Waste+Water+Polishing+Treatment+by+Wetlands

Oct．2012，Volume6，No．10(SerialNo．59)，PP．1423—1428JournalofCivilEngineeringandArchitecture，ISSN1934-7359，USA⋯⋯《WasteWaterPolishingTreatmentbyWetlandsJarmoSallankoandEskoLaksownterResourcesandEnvironmentalEngineeringLaboratoryProcessandEnvironmentalEngineeringDepartment,UniversityofOuluPo．BOX4300,FtnlnndAbstract：Withthecurrenttighteningofenvironmentalregulationsofwastewatertreatment,thereisaneedfl0rtheenhancementofthetreatmentefficiency-Thiscanbedonethroughprocesschanges，orbyaddingafinishingtreatmentaftertheprocess，likeflotationorfiltration．Wetlandsarealsoonepossibilityforthefinishingtreatmentofwastewater．InFinlandWetlandshavebeenusedasapolishingtreatmentformunicipalwastewaterforapprox．20years．Mostofthesearenaturalwetlands．Usingwetlandsafteremcientwastewatertreatmentisaneconomicalwayofproducinghighqualitytreatedwaterandcuttingdownthepollutionloadofwaterbodies．Wetlandshavealsobeenusedinthecon~olofdiffusepollutioninagricultureandforestrvKeywords：Wetland，wastewater，wastewaterpurification，tertiarytreatment，polishingtreatment，BOD，nutrients1．IntroductionThegroundlayerhaslongbeenusedfgr．~municipalwastewaterpurificationinFinlandIntheearly1970s，wastewaterinfiltrationtomarshland(seepagetrenchtechnique)wasusedinmanyplacesinnorthernandeasternFinland．OverlandfloworwetlandtreatmentisnowadaysusedinFinlandasapolishingtreatmentaftermunicipalwastewatertreatment，treatmentofminingefiuentorasawatertreatmentmethodinagriculture．forestryandpeatproductionareas．Wetlandscanbeconstructedwithmajorearthworksandvegetationplanting，ortheycanbemorenatura1．Theyhavebeenusedallovertheworldfortreatingmunicipalwastewaterandnon—pointsourcepollutioncontroJ[1—3】．Wetlandshavealsobeenusedforindustrialwastewatertreatmentandremovalofmetalsfromwastewater【4，5]．TheycanbeusedsuccessfullyinthenorthernScandinavianclimate，withcoldwinters[6]．WetlandsareusedforwastewaterpolishinginfourplacesinFinland：Siikalatva，Inari，RukaandKempele．Threeofthoseplantswerebuiltjnthe1990s，whiletheCorrespondingauthor：JarmoSallanko，D．Sc(Tech．)，