The effect that the COD:TKN ratio had on total nitrogen removal efficiency. as well as, the effect on COD removal efficiency, nitrogen distribution in the effluent streams, and total system mixed liquor suspended solids concentrations in the activated sludge process as a function of the mean cell residence time (θ_c) were examined in this investigation. A definite relationship was shown to exist between the influent COD:TKN ratio, mean cell residence time, and nitrogen removal efficiency by operating two bench scale activated sludge reactors under continuous feeding. Theoretical data, which were generated by applying biokinetic equations and stoichiometric relationships, were compared to laboratory obtained data to evaluate the validity of using stoichiometric relationships to establish design and operational criteria. The mean cell residence time was used as the control parameter in this investigation. It was demonstrated that nitrogen removal efficiency increased via waste sludge incorporation as θ_c was decreased. It was also shown that nitrogen removal efficiency increased with an increase in the influent COD:TKN ratio by both experimental results and theoretical data. Optimum nitrogen removal efficiencies were found to occur at decreasing mean cell residence times and increasing COD:TKN ratios. / M.S.