Abstract
Solubilization of waste activated sludge during thermal pretreatment was experimentally studied. Thermal pretreatment increases biodegradability and gas production of sludge in anaerobic digestion process. In this study, a laboratory scale experiment was conducted to clear the mechanism of thermal pretreatment of sludge. Solubilization of sludge solids, and changes in constituents of organic materials, especialy nitrogenous materials and volatile fatty acids were analyzed. The solubilization mechanism of sludge solids by thermal pretreatment was made, and model of the reaction was proposed. Solubilization of waste activated sludge was promoted with an increase of thermal pretreatment temperature. Relationship between solubilization ratio and pretreatment temperature was approximated by a logistic function with respect to COD and proteins, and approximated by a second order polynomial with respect to carbohydrates. The total solubilization was almost governed by proteins. The liquid phase analysis shows that proteins was hydrolyzed as protein→amino acid→anmonia+volatle acid. The simulation by the model shows that the effect of holding time on solubilization was small over 30 minutes.
