A novel approach to investigate biofilm accumulation and bacterial transport in porous matrices

Abstract

Knowledge of bacterial transport through, and biofilm growth in, porous media is vitally important in numerous natural and engineered environments. Despite this, porous media systems are generally oversimplified and the local complexity of cell transport, biofilm formation and the effect of biofilm accumulation on flow patterns is lost. In this study, cells of the sulphate-reducing bacterium, Desulfovibrio sp. EX265, accumulated primarily on the leading faces of obstructions and developed into biofilm, which grew to narrow and block pore throats (at a rate of 12 micro m h(-1) in one instance). This pore blocking corresponded to a decrease in permeability from 9.9 to 4.9 Darcy. Biofilm processes were observed in detail and quantitative data were used to describe the rate of biofilm accumulation temporally and spatially. Accumulation in the inlet zone of the micromodel was 10% higher than in the outlet zone and a mean biofilm height of 28.4 micro m was measured in a micromodel with an average pore height of 34.9 microm. Backflow (flow reversal) of fluid was implemented on micromodels blocked with biofilm growth. Although biofilm surface area cover did immediately decrease (approximately 5%), the biofilm quickly re-established and permeability was not significantly affected (9.4 Darcy). These results demonstrate that the glass micromodel used here is an effective tool for in situ analysis and quantification of bacteria in porous media.

Optically Transparent Porous Medium for Nondestructive Studies of Microbial Biofilm Architecture and Transport Dynamics

“…Second, hydrodynamic effects can be altered by the presence of the adjacent wall material, commonly represented by a glass coverslip. So-called glass micromodels (15,36,51) comprising hand-drawn templates etched into glass slides are convenient in that they are amenable to conventional transmitted light microscopy. Unfortunately, these systems are not analogous to conventional column experiments.…”

NETmix®, a new type of static mixer: Experimental characterization and model validation

“…Willingham et al 8 used the same techniques to study the effects of the porous media structure and compare the experimental results and numerical predictions for a micromodel made by etching and with a variety of different structures. Other works used micromodels and direct visualization to study other phenomena in porous media, including the movement and dissolution of nonaqueous pollutants in porous media, 9-12 evolution of biomass development and propagation in a porous medium, [13][14][15] twophase flow, 16 bubble growth in porous media, 17 and the comparison between Newtonian and non-Newtonian flow. 18 Zerai et al 19 have used particle image velocimetry (PIV) to visualize the fluid flow in a chamber of a network with a geometrical structure similar to the NETmix V R model, but no attempt to study the influence of the flow conditions and geometrical characteristics is included.…”

Retention of a model pathogen in a porous media biofilm

“…These investigations describe dynamic channel formation (Sharp et al, 2005), reduced porosity (Dunsmore et al, 2004;Tiwari & Bowers, 2004), reduced permeability (Tiwari & Bowers, 2004), and increased friction factors (Cunningham et al, 1991). A similar investigation which aimed at describing flow in biofilm-colonized porous media observed increased dispersion and accelerated breakthrough of a non-reactive tracer (Sharp et al, 1999).…”