2012TropicalApplicationofFloatingTreatmentWe

ARTICLETropicalApplicationofFloatingTreatmentWetlandsS.K.Weragoda&K.B.S.N.Jinadasa&DongQingZhang&RichardM.Gersberg&SoonKeatTan&NorioTanaka&NgWunJernReceived:3October2011/Accepted:16August2012/Publishedonline:29August2012#SocietyofWetlandScientists2012AbstractThetreatmentefficienciesoffloatingtreatmentwetlands(FTWs)containingtwotypesofmacrophytes,TyphaangustifoliaandCannairidiflora,wereinvestigatedinapilotscalestudyinthetropicalclimateofSriLanka.Inbatchexperiments,over80%ofbiologicaloxygendemand(BOD5)andammonium(NH4+-N)removalwasobserved,whilenitrate(NO3−-N)removalwasover40%.TyphaangustifoliashowedslightlyhigherBOD5,NH4+-NandNO3−-NremovalthanCannairidiflora.Becauseofhigherandsteadyrootgrowth,Typhaangustifoliaresultedinabetterperformanceandhasagreaterpotentialtoextractnutrientsfromwastewaterandallowwater-plantinteractionsthanCannairidiflorawhoserootmatisthickandcompact.Similartothebatchsystem,thecontinuousflowsystemsperformedbetteratmosttimeswithTyphaangustifolia.FTWswithTyphaangustifoliamaybeconsideredapossiblesolutionforlakerestorationwheretherearespaceandcostconstraints.KeywordsFloatingtreatmentwetlands.Wastewater.Nutrients.Typhaangustifolia.CannairidifloraIntroductionFloatingtreatmentwetlands(FTWs)areanoveltreatmentconceptthatemployrooted,emergentmacrophytesgrowinginthefloatingmatonthesurfaceofthewaterratherthanrootedinthesediments(TannerandHeadley2011;FonderandHeadley2010).Theplantrootsbeneaththefloatingmatprovideanextensivesurfaceareafortheattachedbiofilmgrowthandentrapmentofsuspendedparticulatematter.Sincetheplantsarenotrootedinthesoilslikesubsurfaceflowconstructedwetlands,theyareforcedtoacquiretheirnutritiondirectlyfromthewatercolumn,whichmayen-hanceratesofnutrientandelementuptakeintobiomass.Theirbuoyancyenablesthemtotoleratewidefluctuationsinwaterdepthandprovidespotentialtoenhancetreatmentperformancebyincreasingthewaterdepthretainedduringfloweventstoextendthedetentiontimeofstormwaterinthewetland(TannerandHeadley2011).ElectronicsupplementarymaterialTheonlineversionofthisarticle(doi:10.1007/s13157-012-0333-5)containssupplementarymaterial,whichisavailabletoauthorizedusers.S.K.WeragodaNationalWaterSupplyandDrainageBoard,KandySouthTreatmentPlant,Kandy20400,SriLankae-mail:[e-mail]lEngineering,UniversityofPeradeniya,Peradeniya20400,SriLankae-mail:[e-mail](*):S.K.Tan:N.W.JernNanyangEnvironment&WaterResearchInstitute(NEWRI),NanyangTechnologicalUniversity,Nanyang639798,Singaporee-mail:[e-mail]-mail:[e-mail]-mail:[e-mail]PublicHealth,SanDiegoStateUniversity,HardyTower119,5500Campanile,SanDiego,CA92182-4162,USAe-mail:[e-mail]ienceandEngineering,SaitamaUniversity,255Shimo-okubo,Sakura-ku,Saitama338-8570,Japane-mail:[e-mail](2012)32:955–961DOI10.1007/s13157-012-0333-5Theneedforthestudyarosefromtheincreasedwaste-watergenerationandincreasinglydegradedwaterqualityofurbanLakeKandy.Althoughusingconventionalwastewa-tertreatmentplantstotreatwastewaterpriortoitsentryintothelakeistechnicallyfeasible,spaceconstraintsintheurbanlandscapemadeatreatmentmethodlocatedawayfromthedevelopedlandscapesuchasfloatingwetlandsapotentiallyidealsolutionforimprovingthelakewaterquality.Artificially-createdfloatingwetlandshavebeenusedforalimitedrangeofapplicationstodate,suchaswaterqualityimprovement,habitatenhancement,andaestheticimprove-mentatornamentalpondsandlakes(BurgessandHirons1992).Intermsofwaterqualityimprovement,themainapplicationsofFTWshaveincludedthetreatmentofstormwater(TannerandHeadley2011),sewage(Kyambaddeetal.2004;AshandTroung2003;VandeMoorteletal.2010),piggeryeffluent(Hubbardetal.2004),pondwater(Tsujinoetal.2010;Katoetal.2009),urbanlakewater(Guimarãesetal.2000),dairymanureeffluent(SooknahandWilkie2004)andwatersupplyreservoirs(Garbutt2004).Howevertodate,verylittleworkofasimilarnaturehasbeendoneundertropicalconditions.Inaddition,althoughtheeffectofthepresenceandthetypeofvegetationontheperformanceofconstructedwetlandshasbeenevaluatedbyotherauthors(Tanneretal.1995;Allenetal.2002),theknowledgeoftheeffectofdifferentplantspeciesontheremovalperformancebyFTWsandtheeffectoftheirpresencecomparetoasystemwithoutvegetationisstillverylimited(KansiimeandvanBruggen2001;Kyambaddeetal.2004).ThispapersummarizesaseriesofmesocosmexperimentsdesignedtobetterunderstandthecapabilitiesofFTWstoremovecommoncontaminantsinthewastewater,andaimstofillthisresearchgapbyinvestigatingtheapplicabilityofFTWsforwastewatertreatmentundertropicalconditionssuchasSriLanka.Performanceforthefloatingmetwithsoilmediaandliveplantiscomparedagainstacontrolunderbatchandcontinuousflowregimesinatropicalclimate.Inparticular,thestudywasaimedtoi)comparethegrowthcharacteristicsoftwolocalemergentmacrophytes(TyphaangustifoliaandCannairidiflora)inFTWs;ii)quantifyremovalefficienciesofBOD5,nitrogen(N)andphosphorus(P)achievedusingFTWs;iii)theinfluenceofbatchversuscontinuousoperation-almodeontheconta