APPLICATION OF CLEAN-BED FILTRATION THEORY TO BACTERIAL DEPOSITION IN POROUS-MEDIA

The objective of this work was to test the use of filtration theory to describe the deposition of bacterial cells in porous media. Suspensions of Pseudomonas aeruginosa were applied to a column packed with glass beads, and effluent cell concentrations were monitored. Experiments were conducted with cells suspended in 10(-2) and 10(-4) M NaCl, conditions which alter the collision efficiency (probability of cell attachment) of bacteria with the surface. At 10(-4) M NaCl, breakthrough of bacteria was complete and similar to that of a fluorescein tracer. In contrast, the effluent concentration attained only about 78% of the influent value at 10(-2) M NaCl. The greater removal observed at the higher salt concentration was consistent with the hypothesis that interaction of similarly charged diffuse layers can impede the deposition of bacteria. The removal of cells was modeled by combining theoretical calculation of particle transport and empirical estimates of collision efficiencies obtained independently in rotating-disk experiments. The extent of agreement obtained between observed and predicted values suggests that mechanistic models of particle transport can be successfully applied to bacteria. Applications of this work include the movement of bacterial contaminants in groundwater and in situ biological remediation of contaminated aquifers.