ISWSCR-429 (1)

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    ILENR/RE-WR-87/1

    WASTES FROM WATERTREATMENT PLANTS:

    LITERATURE REVIEW, RESULTS

    OF AN ILLINOIS SURVEY

    AND EFFECTS OF ALUM SLUDGE

    APPLICATION TO CROPLAND

    James R. Thompson, Governor

    Don Etchison, Director

    Printed by the Authority of the State of Illinois

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    ILENR/RE-WR-87/18Printed: November 1987Contract: WR 4Project: 86/2009SWS Contract Report 429

    WASTES FROM WATER TREATMENT PLANTS:

    LITERATURE REVIEW, RESULTS OF AN ILLINOIS SURVEY

    AND EFFECTS OF ALUM SLUDGE APPLICATION TO CROPLAND

    Prepared by:

    Illinois State Water SurveyWater Quality Section

    P.O. Box 697Peoria, IL 61652

    Principal Investigators:

    S. D. LinC. D. Green

    James R. Thompson, GovernorState of Illinois

    Don Etchison, DirectorIllinois Department of

    Energy and Natural Resources

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    NOTE

    This report has been reviewed by the Illinois Department of Energy andand Natural Resources (ENR) and approved for publication. Statements andcomments expressed herein do not necessarily reflect the view of theDepartment. Additional copies of this report are available by callingthe ENR Clearinghouse at 800/252-8955 (within Illinois) or 217/785-2800(outside Illinois).

    Printed by the Authority of the State of Illinois.

    Date Printed: November 1987

    Quantity Printed: 300

    Referenced Printing Order: IS 3

    One of a series of research publications published since 1975. Thisseries includes the following categories and are color coded as follows:

    Energy Resources - RE-ER - Red

    Water Resources - RE-WR - Blue

    Air Quality - RE-AQ - Green

    Environmental Health - RE-EH - Grey

    Economic Analysis - RE-EA - Brown

    Information Services - RE-IS - Yellow

    Insect Pests - RE-IP - Purple

    Illinois Department of Energy and Natural ResourcesEnergy and Environmental Affairs Division

    325 W. Adams, Room 300Springfield, Illinois 62704-1892

    217/785-2800

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    CONTENTS

    Abst ract

    I nt roduct i on. ,Background

    Obj ecti ves and scope of st udyAcknowl edgments

    Li t erat ure revi ewWastes f romwater t reatment pl ant s

    Previ ous report s . . . .Sources and t ypes of wast e.Wast e character i st i cs

    Pre- sedi ment at i on sl udgeCoagul ant sl udgeLi me sl udgeI ron and manganese sl udgesBr i ne wastesFi l t er backwash wastewat er . . . .Granul ar act i vated carbon wastesDi at omi te f i l t er sl udgeSl udge f romsal i ne wat er conversi on

    Management of sl udgeMi ni mi zi ng sl udge product i on

    Chemi cal conservat i onDi rect f i l tr ati onRecycl i ng .Chemi cal subst i t ut i onChemi cal recovery

    Al um recovery

    Recal ci ni ng. . . .Magnesi um recovery

    Wast e treatmentCo- t reatmentPre- t reat ment

    Fl ow equal i zat i onSol i ds separat i on

    Thi ckeni ngNon- mechani cal dewateri ng

    Lagooni ngDryi ng bedsFreezi ng and t hawi ng ,

    Chemi cal condi t i oni ngMechani cal dewat eri ng . . . .

    Cent r i f ugat i onVacuum f i l t rat i onPressure f i l t rat i onBel t f i l t rat i on. .Pel l et f l occul at i on

    Ul t i mat e sl udge di sposalLand appl i cat i on

    Concl usi on .

    i i i

    PAGE

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    5556667899

    101010111111121212131414

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    CONTENTS (Cont i nued)

    Laws and r egul ati onsPL 92- 500PL 94- 580PL 93-523I mpact s of envi ronment al r egul ati ons on wat er works

    waste di sposal

    I l l i noi s si tuati onEnvi ronment al i mpact assessment s

    Envi ronment al i mpact st udi es of di rect wast e di scharget o recei vi ng streams

    Appl i cat i on of wat er pl ant sl udge to l and

    St udy 1. A survey of wat er pl ant wast esMateri al s and methodsResul t s and di scussi on

    Quest i onnai re ret urnsWat er pl ant s .Raw water sourcesWat er qual i t y

    Treat ment processesChemi cal dosageBasi n i nf ormat i on .Fi l t er i nf ormat i onSl udge product i on and character i st i csSl udge r emovalSl udge di schargeSl udge t reat mentSl udge dewateri ngSl udge f i nal di sposalSl udge di sposal l i mi t at i onsCost s

    Summar y

    St udy 2. Al umsl udge f or agr i cul t ural usesBackgroundMateri al and methods

    Al um sl udgeTest pl otsFi el d operat i onSampl e col l ect i ons

    Soi l sampl esLeaf t i ssuesHarvest ( grai ns)

    Whol e pl ant t i ssuesFi el d measurement s

    Yi el dsPl ant popul at i onSoybean hei ght

    Laborat ory anal ysesSt at i sti cal anal yses

    Resul t s and di scussi onBackground i nf ormati onEf f ects on soi l proper t i es

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    CONTENTS ( Cont i nued) PAGE

    Corn yi el d and pl ant parameters 66Soybean yi el d and pl ant parameters 66Corn grai n anal ysi s 66Soybean grai n anal ysi s 69Corn pl ant t i ssue. . 69Soybean pl ant t i ssue 69

    Leaf t i ssue 69Summar y 71Concl usi on 72

    Recommendat i ons f or f uture research 73

    References 74

    Appendi cesAppendi x A. Sl udge survey quest i onnai re 82Appendi x B. Faci l i t y i nf ormat i on . 86Appendi x C. Communi t i es purchasi ng wat er f romother f aci l i t i es 99Appendi x D. Pl ant descr i pt i ons 104Appendi x E1. Treatment processes - Sur f ace water pl ant s. . . . 112Appendi x E2. Treatment processes - Ground water pl ant s . . . . 115Appendi x F1. Chemi cal dosages 120Appendi x F2. Chemi cal dosages 124Appendi x G. Basi n i nf ormati on 131Appendi x H. Fi l t er i nf ormat i on 137Appendi x I . Basi n sl udge producti on and character i st i cs. . . . 142Appendi x J . Sl udge removal 147Appendi x K. Sl udge di scharge 152Appendi x L. Sl udge t reatment 157Appendi x M. Sl udge dewateri ng 162Appendi x N. Sl udge f i nal di sposal 164

    Appendi x O. Sl udge di sposal l i mi t at i ons, cost s, and remarks. . 167Appendi x P. Dai l y preci pi t at i on records 172Appendi x Q. Summary of weather data 173Appendi x R. Resul t s of soi l t est s

    R1. Tot al sol i ds 174R2. Organi c matter 174R3. Moi st ure content 175R4. Speci f i c gravi ty 175R5. pH 176R6. Aci di ty 176R7. Cati on exchange capaci t y 177R8. Ammoni a ni t rogen 177R9. Ni t rate ni t rogen 178R10. Tot al Kj el dahl ni t rogen 178R11. Total ni t rogen 179R12. Bray P-1.................... 179R13. Tot al phosphorus 180R14. Potassi um. 180R15. Al umi num 181R16. Boron 181R17. Cadmi um 182R18. Cal ci um 182R19. Chromi um . . 183

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    CONTENTS ( Concl uded)

    R20. CopperR21. Tot al i ronR22. LeadR23. Magnesi umR24. ManganeseR25. Ni ckel

    R26. Zi ncR27. SandR28. Si l tR29. Cl ay

    Appendi x S. Crop yi el ds and pl ant parametersAppendi x T. Nut r i ent s and heavy metal s concent rat i ons i n

    grai nsAppendi x U. Nut r i ent s and heavy metal s concent rat i ons i n

    whol e pl ant sAppendi x V. Nut r i ent s and heavy metal s concent rat i ons i n

    l eaves

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    WASTES FROM WATER TREATMENT PLANTS:LI TERATURE REVI EW, RESULTS OF AN I LLI NOI S SURVEY,AND EFFECTS OF ALUM SLUDGE APPLI CATI ON TO CROPLAND

    by Shun Dar Li n and C. Davi d Green

    ABSTRACT

    The obj ecti ves of t hi s st udy were t o updat e i nf ormati on on thecharact eri st i cs and management of wast es f rom water t reat ment pl ant s and toassess t he benef i t s and r i sks of al um sl udge appl i cat i on to cropl and. Thereport has t hree maj or sect i ons: a l i t erature revi ew, a summary of resul t sof a survey of I l l i noi s wat er pl ant wast es, and a di scussi on of f i ndi ngsf roma study of al umsl udge for agr i cul t ural uses.

    The l i t erat ure survey addresses characteri st i cs and management ofsl udge. I t di scusses background i nf ormat i on on sources and t ypes of wast es,

    "and wast e character i st i cs of coagul ant sl udge, l i me sl udge, i ron andmanganese sl udge, br i ne wast es, f i l t er wash wast ewat er , di at omi t e f i l t ersl udge, and sl udge f romsal i ne water conversi on.

    Mi ni mi zi ng sl udge product i on can be achi eved by chemi cal conservat i on,di rect f i l t rat i on, recycl i ng, chemi cal subst i t ut i on, and chemi cal recovery.Methods of wast e t reat ment are co- t reat ment wi t h sewage t reat ment ,pre- t reat ment , and sol i ds dewat er i ng. Pre- t reat ment i ncl udes f l owequal i zat i on, sol i ds separat i on, and t hi ckeni ng. Dewat er i ng can be achi evednon- mechani cal l y ( l agooni ng, dryi ng beds, f reezi ng and thawi ng, and chemi calcondi t i oni ng) and mechani cal l y (cent r i f ugat i on; vacuum, pressure, and bel tf i l t rat i on; and pel l et f l occul at i on) . Land appl i cat i on i s usual l y used asan ul t i mate sl udge di sposal met hod.

    The l i t erature revi ew sect i on al so di scusses l aws and regul at i ons (PL92- 500, PL 94- 580, PL 93- 523) regardi ng waste di sposal f romwat er t reat mentpl ant s, i mpacts of envi ronment al r egul at i ons on water pl ant wast e di sposal ,envi ronment al i mpact st udi es of di rect wast e di scharge to recei vi ng st reams,and wat er pl ant sl udge l and appl i cat i ons.

    To obtai n i nf or mat i on about I l l i noi s wat er pl ant sl udgecharacter i st i cs, 456 sl udge quest i onnai res were sent t o wat er pl antmanagers, and 280 (61. 4%) responses were recei ved. The quest i onnai recovered background i nf ormati on on pl ant operati ons and sl udge. Wast es f romI l l i noi s wat er pl ant s are mai nl y al um sl udge and l i me sl udge. Fl ushi ng i s

    t he most common method f or removi ng basi n sl udge f rom surf ace water pl ant s;whi l e bl ow- down and conti nuous removal are used most by ground water pl ant s.

    The maj ori t y of pl ant s ( 70% of surf ace and 90% of ground water pl ant s)di scharge the wast es to l agoons and t o sani tary sewers f or t r eat ment . Fort ypercent of sur f ace wat er pl ant s and 55% of ground wat er pl ant s ul t i mat el ydi scharge t hei r sl udge t o l andf i l l s, most of whi ch are ut i l i t y- owned. Theannual cost of sl udge treat ment f or the sur f ace water pl ant s averages $ 0. 90per capi t a.

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    The resul t s of al um sl udge appl i cat i on t o agr i cul t ural l and i ndi catethat soi l t est ( 29 par amet er s) l evel s di d not change si gni f i cant l y f romt heappl i cat i on of al umsl udge t o ei t her corn or soybean t est pl ot s. There weresome di f f erences among the sampl i ng dates f or each pl ot .

    The resul t s of a shor t - t erm st udy (Apr i l t hrough Oct ober 1986) showedt hat corn yi el ds i n t he 2. 5 and 10 t / a pl ot s were si gni f i cant l y l ower thani n t he 0 and 20 t/ a pl ot s. Corn yi el ds wer e di rectl y rel at ed t o corn pl antpopul at i ons. The pl ant popul at i on and corn yi el d at t he hi ghest sl udgeappl i cat i on rat e ( 20 t / a) showed no di f f erence f rom t hat of t he cont rolpl ot s. The reduct i on of corn yi el d at t he l ower rat es coul d not bepi npoi nt ed as bei ng caused by the appl i cat i on of sl udge. Soybean yi el ds andsoybean pl ant parameters showed no adverse i mpact due t o al um sl udgeappl i cat i ons.

    Nut r i ent s and heavy met al s anal yses (11 - 16 par ameters) f or gr ai ns,whol e pl ant s, and l eaves of bot h crops showed i nsi gni f i cant ef f ect s f romt headdi t i on of al um sl udge. I t i s concl uded that the appl i cat i on of al umsl udge t o f arml and had nei t her benef i ci al nor adverse ef f ect s on soi l s andcrops.

    I NTRODUCTI ON

    Background

    Most wat er t reat ment pl ant s (especi al l y l arge pl ant s) empl oycoagul at i on, sedi ment at i on, and f i l t rat i on processes f or wat er pur i f i cat i on.

    The maj or sources of wast es are t he sedi ment ati on basi ns and f i l t erbackwashes. Al um coagul at i on sl udges, whi ch are hi gh i n gel at i nous met alhydroxi des, compr i se l arge quant i t i es of smal l par t i cl es. These are among

    the most di f f i cul t sl udges t o handl e because of t hei r l ow set t l i ng rat e, l owpermeabi l i t y t o wat er , and thi xot ropi c characteri st i cs.

    General l y, about 5% of t he tr eat ed wat er i s used f or washi ng f i l t er s.Vol ume reduct i on of backwashes and recycl i ng of washwater t o t he pl anti nf l uent can reduce wast e product i on and cut cost s.

    I n the case of t reat ment pl ant s t hat remove i r on and manganese throughaerat i on or pot assi um permanganat e oxi dat i on, di sposal of sl udge torecei vi ng waters may cause probl ems such as water di scol orati on anddest ruct i on of aquat i c l i f e. Treat ment pl ant s t hat use an i on exchangesof t eni ng process have br i ne wastes (hi gh sal t s) whi ch become cr i t i caldi sposal probl ems, especi al l y when t he sl udge has a hi gh manganese cont ent .

    The sal t s cannot readi l y be recovered or removed f rom t he wast es. Br i newast es are al most i mpossi bl e to t r eat .

    For merl y, wastes f rom wat er t reat ment pl ant s were returned to thei ror i gi nal source or di scharged t o nearby recei vi ng wat er . I l l i noi s l aws andregul at i ons now consi der waste di scharged di rect l y f rom wat er t reat mentpl ant s t o recei vi ng wat er as a pol l ut ant . Al l wast es have t o be t reat ed t oan accept abl e l evel pr i or t o t hei r rel ease i nt o the envi r onment , and wat ert reat ment pl ant wastes are no except i on. However, occasi onal l y asi t e- speci f i c var i ance f or di r ect di scharge may be grant ed by t he pol l ut i on

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    cont rol aut hor i t i es. I n t hese cases, t reat ment of wat er pl ant wast es i s notnecessary bef ore f i nal di sposal .

    , Many water t reatment pl ant s do not have adequat e f aci l i t i es t oi nvest i gat e the quant i t y of wast e produced, i t s character i st i cs andt reat abi l i t y, and appropr i at e wast e di sposal pract i ces. Met hods f orassessi ng waste product i on have not been wel l - def i ned, and t he composi t i onof wast es has" scarcel y been reported i n t he l i t erat ure. Very l i t t l e

    research has been conducted on t he ef f ects of coagul ant and l i me sl udgesappl i ed to f arml ands.

    Obj ecti ves and Scope of St udy

    Thi s st udy had t hree purposes. A l i t erature revi ew was conducted t oobt ai n i nf ormat i on regardi ng the quant i t y and qual i t y of wat er pl ant wast es,methods of di sposal , envi ronment al i mpacts of wast e di sposal , and i mpacts onagr i cul t ural l ands and cr ops. Study 1 was desi gned t o obt ai n and updat ei nf ormat i on on al l t ypes of wast es generated by wat er t reat ment f aci l i t i esi n I l l i noi s. St udy 2 was conducted t o assess t he benef i t s and r i sks ofappl yi ng al umsl udge to f arml and to grow corn and soybeans. '

    The scope of thi s st udy was t o:

    1. Conduct a revi ew of l i t erat ure on wat er t reat ment pl antwast es wi t h respect t o:

    a. def i ni ng the characteri st i cs of wast esb. assessi ng the envi ronment al i mpacts of cur rent

    waste di sposal pract i cesc. obt ai ni ng i nf ormat i on regardi ng t he i mpact of wat er

    pl ant wast es on l and and veget at i on, i f avai l abl e

    2. Conduct a quest i onnai re survey pert ai ni ng t o thecharacter i st i cs, t r eat ment , and di sposal of wast es f romsurf ace and ground- water t reatment pl ant s i n I l l i noi s,i ncl udi ng:

    a. the quant i t y and composi t i on of resi dues producedby water t reatment pl ants

    b. methods of handl i ng and t reat ment of al l t ypesof wast es and resi dues

    c. t he ul t i mate sl udge di sposal methods usedd. t he cost s of sl udge t reat ment and di sposal , i f

    avai l abl e

    3. Conduct a f i el d study on t he appl i cat i on of al umwat er pl antsl udge t o grow corn and soybeans.

    Acknowl edgments

    Thi s proj ect was f ul l y sponsored by t he I l l i noi s Depart ment of Energyand Natural Resources ( ENR) . The cooperat i on of Tom Heavi si des, proj ectmanager at ENR, and Mi chael Mai nz of t he Uni versi t y of I l l i noi s i s

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    gratef ul l y acknowl edged. Mai l i ng l i st s of wat er t reat ment pl ant s i nI l l i noi s were provi ded by J ames Ki rk of t he Wat er Survey; Rober t Sasman,Water Survey ( and Secret ary of t he I l l i noi s Sect i on, Amer i can Wat er WorksAssoci at i on) ; and J ayant Kadaki a of t he I l l i noi s Envi ronment al Pr ot ect i onAgency.

    Thi s st udy was conducted under t he general admi ni st rat i ve di rect i on ofRi chard Schi cht , Acti ng Chi ef of t he I l l i noi s St at e Wat er Survey, and Dr .

    Raman Raman, Head of t he Water Qual i t y Sect i on. The aut hors are grateful t oother members of t he Water Survey who part i ci pated. Dana Shackl ef ord, Bi l lCook, and Davi d Hul l i nger per f ormed chemi cal anal yses. Harvey Adki nsassi sted i n al umsl udge handl i ng. Gai l Tayl or edi t ed t he repor t .

    The aut hors acknowl edge t he water ut i l i t y personnel and ci ty engi neerswho responded to the sl udge quest i onnai re.

    The f ol l owi ng persons revi ewed t he quest i onnai re f orm of the sl udgesurvey:

    Cl arence Bl anck Ameri can Water Works Servi ce Co. ,Ri chmond, I N

    Don Cal ki ns Consul t ant , CH2M, Engl ewood, COChar l es Hal t er Deput y Commi ssi oner , Ci ty of Chi cago, I LFrank Lewi s Past Chai r man, I l l i noi s Wat er Works

    Ass oc, I l l i noi s EPANancy McTi que Amer i can Wat er Works Associ at i on ( AWWA)

    Research Foundat i on, Denver, COWi l l i amH. Ri chardson Consul t ant , Past AWWA Presi dent ,

    Al vord Burdi ck & Howson, Chi cago, I LRoger Sel burg Manager , Publ i c Wat er Suppl y, I l l i noi s

    EPA, Spr i ngf i el d, I LVernon Snoeyi nk Professor of Envi ronment al Engi neer i ng,

    Uni v. of I l l i noi s, Ur bana-

    Champai gn, I LRonal d E. Zegers Di rect or , Wat er Depar t ment , El gi n, I L

    Persons who revi ewed and comment ed on the f i el d st udy pl an and st udymet hods were:

    Lester Boone Agr onomi st , Uni versi t y of I l l i noi s,Urbana-Champai gn, I L

    Wi l l i amJ . Garci a Research Chemi st , Seed Bi osynt hesi sResearch Uni t , Nor t hern Regi onalResearch Cent er , Peor i a, I L

    Rober t G. Hoef t Prof essor of Soi l Fer t i l i t y, Uni versi t y

    of I l l i noi s, Urbana- Champai gn, I LMi chael J . Mai nz Area Agronomi st , Nor t hwestern ResearchCent er , Uni versi ty of I l l i noi s,Monmout h, I L

    Ted Peck Professor of Soi l Chemi st ry, Uni versi t yof I l l i noi s, Urbana- Champai gn, I L

    Roger Sel burg Manager , Publ i c Wat er Suppl y, I l l i noi sEPA, Spr i ngf i el d, I L

    Robert Wal ker Cooperat i ve Extensi on Ser vi ce, Uni v. ofI l l i noi s, Urbana- Champai gn, I L

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    LI TERATURE REVI EW

    Wast es f romWater Treat ment Pl ant s

    Thi s l i t erature revi ew on wastes f romwater t reat ment pl ant s di scussesprevi ous l i t erature revi ews on the subj ect , sources and types of wast e,

    character i st i cs of each t ype of wast e, and waste management . Thedi scussi on of management of sl udge ( waste) covers mi ni mi zi ng sl udgeproduct i on, met hods of sl udge t reat ment , and ul t i mat e sl udge di sposal .

    Previ ous Report s

    Dur i ng t he peri od 1969 to 1981 t he Ameri can Water Works Associ at i on( AWWA) Research Foundat i on and t he AWWA Sl udge Di sposal Commi t t ee prepared aser i es of repor t s wi t h a comprehensi ve l i t erature revi ew on the nat ure andsol ut i ons of wat er t reat ment pl ant wast e di sposal probl ems. The f i rstreport , prepared by the AWWA Research Foundat i on, was di vi ded i nto fourpart s (AWWA Research Foundat i on, 1969a, 1969b, 1969c, 1970) and was ent i t l ed

    "Di sposal of Wast es f rom Wat er Treat ment Pl ant s. " The f i r st par t of t hi sreport (AWWA, 1969a) covered the st atus of research and engi neer i ngpract i ces f or t reat i ng var i ous wast es f rom wat er t reatment pl ant s. Thesecond part (AWWA, 1969b) revi ewed pl ant operati ons f or the di sposal ofvar i ous t ypes of wast es, and the regul atory aspects of di sposal . The thi rdpart ( AWWA, 1969c) descr i bed var i ous t reatment processes empl oyed and thei ref f i ci ency and degree of success, and presented cost anal yses. The l astpart (AWWA, 1970) summari zed research needs, engi neer i ng needs, pl antoperat i on needs, and regul at ory needs.

    Concur rent l y wi t h t he i ni t i al preparat i on of t he repor t by the AWWAResearch Foundati on, t he Water Resources Qual i t y Cont rol Commi t t ee of t he

    I l l i noi s Sect i on of t he AWWA conducted a survey of t he handl i ng of wastesf romwat er t reat ment pl ant s i n I l l i noi s ( Evans et al . , 1970) . Thi s ef f ortwas made to determi ne t he t ype and quant i t i es of waste produced, thecharacter i st i cs of t he wast es, and t he exi st i ng met hods of wast e di sposal i nI l l i noi s.

    I n 1972, t he AWWA Di sposal of Water Treat ment Pl ant Wast e Commi t t eepubl i shed an updated report (AWWA, 1972) . I t deal t wi t h processi ng andre- processi ng i n sl udge product i on, i . e. , sel ecti on and modi f i cat i on oft reatment processes, recl amat i on of l i me and al um, recovery of f i l t erbackwash water, processi ng of wast es to recover useful by- product s,processi ng of wast es f or di sposal , ul t i mat e di sposal , and f ut ure researchneeds.

    I n 1978, the AWWA Sl udge Di sposal Commi t t ee prepared a 2- part art i cl e(AWWA Sl udge Di sposal Commi t t ee, 1978a, 1978b) ent i t l ed "Water TreatmentPl ant Sl udge An Updat e of the St at e of the Ar t . " Par t 1 deal t wi t hregul atory requi rement s, sl udge product i on and character i st i cs, mi ni mi zi ngof wast e product i on, and European and J apanese pract i ces. Part 2 det ai l ednon- mechani cal and mechani cal methods of dewateri ng water pl ant sl udges,ul t i mate sol i ds di sposal , and research and devel opment needs. These repor t sf ocused mai nl y on coagul ant sl udges.

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    I n 1981, the AWWA Sl udge Di sposal Commi t t ee provi ded an overvi ew of theproduct i on, processi ng, and di sposal of l i me- sof t eni ng sl udges; recentt echnol ogi cal advances i n handl i ng, t r eat ment , and di sposal of sof t eni ngsl udges; and research needs ( AWWA, 1981) .

    Sources and Types of Wast e

    A wat er t reat ment pl ant not onl y produces dr i nki ng wat er but i s al so asol i ds generat or . The resi dues ( sol i ds or wast es) come pr i nci pal l y f romcl ar i f i er basi ns and f i l t er backwashes. These resi dues cont ai n sol i ds whi chare der i ved f rom suspended and di ssol ved sol i ds i n t he raw water, theaddi t i on of chemi cal s, and chemi cal r eact i ons.

    Dependi ng on the treat ment process empl oyed, wast es f rom wat ert reatment pl ant s can be cl assi f i ed as al um, i r on, or pol ymer sl udge fromcoagul at i on and sedi ment at i on; l i me sl udge and br i ne wast es f rom sof t eni ng;backwash wast ewat er and spent granul ar act i vat ed carbon f r om f i l t rat i on; andwastes f rom the i ron and manganese removal pr ocess, mi cr ost rai ners, and

    di at omaceous eart h f i l t er s.

    Wast e Character i st i cs

    The amount and composi t i on of wast e produced t hrough each t reat mentprocess are unpredi ct abl e. Because of the wi de var i at i on i n raw wat erqual i t y and t reat ment operat i ons, sl udges are di f f erent i n thei rcharacter i st i cs and quant i t i es f rom t i me t o t i me wi t hi n the same t reat mentpl ant , and f rompl ant t o pl ant .

    Russel mann ( 1968) di scussed general character i st i cs of wat er pl antwast es. I n addi t i on, he addressed speci al character i st i cs of coagul at i onwast es, f i l t er backwashes, i on- exchange br i nes, and screeni ngs f rom a f ewwat er suppl i er s. He concl uded that i t i s i mpossi bl e to make general i zat i onsconcerni ng sl udge product i on i n t erms of mi l l i ons of gal l ons of watert reated because sl udge product i on i s ent i rel y dependent on raw wat erqual i t y, t he met hod of t r eat ment , and ef f i ci enci es of t he t reat mentprocesses.

    Sl udges f rom water t reat ment pl ant s may be di vi ded i nt o ei ght maj orcat egor i es ( West erhof f , 1978) : pre- sedi ment at i on sl udge, coagul ant sl udge,l i me sl udge, i ron and manganese removal sl udge, i on- exchange sl udge ( br i newast e) , act i vated carbon wast es, spent di at omaceous ear t h, and sl udge f romsal i ne wat er conversi on. These cat egor i es, as wel l as f i l t er backwash

    wastewater, are di scussed bel ow.

    Pre-Sedi ment ati on Sl udge

    Some wat er pl ant s t reat i ng hi gh- turbi di t y ' sur f ace wat er s empl oypre- sedi ment at i on pr i or to coagul at i on to reduce the sol i ds l oadi ng on thedownst ream t reat ment pr ocess. The resi dues generat ed consi st of cl ays,si l t s, sands, and ot her heavy set t l eabl e mat er i al s present i n the raw wat er .

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    Treat ment and di sposal of pre-sedi mentat i on resi dues i n and of i t sel fi s not a maj or probl em. They can be treated and di sposed of wi t h ot hersl udge. The cl eani ng cycl e of a pre- sedi ment at i on basi n i s usual l y veryl ong, 10 years or more ( West erhof f , 1978) .

    Coagul ant Sl udge

    Coagul ant sl udge i s generated by water t reat ment pl ant s usi ng met alsal t s such as al umi num sul f ate ( al um) or f er r i c chl or i de as a coagul ant t oremove t urbi di t y. The coagul ant sl udge consi st s of sol i ds removed f rom thecoagul ated water, mai nl y hydroxi de preci pi t at es f rom the coagul ant andmat er i al i n the raw water . I t may al so contai n wat er t reatment chemi calresi dual s such as pol yel ect rol ytes, powdered act i vated carbon, act i vatedcl ay, or unreacted l i me.

    Al um i s the most wi del y used pr i mary coagul ant i n the Uni ted St ates.Acti vated si l i ca, cl ay, or a var i ety of pol ymers are used as coagul ant ai ds.Al um coagul at i on sl udge may cont ai n al umi num hydr oxi de, cl ay and sand,col l oi dal matt er, mi croorgani sms i ncl udi ng al gae and pl anktons, and ot herorgani c and i norgani c matter present i n t he raw water .

    Al um sl udge cont ai ns a hi gh moi st ure cont ent ( 97 to 99. 5%) and a l owsol i ds cont ent . I t s col or var i es f roml i ght brown to bl ack dependi ng on t hecharacter i st i cs of t he source of wat er and the chemi cal s used f or t reat ment .I t i s f eat hery, bul ky, and gel at i nous. Sl udge sol i ds ar e removed f rom t hewater st reami n a set t l i ng basi n under f l ow or as f i l t er backwash wast ewat er .

    The resi dues may be di scharged di rectl y t o a recei vi ng water ( i f permi t t ed)or t o t reatment uni t s and may be al l owed to accumul ate i n sett l i ng basi nsover a l ong per i od of t i me, varyi ng f romdays t o mont hs.

    Al um sl udge general l y set t l es readi l y but does not dewater easi l y. I thas been the most di f f i cul t sl udge t o treat because of several pecul i ar

    propert i es. Al t hough al um sl udge has hi gh 5- day bi ochemi cal oxygen demand( BOD5) and chemi cal oxygen demand ( COD) , i t usual l y does not undergo act i vedecomposi t i on or promote anaer obi asi s.

    The dewater i ng character i st i c of al um sl udge, i n t erms of speci f i cr esi st ance, was measured by Gates and McDermott ( 1968) as 1 x 109 t o 4. 4 x10 secvg, whi ch i s about one order of magni t ude greater t han that ofpr i mary sewage sl udge. Nevert hel ess, Hsu and Wu (1976) cl ai med t hat t hedewater i ng proper t i es of al um sl udge were comparabl e t o t hose of sewagesl udge. Apparent l y the proper t i es of al um sl udge ar e hi ghl y var i abl e f romone pl ant t o another, and even wi t hi n the same t reatment pl ant .

    Al um sl udge has been repor ted t o have a t ot al sol i ds ( TS) cont ent of1000 to 17, 000 mg/ L ( AWWA, 1969a) , of whi ch 75 to 95% i s t otal suspendedsol i ds ( TSS) and 20 t o 35% i s vol at i l e sol i ds ( VS) . - The pH val ue rangesbetween 5 and 7 (Reh, 1978) . The B0D5 of al um sl udge ranges f rom30 t o 150mg/ L. The COD val ues are hi gh, rangi ng f rom 500 t o 15, 000 mg/ L ( AWWA,1969a) . A hi gh rati o of COD t o BOD5. ( 13: 1) was observed i n a Mi ssour i pl ant(O' Connor and Novak, 1978) .

    Usi ng spark-source mass- spect rographi c anal ysi s, Schmi t t and Hal l( 1975) character i zed al um sl udge at t he wat er t reat ment pl ant i n Oak Ri dge,

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    Tennessee. The concent rat i ons of 73 el ement s were determi ned i n sett l edal um sl udge fr om t he sedi ment at i on basi n and fr om f i l t er backwashwastewater.

    Four t een chemi cal , physi cal , and bi ol ogi cal paramet ers were measuredi n t he al umsl udge f romthe cl ar i f i er bl ow- downs at Cent r al i a, I l l i noi s ( Li nand Gr een, 1987) . The raw water source for t hi s communi t y i s a 286- ha( 707- acre) l ake. The annual val ues of t he bl ow- downs based on bi weekl y

    observat i ons are as f ol l ows:

    Geometr i cParameter mean Parameter Average

    TSS, r ag/ L 2800 VSS, mg/ L 750Tur bi di t y, NTU 2000 Set . sol i ds, mg/ L 380Sul f ate, mg/ L 76 Di ssol ved oxygen, mg/ L 8. 8

    T. i r on, mg/ L 58 Temper ature, C 15. 7T. al umi num, mg/ L 240 pH ( medi an) 6. 6Fecal col i f or m/ 100 mL 5 T. al kal i ni t y,Di ssol ved sol i ds, mg/ L 215 mg/ L as CaCO3 95

    B0D5, mg/ L 29

    Set t l i ng basi n al um sl udges cont ai n ext remel y hi gh concent r at i ons ofal umi num and i ron. The observed val ues at t hree water t reat ment pl ant s i nI l l i noi s, whi ch der i ve thei r raw wat er suppl i es f romstr eams and ri ver s, areas f ol l ows (Evans et al . , 1979, 1982; Li n et al . , 1984) :

    Al umi num, mg/ kg I r on, mg/ kgPont i ac 1, 000 - 134, 000 13, 000 - 114, 000Al t on 39, 300 - 55, 000 33, 000 - 41, 000East St . Loui s 13, 900 - 61, 200 24, 600 - 44, 900

    Li me Sl udge

    Li me sl udge i s generated by water t reat ment pl ant s usi ng l i me ( CaO) orl i me/ soda ash ( Na2CO3) sof t eni ng. The quant i t y and composi t i on of t hesl udge produced f rom sof t eni ng may vary wi del y dependi ng on whether or notal um or anot her coagul ant i s used ei t her wi t h or wi t hout a coagul ant aci d.Sl udge f rom the sof teni ng of sur f ace wat er i s a hi ghl y var i abl e mat er i al .I t consi st s mai nl y of cal ci umcar bonat e (85 t o 95% total sol i ds) ; hydr oxi deof magnesi um, al umi num, and ot her met al s; cl ay and si l t par t i cl es; mi noramount s of unreacted l i me; and i norgani c and organi c mat t er. The vol ume ofsl udge produced f rom l i me or l i me- soda sof t eni ng pl ant s r anges f rom 0. 3 t o6%of t he water sof tened (AWWA, 1969b) . The sl udge general l y cont ai ns 85 t o

    95% sol i ds. Sol i ds cont ent of t he sedi ment at i on basi ns at t hese pl ant svar i es f rom2 t o 30%. Sof teni ng sl udge i s general l y whi t e i n col or , has noodor, and i s l ow i n B0D5 and COD.

    Ground wat er s t end t o be rel at i vel y f r ee of t urbi di t y, col or , andobj ect i onabl e l evel s of or gani cs. Sof t eni ng of ground wat er yi el ds arel at i vel y pure resi due contai ni ng cal ci um car bonat e, magnesi um hydr oxi de,and unreacted l i me. The char act er i st i cs of ground- wat er l i me sl udge are( Reh, 1978) : TS, 20, 000 - 100, 000 mg/ L; CaCO3, , 80 - 90%; Mg( 0H) 2, 5 t o 20%;ot her const i t uent s, 5 to 15%; and pH > 9. 0.

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    As wi th coagul ant sl udges, l i me sl udges are removed f rom t he wat erst ream i n the set t l i ng basi n underdrai n and i n f i l t er backwash wast ewat er .Resi dues f rom wat er sof teni ng are usual l y st abl e, dense, and i ner t . Li mesl udge general l y dewat ers readi l y, dependi ng on the rat i o of cal ci um ( Ca) t omagnesi um( Mg) and on the amount of gel ati nous sol i ds present i n the sl udge.

    The magnesi um cont ent pl ays an i mport ant rol e i n t he set t l eabi l i t y,compactabi l i t y, and f i l t erabi l i t y of t he sof t eni ng sl udge. The great er the

    Ca: Mg r at i o, t he easi er t he dewat er i ng. Li me sl udge wi t h a Ca: Mg rat i o ofl ess than 2 i s very di f f i cul t t o dewater, whereas a sl udge wi t h a Ca: Mgrat i o great er t han 5 wi l l dewater easi l y (AWWA, 1981) . A sl udge wi t hcal ci um hydroxi de concent rat i ons great er than 1300 mg/ L wi l l have poordewat er i ng character i st i cs and l arger sl udge vol umes.

    The sett l i ng propert i es of sl udge resul t i ng f rom the sof t eni ng ofground wat er may be poor due to t he col l oi dal f ract i on of t hi s sl udge.Sof t eni ng i s of t en suppl emented wi t h coagul at i on, whi ch generat es tworesi due f r acti ons: 1) preci pi t at es at t he bot t omof t he sof teni ng reactor s,and 2) coagul ated preci pi t ates at t he bot t om of t he sedi ment at i on basi ns.Si nce t hi s sl udge i s rel at i vel y pur e, l i me recovery by recal ci nat i on i sf easi bl e f or l arge pl ant s ( see page 14 f or a di scussi on of r ecal ci ni ng) .

    Iron and Manganese Sludges

    These t ypes of sl udges are produced by t he preci pi t ati on process f orremoval of i ron and manganese f romwater . These sl udges are red or bl ack i ncol or . The sl udge sol i ds consi st of f er r i c oxi de, manganese oxi de, andother i ron and manganese compounds.

    The quant i t y of i ron and manganese sl udges i s comparabl e to t hat ofcoagul ant or sof tened sl udge. These sl udges are general l y removed as f i l t erbackwash wast ewater.

    Br i ne Wast es

    Spent br i ne wast es come mai nl y f rom the ri nse wat er f or theregenerat i on of i on- exchange sof t eni ng uni t s usi ng sodi um zeol i t e as t heresi n. These wast es are i n aqueous sol ut i on. The vol ume of br i ne wastegenerat ed i s about 2 to 10% of the water t r eated, dependi ng on the raw wat erhardness and the operati on of t he i on- exchange uni t ( AWWA, 1969a, 1969b;O' Connor and Novak, 1978) . These wast es cont ai n ext r emel y hi ghconcent rat i ons of chl or i des of cal ci um, magnesi um, and sodi um (theregenerant ) wi t h smal l amount s of var i ous compounds of i ron and manganese.

    Br i ne wast e i s characteri zed by very hi gh chl or i des, t ot al sol i ds, and t ot aldi ssol ved sol i ds ( TDS) . Very f ew suspended sol i ds are present i n br i newastes.

    The hi gh chl ori de cont ent deri ved f romt he sal t s used f or regenerati oncauses probl ems i n the di sposal of br i ne wast es. Chl or i des cannot beremoved f rom wastewater through any i nexpensi ve method. These wast es cangeneral l y be di scharged to deep underground st rat a or oceans wi t h a permi t .

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    Fi l t er Backwash Wastewater

    Fi l t er backwash wast ewat er i s produced dur i ng the f i l t er washi ngoperat i on. Fi l t er s are washed dai l y, once every two days, or l essf requent l y. There i s usual l y a l arge vol ume of washwat er wi t h l ow sol i dscontent . The vol ume of washwater i s l arge because the backwash rate may be10 t o 20 t i mes t he f i l t rat i on r at e. For al umcoagul at i on pl ant s, t he vol umeof washwat er ranges f r om2 t o 5% of t he wat er f i l t ered.

    The composi t i on of backwash wastewater may be si mi l ar t o that ofcoagul ant sl udge, but wi t h much f i ner par t i cl es. Thi s t ype of wast ewat ernormal l y cont ai ns hydroxi des of al umi num and i r on, f i ne cl ay par t i cl es,added chemi cal s and react i on product s whi ch di d not sett l e i n t hesedi ment at i on t ank, and a smal l por t i on of f i l t er medi a and act i vat edcar bon. Si nce the durat i ons of f i l t er backwash operat i ons and rel easepat t erns of sol i ds vary wi del y, i t i s necessary t o caref ul l y assess t hequant i t y and character i st i cs of t he wast es generat ed dur i ng f i l t er washi ngoper at i ons.

    The average sol i ds concent rati on i n wash wast ewater i s general l y l ow.

    However , t he maxi mum TSS concent rati on was f ound t o be about 1800 mg/ L i nt he wat er t reat ment pl ant at East St . Loui s, I l l i noi s ( Li n et al . , 1984) .Average TSS val ues vary wi del y f rom pl ant t o pl ant and f rom t i me to t i mewi t hi n the same pl ant . A hi gh average val ue was ci t ed as 15, 000 mg/ L of TSSf or a pl ant wi t h i ron and manganese removal ( AWWA, 1969a) . About one- f our t ht o one- t hi rd of the t ot al sol i ds are vol at i l e i n most cases ( AWWA, 1969a;Li n et al . , 1984; Li n and Gr een, 1987) . Det ai l ed sol i ds and chemi calanal yses f or f i l t er backwash wast ewat ers of al um coagul at i on pl ant s can bef ound el sewhere (Li n et al . , 1984; Li n and Gr een, 1987; O' Connor, 1971;O' Connor and Novak, 1978) . Granul ar act i vat ed carbon ( GAC) wast es areproduced i n a GAC process as t he resul t of medi a washi ng and quenchi ng andexhaust gas scrubbi ng dur i ng GAC regenerat i on. The most common practi ce i s

    f or GAC t o be pl aced on top of f i l t er sand for t ast e and odor r emoval . Largeamount s of spent GAC can be f ound i n the f i l t er washes af t er i nst al l at i on ofvi rgi n or regenerat ed GAC.

    Granul ar Act i vat ed Carbon Wast es

    Spent GAC wast es consi st mai nl y of acti vat ed carbon wi t h smal l amount sof organi c matt er and chemi cal r esi dues. Novak and Mont gomery ( 1975)repor t ed t hat t he COD val ues f or wat er t reat ment pl ant s cont ai ni ng act i vat edcarbon woul d be hi gh, perhaps on t he order of 10, 000 mg/ L.

    Di at omi t e Fi l t er Sl udge

    Di at omaceous ear t h (DE) i s t he f ossi l skel et on of mi croscopi corgani sms. The smal l number of exi st i ng water t reat ment pl ant s wheredi at omaceous ear t h i s used as a f i l t er medi um are mai nl y wat er suppl i er s ofsmal l amount s of water, such as f or swi mmi ng pool s. Dur i ng f i l t rat i on DE i sadded as a "body f eed" t o prol ong the f i l t rat i on cycl e. Af t er each f i l t ercycl e t he f i l t er medi um and accumul at ed sol i ds ar e di scarded and the newmedi umi s re- i nstal l ed on the f i l t er sept umby means of a "precoat . "

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    Because of t he nat ure of di at omi t e f i l t ers, t he spent di at omaceousear th has character i st i cs si mi l ar t o t he DE i t sel f . DE i s composed al mostent i rel y of pure si l i ca. I t has a dry wei ght of about 10 l b/ cu f t and aspeci f i c gravi ty of approxi mat el y 2. 0 ( AWWA, 1969a) . Si nce t he wasteconsi st s chi ef l y of si l i ca i t i s easi l y dewat ered. The amount of spent DEi s smal l , because t he vol ume of wat er t reated i n a di at omi t e f i l t er i sgeneral l y smal l - .

    Sl udge f romSal i ne Water Conversi on

    There are f ew exi st i ng sal i ne wat er conversi on pl ant s whi ch t reathi ghl y sal i ne wat er s t o produce dr i nki ng wat er . Vi r tual l y no chemi cal s areadded i n t he sal i ne water conversi on process. The wast ewat ers f rom t hesepl ant s are character i zed by a l arge vol ume and a hi gh amount of di ssol vedsal t s or mi neral s whi ch are i ni t i al l y present i n the raw sal i ne wat er .

    These wastewaters are vi r tual l y f ree of BOD5, COD, t urbi di t y, col or , andodor , whi ch are obj ect i onabl e i n a wat er suppl y.

    Fromr aw bracki sh wat ers i n the r ange of 1000 t o 3000 mg/ L of TDS, t hewaste st reamf roma sal i ne wat er conversi on pl ant const i t ut es f r om 10 to 30%of t he water t reated and cont ai ns 5000 to 10, 000 mg/ L of TDS. For sea waterconversi on pl ants the wast ewat er s usual l y consi st of TDS rangi ng f rom al i t t l e above sea wat er concent rat i on ( 35, 000 mg/ L) t o as much as 70, 000 mg/ L

    TDS (Katz and El i assen, 1971) .

    Management of Sl udge

    Tradi t i onal l y the wast e resi dues f roma water t reatment pl ant have beendi scharged to a nearby wat erway and f orgot t en. Cur rent l y i t i s r equi redthat these wast es ( sl udges) be wel l managed. The di rect di scharge of water

    pl ant wast es requi res speci al consi derat i on and appr oval . The di scharge ofwast e can be cont i nuous, i nt ermi t t ent , or seasonal . The cont i nuous pat t erni s pref erabl e f roma wat er qual i t y per spect i ve. Never t hel ess, di rect wast edi scharge i s not l i kel y t o be a f easi bl e method of waste management becauseof regul at i ons concerni ng t he pol l ut i on pot ent i al of the wast es.

    The management of sl udge i ncl udes mi ni mi zi ng sl udge product i on, sl udget reatment , and l and appl i cat i ons. Chemi cal recovery can be used as a way ofboth mi ni mi zi ng sl udge product i on and treat i ng sl udge.

    Minimizing Sludge Production

    The methods and costs f or handl i ng, t reat ment , and di sposal of sl udgeare i nf l uenced by the amount and character i st i cs of t he, sl udge. Thequant i t y and character i st i cs of sl udge are af f ected by the raw wat er qual i t yand the t reat ment chemi cal s used dur i ng t he water t reatment processes.Li t t l e can be done to change the raw wat er qual i t y. However , i t i s possi bl ei n many cases to change t he wat er pur i f i cat i on processes t o mi ni mi ze sl udgeproduct i on. The reduct i on of wast e vol umes r esul t s i n operat i onal costsavi ngs at a pl ant .

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    Sl udge generati on can be mi ni mi zed by t he r emoval of water t o reducet he sl udge vol ume, t he reduct i on of t he sol i ds cont ent present i n thesl udge, or some combi nati on of t he t wo. The methods f or mi ni mi zi ng sl udgeproducti on ar e reducti on of chemi cal dosages (al um or l i me) , di rectf i l t rat i on of t he wat er , recycl i ng of f i l t er washwat er , substi t ut i on ofcoagul ant and sof t eni ng mater i al , and chemi cal recovery ( West erhof f , 1978;AWWA, 1981) .

    Chemi cal Conservat i on. St oi chi omet r i cal l y the reduct i on of each 1 mg/ Lof al umwi l l resul t i n a savi ngs of about 1400 kg ( 3000 l b) of al umper yearand wi l l r educe the al um sl udge by approxi mat el y 360 kg (800 l b) per yearf or a 3785- m/ d ( 1- MGD) pl ant . At many water t reat ment pl ant s excessi veamount s of coagul ant s ar e used si nce i t i s di f f i cul t t o cont i nual l ydet ermi ne the opt i mum coagul ant dosage at a pl ant , especi al l y wi t h rapi dl ychangi ng raw wat er charact er i st i cs. Smal l ut i l i t i es may not have theknow- how, manpower, or ot her r esources t o moni t or and regul ate coagul antdosi ng. Pl ant operat ors must be aware t hat t he excessi ve use of coagul ant sresul t s i n i ncreased cost s, bot h f or t he coagul ant s and f or handl i ng,t reat ment , and di sposal of the ext ra resi dues produced.

    Opt i mi zati on of l i me f eed syst ems can reduce sol i d l oads by maxi mi zi ngt he ef f i ci ency of chemi cal dosages and by mi ni mi zi ng the amount of unreactedl i me i n t he wast e st ream. I mproved mi xi ng i n f eeders, f l ash mi xer s, andf l occul at i on zones reduces excess l i me dosi ng. The wel l - mi xed sol i dscont act cl ar i f i ers use onl y 2 to 3%excess l i me ( AWWA, 1981) .

    By sel ect i ve sof t eni ng to remove onl y cal ci um hardness, wast e vol umesmay be reduced and the dewat er i ng charact eri st i cs of the sof t eni ng sl udgemay be i mproved. However, t hi s sof t eni ng method may be a quest i onabl epract i ce f or some pl ant s because of i ncompl ete removal of hardness. Anot hermethod, reduci ng the degree of sof t eni ng, coul d reduce the chemi cal cost sand al so t he amount of sol i ds produced.

    Di rect Fi l t r at i on. Di rect f i l t rat i on i s a wat er t reat ment process i nwhi ch f i l t rat i on i s not preceded by sedi ment at i on. However , i t may i ncl uderapi d mi xi ng wi t h al um or ot her pr i mary coagul ant s and t he addi t i on of af i l t er ai d i mmedi atel y ahead of t he f i l t er . Cont act t anks may al so bei nstal l ed at some di rect f i l t rat i on f aci l i t i es.

    Di rect f i l t rat i on i s most appl i cabl e t o f aci l i t i es wi t h a rel at i vel yst abl e and hi gh- qual i t y ( l ow- t urbi di t y) r aw wat er source. I n t he process ofdi rect f i l t rat i on coagul ant dosages are general l y l ow and vi r t ual l y al lresi dues ar e produced as f i l t er backwash. Thi s r esul t s i n a si gni f i cantcost savi ngs f or sl udge handl i ng, t r eat ment , and di sposal . West erhof f( 1978) repor t ed a case hi story of di r ect f i l t rat i on pl ant s at t he Ni agara

    Count y Wat er Di st r i ct ' s pl ant i n Lockpor t , New Yor k.

    The Metropol i t an Water Board t reat ment pl ant , l ocat ed i n cent ral NewYork State, has been successf ul i n usi ng di rect f i l t r at i on of Lake Ont ari owater t o serve Syracuse and Onondaga County, New York, wi t h a 94- ML/ d( 25- MGD) . capaci t y. Al um dosages were si gni f i cant l y reduced and sl udgegenerat i on was l essened (Fi t ch and El l i ot t , 1986) .

    Recycl i ng. Di rect recycl i ng of resi dues f rom t he cl ar i f i er s andf i l t ers i s general l y not f easi bl e. I f sl udges ar e concent rat ed, the

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    recycl i ng of f i l t rat es f rom cat ch basi ns and cl ar i f i ed supernat ant f rom t hedewat er i ng process wi l l reduce sol i ds l oads, because these waters have areduced TSS concent rat i on and are sof t ened. Cl ar i f i cat i on and f i l t rat i onwaste vol umes r epresent 3 to 5% of t he total pl ant pumpage. The recycl i ngof t hi s wat er wi l l reduce the waste vol ume by 3 t o 5%.

    I t shoul d be noted that condi t i oni ng al um sl udge wi t h l i me as apreparat ory step pr i or t o f i l t rat i on may cause the re- sol ut i on of humi c

    subst ances i nt o t he process st ream. These di ssol ved organi cs are suspectedof bei ng precursors f or the format i on of possi bl e cancer - produci ngt r i hal omet hanes i n the di si nf ecti on of wat er suppl i es wi t h chl or i ne.

    Recycl i ng of concent rat e or f i l t rate f rom l i me- sof t eni ng sl udges i ssat i sf actory. Recycl i ng of l i me sl udge i mproves the ef f i ci ency of cal ci umcarbonat e preci pi t at i on and reduces l i me usage. The use of a hol di ng basi nand l i mi t at i on of t he recycl i ng rat e to 10% of t he tot al pl ant f l ow aredesi rabl e ( Reh, 1978) .

    Chemi cal Subst i t ut i on. Through the subst i t ut i on of ot her t reat mentchemi cal s f or al l or par t of t he al um and l i me, t he quant i t i es of sl udgegenerated may be reduced and t he dewateri ng characteri st i cs may be i mproved.

    The subst i t ut i on shoul d not degrade t he f i ni shed water qual i t y, l essen t herel i abi l i t y of t he sl udge t reat ment , or i ncrease the t otal cost .

    Reh ( 1980) descr i bed the use of magnesi um carbonate (MgCO3 3H2O) as anal t ernat e coagul ant associ ated wi t h chemi cal recovery and recycl i ng. Thi smet hod was devel oped by A. P. Bl ack of t he Uni versi t y of Fl ori da and wassuccessf ul l y f i el d- tested by t he Uni t ed St at es Envi ronment al Prot ect i onAgency ( USEPA) . When magnesi umcarbonate di ssol ves i n water at a hi gh pH i tf orms magnesi umhydroxi de, Mg( 0H) 2, whi ch has t he same coagul at i on power asal umi num hydr oxi de. I n t hi s process, coagul at i on of raw wat er i s carr i edout by usi ng Mg( 0H) 2 at a pH of about 11. Magnesi umhydroxi de has about thesame coagul at i on power as al umi num hydroxi de ( Reh, 1980) . The sl udge i s

    t hen carbonated to convert Mg(OH) 2 to sol ubl e magnesi um bi carbonat e,Mg( HCO3) 2. A t hi ckener i s used t o separat e Mg( HCO3) 2; i t i s t hen recycl edback t o the f l occul at i on t ank. Most heavy metal s present i n raw water canbe removed because t he coagul at i on process i s carr i ed out at a hi gh pH.

    There i s no aci di f i cati on st ep t o rel ease t he sl udge back t o the l i qui dphase.

    Compl ete repl acement f or al umi s achi eved by the use of i ron sal t s suchas f err i c chl or i de, f er r i c sul f at e, and chl or i nated copperas. Manyf aci l i t i es have used pol ymers f or pr i mary coagul ant s.

    Par t i al subst i t ut i on for al umhas been obt ai ned by decreasi ng the al um

    dosage and addi ng a pol ymer or other coagul ant ai d. Thi s pract i ce i s wi del yused at the present t i me. New and i mproved coagul ant ai ds cont i nue to bedevel oped. The advant ages of thi s process are i n reduci ng the al um dosageand the quant i t y of sl udge produced.

    Sodi umhydroxi de ( caust i c soda) has been used as a par t i al or compl et esubst i t ut e f or soda ash or l i me sof t eni ng. Subst i t ut i ng sodi umhydroxi de i snot wi del y accept ed because i t i s more expensi ve. However, the hi gher costof sodi um hydroxi de can be of f set by l ower sol i ds generat i on and di sposalcosts.

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    When removal of hi gh magnesi umhardness i s r equi red, spl i t t reat ment i sj ust i f i ed because i t el i mi nates t he l i me t reatment f or bypassed water andmi ni mi zes r e- carbonat i on requi rement s and sl udge generati on.

    Chemi cal Recovery. Chemi cal recovery i s t echni cal l y f easi bl e for t herecl amat i on of al um, i r on, and magnesi umcarbonat e and f or the recal ci nat i onof l i me sl udge. I n each case f i ni shed wat er qual i t y, si de st reamdi scharge,

    and gaseous emi ssi on shoul d be consi dered. Chemi cal recovery f rom watert reatment pl ant sl udges can provi de the benef i t s of t he reusabl e chemi cal st hemsel ves, reduced sl udge product i on, reduced cost s f or sl udge di sposal ,and/ or i mprovements i n the t reatabi l i t y of the sl udge.

    Alum Recovery. Al umi s recovered t hrough aci di f i cat i on. When sul f ur i caci d i s added t o the thi ckened sl udge the react i on of al umi num hydroxi dewi t h aci d t akes pl ace al most i nst ant aneousl y to f ormal umi numsul f at e (al um)sol ut i on. Aci dul at i on al so hydrol yzes much of the organi c mat t er .Re- di ssol ved organi c mat t er i s a source of concern wi t h regard t o publ i cheal t h (Ful t on, 1978a) , because some carci nogeni c vol ati l e organi c compoundsand toxi c chemi cal s may al so be pr esent .

    Cornwel l and Susan (1979) report ed that the opt i mum aci d dose f oral most al l sl udges occurred at a sul f ur i c aci d t o t otal al umi nummol ar r at i oof 1. 5: 1. The opt i mal di ssol ut i on corresponded very cl osel y t o t het heor et i cal aci d r equi r ement s. The aci d demand corr esponded t oapproxi mat el y 0. 5 kg sul f ur i c aci d per kg of al umadded to t he raw wat er .

    When sul f ur i c aci d i s added t o al umsl udge, bet ween 70 and 80%recoveryof al um can be achi eved ( Chandl er, 1982; Westerhof f , 1978) . The recoveredal umcan be reused for the water t reat ment process, or i t can be empl oyed asa source of al um f or phosphat e preci pi t at i on i n wast ewat er t r eat ment . Thet ranspor t at i on of the recovered al um shoul d be caref ul l y consi dered. Theresi due has a l ow pH and the resi due cake may requi re neut ral i zati on by l i me

    pr i or t o di sposal on l and. I n case i t i s reused i n t he wat er t r eat mentpl ant , consi derat i on shoul d be gi ven to whet her re- di ssol ved i mpur i t i esmi ght cause a possi bl e degradat i on of the f i ni shed wat er . Thi s i s anexpensi ve process and i t s economi c vi abi l i t y depends upon the capi t al costsof aci d- resi stant equi pment and the rel at i ve cost s of sul f ur i c aci d andf resh al um.

    Recalcining. Li me recovery by recal ci nat i on i s not a new process andi s practi ced at many f aci l i t i es. The recal ci nat i on process i s t he burni ngof sof t eni ng sl udges at a hi gh temperature of 1010C (1850F) as shown i nthe fol l owi ng react i on (AWWA, 1981) :

    (1)

    The process general l y i ncl udes sl udge t hi ckeni ng f rom an i ni t i al 3 t o10%sol i ds t o 18 to 30%.

    Recal ci nat i on has t he pot ent i al t o recover even more l i me t han woul d beused i n the sof teni ng pr ocess, whi l e reduci ng the sl udge wei ght by 80%(West erhof f and Cl i ne, 1980) . At t he same t i me, the carbon di oxi de producedcan be used f or re-carbonati on.

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    Recovered l i me can be sol d f or soi l pH adj ust ment or re- used i n thewater t reatment pl ant . However , t he l i ghter hydroxi des of met al s such asmagnesi um, i ron, and al umi num are undesi rabl e cont ami nant s i n a l i merecal ci nat i on process. Al so the hi gh cost of f resh l i me al ong wi t h t he hi ghcost of energy f or l i me recovery may make recal ci nat i on t oo expensi ve toadopt . Thompson and Mooney ( 1978) di scussed l i me and magnesi um recoveri esf romwat er pl ant sl udge.

    Magnesium Recovery. When magnesi umcar bonate, MgCO3 3H2O, i s added t owat er as a coagul ant at a hi gh pH of about 11. 0, magnesi um hydroxi de,Mg( OH) 2, i s f ormed. The sl udge then i s carbonated to conver t Mg( OH) 2t o t hesol ubl e magnesi um bi carbonate Mg( HCO3) 2. A thi ckener or f i l t er i s used t oseparate Mg(HCO3) 2. The magnesi um i n the f i l t rat e i s recycl ed back t o thef l occul at i on tank f or use and the sol i ds port i on i s di sposed of . Thi scoagul ant i s par t i cul ar l y appl i cabl e i n conj uncti on wi t h l i me recal ci nat i onbecause of the rel ease of carbon di oxi de i n t he recal ci nat i on process. Thi si s used i n turn to re- di ssol ve t he magnesi umhydr at e.

    Wast e Treatment

    Treat ment and di sposal of waste f rom a water t reat ment pl ant depend onthe types of waste and on l ocal condi t i ons. Treat ment methods used f ordomest i c wast ewat er sl udge are most l i kel y appl i cabl e to water pl ant wast es.However , f ur ther st udi es shoul d be conducted t o eval uat e thei r f easi bi l i t y.

    General l y waste t reat ment processes f or wat er pl ant s consi st of threeel ement s: co- t reat ment , pre- t reat ment , and sol i ds dewat er i ng. There areseveral met hods avai l abl e f or each of t hese el ement s.

    Co-Treat ment . Di scharge of water pl ant wastes to a sewage system,ei ther raw or af t er concent rati on, has been a common practi ce f or many

    f aci l i t i es. I t i s probabl y more cost - ef f ecti ve t han usi ng separatedsyst ems, especi al l y f or communi t i es whi ch own both t he wat er and sewersyst ems. Def i ni t e advant ages have been report ed f or" j oi nt dewat er i ng ofal umand sewage sl udges ( Ful t on, 1978b) .

    Hsu ( 1976) cl ai med that j oi nt t reatment of al um sl udge and wast ewat erpl ant sl udge was t he most promi si ng of f - si t e treat ment met hod. Al um sl udgecan be di scharged to the exi st i ng wast ewat er t reat ment pl ant , where i t canbe t hi ckened and mi xed wi t h t he wast ewater sl udge, f ol l owed by dewater i ng ata proper pH. Al um sl udge can serve as a useful wast ewat er sl udgecondi t i oner , rather than a nui sance.

    Li me sl udge can be advant ageous f or i ncreasi ng pH, as a bul ki ng agent ,f or neut ral i zi ng aci d wastes, and f or pre- t reat ment of i ndust r i al wast es;and i t can be i nci nerated t o - produce hi gh al kal i ne ash ( AWWA, 1981) .Wat er - sof t eni ng sl udge tends to set t l e wel l and t o deposi t i n sewers. I tneeds a good vel oci t y to prevent i t s set t l i ng i n sani tary sewer s. Spentbr i nes woul d not have a si gni f i cant ef f ect on sewage treat ment ( Reh, 1978) .Fl ow equal i zat i on i s needed to avoi d abrupt changes of TDS and sal tconcent rat i ons i n the sewage.

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    Pre- Treat ment . Some sort of pre- t reat ment i s needed for ef f ect i ve andeconomi cal wat er pl ant sl udge t reat ment . Pre- t reat ment i ncl udes f l owequal i zat i on, sol i ds separat i on, and sol i ds concent rat i on or sl udgethi ckeni ng ( Ful t on, 1978b) . Pre- t reat ment f aci l i t i es f or a par t i cul ar wat ercan use one of t hese methods or a combi nati on of t he t hr ee.

    Flow Equalization. Fl ow equal i zat i on i s used t o provi de st orage vol umef or hol di ng the quant i t y of wast e di scharge whi ch exceeds t he al l owabl e

    amount bei ng di scharged t o a sewer syst em. Storage requi rement s depend ont he desi gned waste di scharge schedul e.

    Solids Separation. Sol i ds separati on may be accompl i shed by detent i oni n set t l i ng f aci l i t i es wi t h desi gned wast e wi t hdrawal r at es or wi t h adequat eover f l ow. The set t l i ng f aci l i t i es may i ncl ude a si mpl e set t l i ng t ank,decant t ank, or both decant and set t l i ng/ t hi ckeni ng t anks. Fl owequal i zat i on storage precedi ng set t l i ng f aci l i t i es may be needed for f i l t erwash wast ewat er because of rel at i vel y hi gh di scharge r ates.

    As a decant t ank i s f i l l ed i t r emai ns f ul l f or a suf f i ci ent t i me (about2 hours) f or t he set t l i ng of sol i ds wi t hout wi t hdr awal . The sol i ds ar e t henremoved by a mechani cal col l ector f or f ur ther t reat ment and t he supernatanti s drawn of f .

    Thickening. Thi ckeni ng i s used t o reduce the vol ume of sl udge and t oi mprove sl udge dewat er i ng character i st i cs by concent rat i ng the sl udge i n thebot t omof a t hi ckener or l agoon. I t i s an i nexpensi ve and ef f ect i ve devi ce.Al t hough coagul ant sl udge t hi ckens poorl y, i t can be gravi t y- t hi ckened t o asol i ds cont ent of 2 t o 10% ( Westerhof f and Cl i ne, 1980) . Li me- sof t eni ngsl udge whi ch pr i mar i l y cont ai ns cal ci um carbonat e can be thi ckened2 t o 30%sol i ds and more at a t hi ckener l oadi ng rat e of approxi mat el y 4. 6 m / 907 kg( 50 sq f t / ton) / d (AWWA, 1981; West erhof f and Cl i ne, 1980) .

    Unf or t unat el y, the l i t erat ure i ndi cat es t hat most wat er t reat ment

    pl ant s make no ef f or t t o mi ni mi ze sl udge vol ume, al t hough t hi ckeni ng cansave on the cost s f or sl udge di scharge pi pi ng and f or supernat ant r ecycl i ng.

    One of t he mor e ef f i ci ent met hods of sl udge t hi ckeni ng i s t he use of asl ow- st i r rotat i ng pi cket f ence t o enhance sol i ds separat i on. The theory i st hat t hi ckeni ng occur s i ni t i al l y by gravi ty set t l i ng and i s ai ded by t hecompressi ng act i on of the st i r rer on the sl udges. The use of i ncl i ned,paral l el pl at es has al so repor t edl y been successf ul i n i mprovi ng sol i dsseparat i on.

    Non- mechani cal Dewat er i ng. Fol l owi ng col l ect i on and thi ckeni ng, t hesl udge can be fur t her concent rat ed or dewat ered ei t her by co- di sposal wi t hsewage sl udge or by mechani cal or non- mechani cal dewateri ng met hods.Co- di sposal was di scussed previ ousl y. Non- mechani cal sl udge dewat eri ngdevi ces i ncl ude l ag oni ng, dryi ng on sand beds, nat ural or ar t i f i ci alf reezi ng and t hawi ng ( physi cal met hod) , and chemi cal condi t i oni ng.

    Lagooning. Lagoons have been used as an al l - purpose treat ment devi ce.They may f unct i on as a f l ow equal i zer , sol i ds separator, sl udge t hi ckener,and sl udge st orage area al l i n one uni t . Lagoons general l y provi desuf f i ci ent sur f ace area and vol ume f or t r eat ment . They are usual l y equi ppedwi th underdrai ns and decant f aci l i t i es f or sl udge dewat er i ng.

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    Desi gn cri t er i a f or l agoons vary wi t h each part i cul ar pl ant si t uat i ondependi ng on the waste recei ved. General l y at l east two l agoons arerequi red. Li qui d can be di scharged by an underdrai n or through an over f l ow.

    The l agoon can be operated i n a f i l l - and- draw patt ern or i n a cont i nuousmode. Recovered water can be recycl ed t o t he pl ant . Sl udge, cake or wet ,may be removed by eart h- movi ng equi pment af t er i t has been drai ned. Sl udgecan be wi thdrawn wi thout drai ni ng by means of hydraul i c equi pment . I t

    shoul d be noted that sett l ed al um sl udge does not pump wel l even when i t i swet .

    Lagooni ng i s t he most i nexpensi ve but perhaps the l east ef f ect i vedewater i ng method f or al um sl udge, usual l y resul t i ng i n 5% sol i ds.Never t hel ess, a successf ul exampl e was r eported by Ful t on ( 1976) . Onef i l t er pl ant of the Hackensack Water Company i n New J ersey has beendi schargi ng al umsl udge t o set t l i ng basi ns f or over 40 year s. The sl udge i nthe l agoon compacted t o 10% sol i ds wi t h l ong- t erm st orage. On t he otherhand, i t has been reported that t hrough l agooni ng, l i me- soft eni ng sl udge canbe successf ul l y dewatered to greater than 50%sol i ds ( AWWA, 1981) .

    Drying Beds. The sl udge dryi ng bed i s an i mprovement over t he sl udgel agoon. I t i ncorporat es a permeabl e medi um (such as sand and wedge wi r e)and a syst em of underdrai nage. I n Engl and a modi f i ed sand dryi ng systemusi ng wedge wi re was devel oped. The wedge wi re syst em requi red a hi ghcapi t al expendi t ure al t hough mai nt enance cost s were l ow.

    Where rai nf al l and humi di t y condi t i ons permi t and where l arge l andt racts are avai l abl e, sand dryi ng beds are an ef f ect i ve and rel at i vel yi nexpensi ve met hod of dewater i ng water pl ant waste sol i ds. These bedsusual l y consi st of 15 t o 30 cm( 6 t o 12 i n. ) of sand rangi ng i n si ze up to0. 5 mmwi t h graded gravel and drai npi pes ( AWWA, 1969a) . Sl udge i s appl i edi n 30- t o 60- cm( 1- t o 2- f t ) l ayers and al l owed t o dewat er . The beds may becovered or open.

    Rai nf al l i s a maj or f actor i n the ef f ect i veness of sl udge dryi ng beds.Poor dewater i ng of sl udge occurs i n col d or rai ny cl i mat es. The cost s ofthe l arge l and area requi red and of t he sand shoul d be consi dered. Dewateredsl udge can be removed manual l y i f t here i s a l ack of sui tabl e equi pment . Thedi f f i cul ty of sl udge removal t oget her wi t h the l abor - i ntensi ve operat i onmake t hi s method uneconomi cal .

    Sl udge penet rat i on through sands dur i ng the i ni t i al sl udge appl i cat i oni s a probl emwhi ch requi res f requent sand repl acement . Pol ymer condi t i oni ngcan prevent sl udge penet rat i on by i ncreasi ng the gravi ty drai nage rat e by100% and enhanci ng' evaporati on, thereby prevent i ng cake crust f ormat i on(AWWA, 1981) .

    Sand dryi ng beds have been empl oyed for dewateri ng coagul ant sl udgeand, t o a l esser extent , l i me sof teni ng sl udge. Use of these beds i s af easi bl e method f or dewater i ng mi xed coagul at i on- sof t eni ng sl udge.

    Freezing and Thawing. Freezi ng can be nat ural or ar t i f i ci al . Thef reezi ng and thawi ng process was devel oped for sewage sl udge i n 1950. I n1963 i n the Uni ted Ki ngdom the process was f i r st i ni t i ated successf ul l y f orthe treatment of wat er pl ant sl udge at St ocks, Engl and (Doe et al . , 1965) .

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    Pre- t reat ment by t hi ckeni ng reduced the sl udge vol ume. The sl udge wasthi ckened t o 4% sol i ds. The process consi sted of two 45- mi n. f reezi ng cycl esand one 45- mi n. t haw cycl e. I n the f reezi ng process, wat er of hydrat i on wasremoved f rom t he gel at i nous al umi num hydroxi de, changi ng t he sl udgecharacter i st i cs t o smal l granul ar par t i cl es whi ch set t l ed rapi dl y. The f i nalvol ume was r educed t o one- si xth of the or i gi nal vol ume. The capi t al cost sand operat i onal cost s of t hi s process ar e rel at i vel y hi gh.

    I n col d- weat her condi t i ons wi t h a l arge amount of avai l abl e l and,nat ural f reezi ng on open beds i s f easi bl e f or dewat er i ng al um sl udge. Theprocess of f reezi ng and thawi ng has no par t i cul ar benef i t f or l i me- sof t eni ngwast es. A hol di ng f aci l i t y wi t h suf f i ci ent vol ume to store wast e generat eddur i ng non- f reezi ng per i ods i s r equi red. Sl udge i s appl i ed t o the bed i nsuccessi ve l ayers t o f aci l i t at e f reezi ng.

    Freezi ng and t hawi ng of al um sl udge wi l l change sl udge concent rat i onssubst ant i al l y. Recent l y a successf ul f reeze- t haw process i n cent ral New

    York St ate was report ed by Fi t ch and El l i ott ( 1986) . Al um sl udge f rom aset t l i ng basi n wi t h 8% sol i ds was concent rat ed t o 25% by f reezi ng, t hawi ng,and decant i ng. The f i nal sl udge was f ound t o be more granul ar i n character.

    I t was al so observed that regardl ess of t he pumped sl udge concent rati on i tseparated qui ckl y i nt o set t l ed sl udge and cl ear decant . The set t l ed sl udgewas easi l y handl ed by st andard ear t h- movi ng machi nes f or r emoval f rom t hebeds f or l and appl i cat i on. For t he 72- MGD ( 272- ML/ d) pl ant t reat i ng LakeOnt ar i o wat er, the const ruct i on cost f or permanent sl udge- handl i ngf aci l i t i es i ncl udi ng the f reeze- dry beds was about $300, 000 i n 1981.

    Randal l ( 1978) cl ai med t hat l i qui d but ane i s an i deal ref r i gerant f ordi rect sl urry f reezi ng of waste- acti vat ed sl udge to promot e set t l i ng,concent rat i on, and dewat er i ng. Because of the hi gh recovery rat e f orbut ane, the process ef f ect i vel y and economi cal l y accompl i shes wastewatersl udge dewat er i ng.

    Chemical Conditioning. Condi t i oni ng of sl udge may be accompl i shed byj udi ci ous use of organi c pol yel ect rol ytes, i norgani c chemi cal s, andaci di f i cat i on. Ani oni c pol ymers (hydrol yzed pol yacryl ami des) have beenreported t o be par t i cul ar l y ef f ect i ve condi t i oni ng agent s f or coagul at i ngsl udges pr i or to gravi ty or vacuum f i l t rat i on dewat er i ng (Ki ng and Randal l ,1968) .

    Fer r i c chl or i de, l i me, or f l y ash are possi bl y appl i cabl e forpart i cul ar sl udge condi t i oni ng. The use of chemi cal s, separat el y or i ncombi nat i on, shoul d be eval uat ed f or a part i cul ar sl udge.

    Aci di f i cat i on of sl udge i s a good condi t i oni ng met hod, par t i cul ar l y

    wi t h t he al um recovery process. The aci di f i ed sl udge must be neut ral i zedpri or t o i t s ul t i mat e di sposal .

    Mechani cal Dewateri ng. The most f requent l y used mechani cal syst ems f ordewat er i ng wat er pl ant sl udges are cent r i f ugat i on, vacuum f i l t r at i on, andpressure f i l t r at i on. Bel t f i l t rat i on and dual cel l gravi ty sol i dsconcent rat ors have been i nstal l ed t o a l esser ext ent . Pel l et f l occul at i oni s r el at i vel y new and i s used l ess of t en f or sl udge dewat er i ng. For al lmechani cal dewat er i ng syst ems pre- condi t i oni ng i s general l y r equi red.

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    Centrifugation. Cent r i f ugat i on i s the set t l i ng of sl udges by acent r i f uge that uses the gravi t at i onal f orce created by hi gh- speed rot at i ont o separate the sol i ds. Var i ous t ypes of cent r i f uges ar e commerci al l yavai l abl e. General l y, t here ar e two cat egor i es: cont i nuous scrol l t ype andcont i nuous bath bot tomf eed basket ( bowl ) t ype (Hagst romand Mi gnone, 1978) .Feed sol i ds concent rat i on to t he cent r i f uge usual l y r anges f rom 2 to 6%,al though al umsl udge at a concent rat i on of 0. 4 t o 1. 0% has been successf ul l ydewatered ( Westerhof f , 1978) . However , several f ul l - scal e i nstal l at i onshave been found to be unacceptabl e (AWWA, 1969a) . The cent r i f uges f or al umsl udge dewater i ng at Rock I sl and, I l l i noi s, are an exampl e of a f ai l ure.

    The expected cake dryness i s af f ect ed by the cent r i f ugal f orce, f eed r at e,rat e of pol ymer dosage, raw wat er qual i t y, f l oc si ze and densi t y, andresi dence t i me. The wat er that i s removed can be recycl ed to the pl ant orproper l y di sposed of .

    Li me- sof teni ng sl udge i s r epor ted to be easi l y dewatered bycent r i f ugat i on because of i t s hi gh (80 t o 85%) cal ci um carbonat e cont ent .Al ber t son and Gui di ( 1969) repor ted that when a sol i d bowl cent r i f uge wasused, a thi ckened l i me sl udge coul d be dewatered to a cake sol i dsconcent rat i on of 55% wi t h 78 t o 93%sol i ds capt ur e. Dat a f rom pl ant s usi ng

    cent r i f ugat i on showed that t he l i me cake sol i ds concent rat i ons wer e i n therange of 55 t o 70% sol i ds by wei ght ( AWWA, 1969b; Vesi l i nd, 1979) , whi l eal um sl udge cent r i f ugat i on can achi eve onl y 12 t o 20% sol i ds by wei ght( Ful ton, 1978b) .

    Vacuum Filtration. Vacuum f i l t rat i on t ypi cal l y uses a rotary drumwi t ha t i l ter cl oth or medi um str etched across i t s sur f ace. The f i l t er medi umcan be t ravel i ng cl ot h or a precoated t ype. The sel ect i on of a properf i l ter medi umcont r i butes t o the ef f ect i veness of t he pr ocess. The drumi spl aced under vacuum or pressure i n a reservoi r of sl udge that i s t o bedewatered. The precoated f i l t er drum rotat es sl owl y at 5 t o 12 revol ut i onsper mi nut e dependi ng on the permeabi l i t y of t he deposi t ed cake and t he gradeof precoat medi um. The average precoat l ayer of 2 t o 3 i nches i s appl i ed

    and may be shaved of f i n very smal l i ncr ement s. Approxi matel y 50 to 60mi nut es i s requi red f or precoat i ng a vacuumf i l t er ( Westerhof f , 1978) . Theprocess of vacuum f i l t rat i on i ncl udes t hree basi c phases: cake f ormat i on,cake dryi ng, and cake di scharge. The f l oc si ze di st r i but i on i s the keyf actor i n the per f ormance of t he vacuumf i l t er . The sl udge cake devel ops onthe outer surf ace of t he medi umand i s subsequent l y removed by a scr aper anddi sposed of .

    The vacuum f i l t er has l ong been a popul ar method of dewater i ng sl udgesf rom sewage t reat ment pl ant s and chemi cal i ndust r i es. However, t he vacuumf i l t rat i on process has had onl y l i mi ted success when used f or coagul at edsl udge. I t i s di f f i cul t t o dewater al um sl udge generated f rom raw wat er

    wi t h turbi di t i es between 4 and 10 TU ( West erhof f , 1978) . Aci d i s added tothe thi ckened sl udge f pr al umi num recovery. Aci di f i ed al um sl udge i s easi erto dewat er .

    Vacuum f i l t er s ar e of t en successf ul l y used f or dewat er i ngl i me- sof teni ng sl udges. A precoat i s necessary wi t h hydroxi de sl udges. I twas r epor ted that vacuum f i l t er dewater i ng of l i me sl udges produced f i nalcake sol i ds concent rat i ons i n the range of 45 to 65%suspended sol i ds, wi t han acceptabl e f i l t rate produced (AWWA, 1969b) . Fi l t er l oadi ngs were as muchas 293 kg/ m2 / h (60 l b/ sq f t / h) of dry sol i ds per f i l t er sur f ace ar ea.

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    2Dl oughl y and Hager ( 1968) report ed that a l oadi ng rat e up to 439 kg/ m / h ( 90l b/ sq f t / h) yi el ded f i nal cake sol i ds concent rat i ons i n the range of 65 t o75%suspended sol i ds.

    Pressure Filtration. The pressure f i l t er i s basi cal l y made up of anumber of porous f i l t er pl at es cont ai ni ng depressi ons, hel d ver t i cal l y i n asupport i ng f r ame. Each pl at e f ace i s covered wi t h a proper f i l t er cl ot h. A

    common f eed hol e or mul t i pl e hol es f or the sl udge i nl et extend through thepl at es. Under pressure, ei t her by mechani cal or hydraul i c means, sl udge i spumped i nt o the f i l t er t hrough the f eed hol es t o the chambers f ormed by t hedepressi ons bet ween t he pl ates. The l i qui d seeps t hrough t he f i l t er medi um,l eavi ng t he sol i ds behi nd bet ween t he pl ates. Wi t h cont i nual pumpi ng,sl udge cakes f orm and ul t i mat el y f i l l t he chamber . Af t er t he f i l t rat i oncycl e, t he pl at es are separated and the dewatered sol i ds f al l easi l y to adi scharge conveyance. An aut omati c cake remover can al so be used. Detai l sof pressure f i l t ers and operat i onal var i abl es are di scussed el sewhere( Ful t on, 1976; AWWA, 1978b; Vesi l i nd, 1979) .

    The pressure f i l t rati on process was f i r st appl i ed t o water t r eat mentpl ant sl udges i n the Uni t ed St at es i n t he mi d- 1960s. I t s l ack of popul ar i t yi s due t o i t s cycl i cal operat i on. However , t he process i s popul ar i nEur ope. I t has been used extensi vel y i n the. chemi cal i ndust ry f ordewat er i ng sl udges. A number of di f f erent ki nds of pressure f i l t er s ar e onthe mar ket . Pressure f i l t rat i on has t he capaci t y of produci ng f i l t er cakeswi t h a rel at i vel y hi gh sol i ds concent rat i on and hi gh- qual i t y f i l t rat e i nt erms of l ow suspended sol i ds. The process i s f l exi bl e and f i t s anyoperat i onal mode.

    Dewat er i ng of al um sl udge by pressure f i l t rat i on i s l i kel y to needsl udge condi t i oni ng t o l ower t he resi stance t o f i l t rat i on. Thi s can be doneby t he addi t i on of l i me, pol ymers, or f l y ash. The choi ce of condi t i oni ngagent s i s based on the cost s f or each appl i cat i on. Li me i s added t o al um

    sl udge to rai se the pH of the sl ur ry to about 11 wi t h a mi ni mumcont act t i meof 30 mi nut es ( West erhof f , 1978) . I f f l y ash f rom power pl ant s coul d beused successf ul l y for condi t i oni ng al um sl udge t hi s woul d be benef i ci al t oboth i ndust r i es.

    Li t erat ure on the appl i cat i on of pressure f i l t rat i on t o l i me- sof t eni ngsl udge i s l i mi t ed. No condi t i oni ng of the l i me sl udge i s r equi red.

    Belt Filtration. The bel t pr ess, or t he bel t f i l t er press, consi sts oftwo endl ess f i l t rat i on f abr i c bel t s hel d i n cl ose cont act wi t h each ot her bygui de paral l el r ol l er s. The l ower bel t i s made of coarse mesh f abr i c medi aconsi st i ng of twi sted met al , pl ast i c, or mi xed f i ber s. The upper bel t i s

    sol i d. The condi t i oned sl udge i s f ed ont o the bel t press at one end(drai ni ng zone) and i s cont i nuousl y dewat ered by t he pressure appl i edbetween t h t wo bel t s ( press zone and shear zone) . The l i qui d drai ns of f bygravi t y. The sol i ds cake i s scraped of f by a bl ade at the ot her end of thebel ts.

    A number of bel t f i l t er presses have been i nt roduced. These devi ceshave been used i n Europe si nce t he ear l y 1960s f or dewateri ng sewage sl udge.I n the Uni ted St at es, thei r use f or dewater i ng wat er pl ant sl udges i nf ul l - scal e operat i ons i s not document ed. Al t hough bel t presses are wi del y

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    used i n i ndust r i es, especi al l y i n paper and pul p manuf act ur i ng, t he processhas al so been successf ul f or sewage sl udge dewater i ng.

    I n 1982 a bel t f i l t er press was i nstal l ed at t he Bel vi der e, I l l i noi s,wastewat er t reat ment pl ant t o repl ace t wo i nef f i ci ent vacuum f i l t er s. I n1980 the pl ant dewatered 8000 l b/ d of dry sol i ds ( 23. 5 tons/ d of wet sl udgeat 77% cake sol i ds f rom vacuum f i l t er s) . A three- year operat i onal recordshowed an average savi ngs of $60, 000 i n cost s f or power, l abor, and pol ymers

    wi t h t he bel t pr ess. The 1985 total annual cost f or operat i ng the bel tpress was l ess t han $70, 000. The f i nal sl udge cake f rom the bel t presscontai ned 23%sol i ds.

    Pellet Flocculation. Pel l et f l occul at i on i s a rel at i vel y new processand has been devel oped i n J apan, where a f ew pl ant s have been usi ng i t( Chandl er , 1982) . The devi ce basi cal l y consi st s of a sl owl y rotat i nghor i zont al dr um, t he reactor , whi ch i s di vi ded i nto t hree sect i ons. Thecondi t i oned sl udge i s f ed i nto the f i r st sect i on of t he reactor , where therol l i ng acti on causes the f ormat i on of sl udge pel l et s. The l i qui d i sdrai ned of f i n t he second sect i on, and the sl udge i s consol i dated andf ur ther dehydrated by the combi ned ef f ect s of pi l i ng up and rotat i on i n thef i nal secti on.

    Dewat er i ng of sl udge by t he pel l et f l occul at i on process i s a cont i nuousoper at i on. I t s operat i on and mai nt enance cost s are mi ni mal due t o the l owrotat i ng speed. A study of a pel l et f l occul at i on reactor of 0. 5- m di amet erat t he Hul a Fi l t er St at i on, New Zeal and, det ermi ned t hat a f i nal sl udge cakeof 12 to 15% sol i ds was produced f rom a condi t i oned sl udge f eed of 3 t o 4%sol i ds. The uni t per f ormance depended on t he pol yel ect rol yte dose, f eedr ate, and reactor speed ( Chandl er , 1982) .

    An AWWA Commi t t ee Report ( 1981) descr i bed t he sl udge pel l eti zat i onoccur r i ng dur i ng t he suspended- bed col d- sof teni ng process used pr i mar i l y i nthe sout heast ern Uni ted States. The process seems t o work best on

    hi gh- cal ci um, warm- temperat ure ground water . The det ent i on t i me i n asuspended- bed sof teni ng reactor i s about 8 to 10 mi nut es. Li me i s i nj ectedi nto the reactor whi l e the raw wat er f l ow i s gradual l y i ncreased f roma l owi ni t i al rate t o desi gn capaci t y. The l i me reacts wi t h cal ci um bi carbonat eand carbon di oxi de t o f orm cal ci um car bonat e, whi ch preci pi t at es on thesuspended par t i cl es. The pel l et i zed sl udge cont ai ns approxi matel y 60%sol i ds by wei ght as i t l eaves t he reactor . The vol ume of pel l et i zed sl udgei s 10 to 20 t i mes l ess t han that of convent i onal sl udge whi ch i s notdewat ered. The pel l et i zed sl udge has t o be transported away f or f i naldi sposal .

    Ul t i mat e Sl udge Di sposal

    Al though a l i mi ted amount of al um or l i me can be r ecovered andrecl ai med, t hi s quant i t y sti l l represent s a smal l percent age of t he totalsol i ds vol ume. The condi t i oned and dewatered sl udges st i l l need ul t i matedi sposal . Thi s i s a di f f i cul t task f or l arge urban pl ant s. Ul t i mat edi sposal f or wat er pl ant sl udges i s basi cal l y conf i ned to l and or wat erbodi es and can i nvol ve i nci nerat i on, di sposal i nt o sewer syst ems, bargi ng tot he ocean, l agooni ng ( i n rural ar eas) , underground di sposal , composi t i ng,spreadi ng on l and, or l andf i l l .

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    The dewat ered sl udge can be composi t ed wi t h muni ci pal r efuse. I t al socan be used f or cropl and (as a soi l condi t i oner or f er t i l i zer ) , l andrecl amat i on, f or est s, raw mat er i al r ecovery, mi xi ng wi t h soi l , l andscapi ng,and f i l l mat er i al . The most popul ar f orm of ul t i mat e sl udge di sposal i s t oa l andf i l l .

    The advant ages and di sadvant ages of each al t ernati ve f or ul t i mate

    di sposal shoul d be eval uat ed. Each pl ant has i t s own si tuat i on and thef i nal di sposal met hod needs to be approved by r egul at ory agenci es.

    Land Appl i cat i on. Condi t i oned and dewatered sl udges may be di sposed ofon publ i c or pr i vat e l ands, or on l and owned by the ut i l i t y. The operat i onshoul d be cont rol l ed wi t h adequat e provi si ons t o guard agai nst wat er or soi lpol l ut i on resul t i ng f rom hi gh l oadi ng rat es and sur f ace runof f . Thel andf i l l area i s eventual l y recl ai med and grassed.

    The amount of l and requi red f or di sposal of sl udge f rom water pl ant svar i es wi t h the degree of sol i ds cont ent i n t he sl udge. On t he basi s of anannual al um sl udge product i on of 1980 tons ( 4. 16 x 10 pounds) per day and

    at a f i l l i ng dept h of 2. 4 m ( 8 f t ) , t he annual l and requi rement s are asf ol l ows (Reh, 1978) :

    Sl udge concent rat i on, Land requi rement s% sol i ds Acres Hectares

    10 600 24330 230 9350 135 55

    These are net requi rement s and excl ude any al l owances f or r oads,servi ce ar eas, and t he l i ke.

    Li me sl udge can be spread on agr i cul t ural l and f or soi l pH adj ust mentwi t h f er t i l i zer appl i cat i on. The l i me- sof t eni ng sl udge shoul d be t hi ckenedas a l i qui d f rom 1- 5% t o 8- 10% sol i ds or as a sol i d af t er bei ng dewatered toapproxi mat el y 40% sol i ds. Appl i cat i on rat es of 2 t o 3 t ons per acre havebeen used on a 4- t o 7-year schedul e. At t hi s r ate about 11, 300 ha ( 28, 000acres) of l and i s needed for t he di sposal of the est i mat ed l i me sl udgeproduced at a 10- MGD water t reat ment pl ant ( Reh, 1978) .

    I n t he Champai gn- Urbana, I l l i noi s, area 1. 4 to 1. 8 kg ( 3- 4 l bs) ofl i mest one must be appl i ed for each 0. 45 kg (10 l bs) of ammoni a f er t i l i zer,because i t t akes approxi mat el y 4 pounds of agr i cul t ural l i mest one t oneut ral i ze the aci di t y of one pound of ni t r ogen f er t i l i zer whi ch i s appl i ed

    on corn as an ammoni umf orm, urea, ammoni umni t r ate, or manure. The cal ci umcarbonat e equi val ent ( CCE) val ues and the neut ral i zati on power ofl i me- sof t eni ng sl udge are f ound to be hi gher t han those of l i mest one.Sof t eni ng sl udge wi t h 50% sol i ds was successf ul l y appl i ed to farml and i nI l l i noi s (Russel l , 1975, 1980) . Cur rent l y a mi ni mumof 30, 000 tons per yearof "l i qui d l i me" can be market ed i n the Champai gn- Urbana area ( Ki eser ,1986) . Land appl i cat i on of l i me- sof t eni ng sl udge not onl y serves as a wast edi sposal pract i ce but al so ai ds the agr i cul t ural communi t y.

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    Bugbee and Fr i nk ( 1985) st udi ed the use of al um sl udge as a pot t i ngsoi l amendment and al so for appl i cat i on t o f orest l and. A study ofsi l vi cul t ural appl i cat i ons of t wo types of al um sl udge was conducted byGrabarek and Krug (1987) . They f ound t hat t he appl i cat i on of al umsl udge onf orest ed l and woul d not af f ect t ree growth and was a l ow- cost di sposalal t ernat i ve.

    Concl usi on

    Regardl ess of whi ch method of sl udge t reat ment i s used, the end productst i l l must be di sposed of on l and or wat er . Recl amat i on, of cour se, canreduce t he amount of end products. Great er emphasi s shoul d be pl aced onmi ni mi zi ng the amount of sl udge product i on and maxi mi zi ng t he sol i dscont ent . The ef f ect of var i ous t ypes of waste di sposal on t he envi ronmentshoul d al so be eval uat ed.

    The di sposal probl em regardi ng wast es f rom water t reat ment pl ant s i snot new. Each pl ant has a uni que si t uati on. I n desi gni ng a wat er t reatmentpl ant , i t i s not adequat e to consi der onl y the opt i mi zat i on of var i ous

    t reat ment uni t operat i ons and processes wi t hout gi vi ng due consi derat i on towast e di sposal . Pl ans f or t he handl i ng and di sposal of wast es shoul d bei ncl uded i n t he t ot al desi gn f or a wat er t reat ment pl ant . Thi s may be ani mpor tant l i mi t i ng or cont rol l i ng f actor .

    Laws and Regul at i ons

    I n t he l at e 1960s, several stat e pol l ut i on regul at ory aut hor i t i escl assi f i ed wat er wor ks wast es as pot ent i al pol l ut ant s. Not abl y, t he statesof I l l i noi s and New York est abl i shed treat ment st andards f or wat er pl antdi scharges i n t hi s ear l y per i od of envi ronmental awar eness.

    Respondi ng to publ i c demand for cl ean water, af t er two year s of i ntensedebate, negoti at i ons, and compromi ses t he Congress over rode a Presi dent i alvet o on Oct ober 18, 1972 and enacted Publ i c Law 92- 500, ent i t l ed "TheFederal Wat er Pol l ut i on Cont rol Act of 1972. " Thi s was t he most asser t i vestep i n the hi story of nat i onal wat er pol l ut i on cont rol programs.

    Thereaf t er, several l aws and regul ati ons were amended.

    I n I l l i noi s, t he l egal requi rement s appl i cabl e t o wast e di scharges f rompubl i c wat er suppl i es are general l y f ound i n the f ol l owi ng f ederal andI l l i noi s l egi sl at i on ( Reh, 1978; Hunt , 1978; Haschemeyer , 1978; Randt ke,1980) :

    1. PL 92- 500, t he Federal Wat er Pol l ut i on Cont rol Act ( FWPCA) of 1972as amended by t he Cl ean Water Act of 1977

    2. PL 94- 580, the Resource Conservat i on and Recovery Act ( RCRA) of1976

    3. PL 93- 523, the Saf e Dr i nki ng Water Act ( SDWA) of 1974, amendedi n 1977

    4. PL 91- 512, t he Sol i d Waste Di sposal Act of 1976

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    5. Chapt er I : Pol l ut i on Cont rol Board, Subt i t l e C: Wat er Pol l ut i on,Ti t l e 35: Envi ronment al Protect i on, I EPA, revi sed i n 1986

    6. Part 391, Desi gn Cr i t er i a f or Sl udge Appl i cat i on on Land, Chapt erI I , Subt i t l e C, Ti t l e 35, I EPA, 1984

    7. The I l l i noi s Envi ronment al Prot ecti on Act I I I , Chapt er 111 1/ 2,Publ i c Heal t h & Saf et y Sect i on 1001- 1051, amended J an. 5,1984

    PL 92- 500

    I n Publ i c Law 92-500, enacted i n 1972, the f ederal government i ncreasedf undi ng f or const ruct i on of publ i cl y owned wastewater t reat ment pl ant smai nt ai ni ng uni f orm t echnol ogy-based ef f l uent st andards. The obj ect i ve wasto cont rol al l poi nt source pol l ut i on di scharges i n navi gabl e wat er s by 1985( Hunt , 1978) . Thi s l aw per t ai ns to wat er pol l ut i on cont rol .

    There were two phases of i mpl ement ati on i n t he PL 92-500 act . By 1977,

    al l pl ant s were requi red t o i nst al l "best practi cabl e cont rol t echnol ogycur rent l y avai l abl e ( BPCTCA) " t o meet st at e or f ederal wat er qual i t yst andards. For phase 2, i n order t o meet more st r i ngent st andards, al lt reatment pl ant s were t o i nst al l "best avai l abl e t echnol ogy economi cal l yachi evabl e" by J ul y 1, 1983 toward the nat i onal goal of el i mi nat i ng thedi scharge of al l pol l ut ant s, i ncl udi ng recl ai mi ng and recycl i ng of wat er ,and conf i ned di sposal of pol l ut ant s ( f romwast ewat er di schar ge) . Ul t i mat el y,al l poi nt source pol l ut i on cont rol s were di rected t oward achi evi ng thenat i onal goal of the el i mi nat i on of t he di scharge of pol l ut ant s by 1985.

    Sect i on 402 of PL 92- 500 st i pul at es t hat the di scharge of any pol l ut antby any person i s unl awf ul wi t hout a Nat i onal Pol l ut ant Di scharge El i mi nat i on

    System( NPDES) permi t .

    The NPDES permi t t i ng process i n I l l i noi s i s general l y governed by Par tI X, Per mi t s, Subpar t A: NPDES Permi t Sect i ons 901- 916 of Chapt er 3 of theI l l i noi s Pol l ut i on Cont rol Board Rul es and Regul at i ons ( Haschemeyer , 1978) .

    Sect i on 901 of Chapt er 3 st ates:

    "Except as i n compl i ance wi t h the provi si ons of t he Act , BoardRegul at i ons, and the FWPCA, and t he provi si ons and condi t i ons of t he NPDESPermi t i ssued to the di scharger , t he di scharge of any cont ami nant orpol l ut ant by any person i nt o t he wat er s of t he St at e f roma poi nt source ori nt o


Bell 429 ProductSpec2012

Bell 429 ProductSpec2012

429 revistapulso 19871230

429 revistapulso 19871230

Fuze B 429 and B 429 E

Fuze B 429 and B 429 E

Supporting Information · 1•DACH 412, 429(sh) 429[+310] 412[-205] +515 1• DPEA 412, 429(sh) 429[+49] 412[-23] +72 Electronic Supplementary Material (ESI) for Chemical Communications

Supporting Information · 1•DACH 412, 429(sh) 429[+310] 412[-205] +515 1• DPEA 412, 429(sh) 429[+49] 412[-23] +72 Electronic Supplementary Material (ESI) for Chemical Communications

Feral Tribune 429

Feral Tribune 429

Arinc-429 Arinc429 Arinc 429 Tutorial

Arinc-429 Arinc429 Arinc 429 Tutorial

Manual: Handheld ARINC 429 Bus Test System - micma.de · 1. ARINC 429 BUS Test Unit 1.1 System Description The ARINC Spec. 429 is a standard used in the civil aviation to distribute

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one piece 429

one piece 429

ARINC 429 ARINC-429 Tutorial - 1553B Arinc429

ARINC 429 ARINC-429 Tutorial - 1553B Arinc429

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 · 24205 3 m.q.56) 358 - 56 (3) 0-2297-8744, 12 56 nth 1. 429/45 26 45 2, 0403/853 16 56 1. /56 56 2 429/2545 429/45 28 45 2.1 2356 29 n,fl.56 429/45

Lab Two, Part 2: Blood and MSA, pg 429 Lab Two, Part 1: Coagulase Test, pg 429

Lab Two, Part 2: Blood and MSA, pg 429 Lab Two, Part 1: Coagulase Test, pg 429

Theranostic application of miR-429 in HER2+ breast cancer. · 1 Theranostic application of miR-429 in HER2+ breast cancer. Running title: miR-429 is a theranostic molecule for HER2+

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Mentoring 429

Mentoring 429

Edición Nº 429

Edición Nº 429

An improved methodology for estimating future reservoir ...webh2o.sws.uiuc.edu/pubdoc/CR/ISWSCR-446.pdfFOR ESTIMATING FUTURE RESERVOIR STORAGE CAPACITIES: APPLICATION TO SURFACE ...

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STATE ROAD 429

STATE ROAD 429

Snippetz Issue 429

Snippetz Issue 429

ARINC 429 Protocol Tutorial 1

ARINC 429 Protocol Tutorial 1

CHAPTER 429

CHAPTER 429

MEET HAWAI‘I Spring... · Total Acct Dir Goals CY 2013 CY 2014 CY 2015 ... Consumption Benchmark 429 429 429 429 429 429 429 429 3,432 ... Tentative Events 167 106 46 20 14 5 6

MEET HAWAI‘I Spring... · Total Acct Dir Goals CY 2013 CY 2014 CY 2015 ... Consumption Benchmark 429 429 429 429 429 429 429 429 3,432 ... Tentative Events 167 106 46 20 14 5 6