United States
Environmental Protection
Agency
Office of Research and
Development
Washington DC 20460
EPA/540/R-96/503
June 1997
<&EPA EnviroMetal Technologies, Inc.
Metal-Enhanced
Dechlorination of
Organic Compounds Using an
Aboveground Reactor
Innovative Technology
Evaluation Report
SUPERFUND INNOVATIVE
TECHNOLOGY EVALUATION
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EPA/540/R-96/503
June 1997
EnviroMetal Technologies, Inc.
Metal-Enhanced Dechlorination of
Volatile Organic Compounds
Using an Aboveground Reactor
Innovative Technology Evaluation Report
National Risk Management Research Laboratory
Office of Research and Development
U.S. Environmental Protection Agency
Cincinnati, Ohio 45268
Printed on Recycled Paper
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Notice
This document was prepared for the U.S. Environmental Protection Agency's (EPA's)
Superfund Innovative Technology Evaluation (SITE) Program under Contract Nos. 68-
CO-0047 and 68-C5-0037. This document was subjected to the EPA's peer and administra-
tive reviews and was approved for publication as an EPA document. Mention of trade
names or commercial products does not constitute an endorsement or recommendation for
use.
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Foreword
The U.S. Environmental Protection Agency is charged by Congress with protecting the
Nation's land, air, and water resources. Under a mandate of national environmental laws,
the Agency strives to formulate and implement actions leading to a compatible balance
between human activities and the ability of natural systems to support and nurture life. To
meet this mandate, EPA's research program is providing data and technical support for
solving environmental problems today and building a science knowledge base necessary to
manage our ecological resources wisely, understand how pollutants affect our health, and
prevent or reduce environmental risks in the future.
The National Risk Management Research Laboratory is the Agency's center for
investigation of technological and management approaches for reducing risks from threats
to human health and the environment. The focus of the Laboratory's research program is on
methods for the prevention and control of pollution to air, land, water, and subsurface
resources; protection of water quality in public water systems; remediation of contami-
nated sites and groundwater; and prevention and control of indoor air pollution. The goal of
this research effort is to catalyze development and implementation of innovative, cost-
effective environmental technologies; develop scientific and engineering information
needed by EPA to support regulatory and policy decisions; and provide technical support
and information transfer to ensure effective implementation of environmental regulations
and strategies.
This publication has been produced as part of the Laboratory's strategic long-term
research plan. It is published and made available by EPA's Office of Research and
Development to assist the user community and to link researchers with their clients.
E. Timothy Oppelt, Director
National Risk Management Research Laboratory
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Abstract
EnviroMetal Technologies, Inc., of Guelph, Ontario, Canada, has developed a metal-enhanced dechlorina-
tion process to destroy chlorinated volatile organic compounds (VOCs) in aqueous media. The U.S.
Environmental Protection Agency (EPA) Superfund Innovative Technology Evaluation (SITE) Program
evaluated this technology during a demonstration that took place from November 1994 to February 1995.
This Innovative Technology Evaluation Report evaluates the ability of the metal-enhanced dechlorination
technology to destroy chlorinated VOCs in contaminated groundwater; specifically, this report discusses
performance and economic data from a demonstration of the technology and presents four case studies.
The metal-enhanced dechlorination technology employs an electrochemical process that involves oxidation
of iron and reductive dehalogenation of halogenated VOCs in aqueous media. During reductive dehalogenation,
VOCs are converted to hydrocarbons and inorganic halides. The process can be used for either in situ or ex
situ groundwater treatment.
The metal-enhanced dechlorination process was demonstrated under the SITE Program at the SL Industries,
Inc., SGL Printed Circuits site in Wayne, Passaic County, New Jersey, using a pilot-scale, aboveground
treatment reactor containing the reactive iron medium. A flow rate of about 0.5 gallons per minute was
maintained throughout the 13-week demonstration period; about 60,800 gallons of groundwater were treated.
During the demonstration of the aboveground reactor, water samples were collected at influent, intermediate,
and effluent sampling locations and analyzed for VOCs and inorganic parameters. VOCs present in influent
groundwater or generated as degradation by-products were considered critical analytes for the SITE
demonstration. Sampling and analytical procedures were specified in an EPA-approved Quality Assurance
Project Plan.
The analytical results indicated that influent groundwater was contaminated with (1) trichloroethene (TCE) at
concentrations ranging from 54 to 590 micrograms per liter (ug/L); (2) tetrachloroethene (PCE) at concentra-
tions ranging from 4,100 to 13,000 ug/L; and (3) cis-l,2-dichloroethene (cDCE) at concentrations ranging
from 35 to 1,600 ug/L. Vinyl chloride (VC) was not detected in the influent groundwater. Analytical results
for the effluent samples indicated that the metal-enhanced dechlorination process significantly reduced the
total concentrations of chlorinated VOCs in water treated and consistently achieved the demonstration
effluent target level of 1 ug/L for TCE and PCE. The analytical results also indicated that PCE removal
efficiencies were consistently greater than 99.9 percent. In the early part of the demonstration, cDCE
and VC concentrations in the effluent samples were below detectable limits, and the technology
consistently achieved target levels for VC and cDCE for the first 11 weeks. However, during the last
two weeks of the demonstration the process did not consistently achieve the effluent target levels of 2
|ig/L for VC and 5 ug/L for cDCE. Although some cDCE was present in the influent groundwater,
most of the cDCE and VC appears to have formed through the degradation of PCE and TCE. The
incomplete dechlorination of cDCE and VC in the latter portion of the SITE demonstration may have
been caused by PCE persisting to greater depths within the reactor than anticipated or insufficient
residence time for complete dechlorination to occur. These factors may have resulted from a gradual
reduction in the iron's reactive surface area through formation of precipitates. Also, a gradual decrease
in reactor temperature over the demonstration period may have affected system performance.
Based on information obtained from the SITE demonstration, ETI, and other sources, groundwater remedia-
tion costs for an aboveground reactor using the metal-enhanced dechlorination process are estimated to be
about $91 per 1,000 gallons treated. This cost was estimated based on data from a pilot-scale system
operating at a flow rate of 0.5 gpm extrapolated to a 30-year operational period. Long-term costs for a full-
scale remediation system could vary significantly from this estimate due to the differences between the
capabilities of pilot-scale reactors and full-scale systems designed for optimal performance.
iv
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Contents
Acronyms, Abbreviations, and Symbols ix
Conversion Factors xi
Acknowledgments .xii
Executive Summary 1
1 Introduction 5
1.1 Brief Description of SITE Program and Reports 5
1.1.1 Purpose, History, and Goals of the SITE Program 5
1.1.2 Documentation of SITE Demonstration Results 6
1.2 Purpose of the ITER 6
1.3 Background of the Metal-Enhanced Dechlorination Technology in the SITE Program. 6
1.4 Technology Description 7
1.4.1 Process Chemistry 7
1.4.2 Overview of the Metal-Enhanced Dechlorination Technology 8
1.4.3 Innovative Features of the Metal-Enhanced Dechlorination Technology 8
1.5 Applicable Wastes 9
1.6 Key Contacts 10
2 Technology Effectiveness and Applications Analysis 11
2.1 Overview of the Metal-Enhanced Dechlorination Technology SITE Demonstration. 11
2.1.1 Project Background and Technology Description 11
2.1.2 Project Objectives 12
2.1.3 Demonstration Procedures 12
2.2 SITE Demonstration Results 17
2.2.1 Objective PI: Compliance with Applicable Effluent Target Levels 17
2.2.2 Objective P2: PCE Removal Efficiency 21
2.2.3 Objective SI: PCE Concentration as A Function of Sampling Location (Depth) 22
2.2.4 Objective S2: Sulfate, Chloride, Metals, and HC Concentrations. 23
2.2.5 Objective S3: Eh, DO, pH, Specific Conductance, and Temperature 23
2.2.6 Objective S4: Operating and Design Parameters and Changes in Opeerating Problems 26
2.3 Additional Performance Data 30
2.3.1 BordenSite 31
2.3.2 California Semiconductor Facility 31
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Contents (continued)
2.4 Factors Affecting Performance 31
2.4.1 Feed Waste Characteristics 31
2.4.2 Operating Parameters 32
2.4.3 Maintenance Requirements 33
2.5 Site Characteristics and Support Requirements 34
2.5.1 Site Access, Area, and Preparation Requirements 34
2.5.2 Climate Requirements 34
2.5.3 Utility and Supply Requirements 34
2.5.4 Required Support Systems 34
2.5.5 Personnel Requirements 34
2.6 Material Handling Requirements 35
2.7 Technology Limitations 35
2.8 Potential Regulatory Requirements 35
2.8.1 Comprehensive Environmental Response, Compensation, and Liability Act 35
2.8.2 Resource Conservation and Recovery Act 37
2.8.3 Clean Water Act 38
2.8.4 Safe Drinking Water Act 38
2.8.5 Clean Air Act 38
2.8.6 Mixed Waste Regulations 39
2.8.7 Occupational Safety and Health Act 39
2.9 State and Community Acceptance.... 39
Economic Analysis , 41
3.1 Factors Affecting Costs 41
3.2 Assumptions Used in Performing the Economic Analysis 42
3.3 Cost Categories 43
3.3.1 Site Preparation Costs 44
3.3.2 Permitting and Regulatory Costs 44
3.3.3 Mobilization and Startup Costs 44
3.3.4 Capital Equipment Costs 44
3.3.5 Labor Costs 45
3.3.6 Supply Costs 45
3.3.7 Utility Costs 45
3.3.8 Effluent Treatment and Disposal Costs 45
3.3.9 Residual Waste Shipping and Handling Costs 46
3.3.10 Analytical Services Costs 46
3.3.11 Equipment Maintenance Costs 46
vi
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Contents (continued)
3.3.12 Site Demobilization Costs 46
3.4 Conclusions of Economic Analysis 46
4 Technology Status 49
5 References 51
Appendices
A Vendor's Claims for the Technology 53
B Case Studies 79
Figures
1-1 Schematic of aboveground reactor design 9
2-1 PCE concentration vs. distance through reactive iron 14
2-2 TCE concentration vs. distance through reactive iron 14
2-3 cDCE concentration vs. distance through reactive iron 15
2-4 Effluent concentration of VC and cDCE 15
2-5 Temperature and PCE removal vs. time 16,
2-6 PCE removal efficiency vs. depth through reactive iron 16
2-7 Sulfate concentration as a function of sampling location (depth) 24
2-8 Chloride concentration as a function of sampling location (depth) 24
2-9 Dissolved calcium concentration as a function of sampling location (depth).. 25
2-10 Dissolved magnesium concentration as a function of sampling location (depth) 25
2-11 Dissolved barium concentration as a function of sampling location (depth) 26
2-12 Dissolved iron concentration as a function of sampling location (depth) 26
2-13 Dissolved manganese concentration as a function of sampling location (depth) 27
2-14 TIC concentration as a function of sampling location (depth) 27
2-15 Eh as a function of sampling location (depth) 28
2-16 DO as a function of sampling location (depth) 28
2-17 pH as a function of sampling location (depth) 29
2-18 Specific conductance as a function of sampling location (depth) 30
2-19 Temperature as a function of sampling location (depth).... 30
3-1 Distribution of fixed costs 47
3-2 Distribution of annual variable costs 47
VII
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Tables
ES-l Superfund Feasibility Study Evaluation Criteria for the Aboveground
Application of the Metal-Enhanced Dechlorination Technology 4
1-1 Correlation Between Superfund Feasibility Evaluation Criteria and ITER Sections 6
1-2 Comparison of Technologies for Treating Halogenated VOCs in Water. 10
2-1 Critical Parameter VOC Concentrations at Influent and Effluent Sampling Locations 18
2-2 Summary of VOC Data from Weeks 1,5, 9, and 13 19
2-3 Vent Gas Concentrations of PCEandTCE 22
2-4 pH at Influent and Effluent Locations 29
2-5 Summary of Operating and Design Parameters 30
2-6 Summary of Environmental Regulations 36
3-1 Costs Associated with the Aboveground Application of the
Metal-Enhanced Dechlorination Technology 42
VIII
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Acronyms, Abbreviations, and Symbols
AEA
ARAR
CAA
CaC03
CERCLA
Cl
CO32
cDCE
CWA
DO
DOE
Eh
EPA
ETI
Fe°
Fe2+
Fe3+
FeC03
Fe(OH)2
Fe(OH)3
ft
H+
H2(g)
HCO3-
in.
ITER
kwh
LDR
m
MCL
Atomic Energy Act
Applicable or Relevant and Appropriate Requirement
Clean Air Act
Calcium carbonate
Comprehensive Environmental Response, Compensation, and Liability Act
Chloride ion
Carbonate ion
cis-1,2-Dichloroethene
Clean Water Act
Dissolved oxygen
Department of Energy
Oxidation-reduction potential
U.S. Environmental Protection Agency
EnviroMetal Technology, Inc.
Zero-valent iron
Ferrous iron
Ferric iron
Ferrous carbonate or siderite
Ferrous hydroxide
Ferric hydroxide
Feet
Gallons per minute
Hydrogen ion
Hydrogen gas
Bicarbonate ion
Inch
Innovative Technology Evaluation Report
Kilowatt Hour
Land disposal restrictions
Meter
Maximum contaminant level
ix
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Acronyms, Abbreviations, and Symbols (continued)
mg/L Milligram per liter
MnO2(s) Manganese dioxide (solid)
NJDEP New Jersey Department of Environmental Protection
NOEL Nonobservable Effect Level
NPDES National Pollutant Discharge Elimination System
NRC Nuclear Regulatory Commission
NRMRL National Risk Management Research Laboratory
NSPS New Source Performance Standard
O and M Operating and Maintenance
OH* Hydroxyl ion
ORD U.S. EPA Office of Research and Development
OSHA Occupational Safety and Health Act
OSWER Office of Solid Waste and Emergency Response
PCB Polychlorinated biphenyl
PCE Tetrachloroethene
POTW Publicly Owned Treatment Works
ppbv Parts per billion by volume
PPE Personal Protective Equipment
QAPP Quality assurance project plan
QA/QC Quality assurance/quality control
RC1 Chlorinated hydrocarbon
RCRA Resource Conservation and Recovery Act
RH Hydrocarbon
SARA Superfund Amendments and Reauthorization Act
SDWA Safe Drinking Water Act
SGL SGL Printed Circuits
SITE Superfund Innovative Technology Evaluation
SL Industries SL Industries, Inc.
TCE Trichloroethene
TCLP Toxicity characteristic leaching procedure
TER Technology evaluation report
TIC Total inorganic carbon
TSCA Toxic Substances Control Act
|ig/L Microgram per liter
pun micrometer (micron)
VOC Volatile organic compound
WQS Water quality standards
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Conversion Factors
To Convert From
To
Multiply By
Length
Area:
Volume:
inch
foot
mile
square foot
acre
gallon
cubic foot
centimeter
meter
kilometer
square meter
square meter
liter
cubic meter
2.54
0.305
1.61
0.0929
4,047
3.78
0.0283
Mass:
pound
kilogram
0.454
Energy:
kilowatt-hour
megajoule
3.60
Power:
kilowatt
horsepower
1.34
Temperature: (°Fahrenheit - 32) "Celsius
0.556
XI
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Acknowledgments
This report was prepared under the direction and coordination of Dr. Chien T. Chen,
U.S. Environmental Protection Agency (EPA) Superfund Innovative Technology Evalua-
tion (SITE) program project manager in the National Risk Management Research Labora-
tory (NRMRL), Edison, New Jersey. This report was prepared for EPA's SITE Program by
PRC Environmental Management, Inc. (PRC). Primary contributors and reviewers for this
report were Mr. Robert L. Stenburg, Ms. Ann M. Leitzinger, Dr. Taras Bryndzia and Mr.
Vicente Gallardo of EPA NRMRL, Cincinnati, Ohio, Mr. John L. Vogan of EnviroMetal
Technologies, Inc., Guelph, Ontario, Canada, and Ms. Stephanie O'Hannesin of the
University of Waterloo.
Special acknowledgment is given to SL Industries, Inc., Rhodes Engineering, P.C., and the
New Jersey Department of Environmental Protection for their cooperation and support
during the SITE Program demonstration.
xn
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Executive Summary
EnviroMetal Technologies, Inc. (ETI), has developed a metal-
enhanced dechlorination technology to degrade halogenated
volatile organic compounds (VOCs) such as halogenated
methanes, ethanes, and ethenes in aqueous media. This tech-
nology was demonstrated under the U.S. Environmental Pro-
tection Agency's (EPA) Superfund Innovative Technology
Evaluation (SITE) Program at the SL Industries, Inc., SGL
Printed Circuits (SGL) site in Wayne, Passaic County, NJ,
from November 1994 through February 1995.
The purpose of this Innovative Technology Evaluation Report
is to present information that will assist Superfund decision
makers in evaluating this technology for application to a
particular hazardous waste site cleanup. The report provides
an introduction to the SITE Program and the metal enhanced
dechlorination technology (Section 1); evaluates the
technology's effectiveness and applications (Section 2); ana-
lyzes the costs of using the technology to treat groundwater
contaminated with chlorinated VOCs (Sections); summa-
rizes the technology's current status (Section 4); and presents
a list of references (Section 5). Vendor's claims for the tech-
nology and case studies of other applications of the metal-
enhanced dechlorination technology are included in Appendi-
ces A and B, respectively.
This executive summary briefly describes the metal-enhanced
dechlorination technology, provides an overview of the SITE
demonstration of the technology, summarizes the SITE dem-
onstration results, discusses the costs of using this technology
to treat groundwater contaminated with chlorinated VOCs,
and evaluates the technology with respect to the nine Super-
fund feasibility study evaluation criteria.
Technology Description
The metal-enhanced dechlorination technology involves oxi-
dation of iron and reductive dehalogenation of halogenated
VOCs in aqueous media. The technology employs a reactive,
zero-valent, granular iron medium that oxidizes and induces
dehalogenation of halogenated VOCs, yielding simple hydro-
carbons and halogen compounds as byproducts. This technol-
ogy can be installed and operated in either an aboveground
reactor consisting of a vessel containing the reactive iron
medium, or in situ as a permeable treatment wall. In an
aboveground application groundwater is extracted from an
aquifer using pumps, collection trenches, or other methods,
and piped to the reactor. The water flows through the reactor
by gravity. For in situ applications, a permeable reactive wall
is constructed by excavating a trench, oriented perpendicular
to the groundwater flow direction and extending below the
water table, and backfilling the trench with the reactive iron
medium. This creates a reactive iron wall across the natural
flow path of groundwater contaminated with VOCs. For large-
scale applications, either a continuous, permeable wall or a
"funnel and gate" configuration may be used. The "funnel"
consists of a scalable joint sheet pile or slurry wall that directs
water to the reactive wall, or "gate."
An aboveground, pilot-scale reactor was used for the SITE
demonstration at the SGL site. The pilot-scale reactor was
designed to evaluate the technology's suitability for full-scale
remediation at the SGL site, and to gather data regarding full-
scale system design and operating parameters. The reactor
was constructed in an 8-ft diameter fiberglass-reinforced plas-
tic tank. The reactor was 9 ft high and contained a 5.5-ft thick
layer of reactive iron medium placed on top of a 6-in. layer of
coarse silica sand (well sand). Contaminated groundwater
entered the aboveground reactor after passing through an air
eliminator, a 5-u. water filter (to remove suspended solids,
which may inhibit flow through the reactive iron medium),
and a flow meter. Groundwater flowed by gravity through the
reactive iron medium. A passive gas vent in the top of the
reactor prevented accumulation of excess pressure in the
reactor. A manhole located at the top of the reactor had a
sightglass which allowed observation of the reactive iron
surface and access to the reactor interior. The reactor drained
through a collector pipe located in the lower 6-in. layer of well
sand; the collector pipe then connected to the effluent line.
Its developer claims that the metal-enhanced dechlorination
process can treat halogenated methanes, ethanes, and ethenes
over a wide range of concentrations. The developer has not
done testing to determine the applicability of the process for
treating chlorinated aromatic compounds, such as polychlori-
nated biphenyls. Various academic groups are examining the
technology's ability to degrade chlorobenzene, chlorophenols,
and nitroaromatic compounds.
Overview of the Metal-Enhanced
Dechlorination Technology SITE
Demonstration
Prior to 1984, SGL (now known as SL Industries) manufac-
tured printed circuit boards at the SGL site. Groundwater
samples collected at the SGL site indicated the presence of
chlorinated VOCs, including tetrachloroethene (PCE), tri-
chloroethene (TCE), and other compounds, in a shallow,
unconsolidated aquifer and also in an underlying bedrock
aquifer.
The EPA SITE Program evaluated the metal-enhanced dechlo-
rination process as a pilot-scale, aboveground reactor during a
13-wk demonstration at the SGL site. The demonstration
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began on November 21,1994, and was completed on Febru-
ary 15,1995.
During the demonstration the treatment reactor described
above was used to treat groundwater contaminated with PCE
present at concentrations ranging from 4,100 to 13,000 micro-
grams per liter (ug/L) and TCE at concentrations ranging
from 54 to 590 ug/L. During some weeks of testing, cis-1,2-
dichloroethene (cDCE) was also detected in the influent
groundwater, at concentrations ranging from 35 to 1,600 ug/
L. A flow rate of 0.5 gallons per minute (gpm) was maintained
throughout the 13-wk demonstration period; 60,833 gallons of
groundwater were treated. The treatment reactor's design al-
lowed for a contact time between groundwater and reactive
iron medium of about 1 day.
The primary objectives of the technology demonstration were
as follows:
• Determine whether effluent from the treatment reac-
tor meets the most stringent of New Jersey Depart-
ment of Environmental Protection (NJDEP) and fed-
eral maximum contaminant level (MCL) discharge
requirements for all VOCs which were (1) originally
present in the influent during the demonstration
period, or (2) suspected byproducts of the dechlori-
natlon process. These VOCs were TCE; PCE; 1,1-
dichloroethene (1,1-DCE) cDCE; and vinyl chloride
(VC).
• Determine the removal efficiency of PCE from
groundwater
The secondary objectives of the technology demonstration
were as follows:
• Assess PCE concentrations as a function of depth
as groundwater passed through the treatment reac-
tor.
• Determine metals, chloride, sulfate, and total inor-
ganic carbon (TIC) concentrations in groundwater
as it passed through the treatment reactor and use
this data to evaluate precipitate formation, dechlori-
nation, and biological activity within the reactor.
• Document geochemical conditions in groundwater
as groundwater passed through the treatment reac-
tor.
• Document operating and design parameters.
During the SITE demonstration, groundwater samples were
collected at the reactor's influent, intermediate, and effluent
sampling locations. Chlorinated VOCs originally present in
influent groundwater or formed as byproducts of the dechlori-
nation process were the critical analytes for the demonstra-
tion. Samples of the influent and effluent water were collected
weekly and analyzed for EPA Target Compound List (TCL)
VOCs, to determine the concentrations of the critical param-
eters. All other sampling and monitoring parameters (VOCs at
intermediate sampling locations, and dissolved (soluble) met-
als, chloride, sulfate, TIC, and field parameters at all sampling
locations) were considered noncritical. Samples were col-
lected at influent, intermediate, and effluent locations during
wks 1, 5, 9, and 13; during these weeks all samples were
analyzed for TCL VOCs, dissolved metals, TIC, chloride, and
sulfate. In addition, field measurements of dissolved oxygen
(DO), temperature, specific conductance, pH, and oxidation-
reduction potential (Eh) measurements were performed weekly
at the influent and effluent locations, and were also performed
at the intermediate locations during wks 1, 5,9, and 13.
SITE Demonstration Results
The SITE demonstration of the metal-enhanced dechlorina-
tion technology produced the following key findings:
• The metal-enhanced dechlorination process signifi-
cantly reduced the total concentrations of chlori-
nated VOCs present in the water treated. The efflu-
ent water met the target concentration of 1 ug/L for
TCE and PCE and the target level of 2 ug/L for 1,1 -
DCE during each of the 13 wks of testing. No cDCE
or VC was detected in the effluent during wks 1
through 8; however, low concentrations of cDCE
and VC were detected in the effluent in the latter
part of the demonstration. The effluent groundwater
met the target levels of 2ug/L for VC during wks 1
through 11, and 5 ug/L for cDCE during wks 1
through 12. VC concentrations during wks 12 and
13 (2.8 ug/L and 8.4 ug/L, respectively) and cDCE
concentrations during wk 13 (37ug/L) exceeded the
target levels.
• PCE was used as an indicator compound to esti-
mate the removal efficiency of the process. The
PCE removal efficiencies were consistently greater
than 99.9% during each week of testing.
• Results from wks 1, 5, 9, and 13 indicate that PCE
concentrations increased at the intermediate sam-
pling locations, suggesting that PCE was persisting
to increasingly greater depths as the demonstration
progressed.
• The concentrations of chloride and sulfate did not
change significantly as water moved through the
reactor.
• The concentrations of dissolved metals such as
calcium, magnesium, and barium changed as
groundwater moved through the reactor, apparently
as a result of pH increase induced by the process.
Generally, the decrease in concentrations of cal-
cium, magnesium, and barium coincided with an
increase in pH. Iron concentrations were higher at
intermediate sampling locations than iron concen-
trations in the influent and effluent samples, also
possibly due to the effects of pH on solubility of iron
compounds.
• During treatment, the Eh and DO concentrations in
groundwater decreased as a function of vertical
distance through the reactor, indicating that the
reactor was operating under reducing conditions.
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• The groundwater TIC concentration and the specific
conductance decreased as a function of reactor
depth.
• The main operating problem observed during the
demonstration was the deposition of precipitates. A
hard, crust-like layer formed in the upper few inches
of the reactive iron, which according to the devel-
oper was primarily carbonate compounds that had
been produced during the dechlorination process.
The crust was periodically manually broken up dur-
ing the demonstration to maintain unrestricted flow
through the reactor.
• Precipitates may also have affected the reactor's
performance by blocking the iron surfaces available
for reaction, thereby reducing the reactivity of the
upper portion of the iron. Also, variations in reactor
temperature caused by fluctuations in ambient air
temperature may have affected reactor performance.
These factors nay have contributed to the increas-
ing persistence of PCE over the demonstration pe-
riod and the incomplete dechlorination of cDCE and
VC in the latter part of the demonstration.
Economics
Costs for using the metal-enhanced dechlorination process are
highly dependent on site-specific factors, and highly variable.
Costs vary based on the types and concentrations of contami-
nants present, the capacity of the extraction system used,
monitoring and discharge requirements, and other factors.
Using information obtained from the SITE demonstration,
ETI, and other sources, an economic analysis examined 12
cost categories for a scenario in which an aboveground reactor
was assumed to operate for a 30-year period and treat 7.88
million gallons of groundwater. The "cost estimate assumed
that groundwater was contaminated with the same types and
concentrations of chlorinated VOCs present in groundwater at
the SGL site and assumed that design and operating param-
eters for the treatment system were the same as for the pilot-
scale system at the SGL site. Based on these assumptions, the
total costs directly related to the metal-enhanced dechlorina-
tion process are estimated to be $91 per 1,000 gallons of
groundwater treated. Due to potential differences between the
capabilities of pilot-scale systems and full-scale systems de-
signed for optimal performance, and varying site-specific
factors, costs per gallon treated could be significantly less for
a full-scale application of the metal-enhanced dechlorination
process at other sites.
Superfund Feasibility Study
Evaluation Criteria for the Metal-
Enhanced Dechlorination
Technology
Table ES-1 briefly discusses an evaluation of the metal-
enhanced dechlorination process with respect to the nine
Superfund feasibility study evaluation criteria (EPA 1988c)
that Superfund decision makers may use when considering the
technology for remediation of hazardous waste sites.
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Table ES-1. Superfund Feasibility Study Evaluation Criteria for the Aboveground Application of the Metal-Enhanced Dechlorination
Technology
Criterion
Discussion
Overall Protection of Human
Health and the Environment
Compliance with Applicable or
Relevant and Appropriate
Requirements (ARAR)
Long-Term Effectiveness and
Permanence
Reduction of Toxicity, Mobility, or
Volume Through Treatment
Short-Term Effectiveness
Implementability
Cost
Community Acceptance
State Acceptance
The technology is expected to protect human health and the environment by providing treated water
that has significantly lower concentrations of chlorinated VOCs.
Protection of the environment at and beyond the point of discharge should be evaluated based on
uses of the receiving water body, concentrations of residual contaminants and treatment by-
products, and the dilution factor.
The technology's ability to comply with existing federal, state, or local ARARs (for example, MCLs)
should be determined on a site-specific basis.
The technology was able to meet target effluent concentrations based on federal MCLs or NJDEP
groundwater discharge standards.
Human health risk can be reduced to acceptable levels by treating groundwater to site-specific
cleanup levels; the time needed to achieve cleanup goals depends primarily on wastewater
characteristics.
The long-term effectiveness of the metal-enhanced dechlorination technology treatment reactor
depends on periodically replacing the iron medium and/or on backflushing the system.
The treatment is permanent because the metal-enhanced dechlorination process uses a thermody-
namically favorable process to degrade halogenated VOCs to less halogenated compounds.
Periodic review of treatment system performance is needed because application of this technology
to contaminated groundwater at hazardous waste sites is relatively recent.
Although target compounds are dechlorinated to less toxic compounds by the technology, the
reduction in overall toxicity should be determined on a site-specific basis because of the potential for
forming by-products.
Workers using the metal-enhanced dechlorination process are not expected to be subjected to high
VOC concentrations during operation of the technology.
The site must be accessible to typical construction equipment and delivery vehicles.
The reactor system used during the SITE demonstration required about 400 square feet (ft2). The
actual space requirements will depend on the groundwater treatment rate and other site-specific
factors.
Site-specific needs may dictate the need for additional services and supplies.
Construction and discharge permit requirements will depend on site-specific conditions.
Costs will vary based on site-specific factors. For the pilot-scale treatment reactor, 8 ft in diameter
and containing a 5.5-ft thick layer of reactive iron, which was used during the demonstration, fixed
costs (including site preparation, mobilization, capital equipment, and demobilization) are estimated
to be about $78,100. Annual operating and maintenance costs, including those for residual waste
handling, analytical services, labor, and equipment maintenance, are estimated to be about $21,100.
This criterion is generally addressed in the record of decision after community responses are
received during the public comment period. However, because communities are not expected to be
exposed to harmful levels of VOCs, noise, or fugitive emissions, community acceptance of the
technology is expected to be relatively high.
This criterion is generally addressed in the record of decision; state acceptance of the technology will
likely depend on the concentrations of residual organic contaminants and,treatment by-products in
treated wastewater.
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Section 1
Introduction
This section briefly describes the Superfund Innovative
Technology Evaluation (SITE) Program and SITE re-
ports; states the purpose of this Innovative Technology
Evaluation Report (ITER); provides background infor-
mation on the development of the EnviroMetal Tech-
nologies, Inc. (ETI), metal-enhanced dechlorination tech-
nology; describes the metal-enhanced dechlorination
technology; identifies wastes to which this technology
may be applied; and provides a list of key contacts.
1.1 Brief Description of SITE Program
and Reports
This section provides information about the {1) purpose,
history, and goals of the SITE Program, and (2) the
reports used to document SITE demonstration results.
/. 1.1 Purpose, History, and Goals of the
SITE Program
The primary purpose of the SITE Program is to advance
the development and demonstration, and thereby estab-
lish the commercial availability, of innovative treatment
technologies applicable to Superfund and other hazard-
ous waste sites. The SITE Program was established by
the U.S. Environmental Protection Agency (EPA) Office
of Solid Waste and Emergency Response (OSWER)
and Office of Research and Development (ORD) in
response to the Superfund Amendments and Reauthori-
zation Act of 1986 (SARA), which recognized the need
for an alternative or innovative treatment technology
research and demonstration program. The SITE Pro-
gram is administered by ORD's National Risk Manage-
ment Research Laboratory. The overall goal of the SITE
Program is to carry out a program of research, evalua-
tion, testing, development, and demonstration of alter-
native or innovative treatment technologies that may be
used in response actions to achieve more permanent
protection of human health and welfare and the environ-
ment.
The SITE Program consists of four component pro-
grams: (1)the Demonstration Program, (2) the Emerg-
ing Technology Program, (3) the Monitoring and Mea-
surement Technologies Program, and (4) the Technol-
ogy Transfer Program. This ITER was prepared under
the SITE Demonstration program. The objective of the
Demonstration Program is to provide reliable perfor-
mance and cost data on innovative technologies so that
potential users can assess a given technology's suitabil-
ity for specific site cleanups. To produce useful and
reliable data, demonstrations are conducted at hazard-
ous waste sites or under conditions that closely simulate
actual waste site conditions.
Information collected during a demonstration is used to
assess the performance of the technology, the potential
need for pretreatment and posttreatment processing of
the waste, the types of wastes and media that may be
treated by the technology, potential operating problems,
and approximate capital and operating costs. Demon-
stration information can also provide insight into a
technology's long-term operating and maintenance
(O&M) costs and long-term application risks.
Each SITE demonstration evaluates a technology's per-
formance in treating waste at a particular site. Success-
ful demonstration of a technology at one site or on a
particular waste does not ensure its success at other
sites or for other wastes. Data obtained from the demon-
stration may require extrapolation to estimate a range of
operating conditions over which the technology per-
forms satisfactorily. Also, any extrapolation of demon-
stration data should be based on other information
about the technology, such as information available
from case studies.
Implementation of the SITE Program is a significant,
ongoing effort involving ORD, OSWER, various EPA
regions, and private business concerns, including tech-
nology developers and parties responsible for site reme-
diation. The technology selection process and the Dem-
onstration Program together provide objective and care-
fully controlled testing of field-ready technologies. Inno-
vative technologies chosen for a SITE demonstration
must be pilot- or full-scale applications and must offer
some advantage over existing technologies; mobile tech-
nologies are of particular interest. Each year the SITE
Program sponsors demonstrations of about 10 tech-
nologies.
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1.1.2 Documentation of SITE
Demonstration Results
The results of each SITE demonstration are reported in
four documents: a Demonstration Bulletin, Technology
Capsule, Technology Evaluation Report (TER), and ITER.
The Demonstration Bulletin provides a two-page de-
scription of the technology and project history, notifica-
tion that the demonstration was completed, and high-
lights of demonstration results. The Technology Cap-
sule provides a brief description of the project and an
overview of the demonstration results and conclusions.
The purpose of the TER is to consolidate all information
and records acquired during the demonstration. It con-
tains both a narrative portion and tables and graphs
summarizing data. The narrative portion includes dis-
cussions of predemonstration, demonstration, and
postdemonstration activities as well as any deviations
from the demonstration quality assurance project plan
(QAPP) during these activities and their impact. The
data tables and graphs summarize demonstration re-
sults in terms of whether project objectives were met.
The tables also summarize quality assurance and qual-
ity control (QA/QC) data and data quality objectives. The
TER is not formally published by EPA. Instead, a copy is
retained as a reference by the EPA project manager for
responding to public inquiries and for recordkeeping
purposes. The purpose of the ITER is discussed in
Section 1.2.
1.2 Purpose of the ITER
Information presented In the ITER is intended to assist
Superfund decision makers evaluating specific tech-
nologies for a particular cleanup situation. The metal-
enhanced dechlorination process has been evaluated
against the nine feasibility study evaluation criteria used
in the Superfund remedial process, which are listed in
Table 1-1 along with the sections of the ITER where
information related to each criterion is discussed. The
ITER represents a critical step in the development and
commercialization of a treatment technology. The report
discusses the effectiveness and applicability of the tech-
nology and analyzes costs associated with its applica-
tion. The technology's effectiveness is evaluated based
on data collected during the SITE demonstration" and
from other case studies. The applicability of the technol-
ogy is discussed in terms of waste and site characteris-
tics that could affect technology performance, material
handling requirements, technology limitations, and other
factors.
1.3 Background of the Metal-Enhanced
Dechlorination Technology in the
SITE Program
In 1993, SL Industries, Inc. (SL Industries), responded
to a solicitation issued by the SITE Program by submit-
ting a proposal for the SITE Program to evaluate ETI's
metal-enhanced dechlorination technology at the SQL
Printed Circuits (SQL) site in Wayne, NJ. Through nego-
tiations with the New Jersey Department of Environmen-
tal Protection (NJDEP), SL Industries, its consultants
(Rhodes Engineering, P.C. [Rhodes] and James C.
Anderson Associates, Inc.), and ETI conducted tests
using a pilot-scale, aboveground reactor to determine
the suitability of the metal-enhanced dechlorination tech-
nology for remediation of the SQL site. SITE Program
personnel participated in the evaluation of the technol-
ogy by collecting and analyzing groundwater samples at
influent, intermediate, and effluent locations, and by
collecting additional data regarding system design and
operating parameters.
Tabla 1-1. Correlation Between Superfund Feasibility Evaluation Criteria and ITER Sections
Evaluation Criterion* ITER Section
Overall protection of human health and the environment
Compliance with ARARs
Long-term effectiveness and permanence
Reduction of toxlcity, mobility, or volume through treatment
Short-term effectiveness
ImptomentaWlity
Cost
State acceptance
Community acceptance
2.2.1, 2.2.2, 2.2.4, and 2.2.5
2.2.1 through 2.2.4,2.2.6, and 2.8
1.4 and 2.2.6
2.2.1 through 2.2.3
2.2.1 through 2.2.6
1.4, 2.1, 2.2.8, 2.4, 2.5, and 4.0
3.0
2.2.2 through 2.2.6,2.8, and 2.9
2.2.1 through 2.2.6 and 2.9
Note:
•Source: EPA 1988c
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1.4 Technology Description
This section includes descriptions of the principles of
metal-enhanced dechlorination, the treatment system
used for the technology, and innovative features of the
technology.
1.4.1 Process Chemistry
The metal-enhanced dechlorination technology employs
an electrochemical process involving oxidation of iron
and reductive dehalogenation of halogenated volatile
organic compounds (VOCs) in aqueous media. Although
aluminum, copper, brass, standard steel, and zinc have
also been shown to promote reductive dehalogenation
of VOCs, metallic iron has been chosen for use in large-
scale applications of the technology. Metallic iron is
readily available, inexpensive, and induces rapid deha-
logenation of organic compounds (O'Hannesin and
Gillham 1992). The technology induces conditions that
cause substitution of halogen atoms by hydrogen at-
oms. According to Gillham and O' Hannesin (1994) the
following equations may describe the reactions that take
place in the presence of water, zero-valent iron (Fe°),
and a chlorinated hydrocarbon (RCI):
2Fe —> 2Fe2+ + 4e- (1 -1 a)
3H20 — > 3H
30H-
2H+ +2e-—> H2(g)
RCI + H+ + 2e-—> RH + Cl-
d-1c)
2Fe° + 3H20 + RCI
30H- + H.(g) + RH
(1-le)
The conversion of Fe° to ferrous iron (Fe2+), commonly
known as corrosion, is described by Equation 1-1 a.
Equation 1-1b describes the ionization of water. The
electrons released by the corrosion of iron (Equation 1-
1a) react with hydrogen ions (H*) and RCI according to
Equations 1 -1 c and 1 -1 d. The overall reaction that takes
place (Equation 1-1e) results in the formation of Fea%
hydroxyl ions (OH-), hydrogen gas [H2(g)], nonchlorinated
hydrocarbons (RH), and chloride ions (CI-). It is unknown
that the ionization of water (Equation 1-1b) is required
for the dechlorination reaction to occur (Gillham and
O'Hannesin 1994; Gillham 1996).
Because halogenated aliphatic VOCs are in a relatively
oxidized state, their reduction in the presence of re-
duced metals is thermodynamically favorable. The cor-
rosion of Fe° in contact with groundwater creates a
highly reducing environment in solution; this environ-
ment is evidenced by a decline in oxidation/reduction
potential (Eh). Equations 1-1 a - 1-1e show that during
the process the solution pH increases (the concentration
of OH" increases) and electrons are released as the
metal oxidizes, causing hydrogen atoms to replace the
chlorine atom(s) of the chlorinated organic compound
and reduce the chlorine to chloride ions.
The mechanism of dechlorination of a multi-chlorinated
compound, such as tetrachloroethene (PCE) or trichlo-
rpethene (TCE) is not completely understood. The reac-
tion may involve rapid, continuous ("precipitious") mecha-
nism (Gillham 1996), a sequential, continuous mecha-
nism (Chen 1995) or a combination of both types of
mechanisms.
During reductive dehalogenation, a multi-chlorinated VOC
(such as PCE) is converted to lesser-chlorinated hydro-
carbons [such as TCE, trans-1,2-dichloroethene, cis-
1,2-dichloroethene (cDCE), 1,1-dichloroethene and vi-
nyl chloride (VC)] before being completely dechlori-
nated. Gillham and others have theorized that a com-
pound such as PCE is attracted to the iron surface until
sufficient energy is available to cause a precipitious
dechlorination reaction. By this theory, the reaction
causes simultaneous dechlorination of the parent com-
pound and dechlorination byproducts, and when the
reaction is completed significant amounts of the inter-
mediate byproducts do not remain. According to Gillham,
small amounts of the intermediate byproducts escaping
the iron surface before the reaction is complete may
account for the appearance of small amounts of
byproducts in solution. However the amounts of these
byproducts observed are typically small in proportion to
the amount of parent compound dechlorinated, and,
based on this observation, Gillham and others have
suggested that the main reaction is precipitous (Gillham
and O' Hannesin 1994; Gillham 1996).
According to Chen (1996), the results of the SITE dem-
onstration suggested that for this demonstration, the
reaction followed a sequential mechanism, as shown in
the following equations (Chen 1995):
Fe —
H20—>
H+ + OH-
Cl 2C = CCI2
2e- — > CICH=CCI2 + Cr (1 -2c)
CICH = CCI2 + H* + 2e- — > CICH=CHCI + Cl: (1 -2d)
CICH = CHCl + H* + 2e- — > CH2 = CHCI + Cr (1 -2e)
CH2 = CHCI + H* + 2e- — > CH2 = CH2 + Cl- (1 -2f)
During the early part of the SITE demonstration, the iron
was still very reactive and was able to rapidly reduce all
byproducts (TCE, cDCE, and VC) generated as PCE
degraded. However, as the demonstration progressed,
the reactivity of the iron decreased and the produced
TCE could not be immediately reduced, leading to in-
creases in TCE concentrations and incomplete dechlori-
nation of cDCE and VC (see Section 2.2.1). For this
reason, during this demonstration the dechlorination of
multi-chlorinated VOCs appeared to be continuous and
sequential, rather than occurring in one precipitous step
-------
(Chen 1996). (See Appendix A for ETI's interpretation of
the demonstration results.)
The issue of reaction mechanisms does not significantly
affect the overall interpretation of the results with re-
spect to the objectives of this SITE demonstration. How-
ever, for long-term remediation using this technology,
decision makers and technology designers should be
aware of the possibility of formation of byproducts, such
as cDCE and VC through a sequential dechlorination
mechanism.
The dechlorination reaction is accompanied by other
peripheral reactions that may result in the precipitation
of Inorganic compounds. If no oxygen is present and pH
becomes sufficiently high, ferrous hydroxide [Fe(OH)J
will precipitate
Fe2* +2 OH~ -» Fe(OH)2 (s)
(1-3)
In oxygenated water at elevated pH levels, Fe2* is
converted to ferric iron (Fe3*), which in turn may precipi-
tate as ferric hydroxide [Fe(OH)3]
Fe3 + 3OH" -» Fe(OH)3 (s)
(1-4)
At lower dissolved oxygen concentrations, carbonate
(CO,2-) may react with Fe2* to form ferrous carbonate
(FeCO3), known as siderite
Fe
2
COf -> FeCO
(s) (siderite)
(i-5)
Because iron hydroxide and iron carbonate precipitates
are being formed during treatment, the concentrations of
dissolved iron in the effluent are expected to be rela-
tively low.
Tests were conducted by Gillham and O' Hannesin
(1994) to confirm that the reaction process was abiotic.
The tests were conducted using iron in the absence and
presence of formaldehyde, a bactericide. These tests
gave very similar results, indicating that the degradation
process was abiotic (Gillham and O' Hannesin 1994).
1.4.2 Overview of the Metal-Enhanced
Dechlorination Technology
ETI has developed the metal-enhanced dechlorination
technology to treat halogenated VOCs in water. This
technology uses a reactive, zero-valent, granular iron
medium that causes reductive dehalogenation of VOCs,
yielding simple hydrocarbons and inorganic halides as
byproducts.
The technology can be installed and operated
aboveground in a reactor, or in situ as a continuous
permeable reactive wall or "funnel and gate" system.
The funnel consists of a impermeable walls that direct
water to the reactive wall (gate).
Aboveground reactors may be used to simulate the
metal-enhanced dechlorination process at pilot scale,
allowing for measurement, control, modification, and
optimization of design and operating parameters or may
be operated as stand-alone treatment units. Aboveground
reactors may be especially useful for short-term reme-
diation projects requiring treatment of relatively small
amounts of contaminated water or in situations where
excavation and construction activities in the immediate
vicinity of the contaminant plume are impractical.
The aboveground reactor design used during the SITE
demonstration was a pilot-scale system, designed to
determine the technology's ability to treat groundwater
at the SQL site and to determine optimal design and
operating parameters for a full-scale system. The reac-
tor consisted of a 9-ft-high, 8-ft-diameter fiberglass-
reinforced plastic tank containing a 5.5-ft thick layer of
reactive, granular iron (see Figure 1-1). Contaminated
groundwater was pumped to the reactor, and flowed by
gravity through the reactive iron medium. The effluent
was returned to the subsurface through monitoring wells
modified to serve as injection wells.
The thickness, porosity, and permeability of the reactive
iron layer and the configuration of the effluent piping
controlled the flow velocity and volumetric flow rate, and
consequently the residence time, of water in the reactor.
The residence time required for the dechlorination reac-
tion depends on the concentrations and half-lives of the
contaminants present and is typically determined through
bench-sale studies using contaminated groundwater from
the site to be remediated. The specific reactor design for
the SITE demonstration is discussed in detail in Section
2.1.
1.4.3 Innovative Features of the Metal-
Enhanced Dechlorination
Technology
Common methods for treating groundwater contami-
nated with solvents and other organic compounds in-
clude air stripping, steam stripping, carbon adsorption,
biological treatment, chemical oxidation, and
photodestruction. As regulatory requirements for treat-
ment byproducts become more stringent and more ex-
pensive to comply with, the metal-enhanced dechlorina-
tion technology offers a major advantage over many
other treatment technologies: it destroys hazardous sub-
stances on site or in situ, rather than transferring them to
another medium, such as activated carbon or ambient
air. In addition, the metal-enhanced dechlorination pro-
cess often achieves faster reaction rates than other
technologies, such as some biological treatment pro-
cesses.
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Flow meter
Gas vent
Water filter
"
Inflow I
Air eliminator
Manhole
Sealing flange
/ for top
/\
/ X~N 3/4"
Influent (J1
line
Outflow
Effluent line
Figure 1 -1. Schematic of abovegrou nd reactor design.
The innovative features of the metal-enhanced dechlori-
nation technology may be attributed to the use of rela-
tively inexpensive zero-valent metals, such as iron, as a
means of enhancing degradation of chlorinated aliphatic
VOCs. The metal-enhanced dechlorination technology
appears to have the potential for effective, passive, in
situ treatment. In situ remedial technologies are gener-
ally more advantageous than traditional pump-and-treat
systems because of the high cost and performance
limitations of pump-and-treat systems. Possible advan-
tages of the in situ metal-enhanced dechlorination pro-
cess include (1) conservation of groundwater resources,
(2) long-term passive treatment, (3) absence of post-
treatment waste materials requiring treatment or dis-
posal, and (4) absence of invasive surface structures
and equipment that can restrict property use.
Table 1-2 compares the metal-enhanced dechlorination
process to several treatment options for water contami-
nated with chlorinated VOGs.
1.5 Applicable Wastes
ETI claims that its system is applicable to a wide range
of halogenated methanes, ethanes, and ethenes in wa-
ter. The SITE Program examined the technology's abil-
ity to treat only chlorinated ethenes, including TCE,
PCE, cDCE, and VC.
-------
Tobla1-2.
Comparison of Technologies for Treating Halogenated VOCs in Water
Technology
Advantages
Disadvantages
Air stripping
Steam stripping
Air stripping with carbon
adsorption of vapors
Carbon adsorption
Effective for high concentrations;
mechanically simple; relatively inexpensive
Effective for all concentrations
Effective for high concentrations
Low air emissions; effective for high concentrations
Biological treatment (ex situ) Low air emissions; relatively inexpensive
Biological treatment (in situ)
Chemical oxidation
Metal-enhanced
dechtorination technology
Relatively inexpensive
No air emissions; no secondary waste;
VOCs destroyed
Target chlorinated VOCs are destroyed; no
secondary waste generated under optimal
performance; no chemicals (such as O3 or H2O2)
required; uses relatively inexpensive zero-valent
metals; relatively low-maintenance cost; can be
applied in situ or aboveground
Inefficient for low concentrations;
VOCs discharged to air
VOCs discharged to air; high energy consumption
Inefficient for low concentrations; requires
disposal or regeneration of spent carbon; relatively
expensive
Inefficient for low concentrations; requires
disposal or regeneration of spent carbon; relatively
expensive
Inefficient for high concentrations; slow rates of
removal; sludge treatment and disposal required
Slow rate of treatment
Not cost effective for high contaminant
concentrations; high maintenance cost
Inability to treat certain halogenated VOCs;
gradual loss of hydraulic conductivity and
reactivity of iron may necessitate periodic
replacement or treatment of the iron medium;
aboveground systems are relatively expensive;
potential for formation of by-products may require
frequent monitoring until optimal performance is
achieved
1.6 Key Contacts
Additional information on the metal-enhanced dechlori-
nation process, the SITE Program, and the SQL site is
available from the following sources:
The Metal-Enhanced Dechlorination Technology
John L Vogan
Project Manager
EnviroMetai Technologies, Inc.
42 Arrow Road
Gueiph, Ontario, Canada N1K 1S6
(519) 824-0432
or
Chien T. Chen
Work Assignment Manager
U.S. Environmental Protection Agency (MS-104)
National Risk Management Research Laboratory
2890 Woodbridge Avenue, Bldg. 10
Edison, NJ 08837-3679
(908) 906-6985
The SQL Site
John Rhodes
Rhodes Engineering, P.C.
505 South Lenola Road
Moorestown, NJ 08057
(609)273-9517
The SITE Program
Vicente Gallardo
U.S. Environmental Protection Agency
National Risk Management Research Laboratory
26 W. Martin Luther King Drive
(MD215)
Cincinnati, OH 45268
10
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Section 2
Technology Effectiveness and Applications Analysis
This section addresses the effectiveness and applicabil-
ity of the metal-enhanced dechlorination technology for
treating water contaminated with chlorinated VOCs. The
SITE demonstration provided extensive data on the
metal-enhanced dechlorination process. This evaluation
of the technology's effectiveness and potential applica-
bility to contaminated sites is based mainly on the
demonstration results. However, the demonstration re-
sults are supplemented by data from other applications
of this technology and additional information provided by
ETI, Rhodes, and other sources.
This section provides an overview of the SITE demon-
stration, discusses SITE demonstration results, and pro-
vides additional performance data. This section also
discusses the following topics regarding the applicability
of the metal-enhanced dechlorination technology: fac-
tors affecting technology performance, site characteris-
tics and support requirements, material handling re-
quirements, technology limitations, potential regulatory
requirements, and state and community acceptance.
Vendor claims regarding the effectiveness and applica-
bility of the metal-enhanced dechlorination technology
are included in Appendix A. Case studies that describe
other applications of the metal-enhanced dechlorination
technology are presented in Appendix B.
2.1 Overview of the Metal-Enhanced
Dechlorination Technology SITE
Demonstration
The SITE demonstration of the metal-enhanced dechlo-
rination technology was conducted over a 13-wk period
from November 1994 through February 1995 at the SQL
site in Wayne, Passaic County, NJ. SITE Program per-
sonnel participated in the evaluation of the technology
by collecting and analyzing water samples from influent,
intermediate, and effluent locations, and by collecting
data regarding system operating parameters, mainte-
nance requirements, and costs.
The following sections describe the metal-enhanced
dechlorination process as demonstrated at the SQL site,
the SITE demonstration objectives, and the procedures
used to meet the project objectives.
2.1.1 Project Background and Technology
Description
Prior to 1984, SQL (now know as SL Industries) manu-
factured printed circuit boards at the SQL site. Past
groundwater sampling at the SQL site indicated the
presence of chlorinated VOCs, including PCE, TCE, and
other compounds, in a shallow, unconsolidated aquifer
and also in an underlying bedrock aquifer.
In 1993, SL Industries responded to a solicitation from
the SITE Program by submitting a proposal for the SITE
Program to evaluate ETI's metal-enhanced dechlorina-
tion technology at the SQL site. Through negotiations
with NJDEP, SL Industries and its consultants (Rhodes
and James C. Anderson Associates, Inc.) determined to
work with ETI to evaluate the metal-enhanced dechlori-
nation process's suitability for remediating contaminated
groundwater at the SQL site.
In the spring and summer of 1994 ETI conducted bench-
scale batch and column tests using contaminated ground-
water from the SQL site. During these studies ETI
determined the apparent half-lives for chlorinated VOCs
present in the SQL site groundwater samples, and for
the byproducts generated by the dechlorination reac-
tion, to estimate the required residence time (in the
reactor) for complete dechlorination of these compounds.
ETI and Rhodes used the results of the bench-scale
studies to custom design a pilot-scale, aboveground
reactor. The reactor design allowed a residence, time of
approximately 26 hours (1.1 days) for water in the
reactive iron at a flow rate of 0.5 gal per minute (gpm).
The residence time was based on the time required to
completely dechlorinate PCE, TCE, 1,2-DCE, and VC.
The aboveground reactor was constructed and began
operating in November 1994. The reactor was a 9-ft-
high, 8-ft-diameter fiberglass-reinforced plastic tank con-
taining a 5.5-ft-thick layer of reactive granular iron. The
reactive iron rested on top of a layer of coarse silica
sand, referred to as "well sand," placed in the bottom of
the reactor. The well sand in the bottom of the reactor
prevented granular iron from washing out into the efflu-
ent pipe. Pea gravel or well sand can also be placed on
top of the reactive iron to act as a prefilter but was not
11
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used during the SITE demonstration as the reactor feed
line was equipped with an in-line 5-fim prefiiter. Eliminat-
ing the upper filter layer also allowed observation of and
direct access to the top of the iron. The top of the reactor
was equipped with a passive gas vent to prevent accu-
mulation of excess pressure, and a manhole with a
sightgiass to allow observation of the reactive iron sur-
face and access to the vessel interior.
The influent groundwater fed to the reactor was col-
lected from the shallow, unconsolidated zone and the
underlying, fractured bedrock aquifer. Two trenches pas-
sively collected contaminated groundwater from the shal-
low zone. The trenches drained to a common sump;
water was pumped directly from the sump to the feed
line for the reactor. Two pumping wells extracted ground-
water from the bedrock aquifer. Water from these wells
flowed to a common pipe and then directly into the
reactor feed pipe. Based on sampling performed by
SITE Program personnel (see Section 2.1.3) the influent
groundwater contained TCE at concentrations ranging
from 54 to 590 jig/L, PCE at concentrations ranging from
4,100 to 13,000 ng/L, and cDCE at concentrations rang-
ing from less than 25 to 1,200 jig/L
The influent groundwater passed through an air elimina-
tor, a 5-jjm water filter (to remove suspended solids,
which may inhibit flow through the reactive iron me-
dium), and then entered the reactor. Water was pumped
into the reactor at a sufficient rate to maintain a 2-ft-deep
layer of water ponded above the iron at all times to
prevent rust from forming on the iron surface and to
minimize variations in volumetric flow through the reac-
tor. The water then flowed through the reactive iron layer
by gravity. The treated water flowed to a perforated pipe
in the well sand and then out through an effluent pipe.
The volumetric flow rate, flow velocity, and residence
time were controlled by the thickness, porosity, and
permeability of the iron layer and the configuration of the
effluent piping. A flow rate of about 0.5 gpm was main-
tained throughout the SITE demonstration period. The
estimated residence time of 27.5 hours equates to a
vertical flow velocity of about 4.8 ft per day, based on an
assumed iron porosity of about 40%, which is the typical
porosity reported by ETI (Vogan 1996).
During the 13-wk SITE demonstration, about 60,800 gal
of groundwater was treated. Treated water was returned
to the shallow, unconsolidated aquifer through six on-
site monitoring wells modified to serve as injection wells.
SL Industries received a 90-day waiver from NJDEP
allowing the treated groundwater to be returned to the
aquifer without SL Industries obtaining a New Jersey
pollutant discharge permit.
2.1.2 Project Objectives
EPA and PRO established primary and secondary ob-
jectives for the SITE demonstration of the metal-en-
hanced dechlorination process. Project objectives were
developed based on EPA's and PRC's understanding of
the metal-enhanced dechlorination technology, SITE
demonstration program goals, and input from ETI. Pri-
mary objectives were considered to be critical for the
technology evaluation, while secondary objectives in-
volved collecting additional data considered useful, but
not critical, to the process evaluation. The demonstra-
tion objectives were defined in the EPA-approved QAPP
dated October 1994 (PRO 1994).
The primary (P) objectives of the technology demonstra-
tion were as follows:
P1 Determine whether effluent from the treat-
ment reactor meets the most stringent of
NJDEP and federal maximum contaminant
level (MCL) discharge requirements for all
chlorinated VOCs which are (1) originally
present in the influent during the demon-
stration period and (2) suspected byproducts
of the dechlorination process. These VOCs
were TCE, PCE, 1,1-dichloroethene (1,1-
DCE), cDCE, and VC.
P2 Determine the removal efficiency of PCE
from groundwater.
The secondary (S) objectives of the technology demon-
stration were as follows:
S1 Assess PCE concentration as a function of
depth as groundwater passed through the
treatment reactor.
S2 Evaluate metals, chloride, sulfate, and total
inorganic carbon (TIC) concentrations in
groundwater passing through the treatment
reactor and use these data to evaluate pre-
cipitate formation, dechlorination activity, and
biological activity within the reactor.
S3 Document geochemical conditions in
groundwater passing through the treatment
reactor.
S4 Document operating and design parameters.
Primary objectives P1 and P2 were established to di-
rectly evaluate the metal-enhanced dechlorination
process's ability to destroy chlorinated VOCs present in
groundwater at the SQL site and were to be evaluated
based primarily on comparison of influent and effluent
samples. Secondary objectives S1, S2, and S3 were to
be evaluated by comparison of data from all (influent,
intermediate, and effluent) locations, thus providing data
on the performance of the reactor and the dechlorination
reaction mechanism. Objective S4 was established to
provide data for estimating costs associated with use of
the metal-enhanced dechlorination process.
2.1.3 Demonstration Procedures
Groundwater at the SQL site was treated in a reactor
(see Figure 1-1) containing a reactive iron medium. The
reactor began operating on November 15, 1994. The
operating parameters (system design and flow rate)
12
-------
were determined by ETI and Rhodes; the SITE program
evaluated the treatment reactor's effectiveness over a
period of 13 wks by collecting independent data. In
general, three types of data were collected: 1) analytical
data for water samples collected from the reactor; 2)
analytical data for samples of other media (reactive iron
and air), and; (3) operating data and observations, such
as cumulative volume treated, flow rate, and electrical
consumption. Sample and data collection procedures
for the demonstration were specified in the EPA-ap-
proved QAPP written specifically for the metal-enhanced
dechlorination process demonstration (PRC 1994). De-
tailed discussions of the sample collection techniques,
analytical methods, and deviations from the QAPP are
discussed in detail in the TER which is available from
the EPA project manager (see Section 1.6).
PRC observed the placement of the reactive iron me-
dium and collected samples of the iron during construc-
tion of the pilot-scale reactor. The SITE team laboratory
(General Testing, Inc. [GTC]) analyzed the iron samples
to determine the bulk density of the reactive iron me-
dium; the data indicated an average uncompacted bulk
density of approximately 2.32 g/cm3, or 144 pcf. During
placement of the iron, ETI recorded the total amount of
iron used in the reactor and determined that about
42,920 Ib of iron was used. The total volume of reactor
space filled by the iron was about 277 ft3; therefore, the
iron's bulk density after settling was about 155 pcf.
During the demonstration, SITE Program personnel also
recorded the flow rate (through the reactor), cumulative
volume treated, and electrical power consumption weekly
over 3 months. The results of the density analysis and
the operating data are summarized in Table 2-5.
During the demonstration, SITE Program personnel col-
lected groundwater samples at the reactor's influent (11),
control (R1), intermediate (R2 through R5), and effluent
(E1) sampling locations (see Figure 1-1). Sampling loca-
tions 11 and E1 were taps on the reactor's influent and
effluent lines, respectively. The other locations (R1
through R5) consisted of slotted stainless steel tubes
that extended to the reactor's interior. The tubes were
capped when not in use; to obtain samples, the tubes
were uncapped, and water flowed out into the sample
containers. Control sampling location R1 was located in
the ponded water on top of the iron medium, and was
considered to be depth "0" for purposes of plotting
contaminant concentrations versus distance through the
reactive iron (see Figures 2-1 through 2-6). Samples
collected at location R1 also allowed evaluation of any
loss of critical VOCs through volatilization to the air and
changes in the other monitoring parameters during
ponding of groundwater on top of the iron medium.
Sampling locations R2 through R-5 were spaced at
various depths through the layer of reactive iron to
evaluate changes as water passed through the reactive
medium.
From November 21, 1994, through February 15, 1995,
SITE Program personnel collected weekly samples of
the influent and effluent water to determine and monitor
the critical analytes for the demonstration, as specified
in Section 1 of the EPA-approved QAPP (PRC 1994).
GTC analyzed these samples for EPA Target Com-
pound List (TCL) VOCs. The TCL includes 64 VOCs;
however, for the SITE demonstration, only chlorinated
VOCs detected in influent water or generated as dechlo-
ri nation byproducts were critical. Based on these crite-
ria, PCE, TCE, 1,1 -DCE, cDCE, and VC were the critical
parameters for the demonstration.
During wks 1, 5, 9, and 13 of the demonstration, SITE
Program personnel collected water samples from loca-
tions R1, R2, R3, R4, and R5, as well as the influent and
effluent locations. GTC analyzed these samples for TCL
VOCs, dissolved metals, chloride, sulfate, and TIC. With
the exception of VOCs at the influent and effluent loca-
tions, all analytes for samples from wks 1, 5, 9, and 13
were considered noncritical. Although the VOCs at loca-
tions R1 through R5 were considered noncritical param-
eters, these samples indirectly supported the primary
objectives by allowing evaluation of byproducts gener-
ated during the dechlorination process.
In addition to the water samples collected for laboratory
analyses, SITE Program personnel collected samples
for field measurements of dissolved oxygen (DO), tem-
perature, specific conductance, pH, and Eh. These field
parameters were measured weekly at the influent and
effluent locations, and at all locations during wks 1,5,9,
and 13. All field parameter measurements were consid-
ered noncritical.
The first sampling event (wk 1) was performed after
about three pore volumes of groundwater had passed
through the treatment reactor. One pore volume equals
the volume of pore space of the reactive iron medium
and is estimated by the developer as about 40 to 45% of
the total volume of the reactive iron medium. Based on
the volume of iron in the .reactor, the pore space was
about 110 ft3, indicating that the pore space of the iron
probably held approximately 827 gal of water at any
given time during the demonstration. According to ETI,
the system did not approach "steady state" operating
conditions, defined as the time at which system perfor-
mance stabilizes and chlorinated VOCs are degraded at
approximately the same rate at which they enter the
system, until the latter part of the demonstration (see
Appendix A).
At the request of EPA, SITE Program personnel also
collected air gas samples from the headspace of the
reactor interior during wks 5, 9, and 13. Although these
samples were not specified in the QAPP, the air gas
samples provided a qualitative assessment of VOC loss
through volatilization from water ponded above the iron.
The samples were collected from the gas vent at the top
of the reactor, and were analyzed by Quanterra, Inc., a
SITE Program team laboratory.
Throughout the demonstration, SITE Program person-
nel checked the flow meter each week and recorded the
flow rate and cumulative volume of water treated in the
13
-------
10000
Distance through reactive iron (in.)
Notes: 1) Sampling location R1 used as distance x = 0 in. 2) Sampling location
R4 (42 in.) not sampled during week 13. All non-detect values assumed to be 0
for plotting purposes.
Figure 2-1. PCE concentration vs. distance through reactive iron.
500
400
3. 300
200
100
£
f \
— / \
A
' >• /•
- / \ / \
1
- / /*
' OCA
""~ t *X ^ * ^^» • a %\
/ *•/" \ rJ X
_.-"'/ X ^
'i / ^ V »
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0- Weekl
~7*S Week 5
•0- Week 9
" -<^ Week 13
10. 20 30 40 50
Distance through reactive iron (in.)
60
70
Notes: 1) Sampling location R1 used as distance x = 0 in. 2) Sampling location
R4 (42 in.) not sampled during week 13. 3) All non-detect values assumed to be
0 for plotting purposes.
Figure 2-2. TOE concentration vs. distance through reactive iron.
14
-------
!
'
8
ID
8
Distance through reactive iron (in.)
Notes: Sampling location R1 used as distance x = 0 in.
Sampling location R4 (42 in.) not sampled during week 13.
Figure 2-3. cDCE concentration vs. distance through reactive iron.
40
«5
c
o
1
d>
u
§
O
30
20
10
i/Veek of testing
H vc
[^ cDCE
9
<1
1.3
10
1.4
2.4
11
1.2
2.8
12
2.8
2.3
13
8.4
37.0
Note: Only concentrations greater than applicable detection limits are plotted.
Figure 2-4. Effluent concentration of VC and cDCE.
15
-------
60
50
40
30
20
100
80
60
40
20
§
£
I
Timefwks) 1 5 9 13
• Water temperature at R2 54 51 45 42
t Ambient temperature 52 34 46 21
Percent PCE removed at R2 UQQ 52 §S 16
Notes: PCE removal based on comparison between samples from locations R1 and R2.
Ambient temperature shown is average of daily high and low temperatures recorded at
Passafc Valley Water Commission measuring station approx. 1 mile from SQL site.
Figure 2-5. Temperature and PCE removal vs. time.
Week 1
Week 5
Week 9
Week 13
Distance through reactive iron (in.)
Notes: Removal efficiencies calculated using data from R1 as initial PCE concentrations.
Location R1 used as distance x = 0 in.
Figure 2-6. PCE removal efficiency vs. depth through reactive iron.
16
-------
reactor. The electrical meter was also checked to deter-
mine power consumption. Personnel also noted any
other pertinent observations regarding the condition and
performance of the reactor.
Rhodes and ETI continued to operate and evaluate the
reactor after the SITE demonstration ended. Approxi-
mately 6 months after the SITE demonstration was
completed, personnel from ETI and Rhodes collected
core samples of the iron, and ETI and the University of
Waterloo analyzed these samples to evaluate precipi-
tate formation in the reactive iron. The samples were not
collected by SITE Program personnel and were not
collected or analyzed in accordance with an EPA-ap-
proved QAPP. For these reasons, the sample collection
and analytical procedures and the analytical results are
not discussed in detail in this ITER. However, ETI's
report of the New Jersey reactor evaluation, which is
included in Appendix A, presents a detailed discussion
of the iron sampling, including ETI's summary and inter-
pretation of the analytical results.
2.2 SITE Demonstration Results
This section summarizes the results from the metal-
enhanced dechlorination technology SITE demonstra-
tion for both critical and noncritical parameters and
discusses the technology's effectiveness for treating
grpundwater contaminated with chlorinated ethylenes.
This section is organized according to the project objec-
tives stated in Section 2.1.2; Sections 2.2.1 and 2.2.2
address the primary objectives, and Sections 2.2.3
through 2.2.6 address secondary objectives.
Statistical analysis of the VOC data for the influent
groundwater was not performed due to variability and
trends in the influent and effluent VOC data sets, and
therefore the degree of confidence in the data support-
ing objectives PI and P2 could not be statistically dem-
onstrated. (This issue is discussed in more detail in the
TER.) However, QA objectives for the critical param-
eters were generally achieved. Also, the primary objec-
tives were evaluated on a week-by-week basis; interpre-
tation of the data was not based on mean values. For
these reasons, the lack of a statistical evaluation should
not significantly affect interpretation of the results.
2.2.1 Objective P1: Compliance with
Applicable Effluent Target Levels
Table 2-1 presents a summary of critical parameter
VOC concentrations detected in samples collected at
the influent and effluent sampling locations during wks 1
through 13. Table 2-2 summarizes all VOC concentra-
tions detected at all (influent, control, intermediate, and
effluent) sampling locations during wks 1, 5, 9, and 13.
As previously discussed, critical analytes for the SITE
demonstration were determined based on the results of
sampling and included chlorinated VOCs present in the
influent groundwater or generated as dechlorination
byproducts. Based on these criteria, the critical analytes
were PCE, TCE, 1,1-DCE, cDCE, and VC. As shown in
Table 2-2, several other VOCs (styrene, toluene, naph-
thalene, methylene chloride) were sporadically detected
during the demonstration. Styrene appears to have origi-
nated in glue used to repair a crack in the lower part of
the reactor tank before the demonstration commenced,
and chloroform and methylene chloride probably origi-
nated as inadvertent laboratory contamination. The
source of the toluene and naphthalene is unknown.
Because these other VOCs do not appear to have been
-present in the influent groundwater or generated as
dechlorination byproducts, they were not considered
critical parameters and are not discussed further in this
report. (Possible sources of these VOCs are discussed
in detail in the TER).
Also note that the relatively high PCE concentrations in
the influent groundwater necessitated dilution of some
samples to bring the PCE concentrations within the
quantifiable range. In diluted samples the detection lim-
its (the Target Reporting Limits specified in the QAPP)
were adjusted for the dilution factor. For this reason, it is
possible that relatively small amounts of cDCE, VC, and
possibly other VOCs, were present in the diluted samples
and were not detected.
Applicable effluent target levels for all VOCs detected
are summarized in Table 2-1. Compliance with the
target levels was evaluated by comparing the effluent
VOC concentrations with the most stringent effluent
target levels. No effluent samples required dilution; there-
fore, the detection limits achieved for these samples
were all lower than the applicable effluent target levels.
The analytical results shown in Table 2-1 indicate that
the TCE and PCE were .detected in the influent during all
weeks of testing; however, the influent concentrations of
PCE and TCE were variable. Influent TCE concentra-
tions ranged from 54 to 590 ng/L, and influent PCE
concentrations ranged from 4,100 to 13,000 jig/L
Although the concentrations of PCE and TCE varied, the
concentrations were within ranges typically observed at
the SQL site. The types and concentrations of VOCs in
the influent may have varied due to the effects of mixing
of groundwater from the two different zones (the shallow
zone and the bedrock aquifer), which typically contain
different concentrations of the various contaminants.
PRC also reviewed the laboratory QA data and the raw
analytical data to evaluate the possibility of laboratory
error and found no indication that the results were
erroneous.
Based on comparison of influent and effluent samples,
the metal-enhanced dechlorination process significantly
reduced the total chlorinated VOC concentrations in
groundwater treated by the reactor. Concentrations of
PCE and TCE in the effluent were consistently below the
detection limit of 0.9 p.g/L during all weeks of testing and
thus were also below the applicable target effluent level
of 1 pg/L for both compounds. As shown in Figures 2-1
and 2-2, PCE and TCE concentrations at intermediate
17
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18
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Table 2-2. Summary of VOC Date from Weeks 1, 5,9, and 13
Week 1 (November 22,1994)
VOCs Detected
R1
Concentration (u.g/L) Detected at Sampling Location:
R2 R3 R4
R5
E1
1,1-DCE
CDCE
PCE
TCE
VC
chloroform
naphthalene
styrene
250UJ
250UJ
5,900
110J
250UJ
230UJ
250UJ
250UJ
250U
250U
6,100
250U
250U
230U
250
250U
1.0U
1.0U
0.9U
0.9U
1.0U
0.9U
1.0U
1.0U
1.0U
1.0U
0.9U
0.9U
1.0U
1.0U
1.0U
1.0U
1.0U
1.0U
0.9U
0.9U
1.0U
1.0U
1.0U
1.0U
1.0U
1.0U
0.9U
0.9U
1.0U
1.0U
1.0U
1.0U
1.0U
1.0U
0.9U
0.9U
1.0U
1.9
1.0U
46
Week 5 (December 21, 1994)
VOCs Detected
1,1-DCE
cDCE
11
SOU
sou
PCE 13.000J
TCE
VC
chloroform
naphthalene
methylene chloride
toluene
styrene
110
sou
45U
SOU
SOU
SOU
sou
R1
SOU
SOU
8,700
93
SOU
45U
SOU
SOU
SOU
SOU
Concentration (ug/L)
R2
SOU
92
4,200
370
SOU
SOU
SOU
SOU
SOU
SOU
Detected at Sampling Location:
R3
1.0U
18
0.9U
0.9U
4.1
0.9U
1.0U
1.0U
1.0U
1.0U
R4
1.0U
1.0U
0.9U
0.9U
1.0U
0.9U
1.0U
1.5
1.4
1.0U
R5
1.0U
1.0U
0.9U
0.9U
1.0U
1.0U
1.0U
1.0U
1.0U
1.0U
E1
1.0U
1.0U
0.9U
0.9U
1.0U
1.0U
1.0U
1.0U
1.0U
15
Week 9 (January 18, 1995)
VOCs Detected
1,1-DCE
cDCE
PCE
TCE
VC
chloroform
styrene
11
25U
25U
8,900
54
25U
25U
25U
. R1
25U
25U
7,300
54
25U
25U
25U
Concentration (fig/L)
R2
13U
100
3,100
220
13U
13U
13U
Detected at Sampling Location:
R3
11
330
69
170
1.0U
1.0U
1.0U
R4
1.0U
1.0U
0.9U
0.9U
1.0U
1.0U
1.0U
R5
1.0U
1.0U
0.9U
0.9U
1.0U
1.0U
1.0U
E1
1.0U
1.3
0.9U
0.9U
1.0U
1.0U
33
Notes:
All concentrations in micrograms per liter (|ig/L).
J = Concentration estimated due to potential unknown bias or because reported concentration is below quantitation limit.
U = Compound not detected; associated value is quantitation limit.
— = No data available; sample location R4 was inaccessiible during week 13.
(continued)
19
-------
Table 2-2. (Continued)
Week 13 (February 15,1995)
VOCs Detected 11
Concentration (ng/L) Detected at Sampling Location :
R1 R2 R3 R4 R5
E1
1,1-DCE
cDCE
PCE
TCE
VC
chloroform
naphthalene
methylene chloride
toluene
styreno
25U
330
7,900
180
25U
25U
25U
25U
25U
25U
25U
85
7,400
130
25U
25U
25U
25U
25U
25U
25U
110
6,200
200
25U
25U
25U
25U
25U
25U
13 —
380 —
1,600 —
400 —
5.0U —
5.0U —
5.0U —
5.0U —
5.0U —
5.0U —
1.0U
1.0U
0.9U
0.9U
1.0U
1.0U
1.0U
1.0U
1.0U
1.0U
1.0U
37
0.9U
0.9U
8.4
1.0U
1.0U
1.0U
1.0U
1.0
Notes:
All concentrations In mlcrograms per liter ((ig/L).
J « Concentration estimated due to potential unknown bias or because reported concentration is below quantitation limit.
U = Compound not detected; associated value is quantitation limit.
—E No data available; sample location R4 was inaccessible during week 13.
sampling locations generally increased over the demon-
stration period but were reduced to below detectable
levels before exiting the reactor in all weeks of testing.
cDCE was not detected in influent groundwater during
wks 1 to 5 or during wks 7 and 9. cDCE was detected in
the Influent groundwater in wks 6,8,10,11,12, and 13.
The detection limit for VOCs (including cDCE) in the
influent groundwater samples was 25 u.g/L for all weeks
except wks 1 and 7; for these 2 wks the influent detec-
tion limits were 250 uo/L and 50 jig/L, respectively. The
detection limits in the influent samples were elevated
due to dilutions required to bring the PCE concentra-
tions within the quantifiable range. For this reason, it is
possible that cDCE was present in the influent ground-
water throughout the demonstration. The concentrations
of cDCE detected in the influent were highly variable,
ranging from 35 to 1,600 u.g/L
Dilution of effluent samples was not required; therefore
the detection limit of 1.0 jig/L for cDCE was achieved for
effluent samples during all weeks. cDCE was not de-
tected in the effluent during the first 8 wks of the demon-
stration but was detected in the effluent during wks 9
through 13. The technology achieved the NJDEP site-
specific discharge limit of 5 u.g/L for cDCE for all weeks
except wk 13. Although cDCE was detected in the
influent groundwater during some weeks, during wks 1,
5, 9, and 13 the highest cDCE concentrations were
detected at the intermediate locations, indicating that
cDCE was also introduced as a byproduct of the dechlo-
rinatlon of PCE and TCE (see Figure 2-3). Generally,
the concentrations of cDCE in the effluent groundwater
Increased consistently from 1.3 u.g/L during wk 9 to 37
ug/L. during wk 13 (see Figures 2-3 and 2-4).
VC was not detected in the influent groundwater during
the SITE demonstration. Because the detection limits
were adjusted for dilutions, it is possible that VC was
present in the influent samples at low concentrations
and was not detected. However, past groundwater moni-
toring data from the SQL site do indicate that VC is
typically present in site groundwater at significant con-
centrations.
Dilution of effluent samples was not required; therefore
the detection limit for all VC in all effluent samples was 1
uo/L. VC was detected in the effluent samples collected
during wks 10, 11, 12 and 13. The effluent concentra-
tions of VC during these weeks increased from 1.2 ug/L
during wk 10 to 8.4 jxg/L during wk 13 (see Figure 2-4).
VC concentrations in the effluent exceeded the appli-
cable MCL of 2 u.g/L during wks 12 and 13 but were
relatively low (2.8 uo/L during wk 12 and 8.4 p,g/L during
wk 13). VC is a common byproduct of PCE, TCE, and
cDCE dechlorination. Because VC was not detected in
the influent groundwater, it was probably formed during
the reductive dechlorination of PCE, TCE, and cDCE.
1,1 -DCE was not detected in the influent samples during
any week of testing but was detected in samples from
location R3 during wks 9 and 13 at concentrations of 11
and 13 ug/L, respectively. However, 1,1-DCE was not
detected in the effluent samples during any of the 13
wks of testing, indicating that the technology consis-
tently achieved the target concentration of 2.0 ug/L for
1,1-DCE.
In summary, the analytical results presented in Table 2-
1 show that the metal-enhanced dechlorination process
20
-------
achieved the effluent target level of 1 jig/L for TCE and
PCE during the entire 3-month demonstration period.
However, the technology did not consistently achieve
the effluent target levels of 5 jjg/L for cDCE and 2 |ig/L
for VC during the last two weeks of the demonstration.
The incomplete dechlorination of cDCE and VC may
have been caused by insufficient contact time on the
reactor, which may have been because PCE persisted
to greater depths within the reactor than anticipated.
Several factors may have caused a reduction in the
reactor's ability to quickly reduce PCE or to achieve
complete dechlorination of byproducts during the later
part of the SITE demonstration.
Insufficient contact time may have resulted from a gradual
reduction in the iron's reactivity and PCE persisting to
greater depths than1 anticipated. Figures 2-1 and 2-5
show that as the demonstration progressed, PCE per-
sisted to increasingly greater depths within the reactor,
and PCE concentrations increased at the intermediate
sampling locations. Factors contributing to reduction of
the iron's reactivity and the persistence of PCE may
have included the flow rate being too high to allow
sufficient residence time, precipitate formation, and tem-
perature effects.
The results of the bench-scale studies and reactor per-
formance before the demonstration indicated that the
0.5 gpm flow rate allowed sufficient retention time for
complete dechlorination of PCE, TCE, and all treatment
byproducts. However, as the reactor approached steady-
state operating conditions in the latter portion of the
demonstration the retention time resulting from a 0.5
gpm flow rate was insufficient to allow complete dechio-
rination of treatment byproducts. Precipitate formation
and temperature variations may have affected reactor
performance and necessitated increased retention time;
however, the flow rate was not adjusted to compensate
for these factors. Instead, predischarge "polishing" (car-
bon adsorption) of reactor effluent was incorporated into
the system, after the SITE demonstration was com-
pleted, to allow flow rates that would be reasonably
representative of a full-scale remediation system.
The results of the SITE demonstration and
postdemonstration studies performed by Rhodes, ETI,
and the University of Waterloo indicated that metal
compounds such as calcium carbonate were precipitat-
ing in the reactive iron (see Appendix A). Past studies by
Gillham and others have indicated that the ratio of iron
surface area to volume of contaminated groundwater is
proportional to the amount of time required to dechlori-
nate a contaminant (Gillham and O'Hannesin 1994).
The formation and deposition of precipitates may coat
the iron and reduce the surface area available for reac-
tion. Reductions in the available reactive surface area
may have reduced the overall reactivity of the iron
medium and increased the time required for dechlorina-
tion to occur. Deposition of precipitates may also affect
the hydraulics of the reactor by impairing flow through
areas where precipitates have formed and causing
channelized, accelerated flow around these areas.
Channelized flow could result in some of the water
"bypassing" portions of the reactive iron, causing parent
compounds (in this case PCE) to reach deeper portions
of the reactor before being dechlorinated. This effect
probably contributed to the persistence of increasing
concentrations of parent compounds (PCE TCE, and
cDCE) to greater depths within the reactor as the dem-
onstration progressed.
Past studies involving TCE indicated that temperature
affects the dechlorination reaction rate (Gillham 1996).
ETI conducted the bench-scale studies in a controlled
laboratory setting with ambient temperatures at about
73° F. However, the SITE demonstration was conducted
outdoors during the late autumn and winter with ambient
air temperatures ranging from about 3° F to 62° F and
generally decreasing over the demonstration period
(based on data from a monitoring station located about 1
mile from the SGL site). The lower ambient air tempera-
tures during the SITE demonstration affected the tem-
perature of the reactor and piping and probably contrib-
uted to a gradual decrease in the temperature of the
water in the reactor. Figure 2-5 compares ambient air
temperature for the site vicinity and water temperature
at sampling location R2 with reactor performance (per-
cent PCE removed) at sampling location R2 over the
demonstration period. As shown in Figure 2-5, the de-
crease in ambient temperature and water temperature
generally coincided with a gradual reduction in PCE
removal efficiency at location R2. According to ETI, the
colder temperatures may have slowed the reaction rate,
resulting in chlorinated VOCs persisting longer as the
demonstration progressed (ET11995).
2.2.2 Objective P2: PCE Removal
Efficiency
PCE was used as an indicator compound to calculate
the removal efficiency of the metal-enhanced dechlori-
nation technology. In accordance with the QAPP, overall
system removal efficiency for wks 1 through 13 was
calculated based on comparison of PCE data from the
influent (11) and effluent (E1) sampling locations. Be-
cause sampling location 11 was located about 3 ft above
the reactive iron, the values used to plot the removal
efficiency versus depth through the reactive iron for wks
1, 5, 9, and 13 (Figure 2-5) were calculated using data
from location R1 to represent initial PCE concentrations.
The results presented in Table 2-1 indicate that PCE
was consistently removed to concentrations below its
detection limit of 0.9 ng/L. The overall PCE removal
efficiencies, based on comparison of concentrations
measured at the influent and effluent locations, were
consistently greater than 99.97% during each week of
testing.
Figure 2-6 depicts the percent removal of PCE as deter-
mined by analysis of water samples from all sampling
locations during wks 1, 5, 9, and 13. Although overall
system removal efficiency exceeded 99.97% during all
21
-------
weeks, data from the intermediate sampling locations
indicate that PCE persisted to increasingly greater depths
within the reactor as the demonstration progressed. The
increasing persistence of PCE suggests a gradual re-
duction in the iron's removal efficiency (see Figure 2-6).
As discussed in Section 2.2.1 PCE may have persisted
to increasingly greater depths as the demonstration
progressed because steady-state conditions were not
achieved until the latter part of the demonstration. It is
also possible that the rate of dechlorination decreased
due to temperature effects or that the reactivity of the
iron was gradually reduced through precipitate forma-
tion. Groundwater at the SQL site was highly mineral-
ized, and analytical results indicate that precipitates
formed during treatment (see Section 2.2.4).
Although TCE and cDCE were also detected in the
Influent groundwater, removal efficiencies were not cal-
culated for these contaminants because the dechlorina-
tion of PCE may introduce TCE, cDCE, and VC at any
point in the system. During some weeks concentrations
of these potential degradation products were higher at
intermediate sampling locations within the reactor than
in the influent. Based on the sampling performed during
the SITE demonstration, it was not possible to account
for the quantity of TCE or cDCE introduced by the
dechlorination process, and therefore removal efficiency
estimates for these compounds would be inaccurate.
2,2.3 Objective S1: PCE Concentration As
A Function of Sampling Location
(Depth)
Figure 2-1 presents PCE concentrations as a function of
depth through the reactive iron, and Figure 2-5 presents
the percent removal of PCE as a function of sampling
location (depth) and temperature, during wks 1, 5, 9,
and 13. The results show that from wks 1 to 13, the
concentration of PCE increased in the intermediate sam-
pling locations, indicating that PCE persisted to increas-
ingly greater depths as the demonstration progressed.
The reason for the decreased efficiency of PCE dechlo-
rination could be reduction in the reactivity of the reac-
tive iron medium, temperature effects, or insufficient
residence time caused by the flow rate being too high.
Although the concentration of PCE at the intermediate
sampling locations increased over time, it remained
below the analytical detection limit in the effluent during
the 13-wk demonstration period (see Section 2.2.1).
The PCE concentration appeared to decrease between
the influent sampling point and sampling point R1 during
wks 5, 9, and 13. TCE concentrations did not change
significantly between locations 11 and R1. The decrease
in PCE concentrations between influent location 11 and
sampling location R1 was possibly caused by several
factors. Contact with the top surface of the reactive iron
as water ponded above the iron layer may have re-
moved some PCE. It is also possible that small amounts
of PCE were removed through mixing and agitation of
water as it flowed into the reactor, or volatilization of
VOCs into the reactor headspace as water ponded
above the reactive iron medium.
To determine the extent of VOC losses in the ponded
water due to volatilization, PRC collected vent gas
samples for analysis during wks 5, 9, and 13. The
results are presented in Table 2-3. The results showed
that PCE and TCE were present in the vent gas at
concentrations ranging from 19,000 to 39,000 and 230
to 650 parts per billion by volume (ppbv) respectively.
No other VOCs were detected. These results indicate
that VOCs may have volatilized into the head space of
the reactor during the demonstration and escaped in the
vent gas. However, the actual mass of the chlorinated
VOCs potentially lost through volatilization appeared to
be low compared to the mass of chlorinated VOCs
dechlorinated by the reactive iron, and therefore volatil-
ization does not affect calculations of removal efficiency
or the overall evaluation of system performance. (Note:
the data presented above on gas samples were not
obtained using procedures outlined in an EPA-approved
Sampling and Analysis Plan [SAP] or QAPP.)
According to ETI and others, past studies indicate that
the metal-enhanced dechlorination process yields VOC
dechlorination rates consistent with a pseudo-first-order
kinetic model, whereby a plot of logarithmic values of
PCE concentrations at time "t" divided by the initial PCE
concentration (log [C/GJ), versus time (t) yields a straight
line.
Bench-scale tests performed by ETI before the demon-
stration using contaminated groundwater from the SQL
site appeared to support the assumption that the dechlo-
rination reaction is first order with respect to the concen-
tration of PCE. However, data gathered during the SITE
demonstration indicate that the dechlorination reaction
may have been affected by reductions in the available
iron surface area as well as by the high concentration of
PCE in the influent water. For this reason, it is possible
that PCE, TCE, cDCE, and VC were competing for
reduced reactive iron surface area, suggesting that the
reaction deviated from pseudo-first-order kinetic behav-
ior during the SITE demonstration (Chen 1996). Data
from wk 13 was incomplete due to the loss of sampling
location R4, and nondetect values at sampling locations
in the lower part of the reactor further reduced the data
available for plotting. Also, evaluation of the order of the
reaction kinetics would require assuming that flow veloc-
ity was constant and could be accurately estimated
based on the volumetric flow rate, and that depth in the
Table 2-3. Vent Gas Concentrations of PCE and TCE
Weeks
Week 9
Week 13
PCE (ppbv)
TCE (ppbv)
39,000
650
24,000
230
19,000
'590
Note: ppbv = parts per billion by volume
22
-------
reactor could therefore be used as a surrogate for time
in analyzing the data. This assumption may not be valid
for the SITE demonstration data because precipitates
may have restricted flow through some parts of the
reactive iron and induced channelized, accelerated flow
through other areas. Gas buildup may also have af-
fected the permeability and flow velocity in some parts of
the iron.
2.2.4 Objective S2: Sulfate, Chloride,
Metals, and TIC Concentrations
The concentrations of sulfate, chloride, dissolved met-
als, and TIC were measured to evaluate chemical and
biological reactions that may take place during treat-
ment. Specifically, these parameters were analyzed to
evaluate dehalogenation of VOCs, metal precipitation,
and the potential for biological growth.
Sulfate concentrations were measured to evaluate, in
part, the potential for sulfate-reducing bacterial growth
and precipitation of metal sulfates. Figure 2-7 shows
that, except during wk 1, the concentration of sulfate did
not change significantly during or after treatment. During
wk 1, the influent sulfate concentration was 27.3 mg/L,
and the effluent sulfate concentration was less than 5
mg/L. However, even during wk 1 the decrease in
sulfate concentration did not progress consistently
through the reactor. For these reasons the sulfate data
provide no evidence of metal-sulfate precipitation or
bacterial growth.
Chloride concentrations were determined because they
may correlate with dechlorination of VOCs. However,
because the background chloride concentrations are
relatively high compared to the VOC concentrations, no
significant trends'in chloride concentrations were noted
during treatment as a result of VOC dechlorination (see
Figure 2-8).
The concentrations of dissolved calcium, magnesium,
and barium generally decreased as water moved through
the reactor (see Figures 2-9, 2-10, and 2-11). During
wks 1,5, and 9, the decrease in concentrations of these
metals coincided with an increase in measured pH
values, suggesting that geochemical conditions were
conducive to decreased solubility and increase precipi-
tation of some metal compounds (see Section 2.2.5).
The decreasing concentrations of barium, calcium, and
magnesium as water moved through the reactor are
probably indicative of metal compounds such as calcium
carbonate precipitating from the water.
The concentration of iron in the influent was generally
below the target report limit of 0.1 mg/L (see Figure 2-
12). The effluent groundwater contained a detectable
iron concentration of 1.1 mg/L only during wk 1. The iron
concentration in sampling location R2 was relatively
high, ranging from 0.09 mg/L (wk 5) to 2.11 mg/L (wk
13). During wk 13, iron was detected at 0.228 mg/L at
sampling location R3. Iron concentrations at the inter-
mediate sampling locations were higher than the con-
centrations at the influent and control sampling locations
probably because of the iron corrosion process de-
scribed by Equation 1-1 a in Section 1.4.1. The iron
concentrations in the intermediate locations were higher
than the concentrations in the effluent probably because
the groundwater pH at intermediate locations was not as
high as the pH at the effluent location; iron is more
dissolved at lower pH.
The concentration of dissolved manganese increased
consistently from the influent and control sampling loca-
tions to maximum concentrations at sampling locations
R3 or R4 (see Figure 2-13). The increase in dissolved
manganese concentrations can probably be attributed
to the dissolution of insoluble manganese species, such
as manganese dioxide (MnO2(s)), potentially present in
the reactive iron medium, as the groundwater moved
through the reactor.
TIC concentrations generally decreased from concen-
trations measured at the influent and control sampling
locations as the groundwater moved through the reactor
(see Figure 2-14). This decrease in TIC concentration
may be caused by the precipitation of metal carbonate
compounds. As shown in Equation 2-1 b, precipitation of
calcium carbonate (CaCO3) (as well as iron carbonates)
may be attributed to the removal of CO32-. The OH'
produced from the dissolution of water as described in
Equation 1-1b may react with bicarbonate ions (HCO3-)
in the groundwater to produce carbonate ions (CO32-),
which in turn may induce the precipitation of calcium
carbonate, as shown in Equation 2-1:
OH~ -» HO + CO"
Ca2+ -i- CO§" -» CaCO3 (s)
(2-1 a)
(2-1 b)
2.2.5 Objective S3: Eh, DO, pH, Specific
Conductance, and Temperature
Figures 2-15 and 2-16 show that Eh and DO generally
decreased once the groundwater flowed past the influ-
ent and control (R1) sampling locations. The decrease
in Eh and DO indicates that the reactor was operating
under reducing conditions.
Table 2-4 presents the pH values measured at the
influent and effluent sampling locations during all weeks
of testing. Figure 2-17 shows the pH values measured at
all locations during wks 1, 5, 9, and 13. Generally, the
pH increased progressively as groundwater moved
through the reactor during all weeks except wk 13.
Equations 1-1a through 1-1d presented in Section 1.4.1
may explain the increase in pH. In these reactions, H* is
consumed so that significant amounts of OH- ions ap-
pear.
23
-------
O)
m
0>
I
3
50
40
30
20
10
0
Sampling location
Rl distance (in.)
O Weekl
O Weeks
Q Week 9
H Week 13
11
_
27.3
34.1
30.2
32.0
R1
0
33.3
34.6
30.5
31.5
R2
12
30.4
34.2
31.2
32.7
R3
24
46.0
34.4
28.8
30.2
R4
42
8.1
35.6
25.2
Not analyzed
R5
60
<5
34.7
23.6
31.7
E1
66
<5
33.8
26.8
31.9
Notes: Only concentrations greater than applicable detection limits are plotted.
R1 distance ** Distance through reactive iron.
Figure 2-7. Sulfate concentration as a function of sampling location (depth).
100
80
60
40
20
0
Sampling location
Rl distance (in.)
n Weekl
O Weeks
O Week9
• Week 13
11
—
85.8
77.7
70.9
83.3
R1
0
73.3
78.1
69.9
78.7
R2
12
75.9
81.1
74.4
81.1
R3
24
76.4
84.7
76.6
81.9
R4
42
78.7
82.9
75.7
Not analyzed
R5
60
73.2
82.8
72.9
83.7
E1
66
73.7
82.9
76.2
83.5
Notes: Only concentrations greater than applicable detection limits are plotted.
R1 distance = Distance through reactive iron.
Figure 2-8. Chloride concentration as a function of sampling location (depth).
During wk 13 the measured pH of the influent groundwa-
ter (8.90) was higher than during any of the previous
weeks, during which the pH in the influent averaged
about 7.8. During wk 13 the measured pH values re-
mained nearly constant as water moved through the
reactor. The cause of the high influent pH and the
apparently constant pH during treatment in wk 13 is
unknown. The constant pH may be indicative of a loss of
the irons's reactive capacity. Also, as shown by Equa-
tions 1-3 and 1-4, precipitation of iron hydroxides may
have caused hydroxide to be consumed in molar quanti-
ties approximately equal to the amounts produced by
dechlorination, resulting in no measurable change in pH.
However, the relative changes in the other field param-
eter values measured during wk 13 generally exhibited
consistency with patterns observed during previous
weeks. This observation suggests that the geochemical
nature of the influent groundwater during wk 13 was not
significantly different from previous weeks and that the
pH values for wk 13 may therefore be erroneous. It is
possible that the field meter used for pH measurements
malfunctioned during wk 13. (Details regarding field
meter performance and calibration procedures are pre-
sented in the TER.)
24
-------
I
o
'Sampling location n
Rl distance (in.) —
rj Week 1 76.1
j-j Week 5 72.1
U Week 9 68.8
M Week 13 77.6
R1
0
63.1
71.7
66.3
74.8
R2
12
48.6
34.3
37.0
54.2
R3
24
34.8
28.0
28.7
39.3
R4
42
23.1
24.3
24.6
Not analyzed
R5
60
19.4
24.0
23.1
25.8
E1
66
33.4
25.5
.21.1
26.8
Note: R1 distance = Distance through reactive iron.
Figure 2-9. Dissolved calcium concentration as a function of sampling location (depth).
Sampling location
Rl distance (in.)
nweekl •
O Week 5
El Week 9
H Week 13
11
—
25.1
22.8
22.6
24.8
R1
0
19.2
22.5
21.1
23.7
R2
12
21.5
21.8
20.8
23.7
R3
24
15.7
21.9
18.4
23.6
R4
42
2.55
19.2
15.7
Not analyzed
R5
60
1.32
19.2
13.8
20.7
E1
66
10.9
17.9
15.2
23.1
Note: R1 distance = Distance through reactive iron.
Figure 2-10. Dissolved magnesium concentration as a function of sampling location (depth).
The specific conductance of groundwater decreased as
a function of vertical distance through the aboveground
reactor (see Figure 2-18). The decrease in the specific
conductance of groundwater is probably caused by the
removal of ions from groundwater during treatment.
Removal of ions may occur through the formation of
metal-hydroxide or metal-carbonate precipitates. The
formation of these precipitates may remove metal cat-
ions, hydroxyl ions, and carbonate ions from the ground-
water.
Figure 2-19 shows that the influent groundwater tem-
perature varied significantly, ranging frorh about 42°F to
60°F, and generally decreased over the demonstration
period. The variability in influent groundwater tempera-
ture (18°F) is probably due to the effects of ambient air
temperature on the reactor and the influent piping. The
potential effect of temperature on the reaction rate of
PCE in the metal-enhanced dechlorination technology
has not been studied in detail; however, as discussed in
Section 2.2.1, according to ETI, past studies involving
TCE have shown that temperature influences the dechlo-
rination reaction rate.
25
-------
Sampling location
Rl distance (in.)
n Week 1
n WeekS
Q Weeks
@ Week 13
11
-
0.311
0.299
0.298
0.327
R1
0
0.258
0.297
0.255
0.322
R2
12
0.171
0.038
0.036
0.072
R3
24
0.230
0.034
0.035
0.031
R4
42
0.192
0.102
0.031
Not analyzed
R5
60
0.125
0.136
0.065
0.045
E1
66
<0.020
0.148
0.064
. ...0.026,
Notes: Only concentrations greater than applicable detection limits are plotted.
R1- distance = Distance through reactive iron.
Figure 2-11. Dissolved barium concentration as a function of sampling location (depth).
2.5
2
1.5
1
0.5
0
Sampling location
Rl Distance (in.)
n Week 1
D Week 5
D Week 9
• Week 13
11
-
0.114
<0.1
<0.05
<0.05
R1
0
<0.1
<0.1
<0.05
<0.05
R2
12
<0.1
0.091
0.557
2.11
R3
24
<0.1
<0.1
<0.05
0.228
R4
42
<0.1
<0.1
<0.05
Not analyzed
R5
60
<0.1
<0.1
<0.05
<0.05
E1
66
1.05
<0.1
<0.05
<0.05
Notes: Only concentrations greater than applicable detection limits are plotted.
R1 distance - Distance through reactive iron.
Figure 2-12. Dissolved iron concentration as a function of sampling location (depth).
2.2.6 Objective S4: Operating and Design
Parameters and Operating Problems
Table 2-5 summarizes information collected pertaining
to operating and design parameters during the SITE
demonstration.
The operating and design parameters presented in Table
2-5 were used to calculate O&M costs and capital costs
presented in Section 3.0.
Operating problems encountered during the SITE dem-
onstration generally consisted of (1) formation of a pre-
cipitate or silt "crust" on the top surface of the reactive
iron layer, (2) growth of algae in the ponded water above
the iron, (3) freezing/blockage of sampling ports,
and (4) precipitation of metal compounds in the
reactive iron.
During the early part of the SITE demonstration, a layer
of gray, crust-like material was observed on the top of
26
-------
Sampling location
Rl Distance (in.)
QWeekl
0 Week 5
g| W eek 9
|§ Week 13
11
—
0.0122
<0.01
<0.01
0.026
R1
0
0.0367
<0.01
0.0449
0.017
R2
12 •
0.812
0.311
0.166
0.142
R3
24
0.246
1.400
0.470
0.284
R4
42
0.278
0.270
0.883
Not analyzed
R5
60
0.0985
0.025
0.222
0.213
E1
66
<0.01
0.135
0.078
0.649
Notes: Only concentrations greater than applicable detection limits are plotted.
R1 distance = Distance through reactive iron.
Figure 2-13. Dissolved manganese concentration as a function of Ssampling location (depth).
Sampling location
Ri distance (in.)
fj Week 1
Q Week 5
H Week 9
H Week 13
11
—
40.0
38.0
18.0
40.0
R1
0
36.0
39.0
18.0
37.0
R2-
12
18.0
18.0
14.0
31.0
R3
24
4.0
12.0
11.0
19.0
R4
42
<1
4.8
6.5
Not analyzed
R5
60
<1
3.2
4.7
5.3
E1
66
<1
3.7
5.3
8.3
Notes: Only concentrations greater than applicable detection limits are plotted.
R1 distance = Distance through reactive iron.
Figure 2-14. TIC concentration as a function of sampling location (depth).
the iron layer. The material may have been a precipitate
layer, fine silt particles that were suspended in influent
groundwater and were small enough to pass through the
5-pjn prefilter or a combination of precipitates and siit.
To minimize the possibility of this crust-like material
blocking the upper part of the iron and reducing flow,
Rhodes personnel raked the upper surface of the reac-
tive iron and broke up the crust on a monthly basis.
Raking of the upper surface of the iron was accom-
plished without stopping flow to the reactor.
Visual inspection of the aboveground reactor also indi-
cated that algae were present on the upper portions of
the reactor vessel walls and in the ponded water above
the iron. On March 1, 1995, about two weeks after the
SITE demonstration was completed, Rhodes added a
commercial pool algicide (chlorine pellets), in a floating
canister, to the ponded water above the iron. After
several days, the system was temporarily shut down
and the dead algae were removed (see Section 2.4.4).
Rhodes then placed an opaque, black plastic cover over
27
-------
Sampling location
Rt distance (in.)
D Week 1
D Week 5
O Week 9
H Week 13
11
-
-180.1
209.4
154.1
196.8
R1
0
-167.1
205.7
65.5
83.1
R2
12
-244.6
-147.6
-205.1
-193.0
R3
24
-306.3
-191.1
-357.1
-361.0
R4
42
-520.7
-260.9
-355.4
Not measured
R5
60
-450.3
-257.5
-303.1
-321.0
E1
66
-343.0
-238.8
-205.8
-302.0
Note: R1 distance = Distance through reactive iron.
Figure 2-15. Eh as a function of sampling location (depth).
Sampling location
Rl Distance (in.)
O Weekl
O Week 5
D Week 9
g| Week 13
11
_
5.2
6.1
7.9
3.6
R1
0
4.2
5.0
5.7
3.5
R2
12
2.9
2.6
3.8
3.3
R3
24
3.5
2.8
3.3
3.2
R4
42
2.9
3.1
2.6
Not measured
R5
60
4.1
3.0
2.4
2.6
E1
66
2.9
3.4
4.2
3.6
Note: R1 distance - Distance through reactive iron.
Figure 2-16. DO as a function of sampling location (depth).
the reactor to restrict sunlight. No further algal growth
was observed during subsequent reactor operations.
Sampling ports became blocked with ice several times
during the SITE demonstration. SITE program person-
nel used a heat gun to melt the ice and restore flow and
allow sampling as necessary. However, during wk 13,
flow could not be restored to sampling port R4, indicat-
ing that the port was obstructed with some other, unde-
termined form of blockage.
As previously discussed, results of the analyses of the
water samples collected during the SITE demonstration
suggested that metal compounds were precipitating in
the reactive iron. In July 1995, about 5 months after the
SITE demonstration ended, ETI and Rhodes personnel
collected samples of the reactive iron medium to evalu-
ate changes in the iron since emplacement in November
1994. Visual inspection of the reactive iron at the time of
sampling indicated that the top 2 in. of the iron had
become bound into a hardpan-like layer. Below this
hardened layer, the iron was still loose. A small amount
of a white material was observed about 1 in. below the
hardened layer.
ETI and Rhodes personnel collected a core sample of
the iron from immediately beneath the reactor manhole.
The core sample was subdivided into aliquots from 1,2,
28
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Table 2-4 pH at Influent and Effluent Sampling Locations
Q.
8 -
Week
1
2
3
4
5
6
7
8
9
10
11
12
13
pHatH:
pHatEl:
7.52
7.67
7.90
8.42
7.52
7.58
8.11
7.73
7.66
7.57
7.17
7.66
8.90
8.72
8.63
8.72
10.82
10.69
9.57
9.63
9.69
9.36
9.37
9.76
9.60
8.91
Sampling location
Rl distance (in.)
D Week 1
Q Weeks
H Week 9
H Week 13
11
-
7.52
7.52
7.66
8.90
R1
0
7.30
7.43
7.77
8.63
R2
12
7.36
8.75
7.78
8.74
R3
24
7.89
8.48
7.92
8.81
R4
42
8.14
10.72
9.17
Not measured
R5
60
8.32
10.96
9.04
8.73
E1
66
8.72
10.69
9.36
8.91
Note: R1 distance = Distance through reactive iron.
Figure 2-17. pH as a function of sampling location (depth).
4, 6, 8, 10, 12, 18, 24, 30, and 36 in. along the core.
Each aliquot was further divided into three portions. One
portion was analyzed for iron, calcium, and magnesium;
a second portion was analyzed for carbonate content,
and the third portion was examined using scanning
electron microscopy to identify specific precipitate com-
pounds based on crystal structure. Unused reactive iron
samples that had been collected at the time of demon-
stration startup were also analyzed for comparison with
samples collected in July 1995. All samples were ana-
lyzed by the University of Waterloo. The analyses were
not performed in accordance with an EPA-approved
QAPP; therefore, quantitative results are not discussed
in this report or in the TER. However, ETI's report
(Appendix A) provides a detailed discussion of these
analytical techniques and results.
According to ETI, the analytical results showed that
calcium and carbonate concentrations were higher in
the samples from the top 6 in. of the iron than in the
samples from deeper within the iron, and also higher
than in the unused iron samples, suggesting that cal-
cium carbonate was precipitating in the upper part of the
iron layer. Magnesium and total iron concentrations
showed little variance between samples. The analyses
performed did not evaluate variations in concentrations
of specific iron compounds, such as iron carbonate,
Fe(OH)2, or Fe(OH)3. According to ETI, the scanning
electron microscopy confirmed the analytical results,
indicating that calcium and iron carbonate precipitate
were present in the samples from the upper portion of
the reactor (ET11995).
29
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500
Sampling location
Rl distance (in.)
D Week 1
D Weeks
D Week9
• Week 13
11
-
399
NA
437
384
R1
0
364
NA
420
316
R2
12
259
NA
291
R3
24
183
NA
310
283
R4
42
165
NA
286
Mot measured
R5
60
147
NA
275
261
E1
66
160
NA
276
272
Notes: 1) specific conductance not measured during week 5. 2) mho/cm=mhos/centimeter
3) Rl distance=distance tthrough reactive iron
Figure 2-18. Specific conductance as a function of sampling location (depth).
Sampling location
Rl distance (in.)
Q Week 1
O Week5
H- Week 9
• Week 13
11
~
60.3
56.7
48.7
41.7
R1
0
56.2
52.7
46.9
42.1
R2
12
54.4
51.4
45.2
42.4
R3
24
55.9
51,9
48.0
42.1
R4
42
55.8
51.2
48.3
Not measured
R5
60
55.3
51.0
49.3
41.6
E1
66
55.0
51.0
49.6
42.3
Notes: Only concentrations greater than applicable detection limits are plotted.
R1 distance = Distance through reactive iron.
Figure 2-19. Temperature as a function of sampling location (depth).
Table 2-5. Summary of Operating and Design Parameters
Reactive Iron Media
Initial weight
Volume
Bulk density of iron -
uncompacted sample
Iron density - based on
volume used In reactor
Porosity/pore volume
Electricity consumption
Groundwater flow rate/velocity
Cumulative volume of treated water
43,000 Ib or 21.5 tons
277 ft3
2.32 g/cm3 or144.8 lb/ft?
2,48 rj/cm3 or 155 lb/ft3
0.4/830 gallons
5 kwh per day
0.5 gpm/4.8 ft/day
60,800 gallons
The formation of metal precipitates in the upper portion
of the reactor may be one of the most significant O&M
problems encountered in aboveground reactors using
the metal-enhanced dechlorination process. ETI is cur-
rently evaluating O&M methods to inhibit precipitation,
and physical and chemical treatment methods to peri-
odically remove precipitates.
2.3 Additional Performance Data
In addition to the SITE demonstration results, two other
field applications of the metal-enhanced dechlorination
technology were considered to obtain additional infor-
mation about the process. However, analytical results
from these field applications will not be used in this
30
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report to draw conclusions because they may not have
been obtained in accordance with EPA quality assur-
ance guidance for the preparation of Level 2 QAPPs.
These applications consisted of the field test conducted
at the Canadian Forces Base in Borden, Ontario, Canada
(Borden site), and a field test and full-scale installation at
a California semiconductor facility. The application of
the metal-enhanced dechlorination process in each of
these sites is discussed below.
2.3.1 Borden Site
At the Borden site, an in situ reactive wall was installed
in June 1991 to treat groundwater contaminated with
PCE and TCE. The source of the plume was located
about 4 m (13.12 ft) below ground surface and 1 m (3.28
ft) below the water table. Maximum contaminant con-
centrations were about 250,000 and 43,000 pg/L for
TCE and PCE, respectively. The permeable wall was
constructed about 5.5 m (18 ft) downgradient from the
source. The aquifer material was a medium to fine sand,
and the average groundwater flow velocity was about 9
cm/day (0.3 ft/day).
The reactive wall was constructed by driving sealable-
joint sheet piling to a depth of 9.7 m (31.8 ft) to form
temporary walls for subsurface rectangular cell 1.6 m
(5.3 ft) thick, 5.5 m (18 ft) long, and 2.2 m (7.2 ft) deep,
situated 1.3 m (4.3 ft) below the water table. The native
sand inside of the sheet piling cell was excavated and
replaced by the reactive material, consisting of 22% of
iron grindings and 78% coarse carbonate sand by weight.
After the reactive mixture was installed, the sheet piling
was removed, allowing the contaminant plume to pass
through the reactive wall.
Samples were collected and analyzed over a 474-day
monitoring period. The results indicate that PCE and
TCE concentrations decreased consistently while the
concentrations of chloride increased. The average maxi-
mum concentrations of PCE and TCE downstream of
the wall were about 10% of the influent concentration,
indicating a substantial loss within the wall. However,
the concentrations of PCE and TCE were about three
orders of magnitude above site drinking water stan-
dards. The results also indicated that cis- and trans-1,2-
DCE were produced as a result of PCE and TCE degra-
dation in the wall. DCE isomers were degraded as they
passed through the wall, although effluent concentra-
tions remained above site drinking water standards. No
VC was detected in the samples, and no bacterial
growth was observed. pH measurements were also
taken, the results of which showed little change in pH as
a result of treatment. It is suspected that the pH changes
normally seen as a result of treatment were not ob-
served because of the buffering capacity of the carbon-
ate sand used during the treatment process. According
to ETI, examination of samples of the reactive iron using
x-ray diffraction and Scanning Electronic Microscope
(SEM) techniques showed no metal precipitates on the
iron.
Samples were also collected after 4.3 years of opera-
tion. The results indicated that performance had not
changed significantly over the 4.3 years of operation
(O'Hannesin).
2.3.2 California Semiconductor Facility
Groundwater from the California semiconductor facility
contained TCE ranging from 50 to 200 |xg/L, cDCE
ranging from 450 to 1,000 jig/L, VC ranging from 100 to
500 jig/L, and Freon 113 ranging from 20 to 60 jig/L
An aboveground pilot-scale demonstration reactor con-
taining 50% iron and 50% sand by weight was installed
at the site and operated for a period of 9 months. The
groundwater at the site was highly mineralized. Al-
though precipitate formation was evident, it did not
appear to interfere with treatment of the VOCs of con-
cern.
Based on the results obtained from treatment in the
reactor, a full-scale in situ treatment wall was installed in
December 1994. The wall consisted of 100% granular
iron, was 1.2 m (3.9 ft) thick, 12 m (39.4 ft) long, and was
situated vertically between depths of about 4 m (13.2 ft)
and 12 m (39.4 ft) below ground surface. A layer of pea
gravel, about 30 cm (0.98 ft) thick, was installed on. both
the upgradient and downgradient sides of the iron wall.
As of July 1995, data was only available for samples
collected 1 month after installation. No chlorinated or-
ganic compounds were detected in monitoring wells
downgradient from the wall, with one exception; cDCE
was present in one well at a concentration of 4 jig/L
Although the initial results appear to indicate that the
system is effectively dechlorinating VOCs, there is insuf-
ficient data at this time to evaluate long-term perfor-
mance of the in situ treatment system at the site. (Yamane
etal 1995.)
2.4 Factors Affecting Performance
Factors potentially affecting the performance of the metal-
enhanced dechlorination process include (1) feed waste
characteristics, (2) operating parameters, and (3) main-
tenance requirements.
2.4.1 Feed Waste Characteristics
Feed waste characteristics that may affect the perfor-
mance of the metal-enhanced dechlorination technology
include the types and concentrations of organic and
inorganic substances present in the water to be treated.
Organic Compounds
According to its developer, the metal-enhanced dechlo-
rination technology has successfully degraded several
organic compounds (Vogan et al 1995). These com-
pounds are PCE; TCE; cis- and trans-1,2-DCE; 1,1-
DCE; VC; 1,1,1-trichloroethane; trichloromethane; 1,2-
31
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dibromoethane; 1,2,3-trichloropropane; 1,2-dichloropro-
pane; and Freon 113.
The performance of the metal-enhanced dechlorination
technology is typically evaluated based on the half-life of
the compounds in the waste. The half-life is defined as
the time required to degrade a compound to one-half of
its original concentration in the waste being treated. The
half-lives of the different VOCs vary depending on con-
centration and other site-specific factors, and the half-
lives using treatment by the metal-enhanced dechlorina-
tion process generally appear to be less than those
reported for biological and other abiological processes
{Gillham 1995). ETl's estimations of the half-lives for the
contaminants observed in the aboveground reactor at
the SQL site before the SITE demonstration are in-
cluded in ETI's report in Appendix A.
Though the reported half-lives for a particular compound
vary, half-lives tend to increase with decreasing degrees
of chlorination. This is particularly evident when consid-
ering a single group of compounds, such as chlorinated
ethenes. PCE and TCE degrade at reasonably similar
rates; the rate is lower for DCE, and lower yet for VC.
This trend is consistent with reductive dechlorination,
since the most highly chlorinated compounds are the
most oxidized and would be expected to be the least
stable under reducing conditions (Gillham 1995).
Although the degradation of compounds such as chlo-
romethane, diehloromethane, 1,2-dichloroethane, and
1,4-dichIorobenzene is thermodynamically favorable,
these compounds have not been observed to degrade in
the presence of iron. Also, because nonchlorinated aro-
matic compounds such as benzene, toluene, and xy-
lenes are at a reduced state, they are not expected to be
degraded through reductive degradation in the presence
of zero-valent metals. Therefore, these compounds are
not expected to be degraded by the metal-enhanced
degradation process.
Although a large number of chlorinated VOCs can be
degraded in the presence of iron, further studies are
required for many of the VOCs to evaluate the occur-
rence of toxic and persistent degradation products. In
addition, the degradation products generally degrade at
much lower rates than the parent compound. Therefore,
even though they occur at much lower concentrations,
degradation products may be the critical parameter with
regard to determining the required residence time in the
design of metal-enhanced dechlorination technology sys-
tems.
Inorganic Compounds
The effect of inorganic compounds on the VOC degra-
dation process represents the greatest uncertainty with
respect to the long-term, low-maintenance operation of
the metal-enhanced dechlorination technology. As shown
In Equations 1-1 a through 1-1d in Section 1.4.1, Fe2t is
produced from oxidation of Fe° by water and by chlori-
nated hydrocarbons. Equation 1-1 also indicates a net
increase in hydroxyl ions, increasing the pH of ground-
water during treatment. At elevated pH, Fe2* precipitates
as either Fe(OH)2(s) or Fe(OH)3(s), depending on the
dissolved oxygen concentration, and provided that Eh is
sufficiently low. In addition to iron, other metals present
in groundwater may also precipitate. At elevated pH,
iron may precipitate as FeCO3(s), depending on the
carbonate concentration of groundwater. Furthermore,
carbonate precipitates of calcium, magnesium, barium,
and other metals may also form. These precipitates may
be deposited on the reactive iron medium and may limit
the flow of groundwater through the treatment system. It
is also possible that precipitates may block the iron
surfaces available for reaction causing a reduction in the
iron's reactive capacity over time. Therefore, O&M pro-
cedures may need to compensate for the formation of
precipitates during treatment of highly mineralized wa-
ter.
Site- or waste-specific treatability studies are required to
identify the solid phases that may form, to determine
precisely the factors that control their formation, and to
determine the effects on both reductive dehalpgenation
rate and hydraulic properties. Before proceeding with a
full-scale remediation, it may be necessary to develop
operating methods to prevent precipitate formation or
maintenance techniques to periodically remove precipi-
tates once they form.
2.4.2 Operating Parameters
Based on information provided by the developer, sev-
eral operating parameters that may affect system perfor-
mance were identified. These parameters include (1)
iron surface area-to-groundwater volume ratio, (2) pH,
(3) residence time, and (4) temperature of the reactor
and influent water.
Ratio of Iron Surface Area-to-Groundwater
(Solution) Volume
A precise quantitative correlation between the iron sur-
face area-to-water volume ratio on the dechlorination
reaction rate has not been established. Experimental
results indicate that the rate of dehalogenation increases
as the ratio of iron surface area to groundwater volume
increases. For this reason increasing the iron surface
area in contact with the water at any given time should
increase the dechlorination reaction rate, provided all
other factors remain constant (Gillham, and O'Hannesin
1994; Gillhan 1996). Based on this rationale, it therefore
appears that reductions in the amount of iron surface
area, possibly caused by precipitates forming a coating
on the reactive iron granules, could increase contami-
nant half-lives.
pH
Data gathered during the SITE demonstration were not
sufficient to differentiate between the potential effects of
pH and other factors on the reaction rate. In general,
32
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published research regarding the effects of pH on the
dechlorination reaction rate appears to be inconclusive.
If metals are present in the groundwater, increasing pH
may cause them to precipitate. The precipitates formed
may coat the surface of the reactive iron medium, or
they may cause the pore spaces of the reactive iron
medium to clog, resulting in reduced reaction rates.
Bench-scale studies conducted by the developer using
water from the SQL site suggested that formation and
deposition of metal precipitates during treatment would
cause about 12% of the original porosity in a 100% iron
column to be lost annually. However, the amount of
porosity loss is site specific; ETI reports projected poros-
ity losses ranging from 2 to 15% in studies involving
water from other sites. The extrapolation of these esti-
mates to field-scale systems depend on the kinetics of
precipitation under field conditions.
Residence Time
Residence time is defined as the time that a "particle" of
groundwater flows through the reactive iron layer in an
aboveground reactor or through a reactive iron treat-
ment wall in an in situ installation. In an aboveground
reactor, the residence time (volume of pore space in the
reactive iron bed-s-volumetric flow rate) is controlled by
the pore volume, permeability hydraulic conductivity thick-
ness of the reactive iron layer, and the configuration of
the effluent piping. The residence time of groundwater in
the treatment medium must be sufficient to reduce influ-
ent concentrations of VOCs to cleanup standards. The
required residence time for a particular application is
estimated based on the longest residence time required
for any particular compound to degrade to cleanup
standards. To allow for degradation of the VOCs origi-
nally present and possible reaction products, the resi-
dence time required is calculated as the sum of the
longest residence time required for the VOCs originally
present and the longest residence time of any reaction
products. For example, the design of the aboveground
reactor at the SQL site was based on maximum pro-
jected half-lives of about 0.5 hours each for PCE and
TCE, 3.7 hours for cDCE, and 1.2 hours for VC. Based
on these estimates cDCE was the controlling parameter
for the system design (Vogan et al 1995).
In an in situ system, the required thickness of the
reactive wall in the direction of groundwater flow is
determined based on the degradation rate of the com-
pounds in the groundwater and the velocity of ground-
water moving through the wall. The wall must be thick
enough to allow adequate time for chlorinated VOCs to
be reduced from influent concentrations to the appli-
cable water quality criteria and must also allow sufficient
time for dechlorination of any byproducts.
Temperature
Data gathered during the SITE demonstration were
insufficient to quantitatively evaluate the effects of tem-
perature on the dechlorination process, as it was not
possible to differentiate between temperature effects
and other factors that may have affected system perfor-
mance. However, data from a nearby monitoring station
indicates that the average daily temperature in the area
generally declined over the course of the 13-wk demon-
stration. As a result, the temperature of the piping be-
tween the collection points and the reactor, and the
temperature of the reactive iron, also apparently de-
clined, resulting in a gradual decrease in water tempera-
tures measured over the course of the demonstration.
-The decline in temperature appeared to generally coin-
cide with the increasing persistence of PCE within the
reactor as the demonstration progressed. According to
ETI, studies involving TCE have shown that the dechlo-
rination reaction rate may decrease with decreasing
temperature. For these reasons, it appears that ambient
temperature effects must be considered in aboveground
reactor design, especially if the system is located out-
doors in cold climates.
2.4.3 Maintenance Requirements
The maintenance requirements of the ETI system sum-
marized in this section are based on direct observation
and discussions with Rhodes personnel. This section
addresses only maintenance requirements for the reac-
tor vessel of the metal-enhanced dechlorination pro-
cess,, and not general maintenance requirements for
support components, such as the groundwater collec-
tion and distribution systems. Regular maintenance is
required for other system components as outlined in
Sections 2.5.3 and 2.5.5.
High concentrations of suspended solids in influent
groundwater may accumulate and physically block the
reactive iron medium, reducing flow. Also, metal precipi-
tates may coat the reactive iron surface, reducing the
reactivity. Based on the aboveground reactor at the SQL
site, maintenance procedures to counteract these prob-
lems may consist of periodically scarifying the upper
(influent) surface of the iron and periodic replacement of
a portion of or all or of the reactive iron. ETI is also
studying ways to perform in situ chemical treatment of
the iron to remove precipitates, possibly eliminating the
need to periodically replace the iron.
In aboveground reactors, algae may form in the ponded
water and retard flow through the system; however, the
effects of algae and bacterial growth on the dechlorina-
tion reaction are unknown. During the SITE demonstra-
tion, algae were observed on the surface of the ponded
water above the iron; however, no evidence of algae or
biological coatings was observed within the reactive iron
medium. Excessive algal growth in the water above the
iron could eventually restrict the flow of water through
the system; however, as previously discussed, algal
growth can be relatively easily controlled by O&M proce-
dures. Periodic O&M to control algal growth may consist
of limiting light in the reactor and occasional use of
chemical algicides.
33
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2.5 Site Characteristics and Support
Requirements
Site-specific factors can impact the application of the
metal-enhanced dechlorination process, and these fac-
tors should be considered before selecting the technol-
ogy for remediation of a specific site. Site-specific fac-
tors addressed in this section are site access, area, and
preparation requirements; climate; utility and supply re-
quirements; support systems; and personnel require-
ments.
According to ETI, both in situ treatment wall installations
and aboveground treatment reactors are available (see
Section 4, Technology Status, and Appendix A, Vendor's
Claims for the Technology). The support requirements
of these systems are likely to vary. This section presents
support requirements based on the information col-
lected for the reactor used at the SQL site.
2.5.1 Site Access, Area, and Preparation
Requirements
For an aboveground reactor, the site must be accessible
to heavy construction equipment necessary to install a
reinforced concrete pad to support the reactor vessel. A
tractor trailer is necessary to transport the reactor vessel
to the site, and a crane is necessary to move the reactor
vessel into place. A geotechnical evaluation of the site
soils under the pad may be necessary to develop the
design criteria of the concrete pad. Air space under the
swing area of the crane must be clear of obstacles (such
as overhead wires or pipes). The area around the reac-
tor vessel should allow additional space for personnel to
access all surrounding areas and piping.
The reactor vessel must be plumbed to an influent
wastewater supply and effluent discharge line. These
systems direct influent to the reactor for treatment and
remove treated groundwater for discharge.
2.5.2 Climate Requirements
The reactor vessel at the SQL site was installed out-
doors. In regions that are subject to freezing tempera-
tures during the winter months, abovegroundwater lines
and ports may freeze. The plumbing and aboveground
reactor could be installed inside a building to minimize
climatic effects. If the aboveground reactor is to be used
outdoors in a cold climate, provisions should be made
for heating and insulating exposed piping and control
units and Installing insulated housings on control units.
At the SGL site, the water lines carrying groundwater to
and from the reactor were insulated with foam pipe
insulation and heat tape to prevent freezing. Also, the
potential effects of temperature on the dechlorination
reaction rate were discussed in Section 2.4. In cold
climates, system design and operating parameters may
need to compensate for the potential effects of tempera-
ture on reaction rate.
2.5.3 Utility and Supply Requirements
The reactor vessel flow controllers and pumps operate
using 110-volt, 1-phase electrical service. The flow con-
trollers are electrical relays that operate float switches
and pumps to control wastewater flow and reactor ves-
sel liquid levels. The vessel and the flow control system
may periodically require spare parts, most of which are
easily obtained. Spare parts may include electrical re-
lays or float switches in the flow and level control sys-
tem.
Supply requirements may include fresh iron medium to
replace iron that has lost an unacceptable amount of its
reactive capacity and disposable pleated fabric filter
cartridges (see Section 2.5.4).
2.5.4 Required Support Systems
During the demonstration, pretreatment and posttreat-
ment requirements for groundwater entering and exiting
the reactor vessel were minimal. Pretreatment involved
removing suspended solids using a replaceable pleated
fabric filter cartridge. Removal of suspended solids was
required to reduce influent solids and the possibility of
clogging of the reactive iron medium.
Due to the incomplete dechlorination of cDCE and VC
observed in the latter part of the SITE demonstration, a
postreatment system consisting of a carbon adsorption
unit was added after the SITE demonstration ended to
remove residual trace levels of these VOCs from the
effluent prior to discharge. This was necessary to meet
NJDEP permit requirements. Postreatment would prob-
ably not have been necessary if the reactor had main-
tained its initial capacity to remove all byproducts of
PCE and TCE dechlorination throughout the entire dem-
onstration period. As previously discussed, the reactor's
performance may have been affected by precipitate
formation, temperature variations, and other factors.
Full-scale systems may require design features or main-
tenance techniques to minimize variations in system
performance.
As discussed in Section 2.2.5, DO decreases and pH
increases during treatment. Generally, National Pollut-
ant Discharge Elimination System (NPDES) permits have
limits for pH and DO. Therefore, posttreatment to adjust
pH and DO may be required for other applications.
2.5.5 Personnel Requirements
Personnel requirements for the ETI system are minimal.
Generally, the system is checked weekly by a site
engineer. The engineer checks meter readings to track
total flow through the system, checks water levels in the
extraction and injection wells and in the reactor vessel,
and visually inspects the reactor vessel walls and reac-
tive iron medium for the presence of biological growth or
precipitates. It is critical that the level of wastewater in
the reactor vessel is monitored to ensure that untreated
wastewater does not overflow from the reactor vessel.
34
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Samples from influent, intermediate, and effluent ground-
water are obtained periodically to evaluate system per-
formance.
Service personnel (such as a plumber or electrician)
should be available to maintain the water collection and
distribution systems, power supply, and controller, if
problems with these systems are identified.
Before operating the ETI system at a hazardous waste
site, the operator should have completed the training
requirements under the Occupational Safety and Health
Act (OSHA) outlined in 29 CFR §1910.120, which cov-
ers hazardous waste operations and emergency re-
sponse. The operator also should participate in a medi-
cal monitoring program as specified under OSHA.
2.6 Material Handling Requirements
Materials handling requirements for the metal-enhanced
dechlorination technology include those for the reactive
iron medium and pea gravel or well sand used in the
construction of the reactor vessel. Precautions required
for the handling of this material include those normally
employed for nuisance dusts, including the use of respi-
ratory protection for personnel working with these mate-
rials in enclosed areas.
2.7 Technology Limitations
According to the developer, the metal-enhanced dechlo-
rination technology is limited in three ways. The first
limitation concerns inability of zero-valent iron, which is
the reactive media used in the technology, to treat
nonhalogenated contaminants and some chlorinated
VOCs, such as chloromethane; dichloromethane; 1,2-
dichloroethane; and 1,4-dichlorobenzene. In addition,
the technology has not been used to date to success-
fully degrade other halogenated organic compounds
such as chlorinated phenols and pesticides (Vogan et al
1995).
The second limitation concerns the reactive iron medium's
usable life before it loses its reactivity and its hydraulic
conductivity due to the formation of metal precipitates.
According to the developer, the reactive iron medium
will maintain its reactivity for a considerable length of
time; at the Borden site discussed in Section 2.3.1 of this
report, the developer claims that consistent VOC degra-
dation rates were observed for over 4.3 years. The
driving force of the reductive dehalogenation reaction is
the corrosion of iron (the conversion of Fe° to Fe2+).
According to the developer, the measured corrosion rate
of iron indicates that iron will persist for several years to
decades, depending on the concentration of VOCs in
the wastewater and the flow rate through the system.
However, deposition of metal precipitates on the reac-
tive iron medium may adversely affect system hydrau-
lics and the reactivity of the iron. Continuous deposition
of metal precipitates on the reactive iron medium may
necessitate regeneration and/or replacement of the me-
dia. The developer estimates that these O&M proce-
dures may be necessary every 5 to 10 years in most in
situ applications, depending on the characteristics of the
groundwater being treated.
The third limitation involves aboveground systems where
VOC degradation rates with the reactive iron medium
are usually not rapid enough to allow economical, rea-
sonably sized systems to be built. Also, the problems
with the formation and deposition of metal precipitates
are sometimes exacerbated in aboveground systems,
necessitating more frequent periodic replacement or
backflushing of sections of the system.
2.8 Potential Regulatory Requirements
This section discusses regulatory requirements perti-
nent to using the metal-enhanced dechlorination pro-
cess at Superfund, Resource Conservation and Recov-
ery Act (RCRA) corrective action, and other cleanup
sites. The regulations applicable to implementing this
technology depend on site-specific remediation logistics
and the type of contaminated groundwater being treated;
therefore, this section presents a general overview of
the types of federal regulations that may apply under
various conditions. State requirements should also be
considered; because these requirements vary from state
to state, they are not presented in detail in this section.
Table 2-6 summarizes the environmental laws and as-
sociated regulations discussed in this section.
Depending on the characteristics of the groundwater to
be treated, pretreatment or postreatment may be re-
quired for successful operation of the metal-enhanced
dechlorination technology. Each pretreatment or post-
treatment process might involve additional regulatory
requirements that would need to be predetermined. This
section focuses on regulations applicable only to the
metal-enhanced dechlorination technology.
2.8.1 Comprehensive Environmental
Response, Compensation, and
Liability Act
The Comprehensive Environmental Response, Com-
pensation, and Liability Act (CERCLA), as amended by
SARA, authorizes the federal government to respond to
releases of hazardous substances, pollutants, or con-
taminants that may present an imminent and substantial
danger to public health or welfare. Remedial alternatives
that significantly reduce the volume, toxicity, or mobility
of hazardous substances and provide long-term protec-
tion are preferred. Selected remedies must also be cost-
effective, protective of human health and the environ-
ment, and must comply with environmental regulations
to protect human health and the environment during and
after remediation.
Although the metal-enhanced dechlorination technology
often treats contaminated groundwater in situ,
aboveground treatment may also be used, requiring
effluent discharge either on or off site. CERCLA requires
35
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Table 2-6. Summary of Environmental Regulations
Act/
Authority
Applicability
Application to Metal-Enhanced
Dechlorinatlon Technology
Citation
CERCLA
RCRA
CWA
SDWA
CAA
AEAand
RCRA
OSHA
NRC
Cleanups at
Superfund sites
Cleanups at
Superfund and
RCRA sites
Discharges to surface
water bodies
Water discharges,
water relnjection, and
sole-source aquifer
and wellhead
protection
Air emissions from
stationary and mobile
sources
Mixed wastes
All remedial actions
All remedial actions
40 CFR parts 260 to
270
40 CFR parts 122 to
125, part 403
40 CFR parts 141 to
149
This program authorizes and regulates the cleanup 40 CFR part 300
of releases of hazardous substances. It applies to all
CERCLA site cleanups and requires that other
environmental laws be considered as appropriate to
protect human health and the environment.
RCRA regulates the transportation, treatment,
storage, and disposal of hazardous wastes. RCRA
also regulates corrective actions at treatment,
storage, and disposal facilities.
NPDES requirements of CWA apply to both
Superfund and RCRA sites where treated water is
discharged to surface water bodies. Pretreatment
standards apply to discharges to POTWs.
Maximum contaminant levels and contaminant level
goals should be considered when setting water
cleanup levels at RCRA corrective action and
Superfund sites. Reinjection of treated water
would be subject to underground injection control
program requirements, and sole sources and
protected wellhead water sources would be subject
to their respective control programs.
if VOC emissions occur or hazardous air pollutants
are of concern, these standards may be applicable to
ensure that use of this technology does not degrade
air quality. State air program requirements also
should be considered.
AEA and RCRA requirements apply to the
treatment, storage, and disposal of mixed waste
containing both hazardous and radioactive
components. OSWER and DOE directives provide
guidance for addressing mixed waste.
OSHA regulates on-site construction activities and
the health and safety of workers at hazardous waste
sites. Installation and operation of the metal-
enhanced dechlorination process at Superfund or
RCRA cleanup sites must meet OSHA
requirements.
These regulations include radiation protection 10 CFR part 20
standards for NRC-licensed activities.
40 CFR parts 50, 60,
61, and 70
AEA (10 CFR part 60)
and RCRA (see above)
29 CFR parts 1900
to 1926
Note: Acronyms used in this table are defined in the text.
on-site actions to meet ail substantive state and federal
applicable or relevant and appropriate requirements
(ARARs). Off-site actions must comply with both sub-
stantive and administrative ARARs. Substantive require-
ments (for example, effluent standards) pertain directly
to actions or conditions in the environment. Administra-
tive requirements (such as permitting) facilitate imple-
mentation of substantive requirements.
Subject to specific conditions, EPA allows ARARs to be
waived in accordance with Section 121 of CERCLA. The
conditions under which an ARAR may be waived include
(1) an activity that does not achieve compliance with an
ARAR but is part of a total remedial action that will
achieve compliance (such as a removal action), (2) an
equivalent standard of performance can be achieved
without complying with an ARAR, (3) compliance with
an ARAR will results in a greater risk to health and the
36
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environment than will noncompliance, (4) compliance
with an ARAB is technically impracticable, (5) in the
case of a state ARAR, it has not been applied consis-
tently, and (6) for fund-lead remedial actions, compli-
ance with the ARAR will result in expenditures that are
not justifiable in terms of protecting public health or
welfare, given the needs for funds at other sites. The
justification for a waiver must be clearly demonstrated
(EPA 1988a). Off-site remediations are not eligible for
ARAR waivers, and all applicable substantive and ad-
ministrative requirements must be met.
CERCLA requires identification and consideration of
environmental requirements that are ARARs for site
remediation before implementation of a remedial tech-
nology at a Superfund site. Additional regulations perti-
nent to use of the metal-enhanced dechlorination tech-
nology are discussed in the following sections. Regula-
tions addressing wastewater storage, treatment, and
discharge; treatment residuals (reactive iron medium
and bag filters); and potential fugitive air emissions are
discussed below.
2.8.2 Resource Conservation and
Recovery Act
RCRA, as amended by the Hazardous and Solid Waste
Amendments of 1984, regulates management and dis-
posal of municipal and industrial solid wastes. EPA and
the states implement and enforce RCRA and state
regulations. Some of the RCRA Subtitle C (hazardous
waste) requirements under 40 CFR parts 264 and 265
generally apply at CERCLA sites because remedial
actions generally involve treatment, storage, or disposal
of hazardous waste.
Wastewater treated by the metal-enhanced dechlorina-
tion process may be a listed hazardous waste or a
characteristic hazardous waste such that RCRA regula-
tions will apply. Criteria for identifying hazardous wastes
are provided in 40 CFR part 261. Pertinent RCRA
requirements are discussed below.
If the wastewater to be treated is determined to be a
hazardous waste, RCRA requirements for hazardous
waste storage and treatment must be met. The metal-
enhanced dechlorination technology may require stor-
age of liquid hazardous waste in a bladder tank or
equalization tank before treatment. Tank storage of
liquid hazardous waste must meet the requirements of
40 CFR part 264 or 265, subpart J. The reactor for the
metal-enhanced dechlorination process may require oc-
casional backwashing to remove entrapped solids or
precipitate from the reactive iron medium. (This may not
be necessary if the upper part of the reactive iron layer is
periodically replaced). Backwash water may be a RCRA
hazardous waste, and RCRA requirements for hazard-
ous waste disposal (see 40 CFR parts 264 and 265)
may apply. If groundwater or other wastes treated are
hazardous wastes, the treated groundwater must meet
treatment standards under the land disposal restriction
(LDR) (40 CFR part 268) before reinjection or placement
on the land, for example, in a surface impoundment.
RCRA parts 264 and 265, subparts AA, BB, and CC,
address air emissions from hazardous waste treatment,
storage, and disposal facilities. Subpart AA regulations
apply to organic emissions from process vents on cer-
tain types of hazardous waste treatment units. Because
the design of the metal-enhanced dechlorination pro-
cess at this site uses a gas vent, these regulations
would be ARARs. Air emissions from this gas vent could
include VOCs. Subpart BB regulations apply to fugitive
emissions (equipment leaks) from hazardous waste treat-
ment, storage, and disposal facilities that treat waste
containing organic concentrations of at least 10% by
weight. These regulations address pumps, compres-
sors, sampling connecting systems, open-ended valves
or lines, and flanges. Subpart BB regulations could be
ARARs if fugitive emissions were a concern with the
operation of the technology. Many organic air emissions
from hazardous waste tank systems, surface impound-
ments, or containers will eventually be subject to the air
emission regulations in 40 CFR parts 264 and 265,
subpart CC. The Subpart CC regulations were promul-
gated in December 1994 and became effective in De-
cember 1995 for facilities regulated under RCRA. Pres-
ently, EPA is deferring application of the Subpart CC
standards to waste management units used solely to
treat or store hazardous waste generated on site from
remedial activities required under RCRA corrective ac-
tion or CERCLA response authorities (or similar state
remediation authorities). Therefore, Subpart CC regula-
tions may not immediately impact implementation of the
metal-enhanced dechlorination technology in remedial
applications, although EPA may remove this deferral in
the future.
Use of the metal-enhanced dechlorination technology
would constitute "treatment" as defined under RCRA
regulations in 40 CFR 260.10. Because treatment of a
hazardous waste usually requires a permit under RCRA,
permitting requirements may apply if the metal-enhanced
dechlorination process is used to treat a listed or charac-
teristic hazardous waste. Regulations in 40 CFR part
264, subpart X, which regulate hazardous waste stor-
age, treatment, and disposal in miscellaneous units,
may be relevant to the metal-enhanced dechlorination
process. Subpart X requires that to obtain a permit for
treatment in miscellaneous units, an environmental as-
sessment must be conducted to demonstrate that the
unit is designed, operated, and closed in a manner that
protects human health and the environment. Require-
ments in 40 CF.R part 265, subpart Q (Chemical, Physi-
cal, and Biological Treatment), could also apply.
Subpart Q includes requirements for automatic influent
shutoff, waste analysis, and trial tests. RCRA also con-
tains special standards for ignitable or reactive wastes,
incompatible wastes, and special categories of waste
(40 CFR parts 264 and 265, subpart B). These stan-
dards may apply to the metal-enhanced dechlorination
technology, depending on the waste to be treated.
37
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The metal-enhanced dechlorination technology may also
be used to treat contaminated liquids at hazardous
waste treatment, storage, and disposal facilities as part
of RCRA corrective actions. Requirements for corrective
action at these facilities are included in the regulations in
40 CFR part 264, subparts F and S. The regulations
include requirements for initiating and conducting RCRA
corrective actions, remediating groundwater, and oper-
ating corrective action management units and tempo-
rary units associated with remediation operations. In
states authorized to implement RCRA, additional state
regulations that are more stringent or broader in scope
than federal requirements must also be addressed.
2.8.3 Clean Water Act
The Clean Water Act (CWA) is designed to restore and
maintain the chemical, physical, and biological quality of
navigable surface waters by establishing federal, state,
and local discharge standards. If treated liquid is dis-
charged to surface water bodies or publicly owned treat-
ment works (POTW), CWA regulations apply. On-site
discharges to surface water bodies as part of CERCLA
actions must meet substantive NPDES requirements
but do not require an NPDES permit. A direct discharge
of CERCLA wastewater would qualify as "on site" if the
receiving water body is in the area of contamination or in
very close proximity to the site, and if the discharge is
necessary to implement the response action. Off-site
discharges to a surface water body require an NPDES
permit and must meet NPDES permit discharge limits.
Discharge to a POTW is considered to be an off-site
activity, even if an on-site sewer is used. Therefore,
compliance with substantive and administrative require-
ments of the National Pretreatment Program is required
in such a case. General pretreatment regulations are
included in 40 CFR Part 403.
Any applicable local or state requirements, such as local
or state pretreatment requirements or water quality stan-
dards (WQS), must also be identified and satisfied.
State WQSs are designed to protect existing and attain-
able surface water uses (for example, recreation and
public water supply). WQSs include surface water use
classifications and numerical or narrative standards (in-
cluding effluent toxicity standards, chemical-specific re-
quirements, and bioassay requirements to demonstrate
no observable effect level from a discharge) (EPA 1988a).
These standards should be reviewed on a state- and
location-specific basis before discharges are made to
surface water bodies.
2.8.4 Safe Drinking Water Act
The Safe Drinking Water Act (SDWA), as amended in
1986, required EPA to establish regulations to protect
human health from contaminants in drinking water. EPA
has developed the following programs to achieve this
objective: (1) a drinking water standards program, (2) an
underground injection control program, and (3) sole-
source aquifer and wellhead protection programs.
SDWA primary (health-based) and secondary (aesthetic)
MCLs generally apply as cleanup standards for water
that is, or may be, used as drinking water. In some
cases, such as when multiple contaminants are present,
more stringent maximum contaminant level goals may
be appropriate. During the SITE demonstration, the
metal-enhanced dechlorination process's performance
was evaluated to determine its compliance with SDWA
and NJDEP MCLs for several critical VOCs. The results
indicated that the effluent exceeded the SDWA MCL for
VC and the NJDEP discharge limit for cDCE.
Water discharge through injection wells is regulated by
the underground injection control program. Injection wells
are categorized as Classes I through V, depending on
their construction and use. Reinjection of treated water
involves Class IV (reinjection) or Class V (recharge)
wells and should meet SDWA requirements for well
construction, operation, and closure. Reinjection would
apply only on a site-specific basis for aboveground
treatment using the metal-enhanced dechlorination tech-
nology.
The sole-source aquifer and wellhead protection pro-
grams are designed to protect specific drinking water
supply sources. If such a source is to be remediated
using the metal-enhanced dechlorination technology,
appropriate program officials should be notified, and any
potential regulatory requirements should be identified.
State groundwater antidegradation requirements and
WQSs may also apply.
2.8.5 Clean Air Act
i
The Clean Air Act (CAA), as amended in 1990, regu-
lates stationary and mobile sources of air emissions.
CAA regulations are generally implemented through
combined federal, state, and local programs. The CAA
includes pollutant-specific standards for major station-
ary sources that could be ARARs for the metal-en-
hanced dechlorination process. For example, the metal-
enhanced dechlorination technology would usually not
be a major source as defined by the CAA, but if the
system design incorporated a gas vent, an aboveground
reactor could emit airborne VOCs that trigger other
requirements under the CAA. For example, the National
Emission Standards for Hazardous Air Pollutants could
be ARARs, if regulated hazardous air pollutants are
emitted and if the treatment process is considered suffi-
ciently similar to one regulated under these standards.
In addition, New Source Performance Standards (NSPS)
could be ARARs if the pollutant emitted from the metal-
enhanced dechlorination process is sufficiently similar to
a pollutant and source category regulated by an NSPS.
Finally, state and local air programs have been del-
egated significant air quality regulatory responsibilities,
and some have developed programs to regulate toxic air
pollutants (EPA 1989). Therefore, state air programs
should be consulted regarding metal-enhanced dechlo-
rination technology installation and use.
38
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2.8.6 Mixed Waste Regulations
Use of the metal-enhanced dechlorination technology at
sites with radioactive contamination might involve treat-
ment of mixed waste. As defined by the Atomic Energy
Act (AEA) and RCRA, mixed waste contains both radio-
active and hazardous waste components. Such waste is
subject to the requirements of both acts. However, when
application of both AEA and RCRA regulations results in
a situation that is inconsistent with the AEA (for ex-
ample, an increased likelihood of radioactive exposure),
AEA requirements supersede RCRA requirements (EPA
1988a). OSWER, in conjunction with the NRG, has
issued several directives to assist in identification, treat-
ment, and disposal of low-level radioactive, mixed waste.
Various OSWER directives include guidance on defin-
ing, identifying, and disposing of commercial, mixed,
low-level radioactive, and hazardous waste (EPA 1987b).
If the metal-enhanced dechlorination process is used to
treat groundwater containing low-level mixed waste,
these directives should be considered. If high-level mixed
waste or transuranic mixed waste is treated, internal
Department of Energy (DOE) orders should be consid-
ered when developing a protective remedy (DOE 1988).
The SDWA and CWA also contain standards for maxi-
mum allowable radioactivity levels in water supplies.
2.8.7 Occupational Safety and Health Act
OSHA regulations in 29 CFR parts 1900 through 1926
are designed to protect worker health and safety. Both
Superfund and RCRA corrective actions must meet
OSHA requirements, particularly §1910.120, Hazardous
Waste Operations and Emergency Response. Part 1926,
Safety and Health Regulations for Construction, applies
to any on-site construction activities. For example, elec-
tric utility hookups for the ETI system during the demon-
stration were required to comply with regulations in 29
CFR part 1926, subpart K. Any more stringent state or
local requirements must also be met. In addition, health
and safety plans for site remediations should address
chemicals of concern and include monitoring practices
to ensure that worker health and safety are maintained.
2.9 State and Community Acceptance
Because few applications of the metal-enhanced dechlo-
rination technology have been attempted, limited infor-
mation is available to assess state and community ac-
ceptance of the technology. Therefore, this section dis-
cusses state and community acceptance of this technol-
ogy with regard to the SITE demonstration.
Throughout the demonstration, the state was involved in
permitting issues and documenting groundwater quality.
Before the demonstration, the NJDEP agreed to allow
ETI and SL Industries to use a treatment reactor to test
the metal-enhanced dechlorination process to predict its
long-term success at the SQL site. Also, before the
demonstration, SL Industries received a 90-day waiver
from NJDEP allowing the treated groundwater to be
returned to the aquifer without obtaining a State of New
Jersey pollutant discharge permit. As part of the evalua-
tion, the NJDEP requested documentation of concentra-
tions of carbonate, iron, calcium, magnesium, Eh, and
DO in groundwater during the demonstration.
During the SITE demonstration, about 80 people from
NJDEP, EPA Region 2, interested parties of industry,
consulting firms, and potential users attended a Visitors'
Day to observe demonstration activities and ask ques-
tions pertaining to the technology. The visitors expressed
no concerns regarding the operation of the metal-en-
hanced dechlorination process.
39
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Section 3
Economic Analysis
This economic analysis presents cost estimates for us-
ing the metal-enhanced dechlorination technology, in an
aboveground reactor, to treat contaminated groundwa-
ter. The cost estimates are based on a reactor designed
to treat the types and concentrations of halogenated
VOCs observed at the SQL site, and were based on
data compiled during the SITE demonstration and from
additional information obtained from ETI, Rhodes, cur-
rent construction cost estimating guidance, independent
vendors, and SITE Program experience.
Past studies by ETI have indicated that costs for this
technology are highly variable and are dependent on the
types and concentrations of the contaminants present,
regulatory cleanup requirements, and other site-specific
factors. Estimates for total cost and cost per gallon of
water treated are also heavily influenced by assump-
tions regarding the duration of the treatment program
and the cumulative volume treated. Furthermore, a full-
scale system design for the SQL site was not complete
at the time of this report, and therefore the cost data
presented herein are based on the design and operating
parameters for the pilot-scale reactor evaluated during
the SITE demonstration. The purpose of the pilot-scale
system was to determine the optimal design and operat-
ing parameters for a full-scale system; differences be-
tween the capabilities of the pilot-scale and full-scale
systems could significantly affect costs. For these rea-
sons, costs for full-scale systems designed for optimal
performance at other sites may vary significantly from
estimates presented herein.
Due to the numerous factors that potentially affect the
cost of using this technology, various assumptions were
necessary to prepare the economic analysis. Some of
the most significant assumptions were (1) the
aboveground reactor is identical to the pilot-scale reac-
tor used at the SQL site; (2) the reactor will treat water
contaminated with PCE, TCE, cDCE, and VC at concen-
trations observed during the SITE demonstration at the
SQL site; and (3) the reactor operates at 0.5 gpm, as
demonstrated. Also, the cost evaluation is based on
data obtained during the SITE demonstration, extrapo-
lated to a 30-year operational period. The 30-year
timeframe was selected for consistency with cost evalu-
ations of other innovative technologies evaluated by the
EPA SITE Program and because it facilitates compari-
son to typical costs associated with conventional, long-
term remedial options. The 30-year timeframe does not
reflect any estimate of the actual time required to reme-
diate groundwater at the SQL site (or other sites), as the
volume of groundwater requiring treatment is unknown
based on information currently available.
This section summarizes site-specific factors that influ-
ence costs, presents assumptions used in this analysis,
discusses estimated costs, and presents conclusions of
the economic analysis. Table 3-1 presents the esti-
mated costs generated from this analysis. Costs have
been distributed among 12 categories applicable to
typical cleanup activities at Superfund and RCRA sites
(Evans 1990). Costs are presented in July 1995 dollars
and are rounded to the nearest 100 dollars.
3.1 Factors Affecting Costs
Site-specific factors affect the costs of using the metal-
enhanced dechlorination technology and can be divided
into waste-related factors and site features. Waste-re-
lated factors affecting costs include waste volume, con-
taminant types and concentrations, and regulatory
agency-designated treatment goals. Waste volume af-
fects total project costs because a larger volume takes
longer to remediate or requires a higher treatment sys-
tem capacity (flow rate). However, economies of scale
can be realized with a larger-volume project because
the fixed costs, such as equipment costs, are distributed
over the larger volume. The contaminant types and
levels in the groundwater and the treatment goals for the
site determine (1) the appropriate size of the metal-
enhanced dechlorination treatment system, which af-
fects capital equipment costs; (2) the flow rate at which
treatment goals can be met; and (3) periodic sampling
requirements, which affect analytical costs.
Site features affecting costs include geology, groundwa-
ter flow rates, groundwater chemistry (for example, con-
centrations of inorganic substances), and site location.
Geological conditions determine whether the treatment
system must be installed aboveground, as is presented
in this economic analysis, or whether it can be installed
in situ. As observed at the SQL site, the geology also
41
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Table 3-1. Costs Associated with the Aboveground
Application of the Metal-Enhanced
Dechlorination Technology8
Cost Category
Cost
Total Cost
Site Preparation" $ 34,300
Treatability study $20,000
System design 10,000
Preparation 4,300
Permitting and Regulatory" 4,000
Mobilization and Startup6 13,100
Transportation 1,900
Assembly 11,200
Capital Equipment" 24,800
Demobilization" 2,500
Total Estimated Rxed Costs
$ 78,700
Labor"
Supplies0
Filters
PPE
Drums
Sampling equipment
Utilities'
Effluent Treatment and Disposal"
Residual Waste Handling0
Analytical Services0
Equipment Maintenance0-*
7,000
2,000
300
600
100
1,000
1,100
300
2,200
6,500
2,100
Total Estimated Variable Costs
$ 21,200/yr
Total Estimated Rxed and Variable
Costs After 30 Years •
$714,700
Costs per 1,000 gallons treated'
Costs per gallon treated'
$
$
91
.09
Notes:
AH costs presented In 1995 dollars
* Costs estimated based on data from pilot-scale reactor.
* Fixed costs.
8 Variable costs, presented as annual total.
0 Annual total prorated from expense incurred at 5-year intervals.
.* Total costs after 30 years of operations; all annual costs multiplied
by 30, plus total fixed costs.
1 Total of 7.88 million gallons of groundwater treated.
determines the feasibility of installing and using passive
collection trenches. If trenches are not feasible and the
groundwater needs to be pumped to the aboveground
reactor, site preparation costs will be different due to the
construction of extraction wells, pumps, and piping. The
site geology and soil characteristics such as permeabil-
ity also affect the groundwater extraction rate and the
required treatment period.
Groundwater chemistry can affect the reactive iron me-
dium in several ways. High concentrations of dissolved
Inorganic substances in influent groundwater may result
in precipitation of compounds such as calcium carbon-
ate, particularly on the upper/influent side of the iron,
requiring more frequent maintenance. Metal precipitates
can restrict water flow through iron pore spaces, reduc-
ing the groundwater flow rate. Metal precipitates can
also reduce the surface area of the iron available for
reaction, causing contaminants to persist longer and
increasing the retention time required for complete
dechlorination. It is also possible that the temperature of
the influent water and the reactor temperature may
affect the reaction rate, also increasing the required
retention time. These factors could possibly increase the
duration of remediation, affecting consumable and time-
related variable costs and also increasing total mainte-
nance costs.
Site location will impact mobilization, demobilization,
and site preparation costs. Mobilization and demobiliza-
tion costs are affected by the relative distances that
system materials must travel to the site, particularly the
proximity to iron suppliers. Site preparation costs are
also influenced by the availability of access roads and
utility lines and by the need for additional equipment to
withstand freezing temperatures in colder climates.
Electricity costs can vary considerably depending on the
total number of purnps and other electrical equipment
operating. Treatment systems requiring extraction wells
will operate additional pumps that will incur slightly
higher electricity costs depending on the pump sizes.
3.2 Assumptions Used in Performing
the Economic Analysis
This section summarizes major assumptions made with
regard to site-specific factors and equipment and oper-
ating parameters used in this economic analysis. Cer-
tain assumptions were made to account for variable site
and waste parameters. Other assumptions were made
to simplify cost estimating for situations that actually
would require complex engineering or financial func-
tions. In general, most system operating issues and
assumptions are based on information provided by ETI,
Rhodes, and SL Industries, and observations made
during the,SITE demonstration. Cost figures are estab-
lished from information provided by ETI, Rhodes Engi-
neering, SL Industries, Means cost guides (Means 1995),
and SITE demonstration experience.
Assumptions used for the economic analysis include the
following:
• The influent groundwater contaminants and their
concentrations are PCE, TCE, and cDCE at maxi-
mum concentrations of 13,000 jxg/L, 590 pg/L, and
1,600 u,g/L, respectively.
• The most stringent cleanup goals are federal MCL
requirements of 5 jjg/L for both PCE and TCE and
the NJDEP discharge limit of 2 ng/L for cDCE. VC is
a potential treatment byproduct The VC cleanup
goal is the federal MCL of.2 jig/L.
42
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The site is located near an urban area. As a result,
utilities and other infrastructure features (for ex-
ample, access roads to the site) are readily avail-
able.
The site is located in the northeastern U.S. Regional
winter temperatures are below 0°C for several days
in a row, requiring antifreezing measures.
Contaminated water is located in a shallow aquifer
no more than 25 ft below ground surface and exist-
ing monitoring wells and an associated pump and
piping are available for reinjection of treated ground-
water.
The groundwater remediation project involves a to-
tal of nearly 7.9 million gal of water that needs to be
treated. This groundwater volume corresponds to
the volume that the system can treat operating
continuously for 30 years at a flow rate of 0.5 gpm.
(For a full-scale system the flow rate may be differ-
ent—see below).
On-site personnel are assumed to be trained in
hazardous waste site health and safety procedures,
so health and safety training costs are not included
as a direct startup cost.
The treatment system is effective enough to allow
the return of treated groundwater to the aquifer
through injection wells, without additional posttreat-
ment "polishing" with carbon filters or other devices.
The treatment system is operated 24 hours per day,
7 days per wk, 52 wks per year, for 30 years.
Routine maintenance results in a downtime of about
3% of this time and is not considered in the calcula-
tions.
The reactive iron medium needs to be replaced
every 5 years.
The treatment system operates without the constant
attention of an operator, except for maintenance-
related labor.
The individual components of the treatment system
are mobilized to the site and assembled by ETI.
Air emissions monitoring is not needed.
Groundwater will be passively extracted from the
contaminated aquifer using tiles placed at the bot-
tom of collection trenches.
A100-square-ft concrete pad is needed to install the
reactor.
The ETI system is mobilized to the remediation site
from within 500 miles of the site.
• Initial operator training is provided by ETI, and the
costs of this are included in the cost of the capital
equipment.
This analysis estimates costs based on the design and
operating parameters associated with the aboveground
unit demonstrated at the SQL site, which required 20
tons of reactive iron medium. During the demonstration,
the system operated on a continuous flow cycle of about
0.5 gpm, 24 hours per day, 7 days per wk. Based on
these assumptions, the system can treat 262,800 gal
per year. Because most groundwater remediation projects
are long-term projects, this analysis assumes that nearly
7.9 million gal of water needs to be treated to complete
the groundwater remediation project.
It is important to note that sites with different types and
lower concentrations of contaminants may allow higher
flow rates than 0.5 gpm, increasing the volume of ground-
water treated over a 30-year period and reducing the
cost per gallon. Also, the actual flow rate for a full-scale
system at the SQL site may vary from the 0.5 gpm rate
demonstrated in the pilot-scale reactor. The demonstra-
tion results indicated that for the pilot-scale reactor at
the SQL site, the 0.5 gpm rate may have been too high
to allow sufficient contact time to completely dechlori-
nate all byproducts in the latter part of the demonstra-
tion. However, according to ETI and Rhodes, the full-
scale system design may eventually incorporate a se-
ries of reactors, a modified reactive medium, or other
design modifications that would allow higher volumetric
flow rates than 0.5 gpm (ETI 1996; Rhodes 1996).
Although such a full-scale system would incur higher
initial capital costs, the increased volume of water treated
may decrease the cost per gallon for a long-term reme-
diation project.
Depreciation is not considered in this analysis to simplify
presenting the costs of this analysis. Salvage value is
also not considered; after 30 years of use, the equip-
ment is expected to have no salvage value. However,
the iron reactive medium can be recycled and is as-
sumed to bear a credit of 5% of its original value at
demobilization.
For this analysis, annual costs are not adjusted for
inflation, and no net present value is calculated. Most
groundwater remediation projects are long-term, and
usually a net present worth analysis is performed for
cost comparisons. The variable costs for this technology
are relatively low. In addition, no other system configura-
tions or technologies are presented in this analysis for
comparison.
3.3 Cost Categories
Table 3-1 presents cost breakdowns for each of the 12
cost categories. Cost data have been presented for the
following categories: (1) site preparation, (2) permitting
and regulatory, (3) mobilization and startup, (4) equip-
ment, (5) labor, (6) supplies, (7) utilities, (8) effluent treat-
ment and disposal, (9) residual waste shipping and han-
43
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dling, (10) analytical services, (11) equipment mainte-
nance, and (12) site demobilization. Each of these cost
categories is discussed below.
3.3.1 Site Preparation Costs
Site preparation costs include those for conducting a
bench-scale treatability study, conducting engineering
design activities, and preparing the treatment area. Ac-
cording to ETI and Rhodes, a phased treatability study
will take between 2 to 4 months to complete (see
Section 4 for a discussion of the four phases used to
implement the technology). Treatability study costs in-
clude expenses for column tests and labor. According to
ETI, the analytical laboratory costs for column tests for a
project similar to the one at the SQL site will be about
S15,000. The labor for the treatability study will be about
$5,000, inclusive of 50 hours at an average rate of $100
per hour. The total cost of a treatability study will be
about $20,000.
After the study and a preliminary site assessment, ETI
will design the optimal system configuration for a par-
ticular site. ETI estimates the system design costs to be
$10,000. This cost includes about 130 labor hours at an
average rate of $75 per hour.
Treatment area preparation includes installing collection
trenches, a 100-square-ft concrete pad, and fencing.
The trenches are needed to collect groundwater and
direct it to the treatment system. Four 10-ft-long by 3-ft-
wide by 8-ft-deep, tiled trenches similar to the ones used
at the SQL site are constructed. The trenches are back-
filled with sand and gravel and capped with silty clay.
One sump with a pump is located at the downstream
end of the trenches. The pump transfers groundwater
from the sump into the reactor. Trench construction
costs, including tile and backfill materials, (but not in-
cluding costs for the excavation equipment and opera-
tor), are $4.50 per cubic yard, for a total of $200.
The reactor for the SITE demonstration was situated on
a 100-ft2 concrete pad. A bermed, epoxy-coated,
nonreinforced concrete pad can be constructed for $25/
ft2 for a total of $2,500. A 6-ft-high security fence topped
with barbed wire and one gate is needed to limit access
to the treatment system. This analysis assumes the
fence will secure a 20-ft by 20-ft area. Total fencing
costs at $20 per lineal foot are $1,600.
Total site preparation costs are estimated to be $34,300.
3.3.2 Permitting and Regulatory Costs
Permitting and regulatory costs depend on whether
treatment is performed at a Superfund or a RCRA
corrective action site and disposal of treated effluent and
any generated solid wastes. Superfund site remedial
actions must be consistent with ARARs of environmen-
tal laws, ordinances, regulations, and statutes, including
federal, state, and local standards and criteria. Reme-
diation at RCRA corrective action sites requires addi-
tional monitoring and recordkeeping, which can increase
the base regulatory costs, in general, ARARs must be
determined on a site-specific basis.
For this analysis permitting and regulatory costs are
associated with returning treated groundwater to the
subsurface. This disclosure requires a discharge to
groundwater permit, the cost of which is based on the
local environmental regulatory agency. For other sites,
permit fees may be required for discharging treated
water to a POTW or a surface water body. The cost of all
permits is based on the effluent characteristics and
related receiving water requirements.
Total permitting and regulatory costs for this analysis
are estimated to be $4,000. This includes 50 hours of
labor at $75 per hour, and $250 for miscellaneous
expenses such as fees and reproduction costs.
3.3.3 Mobilization and Startup Costs
Mobilization and startup costs consist of delivering the
ETI system components to the site, assembling the
system, and performing the initial shakedown of the
treatment system. ETI provides trained personnel to
assemble and shake down the ETI system. Initial opera-
tor training is necessary to ensure safe, economical, and
efficient system operation. ETI includes initial operator
training to its customers in the cost of the capital equip-
ment.
Transportation costs are site-specific and vary depend-
ing on the location of the site in relation to the various
component suppliers, particularly for the iron reaction
medium. See Section 3.3.4, Capital Equipment Costs,
for a list of treatment system components. Based on
transportation costs incurred at the SQL and other sites,
transportation costs include costs to deliver a reactor
tank at $400 and 20 tons of reactive iron at $75 per ton.
Total transportation costs are estimated to be $1,900.
Assembly costs include the costs of unloading equip-
ment, assembling the ETI system, connecting pipes,
and connecting electricity. A three-person crew works
five 8-hour days to unload and assemble the system and
perform the initial shakedown. Working at a wage rate of
$35 per hour, the assembly wage costs are about $4,200.
Heavy equipment requirements are based on site-spe-
cific conditions. This analysis assumes that a backhoe
operator and backhoe can be contracted for one week at
a cost of $3,000. Electricity connection costs are about
$4,000. Total assembly costs are estimated to be
$11,200.
Total mobilization and startup costs are estimated to be
$13,100.
3.3.4 Capital Equipment Costs
Capital equipment costs consist of the costs of purchas-
ing the ETI treatment system components. ETI config-
ures the complete treatment system based on site-
44
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specific conditions. The components for this analysis 3.3.6 Supply Costs
and their respective costs include one customized 3,400-
gal fiberglass-reinforced plastic reactor tank ($12,000);
20 tons of granular iron ($450 per ton); 2 tons of pea
gravel or well sand ($75 per ton); influent and effluent
piping ($2,000); flow meter ($750); and a S-jim water
filter ($450). The costs of the reactor tank are based on
the pilot-scale tank customized with intermediate sam-
pling ports to allow the intensive sampling regimen
followed during the SITE demonstration. However, sys-
tems at other sites may not require the intermediate
sampling ports, resulting in a lower tank cost.
Necessary supplies as part of the overall groundwater
remediation project include influent water filters, Level D
disposable personal protective equipment (PPE), dis-
posal drums, and sampling and field analytical supplies.
The rate at which influent water filters need to be changed
depends on groundwater characteristics and flow rate.
At the SQL site, filters were changed monthly. Each filter
costs $25, for a total annual cost of $300 per year.
Because the system is installed aboveground, the water
lines are subject to freezing in the winter months. The
system could be installed inside a heated building to
avoid these conditions, assuming that such a building is
already available. Otherwise, the piping and control
units can be insulated using foam pipe insulation with
heat tape at a cost of $400. In warmer climates, this cost
will not be incurred.
This analysis assumes that the equipment will be used
for the duration of the groundwater remediation project,
which for this analysis is 30 years. As a result, no
salvage value is considered because the equipment is
expected to have no value after 30 years of use.
The reactive medium may become clogged or lose its
reductive dehalogenation properties before remediation
is completed. In this case, the reactive iron medium
needs to be treated or replaced. These replacement
costs are presented in Section 3.3.11, Equipment Main-
tenance Costs, because they are incurred regularly over
time and are attributed to system maintenance.
The total capital equipment costs of this treatment sys-
tem are $24,800.
3.3.5 Labor Costs
Once the system is functioning, it is assumed to operate
unattended and continuously except during routine equip-
ment monitoring, sampling, and maintenance activities.
One ETI-trained operator performs routine equipment
monitoring activities. Under normal operating conditions,
an operator is required to monitor the system about 3
hours per wk. It is assumed that this labor could be
contracted at about $45 per hour, resulting in total
annual labor costs of about $7,000 for routine system
monitoring.
Sampling activities require about 4 hours every month,
and are presented in Section 3.3.10, Analytical Services
Costs. Other labor requirements for periodic equipment
maintenance (iron replacement) and demobilization are
presented in Section 3.3.11, Equipment Maintenance
Costs and Section 3.3.12, Site Demobilization Costs.
Disposable PPE typically consists of latex inner gloves,
nitrile outer gloves, and safety glasses. This PPE is
used during monthly sampling activities. Disposable PPE
is assumed to cost about $600 per year for the sampler.
Used filters and disposable PPE are assumed to be
hazardous and need to be disposed of in a 55-gal steel
drum. One drum is assumed to be filled every 6 months,
and each drum costs about $25. Total annual drum
costs are about $50. Based on operations at the SQL
site, any excess water generated during the sampling
process can be collected in a bucket and returned to the
influent side of the iron in the reactor and reprocessed in
the system, eliminating the need for storing the water in
drums.
Sampling supplies consist of sample bottles and con-
tainers, ice, labels, shipping containers, and laboratory
forms for off-site analyses. The numbers and types of
necessary sampling supplies are based on the analyses
to be performed. Costs for laboratory analyses and
sample collection labor are presented in Section 3.3.10.
For this analysis, annual sampling supply costs are
assumed to be $1,000.
Total annual supply costs are estimated to be $2,000.
3.3.7 Utility Costs
Electricity is the only utility used by the ETI system, and
the sump pump and heating tape are the only equipment
drawing electricity. Based on observations made during
the SITE demonstration, the system operating for
24 hours draws about 20 kilowatt hours (kwh) of electric-
ity per day. The total annual electrical energy consump-
tion is estimated to be about 7,300 kwh. Electricity is
assumed to cost $0.15 per kwh, including demand and
usage charges. The total annual electricity costs are
about $1,100.
3.3.8 Effluent Treatment and Disposal
Costs
This analysis assumes that effluent from the treatment
process will be disposed of through existing injection
wells at the site. The costs for this activity include those
for pumping the effluent back into the groundwater. For
this analysis, the cost to dispose of the treated effluent is
assumed to include only the cost of pumping the effluent
45
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into the injection wells. Costs for this activity would
include those for electricity for the pump. This analysis
assumes the same size pump will be used for reinjection
as is used for the sump pump in section 3.3.7. Use of
this assumption yields an annual effluent treatment and
disposal cost of $275.
3.3.9 Residual Waste Shipping and
Handling Costs
Residuals produced during ETI system operation are
used PPE and disposable filter cartridges. This analysis
assumes this material will be disposed of at a permitted
or interim status facility authorized to receive hazardous
waste. This analysis assumes that about 2 drums of
waste are generated annually, and that one drum will be
shipped off-site every 6 months. The cost of handling
and transporting the drums is $500 per load, and dispos-
ing of them at a hazardous waste disposal facility costs
about $600 per drum. Based on these assumptions,
drum disposal costs incurred every year will be about
$2,200.
3.3.10 Analytical Services Costs
Required sampling frequencies, number of samples,
and associated QC requirements are highly site-specific
and are based on treatment goals and contaminant
concentrations. Analytical costs associated with a ground-
water remediation project include the costs of sample
collection, laboratory analyses, data reduction, and QA/
QC. This analysis assumes that one sample of treated
(effluent) water will be collected and analyzed monthly
for VOCs and metals (cadmium, chromium, copper,
lead, nickel). Based on typical costs incurred during the
evaluation of the aboveground reactor at the SQL site,
costs for the VOC and metals analyses are assumed to
be $130/sampIe and $100/sample, respectively. Analyti-
cal costs assume that one trip blank sample will also be
submitted for VOC analysis and that there are no addi-
tional charges for other required QC samples (matrix
spike and matrix spike duplicate). Field duplicate samples
are not assumed to be required since only one aqueous
sample will be collected from the system per month.
Labor associated with sample collection requires about
4 hours each month. This cost estimate assumes that all
sampling and analytical tasks will be performed by inde-
pendent contractors, and labor costs for sampling are
separate from the routine operating labor costs pre-
sented in Section 3.3.5. Sampling labor can be con-
tracted at a rate of $45 per hour. Based on these criteria,
total monthly analytical costs are estimated to be about
$540, resulting in total estimated annual sampling and
analytical costs of about $6,500.
3.3.11 Equipment Maintenance Costs
The results of the SITE demonstration and other studies
by ETI indicate that the reactive iron may eventually lose
its reactive capacity. Also, the iron may become blocked
or coated with metal precipitates. For these reasons,
this cost analysis assumes that the reactive iron will
need to be periodically replaced. The timeframe for
replacement will vary depending on flow rate, ground-
water chemistry, and other factors. This cost estimate
assumes that the reactive iron medium needs to be
changed once every 5 years. For a 30-year project, the
medium will be replaced five times (the cost of the initial
supply of reactive medium is presented in Section 3.3.4,
Equipment Costs). In addition, the reactive iron medium
can be recycled and is assumed to bear a credit of 5% of
its original value. The cost of replacing the reactive iron
medium every 5 years will be $12,550, including the
recycling credit, for a total project cost of $62,750. This
figure also includes heavy equipment ($1,500) and labor
($1,000) costs for each changeout. Although the
changeout cost will not be incurred until the fifth year of
operation, this analysis prorates the total annual cost of
the reactive iron medium replacement to be $2,100.
3.3.12 Site Demobilization Costs
Site demobilization includes treatment system shutdown,
disassembly, and decontamination; site cleanup and
restoration; utility disconnection; and transportation of
the ETI equipment off site. Treatment system shutdown
and disassembly is assumed to require approximately 8
hours of labor; it is assumed that this labor can be
obtained at a cost of $45 per hour, for a total labor cost
for system shutdown and disassembly of about $360.
Decontamination costs will include the costs to decon-
taminate the reactor vessel walls. This analysis uses
costs provided by Means Construction Guide (Means
1995) for steam cleaning of the reactor vessel walls. At a
work rate of 0.027 work hrs/ff, with a reactor surface
area of approximately 400 fF, the time required would be
approximately 11 hours. At a work rate of $45 per hour,
the total cost would be approximately $495. Finally, the
decontamination of the reactor would generate washwater
that would require disposal. Based on a washwater
generation rate of 4 gal/ff approximately 1600 gal of
washwater would be generated. Assuming a cost of
approximately $1 per gal to transport and dispose of this
washwater, the total cost for disposal would be about
$1,600. Total demobilization costs are estimated to be
about $2,500.
3.4 Conclusions of Economic Analysis
This analysis presents cost estimates for treating ground-
water contaminated with PCE and TCE, and byproducts
consisting of cDCE and VC. Operating conditions in-
clude treating the groundwater at 0.5 gpm for a period of
30 years. Table 3-1 shows the costs associated with the
12 cost categories presented in this analysis.
Total fixed costs are estimated to be $78,700. Site
preparation costs comprise 44% of the total fixed costs,
while capital eqiupment accounts for approximately 32%.
Figure 3-1 shows the distribution of fixed costs. Total
annual variable costs are estimated to be about $21,200.
Residual waste handling costs comprise 10% of the
annual variable costs, analytical services comprise 31%
46
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$34,300 (43.6%) Site preparation
$4,000 (5.1%) Permitting
mm
$13,100 (16.6%) Mobilization and Startup
$2,500 (3.2%) Demobilization
$24,800 (31.5%) Capital equipment
Total fixed costs are estimated to be $78,700.
Figure 3-1. Distribution of fixed costs.
(including sampling labor), and labor (ordinary operat-
ing) costs account for about 33%. The variable costs
also include the labor, equipment, and supply costs for
replacing the reactive iron every 5 years; distributed
over the 30-year timeframe iron replacement costs ac-
count for about 10% of the annual variable costs. Figure
3-2 shows the distribution of annual variable costs.
After operating for 30 years, the total costs of the
groundwater remediation scenario presented in this
analysis are $714,700. As mentioned earlier, costs were
not adjusted for inflation. A total of nearly 7.9 million gal
of groundwater would be treated during this time. Based
on these criteria, the total cost per 1,000 gal treated is
$91, or roughly 9.1 cents per gal.
$2,200 (10.4%) Residual waste handling
$1,100 (5.2%) Utilities
$2,000 (9.4%) Supplies
$6,500 (30.7%) Analytical services
$2,100 (9.9%) Equipment maintenance
$7,000 (33.0%) Labor
$300 (1.4%) Effluent treatment and disposal
Notes: 1) Total annual variable costs are estimated to be $21,100.
2) Routine operating labor does not include sampling or replacing iron.
Figure 3-2. Distribution of annual variable costs.
47
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Section 4
Technology Status
ETI has completed about 40 bench-scale studies, sev-
eral pilot-scale tests using aboveground reactors, a field
test using an in situ reactive wall, and 3 full-scale
installations of in situ reactive walls. The SITE Program
is currently evaluating an in situ "funnel and gate" sys-
tem at a New York site. In situ installations are planned
for the near future in North Carolina, Massachusetts,
and Wisconsin. In addition, ETI is completing coopera-
tive research and development/licensing arrangements
with several U.S. multinational industrial firms.
The metal-enhanced dechlorination process can be
implemented in situ or in aboveground installations. The
in situ implementation of the technology involves install-
ing a permeable treatment wall of coarse-grained reac-
tive iron medium across the groundwater plume. The
reactive media degrade chlorinated VOCs as they mi-
grate through the wall under naturally occurring ground-
water flow conditions. When the in situ metal-enhanced
dechlorination technology is applied to treat a large
plume of contaminated groundwater, impermeable sheet
piles or slurry walls may be used to funnel contaminated
groundwater through smaller permeable treatment sec-
tions, known as gates.
Aboveground treatment units are designed to treat ex-
tracted groundwater and may be especially useful for
sites where construction activities in the immediate vi-
cinity of a contaminant plume are impractical.
Aboveground treatment units can be available as trailer-
mounted transportable units or permanent installations.
The configuration of the aboveground units may include
a single unit or several units connected in series or in
parallel. Several types of aboveground reactors could
be used in series to treat multiple contaminant plumes.
The metal-enhanced dechlorination technology is typi-
cally implemented through a five-phase approach; how-
ever, depending on site-specific conditions, certain
phases may not be required or could be omitted to
expedite full-scale application. According to ETI, imple-
mentation of a system takes about 0.5 to 2 years to
complete. A preliminary data assessment is conducted
during phase 1; a bench-scale feasibility evaluation
(column study) is conducted during phase 2; pilot-scale
field testing is conducted during phase 3; full-scale
implementation occurs during phase 4; and phase 5
involves long-term performance monitoring. Phases 1
and 2 may take about 2 to 4 months; phase 3 may take
6 months to 1 year; and phase 4 may take about 6
months. The duration of Phase 5 will depend on site-
specific conditions and regulatory requirements. The
phases are described below.
Phase 1 - Preliminary Assessment
The purpose of a preliminary assessment is to review
existing site data to evaluate site-specific conditions that
may affect the performance of the technology. On the
basis of this review, the site may be placed into one of
two categories. The first category includes sites with a
physical setting and groundwater chemistry similar to
other sites at which the metal-enhanced dechlorination
technology has been shown to be effective. Therefore,
implementation of phase 2 (a feasibility evaluation) is
not necessary before phase 3 activities begin.
The second category includes sites with unique physical
and geochemical properties that may affect the applica-
tion of the metal-enhanced dechlorination technology.
The probability for the successful application of the
technology at these sites is unknown, due to the pres-
ence of untested chemicals, or unique geologic settings.
For these sites, implementation of phase 2 activities is
needed before phase 3 activities can begin. Data that
are necessary to assess a site include
• Groundwater inorganic and organic chemistry:Jhe
inorganic chemistry of groundwater is important be-
cause it indicates whether metals can precipitate
during treatment. The effect of metal precipitation on
the performance of the metal-enhanced dechlorina-
tion process is discussed in Section 2.4. The nature
of organic contaminants present in groundwater de-
termines the appropriateness of the metal-enhanced
dechlorination technology for groundwater treatment.
The effect of the presence of organic contaminants
on the implementation of the metal-enhanced dechlo-
rination process is also discussed in Section 2.4.1.
• VOC characteristics: The metal-enhanced dechlori-
nation process is appropriate for treating chlorinated
49
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methanes (except dichloromethahe), ethanes (ex-
cept 1,2-dichlorethane), and ethenes. Each com-
pound and its potential byproducts have a half-life.
The half-life of each compound and its degradation
byproducts are critical parameters with regard to
residence time when designing a metal-enhanced
dechlorination process treatment system.
• Site geology and so/fe:The depth to water table and
aquifer and aquitard thickness are important consid-
erations for the design and implementation of in situ
installations of the metal-enhanced dechlorination
technology. These factors may also influence the
selection of in situ or aboveground applications.
• Hydrogeotogical data: Hydraulic conductivity and
groundwater velocity may affect the performance of
the metal-enhanced dechlorination technology be-
cause they affect the residence time of groundwater
in the reactive wall.
Phase 2 - Bench Scale Feasibility
Evaluation
If the site is placed into the second category as defined
in Phase 1, a feasibility evaluation is typically performed.
The purpose of phase 2 is to evaluate the efficiency of
the metal-enhanced dechlorination technology under
simulated groundwater flow conditions, by performing
laboratory column tests using representative groundwa-
ter samples collected from the site. Groundwater flow
and geochemical models may be used to assist in the
feasibility evaluation. Feasibility testing should (1) con-
firm that the VOCs present are degraded by the pro-
cess, (2) evaluate the rates of VOC degradation, and (3)
evaluate associated inorganic geochemical reactions.
A feasibility evaluation report is prepared to document
phase 2 testing results. The report interprets the labora-
tory data with respect to the site's hydrogeologic charac-
teristics and provides a preliminary design and cost
estimate for a pilot-scale field test.
Phase 3 - Pilot-Scale Field Test
Following successful laboratory tests, a pilot-scale field
test may be conducted to collect the data required for a
full-scale application of the process. Depending on site-
specific conditions, the pilot-scale field test may not be
necessary. Results of phase 2 laboratory tests are used
to design the pilot-scale system. The system may be in
situ or aboveground, depending on the potential full-
scale application and site conditions. This field test of
the metal-enhanced dechlorination process provides data
on full-scale costs, long-term performance and opera-
tion, and maintenance requirements. A report is pre-
pared during phase 3 to present an evaluation of the
field test and a detailed cost estimate for a full-scale
system.
Phase 4 - Full-Scale Implementation
Phase 4 is the design and installation of a full-scale
system. The results from phase 3 provide the basis for
full-scale design. Design criteria include the required
iron surface area to achieve dechlorination and the
residence time of groundwater through the reactive iron
medium. The iron surface area available for reaction has
a significant effect on the half-lives of the VOCs of
concern (chlorinated VOCs found in the groundwater as
well as their degradation products). The half-lives of
VOCs in influent groundwater and their degradation
byproducts determine the total necessary residence time.
The necessary residence time and the groundwater
velocity determine the required thickness of an in situ
treatment wall; required residence time determines the
thickness of the iron layer and maximum allowable flow
rate for an aboveground treatment reactor.
Phase 5 - Long-Term Performance
Monitoring
Routine performance monitoring and reporting are per-
formed according to regulatory requirements. Perfor-
mance monitoring includes sampling and analysis of
treated groundwater to determine the concentrations of
VOCs of concern. The concentrations of chloride and
dissolved metals are also monitored. Changes in chlo-
ride concentration may be correlated with dechlorination
of VOCs. Decreases in dissolved metal concentrations
indicate formation of insoluble precipitates that may clog
or reduce the reactivity of the reactive iron medium, and
therefore indicate the need to periodically rejuvenate or
replace affected portions of the iron.
50
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Section 5
References
Chen, Chien T. 1995. Excerpts from Presentation Titled
"Iron Reactive Wall." Innovative Site Remediation
Workshop, Sturbridge, Massachusetts, Sept. 13-14.
Chen, Chien T. 1996. Correspondence Regarding the
Metal-Enhanced Dechlorination Reaction
Mechanism. To PRC Environmental management,
Inc. (PRC). April 25.
EnviroMetal Technologies, Inc. Report on Performance
of Test Reactor, former SQL Printed Circuits
Facility, Wayne, New Jersey. September 28.
Evans, G. 1990. "Estimating Innovative Treatment
Technology Costs for the SITE Program." Journal of
Air and Waste Management Association. Vol. 40,
No. 7. July.
Focht, Robert; Vogan, John; and O'Hannesin, Stephanie
1996. "Field Application of Reactive iron Wells for
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Prepared for Submission to the Journal of
Environmental Cleanup Costs, Technologies, and
Techniques.
Gillham, Robert W., and others. 1993. "Metal Enhanced
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Gillham, Robert W., and Stephanie F. O'Hannesin. 1994.
"Enhanced Degradation of Halogenated Aliphatics
by Zero-Valent Iron." Groundwater. Vol. 32, No. 6,
pp. 958 - 967.
Gillham, Robert W., 1995. "In situ Treatment of
Groundwater: Metal-Enhanced Degradation of
Chlorinated Organic Contaminants." Recent
Advances in Groundwater Pollution Control and
Remediation. A NATO Advanced Study Institute.
Kemer, Antalya, Turkey. Springer-Verlag, New York.
Gillham, Robert W., 1996. "In-Situ Treatment of
Groundwater: Metal-Enhanced Degradation of
Chlorinated Organic Contaminants." M. M. Aral
(Editor). Advances in Groundwater Pollution Control
and Remediation. Kluwer Academic Publishers,
Netherlands.
O'Hannesin, Stephanie F., and Robert W. Gillham. 1992.
"A Permeable Reaction Wall for In situ Degradation
of Halogenated Organic Compounds." Paper
Presented at the 1992,45th Canadian Geotechnical
Society Conference. Toronto, Ontario, Canada.
October.
O'Hannesin, Stephanie F., 1993. "A Field Demonstration
of a Permeable Reaction Wall for the In-Situ Abiotic
Degradation of Halogenated Aliphatic Organic
Compounds." (M.Sc. Thesis, University of Waterloo.)
Means, R.S. Company, Inc. 1995. Means Building
Construction Cost Data for 1995.53rd Annual Edition.
PRC Environmental Management, Inc. (PRC). 1994.
EnviroMetal Technologies, Inc. "Metal Enhanced
Abiotic Degradation Technology Demonstration Final
Quality Assurance Project Plan." Submitted to EPA
ORD, Cincinnati, Ohio. October.
Snoeyink, Vernon L. and David Jenkins. 1980. Water
Chemistry. John Wiley & Sons. New York.
U.S. Department of Energy (DOE). 1988. Radioactive
Waste Management Order. DOE Order 5820.2A.
September.
EPA. 1987. Joint EPA-Nuclear Regulatory Agency
Guidance on Mixed Low-Level Radioactive and
Hazardous Waste. Office of Solid Waste and
Emergency Response (OSWER) Directives 9480.00-
14 (June 29), 9432.00-2 (January 8), and 9487.00-
8. August.
EPA. 1988a. Protocol for a Chemical Treatment
Demonstration Plan. Hazardous Waste Engineering
Research Laboratory. Cincinnati, Ohio. April.
EPA. 1988b. CERCLA Compliance with Other
Environmental Laws: Interim Final. OSWER. EPA/
540/G-89/006. August.
EPA. 1988c. Guidance for Conducting Remedial
Investigations and Feasibility Studies Under
CERCLA. OSWER. EPA/540/G-89-004. October.
EPA. 1989. CERCLA Compliance with Other Laws
Manual: Part II. Clean Air Act and Other
Environmental Statutes and State Requirements.
OSWER. EPA/540/G-89-006. August.
EPA. 1996. Metal-Enhanced Dechlorination of Volatile
Organic Compounds Using an Above-Ground
Reactor - Technology Evaluation Report. Prepared
51
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by PRO for EPA Office of Research and Yamane, C.L, and others. 1995. "Installation of a
Development. June. Subsurface Groundwater Treatment Wall Composed
Vogan, John L, and others. 1995. "Site-Specific °LGranulaI Zero-Valent Iron." Preprint Extend
Degradation of VOCs in Groundwater Using Zero- Abstract Presented before the Division of
Valent Iron." Preprint Extended Abstract. Presented Environmental Chemistry, American Chemical
Before the Division of Environmental Chemistry. Society. Anaheim, California.
American Chemical Society (ACS). Anaheim,
California.
52
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Appendix A
Vendor's Claims for the Technology
The following section summarizes EnviroMetal Tech-
nologies, Inc. (ETI), claims regarding the metal-enhanced
dechlorination process, and was prepared by ETI. ETI's
report summarizing the results of the evaluation of the
aboveground reactor at the SGL Printed Circuits site in
New Jersey follows the text in this section.
The metal-enhanced dechlorination technology uses a
metal (usually iron) to enhance the abiotic degradation
of dissolved halogenated organic compounds. Bench-
scale and field-scale pilot studies conducted over the
past 4 years at the Institute for Groundwater Research,
University of Waterloo, and at several commercial sites
in the U.S., have shown that the process can be used
effectively to degrade halogenated methanes, ethanes,
and ethenes over a wide range of concentrations. These
studies have shown that:
requiring subsequent treatment, regeneration, or dis-
posal
The reactive iron is highly persistent with, depend-
ing upon the application, the potential to last for
several years to decades without having to be re-
placed
The process is one of the few that appears to have
potential for passive in situ treatment
The process degrades a wide range of chlorinated
volatile organic compounds, including trichloroeth-
ene, tetrachloroethene, cis-1,2-dichloroethene, and
VC. Preliminary tests suggest that it may be appli-
cable for a wider range of compounds in addition to
chlorinated aliphatic hydrocarbons.
The degradation kinetics appear to be first-order A.2 Technology Status
• With few exceptions, no persistent products of deg-
radation have been detected and degradation ap-
pears to be complete given sufficient time
• The degradation rates of chlorinated compounds
are several orders of magnitude higher than those
observed under natural conditions
A.1 Advantages and Innovative Features
• Reactants {i.e. reactive media) are relatively inex-
pensive
• The treatment is passive and requires no external
energy source for in-situ application
• Contaminants are degraded to harmless products,
rather than being transferred to another medium
The first full-scale in situ installation of the technology
occurred at an industrial facility in California in Decem-
ber 1994. An in situ pilot-scale installation was com-
pleted in upstate New York in May 1995. These in situ
installations and others planned in 1995 will assist in the
assessment of the long-term field performance of the
technology.
The results collected to date show that the metal-en-
hanced dechlorination process could be a highly effec-
tive aboveground or in situ method of remediating wa-
ters containing chlorinated aliphatic compounds. An in
situ permeable treatment wall of coarse-grained reactive
media installed across the plume will degrade com-
pounds as they migrate through the zone under natu-
rally occurring groundwater flow conditions. By utilizing
impermeable sheet piles or slurry walls, a large plume of
contaminated groundwater could be funneled through
smaller permeable treatment sections.
53
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enviro metal
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inc.
28 September 1995
Rhodes Engineering
505 South Lenola Rd.
Moorestown, NS 08057
Attention: Mr. John Rhodes
Dear John:
Reference: 31003.30 • Report on Performance of Test Reactor
Former SGL Printed Circuits Facility, Wayne New Jersey
Further to our recent conversation, we provide the following report for your review and
comment.
1.0 INTRODUCTION
This report presents EnviroMetal Technology Inc.'s (ETI's) interpretation of results obtained
from the ongoing field trial of the above ground test reactor installed at the former SGL
Printed Circuits facility hi Wayne, New Jersey. The reactor was installed to evaluate the
applicability of the EnviroMetal process (metal enhanced reductive dehalogenation) for field
scale remediation of VOC's present hi groundwater beneath the facility.
The design of the reactor is based on column tests completed hi 1993 using groundwater from
the site. Specifically, observed VOC degradation rates were used together with anticipated
influent concentrations to determine the size of reactor needed to treat 0.5 gpm of groundwater
pumped from extraction wells and collection trenches on-site. The column test results and
calculations are contained hi previous correspondence between ETI and Rhodes Engineering,
and are probably best summarized hi a technical paper presented hi April 1995 at the American
Chemical Society's annual meeting (attached as Appendix A of this document).
The field trial was accepted into the EPA's SITE evaluation program in the summer of 1993.
The SITE program contractor, PRC Environmental Management (PRC), was responsible for
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collection and analyses of samples from the reactor during the six month test period discussed
in this report. Dr. Chien Chen of the US EPA-RREL in Edison, New Jersey is the EPA
project manager for this study. PRC is preparing a separate report on various aspects of this
study for release in the fall of 1995.
As shown in Figure 1, the reactor is 8 ft high and 8 ft in diameter, and equipped with 5 sample
ports along the side. Pumped groundwater enters the top of the reactor and flows by gravity
through 5.5 feet of iron before discharging at the bottom of the reactor through a collection
pipe set in pea gravel. The effluent water level is kept above the top of the iron, to prevent
dewatering of the reactive media.
2.0 REACTOR OPERATION
Flow to the reactor commenced on November 15, 1994, at the design flow rate of 0.5 gpm.
most of this flow came from wells MW-2 and MW-7 on the north portion of the site, with
minor contributions from the south collection system. This rate was maintained until February
22, 1995, when the flow rate was increased to 1 gpm (using more water from the south side
collection system) to evaluate reactor performance at this higher flow rate.
The major operations and maintenance (O&M) task that was completed during the test period
involved the need to periodically scarify or break-up the upper surface of the iron at the top of
the reactor. The formation of a very hard layer at this surface caused the ponded water at the
top of the reactor to reach the high level shut-off point on several occasions. At early times
during the test, the layer may have been formed by suspended sediment and/or formation of
precipitates due to oxygenation of influent groundwater, before the groundwater entered the
iron. Later in the test, the ongoing build-up of carbonate precipitates (Section 3) hi the upper
few inches of iron may have caused this decline in hydraulic conductivity. Soon after
increasing the flow rate, algae formed hi the ponded water above the iron, which was removed
and subsequently prevented by placing a commercial algicide "boat" in the pond. This algae
formation is not considered related to the iron media.
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3.0 INTERPRETATION OF CHEMICAL RESULTS
3.1 Rates of VOC Degradation
Canister concentration data obtained from sample ports at various distances in the iron media
(Appendix B) were plotted as concentration vs. time using the average influent flow rate and
an iron porosity of 40%. Degradation rates (half-lives) were then determined by fitting a first
order decay model to the data. The first order decay model was not fit to the concentration
data for the first sampling event (4 pore volumes). At this early time the reactor is considered
to be in transition and the half-life would not be representative of what was occurring in the
reactor. Over the first 14 week test period about 80 pore volumes of water passed through the
canister at an average flow rate of 0.46 gpm. Based on this flow rate the velocity in the
canister during this period was 4.4 ft/day. We do not expect the canister reached steady-state
conditions until 40 to SO pore volumes passed through it (i.e., at weeks 8 to 10). Most of the
following discussion centers on PCE, for which the most complete (multi-point) data sets are
available.
The overall performance of the iron on December 21 (29 pore volumes), January 18 (51 pore
volumes), and February 15 (74 pore volumes) resulted in half-lives for tetrachloroethene
(PCE) of 0.83,1.41 and 1.99 hr respectively (Table 1). These half-lives are about 1.5 to 3
times longer than the half-life (0.64 hr) obtained in the treatability study. Based on more
recent data for trichloroethene (TCE) from other studies, this increase hi half-life is not
unexpected as temperature will have an effect on degradation rates. The temperature of the
canister over the first 14 weeks of operation ranged from 41 to 61°F. These lower
temperatures would result hi lower degradation rates than observed at the 73°F temperature of
the laboratory column study. While the temperature-degradation rate relationship data has
only been determined for TCE, we expect that PCE would show a similar trend. If the trends
indeed are comparable, then the PCE half-life observed in the column study might be expected
to increase to 1.1 to 1.4 hr at the temperature of the canister.
To examine the effects of possible precipitates etc. at the top of the iron, we recalculated half-
lives using data from only this portion of the canister. At the 0.46 gpm flow rate the PCE
half-lives calculated from concentration measurements in the first foot of the iron were 5.2,
4.4, and 21.3 hr. the half-life of 21.3 hr was about four times higher than any other, and
therefore, this half-life is considered an anomalous result. The longer half lives (slower
degradation rates) in the influent portion of the canister may be the result of gas accumulation
and/or precipitate formation. Using a corrosion rate for Master Builders iron of
56
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Rhodes Engineering 28 September 1995
0.7mmol/kg/day (Reardon,1995) and an iron mass of about 21.5 tons, the expected gas
generation rate is about 11.8 ft3 per day. If this gas were to accumulate near the top of the
canister then the porosity would be substantially lower than the 40% used in determining flow
velocities. This would result in faster velocities and correspondingly shorter half-lives than
those calculated using a velocity of 4.4 ft/day. Another possible explanation is the formation
of a greater quantity of precipitates near the influent of the canister, as discussed in section
3.2. These precipitates would not only decrease the porosity but may have formed a surface
coating, inhibiting the degradation process.
On February 22 the flow rate was increased to about I gpm reducing the residence time in the
canister from 1.2 days to 0.57 days. At this flow rate the half-lives for PCE on March 29
(136 pore volumes), April 27 (175 pore volumes), and May 24 (200 pore volumes) were
1.81,2.17, and 1.86 hrs respectively. These half lives are in the same range as the final half-
life measured at the previous flow rate and thus the low concentrations of PCE observed in
the effluent are expected. The concentration data (Appendix 6) also indicate that flow may
have been bypassing sampling port R5 located at 5 feet during this second flow rate. On
February 15 and throughout most of second flow rate test, PCE, trichloroethene (TCE), and
cis-l,2-dichloroethene (cDCE) data are all below detection at sampling port R5 but are present
in higher concentration in the effluent stream. For conservatism the higher effluent
concentrations were used in determining half-lives.
The amount of TCE produced due to PCE degradation was determined from the peak
concentration minus the influent concentration. The highest percentage was observed after 74
pore volumes, when there was an increase of 330 p.g/L TCE indicating a 4.5% conversion of
influent PCE concentration. TCE degradation rates were calculated using data after the peak
concentration (Table 2). After 51 and 74 pore volumes the concentration of TCE after the
peak concentration was below detection, so the detection limit was used to calculate a
conservative half-life. The half-life for TCE (1.27 hr) determined in the column study was
also corrected for field temperatures and the results presented in Table 2. The TCE half-lives
are similar to those for PCE throughout the test period, which is consistent with both the
results of the laboratory column study and other studies.
The greatest amount of cDCE produced was 4.5% due to the dechlorination of PCE and TCE
(54 pore volumes) which was lower than the 10% anticipated in the design. Half-lives at the
0.46 gpm flow rate ranged from 2.1 to 5.7 hr (Table 3) and are consistent with the 3.7 hr used
in the design. At the second flow rate, due to the production of DCE from the dechlorination
of TCE and PCE over the entire canister, the cDCE concentration does not have sufficient
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residence time to degrade and the effluent contains higher concentrations (330 to 630 M.g/L)
than at the first flow rate. Consequently, the percentage of cDCE formed and half-lives were
not determined at the second flow rate. Field temperatures would also cause the cDCE half-
lives to be longer than those determined in the laboratory. However, no temperature-
degradation rate date is available for cDCE.
No vinyl chloride (VC) was detected at the first flow rate until 61 pore volumes (i.e., when
the canister reached steady-state), when VC appeared in the effluent at 1.2 u.g/L. It was also
detected in the effluent at 67 and 74 pore volumes at 2.8 and 8.4 H-g/L. At the second flow
rate it appeared hi the effluent at concentrations from 13 to 24 u.g/L. The appearance of VC in
the effluent was expected, given the longer half-lives for PCE and TCE occurring in the field.
These mean that VC would not be produced until further "downstream" in the reactor, and
would therefore not have sufficient residence time to degrade.
3.2 Inorganic Geochemical Results
Consistent trends in inorganic concentration profiles were observed throughout the test period.
As shown in Table 4, calcium and total inorganic carbon (TIC) concentrations declined over
the entire length of the canister, with the largest declines occurring at the influent end. The
declines in calcium, TIC and low levels of dissolved iron indicate that calcium carbonate and
iron carbonate were precipitating in the canister. Based on expected corrosion rates, we
expect that iron hydroxide precipitates were also forming. Effluent iron concentrations were
generally less than 0.1 mg/L and never exceeded 1.1 mg/L. Magnesium concentration
remained relatively constant at influent levels (19 to 24 mg/L) over the first 2 feet then declined
slightly to between 11 and 23 mg/L. During the 4 pore volume sampling, the magnesium
concentrations were lower at 3.5 and 5 ft than in the effluent, indicating that channelling might
have been occurring. Also at the first sampling, the sulfate concentration decreased from 33
mg/L to <5 mg/L. From 29 to 175 pore volumes the decrease in sulfate was minimal (a
decrease of 7 mg/L). Then at 200 pore volumes the sulfate concentration decreased from
about 52 to 8 mg/L. These declines in sulfate are indicative of some sporadic sulfate reduction
occurring in the canister. Chloride concentrations increased due to the dechlorination of PCE
and TCE. The declines in calcium, TIC, magnesium, and sulfate are similar to those observed
in the laboratory column experiments with a residence time of about 1 day. Other major ion
profiles showed no significant changes as water moved through the canister. Small quantities
of manganese (<1.5 mg/L) appeared in the samples, apparently leaching fronrthe iron.
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To assess the effect on mineral precipitates on porosity, we have derived estimates of porosity
loss up to 200 pore volumes, based on the observed declines in dissolved calcium and TIC
concentrations and on the iron corrosion rate. While approximate in nature, these estimates
will be useful in interpreting the results of solid phase analyses. These analyses are currently
being completed on cores from the reactor collected on July 18, 1995.
From Table 4, the estimated porosity losses due to calcium carbonate, iron carbonate, and iron
hydroxide at the first flow rate (80 pore volumes) are 2.2% for the first foot, 1.5% for the
next foot, and 1.2% for the remainder of the canister. If the flow rate were maintained at 0.5
gpm the yearly (318 pore volumes) porosity loss may reach 9.4%. By the last sample date,
24 May, at 200 pore volumes, the porosity losses totalled 4.4%, 5.4%, and 2.3% for the first
foot, the second foot, and for the remainder of the reactor respectively. These additional
porosity losses would result in an expected yearly loss (636 pore volumes) of 19.5% in the
second foot of the reactor at the higher flow rate of about 1 gpm. The larger decrease in the
first and second foot are due to the greater declines in calcium and TIC in this area. Based on
the column studies, we estimated porosity losses of up to 4% per year from carbonates and an
additional 9% due to iron hydroxides.
4.0 SOLID PHASE ANALYSES
On July 18,1995 samples of the reactive material were collected from immediately beneath the
canister manhole and submitted for the following analyses:
i) leaching and elemental analyses of leachate;
ii) determination of carbonate content; and
iii) scanning electron microscopy (SEM) analyses.
Several cores were taken within the 1 foot radius of the manhole opening through the top of
the canister. The most complete iron core recovered was subsampled at 1, 2,4,6,8,10, 12,
18, 24, 30 and 36 inches. These subsamples were submitted for analysis, together with a
fresh iron sample collected at the time of canister start-up were also analyzed. The results of
these analyses are given in Tables 5 and 6.
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4.1 Results
4.1.1 Leaching Analyses
Leachable calcium, magnesium and iron were determined by leaching the samples with 5%
HNOs, followed by analyses of leachate by ICAP for those elements. Iron values are not
reported, as no clear trends were observed from the data. That is, one cannot differentiate
between the elemental iron present and the iron which may be incorporated into carbonate and
hydroxide precipitates hi the samples. As expected, the highest calcium values were measured
in the samples from the influent, reaching a maximum at 4 inches depth. The level of calcium
drops substantially in samples from 30 and 36 inches depth. Levels of magnesium are
constant over the 3 feet of core, but are substantially higher than in the fresh iron.
4.1.2 Carbonate Content
Determination of carbonate content involved the measurement of CO2 gas evolved when the
sample was treated with a strong acid. From Table 6, sample results show the expected trend,
with highest carbonate content measured at the influent end of the core and reaching a
maximum at 4 inches. These results are in good agreement with those for calcium obtained in
the leaching experiment. The maximum carbonate content at 4 inches is about 7% (7 g/100 g)
of the solid. A series of calculations shown in Table 6 were completed to equate these
measured carbonate contents with possible porosity losses. As shown in Table 6, the
carbonate precipitates may have taken up 14.5% of the pore space at the 4 inch interval. This
interval may represent the point at which the pH increase causes significant precipitation to
occur. From the results hi Table 6, the average porosity loss over the first foot was about
9.7% due to carbonates, which is higher than the 4.4% calculated hi Table 4 from aqueous
geochemical results (up to 24 May for both carbonate and iron hydroxide precipitates). The
latter estimates represent average values over the first foot of the canister based on samples
collected at specific times during the experiment, whereas the solid analyses represent a more
cumulative record of precipitation.
4.1.3 Scanning Electron Microscopy (SEM) Analyses
The SEM analyses of the samples from the canister gave results that were similar to those
observed in previous studies. The most abundant calcium and iron carbonate precipitates were
60
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Rhodes Engineering 28 September 1995
identified near the influent end of the column as expected. As shown on Figures 2 and 3,
calcium carbonate precipitates are the long slender crystals, while iron carbonates exhibit a
square crystal structure. Unfortunately kon hydroxides can not be observed with SEM. We
expect more hydroxide precipitates would occur farther "down" the canister in response to
further pH increases, once the carbonate buffering capacity of the groundwater is exhausted.
4.2 Summary
In general, the solid phase analyses confirmed the aqueous geochemical results which have
been obtained during the previous six months. However, the solid phase analyses show that
even within a 1 foot interval, build-up of carbonate precipitates may occur in thin discrete
layers which represent a significant impediment to downward flow.
5.0 FUTURE FIELD APPLICATION OF THE TECHNOLOGY AT THE
SGL PRINTED CIRCUIT FACILITY
It is our understanding that future field applications of the technology may involve both above-
ground field canisters as interim treatment measures to treat groundwater containing VOC's
elsewhere on site, and the installation of permeable in-situ treatment zones to act as long-term
remedial measures near suspected source areas. The field test results indicate that the
technology could be used effectively hi either application. VOC degradation rates in the field
appear high enough to support the construction of reasonably sized reactors at flow rates of a
few gpm, especially in areas where influent PCE concentrations will be lower than the 5 to 10
ppm treated in the existing reactor. The field trial has provided "field-scale" half-lives which
can be used to refine the design of future field units. We also suggest the above-ground
design be modified so that a highly permeable upper layer of reactive media be created (for
example, a mix of pea gravel and iron) to minimize the effects of precipitate formation
immediately beneath the ponded water. However, we would anticipate that there will still be a
need to periodically scarify this upper surface.
The potential O&M requirements due to precipitate formation in an in-situ treatment zone are
still undetermined. We will use data from the two in-situ treatment systems installed to date to
attempt to correlate precipitation rates observed using pumped groundwater with precipitation
rates observed in-situ. We can then apply this correlation to the SGL field trial results to
evaluate the potential requirements at this site. Given the likely shallow installation depths, the
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O&M requirements may not be too severe. A second key factor in designing in-situ treatment
zones at this site will be determining the velocity expected in-situ, at a specific treatment zone
location.
We hope that this report is of use. If you have any questions or comments regarding the
above, please contact us.
Yours very truly,
ENVmOMETALTECHNOLOGES INC.
John/vogan, M.Sc.
Hydrogeologist, Project Manager
cc: Guy Montfort, PRC Environmental Management
Dr. Chien Chen, US EPA, RREL
JV/je
d:\etiV31003V5I003-3.U7
62
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Access for visual
observation, sampling
Inflow
Outflow
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Inflow
5.5'
6"
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\ /
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3
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i
1'
1
1'
1.5'
1'
6" $
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observation, sampling ~~"JT *^
i n
i i i
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/ Sample port
100% iron
Pea gravel
/
£^-^g^$£p£^
•way vaive
ias vent
Sealing flange
./ior top
[[— - — »• Outflow
(Level adjustable to
allow modification
of reactive media)
Collector tile (perforated pipe)
Note: Dimensions determined based on
laboratory results and expected flow rate.
Figure A-1. Pilot-scale treatability test of EnviroMetal process—unit design: SQL Printed Circuits Facility.
63
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Figure A-2a. SEM photographs of iron grains—iron grain SOX
actual size from six-inch interval.
Figure A-2b. SEM photographs of iron grains—square iron
carbonate precipitates 3.700X actual size from four-
inch interval.
Figure A-3a. SEM photographs of iron grains from ten-inch
Interval—spindle shaped calcium carbonate on iron
grain 2.000X actual size.
Figure A-3b. SEM photographs of iron grains from ten-inch
interval—close-up of calcium carbonate 8.000X actual
size.
64
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TABLE 1: HALF-LIFE OF TETRACHLOROETHENE
a -
b.
__* Pore
Date ,, ,
Volumes
Dec. 21
Jan. 18
Feb. 15
Mar. 29
Apr. 27
May 24
29
51
74
136
175
200
Flow _
Rate
(gpm)a
0.46
0.46
0.46
0.97
0.90
0.77
Half-Lives (hr)
Canister Coiumn*>
First Foot
5.2
4.4
21.3
3.2
6.3
9.2
Overall
0.83
1.41
1.99
1.81
2.11
1.86
1.1
1.2
1.4
Flow rates are calculated from cumulative influent volumes since the start of operation
at flow rates of 0.5 or 1.0 gpm.
Half-life of the laboratory column (0.64 hr) adjusted from 73°F to the temperature of
the canister on that date.
TABLE 2: HALF-LIFE OF TRICHLOROETHENE
Date
Dec. 21'
Jan. 18
Feb. 15
Mar. 29
Apr. 27
May 24
Pore
Volumes
29
51
74
136
175
200
Flow
Rate
(gpm)
0.46
0.46
0.46
0.97
0.90
0.77
Half-Lives (hr)
Sample Points
R2,R3a
R2, R3, R4a
R3, R5a
R3, El
R3,E1
R3, El
Canister
0.6
1.7
1.8
2.4
2.5
3.2
Column
b
2.1
2.4
2.8
* - Detection limits (1 jig/L) used for most conservative estimates of half-life.
*> - Half-life of the laboratory column (1.27 hr) adjusted from 73 F to the temperature of the
canister on that date.
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TABLE 3: HALF-LIFE OF CIS- 1,2-DICHLOROETHENE
Date
Dec. 21
Jan! 18
Feb. 15
Mar. 29
Apr. 27
May 24
Pore
Volumes
29
51
74
136
175
200
Flow
Rate
(gpm)
0.46
0.46
0.46
0.97
0.90
0.77
Sample
Points
R2,
R3,R4*
R3.E1
R3.E1
Half-Lives (hr)
2.1
2.4
5.7
ND
ND
ND
a - Detection limits (1 p.g/L) used for most conservative estimates of half -life.
ND- Not Determined
66
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TABLE 4: ESTIMATED POROSITY LOSSES DUE TO PRECIPITATION
Section
„ °.f Date
Canister
Decline in vdume
Concentration Passed
(mmol/L) •tomato
•
% Porosity
Loss
(fee*) Calcium Carbonate Canister (gal)
0-1 - Nov. 22
Nov. 22 - Dec. 21
Dec.21 - Jan. 18
Jan. 18 - Feb. 15
Feb. 15 - Mar. 29
Mar. 29 - Apr. 27
Apr. 27 - May 24
,1-2 - Nov. 22
Nov. 22 - Dec. 21
Dec.21 - Jan. 18
Jan. 18 - Feb. 15
Feb. 15 - Mar. 29
Mar. 29 - Apr. 27
Apr. 27 - May 24
2-5.5 - Nov. 22
Nov. 22 - Dec. 21
Dec.21 - Jan. 18
Jan. 18 - Feb. 15
Feb. 15 -Mar. 29
Mar. 29 - Apr. 27
Apr. 27 - May 24
0.36 1.50 3400
0.93 1.75 20516
0.73 0.33 18325
0.51 0.50 18592
0.50 1.00 51482
0.47 0.75 32398
0.00 0.00 20646
Total Estimated Porosity Loss
0.34 1.17 3400
0.16 0.50 20516
0.21 0.25 18325
0.37 1.00 18592
0.43 1.00 51482
0.29 1.00 32398
1.87 4.48 20646
Total Estimated Porosity Loss
0.38 0.25 3400
0.10 0.73 20516
0.14 0.53 18325
0.34 1.14 18592
0.41 0.88 51482
0.67 1.13 32398
0.00 0.43 20646
Total Estimated Porosity Loss
0.12
0.85
0.65
0.56
1.15
0.72
0.33
4.38%
0.11
0.43
0.41
0.452
1.13
0.70
2.04
5.36%
0.09
0.36
0.35
0.38
0.29
0.49
0.34
2.28%
67
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TABLE 5: ELEMENTAL ANALYSES RESULTS
Leachate Concentration
Sample Depth (inches) Calcium Magnesium
1 733 7.9
2 918 8.8
4 1,130 11.8
6 1,060 10.8
8 761 , 9.8
10 579 9.2
12 518 9.9
18 319 9.5
24 189 11.9
30 64 10.0
36 49 5.3
68
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TABLE 6: CARBONATE ANALYSES RESULTS
Sample Depth
(inches)
1
2
4
6
8
10
12
18
24
30
36
Fresh
Replicate 1
5.01
6.02
7.18
4.21
3.35
4.53
3.69
1.85
1.68
0.33
0.41
0.15
Example calculation of estimated p
a) density of iron in canister =
42,920 Ibs iron
V = 42n x 5.5
42,290
276.5
Percent Carbonate (g/g)
Replicate 2
5.04
6.56
6.85
4.41
3.13
3.05
2.95
1.87
1.23
0.63
0.48
0.21
>orosity loss at 4 inch interval:
mass iron
canister volume
1 ^ "5 IKc /-ft3
— 10D.Z IDS /It
Average
5.02
6.29
7.02
4.31
3.24
3.79
3.32
1.86
1.45
0.48
0.44
0.18
Percent Porosity
Loss
10.36
12.97
14.47
8.89
6.69
7.82
6.85
3.84
3.00
0.99
0.91
b) convert density to g/cm3
155.2 Ibs /ft3 x •
453.6 g/lb ___3
oc -an .Trr
^.U,_/i/ j
ft
c) use measured % carbonate to estimate mass of carbonate in 1 cm3, ±2.5 g iron x 7%
calcium carbonate (measured value from above table) = 1.74 x 10-1 g carbonate
69
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d) if molar volume = 33 cm3/mol, then this mass of carbonate corresponds to.
1.74 x 10~lg [ 100 1/mol } x (33cm2/mol) = 5.74 x 10'2 cm3 of carbonate
e) corresponding porosity loss due to this carbonate volume:
.057
in 1 cm3 of reactive iron, the total pore space = 0.4 cm3 so carbonate occupies :z""A
w»^
14.476% of original porosity.
70
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Appendix A- Report on Bench Scale Studies (A.C.S. paper presented in April 1995)
"PREPRINT EXTENDED ABSTRACT"
Presented Before the Division of Environmental Chemistry
American Chemical Society
Anaheim, CA April 2-7, 1995
SITE SPECIFIC DEGRADATION OF VOCS IN GROUNDWATER
USING ZERO VALENT IRON
J.L. Vogan, EnviroMetal Technologies Inc., 42 Arrow Road, Guelph, Ontario, NIK 1S6
R.W. Gillham, S.F. O'Hannesin, University of Waterloo, Waterloo, Ontario, N2L 3GI
W.H. Matulewicz, J.E. Rhodes, Rhodes Engineering
505 S. Lenola Road, Moorestown, NJ 08057
The use of zero valent metals for groundwater remediation was commercialized by the
University of Waterloo in 1992, through EnviroMetal Technologies Inc. (ETI). Since that time,
over 15 bench-scale treatability studies have been undertaken by ETI to examine the possible
application of zero valent iron for remediation of groundwater containing VOCs at industrial
facilities across the United States. Table 1 lists the compounds which have been evaluated in
these tests. These results are valuable in that they are highly consistent with the results reported
previously (Gillham and O'Hannesin, 1994). The degradation process appears robust, in that it
appears relatively unaffected by the use of commercial grade iron, by stabilizing agents
commonly added to industrial grade solvents and by inorganic groundwater chemistry. For
example, half-lives for TCE determined in waters from six sites of highly varying conditions,
all fell within a narrow range of 0.3 to 0.6 hr. In this paper, data from a typical study will be
used to illustrate the methodology used in applying the results to subsequent field remediation.
The treatability study was conducted using groundwater from a site in New Jersey. A thin layer
of silty clay till (8-10 feet) overlies fractured bedrock. Groundwater containing VOCs is found
both in the overburden near the bedrock contact, and in the shallow bedrock. Tetrachloroethene
(PCE, ranging from non-detect to 50,000 ug/L) and trichloroethene (TCE, ranging from non-
detect to 3,000 M-g/L) are the major VOCs present in groundwater, and total dissolved solids
ranges from 425 to 450 mg/L. Initially, groundwater obtained from the site was pumped at a
constant rate through two laboratory columns, one containing 100% metallic iron and one
containing 50 wt % iron and 50 wt % silica sand. The iron used is available in large volumes of
a consistent grain size and composition, at a price which makes it feasible to consider its use in
"full-scale" field applications (i.e., where many tons of the material may be required). The
columns were equipped with side sample ports which allowed profiles of VOC concentration
vs. distance to be obtained. Using measured flow velocities, these profiles were converted to
concentration vs. time profiles and first order degradation rate constants and corresponding half-
lives were calculated. Though reasonably good r2 values were obtained from most profiles, in
some cases, only two data points were available for calculation of the rate constant due to the
rapid disappearance of the VOC.
71
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Rates of degradation calculated from these profiles (Figures 1 to 4 and Table 2) indicate the
dependence of degradation rate on reactive surface area, as half-lives in the 100% iron column
were consistently higher than those measured in 50% iron. About 10% of the original summed
concentration of TCE and PCE appeared as 1,2-cis-dichloroethene (cDCE), and about 1% as
vinyl chloride. Both of these compounds also degraded. Half-lives of PCE and TCE of about
0.5 hours were measured in the 100% iron column, but increased to 0.7 and 1.1 hours in the
column containing 50% by weight iron. Half-lives of 1.5 hrs and 1.2 hrs. were calculated for
cDCE and vinyl chloride respectively in 100% iron. From these initial results, it became
apparent that 100%'iron would need to be used to construct a treatment zone of a realistic size,
so a second test was conducted at a second flow rate using the 100% iron column to confirm the
results of the first test. Similar half-lives for PCE and TCE were measured in the second test,
but half-lives of cDCE (3.7 hrs) and vinyl chloride (0.9 hrs) varied considerably from the initial
test.
Major cation and anion analyses were performed on samples of column effluent. The results
shown in Table 3 are typical of those observed over the entire test period. The corrosion of iron
caused the pH of the groundwater to increase, promoting calcium carbonate precipitation. The
amount of dissolved iron in the effluent was less than would be expected from independent
measurements of corrosion rate, indicating that iron carbonate and/or iron hydroxide
precipitation also occurred within the column. The groundwater was supersaturated with
respect to calcium carbonate before entering the iron material, suggesting atmospheric contact
and dissolution of CO2- Therefore, although mineral precipitation is clearly a potential
impediment to application of the technology, precipitation at the site may be less than reflected in
the laboratory tests.
It was initially envisioned that collection trenches installed in shallow bedrock would direct
groundwater to an in situ flow-through bed or chamber containing the reactive material.
However, for purposes of a pilot-scale field trial it was decided to use an above-ground reactor
where flow through the bed and changes in chemistry could be more accurately monitored (i.e.,
water would be pumped from the trench collection system to the reactor). Using conservative
concentration estimates of PCE concentrations and flow of groundwater egressing the trenches,
and the data from the laboratory test, the reactor design shown in Figure 5 was developed
according to the calculations in Table 4. An estimated influent PCE concentration of 30,000
}ig/L was based on historical monitoring data from overburden wells in the vicinity of the trench
system. This is a conservative approach, as PCE levels in shallow bedrock groundwater,
which will also enter the collection system, are considerably lower. The key parameter in the
design is the residence time required to degrade both the VOCs originally present (PCE and
TCE) and any chlorinated compounds (cDCE or vinyl chloride) produced. Key assumptions in
this design were that the time for PCE degradation would be sufficient for any TCE in the
groundwatcr to degrade (as observed in the column tests), and that 10% cDCE and 1% vinyl
chloride would result from PCE and TCE degradation. A half-life of 1.5 hours for cDCE was
used in these calculations, as similar or higher cDCE degradation rates have been observed in
several other studies. The final "design" residence time is 1.1 days. cDCE, though not present
72
-------
in significant concentrations in the influent groundwater, emerged as the limiting parameter in
the design.
The reactor was built in November 1994, and will be tested at an initial flow rate of 0.5 gpm for
three months. Side ports along the reactor allow concentration vs. time profiles to be obtained,
permitting calculation of VOC degradation rates (and inorganic precipitation rates). After three
months, the flow rate may be increased if the influent PCE concentration, as anticipated, is
lower than 30,000 p.g/L. The design of the reactor also allows experimentation with methods to
remove precipitates, if these are indeed a serious problem in the field.
References
GUlham, R.W. and SP. O'Hannesin. 1994. Enhanced Degradation of Halogenated Aliphatics
by Zero-Valent Iron. Groundwater 32,958-967.
73
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TABLE 1; COMPOUNDS EVALUATED DURING TREAT ABILITY STUDIES
Successfully Degraded Unsuccessfully Degraded to Date
tetrachloroethene 1,2-dichloroethane
trichloroethene chloroethane
cis- and trans-1,2-dichloroethene dichloromethane
1,1-dichloroethene
vinyl chloride
1,1,1 -trichloroethene
tetrachloromethane.
trichlpromethane
1,2-dibrpmethane
1,23-trichloropropane
1,2-dichloropropane
freon 113
TABLE 2: OBSERVED VOC DEGRADATION RATES, COLUMN TESTS
Initial 100% Iron 50% Iron
Compound Concentration (ug/L) Half-Life (hrs) Half-Life (hrs)
PCE
TCE
cDCE
Vinvl Chloride
4,000-12,000
1,000
400-475
14
0.4 >
0.5a
1.5a
l.2J
, 0.6b
, 0.7b
i, 3.7b
0.7
1.1
a - first test b - second test
TABLE 3; OBSERVED INORGANIC CHANGES, 100% IRON
Compound
Calcium
Magnesium
Alkalinity
Iron
Influent Change
Concentration (mg/L) (mg/L)
81
26
242
0.1
-67
-6
-198
+0.4
TABLE 4: ABOVE-GROUND REACTOR DESIGN
Compound
PCE
cDCE*
Vinyl Chloride*
Assumed Initial
Concentration (ug/L)
30,000
3,000
300
Half-Life
MCL (ug/L) (hrs)
1 0.6
10 1.5
5 1.0
Required Residence
Time (hrs)
8.9
12.3
5.9
* produced from degradation of PCE
- Initial flow rate 0.5 gpm
- Required reactor size ±256 ft?
74
-------
4800
-+- 47cm/day
•O- 76cm/day
T 1
5 10 15 20
Distance along column (cm)
30
40
50
Figure 1- Degradation of PCE, 100% iron.
7200
7700 -
d
7000 -
900 -
800 -
700 -
600 -
500 -
400 -
300 -
200 -
700 -
0
0
•+• 47cm/day
-O- 76cm/day
10
TT
75
1
20
IT
30
r
40
SO
Distance along column (cm)
Figure 2. Degradation of TCE, 100% iron.
75
-------
500
I
2.5
47cm/day
76cm/ day
V
5 10 15 20
Distance along column (cm)
30 40
60
Figure 3. Degradation of cDCE, 100% iron.
§
u
I
47cm/day
76cm/day
30 40 50
Distance along column (cm)
Figure 4. Degradation of VC, 100% iron.
76
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Air elir
Inflo
6"
5.5'
6»
ninator Water filter ~>
\ /
WH H H
Flow meter
Sample ^—
ports /*
'
8' 1,
Sightglass and access for visual
_^X observation, sampling
1 1
—
V
Ponded ground water
_
Pea gravel
Direction
' of flow
Iron reactive media |
Pea gravel
*.. „
Sealing flange
>/ for top
L_ , :. ...X- — , — 11- , , — '
a - — »• uutnov
(Level adjustable
to allow modifcation
of reactive media)
Collector tile (perforated pipe)
Figure 5. Schematic of above-ground reactor design.
77
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-------
Appendix B
Case Studies
Introduction .76
Semiconductor Facility, South San Francisco Bay, California 76
Canadian Forces Base, Borden, Ontario, Canada B-5 77
Industrial Facility, Kansas B-7 77
Industrial Facility, New York B-8 78
Introduction
This appendix summarizes several case studies on the
use of metal-enhanced dechlorination technology. These
case studies involve bench-scale units, pilot-scale units,
and full-scale units treating contaminated groundwater.
The information available for these case studies ranged
from detailed analytical data to limited information on
system performance and cost. Results from four case
studies are summarized in this appendix.
Case Study B-1
Semiconductor Facility
South San Francisco Bay, California
Project Description
Several studies were performed by EnviroMetal Tech-
nologies, Inc. (ETI), at a former semiconductor manu-
facturing site in South San Francisco Bay, California to
examine the feasibility of constructing and operating an
in situ permeable wall containing a reactive iron medium
to replace an existing pump-and-treat system. Ground-
water at this site was contaminated with trichloroethene
(TCE), cis-1,2-dichloroethene (cis-1,2-DCE), VC, and
Freon 113. Results of laboratory column studies per-
formed by EnviroMetal Technology, Inc. (ETI), indicated
that the concentration of dissolved VOCs in the ground-
water were significantly reduced. Following the labora-
tory studies, pilot- and full-scale units were installed.
Results
Pilot-Scale System
An aboveground demonstration reactor containing 50%
iron by weight and 50% sand by weight was installed
and operated over a 9-month period. Groundwater was
pumped through the demonstration reactor at a
velocity of 4 feet per day.
flow
The groundwater at the semiconductor facility site was
highly mineralized. Although precipitate formation was
evident at the influent end of the test reactor, the rate of
degradation remained relatively constant over the 9-
month test period. The pilot-scale test results are sum-
marized below.
voc
TCE
cis-1,2-DCE
VC
Freon 113
Influent Concentration
(parts per billion)
50 - 200
450-1,000
100-500
20-60
Half-Life
(hours)
<1.7
1 -4
2-4
<1.6
Several other aspects of the metal-enhanced dechlori-
nation process were evaluated during this pilot-scale
test, including the following.
• Metals precipitation—Inorganic geochemical data
collected in the field was used to predict the poten-
tial precipitates from the reactive iron medium. Op-
erations and maintenance requirements for the full-
scale design were based on the evaluation of the
metals precipitation data.
• Hydrogen gas production—Hydrogen gas may be
produced during the reductive dehalogenation reac-
tion in the metal-enhanced dechlorination process.
Rates of hydrogen gas generation measured in the
laboratory (Reardon 1995) were used to evaluate
the need for any hydrogen gas collection system in
the full-scale application. Based on the evaluation,
79
-------
no need for a hydrogen gas collection system
Indicated.
• Microbial Effects—Groundwater from within the reac-
tor was sampled for microbial analysis. The microbial
analysis indicated that the microbial population in the
reactor was similar to the population observed in
untreated groundwater. There was no visual evi-
dence of biomass generation during the test.
Full-Scale System
Based on the pilot-test results, a full-scale in situ treat-
ment wall was installed in December 1994. The reactive
wall was 4 feet thick, 40 feet long, and situated vertically
between depths of about 7 feet and 20 feet below ground
surface. The 4-foot-thick zone of 100% granular iron was
Installed to achieve a hydraulic residence time of about 4
days to treat VOCs to cleanup standards, based on the
estimated groundwater velocity of 1 foot per day. VC
required the longest residence time to degrade to cleanup
standards. A layer of pea gravel about 1 foot thick was
installed on both the upstream and downstream sides of
the reactive wall. The reactive wall was flanked by slurry
walls to direct groundwater flow towards the reactive iron
medium. The construction cost for the reactive wall was
about $225,000. Together with slurry walls, capital costs
were about $720,000.
Minimal data for the full-scale system was available at
the time this report was prepared. Monitoring wells were
installed near the upstream and downstream faces, and
data is only available for samples collected up to one
year after installation. No chlorinated compounds were
detected in the monitoring wells except for cis-1,2-DCE,
which was detected in one well at a concentration of 4
jig/L. Although the initial results are encouraging, insuffi-
cient data is available at this time to evaluate long-term
performance. For further details see Yamane et al 1995.
Case Study B-2
Canadian Forces Base
Borden, Ontario, Canada
Project Description
In May 1991, a small-scale in situ field test was initiated
at the Borden site to treat groundwater contaminated with
TCE and PCE. The source of the contaminant plume at
the site was located about 4 meters (m) below ground
surface and 1 m below the water table. The plume was
about 2 m wide and 1 m thick, with a maximum concen-
tration along the axis of about 250,000 and 43,000 ng/L
for TCE and PCE, respectively. An in situ permeable wall
was constructed about 5.5 m downgradient from the
source. The aquifer material consisted of a medium to
fine sand, and the average groundwater velocity was
about 9 centimeters per day (cm/day).
The reactive wall was constructed by driving sheet piling
to form a temporary cell 1.6 m thick and 5.5 m long. The
was native sand was replaced by the reactive iron medium,
consisting of 22% iron grindings by weight and 78%
coarse sand by weight. After the reactive iron medium
was installed, the sheet piling was removed, allowing
the contaminant plume to pass through the wall.
Rows of multilevel samplers were located 0.5 m
upgradient from the wall, at distances of 0.5 and 1.0 m
into the wall and 0.5 m downgradient from the wall,
providing a total of 348 sampling points.
Results
Samples were collected and analyzed over a 474-day
monitoring period. The results indicated that the effec-
tiveness of the reactive wall in degrading TCE and PCE
did not decline over time. The results also indicated that
299 days after the wall was installed, the average maxi-
mum concentrations of the TCE and PCE downstream
of the wall were about 10% of the influent concentra-
tions. The downstream concentrations were, however,
about three orders of magnitude greater than the drink-
ing water standards. Chloride concentrations were higher
on the downgradient side of the wall, indicating that TCE
and PCE were dechlorinated. In addition, results indi-
cated that DCE isomers were produced by the degrada-
tion of TCE and PCE. The DCE isomers were degraded
as they passed through the wall, although effluent con-
centrations remained above drinking water standards.
No VC was detected as a result of PCE, TCE, or cis-1,2-
DCE degradation, and no bacterial growth was ob-
served. Examinations of the reactive iron medium with
X-ray diffraction and scanning electron microscopy
showed no metal precipitation onto the reactive iron
medium.
Water samples collected about 4.3 years after wall
installation indicated that performance had not changed
significantly over the treatment period. No maintenance
was required during operation of the wall. For further
details see O'Hannesin 1993.
Case Study B-3
Industrial Facility
Kansas
Project Description
A 1,000-foot-long funnel and gate system was installed
at the property boundary of an industrial facility in Kan-
sas in 1996. The system was installed to treat about 100
to 400 ppb (jj.g/L) of TCE in groundwater egressing the
property. The TCE occurs in a basal alluvial sand and
gravel zone overlying the local bedrock, at a depth of
about 30 feet below ground surface. A low natural
groundwater velocity permitted the use of a high funnel-
to-gate ratio; the velocity increase due to the funneling
action permitted a reasonable small treatment zone to
be built.
80
-------
As built, the system had about 490 feet of impermeable
funnel on either side of a 20-foot long reactive gate. The
funnel section at this site consisted of a spil-bentonite
slurry wall. The slurry wall was constructed first; the gate
section was excavated in the middle of the wall after it
had set. The reactive zone was about 13 feet high and
about 3-feet wide (that is, the flow-through thickness
was 3 feet). Weather delays and other non-technical
delays extended the construction period; however, the
construction contractor estimated that under optimal
conditions the slurry wall could have been built in two
weeks, and the reactive gate section in one week.
Results
Costs for the installation (slurry walls and gate) were
about $400,000, including 70-tons of granular, reactive
iron. No performance data were available at the time of
this report. For further details see Focht, Vogan, and
O'Hannesin 1996.
Case Study B-4
Industrial Facility
New York
Project Description
Following successful bench-scale studies, a pilot—scale,
In situ funnel and gate was installed at an industrial
facility in New York sate in May 1995. The system was
designed to treat up to 300 ppb (jig/L) of TCE, about 100
to 500 ppb of cDCE and up to 80 ppb of vinyl chloride.
The contaminants are present in a shallow sand and
gravel aquifer that overlies a dense clay layer about 14
to 15 feet below ground surface. The reactive section
(the gate) is 12 feet long and 3.5 feet thick, and is
flanked by 15-foot sections of sealable joint sheet piling
extending laterally on either side, forming the funnel.
Monitoring wells were installed upgradient from, in, and
downgradient from the reactive zone. Piezometers were
also installed upgradient from the reactive zone to pro-
vide horizontal gradient and flow velocity data.
Results
Costs for the installation of the system, about $250,000,
included $30,000 for approximately 45 tons of iron. This
trial was monitored through the EPA SITE Program for
six months, through the summer and fall of 1995. Draft
VOC data indicates that chlorinated VOC concentra-
tions have been reduced to MCLs within 1.5 feet of
travel through the reactive media and that consistent
performance was maintained over the first six months of
operation. Based on water level data, the groundwater
flow velocity through the zone is about 1 ftfday, and a
portion of the plume about 24 feet wide is being cap-
tured and treated. Preliminary results of microbial analy-
ses on groundwater samples appear to indicate a signifi-
cant decrease in microbial population in the iron relative
to the population present in the aquifer, either upgradient
or downgradient of the reactive zone. For further details
see Focht, Vogan, and O'Hannesin 1996.
81
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