United States
Envfranmsntal Protection
Agency
Sold Waste and
Emergency Response
(S102W)
EPA-542-N-96-001
January 1996
tesue No. 14
vvEPA Qiouixl Water Currents
Developments in innovative ground water treatment
AIR LIFT/AIR STRIPPING COMBINE
TO CLEAN AQUIFERS
By Michelle Simon, EPA National Risk Management Research Laboratory
Tie Weston/IEG UVB tech-
nology is an in situ ground war
ter remediation technology that
combines air-lift pumping and
air stripping to clean aquifers
contaminated with volatile or-
ganic compounds. The UVB
technology, in aSuperrund
Innovative Technology Eval-
uation (SHE) program de-
monstration, has removed
trichloroethene (TCE) and 1,1
-dichloroediene (DCE) from
ground water at Site 31, March
Air Force Base, California.
A UVB system consists of a
single well and two hydrauii-
cally separated screened intervals
installed within a single perme-
able zone. The air-lift pumping
occurs in response to negative
pressure introduced at the well-
head by a blower. This blower
creates a vacuum that draws wa-
ter into a well through the lower
screened portion of the welt
Simultaneously, air stripping
occurs as ambient air (also flaw-
ing in response to the vacuum)
is introduced through a diffuser
plate located within the upper
screened section of the well,
causing air bubbles to form in
the water pulled into the well.
The rising air bubbles provide
the air-lift pump effect that
moves water towards the top of
the well and draws water into
the lower screened section of
the well. This pumping effect is
supplemented by a submersible
pump that ensures that water
flows from bottom to top in the
well at a rate of approximately
20 gallons a minute. As the air
bubbles rise through the water
column, volatile compounds
are transferred from the aque-
ous to the gas phase. The rising
air transports volatile com-
pounds to the top of the well
casing where they are removed
by die vacuum blower. The
lower effluent is treated before
discharge using granular acti-
vated carbon.
The transfer of volatile com-
pounds is further enhanced by a
stripping reactor located imme-
diately above the air difiuser.
The stripping reactor consists of
a fluted and channelized col-
umn that facilitates the transfer
of volatile compounds to the
gas phase by increasing the con-
tact time between the two
phases and by minimizing the
coalescence of air bubbles.
Once the upward stream of
water leaves the stripping reac-
tor, the water falls back through
the well casing and returns to
die aquifer through the upper
well screen. This return flow to
the aquifer, coupled with inflow
at the well bottom, circulates
ground water around the UVB
well. The extent of the circula-
tion pattern is known as the ra-
dius of influence, which deter-
mines the volume of water af-
fected by the UVB system.
The UVB technology dem-
onstration evaluated not only
the reduction ofTCE and
DCE concentrations in the
ground water discharged from
the treatment system, but also,
over the course of the study, the
radius of influence of the system
and the reduction (both verti-
cally and horizontally) of TCE
and DCE concentrations in the
ground water within the radius
ofinfluence. Demonstration
results indicate that TCE con-
centrations were reduced by
greater than 94% in ground wa-
ter discharged from the system.
TCE concentrations were re-
duced from a mean of approxi-
mately 54 micrograms per liter
(|Jg/L) in the system's influent
to approximately 3 Hg/L in the
system's effluent. A meaningful
estimate of the system's ability
to remove DCE could not be
made due to the low (less than
4 JJg/L) influent concentration
of DCE. Based on the results of
the dye tracer study, the radius
ofinfluence was estimated to be
at least 40 ft.
The developer claims that the
technology can also clean up
aquifers contaminated widi
other organic compounds, in-
cluding volatile and semivolatile
hydrocarbons. Additionally,
the developer claims that in
some cases the UVB technology
is capable of simultaneous re-
covery of soil gas from the va-
dosezone.
Far more information, coil
Michelle Simon at EPA's Na-
tional Risk Management Re-
search Laboratory at 513-569-
7469. To get on the mailing list
for the Capsule Report and the
Innovative Technology Evalua-
tion Peport of the demonstration,
send a FAX to l>lichelle Simon at
515-569-7676.
CURRENTS ON-LINE
CROUM3 WATER
CURRENTS BOW wi
be available only by
See
il»e. Access" heading £or
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tshetft en-iine and; other
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SITE Subjects
ELECTRON BEAM TECHNOLOGY FOR VOCS
By Franklin Alvarez, EPA National Risk Management Research Laboratory
EPA's Superfund Innova-
tive Technology Evaluation
(SITE) program demon-
strated the High Voltage
Environmental Applica-
tions, Inc. (HVEA),
electron beam (E-beam)
technology. The E-beam
was developed to destroy
semivolatile and volatile or-
ganic compounds (VOCs)
in liquid wastes, including
ground water, wastewater
and landfill leachate. The
objective of the demonstra-
tion, conducted at the U.S.
Department of Energy
Savannah River Site in
Aiken, South Carolina, was
to determine the effective-
ness of the E-beam for
treating ground water con-
taminated with VOCs.
The E-beam system
treated about 70,000 gal-
lons of ground water. The
principal contaminants
were trichloroethene (TCE)
and tetrachloroethene
(PCE), which were present
at concentrations of about
27,000 and 11,000 micro-
grams per liter (Hg/L), re-
spectively. The ground wa-
ter also contained low lev-
els (40 ug/L) of cis-1,2-
dichlorocthene (1,2-DCE).
Removal efficiencies were
greater than 99% for TCE
and PCE and 91% for 1,2-
DCE.
During a portion of the
demonstration, the ground-
water was spiked with 1,2
dichloroethane (1,2-DCA);
1,1 ,l-trichloroethane
(1,1,1-TCA); chloroform;
carbon tetrachloride
(CC14); and aromatic
VOCs, including the
BTEX compounds ben-
zene, toluene, ethylbenzene
and xylenes. The influent
concentrations of these
spiking compounds ranged
from 100 to 500 Ug/L.
These compounds were
chosen either because they
are relatively difficult to re-
move using technologies
that employ free radical
chemistry such as the E-
beam does (i.e., 1,2-DCA,
1,1,1-TCA, chloroform
and CC14) or because they
are common ground water
contaminants (i.e., BTEX).
Removal efficiencies
ranged from 68 to >98%
for the chlorinated com-
pounds and from >96 to
>98% for BTEX com-
pounds.
The treatment system
effluent met Safe Drinking
Water Act (SDWA) maxi-
mum contaminant levels
(MCL) for 1,2-DCE, CO,
and BETEX at a signifi-
cance level of 0.05. How-
ever, the treatment system
effluent did not meet this
test for the other com-
pounds. In addition, the
effluent LC50 values (the
percentage effluent in the
test water at which at least
50% of the test organisms
died) ranged from less than
6.2 to 8% for water fleas
and from 8.6 to 54% for
flathead minnows.
Here's how the E-beam
works. It irradiates water
with a beam of high-energy
electrons, causing the for-
mation of three primary
transient reactive species:
aqueous electrons, hydroxyl
radicals and hydrogen radi-
cals. Target organic com-
pounds are either mineral-
ized or broken down into
low molecular weight com-
pounds, primarily by these
species.
The HVEA E-beam
system (model M25W-
48S) used for the SITE
demonstration is housed in
an 8 ft. by 48 ft. trailer
and is ra.ted for a maximum
flow rate of 50 gallons per
minute (GPM). The sys-
tem has a strainer basket,
an influent pump, the E-
beam unit, a cooling air
processor, a blower and a
control console.
After particulates larger
than 0.045 inch are re-
moved from the influent by
the strainer basket, the in-
fluent pump transfers con-
taminated water to the E-
beam unit. This unit is
made up of an electron
accelerator, a scanner, a
contact chamber and lead
shielding. The electron ac-
celerator is capable of gen-
erating an accelerating volt-
age of 500 kilovolts and a
maximum beam current of
about 42 milliamps, which
results in a maximum
power rating of 21 kilo-
watts. The scanner deflects
the E-beam, causing the
beam to scan the surface of
the water as it flows through
the contact chamber. The E-
beam significantly heats che
titanium window, which is
cooled by air recirculated
through the contact cham-
ber. The air is conditioned
by a cooling air processor.
E-beam dose is a key oper-
ating parameter for rhis tech-
nology. This is a function of
several parameters, including
the density and thickness of
the water stream; E-bearn
power, which is a function of
beam current and accelerat-
ing voltage; and the length of
time that the water is ex-
posed to the E-beam which
depends on the flow rate.
The carbon adsorber was
used to destroy ozone (O,)
formed in the cooling air
when exposed to the E-beam.
Vapor phase VOCs not de-
stroyed by the E-beam are re-
moved by the carbon
adsorber. Since the SITE
demonstration, HVEA has
replaced the carbon adsorber
with an O3 destruction unit.
For more information, call
Franklin Alvarez at EPA's Na-
tional Risk Management Re-
search Laboratory at 513-569-
7631. Key findings will also be
documented in a SITE Tech-
nology Capsule, an Innovative
Technology Evaluation Report
and the Tec- - tlogy Evaluation
Report; to •' n the mailing
list for these 'ports, send a FAX
to Franklin Alvarez at 513-
569-7677 with your name and
address.
Ground Water Currents
Rceyclcd/Racyclabto
Printed with Soy/Canola ink on paper that contains at least 50% recycled fiber
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NEW FOR THE BOOKSHELF
IN SITU REMEDIATION - STATUS REPORTS
E?A has identified six abi-
otic technologies dial are
emerging as possible cleanup
remedies. These technologies
are: thermal enhancements,
surfactant enhancements,
treatment walls, hydraulic
fracturing/pneumatic fractur-
ing, cosolvents and electroki-
netics. For each technology,
EPA has produced a separate
IN SITU REME-
DIATION TECHNOL-
OGY STATUS REPORT.
The purpose of each report is
to identify research projects
and to describe recent field
demonstrations and commer-
cial applications of die tech-
nology. The technologies
contained in the reports ei-
ther treat ground water and
soil in place or increase the
solubility and mobility of
contaminants so that pump-
and-treat remediation of the
contaminant is improved.
These emerging technolo-
gies grew out of a need identi-
fied by researchers and regula-
tors who recognize that the
source of much ground water
contamination is dense non-
aqueous phase liquids and
other compounds that mi-
grate downward into aquifers,
creating pools of subsurface
contamination. Thus, pump-
and-treat systems can only
treat the symptom, not the
cause. Technologies such as
the ones discussed in these re-
ports are emerging to treat the
cause and improve pump- •
and-treat efficiency.
The reports do not cover
trends in the use of
bioremediation. EPA has
other resources summarizing
the progress of bioremediation
technologies. A brief sum-
mary of the technologies and
report contents follows.
Thermal enhancement
technologies include (1) the
injection of hot water or
steam or (2) the use of radio
frequency or electrical resis-
tance heating to increase the
mobility, solubility or
volatilty of organic contami-
nants, particularly immiscible
compounds. Physical site
conditions, not chemical re-
actions, are the major con-
trolling factors on the use of
this technology. The thermal
enhancement status report
discusses 16 completed, on-
going or future demonstra-
tions. The 11 completed
demonstrations provide some
cost and performance infor-
mation. Most of the demon-
strations treated volatile or-
ganic compounds (VOCs),
semivolatile organic com-
pounds (SVOCs) and the
BTEX compounds (i.e., ben-
zene, toluene, ethylbenzene
and xylene). However, two
demonstrations were de-
signed to treat polyaromatic
hydrocarbons (PAHs) from
wood treating sites; and, one
treated pesticides.
Surfactants increase the
solubility of the contaminant
in water. They also direcdy
mobilize the contaminant by
reducing interfacial tension
between the contaminant
and die soil matrix The re-
port contains nine research
projects, six ongoing or fu-
ture demonstrations, three
completed demonstrations
and one commercial applica-
tion. The target contami-
nants were VOCs, SVOCs,
BTEX and PCBs. Contin-
ued surfactant research is im-
portant. There are a variety
of surfactants available to be
tested; the effectiveness of
each of these to treat a spe-
cific contaminant in a specific
geochemical environment is
usually unknown until labo-
ratory and bench scale
treatability tests are con-
ducted. Treatment walls are
vertical treatment zones in-
stalled across the flow path of
a contaminant plume to treat
the contaminants as the
plume passes through the
zone. These mechanically
simple barriers may contain
metal-based catalysts for de-
grading volatile organics,
chelators for immobilizing
metals or nutrients and oxygen
to enhance bioremediation.
There are 11 research
projects, nine ongoing or fu-
ture demonstrations, two
completed demonstrations
and one commercial applica-
tion. Four of the 11 ongoing
or completed demonstra-
tions are using or have used
in situ metal-enhanced
dehalogenation; and, the
patent for this technology is
held by the University of
Waterloo. The remaining
demonstrations are testing
the use of O2 nutrients for
bioremediation and chemical
reactants to reduce Crt6The
ten research projects are di-
vided between the treatment
of metals and organics.
Hydraulic fracturing/pneu-
matic fracturing consists of
die injection of pressurized
water or air to increase die
size and number of fractures
in a consolidated material or
relatively impermeable un-
consolidated matetial. The
enlarged fractures provide
more treatment area for an in
situ technology or more path-
ways to remove solubilized or
mobilized contaminants.
There are two ongoing or fu-
ture demonstrations and ten
completed demonstrations
discussed in the report.
Cosolvents are a form of in
situ flushing that involves the
injection of a solvent mixture
(e.g., water plus a miscible or-
ganic solvent such as alcohol)
that enhances die solubility
of organic contaminants.
The use of cosolvencs is in
the very early stage of devel-
opment. One research
project was completed in
1991; and, there are three on-
going or future demonstra-
tions. No vendors were iden-
tified who are marketing the
technology. The three
planned demonstrations will
be conducted by a partner-
ship between a federal labora-
tory, a military base and a
university.
Electrokinetics has as its
basis that positively-charged
organic or inorganic con-
taminants can be made to
migrate in an electric field to
a collection point for removal
by pumping. There are ten
research projects, five ongo-
ing or future demonstrations
(continued on page 4)
Ground Water Currents
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BIOATTENUATION ON VIDEO
Data from the St. Joseph,
Michigan, Superfiind sice ware
used in a. peer-reviewed video
entitled "Natural Bioartenua.-
tion of Trichloroediene at die
St. Joseph, Michigan
Superfund Site". Computer
visualizations of die data set
show how trichlorethene, or
TCE, can degrade under natu-
ral conditions. The purpose of
die tape is to present sampling
results from die site to a tech-
nical audience. Aldioughdie
visualizations show the general
distribution of chemicals at die
site, it is not possible to deter-
mine die precise concentra-
tions from the tape. Thus the
data set irself is available in a
companion document.
Analysis of the data from die
St. Joseph site indicates that
natural bioattenuation of TCE
is occuring as die contami-
nants flow toward Lake Michi-
gan. Depletion of oxygen, die
presence of methane and die
appearance of degradation
products indicate that the re-
duction in TCE concentra-
tions is not solely due to vola-
tilization or dilution. Rather,
dicy are indicative of microbial
processes helping to reduce the
contaminant concentrations
below EPA drinking water
standards before the water is
discharged into Lake Michi-
gan.
The authors of die video,
James W. Weaver, John T.
Wilson and Don H.
Kampbell, are with EPA's Na-
tional Risk Management Re-
search Laboratory Subsurface
Protection and Remediation
Division in Ada, Oklahoma
74820. The video (Document
No. EPA/600/V-95/Q01) will
be available upon request from:
Subsurface Remediation Infor-
mation Center, National Risk
Management Research Labora-
tory, U.S. Environmental Protec-
tion Agency, P.O. Box 1198,
Ada, Oklahoma 74820. The
telephone number is 405-436-
8651; the FAX number is 405-
436-8503. The Project Officer is
James Weaver.
There is also an amplified
text version of the narration on
the video available as a Project
Summary (Document No. EPA/
600/SV-95/001). The Project
Summary can be ordered by call-
ing CERJ at 513-569-7562.
(contin-wed from page 3)
and one completed demon-
stration. There are a relatively
large number of universities
conducting research in
electrokinetics, many being
supported by die U.S. Depart-
ment of Energy.
The full status reports can he
ordered from EPA's National
Center for Environmental Info. -
mation and Publications
(NCEPI). You can order the re-
ports by mail or by FAX. The
FAX. number is 513-489-8695.
The mail address is: NCEPI,
11305 Reed Hartman Highway,
Suite 219, Cincinnati, OH
45241. Please refer to the docu-
ment number when ordering.
The individual report document
numbers are: Thermal Enhance-
ments (EPA542-K-94-009);
Surfactant Enhancements
(EPA542-K-94-003); Treat-
ment Walls (EPA542-K-94-
004); Hydraulic Fracturing/
Pneumatic Fracturing (EPA542-
K-94-005); Cosolvents
(EPA542-K-94-006); and Elec-
trokinetics (EPA542-K-94-007).
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