The effect of wastewater treatment processes, in particular ultraoviolet light treatment, on pathogenic virus removal.

Abstract

Municipal wastewater treatment plant discharges are a recognised source of human pathogenic viruses, of which norovirus is of great concern and the leading cause of viral gastroenteritis worldwide. Currently, no legislation (nationally or internationally) exists for the monitoring of viral loads in treated effluent. While primary and secondary treatment processes can reduce virus concentrations, they are not specifically designed for this purpose and so tertiary treatment can be required in many cases. Continuous low- and/or medium-pressure ultraviolet (UV) light systems are used in conventional wastewater treatment plants as a method of pathogen disinfection. Barrier-based systems, such as membrane filtration processes, are widely used in the drinking water sector as a pathogen removal system; however, operational challenges associated with wastewater have limited their use in this industry. The detection of norovirus is limited to molecular methods that do not distinguish between infective and non-infective viruses. This poses a problem when evaluating certain disinfection methods, such as UV light, which does not remove the virus but rather inactivates it. Thus, in this case, overestimation of virus infectivity can occur. The use of a surrogate virus, the F-specific RNA (FRNA) bacteriophage has been suggested as it is morphologically and physiochemically similar to norovirus and it may also be cultivated, i.e. infectivity can be determined.