This technology was developed by EPA's National Risk Management Research Laboratory and IT Corporation (IT) for on-site decontamination of metallic and masonry debris at Comprehensive Environmental Response, Compensation, and Liability Act sites. The entire system is mounted on three 48-foot flatbed semi-trailers and can be readily transported from site to site.
The full-scale debris washing system (DWS) is shown in the figure below. The DWS consists of dual 4,000-gallon spray-wash chambers that are connected to a detergent solution holding tank and rinse water holding tank. Debris is placed into one of two 1,200-pound baskets, which in turn is placed into one of the spray-wash chambers using a 5-ton crane integral to the DWS. If debris is large enough, the crane places it directly into one of the two chambers. Process water is heated to 160 °F using a diesel-fired, 2,000,000-British-thermal-unit-per-hour (Btu/hr) water heater. The water is continuously reconditioned using particulate filters, an oil-water separator, and other devices such as charcoal columns or ion-exchange columns. About 8,000 to 10,000 gallons of water is required for the decontamination process. The system is controlled by an operator stationed in a trailer-mounted control room.
The DWS can be applied on site to various types of debris (scrap metal, masonry, or other solid debris such as stones) contaminated with hazardous chemicals such as pesticides, dioxins, polychlorinated biphenyls (PCB), or hazardous metals.
The first pilot-scale tests were performed in September 1988 at the Carter Industrial Superfund site in Detroit, Michigan. An upgraded pilot-scale DWS was tested at a PCB-contaminated Superfund site in Hopkinsville, Kentucky in December 1989. The DWS was also field tested in August 1990 at the Shaver's Farm Superfund site in Walker County, Georgia. The contaminants of concern were benzonitrile and Dicamba. After being cut into sections, 55-gallon drums were decontaminated in the DWS.
Results from the SITE demonstration have been published in a Technology Evaluation Report (EPA/540/5-91/006a), entitled "Design and Development of a Pilot-Scale Debris Decontamination System" and in a Technology Demonstration Summary (EPA/540/S5-91/006).
In 1993, a manual version of the full-scale DWS was used to treat PCB-contaminated scrap metal at the Summit Scrap Yard in Akron, Ohio. During the 4-month site remediation, 3,000 tons of PCB-contaminated scrap metal (motors, cast iron blocks) was cleaned on site. The target level of 7.7 µg/100 cm² was met, in most cases, after a single treatment with the DWS. The cleaned scrap was purchased by a scrap smelter for $52 per ton. The net costs for the on-site debris decontamination ranged from $50 to $75 per ton. The National Risk Management Research Laboratory and IT estimate that the system can decontaminate 50 to 120 tons of typical debris per day.
At the Carter Industrial Superfund site, PCB reductions averaged 58 percent in batch 1 and 81 percent in batch 2. Design changes based on these tests were made to the DWS before additional field testing.
At the Hopkinsville, Kentucky site, PCB levels on the surfaces of metallic transformer casings were reduced to less than or equal to 10 micrograms PCB per 100 square centimeters (µg/cm²). All 75 contaminated transformer casings on site were decontaminated to EPA cleanup criteria and sold to a scrap metal dealer.
At the Shaver's Farm Superfund site, benzonitrile and Dicamba levels on the drum surfaces were reduced from the average pretreatment concentrations of 4,556 and 23 µg/100 cm² to average concentrations of 10 and 1 µg/100 cm², respectively.
EPA PROJECT MANAGER:
Donald Sanning
U.S. EPA
National Risk Management Research Laboratory
26 West Martin Luther King Drive
Cincinnati, OH 45268
513-569-7875
Fax: 513-569-7620
TECHNOLOGY DEVELOPER CONTACTS:
Michael Taylor or Majid Dosani
IT Corporation
11499 Chester Road
Cincinnati, OH 45246-4012
513-782-4700
Fax: 513-782-4807