Aerobic digestion of thickened activated sludge: Reaction rate constant determination and process performance

Abstract

The aims of this work were to select which parameter—total suspended solids (TSS), volatile suspended solids (VSS) or degradable volatile suspended solids (DVSS)—best expressed the kinetics of aerobic digestion of waste secondary activated sludge: to define the relationship between the reaction rate constant and the initial concentration of sludges; to evaluate the effect of aerobic digestion on the filterability of the treated sludge as measured by the capillary suction time (C.S.T.). Batch experiments of aerobic digestion were performed in our laboratory on samples of sludges at a constant temperature of 20 C. The initial concentration of sludges ranged from 2600 to 22,000 mg l −1. TSS was found to be the parameter which most closely fits the kinetic model of aerobic digestion. The reaction rate constant was a linear, inverse function of the initial sludge concentration with TSS and with VSS as a parameter. Sludge filterability is affected by the process of aerobic digestion; a prolonged aeration time results in poorer dewatering; and the more concentrated the sample, the poorer the dewatering.