MovingBedBiofilmReactorTechnology

MovingBedBiofilmReactorTechnology:ProcessApplications,Design,andPerformanceJamesP.McQuarrie1,JoshuaP.Boltz2*ABSTRACT:Themovingbedbiofilmreactor(MBBR)canoperateasa2-(anoxic)or3-(aerobic)phasesystemwithbuoyantfree-movingplasticbiofilmcarriers.Thesesystemscanbeusedformunicipalandindustrialwastewatertreatment,aquaculture,potablewaterdenitrification,and,inroughing,secondary,tertiary,andsidestreamapplications.Thesystemincludesasubmergedbiofilmreactorandliquid–solidsseparationunit.TheMBBRprocessbenefitsincludethefollowing:(1)capacitytomeettreatmentobjectivessimilartoactivatedsludgesystemswithrespecttocarbon-oxidationandnitrogenremoval,butrequiresasmallertankvolumethanaclarifier-coupledactivatedsludgesystem;(2)biomassretentionisclarifier-independentandsolidsloadingtotheliquid–solidsseparationunitisreducedsignificantlywhencomparedwithactivatedsludgesystems;(3)theMBBRisacontinuous-flowprocessthatdoesnotrequireaspecialoperationalcycleforbiofilmthickness,LF,control(e.g.,biologicallyactivefilterbackwashing);and(4)liquid–solidsseparationcanbeachievedwithavarietyofprocesses,includingconventionalandcompacthigh-rateprocesses.Informationrelatedtosystemdesignisfragmentedandpoorlydocumented.Thispaperseekstoaddressthisissuebysummarizingstate-of-theartMBBRdesignproceduresandprovidingthereaderwithanoverviewofsomecommerciallyavailablesystemsandtheircomponents.WaterEnviron.Res.,83,560(2011).KEYWORDS:biofilm,carbonoxidation,nitrification,denitrification,partialnitritation,Anammox,movingbedbiofilmreactor.doi:10.2175/106143010X12851009156286IntroductionandBackgroundThemovingbedbiofilmreactor(MBBR)canbeoperatedasa2-(anoxic)or3-(aerobic)phasesystemwithbuoyantfree-movingplasticbiofilmcarriersthatrequireenergy(i.e.,mechanicalmixingoraeration)foruniformdistributionthroughoutthebulkphase.Informationrelatedtosystemdesignisfragmentedandpoorlydocumented.TheauthorsrecentlyhavemadecontributionstoestablishingauniformapproachtoMBBRprocessdesignbycomposingrelevantsectionsinaprominentNorthAmericandesignguide(seeBoltz,Morgenroth,deBarbadillo,Dempsey,McQuarrie,Ghylin,Harrison,andNerenberg,2010).SimilardesignguidancealsoexistsinNorthEurope(seeØdegaardetal.,2009).Thesesystemscanbeusedformunicipalandindustrialwastewatertreatment,aquaculture,potablewaterdenitrification,andinroughing,secondary,tertiary,andsidestreamapplications.Theprocessincludesasubmergedbiofilmreactorandliquid–solidsseparationunit.Morethan600MBBRswereoperatingin50differentcountiesin2009.AccordingtoRustenetal.(2006),thefirstMBBRinstalledinNorway(EuropeanPatentNo.0.575,314;U.S.PatentNo.5,458,779)hasbeeninspectedroutinely,andnoperformance-influencingplasticbiofilmcarrierwearhadbeenobservedafter15yearsofcontinuousoperation.Processbenefitsincludethefollowing:(1)Abilitytomeettreatmentobjectivessimilartoactivatedsludge,withrespectto5-daybiochemicaloxygendemand(BOD5)andnitrogenremoval,inasmallertankvolume(Andreottolaetal.,2000).(2)Biomassretentionisclarifier-independent.(3)MBBRisacontinuous-flowprocessthatdoesnotrequireaspecialoperationalcycleforbiofilmthicknesscontrol.(4)Liquid–solidsseparationcanbeachievedwithsedimentationbasins,dissolvedairflotation,ballastedflocculation,granularmediafiltration,cloth-discfiltration,andmembrane(UF/MF)filtration.(5)MBBRsarewell-suitedforretrofitinstallation.ResearchanddevelopmentsupportingtheMBBR-processresultedfromapoliticalagreementamongNorth-Europeancountriestomakeanapproximately50%reductioninnutrientdischargetotheNorthSeaduringtheperiod1985to1995(Hemetal.,1994).GeneralDescriptionAnMBBRmaybeasinglereactororconfiguredasseveralreactors-in-series.Typically,eachMBBRhasalength-to-widthratio(L:W)intherange0.5:1to1.5:1.PlanswithaL:Wgreaterthan1.5:1canresultinthefree-movingplasticbiofilmcarriersbeingnon-uniformlydistributedthroughoutthebioreactor.Asaresult,thesystemissubjectedtopooroxygentransferefficiencyandreducedhydrauliccapacityoftheplasticbiofilmcarrierretentionscreens.TheMBBRscontainaplasticbiofilmcarriervolumeupto67%oftheemptybedliquidvolume(orcarrierfill).PlasticbiofilmcarrierretainingscreenstypicallyareinstalledwithoneMBBRwallandallowtreatedeffluenttoflowthroughtothenexttreatmentstep.AerobicMBBRsuseadiffusedaerationsystemtouniformlydistributeplasticbiofilmcarriersandmeetprocessoxygenrequirements.Plasticbiofilmcarriersindenitri-ficationMBBRsaredistributedbymechanicalmixers.Biofilmthicknessiscontrolledbyairflowormechanicalmixingenergy.1MetroWastewaterReclamationDistrict,Denver,Colorado.2CH2MHILL,Inc.,Tampa,Florida.*CH2MHILL,Inc.,4350WestCypressStreet,Suite600,Tampa,Florida33607,USA;e-mail:[e-mail].560WaterEnvironmentResearch,Volume83,Number6Table1.—Plasticbiofilmcarriercharacteristicsreportedbythemanufacturer.ManufacturerNameBulkSpecificSurfaceArea1Dimensions(Depth;Diameter)CarrierPhotographVeoliaInc.AnoxKaldnesTMK1orK1Heavy500m2/m37mm;10mmAnoxKaldnesTMK3500m2/m312mm;25mmAnoxKaldnesTMBiofilmChip(M)1,200m2/m32mm;48mmAnoxKaldnesTMBiofilmChip(P)900m2/m33mm;45mmAnoxKaldnesTMMatrixTMSol800m2/m34mm;25mmHeadworksBIO(*Licensedby:InfilcoDegremont,Inc.)ActiveCel