Biodegradation of Phenolic Compounds in Creosote Treated Wood Waste by a Composting Microbial Culture Augmented with the Fungus Thermoascus aurantiaciis

摘要

Problem statement: Creosote is used as a wood preservative and water proof agent in railway sleepers, utility poles, buildings foundations and fences and garden furniture. It is a mixture of over 300 hydrocarbons which include 75% polycyclic aromatichydrocarbons, 2-17% phenolic compounds and 10-18% heterocyclic organic compounds. Exposure to creosote may result in several health problems including damage to kidney, liver, eyes and skin. Potential contamination of soil and water exist from creosote treated wood from construction and demolition sites. Approach: The possibility of using an invessel composting process augmented with the ascomycetous fungus Thermoascus aurantiaciis as a mesophilic/thermophihc bioremediation option for the degradation ofphenolic compounds in creosote treated wood waste was evaluated. Results: The temperatures of bioremediation process reached thermophilic phase and mesophilic and thermophilic lag phases were clearly identified. The moisture content decreased significantly indicating that the water produced by microbial respiration did not compensate for the water lost as vapor with the exhaust gases. Initial increases in pH due to the breakdown of organic nitrogen to ammonium and final drop in pH due to the formationof organic acids and loss of ammonium with the exhaust gases in the latter stage were observed. Different degradation rates were observed in the mesophilic and thermophilic stages of composting. The control experiment achieved higher reductions of volatile solids, total carbon and TKN and higher degradation of phenolic compounds, cellulose and lignin, indicating a higher level of activity of microorganisms during the composting process compared with inoculated experimental trial. The stability and maturity of the product of the control experiment were also better than those of the product from inoculated experimental trial. Conclusion: The inoculation of the cellulolytic-thermophilic fungus Thermoascus aurantiacus does not accelerate the bioremediationprocess in degrading phenolic compounds and fungus may have inhibited the growth and metabolic activities of composting organisms.