Improving the efficiency of metal removal from CCA-treated wood using brown rot fungi

The purpose of this study was to evaluate the bioremediation of CCA-treated wood wastes by brown rot fungi, as well as to improve the metal removal from treated wood by altering an existing bioremediation process. In Process I, CCA-treated wood sawdust was added and bioremediated after accumulating oxalic acid in a fermentation broth. In Process II, simplification of the bioremediation process and improvement of metal removal efficiency were attempted. Thus, the treated sawdust and fungal inocula were simultaneously placed in a fermentation broth. In addition, the efficiency of the fermentation broth containing oxalic acid was compared with that of commercial oxalic acid. The results obtained using Process I showed that the greatest reduction in arsenic and chromium (98% and 91%, respectively) was achieved by an unknown Polyporales species. On the other hand, the most efficient removal of copper (82%) was achieved by Daedalea dickinsii, which had the lowest oxalic acid production. Using Process II, the highest copper, chromium and arsenic removal rates (96%, 92% and 98%, respectively) were obtained by Fomitopsis palustris. Process II could be a very valuable method for metal removal from CCA-treated wood when F. palustris is used. Our results also suggest that oxalic acid produced from fungus can be used as an alternative to commercial oxalic acid.