Federal guidelines have been issued which regulate the aqueous discharge concentrations of priority pollutants for the organic chemicals, plastics, and synthetic fibers (OCPSF) Industries. Insufficient data existed in the literature to allow estimations of the removal of priority pollutants by a wastewater treatment plant (WWTP). The removals of eighteen organic xenobiotics were measured in parallel, aerated, continuous, mixed reactors. The influent to the pilot plants was primary effluent from an industrial 30 million gal./day wastewater treatment facility. The kinetic coefficients which characterize removal by biodegradation, powdered activated carbon (PAC) adsorption and air-stripping were obtained, and the values were used to estimate WWTP performance. Agreement between the steady-state model predictions and the WWTP data was surprisingly good for most of the compounds in spite of unsteady-state operation and the six millionfold scaleup. For compounds where severe transients occurred, the steady state model was unsatisfactory. The model was used to design a second stage “PACT” unit and to determine source control requirements. The model also can be used to estimate the relative importance of the three removal mechanisms in order to adjust WWTP operating conditions to enhance the removal of specific compounds.