2014Pollutantremovalfrommunicipalwastewaterem

1AcceptedManuscriptTitle:Pollutantremovalfrommunicipalwastewateremployingbaffledsubsurfaceflowandintegratedsurfaceflow-floatingtreatmentwetlandsAuthors:TanveerSaeed,AbdullahAl-Muyeed,RumanaAfrin,HabiburRahman,GuangzhiSunDOI:10.1016/S1001-0742(13)60476-3ReceivedDate:22May2013RevisedDate:15August2013AcceptedDate:16August2013ThisisaPDFfileofanuneditedmanuscriptthathasbeenacceptedforpublication.Themanuscriptwillundergocopyediting,typesetting,andreviewoftheresultingproofbeforeitispublishedinitsfinalform.Pleasenotethatduringtheproductionprocesserrorsmaybediscoveredwhichcouldaffectthecontent,andalllegaldisclaimersthatapplytothejournalpertain.2Pollutantremovalfrommunicipalwastewateremployingbaffledsubsurfaceflowandintegratedsurfaceflow-floatingtreatmentwetlandsTanveerSaeed1,*,AbdullahAl-Muyeed1,RumanaAfrin1,HabiburRahman2,GuangzhiSun31.DepartmentofCivilEngineering,AhsanullahUniversityofScienceandTechnology,Dhaka1208,Bangladesh.E-mail:[e-mail];[e-mail]ring,BangladeshUniversityofEngineeringandTechnology,Dhaka1000,Bangladesh3.SchoolofEngineeringandPhysicalSciences,JamesCookUniversity,Townsville,QLD4811,AustraliaReceived22May2013;revised15August2013;accepted16August2013Abstract:Thisarticlereportspollutantremovalperformancesofbaffledsubsurfaceflow,andintegratedsurfaceflow-floatingtreatmentwetlandunits,whenarrangedinseriesforthetreatmentofmunicipalwastewaterinBangladesh.Thewetlandunits(ofthehybridsystem)includedorganic,inorganicmedia,andwereplantedwithnineteentypesofmacrophytes.Thewetlandtrainwasoperatedunderhydraulicloadingfluctuationandseasonalvariation.Theperformanceanalyses(acrossthewetlandunits)illustratedsimultaneousdenitrificationandorganicsremovalratesinthefirststageverticalflowwetland,duetoorganiccarbonleachingfromtheemployedorganicmedia.Highermeanorganicsremovalrates(656.0gCOD/(m2·day))didnotcompletelyinhibitnitrificationinthefirststageverticalflowsystem;suchpatterncouldbelinkedtoeffectiveutilizationofthetrappedoxygen,astheflowwasdirectedthroughoutthemediabythebafflewalls.Secondstagehorizontalflowwetlandshowedenhancedbiodegradableorganicsremoval,whichdepletedorganiccarbonavailabilityfordenitrification.Thefinalstageintegratedwetlandsystemallowedfurthernitrogenremovalfromwastewater,vianutrientuptakebyplantroots(alongwithnitrification),andgenerationoforganiccarbon(bythedeadmacrophytes)tosupportdenitrification.ThesystemachievedhigherE.Colimortalitythroughprotozoapredation,E.colioxidation,anddestructionbyUVradiation.Ingeneral,enhancedpollutantremovalefficienciesasdemonstratedbythestructurallymodifiedhybridwetlandsystemsignifythenecessityofsuchmodification,whenoperatedunderadverseconditionssuchas:substantialinputorganicsloading,hydraulicloadingfluctuation,andseasonalvariation.Keywords:constructedwetlands;loadingfluctuation;media;nitrogen;organics;seasonalvariation3DOI:10.1016/S1001-0742(13)60476-3----------------------------------*Correspondingauthor.E-mail:[e-mail];[e-mail]wastewatercontainswidelyvariableamountoforganicsandinorganicssuchasnitrogen,phosphorus,andothersolids,dependingonwaterusagepatternsindifferentcountries(Vymazal,2009).Suchpollutantsofvariableconcentrationsinmunicipalwastewatercanbetreatedvia:steel-and-concrete,andnaturaltreatmenttechnologies.Theformertechnologyoftenentailssubstantialoperationandmaintenancecosts(Ariasetal.,2009;Antoniadisetal.,2010),whereassuchproblemsaregenerallyencounteredbythelattertechnologies.Constructedwetlandtreatmentsystems,generallyreferredtoaslow-cost,greentreatmenttechnologies,aredependentonaninter-connectednetworkofplants,media,biomass,andwaterwhichfacilitatephysical,chemical,andbiologicalremovalofcontaminantsfromwastewater(Fountoulakisetal.,2009).Suchsystemsexhibitbetterefficienciesoforganicsremoval,whenemployedforwastewatertreatment(VymazalandKröpfelová,2009);however,highernitrogenremovalperformancesareoftendifficulttoachieve.Toovercomethesedrawbacks,extensiveresearchisbeingcarriedoutinadjustmentofoperationalandenvironmentalparameters,employingalternativemedia,structural,andarrangementmodificationofwetlands(SaeedandSun,2012).Todate,afewresearchstudiesreportedtheroleofmedia(i.e.organictype),forimprovingclassicalnitrogenreduction(fromwastewater)intreatmentwetlands(SaeedandSun,2011b;Teeetal.,2012).Themechanismforsuchmediaorientedperformanceisinvolvedwithleachingoforganiccarbon(C)fromtheemployedmedia(intobulkwastewater),thatincreasesorganicCavailabilitytosupportdenitrification(alongwithorganicsremoval).Otherstudiesmodifiedstructuralconfigurationsofwetlands,forenhancingremovalmechanism.Baffledhorizontalflow(HF),bio-rack,towery,andintegrateddownflow-upflowwetlandsfallunderthiscategory(YeandLi,2009;Changetal.,2012;Teeetal.,2012;Wangetal.,2012).Enhancedremovalswereobservedinsuchengineeredwetlands,duetoflowdirectionthroughaerobic-anaerobicportions,andimprovedwastewatercontacttimewithincreasedroot4surfacesofmacrophytes.Assuch,combinationofappropriatemedia,alongwithstructuralmodific