The cleanup of dioxin-contaminated sites has moved a step closer to reality. What remains to be seen, however, is how practical the technology used to decontaminate soil will turn out to be.
A treatment process was successfully tested at Times Beach, Mo., state environmental officials announced Thursday. A small machine, using intense heat, was able to reduce dioxin concentrations in soil from more than 100 parts per billion to less than 1 part per billion. At these low levels, dioxin is not considered harmful.
State officials say this technology appeared to be compatible with their cleanup efforts in Missouri, which has the most known dioxin-contaminated sites in the country. Several environmental scientists also applaud the development.
''This is the direction people would like to see,'' says Dr. Mike Kamrin, a professor of natural science at the Center for Environmental Toxicology at Michigan State University. ''You certainly would prefer not to have it (around) for someone else to deal with.''
''I'm all for anything that works,'' says Donald Crosby, a professor of environmental toxicology at the University of California at Davis. What these scientists applaud is a machine called an advanced electronic reactor. It is a demonstration model built by the J. M. Huber Corporation, a privately owned, diversified manufacturing company, based in New Jersey.
From a test plot at Times Beach - the nation's best known dioxin-contaminated site - contaminated soil was poured into the reactor, heated to between 4,000 and 5,000 degrees F., and came out as a sand-like substance.
Still, it remains to be seen how practical the technology will be.
''The reactor (will) have to be demonstrated cost effective and feasible at specific dioxin sites,'' says Fred Lafser, director of the Missouri Department of Natural Resources.
While the thermal-destruction processes are farthest along in development, scientists say it could be too costly to be practical.
''It's pretty expensive to do,'' Dr. Crosby says. ''It takes an awful lot of energy.'' The problem is that a tremendous amount of soil must be heated to process a very small amount of dioxin.
At Times Beach, for example, the Environmental Protection Agency (EPA) estimates there is roughly 150,000 cubic yards of contaminated material. It would take a Huber machine months to process the material. The costs of such a project are unknown, says Gerald Sikes, a personnel and safety manager for the technology group.
This process, already certified by the EPA for treating PCB-contaminated material, is one of many methods being experimented with to treat dioxin contamination.
Scientists say thermal-destruction processes developed so far are the best alternative to burying toxic dioxin material.
Next week, the EPA plans to move its mobile incinerator to southwest Missouri. It plans to begin testing its machine with dioxin-contaminated soil from several nearby sites, perhaps early in January.
But other methods are being experimented with that may prove much less expensive, says Joel Hirschhorn of the Office of Technology Assessment.
''Quite frankly, the people in governmental units are not that enthusiastic about this (thermal-destruction) process.''