IDENTIFYING CONTROLS ON TRICLOSAN LOADING TO THE EAST BRANCH OF THE BRANDYWINE CREEK

Emerging contaminants, especially those associated with pharmaceutical and personal care products, have become a growing area of concern for our waterways during recent years. The commonly used antibacterial agent triclosan is one such contaminant. However, studies documenting both the prevalence and persistence of triclosan in the environment have either focused on its concentrations in areas immediately downstream of municipal wastewater treatment plants (WWTPs) or in WWTP effluent, 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). This study addresses these knowledge gaps by evaluating the range of concentrations and overall controls on triclosan delivery to the East Branch of the Brandywine Creek (EBBC), a rural to suburban watershed located in southeastern Pennsylvania. A total of 29 water samples and discharge measurements were collected throughout the watershed in June 2016 during baseflow conditions. A subset of samples were collected directly above and below 10 National Pollutant Discharge Elimination Systems (NPDES) sites in the watershed, which are associated with small, privately operated WWTPs. Additional samples were collected from tributaries with no NPDES sites to determine whether leach fields are a viable source. Instantaneous triclosan loads and yields calculated for each portion of the watershed were subsequently compared to a variety of factors, such as GIS-determined land use practices as well as the number of NPDES permit sites and the volume of permitted flow above each of the sampling locations, in order to determine controls on its export. Finally, triclosan loading associated with a municipal WWTP in the lower portion of the watershed was compared with the cumulative loading value for the upstream areas in an effort to identify the role of these “non-traditional” sources on total triclosan delivery.