(Organics Destruction and Metals Stabilization)
This technology is designed to destroy hazardous organics in soils while simultaneously stabilizing metals and metal ions (see figure below). The technology causes contaminated liquids, soils, and sludges to react with elemental sulfur at elevated temperatures. All organic compounds react with sulfur. Hydrocarbons are converted to an inert carbon-sulfur powdered residue and hydrogen sulfide gas; treated chlorinated hydrocarbons also produce hydrochloric acid gas. These acid gases are recovered from the off-gases. The hydrogen sulfide is oxidized in a conventional acid gas treating unit (such as ARI Technologies LO-CAT), recovering the sulfur for reuse.
In addition to destroying organic compounds, the technology converts heavy metals to sulfides, which are rendered less leachable. If required, the sulfides can be further stabilized before disposal. Thus, heavy metals can be stabilized in the same process step as the organics destruction.
The technology's main process components consist of the following:
Initial pilot-scale testing of the technology has demonstrated that organic contaminants can be destroyed in the vapor phase with elemental sulfur. Tetrachloroethene, trichloroethene, and polychlorinated biphenyls were among the organic compounds destroyed.
Batch treatability tests of contaminated soil mixtures have demonstrated organics destruction and immobilization of various heavy metals. Immobilization of heavy metals is determined by the concentration of the metals in leachate compared to EPA toxicity characteristic leaching procedure (TCLP) regulatory limits. Following treatment, cadmium, copper, lead, nickel, and zinc were significantly reduced compared to TCLP values. In treatability tests with approximately 700 parts per million of Aroclor 1260, destruction levels of 99.0 to 99.95 percent were achieved. Destruction of a pesticide, malathion, was also demonstrated. The process was also demonstrated to be effective on soil from manufactured gas plants, containing a wide range of polynuclear aromatics.
The current tests are providing a more detailed definition of the process limits, metal concentrations, and soil types required for stabilization of various heavy metals to meet the limits specified by TCLP. In addition, several process enhancements are being evaluated to expand the range of applicability.
The technology is applicable to soils and sediments contaminated with both organics and heavy metals.
This technology was accepted into the SITE Emerging Technology Program in January 1993. Bench-scale testing in batch reactors was completed in 1993. The pilot-scale program was directed at integrating the process concepts and obtaining process data in a continuous unit. The program was completed in 1995 and the Emerging Technology Report will be available in 1997.
EPA PROJECT MANAGER:
Randy Parker
U.S. EPA
National Risk Management Research Laboratory
26 West Martin Luther King Drive
Cincinnati, OH 45268
513-569-7271
Fax: 513-569-7571
TECHNOLOGY DEVELOPER CONTACT:
Stephen Paff
Center for Hazardous Materials Research
320 William Pitt Way
Pittsburgh, PA 15238
412-826-5321, ext. 233
Fax: 412-826-5552