United States
Environmental Protection
Agency
Risk Reduction
Engineering Laboratory
Cincinnati OH 45268
Research and Development
EPA/600/S2-91/040 Sept. 1991
EPA Project Summary
Compatibility of Flexible
Membrane Liners and Municipal
Solid Waste Leachates
Henry E. Haxo, Jr.
In a study designed to determine the
current composition of municipal solid
waste (MSW) leachate and its chemical
resistance with flexible membrane liners
(FMLs), the literature was surveyed and
limited experiments on absorption of
organlcs by FMLs were done. The object
of this survey and study was to assess
how well EPA Method 9090 can evaluate
the resistance of FMLs with MSW
leachate. It should be noted that EPA
Method 9090 was originally developed
for evaluating the chemical resistance of
FMLs with hazardous waste leachate. At
present, It is questionable whether
Method 9090 yields realistic results for
Judging this resistance. The Method may
yield misleading results because of the
instability of the MSW leachate and the
low concentrations of leachate organlcs
presently reported.
This Project Summary was developed
by the principal In vestlgators and EPA's
Risk Reduction Engineering Laboratory,
Cincinnati, OH, to announce key find-
ings of the research project that Is fully
documented In the report listed at the
end of this summary. (See Project Re-
port ordering Information at back.)
Introduction
Early studies indicated that commercially
available FMLs were chemically resistant to
MSW leachates that contacted them. These
studies employed freshly collected, shred-
ded MSW whose leachate contained inor-
ganic salts and volatile acids with no indica-
tion of chlorinated or aromatic organics.
Adding hazardous waste from small-quan-
tity generators and nonhazardous industrial
waste to MSW may result in leachate con-
taining measurable quantities of organics
that could adversely affect FMLs and ren-
derthem unserviceable. When the leachate
contains sufficiently high amounts of ag-
gressive constituents, the resistance of the
FML and the leachate must be determined.
Currently, EPA Method 9090 is usedforthis
determination. Because of the instability of
leachate during the 120-day exposure at
23° and 50°C called for by the Method, it
may not be suitable.
We now need such information as:
• Is the chemical resistance data base
(FMLs with MSW leachates sufficient to
approve commercially available FMLs
without EPA Method 9090 testing?
• Isthere a level of an organic's concentra-
tion (or a mixture's concentration) above
which the testing is required?
• How do the changing characteristics of
MSW leachate affect FMLs during long-
term exposure?
• If Method 9090 testing is necessary, how
credible are the data?
These are questions that must be an-
swered; the literature search and limited
experiments summarized here are a begin-
ning.
The literature was examined to deter-
mine data on composition and characteris-
tics of MSW leachate; data on resistance of
commercial FMLs with MSW leachate; and
the sufficiency of available data to warrant
blanket approval of commercial FMLs for
use as liners in MSW landfills. Limited ex-
periments were done to study the partition-
ing of low concentrations of the organic
constituents found in MSWIeachateto com-
mercially available FMLs.
Printed on Recycled Paper
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Composition of Leachates
From the literature review (and the limited
experiments), MSW leachate is found to be
a highly complex mixture of inorganics, or-
ganics, and bacteriological constituents;
usually generated in an anaerobic MSW
landfill environment; highly oxidizable and
unstable; and subject to rapid composi-
tional changeswhenremovedfrom the MSW
environment. There are limited dataon MSW
leachate generated from recently con-
structed landfills and on the presence of low
co ncentrationsof priority pollutants andother
organics that may be absorbed by FMLs.
Before 1980, information of the composi-
tion of leachate included analyses for trace
metals, organic acids, and many of the
dissolved organics. More recent analyses
show the presence of a variety of volatile
organics and priority pollutants.
In the one study (done in the 1970's but
reported between 1982 and 1988) con-
cerned with the resistance of MSW leachate
and FMLs, the leachate was analyzed for
organic acids, COD, total volatile and non-
volatile solids, and Ph, but notforaromatics,
hydrocarbons, chlorinated hydrocarbons,
or other priority pollutants. The parameters
peaked at about 1 yr and decreased to 10%
of peak at 4-2/3 yr. The maximum effects on
the FML's properties occurred at 1 yr and
then tended to return to original values. No
data were available on currently produced
FMLs based on high-density polyethylene
(HOPE).
Threshold Concentration and
Solubility Parameter
The concept of a threshold concentration
was considered to be the lowest concentra-
tion at which significant effects on FML
properties occurred and at which maximum
adsorption and equilibrium occurred. An
organic dissolved in an aqueous solution
partitions until equilibrium concentration (in
the solution and in the FML) is reached. The
ratio of the concentration of the dissolved
organic in the FML over that in the water
would equal the partitioning coefficient. Over
a practical concentration range (low), this
coefficient would remain constant and the
coefficient would be determined by the solu-
bility parameter pairs (the organic and the
water; the organic and the FML). As the
concentration or organics in the leachate
changes, the equilibrium would change and
so would the concentration in the FML. A
threshold concentration, then, would be
unique to the combination of FML and the
organic or combination of organics.
EPA Method 9090
The EPA Method 9090 test reliability as-
sesses the resistance of FMLs with hazard-
ous wastes, leachates, and waste liquids;
problems exist, however, when determining
the true resistance of a specific FML with a
specific MSW leachate. A detailed analysis
of the leachate is needed to determine the
organics (especially chlorinated and aro-
matic hydrocarbons that have solubility pa-
rameters close to most FML) and their con-
centrations. With the use of solubility data
and a detailed analysis, the amount ab-
sorbed by an FML could be estimated and
the absence or low concentration of these
species would indicate EPA Method 9090
need not be performed.
But the problem is that MSW leachate is
highly oxidizable and unstable, and meth-
ods to preserve the leachate were notfound
in the literature. To protect the leachate
from bacteriological changes, the sample
must be cooled and stored at +5°C immedi-
ately aftercollection. The Method 9090 com-
patibility test is done at 23° and 50°C when
biological activity can result in continuous
property changes. Because the objective is
to maintain in-service conditions as much
as possible, additional experimentation
should be done to assess means to stabilize
the leachate. The concentrations of dis-
solved constituents reflect the composition
of the leachate in service; the leachate
should maintain a constant concentration of
these constituents affecting FMLs during
extended service.
Many of the constituents of MSW leachate
are readily oxidizable, and many organics
(such as chlorinated organics) resist degra-
dation over long periods of time. These are
the organics that remain after other con-
stituents are degraded and that are gener-
ally more aggressive to FMLs.
Under the present EPA Method 9090,
equipment should be modified to ensure
anaerobic conditions and stabilization of
leachates.
Laboratory Experiments
Because of the uncertainties surrounding
the resistance of FMLs and MSW leachate,
limited laboratory experiments were done.
This work involved measuring the absorp-
tion of three dilute, aqueous solutions or
organics commonly found in MSW leachate
(toluene.trichloroethylenefTCE], and methyl
ethyl ketone [MEK] by four representative
polymers (linear low-density polyethylene
[LLDPE]; polyvinyl chloride [PVC]; chlori-
nated polyethylene [CPE]; and a fabric-
reinforced, low-water-adsorption chloro-
sulfonated polyethylene [CSPE-Rj. In the
tests, the changing concentrations of or-
ganics in the solutions were measured until
they became relatively constant. The FML
specimens were then analyzed (GC
headspace procedures) to determine the
amount and type of organics absorbed by
the specimens.
The three experiments were designed to
simulate FMLs in contact with MSW
leachate: what was the weight increase,
how much organics were absorbed; and
what effect did the swelling have on the
tensile properties of the FMLs.
In the first experiment, the solvents were
dissolved at low concentrations (500 ppm)
in Dl water. At equilibrium, the MEK re-
mained in the water and the TCE and tolu-
ene partitioned to the PVC.
In the second experiment, the concentra-
tions of volatile organics in each test cell
were measured by GC analysis. In all cases,
the MEK showed little change—thus little
partitioning of MEK from the water phase to
the FMLs had occurred. The concentration
of toluene and TCE in the watersignrftcantly
dropped, and thus partitioning to the FMLs
had occurred.
Experiment three was done to confirm
experiment two and to measure the effect
on tensile properties of FMLs, with one
specimen cut from the machine direction
and one from the transverse. The results
confirmed those of experiment two and also
showed that tensile stresses showed losses
of up to 25% to 30% at 100% and 200%
elongation.
Results
Based on the present data base, it is
questionable whether blanket approval can
be given for all FMLs used to construct
lining systems for MSW disposal facilities.
At the same time, it is also questionable
whether EPA Method 9090, as presently
performed, will yield realistic results forjudg-
ing the resistance of lining materials with
MSW leachates. Furthermore, EPA Method
9090 may yield misleading results consid-
ering the instability of MSW leachate and
the low concentrations of many of the or-
ganics reported in analyses of currently
produced MSW leachates.
The full report was submitted in fulfillment
of Work Assignment No. 24, Contract No.
68-03-3413, by PEI Associates, Inc., under
the sponsorship of the U.S. Environmental
Protection Agency.
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Henry E Haxo, Jr., is with Matrecon, Inc., Alameda, CA
Robert E. Landreth is the EPA Project Officer (see below).
The complete report, entitled "Compatibility of Flexible Membrane Liners and Municipal
Solid Waste Leachates" (Order No. PB91-231522; Cost: $17.00, 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 Off her can be contacted at:
Risk Reduction Engineering Laboratory
U.S. Environmental Protection Agency
Cincinnati, OH 45268
United States
Environmental Protection
Agency
Center for Environmental
Research Information
Cincinnati, OH 45268
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POSTAGE & FEES PAID
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PERMIT No, G-35
Official Business
Penalty for Private Use $300
EPA/600/S2-91/040
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