Application of reactive transport modelling to growth and transport of microorganisms in the capillary fringe

TL;DR

This paper presents a reactive transport model for simulating microbial growth and transport in porous media, validated with laboratory experiments involving E. coli in a Hele-Shaw cell.

Contribution

The development of a flexible, coupled reactive transport simulator specifically optimized for E. coli behavior in the capillary fringe is a novel contribution.

Findings

Model accurately predicts E. coli growth and transport in porous media.

Laboratory experiments confirm the model's ability to replicate fluorescence-based cell density measurements.

Operator splitting approach enhances solution flexibility.

Abstract

A multicomponent multiphase reactive transport simulator has been developed to facilitate the investigation of a large variety of phenomena in porous media including component transport, diffusion, microbiological growth and decay, cell attachment and detachment and phase exchange. The coupled problem is solved using operator splitting. This approach allows a flexible adaptation of the solution strategy to the concrete problem. Moreover, the individual submodels were optimised to be able to describe behaviour of Escherichia coli (HB101 K12 pGLO) in the capillary fringe in the presence or absence of dissolved organic carbon and oxygen under steady-state and flow conditions. Steady-state and flow through experiments in a Hele-Shaw cell, filled with quartz sand, were conducted to study eutrophic bacterial growth and transport in both saturated and unsaturated porous media. As E. coli cells can form the green fluorescent protein (GFP), the cell densities, calculated by evaluation of measured fluorescence intensities (in situ detection) were compared with the cell densities computed by numerical simulation. The comparison showed the laboratory experiments can be well described by our mathematical model.