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OXIDANT/DISINFECTANT CHEMISTRY AND IMPACTS ON LEAD CORROSION
Citation:
SCHOCK, M. R. AND R. GIANI. OXIDANT/DISINFECTANT CHEMISTRY AND IMPACTS ON LEAD CORROSION. In Proceedings, Sunday Workshop Getting the Lead Out: Analysis and Treatment of Elevated Lead Levels in DC's Drinking Water, San Antonio, TX, November 14 - 18, 2004. American Water Works Association, Denver, CO, 11, (2004).
Impact/Purpose:
provide information
Description:
In response to continued elevated lead levels throughout the District of Columbia's distribution system, a collaboration was begun with the District of Columbia's Water & Sewer Authority (WASA) and Water Resources Division of U. S. Environmental Protection Agency's (USEPA) Office of Research and Development in late winter of 2004 to investigate the causes of the sudden increases in lead release. Chemical analysis of lead pipe scales using X-ray diffraction and XANES spectroscopy revealed that the dominant pipe material was a mix of the tetravalent lead oxide phases plattnerite and scrutinyite. Minor components included some divalent lead phases, which taken together, gave strong evidence that the change in chlorination from free chlorine to chloramine produced a decrease in the oxidation-reduction potential and elevated release of soluble and particulate lead from the pipe scale. These conclusions are corroborated with some laboratory pipe rig data. Very basic questions pertaining to Pb(IV) chemistry remain, and are critical to answer to provide important information necessary for revisions to lead corrosion control guidance, and to properly evaluate disinfection alternatives. More resources need to be mobilized quickly to gather the information needed to provide timely guidance for water systems confronted with needing to evaluate complex and costly major treatment upgrades to meet new regulatory requirements.