Modelling and Simulation of a Planned Bio-Chemical in situ Remediation

In this paper, the simulation of a bio-chemical in situ remediation approach is discussed. We consider a field case of a contaminant plume consisting of dissolved chloroethenes. A regional flow model shows, that the contaminants may reach a water works located 2 km downstream of the spill area. Thus, an in situ remediation is anticipated, where the dechlorination and mineralization of the chloroethenes is stimulated by a sequence of aerobic and anaerobic treatments. The equations of the reactive transport model are discretized using implicit time schemes and locally refined meshes. The resulting discrete equations are solved simultaneously with a Newton method and a point-block multigrid method, which turned out to be an efficient solver for the considered systems. Simulation results for several remediation configurations show a fast bio-chemical degradation of the chloroethenes which is however limited to the vicinity of the injection wells. After two years about 60% of the initial contaminant mass is removed, while a pure pump-and-treat scheme removes only 40% of the initial mass in the same time. The simulations suggest that the remediation scheme could be optimized with respect to the in situ biodégradation efficiency.