Solute Mass Exchange Between Water Phase and Biofilm for a Single Pore

C Z Qin,S M Hassanizadeh

doi:10.1007/s11242-015-0513-x

Abstract

Currently, there are no tractable approaches available for modeling non-equilibrium mass exchange of a solute between water phase and biofilm in porous media. The present work contributes to a quantitative description of the mass exchange of a solute over a single pore domain under a wide range of prevailing conditions. First, we developed a semiempirical model for the rate of solute mass exchange between water phase and biofilm. Then, extensive microscale simulations in a single pore were conducted. Results were averaged over a single pore domain, in order to determine a tube-scale kinetic rate coefficient as a function of various transport and biofilm properties. We illustrated the dependencies of the coefficient on a number of variables like Péclet number, Damköhler number, and biofilm volume fraction. Based on those results, we developed empirical formulae for the tube-scale mass exchange coefficient as a function of Damköhler number and biofilm volume fraction. Finally, we verified the proposed mass exchange rate against microscale simulations of solute transport in a long capillary tube. Good match was obtained over a wide range of conditions.

Highlights

In natural environments, bacteria and other microorganisms tend to attach onto soil grain surfaces
We note that following the procedure used in this work, the conductivity of a pore with arbitrary shape of cross section can be numerically fitted as a function of biofilm volume fraction
The present work has contributed to describing the solute mass exchange between water phase and biofilm over a single pore domain

Summary

Introduction

Bacteria and other microorganisms tend to attach onto soil grain surfaces. Attached bacterial cells are often embedded within a self-produced matrix of extracellular polymeric substance (EPS) which protects the cells from environmentally harsh conditions (Taylor and Jaffé 1990a, b; Ebigbo et al 2010, 2012) These cells together with the surrounding EPS are referred to as biofilm (Iltis et al 2011). Biofilm occupies void pore spaces blocking water flow, which reduces hydrodynamic properties of porous media like porosity and permeability. This leads to a condition known as bioclogging (see Baveye et al 1998). Over the past several decades, the features of bioclogging and biodegradation in porous media with biofilm have given rise to a broad range of applications, such as bioremediation, biobarriers (Baveye et al 1998; Cunningham et al 1991; Mitchell et al 2009), microbial enhanced oil recovery (Afrapoli et al 2011), and protection of steel corrosion (Videla and Herrera 2009; Zuo 2007)

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Results

Conclusion