Aerobic fluidized-bed treatment of polychlorinated phenolic wood preservative constituents

Abstract

Degradation of polychlorinated phenols was studied in continuous-flow fluidized-bed reactors using pure oxygen for aeration and celite carrier for cell immobilization. High dilution rates and chlorophenols as the only source of carbon and energy were used for maintenance of the mixed biofilm cultures. The chlorophenol degradation performance was monitored as release of inorganic chloride and removal of total organic carbon and by direct gas chromatographic analyses. Continuous polychlorophenol biodegradation activity was maintained in a fluidized-bed reactor for 315 days. Chloride release and chlorophenol removal efficiencies of over 99% were achieved at substrate loading rates of up to 430 g 2,4,6-trichlorophenol/m1/d and 400 g 2,3,4,6-tetrachlorophenol/m1/d at 3–5 h hydraulic retention times, respectively. Immobilized mixed cultures biodegraded 2,3,4,6-tetrachlorophenol with partial efficiency at feed concentrations as high as 157 mg/l as indicated by inorganic chloride release. Inorganic chloride release in experiments with practical grade 2,3,4,6-tetrachlorophenol exceeded that which is possible by dechlorination of tetrachlorophenol alone suggesting dechlorination of unidentified chlorinated impurities of the preparation as well. Fluidized-bed treatment of simulated wood preservative contaminated groundwater at a chlorophenol loading rate of 217 g/m1/d and 5 h hydraulic retention time resulted in the following removal efficiencies: 99.5% for 2,4,6-trichlorophenol, 99.6% for 2,3,4,6-tetrachlorophenol and 92.5% for pentachlorophenol.