Characteristics of the community-structure of A2O processes under different dissolved oxygen conditions in plateau areas
Description
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.
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A2O system is selected as a typical sewage treatment process in the study, the microbial characteristics were used as the research content to explore the influence of colonies structure under DO working conditions on plateau environmental factors, and to explore the microbial characteristics of A2O process under the Pilot Scale of DO working conditions under plateau environmental factors. Experimental setup A Pilot-Scale A2O was designed and produced in this research, with an effective volume of 210L, which could be divided into 3 grids, namely, anaerobic tank, anoxic tank, and aerobic tank (volume ratio of 35:58:117), and the effective volume of sedimentation tank was 39L. There were stirring devices at the bottom of both anaerobic tank and anoxic tank, with the stirring speed of 50rpm, and the aerator was installed at the bottom of aerobic tank for oxygen supply. The peristaltic pump was used to control water inflow, sludge and nitrated liquid reflux. In order to ensure the constant temperature in the experiment, constant temperature circulators were used to control the water temperature. Additionally, the sampling place was set on each tank wall. Before the experiment, the activated sludge was cultured for 37 days, with the temperature controlled at 20.0℃. Sludge settling ratio (SV30) is 35% and mixed liquor suspended solids (MLSS) is 4557mg/L. The test water was directly urban sewage of Nyingchi City. The basic control conditions were as follows: mixed liquid reflux ratio(Ri)=200%, sludge reflux ratio(R)=100%; continuous reflux was used in influent and mixed sludge; there are two aeration heads at the bottom of the aeration tank, and the change of DO was achieved by changing the air blowing aeration quantity, and the water quality sampling would be made 72h after the dissolved oxygen reached the design value, and the online DO detector is used to read the data. Designed influent flow is 10.0±0.1L/h, and hydraulic retention time(HRT) is 21.0±0.2h, and temperature is controlled at 20℃ in the aerobic tank, and dissolved oxygen is controlled at 2.0mg/L, 1.5mg /L, 1.0mg /L, 0.5mg /L in the aerobic tank.