An aerobic biodegradation of p-nitrophenol (PNP) by acclimated waste activated sludge in a bubble column was examined at varying initial PNP concentrations (from 12.8 to 128 mg L(-1)), activated sludge concentrations (from 3530 to 6300 mg L(-1)) and aeration rates (from 0.3 to 3.0 L min(-1)). The time course of the biodegradation of PNP in a batch slurry bubble column could be divided into three phases, i.e.. lag phase, exponential degradation phase and ultimate deceleration phase. The complete biodegradation of 128 mg L(-1) of PNP with 3600 mg L(-1) of mixed liquor suspended solids (MISS) and 1.51 min(-1) of aeration rate was accomplished in 150 min. The present results indicate that the acclimated waste activated sludge is very effective for PNP aerobic biodegradation. The change in dissolved oxygen concentration during the aerobic biodegradation process was also measured. It was found that the oxygen supply strongly affects the PNP aerobic biodegradation. A modified Haldane substrate inhibition kinetics taking account of the lag phase as well as the exponential degradation phase and the ultimate deceleration phase was developed to describe the entire time course of the aerobic biodegradation of PNP. The aerobic biodegradation of PNP by acclimated activated sludge in the bubble column was successfully simulated with the correlation factors of approximately 0.95. (C) 2010 Elsevier Ltd. All rights reserved.