United States
Environmental Protection
Agency
Hazardous Waste Engineering
Research Laboratory
Cincinnati OH 45268
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Research and Development
EPA/600/S2 85/129 Dec. 1985
&ER& Project Summary
Treatment of Contaminated
Soils with Aqueous Surfactants
William D. Ellis, James R. Payne, and G. Daniel McNabb
The full report presents the results,
conclusions, and recommendations of a
project performed to develop a technical
base for decisions on the use of chemical
countermeasures at releases of hazard-
ous substances. The project included a
brief literature search to determine the
nature and quantities of contaminants
at Superfund sites and the applicability
of existing technology to in situ treat-
ment of contaminated soils. Laboratory
studies were conducted to develop an
improved methodology applicable to
the in situ treatment of organic chemical
contaminated soil.
Current technology for removing
contaminants from large volumes of
soils (too large to excavate economical-
ly) has been limited to in situ "water
washing." Accordingly, the laboratory
studies were designed to determine
whether the efficiency of washing could
be enhanced significantly (compared to
water alone) by adding surfactants to
the recharge water and recycling them
continuously.
The use of an aqueous nonionic
surfactant pair for cleaning soil spiked
with PCBs, petroleum hydrocarbons,
and chlorophenols was developed
through bench scale shaker table tests
and larger scale soil column tests. The
extent of contaminant removal from the
soil was 92 percent for the PCBs, using
0.75 percent each of Adsee® 799
(Witco Chemical) and Hyonic® NP-90
(Diamond Shamrock) in water. For the
petroleum hydrocarbons, the removal
with a 2 percent aqueous solution of
each surfactant was 93 percent. These
removals are orders of magnitude
greater than obtained with just water
washing and represent a significant
improvement over existing in situ
cleanup technology.
Treatability studies of the contami-
nated leachate were also performed to
investigate separating the surfactant
from the contaminated leachate to allow
reuse of the surfactant. A method for
separating the surfactant plus the con-
taminant from the leachate was devel-
oped; however, all attempts at removing
the surfactant alone proved unsuccess-
ful.
Based upon the results of the labora-
tory work, the aqueous surfactant
countermeasure is potentially useful for
in situ cleanup of hydrophobia and
slightly hydrophilic organic contami-
nants in soil, and should be further
developed on a larger scale at a small
contaminated site under carefully con-
trolled conditions. However, reuse of
the surfactant is essential for cost-
effective application of this technology
in the field. Accordingly, any future
work should investigate the use of other
surfactants/surfactant combinations
that may be more amenable to separa-
tion.
This Pnoject Summary was developed
by EPA's Hazardous Waste Engineering
Research Laboratory, Cincinnati, OH,
to announce key findings of the research
project that is fully documented in a
separate report of the same title (see
Project Report ordering information at
back).
Introduction
The Comprehensive Environmental
Response, Compensation, and Liability
Act of 1980 (CERCLA or Superfund)
recognizes the need to develop counter-
measures (mechanical devices, and other
physical, chemical, and biological agents)
to mitigate the effects of hazardous sub-
stances that are released into the envi-
-------
ronment and clean up inactive hazardous
waste disposal sites. One key counter-
measure is the use of chemicals and
other additives that are intentionally
introduced into the environment for con-
trolling the hazardous substance. The
indiscriminate use of such agents could,
however, worsen the contamination
situation.
The U.S. Environmental Protection
Agency's Hazardous Waste Engineering
Research Laboratory has initiated a
Chemical Countermeasures Program to
define technical criteria for the use of
chemicals and other additives at release
situations of hazardous substances such
that the combination of the released
substance plus the chemical or other
additive, including any resulting reaction
products, results in the least overall harm
to human health and to the environment.
Under the Chemical Countermeasures
Program, the efficacy of in situ treatment
of large volumes of subsurface soils, such
as found around uncontrolled hazardous
waste sites, and treatment of large, rela-
tively quiescent waterbodies contami-
nated with spills of water soluble hazard-
ous substances, will be evaluated. For
each situation, the following activities are
planned: a literature search to compile
the body of existing theory and data;
laboratory studies on candidate chemicals
to assess adherence to theory and define
likely candidates for full-scale testing;
full-scale, controlled-condition, reproduc-
ible tests to assess field operation possi-
bilities; and full-scale tests at a site
requiring cleanup (i.e., a "site of oppor-
tunity").
This project, to develop the use of
aqueous surfactants for in situ washing
of contaminated soils, was the first
technique to be developed under the
Chemical Countermeasures Program.
The results and conclusions from an
information search formed the basis for
the laboratory development work. Simi-
larly, the results and conclusions from
the laboratory work are intended to
provide the basis for another project
involving large-scale testing of a chemical
countermeasure, either in a large test
tank or under controlled conditions at a
site of opportunity.
Information Search
The information search was conducted
to determine the nature and quantities of
hazardous soil contaminants at Super-
fund sites, and to assess the applicability
of existing tech nology for in situ treatment
of contaminated soils. To determine what
2
types of soil contaminants requiring
cleanup were likely to be found at hazard-
ous waste sites, a survey was made of the
contaminants at 114 high priority Super-
fund sites. The classes of chemical wastes
found at the greatest number of sites, in
order of decreasing prevalence, were:
slightly water soluble organics (e.g.,
aromatic and halogenated hydrocarbon
solvents, chlorophenols), heavy metal
compounds, and hydrophobic organics
(e.g., PCBs, aliphatic hydrocarbons).
A variety of chemical treatment meth-
ods were considered that might prove
effective in cleaning up soils contami-
nated with these wastes. However,
methods for in situ chemica I treatment of
soils will probably be most effective for
certain cleanup situations, such as those
in which:
• The contamination is spread over a
relatively large volume of subsurface
soil, e.g., 100 to 100,000 m3, at a depth
of 1 to 10 m; or
• The contamination is not highly con-
centrated, e.g., not over 10,000 ppm,
or the highly contaminated portion of
the site has been removed or sealed
off; or
• The contaminants can be dissolved or
suspended in water, degraded to non-
toxic products, or rendered immobile,
using chemicals that can be carried in
water to the zones of contamination.
For contamination less than 1 m deep,
other methods such as landfarming (sur-
face tilling to promote aerobic microbial
degradation of organics) would probably
be more practical. For highly contami-
nated zones of an uncontrolled hazardous
waste landfill or a spill site, methods such
as excavation and removal, or excavation
and onsite treatment would probably be
more practical than in situ cleaning of the
soil.
Findings under the information search
indicated that aqueous surfactant solu-
tions might be applicble for in situ
washing of slightly hydrophilic (water
soluble) and hydrophobic organics from
soils. Texas Research Institute (TRI) used
a combination of equal parts of Witco
Chemical's Richonate®* YLA, an anionic
surfactant, and Diamond Shamrock's
Hyonic® NP-90, a nonionic surfactant, in
several laboratory column and two-
dimensional modeling studies for displac-
ing gasoline from sand packs.
'Mention of trade names or commercial products
does not constitute endorsement or recommendation
for use
To further verify which organic waste
chemicals should be targeted for counter-
measures development. Field Investiga-
tion Team (FIT) summaries were examined
for the maximum concentrations of
organic contaminants in the soil and
groundwater surrounding 50 Superfund
sites. Results of the survey indicated that
many hydrophobics were detected in the
soils, mainly because hydrophilics tend to
be washed from soil by infiltrating rain-
water. Hydrophobics had the highest
levels of all the organic contaminants,
with 11 compounds averaging in the 1 to
100 ppm range, and with chlordane
exceeding 1,000 ppm at one site. The soil
concentrations of slightly hydrophilic
compounds were in the range of 0.001 to
10 ppm.
Based on these findings, the following
two hydrophobic and one slightly hydro-
philic pollutant groups were chosen as
model contaminants for testing and de-
velopment of an aqueous surfactant
countermeasure:
• High boiling point Murban crude oil
fraction containing aliphatic and aro-
matic hydrocarbons (1,000 ppm)
• PCB mixture in chlorobenzenes (Aro-
clor® 1260 transformer oil) (100 ppm)
• Di, tri-, and pentachlorophenols mix-
ture (30 ppm)
Laboratory Studies
The laboratory research was conducted
to determine whether significant improve-
ments to the cleanup of contaminated
soils with just water, the only in situ soil
cleanup method demonstrated to date,
could be obtained using aqueous surfac-
tants. Further laboratory development of
the surfactant countermeasure included
optimizing the concentration of surfactant
used for cleanup, and development of
contaminated leachate treatment meth-
ods.
The aqueous surfactant countermeas-
ure was tested using two basic methods:
shaker table agitation, to quickly deter-
mine the soil/aqueous surfactant parti-
tioning of the model contaminants under
differing conditions; and gravity flow soil
column tests to verify the cleanup be-
havior of the aqueous surfactant under
conditions resembling field use. Besides
the optimum surfactant concentration,
the effects of leachate treatment and
recycling were also studied.
Soil Characterization
In choosing a soil for the surfactant
washing tests, the applicability of the
-------
results to actual field situations was a
primary consideration. Selection included
identifying the native soils at the ten
Region II Superfund sites for which data
was available, determining the most
commonly occurring soil type series, and
locating a soil of the same soil taxonomic
classification which could be excavated
and used in the testing experiment. In
addition to taxonomic classification, a
permeability rating of 10"2to 10'* cm/sec
was desirable since less permeable soils
would take too long to test.
A Freehold soil series typic hapludult
soil was chosen for the study. The total
organic carbon content (TOC) of the soil
was 0.12 percent by weight, implying a
relatively low contribution by organic
matter to the adsorption of organic con-
taminants. The cation exchange capacity
(CEC) of the soil was determined to be 8.6
milliequivalentsper 100 gms, an extreme-
ly low value, indicating an absence of
mineralogic clay in the soil.
Using a percent moisture content of 11
percent and compacting the soil in the
columns to a density of 1.68 g/cm3 (105
Ib/ft3), an optimum percolation rate of 1.5
x 10~3 cm/sec was obtained under a
constant 60 cm head.
Surfactant Selection
The surfactant combination used by
TRI for flushing gasoline from sand,
Richonate® YLA and Hyonic® NP-90
(formerly called Hyonic® PE-90), was
screened along with several other surfac-
tants and surfactant combinations for the
following critical characteristics: ade-
quate water solubility (deionized water),
low clay particle dispersion, good oil
dispersion, and adequate biodegradabil-
ity. The surfactants selected for ultimate
use in the laboratory studies were Adsee®
799 (Witco Chemical) and Hyonic® NP-9O
(Diamond Shamrock).
Soil Contamination Procedures
Soil was contaminated using an aerosol
spray of the contaminant mixture dis-
solved in methylene chloride. The meth-
ylene chloride was allowed to evaporate,
and the soil was mixed by stirring in pans.
The soil was then tested in shaker or
column studies.
Column Packing
The soil columns used in this study
were 7.6 cm (3 in.) inside diameter by 150
cm (5 ft) long glass columns. A plug of
glass wool was placed at the bottom of
the column and successive plugs of
contaminated soil weighing approximate-
ly 775 g were packed to a height of 10 cm
(4 in.) each. To ensure better cohesion
between layers, the upper 1/4 inch of
each plug was scarified. The soil was
packed to a total height of 90 cm (3 ft) and
compacted to a density of 1.68 to 1.76
g/cm3 (105 to 110 Ib/ft3), yielding a
percolation rate which was comparable
to its natural permeability.
Shaker Table Tests
Shaker table partitioning experiments
were conducted to determine the mini-
mum surfactant concentration required
to accomplish acceptable soil cleanup.
After spiking Freehold soil with PCBs and
hydrocarbons, separately, surfactants
were used to wash the soil by shaking in
containers on a constantly vibrating
shaker table.
One hundred grams of contaminated
soil were agitated with 200 ml of the
appropriate surfactant concentration on a
shaker table for one hour, then centri-
f uged, and decanted. Both soil and leach-
ate were analyzed to determine how
much of the contaminant had been
removed.
So/7 Column Experiments
During the first year of study, the effect
of soil washing with water, followed by
4.0 percent surfactants (2 percent each),
and a final water rinse was investigated
in soil column experiments using Murban
distillate cut, PCBs and di-, tri-, and
pentachlorophenol contaminants. Free-
hold soil was spiked, separately, with
1,000 ppm Murban distillate cut, 100
ppm PCB, and 30 ppm chlorinated
phenols.
Results of these column experiments
showed that the initial water wash had
little effect; however, with surfactant
washing, 74.5 percent of the pollutant
was removed by the leachate after the
third pore volume (i.e., volume of void
space in the soil). Additional surfactant
increased the removal to 85.9 percent
after ten pore volumes. The pollutant
concentration in the soil was reduced to 6
percent of the initial spike value after the
tenth pore volume of surfactant. The final
water rinse also showed only minimal
effects.
Almost identical behavior was observed
for the column experiments using PCB
spiked soil: the initial water wash was
ineffective, but the soil was cleaned
substantially by the4.0 percent surfactant
solution. After the tenth pore volume, 68
percent of the PCBs were contained in the
leachate, leaving only 2 percent on the
soil.
Similar soil column experiments were
also conducted using a mixture of di-, tri-,
and pentachlorophenols, and, in contrast
to the PCB and Murban distillate cut
results, 64.5 percent of the chlorinated
phenols were removed by the first water
wash, and only 0.56 percent remained on
the soil after the tenth pore volume of
water.
Optimization of Surfactant
Concentration
To make soil washing techniques cost
effective, it was necessary to determine
the minimum concentration of surfactant
that would yield acceptable soil cleanup.
Surfactant concentrations were varied
from 0 to 1.0 percent (2 percent total
surfactant) in shaker table experiments
using both PCB and hydrocarbon con-
taminated soils. Column experiments
were then undertaken to verify shaker
table data and to further optimize surfac-
tant concentrations.
Figure 1 shows the effect of surfactant
concentration on PCB partitioning be-
tween soil and leachate. There was
essentially no cleanup of the soil with
surfactant concentrations of 0.25 percent
(0.50 percent total) or below. Similar PCB
partitioning was observed for 0.75 per-
cent and 1.0 percent individual surfactant
concentrations, and the most effective
cleanup occurred at these levels.
As Figure 2 shows, similar soil/leach-
ate partitioning behavior was also ob-
served for Murban hydrocarbons with
varying surfactant concentrations. Indi-
vidual surfactant concentrations of 0.25
percent and below were ineffective; in-
creased surfactant concentrations caused
increased soil cleanup from 0.50 to 0.75
percent surfactant; above 0.75 percent
surfactant concentration little enhance-
ment of soil cleanup occurred.
Column Verification
To ensure that the optimum surfactant
concentration under gravity flow condi-
tions was not significantly different than
under equilibrated shaker table condi-
tions, columns packed with Freehold soil
spiked with 100 ppm PCBs were also
tested with varying surfactant levels.
The columns were treated with one,
two, or three pore volumes of 0.50,0.75,
or 1.0 percent surfactant before sacrifice
and soil analysis. The downward migra-
tion of PCBs is apparent in Figure 3,
which presents the PCB concentrations
in the various portions of the columns as
a function of pore volume for each of the
three surfactant concentrations tested.
PCB mobilization was not much greater
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concentration. After three pore volumes,
the PCB concentrations at the bottom of
the column were of 244 fjg/g with the
0.50 percent surfactant, compared with
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and 562 //g/g using the 1.0 percent
surfactant.
Results of the column experiments,
coupled with the results of the shaker
table experiments, indicate that the opti-
mum surfactant concentration for soil
cleanup is about 0.75 percent of each
surfactant or 1.5 percent total surfactant.
Evaluation of Leachate
Treatment Techniques
Large amounts of surfactants and wash
water are required for field application of
this countermeasure technology. Surfac-
tants are expensive, and for this tech-
nology to be cost effective, surfactant
recycling is an important consideration.
Accordingly, various leachate treatment
techniques were evaluated for their ability
to remove and concentrate the contami-
nants, while leaving the surfactants
behind for further use. All treatment
methods evaluated were ineffective in
separating the contaminants from the
surfactant. However, several leachate
treatment techniques were able to (1)
concentrate the contaminants to facilitate
disposal, and (2) clean the water enough
that it could be sent to a publicly owned
treatment works (POTW) or reused.
Four treatment alternatives were
tested, and the conditions for efficient
leachate treatment were optimized in
preparation for large-scale field testing.
Foam fractionation, sorbent adsorption,
ultrafiltration, and surfactant hydrolysis
were subjected to preliminary laboratory
tests using simulated leachate.
The results of the foam fractionation
tests showed that good cleanup of the
leachate was achieved if the concentra-
tion of surfactant was below about 0.1
percent, while no significant reduction in
surfactant occurred at starting concen-
trations above that.
Eleven solid sorbents were tested for
their efficiency in removing PCBs and the
surfactants from an aqueous solution.
None of the sorbents was very efficient in
removing PCBs from a surfactant solution.
The most efficient sorbent for PCB re-
moval was the Filtrol XJ-8401, with an
efficiency of 0.00045 g/g; WV-G 12x40
Activated Carbon, and Celkate magne-
sium silicate were most efficient in overall
surfactant and PCB removal (0.195 g/g).
-------
Hydrolysis treatment of the surfactant
and contaminant-containing leachate
was also tested. Adsee® 799, a fatty acid
ester, formed a separate organic phase
upon hydrolysis that contained both the
surfactants and 95 percent of the organic
contaminants.
Further treatment of the aqueous sur-
factant solution with a column of activated
carbon (Westvaco Nuchar WV-B 14x35)
yielded a solution containing only 0.01
ppm of PCBs. Foam fractionation was
also used as a polishing method for
removing traces of surfactants from
aqueous solutions. A four-column series
of foam fractionation columns operating
in a continuous countercurrent flow mode
was used. The test results demonstrated
that the residual PCB level (0.0036 ppm)
should be low enough to allow disposal to
a POTW, and low enough to permit reuse
of the leachate water for soil cleaning.
However, the use of hydrolysis was
necessary for the higher surfactant con-
centrations found in the raw leachate.
Evaluation of Leachate
Recycling
To evaluate the effect of recycling the
untreated aqueous leachate on soil
cleanup, column experiments were con-
ducted. The results showed that leachate
recycling—without some sort of treat-
ment—is not an acceptable method, as
contaminants become redistributed back
onto the soil with each successive pass.
However, a column experiment in which
the recycled leachate was treated be-
tween each pass showed very effective
cleanup of soil.
Between passes, fresh surfactant was
added to the treated leachate prior to
recycling, and the soil in the column
received four passes of fresh surfactant;
only the water was recycled. After four
passes, less than 1.0 percent of the
original soil contamination remained.
Conclusions and
R ecommendations
Effectiveness of the Surfactants
Based on bench-scale tests designed to
screen potential surfactants for use as in
situ soil washing enhancers, a 1:1 blend
of Adsee® 799 (Witco Chemical Corp.)
and Hyonic® NP-90 (Diamond Shamrock)
was chosen because of adequate solubil-
ity in water, minimal mobilization of clay-
sized soil fines (to maintain soil perme-
ability), good oil dispersion, and adequate
biodegradability.
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Shaker table and column experiments
show that 4.0 percent of this blend of
surfactants in water removed 93 percent
of the hydrocarbon and 98 percent of the
PCB pollutants from contaminated soil.
These removals are orders of magnitude
greater than those obtained with just
water washing and represent a significant
improvement to the efficiency of existing
technology. Chlorinated phenols were
readily removed from the test soil by
water washing alone.
Shaker table experiments conducted to
determine the optimum surfactant con-
centration for soil cleanup, with PCB and
petroleum hydrocarbon (Murban) con-
taminated soils, showed the optimum
concentration to be 1.5 percent total
surfactant. Individual surfactant concen-
trations of 0.25 percent or less were
unacceptable for effective soil washing,
and individual surfactant concentrations
above 0.75 percent (1.5 percent total)
were excessive, since no significant
enhancement of cleanup resulted. In
addition, similar partitioning between soil
and surfactant solution by the two pollu-
tant types suggests that the resu Its wh ich
would be obtained in further large-scale
experiments with the lowtoxicity hydro-
carbons in a fuel oil like Murban might
reliably model the behavior of other more
toxic hydrophobic pollutant groups, such
as PCBs.
The experiment which evaluated the
effect of leachate recycling, with treat-
ment applied to the PCB leachate between
cycles, showed that:
• Soil cleanup with 1.5 percent total
surfactant is good, with less than 1
percent of the PCB remaining on the
soil.
• The product of hydrolysis represents a
relatively small volume (about 12
percent of the total mass of leachate)
of highly contaminated material, which
can be further treated by incineration,
or disposed of for a minimal cost.
• The use of the sa me water for repeated
cycles precludes the generation of
large volumes of waste leachate.
• The final treated water after four cycles
contains less than 0.0005 percent of
the initial contamination encountered
in the soil.
Additional surfactant tests are war-
ranted before this technology can be
applied in the field. The surfactant com-
bination used was water soluble, and
effective in soil cleanup, and allowed
good soil percolation rates, as the mixture
did not resuspend a significant amount of
the clay-sized particles in the soil, thereby
inhibiting flow. These characteristics are
-------
definitely important; however, for this
technology to be cost effective, reuse of
the surfactant is equally important.
Accordingly, it is recommended that other
surfactants/surfactant combinations be
evaluated that have the same "flushing"
characteristics but are also more amen-
able to separation for reuse. The surfac-
tant should be screened for solubility,
clay dispersion, and oil dispersion, and
should also be screened by mutagenicity
tests to avoid the distinct possibility that
the release situation could be made worse
by the application of a toxic chemical or
other additive.
Effects of the Test Soil
The efficiency of cleanup of the hydro-
phobic organic contaminated Freehold
soil by the aqueous surfactant solution
was directly affected by the low natural
organic carbon content of the soil. The
low TOC (0.12 percent) represented little
organic matter in the soil to adsorb the
organic pollutants spiked onto the soil, so
the contaminant removal could be ex-
pected to be relatively easy compared to a
soil with, for example, a 1 percent TOC.
The removal of hydrophobicorganics from
a 1 percent TOC soil using the Adsee®
799 - Hyonic® NP-90 surfactant pair
would require more surfactant solution.
Also, the surfactants would become
necessary for removing chlorophenols
from a 1 percent TOC soil; water alone
would not be very effective.
If additional laboratory or pilot-scale
testing were undertaken, a second soil
type with greater percentages of organic
carbon should be considered for testing to
expand the overall applicability of the
program results to a broader variety of
soil matrices.
The hydraulic conductivity of the Free-
hold soil packed in the soil columns,
which was measured at 1.05 x 10~3
cm/sec, would be practical for field
implementation of the countermeasure.
However, the time required for surfactant
solution tof low through the soil should be
considered. With this hydraulic conduc-
tivity, if surface flooding were used to
obtain saturated conditions from the
surface to a groundwater depth of 10 m
(33 ft), and assuming a porosity of 50
percent, it would take 5.5 days for one
pore volume of solution to flow through
the soil from surface to groundwater. A
flow rate under similar conditions, with a
soil permeability of 1 x 10~4 cm/sec,
would yield flow rates of about 1.2 m/wk,
which is probably a practical lower limit
for the method.
Potential Target Contaminants
The types of hazardous chemicals for
which the surfactant countermeasure
was more effective than water without
surfactant, included hydrophobicorganics
(PCBs and aliphatic hydrocarbons in the
Murban fraction) and certain slightly
hydrophilic organics (aromatic hydrocar-
bons in Murban). The chemicals for which
the method is probably not applicable are
heavy metal salts and oxides, and cya-
nides. For soils with low TOC values,
chlorophenols and certain other slightly
hydrophilic organics can be removed with
water alone. However, for soils with high
TOC values, the use of aqueous surfac-
tants would significantly improve the
removal efficiency of slightly hydrophilic
organics.
Effective Treatment Methods
A need to conserve both water and
surfactant prompted the investigation of
leachate reuse or recycling. Recycling of
the untreated leachate is unacceptable
because portions of the soil that have
been previously cleaned are recontami-
nated rapidly by the introduction of spent
leachate. The ideal treatment method
removes and concentrates contaminants
while leaving the surfactants behind for
further use. However, the same chemical
and physical properties of the surfactant
mixture that help to extract the pollutants
from the soil also inhibit separation of the
contaminants from the surfactants. Due
to the high (percentage) level of surfactant
contained in the leachate, most of the
treatment methods evaluated were inef-
fective. The best treatment that could be
obtained removed both surfactants and
pollutants, leaving clean water for pos-
sible reuse or easy disposal.
Additional efforts should be directed
toward optimizing feasible and cost-
effective methods of leachate treatment
and in particular separation of the sur-
factant for reuse. Ultrafiltration appears
promising and warrants further investi-
gation along with foam fractionation. The
use of already existing equipment and
technologies should be examined in
greater detail to minimize scale-up costs.
Further Countermeasure
Development Before Field Use
The testing of a new technique, in
which hazardous contaminants are rend-
ered more mobile, presents a potentially
greater environmental threat unless the
tests can be readily stopped at any point
as required to permit the immediate
remedy of any failure by established
techniques. Because the aqueous sur- fl
factant countermeasure is still develop- ^
mental, the field tests should be conducted
on a reduced scale until the procedures
are proven workable and the important
parameters are understood and control-
led.
The laboratory tests have established
that the technique of in situ washing with
aqueous surfactants is sufficiently effec-
tive for soil cleanup to justify tests on a
larger scale. Pilot-scale testing requires
the use of disturbed soil, and will probably
not further the development of the method
as much as controlled-condition .field
testing at a site of opportunity. An appro-
priate site for field testing should have the
following characteristics:
• Moderate to high permeability (coef-
ficient of permeability of 10"4 cm/sec
or better)
• Small size (e.g., 30 m x 30 m x 10 m
deep)
• Minimal immediate threat to drinking
water supplies
• Hydrophobic and/or slightly hydro-
phylic organic contaminants
• Concentrated contamination source
removed or controlled
• Low to moderate natural organic mat-
ter content in soil (TOC 0.5 to 2
percent).
If either small sites, or physically sepa-
rated sections of a large site (e.g., with a
slurry or grout wall) were selected, the
aqueous surfactant countermeasure
described in this report could be applied,
tested further, and improved to a point of
full field countermeasure applicability.
However, future work should evaluate
other surfactants that have the same
cleanup characteristics as those used in
the laboratory studies but are more
amenable to separation for reuse. Also,
prior to any larger scale/site of opportun-
ity studies, the toxicity of the surfactants
should be ascertained.
S. GOVERNMENT PRINTING OFFICE: 1986/646-116/20730
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William D. Ellis, James R. Payne, and G. Daniel McNabb are with Science
Applications International Corporation, McLean, VA 22102.
Anthony N. Tafuri is the EPA Project Officer (see below).
The complete report, entitled "Treatment of Contaminated Soils with Aqueous
Surfactants,"{Order No. PB 86-122 561/AS; Cost: $11.95. subject to change)
will be available only from:
National Technical Information Service
5285 Port Royal Road
Springfield, VA 22161
Telephone: 703-487-4650
The EPA Project Officer can be contacted at:
Hazardous Waste Engineering Resarch Laboratory—Cincinnati
U.S. Environmental Protection Agency
Edison, NJ 08837
United States
Environmental Protection
Agency
Center for Environmental Research
Information
Cincinnati OH 45268
Official Business
Penalty for Private Use $300
EPA/600/S2-85/129
0000129
U S
PS
PROTECTION AGENCY
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