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Lead is a toxic heavy metal and the adverse effects of lead consumption are apublic health concern. Water leaving treatment plants has very low concentrations oflead. However, internal corrosion of lead-containing pipe, fittings, and solder in waterdistribution systems is currently the most significant source of lead to drinking water.While new construction does not use lead pipe, many older buildings retain the originallead service lines and internal plumbing. Concern for lead concentrations in waterdistribution systems motivated the U.S. Environmental Protection Agency (USEPA) to passthe Lead and Copper Rule (LCR) in 1991. The LCR set the lead action level to 0.015mg/L. The understanding of the relationships between water chemistry and the solubilityof lead-containing minerals has increased since the passage of the LCR. However, therecent observations of extremely high lead levels in Washington D.C. tap water highlightthe need for continuing research.Lead concentrations in drinking water are affected by chemical reactions thatoccur within the water distribution system. Previous studies have investigated theequilibrium solubility of lead corrosion products. This project focuses on dissolution rates.Knowledge of lead release rates are useful for evaluating potential effects of treatmentprocess changes on water quality in the distribution system. The dissolution rates of theimportant lead corrosion product, hydrocerussite (Pbsub3/sub(COsub3/sub)sub2/sub(OH)sub2/sub), will be determinedas a function of pH, dissolved inorganic carbon, orthophosphate, and the presence ofchloramines. The lead corrosion products will be characterized with respect to surfacearea, molecular structure, morphology, and mineralogy. The dissolution rates of theselead corrosion products will be quantitatively determined in completely-mixedcontinuous-flow reactors. The experimentally measured dissolution rates will be used togenerate a model for dissolution rates as a function of water chemistry. This model willthen be used to evaluate the dissolution of pipe scales excavated from a water distributionsystem. Includes 19 references, tables, figures.

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Edition: Vol. - No. Published: 11/01/2007 Number of Pages: 17File Size: 1 file , 440 KB