Mutual promotion between waste sludge fermentation and sulfate reduction: Sulfur and carbon metabolism coupling...

Biological sulfate reduction faces challenges due to its dependence on external electron donors, which raises costs and carbon emissions. This study developed an anaerobic fermentation-sulfate reduction (AF-SR) system driven by waste activated sludge (WAS) to simultaneously remove sulfate and reduce sludge. The results showed that 200-800 mg/L sulfate significantly promoted the fermentation, with a 6.6-fold increase in organic matter, which in turn achieved 97.4% sulfate removal. Mechanism analysis revealed that sulfate and its reduction products induced microbial stress, accelerating sludge disintegration and organic matter release. Microbial and metabolic analysis results showed that sulfate addition significantly enriched fermentative bacteria (Thauera and Ottowia) and sulfate-reducing bacteria (Desulfomicrobium and Desulfobacterium). They formed an efficient metabolic network through synergistic interactions in glycolysis, amino acid, short-chain fatty acids and sulfur metabolic pathways. This study elucidated the carbon-sulfur coupling mechanism in AF-SR system, offering an environmentally and economically valuable path for sulfate wastewater and WAS treatment.