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BioresourceTechnology98(2007)1849–18550960-8524/$-seefrontmatter©2006ElsevierLtd.Allrightsreserved.doi:10.1016/j.biortech.2006.06.014TheperformanceofaphaseseparatedgranularbedbioreactortreatingbrewerywastewaterM.I.Balocha,¤,J.C.Akunnab,1,P.J.Collierc,2aWessexWater,BristolWastewaterTreatmentWorks,KingsWestonLane,Avonmouth,Bristol,BS110YS,UKbUrbanWaterTechnologyCentre,SchoolofContemporarySciences,UniversityofAbertayDundee,BellStreet,Dundee,DD11HG,UKcDivisionofBiotechnologyandForensicSciences,SchoolofContemporarySciences,UniversityofAbertayDundee,BellStreet,Dundee,DD11HG,UKReceived17June2005;receivedinrevisedform11May2006;accepted19June2006Availableonline1September2006AbstractThisstudypresentstheperformancecharacteristicsofaplugXowphaseseparatedanaerobicgranularbedbaZedreactor(GRABBR)fedwithbrewerywastewateratvariousoperatingconditions.Thereactorachievedchemicaloxygendemand(COD)removalof93–96%withhighmethaneproductionwhenoperatedatorganicloadingrates(OLRs)of2.16–13.38kgCODm¡3d¡1.ThereactorconWgurationandmicrobialenvironmentencouragedtheacidogenicdominantzonetoproduceintermediateproductssuitablefordegradationinthepredominantlymethanogeniczone.NoticeablephaseseparationbetweenacidogenesisandmethanogenesismainlyoccurredathighOLR,involvingagreaternumberofcompartmentstocontributetowastewatertreatment.Thehighlyactivenatureandgoodsettlingcharacter-isticsofmethanogenicgranularsludgeoVeredhighbiomassretentionandenhancedmethanogenicactivitieswithinthesystem.Thegran-ularstructureintheacidogenicdominantzoneoftheGRABBRwassusceptibletodisintegrationandXotation.Methanogenicgranularsludgewasamulti-layeredstructurewithMethanosaeta-likeorganismsdominantinthecore.©2006ElsevierLtd.Allrightsreserved.Keywords:GranularbedbaZedreactor;Phaseseparation;Anaerobicgranularsludge;Acidogenesis;Methanogenesis;Brewerywastewater1.IntroductionThereareperceptibleadvantagesofanaerobicsystemsoveraerobicmetabolicsystems,andthesehavebeenwidelyreportedinthelastfourdecades(McCarty,1964;Ghoshetal.,1975;Andersonetal.,1980;McCartyandSmith,1986;Lettinga,1995).Breweriesarelargeindustrialconsumersofwateraswellaslargeproducersofwastewater.Duetothehighbiode-gradabilityandvaryingnatureofbrewerywastes,anaero-bicprocesseshavebeenwidelyusedfortheirtreatment(Frankin,2001).ThisindustrialsectorhasbeenspeciWcallymentionedintheEuropeanUnionDirective,i.e.EuropeanUrbanWasteWaterTreatmentDirective(91/271/EEC),whichrequirescontroloftheireZuentdischarge(EuropeanUnionCouncilofMinisters,1991).AnaerobicdegradationprocessesinvolvelargenumbersofdiVerentmicroorganisms;however,theprocessismainlydrivenbytwotypesofreactions,i.e.acidogenesisandmetha-nogenesis(Zoetemeyeretal.,1982).Excessvolatilefattyacid(VFA)concentrationsintheeZuentaremainlyduetoimproperbalancebetweenacidogenesisandmethanogenesisduetothedominanceoftheacidogenicprocessandsuppres-sionofmethanogenicactivity.Inphaseseparationsystems,optimisedconditionsareachievedforthegrowthofacido-gensandmethanogensindiVerentzonestomaximisetheiractivities(PohlandandGhosh,1971;Andersonetal.,1994;BarberandStuckey,1999;Shinetal.,2001).Theintroductionofanaerobicgranularsludgebedtechnologyhasshownnewpotentialsofanaerobicprocessesforindustrialwastewater*Correspondingauthor.Tel.:[phone];fax:[phone].E-mailaddresses:[e-mail](M.I.Baloch),[e-mail](J.C.Akunna),[e-mail](P.J.Col-lier).1Tel.:[phone];fax:[phone]Tel.:[phone];fax:[phone].1850M.I.Balochetal./BioresourceTechnology98(2007)1849–1855treatment(Mulderetal.,2001).Therefore,combiningthecon-ceptofphaseseparationwithagranularbedwillencouragegreaterexploitationofanaerobicwastewatertreatmenttech-nology(BalochandAkunna,2003a,b;Balochetal.,2006).Inthisstudy,thepropertiesofananaerobicbaZedreac-tor(ABR)andgranularsludgehavebeenbroughttogethertocreateananaerobicgranularbedbaZedreactor(GRABBR).TheGRABBRisananaerobicsystemwithplugXow,multi-phasegranularbedcharacteristics(BalochandAkunna,2003a,b;Balochetal.,2006).Thissystemhasbeeninvestigatedwithsyntheticwastewaterforcarbona-ceousmatterremoval(BalochandAkunna,2003a,b).How-ever,thepotentialofthisconWgurationfortreatingnaturalorrealindustrialwastewatershasnotbeenfullyexplored.Hence,thisstudyaimedtoinvestigatetheperformanceoftheGRABBRintreatingbrewerywastewaterintermsoftreat-menteYciencyandtheeVectofmicrobialselectionorsegre-gationwithinthesystemonreactorcharacteristics.2.Methods2.1.ReactorconWgurationA10lworkingvolumelaboratoryscaleperspexreactorwasdividedintoWveequalsizedcompartments,separatedbyverticalbaZesalternativelyhangingandstanding,inordertoachievephaseseparationcharacteristicswithinthesystem.Aconstanttemperatureof35°Cwasobtainedbyrecirculatingheatedwaterthroughawaterjacketattachedtothereactor.Adetaileddescriptionofreactordesignandset-upisgivenelsewhere(BalochandAkunna,2003a).2.2.BrewerywastewaterThebrewerywastewaterwasobtainedfromthetankbot-tomsofalocalbrewery.Theprincipalstagesinbrewingbeeraremashing,boilingandfermentationfollowedbycooling,clariWcation,paste