Ozonation of the antiviral oseltamivir in wastewater effluent: Matrix effect, oxidation pathway, and toxicity assessment

Abstract

The potential environmental impacts of commonly employed antiviral drugs and their byproducts have attracted attention but remain largely unexplored. In this study, ozone (O3) was used to remove the oseltamivir phosphate (OP), a widely used antiviral, from different water matrices, including secondary municipal wastewater effluent (WWE). Over 90 % of OP was removed from a buffer solution using 10 µM of O3 in a short reaction time (30 s), while pseudo-first-order kinetics constants (K) showed a strong linear relationship with the initial O3 dosage. The pH of the solution was found to be an important factor in the ozonation process since the degradation mechanisms and, thereby, the K values are affected by the structural conformations of OP (protonated or deprotonated forms), the generation of hydroxyl radicals (•OH) under mild basic conditions, and the depletion of O3 under extreme basic pH. In addition, common inorganic ions slightly affect the K values, but increasing the ionic strength negatively influences the degradation process. Organic components in WWE also reduced the efficiency; however, over 95 % of OP degradation was achieved using a ratio of O3 dosage to dissolved organic carbon (DOC) of 0.544 g O3 g–1 DOC. Finally, a degradation pathway was proposed based on the detection of byproducts formed by direct ozonation and hydroxylation reactions. Acute toxicity and genotoxicity assessments on ozonated matrices, especially the WWE sample, suggest that these byproducts have no potential toxic effects. All these findings strongly suggest that ozonation can effectively degrade antivirals in municipal effluents.