NUMERICAL MODELLING OF CONTAMINANT TRANSPORT IN GROUND WATER

Abstract

Ground water sources have been under constant threat due to human activities like disposal of industrial and solid waste. The contamination due to these refuse are of localised nature. Modelling of contaminant transport helps us in predicting the extent and nature of contamination, to plan for remedial measures. The Movement of contaminants in subsurface region, from a source is due to convection and dispersion mode. The convection mode is essentially due to the flow velocity i.e. natural or forced movement of ground water where as dispersion is molecular or ionic diffusion resulting from concentration gradient. The present work deals with mathematical modelling of contaminant transport in ground water. The governing equations of transport are the Darcy's equation, the continuity equation for the fluid flow, the continuity equation for the solute. The transport equations have been solved numerically by finite lement method. based on Galerkin weighted residual technique. The available software SUTRA (Saturated unsaturated transport) employing a two dimensional hybrid finite element and integrated finite difference approximation of governing equation has been used. SUTRA is structured in a modular, top-down programming style that allows for code readability, ease in tracing logic and ease in eventual modifications. SUTRA is written in FORTRAN-77. The prediction of contaminant transport has been done for radial dispersion problem. The FEM solution was found to match with exact analytical solution except at the lower bound. The deviation of the front at lower bound could be due to numeri-cal dispersion on account of inappropriate discret