Defining the air sparging radius of influence for groundwater remediation

McCray, John E.; Falta, Ronald W.

doi:10.1016/0169-7722(96)00005-8

Cited by 67 publications

(31 citation statements)

References 20 publications

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“…Since the gas fills the largest pores within a channel, that the gas permeability where gas is present will be well approximated by the gas-saturated value. This concept is quite distinct from the continuum approach used to describe gas sparging (e.g., McCray and Falta, 1996), wherein subtle changes in gas saturation are highly influential to local gas permeability. One particular manifestation of this difference is the predicted variation in pressure in the resident fluid.…”

Section: Continuum Scale Flowmentioning

confidence: 99%

The Local Geometry of Gas Injection into Saturated Homogeneous Porous Media

et al. 2006

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The injection of gases into liquid saturated porous media is of theoretical and practical interest (e.g., air sparging for the removal of volatile organic compounds from contaminated aquifer sediments). The influence of the rate of gas delivery and the vertical distance from the source are developed. The concept of a "near-injection region" is presented in which the pressure gradients exceed buoyant gradients and thus exhibits largely radial flow. The near-injection size is shown to have an area required to carry the injected gas flow under unit gradient. The parabolic movement of gas outside of this area which has often been observed is explained as reflecting the sum of many realizations of gas channels following random lateral movements as they precede upward independent of flux. These concepts are confirmed through comparison with published and experimental data of air injection into slabs consisting of saturated sands of a range of textures.

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Section: Continuum Scale Flowmentioning

confidence: 99%

The Local Geometry of Gas Injection into Saturated Homogeneous Porous Media

et al. 2006

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“…It is possible to estimate the air-sparging gas velocity and gas saturation by considering a one-dimensional vertical gas flow at steady state. When an air-sparging system is at steady state, the water within the sparge zone is essentially static [McCray and Falta, 1996 …”

Section: Saturations During Air Spargingmentioning

confidence: 99%

Numerical modeling of kinetic interphase mass transfer during air sparging using a dual‐media approach

Falta¹

2000

Water Resources Research

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Abstract. A dual-media multiphase flow approach is proposed for modeling the local interphase mass transfer that occurs during in situ air sparging. The method is applied to two-or three-phase flow in porous media to simulate the small gas channels that form during air sparging, allowing resolution of the local diffusive mass transfer of contaminants between the flowing gas phase and nearby stagnant liquid-filled zones. This approach provides a good match with laboratory column experiments in which dissolved trichloroethylene (TCE) is removed by air sparging, and it is shown that the simulation results are very sensitive to the nature of the local mass transfer regime. The numerical model is then applied to hypothetical field air-sparging cases involving either a dissolved plume of TCE or a TCE nonaqueous phase liquid source. In these simulations the local mass transfer appears to play a much smaller role than in the laboratory-scale tests, and significant deviations from local equilibrium simulations only occur when the mass transfer rates are reduced below the calibrated laboratory-scale values.

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“…ROI, one of the key factors in designing an IAS system, can be estimated as a pre-selected gas saturation level, gas pressure, or gas-species concentration based on the contaminated-site conditions . The most common method to estimate ROI is to use the gas-phase saturation profiles in field applications (McCray and Falta 1996).…”

Section: Multiphase Flow and Contaminant Removal Using Single Injectimentioning

confidence: 99%

“…The outcome of IAS modeling may lead to the design of more efficient IAS systems and in solving problems that may occur during an IAS application (Benner et al 2002). Published numerical studies on IAS point toward several important processes associated with IAS including air movement and mass transfer between phases (McCray and Falta 1996;Mei et al 2002;Unger et al 1995;van Dijke et al 1995). However, dynamic flow of gas and water and its impact on contaminant migration and removal in a three-dimensional subsurface environment have not been studied in sufficient detail, the understanding of which is essential to determine the applicability of the IAS and to the design of an optimal operation of an IAS system at a contaminated site.…”

Section: Introductionmentioning

confidence: 99%

Multiphase Flow Fields in In-situ Air Sparging and its Effect on Remediation

Jang

Aral

2008

Transp Porous Med

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In-situ air sparging (IAS) is used for the clean-up of soil and groundwater that are contaminated with volatile organic compounds in relatively permeable subsurface environments. In this study, we investigated the secondary groundwater and gas flow fields that develop in the vicinity of single and multiple air sparging wells. The purpose is to evaluate their effects on contaminant plume migration and thus, remediation. Governing equations describing multiphase flow and contaminant transport in a three-dimensional domain were formulated and solved using the Galerkin finite element technique. Trichloroethylene was selected as a target contaminant. The increase in air injection contributed to an increase in the size of the IAS cone of influence and the gas saturation levels within the cone. This reduced the groundwater velocity within the cone and increased the zone of detour of groundwater around the air sparging wells. This outcome was quantified and compared under several IAS operations. Different soil permeability characteristics also affected the groundwater and gas flow patterns, and this impacted the remedial performance of the IAS system. Under high ambient groundwater velocity, an air sparging system that uses a single injection well caused the detour of contaminant plumes around injection wells, regardless of air injection rates, and failed to meet the remedial goal specified here. This system was successful for relatively low ambient groundwater velocity environments used here. An IAS system with multiple injection wells was effective in capturing and remediating the detoured contaminant plume, and showed superior performance when compared to a single injection well IAS system. Using IAS simulation, we also analyzed the impact of injection rates on site remediation using single or multiple wells. Design criteria that are based on the results of this study would be useful in enhancing the performance of the IAS systems.

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Defining the air sparging radius of influence for groundwater remediation

Cited by 67 publications

References 20 publications

The Local Geometry of Gas Injection into Saturated Homogeneous Porous Media

The Local Geometry of Gas Injection into Saturated Homogeneous Porous Media

Numerical modeling of kinetic interphase mass transfer during air sparging using a dual‐media approach

Multiphase Flow Fields in In-situ Air Sparging and its Effect on Remediation

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