The International Information Center for Geotechnical Engineers

Thermal Desorption - Case Study: Industrial Latex Superfund Site

History and Contamination

Located in Wallington, New Jersey in a mixed residential and industrial area, Industrial Latex (IL) operated from 1951 to 1983. IL was a manufacturer of synthetic rubber compounds as well as chemical adhesives. The manufacturing processes for these products involved using solvents made up of volatile organic compouns (VOCs) as well as polychlorinated biphenyls (PCBs). After the company closed this location, the New Jersey Department of Environmental Protection (NJDEP) conducted an investigation in 1980 in response to complaints from a local official. Approximately 1600 open and leaking drums with various chemical compounds were found around the site (Miller, 1997) in addition, chemicals containing VOCs, SVOCs and PCBs were improperly disposed of in sanitary systems on the property. From 1986 to 1987, the United States Environmental Protection Agency (USEPA) stepped in and removed over 1,200 drums and 22 underground storage tanks. The site was added to the Superfund National Priorities List in March of 1989 after the EPA found contamination extended throughout the site (USEPA, 2003).

 

The property is located in the Passaic River basin (see Figure 5, below) with runoff flows running eastward towards a channel, which only flows during the wet seasons. In 1986, the U.S. Geological Survey measured the groundwater quality of the area (including wells outside the facility’s property limits) to find VOCs present in many of the locations. It was estimated that about 71,000 people used potable water drawn from wells within 3 miles of the site (Miller, 1997).

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Figure 6: Map of Latex Industries facility in relation to Passaic River, note: facility is located in the black trapezoid (Miller, 1997)

 

A remedial investigation and feasibility study was carried out by the USEPA between 1988 and 1992. This investigation declared the severity of the contamination and examined several different methods for remediation. In addition to the drums removed during 1986-1987, the investigation showed that there were also buried drums located around the property (Miller, 1997). A record of decision (ROD) was issued by the USEPA in September of 1992 which selected thermal desorption as the best remedy for the contamination (USEPA, 2003).

 

Remediation Solution and Design

The remediation goals consisted of lowering the concentration of PCBs to less than 1 ppm, the concentration of Arsenic to 20 ppm or less, and the concentrations of SVOCs: BEHP to 46 ppm or less and 3,3’-Dichlorobenzidene to 1.4 ppm or less (USEPA, 2003).

 

A “triple shell dryer” thermal desorption unit manufactured by Tarmac Industries was used for the remediation which is a form of indirect heated thermal desorption. The dryer consists of a rotating cylindrical kiln with two concentric cylinders, which supplied the heat. The system remediated soil at about 225 tons per day. The gases from the system were sent through a scrubber, venturi, and spray tower before finally exiting through activated carbon and high-efficiency particulate air filters. Water was recycled from the scrubber, venturi, and spray tower to rehydrate the treated soils. Treated soils were used as backfill for the site. Filter cakes as well as the recovered contaminants were treated and disposed offsite. A schematic of the design is referenced below in Figure 6.

 

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Figure 7: Triple Shell Dryer thermal desorption schematic (USEPA, 2003)

 

It was found that elevated levels of particulate formed at the stack during operation. To address the issue, engineers altered the HEPA filter housing to use a positive pressure seat and damper so that the combustion pressure would be maintained at a positive level. This did not affect the results of the thermal desorption. With maintenance being performed about once every 2 weeks, the system was operational for about 74% of the 14 months it was in use (USEPA, 2003).

 

Conclusion/Results

During the operation of the remediation plan, from April 1989 to June 2000, a total of 53,685 cubic yards of material were processed through the thermal desorption system. The analysis of the treatment showed that on average, PCBs were reduced to 0.16 mg/kg (equivalent to 0.16 ppm), SVOCs were reduced to 0.37 mg/kg, and 1.63 mg/kg for arsenic. Of the 260 stockpiles of soil, 16 had to be retreated because they did not meet the goals established for the project. The calculated cost came out to about $292 per cubic yard of material (USEPA, 2003). Thermal desorption proved to be a viable option for this case and worked very successfully.

 

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