In this issue, Initiatives revisits three OST-funded technologies that are making strides toward deployment. Since its debut in Initiatives in June 1996, EmporeTM membrane technology won a 1996 R&D 100 Award as developers continue to research and test its expanded use as a field characterization and remediation tool. The concept of using cryogenic, or frozen, soil barriers to temporarily contain plumes (see Initiatives, August 1996) will get a boost as Arctic Foundations carries out its project to construct a frozen wall around a contaminated Oak Ridge pond. An ASTM draft standard will help Expedited Site Characterization users apply ESC consistently (see Initiatives, October 1995 and August 1996).
|EmporeTM membranes filter out radioisotopes
Empore membranes' ability to separate radioactive ions from aqueous waste streams is being applied by the U.S. Department of Energy to streamline sample collection. DOE's Office of Science and Technology is also investigating the separation technology for its use in simplifying and reducing the cost of remediating DOE aqueous waste streams. The 3M Company of St. Paul, Minnesota developed Empore membranes; OST is supporting research and testing to refine the technology for cleanup.
Empore Rad Disks, whose joint development by 3M and Argonne National Laboratory was supported by OST, are showing they have what it takes to be a commercial success. The highly selective membrane technology was chosen as one of R&D Magazine's R&D 100 Award winners for 1996 for its improvement of environmental sampling techniques. The disks, commercially available from 3M, cut the time and cost of analyzing radiochemical samples. DOE is using the disks to test ground water, surface water, and nuclear-fuel storage-pool water. Nuclear power plants also use the disks.
Conventional means of detecting low levels of radioactivity in large volumes of water, such as the ocean or a river, require that a laboratory obtain a large sample quantity. For technetium and cesium testing, 20 liters of water are processed through an ion-exchange column to concentrate the radionuclide so that it can be counted directly on the ion exchanger, or eluted and then counted. Other steps are required to further concentrate the radioactive portion of the sample before the sample is analyzed.
Empore Rad Disks offer a simplified means of collecting a sample in real time. Thin Empore membranes, composed of a weblike matrix material, are densely packed with sorbent particles, such as AnaLig particles (produced by IBC Advanced Technologies). As solutions pass through the mesh, AnaLig particles or other sorbent particles extract ions of interest and hold them in a shallow surface layer on the disk. Nontarget elements pass through the membrane. Because no adhesives or binders are used to hold the ions, they retain their full chemical activity. The Empore membrane, associated with an appropriate ion exchange resin such as the AnaLig particles, can concentrate technetium-99, cesium-134, and cesium-137 from large volumes of water for analysis. The cost of sample preparation is reduced because only the disks are returned to the laboratory for analysis, not the large quantity of water.
Current development is focusing on adapting the membranes for use in field analysis, along with portable counters. The resulting integrated field sampling system could cut total sampling turnaround time from about one week to as little as one hour in some cases.
In addition to streamlining sample collection, the Empore membrane technology can also be applied in a remediation system to selectively remove cesium, strontium, or technetium from aqueous wastes. The efficient separations and processing crosscutting program funded research to investigate the use of sorbent materials attached to Empore membranes to remove radionuclides from a variety of DOE waste streams. By concentrating and removing the most hazardous or most radioactive portions of a waste stream, separations technologies like Empore membranes can reduce the complexity of treatments and the volume of waste slated for expensive high-level waste treatment and disposal.
The tanks focus area, in collaboration with Pacific Northwest National Laboratory in Richland, Washington, is investigating the use of 3M's Empore flow-through membranes, loaded with sorbent material, to remove radionuclides from tank waste. As tank waste passes through the membrane, the specially engineered sorbent particles snare radioactive ions of interest. After the membrane is removed from the waste stream, its trapped ions are eluted with nitric acid or boric acid.
The decontamination and decommissioning focus area is also interested in Empore membranes as a separation technology. In September 1996 at the Chicago Pile-5 Reactor Large-Scale Demonstration Project, Empore membranes configured into cartridges were used to process water containing cobalt-60, cesium-137, and tritium from reactor operations. Three different types of sorbent particles were used in the Empore cartridges to successfully remove the main radionuclides of interest. During the demonstration, in which approximately 4,500 gallons of water were treated, cesium-137 and cobalt-60 were removed to less than 0.02 pCi/ml. The technology is being scaled up to produce a larger-capacity system.
Will frozen barrier stop
A project to demonstrate how a frozen soil barrier can contain a plume is a collaboration among DOE's offices of Science and Technology (EM-50) and Environmental Restoration (EM-40); DOE-Oak Ridge Operations Office; Arctic Foundations, Inc.; Lockheed Martin; the U.S. Environmental Protection Agency's SITE Program; and the state of Tennessee. The project's purpose is to generate cost and performance data that validate the use of frozen barriers to contain a plume while cleanup options are considered.
In May 1997, Arctic Foundations, an Anchorage, Alaska firm, began drilling into the ground and placing thermoprobes around a contaminated pond at Oak Ridge National Laboratory. From 1957 to 1961, the pond was the storage site for low-level liquid waste from the Homogeneous Reactor Experiment-2 evaporator. The pond is primarily contaminated with cesium and strontium, as well as trace amounts of plutonium, uranium, americium, and curium. Polychlorinated biphenyls and heavy metals have also been detected.
The technology is based on a liquid/vapor system. Carbon dioxide, cooled to a liquid state by refrigeration units on the surface, flows down the internal walls of thermoprobes that have been inserted into the ground. The liquid carbon dioxide is warmed by the surrounding soil and changes into a gaseous state. The carbon dioxide's conversion from a liquid to a gas draws heat from the surrounding soil, causing any water present to freeze. The gas returns to the surface to be cooled to a liquid again. The cycle is repeated to maintain the integrity of the frozen barrier.
According to Ed Yarmak, chief engineer at Arctic Foundations, "Freezing is good for many sites because it doesn't change the regime of the ground. When barrier use is over, the soil goes back to the way it was. It's a clean method of containment." The barrier's thickness (about 12 feet) is also an advantage. Yarmak said, "Even if the ground were to shift, the barrier will reheal itself; whereas with a barrier like high-density polypropylene, even a pinhole will cause seepage." President Irv Long said Arctic Foundations' liquid/vapor system avoids a major disadvantage of totally liquid systems: liquids can corrode pipes and lead to destruction of frozen ground.
In May 1997, Arctic Foundations began drilling into the ground and placing thermoprobes around the site. Drilling was completed in July. The system was next piped together at the surface. Freezing began in mid-September and was completed in early November. EPA will verify barrier integrity during the demonstration, and cost and performance data will be collected. Current plans are to turn the barrier over to EM-40 in September 1998.
For more information on this project, call Elizabeth Phillips, the DOE project manager, at (423) 241-6172.
The trend toward rapid, field-based characterization of soil and ground water will soon receive a boost from a new standard practice being developed by the American Society for Testing and Materials (ASTM). The standard is titled Standard Practice for Expedited Site Characterization (ESC) of Vadose Zone and Groundwater Contamination at Hazardous Waste Sites and is expected to be final in January 1998.
"It sounds too good to be true, but the ESC process, when implemented properly, provides higher quality information for decision making in a shorter time and at lower cost than traditional approaches to characterizing contaminated sites," said Russell Boulding, chairman of the ASTM ESC Task Group that generated the draft guidance on ESC.
Through the support of DOE's Office of Science and Technology's characterization, monitoring and sensor technology crosscutting program, ESC was pioneered, demonstrated, fine-tuned, and used within DOE for regulatory cleanups by Argonne National Laboratory and Ames Laboratory. ESC deployments have been successful at a range of sites from DOE's Pantex Plant and the Savannah River Site to an Iowa utility company, numerous U.S. Department of Agriculture Commodity Credit Corporation former grain elevator sites, several military installations, and an international project in Poland. Time and time again, regulators and site owners have been pleased with the quality and efficiency of ESC, leading to the need for a standard guide on how to practice it.
The ESC standard has undergone the most exhaustive review process of any ASTM standard to date, said Boulding. "Because of the broad scope of the document and the wide applicability of ESC, we felt it was important to get consensus beyond our normal boundaries. We're traditionally accustomed to developing technical standards for test methods; but with ESC, we were formalizing a process rather than a particular technique.
"To develop the provisional standard, we sent a draft to all the federal agencies," said Boulding. "In developing the final consensus standard, more than 230 comments were received from 17 state members of the Interstate Technology Regulatory Cooperation group." ITRC was invaluable for getting a perspective on ESC from state and community stakeholders, who typically aren't represented in ASTM membership but whose input was critical to achieving a credible consensus, Boulding explained.
In fall 1997, ASTM's D-18 Committee on Rock and Soil, composed of more than 900 individuals concentrated in the geotechnical or environmental profession, voted on whether to accept the ASTM standard. The balloting raised a few questions about the use of standards, but Starke anticipates that the the committee will likely approve the standard when it meets in January 1998 in San Diego.
"There's a tremendous amount of characterization work that remains to be done throughout the DOE complex," said Tom Starke, environmental stewardship program manager at Los Alamos National Laboratory, who started the move for a new standard with ASTM. "Almost half of Los Alamos' environmental remediation work, for example, is characterization." And even though it's called Expedited Site Characterization, the method applies to much more than just the characterization step within a CERCLA or RCRA cleanup, Starke pointed out. "It's also a very good tool for organizing and identifying the data that needs to be collected for long-term monitoring if, for example, you're putting in a monitoring well system."
"The standard will take ESC beyond a compilation of case studies to a credible procedure," Starke said. "But as with many standards, you can't just stop there. You need a way to communicate the standard with users, and that's where training courses come in. DOE has already developed and taught an ESC course for DOE sites, and the Argonne ESC group is developing an ESC course for site practitioners."
The ESC standard is ASTM's third standard related to site characterization. ASTM Guide to Site Characterization for Environmental Purposes with Emphasis on Soil Rock and the Vadose Zone includes an index of more than 400 specific ASTM test methods, practices, and guides for performing environmental site characterization. A second standard, Guide PS 03-95 for Accelerated Site Characterization, focuses on petroleum release sites.