3D modelling of bioelectrochemical systems with brush anodes under fed-batch and flow conditions

A 3D mathematical model of the different processes occurring in a bioelectrochemical system (BES) equipped with carbon fibres brush anodes has been implemented. The model combines equations of electrical charge conservation, with hydrodynamics, convection, diffusion and kinetics of the involved processes, such as biofilm formation, bioelectrochemical and electrochemical reactions. The model has been solved for different scenarios. A system with a single BES cell was simulated under fed-batch and flow conditions, as three cells hydraulically connected in-series have been also considered. Model parameters were derived from the literature or from experimental data obtained with replicate of a single-chamber BES under different conditions. The model solution provides space profiles of potential and current, concentration of substrate and protons and biofilm under transient conditions. Velocity profiles may also be calculated with simulations under flow conditions. The effects of operative conditions on the performance of the process, both for current generation and substrate removal, have been quantified. The model provides a versatile tool to design and optimise BES reactors with fibre brush anodes.