United States
Environmental Protection
Agency
Solid Waste and
Emergency Response
(SKEW)
EPA-542-N-94-007
September 1994
Ground Water Currents
Developments in innovative ground water treatment
UP-TO-DATE WAYS TO ASSESS WHEN
BIOREMEDIATION WORKS
Robert S. Kerr Environmental Research Laboratory
Vvhen does in situ the current practice for
bioremediation work? And, characterizing sites does not
adequately define the
And,
how can you reliably predict
success? An operational
definition for judging success
of in situ bioremediation at
field scale is that it meet
regulatory goals for ground
water quality in a timely
fashion and at a predictable
cost. Further, in situ bio-
remediation is judged by its
capacity to continue to meet
regulatory goals for water
quality after the active phase
of remediation is complete.
There are two factors to
address in judging success.
First bioremediation, par-
ticularly innovative bio-
remediation that uses an
electron acceptor other than
oxygen, can remove the
compounds of regulatory
concern from the subsurface
while leaving significant
amounts of oily-phase
hydrocarbons. Second, the
extent of weathering of
residual oily-phase material
and the hydrologic envi-
ronment of the residual have
a strong influence on the
potential for ground water
contamination after active
remediation ceases. An
important issue for deter-
mining short-term success
and long-term protection is
one of laboratory studies
versus actual field conditions.
The problem posed is that
amount of contamination
subject to bioremediation.
As a result, laboratory studies
which estimate the re-
quirements at field scale for
electron acceptors and
mineral nutrients for bio-
remediation, and the time
required for remediation,
have much uncertainty when
extrapolated to field scale. In
contrast to laboratory studies,
the extent of remediation
achieved at field scale is
influenced by dilution of
compounds of regulatory
concern in circulated water
and partitioning between
water and the residual oil.
Part of the problem with
the transfer of laboratory
research to the field is that
there are different levels of
inquiry in the laboratory and
in the field. Laboratory
studies deal with biochemical
or physiological processes
with appropriate controls to
ensure that only one mech-
anism is responsible for the
phenomena under study.
However, during field-scale
implementation of bioreme-
diation technology, several
processes operate con-
currently. They may involve
several distinct mechanisms for
biological destruction of the
contaminant, as well as
partitioning of contaminants
to immobile phases, dilution
in ground water and vol-
atilization. Therefore, if
performance monitoring is
limited to the concentrations
of nutrients and electron
acceptors, it cannot ensure
that the biological process
developed in the laboratory
was responsible for contami-
nant removal at full-scale
field conditions. Exper-
imental controls are usually
unavailable during full-scale
implementation of in situ
bioremediation because the
technology is applied
uniformly to the contami-
nated area. So, how do you
know whether it was the
biological process developed
in the laboratory or some-
thing else that reduced
contaminant concentrations?
And, how do you know
whether or not natural
biodegradation will prevent
the regeneration of a plume
of contaminated ground
water when active
remediation ceases?
To overcome these prob-
lems, the appropriate equiva-
lent of experimental controls
is a detailed characterization
of the site, the flow of
remedial fluids and the flux
of amendments. This
characterization allows an
assessment of the influence of
partitioning, dilution or
volatilization on remediation
and provides a basis for
evaluating the relative con-
tribution of bioremediation.
Wells have traditionally
been used to characterize
sites. Ground water mon-
itoring wells alone cannot
estimate the total contam-
inant mass subject to re-
mediation within an order of
magnitude. Most plumes of
organic contamination in
ground water originate from
spills of refined petroleum
hydrocarbons, such as gasoline,
or chlorinated solvents, such as
trichloroethylene.
(See Bioremediation Page 2)
This Month in Currents
THIS MONTH'S CURRENTS CONTAINS VENDOR AND
BULLETIN BOARD INFORMATION.
BIOREMEDIATION
CLEAN UP BULLETIN BOARD
VENDOR DATABASE UPDATE
Recycled/Recyclable • Printed with Vegetable Oil Based Inks on 100% Recycled Paper (50% Postconsumer) . Please recycle as newsprint
-------
GROUND WATER REMEDIATION CLUES
By Gary Turner, Technology Innovation Office, EPA
jf you have not heard about,
or lately have not been on
the EPA's Clean-Up
Information Bulletin Board
System (CLU-IN), you may
he missing out on some new
information and new
features. In the past year,
CLU-IN has upgraded the
software; and, we are still in
the process of implementing
new features and customizing
prompts. As always, CLU-
IN still has three main
components — Bulletins,
Files, Messages.
Bulletins. The bulletins are
short text files that can be
read online while you are
connected to CLU-IN.
CLU-IN has regularly
updated bulletins containing
TECH TRENDS and
GROUND WATER
CURRENTS articles,
FEDERAL REGISTER
updates and COMMERCE
BUSINESS DAILY
announcements. There are
monthly regulatory reports
from EPAs RCRA/
CERCLA/OUST/EPCRA
Hotline, as well as EPA
Office of Solid Waste and
Emergency Response training
course schedules, an-
nouncements of workshops,
meetings, publications and
databases.
Files. The files available on
CLU-IN can be in any
format, including databases,
publications, graphics files,
utilities and spreadsheets.
Although these files cannot
be used online, they can be
downloaded and used on the
user's own computer.
Among the files available for
downloading on CLU-IN are
the Hazardous Waste
Superfund Database, the
Risk Reduction Engineering
Laboratory (RREL)
Treatability Database, the
Hyperventilate program
from the Office of
Underground Storage Tanks
(OUST) and many
publications from the
Technology Innovation
Office.
Messages. CLU-IN also has
an electronic mail capability
that allows users to exchange
messages with individual
users as well as to leave
messages to all of the
approximately 4,000 CLU-
IN users to stimulate wider
discussion. Many users use
this feature to get advice
from other users who have
expertise with similar site
conditions or contaminants.
In addition to these
features that have always
been part of CLU-IN, in the
near future we will be
implementing a major
overhaul of the user interface
to improve the user-friendli-
ness of CLU-IN. We will be
streamlining the Main Menu
and creating sub-menus so
that it will be easier to
maneuver within CLU-IN.
For instance, the bulletins
will be sorted into a main
bulletin menu and submenus
to make it easier to find
bulletins on a given topic.
Users will still be able to
search the text of bulletins
for key words and display all
bulletins that are new since
the last time the user called
into CLU-IN.
We will also be adding two
new online databases to
CLU-IN in the near future.
One database will be a
calendar of upcoming
conferences, meetings and
workshops on hazardous
waste remediation that users
will be able to search by
conference date, location and
topic. The other database
will contain information on
training courses offered by
EPA. Users will be able to
search it by topic to locate
available training.
Changes will be taking
place to CLU-IN content,
interface and features
throughout the fall. We will
profile some of these changes
in more detail in future
articles. We encourage you
to call into CLU-IN and try
it out. Users do not need to
pre-register — you can
register and choose your own
password on your first call.
The dial-in number for
accessing CLU-IN is: 301-
589-8366 (up to 9600 baud;
communications settings are 8
data bits, 1 stop bit and no
parity). EPA users can connect
to CLU-IN using EPA's X.25
network without needing a
modem. For more informa-
tion about CLU-IN, call the
CLU-IN Help Line at 301-
589-8368.
(Bwremetliation continued from page 1)
These substances enter the
subsurface as nonaqueous-
phase oily liquids, traveling
separately from the ground
water. Although wells have
been used to define the
extent of contamination in
the subsurface environment
through measurement of the
contaminants in the ground
water, they cannot reliably
determine the extent of
contamination by oily-phase
materials. This monitoring
deficit is particularly impor-
tant because, as long
as the oily-phase liquid is
present in the subsurface,
it can act as a continuing
source of contamination.
Recent research has docu-
mented that monitoring well
data grossly underestimate
the extent of contamination
and that there is a need for
site characterization tech-
niques that can accurately
estimate the total mass of
contaminants subject to
bioremediation.
The appropriate rigorous
approach to characterize sites
should include the collection
and analysis of core samples
to estimate total contaminant
mass in the subsurface in
order to predict the demand
for nutrients and electron
acceptor that must be met to
complete the remediation.
Then one can use the rate
of supply of the limiting
requirement to estimate
the time required for the
remediation. With core
samples, it is recommended
that they be subsampled
and extracted in the field to
preclude losses to volatiliza-
tion and biodegradation
during shipping to a lab-
oratory. By using inexpensive
headspace analyses in
conjunction with field core
(See Bioremetlultwn Page 3)
Ground Water Currents
-------
VENDOR INFO
GROUND WATER TECHNOLOGIES
IN VISITT DATABASE
By Linda Fiedler, Technology Innovation Office, EPA
Yhe U.S. Environmental technologies, including 201
Protection Agency has that are full-scale and
released VISITT 3.0, the
latest update of its database
on new cleanup technologies.
VISITT (Vendor Infor-
mation System for Inno-
vative Treatment Tech-
nologies) lists current
information on the
availability, performance
and cost of innovative
technologies to remediate
contaminated waste sites.
VISITT now contains data
on 277 innovative
commercially available.
This update includes 46
technologies which are
designed to treat ground
water in situ. They can be
grouped into the following
categories: air sparging
(eight technologies);
bioremediation (18
technologies); chemical
treatment (three tech-
nologies); dual phase
extraction (six technologies);
and thermal enhancements
(11 technologies). The
three chemical treatment
technologies include: surfac-
tant solubilization; fixation
of metals and radionuclides
by pH and redox changes;
and dechlorination of
organics by redox changes.
Thermal enhancements
include radio frequency
heating, electric resistive
heating and steam injection.
According to the technology
vendors that submitted the
information, 35 of the in situ
ground water technologies
are available for full-scale use
and the remainder are in the
bench or pilot scale.
To order VISITT 3.0
diskettes and the user manual
and to become a registered
user, provide your name,
company, address, phone
number and diskette size
needed (3-1/2 inch or 5-1/4
inch) by mail to U.S. EPAJ
NCEPI, P.O. Box 42419,
Cincinnati, OH 45242-2419
or by FAX to 513-489-8695.
(Bioremediation continued from page 2)
samples, results from a
limited number of expensive
core analyses can be extrapo-
lated to a large number of
field headspace analyses.
Headspace analyses are
inexpensive and generate
data in real time, which also
allows the screening in-
formation to be used to
guide decisions about depth
and location of subsequent
cores.
When water is circulated
through an oily-phase spill
during bioremediation, the
concentration of regulated
compounds will drop
because of simple dilution.
Simple partitioning theory
can be used to calculate the
distribution of hydrocarbons
of concern between the
recirculating ground water
and the residual oily-phase
materials. Simple ground
water models can estimate
the volume of water circu-
lated through a spill during
the in situ bioremediation by
predicting amended ground
water flow paths from an
infiltration gallery (sited
above the spill) to recovery
wells. This information can
be coupled with simple
partitioning theory to
estimate the apparent
attenuation due to dilution.
Simple partitioning theory is
also used to predict the
concentrations of hydrocar-
bons that will remain in
ground water that will be in
contact with weathered oily-
phase residual that frequently
remains after bioremediation.
The predictions give an
indication as to whether the
plume will be regenerated.
Seasonal variations and
weathering can cause plumes
to actually move away from
monitoring wells, to possibly
return at a later date. Addi-
tionally, pockets of fine
textured oily-phase material
may still contain high
concentrations of con-
taminants because remedial
fluids tend to pass around
the fine-textured material.
To supplement data from
monitoring wells, many
regulatory authorities require
measurement of residual oily-
phase material left after
bioremediation. However,
ground water quality is
controlled by the relative
concentration of organic
contaminants in the weath-
ered oily-phase residual and
not by the absolute amount of
weathered total petroleum
hydrocarbons. The relative
concentrations of organic
contaminants can be used to
predict the concentrations in
ground water in contact with
the oily-phase residual by
using Raoult's law. The
solution concentration in
water should be proportional
to the mole fraction of the
hydrocarbon in the oily phase.
The issue now becomes
whether any residual oily-
phase hydrocarbon is capable
of producing a plume of
contamination at concen-
trations that exceed the
cleanup goal. Mass transfer
effects control the access of
residual organic con-
taminants to moving ground
water. When active
remediation is stopped, the
concentration of electron
acceptor returns to ambient
conditions in the aquifer, and
the hydraulic gradient
returns to the normal
condition. As a result, the
residence time of water in the
spill area is longer than
during active remediation;
and, the total amount of
hydrocarbon transferred to
the water is greater, although
the supply of electron
acceptor for biological
destruction of the hydro-
carbon is less. Darcy's law
can be used to estimate the
interstitial flow velocity of
the ground water and its
residence time along the
flow path. Under proper
(See Bioremediation, Page 4)
Ground Water Currents
-------
conditions, natural bio-
degradation supported by
ambient concentrations
of electron acceptors and
mineral nutrients may
destroy organic contaminants
as fast as they escape from
the oily-phase residual.
However, currently no
established procedures exist
for determining under
ambient conditions whether
the mass transfer of hydro-
carbons from oily residual
material will exceed the
supply of oxygen or other
natural electron acceptors.
At the present state of
science, only long-term
monitoring can determine if
natural biodegradation will
prevent the regeneration of a
plume of contaminated
ground water.
An assessment of natural
hydrologic conditions at
a site will be necessary to
intelligently locate com-
pliance monitoring wells and
determine an appropriate
schedule of monitoring. An
understanding is required
of the average natural
hydraulic gradient and the
hydraulic conductivity in the
depth interval containing
residual hydrocarbon in
order to predict the velocity
and trajectory of potential
plumes of contaminated
water. Frequency of moni-
toring can be adjusted to
reflect the expected time
required for ground water to
travel through the area
containing residual hydro-
carbon to the point of
compliance.
The summary of research
findings discussed above
draws heavily from, and is
covered in more detail with
research references, in a
National Research Council
report; the citation is:
IN SITU BIOREM-
EDIATION; WHEN DOES
IT WORK?, National
Academy Press, Washington,
D.C. 1993. This work was
supported by the United
States Air Force through
Interagency Agreement
RW 57935 114 between the
Armstrong Laboratory
Environics Directorate (U.S.
Air Force) and the U.S.
Environmental Protection
Agency's (EPA) Robert S.
Kerr Environmental Research
Laboratory (RSKERL) and
EPA's Bioremediation Field
Initiative. It has not been
subjected to EPA review and
therefore does not necessarily
reflect the views of the EPA,
and no official endorsement
should be inferred.
For more information, see
the report referenced above
and/or call John Wilson at
RSKERL at 405-436-8632.
To order additional copies of Ground Water Currents, or to be included on the permanent mailing list, send a fax request to the
National Center for Environmental Publications and information (NCEPI) at 513-489-8695.
or send a mail request to NCEPI, P.O. Box 424 19
Cincinnati, OH 45242-2419. Please refer to the document number on the cover of the issue if available.
Ground Water Currents welcomes readers' comments and contributions. Address correspondence to:
Managing Editor, Ground Water Currents (5102W), U.S. Environmental Protection Agency,
401 M Street S.W., Washington, DC 20460
&EPA
United States
Environmental Protection Agency
National Center for Environmental Publications and Information
P.O. Box 42419
Cincinnati. OH 45242-2419
Official Business
Penalty for Private Use
$300
EPA-542-N-94-007
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