Technology:
Thermal Desorption - Rotary kiln desorber 7 feet in diameter and 28 feet long - Soil heated to 250-400xF and a residence time of 6 minutes - Offgases treated using HEPA filter, baghouse, scrubber, and carbon adsorption
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Contaminants:
Chlorinated Aliphatics; Benzene, Toluene, Ethylbenzene, and Xylenes (BTEX); Polynuclear Aromatic Hydrocarbons (PAHs) - Excavated soil contained up to 3,310 mg/kg TCE, 130 mg/kg Ethylbenzene, and 35 mg/kg Toluene |
Regulatory Requirements/Cleanup Goals:
- Soil performance standard of 0.1 mg/kg for TCE, with retreatment as necessary - Performance standards of 1 mg/kg for individual aromatic organic compounds, 1 mg/kg for individual PAHs, and 10 mg/kg for total PAHs |
Cost Factors:
- Total Cost - $2,900,000 (including salaries and wages, rental, supplies, subcontracts, fuel, and other professional services) |
Description:
The McKin Company (McKin), in Gray, Maine, was a former waste collection, transfer, storage, and disposal facility. Soil at McKin was contaminated with halogenated VOCs and petroleum products, including polynuclear aromatic hydrocarbons (PAHs) and aromatic compounds. During the remedial investigation at McKin, soil contamination levels were measured as high as 1,500 mg/kg for trichloroethylene (TCE), 49 mg/kg for methylene chloride, and 21 mg/kg for xylenes. The ROD identified several areas at McKin that required on-site thermal desorption treatment for contaminated soil. These areas were grouped into a "VOC-Contaminated Area" and a "Petroleum- Contaminated Area." The treatment performance standard, stipulated in the ROD, required treatment of TCE in the soil to a concentration of 0.1 mg/kg.
In addition to the TCE requirement, treatment performance standards for PAHs and aromatic organics were specified for the petroleum-contaminated area. Ambient air monitoring was required during the application.
The thermal desorption system included a rotary kiln desorber with offgases treated using a filter, baghouse, scrubber, and carbon adsorption. Thermal desorption of approximately 11,000 cubic yards of soil was completed at McKin between July 1986 and April 1987. This treatment application is notable for being one of the earliest full-scale applications of thermal desorption to remediate halogenated volatile organic compounds at a Superfund site. Treatment performance and air monitoring data collected during this application indicated that all performance standards and monitoring requirements were achieved through use of the thermal desorption technology.
The total cost for this application was $2,900,000. According to the vendor, this cost included rental supplies, labor, subcontracts, fuel and other professional services, and estimated that over 80% of the cost was associated with the treatment of the contaminated soil. A pilot-scale treatability study indicated that thermal desorption would be effective in treating soils at the McKin site. |
