Disinfection is an essential process in drinking water treatment for eliminating waterborne diseases. Chlorine and monochloramine are common drinking water disinfectants, and they can react with natural organic matter (NOM) and bromide in source water, to generate brominated and chlorinated organic disinfection byproducts (DBPs). Halogenated DBPs have been demonstrated to be cytotoxic, genotoxic, mutagenic and carcinogenic, and trihalomethanes and haloacetic acids were regulated by the U.S. Environmental Protection Agency (U.S. EPA). Monochloramine generates lower concentrations of the regulated DBPs than chlorine. Besides, lead (Pb)-containing plumbing materials are widely present in water distribution pipelines. Lead is a toxic heavy metal to human. Evidence shows that chlorine can oxidize the lead pipeline material to PbO2, which can form an insoluble layer on the inside pipeline surface to protect underlying pipes; while monochloramine oxidizes the lead material to soluble Pb2+. Thus, it is still controvertial whether chloramine should replace chlorine as a drinking water disinfectant. In this study, we compared the lead release, disinfectant residual and halogenated DBPs (including regulated, commonly known and new ones) formation during chlorination and chloramination of simulated drinking water with and without the presence of PbO2. Results show that compared with chlorination, chloramination caused high concentration of lead released into water, but generated much lower concentrations of halogenated DBPs (in terms of total organic halogen). Besides, we used in vitro heterogeneous human epithelial colorectal adenocarcinoma cells (Caco-2 cells) and in vivo polychaete Platynereis dumerilii to assess the toxicity of the lead-containing disinfected drinking waters. Results show that DBPs contributed more to water toxicity than lead, and chloramination generated safer drinking water than chlorination.

Drinking water chlorination and chloramination in water distribution system: Release of lead, formation of disinfection byproducts (DBPs) and toxicity of tap water

2019 Spring National Meeting

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