Biofilm development in a membrane-aerated biofilm reactor: effect of intra-membrane oxygen pressure on performance

The effect on intra-membrane oxygen pressure at a constant carbon substrate loading rate on the development of biofilms of Vibrio natrigens in a membr ane aerated biofilm reactor (MABR) was investigated experimentally and by m athematical modelling. A recently reported technique (Zhang et al., 1998. B iotechnol. Bioeng. 59: 80-89) for the in situ measurement of the substrate diffusion coefficients in a growing biofilm and the mass transfer coefficie nts in the boundary layer at the biofilm liquid interface was used. This ai ded the study of the effect of the heterogeneous biofilm structure and also improved the reliability of the model predictions. The different intramemb rane oxygen pressures used. 12.5, 25 and 50 kPa, with acetate as the carbon substrate. showed a marked effect on the initial biofilm growth rate, on a cetate removal rate, particularly in thick biofilms and on biofilm structur e. The model predicted the substrate limitation regimes, the location of th e active biomass layer within the biofilms and the trends in oxygen uptake rate through the membrane into the biofilms. During the development of the biofilms, the biofilm thickness and the intra-membrane oxygen pressure were found to be the most important parameters influencing the MABR performance while the effect of biofilm structure was less marked.