Pore-scale Hydrodynamics During Biofilm Development in Porous Media: Temporal Evolution and the Effect of Biofilm Properties

Abstract:

Keywords: Pore-scale hydrodynamics, Biofilm development, Velocity distribution, Mean squared displacement, Numerical flow and transport modeling

Biofilm development alters the pore structure and consequently affects the hydrodynamics in porous media. This study aims to understand how flow dynamics and mass transport are affected by i) the influence of biofilm growth scheme and ii) the permeability and porosity of the biofilm. We coupled pore-scale numerical simulations with particle tracking in 2D granular media to evaluate the velocity distribution, mean square displacement, and breakthrough curve in each sample undergoing bioclogging. Models of four biofilm growth schemes—no decay, kinetic decay, degradation, and growth with mechanical detachment—were simulated for 350 hours and used to study the temporal evolution of velocity distribution (Bottero et al., 2013). We find that velocity distributions are described by an exponential function that does not differ significantly between growth schemes. In addition, these distributions evolve only in the first 50 hours, reaching an equilibrium thereafter despite the intermittently shifting location of preferential flow paths. Models that consider the permeability and porosity of biofilms were used to investigate spreading (Karimifard et al., 2020). We find that velocities in these models are gamma distributed, in agreement with published empirical studies, and that biofilm permeability has the single greatest impact on non-Fickian spreading. As a next step, we will upscale the measured pore-scale stochastic particle dynamics to predict anomalous transport behavior at the macro scale with Continuous Time Random Walk theory.