Degradation of pharmaceuticals in sanitary effluent by the combination of oxidation and photo-oxidation processes

Abstract Most conventional sewage treatment systems are not able to fully remove micropollutants found in sewage. Thus, the simultaneous degradation of 11 pharmaceuticals identified in the effluent of a sewage treatment plant in Southern Brazil was herein investigated through advanced oxidation processes based on ozonation, ultraviolet radiation and hydrogen peroxide. For detection, samples were prepared through solid-phase extraction and pharmaceuticals were identified through ultra-high performance liquid chromatography tandem mass spectrometry. Active ingredients such as ciprofloxacin, oxytetracycline, paracetamol, sulfamethoxazole and trimethoprim had their concentrations increased for degradation analysis purposes. Trials were carried out on a bench at room temperature and neutral pH, with aliquots collected at 7.5 and 15 minutes. Two ozone doses (0.5 and 0.9 mg per mg of dissolved organic carbon), and combinations of the lowest ozone dose with photolysis (254 nm) and with 25 mg.L−1 of hydrogen peroxide were evaluated. Pharmaceuticals mineralization efficiency was assessed in a total organic carbon analyzer. The process combining ozone, hydrogen peroxide and ultraviolet radiation was the most efficient in the degradation of all pharmaceuticals detected in this study, since it enabled reducing oxytetracycline by 89.32%, caffeine by 96.79%, trimethoprim by 97.40%, ciprofloxacin by 97.75%, sulfamethoxazole by 99.79%, paracetamol by 99.96%, and clindamycin, ofloxacin, sulfadiazine, sulfathiazole and tylosin by 100%. This process also recorded the highest mineralization rate (60.52%), fact that confirmed the potential to decrease persistent pharmaceuticals found in conventional sewage treatment systems.