Transport of bacteria, viruses and a visual tracer in a saturated 2-dimensional porous media model

This study was designed to provide insight into microbial transport kinetics which might be applied to bioremediation technology development and prevention of groundwater susceptibility to pathogen contamination. Several pilot-scale experiments were conducted in a saturated, 2 dimensional, packed porous media tank to investigate the transport of Escherichia coli bacteria, P22 bacteriophage, and a visual tracer and draw comparisons and/or conclusions. A constructed tank was packed with an approximate 3,700 cubic inches (in3) of a fine grained, homogeneous, chemically inert sand which allowed for a controlled system. Sampling ports were located at 5, 15, 25, and 25 vertical inches from the base of the 39 inch saturated zone and were used to assess the transport of the selected microorganisms. Approximately 105 cells of E. coli or P22 were injected into the tank and allowed to move through the media at approximately 10.02 inches per day. Samples were collected intermittently after injection based off of an estimated sampling schedule established from the visual tracer.

The results suggest that bacteriophages pass through soil faster and with greater recovery than bacteria. P22 in the tank reservoir experienced approximately 1 log reduction after 36 hours. After 85 hours, P22 was still detected in the reservoir after experiencing a 2 log reduction from the start of the experiment. E. coli either did not reach the outlet or died before sampling, while P22 was able to be recovered. Bacterial breakthrough curves were produced for the microbial indicators and illustrate the peak concentrations found for each sampling port. For E. coli, concentrations at the 5 inch port peaked at a maximum of 5170 CFU/mL, and eventually at the 25 inch port at a maximum of 90 CFU/mL. It is presumed that E. coli might have experienced significant filtration, straining and attachment, while P22 might have experienced little adsorption and instead was transported rapidly in long distances and was able to survive for the duration of the experiment.