BACKGROUND: In order to rationalize the optimization of biofilm reactor design and operation in waste gas treatment, it is essential to understand the mass transfer properties in biofilms. In this study, oxygen transport within the biofilms of a membrane biofilm reactor (MBfR) was characterized at different liquid flow velocities. Further, oxygen concentration distributions along the depth of the biofilms were investigated under different operating conditions (different oxygen supply modes, and various toluene loading rates) by using oxygen microelectrodes.
RESULTS: Oxygen fluxes into the biofilm ranged between 0.15 and 0.4 g m h−1 at different liquid velocities of 0 to 0.06 m s−1 operated at a toluene loading rate of 0.08 g m h−1 and a gas residence time of 24 s. In addition, toluene elimination capacities (ECs) obtained in this research ranged from 75 to 550 g m h−1 (0.15 to 1.1 g m h−1) at loading rates (LRs) of 87.5 to 625 g m h−1 (0.17 to 1.25 g m h−1).
CONCLUSIONS: Microelectrode measurements reveal that the liquid flow influences the oxygen transport (reduction of the concentration boundary layer thickness) into the biofilm and plays a major role in controlling the flux of oxygen across the biofilm-water interface, thus increasing the potential for aerobic biodegradation. A maximum oxygen flux of 0.4 g m h−1 was obtained at a linear liquid velocity of 0.06 m s−1. Results provide a possibility to enhance the toluene removal rate with the oxygen supply mode and may lead to rational strategies. Copyright © 2012 Society of Chemical Industry