Three-Dimensional Investigation of Engineered Injection and Extraction for Enhanced Groundwater Remediation

Abstract

Spreading of treatment reagent into a contaminated aquifer is a key factor for determining the efficacy of an in situ groundwater remediation method. Engineered injection and extraction (EIE) is a novel method of enhancing spreading in aquifers by inducing unsteady flow fields using sequential injection and extraction of freshwater around the treatment area. Chaotic advection in response to EIE stretches and folds the contaminant–reagent interface, thereby increasing the efficiency of remediation. Several numerical simulations investigating the effect of chaotic advection in response to EIE in porous media are available in literature but are limited to two-dimensional flow conditions. Considering the three-dimensional nature of real aquifer systems, an innovative addition to the existing two-dimensional models of EIE is introduced in this study. The three-dimensional perspective of EIE was established in this study by replacing fully screened wells in conventional EIE techniques with partially screened wells, thereby performing injection and extraction at a different vertical level. Three-dimensional numerical simulation of EIE in a confined aquifer was carried out using groundwater modeling software. The effect of heterogeneity and anisotropy on spreading in aquifers in the context of EIE also was examined. Results of simulation with variable active screen depth showed a considerable increase in spreading, which was quantified here in terms of area and volume of spread. Lyapunov exponents calculated from three-dimensional simulation results showed the presence of characteristic chaotic advection in three dimensions. Real field conditions such as heterogeneity and anisotropy were found to complement the spreading due to EIE in porous media. The insights obtained from this study can provide crucial guidance for the successful and effective application of EIE in the field.