For the invasion of seawater and the stress of human activities,bromide ion(Br−)exists widely in drinking water sources,and it was found to influence the formation of non-brominated but carcinogenic nitrogen-containin...For the invasion of seawater and the stress of human activities,bromide ion(Br−)exists widely in drinking water sources,and it was found to influence the formation of non-brominated but carcinogenic nitrogen-containing disinfection by-product nitroso-dimethylamine(NDMA)during chloramination(NH2Cl).The presence of Br−leads to the formation of bromine-active species,such as bromamines(NH2Br),bromochloramine(NHClBr),as well as hypobromous acid(HOBr),which are more reactive with NDMA precursors than chlorine-active species,so might promote NDMA generation.This review mainly focuses on the influencing laws,as well as the factors(disinfection conditions and characteristics of water matrixes)that affected NMDA formation during chloramination with Br−.In addition,the possible influencing pathways are discussed.Finally,based on the above summary,measures pertaining to reduce the impact of Br−on NDMA production are concluded.This review would provide a theoretical reference for drinking water treatment plants to deal with bromine-containing water during chloramination.展开更多
The hydroxylation reaction mechanism of nitrosodimethylamine（NDMA） by oxygen atom was theoretically investigated at the B3LYP/6-31G＊＊ level. It has been found that the path of the oxydation of the C―H bond is eas...The hydroxylation reaction mechanism of nitrosodimethylamine（NDMA） by oxygen atom was theoretically investigated at the B3LYP/6-31G＊＊ level. It has been found that the path of the oxydation of the C―H bond is easier than the path involving a Singlet/Triplet crossing. The study of the potential surface shows that both solvent effect at B3LYP/6-31G＊＊ level and different method at more credible MP2/6-311G＊＊ level in the gas phase have no effect on the hydroxylation reaction mechanism. The oxidation hydroxylation process of NDMA by O is exothermic reaction and easy to occur.展开更多
When adding sufficient chlorine to achieve breakpoint chlorination to source water containing high concentration of ammonia during drinking water treatment, high concentrations of disinfection by-products（DBPs） may ...When adding sufficient chlorine to achieve breakpoint chlorination to source water containing high concentration of ammonia during drinking water treatment, high concentrations of disinfection by-products（DBPs） may form. If N-nitrosamine precursors are present, highly toxic N-nitrosamines, primarily N-nitrosodimethylamine（NDMA）, may also form. Removing their precursors before disinfection should be a more effective way to minimize these DBPs formation. In this study, zeolites and activated carbon were examined for ammonia and N-nitrosamine precursor removal when incorporated into drinking water treatment processes.The test results indicate that Mordenite zeolite can remove ammonia and five of seven N-nitrosamine precursors efficiently by single step adsorption test. The practical applicability was evaluated by simulation of typical drinking water treatment processes using six-gang stirring system. The Mordenite zeolite was applied at the steps of lime softening, alum coagulation, and alum coagulation with powdered activated carbon（PAC） sorption. While the lime softening process resulted in poor zeolite performance, alum coagulation did not impact ammonia and N-nitrosamine precursor removal. During alum coagulation, more than67% ammonia and 70%–100% N-nitrosamine precursors were removed by Mordenite zeolite（except 3-（dimethylaminomethyl）indole（DMAI） and 4-dimethylaminoantipyrine（DMAP））. PAC effectively removed DMAI and DMAP when added during alum coagulation. A combination of the zeolite and PAC selected efficiently removed ammonia and all tested seven N-nitrosamine precursors（dimethylamine（DMA）, ethylmethylamine（EMA）, diethylamine（DEA）, dipropylamine（DPA）, trimethylamine（TMA）, DMAP, and DMAI） during the alum coagulation process.展开更多
基金supported by the National Natural Science Foundation of China(No.51878301).
文摘For the invasion of seawater and the stress of human activities,bromide ion(Br−)exists widely in drinking water sources,and it was found to influence the formation of non-brominated but carcinogenic nitrogen-containing disinfection by-product nitroso-dimethylamine(NDMA)during chloramination(NH2Cl).The presence of Br−leads to the formation of bromine-active species,such as bromamines(NH2Br),bromochloramine(NHClBr),as well as hypobromous acid(HOBr),which are more reactive with NDMA precursors than chlorine-active species,so might promote NDMA generation.This review mainly focuses on the influencing laws,as well as the factors(disinfection conditions and characteristics of water matrixes)that affected NMDA formation during chloramination with Br−.In addition,the possible influencing pathways are discussed.Finally,based on the above summary,measures pertaining to reduce the impact of Br−on NDMA production are concluded.This review would provide a theoretical reference for drinking water treatment plants to deal with bromine-containing water during chloramination.
基金Supported by the Foundation of Shanghai Municipal Education Commission,China(No.09YZ390)
文摘The hydroxylation reaction mechanism of nitrosodimethylamine（NDMA） by oxygen atom was theoretically investigated at the B3LYP/6-31G＊＊ level. It has been found that the path of the oxydation of the C―H bond is easier than the path involving a Singlet/Triplet crossing. The study of the potential surface shows that both solvent effect at B3LYP/6-31G＊＊ level and different method at more credible MP2/6-311G＊＊ level in the gas phase have no effect on the hydroxylation reaction mechanism. The oxidation hydroxylation process of NDMA by O is exothermic reaction and easy to occur.
基金supported by US EPA STAR program(No.83517301)Missouri Department of Natural Resourcesthe support from Chemistry Department,Environmental Research Center,and Center for Single Nanoparticle,Single Cell,and Single Molecule Monitoring(CS3M)at Missouri University of Science and Technology
文摘When adding sufficient chlorine to achieve breakpoint chlorination to source water containing high concentration of ammonia during drinking water treatment, high concentrations of disinfection by-products（DBPs） may form. If N-nitrosamine precursors are present, highly toxic N-nitrosamines, primarily N-nitrosodimethylamine（NDMA）, may also form. Removing their precursors before disinfection should be a more effective way to minimize these DBPs formation. In this study, zeolites and activated carbon were examined for ammonia and N-nitrosamine precursor removal when incorporated into drinking water treatment processes.The test results indicate that Mordenite zeolite can remove ammonia and five of seven N-nitrosamine precursors efficiently by single step adsorption test. The practical applicability was evaluated by simulation of typical drinking water treatment processes using six-gang stirring system. The Mordenite zeolite was applied at the steps of lime softening, alum coagulation, and alum coagulation with powdered activated carbon（PAC） sorption. While the lime softening process resulted in poor zeolite performance, alum coagulation did not impact ammonia and N-nitrosamine precursor removal. During alum coagulation, more than67% ammonia and 70%–100% N-nitrosamine precursors were removed by Mordenite zeolite（except 3-（dimethylaminomethyl）indole（DMAI） and 4-dimethylaminoantipyrine（DMAP））. PAC effectively removed DMAI and DMAP when added during alum coagulation. A combination of the zeolite and PAC selected efficiently removed ammonia and all tested seven N-nitrosamine precursors（dimethylamine（DMA）, ethylmethylamine（EMA）, diethylamine（DEA）, dipropylamine（DPA）, trimethylamine（TMA）, DMAP, and DMAI） during the alum coagulation process.
