Alternatives for Managing the Nation's Complex Contaminated Groundwater Sites (2013) / Chapter Skim
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4 Current Capabilities to Remove or Contain Contamination
4 Current Capabilities to Remove or Contain Contamination
Pages 113-160
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From page 113... ...
This chapter reviews more recent data and reports on the ability of currently available remedial technologies to meet remedial action objectives for groundwater restoration. It is noted at the outset that poor design, poor application, and/ or improper post-application monitoring at some sites makes evaluation of these technologies challenging, and reported performance results often appear in non-peer-reviewed documents.
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From page 114... ...
, the Committee concluded that regardless of the technology used, the complete removal of contaminant mass at complex sites is unlikely. Furthermore, the Committee discovered no transformational remedial technology or combination of technologies that can overcome the current challenges associated with restoring contaminated groundwater at complex sites.
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From page 115... ...
, which is discussed further in Chapter 6 of this report. Because remedy selection and effectiveness depend, in part, on the contaminant mass distribution among phases and media (e.g., fine-grained media versus more permeable media, vadose zone versus saturated zone, DNAPL versus dissolved contaminants, etc.)
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From page 116... ...
(2009, 2010a,b) highlight the risks of inadequate site characterization: approximately two-thirds of the 14 thermal remediation case studies with sufficient data to evaluate technology performance ended up leaving mass in place because the treatment zone was smaller than the actual contaminant source zone.
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From page 117... ...
The goal of this chapter is to provide brief reviews of the major remedial technologies used in current remediation practice that can be applied to complex hazardous waste sites, particularly those with DNAPL source zones and/or large downgradient dissolved plumes. These reviews discuss our current knowledge regarding performance and limitations of the technologies, identify remaining gaps in knowledge, and provide case studies supporting these assessments.
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From page 118... ...
Relative to other technologies, some in situ thermal treatment technologies (e.g., ERH) applications result in preferential heating and contaminant removal from lower permeability media.
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From page 119... ...
Most relevant to this report are the post-treatment performance data from in situ thermal treatment sites. Interestingly, post-treatment groundwater monitoring data that could be used to evaluate technology performance were available for only 14 of the 182 sites (8 percent)
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From page 120... ...
SOURCE: Triplett Kingston et al.
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From page 121... ...
ISCO, (2) chemical reduction (discussed in the permeable reactive barriers section)
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From page 122... ...
A 1999 ESTCP report summarizing 42 pilot- and full-scale ISCO projects deemed only 19 to be "successful." Another more recent but smaller evaluation of ISCO used at 29 chlorinated solvent sites found that mass was reduced (1) by 55 to 95 percent with a median reduction of 90 percent, and (2)
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From page 123... ...
TABLE 4-4 Chemicals Used in ISCO Applications, Including Advantages and Disadvantages Specific ISCO Principal Oxidant Pathway Advantages Disadvantages Catalyzed Hydrogen Hydroxyl radical (OH•) Fe+2 + H 2O 2 ➞ Fe+3 + Highly non-selective Nonproductive side reactions, Peroxide Propagation OH• + OH– oxidant, no fouling, cost, rapidly consumed, (Fenton's Reaction)
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From page 124... ...
Approximately 80 percent of the applications were successful in reducing contaminant mass; typically, fuel-related contaminants were more amenable to ISCO treatment relative to chlorinated solvents and less expensive to treat. The DNAPL sites were more likely to require treatment beyond ISCO, which increases costs.
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From page 125... ...
The Kings Bay Naval Base was a targeted application using Fenton's reagent designed to achieve considerable source zone treatment so that natural attenuation could be utilized to address any remaining contaminants. Although mostly successful, the presence of iron shifted the redox conditions from sulfate- to iron-reducing, rendering natural attenuation less effective (Chapelle et al., 2005)
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From page 126... ...
reduction, but significant 2009 rebound of PCE in places Edwards Air Force Base activated persulfate LNAPL Decreases in total Siegal et al., 2009 Base, CA (~8000 pounds) and air hydrocarbons, but not sparging BTEX.
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From page 127... ...
Additionally, active ingredient costs and the need to manage large volumes of delivered and extracted fluids render these technologies most suitable for Scenario A source zones of limited size. Two in situ extraction technologies, surfactant flushing and cosolvent flushing, are discussed in the following sections, with emphasis on lessons learned from field-scale applications.
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From page 128... ...
Hill Air Force Base OU2 7.6% Aerosol® MA + TCE, TCE, PCE, CT 363 L Londergan et al., 2001 4.5% isopropanol + (98.5%)
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From page 129... ...
aExcept when DNAPL was released intentionally, percent mass recovery values are based on estimates of the initial mass present at the site. bThe first value is based on pre- and post-treatment soil cores, while the second value is based on pre- and post-treatment partitioning interwell tracer tests (PITTs)
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From page 130... ...
Several field-scale demonstrations of cosolvent flushing have been conducted, most notably at Hill Air Force Base, Dover Air Force Base, and the former Sages dry cleaner site in Jacksonville, FL (Table 4-8)
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From page 131... ...
Finally, cosolvents are highly flammable liquids and require special safety procedures, both during mixing and injection as well as during treatment or disposal of the effluent waste stream. Some of the problems associated with cosolvent flushing are illustrated by additional work that was performed at the former Sages dry cleaner site.
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From page 132... ...
Sages Dry Cleaner, 95% Ethanol PCE 30 L Jawitz et al., 2000 Jacksonville, FL (63%) Hill Air Force Base OU1 80% t-Butanol + Jet fuel, chlorinated solvents 99 mg/kga Falta et al., 1999 15% Hexanol (80%)
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From page 133... ...
However, despite long-standing concerns regarding cost and performance with regards to contaminant mass removal, P&T remains one of the most widely applied groundwater remediation technologies, appearing in 20 to 30 percent of CERCLA groundwater decision documents, approximately the same proportion as in situ technologies (EPA, 2010b)
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From page 134... ...
. In the Treatment Technologies for Site Cleanup: Annual Status Report (Twelfth Edition)
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From page 135... ...
When designed, installed, and monitored properly, physical containment can be an effective technique for preventing contaminant migration. Contaminant mass is not reduced, but containment can be combined with treatment technologies as long as the treatment applied does not lead to physical damage of the containment barrier or alter it in a chemically adverse way.
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From page 136... ...
for optimal bacterial growth. In contrast to natural attenuation, enhanced bioremediation typically involves biostimulation and/or bioaugmentation.
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From page 137... ...
contaminant concentrations. Laboratory studies conducted in the early 1990s indicated that biodegradation could occur in source zones contaminated with chlorinated solvents, and this bioactivity was able to enhance the rate of PCE dissolution from highly concentrated NAPL pools (Seagren et al., 1993, 1994)
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From page 138... ...
. Recent surveys of source zone remediation technologies reveal that ISB has been used at approximately 25 percent of the sites considered and is one of the most commonly applied in situ treatment methods along with thermal treatment and in situ chemical oxidation (NAVFAC, 2004; ESTCP, 2011)
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From page 139... ...
Tarheel Army Missile Plan Emulsified Oil Substrate TCE, From 1 mg/L to < 5 μg/La ITRC, 2007 petroleum hydrocarbons Dry Cleaner Site, Portland, Hydrogen Release PCE, TCE, cis-DCE From 7,000 μg/L to 50 μg/L ITRC, 2007 OR Compound (PCE) after 1 yrb Cape Canaveral Launch Ethanol, KB-1® TCE From 155 mg/L to 0.2 mg/Lc Hood et al., 2008 Complex 34 (LC 34)
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From page 140... ...
PERMEABLE REACTIVE BARRIERS Permeable reactive barriers (PRBs) are highly permeable zones comprised of material that is either abiotically reactive or that encourages the development of biological reactivity.
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CURRENT CAPABILITIES TO REMOVE OR CONTAIN CONTAMINATION 141 for a 20-year lifespan (Chamberlain et al., 2011) , although future source removal activity could extend the life of the wall.
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From page 142... ...
142 TABLE 4-10 Summary of PRBs for Treatment of Contaminated Groundwater (1994–2004) Type of Site Barrier Media Superfund Industrial U.S.
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. With chlorinated solvents, it must be verified that reaction products that are of similar or greater toxicity than the parent compound are not produced.
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From page 144... ...
. The total length of the contaminated groundwater plume is approximately 5.5 miles.
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From page 145... ...
This was the first site to show that abiotic degradation could be an important component of monitored natural attenuation for chlorinated ethenes like TCE or DCE (which was unexpected at this site)
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From page 146... ...
documented that public opinion of MNA is decidedly wary, with many communities considering it a "do nothing approach." COMBINED REMEDIES It is now widely recognized that even successful application of remedial technologies will not completely remove all of the contaminant mass from most DNAPL source zones. In fact, aggressive source zone treatments are likely to increase the mobility and distribution of the residual mass or stable pools, which may lead to increased aqueous phase concentrations in the short term.
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From page 147... ...
In some cases, it is appropriate to develop a combined remedy at the initiation of a remedial action (e.g., surfactant-enhanced in situ chemical oxidation or thermal treatment followed by bioremediation)
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From page 148... ...
FIGURE 4-3 (A) Plan view diagram of the Bachman Road site source zone and downgradient PCE-contaminated groundwater plume.
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From page 149... ...
CURRENT CAPABILITIES TO REMOVE OR CONTAIN CONTAMINATION 149 A A A 100 100 90 Natural 90 Natural Gradient 80 % Mass Remaining 80 70 Gradient % Mass Remaining BioremediaƟon 70 60 BioremediaƟon 60 50 50 40 SEAR + Bio 40 30 SEAR + Bio 30 20 20 10 B 0 10 0.001 0.01 0.1 1 10 100 1000 10000 100000 B 0 Time (d)
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From page 150... ...
There is a clear need for publicly accessible databases that could be used to compare the performance of remedial technologies at complex sites (performance data could be concentration reduction, mass discharge reduction, cost, time to attain drinking water standards, etc.)
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From page 151... ...
. For complete descriptions of contaminant source remediation technologies, see NRC (2005)
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From page 152... ...
Research is needed on how to better combine existing or new remediation technologies to address complex contaminated sites. There is the potential at most complex sites to combine multiple technologies in space and time to cost-effectively remove/treat contamination in both the source zone and the downgradient dissolved plume.
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From page 153... ...
2005. In situ thermal remediation of DNAPL and LNAPL using electrical resistance heating.
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From page 154... ...
2005. Cou pling aggressive mass removal with microbial reductive dechlorination for remediation of DNAPL source zones: A review and assessment.
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From page 155... ...
2011. In Situ Chemical Oxidation for Groundwater Remediation -- Technology Prac tices Manual ESTCP Project ER-200623.
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From page 156... ...
2009. State-of-the Practice Overview: Critical Evaluation of State-of-the-Art In Situ Thermal Treatment Technologies for DNAPL Source Zone Treatment.
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From page 157... ...
2009. Monitored natural attenuation of manufactured gas plant tar mono- and polycyclic aro matic hydrocarbons in ground water: A 14-year field study.
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From page 158... ...
2011. In Situ Chemical Oxidation for Remedia tion of Contaminated Groundwater.
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From page 159... ...
2010b. Criti cal Evaluation of State-of-the-Art In Situ Thermal Treatment Technologies for DNAPL Source Zone Treatment.
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From page 160... ...
Environmental Science & Technology 33(1)
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