EXPERIMENTAL STUDY ON ANAEROBIC THERMOPHILIC DIGESTION OF PRE-THICKENED WASTE ACTIVATED SLUDGE

摘要

Compared to conventional low solid anaerobic mesophilic digestion, high solid anaerobic thermophilic digestion may offer attractive advantages such as lower viscosity value, higher volatile solid destruction efficiency, higher biogas generation, higher disinfection effect and better dewater ability, then lower reactor volume demand. In this study, two experiments of high solid waste activated sludge were conducted using one liter glass jars and 6 liter CSTR to evaluate the biogas production and thermophilic anaerobic process stability. The sludge was taken from the secondary sedimentation tank of a wastewater treatment plant in Beijing. The sludge should be thickened before anaerobic experiment. In first experiment, the biogas production of 4 one-liter glass jarred actors with solid concentration of 6%, 8%, 10% and 12% respectively at thermophilic (55±l)°C temperatures was observed. The biogas productions in 4 jar reactors were 4,444.00mL, 4,891.00mL, 5,573.00mL and 6,327.00mL respectively and the methane content in biogas of each reactor was kept about 70%. In second experiment, 6 liter CSTR was employed for 12% solid concentration sludge. For 40 days operation, total biogas production was about 52.7L, the methane content of biogas was about 69%, biogas production per gram volatile substance was about 0.34L/g VS. In first 30 days, the cumulative produced biogas amount could reach more than 90% of total biogas production. The results showed that high solid anaerobic thermophilic digestion process for waste activated sludge could be operated steadily. This process could reduce the volume demand of anaerobic reactor dramatically, which could make anaerobic sludge treatment process more attractive and economic.