Changes in microbial communities in a hybrid anaerobic reactor with organic loading rate and temperature.

Poor understanding of the response of microbial communities to sudden changes in organic and hydraulic loads is one of the major reasons for the inability to prevent operational instabilities in anaerobic reactors. Effect of changes in hydraulic retention time (HRT) and organic loading rate (OLR) on reactor performance and its anaerobic microbial community were investigated in two anaerobic hybrid reactors operated at 37 and 55 °C. HRT was reduced stepwise, while OLR was increased along with influent chemical oxygen demand at fixed HRT until the performance of reactor deteriorated. The profile of archaeal 16S rRNA gene amplicons, resolved by denaturing gradient gel electrophoresis, reflected system status during disturbances. The more diverse archaeal community in the reactor operated at 37 °C showed better performance than the communities present at 55 °C at higher OLR and shorter HRT, suggesting that higher diversity is indicative of more stable operation of reactors despite organic and hydraulic shocks.