Evaluation of pathogenic indicator bacteria in structural best management practices.

This study evaluated the bacteria removal efficiency, re-suspension and survivability within two structural Best Management Practices (BMPs) called Vortechs installed at two different sites in Providence, Rhode Island. Twelve rain storms were sampled during years 2004 and 2005. Five pathogenic indicator bacteria, E. coli, enterococci, fecal streptococci, total coliform, fecal coliform, were analyzed. Results showed that Vortechs was effective in partial removal of pathogenic indicator bacteria (PIB, 39-86%), however, the PIB concentrations after Vortechs treatment were still significantly high, which could limit the use of receiving waters and raise concerns for public health. The indicator bacteria concentrations in the sump water were 1.2-2.6 times higher than that contributed by the incoming stormwater. This result suggests some bacteria were re-suspended from the sediments within the Vortechs. Low bacterial survivability of bacteria was found in the sump water at both sampling sites; however, much lower bacteria concentrations were detected at Site 2, suggesting a higher bacteria contamination from highway runoff.