Seltzer's system is closest to market. But how fast these systems become commercial will turn on how quickly EPA promulgates its emissions regulations for incinerators, Burns noted. "Let's be clear, MACT (maximum achievable control technology) is driving this industry," he said. The MACT incinerator proposal, issued last spring, sets air emissions standards and includes CEM requirements for mercury and particulate matter (ES&T, June 1996, p. 235A). If all pollutants could be tested by CEM, Burns said, such a system would have two clear advan-
tages. Residents would have greater peace of mind knowing that emissions are being tested continuously rather than once every few years in a single test burn. And operators would have instant emissions measurements, allowing them to set waste feed, temperature, and other burn parameters to directly control emissions. Thereby they could reduce the costs of testing waste and running test burns. DOE and EPA are also testing a CEM system for dioxin. The system uses a German technology and can measure specific dioxin
congeners down to the part per trillion level. Dioxin emissions have been particularly worrisome, as they are highly toxic and cannot be measured directly. "These tests are only at the 'proof of principal' level," Burns emphasized. However, he said, the CEM system would be an excellent research tool for studying dioxin formation mechanisms because it can measure a host of dioxin compounds every few seconds. "And who knows, maybe in five years we'll have this thing down to a portable unit in a little black box." —JEFF JOHNSON
EPA near completion of "natural attenuation" remediation policy Natural attenuation, a form of bioremediation, has gained EPA acceptance for use at nearly 100 Superfund sites. But despite its success as a technique to reduce petroleum-based plumes in groundwater, state and federal regulators are struggling with the public perception that it is a "do nothing" approach. EPA staff "feel very vulnerable" about the public's view that natural attenuation is a fancy name for doing nothing to remediate a site, said David Ellis, bioremediation leader, DuPont Specialty Chemicals. Residents near some Superfund sites have objected to natural attenuation as a cleanup choice, said Fran Kremer, coordinator for the bioremediation field program in the EPA Office of Research and Development (ORD). In addition, EPA has received conflicting information from regional and private sector site managers who are confused about EPA's position on its use. To address this, an EPA workgroup is developing a natural attenuation policy for the regions and state regulators. Natural attenuation capitalizes on the degradation of certain contaminants by the combination of microbes, nutrients, and oxygen present in groundwater and soil. As a remediation tool, it requires little engineering except monitoring (ES&T, Sept. 1996, p. 398A). But preparations done before the remedy is approved, including site characterization, are usually more intensive than those performed for a traditional cleanup technique.
Researchers at the St. Joseph Superfund site near Lake Michigan have drilled bore holes to monitor degradation of trichloroethene in groundwater. Chemical concentration data are needed to determine the effectiveness of natural attenuation. (Photo courtesy of EPA.)
The approach is included as an option for Superfund cleanups. EPA also recognizes it as an option for Resource Conservation and Recovery Act and Underground Storage Tank groundwater cleanups. The main objective of the workgroup crafting the policy is to explain exactly what EPA considers natural attenuation. The policy will define the approach and describe the supporting documentation EPA expects when natural attenuation is proposed as a remediation tool, Kremer said. The policy statement will be limited, however. For instance, it will not provide step-by-step instructions on how to evaluate a site for natural attenuation, Kremer added. The agency's immediate goal is to clarify its expecta-
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tions when natural attenuation is proposed and encourage its "judicious use," Kremer said. EPA hopes to finalize the policy document by the end of this year. The policy should make natural attenuation more acceptable to residents living near contaminated sites and state regulators, said Ken Lovelace of the EPA Office of Emergency and Remedial Response. Because its use is relatively new for nonpetroleum spills, regulators and remediation firms are careful to avoid negative publicity about the approach. "Nobody wants to see a promising technology be disregarded because of a poor demonstration," Ellis said. EPA is not alone in developing a policy for natural attenuation. This month, at a meeting of the American Society for Testing and Materials (ASTM) a draft standard for natural attenuation at petroleum release sites will be discussed, and the U.S. Air Force has already developed a protocol that describes how indicators proving the natural remediation process is under way can be collected during the site characterization process. Several states, including Wisconsin and Florida, are working on their own natural attenuation policies, Small said. EPA's next regulatory step will be issuing a detailed guidance document for managers evaluating a site that looks promising for natural attenuation. ORD expects to finish this document "sometime next year," Kremer said. —CATHERINE M. COONEY
