United States
Environmental Protection
Agency
Office of
Solid Waste and
Emergency Response
EPA/540/R-93/519b
August 1993
&EPA
Guide for Conducting Treatability
Studies Under CERCLA:
Biodegradation Remedy Selection
Office of Emergency and Remedial Response
Hazardous Site Control Division OS-220
QUICK REFERENCE FACT SHEET
Section 121(b) of the Comprehensive Environmental Response, Compensation, and Liability Act (CERCLA) of 1980 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, toxicity, 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
information is insufficient to ensure the quality of the decision. Conducting treatability studies early in the remedial
investigation/feasibility study (RI/FS) process should reduce uncertainties associated with selecting the remedy and should provide
a sound basis forthe Record of Decision (ROD). Regional planning should factor in thetime and resources required forthese studies.
This fact sheet provides a summary of information to facilitate the planning and execution of biodegradation remedy selection
treatability studies in support of the RI/FS and the remedial design/remedial action (RD/RA) processes. It is intended to provide
Remedial Project Managers (RPMs), On Scene Coordinators (OSCs), Potentially Responsible Parties (PRPs), and other interested
persons with enough information to determine whether biodegradation treatability studies may be considered in the remedy selection
phase of the RI/FS for the CERCLA site of interest. This fact sheet follows the organization of the "Guide for Conducting Treatability
Studies Under CERCLA: Biodegradation Remedy Selection," EPA/540/R-93/514A", 1993. Detailed information on designing and
implementing remedy selection treatability studies for biodegradation is provided in the guidance document.
INTRODUCTION
There are three levels or tiers of treatability studies: remedy
screening, remedy selection, and RD/RA testing. Treatability
studies conducted during the RI/FS phase (remedy screening
and remedy selection) indicate whetherthe technology can meet
the cleanup goals for the site, whereas treatability studies
conducted during the RD/RA phase establish design and
operating parameters for optimazation 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
RD/RA.
Remedy screening studies are designed to provide a quick
and relatively inexpensive indication of whether biological
degradation is a potentially viable remedial technology. The
remedy screening evaluation should provide a preliminary
indication that reductions in contaminant concentrations are due
to biodegradation and not abiotic processes such as
photodecomposition or volatilization.
Remedyselection studies should simulate conditions during
bioremediation, allowing researchers to determine the
technology's performance on a waste-specific basis. Bench-scale
testing is typically used for remedy selection testing; however, it
may fall short of providing enough information for remedy
selection. Pilot-scale testing also may be appropriate for some
sites. Bench-scale studies can, in some cases, provide enough
information for full-scale design.
RD/RAtesting should provide accurate cost and performance
data, confirming that biodegradation rates and cleanup levels
deteremined during remedy selection can be achieved forthe
site.
This fact sheet and its parent document, the "Guide for
Conducting Treatability Studies Under CERCLA: Biodegradation
Remedy Selection," EPA/540/R-93/514A primarily focus on the
remedy selection tier. These documents also briefly discuss
remedy screening and RD/RAtesting.
TECHNOLOGY DESCRIPTION AND
PRELIMINARY SCREENING
Technology Description
Bioremediation generally refers to the breakdown of organic
compounds (contaminants)bymicroorganisms. Bioremediation
treatmenttechnologies can be divided into two categories, in situ
and ex situ, based upon the location of the contaminated medium
during treatment.
In Situ
In situ biological technologies treat contaminats inplace,
eliminating the need for soil excavation and limiting volatile
releases into the atmosphere. As a result, many of the risks and
costs associated with materials handling are reduced or
eliminated.
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In situ bioremediation usually involves enhancing natural
biodegradation processes by adding nutrients, oxygen (if the
process is aerobic), and in some cases, microorganisms to
stimulate the biodegradation of contaminants. The technology
has primarily been used for the treatment of saturated soils. In
situ bioremediation is often in conjunction with a groundwater-
pumping and soil-flushing system to circulate nutrients and
oxygen through a contaminated aquifer and associated soils.
Bioventinq is an in situ biological technology predominantly
used to treat reasonably permeable, unsaturated soils. Aeration
systems, similar to those employed during soil vapor extraction,
are used during bioventing to supply oxygen to the soil. An air
pump, one or more air injection or vacuum extraction probes, and
emissions monitoring at the ground surface are commonly used
during bioventing. In orderto minimize contaminantvolatilization,
low air pressures and air flow rates are typically utilized. Some
systems, however, utilize higher airflow rates, thereby combining
with soil vapor extraction.
Ex Situ
Ex situ biological treatment technologies involve removal of
the contaminated media followed by onsite or offsite treatment.
Although media handling increases the costs of ex situ treatment,
ex situ approaches generally allow greater control of process
variables (e.g., pH, nutrient concentrations, temperature,
aeration).
Solid-phase bioremediation (sometimes referred to as land
treatmentor land farming) is a process that treats soils in above-
ground treatment systems using conventional soil management
practices to enhance microbial degradation of contaminants.
Solid-phase bioremediation at CERCLA sites usually involves
placing excavating soil in an above-ground soil treatment area. If
required, nutrients and microorganisms are added to the soil,
which is tilled at regular intervals to improve aeration and contact
between the microorganisms and the contaminants.
In slurry-phase bioremediation. excavated contaminated soil
is typically placed in an onsite, stirred-tank reactor where the soil
is combined with water to form a slurry. The solids content of the
slurry depends on the type of soil, the type of mixing and aeration
equipment available, and the rates of contaminant removal that
need to be achieved. The water used in the process can be
contaminated surfacewater or groundwater, thus facilitating the
simulataneous treatment of contaminated soil and water. As with
solid-phase biore mediation nutrients and microorganisms may
be added to the reactor to facilitate biodegradation.
Soil heap bioremediation involves piling contaminated soil
in heaps several meters high. Aeration is usually provided by
pulling a vacuum through the heap. Simple irrigation techniques
are generallyusedto maintain moisture content, pH, and nutrient
concentrations within ranges conducive to the biodegradation of
contaminants. The system can be designed to control the release
of VOCs by enclosing the soil pile and passing the exhaust from
the exhaust from the vacuum through activated carbon biofilters.
Composting involves the storage of biodegradable waste with a
bulking (e.g., chopped hay or wood chips). The structurally-firm
bulking agent is usually biodegradable. Adequate aeration;
optimum temperature, moisture, and nutrient concentrations; and
the presence of an appropriate microbial population are
necessary to enhance the decomposition of organic compounds.
The three basic types of composting systems are open windrow
(where the piles are torn down and rebuilt for aeration), static
windrow (where air is forced into the piles), and in-vessel (where
tumbling, stirring, or forced aeration are used).
Biofilters can be used to treat organic vapors in a manner
analogous to the biological treatment of wastewaters. By
providing bacteria with a surface on which to grow and optimal
oxygen, temperature, nutrients, moisture, and pH conditions,
biofiliters can significantly reduce vapor phase organic
contaminants. The primary components of biofilters are: an air
blower, an air distribution system, filter media, and a drainage
system. Removal efficiencies in the range of 95 to 99 percent
have been reported for light aliphatic compounds, while lower
removal efficiencies are common for chlorinated aliphatic and
aromatic compounds.
Technology Status
As of October 1992, approximately 149 CERCLA, Resource
Conservation and Recovery Act (RCRA), and underground
storage tank (LIST) sites, and other government regulated sites
have been identified by EPA Regions and States as either
considering (e.g., performing treatability studies), planning,
operating full-scale, or having used biological treatment systems.
Approximately 62 percent of the sites are CERCLA sites, 14
percent are RCRA sites, and 10 percent are LIST sites. The
remaining 14 percent represent Toxic Substance Control Act
(TSCA), and other Federal and State efforts.
Prescreening Characteristics
Before a treatability study is conducted, a literature search
should be performed to confirm whether the compounds of
interest are known to be amenable to biological treatment.
Evidence of biodegradation under dissimilar conditions, as well
as data relating to compounds of similar structure, should be
considered. If preliminary research indicates that bioremediation
is an unlikely candidate, further research may be warranted.
Before discarding biological remediation as an option, expert
recommendations regarding the technology's potential should be
obtained. The "Guide for Conducting Treatability Studies Under
CERCLA: Biodegradation Remedy Selection", EPA/540/R-
93/514A, lists references and electronic databases that can be
useful when conducting the literature search phase of a
bioremediation project. The guide also provides contacts for
technical assistance when determining the need or scope of a
remedy selection treatability study. One important resource for
OSCs and RPMs is the Technical Support Project (TSP)
coordinated by EPA's Technology Innovation Office (703-308-
8846). The TSP is operated by EPA laboratories and offers
technical assistance ranging from review of contractorwork plans
to assistance in the performance of treatability studies.
The potential biodegradability of the contaminants of concern
is an important characteristic to be examined prior to initiating
treatability studies. Examples of classes of compounds that are
readily amenableto bioremediation are: pertroleum hydrocarbons
such as gasoline and diesel; wood treating wastes such as
creosote and pentachlorophenol; solvents such as acetone,
ketones, and alcohols; and aromatic compounds such as
benzene, toluene, xylenes, and phenols. Several documents and
review articles that present detailed information on the
biodegradabilityof compounds are listed in the reference section
of the complete guidance document. However, discretion should
be exercised when using these reference materials, as
microorganisms that can
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biodegrade compounds that have traditionally been considered
nonbiodegradable are continually being isolated through ongoing
research and development efforts.
Site and soil characteristics that impact bioremediation are
listed in Table 1. The potential effects of these factors upon
candidate biodegradation technologies should also be
considered.
There is no steadfast rule that specifies when to proceed with
remedy screening, when to eliminate biodegradation as a
treatment technology, or when to proceed to remedy selection
testing based on a preliminary screening analysis. An analysis of
the existing literature coupled with the site characterization may
provide the information required to make a decision. However,
when in doubt, treatability studies are recommended.
Technology Limitations
Many factors impact the feasibility of biodegradation. These
factors should be addressed priorto the selection of
Table 1. Site and Soil Characteristics Identified as
Important in Biological Treatment
In situ
Ex situ
Soil type X
Extent of contamination X
Soil profile properties
Boundary characteristics X
Depth of contamination X
Texture* X
Structure X
Bulk density* X
Clay content X
Type of clay X
Cation exchange X
Organic matter content* X
pH* X
Redox potential* X
Hydraulic properties and conditions
Soil water characteristic curve X
Field capacity/permanent wilting point X
Water holding capacity* X
Permeability* (under saturated and a range of X
unsaturated conditions)
Infiltration rates* X
Depth to impermeable layer or bedrock X
Depth to groundwater, including seasonal X
variations*
Flooding frequency X
Runoff potential* X
Geological and hydrogeological factors
Subsurface geological facors X
Groundwater flow patterns and characteristics X
Meterological and climatological data
Wind velocity and direction
Temperature X
Precipitation X
Water budget X
' Factors that may be managed to enhance soil treatment.
biodegradation and prior to the investment of time and funds in
further testing. Some of these factors that may limit the use of
bioremedial technologies include the amount, location, extent,
and variability of the contamination. The physical form in which the
contaminants are distributed, as well as heterogeneities within
the media to be treated, may limit the applicability of
biodegradation.
Soil characteristics, such as nonuniform particle size
distribution, soil type, moisture content, hydraulic conductivity, and
permeability, can also significantly affect biodegradation.
Significant quantities of organic matter (humus, peat, non-
regulated anthropomorphic compounds, etc.) also may cause
high oxygen uptake rates, resulting in depleted oxygen supplies
during in situ application. Contaminant volatility is particularly
important, especially in stirred or aerated reactors where the
contaminants can volatilize before being degraded.
The presence of eitheran indigenous or introduced microbial
population capable of degrading the contaminants of concern is
usually essential to the success of biological processes. Each
contaminant has a range of concentrations at which the potential
for biodegradation is maximized. Below this range microbial
activity may not occur withoutthe addition of a co-substrate. Above
this range, microbial activity may be inhibited and, once
concentrations are reached, eventually arrested. During inhibition,
contaminant degradation generally occurs at a reduced rate. In
contrast, at toxic concentrations contaminant degradation does
not occur. The concentrations at which microbial growth is either
supported, inhibited, or arrested vary with the contaminant, media,
and microbial species.
Although preliminary data may be obtained that seem to
indicate that the technology is capable of reducing contamination
levels to acceptable limits, the rate of contaminant removal from
soil during bioremediation exhibits asymptotic characteristics.
The initial rate of removal, after a potential lag period, is rapid.
With time, the rate decreases to a near-zero value, and the
contaminant concentration in the soil approaches a fixed
concentration that is typically nonzero (the asymptote). Since the
asymptote isdifficultto predict and is sometimes greaterthan the
cleanup criteria, treatability testing must be continued until either
the removal goals are met or the asymptote is reached.
THEUSEOFTREATABILITYSTUDIESIN
REMEDY EVALUATION
Treatability studies should be performed in a systematic
fashion to ensure that the data generated can support the remedy
evaluation and implementation process. A well-designed
treatability study can significantly reduce the overall uncertainty
associated with the decision, but cannot guarantee that the
chosen alternative will be completely successful. Care must be
exercised to ensure that the treatability study is representative of
the treatment (e.g., the sample is representative of waste to be
treated) as it will be employed to minimize uncertainty in the
decision.
Treatability Testing Process
Treatability studies for a particular site will often entail
multiple tiers of testing. By balancing the time and cost necessary
to perform the testing with the risks inherent in the decision, the
level of treatability testing required can be determined. Criteria for
measuring the success of each level of treatability study are listed
in Table 2.
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Remedy screening is the first level of testing. It is used to
determine whether biodegradation is possible with the site-
specific waste material. These studies are generally low cost
(e.g., $10,000 to $50,000) and usually require 1 weekto several
months to complete. Additional time must be allowed for project
planning, chemical analyses, interpretation of test data, and
report writing. Only limited quality control is required. These
studies yield data indicating a technology's potential to meet
performance goals.
Remedy selection testing is the second level of testing. To
the maximum extent practical, remedy selection tests should
simulate site conditions during treatment, allowing researchers
to identify the technology's performance on a waste-specific basis
for an operable unit. These studies are generally of moderate
cost (e.g., $50,000 to $300,000) and may require several weeks
to two years to complete. They yield data that verify that the
technology is likely to meet expected cleanup goals and can
provide information in support of the detailed analysis of the
alternative.
RD/RA testing is the third level of testing. By operating a field
unit under conditions similar to those expected during full-scale
remediation, the study can provide data required forfinal full-scale
design and accurate cost and time estimates. Unit operating
parameters can be optimized and the ability to
achieve cleanup levels can be confirmed. These studies are of
moderate to high cost (e.g., $100,000 to $500,000) and may
require several months or more to complete. They are performed
during the remedy implementation phase of a site cleanup.
Figure 1 shows the relationship of the three levels of treatability
study to each other and to the RI/FS process.
Applicability of Treatability Tests
Before conducting treatability studies, the objectives of each
tier of testing must be established. Biodegradation treatability
study objectives are based upon the specific needs of the RI/FS.
There are nine evaluation criteria specified in the document,
"Guidance forConducting Remedial Investigations and Feasibility
Studies Under CERCLA" (EPA/540/6-89/004). A detailed analysis
of different remedial alternatives using the nine CERCLA criteria
is essential. Treatability studies provide data for up to seven of
these criteria.
These seven criteria are:
! Overall protection of human health and the environment
! Compliance with applicable or relevant and appropriate
requirements (ARARS)
Table 2. Biodegradation Criteria for Each Treatability Study Tier
Criteria
Remedy Screening
Remedy Selection
Remedy design
Biodegradation of most-resistant >20% net removal compared to
contaminants of concern removal in inhibited control
Initial contaminant concentration Optimal for technology
Environmental conditions
Extent of biodegradation
Biodegradation rate
Estimate time to reach cleanup
standards
Mass balance
Toxic byproducts
Process control and reliability
Optimal for technology (include
site conditions if possible)
Estimate*
Crude estimate*
NA
Crude*
Detect*
NA
Meets cleanup standards under
test conditions
Maximum concentration expected
during remediation
Simulate expected site treatment
conditions
Quantify
Defensible estimate
Estimate
Meets cleanup standards under
site conditions
Actual range of concentrations
expected during remediation
Actual site treatment conditions
for the specific technology
Quantify
Quantify
Refined estimate
Closure or defensible explanation Closure or defensible explanation
Test for if appropriate* Test for if appropriate
Assess potential Demonstrate
Microbial activity
Process optimization
Cost estimate for full-scale
Bid specifications
Experimental scale
Crude measure*
NA
NA
NA
Usually bench-scale
Verify/quantify*
Estimate*
Rough, -30%, +50%
NA
Either bench- or pilot-scale
Quantify/monitor*
Refined estimate
Detailed/refined
Nearly complete
Usually pilot- or full-scale
Not required, although sometimes possible to address significantly.
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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
Jmplementation
of Remedy
RD/RA
to Develop Scale-Up,
Design, and Detailed
Cost Data
Figure 1. The Role of Treatability Studies in the RI/FS and RD/RA Process.
! Long-term effectiveness and permanence
! Reduction of toxicity, mobility, or volume through treatment
! Short-term effectiveness
! Implementability
! Cost
The two remaining CERCLA criteria, State and community
acceptance, are based in part on the preferences and concerns
of the State and community regarding alternative technologies. An
available remediation technology may be eliminated from
consideration if the state or community objects to its use. Table
3 shows how the study goals of a remedy selection treatability
test address RI/FS criteria and the experimental parameters
measured to assess the achievement of those goals.
REMEDY SELECTION 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 a technology. The Work Plan, prepared by the
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 also assigns
responsibilities and establishes the project schedule and costs.
The Work Plan must be approved by the RPM
before initiating subsequent tasks. A suggested organization of
the Work Plan is provided in the "Guide for Conducting Treatability
Studies Under CERCLA: Biodegradation Remedy Selection",
EPA/540/R-93/514a.
Test Goals
Remedy selection treatability goals must consider the
existing site contaminant levels and cleanup goals for soils,
sludges, and water at the site. The ideal technology performance
goals for remedy selection treatability tests are the cleanup
criteria for the site. Example remedy selection goals are listed in
Table 3. 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 are risk-based rather than background-based.
Experimental Design
Careful planning during treatability study design is required
to ensure adequate treatability study data are obtained. Among
other requirements, the experiments, the experimental design
must identifythe critical parameters and determine the required
number of replicate tests. Treatability studies can be designed to
simulate aerobic conditions, or may be planned to assess
biodegradation under anaerobic conditions. Ultimately, remedy
selection studies should strive to simulate the conditions
encountered during full-scale applications of the technology
understudy.
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Table 3. Ability of Remedy Selection Treatability Studies to Address RI/FS Criteria
Study goals
Experimental parameters
RI/FS criteria*
Compare performance, cost, etc., of different
treatment systems at a specific site
Dependent on type of treatment systems
compared
Measure the initial and final contaminant
concentrations, and calculate the percentage
of contaminant removal from the soil, sludge,
or water through biodegradation
Estimate the type and concentration of
residual contaminants and/or byproducts left
in the soil after treatment
Develop estimates for reductions in
contaminant toxicity, volume, or mobility
Identify contaminant fate and the relative
removals due to biological and nonbiological
removal mechanisms
Produce design information required for next
level of testing
Develop preliminary cost and time estimates
for full-scale remediation
Evaluate need for pretreatment and
requirements for long-term operation,
maintenance, and monitoring
Evaluate need for additional steps within
treatment train
Assess ability of bioremediation to meet site-
specific cleanup levels
Determine optimal conditions for
biodegradation and evaluate steps needed to
stimulate biodegradation
Contaminant concentration
Contaminant/byproduct concentration
Contaminant concentration, toxicity testing
Contaminant concentrations present in solid,
liquid, and gaseous phases taken from test
and control reactors, oxygen uptake/CO2
evolution
Temperature, pH, moisture, nutrient
concentrations and delivery, concentration
and delivery of electron donors and
acceptors, microbial composition, soil
characteristics, test duration, nonbiological
removal processes
Treatability study cost (i.e., material and
energy inputs, residuals quality and
production, O&M costs, where appropriate),
test duration, time required to meet
performance goals
Soil characteristics, contaminant
concent ration/toxicity
Soil characteristics, contaminant
concentration, nonbiological removal
processes, residual quality (relative to further
treatment and/or disposal requirements)
Contaminant concentration
Temperature, pH, nutrient concentrations and
delivery, concentration and delivery of
electron donors nad acceptors, microbial
composition, soil characteristics, test duration,
contaminant concentration
Overall protection of human health and the
environment
Compliance with ARARs
Long-term effectiveness and permanence
Reduction of toxicity, mobility, and volume
through treatment
Short-term effectiveness
Implementability
Cost
Overall protection of human health and the
environment
Compliance with ARARs
Long-term effectiveness and permanence
Reduction of toxicity, mobility, and volume
through treatment
Overall protection of human health and the
environment
Compliance with ARARs
Long-term effectiveness and permanence
Reduction of toxicity, mobility, and volume
through treatment
Overall protection of human health and the
environment
Long-term effectiveness and permanence
Reduction of toxicity, mobility, and voume
through treatment
Short-term effectiveness
Implementability
Cost
Short-term effectiveness
Implementability
Cost
Compliance with ARARs
Long-term effectiveness and permanence
Short-term effectiveness
Implementability
Cost
Overall protection of human health and the
environment
Long-term effectiveness and permanence
Implementability
Cost
Overall protection of human health and the
environment
Compliance with ARARs
Long-term effectiveness and permanence
Reduction of toxicity, mobility, and volume
through treatment
Short-term effectiveness
Implementability
Cost
Depending on specific components of the remedy selection treatability study, additional study, additional criteria may be applicable.
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A number of factors influence the basic design of biological
studies. These factors have a profound impact on both the
treatability study operation and utility. Important factors to be
considered when designing a biological treatability study included
the following:
Overall test objectives (as dictated by site remediation
objectives)
Specific removal goals or desired cleanup levels (as set for
a specific site)
Soil characteristics (soils with higher permeability are more
amenable to in situ biodegradation)
pH (most microbialdegraders thrive when the pH is between
6.5 and 8.5)
Temperature (optimum range is usually between 15°C and
30°C for aerobic processes and 25°Cto 35°C for anaerobic
processes)
Moisture (optimum range is usually between 40 and 80
percent of field capacity)
Nutrients (concentrations should be maintained at a rea-
sonably moderate but steady-state concentration determined
experimentally)
Electron acceptors (usually oxygen derived from air, pure
oxygen, ozone, or hydrogen peroxide for aerobic studies and
nitrates for anaerobic tests)
Microorganisms (the use of introduced versus indigenous
populations)
Duration of test (sufficientto determine ability of treatmentto
meet removal goals)
Inhibitory compounds and their control (dilution of media may
be required)
Impact of nonbiological removal processes (extent of
volatilization, sorption, photodecomposition, leaching, as
experienced by inhibited controls)
! Toxicity testing (to evaluate the risk reduction experienced
during treatment)
! Bioavailability (contaminants that biodegrade easily will be
utilized earliest)
In situ remedy selection treatability studies are either field
plot or soil column designs. Soil column studies may also be
performed ex situ, usually within a laboratory setting. Three
additional ex situ experimental designs are soil pans, soil
slurries, and contained soil treatment systems. Table 4 presents
information on remedy selection treatability study experimental
designs, including their applicability, scale, typical size, and
duration.
The test system used during remedy selection testing can
consist of a single large reactor or multiple small reactors.
Studies which employ large reactors include field studies, large
flask studies, and soil pan studies. Multiple reactors consisting
of serum bottles, small slurry reactors, and small soil reactors
may be set up in place of a single large system. When a single
reactoris used, small samples may be removed atvarioustimes
and compared to samples from control reactors. When using
large reactors, care should be taken to ensure thatthe availability
of supplements (i.e., oxygen and moisture) are adequate,
allowing for consistent degradation rates within the reactor.
Additionally, sampling must be sized so that it does not affect the
operation of the overall unit. Remedy selection treatability tests
should include controls to measure the impact of nonbiological
processess, such as volatilization, sorption, chemical
degradation, migration, and photodecomposition. Inhibited
controls can be established by adding formaldehyde, mercuric
cholride (during non-EPA studies), sulfuric acid (added to lower
the pH to 2 or below), or sodium azide to retard microbial activity.
Contaminant concentrations are measured in both the test
reactors and the control reactors at the beginning of the study (T0),
at intermediate times, and at the end of the study. The mean
contaminant concentrations in both the control and test reactors
at the end of the test can be compared to their intial
concentrations in both the control and test reactors at the end of
the test can be compared to their initial concentrations to see if a
statisticallysignificant change in concentration has occurred. The
decrease in the control reactors may be attributed
Table 4. Remedy Selection Treatability Study Characteristics
Type of Study
Field plots
Soil columns
Soil pans
Slurry-phase
reactors
Applicability
In situ bioremediation
In situ bioremediation
Solid-phase treatment
Slurry-phase and
solid-phase (occasionally)
treatment
Scale
Field-scale
Lab- and
field-scale
Lab-scale
Field-scale
Size
1 to 1,111 yd2 plot of land*
0.01 -3,200 ft3 of soil,
sand, sediment, or stone
2 to 100 Ibsof soil
Greater than 20 gallons of
slurried media
Duration
2 months to 2 years
1 week to 6 months
1 to 6 months
2 to 3 months
Contained soil
systems
Composting, soil heap
bioremediation, and
solid-phase treatment
Lab-scale
Lab- and
field-scale
1 fluid oz to 20 gallons
7ft3to3,9003ydsofsoil
1 to 8 weeks
10 days to 10 months
* Field plot are given as areas rather than volumes because treatment depths are frequently undefined
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to abiotic mechanisms, while the decrease in the test reactors
would be a result of abiotic and biotic processes. The difference
in mean contaminant concentrations between the test reactors
and the inhibited control reactors will show whether there is a
statistically significant reduction in contaminant concentration due
to microbial activity. Care should be taken to assess the effects
that the different sterilizing agents can have on the chemical
behavior of the soil-contaminant system.
Complete sterilization of soils can be difficultto accomplish.
Incomplete mixing of sterilization agents with soils can result in
pockets of surviving microbes in soil pores. In some cases,
microbial populations can transform and detoxify sterilizing
agents. Additional agents can be provided during the test to
maintain reduced biological activity. The effectiveness of
sterilizing agents can be measured by techniques such as
microbial enumeration, respirometry, and enzyme analysis.
Unless these or similar techniques show very low microbial
activity, it may not be possible to distinguish between removal of
contaminants by abiotic and biological processes in the control
reactors. However, complete sterilization of the control is not
necessary provided biological activity is inhibited to the extent that
a statistically significant difference between the test and control
means can be determined.
When designing a treatabiliity study, the types of equipment
required for the test must be considered. Standard laboratory
equipment such as mixing flasks and sample collection bottles
should be available for all treatability studies. A wide variety of
equipmentis employed during biodegradation treatabiliity testing
to contain the media under study or isolate it from the
environment. During soil column studies, a metal, plastic, or
glass cylinder may be used onsite or offsite as part of a laboratory
study. Field plots, on the other hand, may require that in-ground
barriers, such as sheets ofsteel driven into the ground, orabove-
ground barriers such as berms be used to separate testing plots
from one another or from soil located outside of the testing area.
Slurry reactors, which range in size from 1 fluid ounce vials to
70,000-gallon lagoons, typically utilize 0.1- to 130-gallon vessels.
In contrast, contained soil treatment systems will generally
require a bermed, watertight area in which the soil can be placed.
The vessels required for contained soil teatability studies also vary
considerably, since they may be designed to simulate
composting, soil heaping, or other solid-phase biotreatment
technologies. Depending on the type and scale of the system, a
leachate collection system and other accessories may also be
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). A SAP is required for all field activities conducted
during the RI/FS. The purpose of the SAP is to ensure that
samples obtained for characterization and testing are
representative and thatthe quality of the analytical data generated
is satisfactory. The SAP addresses field 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.
TREATABILITY DATA INTERPRETATION
When conducting treatability studies, the test results and
goals for each tier must be properly evaluated to assess the
treatment potential of bioremediation. The remedy screening tier
establishes the general applicability of the technology. The
remedy selection testing tier demonstrates the applicability of the
technology to a specific site. The RD/RA tier provides information
in support of the evaluation criteria.
Interpretation of remedy selection test results should allow
the RPM or OSC to determine whether the bioremediation
technology used is capable of meeting cleanup standards under
simulated (or actual) site conditions. The experimental design of
the study should have been constructed to produce quantitative
and statistically defensible estimates of the extent and rate of
biodegradation. Ideally, a statistical evaluation of the difference
between biodegradation rates when parameters such as nutrient
addition, loading rate, and microbial composition are varied,
should also be designed. Example 1 describes a remedy
selection treatability test and the interpretation ofthe test results.
Estimation of Costs
Complete and accurate cost estimates are required in
order to fully recommend technologies for site remediation.
Consequently, when making preliminary cost estimates for full-
scale bioremediation, achieveable cleanup levels, degradation
rates, concentration and application frequencies of various
degradation enhancing supplements (e.g., nutrients, lime, water,
etc.), contaminant migration controls, and monitoring
requirements must be considered. The impact these parameters
have on labor, analytical, material and energy costs, as well as
the unit's design and possible pre- and post-treatment
requirements, also must be considered.
Generally, large-scale field tests can be designed to
simulate full-scale performance and costs more accurately than
laboratory studies. However, estimating full-scale cost from
treatability study data can be difficult. Given the variability and
interaction of factors such as soil temperature, pH, moisture,
heterogenous contaminant concentrations, and optimal nutrient
concentrations, empirical results may not always depictthe range
of reasonable bioremediation results. One approach to
examining the variability and interaction of these factors is
simulation modeling. Simulation models (e.g., Monte Carlo
models) attempt to quantify the probability that a certain set of
events or values will occur based upon available empirical data.
Using probabilistic simulation methods can produce time and
cost estimates for a particular confidence level and a specific
level of certainty (e.g., the ability to state with 90 percent certainty
that the cost of the project will be within ±40 percent of the
estimate).
TECHNICAL ASSISTANCE
Information from existing literature and consultation with
experts are important 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" (EPA/540/R-
92/071 a).
It is recommended that a Technical Advisory Committee
(TAG) be used. This committee includes experts who provide
technical support from the scoping phase of the treatability study
through data evaluation. Members of the TAG may include
representatives from EPA (Regions or ORD), other Federal
agencies, States, and consulting firms.
The Office of Solid Waste and Emergency Response and
Office of Research and Development operate the TSP which
provides assistance in the planning, performance, and review
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Example 1
A remedy selection treatability study was performed to evaluate a slurry-phase technology's ability to remediate an
impoundment contaminated with petroleum refinery sludges. Surfactants and nutrients were added. Reactor performance
was monitored by measuring the oxygen uptake rate and oil and grease (O&G) removal. Based on extensive experience with
O&G biodegradation, toxicity was not performed.
The average initial O&G concentration in the sediment was 41,000 ppm, the maximum concentration expected in the full-scale
(70,000 gallon), slurry bioreactor. A cleanup goal of 20,000 ppm O&G was targeted during the study. After 4 weeks, the average
O&G concentration in the inhibited control was reduced to 39,000 ppm, a reduction to 39,000 ppm, a reduction of nearly 5
percent. The average O&G concentration in the biologically active system was reduced to 14,000 ppm, a 66 percent reduction
in the same time period. The leveling out of O&G concentrations at the end of the experiment indicates that the maximum
extent of biodegradation achievable under the test conditions had been reached.
O&G
Sample
T4
Bioreactor
Replicate 1
Replicate 2
Replicate 3
Mean Value
Inhibited Control
Replicate 1
Replicate 2
Replicate 3
Mean Value
39,000
41,000
43,000
41,000
39,000
41,000
43,000
41,000
32,000
34,000
39,000
35,000
36,000
39,000
42,000
39,000
21,000
24,000
24,000
23,000
37,000
40,000
40,000
39,000
13,000
15,000
17,000
15,000
37,000
41,000
39,000
39,000
14,000
16,000
12,000
14,000
42,000
36,000
39,000
39,000
The average contaminant concentration in the slurry-phase bioreactor at each time-point is compared to the average
contaminant concentration in the inhibited control at the same time-point to measure the biodegradation at that time-point.
The inhibited control accounts for contaminant losses due to volatilization, adsorption to soil particles, and chemical reactions.
Some contaminant loss in the control due to biodegradation may occur since total sterilization is difficult to accomplish.
However, an O&G analysis of the extract generated from the slurry-phase reactor indicated that abiotic losses were due mainly
to adsorption. Since a statistically significant difference between the test and control means exists, O&G reductions in the test
bioreactor were attributed to biodegradation.
of treatability studies. For further information on treatability study
support orthe TSP, please contact:
Groundwater Fate and Transport Technical
Support Center
Robert S. Kerr Environmental Research
Laboratory, (RSKERL)
Ada, OK 74820
Contract: Don Draper
(405) 332-8800
Engineering Technical Support Center (ETSC)
Risk Reduction Engineering Laboratory (RREL)
Cincinnati, OH 45268
Contact: Ben Blaney or Joan Colson
(513) 569-7406 or (513) 569-7501
FOR FURTHER INFORMATION
Sources of information on treatability studies and
bioremediation are listed in the "Guide for Conducting Treatability
Studies Under CERCLA" (EPA/540/R-92/071 a) and the "Guide for
Conducting Treatability Studies Under CERCLA: Biodegradation
Remedy Selection" (EPA/540/R-93/541 A). Additionally, the Office
of Emergency and Remedial Response's Hazardous Site Control
for each Region should be contacted for information and
assistance.
ACKNOWLEDGMENTS
This fact sheet and the corresponding guidance document
were prepared for the U.S. Environmental Protection Agency,
Office of Research and Development, Risk Reduction
Engineering Laboratory, Cincinnati, Ohio by Science Applications
International Corporation (SAIC) under Contract No. 68-C8-
0061 and Contact No. 68-CO-0048. Mr. Ed Opatken served as the
EPA Technical Project Monitor. Mr. Jim Rawe served as SAIC's
Work Assignment Manager. Mr. Rawe, Ms. Evelyn Meagher-
Hartzell, and Ms. Sharon Krietemeyer (SAIC) were the primary
technical authors. Mr. Derek Ross (ERM) and Mr. Kurt Whitford
(SAIC) served as a techinical experts.
Many Agency and independent reviewers have contributed
their time and comments by participating in the expert review
meetings or peer reviewing the guidance document.
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