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DEMONSTRATION BULLETIN: TERRA KLEEN SOLVENT EXTRACTION TECHNOLOGY - TERRA-KLEEN RESPONSE GROUP, INC.
Citation:
Engle, S. DEMONSTRATION BULLETIN: TERRA KLEEN SOLVENT EXTRACTION TECHNOLOGY - TERRA-KLEEN RESPONSE GROUP, INC. U.S. Environmental Protection Agency, Washington, DC, EPA/540/MR-94/521, 1994.
Description:
The Terra-Kleen Solvent Extraction Technology was developed by Terra-Kleen Response Group, Inc., to remove polychlorinated biphenyls (PCB) and other organic constituents from contaminated soil. This batch process system uses a proprietary solvent at ambient temperatures to treat the contaminated soil. The system includes a solvent regeneration system that concentrates the extracted contaminants and allows the extracted solvent to be reused. Following treatment, clean soils are returned to the site, and the concentrated contaminant is sent off site for disposal. The system includes the following equipment: five extraction tanks, a sedimentation tank, a microfiltration unit, a solvent purification station, a clean solvent storage tank, and a vacuum extraction system. Since the solvent used is flammable, pneumatic, and spark-proof pumping systems are used to move the solvent and vapor through the system, thus maintaining an intrinsically safe environment. Treatment begins after the excavated soil is loaded into the extraction tanks. Screening of solids is not necessary, but may be advantageous when large rocks and/or debris are present. Clean solvent from the solvent storage tank is then pumped into the extraction tanks. The soil and solvent are held in the extraction tank for a time period sufficient to solubilize organic contaminants, separating them from the soil. The contaminant-laden solvent is then transferred from the extraction tank into the sedimentation tank. Clarified solvent is pumped to the microfiltration unit and the solvent purification station prior to recycling. Solvent wash cycles are continued until a site-specific soil cleanup level is attained. Some residual solvent remains in the soil after the wash cycles are completed. Vacuum extraction is used to remove the majority of the residual solvent by drawing solvent vapor through a condenser and liquid filter. Following vapor extraction, an active biological culture is added to the treated soil to biodegrade any remaining residual solvent. Finally, the treated soils are removed from the extraction tanks.
The solvent regeneration process begins by pumping contaminant-laden solvent from the sedimentation tank through a microfiltration unit and a proprietary solvent purification station. The microfiltration unit removes any fines remaining in the solvent. The solvent purification station separates organic contaminants from the solvent and concentrates them, reducing the volume of hazardous waste for offsite disposal. The regenerated solvent is then pumped into the clean solvent storage tank for use in subsequent wash cycles.