Effect of HRT on Characteristics of Microorganisms in Anaerobic Membrane Bio-reactor

Two anaerobic membrane bioreactors (AnMBRs) (20 L volume, equipped with different membrane pore size (0.4 or 0.05 µm)) were operated at 25°C and fed with domestic wastewater. Hydroulic retention time (HRT) of the reactors were shortened as long as the treatment performance was maintained. Microbial communities of two AnMBR were investigated by 16S rRNA gene amplicon sequencing to see the effects of HRT. Methanosaeta was the most predominant group of methanogens, and the composition of hydrogenotrophic methanogens were changed as HRT decreased. Anaerolineae, Bacteroidia and Clostridia were predominant in both two reactors for their relative abundance were over 55% and Anaerolineae showed its strong connection with the biogas production performance. The population change of hydrogenotrophic methanogens or Anaerolineae can be used as an indicator for process monitoring. Principal coordination analysis revealed that the changes in microbial community in each reactor were consistent with the change of HRT. In addition, we found that not only the HRT, but also the stability of the process is also an important factor for maintaining microbial community structures when microbial community structures in two reactors were compared.