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.1CSOshavebeenidentifiedasimportantsourcesofpolycyclicaromatichydrocarbons,organochlorinecompounds,nutrients,andchemicaloxygendemand.2−5RecentstudieshaveidentifiedCSOsasapotentialsourceofwastewatermicropollutants(WMPs)toreceivingwaters,6−13withsubstantiallyelevatedWMPconcentrationsoccurringinurbanwatersfollowingCSOdischarges.9,12,14−16Forexample,caffeineconcentrationsinurbanstreamsinSwitzerlandwerehigherthanintreatedWWTPeffluent,andstreamconcen-trationswerehighestduringstormflowconditionsandlowestduringbaseflowconditions.17Loadsforibuprofenhavebeenfoundtobeupto100timesgreaterinCSOdischargesthanintreatedeffluents.18PatternsintheenantiomerfractionofthechiralpharmaceuticalpropranololinseveralfreshwatersitesandacoastalbayindicatedthatCSOdischargesandbypassflowswerethelargestsourceofpropranololtocoastalwaters.9Furthermore,CSOsconstituteamoreimportantsourceofbacteriathantreatedWWTPdischarges.19BenottiandBrownawell’smodel7ofCSOsasasourceofWMPstoanurbanestuaryindicatesthatCSOdischargescanhaveconcentrations10ormoretimesgreaterthantreatedwastewater.Thismodelpredictsthatlackoftreatmentisamoreimportantfactorthandilutionbyrainfallrunoffforcompoundswithhighremovalefficiencies;thus,thismodelpredictsthatforcompoundswithhighremovalefficiencies,higherconcentrationscanbeexpectedinCSOflowscomparedtotreatedWWTPflows.Conversely,forcompoundsthatarenotefficientlyremovedbyWWTPprocesses,CSOdischargeconcentrationsshouldbemoresimilartotreateddischargeconcentrations,asdilutionbyrunoffshouldbeamoreimportantfactorthanthelackoftreatment.AlthoughthismodelassumesconstantremovalratesbyaWWTP,removalratescanbeexpectedtodecreaseforcaffeine,propranolol,andestrogens,asflowsincrease(andresidencetimesdecrease)throughaWWTPbecauseofgreaterwater-volumeinputsduringstorms.9,17,20Thus,hormonesandotherWMPsthatareefficientlyremovedbytreatmentduringnormalflows(resultinginlowornondetectableconcentrationsintreatedeffluent)Received:January11,2012Revised:April11,2012Accepted:April16,2012Articlepubs.acs.org/estThisarticlenotsubjecttoU.S.Copyright.PublishedXXXXbytheAmericanChemicalSocietyAdx.doi.org/10.1021/es3001294|Environ.Sci.Technol.XXXX,XXX,XXX−XXXmighthavesubstantiallyelevatedconcentrationsinbothCSObypassandtreatedeffluentflowsduringstormsduetohighflowrates.Consistentwiththeseexpectations,concentrationsofcaffeineandothercompounds,whichweregenerallyefficientlyremovedduringwastewatertreatment,weregreaterinCSObypassflowsandduringstormflowinurbanstreamsreceivingCSOdischargethanintreatedeffluentsinBurlington,Vermont,USA.12Incontrasttoefficientlyremovedcom-pounds,thehighestconcentrationsforgalaxolide(apoorlyremovedcompound)occurredintreatedeffluents,withlowerconcentrationsinCSOdischarges.12ThepresenceofestrogensinCSOdischargeshasbeensuggestedasacauseofendocrinedisruptioninfish,21butthisstudy21didnotdirectlymeasureestrogenconcentrations.LittleisknownabouttherelativecontributionofCSOdischargestohormoneloadsintheenvironment,althoughtheoccurrenceofpeakconcentrationsofestrone(E1)and17β-estradiol(E2)inanurbanstreamduringstormflowshasbeenattributedtoCSOdischarges.22Limitedattentionhasbeenpaid