溶解性有机氮乙酰胺氯化生成饮用水THMs的影响因素研究

Factors Affecting Formation of THMs During Dissolved Organic Nitrogen Acetamide Chlorination in Drinking Water

氯化消毒可以有效杀灭细菌,但同时会产生危害人体健康的消毒副产物(DBPs).溶解性有机氮(DON)是DBPs的重要前体物,为考察DON对THMs的影响,首次选取乙酰胺(AcAm)作为前体物DON的代表物质,采用Plackett-Burman和Box-Behnken方法设计试验,考察了AcAm初始浓度、加氯量、pH、温度、溴离子浓度和反应时间等因素对三卤甲烷(THMs)生成的影响.结果表明,在AcAm生成THMs的过程中,AcAm初始浓度、pH和反应温度3个因素的影响程度较小,溴离子、有效氯和反应时间3因素的影响较大,其中溴离子的影响最为显著.溴离子浓度一定时,改变有效氯的含量,生成的THMs总量变化不大,溴离子对THMs的生成有一定的催化作用,控制溴离子的浓度是减少AcAm生成THMs的有效措施.在有效氯为8.77 mg/L、溴离子为0.77 mg/L及接触时间为6.20 h的条件下,THMs存在最大生成量为45.82μg/L.随着反应时间的推移,溴分配系数n呈上升趋势,控制消毒反应时间,是减少THMs致癌风险的有效方法.同时探讨了AcAm生成THMs的反应路径,表述了溴离子的催化作用机制.

Chlorination disinfection greatly reduced bacteria and virus in drinking water. However, there is an unintended consequence of disinfection, the generation of chemical disinfection by-products （DBPs）. Dissolved organic nitrogen （DON） as the important precursor of DBPs is of current concern. As acetamide （AcAm） occur in important bimolecular, we studied formation pathways for THMs during chlorination of model AcAm. The experiments are designed by Plackett-Burman and Box-Behnken methods. Factors affecting formation of THMs such as AcAm initial concentration, chlorine dosage, pH, temperature, Brconcentration and contact time were investigated. The results indicate that AcAm initial concentration, pH and temperature have little effects on formation of THMs. On the contrary, three other factors have important effects on formation of THMs, especially Br^- concentration. The capacity of THMs generation varies very little when Br^- has a constant concentration. Generation amount of THMs attach maximum under the condition that dosage of active chlorine, Br^- concentration and contact time is 8.77 mg/L, 0.77 mg/L and 6.20 h respectively. Bromine ion plays a catalysis role on THMs formation. Controlling the concentration of bromine ion can reduce total generation amount of THMs via AcAm. Bromine partition coefficient tends to increasing along with contact time lapse. Controlling chlorination reaction time can lower the cancer risk. At last, the pathway is proposed for THMs formation via AcAm, and the catalysis mechanism of Br^- was addressed.