Dense nonaqueous phase liquids DNAPLs

Besides petroleum products, other hazardous substances (see Tables 18.7-18.9) are also stored in USTs. Among them, a common and important group is the dense nonaqueous phase liquids (DNAPLs). This group has some different physical properties from petroleum (especially gasoline) that make them behave differently in the way they move underground. This section presents the important factors associated with the cleanup of DNAPLs. 

In Situ Density Modification of Entrapped Dense Nonaqueous-Phase Liquids (DNAPLs) using Surfactant/Alcohol Solutions... 

Dense nonaqueous-phase liquids (DNAPLs) are widespread at contaminated sites, where they are often distributed deep in aquifers due to their high densities [US EPA, 1993], Surfactant-based remediation techniques have the potential to be very effective at removing DNAPLs from contaminated sites (e.g., [Pennell, et al., 1994 Baran, et al., 1994 Pennell, etal., 1997 Zimmerman, et al., 1999]). However, one risk associated with surfactant-based remediation of DNAPLs is the potential for unwanted... 

Kibbey, T. C. G. Ramsburg, C. A. Pennell, K. D. Hayes, K. F. Effects of Surfactant Properties on Equilibrium and Non-equilibrium Alcohol Partitioning into Dense Nonaqueous-Phase Liquids (DNAPLs) for In Situ Density Modification Applications, presented at the Fall American Geophysical Union national meeting, San Francisco, California, December, 1998. 

The contaminant s aqueous solubility and density greatly influence its final disposition in water-solid systems. Dense nonaqueous phase liquids (DNAPLs) are chemicals with densities greater than water and typically low aqueous solubilities. DNAPLs naturally partition away from the aqueous phase and towards the solid phase, often pooling on top of an impermeable solid layer. On the other hand, light nonaqueous phase liquids (LNAPLs) possess densities less than water and have a tendency to pool on the water s surface where they may be prone to volatilization and photolysis reactions. Various liquid-solid partition coefficients have been... 

The system has two phases an excess oil phase and a water-external microemulsion phase. Because microemulsion is the aqueous phase and is denser than the oil phase, it resides below the oil phase and is called a lower-phase microemulsion. At a high salinity, the system separates into an oil-external microemulsion and an excess water phase. In this case, the microemulsion is called an upper-phase microemulsion. At some intermediate range of salinities, the system could have three phases excess oil, microemulsion, and excess water. In this case, the microemulsion phase resides in the middle and is called a middle-phase microemulsion (Healy et al., 1976). Such terminology is consistent with their relative positions in a test tube (pipette) with the water being the dense liquid. In the environmental sciences and engineering, however, a dense nonaqueous phase liquid (DNAPL) could be denser than water (UTCHEM-9.0, 2000). Fleming et al. (1978) used y, P, and a to name the lower-phase, middle-phase, and upper-phase microemulsions, respectively. 

Holzmer, F.J., Pope, G.A. andYeh, L. (2000) Surfactant-enhanced aquifer remediation of PCE-DNAPL in low permeability sands. In G.B. Wickramanayake, A.R. Gavaksar and N. Gupta (eds), Treating Dense Nonaqueous Phase Liquids (DNAPLs) Remediation of Chlorinated and Recalcitrant Compounds. Battelle Press, Columbus, OH, pp. 187-193. 

Dense nonaqueous phase liquids (DNAPLs) are the chlorinated organic compounds that have a density higher than water. Because of this unique property, DNAPLs will pass through the vadose zone and contaminate groundwater. Some reside in... 

Successfiil inq>lemeiitation of such an approach would considerably reduce both the time and cost of in situ biotreatment. Pretceating groundwaters with sonication techniques would form VOCs that could be removed effectively by either bioremediation technologies or a dual vapor extraction technique (developed by Stanford University under the VOC-Arid Program, now part of Plumes Focus Area). Sonication could also be coupled widi technologies aimed at mobilizing dense nonaqueous phase liquids (DNAPLs) in the subsur ce, such as surfactant floodii. ... 

Nonaqueous-Phase Liquid. (NAPL) Any liquid other than water. In environmental fields the term commonly refers to hydrocarbon liquids less dense than water (light nonaqueous-phase liquid, LNAPL), or chlorinated hydrocarbons that are more dense than water (dense nonaqueous-phase liquid, DNAPL). Example 1,1,1-trichloroethane is a DNAPL. 

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