A simplified mixed-culture biofilm model

A simple dynamic model is presented for fast simulation of the removal of multiple substrates by different bacterial species growing in a biofilm reactor. The model is an extension to the well-known half-order reaction concept that combines a zero-order kinetic dependency on substrate concentration with diffusion limitation. The basic idea behind this model implementation is to decouple the calculations of the two major processes in the biofilm: substrate diffusion and biochemical conversion. The separate assessment of substrate diffusion allows to relate the penetration depth of substrates to a fraction of biomass that is active in conversion. The conversion is then calculated considering only the active fraction of the biomass. The model is compared to experimental data from the literature and is found to be able to closely replicate the overall dynamics in a biofilm system. The major advantage of the proposed model is the simple structure which leads to a reduction of the computational effort as compared to state-of-the-art mixed-culture biofilm models.