Study on the effects of non-uniformity of microbial growth on permeability changes in porous media

Based on the assumption that biofilms are impermeable, we investigated the mechanism and law of the influence of microbial growth non-uniformity on the permeability of porous media in the artificial recharge of groundwater. The relationship between the total permeability of porous media and that of cross section was developed and the coupled Lattice Boltzmann Method-Immersed Moving Boundary-Cellular Automata (LBM-IBM-CA) model was used to simulate the non-uniform microbial growth in porous media. Quantitative analysis was conducted on the impact of the grain sparsity of porous media on the non-uniformity of relative porosity changes and permeability decrease caused by microbial growth. The non-uniformity of relative porosity changes was innovatively introduced into the porosity-permeability relationship. The main results are as follows. (1) The nonuniformity of nutrient concentration distribution in porous media is the fundamental reason for the nonuniformity of microbial growth and relative porosity changes. (2) The non-uniformity of relative porosity changes increases with microbial growth for the porous media with smaller grain sparsity. However, the opposite situation occurs for the porous media with larger grain sparsity. (3) In the event of clogging of porous media, the pressure drop caused by biological growth accounts for more than 90 % of the total pressure drop. (4) In the power-law relationship of the porosity-permeability, the index of non-uniformity of relative porosity changes is closely related to the sparsity of the grain at the entrance of porous media.