An Assessment of Conventional In Situ Air Sparging Pilot Tests

Johnson, Paul C.; Johnson, Richard L.; Neaville, Christopher; Hansen, Erik E.; Stearns, Steve M.; Dortch, Ira J.

doi:10.1111/j.1745-6584.1997.tb00145.x

Cited by 23 publications

(14 citation statements)

References 9 publications

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“…In fact, Johnson et al (1997), using SF 6 gas, were able to show that in a fine sand with interbedded clayey silts, air movement was predominantly lateral, and this lateral migration continued until a monitoring well was intersected. In this simulation, air movement was also mostly through the coarse layers, but it did not significantly impact the desiccation process.…”

Section: 19mentioning

confidence: 99%

Experimental and Numerical Investigations of Soil Desiccation for Vadose Zone Remediation: Report for Fiscal Year 2007

Ward¹,

Oostrom²,

Bacon³

2008

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SummaryApart from source excavation, the options available for the remediation of vadose zone metal and radionuclide contaminants beyond the practical excavation depth (0 to 15 m) are quite limited. Of the available technologies, very few are applicable to the deep vadose zone with the top-ranked candidate being soil desiccation. An expert panel review of the work on infiltration control and supplemental technologies identified a number of knowledge gaps that would need to be overcome before soil desiccation could be deployed. The report documents some of the research conducted in the last year to address some of these knowledge gaps. This work included 1) performing intermediate-scale laboratory flow cell experiments to demonstrate the desiccation process, 2) implementing a scalable version of Subsurface Transport Over Multiple Phases-Water-Air-Energy (STOMP-WAE), and 3) performing numerical experiments to identify the factors controlling the performance of a desiccation system.Four laboratory experiments were conducted in an intermediate-scale flow cell to demonstrate the desiccation process and assess the impact of the energy balance on the desiccation process. One of the experiments was performed in homogeneous medium-grained sand, while the rest of the simulations were completed in a heterogeneous system with an inclusion of a fine-grained sand zone and varying levels of external insulation. Evaporative cooling was observed in the experiments and generally decreased with increased distance from the gas inlet chamber. Observations of temperature in fine-grained sands in the heterogeneous systems show two local minima associated with the cooling because of evaporation in the adjacent medium-grained sand whereas the second is attributed to evaporative cooling in the fine-grained sand itself. The occurrence of these temperature minima coincided with passage of the desiccation front. Results of the laboratory tests are consistent with the theory showing that the injection of air leads to significant temperature and moisture changes in the porous medium. In all the experiments, the injection of dry air proved to be an effective means for removing essentially all moisture from the test media. The results of this study provide a unique data set that will be used to calibrate the STOMP code for use in the designs of field-scale desiccation systems.To aid in the design and evaluation of desiccation technologies, STOMP-WAE-B has been enhanced with the addition of gas injection/withdrawal wells. The upgraded version of STOMP-WAE-B is now available for scalable execution on multiple processor (i.e., parallel) computers. The parallel version of the simulator is written in pure FORTRAN 90 with embedded directives that are interpreted by a FORTRAN preprocessor. Without the preprocessor, the scalable version of the simulator can be executed sequentially on a single processor computer. The scalable version of the simulator is designated as STOMP-WAE-B-Sc and is expected to find applications in the design and optimization of ...

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Section: 19mentioning

confidence: 99%

Experimental and Numerical Investigations of Soil Desiccation for Vadose Zone Remediation: Report for Fiscal Year 2007

Ward¹,

Oostrom²,

Bacon³

2008

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“…At some sites (e.g., HAFB) the helium tracer tests can identify "red flags" that may result in IAS not being used at the site. Finally, while the helium tests are very useful as stand-alone measurements, their diagnostic value is significantly increased when they are used in combination with the other diagnostic tools described in this issue (Johnson, 2001a;b;c) …”

Section: Discussionmentioning

confidence: 98%

“…It is usually assumed that if subambient soil-gas pressures are measured throughout the treatment area, then contaminant vapors are being captured. However, the fieldwork of Johnson et al (1997) demonstrated that this approach does not ensure capture of the contaminant vapors. For example, a stratum present below the water table may cause the injected air to migrate laterally away from the IAS system and outside the SVE capture zone before it emerges from the saturated zone.…”

Section: Introductionmentioning

confidence: 94%

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Helium Tracer Tests for Assessing Contaminant Vapor Recovery and Air Distribution During In Situ Air Sparging

Johnson

et al. 2001

Bioremediation Journal

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Helium tracer tests are used as an alternative to soil-gas pressure measurements to assess the effectiveness of soil vapor extraction (SVE) systems for capturing contaminant vapors liberated by in situ air sparging (IAS). The tracer approach is simple to conduct and provides more direct and reliable measures than the soil-gas pressure approach. The tracer test described here can be used to both determine SVE system capture efficiency and to evaluate air distribution during IAS pilot tests. The tests can also be conducted on operating, full-scale systems to confirm system performance. In addition, the tests can be easily repeated, which allows system parameters to be modified and the impact of those modifications to be quickly assessed. Whether used alone or in conjunction with other diagnostic tools, helium tracer tests provide an important measure of IAS system performance.

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“…While these approaches evaluate volatilization or oxygen delivery, they do not demonstrate whether biodegradation of specific compounds is occurring. Assessing treatment performance based on DO concentrations can be unclear and misleading, as low DO concentrations can be due to poor air distribution (Johnson et al ; Johnston et al ) or consumption during aerobic biodegradation (Kao et al ). A mass balance approach relying on VOC and CO 2 fluxes may be suitable to assess the overall contaminant mass that has volatilized or biodegraded (Aelion and Kirtland ); however, the relative importance of the removal processes for specific contaminants of concern, such as benzene, are not determinable from such data.…”

Section: Introductionmentioning

confidence: 99%

Diagnostic Tools to Assess Mass Removal Processes During Pulsed Air Sparging of a Petroleum Hydrocarbon Source Zone

Bouchard¹,

Marchesi²,

Madsen³

et al. 2018

Groundwater Monitoring Rem

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During remediation of contaminated aquifers, diagnostic tools can help evaluate whether an intended mass removal process was successfully initiated and acted on specific contaminants of concern. In this study, several diagnostic tools were tested in a controlled‐release in situ air sparging experiment that focused on the treatment of target hydrocarbons (e.g., benzene, toluene, ethylbenzene, and xylenes). The tools included compound‐specific isotope analysis (CSIA), expression of functional genes (mRNA), and metabolites characteristic of aerobic and anaerobic biodegradation. Total and compound‐specific mass balances were established and used, along with traditional monitoring parameters, to validate the results from the various tools. CSIA results indicated biodegradation as the main process contributing to benzene and toluene removal. Removal process‐specific isotope shifts were detected in groundwater as well as in the system effluent gas. CSIA, metabolite, and mRNA biomarkers consistently indicated that both aerobic and anaerobic biodegradation of benzene and toluene occurred, but that their relative importance evolved over time and were related to the treatment system operation. While the indicators do not allow quantification of the mass removed, they are particularly useful to identify if a removal process has been initiated, and to track relative changes in the predominance of in situ contaminant attenuation processes resulting from remediation efforts.

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An Assessment of Conventional In Situ Air Sparging Pilot Tests

Cited by 23 publications

References 9 publications

Experimental and Numerical Investigations of Soil Desiccation for Vadose Zone Remediation: Report for Fiscal Year 2007

Experimental and Numerical Investigations of Soil Desiccation for Vadose Zone Remediation: Report for Fiscal Year 2007

Helium Tracer Tests for Assessing Contaminant Vapor Recovery and Air Distribution During In Situ Air Sparging

Diagnostic Tools to Assess Mass Removal Processes During Pulsed Air Sparging of a Petroleum Hydrocarbon Source Zone

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