Modeling the impact of evolving biofilms on flow in porous media inside a microfluidic channel

This study integrates microfluidic experiments and mathematical modeling to study the impacts of biofilms on flow in porous media and to explore approaches to simplify modeling permeability with complicated biofilm geometries. E. coli biofilms were grown in a microfluidic channel packed with a single layer of glass beads to reach three biofilm levels: low, intermediate, and high, with biofilm ratios (β_r) of 2.7%, 17.6%, and 55.2%, respectively. Two-dimensional biofilm structures and distributions in the porous medium were modeled by digitizing confocal images and considering broad ranges of biofilm permeability (k_b) (from 10^-15 m² to 10^-7 m²) and biofilm porosity (ε_b) (from 0.2 to 0.8). The overall permeability of the porous medium (k), the flow pathways and the overall/local pressure gradients were found to be highly dependent on β_r and k_b but were moderately impacted by ε_b when the biofilm levels were high and intermediate with k_b>10^-11 m². When biofilm structures are well developed, simplified biofilm geometries, such as uniform coating and symmetric contact filling, can provide reasonable approximations of k.