Enhanced formation of dichloroacetamide and dichloroacetonitrile during chloramination of drinking water and model organic matters in the presence of copper corrosion products

Abstract

The formation of nitrogenous disinfection byproducts (N-DBPs) occurs in chloraminated water in drinking water distribution systems and may be affected by metal pipe materials and their corrosion products. The effect of copper corrosion products, including Cu2+, CuO, and Cu2O, on the formation of dichloroacetonitrile (DCAN) and dichloroacetamide (DCAcAm) was investigated during chloramination of natural organic matter (NOM), model precursors (carboxylic acids and amino acids), and real water samples. Copper corrosion products enhanced DCAN and DCAcAm formation during chloramination of NOM by 33%–72% and 11%–80%, respectively. Addition of 15N-labeled monochloramine showed that the copper corrosion products primarily enhanced the formation of DCAN using organic nitrogen and monochloramine as nitrogen sources, and the formation of DCAcAm using monochloramine as the nitrogen source, but had a limited impact on the formation of DCAcAm using organic nitrogen as the nitrogen source. A distinct N-DBP formation pathway in the presence of Cu2+ and CuO was observed using tyrosine as a model compound, which included the formation of 1,4-benzoquinone as a dominant intermediate. On reaction with monochloramine, the 1,4-benzoquinone greatly contributed to enhancement of DCAN and DCAcAm formation using monochloramine as the nitrogen source. During chloramination of real water samples, Cu2+ and CuO enhanced DCAN formation by 9–40% and DCAcAm formation by 16–33%. This study increases our knowledge of copper catalyzed DCAN and DCAcAm formation in copper pipes, which will be meaningful for water safety in distribution systems using chloramine disinfection.