UV Inactivation of Indigenous Male Specific and Somatic Coliphages, and Treatment Implications

摘要

The US EPA is considering coliphages as an indicator of fecal contamination in recreational waters. Data on the disinfectability of indigenous coliphages in wastewater treatment plants is limited, so the impact of potential coliphage limits for treatment plants is largely unknown. This study provides data on the concentration and UV disinfection efficacy for indigenous male-specific and somatic coliphages at four wastewater treatment plants. It was found that the secondary effluent coliphage concentrations varied by about 2 logs over the study period, with somatic coliphages having higher concentrations than the male-specific coliphages. Somatic coliphages were, in general, easier to disinfect with UV than the male-specific coliphages. This is consistent with the known UV sensitivities of the few coliphages that have been independently evaluated by others. The UV inactivation kinetics of the mixed populations of indigenous coliphages were not always first order. There was often tailing in the inactivation curves, potentially as a result of having eliminated more UV-sensitive coliphage species with the low doses, leaving the more UV-resistant species to be inactivated with higher doses. Furthermore, indigenous coliphage inactivation kinetics were not consistent from plant to plant, as the UV sensitivity of the indigenous phages was not equal between all plants nor equal over time. This suggests that increased UV doses may be required to consistently meet low effluent coliphage concentrations and that the treatability of coliphages varies depending on both the influent characteristics and the treatment plant.