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In 1979, the Electric Power Research Institute (EPRI) sponsored a multiple laboratory investigation of the variability and reproducibility of the U.S. EPA extraction procedure (EP) used for classifying wastes. In late 1985 and early 1986, EPRI sponsored another round-robin study to compare the results of EPA's new toxicity characteristics leaching procedure (TCLP) with the EP. In this latest study, three laboratories were used to extract and analyze the concentrations of 14 constituents (Ag, As, B, Ba, Cd, Cr, F, Hg, Mn, Pb, Se, SO4, V, and Zn) from seven utility wastes (three fly ashes, two bottom ashes, and two scrubber sludges). The results were evaluated to determine the reproducibility of the two methods, the factors contributing to the variability of the EP and TCLP extracts, and the differences in mean concentrations between the two extract types for the selected wastes. The results show that reproducibility differs by constituent, waste type, and between the two extraction methods. Generally, the concentrations measured in the TCLP results (as measured by the coefficient of variation) are equal to or better than the EP results (for example, for As, B, Cd, Cr, Mn, and V). Differences in the extractions between laboratories accounted for at least 25% of the total variability more frequently for the EP than the TCLP. For the TCLP, the analytical variability components (that is, differences in the analyses between laboratories and differences in analyses of duplicate splits by the same laboratory) accounted for at least 25% of the total variability more frequently.
coal ash, fly ash, bottom ash, scrubber sludge, EP, TCLP, round-robin evaluation, variability in chemical composition, inorganic constituents, RCRA testing, leaching tests
Program manager, Land and Water Quality Studies, Electric Power Research Institute, Palo Alto, CA