Finite Element Methods for Solving Contaminant Trnasport Problems

Abstract

The aim of this work is the comparison between two nite element approaches for solving multispecies contaminant transport problems together with sorption and biodegradation processes which can take place inside a porous matrix aquifer characterizing a stage of subsurface contamination by organic contaminants. Mathematically the problem is described by a nonlinear advection-diffusionreaction partial differential system coupled by reaction terms which are associated to the kinetics that
govern biodegradation processes.
Computational aspects obtained via numerical simulations of a standard fully coupled technique and an operator splitting approach are analyzed. This second methodology deals with convective-diffusive and reactive terms in a sequential way, producing an efcient and natural alternative to numerical solve different types of biodegradation kinetics and sorption conditions. For both methodologies a predictormulti corrector algorithm with Newton-Raphson and stabilized nite element methods are used in time and spatial discretizations, respectively, to approximate the nonlinear transport equations.
Efciency and accuracy to the proposal methodologies are analyzed via three typical contamination scenarios where nonlinear biodegradation processes, equilibrium and non-equilibrium sorption conditions are carried out. This study allow us to choose the most convenient approach for each case. The operator splitting procedure is very attractive for parallel computation, large multidimensional problems
with multiple species, treating in a novel way different types of biodegradation kinetics and sorption conditions. On the other hand, fully coupled techniques are mathematically considered more rigorous procedures, and they have been generally employed to solve nonlinear reactive transport problems.