Characteristics of the community-structure of A2O processes under different dissolved oxygen conditions in plateau areas

This study conducted a Pilot-Scale Anaerobic-Anoxic-Aerobic Process (A2O) experiment in a highland city of Linzhi. Four Dissolved oxygen (DO) working conditions of 2.0 mg/L, 1.5 mg/L, 1.0 mg/L and 0.5 mg/L were designed in this experiment. The 16SrRNA gene sequencing was performed on sludge from the anaerobic, anoxic and aerobic tanks. Through the composition analysis of sludge on Phylum level, Class level, Order level, Family level, Genus level and Species level, it can be found that the number of bacterial community at each level of the bacterial community was relatively low. The indicators of community richness, community evenness and community diversity were relatively low compared to other regions. The bacterial communities at different levels are significantly different from the reported dominant community and abundances. Correlation analysis between environmental factors and bacterial community structure proved that DO had significant correlation with bacterial community structure (P<0.05). The removal rates of the total phosphorous (TP), total nitrogen (TN), Ammonia nitrogen (NH3-N) and Chemical Oxygen Demand (COD) were all affected by the sample communities structure. The composition of the bacterial community structure included nitrifying bacteria, denitrifying bacteria and polyphosphate-accumulating organisms, but the abundances were relatively low. The results also showed that the dominant community in different DO conditions and different reactors have large differences.