April 21, 2008
Researchers Try New Technique to Remove Groundwater Contamination Under Old Ordnance Plant
LINCOLN, Neb. — Researchers from the University of Nebraska-Lincoln and Oklahoma State University are testing promising new methods of removing longstanding groundwater contamination at the former Nebraska Ordnance Plant near Mead.
The method involves pumping sodium permanganate into specially drilled injection wells, where it mixes with contaminants in the groundwater under the former ordnance plant, turning them into harmless carbon dioxide and water.
"Initial results show the permanganate was 75 to 80 percent effective in removing RDX from the groundwater contamination plume under the former (ordnance) plant," said UNL environmental chemist Steve Comfort. Comfort specializes in soil and water remediation and oversees the environmental restoration science degree for UNL undergraduate students.
RDX, TNT and HMX were some of the explosive compounds used in producing bombs, boosters and shells at the Mead plant during World War II and the Korean War. The plant was active in producing munitions for the U.S. military for more than 40 years.
Munitions-producing load lines at the plant were routinely hosed down to clean them and the resulting wastewater, containing high amounts of explosive residues, drained into sumps and ditches at the plant, where it later percolated into the groundwater.
"Complicating these groundwater contamination concerns was extensive use of trichloroethylene, which was used to degrease and clean pipelines at the plant in the 1960s," Comfort said.
The plume of RDX and trichloroethylene contamination in the groundwater beneath the Mead plant now covers several square miles.
With funding assistance from the U.S. Environmental Protection Agency's Region Seven Office in Kansas City, Kan., and the U.S. Department of Defense's Environmental Security Technology Certification Program, Comfort and colleagues from UNL and OSU are interested in seeing how efficient sodium permanganate may be in reducing the Mead plant's groundwater contamination problems and if the procedures they are using can be cost-effectively taught to and used by others at other similarly contaminated locations.
Mead's groundwater contamination problems are well known and are being treated. Comfort and his fellow researchers are using the location as an appropriate test-bed for their new technologies and treatment methods.
"Currently, the problems at Mead are being treated with an activated carbon method that is costing $800,000 per year and could take as long as 125 years to totally eliminate the problems underneath the plant grounds," the UNL School of Natural Resources researcher said.
Before injecting permanganate into the groundwater to remove or reduce explosives-based contamination, OSU researchers use a new technology, similar to ground-mapping radar, to characterize the subsurface area they will treat, which helps them better understand how and where to inject the chemical. The process is known as electrical resistivity imaging, or ERI.
"ERI helps us track the permanganate in the groundwater aquifer and shows zones of high concentrations of the chemical so that we can monitor destruction of the RDX," Comfort said.
It also shows the volume of groundwater impacted by the permanganate injections. Ultimately this helps researchers know where and how effective the permanganate is in reducing contamination within the treated area.
"So, with ERI as a monitoring tool, we can better identify sites that may be treatable with permanganate injections and know more precisely how effective the treatment is," Comfort said.
At Mead, researchers found that RDX decreased the most in monitoring wells closest to where the chemical was injected, but that makeup of subsurface soils, geology and groundwater flow paths in relation to the injection wells all had a bearing on how effective the treatment was.
"The chemistry works and if we had gotten a better distribution of the permanganate in the groundwater, the rates of RDX removal would have been even higher than the 75 to 80 percent we observed," he said.
Comfort and his team hope to use ERI again to improve permanganate delivery to the groundwater and determine the best locations for monitoring wells in future field trials.
"Permanganate is routinely used to treat groundwater with chlorinated solvents like TCE but is just now being considered for RDX and other explosives – maybe after a few more field trials, that will change," he said.
Sodium permanganate is much the same as potassium permanganate, a well-known chemical oxidant commonly used to treat problems as diverse as canker sores to getting rid of the rotten egg smell from hydrogen sulfide in water wells.
The School of Natural Resources is affiliated with the university's Institute of Agriculture and Natural Resources.
4/21/08-SR
Steven Comfort - Ph.D.
School of Natural Resources
Professor
(402) 472-1502
Vitaly A. Zlotnik - Ph.D.
Geoscienes
Professor
(402) 472-2495
Steve Ress UNL Water Center - Communications Coordinator (402) 472-3305
Department: School of Natural Resources
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