Anaerobic Digestion of Oxidation Ditch Sludge at Low Temperatures with Hyperthermophilic Pretreatment

抄録

Centralized anaerobic digestion of dewatered sludge from small scale wastewater treatment plants and other waste biomass such as kitchen garbage is a promising energy recovery technology. Anaerobic digestion at lower temperatures reduces operational cost, while hyperthermophilic pretreatment upgrades anaerobic digestion performance. The applicability of dewatered sewage sludge from an oxidation ditch process to anaerobic digestion was investigated by continuous and batch experiments under combined different temperature conditions. Dewatered sewage sludge was diluted to total solids 5% before feeding. When the organic loading rate was 0.94 kg volatile solids (VS)/(m³·d), biogas production from dewatered sewage sludge at a mesophilic condition (35°C) was 0.20 NL/gVS-added. Under anaerobic digestion conditions at 25, 30 and 35°C with hyperthermophilic pretreatment at 80°C for 24 h, biogas production was higher than 0.20 NL/gVS-added. Effect of different temperatures on digestate characteristics and microbial communities were revealed. An ammonia concentration of the digested sludge with pretreatment was higher than that of the digested sludge without pretreatment. These results proved that the combination of pretreatment and psychrophilic anaerobic digestion is applicable for sludge management in local cities with decentralized small facilities.