Abstract
The characteristics of the degradation of excess activated sludge in the acidogenic phase were investigated by the laboratory-scale batch and continuous experiments at 35±1°C. The effects of organic loading and digestion period on the production of volatile fatty acids and digester gas were studied by the batch experiments. On the other hand, the continuous experiments were performed using four kinds of excess activated sludges collected at different periods at SRTs of 0.5, 1.5, 3.0 and 5.0 days in order to clarify the behavior of the degradation of excess activated sludge. About 60% of total COD of excess activated sludge was degraded in 130 days by batch experiment. The hydrolysis reaction is the rate-limiting step in overall anaerobic digestion. The hydrolytic rate of degradable materials in excess activated sludge is expressed as a linear equation, and hydrolytic rate constants were : 0.44 0.89 days-1 on the basis of volatile suspended solids (VSS) and 0.32 0.65 days-1 on the basis of COD. The distribution ratios of degradable materials in the excess activated sludge are shown in the following order : lipid> protein> carbohydrate.
