MICROBIAL-ASSISTED REMEDIATION OF CREOSOTE-TREATED AND PENTACHLOROPHENOL-TREATED WOOD PRODUCTS

A recycling process designed to recover wood fiber from discarded util ity poles and cross ties was tested. Laboratory and field studies were conducted using a combined physical, chemical and microbiological pro tocol designed for the removal of creosote and pentachlorophenol wood preservatives from wood fiber. Woodchips produced in an industrial typ e wood chipper were batch extracted in methanol. The extractions succe ssfully removed more than 95% of eight major creosote compounds contai ned within the woodchips. An initial combined concentration of 29 262 ppm during the extraction phase was reduced to 95 ppm in the laborator y study and to 1364 ppm in the field study. Biopolishing with a microb ial consortium containing adapted strains from the genera Pseudomonas, Flavobacterium and Acinetobacter further reduced the preservative con centration to 8 ppm and 200 ppm, respectively, with anthracene being t he most recalcitrant compound in both studies. Pentachlorophenol-treat ed wood with an initial concentration of 1190 ppm, when subjected to t he recycling process, yielded end product wood containing less than 2 ppm of the preservative. The solvent/preservative mixture (miscella) p roduced during the extraction process yielded a pure methanol fraction and a still bottom mixture when subjected to flash distillation. Frac tional (vacuum) distillation of the still bottom mixture produced meth anol, creosote, pentachlorophenol, and coal tar fractions.