Scaled-up remediation of CCA-treated wood

Bioremediation is a novel approach to recycling waste wood treated with chromated copper arsenate (CCA). Remediating CCA-treated waste wood diverts this fiber source from our landfills and provides tangible secondary products from the cleaned fiber. On a laboratory scale, this method, which utilizes oxalic acid extraction and bioleaching with a metal- tolerant bacterium, removed up to 78% Cu, 100% Cr, and 97% As from 1 kg chipped CCA-treated southern pine. The two-step sequence of oxalic acid extraction and bioleaching removed more metals than did either acid extraction or bioleaching alone. Scale-up parameters on 11 kg of particulate, flaked, or chipped CCA- treated wood were evaluated in a 150-reactor. This process removed 79% Cu, 70% Cr, and 88% As from particulate wood, 83% Cu, 86% Cr, and 95% As from flaked wood, and 65% Cu, 64% Cr, and 81% As from wood chips. Metals released from CCA-treated wood during bioremediation are potentially recoverable from a liquid medium for reuse or disposal. Remediation methodologies remain cost prohibitive, but they may become economically competitive in the event landfill restrictions are imposed domestically.