Variation and relationship of THMs between tap water and finished water in Yancheng City, China.

In this paper, spatial and temporal variations of trihalomethane (THM) concentrations were analyzed including chloroform trichloromethane (TCM), bromodichloromethane (BDCM), dibromochloromethane (DBCM), and tribromomethane (TBM) in Yancheng City in Jiangsu Province, China. The water samples were collected monthly from January 2014 to January 2017 from four tap water sampling sites (S1, S2, S3, and S4) and two finished water sampling sites (WTP1 and WTP2) for THM analysis. The results showed that the mean concentrations during the study period for TCM, BDCM, DBCM, and TBM were 7, 15.9, 21, and 10.4 μg/L in tap water samples and 3.2, 17.2, 22.7, and 10 μg/L in finished water samples, which indicated that brominated THM concentrations were higher than chlorinated THM concentrations. The results of spatial analysis showed that THM concentrations in WTP1 were related to those in S1 and S4 and THM concentrations in WTP2 were related to those in S2 and S3. The concentrations of TCM, BDCM, and TBM have significant spatial variance, while DBCM and THM concentrations do not. The temporal analysis revealed that the highest THM concentration occurred in April, both in tap water and in finished water, which was also shown by temporal cluster analysis. The lowest THM concentration occurred in seasons with relatively lower temperature in all sampling sites. The results provide important information for environmental protection agencies and health care centers with emphasis on months with higher THM risk.