AWWA JAW64970

In this research, experimental tests and practical case studies from U.S. utilities uncovered the importance of chloride-to-sulfate mass ratio (CSMR). When early investigations of lead contamination in several U.S. cities failed to determine the source of the problem, this work uncovered the first valid explanation for those specific cases by introducing CSMR of water as a major cause of lead leaching to water. The authors conclusively linked higher CSMR to higher levels of lead release through galvanic corrosion of lead-tin solder at copper pipe joints. Water providers may inadvertently alter the CSMR of their water through their coagulant choice. For example, switching from a sulfate-containing coagulant to one containing chloride could increase the CSMR, which in turn could trigger lead contamination at levels above the regulatory action level. Because even seemingly innocuous shifts in water treatment can have unforeseen repercussions, utilities are advised to undertake preliminary studies at bench-scale or desktop to help prevent potential contamination problems in systems with lead-bearing plumbing. Includes 32 references, tables, figures.