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Resources,ConservationandRecycling55 (2011) 1232–1251

ContentslistsavailableatScienceDirect

Resources,ConservationandRecycling

journalhomepage:/locate/resconrec

Review

SustainableoptionsofposttreatmentofUASBeffluenttreatingsewage:Areview

AbidAliKhan

a,∗

,RubiaZahidGaur

a

,

a

,AnwarKhursheed

a

,BeniLew

b

,

InduMehrotra

a

,

a

a

b

DepartmentofCivilEngineering,IITRoorkee,NH58,Uttrakhand247667,India

TheVolcaniCenter,InstituteofAgricultureEngineering,BetDagan50250,Israel

a

rticleinfo

abstract

Articlehistory:

Received19February2010

Receivedinrevisedform16May2011

Accepted17May2011

Keywords:

Highratemicro-aerobictreatmentsystems

NBMS

Postsettlingtreatmentstep

Polishing

methods

Sewage

UASB

posttreatment

Theupflowanaerobicsludgeblanket(UASB)processisreportedtobeasustainabletechnologyfordomes-

ticr,theinabilityof

UASBprocesstomeetthedesireddisposalstandardshasgivenenoughimpetusforsubsequentposttreat-

rtoupgradetheUASBbasedsewagetreatmentplants(STPs)toachievedesiredeffluent

quality

fordisposalorforreuse,varioustechnologicaloptionsareavailableandbroadlydifferentiated

as

primarypost-treatmentfortheremovaloforganicandinorganiccompoundsandsuspendedmatter;

secondarypost-treatmentfortheremovalofhardlydegradablesolublematter,colloidalandnutrients;

,thispaperdiscussesthedifferentsystemsfor

thetreatmentofUASBreactorefflonally,acomparativereview,aneconomic

evaluation

ofsomeoftheemergingoptionswasconductedandbasedontheextensivereviewofdifferent

integrated

combination,-differentaerobicsystems,atreatmentconceptbasedonnaturalbio-

logicalmineralizationrouterecognizedasanadvancedtechnologytomeetallpracticalaspectstomake

itasustainableforenvironmentalprotection,resourcepreservationandrecoveringmaximumresources.

© 2011 Elsevier B.V. All rights reserved.

Contents

1.

2.

1233

PosttreatmentoptionsofUASBreactor’seffl.1235

2.1.

Characteristicsofeffl1235

2.1.1.

1235

................................................................................................................................1235

dcompounds.

.................................................................................................................1235

2.1.4.

1236

1236

1236

1238

2.3.

Physicalandbiologicalmicro-aerobicmethods(includingremoval/orrecoveryofdissolvedgases)........................................1238

tebiologicalaerobicmethods(includingnitrification–denitrificationsteps).........................................................1239

eprimaryposttreatmentsystems(includingvalorization/orremovalofnutrients).................................................1242

1244

1245

1246

1246

Conclusions.

............................................................................................................................................1249

References.

.............................................................................................................................................1249

3.

4.

∗

Correspondingauthor.

E-mailaddresses:abidkdce@,@().

0921-3449/$–seefrontmatter© 2011 Elsevier B.V. All rights reserved.

doi:10.1016/rec.2011.05.017

al./Resources,ConservationandRecycling55 (2011) 1232–12511233

uction

Anaerobictreatmentofdomesticwastewaterisnotanewcon-

ceptandfromtimeimmemorialseptictanks,soakpits,cesspool,

hesesystemscanonlypartiallytreatthe

sewageand,theeffluentstillcontainshighconcentrationoforganic

matter,suspendedsolidsandnutrients,theinterestforsewage

re

numerousaerobictreatmentsystemssomeofwhichinclude,acti-

vatedsludgeprocess(ASP),fluidizedbedreactors(FBR),trickling

filter(TF),lessofthe

goodtreatmentperformanceandlowlandrequirementofaerobic

systems;thesemethodssufferfromplentifuldrawbacksascom-

paredtoanaerobictreatmentsystems(alsosummarizedinTable1)

(Lettinga,2008):

•

Energyintensive;

•

Productionofhighandpoorlystabilizedsludge(60–70%of

incomingCODisconvertedtobiomass);

•

Highinvestmentandoperational/maintenancecost;

•

Complex

infrastructure.

Though,mostoftheabovementioneddrawbacksarenotasso-

ciatedwithoxidationpondsbuthighlandareaisneededwhich

isveryuneconomicalindenselypopulatedcountrieslikeIndia.

Therefore,thesementioneddrawbacksmaketheanaerobicsys-

tems

suitableforruralareasanddevelopingcountries.

Withtheadventofhighrateanaerobicsystemssuchasup-flow

anaerobicsludgeblanketreactor(UASB),anaerobiccontactprocess,

anaerobicfilter(AF)orfixedfilmreactorsandfluidizedbedreac-

tors,whichpromoteagoodcontactbetweentheinflowwastewater

andthemicro-organismsathighconcentrationandconsequently

highorganicmatterremovalatshortretentiontimes,thestrategy

forthetreatmentofsewagewasshiftedbacktoanaerobicprocess

whichhastheadvantagesoflowcost,energyrecoveryintheform

ofbiogas,operationalsimplicity,lowenergyconsumption,andlow

1970s,duetotheenergycrisisand

relativelylessexpensivetreatmentconcept,theUASBprocesswas

recognizedasoneofthemostfeasiblemethodforthetreatmentof

sewageindevelopingtropicalandsub-tropicalcountrieslikeIndia,

BrazilandColombiawherefinancialresourcesaregenerallyscarce.

Since1980,thediscussionontheapplicabilityofUASBpro-

cessforthetreatmentofsewagehasbeenpresentedbyLettinga

andco-researchers(Lettingaetal.,1980,1981,1993;Lettinga

and

HulshoffPol,1986;Seghezzoetal.,2002;vonSperlingand

Chernicharo,2005;Lettinga,2008)andtheresultsindicatedthat

about70%chemicaloxygendemand(COD)removalcanbeachieved

inwarmclimatescountries(Schellinkhoutetal.,1985;Souza,1986;

Siddiqi,1990;Khan,2011).Presentlyabout30UASBbasedSTPs

wereinstalledinIndiasincelate1980sandmorethan20areunder

construction(MoEF,2005and2006).

Therefore,singlestepUASBprocessundoubtedlyexperienced

r,the

treatmentefficiencydecreaseswiththedecreaseintemperature,

reachinga50%CODremovalat15

◦

C(Elmitwallietal.,2001;

SinghandViraraghavan,2002;Lewetal.,2003).TheUASBreactor

performanceatlowtemperaturescanbeimprovedbychang-

ingitsconfigurationlikeincorporatingsettlerabovetheGLSS

(gas–liquid–solidseparator),oraddingtheAFatthetopofthe

UASBreactor,makingitasahighrateanaerobichybridreactorand

extended(staged)typesofUASB-systems,-reactorscom-

pletedwithanAForsupplementedwithadditionalsludgedigester

operatedatoptimaltemperatureforstabilizingsludge‘extracted’

fromtheUASBreactor,whichfollowingitsstabilizationinthe

digesterpartiallywillbereturntotheUASBreactorinorderto

keepthemethanogenicactivityatasuffi-

formance

ofUASB-Digestersystemfororganicmatterremovalwas

observedsubstantiallybetterattemperatureof15

◦

Cascompared

tosinglestepUASBreactoratlowtemperature(Mahmoud,2002).

Thetwo-stepUASBsystemwasstudiedbyvariousauthors(Sayed

andFergala,1995;Halalsheh,2002;Seghezzo,2004).However,

resultsshowedsimilarperformanceofthetwo-stepreactorincom-

parisontoaone-stepsystem,duetolowerremovalefficienciesin

thesecondstage,whichwasattributedtolowsludgeretentiontime

(SRT).TypicalproblemsofhighlyloadedUASBreactorslikesludge

flotationandwashoutofactivebiomasswereobserved,mainlyat

temperaturesbelow20

◦

(1994)evaluatedatwostagesys-

temcomposedofUASB-EGSB(expandedgranularsludgebed)for

maryobjectiveofthe

first-steptreatmentwastheremovalandpartialhydrolysisofsus-

pendedCODandthesecond-stepprocessobservedtoconvertthe

dissolvedCODtoenergyrichmethanegas.

ChernicharoandMachado(1998)studiedpilotscalesystem

composedofthreeunitsviz.;416LUASBreactoroperatedat6h

and4hhydraulicretentiontime(HRT)followedbytwoanaero-

bicfiltersinupflowanddownfl

anaerobicfiltershadatotalcapacityof102L(32Lofpackingmate-

rial),operatedatHRTvaryingfrom24to1.5h(upflowvelocities

variedfrom0.06to1.44m/h).Theselectionofupwardanddown-

flowmodeofAFsoperationwastoidentifytheextentofremoval

oforganicmatterduetophysicalmechanismsofsedimentation

andfiltrationthatarepredominantinupwardmodeorbiochemi-

nflowmode

wasmeanttoinduceattachedgrowthasabiofilmthatfavoursthe

Breactorperformedwellalmost

achievingabove80%ultsdepictedthat

theAFsadditionallypromotedtheremovalwhichimprovedthe

overallefficiencyofthesystemwithintheambitofonlyanaero-

rallCODandbiologicaloxygendemand(BOD)

removalvariedfrom85to95%andtheconcentrationoffinalefflu-

entCODrangedfrom60to90mg/LandtheBODandSSvalueswere

lessthan40and25mg/L,r,theauthorssug-

gestedthatUASB-AFsystemcouldbeanoptionforthetreatmentof

domesticsewageindevelopingcountries,sincethesystemcould

beoperatedatanHRTof6hforUASBand3–4

hforAFresulting

inverycompactandlowcosttreatmentbesidesthistherewasno

energyconsumption.

Similarly,Elmitwallietal.(1999)andLewetal.(2004)com-

paredtheperformancesofahybridUASB-filterandaclassicalUASB

reactorforthetreatmentofdomesticwastewateratdifferentoper-

ational

temperatures(28,20,14and10

◦

C)

eachtemperaturestudiedaconstantCODremovalwasobserved

aslongastheupflowvelocitywaslowerthan0.35m/hinboth

r,atlowertemperatureof14and10

◦

CtheUASB

reactorshowedabetterCODandTSSremovalthanthehybridreac-

tor.

AgainElmitwallietal.(2003)studiedacompositesystemof

twostepanaerobicsystemfollowedbyaerobicsystemconsist-

ingofanaerobicfilter,anaerobichybridreactorandtricklingfilter

(AF+AH+TF)ratingconditionssuchas

HRTandtemperatureweremoreorlesssimilartoothertwostep

atmentperformanceoftwostepanaerobicsystem

(AF+AH)wasimprovedfrom63%to85%

treatedeffluentofthisstagedsystemcanbereusedforrestricted

irrigationandnutrientcanberecycled.

Mahmoudetal.(2004)investigatedacombinedUASB-CSTR

(completelystirredtankreactor)digestersystem,wheretheaccu-

mulatedsludgefromtheUASBreactorwasthendirectedtoa

CSTR-digester,operatingat35

◦

s

showedthattheUASB-CSTRdigesterhadabetterperformancethan

asinglestageUASBreactorat15

◦

ovalefficienciesfor

total,suspended,colloidalanddissolvedCODwere72,74,74and