Impact of agitation and non-agitation on microbiota and reactor performance in anaerobic digestion

Optimizing process conditions in anaerobic digestion could enhance the utilization of organic matter for renewable energy generation. Thus, initial upset substrates with elevated volatile fatty acids were investigated under agitation and non-agitation conditions for optimal bioreactor performance. There were two continuous agitation scenarios for the liquid-state (40 and 100 rpm) with a non-agitated scenario. Similarly, a non-agitated and 40 rpm scenario for the solid-state. The result indicated that the non-agitated liquid-state reactor had the highest methane yield (193 L/kgVS) and lowest retention (51 days) despite delayed microbial adaptation. Of the prominent microbes, the relative abundance of Firmicutes and Archaea_unclassified negatively correlated with VFA at 100 rpm. Contrarily at 40 rpm, Firmicutes correlated positively with VFA, an indication that Firmicutes could withstand acid production at agitation speed ≤40 rpm suggesting that agitation associated with VFA might reduce microbial diversity in an initial upset liquid-state bioreactor. Thus, upset influent could be utilized for energy generation with a non-agitated liquid-state bioreactor.