Comparative survival of enteric indicators, E. coli and somatic and F-RNA bacteriophages on turf-grass irrigated with recycled water

Abstract

The aim of this study was to elucidate whether the current withholding period of 4 hours following irrigation of public recreational areas with some classes of recycled water, as prescribed in some Australian state regulations, is valid or whether the holding time can be reduced under specified ambient conditions. A secondary objective was to evaluate laboratory simulations of ambient field conditions for microbial survival experiments. Results suggest that the currently prescribed 4 hour withholding period achieves a reduction of health risk associated with bacterial enteric pathogens that would not otherwise occur if the withholding period was reduced. However, this may not be the case for viral enteric pathogens as the survival of bacteriophages, PRD-1 and MS-2 on turf-grass did not significantly change even after 6 hours, except PRD-1 under high solar conditions. These results suggest that bacteriophages, PRD-1 and MS-2 are more conservative indicators of enteric pathogen survival on UV exposed turf-grass compared with E. coli. The simulations of field conditions in the laboratory were somewhat problematic, with the variations in natural conditions that occur temporally, sometimes for short periods, difficult to reproduce.