A novel theoretical model for predicting volumetric mass transfer coefficients in bubble aeration systems

Developing theoretical models for the volumetric mass transfer coefficient (kLa) is essential for optimizing airflow rates in wastewater treatment plants. This optimization is complicated by multiple interdependent parameters that collectively govern the mass transfer efficiency. Here, a theoretical model for the liquid-film mass transfer coefficient is derived based on classical fluid mechanics principles, and the specific interfacial area is modeled by simplifying the force analysis during bubble rising. The novel theoretical model for kLa is then constructed by integrating these two models. Four case studies were conducted using field-based monitoring data from previous studies and a re-aeration experiment to evaluate the accuracy of the proposed models under various scenarios. The results show that the relative errors are within acceptable ranges, indicating that the proposed model can accurately predict key parameters of the oxygen mass transfer process. This reduces the reliance on costly monitoring equipment. Furthermore, the theoretical models effectively decouple the complex interrelationships governing oxygen mass transfer.