Pore Network Model for Study of Biofilm Growth Limitations in Porous Substrata

Abstract We present a pore network approach for the simulation and study of biofilm growth inside porous structures under various limiting conditions. The proposed pore-scale model allows us to resolve the interrelationship between growth and diffusive transport based on the solution of coupled ordinary differential equations. Special focus of this study is on diffusion as well as on metabolically limited conditions, which is realized with different second Damköhler numbers. Instead of relying on idealized geometries, the pore network structures are generated using the effective transport properties of thin sintered particles and fibrous felt porous layers derived from high-resolution X-ray micro-CT scans. The great differences in pore sizes and porosities of the regarded structures result in significantly different effective diffusivities. In addition to that, competitive substrate consumption and inhibition is achieved using the experiment-based kinetic model for S. oneidensis from Tang et al. (Tang et al., Biotechnol. Bioeng. 96:125–133, 2007). The primary nutrients are lactate and oxygen. Acetate is both, a by-product and a potential substrate, theoretically enabling dynamic shifts in substrate utilization. With the chosen parameters and conditions, the second Damköhler number can be varied with a significant impact on biomass distribution inside of the two selected pore networks, especially in dependence on oxygen availability in single pores. The simulation results show that biofilm growth is limited by the transport of dissolved oxygen. Interestingly, significantly more biomass per m 3 is produced in the sintered structure because of the generally higher pore utilization degree. Graphical Abstract