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

Aerobic fluidized-bed treatment was employed for psychotrophic bioreme diation of chlorophenol-contaminated groundwater. Laboratory-scale, co ntinuous-flow reactors were inoculated with nonacclimated activated sl udge, the groundwater was amended with inorganic nutrients and a phosp hate buffer, and continuous groundwater feed was started at 14-17-degr ees-C. Chlorophenol concentrations (in mg/L) in groundwater were as fo llows: 7-11 for 2,4,6-trichlorophenol, 32-36 for 2,3,4,6-tetrachloroph enol, and 1.8-2.3 for pentachlorophenol. After the startup period, the treatment temperature was gradually decreased to the ambient groundwa ter 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 chloro phenol 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. Furth er, this is the first paper on high-rate bioremediation at ambient gro undwater temperatures or lower (4-10-degrees-C).