Environmental Cleanup at Navy Facilities Adaptive Site Management (2003) / Chapter Skim
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5. Technology Overview
5. Technology Overview
Pages 198-293
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From page 198... ...
, for example, for initial remedy selection, as replacements for existing remedies that have proved to be unsuccessful, or as additions to current remedies to better achieve cleanup goals or reduce cleanup time. Because the Navy defined sediment contamination and solvents and metals in soil and groundwater as its most pressing current problems, the focus is on these types of contamination and on applicable remedial technologies, including the concept of treatment trains designed to meet multiple goals for multiple contaminants.
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From page 199... ...
Monitored Natural Incineration (onsite) Attenuation Permeable Reactive Landfill Disposal Barrier Mechanical Dredging Phytoremediation Surfactants/Surfactant Recovery(e.g., EM, Physical Separation Flushing in situ RF, ISTD)
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From page 200... ...
Generally, no single technology can remediate an entire site, and the use of treatment trains, sometimes combining in situ and ex situ techniques, is common, as discussed subsequently. The main advantage of in situ treatment is that it allows remediation
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From page 201... ...
. The preferred remediation may involve a treatment train approach (e.g., air sparging/soil vapor extraction, liquid-phase carbon adsorption, and catalytic oxidation for nonhalogenated VOCs, or groundwater pumping, activated carbon adsorption with adsorbate reinfection, and offsite disposal of spent activated carbon for halogenated VOCs)
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From page 202... ...
......................................................................................................... Air sparging Bioremediation Bioslurping Circulating wells Cosolvents and surfactants Dual-phase extraction Dynamic underground stripping Chemical oxidation/reduction Natural attenuation Permeable reactive barriers Phytoremediation Pump-and-treat Steam flushing Vertical barrier walls .
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203 | Maturityd | | g | h | a | b | c | Relevant References ''''''''''''''1''''''''''''''1''''''''''''''1''''''''''''''1'''''' '''''' X X X=—X =—X = XX _===—X MEE, 1995, 1997; FRTR, 1998 EPA, 1994; Evanko and Dzombak, 1997; NRC, 1997b, 1999a; EPRI, 1999; McLellan and Hopman, 2000 NRC, 1997a; EPA, 1998a Fountain, 1998; FRTR, 1998 Schnoor, 1998; Fiorenze et al., 2000 NRC, 1999a MEE, 1997; FRTR, 1998; NRC, 1999a MEE, 1997; Evanko and Dzombak, 1997; NRC, 1999a ..............................................................................
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From page 204... ...
The most common reservoirs for metals are soil and sediment, and the most common treatment technologies include solidification/stabilization, excavation and offsite disposal, and extraction. Depending upon solubility and mobilization potential, metals may also exist in groundwater, and are most frequently treated by ex sits precipitation, filtration, and ion exchange, although in sits treatment by oxidation/reduction and vitrification has occurred.
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From page 205... ...
Table 5-3 summarizes examples of experiential optimization for a variety of remedial systems, including soil vapor extraction, air sparging, bioventing, bioslurping, in situ chemical oxidation, reactive permeable barriers, light nonaqueous phase liquid (LNAPL) free product recovery, dense nonaqueous phase liquid (DNAPL)
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From page 206... ...
to predict groundwater flow paths and hydraulic head distributions at a field site in response to imposed injection or withdrawal stresses, given that site Ethology is adequately characterized in terms of spatially varying soil and rock permeabilities. This allows the user to answer questions regarding the number of wells to install and the effects of well placement and pumping rates on the movement of water through the saturated zone.
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208 C' Icy)
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210 o ._ ._ ._ o ._ o C' Icy)
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212 C' by)
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214 C' Icy)
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A case study of mathematical optimization is presented in Box 5-1. EPA notes that hydraulic modeling does not address mass removal or desired contaminant concentrations.
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From page 217... ...
is quantified. The practice of quantifying uncertainty in subsurface flow and transport modeling is virtually ignored in the literature on coupling flow and transport models with optimization algorithms for improving well placement/pumping rates.
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218 Environmental Cleanup at Navy Facilities: Adaptive Site Management .
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Technology Overview 219 ·:::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::: ·::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::: ·::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::: ·::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::: ·::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::: ·::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::: ·::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::: ·::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::: ·::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::: ·::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::: · ::::::::::::::::::::::::: ·::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::: ·::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::: ·::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::: ·::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::: ·::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::: ·::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::: ·::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::: ·::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::: ·::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::: ·::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::: · :::::::::::::::::::: :: : :: : :::::::: ~ :: :::: ~ : : : :::: : . pumper 1 Be ~ ~SeCa ~ B~C 9~1$ OS ~ ..
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220 Environmental Cleanup at Navy Facilities: Adaptive Site Management .
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From page 222... ...
Cost issues are not discussed in subsequent sections, primarily because complementary cost data for remediation technologies are not readily available for every type of application. However, a recent cost compendium has been prepared to include current information about the costs of bioremediation, thermal desorption, soil vapor extraction (SVE)
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From page 223... ...
Three of the innovative technologies discussed below (in situ chemical oxidation, thermal treatment, and enhanced bioremediation) are broadly classified as source remova1/t technologies because their goal is to reduce substantially the source term (be it solidbound, free-phase or dissolved contamination)
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From page 224... ...
such as trichloroethylene (ICE) and on petroleum hydrocarbons.
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From page 225... ...
Finally, in some cases, vapor extraction is used in conjunction with oxidation in the vadose zone to relieve off-gas pressure, to encourage oxidant migration, and/or to capture any volatile emissions (ESTCP, 1999~. Despite these measures, it should be noted that in sits oxidation reagents, particularly Fenton's Reagent and ozone, are relatively short-lived compared to the rate of groundwater flow in most aquifers, such that oxidant contact with and treatment of contaminants is not significantly mediated
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From page 226... ...
The release of halogenated ions, such as chloride or bromide, from target contaminants is a useful line of evidence if original contaminant concentrations are high enough to result in a significant increase in halogen ion concentrations as a result of contaminant destruction. All injection trials should include one or more control wells where water and tracer are injected into a contaminated zone in order to differentiate dissolved contaminant displacement or dilution from destruction.
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From page 227... ...
Thus, performance monitoring should be conducted in unique lower-permeability and/or high organic carbon layers. Likewise, monitoring for contaminant concentration rebound can guide the design of any subsequent remediation strategies by defining the remaining contaminant reservoir that was not treated by ISO.
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From page 228... ...
Five of the 42 were Navy sites. The results of the Phase I survey were then used to select several
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From page 229... ...
Various key factors have been identified and relate to site characterization needs and design and operational issues. The success of ISO is dependent upon effective contact and mixing with target contaminants, compatible subsurface geochemistry, and the maintenance of sufficient oxidation capacity to overcome oxidant losses from nonspecific oxidation reactions (e.g., reactions with the aquifer matrix and spontaneous oxidant decomposition)
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From page 230... ...
First, there must be better delineation of the contaminant's location and extent and of its sorption potential, particularly for DNAPL accumulations. The degree of soil layering versus the distribution of contaminants is an important parameter to understand because the distribution of oxidants will be limited to more permeable soil horizons unless injection/distribution approaches are tightly controlled.
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From page 231... ...
. Thermal Treatment There are three general methods that can be used to inject or apply heat to the subsurface to enhance remediation: injection of hot gases such as steam or air, hot water injection, and electrical resistance heating (Davis, 1997, 1998~.
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From page 232... ...
The contaminants are driven out of the source zone by a combination of volatilization and thermally induced vaporphase transport. Hence, electrical heating is usually coupled with soil vapor extraction (SVE)
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From page 234... ...
The soil vapor capture system must be capable of overcoming condensate formation in situ and in above-ground equipment; it must be capable of fully capturing the "flash" volatilization of heated nonaqueous phase liquid; and, where applicable, it must be designed to effectively capture contaminants mobilized in the saturated zone. Groundwater extraction systems are often used in concert with soil vapor extraction systems at sites where contaminants are present in or adjacent to the saturated zone.
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From page 235... ...
Technology Evaluation. Of the thermal treatment options, steam injection, electrical resistance heating, 3- or 6-phase heating, and microwave and RF heating have been applied for in sits remediation of subsurface contamination.
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From page 236... ...
Thus, the soil vapor extraction network must be designed such that paths of vapor movement are made available even if condensate is formed in site and air permeability is reduced in certain zones. Unlike soil vapor capture efficiency, which can be negatively impacted by high water content, the performance of electrical resistance heating technologies can be negatively impacted by low water content.
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From page 237... ...
Although improvements in nonreactive barrier walls are being made, they are generally not considered innovative technology. Reactive barrier walls have been called passive reactive barriers or, more recently, permeab1/te reactive barriers (PRB9.
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From page 238... ...
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From page 239... ...
Performance of PRBs is typically assessed by measuring contaminant concentration (and potential products) upgradient and downgradient of the barrier.
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From page 240... ...
PRBs are typically designed for a 20- to 30-year life. As with most remediation technologies, a best-case scenario for process monitoring would be to complete mass and water balances.
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From page 241... ...
Chlorinated solvents, primarily the chlorinated ethenes PCE, TCE, cis-DCE, and VC, and 1,1,1-TCA, are being treated using Fe(O) -PRB at 12 of these installations.
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From page 242... ...
242 Environmental Cleanup at Navy Facilities: Adaptive Site Management ::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::: .............................................................................................................................
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From page 243... ...
Technology Overview 243 were addressed in a recent report summarizing PRB performance at DoD sites, particularly Moffett Field (Box 5-7~. In summary, PRBs offer three potentially significant advantages: (1)
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From page 244... ...
. Enhanced Bioremediation Several terms are currently used to describe the use of biological processes to remediate contaminated sites in situ.
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From page 245... ...
Enhanced bioremediation has been reported to remove contaminants aerobically both as a primary substrate for example, addition of oxygen and nutrients for degradation of petroleum hydrocarbons (Brown et al., : i: ........................
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From page 246... ...
treatment and enhanced aerobic cometabolism of chlorinated aliphatic hydrocarbons to be an "emerging" technology, which is in agreement with recent NRC reports (NRC, 1993, 2000~. There is considerable current interest in adding electron donors to stimulate reductive dechlorination of chlorinated aliphatic hydrocarbons, primarily the chlorinated ethenes.
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From page 247... ...
It should also be noted that recent evidence indicates that source zones or near-source zones may be treated with enhanced anaerobic bioremediation (Carr et al., 2000; Yang and McCarty, 2000b)
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From page 248... ...
, residual NAPE is absent or has been removed, contaminants are not overly hydrophobic, and contamination is not too deep. At the present time, enhanced bioremediation has been shown to work best with petroleum hydrocarbons primarily benzene, toluene, ethy~benzene, and xylene (BTEX)
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From page 249... ...
Technologies for Remediation of Inorganics in Soil and Groundwater The most frequently occurring metal contaminants at Navy sites are lead, zinc, copper, nickel, barium, cadmium, vanadium, aluminum, and beryllium. These heavy metals and other inorganic contaminants (e.g., arsenic, cyanides, perchiorate, and radionuclides)
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From page 250... ...
. The form, or speciation, of inorganic contaminants depends on the source of the waste and the geochemistry of the subsurface at the site.
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From page 251... ...
Examples are chemical treatment, permeable reactive barriers, biological treatment, and phytoremediation.
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From page 252... ...
The metal is removed from the rest of the soil or groundwater by ex situ or in situ techniques such as soil washing, soil flushing, and electrokinetic treatment. Measuring Performance As in all remediation technologies, documenting the success of technologies for control of inorganic contaminants requires evidence that the technology reduces risk by decreasing the mass, concentration, mobility, and/or toxicity of the contaminants and requires identification of the operative mechanisms.
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From page 253... ...
. Although newer in site treatment technologies may soon replace excavation, there are nonetheless recent advances that have improved excavation and all ex site remedies that depend on it mainly by focusing exclusively on soils (or sediments)
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From page 254... ...
The technologies employed include phytoremediation, soil washing, ex site extraction, electrokinetics, solidification and stabilization, and ex site physical separation/chemical treatment. A review of containment technologies, biological treatment technologies, and physical/chemical treatment technologies approved for use by the Navy (from http://erb.nfesc.navy.mil/restoration)
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From page 255... ...
Phytoremediation. Phytoremediation employs metal-accumulating plants to either remove inorganic contaminants from the shallow subsurface or to withdraw soil moisture through evapotranspiration, which can provide hydraulic containment of contaminants (EPA, l999e; Lasat, 2002~.
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From page 256... ...
Two years after treatment was complete, the treatment zone remained anoxic and Cr(VI) remained below detection limits.
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From page 257... ...
Contaminated sediments have resulted from handling and disposal of fuels, bilge water, antifoulants, and other compounds, and from handling of wastewater on shoreline facilities. As discussed in Chapter 1, as many as 110 Navy facilities have identified sediment contamination, with most cleanup efforts still in the RI/FS stage.
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From page 258... ...
control of environmental releases contributing to sediment contamination, · socioeconomic options including reduction of exposure through fish advisories, institution of catch and release fisheries, relocation of exposed communities, and the introduction of economic or other acceptable offsets~, · natural attenuation including intrinsic biodegradation and natural capping by deposition of clean sediment, other in site management via containment or treatment, including capping, and removal and ex site management, which requires application of dredging technologies, pretreatment technologies, ex situ treatment and disposal technologies, and technologies for the management of residual contaminants, including contaminated gaseous and liquid effluents or the residual contaminants in the treated dredged material. Control of the environmental releases leading to sediment contaminat~on is a critical first step in managing contaminated sediments.
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From page 259... ...
In contaminated sediments, contaminants are often relatively immobile and refractory, and the most important natural attenuation process is often the stable burial of contaminants by sedimentation or deposition of clean sediments. Although the concentration or mass of the contaminant may be unchanged, significant reduction in exposure and risk may occur via this process.
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From page 261... ...
A strongly sorbing cap, however, will release essentially no contaminant for a long time but will ultimately accumulate contaminants in the upper layers of the cap, although typically at concentrations much below those originally found in the contaminated sediments. Thin layer (5 to 15 cm)
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From page 262... ...
Box 5-10 illustrates the use of a CAD cell for managing contaminated sediments. Because capping does not normally encourage degradation or transformation of the contaminants, long-term monitoring to ensure cap stability and contaminant containment would normally be required.
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From page 263... ...
Remova1/t Techno1/togies Dredging Options that involve removal of contaminated sediments from a waterbody are significantly more complicated than in situ approaches because of the train of treatment that is triggered. Removal options generally require a pretreatment step for dewatering of the dredged materials, treatment or disposal of the removed materials, and treatment and disposal of any residuals left in the waterway or produced during treatment or disposal.
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From page 264... ...
Debris, bedrock, and large areas of diffuse contamination all work to make dredging less effective as a sediment management option. Even when dredging may be the preferred option, resuspension of contaminated sediments, residual contamination, and dredged material pretreatment, treatment, or disposal requirements may limit the feasibility of the approach, as discussed below.
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From page 265... ...
Pretreatment and Water Treatment. Dredged material requires subsequent treatment or disposal, the first step of which is pretreatment to remove and treat excess water and reduce volume (except in the case of CAD)
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From page 266... ...
It may be possible to build centralized facilities capable of processing the contaminated dredged materials from multiple sites, although significant public acceptance and regulatory barriers would need to be overcome. A second consideration is that treatment technologies require development of a market for the effluents from their processes and regulatory standards that define the acceptability of these effluents for certain uses.
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From page 267... ...
A relative comparison of the potential risks, including the risk of no remedial efforts, can be effective in identifying absolute risks. A convenient comparison for any active remedial approach is the effectiveness or potential risks of the approach relative to those expected with natural attenuation processes.
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From page 268... ...
In wastewater treatment, particle removal, biodegradation, and disinfection are often coupled to meet effluent standards. Another factor contributing to the need for treatment trains is that each waste site is unique.
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From page 269... ...
The above examples of treatment trains pertain to contaminated soils and groundwater, but the concept is equally applicable to contaminated sediments, especially when the remedial options involve removal of contaminated sediments from a waterbody. Removal options involve not only dredging, but other technologies as well to manage the dredged material, the water produced, and any residuals left in the waterway.
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From page 270... ...
270 Environmental Cleanup at Navy Facilities: Adaptive Site Management ............................................................................................................................
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From page 272... ...
Treatment Trains and Source Removal A feature of contaminated sites that necessitates the use of treatment trains is that conceptually, a waste site consists of two distinct components. The first component is a contaminant source area where the bulk of the contaminant mass is usually located.
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From page 273... ...
A reduction in contaminant mass from a source zone is expected to provide several benefits including a decrease in cleanup time, a possible reduction in risk, a decrease in the extent of contaminated groundwater, and improvement in the performance of natural attenuation processes (Sale and McWhorter, 2001~. However, there is no consensus among the technical community on the benefits derived from partial contaminant mass removal from source zones.
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From page 274... ...
274 Environmental Cleanup at Navy Facilities: Adaptive Site Management :::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::: :::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::: :::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::: :::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::: :::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::: :::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::: ............................................................
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From page 275... ...
Technology Overview 275 ..
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From page 276... ...
Enhanced bioremediation can be used in conjunction with surfactant flushing, with a variety of oxidation processes, and with low-temperature physical processes such as soil vapor extraction. Because the properties of inorganic contaminants differ markedly from organic contaminants, remediation technologies for inorganics are potentially compatible with a variety of other remediation techniques.
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From page 277... ...
A second possible negative impact is that source removal could remove a contaminant that is used to enhance the biodegradation of another contaminant. An example is the inadvertent removal of petroleum hydrocarbons, phenols, alcohols, or ketones that are serving as primary substrates for microbes involved in the intended biodegradation of chlorinated solvents in the downgradient groundwater plume, which could slow down or completely stop natural attenuation of the chIorinated solvents.
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From page 278... ...
However, source treatment can interfere with the present or future performance of natural attenuation, principally through disruption of environmental conditions required for the biodegradation reactions (e.g., availability of electron donors and acceptors) and destruction of the microbes (e.g., sterilization via chemical oxidation and thermal treatment)
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From page 279... ...
Optimization can be as simple as ensuring that system components are still appropriate and are operating at design efficiency. Formal mathematical optimization can be used to evaluate well configuration and pumping rates in pump-and-treat or soil vapor extraction systems for potential cost savings.
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From page 280... ...
Thus, the application of thermal treatment technologies should be approached in a site-specific fashion, with a primary focus on site characterization and the design of effective vapor capture and dewatering strategies, particularly for sites where contaminants could exist in the saturated zone. Permeable reactive barriers can effectively treat a limited number of groundwater pollutants under well-defined hydrogeologic conditions.
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From page 281... ...
derived from partial contaminant mass removal from source zones and the compatibility of such treatment with natural attenuation. This analysis will also help PRPs determine if enough of the source mass can be removed to warrant the expense of implementing the technology.
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From page 282... ...
Providing an impermeable barrier to surface water inf~tration into contaminated soil to reduce further contaminant release and transport, or controlled placement of a clean, isolating material cover over contaminated sediments without relocating or causing major disruption to the original bed. Chemical Oxidation/Reduction.
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From page 283... ...
Combination of steam injection and electrical heating for vacuum extraction of nonaqueous phase liquid contaminants from the subsurface. Electrokinetics.
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From page 284... ...
In site soil treatment of contaminants using chemical amendments and fluid pumping to mobilize and recover contaminants. Soil vapor extraction.
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From page 285... ...
1997. Design guidance for application of permeable reactive barriers to remediate dissolved chlorinated solvents.
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From page 286... ...
1998. Technical guidelines for evaluating monitored natural attenuation of petroleum hydrocarbons and chlorinated solvents in groundwater at Naval and Marine Corps facilities.
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From page 287... ...
l999c. Field applications of in site remediation technologies: permeable reactive barriers.
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From page 288... ...
6 Soil vapor extraction and other in situ technologies, 1997, EPA-542R-97-009 Vol. 7 Ex situ soil treatment technologies (bioremediation, solvent extraction, thermal desorption)
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From page 289... ...
2000. Design guidance for application of permeable reactive barriers for groundwater remediation.
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From page 290... ...
GWRTAC Technology Evaluation Report TE-96-02. Pittsburgh, PA: GWRTAC.
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From page 291... ...
1996. Estimating contaminant losses from components of remediation alternatives for contaminated sediments.
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From page 292... ...
2002. The role of modeling in managing contaminated sediments.
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From page 293... ...
2001. Remediation technology evaluation report: permeable reactive barriers: long-term performance (draft report)
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Key Terms
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