United States
Environmental Protection
Agency
Municipal Environmental Research
Laboratory
Cincinnati OH 45268
Research and Development
EPA-600/S2-81-163 Sept. 1981
Project Summary
Field Investigation of
Contaminant Loss from
Chemically Stabilized
Industrial Sludges
Four sites where stabilized industrial
wastes had been disposed were exam-
ined to determine the effects of stabi-
lized waste sludges on surrounding
soils and groundwater. All areas se-
lected for study were in the humid
eastern or southern United States
where rainfall was sufficient to pro-
duce abundant leachate. The sludges
had all been fixed using the same
proprietary process involving addition
of cementitious materials to form a
stable, soil-like product. Two of the
industrial waste sites contained auto
assembly (metal finishing) wastes,
one site contained electroplating
wastes, and the fourth site contained
refinery sludges. A randomization
procedure was used to determine if
consistent, significant differences
existed between samples from under
and outside the waste disposal area.
The physical properties of soils
under the disposal sites were affected
little, if at all, by the disposal operation.
No major changes in the soils' dry
density, water content, hydraulic
conductivity, or percent fines could be
detected.
At one of the auto assembly waste
disposal sites, high background levels
of certain groundwater constituents
masked any escape of pollutants from
the fixed sludge. Elevated levels of
chloride, calcium, and sodium were
found in groundwater under and down
gradient from the disposal area at the
second auto assembly plant. Only
elevated levels of sulfate and boron
were found under and down the
groundwater gradient from the electro-
plating waste site. Elevated levels of
sulfite, nitrite, cyanide, phenols, and
arsenic were noted in groundwater
under and down dip from the disposal
area at the refinery site. Toxic metal
contamination in groundwater was
not a serious pollution problem at the
sites studied at the time of the survey.
Soils beneath treated autoasse/nbly
wastes disposed at two locations
showed elevated levels of manganese,
sodium, and selenium. Soils beneath
treated electroplating waste showed
elevated levels of iron, sodium, mer-
cury, and nickel. At one location
where treated oil refinery waste was
disposed of,! no significant soil con-
tamination was detected. Even in
contaminated soils, the levels of the
determined constituents were well
within the ranges reported for natural
soils.
Distilled water extracts of soils
collected beneath the stabilized wastes
and at comparable elevations outside
the site showed appreciable contrasts
in chemical composition. Some poten-
tial pollutants in extracts from sub-
waste soils were present in consistently
larger quantities than in background
soils. Chromium, lead, and selenium
were found in some extracts at levels
above those considered acceptable for
public drinking water supplies. The
high levels of potential pollutants in
the distilled water extracts suggest
that contaminants from the waste
could be leaching into the ground-
water.
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This Project Summary was developed
by EPA's Municipal Environmental
Research Laboratory, Cincinnati, OH,
to announce key findings of the
research project that is fully docu-
mented in a separate report of the
same title (see Project Report ordering
information at back).
Introduction
Careless disposal of toxic industrial
wastes can cause severe degradation of
groundwater quality, as many case
histories can attest. The potential for
such contamination is enormous con-
sidering that 57 million metric tons
(approximately 125 billion Ib) of hazar-
dous wastes are produced annually in
the United States and that most of this
material is disposed of through landfilling.
A recent EPA-funded survey disclosed
that 43 to 50 land disposal sites
containing large volumes of industrial
waste had caused degradation of
groundwater quality. At 26 of these
sites, hazardous inorganic substances
exceeded federal drinking water stan-
dards. Selenium, copper, barium, cya-
nide, and nickel were the most frequently
occurring inorganic contaminants.
Excessive amounts of arsenic, chro-
mium, and lead were also common.
For many of these wastes, solidifica-
tion/stabilization may greatly reduce
the potential hazard associated with
landfilling yet permit future reclama-
tion. Stabilization of industrial wastes to
prevent or retard the leaching of
contaminants by percolating water was
examined at four sites. Sites containing
stabilized metal finishing, electroplating,
and refinery wastes were .selected
because of the need for treatment of
such wastes throughout industry. Some
of the data presented here have appeared
in earlier reports (1,2); most of the data
are summarized from the third and final
report in the series concerning the
effects of leachate from waste disposal
sites on surrounding soil and ground-
water systems. This document provides
an overall evaluation of results from all
three reports.
Materials and Methods
Site Selection and
Characterization
The four industrial waste disposal
sites were in different geographic
locations in the central Umted States
where rainfall and infiltration rates
were sufficient to produce significant
amounts of leachate. Anonymity was a
condition for gaining permission to
make sample borings at each site, and
therefore the sites are designated only
by letter.
Three principal factors affecting the
character and the amount of the
contaminants leaching from an indus-
trial waste disposal area are the waste
type, the amount of material disposed,
and the length of time the material has
been buried. Secondary factors include
the amount of rainfall and infiltration at
the site, the thickness and surface area
of the solidified waste, and the charac-
ter of the geologic materials under the
disposal site. An attempt was made to
characterize each site carefully. The
important climatic, engineering, and
geologic characteristics of each site are
summarized (Table 1).
The same chemical stabilization/
solidification system used at each of the
four sites involved mixing the wet
sludge with cement, soluble silicates,
and other proprietary additives to
produce a solid waste with soil-like
properties. The exact proportion of
waste and solidification agents used at
these sites is not known.
Site W received approximately 20,000
m3 of treated paint and oil waste residue
in 1973 and 1974. Among the chemical
constituents in this 1.5-hectare (ha)
diked area were iron hydroxides,
calcium, sulfates, silica, and lime putty.
Before it was used as a disposal site for
chemically fixed waste, a portion of the
area served as a waste burning pit. At
the time of sampling, waste lagoons
existed immediately west of the site,
and a surface water catchment basin
was northeast of the site. Each of these
features contained liquid. The disposal
area was not sheltered, and the surface
material was dry and loose. The moisture
content increased with depth, and a
plastic-consistency material was en-
countered at depths of less than 0.5 m.
Site X, a 0.1-ha diked area, received
approximately 1,000 m3 of chemically
fixed electroplating waste. The waste
was processed and deposited on the site
in 1973, and the area has not been
altered. The waste material was reported
to contain oxides, salts, and hydroxides
of zinc, cadmium, chromium, nickel, and
tin. The waste was not covered, and the
surface material was dry and loose. This
condition rapidly degraded into a wet,
plastic material ranging in depth from
25 to 50 cm.
Site Y covered approximately 0.6 ha.
The chemically treated waste was
deposited on the site in 1974. Approxi-
mately 8 months later, the material was
transferred to a local landfill, and the
disposal site was leveled. Areas within
the site probably contained residue of
the waste mixed with the soil, but none
was observed at the time of sampling.
The waste contained paint pigments,
oil, iron, zinc, phosphate, and chromium.
Sludge lagoons were located to the
immediate northwest, and a coal
storage area was southwest of the
sampled site. The site surface was
sparsely vegetated and had some
concrete rubble.
Site Z was a 1.4-ha diked area
containing approximately 15,000 m3 of
treated refinery waste. The sludge
contained 8 to 15 percent organics, 16
to 28 percent sediment, and 60 to 77
percent water. Chemical analyses
confirmed the presence of chromium,
iron, zinc, cadmium, copper, lead,
nickel, and phenol. A drainage/waste
impounding basin was northwest of the
site, and a bay inlet was to the south.
The treated material was covered with
0.5 to 1.5 of top soil and clay and graded
level. This cover was intermixed with
the waste during the covering and
leveling processes, and a precise
interface horizon is not present. The
surface" cover was dry but graded into a
wet, plastic material at depths of less
than 1 m.
Table 2 lists the concentrations of
major potential chemical contaminants
in the stabilized sludge at each site. Site
W had relatively high levels of chro-
mium, manganese, nickel, and zinc. Site
X contained an electroplating waste
notably high in cadmium, chromium,
and copper. The waste at Site Y con-
tained relatively low concentrations of
toxic metals; only manganese was
present in very large amounts. Site Z
had high concentrations of a wide range
of potential pollutants, including chro-
mium, lead, zinc, and mercury. The
waste at Site Z also contained a signifi-
cant amount of phenol, but the concen-
tration was not quantified.
Sampling Procedures
An initial sampling plan for all sites
was based on the hypothetical model
shown in Figure 1. Flexibility was
needed to modify the plan for specific
requirements at each disposal facility.
The sampling plan included seven to ten
borings to be made at each site. Where
possible, two borings were to be drilled
through the industrial waste, and five to
eight borings were to be drilled outside!
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Table 1. Summary of Characteristics of the Four Sites Selected
Characteristic
Geographic area within the U.S.
General geologic setting
Mean annual rainfall
Mean annual air temperature
Nature of waste
Major pollutants detected in
sludge analyses
Liner used below fill
Thickness of waste
Nature of material in
unsaturated zone
Thickness of unsaturated zone
Site W
Central
Glacial drift
102 cm
12°C
Paint, putty
B, Cr, Fe. Pb.
Mn. Ni. Zn
None
1.22-3.05m
(avg. 2.14m)
Sandy clay
3.05 -8.60m
(avg. S.60m)
Site X
North central
Glacial outwash
93 cm
11°C
Electroplating
Cd, Cr, Cu, Mn,
Na.Zn
None
0.91-1. 22m
(avg. 1.07m)
Sandy clay
2. 16-2.93m
(avg. 2.41m)
Site Y
North central
Pleistocene -
lake terrace
88 cm
10°C
Paint, putty
Cr, Fe, Pb,
Mn, Zn
None
Thin*
Clayey sand
1.46-1 1.80m
(avg. 8.79m)
Site Z
South central
Deltaic -
fluvial deposits
117 cm
21°C
Refinery sludge
Pb, Mn, and
phenol
None
1.83-3. 20m
(avg. 3.79m)
Clay
1.04-6. 63m
(avg. 3.79m)
Average hydraulic conductivity
below waste
Character of covering material
Average thickness of cover
Dates of emplacement of fixed
sludge
Type of operation
1.1x10~7 cm/sec
None
0.0
1974
Diked fill
3.45x10~7 cm/sec
None
0.0
1973
Diked fill
2.63x10 * cm/sec
None
0.0
1974*
Fill
4.2x10 7 cm/'sec
Clay
O.5m
1974
Diked fill and cover
*Fixed waste was placed on the ground in April and May 1974; the major portion of the fixed material was, however, removed to a
landfill in January 1975 when the area was regraded.
the disposal area. This sampling pattern
allowed typical, unaffected ground-
water and soil to be compared with
groundwater and soil that were in direct
contact with the migrating leachate.
Undisturbed soil samples were ob-
tained by extruding soil cores from a
Hvorslev* fixed-piston sampler pressed
into the soil directly below the end of an
auger using hydraulic cylinders on a
truck-mounted drill rig. A split-spoon
sampler was used in cases where
objects were encountered in the sub-
surface that could not be penetrated by
the Hvorslev sampler.
Physical Testing Methods
The physical tests run on undisturbed
samples included water content, dry
density, permeability, and grain-size
analysis. Data gathered from these tests
and visual examination of the samples
•Mention of trade names or commercial products
onstitute endorsement or recommendation for use
y the U.S. Environmental Protection Agency.
were used to classify the materials into
standard soil engineering categories.
All testing was done using standard soil
engineering methods.
Results and Discussions
Physical Testing
The goal of the physical testing waste
see if soil characteristics had been
altered in the soils beneath the
industrial disposal operation. When
samples from directly below the waste
were contrasted with those taken at
comparable elevations outside the
landfill, the differences, in most cases,
were very slight. A randomization test
was applied to the data, and in only two
cases were the test results statistically
significant (93 percent confidence
level). The water content of sediments
beneath the waste at site W was
significantly higher than that outside
the disposal area, and the percent fines
(200 mesh) in samples under the site X
landfill was significantly lower than
corresponding samples outside the
disposal area. No consistent pattern of
changes in soil character could be seen.
The expected effects of leachate filtration
at the waste-soil interface were not
generally detectable in the samples
obtained in this study.
Chemical Analysis of
Groundwater
Groundwater samples obtained from
borings at the four industrial waste sites
were chemically analyzed. Wells drilled
up the groundwater gradient from the
disposal sites were considered as
controls or background water samples
not contaminated by the disposal
activities. Wells drilled through the
solidified waste or down the ground-
water gradient from the site were
considered experimental wells where
any possible contamination from the
waste would be detected.
Changes in groundwater quality
attributable to sludge disposal could be
observed in three of the four sites. At
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Table 2. Concentrations of Major Chemical Contaminants in the Fixed Sludge at
Each Site*
Constituent
B
Cd
Cr
Cu
Fe
Pb
Mn
Ni
Se
Na
Zn
Hg
Phenol
Site W
(mg/kgf
43
4.5
230
28
47,000
40
850
75
1
350
1.300
0.05
—
Site X
(mg/kg)
35
105
1.600
1.650
4,000
20
110
50
1.3
1,281
450
0.20
—
Site Y
(mg/kg)
10
0.1
30
18
23,500
40
572
30
0.62
2,000
200
0.02
—
Site Z
(mg/kg)
6.4
1.8
960
130
16.800
3,300
275
25
0.83
1,340
520
6.2
Present
*Data obtained from analyses of sludge samples.
+0n a dry weight basis.
one of the two sites where stabilized
metal finishing and paint wastes had
been disposed of, the levels of chloride,
calcium, and sodium showed significant
increases under and down the ground-
water gradient from the disposal site. At
the disposal site for stabilized refinery
sludge, increased levels of sulfite,
nitrite, cyanide, phenols, and arsenic
were found in water samples taken
under and down the groundwater
gradient from the disposal sites.
With the exception of phenols at site
Z, none of the toxic constituents that
were expected to be pollution problems
on the basis of waste analysis (Table 2)
were found in significantly elevated
concentrations in the groundwater. The
absence of these pollutants may be
attributable to the binding of these
constituents in the stabilization process,
or lack of time for transport of these
materials to the groundwater, or attenu-
ation effects occurring in the soils, or to
all three.
Chemical Analysis of Nitric
Acid Extracts
Chemical analyses were conducted of
nitric acid extracts of soil samples taken
at the sludge/soil interfaces. At site W,
where automobile assembly plant
sludges were disposed of, the major
potential contaminants were boron,
chromium, iron, lead, manganese,
nickel, zinc, sodium, and selenium.
Elevated levels of most contaminants
were only evident in the samples from
the first meter below the sludge/soil
interface. No soil samples recovered
from borings more than 1 m below the
sludge/soil interface had metals level:
above those observed in the surround! nc
uncontaminated soils, except in the
case of selenium. Selenium levels were
higher in deep (greater than 1 m) soils
samples in both experimental boringsai
site W.
For the constituents tested, the soil:
at all four sites showed concentration:
that fell within the typical concentratior
ranges for soils in a natural state in the
eastern United States. Even in the case:
where significant increases in the
constituents under the treated sludge
were found, these elevated levels were
always well within typical ranges foi
eastern soils. For instance, sodium
which was found at levels of 357, 883
and 2,147 mg/kg of dry weight of soi
Experimental
Control Boring
Boring /
Control
Boring
Figure 1. Hypothetical model of leachate and groundwater movement near industrial waste disposal site. Heavy arrows
indicate groundwater movement. {
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under the sludges at sites W, X, and Y,
respectively, has an average concentra-
tion in eastern soils of 2,600 mg/kg—
higher than that of any "contaminated"
sample found.
Three significantly contaminated
soils samples taken at the sludge/soil
interface (selenium at site W, and iron
and nickel at site Y) had maximum
values that were less than twice the
average soil concentration and well
within typical ranges. In the worst case
noted (that of manganese contamination
at site W), the highest contaminant level
was less than four times the average,
and it was still well within typical ranges
for manganese in eastern soils. Even
where significant contamination was
found, the soil was not appreciably
degraded below that of typical eastern
soil.
Chemical Analysis of Distilled
Water Extracts
Distilled water extracts from soil
samples were chemically analyzed. The
soils at all four sites were very thor-
oughly weathered, and the rate of
release of normal soil constituents into
the distilled water extract was extremely
low. In many cases, the background
levels for distilled water extracts were in
the low parts-per-billion range, and
often they were below the minimum
detectable concentration using conven-
tional analytical techniques. The treated
waste, in contrast to the weathered soil,
contains lime and soluble sodium
compounds used in the solidification
process as well as the normal soluble
materials in the sludge.
The constituents found in appreciable
concentrations in the distilled water
extracts are those materials that would
be easily removed from the soil by
natural rainwater leaching. These
constituents are not tightly bound to the
soil and could migrate into the ground-
water. The discovery of high levels
(above standards for public water
supplies) of phenol and toxic metals
(chromium, lead, selenium) in the
distilled water extracts from soil under
the treated waste suggests that in the
future, higher levels of the pollutants
may appear in groundwater or surface
water. The magnitude of any potential
pollution problem depends on how
much of the pollutant the soil below the
waste can remove and the amount of
dilution that occurs as the leachate
.eaves the site.
Conclusions
No consistent physical changes could
be detected in the soils beneath the
landfilled wastes at the four sites where
chemically stabilized industrial wastes
had been deposited. None of the
expected physical effects of disposal
(such as decreased permeability or
increased fines in the subwaste soils)
could be observed using standard
testing procedures.
Changes in groundwater quality that
could be related to the waste disposal
activities were observed at three of the
four sites. At one of the two locations
where stabilized metal finishing and
paint wastes had been landfilled,
calcium, 'sodium, and chloride were
significantly higher in groundwater
under the site and down the ground-
water gradient from the site. At the
electroplating disposal site, sulfate and
boron appeared at higher levels in
groundwater down-gradient from the
waste disposal area. At the site where
stabilized refinery wastes were land-
filled, increased levels of sulfite, nitrite,
cyanide, phenols, and arsenic were
observed in groundwater samples taken
under and down-gradient from the site.
Toxic metal contamination in ground-
water was not detected at levels that
would present a serious pollution
problem.
Nitric acid digests of soils collected
from directly beneath the stabilized
industrial wastes were compared with
samples of soils from similar elevations
outside the sites. Small increases in
manganese, sodium, selenium, and
mercury were found at some sites; but
most major toxic metals showed no
consistent increase traceable to the
wastes. Even the most highly contami-
nated soils were within the range of
composition observed for natural eastern
U.S. soils.
Distilled water extracts of soils
collected from beneath the stabilized
wastes and from comparable elevations
outside the site showed appreciable
contrasts in chemical composition.
Some of the toxic metals were present
in consistently larger amounts in
extracts from soils under the wastes.
Chromium, lead, and selenium were
found in some extracts at levels above
those acceptable for public drinking
water supplies.
No major contamination of ground-
water or soil could be detected under
the stabilized wastes; but the subwaste
soils do contain larger quantities of
teachable toxic metals than do back-
ground soil samples. This suggests that
some toxic materials are escaping from
the stabilized wastes and are held in the
soil in a readily teachable state.
Recommendations
Additional soil samples should be
collected from beneath the disposal
sites to reveal continued or increased
contaminant release rates. Successive
years of leaching and physical weather-
ing may contribute significant amounts
of contaminants to the soil and ground-
water systems. Sampling soils periodi-
cally over several years can provide
input to the established data base and
serve as a case study of one type of
stabilized sludge.
Disposal sites in which untreated
sludges are deposited should similarly
be studied to ascertain the significance
of stabilization. Disposal could be
simulated using test cells with untreated
sludge and others with stabilized
sludges. The test cells would require
limited space, and if they were shallow,
a relatively simple groundwater and
•subsoil monitoring system could be
used.
Data should be obtained from similar
studies of other types of chemically
stabilized and disposed sludges. Such a
compilation would provide an assess-
ment of the success of stabilization
processes.
The full report was submitted in
fulfillment of Interagency Agreement
No. EPA-IAG-D4-0569 by the U.S. Army
Engineer Waterways Experiment Station
under the sponsorship of the U.S.
Environmental Protection Agency.
References
1. Mercer, R.B., Malone, P.G., and
Groughton, J.D., Field Evaluation of
Chemically Stabilized Sludges. In:
Land Disposal of Hazardous Wastes,
David Shultz, ed. EPA-600/9-78-
016, U.S. Environmental Protection
Agency, Cincinnati, Ohio, 1978. pp.
357-365.
2. Jones, L W., Malone, P. G. and
Myers, T. E., Field Investigation of
Contaminant Loss from Chemically
Stabilized Sludges, Disposal of
Hazardous Wastes, David Schultz,
ed., EPA-600/9-80-010, U.S. En-
vironmental Protection Agency,
Cincinnati, Ohio, 1980. pp. 187-202.
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This Project Summary was authored by staff of the Environmental Laboratory,
U.S. Army Engineer Waterways Experiment Station. Vicksburg, Ml 39180.
Robert E. Landreth is the EPA Project Officer (see below).
The complete report, entitled "Field Investigation of Contaminant Loss from
Chemically Stabilized Industrial Sludges," (Order No. PB 81-246 332; Cost:
$11.00, 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 Officer can be contacted at:
Municipal Environmental Research Laboratory
U.S. Environmental Protection Agency
Cincinnati, OH 45268
US. GOVERNMENT PRINTING OFFICE; 1981 — 757-012/7350
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