Iodo-trihalomethanes formation during chlorination and chloramination of iodide-containing waters in the presence of Cu2+

In this study, the impact of Cu 2+ on the formation of iodo-trihalomethanes (I-THMs) during chlorination and chloramination of iodide-containing waters was investigated. Initially, the oxidant consumption and evolution of hypoiodous acid (HOI) were determined during disinfection in the presence of Cu 2+ and the interaction between natural organic matter humic acid (HA) and Cu 2+ was also analyzed. Subsequently, the formation of the I-THMs at various Cu 2+ concentrations was evaluated for chlorination and chloramination. Moreover, in order to explore the possible underlying mechanisms, five model compounds based on the HA structure were used to investigate the I-THMs formation with and without Cu 2+ during disinfection. The results indicated that the presence of Cu 2+ markedly affected the conformation of the HA rather than the HOI evolution during disinfection. The concentration of the I-THMs decreased from 34.5 ± 0.8 to 20.9 ± 0.8 nM as the Cu 2+ concentration increased from 0 to 20 μM during chlorination. In contrast, during chloramination, the total I-THMs concentration decreased from 320.7 ± 7.4 to 267.2 ± 10.7 nM as the Cu 2+ concentration increased from 0 to 5 μM and then increased to 315.0 ± 1.7 nM when the Cu 2+ concentration reached 20 μM. The disinfection experiments with the model compounds suggested that the impact of Cu 2+ on the I-THMs formation largely depended on the organic structures in the HA, thus leading to different results during chlorination and chloramination.