 1975

Renn, 1974

10 80 t o 85 Laboratory Units a t 20 C Bouveng et a 1 . , 1968 0

10 2 5 Laboratory Units a t 5 ' ~ Bouveng -- et a l . , 1968

*Possibly unacclimated

TABLE I (CONTINUED)

Waste Treatment In f luen t NTA NTA Removal Processes Concentration, Ef f ic iency

(mg/R) (percent)

Notes Reference

up t o 110 e s s e n t i a l l y Laboratory Units t o t a l

P f e i l and Lee, 1968

2.2 t o 5 .1 11 t o 96 Range of averages f o r monthly Thayer and Kensler, 1973 d a t a f o r 6-month period from 7 Canadian C i t i e s . Average removal = 72 percent

90 F u l l Sca le

7 5 F u l l Sca le

Shumate e t a l . , 1970 --

'Shumate e t a l . , 1970 --

Tr ick l ing F i l t e r , -- ' over 80 F u l l Sca le data-summer and e a r l y autumn. Eff ic iency dropped when p l an t overloaded o r temperatures low.

Aerated Lagoon

P i l o t s c a l e - f a l l condi t ions

P i l o t scale-cold weather, but f i l t e r heated

Cleasby e t a l . , 1974 --

Cleasby e t a l . , 1974

32 Average f o r 6-month period from Thayer and Kensler, 1973 Canadian Ci ty

36 Average f o r 6-month period from Thayer and Kensler, 1973 Canadian Ci ty

high F u l l s c a l e summer

e s s e n t i a l l y F u l l s c a l e winter zero

Rudd e t a l . , 1973 -- Rudd e t a l . , 1973

TABLE I (CONTINUED)

Waste T rea tmen t I n f l u e n t NTA NTA Removal Notes Re fe rence Process 'es C o n c e n t r a t i o n , E f f i c i e n c y

(mg/ i ) ( p e r c e n t )

S t a b i l i z a t i o n up t o 30 90 360 g a l p i l o t s c a l e - 3 0 day r e t e n t i o n K l e i n , 1974 Pond

u p t o 7 5 , 8 0 360 g a l p i l o t s c a l e - 3 0 day r e t e n t i o n K l e i n , 1974

100 5 0 360 g a l p i l o t s ca l e -30 day r e t e n t i o n K l e i n , 1974

- - n e a r 100 F u l l scale-summer Bouveng e t a l . , 1970

- - low F u l l s c a l e - w i n t e r Bouveng e t a l . , 1970

~ n a e r o b i c D i g e s t i o n

n e a r 100

0 4 L l a b o r a t o r y un i t s -37 C , 30-day K l e i n , 1974 r e t e n t i o n t ime

0 3 L l a b o r a t o r y u n i t s - 3 5 C, 30-day Moore and B a r t h , 1976 r e t e n t i o n t i m e , w i t h pr imary s l u d g e f e e d

o 3 L l a b o r a t o r y u n i t s - 3 5 C, 30-day Moore and B a r t h , 1976 r e t e n t i o n t i m e , w i t h 50% pr imary s l u d g e and 50% by volume was t e a c t i v a t e d s l u d g e

S e p t i c Tank 6 1 2 7 Labora to ry 127 L s e p t i c t a n k K l e i n , 1974

3 1 26 . Labora to ry 127 L s e p t i c t a n k K l e i n , 1974

S e p t i c Tank T i l e up t o 60 e s s e n t i a l l y Aerob ic , b u t w i t h d i s s o l v e d oxygen K l e i n , 1974 F i e l d s 100 c o n c e n t r a t i o n s a s low a s 0 . 5 mg/L

50 10 Anaerobic K l e i n , 1974

Waste Treatment Processes

I n f l u e n t NTA NTA Removal Concentration, Ef f i c iency .

(mglR) (pe rcen t )

Notes Reference

S o i l Systems 40 t o 100 9 5 Aerobic-Yolo sandy loam i n Klein , 1974 l a b o r a t o r y column

10 t o 100 10 t o 15 Anaerobic-Yolo sandy loam Klein , 1974 l a b o r a t o r y column

40 " t o t a l " Aerobic-good removal a t NTA T i e d j e and Mason, 1974 concen t ra t ions as h igh a s

I W \O

600 mglR I

4 0 0 Anaerobic-also, degrada t ion T i e d j e and Mason, 1974 l i m i t e d under m i c r o a e r o p h i l l i c cond i t ions

50 e s s e n t i a l l y Aerobic Dunlap -- e t a l . , 1971 - complete

50 e s s e n t i a l l y Anaerobic Dunlap e t a 1 . , 1971 none ...

-

DEGRADATION OF NTA IN THE ENVIRONMENT

AEROBIC DEGRADATION

FRESH WATER

Significant degradation of NTA can occur in fresh waters such as streams, rivers, and lakes where NTA enters in untreated wastewaters or by incomplete removal in low efficiency and overloaded treatment plants. Warren & Malec (1972) observed, after a 6 week lag, essentially complete degradation of NTA in the Detroit and Meramec Rivers at 6OC with no detectable intermediates accumu- lated. When NTA levels were monitored in Grindstone Creek, a stream receiving wastewater from the Waterdown, Ontario, treatment plant, biodegradation and dilution gave NTA concentrations in the summer months (16-21°C) consistently less than 10 pg/L under different conditions of treatment plant loading (Shannon et a1 1974). At temperatures of 0.5-3OC efficiency of NTA removal in the - .' plant was reduced from >95% to <45% giving stream concentrations as high as 125 g . Despite the lower temperatures subsequent NTA disappearance was somewhat greater than could be accounted for by estimates of the dilution factor. Labora- tory studies with water and microorganisms from Grindstone Creek showed, in fact, that biodegradation of NTA could occur and was slowed by decreasing the temperature of incubation (approximately two fold for each decrement of 10 C).

Laboratory microcosms also accomplish NTA degradation after acclimation (2 weeks) at rates which are directly proportional to the concentration of NTA (Bott -- et al., 1976; Bott, 1977). By contrast Ferguson -- et al. (1971) observed removal of less than 1 mg/L when NTA was added to experimental streams at an influent concentration of 10 mg/!L.

Chau and Shiomi(1972) have shown that NTA is readily degraded in lakes. Concentrations of NTA added at 1, 5 and 10 mg/R to stirred lakewater samples disappeared completely in periods from 5-11 days; after a second addition of NTA degradation was complete in 3-4 days. Formation of nitrate was also noted. Under winter conditions NTA is effectively degraded albeit more slowly (Rudd et al., 1973; Matheson, 1977). -

' SALT WATERS

Bacteria have been isolated from seawater capable of growth with NTA as sole nitrogen or nitrogen and carbon source in a synthetic estuarine medium (Erikson -- et al., 1970). NTA utilization in this system was poor. Gledhill and McDonald (1976) have followed the degradation of 14c-labelled NTA in model marine and estuarine systems. While 97.5% of NTA was removed from the marine system by the sixth week, no significant removal of NTA occurred in estuarine systems by the 12th week. Attempts to isolate from an estuary organisms capable

of degrading NTA i n e s t u a r i n e environments were unsuccessful (Bourquin & Przybyszewski, 1977) whereas such environments yielded organisms capable of degrading NTA i n f r e s h water. Resul t s wi th t h e Pseudomonas s t r a i n i s o l a t e d by . Tiedje (Tiedje -- e t a l . , 1973) e s t ab l i shed t h a t t h i s organism degraded NTA a t reduced r a t e s in+sa l ine environments.' Apparently some f a c t o r i n e s t u a r i n e environments (Na , C 1 o r i o n i c s t rength?) has an inh ib i to ry e f f e c t upon r eac t ions of NTA degradat ion i n f r e s h water organisms. No such e f f e c t i s apparent f o r marine b a c t e r i a a b l e t o degrade NTA. Ef fec t s of ch lor ide and o the r anions on pu r i f i ed monooxygenases have been described (see e a r l i e r s ec t ions ) . Further s t u d i e s a r e required t o expla in t h e s p e c i a l circumstances i n e s t u a r i n e environments a f f e c t i n g NTA-degradation.

I

SOIL

Studies by T ied je and Mason with 14c-NT~ (Tiedje & Mason, 1974) have shown t h a t NTA undergoes conversion t o CO2 i n most s o i l s examined over a wide range of concentrat ions (10-600 ppm) e i t h e r immediately o r a f t e r a l a g of up t o 6 days. D i f f e ren t p a t t e r n s of degradat ion suggested t h a t i n some s o i l s degradat ion was e f fec ted by NTA-utilizers while i n o the r s p a r t i a l degradat ion might be accom- pl ished by non-u t i l izers . Degradation occurred only i n t h e presence of oxygen; while r a t e s of NTA oxida t ion were s i m i l a r with a i r and with 1.0% 02:99% N 2 , reduced oxida t ion r a t e s were seen a t 0.1% 02, and were e s s e n t i a l l y absent under an argon atmosphere. Degradation was s i g n i f i c a n t a t 24OC and 12.5OC but neglig- i b l e a t 2OC. Af te r a period of acc l i ina t iza t ion a t 12.5OC r a t e s of degradat ion a t t h i s temperature were more rapid and measurable a t 2' suggest ing a s h i f t i n t h e b a c t e r i a l populat ion from mesophilic t o psychrophil ic forms. In t h e s o i l s s tud ied by Tabatabai & Bremner (1975), degradat ion of,NTA proceeded a t s i m i l a r r a t e s under aerobic and anaerobic condit ions. Differences i n t h e i r f ind ings from those of Tied je and Mason (1974) may l i e i n t h e d i f f e r e n t methods used t o measure NTA removal. I n t e r e s t i n g l y t h e formation of NO3 i n ae rob ic s o i l s i nd ica t e s t h a t NTA a t t h e concentrat ions used does no t i n t e r f e r e with s o i l n i t r i f i c a t i o n .

ANAEROBIC DEGRADATION

SOILS '

I n t h e i r s t u d i e s of t he breakdown of NTA by s o i l microflora Tied je and Mason (1974) found t h a t no CO2 was formed from NTA under anaerobic condit ions. By con t r a s t NTA was shown t o disappear from d i f f e r e n t s o i l s a t s i m i l a r r a t e s under aerobic and anaerobic condit ions by Tabatabai & Bremner, (1975). Dunlap e t a l . , (1971) found t h a t a f t e r a s u i t a b l e accl imation period, NTA a t 50 mg/L -- was completely and r ap id ly removed from sand, loam and c l ay loam i n percola t ion columns operated under aerobic o r unsaturated condit ions. Under water-logged o r s a tu ra t ed condi t ions , s imulat ing flooded pe rco la t ion f i e l d s serv ing s e p t i c tanks, t h e same columns e f f ec t ed a g r e a t l y decreased removal of NTA, ind ica t ing the p o s s i b i l i t y t h a t NTA could e n t e r ground waters under these condi t ions and even s o l u b i l i z e and t r anspor t metal ions from such s o i l s . Similar f ind ings wi th simulated pe rco la t ion f i e l d s were reported by Klein (1974) where f looding reduced dissolved oxygen and a l s o t h e ex t en t of NTA removal from 100% t o 15-35%. Even then some of t h i s l a t t e r removal was a t t r i b u t e d t o r e s i d u a l disolved oxygen.

GROUND WATER

In an attempt to investigate the anaerbbic degradation of NTA in ground water, Dunlap -- et al. (1971) constructed simulated aquifers. Disappearance of NTA from 30-32 mg/R to essentially zero was observed in a period of 52 days at 20°C. Anaerobic conditions were confirmed by the demonstration of methane formation; when 1 4 ~ - ~ ~ ~ was used the methane formed contained radioisotope.

,Consequently any NTA reaching the water table unchanged by virtue of extensive flooding of a percolation field apparently can undergo anaerobic degradation in aquifers.

LAKE HYPOLIMNIA

The effect of anoxic conditions on NTA degradation in natural waters has formed the basis of a study by'Patrick.et -- al. (1976). Anaerobic conditions did not prevent NTA degradation but- retarded the process relative to its aerobic disappearance.

Prakash (1976) cites a personal communication from R.D. Hamilton, Freshwater Institute, Winnipeg, concerning -- in situ studies of NTA degradation in small lakes (see also Hamilton, 1977). Apparently transient accumulation of NTA in. the hypolimnion can result from its constant input during thermal stratification in summer months. Only during fall overturn could NTA decrease by degradation and dilution. With continued NTA loading in late fall and winter NTA could again accumulate because of slower rates of degradation and poor mixing and could persist until the spring overturn.

FACTORS INVOLVED I N NTA DEGRADATION

ACCLIMATION - A SPECULATION In laboratory and field studies of the aerobic and anaerobic degradation of

NTA, periods of acclimation are frequently necessary before NTA removal occurs at significant rates (Swisher et al., 1967; Shumate -- et al., 1970; Cleasby et al., 1974; Thompson and Duthie, 1968; Pfeil & Lee, 1968; Bouveng et al., 1x8; - Patrick -- et al., 1976). Once acclimated, populations of bacteria generally retain the properties for which they have been selected. Often lag times as long as several weeks or months are needed before useful degrading populations are established. Suggestions concerning enzyme induction and increases in original small subpopulations are inadequate to account for the long lags observed. For NTA, which is not a natural product, degradation is only possible if some organism possesses an enzyme with a sufficiently broad specificity to attack it in a useful manner, and which is already present at sufficient levels within the cell to accomplish a significant degree of conversion. Lacking these prerequisites evolutionary steps are needed, such as mutations in regulatory genes (spontaneous or induced) to give appropriate amounts of enzyme; mutations in structural genes may be needed to develop or alter enzyme specificity in a suitable manner. Such evolution of new functions relies on recruitment of some preexisting enzyme which may be elaborated by only a small fraction of the total microbial flora. According to this theory long lag periods may be needed because the necessary spontaneous mutations are random and many are disadvantageous.

Evolution of NTA-degrading organisms by enzyme recruitment can be seen t o depend on a preexis t ing capacity t o perform a react ion which can be re l a t ed t o NTA. The performance of the s p e c i f i c a l l y r e su l t ing acclimated b a c t e r i a l popu- l a t i o n is of course s t i l l subject t o changes i n subs t ra t e concentration (NTA and oxygen), temperature and other fac tors .

Acclimation of b a c t e r i a l populations t o lowered temperatures is necessary f o r the rapid biodegradation of a l l organic compounds by v i r t u e of t h e general temperature optima f o r d i f f e r e n t microbial groups. A s h i f t from 25°C t o 5°C generally requires t h e subs t i tu t ion of a psychrophilic population f o r a meso- p h i l i c one. Without such population s h i f t s r a t e s of degradation of organic compounds w i l l show pronounced dependence upon ambient temperature. Seasonal changes i n temperature require such population s h i f t s i n treatment p lan t s and elsewhere; f o r d iverse microbial f l o r a capable of degrading a wide v a r i e t y of commonplace organic compounds such s h i f t s can s e l e c t appropriate organisms rapidly from la rge and varied populations. The population of NTA-degrading organisms, es tabl i shed possibly by evolution, is unlikely t o be so varied; a drop i n temperature w i l l p lace a se lec t ion pressure on a l e s s d iverse population which may not develop the appropriate psychrophilic character readily. A separate evolutionary s t ep from a diverse psychrophilic population may be the e a s i e r se lec t ion process. Such l imi ta t ions can be perceived a s important f ac to r s i n the degradation of organic compounds by b a c t e r i a l populations lacking a high degree of heterogeneity. I n na tu ra l waters where microbial numbers a r e considerably lower than i n treatment p lan t s these l imi ta t ions a r e amplified even further .

It should be s t r e s sed , therefore , t h a t less diverse microbial populations a r e more vulnerable t o environmental. change than a r e complex populations, and t h a t acclimation once achieved under one s e t of condit ions may not be so read i ly adapted t o others .

TEMPERATURE

Degradation of NTA by microorganisms has been shown a t temperatures of 2- 30°C. A t temperatures of 10°C and below, the r a t e of i t s degradation in treat,- ment f a c i l i t i e s is subs tan t i a l ly decreased. For example, a t 7.5"C r a t e s can be reduced t o values a s low a s 6682% of those a t 20°C (Eden et a l . , 1972; Rudd & Hamilton, 1972). Select ion from s o i l of microbial populations with improved a b i l i t i e s t o degrade NTA a t low temperatures can occur, however, (Tiedje & Mason, 1974). Slower r a t e s of degradation a t lowered temperatures w i l l be most pronounced where NTA degradation is already slow because of i t s chela t ion t o c e r t a i n metals. (See below).

DEGRADATION OF NTA-CHELATES

A major concern about degradation of NTA i n d i f f e r e n t environments is d i r e c t l y r e l a t ed t o t h a t property which makes i t most useful , - viz. what i s the extent t o which i ts biodegration is impaired by i ts chela t ion t o d i f f e r e n t metal ions? Numerous s tud ies have been conducted on the degradation of d i f f e r e n t chela tes a t varying concentrations i n environments a s d iverse a s f r e sh water, ( ~ j E r n d a 1 -- et a l . , 1972;. Swisher -- e t a l . , 1973; Shannon, 1975; Dunlap -- et a l . , 1971; Chau & Shiomi, 1972) ; s o i l s , (Tiedje & Mason, 1974; Dunlap -- et a l . , 1971) ;

and a c t i v a t e d s ludge , (-FijErndal -- e t a l . , 1972; Forsberg & L i n d q u i s t , 1967; Swisher -- e t a l . , 1967; Walker, 1975; Gudernatsch, 1970, 1975; Huber & Popp, 1972). Warren (1974) h a s summarized many of t h e r e s u l t s of t h i s work. Of t h e v a r i o u s metal c h e l a t e s t e s t e d , t h o s e of NTA w i t h Cu, Cd, N i , and Zn a r e gener- a l l y removed a t n o t i c e a b l y s lower rates than o t h e r s such as Ca, Mg, Fe, and Pb. Slower rates a l s o observed wi th t h e Hg c h e l a t e may b e more d i r e c t l y r e l a t e d t o t h e g e n e r a l t o x i c e f f e c t of Hg ions . An incomplete a t t a c k on, say , t h e Cu-NTA complex may b e r e l a t e d t o a s i m i l a r e f f e c t - t h e t o x i c i t y of Cu i o n s r e l e a s e d from t h e c h e l a t e as degrada t ion proceeds.

When one c o n s i d e r s t h e v a r i o u s meta l c h e l a t e s formed by NTA a t environmenta l ly r e a l i s t i c l e v e l s , i t can b e a p p r e c i a t e d t h a t i n n a t u r a l environments t h e most r e a d i l y degradab le c h e l a t e s w i l l d i sappear f i r s t r e s u l t i n g i n a r e d i s - t r i b u t i o n of c h e l a n t t o accommodate rele-ased ions . I n o t h e r words, NTA degrada- t i o n w i l l b e f u n n e l l e d through t h e more r e a d i l y degraded complexes. A t low NTA c o n c e n t r a t i o n s t h e complexes which NTA w i l l form depend upon t h e c o n c e n t r a t i o n s of meta l i o n s a v a i l a b l e and t h e v a l u e s of t h e d i s s o c i a t i o n c o n s t a n t s f o r each of t h e s e s p e c i e s a t t h e pH considered. The d i s t r i b u t i o n of m e t a l s complexed t o NTA a t a c o n c e n t r a t i o n of 25 ppb i n a t y p i c a l r i v e r water w i l l be 52% Cu, 34% N i , 9% Ca and 5% Zn ( I n t e r n a t i o n a l J o i n t Commission, 1977).

C h e l a t e s of NTA w i t h Mg, Ca, Mn, Ba', S r , and Fe a r e a p p a r e n t l y t r i d e n t a t e complexes w i t h lower d i s s o c i a t i o n c o n s t a n t s than t h e t e t r a d e n t a t e complexes formed wi th Cu, N i , Co, Zn, Cd, and Pb (Warren, 1974). It is f o r t u n a t e , t h e r e - f o r e , t h a t ca lc ium sal ts a r e p r e s e n t a t such h i g h c o n c e n t r a t i o n s i n many b o d i e s of w a t e r , s i n c e t h i s r e s u l t s i n much of t h e NTA b e i n g p r e s e n t i n a complex i n which i t is r e a d i l y degradable .

It is f o r t h i s reason t h a t t h e a d d i t i o n of Ca o r t h e p resence of h i g h l e v e l s of wa te r ha rdness can f a c i l i t a t e degrada t ion of t h e more p e r s i s t e n t c h e l a t e s of NTA w i t h Cd (Huber & Popp, 1972) , and Cu (Bjijrndal, 1972). For t h e same reason i o n exchange p r o c e s s e s wi th Fe- and Ca- c o n t a i n i n g s o i l s and s e d i - ments can l e a d t o i n c r e a s e s i n t h a t f r a c t i o n of NTA p r e s e n t as i t s t r i d e n t a t e c h e l a t e s . Ligand exchange can a l s o l e a d t o a more f a v o r a b l e d i s t r i b u t i o n of NTA i n i t s t r i d e n t a t e complexes. Thus o t h e r o r g a n i c l i g a n d s can compete f o r v a r i o u s meta l ' i ons ; sewage s ludge f o r example can adsorb Cu more r e a d i l y than Cd o r N i (B jz rnda l e t a l . , 1972). Under environmental,conditions, t h e r e f o r e , NTA-chelates undergo m e t a l i o n exchange and l i g a n d exchange r e a c t i o n s i n s o l u t i o n which f a c i l i t a t e degrada t ion of NTA.

Another concern r e l a t i n g t o t h e c h e l a t i n g ' p r o p e r t i e s of NTA is t h a t i t may s o l u b i l i z e t o x i c m e t a l s from such l o c a t i o n s as l a k e sediments and s o i l , and then r e l e a s e t h e s e m e t a l s i n a s o l u b l e form as t h e NTA p o r t i o n of t h e complex is degraded. While i t can be shown t h a t NTA i s capab le of s o l u b i l i z i n g d i f f e r e n t m e t a l s from sediments (Chau & Shiomi, 1972; Tay lor -- et a l . , 1972; Gregor, 1972) and of m o b i l i z i n g m e t a l i o n s i n sand and s o i l columns (Dunlap e t al . , 1971) t h e c o n c e n t r a t i o n s of NTA used i n such s t u d i e s (from 1-100 mg/R) a r e h i g h e r t h a n might r e a l i s t i c a l l y b e a n t i c i p a t e d t o b e p r e s e n t a f t e r waste t r ea tment . Fur the r - more i t h a s been shown by Chau & Shiomi (1972) t h a t as NTA is broken down by t h e

l ake microflora , t h e e a r l i e r so lub i l i zed metal ions no longer remain soluble . Factors such a s water hardness, t h e metals t o which NTA is che la ted , and t h e presence of o the r organic l igands such a s humic ac ids , and amino a c i d s w i l l a l l in f luence t h e q d a l i t a t i v e and q u a n t i t a t i v e a spec t s of s o l u b i l i z a t i o n , but once NTA is degraded, i ts s o l u b i l i z i n g e f f e c t is removed, and metal i ons apparent ly r e t u r n t o t h e i r former inso luble s t a t e a s determined by t h e s o l u b i l i t y products of t h e i r s a l t s . The presence of t h e more p e r s i s t e n t metal c h e l a t e s , i n anaerobic environments, a t low temperatures, where dissolved organics and exchangeable minerals a r e absent , and where t h e r e i s no water hardness, r ep re sen t s a scenar io f o r minimal complex degradation. ' I n t h e un l ike ly event t h a t a l l t h e above condit ions a r e s a t i s f i e d t h e problem is only a temporal one s i n c e water movement w i l l l ead t o a l t e r a t i o n s i n one or more of t hese f a c t o r s , favoring increas ing complex degradation.

Las t ly , i t should be mentioned t h a t NTA has c e r t a i n b e n e f i c i a l e f f e c t s upon degradat ive processes. Metal ions such a s Hg, Cd, Cu, N i and Zn can i n t e r f e r e with t h e degradation of l i n e a r a l k y l benzene su l fona tes i n r i v e r water. The add i t i on of NTA a t 5 mg/2 reduces t h i s i n t e r f e rence i n a l l cases except t h a t caused by Hg (Swisher -- e t a l . , 1973).

Inh ib i to ry e f f e c t s of metal 'ionsa o n . r e s p i r a t i o n and glucose u t i l i z a t i o n by stream microflora were a l s o reduced o r prevented by add i t i on of NTA (Pa t r i ck - e t a l . , 1976).

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Bott , T. L., J. Pres lan , J. Finlay, & R. Brunker 1976. Use of Flowing Water , Microcosms and Ecosystem Streams t o Study Microbial Degradation of Leaf L i t t e r and N i t r i l o t r i a c e t i c Acid. Paper presented a t 1976 SIM Meeting.

Bott T. L. 1977. Communication t o I J C Task Force on Ecological E f f e c t s of Non- phosphate Detergent Builders. Chicago, 1977.

Bourquin, A. W. & V. A. Przybyszewski 1976. D i s t r ibu t ion of Bacter ia with Nitrilotriacetate-Degrading P o t e n t i a l i n an Es tuar ine Environment. Submitted f o r publ icat ion. Prepubl ica t ion Presented t o I J C Task Force on Ecological E f fec t s of Non-Phosphate Detergent Bui lders , Chicago, 1977.

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Eden, G. E., G. E. Culley, & R. C. Rootham 1972. Ef fec t of Temperature on t h e Removal of NTA ( n i t r i l o t r i a c e t i c acid) During Sewage Treatment. Water Res. 6: 877-883.

Erickson, S. J., T. E. Maloney, and J. H. Gent i le 1970. Ef fec t of N i t r i l o t r i - a c e t i c Acid on t h e Growth and Metabolism of Estuarine Phytoplankton. J. Water Pol l . Cont. Fed. 42: R329-R335.

Ferguson, B., R. Todd, H. Holm, ' J. Pope, & H. Kania 1971. Environmental Fate of NTA. Proc. 26th I n d u s t r i a l Wastewater Conference, Purdue University, Lafayet te , Indiana. 1971. Engineering Extension Ser ies Pa r t 1, p. 271-283.

Forsberg, C. & G. Lindquist 1967. ~ x ~ e r ' i m e n t a l s tud ie s on b a c t e r i a l degradation of NTA. Vatten - 23: 265-277.

Gledhi l l , W. E. and P. D. McDonald 1976. Microbial Degradation of Builder M and NTA i n Laboratory Model Marine and,Estuary Systems. Monsanto In t e rna l Report -Interim Report #8448, Sept . 28, 1976. (Cited i n Monsanto/Proct,er & ' .

Gamble Report t o I J C Task Force on Ecological E f fec t s of Non-Phosphate Detergent Builders , Cincinnat i , Ohio, 1977).

Gregor, C. D. 1972. Solubi l iza t ion of lead i n lake and reservoi r sediments by NTA. Env. Sci. Technol. . - 6: 278-279.

Gudernatsch, H. 1970. Behavior of NTA i n t he Sedimentation Process and i n Sewage. Gass. Wasserfach. - 111: 511-516.

Gudernatsch, H. 1975. Biological Degradation of Heavy Metal Complexes of N i t r i l o t r i a c e t i c Acid i n Laboratory Activated Sludge Plants . Gass. Wasserfach. 116: 512-517. - Hamilton, R. D. 1977. Presentat ion t o IJC Task Force on Ecological Ef fec ts of Non-Phosphate Detergent Builders. Cincinnat i , Ohio, 1977.

Huber, W. & K. H. Popp 1972. Biological Degradation of N i t r i l o t r i a c e t a t e Acid i n t h e Presence of Cadmium Ions. F e t t e Seifen. Anstr. - 74: 166-168.

In t e rna t iona l J o i n t Commission. 1977. Presentat ion by Monsanto/Procter & Gamble Companies t o I J C Task Force on Ecological Ef fec ts of Non-Phosphate Detergent Builders, Cincinnat i , Ohio.

Klein, S. A. 1974. NTA Removal i n Sept ic Tank and Oxidation Pond Systems. Jour. Water Pol l . Contr. Fed. - 46: 78-88.

Matheson, D. H. 1977. Presentat ion t o I J C Task Force on Ecological Ef fec ts of Non-Phosphate Detergent Builders, Cincinnat i , Ohio.

Pa t r ick , R. , T. Bott , R. Larson 'and C. Rhyne 1976. The Effec t of N i t r i l o t r i - a c e t a t e Acid (NTA) on t h e S t ruc ture and Functioning of Aquatic Communities. Draft Report of Grant R801951, f o r EPA Env. Res. Lab. Duluth, Minn. ,

pfei11, B. H. & G. F. Lee 1968. Biodegradation of N i t r i l o t r i a c e t i c Acid i n Aerobic Systems. Env. Sci . Tech. - 2: 543-546.

Prakash, A. 1976. NTA ( n i t r i l o t r i a c e t i c a c id ) - An Ecological Appraisal . Nat ional Research C w n c i l Assoc. Committee f o r Environ. Qual i ty , NRCC No. 15023, Dept. Fish. Environ. , Water Po l l . Contr. D i r . , Report EPS-3-WP-76-8.

Rudd, J . W. M. h R. D. Hamilton 1972. Biodegradation of Trisodium N i t r i l o t r i - a c e t a t e i n a Model Aerated Sewage Lagoon. J. F i sh Res. Bd. Canada. - 29: 1203- 1208.

Rudd, J. W. M . , Townsend, B.E. & Hamilton, R. D. 1973. Discharge of n i t r i l o t r i - a c e t a t e (NTA) from two sewage treatment f a c i l i t i e s loca ted i n a midcont inental c l imate . J. F i sh Res. Bd. Canada - 30: 1026-1030.

Shannon, E. E. 1975. E f f ec t of Detergent Formulation on Wastewater C h a r a c t e r i s t i c s and Treatment. J. Water Po l l u t . Control Fed. - 47: 2371-2383.

Shannon, E. E., P. J. A. Fowlie & R. J. Rush 1974. A Study of N i t r i l o t r i a c e t i c Acid (NTA) Degradation i n a Receiving Stream. Technology Development Report No. EPS 4-WP-74-7. Water Po l l u t i on Control Di rec tora te . Environmental Pro tec t ion Service. Environment Canada, Ottawa.

Swisher, R. D . , M. R. Cru tchf ie ld & D. W . Caldwell 1967. Biodegradation of NTA in -Ac t i va t ed Sludge. Env. Sci . Tech. 1: 820-827.

Swisher, R. D . , T. A. T a u l l i & E. J. Malec 1973. Biodegradation of NTA Metal Chelates i n River Water. Trace Metals and Metal-Organic I n t e r a c t i o n s i n Natural Waters. P.C. Singer , Ed. , Ann Arbor Science Publ i shers , Inc. , Ann Arbor, Mich. , 1973, Cht. 8. p. 237-263.

Shumate, K. S., J. E. Thompson, J. 0. Brookhart & C. L. Dean 1970. NTA Removal by Activated Sludge: F ie ld Study. J. Water Po l l . Cont. Fed. - 42: 631-640.

Tabatabai , M. R . & J. M. Bremner 1975. Decomposition of N i t r i l o t r i a c e t a t e (NTA) i n So i l s . S o i l Biol. Biochem. 1: 103-106.

Taylor, J. K. , W. L. Z i e l i n s k i , E. J. Maienthal, R. A. Durst & R. W . Burke 1972. Development of Method f o r NTA Analysis i n Raw Water. EPA-R2-72-057. Environmental P ro t ec t i on Agency. 27p.

Thompson, J. E. & J. R. Duthie 1968. The Biodegradabi l i ty and T r e a t a b i l i t y of NTA. J. .Water Po l l . Contr. Fed. - 40: 306-319.

T ied je , J. M. & B. B. Mason 1974. Biodegradation of N i t r i l o t r i a c e t a t e (NTA) i n So i l s . S o i l Sci . Soc. Amer. Proc. 38: 278-282.

T ied je , J. M . , B. B. Mason, C. B. Warren & E. J. Malec 1973. Metabolism of n i t r i l o t r i a c e t a t e by c e l l s of a Pseudomonas species . Appl. Microbial. - 25; 811-818.

Walker,' A. P. 1975. Ul t imate Biodegradation of N i t r i l o t r i a c e t a t e i n t h e Presence of Heavy Metals. Prog. Water Technol. - 7: 555-560.

Warren, C. B. 1974. Biodegradat ion of N i t r i l o t r i a c e t i c Acid and NTA-Metal Ion Complexes: (The Chemo-Biological L i f e Cycle of a Detergent Bui lde r ) I n , S u r v i v a l i n Toxic Environments. Ed. by Khan, M.A.Q. & Bederka, J .P . , Academic. P r e s s I n c . , N.Y. , San Franc i sco , London. p. 473-496. -

Warren, C. B. & E. J. Malec 1972. Biodegradat ion of N i t r i l o t r i a c e t i c Acid and Re la ted Imino and Amino Acids i n River Water. Science - 176, 277-279.

BIOLOGICAL EFFECTS OF NTA

Canadian monitoring programs (Matheson, 1977; Brownridge, 1977) found de t ec t ab le (g rea t e r than 10 ppb) concentrat ions of NTA i n some r i v e r s and harbors near sewage treatment p l an t o u t f a l l s , p a r t i c u l a r l y i n zones of minimal e f f l u e n t d i l u t i o n . Reported concentrat ions of NTA i n sewage e f f l u e n t were e s s e n t i a l l y t h e same during summer and winter (Brownridge, 1977). S imi la r ly , sewage t reatment p l an t s may r e l e a s e NTA i n t o rece iv ing waters during periods of upset o r overloaded condit ions. The NTA concentrat ions re leased during such periods may approach treatment p l an t i n f luen t conc6ntrations. Thus aqua t i c organisms l i v i n g i n rece iv ing waters can be exposed t o low concentrat ions of NTA over long periods of time o r t o e leva ted concentrat ions f o r s h o r t e r per iods of time. The p o s s i b i l i t y of NTA exposure r a i s e s a number of quest ions concerning i t s tox ico log ica l behavior:

\

1. Are t h e l e v e l s of NTA expected t o occur i n t he environment e i t h e r acu te ly o r chronica l ly t ox ic t o t he b io t a?

2. Are t h e r e sub le tha l e f f e c t s which might a r i s e and the re fo re should be inves t iga ted? These could inc lude reproduct ive, metabolic, h i s - t o log ic , o r n u t r i t i o n a l changes.

3 . Are t h e r e p a r t i c u l a r environmental condi t ions which might enhance t h e t o x i c i t y of NTA t o one o r more spec ies? For example, how does i t s b io log ica l behavior r e l a t e t o temperature and water chemistry?

4 . How does NTA a f f e c t t he t o x i c i t y of o the r t r a c e contaminants such a s metals?

The r e s u l t s of t o x i c i t y t e s t s should be evaluated i n l i g h t of t hese and s i m i l a r quest ions regarding environmental s a fe ty . Since most bioassays, including those wi th aqua t i c organisms, a r e performed with a s i n g l e t e s t spec i e s i n a f ixed environment, t he r e s u l t s a r e not e a s i l y ex t rapola ted t o n a t u r a l ecosystems. Nevertheless they can provide some reasonable boundaries o r l i m i t s f o r t h e predic ted response og organisms t o NTA exposure.

EFFECTS ON A Q U A T I C ORGANISMS

ACUTE TOXICITY

Most of t h e t o x i c i t y t e s t i n g with NTA has involved acute s t a t i c o r flow- through exposures l a s t i n g s e v e r a l days. A v a r i e t y of f i s h and macroinverte- b r a t e s from both freshwater and marine environments have been used. Table 1 and 2 summarize t h e p r i n c i p a l r e s u l t s f o r both of these groups. The acu te LC50 f o r NTA-Na is genera l ly g r e a t e r than 100 mg/R f o r f reshwater f i s h and inver te -

b r a t e s . Rainbow t r o u t and t h e amphipods Gammarus pseudolimnaeus appear t o be t h e most s e n s i t i v e of t h e spec i e s t e s t e d , each having a 96-hour LC50 of 98 mg/R i n s o f t water. Marine organisms t o l e r a t e a t l e a s t a 10 f o l d g r e a t e r concentra- t i o n of NTA. No important d i f f e r ences i n s e n s i t i v i t y between taxa a r e evident .

These repor ted LC50 va lues a r e much g r e a t e r than t h e concent ra t ion of NTA l i k e l y t o be found i n r ece iv ing waters . For example, Brownridge (1977) repor ted a mean concent ra t ion of 0.046 mg/R NTA-Na below sewage p l a n t e f f l u e n t s i n a r e a s us ing de te rgent formulat ions wi th a weighted average of 15% NTA. The maximum measured concent ra t ion of NTA i n raw wastewater was 22.9 mg/R. Assuming t h a t up t o 30% NTA may be used i n de te rgent formulat ions, t h e g r e a t e s t expected NTA concent ra t ions i n un t rea ted wastewater would be approximately 40 mg/R. This va lue i s l e s s than t h e lowest LC50 reported. Maki (1977) ca l cu l a t ed a s a f e t y f a c t o r of 98 f o r rainbow t r o u t and amphipods based on acu t e e f f e c t l e v e l s and a concent ra t ion of 1 mg/R of NTA i n water. Thus i t is unl ike ly t h a t NTA i t s e l f could cause acu t e m o r t a l i t y of aqua t i c organisms i n waters r ece iv ing t r e a t e d o r un t r ea t ed domestic waste.

The a c u t e bioassay r e s u l t s r a i s e a number of i n t e r e s t i n g i s sues . For example, i t i s unc lear whether NTA is t h e a c t u a l cause of dea th i n acu t e tests. Because of i t s low t o x i c i t y , l a r g e q u a n t i t i e s of NTA-Na, exceeding 100 mg/R, must be d i sso lved i n t h e test water. This r a i s e s t h e a l k a l i n i t y of t h e solu- t i o n (Arthur -- e t a l . , 1974) and may a l s o r a i s e pH, e s p e c i a l l y i n s o f t waters ( t h e pH of a 1% aqueous so lu t ion of NTA-Na is 11) . Thus Flannagan (1971), Sprague (1968), and Arthur -- e t a l . (1974) a t t r i b u t e d a t l e a s t some of t h e observed acu t e m o r t a l i t y t o high pH stress. Arthur e t a l . (1974) were a b l e t o -- i nc rease t h e s t a t i c LC50 f o r fa thead minnows from 225 t o 470 mg/R (making i t appear 2x less tox i c ) by ad jus t i ng pH t o 7.7. A t t he o the r extreme, tests us ing t h e f r e e NTA a c i d produce abnormally low pH. The 24 hour " l e t h a l concen- t r a t i o n " of NTA-H was found by Jancovic and Mann (1969) t o be 260 mg/R f o r rainbow t r o u t and 400 mg/R f o r t u b i f i c i d worms i n hard water. However, t h e pH i n t he se t e s t s was 5.0 and 3.4 r e spec t ive ly . Confusion surrounding t h e i n t e r - p r e t a t i o n of such r e s u l t s may be avoided i n t h e f u t u r e by c o n t r o l l i n g pH, a l k a l i n i t y , hardness, and che l a t e concent ra t ion independently.

N T A % t e s t r e s u l t s a r e c l e a r l y r e l a t e d t o t h e concent ra t ion of d iva l en t c a t i o n s i n so lu t ion . A t h igh concent ra t ions NTA is e s s e n t i a l l y a l l che la ted w i th Ca and Mg. The complexes themselves appear t o have no e f f e c t on aqua t i c organisms. Measurable t o x i c i t y occurs when NTA l e v e l s exceed t h e molar equiva- l ence po in t wi th Ca + Mg. Eisler -- et a l . (1972) found g r e a t e r t o x i c i t y t o mummichog a t 15O/00, than a t 25O/00 s a l i n i t y . ' s imilar ly Aca r t i a c l a u s i a marine zooplankter , gave a 24-hr LC50 of 550 mg/R a t 15°/00, bu t 2100 mg/R a t 30°/00, a reduc t ion i n t o x i c i t y of almost 4 fo ld (Tarzwell , 1970). It fol lows t h a t NTA i s more t o x i c t o f reshwater organisms, p a r t i c u l a r l y i n s o f t waters . Biesinger -- e t a l . (1974) repor ted an exce l l en t c o r r e l a t i o n ( r = 0.95) between t o t a l hardness and t h e LC50 t o Daphnia magna exposed f o r t h r e e weeks. The t o x i c i t y i n Lake Superior water , wi th a t o t a l hardness of 45 mg/R a s CaC03, was reduced 4.5 f o l d when hardness was a r t i f i c i a l l y increased t o 200 mg/R. The toxici ty-hardness r eg re s s ion f o r Daphnia p r e d i c t s an LC50 of 50.56 mg/R NTA-Na a t zero t o t a l hardness. This va lue was no t v e r i f i e d experimentally.

It i s very unl ike ly t h a t t he use of NTA i n detergent formulations would lead t o acute mor ta l i t y of freshwater o r marine organisms under normal condi- t ions . Yet t h e r e may be a poss ib le exception i n the case of softwater lakes and streams receiving ac id p rec ip i t a t ion . These can have s u f f i c i e n t l y low pH and hardness t o s t r e s s indigenous communities. It is not c l e a r whether the r e l e a s e of NTA o r o ther che la t ing agent would have an e f f e c t on such extremely s e n s i t i v e ecosystems.

CHRONIC TOXICITY

Chronic bioassays extending over one o r more generat ions have been performed wi th seve ra l freshwater f i s h and inver tebra tes . The maximum no-effect l e v e l s f o r these spec ies exceed the measured,environmental concentrat ions of NTA (Matheson 1977, Brownridge 1977), by seve ra l orders of magnitude. Arthur e t a l . (1974) found su rv iva l and reproduction of fathead minnows t o be unaffected -- by 54 mg/k NTA, t h e highest concentrat ion tes ted . Amphipods, Gammarus pseudolimnaeus, were somewhat more s e n s i t i v e , showing reduced su rv iva l and reproduction above 1 9 mglk. Both chronic t e s t s were performed i n s o f t water a t near n e u t r a l pH. Arthur -- e t a l . (1970) found no e f f e c t on th ree generations of pulmonate s n a i l , Physa in t eg ra , a t 64.4 mg/k. However, Flannagan (1973) reported decreased a d u l t growth and fecundity above 25 mg/R f o r t he s n a i l Helisoma t r i v o l i s . Daphnia magna i n s o f t water exhibi ted a 16% reduct ion i n fecundity a t an NTA concentrat ion of 91 mg/R, s l i g h t l y i n excess of t he molar equivalence poin t wi th calcium (Biesinger -- e t a l . , 1974). The most r e s i s t a n t of t h e inve r t eb ra t e s t e s t e d was t h e midge, Chironomus ten tans , which showed no i l l - e f f e c t s a t 3000 mg/k NTA (Flannagan, 1971). No information is ava i l ab le on the mode of a c t i o n of NTA i n cases where growth o r reproduction was impaired. We do not know, f o r example, whether metal-NTA che la t e s can be absorbed o r metabolized by t h e organism during long term t e s t s . Although NTA deposi t ion has been studied i n mammalian bone t i s s u e ( c i t ed by Thayer and Kensler, 1973) comparable s t u d i e s have not been performed on t h e shell-forming mollusks. The only i n d i r e c t evidence on the s i t e of NTA a c t i v i t y comes from his topathologica l s tud ie s .

HISTOPATHOLOGY

Pathological e f f e c t s of NTA have been reported only f o r marine organisms. This i s su rp r i s ing i n l i g h t of i ts low t o x i c i t y i n seawater. E i s l e r e t a l . (1972) found i n t e s t i n a l l e s ions i n mummichog f i s h exposed f o r 168 hours t o a s l i t t l e as 1 mg/R. S t r iped bass and scup showed no damage a t t h a t concentra- t i on . However, bass and mummichog both exhibi ted damage t o the proximal kidney tubules a t l e v e l s i n excess of 3000 mglk. Grass shrimp exposed t o 100 mg/R were found t o have pathological changes i n i n t e s t i n a l d i v e r t i c u l a and kidney. These changes appear t o be associated wi th a l t e r e d calcium metabolism. E i s l e r e t a 1 (1972) concluded t h a t t h e damage resembles t h a t seen i n i so l a t ed kidney -- t i s s u e maintained i n Ca d e f i c i e n t media, and a l s o the kidney damage i n dogs dosed wi th EDTA. Since the work of E i s l e r e t a l . represents t h e most s e r ious -- b i o l o g i c a l e f f e c t s of NTA reported t o da te , it would be highly des i r ab le t o r epea t and expand on t h i s l i n e of research.

No pa thologica l damage has been de tec ted i n freshwater organisms exp.osed t o NTA. Macek and Sturm (1968) observed no g i l l damage i n b l u e g i l l s exposed t o 98 mg/L f o r 28 days. Kidneys and i n t e s t i n e s ev ident ly were not examined. S imi la r ly , Swisher (1968) found no g i l l changes i n b l u e g i l l sun f i sh exposed t o t h e e f f l u e n t from an ac t iva t ed sludge u n i t which was fed 200 mg/L NTA along wi th peptone and LAS. Hamilton (R. D. Hamilton, Freshwater I n s t i t u t e , Winnipeg, unpublished) exposed rainbow t r o u t t o a s much a s 400 m g / ~ NTA f o r 100 days. No behavioral o r h i s topa tho log ica l s igns were found.

A t t h i s po in t i t is d i f f i c u l t t o say whether metabolic and pa thologica l changes a r e unique t o t h e marine organisms. Calcium metabolism has not been evaluated d i r e c t l y i n any of t h e t e s t s . Furthermore, no chronic s t u d i e s of NTA absorp t ion o r metabolism have been performed on aquat ic spec ies . Hamilton (1977) has expressed t h e b e l i e f that NTA does not pene t ra te g i l l epi thel ium, bu t t h a t t h e che l a t ing agent draws t h e metals out of body f l u i d s . Marine f i s h may have an a d d i t i o n a l rou te of exposure not shared by freshwater forms - i nges t ion and perhaps absorpt ion through t h e gut. This could p a r t i a l l y expla in t h e i n t e s t i n a l l e s i o n s i n mummichog. Further s t u d i e s on t h e mode of ,act ion of NTAwould be use fu l i n determining i ts e f f e c t on o the r spec ies under var ious environmental condi t ions.

METAL INTERACTIONS

There is c l e a r evidence t h a t NTA reduces t h e t o x i c i t y of most d iva l en t meta ls i n so lu t ion . P ro t ec t ion aga ins t copper and z inc t o x i c i t y has been demonstrated wi th f i s h (Sprague, 1968; Shaw and Brown, 1974; Gudernatsch, 1970; Kimmerle, 1974; Chynoweth e t a l . , 1976) and with Daphnia magna (Biesinger e t a 1 Kimmerle, 1974; Glass, 1977). Chynoweth e t a l . have de tec ted t h e -* 9 -- of s t a b l e Cu-NTA complexes i n so lu t ion by anodic s t r i p p i n g voltammetry, and an inverse r e l a t i o n s h i p between Cu binding and its t o x i c i t y . I n t h e presence of 10 mg/L NTA-Na t h e 96-hour copper LC50 f o r juveni le guppies was increased from 0.112 mg/% t o 0.224 mg/ll. Equimolar concentrat ions of NTA have a l s o been shown t o reduce t h e t o x i c i t y of Cd, Pb, and N i (Kimmerle, 1974: E i s l e r e t a l . , 1972; Glass, 1977). However, c o n f l i c t i n g r e s u l t s have been noted f o r pin t h e presence of NTA. E i s l e r -- e t a l . reported decreased t o x i c i t y of Hg t o mummichog. Kania and Beyers (1974) found t h a t 10 mg/L NTA reduced t h e uptake r a t e of mercury by Gambusia i n i t i a l l y , bu t increased it somewhat a f t e r 18 hours. Glass (1977) found no reduct ion i n chronic Hg t o x i c i t y t o Daphnia exposed t o 0.5 mg/L NTA. Apparently Hg is completely bound by ch lor ide and hydroxide, r a t h e r than t o NTA. Likewise i r o n (111) t o x i c i t y d id not change i n t h e presence of NTA (Biesinger -- e t a l . , 1974) perhaps because of hydroxide formation.

Concern has o f t en been expressed t h a t che l a t ing agents such a s NTA may mobil ize t o x i c metals from sediments, making them more a v a i l a b l e f o r uptake by b io t a . I n a s e r i e s of s t a t i c and flow-through t e s t s Barica e t a l . (1973) -- exposed chironomids, c r ay f i sh , and rainbow t r o u t t o c lean and metal contaminated sediments. When NTA was added a t 0.2-5 mg/ll, t h e Fe, Mn, Pb and Zn concentra- t i o n s i n water tended t o increase. However t h e NTA had no s i g n i f i c a n t e f f e c t on metal uptake by t h e organisms. Of a l l t h e metals , only Mn showed a s l i g h t i nc rease i n t r o u t t i s s u e a f t e r e i g h t weeks. Chynoweth e t a l . (1976) found no -- s i g n i f i c a n t c o r r e l a t i o n between NTA binding and Cu uptake by f i s h (even though

t o x i c i t y was reduced). Canadian monitoring programs (Brownridge, 1977; Matheson, 1977) have concluded t h a t metal mobi l iza t ion by NTA is neg l ig ib l e . The Proc ter and Gamble s tudy (Brownridge 1977), demonstrate t h a t i n most cases metals exceeded t h e molar concentrat ion of NTA i n rece iv ing waters. Thus, i t is reasonable t o conclude t h a t (1) t h e NTA w i l l no t enhance t h e bioaccumulation of metals from sediment o r water', and (2) i n most cases it w i l l be present a t too low a concentrat ion t o a f fo rd much pro tec t ion i f metal t o x i c i t y occurs.

TERRESTRIAL ORGANISMS 1

NTA may f i n d i t s way onto land i f present i n appreciable q u a n t i t i e s i n i r r i g a t i o n water o r i n sewage s ludge appl ied t o s o i l s . Since degradation under anaerobic condit ions is slow, NTA may p e r s i s t i n s ludges a t t h e time of d i sposa l . However, once on land t h e NTA is l i k e l y t o degrade. It the re fo re appears unl ike ly t h a t NTA would be present i n amounts l a r g e enough t o pose a hazard t o t e r r e s t r i a l p l a n t s o r animals.

T e r r e s t r i a l animals would be exposed t o NTA primari ly through inges t ion of res idues i n food o r water. Extensive acute and chronic s t u d i e s reviewed by Mottola (1974) and Thayer and Kensler (1973) have shown t h a t mammals a r e t o l e r a n t of l a r g e o r a l doses. For example, dogs and r a t s showed no ill e f f e c t s when f ed 100 mg/kg and 2000 mg/kg respec t ive ly , f o r 90 days. NTA is r e a d i l y absorbed from t h e g a s t r o i n t e s t i n a l t r a c t of r a t s and dogs but not of r a b b i t s o r monkeys ( c i t e d by Thayer and Kensler, 1973). V i r tua l ly a l l of t h e NTA absorbed by r a t s i s excreted, unmetabolized, w i th in a few days of ingest ion. Thus res idue buildup and cumulative t o x i c i t y a r e unl ike ly i n w i l d l i f e exposed t o t h e l e v e l s expected i n t h e environment.

Land animals may a l s o be exposed t o NTA i n combination wi th t o x i c metals i f s ludges o r dredge s p o i l s contaminated with high concentrat ions of metals a r e appl ied t o land. However, s y n e r g i s t i c ac t ion between metals and NTA is not expected. Rat feeding s t u d i e s (Thayer and Kensler, 1973) have shown t h a t NTA does not enhance e i t h e r t h e uptake o r t o x i c i t y of inges ted methylmercury o r cadmium. I n f a c t some of t he , r epo r t ed work shows t h a t NTA reduces t h e e f f e c t s of metal poisoning.

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The inf luence of NTA on t h e absorpt ion of metals by higher p l a n t s is unclear. Abdulla and Smith (1963) found t h a t NTA increased metal uptake by p l a n t s , p a r t i c u l a r l y those growing on a l k a l i n e s o i l . Wallace -- e t a l . (1974) found no such increase , even a t high r a t e s of NTA appl ica t ion . Thus the i n d i r e c t e f f e c t on herbivores of enhanced metal l e v e l s in p l an t t i s s u e cannot be f u l l y evaluated a t t h i s time.

COMMUNITY EFFECTS

The t o x i c i t y of NTA has been determined in con t ro l l ed experiments using a wide v a r i e t y of test organisms. Several t e r r e s t r i a l and aqua t i c spec ies have been exposed chronica l ly t o constant l e v e l s of NTA under labora tory c u l t u r e condit ions. I n some cases , t h e i n t e r a c t i o n of NTA with o the r t ox ican t s has a l s o been reported. Thus i t i s poss ib le t o es t imate t h e d i r e c t e f f e c t s of NTA on p a r t i c u l a r spec i e s i n t h e environment. However, few s t u d i e s have gone beyond t h e s i n g l e spec ies approach t o eva lua t e e f f e c t s a t t h e community o r ecosystem l eve l . Factors such as competit ion, predat ion, d i sease , and f luc tua t -

TABLE 1

ACUTE TOXICITY OF NTA-Na TO FRESHWATER-ORGANISMS

Hardness as Effect Measured NTA-Na Effect Level mg/l CaCOq - Species Reference

~ainbow trout, Salmo gairdneri

Macek 6 Sturm 1973

Fathead minnow, Pimephales promelas

Macek 6 Sturm 1973 35

ca. 45 Fathead minnow,

Pimephales promelas Arthur et al.

1 9 z -

Fathead minnow, Pimephales promelas

Macek 6 Sturm 1973 28 d survival

Bluegill sunfish, Lepomis macrochirus

Weaver, 1970 Weaver, 1970

Bluegill sunfish Lepomis macrochirus 28 d survival >96<173 Macek 6 Sturm

1973

Snail, Weaver, 1970 Weaver, 1970 Physa heterostropha

Amphipod Gammarus pseudolimnaeus

ca. 45 Arthur et al. -- 1974

Amphipod spp . 96-hr survival - >500 Flannagan, 1971

~ a s t r o ~ o d spp. 96-hr survival - >500 Flannagan, 1971

11 insect spp. including midge, caddis f ly , stonefly, magfly, dragonf ly

96-hr survival - >500 Flannagan, 1971

Snail Helisoma trivolvis 96-hr survival > 100 - Flannagan, 1974

Species

TABLE 2

ACUTE TOXICITY OF NTA-Na TO MARINE ORGANISMS

Effects NTA-Na Measured Effect Level Reference

SCUP, 168-hr LC50 2200 Eisler -- et al. 1972 Stenotomus chrysops

Munrmichog , 168-hr LC50 5500 Eisler et al. 1972 -- Fundulus heteroclitus

Striped bass, 168-hr LC50 5500 Eisler -- et al. 1972 Morone saxatilis

Grass shrimp, 168-hr LC50 1800 Eisler et al. 1972 --

Palaemonetes vulgaris

Quahaug c 1 am, 168-hr LC50 >lo, 000 Eisler et al. 1972 -- Mercenaria mercenaria

Hermit crab, 168-hr LC50 1875 Eisler et al. 1972 -- Pagurus longicarpus

Starfish, 168-hr LC50 3000 Eisler -- et al. 1972 Asterias forbesi

American lobster, 168-hr LC50 3150 Eisler -- et al. 1972 Homarus americanus

Bay mussel, 168-hr LC50 3400 Eisler -- et al. 1972 Mytilus edulis

Eastern mud snail, 168-hr LC50 5100 . Eisler -- et al. 1972 Nassarius obsoletus

Sand worm, Nereis virens --

168-hr LC50 5500 Eisler et al. 1972

Zooplankton:

Tisbe furcata 72-hr LC50 270 Tarewell, 1970

Pseudodioptimus coronatus 72-hr LC50 700, Tarewell, 1970

Acartia clausi 72-hr LC50 1350 Tarewell, 1970

Eurytemora affinis 72-hr LC50 1250 Tarewell, 1970

Crab zoea 72-hr LC50 1650 Tarewell, 1970

Tigriopus japonicus 72-hr LC50 3200 Tarewell, 1970

i ng environmental condi t ions produce s t r e s s e s which may enhance chronic t o x i c i t y . On t h e o ther hand, rap id degradation may preclude t h e p o s s i b i l i t y of t o x i c exposures t o organisms. Many of t hese concerns could be addressed by using l a r g e s c a l e model ecosystems o r f i e l d app l i ca t ions of NTA i n t h e presence of o the r known wastewater cons t i t uen t s . Ecological monitoring i n regions cu r r en t ly using NTA i n de te rgents would a l s o be informative.

Abdulla, I., and M. Smith, 1963. Inf luence of Chelating Agents on t h e Concentration of Some Nutr ien ts f o r P l a n t s Growing i n S o i l Under Acid o r Under Alkal ine Conditions. J. Sci. F. Agric. - 14: 98-109.

Arthur, A. W . , A. E. Lemke, V. R. Mattson, and B. J. Hall igan, 1974. Toxic i ty of Sodium N i t r i l o t r i a c e t a t e (NTA) t o t he Fathead Minnow and an Amphipod i n Sof t Water. Water Res. 8 (3): 187-193.

Barcia , J., M. P. S ta in ton , and A. L. Hamilton, 1973. Mobil izat ion of Some Metals i n Water and Animal Tissue by NTA, EDTA, and TPP. Water Res. - 7: 1791-1804. . t

Biesinger , K. E., R. W. Andrew and J. W. Arthur, 1974. Chronic Toxic i ty of NTA ( N i t r i l o t r i a c e t i c Acid) and Metal-NTA Complexes t o Daphnia magna. J. Fish. Res. Board Can. - 31 (4) : 486-490.

Brownridge, F. A . , 1977. Concentrations of NTA i n Canadian Waters. In: P re sen ta t ions Prepared by Monsanto.and Proc ter and Gamble Companies f o r t h e I J C Task Force on Ecological E f fec t s of Non-Phosphate Detergent Builders .

Chynoweth, D. P . , J. A. Black, and K. H..Mancy, 1976. E f fec t s of Organic P o l l u t a n t s on Copper Toxic i ty t o Fish. In: Toxic i ty t o Biota of Metal Ions i n Natural Water, R. W. Andrews, P. V. Hodson, and D. E. Konasewich, eds. , International Joint Comm., pp. 145-157.

E i s l e r , R . , G. R. Gardner, R. J. Hennekey, G. LaRoche, D. F. Walsh and P. P. Yevich, 1972. Acute Toxicology of Sodium N i t r i l o t r i a c e t i c Acid (NTA) and NTA-Containing Detergents t o Marine.Organisms. Water Res. 6 : 1009-1027. - Flannagan, J. F., 1974. Inf luence of Trisodiurq N i t r i l o t r i a c e t a t e on t h e Mor ta l i ty , Growth, and Fecundity of t he Freshwater S n a i l Hilisoma Tr ivo lv i s through fou r generat ions. J. F ish Res. Board can. 31 (2) : 155-161. - Flannagan, J. F., 1971. Toxici ty Evaluation of NTA t o Selected Aquatic Inve r t eb ra t e s and Amphibians. J. Fish. Res. Board Can. Technical Report No. 258.

Glass , E. , 1977. I d e n t i f i c a t i o n and ~ i s t r i b u t i o n of Inorganic Components i n Water: What t o Measure? Presented a t t h e Conference on Aquatic P o l l u t a n t s and Bio logica l E f f e c t s wi th Emphasis on Neoplasia, September 27-29, 1976. The New York Academy of Sciences.

Gudernatsch, H., 1970. Verhalten von N i t r i l o t r i e s s i g s ~ u r e im Klarprozess und i n Abwasser. Gas-WasserFach. 111: 511-516. -

Hamilton, R. D . , 1977. Communications t o I J C Task Force on Eco log ica l E f f e c t s o f Non-Phosphate Detergent B u i l d e r s , Chicago, I l l i n o i s .

Jancov ic , M. and H. Mann, 1969. Untersuchungen Uber D i e Akute Toxische Wirkung Von ~ i t r i l o t r i e s s i g s g u r e (NTA). Archiv. F i s c h e r e i w i s s - 20 ( 2 , 3 ) : 178-181.

Kania, H. J . , and R. J. Beyers, 1974. NTA and Mercury i n A r t i f i c i a l Stream Systems. E c o l o g i c a l Research S e r i e s , EPA-66013-731025, Environmental P r o t e c t i o n Agency. 25 p.

K i m e r l e , R. A., 1974. E f f e c t of NTA on T o x i c i t y of Metals and Accumulation o f Cadmium i n Daphnia Magna and Fathead Minnows. Presen ted a t ASLO Meeting, June, 1974.

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Macek, K. J. and R. N. Sturm, 1973. S u r v i v a l and G i l l H i s to logy of F i s h Continuously Exposed t o Sodium N i t r i l o t r i a c e t a t e (NTA) f o r 28 days. J. F i s h . R e s . Board Can. - 30 ( 2 ) : 323-325.

Maki, A. W . , 1977. Aquat ic Toxicology of NTA. I n : P r e s e n t a t i o n s Prepared by Monsanto and P r o c t e r and Gamble Companies f o r t h e I J C Task Force on E c o l o g i c a l E f f e c t s of Non-Phosphate Bui lde rs .

Matheson, D. W . , 1977. N i t r i l o t r i a c e t i c Acid (NTA) i n t h e Canadian Environment. S c i e n t i f i c S e r i e s No. 74, Environment Canada.

Mot to la , H. A., 1974. N i t r i l o t r i a c e t i c Acid as a Che la t ing Agent: A p p l i c a t i o n s , Toxicology, and Bio-environmental Impact, Toxicol . and Environ. Chem. Rev. - 2: 99-161.

Shaw, T. L. and V. M. Brown, 1974. The T o x i c i t y of Some Forms of Copper t o Rainbow Trout . Water R e s . - 8: 377-382.

Sprague, J. B . , 1968. Promising Ant i -po l lu tan t : Che la t ing Agent NTA P r o t e c t s F i s h from Copper and Zinc. Nature 220: 1345-1346.

Swisher, R. D . , 1968. H i s t o l o g i c a l E f f e c t s of NTA and Its Degradation Produc t s on B l u e g i l l F i n g e r l i n g s . Report t o Monsanto Company, 1 /68 Made A v a i l a b l e a t t h e CCIW Meeting, 5/5/70.

Tarzwel l , C. M . , 1970. An Eva lua t ion of t h e T o x i c i t y o f N i t r i l o t r i a c e t i c Acid t o Marine Organisms. N a t i o n a l Marine Water Q u a l i t y Lab., W. Kingston, R. I., manuscr ipt . 72 pp.

Thayer , P. S . , and C. J. and Human S a f e t y Aspects i n Environmental Control

Kens le r , 1973. Current S t a t u s of t h e Environmental o f N i t r i l o t r i a c e t i c Acid (NTA), CRC C r i t i c a l Reviews , S e p t . , pp. 357-404.

Wallace, A., R. T. Muel le r , and G. V. Alexander, 1974. E f f e c t s o f High Levels of NTA on Metal Uptake by P l a n t s Grown i n S o i l . iron. J. 66: 707-708. -

Weaver, J. E., 1970. Acute E f f e c t s of Sodium N i t r i l o t r i a c e t a t e on F i s h , S n a i l s , and Diatoms. P r o c t e r & Gamble manuscr ipt , 7 pp.

EUTROPHICATION BY NTA

In i t s o r i g i n a l sense eu t rophica t ion r e f e r r e d t o an enrichment wi th p l an t n u t r i e n t s . I f one of t h e added n u t r i e n t s were l i m i t i n g t o t h e system i n ques t ion then, according t o L ieb ig ' s law of t h e minimum, growth of t h e plants--algae o r weeds--would b e s t imulated. Modern usage of t h e term eut rophica t ion r e t a i n s t h i s usage, indeed t h e cu r r en t eva lua t ion of de t e rgen t b u i l d e r s s t e m s from the f a c t t h a t phosphate f r equen t ly i s a l i m i t i n g element t o a lgae i n l akes , but i t goes beyond mere s t imu la t i on of a l g a l o r weed growth. Today what i s genera l ly r e f e r r ed t o a s eu t roph ica t ion i s t h e whole complex of changes, chemical, b io log i ca l , and phys ica l , t h a t r e s u l t s when n u t r i e n t s a r e introduced i n t o aqua t i c ecosystems. I n f a c t , i t i s o f t e n changes o ther than t h e increased growth of a lgae and weeds t h a t cause t h e g r e a t e s t concern. For example, i n in t roduc ing phosphorus t o a l a k e d e f i c i e n t i n i t , the increased a l g a l growth might no t be considered de t r imenta l i f i t were confined t o green a lgae and/or diatoms, but gene ra l l y t h e problem a r i s e s because blue-green a lgae come t o predominate. Thus f a c t o r s lead ing t o a change i n composition of t h e a l g a l communities, a s w e l l a s those causing an increased abundance of a lgae , might be considered a s causing eu t rophica t ion . With regard t o t h e l a t t e r i t should a l s o be recognized t h a t f a c t o r s a f f e c t i n g h igher t roph ic l e v e l s might r e s u l t i n "apparent eu t rophica t ion" , e.g. i f herb ivores were rendered less abundant, a l g a l populat ions would increase . Therefore , i n cons ider ing t h e eu t rophica t ion p o t e n t i a l of NTA a l l such p o s s i b i l i t i e s must be considered.

NTA AS A PLANT NUTRIENT

Sodium NTA conta ins 5.1% ni t rogen , 26.2% carbon, and 25.1% sodium. Although seve ra l years ago the re was a controversy regarding t h e importance of carbon as a primary n u t r i e n t i n aqua t i c ecosystems (Kuentzel, 1969) today i t is genera l ly recognized t h a t carbon-limited s y s t e m s a r e r a r e , and occur only where extreme eu t rophica t ion r e s u l t i n g from inpu t s of phosphorus and n i t rogen e x i s t s a l ready (Schindler , 1974). Thus, t h e r e should be l i t t l e f e a r regarding t h e NTA-caused inc rease i n wastewater carbon. Nitrogen on t h e o t h e r hand can be regarded a s a primary n u t r i e n t because, although c e r t a i n a lgae and b a c t e r i a a r e a b l e t o f i x atmospheric N 2 , most a lgae and macrophytes cannot, and must r ece ive i t a s an inorganic compound--generally a s N O 3 o r NH3. NTA degrades dur ing t reatment and i t is, t h e r e f o r e , of i n t e r e s t t o determine t h e ex t en t t o which NTA-N w i l l con t r i bu t e t o the pool of inorganic n i t rogen a v a i l a b l e f o r p l a n t growth. The Canadian experience monitored by Proc te r and Gamble (Brownridge, 1977) showed t h a t 6% NTA de t e rgen t r e s u l t e d i n a median concent ra t ion of 1.7 mg/R of NTA i n waste water , wi th a maximum of 11.0 mg/R; and t h a t 15% NTA i n de t e rgen t r e s u l t e d i n a median va lue of 3.6 mg/R NTA wi th a maximum of 22.9 mg/R. A s t he se va lues show f a i r p ropor t i ona l i t y

i t is l i k e l y t h a t 30% NTA i n de te rgent , t h e g r e a t e s t amount l i k e l y t o be present , would give a median wastewater i n f luen t value of about 6 mg/R and a maximum concentrat ion of about 40 mg/R. I n t h e Gloucester CFS Detergent Subs t i t u t e S tud ie s (Shannon and Kamp, 1973) where.only NTA detergent was used, i n f l u e n t wastewater NTA averaged 2.19 mg/R, and ranged up t o 14.8 mg/R. A s t h e NTA was measured a s NTA-H, a s NTA-Na i t would be 2.9 mg/R and 19.5 mg/R. The de tergent used had an NTA-H concentrat ion of 19.7%, i . e . 26% a s NTA-Na. Thus, i f 30% NTA-Na had been used t h e average i n f l u e n t concentrat ion would l i k e l y have been 3.4 mg/R and t h e maximum 23 mg/R. These f igu res a r e below those of 6 and 40 c i t e d above, so t h e l a t t e r a r e probably high est imates . Nonetheless, even i f t hese high es t imates a r e used, t h e n i t rogen con t r ibu t ion t o wastewater by NTA, assuming complete degradat ion, would be a maximum of 2 mg N / R , wi th a median value of about 0.3 mg NIL.

The inorganic n i t rogen content o f wastewater e f f l u e n t s i s genera l ly i n . t h e range of 30-40 mg/R. Therefore, on t h i s b a s i s , t h e maximum inc rease i n N would be 5-6.6%, and t h e median increase would b e 0 . 7 5 t o 1%.

Nitrogen sources t o n a t u r a l waters a r e many, including n i t rogen f i x a t i o n , atmospheric p r e c i p i t a t i o n , and land runoff , along with domestic wastes, so t h a t t h e e f f e c t of addi t ion of NTA-N t o any given aqua t i c system would be reduced proport ionately. Assuming, f o r example, t h a t a s much a s ha l f t h e ni t rogen input t o a l ake were t o come from domestic wastewater, t h e NTA cont r ibu t ion would then amount t o l e s s than 3% of t h e t o t a l a t a maximum, and probably l e s s than 0.5%.

Very few lakes appear t o be ni t rogen-l imited, Lake Tahoe being a notab le except ion, s o t h i s danger from NTA appears not grea t . (Many more l akes have been descr ibed t o be ni t rogen-l imited but most of t hese a r e so because of t h e high i n p u t s of phosphorus.- Subs t i t u t ion of NTA f o r phosphorus would help make many of t h e lakes no longer con t ro l l ed by n i t rogen) . S imi la r ly , although marine waters a r e ni t rogen-l imited an inc rease i n wastewater n i t r o g e n , of t h e magnitude noted would have a t most an i n s i g n i f i c a n t eu t rophica t ion e f f e c t .

EFFECTS OF N T A ON ALGAE

Many d i f f e r e n t approaches have been taken t o determine t h e e f f e c t s of NTA on a lgae and t o p r e d i c t t h e consequences of t h e use of NTA. NTA has been t e s t e d a t low concentrat ions (Goldman and F u j i t a , 1970); a t high concentrat ions (Weaver, 1970); a lone ricks on, -- e t a l . , 1970); i n t h e presence of wastes (Sturm and Payne, 1973); aga ins t s ing le spec i e s of a lgae i n syn the t i c media (Chr i s t i e , 1970) ; i n f i l t e r e d lake water (Weiss, 1970) ; i n microcosms (Swisher and Mi tche l l , 1970); small enclosures ( ~ c r g i , 1974) and l a r g e enclosures (Bartsch, e t a l . , 1970); f o r sho r t per iods of time (Goldman and F u j i t a , 1970; and f o r long per iods of time (Landner, 1969). A v a r i e t y of c r i t e r i a have been used t o judge t h e r e s u l t s , ranging from numbers of a lgae (Sturm and Payne, 1973) through carbon-14 f i x a t i o n r a t e s (Goldman and F u j i t a , 1970) t o spec i e s d i v e r s i t y (Swisher and Mi tche l l , 1970). To put iSt simply t h e r e s u l t s have been var iab le . For example, Swisher and Mi tche l l could not f i n d a s i g n i f i c a n t e f f e c t of NTA u n t i l they used 500 mg/R, but Goldman repor ted s t imu la t ion of carbon-14 uptake a t t h e remarkably low concentrat ion of 0.5 micrograms/R.

I n general , t h e r e s u l t s do demonstrate t h a t NTA cannot be counted on t o be s t imula tory but t h a t on occasion i t may appear t o be spec t acu la r ly so. It a l s o seems t o be c l e a r t h a t NTA i t s e l f i s no t a t ox ic substance f o r a lgae a t concentrat ions l i k e l y t o be encountered i n n a t u r a l systems, nor i s i t a s t imulant by i t s e l f , i . e . i n a r t i f i c i a l systems. There i s a l s o abundant evidence t h a t i ts p o s i t i v e e f f e c t s when they do occur a r e not t h e r e s u l t of t h e increased concentrat ions of inorganic n i t rogen afforded by degradat ion of t he NTA.

I n s h o r t i t looks a s though much of t h e v a r i a b i l i t y i n t he r e s u l t s der ives from the v a r i a b i l i t y of t h e systems i n which t h e NTA has been t e s t ed . This has been made c l e a r i n acu te t o x i c i t y s t u d i e s on animal organisms where t h e t o x i c i t y is an inverse funct ion of t h e water hardness (Arthur -- e t a l . , 1970). But t h e r e l a t i o n s h i p s a r e more s u b t l e i n t he case of t h e a lgae . It would seem t h a t t h e v a r i a b i l i t y r e s u l t s from t h e f a c t t h a t (a) d i f f e r e n t systems d i f f e r i n t r a c e metal content , (b) d i f f e r e n t systems d i f f e r i n t h e i r community s t ruc tu re .

With regard t o t r a c e metals most i nves t iga to r s seem t o be aware of t h e che l a t ing p rope r t i e s of NTA, and many do r e l a t e t h e i r r e s u l t s t o t h i s proper ty , and attempt t o expla in them i n t h i s fashion, bu t with notab le l a c k of evidence o r d e t a i l , e.g. Burgi, Goldman. However, t h e r e is mer i t i n t h e proposi t ion. Organisms do l i v e i n a mil ieu i n which they a r e under p o s i t i v e and negat ive inf luences . P o s i t i v e inf luences include having s u f f i c i e n t n u t r i e n t s and t r a c e metals f o r growth. Negative inf luences inc lude t h e presence of organic t ox ins , a n t i b i o t i c s , and de t r imenta l heavy metals. I f , f o r example, photosyn- t h e s i s by an a lga is being inh ib i t ed by copper then che la t ing t h e copper is l i k e l y t o s t imu la t e photosynthesis. Depending on circumstances then, NTA could s t imu la t e o r i n h i b i t a l g a l populat ions, and t h i s might be t h e explanat ion f o r some of t h e v a r i a b i l i t y .

However, i t i s one th ing t o d i scuss reasons f o r t h e v a r i a b i l i t y of t h e r e s u l t s and another t o consider t h e relevancy of t h e r e s u l t s t o t h e problem a t hand. It would appear t h a t most of t h e r e s u l t s a r e i n f a c t not re levant . That is, those s t u d i e s using high concent ra t ions of NTA, o r a r t i f i c i a l media, o r s i n g l e spec ies of a lgae , o r sho r t per iods of observat ion, while i n t e r e s t i n g i n t h a t they provide c lues , cannot t e l l us what w i l l happen i f NTA is re leased t o t h e n a t u r a l environment. Only experiments i n t h e n a t u r a l environment wi th a l l i t s components, and f o r long enough f o r t h e system t o respond, can be usefu l i n t h i s regard. That is t o say, aqua t i c systems a r e ecosystems, no t j u s t h a b i t a t s f o r a lgae but systems having var ious t rophic l eve l s . The abundance and types of a lgae may r e s t a s s t rong ly o r even more s t rong ly on t h e types and abundances of higher t rophic l e v e l s than on t h e amount of n u t r i e n t s . S imi la r ly , t h e types of a lgae i n a system w i l l depend upon competit- i on between t h e var ious spec i e s of a lgae , and t h i s may be sub t l e . We be l i eve now t h a t many f a c t o r s can a f f e c t t hese competit ive r e l a t i onsh ips . For example, lowering pH w i l l s h i f t a mixed populat ion of greens and blue-greens toward t h e greens (Shapiro, 1973). Increas ing t h e NIP r a t i o may do t h e same (Schindler , 1977). So may add i t i ons of ch lor ine (Shapiro -- e t a l . , 1977). On t h e o the r hand, increas ing t h e content of magnesium may f o s t e r blue-greens (Shapiro, unpubl. ) , a s might t h e add i t i on of i ron. (Murphy e t ' a l . , 1977) have suggested t h a t blue-green a lgae exc re t e hydroxamates t h a t che l a t e i r o n and prevent i t

from be ing used by green a lgae . Addi t ion of a c h e l a t o r s u c h a s NTA could change t h i s r e l a t i o n s h i p bu t we would n o t know i t u n l e s s b o t h . t y p e s of a l g a e were p r e s e n t . It would appear , t h e r e f o r e , t h a t t h e most r e l e v a n t work would be t h a t i n which i n s i t u e n c l o s u r e s t u d i e s were done f o r long p e r i o d s wi th n a t u r a l popu la t ions . S e v e r a l e x i s t and a r e summarized below.

(1 ) EPA-SHAGAWA LAKE (Bar tsch e t a l . , 1970)

Hundred- l i ter p l a s t i c bags of e i t h e r Shagawa Lake water o r Burn t s ide River wa te r were incubated f o r 13-32 days w i t h v a r i o u s combinations of N , P , secondary and t e r t i a r y wastewaters , and NTA, t h e l a s t a t 4-5 mill igrams/R. Eva lua t ion was by c h l o r o p h y l l - a .

-

Treatment R e s u l t s

I n Burn t s ide wa te r , t h e r e s u l t s were a s fo l lows :

NTA a l o n e - 3 exper iments + up t o 150%; 2 exper iments s l i g h t l y - -

NTA + P - 5 exper iments + up t o 225% v s P a l o n e NTA + t e r t i a r y wastewater - 1 experiment + c a 70% and

2 s l i g h t l y - v s t e r t i a r y a lone - NTA + secondary wastewater - 2 exper iments + c a 30%

1 ' s l i g h t l y - v s s e c o n d a r y a l o n e -

I n Shagawa wate r , t h e r e s u l t s were a s fo l lows :

NTA a l o n e - 1 experiment + 20%; 3 exper iments 0 o r s l i g h t l y - -

NTA + P - 3 exper iments + 25-300%; 1 experiment - 20% v s P a l o n e -

NTA + t e r t i a r y wastewater - 3 exper iments + 30-100% v s t e r t i a r y a l o n e

NTA + secondary wastewater - 3 exper iments + 25-130% v s secondary a l o n e

Thus, i n a s u b s t a n t i a l p o r t i o n of t h e c a s e s , NTA d i d cause s t i m u l a t i o n . Examination showed t h a t t h e e f f e c t d i d n o t r e s u l t from t h e n i t r o g e n i n t h e NTA, a s i n some c a s e s l i t t l e degrada t ion had occurred.

(2 ) EPA-CLINES POND (Bar t sch e t a l . , 1970)

Two bo t tomless e n c l o s u r e s 4.5 x 4.5 x 3 m deep were i n s t a l l e d i n t h i s e u t r o p h i c pond. F ive mg/R NTA were added t o one and n o t h i n g t o t h e o t h e r . Observat ion was f o r 3 months. The r e s u l t s showed t h a t t h e NTA t r e a t e d pond r e t a i n e d much' g r e a t e r a l g a l p o p u l a t i o n s (Anabaena) d u r i n g J u l y and August. I n f a c t on August 1 0 , a t peak phytoplankton p roduc t ion , the-maximum-rate of carbon f i x a t i o n i n t h e NTA e n c l o s u r e was 280 mg c/m3/hr . compared w i t h only 30 mg c/m3/hr . i n t h e c o n t r o l enc losure . Other parameters such a s c h l o r o p h y l l , t r ansparency , e t c . were i n accord. A n a l y s i s showed t h a t even though a l l NTA had d i sappeared by 60 days , t h e pe r iod of h e a v i e s t a l g a l growth preceded t h e pe r iod of r a p i d NTA decrease .

S i z a b l e popula t ions of mic rocrus taceans 'were p r e s e n t i n bo th e n c l o s u r e s .

, . (3) FISHERIES RESEARCH BOARD (.Hamilton, 1972)

Twenty, one-m d iamete r , p l a s t i c t u b e s c o n t a i n i n g 7,000 l i t e r s each were suspended i n each of two l a k e s . NTA w i t h and wi thou t sewage a t concentra- t i o n s of 2 microgramslQ t o 2 mglQ were used. Moni tor ing was by many parameters f o r a whole summer. The r e s u l t s showed no apparen t e f f e c t s of NTA accord ing t o Hamilton, a l though t h e d a t a have n o t been publ ished.

P l a s t i c bags 1 m x 1 0 were placed i n mesotrophic Lake Lucerne and e u t r o p h i c Gre i fensee (Swi tze r land) . NTA a l o n e , o r i n combination w i t h i r o n was added t o some bags. Concen t ra t ions of NTA used ranged upwards from 50 micrograms1Q. I n Lake Lucerne s i g n i f i c a n t s t i m u l a t i o n by NTA a l o n e occurred, w i t h O s c i l l a t o r i a rubescens , a blue-green a l g a ; w i t h C y c l o t e l l a and Erkenia , d ia toms; wi th Ankistrodesmus and C h l o r e l l a , g reens ; and w i t h Cryptomonas and Rhodomonas, cryptophytes . The diatom T a b e l l a r i a and t h e green Mougeotia were i n h i b i t e d . I n Gre i fensee most s p e c i e s were i n h i b i t e d by t h e NTA a d d i t i o n s .

.(5) PATRICK ET AL.--PHILADELPHLA ACADEMY (1976)

The e f f e c t s of v a r i o u s c o n c e n t r a t i o n s of NTA up t o 200 m i l l i g r a m s l Q were t e s t e d i n smal l s t r eam systems r u n through a l a b o r a t o r y f o r s e v e r a l months. No e f f e c t was noted on b a c t e r i a l a c t i v i t y b u t a l g a l s h i f t s were seen , e.g. Sp i rogyra was more abundant a t 2 mg1Q NTA and t h e r e was a s h i f t t o b lue-greens a t 200 mgIQ, b u t t h e t o t a l biomass was much reduced.

, (6 ) SWISHER AND MITCHELL--MONSANTO (1970)

Microcosms c o n t a i n i n g one l i t e r of mud and seven l i t e r s of l a k e wate r and r e i n o c u l a t e d every two weeks w i t h l a k e water were mainta ined f o r p e r i o d s of up t o two y e a r s . NTA was added w i t h and wi thou t sewage a t c o n c e n t r a t i o n s of from 2 mglQ t o 500 mglQ. T o t a l o rgan ic carbon and d i v e r s i t y index of t h e a l g a l popu la t ions were used a s t h e c r i t e r i a f o r e f f e c t . The only e f f e c t noted was a t 500 mg/R NTA where "excess ive bloom condi t ions" were induced.

(7 ) LANDNER (1969)

During 3 summer months i n 1969 a s t u d y was made i n Sweden on a system of l a k e s and s t reams r e c e i v i n g t h e d i s c h a r g e from a wastewater t r ea tment p l a n t t r e a t i n g an i n f l u e n t c o n t a i n i n g 4-6 mglQ of NTA.

The p l a n t c o n s i s t e d of a t r i c k l i n g f i l t e r , a sed imenta t ion pond, and an o x i d a t i o n pond. The mean e f f l u e n t volume was 1500 m3/day. A number of physico-chemical parameters , a long wi th t h e occurrence and abundance of d i f f e r e n t phyto- and zooplankton organisms a s w e l l a s bottom organisms, were measured a t s e v e r a l s t a t i o n s upstream and downstream of t h e o u t f a l l . No t r a c e of NTA was found i n t h e wa te r system d u r i n g t h e per iod. Landner

be l i eves t h a t none of t h e e f f e c t s observed on t h e b i o t a could be unequivi- c a l l y ascr ibed t o t h e d i scharge of NTA. 'He gives i t a s h i s opinion t h a t because eu t rophic water systems a l ready have a l a r g e amount of n a t u r a l l y che l a t i ng ma te r i a l , add i t i on of a r t i f i c i a l che l a to r s would be of l i t t l e consequence.

A s with t he o the r experiments t h e r e s u l t s of t he se seven were va r i ab l e . St imulat ion was found by t h e EPA us ing Cl ine ' s Pond, Shagawa Lake, and Burnts ide River water , and a l g a l changes were found by ~ u r g i and P a t r i c k , and by Swisher and Mi tche l l , while t h e Swedish s tudy and t h e FRB s tudy were negat ive. However, none of t he se s t u d i e s r e a l l y s a t i s f i e s a l l c r i t e r i a . For example, t h e EPA s t u d i e s used u n r e a l i s t i c a l l y high concent ra t ions of NTA. No a l g a l , composition d a t a a r e given f o r them, and although zooplankton were present i n t h e C l ine ' s Pond system with NTA, t h e i r , s p e c i f i c na tu re i s not descr ibed. Were they daphnids, which could expla in t h e low a l g a l populat ion i n t h e con t ro l ? Were t h e zooplankters i n t h e con t ro l system t h e same? S imi l a r ly , no d a t a a r e a v a i l a b l e t o us from t h e FRB s tud i e s . Was t h e r e a s h i f t i n a l g a l spec ies o r i n zooplankton composition? Bzrg i ' s s tudy i s good i n t h a t spec i e s composition was c a r e f u l l y examined, bu t unfor tuna te ly t h e s tudy was too sho r t . Also t h e reasons f o r t he spec ies changes were no t clear--were they caused by zooplankton? Pa t r i ck ' s s tudy was r e s t r i c t e d t o a very few members of t he s t ream ecosystem. Fovexample, no herbivores were presen t . The Swedish s tudy is d i f f i c u l t t o i n t e r p r e t a s t he e f f e c t of t h e sewage i t s e l f i s very g r e a t . ' F i n a l l y , i t has no t been poss ib l e t o f i nd s t u d i e s of t h e e f f e c t s of NTA on macrophytes, o r on t h e a t tached a lga , Cladophora, which i s a g r e a t nuisance i n t h e inshore waters of t h e Great Lakes, exac t ly where concent ra t ions of NTA would be g rea t e s t . The only near r e l evan t paper i s one by Stockner and Evans (1974) i n which they r epo r t l i t t l e e f f e c t of NTA on a t t ached a l g a l communities.

REFERENCES . , I

Ar thur , J. W . , K. E. Biesinger; A. E. Lemke; R. W. Andrew; V. R. Mattson 1970. D i r e c t Toxic i ty and Some I n t e r a c t i o n P rope r t i e s of N i t r i l o t r i a c e t i c Acid (NTA) t o Aquatic Li fe . Mimeo r e p o r t , Nat ional Water Qual i ty Laboratory, Duluth.

Bartsch, A. R. and 15 o ther authors , 1970. F i e ld and Laboratory Invest iga- t i o n s t o Evaluate t h e Inf luence of N i t r i l o t r i a c e t i c Acid (NTA) on Eutrophica- t ion . May-November, 1970. Unpub. Report t o Commissioner, Federal Water Qual i ty Administration.

1

Brownridge, F. A . , 1977. Report f o r t h e I J C Task Force on Ecological E f f ec t s of Non-Phosphate Detergent Bui lders .

, . ~ G r g i , H. R . , 1974. D i e Wirkung von NTA auf das Wachstum des Phytoplanktons unter besonderer Berucksichtigung des Eisens a l s Mikroelement. Schweiz. Z e i t . f . Hydrol. - 36': 1-70.

C h r i s t i e , A. E . , 1970. Trisodium N i t r i l o t r i a c e t a t e and Algae.' Water and Sewage Works, 1970. pp. 58-59.

Er ickson , S. J . ; T. E. Maloney and J. H. G e n t i l e , 1970. E f f e c t of N i t r i l o - - t r i a c e t i c Acid on t h e Growth and Metabolism of E s t u a r i n e Phytoplankton. J. Water P o l l . Con t r . Fed. - 42: R329-325.

Goldman, C. R. and D. F u j i t a , 1970. The Response of N a t u r a l l y Occur r ing Phytoplankton P o p u l a t i o n s t o NTA i n Lake Tahoe, C a s t l e Lake and C l e a r Lake, C a l i f o r n i a . In : B a r t s c h e t a l . , 1970. --

Hamilton, R. D. 1972. The Environmenta l A c c e p t a b i l i t y of NTA - C u r r e n t Research and Areas of Concern. I n : " N u t r i e n t s and Eu t roph ica t ion" . S p e c i a l Symposia, Vol. 1. ASLO. Ed. G. E. Likens .

Kuen tze l , L. E. , 1969. B a c t e r i a , Carbon Diox ide , and A l g a l Blooms. J . Water P o l l . Contr . Fed. - 41: 1737

Landner, L . , 1969, K a r t l a g g n i n g Av E t t Rec ip ien t sys tem Med ~ Z r s k i l d ~ g n s y n T i l l u t s l a p p Av NTA-Haltigt Kommunalt Av loppsva t t en . Mimeo Repor t , Swedish IVL, Stockholm, December 1969.

Murphy, T. P. ; D. R. S. Lean and C. Nalewajko, 1976. Blue-Green Algae: T h e i r Execut ion of I r o n - S e l e c t i v e C h e l a t o r s Enables Them t o ~ > m i n a t e Other - Algae. S c i . - 192: 900-902.

P a t r i c k , R.; T. B o t t , R. La r son , and C . Rhyne, 1976. The E f f e c t of N i t r i l o - t r i a c e t i c Acid (NTA) on t h e S t r u c t u r e and F u n c t i o n i n g of Aqua t i c Communities. D r a f t Repor t of Grant R801951 f o r EPA Env. Res. Lab. Dulu th , Minnesota.

S c h i n d l e r , D. W . , 1974. E u t r o p h i c a t i o n and Recovery i n Exper imenta l Lakes: I m p l i c a t i o n s f o r Lake Management. S c i e n c e 184: 897-899. - S c h i n d l e r , D. W . , 1977. Evo lu t ion of Phosphorus L i m i t a t i o n i n Lakes . . , Sc ience 195: 260-262. -

Shannon, E. E. and L. J. Kamp, 1973. Detergent S u b s t i t u t i o n S t u d i e s a t C.F.S. G l o u c e s t e r . Tech. Dev. Rept. EPS 4-WP-73-3. Water p o l l u t i o n c o n t r o i D i r e c t o r a t e . EPS, Environment Canada, .Ottawa.

Shap i ro , J . , 1973. Blue-Green Algae: Why They Become Dominant. Sc ience 179: 382-384 .. - S h a p i r o , J . ; G. Zoto, and V. Lamarra, 1977. Exper imen ta l S t u d i e s on Changing A l g a l P o p u l a t i o n s From Blue-Greens t o ~ r e e n s , * ~ n ~ u b . Manuscr ip t .

S tockner , J. G. and D. Evans, 1974. F i e l d and L a b o r a t o r y S t u d i e s on t h e E f f e c t o f N i t r o g e n , Phosphorus and NTA A d d i t i o n s on At tached A l g a l Communities. F i s h . Res. Bd. Canada Tech. Repor t No. 416. 109 pp.

Sturm, R. N. and A. G. Payne, 1973. ~ n v i r o n m e n t a l T e s t i n g of Tr isodium N i t r i l o t r i a c e t a t e : B ioassays f o r Aqua t i c S a f e t y and A l g a l S t i m u l a t i o n . I n : G. E. Glass, (Ed.). B ioassay Techniques-and Environmental Chemistry: 403- 424. Ann Arbor , S c i e n c e P u b l i s h e r s , I n c .

I

I

Swisher, R. D. and D. T. M i t c h e l l , 1970. NTA and t h e Environment. A Review of t h e L i t e r a t u r e and Work i n Progress . I n t e r n a l Report , Inorgan ic Chemicals D i v i s i o n , Monsanto Co.

Weaver, J. E., 1970. Acute E f f e c t s of Sodium N i t r i l o t r i a c e t a t e on F i s h , S n a i l s , and Diatoms. Manuscript submit ted f o r p u b l i c a t i o n . June 1970.

Weiss, C . M. , 1970. I n f l u e n c e o f N i t r i l o t r i a c e t a t e (NTA) on Eut roph ica t ion . I n S i t u and Batch Assays. I n : S a r t s c h -- e t a l . 1970.

MODELLING OF NTA CONCENTRATIONS IN WATER

L i t t l e work h a s been done on t h e model l ing of NTA ( o r any o t h e r o rgan ic l i g a n d ) c o n c e n t r a t i o n s i n n a t u r a l wa te r s . A number of a t t e m p t s have been made t o d e s c r i b e t h e e q u i l i b r i u m d i s t r i b u t i o n of NTA and i t s complexes based on thermodynamic a s p e c t s (Chi lds 1971, Chance 1975, C i l l e y and Nicholson 1971, Winters 1977) , b u t on ly Lerman and C h i l d s (1973) have a t tempted t o i n t e g r a t e a l l f a c t o r s governing expected l e v e l s i n wa te r i n t o a p r e d u c t i v e model. T h i s p a u c i t y of a t t e m p t s i s undoubtedly due t o t h e i n h e r e n t complex- i t y of a model r e q u i r i n g c o n s i d e r a t i o n of n o t on ly thermodynamic r e l a t i o n s h i p s determining complex format ion but a l s o r a t e s of breakdown f o r both t h e l i g a n d and each of i t s complexes. Because t h e breakdown of NTA and i t s complexes i n v o l v e s complex r e a c t i o n s t h a t have a s y e t been q u a n t i f i e d on ly i n a few v e r y s p e c i f i c c a s e s (eg. Shannon, Fowlie and Rush 1974) , a r e a l i s t i c , u s a b l e model h a s y e t t o be de f ined and t e s t e d . The approach of Lerman and C h i l d s is c e r t a i n l y t h e most complete employed t o d a t e and i s o u t l i n e d and commented on below.

The c o n c e n t r a t i o n o f NTA i n n a t u r a l w a t e r s w i l l depend on 3 f a c t o r s :

1 ) thermodynamic r e l a t i o n s h i p s between NTA, o t h e r o rgan ic l i g a n d s , and m e t a l s , i n c l u d i n g adsorp t ion-desorp t ion phenomena. The e q u i l i b r i u m d i s t r i b u t i o n o f NTA between "free" m a t e r i a l and each complex w i l l depend on t h e chemical composit ion o f t h e water i n q u e s t i o n ,

2 ) t h e r a t e o f degrada t ion of NTA and each of i t s complexes,

3) t h e water replenishment r a t e of t h e body of water (which may be modified according t o i t s thermal s t r u c t u r e ) , t h e l o s s of m a t e r i a l by sed imenta t ion , and t h e i n p u t r a t e t o t h e body of water .

A s s t a t e d above, . t h e thermodynamic r e l a t i o n s h i p s governing d i s t r i b u t i o n of NTA between i t s v a r i o u s chemical s p e c i e s have been summarized by s e v e r a l a u t h o r s .

Each metal i o n (M.) may undergo complex format ion wi th a 1

l i g a n d L:

w i t h e q u i l i b r i u m c o n s t a n t Ki = [ M ~ L ] / [ M ~ ] [L] .

The meta l - l igand complex c o n c e n t r a t i o n is t h e n -

where L is t h e t o t a l c o n c e n t r a t i o n of t h e l i g a n d ( i n t h i s c a s e , NTA) T and f is a f r a c t i o n d e f i n e d f o r each given i o n i c composit ion. I f t h e c o n c e n t r a t i o n of t h e o r g a n i c l i g a n d i s small r e l a t i v e t o t h a t of t h e v a r i o u s meta l i o n s , t h e [LT] can be d e f i n e d as:

I f however, [L] is l a r g e , t h e n .,

S o l u t i o n of a s e r i e s of such e q u a t i o n s is p o s s i b l e (by computer) i f m e t a l c o n c e n t r a t i o n s , l i g a n d c o n c e n t r a t i o n s (a l i g a n d s , n o t j u s t NTA), and a l l e q u i l i b r i u m c o n s t a n t s a r e known. The aforementioned r e f e r e n c e s , i n e f f e c t , do j u s t t h a t u s i n g a d e f i n e d d a t a set. The e q u i l i b r i u m d i s t r i b u t i o n of NTA i n w a t e r of a s p e c i f i e d chemical composi t ion can t h e r e f o r e be approximated. However, t h e use of t h i s t echn ique is l i m i t e d by t h e f a c t t h a t most o r g a n i c l i g a n d s i n n a t u r a l wa te r a r e u n c h a r a c t e r i z e d . T h e i r e q u i l i b r i u m c o n s t a n t s a r e t h e r e f o r e unknown, and t h e magnitude of t h e e f f e c t s on t h e d i s t r i b u t i o n of NTA among i t s v a r i o u s forms i s u n c e r t a i n .

The d e g r a d a t i o n of NTA and i t s complexes may occur because of b a c t e r i a l , o x i d a t i v e o r photochemical p r o c e s s e s ( f o r more d e t a i l s s e e p rev ious s e c t i o n s ) . I f , a s a f i r s t approximat ion, i t i s assumed t h a t decomposit ion o c c u r s w i t h o u t e q u i l i b r i u m ; t h a t is, wi thou t con t inuous read jus tment between t h e l i g a n d ' s complexes, then t h e t o t a l r a t e of decay of t h e l i g a n d is:

d [MiLl where -

d t = X.[M.L] and X is t h e f i r s t - o r d e r r e a c t i o n r a t e c o n s t a n t .

1 1 i

There fo re , t h e t o t a l NTA c o n c e n t r a t i o n as a f u n c t i o n of t ime i s given by:

*

if [M.L] at t = o is a fraction, f of LT. 1 i

If, however, there is continuous re-equilibration, then the total concentration of NTA is given by:

In this case, total decomposition occurs at a faster rate.

Other factors that will determine the NTA concentration in a body of water are the input rate (J) of the NTA, flushing rate (p) of the body of water, and the rate of loss to sediments of the NTA. If the body of water is assumed to be instantaneously and homogeneously mixed and if the interaction of NTA with sedi~ents can be described by the Freundlich absorption equation (Cs = KC , where C is the concentration

S of NTA on the substrate, K is a constant, C is the concentration of NTA in the water, and O<n<l), then the rate of change of the concentration of NTA in the body of water can be described by:

1 ,

where A is taken as a decay constant indicative of NTA and all its complexes. The solution to this equation is given by Lerman and Childs, both for the case where the sediment interaction is described by the Freundlich equation and for the simpler case where there is no interaction (ie. dcS/dt = 0). In the latter instance, a steady-state concentration of NTA will be reached more slowly; nevertheless, the acutal concentration attained will be the same whether or not the sediment interaction is taken into account. It is given by:

Clearly, the assumption that a single decay constant (A) can be used to describe the decomposition of all NTA complexes oversimplifies the situation. If, however, this is accepted as a very crude approximation, then estimates of steady-state NTA concentrations ofr water bodies of various flushing rates can be made based on specific values of A. For example, if the "combined" half-life for decomposition of NTA and all its complexes in a given body of water is 2 weeks and the flushing rate = 1 yr-', then the steady-state concentration will be 5.3% of the input concentration.

. .

A more realistic mode1,might incorporate n simultaneous.equations:

w i t h cont inuous thermodynamic e q u i l i b r i u m between t h e n complexes ( i n c l u d i n g " f ree" NTA). The decomposit ion r a t e s , hi, a r e no t o n l y unique b u t are f u n c t i o n s of t empera tu re , e t c . While such a model i s e a s y t o fo rmula te , t h e d a t a r e q u i r e d t o u s e i t do n o t e x i s t .

To s e t upper l i m i t s f o r NTA c o n c e n t r a t i o n s expected, one could assume decomposit ion r a t e s a r e z e r o (A, = 0) and t h a t t h e r e a r e no sediment i n t e r a c t i o n s dCs

The c o k e n c r a t i o n is, t h e r e f o r e , governed by (dt = 0 ) .

i n p u t d i l u t i o n only . Evidence e x i s t s , however, t o show t h a t decomposit ion r a t e s a r e r e l a t i v e l y r a p i d ( i e . l o s s by decomposit ion w i l l be g r e a t e r t h a n l o s s by washout f o r almost a l l bod ies of w a t e r ) ; t h u s , t h i s s imple approach w i l l r e s u l t i n u n r e a l i s t i c a l l y h i g h es t ima ted NTA c o n c e n t r a t i o n s .

I n summary, a l though i t i s p o s s i b l e t o fo rmula te mathemat ica l ly a model t h a t approximates t h e expected behaviour of NTA i n n a t u r a l w a t e r s , t h e d a t a r e q u i r e d t o employ a n even c rude s i m p l i f i c a t i o n of it a r e s o e x t e n s i v e a s t o be p r o h i b i t i v e .

REFERENCES

Chance, J . M . 1975. Computer S imula t ion S t u d i e s on t h e Environmental E f f e c t s of N i t r i l o t r i a c e t i c Acid. M.A. T h e s i s , Univ. of Pennsylvania , Penn., 72 p.

C h i l d s , C.W. 1971. Chemical Equ i l ib r ium Models f o r Lake Water which Conta ins N i t r i l o t r i a c e t a t e and f o r "Normal" Lake Water. Proc. 1 4 t h Conf. Great Lakes Res. :198-210.

C i l l e y , W.A. and D.A. Nicholson. 1971. An Equi l ib r ium Model f o r t h e NTA Complexation of M e t a l I ons i n N a t u r a l Waters. Env. L e t t e r s 2:121- 129.

Lerman, A. and C.W. Ch i lds . 1973. Metal Organic Complexes i n N a t u r a l Waters : . Con t ro l of D i s t r i b u t i o n of Thermodynamic, K i n e t i c and P h y s i c a l Fac to r s . p.201-235. I n P.C. S inger ( ed . ) . T race Meta l s and Metal- Organic I n t e r a c t i o n s i s a t u r a l Waters. Ann Arbor Sc ience Publ. Inc . , Ann Arbor, Michigan.

Shannon, E . E . , P.J.A. Fowlie and R.J. Rush. 1974. A s t u d y of N i t r i l o t r i - a c e t i c Acid (NTA) Degradat ion i n a Receiving Stream. Report No. EPS 4- WP-74-7. 25p.

Winters , R . E . 1977. Chemistry of NTA. 26p. I n P r e s e n t a t i o n Prepared by Monsanto and P r o c t e r & Gamble Companies f o r t h e I J C Task Force on Eco log ica l E f f e c t s of Non-Phosphate De te rgen t Bu i lde r s . C i n c i n n a t i , Ohio.

- ENVIRONMENTAL LEVELS OF NTA

WASTE TREATMENT PLANTS

The c a l c u l a t e d average c o n c e n t r a t i o n of NTA expected i n raw munic ipa l wastewater h a s ranged between 3.2 mg R-1 (Brownridge 1977) and 75 mg R-' ( E p s t e i n 1972). A r e a l i s t i c concen t . r a t ion f o r t h e post-1973 pe r iod when d e t e r g e n t s i n Canada had a n average c o n t e n t of 15% NTA, is 5 mg R-' (Matheson 1976, Can. Dept. Nat. Hea l th Welfare 1972), w i t h l e v e l s expected t o r e a c h 10 mg R-' i f a l l l aundry STPP were rep laced by .NTA. Concen t ra t ions i n household was tes i n r u r a l a r e a s employing s e p t i c ' t a n k - t i l e ' f i e l d o r ho ld ing t a n k sys tems, may each 2 t o 3 t imes t h a t i n municipal wastewater (Can. Dept. Nat. Heal th Welfare 1972), r e s u l t i n g i n l e v e l s of up t o 20-30 mg R-'.

Measured i n f l u e n t c o n c e n t r a t i o n s a r e summarized i n Tab les 1 (from Thayer and Kens l s r 1973) and 3 (from Toetz 1977), a l t h o u g h i n many of t h e s t u d i e s r e p o r t e d , NTA was added t o t h e i n f l u e n t t o a c h i e v e a d e s i r e d c o n c e n t r a t i o n . E f f l u e n t c o n c e n t r a t i o n s which a r e a l s o summarized i n Tab les .l and 2 , were h i g h l y v a r i a b l e (0.01 - 11.7 mg R-') and depend on many f a c t o r s , e .g . t y p e of t r e a t m e n t , i n f l u e n t c o n c e n t r a t i o n , temperature e t c . , a s p r e v i o u s l y d i s c u s s e d .

DOMESTI\C WATER S U P P L I E S

Two major programs des igned t o monitor NTA c o n c e n t r a t i o n s i n d r i n k i n g w a t e r have been under taken. The f i r s t was c a r r i e d o u t i n S u f f o l k and Norfolk Count ies , New York, i n t h e w i n t e r s of 1970 and 1971, and i s summarized by Thayer and Kens le r (1973). Of 279 samples t aken from 129 households , s i x had d e t e c t a b l e NTA l e v e l s of between 25 and 125 pg R- ' , t h r e e of t h e s e from w e l l wa te r s u p p l i e s , and t h r e e from p u b l i c u t i l i t i e s .

The second s tudy , which w a s much more widespread, w a s c a r r i e d o u t i n Canada by P r o c t e r and Gamble and t h e Canada Department of t h e Environment from October 1971 t o . 1 9 7 5 , and inc luded sampling .of wastewater t r ea tment p l a n t i n f l u e n t s and e f f l u e n t s , r i v e r s , s t r eams and l a k e s , and groundwater, a s w e l l a s domestic s u p p l i e s . R e s u l t s have been summarized i n d e t a i l by Matheson (1976) and Brownridge (1977) and w i l l be on ly b r i e f l y o u t l i n e d h e r e .

The d r i n k i n g wa te r s u p p l i e s of 13 towns and smal l c i t i e s (popu la t ion 1,900-64,000) i n s o u t h e r n O n t a r i o were sampled monthly f o r 30 months. The c o n c e n t r a t i o n of NTA was l e s s than 60 pg R-' i n a l l samples, and most (96%) con ta ined l e s s than 25 pg R-' (Table 3 ) . Metal l e v e l s (Cu, C r , Cd, Pb, Zn, N i , A l , Fe, Na) were a l s o monitored, and whi le l e v e l s were ,low, no measurements were made p r i o r t o NTA usage.

I n a d d i t i o n , s u r v e y s of d r i n k i n g water i n o t h e r p a r t s of Canada have been c a r r i e d o u t and r e s u l t s a r e summarized i n Table 4 . A t o t a l of 698

samples were analyzed, of which 33 had NTA concent ra t ions between 10 and 80 pg R-'.

LAKES AND R I V E R S

Some of t h e l a k e s and r i v e r s surveyed f o r NTA a s p a r t of t h e Canadian monitoring program a r e included i n t h e d i scuss ion of Domestic Water Suppl ies (above) a s they served a s domestic water supp l i e s f o r towns o r c i t i e s . o the r s p e c i a l c a se s (Hamilton Harbour, western Lake Ontar io , S t . Lawrence River) a r e discussed i n Spec ia l S tud i e s (below). In addi t ion : r i v e r water upstream and downstream from 13 towns and c i t i e s i n southern Ontar io was monitored by Proc te r and Gamble (Brownridge 1977) f o r 39 months. Median concent ra t ions i n t h e streams above t h e wastewater o u t f a l l s of t h e c i t i e s ranged from 3 t o 28 pg R-' i n t h e period when NTA made up ,6% o f , de te rgent composition, and from < 1 t o 38 pg R-' when de t e rgen t s averaged 15% NTA. In genera l , medians were no t higher i n t h e l a t t e r period. Below t h e wastewater o u t f a l l s , medians ranged from 3 t o 61 pg R-l t 6% NTA and 1 t o 123 pg R-l a t t h e 15% l e v e l , with 1 0 of 1 3 l o c a t i o n s showing increases i n t h e second per iod. Of t h e s e 3 were s i g n i f i c a n t l y d i f f e r e n t a t t he 95% p robab i l i t y l e v e l .

GROUNDWATER

A discuss ion of t h e degradat ion o f L N T A i n groundwater i s given i n an e a r l i e r s ec t i on , and a summary of NTA l e v e l s i n groundwater used f o r domestic water supp l i e s i n Canada has been proyided i n t h e d i scuss ion of Domestic Water Suppl ies (above). Only 1 of 78 samples had a d e t e c t a b l e concent ra t ion (50 pg R-') , and only on one occasion was t h i s s i te found t o be contaminated.

Furthermore, of t h e 13 towns whose dr ink ing waters were ex tens ive ly s tud ied by P roc t e r and Gamble, s i x used groundwater a s a source. Resul t s a r e summarized i n Table 3. I

, In add i t i on , o t h e r s p e c i a l s t u d i e s have been c a r r i e d out t o determine NTA concent ra t ions under condi t ions most l i k e l y t o lead t o contamination of groundwater (Matheson, 1977) : . .

a ) Finch, Ontar io - 21 of 68 w e l l s s i t u a t e d i n shallow overburden (10- 14 f e e t of s o i l on bedrock) had 15 t o 250 pg R-' NTA. Some very high va lues were subsequently found (up t o 1.7 mg R-' , but high concent ra t ions coincided w i t h b a c t e r i a l contamination.

I

b) Stonewall , Manitoba - 1 of 28 'wells was contaminated with NTA (290 pg R-').

C) Brandon, a n i t b b a - 4 of 6 w e l l s had measurable NTA concent ra t ions (13-82 pg R-') , a l l again showing evidence of s a n i t a r y po l lu t i on .

In summary, NTA l e v e l s i n groundwater may be s u b s t a n t i a l , p a r t i c u l a r l y i n c a s e s where contamination by domestic sewage is ev ident . Small, p r i v a t e l y cons t ruc ted w e l l s a r e more l i k e l y t o be contaminated than municipal groundwater sources.

SPECIAL STUDIES

Three a r e a s of s p e c i a l i n t e r e s t have been s tud ied i n Canada a s p a r t of t h e n a t i o n a l monitoring program (summarized by Matheson 1976):

a ) Hamilton Harbour - t h e r e l a t i v e l y small (21 km2, 2.8 x 10' m3), i s o l a t e d western-most por t ion of Lake Ontar io r ece ives wastewater e f f l u e n t from populat ion of 400,000. ~ u r i n ~ t h e time when Hamilton wastewater rece'ived only primary t reatment , t h e mean NTA concentra- t i o n of t h e e f f l u e n t was 0.8 mg R-' which was subsequently reduced

- t o 0.25 mg R-' a f t e r secondary t reatment came i n t o e f f e c t . Monthly monitoring of seven s t a t i o n s from December 1971 t o February 1975

, allowed t h e following important conclusions t o be drawn: . ,

, *

1 ) t h e concent ra t ion i n t h e harbour, d id no t change s i g n i f i c a n t l y a f t e r a reduct ibn i n t h e input r a t e ;

2) t h e concent ra t ions i n win te r were no h igher than those i n summer ; \

3) average concent ra t ion a t s i x s t a t i o n s remote from t h e o u t f a l l was 15 pi: R e ' ; ngarer t h e o u t f a l l i t was 60 pg R - I ; and

4) degradat ion of NTAS'must have occurred i n t h e harbour i t s e l f a s w e l l a s i n t h e t reatment p l a n t ; t h e concent ra t ion i n t h e harbour was, i n f a c t , about 12% of t h a t expected, based on

I

d i l u t i o n of p l an t e f f l u e n t a lone ;

b) Western Lake Ontar io - Seven open water s t a t i o n s were sampled 14 t i m e s i n 1972 and 1973 i n western Lake Ontario. P o s i t i v e va lues (10-160 pg R-') w e r e found. a t s e v e r a l l o c a t i o n s i n t h e f i r s t few months but no t t h e r e a f t e r . ' Drinking water from t e n municipal waterworks wi th i n t akes near shore had < 10 pg R-' i n 38 of 40 samples, t h e h ighes t va lue being 20 pg R-'.

c ) S t . Lawrence River - Monitoring of t h e S t . Lawrence River between Lake Ontar io and Montreal i n t h r e e months of 1973 produced no d e t e c t a b l e l e v e l s of NTA. I n t h e metropol i tan Montreal a r e a , however, samples on occasion contained up, t o 30 pg R - I . D i s t r i b u t i o n of p o s i t i v e samples could be r e l a t e d t o l o c a l discharges. Maximum concent ra t ions below Montreal were 10 pg R-'. Matheson (1976) ca l cu l a t ed t h e e n t i r e undegraded NTA usa e of metropol i tan Montreal would r e s u l t i n a l e v e l of only 30 pg R-' by d i l u t i o n alone: t h u s , t h e r e s u l t s of t h i s survey a r e no t su rp r i s ing .

REFERENCES

Brownridge, F.A. 1977. Report f o r t he I J C Task Force on Ecological E f f e c t s of Non-Phosphate Detergent Builders.

Can. Dept. Nat. H e a l t h Welfare. 1972,. Review of T o x i c i t y and P o t e n t i a l B i o l o g i c a l E f f e c t s o f . NTA. Dept. of Na t iona l Heal th and Welfare , Ottawa, 283 PP

Eps te in , S.S. 1972.. ' Toxico log ica l and Environmental I m p l i c a t i o n s on t h e Use of N i t r i l o t r i a c e t i c Acid a s a Detergent Bui lde r - 1. I n t . J. Environ. S t u d i e s 2:: 291-300. -

Matheson, D.H. 1977. N i t r i l o t r i a c e t i c a c i d (NTA) i n t h e Canadian Environment. S c i e n t i f i c S e r i e s No. 74. Env. Can.

Thayer, P.S. and C . J . Kensler . 1973. Cur ren t S t a t u s of t h e Environmental and Human S a f e t y Aspects of N i t r i l o t r i a c e t i c Acid (NTA). CRC C r i t i c a l Rev. i n Env. Cont ro l - 3: 375-404.

Toetz, D. W. 1977. Fa te , Transpor t and E f f e c t s of NTA i n t h e Aquatic Environ- ment. D r a f t r e p o r t , EPA.

TABLE 1 NTA CONCENTRATION I N TREATMENT PLANT INFLUENTS AND EFFLUENTS

(from Thayer and Kensler 1973)

NTA Concentra t ion (ppm) System . Study I n f l u e n t E f f l u e n t

T r i c k l i n g f i l t e r

Ac t iva ted Sludge

Sweden

Iowa

Sweden

Wisconsin

Ohio

Ohio

V i r g i n i a

Laboratory

Laboratory

Laboratory

8 1 . 5

16 4 (av. )

11-79 < 1

20 1-2.5

30 O< 3

10 (cont inuous) <1

TABLE 2 REMOVAL OF NTA BY WASTEWATER TREATMENT SYSTEMS (from Toetz) 1977

Source NTA Concen t ra t ion , mg/k

Type o f Treatment Locat ion I n f l u e n t E f f l u e n t Receiving Stream % of Removal

Thayer & Kensler (1973) Primary Canada 0.8-3.3 ND 0.02-0.04 10.9-30.1

Thayer & Kenlser (1973) Ac t iva ted Sludge Canada 2.8-5.0 0.01-1.75 0.02-0.18 21.5-82.5

Shannon, e t a l . (1974) Ac t iva ted Sludge Canada 8-20 0.3-0.9 (summer) 0-0.01 9 5 5.4-11.7 (win te r ) 0.03-0.11 4 5

Shannon (1975) Ac t iva ted Sludge Canada 0.67 0.18 2.19 0.86

huma ate, e t a l . (1970) Ac t iva ted Sludge Ohib 2 0 .2 8 0 .8

16* 4 . 0

Renn (1974) Ac t iva ted Sludge V i r g i n i a 40-50* 0.3-1.0 ND . ' 80-90

I Kle in (1974) S e p t i c Tank C a l i f o r n i a 30-60* ND ND 21.8-23.1 w

Klein (1974) I

Aerobic l a t e r a l s C a l i f o r n i a 60* 0.6-3.0 ND 95-99

Kle in (1974) Anaerobic l a t e r a l s l e s s 1 0 . 5 mg/R DO C a l i f o r n i a 60" 4 5 ND 10

Cleasby, e t a l . (1974) T r i c k l i n g f i l t e r Iowa 4-8* 0.5-2,0 ND 82-100

Thayer & Kensler (1973) T r i c k l i n g f i l t e r Canada 1.3-4.5 0.9-2.9 0.01-0.80 21 -6-65

Klein (1974) Oxidat ion ponds C a l i f o r n i a ,2-30" 0.2-3.0 75* 15 loo* 5 0

IJC (1976) Primary Canada 0.01-23 0.01-7.67' 0.005-0.063 - - Act iva ted Sludge Canada 0.01-23 0.03-8.75 0.004-0.912 - - T r i c k l i n g f i l t e r Canada 0.01-23 1.35-10.5 0.003-0.103 - - None Canada 0.01-23 ND 0.00-0.01 - -

*NTA dosed i n t o i n f l u e n t t o g ive s t a t e d l e v e l s

NOTE: ND = No d a t a -

TABLE 3 NTA CONCENTRATION IN DRINKING WATER IN THIRTEEN CITIES IN SOUTHERN ONTARIO

(from ~rownridge 1977)

Frequency Distribution of NTA Concentrations in Drinking Waters

NTA Concentrations % of Samples having less than Stated Value P ~ I E Rivers Wells Lakes

1 24 59 34

TABLE 4

NTA LEVELS MEASURED I N DRINKING WATER SUPPLIES I N CANADA (da ta from Matheson 1976)

No. of Samples with Detectable Source of Locat ion Levels of NTA Water Supply

B r i t i s h Columbia 1 sample of 126 (60 pg R-l)

Alberta 2 of 26 (10-20 pg R-l)

Saskatchewan 4 of 26 (10-20 pg R-')

Manitoba 1 of 28 (20 pg R - ~ )

Ontario

Quebec

Mar it imes

Campbell River

S. Saskatchewan River

r i v e r s

Burntwood River

Great Lakes - S t . Lawrence River - Ottawa River

small r i v e r s

small l akes

groundwater

Richel ieu River

Yamasha River

small l akes

small r i v e r s

groundwater

APPENDIX

FIRST MEETING

OF THE

GREAT LAKES RESEARCH ADVISORY BOARD'S

TASK FORCE ON

Held a t t h e Ai rpor t Hi l ton Hote l (Dorval) Montreal, Quebec December 6, 1976

Members

J. Shapiro P. J. Chapman R. Dick P. Di l lon G. Leduc C. R. O'Melia

Univers i ty of M i ~ e s o t a Univers i ty of Minnesota Univers i ty of Delaware Ontar io Minis t ry of t h e Environment Concordia Univers i ty Univers i ty of North Carol ina

Representing Soap & Detergent Assoc.

F. A. Brownridge F. Kennedy ,

Proc t e r and Gamble Co. Cont inental O i l Company

Representing Federa l Governments

W. Lowe Canada Centre f o r Inland Waters

Secre ta ry

D. R. Rosenberger I n t e r n a t i o n a l J o i n t Commission, Great Lakes Regional Off ice

SECOND MEETING

OF THE

RESEARCH ADVISORY BOARD'S

TASK FORCE ON

ECOLOGICAL EFFECTS ON NON-PHOSPHATE DETERGENT BUILDERS

Held at the Americana Inn Cincinnati, Ohio February 8-9, 1977

Members

J. C. P.' G. R. P. W. W. F. F.

Shapiro R. OfMelia Di llon Leduc Dick J. Chapman E. Lowe J . Lacy A. Brownridge Kennedy

Participants

Amirsakis Gledhill E. Coleridge Blitzer Gale R. Duthie E. Hudson N. Sturm H. Dexter W. Rees Mones Lamber t i Boroman R. Sunoff E. Hall H. Wiers H. Scott E. Winters Maki F. Holman Huber W. Beck G. Scharpf

Secretary

D. R. Rosenberger

University of Minnesota University of North Carolina Ontario Ministry of Environment Concordia University University of Delaware University of Minnesota Canada Centre for Inland Waters Environmental Protection Agency Procter & Gamble continental Oil Company -

W. R. Grace Monsanto Company FMC Corporation Ethyl Corporation Fisheries and the Environment Procter & Gamble Co. Colgate Palmolive Co. Procter & Gamble Co. Hooker Chemicals & Plastics Corp. Ethyl Corporation Lever Brothers Lever Brothers soap and Detergent Association Soap and Detergent Association Procter & Gamble Co. Procter & Gamble Co. Procter & Gamble Co. Procter & Gamble Co. Procter & Gamble Co. Procter & Gamble Co. W. R. Grace Procter & Gamble Co. Monsanto Company

International Joint Commission Great Lakes Regional Office

-84-

THIRD MEETING

OF THE

GREAT LAKES RESEARCH ADVISORY BOARD'S

TASK FORCE ON

ECOLOGICAL EFFECTS OF NON-PHOSPHATE DETERGENT BUILDERS

Held at the Sheraton O'Hare Hotel Chicago, Illinois

February 21-22, 1977

Members

J. Shapiro University of Minnesota P. J. Chapman University of Minnesota P. Dillon Ontario Ministry of the Environment G. Leduc Concordia University C. R. O'Xelia University of North Carolina R. Dick University of Delaware


F. A. Brownridge F. Kennedy

Procter and Gamble Co. Continental Oil Company

Representing Federal Government

W. E. Lowe W. J. Lacy

Participants

H. E. Allen J. Amirsakis J. W. Arthur L. Beck S. M. Blitzer T. L. Bott A. Bourquin Y. K. Chau F. Coglianese S. E. Coleridge T. Dexter W. Gledhill G. F. Graham R. D. Hamilton R. Kimerle R. A. Larson D. Lean H. D. Leth

Canada Centre for Inland Waters Environmental Protection Agency

Illinois Institute of Technology W. R. Grace & Co. Environmental Protection Agency Procter and Gamble Co. Ethyl Corp. Stroud Water Resources Center Environmental Protection Agency Canada Centre for Inland Waters Miles Laboratory FMC Hooker Chemicals Monsanto Company Amway Corp. Freshwater Institute Monsanto Co. Stroud Water Resources Center Canada Centre for Inland Waters W. R. Grace & Company

Participants Cont'd

A. W. Maki T. Maloney E. Mones F. Morel R. Patrick W. M. Sanders E. F. Shannon R. D. Swisher C. Stovic J. M. Tiedje J. M. Weaver R. E. Winters C. R. Woodiwiss

Procter & Gamble Environmental Protection Agency Lever Brothers Massachusetts Institute of Technology Academy of Natural Science Environmental Protection Agency Black Crow & Eloness Inc. Kirkwood, Mo. W. R. Grace & Co. Michigan State University Lever Brothers Co. Procter & Gamble Co. Procter & Gamble Co.

FOURTH MEETING

OF THE


TASK FORCE ON

ECOLOGICAL EFFECTS ON NON-PHOSPHATE DETERGENT BUILDERS

Held a t t h e Cambridge Motor Inn Toronto, Ontario March 14, 1977

Members

J. Shapiro P. J. Chapman P. Di l lon G. Leduc R. Dick C. R. O'Melia

Universi ty of Minnesota Univers i ty of Minnesota Ontario MiniFstry of t he Environment Concordia Univers i ty Univers i ty of Delaware Univers i ty of North Carol ina


F. A. Brownridge P roc t e r and Gamble Corp. F. Kennedy Continental O i l Company

Secre ta ry

D. R. Rosenberger I n t e r n a t i o n a l J o i n t Commission Great Lakes Regional Off ice

FIFTH MEETING

OF THE


TASK FORCE ON

ECOLOGICAL EFFECTS OF NON-PHOSPHATE DETERGENT BUILDERS

Held a t t h e I J C Great Lakes Regional Off ice

Apr i l 19, 1978

Members

J: Shapiro P. J. Chapman P. Di l lon G. Leduc R. Dick C. R. O'Melia

Universi ty of Minnesota Universi ty of Minnesota Ontar io Ministry of t h e Environment Concordia Universi ty Univers i ty of Delaware Universi ty of North Carol ina ,

Representing Soap 6 Detergent Assoc.

F. A. Brownridge Proc ter and Gamble Corp. F. Kennedy Continental O i l Company

I

Secre ta ry

D. R. ~ o s e n b e r ~ e r I n t e r n a t i o n a l J o i n t Commission Great Lakes Regional Off ice

TERMS OF REFERENCE

INTERNATIONAL JOINT COMMISSION - RESEARCH ADVISORY BOARD

TASK FORCE ON ECOLOGICAL EFFECTS OF NON-PHOSPHATE DETERGENT BUILDERS

Eutrophication.of the Great Lakes remains one of the serious problems to which the Great Lakes Water Quality Agreement is addressed. Phosphorus has been acknowledged to be the nutrient limiting algal growth and, for this reason, programs to control the input of phosphorus are presented in Annex 2 of the Agreement.

A significant proportion of the phosphorus entering the Great Lakes is due to phosphates discharged from municipal sewage treatment plants. There-. fore, the Agreement specifies that waste treatment facilities shall be constructed and operated to remove phosphorus from municipal sewage.

The Annual Report of the Water Quality Board and the Final Report of the Upper Lakes Reference Group both presented at the July 1976 meeting of the International Joint Commission addressed the questions of phosphorus discharge from municipal wastewater treatment plants. As a significant proportion of the phosphorus in sewage arises from detergent usage both reports recommend limitations on the phosphorus content of detergents.

As such a ban or limitation on phosphates, in detergents will require alternative builder compounds and/or levels to be utilized, relevent ecological information regarding the effects of such materials must be gathered and interpreted to permit the Commission to evaluate the potential consequences of such detergent reformulation based upon the best available scientific information. To provide this information the Research Advisory Board should review the information on ecological effects of non-phosphate detergent builders in present use. :

To provide this information the Task Force will:

1. Review and summarize the research findings on detergent builder alternatives to phosphate.

2. Identify areas of research in which there are gaps in our knowledge relative to the effects of potential alternate builder materials.

3. Report to the Research Advisory Board on the adequacy of studies pertaining to these materials and identify both these materials which, based on present information, are judged to be ecologically acceptable and those which are not. .

The Task Force will consider:

1. Expected discharge levels and the extent to which ambient concentration will be increased.

2. Effects on the sewage treatment process.

3. Biodegradation and physicochemical transformations.

4. Expected or known degradation products with special reference to the more stable ones.

5. Toxicity to biota.

6. Chelation of trace metals and mobilization of metals.

When used in appreciable quantities., all types of detergent builders ,

can potentially effect the ecosystem of the Great Lakes. Upon completionr of its review of the ecological effects of non-phosphate detergent builders, the Task Force will compare the types and gxtent of impacts expected with the use of non-phosphate builders to that of phosphorus.

I

MEMBERSHIP

Task Force members should include an aquatic biologist, an aquatic toxicologist, an environmental chemist, a modeler, and a waste treatment engineer. To provide necessary liaison with the industry a non-voting member should represent the U.S. and the Canadian Soap and Detergent Associations. Persons selected to serve on the Task Force should be knowledgeable regarding both the open literature and the report literature. To provide the most adequate evaluation and report, scientific information input should be solicited from both government and industry.

TASK FORCE MEMBERS

Professor Joseph Shapiro (Chairman) Limnological Research Center University of Minnesota Minneapolis, Minnesota

Dr. Peter J. Chapman Department of Biochemistry University of Minnesota St. Paul, Minnesota

Dr. Richard Dick J. P. Ripley Prof.. of Engineering Cornell University Ithaca; New York

Dr. Peter Dillon Water Resources Branch Ontario Ministry of the Environment Rexdale, Ontario

Dr. G6rard Leduc (Until Sept. 1977) Associate Professor Department of Biological Sciences Concordia University Montreal, Quebec

Dr. Charles R. O'Melia Professor of Environmental Sciences

and Engineering University of North Carolina Chapel Hill, North Carolina

Dr. Anne Spacie (Effective Oct. 1977) Department of Fisheries and

Natural Resources Purdue University West Lafayette, Indiana

Mr. David R. Rosenberger (Secretary) International Joint Commission Great Lakes Regional Office 100 Ouellette Avenue Windsor, Ontario

LIAISON MEMBERS

Representing Soap and Detergent Association of Canada

Mr. F. Alan Brownridge Manager Professional and Regulatory Services Procter and Gamble Co. of Canada Ltd. Hamilton, Ontario

Representing Soap and Detergent Association, New York

Dr. Flynt Kennedy Manager, Chemical Research Research and Development Department Continental Oil Company Ponca City, Oklahoma

Representing Fisheries and Environment Dr. W. E. Lowe (Until March 1978) Research Subventions Office Environment Canada Ottawa, Ontario

Dr. K. Kaiser (Effective March 1978) Canada Centre for Inland Waters Burlington, Ontario

Representing Environmental Protection , Agency

Dr. W'. J. Lacy (Until Dee. 1977) Principle Engineering-Science Advisor Office of Research and Development U. S. *Environmental Protection Agency Chicago, Illinois

Dr. W. Fairless (Effective Dee. 1977) Deputy Director, Central Region Lab. U. S. Environmental Proection Agency Chicago, Illinois

Ms. Justine Welch (Effective Dee. 1977) Hazard Assessment Group Office of Toxic Substances U. S. Environmental Protection Agency Washington, D. C.

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