Simulation of the fate of selected pharmaceuticals and personal care products in a highly impacted reach of a Canadian watershed M.J. Arlos a,b , L.M. Bragg b , M.R. Servos b , W.J. Parker a, ⁎ a Department of Civil and Environmental Engineering, University of Waterloo, Waterloo, ON N2L 3G1, Canada b Department of Biology, University of Waterloo, Waterloo, ON N2L 3G1, Canada HIGHLIGHTS • Simulation of trace contaminant fate and transport was successful using WASP 7.5. • Flow-driven processes greatly influenced the behavior of contaminants. • In-stream photolysis and biodegradation were also important mechanisms. • Carbamazepine behaved differently and acted as a tracer contaminant. abstract article info Article history: Received 20 February 2014 Received in revised form 19 March 2014 Accepted 19 March 2014 Available online 12 April 2014 Editor: D. Barcelo Keywords: Water quality model Antiandrogens Pharmaceuticals Endocrine disruption Sewage Wastewater treatment Municipal wastewater treatment plants (WWTPs) dispose of numerous trace organic contaminants in the receiv- ing waters that can impact biological function in aquatic organisms. However, the complex nature of WWTP ef- fluent mixtures and a wide variety of potential mechanisms that can alter physiological and reproductive development of aquatic organisms make it difficult to assess the linkages and severity of the effects associated with trace organic contaminants. This paper describes a surface water quality modeling exercise that was per- formed to understand the relevant contaminant fate and transport processes necessary to accurately predict the concentrations of trace organic compounds present in the aquatic environment. The target compounds modeled include a known antiandrogenic personal care product (triclosan) and selected pharmaceuticals (venlafaxine, naproxen, and carbamazepine). The WASP 7.5 model was adapted and calibrated to reflect approx- imately ten kilometers of reach of the Grand River watershed that is highly influenced by a major urban WWTP. Simulation of the fate and transport of the target compounds revealed that flow-driven transport processes (ad- vection and dispersion) greatly influenced the behavior of the target contaminants in the aquatic environment. However, fate mechanisms such as photolysis and biodegradation can play an important role in the attenuation of some compounds. The exception was carbamazepine where it was shown to act as a conservative tracer com- pound for wastewater specific contaminants in the water phase. The calibrated water quality model can now be employed in a number of future applications. Prediction of fate and transport of other trace organic contaminants across the watershed and assessment of the performance of WWTP infrastructure upgrades in the removal of these compounds are just a few examples. © 2014 Elsevier B.V. All rights reserved. 1. Introduction Concerns for effluent quality have expanded beyond traditional pol- lutants, such as biological oxygen demand and nutrients, to include trace organic contaminants that can alter responses in aquatic organ- isms at very low concentrations (Corcoran et al., 2010; Daughton and Ternes, 1999). Trace organic contaminants in wastewater treatment plant (WWTP) effluents collectively include pharmaceuticals, endo- crine disrupting compounds, and personal care products (Daughton and Ternes, 1999; Kolpin et al., 2002; Ternes et al., 2004). The effects of these compounds on aquatic species can be broad or highly specific depending on their mechanism of action (Daughton and Ternes, 1999). In the Grand River watershed in southern Ontario, pharmaceuti- cals ranging from anti-inflammatory drugs to antidepressants have been detected in its water (Arlos, 2013; Lissemore et al., 2006; Tanna et al., 2013; Metcalfe et al., 2010) and biota (Wang et al., 2011; Togunde et al., 2012). A variety of effects have also been re- ported in fish downstream of WWTP effluents in this watershed, in- cluding changes in gene expression (Ings et al., 2011), physiology Science of the Total Environment 485–486 (2014) 193–204 ⁎ Corresponding author at: Civil and Environmental Engineering Department, University of Waterloo, Waterloo, ON N2L 3G1, Canada. Tel.: +1 519 888 4567x36324; fax: +1 519 888 4349. E-mail address: wjparker@uwaterloo.ca (W.J. Parker). http://dx.doi.org/10.1016/j.scitotenv.2014.03.092 0048-9697/© 2014 Elsevier B.V. All rights reserved. Contents lists available at ScienceDirect Science of the Total Environment journal homepage: www.elsevier.com/locate/scitotenv