Soil Properties and Design Factors Influencing Free-Phase Hydrocarbon Cleanup
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- 作者：G. D. Beckett and and David Huntley
- 刊名：Environmental Science & Technology
- 出版年：1998
- 出版时间：January 15, 1998
- 年：1998
- 卷：32
- 期：2
- 页码：287 - 293
- 全文大小：359K
- 年卷期：v.32,no.2(January 15, 1998)
- ISSN：1520-5851
文摘
Light nonaqueous phase liquid (LNAPL) saturation andmovement in the subsurface are controlled by soilcapillarycharacteristics, permeability, and fluid properties.Wherefree-product occurs in monitoring wells, LNAPLsaturations in the formation vary significantly as afunctionof the observed thickness in the monitoring well and soiltype. Fine-grained soils generally exhibit lowerLNAPLsaturations than coarse-grained material for the sameobserved thickness in a monitoring well. MAGNAS3[MAGNAS3. HydroGeoLogic, Inc., Herndon, VA, 1992; Huyakorn, P. S.; Panday, S.; Wu, Y. S. J. Contam. Hydrol.1994,16, 190-130], a three-dimensional, finite-elementmodelthat can simulate movement of three active phases (air,water, and LNAPL), was used to investigate LNAPLrecovery in three different soil types and using severalrecovery designs to examine the effect of these factors onLNAPL recovery. The results of this analysis showthat,because the relative mobility of LNAPL decreases withdecreasing saturation and because the intrinsicpermeabilityof fine-grained soil is less than that of coarse-grainedsoil, free-product pumping or skimming has less likelihoodof success in fine-grained soil. Recovery infine-grainedsoils was minimal, with significant reductions in LNAPLsaturation occurring only within about 10-15 ft of thewell. Recovery of LNAPL in coarse-grained soils wassimulated to be much more successful, with approximately 95% of the original hydrocarbon recoveredthrough fluid pumping. The results of the modelingfurthershows that, for any soil type, recovery decreases LNAPLsaturation and mobility near the well with the effectdiminishing with distance. Therefore, a zone ofdecreasedLNAPL permeability is formed near recovery wells thatacts to impede additional recovery from greater distances.Increases in the hydraulic recovery rate (i.e., notconsideringvolatilization) can be realized in all of the soilsstudiedthrough vacuum enhanced free-product recovery.