United States
                          Environmental Protection
                          Agency
                         Office of
                         Solid Waste and
                         Emergency Response
EPA/540/R-92/074 B
September 1992
   &EPA
Guide for Conducting Treatability
Studies under CERCLA:
Thermal Desorption
   Office of Emergency and Remedial Response
   Hazardous Site Control Division OS-220
                                                                  QUICK REFERENCE FACT SHEET
   Section 121 (b) of CERCLA mandates EPA to select remedies that "utilize permanent solutions and alternative
treatment technologies or resource recovery technologies to the maximum extent practicable" and to prefer remedial
actions in which treatment that "permanently and significantly reduces the volume toxfcrty, or mobility of hazardous
substances, pollutants, and contaminants is a principal element." Treatability studies provide data to support remedy
selection and implementation. They should be performed as soon as it becomes evident that the available in ormation
is insufficient to ensure the quality of the decision. Conducting treatability studies early in the remedial ..vest,gation/
feasibility study (RI/FS) process should reduce uncertainties associated with selecting the remedy and should provide a
sound basis for the Record of Decision (ROD). Regional planning should factor in the time and resources required for
these studies.
   This fact sheet provides a summary of information to facilitate the planning and execution of thermal desorptionremedy
screening and remedy selection treatability studies in support of the RI/FS and the remedial desl9^re™^
RA) processes. Detailed information on designing and implementing remedy screenmg and remedy selectoon treatebdrty
studies for thermal desorption is provided in the 'Guide  for Conducting Treatab.l.ty Studies Under CERCLA: Thermal
Desorption," Interim Guidance, EPA/540/R-92/074 A, September, 1992.
 INTRODUCTION
                           TECHNOLOGY DESCRIPTION AND PRELIMINARY
                           SCREENING
    There are three levels or tiers of treatability studies:
 remedy screening, remedy selection, and remedy design.
 The "Guide for Conducting Treatability Studies Under
 CERCLA: Thermal Desorption" discusses all three levels
 of treatability studies.

    Remedy screening studies provide a quick and relatively
 inexpensive indication of whether thermal desorption is a
 potentially viable remedial technology Remedy selection
 studies provide data that permit evaluation of thermal
 desorption's ability to meet expected site cleanup goals
 and provide information in support of the detailed analysis
 of the alternative (i.e., seven of the nine evaluation criteria
 specified in EPA's RI/FS Interim Final Guidance Document,
 EPA/540/G-89/004, 1988).   Remedy selection tests
 generally have moderate costs, and may require weeks to
 months to complete.  Remedy  design testing provides
 quantitative performance, cost, and design information for
 remediating the operable unit.  Remedy design studies are
 of moderate to high costs and  may require months to
 complete.
                           Technology Description

                              Thermal desorption includes any number of ex situ
                           processes that use either direct or indirect heat exchange
                           to vaporize organic contaminants from soil and 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
                           concentrations  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, and sediment or
                           combinations of these.  The medium is typically heated to
                           200 to 1,000°F; based on the thermal desorption system
                           selected, certain systems operate at higher temperatures.

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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 1 is a general schematic of the
thermal desorption process.

    Materials handling (1) requires excavation and transport
of the  medium to the system.  Typically,  large objects
greater than 1.5 inches are screened from the medium and
rejected. Classified medium is conveyed, via belt or screw
conveyor,  to a feed hopper, and then metered into the
desorber.

    Significant system variation exists in the desorption
step (2).  The desorber can be a rotary dryer, a thermal
screw, a distillation chamber, or a vapor extractor

    Contaminants are  intimately contacted with a heat
transfer surface or hot gases, and highly volatile components
(including  water) are driven off. An inert  gas, such as
nitrogen or steam, may be injected to convey the vaporized
contaminants and water and to ensure contaminants are
not oxidized by reducing the source of oxyuen.

    The actual medium temperature and residence time
are the primary factors affecting performance in thermal
desorption. These parameters can be controlled in the
desorption unit by using a series of increasing temperature
zones, multiple passes of the medium through the desorber
where the operating temperature is sequentially increased,
or separate compartments where the heal transfer fluid
temperature is higher.

    Offgas from desorption (3) will contain entrained dust
(particulate) from the medium, vaporized Contaminant 5,
and water vapor. Particulatesare removed by convention li
equipment such as cyclones, fabric filters, or wet scrubbers.
Volatiles in the offgas may be condensed and then pass* cl
                         through a carbon adsorption bed orother treatment system.
                         Emissions may also be destroyed in an offgas combustion
                         chamber or catalytic oxidation unit. The selection of the
                         gas treatment system will depend on the concentrations of
                         the contaminants, cleanup standards, and the economics
                         of the offgas treatment system(s) employed.

                            Thermal desorption is most applicable for separation
                         of organic contaminants from soils or sludges.  Thermal
                         desorption units have been selected in the ROD for one or
                         more operable units at approximately 14 Superfund sites.
                         These sites include:  McKin (Maine), Ottati & Goss (New
                         Hampshire), Cannon Engineering  (Massachusetts),
                         Resolve (Massachusetts), Wide Beach (New York), Fulton-
                         Terminals (New York), Metaltec/Aerosystems (New Jersey),
                         Caldwel! 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.

                         Prescreening Characteristics

                            The determination of the need for and the appropriate
                         tier of treatability  study  required is  dependent on the
                         literature available on the technology,  expert technical
                         judgement, and site-specificfactors. The first two elements
                         - the literature search and expert consultation - are critical
                         factors of the prescreening phase in determining whether
                         adequate data are available or whether a treatability study
                         is needed.

                            Information on the technology applicability, the latest
                         performance data, the status of the technology, and sources
                         for further information are provided in one of a series of
                         engineering  bulletins being  prepared  by EPA's Risk
                         Reduction Engineering Laboratory in Cincinnati, Ohio.
           Excavate
Material
Handling
                                                 Desorption
                                                                       Gas Treatment
                                                                          System
                                                            Residuals
                                          Oversized Rejects
                                           Treated
                                           Medium
                            Figure 1. Schematic Diagram of Thermal Desorption

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    A literature search should be performed to determine
the physical and chemical properties of the contaminants
of interest. Contaminant characteristics such as volatility
and density are important for the design of remedy screening
studies and related residuals treatment systems. Particle
size distribution and moisture content may be important to
determine pretreatment needs. 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.

    If contamination exists at different soil zones a soil
characterization profile should be developed for each soil
type or zone.  Available  chemical and  physical data
(including averages and ranges) and the volumes of the
contaminated soil 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 contaminant profile of the site. Grab
samples taken from the site ground surface may represent
only a small percentage of the contaminated soils 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 semi-volatile organic compounds
 (SVOCs) 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 be
 removed from the feedstock material during any full-scale
 treatment operations.

 Technology Limitations

     Thermal desorption  limitations may be defined as
  characteristics that hinder cost-effective treatment. 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 endpoint concentration.  The degree of
  mixing, where applicable, and 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. Sf the system isdirect-heated.flammability
  of the contaminant must also be considered in order to
  prevent explosions. 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. Media exhibiting lowpH may similarly corrode
  system components during processing.
THE USE OF TREATABILITY STUDIES IN REMEDY
EVALUATION

    Treatability studies should be performed in a systematic
fashion to ensure that the data generated can support the
remedy evaluation process. The results of these studies
must be combined with other data to fully evaluate the
technology.

    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 are
management-based decisions in which the time and cost
of 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).

    Technologies generally are evaluated first at the remedy
screening level and progress through remedy selection to
the remedy design level. A technology  may enter the
 selection process at whatever level is appropriate based
 on available data on the technology and site-specific
 factors. Figure 2 shows the relationship of the three levels
 of treatability study to each other and to the RI/FS process.

 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 several weeks 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.  These tests  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.
 Screening tests are conducted using laboratory- scale
 equipment.  These tests are generic, not vendor- specific,
 and can be  performed at any laboratory with the proper
 equipment and qualified personnel.

     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 allow for evaluation of the
  potential success of thermal desorption at a site. Information
  on past performance with similar contaminants is useful in
  evaluating the potential applicability of thermal desorption.
  In such cases, remedy selection tests are normally the first
  level of treatability study executed.

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Remedy Selection

    Remedy  selection is  the  second level  of  testing.
Remedy selection studies identify the technology's
performance for a site. These studies have a moderate to
high cost (e.g., $10,000 to $100,000) and require several
months or more to plan, obtain samples, and execute.
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. Frequent ly
these tests 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.

Remedy Design

    Remedy design is the third level of testing and is done
after the ROD. 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. Forcomplexsites(e.g., sites with different types
                                or concentration of contaminants in different medium such
                                as soil, sludges, and sediments), longer testing periods
                                may be required, and costs can 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.


                                TREATABILITY STUDY WORK PLAN

                                   Carefully planned treatability studies are necessary to
                                ensure that the data generated are useful for evaluating
                                the validity or performance of the technology. The Work
                                Plan sets forth the contractor's proposed technical approach
                                to the tasks outlined in the RPM's Work Assignment. It also
                                assigns responsibilities, establishes the project schedule,
                                and estimates costs. The Work Plan must be approved by
                                the RPM before work begins. A suggested organization of
                                the thermal desorption treatability study Work Plan is
                                provided in the "Guide for Conducting Treatability Studies
                                Under CERCLA: Thermal Desorption."
                           Remedial Investigation/
                          Feasibility Study (RI/FS)
                                         Identification
                                        of Alternatives
            Scoping
            -  the  -
             RI/FS
            Literature
            Screening
              and
           Treatability
          Study Scoping
       Site
   Characterization
   and Technology
     Screening
    REMEDY
  SCREENING
   to Determine
Technology Feasibility
                                          Record of
                                          Decision
                                           (ROD)
                                           Remedy
                                           Selection
                             Remedial Design/
                             Remedial Action •
                                (RD/RA)
 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 2. The Role of Treatability Studies in the RI/FS and RD/RA Process

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Test Objectives and Goals

    The overall thermal  desorption treatability study
objectives must meet the specific needs of the  RI/FS.
There are nine evaluation criteria specified in EPA's RI/FS
Interim Final Guidance Document (OSWER- 9335:301).
Treatability studies can provide data from which seven of
these criteria may be evaluated.

    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 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 may indicate  that further testing for remedy
design is appropriate.

    When remedy screening tests are performed, defining
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,
achievement of 75 percent or higher separation efficiencies
in the remedy screening tier would justify proceeding to the
next tier.  RREL's Remedy Screening Lab has used 50
percent as a goal in the past.

    The main goals of the remedy selection 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 system(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.

 Experimental Design

    Careful planning of experimental design and procedures
 are required to produce adequate treatability study data.
 The experimental design  must identify  the  critical
 parameters and determine the number of replicate tests
 necessary.   System design, test procedures, and test
 equipment will vary among vendors.   The information
 presented in this section provides an overview of the test
 equipment and procedures as these relate to each type.

    When considering remedy screening tests, 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 a target
treatment temperature should be minimized to practical
laboratory timeframe such as 5to 10 minutes. Longertime
may be required depending on the specific contaminants
present in the soil.

    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
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.

    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. (Time-at-temperature isdefined
as the elapsed time that the average medium temperature
is at or above a target temperature.) 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.  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 level.

     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 test
systems are able  to  simulate the performance
characteristics of the various desorption systems.

     Remedy selection testing should define the time- at-
temperature and residual concentrations as a function of
 heat input and bed mixing characteristics for a thermal
 desorption device.

     More precision is used in weighing and mixing of the
 sample with an associated increase  in QA/QC costs as
 compared to remedy screening tests. Further care must be
 takento ensure homogeneity of the sample(s) being treated.
 Holding time of media 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 (ortriplicate) test runs are
 completed to ensure reproducibility of the results. This is
 extremely important when non-vendor (generic) tests are
 performed (i.e., DRB or static trays). This series of tests is
 considerably more costly than remedy screening tests, so
 only sites with contaminated medium that show promise in

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the remedy screening phase should be carried forward into
the remedy selection tier.

   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 or chemical characteristics
•  thermal properties of medium
•  degree of agitation (solid/gas mixing).

   The moisture content of the medium affects throughput
rate  due to the energy requirements for drying.  A high
water concentration delays contaminant volatilization or
requires larger heat inputs to remove contaminants from
the medium  if the same throughput is to be maintained.
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. Variability
in contaminant concentration should be expected within
individual samples  used to characterize the  extent of
contamination at the site. Blending waste material into a
more homogeneous mixture is useful for treatability testing.

    The particle size distribution of the medium for the test
 must approximate that expected for the contaminated
volume to be treated. If a significant amount of foreign
objects; large, consolidated chunks of medium; or significant
 medium heterogeneity exist at the site, this may impact the
 selection. This may also indicate the need for additional
 materials 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 T and 1 ,OOOT
 for the medium.

     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 bulkof 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 medium
 type. It may be necessary to identify extreme conditions
 and determine the degree of blending required.
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 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 fie Id sampling,
waste characterization, and sampling and analysis of the
treated wastes and residuals from the testing apparatus or
treatment unit.  The SAP is usually  prepared after Work
Plan approval.

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 the required packaging,
labeling, and shipping procedures.

Quality Assurance Project Plan

    The QAPP should be  consistent with  the  overall
objectives of the treatability study.

    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 directiy impact the technical
objectives of a project. At a minimum, the determination of
the target compound in the initial and treated solids samples,
medium 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.

    The purpose of the remedy selection treatability study
is  to  determine whether thermal desorption can  meet
cleanup goals  and provide  information to support the
detailed analysis of alternatives  (i.e., seven of the nine
evaluation criteria). A higher level of QA/QC is required
because the consequences of an incorrect decision are
 more serious. Concentrations of the target contaminants
 in the soil should be verified by using matrix spikes. The
 QAPP should address the measurement of critical variables,
 including the concentrations of target compounds in the
 initial and treated soil for remedy selection column tests.

    The methodsforanalyzingthetreatability study samples
 are the same as those for chemical characterization of field
 samples. Preference is given to methods in "Test Methods
 for Evaluating Solid Waste", SW-846, 3rd. Ed., November
 1986. Other standard methods may be used, as appropriate.
 Methods other than gas chromatography/spectroscopy
 (GC/MS) techniques are recommended to conserve costs
 when possible.

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TREATABILITY DATA INTERPRETATION
TECHNICAL ASSISTANCE
   To properly evaluate thermal  desorption as a
remediation alternative, the data collected during remedy
screening and remedy selection phases must be compared
to the test goals and other criteria that were established
before the tests were conducted.

   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, or 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 treat ment
times than those discussed in the experimental  design,
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 lessthan
90 percent may be 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.

   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, and to define heat input
requirements,  and to address general  offgas 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 computer simulation
scale-up tool is the GRI/NSF Thermal Treatment Model
being developed at the University of Utah to describe the
decontamination of a solid medium when heated in a rotary
kiln,  The model  describes the heat transfer to the
contaminated medium  and  the  desorption of  the
contaminant from the medium and its subsequent late in
the gas phase.

    The model, which is not  vendor specific, has been
used to predict the performance  of full-scale systems from
data generated in treatability studies. It provides an ideal
method for the  interpretation of both remedy selection and
remedy design data, but it is  relevant to  rotary dryer
desorption systems only.
    Additional literature and consultation with experts are
critical factors in determining the need for and ensuring the
usefulness of treatability studies. A reference list of sources
on  treatability studies  is provided in the "Guide for
Conducting Treatability Studies Under CERCLA: Thermal
Desorption."

    It is recommended that a Technical Advisory Committee
(TAG) be used. This committee includes experts on the
technology who provide technical support from the scoping
phase of the treatability study through data evaluation.
Members of the TAG may include representatives from
EPA (Region and/or ORD), other Federal Agencies, States,
and consulting firms.

    OSWER/ORD and the regions operate the Technical
Support Project (TSP) which provides assistance in the
planning, performance, and/or review of treatability studies.
For further information on treatability study support or the
TSP, please contact:

    Engineering Technical Support Center
    Risk Reduction Engineering Laboratory (RREL)
    Cincinnati, OH
    Contact:  Ben Blaney
    (513)569-7406
FOR FURTHER INFORMATION

    In  addition to the contacts  identified above, the
appropriate Regional Coordinator for each Region located
in the Hazardous Site Control Division/Office of Emergency
and Remedial Response or the CERCLA Enforcement
Division/Office of Waste Programs Enforcement should be
contacted for additional information or assistance.
ACKNOWLEDGMENTS

    This fact sheet and the corresponding guidance
document were prepared for the U.S.  Environmental
Protection Agency, Office of Research and Development
(ORD), 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 Assignment Manager.  These
documents were authored by Mr. Gary Baker, Ms. Margaret
Groeber, and Mr. Jim Rawe of SAIC.  The authors are
especially grateful to Mr. PauldePercinof EPA, RREL who
contributed significantly by serving as a technical consultant
during the development of these documents.

    Many other Agency and independent reviewers have
contributed their time and comments by participating in the
expert review meetings and/or peer reviewing the guidance
document.
                                                                          'U.S. Government Printing Office: 1992— 648-080/60137

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