Abstract
Anaerobic digestion of sewage sludge and utilization of digested sludge as liquid fertilizer is a promising energy and resource recovery technology in small facilities, where oxidation ditch processes (OD) are widely applied. Biodegradability of dewatered sewage sludge from OD were comparatively evaluated in digestion and paddy filed experiments. Anaerobic digestion performance was not different under substrate total solids (TS) of 10% and 5%. Under lower temperature conditions of 15-30°C, anaerobic digestion was possible, while biogas production performance was deteriorated. Volatile solids (VS) decomposition ratios under aerobic and anaerobic conditions were 0.6 and 0.4, respectively. A simulated paddy field experiment fed with the digested sludge showed that a higher VS/ TS ratio of the sludge resulted in higher biogas production amount and reaction rate. Biogas production from the digested sludge was lower than that from rice straw, which is the main substrate of methane emission from paddy fields.
