Technology:
Vitrification:
- Geosafe's pilot-scale vitrification system with a treatment capacity of 2,000 pounds per batch
- System included two cylindrical carbon steel test containers (60 inches high and 50 inches in diameter) set inside carbon steel containment boxes; electrodes were placed inside each container, along with thermocouples to monitor the temperature of the melt
- Off-gas equipment included desiccant and carbon filters, caustic scrubber, vapor-phase carbon filter, and thermal oxidizer
- Batch No. 1 - power applied for 34 hours with an average melt rate of 0.93 in/hr with a total of 785 kWhr of energy consumed; achieved a melt depth of 31.5 inches based on a reading of 1000 C centerline temperature; during this batch, significant steam was generated causing particulates and organics to be released in the off-gas; these problems were attributed to the high moisture content and the fine-grained nature of the sediment
- Batch No. 2 - power applied for 22 hours with an average melt rate of 0.9 in/hr with a total of 522 kWhr of energy consumed; achieved a melt depth of 33 inches based on a reading of 1000 C centerline temperature; to alleviate the problems in Batch No. 1, standing water was decanted from the sediments in the test container prior to the test
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Cleanup Authority:
CERCLA
- ROD signed April 1990
EPA Contact:
James M. Brown
U.S. EPA Region 1 (MC HBO)
1 Congress Street, Suite 1100
Boston, MA 02114
Telephone: (617) 918-1308
E-mail: brown.jim@epa.gov |
Contaminants:
PCBs
- Maximum concentrations in sediments of more than 200,000 mg/kg |
Waste Source:
Discharge of polychlorinated biphenyl (PCB)-contaminated wastewater from electronics manufacturing |
Type/Quantity of Media Treated:
Sediment
- Fine sandy silt with some clay-sized particles present; some small shell fragments present
- Moisture content - >50% by weight |
Purpose/Significance of Application:
Demonstration of vitrification to treat PCB-contaminated sediments |
Regulatory Requirements/Cleanup Goals:
Target goals for demonstration were 50 mg/kg for PCBs and the Toxicity Characteristic Leaching Procedure (TCLP) criteria for metals |
Results:
During Batch No. 1, operational difficulties were encountered as a result of the high moisture content and fine-grained nature of the sediment. Geosafe considered this batch to be an optimization test and Batch No. 2 to be the verification test. Therefore, data from the Batch No. 1 test was not included in the performance analysis
- Data from Batch No. 2 showed that PCB concentrations in the melt were reduced from as high as 2,085 mg/kg to below detectable levels in the treated sediment; the destruction removal efficiency for the process was 99.9905% for PCBs; TCLP metals concentrations in the melt were below the regulatory criteria |
Cost Factors:
The projected full-scale cost for vitrification of sediments was $20,687,000
- Projected full-scale costs were based on treating 18,000 tons sediment, for a unit cost of $1,149 per ton
- According to the vendor, this projected full-scale cost was based on treating sediments with a high moisture content; unit costs for vitrification of dry sludge are generally lower (about $400 per ton) |
Description:
The New Bedford Harbor Superfund Site is located along the northwestern shore of Buzzards Bay in New Bedford Massachusetts, approximately 55 miles south of Boston. From the 1940s to 1978, PCB-contaminated wastewater from electronics manufacturing operations was discharged onto the shoreline and into the harbor. Site investigations determined that sediments were contaminated with PCBs and heavy metals. The site was listed on the National Priorities List in September 1983. The ROD for a five acre area known as the "Hot Spot area" included dredging of PCB-contaminated sediments followed by incineration. However, due to opposition to incineration, EPA postponed the incineration component of the Hot Spot remedy to explore alternative treatment technologies. EPA evaluated four technologies as possible alternatives to incineration - solvent extraction/dechlorination, vitrification, thermal desorption/gas phase chemical reduction, and solidification/stabilization. This report covers the pilot-scale test of a vitrification process.
The pilot test was performed using Geosafe's vitrification system with a treatment capacity of 2,000 pounds per batch. Pilot tests were completed for two batches: Batch No. 1, where power was applied for 34 hours, achieving a melt depth of 31.5 inches; and Batch No. 2, where power was applied for 22 hours, achieving a melt depth of 33 inches. During Batch No. 1, operational difficulties were encountered as a result of the high moisture content and fine-grained nature of the sediment. As such, only data from Batch No. 2 were used for the performance assessment. To alleviate the operational problems from Batch No. 1, water was decanted from the sediments prior to testing of Batch No. 2. The results from Batch No. 2 showed that the vitrification process reduced PCB concentrations from 2,085 mg/kg to below detectable levels in the treated sediment, with a PCB destruction removal efficiency of 99.9905%. TCLP metals concentrations in the melt were below the regulatory criteria. According to Geosafe, full-scale in situ vitrification technology is not the technology of choice for treating soils/sediments with a high moisture content (i.e., fluid media). The first test was performed on sediments that contained standing water. While the water was decanted from the sediment for the second test, the moisture content of the sediment tested was above 50 percent. Geosafe indicated that dewatering the sediment to a moisture content of 10% prior to treatment would address the problem. |
