Occurrence of CX3R-Type Disinfection Byproducts in Drinking Water Treatment Plants Using DON-Rich Source Water

To understand the occurrence of CX3R-type disinfection byproducts (DBPs) in drinking water treatment plants that use dissolved organic nitrogen (DON)-rich water sources, this study surveyed the occurrence of 24 CX3R-type DBPs in finished water of seven drinking water treatment plants with source water from Lake Tai, characterized by a high level of DON. The results showed that the concentrations of trihalomethanes (THMs) ranged from 28.7 to 70.6 mu g/L and met the Chinese total THM guideline. In addition, the concentrations of HAAs and HALs ranged from 0.7 to 20.5 mu g/L and from 4.6 to 13.5 mu g/L, respectively. As for nitrogenous DBPs, the concentrations of haloacetonitriles (HANs), halonitromethanes, and haloacetamides were in the ranges of 2.6-6.0, 1.7-4.2, and 5.4-13.3 mu g/L, respectively, which are higher than those of other areas in China, probably because of the high levels of DON (0.7 mg/L) and serious eutrophication of the source water. Generally, the occurrence of individual CX3R-type DBP species followed the trend Cl-DBPs > Cl-Br-DBPs > Br-DBPs for both carbonaceous DBPs and nitrogenous DBPs. Moreover, the results showed that an advanced treatment process played an important role in promoting the removal of CX3R-type DBP precursors, based on the conventional treatment. Importantly, the calculated cytotoxicity results from this study and the literature all proved that the HANs, with dibromoacetonitrile (DBAN) as the dominant species, were rated as the most important species in finished water. Moreover, a predictive model for the concentration of DBAN was established to understand the formation and fate of DBAN. It revealed that DON and Br- were two indispensable factors for the formation of DBAN; in addition, soluble microbial products and aromatic protein substances likely play a significant role in DBAN formation.