CFD Modeling of Immobilized Phenol Biodegradation in Three-Phase Airlift Loop Reactor

A 3D transient CFD model was developed to simulate the dynamic behaviors of batch phenol biodegradation by immobilized Candida tropicalis in a gas-liquid-solid three-phase airlift loop reactor (ALR), coupling of three-phase fluid flow, species interphase mass transfer, and intrinsic bioreaction, with the bubble size distribution (BSD) determined by the multiple size group (MUSIG) model. Simulation of the time courses of the volume-averaged species mass concentrations in the riser and downcomer of the ALR was performed, whereas the phenol and oxygen concentrations in the liquid phase were validated by corresponding experiments. Source-term comparisons between species interphase mass transfer and bioreaction were done to distinguish the rate-limiting step in the process. Moreover, local transient phenol biodegradation characteristics such as oxygen concentration profiles in the gas, liquid, and solid phases; phenol concentration profiles in the liquid and solid phases; and cell concentration profiles in the solid phase were all predicted reasonably well. Furthermore, the performances of the ALR and a bubble column reactor (BCR) were compared, and the advantage of the former reactor was confirmed.