Comparison of Chlorine and Chloramines on Lead Release from Copper Pipe Rigs

The objective of this study was to assess lead release in a pipe rig system that was disinfected with either chloramines or free chlorine. The study was carried out using pipe loops and copper pipe rigs that had lead solder, which provided the only source of lead. The water quality of the treated water had a low alkalinity ( as ), neutral pH, and low hardness ( as ). However, the study used a corrosion control program that consisted of dosing with 0.8-mg of zinc orthophosphate and controlling the pH to 7.3, that was consistent with the corrosion-control program operated in the host water treatment plant. Key findings from the study confirmed that chloramines would result in lead release under the current corrosion-control program, whereas free chlorine was not as compromising. Lead concentrations were approximately an order of magnitude lower in the free chlorine system than the chloramine systems. In this study, chloramines with a target residual concentration of released and following stagnation times of 24h and 30min, respectively. Furthermore, chloramines with a target residual concentration of resulted in a lead release of and following a stagnation time of 24h and 30min, respectively. By comparison, the pipe rigs that were dosed with a free chlorine target residual concentration of had lead concentrations of and for the 24-h and 30-min stagnation times. This project demonstrates that care needs to be taken when evaluating secondary disinfectants, particularly for those water systems having a low dissolved inorganic carbon concentration.