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 Abstract

  Characterization of Coal Combustion Residues from Electric Utilities Using Wet Scrubbers for Multi-Pollutant Control (113 pp, 1.95 MB) (EPA/600/R-08/077) July 2008

CoverThis report evaluates leaching characteristics of air pollution control residues from coal-fired power plants that use acid gas scrubbers, which may also reduce air emissions of mercury and other pollutants. Leaching of mercury and other constituents of potential concern (COPCs) during land disposal of coal combustion residues (CCRs) is evaluated in this report. The data presented in this report will be used in a future report to evaluate the fate of mercury and other COPCs from the management of CCRs resulting from the use of multi-pollutant control technologies. This research is part of an ongoing effort by EPA to use a holistic approach to account for the fate of mercury and other metals in coal throughout the life-cycle stages of CCR management including disposal and beneficial use.

The specific objectives of the research reported here are to:

  1. Evaluate the potential for leaching to ground water of mercury and other COPCs (i.e., aluminum, antimony, arsenic, barium, boron, cadmium, chromium, cobalt, lead, molybdenum, selenium, and thallium) removed from the flue gas of coal-fired power plants by facilities that use wet scrubbers as part of a multi-pollutant control strategy to reduce air emissions.
  2. Provide the foundation for assessing the impact of enhanced mercury and multi-pollutant control technology on leaching of mercury and other COPCs from CCR management including storage, beneficial use, and disposal; and,
  3. Perform these assessments using the most appropriate evaluation methods currently available. The laboratory leach testing followed the approach developed by Kosson, et al. (2002), which considers the effects of varying environmental conditions on waste constituent leaching.

Air pollution control residues (fly ash, gypsum, and scrubber sludge samples) were obtained from coal combustion electric utility facilities using wet scrubbers. A range of facility configurations was selected representing differences in air pollution control technology configurations and coal rank. Each of the residues sampled has been analyzed for selected physical properties, and for total content and leaching characteristics of selected COPCs. Results of laboratory leaching tests were used to develop estimates of constituent release under field management scenarios. Laboratory leaching test results also were compared to field observations of leaching.

This report includes results for 23 CCRs (5 fly ashes, 6 gypsum samples, 5 scrubber sludges, 7 fixated scrubber sludges) sampled from eight facilities. Each CCR sampled was evaluated in the laboratory for leaching as a function of pH and liquid-to-solid ratio. Results are presented for mercury, aluminum, antimony, arsenic, barium, boron, cadmium, chromium, cobalt, lead, molybdenum, selenium, and thallium.

Contact

Susan Thorneloe

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