The Effects of the Qualities of Separately High-concentrated Sludges and Dosing Bioactive Reagent (Saponin) on the Anaerobic Digestion of Sewage Sludge

Abstract

The anaerobic digestion of sewage sludge was earned out. The sludge used was the mixed sludge of centrifugally thickened excess sludge (TS about 4%) and gravitationally thickened sludge (TS about 5%) from treatment plant of separate sewerage system, and the bio-active regent (saponin 5ppm) was dosed in the anaerobic digestion tank. The temperature of tank was 35°C in the mesophlic digestion. The retention time of sludge was 20, or 7 days. The volume of produced gas was about 20 times compared with that of feed sludge. The produced gas volume per feed organic substace was 0.4-0.55 [l/g-VTS] . The concentration of H₂S and CH₃SH in the gas was remarkably decreased by dosing saponin.