United States
Environmental Protection
Agency
Municipal Environmental Research
Laboratory
Cincinnati OH 45268
&EPA
Research and Development
EPA-600/S2-81-098 July 1981
Project Summary
Effect of Flue Gas
Cleaning Sludges on
Selected Liner Materials
Clarence R. Styron, III, Zelma B. Fry, Jr., and Gordon L. Carr
This project examines the effects of
two flue gas desulfurization (FGD)
sludges on 18 liner materials used to
contain them. Seventy-two special
test cells were constructed 1 ft in
diameter by 2 ft high. Devices were
installed to collect the leachate from
each test cell to determine the leakage
and the leakage rate (permeability)
and to provide storage for subsequent
chemical analyses.
Ten admix liner materials were mixed
with a clayey silt and compacted in the
bottom 6 in. of the test cells. Six
spray-on and two prefabricated mem-
brane liners were placed over 6 in. of
compacted silty sand. Four gal of
sludge was then added to each test
cell along with enough tap water to
bring the liquid to within 4 in. of the
top. Each test cell was covered and
pressurized to simulate a disposal area
approximately 30 ft deep.
Physical tests of the 18 liner materials
were conducted before exposure to
the FGD sludges and after 12 and 24
months of exposure. Chemical tests
for determining heavy metals were
conducted on the two sludges as
received and on the sludge liquor that
passed through the lined test cells
after 12 and 24 months.
This Project Summary was devel-
oped by EPA's Municipal Environmen-
tal Research Laboratory, Cincinnati,
OH, to announce key findings of the
research project that is fully docu-
mented in a separate report of the
same title (see Project Report ordering
information at the back).
Introduction
Ground and surface water contami-
nation resulting from improper disposal
of hazardous wastes is a growing public
concern. Controlling the leachate from
such wastes by providing an impervious
liner for the disposal area could be a
solution to the problem, and it would
allow for the use of more sites as
disposal areas. The use of liners for
such purposes is not a new concept, but
knowledge is lacking on the compatibility
of liner materials with certain toxic
wastes and, particularly, on the life
expectancy of such liners. Much infor-
mation is needed tosupply guidance and
possible future regulations for using
liners in waste disposal areas.
The objectives of this study were to
determine the compatibility of liner
materials with flue gas desulfurization
(FGD) sludges, to estimate liner life, and
to assess the economics of purchasing
and placing various liners. To meet
these objectives, specimens of a variety
of potential liner materials were exposed
to selected FGD sludges over a period of
time under conditions that simulated
disposal areas and changes in the
physical properties of the liner material
with exposure time were determined.
Considerations in selecting liner
candidates were low cost and ease of
placement and construction. Primary
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attention was focused on the use of
admixed or stabilized in situ liner mate-
rials. Spray-on materials were also
considered, and some use was made of
prefabricated membrane liners (the
latter are being tested extensively in
other projects.1'3
The first step was to select two FGD
sludges representative of those that
would be found in disposal areas. Next,
18 types of liners (Table 1) were selected
as potentially usable with FGD sludges.
Test cells were then designed and
constructed to simulate disposal condi-
tions involving a sludge depth of at least
30 ft so that sludge could be applied in
increments over time. Liners were then
exposed for 12- and 24-month periods,
after which physical tests were con-
ducted to determine liner behavior over
time. Any accumulated leachate was
collected and measured for quantity and
quality. Finally, cost data were devel-
oped for the liners.
Table 1. Selected Liner Materials
ID
No.
Material Name and Type"
Methods and Materials
Design and Construction of
Test Cells and Ancillary
Equipment
Design Factors
Factors considered in the design of
the test cells were construction or
installation methods,4 size or amount of
specimen required for physical tests
after exposure periods, cell volume
sufficient to contain the liner and
sludge, and means of simulating a 30-ft
sludge depth.
A decision was made to test each liner
with 6 in. of compacted soil—the mini-
mum practicable for stabilizing admixes
and for limiting differential soil move-
ment under spray-on and membrane
liners. The size of each liner specimen
was determined by the number and
types of tests following the exposure
period. Duplicate specimens were also
Percent/Description/ Type
Admix Liner Material:
12 Lime
10 Port/and cement
15 Cement with lime
11 M179
08 Guartec UF
09 Asphaltic concrete
14 TACSS 020
16 TACSS 025
17 C400
18 CST
Spray-on Liner Material:
03 DCA-1295
04 Dynatech
05 Uniroyal
06 Aerospray 70
07 AC40
13 Sucoat
Prefabricated Membrane Liner:
01 Total Liner
02 T16
HydratedASTM C 747-67J
Type I ASTM C 150-78%
4 percent Type I Portland cement
6 percent hydrated lime
4 percent polymer, bentonite blend
4 percent light gray powder
11 percent asphalt cement
1/2 in. (max.) aggregate
6 percent blackish-brown liquid
6 percent blackish-brown liquid
15 percent finely ground powder
15 percent finely ground powder
3/4 gal/yd2 polyvinyl acetate
3/4 gal/yd2 natural rubber
3/4 gal/yd2 natural latex
3/4 gal/yd2 polyvinyl acetate
3/4 gal/yd2 asphalt cement
As-supplied molten sulphur
As-supplied elasticized polyolefin
As-supplied black chloroprene-coated
nylon
* For manufacturer/address, see Appendix A of full report.
t Standard Specifications for Hydraulic Hydrated Lime for Structural Purposes.
In: 1978 Annual Book of ASTM Standards, Part 13^ Designation: C141-67
(rev 78). Philadelphia, Pennsylvania, 1978.
^Standard Specifications for Portland Cement In: 1978 Annual Book of ASTM
Standards, Part 14, Designation: C150-78. Philadelphia, Pennsylvania, 1978.
used for determining unusual tesl(
results. Pressurization was considered
the most feasible approach to simulating
a 30-ft sludge depth. The use of pressure
(20 psi) permitted minimum amounts of
other materials to be used, including
sludge.
Test Cell Construction
Seventy-two test cells were fabricated
from polyvinyl chloride (PVC), which
was selected as an inert material that
would not react chemically with the
FGD sludge. Schedule 80 PVC pipe (ID
11-3/16 in.) with a pressure tolerance
of 130 psi was selected for the pressure
cells. The PVC base was 2-1 /2 in. thick
and 15 in. square. The PVC top was 15
in. in diameter and 3/8 in. thick. A
schematic view of the test cell is shown
in Figure 1. An additional top plate of
1/4-in. aluminum was required to
prevent buckling of the PVC top as
pressure was increased in the cell.
Ancillary Equipment
Ancillary equipment consisted of a
system for pressurizing the test cells
and a system for collecting the leachate
(Figure 1).
FGD Sludge Selection and \
Characteristics
Sludges were selected from an eastern
coal lime-scrubbed process (Sludge A)
and from an eastern coal limestone-
scrubbed process (Sludge B). Samples
were obtained from disposal ponds at
the plant sites. Sludge A had 47.6
percent solids and a pH of 10.3, and
Sludge B had 34.2 percent solids and a
pH of 9.0. A chemical analysis of the
sludges appears in Table 2 along with
EPA allowable limits. With few excep-
tions, the two sludges are very similar in
composition.
Soil Material and Liner
Selection and Properties
Soil selections were based primarily
on results of previous investigations. A
highly permeable soil was considered
most applicable for evaluating membrane
and spray-on liners because it would
permit any leakage of the liners to be
readily detectable. But the admix mate-
rials required a less permeable soil to
minimize the amount of admix needed.
A silty sand was thus selected to evaluate
the membrane and spray-on liners, and
a clayey silt was used to evaluate the
admix liners. These soil types are con-
sidered representative of typical soils!)
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Regulator
Air
Pressure
Gage
Silicone Seal —
Liner Test
Material -
Porous Disk.
Pressure
Port
r- —^
t;
^-
P
Plastic
/ Tubing
11-13/16"
S/u
dge
Under
Pres
Comp
So
^
r ^
Drain Port *^
sure
acted
il
3
6"
— i ,
r^^
\^
N^ Plastic
( ) Check Valve
Manifold
26%'
Tubing
Leachate
• Plastic
Container
Figure 1.
Schematic of a test cell section with a spray-on or membrane liner
depicted and ancillary equipment.
that might be encountered in a disposal
area.
Liner selection was based on results
of permeability tests. Admix liner mate-
rials were prepared and compacted in a
Harvard miniature test apparatus.5
Spray-on liners were applied to the
surface of soil specimens that had been
prepared and compacted in the Harvard
miniature mold. Both admix and spray-
on liners were allowed to cure for 7 days
under humid conditions. A 2-ft constant
head was maintained on the liners, and
permeability was measured by collecting
water that permeated through the spec-
imen over a period of time. The prefabri-
cated membrane materials were tested
for leakage (pinholes) or other abnor-
malities by covering the bell-shaped end
of a 21-in. standpipe with a sample of
each liner and allowing water to stand
in it for 15 to 20 days. Leakage was
collected in a container beneath the
device.
Results
Physical Tests
Unconfined compression (UC) tests
were used to study the effects of 12- and
24-month inundation/pressurization of
the admix liners, and grab tests were
used to study these effects on the spray-
on and prefabricated membrane liners.
Admix Liners
Physical tests of the admix liners were
made for the 0-, 12-, and 24-month
exposures. Two of the materials (Guartec
UF and M179*) suffered a complete
breakdown at the end of 12 months and
further testing was discontinued.
Moisture contents in all samples
increased slightly during the first 12
months and generally remained about
constant at 24 months, indicating some
initial liquid infiltration. But the dry
density remained about the same during
the 2-year period, which would indicate
that the soil structure had not changed.
During the first 12 months, the UC
strength of the Portland cement, Port-
land cement plus lime, C400, and CST
almost doubled, whereas the lime
strength increased nearly six times. At
24 months, the UC strength of the Port-
land cement and CST remained un-
changed; but the Portland cement plus
lime and the C400 increased an addi-
tional 8 to 10 percent, and the lime
increased an additional 20 percent.
Thus the results indicated that the
performances of the C400 and CST
liners were similar to that of Portland
cement.
Increases in UC strength after curing
time would be expected for silty clay and
lime as well as for other soil types, but
the TACSS 020 and 025 lost 14 and 12
percent UC strengths, respectively, at
the end of 12 months. At the end of 24
'Mention of trade names of commercial products
does not constitute endorsement or recommenda-
tion for use by the U S Environmental Protection
Agency
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Table 2. Chemical Analysis of Sludges and EPA Allowable Limits
Sludge A
Parameter
Arsenic
Beryllium
Cadmium
Chromium
Cyanide
Copper
Mercury
Magnesium
Manganese
Nickel
Lead
Selenium
Zinc
Sulfite
Sulfate
Boron
Chloride
Vanadium
Nitrite, nitrogen
Nitrate, nitrogen
Sludge
Solids
(mg/kg)
0.28
6.8
0.005
133.0
-§
O.S5
0.44
3030.0
84.8
0.84
1.08
1.38
135.0
190.0
—
385.0
1330.0
162.0
<0.04
3.0
Sludge
Liquid
(mg/L)
0.003
0.005
0.001
0.001
0.012
0.009
0.002
10.1
2.3
<0.003
<0.003
<0.003
0.002
<1.0
1281.0
14.0
675.0
—
<0.01
0.5
Sludge B
Sludge
Solids
(mg/kg)
0.16
1.25
0.007
33.3
—
0.35
0.84
5160.0
43.7
0.38
0.68
2.15
278.0
200.0
68750.0
185.0
300.0
53.0
<0.04
3.0
Sludge
Liquid
(mg/L)
0.003
<0.005
<0.001
<0.001
0.018
0.010
0.002
13.8
0.95
0.003
0.003
0.007
0.002
<1.0
2100.0
71.2
670.0
—
<0.01
0.51
EPA
Allowable
Limits*
(mg/L)
0.05
<0.0/7t
0.0?
0.05\
0.005
0.2**
0.002
/v/m
0.05
on
0.05
0.01
5.0**
NA
250.0
0.75M
250.0**
NA
10.0
10.0
*From References 9 and 10 in full report.
•\Freshwater aquatic life criteria.
^Freshwater and marine organisms criteria.
§— = Insufficient sample to analyze for all parameters.
**Secondary standards proposed for drinking water criteria (EPA).
]]NA = Not available.
^Irrigation criteria
months, the TACSS 020 lost an addi-
tional 11 percent (a total of 25 percent,
based on zero-time data), and the TACSS
025 dissociated when cored, thus yield-
ing no data.
The penetration of the asphaltic
concrete increased approximately 10
percent at 12 months and remained
constant at 24 months. The viscosity,
however, increased approximately 13
percent at 12 months but decreased
more than 16 percent after 24 months.
Extensive surface cracks developed in
this liner after 12 months.
Spray-On and Prefabricated
Membrane Liners
Physical test results of the spray-on
and membrane liners indicated that
after 12 months of exposure, the break-
ing strength of all the liners decreased,
and the DCA-1295 continued to lose
strength at 24 months. Although the
overall strength of the liners had de-
creased considerably by the end of the
24-month period, values were slightly
higher at the end of 24 months than
they had been at 12 months for the Total
Liner, T16, Uniroyal, and Dynatech.
The percent of elongation values for
the Total Liner material increased ap-
proximately 400 percent the first year
and remained constant during the
second year. The elongation values for
the T16, Dynatech, and Uniroyal gener-
ally remained constant throughout the
2-year test period. At 24 months, the
Aerospray 70 reversed its 12-month
pattern by increasing, and the DCA-
1295 continued decreasing the second
year.
Chemical Tests
The first 32 oz of liquid issuing from
each test cell was collected and analyzed
chemically to assess the gross effects of
liner behavior and liner composition.
These initial liquid samples consisted of
a mixture of soil pore water, material
from the liners, and sludge liquor.
Material lost from the liners cannot be
seen in most cases because of the con-
centrated liquor from the FGD sludges
and normal background chemistry of
the water associated with the soils.
Some exceptions, however, include
Guartec UF, TACSS 020, and TACSS
025, all of which released levels of
magnesium and manganese higher
than those observed in most samples.
This release may have resulted from
acidic conditions that developed in
these admixes because of decay (in the
case of Guartec) or from reactions with
plasticizers (in the cases of TACSS 020
and 025).
The concentration of a chemical
constituent such as chloride, which is
not effectively attenuated by soil, is an
important indicator of how the sludge
liquor is moving through the membrane.
Low chloride levels suggest that the
sludge liquid is moving uniformly through
the membrane along the entire cross
section of the test cell. This hypothesis
is borne out by observations made on
the liner conditions after 12 months.
Permeability
Because some leakage was caused by
the silicone seals, permeability values
were influenced and in many cases
invalidated. Thus the only permeability
data reported are those for liners that
permitted no leachate to pass or for
liners that were obviously attacked by '
the chemical sludges.
Summary of Liner Performance
Recorded data for physical tests and
chemical analyses indicate that the
following comments are valid and per-
tinent.
1. Total Liner. The density increased
26.2 percent following exposure,
and the breaking strength de-
creased 72 percent. These figures
indicate that the polymer was
compacted and its strength was
greatly reduced. The liner mate-
rial was still soft and pliable, and
it appeared to be in good con-
dition.
2. T16. The density increased 14.5
percent, indicating some com-
paction of the polymer; but there
was little or no change in the
breaking strength. Some small,
crusty formations were observed
on the liner/sludge interface.
3. DCA-1295. The average density
of this liner material decreased
slightly (3.3 percent), but both the
elongation and the breaking
strength decreased significantly.
Visual inspection revealed that ,
this liner was discolored and very \
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thin. The liner was very easily
torn while it was being removed
from the test cell.
4. Dynatech. A 17.3-percent increase
in density indicates some sludge
infiltration into the sprayed ma-
terial or compression of the poly-
mer, but the other physical data
remained essentially unchanged.
Discoloration noted could be due
to chemical attack during the
testing.
5. Uniroyal. A 17.2-percent increase
in density indicates some com-
pression of the polymer and in-
corporation of sludge; the breaking
strength decreased 40 percent.
Liner discoloration noted could
indicate susceptibility to chemical
attack.
6. Aerospray 70. A 33.3-percent in-
crease in density indicates con-
siderable sludge incorporation
and polymer compaction. The
breaking strength decreased 57
percent, although one of these
test cells did not pass any leachate.
Discoloration and thin spots were
observed throughout the liner.
Decomposition was noted on the
membrane/soil interface.
7. AC40. The physical tests per-
formed on this liner material
made it difficult to detect any
chemical degradation of the liner.
The average viscosity appeared
to be very high at the end of the
first 12 months, but this figure
had returned to nearly the original
value by the end of 24 months.
Leachate from these test cells
was passing through the liner
material itself. Chemical data
indicate that this leachate con-
tained four to six times the con-
centrations of chromium, seleni-
um, boron, and sulfate at 24
months than at 12 months.
8. Asphaltic concrete. These physi-
cal tests were identical to those
for AC40 and essentially the
same comments are appropriate.
9. Portland cement. The density of
this liner material remained es-
sentially unchanged, but the DC
strength increased 175 percent.
Chemical data indicate that
leachate from the test cell con-
tained approximately seven times
higher concentrations of sulf ite
and sulfate at 24 months. The
liner was soft and friable in iso-
lated areas.
10. Lime. The 1.1 -percent increase
in density of this liner material
may indicate slight sludge infil-
tration or compaction of the liner,
but it is more likely that this
change represents a normal vari-
ation in density across the speci-
men. The DC values of this liner
increased 464 percent. Chemical
data indicate the leachate from
the test cell contained 5 to 20
times higher concentrations of
chromium and boron after 12
months, whereas the concentra-
tions of magnesium, sulfate,
nitrite, and nitrate were as much
as 150 times lower.
11. Sucoat. This liner was supplied
preformed by the manufacturer,
and it apparently suffered no
chemical decomposition. One
test cell ruptured under pressure
and was discontinued. Chemical
data indicate that leachate from
the test cell contained twice the
concentrations of magnesium
and sulfate, five times the con-
centration of boron, and 100
times the concentrations of nitrite
and nitrate at 24 months than at
12 months. The breaking strength
was reduced 16 percent at the
end of 24 months.
12. TACSS 020 and TACSS 025.
Neither of these two liner mate-
rials evidenced any change in
density other than the change
normally expected during a typi-
cal construction procedure. Sludge
penetrated the surface of the
liner more than 3/8 in. on each
liner type.
13. Portland cement plus lime. No
significant change in density oc-
curred during the 24-month test
(+0.3 percent). Chemical data
indicate that the leachate through
the liner contained approximately
40 times the concentration of
chromium at 12 months than atO
months, whereas the concentra-
tion of magnesium decreased ap-
proximately 0.01 times, and the
concentrations of nitrite, nitrate,
and sulfate decreased 0.01 to
0.001 times. The UC strength
increased 187 percent.
14. C400. No significant change in
density occurred during the 24-
month test (+0.3 percent). The UC
strength increased 106 percent.
The chemistry of the leachate
through the test cell indicates
that approximately three times
the concentrations of arsenic and
boron and 20 times the concen-
trations of chromium and seleni-
um were detected at 24 months
than at 12 months. Indications
were that the copper and lead
concentrations also increased.
15. CST. No significant change in
density occurred during the 24-
month test (+0.3 percent). The UC
strength increased 63 percent.
The chemical concentration of
the leachate at 12 months in-
creased approximately 20 to 100
times for sulfate and nickel,
respectively. Concentrations de-
creased by a factor of 0.001 for
nitrite and nitrate and by approxi-
mately 0.01 for magnesium.
No definite trends were established
from these tests that would permit the
projection of liner life with any degree of
accuracy.
Economic Assessments
Assessments were made of costs
involved with purchase and placement
of various liner materials. Estimates
were based on a typical 15-acre lagoon
that can accommodate 30 ft of water.
The* cost of the land and the initial
preparation (grubbing, clearing, digging,
etc.) are not considered here, as they are
site specific. For the 15 acres, costs for
admix liner materials ranged from
$150,000 for Portland cement, lime,
and Portland cement plus lime to
$4,300,000 for TACSS 025. Costs for
spray-on and membrane liner materials
ranged from $33,000 for AC40 to
$1,350,000 for Sucoat. Total installation
cost for placing the prefabricated mem-
brane liners was estimated at $38,154.
This cost included laborers, operators,
equipment, fuel, and mobilization. The
largest part of this cost occurred in
unfolding, stretching, and placing the
liners—30 laborers at a cost of $10,080.
Construction costs for admix liners vary
with the type of material and location.
The full report was submitted in ful-
fillment of Interagency Agreement EPA-
IAG-D5/6-0785 between the U.S. Envi-
ronmental Protection Agency and the
U.S. Army Engineer Waterways Experi-
ment Station.
References
1. Haxo, H.E., and R.M. White. First
Interim Report; Evaluation of Liner
Materials Exposed to Leachate (un-
published). U.S. Environmental Pro-
tection Agency, Cincinnati, Ohio,
1974.
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2. Haxo, H.E., and R.M. White. Second
Interim Report; Evaluation of Liner
Materials Exposed to Leachate. EPA-
600/2-76-255, U.S. Environmental
Protection Agency, Cincinnati, Ohio,
1976.
3. Haxo, H.E., R.S. Haxo, and R.M.
White. First Interim Report; Liner
Materials Exposed to Hazardous and
Toxic Sludges. EPA-600/2-77-081,
U.S. Environmental Protection Agency,
Cincinnati, Ohio, 1977.
4. Geswein, AJ. Liners for Land Dis-
posal Sites; An Agreement. EPA-
530/SQ-137, U.S. Environmental
Protection Agency, Cincinnati, Ohio,
1975.
5. Wilson, S.D. Small Soil Compaction
Apparatus Duplicates Field Results
Closely. Soil Testing Services, Inc.,
Chicago, Illinois (undated).
Clarence R. Styron, III, Zelma B. Fry, Jr., and Gordon L. Carr are with the U. S.
Army Engineers Waterways Experiments Station, Vicksburg, MS 39180.
Robert E. Landreth is the EPA Project Officer (see below).
The complete report, entitled "Effect of Flue Gas Cleaning Sludges on Selected
Liner Materials," (Order No. PB 81 -213 365; Cost: $9.50, 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:
Municipal Environmental Research Laboratory
U. S. Environmental Protection Agency
Cincinnati, OH 45268
> US GOVERNMENT PRINTING OFFICE 1981 757-012/7246
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Environmental Protection
Agency
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Information
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