Impacts of Source Water Blending on Lead Release

Historically, corrosion control in the United States for Lead and Copper Rule compliance has focused on treatment to reduce the distributed water's plumbosolvency. Corrosion control treatment (CCT) typically focuses on either control of pH and alkalinity, development and maintenance of Pb(IV) scale under oxidized conditions, or use of orthophosphate-based corrosion inhibitors. These CCT methods are influenced by source water quality parameters such as pH and dissolved inorganic carbon; thus, CCT can potentially be affected when source waters with different water qualities blend in the distribution system. If portions of the distribution system are exposed to blends of source waters with disparate water qualities, testing may be warranted to determine whether optimal CCT is being maintained where and when blending occurs, especially in transitional periods. This article discusses the theoretical impacts of blending source waters with different water qualities and presents research that was conducted on waters from two utilities to illustrate the potential impacts that source water changes can have on CCT.