Antibiotic Resistance Mitigation Using Novel Heterogeneous Photocatalysts for Urban Wastewater Treatment and its Reuse in Agricultural Irrigation

Abstract

The Ph. D. project herein deals with the application of a novel photocatalyst and its potential in wastewater treatment. Specifically, for wastewater intended for reuse in crop irrigation and with direct emphasis on antibiotic resistance dissemination. The project is divided in three work packages (WP). WP A - Selection of a suitable photocatalyst deals with the assessment of a number of photocatalyst that was carried out in order to identify a suitable catalyst showing higher efficiencies while having a low-cost synthetic route. The research carried out within this scope resulted in an optimised cerium doped ZnO catalyst which was identified as fitting the pre-established requirements. This catalyst was subsequently studied in the immobilised form in WP B - Catalyst immobilisation here a procedure for coating stainless steel surfaces was set and the catalyst used for the removai of two model antibiotics trimethoprim and sulfamethoxazole, as well as testing the reusability of photocatalytic coatings. Additionally, the immobilised catalyst was used for the inactivation of bacteria in isotonic saline water and for the inactivation of autochthonous bacteria, including antibiotic resistant fractions in reai wastewater. In the latter, Ce-ZnO was more efficient than the industry standard TiO2-P25. This novel catalyst was also applied for controlled irrigation experiments. Lettuce plants (Lactuca sativa) were set up in four groups receiving either Ce-ZnO treated wastewater, chlorinated treated wastewater, fresh water or secondary wastewater in WPC- Both water treatments showed marginai differences in concentrations of thè four selected genes (16S rRNA, blaOXA-10 qnrS and intII) in water concentrations. As for concentrations in soil after thè irrigation campaign, both treatments showed lower levels than those from secondary wastewater but higher levels than fresh water with no major differences between treatments.