"Lasagna process" field success increases DOE's interest Almost all the trichloroethylene (TCE) was removed from lowpermeability soils during the first phase of field tests of the "lasagna" in situ remediation process, according to the developer and EPA and Department of Energy (DOE) officials. The success of the field test has interested Clyde Frank, the head of DOE's Office of Technology Development, and will lead to second-phase testing and cleanup at DOE's Paducah, KY, site. Sa Ho, the Monsanto engineer who heads the project, told ES&T that the results from the first phase were promising. "We had a goal of 90% [removal]. It turned out to be much higher than that," he said. Mass balance studies from the field studies showed that, after four months, an average of 98.4% of the TCE was removed from the Paducah soils, which have a permeability of about 1 0 " cm/s, according to Ho. Starting TCE concentrations were 99% in some places. Significant amounts of TCE also were removed from the areas outlying the test boundaries. The lasagna process uses a continuous, low-voltage electric field generated between electrodes to charge contaminated water trapped in pore spaces in silts and clays. The charged water is drawn toward the electrodes and passes through vertical treatment zones, where the contaminants are captured or degraded. Ho and colleagues have published laboratory results of the process using p-nitrophenol as a model organic contaminant in kaolinite. Their work is the first peer-reviewed research published on the lasagna process (see p. 2528, this issue). In January 1994 EPA announced the signing of a cooperative research and development agreement with a consortium consisting of the Monsanto, DuPont, and General Electric companies, which provided for field demonstration of the remediation
Field technicians help place a section of a treatment zone at the Paducah, KY, test site. First-phase treatment zones removed TCE with activated carbon. Second-phase treatment zones will degrade TCE using zero-valent iron.
technique. Ho and his colleagues briefed Frank August 9 on the first-phase tests. Frank "has given us the goahead to move on with the testing," said Jef Walker, program manager of the DOE Office of Technology Development's (OTD's) Plumes Focus Area. To make the technology competitive in the remediation marketplace, Ho said the consortium must "push down the costs. We have a target of $50 per cubic yard. We were close to that [in phase one]." Technologies that clean low-permeability soils generally require excavation, removal, and treatment, and costs can run as high as $2000 per cubic yard depending on the contaminant's toxicity, Ho said. One way he hopes to reduce costs is to increase the spacing of treatment zones. These are rows of trenches filled with treatment material—activated carbon in first-phase tests—that are spaced at regular intervals between the electrodes. Second-phase testing will demonstrate in situ degradation of TCE using zero-valent iron. The site will be 30 times the size of the first-phase test site to allow
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experimental spacing of treatment zones, Ho said. The tests also will take place at Paducah. "The optimal thing is to do the demonstration, meet the performance standards, and just keep going [into cleanup operations]," Walker said. The technology is a high-priority project both for OTD and the Office of Environmental Restoration, he said. Second-phase testing is scheduled to begin this fall, and may begin as early as late October, Walker said. The researchers were concerned that because TCE is highly volatile, it might escape into the air rather than be captured by the carbon wicks. Because of the high rate of capture in the first phase, Ho said he believes in situ degradation can be accomplished in the second phase. While the consortium has been working with vertical electrodes, EPA has been researching the lasagna process using horizontal electrodes. EPA is just getting out of the lab and has no reportable results yet, said Taras Bryndzia, an EPA researcher. Currently EPA is trying to locate a site for field demonstrations, he said. —DANIEL SHANNON
