Screening and Examining “Exotic” Chemicals in Swift Current Creek, SK, Canada
A wastewater treatment plant (WWTP) is situated on Swift Current Creek, SK. Although the plant carries out complete secondary treatment followed by UV disinfection, a suite of chemicals is still released into the receiving water. In addition, the City of Swift Current used lagoon treatment for 27 years prior to the construction of the WWTP and thus chemicals in the lagoon could also pose a potential threat to nearby ecosystems. Swift Current Creek flows into Lake Diefenbaker on the South Saskatchewan River system, which is a major drinking water source for Saskatchewan residents. Therefore, the aim of this study was to construct a contaminant chemical profile of the WWTP wastewater and the receiving water throughout the year to monitor the release and fate of pollutants. Chemical contaminants of interest included hormones, insecticides/pesticides, industrial chemicals and pharmaceuticals and personal care products. A total of 9 sites upstream, downstream and on-site of the WWTP, including the lagoon, were sampled once or twice a month in 2011 and 2012. Organic compounds were extracted via solid-phase extraction using HLB cartridges for effect-directed analysis. Recombinant H4IIE-luc, MVLN and MDA cell lines were used to detect dioxin- or PAH-like, estrogenic and androgenic activities, respectively. An HPLC Quadrupole-Orbitrap Mass Spectrometer was used to detect and semi-quantify target chemicals by either full scan or by selected ion monitoring. A mixture of twenty-two chemicals representing each group of compounds was used as a standard for the analysis. No dioxin- or PAH-like activities were detected using the H4IIE-luc bioassay. Significant androgenic activities were detected in influents as expected. However, post-treatment effluent samples illustrated near 100% removal of androgenicity. No estrogenic activities could be detected in any samples, probably due to background levels of hormones found in the growth media that compromised the sensitivity of MVLN assay. Therefore, Orbitrap Hi-Res coupled to HPLC was used for instrumental analysis to semi-quantify natural and synthetic estrogen mimics. Estrogen equivalency (EEQ) was calculated from instrument analysis results. Seasonal variations were observed as March samples had the highest concentrations of EEQ. The March effluent sample had an EEQ of 2.26 ng/L compared to <0.5 ng/L from the other three sample periods. Longitudinal variations were also apparent, suggesting that input sources other than the WWTP may be present. Four selected sampling dates representing different seasons of the year (August for late summer, September for early fall, January for middle of winter, and March for early spring) were also analyzed using the Orbitrap. Pesticides were found at greater concentrations in surface water than in raw and treated wastewater. Evidence suggested a major source of input of pesticides to be agricultural leaching and runoff rather than municipal wastewater. Hormones were efficiently removed through the wastewater treatment process as only low levels were detected (mean < 1 ng/L for effluents and downstream surface water). PPCPs exhibited more variable characteristics, as some chemicals had near 100% removal (caffeine and DEET) while others were rather persistent (carbamazepine). Residual concentrations found in effluents and downstream surface waters were in a much wider spectrum, with maximum concentrations of up to hundreds of ng/L. Seasonal variations were observed among PPCPs as well. Concentrations of triclosan and trimethoprim were especially higher in March. Seasons that exhibited elevated chemical concentrations coincided with the spawning seasons of aquatic organisms and thus environmental impacts should be further assessed.
Wastewater, Orbitrap, Cell Bioassay, Effect Directed Analysis, Endocrine Disruption
Master of Science (M.Sc.)