Many drinking water treatment plants in the U.S.have switched from chlorination to chlo-ramination to lower levels of regulated trihalomethane(THM)and haloacetic acid(HAA)dis-infection byproducts(DBPs)in drinking water and meet the current regulations.However,chloramination can also produce other highly toxic/carcinogenic,unregulated DBPs:iodo-acids,iodo-THMs,and N-nitrosodimethylamine(NDMA).In practice,chloramines are gener-ated by the addition of chlorine with ammonia,and plants use varying amounts of free chlo-rine contact time prior to ammonia addition to effectively kill pathogens and meet DBP regu-lations.However,iodo-DBPs and nitrosamines are generally not considered in this balancing of free chlorine contact time.The goal of our work was to determine whether an optimal free chlorine contact time could be established in which iodo-DBPs and NDMA could be mini-mized,while keeping regulated THMs and HAAs below their regulatory limits.The effect of free chlorine contact time was evaluated for the formation of six iodo-trihalomethanes(iodo-THMs),six iodo-acids,and NDMA during the chloramination of drinking water.Ten different free chlorine contact times were examined for two source waters with different dissolved organic carbon(DOC)and bromide/iodide.For the low DOC water at pH 7 and 8,an optimized free chlorine contact time of up to 1 h could control regulated THMs and HAAs,as well as iodo-DBPs and NDMA.For the high DOC water,a free chlorine contact time of 5 min could control iodo-DBPs and NDMA at both pHs,but the regulated DBPs could exceed the regulations at pH 7.

Matthew A.Bloodgood;Srideui Anduri Chowdary;Eric J.Daiber;Honglan Shi;Caroline O.Granger;Susan D.Richardson

Student Services Authority,U.S.Environmental Protection Agency,National Exposure Research Laboratory,Athens,GA 30605,USA;Department of Chemistry,Missouri University of Science and Technology,Rolla,MO 65409,USA;Department of Chemistry and Biochemistry,University of South Carolina,Columbia,SC 29208,USA

环境科学学报（英文版）

[1]Matthew A.Bloodgood;Srideui Anduri Chowdary;Eric J.Daiber;Honglan Shi;Caroline O.Granger;Susan D.Richardson-.A balancing act:Optimizing free chlorine contact time to minimize iodo-DBPs,NDMA,and regulated DBPs in chloraminated drinking water)[J].环境科学学报（英文版）,2022(07):315-325

chloraminated,ramination,trihalomethane,haloacetic,chloramination,unregulated,nitrosodimethylamine,chloramines,pHs

balancing,Optimizing,free,chlorine,contact,minimize,iodo,DBPs,NDMA,drinking,Many,treatment,plants,have,switched,from,chlorination,lower,levels,infection,byproducts,meet,current,regulations,However,can,also,produce,other,highly,toxic,carcinogenic,acids,THMs,In,practice,are,addition,ammonia,use,varying,amounts,prior,effectively,kill,pathogens,nitrosamines,generally,not,considered,this,goal,work,was,determine,whether,optimal,could,established,which,while,keeping,HAAs,below,their,regulatory,limits,evaluated,formation,six,trihalomethanes,during,Ten,different,times,were,examined,two,source,waters,dissolved,organic,carbon,DOC,bromide,iodide,For,optimized,up,control,well,both,but,exceed

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