对数转换光谱数据在线监测应用

Useoflog-transformedabsorbancespectraforonlinemonitoringofthereactivityofnaturalorganicmatterPaoloRoccaroa,*,MingquanYanb,GregoryV.KorshincaDepartmentofCivilEngineeringandArchitecture,UniversityofCatania,VialeA.Doria6,Catania,ItalybDepartmentofEnvironmentalEngineering,PekingUniversity,TheKeyLaboratoryofWaterandSedimentSciences,MinistryofEducation,Beijing100871,ChinacDepartmentofCivilandEnvironmentalEngineering,UniversityofWashington,Box352700,Seattle,WA98195-2700,UnitedStatesarticleinfoArticlehistory:Received26May2015Receivedinrevisedform16July2015Accepted17July2015Availableonline18July2015Keywords:AromaticitySUVASpectralslopeDisinfectionby-productsTrihalomethanesHaloaceticacidsabstractThisstudyexaminedthesignificanceofwaterqualitymonitoringparametersobtainedvialogarithmictransformationoftheabsorbancespectraofrawandtreateddrinkingwater.Thedataweregeneratedusingsamplesoftheinfluent,settledandfilteredwateracquiredweeklyoverasixmonthsperiodattwofullscaletreatmentplants.Examinationoftheweeklyplantsamplescombinedwiththedataoflabo-ratoryfractionationandchlorinationexperimentsshowedthattheslopesofthelog-transformedspectraarecorrelatedwithtypicallyreportedwaterqualityparameters(e.g.,itsspecificabsorbanceat254nm,SUVA254);yetthedeterminationofspectralslopesisconsiderablysimplerandpotentiallyinformation-rich.Thespectralslopesdeterminedfortherangeofwavelength280e350nmwereshowntobecorrelatedwiththeyieldsoftrihalomethanes(THMs)andhaloaceticacids(HAAs).Theseresultssupportthenotionthatmulti-wavelengthmonitoringoftheabsorbancespectraofdrinkingwaterandtheirinterpretationvialogarithmictransformationconstitutesapromisingpracticallyimplementableapproachforonlinewaterqualitymonitoring.©2015ElsevierLtd.Allrightsreserved.1.IntroductionOnlinemonitoringandcontrolareimportantandultimatelyindispensablefordrinkingwateroperationsbecausetheyallowforcontinuoussurveillanceofsourceandtreatedwaterqualityanddetectionofchemical(Halletal.,2007;Izydorczyketal.,2009;Storeyetal.,2011;Aradetal.,2013)andmicrobiologicalthreats(Strathmannetal.,2013;Lopez-Roldanetal.,2013;Hammesetal.,2012;HammesandEgli,2010;Prestetal.,2014;Foladorietal.,2015).Theycanalsoprovideearlywarningindicationsofunex-pectedcontamination,processfailureorotherunusualeventsthusimprovingtheefficiencyofdrinkingwatertreatmentoperationsandenhancingpublichealthprotection(Storeyetal.,2011;Kuklinaetal.,2013;Bannaetal.,2014;Byrneetal.,2014).Currentlyavailableonlinesystemsprovidereliableinformationaboutcommonwaterqualityparameterssuchasturbidity,freeandcombinedchlorine,conductivity,pH,oxidation/reductionpotential,chloride,nitrateandammonia.Theseparametersaremeasuredusingcommerciallyproducedsensorsthatcanalsoprovidedataforwaterabsorbanceatsinglewavelength(typically254nm)orforwiderrangeofwavelengths,andinselectedcaseforfluorescence(Storeyetal.,2011;Bannaetal.,2014).Absorbanceandfluorescence-basedparameterssuitableforonlinemonitoringhavebeenparticularlyusefulformonitoringconcentrationsofnaturaloreffluentorganicmatterindrinkingwaterandwastewater,respec-tively(Reckhowetal.,1990;Korshinetal.,1997a;
SwietlikandSikorska,2004;Chowetal.,2007;Matilainenetal.,2011;Audenaertetal.,2013;Valenciaetal.,2013;Shutovaetal.,2014;Murshedetal.,2014;Bridgemanetal.,2015).Despitetherecentdevelopmentsofavarietyofmoresensitiveandrobustsensorsanddataacquisitionsystemsforonlinewaterqualitymonitoring,itsapplicationsforreal-timecontroloftrace-levelorganiccontami-nantsinwaterremainverychallenging(Korshinetal.,1997b;Roccaroetal.,2008,2009;Gerrityetal.,2012;Zietzschmannetal.,2014;Liuetal.,2015;Anumoletal.,2015).Amongsuchcontaminants,disinfectionby-products(DBPs)notablytri-halomethanes(THMs)andhaloaceticacids(HAAs)arestrictlyregulated(Roccaroetal.,2005)duetotheirubiquity,toxicityandcarcinogenicity(Richardsonetal.,2007).*Correspondingauthor.E-mailaddresses:[e-mail](P.Roccaro),[e-mail](M.Yan),[e-mail](G.V.Korshin).ContentslistsavailableatScienceDirectWaterResearchjournalhomepage:://dx.doi.org/10.1016/j.watres.2015.07.0290043-1354/©2015ElsevierLtd.Allrightsreserved.WaterResearch84(2015)136e143AllaspectsoftheformationandspeciationofTHMs,HAAsandotherDBPsareaffectedbytheconcentrationandreactivityofnaturalorganicmatter(NOM),bromide,ammonia,chlorinedose,pH,temperatureandreactiontime(Reckhowetal.,1990;LeenheerandCroue,2003;CowmanandSinger,1996;Huaetal.,2006;ObolenskyandSinger,2008;PanandZhang,2013;Roccaroetal.,2013,2014).ThecomplexityofNOMhalogenationandchallengesofitsmodelingnecessitatetheuseofeasilymeasurablesurrogateparametersdeemedtobeindicativeofNOMreactivityinDBPfor-mation.Amongsuchparameters,theabsorbanceoflightat254nm(A254)anditsvaluenormalizedbytheconcentrationofdissolvedorganiccarbon(DOC)anddenotedasSUVA254aremosttypical(Croueetal.,1999;Kitisetal.,2001,2002).Duetoitsstrongcor-relationwithNOMaromaticity,SUVA254isagoodpredictoroftheyieldsoftotalorganichalogen(TOX),THMandHAAalbeittheperformanceofSUVA254asanindicatorofNOMreactivityhaslimitations(Weishaaretal.,2003;Atesetal.,2