Improving anaerobic digestion of various sludge types through alkaline pretreatment

Abstract

This study investigates the impact of alkaline pretreatment on the anaerobic digestion of waste activated sludge (WAS) with varying types and total solids (TS) concentrations. Using NaOH, we optimized pretreatment conditions with a pH of 8.5 and a contact time of 2 hours. Our key findings demonstrate that this pretreatment significantly enhances sludge solubilization, evidenced by a notable increase in soluble chemical oxygen demand (SCOD). Specifically, SCOD increased by 57.5% for domestic wastewater (Plant A) and by 12.1% for industrial wastewater (Plant B) at a 0.5% TS concentration. Higher TS concentrations showed similar trends, with improved solubilization and higher methane production rates. Additionally, pretreatment elevated ammonia nitrogen (NH₃-N) and phosphorus concentrations, with greater releases at higher TS levels. These improvements resulted in enhanced anaerobic digestibility, higher total solids (TS) and volatile solids (VS) destruction, and increased specific methane production. The study underscores the effectiveness of alkaline pretreatment in optimizing anaerobic digestion processes, offering practical implications for wastewater treatment efficiency.