Simulation of liquid-gas flow in full-scale Caroussel oxidation ditch with surface aeration

A model for liquid-gas flow (MLGF), considering the free movement of liquid surface, was built to simulate the wastewater velocity field and gas distribution in a full-scale Caroussel oxidation ditch with surface aeration. It was calibrated and validated by field measurement data, and the calibrated parameters and sections were selected based on both model analysis and numerical computation. The simulated velocities of MLGF were compared to that of a model for wastewater-sludge flow (MWSF). The results show that the free liquid surface considered in MLGF improves the simulated velocity results of upper layer and surface. Moreover, distribution of gas volume fraction (GVF) simulated by MLGF was compared to dissolved oxygen (DO) measured in the oxidation ditch. It is shown that DO distribution is affected by many factors besides GVF distribution.