Ozonation against a diverse suite of antibiotic resistance determinants in wastewater

This work aimed at investigating the impact of bench-scale ozonation, as tertiary treatment, on the removal and inactivation of selected antibiotics, antibiotic-resistant bacteria, antibiotic resistance genes and toxicity from wastewaters effluents. The novelty of this study concerns the in-depth investigation of the ozonation process for the removal of a diverse suite of antibiotic resistance determinants in two distinct wastewater matrices, i.e., conventional activated sludge (CAS) and membrane bioreactor (MBR) treated effluents. The results revealed the complete degradation of the antibiotics within 5 min of contact time in both effluents. The inactivation of total cultivable bacteria in the examined wastewater matrices was described by an exposure-based Chick-Watson kinetic model. Furthermore, the abundance of the examined bacterial groups, including antibiotic-resistant bacteria and genes, decreased to values below the limit of quantification, indicating that ozone could improve the quality of wastewater in terms of antibiotic resistance. No substantial mineralization was observed, while the toxicity increased after treatment by ozone compared to the initial (untreated) wastewater effluents. Overall, the results of this study could contribute to the understanding of the fate of both the antibiotics and antibiotic resistance determinants during ozonation, with an emphasis on the impact of the wastewater matrix.