In-situ Permeable Reactive Barrier for the Treatment of Hexavalent Chromium and Trichloroethylene in Ground Water: Volume 3. Multicomponent Reactive Transport Modeling.

摘要

Reactive transport modeling has been conducted to describe the performance of the permeable reactive barrier at the Coast Guard Support Center near Elizabeth City, N.C. The reactive barrier was installed to treat groundwater contamination by hexavalent chromium and chlorinated organic solvents. The conceptual model of the Elizabeth City site described in previous reports provides the basis for the modelling study. The multicomponent reactive transport model MIN3P was used for the simulations. The essential reactions contained in the conceptual model are aqueous complexation reactions, combined reduction-corrosion reaction between the treatment material zero-valent iron and the contaminants or other electron acceptors dissolved in the ambient groundwater and the precipitation of secondary minerals within the reactive barrier. The simulations have been carried out along a cross-section through the barrier that corresponds to a transect of the monitoring network. One- and two-dimensional simulations were conducted. The one-dimensional simulations are carried out along a zone of preferential flow, which conveys the most pronounced Cr(VI)-contamination. The model has been calibrated using field data, laboratory data and reaction rates reported in the literature. The two-dimensional simulations were conducted based on hydraulic conductivities determined from slug-tests. These simulations allow an evaluation of the impact of preferential flow on the treatment of the contaminants and secondary reactions. The model results provide estimates of the potential effects of the consumption of zero-valent iron and the precipitation of secondary minerals on the long-term efficiency of the treatment system.