Potassium permanganate pretreatment effectively improves methane production from anaerobic digestion of waste activated sludge: Reaction kinetics and mechanisms

As a powerful oxidizing agent, potassium permanganate (KMnO4) has attracted widespread interest in sludge treat-ment and contaminant removal. However, its effect on the anaerobic digestion of waste activated sludge (WAS) is ambiguous. This investigation was designed to provide perspectives into this problem. In comparison with the control, 0.3 g KMnO4/g TSS pretreatment enhanced the methane production by 78.82 %. Model analysis demonstrated that the KMnO4 pretreatment enhanced the biochemical methane potential (B0) of WAS. Mechanistic studies elucidated that the KMnO4 pretreatment process generated reactive radicals such as center dot OH, center dot O-2(-) and O-1(2), which contributed to sludge disintegration and biodegradation process of dissolved substances, thus resulting in more substances available for subsequent methane generation. Enzyme activity analysis indicated that KMnO4 pretreatment facilitated the activities of key enzymes associated with anaerobic digestion to various degrees. Microbial analysis illustrated that the relative abundance of functional microorganisms was significantly elevated after KMnO4 pretreatment, which was conducive to methane production.