emerging processes for soil and groundwater cleanup

Environmental Engineering and Management Journal

September/October 2009, Vol. 8, No.5, 1293-1307

http://omicron.ch.tuiasi.ro/EEMJ/

“Gheorghe Asachi” Technical University of Iasi, Romania

______________________________________________________________________________________________

EMERGING PROCESSES FOR SOIL AND GROUNDWATER CLEANUP - POTENTIAL BENEFITS AND RISKS Maria Gavrilescu “Gheorghe Asachi” Technical University of Iasi, Faculty of Chemical Engineering and Environmental Protection, Department of Environmental Engineering and Management, 700050, Iasi, Romania, e-mail: [email protected]

Abstract The cleanup of environmental pollution involves a variety of techniques, ranging from simple biological processes to advanced engineering technologies. Cleanup activities may also address a wide range of contaminants. Technologies to remediate contaminated soil fall into two principal clean-up approaches: in-situ (which is always done onsite), or ex-situ (which can be done on- or off-site). In-situ treatment deals with contamination without removing material from the ground, while ex-situ treatment requires the removal of contaminated soil for treatment or landfilling. Selecting and/or designing the right clean-up approach require skill and innovation. Most contaminated sites contain a complex cocktail of contaminants as well as unique site features (geology, hydrology etc). As such, tailored approaches and technologies are required on a site-by-site basis, as determined through a site characterization and assessment. Other factors involved in technology selection for a particular site include the end goal for clean-up (i.e.: how clean the site is required to be), risk, stakeholder concerns, technological feasibility, available budget etc. The work evidences that excellence in R&D and technology development could be attained by the development of processes to deal more effectively and economically with certain toxic contaminants such as heavy metals, VOCs and in-situ treatment of PCBs, associated with optimization of technologies in-situ under field remediation conditions and requirements, improving capacity and speed, and reducing costs. Taking into consideration this complex domain of environmental engineering and management, new and growing technologies based on natural, physical, chemical and/or biological processes to break down, stabilize, or accumulate pollutants are scrutinized. However, it is evidenced that, with any new technology, come concerns over its misuse and possible negative environmental and health effects. Also, the important barriers to the adoption of new environmental technologies, the confidence of the user in the data about cost and performance of the technology are emphasized.

Key words: contamination, remediation, risk, site characterization, strategy 1. Introduction Contamination od soils and groundwater by various sources may lead to soil failing to support vegetation, as a result of phytotoxic effects of contaminats or disrupted biological cycling of nutrients. (Belyaeva et al., 2005; Scullion, 2006; Siddiqui et al., 2001). Also, the contaminated soils may affect the hydrosphere compromising the quality of groundwater, drinking water resources and menacing the aquatic ecosystems. Humans are exposed at risk from polluted soils through dermal contact, ingestion, consumption of food resulted on polluted areas and inhalation of dusts or vapours (Nathanail and Earl, 2001; Scullion, 2006). The remediation industry was born in the late 1970s, resulting from highly publicized discoveries of

toxic chemicals in landfills, drinking water, and even neighborhoods (Ellis and Hadley, 2009). There has been numerous studies in soil remediation technologies throughout the world during last few decades in response to the growing concern for deteriorating soil environment. Subsurface contamination from spills and leaky underground storage creates environmental problems that usually require corrective actions. Over the years, the field of remediation has grown and evolved, continually developing and adopting new technologies in attempts to improve the remediation process. Anthropogenic activities invariably tend to misuse the environment and the degraded and contaminated soil environment with toxic materials pose a much greater challenge for its cleanup. Depending on the nature of contamination, a range of remediation technologies

Gavrilescu/Environmental Engineering and Management Journal 8 (2009), 5, 1293-1307

have been developed and are being practiced all over the world. Most of these technologies are known to have been based on biological, physical, chemical, physico-chemical, thermal or combinations of several of these (treatment trains). Both in-situ (i.e., without excavation) and exsitu (with excavation and transportation, if necessary) approaches have been in vogue. Also, it is recognized that many of the scientific principles underpinning soil remediation have relevance for groundwater treatment (Scullion, 2006). Pump-and-treat systems operate on the basis of removing contaminated groundwater from the ground, downstream of the contamination site, and then treating it before returning it to the ground (Watlington, 2005). In the past years, emerging technologies such as phytoremediation, bioremediation, and permeable reactive barriers have become popular new tools. These novel treatments have begun to compete with more established technologies such as solidification/ stabilization, soil vapor extraction, and thermal desorption for soil, and pump and treat systems for groundwater (USEPA 2004). 2. Challenges of groundwater and soil cleanup The location and cleanup of contaminant mass in the subsurface is one of the greatest challenges in remediation that can serve as a long-term source of ground water pollution and lead to the formation of extensive plumes of contamination (NRC, 1997). Often, contaminant sources are difficult to locate and delineate. Once found, source material may be inaccessible, lying under structures, or at great depth, or in fractured rock. Ellis and Hadley (2009) developed the concept of sustainable remediation, broadly defined as a remedy or combination of remedies whose net benefit on human health and the environment is maximized through the judicious use of limited resources. This should involve: minimization or elimination of energy consumption or the consumption of other natural resources; reduce or eliminate releases to the environment, especially to the air; harness or mimic a natural process; reuse or recycling of land or otherwise materials; encourage the use of remedial technologies that permanently destroy contaminants (Ellis and Hadley, 2009). They imagined a schematic evolution of remediation strategies, up to those having a sustainable nature, which should be attained up to 2020 (Fig. 1). They also associated the term green remediation, which means incorporating sustainable environmental practices into remediation of contaminated sites that describes remediation methods and approaches that consider all environmental effects of cleanup actions and incorporate strategies to maximize the net environmental benefit.

1294

Fig. 1. Evolution of perception about sustainability in cleanup processes (taken from Ellis and Hadley, 2009)

Some challenges concerning sustainability elements are included in remedial activities, which could be considered as barriers and entail aspects like: regulatory complications and/or resistance, impeding work progress, sustainability metrics override other factors, valuation of resources, stakeholder, incorporation of sustainability into remedy selection (NRC, 1997; Ellis and Hadley, 2009). 3. Sources of groundwater

contaminants

for

soil

and

Contaminants can build up in soils from several sources. They can be released to soil and groundwater as leaks in industrial waste pits and municipal and industrial landfills, accidental spills, custom washing and cleaning of equipment and chemical storage tanks, and a variety of other human activities (Caliman and Gavrilescu, 2009; Gavrilescu et al., 2009; NRC, 1997). Even as most of the early discussions on soil pollution were associated to metals or other inorganic pollutants, there has been an increasing concern over the last few decades regarding organic contaminants, as a consequence of their widespread use in industry as solvents, feedstocks and presence in industrial wastes (Betianu and Gavrilescu, 2006; Collins et al., 2002; Schiopu et al., 2007). Major pollutants of soils and aquifers can be considered fuel hydrocarbons, contaminants from combustion processes, which have led to widespread contamination of soils (with polycyclic aromatic hydrocarbons (PAHs) (Solano-Serena et al., 2001; van Brummelen et al., 1996). Some contaminants are released directly to ground water, for example in water injection wells, while others are released to the soil (Omran and Gavrilescu, 2008; Schiopu et al., 2007) Table 1 is a summary of main sources of contamination as well as respective contaminants. Contaminants released to the soil usually migrate through the soil and may contaminate the underlying groundwater. Others may dissolve in the ground water during their percolation through the soil (Gavrilescu, 2005; Gavrilescu et al., 2009). Some contaminants may dissolve in the gases contained in soil pores and spread before dissolving in the ground water.

Emerging processes for soil and groundwater cleanup

Table 1. Ground water contamination sources Sources designed to discharge substances

Subsurface percolation (e.g., septic tanks and cesspools) Injection wells - hazardous waste - nonhazardous waste (e.g., brine disposal and drainage) - nonwaste (e.g., enhanced oil recovery, artificial recharge, solution mining, and in situ mining) Land application - wastewater (e.g., spray irrigation) - wastewater byproducts (e.g., sludge) - hazardous waste

Sources design to store, treat, and/or dispose of substances; discharge through unplanned release Landfills - industrial hazardous waste - industrial nonhazardous waste Municipal sanitary Open dumps, including illegal dumping Residential (or local) disposal Surface impoundments Waste tailings Waste piles Materials stockpiles Graveyards Animal burial sites Above-ground storage tanks Underground storage tanks Containers Open burning and detonation sites Radioactive disposal sites

Sources designed to retain substances during transport or transmission Pipelines Material transport and transfer operations

The transport of contaminants as a separate, nonaqueous-phase liquid (known as a NAPL that is immiscible in water) leads to their migration separately from the water (Betianu and Gavrilescu, 2006; Pintilie et al., 2007). Mobile colloidal particles from soil composition can sorb contaminants or form complexes with molecules of natural organic matter present in the water (Gavrilescu et al., 2009; NRC, 1997). Table 2 describes some mechanisms of contaminant transport in the soil (NRC, 1997). The models of soil pollution are generally hard to be predicted, although they are important for risk assessment, remediation design and validation of remediation endings. The intensity of human or environmental targets exposure is connected to pollutant hazards is conditioned by the distribution of contaminants among phases and exchange rates between these phases. Scullion, (2006) considers that, at a micro-scale, the distribution of pollutants can be equally heterogeneous (Fig. 2). For example, variations in sorption–desorption capacity and kinetics, especially for organic contaminants are considered to be the result of the differences in soil organic matter characteristics (Gavrilescu et al., 2009; Scullion, 2006). 4. Site characterization and remedial investigation In practical terms, in a polluted soil the concentration of a contaminant exceeds that set out in the relevant regulations. Every soil and/or groundwater remediation project needs the determination of the contamination

Sources discharging substances as consequences of other planned activities Irrigation practices (e.g., return flow) Pesticides applications Fertilizer applications Animal feeding operations De-icing salts applications Urban runoff Percolation of atmospheric pollutants Mining and mine drainage

Sources providing pollution conduits or inducing discharge through altered flow patterns Production wells - oil (and gas) wells - geothermal and heat recovery wells Water supply wells Other wells - monitoring wells - exploration wells Construction excavation Drains

Naturally occurring sources, with discharge created and/or exacerbated by human activity Ground water-surface water interactions Natural leaching Salt water intrusion/brackish water upcoming (or intrusion of other poorquality natural water)

level and site characterization to determine the conditions on and under a site that are relevant for choosing a feasible decontamination method, following some stages, as is presented in Table 3. Identification of the source of contamination and tracing the migration of contaminants are usually not simple operations, since additional data are necessary for control of plume migration and selection of remedial alternatives (Kuo, 1999). Many of the advanced site-characterization tools employ the principles of sustainability in their design or offer data that can be used to characterize the sustainability of remedial options (Ellis and Hadley, 2009). The remedial investigation serves as the means for collecting data to: • characterize site conditions; • determine the nature of the waste; • assess risk to human health and the environment; • conduct treatability testing to evaluate the potential performance and cost of the treatment technologies that are being considered. It is important to note that the complexity of waste sites varies extremely depending on the source of the contamination and the geologic conditions at the site. The contaminants may be present in one or a combination of the locations and phases, as presented in Table 4. The application of onsite assays to improve decision making regarding the extent of pollution in batches of potentially polluted materials has expended in recent years and, therefore, the need for treatment or disposal.

1295

Gavrilescu/Environmental Engineering and Management Journal 8 (2009), 5, 1293-1307

Fig. 2. Distribution of hazards to receptors as a consequence of pathways of contaminants sharing between soil phases (Scullion, 2006) Table 2. Mechanisms of contaminants transport in soil Transport mechanism Vapor-phase transport

Description Vapors of volatile contaminants may spread through the pore spaces in the soil above the water table and then either dissolve in water in soil pore spaces or in infiltrating rain water. The extent to which contaminants migrate in the vapor phase varies by many orders of magnitude.

Aqueous-phase transport

The flowing ground water may dissolve in and transport contaminants, with a rate which depends on contaminant solubility (it varies among contaminants by many orders of magnitude), the extent of contaminant contact with water and contaminant reactions with solids in the aquifer.

Nonaqueous-phase liquid (NAPL) transport

Some contaminants (chlorinated solvents, petroleum products), enter the subsurface in the form of oily liquids (NAPL), which do not mix readily with water and therefore flow separately from ground water. They could be more dense than water (DNAPL) and will tend to go down once it reaches the water table, or less dense than water (LNAPL) and tend to float on the water table. Mobile colloidal particles may sorb or incorporate contaminants into large complexes of natural organic matter and transport them in the flowing ground water.

Facilitated transport

5. Risk evaluation in decision making Risk assessment has become an essential part of site remediation and is increasingly being used in establishing site-specific remediation levels. Also, assessing the bioavailability of soil pollutants is an essential part of the process of risk assessment and of determining the most appropriate approach to remediation (Ellis and Hadley, 2009; Semple et al. 2003). A baseline risk assessment is developed to identify the existing or potential risks that may be posed to human health and the environment by the site (Fig. 3). Because this assessment identifies the primary health and environmental threats at the site, it

1296

also provides valuable input to the development and evaluation of alternatives. Risk and exposure assessment for soil and groundwater environment are very important for both aspects of health and environmental protection as well as making decision of remedial goal for engineering activities (Kawabe et al., 2007; Robu et al., 2007). On a theoretical side, is performing in order to protect humans and ecological receptors from potential harm as a result of exposure to chemicals at a site. In this context, risk assessment should be the measuring tool used to determine if this goal has been achieved and obviously should be part of the decision-making process (LaGoy, 1999).

Emerging processes for soil and groundwater cleanup

Table 3. Main stages in remedial process statement Phase Site Characterization

Remedial Investigation

Remedy Selection

Purpose and function - identification of the presence and type of contamination found in various environmental media - determine if applicable standards, criteria and guidance (SCGs) are exceeded - identification of areas of concern determine if further action is warranted - determination of the nature and extend of contamination for each area of concern - detailed delineation of site environmental media - identification of contaminant sources - identification of contaminant migration pathways - determination of the impact or potential impact of contaminants on public health and the environment collection of data to facilitate selection and design of remedial actions - selection of the most appropriate remedial or cleanup action for a site or area of concern

Tools - utilizes records review, in-field evaluation, sampling and laboratory analysis - typically the first and the most common action taken to determine if a site is contaminated - utilizes in- field testing, sampling and laboratory analysis - typically follows the characterization phase if applicable SCGs are exceeded, adverse impacts to fish & wildlife resources, significant health/environmental threat, or contaminants emanate off-site - includes establishment of remedial action objectives and identification/ evaluation of remedial action alternatives - based on the results of the investigation

Remedial Design/Remedial Action

- design and implementation of the selected remedy

- includes preparation of design documents - includes construction/installation of remedial system - includes implementation of institutional controls, where applicable

Operation, Maintenance and Monitoring

- long-term operation, maintenance and monitoring to ensure acceptable remedy effectiveness

- includes site close out when remedial action objectives are met

Table 4. Possible underground location of contaminants

Location Vadose zone

Groundwater

Phases Vapors in the void Free product in the void Dissolved in soil moisture Adsorbed onto the soil matrix Floating on top of the capillary fringe (for nonaqueous phase liquids [NAPLs]) Dissolved in the groundwater Adsorbed onto the aquifer material Sitting on top of the bedrock (for dense nonaqueous phase liquids [DNAPLs])

On the practical side, a risk assessment can lead to cleanup to site-specific standards with less cost and protective standards. It is commonly established that total contaminant concentrations measured by extensive means stand little relevance to actual risks that contaminants possess towards living organisms (Allan et al., 2007; Kelsey et al., 1997; Latawiec and Reid, 2009).

6. Approaches in soil and groundwater cleanup The problems of contaminated site remediation are receiving increasing attention and two types of broad solutions are addressed (Gavrilescu et al., 2009; Pavel and Gavrilescu, 2008). First, there are increasing efforts to investigate sites that need immediate attention and then to reconsider the remediation end points based on sitespecific risk assessments at sites assessed to have low risks. In this situation it is necessary to determine the criteria by which the sites are prioritized, what are less-stringent end points and the possibility to differentiate between risks (Gavrilescu, 2006; NRC, 1997; Robu et al., 2008). This is considered as a risk-based, site-specific approach and is increasingly popular among both government agencies and private companies facing up to budgetary limitations. In a second type of solution being explored, the development and increased use of innovative and emerging remediation technologies are challenges to create a new policy strategy that gathers together appropriate economic and regulatory drivers to encourage innovation in groundwater and soil cleanup and better environmental stewardship.

1297

Gavrilescu/Environmental Engineering and Management Journal 8 (2009), 5, 1293-1307

Fig. 3. Exposure paths of chemical substance (Kawabe et al., 2007

Fig. 4. Technologies for soil and groundwater remediation based on immobilization, extraction and destruction contaminants

The primary goal of remediation technology development under this new paradigm is to continually increase the diversity and number of technologies included on the set of choices of options considered by site owners, regulators, and consultants (Gavrilescu, 2004; Gavrilescu, 2005; Gavrilescu et al., 2009; NRC, 1997). The selection of a remediation technology is based on issues such as the efficiency of the remedy, applicability, capital and operating costs, time constraints. Also, some prerequisites of remedy selection are accounted, such as: protection of the public via interception of contaminants, reduction of sources, and mitigation of exposure pathways (Ellis and Hadley, 2009).

1298

Generally, remediation technologies are classified into four categories based on the process acting on the contaminant (Gavrilescu 2005, Gavrilescu 2009; http://www.on.ec.gc.ca/pollution/ecnpd/tabs/tab22e.html): 1. Removal: a process that physically removes the contaminant or contaminated medium from the site without the need for separation from the host medium. 2. Separation: a process that removes the contaminant from the host medium (soil or water) 3. Destruction: a process that chemically or biologically destroys or neutralizes the contaminant to produce less toxic compounds.

Emerging processes for soil and groundwater cleanup

4. Containment: a process that impedes or immobilizes the surface and subsurface migration of the contaminant. Removal, separation, and destruction are processes that reduce or remove the contaminant. Containment technologies, on the other hand, control the migration of a contaminant to sensitive receptors without reducing or removing the contaminant. These concepts about site remediation strategies and representative technologies associated with them are summarized in Fig. 4 (http://www.on.ec.gc.ca/pollution/ecnpd/tabs/tab22e.html). Remediation approaches encompass applied physical, chemical and biological environmental sciences (Gavrilescu, 2004; Gavrilescu, 2005; Gavrilescu et al., 2009; Scullion, 2006). Customary, both soil and groundwater cleanup is often linked, since for several remediation methods the distinction between soil and groundwater is of limited practical significance. Historically, the conventional approach to soil cleanup has been to incinerate the contaminated soil on site or off site, to solidify it in place with cementing agents, or to excavate it and dispose of it in a hazardous waste landfill. As a result of the limitations of conventional subsurface remediation technologies, which have become increasingly clear, innovative technologies have become more and more common in the cleanup of contaminated soil and of leaking underground storage tanks containing petroleum products, especially during the 1990s (NRC, 1997). From Fig. 5 it results that innovative technologies have been selected for cleaning up contaminated soil, sludge, and sediments at 43 percent of Superfund sites.

7. Treatability and remedial alternatives Treatability analysis is conducted mainly to supply adequate data to allow treatment alternatives to be fully developed and evaluated during the exhaustive analysis phase and to support the remedial design of selected alternatives. Also, they are addressed to possible opportunities for reducing cost and performance doubts for treatment alternatives to acceptable levels so that a remedy can be selected. From the point of view of treatability, NRC (1997) grouped sites into the four categories (Fig. 6) (NRC, 1997): - highly treatable (site-specific testing of innovative remediation technologies should be required only to develop design specifications) - moderately difficult to treat (field pilot testing should be required to identify conditions that may limit the applicability of the technology to the site) - difficult to treat (laboratory and pilot tests will be necessary to prove efficacy and applicability of the technology at a specific site), - extremely difficult to treat (laboratory and pilot tests will be needed, and multiple pilot tests may be necessary to prove that the technology can perform under the full range of site conditions). The purpose of evaluating various technologies is to identify those technologies with the capability to meet specific cleanup and redevelopment objectives. Testing at several sites using consistent protocols and making cost and performance data available for peer review comprise the essential elements of technology development.

Fig. 5. The weight of various technologies applied for soil cleanup (NRC, 1997)

1299

Gavrilescu/Environmental Engineering and Management Journal 8 (2009), 5, 1293-1307

Fig. 6. Treatability of contaminated sites and levels of site-specific testing of remedial alternative as function of contaminant and geological properties (NRC, 1997)

Fig. 7. Summary of soil cleanup methods in relation with contaminant type

In 2008, the USEPA included the concept of sustainable remediation its documents that means the incorporation of best management practices,

1300

including sustainable practices: waste minimization (e.g., use of low-flow sampling techniques and passive groundwater samplers), the management and

Emerging processes for soil and groundwater cleanup

tracking of investigation-derived waste from siteassessment work, the incorporation of practices that rely on recycling and reusing materials to the greatest extent possible, the use of low environmental impact equipment and alternative energy sources, the use of geophysical tools to minimize investigation-derived waste generation and soil disturbance with mechanical drilling rigs (Ellis and Hadley, 2009; USEPA, 2008). The review and analysis of cleanup alternatives relies on the data collected during the site assessment and investigation phases. The development of alternatives requires: - identifying remedial action objectives; - identifying potential treatment, resource recovery, and containment technologies that will satisfy these objectives; - screening the technologies based on their effectiveness, implementability, and cost; - assembling technologies and their associated containment or disposal requirements into alternatives for the contaminated media at the site or for the operable unit. There are a number of different methods currently employed in the process of dealing with soil contamination (Fig. 7). Often, the selection of the most effective strategy will depend on the nature of the contamination, how the method will impact

surrounding wildlife or humans living in the general vicinity, and the degree of success that can be anticipated from the soil remediation effort. Alternatives can be developed to address contaminated medium, a specific area of the site, or the entire site. Relatively effective and wellunderstood technologies are available for easily solved contamination problems—mobile and reactive contaminants in permeable and homogeneous geologic settings. Comparatively more technologies are available for treating contaminated soil than for treating contaminated ground water. Table 5 reproduce some remediation technologies set by UD Department of Energy (DOE, http://www.frtr.gov/matrix2/appd_b/tableB_1.html). When a ground water or soil cleanup technology is developed and applied, frequently in response to an unsolved problem, its acceptance and application are often limited initially to specific contaminants and specific hydrogeologic conditions. 8. Innovative/emerging technologies 8.1. Short presentation There are a number of innovative or emerging technologies which are not well established, most of them being applied at pilot scale only for in-situ treatment, as is presented in Table 6.

Table 5. Site remediation technologies by waste contaminant Technology Arc Melter Vitrification Bio-Immobilization of Heavy Metals

Biological Destruction of Tank Wastes Electrokinetic Remediation of Heavy Metals and Radionuclides

Media

Description

Treatment Technology

Vitrification Uses bacteria to transform heavy metal ions to an insoluble, less toxic form

Solidification/Stabilization Solidification/Stabilization

Toxic metals

Biosorption

Bioreactors

Heavy metals

Electrokinetic Separation

In situ colloid immobilization of contaminants Immobilization

Solidification/Stabilization

Soils

Metals, inorganics Heavy metals absorbed on clay and silica Heavy metals

Electrical current is supplied between two electrodes, ions of contaminant will be attracted to one of the electrodes Encapsulation of wastes

Soil Ground water, surface water, aqueous streams Supernatants, aqueous streams Soil

Waste Contaminant Toxic Metals Toxic metals

Encapsulation of Hazardous Wastes In situ Ground Water Remediation Using Colloid Technology In Situ Vitrification of Contaminated Soils Mitigation Barrier Covers

Liquid, slurry, solid waste Ground water

Arid soils

Soluble metals

Containment/Treatment

Polyethylene Encapsulation of Radionuclides and Heavy Metals

Aqueous salt and concentrate saltcake, sludge, ash, ion exchange resin in tanks

Toxic metals (e.g., Cr, Pb, Cd)

Encapsulation

Solidification/Stabilization

Solidification/Stabilization Passive/Reactive Treatment Walls Solidification/Stabilization

1301

Gavrilescu/Environmental Engineering and Management Journal 8 (2009), 5, 1293-1307

Remediation of Metals Contaminated Soils Using Ligand-Based Extraction Technology

Soil

Dynamic Underground Stripping of VOCs Electrokinetic Remediation of Heavy Metals and Radionuclides

Soil, ground water Soil

In situ Ground Water Remediation Using Colloid Technology In situ Vitrification of Contaminated Soils Plasma Hearth Process

Ground water

Mixed waste

Soil

Mixed waste

Electrical current is supplied between two electrodes, ions of contaminant will be attracted to one of the electrodes In situ colloid immobilization of contaminants Destruction/Immobilization

Soil, stored waste

Mixed Waste

Waste from Enhancement

Solidification/Stabilization

Ground water, surface water Soil Soil Supernatants, aqueous streams Ground water

Single-ring aromatics, BTEX Organics Organics

Adsorption of aromatic compounds

Adsorption/Absorption

Vitrification Biosorption

Solidification/Stabilization Bioreactors

TCE, PCE, Vinyl, Chloride, DCE, TCA and BTEX Nitroaromatic compounds, TNT VOCs, volatile solvents, petroleum fuels VOCs

Uses a bioreactors to biodegrade unwanted chlorinated chemicals

Bioreactors

Bioremediation

Enhanced Bioremediation

Drying of horizontal soil layer to create a barrier

Landfill Cap

Enhanced Removal

Thermal Treatment

CCl4

Micro-organisms biodegrade CCl4 to harmless chemicals

Enhanced Biodegradation

Destruction of VOCs at room temperature

High energy Destruction

Enhanced Removal

Directional Wells, In Well Air Stripping

In situ colloid immobilization of contaminants Destruction/Immobilization

Solidification/Stabilization

Gas is bubbled through contaminated ground water to liberate contaminants

In- Well Air Stripping

Organics Adsorption of BTEX Using Organozeolites Arc Melter Vitrification Biological Destruction of Tank Waste Bioreactors for Bioremediation

Pb, Hg, Cr

Mixed Waste Mixed waste Enhaced Removal Heavy metals and Radionuclides

Bioremediation of High Explosives by Plants

Soil

Dry Barries for Containment and Remediation at Waste Sites

Soil

Dynamic Underground Stripping of VOCs Engineered System for In Situ Bioremediation of Ground Water

Soil, ground water Ground Water

High-Energy Corona

Gas, aqueous and nonaqueous liquids

In Situ Air Stripping of VOCs Using Horizontal Wells

Permeable soils, ground water

In Situ Ground Water Remediation Using Colloid Technology In Situ Vitrification of Contaminated Soils In well Vapor Stripping

Ground water

VOCs, halogenated solvents (e.g., TCE, PCE, carbon, tetrachloride, chloroform, diesel fuel, gasoline) VOCs, light hydrocarbons, chlorinated solvents, TCE, PCE Pesticides

Soil

VOCs

Ground water

VOCs

1302

Density classification followed by extraction to remove metals from soil

Separation, Chemical Extraction

Thermal Treatment Electrokinetic Separation

Solidification/Stabilization Solidification/Stabilization

Solidification/Stabilization

Emerging processes for soil and groundwater cleanup

Methane-Enhanced Bioremediation for the Destruction of TCE Using Horizontal Wells Mitigation Barrier Covers Plasma Hearth Process Six-Phase Soil Heating Thermal Enhanced Vapor Extraction System

Soil, ground water Arid soils Soil, stored waste Soil Arid soils

Tunable Hybrid Plasma

Air

VOC Off- Gas Membrane Separation

Gas stream

VOC Recovery and Recycle

Air

Biological Destruction of Tank Waste

Supernatant aqueous streams Soil, Process waste streams

Chelators for Application In Radioactive Actinide Waste Remediation Compact Processing Units for Radioactive Waste Treatment Cryogenic Retrieval of Buried Waste Electrokinetic Remediation of Heavy Metals and Radionuclides

Liquid, sludges, slurries Soil, buried waste Soil

Halogenated aliphatic organics, TCA, TCE, PCE VOCs, organisc Organisc

Co-metabolic Destruction

Enhanced Biodegradation

Containment/Treatment Waste Form Enhancement

Passive/Reactive Treatment Walls Solidification/Stabilization

VOCs, SVOCs VOCs, SVOCs, VOC-oil mixtures, chemical with vapor pressures