EVALUATING CONTROLS ON TRICLOSAN EXPORT IN A RURAL TO SUBURBAN WATERSHED: INSIGHTS FROM THE EAST BRANCH OF THE BRANDYWINE CREEK

Over the last decade, there has been a growing urgency to determine both the source and fate of emerging contaminants such as pharmaceuticals and personal care products (PPCP) in our waterways. In particular, many studies have focused on the widely used antimicrobial agent triclosan, due to its link to antimicrobial resistance. However, these initial studies have solely utilized sampling locations downstream of municipal sewage treatment systems, thus overlooking potential inputs from other point sources such as small privately operated sewage systems and non-point sources (i.e., leach fields associated with septic systems). Here we examine the range of concentrations, overall loading, and potential controls on triclosan delivery from non-municipal sources in the East Branch of the Brandywine Creek (EBBC), a rural to suburban watershed located in southeastern Pennsylvania. Samples for triclosan and discharge measurements were collected from 13 locations in the EBBC watershed in July 2014 during baseflow conditions. Detectable concentrations of triclosan in the EBBC ranged over several orders of magnitude from 0.131 to 274 ng/L. Small privately operated sewage treatment facilities and/or non-point sources were found to comprise ~28% of the cumulative triclosan loading in the EBBC. Triclosan concentrations and loads were subsequently compared to existing GIS-based land use data as well as the number of sewage related National Pollutant Discharge Elimination System (NPDES) discharge permits (a proxy for privately operated sewage treatment facilities) above each sampling location in an effort to evaluate controls on its export. No relationship was identified between triclosan concentrations and the relative amount of 15 different land use practices above each sampling location. While the relative number of NDPES permits above the sampling location did play a role in determining the extent of triclosan loading, this was ultimately dependent on the relative volume of the receiving water body. Finally, the presence of detectable concentrations of triclosan in tributaries with no NPDES permits suggests leach fields are also a viable source. These findings suggests we must greatly expand our consideration of sources for PPCPs in our waterways.