Tracking-particle-size-distributions-in-a-moving-bed-biofilm-membrane-reactor-for-treatment

TrackingparticlesizedistributionsinamovingbedbiofilmmembranereactorfortreatmentofmunicipalwastewaterR.M.Åhl*,T.Leiknes*,H.Ødegaard**NTNU-NorwegianUniversityofScienceandTechnology,DepartmentofHydraulicandEnvironmentalEngineering,S.P.Andersensvei5,N-7491Trondheim,Norway.(E-mail:magnus.ahl@ntnu.no,torove.leiknes@ntnu.no,hallvard.odegard@ntnu.no)AbstractAstudyhasbeenconductedtoinvestigatetheeffectofloadingratesonmembranefoulinginamovingbedbiofilmmembranereactorprocessformunicipalwastewatertreatment,especiallyanalyzingthefateofsubmicroncolloidalparticlesandtheirinfluenceonmembranefouling.Twooperatingconditionsdefinedaslowandhighorganicloadingratesweretestedwherethedevelopmentandfateoftheparticulatematerialwascharacterizedanalyzingtheparticlesizedistributionsthroughouttheprocess.Analysisofthemembraneperformanceshowedhigherfoulingratesforthehigh-rateconditions.Thefractionofcolloidalsubmicronparticleswashigherinthemembranereactorindicatingthatfoulingbytheseparticleswasadominantcontributiontomembranefouling.KeywordsParticlesizedistribution,wastewater,membranebioreactors,fouling,INTRODUCTIONMembranebioreactors(MBR)arecommonlyunderstoodasthecombinationofmembranefiltrationandbiologicaltreatmentusingactivatedsludge(AS)wherethemembraneprimarilyservestoreplacetheclarifierinthewastewatertreatmentsystem(vanderRoestetal.,2002).Avarietyofprocessconfigurationsexistwherethemembraneisinstalledeitherinanexternalunitorimmersedintheaerationtankandwherethesystemsaredesignedtobeoperatedunderlow-pressurevacuum.OneofthebenefitsofAS-MBRscomparedtoconventionalactivatedsludgesystemsisthattheycanbeoperatedathighersuspendedbiomassconcentrationsresultinginlongsludgeretentiontimesevenatsmallreactorvolumes.However,ascommonwithallmembraneprocesses,theefficacyoftheMBRislargelyconstrainedbyfouling,i.e.theaccumulationofmaterialsonthesurfaceoforwithinthemembraneresultinginareductioninthemembranepermeability.FoulingisparticularlyaprobleminMBRssincetheprocessdealswithliquorshavinghighconcentrationsoftotalsoli