Oxygen transfer during aerobic biodegradation of pollutants in a dense activated sludge slurry bubble column: Actual volumetric oxygen transfer coefficient and oxygen uptake rate in p-nitrophenol degradation by acclimated waste activated sludge

Volumetric oxygen transfer coefficient and oxygen uptake rate in a dense activated sludge slurry bubble column were measured by varying activated sludge concentrations (from 2000 to 8000 mg/L) and/or aeration rates (from 0.3 to 1.5 L min(-1)). They were separately determined by the dynamic methods. The endogenous oxygen uptake rate of the activated sludge was estimated by monitoring the dissolved oxygen concentration change after turning off the air sparging in a stirred tank. The volumetric oxygen transfer coefficient in a dense activated sludge slurry bubble column was determined using the dissolved oxygen concentration profiles and the oxygen uptake rates predetermined from the separate measurements. While the oxygen uptake rate almost linearly increased with increasing the activated sludge concentration, the volumetric oxygen transfer coefficient decreased with an increase in the activated sludge concentration. Their empirical correlations were obtained as functions of activated sludge concentration by fitting the experimental data. For the aerobic biodegradation of p-nitrophenol (PNP) by acclimated waste activated sludge, the dynamic models for the dissolved oxygen mass balance and PNP degradation kinetics with the proposed correlations for volumetric oxygen transfer coefficient and oxygen uptake rate could successfully simulate the concentration profiles of dissolved oxygen and PNP during the time course of an aerobic biodegradation of PNP. (c) 2010 Elsevier B.V. All rights reserved.