DemonstrationofinnovativeMABRlowenergynutrie

DemonstrationofinnovativeMABRlow-energynutrientremovaltechnologyatChicagoMWRDJ.Peetersa,*,N.Adamsa,Z.Longa,P.CôtébandT.KunetzcaSuezWaterTechnologies&Solutions,Oakville,CanadabCOTEMembraneSeparationLtd,Dundas,CanadacMetropolitanWaterReclamationDistrictofGreaterChicago,Chicago,USA*Correspondingauthor.E-mail:[e-mail]ABR(membrane-aeratedbiofilmreactor)membranetechnologywasdemonstratedattheO’BrienWaterReclamationPlant(OWRP)oftheMetropolitanWaterReclamationDistrictofGreaterChicago(ChicagoMWRD).Thedemonstrationunitwasequippedwithonefull-scalemembranecassette.Thetechnologywasevaluatedforitspotentialtoimproveperformancefortotalsuspendedsolids(TSS)andammoniaremovalduringstressedconditions(specificallycoldtemperaturepeakflowperiods)andtomeetfutureeffluentphosphorouslimits.Overaperiodof9months,theMABRoxygentransferratewasstableandrangedbetween8and12g-O2/d/m2ofmembranesurfacearea.Thenitrificationratevariedbetween0.5and2.5g-N/d/m2andwasaffectedprimarilybytheammonialoadingrateandthefeedcarbontonitrogenratio.Mostoftheoxygentransferredwasaccountedforbynitrification.TheMABRhybridprocessenablesimportantprocessimprovementswhilereducingplantenergyconsumption.Keywords:biologicalnutrientremoval,low-energywastewatertreatment,MABR,membrane-aeratedbiofilmreactorINTRODUCTIONThemembrane-aeratedbiofilmreactor(MABR)isaninnovativebiofilmprocessthatcanbecom-binedwithactivatedsludgetoimplementbiologicalnutrientremovalwhilesignificantlyreducingplantenergyconsumption(Peetersetal.2014).TheMABRprocessemploysagastransfermem-branetodeliveroxygentoabiofilmthatisattachedtothesurfaceofthemembrane.Whenusedinahybridconfigurationwithactivatedsludge,theMABRprocesscanalsoimprovetreatmentper-formanceandintensifytreatmentcapacitybyincreasingthebiomassinventoryinagivenreactorvolume.Theobjectiveofthisstudywastodemonstratehowthetechnologycouldbeusedtoimprovenutri-entremovalinalargeplantwhilereducingenergyconsumption.Thestudyinvolveddeployingafull-scalemembranecassette(i.e.,acommercialsizebuildingblock)inaside-streamconfigurationattheO’BrienWaterReclamationPlant(OWRP)oftheChicagoMWRD,andrunningitforafullyear(June2015–May2016).Thispapercoverstheresultsobtainedinthefirstninemonthsofthestudy.Sincethedemonstrationplantonlyallowedverificationofsomeofthebenefitsofthetechnology,itwascom-plementedwithamodellingexercise.©IWAPublishing2017WaterPractice&TechnologyVol12No4927doi:10.2166/wpt.2017.096O’BRIENWATERRECLAMATIONPLANTTheOWRPemploysprimaryclarificationandconventionalactivatedsludgefortheremovaloftotalsus-pendedsolids(TSS),BODandammonia.Thefacilityiscomprisedoffoursecondarytreatmentbatterieswhereeachbatteryprocessesapproximatelyonequarteroftheflowindedicatedbioreactorsandsecondaryclarifiers.Theplanttreatstypicaldilutemunicipalsewagewithsomeindustrialcontributionatanaveragedailyflowrateof870MLD.Peakflowstypicallyoccurduringspringrun-offandcanreach1,900MLD.Aphosphorouslimitisanticipatedinthefutureandthepreferredsolutiontomeetthislimitisbyimple-mentingbiologicalphosphorousremoval.Withthecurrentprocessconfiguration,thiswouldrequireconstructinganewtreatmentbatterytofacilitatetheintroductionofananaerobiczone.Thekeyinfluentcharacteristicsbasedonyear2013,andcurrentandfutureeffluentrequirementsaresummarizedinTable1.AMABRbiofilmmodelwasdevelopedincooperationwithHydromantisInc.basedontheprovenmovingbedbioreactor(MBBR)biofilmmodel(Kaldateetal.2010).ThisnewmodelallowsevaluatingtheperformanceofaMABRwithinthegeneralframeworkoftheGPS-Xsimulationsoftware.Inthisstudy,itwasusedtopredictperformancewhenoperatingthefull-scaleplantinahybridMABRcon-figuration.AhybridMABRisasystemthatincludesbiomassbothinsuspensionandfixedinabiofilmattachedtoamembrane.OnefullbatteryoftheOWRPwasmodelledinGPS-Xandcomparedtotheactualplantresultsfrom2013.Thesimulationresultsrepresentedthedatawellandconfirmedthattheplantischallengedtomeetitsammonialimitduringspringrun-off.Duringthisperiod,inordertomaintainanitrifyingbio-mass,themixedliquorsuspendedsolids(MLSS)concentrationhastobeincreasedtoabout2,600mg/L,apointwherethesecondaryclarifiersmaybecomeover-loadedandtheeffluentTSSlimitmaybeexceeded.ThemodelwasthenusedtoshowtheimpactofaretrofitincorporatingMABRtechnology.Finebubbleaerationwasturnedoffinthefirst1/3ofthereactorswhereMABRmembraneswouldbeimmersed.Thesimulationresultsshowedthatabout40%oftheammoniawasnitrifiedonthemem-branes,whichalsoshednitrifyingbiomassintothemixedliquorandallowedreducingthesolidsretentiontime(SRT)ofthesuspendedbiomassfrom11to6dayswithoutlosingfullnitrification.ThisinturnreducedtheMLSStobelow2,000mg/L,solvingthemassloadingproblemofthesecondaryclarifiers.Thesimulationsshowedthatthepresenceofananoxic/anaerobiczoneenabledbiologicalphosphorusremovalandofferedthepotentialformeetingthefutureeffluentlimitof1.0mg/Lwhilestillmeetingnitrificationrequirements,allwithoutchemicaladditionorincreasingthereactorvolume.MABRDEMONSTRATIONUNITInafull-scalesolution,MABRmembranecassetteswouldbeimmersedintheexistingplantbio-reactorssuchthatthebiofilmandthesuspendedbiomassworkintandem.However,tofacilitatemonitoringper