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Surfactant-Enhanced Aquifer Remediation: Fundamental Processes and Practical Applications
Published in Subhas K. Sikdar, Robert L. Irvine, Fundamentals and Applications, 2017
Kurt D. Pennell, Linda M. Abriola
The most recalcitrant remediation scenarios addressed by regulatory agencies often involve aquifers containing organic compounds existing as a separate liquid phase or nonaqueous phase liquid (NAPL). Classic examples of NAPLs include chlorinated solvents, such as trichloroethylene (TCE), and petroleum-based products, such as gasoline. Upon entering the unsaturated zone, NAPLs will migrate downward as a result of gravitational and capillary forces. If the volume of NAPL released to the subsurface is sufficient to reach the water table, an organic liquid that is more dense than water (DNAPL) will tend to migrate vertically through the saturated zone until a confining or low-permeability layer is reached (Figure 1). In contrast, an NAPL that is less dense than water (LNAPL) will tend to spread laterally within the capillary fringe, forming a “lens” of free product. Subsequent fluctuations in the water table, however, may result in vertical displacement of the LNAPL lens and consequent redistribution within the saturated zone. The overall distribution of an NAPL within an aquifer formation may be extremely complex due to the presence of small- and large-scale heterogeneities and temporal flow variations.
Contaminant Transport and Behavior in the Subsurface
Published in David J. Wilson, Ann N. Clarke, Hazardous Waste Site Soil Remediation, 2017
James H. Clarke, Danny D. Reible, Robert D. Mutch
Nonaqueous-phase liquids (NAPLs) are organic liquids that are relatively insoluble in water. Nonaqueous-phase liquids are typically differentiated into two classifications. Nonaqueous-phase liquids with densities less than that of water are referred to as light nonaqueous-phase liquids (LNAPLs). Examples include gasoline, kerosene, jet fuel, and nonchlorinated industrial solvents such as benzene and toluene. Nonaqueous-phase liquids with densities greater than that of water are referred to as dense nonaqueous-phase liquids (DNAPLs). Examples include chlorinated solvents such as trichloroethylene, methylene chloride, trichloroethane, and dichlorobenzene. LNAPL and DNAPL materials behave very differently in the subsurface environment.
The Use of Surfactants to Enhance Pump-and-Treat Processes for In Situ Soil Remediation
Published in Donald L. Wise, Debra J. Trantolo, Remediation of Hazardous Waste Contaminated Soils, 2018
Nonaqueous phase liquids (NAPLs) are hydrophobic organic compounds that are slightly soluble or immiscible in water. Examples of NAPLs include chlorinated organics (trichloroethylene (TCE), tetrachloroethylene (PCE), 1,1,1-trichloroethane (TCA), polychlorinated biphenyls (PCBs), pesticides, and pentachlorophenol (PCP)) polynuclear aromatics, creosote, and other long-chain hydrocarbons. NAPLs are widely used compounds and frequent contaminants of soil and water. Because of the chemical stability, ecological persistence, and low water solubility of NAPLs, the potential for extensive long-term contamination of groundwater from contaminated sites is high. In the subsurface, NAPLs act as in situ sources of contamination as the chemicals slowly leach into the groundwater.
Use of GreenZyme® for remediation of porous media polluted with jet fuel JP-5
Published in Environmental Technology, 2020
Valentinos Loukopoulos-Kousis, Constantinos V. Chrysikopoulos
Subsurface contamination by non-aqueous phase liquids (NAPLs), as a result of accidental spills of hydrocarbons from leaking tanks, disposal dumps, and pipelines, is a serious and widespread problem, which has been explored by numerous investigators [1–16]. Entrapped or residual light non-aqueous phase liquid (LNAPL) or dense non-aqueous phase liquid (DNAPL) in subsurface formations may exist in the form of ganglia or pools and they are long-lasting sources of contamination [17,18]. The NAPLs can be classified into two major categories: (i) chlorinated industrial solvents (e.g. trichloroethylene or TCE), and (ii) petroleum fluids (e.g. jet fuel). Understanding the behaviour of NAPLs in the subsurfce is esential for the appropriate design of efficient recovery and remediation methodology.
Remediation of organic contaminated soil by Fe-based nanoparticles and surfactants: a review
Published in Environmental Technology Reviews, 2023
Kien A. Vu, Catherine N. Mulligan
Organic compounds can be identified by their toxicity, classified in the ‘priority pollutants’ list of the US Environmental Protection Agency (EPA). The liquid organic contaminants existing as a separate phase in aqueous media are named nonaqueous phase liquids (NAPLs). NAPLs can be classified as dense nonaqueous phase liquids (DNAPLs), e.g. carbon tetrachloride, chlorophenols, PCBs) and light nonaqueous phase liquids (LNAPLs) (e.g. gasoline, heating oil, jet fuel), which are denser and lighter than water, respectively. Because of the interfacial forces, part of NAPLs will be retained as the immobile ganglia or globules within the soil pores when moving through the subsurface [3].
Effect of salt and NAPL on electrical resistivity of fine-grained soil-sand mixtures
Published in International Journal of Geotechnical Engineering, 2018
Prabir K. Kolay, Sandeep Goud Burra, Sanjeev Kumar
Corwin and Lesch (2003) explain different pathways of current flow in soils. Ross et al. (1990) uses electrical resistivity and imaging system of the underground soil to determine the contaminants, the location of contamination sources and the leakage of leachate. Adepelumi et al. (2006) investigated the feasibility of using the electrical resistivity method for detecting and monitoring of light non-aqueous phase liquid (LNAPL), diesel fuel, spilled or leaked into a clayey sand formation. These days, environmental pollution due to oil spillage or other chemicals remains a major problem of global environmental concern due to the exploration, production and marketing activities of various petroleum and chemical producing companies. Also, other sources of the oil spills include leakage from underground storage tanks, leakage from corroded pipelines, etc. Another current concern is the spilled and entrapped non-aqueous liquid phase (NAPL) pollutants which constitute one of the biggest problems in the bioremediation efforts of contaminated soil and aquifers worldwide. The task of locating and quantifying the amount of light NAPL present in the soil and its subsequent degradation in soils has presented significant challenges to scientists and engineers involved in soil cleanup and remediation (Davis et al.1993). The continuous spillage of classes of contaminants those are deleterious to the health of host communities and the groundwater for that particular region. These contaminants are usually present as light non-aqueous phase liquids (LNAPL’s) and dense non-aqueous phase liquids (DNAPL’s). The presence of such organic contaminants in significant concentrations often poses a severe threat to soils and groundwater aquifers. This in turn can create a serious hazard to public health and the environment, since such contamination will more or less disrupt the ecosystem in the vicinity of the contaminated sites. Their migration appears to be associated with rainfall, seasonal variations and the hydrologic gradient in the area and also on soil nature. Electrical methods are very useful geophysical techniques in the detection and monitoring of immiscible contaminants in porous soils and rocks due to the large difference in electrical properties between the groundwater and contaminants (Schneider and Greenhouse 1992).