Numerical modelling of transient mass transfer in an aquifer with simultaneous first order chemical reaction and second order decay

Warke, A.S., Das, Samir K., Bég, O. Anwar, Takhar, Harmindar S. and Bég, Tasveer A. (2008) Numerical modelling of transient mass transfer in an aquifer with simultaneous first order chemical reaction and second order decay. International journal of fluid mechanics research, 35 (2). pp. 105-126. ISSN 1064-2277

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Abstract

A mathematical model to simulate contaminant dispersion in a homogeneous, isotropic aquifer under the influence of second order decay as well as first order chemical reaction at the boundary is presented. A finite difference implicit (ADI) scheme has been employed to solve the two-dimensional transport equation. Numerical experiments were carried out for two types of disposal scheme, i) Scenario-I: longer duration with low concentration and ii) Scenario-II: short duration with high concentration. In both the scenarios, contaminant inflow rate is considered to be proportionately analogous to the inflow concentration and therefore two types of input correspond to the same amount of waste load. The influence of reaction parameter (Β) and decay parameter (μ) on the contaminant dispersion have been studied for two years, four years and six years of simulations. The reaction at the upper boundary behaves as a catalytic reaction, causing depletion of contaminant plume and its growth. With the increase of reaction parameter (Β), spreading of contaminant is controlled very significantly. The decay parameter (μ) takes a significant role to reduce the plume size when long time is allowed. Model simulations indicate that when the boundary reaction is mild and decay is insignificant, scenario-I can be chosen for a short period after release. If strong treatment is subjected for a long time, scenario-II is a better option as it controls the contaminant spread significantly.