Illumina sequencing reveals bacterial community shift and its role in a full-scale A2O sewage treatment process at low temperatures

Activated sludge and sewage were sampled from the municipal sewage treatment plant of Lanzhou (Northwest China) between November 2014 and January 2015 to investigate bacterial community composition and shift across the full-scale anaerobic-anoxic-oxic (A(2)O) process at low temperatures (<= 12 degrees C) using Illumina MiSeq sequencing. Operational taxonomic unit analysis showed that bacterial community richness changed greatly throughout the A(2)O process but the bacterial community diversity had no significant difference during the A(2)O process. Bacterial community composition was similar between different tanks at the phylum level, although the percentage of dominant phylum had changed significantly. However, at the genus level, the bacterial community composition varied widely across the A(2)O tanks. Redundancy analysis (RDA) and hierarchical cluster analysis demonstrated that the bacterial community shifts between different tanks were related to process-based operational conditions and environmental changes, including dissolved oxygen, NH4+, bichromate chemical oxygen demand, and total phosphorus concentration. RDA also revealed that nitrogen and phosphorus removal mainly occurred in the anaerobic, anoxic, and oxic tanks and that the efficiency of nutrient removal correlated with bacterial community composition, abundance, and environmental variables, respectively. The results of this study may contribute to an understanding of microbial ecology in wastewater treatment systems of high taxonomic rank and explore the environmental parameters which are involved in the selection of the different bacterial taxa at low temperatures.