Escherichia coli transport in porous media: Influence of cell strain, solution chemistry, and temperature

Packed bed column and complementary characterization experiments were carried out with two Escherichia coli strains (D21g and XL1-Blue) under a range of ionic strength (IS) and valence (KCl, CaCl2, and artificial groundwater) to determine the role of bacterial strain and solution chemistry on cell adhesion. Increasing IS and valence had a marked effect on the electrokinetic and surface properties of bacteria and quartz grains; hence resulting in a greater rate of deposition. Distinct deposition trends were observed for the two cell strains, with greater retention observed for D21g versus XL1-Blue across the range of IS. Selected transport and characterization experiments were also conducted with the D21g cells, finding deposition also increasing with IS and valence. In the presence of Ca2+ bacterial deposition behavior deviated from anticipated trends and it is concluded from additional analysis that Ca2+ ions influence bacterial surface charge, hydrophobicity, and extracellular polymers. Further transport experiments were conducted with the D21g cells and colloids to establish the role of temperature (4, 10 and 25 °C). Results suggested that a combination of specific and non-specific interactions occurring between the cells and quartz determines the extent of deposition, rather than transport from the bulk to the collector surface.