Microbial Transport Under River Bank Filtration Conditions

Pilot-scale systems offer the ability to monitor pathogen and surrogate transport in alluvial aquifers at high resolution in the aqueous and stationary phases under a variety of controlled conditions. The objective to have a better understanding of microbial transport in alluvial aquifers. This effort was supported by an intensive microbial monitoring under varies physical and chemical conditions.

Columns were constructed out of 4 inch clear acrylic thin-walled PVC pipe and were packed with Ohio river sand of mean size 245 micron. All the columns were spiked with MS2, PRD1, E. coli and Diatoms. The columns in the last experiment were spiked with Cryptosporidium and Giardia cysts in addition to the other indicators.

Microbial transport at low flow column was assessed by comparing the peak concentration of each indicator at consecutive ports through the column. The transport of MS2, PRD1 and E.coli through the baseline low flow column mainly happened at the top portion of the column and the concentration of all microbes decrease as measured at the lower sampling ports. E. coli had the highest retention in the first 5 CM of the column which may be due to the bigger size of the E. coli versus Bacteriophages. In addition, the microorganisms were collected at the effluent of the low flow baseline column and high flow challenge conditions. All of the indicators demonstrated a higher retention in the low flow column and were transported to a higher extent under high flow condition.

E. coli retention in baseline column versus high flow conditions and bed removal (scouring) were measured. E. coli and PRD1 had a significantly lower retention in the high flow and bed removal conditions. Under acclimated versus non-acclimated (fresh media) columns MS2, PRD1 and E.coli retention were measured. All the microbes demonstrated a higher retention in the acclimated column.