某大型水厂供水区消毒副产物的管网分布

目的了解某大型水厂供水区域内消毒副产物(DBPs)的管网分布水平及分布规律。方法根据与该水厂距离设置采样点1(距水厂1km)、2(距水厂约4km)、3(距水厂约8km)。2008年3月—2009年2月,每月对该大型水厂的管网末梢水进行监测,检测的指标包括4种三卤甲烷(三氯甲烷、一溴二氯甲烷、二溴一氯甲烷和三溴甲烷)、2种氯代卤乙酸(二氯乙酸、三氯乙酸)和相关理化指标(水温、pH值、总氯和A254值)。结果除7月份1份水样的三氯甲烷、2份水样的总三卤甲烷比值高于限值外,其余水样DBPs含量均在限值以下。总三卤甲烷的检出范围为7.08～99.54μg/L,氯代乙酸的检出范围为8.50～49.12μg/L。夏季总三卤甲烷含量高于冬、春两季,差异有统计学意义(P0.01)。夏季氯代乙酸含量高于春、秋两季,差异有统计学意义(P0.05)。与采样点1比较,采样点2、3水中总三卤甲烷、三氯甲烷、一溴二氯甲烷含量较高,二氯乙酸含量较低,差异均有统计学意义(P0.05)。水温与三氯甲烷、一溴二氯甲烷、总三卤甲烷、总三卤甲烷比值、二氯乙酸、氯代乙酸均呈正相关(P0.05或P0.01);A254值与三氯甲烷、一溴二氯甲烷、总三卤甲烷、总三卤甲烷比值、二氯乙酸、三氯乙酸、氯代乙酸均呈正相关(P0.05或P0.01);总氯与三氯甲烷、一溴二氯甲烷、总三卤甲烷、总三卤甲烷比值均呈负相关(P0.05或P0.01),而与二氯乙酸和氯代乙酸呈正相关(P0.05或P0.01);pH值与氯代乙酸呈负相关(P0.05)。各三卤甲烷类的管网分布水平彼此呈正相关(P0.01),氯代乙酸与二氯乙酸、三氯乙酸均呈正相关(P0.01),而三卤甲烷类与氯代乙酸类之间无相关性(P0.01)。结论DBPs的管网分布具有明显的季节性差异,并随管网距离的增加而变化,其分布水平与总氯、水中有机前体物含量、水温、pH值等密切相关。

Occurrence of Disinfection By-products in Drinking Water Served by a Large Water Plant in Wuhan

Objective To investigate the occurrence of disinfection by-products (DBPs) in drinking water served by a large water plant in Wuhan. Methods The water samples were from locations in the distribution system: point 1 (＜1 km from the plant),point 2 (about 4 km from the plant), and point 3 (about 8 km from the plant). During the period of March 2008 to February 2009,drinking water served by a large water plant in Wuhan was monthly monitored. The monitored parameters included four halomethanes (THMs),two ehloro-haioacetic acids (chloro-HAAs) and relevant physicocbemical indices. Results The levels of DBPs met the national standards for drinking water quality except for those of THMs in two samples in July 2008. Levels of THMs and chloro-HAAs ranged 7.08-99.54 g/L and 8.50--49.12 g/L in drinking water, respectively. THMs levels were higher in summer than in winter and in spring (P<0.01),while ehloro-HAAs levels were higher in summer than in spring and in autumn (P＜0.05).Compared with drinking water from the nearest and the middle sampling locations ,that from the farthest location possessed higher THMs levels and lower dichloracetic acid levels (P＜0.05). DBPs levels were correlated to physicocbemical indices in different degrees. Inter-correlations were observed among levels of THMs (P＜0.01). Choloro-HAAs levels were positively correlated with those of dichloroacetic acid and trichloroacetic acid (P＜0.01). However, no correlation was observed between THMs and chloro-HAAs (P＞0.05). Conclusion The occurrence of DBPs varied greatly according to seasons and sampling locations and was affected by chlorine dose, organic eompoundss content, pH value and water temperature.