DISTRIBUTION OF PATHOGENIC INDICATOR BACTERIA IN STRUCTURAL BMP

This study evaluated the bacterial distribution in the sump water and sediments within a structural BMP called Vortechs installed in Providence, Rhode Island. Ten rain storms with precipitations greater than 0.1 inch were sampled over a six month period in year 2004. Five pathogenic indicator bacteria, E. coli, enterococci, fecal streptococci, total coliform, fecal coliform, were analyzed. Results showed that a surge of bacteria in the sump water happened on the day a rain event occurred and one-day after the rain stopped; no re-growth of bacteria in the sump water was found and no significant change in the concentrations of bacteria was detected in the sediments within the Vortechs over time. 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. Temperature affected the survival of bacteria concentrations significantly; results suggested that enterococci and fecal streptococci can survive longer than E. coli. Suspended particles tend to aggregate and form larger particles over time. 80% of E.coli, enterococci and fecal streptococci were associated with particles less than 50 μm in the sump water. 60% of all indicator bacteria were associated with particles less than 106 μm in the sediments.