&EPA
United States
Environmental Protection
Agency
Municipal Environmental Research EPA 600 8 79 001
Laboratory May 1979
Cincinnati OH 45268
Research and Development
Comparison of
Three Waste
Leaching Tests
Executive Summary
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RESEARCH REPORTING SERIES
Research reports of the Office of Research and Development. U.S Environmental
Protection Agency, have been grouped into nine series. These nine broad cate-
gories were established to facilitate further development and application of en-
vironmental technology. Elimination of traditional grouping was consciously
planned to foster technology transfer and a maximum interface in related fields.
The nine series are:
1 Environmental Health Effects Research
2 Environmental Protection Technology
3 Ecological Research
4. Environmental Monitoring
5 Socioeconomic Environmental Studies
6 Scientific and Technical Assessment Reports (STAR)
7 Interagency Energy-Environment Research and Development
8 "Special" Reports
9 Miscellaneous Reports
This report has been assigned to the "SPECIAL" REPORTS series This series is
reserved for reports targeted to meet the technical information needs of specific
user groups The series includes problem-oriented reports, research application
reports, and executive summary documents Examples include state-of-the-art
analyses, technology assessments, design manuals, user manuals, and reports
on the results of major research and development efforts
This document is available to the public through the National Technical Informa-
tion Service, Springfield, Virginia 22161.
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EPA-600/8-79-001
May 1979
COMPARISON OF THREE WASTE LEACHING TESTS
Executive Summary
by
Robert K. Ham
Marc A. Anderson
Rainer Stegmann
Robert Stanforth
Department of Civil and Environmental Engineering
University of Wisconsin-Madison
Madison, Wisconsin 53706
Grant No. R-804773-01
Project Officers
Michael Gruenfeld
Industrial Pollution Control Division
Industrial Environmental Research Laboratory-Cincinnati
Edison, New Jersey 08817
Donald Sanning
Solid and Hazardous Waste Research Division
Municipal Environmental Research Laboratory
Cincinnati, Ohio 45268
INDUSTRIAL ENVIRONMENTAL RESEARCH LABORATORY
OFFICE OF RESEARCH AND DEVELOPMENT
U.S. ENVIRONMENTAL PROTECTION AGENCY
CINCINNATI, OHIO 45268
MUNICIPAL ENVIRONMENTAL RESEARCH LABORATORY
OFFICE OF RESEARCH AND DEVELOPMENT
U.S. ENVIRONMENTAL PROTECTION AGENCY
CINCINNATI, OHIO 45268
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DISCLAIMER
This Executive Summary has been reviewed by the Industrial Environmental
Research Laboratory, the Municipal Environmental Research Laboratory and the
Office of Solid Waste, U.S. Environmental Protection Agency and approved for
publication. Approval does not signify that the contents necessarily reflect
the views and policies of the U.S. Environmental Protection Agency, nor does
mention of trade names or commercial products constitute endorsement or
recommendation for use.
The selection or design of any leachate test will ultimately be decided
by a number of practical, rather than theoretical, considerations. The class-
ification of whether or not a waste is hazardous, via a leaching test, must
assume less than ideal disposal conditions, in order that, its potential for
causing environmental harm can be minimized. It is recognized that a single
test will not be optimal for all disposal conditions. Nevertheless from a
regulatory point of view, developing different tests for each different waste
and disposal option is clearly impractical and probably unworkable.
This Executive Summary is published with the intent of providing quick
and concise information on the results and findings of this project.
11
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FOREWORD
This research effort is a combined response to an environmental need by
two Office of Research and Development Laboratories. The Edison, New Jersey
office of the Industrial Environmental Research Laboratory assisted the Muni-
cipal Environmental Research Laboratory in this effort.
The Industrial Environmental Research Laboratory-Cincinnati develops cost
effective techniques to prevent, control, or abate multi-media (air, water,
solid wastes, etc.) pollutional impacts associated with the extraction, trans-
portation, processing, benefication, conversion, and use of mineral resources
and with industrial processing and manufacturing. The Municipal Environmental
Research Laboratory develops new and improved technology and systems for pre-
venting, treating, and managing waste water and solid and hazardous waste
pollutant discharges from municipal and community sources, for preserving and
treating public drinking water supplies, and for minimizing the adverse eco-
nomic, social, health, and aesthetic effects of pollution. The related pollu-
tional impacts on our environment and the interplay between its components
require a concentrated and integrated attack on the problem.
This report deals with the investigation of three leaching tests as
reliable predictors of the potential environmental effects of the disposal of
thirteen industrial wastes. The advantages and disadvantages of each test
based on the leaching characteristics of the thirteen wastes and the useful-
ness of each procedure as a standard test are analyzed and compared. The re-
port will provide data for decision makers of both government and industry
alike contemplating residue leachate control from industrial sludge
impoundment/municipal landfill co-disposal operations.
David G. Stephan Francis T. Mayo
Director Director
Industrial Environmental Municipal Environmental
Research Laboratory Research Laboratory
m
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ABSTRACT
A comparison of three leaching tests was performed with thirteen indus-
trial wastes to evaluate the potential of each test for use as a standard
leaching test procedure. Such a procedure could be used to assess the leach-
ing characteristics of industrial wastes for land disposal. The study was
done in conjunction with a background study on the development of a standard
leaching test. The advantages and disadvantages of each test based on the
leaching characteristics of the thirteen wastes and the usefulness of each
procedure as a standard test are analyzed and compared. Finally, comments
are provided on the need for careful interpretation of test results.
This report was submitted in partial fulfillment of Grant No.
R-804773-01 by the Department of Civil and Environmental Engineering, Univer-
sity of Wisconsin-Madis.on. The work was completed July 1978.
IV
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CONTENTS
Foreword . . . . - i i 1
Abstract . . . iv
Figures and Tables . . vi
1. Introduction ... . ..... 1
2. Summary and Conclusions . 2
3. Experimental Procedures ..... 7
Leaching tests used 7
Wastes used and sample preparation 7
Release calculations . . . . 10
4. Test Comparison . . . 11
Leachate composition .... 11
Solid-liquid ratio . . . 16
Number of elutions . . ... 18
Agitation technique and surface
area of contact . . 19
Additional test comparisons . . .... 22
References . . ...... . . 23
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FIGURES
Number Page
1 Cu concentration and release from a
sludge in test leachates ............ 15
2 Variation in Na and K concentration and release
from an ink and paint waste with solid-
liquid ratio, using a distilled water
leachate ........................ 17
3 Napthalene concentration and release from
a coal tar waste in test leachates ............. 20
4 Na concentration and release from a
CuO-Na2S04 sludge in test leachates ............ 21
TABLES
Number Page
1 Some features of an ideal standard leaching test ....... 2
2 Abilities and limitations of each test in
comparison to an ideal test ................ 3
3 A summary of the leaching tests used in
the test comparison .................... 8
4 Wastes used in the test comparison ............... 9
5 A summary of test comparison results for
selected parameters from selected wastes .......... 12
6 The number of times each test leaching
solution gave the highest concentration
of an inorganic parameter from a waste for the
different test leachates .................. 13
7 Number of times acid or h^O leaching solutions gave
highest concentrations or release of an inorganic
parameter from a waste for parameters measured in
both acid and t^O leachates ................ 14
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SECTION 1
INTRODUCTION
Developing awareness of the potential of landfilled industrial wastes to
pollute groundwater has led to an interest in a standardized test to discern
the relative leaching potential of a waste. A background study on such a test
has been done by the authors for the U.S. Environmental Protection Agency (EPA)
{!). During this background study a leaching test was developed, called the
SLT. In order to evaluate the SLT, and other leaching tests which might be
used as the standard test, a comparison of three leaching tests was made by
running the tests on a wide variety of industrial wastes and comparing the
relative ease, practicality and amount of information obtained in each of the
tests. The results of the test comparison are given in this report. The test
comparison also serves as a practical evaluation of the SLT.
This report constitutes an Executive Summary of the complete report of
the study as submitted to EPA (2).
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SECTION 2
SUMMARY AND CONCLUSIONS
Certain features of an ideal standard leaching test following the
concepts discussed in Section 4 are given in Table 1. An ideal leach-
ing test is defined herein as a standardized procedure which works on all
wastes and is able to predict quickly and with accuracy the potential water
quality degradation within a landfill represented by the landfill disposal of
a particular waste. It does not evaluate any changes in leachate quality
arising from passage through soils or dilution. The major abilities and
limitations of each test used in this study with regard to these features are
given in Table 2. Column tests are not included in the concept of an ideal
leaching test because of the difficulty of using a column test on a wide
variety of wastes.
TABLE 1. SOME FEATURES OF AN IDEAL STANDARD LEACHING TEST*
1. Use of leaching media corresponding to liquids likely to be in contact
with the waste in the landfill (such as use of both an acid synthetic
municipal landfill leachate and distilled water leaching solutions for
modeling leaching in actively decomposing and stabilized municipal
landfills, respectively).
2. Incorporates procedures to indicate both concentration and release of
parameters likely to be leached from a waste.
3. Use of multiple elutions so secondary effects can be observed.
4. Use of an effective agitation procedure which does not unnaturally or
unnecessarily abrade waste particles.
5. Use of a solid/liquid ratio high enough to minimize analytical and
sampling errors, yet low enough to allow rapid determination of crit-
ical concentration and release information for most parameters.
6. Use of convenient, yet justifiable, elution times and numbers of elu-
tions.
*It is assumed that any useable test would incorporate sampling proce-
dures and sufficient replicates to gain statistical reliability.
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TABLE 2. ABILITIES AND LIMITATIONS OF EACH TEST IN
COMPARISON TO AN IDEAL TEST*
SLT
Positive aspects:
1. Use of two separate procedures to allow prediction of both concen-
tration and release of parameters from waste.
2. Flexibility of leaching media selection such as the use of both
acid synthetic municipal landfill leachate and distilled water as
leaching solutions to model co-disposal with muncipal solid waste.
3. Use of an effective, yet gentle, agitation technique.
4. Use of multiple elutions.
5. Use of an intermediate solid/liquid ratio which lessens the chance
of analytical errors of the Minn, test while generally allowing more
rapid evaluation of release characteristics than does the IUCS test.
6. Incorporates procedures which allowed its direct use on all the
wastes tested in this study.
Limitations:
1. Use of an oxygen sensitive leachate, required for proper modeling
of leachate generated in actively decomposing municipal solid waste
landfills.
2. The laboratory procedures and the amount of information obtained,
especially if both concentration and release results are desired,
require more laboratory effort and interpretive care.
IUCS TEST
Positive aspects:
1. Use of a generally effective agitation technique.
2. Use of multiple elutions.
3. Use of a high solid/liquid ratio gives relatively high concentra-
tions of many parameters.
— (continued)
*i .e., Table 1
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TABLE 2 (continued)
4. Use of a relatively straightforward laboratory procedure.
Limitations:
1. Use of only a distilled water leachate.
2. Lack of a procedure to evaluate the max-imum concentration of a
parameter in leachate.
3. Use of an elution time and number such that work needs to be con-
tinued over weekends.
4. Required adaptations on a waste by waste basis to allow some wastes
to be tested.
5. The fewer numerical results require more careful interpretation and
extrapolation of data than the SLT to apply the results to actual
landfill situations.
MINNESOTA TEST
Positive aspects:
1. Use of both acid and distilled water leachates.
2. Simple and rapid to perform.
Limitations:
1. Acetate buffer models only one aspect of municipal solid waste
leachate affecting its leaching aggressiveness.
2. Low solid/liquid ratio emphasizes subsampling, weighing, and
analytical errors.
3. Use of only one elution gives much less information than either of
the other two tests. No information is provided regarding the
approach to stable results, the rate at which such stability is
reached, or possible secondary effects.
4. Agitation technique allows significant concentration gradients in
the bulk solution, slowing the time needed to approach equilibrium
and reducing the reproducibility of the results.
5. Required adaptations on a waste by waste basis to allow some wastes
to be tested.
(continued)
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TABLE 2 (concluded)
6. Neither concentration nor release information can be obtained with
confidence because it is not known how close the results are, after
one elution, to maximum values attainable or to practical values
reached in actual landfills. Application of test results to actual
landfills is difficult to justify.
A number of different tests could be designed which meet the criteria
of Table 1 and, yet, have considerable differences between them. Thus, once
a standard leaching test has been designed, interpretation of the test
results becomes a crucial factor in determining the applicability of the test.
A standard leaching test provides a reproducible set of numbers that are a
function of the interaction of a waste with a specific leaching solution
under a specific set of conditions. It is up to the decision maker to evalu-
ate those numbers and make a prediction regarding the behavior of the waste
in a landfill. Unfortunately, the multiplicity of factors affecting the
wastes' leaching characteristics, both in the test and in the landfill, and
the variability of landfill conditions, dictate that interpretation be done
with care and with consideration of the waste and landfill characteristics.
Tests results should not be interpreted rigidly; i.e., a certain concentra-
tion of a given parameter in the test leachate should not be taken to indicate
automatically that the waste is hazardous in the landfill. Rather, consider-
ation should be given to such factors as the amount of waste to be disposed,
the annual net infiltration of water or movement of groundwater through the
landfill, the factors affecting the leaching of the waste (as far as can be
determined from the test results), possible waste-leachate interactions, and
the fate of the landfill leachate after it leaves the waste and passes through
additional wastes or soil.
As an example of the need for careful interpretation, consider the
distilled water leachates from the CuO-Na2S04 sludge. These leachates con-
tained low concentrations of copper (<1 mg/1), yet, very high concentrations
of Na (~10,000 mg/1 in the SLT Elution 1 leachates). With regard to Na, the
leachate is probably not very hazardous, at least no more hazardous than sea
water which has approximately the same Na concentration. Yet, in a landfill
or in the soil underneath, the high ionic strength could solubilize potentially
hazardous trace metals through ion exchange mechanisms. Thus, the leachate
itself may not be hazardous, but it may solubilize hazardous materials in
landfill environments. Likewise, several wastes released large amounts of
unidentified organic compounds, as evidenced by the very high COD values in
the distilled water leachates. The potential hazard of these wastes may not
come from the organic compounds released by the waste, if these are not
hazardous, but from the ability of the released organics to solubilize other-
wise insoluble hazardous compounds such as PCBs, chlorinated organic pesti-
cides, or heavy metals. On the other hand, a waste may release small amounts
of hazardous materials which will most likely be removed from the leachate
by passage through the soil under the landfill. The waste might appear to be
-------
hazardous due to the release of this material in a leaching test, while in
the landfill it would actually be of no practical concern. Several wastes
which released trace metals in low concentrations might fall into this cate-
gory. It should be noted that leaching modeled by the test in one or two days
may simulate years of leaching in the field. During this time, bacteria may
convert hazardous compounds into innocuous ones, or vice versa, or they may
completely alter the leaching characteristics of a waste through their action
on the waste matrix.
When interpreting test results, it is important to consider the physical
condition of the landfilled waste. For example, a waste which is landfilled
in large stable chunks or with a stable impervious coating would most likely
behave far differently in a landfill than in a test in which it were ground.
The test results need to be interpreted with regard to particle surface area
both in the test and in the landfill and in light of the .stability of the
chunks of waste or coatings on the waste in the landfill..
An evaluation of the hazardous nature of a waste must include an evalu-
ation of the landfill environment. A waste's hazardous nature is a situation
specific characteristic. A waste may be hazardous to an organism under one
set of environmental conditions, yet, completely innocuous under a different
set of conditions. Furthermore, its hazard may be organism specific; i.e.,
it may be hazardous to one organism and not to another under the same set of
conditions. Thus, a determination of the hazardous nature of a waste must
include an evaluation of its hazardousness to specific organisms under spe-
cific conditions.
The limitations of a standard leaching test and the care needed in in-
terpreting the results do not mean that a standard test is not worth develop-
ing and using. A standard test should provide a rapid evaluation of the param-
eters that are likely to be leached from a waste, and an indication of their
maximum concentrations in the leachate and the total amount to be released
per unit weight of waste. That the test is not perfect in predicting the
long term leaching pattern of a waste or the precise concentration of a par-
ticular parameter in a particular landfill, means that the test results need
to be interpreted with care to avoid unnecessary expenditures for control of
wastes that are not actually hazardous in a particular landfill, or to avoid
unexpected environmental degradation from improper land disposal of a waste.
In summary, of the three tests compared in this study, the SLT gave the
most information in the shortest amount of time. The IUCS test could be
improved if several modifications were incorporated, such as use of an acidic
synthetic municipal landfill leachate when co-disposal of the waste being
tested with municipal solid waste is possible, and if a procedure for measur-
ing maximum concentration were added. The Minn, test would require several
modifications in order to be a widely applicable standard test.
Whatever standard test is used, interpretation of test results is the
crucial factor in determining the test's ultimate value in predicting whether
a waste is hazardous when placed in a landfill. Virtually any leaching test
which is properly interpreted would be more useful in making such a predic-
tion than would be a well designed leaching test which is poorly interpreted.
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SECTION 3
EXPERIMENTAL PROCEDURES
LEACHING TESTS USED
The two tests used in addition to the SLT were selected by EPA as being
among the best tests currently available and as having some variety in the
test conditions. The tests used were the SLT, an IU Conversion System modi-
fied 48-hour shake test (the IUCS test) and a test developed by the Minnesota
Pollution Control Agency (the Minn. test). There are several IUCS shake tests
available, so particular care should be taken to specify the test conditions
when discussing the test. A summary and comparison of the test conditions is
given in Table 3. Note that the IUCS test uses fresh leaching media for each
elution, as does the SLT test procedure R (see note in Table 3).
In addition to the tests mentioned above, a municipal leachate was used
as a leaching medium, using a modified SLT procedure R. The difficulty in
working with highly air sensitive real leachate necessitated the modifications.
The purpose of the real leachate test (RLT) was not to verify the accuracy of
the synthetic leachate used in the SLT, as might be supposed, but rather to
obtain an idea of the leaching ability of a real leachate sample. The leach-
ate was not as aggressive as the leachate upon which the synthetic leachate
was modeled, and so cannot be used as a verification of the synthetic leachate.
WASTES USED AND SAMPLE PREPARATION
Fourteen wastes were used in the test comparison. The wastes and the
tests they were used in are listed in Table 4. Since the intent of the com-
parison was to evaluate the tests themselves, the sample preparation procedure
was kept the same for all tests. This preparation included a solid/liquid
separation procedure that is recommended for sample preparation in the SLT
background study. This technique is not included in either the IUCS or Minn-
tests. Both of these tests, however, were designed for solid or semi-sol id
wastes rather than for predominantly liquid wastes. As many of the wastes
used in the test comparison were predominantly liquid, the designers of both
the IUCS and Minn, tests were asked how to prepare predominantly liquid wastes
for their tests. Both agreed that a solid/liquid separation might be one
approach to sample preparation, although both emphasized that their tests were
not designed for such wastes, and that a solid/liquid separation might not be
the approach they would use to prepare predominantly liquid wastes for their
tests.
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TABLE 3. A SUMMARY OF THE LEACHING TESTS USED IN THE TEST COMPARISON
SLT
IUCS Test
Minnesota Test
Leaching
Solution
Solid/Liquid
Ratio
Synthetic Leachate'
1:10 (Proc. R)
Varied (Proc. C)
1:4
Acetate Buffer"1
H20§
1:40
Time per
Elution
Number of
Elutions
Temperature
Shaking
Technique
24 hrs
3 or more
Room
Slow Tumbling
(rotating)
48 hrs
5
Room
Back and
Forth Shaking
(reciprocal )
24 hrs
1
Room
1 min. shake,
24 hr rest
(separatory funnel )
*Two procedures used, in one of which the solid-linuiH ratio is
varied, replacing the waste with fresh waste in successive elutions
(C), while in the other it is kept constant, replacing the leaching
media in successive elutions (R), maximizing concentration (C) and
release (R), respectively.
A synthetic municipal landfill leachate, with a pH of 4.5 and
composed as follows:
0.15M Acetic Acid
0.15M Sodium Acetate
0.050M Glycine
0.008M Pyrogallol
0.024M Ferrous Sulfate
^pH of 4.5.
§Distilled, deionized water used.
8
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TABLE 4. WASTES USED IN THE TEST COMPARISON
1.
2.
3.
4.
5.
6.
7.
8.
9.
10.
11.
12.
13.
14.
Waste Waste Abbreviation
Adhesive Waste #1
Ink & Paint Waste I.P.W.
Coal Tar Waste
Health and Beauty u 0 r
r> 1 1 j. n.o.u.
Care Waste
Food Grade Waste
Adhesive Waste #6
Petrochemical
Industry-Water/ Petrochemical Sludge
Oil Sludge
Grain Process-
ing Lipids and Grain Fats
Fats
Food Wastes, Clay
Marble Wash
Copper Oxide-
S±te CuO-Na2S04 Sludge
Sludge
Electroplating Fpc-
Sludge
Wastewater Treat- WT<.
ment Sludge ^
Papermill Sludge, pMC. rnn
Test Used in
SLT,
STL,
SLT,
SLT,
SLT,
SLT,
SLT,
SLT,
SLT,
SLT,
SLT,
SLT,
SLT,
SLT
Minn,
Minn,
Minn,
Minn,
Minn,
Minn,
Minn,
Minn,
Minn,
Minn,
Minn,
Mi nn ,
Minn,
IUCS
IUCS
IUCS
IUCS
IUCS
IUCS
IUCS
IUCS
IUCS
IUCS
IUCS RLT
IUCS RLT
RLT
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RELEASE CALCULATIONS
The release of a parameter per unit mass waste for each of the tests
was calculated using the equation given below:
N
2~^ (conc(i), mg/L)(leachate volume, mL)(l L/1000 mL)
Releaseelution(i) (dry weight of solid in test, g )(1 kg/lOOOg)
where i is the elution number and N the total number of elutions. Leachate
volume and dry weight of solid is constant for each test, except for SLT pro-
cedure C. Since the purpose of procedure C is to evaluate maximum concentra-
tion, release using this procedure was not calculated. Except for unusual
release patterns, release in procedure R will be greater than or equal to that
in procedure C.
10
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SECTION 4
TEST COMPARISON
In order to compare results of the different test procedures and leach-
ing media, a comparison can be made of the concentration in the different test
leachates of a single parameter leached from a waste. This has been done in
Table 5 for selected parameters from selected wastes. Such a single parameter
comparison does little good in understanding the relative aggressiveness of
the tests unless the factors affecting the parameter concentration in the
leachates are known. However, the relative aggressiveness of the tests can
be analyzed by comparing the number of times each test gave the highest con-
centration (or release) of a parameter for all the parameters analyzed through-
out the test comparison. This has been done for parameter concentration in
Table 6. As can be seen for the parameters measured, the SLT gave the high-
est concentration much more frequently than the other tests. Table 7 shows a
similar comparison for acid and water leachates, comparing only parameters
that were measured in both. It is obvious from the table that acid leachates
are much more aggressive than distilled water leachates.
A more complete comparison of the tests entails an analysis of the
effects of the differences between the tests on the test results, and the
importance of these differences for interpreting the test results. The tests
were compared as whole units with several factors differing between them.
Therefore, it is not possible with any degree of certainty to isolate one
factor and explain differences between the tests as based on that single fac-
tor. Rather, one can only say that a given factor varied between tests and
that it seems reasonable to ascribe a given difference in the test results to
this factor, as in the following sections.
LEACHATE COMPOSITION
The profound effect of leaching solution composition on the materials
and concentrations leached from a waste is shown with several wastes used in
the test comparison, most notably the CuO-Na2S04 sludge. Using the CuO-Na2S04
sludge as an example, acidic leachates—the synthetic leachate and the acetate
buffer—leached potentially hazardous trace metals in significant concentra-
tions as shown in Figure 1. These metals were either below detection limits
or leached in very low concentrations in the water leachates. The copper
concentrations in the acidic leachates were four orders of magnitude (10,000
times) higher than the copper concentrations in the water leachates. Since
landfills produce acidic leachates comparable with respect to both pH and
buffering capacities to the synthetic leachate used in the tests during part
11
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TABLE 5. A SUMMARY OF TEST COMPARISON RESULTS
FOR SELECTED PARAMETERS FROM SELECTED WASTES
Concentration, no/L
Waste
Parar«ter S
.L.*
Proc C
Ink 1 Paint Waste:
Na
K
V.g
Zn
Pb
Cu
Cd
Cyclohexanone
Napthalene
COO
Coal Tar Waste:
Napthalene
Phenol
Cresol
Quinoline
COO
Health J Beauty Care
Zn
Cd
ft
Cu
COO
Food Intfjstry,
COD
Marble Wash:
fb
CK>
12.7
493
138
307
Uaste:
25.0
0.92
5.60
0 86
1.8
0.95
0.60
SLT
S.L.* H2
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TABLE 6. THE NUMBER OF TIMES EACH TEST LEACHING SOLUTION GAVE THE
HIGHEST CONCENTRATION OF AN INORGANIC PARAMETER FROM A WASTE FOR
THE DIFFERENT TEST LEACHATES
Na
K
Mg
Fe
Zn
Pb
Cu
Cd
COD
Total
Number
Total %
Total %
for Each
Test
SLT
Proc C Proc R Minn IUCS
Hr\ ci u n ci A/~ot" u r\ u n
oU oi_ hoU oL HLC L n^u n«u
*
8 -- -- - 4
1 10 1
17 11
1 -- 1 1
6 52
1 1 4
1 2 1
2
4
16 24 1 11 8 0 6
60.6 18.2 12.0 0 9
SLT Minn IUCS
79% 12% 9%
*Not measured.
13
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TABLE 7. NUMBER OF TIMES ACID OR H20 LEACHING SOLUTIONS GAVE HIGHEST
CONCENTRATIONS OR RELEASE OF AN INORGANIC PARAMETER FROM A WASTE FOR
PARAMETERS MEASURED IN BOTH ACID AND H20 LEACHATES
SLT
Acid H20
Minn
Acid H20
IUCS Total
H20 Acid hLU
TOTAL TESTS
Number of Times GJving Maximum Concentration
K 10 1 1 10 2 12
Mg 8 1 1 9 1 10
Zn 11 2 13 0 13
Pb 2 4 606
Cu 2 1 122 4
Cd 1 J_ 0 J_
41 5 46*
Number of Times Giving Maximum Release
K
Mg
Zn
Pb
CU
Cd
8
8 1
8
1
1
2
4
2
4
5
2
1
12
10
12
6
1 3
_3^
46
0
1
0
0
1
0
2
12
11
12
6
4
_3^
48*
Totals are not equal because two tests may both give the maximum
concentration but have different maximum releases. In cases where the
maximum concentration or release were the same, the results were not
tabulated.
14
-------
4000i-
I60r-
O
1234
ELUSIONS
o>
^O
•»
CO
UJ
-I
UJ
O
80
40
12345
ELUTIONS
A SLT- SL
V MINN - ACETATE
A REAL LEACHATE
NOTE: Cu concentrations in all distilled water leachates were less
than 0.6ppm.
Figure I. Cu concentration and release from a CuO-Na?SO.
sludge in test leachates.
-------
of their life span, and would leach Cu from the CuO-Na2S04 sludge, the need
for such a leachate in the leaching test is apparent. The comparison of the
synthetic leachate and actual leachate is indicated by the results of the SLT
leaching test using municipal landfill leachate. Although not as acidic as
either of the acid leachates, the municipal landfill leachate still leached
much higher concentrations of copper than were obtained using distilled water
as the leachate.
The synthetic leachate gives a more accurate view than does the acetate
buffer of the leaching that would occur in a young municipal landfill. This
is because it models more aspects of municipal leachate than does the acetate
buffer, which models only pH. The synthetic leachate models an anaerobic
municipal leachate. Being anaerobic, it is air sensitive and requires careful
handling to avoid changes brought about by air contact. The most readily
observed change is the formation of an iron precipitate which forms an oxida-
tion. Precipitation introduces the possibility of loss from solution of mate-
rials by either occlusion in or adsorption on the precipitate. Thus, simple
air contact of the synthetic leachate may cause inaccurate results. An alter-
native, an aerobic synthetic leachate, has been developed. This leachate
avoids the oxidation-precipitation problem, but does so at the cost of not
modeling the redox potential of real leachate as completely as does the
anaerobic synthetic leachate.
The anaerobic synthetic leachate is designed to model the leaching
environment found in actively decomposing municipal landfills. Since many
wastes will be landfilled by themselves or with other industrial wastes, other
leaching solutions are needed to model the leaching environment found in those
landfills. For such situations, the SLT procedure recommends use of other
leaching media such as distilled water or that obtained by prior contact of
distilled water with the other wastes in question, or the media may be spe-
cially formulated to relate to the leachate expected from the other wastes.
All three tests use a distilled water leachate which would be more realistic
than synthetic municipal landfill leachate in many landfill situations.
SOLID-LIQUID RATIO
A direct dependence of concentration on solid/liquid ratio was frequently
seen with very soluble parameters, such as Na and K. Good examples of this
behavior are found in the Na and K data derived from leaching ink and paint
waste. A graph of the Na and K concentrations in the first H20 leaching from
ink and paint waste versus the amount of solid present per 100 ml leachate
(Figure 2) shows that the Na or K concentrations fall nearly on a straight
line. This indicates that the concentration in solution is directly dependent
on the amount of solid present for these parameters.
At the other extreme is a parameter whose concentrations are controlled
strictly by solubility equilibrium. In this case, the concentration in solu-
tion would appear to be independent of the amount of solid present and would
be the same in all tests. Such a situation has been ecnountered with the
wastes studied. For most parameters, concentration will probably be controlled
16
-------
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gm WASTE / 100 ml LEACHATE
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Figure 2. Variation in Na and K concentration and release from
an ink and paint waste with solid-liquid ratio (in
grams waste per 100 ml leaching media), using a dis-
tilled water leachate.
17
-------
by a number of competing factors—amount present, solubility, sorption or
desorption, etc.—and the effect of solid/liquid ratio on the concentration
will be more complicated than simple solubility relationships would suggest.
However, several practical considerations enter into the choice of a solid/
liquid ratio for a reliable standard test. A very low ratio, such as that
used in the Minn, test, requires small amounts of solid and generally produces
low concentrations of eluted parameters. This emphasizes analytical and sam-
pling errors. Also, a very low solid/liquid ratio models a much longer leach-
ing time in a landfill than does a higher ratio. While this might at first
appear to be an advantage, the accuracy with which a short test models long-
term leaching in a landfill probably decreases as the landfill time span
modeled gets longer. Thus, a test with a very low solid/liquid ratio is less
accurate for both modeling reasons as well as analytical ones in comparison
with tests using higher ratios. On the other hand, a test with a very high
solid/liquid ratio, while decreasing subsampling and analytical errors,
requires more elutions to deplete a partially soluble parameter in a waste in
order to determine maximum release than does a test with a lower ratio. A
solid/liquid ratio should, therefore, be selected between these two extremes.
Experiments conducted during development of the SLT (1) suggest that the 1 to
40 ratio used in the Minn, test is rather low and that both the 1:10 and 1:4
ratios used in the SLT and IUCS tests, respectively, are reasonable. Either
ratio could be used in a reliable standard test.
It is important to note how the weight of waste material is measured
when calculating the solid/liquid ratio. Dry weight, which is commonly used,
can present analytical difficulties for wastes containing volatile or semi-
volatile components other than water. Experiments with a variety of wastes
during development of the SLT suggested the use of drying at 105°C in a forced
air convection oven for 24 hours as a reasonable procedure to define dry
weight (1).
The choice of a solid/liquid ratio generally is not directly based on
landfill conditions (unless calculated from waste and rainfall conditions)
and, within a range between the extremes discussed above, is, therefore,
arbitrary.
NUMBER OF ELUTIONS
Both the SLT and IUCS tests use multiple elutions. Far more information
can be obtained from multiple elutions than from a single elution as used in
the Minn. test. The IUCS test uses five elutions, while the SLT uses three
(unless the pH in the synthetic leachate samples has not returned to below
5.0, in which case additional elutions are suggested until the pH does return
to 5.0 (1)). The extra elutions in the IUCS test provide more information
than the three elutions in the SLT; however, they also require more work. A
compromise needs to be made between the value of added information obtained.
from the extra elutions and the added work involved in obtaining it.
Multiple elutions provide information about the kinetics of release;
for example, whether the release of a particular parameter is controlled by
solubility or by the release of another parameter (i.e., matrix or surface
18
-------
decomposition triggering subsequent release of parameters held in the matrix
within the waste particles). With one elution, some species may not be
observed leaching from a waste when, in reality, they release in significant
amounts in later elutions. On the other hand, the last elution generally
yields successively less information as more elutions are specified. Thus,
the twentieth elution in a twenty-elution test is likely to yield substan-
tially less information than the third elution in a three-elution test. For
some wastes, one elution will give all the information obtainable; some wastes
will require three elutions, some five, a few wastes, perhaps, fifty. There
is no way of knowing the required number of elutions for a given waste without
running extensive tests to determine when some relative equilibration is
reached. This, obviously, is contrary to the concept of a standard test.
Experiments performed with a variety of wastes in developing the SLT indicated
that more elutions than three generally provided little or no additional
information (1). This was also found to be true in the present study.
Another factor in the selection of the number of elutions for a stand-
ard leaching test is simply convenience. When it is technically feasible,
the number of elutions chosen should be convenient for laboratory personnel.
The IUCS test is more inconvenient and/or expensive than the other tests in
that it requires working on weekends to perform five 48-hour elutions.
It is concluded that selection of the number of elutions should be based
on the number of elutions found useful for a variety of extensively tested
wastes and on convenience. The author's experience is that three is generally
sufficient, but if some key parameter with a particular waste suggests addi-
tional elutions (e.g., pH remaining above 5 using the synthetic leachate),
additional elutions should be run.
AGITATION TECHNIQUE AND SURFACE AREA OF CONTACT
The SLT and the IUCS tests had generally effective agitation techniques
in that little particle abrasion was observed and particle and leaching media
movement was sufficient to avoid visually obvious concentration profiles in
the media. The Minn, test developed pronounced concentration differences
which were observable between the liquid located near the waste particles and
that located away from the particles when colored components were being
leached. These concentration differences are not surprising, since the waste
is not agitated for 24 hours following the initial shaking.
For two wastes, namely, the coal tar waste and the CuO-Na2S04 waste, the
SLT agitation method in itself appeared to be one reason for the higher
release with the SLT test than with the IUCS test. In the SLT agitation pro-
cedure, the waste is always gently tumbling through the leachate. This
exposes more surface area of the waste to leachate contact. The IUCS test
agitation procedure did not provide such particle agitation of the waste,
resulting in approximately the same waste surface being in contact with the
leachate. With coal tar waste, the concentration of napthalene was higher
in the SLT H20 leachates than in the IUCS H20 leachates (Figure 3). Given
the physical nature of coal tar, it is reasonable to ascribe the higher con-
19
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ELUTIONS
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waste in test leachates.
20
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Figure 4. Na concentration and release from a CuO-Na?SO.
sludge in test leachates.
21
-------
centrations to the greater surface area in contact with the leaciiate. Coal
tar is impervious to water and viscous enough to inhibit internal diffusion.
Thus, for unsaturated parameters, the concentration in leachate will depend
on the surface area of contact with the waste. Another probable example of
the effects of agitation on release can be seen in the Na release from the
CuO-Na2S04 sludge (Figure 4). A comparison of the Na release in the SLT and
IUCS tests using H20 as the leaching media shows a more rapid drop off in
release in the IUCS test such that the fifth elution, for example, provided
little additional release beyond that of the fourth elution. The SLT data
indicate that the Na is continuing to be released in the later elutions. It
appears that the waste in the IUCS test formed a thick layer in the test ves-
sel and was subsequently released slowly by diffusion. In the SLT, the
tumbling agitation constantly mixed the waste and leachate in order to mini-
mize the amount of stagnant interstitial water. Thus, the more complete mix-
ing in the SLT promoted continued dissolution of very soluble components.
ADDITIONAL TEST COMPARISONS
The SLT uses either or both of two elution procedures: one in which
fresh waste is contacted with leachate fromthe previous elution (procedure C),
and one in which fresh leachate is contacted with a previously eluted waste
(procedure R). The IUCS test uses only a procedure similar to procedure R;
whereas, the Minn, test uses only one elution. Procedure C gives an indica-
tion of what will happen to a given parameter as the leachate passes through
a large volume of waste; i.e., the procedure will give results which approxi-
mate or approach saturated conditions. As landfills will generally have very
high solid/liquid ratios, at least temporarily, and the leachates will often
be saturated, this information can be very useful. On the other hand, an
estimation of the total amount of a parameter which may potentially be
released to the environment requires information about the maximum release
under landfill conditions per unit mass of waste. The two procedures in the
SLT allow an estimation of both maximum concentration and maximum release.
Neither of the other tests, nor any others known to the authors, allow both
estimations. The IUCS test gives an estimate of maximum release, since it
also involves multiple Teachings of the same waste sample.
The Minn, test results cannot be used by themselves to provide with any
degree of certainty either maximum concentration or release information. The
results may have practical value bv being comparable to results from some full
scale landfills, but there is no way of knowning this in advance without hav-
ing an extensive data base from monitoring actual landfills.
The effects of two test conditions, namely, time per elution and tem-
perature, could not be analyzed from the test results. All the tests were
run at the same temperature (ambient or 20°C). The IUCS test uses a 48-hour
elution time, while both the Minn, and SLT tests use a 24-hour elution time.
The effect of elution time cannot be separated from other variables in compar-
ing the three tests.
22
-------
REFERENCES
1. Ham, R.K., M.A. Anderson, R. Stegmann, and R. Stanforth. Background
Study on the Development of a Standard Leaching Test. Final Report on
EPA Grant R-804773-01, submitted to EPA August, 1978.
2. Ham, R.K., M.A. Anderson, R. Stegmann, and R. Stanforth. Comparison of
Three Waste Leaching Tests. Final Report on the extension of EPA Grant
R-804773-01, submitted to EPA October, 1978.
23
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TECHNICAL REPORT DATA
(Please read Instructions nn thi rt < me hifon1 l
1 REPORT NO.
EPA-600/8-79-001
2.
3. RECIPIENT'S ACCESSION NO.
4. TITLE ANOSUBTITLE
5. REPORT DATE
COMPARISON OF THREE WASTE LEACHING TESTS
Executive Summary
6. PERFORMING ORGANIZATION CODE
May 1979 (Issuing Date)
7 AUTHOR(S)
Robert K. Ham, Marc A. Anderson, Rainer Stegmann,
and Robert Stanforth
8 PERFORMING ORGANIZATION REPORT NO.
9 PERFORMING ORGANIZATION NAME AND ADDRESS
Department of Civil and Environmental Engineering
University of Wisconsin-Madison
Madison, Wisconsin 53706
10. PROGRAM ELEMENT NO.
1DC818, SOS 1, Task 38A
11. CONTRACT/GRANT NO
Grant No. R-804773-01
12. SPONSORING AGENCY NAME AND ADDRESS
Municipal Environmental Research Laboratory—Gin. ,OH
Office of Research and Development
U.S. Environmental Protection Agency
Cincinnati, Ohio 45268
13. TYPE OF REPORT AND PERIOD COVERED
Final Report,Executive Summary
14. SPONSORING AGENCY CODE
EPA/600/14
15. SUPPLEMENTARY NOTES
See also main report "Comparison of Three Waste Leaching Test," EPA-600/2-79-071
Project Officer: Donald Sanning 513/684-7871
16 ABSTRACT
A comparison of three leaching tests was performed with thirteen industrial wastes to
evaluate the potential of each test for use as a standard leaching test procedure.
Such a procedure would be used to assess the leaching characteristics of industrial
wastes for land disposal. The study was done in conjunction with a background study
on the development of a standard leaching test.
The advantages and disadvantages of each test based on the leaching characteristics
of the thirteen wastes and the usefulness of each procedure as a standard test are
analyzed and compared. Finally, comments are provided on the need for careful
interpretation of test results.
17
KEY WORDS AND DOCUMENT ANALYSIS
DESCRIPTORS
Leaching
Tests
Methodology
Selection
Interpretation
Assessments
Evaluation
b. IDENTIFIERS/OPEN ENDED TERMS
Leaching Tests
Industrial Sludges
t. COSATl l-icld/Ciroup
14B
18 DISTRIBUTION STATEMENT
Release to Public
19 SECURITY CLASS (Tliiv Report/
Unclassified
21 NO. OF PAGES
30
20 SECURITY CLASS /Tins page)
Unclassified
22. PRICE
EPA Form 2220-1 (Rev. 4-77)
24
S. GOVERNMENT PRINTING OFFICE: 1979-657-060/1670 Region No. 5-11
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