Impact of biofilm permeability field on flow and transport in three-dimensional porous media: A stochastic study

Bacterial biofilms can form in porous media that are of interest in industrial and particularly environmental applications such as in-situ groundwater remediation. The presence of biofilms modifies pore-scale and bulk hydrodynamics and consequently solutes transport and reaction kinetics. The interplay between the highly heterogeneous flow fields found in porous media and microbial behavior, including biofilm growth, results in highly spatially variable biofilm location and biofilm permeabilities. Random processes are often invoked in porous media (e.g., in subsurface processes) to model variable quantities. Likewise, geostatistical simulations are used to generate multiple, equally probable representations of the spatial distribution of the attribute under study. Our study leverages highly resolved three-dimensional X-ray computed microtomography images of bacterial biofilms in a tubular reactor to numerically compute pore-scale fluid flow and solute transport on a fine grid by considering various realizations of the biofilm permeability field. Comparing with a conservative tracer experiment, we first demonstrate the validity of our flow and transport model. We then show the impact of the biofilm heterogeneous permeability on the fluid flow velocity field and probability distribution. This is further used to understand the impact of the biofilm-porous media heterogeneous permeability field on fluid-fluid mixing and biologically driven reactions.