&EPA
United States
Environmental Protection
Agency
Municipal Environmental Research EPA-600/2-78-095
Laboratory May 1978
Cincinnati OH 45268
Research and Development
Compilation
and Evaluation
of Leaching
Test Methods
600278095
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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 ENVIRONMENTAL PROTECTION TECH-
NOLOGY series. This series describes research performed to develop and dem-
onstrate instrumentation, equipment, and methodology to repair or prevent en-
vironmental degradation from point and non-point sources of pollution. This work
provides the new or improved technology required for the control and treatment
of pollution sources to meet environmental quality standards.
This document is available to the public through the National Technical Informa-
tion Service, Springfield, Virginia 22161.
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EPA-600/2-78-095
May 1978
COMPILATION AND EVALUATION OF
LEACHING TEST METHODS
by
William Lowenbach
MITRE Corporation
McLean, Virginia 22101
Contract No. 68-03-2620
Project Officer
Donald E. Sanning
Solid and Hazardous Waste Research Division
Municipal Environmental Research Laboratory
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 report has been reviewed by the Municipal Environmental Research
Laboratory, U.S. Environmental Protection Agency, and approved for publica-
tion. 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.
11
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FOREWORD
The Environmental Protection Agency was created because of increasing
public and government concern about the dangers of pollution to the health
and welfare of the American people. Noxious air, foul water, and spoiled
land are tragic testimony to the deterioration of our natural environment.
The C9mplexity of that environment and the interplay between its components
require a concentrated and integrated attack on the problem.
Research and development is that necessary first step in problem solu-
tion and it involves defining the problem, measuring its impact, and search-
ing for solutions. The Municipal Environmental Research Laboratory develops
new and improved technology and systems for the prevention, treatment, and
management of wastewater and solid and hazardous waste pollutant discharges
from municipal and community sources, for the preservation and treatment of
public drinking water supplies, and to minimize the adverse economic, social
health, and aesthetic effects of pollution. This publication is one of the
products of that research; a most vital communications link between the
researcher and the user community.
This report is basically a compilation of leaching test methods but it
also provides an insight into useful application and interpretation of these
tests for further evaluation under the overall USEPA program effort being
carried out under a grant to the University of Wisconsin.
iii
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ABSTRACT
Under the Resource Recovery and Conservation Act of 1976, EPA is
required to promulgate criteria for identification of hazardous wastes.
One method of identification is to characterize the leachability of the
waste. This study evaluates those factors important to the design of such
a test. Additionally, existing leachate tests are compiled and from this
listing three tests have been recommended for further evaluation.
This report was submitted in fulfillment of Contract No. 68-03-2620
by Municipal Environmental Research Laboratory under the sponsorship of
the U.S. Environmental Protection Agency. This report covers the period
of May 1977 to August 1977, and work was completed February 21, 1978.
iv
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CONTENTS
Foreword ill
Abstract iv
Figures vi
Tables vii
Acknowledgements viii
1. Introduction 1
Legislative and Regulatory Requirements ... 1
Objectives and Approach ..... 1
Background to SLT Development 2
2. Theoretical Considerations of Leachate Generation 9
Introduction 9
Thermodynamic Relationships 9
General Kinetic Considerations 15
Theoretical Degradation of a Landfill 41
Summary of Relevant Test Parameters 43
3. Compilation and Evaluation of Leachate Generation Methods ... 45
4. Summary and Conclusions 88
Interpretation of Shake Tests 88
Recommended Tests for Further Evaluation 90
References 91
Appendix. Test Procedures 95
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FIGURES
Number Page
1 Generalized model for thermodynamic description of leachate
systems 11
2 Generalized model for chemical dynamic description of
leachate systems 14
3 Steps involved in crystal dissolution 17
4 Relative equilibrium constants as a function of temperature ... 19
5 Solubility of simple salts as a function of the common ion
concentration 22
6 Speciation of cadmium in a four ligand system as a function
of pH 24
7 A partial chemical structure for fulvic acid 33
8 Complexation of a metal ion by humic acid 34
9 Simplified pe - pH diagram for iron in water 37
10 The pe of leachate in landfills as a function of time 38
11 The theoretical degradation of a landfill 42
vi
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TABLES
Number Page
1 Industrial Waste Chemical Analysis .... 4
2 Definition and Significance of Factors Affecting Leachate
Generation 5
3 Analysis of the Ether Extractable Acid Portion of Year Old
Leachate 25
4 Dry Weather Organic Analysis of Leachates from Norway and the
Pacific Northwest 30
5 Nonvolatile and Volatile Constituents of Leachate 31
6 Range of Heavy Metal Concentrations Found in Leachate 40
7 Range of Leachate Composition in Sanitary Landfills in the
United States 44
8 Leachate Generation Methods 46
A-l IUCS Modified 48-Hour Shake Test Chemical Analysis Schedule ... 100
vii
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ACKNOWLEDGEMENTS
The author wishes to acknowledge those who gave so generously of their
time and patience during the compilation of this document. Special thanks
in particular go to Mr. Fred Ellerbusch and Dr. Harvey Abelson of The MITRE
Corporation for their valuable contributions to this document. Finally, the
many helpful suggestions and technical assistance of the following individuals
are greatly appreciated: Mr. Don Banning of the EPA-ORD-Cincinnati; Messrs.
Alan Corson and Donn Viviani of the EPA, Office of Solid Waste, Washington;
and Dr. Barbara Fuller and Ms. Joyce Schlesinger of The MITRE Corporation.
viii
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SECTION 1
INTRODUCTION
LEGISLATIVE AND REGULATORY REQUIREMENTS
One of the major objectives of the Resource Conservation and Recovery
Act of 1976 (P.L. 94-580) is to regulate the management of hazardous wastes.
According to section 1008, the EPA is to develop guidelines which shall
"describe levels of performance, including appropriate methods and degrees
of control (for solid waste management) that provide at a minimum for (A) pro-
tection of public health and welfare; (B) protection of the quality of ground
waters and surface waters from leachates; (C) protection of the quality of
surface waters from runoff through compliance with effluent limitations under
the Federal Water Pollution Control Act, as amended; (D) protection of ambient
air quality through compliance with new source performance standards or re-
quirements of air quality implementation plans under the Clean Air Act, as
amended; (E) disease and vector control; (F) safety; and (G) esthetics."
Section 3001 explicitly directs the administrator of the EPA to "develop
and promulgate criteria for identifying the characteristics of hazardous
wastes and further, to list hazardous wastes which will be subject to the
provisions of the act." These regulations are to take into account toxicity
persistence, degradability in nature, potential for accumulation in tissue
and other related factors such as flammability and corrosiveness.
Thus, as part of a protocol to classify a particular waste as hazardous,
it is proposed first to examine that waste in terms of characteristics such
as reactivity, flammability, corrosiveness, infectiousness, and radioactivity.
If the waste is determined to be non-hazardous with respect to the above
criteria, the waste is further examined in terms of its leachability in a
sanitary landfill under natural conditions. This second stage of testing
involves generation of a leachate from the waste in the laboratory (in a
manner consistent with those natural processes which occur in a landfill)
together with a subsequent evaluation of this leachate. Properties which
might be used to define the hazards associated with this leachate include
toxicity, carcinogenicity, mutagenicity, and teratogenicity.
OBJECTIVES AND APPROACH
At present, there is no standard method for extracting a leachate from
a solid material. Moreover, those processes which govern leachate formation
within a landfill are only poorly understood. As an initial step in the
development of a standard protocol for leachate generation, the MITRE
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Corporation/METREK Division has surveyed existing extraction methods as used
by various industries and academic institutions for assessment of leachate.
The purpose of this document is (1) to identify those mechanisms which most
significantly affect leaching within a natural landfill; (2) to relate these
mechanisms to a laboratory leachate test; (3) to compile the results of the
above survey, along with other available information; (4) to critically
evaluate the various methods; and (5) to provide three candidate interim
standard leaching tests which shall be further tested as part of a separate
grant to the University of Wisconsin.
Test protocols have been obtained in the following ways:
(1) ASTM committee D19 sent approximately 200 question-
aires to its members and other parties who expressed
interest in solid waste leachate generation method
standardization. The results of that survey (19
responses) have been compiled.
(2) Offices responsible for regulation of solid waste
within state environmental agencies have provided
test methods which are either in current use or
under consideration for adoption as a standard
method.
(3) The literature has been surveyed for applicable
leachate generation methods.
To critically evaluate laboratory leachate generation methods, it is
first necessary to consider leaching under natural conditions. From such a
consideration, those parameters which most effect leachate generation and
quality may be identified and evaluated from both a theoretical and practical
viewpoint. Test methods may then be assessed in terms of the above criteria.
Finally three test protocols which promise to best model natural leachate
generation will be selected.
BACKGROUND TO SLT DEVELOPMENT
Definition of Relevant Parameters
Leachate is liquid which has contacted solid material and has extracted
and/or suspended constituents from it. Whenever water comes into direct
contact with solid materials, the potential for leaching exists. Many species
exist in solid materials which may be readily soluble in water. Still others
may be solubilized by the action of leachate upon them. Thus, character of
the leachate depends upon both the composition of the material and on envir-
onmental factors.
The principal concern of leachate assessment is not simply which pollu-
tants are released to the environment, but, rather, the rate at which these
pollutants are released. Because the kinetic rate expression for leaching
is extremely difficult to write from purely theoretical considerations, this
data is best obtained experimentally. Once a leaching rate is known, various
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modeling techniques may be used to describe the transport of this leachate
into the surrounding media.
The materials which are grouped together in the category of solid wastes
contain a wide range of organic and inorganic components. While Table 1 lists
typical analyses of six industrial wastes, analyses of other wastes may be
entirely different. Furthermore Table 1 concentrates specifically on inorganic
components, and organic species (identified only as volatile matter in Table
1) are also important factors in determining the potential hazard of a waste.
Environmental factors which exert a strong influence on the character
of leachate include pH, the redox potential, the chemical composition, (i.e.,
hydophobicity, ionic strength, etc.) and temperature. Factors which primarily
affect leachate transport, i.e., the rate of leachate generation, include the
flow rate of the eluant and the surface area, porosity, and permeability of
the material being leached. The definitions and significance of these and
other relevant parameters are briefly discussed in Table 2.
General Methods of Leachate Generation
An ideal leaching test then, in order to be meaningful and reproducible,
should control those parameters discussed in Table 2 and furthermore should
be quick and inexpensive. Additionally, the test should yield information
regarding the equilibrium concentration of the important constituents of the
leachate, the total amount of each constituent available for leaching from
the waste, and the kinetics of the solubilization reactions, including the
dynamic changes in leachate composition as various compounds are totally
leached from the waste.
No single existing leachate test fulfills all of these requirements.
Existing tests fall into three main categories. They are shake (or batch)
tests, column tests, and field cell tests. Shake tests consist of placing
a sample of the material to be leached in a container with a suitable eluant,
agitating the mixture for a specific period of time and analyzing the result-
ing leachate. This technique can be designed to yield a variety of equili-
brium concentrations, depending on the duration of the test, the liquid to
solid ratio, and the particle size of the waste. Additionally such a test
might conceivably be designed to yield kinetic data if the leachate is
sampled at suitable time intervals. An alternate approach to obtaining
kinetic data from a shake test is to repeatedly extract the sample with
fresh eluant. Shake tests have the advantages of being quick (up to 96
hours), simple (i.e., minimal equipment requirements), and inexpensive.
Shake tests are also likely to be the most reproducible of the three types
of tests since all variables can be carefully controlled. However, data
concerning reaction kinetics are somewhat difficult to obtain from a shake
test; furthermore, even though the variables of a shake test may be relative-
ly easily controlled, the conditions chosen may be difficult to relate to
environmental conditions in a landfill. As a result, the analyses obtained
from such tests may be difficult to interpret.
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TABLE 1
INDUSTRIAL WASTE CHEMICAL ANALYSIS
WASTE CELL NUMBER
Total Solids2 ,
Total Volatile Solids
Moisture
Cr
Ni
Cu
Fe
As
Be
Se
Cd
Cn
Pb2
C1 4
Asbestos
Hg
Sn
Sb ,
Clay Volatile Fibers
Zn
V
B
Tl
REFINERY
SLUDGE
21.00
31.00
79.00
125
23
3500J
5560
1.0
4.8
26.0
0.50
1.0
182
2.35
3.00
10.6
40.0
7.20
BATTERY
PRODUCTION
WASTE
10.75
7.94
89.25
155
32
1125
2950
72
1.8
180
29.0
4.2
3.48^
1.12
208
4.80
6800 ,
1.32
720
120
8.10
ELECTROPLATING
WASTE
20.47
8.98
79.53
1.56^
35
100
1.372
460
0.25
4.50
38.5
460
267
1.35
23.0
14.7
86.0
19.0
INORGANIC
PIGMENT
WASTE
48.25
22.25
51.75
0.50
10
110
1000
3.4
20.2
16.0
10.5
3.4
120
10.0
45.0
7.60
185
40
28.5
CHLORINE
PRODUCTION
BRINE SLUDGE
75.89
1.17
24.11
5.00
65
125
2000
14.5
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TABLE 2
DEFINITION AND SIGNIFICANCE OF FACTORS AFFECTING LEACHATE GENERATION
FACTOR
DEFINITION
SIGNIFICANCE
REMARKS
pH pH is defined as the negative
log of the hydrogen ion concen-
tration. pH is an Indirect
measure of the electro-chemical
potential of protons.
The hydrogen ion concentration
is an important factor affecting
reaction rate and thus pollutant
solubilities.
The pH of rainwater is con-
trolled primarily by dissolved
CO.. With rare exceptions,
proton exchange and associated
processes occur so rapidly that
such systems may be treated in
terms of shifts of true equili-
brium.
pe Is the negative log of the
electron activity of a solution.
EH is the redox potential of a
system as defined by the Nerst
equation. In natural systems E.,
is taken as the measured poten-
tial difference between an inert
electrode (Ft) and a reference
electrode.
pe is an Intensity factor and
measures the oxidizing Intensity
of a system. The redox potential
£„ is a measure of the oxidizing
capacity of a system, pe and pH
are useful as master variables
and provide a framework within
which redox and hydrolysis re-
actions may be compared.
pe and E^ determine, in part,
the aerobic or anaerobic conditions
under which a material is leached.
Large positive values of pe (low
electron activity) represent
strongly oxidizing conditions while
small or negative values (high
electron activity) correspond to
strongly reducing conditions, pe
is a theoretical concept and diffi-
cult to measure in the environment.
is more easily determined, but
ty not yield true equilibrium
values.
Buffer The buffer capacity of a system
Capacity is defined as the response of that
system, in terms of pH change, to
the addition of an acid or a base.
Buffer capacity defines the re-
sistance of a system to changes
in pH upon the addition of acids
or bases.
Naturally occurring leachate
exists as a highly buffered sys-
tem. Total acidity and alkalinity
together with pH operationally
define buffering capacity.
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TABLE 2 (CONTINUED)
FACTOR
DEFINITION
SIGNIFICANCE
REMARKS
Complexation Complexation is defined as the
Capacity formation of a complex from a metal
ion with a netural or negative ion
by means of one or more chemical
bonds.
The effects of Complexation
vary from increasing the solu-
bility of specific metals to
causing their precipitation,
depending on the complexing
agent and the metal ion. Com-
plexation affects the solubili-
ties, reactions amd modes of
transport of leached materials.
The most effective complexing
agents are generally organic
compounds. Fulvic and humic acid
are two naturally occurring com-
plexing agents of possible signi-
ficance in terms of heavy metal
transport.
Ionic Strength The ionic strength of a solution,
I, is defined as I - J^ZC^2, where
C-L is the concentration of an ion in
moles per liter, Z^ is its charge and
the sum is taken over all ions in the
solution.
Ionic strength has a signif-
icant effect on reaction rate and
therefore influences the solubil-
ity of ionic species. In general
the solubility of an ionic salt is
roughly proportional to /T~ for
dilute solvents.
The ionic strength is generally
calculated rather than measured
directly. The ionic strength to-
gether with the dielectric constant
define in part the polarity of a
medium.
Dielectric The dielectric constant is defined
Constant by e in the equation p m
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TABLE 2 (CONCLUDED)
FACTOR
DEFINITION
SIGNIFICANCE
REMARKS
Surface Area The surface area Is somewhat
difficult to define operationally
but practically involves the measure-
ment of.some property that qualita-
tively depends on the extent of surface
development and can be related (by
means of theory) to absolute surface
area. Suitable methods of determina-
tion include particle or pore size
measurement and permeability studies.
Heterogeneous reactions of solids
and liquids are often governed by a
surface process that occurs at a rate
directly proportional to the surface
area of a solid, in addition to the
reagent concentration in the liquid
phase. Finely divided particles have
a greater solubility than large cry-
stals. The surface energy of particles
smaller than ~ly may become large enough
to effect surface properties.
Different methods of surface area
measurement will lead to different
result. For the purpose of dis-
cussing leachate generation within
a landfill, methods based on
permeability studies or particle
size measurement are most useful.
Particle size of materials deposited
in landfill usually decreases with
time due to physical and chemical
weathering processes.
Liquid to The liquid to solid ratio may be de-
Solid Ratio fined for both a landfill and a labora-
tory leachate test. The ratio is best
defined by the weight ratio of an eluant
to the solid.
Increasing the liquid to solid ratio
will Increase the total amount of species
leached; conversely, a low liquid to
solid ratio will minimize the amount
of species leached but will lead to
higher concentrations of the most soluble
species.
The liquid to solid ratio is
difficult to define for natural sys-
tems; moreover any such ratio defined
will vary significantly with time.
In a laboratory test this ratio will
determine the Importance of common
ion effects.
Contact
Time
The amount of time (residence time)
between an eluant and the solid leached.
Maximum species concentrations (in a
batch test) will occur upon the attain-
ment of equilibrium. Equilibrium is a
unique thermodynamic state of a system
depending only on temperature; as such,
this state provides a framework within
which comparisons to other systems may
be made.
True equilibrium, or even steady
state conditions, are unlikely to be
reached in natural systems. For
such systems the extent of reaction
(related to equilibrium) may be a
more useful concept than equilibrium
per se.
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Column tests are performed by placing the material to be leached in a
column, with or without a quantity of fill material from a landfill. Eluant
is allowed to flow through the column, the rate of flow being proportional
to the head (height of water in the column) and the permeability of the
material. Advantages of column tests include low cost, minimal equipment
requirements and a generally more accurate simulation of kinetic factors
affecting environmental systems than is obtained by shake tests. The major
disadvantage is the length of time required to yield meaningful results,
generally in the range of months to years.
Field test cells are controlled scale models of actual waste disposal
sites, usually employing extensive monitoring systems. Field tests are the
most accurate method of determining the quality and quantity of leachage
entering the environment under the specific test conditions. However, they
are expensive, time consuming, and highly site-specific.
Due to the requirements for a quick and inexpensive test, current re-
search emphasis is focused on the shake test. Therefore, the remainder of
this document is primarily devoted to a discussion of those factors which
most affect the design of a shake test.
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SECTION 2
THEORETICAL CONSIDERATIONS OF
LEACHATE GENERATION
INTRODUCTION
Leachate generation, whether under natural or well-controlled conditions
(i.e., in the laboratory), is exceedingly complex. The description of inter-
actions between an eluant and a solid phase, even at the most rudimentary
level, necessitates an understanding of heterogeneous equilibria; furthermore,
both the eluant and solid phase are complex heterogeneous systems in their
own right. Additionally because such systems, in general, will contain both
organic and inorganic matter, chemical characterization is difficult at best.
Currently, available chemical data and phenomenological models are unable
to accurately predict the distribution of species in leachate much less the
kinetics of leachate generation; furthermore, it is doubtful whether any
attempt to describe such systems in full detail will ever be complete. How-
ever, useful insights may be gained by application of equilibrium, and where
possible kinetic, models to simple homogeneous and heterogeneous systems.
Where kinetic information is not available, (and it is generally not) equili-
bria models at least provide boundary conditions within which discrepancies
between observed conditions and the models may be resolved. Thus the major
value of the phenomenological model presented below will lie in the compara-
tive format in which the following questions may be asked: (1) What is the
basic mechanism of leachate generation? (2) What are the most important
factors, i.e., the controlling chemical reactions, in leachate generation?
(3) And finally, how should a laboratory test be designed so as to yield
the most useful information for prediction of leachate generation in the
field?
THERMODYNAMIC RELATIONSHIPS
One common definition of equilbrium (with respect to a particular reac-
tion in a closed system) is, "that state attained when a reaction is allowed
to proceed in the 'forward1 direction (left to right) until there is no net
change in the composition of the system and then to allow the same reaction
to proceed in the 'backward' direction until again no net change is observed";
if chemical equilibrium is reached, the composition of the system will approach
the same limit from both directions. However many systems, notably organic
and redox reactions, do not reach equilibrium over short time spans. For
these systems only kinetic and mechanistic descriptions will suffice. Never-
theless, for a large number of reactions there is sufficient evidence (kinetic
and equilibrium) to justify consideration of real systems at the equilibrium
state.
9
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Equilibrium Model for Leachate Systems
With the preceding discussion serving as a brief review of those elements
of thermodynamics necessary for development of equilibrium models, it is now
possible, in theory at least, to consider the real and complex systems which
occur in the natural environment. However, before discussing the more realis-
tic models, it is useful to discuss chemical equilibria within the conceptually
simpler framework of a closed system. In general such a system (see Figure 1)
consists of a gas phase, an aqueous phase, and a specified number of solid
phases of defined compositions. To develop a rigorous thermodynamic defini-
tion of such a system, information.about concentrations* (or more accurately
activities), and pressure is required.
Construction of an isothermal, isobaric thermodynamic model is, in theory
at least, relatively straight forward. The system is first defined in terms
of relevant species and phases. Care must be taken to ensure the thermo-
dynamic self consistency of the system, (e.g., an equilibrium constant for
each reaction, the stoichiometry of each reaction specified, a net charge of
zero in the solution phase). With the system thus defined and assuming the
availability of required thermodynamic data (free energies, equilibrium
constants), AG is set equal to zero and the composition of the system cal-
culated. To date the only application of this approach has been to inorganic
ocean (Kramer, 1965) and fresh water models (Stumm, 1970; and Morel and Morgan,
1972).i
The above requirements are deceptively simple. It is not a trivial
task to identify pertinent reactions and equilibria of all types require
careful examination because of their influence on pH, buffering capacity
(both pH and pe), and adsorption of inorganic and organic species. Complex
formation equilibria between all possible ligands and cations of interest
must be considered. Where the redox equilibria of multivalent elements
(e.g., the transition metals, nitrogen) are considered, the situation be-
comes even more confused; competing redox systems can often lead to pseudo-
equilibrium conditions.
More import§nt, are the inherent limitations of any thermodynamic
treatment. Reactions predicted to be thermodynamically favored (i.e., a
large negative AG) need not occur at observable rates. Familiar examples
include most organic reactions; the decomposition of acetic acid,
CH COOH == 2H20 + 2C
is predicted to be highly spontaneous (AG = -17.9) but because of the lack
of a suitable kinetic pathway does not proceed at an observable rate. The
lack of any required relationship between the thermodynamics and reaction
rates simply means that while thermodynamic models may provide boundary
values for such systems, kinetic considerations may render such answers of
little practical significance.
*For a rigorous derivation of the relationship between activity and concen-
tration, see Moore (1972), page 307.
10
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P,T
Partial pressure
Fugacity
Concentration
Activity coefficient
Activity
Mole fraction
Activity coefficient
Activity
fl'f2""fn
,...
12 n
PHASE a
Y Y Y
V*2'"' n
Y1,Y2,..-Yn
PHASE 8
x1,x2,...xn
PHASE y
x1,x2,...xn
n
GAS
AQUEOUS
SOLUTION
PHASE
SOLID
PHASES
FIGURE 1. GENERALIZED MODEL FOR THERMODYNAMIC DESCRIPTION
OF LEACHATE SYSTEMS.
11
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Consider the chemical reaction
(1) aA + bB + ... = cC + dD + ...
where a,b,c,d, are the mole numbers of species A, B, C, D, repectively.
Furthermore, assume that the rate of reaction may be expressed in the form
(2) - i- dA. = - 1- 22. = !_d£ = i_dD = k [Aja r^b , ,C[ -.d
where kf and kr represent the rate coefficients of the forward and reverse
reactions and LA], [B], etc. are molar concentrations. At equilibrium the
rate of reaction (equation 2) must go to zero, i.e., the forward and back-
ward velocities, Vf and vr, are equal, then
(3) kf [A]a[B]b... = kr tC]°[D]d...
which upon rearrangement yields
«>'irfC
I
where K is defined as the equilibrium constant. The quotient shown in
equation (4) is in general defined as the reaction quotient Q and equals K
only at equilibrium. In general, then
(5) \ = ^1 = K
V k Q
In an individual reaction (or for that matter, a complex system of
interlocking reactions) the driving force for any chemical change is the
value of the Gibbs free energy,
(6) AG = AG° + RT In [ C] ° [D]d...
[A]a [B]b...
where R is the ideal gas constant and T the temperature in degree Kelvin.
At equilibrium, AG = 0 by definition and Q is equal to K so that the Gibbs
free energy in the standard state is
(7) AG° = -RT In K
More generally, under any conditions, from equations (6) and (7) together
with the definition of Q,
(8) AG = RT In 5.
K
12
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Dynamic Model for Leachate Systems
Any relevant leachate generation model must, however, be designed as an
open system. Figure 2 illustrates the major features necessary for the
formulation of a dynamic model for such a system. While in theory any arbi-
trary model might be studied, the simplest model of a dynamic system is one
at a stationary, nonequilibrium state. In contrast to a closed system at
equilibrium where AG = 0, the stationary state is determined by the fluxes of
reactants and products between the system and its surroundings and by the
reaction kinetics.
The fundamental expression which describes the concentration, C^ of a
constituent i at any point (x,y,z) in a dynamic system is:
(9) 6C. ^ 6C. _, 6C. 6C. 6 D 6C. . 6 D 6C. .
-r^1 + u 7—i + v 7—1 + w 7—i =7— x 7—1 + 7— y 7—1 +
6t Sx <5z 6z 6x 6x 6y } 6y
_A D 6£, _.
6z Z <5z i,n
where u6Cj_/<5x etc. are advective or convective terms, 6/6x(Dx6C^/6x) etc.
are diffusion transport terms, and r^ n denotes the rate of formation or
disappearance of component i by a process n. When component i is at the
steady state, then 6C^/6t = 0. Steady state models have been developed for
various chemical reactions and in different natural water systems. These
models require, however, detailed information on the flows in the system, the
rates of chemical reactions in the system, the diffusion and mixing of com-
ponents, etc. While such models can, in theory, accurately describe the
spatial distribution of chemical species involving a combination of slow
reactions, high rates of material and energy flow, and complex transport pro-
cesses within a landfill, the necessary conditions to achieve a stationary
state will rarely be realized because of large perturbations in the fluxes
of matter and energy.
With the preceeding discussion serving as an overview of the total sys-
tem, consider now those individual parts of the system which make up the whole
as shown in equation (9): transport of species once in solution (all terms
containing C^ and the kinetics of species formation (r^ n). There are
numerous studies concerning the transport of pollutants to the aquatic en-
vironment (e.g., Fuller, 1976). While such information is vital for the
proper design of a landfill facility, these studies have little bearing on
leachate formation per se. For a general review of transport theory, the
reader is referred to Gray (1973).
To understand and at least conceptually model leachate generation in
complex systems, those kinetic processes and mechanisms which influence
leachate composition must be considered; however, because a rigorous kinetic
treatment of leachate generation is beyond the scope of this document (and
probably impossible for any realistic case), only those factors which signifi-
cantly affect such modeling will be considered. The following sections, then,
are specifically intended to (1) set forth those general principals of
13
-------
ENERGY OUTPUTS
AND OUTPUTS
MATERIAL -<—^
OUTFLOWS (02
FROM "
SYSTEM
0
n
E2
n
TRANSPORT. MIXING
Convective Transport, Diffusion,
Gravitational Transport
CHEMICAL REACTIONS
AI
B2 ..
n
BIOLOGICAL PHENOMENA
Direct Chemical Influence
Indirect Chemical Influences
•^—MATERIAL
( ? INFLOWS
TO
SYSTEM
FIGURE 2. GENERALIZED MODEL FOR CHEMICAL DYNAMIC DESCRIPTION
OF LEACHATE SYSTEMS.
14
-------
reactions between solids and water (i.e., physical effects) and (2) discuss,
in general terms, those reactions (and those factors which mediate them)
affecting leachate composition. More complete understanding of these problems
will necessarily come from both laboratory experiments and field observations.
GENERAL KINETIC CONSIDERATIONS
Of necessity, any consideration of the dissolution of a solid phase re-
quires an understanding of heterogeneous equilibria; quite clearly, the nature
of the liquid-solid interface will play an important role and the intent here
is only to provide a brief discussion of those features which especially in-
volve surface chemistry.
The dissolving of a metal in acid solution (an example of a redox reac-
tion), of silicon dioxide by aqueous hydrofluoric acid (an example of
complexation), and of a soluble salt in water (complexation also) are primarily
surface reactions that occur at a rate directly proportional to the surface
area of the solid. Since, in general, chemical attack is also involved, the
reaction rate is also dependent on the concentration of the reagent. It is
important to note that either the chemical reaction at the surface may be
rate controlling, as is the case with the dissolving silica, or the diffusion
of products away from the surface may be the slow step, as is the case with
the dissolving of a soluble salt. Because diffusion processes have been ex-
tensively discussed by numerous other authors*, and, moreover, because the
deliberate direct disposal of large quantities of highly soluble material is
presumed to be precluded from proper landfill operation, only the case where
the chemical reaction is rate controlling (e.g., as in the case of the dis-
solution of sparingly soluble salts), will be considered here.
Kinetics of Dissolution Reactions
Most inorganic systems exhibit surface charge along fracture and cleavage
surfaces due to the rupture of bonds. When such systems are brought into
contact with water, these ions absorb water molecules, which can then dis-
sociate. Dissolution occurs until the equilibrium is established. The extent
of a dissolution (or precipitation) reaction most often has been considered
for systems at equilibrium because kinetic factors are extremely difficult to
assess. Investigations of sparingly soluble salts appear to be limited to
the kinetics of crystal growth rather than dissolution. However, if the
principle of microscopic reversibility is to apply, the general features of
such a mechanism should apply equally to the dissolution of a sparingly
soluble salt. Empirically the rate of crystal growth for many salts may be
described by an equation of the form (Nancollas and Purdie, 1964)
dm ... ,. n
- — = ks (m - mo)
where m is the concentration of a species in solution at time t, k is the rate
constant, s is the available surface area, and n is a constant. This empirical
*See for example Crank (1956).
15
-------
relationship, which is also obeyed for certain dissolution reactions, may be
interpreted in terms of a mechanism involving a rate controlling surface re-
action. A possible mechanism for the dissolution of a solid is shown in
Figure 3 in which the overall dissolution process consists of: (1) art initial
diffusion of the ion, ion pair, or molecule from a kink site (position A) in
the crystal lattice along the step edge to position B which is less stable
than position A since only two surfaces are in contact with the crystal lat-
tice. Thereafter (2) the ion or molecule may diffuse to a still less stable
site (position C) to the bulk of the solution (position D). Experimental
evidence from crystal growth studies point to surface reactions such as (1)
or (2) as the rate determining steps rather than bulk diffusion (3) although
this need not be the case for dissolution.
Physical Effects
Before discussing the more complex relationship between eluant composi-
tion and dissolution rate, it is useful to first consider the kinetic effects
of temperature, ionic strength, dielectric constant*, and surface area.
While the latter may be for the most part, of somewhat less importance than
the eluant composition, such parameters may, under special circumstances out-
weigh the effects of eluant composition. A simple example would be a land-
fill which continually remains at temperatures below those necessary to allow
appreciable biodegradation.
Temperature
The variation of the equilibrium constant, K with temperature obeys the
law
(10) dlnK = A_E
dT = RT2
where R is the ideal gas constant, T the temperature in degrees Kelvin, and
AE the change in energy. Recalling the relationship between the equilibrium
constant K and the rate constants k
(4) kf/kr = K
and combining with equation (10) yields
(11) dink = AE
dT RT2
If equation (11) is integrated and the antilog taken, then
(12) k - Aexp(-EA/RT)
* Although the ionic strength and the dielectric constant are both related
to the composition of a given solution, these parameters, for the purposes
of this document, are considered to be better described in terms of physi-
cal rather than chemical effects.
16
-------
SATURATED SOLUTION
D
step dislocation
CRYSTAl
=$
^
^ B
. PHASE
Source: Nancollus and Purdie, 1964.
FIGURE 3. STEPS INVOLVED IN CRYSTAL DISSOLUTION.
17
-------
where A is a complex term often described as a frequency factor and EA is the
activation energy; thus as temperature increases so does the reaction rate.*
While such treatment is successful in predicting the affect of temperature on
many reactions, there are numerous exceptions. As an example, consider the
effect of temperature on the two most prevalent reactions in a landfill:
simple dissolution reactions (i.e., constant pH and pe) and biological re-
actions.
The net energy change for a simple dissolution process may, from a
thermodynamic viewpoint, be regarded as the sum of the free energy of lat-
tice dissociation and the free energy of solvation. Thus, a large lattice
dissociation energy (i.e., AG >0) tends to make a substance insoluble while
a large solvation energy**(i.e., AG <0) has the opposite effect. By writing
a kinetic expression for each process in the form of equation (12), the
effect of temperature on the overall process may be evaluated. Since the
breaking of lattice bonds is a dissociation process, an increase in tempera-
ture is expected to increase the rate of this process. Conversely, an in-
crease in temperature normally decreases the rate of ion solvation, as the
increased kinetic energy of molecules hinders orientation of the ions in the
solvation shell. Therefore, the effect of temperature on the dissolution
rate will be determined by two opposing terms, the rate of lattice energy
dissociation and the rate of ion solvation. While the solubilities of many
inorganic salts increase with temperature (dominance of the former term), a
number of compounds of interest in leachate (CaCO^, CaSC^) decrease in
solubility with increase in temperature. Figure 4 illustrates the relative
equilibrium constants of various compounds as a function of temperature.
Temperature has a strong effect on both biological activity and organic
reaction rates. For biological systems each microorganism will have an
optimum growth temperature, ranging from 0 C to as high as 80°C. Over a
short temperature range the growth rate increases with increasing temperature
as shown in equation (12). Much above the optimum temperature, however, the
growth rate drops to zero since vital enzymes are presumably destroyed. The
above argument also applies to organic reactions in general and a common
rule of thumb is that a 10°C rise in temperature doubles the reaction rate.
Ionic Strength
Ionic strength, I, is defined as
(13) I = 1/2 X C^2
where C is the concentration and the Z is the ion charge. The latter may be
related to the activity coefficient of a solute by a number of empirical ex-
pressions. The most useful relationship for relatively concentrated solutions
This analysis assumes that: (1) the reaction proceeds by a single pathway;
and (2) EA is independent of temperature.
Jc
Solvation energy is defined to include dipole-dipole and dispersion energies
as well as a positive entropy term.
18
-------
50°C
25°C
0°C
2.00
1.75
? 1.50
+
4->
1.25
4-1
CO
a
8 1.00
03
S 0.75
•H
tfl
0.50
0.25
I '
CaC03(s) * Ca+2 +
°2(g) °2(aq)
C°2(g) - C°2(aq)
3.1 3.2 3.3 3.4 3.5 3.6 3.7
4- x 103
Source: After Stumm and Morgan, 1970.
FIGURE 4. RELATIVE EQUILIBRIUM CONSTANTS AS A FUNCTION
OF TEMPERATURE.
19
-------
(~0.5M), is that of Davies:
(14) log y± = A z z fv/I -.21
" I 1 + /^~ ,
ft O / O
where y is activity coefficient of a solute; A = 1.82 x 10 (eT) (where e
is the dielectric constant; A ~ 0.5 for water at 25°C). From transition
state theory, which postulates that the rate of reaction is proportional to
the concentration of the transition complex, it may be shown that
log k/k = A z z (v/I .21
o + I ! +^
Thus equation (15) requires that ionic reaction rates (e.g., solubility)
increase with increasing ionic strength, a phenomenon which is most pro-
nounced for multivalent ions. Furthermore, because A is a function of
the dielectric constant, an increase in solvent polarity will also increase
the reaction rate.
Particle Size
If the rate of a reaction at a liquid-solid interface is limited by an
actual chemical transformation at the interface rather than by diffusion,
then rate of reaction will be directly proportional to surface area. How-
ever, for particles smaller than about lu> the surface energy may become
sufficiently large to affect surface properties, i.e., finely divided solids
have a greater inherent solubility than large crystals. The latter effect
may be expressed as
(16) InK » fl S
where y is the mean free surface energy of the liquid-solid interface, R is
the ideal gas constant, T the temperature in degrees Kelvin, and S the molar
surface area.
Chemical Effects
Turn now to the more complex task of describing those factors which will
control the composition of leachate in the natural environment. In general,
for an electrolyte that dissolves in water according to the reaction
A B "^
m r
the equilibrium condition is
= m
l(s)
= m
m n
A B = m/ \ /_^\
(aq) (aq)
20
-------
and the solubility is generallly expressed as the solubility product
where the activity of the pure solid phase is set equal to unity. Rarely
however can the solubility of a salt be calculated from its solubility product
alone. The simplest realistic case is illustrated by considering the solu-
bility of a salt in solutions that contain a common ion. Figure 5 is a
graphical representation of the solubility product where the log of the metal
ion concentration is plotted as a function of the log of the common ion. The
solubility may be characterized in this manner because the cations and anions
of the illustrated salts do not undergo protolysis reactions to a significant
extent near pH 7. Furthermore, complex formation between cation and anion
may be assumed to be negligible as long as the free metal ion and the free
cation concentration are small. Dashed lines in the figure indicate where
the foregoing assumptions are no longer valid.
However, even this case, in which solubility can be calculated from both
known concentrations and from the solubility product, is rarely encountered.
Dissolved ions frequently undergo chemical reactions in solutions and there-
fore equilibria other than the solubility product (e.g., complex formation
of the cation or anion with one of the constituents of the solution) must
also be considered. Additionally, cations and anions may further react with
water. As an example, consider the solubility of iron (II) sulfide in aqueous
solution containing sulfide anion. Not only the solubility equilibrium, but
also the hydrolysis equilibria of the cation,
Fe+2 + H 0 -—" FeOH+ + H+
A. t- » O
and the anion,
HS~ + OH~
H2S + OH~
and the equilibria describing complex formation
-*2 _L -2
FeS + S ^ • FeS
L
must be taken into account.
Since any realistic discussion of dissolution equilibria soon becomes
so complex as to become meaningless, practicality dictates consideration of
only those parameters which most affect the solubilities of organic and in-
organic solids. These include: the pH of the solution (leachate); the type
and concentration of complexing ligands and chelating agents; the oxidation
states of the inorganic compounds, and the redox environment of the system.
For complex organic constituents (i.e., high molecular weight compounds)
biological degradation may well be the most important mechanism of aqueous
21
-------
1 2
4-1
(U
o
a
o
60
o
-log {ANION} (pF~, pCl~, oSO~2, pCrO~2)
Source: After Stumm and Morgan, 1970.
FIGURE 5. SOLUBILITY OF SIMPLE SALTS AS A FUNCTION OF THE
COMMON ION CONCENTRATION.
10
22
-------
transport. Secondary effects such as adsoption of metal ions from solution
by the solid phase and ion exchange are not considered explicitly. The
following is a brief discussion of (1) those chemical factors which are rele-
vant to leachate generation in the environment (and hence must be addressed
by a laboratory leachate test) and (2) the general mechanisms by which the
above factors are likely to control important reactions.
pH
The negative logarithm of the hydrogen ion concentration, or pH, along
with the redox environment of the system, is the most important variable
controlling leachate composition. Because dissolution occurs in the aqueous
phase, pH may be considered as a master variable of the system; that is, any
reaction which involves either H+ or OH~ will be affected by the pH of the
medium.* In general, pH may affect dissolution in two principal ways: al-
teration of simple solution equilibrium and direct participation in redox
reactions. An example of dissolution by the first mechanism is the following:
CdCO_ ^^Cd"4"2 + CO"2 pK = 13.74
3 3 sp
however, in the presence of acid the following action takes place:
CO ~2 + 2H+ -[H9C01 -HO + CO
J I I
Thus, a sparingly soluble salt in a neutral solution, may be completely dis-
solved in a sufficiently acidic one. For a more realistic case, where at
least inorganic ligands other than water are present, the speciation of
cadmium is a function of pH as shown in Figure 6. Clearly, the formation
of insoluble ligand complexes may greatly affect the distribution of metals
between the solid and aqueous phases by the formation of precipitates.
The hydrogen ion concentration will also, in part, define the redox
potential of the system. For example, the following reaction is rapid in
moderately acidic solutions (
-------
Percent of Total Cd Concentration
O
c
33
m
o>
>cg
0
o
1-1
n
ro
i-t
ro
n>
rt
CD
o
o
o
o
_ VO
ii
N)
•n
O
C
13
O
>
Z
O
3
m
oo
VO
-------
TABLE 3
ANALYSIS OF THE ETHER EXTRACTABLE^
ACID PORTION OF YEAR OLD LEACHATE
2
Constituent Concentration Percentage of
(g/1) Fraction
Propionic acid
i-butyric acid
n-butyric acid
Valeric acid
4.5
16.5
48.8
5.2
6
22
65
7
Leachate (from which neutral constituents had been removed)
was acidified to pH 2 and extracted continuously for 48 hours
with diethyl ether.
2
Analyzed as methyl esters.
Source: Burrows and Rose (1975).
+3 +3
heavy metals. Most highly charged heavy metal ions, e.g., Fe , Cr , are
strongly hydrolyzed in aqueous solution as a result of the dissociation of
a coordinated water molecule within the hydration shell of the metal ion.
For example, in aqueous solutions, iron (III) hydrolyzes in the following
manner:
Fe(H20)3+ + R20 ^r Fe(H20)5OH+2 + H 0+
and
Fe(H20)5 OH+2 + H20
The extent of this reaction is roughly a function of the ionic charge: thus
highly charged species such as Hf*+ and Th4+ are extensively hydrolyzed while
ions such as Ca+2 and Mg+2 hydrolyze only in basic solution.
Hydrolytic products as shown above may also form polymeric species,
e.g.,
2Fe
25
-------
Such complexes may vary from small discrete ions to large high molecular
weight polymeric compounds; the latter are of considerable interest as they
may be regarded as the kinetic intermediates of insoluble metal oxides.
Buffer Intensity
Leachate must be considered as a highly buffered soltuion because the
organic acids and carbon dioxide produced by biodegradation will be partially
neutralized by basic materials in the landfill. A buffer solution may be
operationally defined as a fairly concentrated solution of a weak acid and
its conjugate base. While it may be unlikely that any single buffering system
is dominant in leachate, to consider further the mechanism of pH control, it
is useful to introduce the concept of buffer intensity, i.e., the capacity
of the solution pH to remain unchanged despite the addition of either acid
of base.
If the assumption is made that the hydrogen ion concentration is small
compared to the concentration of the acid [HA] and its conjugate base [A~],
then the pH of the solution may be expressed as
(18)
pH = PKa - log [HA]
[A-l
Mathmatically, the buffering capacity, p, is conveniently defined as
(19) o _
where A is a strong acid. Thus, the larger the value of B, the better the
buffering system. For a monoprotic acid* the buffer intensity is
(20)
(3= 2.303
,CH*]
where
,-14
Kw - [H+] [OH'] = 10"
An analogous expression may be defined for a polyprotic system.
26
-------
The dissociation constant of water,
[HA]
the dissociation constant of a weak acid HA and,
C - HA + A~ .
For any landfill where acidic and basic solids are present, heterogeneous
equilibria must be considered. The buffer intensity for such a system may
be defined in an analogous manner where the appropriate solubility equilibria
are taken into account. However, whether the system is controlled by homo-
geneous or heterogeneous equilibria does not affect the utility of the concept
of buffer intensity - a measure of the response of the system (in terms of
pH) to wastes which are either strongly acidic or basic.
Organic Constituents
A large variety of organic compounds are likely to be present in a land-
fill. These include natural degradation products of plant and animal matter,
(e.g., amino and humic acids) as well as organic wastes. An important
characteristic of organic compounds which function as ligands, is their
ability to form water soluble and water insoluble complexes with metal ions.
Of special concern is the formation of water soluble metal-organic* complexes
with toxic metals which may increase the concentrations of these constituents
in leachate to levels far in excess of their normal solubilities.
For the complex-formation reactions between metal ions (M) and organic
ligands (L)
the equilibrium constants are
(21) K = -Ml_
*
The term "metal-organic" is used to define structural configurations
in which the metal is bonded to organic matter by (1) carbon atoms
(yielding organo-metallic compounds) (2) carboxylic groups (producing
salts of organic acids), (3) electron-donating atoms, 0, N, S, P,
etc. (forming coordination complexes) or (4) irelectron ligands
(olefinic bonds, aromatic rings, etc.)
27
-------
(where a monodentate ligand is considered and where charges of the species
have been omitted for simplicity). In general, a metal ion will coordinate
with more than one ligand and form complexes in a stepwise manner, e.g.,
Cu2+ , Cu (NH3)2+, Cu(NH3)2+ , Cu(NH3)2+ , Cu(NH3)2+, for which an equilib-
rium constant is defined for each step as above. Furthermore, the concentra-
tion of soecies complexed in solution will be pH dependent since the ligands
are generally acids or bases in their own right and thus dissociate according
to the equilbrium
HT • TI 4. TJ T "" - TT"' I T "~"
Lt j- n T n .. u ' • •»«»• n T Li
n n-1 •"
Natural leachate systems, even though well buffered (and thus considered
to be at constant pH), are considerably more complex since there are numerous
ligands of differing complexing ability competing for coordination of a large
variety of metal ions. While computations of the distribution of ionic
species in a solution containing many metals and ligands can be done with
computers using available programs (Perrin, 1967; Childs, 1969; and Morel,
1970), the following general points will suffice to illustrate the general
principles of complexation of metal ions in natural leachates:
(1) Complexes with monodentate ligands are usually less
stable than those with multidentate ligands. Also
important is that the degree of complexation de-
creases more strongly with dilution for monodentate
ligands than for multidentate ligands.
(2) Metal ions can be buffered (in a manner analagous
to pH buffering) by adding appropriate ligands to
*
a metal ion solution
[M] . _M_
Such buffers resist a change in [ M] and are useful for
investigating phenomena pertaining to metal ions, If
a solution is simply diluted, the activity of the free
metal ion may, because of adsorption, hydrolysis, or
other side reactions, be entirely different from that
calculated by dilution alone.
(3) Where the ligand concentration is small only a "one
ligand" complex is likely to be formed.
(4) And ligands, such as humic acids, phosphates, or poly-
phosphates, when present in concentrations too small
to form soluble complexes, may still aid in the forma-
tion of stable negatively charged colloidial dispersions.
The buffering intensity of M can likewise be defined in a manner analogous
to that of the buffering intensity of H+
28
-------
Unfortunately, little is known concerning complexation in natural leachate;
relatively few studies have even attempted more than a gross identification of
organic constituents. Johansen and Carlson (1976), for example, identified
and quantified the organic compounds shown in Table 4 in a variety of leach-
ates. Because leachate composition is strongly influenced by site specific
conditions (e.g., fill construction, precipitation, age of the fill) the
concentrations shown in Table 4 serve only to illustrate the general concen-
tration ranges of organic constituents. Khare and Dondero (1977), in a
recent study analyzed leachate for a wide variety of inorganic and organic
compounds as shown in Table 5.
Although not identified explicitly in the previous analyses (other than
as carbohydrate or protein - Table 4), Chian and DeWalle (1974, 1976, 1977)
indicate the possible importance of humic* and fulvic acid**, complexation
of metal ions in leachate. While the chemistry of these species is not yet
well understood, a variety of structures and reaction mechanisms have been
considered. Schnitzer (1976) proposes the chemical structure shown in
Figure 7, and notes that this structure is in accord with most empirical
results. Stevenson (1976) further suggests the following general features of
the reaction mechanism for metal complexation by humic acids:
(1) Carboxyl groups play a prominent role in complexation of metal
ions. Mixed complexes are probably formed, the most important
of which is of the phthalic acid type. Other possible combin-
ations in order of importance are: a COOH group and a phenolic
OH group; a COOH group and a quinone group; and a COOH group and
a NH2 group.
(2) Metals serve to link individual molecules together to produce
polymeric structures as shown in Figure 8.
(3) Metal complexes of humic acid are soluble at low metal ion-humic
acid (HA) ratios, but precipitation occurs as the polymeric
structure grows and the isolated COOH groups are neutralized by
salt bridges. Where precipitation occurs, it is a function of
factors such as ionic strength, pH, humic acid concentration, and
the specific metal ion. Figure 8 illustrates the metal ion:
(1) as 2:1 complex linking two groups; (2) as a 1:1 complex and
(3) in a salt linkage with an isolated COOH group.
and Fulvic acids are terms applied to dark-colored, acidic,
predominantly aromatic, hydrophilic, chemically complex polyelectro-
lytes that range in molecular weight from a few hundred to several
thousand whose chemical properties are comparable to synthetic
polyelectrolytes, such as polyacrylic and polymethacrylic acid; they
are best classified on the basis of solubility. If a material con-
taining humic substances is extracted with a strong base and the
resulting solution acidified, the products are (1) a nonextractable
residue called humin, (2) a material which precipitates from the
acidified extract called humic acid, and (3) an organic material
which remains in the acidified solution called fulvic acid.
**
Humic acids have also been suggested to be important for electron
transport in anoxic environments (Schindler et al., 1976).
29
-------
TABLE 4
DRY WEATHER ORGANIC ANALYSIS OF LEACHATES FROM NORWAY AND THE PACIFIC NORTHWEST1
^^"-^^ Landfill
NORWAY
"^^^^ Gronmo Branasdalen Yaggeseth
Parameter ^--^ ^/i .M c/l ma/1 me C/l me/1 me C/l
TOC 100
Total carbohydrate 24
Total protein
Acetic acids <10
Propionic acids <10
Butyric acids <10
Iso butyric acids <10
Valeric acids <10
Iso valeric acids <10
Caproic acids
Total organics identified
250 1700
10 37 15 54
181 94 144
129 52 420
37 18 231
12 7 681
<10 78
<10 219
<10 241
10 185
22
75
168
111
368
42
129
142
1057
Taranrod Isl I
mg/1, mg C/l mg/1 mg C/l
800
113
421
282
318
32
87
19
180
46 57 23
88 46
169 100 40
136 67 32
172 14 8
17 <10
51 <10
41 <10
658 149
U.S.A.
Isl II Cedar Hills
«g/l mg C/l mg/1 OR C/l
30
6 2
30 12 2750'
<10 4375
<10 5875
<10
<10 550
<10
600
14
1100
2100
3173
324
372
7069
Kent Highland
mg/l «R C/l
300
380
260
190
90
120
182
140
112
56
610
Source: Johnson and Carlson (1976).
-------
TABLE 5
NONVOLATILE AND VOLATILE
CONSTITUENTS OF LEACHATE
Constituent
Concentration
mg/L
Nonvolatile:
Sodium
Magnesium
Aluminum
Potassium
Calcium
Manganese
Iron
Copper
Zinc
Cadmium
Lead
Total carbon
Organic carbon
Inorganic carbon
Total nitrogen (Kjeldahl)
Ammonia-N
Nitrite-N
Nitrate-N
Total soluble phosphate-P
Phosphate-P
Sulfate-S
Chloride
136.0
66.0
0.13
66.0
272.0
10.85
0.81
< 0.01
0.09
< 0.01
0.03
767.0
695.0
72.0
52.0
50.0
0.040
0.061
0.152
0.010
39.0
205.0
Volatile:
Methane
Ethane
Ethylene
1-Pentene
Hexane
Heptane
Nonane
Decane
Dodecane
4-Methyl-l-hexene
Acetone
2-Butanone
Chloroform
Detected but not measured
31
-------
TABLE 5
NONVOLATILE AND VOLATILE
CONSTITUENTS OF LEACHATE
Constituent
Concentration
mg/L
Volatile:
Carbon tetrachloride
Benzene
Toluene
Xylene
Methanol
Ethanol
Propanol
2-Butanol
2-Pentanol
2-Hexanol
4-Methyl-2-pentanol
2-Heptanol
2-Octanol
Acetic acid
Propionic acid
Butyric acid
Propanamide
2-Methylethylenimine
Methylamine
Methylamine hydrochloride
Dime thylamine
n-Propylamine
Diethylamine
n-Butylamine
Di-n-propylamine
Di-n-butylamine
n-Hexylamine
Carbon dioxide
Hydrogen
Nitrogen
Oxygen
Argon
Detected but not measured
Source: Khare and Dondero (1977)
32
-------
OH
OH
OH
OH
Source: Schnitzer, 1976.
FIGURE 7. A PARTIAL CHEMICAL STRUCTURE FOR FULVIC ACID.
33
-------
coo
COOH
+M
.+2
2H
,coo
ooc:
M
COO
+2
+M
+EA
00
COO
.OOC.
M
\
COO
ooc
"x" I ==^\/
UNITS !
COO.
CO
COOM+(H20)n
Source: Stevenson, 1976.
FIGURE 8. COMPLEXATION OF A METAL ION BY HUMIC ACID.
34
-------
Because of the ill defined structure and nature of humic and fulvic acids,
their direct effect on complexation in natural leachate is difficult to assess.
Furthermore, realistic modeling in a synthetic leachate with a non-polymeric
compound will be difficult. Comparison between empirical values of stability
constants of fulvic and humic acids and other appropriate ligands, at the
very least indicate systems of similar complexing ability and thus may provide
better models than systems which are intended to mimic the structure.
Oxidation - Reduction Reactions
Leachate is likely to be highly dynamic, rather than in or near equilib-
rium conditions, with respect to oxidation-reduction reactions. First, most
redox reactions are slow compared to acid-base reactions; and second, micro-
organisms in leachate may well be the principal mediators of oxidation-reduc-
tion reactions under natural conditions. Because the above factors make an
exact description of the redox environment of natural leachate impossible,
only those factors which define the redox gradients, and significantly affect
the transport mechanisms within the leachate will be considered.
Meaningful and direct redox measurements are most difficult to obtain
in natural systems. It is possible that many redox environments co-exist in
the same landfill or redox couples may be present in varying degrees of
completeness depending upon kinetic factors. Before discussing the effect of
the redox environment on species transport, it is necessary to establish a
working definition of such an environment. Two terms are generally used to
describe redox systems, the redox potential, Eg, and the relative electron
activity,P£. Formally, in systems where half reactions are written for the
transfer of a single mole of electrons
(22)
" Ai
where A^ designates the participating species, n. their numerical coefficients,
positive for reactants and negative for products, and n the number of electrons
transferred,PEis equal to
(23) pe=pe° + log I TTfA±]
and
(24) p£°- log K
where K is defined by
(25) K -
Thus pc is an intensity factor and measures, in a manner analogous to acid or
base neutralizing capacity with respect to protons, the redox capacity of a
given system.
35
-------
It is also possible to define the redox potential, E , of the same
system using the Nerst equation
^26^ T.O _L. 2-3 RT , PA 1 n-
£„ = E TT + =;— log LA.J i
H H nF i
where R is the ideal gas constant, T is the temperature in degrees Kelvin, F
is equal to Faradays, and other terms as defined previously. Thus E and
pe are related by
(27) P£= F E
2.3 RT
Thus far, distribution of various species in leachate have been considered
in two ways: (1) equilibria between chemical species in a particular oxida-
tion state as a function of pH and solution composition; and (2) equilibria
between chemical species at a particular pH as a function of pe« Of particu-
lar use in consideration of redox environments is a combination of the above
as shown in Figure 9, i.e., pe - pH stability field diagrams which show how
protons and electrons simultaneously shift the equilibria under various
conditions and indicate which species predominate under any given condition
of pe and pH.
Dynamic redox environments in landfills can affect species transport
in two ways: (1) by direct changes in the oxidation state^-of metal ions
and/or (2) by redox changes in available and competing ligands. The range
of typical redox environments in landfills as found by Chian and DeWalle (1976)
are shown in Figure 10.
As previously mentioned, microorganisms act as catalysts for redox
reactions; thus, these organisms do not "oxidize" or "reduce" substrates
but rather mediate the electron transfer between substrates. Therefore,
because their effect is kinetic rather then thermodynamic their influence
on leachate generation is particularly difficult to assess. While specific
microbial mechanisms of redox control remain elusive, their effects (i.e. ,
shift in the potential) on the redox environment may be considered as the
consequence of ligand formation with the original oxidant and products.
Rather than attempt to formulate a complete system (which is an
exceedingly complex problem), it is sufficient for the purposes of this
document to focus only on the direction and extent of shifts of potential
associated with the formation of complexes. Moreover, effects of the system
pH on the ligand equilibria are not considered explicitly; such effects
may best be evaluated from empirical data at different pH numbers. Thus
for the general reaction:
0 + R^z± Products
36
-------
20
18
16
14
12
10
8
6
4
2
0
-2
-4
-6
-8
-10
-12
-14
Fe
Fe(OH).
Fe(OH)
I
I
7 8
pE
9 10 11 12 13 14
FIGURE 9. SIMPLIFIED pe - pH DIAGRAM FOR IRON IN WATER.
37
-------
10
12
2468
Time, years
Source: Chian and DeWalle, 1976.
FIGURE 10. THE pe OF LEACHATE IN LANDFILLS AS A FUNCTION
OF TIME.
38
-------
where 0 and R represent the original oxidant and reductant respectively, the
reactions for formation of complexes with 0 and R and:
and
0 = nL -—r OL
n
R + mL — — T RL
- m
where n and m are the mole numbers. If stepwise formation constants are
neglected (or impossible to measure experimentally) , the following equili
brium equations may be written:
(28) [0]
and
These equations define the degree of complex dissocation and are commonly
known as instability constants. It is further useful to define the following
sums:
(30) SQ = [0] + [OLn]
(31) Sr = [R] + [RLn]
(32) S = SQ + Sr
(33) ST = [ L ] + n [ OL ] + m [ RL ]
L n n
i i
In the case where Ko and Kr are very large, a further simplification can be
made, namely that
(34) SL - [L]
I t
Even if Ko and Kr have very large values, this does not preclude
the formation of considerable amounts of a complex at high values of [L] .
Using the above equations (28) - (34) to define [o] and [R] ,
i
(35) [0] = SoKo
'
and
(36) [R]
K +S
o L
K* +Sm
r r
39
-------
and from the Nerst equation (26), then the potential of the system may be
expressed as*
(37) E = E° + RT In Ko + RT In Kr + SL + RT In fo
H H NF r NF K» + sn 'NF sr
For simplicity it has been further assumed that m = n an^ So = Sr. Thus there
are three non-trivial cases to consider :(1) Ko=Kr; (2) Ko *Kr; and (3) Ko
-------
and maganese represent the bulk of heavy metals present in leachate. Due to
the reduced conditions present in all but very young or old landfills, soluble
metallic species will occur in their reduced states. Thus modelling of any
natural leachate system might well include at least the most predominant of
these metals, iron (II).
In summary, while oxidation or reduction of chemical species is unlikely
to depend solely on a shift of potential, the effects outlined above should
be considered when evaluating the redox environment of natural systems, A
further point to remember when using empirical data of naturally occurring
oxidation-reduction systems is that such data is practically limited to
homogeneous environments whereas these systems occur naturally in very
heterogeneous environments.
THEORETICAL DEGRADATION OF A LANDFILL
As a first step in designing a leachate generation method, it is useful,
as Ham (1977) has done, to consider those processes which may occur in a
hypothetical landfill with a constant energy and water input. As the landfill
ages, the following biological stages may be envisioned as shown in Figure 11:
an aerobic decomposition phase; an anaerobic decomposition phase once the
oxygen originally present is consumed; and a final aerobic stage due to incoming
oxygenated water and cessation of biological activity.
The aerobic phase of decomposition is generally short because of the
high biochemical oxygen demand (BOD) of the waste and limited amount of oxygen
present in a landfill. During this phase a large amount of heat is produced
which raises the landfill temperature to well above that of the surrounding
environment. Leachate during this phase is characterized by the dissolution
of highly soluble salts initially present in the landfill and the presence of
relatively small amounts of organic species from aerobic degradation.
Anaerobic decomposition occurs in two stages. Initially, faculative
anaerobic bacteria predominate and produce large amounts of low molecular
weight aliphatic acids (e.g., acetic acid) and carbon dioxide with concomi-
tant reduction of leachate pH and redox environment. Such changes aid in
the dissolution of sparingly soluble inorganic salts and have the net result
of producing a leachate with a high conductivity. The second stage of anaerobic
decomposition is signaled by an increase in leachate pH due to the degredation
of the low molecular weight acids and other organic matter by methane-producing
bacteria. In general, inorganic species will be less soluble under these
conditions (pH-^6.6-7. 3) . The redox environment of the landfill is also likely
to reach a minimum value during this stage.
The final stage in landfill decomposition is reached when biological
activity ceases due to depletion of suitable substrates. Thus aerobic condi-
tions are once again established by incoming water saturated in both oxygen
and carbon dioxide, and the leaching pattern may, in fact, closely resemble
geological weathering processes.
41
-------
PH
GAS
COMP.
VOLATILE
ACIDS,
ppm
H
M
>
H e
u o
CO
o
REDOX ENVIRONMENT
Pe
min. 4 ~ 5
i
max.~ 60%
max. -50% CH
20%
for several years
max. -18,000 ppm, ACETIC ACID
salts solubilized at low pH
AEROBIC
PHASE
FIRST STAGE
ANAEROBIC
PHASE
TIME
solubilized by
decomposition
SECOND STAGE
ANAEROBIC DEGRADATION
Source: Ham et al., 1977.
FIGURE 11. THE THEORETICAL DEGRADATION OF A LANDFILL.
42
-------
Clearly, environmental conditions can and will alter a theoretical
degradation pattern considerably; however of necessity, degradation has been
considered to be a constant (i.e., uneffected by precipitation rate, temper-
ature changes, etc.) and homogeneous process. While these assumptions are
gross over simplifications and intended only to provide a framework within
which leachate generation may be considered, the trends identified above
roughly follow those of natural leachate as shown by Chian and DeWalle
(1976, 1977) in Table 7. The only significant deviation is that of the redox
potential, which from their data reaches a minimum value early in the life
of landfill (before two years) and then rises to high levels, paralleling
the behavior of pH.
SUMMARY OF RELEVANT TEST PARAMETERS
The determination of specific mechanisms by which organic and inorganic
contaminants in solid waste are leached is an exceedingly complex problem;
indeed, the preceding sections have only constructed, in the broadest terms,
a fremework in which the rudiments of these individual mechanisms have been
discussed. More important, however, has been the identification of those
parameters (and mechanisms in some cases) which most affect leachate composi-
tion.
Clearly, the solubility of inorganic species and coordinative compounds
of metal ions is the most important phenomena responsible for the presence of
toxic contaminants in leachate. The most important parameters affecting
the solubility of inorganic species are (a) the pH of the medium and (b) the
type and concentrations of complexing ligands (both organic and inorganic)
present. Also important, although much more difficult to conceptually model,
is the redox environment of the system. With an understanding of these
factors, the overall mechanism of leaching may be theorized.
Of lesser importance are the parameters of temperature and particle
size. Temperature changes within the environment of a landfill are most
likely to affect the rate of biodegradation. The solubilities of inorganic
species as a whole, while certainly a function of temperature, are unlikely
to change significantly with the temperature changes found in a landfill.
The surface area, or particle size of the waste, should not affect the
equilibrium concentrations of species in leachate, although it may have pro-
found affects on the kinetics of leachate generation.
With these concepts and their relative effects thus defined, existing
leachate generation procedures may now be considered. These concepts,
however, are not rigorous relationships and thus serve only as guidelines
for method evaluation.
43
-------
TABLE 7
RANGE OF LEACHATE COMPOSITION IN SANITARY
LANDFILLS IN THE UNITED STATES'
Parameter Concentration
COD
BOD
TOG
PH
TS
TDS
TSS
Specific Conductance
Alkalinity (CaCO.)
Hardness (CaCO.)
Total P
Ortho-P
NH.-N
NO,+N00-N
Ca3 2
Cl
Na
K
Sulfate
Mn
Mg
Fe
Zn
Cu
Cd
Pb
40 -
81 -
256 -
3.7 -
0 -
584 -
10 -
2,810 -
0 -
0 -
0 -
6.5 -
0 -
0.2 -
60 -
4.7 -
0 -
28 -
1 -
0.09 -
17 -
0 -
0 -
0 -
0.03 -
<0.10 -
89,520
33,360
28,000
8.5
59,200
44,900
700
16,800
20,850
22,800
130
85
1,106
10.29
7,200
2,467
7,700
3,770
1,558
125
15,600
2,820
370
9.9
17
2.0
figures in milligrams per liter except Specific Conductance
which is measured as micromhos per centimeter and pH as pH units.
Source: Chian and DeWalle, 1976
44
-------
SECTION 3
COMPILATION AND EVALUATION
OF LEACHATE GENERATION METHODS
Using the information from Section 2, realistic criteria for critical
evaluation of leachate generation methods may be established. Specifically,
the following points will be considered:
• Does the test protocol address test variable in a reproducible
manner?
• Are the test conditions relevant to those factors which control
leaching in actual landfills? (Severe conditions are not
necessarily irrelevant per se, but unnaturally severe conditions
(e.g., leaching with a concentrated acid) are to be avoided.)
• How may the test data be interpreted? Do they serve the
legislative and regulatory needs of EPA?
In the absence of a quantitative model for leachate generation, any
evaluation will be qualitative and, of necessity, somewhat subjective.
Furthermore, it is important to note that relatively few of the tests com-
piled were specifically designed for assessing leachate generation within a
landfill.
The compilation of laboratory shake test protocols for leachate genera-
tion are presented in Table 8 in the following format:
• Method - Test originator and references
• Variables - Variables addressed by the test
• Description - A concise summary of test procedures
• Advantages, Disadvantages - The relative merits of the tests
based on the criteria listed previously
• Remarks - Purpose of the tests as defined by the test originator
45
-------
TABLE 8
LEACHATE GENERATION METHODS
METHOD
VARIABLES
ADDRESSED
DESCRIPTION
Battelle Laboratories
(Barton, 1965)
PH
Liquid to Solid
Ratio
Temperature
Particle Size
Test Duration
(Mendel, 1973)
The following methods have been used for the
assessment of radioactive wastes.
A sample Is crushed and a (approximately)
1 gram sample of -45 + 60 mesh particles Is
placed In a stainless steel "tea bag". This Is
suspended In 150 ml distilled water at 95 C.
The eluant Is changed (and analyzed) at 24
hour Intervals.
Slow leaching tests have been conducted at
Battelle, Pacific Northwest Laboratories In
the following manner:
Samples are leached at the desired tempera-
ture In an especially designed apparatus
(Mendel, 1973, pages 25-26). The apparatus
Is designed to leach one piece samples, al-
though powdered samples may be leached If the
sample Is supported on sintered glass or con-
tained In a porous bag. The ratio of eluant
volume to sample volume Is comparatively high
In this technique, typically being 100 or
greater. Dynamic contact between eluant and
solid Is maintained by an airlift recirculator.
The eluant is changed periodically, usually
dally, when the initial leach rate is at a
EPRI
(Weir et al., 1975)
pH
Buffering Capacity
Liquid to Solid
Ratio
Test Duration
Agitation Method
A sample is stirred for 24 hours with deion-
ized water in a closed container at a liquid/
solid ratio of 5:1. After filtering with a
porous membrane filter, the leachate may be
analyzed.
The effect -of pH is evaluated by varying pH
between 7.5 and 13 using a carbonate buffering
system.
The kinetics of leachate generation may be
evaluated using procedures similar to thi
above. Samples were agitated for 96 hours
(to insure equilibrium) and the mixtures were
sampled at 2, 5, 10, 60, 480, 1445 and 2080
minutes.
46
-------
TABLE 8 (CONTINUED)
ADVANTAGES
DISADVANTAGES
REMARKS
This method has been rela-
tively well tested and does
provide reproducible leach rate
data from immobilized radio-
active wastes.
Kinetic leaching patterns
may be estimated from the test
data.
The method does not consider
the environmental conditions in
a landfill.
The eluant is distilled water
and as such is not representa-
tive of natural eluants.
The method of Mendel requires
complex testing apparatus which
is not readily available.
This test is specifically de-
signed to determine the character-
istics of the leaching of radio-
active materials from immobilized
waste solids and is proposed as
an accelerated leach test for
leach rate determination.
There are two principal uses
to which the results of leach-
ability measurements on solid
wastes are put:
(1) Comparison of one method of
waste insolubilization with
another; and
(2) Making estimates of the
hazards arising from the contact
of a solidified radioactive waste
with water under conditions
during storage or shipping.
Hespe (1971) under the auspices
of the International Atomic
Energy Agency, has proposed a
standard method for leachate
generation from solid (immobil-
ized) radioactive wastes. This
method is extremely tedious and
requires a test period of many
weeks.
The effect of pH on leachate
generation is considered.
Leachate kinetics are ad-
dressed by this procedure.
The test procedure is rela-
tively simple.
The method does not address
the environmental conditions
in a landfill. Furthermore the
eluant is unrepresentative of
natural eluants in a landfill.
Equilibrium conditions are
not likely to be reached in 24
hours.
The liquid to solid ratio is
relatively low so that common
ion effect may be enhanced with
the result that only the most
soluble species will leach.
This test has been used for
the evaluation of leachate from
bottom and precipitator ash.
Column sorption tests are per-
formed using these leachates.
Relatively small soil columns
are used (height 4cm, width 3.5
cm). The columns are attached
to a vacuum system which is used
to regulate flow.
47
-------
TABLE 8 (CONTINUED)
METHOD
VARIABLES
ADDRESSED
DESCRIPTION
Federal Republic of
Germany
(NATO, 1976)
PH
P«
Buffering Capacity
Liquid to Solid
Ratio
Test Duration
Initially the waste is separated into liquid
and solid phases by centrifugation or filtra-
tion. The solid phase (residue) is mixed with
distilled water at a ratio of 1:10. It is then
agitated for 24 hours. Conductivity measure-
ments are taken periodically to establish
solubility equilibrium. The mixture is fil-
tered and then analyzed for the desired con-
stituents. Additionally the original liquor
from centrifugation is analyzed.
Hydro Research
Laboratories
• Liquid to Solid
Ratio
• Test Duration
• Agitation Method
Dredged material and unfiltered composite
disposal site water are mixed in a 1:4
volumetric ratio. This is done by placing 100
ml of water in a 2000 ml graduated Erlenmeyer
flask, carefully adding dredged material until
the mixture reaches 300 ml, and filling the
flask to 1000 ml with water. The flask is
stoppered with a polyethylene stopper and
shaken virgorously for 30 minutes on a mechan-
ical shaker. The suspension is then carefully
decanted, centrifuged, and filtered through a
0.45 membrane filter. The elutriate is stored
in clean polyethylene bottles.
48
-------
TABLE 8 (CONTINUED)
ADVANTAGES
DISADVANTAGES
REMARKS
Effects such as pH, buffering
capacity, and p« are considered
An attempt is made to deter-
mine whether equilibrium condi-
tions are reached.
The test procedure is rela-
tively simple.
The method does not address
environmental conditions in a
landfill specifically.
The eluant (i.e., 0.1N HC1,
0.1N NaOH) is unnaturally
severe.
The liquid to solid ratio
may enhance the common ion
effect with the result that
only the most soluble species
will leach.
No provision is made for
estimation of leachate genera-
tion kinetics.
This method is intended pri-
marily to determine soluble
chemical species and is not in-
tended to simulate leachate
generation per se.
The waste may be extracted with
fresh eluant to estimate solubil-
ization pattern. The effect of
pH may be evaluated by using the
following eluants: 0.1N HC1; 0.1N
NaOH; and H20 saturated with C02
and Oo.
Environmental conditions at
the site of disposal are con-
sidered.
The test procedure is rela-
tively simple.
This method has been exten-
sively used for evaluation of
dredged material disposal.
Aerobic or anaerobic condi-
tions may be controlled if an
appropriate compressed gas is
used as a means of agitation.
The test method is designed
specifically for dredged mater-
ial assessment.
The liquid to solid ratio is
relatively low and thus may en-
hance the common ion effect.
See entry at Waterways Experi-
mental Station (WES).
49
-------
TABLE 8 (CONTINUED)
METHOD
VARIABLES
ADDRESSED
DESCRIPTION
Illinois Platers'
Waste Task Force
(Illinois Platers'
Waste Task Force,
• pH
• Buffering Capacity
• Liquid to Solid
1977) Ratio
• Test Duration
• Agitation Method
A quantity R (given by Equation 1) of homo-
genized sample is taken and added to approxi-
mately 1000 ml. of deionized water. The pH
of the solution is initially adjusted to pH 5
with 1:1 HC1 or 1 N NaOH. pH measurements are
to be determined electrometrically following
standard calibration procedures. Samples are
to be stirred, using an overhead plastic
stirrer (stainless steel is acceptable in
most instances) or magnetic stirrer for a
period of 24 hours +0.5 hours. pH adjust-
ment is to be maintained during leaching with-
in pH 4.9 - 5.2.
(1) R - D/3 where
R « grams of sample added to one
liter of solvent
D * density of material to be
leached in kg/m
1/3 « conversion factor to approxi-
mate two years of precipitation
pH ADJUSTMENT: The preferred method is a con-
tinuous adjustment of pH as a function of time
(Procedure A), if the equipment is not avail-
able, then (Procedure B) is to be used.
PROCEDURE A: If an automatic titration system
is available with the capability of preselec-
tion of endpoints, or continuous titration to
a specific pH such as the Mettler DK 11, DK 10,
DV 10, DV 11, or similar systems, then after
initial adjustment to pH 5 and calibration as
per manufacturer's specifications, the stirred
leach is constantly adjusted to pH 5 throughout
the 24 hour leaching period.
PROCEDURE B: After initial adjustment to pH 5,
the pH is readjusted at 15, 30 and 60 minute
intervals moving to the next longer interval
if the pH adjustment is within pH 5.0 ± 0.5
during the present interval. This procedure
is to be conducted for a minimum of 6 hours.
Final pH after a 24 hour interval must be with-
in the range 4.9 -.5.2.
50
-------
TABLE 8 (CONTINUED)
ADVANTAGES
DISADVANTAGES
REMARKS
This test il well controlled
with respect to pH and buffer-
ing capacity and Is generally
representative, In term* of the
above, of actual environmental
conditions.
The method attempts to relate
the liquid to solid ratio to
actual site conditions.
The eluant, as a whole, is
unrepresentative of natural
eluants.
Equilibrium conditions are
unlikely to be reached in 24
hours.
The liquid to solid ratio is
likely to enhance common ion
effects.
This test method is relative-
ly complex.
Environmental conditions,
other than precipitation rate,
are not considered.
This test has been unanimously
adopted by the Illinois Platers
Waste Task Force. This procedure
is acceptable to the landfill
industry representatives, the
electroplating industry represen-
tatives, and the Illinois regula-
tory agency representatives when
used as a pre-disposal, reproduci-
ble analytical standard for the
laboratory determination of waste
characteristics.
51
-------
TABLE 8 (CONTINUED)
METHOD VARIABLES DESCRIPTION
ADDRESSED
International Atomic • pR The following procedure has been summarized
Energy Agency • Liquid to Solid from the proposed test protocol:
Ratio
(Hespe, 1971) • Temperature The sampling container is a 5 - cm diameter
• Particle Size cylinder x 5 cm in height open at one end.
• Test Duration
Samples are cast in the leaching container,
subsequently removed from the container and
coated on all surfaces but the top with a
waterproof compound which will adhere strongly
to the specimen surface.
The sample is leached in a suitable inert
container under the following conditions:
Sufficient eluant (distilled, deionlzed
water) is added to ensure that a layer of
solution at least 5 cm deep on stands above
the exposed surface of the specimen. The
eluant is added accurately measured and is
such that the value of the ratio
volume of leaching solution
exposed area of sample
does not exceed 10 cm.
52
-------
TABLE 8 (CONTINUED)
ADVANTAGES
DISADVANTAGES
REMARKS
This method has been rela-
tively well tested and does
provide reporducible leach
rate data from immobilized
radioactive solid wastes.
Data from such teats has
been successfully extrapolated
to transport modeling studies.
The method does not consider
those environmental factors
which are relevant to solid
waste disposal in a landfill.
The eluant (distilled, de-
ionized water) is not repre-
sentative of natural eluants.
This method is relatively
complex and tedious.
This test has been proposed as
a standard method for measuring
the leach rates of immobilized
wastes. As such the specifica-
tion embraces two test methods:
The first, called the "inter-
comparison method" is intended
to provide a firm basis for the
various inte.rcomparisons which
have been found to be necessary
in this field, i.e., between
laboratories, processes, etc. It
is suitable for the immobilizing
materials (cement, bitumen,
plastic, glass) which have been
used up till now. The second is
called the "environmental method."
Since it is impossible to repro-
duce, in the laboratory, the con-
ditions likely to be met in the
field, this method will not pre-
dict the precise performance of
a waste solid under the conditions
of the disposal environment. It
will, however, provide the infor-
mation necessary for a reasonably
realistic hazards assessment of a
proposed "waste solids-environ-
ment" system.
The results shall be expressed
by a plot of the cumulative frac-
tion of radioactivity leached from
the specimen as a function of the
total time of leaching thus
P versus 2t
where aQ *> radioactivity leached
during the leachant renewal per-
iod.
» radioactivity initially pre-
sent in specimen.
F - exposed.surface area of
specimen (cm ). ,
V *» volume of specimen (cm ).
tn - duration (days) of leachant
renewal period.
The results may also be expressed by a plot of the incremental
leaching rate, RQ, as a function of the time, t (days) of leaching,
where ^ . VAo / (F/V)^
and the other terms are as defined above (23). Values for Rn, cal-
culated as above, shall be plotted against tn-(tn - tn_i)/2.
53
-------
TABLE 8 (CONTINUED)
METHOD
VARIABLES
ADDRESSED
DESCRIPTION
IU Conversion Systems
(IUCS, 1977)
Liquid to Solid
Ratio
Test Duration
Agitation Method
Particle Size
From the material to be tested which is at
the moisture content present or anticipated
in the field, select a representative sample
for testing equal to an amount approximately
twice that required for the shake test. When
simulating an actual field placement of sta-
bilized soil or waste material, the relative
density and permeability coefficient of the
material should be known so that these values
can be compared to the actual field values.
ASTM D2049 and D2434 give methods for deter-
mining relative density of cohesion!ess soils
and permeability coefficient of granular soils.
A small portion of the sample is reserved for
water content determinations according to ASTM
standard D2216. (In the case of waste mater-
ials containing components with water of hydra-
tion, the drying temperature should be modified
to 37.8°C (100°F)± 1C (1.8°F) to avoid re-
moving any water of hydration during moisture
content determinations.)
A total of 6 samples are taken, five of which
weigh 125g + 13g (dry weight) and one weighing
500g + 50g (dry weight). In the case of mono-
lithic stabilized soils or waste materials, the
samples should be circular slices from a stand-
ard Proctor or 3" x 6" cylinder.
All samples are leached in sealed polyethy-
lene containers of at least 3000 ml capacity
at a 4:1 liquid to solid ratio (eluant as de-
fined in point (2) under remarks) using a re-
cipricatlng shaker set at an oscillation rate
of 60 to 70 one inch strokes per minute. The
five 125g samples are agitated for 1, 2, 4, 8,
and 24 hours respectively. At the end of each
agitation period the mixture is vacuum filtered
using a 0.45M- membrane filter. The 500g sample.
is agitated for 48 hours. After allowing this
test specimen to settle for 5 minutes, a suit-
able portion of the supernatant is removed for
determination of particulate and dissolved
matter in accordance with ASTM method D1888.
The remaining mixture is filtered as above.
The leachate thus obtained is analyzed for the
desired chemical constituents.
-------
TABLE 8 (CONTINUED)
ADVANTAGES
DISADVANTAGES
REMARKS
This method has been exten-
sively used (by IUCS) to deter-
mine the teachability of a large
number of immobilized industrial
wastes.
This method has been proposed
by ASTM as a tentative method
for leachate assessment.
This method seeks to model
natural leaching conditions by
using the natural eluant and
using the waste in the physical
form in which it is likely to be
disposed (e.g., the surface are
and permeability of the sample
are not modified).
Leachate kinetics may be esti-
mated from this method. Equili-
brium conditions are more likely
to be reached in 48 hours.
Water specific to the field
site (or Type II reagent water
certainly)will not be represen-
tative of eluants in a landfill
The liquid to solid ratio is
such that common ion effects may
be enhanced and thus only the
most soluble species will be
leached in this test.
Conditions within a landfill
(e.g. aerobic or anaerobic
conditions) are not addressed
by this test.
This method covers the deter-
mination of both the surface wash-
ing and the long-term diffusion-
controlled leachate properties of
a soil or waste material. It is
applicable to all solid and semi-
solid materials. The procedure is
to establish representative values
of the surface washing and the
long-term diffusion-controlled
leachate properties of a soil or
waste material as placed in em-
bankments, landfills, and other
disposal or use sites. Such
values can be used in the evalua-
tion of the environmental impact
of disposal or use sites. As
tested these properties result
from prolonged water contact both
on the surface of the soil or
waste materials and on a portion
of the interior of a mass of soil
or waste material as limited by
the permeability of the material.
In an actual site prolonged water
contact may not be the primary
leaching mechanism. The data de-
rived from this procedure should
be carefully interpreted with this
fact in mind.
The following test conditions
are prerequisites:
(1) continuity of water movement
during test with constant rate of
water movement; (2) the water used
in the test shall be representa-
tive of water specific for the
field site or Type II grade rea-
gent water as defined by ASTM
standard D1193; (3) the relative
density and permeability of soil
or waste material evaluated in
test should approximate the rela-
tive density and permeability of
the soil or waste material as
placed or as anticipated in the
field site; and (4) the dry weight
of the test specimens plus the
volume of the water used in the
test must be known accurately.
The six leachate samples are chemically analyzed by the appro-
priate ASTM method for the following parameters: pH, alkalinity
(total and phenolphthalein), hardness, total dissolved solids,
total suspended solids, 803~2, S04~2, Cl", As, Ca, Cd, Cr, Cu, Fe,
Hg, Mn, Na, Pb, Zn. It is suggested that 1, 2, 4, 8 and 24 hour
samples be analyzed at a minimum for pH and total dissolved solids.
The 48 hour sample should be analyzed for all parameters.
55
-------
TABLE 8 (CONTINUED)
METHOD
VARIABLES
ADDRESSED
DESCRIPTION
IU Conversion Systems,
Surface Runoff Test
• Liquid to Solid
Ratio (V/V)
• Test Duration
A representative sample (of which a small
portion is reserved for moisture determina-
tion) is taken as above.
A test box (see below) with dry standard
sand (ASTM C778) to a depth of 2" and
weighed. The waste material is placed in
the box in uniform layers in simulation of
actual site conditions, i.e., the moisture
and relative density of the material in the
box should simulate that of the field site.
For material which will be compacted in the
field, 3 equal layers of waste material are
compacted to the desired density successively
with a manual rammer.
The slope of the waste material is adjusted
to simulate the landfill construction prac-
tice (a 1.5% slope is suggested) by placing a
shim beneath the rear legs of the test box.
One gallon of water, either specific to the
field site or type II reagent water (ASTM
1193) is sprayed over the waste at 20 gallons
per hour. A clear bucket is used to collect
the runoff which is recirculated to the
sprayer. Both runoff and seepage/permeate
may be analyzed as outlined in the IUCS shake
test.
The flow rate of 20 gallons per hour
corresponds to the following linear feed of
surface runoff at the specified rainfall rates
rates:
Rainfall
(in/hr) Linear Feet of Runoff
255
130
65
35
D
1.5"
I
5"
(P
6.5"
J_
V long x 1/8" tMcte-
r1« surrounding body
Bottom Drain
1
•1 Drain Valve
n
56
-------
TABLE 8 (CONTINUED)
ADVANTAGES
DISADVANTAGES
REMARKS
Surface runoff is measured
by this test.
This method has been exten-
sively used (by IUCS) to
determine the leachabllity of
large numbers of immobilized
wastes.
This method seeks to model
natural leaching conditions
by using eluant and the waste
in the physical form in which
it is likely to be disposed
of (e.g., the surface area
and permeability of the sample
are not modified).
This test while probably be
useful to estimate the
quantity and quality of sur-
face runoff, does not address
the conditions which are found
in landfills. Thus, in terms
of leachate. relatively little
Information is provided by
this test other than quantity
and the gross character of
leachate as determined by the
most soluble constituents.
This method covers the deter-
mination of the surface runoff
properties of soil or waste
materials. The procedure is to
establish representative values
of the surface runoff, water
absorption, and permeate pro-
perties of soils and waste
materials as placed in embank-
ments, landfills, or other
suitable disposal sites.
The following test conditions
are prerequisites for suitable
Simulatef field leaching of soil
or waste material to simulate
field conditions in as repre-
sentgtlye and uniform a manner
as ppffjble: (1) Continuity of
water f}g# during test, with
continuous reclrculation of the
resniltant runoff; (2) Slope of
top surface of material in test
apparatus shall approximate that
present In existing or anticipated
field placement of the soil or
waste material; (3) Water used in
test shall be representative of
rainfall at field site or Type .
II grade reagent water as defined
by ASTM standard D1193; (4)
Application rate In test shall be
representative of rainfall rate
at the field site; and (5)
Placement of soil or waste
material in apparatus shall
approximate placement of the
soil or waste material in the
embankment, landfill, or other
suitable disposal site.
This procedure may also be used
to evaluate the effect of ground
water contact with the bottom of
the sample by saturating the
sample for 7 days.
This test can be modified to suit
a number of conditions. For example,
the test can be run on as-received
samples and/or samples cured for
various times, as desired. Another
alternative is to repeat exposure
to a cured sample at regular inter-
vals. Each of these alternatives
may be analyzed using approxima-
tions and appropriate diffusion
equations to give some idea of the
rate of mass transport away from
the soil or waste material
57
-------
TABLE 8 (CONTINUED)
METHOD
VARIABLES
ADDRESSED
DESCRIPTION
Japan Environmental
Protection Agency
• pH
• Temperature
• Test Duration
• Agitation Method
• Liquid to Solid
Ratio
Untreated sludges or solids are mixed with
pure water in a ratio of 1:10 (volumetric
basis). A maximum of 100 ml is prepared. Neu-
tralizing agents (e.g., HC1, CC>2, NaOH) are
added to adjust the pH between 5.8 and 6.3.
The solution is shaken or stirred for 6 hours
under ambient conditions (temperature and
pressure). Solution is then filtered through
filter paper type 5-C and centrifuged at 5000
rpm for 20 minutes and analyzed.
State of Delaware
• pH
• Liquid to Solid
Ratio
• Temperature
• Test Duration
The sample is leached as received (wet
sample) with 25 weights of water per dry weight
of sample (this means adding an amount which
will increase the water content already in the
sludge to 25 times that of the dry weight of
the samples.
Three portions of the sample are to be
treated in this manner, each with the pH ad-
justed to pH 4, 7, and 10. These three solu-
tions should be mixed overnight in a beaker
agitated with a magnetic stirrer at 25-27°C.
Filter the three leachate solutions from the
solid and analyze using procedures further
defined in the U.S. Environmental Protection
Agency Manual of Methods for Chemical Analysis
of Water and Wastes (1974).
58
-------
TABLE 8 (CONTINUED)
ADVANTAGES
DISADVANTAGES
REMARKS
The effect of pH on leachaCe
generation is considered.
The test procedure is rela-
tively simple.
Neutralization with HCl or
NaOH may head to excessive
dissolution of the waste.
The eluant is not represen-
tative of natural eluant8.
Environmental conditions of
disposal site are not consid-
ered.
This method is used for the
evaluation of disposal of solid
wastes in fills not near the sea.
If the evaluation of disposal
sites near the ocean is necessary
or desired, the pH of the eluant
is adjusted to the range of pH
7.8 - 8.3.
The effect of pH on leachate
generation is considered.
The high liquid to solid ratio
is likely to minimize common ion
effects.
The test procedure is rela-
tively simple.
The eluant composition is un-
specified.
The test duration is unspeci-
fied.
This procedure is used to eval-
uate sludge waste materials.
The moisture content of the
sample is first determined by the
following procedure:
(1) Weighing the sample
as received.
(2) Heating it to 103°C
to drive off moisture.
(3) Re-weighing the sample
to constant weight.
59
-------
TABLE 8 (CONTINUED)
METHOD VARIABLES DESCRIPTION
ADDRESSED
Sandia Laboratories • pH The instantaneous leach test consists of
(Lynch, 1977) • Liquid to Solid placing a crushed sample (not screened) into
Ratio a 25-ml Royal Berlin Porcelain filter crucible
with a porous bottom, with an average pore
size of 7 |im, and pouring 100 ml of deionized
water through with the aid of suction. Sample
sizes of 1 g or less are used, and flow is
adjusted to give water contact times of 3 to
4 min. Weight loss is determined on the
sample, and AAS is used to analyze the lea-
chat e. The samples are dried for 1 h at
110 C and cooled in a desiccator for 0.5 h
prior to weighing. A complete set of data can
be obtained within 4 h depending on the number
of elements analyzed for in the leachate. The
results are typically expressed as grams of a
given element leached per gram of sample, e.g.
grams of cesium leached per gram of sample.
The results can also be expressed as the frac-
tion of an element leached from the sample.
60
-------
TABLE 8 (CONTINUED)
ADVANTAGES
DISADVANTAGES
REMARKS
The test procedure is rapid
and simple. Moreover, test
results have shown the test to
encompass a wide range of
teachabilities with reasonable
reproducibility.
Common ion effects will be
minimized at high liquid to
solid ratios.
The method does not consider
the environmental conditions
in a landfill.
The eluant is deionized water
and as such is not representa-
tive of natural eluants.
Equilibrium conditions will
not be reached within 3 to 4
minutes.
During the course of the
Sandia program for solidifica-
tion and consolidation of liquid
radioactive waste by ion exchange
with a hydrated titanate com-
plex, a large number of samples
were generated. The leach test
proved to be the most time-
consuming step in the evaluation
of the various samples. By
experimenting with various ex-
posure times, it became apparent
that in the case of crushed or
powder samples, measurable
leaching took place in a very
short time. Those observations
and the advantage of having a
test of short duration led to the
development of the instantaneous
leach test.
The instantaneous leach test
has proven to be surprisingly
reproducible, considering that
no attempt is made to control
or determine the surface area of
the sample. The scatter in the
results are well within the
acceptable error for measure-
ments of this type.
It must be emphasized that the
instantaneous leach test reveals
nothing of the long-term or high*
temperature behavior of a sample.
which can be varied and complex.
Also, due to the randomness of
the sample and unknown surface
areas, the data are not com-
parable to those of Hespe or any
other standard leach test. How-
ever, the test has proven to be
a highly reliable, self-consis-
tent means for quickly screening
and order ranking materials in a
development program. Candidate
materials can then be subjected
to the more exhaustive, longer
time leach tests.
61
-------
TABLE 8 (CONTINUED)
METHOD VARIABLES DESCRIPTION
ADDRESSED
State of Illinois • pH All solid or semi-solid special wastes should
Environmental Protec- • Liquid to Solid be prepared for analysis by leaching with de-
tlon Agency Ratio ionized water adjusted to a pH of 6.0 (W/HC1 or
• Test Duration NaOH). The supernate should be filtered (#40
Method 1 Whatman) and analyzed.
A pre-determined mass of solid sample is
added to one liter of water and agitated for
48 hours. Extremely moist samples should have
excess liquid decanted prior to leaching, but
the sample should not be oven dried. The mass
of leached sample is determined from the fol-
lowing relationship: R - 5.34D.
Where: R » mix ratio of solid sample to water
as measured in grams of sample added to a liter
of deionized water. D » Density3of sample
as measured in Ibs. per ft. .
62
-------
TABLE 8 (CONTINUED)
ADVANTAGES
DISADVANTAGES
REMARKS
The effect of pH on leachate
generation is considered.
The liquid to solid ratio is
related to the precipitation
rate of the intended disposal
site.
The test procedure is rela-
tively simple.
Equilibrium conditions are
more likely to be reached in
48 hours.
The eluant is not representa-
tive of natural eluants.
The relatively low liquid to
solid ratio may enhance common
ion effects.
Environmental conditions with-
in a landfill are not addressed
This method is proposed for use
with special wastes (liquid,
sludges, and hazardous or poten-
tially hazardous waste).
NOTE: If a solid/semi-solid
waste (i.e., sludge) is intended
for land spreading, the superna-
tant should be analyzed for both
dissolved and suspended components
Thus, the leached supernatant is
split into two samples, only one
of which is to be filtered.
5.34 is a conversion factor.
The mix ratio can be equa ed to
three cubic feet of liquid leached
through one cubic foot of solids.
(i.e., "36" precipitation/yr.) Re-
sults so obtained are considered
to be only an approximation of
reality. The factors of runoff,
evapotranspiration, and the effect
of time are not considered in the
test but might be logically
applied in interpreting these
results.
63
-------
TABLE 8 (CONTINUED)
METHOD
VARIABLES
ADDRESSED
DESCRIPTION
Method 2
Division of Land
Pollution
PH
Test Duration
Enough distilled water is added to a 1/2
gallon sample of the waste solid to fully
saturate the contents of each bottle (in the
case of fly ash, this amounted to about one
liter per sample). The sample is allowed to
sit for 24 hours. The supernatant liquid is
poured off.
A. If the supernatant is sufficiently clear,
chemical analysis of the unaltered leachate
is conducted.
B. If the supernatant is clouded and appears
to contain relatively large amounts of sus-
pended and colloidal material, the super-
natant is filtered thru Whatman #42 filter
paper and is then allowed to sit undis-
turbed for three days; the supernatant is
then poured off and analyzed as above.
The supernatant should be analyzed for Ca,
SO^ and heavy metals.
State of Indiana
Division of Land
Pollution
(Lamm, 1977)
• Liquid to Solid
Ratio
• Temperature
• Test Duration
A 20 gm sample is placed in 1 liter distilled
deionized water and stirred at room temperature
(20°C) for 2 hours using a gang stirrer. The
contents are then filtered through #40 Whatman
filter paper.
64
-------
TABLE 8 (CONTINUED)
ADVANTAGES
DISADVANTAGES
REMARKS
The test procedure is extreme- The eluant is not representa-
ly simple.
tive of natural eluants.
Environment conditions within
a landfill are not addressed.
This test is a saturation
method and thus will estimate
only the amounts of the most
soluble species.
The test procedure, as written
is unlikely to be reproducible
In the Arro version of this test
diffused air is used for agitation
(providing an aerobic condition).
The liquid/solid ratio is progres-
sively increased until a point is
reached where the leachate is no
longer saturated. This typically
occurs at ratios of 10:1 to 20:1.
The test duration (for each ratio)
is 100 hours. The biodegradabil-
ity of certain materials (e.g.,
roof shingles) is tested using
this procedure. In this case, a
synthetic eluant containing bac-
teria nutrients is prepared. For
materials going to a landfill for
the first time, the test is con-
ducted only initially. Certain
parameters may be monitored later
on using in-ground lysimeters.
It should be remembered that
each sample is leached with dis-
tilled water (pH 7.0) and that,
under field conditions, leaching
may be accelerated and intensified
by rainfall, which tends to be
acidic, If the waste is being con-
sidered for final cover or to be
mixed with earth for final cover,
test plots of the material should
be seeded to determine if the
material will support a ground
cover.
The test procedure is extreme-
ly simple.
The high liquid to solid ratio
is likely to minimize common ion
•effects.
The eluant is unrepresentative This test has been applied to
of natural eluants. leachate assessment of combustion
residues.
Environmental conditions with-
in a. landfill are not addresse
Equilibrium is not likely to
be reached in two hours.
65
-------
TABLE 8 (CONTINUED)
METHOD
VARIABLES
ADDRESSED
DESCRIPTION
State of Minnesota, •
Environmental Frotec- •
tion Agency •
pH
Buffering Capacity
Liquid to Solid
Ratio
Test Duration
Agitation Method
A sample of 25 grams is placed in a 2000 ml
glass separatory funnel with 1 liter of eluant
and vigorously shaken for 60 seconds. (Two
eluants have been used: buffered acetic acid
solution and distilled deionized water.) The
mixture is covered and allowed to stand for 24
hours and then shaken again for 60 seconds.
The mixture is now filtered through medium
proposity ashless filter paper and the first
10 ml discarded. The acetic acid solution is
prepared by adding 49.21 gm HOAc and 39.21 gm
NaOAc to enough distilled deionized water to
make a 1 liter folution of pH 4.5. The test
is conducted at room temperature.
66
-------
TABLE 8 (CONTINUED)
ADVANTAGES DISADVANTAGES REMARKS
The test procedure addresses The eluant is not representa- This Is a test procedure used
pH and buffering capacity. tive of natural eluants. for evaluating acceptability of
most types of industrial wastes
The high liquid to solid ratio Equilibrium conditions are for land disposal in a sanitary
is likely to minimize common ion not likely to be reached in 24 landfill or in a separate area
effects. hours. segregated from refuse deposits.
The two eluants used, an acetic
Environmental conditions with- acid solution and distilled de-
in a landfill are not addressed, ionized water, are suggested to
approximate conditions in these
Diffusion effects may control disposal locations.
dissolution kinetics (i.e., in-
sufficient agitation of the
solution may lead to low re-
sults).
67
-------
TABLE 8 (CONTINUED)
METHOD VARIABLES DESCRIPTION
ADDRESSED
State of New Jerseyi • pH 4 500 gram (or otherwise adequate quantity)
Department of Environ- • Liquid to Solid representative sample is oven dried for 24
mental Protection Ratio hours at 130°C and subsequently stored in a
• Test Duration desiccator. A 100 gram portion of the dry
sample is added to a solution of 900 ml of
distilled, deionized water - acetic acid (suf-
ficient to adjust the pH to between 5.0 - 5.5)
of known (i.e., measured) pH and stirred for
not less than 24 hours on a multiple-stirring
(Phipps-Bird Floe Stirrer) apparatus at 50 rpra.
After 24 hours the mixture is vacuum filtered
through a fritted glass filter and the filtrate
analyzed for the following constituents: Al,
As, Ba, Cd, Cr(VI), Cu, Fe, Hg, Mn, Na, Nj, Pb,
Se, Zn, C1-, ON", F-, ABS/LAS (Surfactants),
Nog", pH, phenolic compounds (as phenol), oil
(soxhlet) extraction, sulfate, IDS, COD, and
TOC).
68
-------
TABLE 8 (CONTINUED)
ADVANTAGES
DISADVANTAGES
REMARKS
The effect of pH on leachate
generation is considered.
The eluant is not representa-
tive of natural eluants.
The test procedure is straight Conditions within a landfill
forward and relatively simple, are not modelled.
The sample is dried and may
result in losses of volatile
compounds.
This test is recommended for
leachate assessment from solid
materials intended for disposal
a New Jersey landfill.
in
This leaching test was developed
to afford a consistent basis for
approving or rejecting various
sludge residues destined for land-
fill disposal. A dried, tared
sample added in an approximate
ratio of ten percent (by weight)
to acidified (acetic acid pH 5)
distilled water is suggested to
simulate the leachate generated
from a sanitary landfill. As the
alkaline earth metals and related
anions leach out of a residue, the
pH would increase to some equili-
brium value. This may be construed
as similar to the occurrence of
alkaline leaching within the land-
fill itself. The sample is then
agitated for 24 hours to provide
intimate solid-solution contact
which may simulate, to some degree,
the flushing action of landfill
percolation. Analyses are then
performed for general and specific
constituents although further data
may be in order should the sample
contain a specific hazardous ma-
terial.
The characteristics of the lea-
chate are then considered with re-
gards to:
1. Heavy metals (i.e., lead,
mercury, cadium, etc.)
2. Toxics (i.e., arsenic,
cyanide, selenium, etc.)
3. Organics (i.e., vinyl chlor-
ide, PCB, PBB, Phenol, etc.)
Although data evaluations are
necessarily somewhat subjective,
the State of New Jersey attempt to
follow, insofar as possible, stan-
dard toxilogical limits when for-
mulating final decisions (i.e.,
LD50, TLV, TIM, etc.). Thus,
having both the original residue
analysis and leachate characteris-
tics, the amount of material
leached out over the given period
of time may be estimated.
69
-------
TABLE 8 (CONTINUED)
METHOD
VARIABLES
ADDRESSED
DESCRIPTION
State of Iowa,
Department of Environ-
mental Quality
PH
Liquid to Solid
Ratio
Test Duration
A representative 500 gram sample of the
waste is mixed with 3 liters of water and the
pH of the solution is adjusted to using
This mixture (i.e., water and waste) is
shaken periodically over a 24 hour period.
The liquid is filtered and the aqueous por-
tion analyzed for the desired parameters.
pH Modification Test
A representative 500 gram sample of the
waste is mixed with 3 liters of water.
This mixture (i.e., water and waste) is
shaken periodically over a 24 hour period.
The pH is determined after 1 hour and 24
hours.
If the waste is solid, it should be crushed
to a size of approximately 0.5 cm or less.
State of Michigan,
Department of Natural
Resources
pH
Liquid to Solid
Ratio
Test Duration
A 100 gram sample is mixed with 1 liter of
water.
The mixture is shaken for 6 hours.
The mixture is filtered and the filtrate
analyzed for the desired constituents.
70
-------
TABLE 8 (CONTINUED)
ADVANTAGES
DISADVANTAGES
REMARKS
The effect of pH on leachate
generation is considered.
The test procedure is rela-
tively simple.
The eluant composition is
unspecified.
Test protocol is subject to
various interpretations (e.g.,
what constitutes periodic
shaking?).
This leachate test is conducted
by the Land Quality Management
Division on wastes that are con-
sidered to be toxic or hazardous.
The pH of the eluant is not
specified but rather determined
on the waste and disposal site
conditions.
The parameter to be analyzed is
also left blank and depends on the
waste.
The test procedure is rela-
tively simple.
The eluant is not representa-
tative of natural eluants.
The environmental conditions
within a landfill are not
modelled.
Equilibrium is not likely to
be reached within 6 hours.
Michigan has attempted to stan-
dardize two leachate tests within
the past 3 years: a standard
leachate test (a column test) and
a solubility test (a shake test).
A severe leachate test is sug-
gested for materials which would
not be disposed of in a licensed
landfill. This would include
agitation and possible a range of
pH of the eluant. The filtrate is
then compared to drinking water
standards.
For those materials which don't
pass this test, the waste must be
disposed at a landfill with the
degree of protection being depen-
dent on the degree of severity of
the pollutants in the leachate.
71
-------
TABLE 8 (CONTINUED)
METHOD
VARIABLES
ADDRESSED
DESCRIPTION
State of Pennsylvania,
Department of Environ-
mental Resources
Liquid to Solid
Ratio
Temperature
Test Duration
Agitation Method
A 500 gram sample (either sludge or filter
cake) is added to one liter of distilled
water and agitated with a Phipps-Bird stirrer
at 60 rpm for 48 hours. The resulting super-
nate is filtered through #42 Whatman filter
paper. Total solids are determined on the
filtrate in accordance with Standard Methods
(14th edition).
As modified by Bethlehem
Steel Corp.
• Liquid to Solid
Ratio
• Temperature
• Test Duration
• Particle Size
• Agitation Method
A 500 gram sample ground to pass a 10 mesh
screen is placed in a 1500 ml beaker; 1000 ml
of distilled water are added. The contents
are stirred by hand each hour during the work-
day and allowed to Stand at night over a total
time period of 4-8 hours. The contents are
then vacuum filtered through Whatman #42 fil-
ter paper and collected and stored in acid
washed glass containers covered with aluminum
foil to minimize evaporation. This test is
conducted at room temperature (20°C).
State of Texas
Water Quality Board
• Liquid to Solid
Ratio
• Test Duration
• Method of Agitation
A 250 gram representative sample of the
"dry" material should be taken according to
AOAC or ASTM Standard Methods and placed in a
1500 ml Erlenmeyer flask. One liter of de-
ionized or distilled water should be added to
the flask and the material stirred mechani-
cally at a low speed for five minutes.
Stopper the flask and allow to stand for seven
days. Filter the supernatant solution through
a 0.45 Micron glass filter. The filtered
leachate should be subjected to a quantitative
analysis for those component or ionic species
determined to be present in the analysis of
the waste itself.
72
-------
TABLE 8 (CONTINUED)
ADVANTAGES
DISADVANTAGES
REMARKS
The test procedure is rela-
tively simple.
The eluant is not representa-
tive of natural eluants.
Environmental conditions with
in a landfill are not modelled.
The low liquid to solid ratio
may enhance common ion effects
and thus leaching only the most
soluble species.
Initially the Department of
Environmental Resources was ad-
vocating use of the supernate
instead of the filtered supernate.
However, that portion of the
method was abandoned in favor of
filtration because of the depen-
dency of the suspended solids or
particulate matter.
This test is used to evaluate
rain leaching of metallurgical
wastes. Samples consisted of
blast furnace flue dust, blast
furnace slag, EOF slag, EOF dust,
electric furnace slag, and elec-
tric furnace flue dust.
The test procedure is rela-
tively simple.
The reproducibility of the
test procedure is considered.
The eluant is not representa-
tive of natural eluants.
Environmental conditions with
in a landfill are not modelled.
The low liquid to solid ratio
may enhance common ion effects
thus leaching only the most
soluble species.
Triplicate samples of the waste
should be leached in order to ob-
tain a representative leachate.
73
-------
TABLE 8 (CONTINUED)
METHOD
VARIABLES
ADDRESSED
DESCRIPTION
TRC
(Brookman, 1976)
• Liquid to Solid
Ratio
• Test Duration
• Cycles
A weighed portion of the material to be
tested is placed in a container with a known
volume of distilled water. The resulting mix-
ture is allowed to stand for three days and is
then filtered thru a membrane filter (0.45H-).
The filtrate is analyzed for species of inter-
est.
The media is reweighed and mixed with the
same volume of water and the process repeated
a number of times. A high liquid to solid
ratio (>10 to 1) is used.
United States Army
Corps of Engineers
Method 1
(Lee et al., 1975)
• pe
• Liquid to Solid
Ratio
• Test Duration
• Agitation Method
A representative sample from the disposal
site water column should be collected and
analyzed. Sediment samples are taken with a
grab sampler or corer and should be represen-
tative of the sediment.
A mixture of sediment (ISO ml) and disposal
site water (2850 ml) is placed in a 6 liter
Erlenmeyer flask (20:1 liquid to solid ratio).
A porous diffusion tube is inserted almost
to the bottom of the flask such that the mix-
ture is agitated vigorously by a compressed
gas for 30 minutes. The flasks are swirled
manually at 10 minute intervals to insure
complete mixing. After agitation, the mixture
is allowed to sit for 60 minutes and is then
filtered (0.45). This elutriate is analyzed
for desired constituents.
Method 2
(Maloch et al., 1976)
pH
P<
Buffering Capacity
Liquid to Solid
Ratio
Test Duration
Agitation Method
A 1:4 mixture (by weight) of material and
water is prepared. The water used should be
saturated prior to the test with C02 (pH 4.7).
This slurry is then shaken on a wrist action
shaker for 1 hour. The sample is centrifuged
for 30 minutes at 2500 rpm then filtered using
a 0.45 filter. The leachate is subsequently
analyzed for desired constituents.
74
-------
TABLE 8 (CONTINUED)
ADVANTAGES
DISADVANTAGES
REMARKS
The test procedure ia
extremely simple.
The eluant is not representa-
tive of natural eluants.
Environmental conditions with-
in a landfill are not modelled.
Diffusion effects may control
dissolution kinetics (i.e., in-
sufficient agitation of the
solution.)
Runoff is presumed to be the
primary mechanism of waterborne
pollutant transport. This test is
designed to evaluate leachate po-
tential from material storage
piles (e.g., coal, fly ash, etc.)
Test data cannot be directly
correlated with actual precipita-
tion data, quantity of runoff, and
the transport of runoff.
Environmental conditions at
the site of disposal are con-
sidered.
The test procedure is rela-
tively simple.
This method has been exten-
sively used for evaluation of
dredged material disposal.
Aerobic or anaerobic condi-
tions may be controlled if an
appropriate compressed gas is
used as a means of agitation.
The test method is designed
specifically for dredged mater-
ial assessment.
The liquid to solid ratio is
relatively small and thus may
enhance common ion effects.
This test was designed as a
rapid elutriate test for dredged
sediments. The test provides
information on the chemical com-
pounds released to the water
column during disposal of hydrau-
lically dredged material.
This test is normally run in
triplicate.
Aerobic and anaerobic conditions
may be simulated by using either
oxygen (aerobic) or an inert gas
(anaerobic) to mix the samples.
The test procedure considers The eluant is not representa-
environmental conditions affect- tive of natural leachate but
ing leachate generation, i.e., rather of rainwater.
pH, pc, and buffering capacity.
Equilibrium is unlikely to be
reached within 1 hour.
The test procedure is rela-
tively simple.
This test was utilized as a
rapid leach test for fixed and
raw FGD sludges.
Environmental conditions with-
in a landfill are not modelled.
The liquid to solid ratio is
relatively small and thus may
enhance common ion effects.
75
-------
TABLE 8 (CONTINUED)
METHOD DESCR.FT.ON
United States
Environmental Protection
Agency
Method 1 • Test Duration A slurry is prepared using from 2 to 4 parts
• Agitation Method distllled-deionized water to 1 part solid.
(Statnick, 1976) • Cycles This slurry is shaken continuously for 72
hours at room temperature. The slurry is fil-
tered. The above steps are repeated ten times.
The leachate from each filtration is analyzed.
76
-------
TABLE 8 (CONTINUED)
ADVANTAGES
DISADVANTAGES
REMARKS
The test procedure is rela-
tively simple.
Leachate generation kinetics
may be estimated with this
method.
Equilibrium is more likely
to be reached in 72 hours.
The eluant is not representa-
tive of natural eluants.
Environmental conditions
within a landfill are not
modelled.
The liquid to solid ratio is
small and thus may enhance com-
mon ion effects. Repeated
leaching with fresh eluant, at
least in part, may compensate
for this effect.
Mention of this test does not
imply current endorsement of this
method by EPA.
Experience has shown that some
species are released immediately
from the waste while others are
released in the later leachings.
The effect of pH on leachability
may be determined by adjusting
the pH of the slurry to the de-
sired range and following the
aforementioned procedures for each
pH condition to be evaluated.
A similar test has been used by
lERL-New Jersey. A liquid to
solid ratio of 2.5 is used and
samples are agitated for 24 hours
using a Burrell Shaker.
The Department of Army uses a
similar test; liquid to solid
ratios of from 4:1 to 1:1 are
used. Shake time is 72 hours.
The above steps are repeated 7
times.
77
-------
TABLE 8 .(CONTINUED)
METHOD
VARIABLES
ADDRESSED
DESCRIPTION
Method 2
(Abelson and Lbwenbach,
1977)
pH
P«
Buffering Capacity
Temperature
Liquid to Solid
Ratio
Test Duration
Cycles
Particle Size
Agitation Method
A 10 gram sample (ground to 100/200 mesh) is-
shaken with 250 ml of eluant at a constant
temperature using a wrist-action shaker set
at the maximum rate for 48 hours. The mixture
is filtered and both the filtrate and residue
are analyzed by appropriate analytical proce-
dures.
The eluant should simulate natural condi-
tions. This may be done by saturating dis-
tilled, deionized water with carbon dioxide
under ambient conditions. (An alternative is
the use of plain distilled-deionized water.)
The solid to liquid ratio has been arbitrarily
set at 25:1; what is important, however, is
that species saturation not be reached. Thus,
this ratio should be confirmed experimentally
and adjusted accordingly, if necessary.
78
-------
TABLE 8 (CONTINUED)
ADVANTAGES
DISADVANTAGES
REMARKS
The test procedure considers
environmental conditions affect-
ing leachate generation, i.e.,
pH, pe, and buffering capacity.
The test procedure, by speci-
fying a high liquid to solid
ratio, is likely to minimize
common ion effects.
The eluant is not representa-
tive of natural leachate but
rather of rainwater.
Environmental conditions with-
in a landfill are not modelled.
This test has been designed for
the environmental assessment of
F6C residues. This method is in-
tended to provide a leachate of
"worst case" quality. To estimate
the quantity of leachate generated
the water balance method should
be employed (note that the water
balance method requires a site
survey of topographical, geolo-
gical, hydrological, climatologi-
cal, and meteorological condi-
tions.) The following general
procedure is proposed:
The temperature at which this
test is conducted should be
selected to represent the mean
temperature to which the leached
material would be exposed. It
should be cautioned that wide
variations in test temperature
may have an unpredictable effect
on leachate quality; certain
species (e.g., CaSO^,, CaC03, etc.)
are more soluble while others
(e.g., MgCC>3, MgSO^,) are less
soluble as temperature decreases.
As part of leachate assessment,
the physical properties of test
media should be defined. These
properties include particle size
analysis, specific gravity, bulk
density, dry density, water con-
tent, porosity/void ratio, and
permeability.
79
-------
TABLE 8 (CONTINUED)
METHOD
VARIABLES
ADDRESSED
DESCRIPTION
United States Environ-
mental Protection
Agency
Environmental Monitor-
Ing and Support Lab-
oratory (EPA, 1977)
• Liquid to Solid
Ratio
• Test Duration
• Agitation Method
Collect a minimum volume of two gallons of
receiving water in a clean glass container
with Teflon-covered closure. If it is known
in advance that a large number of measure-
ments are to be performed on the dredge mix
sample, a 5-gallon sample may be advisable.
Analyze the receiving water as quickly as
possible for the constituents of interest,
using approved analytical procedures.
Place a representative portion of the
dredge material into a one-liter graduate,
filling to the mark. Let the dredge material
settle overnight (approximately 16 hours).
Carefully decant and discard supernatant.
Weigh out 500 +1 g of the wet, settled
dredge material, place in a gallon wide-
mouthed jar and add 2 liters of receiving
water at room temperature (22°C+2°). Cap
tightly and shake on an automatic shaker at
about 100 excursions per minute for 1 hour.
At the end of the shaking period remove the
jar from the shaker, stand in an upright
position and let settle for 1 hour.
Carefully decant the supernatant from the
settled dredge mix sample into a clean glass
container.• Analyze for constituents of
interest, shaking the sample thoroughly prior
to each aliquot removal. Use analytical
procedures as stated above.
If it appears that the total volume required
for all measurements is greater than two
liters, proportionately larger weights of
dredge material and receiving water may be
used. Alternately, several dredge mix-re-
ceiving water samples may be prepared,
following the above steps, in which case the
supernatants should be combined.
Calculations:
P - S - W, where
P - Concentration of Constituent Added to
1 liter of Receiving Water by 250 g
of Dredge Material
S » Concentration of Constituent in
Supernatant from Dredge Mix
W » Concentration of Constituent in
Receiving Water
80
-------
TABLE 8 (CONTINUED)
ADVANTAGES
DISADVANTAGES
REMARKS
Environmental conditions at
the site of disposal are
considered.
The test procedure is rela-
tively simple.
This method has been ex-
tensively used for evaluation
of dredged material disposal.
The test method is designed
specifically for dredged
material disposal.
The liquid to solid ratio is
•relatively small and thus may
enhance common ion effects.
This test may be used for
assessing the contribution of
soluble and partly soluble
constituents of dredge materials
to receiving water.
This test will measure (a)
the dissolved materials in the
interstitial waters of the
dredge material, (b) the readily
soluble fractions of the solid
phases of the dredge material,
and (c) the constituents loosely
adsorbed on the solid phases of
the dredge material.
This test will not measure any
of the insoluble or tightly
adsorbed material associated
with rapidly settleable dredge
material.
81
-------
TABLE 8 (CONTINUED)
METHOD
VARIABLES
ADDRESSED
DESCRIPTION
University of Wisconsin
(Hanm, 1977)
PH
P«
Buffering Capacity
Organic Constituents
Liquid to Solid
Ratio
Test Duration
Cycles
Agitation Method
Samples are first separated into a liquid
and solid phase by pressure filtration under
an inert gas (e.g., N2) using a 142 mm 0.45H-
glass filter. Some samples, particularly ones
containing fibrous materials (e.g., paper,
cloth) may require filtration through a wire
or plastic screen prior to pressure filtration.
Solids collected in this step are combined
with those of the second. The resulting fil-
trate (if present) is analyzed for parameters
of interest.
A 28.6 gram sample (ground only to the ex-
tent necessary to place the sample in the con-
tainer) is mixed with 200 ml of eluant (1:7
ratio by weight - see below) in a closed con-
tainer and mixed (rotating shaker (Knabe,
1976)) for 24 hours. The mixture is then
filtered through a 0.45H filter. 200 ml of
fresh eluant is added to filtered solid and
the process repeated while the filtrate is
analyzed for the parameters of interest. The
solid is leached a total of three times with
fresh eluant over a three day period.
No effort is made to control the temperature
under which the solid is extracted (other than
ambient laboratory conditions).
Eluant Composition
0.15M Acetic Acid
0.15M Sodium Acetate
O.OSM Glycine
0.024M Iron (II) Sulfate
0.008M Pyrogallol
82
-------
TABLE 8 (CONTINUED)
ADVANTAGES
DISADVANTAGES
REMARKS
This test is likely to yield Equilibrium conditions are
the most accurate representation not likely to be reached in 24
of leachate generation to date, hours.
The pH, p«, and buffering The eluant is relatively corn-
capacity of the eluant are all plex and unstable (i.e., eluant
similar to that found in natural probably cannot be stored for
leachate. more than 1 week).
Test results from this proce-
dure should be interpretable in
terms of actual leaching charac-
teristics in a landfill.
The test procedure is rela-
tively simple and straight
forward; as such the test may
be performed in a laboratory
with minimal facilities.
Kinetic leaching patterns may
be estimated from this test.
The eluant is toxic and thus,
if bioassay methods are used to
determine the hazard of the
leachate, interpretation of
test results may be difficult.
The relatively low liquid to
solid ratio will probably en-
hance common ion effects and
thus only relatively soluble
species may be leached.
The organic complexing capac-
ity of this eluant is several
orders of magnitude greater
than that of natural leachate;
furthermore, pyrogallol is not
representative of organic con-
stituents commonly found in
landfills.
This test has been designed by
the University of Wisconsin under
EPA Grant No. R804773010. Mention
of this test does not imply cur-
rent endorsement of this method by
EPA.
This test is specifically de-
signed to evaluate the environmen-
tal effects of solid waste dispos-
al in a landfill. As such the
following parameters are suggested
to be of particular importance in
leachate generation:
pH, complexing capacity, redox
environment, water-immiscible or-
ganic solubilizing power, and
ionic strength.
The landfill degradation pro-
cesses affecting these parameters
were studied, their maximum con-
centrations determined, and
compounds were chosen to model
the above parameters.
This synthetic eluant will be
compared with actual leachate to
determine the utility of this
method.
83
-------
TABLE 8 (CONTINUED)
METHOD VARIABLES DESCRIPTION
ADDRESSED
Westlnghouse Research • Liquid to Solid Deipnized water (250 ml) is mixed with the
Laboratories Ratio spent sorbent (25 g) in a 500 ml flask. The
• Test Duration mixture is agitated for 24 hours using an
(Realms et al., 1975) • Agitation Method automatic shaker (Eberbach) at 70 excursions
per minute at room temperature. This super-
natant is filtered (Whatman #42 paper) and
the filtrate analyzed.
This test has been conducted with samples as
received and with samples which are finely
ground. Shaking may be conducted under
aerobic (air atmosphere) or anaerobic con-
ditions (inert atmosphere). Shaking versus
non shaking procedures have been evaluated.
84
-------
TABLE 8 (CONTINUED)
ADVANTAGES
DISADVANTAGES
REMARKS
The test procedure is rela-
tively simple.
Aerobic and anaerobic condi-
tions are addressed by this
procedure.
The eluant is not representa-
tive of natural eluants.
Environmental conditions with-
in a landfill are not modelled.
Equilibrium conditions are
not likely to be reached with-
in 24 hours.
This test has been used as a
rapid test for the evaluation of
waterborne pollutant release from
FBC spent sorbent.
This test has been applied to
residues from pressurized and
atmospheric FBC units (PER,
Westinghouse and Esso Miniplant
units).
Similar test results were ob-
tained despite variations in
media surface area (i.e., grind-
ing of the sample prior to shake
test) and reaction conditions
(aerobic and anaerobic atmos-
pheres) . Leachates are analyzed
for 31 trace elements, pH, speci-
fic conductance, and sulfate.
The following was determined from
leach tests on spent FBC residue:
(1) Calcium and sulfate dissolu-
tion plateaued at concentrations
limited by calcium sulfate solu-
bility; (2) The equilibrium cal-
cium and sulfate concentrations
were high and exceed current
water quality criteria; (3) There
was negligible dissolution of
magnesium species; (4) Insignifi-
cant amounts of heavy metal ions
were leached; (5) The leachates
were alkaline (pH 10.6 - 12.1).
Runoff leachates (similar to a
column test) show a gradual de-
crease in pH with the amount of
eluant.
85
-------
TABLE 8 (CONTINUED)
METHOD VARIABLES DESCRIPTION
ADDRESSED
Roy F. Weston, Inc. • pH The coal sample is shaken with three solu-
• Liquid to Solid tions an acidic solution (pH 3.9), a neutral
(Roy F. Weston, Inc., Ratio solution (pH 7.1), and a basic solution
1974) • Test Duration (pH 10). The procedure is as follows:
• Agitation Method (1) Samples are dried to a constant weight at
105°C. (2) Twenty grams of the sample are
placed in 100 ml of water and the pH adjusted
to the desired value (HC1 and NaOH are used).
(3) The mixture is then transferred to a
shaker table, which is set at the maximum
shake rate for 30 minutes. (4) The superna-
tant is filtered and the filtrate analyzed
for the desired constituents.
86
-------
TABLE 8 (CONCLUDED)
ADVANTAGES
DISADVANTAGES
REMARKS
The effect of pH on leachate
generation ia considered.
The test procedure Is rela-
tively simple.
The eluant is not representa- This test has been used to
tive of natural eluants.
Environmental conditions
within a landfill are not
modelled.
Equilibrium conditions are
not likely to be reached with-
in 30 minutes.
assess the environmental impact
of leachate generation from coal
piles. The results from the test
are suggested to represent worst
case levels of leachate quality.
The results of these shake
tests for coal from the Decker
Coal Mine are as follows:
(1) Acidic conditions - initial
pH 3.9 final pH 9. Heavy metal
concentrations were negligible
(well below proposed EPA stan-
dards in 1973). (2) Neutral
conditions - initial pH 7.1 final
pH 8.5. Again heavy metal con-
centrations were negligible.
(3) Basic conditions: initial
pH 10.0, final pH 9.4. Heavy
metal concentrations were negli-
gible.
87
-------
SECTION 4
SUMMARY AND CONCLUSIONS
The selection or design of any leachate test will ultimately be decided
by a number of practical, rather than theoretical, considerations. It must
be recognized at the outset, however, that a single test will not be
optimal for all wastes. Nevertheless, from a regulatory point of view,
developing different tests for each different waste is clearly impractical
and probably unworkable.
Any evaluation of a test must first be reproducible and second provide
for the rapid assessment of the generation of aqueous toxic contaminants
from the disposal of solid wastes in a landfill. Moreover, the particular
method of hazard evaluation (e.g., direct measurement of a parameter or a
biological assay procedure) must be consistent with the leachate test protocol
chosen. Whatever the method of leachate assessment, it is useful to consider
what information might theoretically be derived from such tests.
INTERPRETATION OF SHAKE TESTS
Shake tests, the most ambitious of which seek to model those processes
which are thought to occur in a landfill, are by definition batch tests. As
such, these tests have been designed to yield "equilibria" (or in the case
where a solid is leached repeatedly with fresh eluant, a series of "equilib-
ria") rather than kinetic data. Leachate generation under natural conditions,
in contrast, is a highly dynamic process rather than a static one. Further-
more, the specific character of leachate, in terms of both quality and quantity,
will be site specific.
To a certain extent, these problems may be overcome by proper test
design, but a fundamental question remains unanswered: Which stage of
leachate generation shall be simulated? Shall the test be designed as a
"worst case"* or shall the test be designed to represent a more realistic
case, and thus, not maximize pollutant release? The answers to these ques-
tions will largely determine the composition of the eluant and the physical
conditions under which the test is conducted. Presumably the most active
phases of a landfill have the greatest environmental impact and therefore the
eluant composition during this stage should be modelled. Thus, by proper
choice of parameters, a shake test may be designed to yield information which
then may be used to estimate pollutant release rates under natural conditions.
*"Worst case" is defined to be that case in which pollutant release is
maximized within the bounds of naturally occurring conditions.
88
-------
The effect of eluant composition has been previously discussed in detail
in Section 2. The most significant parameters in terms of leachate generation
have been shown to be (1) the pH of the eluant, (2) the ratio of eluant to
waste, and (3) the redox environment of the waste. Because a "worst case"
evaluation is generally more useful as a preliminary test, eluant pH should
model the most active phase of landfill degradation, i.e., a pH of four to
five. Furthermore, the eluant should be well buffered in simulation of
natural conditions. To insure that all important species solubilize, the
ratio of eluant to waste should be large enough to minimize common ion effects.
For insoluble wastes, a ratio of 10 to 20:1 is presumed to be sufficient but
should be verified experimentally. Finally, the redox environment should
be considered. At this time, however, the specific processes which control
this environment are poorly understood. Thus, it is recommended that this
modelling be limited to the maintenance of an anaerobic environment by the
simple exclusion of air. This may be done by either conducting the entire
test in an inert atmosphere (e.g., a dry box filled with nitrogen) or by
agitation with an inert gas such as nitrogen.
A principal concern of any test procedure is that of reproducibility;
also related to this is the comparability of test results from different
wastes. The only method of ensuring that both of these requirements are
met is to allow sufficient time for the system to reach equilibrium, which
by definition is a unique state of any system examined. Furthermore, if the
time to reach equilibrium is considered, equilibrium concentrations may be
related to the kinetic leaching pattern within a landfill. However, attain-
ment of equilibrium conditions may require excessive amounts of time (years
or longer). Thus, a more reasonable goal is to reach at least a psuedo-
equilibrium condition.* Because initially, surface reactions are probably
rate controlling, the overall reaction rate (and thus the time needed to
reach equilibrium) increases with the surface area of the solid; thus,
ideally, the surface area of the waste should be maximized. However, such
a procedure may not be practical for all wastes (e.g., a tar or other semi-
solid waste).
A fundamentally different approach, and more useful from a theoretical
viewpoint, is to obtain kinetic information directly; however, such an
approach would require significant analytical effort. The major advantage
of a kinetic study is the acquisition of data, such as the effective
diffusivity and dissolution rate constant for relevant species, which allows
for direct comparison of several wastes. Coupled with solutions of mass
transport equations, such data provide a way to estimate the amount of
material leached from a landfill as a function of time, taking into account
actual site conditions. A major disadvantage, however, is the analytical
cost of such a study.
*Psuedo-equilibrium is defined as a steady-state under controlled redox
conditions.
89
-------
RECOMMENDED TESTS FOR FURTHER EVALUATION
Three tests are recommended for further evaluation: the IUCS shake
test; the State of Minnesota shake test; and the University of Wisconsin
shake test. These tests were chosen for the following reasons: (1) each
test is well written and likely to be reproducible if properly conducted;
(2) the tests chosen are exemplary and range from simple to complex (on the
basis of eluant composition) protocols; and (3) each test has been specifi-
cally designed to assess the environmental impact of solid waste disposal.
Yet each test has fundamental differences which suggest further evaluation.
The IUCS test is perhaps the simplest of the tests. In seeking to
model natural conditions, water specific to the field site is used as an
eluant. Should such water not be available, Type II reagent water is used.
The waste is leached in the physical form in which it is likely to be dis-
posed (i.e., the surface area and permeability of the waste are not modified
by grinding). Furthermore, this method has been extensively used (by IUCS)
to determine the leachability of a large number of industrial wastes. Dis-
advantages of this test include the low eluant to waste ratio (i.e., common
ion effects may be important at a liquid to solid ratio of 4:1) and the lack
of modelling of the redox environment. This test has also been considered
as a tentative standard by ASTM.
A test of intermediate complexity, the State of Minnesota procedure
seeks to model the acidic, highly buffered, nature of leachate. The high
liquid to solid ratio 40:1 should minimize any common ion effects. Dis-
advantages include the short duration of the test (a steady-state condition
may not be reached in 24 hours) and the lack of modelling of natural redox
considerations.
The most complex and comprehensive protocol is the University of
Wisconsin test. Each of the parameters addressed in Section 2 of this
document is addressed in some manner by this test. The eluant pH and
buffering capacity is modelled after natural leachate. The redox potential,
together with the complexing ability of the eluant, are addressed by the
addition of a pyrogallol-iron (II) complex. The agitation method has been
designed to minimize particle attrition during the test. Disadvantages
include the short duration of the test (a steady-state condition may not be
reached in 24 hours) and the relatively low liquid to solid ratio (again
common ion effects may play a significant role at a liquid to solid ratio of
7:1).
Rigorous laboratory evaluation of these shake tests may result in the
modification and refinement of suggested test procedures. Thus, while it is
still possible, indeed probable, that no single test procedure will perfectly
fulfill all of the requirements under section 3001 of the Resource Conserva-
tion and Recovery Act, these tests do represent a starting point for the
solution of a complex problem.
90
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REFERENCES
Abelson, H.A., and W. Lowenbach, "Procedures Manual for the Environ-
mental Assessment of Fluidized - Bed Combustion Processes". The MITRE
Corporation, METREK Division M77-34, January, 1977.
Barton, G.B., "Solidification of High Level Wastes - Part IV", BNWL-80,
Battelle - Northwest, Richland, Washington, July, 1965.
Brookman, Gordon T., "Evaluation of Water-Borne Fugitive Emissions",
The Research Corporation, 1976.
Burrows, W. Dickinson and Robert S. Rowe, "Ether Soluble Constituents
of Landfill Leachate", Journal of the Water Pollution Control Federa-
tion, 4^(5), 921, 1975.
Chian, Edward S. K., and Foppe B. DeWalle, "Removal of Organic Matter
by Activated Carbon Columns", Journal of the Environmental Engineering
Division, ASCE 100. 1089, 1974.
Chian, Edward S.K., and Foppe B. DeWalle, "Sanitary Landfill Leachates
and Their Treatment", Journal of the Environmental Engineering Division,
ASCE, 102, 411, 1976.
Chian, Edward S.K. and Foppe B. DeWalle, "Characterization of Soluble
Organic Matter in Leachate", Environmental Science and Technology. H»
158, 1977.
Childs, C.W., P.S. Hallmon, and D.D. Perrin, "The Application of
Digital Computers in Analytical Chemistry", Talanta, 16^, 1119, 1969.
Clark, W. Mansfield, Oxidation-Reduction Potentials of Organic Systems.
Robert E. Krieger Publishing Company, Huntington, New York, 1972.
Crank, J., The Mathmatics of Diffusion, Clarendon Press, Oxford, U.K.,
1956.
Fuller, Wallace H. (ed.), "Residual Management by Land Disposal - Pro-
ceedings of the Hazardous Waste Research Symposium", U.S. Environmental
Protection Agency, EPA-600/9-76-015, July 1976.
Gray, Donald M. (ed.), Principles of Hydrology. Water Information Center,
Inc., Port Washington, New York, 1973.
91
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REFERENCES (Continued)
Hamm, Robert K., "Development of a Standard Leaching Test - Second
Progress Report", EPA Grant No. R804773010, University of Wisconsin,
January, 1977.
Hespe, I.E.D., "Leach Testing of Immobilized Radioactive Waste Solids",
Atomic Energy Review, 9>, 195, 1971.
Illinois Plater's Waste Task Force. "Leach-Test Laboratory Procedure
for the Evaluation of Electroplaters1 Wastes." Illinois Plater's
Waste Task Force, May 25, 1977.
Industrial Environment Research Laboratory. "Solubility Test".
Personal Communication, R. Statnick, U.S. Environmental Protection
Agency, IERL, Research Triangle Park, North Carolina, Sept. 20, 1976.
IU Conversion Systems, Inc., "Shake Test for Evaluation of the Leaching
Potential from Land Disposal of Waste Materials", Personal Communica-
tion, IU Conversion Systems, Philadelphia, Pennsylvania, Aug. 22, 1977.
Japan Environmental Protection Agency. "Standard for Hazardous Indus-
trial Waste" Environmental Protection Notice No. 13, February 17, 1973.
Johansen, Ole Jakob and Dale A. Carlson, "Characterization of Sanitary
Landfill Leachates", Water Research 10, 1129, 1976.
Keairns, D.C., "Fluidized Bed Coal Combustion Development", Westinghouse
Research Laboratories, Pittsburgh, Pennsylvania EPA - 650/2-75-027c,
September 1975.
Khare, Mohan and Norman C. Dondero, "Fractionation and Concentration
from Water of Volatiles and Organics on High Vacuum System: Examina-
tion of Sanitary Landfill Leachate", Environmental Science and
Technology, LL, 814, 1977.
Kramer, J.R., "History of Sea Water. Constant Temperature - Pressure
Equilibrium Models Compared to Liquid Inclusion Analyses". Geochemica
et Cosmochemica Acta, 29, 921, 1965.
Lee, G.F., M. Piwoni, J. Lopez, G. Marioni, J. Richardson, D. Homer,
and F. Saleh, "Research Study for the Development of Dredged Material
Criteria", Contract Report D-75-4, Environmental Effects Laboratory,
U. S. Army Engineer Waterways Experiment Station, Vicksburg,
Mississippi, 1975.
Lynch, A.W., "A Short-Duration Leach Test .for Radioactive Waste Forms"
Nuclear Technology, .34, 463, 1977.
92
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REFERENCES (Continued)
Mahloch, J.L., D.E. Averett, and M.J. Bartons, Jr., "Pollutant
Potential of Raw and Chemically Fixed Hazardous Industrial Wastes
and Flue Gas Desulfurization Studies", U.S. Army Engineer Waterways
Experiment Station, EPA-600/2-76-182, July 1976.
Mendel, J.E., "A Review of Leaching Test Methods and The Leachability
of Various Solid Media Containing Radioactive Wastes", BNWL-1765,
Battelle-Northwest, Richland, Washington, July 1973.
Moore, Walter J., Physical Chemistry, 4th ed., Prentice-Hall, Inc.,
Englewood Cliffs, New Jersey, 1972.
Morel, F. and J.J. Morgan, "A Numerical Solution for Solution of
Chemical Equilibria in Aqueous Systems", in Aquatic Chemistry,
Stumm, W. and J.J. Morgan, eds. Wiley-Interscience, New York,
New York, 1970.
Nancollas, G.N. and N. Purdie, "The Kinetics of Crystal Growth",
Quarterly Review (London) 18, 1, 1964.
NATO, "Sub-Project on Recommended Procedures for Hazardous Waste
Management", Preliminary Draft, undated.
Perrin, D.D. and I.G. Sayce, "Computer Calculation of Equilibrium
Concentrations of in Mixtures of Metal-Ions and Complexing Species",
Talanta, 14, 833, 1967.
Roy F. Weston, Inc., "Preliminary Environmental Report - Transhipment
Facility Superior, Wisconsin", Roy F. Weston, Inc., April, 1974.
Schindler, J.E., D.J. Williams, and A.P. Zimmerman, "Investigation of
Extracellular Electron Transport by Humic Acids", in Environmental
Geochemistry, Volume 1, Chapter 8, Jerome 0. Nriagu (ed.), Ann
Arbor Science, Ann Arbor, Michigan, 1977.
Schnitzer, M., "The Chemistry of Humic Substances", in Environmental
Geochemistry Volume 1, Chapter 7, Jerome 0. Nriagu (ed), Ann Arbor
Science, Ann Arbor, Michigan, 1977.
State of Delaware, "Procedure for the Extraction of Sludge Waste
Materials", Personal Communication, T.L. Go, Department of Natural
Resources and Environmental Control, Solid Waste Management Section,
Dover, Delaware, July, 5, 1977.
State of Illinois, "Landfill Disposal Criteria-Draft Copy", Personal
Communication, S. Miller, Illinois Environmental Protection Agency,
Hazardous Waste Section, Springfield, Illinois, July, 1, 1977.
93
-------
REFERENCES (CONCLUDED)
State of Indiana, "General Procedure for Preparing a Leachate of a
Solid", Personal Communication, D. Lamm, Indiana State Board of
Health, Solid Waste Management Section, Indianapolis, Indiana, June
29, 1977.
State of Iowa, "Standard Leachate Test", Personal Communication, D.
McAllister, Iowa Department of Environmental Quality, Land Quality
Management Division, Des Moines, Iowa, June 28, 1977.
State of Michigan, "Shake Test", Personal Communication, F. Kellow,
Environmental Protection Bureau, Resource Recovery Division, Lansing,
Michigan, July 18, 1977.
State of Minnesota, "Land Disposal Leach Test", Personal Communication,
R. Silvagni, Minnesota Pollution Control Agency, Division of Solid
Wastes, Roseville, Minnesota, July 10, 1977.
State of New Jersey, "Recommended Leaching Test", Personal Communica-
tion, R.J. Buchanan, Department of Environmental Protection, Trenton,
New Jersey, July 11, 1977.
State of Pennsylvania, "Leachate Methods Simulatively Rainfall Runoff
from Solid Waste Sludge", Personal Communication, F. Grunder, Bethlehem
Steel, Bethlehem, Pennsylvania, April 11, 1977.
State of Texas, "Waste Evaluation/Classification", Texas Water Quality
Board", Industrial Solid Waste Management, Technical Guide No. 1,
(Draft), May 3, 1976.
Stevenson, F.J., "Binding of Metal Ions by Humic Acids" in Environ-
mental Biogeochemistry, Volume 2, Chapter 33, Jerome 0. Nriagu (ed.)
Ann Arbor Science, Ann Arbor, Michigan, 1977.
Stumm, Warner and James Morgan. Aquatic Chemistry, Wiley-Interscience,
New York, New York, 1970.
United States Congress, Public Law 94-580. "Resource Conservation and
Recovery Act of 1976", 94th Congress, October 21, 1976.
Weir, A., S.T. Carlisle, and J. Norris, "The Environmental Effects of
Trace Elements in the Pond Disposal of Ash and Flue Gas Desulfurization
Sludge", Electric Power Research Institute, Research Project 202,
September 1975.
94
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APPENDIX I
IU CONVERSION SYSTEMS, INC.
MODIFIED 48-HOUR SHAKE TEST
1. SCOPE
1.1 This method covers the determination of both the surface washing
and the long-term diffusion-controlled leachate properties of a soil or waste
material. The procedure is to establish representative values of the surface
washing and the long-term diffusion-controlled leachate properties of a soil
or waste material as placed in embankments, landfills, and other disposal or
use sites. Such values can be used in the evaluation of the environmental
impact of disposal or use sites. As tested these properties result from
prolonged water contact both on the surface of the soil or waste materials
and on a portion of the interior of a mass of soil or waste material as limited
by the permeability of the material. In an actual site prolonged water contact
may not be the primary leaching mechanism. The data derived from this procedure
should be carefully interpreted with this fact in mind.
2. FUNDAMENTAL TEST CONDITIONS
2.1 The following test conditions are prerequisites:
2.1.1. Continuity of water movement during test with constant rate of
wafer movement,
2.1.2 Water used in test shall be representative of water specific
for the field site or Type II grade reagent water as defined by ASTM standard
D1193,
2.1.3 Relative density and permeability of soil or waste material
evaluated in test shall approximate relative density and permeability of soil
or waste material as placed or as anticipated in the field site.
2.1.4 Dry weight of test specimen plus volume of water used in test
shall be known accurately.
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3. APPARATUS
3.1 Variable Speed Reciprocating Shaker equipped with box carrier large
enough to hold the leaching containers used. The shaker shall be suitable for
long-term continuous duty use and capable of being set to a shaking rate of
60 to 70 one-inch strokes per minute.
3.2 Membrane Filter Assembly - A borosilicate glass or stainless steel
funnel with a flat, fritted base of the same material, and membrane filters
(0.45ym pore size) to fit. The filters shall be prepared in accordance with
ASTM D1888, section 17.3.1.
3.3 Suction Flask, at least 500 ml capacity.
3.4 Polyethylene Containers, at least 3000 ml capacity, capable of
being sealed watertight.
3.5 Balance capable of weighing at least 1000 g, with a sensitivity
of 0.1 g.
3.6 Graduated Cyli nders, 1000 ml capacity and 20 ml. capacity.
3.7 Drying Oven, adjustable to a temperature of 104°C (219.2°F)±1°C
(1.8°F).
3.8 Vacuum Pump, minimum capacity of 1.67 x 10~5 min/atmospheric
cm^, attainable vacuum of 0.1 microns Hg.
SAMPLE
4.1 From the material to be tested which is at the moisture content
present or anticipated in the field, select a representative sample for testing
equal to an amount approximately twice that required for the shake test.
When simulating an actual field placement of stabilized soil or waste material,
the relative density and permeability coefficient of the material should be
known so that these values can be compared to the actual field values.
ASTM D2049 and D2434 give methods for determining relative density of cohesion-
less soils and permeability coefficient of granular soils.
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5. PREPARATION OF SPECIMENS
5.1 Take a small portion of the sample selected as prescribed in 4.1
for water content determinations according to ASTM standard D2216. In the
case of waste materials containing components with water of hydration, the
drying temperature should be modified to 37.8°C (100°F)±1°C (1.8°F) to avoid
removing any water of hydration during moisture content determinations.
5.2 Take portions of the sample selected as prescribed in 4.1 such
that five specimens weigh 125g ± 13g dry weight and one specimen v/eighs 500g ±
50g dry weight. In the case of monolithic stabilized soils or waste materials,
the samples should be circular slices from a standard Proctor or 3" x 6"
cylinder. Weigh specimens. Record wet weight of each specimen. Calculate
and record dry weight of each specimen.
6. PROCEDURE
6.1 Place each of the specimens of known weight in polyethylene con-
tainers.
6.2 Measure six aliquots of water as defined in 2.1.2 such that the
ratio of ml of water to g, dry weight of test specimen is 4 to 1 for each of
the specimens. Dry sample weights other than those indicated in 5.2 may be
used where necessary, so long as the ratio ml of water to g, dry weight, of
test specimen is maintained at 4 to 1. Record measured water volume in liters
for each test specimen.
6.3 Add the measured water to each of the specimens in the polyethylene
containers.
6.4 Seal containers and place in box carrier of the reciprocating
shaker at an oscillation rate of 60 to 70 one-inch strokes per minute. Be
certain that placement of sample in container and container on shaker allows
for maximum water movement.
6.5 Prepare six leachates in accordance with the following.
6.5.1 Shake one container with 125g sample for 1 hour. Note and
record the condition of test specimen, being sure to include comments on
physical deterioration. Immediately vacuum filter all leachate using membrane
97
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filter assembly prepared as in 3.2. Filters should be prepared plain white
filter discs of the prescribed pore size. Where sample bottles are employed
for sample collection, the entire contents of a sample bottle should be filtered.
6.5.2 Shake one container with 125g sample for 2 hours. Filter as in
6.5.1.
6.5.3 Shake one container with 125g sample for 4 hours. Filter as in
6.5.1.
6.5.4 Shake one container with 125g sample for 8 hours. Filter as in
6.5.1.
6.5.5 Shake one container with 125g sample for 24 hours. Filter as in
6.5.1.
6.5.6 Shake container with 500g sample for 48 hours. Let test specimen
settle for 5 minutes after stopping shake apparatus. Note and record the condi-
tion of test specimen, being sure to include comments on physical deterioration.
Sample a portion of leachate using a pipet of suitable size. Reserve this portion
for determination of particulate and dissolved matter in accordance with ASTM
D1888. Filter remaining leachate in accordance with 6.5.1.
6.6 Chemically analyze the six leachate samples according to the
schedule outlined in Table I. This schedule represents a recommended minimum
analysis program. Depending on test requirements and applicable regulations,
component analyses may be omitted and added as required. These analyses should
be performed according to the appropriate ASTM standard methods. Record all
analysis results, expressing pH in standard pH units and all other parameters
in mg/1 of the specified constituent. Phenolphthalein alkalinity and total
alkalinity shall be expressed as meq/1 and hardness shall be expressed as epm,
in accordance with the ASTM standards indicated in Table I.
7. CALCULATIONS
7.1 For each of the leachate samples, calculate and record the dimen-
sionless weight of dissolved material leached from the test specimen according
to:
98
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r - (TDS)V
G " 2W
Where G = dimensionless weight of dissolved material leached
V = volume of water added to test specimen for each shake
W = dry weight of test specimen(g)
IDS = concentration of dissolved matter in leachate (mg/1)
Using this equation, the dimensionless weight is calculated on the basis of
a test specimen of 500g dry weight.
8. REPORT
8.1 The report of modified 48-hour shake test shall include the
following information:
8.1.1 Project dates, sample number, location, and other pertinent
information.
8.1.2 Relative density and permeability coefficient of test specimens.
8.1.3 Complete test data including the following:
8.1.3.1 Dry and wet weight of test specimens,
8.1.3.2 Volume and water added for each shake period,
8.1.3.3 Chemical analysis and dimensionless weight of dissolved material
leached for each of the six leachate samples,
8.1.3.4 Comments on changes in physical condition on samples after
each of the six shake periods.
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TABLE A-l
IUCS Modified 48-Hour Shake Test
Chemical Analysis Schedule
1 248 24 48
Hour Hour Hour Hour Hour Hour
Constituent Leachate Leachate Leachate Leachate Leachate Leachate
pH (ASTM D1293) X X
Phenol phthalein Alkalinity {ASTM D1067)
Total Alkalinity (ASTM D1067)
Hardness (ASTM D1126)
Sulflte (ASTM 01339)
Sulfate (ASTM 0516)
Chloride (ASTM D512)
Dissolved Matter (ASTM 01 888) X X
Particulate Matter (ASTM 01888)
Arsenic (ASTM 02972)
X X X X
X
X
X
X
X
X
X X X X
X
X
Cadmium (ASTM 02576) X
Chromium (ASTM 01687) X
Copper (ASTM 01688, 02576) X
Iron. (ASTM.01068, 02576) X
Mercury (ASTM 03223) X
Manganese (ASTM 0858, 02576) X
Sodium (ASTM 01428) X
Lead (ASTM 02576) X
Zinc (ASTM 01691, 02576) X
100
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Minnesota Pollution Control Agency
Land Disposal Leach Test - Chemical Analysis
A test procedure to be used for most types of industrial wastes to evaluate the
acceptability for land disposal either in a sanitary landfill or in a separate
area at a sanitary landfill.
Prior to performing a leach test, a qualitative and quantitative analysis of the
waste is to be performed. The analysis should include tests for total solids
content, pH, chemical oxygen demand, and metals. Results for the metals analysis
shall be determined with an accuracy of 0.1 mg/1. Different parameters may be
required depending on the specific waste tested.
To assess possible impacts upon ground water quality, the following test should be
performed to determine the approximately characteristics of leachate generated from
a landfill containing an industrial waste. Two diluents are used to approximate
conditions both in a sanitary landfill or in an area segregated from refuse
deposits.
1. Vigorously shake 25 grams of waste with 1 liter of diluent in a 2000 ml
glass separately funnel for 60 seconds (one diluent consisting of
buffered acetic acid solution and the other diluent consisting of
deionized distilled water).
2. Cover and let the mixture stand for 24 hours.
3. At the end of 24 hours, shake the mixture vigorously for
60 seconds.
4. Filter the mixture through medium porosity ashless (less than
.01% ash) filter paper. The filtered mixture will then be called
leachate. Discard first 10 mis of leachate.
5. The leachate is then analyzed for constituents found in the qualitative
and quantitative analysis. The porosity of filter paper used, methods
of analysis, and final pH and solids content should be reported.
*Solution should be formulated as follows:
1. Measure 49.21 gms. HOAc into a 2 liter container.
2. Add 37.21 gms. NaOAc
3. Add enough deionized distilled water to make a total solution of
1 liter - stir.
4. Solution will have a pH of 4.5.
* Not necessary unless waste is to be
mixed with domestic wastes.
101
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UNIVERSITY OF WISCONSIN SHAKE TEST
Samples are first separated into a liquid and solid phase by
pressure filtration under an inert gas (e.g., N9) using a 142 mm
0.45y glass filter. Some samples, particularly ones containing
fibrous materials (e.g., paper, cloth) may require filtration through
a wire or plastic screen prior to pressure filtration. Solids col-
lected in this step are combined with those of the second. The
filtrate resulting from this first separation is analyzed for the
parameters of interest (e.g., pH, pe, heavy metals).
A representative 28.6 gram sample from the above separation
scheme (ground only to the extent necessary to place the sample in the
container) is mixed with 200 ml of eluant (1:7 ratio by weight - see
below) in a closed container and mixed (rotating shaker (Knabe, 1976))
for 24 hours. The mixture is then filtered through a 0.45y filter.
200 ml of fresh eluant is added to filtered solid and the process
repeated. The solid is leached a total of three times with fresh
eluant over a three day period. The resulting filtrates are analyzed
separately for the parameters of interest (e.g., pH, pe, heavy metals).
No effort is made to control the temperature under which the solid
is extracted (other than ambient laboratory conditions).
Eluant Composition
0.15M Acetic Acid
0.15M Sodium Acetate
0.05M Glycine
0.024M Iron (II) Sulfate
0.008M Pyrogallol
102
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TECHNICAL REPORT DATA
(Please read Instructions on the reverse before completing}
1. REPORT NO.
EPA-600/2-78-095
2.
3. RECIPIENT'S ACCESSION-NO.
4. TITLE AND SUBTITLE
Compilation and Evaluation of Leaching
Test Methods
5. REPORT DATE
May 1978 (Issuing Date)
6. PERFORMING ORGANIZATION CODE
7. AUTHOR(S)
William L61 wen bach
8. PERFORMING ORGANIZATION REPORT NO.
9. PERFORMING ORGANIZATION NAME AND ADDRESS
Mitre Corporation
McLean, Virginia 22101
10. PROGRAM ELEMENT NO.
1DC618
11. CONTRACT/GRANT NO.
68-03-2620
12. SPONSORING AGENCY NAME AND ADDRESS
Municipal Environmental Research Laboratory--Cin.,OH
Office of Research and Development
U.S. Environmental Protection Agency
Cincinnati, Ohio
13. TYPE OF REPORT AND PERIOD COVERED
• Final
14. SPONSORING AGENCY CODE
EPA/600/14
15. SUPPLEMENTARY NOTES
Project Officer: Donald E. Sanning 513/684-7871
16. ABSTRACT
Under the Resource Recovery and Conservation Act of 1976, EPA is required to
promulgate criteria for identification of hazardous wastes. One method of identifica-
tion is to characterize the Teachability of the waste. This study evaluates those
factors important to the design of such a test. Additionally, existing leachate tests
are compiled and from this listing three tests have been recommended for further
evaluation.
This report was submitted in fulfillment of Contract No. 68-03-2620 by Municipal
Environmental Research Laboratory under the sponsorship of the U.S. Environmental
Protection Agency. This report covers the period of May 1977 to August 1977, and
work was completed February 21, 1978.
17.
KEY WORDS AND DOCUMENT ANALYSIS
DESCRIPTORS
b.lDENTIFIERS/OPEN ENDED TERMS C. COS AT I Field/Group
Leaching
Tests
Methodology
Selection
Interpretation
Assessments
Refuse Disposal
Evaluation
Literature Review
Leaching Tests
Compilation
Methods
14B
18. DISTRIBUTION STATEMENT
RELEASE TO PUBLIC
19. SECURITY CLASS (ThisReport)'
UNCLASSIFIED
21. NO. OF PAQES
111
20. SECURITY CLASS (Thispage)
UNCLASSIFIED
22. PRICE
EPA Form 2220-1 (9-73)
103
U. 3. GOVERNMENT PRINTING OFFICE: 1978-757-140/1352 Region No. 5-11
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