A microfluidic approach to investigate the effects of bacteria deposition in porous media containing randomly packed microbeads via real-time pressure measurement

We present a real-time microfluidic permeability characterization device for quantifying effects of bacterial deposition on permeability of porous media. Here, we demonstrate a microfluidic approach that allows the effect of bacterial deposition on permeability alteration to be quantified via the measurement of pressure difference, coupled with direct visualization of bacterial distribution. Our experiments reveal three main findings. First, we observe the average percent of cell trapped to be 44.8 +/- 9.7%, independent of the average bacterial density at three levels of concentration between 2.05 x 10(7) and 2.85 x 10(8) cells/ml. Second, the deposited bacterial cell count appears to follow an exponential reduction in permeability, where the reduction of permeability approaches a pseudo-steady state when a critical number of bacterial cell deposited is achieved. Last, the experiment discerned that bacterial cells tend to preferentially get deposited in regions with larger voids within the porous medium. A theoretical model is developed to determine the relationship between the spatial distribution of voids in the porous medium and the resultant bacterial cell density distribution. The approach described here shows good potential for better understanding the relationship between the spatial distribution of voids and deposited bacteria. More work can be done to further investigate these interactions, such as strategically designed voids to enhance the deposition of bacterial cells, or quantification of inflow bacterial density required to achieve a desired level of pseudo-steady state permeability reduction under various environmental conditions.