Study On Formation Potential And Influencing Factors Of Nitrogenous Disinfection By-products In Drinking Water

The security of the drinking water supply problem was always widely considered by people, the biological safety of drinking water has been always ensured by disinfection technology, however, the greater genetic toxicity and cytotoxicity of nitrogenous disinfection by-products(N-DBPs) may generated in the process of disinfection. Therefore, the study of the formation and control of N-DBPs in drinking water are very important to improve the safety of drinking water. The typical nitrogenous organic matter-amino acids(AA) were chosen as potential precursors. Precursors and mainly factors affecting formation of N-DBPs during chlor(am)ination of amino acids were studied in this text.In order to evaluate the formation potential of N-DBPs during chlor(am)ination of amino acids, the representative eight kinds of amino acids were chosen to do disinfection experiments, and the qualitative and quantitative analyses of N-DBPs were determined by gas chromatography mass spectrometry. The results appear as shown below, the formation potential of N-DBPs during chlor(am)ination of eight amino acids was different. During chlorination, the species of haloacetonitriles(HANs) is mainly dichloroacetonitrile(DCAN), some AA also produced a small amount of trichloroacetonitrile(TCAN), the largest yields of DCAN was generated by tyrosine, followed by tryptophan and asparagine; All AA produced chloropicrin(TCNM), the largest yields of TCNM was generated by tryptophan, followed by asparagine and tyrosine. During chloramination, the species of HANs is only DCAN, TCAN was not detected, the largest yields of DCAN was generated by tyrosine, followed by tryptophan and asparagine; three of AA did not produce chloropicrin(TCNM). In a word, the yields of HANs and TCNM were higher during chlorination than during chloramination.In view of the different formation potential of amino acids, in order to confirm the effects of different structure in the process of DBPs formation, greater formation potential of two amino acids have been further studied, which are tryptophane containing indole function group and tyrosine containing phenolic hydroxyl group. The mainly factors affecting formation of N-DBPs during chlorination/chloramination of tryptophane/tyrosine have been studied, such as reaction time, disinfectant dosage, pH, temperature and bromine(Br-). The results show that reaction time, disinfectant dosage, pH, temperature and Br- had different effects on formation of N-DBPs. Whether tryptophane or tyrosine during chlor(am)ination, HANs and TCNM formation showed the increasing and then decreasing with prolonged contact time, but the time of achieving the max value were different. With increasing temperatures, the yields of TCAN and DCAN were reduced, the yields of TCNM was increased. The yields of TCAN and DCAN shows increased firstly and then decreased with increasing pH, the max yields were all achieved at pH 6; the yields of TCNM increased with increasing pH during chlorination, and the yields of TCNM shows increased firstly and then decreased with increasing pH, the max yields were all achieved at pH 6 during chloramination. In the presence of bromide, HANs were shifted to more brominated ones, changing the distribution of HANs, the yields of HANs were improved.