Simulation of composition and mass transfer behaviour of a membrane biofilm reactor using a two dimensional multi-species counter-diffusion model

The main objective of this paper is to study the growth and transport mechanisms of biofilms in Membrane Biofilm Reactors (MBfRs). A mathematical model incorporating biofilm characteristics is used to simulate the biofilm response and nitrification process to variations in the initial inoculation of biofilm and environmental conditions (in particular, to change in the concentration of substrates and temperature). The model is a highly nonlinear reaction-diffusion system with cross-diffusion that can describe the development of biofilm layers under the effects of counter-diffusion. The simulation results suggest the importance of multi-dimensional modeling to capture the heterogeneity in the biofilm structure. Furthermore, the results indicate that the initial composition and arrangement of biofilm colonies do not significantly affect membrane performance. In contrast, substrate concentrations do have a notable effect on the substrate transport fluxes and nitrification capacity of biofilms.