Modeling BTEX migration with soil vapor extraction remediation under low-temperature conditions

Modeling BTEX migration with soil vapor extraction remediation under low-temperature conditions Contaminant spills in vadose zone are frequently encountered in winter, and the temperature at such times is often under 0 °C. Soil vapor extraction (SVE) is typically effective for the removal of volatile contaminants from vadose zone, but temperature influences its effectiveness. A sandbox laboratory evaluation and a TMVOC numerical model were used to investigate BTEX migration that occurred during SVE remediation processes under low temperatures. The simulation results were consistent with the experimental data obtained in the present study, and the following three conclusions were drawn. (i) The SVE removal rates of benzene, toluene, ethylbenzene, and o-xylene were 89.8%, 71.3%, 29.7%, and 14.4%, respectively. (ii) In two extraction processes, the masses of benzene and toluene in the gas–aqueous–NAPL phases decreased by approximately 20%:70%:10%, with the greatest reduction occurring in the aqueous phase. During the period between these two extraction processes, benzene and toluene migrated from the NAPL phase to the gas and aqueous phases, and their fractions were approximately 30%:70%. (iii) The results proved that under low-temperature conditions, namely −10–5 °C, the SVE removal ratio for benzene was highest among the four tested contaminants. It was therefore determined that TMVOC can provide scientific guidance for determining whether to optimize or terminate SVE operations under low-temperature conditions. http://www.deepdyve.com/assets/images/DeepDyve-Logo-lg.png Journal of Environmental Management Elsevier

Modeling BTEX migration with soil vapor extraction remediation under low-temperature conditions

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Publisher
Elsevier
Copyright
Copyright © 2017 Elsevier Ltd
ISSN
0301-4797
D.O.I.
10.1016/j.jenvman.2017.07.068
Publisher site
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Abstract

Contaminant spills in vadose zone are frequently encountered in winter, and the temperature at such times is often under 0 °C. Soil vapor extraction (SVE) is typically effective for the removal of volatile contaminants from vadose zone, but temperature influences its effectiveness. A sandbox laboratory evaluation and a TMVOC numerical model were used to investigate BTEX migration that occurred during SVE remediation processes under low temperatures. The simulation results were consistent with the experimental data obtained in the present study, and the following three conclusions were drawn. (i) The SVE removal rates of benzene, toluene, ethylbenzene, and o-xylene were 89.8%, 71.3%, 29.7%, and 14.4%, respectively. (ii) In two extraction processes, the masses of benzene and toluene in the gas–aqueous–NAPL phases decreased by approximately 20%:70%:10%, with the greatest reduction occurring in the aqueous phase. During the period between these two extraction processes, benzene and toluene migrated from the NAPL phase to the gas and aqueous phases, and their fractions were approximately 30%:70%. (iii) The results proved that under low-temperature conditions, namely −10–5 °C, the SVE removal ratio for benzene was highest among the four tested contaminants. It was therefore determined that TMVOC can provide scientific guidance for determining whether to optimize or terminate SVE operations under low-temperature conditions.

Journal

Journal of Environmental ManagementElsevier

Published: Dec 1, 2017

References

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