Technology:
Thermal Desorption
- IRHV-200 vacuum-enhanced low temperature thermal desportion system
- Four treatment chambers each equipped with 8 infrared heaters. At 1100F, each heater produced 137,000 BTU/hr
- Liquid seal vacuum pump used to create vacuum of 50 mmHg
- High flow recirculation blower (6,000 acfm)
- Air draw off recirculation stream (300 acfm) directed to air emissions control
- Dry particulate filters, condensors, and carbon adsorption units
- Residence time - 4 hr (batch process)
- Soil temperatire - 350F for a minimum of 5 minutes
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Cleanup Authority:
CERCLA Removal
- Action memorandum date: 9/29/88
On-Scene Coordinator (OSC):
Paul Peronard
EPA Region 4
345 Cortland Street, N.E.
Atlanta, GA 30365
(404) 562-8767 | State Contact:
Randy McElveen
North Carolina DEHNR
P.O. Box 27687
Raleigh, NC 27611
(919) 733-2801 |
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Contaminants:
Pesticides
- Aldrin, chlordane, DDT, DDE, DDD, dieldrin, heptachlor, heptachlor epoxide, methoxychlor, benzene hexachlorides |
Waste Source:
Buried waste pesticides |
Type/Quantity of Media Treated:
Soil - 13,591 cubic yards |
Purpose/Significance of Application:
Vacuum-enhanced low-temperature thermal desorption used to treat pesticide-contaminated soil |
Regulatory Requirements/Cleanup Goals:
- Total pesticides - 1.0 mg/kg
- For the demonstration, air emissions were to meet the EPA Region 4 Air Compliance Section standards for vented air emissions; no air emission standards were set for the full-scale operation. |
Results:
- Treated soil met the cleanup goal of 1 mg/kg total pesticides.
- A one-time stack air monitoring test was performed during the demonstration; all standards were met. |
Cost Factors:
- Total cost of $1,844,600 including $1,696,800 in costs directly associated with treatment.
- Based on 13,591 cubic yards of soil treated, the unit cost was $125 per cubic yard. |
Description:
From 1945 to 1982, the Farmers Cooperative Exchange (FCX) operated a pesticide blending facility and warehouse where it packaged pesticides. The pesticides most frequently handled at the site were chlorinated organic pesticides including chlordane, methoxychlor, dichloro-diphenyl-trichloroethane (DDT), and 1,1-dichloro-2,2-bis(4-chlorophenyl) ethene (DDE). Various other chlorinated and nonchlorinated organic chemicals were used in mixing and blending of pesticides. Outdated or out-of-specification materials were buried in trenches on the FCX property. In 1985, the company filed for bankruptcy, and the building and warehouses were cleaned out. In 1986, the Fred Webb Grain Company (FWGC) purchased approximately 15 acres of the FCX property to be used to store grain under the federal government grain subsidy program. Subsequent investigations of the site performed by EPA and the state indicated that the site was contaminated with pesticides. The site was listed on the NPL in March 1989. The removal site investigation, performed in 1992, identified pesticide contamination in trenches at the site. Approximately 14,700 cubic yards of contaminated soil (total chlorinated pesticides above 1 ppm) were excavated and stock piled for on-site incineration. As a result of objections by the city to on-site incineration and in response to state issues regarding off-site disposal, EPA identified on-site thermal desorption as the remedy for the excavated contaminated soil at FCX.
Vacuum-enhanced, low temperature thermal desorption (LTTD) was used to treat the contaminated soil at the FCX site. The system operated under a vacuum of about 50 mm Hg and used an infrared heat source to desorb contaminants from the soil. By operating under a vacuum, the temperature required to desorb contaminants from the soil and the amount of oxygen present in the treatment chamber are lower than if the unit were operated under atmospheric conditions, helping to reduce the potential for formation of dioxins and furans. The model IRHV-200 mobile LTTD system used at the site included a treatment chamber, and emission control equipment including a dry particulate filter, condenser, and carbon adsorption unit. McLaren/Hart conducted two site demonstrations before full-scale operations began. The initial demonstration, conducted with a batch of clean soil, failed to heat the soil throughout. Several modification were made to the full-scale system to improve heat transfer. Samples of treated soil were collected for each 500-ton lot of soil (total of three lots). The results of the full-scale operation showed that the LTTD met the cleanup goal of 1 mg/kg total pesticides in each of the three lots. Data also showed that concentrations of dioxins and furans in the treated soil were less than in the untreated soil. McLaren/Hart used the results of the FCX application to identify a number of modifications and improvements to the LTTD system to further improve heat transfer rates and to decrease the overall length of the treatment cycles for other applications. A detailed summary of these improvements is included in the report. |
