Viral risks associated with wastewater reuse: modeling virus persistence on wastewater irrigated salad crops.
A model for virus decay on lettuce and carrot crops has been derived as part of a comprehensive wastewater irrigation microbial risk assessment model under development. Results from the decay modeling indicated the presence of a very persistent sub-population of viruses evidenced by an initial rapid phase of decay followed by a very slow phase. In addition, virus counts fitted a negative binomial rather than Poisson distribution indicating over-dispersion. Hence the data indicated that viruses were not uniformly distributed over the surfaces of both crops. The aim of this paper was to investigate the implications of over-dispersion and the presence of a very persistent sub-population of viruses for assessing viral illness from the consumption of lettuces and carrots irrigated with secondary treated effluent. When over-dispersion or clumping of viruses was accounted for, a significant increase in the heterogeneity in the risk estimates arose. In addition, predicted infection rates were significantly underestimated if the presence of a persistent sub-population of viruses was not considered in the decay kinetics of the risk model. Hence, both viral clumping and persistence sub-populations should be accounted for in future risk assessments of enteric viruses associated with wastewater reuse.
Petterson
S R
SR
School of Civil and Environmental Engineering, University of New South Wales, Sydney, NSW 2052, Australia.
Ashbolt
N J
NJ
D000383:Agriculture; D003247:Conservation of Natural Resources; D018552:Daucus carota; D004784:Environmental Monitoring; D005506:Food Contamination; D006801:Humans; D007700:Kinetics; D018545:Lactuca; D008962:Models, Theoretical; D010945:Plants, Edible; D011157:Population Dynamics; D011634:Public Health; D018570:Risk Assessment; D014780:Viruses / Q000378:metabolism*; D014865:Waste Disposal, Fluid