Effective disinfection of antibiotic resistant bacteria and antibiotic resistance genes from water using chlorination, UV and UV/H2O2

Safe, clean water is vital to maintain healthy societies and socioeconomic development, yet providing it remains an evolving challenge for water managers. Among the numerous contaminants that need to be managed, antibiotic resistant bacteria (ARB) and antibiotic resistance genes (ARGs) are recognized globally as a growing priority, and the development of new and improved disinfection methods to remove them and their drivers (e.g., antibiotics) from treated wastewater effluents for recycling or discharge to water bodies is a matter of increasing interest. This study investigated the disinfection efficacy of hydrogen peroxide (H₂O₂), chlorination (Cl₂), ultraviolet light at 254 nm (UV-254), UV-254/H₂O₂, ultraviolet light at 369 nm (UV-369) and UV-369/H₂O₂ treatments against several bacterial strains (i.e., Escherichia coli, Salmonella enteritidis 11RX, Listeria innocua, Pseudomonas aeruginosa and methicillin-resistant Staphylococcus aureus). Disinfection efficacy was assessed in multiple sample matrices, including ultrapure water, wastewater influent, and effluent waters. Irrespective of the bacterial strain, the removal efficacy followed the order: UV-254/H₂O₂ > UV-254 > Cl₂ > UV-369/H₂O₂ > UV-369 > H₂O₂. 4-log reduction (99.99 % removal) of E. coli was achieved at 0.5, 1, 2, 20 and 30 min by UV-254/H₂O₂, UV-254, Cl₂, UV-369/H₂O₂ and UV-369 treatments, respectively, whereas H₂O₂ alone only achieved 97.6 % removal of E. coli after 30 min of treatment. UV-254 and UV-254/H₂O₂ were also able to remove antibiotic resistance genes with an observed rate constant ranging from 0.3445 to 0.6122 min^–1. The findings of this study suggest that coupling H₂O₂ with solar light is a promising alternative approach for reducing the quantity of opportunistic human pathogens in reclaimed water.