SYNERGISTIC EFFECTS OF UV IRRADIATION IN COMBINATION WITH CHLORINE AND CHLORINE DIOXIDE: BENCH- AND LAB-SCALE EVALUATIONS

Chlorine-based disinfectants and Ultraviolet (UV) irradiation have different modes of antimicrobial action. This work examined the use of chlorine (Cl2) and chlorine dioxide (ClO2), acting alone or in combination with UV light on E. coli at the lab-scale and heterotrophic bacteria at the bench-scale. The application of Cl2 or ClO2 to drinking water in combination with UV has been shown to be more effective then either chlorine-based or UV disinfection alone, with a few conditions. Location of UV light in the treatment process appeared to affect the ability of Escherichia coli (E. coli) K12 (ATTC strain #29425) to repair and establish biofilm at the lab-scale level during acclimation. It was found that UV treatment has a positive impact on model organism control at the water treatment plant level and that this benefit could be extended into the distribution system. However the application of UV does not modify the water matrix or mircoflora enough to prevent subsequent regrowth from pathogen intrusion.