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approved: LRedacted for Privacy Kenneth J. Williamson Chlorinated phenols are toxic compounds and often released into natural environments from improper disposal or non-point sources. One important factor in assessing the environmental fate and transport is the rates of microbial degradation in soils and natural waters. In this study, eight chlorophenols (4-chlorophenol (4-CP), 2,4-dichlorophenol (2,4-DCP), 3,4-dichlorophenol (3,4-DCP), 3,5-dichlorophenol (3,5DCP), 2,3,5-trichlorophenol (2,3,5-TCP), 2,4,5-trichlorophenol (2,4,5-TCP), 3,4,5trichlorophenol (3,4,5-TCP), and 2,4,6-trichlorophenol (2,4,6-TCP)) were chosen as the model compounds because they represent the major degradation products for the anaerobic metabolic products of pentachlorophenol (PCP). Aerobic degradation rates of all eight compounds were determined under controlled laboratory conditions. A mixed bacterial culture was seeded from a municipal wastewater treatment plant and were grown with acetate as a primary substrate and the eight chlorophenols as secondary substrates. Rates of degradation were measured in a batch reactor with an initial concentration of acetate of 1000 mg/1 and of the individual chlorophenol of 0.1 mg/l. Rate of acetate and chlorophenols were modelled using a Monod model. The maximum rate of acetate utilization was zero-order in relation to acetate concentration and first-order with respect to organism concentration. The rate of chlorophenol degradation were zero-order in relation to the chlorophenol concentration. The relative rates of degradation were in general as follows: monochlorophenol > dichlorophenols > trichlorophenols. Aerobic Degradation of Chlorophenols