To some extent, the municipal water disinfection process itself introduces contaminants (in the form of organohalogen compounds) into the water supply. This is of interest because several disinfection by-products, such as trihalomethanes (THMs) and haloaceticacids (HAAs), are suspect carcinogens. In Beijing Chlorination has been the most common disinfectant process for domestic drinking water for many years. the main focus of the disinfection by-products is trihalomethanes (THMs). Only limited researches are conducted on other DBPs such as haloacetic acids, haloacetonitriles, haloketones, chloropicrin and chloral hydrate.

In order to understand the consequences of the future application of DBPs and to monitor and control the DBPs of drinking water in Beijing, Prof. WANG Wu-Yi and YANG Lin-Sheng, Institute of Geographic Sciences and Natural Resources Research (IGSNRR) and their colleagues conducted a survey of disinfection by-product occurrence in Beijing city at 15 drinking water treatment plants for the first time. Particular attention was focused on the distribution of the levels of DBPs with an emphasis on their seasonal and spatial evolutions in a water distribution system.

Results showed that THMs and HAAs were the major DBPs found in all water treatment plants. The variation of all DBPs concentration in different water sources was as follow: surface water N mixture water N ground water. In spatial variation, the total DBPs levels were higher in the west than in the east of Beijing. The spatial variation of TCM, DCBM, DCAA, TCAA, DCAN, 1,1-DCP, 1,1,1-TCP, CH and CP was very similar to that of total DBPs. But, DBCM, TBM, DBAA, TCAN, BCAN and DBAN did not show significant spatial variation. In the seasonal variation, THM levels were high in summer and decreased in spring, autumn and winter. The variation of HAA levels is in the order of winter >spring > autumn > summer. The variation of HANs was consistent with HAAs. In the variation of other classes of DBPs, the highest HK levels were observed in winter, CH is observed in autumn, and CP is highest in summer.

Related research results have been published in Science of the Total Environment, 2010, Vol.408, pp.4600–4606.