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Investigation of the content of trihalomethanes in drinking water in Nanjing, 2009-2013

Objective To investigate the concentrations of main trihalomethanes(THMs) constituents in drinking water in Nanjing,China, then analyze the correlation between THMs and the p H and oxygen consumption. Methods The monitoring database of 24 centralized water supply units was collected in Nanjing from 2009-2013, which contained 264 samples of finished water and 284 samples of pipe network water. Several quality indexes, including the concentrations of THMs, p H and oxygen consumption, were analyzed. Results The concentrations of total THMs and the main constituents(including trichlormethane, chlorodibromomethane,bromodichloromethane and tribromethane) were investigated. In the drinking water, the concentrations of these THMs, except tribromethane, showed some common features: an increasing trend year by year, highest concentrations occurring in the third quarter, higher concentrations in the chlorinated water than in the chlorine dioxide disinfected water, and linearly correlated with p H and oxygen consumption. The concentrations of trichlormethane and total THMs were higher in pipe network water than in finished water. Conclusion We should pay attention to the water sources protection, and strengthen the regular process. It is necessary to improve the disinfection process to reduce the byproducts in drinking water, and the effect of bromide ions should be take into consideration. Optimizing the method of disinfection, alternative disinfectants should be explored to reduce chlorinated byproduct formation.