A microbial consortium and Pseudomonas strain (PPO1) were used in studying biodegradation of benzene, toluene, and p-xylene under aeorbic conditions. Studies involved removal of each compound individually as well as in mixture with the others. Both cultures exhibited a qualitatively similar behavior toward each compound. Both the pure culture and the consortium grew on benzene following Monod kinetics, on toluene following inhibitory (Andrews) kinetics, whereas neither could grow on P-xylene. Benzene and toluene mixtures were removed under cross-inhibitory (competitive inhibition) kinetics. In the presence of benzene and/or toluene, p-xylene was cometabolically utilized by both cultures, but was not completely mineralized. Metabolic intermediates of p-xylene accumulated in the medium and were identified. Benzene and toluene were completely mineralized. Cometabolic removal of p-xylene reduced the yields on both benzene and toluene. Except for cometabolism, kinetic constants were determined from data analysis and are compared with values published recently by other researchers. (c) 1994 John Wiley & Sons, Inc.