Column Studies on the Capture and Destruction of E. coli from Simulated Urban Stormwater Runoff Using Conventional Bioretention Media and Iron Oxide-Coated Sand

Given the magnitude of the threat to water quality posed by microbial pollutants in urban stormwater runoff and the untested potential for their removal in bioretention systems, the objectives of this research are to evaluate the capture and destruction of E. coli O157:H7 strain B6914 (as a pathogenic indicator) from synthetic urban stormwater runoff by conventional bioretention media, and to examine the potential of iron oxide-coated sand (IOCS) for enhancing bacterial removal. The results of these column experiments indicate that conventional bioretention media achieved approximately 80% removal of E. coli under the test conditions. Coated iron oxides enhanced bacterial adsorption through surface charge modification, increasing bacterial removal to 99%. However, the die-off rate of trapped cells in conventional bioretention media was far quicker than in the IOCS as studied. More than 99.98% of B6914 cells attached to conventional bioretention media died off within one week. Therefore, conventional bioretention media have a greater potential to render the process sustainable.