Permanganate pretreatment improves the production of short chain fatty acids from waste activated sludge at pH10: Performance and mechanism

Abstract

Anaerobic fermentation of waste activated sludge (WAS) to produce short-chain fatty acids (SCFAs) shows promise. However, SCFAs production is significantly hindered by the high content of extracellular polymeric substances (EPS) and intracellular material in WAS. To overcome this limitation, a strategy combining alkali (pH10) and potassium permanganate (PM) pretreatment was proposed to enhance SCFAs production. Results demonstrated that alkali-PM pretreatment was more effective for SCFAs production. Under pH10 and 0.4 g PM/g TSS conditions, the maximum SCFAs production reached 7169.04 mg COD/L, representing a 7.27 times increase over the control group (985.70 mg COD/L) and a 3.08 times increase over the pH10 group (2324.98 mg COD/L). The pH10-PM pretreatment disrupted the EPS structure, lysed microbial cells, and released more soluble organic matter for microbial metabolism. The mechanism involved hydroxyl radicals (OH) and Mn(III), which played key roles in the efficient pretreatment of WAS by alkali-PM. Additionally, the pH10-PM pretreatment significantly enhanced the activities of protease, α-glucosidase, and acetate kinase by 121.41 %, 216.05 %, and 237.79 %, respectively, while decreasing carbon monoxide dehydrogenase activity to 73.59 %. Microbial community analysis revealed an enrichment of hydrolytic and acidogenic microorganisms, alongside an increase in the abundance of the carbon degradation gene xylA.