Fe3+和Br-对饮用水氯消毒过程中挥发性卤代烃生成的影响

以腐殖酸模拟天然水体中的活性消毒副产物的前体物,研究了含腐殖酸水样中溴离子和三价铁离子对氯消毒反应过程中挥发性卤代烃三卤甲烷(THMs)的生成量和相对分布的影响.结果表明,水样中的溴离子浓度增加将增加溴代三卤甲烷和总三卤甲烷的生成量, 在Br^-离子浓度1.0 mg/L时,THMs的总量为不含Br^-时的2.7倍;当水样中含有溴离子时,在偏酸性条件下三价铁对三卤甲烷的生成有一定的抑制作用,在偏碱性条件下三价铁离子提高了溴离子与腐殖酸的反应活性,从而提高了三卤甲烷的生成总量.Fe³⁺浓度为5 mg/L时,三溴甲烷的生成量与无Fe³⁺存在时相比,由51.7 μg/L增加到79.4 μg/L, 增加幅度达54%,THMs的总量从113.49 μg/L增加到162.09 μg/L.溴离子对饮用水的安全性具有较大的负面影响,溴离子和三价铁离子共存于偏碱性环境中时对加氯消毒后饮用水的致癌风险的影响显著增大,当Br^-含量为0.2 mg/L、Fe³⁺含量为5 mg/L时,在pH为6和8的条件下,致癌风险比饮用水中不含Br^-和Fe³⁺时分别增加2.5和5.1倍.

Effects of Bromide and Ferric Ions on Formation of Tri-Halomethanes During Disinfection of Drinking Water by Chlorine

Effects of bromide and ferric ions on the formation and distribution of tri-halomethanes (THMs) have been investigated. As disinfection by-product (DBP) model precursors of natural water, humic acid solutions were used and a series of experiments were conducted. The results showed that bromide in this reaction system not only contributed to the increase of brominated species, but also the total tri-halomethanes. When the concentration of Br(-) was 1.0 mg/L, the total amount of produced THMs reached to 270% of that without bromide ions. In the presence of bromide, ferric ions decreased the production of THMs at pH 6, but increased the production of THMs at pH 8, especially for the amount of tri-bromomethanes. When the concentration of Fe3+ was 5 mg/L, the amount of produced tri-bromomethanes had an increment of 54% (from 51.7 microg/L to 79.4 microg/L), and the total amount of THMs increased from 113.49 microg/L to 162.09 microg/L. Bromide ions had a significant effect on carcinogenicity risk in disinfection of drinking water by chlorine, and the co-existence of ferric ion and bromide in alkalescent environment can result in the biggest challenge on carcinogenicity risk. Under the condition of 0.2 mg/L Br(-), 5 mg/L Fe3+ and pH 6, the carcinogenicity risk increased 2.5 times than that without Br(-) and Fe3+, and much higher increment of 5.1 times appeared when pH was 8.