HIGH-RATE BIOREMEDIATION OF CHLOROPHENOL-CONTAMINATED GROUNDWATER AT LOW-TEMPERATURES

Aerobic fluidized-bed treatment was employed for psychotrophic bioremediation of chlorophenol-contaminated groundwater. Laboratory-scale, continuous-flow reactors were inoculated with nonacclimated activated sludge, the groundwater was amended with inorganic nutrients and a phosphate buffer, and continuous groundwater feed was started at 14-17-degrees-C. Chlorophenol concentrations (in mg/L) in groundwater were as follows: 7-11 for 2,4,6-trichlorophenol, 32-36 for 2,3,4,6-tetrachlorophenol, and 1.8-2.3 for pentachlorophenol. After the startup period, the treatment temperature was gradually decreased to the ambient groundwater temperature (7-degrees-C) and further to 4-degrees-C. Steady-state fluidized-bed remediation at 5-h hydraulic retention time resulted in effluent concentrations of less than 0.003 mg/L of each chlorophenol at all temperatures tested. At 5-7-degrees-C, over 99.9% chlorophenol biodegradation was achieved at a chlorophenol loading rate of 740 mg L-1 d-1. Inorganic chloride releases were in conformity with the chlorophenol removals indicating mineralization. In conclusion, this system used higher loading rates than previously reported for bioremediation, and the effluent quality was close to drinking water standards. Further, this is the first paper on high-rate bioremediation at ambient groundwater temperatures or lower (4-10-degrees-C).