United States
Environmental Protection
Agency
Hazardous Waste Engineering
Research Laboratory
Cincinnati OH 45268
Research and Development
EPA-600/S2-84-171 Jan. 1985
Project Summary
Feasibility of Using Chemical
Liners for Landfilling Electro-
plating Sludges
H. Tan Phung, S. P. Shelton, P. Pagoria, and K. V. LaConde
Various chemical liners were eval-
uated for use in a segregated
monolandfill for the disposal of elec-
troplating wastewater sludges. The
tests were conducted in an unused por-
tion of a secure landfill in South
Carolina.
Seven cells were constructed, each
2.4 m (8 ft) square and 1.8 m (6 ft) deep.
One cell was reserved as a control, and
the other six were used as replicate test
cells. Agricultural limestone, hydrous
oxides of iron, and fly ash were each
used to line two test cells. The control
cell was lined with sand. All seven cells
were then filled with sludges from the
treatment of electroplating wastewa-
ters.
Leachate was collected under a CO2
environment from below the cells ap-
proximately once a month for 2Vi years
and analyzed to evaluate the capacity
of the liners to retain heavy metals
leached from the sludges. After the last
leachate samples were collected in Au-
gust 1982, each cell was core-sampled
to assess the vertical distribution of
selected metals in the sludge, the liner
and the soils.
The concentrations of metals and sol-
uble salts in the leachate varied widely
during the first 12 to 15 months then
leveled off. The leachate concentra-
tions of the various metals did not ap-
pear to be related to levels found in the
sludges. The volume of leachate col-
lected indicated the permeabilities of
the liners and did not correlate with
rainfall.
The limestone and hydrous-oxides-
of-iron appeared to retain more metals
than did fly ash, but no significant
metal leaching was observed in any of
the test cells. The excavated sludges
showed characteristics similar to the
raw sludges originally deposited. Be-
cause only small amounts of metals
were leached from the sludges, the
overall relative performance of the
liners cannot be judged from this study.
Hydrous oxides of iron (derived from
ferric sulfate) would probably be pro-
hibitively expensive for this applica-
tion, however.
More studies will be needed before
chemical liners can be applied to the
full-scale landfilling of metal-finishing
sludges.
This Project Summary was de-
veloped by EPA's Hazardous Waste En-
gineering Research Laboratory, Cincin-
nati, Ohio, 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
The metal-finishing industry gener-
ates a variety of wastewater streams
containing acids, cyanides, hexavalent
chromium, and other heavy metals.
These wastewater streams are gener-
ally treated separately to remove these
hazardous constituents or to convert
them to less hazardous species. Con-
tinued emphasis on wastewater treat-
ment and reduced effluent discharges
are expected to increase the future
quantities of wastewater treatment
sludges.
Several relatively new hazardous
waste management technologies (e.g.,
chemical fixation, encapsulation, and
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metal recovery) have been proposed for
electroplating sludges, but none is suffi-
ciently developed to be used on a wide
scale. The prevalent disposal method
has been to bury the sludge in a sani-
tary landfill or in a segregated, secure
landfill.
As part of the regulatory effort under
the Resource Conservation and Recov-
ery Act of 1976 (RCRA), the U.S. En-
vironmental Protection Agency (EPA)
directed specific studies of technologies
for the disposal and recovery of elec-
troplating sludges in 1978. Since these
sludges have a potential for future met-
als recovery, emphasis was placed on
developing an environmentally accept-
able, cost-effective disposal method to
facilitate potential recovery. The ap-
proach was to test selected inexpensive
yet promising chemical liners that could
be used in a segregated monolandfill.
The liner concept in the present study
is not related to reduced permeability.
Rather, the chemical liner serves as a
filter for hazardous constituents, par-
ticularly heavy metals. These metals
will be retained either in the metal
sludge or in the liner so that they can
be retrieved or recovered once the tech-
nology proves cost effective and envi-
ronmentally sound.
This field study has two objectives:
1. To determine the effectiveness of
using various inexpensive or waste
materials to line disposal sites for
metal hydroxide sludges, and;
2. To prepare a conceptual design
(including cost estimates) of a full-
scale disposal site using such
liners.
Before the field study began, a literature
review was conducted to gather data on
chemical liners for leachate control.
Materials and Methods
Test Site
A test site was selected in the north-
west quadrant of a secure landfill in
South Carolina. The landfill is situated
in an open-pit opal claystone mining
operation. The area generally has a
mild, humid climate, with normal
Fahrenheit temperatures ranging from
the low 90's in the summer to the 30's
in the winter. Average annual precipita-
tion is just under 119 cm (47 in.) and is
fairly evenly distributed throughout the
year. Average annual evapotranspira-
tion ranges from 91 to 99 cm (36 to 39
in.).
Test Cells
Seven test cells were constructed,
each 2.4 m (8 ft) square and 1.8 m (6 ft)
deep (Figure 1). One cell was reserved
as a control, and the other six were
used as replicate test cells.
Agricultural limestone, hydrous
oxides of iron, and fly ash were each
used to line two test cells. The control
cell was lined with sand. This chemical
liner layer was 30 cm (11.75 in.) thick, a
size selected to allow the liner to filter
the leachate as it passed through and
yet retain the heavy metals and other
hazardous constituents.
Beneath the chemical liner layer were
(1) a layer of bank sand to prevent mi-
gration of chemical liner particles
through the gravel layer below and into
the leachate collection device, (2) a
layer of crushed gravel to support the
chemical liner and facilitate the vertical
flow of leachate toward the collection
device, and (3) a 20-mil polyvinyl
chloride (PVC) liner covering the cell's
bottom and sides to contain any
leachate that might pass through the
chemical liner.
Above the chemical liner was a 76-cm
(30-in.) layer of sludge and a 30-cm (14-
in.) layer of cover soil to simulate actual
landfill conditions.
Chemical Liner Materials
Agricultural Limestone
Agricultural limestone was purchased
from a local distributor. Eighty-one per-
cent of the limestone particles passed
U.S. Sieve No. 8 (0.0937 in.). Crushed
limestone is commonly used to neutral-
ize acidic agricultural soil. As a test
liner, it was expected to neutralize or
retard the formation of acidic leachates
that might mobilize cationic metal
species. Limestone has been used in
such applications at several sludge dis-
posal sites, but little field research has
been done to confirm its expected util-
ity. Thus it was included as a test liner
in this study.
Hydrous Iron Oxides
The hydrous oxides of iron were pre-
pared by mixing an oven-dry, reagent-
grade ferric sulfate with sand at 5 per-
cent of the mixture, resulting in a mix-
ture with a pH of 6.3 and total iron of
0.17 percent. Hydrous iron oxides were
recommended for field trial as a sludge
disposal liner because of their estab-
lished role as scavengers of heavy
metals in soils and water. They are also
inexpensive and readily available.
These factors combined to make iron
oxides an attractive second test liner.
Fly Ash .
Fly ash was obtained from the South "
Carolina Electric and Gas Company of
Lexington, South Carolina. The pH was
6.8 and it contained 2.49 percent
aluminum, 0.01 percent iron, 0.46 per-
cent calcium, 100 ppm manganese, 270
ppm boron, 22.6 ppm arsenic, and 1.4
ppm selenium. Basic fly ash is a by-
product of burning coal for energy and
is thus widely available as a waste prod-
uct. Fly ash contains lime and iron
oxides (which retain trace metals) and
tend to be basic (which favors attenua-
tion of most heavy metals). Despite its
potential as an attenuating liner, fly ash
has not been extensively studied for
this application and was, therefore, con-
sidered an ideal candidate for these
field tests.
Sludges
All seven cells were filled with
sludges from the treatment of electro-
plating wastewaters. Chemical charac-
teristics of the two metal hydroxide
sludges used appear in Table 1. Both
sludges were alkaline (pH 8.8 to 9.1),
but they differed as to metal concentra-
tions, color and moisture content.
Leachate Collection and
Analysis
Leachate was collected under a CO2
environment from below the cells ap-
proximately once a month for 2'/2 years
and analyzed to evaluate the capacity
of the liners to retain heavy metals
leached from the sludges. Each sample
was analyzed for pH, electrical conduc-
tivity (EC), cyanide, boron, arsenic,
selenium, mercury, chromium (III),
chromium (VI), cadmium, nickel, cop-
per, iron, manganese, lead, and zinc.
The samples were also analyzed selec-
tively for. selenium, cyanide, boron and
mercury.
Core Sampling
After the last leachate samples were
collected in August 1982, each cell was
core-sampled through the various
layers in the cells to assess the vertical
distribution of selected metals in the
sludge, the liner and the soils.
Conclusions
The following conclusions can be
drawn from the results of the field
study:
1. The metal hydroxide sludges
showed no significant leaching of
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4" PVC Pipe
Cover Soil
Cover
Soil: 36 cm
Sludge: 76 cm
Liner: 30 cm
Banksand: 15 cm
Gravel: 30 cm
View of
Well Screen
Section
Banksand
Crushed Gravel
Figure 1. Test cell design (not to scale).
Parameter
PH(1:1)
Cr (Total)
Fe
Ni
Zn
Pb
Cu
B
Mn
Hg
Cd
Se
Wolverine Brass'
8.8
(%) *
2.71
0.70
1.16
1.57
0.16
2.06
0.13
(mg/lcg) «
56.0
23.0
3.8
Crescent Tool*
8.8-9.1
0.002
3.60
2.00
0.73
0.28
650
1.0
6.5
'Analyzed by the Environmental Engineering Laboratory, University of South Carolina.
'Date obtained from Department of Health and Environmental Control, Columbia, South
Carolina.
* Oven-dry weight basis.
3.
heavy metals. The excavated
sludges exhibited characteristics
similar to the raw sludges origi-
nally deposited.
The pH, soluble salts, and metal
concentrations of leachate fluc-
tuated in the first 12 to 15 months
but leveled off thereafter. The con-
centrations of various heavy met-
als in the leachates were not re-
lated to their initial concentrations
in the sludges.
The largest volume of leachate
was collected from the limestone
cells and the smallest volume from
the fly ash cells. These volumes in-
dicated the permeability of the
chemical liners and were not di-
rectly correlated with the amounts
of rainfall.
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Table 2. Metal Retention in the Three Chemical Liners
Liner pH Fe Ni Zn
Mn
Pb
Cd
Cu
Cr+s
c/-+3
Hg
ma/ka*
Control
Limestone
Fly Ash
Iron Oxide
7.1
7.9
6.0
(6.8f
7.1
237
248
7,442
(6,212)
195
0.86
17.2
22.7
(17.4)
60.9
0.96
8.15
31.5
(25.8)
37.0
2.06
97.8
45.4
(100)
1.84
0.27
18.1
15.5
(21.2)
3.51
0.02
2.01
0.42
0.18
9.75
12.8
46.0
(36.3)
32.0
0.13
0.17
0.10
0.17
2.4
3.7
24.8
(8.46>
42.4
NAr
0.36
0.04
NA
"Concentrations are expressed on an oven-dry weight basis, and except for the control, they are averages of two replicate cells.
* Concentrations in fly ash before placement in cells. Chromium value is total Cr.
rNot analyzed.
4. Limestone and hydrous oxides of
iron appeared to have higher
metal retention capacities (Table
2) than did fly ash. But because of
the insignificant leaching of metals
from the sludges and the resulting
low metal concentrations mea-
sured in the chemical liners, the
performance of these liners cannot
be judged adequately in this study.
In addition, the integrity and
longevity of the three chemical lin-
ers cannot be determined from the
laboratory data observations dur-
ing cell excavation.
5. Large quantities of iron were re-
leased from the iron oxide cells,
resulting in iron enrichment of
leachate.
6. The costs of the chemical liners ac-
count for the cost differences in
full-scale landfill operations using
these liners. The cost of using hy-
drous oxides of iron (derived from
ferric sulfate) as a chemical liner
would be prohibitive.
Recommendations
Additional studies are recommended
before chemical liners are applied to the
full-scale landfilling of metal-finishing
sludges. The studies may include the
following:
— The arrangement and thickness of
different materials in the cell with
respect to maximum metal ret«J
tion.
— The leachability of metals
troplating sludges of lo1
than those used in this stud
— Protection for and stability of side
slopes in landfill cells lined with
chemical liners.
— Assessment of the permeabilities
of various liner materials under
placement (compaction) and
chemical conditions.
The full inpiirt ¥>irf , ciiK»rr|ittaH in fy||-
ent of eonrraeMUa^fift 01 BflRaiiv -
Engines
of the.
Agency
H. Tan Phung, S. P. She/ton. P. Pagoria, and K. V. LaConde are with SCS
Engineers, Inc., Long Beach, CA 90807.
Robert E. Landreth is the EPA Project Officer (see below).
The complete report, entitled "Feasibility of Using Chemical Liners for Landfilling
Electroplating Sludges," (Order No. PB 85-117 091; Cost: $11.50, 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:
Hazardous Waste Engineering Research Laboratory
U.S. Environmental Protection Agency
Cincinnati, OH 45268
•fr U S GOVERNMENT PRINTING OFFICE, 1985 — 553-016/7891
United States
Environmental Protection
Agency
Center for Environmental Research
Information
Cincinnati OH 45268
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Penalty for Private Use $300
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