Alkaline Pretreatment of Waste Activated Sludge in Anaerobic Digestion

Abstract

Slow degradation of waste activated sludge (WAS) is a disadvantage of anaerobic digestion leading to high sludge retention time in conventional digesters. So, this study was proposed to increase biodegradability of WAS by alkaline pretreatment, and effect of pretreatment on the performance of anaerobic digestion and treatment efficiency was evaluated under both ambient and thermophilic condition. The soluble chemical oxygen demand (SCOD) and biochemical oxygen demand (BOD) fractions increased when pH values were increased. The solubilization had the highest increase in the pH range of 11 to 12 and gradually increased in the pH range of 8-11. However, the BOD 20 /COD ratios decreased for adjusted pH 10 and pH 11, and biodegradation was limited at pH 12. And pH 8 was the optimal value this alkaline pretreatment on anaerobic digestion. In alkaline pretreatment thermophilic anaerobic condition (PTAN), the result remove were 42.16%, 43.15% and 50.64% for TS, VS and COD removal, respectively, which are higher efficiency and gas production when compared to other conditions.