ater characterization and re
Technology
News & Trends
EPA 542-N-13-001 | Issue No. 63, February 2013
This issue of Technology News & Trends highlights the use of nanotechnologies to chemically reduce
chlorinated volatile organic compounds (CVOCs), metals and metalloids such as chromium and arsenic,
and persistent organic cpmpounds contaminating groundwater, soil, or sediment. Nanoscale materials
typically used for remediation involve nanoscale zero-valent iron (ZVI), bimetallic nanoscale particles, or
emulsified zero-valent iron (EZVI). The U.S. Environmental Protection Agency's National Risk
Management Research Laboratory and other agencies or organizations are researching remediation
efficacy as well as fate, transport, and toxicity of these and other nanoscale materials with potential to
adsorb or destroy contaminants as part of in situ or ex situ processes.
Long-Term Results: Chlorinated Solvent Treatment Using EZVI Injection
with Supplemental Bioremediation and Bioaugmentation
Contributed by Regina Dixon Butler. Patrick Air Force Base; John Armstrong. Florida Department of
Environmental Protection; Deda Johansen. Jacobs Engineering Group
Remediation of contaminated groundwater at Patrick Air Force Base's OT030 site combined the
application of emulsified zero-valent iron (EZVI) with enhanced biodegradation. The impacted area
encompasses several facilities where past cleaning and maintenance operations released chlorinated
solvents to groundwater, creating an approximate 36-acre contaminant plume. Investigations indicated a
primary source area covering 0.12 acres where trichloroethene (TCE) exceeded 100 milligrams per liter
(mg/L). Fate and transport modeling predicted that natural degradation would take more than 240 years.
EZVI injection combined with emulsified vegetable oil (EVO) application and bipaugmentation were
selected to accelerate this process. Cleanup goals for the corrective measures included reducing total
plume mass 50% within 25 years, 75% within 40 years, and 100% (achieving state groundwater cleanup
target levels [GCTLs]) within 80 years.
Site soil consists of fine- to medium-grained sand with silt and shell fragments to a depth of
approximately 48 feet below ground surface (bgs). Chlorinated volatile organic compound (CVOC)
contamination is limited to this upper layer of the surficial aquifer due to an underlying clay layer
approximately 20 feet thick. The CVOC plume extends downgradient and nearly reaches the Banana
River Lagoon (BRL), an Outstanding Florida Water. Factors influencing selection of a suitable remediation
technology included proximity to the BRL; the presence of dormitories, offices, and mission-critical
operations; and numerous underground utilities (Figure 1).
Technology News & Trends
February 2013 Issue
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EPA 542-N-13-001 | Issue No. 63
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MAP FEATURES
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Figure 1. CVOC source area and plume at OT030 as of 2012.
Design for full-scale EZVI application at OT030 was based on results of a National Aeronautics and Space
Administration field demonstration at Cape Canaveral Air Force Station, Florida. [For more information
about the demonstration, see the September 2005 issue of Technology News and Trends'!. EZVI relies on
the use of nanoscale or microscale grains of iron mixed in vegetable oil to create an emulsion that
promotes contact between the iron and the chlorinated solvent and brings about direct dechlorination.
The vegetable oil component also acts as a substrate for microbial growth, providing additional long-term
treatment by enhancing reductive dechlorination via native or augmented communities of bacteria.
Figure 2. Pneumatic and product hoses
attached to a 360°-rotatable injection nozzle on
a direct push rig.
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February 2013 Issue
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Groundwater treatment involved multiple injections between 2005 and 2008. Aggressive source reduction
was the initial objective, with EZVI as the primary treatment agent. The emulsion was injected
pneumatically to create a fluidized subsurface lens and S-fopt radius of influence (ROI) (Figure 2). A
proprietary mixture of nanoscale and microscale ZVI, including ZVI measuring 0.2 um, 1.5 um, and 3.0
um, was used to benefit from the greater surface area provided by nanoscale ZVI and the lower cost and
easier availability of microscale ZVI.
Over five months in 2005, a total of 60,100 gallons of EZVI was injected sequentially at 36 points with a
target depth interval of 26-42 feet bgs. To create a zone of enhanced biological reduction, 9,350 gallons
of EVO (as a substrate for microbial growth) were injected in six points on the downgradient side. A
microbial consortium (KB-1™) also was added.
The highest TCE concentration in groundwater decreased 98% (from 350 mg/L to 4.5 mg/L) within one
year after EZVI injection completion. As anticipated, TCE breakdown products c/s-l,2-dichloroethene
(DCE) and vinyl chloride (VC) increased. Concentrations of the three contaminants continued to exceed
the Florida GCTLs of 3, 70, and 1 ug/L, respectively.
In light of the substantial degradation of TCE by EZVI, further use of EVO and bioaugmentation offered
cost-effective treatment for a plume now consisting mainly of breakdown products. A follow-up injection
of 82,876 gallons of EVO was conducted in July 2007 to replenish substrate in the previously treated area
and expand the area of enhanced reductive dechlorination. The 53 injection points also received 402
liters of the microbial consortium. EVO quantities were adjusted based on contaminant concentrations,
varying from 4 to 8% pore space saturation. Conventional drilling equipment was employed during this
injection since recent lessons learned at other local sites demonstrated a sufficient ROI without more
costly pneumatic fracturing. Associated savings allowed a third treatment event. In 2008,
semi-permanent injection ports were installed along the downgradient axis of the source area and
12,000 gallons of EVO mixture were introduced to maintain bioremediation activity.
Sixteen post-injection sampling events occurred between February 2006 and May 2012 at selected wells
throughout the plume. Initial monitoring was robust and focused on the treated areas. More detailed
five-year monitoring data were collected at 39 monitoring wells and 35 ports from 13 multi-chamber
wells to ensure the conceptual site model remains accurate.
Location
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mean ORP of -226 mV, mean pH of 7.05, and dissolved oxygen concentration of 0.44 mg/L.
Evaluation of other geochemical indicators also suggests that biodegradation is occurring. Favorable
trends include increasing dissolved methane (from an average of 113.4 ug/L prior to injections to 2,783
ug/L in October 2011), decreasing sulfate (from 985 mg/L to 551 mg/L), increasing sulfide (from 0.685
mg/L to 31 mg/L), decreasing nitrate (from 0.424 ug/L to 0.07 ug/L), increasing nitrite (from 0.15 ug/L
to 1.03 ug/L), increasing carbon dioxide (84.2 ug/L to 800 ug/L), and increasing alkalinity (from 470
ug/L to 792 jjg/L). In addition, Dehalococcoides screening indicates increasing counts of the gene
capable of dechlorinating VC (VC reductase). October 2011 data across 12 wells yielded an average gene
count of 34,222,182 celfs/L, consistent with the 10' value typically considered effective.
MODFLOW-2000 and RT3D software were used to update the fate and transport model, which now
predicts that GCTLs will be attained in 2080. Continued semi-annual sampling is planned at selected
monitoring wells indefinitely to monit9r natural attenuation and evaluate the need for additional
§roundwater treatment due to potential cis-DCE degradation "stall." In November 2012, an additional
VO injection was completed to provide continued substrate for biodegradation in and immediately
downgradient from the previous treatment area, wherec/s-DCE concentrations continue to exceed 7,000
ug/L.
Costs for treatment and annual monitoring from 2004 (baseline sampling) to the October 2012
monitoring event total approximately $6.5 millipn. Lessons at OT030 paved the way for treatment at
several other sites. Most recently, an EZVI application at Cape Canaveral Air Force StationT
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The first step of PCB treatment is its desorption from the sediment matrix to aqueous-phase. GAG can
facilitate desorption of RGBs in a stable sediment matrix but will not degrade contaminants. Nanoscale
bimetallic systems can be effective in dechlorinating contaminants but depend on the passive contact of
the materials with RGBs. By synergistically combining the two remediation technologies, RAG (Figure 1)
takes advantage of the high adsorptive capacity of GAG and actively attracts hydrophobic RGBs present
in the sediment matrix, while the Fe/Pd facilitates the physical reductive dechlorination reaction.
To synthesize RAG (Figure 2), mesoporous GAG is introduced as support material for Fe particles to
disperse and as an adsprptive material for RGBs to contact with Fe particles. The Fe surface is then
modified with a discontinuous layer of n9ble catalytic metal Pd to facilitate electron generation for PCB
dechlorination. Specifically, the process involves melting relevant iron salt at 55-60°C, mixing with GAG,
drying at 60-70°C and calcining at 300T
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0 10 20 30 40 50
Reaction Time (hrs)
Figure 3. Adsorption of2-CIBP with GAC (a) and RAC (b)
0 10 20 30 40 50
Reaction Time (hrs)
' at different loading rates.
Results from the laboratory study suggested that RAC pellets could potentially be used between thin
geotextile membranes of sediment capping material, which would act as a barrier between contaminated
sediment and water limiting contact between organic matter in the water column and PCBs, which have
high affinity for organic substances. NRMRL is conducting additional bench-scale studies to examine the
effects of reaction environments relevant in natural systems, such as initial concentration, pH, and
co-existing natural organic matter and ionic species, on the implementation of RAC. The full-cycle
transport, reaction, and fate of PCBs in sediment are also being examined to determine the role of
organic carbon and aging.
RAC can be directly mixed with the contaminated sediment matrix for prompt sequestration of PCBs. A
RAC cap can be installed horizontally to contain PCB-contaminated sites, while a RAC barrier can be
installed vertically for flow-through treatment of contaminated groundwater. A field-scale application that
uses a reactive cap and barrier composed of RAC is currently being tested at various locations in the
Sydney Harbour to clean up PCB-contaminated sediment, and at Botany Bay in New South Wales to
prevent migration of chlorinated hydrocarbons from a nearby industrial park.
In addition, joint work between University of Texas at Austin and the N.D. Zelinsky Institute of Organic
Chemistry, Russian Federation, is being performed to examine reductive dechlorination of trichloroethene
(TCE) and tetrachloroethene (PCE) and the stability of TCE and PCE adsorbed to the supported bimetallic
nanoparticles as a function of particle type and reaction conditions. A major focus of the research is the
longevity of the degradation process as a function of contaminant loading.
RAC studies are contributing to a new direction of research on the use of permeable reactive barriers in
variety of hydrogeological settings. RAC also can treat coexisting contaminants, including halogenated
compounds, and consequently provides effective tools to manage PCB-contaminated sites in a manner
that gains regulatory acceptance. Further research can be initiated to better understand the transport,
reaction, and fate of such contaminants on RAC when the technology is used as an environmental risk
management option. To improve full-scale RAC application in the field, future NRMRL research is
expected to focus on exploring the possibility of using more cost-efficient methods to reduce Fe to ZVI,
more environmentally sustainable reducing reagents such as ascorbic acid, and less expensive metals
such as copper and nickel.
CLU-IN Website: Mane-technology: Applications for Environmental
Remediation
This remediation technology area of CLU-IN provides a compendium of guidance materials, application
reports, and other information resources on naturally occurring and engineered materials containing an
active component with submicron dimensions.
Technology News & Trends
February 2013 Issue
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Upcoming Workshop: Applications of Nanotechnoloqy for Safe and
Sustainable Environmental Remediation
Government, industry, academic, and other partners have organized a national workshop to be held at
Southeastern Louisiana University in Hammond, Louisiana, on June 5-7, 2013. The workshop offers a
venue to develop ideas about designing guidelines, criteria, and work practices that support safe and
sustainable nano-enabled environmental remediation, become acquainted with nanotechnology vendors
and other stakeholders, and share case studies of nano-enhanced cleanup technologies. Results of the
workshop are expected to help environmental cleanup practitioners anticipate, recognize, evaluate,
control, and confirm the safe management of potential risks associated with occupational and
environmental exposures to nanomaterials.
SERDP Demonstrations
• Application of Microarravs and aPCR to Identify Phvloaenetic and Functional Biomarkers Diagnostic of Microbial
Communities that Biodearade Chlorinated Solvents to Ethene(ER-1587: January 2013 fact sheet and upcoming
reports). This research established and applied a method of fluorescence-activated cell sorting combined with
whole genome amplification and microarray techniques to examine dilute quantities dUehalococcoides species
without time-consuming culturing steps. The approach may be used to optimize in situ bioremediation
technologies and provide biomarkers that could replace or supplement traditional diagnostics for biodegradation
in anaerobic environments.
• A Portable Surface-Enhanced Raman Sensor for Real-Time Detection and Monitoring of Perchlorate and
Eneraetics(ER-1602: January 2012 final report). Sensitive gold nanoparticle-based surface- enhanced Raman
spectroscopy substrates were developed and integrated with a Raman analyzer (equipped with a near infrared
laser and fiber-optic probe) to create a miniaturized field-deployable sensor that detects energetic and
co-contaminants in groundwater and surface water. Oak Ridge National Laboratory and project partners
demonstrated that the sensor could detect perchlorate, TNT, and RDX in the field at concentrations as low as 0.1
ug/L, 2.3 ug/L, and 0.12 mg/L, respectively.
Recent Publications
• Toxicitv of Nano-Zero Valent Iron to Freshwater and Marine Organisms
University of California-Santa Barbara researchers recently tested whether three commercial forms of nanoscale
ZVI (uncoated, organic coating, and iron oxide coating) applied for soil remediation are toxic to downstream
freshwater and marine organisms. The research findings can be used to design a risk management strategy that
arrests transport of injected nanoscale ZVI beyond the intended remediation area.
• SETAC Technical Workshop Summary: Guidance on Passive Sampling Methods to Improve Management of
Contaminated Sediments
In November 2012, the Society of Environmental Toxicology and Chemistry (SETAC) held a workshop to
promote understanding of passive sampling methods (PSMs) and provide recommendations for their application
in contaminated sediment assessment and management. The workshop focused on PSMs as a means to
quantify the bioavailability of organics or metals, based on the diffusion and subsequent partitioning of
contaminants from sediment to a reference sampling phase. Preliminary findings of the workshop and plans for
developing related issue papers are now available in a SETAC technical workshop summary.
1 tnis newsletter as a means or disseminating userui information regarping innovative ana alternative treatment
technologies and techniques. The Agency does not endorse specific technology vendors.
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