环境工程专业英语文章-(4)

CombinedSewerOverflows:AnEnvironmentalSourceofHormonesandWastewaterMicropollutantsP.J.Phillips,*,†A.T.Chalmers,‡J.L.Gray,§D.W.Kolpin,∥W.T.Foreman,§andG.R.Wall††USGeologicalSurvey,425JordanRoad,Troy,NewYork12180,UnitedStates‡USGeologicalSurvey,Montpelier,Vermont,UnitedStates§USGeologicalSurvey,Lakewood,Colorado,UnitedStates∥USGeologicalSurvey,IowaCity,Iowa,UnitedStates*SSupportingInformationABSTRACT:Datawerecollectedatawastewatertreatmentplant(WWTP)inBurlington,Vermont,USA,(serving30,000people)toassesstherelativecontributionofCSO(combinedseweroverflow)bypassflowsandtreatedwastewatereffluenttotheloadofsteroidhormonesandotherwastewatermicropollutants(WMPs)fromaWWTPtoalake.Flow-weightedcompositesampleswerecollectedovera13monthperiodatthisWWTPfromCSObypassflowsorplantinfluentflows(n=28)andtreatedeffluentdischarges(n=22).AlthoughCSOdischargesrepresent10%ofthetotalannualwaterdischarge(CSOplustreatedplanteffluentdischarges)fromtheWWTP,CSOdischargescontribute40−90%oftheannualloadforhormonesandWMPswithhigh(>90%)wastewatertreatmentremovalefficiency.Bycontrast,compoundswithlowremovalefficiencies(<90%)havelessthan10%ofannualloadcontributedbyCSOdischarges.Concentrationsofestrogens,androgens,andWMPsgenerallyare10timeshigherinCSOdischargescomparedtotreatedwastewaterdischarges.CompoundconcentrationsinsamplesofCSOdischargesgenerallydecreasewithincreasingflowbecauseofwastewaterdilutionbyrainfallrunoff.Bycontrast,concentrationsofhormonesandmanyWMPsinsamplesfromtreateddischargescanincreasewithincreasingflowduetodecreasingremovalefficiency.■INTRODUCTIONCombinedseweroverflows(CSOs)arepresentintheUnitedStates,1Europe2andotherpartsoftheworld.CSOsincludecombinedcollectionsystemofsewageandrainfallrunoff.FlowinthesecombinedsystemscanexceedthecapacityofWWTPs(wastewatertreatmentplants)duringstormflowssothatmixturesofuntreatedsewageandstormwaterrunoffarereleasedtoreceivingwaters.IntheUS,over700citieshaveCSOs,andtheyaremostcommonlylocatedontheeastcoast,GreatLakes,andPacificnorthwest.1CSOshavebeeni