[Occurrence and Prediction Model of Disinfection By-Products in Tap Water]

Disinfection by-products (DBPs) are defined as important parameters that can deteriorate drinking water quality. The investigation was performed at a laboratory located on a campus in H City of the Zhejiang province. The purpose of the work was to obtain knowledge on the occurrence of DBPs in tap water and boiled water taken from the same pipe, to establish a statistical model to predict DBPs information in tap water based on physicochemical parameters, and to evaluate carcinogenic and non-carcinogenic risks caused by DBPs on a predictional level. The results showed three categories of trihalomethanes (THMs), haloacetonnitrile (HANs), and haloacetic acids (HAAs), including 10 species of disinfection by-products detected in drinking water. The detection rate of target DBPs in tap water was 100% and the concentrations varied in the ranges of 10.12-28.39, 0.98-5.19, and 2.65-7.83 μg·L^-1, respectively. In boiled water, bromochloracetonitrile (BCAN) was not detected; the detection rates of tribromomethane(TBM), trichloroacetonitrile (TCAN), and dibromoacetonitrile (DBAN) were 46.43%, 82.14%, and 92.86%, respectively, while the detection rate for other DBPs was 100%. The concentrations of THMs, HANs, and HAAs were in the ranges of 0.60-12.58, 0.02-0.52, and 2.42-5.86 μg·L^-1, respectively. After heating, the concentrations of THMs and HANs decreased by 84.22% and 91.45%, respectively. No obvious decrease was found for HAAs. The pH value and specific ultraviolet absorbance (SUVA) had positive correlation with DBPs, whereas residual chlorine and ammonia nitrogen had negative correlation with DBPs. Based on the correlation between the physicochemical parameters and DBPs, a multiple linear regression prediction model of THMs was established, with deviation less than 10.00%, which can be used for the prediction of THMs in tap water. Based on the EPA recommended health risk assessment model, the carcinogenic and non-carcinogenic risks of chlorine disinfection by-products through oral intake were calculated. It was found that the carcinogenic risks caused by the disinfection by-products in the tap and boiled water were (17.24-84.63)×10^-6 and (25.49-258.82)×10^-7, respectively, and the non-carcinogenic risks were (4.17-50.32)×10^-2 and (6.52-107.74)×10^-3, respectively. The carcinogenic risk caused mainly by THMs and bromodicloromethane (BDCM) contributed the highest cancer risk in tap water, while for boiled water, trichloromethane (TCM) was found to contribute the highest cancer and non-carcinogenic risk. In boiled water, the reduction of THMs was up to 94.38%, and the cancer risk was reduced by 79.00%.