United States
Environmental Protection
Agency
Hazardous Waste Engineering
Research Laboratory
Cincinnati OH 45268
Research and Development
EPA/600/S2-86/074 Dec. 1986
Project Summary
Testing and Evaluation of
Permeable Materials for
Removing Pollutants from
Leachates at Remedial
Action Sites
James E. Park
In order to better understand the poten-
tial effectiveness of permeable treatment
systems, four readily available, low-cost
permeable materials — limestone, coal, fly
ash, and a soil containing clay — were
bench-tested to determine their ability to
remove organic pollutants from two simu-
lated hazardous waste leachates. The
capabilities of various sequentially ordered
layers of these materials were evaluated
with respect to their ability to retain total
organic carbon (TOO and twelve selected
priority pollutants. As a result of testing,
the most effective ordering of materials
was found to be a layer of fly ash, followed
by a layer of coal, followed by a layer of
limestone. Conceptual designs for three
field-scale permeable treatment systems
were developed using the results of the
bench-scale experiments.
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
As the number of hazardous waste sites
requiring remedial action increases, tech-
nological alternatives that not only enclose
sites, but mitigate contamination will
become increasingly popular. One such
alternative might use permeable materials
in systems designed for the retention of
pollutants from hazardous waste leach-
ates. These permeable treatment systems
could be designed as vertical treatment
walls or horizontal treatment beds. In the
former case, the treatment wall would par-
tially or totally encircle a site in a manner
similar to a slurry trench, retaining pollu-
tants as leachates moved through the wall.
In the latter case, the treatment bed would
be used to pretreat pumped leachate prior
to its release to an industrial or municipal
wastewater treatment plant.
In order to determine the feasibility of
the above remedial action alternative, a
study was initiated by the U.S. Environ-
mental Protection Agency. Two goals were
set for this study. The first was to test four
readily available, low-cost permeable
materials — limestone, coal, fly ash, and
a soil containing clay — for their ability to
retain the organic pollutants in two simu-
lated hazardous waste leachates. Various
combinations of the materials, ordered in
sequential layers, were tested, and their
interactions with selected organic pollu-
tants were measured to determine individ-
ual and collective performance character-
istics of the materials. The second goal of
the study was to develop conceptual
designs for three field-scale permeable
treatment systems.
Procedure
The choice of permeable materials was
based on their estimated ability to retain
pollutant concentrations, as well as their
local availability. Natural or waste materials
were judged to have an apparent cost ad-
-------
vantage over such man-made materials as
activated carbon or ion exchange resins.
For this reason, readily available, low-cost
materials were tested. Coal was obtained
from a mine near Stinson, KY, limestone
from a local dealer, fly ash from the Miami
Fort Power Plant near Harrison, OH, and
soil from northern Hamilton County near
Cincinnati, OH. The particle size distribu-
tions for each of these materials are
shown in Figure 1.
The materials were placed in twelve
20.3 cm x 20.3 cm cross-sectional col-
umns. Layer thicknesses were chosen for
comparative purposes of volume, 20 cm
being twice the volume of 10 cm; 6 cm
layers were used mostly for limestone. The
total height of all columns was 36 cm. The
layer orderings used for both experimen-
tal runs are shown in Figure 2. The feed
for each run was common to all columns.
Porous stones connected to external sam-
ple ports were placed between each layer
and at the bottom of each column. These
allowed the TOC concentration to be
monitored daily as the simulated hazard-
ous waste leachate flowed through the
materials in the 12 columns.
Two different simulated leachates were
used in the test. Since organics were of
primary concern, total organic carbon
(TOC) analysis was used as a measure of
their presence in both Runs #1 and #2.
Gas chromatographic (GO analysis for 12
spiked priority pollutants was performed
on the effluents from Run #2 to provide
an indication of their relative mobilities.
The first simulated leachate consisted of
experimental solid waste lysimeter
leachate spiked with phenol and dichloro-
benzene at 400 mg/L and 80 mg/L,
respectively. The TOC level for Run #1
began at 2500 mg/L and decreased to
400 mg/L by the end of the run. Average
column feed concentrations for this run,
based on daily feed volume and average
daily TOC concentration ranged from 1115
mg/L to 1596 mg/L. The simulated leach-
ate for Run #2 was prepared daily and
consisted of 0.1NCaSO4, 850 mg/L po-
tassium hydrogen phthalate (KHP), 100
mg/L toluene and the priority pollutants
listed in Table 1. The average TOC was
421 mg/L.
Calculations of the retentive capacities
were made from the breakthrough curves
for each column. Retention was inter-
preted as the amount of the pollutants, in
this case represented by TOC, that re-
mained on a given amount of material
(mg/kg dry wt). Knowing the total TOC
input and output, the difference is retained
by the permeable materials. Typical
100
80
60
40
20
Fly Ash
Limest.
100
10
1
.1
.01
.001
Figure 1.
mm Diameter
Particle size distributions for permeable materials.
F
L
S
F
L
S
C
L
S
1
C
L
S
F
C
S
F
C
S
Table 1. Priority Pollutants in Feed #2
Actual Con
10
11
12
C
L
S
C
F
L
S
S
L
F
S
L
C
F
C
Bisl2-ethylhexyl)Phthalate
Di-N-Butyl Phthalate
1,4 Dichlorobenzene
2,4 Dichlorophenol
Ethylbenzene
Fluoran thene
Isophorone
Pen tachlorophenol *
Phenanthrene*
Phenol
Pyrene
Naphthalene
163
128
192
109
261
129
120
136
115
135
137
C—Coal F—Fly Ash
S—Soil L—Limestone
Figure 2. Orderings of materials in col-
umns.
examples of breakthough curves are
shown in Figures 3 and 4. The cumulative
flow volume and the TOC concentration
were normalized to the total flow for each
column and the maximum TOC concentra-
tion for each experiment. The areas be-
tween each curve are proportional to the
amount of TOC retained by each layer of
the column. The total amount of pollutants
* These two compounds could not be
distinguished in the analytical procedure.
retained was found by summing the re<
tangular areas between data points.
The overall effectiveness of the orde
ings of materials were comparted by rani
ing four column results: 1) The number <
days until 50% breakthrough, 2) the tot
TOC retained, 3) the linear flow velocil
and 4) the calculated permeability coefl
cient. The first two results are measure
of retention, while the last two are inc
cative of flow. The most effective colurr
then should have both high retention ar
flow.
-------
Run ft 1
Column S
£S
o
.2
Figure 3.
.4 .6
Flow Vol.
Typical breakthrough curve. Run ttl. Column 5.
1.0
Results and Discussion
The retentive capacity results for the
individual permeable material layers are
shown in Figure 5. The range and average
values for the pollutants retained during
the two simulated leachate runs are pre-
sented in Table 2. Coal retained the most
TOC per unit weight in both runs. The soil,
containing about 20% clay-sized particles
retained a large amount of pollutants in
Run #1 and slightly less in Run #2. The fly
ash retention results are similar for both
runs, indicating its retentive capacity may
not be related to strong adsorption reac-
tions. Limestone retained very little of the
organic pollutants, although it did precip-
itate iron eluted from the coal. Rust
colored layers in the limestone were clearly
visible when a coal layer was located
above a limestone layer.
Batch elution tests were run using 300
ml of 0.1NCaSO4 and 50 g of the
concentration-saturated materials from
Run #2. The elution values (mg/kg dry wt.)
are included in Figure 5, in parentheses.
In the case of fly ash, all the retained TOC
was eluted, supporting the contention that
fly ash is not a strong adsorber. The coal
held as much as half the retained TOC
following elution, while the soil elution
results were mixed, most samples eluting
all the retained TOC with a few holding up
to 30%. Thus, coal was the only material
exhibiting relatively strong adsorbtion
capabilities.
The rate of flow through the layers
influenced retention by the permeable
materials. The porosity of the coal layers
allowed rapid movement of TOC. Columns
3 and 7, with 20 cm of coal on the top in
Run #1, provided less retention than the
coal layers in the other columns. Limiting
the flow through the coal by a less perme-
able layer above it, as in Column 6, ap-
peared to increase the retentive capability
of coal. The 20 cm layers of soil in Col-
umns 2 and 4 inhibited flow, while the fly
ash in Columns 1 and 5 only moderated
the flow. In order to better understand the
permeability of the materials used, perme-
ameter tests were run and the results are
shown in Table 3 for coal, fly ash, and soil.
Limestone was not tested in the perme-
ameter since it was a uniformly distributed
granular material that was not expected
to effect liquid flow rates when in com-
bination with the other materials.
The results of the GC analyses for Run
#2 are presented in Table 4. The majority
of the occurrences of the 12 priority pol-
lutants in the effluents were at lower levels
than in the simulated leachate feed. Gen-
erally, even when a compound was
detected at a concentration greater than
100 fjig/L in a sample, it would not be
detected in the subsequent sample. The
detected compounds appeared predomin-
ately in discrete cases. Phenanthrene,
fluoranthene, dichlorophenol, pyrene and
pentachlorophenol were either undetected
or appeared at concentrations less than 20
M9/L. These compounds would be less
likely to migrate than the other com-
pounds listed in Table 1.
The four criteria used for evaluating col-
umn performance were: 1) the number of
days to 50% breakthrough, 2) the total
TOC retained, 3) the linear flow velocity,
and 4) the calculated permeability coeffi-
cient. As previously mentioned, the first
two results are measures of retention,
while the last two results are indicative of
flow. The best performing column then
would have both high retention and high
flow. The overall rankings for performance
were found by assigning numerical values
(1 through 12) to each of the columns for
each of the four results. For example, in
Run #1 Column 12 retained the most TOC
so it was given a "1" ranking, while Col-
umn 7 retained the least and received a
rank of "12." The four ranked results were
then added and the totals ranked again,
1 through 12. The original rankings were
also multiplied together; these products
were then ranked. The additive and multi-
plicative rankings were then added to-
gether. The overall rankings were deter-
mined from these numbers. The additive
and muitiplicative methods were combined
in order to afford better resolution when
two or more columns were closely ranked.
The results are presented in Tables 5 and
6. The overall rankings are indicative of the
responses of the columns to the simulated
leachates used in the two runs. Since the
soil used in the test hindered flow, espec-
ially in Columns 2 and 4, these columns
received lower rankings despite long times
-------
Run #2
Column 5
o
o
.2
Figure 4.
0 .2
Flow Vol.
Typical breakthrough curve. Run #2, Column S.
.8
1.0
to breakthrough. Columns 3 and 7, with
20 cm coal layers, performed poorly in Run
#1 due to high permeability and possible
channelling.
Considering the results of Run #2, the
most appropriate layer orderings were
found in Columns 5 and 6, with fly ash
above a coal layer. Ranked next was Col-
umn 3, which did not repeat its perfor-
mance from Run #1. Column 8 also ranked
high, and exhibited the least occurrences.
of priority pollutants in its effluent. Based
on the results of Run #2 and indications
from Run #1, the most appropriate order-
ing of these materials would be a top layer
of fly ash for flow moderation, followed by
a coal layer as the primary retaining
material, then a limestone layer to adjust
pH and precipitate the iron leached from
the coal.
Conceptual Designs
The secondary goal of this project was
to develop conceptual designs for apply-
ing the permeable materials concept to a
field site. Three such conceptual designs
were developed. The site utilized for this
exercise was a National Priority List (NPL)
site in the Pacific Northwest which had
been characterized both geologically and
hydrologically and for which a reasonable
amount of background environmental data
was available. This site, however, should
not necessarily be construed to be a can-
didate for installation of a permeable treat-
ment system.
The first conceptual design was a down-
gradient permeable treatment barrier in-
tended to retain all pollutants. The second
and third designs make use of a down-
gradient collection system. The second
design incorporates the ability to flush
contaminants from the permeable material,
while the third design is a modular, re-
placeable permeable treatment system.
Only the first conceptual design is
presented in this summary.
The goal of this design is to intercept the
contaminated ground water from the site
with a vertical barrier of permeable mate-
rials for a specified time. Two years wa
chosen based on the large ground-watt
flow and the likelihood of rapid flushing c
organics.
The primary design calculation was the
of the thickness of the permeable barrie
Since the design is for the treatment c
organics, and coal was determined in th
laboratory tests to retain the most orgar
ics (as TOO, the assumption was mad
that the coal portion of the barrier mus
retain the full organic load for 2 years. Th
other materials would then serve to pr<
vide a margin of safety.
The TOC load per day/m2 was found b
multiplying the flow times the concei
tration:
34.5 L/day/m2 (flow per day) x
40 mg/L (average TOC cone.) =
1380 mg TOC/day/m2
Coal's retentive capacity = 400 mg TO
per Kg coal
Dividing the load by the retentive capacit
_ 1380 mg TOC/day/m2 _
400 mg TOC/kg coal
3.45 kg coal used per day
Coal's density in a barrier would h
approximately 900 kg/m3 or 9.0 kg pi
linear cm in a cubic meter.
Dividing the daily coal usage by the line;
density:
3.45 kg coal/day
= .38 cm/day
9.0 kg/cm
This is the amount of coal completel
used in retention each day. Over two yeai
then, 2.8 m of coal would be required (73
days x .0038 m).
Figure 6 shows a plan view of the s'n
with the location of the permeable trea
ment barrier. A cross-sectional schemat
shows the design dimensions chosei
Allowing a margin of safety, 3.0 m of co
would be used. The fly ash serves 1
moderate the flow as well as provic
additional retention. The limestone w
increase the pH of the groundwater as
passes from the coal. The thicknesses (
the fly ash and limestone are proportion
to the layers that were tested in the bencl
scale project.
The permeable materials would be plac
in a trench 5.0 m deep with approximate
2.0 m of freeboard to allow for rises in tr
water table and yet still provide treatmer
Calculations based on in-place densitic
indicated the weights of the three mat
rials needed would be: coal, 6.7 x 106 k
limestone, 5.5 x 106 kg and fly ash, 3.9
106 kg. It would also be advisable 1
cover the barrier with an impermeab
layer to prevent infiltration.
-------
All Values are mg/kg
L = Limestone
C = Coal
F = Fly Ash
S= Soil
F
144
~ro~
S 732
F
261
L87
S
428
C
116
L311
S574
C 629
i- o
S
208
F
115
C
1115
S418
F
147
C
617
so
C
115
L
0
C
1605
F
412
L
0
0 | C
J033\ 562
S
358
L
0
F 548
S
660
L
0
C1535
F
372
C
870
10
11
12
Run ft 2
All Values are mg/kg
( )-Elution
L = Limestone
C = Coal
F = Fly Ash
S= Soil
F
293
(334)
L 33
S203
(363)
F319
(323)
L 35
(309)
S
172
(379)
C
776
(291)
L 0
(287)
S145
(341)
C
467
(351)
L 98
(287)
S
177
(335)
F
360
(350)
C 452
(397)
S 140
(399)
F373
(376)
C
427
(459)
5555
(362)
1 23456
C
535
(222)
L o
(262)
S689
(403)
7
C 364
(294)
F377
(421)
L66
(298)
S
345
(356)
Lo
(270)
S715IF 0
(390} (427)
S
339
(441)
L 21
(341)
C 32
(544)
F
215
(348)
C
463
(237)
8 9 10 11 12
• The most effective ordering sequence
considering the permeable materials
and the simulated hazardous waste
leachate used was a layer of fly ash, fol-
lowed by a layer of coal, followed by a
layer of limestone.
• The experiments helped establish the
efficacy of the concept of using per-
meable materials, but the test appara-
tus is inefficient for rigorous testing.
The second run lasted 47 days and con-
sumed almost 700 L of feed.
Given the results and the observations
made during this project, the following
recommendations are offered.
• A scaled-down, bench test system
should be developed that would provide
results faster than the 30-47 days
required for the experiments performed
for this project. The results from this
new system should be verified by com-
parison with the previously performed
work.
• Various solutions for flushing contami-
nants from the retentive materials
should be tested followed by an as-
sessment of the flushed permeable
materials' retentive capacities. This
would provide information on the utility
of flushable permeable treatment
systems.
• The design and testing procedures for
permeable materials should be demon-
strated by installing and evaluating a
pilot-scale or larger permeable treat-
ment system. Installation at a remedial
action site should be considered.
Table 2. Average Retention Capacities
Run #1 (2500-400 mg/l TOO
Coal
Limestone
Fly ash
Soil
813 mg/kg
0
286 mg/kg
552 mg/kg
Run #2 1421 mg/l TOO
Coal
Limestone
Fly ash
Soil
498 mg/kg
32 mg/kg
323 mg/kg
348 mg/kg
RANGES
(1267 - 473)
(87 - 0)
(548 - 115)
(1033 - 208)
RANGES
(776 - 364)
(98 - 0)
(377 - 215)
(715 - 140)
Table 3. Permeability Results (cm/sec)
Coal
Fly Ash
Soil
1.8- 5.6 x 10~4
5.3 - 7.0 x 10~5
1.7 x 10~4 - 3.5 x
10
-5
Conclusions and Recommendations
• The results of this project showed that
low-cost permeable materials such as
coal, limestone, fly ash, and soil con-
taining clay can retain contaminants
from simulated hazardous waste leach-
ates. Using total organic carbon (TOO
as an indication of the presence of
organic contaminants, coal retained
498-813 mg TOC/kg, fly ash 286-323
mg TOC/kg, limestone 0-98 TOC/kg,
and a soil containing clay 348-522 mg
TOC/kg.
• The priority pollutants spiked into the
feed of Run #2 exhibited various rela-
tive mobilities. Dichlorophenol, phenan-
threne, pentachlorophenol, fluoran-
thene and pyrene had limited mobility,
while Bis (2-ethylhexyl) phthalate, Di-
N-Butyl phthalate, phenol, 1,2, dichloro-
benzene, isophorene, napthalene and
ethylbenzene moved through the col-
umns at the same rates as measured by
the TOC data.
-------
Table 4. Run #2 Priority Pollutant G.C. Analyses
Total Occurences
Column Occurences >100 \tg/L Compounds >100 \tg/L
1
2
3
4
5
6
7
8
9
10
11
12
30
25
21
13
17
16
20
10
21
14
14
13
2
1
1
1
1
3
5
0
5
3
4
3
Dibutylphthalate, Phenol
Phenol
Bis(2-ethylhexyl) Phthalate
Phenol
Bis(2-ethylhexyll Phthalate
Phenol (2), Bisl2-ethylhexyl) Phthalate
Phenol (2), 1, 2 Dichlorobenzene, Bis(2ethyl. . . )
Dibutylphthalate
Bis(2-ehtylhexyl) Phthalate (2), Phenol,
Isophorone, Dibutylphthalate
Napthalene, Dibutylphthalate, Ethylbenzene
Bis(2-ethyl. . . ), Dibutylphthalate 12),
Ethylbenzene
Bis(2-ethyl. . . ), Dibutylphthalate (2)
( ) Indicates more than one occurrence.
Table 5.
Column
1
2
3
4
5
6
7
8
9
JO
11
12
Run #1 Column Performance
Total
Flow (L)
7.18
6.66
6.79
3.93
8.95
7.74
6.47
9.22
6.21
9.23
8.08
8.92
Total rOC
Retained
Img)
6377
7839
5709
5247
7299
6103
5177
10493
6567
11683
7900
12274
Days to 50%
Breakthrough
16
18
9
19
11
12
7
11
12
18
19
7
Linear
Velocity
(cm/day)
19.3
17.2
10.2
7.5
18.8
12.4
9.2
21.4
27.8
23.5
9.4
22.2
Permeability
(cm/day)
.78
.73
.96
.41
.98
.85
.91
1.01
.68
.95
.84
.97
Overall
Ranking
8
6
11
10
4
9
12
2
7
1
5
3
Table 6.
Column
1
2
3
4
5
6
7
8
9
10
11
12
Run #2 Column Performance
Total
Flow (L)
15.86
12.38
25.78
11.86
23.99
24.02
26.12
28.40
74.35
16. 12
17.OO
29.44
Total rOC
Retained
(mg)
4448
3857
7064
4310
6146
7525
6810
7006
3796
3911
4374
6533
Days to 50%
Breakthrough
26
39
30
47
16
37
19
20
13
14
28
15
Linear
Velocity
(cm/day!
34.5
21.7
13.8
8.8
60.5
41.2
14.8
16.0
23.3
25.9
31.1
8.2
Permeability
(cm/day)
.84
.52
1.12
.50
1.47
1.01
1.10
1.19
1.36
1.00
.77
1.23
Overall
Ranking
5
9
3
8
2
1
7
4
11
12
6
10
-------
Direction of Groundwater Flow
Plan View
N
Groundwater
Level
Groundwater
Flow
Detail A-A
Figure 6. Conceptual design 1: boundary barrier.
-------
James E. Park is with the University of Cincinnati, Cincinnati. OH 45221.
Jonathan G. Herrmann is the EPA Project Officer (see below).
The complete report, entitled "Testing and Evaluation of Permeable Materials for
Removing Pollutants from Leachates at Remedial Action Sites," (Order No. PB
86-237 708/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
Official Business
Penalty for Private Use $300
EPA/600/S2-86/074
\
U.S.OFFSGfALM/
U.S,Pfi$W
= 0 .3 2
0000529 PS
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