Multiple benefits of sulfamethoxazole treatment in distillery anaerobic digestion system: Carbon metabolism promotion, methane enhancement and microscopic mechanism

In recent years, the effective treatment of antibiotics and the rational resource utilization of high‑carbon industrial wastewater have become hot research in the industry. However, there is no research on combining the two together for efficient resource recycling. In this study, sulfamethoxazole (SMX) was added to distillery wastewater with high COD for anaerobic digestion (AD), and its effects on substrate metabolism and methane production in AD systems were investigated. The results show that SMX can be completely metabolized in the AD system of the winery. The methane yield is the highest (810.73 mL CH 4 /g·VS) when the concentration is 0.5 mg/L, which is increased by 55.09 %. Polysaccharides and proteins were more susceptible to SMX, accumulated in the extracellular area and then were used as carbon sources in the subsequent microbial activities. The microbial community and macrogenomic analyses showed that SMX regulated the microbial community and enriched the acetate-type methanogens, leading to more methane production. Meanwhile, the analysis of KEGG metabolic pathway showed that the abundance of functional genes of key enzymes synthesizing antioxidant amino acids was enhanced, which resisted the hydroxyl radicals generated by SMX, leading to the additional production of acetic acid under this metabolic pathway. In addition, functional genes related to glycolysis, amino acid metabolism, tricarboxylic acid (TCA) cycle, and methane metabolism were increased in abundance by 20–90 %, resulting in maximized methane production.