Enhanced methane from co-digestion of wheat straw and sludge with KMnO₄ and zero-valent iron

This study proposed a synergistic treatment approach combining KMnO₄ pretreatment and zero-valent iron (ZVI) enhancement, along with co-digestion with waste-activated sludge (WAS), to boost wheat straw (WS) anaerobic digestion. Results show that 0.1 g/g WS of KMnO₄ pretreatment effectively destroys the straw's lignin structure, greatly improving its biodegradability and increasing cumulative methane production by about 238.5% compared to the untreated reactor. The addition of ZVI further improved anaerobic digestion efficiency, leading to an additional 13.8% increase in methane production. The underlying mechanism involves the consumption of H⁺ through corrosion reactions, which alleviates acid inhibition and maintains the pH within the optimal range. Simultaneously, ZVI promotes the activity of key enzymes (e.g., coenzyme F₄₂₀) involved in the hydrogenotrophic methanogenesis pathway. PICRUSt2 functional gene analysis reveals a significant increase in the abundance of key genes associated with the CO₂-dependent methanogenesis pathway in the ZVI reactor.