United States
Environmental Protection
Agency
Solid Waste and
Emergency Response
(OS-1 10W)
EPA/542/N-93/003
March 1993
x°/EPA Ground Water Currents
Developments in innovative ground water treatment
In Situ Degradation of Halogenated Organics by
Permeable Reaction Wall
By Stephanie F. O'Hannesin and Robert W. Gillham, Waterloo Centre for Groundwater
Research, Canada
I he Waterloo Centre for
Groundwater Research in
Ontario, Canada, consistently
is getting good results in the
development of a permeable
reaction wall that degrades
halogenated organic compounds
in situ. The wall consists of a
porous medium containing an
iron-based catalyst that de-
grades the contaminants as they
pass through the wall. This
passive method of remediation
thus prevents further down-
stream migration of contamin-
ation and degrades contamin-
ants many times faster than the
natural rate of degradation.
Because the degradation occurs
in situ, the contaminants are
not transferred from the water
to a different medium, which is
the case with many pump-and-
treat methods. The cost of the
permeable wall system ought to
be much lower than conven-
tional pump-and-treat systems.
Once the catalyst is installed, it
simply remains in place, un-
attended, continuing to purify
water year after year, with mini-
mal disturbance to the surface
environment. The only cost is
for some continued monitoring.
First, studies at the Univer-
sity of Waterloo laboratories
showed that iron degradation
rates were three to six orders of
magnitude greater than those
reported in the literature for
abiotic and biotic degradation.
Next, their bench scale lab-
oratory batch experiments and
treatability column experi-
ments, conducted with sand
aquifer material, confirmed
degradation of carbon tetra-
chloride, chloroform (TCM),
trichloroethene (TCE) and
tetrachloroethene (PCE).
A pilot test at the Cana-
dian Bases Borden site further
confirmed the effectiveness
of the permeable wall. The
source of the plume was lo-
cated about 4 meters below
ground surface and 1 meter
below the water table. The
plume was about 2 meters
wide and 1 meter thick, with
maximum concentrations
along the axis of about
250,000 and 43,000 micro-
grams per liter (iig/L) for TCE
and PCE, respectively. The
permeable wall was installed
about 5 meters downgradient
from the source.
Using sealable-joint sheet
piling, a rectangular cell was
constructed on the surface
and driven to a depth of 9.7
meters. The cell was dewa-
tered; and, the native sand was
replaced by the reactive ma-
terial, consisting of 22% by
weight iron grindings and
78% by weight concrete sand.
The concrete sand, which is
coarser than the native
materials, was used to insure
that the wall would be more
permeable than the surround-
ing sand. After the reactive
mixture was installed, the
sheet piling was removed,
allowing the contaminant
plume to pass through the
wall. The permeable wall di-
mensions were 5.5 meters
long, 1.6 meters thick; and, it
was situated 2.2 meters deep,
which is 1.0 meter below the
water table. Rows of multi-
level monitoring wells were
located 0.5 meters upgradient
of the wall, at distances of 0.5
and 1.0 meters into the wall
and 0.5 meters downgradient
of the wall, for a total of 348
sampling points. The plume
and its migration through the
wall were monitored for over
500 days. Preliminary results
indicate that the TCE con-
centration has been reduced
by 95% and PCE by 91%.
Mass balance studies confirm
an increase in chloride con-
centration downstream of the
wall that is consistent with
the quantity of TCE and PCE
that has been degraded. Field
testing has also been carried
out to determine the presence
of breakdown products. To
date, only trace amounts of
dichlorethene (DCE) have
been detected; but, no vinyl
chloride has been detected.
Further research is currently
in progress to assess remaining
(SEE PERMEABLE WALL, PAGE 2)
This Month in Currents
This month's Currents features news and events
from our friends North of the Border.
In Situ Permeable Reaction Wall
Canadian Grants Aid BTEX Research
Chemical Oxidation
In Situ Bioremediation Evaluated
^X7 Recycled/Recyclable
< £_ \\ Printed with Soy/Canola Ink on paper that
X_]Cy contains at least 50% recycled fiber
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POINTS OF INTEREST
Canada's GASReP Promotes Innovative Petroleum
Hydrocarbon Research
I he Canadian government's
Groundwater and Soil Remed-
iation Program (GASReP)
promotes research on innova-
tive ways to clean up ground
water and soil contaminated
with petroleum hydrocarbons.
Several Canadian provincial
and federal agencies, Canadian
and U.S. petroleum industry
associations and the U.S. Fed-
eral government take part in
the program. The group,
established as a government/
industry venture in 1989, fo-
cuses on basic/applied research
and/or technology develop-
ment. Industry partners and
those in other government
programs are encouraged to
carry GASReP's research find-
ings into the final stage of
technology demonstration.
Additionally, GASReP tech-
nology transfer sessions help to
enhance knowledge in the field
of remediation technologies.
These sessions are comprised
of an annual GASReP sympo-
sium, workshops of GASReP
members and other conferenc-
es or symposia that GASReP
cosponsors.
GASReP has an annual
research grants program.
GASReP allocates seed money
of up to $50,000 per project
per year to co-sponsor research
with other partners. Under
Canadian government
guidelines for intellectual
property, the government will
retain patent rights. However,
to ensure that R&D results
move into the private sector,
contractors will have the first
rights to license the technology.
GASReP solicits proposals
through a two-step process.
First, a call for Letters of
Interest (short proposal) is
issued. The GASReP Tech-
nical Committee reviews and
ranks the Letters and notifies
eligible candidates. The can-
didates then submit detailed
proposals. To help the candi-
dates prepare their proposals, a
document entitled Guidelines
for Proposals is available from
GASReP. GASReP evaluates
the proposals; and, its Techni-
cal Committee makes the
final decisions. Finally,
GASReP sets up contracts for
work after co-sponsors sign
agreements for their share of
the costs. The research
described in the article,
"Canada Evaluates In Situ
Bioremediation of BTEX in
Ground Water" on page 3 of
this issue of Ground Water
Currents, was partially funded
by GASReP. For further
information on the grants
program, call Alex Lye at
GASReP (416-336-6438).
GASReP will co-sponsor
a symposium in Quebec City,
September 8-10, 1993, where
GASReP members summarize
their research on ground water
and soil remediation. Papers
will be presented on topics such
as bioremediation, excavation
and treatment, pumping and
treatment, off-gas treatment
and program initiatives.
Vendors are invited to exhibit
technical posters. Workshops
on topics suggested by atten-
dees will be held after hours.
Other co-sponsors include
DESRT (the Canadian
government' s Development
and Demonstration of Site
Remediation Technology),
the Biotechnology Research
Institute (part of the National
Research Council of Canada),
the Quebec Ministry of the
Environment and the St.
Lawrence Centre. The North
Atlantic Treaty Organiza-
tion's Committee on Chal-
lenges of Modem Society will
provide papers and posters on
some of their remediation
pilot projects. To obtain
information about this year's
meeting, call 416-336-6438.
To obtain a copy of the
Proceedings from last year's
symposium ("Proceedings of
the Second Annual GASReP/
DESRT Symposium on
Groundwater and Soil Remed-
iation," March 25-26, 1992,
Vancouver, British Colum-
bia), contact INFO-TECH,
Suite 200, 1015 Centre Street
North, Calgary, Alberta,
Canada T2E 2P8 (telephone:
403-276-7881); the cost for
the Proceedings is $65.00
which includes shipping.
GASReP maintains a
mailing list of technology
vendors, consultants and
other interested parties. If you
would like to be added to these
lists, please send relevant
information to: GASReP
Manager, Burlington
Environmental Technology
Office, Canada Centre for
Inland Waters, P.O. Box
5050,867 Lakeshore Road,
Burlington, Ontario, Canada,
L7R 4A6. The telephone
number is: 416-336-6438.
The FAX number is: 416-
336-4858.
Permeable
Wall
(from page 1)
questions, such as the long-
term integrity and effective-
ness of the metal in a range of
hydrogeochemical environ-
ments, the reaction mecha-
nism and the formation of
toxic breakdown products
and the most effective means
of pH control.
Depending on the instal-
lation method utilized, the
permeable wall can be placed
to depths of 100 feet or more.
Application of this technol-
ogy for above ground treat-
ment is also being developed.
The Waterloo Centre has
patents pending on the
technology and is linking up
with firms to market it in both
Canada and the United
States. For more informa-
tion, call Stephanie
O'Hannesin (519-885-1211
ex3159) at the Waterloo Cen-
tre for Groundwater Research,
University of Waterloo, Wa-
terloo, Ontario.
Ground Water Currents
-------
DEMO RESULTS
Chemical Oxidation Destroys Organics in Water
By Norma Lewis, Risk Reduction Engineering Laboratory
I he perox-pure™ chemical
oxidation treatment technol-
ogy, developed by Peroxida-
tion Systems, Inc., to destroy
dissolved organic contaminants
in water, has been demonstra-
ted through EPA's Superfund
Innovative Technology
Evaluation (SITE) program.
The technology uses ultra-
violet (UV) radiation and
hydrogen peroxide to oxidize
organic compounds present in
water at parts per million (ppm)
levels. The technology does
not produce air emissions or
generate residue, sludge or spent
media that would require
further processing, handling or
disposal. Ideally, end products
are water, carbon dioxide, hal-
ides and, in some cases, organic
acids. Medium pressure mer-
cury vapor lamps generate the
UV radiation. The principal
oxidants in the system, hy
droxyl radicals, are produced by
direct photolysis of hydrogen
peroxide at UV wavelengths.
The perox-pure™ system
consists of portable, skid-
mounted components: a
chemical oxidation unit, a
hydrogen peroxide feed tank,
an acid feed tank, a base feed
tank, a UV lamp drive and a
control panel. The oxidation
unit has a total volume of 15
gallons and contains six reac-
tors in series with one 5-kilo-
watt UV lamp in each reactor.
The UV lamp is mounted
inside a UV-transmissive
quartz tube in the center of
each reactor so that water
flows through the space be-
tween the reactor walls and
the quartz tube.
About 40,000 gallons of
ground water contaminated
with volatile organic compounds
(VOCs) were treated during
the demonstration conducted
at Lawrence Livermore
National Laboratory Site 300
near Tracy, California. The
principal ground water con-
taminants were trichloro-
ethene (TCE) and tetra-
chloroethene (PCE), which
were present at concentra-
tions of about 1,000 and 100
micrograms per liter (|ig/L),
respectively. The ground
water was spiked with 300 \\%IL
each of chloroform, 1,1-di-
chloroethane (DCA) and
1,1,1-trichloroethane (TCA).
Hydrogen peroxide was added
to the contaminated water
before it entered the first
reactor; however, a splitter
could be used to add hydrogen
peroxide before any of the six
reactors within the oxidation
unit. In some applications,
acid was added to lower the
influent pH and shift the
carbonate-bicarbonate
equilibrium to carbonic acid.
This equilibrium is important
because carbonate and
bicarbonate ions will
scavenge hydroxyl radicals.
After chemical injections, the
contaminated water flowed
through a static mixer and
entered the oxidation unit.
Water then flowed through
the six UV reactors, which
were separated by baffles to
direct water flow. Treated
water exited the oxidation
unit through a pipe equipped
with a temperature gauge, an
effluent sample port and a
base injection point. Basic
compounds may be added to the
treated water to adjust the pH
to meet discharge requirements.
Circular wipers attached to
the quartz tubes housing the
UV lamps were used periodical-
ly to remove any solids that ac-
cumulated on the tubes. Solids
may accumulate as a result of
metals oxidized by the treat-
ment system (such as iron and
manganese), water hardness
or suspended solids that may
precipitate out of the water.
Accumulated solids could
eventually coat the tubes, thus
reducing treatment efficiency.
During the demonstration,
removal efficiencies for TCE
(SEE CHEMICAL OXIDATION, PAGE 4)
NEW FOR THE BOOKSHELF
Canada Evaluates In Situ Bioremediation
in Ground Water
I he Waterloo Centre for
Groundwater Research at the
University of Waterloo in
Canada has evaluated six ap-
proaches to in situ bioremedi-
ation of benzene, toluene, eth-
ylbenzene and xylene (BTEX)
in ground water. They are:
passive bioremediation, oxygen
addition, acclimated microor-
ganisms, the vacuum-vaporizer-
well, land surface application
and subsurface volatilization
and ventilation (SVVS™).
The evaluations consisted of a
review of the literature and
constitute an important first
research step in our under-
standing of these technolo-
gies, pending further research
in laboratories and in real life
circumstances that deal with
a host of varying site condi-
tions. The Waterloo Centre's
evaluation findings are pre-
sented in a report, Reviews of
Six Technologies for In Situ
Bioremediation of Dissolved
BTEX in Groundwater.
The report highlights
principles and limitations of
each approach and identifies
the site information that
should be gathered. Case
studies illustrate how some of
the techniques are applied
and emphasize the need for
thorough demonstrations. A
summary of the report's find-
ings follows.
Passive Remediation. The
study found that passive
remediation (remediation that
relies on natural processes)
takes longer than active ap-
proaches. Baseline data on
passive bioremediation will
provide a benchmark for mea-
suring the effectiveness of ac-
tive approaches.
Oxygen Addition. Oxygen
addition enhances biotrans-
formation of BTEX. A system
that can deliver oxygen where
it is needed in the subsurface
influences the outcome. While
natural dispersive processes
promote transformation by
(SEE EVALUATIONS, PAGE 4)
Ground Water Currants
-------
Evaluations
(from page 3)
mixing oxygenated and con-
taminated water, some
geochemical reactions may
compete for the oxygen and
hinder cleanup.
Acclimated Microorganisms.
Where a population of indige-
nous microorganisms cannot
perform desired biotransfor-
mations, adding acclimated
species provides a desirable
option. This method can be
ineffective if the introduced
microorganisms die or are not
delivered to the contaminat-
ed area.
Vacuum-Vaporizer-Well.
The vacuum-vaporizer-well
technique incorporates air
stripping and in situ
biorestoration below the
surface. If physical conditions
at a site restrict ground water
flow near this treatment well,
or oxygenation of the water
causes adverse chemical
interactions, remediation will
be limited.
Land Surface Application.
Land surface application in-
volves pumping contaminated
ground water to the surface,
then trickling it through rela-
tively well-drained soils. This
technique can economically
treat large amounts of ground
water contaminated with low
levels of BTEX. Despite its
benefit, the system arouses po-
litical and environmental sen-
sitivities because it introduces
contaminated water into clean
soil and may release volatiles to
the atmosphere.
SWS.™ By combining air
sparging to strip volatile con-
taminants from ground water,
and vacuum extraction to re-
move contaminant vapors,
the SWS removes dissolved
BTEX from ground water.
While this approach works
well for relatively shallow
water table aquifers, treat-
ment is restricted to water in
a small area near the well.
A copy of the Waterloo
report can be obtained by con-
tacting the GASReP Manager
at 416-336-6438
[Editor's Note: This article is
based primarily on excerpts from
GASReP PRESSC, a newsletter
on Environment Canada's
Groundwater and Soil Remedi-
ation program.]
Chemical
Oxidation
(from page 3)
and PCE were greater than
99.7% and 97.1%, respectively.
Removal efficiencies for chloro-
form, DCA and TCA were
93.1%, 98.3% and 81.8%,
respectively. The treatment
system effluent met California
drinking water action levels
and Federal drinking water
maximum contaminant levels
for TCE, PCE, chloroform,
DCA and TCA at tin- 95%
confidence leve'i The mur-
ed effluent, h'.iwe'.v , au: nui
pass bioassay tests for acute tox-
icity to freshwater organisms-
The perox-pure™ tech-
nology has been used to treat
landfill leachate, ground
water and industrial waste-
water containing a variety of
organic VOCs, including
chlorinated solvents, pesti-
cides, polynuclear aromatic
hydrocarbons and petroleum
hydrocarbons. When con-
taminant concentrations are
too high for the system to
handle alone (about 500 milli-
grams per liter), the system can
be combined with other
treatment technologies.
For more information,
call Norma Lewis of EPA's
Risk Reduction Engineering
Laboratory at 513-569-7665.
The Applications Analysis Re-
port and the Technology Eval-
uation Report will be available
in the Fall of 1993.
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 513-891-6685, or send a mail request to NCEPI, 11029
Kenwood Road, Building 5, Cincinnati, OH 45242. 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 (OS-110W), U.S. Environmental Protection Agency,
401 M Street S.W., Washington. DC 20460.
United States
Environmental Protection Agency
National Center for Environmental Publications and Information
Cincinnati, OH 45242
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