您好,欢迎访问三七文档
EcologicalEngineering49(2012)170–180ContentslistsavailableatSciVerseScienceDirectEcologicalEngineeringjournalhomepage:flowfromanurbancatchmentbyafloatingwetlandsystemLloydH.C.Chuaa,∗,StephenB.K.Tanb,C.H.Simc,ManishKumarGoyaldaSchoolofCivilandEnvironmentalEngineering,NanyangTechnologicalUniversity,50NanyangAvenue,Singapore639798,SingaporebEnvironmentalEngineeringDivision,CPGConsultantsPteLtd.,238BThomsonRoad,#13-00TowerB,NovenaSquare,Singapore307685,SingaporecCatchment&Waterways,PublicUtilitiesBoard,40ScottsRoad,#15-01,EnvironmentBuilding,Singapore228231,SingaporedDHI-NTUWater&EnvironmentResearchCentre&EducationHub,SchoolofCivilandEnvironmentalEngineering,NanyangTechnologicalUniversity,50NanyangAvenue,Singapore639798,SingaporearticleinfoArticlehistory:Received7May2012Receivedinrevisedform8July2012Accepted10August2012Availableonline5October2012Keywords:BaseflowUrbancatchmentFloatingwetlandsystemNetnutrientreductionRemovalcoefficientTropicalreservoirabstractThisstudyinvestigatedtheperformanceofafloatingwetlandssystem(FWS)plantedwithChrysopogonzizanioides(Vetivergrass),TyphaangustifoliaandPolygonumbarbatumastreatmentunitstoremovenutri-entscontainedinthebaseflowtotheKranjireservoirinSingapore.Phase1ofthestudyconsistedofcontrolledexperimentswithaperspexfloatingwetlandtestcellofdimensions2.5m×2m×1m.Sep-arateexperimentswerecarriedoutusingtheinflowsfromSungeiKangkar,SungeiTengahandSungeiPengSiang,whichdrainintoKranjireservoir.Testswereconductedforeachplantspeciesusingwatertakenfromeachofthetributariesinturn.Watersampleswerecollectedfromtheexperimentalandcontroltanksduringtheexperimentandanalysedfortotalnitrogen,TN(mg/L),totalphosphorus,TP(mg/L),orthophosphate,OP(mg/L)asPO4andammoniacalnitrogen,AN(mg/L)asNH4+.Thenetnutrientreduction(%)forVetiver,TyphaandPolygonumwere19.1,39.2and46.0forTP,and40.8,67.5,7.8forTN,respectively.Therateofdecreaseofnutrientswasfoundtobesignificantwithinthefirstfewdaysandreachedsteadystateafterapproximately10days.Theremovalcoefficient(day−1)forVetiver,TyphaandPolygonumwere0.66,0.87and1.06forTPand0.64,0.68,0.87forTN,respectively.TheremovalsofOPandANcouldnotbeascertainedduetothelowconcentrationsoftheseparameterscontainedinthewaterstested.InPhase2,fieldexperimentswerecarriedoutwiththeFWSinstalledinSungeiPengSiangwiththesameplantspeciesthatwereusedinthecontrolledexperiments.ThegrowthofVetiverandTyphawasmonitoredwhileallthreeplantspeciesweretestedforplantnutrientcontent.PlantTNandTPcontentincreasedrapidlyduringtheinitialrapidgrowthstage,reachedamaximumafterapproximately1monthanddecreased.TyphaachievedthehighestrateofincreaseinnutrientcontentcomparedtoVetiverandPolygonum.TheuptakeofTNbyTypha,VetiverandPolygonumwasestimatedtobe16.2,1.74and2.82(mg/daym2).ThecorrespondinguptakeforTPwas1.57,0.16and0.4(mg/daym2).ForTypha,thematsizerequiredfor50%removalofTNandTPfromthebaseflowwasestimatedtobe0.056and0.031haofmat/haofcatchmentarea.Thisisaconservativeestimatesincenutrientuptakebytherootsystemwasignored.©2012ElsevierB.V.Allrightsreserved.1.IntroductionWetlandresearchhasmostlybeencarriedoutintemperatecountriesandhasmainlyfocusedontheemergentplantvariantoftreatmentwetlands.Tropicaltreatmentwetlandresearchislimitedincomparison(Kivaisi,2001;Limetal.,2001;Meutia,2001;Abiraetal.,2003;Kaseva,2004;Tanakaetal.,2011).Significantly,dif-ferencesbetweentropicalandtemperateenvironmentscanhaveimportantimpactsonthechoiceoftreatmentwetlandstoadopt.Inthetropics,humidityishighyear-roundandthetemperature∗Correspondingauthor.Tel.:+6567905339.E-mailaddress:chcchua@ntu.edu.sg(L.H.C.Chua).doesnotdropbelowfreezingatanytimeintheyear.Thus,thefloatingwetlandsystem(FWS)ismoresuitedintropicalclimates,wherefloatingplantsdonotexperiencelargekillsduringwinterandhenceareabletosupportrobustplantgrowththroughouttheyear.Thefloatingwetlandsystem(FWS)techniqueisavariationofthemorecommonlyusedemergentplantsorconstructedwetlandstreatmentsystem.Traditionally,constructedwetlandsmakeuseofsediment-rootedemergentplantsalthoughwetlandsutilizingfree-floatingaquaticplantsexist.InaFWShowever,theemergentplantsareplantedonafloatormatinsteadofbeingrootedinthesediments,andthefloatisthenplacedonthewatersurface(HeadleyandTanner,2006).Floatingwetlandshavebeenusedtotreatavarietyofwastewatersincludingurbanrunoff,0925-8574/$–seefrontmatter©2012ElsevierB.V.Allrightsreserved.(2012)170–180171municipal,agricultural,andacidicindustrialeffluents.TheycanremovemostpollutantsassociatedwithmunicipalandindustrialwastewaterandstormwaterandareusuallydesignedtoreduceBODandremovenutrientsandsuspendedsolids.FWShavealsobeenusedtoremovemetalsincludingCd,Cr,Fe,Pb,Mn,Se,Znandtoxicorganicsfromwastewater.AsummaryofsomeofthepreviousstudiescarriedoutonFWSisprovidedinTable1.Themajorpartofafloatingwetlandisafloatingraftormat.FWSincorporateastructuralframeandgrowthmediumthroughwhichtheplantrootspenetrateandelongate.Therootswillelon-gateandextendbeyondthefloatingmat,formingarootnetworkdi
本文标题:2012Treatmentofbaseflowfromanurbancatchment
链接地址:https://www.777doc.com/doc-6528685 .html