A gram positive, spore-forming bacterium, which was isolated from a 20-year-old Forest Service test plot of CCA-treated 2 x 4's in Madison, WI., demonstrated the ability to release copper, chromium, and arsenic from CCA-treated wood in liquid culture. CCA-treated sawdust was exposed to this organism, which has been presumptively identified as Bacillus licheniformis. Analysis of the sawdust by atomic absorption spectroscopy revealed 80% reduction in copper and 43% reduction in arsenic when the sawdust was exposed to B. licheniformis in a standard mixed culture for 10 d compared to an untreated control. Enhanced release of metals was demonstrated when CCA-treated sawdust was exposed to the bacterium under continuous culture conditions in a chemostat. Steady-state growth of the bacterium under continuous culture conditions released 93% copper, 45% arsenic, and 6% chromium by weight from the sawdust. Exposure of CCA-treated wood to this isolate of B. licheniformis removed significant amounts of copper and arsenic from the wood.

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