Solvent Extraction/Dechlorination at the New Bedford Harbor Superfund Site, New Bedford, Massachusetts

Site Name:

New Bedford Harbor Superfund Site


New Bedford, Massachusetts

Period of

June 1996


Field demonstration

Solvent extraction/dechlorination
- Basic Extractive Sludge Treatment (B.E.S.T.®) solvent extraction process followed by Solvated Electron Technology (SET®) dechlorination process
- B.E.S.T.® process included feed material preparation, extraction, solids drying, and solvent recovery; diisopropylamine (DIPA) used as the extraction solvent; PCB-concentrated oil sent to SET® process
- SET® process included a mobile SET® unit with a one gallon per day processing capacity; concentrated oil reacted with liquid anhydrous ammonia followed by metallic sodium generating the solvated electron solution to reduce the PCBs
- Pilot testing included optimization testing to identify the optimum process parameters required to maximize extraction of PCBs from the sediment, and verification testing to collect data from the process operating under optimal conditions

Cleanup Authority:
- 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
Technology Vendors:
William Heins
Ionics RCC
3006 Northrop Way, Suite 200
Bellvue, WA 98004
Telephone: (425) 828-2400

Gerry Getman
Commodore Advances Sciences, Inc.
2340 Menaul Boulevard NE, Suite 400
Albuquerque, NM 87107
Telephone: (505) 872-6805
Fax: (505) 872-6827

- 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:
- 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 solvent extraction/dechlorination 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

The B.E.S.T.® process reduced concentrations of PCBs in sediments from as high as 2,515 mg/kg to below the target treatment goal of 50 mg/kg in as few as five extraction cycles, and PCB concentrations below 10 mg/kg were achieved after seven extraction cycles; TCLP metals in the treated sediment were below regulatory levels
- The SET® process reduced concentrations of PCBs in the concentrated oil from the B.E.S.T.® process from 49,000 mg/kg to levels ranging from not detected to 38 mg/kg, below the target treatment goal of 50 mg/kg

Cost Factors:
The projected full-scale cost for treatment of PCB-contaminated sediment using the combined B.E.S.T.® and SET® processes were $12,971,000, including $9,000,000 in capital costs and $3,971,000 in O&M costs
- Projected full-scale costs were based on treating 18,000 tons of sediment, for a unit cost of $721 per ton

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 solvent extraction/dechlorination process.

The pilot test was performed using the patented Ionics RCC B.E.S.T.® solvent extraction process to remove contaminants from the sediments, followed by the Commodore SET® process to treat the high concentration PCB oil from the B.E.S.T.® process. During the pilot test, the B.E.S.T.® process reduced concentrations of PCBs from as high as 2,515 mg/kg to 10 mg/kg; TCLP metals in the treated sediment were below regulatory levels. The SET® process reduced concentrations of PCBs in the concentrated oil from 49,000 mg/kg to below the levels ranging from not detected to 38 mg/kg. During the pilot test, problems were encountered with the feed mechanism for the SET® process, requiring modifications to the design and operation of the unit. These included modifying the feed mechanism design to handle semi-solid, waxy material rather than liquid and using excess sodium to address problems with untreated material contaminating treated material.