Bioanalytical assessment of the formation of disinfection byproducts in a drinking water treatment plant

Disinfection of drinking water is the most successful measure to reduce water-borne diseases and protect health. However, disinfection byproducts (DBPs) formed from the reaction of disinfectants such as chlorine and monochloramine with organic matter may cause bladder cancer and other adverse health effects. In this study the formation of DBPs through a full-scale water treatment plant serving a metropolitan area in Australia was assessed using in vitro bioanalytical tools, as well as through quantification of halogen-specific adsorbable organic halogens (AOXs), characterization of organic matter, and analytical quantification of selected regulated and emerging DBPs. The water treatment train consisted of coagulation, sand filtration, chlorination, addition of lime and fluoride, storage, and chloramination. Nonspecific toxicity peaked midway through the treatment train after the chlorination and storage steps. The dissolved organic matter concentration decreased after the coagulation step and then essentially remained constant during the treatment train. Concentrations of AOXs increased upon initial chlorination and continued to increase through the plant, probably due to increased chlorine contact time. Most of the quantified DBPs followed a trend similar to that of AOXs, with maximum concentrations observed in the final treated water after chloramination. The mostly chlorinated and brominated DBPs formed during treatment also caused reactive toxicity to increase after chlorination. Both genotoxicity with and without metabolic activation and the induction of the oxidative stress response pathway showed the same pattern as the nonspecific toxicity, with a maximum activity midway through the treatment train. Although measured effects cannot be directly translated to adverse health outcomes, this study demonstrates the applicability of bioanalytical tools to investigate DBP formation in a drinking water treatment plant, despite bioassays and sample preparation not yet being optimized for volatile DBPs. As such, the bioassays are useful as monitoring tools as they provide sensitive responses even at low DBP levels.