4.1.2.7 Description of Alternative 7, Solvent Extraction Treatment by solvent extraction would involve the excavation and transportation of all contaminated soil, sludge, and sediment to the pretreatment area located at the CTF (see Figure 4-1). The material would then be screened and sorted in the staging area prior to being fed into the solvent extraction system. All materials that do not pass the screening should be crushed or shredded and screened once more before input into the solvent extraction system. Wastes for which crushing and shredding is not an option such as large appliances would undergo a debris washing stage. Water from this washing would be collected and directed to a wastewater treatment system. The decontaminated debris would then be sampled and sent off site for disposal in an appropriate landfill. The screened materials would then be treated by a solvent extraction system. Treated solids meeting the 2-ppm cleanup standard would be disposed of off site in a solid waste landfill at the disposal facility. Treated solids not meeting the cleanup standard would be disposed of at a TSCA landfill or incinerator. Treatment residuals containing less than 50 ppm of PCBs may be disposed of in a solid waste landfill with written approval of the State. Clean process water generated by dewatering and moisture removal activities could be disposed of after analytical sampling. This water is normally treatable by the local POTW. A concentrated oily waste stream resulting from solvent extraction would require further off-site treatment such as incineration. Figures 4-24 and 4-25 present the material flow diagram for Scenario 1 and Scenario 2 respectively. Three solvent extraction systems are described below in detail. These systems are available at full scale and include the RCC B.E.S.T. process; the CF System's LG-SX process; and the Terra-Kleen Response Group, Inc. Solvent Extraction Treatment System process. The B.E.S.T. system was demonstrated at the Grand Calumet River site in Gary, Indiana, during a pilot-scale SITE demonstration. The LG-SX process was demonstrated at the New Bedford Harbor site in Massachusetts during a pilot-scale SITE demonstration. The Terra-Kleen system was demonstrated at the NASNI site in California during a pilot-scale SITE demonstration. Other solvent extraction systems may be considered during the design stage if solvent extraction is selected. General support requirements of solvent extraction are also discussed below. Resource Conservation Company Basic Extractive Sludge Treatment (B.E.S.T. ) Process The B.E.S.T. process is a solvent extraction system that separates organic contaminants from contaminated materials. The primary distinguishing feature of the process is the extraction solvent, TEA. The system description below details the setup of the B.E.S.T. system during the SITE demonstration at the Grand Calumet River site in Gary, Indiana (EPA 1993d). FIGURE 4-24 MATERIAL FLOW DIAGRAM FOR ALTERNATIVE 7, SCENARIO 1FIGURE 4-25 MATERIAL FLOW DIAGRAM FOR ALTERNATIVE 7, SCENARIO 2 The full-scale system consists of three extractor units, each capable of processing 75 tons per day. It is estimated that with three 75-ton per day units with a total throughput of approximately 125 tons per day and operating 7 days a week for 365 days a year, it would take 6.3 years to remediate the 285,800 tons of contaminated materials under Scenario 1and 8.5 years to remediate 388,000 tons of contaminated materials under Scenario 2. After the contaminated material is screened to particles of less than 1-inch diameter, it would be placed in either a premix tank or in one of three 75-ton per day extractor/dryer units (see Figure 4-26). The premix tank would be used first if the wastes have a high oil and/or water content. In the premix tank, the contaminated materials undergo a cold extraction step to remove excess water and oil. The tank is sealed and purged with nitrogen, and cold TEA solvent is added along with a predetermined amount of caustic. The mixture is agitated for 5 to 30 minutes and then allowed to settle. The resulting solution of solvated oil, water, and TEA is decanted through ports located on one side of the premix tank and drained to the decant pump, which transports the mixture to the centrifuge. Cold extractions may be repeated as necessary. The fine solids suspended in the mixture are separated by centrifugation and directed to the extractor/dryer unit. Once a sufficient volume of moisture-free solids is accumulated, the solids are transferred to a steam- jacketed extractor/dryer. If the material entering the system does not require the premix step (that is, material with low oil and water content), it may be added directly to one of the three 75-ton per day extractor/dryer units. Warm TEA is then added, and the mixture is heated, agitated, allowed to settle, and decanted, thereby extracting the remaining organics. This process may also be repeated as necessary. The concentrate recovered from the extraction stage flows to the oil decanter where it is separated into its aqueous and organic components. The aqueous phase is transferred to a water tank. The organic phase, which contains a mixture of TEA, oil, and water, is pumped from the oil decanter to the solvent evaporator and heated. TEA solvent and water each have unique properties as pure liquids. Once these chemicals are combined, they form a mixture with different properties than either of the original constituents. Properties such as boiling point, melting point, and solubility can change dramatically. By combining water and TEA, a lower boiling point mixture is formed. This mixture is called an azeotrope. In the solvent evaporator, the organic phase is heated so that the low-boiling point azeotrope of solvent and water (boiling point of approximately 170 澹) is evaporated, leaving the oil behind. Heating of the mixture continues until the water is removed. At this point, the temperature of the boiling liquid rises until it reaches the boiling point of pure TEA of 193 澹, and evaporation continues until nearly all the TEA is removed. The TEA and water vapor from the solvent evaporator is condensed in noncontact heat exchangers using 100 澹 cooling water. The condensed stream is only partially miscible, so the TEA can be separated using a continuous-flow solvent decanter. The recovered solvent is recycled back to the solvent storage tank, and the water is drained by gravity to a water storage tank until stripping operations are performed. Oil processing is also performed in the solvent evaporator. Minor amounts of solvent are released by injecting a small amount of water into the oil fraction, which forms an azeotrope with the TEA and evaporates. The recovered oil fraction is typically incinerated off site to destroy the organics. The solids remaining in the steam jacketed extractor/dryer contain TEA that should be removed before the solid material is disposed of. Before drying, a small amount of caustic is added for pH control. The extractor/dryer is equipped with a steam jacket and direct steam injection ports. To dry the treated solids, steam is first supplied to the steam jacket to heat the mixture to 170 澹. After the bulk of the solvent is removed, steam is directly injected into the vessel. The entire drying process is performed with the extractor/dryer mixing paddles rotating. The mixing action increases heat transfer, thus reducing the time required for drying. The solvent and steam form an azeotrope and are then transferred to the dryer condenser. After the drying process is complete, the solids are removed through the discharge port on the bottom of the extractor/dryer. After solids drying, the solids typically retain approximately 150 ppm of the TEA solvent in the form of a nonvolatile triammonium salt. The treated nonhazardous solids could be shipped off site and deposited in a solid waste landfill or a TSCA landfill, depending on the remaining PCB concentration. Once in the landfill, RCC claims the TEA will be degraded through the following three ways: (1) some of the triammonium salt will be biodegraded by the commonly occurring soil bacteria known as "Aerobacter"; (2) some of the triammonium salt will hydrolyze into volatile TEA, enter the water in the landfill, and degrade with a 4.5-hour half-life; and (3) some of the triammonium salt will hydrolyze into volatile TEA and enter the atmosphere, where it will be rapidly, photochemically degraded into nitrogen and carbon dioxide gases (Howard and others 1990). During RCC's studies, the treated soil was neutralized, the moisture content was adjusted, and the soil was mixed with a native, bacteria-active soil (Erikson 1992). Results of this study show that 99 percent of the TEA degraded in 20 hours. It has also been reported that TEA was biodegraded from 200 ppm to a nondetectable level in 18 hours (EPA 1980). The degradation time for the TEA in the landfilled solids cannot be accurately estimated because no data are available for this type of degradation. Available data suggest that TEA degradation is fairly rapid at optimal pH and moisture conditions. Condensed water and TEA are separated using direct-contact steam stripping. Before the TEA is stripped from the decant water, a caustic soda is added to the water to raise the pH. Steam is injected directly into the bottom of the stripping column to heat it to the desired temperature. The water and TEA mixture is preheated and introduced into the top of the stripping column. The mixture flows through the column and is stripped of residual TEA solvent by upflowing steam. The still bottoms are then discharged as product water. This water is sampled and analyzed for the following parameters: pH, total suspended solids, total dissolved solids, oil and grease, residual solvent, conductivity, and PCBs. This product water can then be disposed of properly pending the analytical results. The solvent azeotrope vapors are routed to the water stripper condenser, and the recovered solvent is recycled. The full-scale B.E.S.T. system has an estimated throughput of 125 tons per day for the CD wastes. CF Systems Corporation Liquefied Gas Solvent Extraction Process The CF Systems LG-SX process is a continuous extraction process that uses a mixture of liquified propane and butane to extract organics from contaminated materials. The process provides a reduction in the volume of material requiring treatment by concentrating the organics in an oil stream. CF Systems offers a large variety of units to treat sludge and soil containing organic contaminants. The skid-mounted Pit Cleanup Unit (PCU)-50 has a process capacity of 12 tons per day. The PCU-200, which is mounted on two trailers, can be mobilized or demobilized in 10 to 15 days and can process 50 tons per day. The PCU-500, which can be mobilized or demobilized in 4 to 8 weeks can process 100 tons per day. The PCU-1000, which is skid-mounted and transportable with multiple modules, requires 2 to 3 months for mobilization and demobilization and can process 200 tons per day. These units can also be combined in series or in parallel combinations to speed up the remediation time. The vendor states that the system can be operated by three crews working 8-hour shifts for 24 hours per day for 350 days a year (EPA 1990b). If the PCU-1000 unit is used, 125 tons per day of the CD waste could potentially be processed, resulting in a total treatment time of approximately 6.5 years for the 285,800 tons under Scenario 1 and 8.9 years for the 388,000 tons under Scenario 2. The system description below details the setup of the CF Systems LG-SX technology during the SITE demonstration at the New Bedford Harbor site in New Bedford, Massachusetts (EPA 1990b). If necessary, pretreatment may consist of converting the feed into a slurry through the addition of water to meet system viscosity requirements. Figure 4-27 presents a process flow diagram. The feed is transferred to the feed kettle and suspended by two counter-rotating agitators. The slurried solids are then pumped through a basket strainer, which removes particles of greater than 0.2 inch in diameter. The feed flows into the first extractor and is mixed with the propane and butane solvent. The mixture is then agitated, and the mixture is transferred to a decanter where it is separated into two immiscible layers. The solids and water, which are the denser fractions, settle and proceed to the second extractor. The decanter overflow, which contains extracted organics, propane and butane, and fine solids, flows through a filter and then to the solvent recovery column. The pressure difference between the first decanter and the second extractor moves the solid-liquid stream into the second extractor for second-stage extraction. Fresh liquified solvent from the solvent recovery process is then mixed with the solids and water stream to further extract organic compounds. The mixture is then agitated, and the solvent and organics mixture is removed to a second decanter where two immiscible layers are formed. The solids and water layer flows from the bottom of the decanter and proceeds to the treated solids product tanks. The solvent and organics layer is recycled to the first extractor for extraction. The solvent/organics stream from the first extraction step passes through a filter cartridge that collects fine solids and passes to the solvent recovery column. In the solvent recovery column, the solvent is vaporized and condensed, and the heavy organic contaminants remain as a separate liquid. The mixture of heavy organics, which contains some dissolved propane, gathers in a reboiler and then passes to the extract product tank. The recovered solvent flows into the main compressor. The compressed solvent passes through the column reboiler heat exchanger to provide the necessary heat to boil off the residual solvent present in the extracted organics. The condensed solvent then reenters the extraction system through the second extractor. The residual solvent that vaporizes from the system products in the extract or treated sediment tanks flows to a low-pressure solvent compressor. The outlet stream of the compressor is fed to the main compressor, where it is compressed further along with the vapors from the column overhead. The compressed solvent passes through the column reboiler heat exchanger, is purified, and is sent back to the second extractor. Terra-Kleen Response Group, Inc., Solvent Extraction Treatment System The Terra-Kleen Solvent Extraction Treatment System is a batch process system that uses a proprietary solvent to separate organic contaminants from contaminated materials. The system also concentrates the contaminants, reducing the volume of hazardous wastes for final disposal. Terra-Kleen offers both 1-ton and 5-ton pilot-scale capacity units. A 250-ton system is currently in operation at the NCS-Stockton site in Stockton, California, and consists of 19 roll-off units, each with a 16- to 17-yd3 capacity. The system can be suited to site-specific requirements. The time to clean up the site will depend on the number of solvent wash cycles required to reach the incinerator equivalency of 2 ppm. Each wash cycle should require approximately 8 hours to complete. The system description below details the setup of the Terra-Kleen system used during the pilot-scale demonstration performed at the NASNI site near San Diego, California (PRC 1994a). Figure 4-28 presents a process flow diagram of the Terra-Kleen system used in at the pilot-scale demonstration at the NASNI site. The system consisted of five solvent extraction tanks, Tanks A through E; a sedimentation tank; a microfiltration unit; a solvent purification station; a clean solvent storage tank; and a vacuum extraction system. Because the solvent is flammable, pneumatic and spark-proof pumping systems transport the solvent and vapor through the system to maintain an intrinsically safe environment. Extraction and contaminant removal takes place in the five solvent extraction tanks, which for the SITE pilot-scale demonstration had 1-ton capacities. The contaminated materials are loaded into the tanks with a front-end loader. After the material is loaded into the solvent extraction tanks, proprietary solvent is pumped into the tanks from the solvent storage tank, and the material is mixed with the solvent. Solids and solvent are held in the extraction tank to allow organic contaminants to solubilize in the solvent, separating them from the soil. The contaminant/solvent mixture is then removed from the extraction tanks. Solvent removal time depends on the composition of the contaminated materials; however, Terra-Kleen estimates this time to be 8 hours or less for most waste types. The contaminant-laden solvent is then transferred from the extraction tanks to the sedimentation tank. Suspended solids that settle or coagulate in the sedimentation tank are removed and analyzed. When contaminant concentrations are below the cleanup standard, the solids are added to the treated solids. Solvent washes continue until the site-specific soil cleanup level is attained. On-site air monitoring equipment is used to monitor organic levels during treatment. Wash solvent and treated soil are analyzed to measure the progress of contaminant removal. Final treatment levels are confirmed by off-site gas chromatograph analysis. After the solvent washes, any solvent remaining in the treated solids is removed using vacuum extraction and biological treatment. Vacuum extraction removes most residual solvent by drawing a vacuum on the extraction tank using a centrifugal blower. Solvent vapor and air are drawn out of the tanks, passed through a condenser and liquid filter, and vented to the air. In Terra-Kleen's proposed full-scale system, the treated air is recirculated back to the extraction tanks in a closed-loop configuration. After vapor extraction, an active biological culture and nutrient media are introduced to the treated soil to biodegrade any remaining residual solvent. After biological treatment, treated solids are disposed of in accordance with project requirements and applicable regulations. The solvent regeneration process begins by pumping contaminant- laden solvent from the sedimentation tank through the microfiltration unit and the proprietary solvent purification station. The microfiltration unit removes fines remaining in the solvent. The separated fines are analyzed before addition to the treated solids. The solvent purification station separates organic contaminants from the solvent and concentrates them, reducing the volume of hazardous waste for off-site disposal. Regenerated solvent is then pumped into the clean solvent storage tank for reuse in subsequent wash cycles. During the demonstration and treatability studies, solvent exiting the solvent purification station was sampled to confirm that contaminants were removed. Solvent Extraction Support Requirements Solvent extraction support requirements include site mobilization and access requirements, a treatment building, utilities, pretreatment of contaminated materials and post-treatment of residuals from the system. Mobilization and Access Requirements The site must be cleared to allow construction and access to the treatment system. It is estimated that one 75-ton per day, full- scale B.E.S.T. system will need to be transported on 11 truckloads. The access road must be at least 8 feet wide to admit the trucks. The road should also be capable of supporting loads of up to 40,000 pounds. At least 1 acre should be available for the assembly of the B.E.S.T. system. Once constructed, the system, storage tanks, and auxiliary equipment could occupy approximately 10,000 square feet. Over much of this area, a pad could be required to support the system. In addition, the National Fire Prevention Association (NFPA) requires that a perimeter be established around the solvent extraction equipment, which increases the area required by the system. A separate area should be provided for staging wastes for treatment and for storing treated solids. The required site dimensions will depend on the configuration of the full-scale system, which is somewhat flexible. For a proposed site layout of the B.E.S.T. system, see Figure 4-29. The CF Systems skid-mounted PCU-1000 should require approximately 4,000 square feet. The entire system is easily mobilized by truck and can be transported on public roads. Auxiliary storage buildings for solvents and wastes awaiting treatment would require additional space. Sufficient space is also required for the setup of support facilities such as an office, laboratories, sanitary facilities, power generation station, and a cooling water supply source. Setup of the system is flexible because of the PCU's modular design. More detailed area requirements are project-specific. Site requirements for the Terra-Kleen system range from 300 square feet for small-scale, single- extraction vessel configurations for treatability studies to 4,000 square feet for larger systems, such as the one implemented at the NCS-Stockton site. The system is easily transported by truck and the setup is flexible. More detailed area requirements are project-specific. Building The B.E.S.T. system consists of a mixing tank, an extractor/dryer unit, a centrifuge, storage tanks, an oil and a solvent decanter, a solvent evaporator, and a water stripper. The treatment system does not require a heated enclosure for all- weather operations. The only building requirement is an indoor storage facility for spare parts storage. If one is not available on site, a building must be constructed. In addition, a pad of approximately 10,000 square feet will need to be constructed in order to support the B.E.S.T. system. All other building needs such as an equipment and a laboratory trailer would be brought on site. A storage area would need to be constructed for the treated wastes pending disposal. The LG-SX process consists of extraction tanks, decantation tanks, a filtration unit, a solvent purification station, compressors, and a basket strainer. The location selected for the CTF should be covered with asphalt or a concrete pad where the system is to be placed. In addition, a space for safe storage of liquefied solvent should also be constructed. On operating days when treatment goals are not being met, sufficient storage capacity is required for the contaminated waste that remains untreated. A heated enclosure should be constructed so that operations can be conducted in all weather conditions. This building must be constructed to meet the feed parameter temperature of 60 to 120 澹. Support facilities such as an office trailer, an analytical laboratory, and sanitary facilities can all be transported and set up easily on site. The Terra-Kleen system consists of extraction tanks, a sedimentation tank, a microfiltration unit, a solvent purification station, a clean solvent storage tank, and a vacuum extraction system. The location selected for the CTF would need to be covered with asphalt or a concrete pad where the system is to be placed. An HDPE containment area would need to be constructed at the site before assembly of the Terra-Kleen system. This containment area is designed to prevent migration of potential surface contamination into work areas because of decontamination activities or accidental leaks or spills from the Terra-Kleen system. The containment area would underlie and surround the process equipment area and may consist of two layers of 10-mil thick polyethylene liners and a rubber friction mat. The edges of the HDPE containment area could be secured by wooden two-by-fours wrapped with 10-mil thick liner material. A temporary decontamination pad could be erected within a fenced area at the site. The pad may be constructed of polyethylene liner and may be sloped to create a sump for decontamination water collection. This pad could be used to decontaminate heavy equipment such as the backhoe. A heated enclosure may need to be constructed for the system so that operations can be conducted in all weather conditions. Utilities The only utilities required by the full-scale B.E.S.T. system are electricity and water. The site should have at least 430 kW of three-phase, 440-volt power available. Potable water requirements are 1,000 gallons per day for treatment, decontamination, and other operations. Steam and compressed air would be provided by a boiler and an air compressor that would be transported to the CTF with the system. The electrical requirement of the LG-SX process is a 440-volt, three-phase, 100-ampere electrical service. Process water will need to be supplied at an estimated rate of 5 gpm. This water would need to be maintained at a 60 to 80 澹 inlet temperature. Potable water is required. Canisters of propane and butane solvent would need to be provided. Nitrogen is required to pressure test the system before startup. The above specifications only apply to the pilot-scale PCU-20 unit and are expected to differ for the full-scale commercial unit. The water requirement for the Terra-Kleen process equipment is approximately 6 gpm delivered at a pressure of 60 pounds per square inch (psi). This volume is sufficient to meet the needs of the Terra-Kleen process system and to decontaminate equipment. Electricity is needed for the Terra-Kleen system and the office trailers. The Terra-Kleen system operates on a 220-volt, three- phase, 50-ampere service. Additional electrical power (60 amperes of a 110-volt, single-phase service) could be needed mainly to light the office trailer and to operate the on-site mobile laboratory and office equipment (PRC 1994a). Telephone service is required for obtaining equipment parts and maintenance services, scheduling deliveries and sample pickups, and allowing potential emergency communications. Pretreatment of Contaminated Materials Pretreatment requirements for the B.E.S.T. system consist of screening all contaminated soil to materials of less than 1 inch in diameter. The oversized materials should be handled as discussed in Section 3.3.2.3. Blending the various waste forms (sediment, sludge, and soils) is not necessary, but blending the wastes to achieve a homogenous contamination level would be helpful because only one preliminary bench-scale test would need to be run on the material. Pretreatment requirements for the CF Systems process are site- specific. Possible pretreatment includes removing particles of greater than 0.2 inch in diameter, decreasing waste viscosity, and maintaining feed temperature. In addition, feed consistency should be homogeneous to reduce process uncertainty and improve flow rate control. A sieving or screening method can be used to separate wastes. The oversized materials should be handled as discussed in Section 3.3.2.3. Common storage tanks and mixing equipment are adequate to provide a homogenous source of feed, and heat can be provided by steam addition. The potable water supply can be used to form a slurry that conforms to process viscosity requirements. The Terra-Kleen treatment technology does not require soil screening equipment to remove oversized materials before treatment, although it may be advantageous to remove large rocks, debris, or objects too large for safe handling during loading and unloading of the treatment tanks. Dewatering, which lowers the moisture content of the untreated soil, may be a necessary pretreatment step in the treatment process for soils at the CD sites. Dewatering is necessary to decrease the compactability of the soil, reduce water accumulation in the system, and decrease solvent dilution. Blending the various waste forms (sediment, sludge, and soils) is not necessary, but blending the wastes to achieve a homogenous contamination level would be helpful because only one preliminary bench-scale test would need to be run on the material. Post-treatment of System Residuals The B.E.S.T. process produces three waste streams: treated solids, process water, and concentrated oily waste. The treated solids would require sampling and analytical testing to determine the proper method of disposal. Treated solids meeting the 2-ppm cleanup standard could be disposed of off site at a solid waste landfill. The process water does not usually require further treatment or special handling procedures. Depending on analytical testing results, the water could either be sent to the local POTW or, if characterized as a RCRA waste, may be drummed and disposed of at a RCRA-regulated facility. Treatment for the two product streams generated by the LG-SX process is also required. The extract contains concentrated organics, and the treated slurry contains water and solids. The concentrated oily waste should be drummed and either shipped off site for treatment by dechlorination or incinerated to destroy contaminants. If temporary storage of this waste is required, the drums would be placed in a building with a concrete floor and containment berms such as the materials handling building and stored in compliance with RCRA and TSCA regulations. A volume increase would occur if water is added during pretreatment, and dewatering could be necessary. If dewatering effluent is used during pretreatment, wastewater treatment costs could be minimized. The Terra-Kleen system produces spent filters, regenerated solvent, treated solids, and a concentrated organics stream. Spent filters generated during filtration in the solvent recovery system can be incinerated off site. The disposal of the spent filters is the responsibility of Terra-Kleen. The regenerated solvent should be tested at the end of the pilot-scale study to determine if it is a RCRA characteristic waste. If the regenerated solvent is not considered a RCRA waste, the vendor could reuse the solvent at another site; however, if the regenerated solvent is considered RCRA waste, the vendor would ship the solvent off site to a permitted incineration facility. The disposal and/or reuse of the regenerated solvent is the responsibility of Terra-Kleen. Solids from the settling tank would be transported to the solvent extraction tank for additional treatment. Treated solids meeting the 2-ppm cleanup standard could be disposed of off site either at a solid waste landfill or at a TSCA landfill. Materials containing concentrated organic contaminants (primarily PCBs) should be drummed and shipped off site for incineration. If temporary storage of this waste is required, the drums may be placed in a building with a concrete floor and containment berms such as the materials handling building and stored in compliance with RCRA and TSCA requirements. The additional treatment of solids, the disposal of solids, and concentrated organic contaminants are the responsibility of Terra-Kleen.