The anaerobic digestion microbiome is robust towards variation in the waste activated sludge feed

Abstract Anaerobic digestion stands out as the foremost technology for maximizing the valorisation of waste activated sludge to recover energy and recover resources. The physical/chemical and microbial makeup of waste activated sludge is susceptible to seasonal fluctuations, due to the open-air nature of wastewater treatment facilities, potentially impacting subsequent digester performance and the quality of the resulting digestate. This study delved into a comprehensive analysis of both the initial waste activated sludge and the digestate produced by 12 full-scale digesters during both a summer and winter sampling campaign. A significant influence of seasonal variations was observed on the physical/chemical and microbial composition of waste activated sludge. Interestingly, the digestate microbiome exhibited a high resilience with minimal seasonal fluctuations, but instead showed variations between different digesters. In summary, this research demonstrates that while waste activated sludge composition manifests in specific physical/chemical attributes, it does not exert a discernible influence on the microbial composition of the resulting digestate.