Occurrence of Antimicrobials in the Final Effluents of Wastewater Treatment Plants in Canada

TLDR

The study aimed to assess the presence of antimicrobials in the final effluents of Canadian wastewater treatment plants. Researchers developed or adapted solid‑phase extraction coupled with liquid chromatography–electrospray ionization tandem mass spectrometry to analyze 31 antimicrobials from five classes in effluents from eight WWTPs across five cities. Ciprofloxacin, clarithromycin, erythromycin‑H₂O, ofloxacin, sulfamethoxazole, sulfapyridine, and tetracycline were frequently detected, with sulfapyridine reported for the first time in the environment; veterinary‑specific drugs were absent, concentrations were below 1 µg/L and unlikely to harm aquatic life, and the detected compounds—primarily those heavily prescribed in Canada—should be prioritized for monitoring near WWTP discharges, reflecting regional prescription differences compared to northern Europe.

Abstract

To investigate the occurrence of antimicrobials in the final effluents from wastewater treatment plants (WWTPs) in Canada, analytical methods were developed or modified from previously described methods using solid-phase extraction followed by liquid chromatography−electrospray ionization tandem mass spectrometry. Thirty-one antimicrobials from the macrolide, quinolone, quinoxaline dioxide, sulfonamide, and tetracycline classes were investigated in the final (treated) effluents from eight WWTPs, located in five Canadian cities. Ciprofloxacin, clarithromycin, erythromycin-H2O, ofloxacin, sulfamethoxazole, sulfapyridine, and tetracycline were frequently detected in the effluents. The detection of sulfapyridine in effluents is the first report of this compound in environmental samples. Antimicrobials used exclusively for veterinary applications or treatment of livestock, such as carbadox, olaquindox, and chlortetracycline were not detected in the WWTP final effluents. There appear to be differences in the relative concentrations of antimicrobials detected in WWTP final effluents in Canada relative to concentrations reported previously in northern Europe, particularly for quinolone and sulfonamide compounds. These data may reflect differences in prescription patterns in Canada and northern Europe. The antimicrobials frequently detected in WWTP effluents appear to be those prescribed heavily in Canada for medical applications, and these compounds should be considered priority compounds for monitoring in surface water near WWTP discharges. The concentrations of antimicrobials detected in WWTP final effluents did not exceed 1 μg/L; levels that are unlikely to affect the growth and survival of aquatic organisms.