Dispersion of motile bacteria in a porous medium

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