²ÊÃñ±¦µä

Piscopo, Amy ¹ ; Greene, John ² ; Neupauer, Roseanna ³ ; Kasprzyk, Joseph ⁴

¹ ²ÊÃñ±¦µä
² ²ÊÃñ±¦µä
³ ²ÊÃñ±¦µä
⁴ ²ÊÃñ±¦µä

To remediate contaminated groundwater using in situ chemical oxidation (ISCO), a chemical oxidant is injected into the aquifer to degrade the contaminant in situ. A key challenge of ISCO is to ensure that chemical oxidant is delivered throughout the contaminated region of aquifer, because without contact of chemical oxidant and contaminant (the reactants), no degradation can occur. To address this need, active spreading techniques have been developed, which involve injection and extraction at wells proximate to the contaminated region to reconfigure the reactant plumes in a manner that increases their contact. Different active spreading strategies are proposed for different types of contaminants since the reaction and sorption properties of the contaminant influence how the contaminant plume is spread in the aquifer. For instance, because aqueous contaminants move at the same velocity as groundwater, an effective strategy to increase the contact of an aqueous contaminant with an aqueous chemical oxidant is to stretch and fold the reactant plumes by injecting and extracting clean water at surrounding wells. For sorbing contaminants, which have slower transport than aqueous chemical oxidants, an effective strategy is to inject chemical oxidant into the center of the contaminant plume, causing the faster-moving plume of chemical oxidant to pass through the contaminant plume as both reactants move radially away from the injection well. In this study, we optimize these active spreading strategies for aqueous and sorbing contaminants to maximize contaminant degradation during ISCO, while minimizing factors related to project expenses. For the aqueous contaminant strategy, the size of the initial plume of chemical oxidant is optimized relative to the area encompassed by the surrounding wells used for injection / extraction. For the sorbing contaminant strategy, the mass of chemical oxidant is optimized as well as the rate and duration of its injection. Our optimization results show that effective designs of the active spreading system reflect the reaction and sorption properties of the contaminant and the initial contaminant plume size.