Virus Transport Through Heterogeneous Unsaturated Zone in Guwahati City in Assam Under Transient State Condition

Abstract

Virus present in the groundwater is considered to be an important agent for waterborne diseases in India. In order to predict how far viruses can be transported and how long they can remain infective in soil and groundwater is desirable for proper management of the placement of sources of contamination so that they will not have an impact on drinking-water wells. With respect to that, a one-dimensional virus fate and transport model is developed for transient heterogeneous unsaturated flow to identify the transport parameters in the unsaturated zone. Simulation of virus transport in groundwater aquifer is necessary for predicting the vertical movement of virus in an aquifer and to implement remedial measures to inactive the virus present in the groundwater. The model involves solution of the advection–dispersion equation, which additionally considers virus inactivation rate in the solution. In case of unsaturated porous media, the transport of virus is responsible for some of the parameters such as linear distribution coefficient, hydrodynamic dispersion coefficient and inactivation coefficient for both aqueous and sorbed virus. As there are often changes in the state and content of soil water during flow, it is considered to be a highly nonlinear problem and for such it becomes necessary to solve the flow equation before solving the virus transport equation. In this study, finite element scheme computer-coded software, HYDRUS-1D is used to simulate the one-dimensional flow equation and virus transport equation. This study is mainly carried out for a particular location of Guwahati City, Assam, India. The viruses that is been employed in this study were the male-specific RNA coliphage MS2, and the Salmonella typhimurium phage, PRD1. For simulating the partial differential equation of virus transport equilibrium, solute transport model is selected with Crank–Nicholson as time weight scheme and Galerkin finite elements as space weight scheme. The purpose of this research is to determine the role that unsaturated flow conditions play in virus sorption and inactivation during transport through different soil type. The effects of the moisture content variation on virus transport in unsaturated porous media were also investigated. The results obtained after several simulations indicate that the concentration of virus is affected by the moisture content and the heterogeneity of the soil profile during its flow through unsaturated zone. The model developed in this study can successfully simulate the virus transport through heterogeneous unsaturated columns.