1EPA
United States
Environmental Protection
Agency
Office of Research and
Development
Washington, DC 20460
EPA/625/K-96/001
May 1996
Seminars
Bioremediation of
Hazardous Waste Sites:
Practical Approaches to
Implementation
May 29-30,1996Chicago, IL
June 4-5,1996Kansas City, MO
June 6-7,1996Atlanta, GA
June 18-19,1996San Francisco, CA
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EPA/625/K-96/001
May 1996
Seminars on
Bioremediation of Hazardous Waste Sites:
Practical Approaches to Implementation
Office of Research and Development
U.S. Environmental Protection Agency
Washington, DC
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Notice
Mention of trade names or commercial products does not constitute endorsement or recommenda-
tion for use.
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Contents
Background Information for Bioremediation Applications 1-1
Bioventing 2-1
Bioremediation of Sediments 3-1
Aerated Lagoons: A Case Study 4-1
Oil-Contaminated Shorelines 5-1
Land Treatment 6-1
Land Treatment Unit Case Study:
Champion International Superfund Site 7-1
Phytoremediation 8-1
Development and Application of Composting Techniques for Treatment of
Soils Contaminated With Hazardous Waste 9-1
Biopile Treatment of Soils Contaminated With Hazardous Waste 10-1
Effective Treatment of Hazardous Waste Constituents in Soil by
Lignin-Degrading Fungi 11-1
Slurry Bioreactors for Treatment of Contaminated Soils,
Sludges, and Sediments 12-1
Fixed Film Bioreactors 13-1
Suspended Growth Bioreactors 14-1
Natural Attenuation of Ground Water 15-1
Natural Attenuation of Soils 16-1
Natural Attenuation of Landfills 17-1
Natural Attenuation of Sediments 18-1
Source Control: Free Product Recovery and Hydraulic Containment 19-1
Air Sparging/Air Injection 1 9-5
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State Review: Natural Attenuation of Ground Water and Soils 20-1
Monitoring 21-1
Modeling 22-1
IV
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Sources of Information
Recent EPA Bioremediation Publications
http://www.epa.gov/docs/ORD
Bioremediation in the Field Bulletin
Latest edition EPA/540/N-96/500
Bioremediation in the Field Search System: Database on national and some international field
applications
Version 2.0 EPA/540/R-95/508b
Also on the Internet
Request to be on EPA's bioremediation mailing list or to request specific bioremediation documents
513-569-7562
NRMRL/SPRD Home Page
http://www.epa.gov/ada/kerrlab.html
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Background Information for Bioremediation Applications
Ronald C. Sims
Utah State University, Logan, UT
Introduction
This technology transfer seminar series is sponsored by the U.S. Environmental Protection Agency's
(EPA's) Biosystems Program. The Biosystems Program coordinates research, development, and
evaluation of full-scale bioremediation activities. The seminar series provides participants with
state-of-the-art information on the practical aspects of implementing bioremediation. The series is
divided into the following sections:
Background for Bioremediation Applications
In Situ Treatment of Soils, Sediments, and Shorelines
Ex Situ Treatment With and Without a Reactor
Natural Attenuation
Treatment of the Subsurface
Each section includes discussion of advantages and limitations, materials handling, types of waste
amenable to the treatment process, pre- and posttreatment requirements, and capital and operation
and maintenance costs. The overall focus is on field applications in use today, with some
information on processes that are nearing readiness for field use.
This section has been organized to address the following topics:
Biodegradation and metabolism
Environmental factors affecting biodegradation
Site characterization
General concept of treatability studies
Biodegradation and Metabolism
Biodegradation involves chemical transformations mediated by microorganisms that satisfy
nutritional requirements, satisfy energy requirements, detoxify the immediate environment, or occur
fortuitously such that the organism receives no nutritional or energy benefit (1). Mineralization is the
complete biodegradation of organic materials to inorganic products, and often occurs through the
combined activities of microbial consortia rather than through a single microorganism (2). Co-
metabolism is the partial biodegradation of organic compounds that occurs fortuitously and that
does not provide energy or cell biomass to the microorganism(s). Co-metabolism can result in
partial transformation to an intermediate that can serve as a carbon and energy substrate for
microorganisms, as with some hydrocarbons, or can result in an intermediate that is toxic to the
transforming microbial cell, as with trichloroethylene (TCE) and methanotrophs.
Seminar Series on Bioremediation of Hazardous Waste Sites: Practical Approaches to Implementation
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Two classes of biodegradation reactions are aerobic and anaerobic. Aerobic biodegradation
involves the use of molecular oxygen (O2), where Q (the "terminal electron acceptor") receives
electrons transferred from an organic contaminant:
organic substrate + O2 - biomass + CO2 + H2O + other inorganics
Thus, the organic substrate is oxidized (addition of oxygen), and the O2 is reduced (addition of
electrons and hydrogen) to water (H2O). In this case, the organic substrate serves as the sources
of energy (electrons) and the source of cell carbon used to build microbial cells (biomass). Some
microorganisms (chemoautotrophic aerobes or lithotrophic aerobes) oxidize reduced inorganic
compounds (NH3, Fe+2, or H2S) to gain energy and fix CO2 to build cell carbon:
NH3 (or Fe+2 or H2S) + CO2 + H2 + O2 - biomass + NO3 (or Fe+3 or SO4) + H2O
At some contaminated sites, as a result of consumption of O2 by aerobic microorganisms and slow
recharge of O2, the environment becomes anaerobic (lacking O ), and mineralization,
transformation, and co-metabolism depend upon microbial utilization of electron acceptors other
than O2 (anaerobic biodegradation). Nitrate (NO3), iron (Fe+3), manganese (Mn+4), sulfate (SO4),
and carbon dioxide (CO2) can act as electron acceptors if the organisms present have the
appropriate enzymes (3). JP-4 jet fuel constituents were observed to be biodegraded in the presence
of NO3 as the electron acceptor (4). Iron and manganese are important microbial electron
acceptors, with background concentrations in soils ranging from 20 to 3,000 mg/kg for Mn and
3.8 to 5.2 percent for iron. An evaluation of the degradation of polycyclic aromatic hydrocarbons
(PAHs) in aerobic and anaerobic environments was conducted based on thermodynamic principles
(5). Biodegradation of pentachlorophenol (PCP) has been observed to increase the presence of
added Mn (6).
Halogenated compounds can be used as growth substrates or co-metabolized by aerobic and
anaerobic microorganisms. Dehalogenation can be spontaneous, as in the loss of halogens during
ring cleavage, or enzymatically catalyzed through hydrolytic cleavage or reductive dehalogenation
(1). Halogenated compounds can often serve as the electron acceptor and become reduced in
environments where there is a source of electrons; for example, under methanogenic conditions
(production of methane in reduced environments) reductive dehalogenation of perchloroethylene
(PCE) to TCE, trans-1, 2-dichloroethylene (DCE), vinyl chloride, and ethylene occurs (1). In such
situations, alternative electron acceptors such as NO3 and SO4 may compete with the halogenated
compounds for electrons. TCE can also be biodegraded co-metabolically in an aerobic
environment by methanotrophs when methane is added to cause the formation of TCE-epoxide,
which will abiotically transform to dichloroacetic acid, TCE-diol, formic acid, and glyoxylic acid.
Reduced dehalogenated intermediates often undergo rapid biodegradation by aerobic
microorganisms in the presence of O2 (7).
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Environmental Factors Affecting Biodegradation
Microbial ecologists have identified ranges of critical environmental conditions that affect the activity
of soil microorganisms (Table 1). Many of these conditions are controllable and can be changed
to enhance the biodegradation of organic constituents. A discussion of the factors identified below,
including principles, status of the technology, secondary impacts, equipment, advantages and
disadvantages, and references is provided in the document Handbook on In Situ Treatment of
Hazardous Waste-Contaminated Soils (7).
Table 1. Critical Environmental Factors for Soil Microbial Activity (8).
Environmental Factor
Oxygen
Nutrients
Moisture
Environment (pH)
Environment (redox)
Environment (temperature)
Optimum Levels
Aerobic metabolism: greater than 0.2 mg/L
dissolved oxygen, minimum air-filled pore
space of 1 0%
Anaerobic metabolism: less than 0.2 mg/L
dissolved oxygen, O2 concentration less than
1 % air-filled pore space
Sufficient nitrogen, phosphorus, and other
nutrients so not limiting microbial growth
(suggested C:N:P ratio of 120:10:1)
Unsaturated soil: 25-85% of water holding
capacity, -0.01 MPa; will affect oxygen
transfer into soil (aerobic status);
in saturated zone, water will affect transport
rate of oxygen and therefore will affect rate
of aerobic remediation
5.5-8.5
Aerobes and facultative anaerobes: greater
than 50 millivolts; Anaerobes: less than 50
millivolts
15-45°C (mesophilic)
Oxygen diffuses into the soil from the air above it, and gases in the soil atmosphere diffuse into the
air. Oxygen concentration in a soil may be much less than in air, however, while CO2
concentrations in soil may be orders of magnitude higher than in air. A large fraction of the
microbial population within the soil depends on oxygen as the terminal electron acceptor in
metabolism. When soil pores become filled with water, the diffusion of gases through the soil is
restricted since oxygen diffuses through air 1 0,000 times faster than through water. Oxygen may
be consumed faster than it can be replaced by diffusion from the atmosphere, and the soil may
become anaerobic. Facultative anaerobic organisms, which can use oxygen when it is present or
switch to alternative electron acceptors such as nitrate in the absence of oxygen (e.g., denitrifying
Seminar Series on Bioremediation of Hazardous Waste Sites: Practical Approaches to Implementation
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bacteria), and obligate anaerobic organisms become the dominant populations. Additional
information concerning in situ anaerobic bioremediation can be found elsewhere (7).
Oxygen concentrations in soil systems may be increased by tilling and draining unsaturated soil, for
example, in prepared-bed land treatment systems, in ex situ treatment (e.g., composting, biopiles,
and fungal treatment) and in situ treatment systems, and through the application of bioventing
systems, where air is forced through a soil system and carries oxygen to soil microorganisms to
accomplish aerobic degradation. Hinchee (9) and Hinchee and Downey (10) successfully applied
bioventing for enhancement of biodegradation of petroleum hydrocarbons in JP-4 jet fuel
contaminated soil at Hill Air Force Base, Ogden, Utah, by increasing subsurface oxygen
concentrations. Oxygen and CO2 concentrations were monitored and correlated well with
hydrocarbon biodegradation. A minimum criterion for aerobic biodegradation of PAH in creosote-
contaminated soil was established at 2 percent O2 in air (11).
Within saturated environments, oxygen transport is considered to be the rate-limiting step in aerobic
bioremediation of contaminated hydrocarbons when adequate nutrients are present. At the Traverse
City, Michigan, site contaminated with jet fuel (12), an increase in the oxygen concentration in water
through addition of hydrogen peroxide and was observed to positively affect the rate of
biodegradation of the jet fuel components benzene, xylene, and toluene.
Microbial metabolism and growth depend on adequate supplies of essential macro- and
micronutrients. If the wastes present at a site are high in carbonaceous materials and low in
nitrogen (N) and phosphorus (P), the subsurface may become depleted of available N and P
required for biodegradation of the organic contaminants. Addition of nutrients may be required as
a management technique to enhance microbial degradation, and can be used to treat water from
a pump-and-treat system and applied through reinfiltration or irrigation (13). Recommended ratios
for subsurface systems of carbon (C), N, and P are 120:10:1 on a weight basis. Nutrients have
been added to enhance microbial degradation of hydrocarbon contaminants at many sites (1 4). At
the Champion International Superfund Site in Libby, Montana (15), nutrients are added to enhance
bioremediation in a prepared-bed land treatment system, in an aboveground reactor for treating
extracted ground water, and in injection wells for in situ bioremediation of PAH and PCP.
Moisture content and the soil water matrix potential against which microorganisms must extract
water from the soil regulate their activity. The soil matrix potential is the energy required to extract
water from the soil pores to overcome capillary and adsorptive forces. Soil water also serves as the
transport medium through which many nutrients and organic constituents diffuse to the microbial
cell, and through which metabolic waste products are removed. Soil water also affects soil aeration
status, nature, and amount of soluble materials; soil water osmotic pressure; and the pH of the soil
solution (8). Generally, microbial activity measured as biodegradation rates and rates of
detoxification of contaminants in soil have been found to be highest at soil moisture contents of 60
to 80 percent of field capacity (8). Field capacity is the amount of water held against the force of
gravity, generally equal to 0.1 to 0.3 atmospheres of force.
Soil moisture can be increased using standard agricultural irrigation practices such as overhead
sprinklers or subirrigation. To remove excess water or lower the water table to prevent
water-logging, drainage or well point systems can be used. Also, the addition of vegetation to a site
will increase evapotranspiration (ET) of water and will also retard the downward migration of water
(i.e., leaching) (7, 1 6).
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Other environmental factors, including pH, redox potential, and temperature, are important
parameters that will affect the rate and extent of bioremediation in unsaturated and saturated
subsurface systems. Outside the pH range of 5.5 to 8.5, microbial activity is generally decreased.
Maintaining soils near neutral pH is most often recommended for enhanced bioremediation (7);
however, acidic soils are known to become colonized by fungi over time. Conventional agricultural
practices for increasing soil pH include adding lime periodically and mixing the lime with the acidic
soil (7).
Redox potential of a subsurface environment has an influence on microbial metabolism and activity
(5). For aerobic metabolism the redox potential should be greater than 50 millivolts, for anaerobic
conditions less than 50 millivolts. At low redox potentials, alternative electron acceptors to oxygen
(e.g., nitrate, iron, manganese, and sulfate) act as electron acceptors. A redox potential higher than
50 millivolts is conducive to biodegradation of hydrocarbons. A redox potential of less than 50 is
condusive to degradation of chlorinated hydrocarbons (7).
Soil temperature has an important effect on microbial activity and has been correlated with
biodegradation rates of specific organic compounds (12). Prepared-bed land treatment and in situ
bioremediation should be planned to take advantage of the warm season in cooler climates.
Vegetation can act as an insulator against heat loss and limit frost penetration. Application of
mulches can help control heat loss at night and heat gain during the day (7, 12).
Site Characterization
A contaminated site is a system generally consisting of four phases: 1) solid, which has an organic
matter component and an inorganic mineral component composed of sand, silt, and clay, 2) oil
(commonly referred to as nonaqueous phase liquid, or NAPL), 3) gas, and 4) aqueous (leachate or
ground water). These phases and compartments need to be characterized with regard to extent and
distribution of contamination as well as potential exposure to human and environmental receptors.
Each phase affects bioavailability, i.e., interactions with microorganisms and exposure to human
health and environmental receptors. Each phase can be a site for biological reactions that results
in the transformation of a parent chemical to CO2, H2O, and other inorganic species through the
process of mineralization, or transformation to intermediates that persist or that react with soil
components to chemically bind to soil and therefore alter the bioavailability of the chemicals.
Evaluating the extent and distribution of contamination at a site will provide important information
that can be used as a basis to select specific bioremediation technologies that are addressed in this
seminar series, or to select a treatment train that represents a combination of physical/chemical and
biological technologies. If contamination is widespread and low in concentration, then in situ
treatment or natural attenuation may be feasible. Conversely, with high concentrations of
contaminants, soil excavation and placement in a confined treatment facility (CTF) or a land
treatment prepared-bed reactor may be advisable.
Distribution of contaminants at a site is determined by the physical and chemical properties of the
contaminants and the properties of the site. Contaminant properties will affect whether contaminants
are leachable, volatile, and/or adsorbable, and therefore will indicate which subsurface phases
contain the contaminant(s). Physical phases containing the contaminants require evaluation of
Seminar Series on Bioremediation of Hazardous Waste Sites: Practical Approaches to Implementation
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bioremediation potential. When the physical and chemical properties are evaluated within the
context of site characteristics, a site-based waste characterization can be used to identify the
phases/compartments at the site and the chemicals associated with each phase. Additional
information concerning practical aspects of site characterization for bioremediation of contaminated
ground water is available in the document In Situ Bioremediation of Contaminated Ground Water
(17).
General Concept of Treatability Studies
Treatability studies are conducted in laboratory microcosms, at pilot scale, or in the field. EPA,
through the Biosystems Field Initiative, and the Departments of Defense and Energy indicate an
increased emphasis on field-scale evaluation of bioremediation, with a supportive role for
laboratory-scale treatability testing. Parent compounds, intermediates, and electron acceptor
utilization are evaluated. A mass balance conceptual framework for treatability studies, at any scale,
refers to the characterization of the physcial phases in the soil and the determination of the influence
of the phases on the bioavailability and bioremediation of associated target chemicals (1 8), as
described in the "Site Characterization" section above.
While in the past the goal for bioremediation implied complete mineralization of chemicals to CO2,
H2O, and inorganic chemicals, alternative endpoints that are protective of human health and the
environment are currently being evaluated by the Department of Energy, EPA, the National Science
Foundation, and the Office of Naval Research. Treatability studies that examine the bioavailability
of contaminants in waste matrices, potential for toxic effects of intermediate metabolites during the
degradation process, and interactions between waste chemicals and organisms are desired. The
overall goal of treatability studies is to develop a better understanding of factors that threaten
ecosystems and human health and of chemicals and their degradation products during
bioremediation so that the regulatory community can take into consideration the possibility of
alternatives to complete mineralization (1 9, 20).
References
1. Stoner, D.L. 1 994. Biotechnology for the treatment of hazardous waste. Boca Raton, FL:
CRC Press.
2. Shelton, D.R., and J.M. Tiedje. 1984. Isolation and partial characterization of bacteria in
an anerobic consortium that mineralizes 3-chlorobenzoic acid. Appl. Environ. Microbiol.
48:840-848.
3. Sims, R.C. 1990. Soil remediation techniques at uncontrolled hazardous waste sites. J. Air
Waste Mgmt. Assoc. 40(5):703-732.
4. Hutchins, S.R., G.W. Sewell, D.A. Kovacs, and G.A. Smith. 1991. Biodegradation of
aromatic hydrocarbons by aquifer microorganisms under denitrifying conditions. Environ.
Sci. Technol. 25:68-76.
Seminar Series on Bioremediation of Hazardous Waste Sites: Practical Approaches to Implementation
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5. McFarland, M.J., and R.C. Sims. 1991. Thermodynamic framework for evaluating PAH
degradation in the subsurface. Ground Water 29(6) :885-896.
6. Petrie, R.A., J.E. McLean, and R.C. Sims. 1995. Treatment of pentachlorophenol with
manganese oxide addition to biotic and abiotic sediments. Haz. Waste Haz. Mat.
12(3):271-282.
7. U.S. EPA. 1989. Bioremediation of contaminated surface soils. Robert S. Kerr
Environmental Research Laboratory. EPA/600/9-89/073. Ada, OK.
8. U.S. EPA. 1990. Handbook on in situ treatment of hazardous waste-contaminated soils.
EPA/540/2-90/002.
9. Hinchee, R. 1 989. Enhanced biodegradation through soil venting. In: Proceedings of the
Workshop on Soil Vacuum Extraction, Robert S. Kerr Environmental Research Laboratory,
Ada, OK (April 27-28).
10. Hinchee, R., and D. Downey. 1990. In situ enhanced biodegradation of petroleum
distillates in the vadose zone. In: Proceedings of the International Symposium on Hazardous
Waste Treatment. Air and Waste Management Association and U.S. EPA Risk Reduction
Engineering Laboratory (February 5-8).
1 1. Hurst, J., R.C. Sims, J.L. Sims, D.L. Sorensen, and J.E. McLean. 1 990. Polycyclic aromatic
hydrocarbon biodegradation as a function of oxygen tension in contaminated soil. J. Haz.
Mat. In press.
12. U.S. EPA. 1 991. Site characterization for subsurface remediation. Seminar publication.
EPA/625/4-91/026. Office of Research and Development, Washington, DC.
13. U.S. EPA. 1991. Handbook: Stabilization technologies for RCRA corrective actions.
EPA/625/6-91/026. Office of Research and Development, Washington, DC.
14. U.S. EPA. Bioremediation in the Field Search System (BFSS) database, user documentation.
EPA/540/R-95/508a. Office of Research and Development.
15. U.S. EPA. 1995. Champion International Superfund site, Libby, Montana: Bioremediation
field performance evaluation of prepared bed system, Vols. 1 and 2.
EPA/600/R-95/156a,b.
16. Aprill, W., and R.C. Sims. 1990. Evaluation of the use of prairie grasses for stimulating
polycyclic aromatic hydrocarbon treatment in soil. Chemosphere 20(1 -2):253-265.
17. U.S. EPA. 1992. In situ bioremediation of contaminated ground water.
EPA/540/S-92/003. Office of Solid Waste and Emergency Response.
1 8. Sims, R.C., and J.L. Sims. 1 995. Chemical mass balance approach to field evaluation of
bioremediation. Environ. Prog. 14(1):F2-F3.
Seminar Series on Bioremediation of Hazardous Waste Sites: Practical Approaches to Implementation
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19. Environmental Biotechnology. 1995. In: Biotechnology for the 21st century: New horizons.
National Science and Technology Council.
20. DOE/EPA/NSF/ONR. 1996. Joint program on bioremediation. Interagency Announcement
of Opportunity. National Center for Environmental Research and Quality Assurance, U.S.
EPA.
21. Hurst, J. 1 996. Prepared bed bioremediation as affected by oxygen concentration in soil
gas: Libby, Montana, Superfund site. M.S. Thesis, Department of Civil and Environmental
Engineering, Utah State University, Logan, UT.
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Background
Information for
Bioremediation
Applications
Ronald C. Sims
Utah State University
Logan, UT
Background Information for
Bioremediation Applications
National Status on Applications
Biodegradation and Metabolism
Environmental Factors Affecting
Biodegradation
Site Characterization
General Concept of Treatability
Studies
Superf und Remedial Actions
Technologies Selected in FY94
ioremediation
National Status
on Applications
Incineration
15%
Solvent Extraction
2%
'Thermal Desorption
Superf und Remedial Actions
Technologies Selected in FY89
Incineration^
.oremediation
lushing 3%
Washing 2%
[Solvent Extraction 3%
'hermal Desorption 1%
Legislative Authority for Sites
Using Bioremediation
RCRA
Other
13%
International Government
nternational Private
Sector 0%
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Breakdown of Sites by Type of
Contamination
Wood Preserving
Wastes 10%
Other
10%
Pesticides/Herbicides
Distribution of Bioremediation
Projects by Region
Percentage of Sites Treating
Each Medium
Sediments
Ground Water
32%
idge 2%
Air 1%
urface Water 1%
Breakdown of Processes by
Treatment Technology
(Includes Laboratory-, Pilot-, and Full-Scale)
In Situ
Ex Situ (with
reactor)
15%
Ex Situ (without
reactor)
17%
Top 9 Bioremediation Methods
In Situ Biotreatment Processes
Bioventing
Ground Water
Bioremediation
14%
Soil Bioremediation
14%
Solid Phase, Prepared Bed
All Other Methods
11%
Fixed Film
4%
'Solid Phase, Pile
Treatment 4%
Attached Growth
5%
Air Sparging 6%
Natural Attenuation 6%
20 -
-^T^
L.
_>
Unknown
DTreatability
n Design
Din the Field
Completed
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In Situ Biotreatment Processes
(continued)
Biodegradation and
Metabolism
Biodegradation and
Metabolism
Chemical transformations
mediated by microorganisms:
Nutrition
Energy
Detoxification
Fortuitous (co-metabolism)
Biodegradation
i Biological transformation of an organic compound
to another form without regard to extent
OH
m-chlorophenol
3-chlorophenol
OH
m-chlorocatechol
3-chlorocatechol
Mineralization
i Conversion of an organic compound to carbon
dioxide, water, methane, and other inorganic
forms (e.g., C1-, NH4+)
i Aerobic OH
conditions
i Anaerobic
(methanogenic)
conditions
+ O2 -* CO2 + H2O + Cl- + ATP + Biomass
'Cl
OH
CH4 + CO2+ C1-+ ATP + Biomass
'Cl
Co-metabolism
CH4 + O2
MMO
CH3OH + H2O
Methane Methanotrophs Methanol
TCE +
MMO
Methanotrophs
TCE-EPOXIDE+ H7O
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Aerobic Biodegradation Anaerobic Biodegradation
+
Biomass+ CO9 + H9O
Benzene
Toluene
NO3 - ^ CO2 + N2
Denitrification
Nitrate
HO
Anaerobic
Biodegradation
(Reductive
Dechlorination) H
of Chlorinated
Alkenes
Environmental
Factors Affecting
Biodegradation
Nutrients
Mass
Transport
Electron
Acceptor
Nonaqueous Phase Liquid (NAPL)
(Resistance to mass transport)
Particle
icle"^
Toxicity to Microorganisms
Nutrients
Mass ^ Electron
Transport Acceptor
Mass transport and toxicity limitations to bioremediation
as a function of NAPL concentration
Critical Environmental Factors for
Soil Microbial Activity
Environmental Factor
Oxygen
Nutrients
Moisture
Environment (pH)
Environment (Redox)
Effects
Metabolism: Aerobic/Anaerobic
Degradation Pathways
Nitrogen, Phosphorus Activity
Unsaturated/Saturated Soil
Oxygen Transfer
5.5-8.5
Activity
Aerobes/Facultative Anaerobes: > 50 mV
Anaerobes: < 50 mV
Degradation Pathways
Environment (Temperature) 15-45°C(Mesophilic)
Activity
Reference: (9)
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Oxygen Supply
Oxygen diffuses through
water at a rate that is 10,000
times less than oxygen
diffuses through air
60.
i, Oxygen
Time (days)
Mineralization of 14C-pyrene in non-poisoned soil microcosms as a
function of time and oxygen concentration. Error bars represent the least
significant difference of 7.94. Values are the means for triplicate reactors.
1.0
0.9
0.8
0.7
0.6
0.5
0.4
0.3
0.2
0.1
0.0
% Oxygen
7 14 21 28 35 42 49 56 63 70
Time (days)
Mineralization of 14C-pyrene in poisoned soil microcosms as a function of
time and oxygen concentration. Values are the means for triplicate reactors.
21%
20 40
Time (days)
Mineralization of 14C-PCP in non-poisoned soil microcosms as a function of time and
oxygen concentration. Error bars represent the least significant difference of 4.6 7%.
0.7
0.6
0.5
0.4
0.3
0.2
0.1
0.0
% Oxygen
21%
20 40 60 80
Time (days)
Mineralization of 14C-PCP in poisoned soil microcosms as a function of time
and oxygen concentration. Values are the means for triplicate reactors.
Environmental Factors
Nutrients:
Moisture:
pH:
Redox Potential:
Temperature:
100:10:1 Weight ratio
60-80% Field capacity
5.5-8.5
>50 mV Aerobic
<35 mV Dechlorination
Adaptation
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Physical Phases at a Site To Be Considered
for Bioremediation Technologies
Site Characterization
Non-Aqueous Phase Liquid!
(NAPLs)
General Concept of
Treatability Studies
Treatability Studies
Field-scale more emphasis
Parent compounds
Intermediates
Electron acceptors
Physical Phases at a Site To Be Considered
For Bioremediation Technologies
Mass Balance
Framework
Treatability Studies
Alternative endpoints
DOE/EPA/NSF/ONR
Bio availability
Intermediate metabolites
Interactions or chemicals and
organisms
Risk impact
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Intermediate Metabolites
l-Hydroxy-2-Naphthoicacid
2,3 -Dihydroxy naphthalene
Reference: Ginn, J., WJ. Doucette, andR.C. Sims. f994. Chemical mass balance
approach for estimating fate and transport of poly cyclic aromatic met abohtes in
the subsurface environment. Polycychc Aromatic Compounds 5:225-234.
Experimental Design
> Controls: sterile, no treatment,
field background, number?
> Replicates: duplicate or triplicate?
all time points? all controls?
> Treatments: what are the questions
you want answered?
> How are you going to optimize the
degradation process?
Experimental Design
(continued)
Treatment time: how long should
the study be performed?
Types of analysis: bulk
measurements? waste specific?
Data reduction: raw data?
massaged data? QC/QA?
Cost considerations: how will it
limit scope of test?
Time
Distribution of 14C in Non-poisoned
Microcosms Spiked With 14C-Pyrene
Distribution of 14C in Poisoned
Microcosms Spiked With 14C-Pyrene
Oxygen
Cone.
0%
2%
5%
10%
21%
% 14C
Mineralized
13
54
52
51
46
% 14C Soil
Bound
8
15
16
14
15
% 14C Mass
Recovered
91
91
88
86
86
Reference: (12)
Oxygen
Cone.
0%
2%
5%
10%
21%
% 14C
Mineralized
<0.2
<0.2
<0.2
<0.2
<0.2
% 14C Soil
Bound
9
9
11
12
8
% 14C Mass
Recovered
95
91
89
90
97
Reference: (f 2)
Seminar Series on Bioremediation of Hazardous Waste Sites: Practical Approaches to Implementation
1-15
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Contaminated Site Characterization
Contaminants
( ^
Technologies
Capabilities
Limitations
Site
1 | ^.
Phases
Solid
Liquid
Gas
1 I \
Bioremediation Applications
Seminar Series on Bioremediation of Hazardous Waste Sites: Practical Approaches to Implementation
1-16
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Bioventing
Gregory D. Sayles
Office of Research and Development, National Risk Management Research Laboratory,
U.S. Environmental Protection Agency, Cincinnati, OH
Research conducted in the mid to late 1980s by the U.S. Air Force (1, 2), researchers in the
Netherlands (3-6), the Texas Research Institute (7, 8), Battelle Memorial Institute (2, 9-1 1), Utah
State University (11), and the U.S. Environmental Protection Agency (EPA) (12), among others,
suggests that delivering air to the vadose zone to promote biodegradation could be a low-cost
means of cleaning fuel-contaminated vadose zone soils. This approach was motivated by attempting
to solve two different remediation development problems: 1) soil vacuum extraction for treatment
of contaminated vadose zones involved costly off-gas treatment and only removed the volatile
fraction of the contamination, and 2) oxygen delivery to the vadose zone to promote aerobic
biodegradation by using the approaches attempted in promoting biodegradation in ground water,
namely delivering oxygen-saturated water or aqueous solutions of hydrogen peroxide or nitrate to
the contaminated area, was not efficient or cost-effective.
A process was needed that could deliver oxygen by introducing air into the vadose at a rate that
minimized volatilization of the contamination. Several groups simultaneously developed what is now
known as bioventing.
EPA and the Air Force recognized the potential cost savings of such a technology over traditional
remediation approaches and began an aggressive bioventing development program in 1 990. To
date, this program has demonstrated or is currently developing the use of bioventing for the
following situations:
With air injection (10-17)
In cold climates (18-20)
With soil warming (1 8-20)
For jet fuel and other aviation fuels (1 0-20)
For nonfuel contaminants such as acetone, toluene, polycyclic aromatic
hydrocarbons (PAHs) (21), and trichloroethylene (TCE)
The cumulative knowledge of EPA, the Air Force, and Battelle Memorial Institute regarding
bioventing of fuel contaminated sites was distilled in Principles and Practices Manual for Bioventing,
released in 1996 (22). The manual outlines the physical, chemical, and biological principles used
in bioventing, and accepted approaches to determining site-specific treatability using onsite tests,
design and monitoring of bioventing systems, and site closure.
Seminar Series on Bioremediation of Hazardous Waste Sites: Practical Approaches to Implementation
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Many documents exist that provide valuable information on bioventing. The Army Corps of
Engineers has also released a helpful manual (23). The most current collection of papers on
bioventing research and development is available in the book In Situ Aeration: Bioventing and
Related Remediation Processes (24). The next frontier for aerobic bioventing is the application of
the process to sites contaminated with chlorinated solvents and PAHs. EPA is currently involved in
two laboratory and field projects to develop co-metabolic bioventing. Co-metabolic bioventing is
the promotion of the aerobic biodegradation of chlorinated solvents, such as TCE, in the vadose
zone by delivering oxygen and, if necessary, a volatile co-metabolite to the contaminated site. The
Air Force has developed cost estimates for bioventing of fuels (25). Calculations show that
bioventing can range from $50 to $5 per cubic yard for soil volumes ranging from 2,000 to
20,000 cubic yards, respectively. These costs for bioventing are cheaper than costs estimated for
other onsite remediation methods such as soil vapor extraction, land farming, and excavation
followed by low-temperature thermal desorption.
The available information on bioventing (experimental, performance, cost) easily convince the reader
that bioventing of fuels is probably the most successful in situ bioremediation technology developed
to date. There are an estimated 1,000 sites in the United States that have used or are currently
using bioventing, mostly for fuel-contamination remediation. In the future, expect the bioventing
approach to be shown useful for the cleanup of almost any aerobically biodegradable contaminant.
References
1. Miller, R.N. 1990. A field-scale investigation of enhanced petroleum hydrocarbon
biodegradation in the vadose zone combining soil venting as an oxygen source with moisture
and nutrient additions. Ph.D. dissertation. Utah State University, Logan, UT.
2. Miller, R.N., C.C. Vogel, and R.E. Hinchee. 1991. A field-scale investigation of petroleum
hydrocarbon biodegradation in the vadose zone enhanced by soil venting at Tyndall AFB,
Florida. In: Hinchee, R.E., and R.F. Olfenbuttel, eds. In situ bioreclamation. Stoneham, MA:
Butterworth-Heinemann. pp. 283-302.
3. Staatsuitgeverij. 1986. Proceedings of a Workshop, 20-21 March, 1986.
Bodembeschermingsreeeks No. 9; Biotechnologische Bodemsanering, pp. 31-33. Rapportnr.
851105002, ISBN 90-12-054133, Ordernr. 250-154-59; Staatsuitgeverij Den Haag: The
Netherlands.
4. van Eyk, J. and C. Vreeken. 1 988. Venting-mediated removal of petrol from subsurface soil
strata as a result of stimulated evaporation and enhanced biodegradation. Med. Fac.
Landbouww. Riiksuniv. Gent, 53(4b):l ,873-1,884.
5. van Eyk, J., and C. Vreeken. 1989. Model of petroleum mineralization response to soil
aeration to aid in site-specific, in situ biological remediation. In: Jousma et al., eds. Ground-
water contamination: Use of models in decision-making. Proceedings of an International
Conference on Groundwater Contamination. Boston/London: Kluwer. pp. 365-371.
Seminar Series on Bioremediation of Hazardous Waste Sites: Practical Approaches to Implementation
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6. van Eyk, J., and C. Vreeken. 1 989. Venting-mediated removal of diesel oil from subsurface
soil strata as a result of stimulated evaporation and enhanced biodegradation. In: Hazardous
waste and contaminated sites, Envirotech Vienna, Vol. 2, Session 3. ISBN 389432-009-5.
Essen, Germany: Westarp Wiss. pp. 475-485.
7. Texas Research Institute. 1980. Laboratory-scale gasoline spill and venting experiment.
American Petroleum Institute, Interim Report No. 7743-5JST.
8. Texas Research Institute. 1 984. Forced venting to remove gasoline vapor from a large-scale
model aquifer. American Petroleum Institute, Final Report No. 8210I-F:TAV.
9. Hinchee, R.E., and M. Arthur. 1991. Bench-scale studies of the soil aeration process for
bioremediation of petroleum hydrocarbons. J. Appl. Biochem. Biotech. 28/29:901-906.
10. Hinchee, R.E., and S.K. Ong. 1992. A rapid in situ respiration test for measuring aerobic
biodegradation rates of hydrocarbons in soil. Air & Waste Mgmt. Assoc. 42(1 0):1,305-1,312.
1 1. Dupont, R.R., WJ. Doucette, and R.E. Hinchee. 1 991. Assessment of in situ bioremediation
potential and the application of bioventing at a fuel-contaminated site. In: Hinchee, R.E., and
R.F. Olfenbuttel, eds. In situ bioreclamation: Applications and investigations for hydrocarbon
and contaminated site remediation. Stoneham, MA: Butterworth-Heinemann. pp. 262-282.
12. Wilson, J.T., and C.H. Ward. 1986. Opportunities for bioremediation of aquifers
contaminated with petroleum hydrocarbons. J. Ind. Microbiol. 27:109-1 16.
1 3. Ostendorf, D.W, and D.H. Kampbell. 1 990. Bioremediated soil venting of light hydrocarbons.
Haz. Waste Haz. Mat. 1 (4):31 9-334.
14. Kampbell, D.H., and J.T. Wilson. 1991. Bioventing to treat fuel spills from underground
storage tanks. J. Haz. Mat. 28:75-80.
1 5. Kampbell, D.H., J.T. Wilson, and CJ. Griffin. 1 992. Performance of bioventing at Traverse
City, Michigan. In: Bioremediation of hazardous wastes. EPA/600/R-92/126. pp. 61-64.
16. Kampbell, D.H., CJ. Griffin, and F.A. Blaha. 1993. Comparison of bioventing and air
sparging for in situ bioremediation of fuels. In: Symposium on Bioremediation of Hazardous
Wastes: Research, Development, and Field Evaluations. EPA/600/R-93/054. pp. 61-67.
1 7. Sayles, G.D., R.C. Brenner, R.E. Hinchee, and R. Elliott. 1 994. Bioventing of jet fuel spills II:
Bioventing in a deep vadose zone at Hill AFB, Utah. In: Symposium on Bioremediation of
Hazardous Wastes: Research, Development and Field Applications. EPA/600/R-94/075. pp.
22-28.
18. Sayles, G.D., R.C. Brenner, R.E. Hinchee, A. Leeson, C.M. Vogel, and R.N. Miller. 1994.
Bioventing of jet fuel spills I: Bioventing in a cold climate with soil warming at Eielson AFB,
Alaska. In: Symposium on Bioremediation of Hazardous Wastes: Research, Development and
Field Applications. EPA/600/R-94/075. pp. 15-21.
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19. Leeson, A., R.E. Hinchee, J. Kittel, G. Sayles, C. Vogel, and R. Miller. 1993. Optimizing
bioventing in shallow vadose zones in cold climates. Hydrological Sciences J. 38(4).
20. Sayles G.D., A. Leeson, R.E. Hinchee, C.M. Vogel, R.C. Brenner, and R.N. Miller. 1 995. Cold
climate bioventing with soil warming in Alaska. In: Hinchee, R.E., R.N. Miller, and P.C.
Johnson, eds. In situ aeration: Bioventing and related remediation processes. Columbus, OH:
Battelle Press, pp. 297-306.
21. McCauley, P.T., R.C. Brenner, F.V. Kremer, B.C. Alleman, and D.C. Beckwith. 1994.
Bioventing soils contaminated with wood preservatives. In: Symposium on Bioremediation of
Hazardous Wastes: Research, Development and Field Applications. EPA/600/R-94/075. pp.
40-45.
22. U.S. EPA. 1995. Bioventing: Prinicples and practice. EPA/540/R-95/543.
23. U.S. Army Corps of Engineers. 1 995. Soil vapor extraction and bioventing, engineering and
design. EM 1 1 1 0-1-4001. November.
24. Hinchee, R.E., R.N. Miller, and P.C. Johnson, eds. 1995. In situ aeration: Bioventing, and
related remediation processes. Columbus, OH: Battelle Press.
25. U.S. Air Force Center for Environmental Excellence. 1994. Bioventing performance and cost
summary. July.
Seminar Series on Bioremediation of Hazardous Waste Sites: Practical Approaches to Implementation
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Bio venting
An Aerobic Bioprocess To Treat
Vadose Zone Contaminated Soils
Presented by
Gregory Sayles or Dolloff F. Bishop
Office of Research and Development
National Risk Management Research Laboratory
U.S. Environmental Protection Agency
Cincinnati, Ohio
Outline
What is bio venting?
Site characterization for
bio venting
Treatability for bioventing
Full-scale design
Outline
(continued)
Operation/Monitoring
Field examples
Costs
Bioventing manual
Hydrocarbon Distribution at a
Contaminated Site
Source
Vapor
Phase
Capillary
Fringe
Dissolved
Contaminants
Phase
Distribution of a
148,000 kg Spill (200m3)
Concentration
Contaminate
Volume (m3)
%of
Volume
Mass
(kg)
Recoverable
NAPL
Soil Gas
Ground Water
Residual Soil
Sorbed
1,000 ppm
lOOmg/L
5,600
20,000
10,000mg/kg 6,500
0.2
17.0
62.0
21.0
32
.000011
.000014
66
Courtesy of Rob Hinchee, Parsons Engineering Science Inc.
Natural Oxygen Delivery
Not Adequate
02 O, O,
Residual
Saturation
Vapor
Phase
Seminar Series on Bioremediation of Hazardous Waste Sites: Practical Approaches to Implementation
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Aerobic Biodegradation
Respiration
C6 H6 + 7V2 02 * 6 C02 + 3 H20
3.1 Ib 02/lb C6H6
C6 Hi4 + 9V2 02 ^ 6 C02 + 7 H20
3.5 Ib02/lb C6Hi4
Oxygen Carrier
Mass Requirements
Oxygen Carrier
Carrier/Hydrocarbon
(Ib/lb)
Aqueous Solutions
Air Saturated 400,000
Nitrate (50 mg/L) 90,000
H202(100mg/L) 65,000
Air 13
Conceptual Layout of Bioventing
Process With Air Injection Only
Monit
Bas
(as re
oring in
s merit ^
quired) .
!>
c
I
1
I
I
1
s~~\
Eli Eli
X
Cute
Pre\
Mig
Base
(if ne
1 ^
iodegradation
of Vapors
Soil Gas
Monitoring
i \
rffWellTo
ent
ation to
ment
cessary)
1
t
£
M
m
)
ml
j
Low Rate Air
Injection
m
= |||||||||i|ninate
HP
cl
What Is Bioventing?
Definition
Forced air movement through
contaminated vadose zone soils to
supply the oxygen necessary for
otherwise oxygen-limited in situ
bioremediation
Bioventing vs. SVE
Volatilization and
Biodegradation^
Aerobically Biodegradable
Rates vary from fast to slow:
BTEX Ketones (acetone)
Jet fuel PAHs (naphthalene)
Gasoline Alcohols
Diesel Fuel oil
Mono- or di-chlorinated benzenes, phenols
Mono- or di-chlorinated ethanes, ethylenes
Air Flow Rate
Seminar Series on Bioremediation of Hazardous Waste Sites: Practical Approaches to Implementation
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Site Characterization
Historical Data
Historical data
Soil gas survey
Soil sampling
Purpose: Initial evaluation of feasibility,
help plan soil gas survey
Known spills, overfills, leaks
Soil and GW data
Location and levels
Soil Gas Survey
Purpose: To locate areas where
oxygen levels are low,
minimize soil sampling
Sample soil gas at various:
locations
depths
Analyze gas for O2, CO2, TVH
Schematic of a Soil Gas
Sampling System
Pressure Relief Vacuum^ Tedler Sample Bag Vacuum
Port X uesiccator ,T_.^ Deslccator) Gauge
Tubing
' 1/8 "Flexible Tubing
Soil Probe Extensions
- Soil Probe Drive Tip
Tubing
Soil Gas Survey Results
Low O2, high CO2
Bioactivity present, but needs Q
Candidate location for bioventing
High O2, low CO2
Bioactivity low, something else is
retarding biodegradation
Not a candidate site for bioventing
Soil Sampling
Purpose: To confirm type and extent
of contamination, estimate
of cleanup time
In region of low O2, sample soil at
various:
locations
depths
Analyze for contaminants of
regulatory concern (e.g., TPH, BTEX)
Seminar Series on Bioremediation of Hazardous Waste Sites: Practical Approaches to Implementation
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Site Characterization-Aerial View
G
G
G
G
G
S G S
S
S S
°\
G Low O,
G
G
G
G
G
G
G
G
Field Treatability Tests
^^^^^^^^^^^^^^^^^^^^^^^^^^^^H
Want to know the required:
Air flow rate
Well spacing
Cleanup time estimate
Cost estimate
G = Gas samples
S = Soil samples
Treatability Test
In situ respirometry test
Soil gas permeability test
In Situ Respiration Test
Purpose:
To measure O2 use rate for
feasibility
To calculate air flow rate for
design
To estimate cleanup time
In Situ Respiration Test
Protocol:
1. Install:
air injection tube
soil gas monitoring points
into contaminated area and
background
In Situ Respiration
2. Aerate (air + helium) for 1-2 days,
until soil gas levels steady
3. Shut off aeration
4. Monitor O2, CO2, and He with time
Seminar Series on Bioremediation of Hazardous Waste Sites: Practical Approaches to Implementation
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In Situ Respiration Test Apparatus
In Situ Respiration Test Results for
Tinker AFB, Oklahoma
30
Oxygen 20.
and
Carbon
Dioxide
(%) 10-
Background
.k=0.17%/hr
CO,
5.0
-4.0
.3.0
2.0
1.0
Helium
20 40 60 80 100 120
Time (hours)
In Situ Respiration Test Results
for Kenai, Alaska
Oxygen
and *
Carbon
Dioxide 10-
20 30 40
Time (hours)
3
. 2 Helium
1
0
50
Soil Gas Permeability Test
Purpose:
Radius of influence of air
injection
Well-spacing
Cost
Radius of Influence Test
-)^-
1
1
1
> 1
1 1
1 1
> 1
1 1
1 1
> L/C
I
I
T . . Pressure
Injection Monitoring
Radius of Influence Data, Saddle
Tank Farm, Galena AFS, Alaska
.3 1
0 20 40 60 80 100
Distance From Vent Well (feet)
Seminar Series on Bioremediation of Hazardous Waste Sites: Practical Approaches to Implementation
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Bioventing Decision Tree
O2 Low
02 High
Identify Limiting
Factors
Bioventing Decision Tree (continued)
_L
Respiration
Test
i
High
Rate
Soil Gas
Permeability
Test
Low
Low
Mods
High
Rate
Consider
Alternative
Technology
Radius
rate to
Radius
Full-S
Des
cale
ign
Full-Scale Design
Air flow rate
Wells/Area
Air injection vs. withdrawal
Other well configurations
Flow Rate and Wells
Using O2 use rate
Radius of influence
Calculate Total air flow rate
Number of wells/area
Design Approach
Oxygen Use Rate
Injection vs. Withdrawal
Injection usually preferred:
Minimizes off-gas production
Lowers water tabletreats
capillary fringe
Vapor residence time greater
But, be careful of subsurface structures!
Seminar Series on Bioremediation of Hazardous Waste Sites: Practical Approaches to Implementation
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Conceptual Layout for Bioventing
Process with Air Injection Only
Monit
Bas
(as re
oring in
quired) .
Is
i
1
E
1
/ \
EIE Eli
X
Cutoff Well To
Prevent
^ Migration to
Basement
(if necessary)
1 1
[
iodegradation
of Vapors
|~ Soil Gas
| Monitoring
:
b c
4
\M
L
m
lib
Low Rate Air
Injection
!KT
mi
d
Other Configurations
^^^^^^^^^^^^
Use injection and withdrawal
well combinations to meet
special site requirements
Air Injection System With
Reinjection of Extracted Soil Gas
Contaminated
Soil
Schematic of Bioventing
Under Buildings
Monitoring Point
Blower
Optional
Negative Pressure
» To
Injection
Monitoring
Operation/Monitoring
Soil sampling at selected
time intervals
O2 gas measurements
Soil temperature
Operation/Monitoring (continued)
Respiration tests at least
semi-annually
Operate year round
t = end determined by rate
0
Seminar Series on Bioremediation of Hazardous Waste Sites: Practical Approaches to Implementation
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Results From the Field
> Hill AFB Field Research Study
Arid soil, deep air injection
Jet fuel
» Greenwood Chemical Superfund
site
Tight soil
Toluene, acetone, naphthalene
Hill AFB, Utah, Bioventing Study
^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^H__
Jet fuel contamination
From overfills of old USTs
Contamination to 95 ft deep
Low moisture, high permeability
soil
Air injection operated for SM-yrs
Hill AFK Monitoring Locations
Hill AFB Initial TPH Distribution (1992)
142 - IF- k St* t
(Appro*, surface) 1.5 m$fl. T TPH Coin. In arc
HILL AFB Site 280 - Operations
Injection pressure = 0.8 psig
Monthly soil gas monitoring
Periodic in-situ respiration tests,
surface emissions tests
Mean Oxygen Utilization Rate vs. Time Within the IW
25-ft Zone at Hill Air Force Base 280 Site
-\ h
Seminar Series on Bioremediation of Hazardous Waste Sites: Practical Approaches to Implementation
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BTEX Concentration With in Uie25' Zone
> ' -JWf*tlt* M
TPH Concentration with in me 25 it Zone by Soihiei
GREENWOOD CHEMICAL PLAN VIEW
Compressor
Air Injection Well
Soil Gas Monitoring Poinl
> Final Soil Boring
GREENWOOD CHEMICAL SUPERFUND SHE
Percent Removal of Organic Compounds
!, "A 81* KJ ru
Illllll
Greenwood Chemical Superfund
Site, Virginia, Pilot Test
Specially chemical company
Toluene, acetone, naphthalene,
contamination
Tight silly clay soils
Air injection operated for 15
months
Costs
Example calculation*
5,000 yd3 jet-fuel contaminated soil
3,000 mg/kg TPH
4 injection wells
Contamination, wells to 15 ft deep
* "Bioventing Performance and Cost Summary,"
AFCEE, July 1994.
Seminar Series on Bioremediation of Hazardous Waste Sites: Practical Approaches to Implementation
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Example
(continued)
Item
Cost
Project planning $11,000
Pilot testing $27,000
Regulatory approval $3,000
Example
(continued)
Item
Cost
Full-scale construction $27,000
Monitoring, 2 yrs $6,500
Power, 2 yrs $2,800
Final soil sampling $13,500
Total $90,800
Cost/yd3 $18
PRINCIPLES AND PRACTICES MANUAL PRINCIPLES AND PRACTICES MANUAL
Volume 1: Principles
- microbial processes
- vadose zone gas transport *
AF Biovenling Initiative
Volume 2: Practice
- Air Force protocols for:
soil gas surveys
field instability tests
- lull-scale design
- performance monitoring
Bioventing Manual
Available on the Internet
The Address is:
http://www.epa.gov/docs/ORD
Summary
If your site:
Has soil contamination
Low 02
The contamination is
aerobically biodegradable
Seriously consider bioventing
Seminar Series on Bioremediation of Hazardous Waste Sites: Practical Approaches to Implementation
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Bioremediation of Sediments
Dolloff F. Bishop
Office of Research and Development, National Risk Management Research Laboratory,
U.S. Environmental Protection Agency, Cincinnati, OH
Introduction
Contaminated sediments in rivers, lakes, and harbors in the United States pose a potential risk to
human health and the environment. Bioremediation (1-3), both through natural attenuation (intrinsic
bioremediation) and through enhanced bioremediation, promises possible approaches for
destruction of contaminants in sediments. Using natural processes involving microbial growth and
enzymatic production, bioremediation can convert target contaminants ultimately to nontoxic end
products. High molecular weight contaminants, however, such as polychlorinated biphenyls (PCBs)
and polynuclear aromatic hydrocarbons (PAHs), persist in sediments, biodegrading only slowly while
strongly partitioning to the sediments and bioaccumulating up the food chain (4), ultimately reaching
humans.
Both PCBs and PAHs are biodegradable under appropriate conditions in laboratory studies (1, 3).
PAHs (5) are typically degraded under aerobic conditions. PCBs (1) are typically degraded under
sequential anaerobic and aerobic conditions. Appropriate anaerobic conditions dehalogenate more
highly chlorinated PCBs, usually the meta- and para-chlorines on the biphenyl structure. Aerobic
conditions usually degrade the resulting lightly chlorinated PCBs with the chlorine atoms at the ortho
position.
Reasons why the persistent contaminants in sediments (6) are resistant to microbial degradation
include:
Contaminant toxicity to the microorganisms
Preferential feeding of microorganisms on other substrates
Microorganisms' inability to use a compound as a source of carbon and energy
Unfavorable environmental conditions in sediments for propagation of appropriate
microorganisms
Poor contaminant bioavailability to microorganisms
Indeed, while the intrinsic biodegradation of such recalcitrant compounds is not uncommon in
nature, the degradation process can take many years.
The challenge for successful bioremediation of sediments involves combining appropriate microbial
pathways, biochemistry, and the function of natural microbial communities with innovative
engineering methods to overcome the recalcitrance of the compounds in sediments, thus increasing
Seminar Series on Bioremediation of Hazardous Waste Sites: Practical Approaches to Implementation
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bioremediation effectiveness. Successful acceleration of degradation rates in situ without a
bioreactor would provide a method for preferred sediment remediation, but such approaches have
exhibited limited effectiveness. Sediment dredging, usually to maintain open channels for shipping,
however, also offers the opportunity for alternative ex situ treatment (6), such as biotreatment in
confined treatment facilities (CTFs), slurry reactors, and composting land treatment applications.
Slurry reactor technology has also been applied in situ to contaminated sediments in water bodies
(5).
Field Bioremediation of Sediments
This review examines two pilot field studies on contaminated sediments: one an ex situ CTF
treatment of PCBs in sediments from the Sheboygan River in Wisconsin, the other an in situ slurry
reactor treatment of PCBs in sediments in the upper Hudson River. The CTF study (6) was
conducted for the U.S. Environmental Protection Agency's (EPA's) Region 5 and included a parallel
laboratory study on the Sheboygan River sediments by EPA's Athens Laboratory. The in situ slurry
reactor study (7) was conducted by the General Electric Company using caisson slurry bioreactors
placed in PCB-contaminated sediments in the river.
The 14,000-square-foot aboveground CTF (Figure 1) used in the Sheboygan study was constructed
of steel sheet piling with a containment capacity of approximately 2,500 cubic yards of sediment
in four separate cells: two treatment and two control cells. Each cell (Table 1), lined with high-
density polyethylene, was hydraulically independent. Water accumulating in each cell discharged
through a permeable wall. The cells contained an underdrain system to add nutrients, oxygen, and
other amendments which could also be used for leachate control. The cells were filled with dredged
PCB-contaminated sediments (original source: Arochlor 1248 and 1254) obtained from the river
in late 1 989 and from March to August 1 990. The study attempted to evaluate remediation under
both anaerobic and aerobic conditions in the CTF. Two approaches for oxygenating the contained
sediments in Cell 4 were use of oxygenated (saturated) water from a compressed air saturator (July
1 992) and use of dilute hydrogen peroxide solutions (November 1 993). Mineral nutrient were also
added to the two treatment cells. Finally, laboratory studies were conducted to evaluate enhancing
anaerobic dehalogenation in the Sheboygan sediments.
In the second field evaluation, six steel caisson slurry reactors (Figure 2) were driven into
contaminated sediments in the upper Hudson River to isolate the natural bacteria and sediment from
the river environment. The experimental design in the study (Table 2) featured a low-mix caisson
and a high-mix caisson as unamended controls; two duplicate low-mix caissons with indigenous
organisms amended with ammonium and phosphate nutrients, biphenyl, and hydrogen peroxide;
and one high-mix and one low-mix caisson with indigenous organisms, both amended with
ammonium phosphate nutrients, biphenyl, hydrogen peroxide, and a culture of PCB degraders, A.
eufrophus H850.
The sediments were mixed using high-mix turbines turning at 40 revolutions per minute (rpm) and
low-mix rakes turning at 3 rpm. The target dissolved oxygen level, automatically supported by
addition of hydrogen peroxide solution, was maintained between 6.0 and 6.5 mg/L in four caissons.
Other amendments were added to the four caissons as appropriate. The unamended high-mix
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control became aerobic but was held to less than 2 mg/L liter by nitrogen purging while the low-mix
control remained anaerobic.
Sediment Remediation Performance
In the CTF study (Tables 3 and 4) at Sheboygan (8), the PCBs in the dredged sediments in the
various cells had an average chlorine per molecule of biphenyl ranging from 2.79 to 3.12,
indicating that only limited amounts of highly chlorinated congeners remained in the sediment.
Heavy oxygen demand in the sediment on Cell 4 minimized the oxygen (less than 0.1 mg/L)
available for degradation of lightly chlorinated PCBs. Attempts to aerobically degrade PCBs in the
sediments in Cell 4 thus produced no increased PCB remediation in the sediments. The oxygenation
attempts were unable to supply enough oxygen to overcome the oxygen demand in the sediment
and the sediment in Cell 4 remained anaerobic. The sediments, loaded into the cells over an
extended period, were dredged from various places in the river and were highly heterogenous with
wide variability in PCB concentrations from sampling location to sampling location in each cell. The
heterogeneity produced high variability in each cell's average concentration over the three sampling
events, as shown in Table 5. Under anaerobic conditions in the other CTF cells, statistically valid
increases in dehalogenation of the PCBs also did not occur.
Parallel laboratory studies at the Athens Laboratory (8) revealed (Figure 3) that addition of
octachlorobiphenyl (octa-CB) substantially increased dehalogenation of the PCBs in the historical
Sheboygan sediment. Sterile and live controls revealed no significant change in the PCBs in the
sediment. Increased dechlorination in historical PCB mixtures in the sediment, induced by the added
octa-CB, delayed the onset of transformation of the added octa-CB by 1 to 2 months.
The PCB homologs (Figure 4) revealed essentially no monohomolog and only modest dihomologs
in the initial sediment. The largest homolog was the trihomolog, which accounted for approximately
50 percent of the PCBs. The control test after 30 weeks revealed insignificant changes in PCB
homolog distribution. The amended system with 20 mg/L of octachlorobiphenyl exhibited significant
dechlorination with major increases of mono- and dihomologs (Figure 5).
Three methods were used to examine PCB concentration changes within the slurry reactors in the
Hudson River field study: direct concentration measurement and concentrations normalized to a
recalcitrant reference congener (peak 61, 34-34-/236-S4 chlorobiphenyl) and to sediment total
organic carbon (9). The alternative methods were considered because of sampling variability in the
caissons, reflecting the heterogeneity in PCB distribution and sampling in the field. The two
normalizing methods were the most significant in quantifying PCB changes after 73 days of
treatment in the caissons (Table 5).
The normalized analyses revealed statistically significant PCB losses of 38 to 55 percent in all
amended caissons. The addition of the H850 culture produced no impact on the PCB changes, and
the H850 cultures were not competitive. Congener homolog group analysis (Figure 6) revealed
significant biodegradation of the mono- and dicongeners.
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Conclusions
The results of the Sheboygan River and the Hudson River studies reveal that partial bioremediation
of PCBs in sediments is possible, even without active biotreatment. The remediation, however, is
incomplete, even with active biotreatment. While sequential anaerobic/aerobic approaches may
completely degrade PCBs in aqueous dispersions, portions of the PCBs in sediments are not
available or only slowly available for biotreatment. Additional research is clearly needed to develop
and evaluate improved approaches for sediment bioremediation. Alternative measurements
(endpoints), based on toxicity, need to be evaluated on bioremediated sediments to assess the
potential environmental and health impacts of the residual PCBs after intrinsic bioremediation
(natural attenuation) and after active biotreatment.
References
1. Abramowicz, D.A. 1995. Aerobic and anaerobic PCB degradation in the environment.
Environ. Health Perspective 103, Supplements: 97-99.
2. Liu, S.M., and WJ. Jones. 1 995. Biotransformation of dichloromatic compounds in non-
adapted and adapted freshwater sediment slurries. Appl. Microbiol. Biotechnol. 43:725-
732.
3. Wilson, S.C., and K.C. Jones. 1993. Bioremediation of soil contaminated with aromatic
hydrocarbons (PAHs): A review. Environ. Pollut. 80:229-249.
4. Safe, S. 1980. Metabolism uptake, storage and bioaccumulation. In: Kimbrough, R., ed.
Halogenated biphenyls, naphthalenes, dibenzodioxins, and related products. Elsevier, North
Holland, pp. 81-107.
5. Seech, A., B. O'Neil, and L.A. Comacchio. 1993. Bioremediation of sediments
contaminated with polynuclear aromatic hydrocarbons (PAHs). In: Proceedings of the
Workshop on the Removal and Treatment of Contaminated Sediments. Environment
Canada's Great Lakes Cleanup Fund, Wastewater Technology Centre, Burlington, Ontario.
6. U.S. EPA. 1994. Assessment and remediation of Contaminant Sediments Program,
remediation guidance document. EPA/905/R-94/003. Great Lakes National Program
Office. October.
7. Flathman, P.E. 1992. Bioremediation technology advances via broad research
applications. Genetic Engineering News. October 15.
8. Jones, WJ. 1 996. Personal communication.
9. Harkness, M.R. et al. 1 993. In situ stimulation of aerobic PCB biodegradation in Hudson
River sediments. Science 159: 503-507.
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Bioremediation of
Sediments
Dolloff F. Bishop
Office of Research and Development
National Risk Management Research Laboratory
U.S. Environmental Protection Agency
Cincinnati, OH
Acknowledgements
W. J. Jones
Environmental Res earch Laboratory, Athens
National Environmental Risk Laboratory
U.S. Environmental Protection Agency
and
F. J. Mondello
General Electric Company
Bioremediaton of
Contaminants in Sediments
Natural attenuation (intrinsic bioremediation)
Enhanced bioremediation using amendments
Microbial growth and enzymatic production
often limited by conditions in sediments
PCBs and PAHs as common high molecular
weight contaminants
Conditions Limiting
Bioremediation of Sediments
Contaminant toxicity to microorganisms
Preferential feeding of microorganisms on
other substrates
Inability of microorganisms to use
contaminant as source of carbon and energy
Sediment conditions unfavorable for
appropriate microbial propagation
Contaminants not bioavailable to
microorganisms
Challenge for Sediment
Bioremediation
Combining appropriate microbial pathway s,
biochemistry, and function of natural microbial
communities
Developing innovative engineering methods in sediments
to overcome contaminant recalcitrance to biodegradation
Developing in situ biotreatment without reactors
(preferred but has exhibited limited effectiveness)
Developing in situ treatment of dredged sediments for
enhanced bioremediation
Developing in situ biotreatment with slurry reactors in
water bodies
Field Bioremediation of
Sediments
Ex situ treatment of PCBs in
CTFs with supporting
laboratory studies
In situ aerobic slurry treatment
of PCB in steel caissons
Figure 1. Confined Treatment Facility
for Sheboygan River Sediments
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Table 1. CTF Bioreactor Cells
Figure 2. In Situ Slurry Biodegradation
of Hudson River Sediments
In Situ
Cell No. PCB mg/kg Treatment Condition
1 225 Anaerobic with nutrients
2 185 Anaerobic control
3 100 Anaerobic control
4* 125 Anaerobic with nutrients
*Cell 4 was intended to be aerobic but D.O. never >0.1 mg/L
Table 2. In Situ Slurry Reactor
Experimental Design
Caisson Treatment Initial PCB Cone.
(mg/kg)
R101 High-mix, control 6.0 ±1.9
R102 High-mix, amended H850 20.0 ±11.0
R103 Low-mix, amended H850 30.2 ± 10.6
R104 Low-mix, control 39.9 ±15. 6
R105 Low-mix, amended indig. 49.7 ± 27.8
R106 Low-mix, amended indig. 39.1 ± 17.5
Table 3. Average CL Per
Biphenyl*
Sample date Cell 1 Cell 2 Cell 3 Cell 4
6-1-92 3.14 2.78 2.87 3.22
8-20-92 3.11 2.80 2.82 3.12
11-4-92 3.11 2.79 2.75 2.95
Averages 3.12 2.79 2.81 3.10
*Sheboygan River sediments in CTF
In Situ Slurry Reactor Design
High-mix turbines turning at 40 rpm
Low-mix rakes turning at 3 rpm
Amended with ammonium and
phosphate nutrients biphenyl,
hydrogen peroxide (D.O. 6-6.5 mg/L)
Indigenous organism or indigenous and
H850 organisms
Low-mix control-anaerobic; high-mix,
<2 mg/L D.O.
Table 4. Average PCB
Concentrations*, mg/kg
Sample date Cell 1 jCellJ^ jCellJ^ CjeU 4**
6-1-92 200 115 91 134
8-20-92 273 132 109 230
11-4-92 323 165 180 236
Averages 265 137 127 200
*Sheboygan River sediments in CTF
**Cell 4 was intended to be aerobic but D.O. never >0.1 mg/L
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Figure 3. Induced Dechlorination of
Sheboygan Sediments
Figure 4. Congener Homologs in
Sheboygan River Sediments
Figure 5. Congener Transformation
by Octachlorobiphenyl Amendment
Table 5. PCB Transformations in
Hudson River Sediments
Treatment
High-mix control
High-mix, H850
Low-mix, H850
Low-mix, control
Low-mix, indig.
Low-mix, indig.
Direct
+8.7
-41.0
-36.8
-41.8
-72.6
-68.5
Percent Changed
Measure Peak 61*
-14.4
-42.4
-37.8
-4.3
-40.5
-38.7
TOC**
-30.7
-44.7
-55.5
+8.4
-53.1
-46.0
^Normalized to congener 34-34/236-34 chlorobiphenyl
^Normalized to total TOC
Figure 6. Transformation of PCB
Homologs in Hudson River Sediments
To = Time zero.
Tf = Final time after 73 days.
Conclusions
Partial bioremediation of PCBs in sediments
occurs even without active biotreatment
Remediation is incomplete even with active
biotreatment
Portions of PCBs in sediment are not or only
slowly available for biotreatment
Alternative measurements (endpoints) based
on toxicity need to be conducted on
bioremediation sediments
Research is needed to develop improved
methods of sediment bioremediation
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Aerated Lagoons: A Case Study
Dolloff F. Bishop
Office of Research and Development, National Risk Management Research Laboratory,
U.S. Environmental Protection Agency, Cincinnati, OH
Introduction
In the mid-1960s to the early 1970s, the French Limited Superfund site (Figure 1) was a state-
licensed waste disposal site near Crosby, Texas. About 90 companies contributed petroleum and
petrochemical wastes that were hauled to the site for disposal. At closure of the disposal site in
1971, about 70 million gallons of wastes were in the main waste lagoon. In late 1983, the
potentially responsible parties (PRPs) formed the French Limited Task Group (FLTG) to consider site
cleanup (1). In early 1987, the U.S. Environmental Protection Agency (EPA) issued a record of
decision (ROD) for the site (2) calling for remediation by incineration, at estimated costs of $75 to
$125 million.
Beginning in late 1985 and continuing through 1986, bench-scale bioremediation had already
been successfully conducted on the contaminated sludges and soils in the lagoon. When the ROD
selecting incineration was issued, FLTG began to explore, at field pilot scale, environmentally
protective and less costly in situ bioremediation for French Limited cleanup. After the successful field
pilot study, EPA in late 1 987 modified the ROD to allow in situ bioremediation (2) as the preferred
cleanup technology for the site. Full-scale site remediation, first in one biotreatment cell (one half
of the lagoon) and then in a second cell, was initiated at the site in early 1 992 and was completed
by 1994.
Cleanup Approach
Most contaminants were biodegradable and in a water matrix at a site with a warm climate. Practical
bioremediation at the site needed to manage ambient air quality; mechanically mix microorganisms,
nutrients, oxygen, sludge, soil, and mixed liquor to produce acceptable biodegradation rates in the
12-acre lagoon; and accurately measure cleanup effectiveness over time. The major design
challenges that had to be met included providing oxygenation with minimum air emissions, effective
mixing during reintroduction of lagoon sludges and soils into a suspended mixed liquor, and
effective circulation (mixing) to distribute nutrients and dissolved oxygen throughout the biotreatment
cell.
Several technologies (3) were considered for oxygenation, including fine bubble aeration and pure
oxygen contacting. Dissolved pure oxygen (Table 1) provided the lowest air emissions. The Mixflo
system (Figure 2), designed by Proxair Inc., was selected for the site by EPA, the FLTG, and ENSR
Consulting and Engineering. Mixflo uses pure oxygen in a two-stage process. The system, with a
maximum capacity of 25 tons of oxygen per day, is the largest oxygenation and sludge and soil
mixing system in the world.
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In the first stage, slurry pumped from the lagoon and pressurized in a pipeline was fed high-purity
oxygen. The two-phase mixture flowed turbulently through the pipeline, substantially increasing
oxygen solubility in the slurry under elevated pressure. In the second stage, the oxygen/slurry
dispersion was reinjected into the lagoon using a liquid/liquid eductor (Figure 3) that mixed
unoxygenated slurry with the oxygenated slurry and produced a fine bubble oxygen dispersion before
dispersing the mixture throughout the lagoon.
The mixing of unoxygenated slurry with oxygenated slurry in the eductor before discharging the
mixture reduced the dissolved oxygen concentration below atmospheric pressure saturation. Thus,
dissolved oxygen did not come out of solution in the lagoon. The oxygen not dissolved in the
pipeline contactor also was well distributed as fine bubbles with a low frequency of bubble
coalescence in the lagoon. Further oxygen dissolution then occurred in the lagoon, minimizing air
emissions and providing excellent (90 percent) oxygen dissolution efficiency. To ensure an effective
circulation pattern in the lagoon biotreatment cell, nine 50,000-gallon-per-minute FLYGT banana
mixers were placed on three rafts. The Mixflo system and the FLYGT mixers provided effective
solutions to the engineering challenges. After completion of bioremediation, each biotreatment cell
was subsequently filled with clean soil and planted in cover vegetation.
Bioremediation Performance
In situ aerobic bioremediation met all sludge soil cleanup requirements (4, 5) for the lagoon. Using
indicator contaminants (Table 2) as examples, residual arsenic had to be at or below 7 parts per
million (ppm); benzene at or below 14 ppm; benzo(a)pyrene at or below 9 ppm; total
polychlorinated biphenyls (PCBs) at or below 23 ppm; and vinyl chloride at or below 43 ppm. Actual
concentrations of the indicator contaminants after bioremediation typically were 1 to 2 ppm arsenic,
0.5 to 10 ppm benzene, 1.8 to 10 ppm benzo(a)pyrene, 1 to 1 0 ppm PCBs, and 3 to 1 7 ppm vinyl
chloride.
Ambient air monitoring during remediation (Table 3) revealed that air criteria concentrations to
quantify maximum cumulative concentrations for each of 35 compounds of concern were also fully
achieved. Finally, the direct costs (3) of the lagoon bioremediation (Table 4), including the field pilot
demonstration, were $39 million. Total costs for bioremediation were $59 million, compared with
the estimated $75 to $125 million, for incineration.
Site Closure
A second bioremediation process (6), not presented here, was conducted at the site. The lagoon had
contaminated the surrounding ground water. The ground-water bioremediation process was recently
completed (January 1996). Full site closure with continued ground-water monitoring is nearly
complete.
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References
1. Biotreatment News. 1 991 -1 992. French Limited: A successful approach to bioremediation.
A three-part series.
2. U.S. EPA. 1 992. Superfund at work. EPA/520/P-93/004.
3. Bergman, T.J., et al. 1 992. An in situ slurry-phase bioremediation case with emphasis on
selection and design of a pure oxygen dissolution system. Union Carbide Industrial Gases
Technology Corporation, Tarrytown, NY, and ENSR Consulting and Engineering, Houston,
IX.
4. CH2M Hill. 1995. Site remediation report, Part A: Lagoon remediation verification. EPA
Contract No. 68-W8-0112.
5. U.S. EPA. 1994. Hazardous Waste Management Division first 5-year review: French Limited
site, Crosby, TX. CERCLIS TXD-980514814.
6. Biotreatment News. 1993-1994. In situ bioremediation of ground water and subsoils at
French Limited site, TX. A three-part series.
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Aerated Lagoons
A Case Study of the French Limited
Superfund Site
Presented by
DolloffF. Bishop
Office of Research and Development
National Risk Management Research Laboratory
U.S. Environmental Protection Agency
Cincinnati, Ohio
Acknowledgements
Judith Black
Region VI
U.S. Environmental Protect!on Agency
Richard Sloan
ARCO Chemical Company
French Limited Waste
Disposal Site
Mid 1960 to 1971
Petroleum and petrochemicals
Incineration ROD in 1987 at
estimated costs of $75-125 million
ROD in late 1987 modified to
permit in situ bioremediation
Figure 1. French Limited
Site Location
Engineering Challenges in
Lagoon Bioremediation
Minimize air emissions
Provide efficient shearing and
introduction of sludge and soil into
the lagoon's suspended mixed liquor
Maintain mixing of suspended mixed
liquor
Provide efficient distribution of
nutrients and oxygen
Solutions to Engineering
Challenges
Pure oxygen dissolution using
Mixflo
Liquid/liquid eductor
FLYGT banana mixers on rafts
Figure 2. Mixflo
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Table 1. Comparison of Mixflow
and Fine Bubble Aeration
Mixflo Fine Bubble
Oxygen transfer efficiency (
Gas volume, scfm
Off gas volume, scfm
90 14
112 3,418
12 3,318
Figures. Liquid/Liquid Eductor
Table 2. Performance of
Indicator Compounds
Arsenic
Benzene
Benzo(a)pyrene
Total PCBs
Vinyl Chloride
Cleanup
Required
PPM
7
14
8
23
43
Typical
Residuals
PPM
1-2
0.5-10
1.8-10
1-10
3-17
Table 3. Benzene Ambient Air
Management ACC Ratios
Subdivision
Riverdale
Rogge
Dreamland
ACC*
CellE
0.2393
0.0597
0.0368
Ratios**
Cell D/F
0.1872
0.0402
0.0277
* Air Criteria Concentrations
** Requirement: ACC ratio must be less than 1.0 at end of 2 years.
Table 4. Incineration and
Bioremediation Costs
Incineration* Bioremediation
$ Millions $ Millions
General
Site Preparation
Remediation
Indirect Costs
Contingency
TOTALS
5
7
68
15
30
125
13**
7
19
10
5
54
* On site incineration
** Includes 10 million dollar cost for field pilot demonstration.
Site Re vegetation
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Oil-Contaminated Shorelines
Albert D. Venosa
Office of Research and Development, National Risk Management Research Laboratory,
U.S. Environmental Protection Agency, Cincinnati, OH
Introduction
This case study is based on a field study conducted during the summer of 1 994 by researchers from
the U.S. Environmental Protection Agency's (EPA's) National Risk Management Research Laboratory
and the University of Cincinnati, in cooperation with the Delaware Department of Natural Resources
and Environmental Control (1).
Light crude oil was intentionally released onto plots to evaluate bioremediation. Past field studies
involving bioremediation of oil-contaminated shores have concluded that bioremediation enhances
the removal of crude oil several times more effectively than the intrinsic rate (2-9). Much skepticism
remains in the field, however, because data from all of these investigations have been equivocal to
some extent. The goals of this project were to quantify the effectiveness of natural attenuation due
to levels of background nutrients already present in the Fowler Beach area of Delaware Bay; to
demonstrate the effectiveness of biostimulation and/or bioaugmentation; to determine the extent of
any resulting rate enhancement; and to provide guidelines that can be used by spill responders and
on-scene coordinators for the effective bioremediation of oil-contaminated sandy shores.
Biodegradation was tracked by gas chromatography/mass spectroscopy (GC/MS) analysis of
selected components, and the measured concentrations were corrected for abiotic removal by
hopane normalization. (Hopane is a nonbiodegradable compound that exists in all crude oils.) Five
replicates of three treatments were evaluated: an oiled no-nutrient control, addition of water soluble
nutrients, and addition of water soluble nutrients supplemented with a natural microbial inoculum
from the site.
Approach
Without full replication and random interspersion of treatments, it is impossible to ascribe statistically
significant differences in the response variable(s) to the treatments. A randomized complete block
design was used to assess treatment effects. Five areas (blocks) of beach were selected, each large
enough to accommodate four experimental units or test plots. The blocks were positioned on the
beach parallel to the shoreline. Three treatments were tested on oiled plots: a no-nutrient addition
control, addition of water soluble nutrients (biostimulation), and addition of water soluble nutrients
supplemented with a natural microbial inoculum from the site (bioaugmentation). A fourth treatment,
an unoiled and untreated plot, served as a control for background biological measurements. The
four treatments were randomized in each of the five blocks.
Previously weathered light crude oil from Nigeria (Bonny Light) was the source of crude oil. It was
applied to the plots uniformly by spray nozzles connected to drums. Each plot received 36 gallons
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of oil. Laboratory microcosms indicated that a concentration of 0.5 mg N/L and limited oxygen
uptake and CO2 production, whereas at concentrations greater than 2.5 mg N/L, maximum uptake
was observed. Thus, the target nitrate-N was set at about 1.5 mg/L.
A lithium tracer experiment to determine how frequently fertilizer should be added to maintain the
target nutrient level found that tracer diluted quickly as the plots became submerged by the incoming
tides and waves. In fact, there was a direct correlation between plot submergence and the amount
of tracer remaining in the bioremediation zone. Because the plots for the field study were positioned
within the intertidal zone, nutrients had to be applied every day to maintain the desired 1.5 mg/L in
the interstitial pore water.
The bioaugmentation treatment consisted of an inoculum of oil degraders isolated from the site,
grown in batches on the same crude oil, and added back every week. The indigenous inoculum was
grown for 2 weeks in two 55-gallon stainless steel drums. To allow weekly inoculation with fresh 2-
week cultures, each drum was offset in time from the other by 1 week. The drums contained 40
gallons of seawater from Delaware Bay, the weathered Bonny Light crude oil (600 mL) as the sole
carbon source, and the same nutrients used on the beach.
Results
Nutrient Persistence. The control plots receiving only seawater with no nutrients had measurable
concentrations of nitrate (mean of 0.82 mg/L), which were approximately half the 1.5 mg/L target
level desired for maximum biodegradation. The concentrations in the nutrient and inoculum treated
plots were substantially higher. The Fowler Beach area of Delaware Bay was close to farm land,
where runoff could easily account for the high background levels found.
Physical Loss of Oil. To distinguish physical loss from biodegradative loss of oil, the concentration
of hopane, a known nonbiodegradable biomarker in all crude oils, was quantified in each sand
sample. Data from the three oiled treatments revealed a hopane half-life of 28 days. This was
interpreted to represent physical loss of crude oil due to wave action and tidal inundation. A similar
study of the temporal loss of total extractable organic material (EOM) from the plots revealed an
EOM half-life of 21 days. The EOM first-order rate coefficient was significantly higher than the
hopane disappearance rate. The difference in loss rates (and half-lives) between hopane and EOM
was attributed to biodegradation because EOM includes both biodegradable and nonbiodegradable
components. EOM, however, was not a sensitive enough indicator to discern treatment differences.
Results of Bioremediation. The bioremediation study revealed that, although substantial
hydrocarbon biodegradation occurred in the untreated plots, statistically significant differences
between treated and untreated plots were observed in the biodegradation rates of the hopane-
normalized total alkane and total aromatic hydrocarbons. The rate enhancement was approximately
two-fold for the alkanes and 50 percent for the aromatics. First-order rate constants for
disappearance of individual hopane-normalized alkanes and polycyclic aromatic hydrocarbons
(PAHs) were computed, and the patterns of loss were typical of biodegradation. As the number of
alkyl-substituted groups increased on the aromatic ring structure, the rate of PAH disappearance
decreased. This is known to be typical of biodegradation. In the field, the ratio of biodegradation
rates of unsubstituted parent compounds and lower substituted compounds to the highest substituted
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compound in a homologous series revealed strikingly close agreement with the same ratios
computed from laboratory experiments (except for naphthalene and C,-naphthalene, which are
highly volatile). This signifies that the loss of hydrocarbons due to factors other than biodegradation
(i.e., dissolution and volatilization) was negligible.
Significant differences were not observed between plots treated with nutrients alone and plots treated
with nutrients and the indigenous inoculum. The high rate of oil biodegradation observed in the
untreated plots was attributed to the relatively high background nitrogen concentrations that were
measured at the site.
Conclusions
Significant intrinsic biodegradation of petroleum hydrocarbons occurred naturally when sufficient
nutrients already existed in the affected area. Statistically significant rate enhancement was
demonstrated, even in the presence of an already high rate of natural attenuation, by supplementing
natural nutrient levels with inorganic mineral nutrients; however, bioaugmentation did not
significantly contribute to any further enhancement. Maintenance of a threshold concentration of
about 2 mg nitrate-N/L interstitial pore water permits close to maximum hydrocarbon
bioremediation. The incremental increase in biodegradation rate over the intrinsic rate (i.e., slightly
greater than two-fold for the alkanes and 50 percent for the PAHs) might not have been high
enough to warrant a recommendation to actively initiate a major, perhaps costly, bioremediation
action in the event of a large crude oil spill in that area. Thus, the decision to apply nutrients should
depend on the background concentrations available at the contaminated site, as well as the impact
on ecological and health receptors.
The study showed that better hydrocarbon biodegradation takes place in the upper intertidal zone
than in the lower intertidal zone due to the greater persistence of nutrients and highly aerobic
conditions. Hopane was confirmed as a useful biomarker for tracking biodegradation success in
the field.
For the first time, first-order biodegradation rate constants were developed from field data for the
resolvable normal and branched alkanes and the important two- and three-ring PAH groups (and
at least one four-ring PAH group) present in light crude oil. The relative biodegradation rates of
homologous PAHs measured in the field were found to agree closely with those measured in the
laboratory, thus corroborating the rates as being due to biodegradation and not physical washout
or solubility differences.
Lessons Learned
After a major spill has been beached, the first task is to measure the natural nutrient concentrations
in that environment to determine if they are already high enough to sustain significant intrinsic
biodegradation. Concentrations approaching 1.5 to 2.0 mg N/L in the interstitial pore water should
support near-optimum hydrocarbon biodegradative activity. A determination should be made as to
whether such nutrient levels are normal for the affected area for that time of the year. Oiled sandy
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shorelines should only be treated with nutrients if concentrations are clearly limiting (i.e., well below
1 to 2 mg/L).
If the beach is treated with water-soluble nutrients applied by a spray irrigation system, they should
be applied daily if the area gets completely submerged by tides and waves, even during neap tides.
If the area is submerged only during spring tides, the intertidal coverage by water determines the
frequency of nutrient addition. The Delaware study did not include evaluation of either oleophilic
or slow release granular fertilizer for nutrient enhancement. For large expanses of contaminated
shoreline or areas with difficult access and control (e.g., heavy wave action), oleophilic fertilizers may
be more appropriate.
Degradation effectiveness should be monitored using specific analytes quantified by GC/MS and
then only when analytes are normalized to a recalcitrant compound like hopane. Total petroleum
hydrocarbon (TPH) measurements should not be used to monitor treatment effectiveness; they are
too variable and too much affected by biogenic organic matter that has nothing to do with the
hydrocarbons present.
Bioaugmentation is often unnecessary for accelerating biodegradation of an oil spill on a sandy
beach. Quantifying the hydrocarbon degrader populations in the impact zone is useful, however.
A treatment product should not be considered for use on a shoreline based only on results of
bioremediation studies in a terrestrial environment. The abiotic loss mechanisms that act upon
petroleum, nutrients, and microorganisms are substantially different on a beach than on dry land.
Estimated Cost of Bioremediation
A rough estimate of the costs of an oil spill bioremediation project has been calculated, based on
the Delaware study. The following assumptions have been made for this analysis:
The spill has contaminated a 27-mile-wide intertidal zone of a long stretch of
coarse sandy beach in an area that is easily accessible (unlike Prince William
Sound), such as the Atlantic, Pacific, or Gulf coasts.
Free product and heavy concentrations have already been removed by physical
cleanup procedures.
Pore water nutrient levels are well below the 1.5 to 2.0 mg N/L needed for
optimum biodegradation effectiveness.
Nutrients are added daily via a sprinkler or irrigation system to maximize
bioremediation effectiveness.
Based on these assumptions, an estimated 2 person-years per kilometer (i.e., one supervisor and
three laborers working full-time for approximately 3 months) would be required for cleanup.
Assuming a supervisor salary (with benefits) of $1 00,000 per year and a laborer salary of $50,000
per year, the labor cost would be $62,500. Equipment needs are estimated to be about $75,000,
chemicals $45,000, storage $2,500, and analytical needs $50,000. Total direct costs would thus
Seminar Series on Bioremediation of Hazardous Waste Sites: Practical Approaches to Implementation
5-4
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be approximately $235,000. Applying overhead at the rate of 100 percent yields a total cost of
approximately $470,000 per kilometer of beach contaminated.
The above cost estimates are highly dependent on manpower for daily application of water-soluble
fertilizer. If slow-release granular fertilizer is used (thus mitigating the need for daily application), and
assuming target levels of nitrogen can be achieved for periods approaching a week, then the
manpower and equipment needs will likely be significantly lower than those estimated above.
Detailed economic analysis awaits data from further field evaluations.
Protocol Development
As a result of the Oil Pollution Act of 1 990 (OPA), EPA instituted a research program to develop an
objective protocol assessing the bioremediation effectiveness and toxicity of commercial oil spill
bioremediation agents. A tiered approach was developed in which a product is subjected first to a
laboratory batch screening test and tested against a control for its ability to biodegrade crude oil
(1 0, 11). An acute toxicity test is also performed to assess the product's ability to induce mortality
in mysid shrimp species. The next tier involves further testing of the product compared with a control
in a flow-through microcosm. The final tier consists of an actual field trial of the product. The
laboratory screening test consists of shake flasks containing natural seawater, 5 g/L weathered
Alaska North Slope crude oil, and the product. Two controls are set up: a no-nutrient, no-product
control (i.e., natural seawater and weathered oil) and a nutrient control (natural seawater, weathered
oil, and nitrate and phosphate salts as nutrients). Triplicate flasks are sacrificed at days 0, 7, and 28
to determine the extent of biodegradation of the crude oil components. Measurements are made
by GC/MS. Alkane and aromatic hydrocarbon degraders are also measured by a most probable
number technique (12). For a product to be deemed effective, it must demonstrate statistically
significant removal of both alkane and aromatic hydrocarbons compared with the controls at the
conclusion of the exposure period. EPA is currently attempting to refine the protocol by changing
the natural seawater to a sterile artificial formulation and standardizing the microbial inoculum. Such
refinements would make the test more reproducible. The inoculum would be used as a positive
control for living products, whereas it would serve as the actual biodegrading population in the case
of a non-living product. Products that successfully demonstrate the ability to biodegrade both the
alkane and aromatic components of weathered crude oil are then placed on the National
Contingency Plan product schedule, which makes them eligible for use in an oil spill.
References
1. Venosa, A.D., M.T. Suidan, B.A. Wrenn, K.L. Strohmeier, J.R. Haines, B.L Eberhart, D.
King, and E.L. Holder. 1996. Bioremediation of an experimental oil spill on the shoreline
of Delaware Bay. Environ. Sci. Technol. 30(5): 1,1 64-1,1 75.
2. Bragg, J.R., R.C. Prince, EJ. Harner, and R.M. Atlas. 1994. Effectiveness of
bioremediation for the Exxon Valdez oil spill. Nature 368:41 3-41 8.
Seminar Series on Bioremediation of Hazardous Waste Sites: Practical Approaches to Implementation
5-5
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3. Halmo, G. 1985. Enhanced biodegradation of oil. In: Proceedings of the 1985
International Oil Spill Conference. American Petroleum Institute, Washington, DC.
4. Rosenburg, E., R. Legmann, A. Kushmaro, R. Taube, R. Adler, and E.Z. Ron. 1992.
Petroleum bioremediationA multiphase problem. Biodegradation 3:337-350.
5. Sendstad, E. 1980. Accelerated biodegradation of crude oil on Arctic shorelines. In:
Proceedings of the Third Arctic and Marine Oil Spill Program. Environment Canada.
6. Sveum, P. 1987. Accidentally spilled gas-oil in a shoreline sediment on Spitzbergen:
Natural fate and enhancement of biodegradation. In: Proceedings of the Tenth Arctic and
Marine Oilspill Program. Environment Canada.
7. Sveum, P., and A. Ladousse. 1989. Biodegradation of oil in the Arctic: Enhancement by
oil-soluble fertilizer application. In: Proceedings of the 1989 International Oil Spill
Conference. American Petroleum Institute, Washington, DC.
8. Pritchard, P.M., and C.F. Costa. 1991. EPAs Alaska oil spill bioremediation project.
Environ. Sci. Technol. 25:372-379.
9. Pritchard, P.M., J.G. Mueller, J.C. Rogers, F.V. Kremer, and J.A. Closer. 1 992. Oilspill
bioremediation: Experiences, lessons, and results from the Exxon Valdez oil spill in Alaska.
Biodegradation 3:315-335.
10. Venosa, A.D., J.R. Haines, and B.L Eberhart. 1996. In: Sheehan, D., ed. Protocols in
bioremediation. Totowa, NJ: Humana Press.
1 1. Venosa, A.D., J.R. Haines, W. Nisamaneepong, R. Govind, S. Pradhan, and B. Siddique.
1992. J. Ind. Microbiol. 10:13-23.
12. Wrenn, B.A., and A.D. Venosa. 1 996. Canadian J. Microbiol. 42:252-258.
Seminar Series on Bioremediation of Hazardous Waste Sites: Practical Approaches to Implementation
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O il-C ontaminate d
Shorelines
Presented by
Gregory Sayles or Dolloff F. Bishop
Office of Research and Development
National Risk Management Research Laboratory
U.S. Environmental Protection Agency
Cincinnati, Ohio
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EFFECT OF |N] ON O, UPTAKE AND CO, EVOLUTION
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Location Within ID* Intertidal Zon«
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Seminar Series on Bioremediation of Hazardous Waste Sites: Practical Approaches to Implementation
5-7
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Effect of Plot Coverage on Nitrate Washout from
Bioremedlalion Zona
toot
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in«Kirnum plot coverage, %
A».r»a« and Standard D»vl«Uon of HUal»-N
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Treatment
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Avg.. fngIL SO, mg/L
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Seminar Series on Bioremediation of Hazardous Waste Sites: Practical Approaches to Implementation
5-8
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Rr.t-Order Blodegiidilron Rut* Conmnu
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Seminar Series on Bioremediation of Hazardous Waste Sites: Practical Approaches to Implementation
5-9
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Land Treatment
Daniel Pope
Dynamac Corporation, Ada, OK
Definition of Land Treatment
Land treatment involves use of natural biological, chemical and physical processes in the soil to
transform organic contaminants of concern. Biological activity apparently accounts for most of the
transformation of organic contaminants in soil, although physical and chemical mechanisms may
provide significant loss pathways for some compounds under some conditions. Degradation by
ultraviolet light may serve as a loss pathway for certain hydrophobic compounds at the soil surface.
Volatilization of some low molecular weight compounds also takes place at the soil surface and
provides a significant loss pathway for such compounds. Certain chemical reactions such as
hydrolysis can play an important role in transformation of some compounds. Humification, the
addition of compounds to the humic materials in soil, can be an important route of transformation
for some polynuclear aromatic compounds. The relative importance of these processes varies
widely for different compounds under different circumstances. The land treatment concept serves
as the basis for design and operation of soil bioremediation technologies at a large number of waste
sites requiring cleanup.
In Situ and Ex Situ Land Treatment
Land treatment techniques for bioremediation purposes most often are used for treatment of
contaminated soil, but certain petroleum waste sludges have long been applied to soil for treatment.
Ideally, the contaminated soil can be treated in place (in situ). Often, however, the soil must be
excavated and moved to a location better suited to control of the land treatment process (ex situ).
In situ land treatment is limited by the depth of soil that can be effectively treated. In many soils,
effective oxygen diffusion sufficient for desirable rates of bioremediation extends to a range of only
a few inches to about 12 inches into the soil, although depths of 2 feet and greater have been
effectively treated in some cases.
Ex situ treatment generally involves applications of lifts of contaminated soil to a prepared bed
reactor. This reactor is usually lined with clay and/or plastic liners, provided with irrigation,
drainage, and soil water monitoring systems, and surrounded with a berm. The lifts of contaminated
soil are usually placed on a bed of relatively porous, noncontaminated soil.
The land treatment process may be severely limited in clayey soils, especially in areas of high rainfall.
This limitation is primarily related to oxygen transfer limitations and substrate availability to the
microorganisms. Clayey soils should be applied in shallower lifts than sandy soils. Tilth ("workability"
of the soil) can often be improved by adding bulking agents.
Seminar Series on Bioremediation of Hazardous Waste Sites: Practical Approaches to Implementation
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After application to the land treatment unit, each lift should be tilled at intervals to enhance oxygen
infiltration and contaminant mixing with the microorganisms. The soil should be near the lower end
of the recommended soil moisture percentage range before tilling. Tilling very wet or saturated soil
tends to destroy the soil structure, reduce oxygen and water intake, and cause reduced microbial
activity. Tilling more than is necessary for enhanced oxygen infiltration and contaminant mixing may
be counterproductive because tilling tends to destroy the soil structure and compact soil below the
tilling zone.
Timing of application of succeeding lifts should be based on reduction to defined levels of particular
compounds or categories of compounds in the preceding lift. For instance, the goal might be to
reduce total petroleum hydrocarbons (TPH) to less than a regulatory or risk- calculated limit in the
current lift before application of a new lift. Once desired target levels of compounds of interest are
established, data obtained from land treatment unit (LTU) monitoring activities can be statistically
analyzed to determine whether and when desired levels are reached and the LTU is ready for
application of another lift.
Nutrients, Carbon Sources, and Other Additives
Fertilizers can be used to supply nutrients, and wood chips, sawdust, or straw can supply carbon.
Various animal manures are often used to supply both carbon sources and nutrients. High organic
levels in manures, wood chips, and the other organic amendments increase sorptive properties of
soil, thereby decreasing mobility of organic contaminants and possibly decreasing availability to the
microorganisms. Organic amendments will also increase the water-holding capacity of soil, which
can be desirable in sandy soils but can cause difficulty when land treatment is conducted in areas
of high rainfall and poor drainage.
Agricultural fertilizer is usually supplied in prilled or pelleted form (the fertilizer compounds formed
into pellets with a clay binder) suitable for easy application over large areas. Completely water-
soluble fertilizers can be applied through irrigation systems, allowing application rates to be closely
controlled, applications to be made as often as irrigation water is applied, and immediate availability
to the microorganisms.
Bioaugmentation
Microorganism cultures are often sold for addition to bioremediation units. Two factors limit use
of these added microbial cultures in LTUs: 1) nonindigenous microorganisms rarely compete well
enough with indigenous populations to develop and sustain useful population levels, and 2) most
soils with long-term exposure to biodegradable wastes have indigenous microorganisms that are
effective degraders if the LTU is managed properly.
Certain soil factors may interfere with microbiological activity in the LTU soil. High salt levels,
indicated by high electrical conductivity (EC) readings, may reduce or stop useful microbiological
activity. If levels are too high, it may be necessary to leach the soil with water to remove excess salts
before biodegradation can occur. High levels of sodium may be detrimental to soil structure.
Seminar Series on Bioremediation of Hazardous Waste Sites: Practical Approaches to Implementation
6-2
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Soil Moisture Control
Historically, it has been recommended that soil moisture be maintained at 40 to 70 percent of field
capacity; however, recent experience indicates that 70 to 80 percent of field capacity may be
optimum. A soil is at field capacity when soil micropores are filled with water and soil macropores
are filled with air. This condition allows soil microorganisms to get air and water, both of which are
necessary for aerobic biodegradation to occur. Maintaining soil at somewhat less than 100 percent
of field capacity allows more rapid movement of air into the soil, thus facilitating aerobic metabolism
without seriously reducing the supply of water to microorganisms. If soils are allowed to dry
excessively, microbial activity can be inhibited or stopped; if the wilting point is reached, cells may
lyse or rupture. Continuous maintenance of soil moisture at adequate levels is of utmost
importance. Either too little or too much soil moisture is deleterious to microbial activity. Surface
drainage of the LTU can be critical in high rainfall areas. If soil is saturated more than an hour or
two, aerobic microbial action is reduced.
Underdrainage is generally provided by a sand layer or a geotextile/drainage net layer under the
LTU. The system should be designed so that excess water quickly drains away and thus microbial
activity is not inhibited. The interface between the lift and the drainage layer underneath should be
composed of well-graded materials so that the transition from the (usually) relatively fine soil texture
of the lift to the relatively coarse texture of the drainage layer is gradual rather than sudden. Grading
of the materials reduces the tendency for the soil lift to become saturated before drainage occurs,
which inhibits aerobic biological activity.
Types and Concentrations of Contaminants Remediable by Land Treatment
The types of contaminants most commonly treated in LTUs are petroleum compounds and organic
wood preservatives. Historically, petroleum refineries have used land treatment to dispose of waste
sludges. Although waste petroleum sludges currently are not often applied to soil for treatment, the
technology has been applied to remediation of soil contaminated with many types of petroleum
products, including fuel, lubricating oil, and used petroleum products. Land treatment has
historically been used to remediate contaminated process waters from wood preserving operations.
This technology currently is not used for this purpose but is currently used to remediate soil
contaminated with wood preserving wastes.
Other applications for land treatment technology include remediation of soil contaminated with coal
tar wastes, pesticides, and explosives. Since coal tar wastes are similar to creosote wastes (wood
preserving creosote is made from coal tar), such wastes are considered amenable to land treatment.
Land treatment appears to be potentially useful for certain pesticides, but the evidence for
applicability of this technology to explosives-contaminated soil is inconclusive.
Levels of Contamination Susceptible to Land Treatment
The levels of petroleum product contamination amenable to land treatment vary by waste type and
site conditions. In many cases, soils with higher levels of contaminants than are recommended for
Seminar Series on Bioremediation of Hazardous Waste Sites: Practical Approaches to Implementation
6-3
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land treatment can be mixed with less contaminated soils to bring contamination levels down to
recommended starting levels for treatment. Levels of petroleum product contamination as high as
25 percent by weight of soil have been reported as treatable, although experience indicates that
levels 5 to 8 percent by weight or less are more readily treated.
Soils contaminated with 15,000 to 20,000 mg/kg dry weight creosote wastes have been treated in
soil systems, although more usual starting levels are in the 5,000 to 10,000 mg/kg range.
Pentachlorophenol wastes are rarely treated at more than 1,000 mg/kg starting levels since
pentachlorophenol is quite toxic to microorganisms at the higher levels.
The final levels attainable also vary by waste and site conditions. Generally, once total contaminant
levels are below 50 to 200 mg/kg polynuclear aromatic hydrocarbons, remediation by land
treatment is slow, and further treatment by conventional land treatment techniques may be
ineffective. For instance, land treatment of creosote wastes is generally considered successful if total
carcinogenic polynuclear aromatic hydrocarbons are reduced to below 50 to 100 mg/kg, and
specific components are reduced to their "land ban" levels (for instance, pyrene to 7 mg/kg).
Laboratory treatability studies may be used to assess the "best case" potential for final contaminant
levels, with the assumption that actual final levels in the field would rarely if ever be lower than those
found in laboratory study.
Costs for land treatment are estimated at between $20 to $200 per cubic yard.
Seminar Series on Bioremediation of Hazardous Waste Sites: Practical Approaches to Implementation
6-4
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Land Treatment
Land Treatment
Biological, chemical, physical
processes transform contaminants
Daniel Pope
Dynamac Corporation
Ada, OK
Degradation by Biological
Activity
Most transformation of organic
contaminants
Physical, chemical mechanisms also
involved
Degradation by Ultraviolet
Light
Soil surface
Higher PAHs
Volatilization - Low Molecular
Weight Compounds
BTEX
Naphthalene
Methyl naphthalenes
Hydrolysis - Pesticides
Amides
Triazines
Carbamates
Thiocarbamates
Nitriles
Esters
Phenylureas
Seminar Series on Bioremediation of Hazardous Waste Sites: Practical Approaches to Implementation
6-5
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Humification
Know Thy Waste
Polymerization of contaminants
PAHs known to humify
Relative importance of processes
varies widely for different
compounds under different
circumstances
Compounds Amenable to
Land Treatment - PAHs
Compounds Amenable to
Land Treatment - Phenols
2-ring PAHs - readily degraded,
volatile, leachable
3-ring PAHS - degradable, leachable
4-ring PAHS - fairly degradable,
leachable
5-6-ring PAHs - difficult to degrade
Penta & Tetrachlorophenol
Difficult over 1,000 ppm
Other phenolics
Compounds Amenable to Land
Treatment - Hydrocarbons
Aliphatics 1-8 C chains
Degradable
Volatile
Compounds Amenable to Land
Treatment - Hydrocarbons
Most 12-15+ C chains
Slower degradation
Relatively immobile
Relatively nontoxic
Seminar Series on Bioremediation of Hazardous Waste Sites: Practical Approaches to Implementation
6-6
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Compounds Amenable to
Land Treatment - BTEX
Degradable
Volatile
Compounds Amenable to
Land Treatment
Energetics - more often composted
Phthalates
Pesticides
Bioremediation
What Is It?
Land Treatment
Technology
Two fundamental aspects of
bioremediation . . .
Developing large populations of
microorganisms that can transform
pollutants
Bringing microorganisms into
intimate contact with pollutants
Contaminated soil
Sludge application to soil
In Situ - Ex Situ Land
Treatment
The issue is control
Control of runoff, leachate, volatiles
In Situ - Practical Soil Depth
Based on effective oxygen diffusion
Bioventing for greater depths
Seminar Series on Bioremediation of Hazardous Waste Sites: Practical Approaches to Implementation
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In Situ
Semi In Situ
Treat surface soil, remove
Treat surface soil, deep till
Remove soil to depth
Add lifts back to excavation
for treatment
Tillage Depth
Most tractor-mounted tilling devices
till down to one foot
Large tractors, specialized equipment
till to three feet or more
Large augers move soil from 50-100
feet to surface, but practicality not
fully shown
Ex Situ
Application of lifts of contaminated
soil to prepared-bed reactor
Clay and/or plastic liners
Bed of porous soil
Irrigation, drainage, and soil water
monitoring systems
Berm
Land Treatment - Lift
Depth
Generally limited to 6-24 inches of
soil
Usually 12 inches or less lift depth
Refinery LTU 36 inches or more
Soil Type
Limited in heavy clay soils, especially
in high rainfall areas
Oxygen transfer limitations
Substrate availability
Seminar Series on Bioremediation of Hazardous Waste Sites: Practical Approaches to Implementation
6-8
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Soil Type - Working With
Heavy Soils
Shallow lifts for easier tilling, better
diffusion
Improve tilth with bulking agents
Improving Tilth - Bulking
Agents
Organic matter (sawdust, compost,
manures, etc.)
Add gypsum if soil has high sodium
content
Preparing Soil for
Application
Screen to remove debris greater than
1 in. diameter
Remove large debris that may adsorb
waste compounds
Tilling
Enhances oxygen infiltration
Mixes contaminants with
microorganisms
Disperses contaminants
Tilling
Lower end of soil moisture
percentage range before tilling
Tilling very wet or saturated soil
tends to destroy soil structure,
reduce microbial activity
Wait 24 hours after irrigation or a
significant rainfall event
Tilling Schedule
Compromise of several antagonistic
factors
Loosens soil for oxygen access
Destroys soil structure
Dries soil
Mixes contaminants and bugs
Equipment compacts soil
Seminar Series on Bioremediation of Hazardous Waste Sites: Practical Approaches to Implementation
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Tilling - Mixing
Mostly along line of travel
Till in varying directions
Tilling Equipment
Rotary tiller for tilling, mixing
purposes
Disk harrow often used, may not mix
soil well
Subsoil plow, chisel plow to break up
zone of compaction
Tilling
Subsequent lifts tilled into top 2 in. or
3 in. of previous lift
To mix populations of well
acclimated microorganisms
Avoids sudden transition in
permeabilities if different soil types
being remediated
Lift Application Timing
Based on reduction to defined levels
of particular compounds or
categories of compounds
Usually more detailed sampling to
determine finish
Nutrients, Carbon Sources,
and Other Additives
Carbonaceous (Organic)
Amendments
Animal manures
Wood chips, sawdust
Straw, hay
Seminar Series on Bioremediation of Hazardous Waste Sites: Practical Approaches to Implementation
6-10
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Carbonaceous
Amendments
Supply carbon and some nutrients
Act as bulking agent, adsorbent
Carbonaceous Adsorbents
Slow migration
May sequester contaminants
Increase permeabilityIncreased
oxygen, water flux
Increase oxygen demand due to
microbes breaking down
Increase water holding capacity
Carbonaceous Amendments-
Application Rates
Must be balanced with nutrients
3-4% by weight of soil
Carbonaceous
Amendments
Manures often mixed with bedding-
straw, sawdust, rice hulls
Bedding acts as bulking agent, but
also has a nutrient demand
Carbonaceous
Amendments
Should have moderately small
particle size
Thoroughly mixed with soil
Fertilizers
Can cause pH to drop
Acid forming equivalent indicated
on bag
Seminar Series on Bioremediation of Hazardous Waste Sites: Practical Approaches to Implementation
6-11
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Fertilizers - Soluble Forms
Can be applied through irrigation systems
Application rates may be closely controlled
Applications can easily be made as often as
irrigation water is applied
Immediately available to microorganisms
Equipment meters concentrated nutrient
solutions into irrigation system on demand
Soil Nutrient Levels
Nutrient requirements not thoroughly
studied
Detailed information not available to
indicate optimal levels
Difficult to show response in field
Soil Nutrient Levels
Desired levels based on
concentration in soil, or
concentration ratio of several
nutrients
Micronutrients
Carbonaceous amendments may
contain some micronutrients
Trace amounts in many packaged
inorganic fertilizers
Commercially available as
micronutrient blends
Apply specific micronutrients only if
treatability studies show response
Proprietary Micronutrients
Usually expensive compared with
horticultural fertilizer sources
Generally easily supplied with readily
available horticultural fertilizers
Complex Nutrients
Vitamins, growth factors
Need easily shown in lab culture,
with defined media
Difficult to show effectiveness in
field
Seminar Series on Bioremediation of Hazardous Waste Sites: Practical Approaches to Implementation
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Bioaugmentation
Indigenous microorganisms isolated,
cultured
Nonindigenous microorganisms
Genetically engineered
microorganisms
Bioaugmentation
Nonindigenous microbes rarely compete well
enough to develop, sustain useful population
Most soils with long-term exposure to
biodegradable wastes have indigenous
microorganisms that are effective degraders
given proper management of the LTU
Little data from well-designed experiments to
show efficacy
Perhaps more useful as understanding increases
Soil Moisture Control
Field Capacity
40-80% of field capacity
Usually at high end of range
Soil micropores filled with water
Soil macropores filled with air
Microorganisms get air and water
Soil Moisture
Maintaining 40-80% of FC allows more
rapid movement of air into soil,
facilitating aerobic metabolism without
seriously reducing supply of water to
microorganisms
Soil Moisture
Some evidence that continuous
maintenance at high levels better
Some evidence that low end of range
good for some compounds
Requires careful management to
maintain any given level
Seminar Series on Bioremediation of Hazardous Waste Sites: Practical Approaches to Implementation
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Soil Moisture
If soils dry excessively, microbial
activity seriously inhibited, stopped
Maintenance at proper level is not
trivial
Measuring Soil Moisture
Gravimetricsimple, accurate, slow
Tensiometersimple, fairly accurate for
many soils
Gypsum blocksgood for undisturbed
soil
Capacitance effectaccuracy questionable
Neutron probeaccurate, but uses
radioactive material, expensive eqipment
Surface Drainage
Critical in high rainfall areas
Saturation greater than one hour
greatly reduces microbial action
Surface should be sloped 0.5-1.0%
Greater slopeserosion hazard
Design to allow collection, return of
eroded soil
Internal Drainage
Sand/gravel layer
Geotextile/drainage net layer
Internal Drainage
Initial lifts usually placed on bed of
sand, other porous soil, which
causes a perched water table to
develop
Perched Water Table
Lift takes up water until field
capacity achieved
Then begins to drain excess water
Lower part of lift layer may remain
overly wet
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Internal Drainage
The interface between lift & drainage
layer should have well-graded
materials
The psoil particle size transition from
lift to drainage layer should be
gradual
Water movement through interface
enhanced with gradual transition
Internal Drainage
Good internal drainage reduces
tendency for soil lift to become
saturated
Interface may be graded by tilling lift
into top of drainage layer
LTU Leachate and Runoff
Disposal of Treated Soil
Recycled onto LTU
With or without treatment
Treated (biological or adsorption) and
discharged
Replace in excavation
Disposal cell
LT as Part of a Treatment
Train
High organics (bulking agents,
contaminants) in soil may inhibit
subsequent solidification/stabilization
for metals treatment
LT Disadvantages
Slowtakes a long time for treatment
High contaminant concentrations may be hard
to treat
Low contaminant concentrations may not show
significant reduction
Final levels may not be achievable depending on
the requirements
Space requirements are high
Volatiles/dust/leachate control may be difficult
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LT Costs
Earthmoving$1-2+ per yard
Containmentberm
Monitoringusually major part of
expense
Operations
Volatiles control can be very
expensive
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Land Treatment Unit Case Study: Champion International Superfund Site
Daniel Pope
Dynamac Corporation, Ada, OK
Introduction
The Champion International Superfund Site at Libby, Montana (referred to as the "Libby Site"), is
an operating lumber mill where wood preserving operations using creosote and
pentachlorophenol (PCP) were conducted from 1946 to 1969. Soil, sediments, and ground water
at the site were contaminated with creosote and PCP wood treating solutions and wastes.
Champion International uses three biological processes for environmental remediation at the Libby
site: 1) a prepared-bed, lined land treatment unit (LTU) for treatment of excavated soil; 2) an
abovegrade, fixed-film bioreactor for treatment of extracted ground water, and 3) an oxygen and
nutrient enhanced bioremediation system for in situ treatment of the upper aquifer. As part of the
U.S. Environmental Protection Agency's (EPA's) Bioremediation Field Initiative, a team consisting
of Utah State University, EPA's National Risk Management Research Laboratory (Ada, Oklahoma),
and Dynamac Corporation conducted a performance evaluation of bioremediation systems used
by Champion International at the Libby site.
Objectives of the LTU performance evaluation were to:
Describe and summarize previous and current remediation activities.
Develop an evaluation plan, including statistical requirements for the number,
timing, and location of samples.
Perform a laboratory evaluation of the potential for soil microorganisms to
bioremediate soil contaminants under site conditions of temperature and soil
moisture.
Conduct a comprehensive field evaluation to assess treatment effectiveness,
treatment rate, and detoxification of contaminated soil in the LTU.
SUMMARY OF REMEDIATION AND MONITORING ACTIVITIES CONDUCTED BY CHAMPION
INTERNATIONAL
When full-scale soil remediation began, approximately 75,000 cubic yards of contaminated soil and
sediment at the site was excavated down to the water table from the three primary source areas at
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the site: a former tank farm, an unlined butt-dip area, and an unlined waste pit. Rocks larger than
1 inch in diameter were removed from the excavated material and used to construct subgrade
infiltration galleries upgradient from the waste pit area where substantial residual contamination
remained in the subsurface. Effluent from the abovegrade fixed-film bioreactor was applied to the
infiltration galleries to stimulate biodegradation of any contamination adhering to the rocks, and to
allow infiltration of treated water from the bioreactor back into the subsurface to stimulate
subsurface bioremediation. The excavated soil remaining after rocks were removed (about 45,000
cubic yards) was placed into the waste pit excavation, where it is pretreated by land treatment (tilling,
irrigation, nutrient addition) prior to placement in the LTU.
The geometric means of initial soil concentrations from all three contaminated sites are as follows:
Total carcinogenic polynuclear aromatic hydrocarbons
(TCPAHs)
PCP
189.0 mg/kg
29.0 mg/kg
Note: Maximum concentrations greater than geometric mean by factors of 6 to 90.
Target remediation levels as specified in the record of decision for soil treated in the two LTUs are
as follows:
Naphthalene
Phenanthrene
Pyrene
TCPAHs
PCP
8.0 mg/kg
8.0 mg/kg
7.3 mg/kg
88.0 mg/kg
37.0 mg/kg
LTU Cell Design
The lined, prepared-bed LTU is composed of two cells with a total area inside the outer berm
perimeter of both cells of 2 acres. The berms allow containment, treatment, and ultimate disposal
of additional contaminated soils, if required.
The bottom of the LTU cells are sloped to a central gravel drain (2 percent slope), which is sloped
to a collection sump (1 percent slope) so drainage water can be removed as needed. Leachate is
removed from the collection sump by means of an automated pump and piping system. Beneath
the drainage system is a geotextile filter underlain by a high-density polyethylene liner, which in turn
is supported by a base layer of compacted soil.
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Monitoring
Monitoring, conducted by Champion International, involves periodic collection and analysis of
leachate, soil, ground-water, and air samples both inside and outside treatment cells during
operation and closure periods.
Leachate monitoring involves sampling from LTU sumps on a quarterly basis and during rainfall
events. Monitoring of LTU soil involves operational, confirmation, and compliance sampling.
Operational sampling consists of onsite laboratory analysis of contaminants during lift treatment as
well as assessing nutrient and soil moisture requirements. After operational samples indicate
contaminant target levels have been met in a lift, confirmation samples are analyzed by an offsite
laboratory to confirm attainment of contaminant target levels. Compliance samples may include
previously collected confirmation samples or additional samples, if required, to fully demonstrate
that target levels have been reached.
Ground-water monitoring includes six wells (four downgradient and two upgradient). Monitoring of
the ground-water wells around the LTU is performed semiannually.
Ambient air is monitored for polynuclear aromatic hydrocarbons (PAHs) and PCP by an upwind and
downwind station to characterize concentrations due to unit operations and to protect workers'
health. Moisture is applied to LTU for dust control during operation.
Land Treatment Operations
Contaminated soils are placed in the LTU cells in 6- to 12-inch lifts for treatment during the summer.
Water is applied to the LTU to maintain adequate moisture levels (approximately 40 to 70 percent
of field capacity) in the treatment zone and for dust control.
Nutrients (nitrogen and phosphorus) are added to the LTU dissolved in irrigation water or as solid
fertilizers applied directly to the LTU. The nutrient requirement selected was a carbon:nitrogen ratio
in the soils of approximately 12-30:1 and a nitrogen:phosphorus ratio of approximately 10:1.
Nutrients are added as frequently as every other day, depending on soil moisture and nutrient needs.
The LTU is tilled at least weekly, using a tractor-mounted rototiller. Tilling is suspended if the LTU
contains ponded water.
LAND TREATMENT PERFORMANCE EVALUATION
Introduction . Utah State University conducted a field and laboratory performance evaluation of the
LTUs. During the performance evaluation, soil in the two LTU cells was sampled at several depths
over a 2-year period. Concentrations of the 1 6 priority pollutant PAH compounds and PCP were
determined. The performance evaluation was based on: 1) the changes in concentration of soil
contaminants over time to evaluate the effectiveness of remediation, 2) changes in the concentration
of soil contaminants in a lift after application of additional lifts to evaluate downward migration of
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contaminants, 3) changes in soil toxicity as determined by bioassays to evaluate toxicity reduction,
and 4) a laboratory study of chemical, physical, and biological processes affecting soil contaminant
concentrations to determine the mechanisms responsible for remediation.
Results . Soil sampling indicated that land treatment was able to meet the treatment goals for
reduction of contaminant concentrations in the contaminated soil, and there was no evidence of
downward migration of target PAH compounds and PCP through the LTUs. In addition, pyrene, PCP,
and TCPAH concentrations continued to decrease with time after placement of lifts in both LTUs.
Laboratory Assessment
Two laboratory evaluations of soil microbial metabolic potential were conducted to add information
concerning biodegradation versus physical/chemical mechanisms for disappearance of
phenanthrene and PCP, e.g., volatilization and mineralization. The first laboratory evaluation was
designed to determine rates of biological mineralization and volatilization as affected by
contaminant concentration, temperature, and soil moisture. The second evaluation was designed
to provide information addressing a mass balance of radiolabeled carbon that was used to evaluate
humification of the two chemicals.
Results. The laboratory studies demonstrated that both PCP and phenanthrene were partially
metabolized to carbon dioxide in the contaminated soil matrix at the site. Both were also mineralized
with the indigenous soil microorganisms at temperatures and moisture levels representative of site
conditions. It appears that significant volatilization of PCP or phenanthrene at the full-scale site is
unlikely. The laboratory evaluation corroborates the interpretation that decreases in target chemical
concentrations are due to biological processes rather than physical/ chemical processes.
Laboratory evaluations demonstrated that not all of the parent compounds were mineralized within
soil in the laboratory microcosms. Rather, carbon in the parent compounds also became distributed
among air, solvent extract, and soil-bound phases. A major pathway for 14C for phenanthrene and
PCP was humification (binding to soil), such that the compound is not solvent-extractable from soil.
A significant fraction of 14C was solvent-extractable from the soil, either in the form of the parent
compound or intermediates. Mineralization represented the third most important fraction for 14C in
this laboratory study. Volatilization of phenanthrene and PCP over the 45-day evaluation was less
than 1 percent and therefore not considered to be an important route of compound removal from
soil.
Soil Toxicity Testing . The Microtox assay was used to measure general physiological toxicity, and
the Ames assay was used to measure mutagenicity of soil solvent extracts. Toxicity assays indicated
that soil within the LTUs was detoxified to background soil levels. Average Microtox toxicity
decreased from an EC50 value of 6.6 initially to nontoxic (greater than 100) for all soil samples
tested. The initial mutagenic potential of soil applied to LTU 1 was considered to be approximately
330 revertants per gram of soil (weighted activity). Results of mutagenicity testing for Lift 1 sampled
3 months after application and biological treatment indicated detoxification to soil background
levels (less than 1 50 revertants per gram of soil).
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Conclusions
The field performance evaluation of two full-scale LTUs at the Libby, Montana, Superfund site
indicated that enhanced land treatment of soil contaminated with wood preservative chemicals was
effective and resulted in the treated soil meeting target remediation levels for target contaminants
as specified in the record of decision. Downward migration of target chemicals as a result of the
application of additional lifts was not observed. The contaminated soil was detoxified to background
levels as a result of the treatment, based on the results of toxicity and mutagenicity assays.
In summary, results of the field performance of the LTUs at the Champion International Superfund
site in Libby, Montana, indicated that bioremediation using indigenous microorganisms was the
process that accomplished soil treatment. Soil treatment included degradation of target PAH
compounds and PCP in contaminated soil to target remediation levels and detoxification of soil.
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Land Treatment Case
Study: Libby
Superfund Site
Daniel Pope
Dynamac Corporation
Ada, OK
Land Treatment Case Study:
Champion International
Superfund Site
Currently an operating lumber mill
Creosote/pentachlorophenol wood
preserving from 1946 to 1969
Soil, sediments, & ground water
contaminated with creosote and
PCP wood treating solutions,
wastes
Biological Processes For
Remediation
Prepared-bed, lined land treatment
unit (LTU) for soil
Above grade, fixed-film bioreactor
for extracted GW
Oxygen/nutrient enhanced
bioremediation for in situ
treatment of the upper aquifer
U.S. EPA Bioremediation Field
Initiative Performance
Evaluation
Utah State University
Dynamac Corporation
NRMRL Ada Division
(RSKERL)
Champion International
LTU Performance Evaluation
Objectives
Document remediation
activities
Laboratory evaluation of
bioremediation
Field evaluation: treatment
effectiveness and rate,
detoxification of soil
Remediation/Monitoring
Activities Summary
As conducted by Champion
International
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Full-Scale Soil Remediation
75,000 yards contaminated
soil/sediment excavated
Rocks >1 inch diameter removed
Remaining soil (~45,000 yards)
replaced in excavation
Pretreated by "in situ" LT prior to
placement in LTU
LTU Cell Design
Lined, prepared-bed
land treatment unit
Two cells -1.0 acre
each
Monitoring
(Champion International)
LTU soil
LTU leachate
Ground water (6 wells)
LTU air emissions
Land Treatment Operations
6- to 12-inch lifts
Water -40 to 70% FC
Weekly tilling
Discontinued during winter
Nutrients
Applied in irrigation water or
as solids
C:N ratio 12-30:1
N:P ratio 10:1
Based on TOC, TKN, total
phosphorus
LTU Performance Evaluation
Utah State
LTU cells sampled over two-
year period
Concentrations of 16
priority pollutant PAHs and
PCP
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Performance Evaluation:
Contaminant Concentrations
Contaminant concentration
changes over time
Concentration changes in a
lift after application of
additional lifts
Performance Evaluation:
Toxicity Reduction
Microtox assay - general
physiological toxicity
Ames assay -
mutagenicity
Performance Evaluation:
Contaminant Fate
Lab studies of chemical,
physical, and biological
processes to determine
mechanisms responsible for
remediation
Field Evaluation Results
Contaminant reduction goals
met
No evidence of downward
migration of PAHs, PCP
Pyrene, PCP, TCP AH, decreased
after lifts covered in both LTUs
Laboratory Study
Objectives
Determine fate of
14C-phenanthrene and 14C-
PCP in LTU soil, as affected
by soil moisture, temperature
Laboratory Study
Results
PCP, phenanthrene partially
metabolized with indigenous
soil microorganisms at
temperatures and moisture
levels representative of site
conditions
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Laboratory Study
Results
Significant volatilization of
PCP or phenanthrene in lab
study did not occur
Laboratory Study
Results
Not all of parent compounds
were mineralized within soil in
laboratory microcosms
Carbon in parent compounds
became distributed among air,
solvent extract, and soil-bound
phases
Laboratory Study
Results
Major pathway for phenanthrene,
PCP was humification
Next significant pathway was
solvent-extractable from soil
parent compound or intermediates
Mineralization was third most
important pathway
Volatilization was less than 1%
Soil Toxicity Testing
Microtox - general
physiological toxicity
Ames assay -
mutagenicity of soil
solvent extracts
Average Microtox
Toxicity
Initial EC50 value of 6.6
After treatment, EQ0
value >100 (nontoxic) for
all soil samples tested
Ames Test
Initial mutagenic potential of
applied soil ~330 revertants
per gram of soil
Lift 1 sampled after 3 months
treatment indicated
detoxification to soil
background levels (less than
150 revertants per gram of soil)
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Conclusions: Field
Performance Evaluation
Land treatment of soil
contaminated with wood
preservatives was effective and
resulted in the treated soil
meeting target remediation levels
for target contaminants as
specified in the Record of
Decision (ROD)
Conclusions: Field
Performance Evaluation
Downward migration of target
chemicals as a result of the
application of additional lifts
was not observed
Conclusions: Field
Performance Evaluation
Contaminated soil was
detoxified to background
levels as a result of the
treatment, based on results of
toxicity and mutagenicity
assays
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Phytoremediation
Steve Rock
Office of Research and Development, National Risk Management Research Laboratory,
U.S. Environmental Protection Agency, Cincinnati, OH
Daniel Pope
Dynamac Corporation, Ada, OK
Phytoremediation is the use of higher plants to bioremediate contamination in soil, water, or
sediments. Variations of phytoremediation that have been used in the past include wetlands to treat
municipal sewage or neutralize acidic mine drainage. Currently, phytoremediation is proposed for
remediation of both organic and inorganic contaminants in soil, sediments and water.
Phytoremediation, as with bioremediation using microorganisms, involves the use of natural
processes to change the form or location of contaminants. Roots of higher plants take up water,
nutrients, and other compounds from soil. Water moves throughout the plant, eventually going to
the leaves and out into the atmosphere in the process of transpiration. Ongoing processes of plant
metabolism use water, nutrients, carbon dioxide, and sunlight to synthesize organic compounds,
which are moved throughout the plant for use in growth and for storage of reserves. A large
community of microorganisms thrives in contact with the plant (particularly on the root system) and
is supported to a greater or lesser degree by products of the plant. Plants may transport oxygen
down to the root system and release some of the oxygen to the soil. As the roots grow through the
soil, they form channels that can increase soil aeration, particularly as the roots die and decay,
leaving voids. As with bioremediation using natural microbial processes, it is possible to use these
natural plant processes to remediate contaminants.
Much of the biodegradation associated with certain kinds of phytoremediation occurs in a zone
around the root system called the rhizosphere (Figure 1). The rhizosphere is a zone of enhanced
microbial activity at the interface between the root and the soil. The rhizosphere supports larger
microbial populations than surrounding soil and has different types of microorganisms than
surrounding soil. The enhanced microbial activity in the rhizosphere is thought to be responsible for
degradation of certain contaminants, particularly of some organic contaminants.
The rhizosphere is a narrow zone, with a depth from a few millimeters to perhaps a centimeter. The
actual depth of the rhizosphere is hard to measure, but the "rhizosphere effect" of enhanced
microbial activity appears to diminish rapidly with distance. Since the rhizosphere is closely involved
with phytoremediation, the degree of contact that the root system has with the soil is important.
Plant root systems vary considerably, but in general most root systems can be divided into two
classes: tap root systems, with large main roots emerging from the plant base and branching to
smaller and smaller roots; and fibrous root systems, with many small roots emerging from the plant
base and also branching to smaller and smaller roots. Fibrous root systems generally have more
surface area per length of root than taproot systems. Some plants, notably grasses, have very fine,
fibrous root systems that are highly ramified throughout the soil volume they occupy. This should
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mean that the plant roots actually contact more of the soil, and therefore their affect on remediation
should be more uniform throughout the soil volume occupied.
Plants may transport oxygen into the subsurface; lower the water table by transpiration, thereby
pulling oxygen into the soil from the atmosphere; and increase hydraulic conductivity of the soil as
roots produce channels in soil. Flood-tolerant and wetland plants are especially efficient at
transporting oxygen into the subsurface. These processes are thought to enhance aerobic
biodegradation by increasing oxygen in the subsurface.
As plants transpire, the movement of water through the plant also carries along dissolved
components (Figure 2). Dissolved contaminants such as chlorinated solvents can be removed from
the soil in the transpiration stream and emitted to the atmosphere through the plant leaves. This type
of "remediation" could be undesirable, obviously.
Many plants transpire significant quantities of water under the right conditions, but certain plants,
called phreatophytes, which ordinarily grow their roots down to the water table, can transport
relatively large quantities of water from the soil to the atmosphere. Willow and poplar species are
well known examples. Many plants, particularly the phreatophytes, can significantly influence
ground-water levels, especially in soils of low permeability. Such plants could not only remediate
the ground water by the various mechanism already discussed but also could help protect ground
water by lowering the water table below contaminated zones.
Most plants grow roots down to about 2 meters deep or less, but some plants can reach far deeper
under good conditions. Obviously it might be desirable for phytoremediation to have plants that
grow dense, highly ramified, fibrous root systems down very deep. Research is needed to determine
the depth of influence of plant root systems, and ways to encourage deeper rooting and greater soil
volume coverage.
The community of microorganisms in the rhizosphere has been shown to be involved in degradation
of numerous contaminants, including pesticides, polynuclear aromatic hydrocarbons, petroleum
compounds, volatile organic chemicals, and inorganics. Also, plants can degrade contaminants
during plant metabolic activities; for instance, 2,4,6-trinitrotoluene has been shown to be degraded
by plant enzymes. Plants can use contaminants as nutrients; nitrate contamination of ground water
can serve as a nitrogen source for plants.
Plants can adsorb or take up and accumulate contaminants either in their roots and other
belowground parts or in aboveground parts including stems, leaves, and fruits. Plants are not able
to take up all types of contaminants; small, low molecular weight polar compounds are favored for
uptake into the plant, but large, high molecular weight lipophilic compounds tend to be excluded.
Plants may extract metals from soil and accumulate them in tissues. Accumulators of lead,
cadmium, chromium, nickel, cobalt, copper, zinc, and selenium have been found (Table 1).
Location of the accumulation site in the plant is important. Accumulation of contaminants in the
root may pose problems with removal of the contaminant from the site, since it may be impractical
to harvest the root systems and separate them from the soil. Ideally, the plant would efficiently
extract the contaminant from the soil down to very low levels and accumulate the contaminant to
high concentrations in an aboveground plant part that could be easily harvested without harming
the plant.
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Applications and Examples
In general, phytoremediation appears to be best suited for cleanups over a wide area, with fairly
shallow contaminants in low to medium concentrations. Using plants to remediate a site can be
much less expensive than conventional cleanup options because installation and maintenance costs
are typically very low. Public acceptance of phytoremediation can be very high, in part because
of the added benefits of parklike aesthetics, including providing bird and wildlife habitat. A planted
wetland or interceptor barrier of poplar trees can remediate a chronic problem for years with little
or no attention. The cleanup time can be longer than with some physical or chemical processes,
and like most bioremediation is typically measured in months and years.
Phytoremediation has been shown to reduce concentrations of hydrocarbons from spills and leaking
underground storage tanks; polychlorinated biphenyls from transformers; pentachlorophenol and
creosote from wood preserving sites; nitrates, pesticides, and herbicides from agricultural runoff; and
chlorinated solvents like trichloroethylene from industrial processes. Some plants can extract heavy
metals such as lead, chromium, and uranium. Study in this field is relatively new, with much of the
work done on the laboratory and pilot scale, though some field work is now under way.
Wetlands constructed with reeds and cattails are used to prevent acid mine drainage from polluting
streams. The biological processes in a wetland neutralize the acidity of the water and decrease the
mobility of the metals. Poplar and willow trees are planted as interceptor barriers to remediate
ground-water contamination or to protect surface water from agricultural runoff. The roots of these
trees can "pump and treat" hundreds of gallons of water each day. Contaminants may be degraded
by the microbial community that is supported by the trees or by the tree itself. Plants such as
mustard may be used for extraction of heavy metals by taking up the contaminants into the roots,
then translocating them to the shoots and leaves. Some plants may sequester metals in the root
structure but not move them further into the plant. Alfalfa, ryegrass, and other plants are used for
in situ soil remediation. These plants encourage biodegradation of organic contaminants by
microbes by providing oxygen, nutrients, enzymes, and other key elements in the root zone of
influence or rhizosphere.
Plants are limited as to the depths that they can effectively treat. Mustard plants grow down 12 to
1 8 inches. Ryegrass and fescue can extend roots a few feet. Alfalfa has been found with roots down
to 20 feet. Poplar tree roots can tap a water source 1 0 to 20 feet down, and some claim much
deeper root depth.
Bibliography
1. Anderson, T.A., E.A. Guthrie, and B.T. Walton. 1993. Bioremediation. Environ. Sci.
Technol. 27(13).
2. Aprill, W., and R.C. Sims. 1 990. Evaluation of the use of prairie grasses for stimulating
polycyclic aromatic hydrocarbon treatment in soil. Chemosphere 20(1-2):253(13).
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3. Baker, A.J.M., S.P. McGrath, C.M.D. Sidoli, and R.D. Reeves. 1 994. The possibility of in
situ heavy metal decontamination of polluted soils using crops of metal-accumulating
plants. Resour. Conserv. Recycl. 11(1-4):41.
4. Baker, A.J.M., and R.R. Brooks. 1989. Terrestrial higher plants which hyperaccumulate
metallic elements: A review of their distribution, ecology, and phytochemistry. Biorecovery
1:81-126.
5. Banks, M.K., G.R. Fleming, A.P. Schwab, and B.A. Hetrick. 1994. Effects of the
rhizosphere microflora on heavy metal movement in soil. Chemosphere.
6. Banuelos, G.S., G. Cordon, B. Mackey, J. Ben-Asher, L. Wu, P. Beuselinck, S. Akohoue,
1 993. Boron and selenium removal in boron-laden soils by four sprinkler-irrigated plant
species. J. Environ. Qual. 22(4):786.
7. Bollag, J.-M. 1992. Decontaminating soil with enzymes. Environ. Sci. Technol. 26(10).
8. Brooks, R.R. 1972. Geobotany and biogeochemistry in mineral exploration. New York,
NY: Harper and Row.
9. Brown, S.L., R.L Chaney, J.S. Angle, and A.J.M. Baker. 1994. Phytoremediation potential
of Thlaspi caerulescens and bladder campion for zinc- and cadmium- contaminated soil.
J. Environ. Qual. 23(6):1,1 51.
10. Chaney, R.L. 1983. Plant uptake of inorganic waste constituents. In: Parr, J.F., et al., ed.
Land treatment of hazardous wastes. Noyes Data Corp., Park Ridge, NJ. pp. 5,076.
11. Cunningham, S.-O., and W.R. Berti. 1993. Remediation of contaminated soils with green
plants: An overview. In Vitro Cell. Devel. Biol. Plant 29(4):227-232.
12. Dushenkov, V., P.B.A.N. Kumar, H. Motto, and I. Raskin. 1995. Rhizofiltration: The use
of plants to remove heavy metals from aqueous streams. Environ. Sci. Technol.
29(5):1,239.
13. Entry, J.A., N.C. Vance, M.A. Hamilton, and D. Zabowski. 1994. In situ remediation of
soil contaminated with low concentrations of radionuclides. In: In situ remediation:
Scientific basis for current and future technologies. Proceedings of the 33rd Hanford
Symposium on Health and the Environment, Pasco, WA, November 7-1 1. Battelle Press.
p. 1,055.
1 4. Erickson, L.E., M.K. Banks, L.C. Davis, A.P. Schwab, N. Muralidharan, K. Reilley, and J.C.
Tracy. 1994. Using vegetation to enhance in situ bioremediation. Environ. Prog.
13:226-231.
1 5. Hinchman, R., and C. Negri. No date. The grass can be cleaner on the other side of the
fence. Logos 12(2):8.
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16. Lee, E., and M.K. Banks. 1993. Bioremediation of petroleum-contaminated soil using
vegetation: A microbial study. J. Environ. Sci. Health Environ. Sci. Eng. 28(1 0):2,1 87.
1 7. Licht, L.A., and J.L. Schnoor. 1 990. Poplar tree buffer strips grown in riparian zones for
biomass production and nonpoint source pollution control. In: Proceedings of the
American Society of Agricultural Engineers, Paper 902057. pp. 1-21.
1 8. Pierzynski, G.M., J.L. Schnoor, M.K. Banks, J.C. Tracy, L. Licht, and LE. Erickson. 1 994.
Vegetative remediation at superfund sites. In: Hester, R.E., and R.M. Harrison, eds. Mining
and its environmental impactissues in environmental science and technology, Vol. 1.
Royal Society of Chemistry, pp. 46-69.
1 9. Raskin, I., P.B.A.N. Kumar, S. Dushenkov, and D.E. Salt. 1 994. Bioconcentration of heavy
metals by plants. Current Opinion in Biotechnol. 5:285.
20. Schnoor, J.L, L. Licht, S.C. McCutcheon, N.L. Wolfe, and L.H. Carreira. 1995.
Phytoremediation of organic and nutrient contaminants. Environ. Sci. Technol. 29(7):31 8A.
21. Stomp, A.M., K.H. Han, S. Wilbert, and M.P. Gordon. 1 993. Genetic improvement of tree
species for remediation of hazardous wastes. In Vitro Cell. Devel. Biol. Plant
23F(4):227-232.
22. Walton, B.T., and T.A. Anderson. 1990. Microbial degradation of trichloroethylene in the
rhizosphere: Potential application to biological remediation of waste sites. Appl. and
Environ. Microbiol. 4:1,012-1,016.
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Phytoremediation
Growing plants to clean
contamination from soil,
water, or sediments
Daniel Pope
Dynamac Corporation
Ada, OK
Early Indications of
Phytoremediation Potential
Plants have been used for
prospecting for
mineralsGeobotany
Wetlands have been found to
neutralize acidic mine drainage
Certain plants can help
degrade contaminants,
others can take up
contaminants
Figure 1. Hypothetical
Mechanism
Change In
Root Exudation
Exudates Stimulate
Mlcroblal Community
Figure 2.
Diagram of
Phyto-
remediation
Seminar Series on Bioremediation of Hazardous Waste Sites: Practical Approaches to Implementation
8-6
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Table 1. Examples of Metal
Hy peraccumulators
Metal
ZN
Cu
Ni
Pb
Co
Plant Species
Thlaspi calaminare
Viola species
Aeolanthus biformifolius
Phyllanthus serpentinus
Alyssum bertoloni
and 50 other alyssum
species
Sebertia acuminata
Stackhousia tryonii
Brassuca juncea
Haumaniastrum robertii
Metal in Dry
Weight of
Leaves(%)
<3
1
1
3.8
>3
25 (in latex)
4.1
<3.5
1
Original
Location
Germany
Europe
Zaire
New Caledonia
Southern
Europe and
Turkey
New Caledonia
Australia
India
Zaire
Mature cottonwood or
poplar will pump and
treat 25 to 300 gallons of
water per day
Phy tor erne diation Project for
the Chevron Ogden Terminal
by Phytokinetics
Treating TPH in soil with
grass and alfalfa; Treating
TPH in ground water with
poplar and juniper
Site Map
Phy tor erne diation uses
slightly modified standard
agronomic practices
Seminar Series on Bioremediation of Hazardous Waste Sites: Practical Approaches to Implementation
8-7
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Treatability study in
greenhouse to determine
best species for site
Schematic
of Soil
Column
Phytoremediation in Soil Is
Best Applied to:
Soil: widespread, fairly shallow,
low to medium concentration
contamination
Ground water: shallow (to 20'
easily, some claim deeper)
Treatment
Depth
Poplar Trees
to 20 ft
Mustard Alfalfa
18in. 48in.
Advantages of
Phytoremediation
Less expensive with low
installation and maintenance
cost
High public acceptance
Can clean chronic pollution
sources (i.e., acid mine seeps)
Disadvantages of
Phytoremediation
At least 2-3 years for cleanup
Most contaminants not tested
extensively except for
hydrocarbons, pesticides, and
agricultural nutrients
Seminar Series on Bioremediation of Hazardous Waste Sites: Practical Approaches to Implementation
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Field Experience
Field-scale demonstrations on
hazardous waste are underway in:
Oregon Utah California
Texas Ohio Virginia Maryland
Seminar Series on Bioremediation of Hazardous Waste Sites: Practical Approaches to Implementation
8-9
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Development and Application of Composting Techniques for Treatment of
Soils Contaminated With Hazardous Waste
Carl L. Potter
Office of Research and Development, National Risk Management Research Laboratory,
U.S. Environmental Protection Agency, Cincinnati, OH
Introduction
Historically, composting has been used to degrade solid waste materials such as leaf litter, sewage
sludge, and food wastes. More recently, composting has been investigated as a remediation
technology for hazardous wastes (1). Laboratory and field-scale work has been conducted to
determine the fate of polycyclic aromatic hydrocarbons (2) and explosives (3) in the composting
environment. Composting is not generally employed to treat heavy metals or other inorganics,
although it may be applicable to inorganic cyanides. Other studies have indicated that composting
is potentially effective in degrading or transforming petroleum hydrocarbons (4, 5) and pesticides
(6) to environmentally acceptable or less mobile compounds.
Process Description
Optimum conditions for composting may vary depending on a number of factors, but generally 40
to 60 percent moisture content, a carbon-to-nitrogen ratio of 20:1 to 30:1, and aerobic conditions
are considered best. Bulking agents may consist of sawdust, corn cobs, straw, hay, alfalfa, peanut
hulls, or other organic materials.
The aerobic compost process passes through four major microbiological phases, identified by
temperature: mesophilic (35° to 55°C), thermophilic (55° to 75°C), cooling, and maturation. The
greatest microbial diversity has been observed in the mesophilic phase. Microbes found in the
thermophilic phase have been spore-forming bacteria (Bacillus spp.) (7) and thermophilic fungi (8,
9). Microbial recolonization during the cooling phase brings the appearance of mesophilic fungi
whose spores withstood the high temperatures of the thermophilic phase. Composting can be
anaerobic, but most methods use aerobic conditions.
Composting can be performed in windrows, where material is put into rows and periodically turned;
aerated static piles, where perforated pipes within the pile supply air; and vessels, where material
is periodically mixed inside an aerated containment vessel.
Seminar Series on Bioremediation of Hazardous Waste Sites: Practical Approaches to Implementation
9-1
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Future Research
Despite promising studies, the ability of composting to completely degrade synthetic organic
compounds has not been fully demonstrated. Although composting systems have been used to
biodegrade some hazardous compound, few studies (mostly bench-scale) have provided mass
balance closures or fully investigated all of the intermediate products, final products, and byproducts
of the composting process. The lack of mass balance closure and conclusive evidence of the fate
of contaminants in field-scale applications is not unique to composting. Many other technologies
(both ex situ and in situ) lack conclusive evidence of contaminant fate in field-scale applications.
Future investigations will include technical developments necessary to improve composting
applications for degradation of hazardous waste. This will involve increased application of pilot-scale
composting systems in addition to ongoing research in bench-top composters. Emphasis will be
placed on developing techniques for trapping volatile organic compounds from pilot-scale systems,
determining mass balance of contaminant degradation in the compost, and identifying microbial
species responsible for biodegradation of contaminants.
Future studies will also attempt to validate extrapolation of results from bench-top to pilot-scale and
field demonstration levels. Maintaining a bench-top system at optimum conditions is relatively easy
compared with a large-scale composter where optimum conditions will not prevail at all times. The
degree of variance from optimal conditions requires investigation and approximation in small-scale
systems.
References
1. Ziegenfuss, P.S., and T.R. Williams. 1991. Hazardous materials composting. J. Haz. Mat.
28:91-99.
2. U.S. EPA. 1995. On-scene coordinator's report: Removal action at the Indiana
Woodtreating Corporation Site, Bloomington. Site ID# R.D. Draft.
3. U.S. Army Corps of Engineers, Toxic and Hazardous Materials Agency. 1991.
Optimization of composting for explosives contaminated soil. Final Report No. CETHA-TS-
CR-91053. November.
4. U.S. EPA. 1995. Bioremediation in the field. EPA/540/N-95/500. August.
5. Moore, R.E. 1992. Enhanced bioactivity treats hydrocarbon-contaminated soils. Natl.
Environ. J. January/February:34-37.
6. Michel, F.C., C.A. Reddy, and L.J. Forney. 1995. Microbial degradation and humification
of the lawn care pesticide 2,4-dichlorphenoxyacetic acid during the composting of yard
trimmings. Appl. Environ. Microbiol. July:2,566-2,571.
Seminar Series on Bioremediation of Hazardous Waste Sites: Practical Approaches to Implementation
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7. Nakasaki, K., M. Sasaki, M. Shoda, and H. Kubota. 1985. Change in microbial numbers
during thermophilic composting of sewage sludge with reference to CO2 evolution rate.
Appl. Environ. Microbiol. 49(1):37-41.
8. Strom, P.P. 1 985. Identification of thermophilic bacteria in solid-waste composting. Appl.
Environ. Microbiol. 50(4):906-91 3.
9. Fogarty, A.M., and O.H. Tuovinen. 1 991. Microbiological degradation of pesticides in
yard waste composting. Microbiol. Rev. June:225-233.
Seminar Series on Bioremediation of Hazardous Waste Sites: Practical Approaches to Implementation
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COMPOSTING
Composting
Presented by
Gregory Sayles or Dolloff F. Bishop
Office of Research and Development
National Risk Management Research Laboratory
U.S. Environmental Protection Agency
Cincinnati, Ohio
Definition
... method of solid waste management whereby
the organic component of the solid waste stream
is biologically decomposed under controlled
conditions to a state in which it can be handled,
stored, and/or applied to the land without
adversely affecting the environment
Golueke, 1977
COMPOSTING PROCESS
WASTE STREAMS
MIX SOIL WITH:
Bulking Agent (Sawdust com cobs, straw)
Moisture
Nutrients (Manure, Sludge, Food Scraps)
Wood Treating Waste
Oil Separator Sludge
Pesticides
Halogenated Aromatic Hydrocarbons
Munitions Wastes
COMPOSTING PRINCIPLES
Operation can be conducted under both
aerobic and anerobic conditions
A wide variety of cheap bulking agents
are available
Desired biological activities can be
selected by process manipulation
Can operate under mesophlllc and
thermophillc conditions
Inoculation with nonlndlgenous
microorganisms Is possible
LIMITATIONS OF COMPOSTING
Metals May be Toxic to Microorganisms
Metals Cannot be eliminated by Microorganism
Some Organic Compounds May Not be
Metabolized
Seminar Series on Bioremediation of Hazardous Waste Sites: Practical Approaches to Implementation
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of and
of
Time
* of
-
-
OF
Pile
- air
- Turn pile to
In-Vessel
- air
-
-
Windrow Compost System
Windrow
Mobile Composter
ADVANTAGES
« to of
« low
- pad for
-
-
«
«
DiSAD₯ANTAGES
« Not apace efficient
« Equipment Mtntmunc* can to* significant
Aeration Is highly dapcMtenton opontoc Ull
to
*
volume of buBdng
Pttor of rate In
Schematic Diagram of
Extended Aerated Pile
Bulking Materials and Sludge
Unscreened
or Screened
Compost
Perforated Trap for <
Pipe Water
Filter Pile
Screened
Compost
Composting Extended Piles with Forced Aeration
Seminar Series on Bioremediation of Hazardous Waste Sites: Practical Approaches to Implementation
9-5
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Static Pile Composter
Side View
z
Top View NAsphalt
\
Nutrients
Aeration
Microorganisms
aJtt
Plastic Piping
/(Compatible with Contaminants)
ADVANTAGES
Static Pile Systems
Low capital costs
More space efficient than windrow
Process control may be partly automated
Downflow system can be Interfaced with a
biofilter to control VOCs
DISADVANTAGES
Static Pile Systems
Requires more land than in-vessel option
Requires higher energy input than windrow
Subject to the influence of climate conditions
Poor control of pollutant fate In treatment
system
co,<^Mixer; xlnfeed
Composting
Mix
Air/
In-Vessel
Composter
- Outfeed
ADVANTAGES
In-Vessel Systems
Space efficiency
Improved process control over open
systems
Process control may be automated
Independent of climate
Facilitates mass balance monitoring
DISADVANTAGES
In-Vessel Systems
High capital investment
General lack of operating data
Process susceptible to mechanical disruption
Compost compaction may confound results
Low operational flexibility
Seminar Series on Bioremediation of Hazardous Waste Sites: Practical Approaches to Implementation
9-6
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PAH contaminated soil Rellly Tar Pit
Situ, Si, Louis UN
Soil
40% - am*
Air flow:
Sl/mln
50 (for
Daily Compost Temperature
0 i" i Temperature 40 - 50C
50
' /Vv
Reactor 2
Degrees
C
10- JO JO 40 SO fiO /I) BO
Days ol Composting
Daily Compost Tcmperatyre
to j - '70/30 Soil/Cobs
40 ' ii
Degrees P
f~ ' '
50
i r Formal in "Kilted" -i i
40
Degrees
C
r S
r10
0 10 20 »o so so t,n 7E! an
Days of Comporting
10 20 30 40 SO 60
Days of Composting
Ring PAH
4-6 Ring PAH
2345
Weeks of tomposnrsg
Weeks ol Composting
Seminar Series on Bioremediation of Hazardous Waste Sites: Practical Approaches to Implementation
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Total PAH
50 50 40
bO 50 50
50 50 60
70 30
Killed
Conclusions
Composting reduced soil concentrations
of PAHs over a 10-week treatment period
30% bulking as effective as 50% for
remediation of PAH during first 10 weeks
PAH degraders withstood temperature as
high as 56°C
Weeks ol Compostinq
Field Example
Indiana Woodtreating Corp. Site
22,000 tons of PAH-
contaminated soil
Soil screened to
remove rocks >3
inches
Indiana Woodtreating
Corp. Site
Each 100 tons mixed with:
5 rolls straw
5 bails horse manure
200 Ibs. urea fertilizer
100 Ibs. ammonium nitrate
fertilizer (34-0-0)
Soil treated in 9 piles
Indiana Woodtreating
Corp. Site
Initial total soil
PAH (TPAH): 20,410 mg/kj
Action levels:
TPAH 500 mg/kg
Each carcinogenic PAH 100
Indiana Woodtreating
Corp. Site
Results of Test
After 1 year of
composting:
TPAH <500 mg/kg
Additional 1 year
of treatment
using land
farming: TPAH <100 mg/kg
Seminar Series on Bioremediation of Hazardous Waste Sites: Practical Approaches to Implementation
9-8
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Biopile Treatment of Soils Contaminated With Hazardous Waste
Carl L. Potter
Office of Research and Development, National Risk Management Research Laboratory,
U.S. Environmental Protection Agency, Cincinnati, OH
Introduction
Biopile systems offer the potential for cost-effective treatment of contaminated soils. Like
composting, biopiles provide favorable environments for indigenous microorganisms to degrade
contaminants present in the soil matrix. Although similar to compost piles, these systems differ in
that lesser quantities of bulking agents are used in biopile units. Air is supplied to the biopile system
through a system of piping and pumps that either forces air into the pile under positive pressure or
draws air through the pile under negative pressure (1). Depending on the contaminants in the soil,
conditions are established in the biopile to favor either anaerobic or aerobic microorganisms. In
some cases, exogenous microbes, such as fungi, may be added to the biopile to enhance
contaminant degradation.
Field studies have indicated biopile successes in remediation of soils contaminated with
pentachlorophenol (2) and petroleum hydrocarbons (3). Costs of soil bioremediation using biopiles
range from $30 to $100 per ton of soil, depending on soil conditions and the biodegradability of
contaminants.
Process Description
Biopile structure resembles a static pile compost system. Conceptually, one may think of a biopile
as an ex situ bioventing system in that aeration usually involves forcing air through the soil by
injection or extraction through perforated pipes. Volatile organic compound emissions can be
controlled by aerating the pile with negative pressure and venting off gases into a small compost pile
or biofilter (1).
Optimum conditions for biopiles vary depending on the type of soil, climate conditions, and the
chemical and biological attributes of the soil. Because biopile treatment is an ex situ technology,
most conditions can be controlled to achieve an acceptable range of conditions. Generally,
moisture content between 40 and 85 percent of soil field capacity, a carbon-to-nitrogen ratio of
10:1 to 100:1, and pH between 6 and 8 are acceptable depending on soil conditions. Organic
amendments can be used to increase the water-holding capacity of poor soils.
Wood chips may be added as bulking agents to increase soil porosity and promote aeration and
irrigation. Sawdust or straw can be added to supply carbon. Animal manure (1 to 4 percent w/w)
can supply both carbon and nutrients.
Seminar Series on Bioremediation of Hazardous Waste Sites: Practical Approaches to Implementation
10-1
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Future Studies
Future studies are needed to evaluate the applicability of biopile technology and to optimize systems
for treating an increased variety of contaminants. Alternating between anaerobic and aerobic
conditions may provide a mechanism for degrading heavily chlorinated organic compounds via
reductive dehalogenation combined with oxidative mineralization (4).
Also, soil microbiology and fungal treatment will receive increased focus in the future. Fungal
technology appears promising for biodegradation of recalcitrant contaminants (5). Fungi do not
generally metabolize contaminants; degradation occurs extracellularly by enzymes excreted by the
fungi. Much research remains to be done to identify the fungal strains most capable of degrading
specific contaminants.
References
1. Lei, J., J.-L. Sansregret, and C. Benoit. 1994. Biopiles and biofilters combined for soil
cleanup. Poll. Eng. June:56-58.
2. McGinnis, B., R.R. DuPont, and K.E. Everhart. 1992. Determination of respiration rates
in soil piles to evaluate aeration efficiency and biological activity. Presented at the 85th
Annual Meeting of the Air and Waste Management Association, Kansas City, MO, June 21 -
26.
3. Moore, R.E. 1992. Enhanced bioactivity treats hydrocarbon-contaminated soils. Natl.
Environ. J. January/February:34-37.
4. Sims, J.L., J.M. Suflita, and H.H. Russell. 1991. Reductive dehalogenation of organic
contaminants in soils and ground waters. In: EPA Ground Water. EPA/540/4-90/054.
5. Closer, J.A., and R.T. Lamar. 1995. Lignin-degrading fungi as degraders of
pentachlorophenol and creosote in soil. In: Bioremediation: Science and Applications.
SSSA Special Pub. No. 43:117-133.
Seminar Series on Bioremediation of Hazardous Waste Sites: Practical Approaches to Implementation
10-2
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Biopile s
Aerated Static Soil Piles for
Treatment of Shallow
Contaminated Soil
Schematic Diagram of
Extended Aerated Pile
Nutrient Materials
Presented by
Gregory Sayles or Dolloff F. Bishop
Office of Research and Development
National Risk Management Research Laboratory
U.S. Environmental Protection Agency
Cincinnati, Ohio
Unscreened
or Screened
Soil
Perforated
Pipe
Extended Soil Piles With Forced Aeration
Trap for
Water
Filter Pile
Screened
Compost
Biopile Systems
Biopile Design
Potential to provide cost-effective
treatment
Provide a favorable environment
for indigenous aerobic or
anaerobic microorganisms
Similar to compost piles
Air delivery system
Nutrient enhanced
Pile Size
Height = 3 to 10 feet
Width is unrestrited unless pile is turned
6 to 8 feet if turned
Land Requirements
Amount of soil treated/Pile height
Additional land required for:
Berms
Access
Sloping terrain
Biopile Design (continued)
Aeration Equipment
Blowers or fans
Aeration piping in pile lifts
Turning equipment if pile is turned
Biopile Construction
Site preparation
Clearing and grading
Berms, liners, and covers (if needed)
Piping
Moisture addition
Nutrient addition
Aeration (if forced air)
Biopile Design (continued)
Leachate Management
Collection
Treatment
Soil Pretreatment
Shredding
Blending
Amendments
Bulking agents (increase porosity)
pH adjustment
Seminar Series on Bioremediation of Hazardous Waste Sites: Practical Approaches to Implementation
10-3
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Biopile Soil Conditions
Economic Considerations
Moisture
pH
Temperature
C:N:P
Heavy metals
40% < Field capacity < 85%
6
Field Soil Experiment Characteristics
v.ilpilf Initial PtP
land farm #! ,IH
I.mi1 I-IITII « ?8fl
\inlnl«l 122
\ cnti-fl : 44)
1 !.' I1I..I
Mil |"l- 1SJ
Fin,il PCP
III]
5*6
t«
II
il
ilapstd IIIIK
in i".-.^ >
182
1X6
239
242
. -
tvttlf, ; 1
J 1409!
4 1^\
4 "5J
F Mf.
Seminar Series on Bioremediation of Hazardous Waste Sites: Practical Approaches to Implementation
10-4
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Conclusion
Vented soil piles are as effective if
not more effective than landfarms
Seminar Series on Bioremediation of Hazardous Waste Sites: Practical Approaches to Implementation
10-5
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Effective Treatment of Hazardous Waste Constituents in Soil by
Lignin-Degrading Fungi
John A. Glaser
Office of Research and Development, National Risk Management Research Laboratory,
U.S. Environmental Protection Agency, Cincinnati, OH
Introduction
The diversity of fungi and their remarkable ability to degrade complex and persistent natural
materials (Table 1) such as lignin exemplify the host of useful features (1) found with these
organisms. In contrast to bacteria, fungi are able to extend the location of their biomass through
hyphal growth in search of growth substrates. Lignin-degrading fungi have been investigated for their
enzymatic activity to degrade aromatic organic chemicals, which are structurally related to the
composition of lignin. Enzymes involved in lignin breakdown are extracellular and have low substrate
specificity. Fungi can thoroughly colonize soil and show exceptional tolerance to high concentrations
of toxic pollutants. Chemical structural similarities and expected reactivities between lignin and
organic pollutants have fostered the consideration of these fungi as potential pollutant degraders.
White rot fungi are unique in their ability to transform all components of native lignin to carbon
dioxide and water. Lignin is constructed of an amorphous polymeric network that resists attack by
many microbes. Three major classes of oxidative enzymes designated, lignin peroxidases (LIPs),
manganese-dependent peroxidases (MnPs), and laccases, play an important role in the fungal
degradation of lignin. All three enzymes can oxidize phenolic compounds, thereby creating phenoxy
radicals. Nonphenolic aromatic compounds, however, are oxidized via cation radicals. Laccase can
oxidize nonphenolic compounds with relatively low ionization potential, while nonphenolics with high
oxidation potential are readily oxidized by LIPs and MnPs.
Pollutant Degradation
Extensive lists of xenobiotic organic chemicals currently considered degradable by lignin-degrading
fungi have been compiled. Contaminant categories to which lignin-degrading fungi have been
applied are wood-treating/town gas chemicals, munitions, and pesticides and other chlorinated
organic chemicals. Fungal bioremediation is an emerging technology that has been applied in the
field only to wood treating wastes (pentachlorophenol and creosote). Application to other
contaminants requires field evaluation.
Field-Scale Evaluation
Application of fungal treatment in beds of contaminated soil (2) was studied at an Oshkosh,
Wisconsin site (Figure 1). The contamination was a wood preservative formulation composed of 5
Seminar Series on Bioremediation of Hazardous Waste Sites: Practical Approaches to Implementation
11-1
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percent pentachlorophenol (PCP) in mineral spirits. Soil concentrations of 1 to 4,435 mg/kg to
depths of 30 cm were determined through extensive sampling. Blended soil, with the larger stones
and rocks removed, was added to each soil bed. Two fungi (Phanerochaefe chrysosporium and P.
sordida) were selected as candidate treatment species (Table 2) for the evaluation. The fungi were
added to the contaminated area using spore inoculated/infested wood chips with the appropriate
fungal strain. The pentachlorophenol concentration (Table 3) was depleted by 82 percent for P.
chrysosporium and 85 percent for P. sordida, after 56 days of treatment, despite temperatures that
dipped below the temperature range considered optimal for these fungi. P. sordida is a known soil
inhabitant and can tolerate lower soil temperatures than P. chrysosporium. P. sordida is known to
have a lower optimum temperature (30°C) than P. chrysosporium (40°C).
Some of the decrease in PCP is by methylation-producing pentachloroanisole (PCA), the methyl
ether of PCP (Table 4). PCA accumulation in the treatment plots was monitored and did not increase
with time, suggesting that degradation of PCA occurs in the inoculated soil. Transformation of PCP
to PCA is evident in both liquid and soil cultures and seems to compete with other PCP
transformation reactions (i.e., oxidation). In laboratory soil cultures (3) inoculated with P.
chrysosporium, the amount of soil-bound versus an organic extractable PCP-transformation product,
later identified as PCA, was greatly influenced by soil type. PCP oxidation may be enhanced further
by identifying the soil conditions that favor oxidation over transformation to PCA.
Another treatment effectiveness study (Figure 2) for fungal treatment of PCP-contaminated soil (Table
5) was conducted at an abandoned wood treating site at Brookhaven, Mississippi. The field study
(Figure 3) was a two-phase field assessment. The first phase (4) was designed (Table 6) to evaluate
the ability of three different fungal species to deplete PCP in soil. P. sordida was superior in its ability
to deplete PCP in soil. The results for depletion of PCP by P. sordida paralleled the results of the
Wisconsin study, where the inoculation with either P. chrysosporium or P. sordida was applied to soil
contaminated with 250 to 400 //g/g PCP. In the Brookhaven study, P. sordida treatment (Figure 4)
resulted in an overall decrease of 88 to 91 percent at PCP concentrations of 672 mg/kg in 6.5
weeks. P. chrysosporium treatment reduced PCP by 67 to 72 percent in multiple soil beds at PCP
concentrations greater than 1,000 mg/kg.
The Brookhaven site was also contaminated with 4,017 //g/g of total polynuclear aromatic
hydrocarbons (PAHs), other components of creosote. The effects of solid-phase bioremediation with
P. sordida (with two control treatments) on soil concentrations of 14 priority pollutant PAHs (5) were
determined over a 56-day period.
Depletion of both three- and four-ring PAH analyses (Table 7) in P. sordida-treated soil was greater
than in the controls. Concentrations of the three-ring analyses decreased by an average of 31
percent after 7 days and by an average of 91 1 after 56 days. Four-ring analyses were more
persistent; losses first became apparent between 1 4 and 28 days of treatment, and an average of
45 percent was depleted after 56 days. Five- and six-ring analyses were the most recalcitrant
species, persisting at original levels throughout the course of the study. The persistence of these
compounds in soil is due to their low bioavailability when bound to soil particles. Depletion of five-
ring analyses of PAHs, however, have been reported by some researchers under conditions providing
a higher fungusxontaminant ratio than that used in this evaluation.
Seminar Series on Bioremediation of Hazardous Waste Sites: Practical Approaches to Implementation
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A larger scale demonstration (Figure 5) of the P. sordida treatment (6) was conducted as the second
phase of the study. Inoculation of the soil with a 10-percent dry weight inoculum consisting of fungal
hyphae and growth substrate reduced PCP soil concentrations of greater than 1,000 mg/kg by 64
percent after 20 months of treatment (Figure 6). The two control soil beds showed reductions of 1 8
and 26 percent of the PCP soil concentration.
Low initial amounts (Table 8) of fungal biomass, measured by ergosterol analysis, may have
contributed to the reduced performance. Heavy rains and weather-related modification to the tilling
schedule may also have limited the performance of the P. sordida treatment.
P. chrysospor/um ATCC 24725-based treatment was applied to 6,000 cubic meters of soil
contaminated with a mixture of chlorophenols, known as KY-5, at a site in Finland (7, 8). Initial
concentrations of total chlorinated phenols decreased with depth of excavated soil layers ranging
from 203 to 38 mg/kg. Contaminant composition of the constructed fungal treatment piles varied
with the order of excavation. Soil contaminant reduction depended on the initial contaminant
concentration. Concentrations of total chlorinated phenols between 1 73 and 203 mg/kg were
reduced by 85 and 90 percent after 20 months of treatment (Table 9). After only 12 weeks,
chlorophenol concentrations of 38 to 84 mg/kg were reduced by 80 to 90 percent to target
endpoints of less than 1 0 mg/kg. One of the piles produced poor contaminant depletion kinetics,
which was attributed to soil processing and pile construction.
Conclusions
Removal of PCP has now been demonstrated (Table 6) in a strongly acidic (pH 3.8) Mississippi clay
soil and in alkaline (pH 9.6) Wisconsin sandy gravel soil. This strongly supports the potential of fungi
for treating organic pollutants in a wide range of soils having varied physical and chemical
characteristics.
In the Mississippi test, P. sordida was capable of reducing an initial soil PCP concentration of 672
mg/kg by 89 percent using a 101 inoculum loading level by dry weight. The depletion of three-ring
and four-ring analyses of PAHs (total measured PAHs, 4,017 ppm) by P. sordida was also
promising, with reductions of 85 to 95 percent and 24 to 72 percent, respectively. These
percentage depletions for PCP and the PAH analyses were, in the Mississippi test, obtained after
only 56 days of experimentation.
References
1. Closer, J.A., and R.T. Lamar. 1995. Lignin-degrading fungi as degraders of
pentachlorophenol and creosote in soil. In: Bioremediation: Science and applications. SSSA
Special Publication 43. Soil Science Society of America, pp. 1 1 7-1 33.
2. Lamar, R.T., and D.D. Dietrich. 1990. In situ depletion of pentachlorophenol from
contaminated soil by Phanerochaefe ssp. Appl. Environ. Microbiol. 56:3,093-3,100.
Seminar Series on Bioremediation of Hazardous Waste Sites: Practical Approaches to Implementation
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3. Lamar, R.T., J.A. Closer, and T.K. Kirk. 1 990. Fate of pentachlorophenol (PCP) in sterile
soils inoculated with the white-rot basidiomycete Phanerochaete chrysosporium:
Mineralization, volatilization and depletion of PCP. Soil Biol. Biochem. 22:443-440.
4. Lamar, R.T., J.W. Evans, and J.A. Closer. 1993. Solid-phase treatment of
pentachlorophenol-contaminated soil using lignin-degrading fungi. Environ. Sci. Technol.
27:2,566-2,571.
5. Davis, M.W., et al. 1 993. Field evaluation of the lignin-degrading fungus Phanerochaete
sordida to treat creosote-contaminated soil. Environ. Sci. Technol. 27:2,572-2,576.
6. Lamar, R.T., et al. 1 994. Treatment of a pentachlorophenol- and creosote-contaminated
soil using the lignin-degrading fungus Phanerochaete sordida: A field demonstration. Soil
Biol. Biochem. 26:1,603-1,611.
7. Holroyd, M.L., and P. Count. 1994. Fungal processing: A second generation biological
treatment for the degradation of recalcitrant organics in soil. Land Contamin. Reclam.
O. 1 QO 1 QQ
z: I do-1 do.
8. Holroyd, M.L., and P. Count. 1 995. Large-scale soil bioremediation using white rot fungi.
In: Hinchee, R.E., J. Fredrickson, and B.C. Alleman, eds. Bioaugmentation for site
remediation. Columbus, OH: Battelle Press, pp. 181-187.
Seminar Series on Bioremediation of Hazardous Waste Sites: Practical Approaches to Implementation
11-4
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Effective Treatment of
Hazardous Waste
Constituents in Soil by
Lignin-Degrading Fungi
Presented by
Gregory Sayles or Dolloff F. Bishop
Office of Research and Development
National Risk Management Research Laboratory
U.S. Environmental Protection Agency
Cincinnati, Ohio
Table 1. Rationale for
Fungal Biotreatment
Enzyme systems capable of degrading
complex natural aromatic polymers
Chemical structure of natural
polymers resemble many organic
pollutants
Fungi have the ability to reach remote
areas of the soil by extension of
hyphae
Selection Criteria
Powerful oxidizing enzymes
Extracellular
Broad range substrate specificity
Multiplicity of isoenzymes
Ability to move throughout the soil
Genetic Stability
Classes of Oxidative
Enzymes
Ligninperoxidases
(LIPS)
Manganeses-dependent
peroxidases (Mn Ps)
Laccases
Contaminant Categories Where
Lignin-Degrading Fungi
Applied
Wood treating wastes*
Town gas chemicals
Munitions
Pesticides and other
chlorinated organics
' Only waste having significant field testing
Figure 1. Wisconsin Site Layout
Seminar Series on Bioremediation of Hazardous Waste Sites: Practical Approaches to Implementation
11-5
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Wisconsin Soil
Characteristics
Characteristic
Value
Texture
PH
Pollutant cone.
CEC
Total carbon (96)
Sulfur (96)
Gravel/sand
9.6
250-400 mg/kg
17.22
8.95
0.14
Table 2. Wisconsin
Treatment Systems
Inocula Sterile Organic
Conditions P. chrysosp. P. sordida chips matter
Treatment Al + - + +
A2 - + + +
Controls B - - + +
C - - + -
D - - - +
E - -
Table 3. Wisconsin PCP
Decrease
Percent PCP Decrease
Conditions
Al
A2
B
C
D
E
Day 8
9.1
9.7
4.9
0.5
15.3
10.9
Day 15
33.3
42.2
13.7
-10.0
26.1
13.8
Day 29
70.6
75.9
20.9
7.1
10.7
23.8
Day 46
82.3
85.8
27.5
16.2
3.0
19.1
Table 4. Wisconsin PCA
Conversion
Percent PCP Converted to PCA
Conditions
Al
A2
B
C
D
E
Day 1
1.3
0.8
0.8
1.3
0.5
0.6
Day 15
13.1
6.6
1.4
2.3
0.9
0.9
Day 29
13.0
9.4
1.1
1.4
0.6
0.8
Day 46
14.1
9.1
0.7
1.5
0.6
0.7
Figure 2. Brookhaven Site Location
Table 5. Mississippi Soil
Characteristics
Characteristic
Texture
pH
Pollutant cone.
Total carbon (%
Total nitrogen (
Value
Sandy Clay
3.8
PCP 429-5,200 mg/kg
(ave.) 2,355 mg/kg
2.2
0.04
Seminar Series on Bioremediation of Hazardous Waste Sites: Practical Approaches to Implementation
11-6
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Figure 3. Unit Processes in Site
Preparation
Table 6. Mississippi
Experimental Design
Amendment
Quantity (dry wt)
P. chrysosporium
P. sordida
P. chrysosp./T. hirsuta
T. hirsuta
P. chrysosporium
P. chrysosporium
No treatment, wood chip,
and inoculum controls
5.0% and 10.0%
10.0%
5.0% each
10.0%
13.0%
10.0%; 3.0% (day 14)
-, -, 10.0%
Figure 4. Treatment
Performance
Table 7. Transformation of
PAHs
% Decrease
Compound
Acenapthene
Phenanthrene
Anthracene
Fluoranthene
Chrysene
Init. Cone.
(mg/kg)
429
941
684
972
90
No Treatment
Control
49
69
57
23
6
Carrier
Control
68
49
48
42
14
P. sordida
Treatment
95
90
285
72
233
Figure 5. Demo Treatment Plot
Perspective
Figure 6. Pentachlorophenol
Depletion
Demonstration Study
Seminar Series on Bioremediation of Hazardous Waste Sites: Practical Approaches to Implementation
11-7
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Table 8. Ergosterol
Evaluation
Inoculum
Raw soil
Inoculated soil
Cone, (mg/kg)
Found Expected
241
0.2
4 24
Table 9. Transformation of
Chlorinated Phenols
Finland Field Application (20 Month Treatment)
Treatment Init. TOLX Cone.*
Bed (mg/kg)
Init. TCP Cone.* P. chrysosporium
(mg/kg) Pile pH Treatment Removal
A
B
C
D
2,727
816
203
173
84
38
7.1 85%
94%
7.7 -
*TOLX = Toluene extract; TCP = Total Chlorophenols
Fungal Treatment
Summary
Treatment of pentachlorophenol occurred for
concentrations greater than 1,000 mg/kg
Consistent transformations values for PCP of 80
to 90% occurred for the Wisconsin and
Mississippi sites
Soil pH does not apparently affect the fungal
treatment because pH values for the sites ranged
from 3.5 to 9.2
Fungal treatment in 56 days efficiently
transformed three-ring PAHs by 85-95%; four-ring
PAHs by 24-72%
Seminar Series on Bioremediation of Hazardous Waste Sites: Practical Approaches to Implementation
11-8
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Slurry Bioreactors for Treatment of Contaminated Soils, Sludges, and
Sediments
Paul McCauley and John Closer
Office of Research and Development, National Risk Management Research Laboratory,
U.S. Environmental Protection Agency, Cincinnati, OH
Introduction
A slurry bioreactor may be defined as a containment vessel and apparatus used to create a three-
phase (solid, liquid, and gas) mixing condition to hasten the biodegradation of soil-bound and
water-soluble contamination as a water slurry of the contaminated soil, sediment, or sludge and
biomass (usually indigenous bacteria) capable of degrading targeted contaminants.
Advantages and Limitations
Bioremediation of contaminated soils, sludges, and sediments using slurry bioreactors offers several
advantages over other remediation technologies:
Intimate contact between microbiota and contaminants combined with process
controls such as (but not limited to) pH, temperature, and nutrients provide
conditions favorable for rapid remediation of targeted contaminants.
Since most reactor vessels fully contain the contaminated solid and liquid fractions,
they offer almost unlimited treatment flexibility. Nutrient amendments, which in
some cases may not be permitted in situ (such as ammonium and nitrate), may be
used in a slurry bioreactor. Other amendments that can be used in slurry
bioreactors include designer bacteria, surfactants, and enzyme inducers. Slurry
bioreactors may be fitted to provide sequential anaerobic/aerobic treatment
conditions. Slurry bioreactors may fit into various treatment trains, which must
include particle size separation (most slurry bioreactors do not accept particles
larger than VA inch in diameter) and commonly include soil washing. Slurry
bioreactors can be operated in batch mode (at least 1 0 percent of the slurry should
be reserved for seeding subsequent batches), or several bioreactors can be
sequentially linked for continuous or semicontinuous operation.
Most bioreactor vessels fully contain the contaminated solid and liquid fractions and
can be designed to contain volatile contaminants; they offer a high degree of safety
as related to contaminant containment.
Slurry bioreactors require a relatively small space compared to technologies such
as land treatment, biopiles, and composting. Many slurry bioreactors may be
mounted on trailers and transported for use at several sites.
Seminar Series on Bioremediation of Hazardous Waste Sites: Practical Approaches to Implementation
12-1
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Slurry bioreactors also have limitations:
Bioslurry is an ex situ process, which by definition requires excavation and transport
(even if only a few feet) of the contaminated waste.
Reactor mixers consume energy.
Slurry bioreactors generally will not accept particles larger than VA inch in diameter,
requiring soil sieving or some other type of particle size separation. Sand particles
are highly abrasive in slurry bioreactors, shorten their operating life, and generally
contain a small fraction of the contamination. Operators often choose
hydrocycloning for sand fraction rejection.
Bioslurrys require dewatering after remediation is terminated.
There is a limited history of full-scale bioslurry operations. Although there are many
pilot studies, slurry bioreactors are not easily scaled upward in size. Some
investigation or experimentation may be required to achieve optimal operating
conditions in a full-scale operation. These limitations will increase the cost of
remediation by slurry bioreactors.
Waste Streams
Contaminants that have been successfully remediated using slurry bioreactors include wood treating
waste, oil separator sludge, munitions, pesticides (not including highly chlorinated pesticides), and
halogenated aromatic hydrocarbons. Slurry bioreactors have been used most frequently to remediate
creosote.
Case Study
OHM, Inc., conducted large-scale slurry bioreactor remediation of creosote-contaminated lagoon
solids stabilized with fly ash (total polycyclic aromatic hydrocarbons [PAHs] of 1 1 g/kg). Extensive
classification of contaminated solids was accomplished and included screening and hydrocycloning.
Slurry bioreactors with a 750,000-liter operating capacity were used to treat a 20-percent slurry.
The results were mixed with 82 to 99 percent remediation of the three- to four-ring PAHs and 34
to 78 percent remediation of the five- to six-ring PAHs.
Bibliography
1. Berg, J.D., T. Bennett, B.S. Nesgard, and A.S. Eikum. 1 993. Slurry phase biotreatment of
creosote-contaminated soil. In: Speaker abstracts: In Situ and On-Site Bioreclamation, the
Second International Symposium, San Diego, CA.
Seminar Series on Bioremediation of Hazardous Waste Sites: Practical Approaches to Implementation
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2. Cioffi, J., W.R. Mahaffey, and T.M. Whitlock. 1 991. Successful solid-phase bioremediation
of petroleum-contaminated soil. Remediation 373-389.
3. Closer, J.A., and P.T. McCauley. 1993. Soil slurry bioreactors: A perspective. In: Speaker
abstracts: In Situ and On-Site bioreclamation, the Second International Symposium, San
Diego, CA.
4. Griffin, E.A., G. Brox, and M. Brown. 1 990. Bioreactor development with respect to process
constraints imposed by bio-oxidation and waste remediation. Appl. Biochem. Biotechnol.
24/25:627-635.
5. Irvine, R.L, J.P. Barley, and P.S. Yocum. 1 992. Slurry reactors for assessing the treatability
of contaminated soil. In: Deutsche Gesellschaft fur Chemisches Appartwesen. Frankfurt,
Germany: Chemische Technik und Biotechnologie e.V. pp. 1 87-1 94.
6. Jerger, D., DJ. Cady, S.A. Bentjen, and J.H. Exner. 1993. Full-scale bioslurry reactor
treatment of creosote-contaminated material at southeastern wood preserving Superfund
site. In: Speaker abstracts: In Situ and On-Site Bioreclamation, the Second International
Symposium, San Diego, CA.
7. Luyben, K.ChAM., and RJ. Kleijntjens. 1 992. Bioreactor design for soil decontamination.
In: Deutsche Gesellschaft fur Chemisches Appartwesen. Frankfurt, Germany: Chemische
Technik und Biotechnologie e.V. pp. 195-204.
8. Mahaffey, W.R., and R.A. Sanford. 1 991. Bioremediation of PCP-contaminated soil: Bench
to full-scale implementation. Remediation 305-323.
9. Ross, D. 1990. Slurry-phase bioremediation: Case studies and cost comparisons.
Remediation 61 7N.
1 0. Smith, J.R. 1 991. Summary of environmental fate mechanisms influencing bioremediation
of PAH-contaminated soils, technical report. Remediation Technologies, Inc., Pittsburgh, PA.
11. Smith, J.R. 1989. Adsorption/Desorption of polynuclear aromatic hydrocarbons in
soil-water systems. Technology Transfer Seminar on Manufactured Gas Plant Sites,
Pittsburgh, PA.
12. Stroo, H.F. 1989. Biological treatment of petroleum sludges in liquid/solid contact reactors.
EWM World 3:9-12.
13. Stroo, H.F., J.R. Smith, M.F. Torpy, M.P. Coover, and R.A. Kabrick. No date.
Bioremediation of hydrocarbon-contaminated solids using liquid/solids contact reactors.
Technical report. Remediation Technologies, Inc., Kent, WA.
14. U.S. EPA. 1992. Contaminants and remedial options at wood preserving sites.
EPA/600/R-92/1 82. Cincinnati, OH.
Seminar Series on Bioremediation of Hazardous Waste Sites: Practical Approaches to Implementation
12-3
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15. U.S. EPA. 1990. Engineering bulletin: Slurry biodegradation. EPA/540/2-90/076.
Cincinnati, OH.
16. U.S. EPA. 1989. Innovative technology: Slurry-phase biodegradation. OSWER Directive
9200.5-252FS.
Seminar Series on Bioremediation of Hazardous Waste Sites: Practical Approaches to Implementation
12-4
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Slurry
Bioreactors
Presented by
Gregory Sayles or Dolloff F. Bishop
Office of Research and Development
National Risk Management Research Laboratory
U.S. Environmental Protection Agency
Cincinnati, Ohio
Slurry Bioreactors
For the treatment of
contaminated soils,
sludges, and sediments
A Slurry Bioreactor
Water
and
Soil
Advantages of Slurry Bioremediation
1. Enhanced process control
2. Faster rates of biodegradation of contaminants are
possible
3. Better physical contact between pollutants and
microorganisms
4. Distribution of nutrients, gases (air, oxygen), and
other materials for support of biological process
is greatly improved
5. Optimal soil, sediment, or sludge particle size
distribution can be selected
6. Liquid phase organic solubilities may be enhanced
by surfactant application
Bioreactor Feed Characteristics
Solids particle size: <200 mesh
Solids content in slurry:
10-30% (w/w)
Total organics: <10% (w/w), i.e.,
no free product
pH 4.5-9.0
Contaminated Soil Characterization
Requirements
1. Particle size distribution
2. Texture/composition (silt, clay, sand)
3. Soil nutrients (nitrogen, phosphorous)
4. pH
5. Cation exchange capacity (CEC)
6. Metals (speciated)
7. Total organic carbon
Seminar Series on Bioremediation of Hazardous Waste Sites: Practical Approaches to Implementation
12-5
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Process Components
Soils
or W , Sl'ze -^Pre-Slurry -»- Hydr°-
Sludges ' Classification Cyclone
Big ^
"^^"
Treatment ^
if Needed
t
Big
Clean Big Soil
Small
Process Components (continued)
Small
Particles
Bioreactor
s/w
Separator
11 Water
Big
Particles
Clean
Soil
Treatment
if needed
Clean
Water
Reactor Configurations
Batch (most common)
Sequenced batch
Anaerobicaerobic
Long-short residence time
Types of In-Vessel Mixing
Impeller
Airlift (rising air bubbles
induce slurry circulation)
Combination of above
Slurry Bioreactor Mixing
Air
Candidate Waste Streams
Soils, sediments, and sludges
associated with:
Wood treating waste (PAHs, PCP)
Oil/water separators
Munitions
Pesticides
Halogenated aromatic hydrocarbons
Seminar Series on Bioremediation of Hazardous Waste Sites: Practical Approaches to Implementation
12-6
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Examples of Slurry Bioreactor Use in
the U.S.
Site
Cape Fear
Wood Preserving
Fayetteville, NC
Fennema
Excavating
Byron Center, MI
Pri Mart #7
Buchanan, MT
Contamination
Creosote
Contaminated
Soils and Sludges
Soil Contaminated
With Fuel
Hydrocarbons (PAHs)
Soil Contaminated
With Fuel
Hydrocarbons (PAHs)
Status
Full Scale
Predesign
Full Scale
Underway
Full Scale
Underway
Examples of Slurry Bioreactor Use in
the U.S. (continued)
Site
Wseco Oil #37
Muskegon, MI
Moss-American
Milwaukee, WI
Lone Star Army
Ammunition Plant
Texarkana, TX
Sheridan
Disposal Services
Hempstead, TX
Contamination
Soil Contaminated
With Fuel
Hydrocarbons (PAHs)
Creosote
Contaminated Soils
and Sludges
TNT, TPHs
PCBs and Other
Assorted Organic
Pollutants
Status
Full Scale
Underway
Full Scale
Predesign
Full Scale
Predesign
Full Scale
Predesign
Field Example: Southern Wood
Preserving, Canton, MS
Creosote contaminated lagoon
solids, stabilized with fly ash
pH 6-8
Used extensive size classification
Bioreactor uses impeller and
airlift mixing
Canton Site Layout
Contaminated Material
OHM Canton Site Reactor
^iz,e
Fraction
Large Debris
Power Screen Rejects
Shaker Screen Rejects
Hydrocy clone Rejects
Material for Treatment
TOTAL
rracLioi.
Size
+ 6 inch
-6 + 1/2 inch
-1/2 + 12 mesh
-12 + 200 mesh
-200 mesh
LS
Quantity Air
(yd3)
150
300
1,500
1,500
7,050
10,500
Tons Supply *-
165
330 Impeller _
1,825
1,825
9,995
14,140
Floating Mixer
Soil
1*^1 Diffuser
I "* Assembly
Seminar Series on Bioremediation of Hazardous Waste Sites: Practical Approaches to Implementation
12-7
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OHM Canton Site Reactor
Topside Detail
Diffuser
System
Floating
Mixer
Reactor Operating
Conditions
Volume (L)
Impeller Speed (RPM)
Air Flow Rate (Scfm)
Solids Loading %
750,000
900
350+/-100
20
Reactor Operating
Conditions (continued)
Temperature (C) 30+/-10
pH (S.U.) 7.2+/-1-0
DO (mg/L) >2.0
Ammonia Nitrogen (mg/L) 60+/-20
Phosphorous (mg/L) 20+/-10
Retention Time ?
Canton Site Treatment Results
PAH Treatment
3 RING
Acenaphthene
Acenalthylene
Anthracene
Fluorene
Phenanthrene
Initial
909 ± 230
93 ±81d
1,950 ± 530
630 ±283
1,031 ±661
Final
6± 3
15 ± 5
121 ± 59
14 ±6
34 ±23
Treatment
Effectiveness
99
82
94
97
96
Canton Site Treatment
ReSUltS (continued)
Canton Site Treatment Results
PAH Treatment
Treatment
Initial Final Effectiveness
4 RING
Benzo(a)anthracene 280 ±51 12 ± 5 95
Chrysene 296 ± 59 36 ±11 90
Fluoranthene 1,708 ± 395 32 ± 7 98
Pyrene 1,148 ± 252 33 ± 12 97
Initial
5 & 6 RING
Benzo(b)fluoranthene
Benzo(k)tluoranthene
Benzo(g,h,i)perylene
Benzo(a)pyrene
Dibenzo(a,h)anthracene
Indeno(2 ,3-cd)pyrene
321
± 34
Combined
92 ±
130
92 ±
94 +
82
± 52
82
79
Treatment
Final Effectiveness
208 ± 54
52
with Benzo(b)fluoranthene
18 ± 12
79 ± 15
9 ±6
31 + 5
43
34
78
46
Seminar Series on Bioremediation of Hazardous Waste Sites: Practical Approaches to Implementation
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Canton Site: Cost of Operation Only
Cost for Full-Scale Slurry-Phase Bioremediation of RCRA
K001 Waste Per Ton of Contaminated Soil
Canton Site: Cost of Project
Components
Project Costs for Full-Scale Application of Slurry Treatment
to K001 Contaminated Soil
Cost
Category
Soil Slurry
Preparation Treatment
Unit Task
Cost*
Labor/Equipment $30-35 $10-15
Supplies/Utilities $20-25 $25-30
Analytical Support <$5 $5-10
Treatability Testing
Predesign Engineering
Slurry Treatment
Slurry Dewatering
Site Preparation and Closure
Administration and Support
$200,000
$100,000
$800,000
$700,000
$400,000
$500,000
TOTAL
S50-60
S40-55
TOTAL (Price per ton)
$190-200
Seminar Series on Bioremediation of Hazardous Waste Sites: Practical Approaches to Implementation
12-9
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Fixed Film Bioreactors
Dolloff F. Bishop and Richard C. Brenner
Office of Research and Development, National Risk Management Research Laboratory,
U.S. Environmental Protection Agency, Cincinnati, OH
Introduction
Fixed film bioreactors have become conventional technology for treating biodegradable
contaminants in air and water. Principal fixed film bioreactor applications include treatment of
industrial wastewaters, leachates or ground water, and air emissions of volatile organic compounds
(VOCs). In the reactors, biological activity usually converts contaminants to innocuous end products
such as carbon dioxide, methane, and water. Conventional fixed film reactor approaches involve
aerobic, aerobic co-metabolic (with aliphatic and aromatic organic inducers), and anaerobic
metabolism. Emerging reactor approaches also include sequential anaerobic/aerobic metabolism.
Fixed film bioreactors use either fixed, expanded, or fluidized beds of inert or adsorptive media to
support the biofilm's biodegradation of contaminants. Practical inert media include plastic, stone,
sand, wood, and ceramics. Contaminant removal from the air or water is achieved through biofilm
sorption. Adsorptive media, typically peat or granular activated carbon (GAC), remove contaminants
from the air or water through both biosorption and physical adsorption. While highly efficient
adsorptive media such as GAC are expensive, the high adsorptive capacity provides improved
protection to the biofilms by limiting microbial inhibition from toxic contaminants while increasing
contaminant removal efficiencies, especially during treatment startup. GAC media also improve
biosystem response to widely varying contaminant concentrations.
Representative Reactor Systems
Many contaminants can be biodegraded using aerobic metabolic or co-metabolic pathways. A few,
however, require anaerobic conditions for efficient biodegradation. Selection and design of reactor
systems depend on several factors: contaminant biodegradation kinetics, contaminant sorptive
properties, metabolic or co-metabolic pathways of the individual contaminants, contaminant
concentration(s), and reactor system temperature and pH. Representative reactor systems include
aerobic fluidized-bed GAC filters (1, 2), anaerobic expanded- or fluidized-bed GAC filters (3-5) for
aqueous streams, and biofilters (6-8) for contaminated air.
Aerobic fluidized-bed GAC filters (Figure 1) are best suited for low to moderate concentrations of
contaminants such as typically found in ground water and leachates. These filters can treat slowly
aerobically degradable, poorly biosorbable, or inhibitory contaminants. Some contaminants will
require the addition of appropriate co-metabolites for efficient biodegradation. Where only
aerobically degradable (metabolic and co-metabolic) and noninhibitory contaminants are found in
the aqueous stream, however, fixed film bioreactors with inert media may be used.
Seminar Series on Bioremediation of Hazardous Waste Sites: Practical Approaches to Implementation
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Envirex Ltd. and Envirogen Ltd. employ, before the inlet to the bioreactor, efficient pure oxygen
contacting approaches, with oxygen recycle that limits stripping of VOCs into the gas phase and
prevents difficult-to-control three-phase flow in the bioreactor. With aqueous stream recycle,
transferred dissolved oxygen is sufficient to meet the biological oxygen demand (BOD) of ground-
water contaminants.
Anaerobic expanded- or fluidized-bed GAC filters (Figure 2) are best applied to moderate to high-
strength aqueous waste streams such as leachates and industrial wastewaters. In these waste
streams, most contaminants are at least slowly anaerobically biodegradable. Highly halogenated
contaminants and aromatic contaminants with multiple nitro groups (munitions), however, are
recalcitrant or require a co-metabolite for aerobic degradation. The presence of these compounds
requires or favors anaerobic biotreatment. A significant advantage of anaerobic fixed film
bioreactors is that oxygen does not have to be transferred to the aqueous stream, producing
substantial operating cost savings, especially for high BOD streams. A major disadvantage is that
slow anaerobic degradation rates for many compounds mean bigger reactors are required.
Air biofilters use two alternative reactor approaches: biofilters (Figure 3) with natural media (e.g.,
peat, compost, wood bark) and trickling biofilters (Figure 4) with inert or adsorptive media and
continuous recycling of nutrients and buffer solutions. Commercial peat and compost biofilters
require efficient air humification to maintain biofilm activity and to prevent irreversible channeling
of the bed, which causes bypassing of VOCs into the filter's effluent air stream. High contaminant
concentrations (greater than 100 parts per million volume) at ambient temperatures produce
plugging of commercial biofilters by excess biomass. Periodic (1 - to 5-year) media replacement in
commercial biofilters is also required because of consumption of available nutrients and
deterioration of media structure.
Trickling biofilters, an emerging technology, use recycling of nutrient and buffer solutions to support
metabolic activity and maintain desired reactor pH. These biofilters can treat higher loadings (800
to 1,000 parts per million volume) but require media cleaning at the high loadings to prevent filter
plugging and excessive pressure loss. Cleaning of ceramic pellet media through regular hydraulic
backwashing has been successfully demonstrated at pilot scale. Cleaning of complex media
structures is under study.
Novel media designs (Figure 5) to permit treatment of all VOCs have also been evaluated, typically
at bench scale. Carbon coating of inert media or carbon pellets produces improved filter
performance for slightly soluble VOCs. VOC permeable silica gel pellets with retarded oxygen
transport and with encapsulated biomass produce sequential anaerobic/aerobic treatment. Partial
dehalogenation of perchloroethylene (PCE) and trichlorethylene (TCE) occurs in the pellet core.
Then, aerobic degradation of the daughter products (e.g., vinyl chloride) occurs in the outer zone
of the pellet. Sodium formate is added to the nutrient and buffer solution to provide an energy
source for the dehalogenation.
Seminar Series on Bioremediation of Hazardous Waste Sites: Practical Approaches to Implementation
13-2
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Performance and Costs
Aerobic fluidized-bed GAC bioreactors treating typical contaminant concentrations in ground water
efficiently remove most contaminants. As an example, in a reactor (Table 1) with a 5-minute
hydraulic residence time (HRT), concentrations of benzene, toluene, ethylbenzene, and xylenes (BTEX)
were reduced (1) from 5,420 to 64 parts per billion (98.9 percent removal). Benzene removal
exceeded 99.9 percent (less than 1 part per billion residual benzene). Anaerobic fluidized-bed GAC
bioreactors (5) treating moderate- to high-strength leachate (Table 2) produced highly efficient
removals (98 to 99 percent of chlorinated aliphatic VOCs, 85 to 97 percent of aromatic and ketone
VOCs, and 97 to 99 percent removal of semivolatile organic compounds) at HRTs of 3 to 12 hours.
Commercial biofilters (Table 3) with natural media (6) very efficiently remove soluble aerobically
degradable VOCs, such as alcohols, ketones, and phenols; efficiently remove moderately soluble
aerobically degradable VOCs, such as BTEX; and minimally remove slightly soluble or aerobically
recalcitrant VOCs, such as pentane, cyclohexane, PCE, and TCE. Trickling biofilters with adequate
retention time and appropriate media very efficiently treat all types of VOCs (Table 4). Examples of
performance with hydraulic backwashing to control pressure losses are shown in Figures 6 through
8.
The costs of these fixed film systems (Figures 9 through 12) vary depending on the application
characteristics. Capital costs are generally competitive with alternative technologies such as activated
carbon adsorption, but operating costs, especially long term, are substantially lower than those of
alternative technologies.
References
1. Mickey, R.F., et al. 1 990. Combined biological fluid bed-carbon adsorption system for BTEX
contaminated ground-water remediation. Paper presented at the Fourth National Outdoor
Action Conference on Aquifer Restoration, Groundwater Monitoring and Geophysical
Methods, Las Vegas, NV.
2. Mickey, R.F., et al. 1 993. Applications of the GAC-FBR to gas industry wastewater streams.
Paper presented at the Sixth International IGT Symposium on Gas, Oil and Environmental
Biotechnology, Colorado Springs, CO.
3. Suidan, M.T., et al. Anaerobic treatment of a high strength industrial waste bearing
inhibitory concentrations of 1,1,1-trichloroethane. Water Sci. Tech. 23:1,385-1,393.
4. Suidan, M.T., et al. 1 987. Anaerobic treatment of coal gasification wastewater. Water Sci.
Tech. 19:229-236.
5. Suidan, M.T., and R.C. Brenner. 1996. Expanded-bed GAC anaerobic bioreactorsan
innovative technology for treatment of hazardous and inhibitory wastes. In: Sikdar, S., and
R. Levine, eds. Bioremediation: Principles and practices. Lancaster, PA: Technomic
Publishing Company. In press.
Seminar Series on Bioremediation of Hazardous Waste Sites: Practical Approaches to Implementation
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6. Leson, G. 1996. Biofilters in practice. In: Sikdar, S., and R. Levine, eds. Bioremediation:
Principles and practices. Lancaster, PA: Technomic Publishing Company. In press.
7. Govind, R., and D.F. Bishop. 1996. Biofiltration for treatment of volatile organic
compounds (VOCs) in air. In: Sikdar, S., and R. Levine, eds. Bioremediation: Principles and
practices. Lancaster, PA: Technomic Publishing Company. In press.
8. Leson, G., and A.M. Winer. 1991. Biofiltration: An innovative air pollution control
technology for VOC emissions. J. Air Waste Mgmt. Assoc. 41:1,045.
Seminar Series on Bioremediation of Hazardous Waste Sites: Practical Approaches to Implementation
13-4
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Fixed Film
Bioreactors
Dolloff F. Bishopor Gregory Sayles
Office of Research and Development
National Risk Management Research Laboratory
U.S. Environmental Protection Agency
Cincinnati, OH
Fixed Film Bioreactors
for Air and Water
^^^^^^^M ^^^^^^m
Fixed, expanded, and fluid!zed
beds
Aerobic metabolism
Aerobic co-metabolic metabolism
Anaerobic metabolism
Sequential anaerobic/aerobic
metabolism
Fixed Film Support Media
Inert media - plastic, stone, sand,
wood, ceramics, and glass
Adsorptive media - granular activated
carbon, peat compost, resins
Contaminant removal - inert media by
biosorption and biodegradation,
adsorptive media by biosorption,
physical adsorption and
biodegradation
Bioreactor Selection and
Design Criteria
Contaminant biodegradation
kinetics
Contaminant sorptive properties
Contaminant metabolic pathways
Contaminant concentrations
Reactor system temperature and pH
Figure 1. Aerobic Fluidized-Bed
GAC Filter
GAG-Fluid Bed Advantages
Low ppb residuals in effluents
Small size
No off gas
Good stability
No carbon regeneration
Seminar Series on Bioremediation of Hazardous Waste Sites: Practical Approaches to Implementation
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Figure 2. Anaerobic Expanded
or Fluidized-Bed GAC Filter
Figure 3. Commercial
Biofilters
Figure 4. Trickling Biofilters
Clean Air
JL
MICROORGANISMS
IMMOBILIZED ON
SUPPORT MEDIA
IMPROVED BIOFILTER
Commercial Biofilter
Characteristics
VOC destruction unlike some
control technologies
Some VOC poorly removed
Low energy usage
Efficient moisture control essential
Plugging at high VOC loading
Periodic media replacement
Trickling Biofilter
Characteristics
Destruction of all VOCs
Recycling of nutrient and buffer
solution
Low energy usage
Media cleaning at high VOC
loadings
No media replacement
Figure 5. Novel Media Designs
Porous Ceramic and
Carbon Coated Media
Silica Gel Pellets
Aerobic Zone
1 k
1
\
Wire Mesh Anaerobic Zone
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Table 1. BTEX Removal in a
Fluidized-Bed GAC Reactor
Compound
Benzene
Ethylbenzene
Toluene
P,M Xylenes
O-Xylenes
Influent
(ppb)
1,100
137
1,079
751
234
Effluent
(ppb)
>1
>1
1.3
5.1
0.7
% Removal
>99.9
>99.9
99.9
99.3
99.7
Table 2. Anaerobic GAC
Bioreactor Performance
Compound
Perchloroethylene
Chlorobenzene
Penta chlorophenol
Methyl Isobutyl-Ketone
Naphthelene
Influent
Cone (mg/L)
20
1.1-20
1.3-20
10
30
% Removal
>99
>85
>99
>94
>99
Table3. Commercial Biofilter
Performance
Compound
Aliphatic hydrocarbons
Aromatic hydrocarbons
Alcohols, aldehyeds, and
ketones
Sulfur compounds
Chlorinated hydrocarbons
(low concentrations)
Removal*
Low-moderate
Moderate-high
High
Moderate-high
Low-moderate
High = >95%, Moderate = 85-95%, and Low = >85%
Table 4. Trickling Biofilter
Performance
Compound
Toluene
Methylene Chloride
Trichloroethylene
Ethylbenzene
Chlorobenzene
Influent Cone.
(ppmv)
430
150
25
20
40
% Removal
>99
>99
-35 (>99)*
>99
>95
"Addition of co-metabolite phenol to nutrient and buffer
solution.
Figure 6. Biofilter Performance on
BTEX Removal
Figure 7. Biofilter Performance on
Individual BTEX Components
Seminar Series on Bioremediation of Hazardous Waste Sites: Practical Approaches to Implementation
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Figure 8. Typical Toluene Removal Recovery
Following Biofilter Backwashing Cycle
Figure 9. Life Cycle Cost
Comparison
Figure 10. Cost Comparison
Figure 11. Comparison of Total Capital
Investment (TCI) for Biofilters (Three
Residence Times) and RTO
Figure 12. Comparison of Energy
Cost for Biofilters and RTO
Seminar Series on Bioremediation of Hazardous Waste Sites: Practical Approaches to Implementation
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Suspended Growth Bioreactors
Dolloff F. Bishop and Richard C. Brenner
Office of Research and Development, National Risk Management Research Laboratory,
U.S. Environmental Protection Agency, Cincinnati, OH
Introduction
Suspended growth bioreactors are standard technology for treating organic contaminants in
aqueous and waste sludge systems. The reactors use microbial metabolism under aerobic,
anaerobic, or sequential anaerobic/aerobic conditions to biosorb organic compounds and
biodegrade them to innocuous residuals. The microbial activity in the systems produces biomass that
is removed by gravity sedimentation, with a portion of the settled biomass recycled to maintain a
desired mixed liquor suspended solids concentration in the bioreactor. The excess biomass is wasted
to a sludge disposal process. Reactor configurations include sequencing batch reactors (SBRs),
completely mixed activated sludge systems, plug flow activated sludge systems, and aerobic and
anaerobic digesters.
The reactor systems used to efficiently treat hazardous wastes in aqueous streams or sludges require
sufficient amounts of organic carbon in the stream or sludge to support a stable microbial culture
in the bioreactor (i.e., at least 5 to 1 0 pounds influent biochemical oxygen demand [BOD] per day
per 1,000 cubic feet of bioreactor volume and at least 100 pounds influent volatile suspended
solids [VSS] per day per 1,000 cubic feet of aerobic or high-rate anaerobic digester volume) (1).
Conversely, influent concentrations and/or loadings of hazardous wastes high enough to cause
inhibitory effects and process performance disruption must be avoided. Typical loading ranges for
suspended growth processes (1) are shown in Tables 1 and 2.
The restrictions noted above limit application of suspended growth reactors in hazardous waste
biotreatment, although addition of powdered activated carbon to a bioreactor (1) may expand the
application area. Thus, ground water or leachates contaminated with low levels of BOD often will
not be efficiently treated at the contaminated source by onsite suspended growth bioreactors without
the addition of supplemental organic carbon. With this limitation, an alternative approach for
treatment of dilute hazardous waste streams in suspended growth bioreactors can be considered.
The dilute waste stream can be discharged to a central wastewater treatment plant (with plant
management approval) for combined offsite treatment with municipal wastewater.
Representative Reactor Systems
A typical system for onsite treatment (2) of aqueous waste streams (Figure 1) for leachates or highly
contaminated ground water includes an equalization tank, a splitter box, and a contact stabilization
activated sludge process with a secondary clarifier. Ancillary processes include a waste sludge
digester with supernatant return to the equalization tank and a volatile organic compound (VOC)
stripper for unproved management of poorly degradable VOCs in the aqueous effluent. This
Seminar Series on Bioremediation of Hazardous Waste Sites: Practical Approaches to Implementation
14-1
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relatively complex biosystem may also require tertiary treatment processes such as sand filtration
and/or carbon adsorption to meet effluent discharge standards. Carbon adsorption may also be
applied to VOC stripper air discharges, if required.
The alternative approach of discharging the hazardous waste stream to a central wastewater
treatment plant (3), if available, offers more cost-effective biotreatment. U.S. Environmental
Protection Agency (EPA) evaluated such an approach in two pilot clarification/activated sludge
systems (Table 3) typical of continuous plug flow municipal wastewater treatment plants. One
bioreactor was operated at a sludge retention time (SRT) of 4 days, the other at an SRT of 8 days.
The municipal wastewater fed to the systems was spiked with up to 28 hazardous organic
compounds. The spiked concentrations in the wastewater were less than or equal to 0.25 mg/L and
less than or equal to 0.5 mg/L for the 4- and 8-day SRT systems, respectively. Finally, the sludges
produced in the municipal pilot system receiving wastewater with 0.5 mg/L of spiked contaminants
were treated in pilot anaerobic digesters to evaluate the impact of the hazardous contaminants in
the wastewater sludges on the anaerobic digestion process (4). Three completely mixed pilot-scale
digesters (Figure 2) maintained at 35.5°C with a 30-day solids retention time were used to simulate
typical digester operation. Two of the digesters were fed contaminated primary and secondary
sludges from the pilot study. The third digester (used as a control) was fed similar sludges without
the hazardous organic contaminants.
Performance and Conclusions
The onsite activated sludge system achieved moderate to high removal efficiencies (Table 4) of
benzene, toluene, ethyl benzene, and xylenes (BTEX) and low to high removals (Table 5) of
chlorinated solvents (2). The performance of the complex onsite system suggests that tertiary
treatment may be necessary if stringent effluent discharge standards are required. Alternative fixed
film bioreactors, in general, would provide superior and more cost-effective bioremediation.
The alternative approach, evaluated by EPA, of discharging contaminated ground water or leachates
to a central wastewater treatment plant generally resulted in high removals (Tables 6 and 7) of the
influent hazardous contaminants (3). Removals were superior to those provided by the onsite
activated sludge system. The two treatment systems were not identical, however, and did not treat
the same contaminants. The superior performance at the central plant may have been related to
more effective biomass generated by the large amount of easily degradable organic substrate in the
municipal wastewater. In any event, the complex onsite system will exhibit substantially increased
costs per unit of contaminant removed when compared with costs at central treatment plants.
The performance of anaerobic digestion on the contaminated sludges from the pilot study evaluating
the central treatment plant alternative was compared with that of a control digester (4). Gas
production and solids reduction for digestion of contaminated sludges and control sludges were
nearly identical. Degradation of the hazardous contaminants (Table 8) was apparent. Twelve
chemicals appeared consistently in the digester treating contaminated sludge, and, at steady state,
Seminar Series on Bioremediation of Hazardous Waste Sites: Practical Approaches to Implementation
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contaminant degradation or transformation ranged from 93 to 98 percent. Sorption into the
digester solids also was an important removal mechanism, especially for aromatics.
EPA generated an integrated model for predicting the fate of organics in wastewater treatment plants
(5), which includes components for stripping or volatilization, sorption on solids, and
biodegradation. The biodegradation component (6) includes a structural activity group contribution
method for estimating contaminant biodegradation kinetics.
The experimental data generated by the EPA studies described above were used to successfully
validate the integrated model.
References
1. Metcalf & Eddy. 1 991. Wastewater engineering: Treatment, disposal, and reuse, 3rd ed.
In: Tchobanoglous, G., and F.L. Burton, eds. New York, NY: McGraw-Hill.
2. Nelson, C., et al. 1 993. Reactors for treatment of solid, liquid, and gaseous phases. In:
Proceedings of Seminars on Bioremediation of Hazardous Waste Sites: Practical
Approaches to Implementation. EPA/600/K-93/002. Washington, DC.
3. Bhattacharya, S.K., et al. 1990. Fate and effects of selected RCRA and CERCLA
compounds in activated sludge systems. In: Proceedings of the Fifteenth Annual Research
SymposiumRemedial Action, Treatment, and Disposal of Hazardous Waste.
EPA/600/9-90/006. U.S. EPA, Risk Reduction Engineering Laboratory, Cincinnati, OH.
4. Govind, R., et al. 1 991. Fate and effects of semivolatile organic pollutants during anaerobic
digestion of sludge. Water Res. 25:547-556.
5. Govind, R., et al. 1991. Integrated model for predicting the fate of organics in wastewater
treatment plants. Environ. Prog. 10:13-23.
6. Desai, S.M., R. Govind, and H. Tabak. 1 990. Development of quantitative structure-activity
relationships for predicting biodegradation kinetics. Environ. Toxicol. Chem.
9:1,092-1,097.
Seminar Series on Bioremediation of Hazardous Waste Sites: Practical Approaches to Implementation
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Suspended
Growth Reactors
Dolloff F. Bishop or Gregory Sayles
Office of Research and Development
National Risk Management Research Laboratory
U.S. Environmental Protection Agency
Cincinnati, OH
Suspended Growth Bioreactor
Configurations
Completely mixed activated sludge systems
(continuous wastewater feed)
Plug flow activated sludge systems
(continuous wastewater feed)
Sequencing batch reactors (batch wastewater
feed)
Aerobic digesters (batch or continuous
sludge feed)
Anaerobic digesters (batch or continuous
sludge feed)
Table 1. Activated Sludge
Loading Ranges
Reactor Configuration
Plug flow (conventional)
Completely mixed
Step feed
Contact stabilization
Extended aeration
SBR
Detention
Time (hr)
4-8
3-5
3-5
1.5-3
18-36
12-50
Volumetric Loading
(Ib BOD /day /l.OOO ft3)
20-40
50-120
40-60
60-75
10-25
5 -15
Table 2. Sludge Digester
Loading Rates
Sludge Digester
Type
Aerobic
Waste activated sludge (WAS)
Primary + WAS
Standard-rate anaerobic
High-rate anaerobic
Retention
Time (day)
10-15
15-20
30-60
15-20
Solids Loading
(IbSS/day/l.OOOfP)
100-300
100-300
40-100
100-200
Applications of Suspended
Growth Reactors
Onsite applications limited to moderate or
high strength leachates or ground water
Inhibitory concentrations of hazardous
wastes can prevent onsite application
PAC addition to activated sludge reactors can
extend onsite inhibitory waste applications
Alternatively, ground water and leachates
can be routed to and processed at central
wastewater treatment plants
Figure 1. Onsite Activated Sludge System
|VOC Stripper],
Waste Sludge
*" E
|
1
h m Splitter Box
\^
qualization
Tank
lernatant |
1 r
|
Contact
Tank
1
Reaeration
Tank
J Clar
^^
Activated
Sludge
To voc
Stripper and
Tertiary Filter for
Further Treatment
Seminar Series on Bioremediation of Hazardous Waste Sites: Practical Approaches to Implementation
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Table 3. Conventional Operating
Performance of Pilot Systems*
% Removals
Component
TSS
COD
NH4-N
4 -day
Continuous
97
82
76
SRT
Intermittent**
97
81
81
8-day SRT
Continous Intermittent**
95
88
88
94
87
98
*Feed to systems was Mill Creek municipal wastewater at the EPA Test
and Evaluation Facility in Cincinnati, OH
**Continous or intermittent hazardous contaminant addition
Figure 2.
Pilot
Digester
System
Table 4. Representative Onsite
Activated Sludge System Performance
for BTEX Compounds
Compound
Influent Cone.
(ppb)
Removal
Benzene
Toluene
Ethylbenzene
Xylenes (total)
120
1,000
270
700
78
89
94
95
Table 5. Representative Onsite Activated
Sludge System Performance for Chlorinated
Compounds
Compound
Chlorobenzene
Methylene chloride
Trichloroethane
1,2-Dichloroethane
1,2-Dichloropropane
Influent
Cone.
(ppb)
180
31
250
100
21
% Removal
78
100
80
56
67
Table 6. Representative Removals in
Acclimated Pilot System Operating at
Table 7. Representative Removals in
Pilot System Operating at 8-Day SRT
Compound
Toluene
Xylenes (total)
Chlorobenzene
Trichloroethane
1,2-Dichloropropane
Influent
Cone.
(ppb)
284
175
255
201
228
% Removal
99
99
99
97
77
Influent
Compound
Di-n-bytylphthalate
1,4-dichlorobenzene
Lindane
Naphthalene
1,2,4-trichlorobenzene
Cone.
(ppb)
428
391
425
431
655
% Removal
96
95
56
98
85
Seminar Series on Bioremediation of Hazardous Waste Sites: Practical Approaches to Implementation
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Table 8. Fate of Representative Model for Predicting Fate of Organics
Organics in Digesters in Wastewater Treatment
Feed Fate Mechanism (% Distribution) Primary sedimentation mass balances
Compound mg/kg Sol. Vol. Sorpt. Biodeg. .
Mass balances in secondary treatment
Di-n-bytylphthalate 270 1 0 3 96 _,_,
Biodegradation
1,4-dichlorobenzene 275 4 16 68 13
Sorption
Lindane 490 0 0 2 98 ,. , ... ,,. , . .
Volatilization (diffused aeration)
Naphthalene 230 4 4 65 27 Cl . . , , _. .
Stripping (surface aeration)
1,2,4-trichlorobenzene 750 3 5 66 26
Group contribution method for estimating
biokinetics
Seminar Series on Bioremediation of Hazardous Waste Sites: Practical Approaches to Implementation
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Natural Attenuation:
Site Characterization
Attenuation of Petroleum
Hydrocarbons and Solvents
in Ground Water
John Wilson
Office of Research and Development
National Risk Management Research Laboratory
U.S. Environmental Protection Agency
Cincinnati, Ohio
Two Basic Questions for
Bioremediation
When to start?
When to stop?
When to Stop?
When proactive remediation is
no longer doing any good
When proactive remediation is
no faster than intrinsic
remediation or natural
attenuation
After Proactive
Remediation
Is the spread of contamination
contained by natural attenuation?
Yes? Go into long-term
monitoring
No? Implement another
approach
Natural Attenuation or
Passive Bioremediation
The preferred description is
natural attenuation
All bioremediation is "natural"
Neither the microorganisms
nor the microbiologists are
"passive"
Natural Attenuation
Usually implemented as a
component of a comprehensive
remedial strategy that includes
source control or source removal
Free product recovery
Soil vacuum extraction
Bioremediation
Seminar Series on Bioremediation of Hazardous Waste Sites: Practical Approaches to Implementation
15-1
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Natural Attenuation
Natural Attenuation
Determination is site specific
Requires extensive site
characterization
Requires a risk assessment
Burden of proof is on the
proponent, not the regulator
Not a default technology or
presumptive remedy
Not complete until goals of the
regulatory agency have been
reached to their satisfaction
Patterns of Natural
Bioremediation
Limited by supply of a soluble
electron acceptor
Aerobic respiration
Nitrate reduction
Sulf ate reduction
Controlled by mixing processes
(bioplume)
Patterns of Natural
Attenuation
Limited by biological activity
Iron reduction
Methanogenesis
Sulfate reduction
First-order kinetics
Patterns of Natural
Attenuation
Limited by supply of
electron donor
Reductive dechlorination
Controlled by supply of
electron donor
Initial Elements of a
Quantitative Assessment of
Natural Attenuation
1. Thoroughly delineate the extent of
contaminated ground water
2. Determine trajectory of ground-
water flow
3. Install monitoring wells along
plumes
Seminar Series on Bioremediation of Hazardous Waste Sites: Practical Approaches to Implementation
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Additional Elements of a
Quantitative Assessment of
Natural Attenuation
4. Determine apparent attenuation along
plumes
5. Correct apparent attenuation for dilution or
sorption
6. Assume corrected attenuation is
bioattenuation
7. Confirm bioattenuation from stoichiometry
of electron acceptors or donors
Lines of Evidence
Documented loss of
contaminants at the field scale
Geochemical indicators
Laboratory microcosm studies,
accumulation of metabolic end-
products, volatile fatty acids,
FAME
Document Occurrence of
Natural Attenuation
Use geochemical data to support natural
attenuation
Trends during biodegradation (plume
interior vs. background concentrations)
Dissolved oxygen concentrations below background
Nitrate concentrations below background
Iron II concentrations above background
Sulfate concentrations below background
Methane concentrations above background
SDS.-MRB""
SITE MAP
HLL AM.UTAH
TOTAL BTEX, HILL AFB
Benzene Oxidation
Aerobic Respiration
AUGUST 1993
X| 8,000 -10,000 ppb
B 4,000 - 8,000 ppb
ijj 0 - 4,000 ppb
_>, r ;i "7^$^;
yy^j"
JULY f 994
| 20,000 - 22,000 ppb
tjjj 8,000 -20,000 ppb
i«j 4,000 -8,000 ppb
t«
« ^ i.-k;-J 0-4,000 ppb
7.502+C6H6^6C02(g) +
3H2O
AG°r = - 3566 kJ/moie Benzene
Mass Ratio of O2 to C6H6 = 3.1
0.32 mg/L C6H5 Degraded per mg/L O2 C
1
onsumec
Seminar Series on Bioremediation of Hazardous Waste Sites: Practical Approaches to Implementation
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TOTAL BTEX
DISSOLVED OXYGEN
8,000-10.000 ppb yi f 3-5mg/L
4,000 - 8,000 ppb I j^jj 1 - 3 mg/L
0-4,000 ppb . . ' [~7] <1mg/L
HILL AFB, UTAH AUGUST 1993
TOTAL BTEX AND DISSOLVED OXYGEN
6.000 - 10.000 ppb Total BTEX
- 4,OQQ- 8,000 ppb Total BTEX
0- 4,000 ppfa Total BTEX
Une of Equal Dissolved
Oxygen Concentration (mg/L}
(Background - 6 rng/L}
Aerobic Biodegradation
Background Dissolved
Oxygen Concentration = 6.0 mg/L
0.32 mg/L BTEX (6.0 mg/L O2)
1 mg/L O2
Assimilative Capacity - Aerobic Biodegradation
1.92 mg/L
192dLig/L
Benzene Oxidation
Denitrifi cation
6NO3 +6H++C6H6-
-6C02(g)+6H20
AG°r = - 3245 kJ/mole Benzene
Mass Ratio of NO3- to C6H6= 4.8:1
0.2 mg/L C6H6 Degraded per mg/L NO3- Consumed
TOTAL BTEX
NITRATE
TOTAL BTEX AND NITRATE
|H 8,000-10,000 ppb "i ^j 3-5 mg/L
^| 4,000 - 8,000 ppb I ffl 1 - 3 mg/L
[Tj 0 - 4,000 ppb . . ? H?, < 1 mg/L
HILL AFB, UTAH AUGUST 1993
BSJ S.OOO-10,000 ppb Total BTEX
U] 4 000-8.000 ppb Total BTEX
0 4 000 ppb Total BTEX
Line of Equal Nitrate
Concentration (mg/L)
(Background = 17 mg/L)
HILL AFB, UTAH
AUGUST 1993
Seminar Series on Bioremediation of Hazardous Waste Sites: Practical Approaches to Implementation
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Denitrlfication
Background Nitrate
Concentration = 8.0 mg/L
0.21 mg/L BTEX (8.0 mg/L NO3-)
1 mg/L NO3-
Assimilative Capacity - Denitrification
1.68 mg/L
Benzene Oxidation
Iron Reduction
60H++30Fe(OH)3(a)+C6H6 -
-6C02(g)+'30Fe2++78H2O
AG°r = - 2343 kJ/moie Benzene
Mass Ratio of Fe(OH)3to C6 Hs = 41:1
Mass Ratio of Fe2* Produced to CeH6 Degraded = 15.7:1
0.06 mg/L C6H6 Degraded per mg/L Fe2+ Produced
TOTAL BTEX
FERROUS IRON
8,000-10,000 ppb
4,000 - 8,000 ppb
0-4,000 ppb
TOTAL BTEX AND FERROUS IRON
H3 8,000 - 10.000 ppb Total 8~EX
:^ [ ^ 000 - 8.000 ppb Total BTEX
0-4.000 ppb Total BTEX
Line ol Eoual Ferrous
Iron Concentration (mg/L'i
(Background - 0 mg/_)
HILL AFB, UTAH
AUGUST 1993
HILL AFB, UTAH AUGUST 1993
Iron Reduction
Background Ferrous Iron Concentration = 0 mg/L
Highest Measured Ferrous Iron Concentration = 51 mg/L
0.05 mg/L BTEX (51 mg/L Fe2+)
1 mg/L Fe2+
Assimilative Capacity - Iron
2.55 mg/L
2550 ug/L
Benzene Oxidation
Sulfate Reduction
7.5H++3.75S042-+C6H6- 6C02(Q)+3.75H2S + 3H2O
AG°r = - 340 kJ/mole Benzene
Mass Ratio of S042- to CSH6 = 4.6:1
0.22 mg/L C6H6 Degraded per mg/L Sulfate Consumed
Seminar Series on Bioremediation of Hazardous Waste Sites: Practical Approaches to Implementation
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TOTAL BTEX
SULFATE
TOTAL BTEX AND SULFATE
8,000-10,000 ppb 'i H 40 - 60 mg/L
4,000 - 8,000 ppb |H 20 - 40 mg/L
i &S3
0 - 4,000 ppb ,__. J; . ; | 0 - 20 -ng/L
HILL AFB, UTAH AUGUST 1993
8.000 - 1 u.OOO ppb Total BTEX
4 ODD-8.000 ppb Tots! BTEX
0 - 4.000 ppo Total BTEX
^ Line of Eausl Sulfate
20 Concentration (mg/L!
(Background = 100 mgiL}
HILL AFB, UTAH
AUGUST 1993
Sulfate Reduction
Background Suifate
Concentration = 100 mg/L
0.21 mg/L BTEX (100 mg/L SO
1 mg/L SO42-
2-"i
Assimilative Capacity - Suifate Reduction
21 mg/L
21,OOOLig/L
Benzene Oxidation
Methanogenesis
4.5 H9O + CKHfi
2.25 CO2(g)+ 3 .75 CH,
AG°r = -135.6 kJ/mole Benzene
Mass Ratio of CH4 Produced to C6H6 =0.8:1
1.25 mg/L C6H6 Degraded per mg/L CH4 Produced
TOTAL BTEX
METHANE
TOTAL BTEX AND METHANE
8,000- 10,000 ppb
4,000 - 8,000 ppb
0 - 4,000 ppb
0.05 - 0.5 mg/L
gp 0.5 -1.0 mg/L
P|] 1-2 mg/L
HILL AFB, UTAH AUGUST 1993
gig 8.000-10.ODO ppb Total BTEX
U| 4,000)- 8.000 ppb Totai BTEX
j~J 0-4,000 upb Total BTEX
Line of Equal Methane
Concentration (mg/L)
(Background = 0 mg/L)
HILL AFB, UTAH
AUGUST 1993
Seminar Series on Bioremediation of Hazardous Waste Sites: Practical Approaches to Implementation
15-6
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Methanogenesis
Background Methane Concentration = 0 mg/L
Highest Measured Methane Concentration = 2.0 mg/L
1.28 mg/L BTEX (2.0 mg/L CH4)
1 mg/L CH4
Assimilative Capacity - Methanogenesis
2.56 mg/L
2560
Expressed Assimilative Capacity
Hiil AFB, Utah
Oxygen = 1,920
Denitrification = 1,680
Iron Reduction = 2,550
Sulfate Reduction = 21,000
Methanogenesis = 2,560
Expressed Assimilative Capacity = 29,710
Highest BTEX Concentration = 21,475
M9/L
pg/L
Relative Importance of Blodegradation
Mechanisms at 25 Sites
Correcting Attenuation for
Dilution or Sorption
^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^m
Identify a component of
the plume that can serve
as a tracer
Correcting Attenuation for
Dilution or Sorption
To correct apparent
attenuation for dilution or
sorption, divide the
concentration of contaminants
by the concentration of a
conservative tracer
A Good Tracer
Is not biodegradable in the
absence of oxygen
Seminar Series on Bioremediation of Hazardous Waste Sites: Practical Approaches to Implementation
15-7
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A Good Tracer
Is present in the plume
source area at
concentrations at least
100 times its detection
limit
A Good Tracer
Has the same sorptive
properties as the regulated
compounds
Poorly Sorttd SoM<
SiKy or Cloy** Sandi
Silt and Silty Clay
Storm Sewer
82 I
MW-11
82D
82C
82F
82E
BTEX & Oxygen Nitrate Sulfate
TMB Nitrogen
(mg/liter)
7.7
2.1
1.3
2.1
0.1
1.3
0.5
<0.001 1.1
<0.001 5.6
0.4
0.5
0.1
7.4
4.4
98
193
50
64
40
Benzene Toluene Ethyl- 1,2,4-TMB
benzene
p-Xylene m-Xylene o-Xylene 1,2,4-TMB
821 2740 327 486 495
MW-11 336 90 139 165
82D 96 10 147 183
82C 4.9 3.1 27 324
82B <1 4.3 <1 1.4
82F <1 <1 <1 <1
821 784
MW-11 230
82D 149
82C 43
82B <1
82F <1
(ug/liter)
1370 1140 495
635 204 165
383 103 183
47 2.6 324
<1 <1 1.4
<1 <1 <1
Seminar Series on Bioremediation of Hazardous Waste Sites: Practical Approaches to Implementation
15-8
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1A5-
TMB
TMB
1,2,3-
TMB
821
MW-11
82D
82C
162
100
71
44
129
80
238
147
(percent/
495
100
165
33
183
37
324
65
240
100
69
29
89
37
120
50
Near Source
I DRAIN
Oxygen
Nitrate
Sulfate
Iron II
Methane
Alkalinity
82-I
82-J
82-D
(mgflHer)
0.0
<0.05
<0.5
10.3
1.9
491
<0.05
<0.5
1.3
0.05
430
0.2
<0.05
<0.5
7.4
0.002
657
Benzene
Toluene
Ethybenzene
p-Xytene
m-Xytene
o-XyJene
1,2,4-TMB
82-I
82JJ | 82-D
(\lQfmBf)
5600
5870
955
1620
5130
2300
1270
4260
3910
816
1370
4220
1760
1310
456
10
454
272
442
51
176
Seminar Series on Bioremediation of Hazardous Waste Sites: Practical Approaches to Implementation
15-9
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Toe of the Plume
Oxygen
Nitrate
SuHate
Iron II
Methane
Alkalinity
82-P
82-L
82-B
(mgfliter)
0.1
<0.05
<0.5
0.2
0.004
792
0.3
<0.05
<0.5
2.4
0.018
730
0.4
0.15
74
0.1
0.001
428
Benzene
Toluene
Ethylbenzene
p-Xylene
m-Xytene
o-Xytene
1,2,4-TMB
82-C
82-P | 82-L
82-B
(ugfliter)
7
10
23
26
18
3
143
<1
<1
4
12
17
6
159
6
18
103
379
572
604
433
<1
<1
<1
<1
<1
<1
<1
Remediated
Seminar Series on Bioremediation of Hazardous Waste Sites: Practical Approaches to Implementation
15-10
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Oxygen
Nitrate
Sulfete
Iron II
Methane
Alkalinity
82-F | 82-O
82-M
(mgfliter)
0.1
1.7
52
0.5
0.58
490
0.2
1.6
37
<0.05
0.001
cee
OwO
0.2
1.8
35
<0.05
0.12
666
Benzene
Toluene
Ethybenzene
p-Xylene
m-Xytene
o-Xytene
1,2,4-TMB
82-F
82-O
82-M
(ugffiter)
<1
<1
<1
<1
<1
<1
<1
<1
<1
<1
<1
<1
<1
<1
<1
3
2
3
8
5
4
Background
Oxygen
Nitrate
Sulfote
Iron
Methane
Alkalinity
82-E
82-N
82-K
82-H
(mgflitei)
3.7
4.4
37
<0.05
0.001
375
2.0
1.1
43
<0.05
0.004
256
2.0
4.4
60
<0.05
0.003
498
5.9
1.5
62
<0.05
0.001
492
Benzene
Toluene
Ethylbenzene
p-Xytene
m-Xytene
o-Xytene
1,2,4-TMB
82-E
82-N | 82-K
(tig/liter) -
82-H
Seminar Series on Bioremediation of Hazardous Waste Sites: Practical Approaches to Implementation
15-11
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Natural Attenuation of
Chlorinated Solvents
Mechanism of Chloroethene
Biotransformation
Reductive dehalogenation:
Oxidation/reduction reaction where electrons are transferred
from donor to chlorinated hydrocarbon acceptor
Co-metabolic process:
Organisms growing on alternate carbon sources
Primary substrates:
Potential for natural (soil organic matter) and anthropogenic
sources
Alternative Pathways for
Chloroethene Biotransformation
DCE ""--^
vc-"""^
k CO
Oxidative biodegradation:
Vinyl chloride shown to biodegrade under aerobic conditions
Fe reducers may also oxidize vinyl chloride
Supporting evidence:
Transport properties (migration) of DCE and VC relative to TCE
Aerobic biodegradation of vinyl chloride to CO 2 demonstrated in
microcosms
Native
Biotrans-
formations for
Chloroethenes
Patterns of Natural
Attenuation Sites
Type I Low background organic matter
concentrations, dissolved oxygen
and possibly nitrate greater than
lmg/L
Type II Anthropogenic carbon sources (e.g.,
BTEX, landfill leachate) are present
Type III Native organic carbon drives
dechlorination
Seminar Series on Bioremediation of Hazardous Waste Sites: Practical Approaches to Implementation
15-12
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Sets
-t TrichloHwthBrw
' J
n>: 1.337
FEET
598
CHEMIC4L VinylCMwIde
TTiANSECT: 4
MASS (kg/in) DiBBB
Cortcentralicii
2001 VERTICALEXAGGERA71ON1:10
SCALE
T5-3
NORTH
PARKING LOT
T1-4 T2-5 TOW-134
CLAV
Methods to Estimate Rate Constants
1) Change in concentration from well to well
along a flow path (must correct for dilution)
2) Change in flux (mass per unit time) between one
transect and another perpendicular to the flow path
3) Laboratory Microcosm Study
MASS FLUX AND TRAVEL TIMES
Advectiva mass fluxes estimate* from
calibrated ground water model
(MODFLOW-Tiedeman and Gorellck, 1993)
and
transect averaged concentrations
Travel times for each chemical from:
transect locations
seepage velocities
retardation factors
Average hydraulic conductivities with 95% confidence limits
give a range of estimates for thejravel times
Seminar Series on Bioremediation of Hazardous Waste Sites: Practical Approaches to Implementation
15-13
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Attenuation in West Plume
Mass Flux (kg/y) vs Distance from Transect 2 (m)
at St. Joseph, Michigan
Distance Chloride Organic TCE c-DCE
Chlorine
Meters
Background
130
390
550
855
(mg/liter)
14
55
109
71
57
0
151
15
0.8
<0.1
0
68,000
8,700
56
1.4
. im-ji
0
128,000
9,800
870
0.8
1U
102
Vinyl 10'
Chloride Mass flux (kgty) o
0 10
4,400 10*
1,660 10-
205
0.5
TCE
o-DCE
t-DCE
1.1-DCE
Vinyl Chloride
Sum
0 200 400
Distance from Tr;
\
600 80C
insect 2 (m
Chemical Mass Flux for the Sum of the
Chlorinated Ethenes
Transect
High Estimate
Low Estimate Average
(k.= 4.92 mid) (k.= 7.51 mid) (k.= 10.1 m/d)
(kg/y) (kg/y)
-------
Microcosm Studies for
Complex Technical Issues
Resources Required
To conduct ground-water
microcosm studies:
18-24 months
$100-$300K
TCE Attenuation in Microcosms (per Year)
6 T
4 --
2 --
1234567
TCE Attenuation in the Field (per Year)
2-r
1.5-
1 -
0.5-
1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17
How is residence time at field scale being
determined (Spring 1996)?
Remedial Investigations or Natural
Attenuation Treatability Studies usually use
Darcy's Law and assume the aquifer is
homogeneous.
Information needed:
Hydraulic conductivity from aquifer test.
Jdydraulic gradient from water table
elevations in monitoring wells.
Effective porosity from Freeze and Cherry.
As an approximation:
After acclimation, the kinetics of natural
attenuation of chlorinated solvents can be
described as being first-order on residence
time in the aquifer (follows a half-life rule).
The range of rate constants is relatively
narrow. Most of the uncertainty in
estimating the contribution of natural
attenuation of chlorinated solvents is in the
estimate of residence time in the aquifer.
Seminar Series on Bioremediation of Hazardous Waste Sites: Practical Approaches to Implementation
15-15
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Proposed preliminary screening approach to
determine if further characterization of
natural attenuation of chlorinated organic
compounds is warranted.
1) Measure geochemical parameters to
determine if reductive dechlorination is
expected. Ifso-
2) Assume a first order rate of attenuation of
1.0 per year (half life of eight months).
3) Conduct a rigorous estimate of the
residence time to the point of compliance.
4) Calculate the expected concentration at
the point of compliance from the assumed
rate of attenuation and the residence time.
5) Compare expected concentrations to
measured concentrations, if available.
6) If within an order of magnitude, complete
the characterization.
What is the problem with this approach?
Aquifers are not homogeneous. They have
more permeable regions and less permeable
regions.
What is the consequence?
Plumes find their way to the more permeable
regions, and move much faster than
expected from average conditions.
Frequently they move as much as ten times
faster.
Current Approach:
1) How much water will a well yield?
Conduct an aquifer test in an existing well
that is screened across the aquifer.
2) How permeable is the aquifer around the
well?
Divide the transmissivity determined from
the aquifer test by the length of the screened
interval to estimate hydraulic conductivity.
3) How fast does the water flow?
Darcy's Law says that the flow in a aquifer is
proportional to the permeability and to the
slope of the water table. Multiply the
hydraulic conductivity by the hydraulic
gradient to estimate Darcy flow.
4) How fast does the plume move?
Ground water moves through the pores.
Divide Darcy flow by porosity to estimate
interstitial seepage velocity.
How can we do a better job of estimating
true plume velocity?
Down-hole flow meters can be used to
identify the vertical intervals that
significantly contribute to flow to a well, and
can contribute to flow in an aquifer.
Divide the transmissivity as determined from
an aquifer test by the depth of the intervals
contributing to flow, instead of the total
screened interval of the well.
Seminar Series on Bioremediation of Hazardous Waste Sites: Practical Approaches to Implementation
15-16
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Apparatus
and
Geometry
Associated
with a
Borehole
Flowmeter
Test
Hydraulic Conductivity (cm/s)
0.04 0.06 0.08
Elevatio
(meters)
c
335 57
834.73
333.78
832.84
831.89
830.95
830.00
829.06
828.11
827.17
826.22
825.28
Hydraulic Conductivity (cm/si
0.01 0.02 0.03 0.04 0.05 0.06
-»
:
I
1
§
Vertical distribution of hydraulic conductivity in the aquifer sampled by well MW-27
Vertical distribution of hydraulic conductivity In the aquifer sampled by well MW-29
Elevation
(meters)
C
B35 00
834.02
833.08
831.19
830.24
829.30
828.35
827.41
826.47
825.52
824.58
B23.63
Hydraulic Conductivity (cm/5)
0.05 0.1 0.15 0.2 0.25
L__.____^
a
Error produced by using the
average hydraulic conductivity as
revealed by a conventional
aquifer test to estimate the
interstitial seepage velocity (and
thus residence time) of the JP-4
plume at George AFB
Vertical distribution of hydraulic conductivity in the aquifer sampled by well MW-31
Seminar Series on Bioremediation of Hazardous Waste Sites: Practical Approaches to Implementation
15-17
-------
Monitoring
Well
MW-27
MW-28
MW-29
MW-31
MW-45
MW-46
Average
Hydraulic
Conductivity
(cm/sec)
0.0074
0.0046
0.0028
0.013
0.0032
0.018
Hydraulic
Conductivity
of Most
Transmissive
Interval (cm/sec)
0.11
0.022
0.062
0.26
0.0056
0.40
Bioscreen Input Screen
Bioscreen Input Screen
Hydraulic Conductivity
Hydraulic Gradient
Porosity
2 DISPERSION'
Longitudinal Dispeisivily'
Vertical Disperaivity*
or
3. ADSORPTION"
S. GENERAL
Modeled Area Length* I 2000 [[
Modeled Area Widtfi" 22Q~j(
Simulation Time" [ 100[(
S. SOURCE DATA
Source ThtcfcnaM m Sal Zone'f
Source ZanoV"
i) Cone jmg/Li'
7. FIELD DATA FOR COMPARISON
Concentration (1
DisL from Source (ft)|
8. CHOOSE TYPE OF OUTPUT TO SE
(ft)
Bioscreen
Bioscreen will be available on the
NRMRL/SPRD Web page:
www.epa.gov/ada/kerrlab.html
A Retrospective Evaluation
of In Situ Bioremediation
Procedure used to estimate the
impact of residual petroleum
hydrocarbons on ground-water
quality at the Public Services site
in Denver, Colorado.
Seminar Series on Bioremediation of Hazardous Waste Sites: Practical Approaches to Implementation
15-18
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Vertical Exaggeration 2X
In many floodplain landscapes, the
most important transfer of
contaminants from LNAPL to ground
water is through diffusion from the
LNAPL to transmissive layers in the
aquifer, rather than through
dissolution and direct advection.
This suggests an approach to
estimate the impact of spills of
petroleum hydrocarbons on ground
water.
5300
sz»
3280
5260
Will the Plume Return?
Has active treatment weathered
the spill to the point that intrinsic
bioremediation prevents
development of a plume?
WiU a Plume of
Contaminated Ground
Water Return?
Is the election acceptor supply
greater than the demand?
What is mass transfer from
residual oily phase to moving
ground water?
State of Practice for Determining
Contaminant Mass
Subsample cores hi the field
for extraction and analysis of
specific contaminants and total
petroleum hydrocarbons.
Cores can be screened with a
hydrocarbon vapor analyzer.
9 ' ii OC
CbnnunMf M CM
Seminar Series on Bioremediation of Hazardous Waste Sites: Practical Approaches to Implementation
15-19
-------
218-
216-
214-
212-
210-
208-
2OB-
Sleeping Bear Dunes NLS
Former Casey's Canoe Livery
w»i«.
Tabl* R«itdu4l Gltoim* Lend Surface
0 5 10 15 20 25 30 35 4O 45 50 55
Auger Column
Barrel Sampler
Auger Head
Seminar Series on Bioremediation of Hazardous Waste Sites: Practical Approaches to Implementation
15-20
-------
1/4 inch PVC Tubing
Ground Surface
Water Table
1" Steel Pipe
Pcdstalic Pump
45cm
Calibration of Aquifer Test
Using a Geoprobe
Calibration Factor for
SPRD/NRMRL Geoprobe
Hydraulic Conductivity
(cm/sec)
equals
Yield (mL per sec per cm
drawdown)
multiplied by 0.03
TPIIorDTEXdngflig)
500 1Wi
Fuel Derived Organic Compounds
at the Public Services Site
Seminar Series on Bioremediation of Hazardous Waste Sites: Practical Approaches to Implementation
15-21
-------
Electron Acceptor Supply at the
Public Services Site
1. Determine hydraulic conductivity in
the first transmissive interval below
the LNAPL.
2. Determine hydraulic gradient in that
interval.
3. Assume a porosity, and calculate a
seepage velocity under the LNAPL.
4. Determine the length of the LNAPL in
the direction of ground-water flow.
5. Calculate residence time of water in the
transmissive interval moving under the
LNAPL.
6. Determine the highest concentration of
contaminant dissolved in ground water
in contact with LNAPL (Raoult's Law
using core samples or direct
measurement on water).
7. Measure the vertical distance between
the bottom of the LNAPL and the top of
the transmissive part of the aquifer.
8. Calculate the diffusion gradient.
9. Look up the diffusion coefficient of the
contaminant in water (Chemical
Engineering).
10. Calculate the diffusive flux from the
LNAPL to the transmissive part of the
aquifer.
11. Use the residence time of ground water
under the NAPL to calculate total loading
by diffusion to the transmissive part of
the aquifer.
12. Determine the volume of water in the
transmissive part of the aquifer.
13. Estimate the concentration of
contaminant in the transmissive part of
the aquifer in the absence of
biodegradation.
14. Measure the supply of oxygen, nitrate,
and sulfate in the uncontaminated
ground water upgradient of the spill.
15. Compare the electron acceptor demand
of the contaminants to the electron
acceptor supply associated with oxygen,
nitrate, and sulfate in ground water
upgradient of the spill.
16. If methane concentrations in the ground
water in contact with the LNAPL are
greater than 0.1 mg/L, include methane
in the calculation of electron acceptor
demand.
Residence time 235 days
Highest cone. BTEX 175 mg/L
Diffusion path length 1.5 meters
Thickness of transmissive
interval 1.2 meters
Loading BTEX 0.6
mg/liter
BTEX capacity 51 mg/L
Seminar Series on Bioremediation of Hazardous Waste Sites: Practical Approaches to Implementation
15-22
-------
What are the prospects that
natural attenuation is
preventing the spread of
BTEX contamination in
ground water? (containment,
not remediation)
Where Should It Work?
River valley alluvial deposits
Unglaciated coastal
environments on the Gulf of
Mexico and Atlantic Ocean
What To Watch Out For!
Glacial outwash
Upland landscapes
Fractured bedrock aquifers
Karst landscapes, limestone
aquifers
Seminar Series on Bioremediation of Hazardous Waste Sites: Practical Approaches to Implementation
15-23
-------
How far will a plume move if it
is subject to Natural
Attenuation?
How far will ground water move
in 10 years?
How fast is water moving
through the source of ground-
water contamination?
What is the hydraulic
conductivity of the most
transmissive material that has
LNAPL?
What is the hydraulic gradient?
Multiply conductivity by
gradient, then divide by
porosity (0.3) to predict plume
velocity, use velocity; to predict
plume length after ten years.
Hydraulic conductivity >10 feet
per day: Might have a huge plume
Hydraulic conductivity 10 to 0.1
feet per day: Need more
information
Hydraulic condictivity <0.1 foot
per day: Natural Attenuation often
will take care of it
Seminar Series on Bioremediation of Hazardous Waste Sites: Practical Approaches to Implementation
15-24
-------
Appendix: Procedure Used To Estimate the Impact of Residual Petroleum
Hydrocarbons on Ground-Water Quality at the Public Services Site in
Denver, Colorado
John Wilson
Office of Research and Development, National Risk Management Research Laboratory,
U.S. Environmental Protection Agency, Cincinnati, OH
1. Determine hydraulic conductivity in the first transmissive interval below the light nonaqueous
phase liquid (LNAPL).
This was done using a Geoprobe to conduct a series of aquifer tests.
2. Determine the hydraulic gradient in that interval.
This was calculated using water elevations in monitoring wells. It also corresponded with the
gradient of the Platte River on a topographic map. Flow in the transmissive layers of the
floodplain was parallel to the river.
3. Assume a porosity, and calculate a seepage velocity under the LNAPL.
The assumed porosity was 0.35. Seepage velocity is the product of the hydraulic
conductivity (0.058 cm/sec) multiplied by the hydraulic gradient (0.0012 meter/meter) and
then divided by the assumed porosity (0.35). In this case, seepage velocity was 0.1 7 meter
per day.
4. Determine the length of the LNAPL in the direction of ground-water flow.
The length is based on analysis of core samples. It is estimated to be 40 meters.
5. Calculate residence time of water in the transmissive interval moving under the LNAPL.
Residence time is the length of the LNAPL divided by the seepage velocity of the ground
water. In this case, 40 meters divided by 0.1 7 meters per day or 235 days.
Seminar Series on Bioremediation of Hazardous Waste Sites: Practical Approaches to Implementation
15-25
-------
6. Determine the highest concentration of contaminant dissolved in ground water in contact
with LNAPL (Raoult's Law using core samples or direct measurement on water).
Raoult's Law says that the concentration of a particular compound in solution in ground
water should equal the water solubility of that compound multiplied by its mole fraction in
the NAPL. We will make two important conservative assumptions. Because most fuels are
a "boiling cut" at the refinery, we will assume that the molecular weights of the components
are approximately the same, and that mass fraction equals mole fraction. We will also
assume that the solubility of benzene, toluene, ethylbenzene, and xylenes (BTEX) is the
solubility of the most soluble component, benzene. The hot spot contained 206 mg/kg BTEX
in 1,176 mg/kg total petroleum hydrocarbon (TPH), predicting a mole fraction of 0.18.
Multiplying that mole fraction by the solubility of benzene (1,000 mg/liter) predicts a
concentration of BTEX of 1 80 mg/liter.
Direct measurements often underestimate the true concentrations estimated from analysis
of core samples due to dilution from uncontaminated water.
7. Measure the vertical distance between the bottom of the LNAPL and the top of the
transmissive part of the aquifer.
This was done by "sniffing" core samples and by analysis of TPH in core samples, and by
close-interval measurement of hydraulic conductivity using the Geoprobe. In this case, the
vertical distance was 1.5 meters.
Calculate the diffusion gradient.
The gradient is the change in concentration divided by the depth interval. The conservative
assumption is that the concentration at the bottom of the gradient is zero. Under this
assumption, the gradient is estimated as the highest concentration in contact with the NAPL
divided by the depth interval to the transmissive layer. In this case, the gradient is 1 80
mg/liter to zero over 1.5 meters. The gradient is 1 80 mg/liter per 1 50 centimeters, or 1.2
E-03 mg/cubic centimeter per centimeter.
9. Look up the diffusion coefficient of the contaminant in water.
A variety of chemical engineering handbooks are available, such as Chemical Engineering.
In general, diffusivity is inversely proportional to the square root of molecular weight. Of the
BTEX compounds, benzene is the lightest and diffuses the fastest. The diffusion coefficient
of benzene is 0.8 E-05 square centimeters per second.
I 0. Calculate the diffusive flux from the LNAPL to the transmissive part of the aquifer.
The flux is estimated by multiplying the diffusion gradient by the diffusion coefficient and
then by the porosity. In this case 1.16 mg/cubic centimeter per centimeter multiplied by 0.8
Seminar Series on Bioremediation of Hazardous Waste Sites: Practical Approaches to Implementation
15-26
-------
E-05 centimeter squared per second, then by 0.35 cubic centimeters water per cubic
centimeter aquifer material equals 3.2 E-09 mg/square centimeter per second, or 2.8
mg/square meter per day.
Use the residence time of ground water under the NAPL to calculate total loading by
diffusion to the transmissive part of the aquifer.
The loading is the flux multiplied by the residence time. In this case, 2.8 mg/square meter
per day multiplied by the residence time of 235 days is 658 mg per square meter.
12. Determine the volume of water in the transmissive part of the aquifer.
The volume is the thickness of the transmissive interval multiplied by the porosity. Based on
the vertical mapping of hydraulic conductivity using the Geoprobe, the effective thickness
is 1.2 meters. Under each square meter there is 1.2 cubic meters of aquifer material in the
transmissive zone. The assumed porosity is 0.35, equivalent to 0.42 cubic meters or 420
liters of ground water under each square meter.
13. Estimate the concentration of contaminant in the transmissive part of the aquifer in the
absence of biodegradation.
The estimated concentration is the loading due to diffusion divided by the volume of water
in the transmissive interval. In this case, 235 mg per square meter divided by 420 liters
under each square meter equals 0.6 mg/liter BTEX.
1 4. Compare the electron acceptor demand of the contaminants to the electron acceptor supply
associated with oxygen, nitrate, and sulfate in ground water upgradient of the spill.
In this case, the analysis will be done on water samples at the downgradient edge of the
LNAPL. Based on the stoichiometry of bacterial metabolism, 0.21 mg/liter of BTEX is
consumed for each mg/liter of sulfate, 0.21 mg/liter of BTEX is consumed for each mg/liter
of nitrate, and 0.32 mg/liter of BTEX is consumed for each mg/liter of oxygen.
Concentrations of 0.5, 4.9, and 239 mg/liter of oxygen, nitrate, and sulfate have the
capacity to support microbial metabolism of 0.16, 1.0, and 50 mg/liter of BTEX,
respectively. This compares favorably with an estimated loading of only 0.6 mg/liter BTEX.
Seminar Series on Bioremediation of Hazardous Waste Sites: Practical Approaches to Implementation
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Natural Attenuation of Soils
Daniel Pope
Dynamac Corporation, Ada, OK
Generally, the following factors must be considered when evaluating contaminated soil for the use
of natural attenuation as a remedial alternative:
The mass/concentration, mobility, and toxicity of contaminants.
The proximity of receptors, including both human and environmental receptors, with
particular emphasis on sensitive human receptors and threatened/endangered
species/habitats.
The current and planned use of the aquifer underlying or adjacent to the site for
public and private water supplies.
The applicability and practicality of using of institutional controls to reduce the risk
of exposure of sensitive receptors and ground water to soil contamination.
Site investigation may reveal one of the following scenarios in which natural attenuation of
contaminated soil is a viable option:
1. Contamination is found essentially only in the unsaturated zone, and the
contamination concentration/mass and mobility are low enough that no significant
threat to ground-water quality exists. In this case, natural attenuation may be
considered as a primary remedy.
2. Active remediation has reduced soil contamination to the equivalent of Scenario 1.
3. Active remediation is ongoing, but Scenario 1 is applicable in certain areas of the
site; natural attenuation can be used for those areas while active measures
continue in the areas not suitable for natural attenuation.
Natural attenuation in soils in the unsaturated zone involves a complex interaction among the
chemical, physical, and biological properties of the site and contaminants. As in the saturated zone,
evaluation of natural attenuation involves assessment of site characteristics, including geology, water
flux, and soil chemistry; site microbiology, including microbial populations, microbial ability to
degrade contaminants, and degradation rates; and contaminant characteristics, including solubility,
toxicity, volatility and degradability.
Contaminants in the unsaturated zone may be dissolved in the soil pore water adsorbed to soil
particles, or retained as residual saturation of free-phase liquid in soil pores or as vapor in the soil
gas. The applicability of natural attenuation depends on the interrelationship between the
contaminant parameters (e.g., mass/concentration, toxicity) and the factors that affect contaminant
mobility and degradation. If mobility of the contaminants is low enough that sensitive receptors are
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not at risk and other attenuation mechanisms can operate to reduce contaminant concentration or
mass to the desired levels, then natural attenuation may be applicable as an alternative remedy.
Mobility of contaminants in each compartment of the unsaturated zone varies according to the
contaminant, soil type and chemistry, water flux, and associated factors. Estimates of mobility
should be made using one of the models applicable to contaminants in the unsaturated zone.
Attenuation mechanisms include those that essentially dilute the contaminant concentration, those
that reduce contaminant mobility (adsorption, and for metals a change of oxidation state), and those
that change the contaminant to less harmful forms, such as biodegradation of organics and change
of oxidation state for metals.
In the unsaturated zone, evaluation of natural attenuation of organic contaminants focuses on
biodegradation, because the other significant components of natural attenuation for most
contaminants either transfer the contaminants to another location (leaching, volatilization) or merely
reduce contaminant mobility and perhaps biodegradability (adsorption). The site characteristics
favorable for natural attenuation of soils and sediments are essentially those favorable for aerobic
bioremediation, because in unsaturated zone soils, aerobic bioremediation is usually the most
important factor in bioremediation. Even in an aerobic zone, however, anaerobic degradation may
be occurring. For instance, it has been found that pentachlorophenol (PCP) may degrade better in
soils that are "moderately aerobic" than in soils with high oxygen content or very low oxygen content.
Anaerobic microsites in the soil may favor removal of chlorine from the aromatic ring of PCP, and
then aerobic bioremediation could complete the degradation.
Soil oxygen levels greater than or equal to 2 percent are usually enough to support aerobic
remediation. Earlier workers recommended that soil oxygen be above 1 0 percent, but experience
indicates that many sites do not seem to show a significant increase in biodegradation as soil oxygen
is raised above 2 percent.
A redox potential (Eh) of 50 millivolts is considered the minimum for oxidizing, aerobic conditions.
An Eh below 50 millivolts (mV) indicates reducing, anaerobic conditions. An Eh of 400 to 800 mV
indicates highly aerated conditions, while 100 to 400 mV indicates less aerated but still aerobic
conditions. Generally, if the redox potential is less than 100 mV, active measures would be
considered if aerobic conditions are desired. Soil color can give a qualitative estimate of redox
conditions: reds, yellows, or browns indicate oxidizing conditions; gray or blue indicates reducing
conditions; and mottled colors indicate spatial variability of redox conditions.
Soil pH strongly influences the microbial activity, availability of nutrients, and chemistry of some
contaminants. Usually a pH of 5 to 9 is acceptable for bioremediation, although pH may affect
bioremediation of varying contaminants differently, and specific types of degradation may not occur
at certain pHs.
Soil moisture is closely associated with soil biological activity. Low soil moisture usually causes low
biological activity. Low soil moisture may decrease contaminant mobility, allowing more time for
bioremediation to work. Generally, soil moisture is optimum for bioremediation at about 50 to 80
percent of field capacity, where the large pores are filled with air and the small soil pores are filled
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with water. At least 1 0 percent air-filled porosity is recommended for oxygen diffusion.
Soil temperature is closely related to biological activity. Biodegradation essentially stops at 0°C.
Most biodegradation rates are determined at about 20 to 25°C. Generally, metabolic activity is
halved by a 10°C drop in temperature, all other conditions staying the same. This does not
necessarily mean that biodegradation is twice as fast at a site where the mean temperature is twice
that of another site. For instance, there is at least some evidence that microbes acclimated to low
temperatures can biodegrade petroleum hydrocarbons at low temperatures about as fast as
microbes acclimated at 20°C can degrade contaminants at 20°C.
Microorganisms require nutrients such as nitrogen and phosphorus for metabolic activity. Soil
nutrient levels are usually considered from a soil concentration perspective or from the perspective
of ratios of the nutrients. For instance, a desirable concentration range for nitrogen and phosphorus
in the soil solution might be 150 to 200 ppm nitrogen and 25 to 35 ppm phosphate, although firm
evidence for recommending particular levels for bioremediation is generally lacking. From a nutrient
ratio perspective, a carbon:nitrogen:phosphorus (C:N:P) ratio of 120-300:10:1 is often
recommended. This ratio was originally based on the ratio of nutrients in microbial cells, with the
assumption that the ratio of nutrients presented to the microorganism in its environment should be
the same as the ratio in the cell. There has been little research conducted in the field to determine
the best soil nutrient concentrations or ratios for bioremediation. Also, there is little information
available on the desirable amount of trace nutrients in soils, although apparently enough trace
nutrients are available in most soils and sediments so that increasing their levels has no discernable
effect on bioremediation.
For the biological component of natural attenuation to be effective, there must be a suitable
microbial community at the site that can degrade the contaminants. Microorganism communities
can be evaluated in many ways. Unfortunately, most of the evaluation methods do not give clear
answers to the question of most practical importance: Will the indigenous microorganisms degrade
the contaminants quickly enough to levels low enough that the contaminants will be prevented from
reaching sensitive receptors at toxic levels?
Microbial evaluation techniques include measures of microbial presence and activity such as
population counts, community profiles, degradation ability, and metabolic activity. Microbial
population counts ordinarily range from 1 to 1 0 x 1 O6 counts/g soil, depending on the soil and the
method of counting. The correlation between population counts and biodegradation rates is difficult
to determine. Microbial identification techniques include techniques for identification of particular
species, as well as community assessment techniques including FAME profiles and sole carbon
source profiles. Generally, species identification is of limited usefulness for making decisions in field
remediation activities.
Of more interest are techniques to determine microbial ability to degrade the contaminants of
interest under laboratory conditions. Indigenous microorganisms can be grown in culture media
containing the contaminants of interest, or simply in samples of the site soil. Contaminant
degradation rates can be determined from these types of studies, although the laboratory rates may
not be representative of the rates that will be found in the field. In cases where microbial ability to
degrade the contaminants is in question, however, these tests can be helpful to establish the
feasibility of using bioremediation/natural attenuation at the site.
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Also useful both in the field and in the laboratory are tests to indicate microbial activity. Respiration
measurements to determine O2 consumption and CQ production are most commonly used.
Measuring CO2 production alone can be misleading, since CQ sources and sinks other than
microbial activity may be significant. O2 depletion in contaminated zones compared with similar
"background" zones is strong evidence for biological degradation of contaminants when O2
depletion data parallels contaminant disappearance, daughter product appearance, and secondary
indicators.
Contaminants vary in their biodegradability. Generally, more water soluble compounds are more
degradable. For instance, petroleum hydrocarbons with longer chains or more rings are less water
soluble and less easily degraded. Specific examples include n-alkanes, n-alkylaromatics, and
aromatics from 5-22 carbons, which usually are biodegradable. Petroleum hydrocarbons with more
than 22 carbons tend to have fairly slow biodegradation rates. Fused aromatics and cycloparaffinics
with four rings or more may be very slow to biodegrade. The larger compounds tend to be more
strongly adsorbed to soil or trapped in soil pores, reducing their bioavailability, mobility, and
potential to reach receptors.
Wood preserving contaminants, also often candidates for bioremediation/natural attenuation, vary
widely in biodegradability, since wood preservatives by definition are selected for their toxicity to
microorganisms. Polynuclear aromatics (PAHs) of three rings or less are generally considered to be
readily biodegradable. Chlorinated phenols, such as PCP and tetrachlorophenol, are biodegradable,
but their toxicity to microorganisms is a significant factor in their resistance to biodegradation at high
concentrations. Dibenzodioxins and dibenzofurans appear to be difficult to biodegrade.
Physical and chemical components of natural attenuation in the unsaturated zone include
volatilization and leaching as the most significant factors, although chemical reactions such as
hydrolysis can be significant for some contaminants, such as pesticides. Adsorption significantly
affects contaminant mobility, availability, and potential biodegradability. Volatilization can be a
significant factor for those contaminants with high vapor pressure, such as gasoline and similar
petroleum contaminants, naphthalene, methyl naphthalene, and three-ring PAHs, and chlorinated
aliphatics. Loss of contaminants by volatilization is more likely in the unsaturated zone than in the
saturated zone. Leaching of contaminants must be monitored and controlled, since leaching to
ground water is one of the most important potential impacts of soil contaminants. Lysimeters can
be used so that excessive leaching can be detected before the contaminants enter ground water.
Both the potential for leaching and volatilization can be modeled to estimate the part these play in
attenuation of the contaminants.
Seminar Series on Bioremediation of Hazardous Waste Sites: Practical Approaches to Implementation
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Natural
Attenuation
of Soils
Daniel Pope
Dynamac Corporation
Ada, OK
What Are the Requirements
for NA To Be Used as the
Primary Remedy for Soils?
Further impairment to GW
quality not a serious threat
Receptors not impacted
Site is controllable through
institutional controls
What Are the Requirements
for NA To Be Used as a
Secondary Remedy for Soils?
Along with ongoing active
remediation alleviating serious
threats
After active remediation
alleviated serious threats
Natural Attenuation as a
Remedial Alternative
for Soils
Contaminant Releases
Migrate from source area
Area of contamination
expand until equilibrium
reached
Natural attenuation equals
source output
When/Where Is
Equilibrium Reached?
Site factors - Soil type,
precipitation influx . . .
Contaminant factors -
Solubility, concentration,
carrier . . .
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Equilibrium
Eventually, natural attenuation
exceeds rate of source output,
and concentration of
contaminant(s) stabilizes or
decreases
Importance of source control as
the primary remedial alternative
Advantages of Natural
Attenuation
Actual contaminant degradation in
many cases, rather than just phase
transfer or sequestration
Nonintrusive - allows continued
use of site
Less potential for releases due to
site disruption, lack of control of
remedial process
Advantages of Natural
Attenuation
Works in conjunction with other
technologies
Generally less costly than
alternatives
Can be evaluated by site
characterization and monitoring
Advantages of Natural
Attenuation
Data necessary for proving
applicability of natural attenuation
are readily applicable to other
technologies
Site accessibility, equipment
limitations are not a problem
Common contaminants of regulatory
concern (BTEX) are susceptible to NA
Disadvantages of Natural
Attenuation
Upfront costs may be greater than
other technologies, though long-
term costs will probably be lower
Evaluating the Potential
for Natural Attenuation
in Soils
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Site Characterization
Soil Oxygen Levels
What site characteristics are
favorable or unfavorable for
NA?
Favorable for aerobic
bioremediation of vadose zone
Soil oxygen levels >2%?
May be enough for aerobic
remediation
Redox Potential
Redox Potential
Eh >50 millivolts = oxidizing,
aerobic conditions
Eh <50 millivolts = reducing,
anaerobic conditions
400-800 mV highly aerated
conditions
100-400 mV less aerated, but
still aerobic
Soil Color
SoilpH
Reds, yellows, browns indicate
oxidizing conditions
Gray or blue indicates reducing
conditions
Mottled colors indicate spatial
variability
Usually 5-9 is acceptable
High pH may not inhibit
bioremediation
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Soil Moisture
Soil Moisture
Low moisture, low biological
activity
But mobility may be low, so
may have a long time available
for bio
50-80% of field capacity
Large pores filled with air,
small pores filled with water
Air/Water in soil inversely
related
Soil Moisture
Air-Filled Porosity
Sandy Soils
Loams
-0.1 - 0.15 Bar
-0.3 - 0.5 Bar
>10% recommended
for oxygen diffusion
Soil Permeability
Soil Temperature
Saturated hydraulic
conductivity >10~5 cm/sec
Biodegradation stops at 0°C
Most rates determined around
20-25°C
Metabolic activity halved by
10°C drop
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Soil Nutrient Levels
Nutrient Concentrations
Soil concentration
Concentration ratio
TON>1.5%
Nutrient Ratios
Trace Nutrients
C:N:P 120-300:10:1 often
recommended
Largely based on ratios in cell
mass
Little research conducted in
field
Little specific information for
bioremediation in soils
Apparently enough available in
most soils
Measures of Microbial
Presence and Activity
Population counts
Community profiles
Degradation ability
Metabolic activity
Microbial Population Counts
From 1 to 10 x 10 exp6
counts/g soil
Relationship to transformation
rates is minimal
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Microbial Identification
Isolation of specific degraders
FAME profiles
Community profiles by
exposure to range of carbon
sources
Microbial Ability To Degrade
Contaminants
Culture tests
Microcosm tests
Microbial Activity
Respiration O2/CO2
ATP
Biodegr ad ability of Petroleum
Compounds
More water soluble, more
degradable, usually
Longer chains, more rings less
water soluble
Biodegr ad ability of Specific
Petroleum Compounds
n-alkanes, n-alkylaromatics,
aromatics from C5-C22 usually
fairly biodegradable
above C22 usually are fairly slow
biodegradation rates
Fused aromatics, cycloparaffinics
>4 rings may be very slow
Biodegradability of Wood
Preserving Contaminants
» Polynuclear aromatics (PAHs)
» Chlorinated phenols
» Dibenzo - dioxins and furans
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Biodegradability of
Chlorinated Solvents
Methylene chloride
1,2-DCA
Chloroethane
Monitoring Plan
Soil and possibly GW
Soil gas, soil borings, pore
water
Case Study
Site History
Waste oil recycling facility
Oil blended with benzene,
toluene, or xylene
Two tank farms, with
sludge/water in bermed area
Site History (continued)
Victoria clay soil: low
permeability, high water-holding
capacity, high to very high shrink-
swell potential, poor drainage
Caliche fill in driveway
Apparently no GW contamination
Remedial Plan
Removal of tanks, barrels,
buried piping, debris and
sludges
2,200 yd of soil remaining (TPH
up to 50,000 ppm)
Seminar Series on Bioremediation of Hazardous Waste Sites: Practical Approaches to Implementation
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Treatment Goals for Soil
<\% oil and grease (O&G)
10,000 mg/kg TPH
Land treatment chosen as
remedial technology
Evaluation for Natural
Attenuation
i Contaminant characteristics
i Site characteristics
i Ecological and health receptors
Contaminant
Characteristics
Are the contaminants of
concern readily biodegradable?
Suppose they are not readily
biodegradable, but mobility is
low?
Contaminant Distribution
Contaminants in sludge not
readily biodegradable in situ
Contaminants in soil or
dissolved probably degradable
Site Characteristics
Are site conditions favorable?
Can they be made favorable with
minimum input?
Will they be favorable after active
remediation is done?
Receptors
Time Required for Natural
Attenuation
Once contaminants are identified
as biodegradable, time/mobility
are the main factors
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Time Required for Natural
Attenuation
Is the timeframe necessary for
NA reasonable, considering site-
specific circumstances?
What Is a Reasonable
Timeframe?
Depends on amount of contaminant,
toxicity, and mobility
Proximity of receptors - humans,
environmental
Especially sensitive humans, threatened/endangered
species
Public/private water supplies
Potential use of aquifer
Reliability/enforceability of institutional
controls
Contaminated Soil
Contaminated Soil
Free phase residual
Adsorbed material
Dissolved contaminant
Evaluate mobility of
contaminants
Evaluate means to reduce
mobility
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Natural Attenuation of Landfills
Dolloff F. Bishop
Office of Research and Development, National Risk Management Research Laboratory,
U.S. Environmental Protection Agency, Cincinnati, OH
Introduction
Evidence is emerging that indicates natural attenuation may play a valuable role in addressing
certain types of landfills. Landfills are usually closed municipal fills that may have received mixed
wastes, including municipal solid wastes as well as a variety of industrial and hazardous wastes.
Some of these landfills may pose a low risk to human health and the environment and, therefore,
be candidates for consideration for use of natural attenuation. This decision must be made on a site-
by-site basis. It does not indicate a preference over the Agency's current policy to manage landfill
content, leachate, and gases by use of containment systems including covers and bottom liners.
The complex mixtures (1) of organic and inorganic nonhazardous and hazardous materials in
landfills are slowly being degraded or transformed through natural attenuation (natural abiotic and
microbial processes). The contaminants are also being leached (2-4), by rainfall or by ground-water
intrusion, from the fill into the ground-water aquifers below. Volatile organic compounds (1) may
also volatilize with the principal landfill gases of methane and carbon dioxide. What needs to be
defined are the types of hazardous waste landfills and the appropriate conditions where natural
attenuation would be considered.
Based on mass balance approaches, municipal landfills also are recognized as globally significant
sources (5) of atmospheric methane, but methane field emission measurements are limited and
extremely variable. There has been no attempt to reconcile national or global estimates of projected
mass balance yields of methane generation with the limited field data on methane emissions (6).
Recent research (7), however, has surprisingly revealed that landfills in the active methanogenic
stage with aerobic soil covers and with gas recovery systems actually act as methane sinks, removing
methane from the atmosphere rather than emitting landfill methane. The effect is attributed to high
capacities for methane oxidation to carbon dioxide by indigenous methanotrophs in aerobic soil
covers.
With aerobic permeable soil covers, uncapped landfills with substantially stabilized organic fill and
limited gas emissions and sites with gas recovery and flaring systems also should develop indigenous
methanotrophic and heterotrophic aerobic bioprocesses in aerobic, permeable soil cover. These
aerobic processes should degrade both methane emissions and most volatile organic chemicals in
the landfill gases. In addition, evidence is evolving that indicates that natural attenuation (intrinsic
bioremediation) can stabilize and even shrink contaminated ground-water plumes below landfills.
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Landfill Lysimeter Studies
EPA's National Risk Management Research Laboratory conducted a lysimeter study (1) on the West
KL Landfill in Kalamazoo, Michigan, to assess bioactivity and the fate of the hazardous contaminants
in the fill material under capped and rainfall simulations. The wastes were obtained from an area
of the West KL Landfill with industrial wastes and were transported under nitrogen to EPA's Test and
Evaluation Facility in Cincinnati. The materials were hand mixed, also under nitrogen, to reduce fill
heterogeneity, then placed in lysimeters operated at 35°C. The anaerobic lysimeters, pertinent to
assessment of natural attenuation, included three replicate microcosms of capped systems with two
abiotic controls and three replicate microcosms simulating rainfall with two abiotic controls. The
abiotic controls used sodium azide to minimize anaerobic activity.
The bioactivity in the lysimeters was monitored by measurement of gas production and by assessing
the fate of specific contaminants in the fill. The cumulative gas productions (Figures 1 and 2) of the
capped and rainfall simulators in the 400-day study revealed a long period of approximately 1 50
days before redevelopment of bioactivity in the disturbed fill in the rainfall simulator and only
marginal bioactivity in the capped simulators. Fill gas analysis on carbon dioxide and methane also
confirmed substantial bioactivity in the rainfall simulators compared with the marginal activity in the
capped simulators.
Analyses of the fate of specific contaminants in the fill was difficult, unfortunately, with significant
variability in the mass balances caused by heterogeneity in the fill and analytical variability
associated with fill material. Trends on dehalogenation of highly chlorinated solvents (Figures 3 and
4) for example, also suggested improved bioactivity in the rainfall lysimeters compared with the
capped lysimeters. Unfortunately, the poor mass balance results and variability from lysimeter to
lysimeter prevented statistically valid assessments of the fate of specific contaminants.
Research Approach
Clearly, with bioactivity in permeable soil covers and with intrinsic bioremediation in ground water,
responsible risk/benefit management requires assessing the applicability of natural attenuation
processes as cost-effective approaches for managing risk in contaminated high-volume landfills,
both as control options when active remediation can be discontinued and as the principal
remediation approach in contaminated areas when risk is acceptably low. These natural attenuation
processes, however, will require appropriate monitoring to ensure acceptable risk management of
the variety of contaminants in landfills. Monitoring methods will include standard individual
contaminant analyses in soils, leachates, and gases, as well as ecological and health effects assays.
The rate of natural attenuation of contaminants in landfills is the sum of the rates of several biotic
and abiotic processes. These processes include intrinsic biodegradation of the contaminants, the
chemical transformation of the contaminant (humification) into the organic matter associated with
landfills, and the rates of mass transport of contaminants to the locations of these reactions. The
development of a protocol for assessing the use of natural attenuation in landfills on a site-specific
basis requires the compilation of a database on rates of pertinent biotic and abiotic processes for
various contaminants and environmental settings, and the development or improvement of fate and
transport models that employ the rates to describe the activity of these processes.
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The tasks in the development of the protocol are to:
Review and summarize pertinent biotic and abiotic degradation and stabilization
(containment) science and engineering in the surface and subsurface of landfills
including bioavailability and alternative endpoints. Develop critical supplemental
attenuation rate data to support protocol development.
Develop supplemental attenuation rate data using laboratory and field studies.
Review, evaluate, improve, and summarize existing fate and transport models for
hazardous compounds in landfills.
Review and summarize available monitoring and sampling tools for landfill
characterization.
Prepare a draft protocol and validate with lab, pilot, and field studies.
References
1. U.S. EPA. 1995. Laboratory evaluation of in situ biodegradation of hazardous pollutants
in Superfund landfills. Contract No. 68-C2-0108. National Risk Management Research
Laboratory, Cincinnati, OH.
2. Schultz, B., and P. Kjeldsen. 1 986. Screening of organic matter in leachates from sanitary
landfills using gas chromatography combined with mass spectroscopy. Water Res. 20:965-
970.
3. Dewalle, F.B., and E.S.K. Chiang. 1 981. Detection of trace organics in well water near
a solid waste landfill. J. Am. Water Works Assoc. 73:206-21 1.
4. Dunlap, W.J., et al. 1 976. Organic pollutants contributed to ground water by a landfill.
In: Proceedings of the Research Symposium on Gas and Leachates From Landfills, Rutgers
University Cooks Colleges, New Brunswick, NJ, March 24-26, 1 975. EPA/600/9-76/004.
pp. 96-110.
5. U.S. EPA. 1995. Estimate of global methane emissions from landfills and open dumps.
EPA/600/R-95/019. Washington, DC.
6. Bogner, J., and R. Scott. 1995. Landfill methane emissions: Guidance for field
measurements. Final report to International Energy Agency, Expert Working Group on
Landfill Gas.
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7. Bogner, J., et al. 1995. Landfills as atmospheric methane sources and sinks.
Chemosphere 31:4,1 1 9-4,1 30.
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Natural Attenuation of
Landfills
Dolloff F. Bishop
Office of Research and Development
National Risk Management Research Laboratory
U.S. Environmental Protection Agency
Cincinnati, OH
Characteristics of Typical
Hazardous Waste Landfills
» Usually closed municipal landfills with
permeable soil cover
» No impermeable liners to minimize
leachate transport
» Partial anaerobic stabilization of
organic materials
» Gas production often highly variable
» Municipal solid wastes and a variety of
industrial and hazardous wastes
Landfill Emissions
Leachate with a variety of
contaminants entering ground-
water aquifer
Carbon dioxide and methane gas
emissions
Variety of VOCs at low
concentrations in gas emission
Natural Attenuation at Landfills
Anaerobic bioprocesses degrade municipal solid
wastes and many hazardous contaminants in fill
Intrinsic bioremediation (anaerobic and aerobic
processes) occurs in ground water at varying rates
Aerobic methanotrophs bioxidize methane in
permeable aerobic soil cover
Aerobic bioxidation of VOC can occur in aerobic soil
cover
With aerobic soil cover and gas recovery systems,
landfill can remove methane from atmosphere rather
than emit methane
Landfill Lysimeter Study
Superfund West KL Landfill in Kalamazoo,
Michigan
Selected waste from industrial area of the fill
Hand mixed under nitrogen to reduce
heterogeneity
Lysimeters operation with 3 replicates and 2
abiotic controls simulating capped and
rainfall conditions at 35°C
Bioactivity confirmed by measuring gas
production and assessing specific
contaminant fate
Figure 1. Cumulative Gas
Production for Capped Columns
Capped Landfill Lysimeters
CAP 1 No-moisture addition
CAP 2 No moisture addition
CAP 3 No moisture addition
CAP 4 Abiotic control without moisture
CAP 5 Abiotic control without moisture
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Figure 2. Cumulative Gas
Production for Uncapped Columns
Uncapped Landfill Lysimeters
UNC 1 (rainfall)
UNC 2 (rainfall)
UNC 3 (rainfall)
UNC 4 Abiotic control
UNC 5 Abiotic control
Figure 3. Distribution of
Tetrachloroethylene for CAP 3
Mass Biodegraded
78%
Mass in Carbon
Mass Remaining in Soil
13%
Figure 4. Distribution of
Tetrachloroethylene for UNC 3
Mass Biodegraded
Mass in Leachate
0%
Mass in Carbon
8%
Mass Remaining in Soil
Natural Attenuation Research
Approach
Review and extend current science in
natural attenuation of contaminated
landfills
Review and summarize available natural
attenuation rates at sites
Develop supplemental attenuation rate
data
Review and improve fate and transport
models
Natural Attenuation Research
Approach (continued)
Review available monitoring tools
Evaluate biological and health assays to
assess cleanup objectives
Prepare a draft protocol with
information summaries
Validate and improve protocol with
laboratory, pilot and field studies
Seminar Series on Bioremediation of Hazardous Waste Sites: Practical Approaches to Implementation
17-6
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Natural Attenuation of Sediments
Dolloff F. Bishop
Office of Research and Development, National Risk Management Research Laboratory,
U.S. Environmental Protection Agency, Cincinnati, OH
Introduction
Contaminants in sediments (1) include a wide variety of organic compounds and metals. Metals
cannot be destroyed but often can be transformed by bioprocesses to less toxic forms. As
representative organic contaminants, high molecular weight polychlorinated biphenyls (PCBs) and
polynuclear aromatic hydrocarbons (PAHs), from widely used multicomponent Arochlors and
creosotes, partition strongly to and persist in sediments (2). They bioaccumulate up the food chain
and thus produce potential human health and environmental risks (3).
Intrinsic bioremediation (natural attenuation), even of these persistent compounds, occurs naturally
but slowly in sediments, using indigenous microorganism and enzymatic pathways of both aerobic
and anaerobic processes (2, 5, 6). In general, increasing the molecular weight of the organic
contaminants (Figures 1 and 2) increases partitioning and reduces the bioavailability of the organic
compounds, thus reducing the biodegradation rate and extent of degradation.
PAHs biodegrade most rapidly through aerobic processes, with the degradation rates usually
decreasing as aromatic ring structure increases from two to six rings (5-7). In PCB biodegradation,
anaerobic processes (8-10) slowly dechlorinate the highly chlorinated PCB congeners to lightly
chlorinated congeners. Aerobic processes (11, 12) then biodegrade the lightly chlorinated
congeners.
Quiescent sediments with substantial contamination are anaerobic (1) except in the upper layer
adjacent to water. Dissolved oxygen of approximately 8.0 mg/L in water, slow oxygen diffusion into
sediments, and slow diffusion of contaminants to the sites of microbial activity limit the kinetically
more rapid aerobic degradation processes. The mass transport limitations reduce bioavailability and
increase the persistence of PAHs, lightly chlorinated biphenyls, and other aerobically degradable
organic contaminants in sediments. Natural turbulent mixing of sediments with the water column
and slow oxygenation at the surface of quiescent sediments do produce limited and slow
biodegradation of aerobically degradable contaminants (1 1).
In contrast, highly chlorinated congeners of PCBs and other chlorinated contaminants are gradually
dechlorinated naturally in contaminated sediments, the PCBs (2) to mono-, di-, and trihomologs.
The products of anaerobic dechlorination accumulate, increasing concentrations of lightly
chlorinated PCBs and other partially dechlorinated contaminants in sediments (1 1-13). Lightly
chlorinated PCBs and other partially dechlorinated organic contaminants, in general, bioaccumulate
less strongly. These PCBs have less potential human toxicity (14, 15) than the highly chlorinated
congeners.
Seminar Series on Bioremediation of Hazardous Waste Sites: Practical Approaches to Implementation
18-1
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Natural Attenuation Evaluation
With a pattern of slow natural dechlorination of highly chlorinated contaminants and slow aerobic
biodegradation of the less chlorinated residuals and other aerobically biodegradable contaminants
(such as PAHs), the U.S. Environmental Protection Agency's (EPA's) Bioremediation Program plans
to examine natural attenuation as a possible approach for management of contaminated sediments
and will prepare a protocol for assessing the use of natural attenuation as a best management
practice for managing risk at specific sites with contaminated sediments.
These natural attenuation processes will require appropriate monitoring to ensure acceptable risk
management. The initial priority contaminants are PAHs and metals, found at petroleum, wood
preserving, and town gas wastes sites, and PCBs. Monitoring methods will include standard
individual contaminant analyses and ecological and health effects assays (alternative endpoints).
The rates of natural attenuation of contaminants in sediments are the sum of the rates of several
biotic and abiotic processes. These processes include intrinsic biodegradation of the contaminants,
the chemical transformation of the contaminant into organic matter associated sediments
(humification), and the rates of mass transport of electron donors or acceptors, amendments, or
contaminants to locations where the microbial reactions occur. The development of a protocol for
assessing natural attenuation at specific sites requires the compilation of databases on the rates of
the biotic and abiotic processes for various contaminants and environmental conditions, as well as
the improvement and validation of fate and transport models that employ the rates to describe the
integrated action of these processes. Research and development includes:
Review and summarize pertinent biotic and abiotic degradation and stabilization
(containment) science and engineering in sediments, including contaminant
bioavailability and alternative endpoints. Extend through experimental and field
research.
Review, evaluate, and improve existing fate and transport models for hazardous
compounds in sediments.
Review and summarize available monitoring and sampling tools for sediment site
characterization.
Prepare a draft protocol, including information summaries.
Seminar Series on Bioremediation of Hazardous Waste Sites: Practical Approaches to Implementation
18-2
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References
1. U.S. EPA. 1994. Assessment and remediation of contaminants sediments program:
Remediation guidance document. EPA/905/R-94/003. Great Lakes National Program
Offices.
2. Abramowicz, D.A. 1995. Aerobic and anaerobic PCB degradation in the environment.
Environ. Health Perspec. 103(5):97-99.
3. Safe, S. 1980. Metabolism uptake, storage and bioaccumulation. In: Kimbrough, R., ed.
Halogenated biphenyls, naphthalenes dibenzodioxins and related products. Elsevier, North
Holland: pp. 81-107.
4. Bedard, D.L., and RJ. May. 1996. Characterization of the polychlorinated biphenyls in
sediments of woods pond: Evidence for microbial dechlorination of Arochlor 1260 in situ.
Environ. Sci. Technol. 30:237-245.
5. Cerniglia, C.E. 1992. Biodegradation of polycyclic aromatic hydrocarbons.
Biodegradation 3:351-368.
6. Shuttleworth, K.L., and C.E. Cerniglia. 1995. Environmental aspects of PAH
biodegradation. Appl. Biochem. Biotechnol. 54:291-302.
7. Seech, A., B. O'Neil, and L.A. Comacchio. 1993. Bioremediation of sediments
contaminated with polynuclear aromatic hydrocarbons (PAHs). In: Proceedings of the
Workshop on the Removal and Treatment of Contaminated Sediments. Environment
Canada's Great Lakes Cleanup Fund, Wastewater Technology Centre, Burlington, Ontario.
8. Brown, J.F., et al. 1984. PCB transformations in upper Hudson sediments. Northeast
Environ. Sci. 3:167-179.
9. Brown, J.F., et al. 1987. Environmental dechlorination of PCBs. Environ. Toxicol. Chem.
6:579-593.
10. Quensen, J.F., III, S.A. Boyd, and J.M. Tiedje. 1990. Dechlorination of four commercial
polychlorinated biphenyl mixtures (Arochlor) by anaerobic microorganisms from sediments.
Appl. Environ. Microbiol. 56:2,360-2,369.
11. Flanagan, W.P., and RJ. May. 1993. Metabolic detection as evidence for naturally
occurring aerobic PCB biodegradation in Hudson River sediments. Environ. Sci. Technol.
27:2,207-2,212.
12. Harkness, M.R., etal. 1993. In situ stimulation of aerobic PCB biodegradation in Hudson
River sediments. Science 259:503-507.
Seminar Series on Bioremediation of Hazardous Waste Sites: Practical Approaches to Implementation
18-3
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1 3. Liu, S.M., and WJ. Jones. 1 995. Biotransformation of dichloromatic compounds in non-
adapted and adapted freshwater sediment slurries. Appl. Microbiol. Biotechnol. 43:725-732.
14. Safe, S. 1992. Toxicology structure-function relationship and human environmental health
impacts of polychlorinated biphenyls: Progress and problems. Environ. Health Perspec.
100:259-268.
15. Abramowicz, D.A., and D.R. Olson. 1995. Accelerated biodegradation of PCBs.
Chemtech. 24:36-41.
Seminar Series on Bioremediation of Hazardous Waste Sites: Practical Approaches to Implementation
18-4
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Natural Attenuation
of Sediments
Dolloff F. Bishop
Office of Research and Development
National Risk Management Research Laboratory
U.S. Environmental Protection Agency
Cincinnati, OH
Contaminants in Sediments
Wide variety of organic compounds and
metals
Persistent high molecular weight organic
compounds
Widely distributed contaminants: PCBs
and PAHs
Bioaccumulation in food chain may cause
health and environmental risk
Natural attenuation occurring slowly using
aerobic and anaerobic processes
PAH and PCB Natural
Attenuation
PAHs biodegrade most rapidly through aerobic
processes
Rates decrease as aromatic ring structure
increases from 2 to 6 rings
PCBs biodegrade usually through sequential
anaerobic/aerobic processes
High chlorinated PCBs dechlorinate
anaerobically to lightly chlorinated congeners
Lightly chlorinated PCB congeners biodegrade
aerobically
Figure 1. Representative PAH Ring
Structures
4-Ring (Pyrene)
2-Ring (Naphthalene)
3-Rings (Anthracene)
5-Rings (Perylene)
Figure 2. Representative PCB
Congeners
a ci
Lightly
Chlorinated
Highly
Chlorinated
Sediment Conditions
Contaminated sediments are anaerobic below
surface layer
Surface layer adjacent to water is aerobic
Slow mass transport in sediments limit
bioavailability and degradation
Quiescent sediments favor slow accumulation of
lightly chlorinated compounds, especially mon,
di, and tri PCB homologs
Natural turbulent mixing of sediment and water
increases aerobic degradation of PAHs and lightly
chlorinated PCBs
Seminar Series on Bioremediation of Hazardous Waste Sites: Practical Approaches to Implementation
18-5
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Natural Attenuation
Evaluation
Pattern of slow natural dechlorination and slow
biodegradation of aerobically degradable
contaminants
Assessing use of natural attenuation for
managing risks
Priority contaminantsPAHs, metals, and PCBs
Monitoring to ensure acceptable risk management
Monitoring methodsindividual contaminant
analyses, and ecological and health effect assays
Rates of Natural Attenuation
Processes
Anaerobic vs. aerobic
Chemical transformation with
sediment organic matter
(humification)
Mass transport of electron donors
and acceptors, amendments, and
contaminants
Protocol Development
Compilation of databases on rates
of attenuation for various
contaminants and environmental
conditions
Improvement and validation of
fate and transport models
describing integrated activity of
the attenuation processes
Research and Development
Approach
i Review and extend and summarize
current science in natural attenuation
i Review and summarize available
natural attenuation rates of sites
i Develop supplemental attenuation
rate data
i Review and improve fate and
transport models
Research and Development
Approach (continued)
Review and summarize available
monitoring tools
Draft protocol including
information summaries
Validate protocol in laboratory,
pilot and field studies
Provide technology transfer
Seminar Series on Bioremediation of Hazardous Waste Sites: Practical Approaches to Implementation
18-6
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Source Control: Free
Product Recovery and
Hydraulic Containment
John Wilson
Office of Research and Development
National Risk Management Research Laboratory
U.S. Environmental Protection Agency
Ada, OK
Nonaqueous Phase
LiquidsNAPLS, LNAPLS,
DNAPLS
The NAPLs define the source area
of the ground-water plume
To the extent feasible, these
materials should be removed
before bioremediation proceeds
Site Characterization
Requirements Specific to the
Subsurface
Goals:
Map the contaminant mass in three
dimensions
Determine the co-distribution of
contaminant and hydraulic or
pneumatic conductivity
Problems With Monitoring
Wells
They cannot estimate contaminant
mass in NAPLs
They cannot estimate contaminant
mass adsorbed to solids
They do not sample contaminant
mass above the water table
Comparison of Contaminant Mass
in Ground Water to Total
Contaminant Mass
At a pipeline spill in Kansas:
Mass in Mass in
Ground Water Subsurface
Benzene
BTEX
TPH
22kg
82kg
115kg
320kg
8,800 kg
390,000kg
When Total Contaminant
Mass Is Unknown
Cannot estimate requirements for
electron acceptors
Cannot estimate requirements for
nutrients
Cannot determine time required
for cleanup
Seminar Series on Bioremediation of Hazardous Waste Sites: Practical Approaches to Implementation
19-1
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Relationship Between Free
Product in Monitoring Wells and
Contaminant Mass in Aquifer
Position and quantity in wells does
not relate to position and quantity
in aquifer
Amount of free product related to
location of water table
Relationship Between Free Product
in Monitoring Wells and Contaminant
Mass in Aquifer
Free product is greatest when
water table is low
Free product can disappear
when water table is high
Methods To Remove
Nonaqueous Phase Liquids
Free product recovery
Bioslurping
Soil vacuum extraction
LNAPL Remediation
Soil Vent System
Vent Well
Vent Well
Contaminated Soil
Seminar Series on Bioremediation of Hazardous Waste Sites: Practical Approaches to Implementation
19-2
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Plattsburg AFB
Fire Protection Training Area
0 50 100 150 200
^H_
Put
LIF Optical Module
Sacrificial Tip
Fiber Optic Cables
« Sapphire Window
Friction Sleeve
Pittsburgh AFB FPT pit 1
1 itjlPetrolejm H,Jnxub
0 5000 10000 15000
Fluorescence Intensity
Total Petroleum Hydrocarbons (nig/kg)
Hamburgh AFB
Fire Protection Training Are) - Combined Samples
TPH (kg(a<
10 - 20
m 20
30
40
5D
H (0
ED 70
ED BD
3D
40
50
to
70
100
0 50 100 150 200
Seminar Series on Bioremediation of Hazardous Waste Sites: Practical Approaches to Implementation
19-3
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Bottom Line
12,000 gallons of LNAPL
removed
122,000 gallons of LNAPL
remain
Seminar Series on Bioremediation of Hazardous Waste Sites: Practical Approaches to Implementation
19-4
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Air Sparging/
Air Injection
Need for Efficient,
Inexpensive Delivery of
Oxygen to Saturated Zone
John Wilson
Office of Research and Development
National Risk Management Research Laboratory
U.S. Environmental Protection Agency
Ada, OK
*** Air Sparging ***
Air Sparging
Injection of air under pressure
below the water table
Creates transient air filled
porosity
Air Sparging System
Monitoring Vapor Extraction
Probe Well \
Air Sparger Monitoring
/ Well ,. Probe
Vent Radius = f(Vacuum)
Sparge Radius = f(Depth)(Pressure)
Transient Air
Filled Porosity
Effects of Air Sparging
Enhanced oxygenation
Enhanced dissolution
Volatilization
GW stripping
Physical displacement of GW
Enhanced Oxygenation
Replenishes oxygen depleted by
chemical/biological processes
Normal replenishment relies on
diffusion from water table surface
Sparged air, distributed throughout
aquifer, has short diffusion path
Enhanced oxygenation stimulates
biodegradation
Seminar Series on Bioremediation of Hazardous Waste Sites: Practical Approaches to Implementation
19-5
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Air Flow Paths
Injected air travels horizontally,
vertically
Flow impedance by lithological barriers
blocking vertical air flow
Channelizationhorizontal air flow
captured by high permeability channels
Small permeability differences can
change flow paths
Inhibited Vertical Air Flow Due to
Impervious Barrier
Impervious Barrier
Contaminated Soil
Dissolved Particles
"Air Contaminant Migration
Channeled Air Flow Through Highly
Permeable Zone
High Permeability Zo:
Air/Contaminant
Migration
Case Studies on Air
Sparging or Air Injection
Worked well: Traverse City,
Michigan
Worked well enough: Elizabeth
City, North Carolina
Didn't work: Plattsburgh, New
York
RUBBER BOOT
5" DIA PVC
4" DIA PVC
Sol On I
, itF* lira WI/*»
Seminar Series on Bioremediation of Hazardous Waste Sites: Practical Approaches to Implementation
19-6
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QJ 596
594
o-9/SO
.10/91
1000 2000 3000 4000
Pud Carbon, mgKg Cm Material
Vertical Profile Oily Phase Residue in Bioventing South Plot
CHANGE IN TPH TN NORTH PLOT
DURING PROJECT
Sept. 1990 Oct. 1991
mg / sq. ft. area
Above Water Table 48800 302
Below Water Table 227000 178000
Ground Water Quality after
Biosparging
Well Benzene Toluene Ethylbenzene m+p Xylene o-Xylene
ug/lit e r
3 feet <1 <1 <1 <1 <1
6 feet <1 <1 <1 <1 <1
I"
"a
0.01
0.001
0.0001
Biosparge
03 «»1215U21M27
Time (months)
4
w ,
& 3
s
a
2-
Sf
I-
Biovent »
4
t
n.
* olOSpdl^C *
A
;
Time (months)
Explanation
70C TOY
u
Seminar Series on Bioremediation of Hazardous Waste Sites: Practical Approaches to Implementation
19-7
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Prior to Remediation
During Remediation
Total TPH Concentration, Fire Station Site
Baseline Total ETEX,
Fire Station Site
6th Period BTEX,
Fire Station Site
Monitoring wells screened from 7 to 10 meters
below grade, 15 and 30 meters down gradient
of the NAPL
Benzene
MTBE
Monitoring Well 4
Predicted
40
184
Actual
[ug/litei
1.9
325
Monitoring Well 6
Predicted
r\
40
184
Actual
1.3
442
Seminar Series on Bioremediation of Hazardous Waste Sites: Practical Approaches to Implementation
19-8
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K at 70DC (cm/sec)
0 0.005 0.01
15 10 5 0 750 1500 0 2 4 «
Sleeve Friction Tip Friction
Stress
(psi)
Ratio
MTBE (ug/liter)
500 1000 1500
0 0.002 0.004 0.006 0.008 0.01
Hydraulic Conductivity (cm/sec)
Conditions of Sparge
Efficiency Test
Injected air at 3 cubic feet per minute at
18 psi
Injected air for four days over a six day
interval
Total air injected: 17,300 cubic feet
Total porosity to 3 feet from sparge well:
250 cubic feet
Total porosity to 10 feet from sparge
well: 2,800 cubic feet
1000 -r
1234
Days of Sparging
Seminar Series on Bioremediation of Hazardous Waste Sites: Practical Approaches to Implementation
19-9
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234
Days of Sparging
Why didn't air sparging strip
Vinyl Chloride and increase
the concentration of Oxygen?
The air moved inRibbons,
fixed channels of preferential
flow.
Air sparging worked well when
the contaminant was near the
water table and the sand grains
were all the same size
Air sparging did not work well
when the contaminants were
deep, and there were a mixture
of particle sizes
Seminar Series on Bioremediation of Hazardous Waste Sites: Practical Approaches to Implementation
19-10
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State Review: Natural Attenuation of Ground Water and Soils
Daniel Pope
Dynamac Corporation, Ada, OK
The U.S. Environmental Protection Agency (EPA) recently conducted a survey to determine how
different states are proceeding with natural attenuation efforts. States were asked whether they
Encourage or discourage the use of natural attenuation (NA)
Have any formal or informal policies or guidelines that address NA
Use any particular model when deciding on NA
Consider any compounds other than petroleum hydrocarbons for NA
The table below summarizes the information obtained from this survey.
State
Alabama
Alaska
Arizona
Arkansas
California
Colorado
Connecticut
Encourage/
Discourage
NAof
Petroleum
Encourage
case-by-case
Encourage
case-by-case
Neither
Neither
case-by-case
Discourage
Neither
case-by-case
Neither
Guidelines or Rules
No guidelines. Considers NA for
petroleum on a case-by-case
basis.
Developing RBCA/ASTM (draft).
Working with Wisconsin to
develop soil guidance using NA.
Drafting interagency policy for
ground-water contaminated sites.
Developing RBCA and SSL.
Considers NA mostly at UST
sites.
Informal guidelines. Looks at
property boundaries. Determines
NA on a case-by-case basis.
Revising Resolution 92-49 to
include "containment zones."
Meets water-quality standards at
"point of compliance" (property
boundary). However,
water-quality standards may
be used as "guidelines" by oil
inspectors based on technical
and economic feasibility.
Remedial standards allow NA.
Uses a ground-water
classification system for remedial
decision-making.
Specific
Models to
Determine
NA
AT123D,
SESOIL
Developing
BAN Model
Half-lives of
contaminants
(non-UST)
Encourage/
Discourage NA of
Nonpetroleum
Discourage
case-by-case
Discourage
case-by-case
Discourage
case-by-case
Neither
case-by-case
Discourage
Discourage
case-by-case
Neither
case-by-case
Seminar Series on Bioremediation of Hazardous Waste Sites: Practical Approaches to Implementation
20-1
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State
Delaware
Florida
Georgia
Hawaii
Idaho
Illinois
Indiana
Iowa
Encourage/
Discourage
NAof
Petroleum
Encourage
Encourage
Neither
case-by-case
Encourage
Encourage
case-by-case
Neither
case-by-case
Neither
case-by-case
Encourage
case-by-case
Guidelines or Rules
Informal guidelines for petroleum
does not use RBCA. Guidance
uses "passive action;" after 2
years need permission to
continue. Looks at property
boundaries. Non-UST use
ground-water management
zones. Assesses for "no further
action" and deed restriction.
Have voluntary action program
and Brownfields.
Incorporates RBCA in statutes;
is developing NA guidelines. NA
now allowed if low
concentrations. Expanding to
allow higher concentrations, and
more widespread contamination
and to broaden types of sites.
Hazardous waste section
considers NA for soils only.
No formal policy. Remediation
site specific. Threshold
representative standards. Looks
at media and risk.
Guidance no policy. Revising
manual on risk-based guidance.
Source and free product
removal.
Developing new ground-water
rule. Brownfields beginning.
Use beneficial-use criteria.
Informal guidelines. Drafting
RBCA and SSL approach in
developing guidance. RBCA for
UST and non-UST. Looks at
property boundaries. Brownfields
in development.
No formal protocol. Developing
RBCA.
Uses RBCA. Plans policy
changes. Hazardous waste
section considers "passive
remediation" if exposure risk is
low along with source removal
and monitoring.
Specific
Models to
Determine
NA
SESOIL
RBCA & SSL
Encourage/
Discourage NA of
Nonpetroleum
Neither
case-by-case
Discourage
case-by-case
Discourage
case-by-case
Neither
case-by-case
Neither
case-by-case
Neither
case-by-case
Neither
case-by-case
Neither
case-by-case
Seminar Series on Bioremediation of Hazardous Waste Sites: Practical Approaches to Implementation
20-2
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State
Kansas
Kentucky
Louisiana
Maine
Maryland
Massachusetts
Michigan
Encourage/
Discourage
NAof
Petroleum
Neither
case-by-case
Encourage
Neither
case-by-case
Encourage
Encourage
Encourage
Encourage
Guidelines or Rules
Considers NA for petroleum.
Evaluates aquifer beneficial uses,
property boundaries, and
receptors. Has dry cleaning state
trust fund for solvent waste.
Informal guidance for UST.
Generally only considers NA for
UST. Monitors until plume
dissipates. Non-UST use deed
restrictions to risk factor of 1 0~6.
No guidance or protocol.
Requires site characterization,
source removal, and monitoring
before using NA.
Developing in-house guidance
on NA of petroleum (end of
May). Considers NAwhen
exposure is low. Gathering
information on non-UST for
consideration.
No official documents on NA.
Uses RBCA approach. NA
allowed in areas not
environmentally sensitive. Risk
is primary factor. CERCLA does
not promote NA.
No NA guidelines. State statutes
use RBCA with NA implied in less
stringent cleanup standards
versus water-quality standards.
Drafting bioremediation
guidance document with NA
(within year). Considers other
wastes (e.g., solvents). Requires
monitoring and proof that NA
occurs before reaching receptors.
RBCA uses "Guidance Document
for RBCA at LUSTs."
Specific
Models to
Determine
NA
AT123D,
SESOIL,
VLEACH
Performance
model
May use
Bioplume III in
future
Bioplume II,
Modflow
Encourage/
Discourage NA of
Nonpetroleum
Discourage
case-by-case
Discourage
case-by-case
Discourage
case-by-case
Neither
case-by-case
Discourage
case-by-case
Discourage
case-by-case
Encourage
case-by-case
Seminar Series on Bioremediation of Hazardous Waste Sites: Practical Approaches to Implementation
20-3
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State
Minnesota
Mississippi
Missouri
Montana
Nebraska
Nevada
Encourage/
Discourage
NAof
Petroleum
Encourage
Encourage
Neither
Encourage
Encourage
Neither
case-by-case
Guidelines or Rules
UST has own RBCA rules
addressing NA. Draft policy
statement for non-UST in early
development: "Site Response
Risk Based Guidance for
Cleanup of Site Other Than
Petroleum Waste in Ground
Water." Uses risk and cost.
Remedial action levels in
drinking water aquifers, remedial
goals for potential drinking water
aquifers, and multiple levels for
other aquifers.
Encourages use of NA for
petroleum only. UST section
adopted RBCA 6 months ago
and uses that to address NA.
Hazardous waste section
beginning to look at NA.
No policy. Expanding state RBCA
system on NA. Source removal
not required if economically
unfeasible or near cleanup
levels. Uses property boundaries.
Superfund uses deed restrictions.
Have informal policy in UST
section. No degradation policy in
ground-water section. Superfund
considers deed restrictions. Will
consider NA if best or only
technology.
Risk-based guidance
incorporates NA. Combining
EPA, ASTM, and state guidance.
Regulations based on cleanup
levels. Superfund allows NA if
concentrations low and no
receptors. Determines beneficial
uses; if drinking water aquifer no
NA, if no potential for drinking
water consider NA.
No formal NA policy. Adhere to
federal UST program. Soil
contamination level 100 ppm.
Cleanup required if over level.
Specific
Models to
Determine
NA
Risk-based
model being
developed to
assess NA
Encourage/
Discourage NA of
Nonpetroleum
Neither
case-by-case
1 site allows NA of
chlorinated solvents &
metals
Discourage
case-by-case
Discourage
case-by-case
Discourage
case-by-case
Discourage
case-by-case
Discourage
case-by-case
Seminar Series on Bioremediation of Hazardous Waste Sites: Practical Approaches to Implementation
20-4
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State
New
Hampshire
New Jersey
New Mexico
North
Carolina
North Dakota
Encourage/
Discourage
NAof
Petroleum
Encourage
Encourage
Encourage
Encourage
Encourage
case-by-case
Guidelines or Rules
Guidance but no policy on NA.
Developing ground-water
management zones. Other
sections are looking at NA.
About to pass the Brownfields
and have a voluntary action
program.
Written policy on NA; involves
characterization, source removal,
and monitoring. Must identify
ground water uses based on 25-
year plan. Requires at least eight
quarters of monitoring. Sentinel
well 3 years time of travel
upgradient of receptor.
No formal guidance.
Incorporating NA into regulations
as part of RBCA. Looks at
property boundaries,
cost/benefit, and risk.
Source removal and low
concentrations use NA. Loosely
subscribes to Chevron indices to
determine extent of
bioremediation. Not as many
non-UST sites but has two using
NA. Contaminants include
carbon tetrachloride and
perchloroethylene.
Developed NA Rules in 1993.
Over 150 sites approved. Must
monitor until reaching cleanup
levels. Expanding rules to allow
some sources to remain if no
further leaching occurs and to
consider more compounds for
NA.
No state policy. Believes NA
works in significant number of
cases. NA approved at over
200 petroleum and 20 solvent
sites. Monitoring minimum of 2
years to verify that
concentrations are decreasing.
Specific
Models to
Determine
NA
RBCA
Accepted
USGS models
Encourage/
Discourage NA of
Nonpetroleum
Neither
case-by-case
Neither
case-by-case
Neither
case-by-case
2 cases
Neither
case-by-case
Encourage
case-by-case
Seminar Series on Bioremediation of Hazardous Waste Sites: Practical Approaches to Implementation
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State
Ohio
Oklahoma
Oregon
Pennsylvania
Rhode Island
South
Carolina
South Dakota
Tennessee
Encourage/
Discourage
NAof
Petroleum
Encourage
Encourage
case-by-case
Encourage
Neither
case-by-case
Neither
case-by-case
Encourage
Neither
case-by-case
Discourage
case-by-case
Guidelines or Rules
LUST follows RBCA guidelines.
New Voluntary Action Program,
Brownfields. Working on draft
rule for hazardous waste and
petroleum. Various models used.
One PRP used POLLUT to
demonstrate NA.
No formal policy on NA.
Evaluates on a case-by-case
basis. Property boundaries used
as point of compliance.
No state guidance. Revising the
ASTM, and NA issue may arise
when adopting rules on USTs.
No NA policy. Not using RBCA.
Developed "Act 2," which drives
state programs. Site-specific
standards based on risk
assessment. "No action" may
be designated to sites.
No guidelines. NA reviewed on a
case-by-case basis.
Intrinsic remediation written into
RBCA in evaluating LUST sites.
Working with USGS on field
studies addressing NA. Flexibility
in modeling for NA.
Uses ASTM RBCA system. No
formal NA procedures. NA
factors include contaminant
type/extent and beneficial uses of
aquifer. Looks at property
boundaries. Soil cleanup
required. Consult handbook,
soil cleanup regulations, and
ground-water quality standards
used. Must meet water-quality
standards for 1 year before
closure.
NA not encouraged, but
considers on a case-by-case
basis. Encourages an accelerated
bioremediation approach.
Specific
Models to
Determine
NA
Include
SESOIL,
VLEACH
SESOIL,
AT123D
RBCA
Encourage/
Discourage NA of
Nonpetroleum
Neither
case-by-case
Neither
case-by-case
Case-by-case
Neither
case-by-case
Discourage
case-by-case
Discourage
case-by-case
Neither
case-by-case
Discourage
case-by-case
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State
Texas
Utah
Virginia
Washington
West Virginia
Wisconsin
Wyoming
Encourage/
Discourage
NAof
Petroleum
Encourage
Encourage
Neither
case-by-case
Encourage
Encourage
Neither
Neither
Guidelines or Rules
Developing risk-based rules
addressing NA for UST; ready by
end of year. Volunteer cleanup
program started. Has guidance
on NA of soils and is developing
guidance for ground water.
Risk-based approach. Approves
NA for petroleum but not for
other compounds. Non-UST has
two levels of industrial risk, 1 0~4
and 1 0~6. Uses deed restrictions.
No guidance. Recognizes NA
occurs with petroleum. Non-UST
uses risk-based standards. NA
depends on aquifer beneficial
use. Have voluntary action
program.
Actively looking at NA,
particularly soil to ground water.
Using SSL after EPA.
No definitive rule. Developing
state policy for NA incorporating
soil cleanup levels. Plans
interagency risk-based approach.
Brownfields just passed.
Developing preliminary guidance
for a range of contaminants to
be ready by end of year for
ground water. Aquifer
characteristics, risk, beneficial
uses, and aquifer type will be
considerations. Has guidance on
NAof soils.
NA considers risk, beneficial
uses, aquifer characteristics.
Considers NA in industrial areas
and no potential receptors.
Developing guidance (end of
year) looking at a range of
contaminants.
Specific
Models to
Determine
NA
REAMS
(SESOIL,
AT123D)
Encourage/
Discourage NA of
Nonpetroleum
Neither
case-by-case
Discourage
case-by-case
Discourage
case-by-case
Neither
case-by-case
Neither
case-by-case
Neither
case-by-case
Neither
case-by-case
North Carolina and New Jersey are the only states with formal guidance or rules addressing NA as
a remediation option in both ground water and soils. Texas and Wisconsin have written formal
guidance with regard to NA in soils and are currently working on ground-water guidance. States
with informal policies or guidelines include Arkansas, Delaware, Illinois, Kentucky, Montana, North
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Dakota, South Dakota, and Vermont. In the North Carolina Implementation Guidance, "the
Corrective Action Plan (CAP) must document that conditions at the subject site are conducive to
natural remediation processes and should present any evidence that natural attenuation is occurring
at the site." NA is generally used as part of a treatment which may include source removal or other
types of active remediation. Monitoring data are generally used to demonstrate decreases in volume
and concentration over time. For sites where the plume is still expanding, NA could also be
demonstrated if it can be shown that the rate of contaminant transport is significantly less than the
estimated rate of linear ground-water velocity. Degradation products must also be evaluated since
they can sometimes be more toxic the original contaminant of concern.
State agencies widely accept that NA does occur in petroleum-contaminated sites. EPA's Office of
Underground Storage Tanks (OUST) found that remediation at leaking underground storage tanks
has shifted to using NA across the United States. In 1993, landfilling was the predominant
remediation for soils and pump-and-treat the most common in ground-water treatment. As of 1 995,
NA of soils (28 percent) was a close second to landfilling (34 percent), while NA (47 percent) is the
most common form of remediation at ground-water sites. The policy is, however, that NA is not to
be regarded as a "default" remediation technology, and free product removal is a prerequisite.
Leaks from underground storage tanks (USTs) are one of the most common causes of ground-water
contamination. Many states are using or developing a risk-based corrective action approach when
addressing these sites. The Emergency Standard Guide for Risk-Based Corrective Action applied at
petroleum release sites, issued by the American Society for Testing and Materials (ASTM), looks at
"demonstrated and predicted attenuation of hydrocarbon compounds with distance." Corrective
action goals are determined based on a tiered approach, the most conservative being at Tier 1,
where risk to human health or the environment is high. The other two tiers may allow for site-specific
goals to be developed where risk is not imminent. Revisions to RBCA are under way to incorporate
the premise that the further a receptor is from a contaminated area, the less likely it is to be affected,
consequently allowing for greater amounts of contaminants to be left in place the farther they are
from a receptor. Natural attenuation is "assumed" to occur between the source and the receptor.
In risk-based decision-making, proof of NA may not always be as important as the potential impact
on a given receptor, the classification or use of the ground-water aquifer, or simply the approaches
that are technologically feasible or cost-effective. Some states are assigning different levels of
cleanup based on these other factors. Alternate protection levels may be assigned based on the
beneficial-use designation of the aquifer. Even in highly populated areas, if the ground water is
already contaminated and is not being used as a water supply, then cleanup may not be required.
These decisions, although they may be in part based on assumed NA, may not be the main
consideration. Many states view remediation with regard to property boundaries. As long as the
contamination remains within the property boundaries, then no action may be taken. If a plume
migrates off the property, however, NA may be used to address contamination at that point. Some
states using "monitoring only" may not necessarily be basing these decisions on the basis of site-
specific NA, but on risk. Other states are claiming NA by default, simply due to the length of time
required for active cleanup. Also, not all states are requiring source removal before using NA.
Seminar Series on Bioremediation of Hazardous Waste Sites: Practical Approaches to Implementation
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Summary
New Jersey and North Carolina have developed policies addressing NA as a stand-alone option for
both ground water and soils, primarily for petroleum compounds. North Carolina developed its rule
on NA in 1 993 and has approved approximately 150 sites for the process. NA is only appropriate
after site conditions have been fully evaluated and it has been concluded that natural remediation
is a viable option for ground water. This involves an evaluation of all potential impacts in the vicinity
of the site, including impacts on ground water used for potable purposes, surface water bodies, and
wetlands, to ensure that receptors will not be affected as the contaminant concentrations degrade.
Source removal is generally required. Most of these are petroleum sites, but a couple of sites in
North Carolina have also included solvents and even lead. Although some of these compounds are
not readily biodegradable, North Carolina also looks at sorption and removal of the source. Source
removal may not even always be required if it can be proven that no further leaching will occur.
Texas and Wisconsin have written formal guidance regarding NA of soils. They are in the process
of developing guidance pertaiing to NA of ground water as well. Wisconsin is currently working with
Alaska in developing guidance for soils in that state.
Other states have developed informal guidance for ground-water and soil contamiantion focusing
on petroleum waste. Delaware has informal guidelines concerning petroleum waste that allows for
a "passive corrective action" plan. Passive action is remediation through natural degradation.
Assurance that contaminants will not pose a threat to human health or the environment is required.
One year of monitoring must show that the remediation is sufficient for site closure. After 2 years,
written permission is required to continue using passive action. Florida recognizes NA and expects
this to be a big part of remediation in the future. The state intends to expand NA activities during the
next year and broaden the types of sites that will be considered. Monitoring for NA will be allowed
at sites with higher contaminant concentrations and more widespread contamination. Michigan is
developing a draft bioremediation guidance document to determine criteria considered for
bioremediation, including NA. A final version, expected within the year, will not only consider
petroleum waste but other wastes, including solvents. Texas is beginning to look at chemicals other
than petroleum to be considered for NA as well. A document was recently prepared entitled Present
Remedies Guidance Document for Soils at Texas Superfund Sites. A similar document on ground
water will soon be written and will address NA. Nebraska's Superfund section may also look at NA
by allowing it at sites with low levels and simply monitoring. New Mexico has allowed a few sites to
use NA of more refractory chlorinated compounds. For example, at one site it was found that
carbon tetrachloride was degrading fairly well to methylene chloride, another with NA of PCE
contamination. Wisconsin and Wyoming are developing some very preliminary guidance or
protocols looking at a range of contaminants; these should be ready by the end of the year.
Considerations for use of NA will be based not only on the risk and beneficial uses but other
characteristics of the aquifer as well.
Most of the states are either using RBCA or are incorporating it into state guidelines regarding NA
of petroleum hydrocarbons at UST sites. California, Iowa, Mississippi, Montana, North Carolina,
Washington, and West Virginia are the only states that were not using and did not plan to use the
RBCA at petroleum sites. Interested parties in West Virginia, however, recently met to develop a state
policy for NA incorporating soil cleanup levels. The state is in the process of accumulating
information from other states. A risk-based approach is in review for eventual incorporation into the
Seminar Series on Bioremediation of Hazardous Waste Sites: Practical Approaches to Implementation
20-9
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overall statewide policy. The state plans to have an interagency approach including UST, RCRA and
CERCLA Idaho is developing a new ground-water rule. Maine is developing a guidance document
(draft by the end of May) for in-house staff to determine when intrinsic remediation of petroleum
hydrocarbons is appropriate. States have also indicated that NA may be incorporated in other
programs as well. In the survey, Illinois, Idaho, West Virginia, Texas, and Ohio are only a few of the
states that indicated they have a voluntary action program and have passed state legislation
concerning the "Brownfields" Act.
Natural attenuation can play a role in the cleanup of Brownfields sites. Brownfields are abandoned,
idled, or underused industrial and commercial sites where expansion or redevelopment is
complicated by real or perceived environmental contamination that can add cost, time, or
uncertainty to a redevelopment project. In recent years, states have developed voluntary cleanup
programs designed to provide liability protection to private parties that clean up Brownfields sites.
EPA supports these state cleanup programs and pledges that the successful cleanup of a site under
a state program will also satisfy EPA regulations. Eighteen Brownfields National Pilots are currently
under way in Alabama, California, Connecticut, Indiana, Kentucky, Louisiana, Maryland,
Massachusetts, Michigan, New Jersey New York, Ohio, Oregon, Pennsylvania, Rhode Island, Texas,
Virginia, and Washington.
Bibliography
1. Barkan, C. 1 996. State-by-state summary on RBCA approaches. Soil & Groundwater
Cleanup. April: 41.
2. Bryant, C. 1995. Recent developments in laws and regulations. Remediation. Winter:
111.
3. Copeland, T.L., R. Pesin, et al. 1995. Using risk assessment to achieve cost-effective
property transfers and site closures for former UST sites. Remediation. Winter: 1.
4. EERP. 1993. ERRP issues guidance on natural biodegradation. Wisconsin Department of
Natural Resources Emergency and Remedial Response Section.
5. NJDEP. 1996. Site remediation program, technical requirements for site remediation,
proposed readoption with amendments. New Jersey Administrative Code (NJAC) 7:26E.
New Jersey Department of Environmental Protection.
6. NCDEQ. 1 995. 15A North Carolina Action Code (NCAC) 2L Implementation Guidance.
North Carolina Department of Environmental Quality.
7. NCDEQ. 1993. 15A North Carolina Action Code (NCAC) Title 15A, Subchapter 2L,
Sections .0100, .0200, .0300. Classifications and water quality standards applicable to
the ground waters of North Carolina. North Carolina Department of Environment, Health,
and Natural Resources Division of Environmental Management.
Seminar Series on Bioremediation of Hazardous Waste Sites: Practical Approaches to Implementation
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8. Penelope, P.A., K.D. Reece, et al. 1995. Sensitivity analysis for setting soil cleanup
standards. Remediation. Winter: 19.
9. Rite, S.M. 1 996. States speak out on natural attenuation. Soil & Groundwater Cleanup.
January-February: 18.
10. Tulis, D. 1996. The growth of remediation by natural attenuation at LUST sites in the U.S.
Presented at UST/LUST National Conference (March 1 1). U.S. EPA Office of Underground
Storage Tanks.
Seminar Series on Bioremediation of Hazardous Waste Sites: Practical Approaches to Implementation
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State Review
Natural Attenuation of
Ground Water and Soils
Daniel Pope
Dynamac Corporation
Ada, OK
Natural Attenuation of
Petroleum Hydrocarbons
Leaks from USTs are the most
common cause of ground-water
contamination
As of June 1995, there have
been over 295,000 confirmed
releases
Remediation at LUST Has Shifted
to Using Natural Attenuation
In 1993, landfilling was the
predominant remediation for soils, and
pump-and-treat the most common in
ground-water treatment.
As of 1995, NA of soils (28%) only
second to landfilling (34%), while NA of
ground water (47%)
(information obtained from EPA's Office of
Underground Storage Tanks [OUST])
Use of Soil Cleanup Technologies
at UST Sites
Incineration
Landfilling
Thermal Desorption
ndfarming
Soil Vapor Extraction
Biopiles
Adapted from Dana Tulis, EPA
UST/LUST National Conference
Talk, March 11, 1996
Natural Attenuation
Use of Groundwater Cleanup
Technologies at UST Sites
Dual-Phase Extraction Biosparging
itu Bioremediation
Pump-and-Treat
Air Sparging
Natural
Adapted from Dana Tulis, EPA
^ National Conference
Talk, March 11, 1996
Programs That May Look at Natural
Attenuation in Cleanup
UST
CERCLA
RCRA
State Voluntary Cleanup Program
Brownfields Sites
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Risk-Based Corrective Action
(RBCA) and NA at UST Sites
Emergency Standard Guide for RBCA by ASTM
Most states using/incorporating RBCA into
guidelines
Demonstrated and predicted attenuation of
hydrocarbons with distance
Corrective action goals based on a tiered
approach
Tier 1 most conservative; high risk
Two lower tiers allow site-specific goals; risk not
imminent
ASTM Revisions
Currently assembling NA document
Limited petroleum compounds
May consider other compounds (e.g.,
solvents) in future
Document purpose
Remove stigma that NA is equivalent to
"no further action"
Serve as a conceptual framework in NA
decision-making and information needs
EPA's Policy on Natural
Attenuation
Office of Underground Storage Tanks
(OUST)
NA is not a "default" remediation technology for
LUST sites
Supports use of the most appropriate technology
Technology selection should be risk-based on a site-
by-site basis
NA is an active choice, includes site
characterization, risk assessment, and monitoring
Free product removal is a prerequisite to using NA
Cleanup not complete until reaching state or local
cleanup levels
Brownfields
Abandoned industrial/commercial
sites
Redevelopment complicated by real or
perceived contamination
Successful cleanups under State
programs would satisfy EPA
regulations
18 States currently with Brownfields
National Pilot Studies
U.S. EPA Survey Asked
States:
(1) Whether they encourage or discourage
the use of natural attenuation (NA)
(2) If there are any formal or informal
policies or guidelines for NA
(3) If they use any particular model when
deciding on NA
(4) If compounds other than petroleum
hydrocarbons would be considered for
NA
States With Formal Guidance
on Soils Using NA
Texas
Wisconsin
Seminar Series on Bioremediation of Hazardous Waste Sites: Practical Approaches to Implementation
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States Developing Soils
Guidance With NA
Alaska
Arizona
Florida
Michigan
South Dakota
West Virginia
Vermont
State Guidelines on Natural
Attenuation in Soils
D Written Guidelines
Developing Guidelines
QNo Guidelines
States With Natural Attenuation
Policy on Ground Water
North Carolina
New Jersey
Each State Requires:
Full plume definition and receptor analyses
Appropriate modeling to predict plume
degradation
Source removal or control
Monitoring program to demonstrate NA
North Carolina
Developed rule on natural attenuation in 1993
Approved approximately 150 sites for NA
Most are petroleum sites, but some included
solvents and even lead
Looks at sorption and source removal as part of
NA, hence NA for Pb possible
Assesses potential for toxic byproducts
Source removal may not be required if no further
leaching to ground water is proven
Future land use in the vicinity of the site
required
New Jersey Natural
Attenuation Rules
Assess potential impacts, ensure no impact to
receptors, and remove/remediate sources
NA may be used at sites deemed technically
impractical for active remediation
Identify current and potential ground-water
uses based on a 25-year plan
Costs of remedy includes long-term
monitoring
Historical data determine the duration and
frequency of sampling
Monitoring Requirements
New Jerseyat least eight quarters of
monitoring
North Carolinamonitor until appropriate
ground-water quality standards achieved
Both require sentinel wells downgradient of
plume if receptor involved
Minimum time of travel upgradient of receptor:
3 years - New Jersey
1 year - North Carolina
Monitoring assesses past predictions, plume
behavior, and modification needs
Seminar Series on Bioremediation of Hazardous Waste Sites: Practical Approaches to Implementation
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Other States Addressing
Natural Attenuation
Delaware UST Section's
Technical Guidance Manual
» "Passive corrective action" allows NA if
no threat to receptors
» Source and free product removal a goal
» Monitor 1 year to demonstrate
sufficient remediation for site closure
» Passive action not allowed beyond 2
years without written approval
States Developing Natural Attenuation
Guidance on Ground Water
TEXAS Ground-water guidance similar to
"Present Remedies Guidance Document
for Soils at Texas Superfund Sites"
MICHIGAN Draft bioremediation guidance to
determine criteria considered for
bioremediation including NA. Not only
petroleum waste will be considered.
MAINE In-house guidance document to
determine intrinsic remediation of
petroleum
States Developing Natural Attenuation
Guidance on Ground Water (continued)
WISCONSIN Preliminary guidance based on
risk, beneficial uses, and aquifer
characteristics
FLORIDA Petroleum cleanup rules/
mandating RBCA in State
Legislative statutes
SOUTH Performing field studies with
CAROLINA USGS that address intrinsic
remediation
WYOMING Preliminary guidance considering a
range of contaminants
Other States Approaches
CALIFORNIA Does not use NA. Revisions to Reso-
lution 92-49 refer to "containment
zones" out of which the contaminant
is not allowed to migrate.
TENNESSEE Does not encourage use of NA. Does
encourage more accelerated forms of
bioremediation.
CONNECTICUT Use ground-water classification to
establish cleanup standards. Aquifers
with lower designation more likely to
be considered for NA as a remedial
option.
Natural Attenuation
Models
Most states allow PRP to use any
peer reviewed model
Some states have indicated they
use mostly SESOIL, VLEACH, and
AT123D
One State indicated interest in
Bioplume III when available
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Survey Summary
There are 2 states that have
developed official policy
There are about 7 states
developing guidance
There are about 13 states with
unofficial guidance
State Policies Regarding Natural
Attenuation in Ground Water
Written policies and guidelines
Developing policies and guidelin
B Informal policies and guidelines
Informal guidelines/Do not
consider non-UST waste
n Do not have any formal policy
Conclusion
Interest in NA is increasing and being
incorporated into more state environmental
regulations and programs.
Although NA is gaining acceptance, it should
be remembered that complete site
characterization is an essential part in
deciding if this remediation option is
appropriate.
NA is a remedial approach that should be
based on the likelihood of success and is not
a "no action" alternative.
Seminar Series on Bioremediation of Hazardous Waste Sites: Practical Approaches to Implementation
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Monitoring
Daniel Pope
Dynamac Corporation, Ada, OK
Monitoring of bioremediation and natural attenuation can be considered from several viewpoints.
First are the contaminant-oriented questions: Are the contaminants disappearing, and, if so, how?
The mechanism of disappearance is of interest: Are contaminants being biodegraded, or to what
degree are volatilization, leaching, adsorption, or other mechanisms involved?
Next, if the contaminants are being biodegraded, are the contaminants being broken down to
intermediate products (which may be innocuous or toxic), mineralized to carbon dioxide and water,
or polymerized/humified? Toxicity changes may be monitored to determine whether toxicity is
decreasing or whether degradation products may be of higher toxicity than the original
contaminants. Finally, the rate of contaminant loss helps to estimate remediation times and to
assess degradation relative to contaminant mobility to sensitive receptors.
Geochemical factors associated with contaminant degradation may be monitored. Degradation may
cause changes in pH, redox potential, electron acceptors, and alkalinity; these changes may be
monitored to help prove remediation is taking place, to establish areas on the site where different
kinds of remediation are taking place, and to estimate remediation rates. In addition to the
geochemical factors already mentioned, temperature and salinity may affect microbial processes
and therefore degradation rates. Operational parameters require monitoring to determine whether
appropriate levels of nutrients, electron acceptors, and water necessary for bioremediation are
present.
Monitoring of microbial parameters may be required. The various estimates of contaminant
degradation, electron acceptor change, and other geochemical changes indirectly measure
microbial activity, but there may be a need to measure certain aspects of the microbial population
directly. Microbial populations may be estimated by plate counts, most probable number techniques
(MPN), or direct microscopic examination. In addition to respiration measurements, ATP activity
measurements can estimate microbial metabolic activity. FAME profiles and sole carbon source
profiles measurements may provide information about microbial community structure. Several types
of culture tests can indicate the ability of the microbial population to degrade contaminants of
interest. Generally, microcosm tests using soil or water samples from the site under conditions as
similar as possible to site conditions are most likely to yield information about microbial activity and
contaminant degradation that can be readily used for making decisions about site activities.
Monitoring may be required to establish the success (or failure) of bioremediation/natural
attenuation, give timely warning of the impending impact on sensitive receptors, and determine the
potential for site closure. Generally, monitoring is required for a number of years to develop
sufficient data to establish that risk to sensitive receptors is not significant, and that the site is ready
for closure.
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Bibliography
1. Blackwood, L.G. 1 991. Assurance levels of standard sample size formulas: Implications for
data quality planning. Environ. Sci. Technol. 25:8.
2. Dragun, J. 1 988. The soil chemistry of hazardous materials. Hazardous Materials Control
Research Institute, Silver Spring, MD.
3. Eklund, B. 1992. Practical guidance for flux chamber measurements of fugitive volatile
organic emission rates. J. Air Waste Mgmt. Assoc. 42:1,583-1,591. December.
4. Gilbert, R.O. 1987. Statistical methods for environmental pollution monitoring. Van
Nostrand Reinhold.
5. Gilbert, R.O., and J.C. Simpson. 1990. An approach for testing attainment of soil
background standards at Superfund sites. In: American Statistical Association 1 990, Joint
Statistical Meetings, Anaheim, CA. August 6-9, 1 990. Pacific Northwest Laboratory,
Richland, WA.
6. Hawley-Fedder, R., and B.D. Andresen. 1991. Sampling and extraction techniques for
organic analysis of soil samples. UCRL-ID-106599. Lawrence Livermore National
Laboratory, Berkeley, CA. February.
7. Keith, L.H., ed. 1988. Principles of environmental sampling. American Chemical Society.
8. Lewis, I.E., A.B. Crockett, R.L. Siegrist, and K. Zarrabi. 1 991. Soil sampling and analysis
for volatile organic compounds. EPA/540/4-91/001. Superfund Technology Support
Center for Monitoring and Site Characterization, Environmental Monitoring Systems
Laboratory, Las Vegas, NV. February.
9. Norris, et al. 1 994. Handbook of bioremediation. Lewis Publishers, CRC Press.
1 0. Soil Science Society of America 1 987. Glossary of soil science terms. Soil Science Society
of America, 677 South Segoe Road, Madison, Wl.
11. U.S. EPA. 1985. Practical guide for ground-water sampling. EPA/600/2-85/104.
September.
12. U.S. EPA. 1 986. Permit guidance manual on unsaturated zone monitoring for hazardous
waste land treatment units. EPA/530/SW-86/040. Environmental Monitoring Systems
Laboratory, Las Vegas, NV. October.
1 3. U.S. EPA. 1 990. A New approach and methodologies for characterizing the hydrogeologic
properties of aquifers. EPA/600/2-90/002. January.
14. U.S. EPA. 1990. Handbook: Ground waterVol. I: Ground water and contamination. Vol.
II: Methodology. EPA/625/6-90/01 6a,b.
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15. U.S. EPA. 1990. Basic concepts of contaminant sorption at hazardous waste sites.
EPA/540/4-90/053. October.
1 6. U.S. EPA. 1 991. A guide: Methods for evaluating the attainment of cleanup standards for
soils and solid media. Quick reference fact sheet. 9355.4-04FS. Office of Emergency and
Remedial Response, Hazardous Site Control Division. July.
1 7. U.S. EPA. 1 991. Dense nonaqueous phase liquids. EPA/540/4-91 -002. March.
1 8. U.S. EPA. 1 991. Description and sampling of contaminated soils: A field pocket guide.
EPA/625/12-91/002. November.
19. U.S. EPA. 1991. Handbook of suggested practices for the design and installation of
ground-water monitoring wells. EPA/600/4-89/034. Environmental Monitoring Systems
Laboratory, Las Vegas, NV. March.
20. U.S. EPA. 1992. General methods for remedial operations performance evaluations.
EPA/600/R-92/002. January.
21. U.S. EPA. 1993. Subsurface characterization and monitoring techniques: A desk reference
guideVol. 1: Solids and ground water, Appendices A and B. Vol. II: The vadose zone,
field screening and analytical methods, Appendices C and D. EPA/625/R-93/003a,b.
May.
22. U.S. EPA. 1993. Use of airborne, surface and borehole geophysical techniques at
contaminated sites: A reference guide. EPA/625/R-92/007. Center for Environmental
Research Information, Cincinnati, OH. September.
23. U.S. EPA. 1994. Methods for monitoring pump-and-treat performance. EPA/600/R-
94/123. June.
24. Wiedemeier, T.H., et al. Technical protocol for implementing intrinsic remediation with long-
term monitoring for natural attenuation of fuel contamination dissolved in groundwater,
Vols. I and II. Air Force Center For Environmental Excellence, Technology Transfer Division,
Brooks Air Force Base, San Antonio, TX.
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Monitoring
Daniel Pope
Dynamac Corporation
Ada, OK
Monitoring
Bioremediation/Natural
Attenuation
Much information available on
monitoring technologies
This presentation mainly a
checklist: what should be
monitored, and why?
References for specific techniques
in handout
Monitoring To Determine
Remediation Rates (contaminant
disappearance)
Are contaminants
disappearing?
Rate of disappearance
Monitoring To Determine
Daughter Products
Estimate remediation rates
Determine toxic products (e.g.,
vinyl chloride from TCE)
Monitoring for
Operational Purposes
Addition of electron acceptors
Nutrients
Water
Monitoring To Warn of Potential
Impact on Sensitive Receptors
At or before point of compliance
Must allow time for remedial
measures
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Monitoring Mass Balance
Approach
Contaminants "disappear" from analytical
view without actually being remediated
Monitor each phase (soil solids, gas, water,
and nonaqueous phase liquid) to
determine how much of each waste
component is in each phase
Determine whether remediation is
actually taking place or whether
contaminants are merely being moved to
different phases
Monitoring Breakdown
Products
i Many breakdown products known
i Monitoring is not common, except
for breakdown products of known
high toxicity, such as vinyl
chloride, or those that are easy to
measure, such as carbon dioxide
Monitoring Toxicity -
Microtox Microbial Bioassay
Cultures of phosphorescent (light-
emitting) marine bacteria are
exposed to contaminated media or
extracts, and decline in light
output over time is measured
Microtox assay measures general
metabolic inhibition
Monitoring Toxicity -
Microtox Microbial Bioassay
Major advantages: quick, easy,
repeatable, inexpensive, and has a large
amount of published literature about
its uses and results
Major disadvantage (as for most acute
bioassays): results of the assay have no
direct relationship to toxicity of the
contaminants to humans or ecology
Monitoring Toxicity -
Ames Assay
A measure of mutagenic potential
of a sample
High correlation between
mutagenicity (as measured in the
Ames test) and carcinogenicity
Several days to complete, more
expensive than Microtox
Monitoring Toxicity -
Other Assays
Many other species have been
used for assessing toxicity of
environmental samples
EPA conducting R&D on ecological
and health assays to develop
alternative endpoints
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Monitoring Microbial
Activity
Plate counts
Most Probable Number (MPN)
counts
Direct microscopic counts
Respiration measurements
ATP activity measurements
Monitoring Microbial
Activity
Oxygen, carbon dioxide levelsgeneral index
of microbial activity
Monitoring oxygen or carbon dioxide alone
can be deceiving since abiotic processes can
affect oxygen or especially carbon dioxide
Because the respiration estimated may not
result only from transformation of the
compounds of interest, respiration cannot be
used as a direct measure of transformation of
these compounds
Monitoring Microbial
Activity
Soil gas concentrations of CQ, O2
fluctuate daily due to microbial
activity
Measure CO2 and O2 at the same
time of day for each sampling
event
Monitoring Microbial
Activity
Soil microorganisms can be cultured on
specific media to determine counts of
"specific degraders"
If PAHs are added to a media with no
other carbon sources present, any
microorganisms that grow in the media
can be assumed to have the capability
of using PAHs as a sole source of
carbon
Monitoring Soil Moisture
"Visual" methodsrequire
experience
Gravimetric methodsaccurate, but
time consuming
Neutron probesaccurate,
expensive, use radioactive material
Porous cup tensiometers
Capacitancenot very accurate
Nutrients
Several standard tests
Carbon to nitrogen to phosphorus
(C:N:P) ratios of 100-300:10:1
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Volatilization
Leaching
Usually volatiles released from the
soil surface
Canopy placed over defined area
of contaminated soil
Vapors collected under canopy
swept into adsorbent for later
extraction and analysis
Sampling pump at site perimeters
Porous cup and pan lysimeters
Porous cup lysimeters work even
when soil is relatively dry
Pan lysimeters collect only water
that is actively moving down
through soil
Most LTUs, soil piles, compost
units are lined to collect leachate
Sampling Program Goals
Sample Location
Average contaminant
concentration to +/- x ppm
Highest contaminant concentration
< x
Desired confidence limits
Random
Stratified random
Grid, with random start
What Should Monitoring
Show?
Plume type (stable, shrinking,
expanding)
Remediation rates
Warning of potential impact on
sensitive receptors
What is Required To Show That
Bioremediation/Natural
Attenuation Is "Working?"
Documented loss of contaminants from site
Daughter product appearance
Appropriate geochemistry
Electron acceptor disappearance/product
appearance
Laboratory assays showing microorganisms
from site samples have potential to transform
contaminants under expected site conditions
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Monitoring - Primary
Evidence
Plume behavior (stable,
shrinking, expanding)
Monitoring - Primary
Evidence
If the plume is stable or shrinking,
this is primary evidence that
natural attenuation is occurring
If the plume is expanding more
slowly than GW movement
adjusted for retardation, this is
evidence that natural attenuation
is occurring
Monitoring - Secondary
Evidence
Historical data may not be
available to indicate the plume
state
Then, secondary evidence can be
used while information on plume
state is being accumulated
Monitoring - Secondary
Evidence
Electron acceptor/reduction
product concentrations
Monitoring - Secondary
Evidence
Monitoring - Secondary
Evidence
Alkalinity
Inverse correlation between
electron acceptors and
contaminant concentrations
Daughter products
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Determining Natural
Attenuation Rates
Mass balance (for any plume type)
Concentration versus time
(for shrinking plumes)
Concentration versus distance
(for stable plumes)
Mass Balance Approach
Requirements
Estimate of source area
perpendicular to GW flow
Estimate of hydraulic conductivity
and gradient
Concentration versus Time
Approach Requirements
Concentration versus Distance
Approach Requirements
Wells with measurable
contaminant outside free product
zone
Two or three downgradient wells,
along direction of GW flow, with at
least two wells with measurable
contaminant concentrations,
differing by several fold
Warning of Impact on
Sensitive Receptors
Sentinel wells located at
compliance point between
contaminated GW and sensitive
receptor
Location must allow time for
remedial measures to be taken
before contamination moves past
sentinel well to sensitive receptor
Monitoring Frequency -
Factors
Plume status
Water table fluctuations
Seasonal variability
GW velocity
Distance from plume to sensitive
receptor
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Monitoring Frequency
Monitoring Frequency
One year of quarterly monitoring
often sufficient to establish
relationship between readily
degraded contaminants and electron
acceptor/reduction products
concentrations
More than one year may be
necessary to establish whether a
plume is stable, shrinking, or
expanding
Previous monitoring efforts may
reduce need for more wells,
monitoring data
Laboratory Assays for
Biodegradation
Determine biodegradation rates, but
may not reliably indicate field rates
Establish potential for
bioremediation, but may not be
necessary for simple petroleum
contaminants
Determining need for nutrient,
electron acceptor addition
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Modeling
Daniel Pope
Dynamac Corporation, Ada, OK
Introduction
A mathematical description of bioremediation establishes a framework for evaluating laboratory
treatability data and field data that are useful for determining treatment potential under site and
environmental constraints. Mathematical models provide an approach for integrating simultaneous
processes of degradation, mass transport, and partitioning within subsurface and surface systems
so that an assessment can be made of the presence of target chemicals in leachate, soil, and air.
Models provide an estimate of the potential for ground-water and air contamination through a
determination of the rate and extent of contaminant transport and biodegradation as related to
specific subsurface or surface characteristics. Models also allow identification of those chemicals
requiring management to reduce or eliminate risk to human health and the environment. Thus,
mathematical models represent tools for ranking design, operation, and management alternatives
as well as for the design of monitoring programs for engineered (active) and nonengineered
(passive) biological treatment systems.
Model Types
To address the complex processes occurring at a site with regard to bioremediation, four types of
models are described: 1) saturated flow, 2) multiphase flow, 3) geochemical, and 4) reaction rate
models (1). Saturated flow models are derived from basic principles of conservation of fluid mass
and describe the flow path and rate of transport of water and dissolved contaminants (using
principles of conservation of chemical mass) through the saturated zone. In special cases,
biodegradation reactions, based on simple first-order kinetics, can be incorporated into the model.
Often, however, biodegradation processes are too complex to be simply incorporated; therefore,
special modeling tools are needed.
Multiphase flow models describe systems where two or more fluids exist together in a porous
medium. With regard to unsaturated flow, water and air are two fluids that exist together. Addition
of gasoline represent a third fluid within the unsaturated zone. Dense nonaqueous phase liquids
(DNAPLs) often occur within the saturated zone and are immiscible (nonmixing) with water.
Complex interactions among water, air, NAPLs, and solids renders multiphase flow models that are
more complex and less accurate due to the relatively large number of transport parameters required.
Geochemical models identify how thermodynamics of chemical reactions in the subsurface control
the speciation of target chemicals. Geochemical models are primarily concerned with inorganic
contaminants, for example, metal mobility. The lack of application to bioremediation of such
models is due to 1) lack of incorporation of organic chemicals, 2) equilibrium orientation (rather
Seminar Series on Bioremediation of Hazardous Waste Sites: Practical Approaches to Implementation
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than kinetic orientation of biodegradation models), and 3) high complexity and cost without the
incorporation of biological components.
Reaction rate models, including biological models, describe the rate of microbial transformation of
target organic chemicals. Biodegradation rate expressions can be incorporated into a model that
takes into account the rate of reaction as a function of active biomass present, contaminant
concentration, and electron acceptors present. Determination of appropriate rate expressions,
especially for the description of co-oxidation or co-metabolism, is an area of current development.
Biodegradation models are most easily combined with flow models when one rate-limiting material
can be identified. The rate-limiting material often is the primary electron donor or electron acceptor.
The biodegradation of petroleum hydrocarbons can often be modeled with oxygen as the
rate-limiting parameter.
Modeling Biodegradation
Main approaches used for modeling biodegradation include 1) first-order degradation models, 2)
biofilm models, 3) instantaneous reaction models, and 4) dual-substrate Monod models. Additional
information regarding these modeling efforts is given in Bedient and Rifai (2). Where a biofilm
approach is used, as often occurs in the subsurface, three processes are described: 1) mass
transport from the bulk liquid, 2) biodecomposition within the biofilm, and 3) biofilm growth and
decay.
Borden and Bedient (3) developed the first version of the BIOPLUME model. They developed a
system of equations to simulate the simultaneous growth, decay, and transport of microorganisms
combined with the transport and removal of hydrocarbons and oxygen. Simulation indicated that
any available oxygen in the region near the hydrocarbon source will be rapidly consumed. In the
body of the plume, oxygen transport will be rate limiting, and the consumption of oxygen and
hydrocarbon can be approximated as an instantaneous reaction.
Rifai and others (4, 5) expanded the original BIOPLUME and developed a numerical version
(BIOPLUME II) by modifying the U.S. Geological Survey (USGS) two-dimensional method of
characteristics (6). Transport of oxygen and contaminants in the subsurface is simulated, and
biodegradation is approximated by the instantaneous reaction model. The only input parameters to
BIOPLUME II that are required to simulate biodegradation are the amount of dissolved oxygen in
the aquifer prior to contamination and the oxygen demand of the contaminant determined from a
stoichiometric relationship. Other parameters are the same as required for the USGS model (6).
BIOPLUME II was used to model biodegradation of aviation fuel at the U.S. Coast Guard Station
in Traverse City, Michigan.
Unsaturated zone modeling has been presented in Stevens et al. (7), where the model developed
by the U.S. Environmental Protection Agency, Regulatory and Investigative Treatment Zone (RITZ),
was expanded. The Vadose Zone Interactive Processes (VIP) model allows for the prediction of the
dynamic behavior of chemicals in the unsaturated zone under variation of temperature,
precipitation, and waste spill frequency (7). The VIP model accounts for biodegradation, effect of
Seminar Series on Bioremediation of Hazardous Waste Sites: Practical Approaches to Implementation
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oxygen concentration on biodegradation rate, volatilization, sorption/desorption, advection, and
dispersion of target chemicals within a vadose zone system.
The BIOSCREEN model is an easy-to-use screening tool for simulating natural attenuation of
dissolved hydrocarbons at petroleum release sites (8). The software uses a Microsoft Excel
spreadsheet environment and is based on the Domenico analytical solute transport model.
BIOSCREEN has the ability to simulate advection, dispersion, adsorption, and aerobic decay as well
as anaerobic reactions, which have been shown to be the dominant biodegradation processes.
BIOSCREEN included three types of models: 1) solute transport without decay, 2) solute transport
with first order decay, and 3) solute transport with biodegradation assuming an "instantaneous"
biodegradation reaction. It is possible to modify BIOSCREEN to simulate intrinsic remediation of
chlorinated hydrocarbons.
With regard to the application of all models, the limitations must be identified and constraints
addressed. For all models, validity must be established on a site-by-site basis. No "off-the-shelf"
models are available for use on a routine basis regarding biodegradation. In addition,
measurement of input parameters often are extensive and sometimes are expensive (1). While
modeling has several limitations, the approach is a useful tool for understanding the dynamic
changes that occur in field sites during bioremediation.
References
1. National Research Council. 1993. Evaluating in situ bioremediation. In: In situ
bioremediation: When does it work? Washington, DC: National Academy Press, pp.
63-90.
2. Bedient, P.B., and H.S. Rifai. 1993. Modeling in situ bioremediation. In: In situ
bioremediation: When does it work? National Research Council. Washington, DC:
National Academy Press, pp. 153-159.
3. Borden, R.C., and P.B. Bedient. No date. Transport of dissolved hydrocarbons influenced
by reaeration and oxygen limited biodegradation. I. Theoretical development. Water
Resour. Res. 22:1,973-1,982.
4. Rifai, H.S., P.B. Bedient, R.C. Borden, and J.F. Haasbeek. 1 987. BIOPLUME II computer
model of two-dimensional contaminant transport under the influence of oxygen limited
biodegradation in ground-water, user's manual version 1.0. Rice University, National
Center for Ground Water Research, Houston, TX.
5. Rifai, J.S., P.B. Bedient, J.R. Wilson, K.M. Miller, and J.M. Armstrong. 1988.
Biodegradation modeling at a jet fuel spill site. American Society of Civil Engineers. J.
Environ. Eng. Div. 114:1,007-1,019.
6. Konikow, L.F., and J.D. Brederheoft. 1978. Computer model of two-dimensional solute
transport and dispersion in ground water. Techniques of water resources: Investigations
of the U.S. Geological Survey. Washington, DC.
Seminar Series on Bioremediation of Hazardous Waste Sites: Practical Approaches to Implementation
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7. Stevens, O.K., WJ. Grenney, Z. Yan, and R.C. Sims. 1 989. Sensitive parameter evaluation
for a vadose zone fate and transport model. EPA/600/2-89/039. Ada, OK.
8. Newell, C.J., and J. Gonzales. 1 996. BIOSCREEN intrinsic remediation decision support
system. In: Proceedings of the Conference on Intrinsic Remediation of Chlorinated
Solvents, Salt Lake City, UT (April 2). Sponsored by Hill Air Force Base, UT, in cooperation
with Battelle Laboratories, Columbus, OH.
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Modeling
Quantifying Biodegradation of
Subsurface Pollutants
Daniel Pope
Dynamac Corporation
Ada, OK
Modeling
Provides framework for organizing
information about a site
Provides an approach for
integration of degradation,
transport, and partitioning
processes
Useful tools for managing field sites
and evaluating bioremediation
Modeling
Evaluation of In Situ
Bioremediation
Contaminant loss explained by
abiotic reactions?
Contaminant loss explained by
biological reactions using
reasonable processes
Model Types
Saturated flow
Multiphase flow
Geochemical
Reaction rate
Water
Two or more
fluids together
Speciation/
thermodynamics
Biological,
chemical
Challenges
Physical, chemical, and biological
processes must be incorporated
Lack of field data on
biodegradation
Lack of numerical schemes that
accurately simulate relevant
processes
Biodegradation Kinetics
Main Approaches for Modeling
First-order degradation models
Biofilm models (including
kinetic expressions)
Instantaneous reaction models
Dual-substrate monod models
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Biofilm Model Processes
Bioplume Model
Mass transport from the bulk
liquid
Biodecomposition within the
bio film
Biofilm growth and decay
Borden and Bedient (1986)
Microorganism growth, decay,
and transport
Hydrocarbon transport and
removal
Oxygen transport and removal
Bioplume Model
Oxygen near hydrocarbon
source rapidly depleted
Oxygen transport limiting in
the body of the plume
Consumption of oxygen and
hydrocarbon considered
instantaneous
Bioplume Model
Major Sources of Oxygen
Transverse mixing
Advective fluxes
Vertical exchange with unsaturated
zone
Bioplume II
Rifaietal. (1987, 1988)
Improvement
Simulate transport of
oxygen and contaminants
Bioplume Applications
Conroe, Texas sitePAH
contamination
Traverse City,
Michiganaviation fuel
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Unsaturated Zone Modeling Unsaturated Zone Modeling
Vadose Zone Interactive Processes (VIP)
EPA model
Grenney and Stevens (1988-1989)
Enhancement of Ritz model (EPA)
Regulatory and Investigative Treatment
Zone
Vadose Zone Interactive Processes (VIP)
Biodegradation
Effect of O2 concentration on
biodegradation
Volatilization
Sorption/desorption
Advection
Dispersion
Unsaturated Zone Modeling
Vadose Zone Interactive Processes (VIP)
Dynamic behavior under variable
conditions of:
Precipitation
Temperature
Spill frequency
Model Applications
Mass of parent compound
remaining with time and
distance
Apparent mass of parent
compound remaining with time
and distance
Predict effects of source
removal on lifetime of plume
Bioscreen Model
Bioscreen Model
U.S. Air Force
Microsoft Excel spreadsheet
environment
Based on Domenico analytical
solute transport model
Simulate natural attenuation of
dissolved hydrocarbons at
petroleum release sites
Can be modified to simulate
natural attenuation of
chlorinated hydrocarbons
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Bioscreen Model
Processes Simulated
Advection
Adsorption
Dispersion
Aerobic decay
Dominant anaerobic reactions
Bioscreen Model
Includes 3 Model Types
1. Solute transport without decay
2. Solute transport with first-order
decay
3. Solute transport with
biodegradation assuming as
"instantaneous" biodegradation
reaction
Limitations of Models
Validity must be established on
"site-by-site" basis
No "off-the-shelf" models are
available for evaluating
bioremediation on a routine basis
Measurement of input parameters
often extensive and/or expensive
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