Inactivation and Photorepair of Enteric Pathogenic Microorganisms with Ultraviolet Irradiation

Ultraviolet inactivation of enteric pathogenic microorganisms, including Shigella dysenteriae, Salmonella typhimurium, and human rotavirus (HRV-Wa) and somatic coliphages (MS2 and T4), was investigated in different water samples. Significant differences in the sensitivity of the bacteria and viruses to ultraviolet radiation were observed. Viruses were more resistant to ultraviolet disinfection than all the enteric bacteria tested in this study. With the exception of S. typhimurium, which showed flattening and tailing, strong first-order relationships between the logarithm of survival and the ultraviolet dose were observed. While S. dysenteriae and S. typhimurium were found to undergo photoreactivation after ultraviolet exposure, the photoreactivation decreased significantly with higher ultraviolet doses. Moreover, the inactivated bacteria exhibited different photoreactivation rates with different water samples. Combination of a low ultraviolet dose and a low concentration of chlorine not only inhibited the photoreactivation of ultraviolet-damaged bacteria but also effectively inactivated the bacteria.