DNAPL

Application of in situ thermal remediation technologies for DNAPL removal.

Nahold, "Biogeochemical gradients above a coal tar DNAPL," Science of the Total Environment, vol.

Field and laboratory evaluation of the treatment of DNAPL source zones using emulsified zero-valent iron.

L., 2000, "Biologically Enhanced Dissolution of Tetrachloroethene DNAPL," Environ.

Once below ground, it is "difficult or impossible to recover all of the trapped residual DNAPL," EPA says.

For the last few years, crews have been removing 75 to 100 gallons of DNAPL every month, and the cleanup will continue indefinitely.

The hydrophilic properties of nZVI enable the remediation of aqueous-phase contaminants, including DNAPLs. Because the addition of nZVI in the source zone reduces" contaminants, it increases the concentration gradient between the aqueous phase and DNAPLs, thereby increasing the mass transfer of contaminants from DNAPLs to the dissolved aqueous phase, where they are then treated (Watlington 2005).

Several DNAPL source zone characterization tools have been developed and demonstrated in the last few years (ITRC 2003).

A number of innovative technologies have been developed to enhance contaminant removal from DNAPL source zones [National Research Council (NRC) 1994, 1997, 1999).

No pools of free DNAPL were obvious within the TCE-treated columns.

Chlorinated solvent contamination is common in groundwater systems, resulting from subsurface accumulations of immiscible solvents which are part of a larger group of Dense Non-Aqueous Phase Liquids known as DNAPLs. Trichloroethylene (TCE; [C.sub.2][Cl.sub.3]H) and tetrachloroethylene (also known as perchloroethylene or PCE; [C.sub.2][Cl.sub.4]) are two of the most widely used solvents.

For example, contaminants such as dense nonaqueous-phase liquids (DNAPLS) may move through fractures with little or no retardation (Kueper and McWhorter 1991), whereas other contaminants may be strongly sorbed onto fracture walls and enter matrix materials by diffusion.