Historical Trends and Concentrations of Fecal Coliform Bacteria in the BrandywineCreek Basin, Chester County, Pennsylvania

摘要

The Brandywine Creek in Chester County is used for recreation and as an importantsource of drinking water. For this study, 40 sites were established for collection of water samples for analysis of fecal coliform and Escherichia coli bacteria in 1998-99. Samples were collected during base-flow conditions and during five storms in which rainfall exceeded 0.5 inch. During baseflow conditions, the median concentrations of fecal coliform bacteria exceeded 200 col/100 ML at 26 of the 40 sites (65 percent). During stormflow conditions, the median concentration of fecal coliform bacterial exceeded the Pennsylvania Department of Environmental Protection (PaDEP) criterion of 200 col/100 mL at 30 of 33 sites samples (91 percent). Trends in fecal coliform bacteria concentrations were downward for the period 1973-99 at three long-term water-quality monitor stations, the result of upgrades in wastewater treatment plants, decreases in point-source discharge, and a decrease in agricultural land.