Management of Arsenical Wood Preserving Residuals by Recovery and Immobilization

摘要

Chromated copper arsenate (CCA) is the predominant wood preservative used in the U.S. (67% by volume of wood treated). The residuals from pressure treatment of lumber consist of washdown waters, drippage, treating cylinder sediment, spent formulations and filter screenings. Analyses of these materials indicate arsenic, copper, and chromium concentrations of 1-3 percent each. The solid residues are currently land disposed in RCRA permitted facilities after stabilization and meeting a leachate standard of 5.0 mg/L for arsenic and chromium characteristic wastes. Bench-scale research studies were conducted by the EPA and the private sector to investigate the extractability of the arsenic and metals for reuse by the wood preserving facilities and to determine whether the solid residues are rendered nonhazardous by extraction. Stabilization techniques were also evaluated for immobilization of the arsenic and other metals. The feasibility for recovery of CCA from treatment residues has been demonstrated. Conventional stabilization did not effectively immobilize the arsenic or chromium.