CHAOTIC ADVECTION AND CONTAMINANT DEGRADATION DURING ENGINEERED INJECTION AND EXTRACTION IN HETEROGENEOUS POROUS MEDIA

During in situ remediation of contaminated groundwater, a treatment solution is often injected into the contaminated area to initiate reactions that degrade the contaminant. Since the degradation reactions only occur where the treatment solution and the contaminated groundwater are in contact with each other, the success of in situ remediation relies on spreading the treatment solution into the contaminated area. Engineered injection and extraction (EIE) is an approach that induces spreading during in situ remediation by sequentially injecting and extracted uncontaminated water in wells surrounding the contaminated area to create unsteady flow fields that promote plume spreading. The EIE system can be designed to generate chaotic advection, which is known to enhance spreading in laminar flows. Spreading also occurs naturally in heterogeneous porous media; in this case, spreading can be enhanced by both the chaotic advection and the heterogeneity. Through numerical simulations, we investigate the chaotic behavior of EIE-induced flows in heterogeneous porous media. To represent heterogeneity, we use random fields of transmissivity with known statistical properties. We investigate the effects of chaotic advection on plume spreading and on the amount of contaminant that is degraded. We demonstrate that as the degree of heterogeneity increases, the amount of plume spreading and the amount of contaminant mass that is degraded both increase, thereby improving the success of in situ remediation.