Effect of UV-A-assisted iron-based and UV-C-driven oxidation processes on organic matter and antibiotic resistance removal in tertiary treated urban wastewater

Antibiotic resistance is frequently being observed in treated urban effluents as an alarming wastewater treatment issue and health risk. The potential of UV-A-assisted iron-based and UV-C-driven advanced oxidation processes to inactivate the ABR E. coli J53 strain bacteria and its aphA (kanamycin resistance gene) and tetA (tetracycline resistance gene) located on the plasmid RP4 was investigated in real tertiary treated urban wastewater. Besides inactivation performance, dissolved organic carbon (DOC) removals were also followed to evaluate the mineralization degree that could be achieved by the proposed photochemical/photocatalytic treatment systems. For UV-A-assisted Fenton/Fenton-like processes, antibiotic resistance and DOC removals (≈20 %) were rather limited. UV-C activation of the oxidants hydrogen peroxide (HP), persulfate (PS) and peroxymonosulfate (PMS) were the key photochemical advanced oxidation processes for efficient inactivation of multi-resistant E. coli bacteria (>6.5-log reduction) and gene copies (>3.0-log reduction) as well. Besides, 31 %, 40 % and 59 % DOC removals were achieved at a UV dose of 0.45 W/m² for 2.0 mM HP-, PMS- and PS/UV-C treatments, respectively.