Background: In this study, laboratory-scale A2O wastewater treatment was performed in Linzhi at an altitude of 3000 meters. Water temperatures were maintained at four operating conditions (25°C, 20°C, 15°C, and 10°C). Sludge in the aerobic tank was assessed by 16SrRNA sequencing and composition analysis. The Phylum, Class, Order, Family, Genus, and Species of the sludge were also confirmed.Results: The bacteria within the sludge showed significant differences at varying temperatures (P<0.05). A significant correlation between the bacteria numbers in anaerobic tanks and anoxic tanks also occurred. Indicators of community richness, community uniformity, community diversity and other areas showed differences. Significant differences in bacteria abundance were also observed and differed to those of previously reported superior community categories and proportions. T-tests were used to identify temperature-sensitive community at each level. Correlation analysis of environmental factors and colony structure further confirmed the association between temperature and colony structure (P<0.05). The removal rates of TP, TN, NH3-N, and COD were all affected by the sample community structure. The variety of colony structure include nitrifying bacteria, denitrifying bacteria, phosphorus accumulating bacteria and other bacterial differed, but their proportions were relatively low. Heatmaps were used to identify species sensitive to temperature, TP, TN, NH3-N, COD at the species level.Conclusions: Amongst the common dominant bacteria at the species level, Bacteroidetes_bacterium_OLB10 was significantly related to temperature. Other common dominant bacteria that were related to temperature metagenome_g__Gordonia, unclassified_f__Burkholderiaceae, uncultured_bacterium_g__norank_f__Saprospiraceae.

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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, 1.5, 1.0, and 0.5 mg/L was 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, Class and Genus level, it can be found that the number of bacterial community at each level of the bacterial community was relatively low. 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 abundance. 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 abundance was relatively low. The results also showed that the dominant community in different DO conditions and different reactors has large differences.

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