Solvent extraction and soil washing treatment of contaminated soils from wood preserving sites: Bench-scale studies

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Solvent Extraction and Soil Washing Treatment of Contaminated Soils from Wood Preserving Sites: Bench-Scale Studies Endalkachew Sahle-Demessie Do.Jtg-las W Grosse Edward R. Bates Endalkachew Sahle- Demessie is a research engineer at the US. Environmental Protec- tion Agency (EPA), National Risk Manage- ment Research Labora- toty, Cincinnati, Ohio. He has been working on the application of emerging treatment technologies for remediating contami- nated soils. Doughs W Grosse has worked as an environmental engineer at the US. EPA in Cincin- nati, Ohio, f o r the past 21 years. Currently, he is working in Technology Transfer by serving as a specialist in site remediation and indus- trial wastewater treat- ment. Edward R. Bates has been with the US. EPA in Cincinnati, Ohio, as a physical scientist since 197% Since 1989 his principal duties have been to provide expert technical assistance on all aspects of Superfund site remediation, includ- ing characterization, remedy selection, remedy design, and field imple- mentation. Beizch-scalesol2iel.zt extmction and soil uashing studies wereperformed on soilsamples obtnzned from three abandoned woodpreservingsites zncluded in the Nationnl Priority List. %e soilsamples from thesesites were contumi- nated zuith high levels of po4yuromatic h-ydrocarboizs (PAHs), pentachlo- mphenol (PCP), dioxiizs, and heaty metals. The efectiveness of the solzient extraction process was assessed iwing liquefiedpropane or dimethyl ether as soheyits ozw a raiige of operating conditions. Tl2ese studies hatie demonstrated that a two-stage solvent extraction process using dimethyl ether as a solvent at a ratio of 1.6lperkg ofsoil could decrease dioxin leuels ipi thesoil by9-3 0t098.9percent9 andPCPlevels b y 9 5 lpercent. Reductioiz percentages. for benzo(a)py-ene (BaPl potenc-y estimnte and total detected PAHs wwe 82 4 mid 98.6percent, respectively. Metals coizcentratioiis were not reduced by the solvetit extraction treatment. i%ese remorial levels could be signiJicaiat(iI improved usiizg a multistage extraction system. Coin vier- cia1 scale solrwit extraction usiiig liquefied gases costs about $220per topi of contami?iatec/ soil. However, ,field application of this technology at the United Creosote site, Conroe, Te.xas, failed to perform to the leuel obsemJed at beiich scale due to the excessitie foaming and air emissiori problem Soil washijig using sqfactant solution and wet screening treatability studies were alsoperformed on thesoilsamples iiz order to assess remediation stra tegies jo I sites. A lth ot g h aqz 1 eo us phase solubility of co rz ta I n i 1. z ci nts seemed to be the most iinportaizt factor affecting removnl of contaminants @on% soil, sir ifiictant solutions (3 percent by weight) bavirzg iaonionic surfactmts with hydrophile-lipophile balance (HLB) of about 14 (Mukon- 12 artd Igepul CA 720) reduced the PAHlevels by an average of 71percent, Citation of product. company, or trade names do not constitute endorsement by the US. Environmental Protcction Agency and are provided only for the purpose of better describing inforniation in this article. Opinions expressed are those of the authors and should not be construed as representing positions or policy of the U.S. Environmental Protection Agency. 0 2000 John Wiley & Sons, Inc. 85 ENDALKACHEW SAHLE-DEMESSIE DOUGLAS W. GROSSE EDWARD R BATES Many wood preserving facilities date back to the rapid development of railroads in the nineteenth century where creosote treated wooden ties were used. compared to no measurable change when pure deionized water was used. Large fractioza of clay and silt (SOLVENT EXTRACTION AND SOIL WASHING TREATMENT OF CONTAMINATED SOILS FROM WOOD PRESERVING SITES Solvent extraction is a method of reducing the volume of the contaminated material that requires further treatment or disposal by concentrating the contaminants into a smaller volume of material. on the rate and effectiveness of extraction. Previous bench- and pilot-scale treatability studies have shown that solvent extraction may be an effective method for remediation of soils contaminated with organic wastes (Assink, 1985). However, a full-scale field application at the United Creosote site in Conroe, Texas, did not work as expected and was abandoned in favor of removing the wastes for off-site disposal. This paper presents the results of bench-scale solvent extraction studies performed on surface soils contaminated with PAHs, PCP, and dioxins obtained from the McCormick and Baxter Wood Preserving site in Stockton, California. The objectives of these studies were to select appropriate solvent or solvent mixtures; identify factors that affect the rate and efficiency of contaminant removal such as method of contacting, solvent/soil ratios, pretreatments, soil characteristics, and the number of contacting stages; and optimize the design and operation of the process to achieve remediation goals. The other remediation technology presented in this paper is soil washing. Although aqueous solubility of the contaminant seems to be the most important factor affecting removal of contaminants from soil, surfac- tants have expanded the application of soil washing for low solubility contaminants. Bench-scale soil washing studies were conducted on soils contaminated with PAHs, PCP, and dioxins obtained from the McCormick and Baxter Wood Preserving site, the RAB Valley site in Panama, Oklahoma, and the American Creosote Works site in Jackson, Tennessee. Solvent Extraction Overview Solvent extraction is a method of reducing the volume of the contaminated material that requires further treatment or disposal by concentrating the contaminants into a smaller volume of material. It is a method of removing contaminants from the solid phase by contacting the solids with a nonaqueous fluid that selectively dissolves and mobilizes the contaminants. The fluids used are usually organic solvents, liquefied gases, or supercritical fluids that have high affinity for the contaminants. Solvent extraction has been demonstrated to be an effective method for reducing contaminants below the cleanup goals for sediments and soils contaminated with PCBs, oil refinery wastes, and pesticides (Hall & Sandrin, 1990). A flow diagram for a typical solvent extraction system is shown in Exhibit 1. The process consists of soil extraction and solvent recovery,' recycle. Several solvent extraction systems have been proposed and tested in the US EPA's Superfund Innovative Technology Evaluation (SITE) program. These systems were investigated for degree of contaminant reduction achieved, treatment cost, and emission problems. Most of the extraction processes have been tested on polychlorinated biphenyls (PCB) contaminated soils and sludges, and have been shown to reduce concentrations of PCB from the contaminated sediment by more than 99 percent (Meckes et al., 1992). Each extraction system has a unique contacting method, solvent type, and requirement for pre- or post- treatments (Meckes et al., 1993; US EPA, 1993a). Selection of the best REMEDIATION/SUMMER 2000 87 ENDALKACHEW SAHLE-DEMESSIE DOUGLAS W. GROSSE EDWARD R BATES Exhibit 1. Flow Diagram for a Solvent Extraction System Soil Feed Make-up Solvent I Solvent I A Non-condensable Gases Solvent Solvent Regeneration and Recovery Solid-Liquid Soh Separation Removal v Clean soil Concentrated Contaminant to Destruction process or Hazardous Waste extraction solvent for a particular contaminant is not obvious, and extraction efficiencies vary for different types of soils, levels of contami- nant, and site-specific parameters. Properties of solvents that are impor- tant are dissolving power, cost, volatility, flammability, surface tension, and heat of vaporization. Additionally, the solvent used must not be a US EPA listed hazardous waste. The effectiveness of solvent extraction for remediating soils contami- nated by PCBs, pesticides, and other hydrocarbons has been demonstrated (Sahle-Demessie et al., 1996; US EPA, 1995b; 1992; 1993b). However, the application of solvent extraction technology for wood preserving sites and measuring its efficacy in treating soils with high levels of dioxins, PAHs, and PCP has not been systematically investigated. The objective of this treatability study was to answer some of these questions. EXPERIMENTAL DESIGN Soil samples for this study were obtained from the McCormick and Baxter (MCB) Wood Preserving site in Stockton, California. This site is a 88 REMEDIATION/SUMMER 2000 SOLVENT EXTRACTION AND SOIL WASHING TREATMENT OF CONTAMINATED SOILS FROM WOOD PRESERVING SITES 29-acre foriner wood treatment facility. Preservative solutions used at the site contained creosote oil, PCP, and water-based compounds containing chromated coppei- arsenate (CCA) and aniiiioniacal copper zinc ai-senate (ACZA) (US EPA, 1978). PCP and PAHs have been found in the ground- water at the depth of 175 feet below the ground surface. Soil samples were collected from the surface to about 3 feet deep from the retort area, screened with a 0.5 inch screen and then homogenized using drum rollers. The soil has 2.8 percent total organic carbon, and is composed of brown silt or clay with 3 percent gravel and 38 percent sand. Sixty percent of particles are finer than 0.081 iiini. Extractions were perfornied by CF Systems Inc. using liquefied dimethyl ether (DME') as a solvent at moderate pressures of 160 to 250 pounds per square inch (psi) and a temperature of48 "C. A typical pressure and temperature history of a two-stage extraction process is shown in Exhibit 2. A total of seven batch extractions tests were made with each batch of soil treated in a two-stage process (Exhibit 3). Feed was honiogenized to provide consistent and adequate flow rates. The screened untreated soil was charged to the windowed high-pressure extraction vessel, which was equipped with an air driven mixer. Preliminary runs were iiiacle to determine the appropriate mixing speed, settling time, and solvent-to-soil ratios. The vessel was sealed and liquid dimethyl ether was Exhibit 2. Temperature and Pressure History for a Two-Stage Extraction Process Using Dimethyl Ether as a Solvent 55 50 0 * - 45 t! 40 35 3 a, F +2+ Temperature. CI -+- Pressure 280 240 .- 200 v) e 160 L 80 40 I 25 ' I I I I I 10 Time, min 0 10 20 30 40 50 60 REMEDIATION/SUMMER 2000 89 ENDALKACHEW SAHLE-DEMESSIE DOUGLAS W. GROSSE EDWARD R BATES pumped into the heated vessel until the pressure reached, approximately, 200 psi. A steam jacket was used to heat the extraction vessel and its contents to a preselected temperature. Compressed nitrogen was used to increase the pressure in the extraction vessel without interfering with the extraction process. The soil was treated in seven batches of approximately 1 kg each. The solvent and soil mixture was mechanically agitated at 62 revolutions per minute for 25 minutes during each extraction stage. The treatment of each batch consisted of two extraction stages, with each extraction stage utilizing 1.5 1 of DME, resulting in a solvent-to-soil ratio of approximately 1 to 1 on a weight basis. The temperature and pressure in the extraction vessel were monitored. Since the extraction vessel was operated as a closed system during all extractions, the pressure increased with an increase in temperature. The initial pressure varied, depending on the pressure in the solvent reservoir and whether compressed nitrogen was used to transfer the solvent into the extraction vessel. Exhibit 3. Process Data for Bench-Scale Solvent Extraction of MCB Soil Batch Extraction Stage 1 2 1 2 1 2 1 2 1 2 1 2 1 2 Run Time (min) 25 25 25 25 25 25 25 25 25 25 25 25 25 25 Temp. O C 49.5 49.5 46 49.5 46 49.5 46.5 47.2 49 47.8 49 47.8 49.5 48.5 Max. Pressurc psi 205 350 160 245 160 160 160 170 170 165 160 170 175 155 90 REMEDIATION/SUMMER 2000 SOLVENT EXTRACTION AND SOIL WASHING TREATMENT OF CONTAMINATED SOILS FROM WOOD PRESERVING SITES The soiljsolvent mixture was stirred and allowed to settle into two distinct phases: an organic rich solvent phase (extract) and a soil/water residual phase. Extract was then removed overhead through a pressure reduction valve to a collection vessel operating at a reduced pressure of between 50 and 100 psi. Simultaneously, fresh liquid gas was introduced into the extractor in order to maintain a constant pressure of 200 psi. In the low-pressure collection vessel, DME was vaporized and sent to a dry test meter in order to quantify the amount of solvent used. Following the final stage of extraction, the organic extracts remaining in the collection vessel and the water/soil residue remaining in the extractor were collected, weighed, labeled, and refrigerated in zero head space containers for analytical testing and subsequent treatment/disposal. Analytical Method Procedures for extraction and analysis used to determine the levels of contaminants in the untreated soil, treated soil, and organic portion of the extract are listed in Exhibit 4. The sample extracts from both the soils and the organic extract underwent a derivatization step prior to analysis to provide increased sensitivity for the chlorophenols. An internal standard/ surrogate (13Ci-pentachlorophenol) was added to the samples prior to extraction. Following concentration, the sample extracts were reacted with pyridine and acetic anhydride to form the derivatized products (acetylated chlorophenol). Prepared sample extracts were analyzed by gas chromatog- raphy/mass spectroscopy (GUMS), with the MS operated in the Selected Ion Monitoring (SIM) mode. Significant dioxidfuran concentrations were expected in the untreated soil and organic extract samples, however, the Exhibit 4. Analytical Procedures Utilized in Extraction and Analysis of Contamination in the Untreated and Treated Soil and Organic Portion of the Extract Analytical Method Method Matrix Parameter Number Reference Treated/ Arsenic 3050A/7062 SW-846" Untreated Soil Chromium 3050A/7170 SW-846' Copper 3050A/7 2 10 ~ w - 8 4 6 ~ Zinc 3050A/7750 SW-846-' Lead 3050A/7420 ~ w - 8 4 6 ~ SVOCS 3540B/8270B SW-84Q Dioxins/Furans 8270 SW-846.l Organic Portion SVOCS 3580A/8270B SW-846-' of Extract Dioxins/Furans 8270 ~ w - 8 4 6 ~ ' SVOC Sernivolatile organic compound (USEPA, 1987) REMEDIATION/SUMMER 2000 91 ENDALKACHEW SAHLE-DEMESSIE DOUGLAS W. GROSSE EDWARD R BATES In order to achieve the desired low detection limits, a second analysis of each of the samples was performed utilizing larger sample aliquots (30 times larger). concentration of dioxidfuran in the treated soil sample was unknown. Therefore, the original analyses for the untreated soil, treated soil, and organic extract samples were performed using small sample aliquots to avoid saturating the GC/MS system. These analyses yielded results for the more highly chlorinated congeners (hepta- and octa-) within the calibra- tion range of the instrumentation. Unfortunately, nondetected results were obtained for many of the tetra-, penta-, and hexachlorinated isomers due to the elevated detection limits caused by the small sample aliquots. In order to achieve the desired low detection limits, a second analysis of each of the samples was performed utilizing larger sample aliquots (30 times larger). Additional cleanup steps were applied to the sample extracts, including several additional acid and base extractions, additional charcoal column cleanup, and additional alumina column chromatography. After these cleanups, the sample extracts were analyzed by G U M S for the penta- and hexachlorinated congeners. After these G U M S analyses, the remain- ing portions of the sample extracts were cleaned up on the basic alumina column, and only the effluent fraction containing the tetrachlorinated congeners was collected. This fraction was then analyzed by GUMS for the tetrachlorinated congeners. RESULTS AND DISCUSSION ON SOLVENT EXTRACTION The soil samples from the McCormick and Baxter site contained 1,450 ing/kg of PAHs, 1,490 mg/kg of PCP, 13.60 mg/kg of dioxins, and 793 mg/ kg of heavy metals. The types and levels of PAHs and chlorinated phenols in the untreated soil and for soils extracted with DME are summarized in Exhibit 5 . Dioxin and furans levels for untreated and treated soils are shown in Exhibit 6. Preliminary experiments show that sufficient time must be provided to effectively extract the contaminant from the waste. The time necessary to extract a given contaminant is dependent on the solubility of the contaminants and their desorption from the organic matter in the soil. The high solubility of the contaminants in DME resulted in rapid extraction rates, with the system reaching a quasi-equilibrium state in 25 minutes. The first substance that was extracted and collected in the receiver vessel was a thick, black concentrated organic phase that settled to the bottom of the separation vessel. A large volume of aqueous material and a second foamy organic phase that contained residual amounts of DME followed this heavy organic. Foaming in the extracted contaminant vessel was evident because of the residual amount of DME. Foaming has adverse effects by increasing the volume of the extract stream and by entraining the contaminants in the foam. The extraction period and the number of extraction stages required to achieve cleanup goals is usually waste and soil specific. The percent reduction in contaminant concentration between the untreated soil and the treated soil was calculated for all compounds (except metals) detected in the untreated soil. These percent reductions are presented in Exhibits 5 and 6. When a given contaminant was not detected in the treated soil, its percent reduction was calculated using the reporting limit (stated in 92 REMEDIATION/SUMMER 2000 SOLVENT EXTRACTION AND SOIL WASHING TREATMENT OF CONTAMINATED SOILS FROM WOOD PRESERVING SITES Exhibit 5. Concentrations of PAHs and Chlorinated Phenols in MCB Soil for the Average of Seven DME Extractions (on Diy Weight Basis) (US EPA, 1798) Concentration in Untreated Soil Treated Organic % Reduction in Compound Name (mg/kg 1 Soil Extract Soil Dry Weight PAHs (mg/kg) (nig/kg) Basis Acenaphthene # Acenaphthylene # Anthracene # Benz(a)anthracene # Benzo(b jfluoranthene # Benzo(k)fluoranthene # Benzo(ghi)perylene # Benzo(a)pyrene # 2-Chloronaphthalene # Chrysene # Dibenz(a,h)anthracene # Dibenzofuran # Fluoranthene # Fluorene # Indeno(l,2,3-cd)pyrene # 2-Methylnaphthalene # Naphthalene # Phenanthrene # Pyrene # BAP potency estimate* Total detected PAHs** Total PAHs*** 95 .7 ND (5.43) ND (16.6) ND (5.43) 66.5 ND (5.43) 77 ND (5.43) 62.1 ND (5.43) 52.2 ND (5.43) ND (16.6) ND (5.43) 38.7 ND (5.43) ND (16.6) ND (5.43) 74.7 ND (5.43) ND (16.6) ND (5.43) ND (16.6) ND (5.43) 306.0 5.43 21.3 6.89 ND (16.6) ND (5.43) ND (16.6) ND (5.43) ND (16.6) ND (5.43) 95.3 ND (5.43) 406.0 6.26 71.7 ND (12.5) 1,320.0 17 1,450.0 105 2330.0 ND (333) 1920 2000.0 1780.0 1350.0 ND (333) 847 ND (333) 2210.0 ND (333) 367 580 ND (333) ND (333) ND (333) 2870 7300 1610 32500 34800 6910 >94.3 NC >71.8 >72.9 >91.2 >a9.5 NC %6.0 NC >74.2 NC NC 98.2 67.6 NC NC NC >74.3 78.5 ~ 3 2 . 4 98.6 92.7 Other SVOCs 4-Nitrophenol 171.0 ND (17.2) 4610 NC Pentachlorophenol 1470 72.4 12900.0 95.1 2,3,4,6-Tetrachlorophenol 17.8 0.835 177 75.1 NC = Not calculated. * The benzo(a)pyrene potency estimate is based on the relative potency factors provided in US EPA (1993a). "* Total detected PAHs = the sun1 of the results for detected PAHs *** Total PAHs = the sum of the results for detected PAHs and the reporting limits for nondetected PAHs. # Indicates SVOCs that have been designated as target PAHs. ND = Not detected nt the reporting limit. Reporting limit stated in parentheses REMEDIATION/SUMMER 2000 __ 93 ENDALKACHEW SAHLE-DEMESSIE DOUGLAS W. GROSSE EDWARD R BATES Exhibit 6. Concentrations of Dioxins and Furans for the Average of Seven DME Extractions of MCB Soil (on Dry Weight Basis) Concentration in Organic % Reduction in Untreated Soil Treated Soil Extract Soil Dry Weight Compound Name W k g ) (Wkg) (CLg/kg) Basis 2378-TCDD 2378-TCDF 12378-PeCDF 12378-PeCDD 23478-PeCDF 123478-HxCDF 123678-HxCDF 123478-HxCDD 123678-HxCDD 234678-HxCDF 123789-HxCDD 0.241 0.423 1.08 0.85 1.38 8.8 3.91 2.24 22.6 5.27 1.54 0.0062 0.0107 0.0292 0.0286 0.0360 0.311 0.188 0.0737 0.178 0.0509 0.611 3.8 5.47 21.4 18.1 26.8 178 86.4 45.9 44 1 104 33.5 97.4 97.5 97.3 96.6 97.4 96.5 95.2 96.7 97.3 96.6 96.7 123789-HxCDF 0.231 (0.00699) 5.53 >97.4 1234678-HpCDF 116 5.68 2,280 95.1 1234678-HpCDD 621 21.4 12,600 96.6 1234789-HpCDF ND (0.958) ND NC OCDD 12,100 610 183,000 95.0 OCDF 1,030 71.8 16,900 93.0 Total TCDD 1.70 0.0179 27.4 98.9 Total PeCDD 5.85 0.110 117 98.1 TCDD-TEQ 29.2 1.19 95.9 Total HxCDD 92 2.43 1,750 97.3 Total HpCDD 1,430 40.6 24,700 97.2 Total TCDF 3.21 0.0475 41.4 98.5 Total PeCDF 26.7 0.699 526 97.4 Total HxCDF 171 5.36 2,920 96.9 Total HpCDF 57 1 24.8 12,400 95.7 Total CDFs 1,930 101 32,900 94.8 Total CDDs 13,600 653 209,000 95.2 Total CDFs/CDDs 15,600 754 242,000 95.2 NC = Not calculated. ND = Not detected at the reporting limit. Reporting limit stated in parentheses 94 REMEDIATION/SUMMER 2000 SOLVENT EXTRACTION AND SOIL WASHING TREATMENT OF CONTAMINATED SOILS FROM WOOD PRESERVING SITES The solvent extraction process using DME as a solvent was demonstrated to be effective for treatment of soils with high levels of PCP, PAHs, dioxins, and firans. parentheses) and its percent reduction is stated as a greater than value (e.g., >97.4). Solvent Extraction of SVOCs For semivolatile organic compounds (SVOCs), including PAHs and chlorophenols, reductions ranged from 67.6 percent to 98.5 percent. Exhibit 5 presents several calculated results: benzo(a)pyrene (BaP) potency estimate, total detected PAHs. Values are rounded to three significant figures. BaP potency estimates were calculated based on the relative potency factors provided in other works (US EPA, 1995c, 1989). Total detected PAHs is the sum of the results for all target PAHs that were detected; total PAHs is the sum of the results for all target PAHs that were detected and the reporting limits for all target PAHs that were not detected. Percent reductions were also calculated for BAP potency estimate (X32.4 percent), total detected PAHs (98.6 percent), and total PAHs (92.7 percent). Extraction of Dioxins Percent reductions for dioxins/furans ranged from 93 percent to 98.9 percent. Dioxidfuran toxicity equivalents (TEQs) for all dioxidfuran results are presented in Exhibit 6. These TEQs were calculated using the 1989 update to EPAs Interim Procedures for Estimating Risks Associated with Exposures to Mixtures of Chlorinated Dibenzo-p-Dioxins and Dibenzofurans (CDDs and CDFs) (US EPA, 1989). The reduction of dioxin concentrations in terms TCDD-TEQ is 95.9 percent. The solvent extraction process using DME as a solvent was demon- strated to be effective for treatment of soils with high levels of PCP, PAHs, dioxins, and furans. Metals concentrations were not reduced by the solvent extraction treatment. The physical properties of liquefied DME, such as low viscosity and high diffusivity, enhance mass transfer rates. The gases are easily recoverable by using a simple vapor recompression cycle. The process includes extraction, phase separation, and solvent recovery. The process must be monitored continuously for pressure losses and emission to the atmosphere that could constitute a fire hazard. The concentrated extract from the solvent extraction process was subsequently detoxified by a base catalyzed dehalogenation method. Soil Washing Overview Soil washing is a water-based ex-situ process in which contaminants are mechanically scrubbed and removed from the soil. This process can remove Contaminants by either solubilizing and suspending them in a wash solution or by concentrating them into a smaller volume of soil through particle size separation. The concept of soil washing is based on the following assumptions: (1) that most of the organic and some of the inorganic contaminants tend to bind or adsorb, either physically or chemically, to the clay, silt, and humic components (fines) of the soil matrix; (2) the silt and clay are attached to the sand and gravel by physical phenomena such as compaction and adhesion; and (3) washing tends to REMEDIATION/SUMMER 20 0 0 95 ENDALKACHEW SAHLE-DEMESSIE DOUGLAS W. GROSSE EDWARD R BATES Contaminant recovery mechanisms with the use of surfactants are based on the interfacial tension reduction between hydrophobic organic contaminants (HOCs) and aqueous fluid, which allows the HOCs to solubilize. scrub and separate the fines from the larger sand and gravel-size particles, effectively concentrating the contaminants into a smaller volume of soil. Soil washing has been applied on a wider scale in Europe than in the United States (Chmielewska et al., 1997). Soils that contain high percentages of silt- and clay-sized particles adsorb Contaminants strongly and are difficult to remove. Hydrophobic contaminants generally require surfactants for their removal. Sites with complex mixtures of contaminants in the soil (such as a mixture of metals and semivolatile organics) and frequent changes in contaminants composition and soil matrix are difficult to formulate wash fluid for. Therefore, site-specific studies are recommended. Surfactant solutions have been used to release contaminants from soil surfaces for both ex-situ and in-situ applications. Surfactant molecules are composed of an oil-soluble hydrocarbon chain and a water-soluble ionic group. Surfactants form aggregates of molecules or ions called miscelles when the concentration of the surfactant solute in the bulk of the solution exceeds a limiting value, called the critical micelle concentration. Surfac- tants are classified depending on the charge of the surface-active moiety. This moiety can have a negative, a positive, or no charge resulting in anionic, cationic, or nonionic surfactants, respectively. Contaminant recovery mechanisms with the use of surfactants are based on the interfacial tension reduction between hydrophobic organic contaminants (HOCs) and aqueous fluid, which allows the HOCs to solubilize. Surfactant concentrations employed range from less than 1 percent to approxiniately 5 percent in water. Nonionic, anionic, and cationic types of surfactants have been evaluated. Examples of some of the types include alcohol ethoxylates, alkylphenol ethoxylates, sulphonates, aromatic oxides, disulfones, and ethoxylated sorbitan esters. Earlier studies of surfactants used for soil remediation relied upon the physical mecha- nism of contaminant removal (Borchardt, 1995). The surfactants used in this study were selected from a list of candidates used for crude oil recoveiy. The effectiveness of surfactants for soil washing has been demonstrated on various contaminants including nitrobenzene (Chiu & Dural, 19971, inorganic arsenic-contaminated soil (Legiec at al., 19971, and TNT (Li et al., 1997). Examples of soil washing for heavy metal contami- nated soils include chromium and lead contaminated soils (Pichtel & Pichtel, 19971, and lead contaminated soils with acid and ethylenediaminetetraacetic acid (EDTA) solutions (Davis & Hotha, 1998), Soil samples contaminated with pesticides were effectively washed with 3 percent and 5 percent nonionic detergent solutions consisting of a mixture of Igepal ICO-630 and Triton X-114 (Evdokimov & von Wandruszka, 1998; Koustas & Fischer, 1998). A mathematical model of soil washing that incorporates the surfactant enhanced mobilization and solubilization of organic compounds was developed by Cheah et al. (1998). Other models were developed that describe leaching of heavy metals from contaminated soils as applied to hazardous-waste-site soils contaminated with lead (Ganguly et al., 1998). The objectives of this study were (1) to determine the distribution of the major contaminants in soil fractions for various particle sizes; ( 2 ) to 96 REMEDIATION/SUMMER 2000 SOLVENT EXTRACTION AND SOIL WASHING TREATMENT OF CONTAMINATED SOILS FROM WOOD PRESERVING SITES evaluate the potential application of soil washing technology for soils contaminated with PCP, PAHs, dioxins, and furans; and (3) to determine the partition coefficients for contaminants in soil and surfactant solutions. Surfactants were selected based on literature review of previous soil washing tests, surfactant vendor information andlor on test tube assessments. Surfactant Selection Surfactants were selected based on literature review of previous soil washing tests, surfactant vendor information and/or on test tube assess- ments. As a class, cationic surfactants were excluded from this study since they have poor biocompatibility. Natural surfactants obtained from plants offer an attractive alternative to synthetic surfactants in the remediation of contaminated soils since they are more biodegradable (Roy et al., 1997). To select surfactants from the remaining anionic and nonionic surfac- tants, the criterion used was the hydrophile-lipophile balance (HLB) scale of surfactants. HLR is a measure of the weight percent of the polar head and varies between 0 and 20. The HLB scale is a tool for ranking the hydrophilic/lipophilic character of surfactants with different structural families. For example, two surfactants with different functional groups but the same HLB value will show similar emulsification properties as a result of similar phase partition characteristics. Previous studies have shown that the optimum surfactant HLB that can provide complete eiiiulsification of creosote in less than 10 minutes was 14 (Currie et al., 1992). Surfactants with HLB of 14 include Makon-12, Neodol 91-8, and Igepal CA-720. Surfactants for Wood Preserving Sites The mobility of wood preserving containinants depends upon their aqueous solubility, adsorbance to soil particles, and the presence of a free oil phase (Jackson & Bisson, 1990). Surfactants that have alcohol ethoxylate have been shown to increase the solubility of PAHs in aqueous media, promoting their detachment from soil surfaces (Dennis et al., 1994). Noticeably, the surfactants were effective when used below their critical micelle concentration. Dissolution of PAHs from soil contaminated with multicomponent coal tar was investigated using a polymeric adsorbent, Tenax-TA, and a nonionic surfactant, Brij 30. Tenax created maximum concentration gradient at the soil/ water interface, thus maximizing interfacial mass transfer (Yeom et al., 1996). Experimental Design Soils used for these studies were obtained from three NPL sites. The McCormick and Baxter site in Stockton, California, was the site for wet screening tests. and the American Creosote Works site in Jackson, Tennessee, and the RAB Valley site in Panama, Oklahoma, were used for the soil washing study. These sites are more fully described in the accompanying article by Bates et al. and the soils used for this study are described in a US EPA report (1998). soil washing using surfactants The soil washing process involves soil preparation, suspending fines in the wash slurry along with dissolved or solubilized contaminants, and REMEDIATION/SUMMER 2000 97 ENDALKACHEW SAHLE-DEMESSIE DOUGLAS W. GROSSE EDWARD R. BATES Makeup Water Surfactant Contaminated Soil soil and water separation. Soil characterization, including contaminant concentration, pH, and particle size analysis, was conducted on the soil samples (US EPA, 1998). Particle size analysis was determined using dry sieving and hydrometer techniques. Most of the organic contaminants found at wood preserving sites have low water solubility and are nonvolatile. Washing these contaminated soils with water alone may not remove most of the nonwater soluble organics. Washing with water and an appropriate additive can potentially achieve high removals (90+ percent) of the SVOCs. Soil washing makes concentrations of contaminants in the soil amenable to further treatment. Various additives (i.e., acids, bases, chelates, and surfactants) can be used with water along with pH and temperature adjustments to enhance contaminant separation, however, some additives tend to interfere with downstream wastewater treatment. A flow diagram for the typical soil washing system is shown in Exhibit 7 (US EPA, 1990b). The first phase in the soil washing technique includes the excavation of the soil, the removal of large rocks and debris, and the sorting of soils for screen size separation by placing them in a rotary drum or vibrating screen. Rinsing and returning large soil particles to the site completed this phase. During the second phase, the remaining contami- nated soil and debris were passed through a processing unit where they were washed with surfactant solution with the fines (less than 0.063 mm) separated. Processed soils were then washed, analyzed and returned to the site. The highly contaminated soil fraction (i.e., fines) was recovered via Recycle water A Exhibit 7. Flow Diagram Typical Soil Washing Test Procedure (US EPA, 1990) Volatiles to Emission control L 1 ~11 98 REMEDIATION/SUMMER 2000 Soil Washing Rinsing & Size Separation Soil - Preparation --j Treated Waste Water + Treatment i * Sludge v Washedsoil * clean soil SOLVENT EXTRACTION AND SOIL WASHING TREATMENT OF CONTAMINATED SOILS FROM WOOD PRESERVING SITES gravity or cyclone separation and can be processed further using other technologies, such as slurry bioremediation. The cleaned soil fraction (sand and gravel-size particles) can be either returned to the site as backfill material, provided that this material meets remedial standard, or undergoes further stabilization. Blowdown water may need treatment, such as biological or carbon treatment, to meet appropriate discharge standards prior to release to a local, publicly owed wastewater treatment works or receiving stream. Air emissions from the waste preparation area or the Bive bench-scale Soil washing studies were conducted using a washing chamber. - washing unit should be collected and treated to meet regulatory standards. Bench-Scale Tests Bench-scale tests were conducted to determine the best surfactants by mixing 100 ml of water, 1 ml creosote, and 5x10. mol/l surfactant in a tube and shaking the mixture. After 10 minutes the amount of creosote emulsified and the stability and clarity of the emulsion were observed. The surfactant concentrations were above the critical micelle concentra- tion (CMC) values obtained from the vendors. Surfactant chemistry, temperature, ionic strength, and the presence and type of organic additives can affect the CMC. For a given surfactant, the amount of dissolved substrate depends on the number of surfactant micelles present, with solubilization increasing linearly with surfactant concentra- tions above the CMC. Since the soil contaminants were more heteroge- neous than the contaminants in the test tube test, these investigations were used to screen out surfactants which were not effective. Therefore, running the soil washing test using the best surfactant at a concentration of 3 weight percent would provide most of the information needed to determine effectiveness. The two surfactants selected for the second bench-scale test were nonyl phenol ethoxylate (Makon-12) and branched alkyl surfactant (Igepal CA-720). Makon-12 has a large hydrophilic head group and HLB value of 14 and the hydrocarbon tail of Igepal CA-720 has a branched structure and HLB value of 14.6. Five bench-scale soil washing studies were conducted using a washing chamber. The chamber consisted of a temperature controlled stirred vessel and a laboratory stirrer for mixing the soil. Based on the results of previous soil washing studies (Currie et al., 1992) and earlier screening tests, the conditions for surfactant soil washing experiments were limited to those outlined in Exhibit 8. A 6:l ratio of wash solution to soil (by weight) was added to the wash chamber. The surfactant concentrations were based on a percent by weight concentration in water and deionized water was used for all wash solutions. The wash solution mixture was heated to the desired temperature and the pH of the mixture was adjusted using sodium carbonate. A 1.5 kg quantity of contaminated soil was placed in a washing chamber with the surfactant. The soil/surfactant solution mixture was agitated using a laboratory mixer. After one hour of agitation, the mixer was turned off and the heavy solids were allowed to settle. The wash solution and any floating oil were then decanted using a peristaltic pump. A sample of the finedwash-water mixture or samples of concentrated fines and wash-water was collected and analyzed ~~ REMEDIATION/SUMMER 2000 99 ENDALKACHEW SAHLE-DEMESSIE DOUGLAS W. GROSSE EDWARD R BATES Experiment Exhibit 8. Soil Washing Bench-Scale Test Conditions Wash Solution Soil Source RAB Valley Stage 1 American Creosote Work Surfactant 1' Surfactant 2 Water alone Stage 2 Surfactant l1 or 2* Water alone Constants pH = 9 T = 49 "C Surfactant 1 is Makon 12 and Surfactant 2 is Igepal CA 720. ' Constant surfactant concentration = 3 weight percent. The best surfactants were selected from Stage 1 experiments. The formulation to adjust pH may include sodium carbonate. for the contaminants of concern. The type of sample(s) collected was based on whether solid concentration is required by the postsoil washing treatment vendors. For each test condition three samples were collected for the coarse/ washed soil. Note that subsequent treatment of residues was not pursued unless results of the soil washing test were promising. Results and Discussion of Soil Washing Experiments Each of the soils was analyzed on a dry weight basis for metals, semivolatiles, and dioxins/furans using EPA methods 6000/7000 series, 8270, and 8290, respectively (US EPA, 1998). The moisture content, total organic matter, and the sand fractions of the soil samples are given in Exhibit 9. Particle size distribution of soil samples from the three sites is also shown in Exhibit 10. The soil at the American Creosote Works site was coarse with only 15 percent of the soil particles smaller than 125 pm. Conversely, approximately 51 to 74 percent of the RAB Valley soil was made of particles that were smaller than 125 pm. Soil washing may therefore be a more economical remediation technology for the ACW site than for the RAB Valley site, since a higher reduction of contaminated volume is possible. Particle size distribution should not be the only consideration for employing soil washing technology. Other soil and contaminant properties such as miscibility and dispersability are also important. However, most of the contaminants at wood preserving sites have low water solubility and particle size is critical in choosing this technology. 100 REMEDIATION/~UMMER 2000 SOLVENT EXTRACTION AND SOIL WASHING TREATMENT OF CONTAMINATED SOILS FROM WOOD PRESERVING SITES Sample Source RAB Valley Wood Preserving Site American Creosote Works McCorniick & Raxter Site Exhibit 9. Soil Characteristics from the Three Wood Preserving Sites Moisture Solids Total Organic Sample YO % Carbon % Description 13.1 86.9 2.9 8% gravel 17% sand 21.7 77.2 2.8 6% gravel 78% sand 16.7 83.3 2.8 3% gravel 58% sand To determine the potential of meeting remediation requirements for the ACW and RAB Valley sites, bench-scale soil washing studies were conducted using pure water and surfactant solutions. For the ACW site a surfactant solution of 3 wt percent Makon-12 was used, whereas for the RAB Valley site two surfactant solutions of 3 percent Makon-12 and 3 Exhbit 10. Particle Size Analysis of Soil Samples from the Three Sites 100 80 60 40 20 0 Silt + Difficult for Soil washing - Amer. Creosote Works o RABValley 'I McCormic k & Baxter 0.001 0.01 0.1 1 10 I00 Particle Diameter, mm REMEDIATION/SUMMER 2000 101 ENDALKACHEW SAHLE-DEMESSIE DOUGLAS W. GROSSE EDWARD R BATES percent Igepal were used. The effectiveness was measured for each test by determining the ratio of critical contaminant concentrations (e.g., 2,3,7,8- TCDD/TEQ and target SVOCs) in the wash-water and soil fractions. Two toxicity measurement factors benzo(a)pyrene (B(a)P) equivalent and 2,3,7,8-Tetrachlorodibenzo-p-dioxin (2,3,7,8-TCDD) toxicity equivalency factor (TCDD-TEF) were used to determine equivalent toxicity for seven different PAH compounds, and 11 isomers of 2,3,7,8-substituted polychlo- rinated dibenzo-p-dioxins and dibenzofurans, respectively (US EPA, 1989, 1993a). PCP, TCDD, and selected PAHs concentrations in soil and aqueous extracts generated using the batch extraction procedure were used to calculate soil-water partition coefficients from the following equation: where Kpsu, is the soil-water partition coefficient, Cs is the concentration of the analyte in soil (pg/kg), and Cu, is the aqueous phase concentration of the analyte in pg/L. Concentration ratios of critical contaminants in wash- water and soil are given for two soil samples and various wash solutions (Exhibit 11). The results summarized in Exhibit 11 represent a 10 to 1,300- fold increase in partition coefficient for some of the critical contaminants when surfactant was added. Exhibit 11. Concentration Ratios of Critical Contaminants in Wash Solution and Soil (U.S. EPA, 1998) I 3% solution of Makon-12 in deionized water. I 3% solution of Igepal in deionized water. 2,3,7,8 - Substituted PCDDs and PCDFs expressed as TCDD-TEQ as determined by I-TEF/89 102 REMEDIATION/SUMMER 2000 SOLVENT EXTRACTION AND SOIL WASHING TREATMENT OP CONTAMINATED SOILS FROM WOOD PRESERVING SITES The results of soil washing conducted with deionized water and surfactant solution of the ACW site are given for the concentrations of the individual chemicals (PAHs and PCP) and the calculated toxicity factor for dioxins (TCDD-TEQ) (Exhibit 12). Analytical results for the soil washing Exhibit 12. Selected Results for Soil Washing of American Creosote Works' Contaminant Untreated soil MS, rng/k?g Acenaphthene Acenaphthylene Anthracene Benzo(a1anthracene Benzo(b)fluoranthene Benzo(k)fluoranthene Benzo(ghi)pyt-ene Benzo(a)pyrene Chrysene DibenzCa, hh thracene Fluoranthene Fluorene Indeno(l,2,3-cd)pyrene 2-Methylnaphthalene Naphthalene Phenanthrene Pyrene Wal PAHs, m@g 3(a>P Potency Estimate Pther SVOCs, m@g >ibenzofuran 'entachlorophenol Phenol XDD-TEQ, pg/kg 440 16 2800 220 310 120 57 130 350 16 940 60 470 380 1500 800 760 9400 215 480 650 ND (54) 38.780 with Deionized Water 630 ND (11) 2300 240 260 92 54 120 350 16 1300 1300 59 510 460 1900 1100 11,000 190 640 620 2.7 256.259 with 3% reduction Makon-12 with 110 5.5 1000 58 71 24 18 36 84 4.4 350 160 20 100 86 430 320 solution Makon YO I 75 66 64 74 77 80 68 72 76 73 63 79 67 79 77 71 60 ND (12) 11.079 * Sampling from hot spot areas. ND=Not detected at the reporting limit. Reporting limit stated in parentheses REMEDIATION/SUMMER 2000 103 ENDALKACHEW SAHLE-DEMESSIE DOUGLAS W. GROSSE EDWARD R BATES of selected contaminants of concern (COCs) are also shown in Exhibit 13. For soil washed with 3 percent Makon-12 solution the average removal of contaminant was 69 percent for PAHs, 74 percent for B(a)P potency estimate, 83 percent for PCP, and 71 percent for TCDD-TEQ (Exhibit 12). Results of soil washing on the RAB valley soil using deionized water, water/ 3 percent Makon-12, and water/3 percent Igepal solution are shown in Exhibit 14. Although both surfactants have HLB value of about 14 and can increase contaminant solubility, the surfactant with the larger hydrophilic head group (Makon-12) removed two to five times more contaminants than the branched-tailed surfactant (Igepal-720). Concentrations of contami- nants of concern in raw and washed soils obtained from the RAB Valley Wood preserving site are shown in Exhibit 14 and Exhibit 15. The washing with water/3 percent Makon-12 solution showed to be much more effective on removing PCP and dioxins than washing with dionized water or water/3 percent Igepal solution. Three percent Makon-12 is more effective on PCP and dioxins. Earlier studies indicated that PCP and low molecular weight PAHs have a relatively high potential for soil washing remediation due to their greater solubility in surfactant solutions; whereas PCDD and PCDF adsorbed to the soil were resistant to leaching by surfactant solution (US. Congress, 1991). However, this study showed that the two surfactant/water solutions were equally effective on PCDD and PCDF as on PAHs. Both the percentage removal and the residual contaminant levels were lower than previously reported values (Dennis et Exhibit 13. Contaminants of Concern in Raw and Washed Soils Obtained from the American Creosote Works 2 2000 1. E" 1750 i .P 1500 6 e 1250 aa 0 c (II .c, E 1000 0, 750 *s 8 0 C 500 3 250 c RawSctl Dionized water washed &&&A 3% Makon sdution witshed Phenan. Flouran. Pyrene D.B.Furan PCP TCDD-TEF Contaminants of Concern 104 REMEDIATION/~UMMER 2000 SOLVENT EXTRACTION AND SOIL WASHING TREATMENT OF CONTAMINATED SOILS FROM WOOD PRESERVING SITES Exhibit 14. Selected Results for Soil Washing of RAB Valley Soil with Deionized Water and Surfacant Solutions Contaminant Percent Reduction 010 for soil washed with Makon (Igepal) 010 Untreated Soil Washed Soil Washed Soil Washed With Deionized with 3% with 3'10 IgePd soil Water solution Makon-12 solution PMS, nzg& Acenaphthene Acenaphthylene Anthracene Benz( a)anthracene Renzo( bXlouranthene Aenzo(k)flouranthene Benzo(ghi)pyrene Renzo( alpyrene Chrysene F1 u oran thene Fluorene Incleno(1~ 2,3-cd)pyrene 2-Methylnaphthalenc Naphthalene Plienanthrene Pyrene Dihenzo(a ,h)anthracene 176 5 903 96 84 33 18 42 126 6 626 356 3 73 50 967 480 81 (38)* 58 ( -27) 30 (-188) 73 (14) 95 (25) 21 (36) 92 (17) 74 (18) 73 (21) 77 (30) 81 (23 ) 72 (-26, 77 (13) 64 (-36) 78 [-1+) 79 (17) -100 (-620) 33 110 6 2600 83 63 21 15 35 100 4 480 450 18 64 68 1100 400 630 26 26 1.4 11 34 1 .it 1 20 100 5 17 18 210 100 4 Total PAHs 67 73 129) 18 55 B(a)P Potency Estimate Other SVOCs, m@g Pentachlorophenol Dibenzofuran 210 43 82 (63) 75 ( 2 3 ) 10 117) 1206 170 440 130 24 29 23 26 Sampling from hot spot areas. :'' Percent reduction for washing with Makon-12 solution and (Igepal solution) al., 1994). This could be attributed to the large percentage of huniuslike compounds and high initial concentrations of contaminants, CONCLUSIONS Solvent extraction using liquefied dimethyl ether in treating soils, sludges, sediments, and wastewater has many potential advantages REMEDIATION/SUMMER 2000 105 ENDALKACHEW SAHLE-DEMESSIE DOUGLAS W. GROSSE EDWARD R BATES Exhibit 15. Contaminants of Concern in Raw and Washed Soils Obtained from the RAB Valley Wood Preserving Site 1400 ZI, s F 1200 .- : 1000 * m, = 8) 800 6 600 400 * 200 0 0 .c, C E 5 cp 0 I I 1 = Raw Soil L Z B Dionized water washed 3% lgepal solution washed 3% Makon solution washed Phenan. Flouran. Pyrene D.B.furan PCP TCDD-TEF Contaminants of Concern including the high removal efficiencies and low residual values for a wide range of organic contaminants such as PAHs, chlorinated phenol (mainly PCP), and dioxins; a high concentration factor resulting in two to three order magnitude reduction in the volume of material requiring additional treatment; the potential to operate at intermediate temperatures (below 50 C), and the ability to recycle the solvent. The ease of solvent recycling for DME makes solvent extraction technology more cost competitive with other soil treatment technologies. The cost associated with this treatment ranged from $80 to $250 per ton soil, excluding excavation, disposal, or recovery of contaminants from the concentrated wash liquid. The material-handling process including the solvent recycling step affects the cost effectiveness of the solvent extraction process. Evaporation of the solvent is an effective way to separate the extract from the solvent and recycle back the solvent. However, the problem of foam formation associated with large-scale use of liquefied solvent extraction has yet to be resolved. The operating and maintenance cost of solvent extraction using liquefied gases is estimated to be $220 per ton of contaminated soil. However, field application of this technology at the United Creosote site, Conroe, Texas, failed to perform to the level observed at bench scale due to the excessive foaming and air emission problem (Innovative Technol- ogy, 1998). Further studies are required on the use of foam suppressants and emission control systems to alleviate these problems. 106 REMEDIATION/~UMMER 2000 SOLVENT EXTRACTION AND SOIL WASHING TREATMENT OF CONTAMINATED SOILS FROM WOOD PRESERVING SITES Evaluation of nonionic surfactant enhanced soil washing for two different soils contaminated with PAHs, PCP, PCDD, and PCDFs showed that the contaminant levels were reduced by 69 to 83 percent. Evaluation of nonionic surfactant enhanced soil washing for two different soils contaminated with PAHs, PCP, PCDD, and PCDFs showed that the contaminant levels were reduced by 69 to 83 percent. For some sites, soil washing may have a limited effect in reducing contaminants or may require costly feed soil preparation and residual treatments. Large fractions of clay and silt (< 0.06 mm1, high levels of organic contaminants and humic acid can make soil washing less applicable. Commercial scale soil washing processes were estimated as have an operating and niainte- nance cost between $40 and $200 per ton (US EPA, 1997). The technologies for the destruction, disposal, and recovery of contaminants from concen- trated wash-liquid include base catalyzed decomposition, membrane technology (Sikdar et al., 19981, and anaerobic treatment (Miller et al., 19981. REFERENCES Assink, J.W. (1985). Extractive methods for soil decontamination, a general survey and review of operational treatment installations. Netherlands, Apeldoom. Borchardt, J. K. (1995). Dealing with soil contaminants. Todays Chemist at Work. Burton, M. B., Martinson, M. M., & Barr, K. D. (1988). Bioreniediation of contaminated soil and water. In Biotech USA, 1988, Proceedings of Annual Ind. Water Waste Conference; November, San Francisco, CA. Norwalk, CT: Conference Mangement Corp. Cheah, E.P.S., Reible, DD., Valsaraj, K.T., Constant, W.D., Walsh, B.W., &Thibodeaux, L.J. (1998). Simulation of soil washing with surfactants. J. of Hazardous Materials, 59 (2-31,107- 122. Chiu, S.L., & Dural, N.H. (1997). Feasibility study on salting-in of organic pollutants to enhance the effectiveness of ex-situ soil washing. Indust. & Engi. Chemist. Research. 36 (6), 2435-2439. Chmielewska, E., Nussbaum, M.T., & Szytenchelni, R. (1997). An attempt to implement soil washing for central-Europe cleanup activities. Chemicke Listy, 91 (61, 438-443. Currie, J.K., Bunge, A.L., Updegraff, D.M., & Batal, W.H. (1992). Surfactant enhanced remediation of creosote contaminated soils. In P. T. Kostecki, E. J. Calabrese, B M. Bonazountas (Eds. ), Hydrocarbon contaminated soils: Vol. 11. Ann Arbor: Lewis Publishers. Davis, A.P., & Hotha, B.V. ( 1998). Washing ofvarious lead compounds from a contaminated soil column. J. Environ. Eng.-ASCE, 124 ( l l ) , 10661075. Dennis, R.M., Dworkin, D., & Zupko, AJ. (1994). Soil-washing processes for site remediation. In D.L. Wise, 8: D.J. Trantolo (Eds.), Remediation of hazardous waste contaminated soils. New York: Marcel Dekker. Evdokimov, E. , & von Wandruszka, R. (1998). Decontamination of DDT-polluted soil by soil washing cloud point extraction. Anal. Lett., 31(13), 2289-2298. Ganguly, C., Matsumoto, M.R., Rabideau, A.J., & Van Benschoten, J.E. (1998). Metal ion leaching from contaminated soils: Model calibration and application. J. Environmental Engin.-ASCE, 124( 121, 1150-1158. Hall, D.W. & Sandrin,J.A. (1990). An overview of solvent extraction treatment technologies. Envir. Progress, 9(2), 98-104. Innovative technology fails at Unite Creosoting, site gets amended ROD. (1998). Superfund Week, 12, 27, 1-2. Jackson, D.R., 8: Hisson, D.L. (1990). Mobility of polychlorinated aromatic compounds in soils contaminated with wood-presewing oil. J. Air Waste Manage. Assoc., 40, 1129-1133. REMEDIATION/~UMMER 2000 107 ENDALKACHEW SAHLE-DEMESSIE DOUGLAS W. GROSSE EDWN R BATES KOLIS~AS. R.N., 8 Fischer, D. (.1998). Review of separation technologies for treating pesticide- contaminated soil. J. The Air & Waste Management Association, 48(5), 434440. Legiec, LA., Griffin, L.P., Walling, P.D., Breske, T.C., Angelo, M.S.. Isacson, R.S., 8 Lanza, M.B. (1997'). DuPont soil washing technology program and treatment of arsenic contami- nated soils. Environ. Progress, 16 (l), 29-34. Li, Z.M., Peterson, M.M., Comfort, S.D., Horst, G.L., Shea, P.J. & Oh, R.T. (1997). Remediating TNT-contaminated soil by soil washing and Fenton oxidation. Science of the Total Environment, 204(2), 107-115. Meckes, M. C., Renard, E., Rawe,J., & Wahl, G. (1992). Solvent extraction process: A survey of systems in the SITE program. J. Air 8 Waste Management Assoc., 42(8), 1118-1161. Meckes. M. C., Wagner, TJ., Tillman, J., & Krietemeyer, S. (1993). SITE demonstration of the basic extractive sludge treatment process. J. Air 8 Waste Management Assoc., 43, 9. Miller, K.M., Suidan, M.T., & Sorial, G.A. (1998). Anaerobic treatment of soil wash tluids from a wood preserving site. Water Sci. Technology, 38 (.7), 63-72. Mueller, J.G., Chapman, P.J., & Pritchard, P. H. (1989). Creosote contaminated sites. Environ. Sci. Technol., 23, 1197-1201. Mueller, J.G., Chapman, P.J., Blattmann, B.O., 81 Pritchard P.H. (1990). Isolation and characterization of a fluoranthene utilization strain of pseudomonas pauciniobilis. Appl. Environ. Microhiol., 56, 1079-1086. Pichtel, J., & Pichtel. T. M. (1997). Comparison of solvents for ex-situ removal of chromium and lead from contaminated soil. Environmental Eng. Science, 14(2) 97-104. Roy, D., Kommalapati, R.K., Mandava. S.S., Valsaraj, K.T., 8 Constant, W.D. (1997). Soil washing potential of a natural surfactant. Environm. Science & Technol., 31(3), 670-675. Raniaswami, A,, & Luthy, R.G. (1997). Mass transfer and bioavailability of PAH compounds in coal tar NAPL-slurry system. Environ. Sci. & Technol., 31(8) 2260-2267. Sahle-Demessie, E., Meckes, M.. 8 Richardson, T. (1996). Remediating pesticide contanii- nated soils using solvent extraction. Environmental Progress. 15(4), 293-300. Sikdar, S.K., Grosse, D., 8 Rogut, I. (1998). Membrane technologies for remediating contaminated soils: A critical review. J. Membrane Sci., 151(1), 75-85. United States. Congress, Office of Technology Assessment. (1991 ). Dioxin treatment technologies-background paper (OTA-BP-0-93). Washington, DC: U. S . Government Printing Office. United States Environmental Protection Agency. (1987, November)). Test methods for evaluating solid waste (SW-846) (3rd ed). United States Environmental Protection Agency. (1989). Interim procedures for estiinating risks associated with exposures to mixtures of chlorinated dibenzo-p-dioxins and dibenzofurans (CDDs and CDFs) and 1989 update (EPA/625-3-89/016). United States Environmental Protection Agency. (1990a). Engineering bulletin: Soil washing. Washington. DC: US EPA, Office of Emergency and Remedial Response and (EPA/ 540/2-90/017) and Cincinnati, OH: US EPA. United States Environmental Protection Agency. (1990b). Approach to remediation of uncontrolled wood preserving sites (,EPA/625/7-90/011). US EPA. United States Environmental Protection Agency. (1992). Guide for conducting treatability studies under CERCLA: Solvent extraction (EPA/540/R-92/016a). Office of Research and Development, RREL. United States Environmental Protection Agency. (1993a). Provisional guidance for quanti- tative risk assessment of polycyclic aromatic hydrocarbons (EPA/600/R-93/089 1. United States Environmental Protection Agency. (1993b). Resources conservation company B.E.S.T. solvent technology [Applications Analysis Report, EPA/540/Ar-92/079). 108 REMEDIATION/SUMMER 2000 SOLVENT EXTRACTION AND SOIL WASHING TREATMENT OF CONTAMINATED SOILS FROM W O O D PRESERVING SITES United States Environmental Protection Agency. (1995a). Presumptive remedies for soils, sediments and sludges a t wood treater sites (EPA/540/R-95/128). OSWER, US EPA. United States Environmental Protection Agency. (199%). Innovative site remediation technology: Solvent/chemical extraction (EPA 542-B-94-005). Vol. 5, OSWER. United States Environmental Protection Agency. (1995~). Test methods for evaluating solid waste (SW-846) (3rd. ed.), through Update IIB. United States Environmental Protection Agency. (1997). Treatment technology perfor- mance and cost data for the remedidtion of wood preserving sites (EPA/625/R-97/009). United States Environmental Protection Agency. (1998). Treatability studies for wood preserving sites (EPA/600/R-98/026) CNTIS PB 98-132400. Yeom, I.T., Ghosh. M.M., Cox, C.D., Sr Ahn, K.H. (1996). Dissolution of polycyclic aromatic hydrocarbons from weathered contaminated soil. Water Science and Tech., 34(7-8), 335- 342. REMEDIATION/~UMMER 2 0 0 0 109

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