Nitrogenremovalperformanceandmicrobialcommuni

ecologicalengineering32(2008)256–262availableatfilmreactorSiqingXia∗,JunyingLi,RongchangWangStateKeyLaboratoryofPollutionControlandResourceReuse,KeyLaboratoryofYangtzeRiverWaterEnvironment,MinistryofEducation,CollegeofEnvironmentalScienceandEngineering,TongjiUniversity,Shanghai200092,PRChinaarticleinfoArticlehistory:Received13August2007Receivedinrevisedform14November2007Accepted24November2007Keywords:Suspendedcarrierbiofilmreactor(SCBR)MicrobialcommunitystructureSimultaneousnitrificationanddenitrification(SND)Denaturinggelgradientelectrophoresis(DGGE)Fluorescenceinsituhybridization(FISH)MicrobialcommunitystructureRatioofcarbontonitrogen(C/N)abstractAcompactsuspendedcarrierbiofilmreactor(SCBR)wasdevelopedforsimultaneousnitrifi-cationanddenitrification(SND)inasinglereactorandtheperformanceofnutrientremovalwasinvestigated.Microbialcommunitystructureresponsetodifferentratioofcarbontonitrogen(C/N)wasdeterminedbydenaturinggelgradientelectrophoresis(DGGE)profilesof16SrDNAV3regionandamoAgeneamplifications.Inaddition,thepopulationdynamicsofammonia-oxidizingbacteria(AOB)andnitrite-oxidizingbacteria(NOB)wereestimatedbyfluorescenceinsituhybridization(FISH)with16SrDNA-targetedoligonucleotideprobes.ResultsshowedthatthecompactSCBRwasefficientinnutrientremovalwithCODCrremovalefficiencyover90%andSNDefficiency(ESND)about83.3%.Thediversityofmicrobialcom-munitystructurewaspositivelycorrelatedwithC/Nratio,whilethethreecommunitiesofamoAgenewererelativityhomogenous.Thepopulationofnitrifierswasininversepropor-tionstoC/NratiowiththeaveragefractionofAOBandNOBtoallbacteria5.4,4.8,3.1%and4.6,3.5,2.7%respectivelyasC/Nratiochangingfrom3:1,5:1to10:1.ThereforewecouldreachaconclusionthatthecompactSCBRwaspracticaltotreatmunicipalwastewaterandtheshiftofmicrobialcommunitymonitoredbymoleculartechnologiescouldofferguidancetotheprocessoptimizationinengineering.©2007ElsevierB.V.Allrightsreserved.1.IntroductionThecurrentwastewatertreatmentsystemisrequiredforremovalofnitrogenouscompoundswhichcancausetheeutrophicationofsurfacewaterbodies.Biologicalnitro-genremovaltechnologiesarecommonlyusedduetolowerenergyconsumptionandoperationcost.Nowadayswithmoreresearchintothemechanismsofnitrogencycle,e.g.,shortcutnitrification–denitrification,SND,moreandmoresustain-∗Correspondingauthor.Tel.:[phone].E-mailaddress:[e-mail](S.Xia).ableprocesseshaveappeared,includingthesinglereactorhighactivityammoniaremovalovernitrite(SHARON)pro-cess,oxygen-limitedautotrophicnitrification–denitrification(OLAND),anaerobicammoniumoxidation(ANAMMOX)andcompletelyautotrophicnitrogenremovalovernitrite(CANON)processes(Paredesetal.,2007).Biofilmsoccurubiquitouslyinnatureandthenaturalimmobilizationallowsexcellentbiomassretentionandaccumulationwithouttheneedforseparatesolids-separationdevices.Becauseofsimple,reliable0925-8574/$–seefrontmatter©2007ElsevierB.V.Allrightsreserved.doi:10.1016/j.ecoleng.2007.11.013ecologicalengineering32(2008)256–262257andstablecharacteristics,biofilmprocessessuchastricklingfilter,biologicalaeratedfilter(BAF)(Rotheretal.,2002),rotatingbiologicalcontactor(RBC)(Wyffelsetal.,2003),fluidizedbedreactor(FBR)(Prudenetal.,2003),suspendedcarrierbiofilmreactor(SCBR)(Wangetal.,2005)andmembranebio-reactor(MBR)(Choietal.,2006)havebeenfoundtoremovenutri-entsandotherpollutantsbothfromdomesticandindustrywastewater.Thekeyofefficientbiologicalwastewatertreatmentreliesonknowingtotheorganismsinvolvedandhowtheyrespondtodifferentoperationalconditions.Muchresearchhasbeendoneaboutthemembersandstructureofmicrobialcommu-nitybasedontraditionalcultivationtechnologyandmolecularmethodsincludingthe16SrDNA-basedmoleculartechnolo-giessuchasPCR-DGGE,FISH,clonelibraryandterminalrestrictionfragmentlengthpolymorphisms(T-RFLP),whichhavebeenshowntobepowerfultoolsformonitoringthedynamicsofmicrobialcommunityandthecompositionofgroup-specificorganismsinwastewatertreatmentsystems(SanzandKochling,2007;Ishidaetal.,2006;SwigerandTucker,1996;MoterandGobel,2000).Thesemoleculartechniqueswithitsmainadvantagesanddrawbackshavebeendevelopedatmostlyatlab-scale.Toengineers,thereisarealpotentialforcombiningthecontributionsfrommolecularbiologywiththedesignprinciplesofecologicalengineering(MitschandJorgensen,2003;ToddandJosephson,1996).Thisisthebiggestchallengeandpowerfultoolsfordesignofmoreefficientsys-temsfacingenvironmentalmicrobiology.Thetraditionalnitrogenremovalprocessconsistsofacom-binationofaerobicnitrificationcatalyzedbyautotrophsandanaerobicdenitrificationbyheterotrophs,whichmeansthatnormallytworeactorshavetobeconstructedseparatelyforcompletenitrogenremoval.Otherstudiesshowedthatnitri-ficationanddenitrificationoccurredconcurrentlyinasinglereactorunderaerobicconditions(Guoetal.,2005b;Yooetal.,1999).Ascarbonsourceandelectrondonors,composi-tionofcarbonandnitrogenoussubstratesiscriticalduringthecompetitionbetweenautotrophsandheterotr