Modeling biofilms on gas-permeable supports: Concentration and activity profiles

Several investigators have shown that membrane oxygenation provides a number of advantages in biological treatment. These include operational flexibility, reduced energy requirements, and less stripping of volatile compounds. Membranes have also been observed to provide a support surface for microbial growth. This steady-state model study investigates the microbial uptake of oxygen and a carbon-source substrate for aerobic, heterotrophic biofilms on gas permeable membrane- and impermeable solid-supported surfaces. The model predictions indicate that very different concentration and activity profiles may be found in biofilms grown on solid surfaces and gas permeable membranes. For a solid-supported biofilm the highest concentrations of oxygen and substrate and the greatest microbial activity are located on the outside of the biofilm. For a membrane-supported film, the oxygen and substrate are never present at the same location in their maximum concentrations, and the location of maximum biological activity in the biofilm can occur at other locations within the film. These differences may lead to significant differences in the microbial ecology and populations of biofilms and, in turn, in biofilm morphology.