Optimization simulation of the synergistic effect of the impellers and aerator in the Oxidation Ditch

• The synergy of impellers and aeration affected the hydraulic behavior of the oxidation ditch. • 2.The overall average velocity of sewage under impellers-aeration synergistic condition increased by 32%. • 3.New impellers-aeration synergistic strategy reduces the low-velocity zone of bottom to 12.8%, and the flow is more uniform. The synergistic operation of impellers and aeration in oxidation ditch was crucial for the efficiency of wastewater treatment. This study employed a gas-liquid two-phase flow model for micro- aeration oxidation ditch, and simulated conditions with both single impeller and the synergistic operation of impellers and aeration. The focus was on analyzing the flow characteristics within the aeration zone. The simulation results indicated the formation of a vertical vortex structure in the aeration zone. Compared to the operation with a single impeller, the synergistic operation significantly enhanced overall flow performance—average flow velocity increased by 32%, the area of low-velocity zones at the channel bottom decreased by 29%, and mixing efficiency improved. These findings suggested that the synergistic effect mainly originated from changes in the flow patterns within the aeration zone. To further optimize the synergistic effects, the study adjusted the horizontal position of the impellers. The results demonstrated that when the horizontal spacing was 11.76 m, the hydraulic characteristics achieved an optimal state— cross-sectional flow was more uniform (exhibiting the minimum inhomogeneity coefficient), the area of low-velocity zones at the channel bottom was minimized, and the average flow velocity reached its peak.