Microbial communities and interactions in full-scale A2/O and MBR wastewater treatment plants

Microorganisms are key to stable system operation and efficient pollutant removal in wastewater treatment plants (WWTPs), whereas the critical information on their seasonal variations is still lacking. Impacts of process types and seasonal variations on microbial communities, metabolisms, and interactions were examined in the anaerobic/anoxic/aerobic (A2/O) and membrane bioreactor (MBR) WWTPs. Environmental factors had a greater impact on pollutant removal than process types. Dissolved oxygen concentration and pH were crucial environmental factors that could simultaneously affect nitrogen metabolism and microbial interactions. Bacteroidetes, Proteobacteria, and Chloroflexi were the dominant phyla. Quorum sensing (QS) systems were detected in these WWTPs, and the N-acyl homoserine lactones QS system was the key pathway responsible for microbial interactions. The obtained microbial information in the full-scale A2/O-WWTP and MBR-WWTP and the potential correlations between microorganisms and environmental factors could provide valuable clues for system optimization.