| 초록 |
In this study, combined sludge digestion process was improved with recirculation of solid sludge in the effluent. The recirculation effect to the combined sludge digestion process was investigated. The VSS removal rate was increased from 76% to 97% by applying of internal recirculation and maintained stable until the end of experiments. The concentrations of VSS in each digester also showed steady profiles. Methane production of combined process was decreased from 260mL/L/day to 170mL/L/day as the strength of pre-treatment is decreased. In this experiment, we investigated that sudden introduction of thermophilic microbial community can break mesophilic sludge digestion activity. On the other hands, thermophilic aerobic digester has enough capacity for sludge digestion by its high activity. Thus, pre-treatment of influent and recycled sludge is necessary for energy production in the improved combined process but not essential for sludge removal. |
