United States
Environmental Protection
Agency
Municipal Environmental Research
Laboratory
Cincinnati, OH 45268
Research and Development
EPA-600/S2-82-097 Mar. 1983
Project Summary
Liner Materials Exposed to
Municipal Solid Waste Leachate
Henry E. Haxo, Jr., Richard M. White, Paul D. Haxo, and Michael A Fong
A laboratory study was conducted to
determine the potential of various lining
materials for controlling the movement
of leachate from municipal solid waste
(MSW) landfills. In the course of the
study, 65 materials were subjected to
at least one of seven different tests in
which they were exposed to MSW
leachate. These exposure tests involved
placing liner samples in (1) landfill
simulators containing 8 ft of compacted,
shredded refuse, (2) immersion tanks
containing MSW leachate or water,
and (3) polybutylene bags containing
deionized water. Materials tested in-
cluded 4 admix materials, 2 asphaltic
membranes, 50 commercial polymeric
membranes, and 9 miscellaneous ma-
terials.
Exposing a wide range of polymeric
membranes to a typical MSW leachate
in the landfill simulators for up to 56
months produced only limited changes
in liner properties. Asphaltic materials
did exhibit deficiencies that might af-
fect their serviceability as linings for
MSW waste disposal facilities. The
properties of soil cement tended to
improve during exposure.
This Project Summary was developed
by EPA's Municipal Environmental Re-
search 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
Leachates generated by water percolat-
ing through sanitary landfills can seriously
degrade suface and groundwaters, par-
ticularly in areas subject to high humidity
and rainfall. Lining landfills with materials
of very low permeability could provide a
long-term solution to the problem of
leachate pollution and could also make
previously unacceptable sites usable as
landfills. This project investigates the
potential of various lining materials for
controlling the movement of leachate from
landfills by examining their properties after
different types of exposure to municipal
solid waste (MSW) leachate.
Little was known about the durability of
lining materials in contact with MSW
leachate when this project was initiated in
1973. The scope of the work and the
objectives were updated periodically to re-
flect the changing liner technology. The
principal objectives of the project were as
follows:
1. to determine the long-term effects of
MSW leachate on a wide variety of
materials that could be used as landfill
liners,
2. to determine the effective service lives
of these materials when in prolonged
contact with leachate or landfill con-
ditions,
3. to develop laboratory tests for as-
sessing the properties of membrane
liners under simulated field conditions,
4. to generate a useful data base for
MSW landfill liners, and
5. to analyze costs associated with the
use of landfill liners.
Methods and Materials
In the course of this study, 65 materials
were subjected to at least one of seven
different exposure tests. These materials
included 4 admix materials, 2 asphaltic
membranes, 50 commercial polymeric mem-
brane liners, and 9 miscellaneous materials.
The number and types of liners and types of
exposures are summarized in Table 1.
The exposure tests involved placing
liner samples in (1) landfill simulators con-
taming 8 ft of compacted, shredded refuse,
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(2) immersion tanks containing MSW
leachate or water, and (3) polybutylene
bags containing deionized water. (The
latter test was known as the pouch test
because membrane samples were formed
into pouches before immersion and filled
with leachate or 5% salt solution.)
Exposure Tests in Landfill
Simulators
Exposure tests in landfill simulators were
performed on 12 different primary samples
sealed into the bases of the simulators and
on 40 different secondary samples buried
in the sand above the primary liners (see
Table 2).
The simulators in which the liners were
exposed and in which the leachate was
generated consisted of 10-ft columns
containing 8 ft of compacted shredded
Table 1. Scope of Exposure Tests
refuse (see Figure 1). The primary liners
were sealed into the simulator bases with
a rapid-set epoxy resin to prevent the
leachate from bypassing the liners. Thus
any seepage through the liner could be
measured. A hydraulic head of 1 ft of
leachate was maintained on the liners, and
leachate was collected continuously.
The leachate was generated by percolat-
ing 25 in. oftapwaterperyearthroughthe
8-ft colu mn of g rou nd refuse i n each of the
simulators. Leachate quality for all 24
simulators was in the normal range for
leachate generated by full-scale landfills.
Liner properties were measured during
the course of the exposure to determine
changes. All specimens in the simulators
were tested before and after 12 and 56
months of exposure. The asphaltic and
the secondary polymeric membranes were
Gauge -
3/4" Drain Rock 3" Thick
Type of exposure
Primary, in simulators
Buried, in simulators
Number
of
liners
6
4
2
31
9
Type of
liner or material
Polymeric membrane
Admix
Asphaltic membrane
Polymeric membrane
Miscellaneous materials
Length of
exposure,
months
12,56
12,56
12, 43, 56
12, 13, 43, 56
12, 43, 56
Immersion, in tanks
Pouch test:
With leachate
With NaCI solution
28 Polymeric membrane
14 Polymeric membrane
12 Polymeric membrane
8, 19, 31
11-40
10-38
Water absorption
(ASTM D570)
At room temperature
At 70°C
11
11
Polymeric membrane
Polymeric membrane
43
43
Table 2. Materials Used in Landfill Simulator Exposure Tests
Primary liner materials
Secondary liner materials
Admixes:
Paving asphalt concrete
Hydraulic asphalt concrete
Soil asphalt
Soil cement
Asphaltic membranes:
Bituminous seal
Emulsified asphalt on nonwoven fabric
Flexible polymeric membranes:
Butyl rubber
Chlorosulfonated polyethylene
Ethylene propylene rubber
Low-density polyethylene
Polyvinyl chloride
Polymeric membranes:
Butyl rubber
Chlorinated polyethylene
Chlorosulfonated polyethylene
Elastic/zed polyolefin
Ethylene propylene rubber
Neoprene
Polybutylene
Polyester elasomer
Low-density polyethylene
High-density polyethylene
Polyvinyl chloride
Miscellaneous materials:
Asphalt roofing felt
Polypropylene
Thermoplastic rubbers
Commercial gasket materials based on
natural rubber
Styrene-butadiene rubber
Urethane
Neoprene
Shredded Refuse-
Mastic Ses/s
Concrete Base^
Sand-
Sealing Ring-
Gravel
'-'v.
-Soil Cover
1 3/4 ft. Thick
-Polyethylene
- Spiral-Weld Pipe
2ft.Dia.x10 ft.
High
-Liner Specimen
Drain Above Liner
Drain Below Liner
Figure 1. Landfill simulator used to evalu-
ate liner materials exposed to
sanitary landfill leachate.
also tested before and after 13 and 43
months, and miscellaneous secondary
samples were also tested after 43 months.
Seepage was collected continuously during
the operation of the simulators.
The membrane liners were tested for
absorption of leachate and for changes in
tensile strength, tear resistance, puncture
resistance, seam strength, and permea-
bility. The other materials were tested for
appropriate properties.
Because available information indicated
that the seams in polymeric membrane
liners were the most likely source of liner
failure, seams were incorporated into as
many of the test specimens as possible.
Factory seams or seams made according
to the manufacturer's recommended prac-
tice were used for all primary liner speci-
mens in the landfill simulators. Adhesives
supplied by the manufacturer were used
in most cases. Test joints were also
incorporated into the strips buried in the
sand above the primary liners. Some
systems suggested by manufacturers of
other liners based on the same polymer
were tested although they had not been
recommended by the manufacturer of the
specific material.
Exposure Tests in Immersion
Tanks Containing Leachate
and Water
To investigate the effects of immersion
in MSW leachate, three sets of slab speci-
mens of 28 different polymeric sheetings
(Table 3) were immersed in MSW leachate
generated in the simulators. Because
MSW leachate is principally water (which
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by itself can be aggressive to many ma-
terials), water absorption tests were also
conducted by immersing 11 membrane
liners in water for uptol 86 weeks, both at
room temperature and at 70°C.
Similar immerson tests were attempted
with admix specimens, but in their uncon-
fined state, they crumbled apart when
hung in the leachate.
The immersion system was designed to
allow blended leachate from the 1 2 sim-
ulators to flow slowly through a series of
high-density polyethylene tanks in which
the membrane-slab specimens were hung
(Figure 2). This arrangement was accept-
able because polyethylene has low per-
meability to air, and only small changes in
leachate composition were observed when
the leachate was stored in these containers
for a month at room temperature. Further-
more, this design exposed more specimens
easily, exposed all specimens to the same
leachate, and required considerably less
time to construct and monitor than in-
dividual tanks or bags attached to the
simulators. A Masterflex* pumpdelivered
leachate at the rate of 14 mL/min through
the tanks, recirculating the supply of
leachate in about 12 days.
Three sets of the 28 membranes were
immersed in the leachate so that one set
could be removed after each exposure
period (8, 19, and 31 months). The 8- x
10-in. specimens were hung vertically
0.92 in. apart in the tanks (Figure 2).
Pouch Tests
The pouch test involved fabricating a
small pouch from the membrane liner,
filling it with test fluid (such as leachate),
and placing it in a deionized water solution
in a polybutylene bag (Figure 3). This test
offers the opportunity of exposing liner
materials to two fluids at the same time-as
would be the case in a landfill where
leachate would contact one side of the
membrane and goundwater the other.
The pouch test was used primarily to
test permeability, but other properties of
the membranes were also tested after
exposure. Two "fluids were tested in the
pouches: one set of pouches was filled
with leachate, and another set was filled
with a 5% aqueous solution of sodium
chloride. The latter solution was of known
composition and was therefore used to
measure the movement of ions and to set
up a known concentration differential
across the membrane.
The liner materials used in these pouch
tests included chlorinated polyethylene,
chlorosulfonated polyethylene, elasticized
polyolefin, polyester elastomer, and poly-
vinyl chloride (three different formulations).
The following tests were performed
during the exposure of these pouches:
1. The diomzed water surrounding the
leachate-containing pouches was
tested periodically for pH, conductiv-
ity, and the odor of butyric acid.
2. The pouches containing thetestfluid
(leachate or salt solution) were re-
moved periodically from the deionized
water and weighed.
Results and Conclusions
Effects of Leachate Exposure
on Liner Properties
Polymers
Exposing a wide range of polymeric
membranes to a typical MSW leachate in
the landfill simulators for up to 56 months
produced only limited changes in their
properties. Only one type of liner—the
polyester elastomer-showed a potentially
significant loss of properties.
Some of the polymeric membrane liners
exhibited significant swelling during the
Table 3. Liners Immersed in MSW Leachate
Type of polymer
Number of different
sheetings immersed
Butyl rubber fllR)
Chlorinated polyethylene (CPE)
Chlorosulfonated polyethylene (CSPE)
Elasticized polyolefin (ELPOj
Ethylene propylene rubber (EPDM)
Neoprene (CR)
Polybutylene (PB)
Polyester elastomer
Low density polyethylene (LDPE)
Polyvinyl chloride (PVC)
PVC and pitch
3
3
/
5
4
1
1
1
7
Leachate In
Leachate Out
Cover Detail
Specimens
Specimens
Attach to Hooks
Note: Plastic Weld
Seals Container
Cross Section
Leachate ln~^ ^Leachate Out
Polyethylene Tank
* Mention of trade names or commercial products does
not constitute endorsement or recommendation for
Figure 2. Individual polyethylene immersion tank, showing method of holding speciments and
the inlet and outlet for the leachate.
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Inner Bag
Membrane Under Test
Leachate or
NaCI Solution
(Inside Inner Bag)
Deionized Water
Outer Bag
Polybutylene
Figure 3. Schematic of pouch assembly, showing inner bag made of membrane material
under test. The inner bag is filled with leachate or 5% salt solution and sealed at the
neck. The outerpolybutylene bag, which can be easily opened, is filled with deionized
water. The water in the outer bag is monitored for pH and conductivity; the inner bag
is monitored for weight change.
exposure periods and losses in tensile
strength and other physical properties.
Swelling of membranes in leachate was
greater than that in water, which indicates
the importance of the organic components
of the leachate with respect to the swelling
of polymeric materials.
The immersion of polymeric materials in
leachate somewhat accelerated the effects
of the leachate on the liner materials and
demonstrated that the exposure to two
sides of a sheeting was more severe than
one-sided exposure.
Among the polymeric lining materials,
the partially crystalline thermoplastic ma-
terials showed the least amount of swell
and the fewest changes in properties.
Generic classification of polymeric ma-
terials by polymer type is not sufficient to
predict the performance of a given liner.
Variation in grade and the presence of other
compounding ingredients affect the per-
formance of a polymeric composition.
Variations also arise with the use of fabric
reinforcements.
Asphaltic Materials
The asphaltic materials, whether con-
cretes or membranes, did exhibit some
deficiencies after leachate exposure that
might ultimately affect their serviceability
as linings for MSW waste disposal facilities.
The concretes tended to lose strength, and
the membranes absorbed leachate and lost
in ductility and elongation. The asphaltic
membranes that had been exposed for 56
months showed areas that had lost induc-
tility and elongation and had become
"cheesy." On drying, the cheesy section
of the ashpalt returned to normal and
showed very little or no change in basic
properties compared with the original
asphalt.
Soil Cement
The properties of the soil cement speci-
men tended to improve during exposure.
The specimen was very small, however (2
ft in diameter).
Effects of Leachate Exposure
on Seams
The seaming of membrane liners by
heat or welding with solvents or bodied
solvents that are solutions of the liner
compound appears to yield seams with
the highest integrity. Results also showed
that values could vary greatly as a result of
poor workmanship. Adhesives that differ
in composition from the liner introduce a
new composition that must be assessed
for compatibility in a given waste stream.
The low-temperature vulcanizing adhe-
sives, which are required in the seaming of
vulcanized or crosslinked sheetings, gen-
erally yielded lower seam strength values;
but in some cases, they showed increases,
probably because of additional cure. A
significant problem with this type of ad-
hesive system arises over time because of
their fewer crosslinks compared with the
vulcanized sheeting. That condition can
cause the adhesive to swell considerably
more during exposure and thus lose
strength.
Simulator Design
The design of the simulator that was
used in this project appears to be versatile
and useful for investigating the character-
istics of MSW, methane gas generation,
liners, etc. The size was large enough to
simulate landfills and to obtain exposure
data on liner materials, but it was small
enough to be manipulated by a forklift for
examination of the materials inside during
exposure. A better choice of epoxy resins
would ensure complete sealing of the liner
specimens without the degradation of the
seal that took place in several of the simu-
lators.
Recommendations
Feedback is needed from the field re-
garding the performance of lining materials
in actual service so that laboratory results
can be correlated with field performance.
The open literature contains virtually no
data on liner performance in full-scale
landfills containing MSW leachate.
When liners are placed, samples should
be retained and provisions should be made
in the design to place samples in contact
with the leachate that will be generated in
the landfill. These samples should then be
recovered at various times to measure the
effects of the exposure on properties.
Monitoring of the groundwater below a fill
and the development of leak detection
devices would also be helpful in assessing
liner performance.
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Information on liners for disposal facili-
ties such as would be developed in the
permit process should be accumulated
along with performance data. This in-
formation could then be used to develop
correlations with laboratory test methods
and to help select materials for liner use.
Liner specifications should be estab-
lished that relate liner performance in
service to both the materials and the
installation.
The use of the pouch test should be
extended as a means for evaluating new
liner materials for MSW landfills.
The full report was submitted in fulfill-
ment of Contract No. 68-03-2134 by
Matrecon, Inc. under the sponsorship of
the U.S. Environmental Protection Agency.
Henry E. Haxo, Jr., Richard M. White, Paul D. Haxo, and Michael A. Fongare with
Matrecon, Inc., Oakland, CA 94623.
Robert Landreth is the EPA Project Officer (see below).
The complete report, entitled "Linear Materials Exposed to Municipal Solid Waste
Leachate," (Order No. PB 83-147 801; Cost: $ 17.50, 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
. S. GOVERNMENT PRINTING OFFICE: 1983/659-095/1911
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United States
Environmental Protection
Agency
Center for Environmental Research
Information
Cincinnati OH 45268
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