Multiscale Model for Assessing Effect of Bacterial Growth on Intrinsic Permeability of Soil: Model Description

A multiscale model is proposed for assessing the impact of bacterial growth attached to soil particles on intrinsic permeability of soil. The model combines two modules. One of the modules solves the equations describing multiphase reaction-diffusion-transport model at the macroscopic [Representative Elementary Volume (REV)] scale, augmented with an equation for attached biomass growth. This module is used as an upscaling environment. The other module in the coupling set is a cellular automaton (CA) model for bacterial growth attached to soil particles. The coupling is achieved by having the CA module model bacterial growth at the pore level and integrating the result to provide information at the REV level. The details of the two modules, the links between them and an algorithm for simulation using the coupled model are described. The two modules are designed to work alternately till the end of a simulation period. The continuum module (reaction-diffusion-transport augmented with attached biomass growth equation) calculates the change in attached biomass. This is followed by the determination of a change in the states of cells in the CA module. Any change in the states necessitates a recalculation of permeability values to be used for the next time step of the continuum module. A companion paper gives results on using this coupled model to simulate a column experiment.