News
A Greener, Cleaner Groundwater Cleanup Process
A new bioremediation process developed at the U.S. Department of Energy's (DOE) Idaho National Engineering and Environmental Laboratory (INEEL) is making the difficult job of removing chlorinated solvents from groundwater much easier.
Finding solutions to groundwater cleanup has long been a challenge for industry professionals. Groundwater plumes contaminated with chlorinated solvents are common and present unique obstacles related to the chemicals' high density and low solubility.
North Wind Environmental Inc., a locally owned engineering and consulting firm, has obtained a license to use the INEEL's innovative process called Bioavailability Enhancement TechnologyTM (B.E.T.).
B.E.T. was tested at the INEEL's Test Area North (TAN) with very good results. Scientists were trying to find a cost-effective way to clean up the underground aquifer beneath TAN, which was contaminated with organic sludge and wastewater, resulting in a two-mile long trichloroethene (TCE) groundwater plume.
TCE, used extensively for degreasing and one of the most common groundwater contaminants at hazardous waste sites in the United States, had been injected into the aquifer over a period of 15 years.
While laboratory tests performed at the INEEL and elsewhere had shown the potential for success of TCE bioremediation, the results in the field far exceeded expectations. Not only did TCE concentrations in the source area drop below detection limits, but breakdown of the TCE also was increased.
"TCE contamination is one of the most prevalent environmental problems in the world," said Lyman Frost, INEEL Technology Transfer director. "This is an excellent example of teaming between industry and national laboratories. The technology was conceived and developed at the INEEL, and by transferring this technology to the industrial sector, it will be rapidly applied across a wider spectrum of needs."
The bioremediation process takes advantage of natural biological processes that break down TCE when bacteria already present at the site are given an appropriate food source. Scientists found that the INEEL process helps dissolve the TCE, which accelerates its degradation. The process is much cheaper than conventional methods and because the remediation is done underground, there is no secondary waste stream. The land site essentially remains undisturbed.
Success of the large-scale test of B.E.T. at the INEEL has won the approval of the state of Idaho and the U.S. Environmental Protection Agency (EPA). B.E.T., combined with monitored natural attenuation -- the contaminant degradation that takes place naturally in the TCE plume -- is expected to save $23 million at TAN. Cost savings achieved at TAN were the direct result of integration of cleanup operations funded through the DOE-HQ Office of Project Completion with an Accelerated Site Technology Deployment project funded through the DOE-HQ Office of Science and Technology.
Kent Sorenson, North Wind director for Applied Research and former INEEL scientist, is excited about the results.
"B.E.T. is part of a breakthrough in the understanding of bioremediation that has the potential to revolutionize the cleanup of chlorinated solvent source areas, which are one of the biggest environmental challenges facing industry, the government and cleanup professionals today," said Sorenson.
"We are very excited to have this opportunity to team with the INEEL," said Sylvia Medina, North Wind founder and president. "The scientific research being done at the laboratory can have a direct impact on local small business. The innovative tools and techniques developed are a great complement to our practical skills and experience."
"The INEEL is pleased to see North Wind Environmental agree to locate within the rapidly developing Eastern Idaho Technology Corridor (EITC)," said Frost. "Environmental technology is one of the focus points for EITC."
The INEEL is a science-based, applied engineering national laboratory dedicated to supporting the U.S. Department of Energy's missions in environment, energy, science and national security. The INEEL is operated for the DOE by Bechtel BWXT Idaho, LLC.
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Vacuuming Vapors from the Vadose Zone
Three extraction units, similar to industrial-sized vacuums, are pulling harmful vapors from the vadose zone -- the unsaturated layers of rock and soil between the ground surface and the water table -- at the U.S. Department of Energy's (DOE) Idaho National Engineering and Environmental Laboratory. The vapor vacuum extraction units have successfully removed and treated approximately 110,000 pounds of volatile organic compounds since January 1996, including more than 70,000 pounds of carbon tetrachloride.
The project is one of the INEEL's ongoing environmental cleanup efforts to limit contaminants reaching the Snake River Plain aquifer, which is located in Idaho. Volatile organic compounds have been detected at levels slightly above safe drinking water standards in the aquifer near the Radioactive Waste Management Complex (RWMC). While the levels present don't pose an immediate risk, this remedial action was undertaken to restrict migration of contaminants to the groundwater at the RWMC.
The extraction units pull hazardous vapors from soil and the basalt rock above the 110-foot level in the subsurface. Two treatment processes are used to destroy the volatile organic compounds. Two thermal units use elevated temperatures to destroy the organic compounds and one unit uses a catalyst to destroy them -- a process similar to the catalytic converter in automobiles.
Lisa Harvego, INEEL manager for the project, says the units were put into operation in 1996 to meet the requirements of the Record of Decision under the Comprehensive Environmental Response Compensation and Liability Act (CERCLA), also known as Superfund. She says the extraction system could be used for as long as 20 to 30 more years to treat the vapors in the vadose zone to prevent migration to the aquifer. The older thermal treatment units will be replaced with newer, more efficient and cost-effective models over the next several years.
INEEL is a science-based, applied engineering national laboratory dedicated to supporting the DOE's missions in environment, energy, national security and science. The INEEL is operated for the DOE by Bechtel BWXT Idaho, LLC.
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Corrosion Monitoring Technology Makes Noise in the Radioactive Liquid Waste World
Los Alamos National Laboratory, in collaboration with scientists from four other DOE sites and several private companies, is coordinating the development of a technology for real-time monitoring of corrosion within large, underground stainless and carbon-steel radioactive liquid waste storage tanks.
The project is part of an effort funded by DOE's Office of Environmental Management.
Past weapons production and nuclear fuel reprocessing activities, in support of national defense, created millions of gallons of radioactively contaminated waste. Much of this liquid waste is stored in underground tanks that face the potential of corrosion, a destructive electrochemical process that eats away at metallic surfaces, eventually destroying the integrity of the material if not addressed.
Until this waste can be removed from the storage tanks and stabilized for long-term storage and disposal, it must be safely stored and monitored.
Historically, corrosion monitoring has been accomplished by comparing the results of chemical analysis of waste samples drawn from the tank against established standards or by evaluating tank material test strips, called coupons, immersed in the waste for long periods of time and withdrawn for analysis. Pulling the coupons from a tank is expensive - sometimes $100,000 per sample - and presents exposure risks to workers. Also, neither sample nor coupon exposure methods provide rapid results that are needed to initiate corrective measures quickly.
A new monitoring technique using electrochemical noise (EN) provides real-time corrosion information and significantly reduces the potential for exposing workers to radiation. In addition, the enhanced corrosion data can lower operating costs through improved tank-waste management.
EN corrosion monitoring tracks extremely small current and voltage fluctuations among three electrodes, made of material as similar as possible to the waste tank material, placed in the waste solution.
Current is measured between two electrically coupled electrodes (a working electrode and a counter electrode), while the third electrode is connected between the working electrode and a pseudo-reference electrode to measure the voltage.
The magnitude and polarity of the signals, as well as the relationship of the timed signal traces to each other, provide indicators of type and significance of the corrosion processes occurring in the tank. Particular types of corrosion have unique and potential signatures that indicate when pitting or stress corrosion cracking is occurring.
"Because the chemistry near the electrodes and tank walls are similar, whatever happens on the electrodes, after some period of gaining equilibrium, is the same as what's happening on the tank walls," says Los Alamos Project Manager Mike Terry.
Using electrochemical noise to detect corrosion is not new. It was used in the oil and gas industry for 10 years before a test program was initiated in 1995 by the DOE's Tanks Focus Area (TFA) to evaluate EN's application in radioactive waste storage tanks.
"It's not a new technology, but it's definitely an emerging technology for our application," says Terry, who represents Los Alamos' involvement in the TFA as Safety Technology Integration Manager.
Because of the range of tank construction materials, tank designs and varied waste chemistries encountered, different probe/electrode designs are being tested to confirm meaningful signatures are being generated and that measurements can be accurately interpreted.
The primary focus is to determine if pitting or stress corrosion cracking occurs and to what extent. If corrosion is detected, then inhibitors can be added to the waste to halt the corrosion.
In addition to Los Alamos, TFA collaborators on the corrosion-monitoring project include researchers, technology developers and managers from the Hanford site, Savannah River site, Oak Ridge National Laboratory, Idaho National Engineering and Environmental Laboratory, HiLine Engineering and Fabricators of Richland, Wash., EIC Laboratories of Norwood, Mass. and AEA Technology based in the United Kingdom.
TFA launched an initial deployment of EN detection probes at Hanford Site in Washington to develop EN technology for use in tanks of different types and with different waste contents.
With successful development of a corrosion monitoring system for Hanford, TFA funded development efforts for similar systems at Hanford, Oak Ridge and Idaho National Engineering and Environmental Labs.
The EN method is intended to provide needed data to the DOE to help assure that the integrity of the tanks holding the liquid radioactive waste can be safely maintained until the contents can be properly and safely disposed of. The Tanks Focus Area receives funding through the Office of Science and Technology whose mission is to deliver science and technology solutions in support of the Office of Environmental Management.
"This is just a piece of the puzzle, to protect the world from this waste until we can complete our mission to clean it up," says Terry. "The potential to save personal exposure and cleanup dollars, in addition to giving us a better understanding of what's really happening in those tanks, is very valuable to the sites. It's part of the single most challenging cleanup issue in the United States, figuring out safer, faster and cheaper ways to get rid of our legacy waste."
Los Alamos National Laboratory is operated by the University of California for the National Nuclear Security Administration (NNSA) of the U.S. Department of Energy and works in partnership with NNSA's Sandia and Lawrence Livermore National Laboratories to support NNSA in its mission.
Los Alamos enhances global security by ensuring safety and confidence in the U.S. nuclear stockpile, developing technologies to reduce threats from weapons of mass destruction and improving the environmental and nuclear materials legacy of the cold war. Los Alamos' capabilities assist the nation in addressing energy, environment, infrastructure and biological security problems.
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Supercritical Carbon Dioxide/Water Emulsion Found Effective for Remediating Metal Contaminants in Waste
Modifying a technique already used to remove caffeine from coffee and undesirable agents from semiconductor wafers, a research team at the U.S. Department of Energy's (DOE) Los Alamos National Laboratory is developing the promise of an environmentally friendly method for using supercritical carbon dioxide and water to remove radioactive particles and hazardous metals from mixtures of waste.
In early tests, the technique removed virtually all of the contaminants from exposed materials. The researchers believe the technique ultimately could be used to extract contaminants from containers and other types of refuse generated by workers in laboratories and industrial plants. This would result in the need to dispose only of small volumes of contaminants rather than using water in bulk for cleaning or putting the vast volumes of contaminated work materials into the waste stream.
An advance over previous research in the field, the Los Alamos team worked with a microemulsion comprised of supercritical carbon dioxide and water, which was modified with the addition of a polyether. Research results were presented on April 11 at the 2002 meeting of the American Chemical Society in Orlando, Fla.
By itself, supercritical carbon dioxide, which is CO2 under pressure and at a certain temperature, is an effective solvent for a number of materials except metal ions, said Los Alamos research team leader Mark McCleskey. Carbon dioxide is abundant and low in cost. It is also environmentally benign because it is inert, nontoxic and nonflammable. But the only way previously known to employ it in metal ion extraction was by combining it with a special kind of molecule known to combine with certain kinds of metals. The effectiveness of this method, however, is limited.
Water could be a desirable transport medium in a supercritical solvent system, McCleskey said, except that water does not stabilize in carbon dioxide. What's more, water by itself tends to trap on the surface of solid materials and in low volumes cannot effectively penetrate deep into the pores to get at all of the contaminants.
To test their theory that small amounts of water could be employed in metal-contaminant remediation, the team worked with a supercritical carbon dioxide microemulsion modified with the addition of an inert polyether known to stabilize water. They used the emulsion to extract copper and europium from filter paper, wood, cement and activated carbon. Copper and europium were selected for extraction because these elements are spectroscopically active and would yield information on the microemulsion's effects.
After applying the microemulsion to the materials, the team achieved 98 percent contaminant recovery.
"We found that the metals targeted for extraction concentrated in the nanodroplets of water in the microemulsion, allowing us to separate the metals from the contaminated materials easily," McCleskey said. "In addition, the properties of this microemulsion allow penetration even into small pores of contaminated materials usually not accessible to bulk water."
Microemulsions are especially advantageous for extracting metals from waste, he said, because the amount of water required is proportional to the amount of contaminant being removed, not to the amount of waste to be cleaned. "The result is that grams of contaminants can be captured with just a few milliliters of water."
To remove the captured contaminant from the microemulsion, the team adjusted the carbon dioxide pressure and added water. This phased separation of contaminant from carbon dioxide has the potential of providing an easy recycle system for the microemulsion. One test showed that 81 percent of a microemulsion's initial capacity was retained for its second application.
If further research produces consistent results, McCleskey believes the technique has potential to become an environmentally friendly method for remediating hazardous wastes.
In addition to virtually complete removal of metal contaminants from exposed materials, it would greatly reduce the amount of water used in remediation, as well as the resources needed to handle and transport large volumes of contaminated refuse, he said.
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This article originally appeared in the July/August 2002 issue of Water & Wastewater Products, Volume 2, Number 4, page 34.
This article originally appeared in the 07/01/2002 issue of Environmental Protection.