Degradation of carbamazepine and disinfection byproducts formation in water distribution system in the presence of copper corrosion products

Abstract

Copper ion (Cu²⁺), a common corrosion product released from copper pipes, is widely present in water distribution system (WDS). Cu²⁺ was confirmed to be capable to catalyze the decay of monochloramine (NH₂Cl), which is a commonly used disinfectant and need to maintain a minimum concentration in WDS. Cu²⁺ and NH₂Cl form a system in WDS and their interaction with other substances in WDS is unclear. In this study, the performance of Cu²⁺/NH₂Cl system on degradation of trace pollutants, taking carbamazepine (CBZ) as an example, in WDS was investigated, and significant promotion on CBZ degradation was observed. The acceleration was due to the generation of Cl, OH and other oxidants, which were identified by scavenge experiments. CBZ degradation in Cu²⁺/NH₂Cl system was highly pH-dependent, because the catalytic effect of Cu²⁺ can only work at low pH (Cu²⁺ precipitating at pH > 6.0). The removal of CBZ increased with the concentration of Cu²⁺ increasing. Water matrix (NOM, HCO₃^- and Br^-) can inhibit the removal of CBZ in Cu²⁺/NH₂Cl system. Further, five disinfection byproducts (DBPs), namely, trichloromethane (TCM), dichloroacetonitrile (DCAN), dichloroacetone (DCP), trichloronitromethane (TCNM) and trichloroacetone (TCP), were detected in chloramination in the presence/absence of Cu²⁺. Compared with chloramination without Cu²⁺, the cytotoxicity and genotoxicity of formed DBPs increased significantly in the presence of Cu²⁺, indicating that the chemical safety in WDS deserves more attention.

Keywords: Carbamazepine; Copper ions; Disinfection byproducts; Monochloramine; Water distribution system.