Research progress of numerical model of secondary sedimentation tank in sewage treatment plant

Numerical model simulation has irreplaceable advantages in the design, operation, and optimization of the secondary sedimentation tank of the sewage treatment plant. It is very important to summarize existing numerical models for the selection and establishment of models in practical applications. The principles of multiphase models such as Euler-Lagrange model, Euler-Euler model, and Mixture model for numerical simulation of secondary sedimentation tank were introduced. The applicability of each model was described, the advantages and disadvantages of each model put forward, and the application principles of the single-phase model in sludge sedimentation explained. The single-phase model described the movement law of sludge sedimentation by coupling a single solid-phase transport equation, which was better than multiphase model in predicting the distribution of sludge mass concentration in the secondary sedimentation tank. The research status of the sludge sedimentation velocity model was discussed, including the model of intermittent sludge settlement using batch settlement test and the model of continuous flow sludge settlement describing the secondary sedimentation tank of the sewage treatment plant. The influence of sludge load, geometry structure, and temperature on water quality simulation of the secondary sedimentation tank was systematically reviewed. Finally, the selection of mathematical models for secondary sedimentation tank of the sewage treatment plant and future research on sedimentation models were prospected, to provide a theoretical basis and technical reference for the operation and design optimization of the secondary sedimentation tank of the sewage treatment plant.