NEWS TECHNOLOGY Bioremediation consortium to tackle chlorinated solvents What experts say are some of the most robust techniques for in situ bioremediation of chlorinated solvents will be demonstrated over the next five years at federal facilities. On August 9 EPA announced a collaboration with the Department of Energy, U.S. Air Force, and a consortium of manufacturers: Monsanto, Dow, DuPont, General Electric, Ciba, and Zeneca Inc. The consortium will demonstrate intrinsic and accelerated anaerobic bioremediation for chlorinated solvents, specifically tetrachloroethylene (PCE) and trichloroethylene (TCE), in groundwater and cometabolic bioventing for TCE in subsurface soils. The demonstration will take place at Dover Air Force Base and an undetermined federal facility. The project will cost about $13 million to $15 million over five years. EPA's cost will be only about $1 million, said Larry Fradkin, Federal Technology Transfer Act Coordinator for EPA's Office of Research and Science Integration. The demonstration will conduct a three-pronged attack on chlorinated compounds, according to Greg Sayles, the EPA engineer overseeing the project. In a chlorinated solvent spill, much of the contaminant passes through the unsaturated zone into the groundwater where it concentrates into a highly contaminated source area and begins to disperse into a low-concentration plume, Sayles said. The emphasis will be to "cut the heart out of a plume," said Dave Ellis, a senior consultant with DuPont and chair of the consortium. Intrinsic bioremediation will be used in the low-concentration plume area, Sayles said. Simultaneously, using accelerated anaerobic bioremediation, "we hope to generate more anaerobic activity by introducing nonhazardous substrate into the groundwater," in the source area. "What we hope to show is that the plume is not going anywhere," he said. The consortium also will use cometabolic bioventing for soil
plumes. In this method, air and a gaseous food source, such as methane, are injected into the unsaturated zone. As bacteria metabolize the food source, "TCE gets caught up in the metabolic process," Sayles said. Chlorinated contaminants are widespread; nearly 80% of Superfund sites and all Department of Energy (DOE) sites are contaminated in part by mem, according to EPA and DOE sources. DOE will fund demonstrations of two of the three techniques, according to DOE's Jef Walker, program manager of the Plumes Focus Area at the Office of Technology Development. DOE's interest lies in the accelerated anaerobic method, which Walker said "is the best thing for high concentrations of chlorinated solvents." DOE would like to see it used widely at its cleanup sites. If the demonstrations successfully prove the methods, "there will be a big impact on a national level, especially concerning the demonstration of the intrinsic bioremediation," said Ellis. Intrinsic bioremediation of hydrocarbons already is widely accepted, he said, adding that he expects the same for chlorinated compounds in the near future. Intrinsic bioremediation is a passive method that requires accurate
prediction and monitoring. "It is not a 'do nothing' approach," Ellis said. The cost is much lower than that of more aggressive methods. Because the cost of intrinsic bioremediation is low, one of the greatest impacts of a successful demonstration will be felt by small businesses, such as dry cleaners, Ellis said. Small, independent dry cleaners use chlorinated solvents extensively in their operations and cannot afford to pay for the more expensive cleanup techniques for releases. Accelerated anaerobic bioremediation "is the hottest thing going, the most worthwhile thing for EPA to pursue," said Sam Fogel of Bioremediation Consultants Inc., a Newton, MA, bioremediation services firm. PCE kills most bacteria, and TCE is toxic to them at high concentrations, said Fogel. "These bugs can not only deal with PCE, but with saturated concentrations of PCE and TCE." If successful, Fogel said, "the biggest aspect is that ultimately those methods might be used for nonaqueous-phase liquids . . . which could be biodegraded essentially at the source." Ellis was more tentative. "We'll push this as far as we can but we don't understand [NAPLS] yet," he said. —DANIEL SHANNON
Bioremediation methods undergo testing
In accelerated anaerobic bioremediation, groundwater is extracted from the plume, circulated through a tank filled with nutrients, and reinjected just upstream of the high-concentration source area. Intrinsic bioremediation will be used as a control and as the cleanup method for the less-contaminated plume.
4 0 2 A • VOL. 29, NO. 9, 1995 / ENVIRONMENTAL SCIENCE & TECHNOLOGY
