Gas–solid packed and fluidized bed models for bioremediation of volatile organic compounds in air

A steady state, one-dimensional model is developed to describe biodegradation of a volatile organic compound (VOC) in a gas–solid fluidized bioreactor. For comparison purposes, biodegradation in a packed bed bioreactor is also modelled. The models are used to predict outlet concentrations of a VOC substrate (ethanol) and the estimates are compared to experimental data. The fluidized bioreactor model includes properties of the bubbles such as rise velocity, bubble size and gas exchange rate with the emulsion phase surrounding the bubbles. The overall rate of biodegradation is modelled with the two limiting cases of zero and first order kinetics with respect to the substrate, which depend on whether the overall resistance is limited by microbial growth or mass transport. The models highlight how maximum elimination capacity and removal efficiency are influenced by bubble properties, residence time, maximum specific growth rate of the microorganisms, and microbial population.