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APPROVAL DATE:
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ORIGINATING OFFICE: office of solid Waste
STATUS: 'A
REFERENCE (other documenU):
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OSWER Policy Directive 39487.00-2A
PROHIBITION ON THE PLACEMENT OF BULK LIQUID
HAZARDOUS WASTE IN LANDFILLS -
-STATUTORY INTERPRETIVE GUIDANCE-
March 31, 1986
U.S. Environmental Protection Agency
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OSWER Policy Directive 39487.00-2A
TABLE OF CONTENTS
Section 1 - Introduction 1-1
Section 2 - Statutory Requirements 2-1
Bulk Liquid Hazardous Wastes Prohibited 2-1
Use of Absorbents 2-3
Location of Mixing Facility.; 2-6
Section 3 - Guidance 3-1
General Guidance 3-1
Absorbents 3-3
Treatment Technoloqies 3-6
Liquid-Solid Separation Processer 3-6
Biological Treatment 3-7
Thermal Treatment 3-8
Chemical Treatment 3-8
Test Methods 3-11
Time Factor 3-19
Implementation 3-20
References 3-21
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OSWER Policy Directive //9487.00-2A
LIST OF EXHIBITS
Exhibit 1 - Bulk Liquids Testing Procedures 3-12
Exhibit 2 - Compressive Strength Data 3-16
Exhibit 3 - Unconfined Compressive Strength of Stabilized .... 3-18
Soils
11
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for Review
Date
Informat on
Prohibition on the Disposal of Bulk Liquid Hazardous Waste in Landfills
Statutory Interpretive Guidance
Summary ot Directive
This document was written in order to provide guidance to owners and operators
of hazardous waste landfills who dispose of bulk liquid hazardous wastes.
•Hie document addresses Section 3004(c)(1) of RCRA. The document will
ensure that owners and operators will understand the legal requirements of
the provision along with the technical requirements.
Key Words:
Hazardous waste Landfills, Bulk Liquids, Chemical Stabilization, & Absorption
Type of Directive {Manual. Policy Directive. Announcement, etc.I
Guidance Manual
' Status
I
D Draft
ED Final
D New
L_l Revision
Does- this Directive Supersede Previous Directives;' | | Yes K I No Does It Supplement Previous DirtctivMsl' | | Y«s fX| No
K "Yes" to Either Question. What Directive (number, title!
Review Plan
uD AA-OSWER
E?OSW
D OUST
03 OWPE
LM Regions
OECM
OGC
I_J
Oiner (Specify/
This Request Meets OSWER Directives System Format
Signature o) Lead Office Directives Officer
i Date
Signature of OSWER Directives Officer
TOate
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OSWER Policy Directive //9487.00-2A
UNITED STATES ENVIRONMENTAL PROTECTION AGENCY
WASHINGTON, D.C. 20460
MAY I !9Sc
MEMORANDUM
OFFICE OF
SOLID WASTE AND EMERGENCY RESPONSE
SUBJECT: Statutory Interpretive Guidance—Treatment of
Bulk Liquid Hazardous Wastes
FROM: Marcia E. Williams, Director
Office of Solid Waste (WH-562
TO: J. Winston Porter
Assistant Administrator (WH-562A)
I am submitting for .your approval the attached guidance
document for the bulk liquid hazardous waste provision of the
Hazardous and Solid Waste Amendments (HSWA) of 1984. The
guidance discusses methods for the treatment of bulk liquid
hazardous wastes.
In March, 1985, the Regions, States, and members of the
regulated community were given an opportunity to comment on
our first draft of this guidance. On May 9, 1985, we distributed
a redraft that incorporated those comments received. This
final version of the guidance is necessary to further clarify
the distinction between the terms "absorption" and "adsorption"
and to provide an objective test and criteria to distinguish
between a chemical stabilization process and a process that is
solely physical treatment by a sorbent.
Also attached is a memorandum for you to transmit this
guidance for Red Border and OMB review, so that we can notice
it in the Federal Register. Paul Cassidy, in the Land Disposal
Branch, can respond to any technical questions that your staff
may have on the guidance. He can be reached at 382-4682.
Attachments
cc: John P. Lehman
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OSWER Policy Directive //9487.00-2A
UNITED STATES ENVIRONMENTAL PROTECTION AGENCY
WASHINGTON, D.C. 20460
MAY 91986
OFFICE OF
SOLID WASTE AND EMERGENCY RESPONSE
MEMORANDUM
SUBJECT: Submission of Statutory Interpretive Guidance for
Red Border and OMB Review—Treatment of Bulk Liquid
.^Hazardous Wastes
FROM:
Assistant Administrator (WH-562A)
TO: Milton Russell, Assistant Administrator
for Policy, Planning, and Evaluation (PM-219)
I am submitting for Red Border and OMB review the attached-
guidance concerning the bulk liquid hazardous waste provision
(Section 3004(c)(D) of the Hazardous and Solid Waste Amendments
(HSWA) of 1984. The guidance discusses methods for the treat-
ment of bulk liquid hazardous wastes, and addresses the legal
requirements of the provision.
BACKGROUND
The provision prohibits the placement of bulk liquid
hazardous wastes in landfills (whether or not absorbents have
been added) after May 8, 1985. Congress was particularly
concerned with the use of materials that function solely as
absorbents as a treatment method for bulk liquid hazardous
wastes. Congress was concerned with absorbents because they
may release the absorbed liquid back to the environment. The
legislative history to this provision suggests that processes
such as chemical stabilization that, unlike absorbents, render
liquids permanently unavailable to the environment, should be
deemed appropriate forms of pretreatment for liquid hazardous
wastes.
CONTENT OF GUIDANCE
The guidance lists the following acceptable forms of
treatment for bulk liquid hazardous wastes. These treatment
methods are not meant to be all inclusive.
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OSWER Policy Directive //9487.00-2A
1. Liquid-Solid Separation Processes
a. sedimentation or decanting
b. flotation
c. filtration
d. centrifugation
e. evaporation
f. distillation
2. Chemical Treatment
a. chemical stabilization
3. Biological Treatment
a. activated sludge systems
b. trickling filters
4. Thermal Treatment
a. liquid injection incineration
b. rotary kiln incineration
The guidance provides a definition for the terms "absorbent"
and "'adsorbent." "Absorbent" is defined in the guidance, as a
material that is capable of holding a liquid throughout the
body of the absorbing material. In an absorbent, the liquid
penetrates into the inner structure of the absorbing material.
"Adsorption" is a process where the liquid adheres to the
surface of the adsorbing material. Adsorption is the result of
intermolecular attractive forces between the adsorbent and the
adsorbed liquid. The intermolecular forces of attraction are
normally weak, and the phenomenon is therefore readily reversible.
In certain instances, a chemical interaction between the adsorbent
and adsorbed liquid may occur and this is called chemisorption.
The guidance specifies that neither absorption nor adsorp-
tion involves a chemical transformation of the sorbed liquid
(with the exception of chemisorption). Since Congress was
concerned with treatment methods that failed to render wastes
unavailable to the environment, the guidance states that the
ban on "absorbents" has been interpreted to include materials
that sorb wastes through either absorption or adsorption. The
guidance further lists examples-of banned sorbents.
The guidance states that the Paint Filter Liquids Test
(issued by EPA on April 30, 1985, in 50 FR 18370) must be used
to determine the presence or absence of liquids or free liquids
in a waste sample. If the waste passes the Paint Filter Liquids
Test, the material is not subject to this prohibition and can
be landfilled provided it is not prohibited because of the use
of a sorbent. If the waste fails the Paint Filter Liquids Test
(i.e., contains liquids or free liquids), additional treatment,
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OSWER Policy Directive //9A87.00-2A
consistent with this guidance, is required. After such treatment,
the waste must pass the Paint Filter Liquids Test before it is
allowed to be landfilled.
The guidance also discusses these situations: 1) a spill
of a hazardous waste, and 2) soils contaminated by a spill. A
spill of a hazardous waste is not allowed to be placed in a
landfill, in a bulk form, if a sorbent is used to clean up the
spill. We believe that the statute prohibits this type of con-
duct. On the other hand, we believe that the ban on landfilling
sorbed wastes was not intended to encompass soils contaminated
by accidental spills into the ground. Consequently, unintentionally
contaminated soils may be landfilled if the contaminated soil
(without the addition of an absorbent) passes the Paint Filter
Liquids Test.
The guidance has also been revised to include a reference
to an ASTM Unconfined Compressive Strength Test. This test
and the criteria to pass the test were developed to aid permit
writers in distinguishing between a chemical stabilization
process and a process that is solely physical treatment by a
sorbent. It is often difficult to determine whether a particular
process involves stabilization or is merely sorption. EPA
expects owners and operators to demonstrate that chemical
transformations have occurred. The owner or operator should
submit laboratory data showing that the appropriate "recipe"
has been developed. If, however, it is not apparent to the
permit writer that chemical stabilization has occurred, then
the unconfined compressive strength test is recommended as a
means of demonstrating chemical stabilization.
DEVELOPMENT OF GUIDANCE
In March, 1985, the Regions, States, and members of the
regulated community were given an opportunity to comment on
our first draft of this guidance. Twenty sets of comments
were received. The comments addressed such items as spills of
liquid wastes, the appropriate time to conduct the Paint Filter
Liquids Test, and generator certification.
On May 9, 1985, we distributed a redraft that incorporated
those comments previously received. The May 9, 1985, redraft
was also submitted to Red Border for review. During Red Border
review, we received comments that addressed the need for a clearer
discussion concerning the technology of chemical stabilization.
We also received comments concerning our definitions of the
terms "absorbent" and "adsorbent", and our guidance language
dealing with the spill of a waste vs. the spill of a product.
All of these areas of concern have been addressed through the
work group process.
This guidance was also developed through the work group on
bulk liquid hazardous wastes, which had representatives from
the following offices: Office of General Counsel, Office of
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OSWER Policy Directive //9487.00-2A
Policy Analysis, Office of Enforcement and Compliance Monitoring,
Office of Waste Programs Enforcement, and Office of Solid Waste.
Attachment
cc: Marcia Williams
Gene Lucero
Henry Longest
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OSWER Policy Directive //9487.00-2A
SECTION I
INTRODUCTION
On November 8, 1984, the Hazardous and Solid Waste Amendments
of 1984 were signed into law. Section 3004 (c)(l) addresses
bulk liquid hazardous waste in landfills. This provision
states that:
Effective 6 months after the date of enactment of the
Hazardous and Solid Waste Amendments of 1984, the
placement of bulk or noncontainerized liquid hazardous
waste or free liquids contained in hazardous waste
(whether or not absorbents have been added) in any
landfill is prohibited.
The bulk liquid hazardous waste provision became effective
on May 8, 1985. The Agency is issuing this guidance to
ensure that owners and operators of hazardous waste landfills
regulated under the Resource Conservation and Recovery Act
understand the legal requirements of this provision (presented
in Section 2 of this guidance) and to provide technical
guidance that will aid owners or operators in complying with
the provision (presented in Section 3 of this guidance).
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OSWER Policy Directive //9487.00-2A
SECTION 2
STATUTORY REQUIREMENTS
BULK LIQUID HAZARDOUS WASTES PROHIBITED
.Section 3004 (c)(l) calls for an absolute ban after May 8, 1985,
on the placement of bulk or non-containerized liquid hazardous
waste or free.liquids contained in hazardous waste in any
landfill that is subject to regulation under Subpart N of 40
CFR Parts 264 and 265. The intent of the provision is to
prohibit the direct placement of bulk liquid hazardous wastes into
landfills, regardless of the presence of liners or leachate
collection and removal systems. The statute makes it clear
that the ban encompasses bulk hazardous waste containing
free liquids even if.absorbents have been added.
The Agency interprets the ban on "placement" of bulk liquid
hazardous wastes to include, but not be limited to: 1) placing
bulk liquid hazardous wastes into any part of the active
landfill unit where the liquids are solidified and then
transferred to another part of the active landfill unit,
and 2) placing treated bulk liquid hazardous wastes still in
liquid form into a landfill cell prior to solidification.
The legislative history of a related statutory provision,
section 3004(b) (banning the placement of liquid hazardous
waste in salt domes, underground mines, or caves) supports the
view that Congress intended the ban on "placement" to be
construed broadly to prohibit storage of material while
awaiting further treatment or disposal, and to preclude use
of such locations as treatment chambers (129 Cong. Rec.
H8141 (daily ed. Oct. 6, 1983)). Thus, the ban is effective
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regardless of the purpose of placing the liquids into a
landfill.
In order to comply with this provision, the owner or operator
must determine whether a bulk hazardous waste (i.e., non-contain-
erized waste) is a liquid or contains free liquids. EPA
regulations define "free liquids" as "liquids which readily
separate from the solid portion of a waste under ambient
temperature and pressure" (40 CFR Part 260.10). Congress
anticipated that EPA would specify an appropriate test for
free liquids (see Senate Report No. 284, 98th Cong., 1st
Sess. 22 (1983)). EPA believes that the Paint Filter Liquids
Test is the appropriate test method to be used to-determine
the absence or presence of free liquids in both bulk and
containerized wastes. On April 30, 1985, EPA promulgated
a final rule requiring the use of the Paint Filter Liquids Test
(Method 9095). (See 50 FR 18370.) This final rule requires
the owner or operator of a hazardous waste landfill to
use the Paint Filter Liquids Test to determine whether a
bulk hazardous waste is a liquid or contains free liquids,
if it is not obviously clear to the owner or operator that
the waste does or does not contain free liquids. "Liquids"
and "free liquids" subject to this provision include liquids
that separate out during transportation to the landfill.
If a sample passes the Paint Filter Liquids Test (i.e., no
liquid is detected), the bulk hazardous waste is not subject
to the ban in Section 3004 (c)(l) and can be landfilled
(assuming no absorbent has been added, as discussed below).
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If the sample fails the test, the bulk hazardous liquid
waste should be treated prior to landfilling using a treatment
technology that does not solely involve the use of a material that
functions primarily as an absorbent. These treatment technologies,
include, chemical stabilization processes, and are discussed
under Treatment Technologies. If, after reviewing a particular
stabilization process, it is not obvious that chemical stabilization
has taken place (i.e., if there are any concerns that "stabilization1
is occurring primarily due to the addition of sorbents),
then a representative sample of the treated waste should
pass the indirect chemical stabilization test (unconfined
compressive strength) as described under Test Method. The
purpose of using a chemical stabilization test is to help
assure that the treatment of bulk liquids has been accomplished
in a manner that does not solely involve the use of a material
that functions primarily as an absorbent.
Once it has been demonstrated, where necessary, that a
particular stabilization process used for a particular waste
will result in a treated product that passes the stabilization
test, then samples of each batch would only be required to
pass the Paint Filter Liquids Test prior to placement in the
landfill. If there are any changes in the treatment process
and/or composition of the waste to be treated, stabilization
testing should be repeated.
USE OF ABSORBENTS
A major issue raised by the language of Section 3004 (c)(l)
is the scope of the prohibition on absorbents. The Agency
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is convinced that Congress did not want materials that function
solely as absorbents to be used in the treatment of bulk
liquid hazardous wastes that are to be placed in a landfill.
If Congress had intended to allow any or a certain subset of
"acceptable" absorbents to be used in the treatment of bulk
liguid hazardous wastes, Congress would have specified this,
as it did in the provision concerning the landfilling of
containerized hazardous wastes (see Section 3004(c)(2)).
The Agency believes, however, that the term "absorbent" does
not include reagents used in: 1) any treatment technology
that involves no absorption and produces a bulk solid, or 2)
a treatment technology that chemically stabilizes, encapsulates,
or solidifies a bulk liquid hazardous waste. EPA believes that
Congress was particularly concerned about the use of materials
that function solely as absorbents as a treatment method for
bulk liquid hazardous wastes in order to force the use of
other treatment methods (see Treatment Technologies for
preferred treatment methods) and because an absorbent may
release the absorbed liquid back to the environment. (See 129 Cong.
Rec. H8141 (daily ed. Oct. 6, 1983)). The legislative history
to this provision suggests that processes, such as chemical
stabilization, which, unlike absorption, render liquids
permanently unavailable to the environment, should be deemed
appropriate forms of pretreatment of liquid hazardous wastes
(129 Cong. Rec. H8141 (daily ed. Oct. 6, 1983)). See also
130 Cong. Rec. S9177 (daily ed. July 25, 1984). Consequently,
the Agency interprets the statute to permit the landfilling
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of bulk liquid hazardous wastes that have been chemically
treated and stabilized so as to contain no free liquids.
If an absorbent material is used to clean up a spill of
hazardous waste, this mixture cannot be placed directly in a
landfill. The reason, as stated before, is that the language
of the statute makes it clear that any liquid hazardous
waste, when contained and treated solely by the use of an
absorbent, is prohibited from being placed in a landfill in
a bulk or non-containerized form. Congress did not specifically
exclude spills from the statutory prohibition. If a spill
is treated solely by the use of absorbents, the absorbed
material may be containerized and placed in a landfill (subject
to any EPA regulation relating to absorbents in containers
under Section 3004(c)(2)), placed tn a surface impoundment,
or treated in a manner consistent with this guidance.
Although spills treated with absorbents are subject to
the ban on landfilling of bulk liquid hazardous wastes to
which absorbents have been added, EPA believes that this ban
was not intended to encompass soils contaminated by accidental
spills into the ground. The Agency believes, based on the
legislative history relating to absorbents, that Congress
was primarily concerned about controlling the use of absorbents
as a waste management method. See 130 Cong. Rec. S9177
(daily ed. July 25, 1984). There is no evidence that Congress'
concern extended to banning the placement in a landfill of
soils accidentally contaminated by spills of liquid hazardous
waste. In consequence, contaminated soils will be subject
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to the same requirements as other hazardous wastes. If the
contaminated soil passes the Paint Filter Liquids Test, it
will be allowed to be landfilled. If, however, the contaminated
soil fails the Paint Filter Liquids Test, then the contaminated
soil must be subject to additional treatment as outlined in
this guidance.
LOCATION OF MIXING FACILITY
The Agency also believes that in banning the placement of
bulk liquid hazardous wastes "whether or not absorbents have
been added," Congress intended to ban the placement in a
landfill of bulk liquid hazardous wastes that are treated
with materials that function solely as absorbents, whether
or not the treatment or mixing took place inside or outside
the landfill unit. ' Congress was concerned with the consequences
of placing the absorbed liquid wastes into the landfill unit
as well as with placing free liquids in the landfill.
In some cases, the generator may have added an absorbent
to a bulk liquid hazardous waste. As noted above, the statute
bans the placement in a landfill of bulk liquid hazardous wastes
if an absorbent was added to the waste regardless of where
the absorbent was added. Therefore, EPA believes that an owner
or operator has the obligation to determine whether a generator
has added a material that functions solely as an absorbent to
a waste in order to eliminate free liquids. Owners or operators
are not in compliance with the bulk liquids provision if they
place bulk liquid mixtures with absorbents in landfills.
The Agency believes that responsibility for compliance
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with this provision rests solely with the landfill owner or
operator. In developing this approach, the Agency also
considered whether responsibility for ensuring compliance
with the bulk liquids provision should be shared jointly by the
generator and the owner or operator. For instance, if the
generators had treatment performed on the bulk liquids, the
generators would certify to landfill owners or operators that
no absorbents were used. If no treatment was performed, they
would certify that no absorbent was added to the waste. The
Agency rejected this approach because it was overly burdensome
to the generators. As is currently practiced, the off-site
landfill owner or operator may enter into a private contractual
agreement with generators regarding the use of absorbents in
wastes to be landfilled. A contractual agreement, however,
will not relieve the landfill owners or operators from their
responsibilities to ensure that absorbents were not used
in the treatment of the bulk liquids.
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OSWER Policy Directive #9487.00-2A
SECTION 3
GUIDANCE
GENERAL GUIDANCE
The goal of banning the placement of bulk liquid hazardous
wastes in landfills is to reduce the migration of liquid
wastes and hazardous constituents. To this end, the preferred
methods for managing bulk liquid hazardous wastes are: 1)
reduction in liquid waste generation by process design changes
(e.g., using less liquid or recirculating rinse water) and
by not mixing hazardous wastes with liquids, 2) recycling
and recovery (e.g., solvent extraction), 3) treatment by
destruction (e.g., incineration), 4) treatment to render the
waste or liquid fraction nonhazardous, 5) treatment by removing
liquids (e.g., decanting, centrifuge, vacuum drum or conveyor,
filter press, distillation, reverse osmosis), and 6) treatment
by mixing with agents (e.g., chemical reagents that remove
free liquids or chemically transform them into solids). [See
130 Cong. Rec. S9177 (daily ed. July 25, 1984).]
The owner or operator must use the Paint Filter Liquids Test
to determine if the bulk hazardous waste is subject to this
provision (i.e., the waste is a liquid or contains free
liquids). If a hazardous waste fails the Paint Filter Liquids
Test, it must be treated before landfilling using a treatment
technology that does not involve the use of a material that
functions solely as an absorbent. If such treatment is considered
chemical stabilization, it may be necessary for a representa-
tive sample of the treated waste to pass the chemical
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OSWER Policy Directive 09487.00-2A
stabilization test if it's not clear that stabilization
has occurred before the waste may be landfilled. A bulk
liquid that has been treated with an absorbent may also be
landfilled in a container if it does not contain free-standing
liquids (40 CFR Parts 264.314 and 265.314), subject to any
\
future EPA regulations relating to the use of absorbents in
containers.
The Agency believes that the phrase "whether or not absorbents
have been added" requires that bulk liquid hazardous wastes
intended for disposal in a landfill should first be chemically,
thermally, physically, or biologically treated without the
use of absorbents. Examples of these treatment technologies
were summarized above and are discussed further below.
Depending on the treatment technology selected, some bulk . .
liquid hazardous wastes will no longer be placed in landfills
while others will be converted to bulk solids that will then
be placed into the landfill. The treatment methods listed below
are not meant to be all inclusive. Some methods are listed because
they are alternatives to the placement of bulk liquid hazardous
wastes in landfills (i.e., not all the treatment methods are
directed toward the removal of liquids so that the bulk
hazardous liquid waste can be landfilled). Of course, the
selection of the treatment method should comply with the
guidance of this provision.
As stated above, the Agency will exclude from the definition of
"absorbent" reagents used in: 1) any treatment technology that
involves no absorption and produces a bulk solid, or 2) a
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treatment technology that chemically stabilizes, encapsulates,
or solidifies a bulk hazardous liquid. The definitions of
absorbent and chemical stabilization are presented in the
following sections.
It is also important to remember that if the treatment of bulk
liquid hazardous wastes occurs in a tank, the treatment unit
may be subject to a RCRA permit. If incineration is used,
this treatment is regulated under Part 264 or 265, Subpart
0. It is also important to remember that the selected treatment
method (e.g., mixing) must not occur within the landfill
unit.
ABSORBENTS
The Agency classifies an absorbent as a material that is
capable -of holding a liquid throughout the body of the absorbing
material. In an absorbent, the liquid penetrates into the
inner structure of the absorbing material. In many absorbents,
the volume of the absorbing material increases (i.e. swells)
as liquid is absorbed into the body of the absorbent. The
use of a material that functions primarily as an absorbent
is prohibited as a means of treatment for bulk liquid hazardous
wastes if the absorbed mixture is to be placed in a landfill.
The literature is confusing on the use of the terms absorbent
and adsorbent. While absorption relies on liquid penetration
into the inner structure (i.e., within the void spaces between
solid particles) of the material, adsorption is a process
where the liquid or gas adheres to the surface of the adsorbing
material. Adsorption is the result of intermolecular attractive
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forces between the adsorbent and the adsorbed gas or liquid.
The liquid is thus distributed over the surface of the adsorbing
material in a layer that is only one atom or molecule thick.
A material must have a high ratio of surface area to mass to
be an effective adsorbent. The intermolecular forces of
attraction are normally weak, and the phenomenon is therefore
readily reversible. In rare instances, however, a chemical
interaction between the adsorbent and the adsorbed substance
may occur. In this process, known as chemisorption, a
chemical reaction occurs resulting both in a molecular change
in the adsorbed material, and much stronger intermolecular
forces than are found with simple adsorption. This process
is addressed later in this guidance.
While the differences between absorption and adsorption
are easily defined on paper, it is much more dfficult to
determine whether a particular material acts as an absorbent
or adsorbent. Standard test methods exist for determining
the holding power of materials, but these methods do not identify
the holding mechanism (i.e. absorption or adsorption). In
reality, most materials are capable, to various extents of
holding materials by both mechanisms.
In keeping with the intent of Congress, however, it is
not important to identify if absorption, adsorption, or both
are occurring, since neither process involves a chemical
transformation or encapsulation of the sorbed liquied (with
the exception of chemisorption). Congress is concerned
about banning landfill disposal of liquid wastes that have
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not been treated in such a manner that they are permanently
unavailable to the environment. Both absorption and adsorption
are reversible, and can release the sorbed material back
into the landfill. The Agency therefore interprets the ban
on "absorbents" to include materials that sorb wastes through
either absorption or adsorption. Because of this interpretation
the Agency will simply consider adsorption and absorption
as physical processes and will thus refer to both as sortion
or sorbents. Examples of banned sorbents include vermiculite,
Fuller's earth, bentonite, fine-grained sands, shredded
paper, and sawdust. A sorbent material may, however, be
used as one of the ingredients in a chemical stabilization
process if the final product passes the unconfined compression
strength test discussed under the Test Method section, if it is '"
necessary to use such a test.
The use of a sorbent material will be considered an acceptable
treatment method for bulk hazardous liquid wastes under
appropriate conditions. The owner or operator must first
demonstrate that the individual material irreversibly binds
a particular liquid waste through a chemical reaction (i.e.
chemisorption) rather than through the weak forces of absorption
or adsorption. Chemisorption reactions are specific to the
chemical structure of both the sorbent and waste materials.
The owner or operator must therefore demonstrate that an
irreversible binding reaction has occurred for each particular
sorbent/waste combination.
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TREATMENT TECHNOLOGIES
Liquid-Solid Separation Processes
Various liquid-solid separation processes are available to
separate the liquid and solid fractions of a bulk liquid
hazardous waste. These include such operations as sedimentation
or decanting, flotation, filtration (including vacuum filtration),
centrifugation, evaporation, and distillation. Sedimentation
or decanting is the removal of solid particles suspended in a
liquid by gravity settling. Flotation involves the separation
of solids from liquids by the attachment of tiny air bubbles
to the solid particles. The solid particles with the attached
air bubbles then rise to the surface of the liquid, agglomerate
there, and are skimmed off. Filtration is the passage of
liquids through a fine mesh material that prevents the solid
material from passing. Filtration can be enhanced by stirring
and by using vacuum or pressure rather than just gravity to
cause liquid flow. Vacuum conveyors and drums can be used.
Centrifugation separates the solid and liquid components of
a waste stream by rapidly rotating the mixture in a vessel.
Evaporation is a physical separation process involving vaporization
of a liquid from a solution or a slurry. Distillation is
evaporation of the more volatile component(s) within a mixture
with subsequent condensation to recover the evaporated liquid.
Bulk liquid hazardous wastes can be subjected to such
liquid-solid separation processes, or a series of such processes
because some processes alone do not completely remove free
liquids. The solid residuals can be isolated and then tested
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for the presence of free liquids using the Paint Filter
Liquids Test. If the solids pass the test, they may be
placed into the landfill. If they fail, additional liquid-solid
separation processes (or another form of treatment) would be
required to remove or eliminate the free liquids. If the
liquid fraction isolated from the liquid-solid separation
process is a hazardous waste, it is subject to Section 3004(c)(l)
and should not be landfilled, unless one of the treatment
methods described below is employed. Regardless of whether
the waste component is solid or liquid, it is still a hazardous
waste unless it is delisted, if it is a listed waste, or no
longer meets a characteristic of a hazardous waste. The
characteristics of a hazardous waste are given in 40 CFR
Parts 261.21 - 261.24.
Biological Treatment
Owners and operators may wish to consider other alternatives to
the treatment methods described above. One alternative
could be biological treatment. Biological treatment is a
generic term applied to processes that use living microorganisms
to decompose or detoxify organic wastes into either water,
carbon dioxide, non-toxic organics, non-toxic inorganics, or
acids and bases. The principal types of conventional biological
treatment that might be useful for the treatment of bulk
liquid hazardous wastes are:
o activated sludge systems
o trickling filters
o aerated lagoons
o waste stabilization ponds
These treatment methods typically occur—in tanks or surface
3-7
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impoundments. These hazardous waste units are subject to
regulation under Subparts J and K, respectively, of 40 CFR
Parts 264 and 265.
Thermal Treatment
Another alternative is thermal treatment. The treatment of
many non-aqueous bulk hazardous liquids (e.g., solvents and
other organics) can be achieved with high temperature destruction.
The goal of thermal destruction processes is the oxidation
of hazardous waste to water, carbon dioxide, aldehydes,
acids, etc. Various thermal destruction methods can be
considered, such as:
o liquid injection incineration
o rotary kiln incinerators
o multiple hearth incinerators
Units used for such treatment are subjecJt to regulation under
Subpart 0 of 40 CFR Parts 264 and 265.
Chemical Treatment
Chemical stabilization is a method that may be used to treat
bulk hazardous liquids prior to landfilling. The majority
of the chemical stabilization techniques in use today: 1)
chemically react with the waste to transform free liquids
into solid or gel-like materials, 2) result in the production
of either a soil-like or clayey material, a thick sludge, a
monolithic block with high structural integrity, or a gel-like
material with high plasticity, and 3) have the additional
benefit of limiting one or more of the following: mobility,
solubility, and toxicity. Stabilization usually involves
the addition of materials that ensures that the liquid portion
3-8
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Df the waste is chemically transformed into a solid and that
the hazardous constituents are maintained in their least
soluble and/or least toxic form. In general, higher quantities
of stabilization additives result in a more solid product
having higher strength and greater stability.
Sorption of a liquid is not the same as chemical stabilization.
Sorption is a physical process that may often be reversed,
whereas stabilization involves a physical and chemical reaction
between the liquids and waste constituents and the stabilizing
reagents. •
Examples of the most commonly used stabilization technologies
are Portland cement-based and pozzolanic processes. The
cement-based process is especially effective for wastes with
'high levels of toxic metals,-because at the pH of the cement
mixture, most multivalent cations are precipitated as hydroxide
or carbonate minerals of very low solubility. The Portland
cement-based process is also effective in removing liquids
because the reaction of the anhydrous cement powder and
water (liquids) incorporates the water into the solid mineral
species. The reaction first produces a colloidal calcium-silicate-
hydrate gel of indefinite composition and structure. Hardening
of the cement is brought about by the interlacing of thin,
densely-packed, silicate fibrils growing from the individual
cement particles.
Waste stabilization techniques based on lime products (as
opposed to Portland cement) usually depend on the reaction
of lime with a fine-grained siliceous (pozzolanic) material
3-9
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and water to produce a solid that is sometimes referred to
as pozzolanic cement. The most common pozzolanic materials
used in waste treatment are fly ash, ground blast-furnace
slag, and cement kiln dust.
The stabilized waste product from both cement-based and
pozzolanic processes can vary in consitency from a weak
soil-like or clay-like material a hard, concrete-like mass.
The consistency depends on a variety of factors including
waste type, moisture content, organic content, and the type
and amount of stabilization additives used.
These chemical stabilization techniques require a thorough
knowledge of the chemistry of the wastes and treatment reagents.
In many cases, special proprietary reagents (usually polymers)
are added. This is often required to control the adverse
effects of organic compounds on the cementation process.
Cement and pozzolanic stabilization may be ineffective in
treating many organic compounds. The treatment must be
conducted in a well-controlled procedure that employs sophisticated
quality control/quality assurance methods. This treatment
typically occurs within specially designed vessels, using
special apparatus to control the addition and blending of
reagents. The units in which these processes occur are
typically classified as tanks; these would generally be
subject to regulation under Subpart J of 40 CFR Parts 264
and 265. These tanks could be situated in the landfill
provided that both the tank and the landfill are regulated
in accordance with applicable standards.
3-10
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TEST METHOD
Because it is often difficult to determine whether a particular
process involves stabilization, or is merely absorption, EPA
expects owners and operators using a chemical stabilization
process to demonstrate that the chemical transformations
described above occur. Laboratory data showing that an appropriate
"recipe" has been developed and used, plus a demonstration
that stabilization has occurred may be necessary in cases where
there is a question of whether a particular process actually
involves stabilization"rather than sorption. Descriptions
of the treatment apparatus and quality control methods should
als'o be available, and provided with permit applications.
To aid owners or operators in demonstrating that chemical
stabilization -has occurred, the Agency 'is recommending a
testing scheme as shown in Exhibit 1. Under this method, any
bulk hazardous waste (i.e., no sorbents added) that may contain
free liquids is subject to the Paint Filter Liquids Test.
If the waste passes the test, it is not subject to the ban
(i.e. it can be disposed in a landfill). If the waste fails
the test, it may then be treated by a chemical stabilization
process prior to landfill disposal. (NOTE: It may be determined
that one of the other waste treatment methods described in
Treatment Technologies is preferred.) If the waste is treated
using a chemical stabilization process, and if it is not
obvious that true chemical stabilization has occurred (i.e.,
if it is suspected that a material that functions solely
as a sorbent has been used), then a representative sample of
3-11
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I
BULK
HAZARDOUS
WASTE
Paint Filter
Liquids Test
Pass (no free Liquids!
(Provided no sorbents
have been added)
Landfill
Disposal
Fail (Contains Free Liquids)
Chemical Stabilization
Process
I
Confirmation of
CheraiC'. Stabiliza-
tion by State or
Regions based on data
Supplied
Unconfined Compressive
Strength Test
50 psi Minimum
Fail1
Pass
Pass
Fail
Landfill
Disposal
Alternative
Treatment
EXHIBIT 1
Bulk Liquid Testing Procedures
3-12
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the waste should then pass the chemical stabilization test
before it can be disposed in a landfill. ,
Once it has been demonstrated that a particular process used
for a particular waste will result in a treated product that
passes the stabilization test, then samples of each batch
would only be required to pass the Paint Filter Liquids Test
prior to placement in the landfill. If there are any changes
in the treatment process and/or composition of the waste to
be treated, stabilization testing should be repeated.
A wide range of tests were consider for determining if chemical
stabilization has occurred. Tests exist that determine
whether or not a chemical reaction has taken place. However,
these tests are specific to the reacting materials. The
wide range of wastes and treatment processes results in an
essentially unmanagable number of these confirmatory tests
for chemical reactions.
Rather than proposing a series of chemical analyses tests,
it is desired to have a single test method that can be used
for all types of wastes. The unconfined compressive strength
test is proposed as an indirect method for determining the
stability of treated waste products. If the owner or operator
wishes to use a different method to show that chemical stabilization
rather than sorption has occurred, this information should
be provided with the facility's Waste Management Plan (for
Interim Status Units) or the hazardous waste permit application.
As previously discussed, chemical treatment methods that
solidify liquid wastes typically result in either cemented
3-13
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masses comparable to concrete or discrete particles and low
strength mixtures such as sand, soil, weak clay, or sawdust.
The most common of these processes are cement-based and
pozzolanic processes. It is known that these reactions
produce a product having greater strength than the original
materials. Compressive strength can therefore be used as
an indirect measure of the extent of chemical stabilization
when these methods are used to treat liquid wastes.
It is highly desirable to have a single compression test
that could be used for most of these stabilized wastes,
regardless of the specific waste type or stabilization process
used. It is also desired that the test be performed with
unconfined samples. Unconfined tests can be performed only
on cohesive materials. Since the addition of sorbents generally
results in a non-cohesive product, the use of the unconfined
test will help assure that wastes treated solely by sorbents
are not placed in the landfill.
The unconfined compressive strength test should be modeled on
ASTM D2166-85, Unconfined Compressive Strength of Cohesive
Soil. The selection of the unconfined compressive strength
test, based on soil testing methodology, is aimed at the
cemented or pozzolanic class, but is very applicable to the
stiffer, less ductile plastics. A minimum allowable strength
is selected as the measure of adequate bonding. The minimum
strength recommended is 50 psi. The rationale for selecting
this value is an effort to require a bonding level in excess
of that achieved with sorbents. The electrostatic and surface
3-14
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tension bonding that is present in most of these materials
is most strongly present in very stiff clays. For comparative
purposes, the compressive strengths of a variety of materials
are shown in Exhibit 2. As shown in Exhibit 2, very stiff
clays typically have unconfined compressive strengths of 28
to 57 psi. It is felt that a compressive strength limit
nearer the high end of this range will assure that chemical
bonding, and not just absorption or adsortion, is present.
The 50 psi minimum compressive strength limit should also
assure that the1treated waste has at least as much strength
as the soil surrounding the disposal site.
The second common class of products resulting from stabilization
processes are the low strength soil-like and clay-like materials,
including cohesionless sandy products. If it is.not apparent that
the process is indeed "stabilization" then it would be necessary
to use the unconfined compressive strength test. However,
further treatment may be necessary to achieve the 50 psi limit,
however, the amount of treatment is expected to be minimal.
In an attempt to predict how easily various types of soils or
soil-like wastes could be treated to increase their unconfined
compressive strengths, the results of a series of soil-stabilization
studies are presented [8]. These studies were performed
using nine different soil types. Prior to the addition of
stabilization compounds, test specimens were molded according
to ASTM D1632-63: Standard Method of Making and Curing Soil-Cement
Compression and Flexure Test Speciments in the Laboratory.
After seven days of controlled storage, the unconfined compressive
3-15
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EXHIBIT 2. OPPRESSIVE STRENGTH DATA (PSI)
Material
BRICK
Grade SW
Grade MW
Grade NU
CERAMICS, GLASS, CARSON
Alumina Ceramics
Carbon, Coal based
Carbon, Petroleum based
Industrial Graphite
Polycrystal line Glass
Porcelain
Stoneware
Tungsten Carbide
CLAY (UNCONFINED)
Very Soft
Soft
Medium
Stiff
Very Stiff
Extremely Stiff
CONCRETE
Low Strength
Medium Strength
High Strength
METALS
Cast Iron, grey
PLASTICS AND ELASTOMERS
Acrylics, cast
Cellulose Acetate, molded
Epoxy, amine
Epoxy, general purpose
Epoxy, poly amide
Nylons
Phenolics, cast, type 1
Phenol ics, molded, general purpose
Polyester, cast, rigid
Polyester, cast, flexible
Polypropylene
Polystyrene, general purpose
Polytetraf luoroethylene (Teflon)
Si 1 icone, cast, type 1
STONE
Grani te
Limestone
Marble
Sandstone
Slate
Compressive Strength
3,000
2,500
1,500
350,000
1,700-2,400
6,300-9,000
1,900-8,500
50,000
60,000-90,000
40,000-80,000
600,000
Less than 3.6
3.6 to 7.1
7.1 to 14
14 to 28
28 to 57
Over 57
2,000
3,000-4,000
5,000
120,000
12,000-18,000
20,000
4,000
30,000
6,000
2,400-9,700
14,000-18,000
30,000
12,000-37,000
1,000-17,000
5,500-6,500
14,000
700-1,800
14,000-18,000
13,000-55,000
2,500-28,000
8,000-27,000
5,000-20,000
9,000-10,000
Reference
1
1
1
2
3
3
3
3
4
4
2
5
5
5
5
5
5
2
2
2
6
7
2
4
2
4
3
7
2
3
3
3
2
3
7
1
1
1
1
1
3-16
-------
strength of each soil type was measured according to ASTM
D1633-63: Test for Corapressive Strength of Molded Soil-Cement
Cylinders. The results, shown in Exhibit 3, indicate strengths
ranging from 26 to 56 psi. All values in Exhibit 3 are the
average of three specimens.
Samples of each of the nine soil types were then mixed with
simple stabilization compounds. Two different stabilization
additives, cement and lime, were used for each soil type.
The cement additive consisted of a blend of three brands.
The lime consisted of a blend of two brands. For each additive,
two different quantities, 3 percent and 5 percent, were
used, resulting in four different mixtures for each soil
type.
Specimens were prepared in accordance with ASTM D1632. Specimens
were molded either immediately after machine mixing of the
soil/additive blend (denoted as no compaction in Exhibit 3)
or after a 24-hour delay. During the delay, the material
was stored at 73 degrees F. Any moisture lost during the
delay was replaced. The materials were remixed prior to
molding.
The results of the unconfined compressive strength tests for
both the no-delay and 24-hour delay specimens appear in
Exhibit 3. Final strength increase, as measured against the
strength of the untreated soils, ranges from 56 percent to
1,800 percent. It is especially important to note that
small additions of either cement or lime yieldec dramatic
increases in compressive strength of soils. Increases of
3-17
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EXHIBIT 3. UNCONFINED COMPRESSIVE STRENGTHS (PSD
Soi I
Number Additive
1 None
3X Cement
3% Lime
5X Cement
5X Lime
2 None
3% Cement
3/1 Lime
5X Cement
5X Lime
3 None
3% Cement
3X Lime
5X Cement
5X Lime
4 None
. 3% Cement
3X Lime
5X Cement
5% Lime
5 None
3X Cement
3X Lime
5X Cement
SX Lime
6 None
3X Cement
3X Lime
5X Cement
5X Lime
7 None
3X Cement
3X Lime
5X Cement
5X Lime
8 None
3X Cement
3X Lime
5X Cement
5% Lime
9 None
3% Cement
3X Lime
5% Cement
5% Lime
No
7-day
Strength
56
98
76
160
120
26
316
80
445
103
29
216
89
332
115
23
210
64
323
111
41
124
78
172
95
26
234
116
405
137
37
158
149
243
172
54
114
98
174
111
38
147
131
237
175
Compact i on
28-day
Strength
..
135
128
233
190
, .
374
136
495
161
277
153
426
174
269
117
414
171
149
97
232
164
276
184
452
204
202
184
310
260
158
150
234
216
186
234
377
292
Delay
90 -day
Strength
. .
189
155
311
274
• •
• •
* -
• •
• *
::
• •
254
218
379
313
240
270
466
369
24-Hr. Compact
7-day
Strength
83
86
V35
132
243
75
270
84
179
95
256
121
.
141
58
234
98
100
81
158
93
156
88
217
101
135
174
219
198
84
103
141
145
107
118
204
202
ion Delay
28-day
Strength
128
143
207
193
324
117
371
138
•-
238
146
320
192
185
103
302
184
133
114
213
175
267
166
346
193
192
221
283
292
140
143
205
252
137
166
294
322
Source: C 3 3
»U compressive strengths are the averse of three species.
3-18
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two-fold to fourteen-fold resulted from the addition of only
3 percent cement. The unconfined compressive strengths of
the soils treated with lime also appear in Exhibit 3. These
strengths range from 76 psi to 369 psi. The strength increase,
as measured against the strength of the untreated soils,
ranges from 36 percent to 870 percent. Again, it is important
to note that the addition of only 3 percent or 5 percent
lime results in a dramatic increase in the unconfined compressive
strength.
These studies show 'that the recommended 50 psi unconfined
compressive strength limit is easily attainable for soil-like
products. The addition of minimal amounts of cement or lime
can be used. All of the soils treated with 3 percent cement
exceeded the 50 psi criteria within 7 days.— All of"the
soils treated with 3 percent lime also reached the criteria
within the 7 days. The compressive strengths of all of
the tested soils were even greater after 28 days. Changes
in product strength as a function time are further discussed in
the following section.
TIME FACTOR
The Agency knows that time is necessary for complete and
final chemical stabilization to occur. This time has been
stated to be from several hours to 7 days or more, depending
on the waste type and treatment process used. As noted
earlier, EPA interprets the statutory language as banning the
placement of treated bulk liquid hazardous wastes in a
landfill prior to the treated material passing the Paint
3-19
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Filter Liquids Test. Unconfined Compressive strength testing,
when necessary, should be performed in advance for each
waste to be treated by a particular process. This preliminary
testing will identify the acceptable cure times required for
a stabilized waste to meet the 50 psi limit.
This guidance does not contain a list of acceptable
stabilization materials because a material may be both a
sorbent and an ingredient in a stabilization process.
General technical reference information on chemical stabilization
methods is available in the Guide to the Disposal of Chemically
Stabilized and Solidified Waste (EPA, 1982). This is available
from the U.S. Government Printing Office, Washington, D.C.
20401 under stock number 055-000-00226-6, for $6.00.
IMPLEMENTATION __
Process changes at some facilities with hazardous waste
landfills may be necessary in order to comply with this
statutory prohibition. These process changes may be in the
form of additional storage or treatment units. Section
270.72 allows changes in the processes for the treatment or
storage of hazardous waste at the facility or the addition
of other units if the owner or operator submits a revised
Part A permit application to EPA (or an authorized State)
prior to such a change along with justification explaining
the need for the change and the Regional Administrator (or
the Director of the State agency in an authorized State)
approves such a change. The Regional Administrator (or the
Director of the State agency in an authorized State) may
3-20
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OSWER Policy Directive //9A87.00-2A
approve such changes because they will be necessary to comply
with this new statutory requirement.
REFERENCES
1. Baumeister, T., E.A. Avallone, and T. Baumeister III, Editors,
Marks' Standard Handbook for Mechanical Engineers,
Eighth Edition, McGraw-Hill Book Company, New
York, 1978, pp. 6-149 to 6-159.
2. Richards, C.W., Engineering Materials Science, Wadsworth Publishing
Company, Inc., Belmont, California, 1961, pp. 518-521.
3. Materials Selector 76, Materials Engineering Magazine, 82(4),
Mid-September, 1976.
4. Perry, R.H. and D.W. green, Editors, Chemical Engineers'
Handbook, Sixth Edition, McGraw-Hill Book Company,
New York, 1984, pp. 23-58 to 23-62.
5. Terzaghi, K., and R.B., Peck, Soil Mechanics in Engineering
Practice, John Wiley and Sons, New York, 1948, p. 31.
6. Popov, E.P., Mechanics of Materials, Second Edition,
Prentice Hall, Inc., Englewood Cliffs, New Jersey,
1976, page 570.
7. Perry, R.H., and C.H. Chilton, Editors, Chemical Engineers'
Handbook, Fifth Edition, McGraw-Hill Book Company,
New York, 1973, pp. 23-62.
8. Christensen, A.P., Cement Modification of Clay Soils,
Portland Cement Association, 1969.
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