UVC-based advanced oxidation processes for antibiotics and pesticides removal in water matrices: By-products identification and toxicity assessment

Abstract

Contamination of surface water with antibiotics and pesticides is increasing the demand for advanced treatment technologies and stricter regulation of synthetic organic pollutants (SOPs). UV-based advanced oxidation processes represent a promising approach for water and wastewater treatment due to their high oxidation rate constants without mass transfer limitations. In this work, four SOPs (NOR: norfloxacin, CIP: ciprofloxacin, ENRO: enrofloxacin, and IMD: imidacloprid) were simultaneously oxidized using a low-power (5 W) UVC lamp combined with H2O2 and Na2S2O8 oxidants under neutral conditions in ultrapure water, tap water, and a simulated effluent. All SOPs were completely removed within 1 h using 500 μM of oxidants. For IMD, no synergistic effect was observed, and UVC irradiation alone achieved complete degradation. Although UVC radiation played the main role in promoting oxidation of SOPs, elimination of the antibacterial activity of fluoroquinolones against Escherichia coli required the presence of oxidants. Electron paramagnetic resonance (EPR) and scavenging experiments indicated the involvement of superoxide radicals and singlet oxygen, while the main oxidation by-products of SOPs resulted from hydroxylation addition reactions, as confirmed by LC-MS/MS analysis. Preliminary laboratory-scale cost estimates were approximately 1 and 7 US$ m−3 order−1 for the UVC/H2O2 and UVC/Na2S2O8 processes, respectively, with chemical oxidants accounting for major contribution to overall costs. The influence of target pollutants and water matrices on treatment costs was found to be negligible.