Chlorferon and diethylthiophosphate (DETP) are the hydrolysis products of coumaphos, an organophosphate pesticide. In this research, two consortia of bacterial cultures, one responsible for degrading chlorferon and the other for degrading DETP, were selectively enriched from waste cattle dip solution. The enriched cultures were used as inocula to grow biomass for biodegradation studies. For chlorferon degradation, the optimum biomass concentration was found to be 80 g/L, and pH 7.5 was selected as the optimal operating pH. Chlorferon degradation was characterized by substrate inhibition kinetics with parameter values estimated to be V-m = 0.062 +/- 0.011 mg/(g-biomass) h, K-m, = 21 +/- 17 mg/L, and K-Si = 118 +/- 45 mg/L. For DETP degradation, the optimum biomass concentration was found to be 60 g/L, and the optimum pH was in the range of 7.5-8. DETP degradation was characterized by Michaelis-Menten kinetics with parameter values estimated to be V-m = 1.52 +/- 0.10 mg/(g-biomass) h and K-m = 610 106 mg/L. (c) 2006 Elsevier Ltd. All rights reserved.