Alkaline-mechanical pretreatment process for enhanced anaerobic digestion of thickened waste activated sludge with a novel crushing device: Performance evaluation and economic analysis

Although various pretreatments have been widely investigated to enhance the anaerobic digestion (AD) of waste activated sludge (WAS), economic feasibility issues have limited real-world applications. The authors examined the performance and economic analysis of an alkaline-mechanical process with a novel mechanical crushing device for thickened WAS pretreatment. The pretreatment at 40 g TS/L, pH 13, and 90 min reaction time achieved 64% of solubilization efficiency and 8.3 times higher CH4 yield than the control. In addition, a synergistic CH4 yield enhancement was observed when the pretreated and raw WAS were used together as feedstock, and the greatest synergy was observed at a volumetric mixture ratio of 50:50. Economic estimates indicate that up to 22% of WAS treatment costs would be saved by the installation of the suggested process. The experimental results clearly indicate that the alkaline-mechanical process would be highly effective and economically feasible for the AD of thickened WAS.