Effect of anion on anaerobic digestion of sewage sludge: Methane production and microbial characterization

Anaerobic digestion (AD) is one of the most widely used technologies for water-energy-carbon conversion in Wastewater Treatment Plants (WWTPs). The presence of anions derived from wastewater can potentially interfere with the AD process of sludge, yet few research has been conducted to investigate these effects and the underlying biological mechanism. This research comprehensively studied the impact of NO3- , NO2- , SO4 2- and ClO3on the methane production during AD of sewage sludge, as well as their influence on microbial community structure. In batch AD experiments, a slight increase in methane production was observed with NO3 - addition, while significant inhibition occurred with high concentration NO2 - and ClO3- . For SO4 2- addition, the methane production increased initially and decreased subsequently. Further investigation revealed that nitrate promotes the acidification step and leads to a substantial increase in fermentative bacteria such as Lactobacillus after nitrate addition. However, high concentrations of NO2 - would inhibit methanogenesis rather than hydrolysis and acidogenesis. Addition of ClO3- resulted in ammonia nitrogen accumulation, thereby suppressing the growth of Lactobacillus and Fastidiosipila. Moreover, sulfate-reducing bacteria outcompeted methanogenic archaea leading to reduced methane production when SO4 2- was added, resulting in an increased relative abundance of Arcobacter consequently. These findings provide valuable insights for optimizing AD processes of sewage sludge under conditions influenced by anions.