When Toxics Meet Metal

by Virginia Fairweather, Editor in Chief; Civil Engineering Magazine, ASCE World Headquarters, 345 East 47th Street, New York City, NY.,

Serial Information: Civil Engineering—ASCE, 1996, Vol. 66, Issue 5, Pg. 44-48

Document Type: Feature article


Zero-valent iron is an emerging remediation technology that transforms chlorinated solvents to harmless substances. Engineers and researchers have been studying the process for about five years, and there are several pilot and demonstration projects and three small full-scale applications so far. More are planned, and data collection is proceeding. So far the method has been shown to reduce hard to treat compounds such as trichloroethyene, perchloroethylene, and vinyl chloride swiftly and safely. Proponents also see low or negligible operation and maintenance costs as a major advantage, especially as compared to pump and treat methods. The zero valent iron walls are below the surface, require no surface equipment and so property can be used for other purposes. Remediation occurs as contaminated ground water flows through a subsurface permeable reactive wall of zero valent iron. The chemical reaction is somewhat like what occurs during corrosion, and in this case, as the iron oxidizes, it dechlorinates solvents, reducing them to chloride and hydrocarbons. The ground water is typically directed toward the wall, by slurry or sheet pile walls, but sometimes the plume flows to the wall without such barriers. It is still unknown how long the subsurface walls will maintain their integrity, or whether they will need maintenance or replacement periodically. Metals other than iron are also being tested. The Environmental Protection Agency is sponsoring research and demonstration projects along with the Department of Defense, and developing a design manual on the method.

Subject Headings: Iron compounds | Groundwater flow | Surface properties | Groundwater pollution | Toxicity | Metals (chemical) | Remediation | Solvents

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