Performance and mechanism of sequential UV-NaClO disinfection: Inactivation and reactivation of antibiotic-resistant bacteria, disinfection byproduct formation and microbial community variation

Because of the shortcomings of both ultraviolet (UV) and sodium hypochlorite (NaClO) disinfection in mitigating the spread of antibiotic resistance from wastewater treatment plants to the environment, this study evaluated the effect of sequential UV-NaClO disinfection versus UV and NaClO standalone disinfection on inactivation of antibiotic-resistant bacteria (ARB), reactivation of inactivated ARB, formation of disinfection byproducts (DBPs), and microbial community variation. In comparison with NaClO standalone disinfection, it is found that the UV-NaClO disinfection not only achieves a comparable ARB inactivation with a lower dosage but also produces lower DBPs. In addition, reactivation efficiencies of ARB by UV-NaClO disinfection are mostly lower than UV standalone disinfection in terms of the extended reactivation time or lower ARB reactivated abundance. Moreover, the bacteria community analysis shows that UV-NaClO disinfection is more effective in sterilizing potentially pathogenic, biofilm-forming, and stress-tolerant bacteria than UV and NaClO. These results indicate that the sequential UV-NaClO disinfection method is promising due to its excellent treatment performance and lower disinfection dosage. Therefore, UV-NaClO disinfection has been proven to be more effective and economical in ensuring the safety of reclaimed water reuse.