Effects Of Copper Corrosion Products On The Formation Of Iodo-trihalomethanes During Drinking Water Disinfection

Disinfection by-products(DBPs)have attracted public attentionas it pose risks to human health.As a kind of newly discovered DBPs,iodo-trihalomethane(I-THMs)has attracted more and more attention because of its high genotoxicity and cytotoxicity.During the transportation of drinking water,corrosion products of pipes may affect the formation of DBPs.Copper pipes are widely used and would be corroded to produce Cu2+and copper oxides(i.e.Cu2(OH)2CO3?CuO and Cu2O)in the long-term use.In this paper,the impact of copper corrosion products on I-THMs formation during disinfection of iodide-containing waters was investigated.The main research contents and results are summarized as follows:1.The effect of Cu2+ on the formation of I-THMs during chlorination and chloramination was explored.Initially,the oxidant consumption and evolution of hypoiodous acid(HOI)were determined during disinfection in the presence or absence of Cuu+and the interaction between natural organic matter humic acid(HA)and Cu2+was also analyzed.Subsequently,the formation of the I-THMs at various Cu2+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 Cu2+during disinfection.Finally,the effects of phosphate and pH on the formation of I-THMs in the presence or absence of Cu2+were conducted.The results showed that the presence of Cu2+could promote the consumption of chlorine(C12)while did not affecte the consumption of chloramine(NH2CI)in the process of HA disinfection.And Cu2+ had no effect on the reaction between I-/HOI and Cl2/NH2CI.Cu2+preferentially complexed with humic-like components in HA and had obvious influence on its conformation.The concentration of the I-THMs decreased from 34.5±0.8 to 20.9±0.8 nM as the Cu2+concentration increased from 0 to 20 LM 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 Cu2+concentration increased from 0 to 5 ?M and then increased to 315.0± 1.7 nM when the Cu2+concentration reached 20?M.The disinfection experiments with the model compounds suggested that the impact of Cu2+on thel-THMs formation largely depended on the organic structures in the HA,thus leading to different results during chlorination and chloramination.Besides,at lower pH values,the presence of Cufu could more effectively reduce the formation of I-THMs.The addition of phosphate would not affect the fotmation of I-TI-HMs during disinfection in the presence or absence of Cue+.2.The effect of copper oxides on I-THMs formation during chloramine was studied.The effect of different copper oxides on the decay of chloramination and HOI was investigated.Besides,the influences of various parameters,including copper oxides,I",HA,Br concentration,pH and different organic substrates,on the formation of I-THMs were studied for each copper oxides.Experimental results showed that the presence of copper oxide could catalyze the decomposition of NH2CI and HOI.In the process of HA chloramination,the total concentration of I-THMs increased as Cu2(OH)2CO3 concentration increased.While the total I-THMs concentration decreased with the increase of CuO or Cu2O concentration,and the inhibition effect of Cu2O was more obvious.In the presence or absence of copper oxides,during HA chloramination,low concentration of HA and high concentration of I:were more conducive to the formation of I-THMs,and the presence of Br'could lead to the formation of bromo-I-THMs and increase the formation of total I-THMs,while the formation of I-THMs increased first and then decreased with the increase of pH.Besides,in the case of higher I-/HA,the presence of copper oxide was more favorable to the generation of CHI3.Under acidic and alkaline conditions,the addition of copper oxide was more conducive to inhibiting I-THMs fomation.Moreover,when used different organic substrate,the effect of copper oxides on the formation of I-THMs was quite different.