Technology:
Thermal Desorption
- X*TRAX™ Model 200 - thermal separation system, gas treatment system, and liquid storage and processing system
- Dryer feed rate - 120 tons/day
- Dryer temperature - 500 to 1100° F
- Treated soil temperature - 700 to 750° F (average 732° F)
- Residence time - 2 hours
- Condensate water generated by the system was treated in the on-site multi-stage treatment system (oxidation; flocculation and sedimentation; filtration; air stripping; liquid-phase carbon adsorption; vapor-phase carbon adsorption)
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Cleanup Authority:
CERCLA
- ROD date: 9/24/87
- ESD date: 6/11/93
EPA Remedial Project Manager:
Joseph LeMay
EPA Region 1
John F. Kennedy Federal Building, Room 2203
Boston, Massachusetts 02203
(617) 573-9622 | State Contact:
Nikki Korkatti
Project Manager
Massachusetts Department of Environmental Protection
Bureau of Waste Site Cleanup
One Winter Street, 5th Floor
Boston, Massachusetts 02108
Telephone: (617) 574-6840 |
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Regulatory Requirements/Cleanup Goals:
- The ROD specified a cleanup level of 25 mg/kg for PCBs in soil.
- Process vent emission rate was limited to 0.38 lb/hr of total hydrocarbons (THC).
- Perimeter air monitoring was required for VOCs and dust during excavation; if action levels were exceeded, excavation was to be stopped and control measures implemented.
- Effluent was required to meet daily and monthly limits for VOCs, PCBs, and metals. |
Results:
- The treated soil met the cleanup goal of 25 mg/kg PCBs, with concentrations ranging from 0.59 mg/kg to 21 mg/kg.
- Greater than 99% of the soil met the cleanup goal after one pass through the treatment system; only 0.5 percent required retreatment.
- The process vent emissions met the air emission standard; THC emissions ranged from 0.002 to 0.296 lb/hr.
- Treated water generally met the effluent standards. For the few exceedances, the vendor determined that the concentrations would not be higher than the concentration used in developing a discharge permit; however, information was not provided on any actions by the state as a result of the exceedances. |
Description:
Re-Solve operated a waste chemical reclamation facility in North Dartmouth, Massachusetts from 1956 until 1980. Hazardous materials handled at the site included polychlorinated biphenyls (PCBs), solvents, waste oils, organic liquids and solids, acids, alkalies, and inorganic liquids and solids. On December 23, 1980, the state accepted Re-Solve's offer to surrender its disposal license, on the condition that all hazardous waste be removed from the site. In late 1981, Re-Solve removed drums and other debris, including buildings, from the site; however, contents of four on-site lagoons and a cooling pond and the residue from an oil spreading operation were not removed. The site was placed on the the National Priorities List (NPL) in September 1983. The results of the Remedial Investigation indicated that soil and groundwater at the site were contaminated with PCBs and other compounds. In response to a 1983 ROD, soil contaminated with PCBs was excavated and shipped off-site for disposal. However, the results of additional investigations conducted to evaluate the effectiveness of the remedial action indicated that extensive PCB contamination remained in areas beyond the remediated lagoons, cooling pond, and oil spreading area. A second ROD for the site, signed in September 1987, called for excavation of additional contaminated soil and treatment by thermal desorption and dechlorination (DECHLOR). However, the results of a pilot-scale demonstration of the DECHLOR process indicated that the process would not be cost-effective or economically feasible on a full-scale basis. In June 1993, EPA issued an ESD to remove the DECHLOR process from the full-scale treatment system and specify the treatment of the concentrated oil contaminated with PCBs that was recovered in the X*TRAX™ system at an off-site incinerator permitted under the Toxic Substances Control Act (TSCA).
The X*TRAX™ Model 200 system consisted of three main components - thermal separation system, gas treatment system, and liquid storage and processing system. In the thermal separation system, contaminated solids were fed into a propane-fired rotary dryer, and heated indirectly to volatilize the moisture and organic contaminants; the dryer consisted of a long steel cylinder rotating inside of a furnace. The moisture, contaminants, and a small amount of dust were swept continuously from the dryer to the gas treatment system by a nitrogen carrier gas. The gas treatment system removed moisture and contaminants from the carrier gas and reconditioned the gas before recycling it to the dryer. Materials that accumulated within and later exited the system were considered residues of treatment. All treated soil met the cleanup goal of 25 mg/kg for PCBs. Greater than 99 percent of the soil met the cleanup goal after the first pass, with only 0.5 percent of the soil requiring retreatment. |
