The 11th International Conference on Water Resource and Environment (WRE 2025)

Abstract: Maintaining a residual disinfectant/oxidant, such as chlorine and chlorine dioxide, is a generally used strategy to control microbial contaminants and bacterial growth and to improve the hygienic drinking water quality in distribution systems. Secondarily oxidant, such as hypobromous acid (HOBr), can be formed during chlorination of bromide-containing waters. In copper pipe distribution systems, corrosion of pipes gives rise of cupric oxide (CuO). CuO generally enhanced the decay of these halogen-containing oxidants, leading to the loss of residual oxidants. Three pathways are involved: 1) catalytic disproportionation to yield an oxidized form of halogen (i.e., halate) and reduced form (halide or chlorite for chlorine dioxide), 2) oxygen formation, and 3) oxidation of a metal in a reduced form (e.g., cuprous oxide) to a higher oxidation state. The complexation of hypohalous acids (HOX, e.g., HOCl and HOBr) by the Lewis acid CuO increased their reactivities, leading to the formation of CuO-HOCl or CuO-HOBr complex and thereby enhancing the disproportionation, leading to the formation of bromate or chlorate. In the presence of dissolved organic matter (DOM), the CuO-HOX complex reactions with DOM moieties with slow reacting sites can prompt the the formation of one- to two-carbon-atom disinfection byproducts (DBPs) during water chlorination. In addition, results showed that 0.1 g L-1 CuO elevated the Chinese hamster ovary cell cytotoxicity of chlorinated waters by 20% and 120% at initial bromide concentrations of 15 and 415 µg L-1, respectively. The preferential formation of brominated DBPs in the presence of CuO was ascribed to the higher formation rate constant of CuO-HOBr than CuO-HOCl complex and lower adsorption energies based on density functional theory calculation. Furthermore, the CuO-HOCl complex exhibits a higher reactivity towards hypoiodous acid, trichloroacetaldehyde, oxalic acid, and phenolic compounds than chlorine alone. These results demonstrate that CuO can enhance the oxidation capacity of chlorine for selected compounds. This work provides insights into the role of CuO into oxidative water treatment processes.

Biography: Dr. Chao Liu is a full Professor of Environmental Engineering and group leader at the Research Center for Eco-Environmental Sciences (RCEES), Chinese Academy of Sciences. He also holds adjunct appointments with University of the Chinese Academy of Sciences (UCAS). Prof. Liu received his Ph.D. in Environmental Engineering from UCAS in 2009. After his Ph.D, he had worked at King Abdullah University of Science and Technology (KAUST) and Swiss Federal Institute of Aquatic Science and Technology (Eawag). Before joining RCEES in 2020, he was a faculty at Clemson University. Dr. Liu’s research focuses on the development of innovative hybrid water treatment processes for the provision of safe and clean drinking water from non-conventional source waters. His primary research is on the removal of undesired constituents and mitigating the formation of toxic by-products in water treatment. His research was supported by the National Natural Science Foundation of China, Ministry of Science and Technology of China, U.S. National Science Foundation (NSF), U.S. Water Research Foundation, and industry. His findings have been published in the premier journals of his field – Nature Water, Environmental Science and Technology, and Water Research. Professor Liu is a recipient of the National Overseas High-level Talent Program. He is an Associate Editor of the journal of Water Research. He also serves various Advisory Committees both nationally and internationally.