&EPA
United States
: Environmental Protection
Office of Emergency and
Remedial Response
Washington, DC 20460
Qffica of
Research and Development
Cincinnati, OH 45368
EPA/540/S-94/502
April 1994
Engineering Bulletin
In Situ Biodegradation
Purpose
Section 121(b) of the Comprehensive Environment
Response, Compensation, and Liability Act (CERCLA) man-
dates the Environmental Protection Agency (EPA) to select
remedies that "utilize permanent solutions and alternative
technologies or resource recovery technologies to the maxi-
mum extent practicable" and to prefer remedial actions in
which treatment "permanently and significantly reduces
the volume, toxicity, or mobility of hazardous substances,
pollutants and contaminants as a principal element." The
Engineering Bulletins comprise a series of documents that
summarize the latest information available on selected
treatment and site remediation technologies and related
issues. They provide summaries of and references for the
latest information to help remedial project managers, on-
scene coordinators, contractors, and other site cleanup
managers understand the type of data and site characteris-
tics needed to evaluate a technology for potential applica-
bility to their Superfund or other hazardous waste site.
Those documents that describe individual treatment tech-
nologies focus on remedial investigation scoping needs.
Addenda will be issued periodically to update the original
bulletins.
Abstract
In situ biodegradation may be used to treat low-to-
intermediate concentrations of organic contaminants in-
place without disturbing or displacing the contaminated
media. Although this technology has been used to degrade
a limited number of inorganics, specifically cyanide and
nitrate, in situ biodegradation is not generally employed to
degrade inorganics or to treat media contaminated with
heavy metals.
During in situ biodegradation, electron acceptors (e.g.,
oxygen and nitrate), nutrients, and other amendments may
be introduced into the soil and groundwater to encourage
the growth of an indigenous population capable of degrad-
ing the contaminants of concern. These supplements are
used to control or modify site-specific conditions that
impede microbial activity and, thus, the rate and extent of
contaminant degradation. Depending on site-specific
cleanup goals, in situ biodegradation can be used as the
sole treatment technology or in conjunction with other
biological, chemical, and physical technologies in a treat-
ment train. In the past, in situ biodegradation has often
been used to enhance traditional pump and treat technolo-
gies by reducing the time needed to achieve aquifer cleanup
standards.
One of the advantages of employing an in situ technol-
ogy is that media transport and excavation requirements
are minimized, resulting in both reduced potential for
volatile releases and minimized material handling costs.
Biological technologies that require the physical displace-
ment of media during treatment (e.g., "land treatment"
applications involving excavation for treatment in lined
beds or tilling of non-excavated soils) assume many of the
risks and costs associated with ex situ technologies and
cannot strictly be considered in situ applications.
As of Fall 1993, in situ biodegradation was being
considered or implemented as a component of the remedy
at 21 Superfund sites and 38 Resource Conservation and
Recovery Act (RCRA), Underground Storage Tank (UST),
Toxic Substances Control Act (TSCA), and Federal sites with
soil, sludge, sediment, or groundwater contamination
[1, p. 13]'[2][3]. This bulletin provides information on
the technology's applicability, the types of residuals pro-
duced, the latest performance data, the site requirements,
the status of the technology, and sources for further
information.
Technology Applicability
In situ biodegradation has been shown to be poten-
tially effective at degrading or transforming a large number
of organic compounds to environmentally-acceptable or
less mobile compounds [4, p. 54][5, p. 103][6][7][8][9].
Soluble organic contaminants are particularly amenable to
biodegradation; however, relatively insoluble contaminants
may be degraded if they are accessible to microbial degrad-
* [reference number, page number]
Printed on Recycled Paper
-------
v>EPA
United States
Environmental Protection
Agency
Office of Emergency and
Remedial Response
Washington, DC 20460
Office of
Research and Development
Cincinnati, OH 45268
EPA/540/S«94/50a
ApriM994
Engineering Bulletin
Ih Situ Biodegradation
Treatment
Purpose
Section 121(b) of the Comprehensive Environment
Response, Compensation, and Liability Act (CERCLA) man-
dates the Environmental Protection Agency (EPA) to select
remedies that "utilize permanent solutions and alternative
technologies or resource recovery technologies to the maxi-
mum extent practicable" and to prefer remedial actions in
which treatment "permanently and significantly reduces
the volume, toxicity, or mobility of hazardous substances,
pollutants and contaminants as a principal element." The
Engineering Bulletins comprise a series of documents that
summarize the latest information available on selected
treatment and site remediation technologies and related
issues. They provide summaries of and references for the
latest information to help remedial project managers, on-
scene coordinators, contractors, and other site cleanup
managers understand the type of data and site characteris-
tics needed to evaluate a technology for potential applica-
bility to their Superfund or other hazardous waste site.
Those documents that describe individual treatment tech-
nologies focus on remedial investigation scoping needs.
Addenda will be issued periodically to update the original
bulletins.
Abstract
In situ biodegradation may be used to treat low-to-
intermediate concentrations of organic contaminants in-
place without disturbing or displacing the contaminated
media. Although this technology has been used to degrade
a limited number of inorganics, specifically cyanide and
nitrate, in situ biodegradation is not generally employed to
degrade inorganics or to treat media contaminated with
heavy metals.
During in situ biodegradation, electron acceptors (e.g.,
oxygen and nitrate), nutrients, and other amendments may
be introduced into the soil and groundwater to encourage
the growth of an indigenous population capable of degrad-
ing the contaminants of concern. These supplements are
used to control or modify site-specific conditions that
impede microbial activity and, thus, the rate and extent of
contaminant degradation. Depending on site-specific
cleanup goals, in situ biodegradation can be used as the
sole treatment technology or in conjunction with other
biological, chemical, and physical technologies in a treat-
ment train. In the past, in situ biodegradation has often
been used to enhance traditional pump and treat technolo-
gies by reducing the time needed to achieve aquifer cleanup
standards.
One of the advantages of employing an in situ technol-
ogy is that media transport and excavation requirements
are minimized, resulting in both reduced potential for
volatile releases and minimized material handling costs.
Biological technologies that require the physical displace-
ment of media during treatment (e.g., "land treatment"
applications involving excavation for treatment in lined
beds or tilling of non-excavated soils) assume many of the
risks and costs associated with ex situ technologies and
cannot strictly be considered in situ applications.
As of Fall 1993, in situ biodegradation was being
considered or implemented as a component of the remedy
at 21 Superfund sites and 38 Resource Conservation and
Recovery Act (RCRA), Underground Storage Tank (UST),
Toxic Substances Control Act (TSCA), and Federal sites with
soil, sludge, sediment, or groundwater contamination
[1, p. 13]'[2][3]. This bulletin provides information on
the technology's applicability, the types of residuals pro-
duced, the latest performance data, the site requirements,
the status of the technology, and sources for further
information.
Technology Applicability
In situ biodegradation has been shown to be poten-
tially effective at degrading or transforming a large number
of organic compounds to environmentally-acceptable or
less mobile compounds [4, p. 54][5, p. 103][6][7][8][9].
Soluble organic contaminants are particularly amenable to
biodegradation; however, relatively insoluble contaminants
may be degraded if they are accessible to microbial degrad-
* [reference number, page number]
Printed on Recycled Paper
-------
ers. Classes of compounds considered amenable to biodeg-
radation include petroleum hydrocarbons (e.g., gasoline
and diesel fuel), nonchlorinated solvents (e.g., acetone,
ketones, and alcohols), wood-treating wastes (e.g., creo-
sote and pentachlorophenol), some chlorinated aromatic
compounds (e.g., chlorobenzenes and biphenyls with fewer
than five chlorines per molecule), and some chlorinated
aliphatic compounds (e.g., trichloroethene and
dichloroethene). As advances in anaerobic biodegradation
continue, many compounds traditionally considered resis-
tant to aerobic biodegradation may eventually be de-
graded, either wholly or partially, under anaerobic condi-
tions. Although not normally used to treat inorganics (e.g.,
acids, bases, salts, heavy metals, etc.), in situ biodegrada-
tion has been used to treat water contaminated with ni-
trate, phosphate, and other inorganic compounds.
Although in situ biodegradation may be used to
remediate a specific site, this does not ensure that it will be
effective at all sites or that the treatment efficiency achieved
will be acceptable at other sites. The complex contaminant
mixtures found at many Superfund sites frequently result in
chemical interactions or inhibitory effects that limit con-
taminant biodegradability. Elevated concentrations of pes-
ticides, highly chlorinated organics, and some inorganic
salts have been known to inhibit microbial activity and thus
system performance during in situ biodegradation.
Treatability studies should be performed to determine the
effectiveness of a given in situ biological technology at each
site. Experts based out of EPA's Risk Reduction Engineering
Laboratory (RREL) in Cincinnati, Ohio and the Robert S. Kerr
Environmental Research Laboratory (RSKERL) in Ada, Okla-
homa may be able to provide useful guidance during the
treatability study and design phases. Other sources of
general observations and average removal efficiencies for
different treatability groups are contained in the Superfund
Land Disposal Restrictions (LDR) Guide #6A, "Obtaining a
Soil and Debris Treatability Variance for Remedial Actions,"
(OSWER Directive 9347.3-06FS, September 1990) [10] and
Superfund LDR Guide #6B, "Obtaining a Soil and Debris
Treatability Variance for Removal Actions," (OSWER Direc-
tive 9347.3-06BFS, September 1990) [11].
Limitations
Site- and contaminant-specific factors impacting con-
taminant availability, microbial activity, and chemical reac-
tion rates may limit the application of in situ biodegrada-
tion. Variations in media composition and contaminant
concentrations can lead to variations in biological activity
and, ultimately, inconsistent degradation rates. Soil char-
acteristics (e.g., non-uniform particle size, soil type, mois-
ture content, hydraulic conductivity, and permeability) and
the amount, location, and extent of contamination can also
have a profound impact on bioremediation. The following
text expands upon these factors.
The biological availability, or bioavailability, of a con-
taminant is a function of the contaminant's solubility in
water and its tendency to sorb on the surface of the soil.
Contaminants with low solubility are less likely to be distrib-
uted in an aqueous phase and may be more difficult to
degrade biologically. Conversely, highly soluble com-
pounds may leach from the soil before being degraded. In ^m^.
general, however, poor bioavailability can be attributed to '^^k
contaminant sorption on the soil rather than a low or high /
contaminant solubility. The tendency of organic molecules
to sorb on the soil is determined by the physical and
chemical characteristics of the contaminant and soil. In
general, the leaching potential of a chemical is proportional
to the magnitude of its adsorption (partitioning) coefficient
in the soil. Hydrophobic (i.e., "water fearing") contami-
nants, in particular, routinely partition from the soil water
and concentrate in the soil organic matter, thus limiting
bioavailability. Additionally, contaminant weathering may
lead to binding in soil pores, which can limit availability
even of soluble compounds. Important contaminant prop-
erties that affect sorption include: chemical structure,
contaminant acidity or basicity (pKa or pKb), water solubil-
ity, permanent charge, polarity, and molecule size. In some
situations surfactants (e.g., "surface acting agents") may
be used to increase the bioavailability of "bound" or in-
soluble contaminants. However, it may be difficult to iden-
tify a surfactant that is both nontoxic and not a preferred
substrate for microbial growth.
Soil solids, which are comprised of organic and inor-
ganic components, may contain highly reactive charged
surfaces that play an important role in immobilizing organic
constituents, and thus limiting their bioavailability. Certain
types of inorganic clays, possess especially high negative
charges, thus exhibiting a high cation exchange capacity.
Alternatively, clays may also contain positively charged •^^
surfaces, causing these particles to exhibit a high anion J
exchange capacity. Soil organic matter also has many
highly reactive charged surfaces which can limit
bioavailability [12].
Bioavailability is also a function of the biodegradability
of the target chemical, i.e., whether it acts as a substrate,
co-substrate, or is recalcitrant. When the target chemical
cannot serve as a metabolic substrate (source of carbon and
energy) for microorganisms, but is oxidized in the presence
of a substrate already present or added to the subsurface,
the process is referred to as co-oxidation and the target
chemical is defined as the co-substrate [12][1 3, p.4]. Co-
metabolism occurs when an enzyme produced by an organ-
ism to degrade a substrate that supports microbial growth
also degrades another non-growth substrate that is neither
essential for nor sufficient to support microbial growth. Co-
oxidation processes are important for the biodegradation
of high molecular weight polycyclic aromatic hydrocarbons
(PAHs), and some chlorinated solvents, including
trichloroethene (TCE). However, like surfactants,
cometabolites (e.g., acetate and phenol) may be more
readily mineralized by the indigenous microorganisms than
the target organics [1 3, p. 4].
Microbial activity can be reduced by nutrient, mois-
ture, and oxygen deficiencies, significantly decreasing bio-
degradation rates. Extreme soil temperatures, soil alkalin- ^^^
ity, or soil acidity can limit the diversity of the microbial *^N
population and may suppress specific contaminant degrad-
Engineering Bulletin: In Situ Biodegradation Treatment
-------
r
ers. Spatial variation of soil conditions (e.g., moisture,
oxygen availability, pH, and nutrient levels) may result in
inconsistent biodegradation due to variations in biological
activity. While these conditions may be controlled to favor
biodegradation, the success of in situ biodegradation de-
pends in a large part on whether required supplements can
be delivered to areas where they are needed. Low hydraulic
conductivity can hinder the movement of water, nutrients,
aqueous-phase electron acceptors (e.g., hydrogen perox-
ide and nitrate), and, to a lesser extent, free oxygen through
the contamination zone [14, p. 155]. Restrictive layers
(e.g., clay lenses), although more resistant to contamina-
tion, are also more difficult to remediate due to poor
permeability and low rates of diffusion [1 3, p. 4]. Low
percolation rates may cause amendments to be assimilated
by soils immediately surrounding application points, pre-
venting them from reaching areas that are more remote,
either vertically or horizontally. During the simultaneous
addition of electron acceptors and donors through injec-
tion wells, excessive microbial growth or high iron or
manganese concentrations may cause clogging in the well
screen or in the soil pores near the well screen [15]. Variable
hydraulic conductivities in different soil strata within a
contaminated area can also complicate the design of flow
control; minor heterogeneities in lithology can, in some
cases, impede the transfer of supplements to specific sub-
surface locations.
Microbial activity may also be influenced by contami-
nant concentrations. Each contaminant has a range of
concentrations at which the potential for biodegradation is
maximized. Below this range microbial activity may not
occur without the addition of co-substrate. Above this
range microbial activity may be inhibited and, once toxic
concentrations are reached, eventually arrested. During
inhibition, contaminant degradation generally occurs at a
reduced rate. In contrast, at toxic concentrations, contami-
nant degradation does not occur. The concentrations at
which microbial growth is either supported, inhibited, or
arrested vary with the contaminant, medium, and micro-
bial species. Given long-term exposure, microbes have
been known to acclimate to very high contaminant concen-
trations and other conditions inhibiting microbial activity.
However, if prompt treatment is a primary goal, as is the
case during most remedial activities, toxic conditions may
need to be addressed by pH control, metals control (e.g.,
immobilization), sequential treatment, or by introducing
microbial strains resistant to toxicants.
Numerous biological and non-biological mechanisms
(e.g., volatilization, sorption, chemical degradation, migra-
tion, and photodecomposition) occur during biological
treatment. Since some amendments may react with the
soil, site geochemistry can limit both the form and concen-
tration of any supplements added to the soil. Thus, care
must be employed when using amendments to "enhance"
biological degradation. For example, ozone and hydrogen
peroxide, which can be added to enhance dissolved oxygen
levels in soil or groundwater systems, may react violently
with other compounds present in the soil, reduce the
sorptive capacity of the soil being treated, produce gas
bubbles that block the pores in the soil matrix, or damage
the bacterial population in the soil [4, p. 43]. Nitrogen and
phosphorus (phosphate) must also be applied cautiously to
avoid excessive nitrate formation [4, p.47] and the precipi-
tation of calcium and iron phosphates, respectively. Exces-
sive nitrate levels in the groundwater can cause health
problems in humans, especially children. If calcium con-
centrations are high, the added phosphate can be tied up
by the calcium and, therefore, may not be available to the
microorganisms [16, p. 23]. Lime treatment for soil pH
adjustment is dependent on several soil factors including
soil texture, type of clay, organic matter content, and
aluminum concentrations [4, p. 45]. Since changes in soil
pH may also affect the dissolution or precipitation of mate-
rials within the soil and may increase the mobility of
hazardous materials, pH amendments (acid or base) should
be added cautiously and should be based on the soil's
ability to resist changes in pH, otherwise known as the soil's
"buffering capacity" [4, p. 46]. Since the buffering capacity
varies between soils, lime and acidification requirements
should be determined on a site-specific basis.
Finally, high concentrations of metals can have a det-
rimental effect on the biological treatment of organic
contaminants in the same medium. A number of metals can
be oxidized, reduced, methylated (i.e., mercury), de-
methylated, or otherwise transformed by various organ-
isms to produce new contaminants. The solubility, volatil-
ity, and sorption potential of the original soil contaminants
can be greatly changed in the process [1 7, p. 144], leading
to potential significant lexicological effects, as is the case
during the methylation of mercury. To avoid these compli-
cations, it is sometimes possible to pretreat or complex the
metals into a less toxic or teachable form.
Technology Description
During in situ biodegradation, site-specific characteris-
tics are modified to encourage the growth of a microbial
population capable of biologically degrading the contami-
nants of concern. Presently, two major types of in situ
systems are being employed to biodegrade organic com-
pounds present in soils, sludges, sediments, and groundwa-
ter: bioventing systems and "traditional" in situ biodegra-
dation systems, which usually employ infiltration galleries/
wells and recovery wells to deliver required amendments to
the subsurface. In general, bioventing has been used to
treat contaminants present in the unsaturated zone. Tradi-
tional in situ biodegradation, on the other hand, has mostly
been used to treat saturated soils and groundwater. The
occasional treatment of unsaturated soil using traditional in
situ biodegradation techniques has been generally limited
to fairly shallow regions over groundwater that is already
contaminated.
Traditional In Situ Biodegradation
Traditional in situ biodegradation is generally used in
conjunction with groundwater-pumping and soil-flushing
systems to circulate nutrients and oxygen through a con-
taminated aquifer and associated soil. The process usually
Engineering Bulletin: In Situ Biodegradation Treatment
-------
involves introducing aerated, nutrient-enriched water into
the contaminated zone through a series of injection wells or
infiltration trenches and recovering the water down-gradi-
ent. Depending upon local regulations and engineering
concerns, the recovered water can then be treated and, if
necessary, reintroduced to the soil onsite, discharged to the
surface, or discharged to a publicly-owned treatment works
(POTW). A permit may be required for the re-injection of
treated water. Note that a variety of techniques can be used
to introduce and distribute amendments in the subsurface.
For example, a lower horizontal well is being used at the
Savannah River Site near Aiken, North Carolina to deliver air
and methane to the subsurface. A vacuum has been applied
to an upper well (in the vadose zone) located at this site to
encourage the distribution of air and methane within the
upper saturated zone and lower vadose zone [18][19].
Figure 1 is a general schematic of a traditional in situ
biodegradation system [20, p. 113][16, p. 13]. The first
step in the treatment process involves pretreating the
infiltration water, as needed, to remove metals (1). Treated
or contaminated groundwater, drinking water, or alterna-
tive water sources (e.g., trucked water) may be used as the
water source. If groundwater is used, iron dissolved in the
groundwater may bind phosphates needed for biological
growth. Excess phosphate may be added to the infiltration
water at this point in the treatment process in order to
complex the iron [20, p. 111 ]. The presence of iron will also
cause a more rapid depletion of hydrogen peroxide, which
is sometimes used as an oxygen source. Surface active
agents may also be added at this point in the treatment
process to increase the bioavailability of contaminants,
especially hydrophobic or sorbed pollutants, while meth-
ane or other substances may be added to induce the co-
metabolic biodegradation of certain contaminants. In
continuous recycle systems, toxic metals originally located
in the contaminated medium may have to be removed from
the recycled infiltration water to prevent inhibition of
bacterial growth. The exact type of pretreatment will vary
with the water source, contamination problem, and treat-
ment system used.
Following infiltration water pretreatment, a biological
inoculum can be added to the infiltration water to enhance
the natural microbial population (2). A site-specific inocu-
lum enriched from site samples may be used; commercially
available cultures reported to degrade the contaminants of
concern can also be used (e.g., during the remediation of
"effectively sterile soils"). Project managers are cautioned
against employing microbial supplements without first as-
sessing the relative advantages associated with their use
and potential competition that may occur between the
indigenous and introduced organisms. The ability of mi-
crobes to survive in a foreign and possibly hostile (i.e.,
toxic) environment, as well as the ability to metabolize a
wide range of substrates should be evaluated. The health
effects of commercial inocula must also be carefully evalu-
ated, since many products on the market are not carefully
screened or processed for pathogens. It is essential that
independently-reviewed data be examined before employ-
ing a commercially-marketed microbial supplement [21].
Nutrient addition can then be employed to provide
nitrogen and phosphorus, two elements essential to the
biological activity of both indigenous and introduced or-
ganisms (3). Optimum nutrient conditions are site-specific.
Trace elements may be added at this stage, but are normally
available in adequate supply in the soil or groundwater.
During contaminant oxidation, energy is released as
electrons are removed. Since oxygen acts as the terminal
electron acceptor during aerobic biodegradation, oxygen
concentrations in the subsurface may become depleted. To
avoid this complication, air, oxygen, and other oxygen
Figure 1.
Schematic Diagram of Traditional In Situ Biodegradation of Soil and Groundwater
_^;^_^. „,, „ _ n\ I \\ i i\
?»,&-$&v ^;^^>, :s -1\, ,^/Ao or^1J, 1V>• i-V i 4\
i f ^ ^v"* vv c% %% 'j^ < •• * K ** ^^^- ^ ''''•"*< ^r
, s J^t.-/'. \'^u<'A^;«.,^.-XC':*'-;
Direction of
Groundwater Flow
Zone of low permeability
(i.e., clay, bedrock)
^\
Engineering Bulletin: In Situ Biodegradation Treatment
-------
r
sources (hydrogen peroxide and ozone) can be added to
the infiltration water (4). To prevent gas binding in the
subsurface, and a subsequent reduction in the effective soil
permeability, oxygen amendment/supplementation meth-
ods must be carefully selected. During anaerobic degrada-
tion, alternative electron acceptors (nitrate, carbonate, or
sulfate) may be added to the infiltration water in place of
oxygen. Alternatively, during the co-oxidation of a target
substrate, a co-substrate (methanol or acetate) may be
added to the infiltration water [22].
just before the water is added to the soil or groundwa-
ter, chemical additives may be used to adjust the pH
(neutral is recommended for most systems) and other
parameters that impact biodegradation (5). Care should be
taken when making adjustments to the pH, since contami-
nant mobility (especially of metals) can be increased by
changing the pH [4, p. 45]. Site managers are also cau-
tioned against employing chemical additives that are per-
sistent in the environment. The potential toxicity of addi-
tives and any synergistic effects on contaminant toxicity
should also be evaluated.
During in situ bioremediation, amendment concentra-
tions and application frequencies can be adjusted to com-
pensate for physical/chemical depletion and high microbial
demand. If these modifications fail to compensate for
microbial demand, remediation may occur by a sequential
deepening and widening of the active treatment layer (e.g.,
as the contaminant is degraded in areas near the amend-
ment addition points, and microbial activity decreases due
to the reduced substrate, the amendments move farther,
increasing microbial activity in those areas). Additionally,
hydraulic fracturing may be employed to improve amend-
ment circulation within the subsurface.
The importance of using a well-designed hydraulic
delivery system and thoroughly evaluating the compatibil-
ity of chemical supplements was demonstrated at sites in
Park City, Kansas; Kelly AFB, Texas; and Eglin AFB, Florida.
Air entrainment and iron precipitation resulted in a contin-
ued loss of injection capacity during treatment at the Park
City site [23][24] and calcium phosphate and iron precipi-
tation resulted in the failure of the two field tests at Kelly
and Eglin AFBs, respectively [25].
Bioventing
Bioventing uses relatively low-flow soil aeration tech-
niques to enhance the biodegradation of soils contami-
nated with organic contaminants. Although bioventing is
predominantly used to treat unsaturated soils, applications
involving the remediation of saturated soils and groundwa-
ter (e.g., using air sparging techniques) are becoming more
common [26][27]. Aeration systems similar to those em-
ployed during soil vapor extraction are used to supply
oxygen to the soil (Figure 2). Typically a vacuum extrac-
tion, air injection, or combination vacuum extraction and
air injection system is employed [28]. An air pump, one or
more air injection or vacuum extraction probes, and emis-
sions monitors at the ground surface are commonly used.
Although some systems utilize higher air flow rates, thereby
combining bioventing with soil vapor extraction, low air
pressures and low air flow rates are generally used to
maximize vapor retention times in the soil while minimizing
contaminant volatilization. An interesting modification to
traditional aeration techniques has been proposed at the
Picatinny Arsenal in New jersey. Here researchers and
project managers have proposed collecting TCE vapors at
the surface, amending them with degradable hydrocar-
bons (methane, propane, or natural gas) capable of stimu-
lating the cometabolic degradation of vapor-phase TCE,
and then re-injecting the amended vapors into the unsatur-
ated zone in an attempt to encourage the in situ
bioremediation of the TCE remaining in the subsurface
[29][30][31][32][27].
Off-gas treatment (e.g., through biofiltration or car-
bon adsorption) will be needed during most bioventing
applications to ensure compliance with emission standards
and to control fugitive emissions. Off-gas treatment sys-
tems similar to those employed during soil vapor extraction
may be used. These systems must be capable of effectively
collecting and treating a vapor stream consisting of the
original contaminants and/or any volatile degradation prod-
ucts generated during treatment. Although similar vapor
treatment systems may be employed during soil vapor
extraction and bioventing, less concentrated off-gases would
be expected from a bioventing system than from a soil
vapor extraction system employed at the same site. This
difference in concentration is attributed to enhanced bio-
logical degradation within the subsurface.
Nutrient addition may be employed during bioventing
to enhance biodegradation. Nutrient addition can be
accomplished by surface application, incorporation by till-
ing into surface soil, and transport to deeper layers through
applied irrigation water. However, in some field applica-
tions to date, nutrient additions have been found to provide
no additional benefits [33], Increasing the soil temperature
may also enhance bioremediation, although in general
high temperatures should be avoided since they can de-
crease microbial population and activity. Heated air, heated
water, and low-level radio-frequency heating are some of
the techniques which can be used to modify soil tempera-
ture. Soil core analyses can be performed periodically to
assess system performance as determined by contaminant
removal. A control plot located near the bioventing system,
but not biovented, may also be used to obtain additional
information to assess system performance.
Process Residuals
During in situ biodegradation, limited but potentially
significant process residuals may be generated. Although
the majority of wastes requiring disposal are generated as
part of pre- and post-treatment activities, process residuals
directly arising from in situ biological activities may also be
generated. These process residuals may include: 1) par-
tially degraded metabolic by-products, 2) residual con-
tamination, 3) wastes produced during groundwater pre-
and post-treatment activities, and 4) volatile contaminants
that are either directly released into the atmosphere or
Engineering Bulletin: In Situ Biodegradation Treatment
-------
collected within add-on emission controlXtreatment sys-
tems. The following text expands upon the specific types
of process residuals, their control, and their impact on
disposal requirements.
Ultimately biological technologies seek to mineralize
hazardous contaminants into relatively innocuous by-prod-
ucts, specifically carbon dioxide, water, and inorganic salts.
However, a number of site- and contaminant-specific fac-
tors may cause the partial degradation or "biotransforma-
tion" of a contaminant and the generation of an intermedi-
ate by-product. These metabolic by-products may be
located in either the saturated or unsaturated zones. The
identity, toxicity, and mobility of these partially degraded
compounds should be determined since intermediate deg-
radation products can be as toxic or more toxic than the
parent compound. Since metabolic by-products can accu-
mulate in the soil and groundwater, future remedial actions
may be necessary.
In addition to intermediate degradation by-products,
residual contamination may persist in the soil following
treatment. Microbes are capable of degrading only that
fraction of the contamination that is readily available for
microbial incorporation. As a result, biologically resistant
contaminants and contaminants that remain sorbed to the
soil and sediment during the remedial action cannot be
degraded. Depending on the nature of the contaminants
and media, the "bound" fraction may slowly desorb over
long periods of times (months to years), potentially re-
contaminating "treated" media near the residual contami-
nation [34][35]. Additionally, fluctuations in the water
table may result in the recontamination of previously
remediated soils if groundwater contamination, specifically
contamination associated with the presence of a light non-
aqueous phase layer (LNAPL), has not been effectively
addressed.
Above-ground activities taken to ensure that the reme-
dial action complies with regulatory requirements and
adequately guards against cross-contamination and un-
controlled releases may result in the generation of a signifi-
cant volume of waste requiring disposal. For example,
when groundwater is used to deliver amendments to the
subsurface, it may be necessary to pre-treat the water
before it can be re-introduced to the subsurface. Addition-
ally, in order to protect water quality outside of the treat-
ment zone from contaminant or amendment migration, a
down-gradient groundwater recovery and treatment sys-
tem designed to collect and treat amendment- and con-
taminant-laden groundwater may be needed. The residu-
als produced by these add-on treatment processes will
eventually require disposal.
Significant volatile emissions may also be produced
during in situ biodegradation (e.g., bioventing). Depend-
ing on their concentration, toxicity, and total volume, these
emissions, which may consist of the original contaminant or
any volatile degradation products produced during treat-
ment, may need to be controlled, collected, or treated.
Ultimately, the by-products of an emissions treatment/
control system will require disposal.
Site Requirements
In situ biodegradation normally requires the installa-
tion of wells or infiltration trenches; therefore, adequate
Figure 2. Bioventing
Low rate
air injection
Surface monitoring
to ensure
no emissions
Air extraction
Air extraction
Biodegradation
of contaminated
soils
Monitoring of soil
gas to assess vapor
biodegradation
Biodegradation of vapors
Engineering Bulletin: In Situ Biodegradation Treatment
-------
access roads are required for heavy equipment such as well-
drilling rigs and backhoes. Soil-bearing capacity, traction,
and soil stickiness can limit vehicular traffic [17, p. 61].
In general, the area required to set up mixing equip-
ment is not significant. However, space requirements
increase as the complexity of the various pre- and post-
treatment systems increases. During the installation of
infiltration galleries and wells, several hundred up to several
thousand square feet of clear surface area will be required.
Climate can also influence site requirements. If periods of
heavy rainfall or extremely cold conditions are expected, a
cover may be required.
Electrical requirements will depend on the type of
technology employed. Standard 220V, three-phase electri-
cal service may be used to supply power to pumps and
mixing equipment. Since water is used for a variety of
purposes during biological treatment, a readily available
water supply will be needed at most sites. Municipal water
or clean groundwater may be used. Contaminated ground-
water may be used if permitted by the appropriate regula-
tory agency. The quantity of water needed is site- and
process-specific. Waste storage is not normally required for
in situ biodegradation.
Onsite analytical equipment for conducting pH and
nutrient analyses will help improve operation efficiency and
provide better information for process control. During
bioventing applications, air emissions monitors at the ground
surface are commonly used.
Regulatory Considerations and
Response Actions
Federal mandates can have a significant impact on the
application of in situ biodegradation. RCRA LDRs that
require treatment of wastes to best demonstrated available
technology (BDAT) levels prior to land disposal may some-
times be determined to be applicable or relevant and
appropriate requirements (ARARs) for CERCLA response
actions. The in situ biodegradation technology can pro-
duce a treated waste that meets treatment levels set by
BDAT, but may not reach these treatment levels in all cases.
The ability to meet required treatment levels is dependent
upon the specific waste constituents and the waste matrix.
In cases where in situ biodegradation does not meet these
levels, it still may, in certain situations, be selected for use
at the site if a treatability variance establishing alternative
treatment levels is obtained. Treatability variances are
justified for handling complex soil and debris matrices. The
following guides describe when and how to seek a treatability
variance for soil and debris: Superfund LDR Guide #6A,
"Obtaining a Soil and Debris Treatability Variance for Reme-
dial Actions" (OSWER Directive 9347.06FS, September 1990)
[10], and Superfund LDR Guide #6B, "Obtaining a Soil and
Debris Treatability Variance for Removal Actions" (OSWER
Directive 9347.06BFS, September 1990) [11]. Another
^^ approach could be to use other treatment techniques with
//2P^ in situ biodegradation to obtain desired treatment levels,
for example, carbon treatment of recovered groundwater
prior to re-infiltration into the subsurface.
When determining performance relative to ARARs and
BDATs, emphasis should be placed on assessing the risk
presented by a bioremediation technology. As part of this
effort, risk assessment schemes, major metabolic pathways
of selected hazardous pollutants, human health protocols
for metabolite and pathogenicity tests, and fate protocols
and issues for microorganisms and metabolites must be
assessed [36]. A detailed summary of the findings of the
June 17-18, 1993 EPA/Environment Canada Workshop in
Duluth, Minnesota addressing Bioremediation Risk Assess-
ment should be available in early 1994.
Performance Data
Performance data for Superfund sites are limited. The
first record of decision (ROD) selecting in situ biodegrada-
tion as a component of the remedy was in FY87. Since then,
in situ biodegradation of soil or groundwater contaminants
has either been considered or selected at 22 Superfund sites
and 30 RCRA, UST, TSCA, and Federal sites [1][2][3]. The
following two subsections address traditional in situ and
bioventing applications, respectively; a third subsection
has been included to briefly address information sources
and data concerns related to remedial efforts performed in
the private sector.
Traditional In Situ Bioremediation
Methane and phenol were employed during a series of
stimulus-response studies investigating the co-metabolic
degradation of TCE, cis-dichloroethene (c-DCE), trans-
dichloroethene (t-DCE), and vinyl chloride (VC) at the
Moffet Field site in California. Both sets of experiments
used indigenous bacteria and were performed under the
induced gradient conditions of injection and extraction.
During the first set of experiments, methane, oxygen, and
TCE (from 50 to 100 ^ig/L), c-DCE, t-DCE, and VC were
added to the soil to stimulate methanotrophic degradation
of the injected chlorinated aliphatic compounds. Approxi-
mately 20 percent of the TCE added to the system was
degraded within the 2-meter hydraulically-controlled
biostimulated zone. Approximately 50 percent of the c-
DCE, 90 percent of the t-DCE, and 95 percent of the VC
were also degraded. During the second set of tests, meth-
ane was replaced with phenol in order to stimulate growth
of an indigenous phenol-utilizing population. During 4
weeks of testing, the concentration of TCE injected into the
subsurface was raised from an initial concentration of 62
jig/L to a final concentration of 1000 ng/L A bromide
tracer was used to determine transformation extent. Up to
90 percent of the TCE in the 2-meter biostimulated zone
was degraded, demonstrating that even at relatively high
TCE concentrations significant removal efficiencies can be
achieved in situ through phenol and dissolved oxygen (DO)
addition. During the course of the project, transformation
yields (i.e., grams of TCE per grams of phenol) ranging from
0.0044 to 0.062 were obtained for varying concentrations
Engineering Bulletin: In Situ Biodegradation Treatment
-------
of phenol and TCE. Future studies at the site will determine
whether a compound more environmentally acceptable
than methane or phenol can be used to induce an indig-
enous population that effectively degrades TCE [37][7][8].
A 40- by 120-foot test zone in an aquifer that receives
leachate from an industrial landfill at the Du Pont Plant near
Victoria, Texas was used to demonstrate the in situ biotrans-
formation of tetrachloroethene (PCE), TCE, DCE,
chloroethane, and VC to ethane and ethylene using micro-
bial reductive dehalogenation under sulfate-reducing con-
ditions. Croundwater from this zone was alternately
amended with either benzoate or sulfate and circulated
through the aquifer. Initially PCE and TCE concentrations
were approximately 10 and 1 micro-mole (uM), respec-
tively. After a year of treatment the halogenated com-
pounds were reduced to concentrations near or below 0.1
^iM. PCE and TCE degraded to DCE rapidly following the
introduction of benzoate. A decrease in sulfate concentra-
tions led to increases in the vinyl chloride concentrations.
Therefore, sulfate concentrations were kept above 10 mg/
L until the DCE was further biodegraded. After approxi-
mately 6 months of treatment, most of the DCE,
chloroethane, and VC biodegraded to produce ethane and
ethylene [38].
A field-scale in situ bioremediation system, consisting
of down-gradient groundwater extraction wells and an up-
gradient infiltration system, was installed at a gasoline-
contaminated site owned by the San Diego Gas and Electric
Company. [Note: extracted groundwater was amended
with nutrients (nitrate and phosphate) prior to re-infiltra-
tion into the subsurface]. Due to the relatively low rate of
groundwater extraction (approximately 800 to 900 gallons
per day) and the low hydraulic gradient at the site (0.004),
it took nearly 2 years (until June/July 1991) for the added
nitrate to reach the down-gradient well and overtake the
xylene (BTX) plume. BTX concentrations, which ranged
from 25 to 50 mg/L for the preceding 2-year period,
dropped markedly as nitrate levels in the groundwater
increased. By late August 1991, benzene and toluene
concentrations had dropped below the detection limit
(0.01 mg/L), and total xylene concentrations had dropped
to 0.02 mg/L. The coincident occurrence of nitrate appear-
ance and BTX loss in the aquifer, as well as an eight-fold
increase in the percentage of denitrifiers present in the
groundwater (from 1 to 8 percent), points to a potential
stimulatory effect nitrate may have on BTX loss in situ [5].
An in situ bioremediation system consisting of four
injection and three recovery wells was employed to treat
gasoline contamination present in the saturated zone at a
former service station in Southern California. During treat-
ment, recovered groundwater was amended with hydro-
gen peroxide (from 500 to 1,000 mg/L) and nutrients and
re-injected into the aquifer. Prior to treatment, total fuel
hydrocarbons in the saturated clay soils ranged from below
detection limits to 32 mg/kg as BTX. Maximum groundwa-
ter concentrations were 2,700 ^ig/L for benzene; 6,600 ^ig/
L for toluene; 4,100 ng/L for xylene; and 45,000 ng/L for
TPH [4]. After 10 months, BTX and TPH levels in the
groundwater and saturated soils had dropped below the
detection limits. Roughly 1,350 kilograms of hydrogen
peroxide were introduced to the aquifer over 10 months,
roughly two times the estimated requirements based on the
estimated mass of hydrocarbon in the saturated zone (i.e.,
110 kg of fuel hydrocarbon and 2 to 3 kg of dissolved
hydrocarbons). After 34 months of treatment, soil hydro-
carbon concentrations ranged from below the detection
limit to 321 ppm as TPH; benzene was not detected in any
samples [39].
Following successful laboratory treatability testing,
General Electric performed a 10V2-week field study to
investigate the biodegradation of polychlorinated biphe-
nyls (PCBs) in the Hudson River sediment. Initial PCB
concentrations in the sediment ranged between 20 and 40
ppm. The study attempted to enhance the aerobic bacteria
native to the upper Hudson River. Six caissons were
installed at the Hudson River Research Station (HRRS) to
isolate sections of the river bottom for this field study.
Because of extensive, naturally occurring dechlorination,
approximately 80 percent of the total PCBs encountered in
the sediments were mono-, di-, and trichlorobiphenyls.
Biodegradation was stimulated using oxygen and nutrient
addition. Mixing was employed to enhance the dispersal of
oxygen and nutrients within the sediment. Between 38 and
55 percent of the PCBs present in the sediment were
removed by aerobic degradation during the study.
This corresponds to the percentage biologically available
PCBs [9].
Bioventing
In May 1992, the U.S. Air Force began a Bioventing
Initiative to examine bioventing as a remedial technique at
contaminated sites across the country. The Air Force's
decision to examine bioventing on such a large scale was
prompted by a successful demonstration of the technology
at Tyndall AFB, Florida, where bioventing coupled with
moisture addition removed one-third of the TPH and nearly
all of the BTEX in JP-4 contaminated soils during 7 months
of treatment. The Bioventing Initiative targets 138 sites
with diesel fuel, jet fuel, or fuel oil in soil. In selecting sites
for the initiative, the Air Force looked for characteristics
appropriate for bioventing, such as deep vadose soil, heavy
hydrocarbon contamination, and high air permeability.
The chosen sites represent a wide range of depths to
groundwater, hydrocarbon concentrations, and soil tex-
tures. Preliminary testing has been completed and 33
systems have been installed at Battle Creek Air National
Guard Base and the following AFBs: Beale, Eglin, Eielson,
F.E. Warren, Galena, Hanscom, Hill, K.I. Sawyer, McGuire,
Newark, Offutt, Plattsburgh, Robins, Vandenberg, and
Westover. According to the Air Force, initial results are very
promising with degradation rates measured as high as
5,000 mg/kg per year [40][41].
The EPA RREL, in collaboration with the U.S. Air Force,
initiated two 3-year pilot-scale bioventing field studies in
mid-1991 at JP-4 contaminated fuel sites located at Eielson
AFB near Fairbanks, Alaska and at Hill AFB near Salt Lake
City, Utah. Four soil plots are being used to evaluate
passive, active, and buried heat tape soil-warming methods
8
Engineering Bulletin: In Situ Biodegradation Treatment
-------
during the Eielson study. The fourth plot was vented with
injected air but not artificially heated. Roughly 1 acre of soil
is contaminated from a depth of 2 feet to the water table at
6 to 7 feet. At the Hill site, a series of soil gas cluster wells
capable of obtaining samples up to 90 feet deep is being
used with a single air injection well and two groundwater
wells to remediate JP-4 contamination found at depths
ranging from 35 feet to perched water at approximately 95
feet. Inert gas tracer studies, regular soil gas measurements
at several locations and depths, and periodic in situ respirom-
etry tests to measure in situ oxygen uptake rates are being
performed. Final soil hydrocarbon analyses will be con-
ducted at both sites in mid-1994 and compared with the
initial soil data. In situ respirometry data from the Hill site
(Table 1) indicate that petroleum hydrocarbons are being
removed at a significant rate. Intermediate respirometry
data from the test and control plots at the Eielson site
indicate that higher biodegradation rates are being ob-
tained at higher soil temperatures.[42][43].
Table 2.
Groundwater Quality After Seven Months of
Biosparging at the U.S. Coast Guard Air Station in
Traverse City, Michigan
Well
Depth (ft)
Control
16
17.5
20.5
22
Sparge Plot
15
18
19.5
21
Benzene
(US/L)
9.9
228
70
57
1.9
<1
<1
<]
Xylenes
(ng/L)
19
992
38
7.7
5.3
5.0
<1
<"•
Total Fuel
Carbon (u,g/L)
2,880
4,490
956
783
559
<6
<6
<6
Table 1.
Rates of Biodegradation, Averaged Over Depth, at
Three Wells at Hill AFB
Well
CW-1
CW-2
CW-3
Depths
(ft)
20-90
60-90
10-90
Rate (mg/kg/day)
September 1991
0.97
0.59
0.56
September 19921
0.30
0.36
0.32
1 Since bioventing is being performed on a sandy soil, with
little to no naturally occurring organic matter, a biodegradation
rate approaching zero would indicate that biodegradation had
finished.
In November 1991, a pilot-scale bioventing system
originally used to treat gasoline-contaminated vadose soils
at the U.S. Coast Guard Air Station in Traverse City, Michi-
gan was converted into a groundwater biosparging pro-
cess. Eight 2-inch diameter sparge wells were installed to
a depth of 10 feet below the water table. A control plot
located in the vicinity of the contaminated plume, but not
biosparged, was established to help assess the system's
performance. After 12 months of biosparging, one-third of
the oily phase residue below the water table, as well as
almost all the BTEX initially present within the groundwater
plume, was removed. (See Table 2 for groundwater quality
data after 7 months of biosparging.) The globular nature of
the oily residue limited the surface area in contact with the
introduced air, thus restricting the biodegradation and
vaporization of the oily-phase contaminants [44][45].
Non-Superfund Sites
In situ biodegradation has been applied at many sites
in the private sector. Those interested in accessing informa-
tion generated in the private sector may want to refer to the
following EPA Publications:
U.S. Environmental Protection Agency.
Bioremediation Case Studies: Abstracts.
EPA/600/R-92/044, March 1992.
U.S. Environmental Protection Agency.
Bioremediation Case Studies: An Analysis of
Vendor Supplied Data. EPA/600/9-92/043,
March 1992.
Most of the data contained in these resources were
directly supplied by the vendor and have not been techni-
cally reviewed by EPA. Since independently-reviewed data
are not always available from privately sponsored remedial
efforts, in part due to proprietary issues [46, p. 1 -1 ], readers
should use these data cautiously. Often the quality of the
data used to determine system effectiveness has not been
substantiated by the scientific community. Thus, many
vendor claims of effectiveness, specifically regarding intro-
duced organisms and surface-active agents, are not sup-
ported within the scientific literature. Furthermore, many
bioremediation firms have only limited experience working
with the complex wastes normally associated with Super-
fund sites. Typically these firms deal only with gasoline and
petroleum product leaks and spills. Additionally, many of
the systems currently on the market involve the use of in situ
biodegradation in combination with other above-ground
treatment technologies such as carbon adsorption, air
stripping, and biological reactors. In situ biodegradation is
believed to enhance the total removal efficiency of the
system. However, in many cases, it is unclear how much of
the degradation occurred as a result of biological or non-
biological mechanisms (volatilization, chemical destruc-
tion, etc.). How much biodegradation actually takes place
in the soil or groundwater, in contrast to ex situ biodegra-
dation, is not always clear.
Engineering Bulletin: In Situ Biodegradation Treatment
-------
Technology Status
In situ biodegradation either has been considered or
selected as the remedial technology at 21 Superfund sites,
as well as 38 RCRA, UST, TSCA, and Federal sites[l][2][3].
Table 3 lists the location, primary contaminants, treatment
employed, and status of these sites. Information has also
been included on three in situ biotechnology demonstra-
tions presently being performed under the U.S. EPA Super-
fund Innovative Technology Evaluation (SITE) Program and
seven sites selected for performance evaluations under the
U.S. EPA Bioremediation Field Initiative. The data obtained
during the SITE demonstrations and Bioremediation Field
Initiative performance evaluations will be used to develop
reliable cost and performance information on biotreatment
technologies and applications.
The majority of the information found in Table 3 was
obtained from the August 1993 version of "Bioremediation
in the Field" [1], These sites have been sorted numerically
by Region and then alphabetically by site name. Sites
employing "in situ land treatment" were not included in
this list since these applications typically involve a signifi-
cant amount of material handling. Additionally, some of
the information was modified based on phone calls made to
the various site project managers. This resulted in the
removal of the American Creosote Works site in Florida and
four pesticides sites (i.e., the Joliet Weed Control District
site in the Joliet, Montana; the Lake County Weed Control
site in Ronan, Montana; the Miles Airport site in Miles City,
Montana; and the Richey Airport site in Richey, Montana)
[47], which are no longer considering in situ treatment.
Quarterly updates of this information can be obtained from
subsequent versions of "Bioremediation in the Field".
Most of the hardware components of in situ biodegra-
dation systems are available off-the-shelf and present no
significant availability problems. Selected cultures, nutri-
ents, and chemical/biological additives are also readily
obtainable.
Bioremediation, particularly in situ applications, which
avoid excavation and emissions control costs, are generally
considered cost effective. This can be attributed in part to
low operation and maintenance requirements. During set
up and operation, material handling requirements are mini-
mal, resulting in lowered worker exposures and reduced
health impacts. Although in situ technologies are generally
slow and somewhat difficult to control, a large volume of
soil may be treated at one time.
It is difficult to generalize about treatment costs since
site-specific characteristics can significantly impact costs.
Typically, the greater the number of variables requiring
control during biological treatment, the more problematic
the implementation and the higher the cost. For example,
it is less problematic to implement a technology in which
only one parameter (e.g., oxygen availability) requires
modification than to implement a remedy that requires
modification of multiple factors (e.g., pH, oxygen levels,
nutrients, microbes, buffering agents, etc.). Initial concen-
trations and volumes, pre- and post-treatment require-
ments, and air emissions and control systems will impact
final treatment costs. The types of amendments employed
(e.g., hydrogen peroxide) can also impact capital cost and
costs associated with equipment and manpower required
during their application.
In general, however, in situ bioremediation is consid-
ered to be a relatively low-cost technology, with costs as
low as 10 percent of excavation or pump and treat costs [7,
p. 6-16]. The cost of soil venting using a field-scale system
has been reported to be approximately $50 per ton as
compared to incineration, which was estimated to be more
than ten times this amount. A cost estimate of about $15
per cubic yard for bioventing sandy soil at a JP-4 jet fuel
contaminated site has been reported by Vogel [48]. Exclu-
sive of site characterization, the biological remediation of
JP-4 contaminated soils at the Kelly Air Force Base site was
estimated to be $160 to $230 per gallon of residual fuel
removed from the aquifer [9]. At the French Limited site in
Texas, the cost of bioremediation is projected to be almost
three times less expensive than incineration. Because of the
large amount of material requiring treatment at this site, it
has been projected that cleanup goals will be achieved in
less time by using bioremediation rather than incineration.
EPA Contact
Technology-specific questions regarding in situ bio-
degradation may be directed to:
Steve Safferman, EPA-RREL
Cincinnati, Ohio
(513)569-7350
John Matthews, EPA-RSKERL
Ada, Oklahoma
(405) 436-8600
Acknowledgments
This bulletin was prepared for the U.S. Environmental
Protection Agency, Office of Research and Development
(ORD), Risk Reduction Engineering Laboratory (RREL), Cin-
cinnati, Ohio, by Science Applications International Corpo-
ration (SAIC) under Contract No. 68-C8-0062 and Contract
No. 68-CO-0048. Mr. Eugene Harris served as the EPA
Technical Project Monitor. Mr. Jim Rawe served as SAIC's
Work Assignment Manager. This bulletin was authored by
Mr. Rawe and Ms. Evelyn Meagher-Hartzell of SAIC.
The following other Agency and contractor personnel
have contributed their time and comments by participating
in the expert review meetings or independently reviewing
the document:
Mr. Hugh Russell
Ms. Tish Zimmerman
Mr. Al Venosa
Dr. Robert Irvine
Dr. Ralph Portier
Mr. Clyde Dial
EPA-RSKERL
EPA-OERR
EPA-RREL
University of Notre Dame
Louisiana State University
SAIC
w
Engineering Bulletin: In Situ Biodegradation Treatment
-------
Table 3. Superfund, RCRA, UST, TSCA, and Federal Sites
Site Location
(Regions)
Primary Contaminants
Status/Cost
Treatment
Chariestown Navy Yarc
Boston, MA (t)
General Electric -
Woods Pond
Pittsfield, MA(1)
FAA Technical Center -
AreaD
Atlanta County, Nj (2)
General Electric -
Hudson River, NY (2)
Knispel Construction
Site
Horsehead, NJ (2)
Picatinny Arsenal
NJ(2)
Plattsburgh AFB
Plattsburgh, NY (2)
ARC
ainesville, VA (3)
Dover AFB
Dover, DE (3)
.A. Clarke & Son
redericksburg, VA (3)
Charleston AFB
Iharieston, SC (4)
glin AFB
L(4)
avannah River Site
Uken, NC (4)
tallworth Timber
eatrice, AL (4)
Hied Chemical
onton, OH (5)
moco Production Co.
alaska, Ml (5)
&F Trucking
ompany
ochester, MN (5)
endixCorp./Allied 1
utomotive Site
. Joseph, Ml (5)
Sediments: wood preserving (PAHs).
Sediments: PCBs.
Volume: 250 gallons.
Soil (saturated sand)/groundwaten
petroleum (Jet fuel, NAPLs).
Volume: 33K cubic yards.
Sediments: PCBs, cadmium,
chromium, lead.
Volume: 150 cubic feet.
Soil/groundwater: petroleum.
Soil (vadose)/soil vapors: solvents
CTCE).
Groundwater: petroleum.
oil: solvent (chlorobenzene).
Volume: 2,000 cubic yards.
Soil (vadose sand and silt)/ground-
water: petroleum, PAHs, TCE, solvents,
metals (lead, iron, manganese).
'olume: 365K cubic yards.
Sediments/soil: wood preserving.
/olume: 119K cubic yards.
oil (vadose sand): petroleum (jet
uel), solvents (1,1 -DCE; 1,1,1 -TCA;
TCE; VC; trans-1,2-DCE; PCE; and
ichloromethane), lead.
/olume: 25 cubic yards.
oil (vadose): petroleum (jet fuel).
oil(yadose)/groundwater/sediments:
hlorinated solvents (TCE and PCE).
oil (sand, silt)/groundwater: wood
reserving (PCP).
ediments (coal and coke fines): PAHs,
rsenic,
olume: 500K cubic yards.
oil (saturated)/groundwater: BTEX.
oil (vadose and saturatedrg)/ground-
ater: petroleum (lube oil).
olume: 700 cubic yards.
roundwater: solvents (TCE, DCE,
CA, VC).
Design: pilot scale TS underway.
Design: lab scale TS underway.
Design: pilot scale TS completed
8/927
Expected cost: capital, S286K;
O&M, S200K
Predesign: lab scale TS
completed.
Incurred cost: S2.6M.
Completed: full scale 10/89
Start date: 01/89.
ncurred cost: O&M, $25K.
Design: lab scale studies
completed.
Design: pilot scale.
Start date (est.): 3/94.
Completed: full scale 6/91.
"tart date: 10/89.
Four separate processes are
planned. Field and lab TS results
are expected 2/94 and 11/94.
Design: pilot scale TS started
7/92
Expected cost: $23M.
>ilot scale TS started 11/92.
Expected completion 12/93.
Completed field scale study.
Operational: pilot scale research
tudy.
redesign.
esign: pilot scale TS study
ompleted.
xpected cost: $26M
lot scale TS completed.
perational: full scale.
tart Date: 4/91.
curredcost: J341K.
edesign: lab scale TS underway.
In situ treatment. Ex situ treatment
Aerobic and anaerobic.
Anaerobic treatment, confined treatmen
facility, nutrient addition.
Nutrient addition (soil, water).
Groundwater re-injection.
Aerobic treatment. Less than 1% of site
underwent bioremediation.
Aerobic treatment, hydrogen peroxide,
nutrient addition (water). 100% of site
underwent bioremediation [25].
Aerobic treatment, bioventing.
Co-metabolic degradation (methane,
propane, or natural gas) [27].
Aerobic treatment, bioventing.
Aerobic treatment, bioventing.
Exogenous organisms. 5% of the site
underwent bioremediation.
Aerobic treatment, bioventing, air
parging. Ex situ land treatment.
T situ treatment, creosote recovery.
5% of site will undergo bioremediation.
ierobic treatment, bioventing. Less than
0% of the site under bioremediation.
Aerobic treatment, bioventing. Nutrient
nd hydrogen peroxide addition [27].
erobic treatment, horizontal wells,
methane addition [18][19],
n situ aerobic treatment, nutrient
ddition. Ex situ treatment, activated
udge, continuous flow. Exogenous and
idigenous organisms. 100% of site will
ndergo bioremediation.
erobic treatment 50% of site will
ndergo bioremediation.
erobic treatment, air sparging [49].
situ treatment. Ex situ treatment
equencing batch reactor, continuous
ow. AeroDic conditions. 75% of site
nder bioremediation.
erobic and anaerobic treatment.
Engineering Bulletin: In Situ Biodegradation Treatment
11
-------
Table 3. Superfund, RCRA, UST, TSCA, and Federal Sites (continued)
Site Location
(Regions)
Primary Contaminants
Status/Cost
Treatment
n-named site2
uchanan, Ml (5)
alesburg/Kopper
alesburg, IL (5)
entchells
raverse City, Ml (5)
enworth Truck Company
hillicothe, OH (5)
J. Sawyer AFB
vlarquette, Ml (5)
vlayville Fire Department
vlayville, Ml (5)
vlichigan Air National Guard
-attle Creek, Ml (5)
Newark AFB
Newark, OH (5)
Onalaska Municipal Landfill
Lacrosse County, Wl (5)
Parke-Davis
Holland, Ml (5)
Reilly Tar & Chemical 1«2
St. Louis Park, MN (5)
Sheboygan River and Harbor
Sheboygan, IL (5)
West K&L Avenue e Landfill 1
Kalamazoo, Ml (5)
Wright-Patterson AFB
Dayton, Ohio (5)
Dow Chemical Company
Plaquemine, LA (6)
French Limited
Crosby, TX (6)
Kelly AFB
San Antonio, TX (6)
roundwater: BTEX, PCE, TCE, DCE.
oil: phenols, chlorophenol, PNAs,
CP, PAHs.
oil/groundwater: petroleum.
oil (vadose)/groundwater:
olvents (BTEX, acetone, TPH).
oil (vadose sand): petroleum.
iroundwater: petroleum.
>oil (vadose: sand, silt): petroleum,
heavy metals.
Soil (vadose: silt, clay): petroleum
gasoline).
volume: 60 cubic yards.
Soil (vadose and saturated sand):
solvents (TCE), petroleum (total
lydro-carbons), wood preserving
naphthalene).
Volume: 5,000 cubic yards.
Soil/groundwater: petroleum,
solvents, arsenic, chloride, zinc.
Soil (vadose loam): wood preserving
(PAHs).
Sediments (sand, silt, clay): PCBs.
Volume: 2,500 cubic yards.
Croundwater: solvents (acetone;
TCE; trans-1,2-DCE; 1,2-DCA;
1,1-DCA; BTEX; VC; methyl isobutyl
ketone; MEK.
Soil (vadose: sand, silt, clay):
petroleum (jet fuel).
Volume: 7.5K cubic yards.
Croundwater: solvents (1,1-DCA;
1,2-DCA;1,1,1-TCA;1,1-DCE,
chloroethane).
Volume: 90K cubic yards.
Sediments (sand, silt)/sludge/soil
(sand, silt, clay)/groundwater:
PCBs, arsenic, roleum (BAP, VOCs),
arsenic.
Soil (vadose clay): petroleum (jet
fuel), solvents (Pc£ TCE, VC, DCE).
ilot field study started 3/93.
xpected completion 3/94.
redesign.
tart date (est): 12/92.
)perational: full scale.
tart date: 9/85.
esign: lab scale TS completed.
ull scale system being installed.
ield TS report expected 10/93.
Operational: full scale since 5/90.
Completion date (est): 1 /94.
Design: pilot scale TS started
->/92
tart date (est): 9/93
Expected cost: capital, $3,000;
O&M, $1,268.
Design: pilot scale TS started
8/92. Expected completion
8/94.
Expected cost: capital, $35K;
O&M, $2K.
Design: lab scale TS completed
3/92.
Expected cost: capital, $400K;
O&M, $20K.
'redesign.
Design: pilot scale TS started
11 /92. Expected completion
11/95.
ncurred cost: $25K.
Expected cost: $70K.
Lab and pilot scale TS are being
conducted.
Design: pilot and lab scale TS
ongoing.
Predesign: pilot scale studies
planned.
Expected completion 3/94.
Design: pilot scale started 3/93.
Expected cost: capital, $1M;
O&M, $50K.
Incurred cost: capital, $250K;
O&M, $10K.
Operational: full scale since 1 /92
Expected cost: $90M.
Operational: full scale since 2/93
Completion data (est): 9/94.
erobic treatment.
Nutrient addition. 100% of site
nder bioremediation.
erobic treatment, biosparging.
situ aerobic treatment, hydrogen
eroxide, nutrient addition
nitrogen, phosphorus). Ex situ
reatment, CAt bioreactor. 100% of
te will undergo bioremediation.
Aerobic treatment, bioventing.
Aerobic treatment, air sparging.
00% of site will undergo
lioremediation.
icrobic treatment, bioventing.
00% of site will undergo
jioremediation.
Aerobic treatment, bioventing. 40%
of site under bioremediation.
Aerobic treatment, bioventing. 20%
of site will undergo bioremediation.
n situ treatment. Ex situ treatment,
ixed film.
Aerobic treatment, bioventing,
nutrient addition [50].
n situ treatment, capping of
sediments. Ex situ treatment,
confined treatment facility (tank).
Aerobic and anaerobic conditions.
Anaerobic treatment under sulfate
reducing conditions.
Aerobic treatment, bioventing.
100% of site will undergo
bioremediation.
Anaerobic treatment, nutrient
addition. Less than 1% of site under
bioremediation. Experiencing;
nutrient dispersion problems [46].
Aerobic treatment, pure oxygen
dissolution system, nutrient addition
(soil, water, sediments). 100% of
site under bioremediation.
Aerobic treatment, bioventing.
12
Engineering Bulletin: In Situ Biodegradation Treatment
-------
Table 3. Superfund, RCRA, UST, TSCA, and Federal Sites (continued)
Site Location
(Regions)
Primary Contaminants
Status/Cost
Treatment
Fairfield Coal & Gas
Faiffield,IA(7)
Offutt AFB
LaPlatte, NE (7)
ParkCrty1
Park City, KS (7)
Burlington Northern Tie
Plant
Somers, MT (8)
Geraldine Airport
Geraldine, MT (8)
Idaho Pole Company
Bozeman, MT (8)
Hill AFB1
Salt Lake City, UT (8)
Libby Groundwater Site1
Libby, MT (8)
Public Service Company1
Denver, CO (8)
Beale AFB
Marysville, CA (9)
Converse/Montabello
Corporation Yard
Montabello, CA (9)
:ormer Service Station
Los Angeles, CA (9)
Orvi
ppers Company, inc.
Marine Corps Air/
Ground Combat Center
Twenty-Nine Palms,
CA(9)
^aval Air Station Fallen
allon, NV (9)
slaval Weapons Station
>eal Beach, CA (9)
Oakland Chinatown
Oakland, CA (9)
Soil (saturated: sand, silt
clay)/groundwater: coal tar (BTEX,
PAHs):
Soil (vadose: sand, silt): petroleum
(TRPH), arsenic, barium, lead, zinc.
Volume: 700 cubic yards.
Groundwater: petroleum (lube oil),
benzene.
Volume: 700K cubic feet.
Soil/groundwater: wood preserving
(PAHs).
Volume: 82K cubic yards.
Soil (vadose: sand, silt, loam, clay):
pesticides (aldrin; dieldrin; endrin;
chlordane; toxaphene; b-BHC;
4,4'-DDE; 4,4'-DDT; 4,4'-DDD);
herbicides (2,4-D).
Sediments/soils/groundwater: PCP,
PAHs, dioxins/furans.
Soil: petroleum (JP-4 jet fuel).
Soil (vadose and saturated)/
groundwater: wood preserving (PAHs,
Dyrene, PCP, dioxin, naphthalene,
anenanthrene, benzene, arsenic).
/olume: 45K cubic yards.
roundwater: petroleum.
Volume: 12M gallon.
Soil (vadose silty clay): petroleum
[gasoline, diesel), solvents (TCE), lead.
volume: 163K cubic yards.
Soil (vadose silt): petroleum (gas,
diesel).
oil/groundwater: petroleum.
Volume: 3,000 cubic yards.
Soil (vadose: sand, clay, gravel,
cobbles): wood preserving (PCP,
PAHs, dioxins/furans), arsenic,
chromium.
Volume: 110K cubic yards.
Soil: petroleum (jet fuel, gasoline,
diesel, aviation fluid,
luid).
transmission
Soil (vadose and saturated
ilt)/groundwater: petroleum (jet fuel,
>-xylene. naphthalene, 1-methyl
naphthalene, n-butylbenzene),
irsenic.
Jroundwater: petroleum.
oil (saturated sand): groundwater:
petroleum.
Design: pilot scale TS started
12/91. Expected completion
12/93.
Expected cost: 51.6M.
Design: pilot scale TS started
8/92
Design: pilot scale TS completed.
Incurred cost: J275K.
Expected cost: J650K.
Installed: full scale.
Start date (est): 7/92.
Expected cost: J11M.
Predesign.
Predesign.
Operational: full scale since 9/91.
Completion date (est): 9/94.
Operational: three pilot scale
efforts ongoing.
ncurred cost: $4M.
TS results available (est): 8/93
and 4/94.
Completed: full scale 3/92.
Start date: 06/89.
incurred cost: S500K.
Seven processes are planned.
4 are in design (pilot scale),
2 are in predesign (full scale), and
1 is presently operating
completion date 7/95).
Lxpected cost: capital J500K;
O&M, 136K.
Design: pilot scale TS started
5/93
Expected completion 12/93.
Completed: full scale 3/91
Start date: 11/88.
ncurred cost: 51.6M.
'redesign; pilot scale TS planned.
Ixpected completion 11 /94,
Expected cost: capital, S4.5M;
O&M, S7.7M,
Design: full scale.
Design: pilot scale TS started
0/92.
S conducted or in progress:
aboratory scale.
'olume: 10K cubic yards.
Completed: full scale 8/90.
>tart date: 3/89.
Aerobic treatment, injection and
extraction wells, hydrogen peroxide,
nitrate addition.
Aerobic treatment, bioventing. 10% of
site under bioremediation.
Groundwater: in situ treatment. Possible
bioventing for soils. Anaerobic and
aerobic conditions [23][24].
In situ treatment. Ex situ land treatment.
Aerobic conditions. 80% of site will
undergo bioremediation.
In situ treatment. Ex situ treatment.
Aerobic and anaerobic conditions.
In situ treatment, oxygen enhancement,
nutrient addition. Ex situ treatment,
fixed film, slurry reactor. Aerobic
conditions.
Aerobic treatment, bioventing. 100% of
site under bioremediation [4(5].
In situ treatment (groundwater), ex situ
and treatment (soil), nutrient addition
[soil, water). Also, treatment of
groundwater in bioreactor. Aerobic
:onditions. 75% of site under
bioremediation.
Aerobic treatment, hydrogen peroxide,
nutrient addition, combined bioprocess.
n situ aerobic treatment, bioventing.
:x situ aerobic treatment, pile. Results of
4 bioventing TS expected 2/94.
Aerobic treatment, bioventing, nutrient
addition. 10% of site under
bioremediation.
Aerobic treatment, hydrogen peroxide,
nutrient addition (water), closed loop
system. 65% of site underwent
)ioremediation.
Aerobic treatment, nutrient addition.
30% of site will undergo bioremediation.
'20 year remedial effort)
Aerobic treatment, bioventing.
Aerobic treatment, bioventing, nutrient
addition (soil), oil/water separation.
Aerobic and anaerobic treatment.
Aerobic treatment, hydrogen peroxide
nd nutrient addition.
Engineering Bulletin: In Situ Biodegradation Treatment
13
-------
Table 3. Superfund, RCRA, UST, TSCA, and Federal Sites (continued)
Site Location
(Regions)
Primary Contaminants
Status/Cost
Treatment
San Diego Cas and
Electric
San Diego, CA (9)
Williams AFB2
Phoenix, AZ (9)
East 15th Street Service
Station
Anchorage, AK (10)
Eielson AFB'
Fairbanks, Alaska (10)
FairchildAFB
Spokane, WA (10)
Soil (sand): petroleum (gasoline).
Volume: 1,200 cubic yards.
Soil (vadose): petroleum (JP-4 jet fuel).
Soil: petroleum (TPH diesel).
Volume: 1,500 cubic yards.
Soil (sand/silt): petroleum QP-4 jet
fuel).
Soil (vadose and saturated
silt)/groundwater: petroleum, solvents
(TCE).
Completed: full scale 4/93.
Start date: 10/89.
Pilot field testing started 5/92.
Test completed 6/93.
Operational: full scale since 6/92.
Incurred cost: J75K.
Expected cost: $200K.
Operational: pilot full scale.
Start date: 9/91.
Completion date (est): 9/94.
3 separate processes are planned.
The first process is in pre-design;
a pilot scale TS should start 1/95.
The remaining two started pilot
scale TSs in 4/93.
Aerobic treatment. 100% of site
underwent bioremediation [5].
In situ treatment, bacterial
supplementation (non-indigenous micro
aerofilic bacteria).
Aerobic treatment, bioventing. 20% of
site under bioremediation.
Aerobic treatment, bioventing, soil
warming [42]
Aerobic treatment, bioventing, nutrient
addition.
TS - Treatability Study
1 Bioremediation Field Initiative
2 Superfund Innovative Technology Evaluation (SITE) Demonstration
REFERENCES
1. U.S. Environmental Protection Agency. Bioremediation
in the Field. EPA/540/N-93/002, August 1993.
2. U.S. Environmental Protection Agency. Superfund Inno-
vative Technology Evaluation Program: Technology Pro-
files, Sixth Edition. EPA/540/R-93/526, November
1993.
3. U.S. Environmental Protection Agency. Bioremediation
Field Initiative. EPA/540/F-93/510, September 1993.
4. U.S. Environmental Protection Agency. Handbook on
InSitu Treatment of Hazardous Waste-Contaminated
Soils. EPA/540/2-90/002, Cincinnati, Ohio, January
1990.
5. Gersberg, R.M., W.J. Dawsey, and H. Ridgeway. Draft
Final Report: In-Situ Microbial Degradation of Gasoline.
EPRI Research Report Number RP 2795-2.
6. Norris, R.D., K. Dowd, and C. Maudlin. The Use of Mul-
tiple Oxygen Sources and Nutrient Delivery Systems to
Effect In Situ Bioremediation of Saturated and Unsatur-
ated Soils. Presented in: Symposium on Bioremediation
of Hazardous Wastes: Research, Development, and
Field Evaluations. EPA/600/R-93/054, May 1993.
7. Hopkins, G.D., L. Semprini, and P. McCarty. Field
Evaluation of Phenol for Cometabolism of Chlorinated
Solvents. In: Symposium on Bioremediation of Hazard-
ous Wastes: Research, Development, and Field Evalua-
tions. EPA/600/R-93/054, May 1993.
8.
9.
Hopkins G.D., L. Semprini, and P.L. McCarty. Evalua-
tion of Enhanced In Situ Aerobic Biodegradation of CIS-
and Trans-1-Trichloroethylene and CIS- and Trans-1,2-
Dichloroethylene by Phenol-Utilizing Bacteria. In:
Bioremediation of Hazardous Wastes. EPA/600/r-92/
126, August 1992.
Abramowicz, et al. 1991 In Situ Hudson River Research
Study: A Field Study on Biodegradation of PCBs in
Hudson River Sediments - Final Report. February 1992.
10. U.S. Environmental Protection Agency. Superfund LDR
Guide #6A: Obtaining a Soil and Debris Treatability Vari-
ance for Remedial Actions. OSWER Directive 9347.3-
06FS, September 1990.
U.S. Environmental Protection Agency. Superfund LDR
Guide #6B: Obtaining a Soil and Debris Treatability Vari-
ance for Removal Actions. OSWER Directive 9347.3-
06BFS, September 1990.
Sims, ]., R. Sims, and J. Matthews. Bioremediation of
Contaminated Surface Soils. EPA/600/9-89/073, August
1989.
Sims, J., R. Sims, R. Dupont,). Matthews, and H. Russell.
Engineering Issue - In Situ Bioremediation of Contami-
nated Unsaturated Subsurface Soils. EPA/540/S-93/501,
May 1993.
Piotrowski, M.R. Bioremediation: Testing the Waters.
Civil Engineering, August 1989. pp. 51-53.
11
12
13.
14.
14
Engineering Bulletin: In Situ Biodegradation Treatment
-------
15. U.S. Environmental Protection Agency. International
Evaluation of In-Situ Biorestoration of Contaminated Soil
and Groundwater. EPA/540/2-90/012, September
1990.
16. U.S. Environmental Protection Agency. Handbook: Re-
medial Actions at Waste Disposal Sites (Re-
vised). EPA/625/6-85/006, Cincinnati, Ohio, October
1985.
17. U.S. Environmental Protection Agency. Review of In-
Place Treatment Techniques for Contaminated Surface
Soils. Volume 2: Background Information for In Situ
Treatment. EPA/540/2-84/003b, Cincinnati, Ohio, No-
vember 1984.
18. Hazen, T.C. Test Plan for In Situ Bioremediation Dem-
onstration of the Savannah River Integrated Demonstra-
tion Project DOE/OTD TTP No.: SR 0566-01 (U). U.S.
Department of Energy, WSRC-RD-91-23, Revision 3,
April 23, 1992.
19. U.S. Department of Energy. Cleanup of VOCs in Non-
Arid Soils - The Savannah River Integrated Demonstra-
tion. WSRC-MS-91-290, Rev. 1, pg. 6.
20. U.S. Environmental Protection Agency. Technology
Screening Guide for Treatment of CERCLA Soils and
Sludges. EPA/540/2-88/004, September 1988.
21. U.S. Environmental Protection Agency. SITE Demon-
stration Bulletin - Augmented In Situ Subsurface
Bioremediation Process, BIO-REM, Inc., EPA/540/MR-
93/527, November 1993.
22. McCarty P. and J. Wilson. Natural Anaerobic Treatment
of a TCE Plume, St Joseph, Michigan, NPL Site. In:
Bioremediation of Hazardous Wastes. EPA/600/R-92/
126, August 1992.
23. Hutchins, S.R., and J.T. Wilson. Nitrate-Based
Bioremediation of Petroleum-Contaminated Aquifer at
Park City, Kansas: Site Characterization and Treatability
Study. In: Hydrocarbon Bioremediation. R.E. Hinchee,
B.C. Alleman, R.E. Hoeppel, and R.N. Miller, ed. CRC
Press, Boca Raton, Florida, 1994.
24. Kennedy, L.G., and S.R. Hutchins. Applied Geologic,
Microbiological, and Engineering Constraints of In-Situ
BTEX Bioremediation. Remediation. Winter 1992/93.
25. New York State Department of Environmental Conserva-
tion. Final Report, Knispel Construction Company,
Horseheads, New York, October 1990.
26. Marley, M.C., et al. The Application of the In Situ Air
Sparging as an Innovative Soils and Groundwater Reme-
diation Technology. Groundwater Monitoring Review,
pp. 137-144, Spring 1992.
27. Federal Remediation Technologies Roundtable. Synop-
ses of Federal Demonstrations of Innovative Site Reme-
diation Technologies. EPA/542/B-92/003, August 1992.
28. U.S. Environmental Protection Agency. Vendor Informa-
tion System for Innovative Treatment Technologies
(VISITT). EPA/540/2-91/001, June 1991.
29. U.S. Environmental Protection Agency. A Citizen's
Guide to Bioventing. EPA/542/F-92/008, March 1992.
30. U.S. Environmental Protection Agency. Bioremediation
in the Field. EPA/540/2-91 /018, August 1991.
31. U.S. Environmental Protection Agency. Bioremediation
in the Field. EPA/540/N-91/001, March 1992
32. U.S. Environmental Protection Agency. The Superfund
Innovative Technology Evaluation Program: Technology
Profiles, Fifth Edition. EPA/540/R-92/077, December
1992.
33. Hinchee, R.E., D.C. Downey, R.R. DuPont, P.K.
Aggarwal, and R.N. Miller. Enhancing Biodegradation
of Petroleum Hydrocarbons through Soil Venting. Jour-
nal of Hazardous Materials, Vol. 27, 1991.
34. Nelson, C.H. A Natural Cleanup. Civil Engineering,
March 1993.
35. Wilson, J.T., and D.H. Kampbell. Retrospective Perfor-
mance Evaluation on In Situ Bioremediation: Site Char-
acterization. In: Symposium on Bioremediation of
Hazardous Wastes: Research, Development, and Field
Evaluations. EPA/600/R-93/054, May 1993.
36. Day, S., K. Malchowsky, T. Schultz, P. Sayre, and G.
Saylor. Draft Issue Paper: Potential Risk, Environmental
and Ecological Effects Resulting From the Use of GEMS
for Bioremediation. U.S. Environmental Protection
Agency, Office of Pollution Prevention, April 1993.
37. Hopkins, G.D., L. Semprini, and P.L. McCarty. Field
Study of In Situ Trichloroethylene Degradation in
Groundwater by Phenol-Oxidizing Microorganisms. In:
Abstract Proceedings Nineteenth Annual RREL Hazard-
ous Waste Research Symposium. EPA/600/R-93/040,
April 199 3.
38. Beeman, R., S. Shoemaker, j. Howell, E. Salazar, and J.
Buttram. A Field Evaluation of In Situ Microbial Reduc-
tive Dehalogenation by the Biotransformation of Chlori-
nated Ethylenes. In: Bioremediation of Chlorinated
Polycyclic Aromatic Hydrocarbon Compounds. R.E.
Hinchee, A. Leeson, L. Sempini, and S.K. Ong, ed. CRC
Press, Boca Raton, Florida, 1994.
39. Norris, R.D., K. Dowd, C. Maudlin, and W.W. Irwin. The
Use of Multiple Oxygen Sources and Nutrient Delivery
Systems to Effect In Situ Bioremediation of Saturated
and Unsaturated Soils In: Hydrocarbon Bioremediation.
R.E. Hinchee, B.C. Alleman, R.E. Hoeppel, and R.N.
Miller, ed. CRC Press, Boca Raton, Florida, 1994.
40. U.S. Air Force Correspondence. Subject: Air Force's
Bioventing Initiative. July 1993.
41. U.S. Environmental Protection Agency. Bioremediation
in the Field. EPA/540/N-92/004, October 1992.
42. Sayles, G.D., R.E. Hinchee, C.M. Vogel, R.C. Brenner,
and R. N. Miller. An Evaluation of Concurrent
Bioventing of Jet Fuel and Several Soil Warming Meth-
ods: A Field Study at Eielson Air Force Base, Alaska. In:
Symposium on Bioremediation of Hazardous Wastes:
Research, Development, and Field Evaluations. EPA/
600/R-93/0-54, May 1993.
43. Sayles, G.D., R.E. Hinchee, R.C. Brenner, and R. Elliot.
Engineering Bulletin: In Situ Biodegradation Treatment
75
GOVERNMENT PRINTING OFFICE: 1994 - 550-067/80224
------- |