Stochastic analysis of virus transport in aquifers

A large-scale model of virus transport in aquifers is derived using spectra l perturbation analysis. The effects of spatial variability in aquifer hydr aulic conductivity and virus transport (attachment, detachment, and inactiv ation) parameters on large-scale virus transport are evaluated. A stochasti c mean model of virus transport is developed by linking a simple system of local-scale free-virus transport and attached-virus conservation equations from the current literature with a random-field representation of aquifer a nd virus transport properties. The resultant mean equations for free and at tached viruses are found to differ considerably from the local-scale equati ons on which they are based and include effects such as a free-virus effect ive velocity that is a function of aquifer heterogeneity as well as virus t ransport parameters. Stochastic mean free-virus breakthrough curves are com pared with local model output in order to observe the effects of spatial va riability on mean one-dimensional virus transport in three-dimensionally he terogeneous porous media. Significant findings from this theoretical analys is include the following: (1) Stochastic model breakthrough occurs earlier than local model breakthrough, and this effect is most pronounced for the l east conductive aquifers studied. (2) A high degree of aquifer heterogeneit y can lead to virus breakthrough actually preceding that of a conservative tracer. (3) As the mean hydraulic conductivity is increased, the mean model shows less sensitivity to the variance of the natural-logarithm hydraulic conductivity and mean virus diameter. (4) Incorporation of a heterogeneous colloid filtration term results in higher predicted concentrations than a s imple first-order adsorption term for a given mean attachment rate. (5) Inc orporation of aquifer heterogeneity leads to a greater range of virus diame ters for which significant breakthrough occurs. (6) The mean model is more sensitive to the inactivation rate of viruses associated with solid surface s than to the inactivation rate of viruses in solution.