Abstract
Toxic organic chemicals, volatile organic compounds, (VOCs) and pesticides, in wastewaters were biologically degraded by utilizing waste activated sludge in a gas-liquid-solid three-phase slurry bioreactor. The biodegradation kinetics of toxic organic chemicals was examined in batch experiments at varying initial toxic organic chemical concentrations, waste activated sludge concentrations and aeration rates. The bioreactor constructed from plexiglass had an internal diameter of 75 mm and a working volume of 2 L. As an activated sludge, waste activated sludge obtained from Kawagoe City Wastewater Treatment Plant located in Saitama, Japan was used. It was found that the biodegradation rates of toxic organic chemicals were approximately described by first order kinetics. However, in the case of the VOC used in this study, o-cresol, the shape of the curves for specific biodegradation rates of was typical for the substrate inhibition kinetics. Therefore, the kinetic parameters of aerobic o-cresol biodegradation were estimated using Haldane's substrate inhibition equation. The oxygen consumption during the biodegradation process was also examined. The oxygen consumption rate was adequately described by the Haldane type model. The biodegradation of toxic organic chemicals by waste activated sludge and the change of dissolved oxygen concentration in the slurry bioreactor were successfully simulated.
