United States
Environmental Protection
Agency
Office of Research and
Development
Washington DC 20460
Office of Solid Waste and
Emergency Response
Washington, DC 20460
Superfund
EPA/540/R-92/074A
September 1992
4»EPA Guide for Conducting
Treatability Studies under
CERCLA: Thermal
Desorption Remedy
Interim Guidance
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EPA/540/R-92/074 A
September 1992
GUIDE FOR CONDUCTING TREATABILITY STUDIES
UNDER CERCLA: THERMAL DESORPTION
REMEDY SELECTION
INTERIM GUIDANCE
Risk Reduction Engineering Laboratory
Office of Research and Development
U.S. Environmental Protection Agency
Cincinnati, Ohio 45268
and
Office of Emergency and Remedial Response
Office of Solid Waste and Emergency Response
U.S. Environmental Protection Agency
Washington, D.C. 20460
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DISCLAIMER
The information in this document has been funded
wholly or in part by the U.S. Environmental
Protection Agency (EPA) under Contract No.
68-C8-0062, Work Assignment 3-46, to Science
Applications International Corporation (SAIC). It
has been subjected to the Agency's peer and
administrative reviews and it has been approved
for publication as an EPA document. Mention of
trade names or commercial products does not
constitute endorsement or recommendation for
use.
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FOREWORD
Today's rapidly developing and changing technologies and industrial
products and practices frequently carry with them the increased
generation of materials that, if improperly dealt with, can threaten
both public health and the environment. 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. These laws direct the EPA to perform research to define our
environmental problems, measure the impacts, and search for
solutions.
The Risk Reduction Engineering Laboratory is responsible for
planning, implementing, and managing research, development, and
demonstration programs to provide an authoritative, defensible
engineering basis in support of the policies, programs, and
regulations of the EPA with respect to drinking water, wastewater,
pesticides, toxic substances, solid and hazardous wastes, and
Superfund-related activities. This publication is one of the products
of that research and provides a vital communication link between
the researcher and the user community.
The primary purpose of this guide is to provide standard guidance
for designing and implementing a thermal desorption treatability
study in support of remedy selection. Additionally, it describes a
three-tiered approach, that consists of 1) remedy screening, 2)
remedy selection, and 3) remedy design to thermal desorption
treatability testing. It also presents a guide for conducting
treatability studies in a systematic and stepwise fashion for
determination of the effectiveness of thermal desorption (in
conjunction with other treatment technologies) in remediating a
CERCLA site. The intended audience for this guide comprises
Remedial Project Managers (RPMs), On-Scene Coordinators
(OSCs), Potentially Responsible Parties (PRPs), consultants,
contractors, and technology vendors.
E. Timothy Oppelt, Director
Risk Reduction Engineering Laboratory
m
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ABSTRACT
Systematically conducted, well-documented treatability studies are
an important component of the remedial investigation/feasibility
study (RI/FS) process and the remedial design/remedial action
(RD/RA) process under the Comprehensive Environmental
Response, Compensation, and Liability Act (CERCLA). These
studies provide valuable site-specific data necessary to aid in the
selection and implementation of the remedy. This manual focuses
on thermal desorption treatability studies conducted in support of
remedy selection prior to developing the Record of Decision.
This manual presents a standard guide for designing and
implementing a thermal desorption remedy selection treatability
study. The manual presents a description of and discusses the
applicability and limitations of thermal desorption technologies and
defines the prescreening and field measurement needed to
determine if treatability testing is required. It also presents an
overview of the process of conducting treatability tests and the
applicability of tiered treatability testing for evaluating thermal
desorption technologies. The specific goals for each tier of testing
are defined and performance levels are presented that define which
levels should be met before additional tests are conducted at the
next tier. The elements of a treatability study work plan are also
defined with detailed discussions on the design and execution of the
remedy screening and remedy selection treatability studies.
The manual is not intended to serve as a substitute for
communication with experts or regulators nor as the sole basis for
the selection of thermal desorption as a particular remediation
technology. Thermal desorption must be used in conjunction with
other treatment technologies since it generates residuals. This
manual is designed to be used in conjunction with the Guide for
Conducting Treatability Studies Under CERCLA (Interim Final).(28)
The intended audience for this guide comprises Remedial Project
Managers (RPMs), On-Scene Coordinators (OSCs), Potentially
Responsible Parties (PRPs), consultants, contractors, and
technology vendors.
IV
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TABLE OF CONTENTS
Section Paa
DISCLAIMER 11
FOREWORD 111
ABSTRACT iv
FIGURES vi
TABLES vii
ACKNOWLEDGMENT viu
1. Introduction 1
1.1 Background 1
1.2 Purpose and Scope of this Manual 1
1.3 Intended Audience 1
1.4 Use of This Guide 2
2. Technology Description and Preliminary Screening 3
2.1 Technology Description 3
2.2 Preliminary Screening and Technology Limitations 5
3. The Use of Treatability Studies in Remedy Evaluation 11
3.1 The Process of Treatability Testing in Selecting a Remedy 11
3.2 Application of Treatability Tests 11
4. Treatability Study Work Plan 17
4.1 Test Goals 17
4.2 Experimental Design 18
4.3 Equipment and Materials 24
4.4 Sampling and Analysis 24
4.5 Data Analysis and Interpretation 25
4.6 Reports 26
4.7 Schedule 26
4.8 Management and Staffing 27
4.9 Budget 27
5. Sampling and Analysis Plan 29
5.1 Field Sampling Plan 29
5.2 Quality Assurance Project Plan 29
6. Treatability Data Interpretation 33
6.1 Technology Evaluation 33
6.2 Estimation of Costs 36
7. References 37
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FIGURES
Number Page
2-1 Schematic Diagram of Thermal Desorption 4
3-1 Flow Diagram of the Tiered Approach 12
3-2 TheRoleof Treatability Studies in the RI/FS and RD/RA Process 13
4-1 Cut-a-way view of Static Tray Test Oven With the Tray Insert 20
4-2 Cut-a-way View of the Differential Bed Reactor (DBR) Assembly 20
4-3 Example Project Schedule for a Thermal Desorption Treatability Study Program 26
4-4 Organizational Chart 27
VI
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TABLES
Number Page
2-1 Effectiveness of Thermal Desorption on General Contaminant Groups
for Soil, Sludge, Sediments, and Filter Cakes 7
2-2 Key Prescreening Characteristics for Thermal Desorption Treatability Testing 9
4-1 Suggested Organization of Thermal Desorption Treatability Study Work Plan 17
4-2 Analyses Required in Remedy Selection Testing 24
4-3 Major Cost Elements Associated with Remedy Selection Thermal Desorption Studies 28
5-1 Suggested Organization of Sampling and Analysis Plan 30
VII
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ACKNOWLEDGMENTS
This document was prepared for the U.S. Environmental Protection
Agency, Office of Research and Development, Risk Reduction
Engineering Laboratory (RREL), Cincinnati, Ohio, by Science Applications
International Corporation (SAIC), under Contract No. 68-C8-0062. Mr.
Mark Meckes served as the EPA Technical Project Monitor. Mr. Jim Rawe
was SAIC's Work Assignment Manager. Mr. Gary Baker and Ms. Peggy
Groeberof SAIC were the primary technical authors, and the project team
included Mr. Torn Wagner and Mr. Michael Giordano of SAIC. Mr. Clyde
Dial served as SAIC's Senior Reviewer. The authors are especially grateful
to Mr. Paul de Percin, Ms. PatLafomara, and Mr. Jim Yezzi of EPA, RREL;
Dr. JoAnn Lighty of the University of Utah; and Mr. Bill Troxler and Mr.
Jim Cudahy of Focus Environmental who contributed significantly by
serving as technical consultants during the development of this
document.
The following Agency and Contractor personnel have contributed their
time and comments by participating in the technical workshop and/or peer
reviewing the draft document:
George Sullivan
George Chedsey
Carl Swanstrom
Ed Alperin
Mark McCabe
David Linz
Sardar Hassan
Brian Home
Vic Cundy
G.F. Kroneberger
Rodney Hodgson
Harsh Dev
Mike Cosmos
Tom Scelfo
Brett Burgess
Joe Tessitore
Charles Quinlan
Lynton Dicks
Chetan Trivedi
Hilda Teodoro
Michael Anderson
Bob Cygnarowicz
Andre P. Zownir
Michelle Simon
Richard Lauch
Recycling Sciences
Soil Remediation Co.
Chemical Waste Management, Inc.
IT Corporation
ReTec
Gas Research Institute
University of Cincinnati
Southdown Thermal Dynamics
Louisiana State University
Komline-Sanderson
Hazen Research
IIT Research Institute
Weston
Wehran Engineering Corp.
Harmon Environmental
Cross-Tessitore & Assoc.
KSE, Inc.
Shell Development
Canonie/SoilTech
In-Process Technology
Weston
Weston
U.S. EPA,ERT
U.S. EPA, RREL
U.S. EPA, RREL
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SECTION 1
INTRODUCTION
1.1 BACKGROUND
Section 121 (b) of the Comprehensive Environmental Response,
Compensation, and Liability Act (CERCLA) mandates EPA to
select remedies that "utilize permanent solutions and
alternative treatment technologies or resource recovery
technologies to the maximumextent practicable" and to prefer
remedial actions in which treatment that "permanently reduces
the volume, toxicity, or mobility of hazardous substances,
pollutants, and contaminants is a principal element."
Treatability studies provide data to support treatment
technology selection and remedy implementation. If treatability
studies are used, they should be performed as soon as it is
evident that insufficient information is available to ensure the
quality of the decision. Conducting treatability studies early in
the remedial investigation/feasibility study (RI/FS) process
reduces uncertainties associated with selecting the remedy
and provides a sound basis for the Record of Decision(ROD).
EPA Regional planning should factor in the time and resources
required for these studies.
Treatability studies conducted during the RI/F S phase indicate
whether the technology can meet the cleanup goals for the
site, whereas treatability studies conducted during the
remedial design/remedial action (RD/RA) phase establish
design and operating parameters for optimization of
technology performance. Although the purpose and scope of
these studies differ, they complement one another since
information obtained in support of remedy selection may also
be used to support the remedy design.(38)
This document refers to three levels or tiers of treatability
studies: remedy screening, remedy selection, and remedy
design. Three tiers of treatability studies are also defined in the
Guide for Conducting Treatability Studies Under CERCLA,
Interim Final/28' referred to as the "generic guide" hereafter in
this document. The generic guide refers to the three treatability
study tiers, based largely on the scale of test equipment
described as laboratory screening, bench-scale testing, and
pilot-scale testing. Laboratory screening is typically used to
screen potential remedial technologies and is equivalent to
remedy screening. Bench-scale testing is typically used for
remedy selection, but may fall short of providing information
for remedy selection. However, bench-scale studies can, in
some cases, provide enough information for full-scale design.
Pilot-scale studies are normally used for remedial design, but
may be required for remedy selection in some cases due to the
complexity of equipment needed for some processes. Because
of the over lap between these tiers, and because of differences
in the applicability of each tier to different technologies, the
functional description of treatability study tiers (i.e., remedy
screening, remedy selection, and remedy design) has been
chosen for this document.
The need for and the level of treatability testing required are
management decisions. Some or all of the levels may be
needed on a case-by-case basis. The time-and cost necessary
to perform the testing are balanced against the improved
confidence in the selection and design of treatment
alternatives. These decisions are based on the quantity and
quality of data available and on other factors (e.g., state and
community acceptance of the remedy, new site data, or
experience with the technology). Section 3 discusses using
treatability studies in remedy selection in greater detail.
1.2 PURPOSE AND SCOPE
This guide helps ensure a reliable and consistent approach in
evaluating whether thermal desorption should be considered
for site remediation. This guide discusses the remedy
screening and remedy selection levels of treatability testing.
Remedy screening studies provide a quick and relatively
inexpensive indication of whether thermal desorption is a
potentially viable remedial technology. The remedy selection
treatability test provides data to help determine if reductions
in contaminant concentrations will allow cost-effective
treatment of residual contamination to meet site cleanup goals.
Remedy selection studies also provide a preliminary estimate
of the cost and performance data necessary to scope either a
remedy design study or a full-scale thermal desorption system.
In general, remedy design studies will also be required to
determine if thermal desorption is a viable treatment alternative
for a site by providing detailed cost and operating parameters
acceptable for scale-up.
1.3 INTENDED AUDIENCE
Intended use of this document is by Remedial Project
Managers (RPMs), On-Scene Coordinators (OSCs), Potentially
Responsible Parties (PRPs), consultants, contractors, and
technology vendors. Each has different roles in conducting
treatability studies under CERCLA. Specific responsibilities for
each can be found in the generic guide/28'
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1.4 USE OF THIS GUIDE
This guide is organized into seven sections, which reflect the
basic information required to perform treatability studies
during the RI/FS process. Section 1 is an introduction which
provides background information on the role of the guide and
outlines its intended audience. Section 2 describes different
thermal desorption processes currently available and
discusses how to conduct a preliminary screening to determine
if thermal desorption is a potentially viable remediation
technology. Section 3 provides an overview of the different
levels of treatability testing and discusses how to determine
the need for treatability studies. Section 4 provides an
overview of the remedy screening and remedy selection
treatability studies, describes the contents of a typical work
plan, and discusses the major issues to consider when
conducting a treatability study. Section 5 discusses sampling
and analysis and quality assurance project plans. Section 6
explains how to interpret the data produced from treatability
studies and how to determine if further remedy design testing
is justified. Section 7 lists the references.
This guide, along with guides being developed for other
technologies, is a companion document to the generic
guide.1-28-1 In an effort to avoid redundancy, supporting
information in the generic guide and other readily available
guidance documents is not repeated in this document.
The document is not intended to serve as a substitute for
communication with regulators and/or experts in the field of
thermal desorption. This document should never be the sole
basis for the selection of thermal desorption as a remediation
technology or the exclusion of thermal desorption from
consideration.
As treatability study experience is gained, EPA anticipates
further comment and possible revisions to the document. For
this reason, EPA encourages constructive comments from
outside sources. Direct written comments to:
Mr. Paul de Percin
U. S. Environmental Protection Agency
Office of Research and Development
Risk Reduction Engineering Laboratory
26 W. Martin Luther King Drive
Cincinnati, Ohio 45268
(513) 569-7797
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SECTION 2
TECHNOLOGY DESCRIPTION AND
PRELIMINARY SCREENING
This section presents a description of thermal desorption
systems that can be used for remediation of Superfund sites.
Subsection 2.1 describes the technology and the types of
residual streams produced. Subsection 2.2 discusses
recommended literature and database searches, the technical
assistance available, and the review of field data required to
prescreen the thermal desorption technology. Also presented
in this subsection are the major limitations and considerations
imposed by application of the technology to a Superfund site.
2.1 TECHNOLOGY DESCRIPTION
This subsection presents a description of the principle of
operation forthe technology, an overview of the current status
of application of thermal desorption at Superfund sites, general
materials handling and preparation requirements, a focused
discussion on the major configurations of thermal desorbers,
and a brief discussion of the type of residuals produced. Four
types of desorption units are described: rotary dryers, thermal
screws, vapor extractors, and distillation chambers.
Additional information on thermal desorption systems are
described in an EPA Engineering Bulletin/26' The bulletin
provides information on the technology applicability at
Superfund sites, limitations, the types of residuals produced,
the latest performance data, site requirements (for full-scale
operation), the status of the technology and sources of further
information. This bulletin should be consulted for an overview
of the status of the technology.
Thermal desorption in this guide is limited to any number of ex
situ processes that use either direct or indirect heat exchange
to vaporize organic contaminants from soil or sludge. Air,
combustion gas, or inert gas is used as the transfer medium for
the vaporized components. Thermal desorption systems are
physical separation processes and are not specifically
designed to provide organic decomposition. Thermal
desorption is not incineration, since the decomposition of
organic contaminants is not the desired result, although some
decomposition may occur. The concentration of contaminants
and the specific cleanup levels for the site will influence the
technology's applicability for that site. System performance is
typically measured by comparison of untreated soil/sludge
contaminant levels with those of the processed soil/sludge.
For the purpose of clarity and brevity in this report, the term
medium will refer to contaminated soil, sludge, sediment, or
combinations of these. The medium is typically heated to a
target temperature of 200 to 1,000 °F based on the thermal
desorption system, selected, although certain systems operate
at higher temperatures. An important operating design
parameter is time-at-temperature, which is defined as the
elapsed time that the average medium temperature is at or
above the target temperature. Figure 2-1 is a general schematic
of the thermal desorption process.1-26-1
Thermal desorption is most applicable for separation of
organic contaminants from soils or sludges. Thermal
desorption units have been selected in the Record of Decision
for one or more operable units at approximately fourteen
Superfund sites.(19)(26)(33) These sites include: McKin (Maine),
Ottati & Goss (New Hampshire), Cannon Engineering
(Massachusetts), Resolve (Massachusetts), WideBeach (New
York), Fulton-Terminals (New York), Metaltec/Aerosystems
(New Jersey), Caldwell Trucking (New Jersey), Outboard
Marine/Waukegan Harbor (Illinois), Reich Farms (New Jersey),
Waldick Aerospace Devices (New Jersey), Wamchem (South
Carolina), and two Stauffer Chemical sites in Alabama.
If a site is contaminated with organics, thermal desorption
offers the advantage of separating the contaminant from the
medium to an offgas stream where the vapors are either treated
directly or condensed before treatment. Vapor or liquid phase
treatment includes: carbon adsorption, catalytic or thermal
oxidation, condensation, and/or chemical neutralization. The
total volume of chemicals requiring subsequent treatment is
typically small in comparison to the volume of contaminated
medium at any given site. Thermal desorption may be viewed
as a step in the sequence of remediating a site where isolating
and concentrating the contaminants is useful. The technology
must be used in concert with other treatment technologies
since its purpose is simply the physical separation of
contaminants from the mediuni-21).
Groups of organic contaminants can be selectively removed
from the medium by careful control of the treatment
temperature in the desorption unit. Knowing how vapor
pressure varies as a function of temperature for specific
contaminants is important in evaluating the applicability of a
particular thermal desorption system. Medium type, the
interaction between contaminant and medium (i.e., adsorption),
moisture content, thermal properties of contaminant mixtures,
and contamination
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Excavate
Material
Handling
Desorption
Gas Treatment
System
Residuals
Oversized Rejects
Treated
Medium
Figure 2-1. Schematic diagram of thermal desorption.
levels are also important design considerations in determining
if thermal desorption is applicable at a specific site.
All thermal desorption systems require excavation and
transport of the contaminated medium, using material
handling/classification equipment and feeding of the into the
desorption unit. Excavation is material accomplished by
backhoe, front-end loader, or similar equipment. Belt
conveyors are typically used to transfer the medium from a
hopperto vibratory screens (or similar device) to remove large
objects such as rock, glass, and metal from the medium.
Consolidated media larger than about 38 mm (1.5 inches) on
any edge are typically rejected. These large objects may
restrict the passages in some desorption units and can result
in uneven heating of the media. If the rejected objects are
contaminated, they may be crushed and fed through the
desorption unit. If they are not processed by the thermal
desorption system, they should be containerized and sampled
so that subsequent treatment, if required, can be selected. The
larger rejects, such as oversized gravel, cobbles, and boulders,
may be amenable to soil washing techniques before they are
returned to the site. Additionally, some soil types may tightly
agglomerate and require milling or shearing operations to
prepare the medium for thermal desorption equipment. This
problem should be identifiable during the excavation process
or during the remedy screening or remedy selection testing.
The classified medium is conveyed, via belt or screw
conveyors, to a feed hopper and then metered. into the
desorber.
Precautions to minimize fugitive dust (particulates) and volatile
releases may be required during excavation and transport of
contaminated medium. These methods include consideration
of weather conditions during excavation (e.g., high winds),
aerodynamic considerations (e.g., excavating on a still side of
a hill or behind a windscreen), application of foams, water
sprays, organic/inorganic control agents, synthetic covers, or
by simply minimizing the surface area of waste exposed to the
air. The most sensitive sites may require physical enclosures
and independent dust/vapor controls over the excavation,
classification, and feed systems. In addition, real time air
monitoring can be employed in some situations to minimize air
impacts.
Significant variation exists in the configuration and operation
of thermal desorption units. Volatilization of the contaminants
can be effected by use of a rotary dryer, thermal screw, vapor
extractor, or distillation chamber. The following subsection
presents a description of these basic systems.
2.1.1 Full-Scale Thermal Desorption Units
Rotary Dryer
Rotary dryers are horizontal cylinders which can be indirect -
or direct-fired. The dryer is normally inclined and capable of
being rotated. The dryer rotates as the contaminated medium
is metered into it. Turning vanes or lifters inside the dryer drum
pick up the medium and move it in the dryer where it is heated.
In direct-fired units, hot gases are produced by the
combustion of fossil fuel (natural gas, fuel oil, propane) and
directed through the dryer by use of a blower or induced draft
fan. The hot gases may flow in the same or in an opposite
direction with the contaminated medium (co-current or
countercurrent). In indirect-fired units, the hot gases are
created in a separate firing section so the medium does not
directly contact the flame. A typical indirect-fired unit would
consist of an outer furnace which is heated and a rotating
inner drum containing the contaminated medium. The inner
drum rotates inside of the furnace. The medium is primarily
heated by direct contact with the drum and by radiation from
the drum walls.
The heat exchange between the medium and hot gases
(direct-fired) or between the medium and the walls of the rotary
dry er (indirect-fired) volatilizes water and certain contaminants.
The specific contaminants separated by the process are a
function of the time-temperature history in the dryer and
moisture content of the medium. Residence time in the
desorber unit is carefully controlled
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by the angle of inclination of the dryer, its rotational speed,
and the arrangement of the turning vanes. The ability to
rapidly exchange heat permits relatively high medium
processing rates. Vendor data indicate full-scale units can
process 5 to 55 tons per hour (TPH).(4)
Thermal Screw
Screw conveyers or hollow augers are used to transport the
medium continuously through an enclosed trough. Hot oil or
steam circulate through the conveyor or auger, although
molten salts have been used in limited applications, to
indirectly heat the medium. A heat transfer fluid is also
pumped through the walls of the trough for additional heat
transfer.
One, two, or four augers may be arranged in a trough to
provide mixing in the process of heating and conveying the
medium. More than one trough system can be configured in
series to achieve the bed temperature and residence time
desired. A clean sweep gas (such as nitrogen or steam) is
typically used to convey the vaporized contaminants and
water from the trough(s). The sweep gas also may be used to
ensure contaminants are not oxidized by reducing the source
of oxygen. The maximum medium-bed temperature is limited by
the thermal properties of the heat transfer fluid and the
materials used to construct the equipment. It is also dependent
on the speed of conveyance of the medium through the
trough(s) and the operating temperature of the heat transfer
fluid. Advantages of this type of desorption unit include
simplicity of operation and temperature control as well as
reduced fines or dust generation. Equipment capacity can
rangefrom3tol3TPH.(20)
Vapor Extractor
A vapor extraction system mixes hot gases and the
contaminated medium to volatilize the contaminants. Classified
material is fed continuously into the unit on a belt conveyor
where it contacts a hot gas stream (1,000-1,500 °F) generated
in a fossil fuel-fired air heater. Hot gases are injected into the
unit through a series of gas jets at a rate sufficient to fluidize
the feed material. Blades or rollers turn the medium as it is
being fluidized by the hot gas to provide effective medium/gas
contact. The hot gas (320 °F) flows out of the unit to the gas
treatment section while the treated medium is removed from the
bottom of the unit. One vendor specifies portable plant system
capacities of 10 to 73 TPH.(20)
Distillation Chamber
Distillation chambers are a series of cylinders that are
externally heated to a specific temperature. Contaminated
medium is introduced into the first of a series of chambers (3
to 5 total) of increasing temperature. This allows the
vaporization, condensation, and recovery of specific
contaminants from each distillation zone in a segregated
fashion. A nitrogen sweep gas is used to transport the
volatilized contaminants and prevents oxidation as a system of
annular augers conveys the medium through each chamber.
The entire system is sealed and operated at negative pressure
until the segregated effluents leave the system. The capacity
of this type of system is 1 to 17 TPH(4). The system may be
operated in an "oxygen-free" environment, and effect
pyrolysis, or cracking of organics.
2.1.2 Offgas Treatment
All thermal desorption systems share the requirement for
treatment of residuals and offgas produced by the unit. Since
the treated medium is typically dry, less than one percent
moisture, spraying and mixing with clean water will suppress
dust generation.
Offgas from a thermal desorption unit will contain entrained
dust (particulates) from the medium, vaporized contaminants,
and water vapor. Particulates are removed by conventional
equipment such as cyclone dust collectors, fabric filters, or wet
scrubbers. Collected particulates may be recycled through the
thermal desorption unit or blended with the treated medium,
depending on the amount of carryover contamination present.
The vaporized organic contaminants can be captured by
condensing the offgas and then passing it through a carbon
adsorption bed or other treatment system. Emissions may also
be destroyed by use of an offgas combustion chamber or a
catalytic oxidation unit.
When offgas is condensed, the resulting water stream may
contain significant contamination depending on the boiling
points and solubility of the contaminants and may require
further treatment (i.e., carbon adsorption). If the condensed
water is relatively clean, it may be used to suppress the dust
from the treated medium. If carbon adsorption is used to
remove contaminants from the offgas or condensed water,
spent carbon will be generated, which is either returned to the
supplier for reactivation/incineration or regenerated onsite.
When offgas is destroyed by a combustion process,
compliance with incineration emission standards may be
required. Obtaining the necessary permits and demonstrating
compliance may be advantageous, however, since the
incineration process would not leave residuals requiring
further treatment. If incineration is used, the heat from the
incineration process may be used in the desorption process
unit.
2.2 PRELIMINARY SCREENING AND
TECHNOLOGY LIMITATIONS
The determination of the need for and the appropriate level of
treatability studies required is dependent on available
literature, expert technical judgment, and site specific factors.
The first two elements - the literature search and expert
consultation - are critical factors in determining if adequate
data are available or whether a treatability study is needed to
provide those data.
2.2.1 Literature/Database Review
Several reports and electronic databases exist which should be
consulted to assist in planning and conducting treatability
studies and to help prescreen thermal desorption for use at a
specific lite. Existing reports include:
Guide for Conducting Treatability Studies Under
CERCLA, Interim Final. U.S. Environmental Protection
Agency, Office of Research and
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Development and Office of Emergency and Remedial
Response, Washington, D.C. EPA/540/2-89/058,
December 1989.
Guidance for Conducting Remedial Investigations and
Feasibility Studies Under CERCLA, Interim Final. U.S.
Environmental Protection Agency, Office of Emergency
and Remedial Response, Washington, D.C.
EPA/540/2-89/001, March 1989.
Superfund Treatability Clearinghouse Abstracts. U.S.
Environmental Protection Agency, Office of Emergency
and Remedial Response, Washington, D.C.
EPA/540/2-89/001, March 1989.
The Superfund Innovative Technology Evaluation
Program: Technology Profiles. U.S. Environmental
Protection Agency, Office of Solid Waste and Emergency
Response and Office of Research and Development,
Washington, D.C. EPA/540/5-91/008, November 1991
(updated annually).
Summary of Treatment Technology Effectiveness for
Contaminated Soil. U.S. Environmental Protection
Agency, Office of Emergency and Remedial Response,
Washington, D.C., EPA/540/8-89/053,1989.
Technology Screening Guide for Treatment of CERCLA
Soils and Sludges. U.S. Environmental Protection Agency.
EPA/540/2-88/004, September 1988.
RREL in Cincinnati is currently expanding its Superfund
Treatability Database. This database contains data from
treatability studies conducted under CERCLA. A repository
for the treatability study reports will be maintained at RREL in
Cincinnati. The contact for this database is Glenn Shaul
(513)569-7408.
The Office of Solid Waste and Energy Response (OSWER)
maintains the Cleanup Information (CLU-IN) Bulletin Board
System as a tool for communicating ideas, disseminating
information, and as a gateway for other OSW electronic
databases. Currently, CLU-INhas eight different components,
including news and mail services, and conferences and
publications on specific technical areas. The contact is Dan
Powell at (703)308-8827.
ORD headquarters maintains the Alternative Treatment
Technology Information Center (ATTIC), which is a
compendium of information from many available data bases.
The EPA contact for ATTIC is Joyce Perdek at (908) 321-4380.
Data relevant to the use of treatment technologies in
Superfund actions are collected and stored in ATTIC. ATTIC
can be accessed through the RCRA/CERCLA Hotline
(800-424-9346) or CLU-IN. ATTIC serves as a mechanism for
searching other information systems and databases and
integrates the information into a response to a query. It also
includes a pointer sy stem to refer the user to individual experts
in EPA. The system is currently made up of technical
summaries from SITE program abstracts, treatment technology
demonstration projects, industrial project results, and
international program data. For more information, contact the
ATTIC System Operator at (301)670-6294, or access the
database via modem by calling (301)670-3808.
2.2.2 Technical Assistance
Technical assistance can be obtained from the Technical
Support Project (TSP) team which is made up of six Technical
Support Centers and two Technical Support Forums. It is a
joint service of OSWER, ORD, and the Regions. The TSP
offers direct site-specific technical assistance to OSCs and
RPMs and develops technology workshops, issue papers, and
other information for Regional staff. The TSP:
Reviews contractor work plans, evaluates remedial
alternatives, reviews RI/FS, assists in selection and
design of final remedy
Offers modeling assistance and data analysis and
interpretation
Assists in developing and evaluating sampling plans
Conducts field studies (soil gas, hydrogeology, site
characterization)
Develops technical workshops and training, issue papers
on groundwater topics, generic protocols
Assists in performance of treatability studies
The following support center provides technical information
and advice related to treatability studies:
Engineering Technical Support Center (ETSC)
Risk Reduction Engineering Laboratory (RREL)
Cincinnati, OH 45268
Contact: Ben Blaney
(513) 569-7406
The Engineering Technical Support Center is sponsored by
OSWER but operated by RREL. The Center handles
site-specific remediation engineering problems. Access to this
support center must be obtained through the EPA remedial
project manager.
RREL offers expertise in contaminant source control
structures; materials handling and decontamination; treatment
of soils, sludges and sediments; and treatment of aqueous and
organic liquids. The following are examples of the technical
assistance that can be obtained through the ETSC:
Screening of treatment alternatives
Review of the treatability aspects of RI/F S
Oversight of RI/FS treatability studies
Evaluation of alternative remedies
Assistance with studies of innovative technologies
Assistance in full-scale design and start-up
The following program provides technical advice and
information on air impacts due to remediation.
Air/Superfund Coordination Program
Office of Air Quality Planning and Standards
Research Triangle Park, NC 27711
Contact: Joseph Padgett
(919) 541-5589
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The Air/Superfund Coordination program is designed to help
RPM's design ways to mitigate air impacts at Superfund sites,
provide Air Office liaisons to Regional Superfund Offices, and
provide technical assistance and recommendations.
The Air/Superfund Coordination Program offers:
Direct support: site evaluation, remedy selection,
modeling assistance, monitoring air pollution control
devices
Support services: inter-program coordination, training,
resolution of inter-program issues
National Technical Guidance Studies (NTGS) to improve
quality and consistency of procedures and data
collection. NTGS reports cover baseline air emissions, air
emissions from remediation, modeling and monitoring
protocols, air pathway analysis procedures, and
remediation field support procedures.
2.2.3 Prescreening Characteristics
Prescreening activities for the thermal desorption treatability
testing include interpreting any available site related field
measurement data. The purpose of prescreening is to gain
enough information to eliminate from further treatability testing
any treatment technologies which have little chance of
achieving the cleanup goals.
The applicability of thermal desorption for general contaminant
groups for soil, sludge, sediments, and filter cakes is shown in
Table 2-l.(26) The process is applicable for the separation of
organics from refinery wastes, coal-tar wastes, wood-treating
wastes, creosote-contaminated soils, pesticide-contaminated
soils, mixed (radioactive and hazardous) wastes,
synthetic-rubber processing wastes, and paint wastes. PX23^24)
If contamination exists at different medium zones, a medium
characterization profile should be developed for each medium
type or zone. Available chemical and physical data (including
averages and ranges) and the volumes of the contaminated
medium requiring treatment should be identified. For "hot
spots", separate characterizations should be done so they can
be properly addressed in the treatability tests if quantities are
such that blending will not provide a homogeneous feed
stream. Thermal desorption may be applicable to some parts of
a site, but not to other parts.
Characterization test samples should be broadly representative
of the medium profile of the site. Grab samples taken from the
site ground surface may represent only a small percentage of
the contaminated medium requiring remediation. Deeper,
subsurface strata affected by contaminants may vary widely
in composition (soil classification, total organic carbon, and
contamination levels) from those found at the surface, and
should also be characterized so that the fractions of volatile
organic compounds (VOCs) and semivolatile organic
compounds (S VOCs) can be identified as to their location and
concentration. The quantity and distribution of rubble and
debris at the site should also be determined as part of the
characterization process. This material may have to
Table 2-1. Effectiveness of Thermal Desorption on
General Contaminant Groups for Soil,
Sludge, Sediments, and Filter Cakes
Contaminant Croups
V
1
«
i!
I
Halogenated volatile:
Halogenated semivolatiles
Nonhalogenated volatile!
Nonhalogenated semivolatiles
PCBs
Pesticides
Dloxins/Furans
Organic cyanides
Organic corrosives
Volatile metals
Nonvolatile metals
Asbestos
Radioactive materials
Inorganic corrosives
Inorganic cyanides
Oxidteers
Reducers
ttfectlveneu
Sett- fitter
SoH Sludge ments Cakes
T
Q
Q
Q
Q
U
Q
Q
Q
T
T
T
T
T
T
T
T
a
T
Q
Q
Q
Q
Q
a
Q
T
T
T
T
T
T
T
T
a
T
a
a
a
a
a
a
a
T
T
T
T
Q
T
a
Q
Q
Q
Q
D
Q
Demonstrated Effectiveness: Successful treatability test at some scale
completed
T Potential Effectiveness: Expert opinion that technology wiH work
Q No Expected Effectiveness: Expert opinion that technology will not
work
be removed from the feedstock material during full-scale
treatment operations. Pretreatment methods can be applied to
reduce the dimensions of any oversized debris.
Chemical and physical properties of the contaminant should
also be investigated. Other contaminant characteristics such
as volatility and density are important for the design of remedy
screening studies and related residuals treatment systems.
Prescreening characterization data should be assembled and
organized in a concise tabular form before remedy screening.
If enough information is obtained by prescreening to allow a
decision to be made regarding the potential success of thermal
desorption, remedy screening may be skipped. A listing of key
prescreening data is presented in Table 2-2.
The need for a treatability study is determined near the
beginning of the RI/FS when a literature survey of remedial
technologies is performed. Remedial technologies are
identified based on compatibility with the type of
contaminants present at the site, the medium (soil, water, etc.),
and the anticipated cleanup objectives. Remedial technologies
are prescreened for effectiveness, implementability, and cost.
The prescreening is done using available technical literature,
databases, and manufacturer's information. Based upon this
initial technology prescreening, thermal desorption may be one
of several candidate remedial technologies eliminated before
or during the remedial investigation/feasibility study. See the
generic guide for more specific details on screening of
treatment technologies and on determining the need and type
of treatability tests which may be required for evaluating
treatment technology alternatives.1-28-1
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2.2.4 Thermal Desorption Limitations
Thermal desorption limitations may be defined as
characteristics that hinder cost-effective treatment. Thermal
desorption has proven effective in treating contaminated soils,
sludges, and sediments. Chemical contaminants for which
bench-scale through full-scale treatment data exist include
primarily VOCs, SVOCs and even higher boiling point
compounds such as polychlorinated biphenyls
(PCBs).(1)(6)(9)(13)(1(i)(33) The technology is generally not used in
separating in organics from the contaminated medium;
although thermal desorption has been used to recover very
high concentrations of mercury metal from soil/11' Inorganic
constituents and/or metals that are not particularly volatile will
likely not be effectively removed by thermal desorption. The
maximum bed temperature and the presence of chlorine or
another chlorinated compound may result in volatilization of
some inorganic constituents in the waste.
The primary technical factors affecting thermal desorption
performance are the maximum bed temperature achieved, total
residence time, organic and moisture content, contaminant
characteristics and medium properties. Since the basis of the
process is physical removal from the medium by volatilization,
bed temperature directly determines the end point
concentration. The degree of mixing and, where applicable, the
sweep gas rate also affect removal rate. In some cases,
achieving and maintaining the desired results are too costly for
sites that are heavily contaminated with organics or that have
a high moisture content. If the system is direct-heated,
flammability of the contaminant must also be considered in
order to prevent explosions.1-37-1 As in most systems that use a
reactor or other equipment to process wastes, media exhibiting
a very high pH (greater than 11) may corrode the system
components/35' Media exhibiting a low pH may similarly
corrode system components during processing.
The contaminated medium must contain at least 20 percent
total solids (by weight) to facilitate placement of the waste
material into the desorption equipment/1' Some systems
specify a minimum of 30 percent solids/20' If the moisture
content of the contaminated medium is high, it may have to be
dewatered prior to treatment to reduce the energy required to
volatize the water.
Material handling of soils that are tightly aggregated, are
largely clay, or contain rock fragments or particles greater than
1.5 inches can result in poor processing performance. This can
be minimized-by media pretreatment such as screening,
crushing, milling, grinding, shredding, etc. Also, if a high
fraction of fine silt or clay exists in the matrix, excessive dust
may be generated which places a greater dust loading on the
downstream air pollution control equipment/20^35'
The treated medium will typically contain less than 1 percent
moisture. Dust can easily form in the transfer of the treated
medium from the desorption unit, but can be mitigated by
water sprays. Some type of enclosure may be required to
control fugitive dust water sprays are not effective.
Caution should be taken regarding the disposition of the
treated material, since pretreatment and/or treatment processes
can alter the physical properties of the material. For example,
this material could be susceptible to such destabilizing forces
as liquefaction, where pore pressures are able to weaken the
material to the point of failure. It may be advantageous to
avoid backfilling such treated material on sloped areas or
places where materials must support a load (i.e. roads for
vehicles, subsurfaces of structures, etc.). To achieve or
increase the required stability of the treated material, it may
have to be mixed with other stabilizing materials and/or
compacted in a layered fashion. A thorough geotechnical
evaluation of the treated productbased on treatability
testscan provide the necessary design resolution to
post-treatment solid stabilization. Screening tests of untreated
soils should also be considered as away of identifying
potential impacts on the medium. An example of a prescreening
evaluation and the decision to conduct further testing is
provided in Example 1.
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Table 2-2. Key Prescreening Characteristics For Thermal Desorption Treatability Testing
Parameter
Chemical
Organics
-Volatile
-Semivolatile
-PCB
Total organic carbon
(TOC)
or
Total recoverable petro-
leum hydrocarbon
or
Oil & Grease
Metals
Toxicity Characteristic
Leaching Procedure
(TCLP)
Physical
Grain size
analysis/particle size
distribution
Moisture content
Bulk density
PH
Description of Test
GC/MS
GC/MS
GC
Combustion
Infrared
Gravimetric
ICP, GFAA, CVAA
Soil leaching\
analysis of leachate
Sieve screening using
a variety of screen
sizes
Drying oven at 110!C
Drive cylinder method
Sand cone method
SoilPH
Method
Method 8240
Method 8270
Method 8080
Method 9060
Method 9071/41 8.1
Method 9071
Method 3050/6000,
7000 series
Method 1311
ASTM D422
ASTMD2216
ASTM D2937
ASTM D 1556
Method 9045
Purpose and Comments Application of
Data
To determine concentration of Remedy Screening
target or interfering constituents,
pretreatment needs, extraction
medium
To determine the presence of Remedy Screening
organic matter
To determine the potential emis- Remedy Screening
sions of volatile metals and
inorganic alkali
To determine leachability of RemedV Selection
selected organic and inorganic
compounds in liquid/solid
residuals
To determine volume reduction Remedy Selection
potential, pretreatment needs
To determine pretreatment needs Remedy Selection
and medium processing rate
To estimate total mass of soil to Remedy Selection
be treated
Potential for system corrosion Remedy Selection
Ref.
36
36
36
36
36
3
2
3
3
36
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Example 1. Prescreening Initial Data
BACKGROUND
A 3.0-acre industrial site in the northeastern United States was used from 1950 until 1964 as a storage yard
for a company that installed asphaltic roofing materials. From 1968 until 1978 the site was used as a storage
facility and transfer station for solvents that were being sent to a recycling facility. Remedial investigations
indicated that waste disposal and chemical spills over a period of years have contaminated the surface soil
and underlying groundwater. The soil at the site consists primarily of a highly plastic inorganic clay with
some debris present near the surface.
USE OF DATA TO PRESCREEN THERMAL DESORPTION
The prescreening was performed by conducting a literature survey, reviewing existing data, and obtaining
expert opinion. Contaminants that have been identified on the site include the base neutral compounds
pyrene, chrysene, and naphthalene at an average concentration of less than 100mg/kg each. These
compounds are primarily located in the top 2 feet of surface soil. The volatile organic compounds methylene
chloride, toluene, and 1,1,1-trichloroethane have been identified at concentrations of upto 1,000 mg/kg down
to the surface of the groundwater table (depth of approximately 12 feet). The groundwater is also
contaminated with VOCs. Arsenic has been identified within an area of the site at a concentration of up to
1,000mg/kg. Arsenic emissions from point sources are regulated under state air toxics regulations.
A risk assessment at the site has established the f6liowing preliminary cleanup levels for selected indicator
compounds:
Methylene chloride 5.5 mg/kg
Toluene 3.0 mg/kg
1,1,1-trichloroethane 2.0 mg/kg
Pyrene 15.5 mg/kg
Chrysene 13.2 mg/kg
Naphthalene 25.0 mg/kg
The prescreening study indicates the following:
Thermal desorption has demonstrated from 90 to greater than 95 percent removal efficiencies for the
VOCs
that have been identified.
Thermal desorption has demonstrated 75 to 95 percent removal efficiencies for the base/neutral
compounds that have been identified.
Toluene and pyrene have the highest boiling point temperatures of the volatile and base/neutral
compounds, respectively, that have been identified at the site.
No data on the partitioning of arsenic to the offgas at thermal desorption operating
conditions could be located.
The clay has very cohesive properties at a moisture content of greater than 18 percent.
The experts recommend thermal desorption for further consideration as a site remedy. Remedy screening
treatability studies are to be conducted.
10
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SECTION 3
THE USE OF TREATABILITY STUDIES IN
REMEDY EVALUATION
This section presents an overview of the use of treatability
test in confirming the selection of thermal desorption as the
technology remedy under CERCL A. It also provides a decision
tree that defines the tiered approach to the overall treatability
study program with examples of the application of treatability
studies totheRI/FS and remedy selection process. Subsection
3.1 presents an overview of the general process of conducting
treatability tests. Subsection 3.2 defines the tiered approach to
conducting treatability studies and the applicability of each
tier of testing, based on the information obtained, to assess,
evaluate, and confirm thermal desorption technology as the
selected remedy.
3.1
PROCESS
TESTING
REMEDY
OF TREATABILITY
IN SELECTING A
Treatability studies should be performed in a systematic
fashion to ensure that the data generated can support the
remedy evaluation process. This section describes a general
approach that should be followed by RPMs, PRPs, and
contractors during all levels of treatability testing. This
approach includes:
Establishing data quality objectives
Selecting a contracting mechanism
« Issuing the Work Assignment
Preparing the Work Plan
Preparing the Sampling and Analysis Plan
Preparing the Health and Safely Plan
Conducting community relations activities
Complying with regulatory requirements
Executing the study
Analyzing and interpreting the data
« Reporting the results
Developing cleanup criteria
These elements are described in detail in the generic guide/28'
That document gives information applicable to all treatability
studies. It also presents information specific to remedy
screening, remedy selection testing, and remedy design
testing.
Treatability studies for a particular site will often entail multiple
tiers of testing. Duplication of effort can be avoided by
recognizing this possibility in the early planning phases of the
project. The Work Assignment, Work Plan, and other
supporting documents should include all anticipated activities.
There are three levels or tiers of treatability studies: remedy
screening, remedy selection, and remedy design. Some or all of
the levels may be needed on a case-by-case basis. The need
for and the level of treatability testing required are
management decisions in which the time and cost necessary
to perform the testing are balanced against the risks inherent
in the decision (e.g., selection of an inappropriate treatment
alternative). These decisions are based on the quantity and
quality of data available and on other decision factors (e.g.,
state and community acceptance of the remedy, new site data,
or experience with the technology). The flow diagram for the
tiered approach in Figure 3-1 traces the step wise review of
study data and the decision points and factors to be
considered.
Technologies generally are evaluated first at the remedy
screening level and progress through remedy selection to
remedy design. A technology may enter the selection process,
however, at whatever level is appropriate based on available
data on the technology and site-specific factors. For example,
a technology that has been successfully applied at a site with
similar conditions and contaminants may not require remedy
screening to determine whether it has the potential to work.
Rather, it may go directly to remedy selection to verify that
performance standards can be met. Treatability studies, at
some level, will normally be needed even if previous studies or
actual implementation have encompassed similar site
conditions to assure that the site-specific target cleanup goals
are going to be achieved. Figure 3-2 shows the relationship of
the three levels of treatability study to each other and to the
RI/FS process.
3.2 APPLICATION OF TREATABILITY
TESTS
Before conducting treatability studies, the objectives of each
tier of testing must be established. Thermal desorption
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MANAGEMENT DECISION FACTORS:
State and Community Acceptance
Schedule Constraints
Additional Data
Technology
Screening
Characterization
Technology
Potentially
Viable?
Treatability
Studies
Heeded?
Mariagsment
Decision Factors
eehrwlogy
Demonstrated
or Contaminan
Matrix?
Remedy
Screening
Studies
Remedy
Selection
Studies
Meet
Performance
Goals?
I Detailed Analysis
of Alternatives
Remedy
Design
Studies
Figure 3-1. Flow diagram of the tiered approach.
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Remedial Investigation/
Feasibility Study (RI/FS)
Identification
of Alternatives
Record of
Decision
(ROD)
Remedy
Selection
Remedial Design/
Remedial Action -
(RD/RA)
Scoping
- the -
RI/FS
Literature
Screening
and
Treatability
Study Scoping
Site
Characterization
and Technology
Screening
REMEDY
SCREENING
to Determine
Technology Feasibility
Evaluation
of Alternatives
REMEDY SELECTION
to Develop Performance
and Cost Data
Implementation
of Remedy
REMEDY DESIGN
to Develop Scale-Up, Design,
and Detailed Cost Data
Figure 3-2. The role of treatability studies in the RI/FS and RD/RA process.
treatability study objectives are based upon the specific needs
of the RI/FS. There are nine evaluation criteria specified in the
document, Guidance for Conducting Remedial Investigations
and Feasibility Studies Under CERCLA (Interim Final);(27) the
treatability studies provide data for up to seven of these
criteria. These seven criteria are:
Overall protection of human health and environment
Compliance with applicable or relevant and appropriate
requirements (ARARs)
Reduction of toxicity, mobility, or volume through
treatment
Short-term effectiveness
Implementability
Long-term effectiveness and permanence
Cost
The first four of these evaluation criteria deal with the degree
of contaminant reduction achieved by the thermal desorption
process. What will be the remaining contaminant
concentrations? Will new contaminants be produced? Will the
residual contaminant levels be sufficiently low to meet the
established ARARs and the risk-based contaminant cleanup
levels? What are the contaminant concentration and physical
and chemical differences between the untreated and the
treated solids fractions (e.g., has contaminant toxicity,
mobility, and volume been reduced)? The fourth criterion,
short-term effectiveness, also addresses the effects of the
treatment technology during construction and implementation
of a remedy. This evaluation is concerned not only with
contaminant concentration and toxicity, but also with the
potential for exposure to off gases or residuals which may be
harmful.
The implementability assessment evaluates the technical and
administrative feasibility of the technology and the availability
of required goods and services. The following questions must
be answered in order to address the implementability of
thermal desorption:
Will ambient releases of volatile contaminants that occur
during excavation and classification require controls?
Is there a need for a blending program to ensure hot spots
can be accommodated by the thermal desorption system?
Is the water content of the waste/sludge too high or
highly variable?
Has the degree of particulate entrainment been
determined, and will the particulate need to be recycled?
Have the volumes and characteristics of residuals been
approximated, and are residuals treatment and disposal
options established (e. g., do metals in the treated medium
need further treatment)?
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« Are there appropriate air emission controls for process
emissions?
Long-term effectiveness assesses how effective treatment
technologies are in maintaining protection of human health
and the environment after response obj ectives have been met.
The magnitude of any residual risk and the adequacy and
reliability of controls must be evaluated. Residual risk, as
applied to thermal desorption, assesses the risks associated
with treatment residuals at the conclusion of all remedial
activities. Analysis of residual risk from other treatment train
processes should be included in this step. An evaluation of
the reliability of treatment process controls assesses the
adequacy and suitability of any long-term controls (such as
site access restrictions and deed limitations on land use) that
are necessary to manage treatment residuals at the site. Such
assessments are usually beyond the scope of a remedy
selection treatability study, but may be addressed
conceptually based on remedy selection results. Performance
objectives must consider the existing site contaminant levels
and relative cleanup goals for soils, sludges, and sediments at
the site. In previous years, cleanup goals often reflected
background site conditions. Attaining background cleanup
levels through treatment has proved impractical in many
situations. The present trend is toward the development of
site-specific cleanup target levels that risk-based rather than
background-based.
The final EPA evaluation criterion which can specifically be
addressed during a treatability study is cost. Remedy selection
treatability studies can provide data to estimate the following
important cost factors:
The ultimate cleanup level that can be achieved
« The volume and characteristics of residuals which require
treatment or disposal
The degree to which medium pretreatment or process
modifications can enhance the efficiency of the process
The amount of energy required to heat and clean the
medium and approximate fuel costs
The first three factors provide information about the costs of
downstream treatment by determining the amount and
character of the contaminated residuals. The last factor helps
estimate the costs of supplies and utilities.
3.2.1 Remedy Screening
Remedy screening is the first level of testing. It is used to
establish the ability of a technology to treat a waste. Remedy
screening is generally low cost (e.g., $8,000 to $30,000) and
requires several days to three months to complete. Time must
be allowed for project planning, chemical analyses,
interpretation of test data, and report writing. Limited quality
control is required for remedy screening studies. They yield
data indicating a technology's potential to meet performance
goals and applicability to the specific waste sample. Remedy
screening tests can identify operating parameters for
investigation during remedy selection or remedy design. They
generate little, if any, design or cost data and should not be
used as the sole basis for selection of a remedy.
In some instances, thermal desorption remedy screening
treatability studies can be skipped, if enough information
about the physical and chemical characteristics of the
contaminants and medium would allow for evaluation of the
potential success of thermal desorption at a site. In such
cases, remedy selection tests are normally the first level of
treatability study executed. Screening tests are conducted
using laboratory-scale equipment. These tests are generic, not
vendor-specific, and can be performed at laboratories with the
proper equipment and qualified personnel.
3.2.2 Remedy Selection
Remedy selection is the second level of testing. Remedy
selection studies identify the technology's performance at a
site. These studies have a moderate to high cost (e.g., $10,000
to $100,000) and require several months to plan, obtain
samples, and execute.(24) Remedy selection studies yield data
that verify that the technology can meet expected cleanup
goals, provide information in support of the detailed analysis
of alternatives, and give indications of optimal operating
conditions.
The remedy selection tier of thermal desorption testing
consists of either bench-scale tests or pilot tests. Frequently,
thesetests will be technology-specific. The key question to be
answered during remedy selection testing is whether the
treated medium will meet the cleanup goals for this site. The
exact removal efficiency or acceptable residual contaminant
level specified as the goal for the remedy selection test is site-
specific. A remedy design study would follow a successful
remedy selection study, although they are usually not
conducted until after a Record of Decision (ROD) has been
issued.
3.2.3 Remedy Design
Remedy design is the third level of testing. It provides
quantitative performance, cost, and design information for an
operable unit. This testing also produces the remaining data
required to optimize performance. These studies are of
moderate to high cost (e.g., $50,000 to $200,000) and require
several months to complete.(24) For complex sites (e.g., sites
with different types or concentration of contaminants in
different media such as soil, sludges, and sediments), longer
testing periods may be required, and costs will be higher.
Remedy design tests yield data that verify performance to a
higher degree than the remedy selection and provide detailed
design information. They are most often performed during the
remedy design phase of a site cleanup.
Remedy design tests usually consist of bringing a mobile
pilot-scale treatment unit to the site, or constructing a
small-scale unit for non-mobile technologies. Remedy design
tests can also be conducted using vendor-specific pilot-scale
equipment at the vendor's site which is generally much
cheaper than onsite mobilization or construction. Applicable
permits would have to be obtained for onsite testing; however,
waivers may be available under certain conditions. The goal of
this tier of testing is to confirm the cleanup levels and
operating conditions specified in the Work Plan (see
subsection 4.1.1). This is best achieved by operating a field
unit under conditions similar to those expected in the full-
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scale remediation project. If remedy selection testing was performed using pilot-scale
equipment, this may provide sufficient data to make any
Data obtained from the remedy design tests are used to: further remedy design testing unnecessary. Given the limited
amount of full-scale experience with innovative technologies,
Specify equipment type for a full-scale unit such as thermal desorption, remedy design testing will
generally be necessary in support of the final process
. Determine feasibility of thermal desorption based on selection and implementation of a remedy. As technologies
target cleanup goals mature, the need for remedy design testing will decrease.
Refine cleanup time estimates
Refine cost predictions
15
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SECTION 4
TREATABILITY STUDY WORK PLAN
This chapter focuses on specific elements of the Work Plan for
thermal desorption treatability studies. These include test
goals, experimental design, equipment and materials, sampling
and analysis, data analysis and interpretation, reports,
schedule, management and staffing, and budget. These
elements are described in subsections 4.1 through 4.9.
Complementing the above subsections are section 5, Sampling
and Analysis Plan and Quality Assurance Project Plan, and
section 6, Treatability Data Interpretation. Table 4-1 lists all of
the Work Plan elements.
Table 4-1. Suggested Organization of Thermal
Desorption Treatability Study Work Plan
No. Work Plan Elements
Subsection
1.
2
o
J.
4.
5.
6.
7.
8.
9.
10.
11.
12.
13.
14.
15.
Project Description
Remedial Technology Description
Test Goals
Experimental Design
Equipment and Material
Sampling and Analysis
Data Management
Data Analysis and Interpretation
Health and Safety
Residuals Management
Community Relations
Reports
Schedule
Management and Staffing
Budget
4.1
4.2
4.3
4.4
4.5
4.6
4.7
4.8
4.9
Carefully planned treatability studies are necessary to ensure
the data generated are useful for evaluating the applicability or
performance of a technology. The Work Plan, usually prepared
by a contractor when the Work Assignment is in place, sets
forth the contractor's proposed technical approach for
completing the tasks outlined in the Work Assignment. It
assigns
responsibility and establishes the project schedule and costs.
The Work Plan must be approved by the RPM before initiating
subsequent tasks. For more information on each of these
sections, refer to the generic guide.(28)
4.1 TEST GOALS
Setting goals for the treatability study is critical to the ultimate
usefulness of the data generated. Objectives must be defined
before starting the treatability study. Each tier of the
treatability study needs performance goals appropriate to that
tier. For example, remedy selection tests are used to answer the
question, "Will thermal desorption work on this
medium/contaminant matrix?" It is necessary to define "work"
(e.g., set the goal of the study). The remedy selection test
measures whether the process has the potential to reduce
contamination to below the anticipated performance criteria to
be specified in the ROD. This would indicate that further
testing for remedy design is appropriate.
The ideal technology performance goals are the same as the
anticipated cleanup criteria for the site. For several reasons,
such as ongoing waste analysis and ARARs determination,
cleanup criteria are sometimes not finalized until the ROD is
signed, long after treatability studies must be initiated.
Nevertheless, treatability study goals need to be established
before the study is performed so that the success of the
treatability study can be assessed. In many instances, this may
entail an educated guess as to what the final cleanup levels
may be. In the absence of final cleanup levels, the RPM can
estimate performance goals for the treatability studies based
on the first two criteria listed in subsection 3.2 of this guide.
Existing treatability study results from other sites may provide
the basis for an estimate of the treatability study goals for a
specific case.
4.1.1 Remedy Screening Goals
When remedy screening tests are performed, determining the
minimum temperature of the medium and residence time needed
to achieve the required cleanup criteria are the desired goals.
The remedy screening treatability study goals must be
determined on a site-specific basis. Typically, 75 percent or
higher separation efficiencies are achieved in the remedy
screening tier. RREL's Remedy Screening Lab has used 50
percent as a goal in the past. Since thermal desorption remedy
screening tests may be
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a simple test, such as the use of a flat tray of contaminated
medium inserted into a small lab furnace, the level of
volatilization efficiency achieved should not be used as the
sole criteria for conducting further treatability testing.
Example 2 describes a series of remedy screening tests
conducted at a Superfund site introduced in Example 1. The
example illustrates how to decide whether the remedy selection
treatability studies using thermal desorption should be
performed.
4.1.2 Remedy Selection Treatability
Study Goals
The main goals of this tier of testing are to obtain information
on operating parameters relevant to a full-scale thermal
desorption system. Inclusive in these goals are determining
actual contaminant concentrations achieved after treatment,
definition of the heat input requirements, and average bed
temperatures achieved, as well as limited performance data for
the offgas treatment sy stem(s) thought to be applicable to the
medium/contaminant matrix. The actual goal for separation
efficiency must be based on site- and process-specific
characteristics. Typical separation efficiencies are 90 percent
and higher. The specified separation efficiency must meet
site-specific cleanup goals, which are based on a site risk
assessment.
Example 3 continues from Example 2 and illustrates the goal of
a remedy selection treatability study at the Superfund site. In
this example, the remedy selection treatability studies show
that pilot-scale testing should be conducted.
4.2 EXPERIMENTAL DESIGN
4.2.1 Remedy Screening Tier
Remedy screening tests can be rapidly performed in a
laboratory to evaluate the potential performance of thermal
desorption. When assessing the need for remedy screening
tests, the investigator should use available knowledge of the
site and any preliminary analytical data on the type and
concentration of contaminants present. If it is confirmed that
the concentration of metals is low, the
Example 2. Remedy Screening
BACKGROUND
In Example 1, recommendations were made to proceed with remedy screening treatability tests to check the
potential feasibility of thermal desorption. Pyrene, arsenic, and toluene were chosen as the indicator
contaminants.
RESULTS OF TESTING
Static tray muffle furnace tests were conducted by a thermal desorption contractor in accordance with the
procedures described in Section 4.0 of this document. Tests were conducted at soil temperatures of 400°F,
800°F, and 1,000°F and a residence time at temperature of 10 minutes for each test. Tests at all conditions
showed that the concentration of toluene could be reduced to less than 0.5 mg/kg (>96 percent). The
concentration of pyrene was reduced by 50 percent, 85 percent, and 95 percent, respectively in the three tests.
The concentration of arsenic in the soil was not appreciably reduced at the two lower temperature conditions.
At the test temperature of 1,000°F, the concentration of arsenic in the treated material was approximately 30
percent less than the concentration in the untreated sample.
RPM'S DECISION
The remedy screening tests indicate that the VOCs can be removed to acceptable residual concentrations over
a broad range of thermal desorption operating temperatures. Removal of base/neutral compounds at greater
than 90 percent efficiency will require operating near the upper temperature limits of a thermal desorption
system. However, at this condition, some of the arsenic apparently volatilizes to the gas phase. The RPM
decides to conduct further treatability testing (remedy selection) to refine operating conditions required to
achieve target residual concentrations for pyrene and to determine the fate of arsenic at these operating
conditions.
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Example 3. Remedy Selection Treatability Test Using Rotary Thermal Apparatus
BACKGROUND
In Example 2, recommendations were made to proceed with remedy selection treatability tests to bracket
operating conditions for thermal desorption and determine the fate of arsenic at these conditions. Pyrene and
arsenic were chosen as the indicator contaminants.
RESULTS OF TESTING
Rotary thermal apparatus tests were conducted by a thermal desorption contractor in accordance with the
procedures described in Section 4.0 of this document. Tests were conducted at soil temperatures of 800°F,
900°F and 1,000°F, and a time-at-temperature of 10 minutes for each test. Tests showed that the concentration
of pyrene in the treated soil sample could be reduced to 25 mg/kg, and 7 mg/kg at soil temperatures of 800°F,
900°F, respectively. Tests at all conditions confirmed that the residual concentration of toluene in the treated
soil was less that 0.5 mg/kg.
Sample of offgas from the rotary thermal apparatus were passed through a condenser. Gas samples were
collected both upstream and downstream of the condenser. A material balance was performed for arsenic for
each test. Tests at both 900°F and 1,000°F indicated that greater than 10 to 20 percent of the arsenic in the
sample partitioned to the gas phase and was not appreciably removed by passing the gas through a condenser.
RPM'S DECISION
The remedy selection treatability tests indicated that a thermal desorption system that operates at a soil
temperature of up to 900°F will be required to meet the treatment criteria for the base/neutral compounds.
Approximately 10 to 20 percent of the arsenic is partitioned to the offgas and is not removed in a condensation
system. The RPM believes that the arsenic in the attributable both to particulate carryover and volatilization
of arsenic. The volatilized fraction may condense to a fine fume and would require a sophisticated air pollution
control system.
The RPM decides to conduct a remedy design treatability test of a thermal desorption process and associated
gas treatment system to confirm removal efficiency projections for base/neutral compounds and to obtain an
estimate of arsenic emissions from a full-scale system. A pilot thermal desorption system that includes a
venturi scrubber to treat offgas is recommended as the test equipment.
contaminants are generally represented in the classes of
contaminants shown in Table 2-1, and the general limitations
described in section 2 are met, then the remedy screening
tiermay be precluded. Remedy selection studies would yield
more valuable data and save time and money in this case.
When considering remedy screening testing, a number of
systems can be used, such as a static tray or differential bed
reactor (DBR). In the tray test, contaminated medium is
heated in a muffle furnace equipped with an electronic
temperature controller. The furnace should be capable of
achieving an internal temperature up to 1,400°F with a
relatively fast heat-up rate. The depth of the soil should
be kept at a minimum to eliminate temperature and
concentration gradients within the soil bed. The temperature
of the medium should be monitored very closely, and care
should be taken that the thermocouple(s) are completely
immersed in the solid material. The time to reach the target
treatment temperature should be minimized to a practical
laboratory timeframe such as 5 to 10 minutes. Longer time
may be required depending on the specific contaminants
present in the soil. Figure 4-1 shows a schematic of a static
tray test oven.1-4-1
In a DBR, a thin bed of medium is placed in a furnace
between two screens. Preheated gas passes through the bed
which eliminates concentration and temperature
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Oven Indicator
Thermocouple
Interior of Oven Chamber
Test Thermocouple
Soil Thermocouple
Gas Exit at Door Seal
Figure 4-1. Cut-a-way view of static tray test oven with the tray insert.
gradients within the bed. In this reactor, the temperature of the
medium should also be monitored and the bed should reach its
target temperature within 5 to 10 minutes. Figure 4-2 shows a
schematic of the DBR.(8)
In remedy screening tests, the offgas may be analyzed for
volatiles and semivolatiles; however, particulate control
equipment is not necessary. Remedy screening tests alone do
not produce enough information to perform an economic
analysis of a thermal desorption process, but do generate data
on time-at-temperature requirements.
To reduce analytical costs during the remedy screening tier,
the list of known contaminants must be reduced to a few key
compounds selected as indicators of performance. The
selection of indicator chemicals for remedy screening testing
should be based on the following:
1) Select one or two contaminants that have low volatility.
2) Select one or two contaminants present in the medium
that are most toxic or most prevalent.
3) Select indicator compounds to represent other
compounds within those groups (e.g., TCE for chlorinated
volatiles, benzene for nonchlorinated volatiles).
Desorbing gas inlet
Gas
heat
exchanger
Electric
cylindrii
furnace
Suction
pyrometer for
gas temperature
Solid bed
between.
400 mesh
SS Screens
Ceramic
Block
Sampling Probe
Port for gas samples
Exhaust
4) Select a representative sample either composite or hot
spot (for worst case, see subsection 4.4.1)
5) Select polar contaminants since they tend to adsorb
strongly to some media.
Figure 4-2. Cut-a-way view of the Differential Bed
Reactor (DBR).
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Mass balance calculations are usually limited by analytical
results on solids and liquid feed and discharge streams during
remedy screening. Normally, gaseous emissions are not tested
at this tier.
4.2.2 Remedy Selection Tier
Remedy selection testing is intended to more accurately
estimate the performance of a full-scale thermal desorption
system. The tests may be conducted in either batch or
continuous treatment systems that simulate the heat and mass
transfer characteristics of specific full-scale thermal desorption
processes. Data collected at this level can be used to model
thermal desorption under various experimental conditions.
Information from modeling can then be used to predict time
and temperature requirements in full-scale operating systems.
Remedy selection treatment systems are available to simulate
the performance characteristics of the various desorption
systems.
Remedy selection testing should define the time-at-
temperature and residual contaminant concentrations as a
function of heat input and bed-mixing characteristics for a
thermal desorption device. Under certain conditions remedy
selection testing can be conducted using a static tray orDBR.
After conducting the tray tests, remedy selection usually will
lead to a vendor pilot-scale unit that generates data applicable
to that vendor's full-scale unit. Currently, there is no remedy
selection system available that permits concurrent evaluation
of the specific full-scale thermal desorption processes.
More precision is used in weighing and mixing of the sample,
with an associated increase in QA/QC costs. Further care must
be taken to ensure homogeneity of the sample(s) being treated.
Holding time of the medium and offgas samples in the lab
before extraction and analysis can be an important
consideration for some contaminants. At this phase of remedy
selection, it is recommended that duplicate (or triplicate) test
runs are completed to ensure reproducibility of the results.
This is extremely important when non-vendor (generic) tests
are performed (i.e., DBR or static tray). This series of tests is
considerably more costly than remedy screening tests, so only
sites with contaminated media that show promise in the
remedy screening phase should be carried forward into the
remedy selection tier. If sufficient data are available in the
prescreening step, the remedy screening step may be skipped.
The objective of the remedy selection thermal desorption
design is to meet the goals discussed in subsection 4.1.2.
Variables that should be documented and/or controlled during
this level of treatability testing include:
moisture content of medium
« contaminant concentration in medium
particle size of medium
treatment temperature or minimum solids temperature
time-at-temperature or total residence time
medium physical and chemical characteristics
« thermal properties of contaminated medium
« degree of agitation (solid/gas mixing)
purge gas flow, composition, and temperature
The moisture content of the medium affects the throughput
rate due to the energy requirements for drying. A high water
concentration delays contaminant volatilization or requires
larger heat input to remove contaminants from the medium, if
the same throughput rate is to be maintained. Data exist,
however, that suggest that some contaminants may be
removed at lower temperatures by the physical action of steam
stripping as water boils off/15' Treatability testing should be
performed with medium samples that represent the average
moisture content expected during full-scale thermal desorption
operations.
Samples should be representative of site conditions for the
range of concentration of contaminants. Some variability in
contaminant concentration should be expected in individual
samples which are used to characterize the extent of
contamination at the site. Blending waste material into a more
homogeneous mixture can lessen this variability.
The particle size distribution of the medium should
approximate that expected for the contaminated volume to be
treated. If a significant amount of foreign objects; large,
consolidated chunks of medium; or significant media
heterogeneity exist at the site, this may impact the selection.
This may also indicate the need for additional material
handling equipment if the next tier of testing is conducted.
Thermal desorption treatability tests are normally conducted
at temperatures within the operating ranges of full-scale
thermal desorption systems. This temperature range is
normally between 200°F and 1,000°F for the medium.
Example 4 shows data obtained from using a vendor-specific
bench-scale unit while proceeding with remedy selection
testing. This shows background information, sample handling,
test operating conditions, and cleanup objectives. The test
results, along with estimated cleanup costs are detailed in
section 6 as Example 5. These examples describe a case study
and should not be considered directly transferrable to a
specific site.
The decision on whether to perform remedy selection testing
on hot spots or composite soil samples is difficult and must be
made on a site-by-site basis. Hot spot areas should be factored
into the test plan if they represent a significant portion of the
waste site. However, it is more practical to test the specific
waste matrix that will be fed to the full-scale system over the
bulk of its operating life. If the character of the medium
changes radically over the depth of contamination, then tests
should be designed to separately study system performance
on each media type. It may be necessary to identify extreme
conditions and determine the degree of blending required.
Additional guidance on soil sampling techniques and theory
can be found in Soil Sampling Quality Assurance User's
Guide1-34-1 and Methods for Evaluating the Attainment of
Cleanup Standards.00
If the contaminants and particular medium type(s) present are
similar to those where the technology has been
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demonstrated at full-scale applications, remedy screening and
remedy selection treatability testing may be unnecessary. The
RPM/OSC must carefully compare the
initial conditions at the previous site and the full-scale data
generated with those of the site being considered. Remedy
design testing may represent a prudent step in
Example 4. Remedy Selection Using Vendor-Specific Laboratory-Scale Unit
BACKGROUND
The treatability study was conducted on soil from an abandoned facility which was used to formulate and
package pesticides, herbicides, and other types of chemicals. The bench-scale unit directly reflects operating
conditions of the vendor's full-scale unit. Feed rates for this test were conducted within the test unit capacity
of 20 g/min. Temperature and residence time are varied within the ranges available for the full-scale unit. The
practical residence time for the large unit is 45 to 120 minutes. A test series was developed to hold the
material within the unit (from feed to discharge) for 85 minutes.
Thermocouples on the test unit measure temperatures at three zones on the outside shell as well as the
discharge bed temperature. For this test series, the center zone shell temperature was to be held at the two
conditions of 900° F and 800° F. At the conclusion of the first test, the bed temperature was noted to have
fluctuated greater than the 5°F variance that the vendor requires to call the test a "steady state" test.
Conditions of the first test were immediately repeated with steady state results during this second trial.
CONDITIONS OF THE TESTING
Representative sampling was performed at the site to determine quantities of soil for cleanup and areas of
differing contaminant concentrations. Hot spots were characterized and composites were taken to generate
an equivalent "blended" concentration sample for this treatablility test. The material was screened to less than
1/4" due to the size constraints for feeding into the test unit. A representative sample of this final material was
taken to get "feed" contaminant concentrations. Table A provides contaminant concentration ranges for both
the site materials and the blended sample along with proposed cleanup goals.
The function of the bench-scale unit used for this study was to provide a preliminary assessment of the
vendor's capability for treating specific contaminated wastes and identification of operating parameters. If the
laboratory-scale testing met the treatment goals, the operating data could be used to estimate preliminary
costs for a full-scale remediation. Prior experience had shown a close correlation between this laboratory unit
and the vendor's full-scale system removal efficiencies. The most significant variables affecting removal
efficiency were the temperature and residence time.
Table A. Site Contamination Levels and Clean-up Goals
Contaminant
Concentration
Range
(mg/kg)
Blended Average
Concentration
(mg/kg)
Proposed
Clean-up Goals
(mg/kg)
Chlordane
Edrin
Heptachlor
Pentachlorophenol
10
15
5-
4-
-31
-70
-92
-33
15
20
38
6-
-22
-40
-72
-24
<1
<
<
<
10
5
3
5
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Example 4. (continued)
OPERATING DATA SUMMARY
The bench unit was operated at three test conditions defined by the Zone 2 outside shell temperature and
solids residence time as follows:
Condition 1: 900°F/85 min.
Condition 2: 900°F/85 min.
Condition 3: 800°F/85 min.
Conditions 1 & 2 are similar, but the treated material exit temperature increased from 831 °F to 842° F for
an average of 837°F during the first condition. The steady state condition was maintained in Condition 2
with a bed temperature of 841° F. Table B summarizes the results from the operating conditions.
Table B. Summary of Operating Conditions
Cond.
No.
1
2
3
Average
Feed
Rate
(g/min)
13.1
13.9
14.5
Dryer
Fill
Volume*
(%)
6.2
6.6
6.9
Total
Residence
Time
(min)
85
85
85
Temperature (F°)
Zone 1
861
860
763
Zone 2
900
900
800
Zone 3
926
925
820
Treated
Material
Exit
837
841
747
* Fill volume = percentage of dryer cylinder cross section filled with solids, based on measured products
loose density of 1.09 g/cc
DISCUSSION OF TEST
This remedy selection test was designed to mimic full-scale conditions in terms of operating temperature,
residence time, and (scaled-down) throughput. The sample concentrations were representative of average
contaminant loadings, and preliminary cleanup standards were used to structure the design and assess the
success of the test (See Section 6, Example 5).
This particular remedy selection equipment was an indirect fired rotary kiln. Obviously, the operating
parameters collected (i.e., temperatures from three shell zones) would not be applicable to the operating
parameters necessary to evaluate a thermal screw remedy selection unit.
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detailing the site-specific requirements posed by thermal
desorption, and assuring compliance with the cleanup
requirements.
4.3 EQUIPMENT AND MATERIALS
The Work Plan should specify the equipment and materials
needed for the treatability test. Standard laboratory methods
normally dictate the types of sampling containers which can be
used with various contaminant groups. Appropriate methods
for preserving samples and specified holding times for those
samples should be used.
The following equipment is typically needed for remedy
screening thermal desorption tests:
muffle furnace, vapor extractor, DBR, or similar devices
exhaust hood (for control of fugitive dust and volatilized
compounds)
tray or some other device to hold contaminated media
thermocouples (to record medium and gas temperature)
rotameter (to regulate purge gas flow rate)
Equipment for remedy selection testing is typically
vendor-specific and may include the following systems:
Rotary dryer
Thermal screw
Vapor extractor
Distillation chamber
Associated offgas controls for each
A number of vendors have bench-scale to pilot-scale size
systems available.
4.4 SAMPLING AND ANALYSIS
The Work Plan should describe the procedures to be used in
field and treatability study sampling. The procedures to be
used will be site-specific.
4.4.1 Field Sampling
A sampling plan should be developed for the collection of
representative samples from the site for the treatability test.
The sampling plan is site-specific. It describes the number,
location, and volume of samples. If the objective of the testing
is to investigate the performance of thermal desorption at the
highest contaminant concentration, the sample collection must
be conducted at a "hot spot". This will require conducting a
preliminary site sampling program or analyzing existing data to
identify the locations of highest contaminant concentration.
(This information is generated early in the RI process.) If the
medium and types of contaminants vary throughout the site,
extensive sampling may be required. If thermal desorption is
being considered only for certain areas of the site, the
sampling program may be simplified by concentrating on those
areas.
If the objective of the testing is to investigate the use of the
technology for a more homogenous waste, an "average"
sample for the entire site must be obtained. This will require a
statistically-based program of mapping the site and selecting
sampling locations that represent the variety of waste
characteristics and contaminant concentrations present. The
selection of sampling locations should be based on knowledge
of the site. Information from previous samples, obvious odors,
or residues are examples of information which can be used to
specify sample locations. Table 4-2 lists the type of analyses
required for samples in remedy selection testing.
These analyses are typically required for any thermal
desorption system. Additional analyses fortotal metals, TCLP
parameters, PCBs, PAHs, dioxins, or furans may also be
required depending on the site.
Chapter 9 of Test Methods for Evaluating Solid Waste(36)
presents a detailed discussion of representative samples and
statistical sampling methods. Additional sources of
information on field sampling procedures can be found in
Annual Book of ASTM Standards/3' NIOSH Manual of
AnalyticalMethods (February 1984),(17) and EPA publications
Soil Sampling Quality Assurance User's Guide1-34-1 and Methods
for Evaluating the Attainment of Cleanup Standards/3 r> These
documents should be consulted to plan effective sampling
programs for either simple or complex sites.
4.4.2 Waste Analysis
Subsection 2.2.3 detailed the physical tests that are useful in
characterizing the contaminated medium during the
prescreening step. The key for successful thermal desorption
treatability studies is to properly select the medium samples
based on the initial prescreening and
Table 4-2. Analyses Required in Remedy Selection Testing
Parameter
Sample
Feed Stream
Treated Stream
Offgas/Condensate
voc
X
X
X
svoc
X
X
X
PH
X
X
X
Moisture
X
X
Ash
X
X
Oil/Grease
X
X
Particle Size
X
X
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additional medium characterizations. Analyses conducted
during the RI/FS for contaminants at Superfund sites should
identify the contaminants of concern. The spatial distribution
and variations in the concentrations of contaminants will be
important for the design of treatability studies. If the site
contains complex mixtures of contaminants, it may be difficult
to treat economically. In some instances, frequent changes in
contaminant composition can cause dramatic changes in
thermal desorption performance.
4.4.3 Process Control Measurements
Process control and monitoring measurements are essential for
remedy screening and remedy selection tests. Placement of
thermocouples is dependent on the type of equipment used.
They generally are placed within the various zones of the
desorption unit to measure medium temperature throughout
the test run. Mass flow rates in and out of the desorber are
measured. Treatment times (i.e., time-at-temperature for the bed
or total residence time) are also recorded.
4.4.4 Residual Sampling and Analysis
The complement of tiers of treatability studies seeks to
characterize the performance of the desorption unit in
separating organic contaminants from the medium, and
approximate the full-scale equipment needs and throughputs.
Residuals from thermal desorption requiring sampling and
analysis include treated medium, condensate, and particulate
control system dust.
Thermal desorption is not a stand-alone process (see
subsection 2.1.1), but a separation process that can leave the
bulk of the clean solid media onsite. It generates small
quantities of residuals which must be disposed of properly.
The primary residuals are the concentrated contaminants
which are typically removed from the offgas. Sometimes, a
useable oil may be produced from condensation of the offgas.
Because the nature of thermal desorption equipment and
processes varies greatly between vendors, remedy design
testing is frequently necessary to evaluate the type, quantity,
and properties of residuals. The remedy design treatability
testing tier will not be discussed in detail in this document.
Process residuals should be analyzed for the contaminants
identified in the original soil analyses as well as any by-
products that may have been formed. In many cases, indicator
contaminants, which are representative of a larger group of
contaminants, can be analyzed in place of a full scan. Caution
must be exercised in using indicator contaminants since
thermal desorption efficiencies can vary from one contaminant
to another. The process efficiency may be either understated
or overstated when analyzing for indicator compounds.
4.4.5 Sampling and Analysis Plan
(SAP) and Quality Assurance
Project Plan (QAPP)
A SAP is required for all field activities conducted during the
RI/FS. The SAP consists of the Field Sampling Plan and the
QAPP. This section of the Work Plan describes
how the RI/FS SAP is modified to address field sampling,
medium characterization, and sampling activities supporting
treatability studies. It describes the samples to be collected
and specifies the level of QA/QC required. See section 5 for
additional information on the SAP.
4.5 DATA ANALYSIS AND
INTERPRETATION
The Work Plan should discuss the techniques to be used in
analyzing and interpreting the data. The objective of data
analysis and interpretation is to provide sufficient information
to the RPM and EPA management to assess the feasibility of
thermal desorption as a remediation technology. After remedy
selection testing is complete, the decision must be made
whether to proceed to the remedy design tier or full-scale
thermal desorption remediation, or to rule out thermal
desorption as an alternative. The data analysis and
interpretation are a critical part of the remedy selection
process. When comparing contaminant concentrations in the
feed material versus levels in product streams it is always
necessary to use the same basis. Laboratories normally report
concentrations on a dry-weight basis;this should be required
to eliminate any dilution effects of adding water to the treated
medium.
Temperature, treatment times, and residual contamination can
be used for screening thermal desorption systems to determine
if they can meet specific cleanup criteria. The key results from
a remedy screening test usually include:
! temperature (continuous measurement)
! treatment times (continuous measurement)
! initial contaminant concentration
! treated medium contaminant concentration
! residuals
Remedy screening tests are normally conducted by fixing all
but one test parameter (independent variable) and running a
series of tests while varying the independent variable. The
independent variable is generally a parameter that directly
affects the thermal desorption performance. Parameters that
have a direct affect on thermal desorption performance include
temperature, soil classification, contaminant type, treatment
time, moisture content, and solid /gas mixing.
Remedy selection testing is nearly always required in the
absence of relevant full-scale performance data. Temperature,
treatment times, and residual concentration data from remedy
screening tests can be used to establish target operating
temperatures. One or more of the following performance criteria
may also be addressed during this tier of testing:
! Throughput rate expected for the applicable remedy design
or full-scale thermal desorption device (including energy
input)
! Material handling system design requirements (pre-and
post-treatment)
! Air pollution control system design requirements
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! Need for air pollution control measures during excavation,
transport, and feeding
4.6 REPORTS
The last step of the treatability study is reporting the results.
The Work Plan discusses the organization and content of
interim and final reports. Complete, accurate reporting is critical
because decisions about implementability will be partly based
upon the outcome of the study. However, the RPM may not
require formal reports at each thermal desorption study tier.
Interim reports should be prepared after each tier. Project
briefings should be provided to determine the need and scope
of the next tier of testing. To facilitate the reporting of results
and comparisons between treatment alternatives, a suggested
table of contents is presented in the generic guide.1-28-1 At the
completion of the study, a formal report is always required.
OERR requires that a copy of all treatability study reports be
submitted to the Agency's Superfund Treatability Database
repository. One copy of each treatability study report must be
sent to:
U. S. Environmental Protection Agency
Superfund Treatability Database
ORD/RREL
26 West Martin Luther King Dr.
Cincinnati, Ohio 45268
Attention: Glenn Shaul, MS-445
4.7 SCHEDULE
The Work Plan includes a schedule for completing the
treatability study. The schedule gives the anticipated starting
date and ending date for each of the tasks described in the
Work Plan and shows how the various tasks interface. The
time span for each task accounts for the time required to obtain
the Work Plan, subcontractor, and other approvals [e.g.,
disposal approval from a commercial Treatment, Storage, and
Disposal Facility (TSDF)]; analytical turnaround time; and
review and comment period for reports and other project
deliverables. Some slack time should also be built into the
schedule to accommodate unexpected delays (e.g., bad
weather, equipment downtime) without affecting the project
completion date.
The schedule is usually displayed in the form of a bar chart
(Figure 4-3). If the study involves multiple tiers of
Months From Project Start
Activity Description
Data Review
WP Prep
SIC, SAP, HSP, CRP Prep
Remedy Screening
(Tray Tests)
Testing and Analytical
Data Analysis
Report
Remedy Selection
(Bench Scale Tests)
Testing and Analytical
Data Analysis
Report
(Pilot Scale Test)
Testing and Analytical
Data Analysis
Report
Final Report
Site Remediation
and RI/FS
Schedule Overview
Figure 4-3. Example project schedule for a thermal desorption treatability study program.
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CONTRACT WORK ASSIGNMENT MANAGER
Report to EPA Remedial Project Manager
Supervise Overall Project
QA MANAGER
Oversee Quality Assurance Program
Prepare applicable sections of Report and
Work Plan
ENVIRONMENTAL/ CHEMICAL ENGINEER
Oversee Treatability Study execution
Oversee sample collection
Prepare applicable sections of Report and
Work Plan
CHEMIST
Oversee sample collection and analysis
Prepare applicable section of Report and
Work Plan
LAB TECHNICIANS
Execute Treatability Studies
Execute sample collections and analysis
Figure 4-4. Organization chart.
testing, all tiers should be shown on one schedule. Careful
planning before the start of the tests is essential. Depending
on the review and approval process, planning can take up to
several months. Remedy screening tests typically take up to
three months. It is not unusual for the remedy selection
thermal desorption treatability test to be a several-month
project.
Barring any difficulties such as acquiring sampling equipment
and site access, the sampling and analysis phase can generally
be accomplished in several months. Contracting with an
external lab for treatability study analysis may take a month.
Laboratory results can often be available in less than 30 days.
Shorter analytical turnaround time can be requested, but this
will normally increase the costs. Compounds such as
pesticides and PCBs may require longer turnaround times due
to the extractions and analyses involved. Interpretation of the
results and final report writing may take up to 3 months, but
this is highly dependent on the length of time for the review
process.
4.8 MANAGEMENT AND STAFFING
The Work Plan discusses the management and staffing of a
treatability study. The Work Plan specifically identifies the
personnel responsible for executing the treatability study by
name and qualifications. Generally, the following typical
expertise is needed for the successful completion of the
treatability study:
! Project Manager (Work Assignment Manager)
! QA Manager
! Environmental/ Chemical Engineer
! Chemist
! Lab Technician
Responsibility for various aspects of the project is typically
shown in an organizational chart such as the one in Figure 4-4.
4.9 BUDGET
The Work Plan discusses the budget for completion of a
treatability study. Remedy screening, with its associated lack
of replication and detailed testing, can range from $8,000 to
$30,000. These estimates are highly dependent on the factors
discussed in Section 4. Not included in these costs are the
cost of governmental procurement procedures, including
soliciting for bids, awarding contracts, etc.
Costs for remedy selection depend on a variety of factors.
Table 4-3 provides a list of potential major cost estimate
components for this tier. Sites where the medium, contaminant
types, and contaminant concentration vary widely will usually
require more samples than sites where the medium and
contamination is more homogeneous. It is not unusual for the
sampling, analysis, and QA activities
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Table 4-3. Major Cost Elements Associated with
Remedy Selection Thermal Desorption Studies
Cost Element
Initial Data Review
Work Plan Preparation
Sampling & Testing
Analysis, QA/QC Activities
Data Presentation/Report
TOTAL COST RANGE
Cost Ranges ($)
1,000-10,000
1,000-5,000
3,000-60,000
3,000-20,000
2,000-5,000
$10,000-$100,000
to represent over 50 percent of the total study cost. In general,
the costs for analyzing organics are greater than for metals.
Actual costs will vary according to individual laboratories,
required turnaround times, volume discounts, and any
customized analytical requirements.
Sampling costs will be influenced by the contaminant types
and depth of contamination found in the medium. The health
and safety considerations during sampling activities are more
extensive when certain contaminants, (e.g., volatile organics),
are present in the medium. Level B personal protective
equipment (PPE) rather than Level D PPE can increase this cost
component an order of magnitude. Sampling equipment
requirements for surface samples are much less complicated
than those for depth samples. Residuals from treatability
testing require proper treatment and/or disposal. If the
residuals are considered hazardous wastes, treatment and
disposal of them will increase costs significantly. It is common
to return the test residuals to the site for storage until remedial
actions are started. This includes contaminated PPE from
sampling, testing, and analysis.
Other factors to consider include report preparation and the
availability of vital equipment and laboratory supplies.
Generally, an initial draft of the report under goes internal
review prior to the final draft. Depending on the process, final
report preparation can be time-consuming as well as costly.
Procurement of testing equipment and laboratory supplies will
also increase the costs.
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SECTION 5
SAMPLING AND ANALYSIS PLAN
The Sampling and Analysis Plan (SAP) consists of two parts,
the Field Sampling Plan (FSP) and the Quality Assurance
Project Plan (QAPP). The purpose of this section is to identify
the contents and aid in the preparation of these plans. The
RI/FS requires a SAP for all field activities. The SAP ensures
that samples obtained for characterization and testing are
representative and that the quality of the analytical data
generated is known and appropriate. The SAP addresses field
sampling,medium characterization, and sampling and analysis
of the treated medium and residuals from the testing apparatus
or treatment unit. The SAP is usually prepared after Work Plan
approval.
5.1 FIELD SAMPLING PLAN
The FSP component of the SAP describes the sampling
objectives; the type, location, and number of samples to be
collected; the sample numbering system; the equipment and
procedures for collecting the samples; the sample
chain-of-custody procedures; and there required packaging,
labeling, and shipping procedures.
Field samples are taken to provide baseline contaminant
concentrations and contaminated material characteristics for
treatability studies. The sampling objectives must be
consistent with the treatability test objectives.
The primary objectives of remedy selection treatability studies
are to evaluate the extent to which specific chemicals can be
removed from soils, sediments, or sludges. The primary
objectives for collecting samples to be used in treatability
testing include:
Acquisition of representative samples. In some cases
statistically designed field sampling plans may be required
to ensure samples taken are representative of the entire
site. However, professional judgment regarding the
sampling locations may be exercised to select sampling
sites that are typical of the area (pit, lagoon, etc.) or
appear above the average concentration of contaminants
in the area being considered for the treatability test. This
may be difficult because reliable site characterization data
may not be available early in the RI stage.
Acquisition of sufficient sample volumes necessary for
testing, analysis, and quality assurance and quality
control.
From these two primary objectives, more specific
objectives/goals are developed. When developing the more
detailed obj ectives, the following types of questions should be
considered:
Are there adequate data to determine sampling locations
indicative of the more contaminated areas of the site?
Have soil gas surveys been conducted? Contaminants
may be widespread or isolated in small areas (hot spots).
Contaminants may be mixed with other contaminants in
one location and appear alone in others. Concentration
profiles may vary significantly with depth.
Are the soils homogeneous or heterogeneous? Soil types
can vary across a site and will vary with depth.
Depending on professional judgement contaminated
samples for various soil types may have to be taken to
conduct treatability tests.
Are contaminants present in sediments or sludges?
Different sampling methods must be used for these media.
Is sampling of a "worst-case" scenario warranted?
Assessment of this question must be made on a site-
by-site basis. Hot spots and contaminants indifferent
media may be difficult to treat. These should be factored
into the test plan if they represent a significant portion of
the site.
After identifying the sampling objectives, an appropriate
sampling strategy is described. Specific items that should be
briefly discussed and included are listed in Table 5-1.
5.2 QUALITY ASSURANCE PROJECT
PLAN
The QAPP consists of 11 sections. Since many of these
sections are generic, applicable to any QAPP, and covered in
available documents, WW this guide will discuss only those
aspects of the QAPP that are affected by the treatability
testing of thermal desorption.
5.2.1 Experimental Description
Section 1 of the QAPP must include an experimental project
description that clearly defines the experimental design, the
experimental sequence of events, each type of critical
measurement to be made, each type of matrix
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(experimental setup) to be sampled, and each type of system
to be monitored. This section may reference section 4 of the
Work Plan. All details of the experimental design not finalized
in the Work Plan should be defined in this section.
Table 5-1. Suggested Organization of Sampling
and Analysis Plan
Field Sampling Plan
1. Site Background
2. Sampling Objectives
3. Sampling Locating and Frequency
Selection
Medium Type
Sampling Strategy
Location Map
4. Sample Designation
Recording Procedures
5. Sampling Equipment and procedures
Equipment
Calibration
Sampling Procedures
6. Sampling Handling and Analysis
Preservation and Holding Times
Chain-of Custody
Transportation
Quality Assurance Project Plan
1. Project Description
Test Goals
Critical Variables
Test Matrix
2. Project Organization and Responsibility
3. QA Objectives
Precision, Accuracy, Completeness
Representativeness and Comparability
Method Detection Limits
4. Sampling Procedures
5. Sample Custody
6. Calibration Procedures and Frequency
7. Analytical Procedures
8. Data Reduction, Validation, and Reporting
9. Internal QC Checks
10. Performance and System Audits
11. Preventive Maintenance
12. Calculation of Data Quality Indicators
13. Corrective Action
14. QC Reports to Management
15. References
16. Other Items
Items in this section include, but are not limited to the
following:
Number of samples (areas) to be studied
Identification of treatment conditions (variables) to be
studied for each sample
Target compounds for each sample
Number of replicates per treatment condition
Criteria for technology retention or rej ection for each type
of remedy evaluation test
The Project Description clearly defines and distinguishes the
critical measurements from other observations and system
conditions (e.g., process controls, operating parameters, etc.)
routinely monitored. Critical measurements are those
measurements, data gathering, or data generating activities
that directly impact the technical objectives of a project. At a
minimum, the determination of the target compound in the
initial and treated solid samples, bed temperature, and time-at-
temperature will be critical measurements for remedy selection
tests. Concentration of target compounds in all fractions will
be critical measurements for remedy design tests.
5.2.2 Quality Assurance Objectives
Section 2 of the QAPP lists the QA objectives for each critical
measurement and sample matrix defined in section 1. These
objectives are presented in terms of the six data quality
indicators: precision, accuracy, completeness,
representativeness, comparability, and where applicable,
method detection limit.
5.2.3 Sampling Procedures
The procedures used to obtain field samples for the treatability
study are described in the FSP. They need not be repeated in
this section, but should be incorporated by reference.
Section 3 of the QAPP contains a description of a credible plan
forsubsampling the material delivered to the laboratory for the
treatability study. The methods for aliquoting the material for
determination of chemical and physical characteristics such as
bulk density or specific gravity, moisture content, contaminant
concentration, etc. must be described.
5.2.4 Analytical Procedures and
Calibration
Section 4 describes or references appropriate analytical
methods and standard operating procedures for the analytical
method for each critical measurement made. In addition, the
calibration procedures and frequency of calibration are
discussed or referenced for each analytical system, instrument,
device, or technique for each critical measurement.
The methods for analyzing the treatability study samples are
the same as those for chemical characterization of field
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samples. Preference is given to methods in "Test Methods for
Evaluating Solid Waste, SW-846,3rd. Ed.,"November 1986.(36)
Other standard methods may be used, as appropriate. P^xso)
Methods other than gas chromatography/mass spectroscopy
(GC/MS) techniques are recommended to conserve costs when
possible.
5.2.5 Data Reduction, Validation and
Reporting
Section 5 includes, for each critical measurement and each
sample matrix, specific presentation of the requirements for
data reduction, validation, and reporting. Aspects of these
requirements are covered in subsections 4.5,4.6, and 6.1 of this
guide.
5.2.6 Quality Control Reports
Section 10 describes the QA/QC information that will be
included in the final project report. As a minimum, reports
include:
Changes to the QA Project Plan
« Limitations or constraints on the applicability of the data
The status of QA/QC programs, accomplishments, and
corrective actions
Results of technical systems and performance evaluation
QC audits
Assessments of data quality in terms of precision,
accuracy, completeness, method detection limits,
representativeness, and comparability
The final report contains all the QA/QC information to support
the credibility of the data and the validity of the conclusions.
This information may be presented in an Appendix to the
report. Additional information on data quality objectives1-25-1
and preparation of QAPPs(32) is available in EPA guidance
documents.
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SECTION 6
TREATABILITY DATA INTERPRETATION
The remedy screening tier establishes the general applicability
of the technology. The remedy selection tier demonstrates the
applicability of the technology to a specific site. The remedy
design tier provides information in support of the evaluation
criteria after the ROD. The test goals for each tier are based on
established cleanup goals or other performance-based
specifications. Proper evaluation of the potential of thermal
desorption for remediating a site must compare the test results
(described in subsection 4.5) to the test goals (described in
subsection 4.1) for the remedy selection tier. The evaluation is
interpreted in relation to seven of the nine RI/FS evaluation
criteria, as appropriate.
Subsection 4.6 of this guide discusses the need for the
preparation of interim and final reports and refers to a
suggested format. In addition to the raw and summary data for
the treatability study and associated QA/QC, the treatability
report should describe what the results mean and how to use
them in the feasibility study in screening/selecting
alternatives. The report must evaluate the expected
performance of the technology and give an estimate of the
costs of further treatability studies and final remediation with
the technology.
6.1 TECHNOLOGY EVALUATION
Remedy screening treatability studies are designed to gain
fundamental information regarding the proof of concept for the
technology. Tests are typically conducted using laboratory
equipment such as a static tray, DBR, or other screening
devices. The contaminant concentration in the medium before
treatment is compared to the contaminant concentration after
treatment. If the measured separation efficiency is sufficient,
additional treatability studies are warranted. If the operating
parameters are properly selected, separation efficiency can be
high. This would indicate success on the screening level, and
testing should proceed to remedy selection. If remedy
screening tests are conducted at lower temperatures and/or
shorter treatment times than those discussed in subsection 4.2,
removal efficiencies may be lower. It may not be appropriate to
eliminate thermal desorption as a treatment alternative under
such cases, since screening tests may be redesigned under
different conditions to demonstrate higher removal
efficiencies. At certain sites, removal efficiencies less than 90
percent maybe acceptable in meeting expected cleanup goals
and testing can proceed to remedy selection. Before and after
concentrations can normally be based on duplicate samples for
each test run. The mean values from these analyses are
compared to assess the success of the study. A number of
statistical texts are available if more information is needed.^-"-12-1
The remainder of this section discusses the interpretation of
data from remedy selection treatability studies. Subsections 4.1
and 4.2 of this guide discussed the goals and design of remedy
selection treatability studies, respectively. The goals of
remedy selection are:
to address general medium pretreatment and materials
handling requirements
to estimate performance and cost data of full-scale
systems
« to verify that thermal desorption can meet cleanup levels
at normal operating conditions
to define heat input requirements
to address general off gas treatment and residuals disposal
requirements
Data obtained from remedy selection need to be interpreted
with a scale-up tool (i.e. past experience or computer
simulation). Vendors use past experience to scale up to their
own systems. A properly validated computer simulation can be
another scale-up tool.
One such computer simulation is the GRI/NSF Thermal
Treatment Model(18:i being developed at the University of Utah
to describe the decontamination of a solid medium when
heated in a rotary dryer. The model describes the heat transfer
to the contaminated medium, the desorption of the
contaminant from the medium, and its subsequent fate in the
gas phase. The model consists of two major submodels:
1. A heat transfer model which predicts the medium
temperature as a function of kiln residence time for both
direct and indirect heated systems which may be
cocurrent or countercurrent. The model accounts for
heating the medium by convection, radiation, and
conduction in a series of perfectly mixed axial zones. Heat
can be transferred to the medium from hot gases or from
the heated shell.
2. A mass transfer model which predicts organic desorption.
This requires data from laboratory tests to define a series
of adjustable parameters which are contaminant and
medium dependent.1-14-1
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3. The model, which is not vendor-specific, has been used Example 5 continues from Example 4 and illustrates typical
to predict the performance of full-scale systems from data results presented from remedy selection treatability tests. This
generated in treatability studies. It provides an ideal example goes on to give the vendor's estimated costs for the
method for the interpretation of both remedy selection full-scale remediation. Costing is described further in
and remedy design data, but it is relevant to rotary dryer subsection 6.2 of this guide.
desorption systems only .(14)
Example 5. Remedy Selection Treatability Test Results
BACKGROUND
In Example 4, the site history, equipment used, and test conditions were reviewed. The same vendor-specific
treatability test is continued toshow how results could be presented and interpreted.
RESULTS OF TESTING
The mass balance isbased on the total time that solids were fed to and discharged from the system. All solid
products recovered are assumed to be the average of the three product samples analyzed. Contaminant
concentrations were measured in the solid and liquid streams only. Analysis of the contaminants in the gas
phase was not within the scope of this test series. The component recovery calculations are based on the mass
of the contaminant in the untreated soil feed. The major component recoveries for this study are summarized in
Table C.
Table C. Major Component Material Balance
Component Total Mass In (g) Total Mass Out (g) % Recovery
Solids 9,363 8,912 95.2
Water* 1,783 2,057 115
Oil and Grease ^.07 0.177 16.5
*Based on water content of feed only
The removal efficiencies of the POHCs are shown in Table D. The analytical results indicate the concen-
trations were significantly reduced.
Table D. POHC Removal Efficiency
Proposed
Run Feed Product % Cleanup Standard
Contaminant (mg/kg) (mg/kg) Removal (mg/kg)
Chlordane (total) 2Q 2 QQQ Q5 7 1Q
Endrm 35.7 0.86 97.6 5
Heptachl°r 63.1 <0.33 >99.5 3
Pentachlorophenol 1Ro ,.n RI
34
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Example 5. (continued)
Based on the test results available versus proposed treatments goals, the vendor process is a suitable
alternative treatment technology for the pesticide-contaminated soils at the site. For this type of clayey
soil with a moisture content between 15 and 20 percent, the vendor could process 100 to 130 tons per
day. To estimate the total amount of material requiring treatment, the site soil volume estimates were
converted to mass using a calculated in situ density of 1.5 ton/yd3. Table E shows the vendor estimated
treatment costs, using the Remedy Selection test results and the vendor's experience as a scale-up tool.
Table E. Vendor's Treatment Cost Estimate From
Remedy Selection Test Results
Item ($/ton)
Mobilization/Demobilization 15.0
Operating Labor 24.5
Maintenance 22.5
Capital Charge 44.0
Utilities
Electricity 12.0
Propane 21.5
Consumables
Nitrogen 9.5
Carbon 6.0
Miscellaneous 3.5
Residual Management
Condensed Water 6.0
Condensed Organics 2.5
Filter Cake Recycle 6.5
Total Treatment Cost 172.5
Assumptions:
1) Soil Density =1.5 tons/yd3 (111 Ib/ft3)
2) Feed Rate = 106 tons/day
3) Soil Moisture = 20 percent
4) Total Volume for Treatment = 24,000 yd3
CONCLUSIONS
Using a representative sample and a vendor's bench-size, scaled model of their production unit, the
efficiency of contaminant removal is estimated. This vendor predicted feed rates, organic removal rates,
and operating costs for the full-scale production unit.
With this data available, the RPM can decide if the cleanup levels achieved are acceptable, the
economics are justifiable, and whether thermal desorption is a viable alternative. If efficiencies are low
and/or cost data can't be provided, the decision could be to move to remedy design testing for detailed
information.
35
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6.2 ESTIMATION OF COSTS
Reasonable preliminary cost estimates are crucial to the
feasibility study process. Comparisons of various
technologies must be based on the most complete and
accurate estimates available. Remedy screening treatability
studies cannot provide this type of information. Preliminary
co st estimates for full-scale remediation are generally possible
from remedy selection data. Such estimates may be good
enough for comparisons to other technologies at the same tier
of testing. On this basis, the estimates can form the basis of
the ROD. Remedy design studies, which are conducted after
the ROD has been signed, may be necessary to provide a more
accurate estimate of the eventual cost of full-scale thermal
desorption remediation. This is especially true since thermal
desorption will form only one component of a treatment train.
6.2.1 Thermal Desorption Remedy
Selection Cost Estimates
Remedy selection tests can be used to obtain preliminary cost
estimates for full-scale systems.
Data obtained from remedy selection which are needed to
estimate full-scale costs include:
« medium pretreatment and materials handling
moisture content
contaminant identification and concentration
operating temperature
treatment time
« residual contaminants and contaminant concentrations in
the treated medium
offgas treatment
Medium characterization (i.e., moisture content and
contaminant concentration) is needed to determine the size
and throughput of the thermal desorption unit. Moisture
content not only determines the heat input that is required but
also the time required to dry soil. If soil moisture is low or
minimized through pretreatment, increased throughput rates
should be realized. (Pretreatment costs must be factored into
the cost estimate.) Although moisture and concentration
levels may vary throughout the site, average values are
needed to make some sort of throughput determination.
Operating temperature and treatment time, which are
dependent on moisture content and contaminant identification
and concentration, are needed as part of the thermal
desorption unit size determination.
The presence of metals or other inorganic contaminants, which
may indicate additional treatment is necessary, needs to be
determined. Residual contaminant concentrations from
treatability testing are generally not the same as residual levels
from full-scale cleanups. However, they are needed to make
preliminary cost estimates for full-scale systems; any existing
or even empirical full-scale data should be evaluated with
treatability test data to help compensate for inherent scale-up
uncertainties. Offgas treatment and material handling are
important cost considerations in any thermal desorption
system. Preliminary cost estimates for material handling cannot
be determined directly from most remedy selection tests but
can be derived from site characterization data. The total
volume of medium, moisture content, particle size distribution,
and the presence of any debris are important factors in
determining material handling costs. Offgas treatment cost
estimates can be derived from offgas analysis conducted in the
treatability study, although they should only be considered
order of magnitude.
6.2.2 Full-Scale Thermal Desorption
Cost Estimates
Various thermal desorption systems are operating at several
Superfund sites. Vendors have documented processing costs
perton of feed processed. The overall range varies from $80 to
$350/ton of medium processed. Caution is recommended in
using costs out of context because the scope of work may
vary from site to site. It is important to know what costs are
included (e.g., engineering design, excavation, pretreatment,
residual disposal) and what is the base year. Costs also are
highly variable due to the quantity of medium to be processed,
throughput rate (the capacity of the thermal desorption unit),
term of the remediation contract, moisture content, organic
constituent variation of the contaminated medium, and cleanup
standard to be achieved. Similarly, cost estimates should
include such items as preparation of Work Plans, permitting,
testing excavation, processing, sampling and analysis, QA/QC
verification of treatment performance, and reporting of data.
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SECTION 7
REFERENCES
1. Abrishamian, R. Thermal Treatment of Refinery Sludges
and Contaminated Soils. Presented at American
Petroleum Institute, Orlando, Florida, 1990.
2. American Society of Agronomy, Inc. Methods of Soil
Analysis,Part 1, Physical andMineralogical Properties
Including Statistics of Measurement and Sampling. 1986
3. American Society for Testing and Materials. Annual
Book of ASTM Standards. November 1987.
4. Baker, G.E. Notes form the Review Meeting on the
Thermal Desorption Treatability Study Guide
-Strawman. In-house files. Meeting conducted June 3-4,
1991. Cincinnati, Ohio.
5. Bevington, P.R. Data Reduction and Error Analysis for
the Physical Sciences. McGraw-Hill, Inc., New York,
New York, 1969. 336pp.
6. Canonie Environmental Services Corp, Low
Temperature Thermal Aeration (LTTA) Marketing
Brochures, circa 1990.
7. Cudahy, J. and W. Troxler. 1990 Thermal Remediation
Industry Contractor Survey. Journal of the Air and
Waste Management Association, 40 (8): 1178-1182,
August 1990.
8. Eddings, E.G. and J.S. Lightly. Fundamental Studies of
Metal Behavior During Solids Incineration.
Unpublished. Submitted to Combustion Science and
Technology.
9. Fox, R., etal. Thermal Treatment for the Removal of
PCB's and Other Organics for Soil. Environmental
Progress, 10(1), February, 1991.
10. Hokanson, S., et al. Treatability Studies on Soil
Contaminated with Heavy Metals, Thiocyanates,
Carbon Disulfate, Other Volatile and Semivolatile
Organic Compounds. In: Superfund '90 Proceedings of
the 11th National Conference. Sponsored by Hazardous
Materials ControlResearchlnstitute, Washington, D. C.,
November 26-28,1990.
11. Ikeguchi, T., and S. Gotoh. Thermal Treatment of
Contaminated Soil with Mercury. Presented at
Demonstration of Remedial Action Technolgies for
Contaminated Land and Groundwater, NATO/ CCMS,
Second International Conference, Bilthoven, the
Netherlands, 1988.
12. Kleinbaum, D.C. andL.L. Kupper. Applied Regression
Analysis and Other Multivariable Methods. Duxbury
Press, North Scituate, Massachusettes, 1978. 556 pp.
13. Law Environmental Onsite Engineering Report for
Evaluation of the HT-5 High Temperature Distillation
Sy stem for Treatment of Contaminated Soils Treatability
Test Results for a Simulated K051 API Separator
Sludge, Vol 1: Executive Summary, 1990.
14. Lighty, J.S., G.D. Silcox, and D.W. Pershing.
Investigation of Rate Processes in the Thermal
Treatment of Contaminated Soils. Final Report for the
Gas Research Institute, GRI-90/0112, 1990.
15. Lighty, J.S., et al. On the Fundamentals of Thermal
Treatment for the Cleanup of Contaminated Soils.
Presented at the 81st Annual Meeting of the Air
Pollution Control Association, Paper 88-17.5, Dallas,
Texas, June 19-24, 1988.
16. Lighty, J.S., et al. Rate Limiting Processes in the
Rotary-Kiln Incineration of Contaminated Soils.
Combustion Science and Technology, 74:31-39, 1990.
17. National Institute for Occupational Safety and Health
(NIOSH) Manual of Methods, U.S. Department of
Health and Human Services, February 1984.
18. Owens, W.D., G.D. Silcox, J.S. Lighty, X.X. Deng, D.W.
Pershing, V.A. Cundy, C. B. Leger, and A.L. Jakway.
Thermal Analysis of Rotary Kiln Incineration:
Comparison of Theory and Experiment. Combustion
and Flame, 86:101-114.
19. Personal Communications with various EPA Regional
Project Managers, April, 1991.
20. Recycling Sciences International, Inc., DAVES
Marketing Brochures, circa 1990.
21. Reintjes, R. and Schuler, C. Seven Years Experience in
Thermal Soil Treatment. Forum on Innovative
Hazardous Waste Treatment Technologies: Domestic
and International, Atlanta, Georgia, June 1989.
22. Swanstrom, C. and C. Palmer. X*TRAX Transportable
Thermal Separator for Organic Contaminated Solids.
Presented at the Second Forum on Innovative
Hazardous Waste Treatment Technologies: Domestic
and International, Philadelphia, Pennsylvania, 1990.
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23. T.D.I. Services, Marketing Brochures, circa 1990.
24. Troxler, W.L., et al. Guidance Document for the
Application of Thermal Desorption for Treating
Petroleum Contaminated Soils. Prepared for U.S.
Environmental Protection Agency, October 1991.
(unpublished)
25. U.S. Environmental Protection Agency. Data Quality
Objectives for Remedial Response Activities. EPA/
540/G-87/004, OSWER Directive 9355.0-7B, 1987.
26. U.S. Environmental Protection Agency. Engineering
Bulletin: Thermal Desorption Treatment. EPA/540/
2-91/008,1991.
27. U.S. Environmental Protection Agency. Guidance for
Conducting Remedial Investigations and Feasibility
Studies Under CERCLA, Interim Final.
EPA/540/G-89/004, OSWER-9335.3-01,1988.
28. U.S. Environmental Protection Agency. Guide for
Conducting Treatability Studies Under CERCLA,
Interim Final. EPA/540/2-89/058,1989.
29. U.S. Environmental Protection Agency. Inventory of
Treatability Study Vendors. EPA/540/2-90/003a, March
1990.
30. U.S. Environmental ProtectionAgency. Methods for
Chemical Analysis of Water and Wastes. EPA/600/
4-79/020,1979.
31. U.S. Environmental ProtectionAgency. Methods for
Evaluating the Attainment of Cleanup Standards,
Volume 1: Soils and Solid Media. EPA/230/2-89/042.
32. U.S. Environmental Protection Agency. Preparation
Aids for the Development of Category III Quality
Assurance Project Plans. EPA/600/8-91/005, February
1991.
33. U.S. Environmental Protection Agency. Selected Data
on Innovative Treatment Technologies: For Superfund
Source Control and Groundwater Remediation, August
1990.
34. U.S. Environmental ProtectionAgency. SoilSampling
Quality Assurance User's Guide. EPA/600/4-84/043,
1984.
35. U.S. Environmental Protection Agency. Technology
Screening Guide for Treatment of CERCLA Soils and
Sludges. EPA/540/2-88/004, 1988.
36. US. Environmental Protection Agency Test Methods
for Evaluating Solid Waste. 3rd Ed, SW-846, 1986.
37. U. S. Environmental Protection Agency. The Superfund
Innovative Technology Evaluation Program-Progress
and Accomplishments Fiscal Year 1989, A Third Report
to Congress, EPA/540/2-88/004, Cincinnati, Ohio, 1988.
38. U.S. Environmental Protection Agency. Treatability
Studies Under CERCLA: An Overview. OSWER
Directive 9380.3-02FS, 1987.
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