Cost-Effective Approach has Potential for Wide Use
Researchers have removed up to 99 percent of trichloroethylene from contaminated soil during the first field tests of an innovative remediation method called Lasagna™ technology, which uses electrical current fed to electrodes buried in the ground.
Trichloroethylene is used for cleaning and degreasing metal, in the production of rubber and plastics, in dry cleaning processes and in household solvents. It has been associated with a possible increased risk of cancer in people.
The tests exceeded the researchers' expectations for remediation of the soil, according to two related research articles in the April 1 print edition of the peer-reviewed journal Environmental Science & Technology, published by the American Chemical Society, the world's largest scientific society.
Scientists from Monsanto, General Electric and DuPont describe the Lasagna technology as "very successful" and claim it is cost-effective in cleaning up trichloroethylene-contaminated soil in place. The research was initially published on the journal's web site Feb. 25.
Called "lasagna" because of the layered placement of 'treatment zones' within the buried electrodes, "the technology utilizes an electrical current to drive contaminants from soil into in situ treatment zones for destruction," says the report's lead author, Sa V. Ho, Ph.D., of the Monsanto Company in St. Louis, Mo. Doing the treatment in place, rather than moving it to a central remediation site, means "the technology has minimal disturbance to the environment, generates no waste, can be cost-effective and has the potential for wide application," he claims.
Applying electricity to the electrodes, which were buried up to 45 feet deep in the larger of two field tests that were conducted, causes water in the soil to move toward the electrodes and into the treatment zones where iron filings mixed with clay destroy (dechlorinate) the trichloroethylene carried by the water. All the materials used in the electrodes and treatment zones "are innocuous to the environment and are designed to be left in place after the cleanup is completed," claims the research article.
The Lasagna testing, done in collaboration with the U.S. Department of Energy and the U.S. Environmental Protection Agency, was conducted at the Paducah Gaseous Diffusion Plant in Paducah, Ky., which produces enriched uranium. The U.S. Department of Energy, original owner of the plant, is responsible for environmental restoration of the plant's land, consisting mostly of low permeability clay that is "very difficult to treat with other technologies," notes Ho.
Kentucky officials initially had called for concentrations of trichloroethylene in the soil at the Paducah site, which ranged as high as 300 parts per million (ppm) prior to the Lasagna treatment, to be reduced to no more than five ppm. Following treatment, the contamination levels were as low as 0.2 ppm in some cases.
Lasagna treatment should range from $45 to $80 per cubic yard for contaminated sites of about one acre, compared to $200 to $1,000 for traditional excavation and incineration treatment, says Ho.
A nonprofit organization with a membership of nearly 159,000 chemists and chemical engineers, the American Chemical Society publishes scientific journals and databases, convenes major research conferences, and provides educational, science policy and career programs in chemistry. Its main offices are in Washington, D.C., and Columbus, Ohio.
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