COMPARATIVE ENERGETIC POTENTIAL EVALUATION OF SLUDGE FROM SMALL WASTEWATER TREATMENT FACILITIES FOR ANAEROBIC CO-DIGESTION

Abstract

 Scattered small scale domestic wastewater treatment systems managed by different ministries and their sludge disposal are operated ineffectively. Various types of sludge from small wastewater treatment facilities are analyzed in terms of energy contents, focusing on volatile solids (VS)/ total solids (TS) ratio, calorific value, and anaerobic digestion performance. Higher heating value and biogas production performance in anaerobic digestion are correlated with VS/TS ratio, regardless of sludge types. Sludge in personal on-site wastewater treatment facilities (jokaso) is typically withdrawn once a year, while jokaso sludge withdrawn once every one to three months has higher VS/TS ratio as well as higher biogas production performance of 0.4～0.5 NL/gVS-added, which is similar to that of typical mixed sewage sludge. These results are useful for designing and operating co-digestion, which accepts various types of waste biomass, including small scale wastewater treatment sludge.