United States Office of Solid Waste SW-872
Environmental Protection and Emergency Response September 1982
Agency Washington DC 20460 Revised Edition
x°/EPA Guide to the Disposal
of Chemically Stabilized
and Solidified Waste
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GUIDE TO THE DISPOSAL OF CHEMICALLY
STABILIZED AND SOLIDIFIED WASTE
by
Environmental Laboratory
U.S. Army Engineer Waterways Experiment Station
Vicksburg, Mississippi 39180
Interagency Agreement No. EPA-IAG-D4-0569
Project Officer
Robert E. Landreth
Solid and Hazardous Waste Research Division
Municipal Environmental Research Laboratory
Cincinnati, Ohio 45268
y <; •".-.'"•" ,,' ! T;,,:cc;ioii Agency
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Caicuo, nti.'.ulj 6wb04
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. Mention of trade names or commercial products does not constitute
endorsement or recommendation for use.
r>. i
. . "f--.- '•'--. f. .
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ii
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FOREWORD
The Environmental Protection
public and governmental concern about
and welfare of the American people.
land are tragic testimony to the
The complexity of the environment
require a concentrated and integral
Agency was created because of increasing
the dangers of pollution to the health
Noxious air, foul water, and spoiled
deterioration of our natural environment.
the interplay between its components
ed attack on the problem.
and
the
Research and development is
it involves defining the problem,
lutions. The Municipal Environmental
improved technology and systems to
the solid and hazardous waste
ity sources; to preserve and treat
minimize the adverse economic,
tion. This publication is one of
communications link between the
social
the
This study examines procedures
wastes for disposal, including physical
lines options for ultimate disposal
ify or chemically stabilize industrial
preservation of human health and tbje
isolate toxic materials.
first necessary step in problem solution;
treasuring its impact, and searching for so-
Research Laboratory develops new and
prevent, treat, and manage wastewater and
pollutant discharges from municipal and commun-
public drinking water supplies; and to
health and aesthetic effects of pollu-
products of that research—a vital
res|earcher and the user community.
for the treatment of hazardous industrial
and chemical test procedures and out-
of treated wastes. Techniques that solid-
waste products may contribute to the
environment by helping us immobilize and
FRANCIS T. MAYO
Director
Municipal Environmental Research
Laboratory
iii
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PREFACE
The land disposal of hazardous waste is subject to the requirements
of Subtitle C of the Resource Conservation and Recovery Act of 1976. This
Act requires that the treatment, storage, or disposal of hazardous wastes
after November 19, 1980 be carried out in accordance with a permit. The
one exception to this rule is that facilities in existence as of November
19, 1980 may continue operations until final administrative disposition is
made of the permit application (providing that the facility complies with
the Interim Status Standards for disposers of hazardous waste in 40 CFR
Part 265). Owners or operators of new facilities must apply for and receive
a permit before beginning operation of such a facility.
The Interim Status Standards (40 CFR Part 265) and some of the adminis-
trative portions of the Permit Standards (40 CFR Part 264) were published
by the Environmental Protection Agency in the Federal Register on May 19,
1980. The Environmental Protection Agency published interim final rules
in Part 264 for hazardous waste disposal facilities on July 26, 1982.
These regulations consist primarily of two sets of performance standards.
One is a set of design and operating standards separately tailored to each
of the four types of facilities covered by the regulations. The other
(Subpart F) is a single set of ground-water monitoring and response require-
ments applicable to each of these facilities. The permit official must
review and evaluate permit applications to determine whether the proposed
objectives, design, and operation of a land disposal facility will comply
with all applicable provisions of the regulations (40 CFR 264).
The Environmental Protection Agency is preparing two types of documents
for permit officials responsible for hazardous waste landfills, surface
impoundments, land treatment facilities and piles: Draft RCRA Guidance
Documents and Technical Resource Documents. The draft RCRA guidance
documents present design and operating specifications which the Agency
believes comply with the requirements of Part 264, for the Design and
Operating Requirements and the Closure and Post-Closure Requirements
contained in these regulations. The Technical Resource Documents support
the RCRA Guidance Documents in certain areas (i.e., liners, leachate
management, closure, covers, water balance) by describing current techno-
logies and methods for evaluating the performance of the applicant's design.
The information and guidance presented in these manuals constitute a
suggested approach for review and evaluation based on good engineering
practices. There may be alternative and equivalent methods for conducting
the review and evaluation. However, if the results of these methods differ
from those of the Environmental Protection Agency method, they may have to
be validated by the applicant.
iv
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In reviewing and evaluating the permit application, the permit official
must make all decisions in a well defined and well documented manner. Once
an initial decision is made to issue or deny the permit, the Subtitle C
regulations (40 CFR 124.6, 124.7 and 124.8) require preparation of either a
statement of basis or a fact sheet that discusses the reasons behind the
decision. The statement of basis or fact sheet then becomes part of the
permit review process specified in 40 CFR 124.6-124.20.
These manuals are intended to assist the permit official in arriving
at a logical, well-defined, and well-documented decision. Checklists and
logic flow diagrams are provided throughout the manuals to ensure that
necessary factors are considered in the decision process. Technical data
are presented to enable the permit official to identify proposed designs
that may require more detailed analysis because of a deviation from suggested
practices. The technical data are not meant to provide rigid guidelines
for arriving at a decision. The references are cited throughout the manuals
to provide further guidance for the permit officials when necessary.
There was a previous version of this document dated September 1980.
The new version supercedes the September 1980 version.
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ABSTRACT
Stabilization/solidification of Industrial waste is a pretreatment
process that has been proposed to insure safe disposal of wastes containing
harmful materials. This manual examines the regulatory considerations, cur-
rent and proposed technology, testing procedures and design of landfills,
and other options involved in disposal systems using stabilization/
solidification of wastes. A summary of the major physical and chemical
properties of treated waste is presented. A listing of major suppliers of
stabilization/solidification technology and a summary each process is
included.
vi
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CONTENTS
Foreword ill
a
Preface iv
Abstract vi
Figures ix
Tables x
Acknowledgment xi
1. Introduction 1
1.1 Purpose 1
1.2 The Terminology of Waste Solidification/Stabilization . . 1
1.3 Legislative Background 2
1.4 Characteristics of Wastes for which Stabilization/
Solidification are Effective and Economical 6
1.5 Delisting Treated Hazardous Waste Products 7
2. Waste Stabilization/Solidification Technology 10
2.1 Current Waste Stabilization/Solidification Technology. . . 10
2.2 Cement-Based Processes 12
2.3 Pozzolanic Processes (Not Containing Cement) 15
2.4 Thermoplastic Techniques (Including Bitumen, Paraffin
and Polyethylene) 16
2.5 Organic Polymer Processes 18
2.6 Surface Encapsulating Techniques (Jacketing) 19
2.7 Self-Cementing Processes 20
2.8 Classification and Production of Synthetic Minerals or
Ceramics 22
2.9 Summary 23
3. Properties of Stabilized/Solidified Wastes 26
3.1 Characterizing Wastes to be Treated 26
3.2 Requirements for Ideal Waste Stabilization/Solidification. 26
3.3 Compatability of Wastes and Treatment Additives 27
3.4 Testing the Physical Properties of Stabilized Wastes ... 30
3.5 Chemical Leach Testing of Stabilized Wastes 40
3.6 Effects of Biological Attack on Treated Wastes 43
3.7 Effects of Curing and Aging Processes on Treated Material. 44
3.8 Economic Considerations of Treatment Options 44
4. Assessment of Current Data on Physical and Chemical Properties
of Treated Wastes 49
4.1 Existing Data on Physical Properties of Treated Wastes . . 49
4.2 Existing Data on Chemical Properties of Treated Wastes . . 50
4.3 Correlation of Physical and Chemical Properties 54
4.4 Interpretation of Physical and Chemical Data 54
vii
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CONTENTS
5. Design Considerations for Solidified and Stabilized Waste
Disposal Facilities 56
5.1 Special Considerations for Handling and Disposal of
Stabilized/Solidified Wastes 56
5.2 Design Factors for Hazardous Waste Landfills 57
5.3 Use of Land Treatment of Biodegradable Industrial Wastes . 58
5.4 Operation and Management of Disposal Facilities for
Treated Wastes 59
6. Stepwise Evaluation of Stabilized/Solidified Wastes 62
6.1 Step 1. Evaluation of Hazardous Nature of Treated Waste . 62
6.2 Step 2. Determination of Maximum Toxic Hazard Under
Normal Conditions 64
6.3 Step 3. Determination of Physical Integrity and
Durability 64
6.4 Step 4. Estimation of Leaching Loss Over a Long Term. . . 65
6.5 Step 5. Assessment of Land Burial Sites 66
6.6 Step 6. Evaluation of Monitoring and Closure Programs . . 66
6.7 Step 7. Quality Control of Waste Treatment 69
6.8 Step 8. Evaluation of Aged Material 69
6.9 Permitting and Operating Experience 69
Appendices
A. Sources of Fixation Technology 72
B. Proposed Uniform Leach Procedure 97
Glossary 108
viii
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FIGURES
Number Page
2-1 Examples of solidified electroplating waste 11
2-2 Close-up of plastic-jacketed electroplating waste 21
3-1 Compression testing of plastic-jacketed wastes 34
3-2 Typical solidified waste test specimens after 4 wet-dry test
cycles 36
6-1. Percent of constituents remaining in barrel-sized, cylindrical
ingots (90 cm long x 55 cm diam.) of solidified waste over
100 years of.leaching for wastes having diffusivities of
10 to 10 cm /sec 67
6-2 Percent of constituent remaining in semi-infinite slab (10 cm
thick) of solidified waste over 100 years of leaching for
wastes having diffusivities of 10 to 10 cm /sec .... 68
ix
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TABLES
Number Page
1-1 Treatment Codes for EPA Hazardous Waste Manifests 3
1-2 Some Attributes of Commonly Available Waste Treatment Options . 4
3-1 Reactions Occurring Between Incompatible Wastes 28
3-2 Compatibility of Selected Waste Categories with Different
Waste Solidification/Stabilization Techniques 31
3-3 Long-Term Chemical Resistance of Organic Polymers (Resins)
Used in Solidifications 32
3-4 Standard Tests of Physical Properties 33
3-5 Typical Results from Physical Testing of Stabilized and
Untreated Industrial Wastes 37
3-6 Present and Projected Economic Considerations for Waste
Stabilization/Solidification Systems 46
4-1 Results of Physical Property and Leaching Tests Made by Sludge
Stabilization Vendors 51
4-2 Relationship Between Percent Solids, Unconfined Compressive
Strength and Cement Content of a Chemically Stabilized
Sludge 53
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ACKNOWLEDGMENTS
This manual was prepared by the Environmental Laboratory (EL) of the
U. S. Army Engineer Waterways Experiment Station (WES) under sponsorship of
the Municipal Environmental Research Laboratory, U. S. Environmental Protec-
tion Agency.
The contributing authors are Dr. Philip G. Malone, Dr. Larry W. Jones,
and Robert J. Larson. Mr. Norman R. Francingues reviewed the manuscript and
provided valuable criticism. The abstracts presented in Appendix B are
available through the efforts of the many companies that responded to in-
quiries and submitted technical information for inclusion in this publica-
tion. The project was conducted under the general supervision of Dr. John
Harrison, Chief, EL; Mr. Andrew J. Green, Chief, Environmental Engineering
Division; and Mr. Norman R. Francingues, Jr., Chief, Water Supply and Waste
Treatment Group.
The guidance and support of Mr. Robert E. Landreth, Mr. Norbert B.
Schomaker and the Solid and Hazardous Waste Research Division, Municipal
Environmental Research Laboratory, U. S. Environmental Protection Agency are
gratefully acknowledged. The diligent and patient efforts of Ms. Billie
Smith and the staff of the EL Word Processing Section are also gratefully
acknowledged. Illustrations and figures were prepared by Mr. Jack H.
Dildine. The Director of WES during the course of this work was COL Nelson
P. Conover, CE. Technical Director was Mr. F. R. Brown.
xi
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SECTION 1
INTRODUCTION
1.1 PURPOSE
The purpose of this manual is to provide guidance in the use of chemi-
cal stabilization/solidification techniques for limiting hazards posed by
toxic wastes in the environment, and to assist in the evaluation of permit
applications related to this disposal technology. The document addresses
the treatment of hazardous wastes for disposal or long-term storage and
surveys the current state and effectiveness of waste-treatment technology.
This guide provides the background information needed for waste generators
and regulatory officials to determine the testing program and/or product
information necessary for them to make the best engineering judgments con-
cerning the long-term effectiveness in site-specific conditions.
The manual assumes the permit writer and/or other readers are familiar
with the latest regulations concerning the disposition and disposal of haz-
ardous and nonhazardous bulk-liquid and semisolid sludges and wastes in
secure and sanitary landfills. Some familiarity with general soil charac-
teristics, water balance, climatic conditions, and fundamentals of leachate
generation would also be helpful to the manual user.
1.2 THE TERMINOLOGY OF WASTE SOLIDIFICATION/STABILIZATION
The current interest in the technology of waste stabilization/solidifi-
cation in this country reflects recent social and political priorities
placed on environmental protection. Current terminology in the field
includes new terms and terms borrowed from other fields which are given new
and specific meanings. As a matter of necessity, the following terms are
used in this manual with the meanings as noted below. These words have not
been officially defined by EPA as have those appearing in the glossary at
the end of the manual.
"Solidification" and "stabilization" as used here both refer to treat-
ment systems which are designed to accomplish one or more of the following:
(a) improve handling and physical characteristic of the waste, (b) decrease
the surface area across which transfer or loss of contained pollutants can
occur, (c) limit the solubility of, or to detoxify, any hazardous con-
stituents contained in the wastes. Solidification implies that these re-
sults are obtained primarily, but not necessarily exclusively, via the
production of a monolithic block of treated waste with high structural
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integrity. Stabilization techniques are those which have their beneficial
action primarily by limiting the solubility or by detoxifying the waste con-
taminants even though the physical characteristics of the waste may or may
not be changed and improved. Stabilization usually involves addition of
materials that ensure the hazardous constituents are maintained in their
least soluble and/or toxic form.
The term "fixation," has fallen in and out of favor but is widely used
in the waste treatment field as generally meaning any treatment system which
solidifies and/or stabilizes the waste as just described above. This is the
restricted use of the term as it is employed in this document. Other deriva-
tives of this term such as "to fixate" (or "fixated" waste), to "fix" (or
"fixed" waste), and even "fixalated" are not used in this manual.
The term "treatment" has been legally defined by the EPA. The EPA has
taken the broadest meeting of the term including any method of modifying the
chemical, biological, and/or physical character or composition of a waste
(see Glossary). Table 1-1 lists the types of treatment processes and their
EPA identification numbers which are used in the manifest system. As seen
from the listing, treatment includes a wide array of specific techniques;
but neither solidification nor stabilization is included. Chemical fixation
(T21) is listed under chemical treatment but is not specifically defined.
The chemical fixation category is the one under which all treatment
processes discussed in this document would fall except for the encapsulation
techniques for which a separate category is listed under physical methods
(T39). Table 1-2 lists some of the attributes of commonly-available,
hazardous waste treatment processes. Note that different types of treatment
fulfill different functions on different forms and types of wastes. Many
processes in Table 1-2 result only in volume reduction or waste separation
and thus still require solidification and stabilization of the waste prior
to ultimate disposal.
"Surface encapsulation" as used here is a technique of waste treatment
involving isolation of the waste material by placing a jacket or membrane of
impermeable, chemically inert material between the waste and the environment.
Ideally the jacket is bonded to the external surface of a solidified waste.
Encapsulation of small particles is sometimes called "microencapsulation,"
but this term is used by processors to describe a wide array of different
techniques and therefore has no specific meaning.
1.3 LEGISLATIVE BACKGROUND
The Resource Conservation and Recovery Act (RCRA) of 1976 (PL 94-580)
established a national hazardous waste regulatory program. This law is the
most comprehensive attempt to date at guaranteeing the secured disposal of
materials that could represent potential threats to human health and the
environment. The Act includes provisions for developing criteria to deter-
mine which wastes are hazardous, instituting a manifest system, and estab-
lishing standards for siting, design, and operation of disposal facilities.
The Act encourages the States to conduct their own regulatory programs, but
it authorizes the U. S. Environmental Protection Agency (EPA) to administer
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TABLE 1-1. TREATMENT CODES FOR EPA HAZARDOUS WASTE MANIFESTS
EPA
Code #
Treatment
EPA
Code #
Treatment
(a) Thermal Treatment
T06 Liquid injection incinerator
T07 Rotary kiln incinerator
T08 Fluidized bed incinerator
T09 Multiple hearth incinerator
T10 Infrared furnace incinerator
Til Molten salt destructor
T12 Pyrolysis
T13 Wet air oxidation
T14 Calcination
T15 Microwave discharge
T16 Cement kiln
T17 Lime kiln
T18 Other (specify)
(b) Chemical Treatment
T19 Absorption mound
T20 Absorption field
T21 Chemical fixation
T22 Chemical oxidation
T23 Chemical precipitation
T24 Chemical reduction
T25 Chlorination (d)
T26 Chlorinolysis
T27 Cyanide destruction
T28 Degradation
T29 Detoxification
T30 Ion exchange
T31 Neutralization
T32 Ozonation
T33 Photolysis
T34 Other (specify)
(c) Physical Treatment
(1) Separation of components
T35 Centrifugation
T36 Clarification
T37 Coagulation
T38 Decanting
T39 Encapsulation
T40 Filtration
T41 Flocculation
T42 Flotation
T43 Foaming
T44 Sedimentation
T45 Thickening
T46 Ultrafiltration
T47 Other (specify)
(2) Removal of Specific Components
T48 Absorption-molecular sieve
T49 Activated carbon
T50 Blending
T51 Catalysis
T52 Crystallization
T53 Dialysis
T54 Distillation
T55 Electrodialysis
T56 Electrolysis
T57 Evaporation
T58 High gradient magnetic
separation
T59 Leaching
T60 Liquid ion exchange
T61 Liquid-liquid extraction
T62 Reverse osmosis
T63 Solvent recovery
T64 Stripping
T65 Sand filter
T66 Other (specify)
Biological Treatment
T67 Activated sludge
T68 Aerobic lagoon
T69 Aerobic tank
T70 Anaerobic lagoon
T71 Composting
T72 Septic tank
T73 Spray irrigation
T74 Thickening filter
T75 Trickling filter
T76 Waste stabilization pond
T77 Other (specify)
T78-79 (Reserved)
NOTE: Taken from reference 1-1.
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the program until suitable State programs are established. Should a State
choose not to develop a hazardous waste program or not to gain approval and
authorization for a program, EPA must administer the program in its stead.
Regulations have now been promulgated under the RCRA that direct the
generation, handling, treatment, and safe disposal of hazardous and nonhaz-
ardous wastes. Legal definitions of what is hazardous and of what consti-
tutes safe disposal have been developed (1-1).
The RCRA augments and overlaps in some areas the authority delegated
to the agency in other legislation. Previous legislation had addressed the
problem of hazardous waste disposal indirectly by regulating the effects of
waste disposal on surrounding air and water quality.
The Federal Water Pollution Control Act, as amended in 1972
(PL 92-500), and the Clean Water Act of 1977 (PL 95-217) direct the estab-
lishment of an effluent permit plan for municipalities and industries, but,
then do not specifically regulate discharges from solid or hazardous waste
disposal activities. However, in regional water quality planning (Sec-
tion 208 of the PL 92-500), any plan prepared must include a process to
control the dispersal of pollutants on land and in subsurface excavations to
protect the ground and surface waters. Technically, waste disposal would be
controlled indirectly by enforcing a regional plan to insure ground and
surface water quality.
Under the Safe Drinking Water Act of 1974 (PL 93-523), the EPA Adminis-
trator is charged in Section 1442 with controlling subsurface emplacement of
waste. The broad goal of this section is to discover and control potential
threats to the quality of groundwater. This Act is the basis for regula-
tions on the subsurface injection of liquid waste and for surface impound-
ments. An impoundment is defined as a natural depression, artificial
excavation, or diked enclosure used for storage, treatment, or disposal of
wastes in the form of liquids, semisolids, or solids. In its broadest inter-
pretation, the Safe Drinking Water Act overlaps and reinforces the RCRA.
The Toxic Substances Control Act of 1976 (PL 94-469) established as
national policy that data should be developed on the effects of the manufac-
ture, use, and disposal of chemical substances on health and the environment.
The EPA administrator is empowered to prohibit or otherwise regulate any
manner or method of disposal of a toxic substance by its manufacturer or by
any person who uses or disposes of a toxic chemical in a commercial opera-
tion. This provision includes all disposal of toxic substances on the land
or in landfills or impoundments. The administrator is authorized to take
action against persons disposing of a toxic chemical in any manner posing an
unreasonable risk to health and the environment.
The Occupational Safety and Health Act of 1970 specified the maximum
permissible exposure limits for volatile, hazardous chemicals in the work
place. Criteria established under this legislation have been adopted for
the disposal of hazardous industrial chemicals that pose a risk for airborne
contamination. Under the RCRA and related legislation, the EPA is now
responsible for all phases of hazardous waste disposal.
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Solidification/stabilization options are treated indirectly in these
regulations. For example, rules for landfilling waste (1-1) state that
"liquids be modified and/or treated to a non-flowing consistency prior to
landfilling or in situ." No solidification requirement beyond this is for-
mally required. Stabilization or chemical binding to prevent loss of toxic
constituents, is mentioned in a relation to the effect to be obtained, not
as a specific system to be required. The rules state treatment renders the
waste "...nonhazardous, safer to transport,..." No specific treatment
systems are indicated (1-1). The performance in hazard reduction is the
important factor in selecting or requesting stabilization of toxic wastes.
This approach encourages inventiveness and allows for flexibility in dis-
posal systems (1-2).
1.4 CHARACTERISTICS OF WASTES FOR WHICH STABILIZATION/SOLIDIFICATION ARE
EFFECTIVE AND ECONOMICAL
Not all wastes justify treatment. The practical and economic decision
concerning which wastes should or should not be submitted to expensive treat-
ment systems is based upon an overall consideration of the amount, composi-
tion, physical properties, location, and disposal problems associated with
the specific waste. Also of importance is the proven effectiveness and the
costs associated with the commercially available treatment systems which are
applicable to the specific wastes in question. Wastes which are designated
as hazardous by the EPA and are produced in large amounts, are those most
commonly considered for solidification and/or stabilization. Thus, the
treatment of high volume hazardous waste forms the bulk of the discussion in
this manual.
Some types of legally non-hazardous wastes also benefit from treatment
processes which would render the waste more easily handled or less likely to
lose undesirable constituents to the local groundwater. For instance, flue
gas cleaning sludges, although specifically exempted as nonhazardous solid
waste by EPA (1-1), have been the subject of a number of solidifications/
stabilization studies since their run-off water and leachates are typically
high in calcium (600-800 ppm) and sulfate (1200-1500 ppm) and represent a
significant threat to the local groundwater even if no heavy metals are
present (1-3). Other wastes, whose disposal might benefit from treatment
are: mining overburden returned to the mining site; fly ash, bottom ash,
and slag wastes; flue gas emission control wastes generated from the burning
of fossil fuels; and oil, gas, or geothermal drilling fluids. These and
other wastes have been specifically listed as solid wastes which are non-
hazardous.
Organic wastes are less amenable to currently available treatment tech-
nology than are inorganic wastes. This generalization holds for a wide
variety of organic compounds with a diverse array of properties which occur
in common wastes streams. Wastes with greater than 10 to 20 percent organic
constituents are not generally recommended for treatment by current,
commercial fixation techniques as the organics interfere with the physical
and chemical processes which are important in binding the waste materials
together (1-4). Some processors who handle large volumes of inorganic
-------
wastes will accept relatively small volumes of selected organic wastes which
are mixed to a low concentration in the inorganic waste treatment stream.
Organic wastes lend themselves to destructive treatment by processes
such as incineration, UV-ozone or biological systems. Such treatments prop-
erly employed produce innocous products (mainly CO and water) which after
scrubbing can be vented directly to the atmosphere. Since the hazardous
organic-waste components are destroyed, all of the problems associated with
ultimate disposal such as leachate or vapor losses, land use and reclamation,
and long-term manifest or record keeping are eliminated. Even for wastes
containing only moderate to small amounts of organics, the organic fraction
is often best first separated by solvent extraction or distillation so that
it can be disposed of separately. The volume of ash and/or flue gas
scrubber sludge left after destructive treatment will vary widely with the
type of organic material being treated, but will almost always be a small
fraction of the original organic waste.
In summary, the wastes most effectively stabilized/solidified consist
mainly of inorganic materials in aqueous solution or suspension which con-
tain appreciable amounts of toxic heavy metals and/or inorganic salts. It
is also towards these waste types that most stabilization/solidification
techniques are directed.
1.5 DELISTING TREATED HAZARDOUS WASTE PRODUCTS
Hazardous wastes which have undergone any treatment processes are still
considered hazardous unless an exemption has been petitioned for, and
granted, by the EPA for the specific waste in question. The process of
removing a particular waste from the hazardous waste category (called "de-
listing") is considered by EPA as a modification of the original listing
determination and is, therefore, treated as an amendment to the lists of
hazardous waste.
To be successful, the petitioner must demonstrate that the waste pro-
duced by a particular process or treatment facility does not meet any of the
criteria under which the waste which was listed as a hazardous waste. If
the treated waste is a mixture of solid waste, and if one or more of the
wastes is listed as hazardous (or is derived from one or more hazardous
wastes), the demonstration of non-hazardous character may be made with
respect to each constituent listed as a hazardous waste, or the waste mix-
ture as a whole. If the waste is listed as hazardous because it exhibits
one of the characteristics of hazardous wastes (ignitability, corrosivity,
reactivity, or extractant procedure toxicity), then the petitioner must show
that demonstration samples of the treated waste products do not exhibit that
characteristic. The applicable testing procedures must be employed.
If any of the hazardous wastes present in the treated wastes are listed
because they are made up of, or contained, toxic components then the peti-
tioner must demonstrate that the treated waste no longer contains the toxic
component, or if still present, that the toxic component is not capable of
posing a substantial present or potential threat to human health or the
-------
environment. If the waste was listed because it contains an "acute hazardous
waste," in addition to demonstrating lack of toxicity, the waste must be
shown to be non-fatal to humans in low doses or, if human data is not avail-
able, to not be fatal to other mammals at doses higher than those prescribed.
Thus delisting of solidified/stabilized waste is possible upon the
demonstration to EPA's satisfaction that the component or characteristic for
which the waste was listed is no longer present or applicable to the treated
product. This determination of the non-hazardous character of the waste
product makes possible the much cheaper and less rigorous disposal of the
wastes in any solid waste landfill. The use of the waste in any productive
way (such as foundation, fill, or construction materials) must be preceded
by the delisting of the product as a hazardous waste. It is unlikely that a
whole waste-stream can be permanently delisted, or that a particular waste
fixation process can be certified as producing a non-hazardous product irre-
gardless of changes in the process parameters or in the wastes being treated.
-------
REFERENCES
1-1. U. S. Environmental Protection Agency. Hazardous Wastes Management
System. Federal Register, 45(98):33063-33285, May 19, 1980.
1-2. Wright, A. P. and H. A. Coates. Legislative Initiatives for
Stabilization/Solidification of Hazardous Wastes. In: Toxic and
Hazardous Waste Disposal, Vol. 2, R. B. Pojasek, ed. Ann Arbor
Science Publ. Inc., Ann Arbor, MI, 1978. pp. 1-15.
1-3. Duvel, W. A. and others. State-of-the-Art of FGD Sludge Fixation.
EPRI FP-671. Electric Power Research Institute, Palo Alto, California,
1978. 268 pp.
1-4. Malone, P. G. and L. W. Jones. Survey of Solidification/Stabilization
Technology for Hazardous Industrial Wastes. EPA 600/2-79-056. U. S.
Environmental Protection Agency, Municipal Environmental Research
Laboratory, Cincinnati, Ohio, 1979. 41 pp.
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SECTION 2
WASTE STABILIZATION/SOLIDIFICATION TECHNOLOGY
2.1 CURRENT STABILIZATION/SOLIDIFICATION TECHNOLOGY
Several stabilization/solidification methods now available or under de-
velopment have as their goal the safe ultimate disposal of hazardous waste
either via a productive way or by landfilling. Ultimate disposal implies
the final disposition of persistent, nondegradable, cumulative, and/or harm-
ful waste. The four primary goals of treating hazardous waste for ultimate
disposal are: (a) to improve the handling and physical characteristics of
the waste, (b) to decrease the surface area across which transfer or loss of
contained pollutants can occur, (c) to limit the solubility of any pollu-
tants contained in the waste, and (d) to detoxify contained pollutants.
These goals can be met in a variety of ways, but not all techniques attempt
to meet all the goals. Thus individual treatment techniques may solve one
particular set of problems but be completely unsatisfactory for others.
Process selection becomes weighing advantages and disadvantages for the
particular situation.
The following major categories of industrial waste fixation systems are
discussed in this section:
a. Cement-based processes
b. Pozzolanic processes (not including cement)
c. Thermoplastic techniques (including bitumen, paraffin, and poly-
ethylene incorporation)
d. Organic polymer techniques (including urea-formaldehyde, unsaturated
polyester)
e. Surface encapsulation techniques (jacketing)
f. Self-cementing techniques (for high calcium sulfate sludges)
g. Classification and production of synthetic minerals or ceramics
Examples of treated waste materials are shown in Figure 2-1. Since these
waste treatment systems vary widely in their applicability, cost, and pre-
treatment requirements, many are limited as to the types of waste that can
be economically processed. Selection of any particular technique for waste
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treatment must include careful consideration of the containment required,
the cost of processing, the increase in bulk of material, and the changes in
the handling characteristics. The design and location of any placement area
or landfill that eventually receives the treated waste is also a major con-
sideration in deciding on the degree of containment and the physical prop-
erties that will be required.
2.2 CEMENT-BASED PROCESSES
Common (portland) cement is produced by firing a charge of limestone
and clay or other silicate mixtures at high temperatures. The resulting
clinker is ground to a fine powder to produce a cement that consists of
about 50% tricalcium and 25% dicalcium silicates (also present are about 10%
tricalcium aluminate and 10% calcium aluminoferrite). The cementation pro-
cess is brought about by the addition of water to the anhydrous cement
powder. This first produces a colloidal calcium-silicate-hydrate gel of in-
definite composition and structure. Hardening of the cement is a lengthy
process brought about by the interlacing of thin, densely-packed, silicate
fibrils growing from the individual cement particles. This fibrillar matrix
incorporates the added aggregates and/or waste into a monolithic, rock-like
mass.
Five types of Portland cements are generally recognized, based on varia-
tions in their chemical composition and physical properties (3-!).
a. Type I is the typical cement used in the building trade, and consti-
tutes over 90% of the cement manufactured in the United States.
b. Type II is designed to be used in the presence of moderate sulfate
concentrations (150 to 1500 mg/kg) or where moderate heat of hydra-
tion is required.
c. Type III has an high early strength and is used where a rapid set
is required.
d. Type IV develops a low heat of hydration and is usually prescribed
for large-mass concrete work but has long set time.
e. Type V is a special low-alumina, sulfate-resistant cement used with
high sulfate concentrations (>1500 mg/kg).
The types that have been used for waste solidification are Type I and, to a
smaller extent, Types II and V.
Most hazardous waste slurried in water can be mixed directly with
cement, and the suspended solids will be incorporated into the rigid ma-
trices of the hardened concrete. This process is especially effective for
waste with high levels of toxic metals, since at the pH of the cement mix-
ture, most multivalent cations are converted into insoluble hydroxides or
carbonates. Metal ions may also be incorporated into the crystal structure
of the cement minerals that form. Materials in the waste such as sulfides,
12
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asbestos, latex, and solid plastic wastes may actually increase the strength
and stability of the waste concrete.
Interfering Compounds—
The presence of certain inorganic compounds in the hazardous waste and
the mixing water can be deleterious to the setting and curing of the waste-
containing concrete (2-1). Also, impurities such as organic materials, silt,
clay, or lignite may delay the setting and curing of common portland cement
for as long as several days. fiAll insoluble materials passing through a
No. 200 mesh sieve ( 74 x 10 m particle size) are undesirable, as they may
be present as dust or may coat the larger particles and weaken the bond
between the particles and the cement. Soluble salts of manganese, tin, zinc,
copper, and lead may cause large variations in setting time and significant
reduction in physical strength. Salts of zinc, copper, and lead are the
most detrimental. Other compounds that are especially active as setting
retarders in portland cement include sodium salts of arsenate, borate, phos-
phate, iodate, and sulfide—ev^n at concentrations as low as a few tenths of
a percent of the weight of the cement used. Products containing large
amounts of sulfate (such as flue gas cleaning sludges) not only retard the
setting of concrete, but by reacting to form calcium sulfoaluminate hydrate,
they cause swelling and spalling in the solidified waste-containing concrete.
To prevent this reaction, a special low-alumina (Type V) cement was devel-
oped for use in circumstances where high sulfate is encountered.
Additives—
A number of additives have been developed for use with cement to im-
prove the physical characteristics and decrease the leaching losses from the
resulting solidified sludge. Many of the additives used in waste treatment
are proprietary and cannot be discussed here. Experimental work on the
treatment of radioactive waste has shown some improvement in cement-based
fixation and retention of nuclear waste with the addition of clay or vermi-
culite as absorbents (2-2). Soluble silicate has reportedly been used to
bind contaminants in cement solidification processes, but this additive
causes an increase in volume to occur during the setting of the cement-waste
mixture. A recently proposed adaptation of this technique involves dissolv-
ing the metal-rich waste with fine-grained silica at low pH and then poly-
merizing the mixture by raising the pH to 7. The resulting contaminated gel
is mixed with cement and hardens within 3 days.
Recent testing by Brookhaven National Laboratory indicates that a mix-
ture of sodium silicate and Type II portland cement produces a rapid set
with no retardation from metallic ions (2-2). The sodium silicate appears
to precipitate most interfering ions in a gelatinous mass and so to remove
their interferences and to speed setting. Of the wastes tested, only boric
acid waste inhibited the set of the cement mixture. The development of a
gel is important in the setting of the cement-waste-silicate mixtures. Ex-
cessive mixing after the gel forms seems to cause slower setting and lessen
final strength of the product.
Polymer Impregnation—
The Brookhaven National Laboratory also developed a polymer impregnation
13
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process that can be used to decrease the permeability of concrete-waste
mixtures (2-3). The pores of the waste-concrete are filled by soaking in
styrene monomer. The soaked material is then heated to bring about polymer-
ization. This process results in a significant increase in the strength and
durability of the concrete-waste mixture.
Coatings—
Surface coating of concrete-waste composites has been examined exten-
sively. The major problems encountered have been poor adhesion of the coat-
ing onto the waste or lack of strength in the concrete material containing
the waste. Surface coating materials that have been investigated include
asphalt, asphalt emulsion, and vinyl. However, no surface coating system
for cement-solidified material is currently being advertised.
Advantages and Disavantages—
Advantages of the cement treatment systems are:
a. The amount of cement used can be varied to produce high bearing
capacities (making the waste concrete good subgrade and subfounda-
tion materials) and low permeability in the product.
b. Raw materials are plentiful and inexpensive.
c. The technology and management of cement mixing and handling is well
known, the equipment is commonplace, and specialized labor is not
required.
d. Extensive drying or dewatering of waste is not required because
cement mixtures require water, and the amount of cement added can
be adapted through wide ranges of water contents.
e. The system is tolerant of most chemical variations. The natural
alkalinity of the cement used can neutralize acids. Cement is not
affected by strong oxidizers such as nitrates or chlorates. Pre-
treatment is required only for materials that retard or interfere
with the setting action of cement.
f. Leaching characteristics can be improved where necessary by coating
the resulting product with a sealant.
Disadvantages of cement-based systems are:
a. Relatively large amounts of cement are required for most treatment
processes (but this may partly be offset by the low cost of mate-
rial) . The weight and volume of the final product is typically
about double those of other solidification processes.
b. Uncoated cement-based products may require a well-designed landfill
for burial. Experience in radioactive waste disposal indicates
that some wastes are leached from the solidified concrete, espe-
cially by mildly acidic leaching solutions.
14
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c. Extensive pretreatment, more expensive cement types or additives
may be necessary for waste containing large amounts of impurities
such as borates and sulfates that affect the setting or curing of
the waste-concrete mixture.
d. The alkalinity of cement drives off ammonium ion as ammonia gas.
e. Cement is an energy-intensive material.
2.3 POZZOLANIC PROCESSES (NOT CONTAINING CEMENT)
Waste fixation techniques based on lime products usually depend on the
reaction of lime with a fine-grained siliceous (pozzolanic) material and
water to produce a concrete-like solid (sometimes referred to as a pozzolanic
concrete). The most common pozzolanic materials used in waste treatment are
fly ash, ground blast-furnace salg, and cement-kiln dust. All of these mate-
rials are themselves waste products with little or no commercial value at
this time. The use of these waste products to consolidate another waste is
often advantageous to the processor, who can treat two waste products at the
same time. For example, the production of a pozzolanic reaction with power
plant fly ash permits the flue gas cleaning sludge to be combined with the
normal fly ash output and lime (along with other additives) to product an
easily-handled solid. Many, if not all, of the comments associated with the
cement systems apply to the pozzolanic systems including advantages and
disadvantages.
Advantages of lime-based treatment techniques that produce pozzolanic
cement are several:
a. Product is generally a solid with improved handling and permeabil-
ity characteristics.
b. The materials are often very low in cost and widely available.
c. Little specialized equipment is required for processing, as lime is
a common additive in other waste streams.
d. The chemistry of lime-pozzolanic reactions are relatively
well-known. Sulfate does not cause spalling or cracking.
e. Extensive dewatering is not necessary because water is required in
the setting reaction.
The lime-based systems have many of the same potential disadvantages as
cement-based techniques:
a. Lime and other additives add to the weight and bulk to be trans-
ported and/or landfilled.
b. Uncoated lime-treated materials may require specially designed
landfills to guarantee that the material does not lose potential
pollutants by leaching.
15
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Certain treatment systems fall in the category of cement-pozzolanic
processes and have been in use for some time outside the U. S. In this case
both cement and lime-siliceous materials are used in combination to give the
best and most economical containment for the specific waste being treated.
In general, the bulk of the comments under both classifications above hold
for techniques using a combination of treatment materials.
2.4 THERMOPLASTIC TECHNIQUES (INCLUDING
BITUMEN, PARAFFIN AND POLYETHYLENE)
The use of thermoplastic solidification systems in radioactive waste
disposal has led to the development of waste containment systems that can be
adapted to industrial waste. In processing radioactive waste with bitumen
or other thermoplastic material, the waste is dried, heated, and dispersed
through a heated plastic matrix. The mixture is then cooled to solidify the
mass, and it is usually buried in a secondary containment system such as a
steel drum. Variations of this treatment system can use thermoplastic or-
ganic materials such as paraffin or polyethylene.
The process requires some specialized equipment to heat and mix the
waste and plastic matrices, but equipment for mixing and extruding waste
plastic is available. The ratio of matrix to waste is generally quite
high—a 1:1 to 1:2 ratio of incorporation material to waste (on a dry-weight
basis). The plastic in the dry waste must be mixed at temperatures ranging
from 130° to 230°C, depending on the melting characteristics of the material
and type of equipment used.
A variation of this process uses an emulsified bitumen product that is
miscible with a wet sludge. In this process, the mixing can be done at any
convenient temperature below the boiling point of the mixture. The overall
mass must still be heated and dried before it is suitable for disposal.
Ratios of emulsions to waste of 1:1 to 1:1.5 are necessary for adequate in-
corporation (2-2).
In many cases, the types of waste rule out the use of any organic-based
treatment systems. Organic chemicals that are solvents for the matrix obvi-
ously cannot be used directly in the treatment system. Strongly oxidizing
salts such as nitrates, chlorates, or perchlorates will react with the
organic matrix materials and cause slow deterioration. At the elevated tem-
peratures necessary for processing, the matrix-oxidizer mixtures are ex-
tremely flammable.
Leach or extraction testing undertaken on anhydrous salts embedded in
bitumen as a matrix indicates that rehydration of the embedded compound can
occur when the sample is soaked in water and can cause the asphalt or bitumen
to swell and split apart, greatly increasing the surface area and rate of
waste loss (2-2). Some salts (such as sodium sulfate) will naturally dehy-
drate at the temperatures required to make the bitumen plastic; so these
easily dehydrated compounds must be avoided in thermoplastic stabilization.
The major advantages of the thermoplastic-based disposal systems are:
16
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a. The rate of loss to contacting fluids are significantly lower than
those observed with cement-based and pozzolon systems.
b. By disposing of the waste in a dry condition, the overall volume of
the waste is greatly reduced.
c. Most thermoplastic matrix materials are resistant to attack by
aqueous solutions, and microbial degradation is minimal.
d. Most matrices adhere well to incorporated materials.
e. Materials embedded in a thermoplastic matrix can be reclaimed if
needed.
The principal disadvantages of the thermoplastic-based disposal systems
are:
a. Expensive, complicated equipment requiring highly specialized labor
is necessary for processing.
b. The plasticity of the matrix-waste mixtures may require that con-
tainers be provided for transportation and disposal of the mate-
rials, which greatly increases the cost.
c. The waste materials to be incorporated must be dried, which re-
quires large amounts of energy. Incorporating wet wastes greatly
increases losses through leaching.
d. These systems cannot be used with materials that decompose at high
temperatures, especially citrates and certain types of plastics.
e. There is a risk of fire in working with organic materials such as
bitumen at elevated temperatures.
f. During heating, some mixes can release objectionable oils and odors
causing secondary air pollution.
g. The incorporation of tetraborates of iron and aluminum salts in
bitumen matrices causes premature hardening, and can clog and
damage the mixing equipment.
h. Strong oxidizers usually cannot be incorporated into organic mate-
rials without the occurrence of oxidizing reactions. High concen-
trations of strong oxidizers at elevated processing temperatures
can cause fires.
i. Dehydrated salts incorporated in the thermoplastic matrix will
slowly rehydrate if the mixture is soaked in water. The rehydrated
salt will expand the mixture causing the waste block to fragment
and increasing its surface area greatly.
17
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2.5 ORGANIC POLYMER PROCESSES
Organic polymer techniques were developed as a response to the require-
ment for solidification of waste for transportation. The most thoroughly
tested organic polymer solidification technique is the urea-formaldehyde (UF)
system. The polymer is generally formed in a batch process where the wet or
dry wastes are blended with a prepolymer in a waste receptacle (steel drum)
or in a specially-designed mixer. When these two components are thoroughly
mixed, a catalyst is added, and mixing is continued until the catalyst is
thoroughly dispersed. Mixing is terminated before the polymer has formed
and the resin-waste mixture is transferred to a waste container if necessary.
The polymerized material does not chemically combine with the waste—it
forms a spongy mass that traps the solid particles. Any liquid associated
with the waste will remain after polymerization. The polymer mass must
often be dried before disposal.
Several organic polymer systems are available that are not based on UF
resins. Dow Industrial Division is developing a vinyl ester-styrene system
(Binder 101) for use with radioactive waste (2-4). Testing of this material
is currently underway in the Nuclear Regulatory Commission Research Programs.
The Polymeric Material Section at Washington State University has de-
veloped a polyester resin system that is being used in solidification of
waste. This system is currently in a pilot-plant stage in the processing of
hazardous wastes (2-5, 2-6, 2-7).
The major advantages of the organic polymer systems (especially the
UF-resin system) are:
a. Less treatment reagent is required for solidifying the waste than
in other systems. The waste-to-reagent ratio is usually about 30%
greater for a UF organic polymer system than with cement.
b. The waste material treated is usually dewatered, but it is not
necessarily dried as in thermoplastic processes. (The finished,
solidified polymer, however, must be dried before ultimate
disposal.)
c. The organic resin used is consistently less dense (specific gravity
is approximately 1.3) than cement. The low density reduces the
transportation cost related to the reagents and to the treated
products.
d. The solidified resin is nonflammable, and high temperatures are
not required in forming the resin.
The major disadvantages of the organic resin techniques, especially
the UF resin systems are:
a. No chemical reactions occur in the solidification process that
chemically binds the potential pollutants. The particles of waste
18
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material are trapped in an organic resin matrix, and breakdown or
leaching of the matrix will release many of the waste materials.
b. Catalysts used in the UF systems are strongly acidic, and the
waste-UF mixture must be maintained at pH 1.5 ± 0.5 for solidifica-
tion to occur in a rapid manner. The low pH can put many waste
materials into solution. If the pH is not lowered to 1.5, the
polymerization is slow; solids will thus settle out, and the waste
material will not be trapped effectively.
c. Uncombined or weep water is often associated with polymerized
waste. This must be allowed to evaporate to produce a fully-cured
polymer. This weep water may be strongly acidic and may contain
high levels of pollutants. Waste-UF mixtures shrink as they age
and will produce weep water during aging.
d. Some catalysts used in polymerization are highly corrosive and re-
quire special mixing equipment and container liners.
e. The reaction producing the resin may release fumes that can be
harmful or disagreeable even in low concentrations.
f. Some cured resins, especially UF-based systems, are biodegradable
and have a high loss of chemical oxygen demand.
g. Secondary containment in steel drums is a common practice in the
use of organic resins, which increases the cost of processing and
transportation.
2.6 SURFACE ENCAPSULATION TECHNIQUES (JACKETING)
Many waste treatment systems depend on binding particles of waste mate-
rial together. To the extent to which the binder coats the waste particles,
the wastes are encapsulated. However, the systems addressed under surface
encapsulation are those in which a waste that has been pressed or bonded
together is enclosed in a coating or jacket of inert material. A number of
systems for coating solidified industrial wastes have been examined by TRW
Corporation (2-3). In most cases, coated materials have suffered from lack
of adhesion between coatings and bound wastes, and lack of long-term integ-
rity in the coating materials. After investigating many alternative binding
and coating systems, TRW Corporation produced detailed plans for what it
considered to be the optimum encapsulation system. The TRW—developed system
has been tested and published data on the processes are available (2-8).
The TRW surface encapsulation system requires that the waste material
be thoroughly dried. The dried wastes are stirred into an acetone solution
of modified 1,2-polybutadiene for 5 min. The mixture is allowed to set for
2 hr. The optimum amount of binder is 3% to 4% of the fixed material on a
dry-weight basis. The coated material is placed in a mold, subjected to
slight mechanical pressure, and heated to between 120° and 200°C (250° and
400°F) to produce fusion. The agglomerated material is a hard, tough, solid
19
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block. A polyethylene jacket 3.5 mm (1/4 in.) thick is fused over the solid
block and adheres to the polybutadiene binder. In a 360- to 450-kg (800- to
1000-lb) block, the polyethylene would amount to 4% of the fused waste on a
weight basis (see Fig. 2-2).
The major advantages of an encapsulation process are:
a. The waste material never comes into contact with water, therefore,
soluble materials such as sodium chloride can be successfully sur-
face encapsulated.
b. The impervious jacket eliminates all leaching into contacting waters
as long as the jacket remains intact.
The major disadvantages of encapsulation are:
a. The resins required for encapsulating are expensive.
b. The process requires large expenditures of energy in drying, fusing
the binder, and forming the jacket.
c. Polyethylene is combustible, with a flash point of 350°C, making
fires a potential hazard.
d. The system requires extensive capital investment and equipment.
e. Skilled labor is required to operate the molding and fusing
equipment.
2.7 SELF-CEMENTING PROCESSES
Some industrial wastes such as flue-gas cleaning or desulfurization
sludges contain large amounts of calcium sulfate and calcium sulfite. A
technology has been developed to treat these types of wastes so that they
become self-cementing (2-9). Usually a small portion (8% to 10% by weight)
of the dewatered waste sulfate/sulfite sludge is calcined under carefully
controlled conditions to produce a partially dehydrated cementitious calcium
sulfate or sulfite. This calcined waste is then reintroduced into the bulk
of the waste sludge along with other proprietary additives. Fly ash is
often added to adjust the moisture content. The finished product is a hard,
plaster-like material with good handling characteristics and low permeabil-
ity. The major advantages of self-cementing systems are:
a. The material produced is stable, nonflammable, and
nonbiodegradable.
b. There are reports of effective heavy metal retention, which is
perhaps related to chemical bonding of potential pollutants.
c. No major additives have to be manufactured and shipped to the
processing site.
20
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d. The process is reported to produce faster setting time and more
rapid curing than comparable lime-based systems.
e. These systems do not require completely dry waste. The hydration
reaction uses up water.
The major disadvantages of self-cementing systems are:
a. Self-cemented sludges have much the same leaching characteristics
as cement and lime-based systems.
b. Only high calcium sulfate or sulfite sludges can be used.
c. Additional energy is required to produce the calcined cementitious
material.
d. The process requires skilled labor and expensive machinery in cal-
cining wastes and mixing the calcined wastes back to the bulk of
the waste with proprietary additives.
2.8 CLASSIFICATION AND PRODUCTION OF SYNTHETIC MINERALS OR CERAMICS
Where material is extremely dangerous or radioactive, it is possible
to combine the waste with silica and either fuse the mixture in glass or to
form a synthetic silicate mineral (2-10, 2-11). Glasses or crystalline
silicates are only very slowly leached by naturally occurring waters, so
these waste products are generally considered to be safe materials for dis-
posal without secondary containment. No work using glassification of
industrial wastes are now going on.
The major advantages of glassification or mineral synthesis are:
a. The process is assumed to produce a high degree of containment of
wastes.
b. The additives used can be relatively inexpensive (syenite and
lime).
The major disadvantages of these processes are:
a. Some constituents (especially metals) may be vaporized and lost
before they can bind with the molten silica if high-temperature
processes are used.
b. The process is energy-intensive. The waste-silicate charge must
be heated (often up to 1350°C) for melting and fusion.
c. Socialized equipment and trained personnel are required for this
type of operation.
22
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2.9 SUMMARY
A wide variety of possible techniques exist for waste treatment.
Obviously, no system is applicable to every waste in all situations. The
amount and character of the material to be stabilized, the economics in-
volved and the properties of the disposal site (see Section 7) are all
important factors in deciding which treatment procedures are best for any
given situation. By careful evaluation of economics, the hazardous nature
of the material, and the containment provided by geologic and hydrologic
situations at nerby landfills, it should be possible to establish a minimum
cost for responsible disposal of a particular waste. A list of companies
marketing stabilization/solidification technology in the United States is
given in Appendix B.
The cost for waste treatment processes depends on the volume of the
waste to be fixed. Therefore, it may become cost-advantageous to concentrate
hazardous wastes into a minimum volume to reduce handling and additive re-
quirements. When hazardous wastes are concentrated, the precautions involved
in handling and transportation are necessarily increased, so onsite stabili-
zation or solidification is desirable. In fact, stabilization/solidification
may become a unit operation to complete a waste treatment system. The waste
treatment operations could be tailored to produce the hazardous residue in a
minimum volume with a pH and chemical composition compatible with the treat-
ment system that is required to insure safe containment under specific land-
fill conditions.
23
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REFERENCES
2-1. Popovics, Sandor. Concrete-Making Materials. McGraw-Hill, New York,
N. Y., 1979. 370 pp.
2-2. Columbo, P. and R. M. Neilson, Jr. Properties of Radioactive Wastes
and Waste Containers. Progress Report No. 7, BNL-NUREG 50837, Brook-
haven National Laboratory, Upton, N. Y., 1978. 61 pp.
2-3. Burk, M. R., R. Denham, and H. Lubowitz. Recommended Methods of Re-
duction, Neutralization, Recovery or Disposal of Hazardous Wastes.
Vol. 1Y TRW Systems Group, Inc., Redondo Beach, Calif. June 1974.
89 pp.
2-4. Columbo, P. and R. M. Neilson, Jr. Properties of Radioactive Wastes
and Waste Containers. Progress Report No. 5, BNL-NUREG 50763, Brook-
haven National Laboratory, Upton, N. Y., 1977. 32 pp.
2-5. Mahalingam, R., M. Juloori, R. V. Subramanian, and Wen-Pao Wu. Pilot
Plant Studies on the Polyester Encapsulation Process for Hazardous
Wastes. In: Proceedings of the National Conference on Treatment and
Disposal of Industrial Wastewaters and Residues, Houston, Texas, 1977,
107 pp.
2-6. Subramanian, R. V., Wen-Pao Wu, R. Mahalingam and M. Juloori. Poly-
ester Encapsulation of Hazardous Industrial Wastes. In: Proceedings
of the National Conference on Treatment and Disposal of Industrial
Wastewaters and Residues, Houston, Texas, 1977. 107 pp.
2-7. Subramanian, R. V. and R. Mahalingam. Immobilization of Hazardous
Residuals by Polyester Encapsulation. pp 247-269 In: R. B. Pojasek,
ed. Toxic and Hazardous Waste Disposal, Vol. 1. Ann Arbor Science
Publishers, Inc., Ann Arbor, Mich., 1979. 407 pp.
2-8. Lubowitz, H. R., R. L. Denham and G. A. Zakrzewski. Development of
a Polymetric Cementing and Encapsulating Process for Managing Haz-
ardous Wastes. EPA-600/2-77-045, U. S. Environmental Protection
Agency, Cincinnati, Ohio, 1977. 167 pp.
2-9. Valiga, R. The SFT Terra-Crete Process, pp. 155-166, In: R. B.
Pojasek, ed. Toxic and Hazardous Waste Disposal, Vol. 1. Ann
Arbor, Mich., 1979. 407 pp.
24
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2-10. Gilmore, W. R. (ed). Radioactive Waste Disposal, Low and High
Level. Noyes Data Corp., Park Ridge, N. J., 1977. 363 pp.
2-11. Kerr, R. A. Nuclear Waste Disposal: Alternatives to Solidification
in Glass Proposed. Science 204:289-291, 1979.
25
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SECTION 3
PROPERTIES OF STABILIZED/SOLIDIFIED WASTES
Selection of the best treatment system requires detailed knowledge of
the constituents and characteristics of the waste to be treated, the amount
of waste to be handled, and the location and environment of the waste dis-
posal site. This section deals with the characteristics that an ideal
treatment system and its product would be expected to have and the major
considerations that are involved in the selection of the best treatment sys-
tem for a specific waste stream.
3.1 CHARACTERIZING OF WASTES TO BE TREATED
The first step in selection of the best system involves a detailed
knowledge of the wastes to be treated. A complete inventory of all constit-
uents in the waste streams should be made. The source and amount of each
waste type (including the process or operation that produces it, how it is
transported, stored, and treated, and its production rate and production
schedule) should be determined. This information is necessary for selection
processes and will be required for disposal planning.
A complete knowledge of all components of all waste streams at a par-
ticular site is of great importance. Much information can be gained from
the knowledge of the process or operation by which the waste is produced.
This detailed information should include types of materials and concentra-
tions, organic constituents, solvents, etc. Where organics are present, it
is essential to know details about chemical stability, flash points, and
heating value. The inorganic components and their relative concentrations
must be determined. Toxic heavy metals, even in small concentrations, are a
major concern. The pH, buffering capacity, and water content of the waste
are of critical importance in many solid waste treatment systems.
3.2 REQUIREMENTS FOR IDEAL WASTE STABILIZATION/SOLIDIFICATION
The ideal fixation process renders the noxious constituents chemically
nonreactive and/or immobile so that no secondary containment is necessary
for safe disposal. For example, incorporation into a stable crystal lattice
effectively isolates noxious materials from any environmental interactions,
and maintaining the pH in the range of 9 to 11 immobilizes most multivalent
cations as insoluble hydroxides and other compounds. Sludges with high
concentrations of particular cations can be treated with additives chosen
specifically to immobilize these contaminants. Anions, although typically
much less toxic, are much more difficult to bind into an unleachable product,
Chlorides and sulfates, the most common anionic sludge components, produce
26
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only a few insoluble salts. To contain anions such as these the waste must
be physically isolated from any leaching medium by secondary containment or
special landfill covers.
To be completely effective, the waste treatment must produce a final
mixture whose physical properties are such that its disposal does not perma-
nently render the land unsuitable for alternative uses such as building
sites or agriculture. However, the production of treated wastes with "soil-
like" character that might be suitable for agricultural use seems unlikely
in cases where the major contaminants are toxic metals, certain organics,
and/or high levels of salt. The long-term action of organic acids normally
produced by the biological activity in agricultural soils would be expected
to mobilize even the most tightly bound contaminant eventually. Such mobi-
lized constituents would then be taken into the food chain or washed into
the groundwater. The most secure final form of treated waste appears to be
monolithic mass that has good dimensional stability, freeze-thaw resistance,
low permeability, a high bearing capacity, and resistance to attack by
biological agents. An end product such as this could be used as a founda-
tion for buildings or roads, or simply buried and covered over in a landfill.
The ideal treatment process does not require extensive heat treatment
or large amounts of energy-intensive reactants. Also, the waste material
should be reclaimable by some reasonable technique, since some of the sludge
contaminants (e.g., manganese and chromium) are predicted to be in critical
supply in the future.
These are rather stringent requirements for any waste treatment pro-
cess. A great deal of study by private industry and government is going
into the development of better treatment procedures. However, with current
technology and with complete knowledge of the waste to be treated and the
treatment processes available, the production of finished products that will
approximate the ideal stabilized material is possible.
3.3 COMPATIBILITY OF WASTES AND TREATMENT ADDITIVES
As in any hazardous waste handling operation, care must be taken
during stabilization/solidification to avoid mixing together materials that
can react with one another in a detrimental way. In waste treatment, this
requirement of nonreactivity must also apply to the reagents or materials
used in treatment. Potential detrimental consequences of mixing wastes
include:
a. Heat generation.
b. Release of toxic materials or flammable gases.
c. Fire or explosion.
Table 3-1 summarizes some typical reactions that could occur during hazard-
ous waste treatment and handling.
27
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Many treatment systems require the mixing of reactive waste and/or
reagents of many kinds to produce a more stable or nonreactive product.
This process requires great expertise and knowledge of the precise nature
and composition of the waste and of the waste reagents. Such mixing is
typically carried out in treatment systems which accept diverse types of
waste from diverse sources.
In addition to waste incompatibility problems, it is also necessary to
note incompatibility of waste and stabilization/solidification materials
over both long and short time periods. Though many reactions between waste
materials and treatment reagents occur very slowly, the result may be accel-
erated deterioration of the treated waste and loss of containment proper-
ties. Table 3-2 summarizes major incompatibility problems that can be
encountered with various waste solidification/stabilization techniques.
Most of the difficulties are similar to those found in any hazardous waste
handling operation. For example, without great care and knowledge, oxi-
dizers and easily oxidized materials should not be mixed; strong acids, and
strong bases should not be combined; cyanides and sulfides should not be
acidified; and organic solvents must be isolated from soluble materials they
attack or dissolve.
Some solidifying reagents may never set or harden if the wastes con-
tain inhibiting materials. Silicate polymer reactions can be slowed by
organics or high concentrations of certain metals. Organic polymers can be
broken down by solvents, strong oxidizers, or strong acids (Table 3-3).
Organic polymers are also degraded by ultraviolet radiation (exposure to
sunlight).
Care must be taken in all systems requiring the mixing of hazardous
wastes with other waste materials or with reagents required for solidifica-
tion or stabilization. In general, the silicate-based (cement or pozzolan)
containment systems are most tolerant to a wide variety of wastes, both
inorganic and organic.
3.4 TESTING THE PHYSICAL PROPERTIES OF STABILIZED WASTES
The physical properties of the waste are modified by the stabilization/
solidification process. The end product of many treatment processes is a
solid block resembling low-strength concrete, which can be subjected to
standard tests of physical properties so that its durability under field
conditions can be predicted (3-1). Some processes produce a friable or
soil-like product that must be subjected to tests more typically used for
soil-cement (3-2). Prediction of chemical containment characteristics of
these stabilized wastes from physical properties is much more difficult than
prediction of long-term physical characteristics.
The primary aims of physical testing of treated and untreated wastes
are to (1) determine particle size distribution, porosity, permeability and
wet and dry densities, (2) evaluate their bulk properties, (3) predict the
reaction of a material to applied stress in embankments, landfills, etc.,
and (4) evaluate durability. A variety of physical properties tests are
30
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TABLE 3-3. LONG-TERM CHEMICAL RESISTANCE OF ORGANIC POLYMERS (RESINS)
USED IN SOLIDIFICATION*
Chemical
Acetic acid 50%
Benzene
Butadiene
Carbon tetrachloride
Chloroform
Chromic Acid
Cresol
Dichlorobenzene
Diethyl ether
Gasoline
Metallic salt sol.
Sulfuric acid (cone.)
Trichloroethane
Conventional
polyethylene
Excellent
Poor
Not resistant
Poor
Poor
Excellent
Poor
Poor
Not resistant
Poor
Excellent
Moderate
Not resistant
Resistance of resins
Linear
(high density)
polyethylene
Excellent
Moderate
Not resistant
Moderate
Moderate
Excellent
Poor
Poor
Not resistant
Moderate
Excellent
Moderate
Not resistant
Polyvinyl
chloride
Moderate
Not resistant
Not resistant
Moderate
Not resistant
Excellent
Poor
Not resistant
Not resistant
Poor
Excellent
Not resistant
Not resistant
* Adapted from information given by Nalge Chemical Company.
32
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TABLE 3-4. STANDARD TESTS OF PHYSICAL PROPERTIES
Test
Source
Bulk and dry unit weight
Unconfined compressive strength
Permeability
Wet/dry durability
Freeze/thaw durability
Appendix II of EM 1110-2-1906*
Appendix XI of EM 1110-2-1906 and
ASTM Method D2166-66**
Appendix VII of EM 1110-2-1906
ASTM Method D559-57
ASTM Method D560-57
* See Reference 3-3.
** See Reference 3-4.
applicable to treated and untreated wastes. Five standardized tests that
have been used in the past and for which some data are available are dis-
cussed briefly. A complete description of these testing procedures can be
found in the sources listed in Table 3-4.
3.4.1 Bulk and Dry Unit Weight
The bulk unit weight is the weight (solids plus water) per unit of
total volume of material mass, irrespective of the water content (see
Table 3-4). The dry unit weight is the ratio of the oven-dried weight to
the total volume. The volume of the sample tested is usually computed from
measurements of a regularly shaped mass produced by molding or trimming.
The drying temperature used to obtain the dry weight of the material should
be specified. Unit weights provide information for weight-volume relation-
ships and are used to compute earth pressure or over-dirt pressure in con-
struction. They are a measure of density and, indirectly, of void volume.
3.4.2 Unconfined Compressive Strength
The unconfined compressive strength is defined as the maximum unit
axial compressive stress at failure or at 15% strain, whichever occurs
first (see Table 3-4). The unconfined compressive strength test is appli-
cable only to cohesive or cemented material. To determine compressive
strength, a cylindrical specimen is prepared and loaded axially. The re-
sults are usually presented as a graph of compressive stress sustained by
the sample versus strain. The shear strength of a cohesive material is
obtained by multiplying the unconfined compressive strength by 0.5. Shear
strength is an important factor in determining ultimate bearing capacity of
the treated waste, stability of the embankments formed from solidified
wastes, and pressure against retaining walls surrounding waste materials.
Figure 3-1 shows testing of jacketed materials.
33
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Figure 3-1. Compression testing of
plastic-jacketed wastes.
34
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3.4.3 Permeability
Permeability can be defined as the ability of a material to conduct or
discharge water when placed in a hydraulic gradient (3-3). The permeability
of a material depends on various parameters, including density, degree of
saturation, and particle size distribution. Previous work has indicated
that two types of tests are needed for determining permeability of treated
and untreated sludges (3-2). A falling head permeability test can be used
on raw sludges, and fixed sludges can be tested using a modified constant
head test in a triaxial compression chamber with back pressure used to
ensure complete saturation. A complete description of the two tests can be
found in the USAE Soil Testing Manual (3-3). The permeability of a material
indicates the ability of the material to permit or prohibit the passage of
water. Permeability is an important factor in waste disposal because it
influences the rate at which contaminants in the waste may be released to
the environment.
3.4.4 Wet/Dry Durability
The wet/dry durability test is used to evaluate the resistance of soil-
cement mixtures to the natural weathering stress of wetting and drying. In
the test procedure (see Table 3-4), cured specimens are subjected to 12 test
cycles, each consisting of 5 hr of submergence in water and 42 hr of low-
temperature oven drying. Each cycle is followed by two firm strokes on all
surface areas with a wire scratch brush. Test results are generally ex-
pressed as weight loss after 12 wet-dry cycles or the number of cycles that
cause sample disintegration, whichever occurs first. Specimens that fail
this type of test cannot be expected to have good long-term containment prop-
erties for those processes that depend upon isolating the waste. Figure 3-2
shows typical solidification test specimens after 4 wet-dry test cycles.
3.4.5 Freeze/Thaw Durability
The freeze/thaw durability test is used to evaluate the resistance of
soil-cement mixtures to the natural weathering stress of freezing and thaw-
ing. In the test (see Table 3-4), cured specimens are subjected to 12 test
cycles, each consisting of freezing for 24 hr, thawing for 23 hr, and two
firm strokes with a wire scratch brush on all surface areas. Performance is
evaluated by determining the weight loss after 12 cycles or the number of
cycles that cause disintegration, whichever occurs first. Specimens that
lack freeze/thaw durability must be protected from frost if containment is
to succeed for those processes that depend upon isolating the waste or
lessening its surface area.
3.4.6 Summary
Some typical results of physical testing of stabilized and untreated
industrial waste are listed in Table 3-5. The data show that stabilization
processes generally increase density and strength, and decrease permeabil-
ity. Note that many of the treated sampes lack durability. The most strik-
ing feature of these results is the treatment processes do not produce
35
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products with similar physical properties. The lime-based pozzolan products
are similar to low-strength concrete with high bulk and dry unit weights,
relatively high compressive strengths, and low permeability. The cement-
based, concrete-like product also has these same properties. The soil-like
product on the other hand had little increased strength and had increased
permeability. Strength and impermeability would be of value if isolation of
the waste constituents in a strong, monolithic block of material was the
intent of the treatment process. Dense, impervious products would be ex-
pected to lose little pollutant to the environment because of the decreased
surface area of waste that is exposed to the leaching medium. The solidi-
fied blocks must be nearly impermeable to produce effective containment,
because even small volumes of water moving through the waste will carry off
appreciable amounts of contaminants. A large difference between bulk unit
weight and dry unit weight is indicative of a large amount of pore space
(void space), which allows for a high permeability and/or relatively rapid
diffusion of materials from within the solidified waste. Plastic encapsula-
tion (see electroplating waste in Table 3-5) yields the optimum result of
producing an impermeable material. The plastic coating over the waste com-
pletely blocks water passage in or out of the waste so that the bulk and dry
unit weights are identical, and the permeability is unmeasurably low (i.e.,
the block is impervious). Very little diffusion of material or flow in or
out of this product is possible as long as the jacket remains intact.
The process using patented additives to produce a soil-like material
attempts to stabilize the waste constituents using a different procedure.
Basically the process adjusts the pH to a preselected range and then adds an
ingredient (sodium silicate) that tightly binds the inorganic constituents
of the waste so that they will be held in the treated waste matrix. The end
result is a soil-like waste mixture that has a high differential between
bulk and dry unit weights (large amount of pore space), low strength, and
relatively high permeability. This system depends on precipitation and
adsorption phenomena to produce containment.
Preliminary results indicate that either treatment system, physical
isolation or chemical immobilization, can be effective for specific waste
contaminants. Physical properties alone are not effective in predicting the
ability of any treatment process to contain a particular waste type. De-
tailed knowledge of the method of containment of a particular treatment
process and of the waste to be treated is necessary before the physical
properties have any predictive value.
3.4.7 Other Tests of Physical Properties
Other physical tests may be appropriate for determining the suitability
of treatment processes for wastes with different or unusual properties or
for specialized applications of the final treated waste product.
Soil Tests—
Additional soil analyses that might prove useful with treated wastes
under special circumstances include tests for compaction, Atterberg limit,
triaxial compression, and bearing capacity. Compaction tests are used to
38
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determine the maximum unit weight or minimum void ratio that can be obtained
for a soil-like material. The density of this material has a maximum at the
optimum water content. A compaction test is generally conducted on soils or
treated wastes to determine suitability for use in a landfill where struc-
tures are to be placed on the site.
Atterberg limit tests are used to determine the water content at the
boundaries between liquid and plastic states. The tests are applicable only
to fine-grained cohesive materials. The water contents are used to estimate
properties such as compressibility, strength and swelling characteristics,
which provide an indication of how the material will react when stressed.
Triaxial compression tests are used to determine the shear strength of
soil-like materials under controlled drainage conditions. The shear strength
provides an indication of the bearing capacity of the material and the sta-
bility of embankments constructed of the material. Bearing tests are com-
monly used to evaluate subgrades for pavements. These tests provide
structural settling data with regard to applied load for the material being
tested. Since some waste samples that appear stable or solid may liquefy if
vibrated, strength determinations should include a vibrated series of
specimens.
One area of soils testing that has been generally ignored but that has
application for landfilling of treated sludge or waste is trafficability
testing. Disposal of stabilized waste in any large quantities requires the
use of tracked and wheeled vehicles to move and place the material. It is
important to know what type of vehicle can be used on the material and what,
if any, curing time is required before a vehicle can cross it. This infor-
mation can be obtained by performing cone penetration tests along with other
soil tests already discussed. Most earthmoving equipment companies can
provide the information needed on their particular equipment to complete
trafficability evaluations.
Concrete Tests—
Of the additional concrete tests that are applicable to soil-cement
mixtures, one test in particular that might prove useful in evaluating
stabilized waste for commercial use is a strength versus curing time test.
In this test, a determination similar to the unconfined compressive strength
test is used to determine the compressive strength of the curing cement-
waste mixture. Strength tests are generally conducted each day until maxi-
mum strength is reached. Strength versus curing time tests are useful for
determining the necessary curing time needed for safe application of a load
to a material after placement.
The problem noted with regard to sulfate reaction in stabilized
sludges indicates that a swelling test of the type used with concrete might
also be appropriate. Standard swelling tests use a sulfate solution (3-5).
A simple adaptation of this test can be made by substituting distilled water
for the sulfate solution used with concrete samples. Significant changes
and dimensions and/or loss of strength and spalling indicates a failure.
39
-------
The additional testing procedures described above are useful in eval-
uating stabilized sludges that are to be used in special applications. The
additional cost of these tests cannot be justified for routine landfilling
operations.
3.5 CHEMICAL LEACH TESTING OF STABILIZED WASTES
3.5.1 General
Chemical leach testing of wastes is a technique that is used to examine
or predict the chemical stability of treated wastes when they are in contact
with aqueous solutions that might be encountered in a landfill. The proce-
dures demonstrate the degree of immobilization of contaminants produced by
the treatment process. A great number of techniques for leach testing are
available (3-6). Unfortunately, no single leach testing system can dupli-
cate the variable conditions that may be encountered by landfilled treated
wastes.
Most test procedures are conducted at temperatures (20° to 25°C) and
pressures normally occurring in the laboratory. The major variables en-
countered in comparing different leaching procedures are:
1. Nature of the leaching solution.
2. Waste-to-leaching solution ratios.
3. Number of elutions of leaching solution used.
4. The time of contact of waste and leaching solution.
5. Surface area of waste.
6. Agitation technique employed.
There is no uniform opinion as to how each of these variables should
be treated in a testing procedure (3-7).
Nature of the Leaching Solution—
Ideally, the leaching solution employed in any testing procedure should
approach the actual fluid that is in contact with the wastes in the landfill
environment. Unfortunately, there is no way of developing a single leaching
solution that represents all the varying conditions with regard to pH,
oxidation-reduction potential (Eh), presence of chelating or complexing
agents, etc. that might be present in a landfill. The general tendency in
most investigations is to use an agressive leaching solution with low pH and
low Eh to simulate a the worst case landfill environment.
Further practical restraints are placed on the composition because the
test solution must be useful in an ordinary laboratory situation. Prepara-
tions that require handling under inert gases or that require reagents that
cannot be obtained in an adequately pure form without great expense are not
40
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appropriate for a generalized testing system. Most investigators have se-
lected weakly acidic solutions such as carbonic acid (CO -saturated water)
or acetic acid as leaching media (3-7).
Use of these mildly acidic leaching solutions has its basis in the fact
that natural precipitation and soil waters (which contain CO ) are mildly
acidic. Simple acetate buffer systems have long been used in estimating the
availability of trace metals in agriculture. For example, Morgan's solution,
an acetic acid-sodium acetate buffer, is routinely used to assess availabil-
ity of metals in agricultural soils. To the extent that these mildly acid
systems reflect increased solubility in rainwater or soil water, they repre-
sent the best compromise as a leaching medium. The groundwater in a land-
fill (especially in a landfill containing only solidified industrial wastes)
may never reach the low pH observed in the acetic acid-based solutions, but
roots growing down into the waste could possibly reduce the pH in their
immediate vicinity to levels similar to those seen in acetic acid and
acetate buffer solutions.
Waste-to-Leaching-Solution Ratios—
The decision as to the ratio of waste to the amount of leaching solu-
tion is always a compromise. Obviously, a waste can come into contact with
an enormous quantity of leaching solution (rainwater, groundwater, etc.)
after disposal. Where the waste-to-leaching solution ratio is very large,
(1:1 or 1:2), common ion effects can reduce the solubility of certain chemi-
cal constituents. Smaller waste-to-leaching-solution ratios (1:5, 1:40) are
considered to be appropriate (3-6).
In most cases, the practical restraints on the testing require that a
large enough volume of leaching liquid be used to allow the analyses to be
performed at the low levels necessary to assure the health and safety of
persons coming into contact with a leachate from the waste. Thus if a level
of a toxic organic compound must be determined to part-per-billion levels,
several liters of leachate must be available from the test procedure.
The ability to generate a relatively large volume of leachate by run-
ning tests in duplicate or triplicate is a very practical asset in the
design of a testing procedure.
Number of Elutions of Leaching Solution Used—
In most leachate testing, the initial samples of leachate produced can
be considered to contain the maximum concentrations of potential contaminants
that will be observed in the test procedure. The reason is that the initial
leach liquid samples are exposed to the waste while the highest concentra-
tions of soluble contaminants are present on the fresh waste surfaces. Also,
the maximum amount of fine-grained solid material (which would have a greater
inherent solubility because of its small particle size) is available in the
waste during the first elution.
Surface Area of Waste—
The ideal testing system would expose a leaching solution to the same
surface area that it would be exposed to in a landfill. In the case of a
41
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dense impermeable waste material, this surface area could equal only the
boundary surface of a waste monolith. In a loose, powdery material or a
sludge, however, the surface area may be hundreds or thousands of times
greater than the boundary surface of the waste mass.
One of the objectives of many waste solidification/stabilization
systems is to produce a monolithic mass with a minimum surface area across
which loss of pollutants can occur. Testing techniques that call for the I/
waste to be ground to a powder destroy much of the advantage produced by
solidification by these processes. However, some processes are designed to
contain the waste even after being ground to a fine powder.
A compromise is to test the coherence of a solid waste by impact test-
ing and to use the monolith or fragmented monolith as a test specimen. This
approach offers the advantage of allowing a material that would not normally
be landfilled in fragments to be tested in the configuration in which it has
a minimum area for contaminant loss. The major disadvantages of such a
physical and chemical testing system are that:
a. The exact stress that should be applied to fracture a coherent
waste specimen as it might be fractured during landfilling or com-
paction cannot be accurately determined for all cases.
b. The surface area of the test specimen cannot be known with any
precision after the specimen has been fragmented. This is impor-
tant if rate of transfer of contaminant per unit surface area is
to be considered.
c. Physical testing of solidified/stabilized materials indicates that
wetting/drying and freezing/thawing cycles can produce rapid dis-
integration of many treated wastes. In many cases this fragmenta-
tion may be more complete than simply cracking the specimen in
impact test apparatus.
d. The variation in fracture patterns between specimens of the same
waste introduces another level of variability into the testing
procedure and reduces the repeatability of the test.
Agitation Employed—
The agitation of test samples during leaching or the stirring of the
leaching solution has been advocated to permit more rapid equilibrium to
occur between the specimen and the leaching solution. However, there is no
real analogy in nature for an agitated leaching solution in contact with a
solidified waste. In most cases where the waste would be landfilled, the
water or leachate in contact with the waste would be stationary or flowing
very slowly so that effective diffusivities characteristics are of prime
importance.
The major objection to agitating or mixing the leachate and solid
wastes is that mixing or shaking can grind the test specimen to smaller
pieces, thereby increasing the surface area exposed to the leaching solution
and invalidating the test.
42
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3.5.2 The EPA Extraction Procedure (EP Toxicity Characteristic)
The EPA extraction procedure (EP) is the only leach testing system
currently proposed by EPA as a definitive part of the procedure for the
identification of hazardous wastes (3-8). Analysis of waste materials can
be used to demonstrate the toxicity of wastes, but no simple test exists to
show the degree to which these hazardous materials will be released into the
surroundings. The goal of the EP is to determine the amount of contaminant
that is released under circumstances approaching those that occur during the
improper management of hazardous wastes. The EP involves exposure of the
waste to a mild acid leaching solution. The EP can be considered an aggres-
sive procedure for stabilized/solidified waste because it simulates
the environment to which the wastes would be exposed if they were placed in
a municipal landfill and saturated with landfill leachate. In cases where
the stabilized/solidified wastes are cast in large monolithic masses, cer-
tain minor modifications of the test procedure are required. Details of the
Extraction Procedure and its associated tests are discussed in Section 7.
3.6 EFFECTS OF BIOLOGICAL ATTACK ON TREATED WASTES
In long-term containment of treated hazardous and toxic wastes, biologi-
cal attack can be a major problem. Biological attack can occur by direct
utilization of some solidification material (such as UF resin) as a substrate
for bacterial growth, or by the biological production of acid materials that
can attack and corrode treated wastes.
Columbo and Neilson (3-9) approached the problem of possible direct bio-
degradation of solidification matrix materials by measuring the total amount
of organic carbon released into leaching waters. Of the four solidification
materials studied (Portland Type II Cement, Urea-Formaldehyde (UF) resin,
asphalt, and vinyl ester-styrene) the UF resin showed the greatest problem
with organic carbon release. In an 18-day leaching program, a 211.7 g sample
released 4.48 g of carbon. No other solidification material approaches this
carbon release. UF is generally conceded to be biodegradable.
Other biological reactions can affect solidified wastes indirectly.
For example, if wastes containing metallic sulfides are incorporated in a
cement matrix, reactions similar to those occurring in the production of
acid mine drainage can occur. The sulfides can oxidize to sulfate and pro-
duce sulfuric acid, which can attack and dissolve concrete. This type of
reaction occurs during the oxidation of pyrites and amorphous iron sulfides.
Atmospheric oxygen is necessary for this reaction to proceed, and therefore
such reactions typically occur at the top of the saturated zone in sulfide-
rich landfills or waste piles.
Plant roots are another source of acid that can remobilize wastes.
Root hairs typically discharge carbon dioxide into surrounding water and
create a mild acid (carbonic acid) that is capable of putting many toxic
metals into solution as bicarbonates. Organic acids released by decaying
roots can also cause corrosion of some waste materials, particularly those
solidified with a lime or cement-based process.
43
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3.7 EFFECTS OF CURING AND AGING PROCESSES ON TREATED MATERIAL
Curing and aging processes affect various treated (solidified) wastes
in widely different ways. Some polymeric materials add linkages during cur-
ing and become stronger and less prone to leaching. In other polymers,
where the waste is not an integral part of the structure, separation of
solid and aqueous phases can occur.
Examples of these different effects can be seen in the contrasts between
cementitious (silicate) solidification systems and UF systems. Moore and
others (3-10) demonstrated that for cementitious systems less leaching was
observed when cement-based samples had been cured more than 100 days. The
conditions of curing were also important. Specimens cured under humid con-
ditions (where polymerization would be accelerated) were less leachable than
samples that were allowed to dry during curing.
In contrast to cement-based systems, UF solidification results in the
formation of a weep water that is not bound into the polymer structure.
Aging of this material produces shrinkage and additional excess water (3-11).
Containment of waste decreases with aging.
Other waste treatment systems that involve bitumen-based or water ex-
tensible polymer systems may also show long-term curing changes, but no data
are currently available to demonstrate whether aging/curing effects will be
detrimental to waste containment properties.
Obviously, where encapsulation systems use a surface coating of polymer,
aging effects will be especially critical. If isolation depends on the in-
tegrity of a polyethylene or organic polymer jacket, any weaking or embrit-
tlement will severely compromise waste containment (3-12).
Each proposed treatment system will require testing after aging to
assure long-term waste containment.
3.8 ECONOMIC CONSIDERATIONS OF TREATMENT OPTIONS,
Most waste materials that are currently being considered for disposal
have no present value, and thus all solidification/stabilization costs repre-
sent additional expenses to be added to the ultimate cost of the product or
service sold. A complete economic analysis must consider costs of waste
transportation, materials and equipment required for stabilization/
solidification, skill levels of treatment plant operators, fees or royalties
for use of patented processes, and cost of transporting and landfilling
treated wastes. This type of analysis often must be undertaken oa^a^case-
by-case basis. However, to obtain an initial impression of the usefulness
of different waste treatment systems now and in the future, it is possible
to restrict economic considerations to present and projected costs for mate-
rials, equipment, and energy. In most treatment systems, the cost of mate-
rials required is the major item regulating present and projected costs.
Table 4-6 outlines the present and future economic considerations for major
waste stabilization/solidification systems.
44
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As shown in Table 3-6, the silicate-based systems (cement-based and
pozzolanic) operate with the least expensive materials and have the most
stable pricing structures for raw materials. The organic polymer systems
(including bitumen) have the most easily disturbed raw material costs be-
cause the prices of raw materials used in these systems are tied to the
price of oil. At present economic considerations appear to be heavily
weighted toward low-temperature silicate systems and against organic
polymers.
45
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REFERENCES
3-1. Mahloch, J. L., D. E. Averett, and M. J. Bartos. Pollutant Potential
of Raw and Chemically Fixed Hazardous Industrial Wastes and Flue Gas
Desulfurization Sludges. EPA-600/2-76-182, U. S. Environmental Pro-
tection Agency, Cincinnati, Ohio, 1976. 117 pp.
3-2. Bartos, M. J. and M. R. Palermo. Physical and Engineering Properties
of Hazardous Industrial Wastes and Sludges. EPA-600/2-77-139, U. S.
Environmental Protection Agency, Cincinnati, Ohio, 1977. 87 pp.
3-3. Engineering and Design - Laboratory Soils Testing. Engineering Man-
ual, EM 1110-2-1906, U. S. Department of the Army, Washington, D. C.,
1970.
3-4. Annual Book of ASTM Standards, Part II. American Society for Testing
and Materials, Philadelphia, Pa., 1973. 874 pp.
3-5. Bogue, R. H. The Chemistry of Portland Cement, 2nd ed. Reinhold
Publishing, New York, N. Y., 1955. 793 pp.
3-6. Lowenbach, W. A. Compilation and Evaluation of Leaching Test Methods.
EPA-600/2-78-095, U. S. Environmental Protection Agency, Cincinnati,
Ohio, 1978. 102 pp.
3-7. Anderson, M. A., R. K. Ham, Rainer Stegman, and Robert Stanforth.
Test Factors Affecting the Release of Materials from Industrial
Wastes in Leaching Tests, pp. 145-168. In: Pojasek, R. B., ed.
Toxic and Hazardous Waste Disposal, Vol. 2, Ann Arbor Science Publ.
Inc., Ann Arbor, Mich., 1978. 259 pp.
3-8. U. S. Environmental Protection Agency. Hazardous Waste Management
System. Federal Register, 45(98):33063-33285. May 19, 1980.
3-9. Colombo, P. and R. M. Neilson, Jr. Properties of Radioactive Wastes
and Waste Containers Progress Report No. 5, April-June 1977. Publ.
No. BNL-NUREG-50763, Brookhaven National Laboratory, Upton, N. Y.,
1977. 43 pp.
3-10. Moore, J. G., H. W. Godbee, and A. H. Kibbey. Leach Behavior of
Hydrofracture Grout Incorporating Radioactive Wastes. Nuclear Tech-
nology, 32:39-52, 1977.
3-11. Columbo, P. and R. M. Neilson, Jr. Properties of Radioactive Wastes
and Waste Containers. BNL-NUREG - 50692, Brookhaven National Labora-
tory, Upton, N.Y., 1977. 53 pp.
47
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3-12. Lubowitz, H. R. , R. L. Denham and G. A. Zakrzewski. Development of a
Polymeric Cementing and Encapsulating Process for Managing Hazardous
Wastes. EPA-600/2-77-045, U. S. Environmental Protection Agency,
Cincinnati, Ohio, 1977. 167 pp.
-------
SECTION 4
ASSESSMENT OF CURRENT DATA ON PHYSICAL AND CHEMICAL
PROPERTIES OF TREATED WASTES
Recent interest in chemical stabilization of hazardous industrial
wastes is beginning to bring about the accumulation of data from studies
dealing specifically with these solidified waste products. Most information
found in this section comes either from a few government-sponsored studies
or from the vendors of waste treatment systems themselves. The results
presented here are intended to be representative of the kinds of tests that
are commonly performed and the ranges of data that are typically found.
Many of the data have been transformed into common units to give uniformity
and comparability to the results.
4.1 EXISTING DATA ON PHYSICAL PROPERTIES OF TREATED WASTES
Because no physical testing regime specific for solidified waste has
been designed, most tests performed are those commonly used to determine the
properties of soils and concrete. Thus, the test results do not always
represent the best information needed to judge the containment capability of
the treated waste, but they are useful in making comparisons with other ma-
terials whose properties are described in the literature. The incompleteness
of the data and the variability in the testing techniques make correlation
of physical properties with leaching characteristics very difficult. Cor-
relations should be made only in cases where the physical properties are
known to be determined on replicates of the actual samples used in the leach-
ing test. Details of the typical test and interpretation of the results are
discussed in Section 3.4.
Another important consideration in discussing the physical properties
of treated wastes is that the physical properties that are important to the
containment success of the different types of treatment processes vary
greatly with the treatment type. For instance, the unconfined compressive
strength of a treated product is meaningful only for those processes that
limit contaminant loss by producing a solid monolith. Processes that produce
soil-like or plastic, spongy masses or encapsulates require completely dif-
ferent testing regimes. Even typical soil tests such as Atterberg limits or
undrained shear strength may not have an important bearing on containment
properties of the soil-like products of some treatment systems. The physi-
cal tests that are indicative of treatment success are process-specific and
must be determined for each individual case.
Unconfined compressive strength (or analogous measurements) and permea-
bility are most commonly reported for the treatment processes that produce
49
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monolithic products for which high strength values and low permeabilities ,-
are said to be indicative of good containment^ Compressive strengths of 10
to 10 N/m and permeabilities of 10 to 10 cm/sec are not unusual for
concrete-based treatment systems (Table 4-1). Organic admixture systems
generally are plastic (with low strength) and vary from highly permeable to
impermeable depending on the kinds and amounts of additives used. The treat-
ments that produce clay or soil-like products cannot be tested using the
physical testing procedures designed for concrete-like products. These
products usually have relatively high permeability and depend on containing
the pollutants by binding them inside a molecular matrix. A summary of the
kinds of physical tests reported by the major vendors in the field are pre-
sented in Table 5-1 along with the process type and comments of performance
in leach tests.
The details of the tests that are performed are quite important and
should be indicated for each test made. Table 4-2 illustrates the changes
in the unconfined compressive strength of samples of treated products made
with varying amounts of cement and water content of the particular sludge
being fixed. Note that a 10% to 15% change in the water content will change
the compressive strength of the product several fold. Small changes in the
amounts of impurities or the sludge pH can also have profound effects on the
properties of the final product.
A comprehensive study of physical and engineering properties of treated
and untreated flue-gas cleaning and hazardous industrial sludges has been
performed by the U. S. Army Engineers, Waterways Experiment Station (WES)
(4-1, 4-2, 4-3). The same treated and untreated sludge samples were also
used in several leaching tests, some of which are still in progress. Five
flue-gas cleaning sludges and five hazardous industrial sludges were treated
by up to seven different solidification/stabilization vendors. The wide
variety of final products made it difficult to choose which physical and
engineering property tests to run. Physical property tests that could be
run on all treated sludges were specific gravity, water content, void ratio,
velocity, bulk unit waste, and dry unit waste. Tests for engineering prop-
erties included compaction, unconfined compression, modulus of elasticity,
permeability, and durability. Wet-dry and freeze-thaw cycle tests were also
performed. Results reported to date for the leaching tests on the same batch
of samples indicate that none of the physical properties tested were of
significant value in estimating loss rate in all leaching tests. The results
of the physical tests appeared to useful only for predicting handling char-
acteristics or disposal site requirements. The tests might be useful pre-
dicting the success of a specific treatment system on a particular waste
type, but were not valid when comparing between treatment types.
4.2 EXISTING DATA ON CHEMICAL PROPERTIES OF TREATED WASTES
Results of leaching tests are commonly reported by vendors of waste
treatment systems. However, the protocols of leaching tests vary widely,
from a 1-hr unstirred, distilled-water leaching test on undisturbed treated
waste samples to extended, repeated leaching of ground samples by aggressive
leaching solutions. Some vendors report results of field tests. Table 4-1
50
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lists typical types of leaching tests and results from the major vendors of
waste treatment systems.
4.3 CORRELATION OF PHYSICAL AND CHEMICAL PROPERTIES
The great variety of treatment techniques makes it difficult to consis-
tently correlate physical and chemical properties in treated materials. The
asphaltic materials and the plastic-jacket encapsulates are imprevious
solids and both show excellent waste retention. When admixes of wastes and
pozzolan or Portland cement are attempted the results become less easily in-
terpreted. Some admix systems depend on chemical binding and adjustment of
pH, thus impermeability, increased strength and decreased void space are not
as important as the chemical composition and potential binding reactions in
the mix.
4.4 INTERPRETATION OF PHYSICAL AND CHEMICAL DATA
Interpreting the chemical and physical data collected on stabilized/
solidified wastes is very complex. How much waste containment must a sta-
bilized specimen exhibit? How strong physically must a treated waste mate-
rial be? Absolute guidelines may be set, or the best judgment of regulatory
officials may be used. Two major methods of data interpretation exist: At-
tempting to predict environmental impact, or using rigid standards for waste
materials that ensure some degree of containment regardless of surrounding
conditions.
No presently required chemical leach test is designed to predict the
ultimate containment of treated toxic waste, but test protocols developed
for the nuclear waste industry can be employed to model waste containment
(4-4, 4-5, 4-6). The problem of radionuclear waste escape from solids
formed using matrices of cement, asphalt, ceramic, or glass media can be
modeled using expressions that take into account diffusion and concentration-
dependent dissolution. Details of tests based upon the predictive Inter-
national Atomic Energy Agency testing procedure are given in Appendix B and
further discussion of predictive models is given in Section 6.
54
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REFERENCES
4-1. Mahloch, J. L., D. E. Averett and M. J. Bartos, Jr. Pollutant Poten-
tial of Raw and Chemically Fixed Hazardous Industrial Wastes and Five
Gas Desulfurization Sludges—Interim report. EPA-600/2-76-182, U. S.
Environmental Protection Agency, Cincinnati, Ohio. 1976. 105 pp.
4-2. Bartos, J. J., Jr., and M. R. Palermo. Physical and Engineering Prop-
erties of Hazardous Industrial Wastes and Sludges. EPA-600/2-77-139.
U. S. Environmental Protection Agency, Cincinnati, Ohio. 1977. 77
pp.
4-3. Thompson, D. W. and P. G. Malone. Physical Properties Testing of Raw
and Stabilized Industrial Sludges. Pp. 35-50. In: Pojasek, E. B.
(ed.). Toxic and Hazardous Waste Disposal, Vol. 2, Ann Arbor Press.
Ann Arbor, Mich., 1979, 259 pp.
4-4. Godbee, H. W., and D. S. Joy. Assessment of the Loss of Radioactive
Isotopes from Waste Solids to the Environment. Part I Background and
Theory. Publ. ORNL-TM-4333, Oak Ridge National Laboratory, Oak Ridge,
Tenn., 1974. 57 pp.
4-5. Moore, J. G., H. W. Godbee, A. H. Kibbey, D. S. Joy. Development of
Cenentitious Grouts for the Incorporation of Radioactive Wastes. Part
I Leach Studies. Publ. ORNL-4962, Oak Ridge National Laboratory, Oak
Ridge, Tenn., 1975. 116pp.
4-6. Moore, J. G. Development of Cementitious Grouts for the Incorporation
of Radioactive Wastes. Part 2. Continuation of Cesium and Strontium
Leach Studies. Publ. ORNL-5142, Oak Ridge National Laboratory, Oak
Ridge, Tenn., 1976. 144pp.
55
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SECTION 5
DESIGN CONSIDERATIONS FOR SOLIDIFIED AND STABILIZED
WASTE DISPOSAL FACILITIES
Disposal of treated wastes is subject to the same regulatory and oper-
ational constraints and considerations as the disposal of any other waste
stream, even though the end product is nonhazardous and/or easily managed or
transported. This section addresses special aspects of treated wastes that
may be important to the disposal operation, and the general aspects and
alternatives of waste disposal under currently proposed regulations and
technology. The major emphasis of this section concerns nonhazardous dis-
posal technology and regulations under RCRA definitions and procedures
necessary to avoid the more rigorous hazardous waste disposal requirements.
5.1 SPECIAL CONSIDERATIONS FOR HANDLING AND DISPOSAL OF STABILIZED/
SOLIDIFIED WASTES
Chemical treatment usually strives to produce a solid monolith in order
to exclude leaching waters from the bulk of the waste materials. The larger
the treated waste block, the greater is the proportion of the waste that is
isolated from environmental interactions. The treated waste may also require
secondary containers such as drums or tanks. Some treated wastes present
unique problems to the typical waste handling and compacting equipment de-
signed for loosely packed refuse or semisolid sludges. The solid block
should be formed and covered with a minimum of fracturing to retain the ben-
efits of treatment.
A very common practice (especially for hazardous sludges) is to combine
the treatment and disposal operation. In this method, the wastes are trans-
ported to the facility in their original (and perhaps hazardous) condition,
where they may undergo chemical treatment. The wastes are mixed with the
appropriate chemical additives and pumped directly to the waste disposal area
as a semisolid slurry that solidifies in place into a single monolithic mass.
As yet, no specific regulations have been written concerning this type of
operation, but it appears that if hazardous wastes are involved, the treat-
ment phase of the operation would be covered by the more rigorous hazardous
waste regulations with regard to storage and treatment operations.
All treated wastes are susceptible to breakdown and release of the
contained wastes if they encounter an aggresive environment in the waste
disposal site. Even mildly acid environments will slowly breakdown most
cement- and pozzolan-treated wastes. High sulfate concentrations in the
contacting waters will cause surface spalding and structural breakdown of
56
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cement-based products. Organic solvents, and even oils and greases, can
cause loss of integrity in asphalt-based treated wastes. Strong oxidants
can cause breakdown of many organic-based treated wastes. Even glass-
containing wastes can be etched and devitrified in strongly alkaline
environments.
Sanitary landfills are currently being studied as depositories of non-
hazardous treated wastes, since they represent a common and well understood
disposal system (5-1). Although long-term results are not available, it now
appears that the increased rate of dissolution of the cement- and pozzolan-
treated wastes is more than offset by the large exchange capacity of the
cellulosic residue in the municipal waste. Little heavy metal release to
the surrounding environment occurs. Attenuation of the pollutants by the
municipal refuse may be only temporary however, since after the bulk of the
organic material is broken down, release may occur. Sanitary landfills are
best presumed to be unsuitable for disposal of treated wastes.
5.2 DESIGN FACTORS FOR HAZARDOUS WASTE LANDFILLS
Treated wastes that meet the EPA criteria for hazardous waste must be
disposed of in a landfill that has been designed and approved for handling
hazardous solid waste. In general terms, hazardous waste landfills must
provide complete, long-term protection of the quality of surface and sub-
surface waters from any of the hazardous constituents disposed therein and
from any hazards to public health and the environment. Such sites must be
located or engineered to avoid direct hydraulic continuity with surface and
subsurface waters. Subsurface flow of groundwater into the disposal area
must be prevented. Leachate generation shquld be avoided; any produced must
be collected and treated. Monitoring wells must be installed, and a
sampling and analysis program must be designed and approved. These require-
ments would also be desirable for typical, sanitary landfills. The primary
difference involves the degree of concern and care, and the record keeping
that must be involved where hazardous materials are involved.
The state of the art for predicting discharges or releases from land-
fills is poor. Therefore EPA states in their proposed rules that the only
option available to insure protection of human health and the environment is
to prescribe design and operating standards for hazardous waste landfills
that provide maximum containment. An inert, essentially impermeable liner
is required at all hazardous waste landfills. Furthermore, in localities
where climatic and natural geologic conditions are such that leachate
buildup might be expected (where evaporation does not exceed precipitation
by 20 in. or more), an active leachate collection system is required so that
any leachate generated can be removed and treated. Landfills located over
an underground drinking water source must install groundwater and leachate
monitoring systems and provide for up to quarterly sampling and analysis of
specified parameters. Sampling, analysis, and record keeping are required
for at least 20 years after closure of the landfill. Exact location of each
hazardous waste (with respect to permanently surveyed benchmarks) and the
dimensions and compositions of the waste must be recorded and kept available
for inspection.
57
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EPA has proposed to restrict hazardous waste landfills from accepting
ignitable, reactive, or volatile wastes, or wastes that are bulk liquids,
semisolids, or sludges. Liquid wastes in containers are prohibited but
liquids may be solidified in the container. Bulk liquids can be fixed to
meet regulations.
5.3 USE OF LAND TREATMENT OF BIODEGRADABLE INDUSTRIAL WASTES
Landfarming incorporates biological, chemical, and physical processes
of the upper soil horizons to effectively treat biodegradable industrial
wastes. Selection, deposition, and postdepositional care must be adminis-
tered to maximize the effectiveness of waste degradation. Disposal of
hazardous waste by landfarming may require pretreatment to eliminate com-
bustion, reaction, or volatilization hazards. Such treatment must result in
waste attributes conducive to the landfarming degradation processes.
Similarities between this recycling of waste products and agricultural
farming all depend on planning and readily available, dependable, large-scale
equipment. Combined agricultural techniques and landfarming of wastes can
result in improved land surface and soil characteristics, but the primary
objective is to dispose of waste continuously while maintaining or improving
the soils disposal efficiency for long-term usage.
The densities and makeup of microbial populations vary with soil depth
and geographic location. Geographic location also affects the seasonal dura-
tion and intensity of microbial activity. The surface or near-surface dep-
osition of waste materials and mixing by conventional plow techniques exposes
concentrated waste material to large populations of microbes.
Whether waste material is deposited on or beneath the soil surface is
determined by many factors such as the character of the waste, the microbes,
and the soil. The function of the created waste-soil system is to produce
harmless volatiles, water soluble components, and decomposition products
available for uptake by vegetation. Absorption of waste components by
mineral constituents of the soil must be avoided or the storage capacity
will eventually be reached and waste will be transmitted to groundwater
systems. Depending on future site use, the landfarm can become a repository
of nonbiogradable materials, although such is not the purpose of a landfarm.
Pretreatment could provide nonbiodegradable material in a fixed form, pos-
sibly improving soil texture.
Although the interactions among the soil constituents and waste mate-
rials are complex, a list of general factors is given as follows:
Temperature
Moisture content
pH
Inorganic nutrients
Oxygen availability
Chemical composition of wastes
Physical characteristics
58
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The requirements for landfarming delineate environmental concerns pri-
marily related to water quality. The landfarm must not have direct contact
with surface water or groundwater systems. Erosion problems are generally
not associated with landfarm areas because of restrictions posed by surface
slope requirements. However, any direct exposure of waste materials by ero-
sion must be considered. Subsurface geology must prevent possible ground-
water contamination. The surface slope must be sufficiently steep to prevent
ponding, but it must be gentle enough to prevent erosion. The soil pH must
be above 6.5 to prevent leaching of toxic metals. Soil characteristics
throughout the site must be ascertained before, during, and after the site
is in active use. This requirement establishes that the soil has been
returned to an equivalent preexisting condition before closure. Ignitable,
reactive, volatile, and incompatible wastes are not permitted in a landfarm
disposal system. Some treated waste may prove to be suited to landfarming
if release of degradable compounds occurs at a rate comparable to their
destruction. The technical resource document on Design and Management of
Hazardous Waste Land Treatment Facilities (5-2) should be consulted for
further detail.
5.4 OPERATION AND MANAGEMENT OF DISPOSAL FACILITIES FOR TREATED WASTES
Many of the listed operational procedures discussed below are not now
required for waste disposal facilities that are permitted to accept only
nonhazardous waste. However, because most treated wastes would be catego-
rized as hazardous if they were not treated, procedures suitable for hazard-
ous waste should be followed insofar as possible. In the case of long-term
instability of the treated product, such precautions may prevent environmen-
tal or groundwater degradation in the vicinity of the disposal site. Most
procedures protect the operators of the disposal site as well as the general
public, and they can be accomplished with relatively small expense. EPA's
position at this time is that treatment of any kind does not reduce the need
for a complete monitoring program.
5.4.1 Monitoring of Ground and Surface Waters
The most frequent and serious environmental impact in the disposal
facility is also the most easily overlooked and most expensive to rectify—
that of losing leachate and pollutants to the groundwater. Monitoring of
the groundwater quality to ascertain whether pollutants are being lost from
the disposal sites is the only method to be certain that no hazardous con-
stituents are being lost. Monitoring should begin before opening of the
site to provide baseline data on the water quality in the area. Ideally,
background samples should be taken throughout all hydrological seasons, as
considerable variation can occur within the year.
Monitoring wells should be placed both up and down the groundwater
gradient from the disposal site. Changes in the overall groundwater quality
in the area would not be seen equally in water samples from all wells. Pol-
lutants from the disposal site itself should only show up in the water sam-
ples from wells down the groundwater gradient.
59
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Any elevated or abnormal concentrations should immediately be double-
checked with new water samples so that immediate remedial action can be
taken. A quick response to stop the source of the leachate infiltration is
always cheaper and more effective than efforts at cleaning up an aquifer
after extensive pollution has occurred.
5.4.2 Gas Monitoring
Landfills containing putresable materials produce large amounts of
methane and carbon dioxide. Other gases (hydrogen, ammonia, hydrogen sul-
fide, etc.) can be produced in appreciable quantities from particular wastes
typically found in some landfills. These reactive gasses can migrate and
attack treated wastes causing a greatly increased loss of constituents.
Depending on the geology and soil permeabilities at the site, gases can
migrate long distances underground and accumulate under any structures on
or near the disposal site. Explosive gases, especially methane, should be
monitored. Toxic or asphyxiating gases should also be monitored on a
regular basis with appropriate instruments. The presence of such gasses
should bring about a reassessment of the containment properties of the
treated wastes.
Gas migration through the soil is especially prevalent in sandy,
permeable soils and in rainy periods as the influx of rainwater into the
soil forces gases into the surrounding areas. Landfill gases are elusive,
and concentrations can vary greatly at the same sampling point over the
course of a few hours or between simultaneous sampling at two adjacent
sampling points. Areas with stunted or dying vegetation should be checked
as likely areas of gas migration and/or collection.
60
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REFERENCES
5-1. Myers, T. E., and others. Chemically Stabilized Industrial Wastes
in a Landfill Environment. Paper presented at 6th Annual Solid
and Hazardous Wastes Research Symposium, Chicago, 111., March 17-20,
1980.
5-2. Brown, K. W. 1980. Design and Management of Hazardous Waste Land
Treatment Facilities. SW-874. Office of Solid Wastes, U. S. Environ-
mental Protection Agency, Washington, D.C. In press.
61
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SECTION 6
STEPWISE EVALUATION OF STABILIZED/SOLIDIFIED WASTES
In any waste disposal operation that involves a treatment such as
stabilization/solidification applied to a waste and ultimate land disposal
of the solid product, a number of considerations immediately arise:
a. Is the waste still ignitabile, reactive, or toxic?
b. What is the maximum toxic hazard presented by the solidified waste
under normal conditions?
c. Will the stabilized/solidified material remain in a solid condition
(with low permeability) in the disposal site?
d. What is the best estimate of leach losses over a long term (i.e.
100 years)?
e; What are the operating plans at the site selected?
All of these questions are important in judging the acceptability of a
hazardous waste disposal operation. Unsatisfactory answers to any one of
these questions would require revision of the disposal program.
•The evaluation procedure outlined in this section uses examples from a
common case—disposal of a waste that has been treated using a cement-based
or pozzolan system for shallow land burial. The procedure outline may
require modification for other treatment systems where plastic incorporated
waste materials are produced or where secondary containers such as drums are
employed. Parts of this section are based upon EPA's Hazardous Waste
Management System; Part III, Identification and Listing of Hazardous Waste
(6-1).
6.1 STEP 1. EVALUATION OF HAZARDOUS NATURE OF TREATED WASTE
6.1.1 Determination of Ignitability.
To be classified on non-hazardous, the treated waste must not be ignit-
able and must not cause fires through friction, absorption of moisture, or
spontaneous chemical changes nor burn persistantly or vigorously. If any
free liquid is present in the sample, the liquid must pass the test proce-
dure outlined in ASTM Standard D-93-79 or D-3278-78. The waste is classified
62
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as hazardous if it has a flash point less than 60°C. If gases are evolved
from the treated waste, they shall not be ignitable as determined by
49 CFR 173.300.
Example: If a waste hydrocarbon is to be blended into a cement mix,
ignitability tests should be run on any liquid or supension associated with
the treated wastes. Solid samples of the treated waste should be tested to
determine if a sustained fire is possible when the wastes are ignited. The
Pensky-Martens Closed Cup Tester (ASTM D-93-79) is particularly suited to
working with suspensions of solids and materials that form fumes when heated.
Sustained burning of treated solid material can be judged using results from
tests such as ASTM F 501. Data from ASTM F 501 should include flame time,
glow time, drip flaming time, and burn length.
6.1.2 Determination of Corrosivity.
Any liquid associated with treated wastes must have a pH equal to or
greater than pH 2 and equal to or less than pH 12.5 (6-2, 6-3). Treated
materials must not corrode steel (SAE 1020) at a rate greater than 6.35 mm
(0.250 in.)/yr at a test temperature of 55°C (130°F) as determined by the
National Association of Corrosion Engineers Standard TM-01-69 (6-3).
Most cement or pozzolan-based treatment systems will maintain a pH near
12.5 in any associated liquid due to the calcium hydroxide present in the
additives. The pH of a saturated aqueous solution of calcium hydroxide at
25°C is 12.4. Therefore it would be possible for any liquid associated with
treated material to fail this corrosivity test. The pozzolan or cement-
based treated material might only be acceptable under the corrosivity stan-
dard if no free liquid is present.
6.1.3 Determination of Reactivity.
To be classified as non-hazardous the treated waste should be normally
stable and not undergo violent chemical changes. Materials that react with
water will obviously have reacted during processing using cement or pozzolan
incorporation. Compounds that are normally reactive will be diluted; but in
general will remain reactive. Under the alkaline conditions involved in
cement incorporation, sulfides and cyanides will not normally decompose, but
if later exposed to acid groundwater, hydrogen sulfide or hydrogen cyanide
gas can be produced. Both of these materials would be inappropriate for
pozzolan or cement incorporation. Solutions with high concentrations of
ammonium compounds can decompose to produce ammonia gas in a strongly alka-
line environment. These materials may present problem during processing and
disposal of treated wastes.
Materials that are explosive, oxidizers or autopolymerizable substances
should also be disallowed in treated wastes. The Explosive Temperature Test
(40 CFR 250.13) could appropriately be applied to treated wastes where ex-
plosive potential is suspected. Treated wastes that contain materials un-
stable to mechanical shock will, although diluted, can retain their insta-
bility in the blended product. Bureau of Explosives impact testing
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(49 CFR 173.53(b), (c), (d), and (f)) could be appropriately used for testing
treated wastes.
6.1.4 Determination of EP Toxicity
The standard EPA Extraction Procedure (EP) and maximum acceptable con-
taminate levels are outlined in reference 6-1. The list of contaminants rep-
resents only the minimum requirement at this time and therefore does not
include many other potentially dangerous materials that might be present in
the incorporated wastes. The analytical requirements should be selected to
suit the specific wastes blended into the treated solid. For example,
electroplating wastes commonly contain degreasing compounds and phenolics.
It would be appropriate to look for these materials in the extracts from any
treated electroplating sludge.
The extraction procedure is not efficient in assessing the loss of
every contaminant. Organic contaminants may not be efficiently extracted
from all matrices. Where serious organic contamination is suspected, addi-
tional testing using a variety of leaching solutions would be prudent.
6.2 STEP 2. DETERMINATION OF MAXIMUM TOXIC HAZARD UNDER NORMAL CONDITIONS
Because the solidified waste is to be landfilled, it will be exposed to
rainwater, soil water or possibly even groundwater (assuming the water table
could rise into the landfill). The surrounding water could become saturated
with respect to any toxic or noxious compounds present as the wastes.
In order to discover if the waste can release objectionable levels of
toxic substances, a maximum possible concentration (MPC) type of test can be
performed. The solid sample is dried and ground to a powder ( 200 mesh).
The ground sample is shaken or stirred in smallest practical volume of dis-
tilled water (at 20°-25°C) until the concentration of potentially toxic con-
stituents no longer increases in the solution in contact with the waste. If
it is suspected that a very soluble toxic material is present in the ground
waste; the solution should be removed and placed in contact with a fresh
(unleached) aliquot of ground waste. The goal of this type of test is to
determine as nearly as possible what concentration of toxicants can be
expected in water saturated with respect to the compounds in the waste.
An example of an effective MPC test protocol used in Harwell Labora-
tories (U. K.) is given in reference (6-4). The Harwell testing procedure is
a multiple shake test that uses a minimum amount of leachate to assure that
a saturated condition is produced in the liquid. Such tests represent a
worst-case situation. Materials that can show very low concentration of
potential pollutants would rank well in selection of treated materials for
disposal.
6.3 STEP 3. DETERMINATION OF PHYSICAL INTEGRITY AND DURABILITY
In many stabilized/solidified wastes the containment properties depend
on limiting the surface area across which transfer of potential pollutants
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can occur. Physical testing systems are required to judge the durability of
the solidified waste.
Physical testing of waste materials becomes very important where the
conditions for shallow land burial are not ideal. For example, durability
testing is important where cover will not be sufficient to prevent cyclic
wetting and drying, or freezing and thawing. If the cover is permeable, all
of the containment for the waste may depend on the production of an imper-
meable monolith. However, for treated materials that can be ground to a
powder and still not lose materials to leaching as in the MPC testing, the
durability tests would be important only for structural integrity and would
have little meaning for containment characteristics.
Physical properties testing is covered in Section 3. In general the
stronger, more impermeable, and durable a treated waste, the more effective
will be its containment. If the material does not fragment to create dust
or increase the surface area for exchange, losses will be minimized. Cement-
based treated wastes can be prepared with properties that approach com-
mercial concrete. Tests have shown compressive strengths up to 2500 Ibs/ sq
in., with excellent durability, permeabilities of 7.9 x 10 cm/sec and less
than 20 % weight loss after 12 freeze-thaw cycles (6-4). Column leach test-
ing has shown that in cement-based systems the strongest material, has the
minimum contaminant loss (6-6).
Where the maximum possible concentration tests show potentially hazard-
ous levels of toxicants, durability would have to be very high to demon-
strate that physical characteristics of the material will prevent this
"worst case" situation from occurring.
6.4 STEP 4. ESTIMATION OF LEACHING LOSS OVER A LONG TERM
Stabilized/solidified waste is meant to be landfilled and to remain
buried indefinitely. In cases where infiltration is minimal and dilution of
any potential leachate occur, no contamination from the waste will be
detectable.
When solidified wastes are buried the major factor limiting the loss of
material from the monolithic mass is diffusion of the chemical constituents
to the surface of the solid. The rate of solution of material at the sur-
face is large compared to the diffusion rate. Diffusion in a solid can be
assessed using tests such as the Uniform Leaching Procedure (ULP) given in
Appendix B. The results of the ULP are given as effective diffusivities
(measured in cm /sec).
Effective diffusivities or leachability constants can be used in com-
paring the containment afforded by different solidification systems and for
predicting the long-term losses from masses of wastes (6-7). Very little
information is available on effective diffusities of solidified industrial
wastes. Johnson and Lancione (6-8) presented some data on diffusivities of
stabilized/solidified arsenic wastes; but the testing protocol used varied
significantly from the standard system. Most data on leachabilities of
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solidified waste come from nuclear waste treatment. Usually the elements
and the types of material treated differ greatly from typical industrial
wastes. In general, glass-fused wastes have had lower loss rates then
plastic (bitumen) encapsulated materials and plastic (bitumen) materials
have lower loss rates than cement-based materials (6-9). Determining ef-
fective diffusinities is the best documented system for comparing the reten-
tion of different constituents of waste using the same solidification system
as for comparing the containment produced by different solidification sys-
tems on one waste.
Diffusivities for different constituents can also be used to model the
long-term loss of specific materials from solidified waste materials that
have known shapes and dimensions. Details of modeling are given by Anders,
Bartel, and Altschuler (6-7). If the size and shape of a waste mass are
known and if it can be assumed that diffusion into a very dilute solution is
the principal transport mechanism, a model for the loss of individual con-
stituents can be set up. Figures 6-1 and 6-2 give the calculated retention
rates for cylindrical barrel-size ingots and for flat slabs (10 cm thick)
for 100 years for materials having diffusinities ranging from 1 x 10 to
1 x 10~ .
For example, if a cement-solidified cadmium waste were being evaluated,
results from the ULP can be used to select an appropriate curve. If the
wastes are solidified in drums, the appropriate diffusivity curve from Fig-
ure 6-1 would be selected and the percent loss of cadmium from a single
ingot could be estimated. A steel drum would normally last 15 years so
solution losses could be estimated from a point 15 years from the time of
burial when the solidified waste would be exposed. Similarly Figure 6-2
could be used to predict waste losses from a semi-infinite slab of waste
10 cm thick. Other waste configurations can be modeled from equations
available for less common shapes such as spheres or parallelepeds, etc.
(6-7).
6.5 STEP 5. ASSESSMENT OF LAND BURIAL SITES
Other manuals in this series have examined performance of land burial
sites and should be consulted (6-10, 6-11). In the case of treated wastes
where designs call for creating low permeability monoliths, the escape of
potential contaminants has been assumed to occur principally along the sur-
face of the emplaced mass. If the physical properties of the waste indicate
a durable final material, a maximum escape rate for contaminants based on
the surface area of the emplaced waste mass can be estimated. This would be
a maximum rate that would assume a maximum diffusion gradient (6-7). Other
procedures such as estimation of percolation rate from cover parameters and
examination of liner and drain performance would precede as with landfills
designed to receive untreated wastes.
6.6 STEP 6. EVALUATION OF MONITORING AND CLOSURE PROGRAMS
Monitoring and closure of a solidified hazardous waste site would be
similar to any other hazardous waste facility. Manuals for assessing these
66
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BARREL SIZED INGOT
(90cm XSScm)
10 20 30
90 100
40 50 60 70
YEARS
Figure 6-1. Percent of constituents remaining in barrel-sized,
cylindrical ingots (90 cm long x 55 cm diam) of solidi-
fied waste over 100 years of leaching for wastes
having diffusivities of 10~ to 10~ cm /sec
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100
SLAB SIZE
10 em THICK
40 5© 60
YEARS
Figure 6-2. Percent of constituent remaining in a sami-infinite
slab (10 cm thick) of solidified waste over 100 ye^rs
of leaching^for wastes having diffusitities of 10
to 10 cm /sec.
100
~
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aspects of landfill design should be consulted. If the treated wastes were
classified as non-hazardous by EPA, then closure of the facility would be no
different than any other waste disposal area.
6.7 STEP 7. QUALITY CONTROL OF WASTE TREATMENT
Treated waste material may vary greatly from batch to batch due to
variation in wastes incorporated or the conditions of treatment. In cement
or pozzolan-based systems, small amounts of interfering materials can reduce
strength, durability and chemical containment drastically. In some solidi-
fication operations in which the material is poured out to solidify as a
monolithic mass, solidification may not occur and if an additional layer is
poured over the unsuccessfully solidified wastes, a highly leachable zone in
the waste mass is created. Such poor operating practices should be avoided.
Any treatment process should include a system for determining the char-
acter of the treated waste and a provision for reprocessing the material
before final deposition if the treatment process was unsuccessful. The
exact sampling pattern for determining treatment quality would depend on the
variability of the feedstock for the treatment system and the quantity of
waste treated. In batch operations, each separate batch should be leach
tested and tested to determine selected physical properties. In a cement-
or pozzolan-based system, any large changes in set-time or texture of the
treated waste should be cause for a more complete testing sequence. Sam-
pling procedures are outlined in references on industrial sampling designs
(6.12).
6.8 STEP 8. EVALUATION OF AGED MATERIAL
Periodically samples should be cored from aged solidifed wastes to
determine if breakdown and loss of contaminants has occurred. If the physi-
cal properties, strength and durability have not decreased and the perme-
ability of core materials has remained low, the assumption of a low-
permeability monolith of waste is justified. Leach testing of core material
can be used to ascertain any decrease in containment properties with age.
If a landfill operation can demonstrate that the treated waste is not break-
ing down, longer periods can be permitted between resampling of treated
waste. For example in the first year of operation one core per 1000 cubic
meters volume might be judged adequate. If the sample appears uniform and
unchanged the core requirement could be halved.
6.9 PERMITTING AND OPERATING EXPERIENCE
There are at present few long-term records for operating hazardous
waste landfills where treatment is being employed. Only small amounts of
treated wastes have been emplaced at various manufacturing localities in the
United States. Where these sites have been investigated, no major contami-
nation of groundwater or sub-waste soil has occurred (6.13, 6.14). The lack
of experience with treated wastes and the potential for application of
treatment processes to inappropriate waste dictates that caution be exer-
cised in granting permits.
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REFERENCES
6.1. U. S. Environmental Protection Agency. Hazardous Waste Management
System; Part III, Identification and Listing of Hazardous Wastes.
Federal Register 45(98):33083-33133. May 19, 1980.
6.2. U. S. Environmental Protection Agency. Test Methods for the Evalua-
tion of Solid Waste, Physical/Chemical Methods. SW-646. Office of
Water and Waste Management, Washington, D.C., 1980. 584 pp.
6.3. U. S. Environmental Protection Agency. Methods for Chemical
Analysis of Water and Wastes. EPA 600/4-79-020, Environmental Moni-
toring and Support Laboratory, U. S. Environmental Protection Agency,
Cincinnati, Ohio, 1979. 1970. 298 pp.
6.4 Wilson, D. C., and S. Waring. The Safe Landfilling of Hazardous
Wastes. Paper presented at 3rd Int. Industrial Waste Waters and
Waste Congress, IUPAC, Stockholm, Sweden, Feb, 1980. 14 pp.
6.5. Bartos, M. J., and M. R. Palermo. Physical and Engineering Proper-
ties of Hazardous Industrial Wastes and Sludges. EPA 600/2-77-139.
U. S. Environmental Protection Agency, Cincinnati, Ohio, 1977. 89 pp.
6.6. Jones, L. W., and P. G. Malone. Physical Properties and Leach Testing
of Solidified/Stabilized Flue Gas Cleaning Wastes. U. S. Environ-
mental Protection Agency, Cincinnati, Ohio. (in preparation).
6.7. Anders, 0. U., J. F. Bartel, and S. J. Altschuler. Determination of
Leachability of Solids. Analytical Chemistry. 50(4):564-569. 1978.
6.8. Johnson, J. C., and R. L. Lancione. Assessment of Processes to
Stabilize Arsenic-Laden Wastes, pp. 181-186. In: Disposal of
Hazardous Wastes. EPA-600/9-8-010. Environmental Protection Agency,
Cincinnati, Ohio, 1980.
6.9. Moore, J. G., H. W. Godbee, and A. H. Kilbey. 1977. Leach Behavior
of Hydrofracture Grout Incorporating Radioactive Wastes. Nuclear
Technology 32:39-52. 1977.
6.10. Moore, C. H. Landfill and Surface Impoundment Performance Evaluation
Manual. U. S. Environmental Protection Agency, Cincinnati, Ohio.
(in press).
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6.11. Perrier, E., and A. C. Gibson. Hydrologic Simulation on Solid Waste
Disposal Sites. U. S. Environmental Protection Agency, Cincinnati,
Ohio. (in press).
6.12. U. S. Environmental Protection Agency. Samplers and Sampling Pro-
cedures for Hazardous Waste Streams. EPA/600/2-80-018. U. S. En-
vironmental Protection Agency, Cincinnati, Ohio, 1980.
6.13. Mercer, R. B., P. G. Malone, and J. D. Broughton. Field Evaluation
of Chemically Stabilized Sludges, pp 357-365. In Shultz, D. W.
(ed.). Land Disposal of Hazardous Wastes. EPA 600/9-78-016. U. S.
Environmental Protection Agency, Cincinnati, Ohio, 1978. 453 pp.
6.14. Jones, L. W., P. G. Malone, and T. E. Myers. Field Investigation of
Contaminant Loss from Chemically Stabilized Sludges. Presented at
Sixth Annual EPA Solid and Hazardous Waste Research Symposium,
Chicago, Illinois, March 17-20, 1980. 15 pp.
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APPENDIX A
SOURCES OF FIXATION TECHNOLOGY
The data in this appendix were obtained from: Environmental Labora-
tory, U. S. Army Waterways Experiment Station. Survey of Solidification/
Stabilization Technology for Hazardous Industrial Wastes. (EPA-600/2-79-056,
U. S. Environmental Protection Agency, Cincinnati, OH. 1979.) Addition and
changes contained in this appendix are from new communications from vendors.
NOTE: All information given in Appendix A has been taken directly from
vendor literature and sales brochures. No attempt has been made to verify
or interpret any vendor claims. This listing is given for illustrative and
informational purposes only and should not be used for design or permit
functions.
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a. Name of Vendor: Atcor Washington Inc.
Division of Chem Nuclear Systems, Inc.
Park Mall
Peekskill, NY 10566
Contact: M. Brownstein, Director
(914) 739-9000
b. Category of fixing process: The process is classed as a masonry-based
solidification systems (using cement).
c. Types of wastes treated: System is primarily designed to effectively
solidify typical wastes from both boiling water reactor and pressurized water
reactor nuclear power plants (which include 25% Na^SO,, 12% H^BOo, bead type
ion exchange resin and various filter media - solka floe, diatomeccous earth
and filter aid). The Atcor Radwaste Solidification System includes an
in-line mixer/feeder which fills any size container, permits inclusion of
bulky items and flushes clean with a minimum of water. All operation
procedures are remote and/or automatic.
d. Types of waste excluded from treatment: sludges which do not combine
with cement could not be handled, however, testing for specific sludges is
required to ensure application suitability.
e. Cost of fixation: Cost is variable depending upon waste to be treated.
Dry masonry cement is added up to volume equal to the volume of waste which
gives final product about 130% of volume of original waste. Cement cost is
approximately 9 cents per kilogram, but capital expenditure, transportation
and personnel costs will vary greatly with the individual job.
f. Leach and strength tests: Leach and strength studies showing product
acceptability for cement-based radwaste systems are numerous. The product
is a monolithic cement structure exhibiting no free water and an acceptable
leach rate for shallow-land burial.
g. Examples of past applications and current contracts: At present the
Atcor system is used solely within the commercial nuclear power industry,
however, studies are currently under way to use system for solidifying
arsenic wastes and incinerator-generated wastes. Radwaste solidification
systems have been purchased by 11 major power companies including: Northern
States Power Company (Monticello and Prairie Island), Wisconsin Public
Service Co. (Kewanee), Wisconsin Electric and Power Co. (Point Beach), Ten-
nessee Valley Authority (Beliefonte), Taiwan Power Co. (Chin-Shan and
Kwosheny), Duquesne Light Co. (Beaver Valley), and others.
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a. Name of Vendor: Canadian Waste Technology, Inc.
160 Torbay Road
Markham, Ontario L3R-1G6
Canada
Contact: David Krofchak, President, Canadian Waste Technology, Inc.
(416) 495-9502
b. Category of fixing process: The solidification process is based upon
the production of stable silicate compounds analogous to natural geologic
materials.
c. Type of waste treated: All inorganic wastes from heavy, medium and light
industries such as waste pickle liquor, plating wastes, etc., containing
acids, chromium, copper, iron, magnesium, manganese, nickel, zinc, cadmium,
lead, mercury, vanadium, chlordies, sulphates, phosphorous and virtually any
inorganic chemical or combination thereof. Specialized applications have
been designed to treat mine tailing wastes and sewage sludges from primary
and secondary treatment plants.
d. Types of waste excluded from treatment: The process is ineffective
against some organic wastes, but organic wastes of up to 20% of the volume
of the formulated inorganic wastes have been treated successfully on a case
to case basis.
e. Approximate cost of processing: Each location where wastes are treated
has different costs depending upon quantity of wastes and the method of
operation. However, costs of approximately $8.00 per cubic meter ($6.00 per
cubic yard) or 0.8 cents per liter (3 cents per gallon) are easily achieved
(August 1977), This price assumes no cost for removal of solidified material
from the site. No apparent increase in fixed material to raw sludge volume
has been found.
f. Data on leach and strength tests: Extensive strength and leach tests
have been made by the company; those cited below were in cooperation with
the Ontario, Canada, Ministry of the Environment, Pollution Control Branch,
Industrial Section (from a paper entitled "An Assessment of a Process for
the Solidification and Stabilization of Liquid Industrial Wastes, 1976, by
G. A. Kerr, Q.C., Minister) the conclusions of this report were:
(1) The solidification process appeared to hold and stabilize most of
the heavy metals contained in the liquid (acidic metal-bearing liquid indus-
trial wastes). Heavy metal values in the leachates (laboratory and field)
were commonly below 1 mg/liter.
(2) Leachates from the testing of processed material contained high
concentrations of dissolved solids.
(3) The bulk of the common heavy metals present in the waste were re-
tained in the processed material during extended period of leaching with
distilled water when considered on a mass basis. Losses of heavy metals
were relatively minor.
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(4) Landfilling may be used to dispose of the processed material pro-
viding adequate facilities are available for the collection and treatment of
leachate and run-off. The concern over dissolved solids contamination will
dictate the adequacy of the facilities required.
/• o
Material with up to 20.7 x 10 N/m (3000 psi) unconfined compres-
sive strength has been produced, but for reasons of cost, the end product is
generally of low strength.
g. Examples of past applications and current contracts: Currently over
380,000 liters/day (100,000 gpd) are being treated at a treatment site in
the city of Hamilton, Ontario. The fixed material is being used as a cover
for the sanitary landfill. Negotiations are currently underway with com-
panies in the United States and in Canada for the licensing of the technology
to operate similar sites and many cases to treat company wastes on site.
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a. Name of Vendor: Chemfix, Inc.
1675 Airline Highway
Kenner, Louisiana 70062
or mail correspondence to:
P. 0. Box 1572
Kenner, Louisiana 70063
Contact: M. W. Duncan, President
(504)729-4561
b. Category of fixing process: Inorganic chemical additives (cements and
soluble silicates) are mixed with the wastes to produce a gelling reaction
that is followed by hardening. Mobile treatment plants that can each handle
1,000,000 liters/10 hour shift are provided. The process is also applied in
fixed installations. The additives consist of less than 5% up to 10% by
volume of the waste. The process varies with the percent solids and nature
of the wastes. Generally the higher the percent solids the lower the
additive requirement.
c. Types of wastes treated: Most types of waste can be accepted for this
processing. The additives react with polyvalent metal ions producing stable,
insoluble, inorganic compounds. Nonreactive materials (e.g. certain
organics and asbestos) are physically entrapped in the matrix structure
resulting from the reaction process. Process is usually custom designed
for each type of waste.
d. Types of waste excluded from treatment: Some wastes containing certain
organic compounds and/or toxic anions are not normally treated, however, in
some such cases, specified pretreatment will allow solidification/fixation.
e. Approximate cost of processing: Varies greatly with the % solids and
nature of the waste. Laboratory testing to determine cost is provided.
Reagent costs would typically fall in 1 to 5
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a. Name of Vendor: Dravo Lime Company
650 Smithfield Street
Pittsburgh, PA 15222
Contact: C. J. McCormick
(412) 566-4433
b. Category of fixing process: Dravo Lime Company's solidification addi-
tive, Calcilox, is a dry, free flowing, light grey-colored powder of inor-
ganic origin. It is hydraulically active and when added to the slurry
improves its handling and ultimate land disposal characteristics by imparting
structural integrity to the settled slurry. The process could probably best
be classed as pozzolanic or cementitious.
c. Type of waste treated: Calcilox is applicable to all calcium-based SO
scrubber waste as typically produced from coal-fired utility scrubbers.
Calcilox is also applied to many inorganic mineral processing tailings that
contain a large percentage of silica and alumina. Typical applications are
on fine coal preparation wastes and uranium mill tailings.
d. Type of waste excluded from treatment: Sludges containing organics and
sewage wastes cannot be treated.
e. Approximate cost of processing: The weight percent of Calcilox additive
dosage ranges from 5 to 15% of the dry slurry solids weight. Low dosages
(5-10%) are used with mechanically dewatered wastes (55 to 70% solids) and
higher dosages (10-15%) with lower solids slurries such as thickener under-
flows with 25 to 35% solids. Costs are site and process dependent: no firm
estimates are available.
f. Data on leach and strength tests: Leach data are available from field
tests on flue gas cleaning waste and indicate reduced leach rates when com-
pared to raw sludges. Typically, leaching rates are reduced one to two
orders of magnitude below untreated wastes. The strength of the product is
controlled by the mixing ratios, but the product has a dry, clay-like con-
sistency similar to compacted clayish soil.
g. Examples of past application and current contracts: Extensive experience
has been gained through contracts with several large power plants such as
the Bruce Mansfield Power Station in Shippingport, PA, the Duquesne Light
Company Phillips Power Station, and Allegheny Power Service Company's
Pleasants Station. Current coal waste applications are at several large
American Electric Power Company mines and at smaller independent operations
in Ohio and West Virginia. Ongoing tests are being conducted with several
uranium producers in the western United States under a Department of Energy
contract.
"Calcilox" is a registered trademark of Dravo Lime Co.
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a. Name of Vendor: Environmental Technology Corporation
Suite 200
1517 Woodruff Street
Pittsburgh, PA 15220
Contact: Albert R. Kupsiec, Vice President
(412) 431-8586
b. Category of fixing process: The ETC Solidification System requires com-
monly available reagents in addition to the lime which is currently used in
wastewater processes. The hazardous wastes are neutralized and solidified
resulting in a sludge which totally encapsulates the moisture and chemically
binds heavy metals and other chemicals within the sludge.
Lime is required to neutralize the acidity of the hazardous waste and to
complex most of the heavy metal cations as insoluble hydroxides. Chemistry
of the reagents is well known, but before now they had not been used in a
single system. One of the reagent acts as an ion exchange media for complete
heavy metal removal and removes excess water within the system. The other
reagents act as binders which bridge the sludge particles and increases the
physical strength and load-bearing capacity of the final sludge. The final
sludge produced is soil-like in appearance.
c. Types of waste treated: The hazardous wastes involved in the development
of the ETC system are mostly spent pickling acids from steel mills. Sulphu-
ric acid composes the largest amount of wastes by volume. Other types of
wastes treated include (1) hydrochloric acids; (2) other pickling acids;
(3) spent plating solutions; (4) sludge from industrial waste treatment
plants; (5) scrubber sludges; and (6) organic sludges.
d. Types of waste excluded from treatment: None listed.
e. Approximate cost of processing: Cost of neutralizing and solidification
of waste pickle liquors varies with the method of mixing and type of lime
used. Treatment with dry lime followed by ETC reagents costs one cent per
liter. Addition of lime as a slurry increases the amount of the other re-
agents required so that the costs rise. Other sludges can be stabilized at
costs of 0.40 cents to 3.00 cents per liter.
f. Data on leach and strength tests: Leach tests were conducted in the open
in lined, V-shaped trenches fixed with perforated plastic pipe which directed
all leached liquid into plastic collection buckets. After about one month
the leachate from 10 different sludges had from 1000-5000 mg/1 total dis-
solved solids, 500-800 mg/1 SO^ and 150-600 mg/1 Cl. Analysis for heavy
metals showed less than 0.01 mg/1 of nickel, zinc, iron, chromium and manga-
nese. Only copper was present at 0.03-0.04 mg/1 levels. Hardness (i.e.
physical strength) is a function of the total amount of solids present and
the quantity of reagents added.
g. Examples of past applications and current contracts: None reported.
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a. Name of Vendor: Envirotech
3000 Sand Hill Road
Menlo Park, CA 94205
Contact: David L. Keaton, Vice-President
NOTE: For information on treatment of S02 sludges contact:
Walter Renburg, Jr.
Air Group/Pittsburgh
Envirotech Corporation
Two Airport Office Park
400 Rouser Road
Pittsburgh, PA 15108
b. Category of fixing process: The process is sodium silicate and cement-
based. (U. S. Patent 3,837,872) Envirotech is the exclusive licensee in
the field of fixed treatment units for National Environmental Control, Inc.
(parent company of Chemfix Corporation).
c. Types of waste treated: Details available from company.
d. Types of waste excluded from treatment: Details available from company.
e. Approximate costs of processing: Figures available from company.
f. Data on leach and strength tests: Can be obtained from company.
g. Examples of past applications and current contracts: Contact company
directly.
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a. Name of Vendor: Hittman Nuclear and Development Corporation
9190 Red Branch Road
Columbia, MD 21045
Contact: Charles W. Mallory
Vice President, Engineering
(301) 730-7800
b. Category of fixing process: Hittman Corp. uses a variety of volume
reduction and binding techniques to produce waste containment. They have
experience with ion-exchange, carbon adsorption, evaporation, and incin-
eration with cement, gypsum and organic binders (such as Dow binder).
Selected chemical additives are used with binders to ensure waste retention.
c. Types of wastes treated: Hittman has had experience with radioactive
waste including aqueous solutions, sludges, filter media, oils, and organic
liquids.
d. Type of waste excluded from treatment: None encountered.
e. Approximate cost of processing: This is application dependent and must
be determined on a case-by-case basis.
f. Leach and strength tests: Representative data are available from the
vendor.
g. Examples of past applications and current contracts: Hittman Corp.
operates solidification/stabilization services for 15 to 20 nuclear power
plants across the United States.
80
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a. Name of Vendor: I. U. Conversion Systems, Inc.
115 Gibraltar Road
Horsham, PA 19044
Contact: Norman F. O'Leary, Vice President, Marketing; or
Richard W. Patton, Industrial Sales Manager
(215) 441-5920
b. Category of fixing process. The IUCS Poz-0- Tec process utilizes fly ash
and other additives. The Poz-0-Tec chemistry is a combination of two simul-
taneous reactions: a rapid reaction that occurs between the soluble salts
present in fly ash and the lime and alumina that is found in the fly ash
glass; and a slower pozzolanic reaction that occurs between the silica in
the fly ash and lime. The latter reaction occurs over a period of months.
c. Types of waste treated: This solidification system was developed ini-
tially for the electric utility industry for SO- scrubber sludge stabiliza-
tion. Four million tons of FGC sludge is treated by this process in a single
year.
Conversion Systems has also successfully stabilized and tested electro-
plating wastes, steel mill wastes, and chemical process wastes. Based upon
these results, the process can stabilize or encapsulate wastes having the
potential of leaching salts or heavy metals into the environment.
d. Wastes not suitable for treatment: Some organic wastes.
e. Approximate cost of fixation: Each waste must be evaluated for each
client by Conversion Systems. Several alternative methods are available
which result in somewhat different scopes of service. Preliminary cost es-
timates for processing sludges usually fall in the range of 1 to 7 cents per
liter of waste. Some parameters influencing this range are quantity to be
processed, water content, waste toxicity, equipment redundancy, desired
methods of operation and scheduling requirements.
f. Leach and strength tests: Physical and environmental properties of Poz-
0-Tec improve with time as the pozzolanic reactions proceed. The cementi-
tious reaction produces a monolithic mass of low permeability which is
subject to surface leaching only. The following is a compilation of typical
structural properties of Poz-0-Tec stabilized material:
Wet density 1360-1600 kg/nu (85-100 Ib/cu ft)
Dry density 1040-1360 kg/m (6585 Ib/cu ft)
Moisture content 2550% moisture,.,
Cohesion >95.7 x 10 N/m (>2000 Ib/sq ft)
Unconfined compressive
strength >!. x lO^N/m (>25 Ib/sq ft)
Permeability coefficient 10 to 10~ cm/sec
Allowable bearing
capacity 2.87 x 10 N/m (3 tons/sq ft)
Stable fill slope 2 horizontal to 1 vertical
Saturation incomplete
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Poz-0-Tec stabilized sludge may occupy more volume than the unstabilized
sludge, but any increase in material is offset by the weight reduction
brought about by dewatering the sludge before treatment and the greater
heights to which the fixed sludge pile can be built in the disposal area.
g. Examples of past applications and current contracts: Conversion systems
currently has contracted to fix 8 million metric tons of SO scrubber sludge
produced at eleven electric power plants in the U. S. It is also stabilizing
all wastes from an SO scrubber and water treatment plant of a large battery
manufacturer.
The company is also developing alternative disposal applications where
the physical characteristics of the fixed sludge can be used to advantage.
Poz-0-Tec stabilized materials have been used as a base in parking lot and
road beds. Cast Poz-0-Tec blocks are currently under study for use in con-
structing artificial reefs.
Poz-0-Tec is a registered trademark of I. U. Conversion Systems, Inc.
82
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a. Name of Vendor: Industrial Waste Management, Inc.
Suite 70, 340 E. 64th Street
New York, New York 10021
Contact: B. Alva Schoomer, President
(212) 355-1979
b. Category of fixing process: The Enviroclean process may utilize portland
cements or lime and pozzolans or cement and lime and pozzolans depending upon
desired results and local availability in some instances. Processed waste is
soil-like in consistency and becomes concrete-like mass. Strength continues
to develop over period of years. U.S. patent pending on process. Company
emphasis is on recycling of wastes by processing right on site into roadways,
parking lots and walkways.
c. Types waste treated: Industrial, utility and certain municipal wastes.
d. Wastes not suitable for treatment: Most organics and wastes of less than
15% solids for reasons of economics.
e. Approximate cost of fixation: $12/yd3 to $20/yd3 ($15.60 to $26.20/m3)
not including removal, hauling or final disposal. Cost will vary with in-
dividual sludge chemical composition, water content and volume to be
processed.
f. Leach and strength tests: Both leach test results and strength develop-
ment as well as permeability will vary by the chemical addition rate and the
type of sludge. ^Initial strengths in the 15 to 40 Ibs/ft range develop^
75 to 400 Ibs/ft range in 3 to 6 months typically and 300 to 700 Ibs/ft
in two years.- Permeabilities initially in the 10 to 10 cm/sec range will
reduce to 10 to 10 within one month. A 48 hr. leachate test with dis-
tilled water from a toxic metal hydroxide sludge from an etching operation
report ion concentrations below 0.5 ppm for Cu, Fe, Pb, Zn, Cr (total), PO ,
Ni and Cd.
Volume increase from addition of materials for chemical stabilization
will vary from 1.1 to 1.6 times pretreatment volume.
g. Examples of past application and current contracts: Company is currently
entering U.S. market. Past applications available directly from company.
Enviroclean is a pending service mark of Industrial Waste Management, Inc.
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a. Name of Vendor: Newport News Industrial Corp.
230 41st Street
Newport News, VA 23607
Contact: J. R. May, Manager, Radwaste Management Systems
(804) 380-7761
Newport News Industrial Corporation is primarily involved with volume
reduction and waste handling techniques for radioactive materials. They
have broad experience with producing compact wastes that are compatible with
solidifying agents such as urea-formaldehyde, water extendable polyesters
and bitumen. They are currently in the process of developing a new solidifi-
cation method applicable to hazardous chemical wastes including radwastes.
b. Category of fixing process: Not available.
c. Type of waste treated: Not available.
d. Type of waste excluded from treatment: Not available.
e. Approximate cost of processing: Not available.
f. Data on leach and strength tests: Not available.
g. Examples of past application and current contacts: Process still in
developmental stage.
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a. Name of Vendor: Polymeric Materials Section
Department of Materials Science and Engineering
Washington State University
Pullman, WA 99164
Contact: R. V. Subramanian
(509) 335-6784
NOTE: The Department of Materials Science and Engineering, Polymeric
Materials Section is not a vendor of the raw materials and equipment neces-
sary for fixation, but has extensive experience and developmental expertise
in the polyester encapsulation of hazardous wastes. In cooperation with
members of the Department of Chemical Engineering, this technology has suc-
cessfully been developed through the pilot plant stage.
b. Category of fixing process: An organic polymer (polyester resin) is used
to solidify the wastes.
c. Types of waste treated: Although very broadly effective, the process
appears to be quite effective for low-level radioactive wastes, metal ion
wastes, cyanides, arsenic wastes, and some specific organic wastes such as
kepone, PCB, and some pharmaceuticals.
d. Type of waste excluded from treatment: The process is not effective on
very highly acidic sludges (especially at pH less than 1.0).
e. Approximate cost of processing: The price of polyester resin is about
$1.00/kg (45 cents/lb). Since the maximum volume fraction of close-packed
spheres is 74%, the minimum amount of resin which must be added to the waste
is about 25% by volume. The fixed waste is usually 133% to 175% of the vol-
ume of the unfixed waste.
f. Data on leach and strength tests: Tests made using a fixed product
encapsulating 60% by weight of,a 24% sodium sulfate solution indicated com-
pressive strength of 15.0 x 10 N/m (2180 psi). Irradiation with 600 Mgad
gamma radiation actually increased the compressive strength to 20.7 x 10
N/m (3000 psi). The strength of the product is dependent upon the type,
proportion and form of waste incorporated.
The leachabilities of Co-58, Sr^85 and Cs-134 from a similar encapsulated
sodium sulfate waste were 3.2 x 10 , 3.5 x 10 , and 5.9 x 10 cm, respec-
tively over a period of 120 days. The leach curves leveled off at this value
after an initial rise in the first 20 days. Thus, the leachability, after
the initial dissolution of surface material, was practically negligible.
g. Examples of past applications and current contracts: Ontario Hydro,
Toronto, Ontario is pursuing this process for rad waste encapsulation.
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a. Name of Vendor: Sandia Laboratories
Albuquerque, NM 87115
Contact: R. L. Schwoebel, Manager
Chemistry and Materials Characterization Department
(505) 264-4309, ext. 5820
NOTE: Sandia's waste management program is wholly oriented toward sta-
bilization of radiation containing wastes (July 1975).
b. Category of fixing process: The Sandia Solidification Process project
is a feasibility study of the solidification of solid wastes. Fission prod-
ucts cations and actinides undergo ion exchange on inorganic ion exchangers
being developed at Sandia Laboratories. These ion exchangers are hydrous
oxides of Ti, Zr, Nb, Ta.
c. Type of waste treated: The process is designed for high-level radio-
active wastes such as the high level waste stream resulting from commercial
nuclear fuel reprocessing was well as caustic defense waste streams with high
salt (NaNO ) contents.
d. Type of waste excluded from treatment: The high cost of process pre-
cludes low value, low hazard wastes.
e. Approximate cost of processing: Cost estimates for continuous column
flow systems are comparable to glassification processes. Periodic batch
processing would probably be cheaper than glassification.
f. Data on leach and strength tests: The final product, subsequent to ion
exchange, could be fired to produce a ceramic product (mixed titanates and
titania) having leach rates as much as an order of magnitude lower than that
of borosilicate glass stabilized waste.
g. Examples of past applications and current contracts: Process in feasi-
bility study stage only.
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a. Name of Vendor: Sludge Fixation Technology, Inc.
227 Thorn Avenue
P. 0. Box 32
Orchard Park, NY 14127
Contact: Richard E. Valiga
(716) 662-1005
b. Category of fixing process: The Terra Crete process is a "self-cementing
process" based on the production of a cementitious material from calcium
sulfite hemihydrate or calcium sulfate. A portion of the sulfite/sulfate
sludge stream is dried and calcined to produce a cementitious agent. This
material and other additives (as needed) are introduced into the waste stream
and react to form a hard, low permeability mass from the sludge.
c. Types of waste treated: The system is primarily designed to operate with
sulfite/sulfate-based sludges produced from SO stack scrubbing operations
but is adaptable to other situations where calcium sulfite/sulfate sludges
can be obtained.
d. Types of wastes excluded from treatment: Not specified.
e. Cost of fixation: A flue gas cleaning sludge would cost between $2.00
-2.75 per ton for fixation.
f. Leach and strength tests: Data on leaching of antimony and lead-rich
flue gas cleaning sludge shows 0.01 ppm lead in the leach liquid. The un-
confined compressive strength obtained from the Terra Crete material depends
on the amounts of additive used, but data showing strengths from 9.57 x 10
N/m (200 Ibs/ft ) to 5.74 x 10 a/m (12,000 Ibs/ft ) are available. Per-
meabilities are on the order of 10 " to 10 cm/sec.
g. Examples of past applications and current contacts: None specified.
Terra Crete is a registered trademark of Sludge Fixation Technology, Inc.
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a. Name of Vendor: Southwest Research Institute
8500 Culebra Road
P. 0. Drawer 28510
San Antonio, Texas 78284
Contact: John M. Dole, Manager
Process Research & Engineering
NOTE: Southwest Research Institute (SRI) is a contract research organi-
zation and as such is not marketing processes or products.
b. Category of fixation process: Two fixation processes have been
developed:
(1) SRI has developed a thermoplastic epoxy system that combines the
better features of thermosetting epoxy system with the better features of
thermoplastic systems. Low-cost extended epoxy resins and hardeners which
are solids at ambient temperatures are heated (204°C) where they become low
viscosity liquids. They are then combined and mixed with heated fillers or
aggregates and discharged. They set instantly as thermoplastic materials
and then cure as a thermosetting material to provide the typical physical
property features of epoxy containers. These epoxy materials can be used as
coatings for other fixation processes.
(2) Three different systems using sulfur have been developed for indus-
trial sludge stabilization. These systems are: (a) a modified sulfur
process where sulfur is used as a binder for the toxic sludge to produce a
concrete-like material. Since sulfur melts at about 120°C, the sludge must
be heated and dried before processing. Because of the brittle nature of
sulfur, a modified form is usually found to be superior for concrete applica-
tions; (b) the plasticized liquid sulfur system is a new development in which
sulfur is modified to the extent that it can be used as a substitute for
asphalt; (c) the third process is sulfur impregnation. Surfur has been used
previously as an impregnation agent for concrete, gypsum, porous brick, tile
and mud block. In addition to filling the voids to reduce water absorption,
considerable strength improvements also result. This system is of use in
increasing the strength and leach resistance of sludge fixed by other methods
such as concrete admixing. Most of the sulfur composite work listed above
is still in the developmental stage.
c. Types of wastes treated: Not fully determined.
d. Wastes not suitable for treatment: Not fully determined.
e. Approximate cost of fixation: Not determined.
f. Leach and strength tests: Not yet available.
g. Examples of past applications and current contracts: Currently in de-
velopment and testing phase.
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a. Name of Vendor: Stabatrol Corporation
1402 Conshohocken Road
Norristown, PA 19401
Contact: Richard E. Valiga
(215) 279-3992
b. Category of fixing process: The Terra Tite process involves the addition
of cementitious materials to the waste sludge to produce a concrete-like
material.
c. Types of waste treated: Most industrial wastes can be treated. The
Terra Tite process has great technical flexibility.
d. Types of wastes excluded from treatment: None specified.
e. Cost of fixation: None specified.
f. Leach and strength tests: Permeabilities on the order of 10 cm/sec
are obtained. Leaching is insignificantly low. Terra^Tite^material has
shown unconfined compressive strengths up to 4.78 x 10 N/m (5 tons/sq ft).
g. Examples of past applications and current contacts: Heavy metal sludges,
50,000 tons; heavy metal salt cake, 10,000 tons; contaminated soils,
5,000 tons.
Terra Tite is a trademark of Stabatrol Corporation.
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a. Name of Vendor: Stablex Corporation
Suite 112
2 Radnor Corporation Center
Radnor, PA 19087
Contact: John Scofield
(215) 688-3131
b. Category of fixing process: The patented technology, described as
Sealosafe, involves adding two silicate-based powders to the waste which is
dissolved or dispersed in water thereby producing a slurry and the slurry
sets into a rigid, rock-like cast. Due to its physical and chemical form,
this mass is referred to as synthetic rock.
The physical and chemical interactions which take place simultaneously
are referred to as the mechanism of crystal capture. Up to ten additional
ingredients are also used, depending upon the type of waste to be treated,
to enable the crystal capture mechanism to operate under optimum conditions.
c. Types of wastes treated: The process is suitable for:
(1) All inorganic wastes.
(2) Organic wastes which can be homogenously incorporated into an
aqueous phase either by dissolution, suspension, or absorption.
(3) Wastes in (1) or (2) above in liquid, solid, or sludge form, includ-
ing contaminated articles such as filter cartridges, clothing, rubber boots,
etc.
(4) The process is exceptionally successful in treating all heavy
metals, arsenic, mercury and asbestos. The process also deals with anionic
wastes such as fluoride, chloride, etc.
d. Wastes not suitable for treatment: The process is not suitable for
solidification of:
(1) Oils, solvents, and greases which are not miscible with an aqueous
phase.
(2) Very large quantities of water with minimal amounts of toxic
ingredients.
e. Approximate cost of fixation: In typical applications one ton of waste
would yield 1.15 to 1.4 tons of end product, called Stablex. The volume
increase in this weight increase is between 5% and 10%.
Precise cost estimates are not possible because of the different prop-
erties of the wastes to be treated. Experience indicates an extremely broad
range of between $5.00 to $350.00 per ton depending upon the type, quantity
and complexity of the waste involved.
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f. Leach and strength tests: Extensive experience and information is
provided by the company. The product, Stablex, is 10 times less permeable
than concrete. Leaching tests in which fixed samples are ground to a fine
powder and totally immersed and wetted in ten-times their weight of dis-
tilled water for one hour indicate that very little material is lost to the
water. One example using a solid waste fixed by the process and hardened for
three days (and containing 39,000 ppm copper, 46,000 ppm zinc, and 42,000 ppm
chromium) lost less than one ppm of these toxicants. The product, Stablex,
has an unconfined compressive strength about equal to that of the grouts used
for void filling and soil stabilization but much lower than concretes and
mortars.
g. Examples of past applications and current contracts: A treatment center
near Birmingham in the United Kingdom has a current throughput of 200,000
tons of waste per year (its capacity will be increased from 70,000 tons per
year in 1978). Another treatment center near London, U.K., was commissioned
in 1978 with a capacity of 400,000 tons per year. Both plants operate as
regional treatment plants handling a variety of wastes from different
sources. Construction of two plants in Japan and the first plant in the
U. S. has been scheduled to begin in 1979.
The Sealosafe Service includes a process protected by patents and patent ap-
plications in the United States and overseas and Sealosafe and Stablex are
trademarks of the Stablex Group of Companies.
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a. Name of Vendor: TJK, Inc.
7407 Fulton Avenue
North Hollywood, CA 91605
Contact: Masaaki Endo, General Manager
(213) 875-0410
NOTE: This company has contracted to market the Takenaka Sludge Treat-
ment (TST) System (Takenaka Komuten Co., Osaka, Japan) in the U. S. Studies
conducted by EPA on Kepone and arsenic disposal problems are now underway.
b. Category of fixing process: Hardeners are principally cement-family or
cement-based materials. In addition, special additives are used for sta-
bilizing harmful substances. Several series of hardeners are used depending
upon the specific mud or sludge to be treated.
c. Type of waste treated: The TST system is a technique for solidifying
mud of comparatively high water content or sludge discharged from factories
and plants. It transforms the material into a form easy to handle for uti-
lization in land reclamation and pollutant control. Treatable material can
be widely dispersed, settled sludge or sludge obtained directly from the
factory or plant. In the case of sludges with toxic substances such as
mercury, chromium and cadmium, TST treatment stabilizes and chemically fixes
these harmful substances.
d. Types of waste excluded from treatment: Two types of sludges tested but
found unsuitable are sludge produced from a wool scouring plant (greater than
20% fats and oils) and sludges containing large amounts of paints wastes.
e. Approximate cost of processing: Costs of processing will, of course,
vary with the type of sludge and additives required but will run from about
$10/m ($8/yd ) to $20/m ($16/yd ). These estimates do not include trans-
portation or disposal. Volume increase upon treatment is from 1.05 to 1.15
times pretreatment volume.
f. Data on leach and strength tests: Extensive leach testing has been
carried out by the company. In their standard leach test, the treated sludge
is ground to a particle size between 0.5 mm and 5 mm. This powder is then
mixed with distilled water and adjusted to pH of between 5.8 and 6.3 with
HC1 or C02. The final mixture (100 ml) is 10% (weight/volume) sludge to
water. This mixture is stirred for 6 hours at room temperature and 1 atmo-
sphere and then filtered or centrifuged before analysis. Results of tests
made with a wide variety of sludges and muds containing a wide variety of
toxic metal ions show that only low levels of pollutants are released even
in this relatively severe leaching test. (Ions reported and their maximum
allowable concentrations: Alkyl-Hg and Hg, no detectable; Cd, 0.3 mg/1; Pb,
3 mg/1; organic-P, 1 mg/1; Cr , 1.5 mg/1; As, 1.5 mg/1 and CN, 1 mg/1.)
Unconfined compressive strength varies widely with the type of sludge
and kind and amount of additives used, but values of 5-10 x 10 N/m are not
unusual with 20% (w/v) additives.
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g. Examples of past applications and current contracts: Twenty-six projects
have been completed since 1973. Seventeen projects involved deposits under
water (46,000 m ), seven involved factory discharges (14,500 m ) . In the
majority of these projects toxic substances were successfully contained.
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a. Name of Vendor: Teledyne Energy Systems, Inc.
110 West Timonium Rd.
Timonium, MD 21093
Contact: William E. Osmeyer, Product Manager
(301) 252-8220
b. Category of fixing process: The company sells cement, asphalt, and
organic polymer solidification (Dow licensee) systems primarily for the
nuclear industry.
c. Types of waste treated: Company has extensive experience with nuclear
wastes, both in solidification and disposal. Details are available from the
company.
d. Types of waste excluded from treatment: Consult company directly.
e. Cost of fixation: Information available from company.
f. Leach and strength test: Details on testing with radwastes available.
g. Examples of past applications and current contracts: Available directly
from company.
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a. Name of Vendor: Todd Shipyards Corporation
Research and Technical Division
P. 0. Box 1600
Galveston, Texas 77553
Contact: C. E. Winters, Jr., Sales/Marketing Representative
(800) 2312868/2869 (713) 744-7141
b. Category of fixing process: The organic polymer product called "Safe-T-
Set", is a non-toxic, non-hazardous, powdered, thixotropic thickner which is
effective with concentrated wastes as well as liquids. Safe-T-Set solidifies
into a homogenous mix with no liquid displacement. It is not a urea-
formaldehyde formulation.
c. Types of waste treated: This product was designed specifically for in-
dustrial radioactive waste sludges. Tests have not been made with general
industrial wastes at this time (Dec 1978).
d. Type of waste excluded from treatment: No extensive tests have been
made.
e. Approximate cost of processing: Costs will vary with the amount of addi-
tive used to solidify the mass. Typical data given by the company indicate
that 6 to 20% Safe-T-Set are typical and give hardening time of 14 to 3 min-
utes respectively at 21°C. The cost of Safe-T-Set is approximately $6.60/kg
in 500 kg quantities (4/77). Additive costs (at 10%) would be approximately
$600 per ton of fixed waste.
f. Data on leach and strength tests supplied by the company: Extensive
leaching and strength tests are reported by the company. These tests were
conducted with simulated radioactive wastes and were designed to prove that
Safe-T-Set, when mixed with radioactive liquid waste, would minimize activity
release if container integrity was lost during transportation or after dis-
posal by burial. Nine tests were performed: Escape of radioactive material
through Safe-T-Set and soil, temperature cycle test, immersion study of pH
dependance, pH of fixation, immersion study at pH 7.0, off gas study, sta-
bility when innoculated with bacteria, irradiation and toxicity.
g. Examples of past applications and current contracts: No information
available.
Safe-T-Set is a trademark of Todd Shipyards Corp.
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a. Name of Vendor: TRW Systems Group
One Space Park
Redondo Beach, CA 90278
Contact: H. R. Lubowltz, Staff Scientist
(213) 535-4321
NOTE; TRW Company has done extensive testing, development and evaluation
on fixation technology for the EPA. Data below was taken from Recommended
Methods of Reduction, Neutralization Recovery or Disposal of Hazardous Waste
by Burk, Derham, and Lubowitz of TRW, USEPA contract #68-03-0089, 21 June
1974, and Lubowitz and others, 1977, Development of a Polymeric Cementing
and Encapsulating Process for Managing Hazardous Wastes, EPA-600/2-77-045.
b. Category of fixing process: The two types of fixation additives which
were selected for best overall potential and then studied and tested exten-
sively were:
(1) Inorganic cements: Type 2 Portland cement, plaster of paris
(calcium sulfate hemihydrate) and lime (pure calcium oxide).
(2) Polybutadiene resins of specific stereo configurations (atactic 1,
2-polybutadiene).
All fixation techniques were tested with and without jackets of both thermo-
plastic and thermosetting resins and asphalt.
c. Types of waste treated: All types of solid wastes and sludges were felt
to be treatable, but the specific wastes treated in this study were simulated
solid wastes and sludges containing compounds of six toxic elements: arsenic,
mercury, selenium, chromium, cadmium, and lead.
d. Wastes not suitable for treatment: None given.
e. Approximate cost or processing: Process design and economics were
covered extensively in the study. Details of the design and economics of
both the organic and inorganic encapsulation processes, cost benefit analysis
and a summary of results were included. Raw material cost was the factor
most affecting the process costs and was a primary consideration in the
original selection of the fixation processes.
f. Data on leach and strength tests: Extensive tests were made and results
are available. Tests made included: mechanical testing, determination of
bulk density, surface hardness, and compressive strength; microscopic exam-
ination of the interface between fixed specimen and the coating and leaching
experiments using three leaching solutions (distilled water, saturated car-
bonic acid of pH 3.8 to 4.0, and O.lM sodium sesquicarbonate solution).
Leaching was conducted at room temperature in 750 ml of leaching solution
which was mildly agitated twice per day.
g. Examples of past applications and current contracts: Not available.
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a. Name of Vendor: Werner and Pfleiderer Corp.
160 Hopper Ave.
Waldwick, NJ 07463
Contact: John Stewart or Richard Doyle
(201) 6528600
NOTE: Werner and Pfleiderer Corporation manufactures equipment for in-
corporating low and intermediate level radwastes into a bitumen or plastic
matrix. Their equipment and their techniques have been used in almost all
testing of bitumen encapsulation of hazardous industrial wastes.
b. Category of fixing process: The technique used is bitumen encapsulation
or incorporation using a screw extruder.
c. Types of wastes treated: No industrial wastes are currently being sta-
bilized by asphalt encapsulation but, testing of asphalt encapsulated
arsenical wastes has been undertaken by the U. S. Environmental Protection
Agency.
d. Types of wastes excluded from treatment: Sludges containing strong
oxidizers such as nitrates, chlorates, perchlorates and persulfates should
not be encapsulated in asphalt. Sludge containing borates may require
special handling because they tend to cause early hardening of asphalt
materials. Salts that swell excessively on rehydration may require special
processing.
e. Cost: Not available for industrial wastes at this time. Usually wastes
are mixed on 1-to-l weight ratio asphalt to dry wastes. Asphalt of suitable
grade for blending cost 13 to 35 cents per kg. Capital, operating expenses
are presently not available for non-radioactive disposal operations. The
cost of secondary containers (55-gallon steel drums) must also be added in.
f. Leach and strength tests: According to information furnished by the
company, leach rates 100 times less than those observed with comparable
cement mix can be expected. If the microdispersed salt/asphalt mix is coated
with as little as 5 mm (0.2 in.) of pure asphalt the leach rate was zero in
distilled water over a period of two and one-half years. Strength test data
are not obtained for asphaltic mixes as there are plastic solids that are
usually placed in steel containers.
g. Examples of past applications and current contracts: Full scale radwaste
encapsulation units are in operation at Marcoule, France and Karlsruhe, West
Germany. No one is presently using similar equipment in industrial waste
processing.
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APPENDIX B
PROPOSED UNIFORM LEACH PROCEDURE
B.I BACKGROUND
The leachability of a solidified waste can be considered to be a physi-
cal property of the material much like specific gravity or unconfined com-
pressive strength. As such, the leaching characteristics of the solid can
be measured to a high degree of accuracy using uniform or "standard" leach-
ing procedures. Uniform methodology is needed because leachability is
specific for the species being leached, the composition and rate of flow (or
replacement time) of the leaching medium, and other details of the leaching
vessel and procedure. The procedure proposed is analogous to those used to
determine other physical and/or chemical properties in that environmental
and long-term factors which might effect the property are not taken into
account.
Consideration of the leaching characteristics of a solidified waste
material is also best separated from any environmental factors which might
be encountered at the disposal site, and from the attributes of any packag-
ing or jacketing material. For most purposes, the single most important
characteristic of the waste solid itself is the rate at which it will lose
constituents to the environment, and particularly, to contacting waters—
i.e. its leachability. For this reason, a wide array of "standard" leach
tests have been derived for specific waste products and/or conditions which
have little commonality or theoretical basis. Comparison of results from
different leach testing procedures is difficult or impossible.
The Uniform Leach Procedure (ULP) presented here is proposed as a prac-
tical, reproducible, and rapid test which will provide data that can be used
to compare directly the leaching characteristics, different solidified waste
products, and/or to give a quantification of the leaching property of dif-
ferent production runs of the same treatment process for quality assurance.
It is not proposed to assess parameters which might be significant at spe-
cific waste disposal sites or for single samples of individual waste
solidication/stabilization processes. No attempt is made to mimic the
actual conditions that the waste might encounter upon shallow burial or
other disposal activity. No accelerating conditions, such as caustic leach-
ing media or elevated temperatures are used. The ULP is designed only to
give a quantitiatve and comparable measure of the waste solid's leachabil-
ity. It is similar in conception, practice, and interpreation to the Inter-
national Atomic Energy Agency standard leach test proposed originally in
1971(C-4) and to its subsequent modifications, such as the "Standard on
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Leachability of Solidified Radioactive Waste" being developed by the Ameri-
can Nuclear Society Working Group ANS-16.1 (0. U. Anders, personal
communication).
The long-term leaching rate is strongly influenced by many factors such
as the occurrence of chemical reactions between the leaching fluid consti-
tuents (such as dissolved C02 or oxygen) and the surface of the solid,
changes in the leachate pH and erosion, corrosion, or product spalling or
cracking. These factors which present the greatest difficulty to the pre-
diction of the long-term stability of the treated waste product cannot be
approached by short-term leaching tests and require long-term, site-specific
laboratory or field studies to determine. For specific situations, the ULP
can be run in conjunction with leaching tests which incorporate site or
process specific parameters such as leaching medium composition, temperature
changes, time and numbers of elutions, ratio of leaching medium volume to
weight of waste, etc. Results of these site-specific, specialized leach
tests, when compared to the uniform test results, will serve to estimate the
degree to which the particular disposal conditions will affect the release
of contaminants from the treated wastes—i.e. their leachability. Such
leach procedure results, thus "calibrated", can be used to monitor the con-
tinued effectiveness of the treatment process or variations of it, over the
permit period.
The products of all common solidification/stabilization processes can
be evaluated using the Uniform Leach Procedure. Wastes treated with cement,
lime or flyash, asphalt or other organic binders such as urea-formaldehyde
resin and other plastics, or glass and ceramic materials and their com-
posites can be evaluated using the ULP and the results compared directly
with each other.
B.2 THEORETICAL BASIS OF THE UNIFORM LEACH PROCEDURE
Several mechanisms which are responsible for the loss of constituents
from solid masses have been identified and described in various studies of
leaching behavior of solid materials (B-l to B-7). An early effect in any
leach test is an initial "wash-off" of small particulates adhering to the
surface of the test speciman in which the concentrations of most potential
contaminants are usually very high. After this phase, the concentration of
contaminant species in the leachate is determined either by their maximum
solubility in the leaching medium or by their rate of diffusion to the sur-
face of the solid where solution can take place. The ULP incorporates both
an initial rinse or "wash-off" and a relatively short-term (14 day) static
leaching test. Results are evaluated using solution or diffusion kinetic
theory.
The initial "wash-off" portion of the test produces a measure of the
amount of material on the surface of the solidified material which is not
incorporated into the solid matrix and is thus immediately available to the
leaching medium. This aspect of the leaching of treated waste products is
ignored altogether in most test procedures or simply lumped together with
the initial leachate samples. However, it represents a serious problem to
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the interpretation of the leaching test results. The "wash-off" material is
also a separate problem from the longer term loss of contaminants. The
amount of "wash off" material often can be modified directly by attention to
mold design or curing techniques. Solidified products which have extremely
high "wash-off" contaminant levels may be refused or rejected on this ground
alone. The ULP allows airblasting of the product surface prior to testing,
these high initial values must represent a highly mobile surface deposit.
An initial leach rate which is lower than can be explained by diffusion or
solution theory may be due to factors such as a delay in filling of any
surface voids in the specimen or the presence of a surface film or other
passive surface phenomenon which delays surface "wetting" or interaction
of the surface with the leaching medium.
Solubility limited constituents in the leachate samples typically
follow a pattern in which their concentration remains relatively constant at
or near the maximum solubility of the constituent in the leaching solution.
In this case, the amount of the constituent available to the leaching solu-
tion at the surface of the solid is greater, or is replaced more rapidly,
than it is removed by solution in the leaching medium. Solubility limited
leach rates or leaching kinetics are often found for major constituents in
the waste or matrix material. Such is the case for calcium and sulfate ions
in flue gas cleaning sludges or in many high sulfate industrial sludges
which are neutralized with lime. Constituents present in low concentration
in the waste but which have low solubility can also exhibit solubility
limited leaching kinetics. For example, many heavy metals have constant
leach rates in leaching tests made with alkaline, treated or untreated,
industrial sludges (B-6). Minor variations in the pH, temperature, or
presence of other competing ions in the leaching medium can cause rapid and
erratic concentration changes of solubility limited leachate constituents by
causing major changes in the solubility of the leaching species. Depletion
of the low solubility constituents from the surface of the solidified waste
will cause a change to internal diffusion-limited kinetics.
Those constituents which have solubility in the leaching medium higher
than their availability for solution at the surface of the solid matrix show
leaching kinetics which are described by classical diffusion theory—the
rate of their appearance at, and solution from, the surface being dependent
upon the rate of their diffusion from inside the matrix of the solidified
waste to the surface. These internal diffusion-limited leachate constitu-
ents have high initial concentrations which decrease over time due to the
depletion of the constituent in the surface layers of the solid matrix.
Solution of the mass transport equations for diffusion of a constituent
from a semi-infinite medium (the waste-containing solid) has been shown to
give the following expression (B-2):
h
£A 9C / D
n = 2S I e
A V \ 7T
o ^
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where
LA = total amount lost in (n) leaching periods, mg
n
A = initial amount in specimen, mg
o
t = lapsed time to (n) sample, sec
2
S = exposed surface area, cm
3
V = volume, cm
2
D = effective diffusivity (or diffusion coefficient), cm /sec
e
Equation (1) upon rearrangement yields:
/ZA (V) \2
M
-------
where
At -
A = amount of constituent lost in leaching period (n), mg
At = duration of (n) leachate renewal period, sec
t /2 = elapsed time at middle of (n)leachate renewal period, sec
Solving Equation (3) for the diffusion coefficient, D , yields:
D
t -
At
(4)
For specimens which have high initial "wash-off" levels of the leaching
species, a correction for the initial amount can be made by either leaving
that value out of the accumulated fraction leached or by using the
relationship:
A
(5)
Where (A /A ) is the fractional amount of the constituent lost in the
initial rapid "wash-off" operation. Use of- the incremental mass loss
(Equations 3 and 4) will also alleviate problems with high or low initial
losses.
The amount of the species of interest leached (referred to as £A /A
or A /A ) is dependent upon both the shape and the size of the leaching
specimen. To compare between leach tests using differently shaped and sized
waste solids, the equations for the amount leached incorporate the speci- „
men's surface to volume ratio (S/V). Thus, the values of surface area (cm )
and volume (cm ) must be known accurately so that meaningful comparisons of
the data can be made.
B.3 THE LEACH TEST PROCEDURE
The ULP intentionally prescribes a detailed protocol to be followed
explicitly as to leaching medium composition, leachate renewal frequencies,
and other test conditions such as temperature and pressure. The major pur-
pose of the ULP is to determine the effective diffusivity of the solidified
material as supplied for comparative or quality assurance purposes. Other
testing conditions and leaching medium compositions may be required to more
nearly represent anticipated conditions under which the specific waste may
be disposed; but such tests are not part of the ULP as proposed here. The
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ULP is designed to be accomplished as reproducibly, and as simply and
quickly as possible.
Specimen Preparation
The waste to be solidified should be thoroughly mixed to assure a rep-
resentative sample is used and should undergo preparative treatment as close
to that experienced by the actual treated waste product as possible. Core
drilling of large waste forms may be used to prevent edge effects in the
small molds or disparity in treatment techniques due to scaling effects.
The solid specimen must have a defined and known size and shape (such as a
monolithic cylinder, parallelepiped or sphere). Cylinders must have
diameter-to-length ratios, and parallelpipeds a minimum thickness-to-length
ratios, of from 0.2 to 5. A cylindrical shape is preferred. The minimum
dimension in any direction is 1 cm. All details of solidification, casting,
curing, and storage conditions and containers shall be reported.
The surface of the specimen must be smooth, without voids, and homo-
geneous so that the calculated surface area approximates the true surface
exposed to the leaching medium. The surface should not be washed or wetted
before testing but may be air blasted to remove lose particles and dust.
Leaching Test Vessel
No specific vessel shape or dimensions are required, but the following
points must be noted. The vessel must be nonreactive with respect to the
leachate and the waste test specimen and must not adsorb species of interest
during the leaching test. It must prevent excessive evaporation of leachate.
The geometry of the vessel must allow all of the external surface of the
specimen to be exposed to the leaching medium using the volume of leachate
specified below and to have sufficient free space to allow handling of the
leachate and the test specimen. Sufficient space must be available in the
vessel so that the test specimen is surrounded on all sides by leaching
medium at a depth equal to or greater than the smallest specimen dimension.
A support for the test specimen to rest upon must be provided in the vessel;
it must not interfere with leachate addition or removal, cause damage to the
specimen, or cover more than 2% of the surface of the specimen.
Leaching Medium
The leaching medium used in all Uniform Leach Procedures is deminera-
lized water with an electrical conductivity of less than 10 mho/cm at 25°C
and a total organic carbon content of less than 5 ppm. The leaching medium
should be equilibrated with air so that it is saturated with respect to
oxygen and carbon dioxide, and has a pH of between 4 and 5.5.
The volume of leaching medium used for each leaching interval shall be
related to the surface area of the specimen by the following relationship:
3 2
leaching medium (cm )/surface area (cm ) = 10.0
This ratio was selected as a compromise between having sufficient
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volume to minimize leachate changes and solubility limits during the short
leachate-renewal intervals and having a small enough volume to produce
measurable changes in concentrations of the leached species analyzed.
Test Procedures
Initial Rinse—
An initial rinse or "wash-off" of the test specimen shall be made be-
fore the actual leaching is begun. The specimen is immersed in one leachate
volume (see above) for 30 seconds, then removed and placed in the leaching
vessel. This initial rinse volume is analyzed for all constituents of
interest. The analytical results are presented in the report section.
Changing the Leaching Medium—
The following procedure should be followed at the end of each leaching
interval. The leachate should be removed from the leaching vessel, divided
into necessary aliquots and preserved for analysis. The leachate should be
stirred to suspend any particulates before sample splits are made since the
analyses to be made should include particulate as well as dissolved mate-
rials. Precipitation which occurs in the leachate during the leaching
interval must also be included in the analyses. The leachate should not be
filtered to remove particulates. In some cases, the leachate will have to
be acidified to make representative samples.
The leaching vessel (but not the test sample) should be rinsed in
demineralized water to remove all traces of the previous leachate. The test
specimen should be exposed to the air for as short a time as possible; in no
case shall its surface be allow to dry. The leaching medium (demineralized
water) for the next leach interval is then added and the apparatus left for
the next time interval. The leachate is not agitated or stirred during the
leaching interval.
An alternative method which may be employed if practical is to remove
the test specimen from the leaching vessel and to quickly place it in a new,
freshly.rinsed leaching vessel. Care should be taken to not scar or scratch
the specimen surface (or to drop it) during the operation. In all cases the
leachate should be preserved and analyzed as soon as possible.
Leachate Replacement Frequency—
Since the length of the time intervals between leachate renewal will
affect the rate of constituent release (B-l, B-2) and therefore the diffu-
sion coefficient found, a uniform replacement schedule is required. The
leachate shall be replaced completely after cumulative leaching times of 2,
7, and 24 hours after initiation of the test. Further leachate replacements
are to be made at 24 hour intervals for the next 4 days and then at 72 hour
intervals for the next 9 days which completes the ULP testing for that speci-
men. This procedure gives 10 data points—three in the first 24 hours, 7 in
the first 5 days—to evaluate the leaching characteristic of the solidified
waste product. The procedure is completed in 14 days.
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B.4 ORGANIZATION AND PRESENTATION OF THE RESULTS
The results of the ULP include all of the details of the procedure as
actually used so that adequate comparisons can be made with the results of
ULP tests performed on other materials made by other treatment processes or
at different times. The following list includes the principal information
required. Items should be reported in the order that they appear below.
a. Waste description; The type and source of waste, its percent
solids, and its composition in mg/kg dry solids of all constituents of
interest should be presented in as much detail as practical.
b. Treatment description; The type and composition of the solidifi-
cation reagents including all additives; proportion of waste solids and
treatment reagents and additives in the final solid waste product (on a
weight/weight basis) should be included. Any deviations from standard
preparation methods must be given.
c. Test specimen preparation; The method of specimen preparation
should include mold type and releasers used, or coring procedures. The
shape, mass, and accurate dimensions of the actual leaching specimen, the
history of the specimen between preparation and leaching including time
since preparation, temperature during curing, humidity during curing and
storage, container(s) used, and any other relevant information should also
be reported.
d. Leaching test procedures; For each leaching interval—report time
to nearest minute and date of beginning and end of interval, electrical con-
ductivity and temperature of leachate removed and of the new leaching medium.
The volume of leaching medium used, and treatment of aliquots made up and
preserved for analysis must be reported.
e. Integrity of test specimen; Appearance of the surface of the speci-
men before and after leaching; observed changes in shape or dimensions, and
nature and description of any particulates or precipitates in the leachate
must be included in the formal test results.
f. Analytical results; Tables must be prepared that include the con-
centration (in mg/f) of each constituent of interest (see below) present in
each leachate sample including the initial rinse, the amount of each con-
stituent in each leachate sample (multiply the concentration in mg/f times
leachate volume in t to give mass in mg), the fraction of the constituent
present in the test specimen which has been leached in each sample, and the
accumulated mass and fraction leached in the composite leachate samples and
in the initial rinse, and the accumulated masses corrected for the volume-
to-surface area ratio for comparison purposes, (ZA /A ) (V/S).
n o
g. Diffusion coefficient (effective diffusivity); The diffusion coef-
ficient (D ) as computed by any of the methods and equations given above, or
any description of the variation in D if no single value can be logically
calculated must be presented in the test results.
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B.5 INTERPRETATION OF RESULTS OF ULP
After the initial removal of mobile surface constituents in the rinse
procedure, the early leach rates observed with solidified waste products
most often fit kinetics best explained by internal diffusion within the
solid matrix. Other mechanisms such as erosion, spalling, corrosion, or
dissolution are not usually important until longer leaching periods have
elapsed. Until about 20% of a leachable species has been lost from a uni-
form, regular shaped solid, its leaching behavior when diffusion controlled
approximates that for a semi-infinite medium (B-l).
The mean value of the 10 diffusion coefficients (D ) calculated from
the 10 leaching intervals (Equation 4, above) is the experimental value best
describing the leaching properties of the waste solid. Ranges in values
calculated for the diffusion coefficient using this technique which are
greater than about 25% are considered to be excessive. In cases where vari-
ation of D is large, another specimen should be tested or other explana-
tions, sucn as solubility limitations or high initial values, be pursued.
Another test of the validity of the data set can be made by comparing the
mean of the first five D values with the mean of the last five values; if
these means vary more than about 5%, the data should be considered as biased
and further tests made to verify the bias.
If single-parameter diffusion is the only leaching mechanism, the
solidified waste is homogeneous and stable over the test period, then the
diffusion coefficient has specific meaning. Using it, the rate of loss of
the constituent in question can be predicted from large waste form under
similar conditions and long-term movement of the constituent in the waste
mass can be estimated. However, these theoretically derived models of
simple, internal diffusion hold exactly only when:
a. The leaching medium is continuously moving and does not change in
composition or character significantly.
b. The solidified waste material is homogenous and remains chemically
and physically unchanged, and its surface is smooth and does not deteriorate
with time.
c. The leachable species is rapidly mobilized by the leaching medium
so that bulk diffusion is the limiting process.
d. No chemical interactions between the leaching species and the
leaching medium, the matrix, or other leaching constituents occur.
e. The leaching species is present in but one chemical and physical
form.
Surface irregularities and roughness, swelling, fissuring, surface
deterioration, and chemical or physical breakdown of the matrix material all
will increase the rate of loss of the leaching species. Irregular or
stagnant leachate flow which allows build up of the concentration of the
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leaching species in the leaching medium, curing or chemical changes which
influence the diffusivity in the matrix, or the presence of inhomogeneous
portions of the matrix all tend to retard the leaching loss. The effective
diffusivity should be considered a purely material property of the waste
solid like density or heat capacity. Knowledge of its value is important to
the prediction of the leaching properties of the waste solid, but its use
required judgment and a thorough knowledge of other parameters of the waste
material and the environment to which it will be subjected.
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REFERENCES
B-l. Anders, 0. U., J. F. Bartel, and S. J. Altschuler. Determination of
Leachability of Solids. Analytical Chemistry. 50:564-569. 1978.
B-2. Godbee, H. W. and D. S. Joy. Assessment of the Loss of Radioactive
Isotopes from Waste Solids to the Environment. Part 1: Background
and Theory. ORNL-TM-4333. Oak Ridge National Laboratory, Oak Ridge,
TN. February, 1974.
B-3. Godbee, H. W. et al. Application of Mass Transport Theory to the
Leaching of Radionuclides from Waste Solids. Nuclear and Chemical
Waste Management. 1:29-35. 1980.
B-4. International Atomic Energy Agency. Leach Testing of Immobilized
Radioactive Waste Solids, A Proposal for a New Standard Method. In:
Atomic Energy Review, Vol 9, pp. 195-207. E. D. Hespe, Ed. 1971.
B-5. Johnson, J. C. and R. L. Lancione. Assessment of Processes to Stabi-
lize Arsenic-Laden Wastes, pp. 181-186. In: Disposal of Hazardous
Waste. EPA-600/9-80-010. Environmental Protection Agency, Cincinnati,
OH. March, 1980.
B-6. Jones, L. W. and P. G. Malone. Physical Properties and Leach Testing
of Solidified/Stabilized Flue Gas Cleaning Wastes. U. S. Environmental
Protection Agency, Cincinatti, OH. (in press).
B-7. Moore, J. G., H. W. Godbee, and A. J. Kibbey. Leach Behavior of Hydro-
fracture Grout Incorporating Radioactive Wastes. Nuclear Technology.
32-39-52. January, 1977.
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GLOSSARY
NOTE: The following terms are defined as in the Environmental Protec-
tion Agency, Rules and Regulations: Hazardous Waste Management System
which appeared in the Federal Register on May 19, 1980; Vol 45, pages 33073-
33076.
Definitions of terms not officially published in EPA regulations but
germane to this manual (such as solidification, fixation, etc.) are dis-
cussed in Section 1.2.
aquifer: a geologic formation, group of formations, or part of a formation
capable of yielding a significant amount of groundwater to wells or
springs.
confined aquifer: an aquifer bounded above and below by impermeable beds or
by beds of distinctly lower permeability than that of the aquifer
itself; an aquifer containing confined groundwater.
container: any portable device in which a material is stored, transported,
treated, disposed of, or otherwise handled.
contingency plan: a document setting out an organized, planned, and coordi-
nated course of action to be followed in case of a fire, explosion, or
release of hazardous waste or hazardous waste constituents which could
threaten human health or the environment.
designated facility: a hazardous waste treatment, storage, or disposal
facility which has recieved an EPA permit (or a facility with interim
status) in accordance with the requirements of 40 CFR Parts 122 and
124, or a permit from a State authorized in accordance with Part 123.
dike: an embankment or ridge of either natural or man-made materials used
to prevent the movement of liquids, sludges, solids, or other materials.
discharge (or hazardous waste discharge): the accidental or intentional
spilling, leaking, pumping, pouring, emitting, emptying, or dumping of
hazardous waste into or on any land or water.
disposal: the discharge, deposit, injection, dumping, spilling, leaking, or
placing of any solid waste or hazardous waste into or on any land or
water so that such solid waste or hazardous waste or any constituent
thereof may enter the environment or be emitted into the air or dis-
charged into any waters, including ground waters.
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disposal facility: a facility or part of a facility at which hazardous
waste is intentionally placed into or on any land or water, and at
which waste will remain after closure.
existing hazardous waste management facility: a facility which was in op-
eration, or for which construction had commenced, on or before October
21, 1976. Construction had commenced if:
(i) The owner or operator has obtained all necessary Federal,
State, and local preconstruction approvals or permits; and
either
(ii)(a) A continuous physical, on-site construction program has
begun, or
(b) The owner or operator has entered into contractual
obligations—which cannot be cancelled or modified without
substantial loss-for construction of the facility to be
completed within a reasonable time.
facility: all contiguous land, and structures, other appurtenances, and
improvements on the land, used for treating, storing, or disposing of
hazardous waste. A facility may consist of several treatment, storage,
or disposal operational units (e.g., one or more landfills, surface
impoundments, or combinations of them).
food-chain crops: tobacco, crops grown for human consumption, and crops
grown for feed for animals whose products are consumed by humans.
freeboard: the vertical distance between the top of a tank or surface im-
poundment dike, and the surface of the waste confined therein.
free liquids: liquids which readily separate from the solid portion of a
waste under ambient temperature and pressure.
generator: any person, by site, whose act or process produces hazardous
waste identified or listed in EPA regulations.
groundwater: water below the land surface in a zone of saturation.
incinerator: an enclosed device using controlled flame combustion, the
primary purpose of which is to thermally break down hazardous waste.
Examples of incinerators are rotary kiln, fluidized bed, and liquid
injection incinerators.
incompatible waste: a hazardous waste which is unsuitable for:
(i) Placement in a particular device or facility because it may
cause corrosion or decay of containment materials (e.g.,
container inner liners or tank walls); or
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(ii) Commingling with another waste or material under uncontrolled
conditions because the commingling might produce heat or
pressure, fire or explosion, violent reaction, toxic dusts,
mists, fumes, or gases, or flammable fumes or gases.
individual generation site: the contiguous site at or on which one or more
hazardous wastes are generated. An individual generation site, such as
a large manufacturing plant, may have one or more sources hazardous
waste but is considered a single or individual generation site if the
site or property is contiguous.
in operation: refers to a facility which is treating, storing, or disposing
of hazardous waste.
injection well: a well into which fluids are injected. (See also "under-
ground injection.")
inner liner: a continuous layer of material placed inside a tank or con-
tainer which protects the construction materials of the tank or con-
tainer from the contained waste or reagents used to treat the waste.
landfill: a disposal facility or part of a facility where hazardous waste
is place in or on land and which is not a land treatment facility, a
surface impoundment, or an infection well.
landfill cell: a discrete volume of a hazardous waste landfill which uses a
liner to provide isolation of wastes from adjacent cells or wastes.
Examples of landfill cells are trenches and pits.
land treatment facility: a facility or part of a facility at which hazard-
ous waste is applied onto or incorporated into the soil surface; such
facilities are disposal facilities if the waste will remain after
closure.
leachate: any liquid, including any suspended components in the liquid,
that has percolated through or drained from hazardous waste.
liner: a continuous layer of natural or man-made materials, beneath or on
the sides of a surface impoundment, landfill, or landfill cell, which
restricts the downward or lateral escape of hazardous waste, hazardous
waste constituents, or leachate.
hazardous waste management: the systematic control of the collection,
source separation, storage, transportation, processing, treatment,
recovery, and disposal of hazardous waste.
manifest: the shipping document originated and signed by the generator
which contains the information required by EPA regulations.
manifest document number: the serially increasing number assigned to the
manifest by the generator for recording and reporting purposes.
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mining overburden returned to the mine site: any material overlying an
economic mineral deposit which is removed to gain access to that de-
posit and is then used for reclamation of a surface mine.
movement: that hazardous waste transported to a facility in an individual
vehicle.
new hazardous waste management facility: a facility which began operation,
or for which construction commenced after October 21, 1976. (See also
"Existing hazardous waste management facility.")
on—site: the same or geographically contiguous property which may be divided
by public or private right-of-way, provided the entrance and exit be-
tween the properties is at a cross-roads intersection, and access is by
crossing as opposed to going along, the right-of-way. Non-contiguous
properties owned by the same person but connected by a right-of-way
which he controls and to which the public does not have access, is also
considered on-site property.
open burning: the combustion of any material without the following charac-
teristics:
(i) Control of combustion air to maintain adequate temperature
for efficient combustion.
(ii) Containment of the combustion-reaction in an enclosed device
to provide sufficient residence time and mixing for complete
combustion, and
(iii) Control of emission of the gaseous combustion products.
(See also "incineration" and "thermal treatment.")
operator: the person responsible for the overall operation of a facility.
owner: the person who owns a facility or part of a facility.
personnel (or facility personnel): all persons who work at, or oversee the
operations of, a hazardous waste facility, and whose actions may result
in noncompliance.
pile: any noncontainerized accumulation of solid, nonflowing hazardous
waste that is used for treatment or storage.
point source: any discernible, confined, and discrete conveyance, includ-
ing, but not limited to any pipe, ditch, channel, tunnel, conduit,
well, discrete fissure, container, rolling stock, concentrated animal
feeding operation, or vessel or other floating craft, from which pol-
lutants are or may be discharged. This term does not include return
flows from irrigated agriculture.
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publicly owned treatment works (or POTW): any device or system used in the
treatment (including recycling and reclamation) of municipal sewage or
industrial wastes of a liquid nature which is owned by a State or munic-
ipality. This definition included sewers, pipes, or other conveyances
only if they convey wastewater to a POTW providing treatment.
representative sample: a sample of a universe or whole (e.g., waste pile,
lagoon, ground water) which can be expected to exhibit the average
properties of the universe or whole.
run-off: any rainwater, leachate, or other liquid that drains over land
from any part of a facility.
run-on: any rainwater, leachate, or other liquid that drains over land onto
any part of a facility.
saturated zone (or "zone of saturation"): that part of the earth's crust in
which all voids are filled with water.
sludge: any solid, semisolid, or liquid waste generated from a municipal,
commercial, or industrial wastewater treatment plant, water supply
treatment plant, or air pollution control facility exclusive of the
treated effluent from a wastewater treatment plant.
storage: the holdings of hazardous waste for a temporary period, at the end
of which the hazardous waste is treated, disposed of, or stored
elsewhere.
surface impoundment (or impoundment): a facility or part of a facility
which is a natural topographic depression, man-made excavation, or
diked area formed primarily of earthen materials (although it may be
lined with man-made materials), which is designed to hold an accumula-
tion of liquid wastes or wastes containing free liquids, and which is
not an injection well. Examples of surface impoundments are holding,
storage, settling, and aeration pits, ponds, and lagoons.
tank: a stationary device, designed to contain an accumulation of hazardous
waste which is constructed primarily of non-earthen materials (e.g.,
wood, concrete, steel, plastic) which provide structural support.
thermal treatment: the treatment of hazardous waste in a device which uses
elevated temperatures as the primary means to change the chemical,
physical, or biological character or composition of the hazardous
waste. Examples of thermal treatment processes are incineration,
molten salt, pyrolysis, calcination, wet air oxidation, and microwave
discharge. (See also "incinerator" and "open burning.")
totally enclosed treatment facility: a facility for the treatment of haz-
ardous waste which is directly connected to an industrial production
process and which is constructed and operated in a manner which pre-
vents the release of any hazardous waste or any constituent thereof
113
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into the environment during treatment. An example is a pipe in which
waste acid is neutralized.
transportation: the movement of hazardous waste by air, rail, highway, or
water.
transporter: a person engaged in the offsite transportation of hazardous
waste by air, rail, highway, or water.
treatment: any method, technique, or process, including neutralization,
designed to change the physical, chemical, or biological character or
composition of any hazardous waste so as to neutralize such waste, or
so as to recover energy or material resources from the waste, or so as
to render such waste non-hazardous, or less hazardous; safer to trans-
port, store, or dispose of; or amenable for recovery, amenable for
storage, or reduced in volume.
underground injection: the subsurface emplacement of fluids through a
bored, drilled or driven well; or through a dug well, where the depth
of the dug well is greater than the largest surface dimension. (See
also "injection well.")
unsaturated zone (or zone of aeration): the zone between the land surface
and the water table.
well: any shaft or pit dug or bored into the earth, generally of a cylin-
drical form, and often walled with bricks or tubing to prevent the
earth from caving in.
;.':•,« Agency
*U.S. GOVERNMENT PRINTING OFFICE: 1982 0-361-082/320 1 14
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