noncombustion technologies for remediation of persistent organic pollutants in stockpiles and soil

23

REMEDIATION Autumn 2006

Persistent organic pollutants (POPs) are a set of chemicals that are toxic, persist in the environment

for long periods of time, and biomagnify as they move up through the food chain. Combustion

technologies have been the principal technology used to destroy POPs. However, combustion tech-

nologies can create polychlorinated dibenzo-p-dioxins and polychlorinated dibenzo-p-furans,

which are human carcinogens. Two organizations, the United Nations Environment Programme

(UNEP) and the International HCH and Pesticides Association (IHPA) have developed detailed re-

ports and fact sheets about noncombustion technologies for POP treatment. This article is intended

to update and summarize these reports in a concise reader’s guide, with links to sources of further

information. The updated information was obtained by reviewing various Web sites and documents,

and by contacting technology vendors and experts in the field. © 2006 Wiley Periodicals, Inc.*

INTRODUCTION

Persistent organic pollutants (POPs) are toxic compounds that are chemically stable, donot easily degrade in the environment, and tend to accumulate and biomagnify as theymove up through the food chain. Serious human health problems are associated withPOPs, including cancer, neurological damage, birth defects, sterility, and immune sys-tem suppression. Restrictions and bans on the use of POPs have resulted in a significantnumber of unusable stockpiles of POP-containing materials internationally. In addition,deterioration of storage facilities used for the stockpiles, improper storage practices, andpast production and use of POPs have resulted in contamination of soils around theworld. Because of their chemical stability, tendency to bioaccumulate, adverse health ef-fects associated with POPs, and widespread POP contamination, remediation technolo-gies are needed to treat these pollutants.

In the past, POPs have been destroyed by combustion technologies (incineration).However, concern has been expressed about the potential environmental and health ef-fects associated with combustion of POPs. Combustion technologies can create poly-chlorinated dibenzo-p-dioxins (dioxins) and polychlorinated dibenzo-p-furans (furans),which have been characterized by the US EPA as human carcinogens and are associatedwith serious human health problems. Because of these concerns and an ongoing desireto find more cost-effective solutions, environmental professionals are examining the ap-plication of noncombustion technologies to remediate POPs in stockpiles and soil.

Exhibit 1 lists the 12 specific POPs identified by the Stockholm Convention, whichinclude nine pesticides and three industrial chemicals or by-products (US EPA, 2005).The Stockholm Convention (http://www.pops.int) is a global treaty intended to protect

© 2006 Wiley Periodicals, Inc. *This article is a U.S. government work and, as such, is in the public domain in the United States of America.Published online in Wiley Interscience (www.interscience.wiley.com). DOI: 10.1002/rem.20099

Ellen Rubin

Younus Burhan

Noncombustion Technologies forRemediation of Persistent OrganicPollutants in Stockpiles and Soil

human health and the environment from POPs.There are 150 signatories to the treaty.The United States has signed the treaty but has not ratified it (http://www.pops.int/documents/signature/).

This article is intended to provide a summary of information on the applicability of ex-isting and emerging noncombustion technologies for the remediation of POPs in stockpilesand soil.Two organizations, the United Nations Environment Programme (UNEP) and theInternational HCH and Pesticides Association (IHPA) have recently developed detailed re-ports and fact sheets about noncombustion technologies for POP treatment (IHPA, 2002;UNEP, 2004).The UNEP report provides a summary overview of noncombustion tech-nologies that are considered to be innovative and emerging and that have been identified aspotentially promising for the destruction of POPs in stockpiles.The report was originally abackground document for the Scientific and Technical Advisory Panel of the GlobalEnvironment Facility workshop held in Washington, D.C., in October 2003 and was basedon work done by the International Centre for Sustainability Engineering and Science,Faculty of Engineering, at the University of Auckland, New Zealand (UNEP, 2003).TheIHPA report describes emerging noncombustion alternatives for the economical destruc-tion of POPs. John Vijgen of the IHPA collected the technology data and authored the re-port, which included 11 fact sheets.This article summarizes and updates these reports.

TECHNOLOGIES FOR REMEDIATION OF PERSISTENT ORGANICPOLLUTANTS IN STOCKPILES AND SOIL

This article presents technology overviews and is divided into four subsections based on thescale of application of the technologies (full-scale, pilot-scale, bench-scale, and potentiallyapplicable for POP treatment).The list of noncombustion technologies was prepared usingthe available information, such as technical literature, US EPA reports, and US EPAdatabases such as the Federal Remediation Technologies Roundtable (FRTR) (www.frtr.gov)and the Remediation and Characterization Innovative Technologies (REACHIT) system(www.epareachit.org), as well as by contacting technology vendors and experts in the field.

Exhibit 2 lists the selected technologies and summarizes available technology-specific information, including scale, capability to handle waste strength, ex situ or in situapplication, contaminant treated, cost, pretreatment needs (defined as any process that

Noncombustion Technologies for Remediation of Persistent Organic Pollutants

Remediation DOI: 10.1002.rem © 2006 Wiley Periodicals, Inc. 24

Exhibit 1. POPs identified by the Stockholm Convention

Pesticides Industrial Chemicals or By-ProductsAldrin Polychlorinated biphenyls (PCB)Chlordane DioxinsDichlorodiphenyltrichloroethane (DDT) FuransDieldrinEndrinHeptachlorHexachlorobenzene (HCB)MirexToxaphene

precedes the primary treatment technology wherein the contaminants are transferredfrom one media/phase to another), power requirements, configuration, and location oftechnology fact sheets.The exhibit indicates whether the technologies have been appliedat a full, pilot, or bench scale for treatment of POPs.Waste strength refers to high- andlow-strength wastes. High-strength waste includes stockpiles of POP-contaminated ma-terials and highly contaminated soil. Low-strength waste includes soil contaminated withlow concentrations of POPs.

Full-Scale Technologies for Treatment of POPs

This section describes six technologies that have been implemented to treat POPs at fullscale. A full-scale project involves use of a commercially available technology to treat haz-ardous waste and to remediate an entire area of contamination. Six full-scale technologieswere identified for the treatment of POPs and are described in the sections that follow.

Anaerobic Bioremediation Using Blood Meal for Treatment of Toxaphene in Soil and Sediment

This technology uses biostimulation with amendments to promote degradation oftoxaphene in soil or sediment by native anaerobic microorganisms. It involves the additionof biological amendments such as blood meal (dried and powdered animal blood), which isused as a nutrient, and phosphates, which are used as a pH buffer (Allen et al., 2002).Thesoil to be treated is mixed with the amendments and water.The homogenized mixture istransferred to a lined cell, and water is added to produce a slurry. Up to a foot of watercover is provided above the settled solids.The water cover helps to minimize the transferof atmospheric oxygen to the slurry so that anaerobic conditions are maintained.The linedcell is covered with a plastic sheet, and the slurry is incubated for several months.

Anaerobic bioremediation using blood meal has been implemented to treat low-strength waste contaminated with toxaphene.This technology has been used to treattoxaphene at numerous livestock dip vat sites. Dip vats are trenches with a pesticide for-mulation used to treat livestock infested with ticks. Performance data from six dip vatsite applications are presented in Exhibit 3. In 2004, cleanup costs in U.S. dollars (USD)for full-scale implementations ranged from $98 to $296 per cubic yard (US EPA,2004a).The technology was developed by the US EPA’s Environmental Response Team(ERT).This technology is publicly available and is not patented (Allen et al., 2005).

DARAMEND®

DARAMEND® is an amendment-enhanced bioremediation technology that has beenused to treat low-strength wastes contaminated with toxaphene and dichlorodiphenyl-trichloroethane (DDT).The DARAMEND® technology can be implemented ex situ or insitu.This technology involves the creation of sequential anoxic and oxic conditions(Phillips et al., 2001).The treatment process involves the following steps:

1. Addition of a solid-phase DARAMEND® organic soil amendment of a specificparticle size distribution and nutrient profile, zero-valent iron, and water to pro-duce anoxic conditions;


© 2006 Wiley Periodicals, Inc. Remediation DOI: 10.1002.rem 25

A full-scale project involvesuse of a commerciallyavailable technology totreat hazardous waste andto remediate an entire areaof contamination.



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2. Periodic tilling of the soil to promote oxic conditions; and3. Repetition of the anoxic-oxic cycle until cleanup goals are achieved.

DARAMEND® has been used to treat soil and sediment containing low concentrationsof pesticides such as toxaphene and DDT as well as other contaminants.The technology hasnot been used for treatment of other POPs such as PCBs, dioxins, or furans.AdventusRemediation Technologies, Inc. (ART), the developer of the technology, indicated thatDARAMEND® had not been successful in bench-scale treatment of PCB-contaminated soil.DARAMEND® has been used to treat POPs at the T.H.Agriculture and NutritionSuperfund site in Montgomery,Alabama, and the W.R. Grace site in Charleston, SouthCarolina. Exhibit 4 presents the performance data from these applications.The averagetreatment cost (in 2004 USD) at the site in Montgomery was $55 per ton; the vendor didnot specify the components included in this cost (http://www.adventusremediation.com;D. Raymond, personal communication,August 25, 2004; US EPA, 1996a, 2004d).

GeoMelt™

GeoMelt™ vitrification is a high-temperature technology that uses heat to destroy POPsand to permanently immobilize residual contaminants by incorporating them into the vit-rified end product. GeoMelt™ has been used to treat high-strength wastes containingPOPs both in situ and ex situ. GeoMelt’s in situ process is available in two main configura-tions, In SituVitrification (ISV) and Subsurface Planar Vitrification (SPV™). Both configura-tions use electrical current to heat, melt, and vitrify material in place.Typical operating



Exhibit 3. Performance of anaerobic bioremediation using blood meal for toxaphene treatment

Quantity Untreated Treated Period of Soil Concentration Concentration

Site Location (Days) Treated Scale (mg/kg) (mg/kg)

Gila River Indian Community (GRIC)

GRIC Cell 1 Chandler, 272 3,500 cy Full 59 4Arizona

GRIC Cell 2 272 Full 31 4GRIC Cell 3 272 Full 29 2GRIC Cell 4 272 Full 211 3

Navajo Vats Chapter

Laahty Family Zuni Nation, 31 253 cy Full 29 4Dip Vat New Mexico

Henry O Dip Vat Zuni Nation, 68 660 cy Full 23 8New Mexico

Sources: Allen et al. (2002) and H. T. Allen (personal communication, January 25, 2005).

Notes: cy � cubic yard; mg/kg � milligrams per kilogram

temperatures range from 1,400 to 2,000°C. ISV is suitable for treatment to depths ex-ceeding 10 feet. SPV is suitable for more shallow applications. GeoMelt™ also provides avariation of SPV called Deep-SPV, which facilitates focused vitrification of limited-thickness treatment zones greater than 30 feet deep. GeoMelt’s ex situ process, which iscalled In Container Vitrification (ICV™), involves heating contaminated material in a re-fractory-lined container. A hood placed over the container collects off-gases.Typical oper-ating temperatures range from 1,400 to 2,000°C. At these temperatures, the waste matrixmelts, and organic contaminants are destroyed or volatilized.The off-gas from the processenters an off-gas treatment system, which includes a baghouse particulate filter, high-efficiency particulate air (HEPA) prefiltration, a NOx (oxides of nitrogen) scrubber, a hy-drosonic scrubber, a mist eliminator, a heater, and one or two HEPA filters. After treat-ment, the hood is removed and a lid is installed on the refractory-lined container.Whenthe melt has solidified, the vitrified waste-filled container is disposed in a landfill based onthe results of US EPA Toxicity Characteristic Leaching Procedure (TCLP) analysis.

GeoMelt™ is a full-scale treatment technology and has been used to treat suchPOPs as dieldrin, chlordane, heptachlor, DDT, hexachlorobenzene (HCB), polychlori-nated biphenyls (PCBs), dioxins, and furans (GeoMelt® Technologies/AMEC Earth andEnvironmental Inc., 2005). GeoMelt™ has also been used to treat radioactive waste.Exhibit 5 provides performance information for the technology. GeoMelt™ is commer-cially available from AMEC Earth and Environmental, the sole licensee of this technol-ogy in the United States (http://www.geomelt.com).

In Situ Thermal Desorption

In situ thermal desorption (ISTD) is a thermally enhanced technology that uses conduc-tive heating to directly transfer heat to environmental media, which has been used totreat both high- and low-strength wastes containing POPs. ISTD is primarily an in situtechnology but has also been used ex situ on constructed soil piles.The most commonISTD methods include steam and resistive heating. ISTD, sometimes also known as “insitu thermal destruction,” is a patented technology developed by Shell Oil Co. and



Exhibit 4. Performance of DARAMEND® technology

Quantity of Untreated Treated Year Period Soil Treated Concentration Concentration

Site Location Implemented (Months) POP (Tons) Scale (mg/kg) (mg/kg)T.H. Agriculture Montgomery, 2003 5 Toxaphene 4,500 Full 189 21and Nutrition Alabama DDT 84.5 8.65Superfund site

W.R. Grace Site Charleston, 1995 8 Toxaphene 250 Pilot 239 5.1South Carolina DDT 89.7 16.5

Source: http://www.adventusremediation.com

Note: mg/kg � milligrams per kilogram

TerraTherm, which holds the exclusive license to the technology and is currently theonly vendor.

There are three basic elements in the ISTD process (TerraTherm Inc., 2005):

1. Application of heat to contaminated media by thermal conduction,2. Collection of desorbed contaminants through vapor extraction, and3. Treatment of collected vapors.

ISTD uses surface heating blankets or buried electrically powered heaters to heatcontaminated media. In the most common setup, a vertical array of heaters is placed inwells drilled into the remediation zone. Surface heating blankets are less commonlyused. As the matrix is heated, adsorbed and liquid-phase contaminants begin to vaporize.Once high soil temperatures are achieved, a significant portion of the organic contami-nants either oxidizes (if sufficient air is present) or pyrolizes. Desorbed contaminants arerecovered through a network of vapor extraction wells. Contaminant vapors captured bythe extraction wells are conveyed to an off-gas treatment system for treatment prior totheir discharge to the atmosphere (R. Baker, personal communications with ChitranjanChristian, October 27 and November 8, 15, 24, and 29, 2004; US EPA, 2004c). ISTDwas field-tested by the US EPA’s Superfund Innovative Technology Evaluation (SITE)program to evaluate the performance of the technology at the Rocky Mountain Arsenal(RMA) site near Denver, Colorado (US EPA, 2004b).



Exhibit 5. Performance of GeoMelt™ technology

Untreated Treated Quantity of Concentration Concentration

Site Location Period POP Soil Treated Scale (mg/kg) (mg/kg)

Parsons Chemical/ Grand Ledge, 1993 to 1994 DDT 4,350 tons Full 340 � 4ETM Enterprises Michigan Chlordane 89 � 1Superfund Site Dieldrin 4.6 � 0.08

TSCA Spokane Spokane, Washington 1994 to 1996 PCBs 5,375 tons Full 17,860 ND

Wasatch Chemical Salt Lake City, 1995 to 1996 Dioxins 5,440 tons Full 0.011 NDUtah DDT 1.091 ND

Chlordane 535 NDHCB 17 � 0.08

WCS-Commercial Andrews, Texas 2005 PCBs 5 tons Full 496 NDTSCA cleanup

WCS-Rocky Flats Andrews, Texas 2005 PCBs 11 tons Pilot 130 ND

Sources: K. Finucane (personal communication, May 23, 2005) and IHPA (2002).

Notes: mg/kg � milligrams per kilogram; ND � below detection limit; TSCA � Toxic Substance Control Act; WCS � Wasatch Chemical Superfund

Pilot- and full-scale applications of ISTD have been used to remove PCBs, dioxins,and furans. Four full-scale ISTD projects at POP-contaminated sites were identified. Ingeneral, treatment costs in USD at these sites ranged from $200 to $600 per cubic yard.Projects involving ISTD treatment of larger volumes of waste will have lower unit costs.Available performance information for the technology is presented in Exhibit 6.

Mechanochemical Dehalogenation

The mechanochemical dehalogenation (MCD™) technology uses mechanical energy to pro-mote reductive dehalogenation of contaminants to treat high-strength wastes containingPOPs. In this process, contaminants react with a base metal and a hydrogen donor to gener-ate reduced organics and metal salts.The base metal is typically an alkali-earth metal, analkaline-earth metal, aluminum, zinc, or iron.The hydrogen donors used include alcohols,ethers, hydroxides, and hydrides.The process occurs ex situ in an enclosed ball mill, and thegrinding medium provides the mechanical energy and mixing.The technology is applicableto soil, sediments, and mixed solid-liquid phases.The by-products generated at the end ofthe process are nonhazardous organics and metal salts (Thiess Services NSW, 2004).

One MCD™ process developed by Environmental Decontamination Ltd. (EDL) isbeing used at full scale to treat soil at the Fruitgrowers Chemical Company site inMapua, New Zealand.The site is the location of a former pesticide and herbicide manu-facturing plant and contains soil contaminated with DDT, dichlorodiphenyldichloro-ethane (DDD), dichlorodiphenyldichloroethylene (DDE), aldrin, dieldrin, and lindane.Proof-of-performance testing of the MCD™ process was conducted at the site betweenFebruary 16 and April 23, 2004. During the proof-of-performance testing at theFruitgrowers Chemical Company site in Mapua, New Zealand, the MCD™ system



Exhibit 6. Performance of ISTD technology

Quantity of Untreated TreatedSite Location Period POP Soil Treated Scale Concentration Concentration

Former South Glens Moreau, 1996 PCBs NA Full 5,000 mg/kg 0.8 mg/kgFalls Dragstrip New York

Tanapag Village Saipan, Northern July 1997 to PCBs 1,000 cy Full 10,000 mg/kg � 1 mg/kgMariana Islands August 1998

Centerville Beach Ferndale, September to PCBs 667 cy Full 860 mg/kg � 0.17 mg/kgCalifornia December 1998 Dioxins 3.2 µg/kg 0.006 µg/kg

and Furans

Alhambra Alhambra, May 2002 to Dioxins 16,200 cy Full 194 µg/kg � 1 µg/kg“Wood Treater” California January 2005

Sources: Baker and Kuhlman (2002); Stegemeier and Vinegar (2001); TerraTherm Environmental Services (1999); and TerraTherm Inc. (2005).

Notes: cy � cubic yard; µg/kg � micrograms per kilogram; mg/kg � milligrams per kilogram; NA � not available

exhibited a maximum treatment rate of 139 cubic meters per week. Exhibit 7 lists theinitial and final mean contaminant concentrations in the soil treated in the MCD™ reac-tor. Subsequent to the proof-of-performance testing, EDL was commissioned to remedi-ate the site, with an expected completion date in 2006.The MCD™ technology is avail-able from EDL in Auckland, New Zealand (http://edl.net.nz/about.php), and fromTribochem in Wunstrof, Germany (http://www.tribochem.com) (Birke, 2002).Information was provided by EDL.Tribochem has not provided process details, perfor-mance data, or costs for its technology.

Xenorem™

Xenorem™ is a bioremediation technology that uses an enhanced composting technologyconsisting of aerobic and anaerobic treatment cycles to treat low-strength wastes con-taining chlordane, DDT, dieldrin, and toxaphene contamination. Organic amendmentssuch as manure and wood chips are added to contaminated soil, which can increase thefinal amended soil volume by as much as 40 percent (Gray et al., 2002).

A self-propelled SCAT windrow incorporates the amendments into the soil andprovides aeration creating aerobic conditions.The presence of high levels of available nu-trients from the amendment increases the metabolic activity in the amended soil and de-pletes the oxygen content, creating anaerobic conditions.The anaerobic conditions pro-mote dechlorination of organochlorine compounds.The length of the anaerobic phase isdetermined by bench-scale studies. At the end of the anaerobic phase, the SCAT unit isused to mix the amended soil, creating aerobic conditions again.The anaerobic and aero-bic cycles are repeated until the desired contaminant reductions are achieved.Typically,the organic amendments are spent after 14 weeks. Soil samples are collected from thetreated soil, and if the contaminant concentrations do not meet the cleanup goals, moreorganic amendments are added and the treatment is continued as long as necessary.

This technology was applied in a full-scale cleanup at the Stauffer ManagementCompany Superfund site in Tampa, Florida.The site is the location of a pesticide manufactur-ing and distribution facility that operated from 1951 to 1986 (US EPA, 1996b). Soil on the40-acre site was contaminated with chlordane, DDD, DDE, DDT, dieldrin, molinate, andtoxaphene.The Xenorem™ technology was applied to two 4,000-cubic-yard batches of soil.



Exhibit 7. Performance of MCD™ technology at the Mapua site

Untreated Treated Concentration Concentration Percent

POP (mg/kg) (mg/kg) ReductionDDX 717 64.8 91%Aldrin 7.52 0.798 89%Dieldrin 65.6 19.8 70%Lindane 1.25 0.145 88%Aldrin�Dieldrin�Lindane 73.245 20.612 72%

Source: Thiess Services NSW (2004).

Note: mg/kg � milligrams per kilogram

Exhibit 8 presents the performance data for Batch 1 and Batch 2. DDD was reduced by 65percent, DDE was reduced by 68 percent, DDT was reduced by 88 percent, and toxaphenewas reduced by 94 percent; however, neither batch achieved the site cleanup goals for DDTand toxaphene.Typical treatment costs in USD using Xenorem™ were provided by the ven-dor and are approximately $132 per cy of contaminated soil (US EPA, 2000a).

The Xenorem™ technology was applied to a third batch of contaminated site soil.Batch 3 was treated for one year but did not achieve the cleanup goals for chlordane,DDT, dieldrin, and toxaphene. Because the selected remedy did not fully meet thecleanup goals, the remedial design for the site is being modified.The US EPA is awaitingdetails of the modification proposal. Eventually, the US EPA will prepare an Explanationof Significant Difference (ESD) fact sheet explaining the selection of a new remedy (N.C. C. Gray, personal communication, December 15, 2004).

Xenorem™ is a patented technology developed by Stauffer Management Company, asubsidiary of AstraZeneca Group PLC in Mississauga, Ontario, Canada. Recently, this tech-nology was sold to the University of Delaware (N. C. C. Gray, personal communication,December 15, 2004). Additional information on the technology can be obtained from theTechnology Transfer Corporation at the University of Delaware in Newark, Delaware.

Pilot-Scale Technologies for Treatment of POPs

This section describes technologies that have been implemented to treat POPs at thepilot scale. A pilot-scale project is usually conducted in the field to test the effectivenessof a technology and to obtain information for scaling up a treatment system to full scale.Four pilot-scale technologies were identified for the treatment of POPs and are de-scribed in the sections that follow.



Exhibit 8. Performance of Xenorem™ technology at the Tampa site

Batch 1a Batch 2b

Site Untreated Treated Untreated Treated Cleanup Goal Concentration Concentration Percent Concentration Concentration Percent

Pesticide (mg/kg) (mg/kg) (mg/kg) Reduction (mg/kg) (mg/kg) ReductionChlordane 2.3 3.8 � MDL NA 4.5 1.2 75%DDD 12.6 26 9.3 65% 24 14 42%DDE 8.91 6.6 2.1 68% 6.1 2.6 57%DDT 8.91 82 9.8 88% 196 14 93%Dieldrin 0.19 2.4 � MDL NA 2.7 0.7 74%Molinate 0.74 0.2 � MDL NA 0.4 � MDL NAToxaphene 2.75 129 7.8 94% 139 23 83%

Source: Gray et al. (2002).

Notes: MDL � method detection limit (the MDL was not provided in the source document); mg/kg � milligrams per kilogram; NA � not available a For Batch 1, treated concentrations are at the end of a 24-week period.b For Batch 2, treated concentrations are at the end of a 12-week period.

Quantity treated: 4,000 cy of soil (Batch 1 and Batch 2).

Base-Catalyzed Decomposition

Base-catalyzed decomposition (BCD) is an ex situ technology that has been used in pilottests to treat high-strength soil containing POP contamination.The BCD technologyuses a two-stage process. In the first stage of the treatment process, contaminated soil ismixed with an alkali such as sodium bicarbonate, and the mixture is heated in a thermaldesorption reactor to temperatures ranging from 315 to 500°C.The heat separates thehalogenated compounds from the soil by evaporation. In the second stage of the process,the volatilized contaminants pass through a condenser.The condensate is then sent to aBCD liquid tank reactor (LTR). Sodium hydroxide, a proprietary catalyst, and carrier oilare added to the LTR, which is then heated to above 326°C for three to six hours.Thecarrier oil serves both as a suspension medium and a hydrogen donor.The heated oil isthen cooled and sampled to determine whether it meets disposal criteria. If the oil doesnot meet the disposal criteria, it is returned to the LTR, reagents are added, and the re-actor is reheated (T. Lyons, personal communications, January 19 and August 10, 2005).The treated soil can be used as backfill on site.

BCD has been implemented to treat soil contaminated with POPs by the US EPA’sNational Risk Management Research Laboratory in Cincinnati, Ohio. Results from thestudy indicate that total PCBs were reduced from 81,100 mg/kg to below the detectionlimit of 5 mg/kg.Total tetrachlorodibenzodioxin (TCDD) was reduced from 5,800nanograms per kilogram (ng/kg) to 9.1 ng/kg. A second bench-scale study indicatedthat PCBs were reduced from 5,280 mg/kg to below the detection limit of 5 mg/kg.Total TCDD was reduced from 5,800 ng/kg to 15.0 ng/kg (T. Lyons, personal commu-nications, January 19 and August 10, 2005; http://www.epa.gov/ORD/NRMRL/lrpcd/rr/projects/56585.htm).

The US EPA holds the patent rights to this technology in the United States.The for-eign rights for this technology are held by BCD Group Inc., Cincinnati, Ohio.The tech-nology has been licensed by BCD Group Inc. to environmental firms in Spain, Australia,Japan, and Mexico. Since the invention of the BCD technology in 1990, considerabletechnology advancements have been made with the discovery of a new catalyst.The cata-lyst used in the second-generation BCD technology reduces the reaction time in theBCD reactor (C. Rogers, personal communications, December 9 and 13, 2005).Thissecond-generation technology has been used in Australia, Mexico, and Spain to treatPCB-contaminated oil.Two commercial BCD plants are being constructed in the CzechRepublic and will begin operations in 2006. At this time, performance data for the BCDoperations in Australia, Mexico, and Spain are not available from the vendors.

Phytoremediation

Phytoremediation is a process that uses plants to remove, transfer, stabilize, or destroy con-taminants in soil, sediment, and groundwater. It may be applied in situ or ex situ to treat low-strength soils, sludges, and sediments contaminated with POPs.The mechanisms include:

• enhanced rhizosphere biodegradation (degradation in the soil immediately sur-rounding plant roots),

• phytovolatilization (the transfer of the pollutants to air via the plant transpira-tion stream),



BCD has been imple-mented to treat soil con-taminated with POPs by theUS EPA’s National Risk Man-agement Research Labora-tory in Cincinnati, Ohio.

• phytoextraction (also known as phytoaccumulation, the uptake of contaminantsby plant roots and the translocation/accumulation of contaminants into plantshoots and leaves),

• phytodegradation (metabolism of contaminants within plant tissues),• phytostabilization (production of chemical compounds by plants to immobilize

contaminants at the interface of roots and soil), and• hydraulic control (the use of trees to intercept and transpire large quantities of

groundwater or surface water for plume control).

Phytoremediation of POPs is not feasible for stockpiles of contamination but it is an ap-propriate polishing technology for residual contamination in soils. Initial laboratory researchidentified enhanced degradation of PCBs in the rhizosphere (Donnelly et al., 1994; Gilbert& Crowley, 1997; Leigh et al., 2003). Other researchers are finding promising results forphytoextraction in the laboratory and pilot-scale phase.The Connecticut AgriculturalExperimental Station’s preliminary data has shown that a narrow range of plant species (cer-tain cucurbitas) can effectively accumulate significant amounts of highly weathered pesticideresidues such as DDE and chlordane from soil (White et al., 2005).The Royal MilitaryCollege of Canada has also demonstrated that certain plant species can extract and store sig-nificant levels of PCBs and DDT (Zeeb et al., 2005). Both the Ukraine and Kazakhstan havebeen conducting research on the use of plants to clean up soils laced with pesticides. In theUkraine, laboratory experiments have shown that bean plants can accumulate and decom-pose DDT (Moklyachuk et al., 2005). In Kazakhstan, native vegetation that can tolerate andaccumulate pesticides has been identified (Nurzhanova et al., 2005).

Field-scale projects include a 40-year-old scrap yard site with PCB-contaminatedsoils at the 225 ppm level.The site contamination was approximately two acres andthree feet deep.The cleanup project demonstrated that PCB concentrations decreased(over 90 percent) in the presence of red mulberry trees and bermuda grasses within twoyears’ time (Hurt, 2005). Another example is an evapotranspiration cover that will beconstructed at the Rocky Mountain Arsenal National Wildlife Refuge near Denver,Colorado, for the contaminants aldrin, chlordane, DDT, dieldrin, and endrin (InterstateTechnology Regulatory Council, 2003). Furthermore, two US EPA Superfund sites haveutilized phytotechnology as a treatment for POPs:

• Aberdeen Pesticides Dumps utilized phytotechnology for residual contaminants(dieldrin and HCB) using poplar trees and grasses.This is an ongoing project.

• Fort Wainwright utilized ex situ phytotechnology for aldrin and dieldrin with wil-low trees.The soil was deposited of after treatment in the site landfill rather thana hazardous landfill.

Sonic Technology

Sonic technology is an ex situ technology that is used to treat low- and high-strength soilscontaining PCB contamination. In this process, contaminated soil is first mixed with asolvent.The mixture is then subjected to sonic energy generated by a proprietary low-frequency generator. Using sonic energy, the mixture is agitated and the PCBs from thesoil are extracted and suspended in the solvent.The solvent is then separated from themixture using multistage liquid separators.The solvent is then mixed with elemental



Phytoremediation of POPsis not feasible for stock-piles of contamination butit is an appropriate polish-ing technology for residualcontamination in soils.

sodium and subjected to sonic energy again.The sonic energy activates dechlorination ofthe PCBs in the solvent.The spent solvent can then be recycled through the system. Anyoff-gas from the process is treated using condensation, demisting, and multistage carbonfiltration (Sonic Environmental Solutions Inc., 2005).

In a pilot-scale application of the technology to treat PCB-contaminated soil, theconcentrations of PCBs before treatment were 388–436 mg/kg, and the concentrationsafter treatment were 0.35–0.81 mg/kg.The technology is being implemented at fullscale to treat approximately 3,000 tons of PCB-contaminated soil at the Juker Holdingssite in Vancouver, British Columbia, Canada (Sonic Environmental Solutions Inc., 2005).Additional performance data of the full-scale application of this technology are not cur-rently available.The technology was developed by Sonic Environmental Solutions Inc. inVancouver, British Columbia, Canada (http://www.sesi.ca).

CerOx™

CerOx™ is an ex situ electrochemical reaction technology that has been used in pilottests to treat low-strength liquids containing POP contamination.We could not find anypilot-scale tests that used CerOx™ for soil or sediment contaminated POP waste. Priorto treatment, solid waste such as soil or sediment is mixed with water to produce a fluidwaste stream.This waste stream is injected with cerium (IV) from an electrochemicalcell, agitated through sonication, and transferred to a liquid-phase reactor at a tempera-ture between 90 and 95°C. During this process, cerium (IV) is reduced to cerium (III).Cerium (III) and unreacted cerium (IV) are returned to the electrochemical cell for re-cycling, and the treated medium is removed from the system. Gases produced duringthe liquid-phase reaction usually include carbon dioxide, chlorine gas, and unreactedvolatile organic compounds (VOCs).These gases are processed through a gaseous-phasereactor that uses cerium (IV) to destroy VOCs.The remaining gases are passed through ascrubber to remove acid gases and are then vented to the atmosphere. Liquid from thescrubber is discharged (CerOx™ Corporation, 2005).

The CerOx™ system was installed at the University of Nevada at Reno (UNR).Thesystem was tested in May 2000 with chlordane.The system is reported to have achieveda chlordane destruction efficiency of 99.995 percent in the gaseous-phase reactor(American Chemical Society, 2000).The vendor performed additional tests of the UNRsystem on August 29, 2000, to determine the ability of CerOx™ to treat PCBs and diox-ins in isopropyl alcohol.The initial concentration was five parts per billion (ppb), andthe final concentrations ranged from 0.432 ppb to nondetect (0.0397 ppb is the detec-tion limit) (http://www.cerox.com).

The technology was developed by CerOx™ Corporation in Santa Maria, California.CerOx™ Corporation offers a variety of CerOx™ treatment systems for commercialuse.The systems range in size from modules with 25-gallon-per-day (gpd) treatmentcapacities to multimodular plants with 100,000-gpd treatment capacities (http://www.cerox.com/systems_process.html).

Bench-Scale Technologies for Treatment of POPs

This section lists the technologies that have been implemented to treat POPs at thebench scale. A bench-scale project is conducted on a small scale, usually in the



CerOx™ is an ex situ elec-trochemical reaction tech-nology that has been usedin pilot tests to treat low-strength liquids contain-ing POP contamination.

laboratory, to evaluate a technology’s ability to treat soil, waste, or water.Three bench-scale technologies were identified for the treatment of POPs and are described in thesections that follow.

Activated Persulfate

Klozur™ sodium persulfate upon activation generates the sulfate radical SO4–, a strong

oxidizing agent that destroys recalcitrant compounds either in situ or ex situ.TheUniversity of Connecticut Environmental Research Institute evaluated the use of acti-vated persulfate with and without lime addition. General conclusions reported that theheated persulfate degraded PCBs in sediment.They detected increased degradation athigher temperatures and in the presence of lime.

FMC Corporation has developed patent pending activation chemistries for Klozur™

persulfate and chelated metals for improved transportability, pH control for the forma-tion of energetic persulfate radicals, or hydrogen peroxide for dual-oxidant destruction(http://www.klozur.com).

Self-Propagating High-Temperature Dehalogenation

Self-propagating high-temperature dehalogenation (SPHTD) is an ex situ technology usedto treat stockpiles at bench scale containing HCB contamination. HCB-containing stock-piles are mixed with calcium hydride or calcium metal, and the mixture is placed in areaction chamber containing a tungsten coil. Addition of purified argon gas causes thereaction chamber to become pressurized, and an electrical pulse to the tungsten coil ini-tiates the reaction. Once initiated, the reductive reactions that occur in the reactionchamber are exothermic and self-propagating.The reaction chamber can reach a temper-ature of 3,727°C, which creates thermochemical conditions that convert HCB to cal-cium chloride, carbon, and hydrogen (G. C. Ing, personal communication, December12, 2004; UNEP, 2004).

TDR-3R™

TDR-3R™ is an ex situ technology used to treat high- and low-strength soils containingHCB contamination through the use of a continuous low-temperature anoxic thermaldesorption process. Contaminated soil is heated in a specially designed, indirectly fired,horizontally arranged rotary kiln to a temperature typically between 300 and 350°Cunder an applied vacuum of 0–50 Pascal.The contaminants in the soil desorb, and thevaporized contaminants are recovered from the kiln and combusted in a thermal oxi-dizer for at least two seconds at a temperature exceeding 1,250°C. Off-gas from thethermal oxidizer is rapidly cooled, passed through a wet gas multi-venturi scrubber, anddischarged. Process water from the scrubber is treated and discharged.Treated soil exit-ing the kiln is cooled indirectly and removed (http://www.terrenum.net/index.htm;IHPA, 2002).

TDR-3R™ has been implemented at a bench scale in Gare, Hungary, to treat 100 kgof soil contaminated with HCB.Treatment occurred at a temperature of 450°C under avacuum of 30 Pascal.The technology reduced the soil’s HCB concentration from 1,215to 0.1 mg/kg (Thermal Desorption Technology Group, 2004).TDR-3R™ is marketed



TDR-3R™ is an ex situ tech-nology used to treat high-and low-strength soils con-taining HCB contamina-tion through the use of acontinuous low-tempera-ture anoxic thermal des-orption process.

by Terra Humana Clean Technology Engineering Ltd. in Hungary.This firm is a sub-sidiary of Thermal Desorption Technology Group LLC in the United States (http://www.terrenum.net).

Full-Scale Technologies with Potential to Treat POPs

This section describes technologies that have been implemented to treat non-POPs atfull scale and that are potentially applicable for treatment of POPs. Each subsection fo-cuses on a single technology and includes a description of the technology and informa-tion about its application at specific sites.

Plasma Arc Technologies

Plasma arc technologies use a thermal plasma field to treat contaminated wastes.Theplasma field is created by directing electric current through a gas stream under lowpressure to form a plasma with a temperature ranging from 1,600 to 20,000°C.Bringing the plasma into contact with the waste causes contaminants to dissociate intotheir atomic elements.The separated elements are subsequently cooled, which causesthem to recombine to form inert compounds.The process may also destroy organiccompounds through pyrolysis.The end products are typically gases such as carbonmonoxide, carbon dioxide, hydrogen, and inert solids. If chlorinated compounds arepresent in the waste, acid gas is also generated as an end product.The off-gas from theplasma arc system passes through an off-gas treatment system and is then discharged.The plasma arc technologies that are used to treat organic wastes include PLASCON™

(http://www.srlplasma.com.au/srlpages/srlframe.html), Plasma Arc CentrifugalTreatment (http://www.retechsystemsllc.com/PACT%20webpagesC/index.htm), andthe Plasma Converter System (http://www.startech.net/plasma.html).The PLAS-CON and Plasma Converter System may potentially remediate POPs; however, thePACT technology has treated POP contamination at the pilot scale (http://www.retechsystemsllc.com/PACT%20webpagesC/index.htm; CMPS&F–EnvironmentAustralia, 1997).

Supercritical Water Oxidation

Supercritical water oxidation (SCWO) is an ex situ enclosed technology system at atemperature and pressure above the critical point of water (374°C and 22.1 � 106

Pascal) that has been used to treat solid and liquid wastes. Under these conditions, thegas-liquid phase boundary ceases to exist and water exists in a fluid state that is neitherliquid nor gas; contaminants have a higher solubility in supercritical water. An addedoxidant such as oxygen or hydrogen peroxide reacts with dissolved organic contami-nants in the supercritical water to form carbon dioxide, water, inorganic acids, andsalts (L. Johnson, personal communication with Chitranjan Christian, February 15,2005; US EPA, 2000b).

The Assembled Chemical Weapons Assessment (ACWA) Program was establishedin 1997 to test and demonstrate at least two alternative technologies to the baselineincineration process for the demilitarization of assembled chemical weapons. In 2003,the Bechtel Parsons Blue Grass Team was awarded a contract to design, construct,



Supercritical water oxida-tion is an ex situ enclosedtechnology system at atemperature and pres-sure above the criticalpoint of water that hasbeen used to treat solidand liquid wastes.

test, operate, and close the Blue Grass Army Depot Destruction Pilot Plant usingSCWO. As of January 2005, the SCWO system is in the design phase. SCWO was alsoselected for use at the Newport Army Depot to destroy 1,269 tons of liquid agent VX(http://www.pmacwa.army.mil/about/index.htm; Global Security, 2005; IHPA,2002; UNEP, 2004).

In the United States, SCWO technology is available from General Atomics’ AdvancedProcess Systems division (http://demil.ga.com/).Turbosystems Engineering Inc. also de-signs and markets SCWO systems in the United States (http://www.turbosynthesis.com/summitresearch/sumhome.htm).

CONCLUSION

Persistent organic pollutants are a set of chemicals that are toxic, persist in the envi-ronment for long periods of time, and biomagnify as they move up through the foodchain. Restrictions and bans on the use of POPs have resulted in a significant numberof unusable stockpiles of POP-containing materials internationally. Deterioration ofstorage facilities used for the stockpiles, improper storage practices, and past produc-tion and use of POPs have resulted in contamination of soils around the world.Combustion technologies (incineration) have been the principal technology used todestroy POPs. However, combustion technologies can create polychlorinated dibenzo-p-dioxins (dioxins) and polychlorinated dibenzo-p-furans (furans), which have beencharacterized by the US EPA as human carcinogens and are associated with serioushuman health problems.

Two organizations, the United Nations Environment Programme (UNEP) and theInternational HCH and Pesticides Association (IHPA) have developed detailed reportsand fact sheets about noncombustion technologies for POP treatment.With the passageof time, some of the technologies discussed in these comprehensive documents thatwere in the development stage are now commercialized, while other commercial tech-nologies are no longer being developed. Also, new promising destruction technologiesfor POPs have been developed.This article is intended to update and summarize olderreports in a concise reader’s guide, with links to sources of further information. In doingso, this article identifies and describes six full-scale technologies, four pilot-scale tech-nologies, three bench-scale technologies, and two full-scale technologies with the poten-tial to treat POPs.The updated information was obtained by reviewing various Web sitesand documents, and by contacting technology vendors and experts in the field.

NOTICE

This article is drawn from the EPA Report “Reference Guide to Non-CombustionTechnologies for Remediation of Persistent Organic Pollutants in Stockpiles and Soils”EPA-542-R-05-006 (http://www.cluin.org/POPs).

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