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7 - Understanding subsurface contamination using conceptual and mathematical models
- Edited by John A. Wiens
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- Book:
- Oil in the Environment
- Published online:
- 05 July 2013
- Print publication:
- 18 July 2013, pp 144-175
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Summary
Introduction
Petroleum spills and other sources of hydrocarbon contamination represent risks for society. Regardless of whether oil is stranded on a shoreline, spilled from a pipeline, or leaked from underground storage tanks, the same basic physical and chemical principles characterize exposure levels of contaminants. The purpose of this chapter is to explain and illustrate these principles. In particular, we use these principles to explain the apparent paradox of how oil residues persist at some shorelines of Prince William Sound (PWS) as isolated subsurface patches, but yet pose little if any exposure risk to the local ecology. We resolve this apparent paradox using well-established scientific and engineering tools.
One of the biggest challenges of any study of a contaminated site is identifying the most important questions and the most important observations and data needed to answer these questions. This challenge is discussed in this chapter in both a general way and for the PWS study in particular. One of the key lessons learned from this study was the need for experts in multiphase flow in contaminated sediments to be a central part of the team addressing these questions. Our goal is to convey a coherent understanding and perspective that brings all of the observations and measurements by various environmental experts of different scientific disciplines into a consistent explanation.
11 - Surfactant Enhanced Aquifer Remediation
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- By Varadarajan Dwarakanath, Center for Petroleum and Geosystems Engineering, The University of Texas at Austin, Austin, TX 78712, Gary A. Pope, Duke Engineering and Services, Inc., Austin, TX
- Edited by Laurier L. Schramm, Petroleum Recovery Institute, Calgary, Canada
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- Book:
- Surfactants
- Published online:
- 29 October 2009
- Print publication:
- 23 March 2000, pp 433-460
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Summary
The use of surfactants to remediate groundwater contaminated by nonaqueous phase liquids has been under investigation and field testing since at least the 1980s. Surfactant enhanced aquifer remediation (SEAR) is especially important for dense nonaqueous phase liquids such as chlorinated solvents because they are difficult to remediate and because there are few good alternatives to SEAR to remove these contaminants from groundwater. The technology has continued to improve and recent field demonstrations at superfund sites have shown that under certain conditions very favorable results can be obtained with SEAR. Some of these advances can be attributed to the adaptation of technology developed for surfactant enhanced oil recovery over the past 30 years. The emphasis on phase behavior for screening and evaluating surfactants is especially noteworthy and important. In this chapter, we first briefly review the phase behavior of surfactants when mixed with organic liquids of interest, and then give a detailed example of a study done at the University of Texas to further evaluate surfactant candidates in soil column tests in the laboratory.
Introduction
The contamination of groundwater by nonaqueous phase liquids (NAPLs) is a cause for concern throughout the world. NAPLs can be classified by their density as those lighter than water (LNAPLs) and denser than water (DNAPLs). NAPLs migrate into aquifers because of gravity and capillary forces and may be trapped in the form of immobile blobs or ganglia or when present in sufficient volume DNAPLs may form pools above aquitards.