Effect of substrate compositions on microbial communities in full-scale anaerobic digesters

The microbial community of anaerobic digester (AD) systems is known to be affected by operational temperature and substrate composition. However, how the underlying relationship is reflected in the microbial communities of different digester types is less well-described. This work presents a comparison of 54 full-scale AD systems processing either food waste, manures, wastewater sludge as their primary substrate, or a mixture of these substrates. The digesters were operated across a representative set of operational configurations. Comparison of microbial community profiles revealed that wastewater sludge-based systems likely present a more distinctive microbial ecosystem compared to the other investigated substrate types, and that manure-based digesters are more similar in microbiome regardless of operational temperature. Major parts of the methanogenic populations had a degree of redundancy in all sampled digesters, however the genera Candidatus Methanofastidiosum, Methanolinea and Methanothrix were almost uniquely observed in mesophilic wastewater sludge digesters, and those with thermal hydrolysis. Finally, the microbes associated with a primary waste type were also found in mixed substrate AD systems receiving the same substrate. The present study showed that AD microbiomes reflect the substrates applied in all stages of the anaerobic digestionprocess, and supports that regular microbial community monitoring in AD systems can provide important information relating to how the microbiomes respond to different operational configurations and scenarios. Application of microbial data in existing management strategies represents an important step toward achieving holistic management of anaerobic digesters.