Hydrodynamic effect of dispersed phase fraction on the mass transfer and uptake rate of hexadecane by an oil-degrading microbial consortium in an airlift bioreactor

Abstract

An investigation was made into the hydrodynamics related to mass transfer of the oil and gaseous phase in an airlift reactor (ALR), using a high dispersed phase fraction (φ=0.1) for biodegradation purposes, in a simulated biotic medium. The highest Reynolds differences (3400<Re<5400) and low liquid velocity differences between the aqueous and oil phase (0.02–0.05ms−1) were obtained in the riser at assayed superficial gas velocity (Ug). The hexadecane (HXD) specific mass transfer area was increased due to the presence of a greater HXD volume, which enhanced the volumetric hexadecane gas-liquid mass transfer coefficient (kLaHXD) compared to other works at φ<0.1. Thus, high HXD transfer rates were obtained through a 14-day batch culture. Conversely, the high φ value promoted a volumetric oxygen gas-liquid mass transfer coefficient (kLaO2) enhancement. The oxygen transfer rates were improved because of an increase in the oxygen saturation concentration. The maximum uptake rates obtained were 3.44–7.74g HXD L−1h−1. The increase in Ug with a high φ value, led to a positive effect that improved the mass transfer of HXD and oxygen, allowing high HXD uptake rates.