title: Copper increases reductive dehalogenation of haloacetamides by zero-valent iron in drinking water: Reduction efficiency and integrated toxicity risk.
abstract: The haloacetamides (HAcAms), an emerging class of nitrogen-containing disinfection byproducts (N-DBPs), are highly cytotoxic and genotoxic, and typically occur in treated drinking waters at low μg/L concentrations. Since many drinking distribution and storage systems contain unlined cast iron and copper pipes, reactions of HAcAms with zero-valent iron (ZVI) and metallic copper (Cu) may play a role in determining their fate. Moreover, ZVI and/or Cu are potentially effective HAcAm treatment technologies in drinking water supply and storage systems. This study reports that ZVI alone reduces trichloroacetamide (TCAcAm) to sequentially form dichloroacetamide (DCAcAm) and then monochloroacetamide (MCAcAm), whereas Cu alone does not impact HAcAm concentrations. The addition of Cu to ZVI significantly improved the removal of HAcAms, relative to ZVI alone. TCAcAm and their reduction products (DCAcAm and MCAcAm) were all decreased to below detection limits at a molar ratio of ZVI/Cu of 1:1 after 24 h reaction (ZVI/TCAcAm = 0.18 M/5.30 μM). TCAcAm reduction increased with the decreasing pH from 8.0 to 5.0, but values from an integrated toxic risk assessment were minimised at pH 7.0, due to limited removal MCAcAm under weak acid conditions (pH = 5.0 and 6.0). Higher temperatures (40 °C) promoted the reductive dehalogenation of HAcAms. Bromine was preferentially removed over chlorine, thus brominated HAcAms were more easily reduced than chlorinated HAcAms by ZVI/Cu. Although tribromoacetamide was more easily reduced than TCAcAm during ZVI/Cu reduction, treatment of tribromoacetamide resulted in a higher integrated toxicity risk than TCAcAm, due to the formation of monobromoacetamide (MBAcAm).
authors.affiliation: State Key Laboratory of Pollution Control and Resources Reuse, Institute of Disinfection By-product Control in Water Treatment, College of Environmental Science and Engineering, Tongji University, Shanghai, 200092, China. Electronic address: feedwater@126.com.
authors.forename: Wenhai
authors.initials: W
authors.lastname: Chu
authors.affiliation: State Key Laboratory of Pollution Control and Resources Reuse, Institute of Disinfection By-product Control in Water Treatment, College of Environmental Science and Engineering, Tongji University, Shanghai, 200092, China.
authors.forename: Xin
authors.initials: X
authors.lastname: Li
authors.affiliation: Department of Civil and Environmental Engineering, Imperial College London, London, SW7 2AZ, UK.
authors.forename: Tom
authors.initials: T
authors.lastname: Bond
authors.affiliation: State Key Laboratory of Pollution Control and Resources Reuse, Institute of Disinfection By-product Control in Water Treatment, College of Environmental Science and Engineering, Tongji University, Shanghai, 200092, China.
authors.forename: Naiyun
authors.initials: N
authors.lastname: Gao
authors.affiliation: State Key Laboratory of Pollution Control and Resources Reuse, Institute of Disinfection By-product Control in Water Treatment, College of Environmental Science and Engineering, Tongji University, Shanghai, 200092, China.
authors.forename: Xu
authors.initials: X
authors.lastname: Bin
authors.affiliation: State Key Laboratory of Pollution Control and Resources Reuse, Institute of Disinfection By-product Control in Water Treatment, College of Environmental Science and Engineering, Tongji University, Shanghai, 200092, China.
authors.forename: Qiongfang
authors.initials: Q
authors.lastname: Wang
authors.affiliation: State Key Laboratory of Pollution Control and Resources Reuse, Institute of Disinfection By-product Control in Water Treatment, College of Environmental Science and Engineering, Tongji University, Shanghai, 200092, China.
authors.forename: Shunke
authors.initials: S
authors.lastname: Ding
mesh_terms: D003300:Copper; D060766:Drinking Water; D054879:Halogenation; D007501:Iron; D014874:Water Pollutants, Chemical; D018508:Water Purification
chemical_list: D060766:Drinking Water; D014874:Water Pollutants, Chemical; D003300:Copper; D007501:Iron
keywords: Dechlorination; Disinfection byproducts; Drinking water; Haloacetamides; Integrated toxicity risk; Zero-valent iron/copper