CFD modelling of phenol biodegradation by immobilized Candida tropicalis in a gas–liquid–solid three-phase bubble column

A three-dimensional transient model, combining three-phase fluid flow, interphase mass transfer and intrinsic bioreaction kinetics, was developed to simulate the dynamic behaviors of batch phenol biodegradation by immobilized Candida tropicalis in a gas–liquid–solid three-phase bubble column (BC). A computational fluid dynamics (CFD) method was used, with a multiple size group model adopted to determine the bubble size distribution, based on a previous three-phase BC hydrodynamic CFD model [1]. Current simulation results of phenol and oxygen concentration changes in the liquid phase were validated by corresponding experimental measurements under various operating conditions. Furthermore, local transient batch phenol biodegradation characteristics such as the oxygen concentration profiles in the gas, liquid and solid phases, the phenol concentration profiles in the liquid and solid phases, and the cell concentration profile in the solid phase were predicted. Comparisons between species interphase mass transfer and bioreaction rates were carried out to identify the rate-limiting step in the immobilized batch phenol biodegradation processes.