Chloramphenicol photo-Fenton degradation and toxicity changes in both surface water and a tertiary effluent from a municipal wastewater treatment plant at near-neutral conditions

Abstract

Antibiotics are known to be refractory to natural biological degradation and conventional water treatments. Their presence in the effluent of sewage treatment plants and surface waters may harm aquatic environments, making it important to evaluate new technologies and to assess their degradation potential at near-neutral conditions. This study thus describes the degradation of the antibiotic chloramphenicol in both surface water and a tertiary effluent from a municipal wastewater treatment plant by the photo-Fenton process under black-light and solar irradiation conditions. The best results in surface water at an initial pH of 5.8 (natural of this matrix) were obtained using 48 μmol L−1 FeOx and 44 μmol L−1 H2O2, with a 144 μmol L−1 oxalate added at 10 min, reaching 88% degradation after 15 min of black-light irradiation. However, in a previous step where the pH was adjusted from 7.7 to 6.0, high FeOx (192 µmol L−1) and H2O2 (1500 µmol L−1) concentrations were needed to achieve 79% chloramphenicol degradation in the tertiary effluent after 20 min of black-light irradiation. Using the same experimental conditions for each matrix, the best results, in terms of chloramphenicol degradation rate as by-products of low toxicity, were obtained under solar irradiation, as confirmed by the blank experiments using the matrices in the absence of chloramphenicol. These results show the viability and effectiveness of FeOx as a photocatalyst for the treatment of wastewaters containing this pollutant at near-neutral conditions under solar irradiation, as well as the added savings in energy costs associated with the photo-Fenton treatment.