Quantifythecontributionofanammoxforenhancednitroge

QuantifythecontributionofanammoxforenhancednitrogenremovalthroughmetagenomicanalysisandmassbalanceinananoxicmovingbedbiofilmreactorJianweiLia,YongzhenPenga,*,LiangZhanga,JinjinLiua,XiaodanWanga,RuitaoGaoa,LuPangb,YaxuZhoubaNationalEngineeringLaboratoryforAdvancedMunicipalWastewaterTreatmentandReuseTechnology,EngineeringResearchCenterofBeijing,BeijingUniversityofTechnology,Beijing,100124,PRChinabXi'anWaterGroupCompanyLimited,Shaanxi,710018,PRChinaarticleinfoArticlehistory:Received19January2019Receivedinrevisedform14May2019Accepted21May2019Availableonline22May2019Keywords:BiologicalnitrogenremovalAnammoxAnoxic-carrierbiofilmsLowC/NratioMetagenomicanalysisMunicipalwastewaterabstractInthisstudy,enhancednitrogenremovalthroughinsituenrichmentofanammoxbacteriawassuc-cessfullyobtainedinafull-scalemunicipalwastewatertreatmentplant(WWTP).TheWWTPwasananaerobic-anoxic-oxic(AAO)processandupgradedbyaddingmovingcarriersintotheanoxiczone.Enhancednitrogenremovalwasobtainedduringalmosttwoyearsofoperation.Thesignificantnitrogenremovalmightbeassociatedwiththeinsituenrichmentofanammoxbacteriaontheaddingcarriers,asrevealedbythecomprehensiveresultsofmolecularanalysisand15N-stableisotopetracingtests.QuantitativePCRresultsindicatedthatanammoxbacteriaintheanoxic-carrierbiofilmspresentedahigherabundancethanflocculentsludge(16SrRNA:P0.005;HzsB:P0.042).The16SrRNAampliconsequencingshowedsignificantdifferencesinthephylumPlanctomycetes(P0.001)betweenanoxic-carrierbiofilmsandflocculentsludge.Andmetagenomicsequencinganalysisfurtherrevealedtheanammoxrelativeabundanceintheanoxic-carrierbiofilmswassignificantlyhigherthanthereportedlevelintheflocculentsludgeofconventionalWWTPs.Inaddition,15N-stableisotopetracingtestsshowedthatanammoxcouldbecombinedwithnitratereductionbytheanoxic-carrierbiofilms.Thus,enrichedanammoxbacteriamightcontributetonitrogenlossandleadtoimprovementsinthenitrogenremoval,whichwasalsosupportedbythemassbalanceanalysisoforganiccarbon,nitrogen,andphosphorusoftheWWTP.Overall,thisstudysuggeststhatanoxic-carrierbiofilmsmightbeacandidatetoenhancenitrogenremovalthroughpartialanammoxinmunicipalWWTPs.©2019PublishedbyElsevierLtd.1.IntroductionAnaerobicammoniumoxidation(Anammox)isapromisingnitrogenremovalprocess(vanLoosdrechtetal.,2014).Inthisprocess,ammoniumisoxidizedusingnitriteastheelectronacceptortodinitrogengasunderananoxiccondition,andnoorganiccarbonsourceisrequired(Kuenen,2008;Strousetal.,1998).Todate,anammoxtechnologyhasbeensuccessfullyindus-trializedfortreatinghigh-ammoniawastewaterundermoderateconditions(Lackneretal.,2014).Therecentfocusofanammoxtechnologyhasmovedtoapplicationsinmainstreamtreatments(Kartaletal.,2010;Gilbertetal.,2014;Lottietal.,2014a;Winkleretal.,2012),becauseanammoxexhibitsgreatenergysavingpo-tentialformunicipalwastewatertreatmentcomparedwiththeconventionalnitrification/denitrificationprocess(Siegristetal.,2008).Fromtheperspectiveofnitrogentransformation,thesewageanammoxprocessisprimarilyassociatedwithtwodifferentpath-ways.Oneisanammoxcombinedwithpartialnitrification(ammoniatonitrite)(Gilbertetal.,2014;Laurenietal.,2016;Pootetal.,2016;vanDongenetal.,2001;Wangetal.,2014),andtheotherisanammoxcombinedwiththereductionofnitrate(nitratetonitrite)(Castrobarrosetal.,2017;Duetal.,2016;Kartaletal.,2008;Maetal.,2017;Xieetal.,2018).Theabovepathwaysinvolvedifferentprocessesandprovideavarietyofpossibleroutesformainstreamapplicationsofanammox(Agrawaletal.,2018;Ma*Correspondingauthor.E-mailaddress:[e-mail](Y.Peng).ContentslistsavailableatScienceDirectWaterResearchjournalhomepage:://doi.org/10.1016/j.watres.2019.05.0700043-1354/©2019PublishedbyElsevierLtd.WaterResearch160(2019)178e187etal.,2016).Moreover,differentresearchgroupshaveconductedtheimportantstudiesinvestigatingthestabilityofsewageanam-moxtechnology,includinglowtemperatures(Gilbertetal.,2014;Isantaetal.,2015;Laurenietal.,2016),influentcomposition(Laurenietal.,2015;Lottietal.,2014b;Lietal.,2017)andmicrobialcommunityshifts(Reinoetal.,2018;Wenetal.,2017).Thesesig-nificantprogressesstronglysupportthepotentialofapplyinganammoxtechnologytotreatlow-ammoniamunicipalwastewater.Althoughsewageanammoxtechnologyhasbeenwidelystud-ied,theapplicationofanammoxinthefull-scalewastewatertreatmentplant(WWTP)remainstobefullystudied.Oneofthemostconcerningobstaclesistheslowgrowthrateofanammoxbacteria(Gilbertetal.,2014;Laurenietal.,2016).Previousstudieshavereportedthatanammoxbacteriaexistuniversallyintradi-tionalfull-scalemunicipalWWTPs(Guoetal.,2017;Nejidatetal.,2018;Shuetal.,2015;Tsushimaetal.,2007;Wangetal.,2015).However,thedirectapplicationofanammoxtechnologytoWWTPsisdifficultsinceanammoxbacteriaarelowinabundanceandsensitivetoenvironmentalconditionssuchashighdissolvedoxy-gen(DO)andorganiccarbonconcentrations(Jettenetal.,1998).Recentpilot-andfull-scaledemonstrationsofsewageanammoxtechnologyhaveusuallybeentestedusingtheinoculationofanammoxsludgefromasidestreamtreatment(Lemaire,2014;Lottietal.,2014a)andthereductionofinfluentorganiccarbonthroughpretreatment(Laurenie