Nitrogenremovalfromwastewaterusingmembraneaerated

NitrogenremovalfromwastewaterusingmembraneaeratedmicrobialfuelcelltechniquesChang-PingYua,b,ZhihuaLianga,AtreyeeDasa,ZhiqiangHua,*aDepartmentofCivilandEnvironmentalEngineering,UniversityofMissouri,E2509LafferreHall,Columbia,MO65211,USAbKeyLaboratoryofUrbanEnvironmentandHealth,InstituteofUrbanEnvironment,ChineseAcademyofSciences,Xiamen,361021,ChinaarticleinfoArticlehistory:Received26August2010Receivedinrevisedform22October2010Accepted4November2010Availableonline20November2010Keywords:WastewatertreatmentNutrientremovalMembraneaeratedsystemMicrobialfuelcellabstractNitrogenremovalmainlyreliesonsequentialnitrificationanddenitrificationinwaste-watertreatment.Microbialfuelcells(MFCs)areinnovativewastewatertreatmenttech-niquesforpollutioncontrolandenergygeneration.Inthisstudy,bench-scalewastewatertreatmentsystemsusingmembrane-aeratedMFC(MAMFC)anddiffuser-aeratedMFC(DAMFC)techniqueswereconstructedforsimultaneousremovalofcarbonaceousandnitrogenouspollutantsandelectricityproductionfromwastewater.During210daysofcontinuousflowoperation,whenthedissolvedoxygen(DO)inthecathodiccompartmentwaskeptat2mg/L,bothreactorsdemonstratedhighCODremoval(99%)andhighammoniaremoval(99%)butlownitrogenremoval(20%).WhenalowerDO(0.5mg/L)wasmaintainedafterday121,boththeMFC-basedreactorsstillhadexcellentCODremoval(97%).However,thenitrogenremovalofMAMFC(52%)was2-foldhigherthanthatofDAMFC(24%),indicatinganenhancedperformanceofdenitrificationafterDOreductioninthecathodiccompartmentoftheMAMFC.Meanwhile,terminalrestrictionfragmentlengthpolymorphism(T-RFLP)analysisofammonia-oxidizingbacteria(AOB)populationintheMAMFCindicatedthediversityofAOBwithequallyimportantNitrosospiraandNitrosomonasspeciespresentinthecathodicbiofilmafterDOreduction.TheaveragevoltageoutputintheMAMFCwassignificantlyhigherthanthatinDAMFCunderbothDOconditions.TheresultssuggestthatMAMFCsystemshavethepotentialforwastewatertreatmentwithimprovednitrogenremovalandelectricityproduction.ª2010ElsevierLtd.Allrightsreserved.1.IntroductionDecentralizedoron-sitewastewatertreatmentsystemsarewidelyusedinsuburbs,smalltowns,andruralareas.AccordingtotheU.S.EnvironmentalProtectionAgency(USEPA),approximately25%oftheU.S.populationreliesonsuchsmallwastewatertreatmentsystems(USEPA,2002,2005).Duetolowremovalefficiency,higheffluentconcen-trationsoforganicmatterandnutrientsfromon-sitewaste-watertreatmentfacilitiesarethesubstantialburdenofreceivingwaterbodies(USEPA,2002).Carbonaceousandnitrogenouscompoundscanbeeffec-tivelyremovedinmunicipalwastewatertreatmentplants(WWTPs)usingalternatingaerobiceanoxicprocesses.Conventionalnitrogenremovalmainlyreliesonsequentialnitrificationanddenitrificationbyautotrophicandheterotro-phicmicroorganisms,respectively.Technologiesforefficientnitrogenremovalinsmallwastewatertreatmentsystems,however,havebeenverylimitedbecausethesophisticatedoperationalrequirementsfromWWTPsaredifficulttoapplytodecentralizedsystems.Furthermore,conventionalnitrogenremovalprocessesrequireasignificantamountofreadily*Correspondingauthor.Tel.:þ1(573)8840497;fax:þ1(573)8824784.E-mailaddress:[e-mail](Z.Hu).Availableat(2011)1157e11640043-1354/$eseefrontmatterª2010ElsevierLtd.Allrightsreserved.doi:10.1016/j.watres.2010.11.002biodegradableorganicmatter,oxygen,andthushigh-energyconsumption,resultinginlargeamountsofsludge.Effortsforsimultaneousorganicandnitrogenremovalfromwastewatercontinuetogrow.Inonestudy,anactivatedsludgewastewatertreatmentprocesswithextendedaerationandsludgerecirculationcoupledwithion-exchange,hasbeendemonstratedtoimprovenitrogenandphosphorusremoval(Saffermanetal.,2004).Membranebioreactors(MBR)havealsobeenappliedtoimproveeffluentwaterqualityfromdecentral-izedsystems(Meuleretal.,2008).Theseadvancedtreatmenttechniquesaremoreefficientthancurrentonesusedindecen-tralizedsystems.However,high-energyconsumptionandprohibitivecapitalcostspreventtheirlargescaleapplications.Microbialfuelcells(MFCs)areanemerginginnovativetechniqueofwastewatertreatmentforpollutantremovalandelectricityproduction.Inrecentstudies,simultaneousorganicmatter,nitrateremoval,andpowerproductionwereachievedintwo-chamberMFCreactors(totalvolumefrom0.25to1.3L)wheredenitrificationwasaccomplishedbymicroorganismsinthecathode(Clauwaertetal.,2007;Lefebvreetal.,2008).ArecentlydevelopedMFCwithareactorvolumeof0.336LwascoupledwithanexternalaerobicnitrificationreactortoconvertammoniainthefeedsolutiontonitratebeforeitwascirculatedtotheMFCcathodicchamberfornitrogenremoval(Virdisetal.,2008).However,theset-upofanadditionalexternalnitrifyingbioreactormakesitdifficulttouseinthefield.Meanwhile,recentwastewaterresearchusedamembraneaeratedbiofilmreactor(MABR)processtoremovenitrogenviasimultaneousnitrificationanddenitrification(Huetal.,2009;Semmensetal.,2003).MABRprovidesacounter-diffusionsystemwhereoxygensuppliedtothebaseofthebiofilm(membranetubing)diffusesoutofthebiofilmwhilethesubstratefromthebulkliquidphase,suchasNH4þandorganiccarbon,diffusesintothebiofilm.Withefficientoxygentransf