Influence of feed concentration on the kinetics of biodegradation of phenol in a continuous stirred reactor

The rate of phenol degradation by activated sludge was studied in a completely mixed continuous-flow reactor with sludge recycle, operated at steady-state conditions at 20°C. Monod kinetics was followed when the influent concentration ( C s °) was kept constant. When using different C s ° levels, the phenol removal rate was found to have an inverse dependence on C s °. It is suggested that this kinetic anomaly is due to inhibition of the biooxidation by some secondary reaction product(s). A kinetic model based on this concept is able to interpret experimental facts.