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During in-situ remediation of contaminated groundwater, a chemical or biological amendment is introduced into the contaminant plume to react with the contaminant. Reactions occur only where the amendment and contaminant are in contact with each other, so active spreading has been proposed to increase the contact area between the two reactants. With active spreading, wells are installed in the vicinity of the contaminant plume and are operated in a pre-defined sequence of injections and extractions to create a spatio-temporally varying flow field that changes the shapes of the reactant plumes, generally leading to an increase in contact area and therefore an increase in reaction. The design of the active spreading system depends on the reaction chemistry of the contaminant. This study considers active spreading scenarios for contaminants with three different types of reactions: (1) non-sorbing aqueous contaminant, A, that degrades irreversibly to a benign chemical, C, through reaction with a non-sorbing aqueous amendment, B; (2) sorbing contaminant, A, the degrades irreversibly to a benign chemical, C, through reaction with a non-sorbing aqueous amendment, B, where sorption of A is independent of the concentration of B; and (3) contaminant, A, that exhibits reversible equilibrium surface complexation with concentrations in the mobile and immobile phases dependent on the concentration of the amendment, B. We compare the active spreading strategies for these three types of reactions and identify the characteristics each strategy that lead to enhanced removal of groundwater contaminants.
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Numerical and Experimental Investigation of Active and Passive Spreading for Groundwater Remediation
During in situ remediation of contaminated groundwater, a chemical or biological amendment is introduced into a contaminant plume to react with and degrade the contaminant. Since the degradation reactions only occur where the amendment and the contaminant are sufficiently close, the success of in situ remediation is controlled by the degree to which the amendment spreads into the contaminant plume. Spreading is defined as the reconfiguration of the plume geometry, which occurs as a result of spatially and temporally varying flow fields. Spreading can occur passively due to spatially varying velocity caused by aquifer heterogeneity. Spreading can also occur actively by inducing spatially and temporally varying flow fields through injections and extractions of clean water in wells surrounding the contaminated site. We used coupled numerical investigations and laboratory experiments to explore the effects of active spreading and passive spreading on contaminant degradation. We report here on the effects of passive spreading on contaminant degradation. We analyze the features of the flow field and plume geometry that encourage spreading contaminant degradation, so that the results from the numerical investigation and experiments can be used to design active spreading pumping sequences for other aquifers with other heterogeneity patterns.
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- Award ID(s):
- 1417017
- PAR ID:
- 10397856
- Date Published:
- Journal Name:
- 2020 World Environmental and Water Resources Congress
- Page Range / eLocation ID:
- 97 to 103
- Format(s):
- Medium: X
- Sponsoring Org:
- National Science Foundation
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- Free Publicly Accessible Full Text
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Accepted Manuscript1.0
- Conference Paper:
- https://doi.org/10.1061/9780784482964.010
