Effect of the zero-valent copper and lead in aqueous solution on the formation of disinfection byproducts during chlorination

Zero-valent metal in drinking water distribution system would affect the free chlorine concentration and the formation of disinfection byproducts (DBP). The effect of single zero-valent metal materials on the DBPs formation was well-documented, while the interaction mechanism between composite metals is still unclear. In this paper, the attenuation of the free chlorine concentration and the formation of typical trihalomethanes (THM) with zero-valent copper, lead and copper-lead mixed systems were studied. Results show that the chlorine concentration attenuated with the largest rate in the zero-valent copper system, and the rate accelerated with the decreasing pH value and the increasing metal content. The microbattery effect in the mixed system could accelerate the formation of passivation layer, consequently inhibiting the decay of free chlorine. The formation of THMs was independent on pH (6-8), while decreased with the increasing metal content.When 1g/L zero-valent coppe was added to the system, the total amount of target trihalomethane production was reduced by 33%. The THM production was positively correlated with the concentration of humic acid and negatively correlated with the concentration of bromine ion. This study provides a scientific basis for the mechanism of DBP formation in pipes, and also lays a foundation for improving the safety of drinking water.