Disinfection profiles and mechanisms of E. coli, S. aureus, and B. subtilis in UV365/chlorine process: Inactivation, reactivation, and DBP formation

UV/chlorine is an emerging process that can simultaneously control waterborne bacteria and disinfection byproducts (DBPs). In this study, performance of UV365/chlorine process on bacterial inactivation was comprehensively investigated, which showed better performance than UV365 alone and chlorine alone processes. The better performance could be attributed to the reactive species (especially O3 and HO) generated in UV365/chlorine process. Inactivation of E. coli, S. aureus, and B. subtilis was further reflected via the evaluation of membrane permeability, leakage of adenosine-triphosphate (ATP), and damage of cell surface morphology. The results also demonstrated that bacterial inactivation generally follow the order of E. coli, S. aureus, B. subtilis. To ensure the disinfection efficiency, reactivation of three bacteria after complete treatment by UV365 alone, chlorine alone and UV365/chlorine processes was evaluated, and the combined process showed the lowest reactivation potential. Further, formation of disinfection byproducts (DBPs) from the bacterial suspensions with/without UV365/chlorine pretreatment was determined. Bacterial suspensions treated with UV365/chlorine process generated fewer DBPs than that in direct chlorination. Overall, our present study could provide much useful information on the actual application of UV365/chlorine process in drinking water treatment plants.