Generation of iodinated trihalomethanes during chloramination in the presence of solid copper corrosion products

Abstract

Copper water pipelines are widely used in water distribution systems, but the effects of solid copper corrosion products (CCPs) including CuO, Cu2O and Cu2(OH)2CO3 on the generation of iodinated trihalomethanes (I-THMs) during chloramination remain unknown. This study found that the formation of I-THMs during chloramination of humic acid (HA) was inhibited by the presence of CuO and Cu2O, but promoted with the addition of Cu2(OH)2CO3. The negative effect of CuO and Cu2O is mainly exerted by promoting the decay of both NH2Cl and HOI. Although Cu2(OH)2CO3 also accelerated the decomposition of NH2Cl and HOI, it was found that the complexes formed between Cu2(OH)2CO3 and HA facilitated, through carboxyl functional groups, the reaction between HA and HOI, leading to an enhancement of I-THM generation during chloramination, which was further confirmed by model compound experiments. Additionally, this study demonstrated that the effects of solid CCPs on I-THM generation during chloramination were solid CCP- and HA-concentration dependent, but almost unaffected by different initial I− and Br− concentrations. This study provides new insights into the health risks caused by the corrosion of copper water pipelines, especially in areas intruded by sea water.