Pharmaceuticals and Personal Care Products in an Effluent-Dominated Stream: Seasonal Variability and Downstream Fate

Wastewater treatment plant (WWTP) effluents are major sources of pharmaceuticals and personal care products (PPCPs) in the environment and effluentdominated streams (EDSs) represent worst-case scenarios for PPCP exposures to aquatic organisms. The concentrations of PPCPs downstream from a WWTP can be altered by dilution and fate processes such as biodegradation, photodegradation and sorption. The relative importance of these processes depends on the individual PPCPs and environmental variables that vary seasonally. The primary objective of this study was to determine the concentrations of selected PPCPs in an EDS as a function of season and distance from a WWTP with the hypothesis being that the downstream attenuation of the PPCPs would vary based on their corresponding physicochemical properties. A secondary objective was to evaluate the ability of the constructed wetlands located between the plant and creek to reduce PPCP concentrations. Samples were collected seasonally from above and below the East Canyon Water Reclamation Facility (ECWRF) and within the constructed wetlands for selected PPCPs. Except for caffeine, downstream PPCP concentrations were higher than upstream, indicating that the ECWRF effluent is the major source of PPCPs in East Canyon Creek. Generally, the highest PPCP concentrations in the stream were observed in July and the lowest in May corresponding to the times of lowest and highest ratio of stream to effluent flows, respectively. Dilution was the major factor associated with the declining PPCP concentrations downstream of the ECWRF but the extent of decline varied between compounds suggesting other fate mechanisms also play a role. Sorption of PPCPs to wetland sediments was greater than stream sediments but overall the retention time within the wetlands was too short to significantly reduce the amount of PPCPs moving into the stream. The observed concentrations of individual PPCPs in East Canyon Creek were lower than those expected to negatively impact the health of aquatic organisms but mixture effects are still a potential concern