The patent-pending technique, which uses a macroemulsion composed of alcohol and food-grade surfactants, simultaneously reduces the density of the pollutant to keep it from sinking farther into the groundwater and helps separate it from soil particles so it can be flushed out. Known as "density modified displacement," the approach could cut the cost of environmental remediation by reducing both the time required for clean up and the amount of contaminated effluent that must be treated.
The technique was reported in the August 15 online version of the journal Environmental Science and Technology, and will be published in the journal's September 15th print issue. Researchers from the Georgia Institute of Technology, the University of Michigan and the University of Oklahoma participated in the research, which was sponsored by the U.S. Environmental Protection Agency (EPA).
"We're trying to make remediation of contaminated groundwater more efficient, because it is now largely driven by economics," said Kurt Pennell, an associate professor in Georgia Tech's School of Civil and Environmental Engineering. "The idea is to make this process so efficient that the cost of cleaning up a site is less expensive than traditional approaches which rely on groundwater extraction and long-term monitoring."
The technique offers a new approach to removing dense nonaqueous phase liquids (DNAPLs), including tetrachloroethane (PCE), trichloroethene (TCE) and chlorobenzene (CB), heavier-than-water compounds. Relatively stable chemicals that don't readily degrade, their concentrations in groundwater must be kept to a few parts-per-billion (ppb) to meet environmental standards.