AWWA JAW10080

This report discusses experiments which were conducted to study the effect of a pH equal to or greater than 9.0 and a low total in organic carbonate (TIC) concentration of 10 to 80 mg as calcium carbonate per liter (CaCO3/L) on lead solubility. The results were compared with those of earlier experiments in which the pH was 8.0 to 8.5. In the experiments that had pHs equal to or greater than 9.0, lead leaching was reduced, as was consumption of both residual free chlorine and dissolved oxygen. The results closely followed the predictions of a solubility model that allowed for aqueous lead complexation and control by the solid basic lead carbonate under the experimental pH and TIC conditions. The authors caution that before a treatment program to reduce lead dissolution by increasing pH is selected, the impact of this action on other water quality characteristics, particularly the formation of trihalomethanes, must be considered. Includes 26 references, tables, figures.