Enhanced Methane Production from Sludge Anaerobic Digestion with the Addition of Potassium Permanganate

This work aims to reveal the effect of potassium permanganate (KMnO₄) on the sludge anaerobic digestion process, as well as the relevant mechanisms. Experimental data showed that the biomethane production was gradually increased from 159.3 ± 3.0 to 211.5 ± 5.1 mL/g VSS (volatile suspended solids) when the KMnO₄ content was increased from 0 to 0.08 g/g VSS, with an increasing rate of 32.8%. A further increase in the KMnO₄ dosage however resulted in the decline of the methane yield. First-order kinetic model analysis indicated that higher methane production potentials and hydrolysis rates were achieved in KMnO₄-added reactors than in the control. Mechanism analysis demonstrated that KMnO₄ not only efficiently disintegrated the sludge flocs, which resulted in the increased contents of dissolved organics, but also enhanced the proportion of biodegradable substances in the sludge liquor. Meanwhile, the biodegradabilities of recalcitrant humus and lignocellulose substances were found to be promoted by KMnO₄ treatment as higher methane yields were attained from KMnO₄-treated model substrates. 16S rRNA analysis illustrated that the functional microbes participated in anaerobic digestion were largely enriched in the KMnO₄-pretreated digestor. Furthermore, efficient inactivation of the fecal coliform was achieved by KMnO₄ pretreatment.