LAGRANGIAN BASED SAMPLE SETS--FATE AND TRANSPORT OF EMERGING CONTAMIANTS IN A WASTEWATER DOMINATED STREAM

Research has documented the prevalence of a wide variety of pharmaceuticals and other emerging contamiants (ECs) in streams across the United States. Wastewater treatment plants (WWTPs) have been found to be an important source and collection point of ECs to streams as many ECs are incompletely removed during treatment. In this study, a Lagrangian sampling approach was used to determine in-stream removal rates for a variety of inorganic and organic constituents commonly detected in wastewater effluent. Dye tracing and time-of-travel measurements used to estimate data collection times for all Lagrangian sample sets. In addition, fish electro-shocking above and below the WWTP effluent provided important ecological information when combined with the water chemistry data.

The study was conducted along an 8.4 kilometer reach of Fourmile Creek near Ankeny, Iowa. Fourmile Creek is a low gradient stream (1m/km), that is wastewater dominated, with negligible other flow inputs, in a small drainage basin (less than 60 square kilometers). In general, Fourmile Creek is typical of many streams in Iowa and across the Midwest that transport WWTP effluent from small to mid-sized cities (less than 50,000 population). The similarity in chemical concentrations between the WWTP effluent and proximal downstream sampling points clearly shows the contribution of WWTPs to EC concentrations in Fourmile Creek. Significant reductions occurred both in the number of ECs detected and total EC concentrations through the 8.4 km study reach by undefined natural processes (e.g. sorption, microbial degradation, photolysis). However, certain ECs were found to vary in their type of transport (conservative versus nonconservative) and were persistent throughout the study reach. In addition, there were differences in the fish population (type of species and diversity) when comparing fish collected above the WWTP effluent to below the WWTP.