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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