Dispersion of motile bacteria in a porous medium

Abstract

Understanding flow and transport of bacteria in porous media is crucial to technologies such as bioremediation, biomineralization and enhanced oil recovery. While physicochemical bacteria filtration is well documented, recent studies showed that bacterial motility plays a key role in the transport process. Flow and transport experiments performed in microfluidic chips containing randomly placed obstacles confirmed that the distributions of non-motile bacteria stays compact, whereas for the motile strains, the distributions are characterized by both significant retention as well as fast downstream motion. For motile bacteria, the detailed microscopic study of individual bacteria trajectories reveals two salient features: (i) the emergence of an active retention process triggered by motility, (ii) enhancement of dispersion due to the exchange between fast flow channels and low flow regions in the vicinity of the solid grains. We propose a physical model based on a continuous time random walk approach. This approach accounts for bacteria dispersion via variable pore-scale flow velocities through a Markov model for equidistant particle speeds. Motility of bacteria is modelled by a two-rate trapping process that accounts for the motion towards and active trapping at the obstacles. This approach captures the forward tails observed for the distribution of bacteria displacements, and quantifies an enhanced hydrodynamic dispersion effect that originates in the combined effect of pore-scale flow variability and bacterial motility. The model reproduces the experimental observations, and predicts bacteria dispersion and transport at the macroscale.

Blind zones in radiating dispersion at high Péclet number driven by non-Newtonian fluids in porous media

“…2021; Dentz et al. 2022), and the flow rate of the solvent does not decay. Figure 2( b ) shows that the solution in a circular porous chip will also find the high-velocity channel with the least flow resistance/drag.…”

“…Overall, the solution will flow along the pores to the exterior. In a rectangular channel with porous media, the solution flow will seek out high-velocity channels and develop low-velocity micropockets (Maggiolo et al 2020;de Anna et al 2021;Dentz et al 2022), and the flow rate of the solvent does not decay. Figure 2(b) shows that the solution in a circular porous chip will also find the high-velocity channel with the least flow resistance/drag.…”

Comparison of Microbial Profiling and Tracer Testing for the Characterization of Injector-Producer Interwell Connectivities

“…Injectate microbes may have been attached to fracture surface sites to which the cell membranes have good affinity [56,58]. Motile microbes, in particular, may be especially prone to filtration because of their higher tendency to diffuse into the immobile water in small cracks/pores and get attached [56,65,66].…”

“…The mean residence time for the C-Dots tracer in this work was several hours (Figure 2e-h), which might be too short for cell survival issues to matter. However, the residence time for the injected microbes can be longer than the inert tracer due to attachment to mineral surfaces or diffusion into smaller cracks [56,58,66]. Furthermore, the continuous input of injectate microbes (i.e., a "step input" as opposed to the "pulse input" of tracer) justifies considering the residence time of injected microbes (especially those potentially retained and accumulated in the aquifer) to be on the order of months.…”

Corner Flows Induced by Surfactant-Producing Bacteria Bacillus subtilis and Pseudomonas fluorescens

“…In most studies, bacterial spreading was attributed to advection and hydrodynamic dispersion ( 7 , 8 ), filtration ( 9 , 10 ), adsorption ( 11 , 12 ), and desorption ( 11 ), as well as bacterial motility ( 12 ). Many empirical studies also show that the addition of surfactants enhances bacterial spreading in porous media ( 13 , 14 ).…”