United States
Environmental Protection
Agency
Hazardous Waste Engineering
Research Laboratory
Cincinnati, OH 45268
Research and Development
EPA/600/S2-86/041 July 1986
v>EPA Project Summary
Gas Characterization,
Microbiological Analysis, and
Disposal of Refuse in GRI
Landfill Simulators
Riley N. Kinman, Janet Rickabaugh, David Nutini, and Martha Lambert
The full report describes the termination
of a five-year, pilot scale project that
evaluated methane production and gas
enhancement techniques in sanitary land-
fills. Sixteen simulated landfills were con-
structed in 1980 and operated until
January 1985. Data collected during this
termination study consisted of character-
ization of the trace volatile constituents of
the gas generated by the experimental
landfills and microbiological analysis of the
refuse.
The trace volatile organic compounds
were found in higher concentrations than
previously reported in the literature.
Xylenes, ethylbenzene, methylene chlo-
ride, toluene, and benzene were found in
all of the gas samples analyzed. Xylenes
were found in greatest concentrations of
the trace compounds analyzed, ranging
from 12 mg/m3 to 500 mg/m3. The levels
and types of trace organics found in the
gas indicate that landfill gas could be
potentially corrosive and might contain
toxic levels of some compounds.
All samples had relatively high aerobic
and anaerobic plate counts, Clostridium
perfringens. and fungi levels. These same
samples indicated relatively low levels of
total coliforms, fecal coliforms, fecal strep-
tococci, and gram negative rods. Relative
numbers and types of microorganisms ap-
peared to reflect the enhancement tech-
nique applied to the cell. For example, the
highest numbers of microorganisms were
found in a cell that had a sewage sludge
enhancement.
This Project Summary was developed
by EPA's Hazardous Waste Engineering
Research Laboratory, Cincinnati, OH, to
announce key findings of the research pro-
ject that is fully documented in a separate
report of the same title (see Project Report
ordering information at back).
Introduction
Methane from sanitary landfills is a
potential source of energy that may some-
day routinely supplement declining natural
gas reserves. Currently, gas production
from the landfill is often of inconsistent
quality and is not produced in sufficient
quantities to be a reliable source of gas.
The work in the full report represents the
termination of a five-year project in which
enhancement techniques for optimizing
methane production resulting from
anaerobic decomposition were investi-
gated. The techniques investigated were
moisture addition, elevation of temper-
ature, leachate recycle, sewage sludge
addition, buffer addition, and nutrient
addition. Several years into the study, the
cells were reloaded with different or
additional enhancements. Table 1 sum-
marizes the enhancement techniques
applied to each of the test cells throughout
the project. The project clearly demon-
strated that certain enhancements can
affect gas production in terms of the quan-
tity of gas produced, the rate at which it
is produced, and the amount of methane
produced. The original project did not ad-
dress one significant problem associated
with landfill gas utilization; it is that land-
fill gas may contain trace gases that will
not support combustion and may create
problems from incomplete combustion
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Table 1. Enhancement Techniques
Test Enhancement Technique
Cell Feb. '80 - Jan. '82
Enhancement Technique
Feb. '83 - Jan. '85
20 Low Infiltration
21 Low Infiltration
22 High Infiltration
23 High Infiltration
24 High Infiltration, Leachate Recycle
25 High Infiltration, Leachate Recycle
26 High Infiltration, Leachate Recycle,
Buffer Addition
27 High Infiltration, Leachate Recycle,
Buffer Addition
28 High Infiltration, Leachate Recycle,
Nutrient Addition
29 High Infiltration, Leachate Recycle,
Nutrient Addition
30 High Infiltration, Leachate Recycle,
Buffer Addition, Nutrient Addition
31 High Infiltration, Leachate Recycle,
Buffer Addition, Nutrient Addition
32 High Infiltration, Buffer Addition
33 High Infiltration, Buffer Addition
34 High Infiltration, Nutrient Addition
35 High Infiltration, Nutrient Addition
No Change
Increase Moisture Content
No Change
No Change
No Change
Sludge Addition
No Change
Sludge Addition
No Change
Sludge Addition
Temperature Increase
Temperature Increase
No Change
Buffer Slurry Addition
No Change
Nutrient Slurry Addition
products. Therefore, one of the objectives
of this termination study was to obtain gas
samples from five of the higher gas pro-
ducing cells in order to discern the trace
volatile organic compounds present in the
simulated landfill gas.
Because methane production is a com-
plex microbial process, it was important
to determine which microorganisms were
present and were therefore actively sta-
bilizing the waste. Furthermore, the refuse
was ground before loading in the cells and
since similar microbial investigations of
unground refuse were recently reported,
the microbiology of these cells was of
special interest. The microbiological
analyses consisted of routine indicator
analyses, examination for fungi, methane-
producing bacteria, Clostridium and total
plate counts distinguishing between
aerobic and anaerobic bacteria.
Procedures
Of the sixteen original test cells, only ten
were dismantled during the course of this
project. Six cells remain active as part of
a study on gas production prevention by
lime injection. Specific cells were selected
for gas and microbiological analysis. A
summary of the cells selected for each
analysis and the final disposition of each
cell can be seen in Table 2.
All refuse was removed by hand by a
team of two researchers. The ten dis-
mantled cells were evaluated for the
overall test cell condition. The refuse was
examined to ascertain its condition after
five years of disposal and to determine if
any recognizable items survived the grin-
ding and disposal.
Five test cells were selected for gas
analysis (Table 2). One hundred ml sam-
ples were taken directly from the five lysi-
meters on two different days. These
samples were collected on Tenax traps.
Selected volatile organic compounds were
analyzed by GC/MS using EPA Method
624. The contents of the sample traps
were spiked with 5 u\ of internal stan-
dard. This internal standard was com-
posed of bromochloromethane, 1,4-difluor-
obenzene, and d5-chlorobenzene. After
the traps were spiked with the internal
standard, they were thermally desorbed
for 10 minutes at 180 °C with organic-free
nitrogen bubbled through 5 ml of organic-
free water and trapped on an analytical
trap. After the ten-minute desorption, the
analytical adsorbent trap was rapidly
heated to 180 °C with carrier gas flow
reversed so that the effluent flow from the
analytical trap was directed onto a 6-foot
glass column packed with SP-1000 on Car-
bopack B. The volatile organic compounds
were separated by temperature-
programmed gas chromatography and
detected by low resolution mass spec-
tometry. The mass of the compounds pre-
sent was calculated using the internal
standard technique.
Six of the test cells were selected for
microbiological analyses (Table 2). The
microbiological samples were collected at
two depths from each of the six cells
selected for analysis. One sample was col-
lected near the top of the refuse layer
(designated sample T) and the other was
collected near the bottom of the refuse
layer (designated sample B). The samples
consisted of five grab samples composited
to a total of about 1 kg from each sampl-
ing location. Although the refuse was
coarsely ground, some large items
Table 2. Analysis Summary and Final Test Cell Disposition
Test
Cell Micro GC/MS Disposal
20 M
21 G
22 G
23 M G
24
25 M
26 M
27
28
29
30 M
31
32
33 G
34
35 M G
D
D
D
D
D
D
D
D
D
D
Lime Injection Study
L
L
L
L
L
L
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escaped the grinding process and were
simply balled into fist-sized clumps. These
large, inert items were intentionally
avoided in the micro sampling. All micro
methods were standard methods for water
and wastewater with the exception of the
methane former analysis. This was essen-
tially a qualitative analysis in which the gas
produced by the bacteria was analyzed for
methane, indicating the presence or
absence of methane-producing bacteria.
Results and Discussion
All of the test cells were in excellent
condition. Seals were intact and the cells
were gastight. Since the refuse had been
ground before placing it in the lysimeters.
the cell contents were well mixed. No
layering or pockets of materials was noted.
Many items survived the grinding process
and were able to be identified. The arti-
facts found documented the resistance of
plastic, paper, rubber, dyes, synthetic
fabrics, bulk metal, stainless steel, wood.
glass, stone and combinations of these
materials to biological attack. Other readily
biodegradable items such as bread, corn
cobs and bits of cheese were protected
from biological activity to some extent by
plastic and paper that surrounded these
items. During the five years that the waste
was in the lysimeter, decomposition clear-
ly occurred but was relatively slow. It ap-
peared that most of the refuse placed in
the cells was still present.
Gas Analysis
Twenty volatile organic compounds
representing a cross section of potential
problem-causing compounds were
selected for analysis (Table 3). Some of
these compounds may cause corrosion of
the gas burner and others may produce
toxic end products when burned. Some
are thought to be carcinogenic or
mutagenic and may be a health threat to
landfill gas recovery personnel. All have
been repeatedly observed in landfill gas
and are considered to be characteristic
trace components at full-scale landfill
sites.
Seven of the original 20 compounds
were not found in any of the samples
taken. These were 1,1-dichloroethane,
chlorobenzene, isooctane, isopropylben-
zene, naphthalene, nonane and 1,1,2-trich-
loroethane. Three additional VOCs—
tetrahydrofuran, freon, and carbon
disulfide— were found in relatively high
levels in many samples and therefore were
included in the results. Tables 4 and 5 list
the results of the gas sample analyses.
At the time of initial loading of the test
cells, a spike of benzene, ethylbenzene.
Table 3. Target Volatile Organic Compounds
Compound Name Synonym
Pentane
Benzene
Dichloromethane
Hexane
Toluene
1, 1-Dichloroethylene
1,2-Dichloroethylene
1, 1-Dichloroethane
m,p-Xylene
o-Xylene
Ethylbenzene
Chlorobenzene
Iso-Octane
Isopropylbenzene
Propylbenzene
Naphthalene
Nonane
Trichloroethylene
1,1,2-Trichloroethane
Tetrachloroethylene
Methylene chloride
Methylbenzene
Vinyl/dene chloride
Monochlorobenzene
Cumeme
TCE
Vinyl trichloride
Perchloroethylene
Molecular Weight
72
78
85
86
92
97
97
99
106
106
106
113
114
120
120
128
128
131
133
166
Table 4. Trace VOC Concentrations, mg/mj at 25°C
Lysimeter
Sample Date
Compound
Pentane
Tetrahydrofuran
Freon
Benzene
Dichloromethane
Hexane
Toluene
1, 1-Dichloroethylene
1,2-Dichloroethylene
1, 1-Dichloroethylene
o,m,p-Xylenes
Ethylbenzene
Chlorobenzene
Iso-octane
Isopropylbenzene
Propylbenzene
Carbon Disulfide
Naphthalene
Nonane
Trichloroethylene
1,1,2-Trichloroethane
Tetrachloroethylene
* High sample volume, results
P Identified but not quantified.
2i*i 2/f
5/22/85 6/20/85
mg/m3 mg/m3
ND 6.42
ND ND
ND 67. 7
12.2 12.1
0.05 27.7
P 101
11.2 128
0.04 ND
0.99 0.54
ND ND
13.3 175
8. 78 105
ND ND
ND ND
ND ND
P 33.7
ND 67. 7
ND ND
ND ND
0.149 0.506
ND ND
0.292 ND
tend to be low.
22
6/20/85
mg/m3
0.20
0.406
0.203
1.02
0.71
1.02
20.3
ND
1.31
ND
112
24.4
ND
ND
ND
8.11
0.965
ND
ND
0.193
ND
ND
22
7/01/85
mg/m3
1.33
ND
13.3
1.05
54.1
26.4
21.1
ND
1.85
ND
118
25.1
ND
ND
ND
11.8
128
ND
ND
0.185
ND
0.146
23*
5/22/85
mg/m3
P
ND
ND
0.40
0.017
P
3.62
0.032
1.27
ND
12.2
4.58
ND
ND
ND
ND
0.018
ND
ND
0.389
ND
0.155
ND Not detected, <5 ng in sample trap.
t Waste spiked with benzene.
toluene, and ethylbenzene.
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Table 5. Trace VOC Concentrations, mg/m3 at 25°C
Lysimeter
Sample Date
Compound
Pentane
Tetrahydrofuran
Freon
Benzene
Dichloromethane
Hexane
Toluene
1, 1-Dichloroethylene
1,2-Dichloroethylene
1, 1-Dichloroethylene
o,m,p-Xylenes
Ethylbenzene
Chlorobenzene
Iso-octane
Isopropylbenzene
Propylbenzene
Carbon Disulfide
Naphthalene
Nonane
Trichloroethylene
1,1,2-Trichloroethane
Tetrachloroethylene
33
6/20/85
mg/m3
ND
0.653
1.08
1.30
2.71
1.08
33.5
ND
ND
ND
249
68.3
ND
ND
ND
ND
8.02
ND
ND
ND
ND
ND
33
7/01/85
mg/m3
ND
0.626
31.3
0.725
115
30.5
20.8
ND
0.061
ND
9.14
25.6
ND
ND
ND
3.66
112
ND
ND
0.165
ND
0.032
35
6/20/85
mg/m3
2.13
0.408
ND
0.821
0.321
2.00
48.00
ND
0.651
ND
120
97.1
ND
ND
ND
3.00
10.8
ND
ND
0.13
ND
ND
35
(duplicate)
6/20/85
mg/m3
0.90
1.08
9.71
1.18
38.4
10.7
65.2
ND
1.50
ND
513
138
ND
ND
ND
5.34
0.142
ND
ND
0.171
ND
ND
ND Not detected, <5 ng in sample trap.
and toluene was placed in cells 20 and 21.
Although this spiking was performed in
conjunction with a Ph.D dissertation rather
than directly with the five-year gas
enhancement project, it provided a basis
for comparing the gas data generated. The
three spike compounds as well as xylenes
and dichloromethane were found in all of
the samples analyzed. Xylenes were found
in the highest concentrations of any of the
VOCs determined.
All of the samples contained chlorinated
compounds. Dichloromethane, freon,
1,2-dichloroethylene, trichloroethylene and
tetrachloroethylene were found in many of
the samples. The chlorinated compounds
are of special interest, since incomplete
combustion of the compounds can pro-
duce toxic end products.
Carbon disulfide was found in varying
concentrations for all test cells, although
not in every sample analyzed. Because
carbon disulfide contains sulfur, its pres-
ence in the gas generated is also of con-
cern. Both sulfur dioxide, S02, and
sulfuric acid, H2S04 are potential decom-
position products and both are very
corrosive.
Of those compounds found, concentra-
tions were generally higher than has been
reported in the literature, primarily because
of the controlled setting in the lysimeter.
Most literature data comes from sites
where the gas releases cannot be controll-
ed, such as at large landfills or hazardous
waste sites. The landfill is constantly ex-
posed to atmospheric changes, and am-
bient air moves to and from the landfill as
pressure increases or decreases, thus
causing the gas to dilute and disperse
within the landfill. The lysimeter gas,
however, was taken directly from the test
cell piping. Therefore, there was no dilu-
tion of the sample by ambient air.
Microbiology
Before the microbiological results are
reviewed, two factors should be pointed
out relating to the original gas enhance-
ment study that undoubtedly influenced
the microbiology of the test cells. The
grinding process used to shred the refuse
involves extremely high temperatures that
can and probably did destroy some of the
microbial population. Since no microbi-
ology was performed on the original bulk
refuse or on the original shredded refuse,
the actual impact of the grinding process
could not be quantified. Second, the ex-
perimental landfills were loaded without
a clay liner on top of the refuse, as would
be found in a full-scale landfill and as is
commonly done in experimental landfill
design. This was purposefully omitted in
order to concentrate on the effects of the
enhancement technique applied; however,
the result to these lysimeters was that no
source of microorganisms was available to
reseed the refuse. Since some of the
microorganisms were undoubtedly des-
troyed in the grinding process, this lack of
a source of microorganisms probably
slowed the decomposition process and
perhaps limited the levels of organisms
found in the refuse during this study.
Microbiological analyses appeared to fall
into three distict groups. Group 1 con-
sisted of the organisms found in relatively
high numbers in all samples. The Group 1
organisms were the fungi, Clostridium per-
fringens, and both the aeraobic and
anaerobic standard plate counts. Group 2
consisted of the organisms generally
found in lower numbers and often not
found at all in the lowest dilutions an-
alyzed. This group consisted of the gram
negative rods, total and fecal coliforms,
fecal streptococci, and the clostridia, as
determined by tryptone sulfite cycloserine
agar plate counts. The last group con-
sisted solely of the methane bacteria.
The Group 1 organisms are shown in
Figure 1. The numbers and types of
organisms present in the refuse appeared
to reflect the type of enhancement applied
to the cell. This was most clearly
demonstrated in cell 25, which showed
the most dramatic change in organism
levels from the top sample to the bottom
sample. The aerobic standard plate count
from the top sample in cell 25 was the
highest count recorded in any of the
samples. The anaerobic plate count and
Clostridium perfringens counts were also
higher than in most other samples, due to
the addition of anaerobically digested
sludge at the time of cell reloading. This
would not only introduce large numbers of
organisms but also provide excellent con-
ditions for organism growth and survival.
The Group 2 organisms can be seen in
Figure 2. None of the samples had counts
for all of these organisms. In fact, cell 26
did not show the presence of any of these
organisms at the lowest dilutions used.
The traditional indicator organisms were
present only in numbers high enough to
quantify in three of the twelve samples.
The grinding process would have des-
troyed or removed many of the original
microbes, and the environment found in
the lysimeter would have been so different
from the natural environment of the in-
-------
O)
8
I
12.0
11.0
10.0-
9.0
8.0
7.0
6.0
5.0
4.0
3.0
2.0
1.0
0.0
Group 1 Organisms
C. perfringens, Plate Counts & Fungi
u C. perfringens
•*• Std. Plate Count (aer)
0 Std. Plate Count (an)
A Fungi
\\i\\\
20T20B 23T23B 25T25B 26T26B 30T30B 35T3SB
Sample Number
Figure 1. Fungi and Clostridium perfringens total plate count (aerobic and anaerobic).
Group 2 Organisms
Indicator Organisms & Clostridia
"5;
**
^
8
**.
N
5
1
-J
11.0-
10.0 -
9.0-
8.0-
7.0-
6.0-
B.O-
4.0-
3.0-
2.0 -
1.0 -
n n -
*
*
A *
+
.
^^4
\
\X
\
•f Clostridia (TSCJ A
« Gram Negative Rods
A Fecal Streptococci
x Total Coliforms
' Fecal Coliforms
^•v iiiiiiiiiii
20T20B 23T23B 2ST25B 26T26B
I 1 I 1
30T30B
I 1
35T35B
bacteria are present, then the gas produc-
ed in each test vial will contain measurable
quantities of methane. Figure 3 confirms
the presence of methane bacteria in each
of the cells analyzed.
Summary and Conclusions
Refuse and gas were sampled and
analyzed from test lysimeters being dis-
mantled upon termination of a five-year
gas enhancement study. Gas analysis for
20 selected volatile compounds indicated
the presence of many potentially harmful
compounds in relatively high concentra-
tions in some of the lysimeters. The trace
volatile organic compounds were generally
found in higher concentrations than pre-
viously reported in the literature. Xylenes
were present in the highest concentra-
tions, ranging from 12 mg/m3 to 500
mg/m3 in the samples analyzed. Chlor-
inated and sulfur containing compounds
were found in every test cell. The poten-
tial for problems arising from incomplete
combustion of these compounds com-
plicates landfill gas utilization. Microbial
populations reflected the enhancement
technique applied to the cell. Enhance-
ments that provided a suitable source or
medium for supporting microbial growth
(for instance, sludge addition) showed
higher numbers of microorganisms. Cells
with enhancements that created less
favorable conditions for microbial
survival—leachate recycle, for example —
showed fewer organisms.
The full report was submitted in fulfill-
ment of Contract 68-03-3210, Task 12, by
the University of Cincinnati under the
sponsorship of the U.S. Environmental Pro-
tection Agency.
Figure 2.
Sample
Fecal streptococci, Clostridia, and gram negative rods.
dicator organisms that conditions would
not have been amenable to survival or
growth of these populations.
The Group 3 organisms, the methane
bacteria, can be seen in Figure 3. This was
essentially a qualitative test. If methane
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Methane Bacteria Analysis
% Methane After 60-Day Incubation
50
0)
40 -
30-
20 -
10-
77!
Y /\ ' / ' /
NA 7/\YA VA V/
I ~ ~I II I ] I I II
20T20B 23T23B 25T25B 26T26B 30T30B 35T3BB
Cample Number
ZZ! 5.0 g
Figure 3. Methane bacteria after 60-day incubation.
Riley N. Kinman, Janet Rickabaugh, David Nutini, and Martha Lambert are with
Department of Civil and Environmental Engineering, University of Cincinnati,
Cincinnati, OH 45221,
Joseph K. Burkart is the EPA Project Officer (see below).
The complete report, entitled "Gas Characterization, Microbiological Analysis and
Disposal of Refuse in GRI Landfill Simulators, "(Order No. PB 86-179 504 /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 Research Laboratory
U.S. Environmental Protection Agency
Cincinnati, OH 45268
-------
United States
Environmental Protection
Agency
Center for Environmental Research
Information
Cincinnati OH 45268
Rill K RATF
Official Business
Penalty for Private Use $300
EPA/600/S2-86/041
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