INNOVATIVE INJECTION AND EXTRACTION SCHEMES TO ENHANCE MIXING IN AQUIFERS

Remediation of contaminated groundwater may involve the injection of one or more reactants into the aquifer to stimulate degradation of contaminants, coupled with removal of water from an extraction well to increase circulation. The degradation reactions occur at the material interface between the native contaminated groundwater and the injected solution, where the two solutions are mixed; thus the length of the interface is a critical parameter in controlling the reaction rates. In addition, the width of the interface grows due to molecular diffusion and mechanical dispersion, increasing mixing and therefore also affecting the reaction rate. In standard dipole flow, the length of the interface increases over time due to diverging flows near the injection well and aquifer heterogeneity; however, due to the laminar flows characteristic in porous media, mixing in groundwater is an inherently slow process. In contrast, mixing occurs more readily in rotational flows, such as turbulent flow in streams, in which a material interface will be stretched and folded within the domain due to transient vortices. We investigate the possibility of applying this paradigm in aquifers. Specifically, we will explore how well injection and extraction schemes can enhance stretching and folding of a material interface within an aquifer, leading to increased mixing and accelerated reaction rates.