Disinfection By-products and the Relevant Health Risk in the Water Supply System in H City of Zhejiang Province

Abstract

The occurrence of 18 types of disinfection by-products (DBPs) in two waterworks and the corresponding water supply networks of H City in Zhejiang Province was determined by gas chromatography coupled with electron capture detector (GC-ECD). The correlation between DBPs and organic precursors, and health risks caused by DBPs, were discussed. Results showed that the disinfection by-products detected in drinking water in H City mainly include trihalomethanes (THMs), haloacetic acid (HAAs), haloacetonitrile (HANs) and trichloronitromethane (HNMs), with highest concentrations of THMs followed by HAAs. In the finish water of CX Waterworks and tap water supplied by CX Water works, concentrations of THMs ranged from 7.70 to 32.73μg·L-1and 9.00 to 51.42μg·L-1, respectively, and those of HAAs 3.05 to 21.30μg·L-1 and 6.00 to 26.79μg·L-1, respectively. The THMs in finished water and tap water of TH Waterworks were in the range 8.65-38.76μg·L-1 and 12.09-42.04μg·L-1, respectively, and those of HAAs were 2.42-14.79μg·L-1 and 2.80-33.40μg·L-1, respectively. The DBPs in the finished and tap water of the two waterworks were at lower levels than the limitations regulated by the Sanitary Standard for Drinking Water (GB 5749-2006). The index of dissolved organic carbon (DOC) and UV254 were adopted to describe the organic compounds, and it was found that trichloromethane (TCM) was significantly negatively correlated with DOC and UV254in tap water. Based on the EPA recommended health risk assessment model, the carcinogenic and non-carcinogenic risks of chlorine disinfection by-products in the oral intake route were calculated. It was found that the carcinogenic risks caused by the disinfection by-products in the finished water and tap water of H City were 5.94×10-6-4.76×10-5 and 5.94×10-6-5.56×10-5, respectively, while the non-carcinogenic risks were 0.91×10-2-4.20×10-2 and 1.26×10-2-4.72×10-2, respectively. The carcinogenic risk is mainly from THMs:bromodichloromethane (BDCM) contributes the highest cancer risk, and the non-carcinogenic risk is mainly from TCM.