Distribution of pathogenic indicator bacteria in structural best management practices.

This study evaluated the bacterial distribution and the survivability of bacteria associated with different particle size ranges in the sump water and sediments within two structural Best Management Practices (BMPs), called Vortechs, installed at two different sites in Providence, Rhode Island. Ten rain storms were sampled in year 2004. Five pathogenic indicator bacteria, E. coli, enterococci, fecal streptococci, total coliform, fecal coliform, were analyzed for samples in the sump water and sediments within two Vortechs. In both sump water and sediments within Vortechs, most of the bacterial were found to be associated with smaller particles, i.e., 80-95% of all pathogenic indicator bacteria were associated with particles less than 50 micro meter in the sump water, and 60-80% of all indicator bacteria were associated with particles less than 106 micro meter in the sediments. In the sump water, it was found that a surge of all indicator bacteria concentrations happened one-day after the rainfall stopped. This result was most significant for the bacteria associated with smaller particles. On the contrary, in the sediments, no dramatic change of bacterial concentrations was detected over the 5-day dry period following rain. At both sampling sites, much higher bacterial concentrations were detected in the sediments than in the sump water suggesting that sediments may have provided a favorable living environment for bacteria. The two sampling sites showed almost identical results in many aspects. Except the sump water at Site 2 had much lower bacterial concentrations than that at Site 1 suggesting higher bacterial contamination from highway runoff.