Indian Geotechnical Conference IGC2016 15-17 December 2016, IIT Madras, Chennai, India 1 Virus Transport through Heterogeneous Unsaturated Zone in Guwahati city in Assam under Transient state condition Mamata Das 1 Triptimoni Borah 2 Post Graduate Student 1 and Assistant Professor 2 , Department of Civil Engineering, Assam Engineering College Guwahati, Assam, India, Guwahati- 781013, 1 mamtadas4@gmail.com and 2 btriptimoni@gmail.com ABSTRACT: Virus present in the groundwater is considered to be an important agent for water borne 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 are responsible for some of the parameters such as linear distribution coefficient, hydrodynamic dispersion co-efficient and inactivation coefficient for both aqueous and sorbed virus. As there is often changes in the state and content of soil water during flow so 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 indicates 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. KEYWORDS: Virus, heterogeneous, transient, HYDRUS, unsaturated, Crank-Nicholson, Galerkin. advection, dispersion. 1 INTRODUCTION: Hazardous wastes, sewage sludge, fertilizers and pesticides from the ground surface are removed by filtering action of the unsaturated zone. This may result in high contents of organic matters and clay, which undergoes biological degradation, transformation of contaminants and sorption. Therefore, the unsaturated zone can be considered as a buffer zone for protecting the groundwater. Virus that is present in waste water and sewage sludge are mainly the pathogenic microbial organisms which may lead to waterborne diseases. In order to understand spatial and temporal movement of these microorganisms one has to simulate the fate and transport processes. These two processes are mainly governed by four processes: advection, hydrodynamic dispersion, inactivation process and adsorption onto the soil matrix. In this zone the virus sorption and inactivation are influenced by the soil moisture content and subsurface temperature fluctuations (Vilker and Burge, 1980; Vilker, 1981; Thomson and Yates, 1999), so the flow equation is solved before solving the transport equation. Several mathematical models are developed for predicting the movement of viruses in porous media. (Tim and Mostaghimi, 1991) developed a numerical model, VIROTRANS for simulating vertical movement of water and virus through soil treated with waste water effluents and sewage sludges. (Yates and Ouyang, 1992) developed a predictive model of virus fate and transport, VIRTUS which studies the effect of temperature-dependent