United States
Environmental Protection
Agency
Hazardous Waste Engineering
Research Laboratory
Cincinnati OH 45268
EPA/540/2-86/001
June 1986
IcvEPA
Superfund
Handbook for
Stabilization/
Solidification of
Hazardous Wastes
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EPA/540/2-86/001
June 1986
HANDBOOK FOR STABILIZATION/SOLIDIFICATION OF HAZARDOUS WASTE
by
M. John Cullinane, Jr., Larry W. Jones, and Philip G. Malone
Environmental Laboratory
USAE Waterways Experiment Station
Vicksburg, MS 39180
Project Officer
Janet M. Houthoofd
Land Pollution Control Division
Hazardous Waste Engineering Research Laboratory
Cincinnati, Ohio 45268
HAZARDOUS WASTE ENGINEERING RESEARCH LABORATORY
OFFICE OF RESEARCH AND DEVELOPMENT
U.S. ENVIRONMENTAL PROTECTION AGENCY
CINCINNATI, OHIO 45268
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NOTICE
The information in this document has been funded,
wholly or in part, by the U. S. Environmental Pro-
tection Agency Under Interagency Agreement
No. AD-96-F-2-A145 with the'U.S. Army Engineer Water-.
ways Experiment Station. It has been subject to the
Agency's peer and administrative review and has been
approved for publication as an EPA document.
This handbook is intended to present information, on
the application of a technology for the control of
specific problems caused by uncontrolled waste sites.
It is not intended to address all waste site problems
or all applications of this technology. Mention of
trade names or commercial products does not constitute
endorsement,or recommendation for .use.
ii
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FOREWORD
Today's rapidly developing and changing technologies and industrial
products and practices frequently carry with them the increased generation of
solid and hazardous wastes. These materials, if improperly dealt with, can
threaten both public health and the environment. Abandoned waste sites and
accidental releases of toxic and hazardous substances to the environment also
have important environmental and public health implications. The Hazardous
Waste Engineering Research Laboratory assists in providing an authoritative
and defensible engineering basis for assessing and solving these problems.
Its products support the policies, programs and regulations of the Environ-
mental Protection Agency, the permitting and other responsibilities of State
and local governments and the needs of both large and small businesses in
handling their wastes responsibly and economically.
This report describes reagents and methodology which have been found
useful for stabilization/solidification of hazardous wastes and will be use-
ful to industrial and engineering firms which have occasion to deal with
waste handling and disposal. It should also be of value for regulatory and
environmental groups to assess the technical solutions proposed for specific
sites requiring remedial action. For further information, please contact the
Land Pollution Control Division of the Hazardous Waste Engineering
Laboratory.
Thomas R. Hauser, Director
Hazardous Waste Engineering Research Laboratory
iii
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ABSTRACT
This Handbook provides designers and reviewers of remedial action plans
for hazardous waste disposal sites with the information and general guidance
necessary to judge the feasibility of stabilization/solidification technology
for the control of pollutant migration from hazardous wastes disposed of on
land. Stabilization/ solidification is an alternative technology that must
be identified, analyzed, and evaluated in the feasibility study process.
First reviewed is the chemical basis for this technology and for commer-
cial formulations in common use (Section 2), which is followed by a detailed
discussion of waste characterization and site considerations appropriate for
treatment process evaluation (Section 3). Methods and techniques for deter-
mining the success of stabilization/solidification trials (including specific
laboratory testing and leaching protocols) are then described. This ensures
that adequate treatment specifications and required characteristics of the
final product can be included in process and permitting documentation
(Section 4). Bench- and pilot-scale testing are recommended and considered
in Section 5.
The actual processing technology used in waste stabilization projects is
quite diverse. Four stabilization/solidification scenarios are developed
that give a good cross section of the broad spectrum of handling, mixing, and
processing equipment currently in use (Section 6). Included are project se-
quencing and estimated comparative costs for treating 500,000 gallons of
waste by the four treatment alternatives. These scenarios illustrate the
strengths and weaknesses of each alternative and give guidance as to which
processing technology is most suited to specific waste types and site
conditions.
Safety, quality control, and environmental considerations also relate to
this technology (Section 7). Sampling and testing protocols for assessing
containment efficiency and uniformity are given. Final cleanup of the site
and equipment, site monitoring, and capping are also discussed as they per-
tain to treated wastes (Section 8) .
This report was submitted in fulfillment of Interagency Agreement AD-96-
F-2-A145 by the Environmental Laboratory of the U.S. Army Engineer Waterways
Experiment Station under the sponsorship of the U.S. Environmental Protection
Agency. This report covers the period of September .1982 to September 1984,
and the work was completed as of September 1984.
iv
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CONTENTS
Page
FOREWORD ...
ABSTRACT ....!!*' ll
FIGURES '. ^T
TABLES '.'.'. '
UNIT CONVERSIONS !!!!!!!!! _x
ACKNOWLEDGEMENTS '.'.'.'.'.'.'.'.'.'.'.'. xiii
1. INTRODUCTION 1-1
1.1 Background and Definitions . ! . 1-1
1.2 Purpose and Scope of this Handbook . . . . . .....! j .* '.''.'. 1-2
1.3 Regulatory Basis for Use of .......
Stabilization/Solidification . 1.4
2. BASIS OF STABILIZATION/SOLIDIFICATION TECHNOLOGY 2-1
2.1 Types of Treatment Reagents and Processes 2-2
2.2 Compatibility of Wastes and Treatment Processes 2-18
2.3 Pretreatment Techniques for Waste Solidification 2-20
3. PHYSICAL AND CHEMICAL CHARACTERIZATION OF UNTREATED
WASTES 3-1
3.1 Physical Characterization [, ^-1
3.2 Chemical Characterization ] 3.4
4. SELECTION OF STABILIZATION/SOLIDIFICATION PROCESSES 4-1
4.1 Background 4-1
4.2 Specifications for Stabilized/Solidified Wastes ...... 4-2
4.3 Example Specifications 4_9
5. BENCH- AND PILOT-SCALE TESTING OF SELECTED TREATMENT
PROCESSES 5-1
6. FULL-SCALE TREATMENT OPERATIONS 6-1
6.1 Project Planning . 6-1
6.2 Cost Analysis and Comparison 6-2
6.3 In-Drum Mixing Alternative 6-3
6.4 In-Situ Mixing Alternative 6-10
6.5 Mobile Plant Mixing Alternative .... 6-18
6.6 Area Mixing or Layering Alternative 6-31
6.7 Summary 6-36
v
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CONTENTS (continued)
Page
7. QUALITY CONTROL, SAFETY, AND ENVIRONMENTAL CONSIDERATIONS
FOR WASTE TREATMENT 7-1
7.1 Sampling of Treated Wastes ...... 7-1
7.2 Testing of Stabilized and Solidified Wastes 7-2
7.3 Safety and Environment 7-2
8. CLEANUP AND CLOSURE ... . ... . . . . . 8-1
8.1 Cleanup of Equipment . 8-1
8.2 Site Monitoring 8-1
8.3 Capping of Solidified Wastes 8~2
APPENDIX A - ACQUISITION AND COSTS OF REAGENTS . . A-l
A.I Purchase Price ........... A-l
A.2 Transportation Costs A~2
A. 3 Onsite Chemical Handling .-... A-3
A.4 Quantity and Cost of Chemicals Required A-4
APPENDIX B - TYPICAL STABILIZATION/SOLIDIFICATION EQUIPMENT .... B-l
B.I Chemical Storage Facilities B-l
B.2 Materials Handling Equipment ........ . . . . B-4
B.3 Materials Mixing Equipment ....... .... B-15
B.4 Materials Control Equipment B-25
INDEX INDEX-1
vi
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FIGURES
Number
1-1 Flowchart for Evaluation of the Stabilization/Solidification
Option 1-3
2-1 Mechanisms Retaining Water and Ionic Materials on and in
Solid Phases 2-4
2-2 Theoretical Solubilities of Selected Amphoteric Metal
Hydroxides 2-21
6-1 In-Drum Mixing Using a Top-Entering Propeller Mixer ... . . . 6-6
6-2 Typical Spill Cleanup System v . ... ...... . . . . . . . , t. 6-10
6-3 In-Situ Mixing with a Backhoe at a Large Site ... . . . . .... . 6-12
6-4 In-Situ Mixing by Direct Reagent Injection . . . , . .; . . . . 6-16
6-5 In-Situ Mixing Equipment 6-16
6-6 Schematic of Plant Mixing Scenario . 6-19
6-7 Schematic of a Trailer-Mounted Mobile Mixing Plant ...... 6-21
6-8 Schematic of a Van-Mounted Mobile Mixing Plant 6-21
6-9 Open Mobile Mixing Plant 6_22
6-10 Enclosed Mobile Mixing Plant 6-22
6-11 Drum Handling Mobile Mixing Plant 6-23
6-12 Small Modular Mixing Plant 6-23
6-13 Large Modular Mixing Plant 6-24
6-14 Modular Mixing Plant for Heavy Slurries .... 6-24
6-15 Portable Plant Mixing Followed by Drum Encapsulation 6-31
6-16 Spreading Untreated Material for Area Mixing 6-33
vii
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FIGURES (continued)
Number
6-17
6-18
A-l
B-l
B-2
B-3
B-4
B-5
B-6
B-7
B-8
B-9
B-10
B-ll
B-12
B-13
B-14
B-15
B-16
B-17
B-18
B-19
B-20
Adding Stabilizatibn/Solidif ication Reagent for Area
Mixing Waste Materials with Stabilization/Solidification
Reagents in Area Mixing
Installed Cost of Dry Chemical Storage . . . . . . . ''*> .
Installed Cost of Liquid Reagent Storage . . . .... . . .
Trailer-Mounted Centrifugal Pump . . . . . . . ' . . . .
Typical Floating Centrifugal Pump ....
Typical Costs for Pumping Systems
Typical Costs for Trailer-Mounted Concrete Pumps ......
Backhoe-Dump-truck Operation for Removal of Contaminated
Soils
Installed Portable Conveyor System Costs .....
Typical High Speed Rotary Mixer
Typical Base Stabilization Plant
Installed Cost for Base Stabilization Plant
Installed Cost for Mobile Concrete Batching Facility ....
Installed Cost for Concrete Tilting Mixers
Typical Change-Can Mixer
Installed Cost for Change-Can Mixers
Typical Ribbon Blender
Installed Cost for Ribbon Blenders
Typical Muller Mixer .
Installed Cost for Muller Mixers
Page
6-33
-34
A-4
. B-3
, B-5
. B-6
. B-7
. B-8
. B-9
. B-14
B-14
. B-16
B-16
B-17
. B-17
B-18
B-20
, B-21
B-22
B-22
. B-23
B-23
viii
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FIGURES (concluded)
Number
B-21
B-22
B-23
Page
Typical Twin Shaft Rotor Mixer . . . . . . . . . ..... . . . . . - B_24
Installed Cost for Rotor Mixers g_24
Typical Top-Entering Propeller Mixer ... B-25
B-24 Weigh Batcher System for Waste Materials Control . . B-26
B-25
B-26
B-27
Typical Screw Feeder ............... B-27
Typical Weigh Feeder System. ................. B-28
Typical Belt Scale System . . .... . . . . . . . . . . . . . E-29
ix
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TABLES
Number
2-1
2-2
2-3
2-4
2-5
2-6
2-7
3-1
4-1
4-2
6-1
6-2
6-3
6-4
6-5
Typical Physical and Chemical Properties of Commonly Used -
Natural Sorbents
Natural Sorbents and Their Capacity for Removal of Specific
Contaminants from Liquid Phases of Neutral, Basic, and
Acidic Wastes
Synthetic Sorbents Used with Hazardous Wastes
Undesirable Sorbent/Waste Reactions
Approximate Reagent Requirements for Solidification of
Various Waste Types Using Lime Fly Ash .......
Approximate Portland Cement/Fly Ash Requirements for
Solidification of Various Waste Types
Compatibility of Selected Waste Categories with Different
Stabilization/Solidification Techniques
Hazardous Waste Consistency Classification
Recommended Testing Procedures for Physical Characteristics
that Relate to Waste Settlement . . .
Example Specifications for Solidified Waste for Land
Burial
Cost Estimation for In-Drum Treatment Alternative
Cost Estimation for In-Situ Treatment Alternative
Cost Estimation for the Mobile Plant Mixing Alternative for
Pumpable Wastes (Type 1)
Cost Estimation for the Modular Plant Mixing Alternative for
Unpumpable or Solid Wastes (Type 2) ....
Cost Estimation for the Area Mixing, or Layering,
Alternative
Page
2-6
2-7
2-8
2-8
2-11
2-13
2-19
3-2
4-7
4-10
6-7
6-14
6-26
6-28
6-35
x
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TABLES (concluded)
Number
6-6
6-7
7-1
7-2
A-l
A-2
B-l
B-2
Summary Comparison of Relative Cost of Stabilization/
Solidification Alternatives
Comparison of Treatment Costs with Different Reagents.
Citations for Current OSHA Regulations Likely to be
Applicable at Land-Based Disposal Sites. . . ... .
Policies Applicable to Remedial Actions.
Typical Costs of Chemicals Used for Stabilization/
Solidification .
Specific Weights for Common Materials at Remedial Action
Sites
Typical Job Efficiency Factors
Approximate Rental Rates for Construction Equipment Used for
Stabilization/Solidification Projects . .
6-37
6-40
7-4
7-5
A-2
A-6
B-ll
B-12
xi
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UNIT CONVERSIONS
Multiply US Customary Units
Area:
Acres
Square feet
Square yards
Flow rate:
Cubic feet per second
Gallons per day
Million gallons per day
Length:
Feet
Inches
Power:
Horsepower
Pressure:
Pounds per square inch
Volume:
Cubic feet
Cubic feet
Gallons
Cubic yards
By
0.4707
0.0929
0.8361
0.0283
0.0438
3,785
0.3048
25.4
0.7457
6.895
28.3
0.0283
3.785
0.7646
To Obtain SI Units
Hectares
Square meters
Square meters
Cubic meters per second
Liters per second
Cubic meters per day
Meters
Millimeters
Kilowatts
Kilopascals
Liters
Cubic meters
Liters
Cubic meters
xii
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ACKNOWLEDGEMENTS
This Handbook was developed by the Environmental Laboratory of the U. S.
Army Engineer Waterways Experiment Station (WES) under the sponsorship of the
U. S. Environmental Protection Agency (EPA). Authors were Mr. M. John
Cullinane, Jr., Dr. Larry W. Jones, and Dr. Philip G. Malone. The Handbook
was edited by Ms. Jamie W. Leach of the WES Publications and Graphic Arts
Division.' The project was conducted under the general supervision of
Dr. John Harrison, Chief, Environmental Laboratory; Dr. Raymond L.
Montgomery, Chief, Environmental Engineering Division; and Mr. Norman
Francingues, Chief, Water Supply and Waste Treatment Group. Director of WES
during the course of this work was Col. Allen F. Grum, USA. Technical
Director was Dr. Robert W. Whalin.
Preparation of this Handbook was aided greatly by the constructive con-
tributions of the following reviewers:
Carlton Wiles
Roy Murphy
Ann Tate
Richard Stanford
Andrew T. McCord
Tom Ponder
Radha Krishnan
EPA, HWERL
EPA, OWPE
EPA, CERI
EPA, OERR
Snyder, N. Y. 14226
PEDCo. Environmental, Inc.
PEDCo. Environmental, Inc.
Janet M. Houthoofd of the Land Pollution Control Division, Hazardous Waste
Engineering Research Laboratory, was the EPA project officer.
A major part of this study included the evaluation of equipment and pro-
cesses applied to the solidification/stabilization of hazardous materials.
The information contained herein could not have been compiled without the
valuable assistance of a number of representatives from industry. The fol-
lowing industries are acknowledged for providing information and assistance:
Albert H. Halff Associates, Inc.
Consulting Engineers and Scientists
8616 Northwest Plaza Drive
Dallas, TX 75225
(214) 739-0094
American "Resources Corporation
P.O. Box 813
Valley Forge, PA 19482-0813
(215) 337-7373
Beardsley & Piper
Division of Pettibone Corp.
5501 W. Grand Avenue
Chicago, IL 60639
(312) 237-3700
BFI Waste Systems
P.O. Box 3151
Houston, TX 77001
(713) 870-7857
xiii
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Charles Ross & Son Company
710 Old Willets Path
Hauppauge, NY 11787
(516) 234-0500
Chemfix Technologies, Inc.
1675 Airline Highway
P.O. Box 1572
Kenner, LA 70063
(504) 467-2800
The Gorman-Rupp Company
305 Bowman Street
P.O. Box 1217
Mansfield, OH 44903
(419) 755-1011
Hittman Nuclear & Development
Corp.
9151 Rumsey Road
Columbia, MD 21045
(301) 730-7800
Mixing Equipment Co.,
135 Mt. Read Blvd.
P.O. Box 1370
Rochester, NY 14603
(716) 436-5550
Inc.
Rollins Environmental Services
P.O. Box 73877
Baton Rouge, LA 70807
(504) 778-1234
Soil Recovery, Inc.
101 Eisenhower Parkway
Roseland, NJ 07068
(201) 226-7330
Solidtek, Inc.
5371 Cook Road
P.O. Box 888
Morrow, GA 30260
(404) 361-6181
The Vaughan Pump Company, Inc.
364 Monte Elma Road
Montesano, WA 98563
(206) 249-402
The Vince Hagan Company
P.O. Box 5141
Dallas, TX 75222
(214) 339-7194
xiv
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SECTION 1
INTRODUCTION
1.1 Background and Definitions
The terms "stabilization" and "solidification" are used in this Handbook
as defined in the EPA publication, "Guide to the Disposal of Chemically
Stabilized and Solidified Waste" (Malone et al. 1980). Both stabilization
and solidification refer to treatment processes that are designed to
accomplish one or more of the following results: (1) improve the handling
and physical characteristics of the waste, as in the sorption of free
liquids; (2) decrease the surface area of the waste mass across which
transfer or loss of contaminants can occur; and/or (3) limit the solubility
of any hazardous constituents of the waste such as by pH adjustment or
sorption phenomena.
Stabilization techniques are generally those whose beneficial action is
primarily through limiting the solubility or mobility of the contaminants
with or without change or improvement in the physical characteristics of the
waste. Examples include the addition of lime or sulfide to a metal hydroxide
waste to precipitate the metal ions or the addition of an absorbent to an
organic waste. Stabilization usually involves adding materials which ensure
that the hazardous constituents are maintained in their least mobile or toxic
form.
Solidification implies that the beneficial results of treatment are ob-
tained primarily, but not necessarily exclusively, through the production of
a solid block of waste material which has high structural integritya prod-
uct often referred to as a "monolith." The monolith can encompass the entire
waste disposal sitecalled a "monofill"or be as small as the contents of a
steel drum. The contaminants do not necessarily interact chemically with
reagents, but are mechanically locked within the solidified matrixcalled
"microencapsulation." Contaminant loss is limited largely by decreasing the
surface area exposed to the environment and/or isolating the contaminants
from environmental influences by microencapsulating the waste particles.
Wastes can also be "macroencapsulated," that is, bonded to or surrounded by
an impervious covering. These techniques are also considered to be stabili-
zation/solidification processes.
The term "fixation" has fallen in and out of favor, but is widely used
in the waste treatment field to mean any of the stabilization/solidification
1-1
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processes as described above; "fixed" wastes are those that have been treated
in this manner.
Both solidification and chemical stabilization are usually included in
commercial processes and result in the transformation of liquids or semi-
solids into environmentally safer forms. For example, a metal-rich sludge
would be considered stabilized if it were mixed with a dry absorber such as
fly ash or dry soil. The benefits could be carried further if the sorbent
and waste were then cemented into an impermeable, monolithic block. Or a
waste would be considered chemically stabilized if the pH of the sludge were
raised by the addition of lime (Ca(OH)2) so that potential contaminants such
as toxic metals were less soluble and thus less easily leached.
1.2 Purpose and Scope of this Handbook
This Handbook provides guidance for the evaluation, selection, and use
of stabilization/solidification technology as a remedial action alternative
at uncontrolled, hazardous wastes sites. The Handbook is designed to permit
engineering personnel to proceed through concept development, determination
of design requirements, and preliminary cost estimating for selected stabili-
zation/solidification alternatives. A flow chart for evaluating considera-
tions and procedures important to the stabilization/solidification option is
shown in Figure 1-1.
The Handbook systematically reviews the technical basis for available
stabilization/solidification systems, especially those suitable for onsite
application at uncontrolled, hazardous waste sites. The general chemical
systems involved in waste stabilization/solidification are discussed to pro-
vide the background information necessary for the selection of the optimum
treatment system for a specific waste. Also described are the testing and
analysis techniques commonly used to characterize a waste to aid in the
selection of pretreatment and stabilization/solidification processes. The
compatibility of specific classes of wastes and additives, and the testing
systems needed for the evaluation of the stabilized/solidified wastes once
treated are also reviewed.
Specific materials and equipment that are used in waste stabilization/
solidification treatment and processing are discussed. Based on field
surveys, four stabilization/solidification scenarios, including costs for
materials, equipment, and operations associated with each, are developed and
compared to provide a basis for planning-level cost evaluation of the many
stabilization/solidification alternatives. Safety, environmental concerns,
and cleanup and closure of waste processing and final disposal are
considered.
1-2
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JWASTE CHARACTERIZATION
h
I SITE CONSIDERATIONS
FLAMMABILITY
CORROSIVITY
REACTIVITY
INFECTIVITY
TOXICITY
PRETREATMENT
OR
WASTE MIXING
SELECTION OF FEASIBLE
S/S OPTIONS
GEOLOGICAL AND
HYDROLOGICAL
SETTINGS
DISTANCES TO:
-SECURE LANDFILL
-ADDITIVE SOURCES
SITE MODIFICATIONS FOR
ULTIMATE DISPOSAL
-LINERS
-COVERS
-LEACHATE COLLECTION
CONSIDERATION OF REMEDIAL
ACTION ALTERNATIVES
BENCH TESTINGl
-ECONOMIC CONSIDERATIONS
-REGULATORY CONSIDERATIONS
-SOCIOLOGICAL CONSIDERATIONS
SCENARIO SELECTION AND
DEVELOPMENT OF SPECIFICATIONS
REAGENT ACQUISITION
AVAILABLE EQUIPMENT
PILOT TESTING
FULL-SCALE DESIGN
-IN DRUM
-IN SITU
-PLANT MIXING
-AREA MIXING
QUALITY CONTROL AND
QUALITY ASSURANCE
SAFETY AND ENVIRONMENT
WASTE PROCESSING AND DISPOSAL
CLEANUP AND CLOSURE
Figure 1-1. Flow chart for evaluating the stabilization/solidification
(S/S) option.
1-3
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1.3 Regulatory Basis for Use of
Stabilization/Solidification
The EPA hazardous site cleanup program, referred to as Superfund, was
authorized and established in 1980 by the enactment of the Comprehensive
Environmental Response, Compensation, and Liability Act (CERCLA), Public
Law (PL) 96-510. This legislation allows the Federal government (and cooper-
ating State governments) to respond directly to releases and threatened
releases of hazardous substances and pollutants or contaminants that may :
endanger public health or welfare or the environment. Prior to the passage
of PL 96-510, the Federal authority with respect to hazardous substances was
mostly regulatory through the Resource Conservation and Recovery Act (RCRA)
and the Clean Water Act and its predecessors. The general guidelines and
provisions for implementing CERCLA are given in the National Oil and
Hazardous Substances Contingency Plan (NCP) (Federal Register, 40 CFR 300,
1982).
Three classes of actions are available when direct government action is
called for:
a. Immediate removals are allowed when a prompt response is needed to
prevent harm to public health or welfare or to the environment.
These are short-term actions usually limited to 6 months and a total
expenditure of $1 million.
b. Planned removals are expedited, but not immediate, responses. These
are intended to limit danger or exposure that would take place if
longer term projects were implemented and responses were delayed.
c. Remedial actions are longer term activities undertaken to provide
more complete remedies. Remedial actions are generally more expen-
sive and can only be undertaken at sites appearing on the National
Priorities List of the NCP.
Remedial actions may present technically complex problems that are
expensive to resolve. The selection of technical measures takes place only
after a full evaluation of all feasible alternatives based upon economic,
engineering, environmental, public health, and institutional considerations.
Offsite transportation and disposal of waste is generally an expensive option
and is justified only when proven cost-effective, and then only in facilities
that comply with current hazardous waste disposal regulations under
Subtitle C of RCRA.
Waste stabilization is specifically included in the NCP as a method of
remedying releases of hazardous materials and controlling release of waste to
surface water. Solidification and encapsulation are mentioned as techniques
available for onsite treatment of contaminated soils and sediments. Under
the general requirement to evaluate all alternatives for remedial action, it
1-4
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will be necessary to evaluate the cost effectiveness of stabilization/
solidification systems as applied to specific sites even if the technology is
not selected in the final analysis of remedial techniques. Costs and engi-
neering considerations are critical to these evaluations.
The performance expected from stabilized/solidified waste must also be
as accurately assessed as possible. Cost estimates must take into considera-
tion future expenditures needed to maintain the final waste disposal site
after response work is complete. The NCP emphasizes the selection of reli-
able, tested remedial technologies. Examples of successful applications are
an important part of any technical evaluation.
A further goal of this Handbook is to provide data necessary for the
technical decisions required by law and for preliminary cost estimates.
Other handbooks are available to supplement this document in developing plans
for specific site activities. Overall guidance on remedial action technolo-
gies, including a survey of stabilization/solidification, is provided in a
Technology Transfer Handbook by the EPA (U.S. EPA 1985a). The decision to
implement the stabilization/solidification option must be preceded by the de-
tailed investigation of many variables. Both waste and site characteristics
must be evaluated to ensure that the stabilization/solidification alternative
is cost-effective and environmentally acceptable. The U.S. EPA (1985b,
1985c) has provided general guidance on the procedure to be followed in
selecting the most appropriate remedial actions.
1-5
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REFERENCES
Federal Register. 1982. National Oil and Hazardous Substance Contingency
Plan. (40 CFR 300), Volume 47, No. 137, July 16, 1982.
Malone, P. G., L. W. Jones, and R. J. Larson. 1980. Guide to the Disposal
of Chemically Stabilized and Solidified Waste. SW-872, Office of Water and
Waste Management, U. S. Environmental Protection Agency, Washington, D.C.
126 pp.
U.S. EPA. 1985a. Remedial Action at Waste Disposal Sites (Revised).
EPA-625/6-85-006, U.S. Environmental Protection Agency, Cincinnati, Ohio.
497 pp.
U.S. EPA. 1985b. Guidance on Feasibility Studies under CERCLA.
EPA-540/G-85-003. Office of Emergency and Remedial Response, U.S. Environ-
mental Protection Agency, Washington, D.C.
U.S. EPA. 1985c. Guidance on Remedial Investigations under CERCLA.
EPA-540/G-85-002. Office of Emergency and Remedial Response, U.S. Environ-
mental Protection Agency, Washington, D.C.
1-6
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SECTION 2
BASIS OF STABILIZATION/SOLIDIFICATION TECHNOLOGY
Stabilization processes and solidification processes have different
goals. Stabilization systems attempt to reduce the solubility or chemical
reactivity of a waste by changing its chemical state or by physical entrap-
ment (microencapsulation). Solidification systems attempt to convert the
waste into an easily handled solid with reduced hazards from volatilization,
leaching, or spillage. The two are discussed together because they have the
common purpose of improving the containment of potential pollutants in
treated wastes. Combined processes are often termed "waste fixation" or
"encapsulation."
Solidification of waste materials is widely practiced in the disposal of
radioactive waste. Many developments relating to solidification originated
in low-level radioactive waste disposal. Regulations pertaining to disposal
of radioactive waste require that the wastes be converted into a free-
standing solid with a minor amount of free water. Most processes used for
nuclear waste include a step in which granular, ion exchange waste and
liquids are incorporated in a solid matrix using a cementing or binding agent
(for example, Portland cement, organic polymers, or asphalt). The resulting
block of waste, with relatively low permeability, reduces the surface area
across which the transfer of pollutants can occur. No such requirement for
producing a free-standing solid exists for hazardous waste disposal, and
solidification usually involves only the addition of an absorbent (without a
binding agent) to produce a finely particulate waste that has no free liquid.
Waste stabilization has also been practiced in radioactive waste dis-
posal and has involved processes such as (1) selecting inert, nondegrading
sorbents that take up and retain specific radionuclides, (2) adjusting pH and
oxidation-reduction conditions in the waste to prevent waste solubilization
in ground water, and (3) using zeolites rather than biodegradable organic
polymers as ion exchange media.
In hazardous waste disposal, an effort is usually made to have the
treated waste delisted, usually by passing the EPA Extraction Procedure (EP)
leaching test. To accomplish this goal, a variety of strategies may be used
to prevent contaminant leaching, including neutralization, oxidation/
reduction, physical entrapment, chemical stabilization, and binding of the
stabilized solid into a monolith. The development of an appropriate treat-
ment strategy includes the following considerations:
a. The waste should be treated to obtain the most inert and insoluble
form chemically and economically feasible.
2-1
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b. Media should be added to absorb any free liquid present.
c. When necessary, a binding agent should also be added.
The binding agent may be selected to stabilize the waste further, for
example -the addition of alkalinity in portland cement. In cases where the
waste is extremely soluble or no suitable chemical binder can be found, the
waste may be contained by encapsulation in some hydrophobic medium, such as
asphalt or polyethylene. This may be done either by incorporating the waste
directly in the partially molten material or by forming jackets of polymeric
material around blocks of waste.
Several generic treatment systems have been developed for waste stabili-
zation and solidification, but not all have been employed in remedial action
on uncontrolled waste sites. The volumes of waste involved at uncontrolled
waste sites generally require that only the least expensive systems that are
effective be used. The large quantities and varieties of wastes that are
usually present also require the use of adaptable systems that are effective
over a wide range of conditions. The treatment systems that generally sat-
isfy these needs are the pozzolan- or Portland-cement-based systems. Inex-
pensive absorber materials such as clay, native soil, fly ash, or kiln dust
may also be added. Under specific circumstances, it may be necessary to
select other systems that offer particular advantages such as improved waste
containment or compatibility with specific wastes. This Handbook concen-
trates on the major stabilization/solidification systems that can be applied
inexpensively to a wide variety of wastes. Systems that have limited appli-
cation to mixed wastes (such as glassification or organic polymers) or sys-
tems that require specific waste materials (such as self-cementation in sul-
fate waste) are covered in other references such as Malone et al. (1980),
Malone and Jones (1979), and ladevaia and Kitchens (1980).
2.1 Types of Treatment Reagents and Processes
Most stabilization/solidification systems being marketed are proprietary
processes involving the addition of absorbents and solidifying agents to a
waste. Often the marketed process is changed to accommodate specific wastes.
Since it is not possible to discuss completely all possible modifications to
a process, discussions of most processes have to be related directly to
generic process types. The exact degree of performance observed in a spe-
cific system may vary widely from its generic type, but the general charac-
teristics of a process and its products can be discussed. Comprehensive
general discussions of waste stabilization/solidification are given in
Malone et al. (1980), Malone and Jones (1979), and ladevaia and Kitchens
(1980).
Waste stabilization/solidification systems that have potentially useful
application in remedial action activities and are discussed in detail here
include:
2-2
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a. Sorption
b. Lime-fly ash pozzolan processes
c. Pozzolan-portland cement systems
d. Thermoplastic microencapsulation
e. Macroencapsulation. ;
Other technologies such as fusing waste to a vitreous mass or using
self-cementing material are too specialized or not sufficiently field appli-
cable to be used at present (Malone et al. 1980).
Sorption involves adding a solid to soak up any liquid present, and it
may produce a soil-like material. The major use of sorption is to eliminate
all free liquid. Nonreactive, nonbiodegradable materials are most suitable
for sorption. Typical examples are activated carbon, anhydrous sodium sili-
cate, various forms of gypsum, celite, clays, expanded mica, and zeolites.
Some sorbents are pretreated to increase their activity toward specific con-
taminants and many are sold as proprietary additives in commercial processes.
Lime/fly ash pozzolanic processes use a finely divided, noncrystalline
silica in fly ash and the calcium in lime to produce low-strength cementa-
tion. The waste containment is produced by entrapping the waste in the poz-
zolan concrete matrix (microencapsulation).
Pozzolan-Portland systems use Portland cement and fly ash or other poz-
zolan materials to produce a stronger type of waste/concrete composite. The
waste containment is produced by microencapsulation in the concrete matrix.
Soluble silicates may be added to accelerate hardening and metal containment.
Thermoplastic microencapsulation involves blending fine particulate
waste with melted asphalt or other matrix. Liquid and volatile phases asso-
ciated with the wastes are driven off, and the wastes are isolated in a mass
of cooled, hardened asphalt. The material can be buried with or without a
container. .
Macroencapsulation systems contain a waste by isolating large masses of
waste using some type of jacketing material. The most carefully researched
systems use a 208-J!, drum or a polyethylene jacket fused over a monolithic
block of solidified wastes.
2.1.1 Sorption
2.1.1.1 General
Most waste materials considered for stabilization/solidification are
liquids or sludges (semisolids). To prevent the loss of drainable liquid
2-3
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and improve the handling characteristics of the waste, a dry, solid absorbent
is generally added to the waste. The sorbent may interact chemically with
the waste or may simply be wetted by the liquid part of the waste (usually
water) and retain the liquid as part of the capillary liquid. Figure 2-1
illustrates five common mechanisms by which sorbents can interact and
immobilize small, polar molecules like water or charged ions on their surface
or interstices, or react chemically to form new products.
'COORDINATED
WATER
NONCOORDINA TED
WATER
S OO
Ca ฎH2O
CHEMICALLY BOUND WATER
H20 O HYDROXYL O Mg OR Al
OH2 OOXYGEN SILICON
STRUCTURAL WATER
CAPILLARY
WATER
SOLID
PHASE-
SURFACE
WETTING
SURFACE ABSORBED
WATER
CAPILLARY WATER
OR PORE WATER
Figure 2-1. Mechanisms retaining water and ionic materials on and in
solid phases.
2-4
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The most common sorbents used with waste include soil and waste products
such as bottom ash, fly ash, or kiln dust from cement and lime manufacture.
In general, selection of sorbent materials involves trade-offs among chemical
effects, costs, and amounts required to produce a solid product suitable for
burial. Table 2-1 summarizes chemical binding properties of natural sorbents
for selected waste leach liquids. Where the ability of a sorbent to bind
particular contaminants is important to containment, sorbents with specific
chemical affinities can be selected (Table 2-2). The pH of the waste
strongly affects sorption/waste interactions, and pH control is an important
part of any sorption process.
Artificial materials have also been advocated for use as sorbents in
solidification; however, the relatively high cost of these materials has pre-
vented their widespread use. Synthetic materials have generally found use
where the binding of a specific contaminant in the waste is of paramount im-
portance. Table 2-3 lists several synthetic sorbent materials that have been
developed or tested for use with hazardous wastes.
Several major technical considerations are important in selecting a
sorbent:
a. Quantity needed to satisfy the requirement for having no free
liquid.
b. Compatibility or reactivity of the waste and the sorbent.
c. Level and character of contamination that might be introduced in the
sorbent.
d. Chemical binding properties of sorbent for specific contaminants.
The quantity of absorbent necessary for sorbing all of the liquid in a
waste to ensure that no free liquid is available varies widely depending on
the nature of the liquid phase, the original solids content of the waste, the
moisture level in the sorbent, and the availability of any chemical reactions
that take up liquids during reaction. The high degree of variability seen in
sorbents, and the changes in moisture content that can be brought about by
storage and aging of sorbents, make it necessary to test sorbent batches on a
bench scale rather than accepting specific ratios of sorbent-to-waste as con-
stant. Typically when fly ash or kiln dust is being used to sorb an oil
sludge (50% oil, 20% water), soil, fly.ash, or kiln dust ratios of 1:1
(absorbent-to-sludge) up to 2.5:1 would be satisfactory. In field practice,
extra sorbent is usually supplied. A program for testing sorbed waste for
release of free liquid should be a standard part of sorption operations.
The ideal sorbent is an inert, nondegradable, nonreactive material.
Though some sorbents are relatively inert, undesirable, or even hazardous,
reactions can occur unless attention is paid to the potential for waste and
sorbent to react. Table 2-4 lists a few of the possible reactions that
should be considered when selecting sorbents.
2-5
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TABLE 2-1. TYPICAL PHYSICAL AND CHEMICAL PROPERTIES OF
COMMONLY USED NATURAL SORBENTS
Sorbent
Cation-
exchange Anion-
Bulk capacity exchange
density (meq/100 (meq/100
(kg/m3) gms) gms)
Slurry Major mineral species
pH present
Fly ash, acidic 1187
Fly ash, basic 1187
Kiln dust
Limestone
screenings
Clay minerals
(soils)
Kaolinite
Vermiculite
Bentonite
Zeolite
641-890
1519
5-15
6-20
100-500 4
100-120
1543 100-300
4-5 Amorphous silicates,
hematite, quartz,
mullite, free carbon.
9-10 Calcite, amorphous
silicates, quartz,
hematite, mullite,
free carbon.
9-11 Calcite, quartz, lime
(CaO) anhydrite.
6-7 Calcite, dolomite.
Various (e.g., illite)
Can be relatively pure
kaolonite.
Can be relatively pure.
Smectite, quartz,
illite, gypsum,
feldspar, kaolinite,
calcite.
Zeolite (e.g.,
heulondite, laumonite,
stilbite, chabazite,
etc.)
From: Sheih (1979), Haynes and Kramer (1982), Grim and Guven (1978).
2-6
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TABLE 2-2. NATURAL SORBENTS AND THEIR CAPACITY FOR REMOVAL OF SPECIFIC
CONTAMINANTS FROM LIQUID PHASES OF NEUTRAL, BASIC, AND ACIDIC WASTES
Neutral waste Basic waste Acidic waste
(calcium fluoride) (metal finishing sludge) (petroleum sludge)
Contaminant
Ca
Cu
Mg
Zn
Ni
Zeolite
Kaolinite
(5054)* Illlte
(857) Zeolite
Kaolinite
Zeolite (8.2)
Kaolinite (6.7)
Acidic F.A.t (2.1)
Basic F.A. (155)
Illite (175)
Kaolinite (132)
Acidic F.A. (102)
Total
CN-
COD
Acidic F.A. (690)
Illite (108)
Zeolite
Kaolinite
Acidic F.A.
Zeolite
Illite
Basic F.A.
Zeolite
Illite
Acidic F.A.
Kaolinite
Illite
Illite
Acidic F.A.
Vermiculite
(1280) Zeolite (1390)
(1240) Illite (721)
(733) Kaolinite (10.5)
(85) Zeolite (5.2)
(24) Acidic F.A. (2.4)
(13) Kaolinite (0)
(1328) Zeolite (746)
(1122) Illite (110)
(176) Basic F.A. (1.7)
Zeolite (10.8)
Vermiculite (4.5)
Basic F.A. (1.7)
(13.5)
(5.1)
(3.8)
(2.6) Illite (9.3)
(2.2) Acidic F.A. (8.7)
Kaolinite (3.5)
Illite (12.1)
Vermiculite (7.6)
Acidic F.A. (2.7)
(1744) Vermiculite (6654)
(1080) Illite (4807)
(244) Acidic F.A. (3818)
* Bracket represents sorbent capacity in micrograms of contaminant removed
per gram of sorbent used. After Sheih (1979) and Chan et al. (1978).
t F.A. = fly ash.
2-7
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TABLE 2-3. SYNTHETIC SORBENTS USED WITH HAZARDOUS WASTES
Sorbent
Waste treated effectively
Activated alumina
Activated carbon
Hazorb*
Locksorbt
Imbiber beads*
Sorbs fluoride in neutral wastes
Sorbs dissolved organics
Sorbs water and organics
Oil emulsions
Inert spirits-type liquids
(cyclohexane)
* Product of Diamond Shamrock Corp.
t Product of Radecca Corp., Austin, TX.
* Product of Dow Chemical Co., Midland, MI.
Sources: Product literature, Pilie et al. (1975), and Shieh (1979).
TABLE 2-4. UNDESIRABLE SORBENT/WASTE REACTIONS
Sorbent
Waste type
Reaction
Acidic sorbent
Acidic sorbent
Acidic sorbent
Alkaline sorbent
Alkaline sorbent (with
carbonates such as
calcite or dolomite)
Carbonaceous sorbent
(carbon, cellulose)
Siliceous sorbent
(soil, fly ash)
Metal hydroxide
Cyanide
Sulfide
Ammonium compounds
Acid waste
Oily waste
Solubilizes metal
Releases hydrogen cyanide
Releases hydrogen sulfide
Releases ammonia gas
Releases carbon dioxide,
which can cause frothing
May create pyrophoric waste
Hydrofluoric acid May produce soluble
fluorosilicates
2-8
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2.1.1.2 Usefulness
Sorption has been widely used to eliminate free water and improve han-
dling. Some sorbents have been used to limit the escape of volatile organic
compounds. Sorbents may also be useful in waste containment when they modify
the chemical environment and maintain the pH and redox potential to limit the
solubility of the waste.
2.1.1.3 Limitations
Sorption eliminates the bulk flow of wastes from the site, but in many
cases leaching of waste constituents from the sorbent can be a significant
source of pollution. Sorbents are widely used in lined landfills to elimi-
nate or control the pressure head on the liner, but the liner is the major
protection for the surrounding environment.
2.1.1.4 Equipment Requirements
Sorption of wastes requires only that the waste be mixed with the sor-
bent. This can be done with nothing more than a mixing pit and a backhoe.
More elaborate equipment such as a pug mill or ribbon blender can be used if
better quality control is needed and if other materials handling equipment
(pumps or conveyors) is available.
2.1.1.5 Applications
Most large, hazardous waste landfills are currently using sorption to
satisfy requirements prohibiting burial of liquids. A discussion of success-
ful application of sorption in waste disposal is presented in Morgan et al.
(1982) and summarized in U.S.EPA (1984). Nineteen million liters (5 million
gal) of oil sludge from a former refinery site was landfilled onsite after
treatment with cement kiln dust. The process required 3.71 x 10 kg
(40,939 tons) of kiln dust. The mixing was done primarily with standard con-
struction equipment at a cost of approximately $15 per cubic meter.
2.1.2 Lime/Fly Ash Pozzolan Treatment Process
2.1.2.1 General
Pozzolanic materials are those that set to a solid mass when mixed with
hydrated lime. Natural pozzolanic materials (called pozzolana) consist of
2-9
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either volcanic lava masses (tuff) or deposits of hydrated silicic acid of
mostly organic origin (e.g., diatomaceous earth); these are the "natural ce-
ments" used by the Romans to produce their famous, long-enduring aqueducts.
Artificial pozzolana are materials such as blast- furnace slag, ground brick,
and some fly ashes from powdered coal furnaces. A common feature of all
pozzolana is the presence of silicic acid (i.e. silicic mineral components
that can react with lime) and frequently appreciable levels of aluminum
oxide. Portland cement differs from pozzolana in that it is a defined mix-
ture of powdered oxides of calcium, silica, aluminum, and iron which result
from the kiln burning (at 1400-1500ฐ C) of raw material such as limestone and
clay (marl).
Solidification/stabilization of waste using lime and pozzolanic material
requires that the waste be mixed with a carefully selected, reactive fly ash
(or other pozzolanic material) to a pasty consistency. Hydrated lime (cal-
cium hydroxide) is blended into the waste-fly ash mixture. Typically, 20 to
30% lime is needed to produce a strong pozzolan. The resulting moist mate-
rial is packed or compressed into a mold to cure or is placed in the landfill
and rolled.
Standard testing systems (ANSI/ASTM C-311-77) and standard specifica-
tions (ASTM C618-80) exist for pozzolanic materials, especially for fly ash
(ASTM 1973) . The specifications take into account both the chemical composi-
tion (%SiO,
J2>
%SO_, and moisture content) and physical properties (fineness,
pozzolanic activity with lime, specific gravity). By using fly ash that
meets the specification for a bituminous coal fly ash (Type F) or a sub-
bituminous coal fly ash (Type C), pozzolanic activity greater, than a speci-
fied minimum can be guaranteed. Type C fly ashes have enough lime (more than
10% Ca(OH)?) that they are not only pozzolanic but are also self-cementing.
2.1.2.2 Usefulness
Lime/fly ash treatment is relatively inexpensive, and with careful selec-
tion of materials an excellent solid product can be prepared. In general,
fly ash/lime solidified wastes are not considered as durable as pozzolan-
Portland cement composites (Malone et al. 1980). Leaching losses from
pozzolan-waste materials have been considered to be relatively high compared
with those for pozzolan-Portland cement waste products (Malone et al. 1983).
In diffusion-type leach testing of a variety of solidified waste produced
from a standard metal-rich waste, the lime-fly ash based material prepared
from a metal solution or a liquid sludge showed levels of containment that
were as good as any pozzolan-Portland cement treated waste. However, the
sample of lime/fly-ash-treated waste disintegrated in the leaching solution
(Cote and Hamilton 1983).
Table 2-5 estimates the quantity of additives required per unit volume
of waste for adequate treatment of six different waste types. This table is
furnished to provide an example of an application, not design information.
2-10
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Note that when waste lime was used, the materials requirement increased 60%
to 70%. Bentonite addition reduced substantially the amount of fly ash
required.
TABLE 2-5. APPROXIMATE REAGENT REQUIREMENTS FOR SOLIDIFICATION OF VARIOUS
WASTE TYPES USING LIME AND FLY ASH*
Waste
Commercial lime
(kg/A)
Waste lime
(kg/A)
Lime,, fly ash,
and bentonitet
(kg/4)
Spent brine
Metal hydroxide sludge
Copper pickle
liquor sludge
FeCl pickle
liquor sludge (>1.5% HC1)
Sulfuric acid
plating waste
Oily metal
sludge (oil and grease)
3.2
2.9
1.8
2.5
3.0
0.6
5.4
5.6
2.6
4.0
5.2
0.84
2.2
1.1
0.7
1.9
2.3
0.54
* After Stanczyk et al. (1982)
t Proportions not specified.
2.1.2.3 Limitations
Common problems with lime-pozzolan reactions involve interference with
the cementitious reaction that prevents bonding of materials. The bonds in
pozzolan reactions depend on the formation of calcium silicate and aluminate
hydrates. A number of materials (such as sodium borate, calcium sulfate,
potassium bichromate, and carbohydrates) can interfere with this reaction.
Oils and greases can also physically interfere with bonding by coating waste
particles. The cementing system is strongly alkaline and can react with cer-
tain waste to release undesired materials such as gas or in leachate.
2.1.2.4 Equipment Requirements
The use of the lime/fly ash pozzolan processes requires more complex
equipment than systems using sorbent materials only. In one treatment system
2-11
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used for open sludge ponds, fly ash is mixed with a waste using a backhoe to
form a moist mass that can be easily handled with a shovel. The waste/fly
ash mixture is then loaded onto a weighing conveyor, and a metered amount of
lime is added. The mixture is run through a pug mill and loaded for place-
ment in a landfill. Other systems pump the sludge directly into a pug mill
or ribbon blender, where the reagents are blended; they then pump the treated
product directly to the final disposal area.
2.1.2.5 Applications
Lime/fly ash stabilization/solidification systems have been successfully
used in managing hazardous wastes. However the containment performance gener-
ally is such that a hazardous waste would still be classed as hazardous after
processing. Lime/fly ash-sorbent-based landfills have been established using
liner and monitoring systems to ensure safe disposal.
2.1.3 Pozzolan-Portland Cement Systems
2.1.3.1 General
A wide variety of treatment processes incorporate Portland cement as a
binding agent. Pozzolanic products (materials with fine-grained, noncrystal-
line, reactive silica) are frequently added to Portland cement to react with
any free calcium hydroxide and thus improve the strength and chemical resis-
tance of the concrete-like product. In waste solidification, the pozzolanic
materials (such as fly ash) are often used as sorbents. Much of the pozzolan
in waste processing may be inactivated by the waste. Any reaction that does
occur between the Portland cement and free silica from the pozzolan adds to
the product strength and durability.
Waste-solidifying formulations based on Portland and pozzolan-Portland
systems vary widely, and a variety of materials have been added to change
performance characteristics. These include soluble silicates (Falcone et al.
1983), hydrated silica gels, and clays such as bentonite, illite,^or attapul-
gite. Approximate reagent requirements for some example applications are
given in Table 2-6.
The types of Portland cement used for solidification can be selected so
as to emphasize a particular cementing reaction (Bogue 1955). Five major
types of Portland cement are commonly produced:
a. Type I is the typical cement used in the construction industry. It
constitutes more than 90% of the cement manufactured in the United
States.
2-12
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TABLE 2-6. APPROXIMATE PORTLAND CEMENT AND FLY ASH REQUIRE-
i MENTS FOR SOLIDIFICATION OF VARIOUS WASTE TYPES*
Waste
Cement/fly ash
(kg/Si waste)
Spent brine
Metal hydroxide
sludge
Copper pickle
liquor sludge
FeCl2 pickle
liquor sludge (>1.5% HC1)
Sulfuric acid
plating waste
Oily metal
sludge
3.8
2.4
1.9
3.5
3.8
0.96
* After,Stanczyk e.t al. (1982). The proportion of portland
cement to fly ash was not given.
c.
d.
b., Type II is designed to be.used in the .presence of moderate sulfate
concentrations (150 to 500 mg/kg), or where moderate heat of hydra-
tion is required. Type II has a low-alumina-content (less than 6%
Al 0,) cement.
Type III has a high early strength and is used where a rapid set is
required.
Type IV develops a low heat of hydration and is usually prescribed
for large-mass concrete work. This type typically has a long set
time.
e. Type V is a special low-alumina, sulfate-resistant cement used with
high sulfate concentrations (i.e more than 1500 mg/kg).
Type I Portland cement is widely used for waste solidification due to
its availability and low cost. Types II and V have been used to a limited
extent. They offer the advantage of having relatively low tricalcium alumi-
nate content. Higher aluminum-content cement can undergo a rapid reaction
with sulfates (Na^, K,^, (NH^SO^ and MgS04) from a waste or sur-
rounding ground water to form crystals of hydrated calcium alumino-sulfate.
The reaction products occupy a much larger volume than the original
2-13
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calcium aluminate hydrate and the expansion cracks the curing waste/concrete
mass.
Cement/fly ash processes typically are used in conjunction with sorbents
or other additives which decrease the loss of specific hazardous materials
from the rather porous, solid products. Such adaptations of the technology^
are also often necessary because some materials inhibit the binding action in
Portland cement. Additives used in Portland cement have included:
a. Soluble silicates, such as sodium silicate or potassium silicate.
These agents will generally "flash set" Portland cement to produce
a low-strength concrete. Research with soluble silicates indicates
that these materials are beneficial in reducing the interference
from metal ions in the waste solution (Columbo and Neilson 1978;
Falcone et al. 1983).
b. Selected clays to absorb liquid and bind specific anions or
cations. Work with bentonite as an additive indicates that they
reduce the amount of absorbent required in low-solids mixtures
(Stanczyk et al. 1982).
c. Emulsifiers and surfactants to allow the incorporation of immis-
cible organic liquids. Research in the nuclear waste field has
indicated that waste turbine oil and grease can be mixed into
cement blends if dispersing agents are used and if the proper
mixing system is employed, but process details were not discussed
(Phillips 1981).
d. Proprietary absorbents that selectively bind specific wastes.
These materials include carbon, silicates, zeolitic materials, and
cellulosic sorbents; they hold toxic constituents and are encapsu-
lated with the waste.
e. Lime (GaO) to raise the pH and the reaction temperature and thereby
improve setting characteristics.
2.1.3.2 Usefulness
Cement-based solidification and stabilization systems have proved to be
some of the most versatile and adaptable methods. Waste/concrete composites
can be formed that have exceptional strength and excellent durability, and
that retain wastes very effectively (Malone et al. 1980). The addition of
selected sorbents and/or emulsifiers often overcomes the problem of pollutant
migration through the rather porous solid matrix and consequently lowers the
leaching losses from the treated wastes.
2-14
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2.1.3.3 Limitations
Pozzolan-Portland cement wastes have limitations that relate to the ef-
fects of the waste on the setting (retardation from calcium sulfate, borates
carbohydrates, etc.) and stability of the silicates and aluminates that form
when Portland cement hydrates. Additionally other materials such as oil and
grease or large amounts of soft, fine wastes can prevent bonding of particles
in the waste and lower strength. Acidic or acid-producing materials such as
sulfides can react with carbonate and hydroxides and destroy concrete after
setting has occurred.
The very high alkalinity of hydrating Portland cement can cause the evo-
lution of ammonia gas if ammonium ion is present in abundance in the waste
Some metals have increased solubility at the very high pH's that occur in the
cement hydration reaction (e.g. nickel, lead, and zinc).
2.1.3.4 Equipment Requirements
Commercial cement mixing and handling equipment can generally be used
with .wastes. Weighing conveyors, metering cement hoppers, and mixers similar
to concrete batching plants have been adapted in some operations. Unless
severe corrosion occurs, no adaptation of equipment is required. Where ex-
tremely dangerous materials are being treated, remote-control-*, in-drum mixing
equipment such as that used with nuclear waste can be employed.
2.1.3.5 Applications
A number of commercial solidification vendors are currently operating
using variations of pozzolan-Portland cement systems. Many use specific
sorbents, additives, and proprietary formulations developed to answer the
needs of specific clients.
2.1.4 Thermoplastic Microencapsulation
2.1.4.1 General
Thermoplastic microencapsulation has been successfully used in nuclear
waste disposal and can be adapted to special industrial wastes. The tech-
nique for isolating the waste involves drying and dispersing it through a
heated, plastic matrix. The mixture is then permitted to cool to form a
rigid but deformable solid. In most cases it is necessary to use a container
such as a fiber or metal drum to give the material a convenient shape for
transport. The most common material used for waste incorporation is
2-15
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asphalt; but other materials such as polyethylene, polypropylene, wax, or
elemental sulfur can be employed for specific wastes where complete contain-
ment is important and cost is not a limiting factor.
2.1.4.2 Usefulness
The major advantage that thermoplastic (asphalt) encapsulation offers is
the ability to solidify very soluble, toxic materials. This is a unique
advantage that cement and pozzolan systems cannot claim. If, for example,
the wastes are spray-dried salt, there are few useful alternatives ,to micro-
encapsulation. The asphalt encapsulation process can be used with moist salt
and the mixer-extruder can be used to remove (and recover, if necessary)
water or other solvents associated with the wastes. Drying the waste results
in a substantial weight reduction over the original material and partly com-
pensates for the additional weight of the asphalt matrix.
2.1.4.3 Limitations
Compatibility of the waste and the matrix becomes a major consideration
in using thermoplastic microencapsulation. Most matrices employed with
wastes are reduced materials (solid hydrocarbons or sulfur) that can react
(combust) when mixed with an oxidizer at elevated temperatures. The reaction
can be self-sustaining or even explosive if perchlorates or nitrates are
involved.
Other compatibility problems relate to unusual softening or hardening of
the waste/matrix mix. Some solvents and greases can cause asphalt materials
to soften and never become rigid solids. Borate salts can cause hardening at
high temperatures and can stall or clog mixing equipment. Xylene and toluene
diffuse quite rapidly through asphalt.
Salts that partially dehydrate at the elevated temperatures used in mix-
ing can be a problem. Sodium sulfate hydrate, for example, will lose some
water during asphalt incorporation and if the waste/asphalt mix containing
the partially dehydrated salt is soaked in water, the mass will swell and
crack due to rehydration. This outcome can be avoided by eliminating easily
dehydrated salts or by coating the outside of the asphalt/waste mass with
pure asphalt (Doyle 1979). Chelating and complexing agents (cyanides and
ammonium compounds) in waste have been shown to seriously compromise the con-
tainment of heavy metal wastes (Rosencrance and Kulkarni 1979). If care is
taken to pretreat the waste to eliminate oxidizers and destroy complexing
agents, the containment of the waste in asphalt is superior to pozzolan or
pozzolan-Portland cement solidification.
Thermoplastic encapsulation requires complex, specialized mixing equip-
ment and a trained operations staff to ensure safe, consistent operation.
The requirement for drying the waste and melting the matrix material makes
2-16
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the power consumption for waste solidification quite high compared with that
for pozzolan and pozzolan-Portland cement systems.
2.1.4.4 Equipment Requirements
Specialized equipment is required to ensure thorough mixing of the vis-
cous material under controlled temperature conditions. The mixers or extru-
ders used in waste solidification are similar to those used in the plastic
industry where coloring and filler materials are generally added to raw
plastics. When hazardous wastes are treated, the waste materials replace the
filler. Temperatures ranging from 130ฐ to 230ฐ C are used during mixing.
Screw-extruders that are routinely used in preparation of plastics for
molding are the major type of equipment used in waste microencapsulation.
These systems have staged heating and kneading of the waste and matrix mate-
rial to ensure homogeneous blending of waste and matrix. Waste treatment
systems are adapted from standard extruders by adding fume control, safety
equipment interlocks, and systems for handling wastes without exposing the
operators to undue hazard.
2.1.4.5 Applications
Thermoplastic microencapsulation has been widely used in nuclear waste
disposal, and application to industrial waste disposal has been projected,
for instance, in disposal of arsenical wastes. Success with nuclear waste
disposal has been well documented (Doyle 1979).
2.1.5 Macroencapsulation or Jacketing Systems
2.1.5.1 General
Macroencapsulation systems contain potential pollutants by bonding an
inert coating or jacket around a mass of cemented waste or by sealing them in
polyethylene-lined drums or containers. This type of waste stabilization is
often effective when others are not because the jacket or coating of the out-
side of the waste block completely isolates the waste from its surroundings.
The waste may be stabilized, microencapsulated, and/or solidified before
macroencapsulation so that the external jacket becomes a barrier designed to
overcome the shortcomings of available treatment systems.
A macroencapsulation system that has been proposed for use with hazard-
ous wastes involves drying the wastes and bonding the dried material into a
compressed block using polybutadiene. Polymerization of the binder requires
heating the waste sample to 120ฐC to 200ฐC under slight pressure. The block
is placed in a mold and surrounded with powdered polyethylene. The
2-17
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polyethylene is then fused into a solid jacket using heat and pressure.
the proposed system, a 3.5-mm-thick jacket would be fused over a 450-kg
block. The polyethylene would amount to approximately 4% of the mass by
weight (Lubowitz and Wiles 1978).
In
2.1.5.2 Usefulness
Macroencapsulation can be used to contain very soluble toxic wastes.
Leaching of the waste can be eliminated for the life of the jacketing mate-
rial. This process has been used at remedial sites as drum over-packs to
contain weak or leaking drums and containers.
2.1.5.3 Limitations
In some systems, the wastes have to be dried before they are fused into
a block, thus increasing the risk of the release of volatile toxics. Fur-
thermore, the waste must not react with the binder or jacket materials at the
elevated temperatures required for fusing and forming a jacket. The jacket-
ing material may have to be protected from chemical or photo degradation or
physical stresses after disposal. Equipment such as special molds on pro-
cessing machinery is highly technical and requires highly skilled labor
unless loose-fitting over-packs are used.
2.1.5.4 Equipment Requirements
Macroencapsulation requires special molds and heating equipment for fus-
ing the waste and forming the jacket. . Molding equipment would have to be
custom fabricated for waste handling.
2.1.5.5 Application
Macroencapsulation has been bench tested on a number of different
wastes, but it has not been tested in a full-scale operation (Lubowitz and
Wiles 1979) . Results of bench testing are encouraging, but larger-scale
operations have not been pursued.
2.2 Compatibility of Wastes and Treatment Processes
The chemical reactivity of the waste generally controls the selection of
waste stabilization/solidification options and its optimization. Table 2-7
summarizes the major chemical considerations that direct the selection of a
2-18
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TABLE 2-7. COMPATIBILITY OF SELECTED WASTE CATEGORIES WITH DIFFERENT STABILIZATION/
SOLIDIFICATION TECHNIQUES
I
\
vo
Treatment Type
Waste component
Organics
Organic solvents
and oils
Solid organics
(e.g., plastics,
resins, tars)
Inorganics
Acid wastes
Cement based
May impede setting,
may escape as
vapor
Good often in-
creases
durability
Cement will neu-
Pozzolan based
May impede setting,
may escape as
vapor
Good often increases
durability
Compatible, will
Thermoplastic
microencapsulation
Organics may vaporize
on heating
Possible use as
binding agent in
this system
Can be neutralized
Surface encapsulation
Must first be absorbed on
solid matrix
Compatible many encapsulation
materials are plastic
Oxidizers
Sulfates
Halides
Heavy metals
Radioactive
materials
f tralize acids
Compatible
May retard setting
and cause spal-
ling unless
special cement is
used
Easily leached from
cement, may
retard setting
Compatible
Compatible
neutralize acids
Compatible
Compatible
May retard set,
most are easily
leached
Compatible
Compatible
before incorporation
May cause matrix
breakdown, fire
May dehydrate and
rehydrate causing
splitting
May dehydrate
and rehydrate
Compatible
Compatible
incorporation
May cause deterioration of
encapsulation materials
Compatible
Compatible
Compatible
Compatible
After Malone et al. (1980).
-------
particular waste stabilization/solidification system. Most solidification
systems will work under adverse circumstances if adaptations are made in the
waste or the processing train. Many compatibility problems can be overcome
by specifying pretreatment steps to destroy or tie up some undesirable waste
constituent.
2.3 Pretreatment Techniques for Waste Solidification
Pretreatment systems, which overlap with stabilization and sorption pro-
cesses, can be used to achieve a number of results that condition the waste
to ensure better and more economical containment after the remaining mate-
rials have been stabilized and solidified. These include:
a. Destruction of materials (such as acids or oxidizers) that can react
with solidification reagents (lime or Portland cement).
b. Reduction of the volume of waste to be solidified (using processes
such as settling or dewatering).
c. Chemical binding of specific waste constituents to solid phases
added to scavenge toxic materials from solution and hold them in
solids.
d. Techniques for improving the scale on which waste processing can be
donefor example, bulking and homogenizing waste to allow a single
solidification system to be used without modification on a large
volume of waste.
Neutralization, oxidation or reduction, and chemical scavenging stabil-
ize the waste in that they bring the chemical waste into an inert or less
soluble form. Dewatering, consolidation, and waste-to-waste blending are
also useful pretreatment methods which reduce the waste volume or numbers of
different waste forms requiring treatment.
2.3.1 Neutralization
Most binder systems can operate well with wastes that are approximately
neutral (pH 7.0), though alkaline wastes, are also desirable in many circum-
stances where it is necessary to minimize solubility. Many toxic metals are
amphoteric (show increased solubility at both high and low pH's) and by ad-
justing the pH it is possible to produce a minimum amount of metal in the
supernatant liquid (Figure 2-2). Depending upon the metals present, the op-
timum pH is usually between 9.5 and 11, which offers the advantage of requir-
ing less treatment of the discharged water produced by subsequent dewatering.
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Figure 2-2. Theoretical solubilities of selected amphoteric metal
hydroxides.
The selection of a neutralization agent is important in reducing the
amount of leachable material in the waste. A common base used in neutraliza-
tion is sodium hydroxide; however, resulting sodium salts typically have very
high solubilities, and the supernatant liquid and sludge produced in neutral-
ization will have higher levels of soluble materials than if other bases were
used. Calcium hydroxide or calcium carbonate may be a better choice for neu-
tralization because the resulting salts are generally less soluble than
sodium salts. Calcium hydroxide and calcium carbonate also are available
inexpensively in a relatively pure form.
2-21
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Calcium carbonate offers the advantage that many carbonate metal salts
are insoluble (for example, lead carbonate has a low solubility) and the car-
bonates are compatible with both Portland cement and pozzolan material. How-
ever, neutralization with carbonates can cause frothing due to evolution of
carbon dioxide. Excess calcium hydroxide in Portland cement is thought to
make the material more reactive to sulfate attack (Ramachandran 1976; Bogue
1955). In pozzolan materials, excess lime would react with free silica and
should not pose a problem. DeRenzo (1978) and EPA (1982) discuss equipment
needs and design for precipitation systems that use neutralization.
2.3.2 Oxidation/Reduction
In some cases, the most insoluble form of a toxic constituent is associ-
ated with a specific oxidation/reduction state. Iron, for example, is much
less soluble at alkaline pH's in its oxidized state. Chromium in its oxi-
+6 +3
dized state (Cr ) is more mobile than the reduced chromium (Cr ) in an
alkaline solution.
The usual technique involved in oxidizing or reducing hazardous materi-
als to a stable, insoluble state involves addition of hypochlorite, chlorate,
persulfate chlorine or peroxide (oxidizers), or sulfides, ferrous salts, or
sulfur dioxide gas (reducing agents). A discussion of oxidation-reduction
systems along with equipment design is given in DeRenzo (1978), U.S. EPA
(1982), and Nemerow (1971).
Oxidation of toxic organic constituents using UV-ozone or chemical oxi-
dizers can lower the toxicity of the final product and the amount of .fixation
reagents required. And, of course, incineration can be considered an oxida-
tive pretreatment because it usually generates a residue or scrubber sludge
residual which often requires further treatment and disposal.
2.3.3 Chemical Scavenging
Chemical scavenging involves the use of some solid chemical agent to
chemsorb or react with and bind up some specific waste constituent. This
procedure is significantly different from adsorption, where the goal of the
operation is to soak up free liquid and adsorb ions in solution. Chemical
scavenging agents, many of which are proprietary, include chemically active
adsorbents (for example, activated carbon), specific types of clays, ion
exchange resins, natural and artificial zeolites, silica gels, and finely
divided metal hydroxides (ferric hydroxide or aluminum hydroxide).
In all cases, an attempt should be made to ensure that the scavenging
agent is compatible with the waste and the solidification reaction. Selected
use of scavengers can greatly reduce the requirement to treat the discharge
water after dewatering of the wastes. Scavenging can also assist in compli-
cated treatment problems. For example, in the solidification of a paint
2-22
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i O
stripping waste that contained phenol and a chrome (Cr ) paint pigment,
attempts to oxidize the phenol with permanganate also oxidized the chromium
and increased its leaching. Without treatment, the phenol leaching rate was
unacceptable. A suitable scavenging material such as formaldehyde would be
able to react with the phenol and reduce its leaching rate while leaving the
chromium in its lower (less soluble) valance state.
Scavenger materials often improve solidification performance without
adding appreciably to the volume of the waste. Scavenging materials, such as
flocculating agents like polyelectrolytes or aluminum hydroxide or iron hy-
droxide, also assist in waste concentration or dewatering by improving the
settling characteristics of fine-grained wastes in suspension.
2.3.4 Dewatering and Consolidation
Solidification systems can be made more economical by reducing the vol-
ume of waste to be treated by dewatering. Dewatering can also be used to
lower the water content of the solidified waste which, in turn, lowers the
leachability of the waste. A strong correlation is found between the leach-
ability and the water content of solidified waste, which indicates diffusion
of contaminants probably occurs through the pore liquid in solidified waste
matrices (Cote and Hamilton 1983); thus a dryer, solidified product will have
lower contaminant mobility.
Design of dewatering systems is discussed in DeRenzo (1978) and EPA
(1982). A comparison of stabilization of dewatered and undewatered indus-
trial sludge reported by Cote and Hamilton (1983) indicated the final volume
after dewatering for a typical metal hydroxide waste was about 35% of the
initial volume. Dewatering the metal waste increased containment (as mea-
sured by diffusion testing) and decreased costs due to lower fixation reagent
requirements and less final product requiring disposal.
2.3.5 Waste-to-Waste Blending
Except in the case of extremely toxic wastes, it is generally not prac-
tical to set up stabilization/solidification systems to handle small volumes
of waste, especially if the wastes vary significantly in their compatibility
and containment performance in a selected process. At some point in the re-
medial action planning it is necessary to mix or bulk wastes in order to ob-
tain sufficient volume for efficient pretreatment, stabilization, and/or
solidification. If the nature of the waste permits bulk mixing before a
treatment, then a simpler, large-scale pretreatment operation can be under-
taken and a large mass of homogeneous material (feed stock) will be available
for processing. Guidelines fo.r mixing or bulking of wastes are given in
Chemical Manufacturers Association (1982) and in Hatayma et al. (1981). The
water separation and blending systems depend on identifying materials that
have similar composition and pH and oxidation/reduction characteristics.
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This same type of waste classification and blending is needed to develop feed
stocks for pretreatment as well as to provide economy by processing large
volumes.
When the reactions between different types of wastes (for example, acids
and bases, or oxidizers and reducers) can be controlled and no unwanted side
reactions occur (such as generation of H~S or HCN gas), the waste blending
becomes a treatment step where the wastes themselves are treatment reagents.
Blended waste can then be further treated if additional pH adjustment or oxi-
dation-reduction treatment is needed.
2-24
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REFERENCES
American Society for Testing and Materials (ASTM). 1973. Annual Book of
ASTM Standards, Part II. American Society for Testing and Materials,
Philadelphia, Pennsylvania.
Bogue, R. H. 1955. The Chemistry of Portland Cement.
Corp., 2nd ed., 793 pp.
Reinhold Publishing
Chan, P. C., et al. 1978. Sorbents for Fluoride, Metal Finishing, and
Petroleum Sludge Leachate Contaminant Control. EPA-600/2-78-024, U.S.
Environmental Protection Agency, Cincinnati, Ohio. 94 pp.
Chemical Manufacturers Association. 1982. A Hazardous Waste Management
Plan. Chemical Manufacturers Assoc., Washington, D.C., Loose-leaf.
Columbo, P., and R. M. Neilson. 1978. Properties of Wastes and Waste Con-
tainers. Progress Report No. 7. BNL-NUREG 50837, Brookhaven National Labora-
tory, Upton, New York.
Cote, P. L., and D. P. Hamilton. 1983. Leachability Comparison of Four Haz-
ardous Waste Solidification Processes. Presented at the 38th Annual Purdue
Industrial Waste Conference, LaFayette, Indiana, May 10, 11, 12, 1983.
17 pp.
DeRenzo, D. J. (ed). 1978, Unit Operations for Treatment of Hazardous
Wastes. Noyes Data Corp., Park Ridge, New Jersey.
Doyle, R. D. 1979. Use of an Extruder/Evaporator to Stabilize and Solidify
Hazardous Wastes. In: Pojasek, R. B (ed.), Toxic and Hazardous Waste Dispo-
sal, Vol. 1, Ann Arbor Science Publishers, Ann Arbor, Michigan, pp. 65-91.
Falcone, J. S., Jr., R. W. Spencer, and R. H. Reifsnyder. 1983. Chemical
Interactions of Soluble Silicates in the Management of Hazardous Wastes.
Draft Report. The PQ Corp., Lafayette Hill, Pennsylvania.
Grim, R. E., and N. Guven. 1978. Bentonites. Elsevier Scientific Publishing
Co., New York. 256 pp.
Hatayma, H. K., et al. 1981. Hazardous Waste Compatibility Protocol.
California Department of Health Services, Berkeley, Calif., Rept. on Grant
R804692010, U. S. Environmental Protection Agency, Cincinnati, Ohio.
Haynes, B. W., and G. W. Kramer. 1982. Characterization of U. S. Cement
Kiln Dust. Bureau of Mines Information Circ. 885, U. S. Dept. of Interior,
Washington, D.C. 19 pp.
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ladevaia, Rosa, and J. F. Kitchens. 1980. Engineering and Development
Support of General Decon Technology and the DARCOM Installation Restoration
Program. Task 4. Draft Rept. Atlantic Research Corp. Alexandria,
Virginia. 77 pp.
Lubowitz, H. R., and C. C. Wiles. 1978. Encapsulation Technique for Control
of Hazardous Materials. In: Land Disposal of Hazardous Waste, Proceedings
of 4th Annual Research Symposium, EPA-600/9-78-016, U. S. Environmental
Protection Agency, Cincinnati, Ohio. pp. 342-356.
Lubowitz, H. R., and C. C. Wiles. 1979. Encapsulation Technique for Control
of Hazardous Wastes. In: Pojasek, R. B. (ed.), Toxic and Hazardous Waste
Disposal, Vol. 1, Ann Arbor Science Publishers, Inc., Ann Arbor, Michigan.
pp. 198-232.
Malone, P. G., and L. W. Jones. 1979. Survey of Solidification/
Stabilization Technology for Hazardous Industrial Wastes. EPA-600/2-79-056,
U. S. Environmental Protection Agency, Cincinnati, Ohio. 41 pp.
Malone, P. G., L. W. Jones, and J. P. Burkes. 1983. Application of
Solidification/Stabilization Technology to Electroplating Wastes. In: Land
Disposal of Hazardous Waste, Proceedings of the 9th Annual Research
Symposium, U. S. Environmental Protection Agency, Cincinnati, Ohio.
pp. 247-261.
Malone, P. G., L. W. Jones, and R. J. Larson. 1980. Guide to the Disposal
of Chemically Stabilized and Solidified Waste. SW-872, Office of Water and
Waste Management, U. S. Environmental Protection Agency, Washington, D.C.
126 pp.
Morgan, D. S., J. I. Novoa, and A. H. Halff. 1982. Solidification of Oil
Sludge Surface Impoundments with Cement Kiln Dust (Draft Report). Albert
Halff Associates, Inc., Dallas, Texas.
Nemerow, N. L. 1971. Liquid Waste of Industry: Theories, Practices, and
Treatment. Addison-Wesley, Reading, Massachusetts. 584 pp.
Phillips, J. W. 1981. Applying Techniques for Solidification and Transpor-
tation of Radioactive Waste to Hazardous Waste. In: Proceedings of National
Conference on Management of Uncontrolled Hazardous Waste Sites, Hazardous
Materials Control Research Institute, Silver Spring, Maryland, pp. 206-211.
Pilie, R. J., et al. 1975. Methods to Treat, Control and Monitor Spilled
Hazardous Materials. EPA-670/2-75-042, U. S. Environmental Protection
Agency, Cincinnati, Ohio. 148 pp.
Ramachandran, V. S.
Publ. Ltd., London.
1976. Calcium Chloride in Concrete. Applied Science
216 pp.
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Rosencrance, A. B., and R. K. Kulkarni. 1979. Fixation of Tobyhanna Army
Depot Electroplating Waste Samples by Asphalt Encapsulation Process. Techni-
cal Rept. 7902, U. S. Army Medical Research and Development Command,
Ft. Detrick, Maryland. 23 pp.
Sheih, M. S. 1979. The Use of Natural Sorbents for the Treatment of Indus-
trial Sludge Leachate. Ph.D. Dissertation, New Jersey Inst. of Tech., Newark,
New Jersey. 144 pp.
Stanczyk, T. F., B. C. Senefelder, and J. H. Clarke. 1982. Solidification/
Stabilization Process Appropriate to Hazardous Chemicals and Waste Spills.
In: 1982 Hazardous Materials Spills Conference, Government Institutes Inc.,
Rockville, Maryland, pp. 79-84.
U.S. EPA. 1985. Handbook for Remedial Action at Waste Disposal Sites (Re-
vised). EPA-625/6r-85-006, U.S. Environmental Protection Agency, Cincinnati,
Ohio. 497 pp.
U.S. EPA. 1984. Case Studies 1-23: Remedial Response at Hazardous Waste
Sites. EPA-540/2-84-002b, Office of Emergency and Remedial Response, U. S.
Environmental Protection Agency, Washington, D.C. 637 pp.
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SECTION 3
PHYSICAL AND CHEMICAL CHARACTERIZATION OF UNTREATED WASTES
3.1 Physical Characterization
The physical characteristics of a waste material are important in deter-
mining the handling requirements for a waste. The equipment and methods for
moving, storing, and mixing the waste will be determined by the range of
physical characteristics involved. In many cases initial testing will result
in a decision to introduce a preliminary dewatering or sorption step to pro-
vide a more easily handled solid with uniform physical characteristics. Phy-
sical characteristics that would be determined include:
a. Percent moisture (water content)
b. Suspended solids *
c. Bulk density
d. Grain-size distribution
e. Atterberg limits
f. Cone index or California bearing ratio
g. Unconfined compressive strength
Obviously some of these characteristics may not be useful because of the con-
ditions of a particular material. If the waste is impounded, the testing
program should be designed to consider the condition of the waste after re-
suspension or partial dewatering or addition of an adsorbent. A detailed
discussion of a range of physical testing procedures applicable to solidifi-
cation and stabilization of hazardous materials is presented in Bartos and
Palermo (1977).
3.1.1 Percent Moisture or Water Content
Water content is defined as the ratio of the weight of water to the
weight of solids and fs expressed as a percentage. The percent moisture or
water content is used to develop requirements for pretreatment (settling,
flocculating, filtering, and absorbing) and for designing solidification
3-1
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procedures for the treated materials. Procedures for determining water
content are given in Appendix I of U.S. Army (1972) and ASTM D2216-71 (ASTM
1973).
3.1.2 Suspended Solids
The amount of suspended solids is used to determine the materials han-
dling requirements for the wastethat is, to determine if the waste can be
pumped or whether another conveying system should be used. The suspended
solids can also be used to predict volume decrease due to settling (primary
consolidation) or water removal. Table 3-1 gives a typical classification
system for the consistencies of slurried materials based on handling and
processing requirements (Wyss et al. 1980).
TABLE 3-1. HAZARDOUS WASTE CONSISTENCY CLASSIFICATION
Consistency category
Characteristics
Liquid waste
Pumpable waste
Flowable waste
Nonflowable waste
<1% suspended solids,* pumpable liquid, generally too
dilute for sludge dewatering operation.
<10% suspended solids,* pumpable liquid, generally
suitable for sludge dewatering.
>10% suspended solids,* not pumpable, will flow or
release free liquid, will not support heavy equip-
ment, may support high flotation equipment, will
undergo extensive primary consolidation.
Solid characteristics, will not flow or release free
liquids, will support heavy equipment, may be 100%
saturated, may undergo primary and secondary
consolidation.
* Suspended solids ranges are approximate,
From Wyss et al. (1980).
Suspended solids (or settleable matter) can be determined using
Method 224F(a) as given in APHA (1971). This method is equivalent to EPA
Standard Method for Settleable Matter (Storet No. 5008G) as given in U.S. EPA
(1979) . Settleable matter is usually given in milliliters per liter volume
of waste suspension.
3-2
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3.1.3 Bulk Density
The bulk density, or bulk unit weight, is the ratio of the total weight
(solids and water) to the total volume. These basic data are needed to
convert weight to volume in materials handling calculations. Procedures for
determining bulk unit weight are given in Appendix II of U.S. Army (1972).
3.1.4 Grain-Size Distribution
The grain-size distribution of an industrial waste becomes important in
designing remedial actions. Fine-grained wastes generally present more han-
dling problems and are subject to wind dispersion. Fine-grained wastes also
present problems in producing high-strength solidified waste. Large percen-
tages of fines lower the ultimate strength developed in concrete/waste
composites.
Grain-size analyses are performed using methods described in Appendix V
of U.S. Army (1972) or ASTM D422-63 (ASTM 1973). Preparation of samples for
grain-size analysis usually follows specifications given in ASTM D421-58
(ASTM 1973).
3.1.5 Atterberg Limits
The Atterberg limits test determines the water contents of the material
at the boundaries between its plastic and liquid states. The plastic limit
is the water content at which the waste will start to crumble when rolled
into a 3-mm thread under the palm of the hand. The liquid limit is defined
as the lowest water content at which the sludge will flow as a viscous liq-
uid. The Atterberg limits are used in classifying fine-grained materials to
estimate their properties such as compressibility, strength, and swelling
characteristics; these provide an indication of how the material will react
when stressed.
A full discussion of the test and the equipment involved is given in
Appendices III and IIIA of U.S. Army (1972) and ASTM tests D424-59 and
D423-66 (ASTM 1973).
3.1.6 Cone Index
These tests involve forcing a standard cone into a sample of soil or
other granular material and determining the resistance offered by the medium
being tested. These tests are typically used to examine the ability of a
subgrade soil to support a load (trafficability), but they are equally valu-
able in examining the strength of in-place wastes. Details on the test
3-3
-------
procedures and interpretation are given in Sowers and Sowers (1970) and
U.S. Army (1972).
3.1.7 Unconfined Compressive Strength
Unconfined compressive strength can only be measured on samples of cohe-
sive or cemented waste. This type of test involves preparing a cylindrical
specimen and loading it axially to failure. The test load is applied at a
fixed rate of strain and compressive stresses are recorded as loading pro-
gresses. Unconfined compressive strength tests are used to determine bearing
capacity and shear strength of cohesive materials. Shear strength is an
important factor in determining the ultimate bearing capacity of the mate-
rial, embankment stabilities, and pressures on retaining walls holding the
material in place.
The standard test procedure is given in Appendix XI of U.S. Army (1972)
and ASTM Standard Method D2166-66 (ASTM 1973). This type of testing requires
that an average value be determined from a series of multiple samples.
3.2 Chemical Characterization
The requirements for chemically characterizing wastes present at reme-
dial action sites vary widely depending on preliminary information on the
types of waste involved. Any program of chemical analyses and testing should
be designed to discover the following:
a. The degree of hazard involved in handling and treating the wastes.
These data are used to develop requirements for protective clothing
and adaptations required for mixing and transporting equipment.
b. The presence of interfering materials that can complicate
stabilization/solidification. These data are used to develop pre-
treatment alternatives.
c. The compatibility of wastes that would permit the mixing and consol-
idation of wastes for pretreatment and stabilization/
solidification. This type of testing allows more economical opera-
tion and continuous processing of bulked wastes.
Testing programs oriented toward defining the degree of hazard involved
in a waste material are outlined in U.S. EPA (1980). This type of testing
concentrates on quantification of potential toxicants and screening for pri-
ority pollutants. Any program designed to evaluate the containment developed
during stabilization/solidification must be based on consideration of the
bulk composition of the waste. Leach testing of the treated waste will gen-
erally concentrate on the most potentially dangerous or soluble compounds
discovered in the waste.
3-4
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Chemical compounds that can present problems during stabilization/
solidification may be relatively common, nontoxic materials. Oil and grease
may interfere with pozzolan-Portland cement based processes. High concentra-
tions of sulfate can cause swelling and spalling of pozzolan-Portland cement
solidified wastes. High sulfate concentrations can be reduced by lime addi-
tion. The testing and analysis program will vary with the solidification
process or processes being considered for use. Table 2-7 lists some of the
constituents that can affect the performance of different stabilized/
solidified waste materials and pretreatment options available to alleviate
the problem.
Testing procedures for consolidating hazardous wastes have been devel-
oped to assist in segregating chemically compatible waste for storage and
transportation. These same protocols can be adapted for screening hazardous
waste for pretreatment and stabilization/solidification. A general system
designed for consolidating drummed waste is given in Chemical Manufacturers
Association (1982). A more general compatibility testing procedure and a
waste compatibility matrix are available in Hatayma et al. (1981).
3-5
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REFERENCES
American Public Health Association (APHA). 1971. Standard Methods for the
Examination of Water and Wastewater. Amer. Public Health Assoc., New York,
New York. 874 pp.
American Society of Testing and Materials (ASTM). 1973. Annual Book of ASTM
Standards, Part II, Philadelphia, Pennsylvania.
Bartos, M. J., Jr., and M. R. Palermo. 1977. Physical and Engineering
Properties of Hazardous Industrial Wastes and Sludges. EPA-600/ 2-77-139,
U.S. Environmental Protection Agency, Cincinnati, Ohio. 89 pp.
Chemical Manufacturers Association. 1982. A Hazardous Waste Management
Plan. Chemical Manufacturers Assoc., Washington, D.C., Loose-leaf.
Hatayma, H. K., et al. 1981. Hazardous Waste Compatibility Protocol.
California Department of Health Services, Berkeley, Calif., Rept. on Grant
R804692010, U.S. Environmental Protection Agency, Cincinnati, Ohio.
Sowers, C. B., and G. F. Sowers. 1970. Introductory Soil Mechanics and
Foundations. 3rd ed., The Macmillan Co., London.
U.S. Army, Office, Chief of Engineers. 1972. Laboratory Soils Testing,
Engineer Manual 1110-2-1906, U.S. Army Corps of Engineers, Washington, D.C.
U.S. EPA. 1979. Manual of Methods For Chemical Analysis of Water and
Wastes. EPA-600/4-79-020, U.S. Environmental Protection Agency, Cincinnati,
Ohio. 298 pp.
U.S. EPA. 1980. Test Methods for Evaluating Solid Waste. SW-846, U.S.
Environmental Protection Agency, Washington, D.C. Unpaginated.
Wyss, A. W., et al. 1980. Closure of Hazardous Waste Surface Impoundments.
SW-873, Office of Water and Waste Management, U.S. Environmental Protection
Agency, Cincinnati, Ohio. 92 pp.
3-6
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SECTION 4
SELECTION OF STABILIZATION/SOLIDIFICATION PROCESSES
4.1 Background
In undertaking any remedial action involving stabilization/
solidification at an uncontrolled waste site, a number of problem areas have
to be addressed. These include:
a.
b.
Characteristics of the present waste disposal site. The geologic
and hydrologic setting of the site determines;to a great degree the
feasibility of leaving the treated waste material on the site. An
action could involve closing a site in place or constructing a new
facility to contain the solidified waste onsite. Stabilization and
solidification always increases the volume and mass of material to
be disposed; therefore, solidification and transportation offsite
is generally a more expensive option than shipping untreated wastes
to a hazardous waste landfill.
Character and volume of the waste to be stabilized or solidified.
Wastes that are hazardous due to flammability, corrosivity, reactiv-
ity, infectiousness, or other properties that would normally exclude
secure land burial usually cannot be solidified and disposed of by
landfillirig without adequate pretreatment. Wastes which are hazar-
dous due to toxicity as defined by the Extraction Procedure (EP)
testing benefit by stabilization and solidification in that it can
decrease the concentration of toxic material in the EP leachate.
Wastes that present specific problems (such as escape of volatile
organics) may not be effectively contained using any economical
stabilization/solidification technique although new sorbents are
being developed to overcome these difficulties. Mixed wastes that
require several pretreatment steps to produce solidification can
become too expensive to process when costs are compared with those
for transportation and secure land burial in a RCRA-permitted site.
Small volumes of waste are often not economical to solidify or
stabilize. At some sites where the wastes can be most easily
handled by transportation and burial in a secure landfill, the least
contaminated residual materials, such as sludges and contaminated
soils, can be stabilized/solidified and landfilled in place. In
every case, a cost comparison is a prime concern in examining
stabilization/solidification options.
4-1
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c.
d.
Degree of hazard involved in handling the waste. The safety re-
quirement for handling wastes in some circumstances is so great that
stabilization/solidification for onsite disposal must be passed over
to reduce long-term exposure to site personnel and inhabitants in a
local area. Again, in such cases, marginally contaminated, high
volume materials (soils or absorbents) may be the only material
solidified and left onsite, although the bulk of the waste may be
fixed to make its handling or its ultimate disposal safer and more
economical.
Possible site modifications to provide for ultimate disposal. Where
the waste site in an unmodified condition would be unacceptable due
to an undesirable geologic or hydrologic setting, engineering modi-
fication such as liners and drainage control may overcome site prob-
lems. Waste solidification can provide part of the required con-
tainment, and site modifications can complete the safe containment
program.
A definition of how stabilization/solidification is to be employed at a
specific remedial action site should result from these considerations. For
instance, the wastes may be solidified and ultimate disposal involve burial
onsite, or contaminated soils or absorbers may be solidified and buried on-
site, while the waste themselves are transported. If solidification systems
alone do not provide a high enough degree of protection, it may be necessary
to modify the site to provide improved waste isolation.
Once decisions have been made on the role of solidification and the
types and quantities of material to be solidified, it is possible to develop
specifications for the stabilized/solidified waste. The nature of the waste
and the containment properties required of the stabilized/solidified material
determine the type of processing that can be used.
4.2 Specifications for Stabilized/Solidified Wastes
Specifications for stabilized/solidified wastes can include these
characteristics:
a. Leachability of waste components to contacting water.
b. Free liquid content of waste.
c. Physical stability of waste under burial conditions.
d. Reactivity of waste.
e. Ignitability or pyrophoricity.
f. Susceptibility to biodegradation.
g. Strength or bearing capacity of the waste.
4-2
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h. Permeability of the waste.
i. Durability of the waste under conditions of surface exposure
(freeze-thaw and wet-dry testing).
No standards for testing of stabilized/solidified waste have been devel-
oped. The specification and testing procedures outlined in this section are
a minimum suggested testing program, and the specifications indicated are
desirable but not mandated.
4.2.1 Leachability
A wide variety of extraction or leaching tests have been proposed for
hazardous waste. None have been totally satisfactory for all types of
stabilized/solidified wastes (Lowenbach 1978). Three major types of test
procedures are usually involved in any evaluation procedure: Testing for
regulatory purposes, testing for maximum hazard assessment, and testing for
design of landfill facilities.
The regulatory testing procedures involve mixing the waste with some
specified amount of extracting fluid (usually dilute acid or distilled water)
and analyzing the resulting extractant for a required number of potential
contaminants. Regulations may require that the waste be tested as a monolith
or broken in a specific procedure such as the EPA Structural Integrity Pro-
cedure (Federal Register 1980, page 33128). The sample may or may not have
to be sieved prior to testing. A set of criteria usually based on multiples
of concentrations specified in the Primary or Secondary Drinking Water Stan-
dards are provided. Regulatory tests vary widely but the most accepted is
the EPA Extraction Procedure or EP Toxicity Test Procedure (40 CFR 261.24,
Appendix II, Federal Register 1980, page 33127). The maximum concentration
of contaminants allowable in the EP leachate is 100 times the National
Interim Primary Drinking Water Standard. Leachates containing greater than
this level cause the waste to be defined as hazardous and be subject to all
regulatory provisions; leachates with lower levels of all listed contaminants
cause the waste to be classified as nonhazardous and thus not covered by
these regulations.
Any test developed to assess the maximum hazard posed by a waste that is
landfilled must be a generally flexible procedure that can handle a wide
variety of wastes with a broad range of contaminant concentrations. This
type of test assesses the maximum concentration of contaminants that can be
developed in water contacting the wastes to be disposed. Procedures can be
varied with the type of waste being tested. The waste is ground to a fine
powder to ensure that a maximum surface area is presented to the contacting
liquid. The ratio of waste to leaching medium is varied in such a way as to
achieve a solution saturated with respect to compounds in the waste. Thus,
the leach liquid may be separated from the waste and added to fresh wastes
until the concentration of contaminants in the leachate no longer increases.
4-3
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If the composition of the waste indicates that common ion effects are
preventing some potential contaminants from appearing in equilibrium concen-
trations as they would if the waste contained only the pure contaminant com-
pound, the waste can be leached with successive volumes of fresh leaching
medium until a maximum concentration for the contaminant of interest is
found. This type of test has no fixed level for rejection of the waste as
hazardous, but concentrations of potential contaminants that go above the
levels considered harmful to human health and the environment are noted. One
example of this type of protocol is the Maximum Possible Concentration (MFC)
Test outlined in Malone et al. (1980).
Leaching tests developed for engineering purposes attempt to develop
leachate that duplicates that obtained from the landfilled wastes. This type
of test is used to provide a basis for designing leachate treatment systems
for proposed landfills and in evaluating the performance of treated (solidi-
fied) wastes developed for landfill disposal.
Several engineering tests have been proposed. The Solid Waste Leaching
Procedure (SWLP) tumbles ground or monolithic waste samples in ten volumes of
water per unit weight of sample (Garrett et al. 1981). A minimum of four
successive extractions are performed to determine the changing character of
the leachate.
Another proposed test for solidified industrial wastes is the Uniform ;
Leaching Procedure (ULP) outlined in Malone et al. (1980) and discussed in
detail in American Nuclear Society (1981), Cote and Isabel (1983), and Cote
and Hamilton (1983). The ULP is a static leaching test that assumes that
diffusion from the surface of a solidified waste is the major mechanism for
contaminant transfer to surrounding water. A specific volume of was.te is
exposed to a fixed volume of water (or other leaching medium) that is changed
on a regular schedule. If the surface area of the emplaced waste is known,
estimates of the loss of contaminants from diffusion can be developed.
Concentrations of contaminants in leachate can be used to postulate the
environmental impact of the emplaced wastes.
The ULP and other static leaching tests for industrial wastes have been
criticized because of the low reproducibility (only one order of magnitude in
a leachability index) and the low levels of contaminants that must be quanti-
fied in the leachate (Cote and Isabel 1983). These problems can be overcome
by concentrating contaminant from the leachate or by using tracer or surro-
gate compounds that can be added to the waste in appreciable quantities.
Surrogate compounds can be selected that mimic the behavior of the toxic com-
ponents in the waste and are easily determined at low concentrations; how-
ever, these newer methods of increasing the reliability of leaching tests
have not been widely used or accepted.
Current guidelines for solidified low-leveX nuclear waste state that
waste developed for land burial must have a leachability index greater than
eight when measured using the standard static leaching test proposed by the
American Nuclear Society (Nuclear Regulatory Commission 1983). Pozzolan-
based and pozzolan-Portland-cement-based solidified industrial wastes pre-
pared from dewatered industrial-type sludge all had leachability indices of
4-4
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ten and above for arsenic, cadmium, chromium,: and lead (Cote and Hamilton
1983). Industrial waste can be prepared to meet the Nuclear Regulatory Com-
mission criteria if the waste is properly pretreated to eliminate highly
leachable constituents and solidified using carefully developed procedures.
Any procedures for evaluating the leachability of stabilized/solidified
waste should include all three types of testing: regulatory, risk assess-
ment, and engineering design tests. The data developed in each type of test
are useful for specific purposes such as delisting the waste as nonhazardous
and determining the degree of containment needed in the disposal site.
4.2.2 Free Liquid Content
Free liquids in solid wastes are defined as liquids which readily sepa-
rate from the solid portion of a waste under ambient temperature and pres-
sure. Current regulations prohibit disposal of solid waste containing free
liquids in landfills without pretreatment (i.e. mixing with an absorbent
material) or treatment by in-situ absorption in the landfill.
A number of tests for free liquid have been proposed or can be adapted
from other testing operations. Many test protocols, such as the inclined
plane test or a simple gravity drainage test, do not take into account the
pressure of overburden on the waste at the bottom of a landfill. A review of
the test procedures is given in SMC-Martin (1981). Most solidified wastes
are designed to be landfilled to an appreciable depth (10 to 20 m) of mate-
rial. Therefore, any test for free liquid should take into account the in-
creased pressure due to the overburden. To simulate overburden, a sample of
material can be subjected to pressure while it is in an apparatus that will
permit any exuded liquid to be collected. SMC-Martin (1981) outlines large
and small pressure cells developed to measure free liquid production in moist
refuse produced by overburden pressure.
A very simple approach is to place a solidified waste sample of specific
size and weight between weighed clean filter pads and load the block of waste
to pressures comparable to those developed in landfilling (10-m depth = about
200 kPa, or 30 psi). The exuded liquid is collected on the filter pads and
the weight difference of the pads before and after pressure is applied is
used to quantify the amount of exudate.
Current EPA regulations indicate that no free water should be present in
the waste. The Nuclear Regulatory Commission (1983) has specified that
solidified low-level radioactive wastes must be free-standing monoliths and
that no more than 0.5 percent of the waste volume can be free liquid.
4.2.3 Reactivity and Ignitability
Stabilized/solidified wastes that are to be disposed of in a landfill
(onsite or offsite) should meet the criteria for landfilled hazardous waste
4-5
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in that due care must be exercised if the treated wastes are ignitable or
reactive (40 CFR 265.312, Federal Register 1980). In most circumstances
where stabilization and solidification are used, the waste can be rendered
nonreactive or nonignitable in treatment. Tests for ignitability and pyro-
phoricity are given in Malone et al. (1980). Solidified/stabilized wastes
developed for radioactive waste burial must not only be nonignitable, they
must also be nonpyrophoric (i.e, will not support combustion if ignited) and
must be nonreactive and nonexplosive (Nuclear Regulatory Commission 1983).
Similar specifications for solidified industrial waste are desirable.
4.2.3.1 Reactivity.
Solidified wastes can contain reactive compounds that remain reactive
after treatment. The wastes should be tested for compatibility with mate-
rials (absorbents, liners, other wastes) they would contact during land-
filling. Procedures discussed in Hatayama et al. (1981) are useful for this
purpose. Where possible, reactive materials should be destroyed or neutra-
lized before stabilization.
If the potential for explosive reactions in waste exists, the Explosive
Temperature Test (40 CFR 250.13) can be used to verify the hazard. Bureau of
Explosives impact testing (49 CFR 173.53 (b), (c), (d) and (f)) can also be
employed with solidified waste. Explosive and reactive wastes are not accep-
table for landfilling.
4.2.3.2 Ignitability.
Solidified waste should not cause fires through friction, absorption of
moisture, or spontaneous chemical changes. If ignited the material should
not burn persistently (it should be self-extinguishing) or vigorously. Many
biodegradable wastes produce methane under anaerobic conditions.
Many solidification systems which use cement and pozzolanic materials
are inherently nonignitable and safe. Encapsulation systems using organic
materials such as asphalt or polyethylene may require ignitability testing.
Any liquid associated with the solid should be subjected to the test proce-
dure given in ASTM Standard D-93-79 or D-3278-78 (ASTM 1973). Materials
having flash-points less than 60ฐ C are unacceptable. Any gases evolved from
the waste should be nonignitable and nontoxic as specified in 49 CFR 173.300.
The solid waste itself should not be capable of sustained burning if ignited.
Tests such as ASTM F501 can be used to evaluate this property (Malone et al.
1980).
4-6
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4.2.4 Physical Stability
Physical stability of the waste under conditions of burial is necessary
to ensure that the waste can support necessary construction equipment and
that, over the long run, it does not consolidate and cause the landfill cover
to collapse or fracture. Membrane covers can fail through shear if the
underlying waste consolidates or shrinks unevenly. Consolidation and shrink-
age are problems that occur most often in moist, organic-rich wastes.
The amount of settlement that can be tolerated depends on the type of
cover on the landfill and any future use of the filled area. If a soil cover
is used and no future construction occurs on the landfill, then extensive
settlement may not disrupt drainage or impair performance. If the final
cover includes a membrane cover, settlement should be limited to the lowest
achievable value. Table 4-1 lists the suggested test procedures for deter-
mining characteristics that relate to settlement of stabilized waste resid-
uals. Some of these characteristics such as particle-size distribution and
compaction may not be measurable on strongly cemented wastes. Wyss et al.
(1980) discuss typical testing programs for consolidation.
TABLE 4-1. RECOMMENDED TESTING PROCEDURES FOR PHYSICAL
CHARACTERISTICS THAT RELATE TO WASTE SETTLEMENT
Test
Procedure
Particle-size distribution
density
Compaction
Consolidation
Compressive strength
Unconfined
Triaxial shear
Plate load
Permeability
ASTM D422-63 or
EM 1110-2-1906 Appendix II*
ASTM D698-70t
ASTM D2435-70
ASTM D2166-66
ASTM D2850-70
ASTM D1194-72
ASTM 2434-68 or
EM 1110-2-1906 Appendix III*
* U.S. Army (1972).
t ASTM (1973).
4-7
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4.2.5 Biological Stability
Biological activity in stabilized/solidified wastes is usually not
desirable. Many biological reactions, such as sulfide oxidation or decompo-
sition of hydrocarbons, can produce acids that attack lime-based solidifica-
tion processes and increase the potential for leaching from the wastes.
Methane gas can also be produced in large quantities under anaerobic condi-
tions. Tests such as ASTM G21 and ASTM G22 (ASTM 1973) can be used to
directly determine the ability of the wastes to support biological activity.
The Nuclear Regulatory Commission (1983) requires that nuclear waste solidi-
fied with cement-based processes support no biological growth. Bituminous
materials are permitted if only one bacterial colony develops per sample,
using a sample of the size specified in ASTM C39 or ASTM D621 (ASTM 1973).
Indirect measuring systems can also be used. In indirect systems sam-
ples of the waste are subjected to biological testing and then followed by
strength testing so that any decrease in strength can be documented.
4.2.6 Strength or Bearing Capacity
The ability of the treated waste to support the cover material relates
directly to the strength and bearing capacity of the waste. Most measure-
ments made on waste have used standard procedures such as ASTM D2166-66 or
ASTM C39, where a sample of brittle material is tested to failure. Where
bituminous materials containing wastes are included in the test procedure,
ASTM D621 Method A (Nuclear Regulatory Commission 1983) has been recommended.
The dutch cone test and plate load test have been suggested as supple-
mentary systems of testing solidified wastes (Brown and Assoc. 1981). These
tests yield less precision but are applicable in the field.
Unconfined compressive strengths measured on solidified wastes have
4
ranged from 5.5 kPa (0.8'psi) to 3.1 x 10 kPa (4500 psi) (Bartos and Palermo
1977). The Nuclear Regulatory Commission (1983) guidelines call for a com-
pressive strength of 103.5 N/sq cm (150 psi) for rigid materials. Bituminous
materials must show less than 20 percent deformation at this pressure.
Where it is suspected that the increasing the water content of the waste
causes the waste to lose strength, a program of testing unsaturated and sat-
urated specimens can be undertaken. Where soluble cementing materials like
CaSO, are being used, wet-dry cycling should be required to demonstrate that
the solidified waste will not lose strength after placement.
4-8
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4.2.7 Permeability
Solidified wastes normally require the use of a falling head permeabil-
ity test conducted in a triaxial compression chamber with back pressure to
ensure complete saturation (U.S. Army 1972). Permeabilities measured in
solidified waste typically range from around 10~4 to 10~8 cm/sec. No stan-
dards related to permeability have been developed for solidified waste. Such
low permeabilities indicate decreased mobility in the treated waste and a
slower transfer of contaminants from the solid mass to leaching waters
4.2.8 Durability
Most solidified wastes do not have high durability when subjected to
standard freeze-thaw or wet-dry test procedures (Bartos and Palermo 1977)
However, solidified wastes are generally buried and not subjected to varying
conditions. An adequate cover usually can minimize temperature and moisture
variations in the wastes. Durability testing becomes important where un-
covering of the waste by erosion or human activity is likely or where lone-
term durability must be estimated.
Durability testing is usually done using soil-cement test protocols.
These include ASTM D560-57 for freeze-thaw testing and D559-57 for wet-drv
testing. J
4.3 Example Specifications
To select or develop an optional solidification system, it is necessary
to specify the performance required under the conditions of burial that are
being considered. Table 4-2 is an example of a specification that might be
developed for a solidified waste. Some features of the waste can only be
specified as landfill design is evaluated. For example, the loading under
which the free liquid test would be run would depend on the maximum depth or
loading proposed in the landfill. The durability testing may be restricted
to the expected number of cycles that might occur after waste placement and
before cover placement.
4-9
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TABLE 4-2. EXAMPLE SPECIFICATIONS FOR SOLIDIFIED WASTE FOR LAND BURIAL
Characteristic
Recommended Value
Leachability
Free liquid content
Physical stability
Reactivity of waste
Ignitability
Ability to support
microbial growth
Strength
Permeability
Durability
For major toxic components leachability is greater
than 6 using ANS 16.1. Must pass EP test.
No liquid exuded under maximum loading proposed in
landfill design.
Will not allow unacceptable settlement under land-
fill design conditions.
Nonreactive.
Nonpyrophoric. Flash point below 60ฐ C using
ASTM D-93-79 or D3278-78.
No microbial growth observed using ASTM G21 or G22.
Greater than 1000 kPa (150 psi) using ASTM 39 or
ASTM D621.
Less than 1 x 10 cm/sec when measured using upflow
triaxial procedure.
As required by site design. Measured using
ASTM D560-57 and ASTM D559-57.
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REFERENCES
American Nuclear Society. 1981. Measurement of the Leachability of Solidi-
fied Low-Level Radioactive Wastes. Draft of Standard ANS-16.1. 47 pp.
American Society for Testing and Materials (ASTM). 1973. Annual Book of
ASTM Standards, Part II. Philadelphia, Pennsylvania.
Bartos, M. J., Jr., and M. R. Palermo. 1977. Physical and Engineering Prop-
erties of Hazardous Industrial Wastes and Sludges. EPA-600/2-77-139,
U.S. Environmental Protection Agency, Cincinnati, Ohio. 89 pp.
Cote, P. L., and D. Isabel. 1983. Application of a Static Leaching Test to
Solidified Hazardous Wastes. Presented at ASTM International Symposium on
Industrial and Hazardous Solid Wastes, Philadelphia, Pennsylvania, March 7-10,
1983.
Cote, P. L., and D. P. Hamilton. 1983. Leachability Comparison of Four
Hazardous Waste Solidification Processes. Presented at the 39th Annual
Purdue Industrial Waste Conference, Lafayette, Indiana, May 10-21, 1983.
Federal Register. 1980. Hazardous Waste and Consolidated Permit Regulations
Vol 45, No. 98, Book 2, pp. 33063-33285, May 19, 1980.
Garrett, B. C., et al. 1981. Solid Waste Leaching Procedure Manual. Draft
Report Contract 68-03-2970, U.S. Environmental Protection Agency,
Cincinnati, Ohio. 53 pp.
Hatayma, H. K., et al. 1981. Hazardous Waste Compatibility Protocol.
California Department of Health Services, Berkeley, California, Report on
Grant R804692010, U.S Environmental Protection Agency, Cincinnati, Ohio.
Lowenbach, W. 1978. Compilation and Evaluation of Leaching Test Methods.
EPA-600/2-78-095, U.S. Environmental Protection Agency, Cincinnati, Ohio.
Ill pp.
Malone, P. G., L. W. Jones, and R. J. Larson. 1980. Guide to the Disposal
of Chemically Stabilized and Solidified Wastes. SW- 872, Office of Water and
Waste Management, U.S. Environmental Protection Agency, Washington, D.C.
126 pp.
Nuclear Regulatory Commission. 1983. Branch Technical Position on Waste
Form. Document 204.1.5/TCJ/1/5/83, Nuclear Regulatory Commission,
Washington, D.C. 10 pp.
SMC-Martin. 1981. Test Protocol for Free Liquid Content of Hazardous Waste.
Phase I, Contract No. 68-01-3911, U.S. Environmental Protection Agency,
Washington, D.C. 128 pp.
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U.S. Army, Office of Engineers. 1972. Laboratory Soils Testing. Engineer
Manual 1110-2-1906, U.S. Army Corps of Engineers, Washington, B.C.
Wyss, A. W., et al. 1980. Closure of Hazardous Waste Surface Impoundments.
SW-873,"office of Water and Waste Management, U.S. Environmental Protection
Agency, Washington, B.C. 92 pp.
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SECTION 5
BENCH- AND PILOT-SCALE SCREENING OF SELECTED TREATMENT PROCESSES
After preliminary selection of a stabilization/solidification system, a
pilot-scale or bench-scale study can be developed to obtain detailed informa-
tion on factors such as:
a. Safety problems in handling waste.
b. Waste uniformity and mixing and pumping properties.
c. Development of processing parameters and the level of processing
control required.
d. Volume increases associated with processing.
Safety problems on larger scale stabilization/solidification operations
may involve fuming, heat development, and volatilization of organic mate-
rials. Allowance may have to be made to adapt equipment for vapor control or
cooling of. reaction areas. Rapid addition of a reactive solidification agent
(such as unhydrated lime) can cause rapid volatilization of organic compounds
having low boiling points, with the possibility of a flash fire occurring. A
fire believed to be caused this way occurred when lime was added to a sludge
pit at Utica, Michigan, in 1983.
Heat transfer characteristics may be very different as a treatment or
reaction system is scaled up and dimensions increase. With lower heat
losses, temperatures rise, reaction rates are accelerated, and the solidi-
fication processes can become self-promoting. This is a common problem in
operating with any large exothermic reaction such as hydration of Portland
cement or the solidification of some organic polymers. Standard test proce-
dures for heat of hydration of cements can be used in bench- and pilot-scale
evaluation to predict heat generation and calculate temperature increases. A
typical bench-scale procedure would be ASTM C 186, Test for Heat of Hydration
of Hydraulic Cements (U.S. Army 1949).
A larger pilot-scale test involving 0.22 m3 (8 cu ft) of cement or poz-
zolan is given in the Corps of Engineers Test of Temperature Rise in Con-
crete (CRD-C 38 in U.S. Army 1949). Adaptations of this test, such as fume
collection and temperature monitoring, may be made to allow the effects of
volatilization of organic compounds to be considered. The insulated block
may have to be vented to simulate loss of low-boiling-point waste components.
5-1
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When fumes from a solidifying waste are anticipated to be a problem, it
is necessary to examine the headspace gases that develop in a closed con-
tainer such as partially filled drums containing solidifying wastes. Stan-
dard organic vapor or gas monitoring equipment can be used to estimate the
severity of the problem. Hatayama et al. (1981) outline the usual procedures
that would be used to determine whether a potentially hazardous reaction will
occur when solidification or stabilization reagents are added to a waste.
Typical equipment includes organic vapor analyzers of the gas chromatograph
or infra-red absorption types or detectors based on colorimetric systems.
The objective of testing would be to determine the peak concentrations of
irritating or toxic volatiles that might be produced with an addition of a
given reagent. If the concentration of toxic volatiles obtained exceeds
safety standards (after assuming a reasonable dilution for the site), then an
enclosed or vent-controlled mixing and reaction system may be required.
Mixing and pumping problems can arise from variations in the pumpability
of the waste onsite (c.f., Table 3-1). Mixing can become a problem if the
solidifying waste changes viscosity rapidly during setting. If a specific
mixing or pumping technique is to be used in the field, pilot testing can be
used to evaluate the performance of mixers and pumps. Standard test
CRD-C 55-78 outlines techniques to be used in evaluating concrete mixer per-
formance (U.S. Army 1949).
Where the flowability or pumpability of a waste/solidifier mix is
required, tests such as CRD-C 611-80 would be appropriate, or tests such as
CRD-C 612-80, Test Method for Water Retentivity of Grout Mixtures, can be
used to predict the amount of fluid separation to be expected from a waste/
solidifier mix (U.S. Army 1949).
Processing parameters such as mix ratios, mix times, set times, and con-
ditions of treated waste curing have to be examined in each specific waste
solidification project. The detail of work involved approaches that used in
designing concrete mixes. Much of the pilot testing can be patterned after
concrete design procedures (U.S. Army 1949), but it is largely trial and
error because of the wide variety of waste types and reagent properties. For
instance, fly ash, which is a most common reagent, varies in sorption and
pozzolanic activity depending upon the coal source and firing conditions in
the furance, and its age and moisture content. Wastes will also vary between
batches and even between the top and bottom of a single drum.
All solidification or absorption procedures result in some increase in
waste volume. The volume increase can be seriously underestimated if too few
measurements of additive requirements are made or if the moisture content of
the absorbent or additive is greater in field specimens than in laboratory
materials. Pilot tests with large, typical samples of additives usually pro-
vide more reliable estimates of additive volumes than laboratory bench
studies, especially if care is taken to characterize additives (bulk density,
moisture content, reactivity, etc.).
There is no substitute for a pilot study to evaluate a solidification
program and develop production techniques in large-scale solidification
5-2
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projects. Pilot studies also provide large samples of material required for
more accurate, realistic testing, and permit reconciliation of the complica-
tions with equipment and material handling. Pilot studies can also be used
to train equipment operators on the characteristics of the waste and the
solidified product. Although quite expensive and time-consuming, pilot
studies can reduce the possibility of a major accident, reduce work stop-
pages, and increase product consistency and process reliability. Pilot
studies pay for themselves many times over in large-scale projects.
5-3
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REFERENCES
U.S. Army. 1949. Concrete Handbook. U.S. Army Engineer Waterways Experi-
ment Station, Vicksburg, Mississippi, Loose-leaf revised quarterly.
Hatayma, H. K., et al. 1981. Hazardous Waste Compatibility Protocol.
California Department of Health Services, Berkeley, California, Report on
Grant R 804692010, U.S. Environmental Protection Agency, Cincinnati, Ohio.
5-4
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SECTION 6
' FULL-SCALE TREATMENT OPERATIONS ' .
6.1 Project Planning
Planning for the application of stabilization/solidification technology
at a particular remedial action site is divided into two distinct stages as
described in Section 1 (see Figure 1-1). The first planning stage considers
the specific treatment technology and reagents best suited to the particular
waste, including factors such as waste physical and chemical characteristics,
reagent cost and availability, and environmental desirability; this phase has
been considered in detail in the first five sections of this handbook. The
second phase, which is covered in this and succeeding sections, is concerned
with the overall operational and engineering plans for the actual completion
of the project at the specific sitei.e., the treatment scenario. Specific
aspects of this stage concern the development of equipment requirements,
construction sequencing, and cost estimation for the stabilization/
solidification portion of the remedial action project.
The development and selection of the solidification/stabilization opera-
tions plan for a particular remedial action site are dependent on several
factors such as the nature of the waste material, the quantity of the waste
material, the location of the site, the physical characteristics of the site,
and the solidification process to be utilized. When the solidification pro-
gram is being developed, the primary goal is to create optimum efficiency
which is constrained by both short- and long-term environmental and public
health considerations.
This section identifies four alternative scenarios as applied to the
solidification/stabilization of hazardous wastes at remedial action sites and
examines their technical feasibility and comparative costs. The treatment
here is primarily concerned with the evaluation of equipment and project se-
quencing rather than with process chemistry. For purposes of this section,
it is presupposed that the waste solidification/stabilization process has
been selected and optimized, and that the site is geographically and geologi-
cally suitable for onsite disposal. The additional cost of transport and
offsite disposal of the final product may be incurred if onsite disposal is
not possible, but this possibility should not affect the validity of these
discussions.
Onsite solidification/stabilization programs can be classified according
to the manner in which the reagents are added to and mixed with the materials
being treated. Four onsite solidification/stabilization alternatives are
6-1
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examined in this document: in-drum mixing, in-situ mixing, mobile plant mix-
ing, and area mixing. Modifications to these basic operational techniques
are identified and discussed where appropriate. The selection of an appro-
priate solidification/stabilization technique is based on an analysis of
waste, reagent, and sitespecific factors. As a result, only generalized
criteria can be developed as applied to conditions expected at any given
remedial action site.
In-drum mixing is best suited for application to highly toxic wastes
that are present in relatively small quantities. This technique may also be
applicable in cases where the waste is stored in drums of sufficient integ-
rity to allow rehandling. In-drum mixing is typically the highest-cost al-
ternative when compared with in-situ, mobile plant, and area mixing scenar-
ios . Quality control also presents serious problems in small batch mixing
operations; complete mixing is difficult to achieve, and variations in the
waste between drums can cause variations in the characteristics of the final
product.
In-situ mixing is primarily suitable for closure of liquid or slurry
holding ponds. In-situ mixing is most applicable for the addition of large
volumes of low reactivity, solid chemicals. The present state of technology
limits application of in-situ mixing to the treatment of low solids content
slurries or sludges. Where applicable, in-situ mixing is usually the lowest
cost alternative. Quality control associated with in-situ mixing is limited
with present technology.
Mobile mixing plants can be adapted for application to liquids, slur-
ries, and solids. This technique is most suitable for application at sites
with relatively large quantities of waste materials to be treated. It gives
best results in terms of quality control. Mobile plant mixing is applicable
at sites where the waste holding area is too large to permit effective in-
situ mixing of the wastes or where the wastes must be moved to their final
disposal area.
Area mixing consists of spreading the waste and treatment reagents in
alternating layers at the final disposal site and mixing in place. This
technique is applicable to those sites where high-solids-content slurries or
where contaminated soils or solids must be treated. Area mixing requires
that the waste materials be handled by construction equipment (i.e., dump-
trucks, backhoes, etc.) and is not applicable to the treatment of liquids.
Area mixing is land-area intensive, as it requires relatively large land
areas to carry out the process. Area mixing presents the greatest possi-
bility for fugitive dust, organic vapor, and odor generation. Area mixing
ranks below in-drum and plant mixing in terms of quality control.
6.2 Cost Analysis and Comparison
The cost analyses in this chapter are by necessity general and based on
generic techniques and equipment. They are included not as definitive num-
bers but as illustrations of the kinds of considerations which go into such
6-2
-------
analyses. They also give a feel for the applicability of the different pro-
cedures which .are discussed. We wish to emphasize that specific site and/or
waste characteristics can change these estimates by severalfold.
To increase the usefulness of comparisons the cost calculations are
based upon factors and assumptions which are consistent for the different
alternatives. Further, they illustrate the relative proportion that each
cost subcategory contributes to the overall cost of the process and then
allow estimates of the effect of substitution of alternate reagents or
equipment on the total process cost. The treatment reagents chosen for all
alternatives, Portland cement and sodium silicate, are not universally
applicable as might be implied by their inclusion in all alternatives; but
they are used in all examples because they make the comparisons valid and
because their cost is typically about average or slightly higher than other
reagents. Discussion and comparisons with other treatment reagents are
included in the summary (Section 6.7.2).
Labor costs shown in the illustrations are uniform throughout and in-
clude 25% fringe benefits. Reagents are priced at onsite costs as shown in
Appendix A. All equipment is charged at a daily rate of 0.5% of market value
which includes all fuel, interest, maintenance, and depreciation (3-year ,
base); this rate is unrealistic in some cases, but it serves well for compar-
ison purposes. The equipment rental rates thus calculated are in line with
those quoted by industrial sources (see Appendix B).
6.3 In-Drum Mixing Alternative
The disposal of drums containing toxic and hazardous liquids and sludges
in landfills or open outdoor storage areas has been a common practice in the
United States. Many of the problems with uncontrolled disposal sites can, in
part, be linked to inadequate drum disposal activities. Typically, these
drums are 55 gallons (208 liters) in size although other sizes may also be
encountered. In-drum solidification is an attempt to utilize onsite assets
(i.e. drums) as both mixing vessel and container for the solidified_waste
materials.
:Handling of the drums of materials onsite and offsite before and after
solidification/stabilization is a major consideration in this alternative.
Related problems of selection and implementation of equipment and methods for
handling drums must be independently determined. Factors that influence the
selection of drum handling equipment or methods include worker safety, site-
specific variables, environmental protection, and costs. An EPA (19,83)
manual reviews the applicability, advantages and disadvantages of equipment,
and methodologies for handling drums. The manual addresses detecting and
locating drums, determining drum integrity, excavation and onsite transfer of
drums, recontainerization and consolidation, and storage and shipping.
In-drum mixing can use existing or new drums.. Where drum integrity
allows, the reagents are added directly to the drum in which the waste has
been previously stored. Drum reuse has the advantage that maximum use is
6-3
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made of onsite assets, and drum crushing and disposal considerations are
eliminated, with subsequent cost savings. However, in-drum mixing is often
precluded because the poor condition of the drums or the need for head space
in the drum does not allow for addition of the solidification/stabilization
reagents and resulting expansion of the treated wastes. Typical head space
requirements range between 50% and 30% of drum volume. Thus, if all drums
have sufficient integrity for use, 0.5 to 1 additional drum is required for
each drum of existing wastes.
Most drums found at abandoned waste sites have only a bung hole in a
solid top. These drums pose a special problem because the opening is too
small to insert bulk reagents or an adequate mixing apparatus. Testing of
the composition of the contents or of their homogeneity is also difficult.
The most common procedure used to overcome these problems is to redrum the
contents in new or used, open-topped drums at which time the contents can be
visually inspected for uniformity or phase separation. A second alternative
is to cut a larger opening in the drum top for access. Although this proce-
dure is cost-effective with drums which are in good condition, the added la-
bor and equipment cost and exposure of employees lessens the benefits of the
latter method. Care should be taken to use a nbnsparking cutting apparatus
(e.g., one of bronze), as the head space may contain explosive gas mixtures.
If new drums are required, the cost of the in-drum mixing option is sub-
stantially increased. Although the labor cost increases because of implied
redrumming requirements, the primary increase in cost is that of the drums.
The cost of drums (July 1983) ranged between $10 and $60 per drum depending
on the supplier and transportation costs.
6.3.1 Project Sequencing
Project sequencing for in-drum solidification can be divided into seven
steps:
a. The contents of each drum to be treated must be evaluated and/or
identified. Particular care must be taken to ensure compatibility
with the proposed solidification/stabilization process and the
wastes. Each drum should be marked with appropriate identifying
information. Costs associated with this testing are not included in
this analysis and can be substantial.
b. The condition of each drum should also be evaluated. Drums that are
in sufficiently good condition for reuse should be marked. Head
space in each drum should be noted on the exterior of the drum, and
materials should be redrummed as required to accommodate head space
and drum condition requirements.
c. A materials handling location should be prepared. Chemical storage
and mixing equipment should be centrally located. A concrete pad or
gravel surface should be prepared to ensure an adequate materials-
handling facility for all weather conditions. Consideration should
6-4
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be given to materials flow, including incoming empty drums, incoming
drums containing waste materials, and outgoing product drums. For
large sites, multiple materials handling locations may be cost-
effective.
d. Solidification/stabilization chemicals should be added to and mixed
with the wastes being treated.
e. The drums of mixed materials should be placed in a secure area and
allowed to set or cure until stable enough for safe handling.
f. After curing, any remaining head space should be filled with inert
material and the top replaced.
g. The drums should be removed for final disposal.
6.3.2 Equipment Requirements
Equipment requirements for the in-drum mixing process include: onsite
chemical storage system, chemical batching system, mixing system, and drum
handling system. Prior to actual solidification, a temporary, enclosure for
the equipment should be erected. The mixing equipment should be installed on
a prepared surface that will facilitate the cleanup of spills and ensure ease
of daily cleanup. Requirements for the mixing area depend on the size of the
remedial action process and the nature of the wastes being treated. The en-
closure serves to protect personnel from the elements and provides a con-
trolled environment to minimize airborne hazards.
Mixing equipment for in-drum solidification includes the change-can
mixer and the top-entering propeller. Figure 6-1 illustrates in-drum solidi-
fication using the top-entering propeller.
6.3.3 Costs
In-drum mixing has the highest per unit cost of the four solidification/
stabilization techniques examined (Table 6-1). The total cost of cement-
silicate solidification using the equipment, labor, and assumptions listed
below is over $50 per drum holding only 40 gal of waste. Since reagent costs
are only a small part (about 12%) of the total cost per drum, using smaller
amounts of cheaper reagent would not greatly affect the overall cost (see
Section 6.7.1). Labor, equipment rental, and used drums each account for
between 15% and 25% of the total cost, for a total of about 60% of the total
(not including the 30% for profit and overhead). The high labor and equip-
ment costs result from the very low throughput of the systemonly 4.5 drums
per hour, which is less than 1 cu yd. Increasing this throughput would pro-
duce an appreciable reduction in treatment costs since over half of the cost
is sensitive to the production rate. The cost of treating 500,000 gal of
waste using this system is about $750,000about $1.50 per gallon. Economic
6-5
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Figure 6-1.
mixer.
In-,drum mixing using a top-entering propeller
considerations alone limit this treatment system to small amounts of very .
toxic wastes; it cannot compete with the dedrumming and bulk treatment of
compatible wastes as done in other alternative techniques to be discussed.
Even for wastes already contained in re-usable drums, the total cost would
decrease only by about 20% to about $207/ton ($40.90/drum) in this example.
Costs of initial classification, screening, and handling from remote site
locations and to the point of final disposal and final disposal are not
included.
The procedure for estimating the cost of in-drum solidification/
stabilization is summarized in Table 6-1 and detailed as follows:
a. Assumptions.
(1) Solidification/stabilization process selected using Type I
Portland cement (30%) and sodium silicate (2%).
(2) Specific weight of waste to be solidified/stabilized is
85 Ib/cu ft.
(3) Approximately 40 gal of untreated waste can be placed in a drum
and leave enough head space for reagent addition.
(4) Processing rate averages 4.5 drums per hour.
6-6
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TABLE 6-1. COST ESTIMATES FOR THE IN-DRUM TREATMENT ALTERNATIVE
Note: Stabilization/solidification with 30% (w/w) Portland cement (Type I)
and 2% sodium silicate of 40 gal of waste (85 Ib/cu ft) in 55-gal drums at
4.5 drums per hour throughput.
TREATMENT REAGENTS:
30% Portland cement = 137 Ib/drum x ($0.0275/lb) = $3.77/drum
2% sodium silicate^ 9 Ib/drum x ($0.10/lb) = $0.90/drum
Total cost for 12,500 drums: $58,275
$ 4.67/drum
LABOR COST FOR TREATMENT:
1 ea Project supervisor
2 ea Laborers @ $12.50
$27.50/hr = $6.1I/drum
25.00/hr = 5.55/drum
Total labor cost for 12,500 drums: $145,750
$11.66/drum
MATERIALS: Used, reconditioned drums: 12,500 for $137,500
$11.00/drum
EQUIPMENT RENTAL:
Chemical storage silo
Change-can mixer
Forklift
Chemical feed system
Total rental for 12,500 drums: $106,000
Capacity
2,000 cu yd
5 cu yd
1 ton
100 Ib/min
Value
$20,000
15,000
14,250
8,700
Per hour
$13.15
9.90
9.40
5.70
Per drum
$2.92
2.20
2.09
1.27
$ 8.48/drum
MOBILIZATION-DEMOBILIZATION AND CLEANUP: 10% add-on = $44,750 $ 3.58/drum
TOTAL COST OF TREATMENT: 12,500 drums for $492,275
PROFIT AND OVERHEAD (<ง 30% of cost): $147,682
TOTAL CONTRACTED PRICE PER DRUM:
TOTAL CONTRACTED PRICE FOR 12,500 DRUMS
(500,000 gal or 2,850 tons of waste):
$39.36/drum
$11.81/drum
$51.17/drum
$639,957 or $224.29/ton
6-7
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b.
c.
d.
(5) Onsite cost of reagents is approximately $0.0275 per pound
($55 per ton) for Portland cement and $0.10 per pound ($200 per
ton) for sodium silicate.
(6) Onsite labor dedicated to the solidification process includes
two general laborers at $12.50 per hour, and one project
supervisor at $27.50/hr.
(7) Reconditioned drums costing $11.00 each are used.
new drums can cost up to $40.00 each.
Chemical requirements per drum.
(1) Portland cement at 30% by weight:
(40 gal/drum) * (85 Ib/cu ft) * (0.30)
(7.48 gal/cu ft)
(2) Sodium silicate at 2% by weight:
Note that
137 Ib/drum
(40 gal/drum) * (85 Ib/cu ft) * (0.02) = lb/drum
(7.48 gal/cu ft)
Equipment rental and operation cost. Equipment rental and operation
costs are computed for a 2,000-cu-yd chemical storage silo ($20,000),
a 5-cu-yd change-can mixer ($15,000), a 1-ton forklift ($14,250), and
a 100-lb/min chemical feed system ($8,700).
Allowance for profit and overhead. Profit and overhead allowances
for this type work (based on construction company rates) range
between 20 and 40%. Since this is assumed to be a high-risk opera-
tion, assume 30% profit and overhead.
Costs not included. Note that the above cost includes the
solidification/stabilization process and handling immediately before
and after mixing. The following costs, which may be substantial, are
not included: Identification and evaluation of drum contents,
evaluation of drums, transport of drums to treatment area and of
solidified/stabilized material to the final disposal site, and site
preparation and closure activities.
Summary of in-drum mixing. As seen in Table 6-1, the estimated
actual cost of stabilization/solidification including profit and
overhead is around $51 per drum ($244/cu yd or $258/ton). Of this,
only about 10% is for the treatment reagents, while 30% goes for
labor (including mobilization-demobilization), 21.5% for recondi-
tioned drums, and about 16.5% for equipment. Since only about half
of the cost of treatment is fixed per unit of waste (drums and re-
agents) , the unit price is quite sensitive to production rate.
Doubling the rate from 4.5 drums per hour to 9 drums per hour with
the same equipment essentially lowers the unit treatment cost by
6-8
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about 25% to around $148/ton ($29.32/drum) or total cost with profit
and overhead to $192.50/ton ($38.11/drum). If original drums are
usable, the total cost of treatment will drop another 25%.
6.3.4 Safety and Environment
In-drum solidification/stabilization can provide the safest and most en-
vironmentally controlled work environment. Equipment can be purchased and
installed to meet all Occupational Safety and Health Administration (OSHA)
standards. A variety of standard accessories including dust hoods, dust
shields, and vacuum hoods are available for the change-can mixer (these items
are not included in costs shown in Table 6-1). In addition, the equipment can
be easily operated by personnel in protective clothing. Typical protective
clothing will include rubber gloves, safety glasses, hard hat, and dust mask
or respirators. Equipment operation can also be accomplished in full air
pack. Note that if full air pack protective equipment is required, a 50% to
60% reduction in productive capacity can be anticipated.
6.3.5 Modifications
In-drum or in-container solidification has been used extensively in the
disposal of low-level radioactive waste materials. Specialized in-drum mixing
equipment has been developed for this application. Particular attention has
been given to the safety-related aspects of such equipment. Special drum
fill-heads and remote monitoring systems have been developed to allow the drum
to be filled, the reagents to be added, the contents mixed, and the drum
sealed by operators isolated from the waste. Because of the high cost of
these systems, they have not been widely used for the treatment of toxic and
hazardous waste materials. They may have applicability to the solidification/
stabilization of extremely toxic or hazardous wastes.
Another product of the nuclear industry is the prepackaged spill solidi-
fication kits. These systems are designed for the cleanup of small spills and
include the mixing drum, premeasured solidification reagents, and disposable
mixing blades. Kits come in a variety of available sizes complete with in-
structions. The user must supply a driver for the mixing blades. Figure 6-2
illustrates a typical spill cleanup drum solidification system. A 1981 price
quote for a 55-gal drum system (40-gal maximum waste volume) was $600 per
pallet of four drums f.o.b. plant of manufacture. These systems are con-
sidered for specialty purposes only and are not economically practicable for
large-scale sites.
A final modification of the in-drum solidification scenario is the bulk-
ing of drummed liquids, solidification of the bulked liquids in a mobile or
portable plant (Section 6.5), and repackaging of the solidified wastes in
salvaged or new drums. This modification may be appropriate at sites with
significant numbers of broken or leaking drums containing compatible wastes,
6-9
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LUBRICATOR
CAT. NO. NL-8
INGERSOLL-RAND
OREO.
MULTI-VANE AIR MOTOR
CAT. NO. 48405
INGERSOLL-HAND
OREO.
VICE-GRIP
9" WELDING'
CLAMP
NO. 9R
Figure 6-2. Typical spill cleanup system
(Courtesy Delaware Custom Materials).
or as a method to reduce the unit cost by increasing the production rate and
simplifying the equipment required.
6.4 In-Situ Mixing Alternative
The simplest solidification/stabilization alternative examined in this
study is in-situ mixing which incorporates the use of common construction
machinery (typically a backhoe or pull-shovel) to accomplish the mixing pro-
cess. Where large lagoons are being treated, clamshells and/or draglines have
also been utilized. This technique is suitable for application to liquids or
light flowable sludges having a high liquid content. The technique is suited
more to those solidification/stabilization processes incorporating the addi-
tion of large amounts of bulk powdery solids (kiln dust, fly ash, etc.) to the
waste materials. In those cases where small amounts of admixture (fluidizers,
plasticizers, retardants, etc.) are to be added, the mixing efficiency of
available in-situ processes is not uniform. Data are not currently available
on the mixing efficiency of the in-situ processes when applied to large-scale
field projects.
6-10
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6.4.1 Project Sequencing
Two in-situ solidification/stabilization alternatives are developed. In
the first, the existing lagoon is used as both the mixing vessel and the
final site for disposal of the treated wastes so that the waste materials are
not removed from the existing lagoon or holding pond. In the second, the
waste material is removed from the holding pond and placed in specially pre-
pared mixing pits. After mixing, the treated wastes are either removed from
the mixing pits to a prepared disposal site or are left in the mixing pits
which become the final disposal site.
Under the first alternative, the existing holding lagoons are used as
the final disposal site. The reagents are added to the lagoon by pneumatic
or mechanical means. Pneumatic addition uses blowers to distribute the
reagents over the surface of the lagoon. Mechanical addition incorporates
the use of dump trucks, front-end loaders, or clamshells to mechanically add
the required reagents. Mixing of the reagents is accomplished with a back-
hoe, clamshell, or dragline. The selection of mixing equipment is based on
the size of the lagoon being treated and general site topography. Lagoons
less than about 30 ft (10 m) in radius (or effective radius in the case of
rectangular or odd-shaped lagoons) are amenable to backhoe mixing. Larger
lagoons would require the use of a clamshell or dragline to ensure an adequate
reach for mixing the contents in the middle of the lagoon.
The second alternative involves the preparation of special, onsite mix-
ing pits. The waste material is transferred from the holding lagoon to the
mixing pit. Pumps can be used to transfer liquids and light sludges whereas
clamshells and trucks can be used to transfer heavy sludges. Reagents are
added using the same methods described in the first alternative. Since the
mixing pit can be constructed to a specified size, mixing is generally
accomplished with a backhoe. After thorough mixing, the material is allowed
to gel, or set, for the required amount of time. The solidified/stabilized
material is then either capped in place (in the mixing pit) or removed to a
prepared onsite disposal facility.
6.4.2 Equipment Requirements
Equipment required for in-situ solidification/stabilization varies with
the specific site. Generally, an average site would require equipment in the
following categories: dump trucks, front-end loader, excavator or backhoe,
and onsite chemical storage and handling facilities. The size and amount of
equipment depend on the location and topography of the remedial action site as
well as the quantity of material to be treated. Figure 6-3 illustrates
in-situ mixing using a backhoe.
6-11
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Figure 6-3. In-situ mixing with a backhoe at a large site.
(Courtesy Albert H. Halff Associates)
6.4.3 Costs
The cost of in-situ solidification/stabilization techniques is based pri-
marily on the production rate achieved by the equipment mix selected for the
specific remedial action project. Field data for the cost of in-situ mixing
alternatives applied to remedial action sites are not available. However,
production rates were determined for two RCRA sites using the backhoe-mixing
pit technique. A daily (8-hr shift) production rate ranging from 1,000 to
1,200 cu yd (approximate 1000 cu m) of wastes solidified/stabilized was re-
ported under the following conditions:
a. Construction of an earthen mixing basin (5 to 10 ft deep, 40 to 50 ft
in diameter).
b. Introduction of liquid wastes received in bulk tankers or from
de-drumming of liquids received in drums.
c. Addition of 40% to 60% (by volume) of fresh kiln dust, mechanically
added with a front-end loader.
d. Mixing with backhoe (Caterpillar 225) until solidification/
stabilization process begins.
6-12
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e. Setting or gelling for 24 to 48 hr in the pit.
f. Removal of solidified/stabilized material from pit with front-end
loader or backhoe and spreading in secure landfill with dozer.
Another RCRA site using a similar scheme and equipment, except for the
substitution of permanent concrete mixing pits (4 pits, 100 ft x 20 ft x
10 ft), reported daily (8-hr shift) production rates of 2,000 cu yd. This
second RCRA site also had the capability of pneumatically adding bulk solid
reagents.
The cost of solidification/stabilization at these RCRA sites was reported
to range between $10 and $20 per cubic yard of waste material treated. The
primary variable was the amount of kiln dust required for a specific waste.
This factor affected chemical costs, material handling costs, and mixing labor
costs.
The daily production rate for the backhoe mixing technique depends on the
material being handled, size and quantity of equipment being used on a partic-
ular project, site conditions, quantity of material being treated, and quan-
tity of reagent being added. Production rates for a remedial action site are
expected to be somewhat less than those associated with a permanent installa-
tion. An in-situ treatment scheme incorporating one backhoe (Caterpillar 225
or equivalent) is anticipated to have a daily (8-hr shift) production rate
ranging between 750 and 1,500 cu yd.
The procedure for estimating the cost of in-situ solidification/
stabilization is presented below and summarized in Table 6-2:
a. As sump t ions.
(1) Approximately 500,000 gal of waste liquids and light sludges is
to be solidified in situ using cement and sodium silicate.
Mixing will be accomplished with a backhoe (Caterpillar 225 or
equivalent). Wastes to .be treated are contained in a
rectangular-shaped lagoon approximately 120 ft .x 60 ft x 10 ft.
(2) Bench-scale studies indicate that the reagent must be added on a
weight-to-weight ratio of 30% cement and 2% sodium silicate.
(3) Waste and reagents will be mixed in the lagoon and left in
place.
(4) Onsite cost of cement is $55.00 per ton; sodium silicate is
$200 per ton.
(5) The remedial action site is located 200 miles from the nearest
equipment.
6-13
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TABLE 6-2. COST ESTIMATES FOR THE IN-SITU TREATMENT ALTERNATIVE
Note: Stabilization/solidification with 30% (w/w) Portland cement and 2%
sodium silicate of a pumpable waste (85 Ib/cu ft) from bulk tankers or drums
mixed with a backhoe in an 8-ft-deep, 40-ft-diameter earthen mixing basin, and
removed after 24 to 48 hr setting time. Total waste 500,000 gal (2,475 cu yd
or 2,850 tons) and production rate is 800 cu yd per 8-hr shift (4 days
required).
TREATMENT REAGENTS:
30% Portland cement
2% sodium silicate
855 tons x ($55/ton)
57 tons x ($200/ton)
Total cost of treatment reagents:
$47,025
$11,400
$58,425
$20.50/ton
LABOR COST FOR TREATMENT:
1 ea Project supervisor
2 ea Heavy equip, operators @ $22.
1 ea Laborer
Total labor cost:
Expenses: @ $75/day for 4 men 4 days
= $27.50/hr >
= $44.00/hr >
= $12.50/hr >
< 32 hr = $ 880
< 32 hr = 1,408
< 32 hr = 400
= $2,688 $ 0.94/ton
= $1,200 $ 0.42/ton
EQUIPMENT RENTAL:
Backhoe
Front-end loader
Total rental cost:
Capacity
(1.5 cu yd)
(1 cu yd)
Value Per hour Per 6 days
$95,000 $62/hr = $2,976
29,000 $20/hr = 960
$3,936 $ 1.38/ton
MOBILIZATION-DEMOBILIZATION AND CLEANUP:
Labor and expenses for 3 days: $2,016 + $900
Transportation: 200 mile/trip x 4 trips x $2/mile
Total
TOTAL COST OF TREATMENT: 500,000 gal = $70,765
PROFIT AND OVERHEAD: (@ 30% of cost) = $21,230
TOTAL CONTRACTED PRICE: 500,000 gal = $91,995
= $2,916
= 1,600
$4,516
$ 1.58/ton
$24.83/ton
$ 7.45/ton
$32.28/ton
6-14
-------
b. Mobilization and demobilization costs. Mobilization costs are those
incurred in preparing the equipment for shipment, transporting it to
the site, and setting it up for mixing. Demobilization includes
cleanup of the equipment and site and transportation back to origin.
Mobilization-demobilization will take about 1 day each. Transporta-
tion costs are those associated with actually transporting the
equipment to the site. For this example, it is assumed that local
equipment rental is not available. Two tractor trailer loads will
be required. The estimated cost of heavy equipment transport is
$2.00 per load mile.
c. Project duration.
(1) Based on field experience, a daily production rate (8-hr
shift) is estimated to be 700 cu yd/day of wastes mixed.
(2) Required project time is calculated as follows:
500,000 gal r 7.48 gal/cu ft v 27 cu ft/cu yd
* 700 cu yd/day = 3.54 days (use 4 days).
(3) Since processing will be accomplished at a remote site, person-
nel will be reimbursed for onsite expenses. Assume an expense
rate of $75.00 per man per day.
d. Summary of in-situ costs. The in-situ treatment alternative is the
fastest and least expensive of those discussed in this section. The
speed and economy are largely due to the reduction in the amount of
handling of the waste mass. Other than for mixing, the wastes are
usually moved only once, or if not hazardous, they are often not
even removed from the original waste lagoon but mixed and left in
place. The method lends itself best to liquid or low-solids sludges
which are easily mixed. However, heavy sludges can be mixed with
heavy equipment like draglines or clamshells, but with less uniform-
ity in the treated product. The low labor and equipment require-
ments result in the highest proportion of the cost (63%) going for
the treatment reagent. Thus the cost of the method is quite sensi-
tive to reagent cost and proportion. Major limitations of the
method are the low amount of mixing attained and the inability to
control accurately the proportion of reagent to waste which can
result in a nonuniform, unevenly mixed final product. This can be
overcome to some extent by using excess reagent to decrease zones of
low reagent content, but this increases cost and treated product
bulk.
Two new pieces of equipment which are designed and used specifically for
in-situ mixing have recently been introduced; they are shown in Figures 6-4
and 6-5. These items pneumatically meter and inject the reagent directly
into the waste mass at the lower end of the cylinders, which are used to stir
and mix the wastes. One design (Figure 6-5) has augers at the ends of the
6-15
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Figure 6-4. Ih-situ mixing by direct reagent injection
(Courtesy ENRECO, Inc.).
Figure 6-5. In-situ mixing equipment
(Courtesy American Resources Corporation)
6-16
-------
cylinders which can be used to dig into underlying soils or sludges which may
also be contaminated and incorporate them into the total waste mass.
6.4.4 Safety and Environment
In-situ mixing is the most difficult alternative in terms of control of
safety and environmental considerations. Since the entire process is open to
the atmosphere, anticipated problems include the generation of odors, vapors,
and fugitive dust. In addition to the standard safety precautions associated
with the operation of construction equipment, a strict program for minimizing
exposure of personnel and equipment to the materials being treated should be
implemented. Equipment should be decontaminated on a daily basis and the
wash water should be collected for treatment or solidification.
Standard personnel protective procedures should be implemented as neces-
sary, depending on the waste being handled. Reduction in production effici-
ency can be anticipated to be a function of the degree of protective appara-
tus required. Level A protection is expected to reduce production by up to
75 percent.
The ability to control adequately the in-situ mixing process is a sub-
ject of concern. Quantitative measurement of the degree of mixing produced
by in-situ processes is not available. Most in-situ mixing operations are
found at RCRA waste disposal sites where the mixed waste and solidification
reagents are removed to a landfill after gelling. The rehandling of the pro-
cessed materials allows some quality control of the adequacy of waste-reagent
mixing. This additional level of quality of control may be lacking in the
field environment unless the materials are rehandled and transported to a
separate disposal area. Assurance of adequate quality control requires sig-
nificant levels of experienced, onsite inspection and supervision.
6.4.5 Modifications
The chemical addition and mixing techniques currently used for in-situ
solidification have been adopted from the construction industry and as such
are relatively unsophisticated. Major modifications to in-situ
solidification/stabilization include the development of reagent addition or
mixing equipment that allows better control of the process. Equipment speci-
fically designed for in-situ solidification/stabilization operations at pits,
ponds, and lagoons is currently being used and marketed commercially. The
equipment combines the injection of fly ash or kiln dust into the wastes by
use of an injection head using a hydraulic/pneumatic system with the mixing
of the materials by the injection head (Figures 6-4 and 6-5). The fly ash or
kiln dust is added to the basin material at a predetermined rate until the
consistency of the mix is sufficient for setting to occur within 1 to 3 days.
An air compressor is used in conjunction with the injector head which is in-
stalled on a boom on a tracked vehicle. A hydraulic pump provides the drive
for hydraulic motors on the injection head.
6-17
-------
In one configuration (Figure 6-4) the hydraulic pump is mounted on the
rear of a tracked vehicle for convenience of operation and to counterbalance
the injection head boom when the boom is fully extended. Fly ash is delivered
to the multibarreled injection head via a compressed air system. Besides
providing a delivery system, the pneumatic system also prevents back flow of
the basin material into the submerged ends of the barrels. Hydraulically
driven augers in the lower section of the barrel force the fly ash out of the
barrel into the basin contents. As fly ash is forced from the barrels into
the waste, the boom simultaneously moves the injection head back and forth
(in the plane of the boom) as well as up and down. This motion provides mix-
ing of the fly ash and basin contents. Approximately 1,000 cu yd of waste
material can be solidified per day. This equipment is best applicable to
basins deeper than approximately 4 ft. In shallower basins, the necessary
pneumatic pressure on the fly ash delivery to the injection heads causes loss
of fly ash to the air at the basin surface which results in a burst of fly
ash dust. Basins deeper than 4 ft require a larger injection head system and
appropriately heavier duty equipment. New adaptations of this equipment
which overcome these difficulties have been introduced (see Figure 6-5).
6.5 Mobile Plant Mixing Alternative
Plant mixing refers to those systems which incorporate mobile or fixed
units to handle, meter, and mix the solidification/stabilization reagents and
the wastes being treated. In this alternative, the wastes being treated are
physically removed from their location, mechanically mixed with the
solidification/stabilization reagents, and then redeposited in a prepared
disposal site. Plant mixing is primarily oriented towards the treatment of
pumpable liquids and high-liquid-content sludges; however, special equipment
adaptations have been utilized to handle sludges with high solids contents
and contaminated soils. A schematic of a typical plant mixing scenario is
illustrated in Figure 6-6. Two plant mixing examples will be discussedone
used with pumpable wastes and one with high solids content wastes which must
be handled with construction equipment.
6.5.1 Project Sequencing
Many plant mixing systems include all required solidification/
stabilization equipment in one trailer- or truck-mounted unit, whereas others
are transported in modular form and are put together at the remedial action
site.
Basic project sequencing for plant mixing is as follows:
a. Prepare site for installation of the mobile system. This step
includes any necessary utility hookup such as electricity. Some
mobile systems have on-board power generation systems and require no
onsite power connections.
6-18
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BULK
SOLIDS
STORAGE
LIQUID CHEMICAL
FEED PUMP
WASTE
FEED
PUMP
MIXER
-G>
TO DISPOSAL
-*- OR CURING
AREA
Figure 6-6. Schematic of plant mixing scenario.
b. Prepare final disposal area for solidified/stabilized wastes.
c. Install raw and treated waste handling systems. These usually in-
clude centrifugal or diaphragm pumps with electrical or gasoline-
powered drivers, but they may be simple construction equipment for
high-solids wastes.
d. Transport the portable system to the remedial action site and erect
equipment, interfacing with utilities.
e. Initiate solidification/stabilization process and monitor as
required.
6.5.2 Equipment Requirements
Mobile, trailer-mounted plants may come complete with chemical storage
hoppers, chemical feed equipment, mixing equipment, and waste handling equip-
ment. Some mobile plants have on-board power generation facilities; however,
more commonly, an onsite power hookup or separate power generation system is
required. Although the basic concept for the systems illustrated is identi-
cal, significant variations exist in the details of construction of each.
Variations found in those systems examined during this study were in the
mounting configuration (trailer or closed van), in the types of chemical feed
systems, in the types of mixing apparatus, and in the setup requirements.
6-19
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Both weight- and volume-based chemical feed systems are used.
Volumetric-based systems are utilized exclusively for the addition of liquid
reagents, whereas the addition of bulk solid reagents may be controlled with
either weighing conveyor systems, batch weighing systems, or volumetric screw
feeder systems. Flow of the waste is controlled by the capacity of the
transfer pumps used to transfer the wastes from the holding area to the mix-
ing vessel.
A variety of mixing systems have been successfully used on the mobile
plants currently in use. These include ribbon blenders and single and double
shaft rotor mixers. The type of mixer utilized appears to have little effect
on the quality of the final product, but production efficiency may be
affected. Illustrations and photographs of currently available mobile mixing
plants in operation are presented in Figures 6-7 through 6-11.
The design of mobile plants has been oriented toward the treatment of
liquids and light slurries. Materials handling is most often accomplished
using pumps. The capacity of the typical mobile plant ranges from 60,000 to
150,000 gal per 24-hr day of waste material treated. The controlling factor
in determining capacity is generally the handling characteristics of the
waste materials being treated. Thus the capacity of the same equipment will
vary significantly from job to job. The size of the equipment applicable to
mobile plants is limited by weight, length, and width restrictions associated
with over-the-road transportation requirements.
Modular plant systems consist of separate pieces of equipment that can
be tailored more closely to fit specific site requirements. Whereas mobile
plants are usually self-contained on one van or trailer, modular plants are
usually delivered to the site on several trailers. Typical modular plant
installations are illustrated in Figures 6-12 through 6-14.
The typical modular plant will include equipment modules for: pnsite
chemical storage, usually a silo; chemical feed system, usually a weight
batching system; a mixing system of a type dependent on the waste materials
being treated; a raw waste handling system of a type also dependent on the
waste material; and a final product handling system.
The modular system illustrated in Figure 6-12 is designed primarily to
handle liquids and light flowable sludges up to 30% solids content. Mixing
is accomplished in a 1-1/2-cu yd ribbon blender. Waste materials can be
charged to the ribbon blender using pumps, a clamshell, or a front-end
loader. Mixing time is approximately 1-1/2 to 2 min depending on the mate-
rial being handled. Solidified/stabilized material is discharged at the base
of the ribbon blender and removed by front-end loader. Material can be
transported to the final disposal site by dump truck.
The modular system illustrated in Figure 6-14 is designed to handle
heavy materials such as contaminated soils and low moisture content sludges.
In this particular application, the waste materials were slurried in order to
ensure reaction with the solidification/stabilization agents. A unique
aspect of this system was the use of concrete transit mixers to mix the
6-20
-------
Figure 6-7. Schematic of a trailer-mounted mobile mixing plant
(Courtesy Beardsley & Piper).
- - "
" : DISCHARGE PUMP
Figure 6-8. Schematic of a van-mounted mobile mixing plant
(Courtesy Chemfix).
6-21
-------
4J
H
ft
60
H >-1
S ft
CO -H
r-l P-l
H
O
0 SJ1
fi H
CD CO
ft 13
O >-l
CU
pq
o\
VO CO
cu
CU 4-1
00 O
H O
jj .
H
M-l
CO
cu
u
n
o
o
4-1
fl
CO
H
ft
00
rl
1
cu
co
o
rH
t)
I
VO
H
-------
Figure 6-11. Drum handling mobile mixing plant (Courtesy
Solid Tek).
Figure 6-12. Small modular mixing plant (Courtesy Solid Tek)
6-23
-------
Figure 6-13. Large modular mixing plant- (Courtesy IU Conversion),
ซ*. i 't!^ x f'f
"^jiEa. .!>ป a^:i^., IV.
Figure 6-14. Modular mixing plant for heavy slurries
(Courtesy Solid Tek).
6-24
-------
wastes with the reagents. Reagents and waste materials were batched into the
transit mixer. Mixing was accomplished while in transit to the final dis-
posal site.
6.5.3 Costs
The costs of using mobile or portable mixing plants for a particular proj-
ect are dependent on the process selected (reagent to be added) and the waste
material being handled. These factors are the primary variables in determin-
ing the production rate on a particular project. Project costs include both
fixed costs (i.e. transportation to and from the site and setup costs) and
variable costs (i.e. chemicals and processing labor), which depend on the
quantity and type of material treated.
General ranges of costs for application of both mobile and portable mix-
ing plants to remedial action sites were provided by the owners of equipment
discussed previously. Costs ranged between $20.00 and $75.00 per cubic yard
of material treated. These costs included handling of the waste materials
from their existing holding area to an onsite disposal site. Costs presented
do not include the further handling of the material at the disposal area or
capping and landscaping of the disposal area.
6.5.3.1 Mobile Mixing Plant for Pumpable Wastes.
The procedure for estimating the cost of mobile plant
solidification/stabilization of a pumpable waste is presented below and
summarized in Table 6-3.
a. Assumptions.
(1) Approximately 500,000 gal of waste liquids and pumpable
sludges in an open lagoon are to be solidified using a two
reagent process consisting of Portland cement and sodium
silicate.
(2) Bench-scale studies indicate that the reagents need to be
added in weight-to-weight ratios of 30% Portland cement and 2%
sodium silicate.
(3) An onsite disposal area is available.
(4) The onsite cost of the reagents is $55.00 per ton for Portland
cement and $0.10 per pound for liquid sodium silicate.
(5) The remedial action site is located 200 miles from the nearest
mobile unit.
6-25
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TABLE 6-3. COST ESTIMATES FOR THE MOBILE PLANT MIXING
ALTERNATIVE FOR PUMPABLE WASTES
Note: Stabilization/solidification with 30% (w/w) Portland cement and 2%
sodium silicate of 500,000 gal (2,850 tons) of pumpable sludge (85 Ib/cu ft)
in a mobile mixing plant with daily throughput of 250 cu yd (10 days
required). Onsite disposal available.
TREATMENT REAGENTS:
30% Portland cement = 855 tons x ($55/ton) = $47,025
2% sodium silicate = 57 tons x ($200/ton) = $11,400
Total costs of treatment reagents: $58,425
$20.50/ton
LABOR COST FOR TREATMENT
1 ea Project supervisor
2 ea Technicians @ $18.50
2 ea Laborers @ $12.50
$27.50/hr x 80 hr
$37.00/hr x 80 hr
25.00/hr x 80 hr
Total labor cost:
Expenses: @$75/day for 5 men 10 days
$ 2,200
2,960
2,000
$ 7,160
$ 3,750
$ 2.51/ton
$ 1.32/ton
EQUIPMENT RENTAL:
2 ea Trash pumps
1 ea Mobile plant
Total rental cost:
Capacity
(6 in.)
Value
$31,000
180,000
Per hour
$20/hr =
120/hr =
Per 10 days
$1,600
9,600
$11,200 $ 3.93/ton
MOBILIZATION-DEMOBILIZATION AND CLEANUP:
Labor and expenses for 3 days: $2,148 + $1,125
Transportation: 200 mile/trip x 2 trips x $2/mile
Total
$3,273
800
$4,073
$ 1.43/ton
TOTAL COST OF TREATMENT: 500,000 gal = $84,608
PROFIT AND OVERHEAD (@ 30% of cost) = $25,382
TOTAL CONTRACTED PRICE: 500,000 gal = $110,000
$29.69/ton
$ 8.91/ton
$38.60/ton
6-26
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c.
' Mฐb3-lization and demobilization cost. Mobilization costs are those
costs incurred in preparing the equipment for shipment, transporting
the equipment, and setting the equipment up for actual waste pro-
cessing; these costs include labor costs and transportation costs.
Demobilization includes cleanup of site and equipment and transpor-
tation back to origin. These activities are expected to take about
3 days total. Transportation is the cost of actually transporting
the equipment The estimated cost of transporting the equipment is
iM.OO per load mile. Assuming that there will be the equivalent of
two tractor trailer loads, we obtain a $4.00 per mile cost.
Project duration. Total processing time is based on the estimated
production rate of the mobile unit. For the material to be proces-
sed, a production rate of 250 cu yd per day (8-hr shift) is assumed
so that 10 working days is necessary to treat the entire lagoon
(2,475 cu yd). This includes only the solidification activity.
d> Cost summary for plant mixing of pumpable wastes. Plant mixing
techniques used with pumpable wastes are the least expensive of the
alternatives developed here, except for the in-situ mixing scenario.
The efficiency is largely due to the economical movement of the
materials by pumps rather than by loading and trucking. For appli-
cable wastes, this method permits precise reagent addition and com-
plete and uniform mixing, both of which are lacking in the in-situ
methodology at this time. This tighter control of mixing propor-
wl- anVUratiฐn 8ฑves the ability to precisely tailor the reagent
addition for maximum efficiency and effectiveness. The use of less
reagent to attain adequate stabilization results in less final prod-
uct to be disposed of which often makes this method quite competi-
tive with in-situ methodology. ^"ipei-x
6.5.3.2 Modular Mixing Plant for Unpumpable Wastes.
Table 6-
Procedure for estimating the cost of in-situ solidification/
* ง SฐlldS ^^ ฑS Presented below *nd summarized in
a. Assumptions.
(1) Approximately 500,000 gal of nonpumpable, high solids sludge
is to be solidified using a two reagent process consisting of
Portland cement and liquid sodium silicate.
(2) Bench-scale studies indicate that the reagents must be added in
weight-to-weight ratios of 30% Portland cement and 2% sodium
silicate.
(3) Onsite equipment will include a mobile plant that has a silo
for cement storage, a weight batcher for control of the cement
feed, a ribbon blender for mixing, a front-end loader for
6-27
-------
TABLE 6-4. COST ESTIMATES FOR THE MODULAR PLANT MIXING ALTERNATIVE
FOR UNPUMPABLE OR SOLID WASTES
Note: Stabilization/solidification with 30% (w/w) Portland cement and 2%
sodium silicate of 500,000 gal (2,850 tons) of unpumpable sludge or solid
waste (85 Ib/cu ft) in a mobile mixing plant with daily throughput of
180 cu yd (14 days required). Onsite disposal available.
TREATMENT REAGENTS:
30% Portland cement = 855 tons x ($55/ton) = $47,025
2% sodium silicate = 57 tons x ($200/ton) = $11,400
Total costs for treatment reagents: $58,425
$20.50/ton
LABOR COST FOR TREATMENT
1 ea Project supervisor = $27.50/hr x
1 ea Technician @ $18.50 = $37.00/hr x
2 ea Truck drivers @ $15.00 - 30.00/hr x
2 ea Laborers @ $12.50 = 25.00/hr x
Total labor cost:
Expenses: @ $75/day for 6 men 14 days
EQUIPMENT RENTAL:
Capacity Value
1 ea Mobile plant $125,000
1 ea Front-end loader 2 yd 44,000
2 ea Dump trucks 12 yd 54,000
1 ea Backhoe 1.2 yd 68,000
Total rental cost:
MOBILIZATION-DEMOBILIZATION AND CLEANUP:
Labor and expenses for 4 days: $3,840 +
Transportation: 200 mile/trip x 2 trips
Tป^+.ซ1
112 hr =
112 hr =
112 hr =
112 hr =
=
=
Per hour
$82.25 =
29.40 =
33.60 =
44.70 =
$1,800
x $2 /mile
$ 3,080
2,072
3,360
4,928
$13,440
$ 6,300
Per 14 days
$ 9,212
3,293
3,987 '
5,006
$21,498
= $5,640
800
$6,440
$ 4.72/ton
$ 2.21/ton
TOTAL COST OF TREATMENT: 500,000 gal = $106,103
PROFIT AND OVERHEAD (@ 30% of cost) = $31,831
TOTAL CONTRACTED PRICE: 500,000 gal = $137,934
$ 7.54/ton
$ 2.26/ton
$37.23/ton
$11.17/ton
$48.40/ton
6-28
-------
b>
c.
materials handling, two dump trucks to transport the raw and
treated wastes, and a backhoe to load raw waste into the dump
truck. F
(4) An onsite disposal area is available.
(5) The onsite cost of the reagents is $55.00 per ton for Portland
cement and $0.10 per pound for the sodium silicate.
(6) The remedial action site is located 200 miles from the nearest
portable unit.
Mฐbilization and demobilization costs. Mobilization costs are those
incurred in preparing the equipment for shipment, transporting the
equipment, and setting the equipment up for actual waste processing.
Mobilization costs include labor, equipment, and transportation
costs. Demobilization costs include site and equipment cleanup and
transportation of equipment back to its source. These activities
are expected to take 4 days to complete. Transportation is the cost
of actually transporting the equipment. There are two loads to be
transported at a cost of $2.00 per load mile.
Project duration. Estimated production rate for the modular mixing
Plant and peripheral equipment is 180 cu yd per day. Thus about
14 working days are required to process the 2,475 cu yd
(500,000 gal). This includes only the solidification activity.
CฐSt summary for plant mixing of unpumpable wastes. The more expen-
sive and time-consuming handling and transportation of high solids
waste which cannot be moved by pumps, or transport distances which
make pumping impractical, increase the cost of the plant mixing
alternative. Labor and equipment costs are about doubled in the
example given here (Table 6-4) over the more easily handled, pump-
able wastes so that this is the most expensive of the bulk-handling
treatment options. This method does retain the precision of reagent
dosing and mixing uniformity so that some efficiencies can be gained
by producing treated waste with a lower proportion of treatment
reagents, and therefore less total volume for disposal. This method
is often the method of choice for highly toxic or hazardous wastes
since the mixing process is under close control.
6.5.4 Safety and Environment
_ Special safety and environmental concerns associated with plant mixine
include the generation of odors, organic vapors, and fugitive dust. Under
.normal conditions, the process is open to the atmosphere and thus presents a
greater potential for problems than pumping liquid wastes or in-drum mixing.
Equipment moving around the site should be decontaminated daily. Stationary
processing equipment should be cleaned as operational requirements necessi-
tate and decontaminated after project completion.
6-29
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Standard personnel protective measures should be implemented as neces-
sary, depending on the waste being handled. The reduction in production
efficiency can be anticipated as a direct function of the level of protective
apparatus required. Level A protection is anticipated to reduce production
rate by 50 to 75 percent.
Quality control for plant mixing scenarios is expected to be better than
that associated with area and in-situ mixing and similar to that obtainable
with in-drum mixing. The material handling and rehandling requirements give
better control of the chemical addition and mixing process; however, they
also provide added potential for offsite contamination.
The solidification equipment proposed above should incorporate several
fail-safe design features. First, the motor for the mixer is located outside
the solidification area and contains a hand crank. This permits emptying of
the mixer should the process be stopped in mid-stream due to motor failure or
loss of electrical power. Maintenance on the motor can also be performed
without entering a contaminated area. Second, the system flush is controlled
through a flush module mounted outside the solidification area, again for
maintenance purposes. The flush water is kept under pneumatic pressure at
all times so that it is available even during loss of electrical power.
Capped containers are inspected and tested for external contamination and
decontaminated if necessary. The container is labeled and stored for ship-
ment to the final disposal area.
6.5.5 Modifications
Both mobile and modular mixing systems have been developed for the
solidification of low-level radioactive waste materials usually associated
with the nuclear power industry. These facilities are similar in concept to
the mobile plants that have been developed for the treatment of hazardous
wastes; however, the attention given to operator safety is significantly
greate^ than th^t associated with the hazardous waste^plants. The primary
concern is shielding of the operator and decontamination of equipment that
has come in contact with the waste materials. Use of remote and automatic
control systems is stressed in the nuclear environment. The emphasis on
safety generally raises the cost per unit of waste treated with these systems
significantly above that typically found in the treatment of hazardous
wastes. The number and kinds of modifications of mobile and modular treat-
ment facilities are as numerous as the vending companies which offer their
services, as can be seen in the illustrations (Figures 6-7 to 6-14). They
vary in size from large, semipermanent installations at very large sites
which can treat 500 to 1,000 cu yd per day, to very small, portable units
which treat 10 to 50 cu yd per day. Mixing, storage, and measuring facili-
ties also are sized and changed to optimize the equipment for the specific
job and level of hazard encountered.
A modification of the plant mixing alternative is the use of the plant to
add and mix the reagents with the waste materials and then package the treated
materials in drums. This modification incorporates the bulk materials handling
6-30
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features of plant mixing with the secure containerization features of in-drum
mixing. If containerization is required, this procedure offers significant
labor saving over the in-drum scenario. These savings, however/are substan-
tially offset by the cost of the drums. Field experience indicates that
approximately 300 drums per 8-hr shift could be handled using a typical
portable mixing plant. Costs for this modification are anticipated to ranee
between $30.00 and $50.00 per drum ($0.55 to $0.91 per gallon). Figure 6-15
illustrates a portable plant being used for this purpose.
Figure 6-15. Portable plant mixing followed by drum encapsulation
(Courtesy Solid Tek) .
6.6 Area Mixing or Layering Alternative
Area mixing, or in-place layering, provides an economical method for
stabilization/solidification of homogeneous and nonhomogeneous waste liquids
and sludges. The system avoids the use of conventional, stationary mixing
equipment. The waste is placed in layers over the disposal area in lifts of
from 2 in. to 24 in., depending upon its consistency and handling ability.
The waste is then overlaid with a layer of treatment reagents which have been
selected for the specific waste being treated. Once the two lifts are
placed, a mechanized vehicle lifts and turns the layer much like a roto-
tiller, using multiple passes. The resulting mixture is left to air dry
and/or is compacted in-place using standard earth compaction equipment.
Additional layers are then constructed over the lift in an identical manner
until the final height of material has been attained. Typically the final
lift is covered with earth, seeded, and maintained as the final cap. Alter-
natively, after mixing, the treated waste can be removed to a final disposal
area using standard earth-moving equipment; but this may leave a very large
area to clean up if hazardous wastes are being treated.
6-31
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6.6.1 Project Sequencing
Project sequencing for area mixing is patterned after the construction
techniques used for the soil cement or lime stabilization of roadway subbase
materials. A typical project incorporates the following steps:
a. Select and prepare the onsite disposal area.
b. Excavate the untreated material from the holding lagoon and trans-
port it to the disposal area.
c. Spread the untreated material in a lift of desired thickness on the
disposal area using standard construction techniques (Figure 6-16).
d. Spread the solidification/stabilization reagents over the material
in the required amount (Figure 6-17).
e. Mix the materials using a high-speed rotary mixer such as a pulvi-
mixer. This equipment, illustrated in Figure 6-18, works in a
manner similar to a large rototiller and can mix layers up to 24 in.
in depth.
f. Compact the mixed material as required with*standard roadway compac-
tion equipment.
g. Repeat steps b through f until all material has been treated or
until the designed depth of material has been attained.
6.6.2 Equipment Requirements.
Equipment requirements are based on the nature and quantity of waste
material to be treated. An additional consideration is the location, topogra-
phy, and size of the remedial action site. Minimum equipment requirements
would include a backhoe, clamshell, or front-end loader to excavate the
material from the holding lagoon; one or two dump trucks to haul the material
to the disposal site; a motor grader, excavator, or dozer to spread the mate-
rial in lifts; a high speed rotary mixer; a dry-chemical spreader; and a
pneumatic-tired roller or vibratory compactor.
Depending on the size of the project, additional equipment could be
efficiently added. Production rates will be a function of equipment size,
mix, and quantity. Production rates ranging from 400 to 500 cu yd per day
were obtained with the following equipment mix: two 10-yard dump trucks,
two excavators, two chemical spreaders, two high-speed rotary mixers, two
compactors, and one motor grader.
6-32
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Figure 6-16. Spreading untreated material for area mixing
(Courtesy Soil Recovery).
Figure 6-17. Adding stabilization/solidification reagent for area
mixing (Courtesy Soil Recovery).
6-33
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Figure 6-18. Mixing waste materials with stabilization/
solidification reagents in area mixing (Courtesy Soil
Recovery).
6.6.3 Costs
The procedure for estimating the cost of area mixing for solidification/
stabilization of an applicable waste is presented below and summarized in
Table 6-5.
a. Assumptions.
(1) Approximately 500,000 gal (2,850 tons or 2,575 cu yd) of non-
pumpable, high solids sludge is to be solidified using 30%
cement and 2% sodium silicate.
(2) The waste sludge is handleable using construction equipment
such as a front-end loader and will support the spreading and
mixing equipment when layered on the disposal area. Sludges
often must be pretreated in situ with an absorbent such as fly
ash to produce such a handleable product. Pumping lower solids
sludges onto the disposal site to dry to a manageable solids
content is feasible, but the additional time required and the
low lift height attainable by this method often makes this
option infeasible.
(3) Onsite cost of cement is $55.00 per ton; sodium silicate is
$200 per ton.
(4) The waste site is 200 miles from the nearest equipment.
6-34
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TABLE 6-5. COST ESTIMATES FOR THE AREA MIXING (OR LAYERING) ALTERNATIVE
Note: Stabilization/solidification with 30% (w/w) Portland cement and 2%
sodium silicate of 500,000 gal (2,850 tons) of high solids waste
(85 Ib/cu ft) in 12-in. lifts of waste to which a reagent layer is added and
mixed with a high speed rotary mixer. Daily capacity is 250 cu yd (10 days
required). Onsite disposal available.
TREATMENT REAGENTS:
30% Portland cement = 855 tons x ($55/ton) = $47,025
2% sodium silicate = 57 tons x ($200/ton) = $11,400
Total cost of treatment reagents: $58,425
$20.50/ton
LABOR COST FOR TREATMENT
1 ea Project supervisor
3 ea Heavy eq. operators @ $22
3 ea Truck drivers
1 ea Laborer
Total labor cost:
$27.50/hr x 80 hr
66.00/hr x 80 hr
@ $15 = 45.00/hr x 80 hr
= 12.50/hr x 80 hr
Expenses: @ $75/day for 8 men 10 days
$ 2,200
5,280
3,600
1,000
$12,080
$ 6,000
$ 4.24/ton
$ 2.11/ton
EQUIPMENT RENTAL:
1 ea Front-end loader
1 ea Dump truck
1 ea Chem. spreader
1 ea Rotary mixer
1 ea Roller compactor
1 ea Motor grader
Total rental cost:
Capacity
2 yd
12 yd
8 ton
12 ft
14 ton
14 ton
Value
$44,000
27,000
22,500
36,000
28,000
61,500
Per hour
$29.40 =
17.80 =
14.80 =
23.70 =
18.75 =
40.63 =
Per 10 days
$ 2,352
1,424
1,184
1,896
1,500
3,250
MOBILIZATION-DEMOBILIZATION AND CLEANUP:
Labor and expenses for 1 day: $1208 + $600
Transportation: 200 mile/trip x 4 trips x $2/mile
Total
TOTAL COST OF TREATMENT: 500,000 gal = $ 91,519
PROFIT AND OVERHEAD (@ 30% of cost) = $ 27,456
TOTAL CONTRACTED PRICE: 500,000 gal = $118,975
$11,606 $ 4.07/ton
$1,808
1,600
$3,408
$ 1.20/ton
$32.11/ton
$ 9.63/ton
$41.75/ton
6-35
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(5) Sufficient land area is available at the site for the complete
treatment process.
b. Mobilization and demobilization costs. Transportation of equipment
to the site is estimated to require four trips of 200 miles with
flat-bed trucks @$2.00 per mile, for $1,600 total. Other than
transportation costs, area mixing requires little equipment setup or
break-down at the waste site since only standard construction equip-
ment is required. One day should be sufficient for equipment
cleanup. Unusual preparation of the disposal site (such as grading
uneven terrain or installing leachate collection systems or final
cover) is not included in these costs.
c. Project duration> The daily production rate, considering loading,
transporting, spreading, mixing and compacting operations, is esti-
mated to be about 250 cu yd per day when using a single loader and
dump truck, and an eight-man crew (see 6.6.2, above). Therefore,
approximately 10 days would be-required to complete the 2,575 cu yd
of waste. Some efficiencies might be realized by using a larger
crew with more or larger equipment.
d. Summary of area mixing costs. 'Project costs are dependent upon the
quantity of material treated, the distance to the disposal site, the
amount and size of equipment used, and the type of reagents se-
lected. Cost estimates for area mixing of 500,000 gal of waste are
summarized in Table 6-5 in a form comparable with that used for the
other alternatives. Total cost of treatment in this example is
about $32 per ton (~$28 per cu yd) of which about 65% is for treat-
ment reagents and about 20% each for labor and equipment.
Costs shown include disposal site preparations, excavation of waste
material, transportation to treatment and disposal area, treatment reagents,
and mixing and compaction of the treated product. Not included are any pre-
treatment costs, land cost (which may be quite high), capping and revegeta-
tion of the site, treatment of any decanted liquid, or removal of the waste
to a final disposal site, if necessary. Total costs reported for actual re-
medial site stabilization projects including all of the above-listed param-
eters have run from $95 to $105 per cu yd (110 to $120 per ton).
6.6.4 Safety and Environment
Special safety and environmental concerns associated with the plant area
mixing scenario are similar to those associated with in-situ and, plant mix-
ing. Of primary concern is the generation of fugitive dust, release of or-
ganic vapors, release of odors, and decontamination of equipment. Each of
these areas of concern should be addressed in detail in the overall remedial
action plan.
To date, the use of the area mixing scenario has generally been limited
to the treatment of oil sludges and other semisolid wastes with relatively
6-36
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low associated hazard levels so that little emphasis has been given to asso-
ciated safety and environmental concerns. The potential for offsite release
of contaminants, particularly fugitive dust and vapor releases, should re-
ceive additional scrutiny should this scenario be adopted.
., 6.6.5 Modifications
Major modifications have not been identified. Modifications are
expected to be limited to the types of solidification reagents used in the
process and the types of equipment used to handle the waste materials and
solidification reagents.
6.7 Summary
The number of waste processing, handling, and mixing technologies is as
varied as the number of treatment reagent-waste formulations. Waste and site
characteristics, and reagent cost and availability are the major factors
which must be weighed in project planning to ascertain the most cost-
efficient and reliable containment strategy. This section has discussed a
representative sampling of possible stabilization/solidification scenarios,
all of which are currently available commercially. This should give the
reader a good understanding of the wide diversity of applicable technology
now in use. A formal decision process outline as recommended for remedial
action alternatives is discussed in an EPA Guidance Manual (U.S. EPA 1983).
6.7.1 Comparison of Treatment Alternative Costs
Attributes of the four stabilization/solidification alternatives dis-
cussed in this section are summarized in Table 6-6. Similar assumptions were
used in all of the alternative cost estimates, as were production rates from
actual equipment now in use at remedial action sites. It is emphasized that
these estimates are for comparison purposes only and cannot be extended to
specific wastes and/or sites, as cost and reliability of all processing tech-
nologies are quite waste- and site-specific.
In-drum mixing is by far the most expensive and takes the greatest
amount of production time due obviously to the very small quantities pro-
cessed in each batch. Mixing done inside the drum is reasonably complete but
difficulties are often encountered in the corners, especially if the complete
top of the drum cannot be removed. In-drum mixing is most applicable to
sites which have a wide variety of incompatible and highly toxic wastes which
occur in individual drums. Since each drum must be analyzed individually (an
expense not included in the estimates), customized formulations of reagents
and mixing times can be determined for each drum or waste type. The cost of
reagent is a small fraction of the whole (generally less than 10%), while
labor and equipment make up about half of the total cost. If sufficient
6-37
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TABLE 6-6. SUMMARY COMPARISON OF RELATIVE COSTS FOR STABILIZATION/
SOLIDIFICATION ALTERNATIVES
Plant Mixing
Parameter
In-drum In-situ Pumpable Unpumpable Area mixing
NOTE: In all cases, 500,000 gal (2,850 tons) of waste was treated with 30%
Portland cement and 2% sodium silicate with onsite disposal; costs include
only those operations necessary for treatment. All costs are per ton of waste
treated. Data taken from Tables 6-1 through 6-5.
Metering and
mixing efficiency Good
Processing days
required 374
Fair
Excellent Excellent
10
14
Good
10
Cost/ton
Reagent
Labor and per diem
Equipment rental
Used drums
@ $1 I/drum
Mobilization-
demobilization
Cost of treatment
process
Profit and
overhead (30%)
TOTAL COST/TON
$ 20.50
(9%)*
51.07
(23%)
37.14
(17%)
48.18
(21%)
15.68
(7%)
$172.57
51.72
(23%)
$224.29
$20.50
(63%)
1.36
(4%)
1.38
(4%)
-
1.58
(5%)
24.83
7.45
(23%)
32.28
$20.50
(53%)
3.83
(10%)
3.93
(10%)
-
1.43
(4%)
29.69
8.91
(23%)
38.60
$20.50
(42%)
6.93
(14%)
7.54
(16%)
2.26
(5%)
37.23
11.17
(23%)
48.40
$20.50
(49%)
$ 6.35
(15%)
4.07
(10%)
1.20
(3%)
32.11
9.63
(23%)
41.75
* % of total cost/ton for that alternative.
6-38
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drums of identical or compatible wastes are found, it is much more economical
to bulk the wastes and use other mixing techniques, as this greatly decreases
cost and increases mixing efficiencies. This is also true when it is desired
to place the treated waste back into drums, either for ease of handling or for
increased, short-term containment; the output from bulk mixers usually can be
easily loaded directly into new drums or rinsed original drums.
The remaining bulk mixing alternatives are much more consistent in cost
and production rates, the two handling liquid or pumpable wastes being the
less expensive alternatives. All are quite sensitive to reagent cost since
it typically makes up from 40 to 65% of the total cost. The in-situ tech-
nique is the fastest and most economical of the bulk methods because the
wastes typically need to be handled only once, or not at all if they are to
be left in place, as is done with most nonhazardous wastesonly the reagent
is handled. Labor and equipment each make up less than 5% of the total
treatment cost. However, in-situ mixing is the least reliable because of
difficulties in accurate reagent measurement and in getting uniform and/or
complete mixing of wastes and treatment reagents. Also, in-situ mixing re-
quires a liquid or a semisolid sludge. If the wastes are to be left in
place, the waste site must be dedicated as the final waste disposal area. In
some cases, liquid or sludge wastes are stabilized or solidified in situ so
that they can later be removed from the site using standard earth-moving
equipment.
Mobile or modular mixing plants, although giving excellent mixing and
relatively high production rates, require that both the untreated waste and
the treated product be handled. The cheapest and fastest material handling
technique is that in which the waste can be pumped directly from the waste
lagoon, mixed, and then pumped to the final disposal site. Pumpable waste
can be treated for about 15% less, in which case, labor and equipment cost
each make up only about 10% of the total treatment cost. Nonpumpable waste
requires more manpower and machinery for material handling and transport so
that labor and equipment costs each increase to around 15%. Plant mixing
scenarios are probably the most used alternatives for large amounts of bulk
or drummed waste which have a high degree of hazard, as the wastes are always
under control of the operators, and reagent dosing is the most accurate and
the mixing the most complete of any of the bulk processes.
In area mixing technology, the waste is usually moved only once to the
final disposal site where it is mixed and compacted in place. The waste can
be removed to another site if needed, but this lessens the other benefits of
the technique and leaves large areas to be cleaned up. Very large and stan-
dard construction equipment can be used for increased efficiency. Major dis-
advantages of this technique are that larger land areas are often necessary,
and mixing reagent dosing cannot be as accurately controlled.
6.7.2 How Using Different Treatment Reagents Affects Cost
For comparison purposes, all treatment alternatives were developed using
the 30% Portland cement, and 2% sodium silicate formulation which is about
6-39
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average in reagent cost. However, this formulation is not really universal
as implied. It lends itself especially to in-drum and plant mixing tech-
niques with their better mixing efficiencies, and to inorganic, aqueous
sludges with toxic heavy metals. In-situ and area mixing techniques do not
usually lend themselves to the addition of liquid reagents (although it has
been done) or to formulations where uniform and/or extensive mixing are nec-
essary. The higher unit cost of these reagents tends to limit their use to
those techniques with good mixing efficiencies.
Table 6-7 compares the costs of the four alternatives using different
amounts of other common treatment reagents with different delivered cost. In
these examples it is assumed that the 'change in reagents will not affect
equipment requirements or production rates. Total cost of each alternative
and proportional cost of the reagent only are shown in each case.
Changing reagent costs from $34/ton to $0/ton has only a small effect on
the total cost of in-drum mixing since it is labor- and equipment-intensive.
In-situ mixing is the most sensitive to reagent cost, since it is by far the
largest part of the total cost of this technique. Other bulk mixing tech-
niques are also quite sensitive to reagent costs; as reagent costs decrease,
the proportional differences among the four increase, but their ranking re-
mains the same. The sensitivity of total treatment cost to delivered reagent
price is well illustrated in these calculations.
Reagent costs for the other waste products such as fly ash, cement or
lime kiln dust, or furnace slag are highly variable. The major component of
their cost is usually transportation to the site. The reagent used is typi-
cally based upon the nearest source of suitable pozzolanic materials and not
through preference of one over the others. As these waste materials have
been incorporated into waste treatment systems, they have come to have appre-
ciable value in some areas.
6-40
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TABLE 6-7. COMPARISON OF TREATMENT COSTS WITH DIFFERENT REAGENTS
Reagent type, Plant Mixing
amount, and cost In-drum In-situ Pumpable Unpumpable
1. 80% fly ash (Type F) @ $30/ton, 20% lime @ $50/ton
Total reagent cost/ton of waste = $34
Reagent cost 12.5% 68%, 60% 52%
Total cost/ton $237.06 $49.89 $56.15 $65.95,
2. 30% Portland cement @ $55/ton, 2% sodium silicate @ $200/ton
. - Total reagent cost/ton of waste = $20.50
Reagent cost 9% 63% 53% 42%
Total cost/ton $224.29 $23.28 $38.60 $48.40
3. 50% fly ash (Type C) @ $20/ton
Total reagent cost/ton of waste = $10
Reagent cost 4% 54% 40% 29%
Total cost/ton $209.90 $18.63 $24.95 $34.75
4. Free reagent (including delivery)
Reagent cost 0% 0% 0% 0%
Total cost/ton $198.57 $5.63 $11.95 $21.75
Area mixing
57%
$59.30
49%
$41.75
36%
$28.04
0%
$15.10
NOTE: Data are from Table 6-6. They have been recalculated for different
reagent cost, but for the same equipment, project duration, and mobilization
costs. All reagent proportions are in weight of reagent per weight of waste.
6-41
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REFERENCE
U.S. EPA. 1985. Guidance on Feasibility Studies under CERCLA. EPA-540/
G-85-003, Office of Emergency and Remedial Response, U.S. Environmental
Protection Agency, Washington, D.C., 103 pp.
BIBLIOGRAPHY
Carson, A. B. 1961. General Excavation Methods. F. W. Dodge Corporation,
New York, New York.
Caterpillar Tractor Co. 1981. Handbook of Earthmoving. Caterpillar Tractor
Company, Peoria, Illinois.
Caterpillar Tractor Co. 1982. Caterpillar Performance Handbook. Caterpillar
Tractor Company, Peoria, Illinois.
Gallagher, G. A. 1981. Health and Safety Program for Hazardous Waste Site
Investigation. New England Section of the Association of Engineering
Geologists, Boston, Massachusetts.
Perry, R. H. 1973. Chemical Engineers' Handbook. McGraw-Hill Book Company,
New York, New York.
Peurifoy, R. L. 1956. Construction Planning Equipment and Methods. McGraw-
Hill Book Company, New York, New York.
Peurifoy, R. L. 1975. Estimating Construction Costs. McGraw-Hill Book
Company, New York, New York.
Robert Snow Means Company, Inc. 1983. Site Work Cost Data. Construction
Consultants & Publishers, Kingston, Massachusetts.
Terex. 1981. Production and Cost Estimating of Material Movement with
Earthmoving Equipment. Terex Corporation.
U.S. Army Corps of Engineers. 1980. General Safety Requirements Manual.
Washington, D.C.
U.S. Army Corps of Engineers. 1983. Preliminary Guidelines for Selection
and Design of Remedial Systems for Uncontrolled Hazardous Waste Sites.
Washington, D.C.
U.S. EPA. 1980. Closure of Waste Surface Impoundments. SW-873. U.S. Envi-
ronmental Protection Agency, Office of Waste Management,
Washington, D.C.
6-42
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U.S. EPA. 1981. Interim Standard Operating Safety Procedures,
ronmental Protection Agency, Washington, D.C.
U.S. Envi-
U.S. EPA. 1982. Inplace Closure of Hazardous Waste Surface Impoundments.
U.S. Environmental Protection Agency. Municipal Environmental Research
Laboratory, Cincinnati, Ohio.
U.S. EPA. 1985a. Drum Handling Practices at Hazardous Waste Sites (Draft).
U.S. Environmental Protection Agency, Municipal Environmental Research
Laboratory, Office of Research and Development, Cincinnati, Ohio.
U.S. EPA. 1985b. Remedial Action at Waste Disposal Sites (Revised). EPA-
625/6-85-006, Municipal Environmental Research Laboratory, U.S. Environ-
mental Protection Agency, Cincinnati, Ohio.
U.S. EPA. 1985c. Guidance on Remedial Investigations under CERCLA.
EPA-540/G-85-002. Office of Emergency and Remedial Response. U.S. En-
vironmental Protection Agency, Washington, D.C.
U.S. EPA. 1985d. Remedial Action at Waste Disposal Sites. EPA-625/
6-85-006. U.S. Environmental Protection Agency, Washington, D.C.
6-43
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SECTION 7
QUALITY CONTROL, SAFETY, AND ENVIRONMENTAL CONSIDERATIONS
FOR WASTE TREATMENT
The waste stabilization and solidification processes are similar to any
chemical treatment operation in that the product must be periodically tested
to ensure that the physical integrity and containment characteristics are ade-
quate. The treated waste must be sampled in such a way that representative
material is obtained and tested using reliable screening tests to verify
performance.
7.1 Sampling of Treated Wastes
Stabilization and solidification systems which are batch operations bear
some similarity to batch cement blending systems. Approaches similar to those
for fresh concrete can be employed for fluid waste, whereas cured material can
be sampled using sampling techniques employed with hardened concrete. Stan-
dard ASTM method C 172-71, Standard Method of Sampling Fresh Concrete
(U.S. Army 1949; CRD-C4-71) outlines procedures to be used in taking samples
from stationary and truck mixers, paving machines, and agitating and non-
agitating concrete transports. Standard method CRD-C 620-80 outlines tech-
niques for sampling grouts from mixers, pumps, and discharge lines (U.S. Army
1949).
For solidified or hardened concrete, techniques such as those recom-
mended in ASTM C 823-75 (U.S. Army 1949) or in Abdun-Nur (1978) can be used.
In general, careful visual inspection and selected sampling can be used to
augment purely random approaches. The objective of any waste testing program
is to ensure complete treatment of all materials so that nonrandom testing in
areas of poorly performing waste (for example, materials that fail to
solidify or have excessive weep water) is justified. If waste treatment is a
batch operation, each successive batch should be tested. Some solidification
systems that are used with flue gas cleaning wastes have similar problems
with regard to producing a consistent set. Interim ponding systems where the
treated sludge is allowed to cure for 30 days have been developed to ensure
that treatment is complete before disposal. This approach requires double
handling of the treated wastes, but it ensures that unsatisfactory materials
can be retrieved for reprocessing (Duvel et al. 1978).
7-1
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7.2 Testing of Stabilized and Solidified Wastes
Early testing of any product that cures slowly presents problems in that
the ability to predict the final properties of the cured material from short-
term tests is generally poor (Arni 1978) . This problem has been thoroughly
studied with regard to early strength development in concrete, and no gener-
ally satisfactory testing and prediction system has evolved.
In a waste treatment system where the treated material must be placed in
a land disposal area shortly after treatment, it is necessary to develop
testing that will ensure waste containment in a minimum period of time. This
testing can take the form of early strength testing (24-hr compressive
strength) and leach testing of cured, ground material (where strength is not
a primary consideration). Details of the types of testing that can be used
for these purposes are given in Sections 3 and 4 of this report.
7.3 Safety and Environment
In this handbook the solidification/stabilization process is considered
to be a subset of the remedial action plan as a whole. As such, it may be
assumed that the environmental and safety aspects of the solidification/
stabilization process will be addressed in development of the overall reme-
dial action plan. A brief summary of the major safety and environmental
aspects of a solidification/stabilization project is presented in the fol-
lowing paragraphs. Detailed safety and environmental guidance may be found
in the following publications:
a. Chemical Manufacturer's Association, Inc. 1982. Hazardous Waste
Site Management Plan, Washington, D.C.
b. Environmental Protection Agency. 1981. Hazardous Materials Inci-
dent Response Operations: Training Manual. National Training and
Operational Technology Center, Cincinnati, Ohio.
c. Environmental Protection Agency. 1981. Technical Methods for
Investigating Sites Containing Hazardous Substances Training Pro-
gram. Technical Monograph Nos. 2, 3, and 12.
d. Environmental Protection Agency. 1985. Remedial Action at Waste
Disposal Sites. EPA 625/6-85-006, Office of Emergency and Remedial
Response, Washington, D.C.
e. Meluold, R. W., S. C. Gibson, and M. Dv Rogers. 1981. Safety Pro-
tection for Hazardous Materials Cleaning: Management of Uncon-
trolled Hazardous Waste Sites. American Society of Civil Engineers,
New York, New York.
7-2
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f. U.S. Army Corps of Engineers. .1984. Preliminary Guidelines for
Selection of Remedial Actions for Hazardous Waste Sites.
EM 1110-2-505 (Draft), Washington, B.C.
7.3.1 Safety
Safety concerns associated with solidification/stabilization of hazar-
dous wastes are primarily related to the protection of onsite personnel.
These concerns can be addressed through development of a Personnel Protection
Program (PPP). At a minimum, the PPP should include the following elements:
a. Medical Surveillance Plan.
b. Industrial Hygiene Support Plan.
c. Employee Training Plan.
d. Entry Control Plan.
e. Respiratory Protection Plan.
f. Eye Protection Plan.
g. Skin Protection Plan.
h. Personnel and Equipment Decontamination Plan.
i. Emergency Response Plan.
j. Record Keeping and Reporting Plan.
The detailed requirements of the PPP must be developed on a site-specific
basis. Obviously, the more hazardous the waste, the more rigorous must be
the PPP.
Good management and work practices, as well as legal requirements,
emphasize the need for placing top priority on the health and safety of the
worker. Various legal and regulatory requirements establish the minimum
guidelines for the development and implementation of a comprehensive health
and safety program. The Occupational Safety and Health Administration (OSHA)
has established regulations designed to decrease accidents associated with
the construction site. Many of these requirements are also applicable to the
solidification/stabilization process itself. The regulations may be found in
Title 29 of the Code of Federal Regulations. Examples of the specific parts
and subparts most likely to apply to the solidification/stabilization scenar-
ios are listed in Table 7-1. Compliance with applicable OSHA regulations
should be a mandatory requirement of the PPP. In addition, the EPA has
referenced various policies and mandatory requirements for occupational
health and safety. A listing of pertinent documents is presented in
Table 7-2.
7-3
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TABLE 7-1. CITATIONS FOR CURRENT OSHA REGULATIONS LIKELY TO BE
APPLICABLE AT LAND-BASED DISPOSAL SITES
Subpart D
Subpart E
Subpart F
Subpart G
Subpart L
Subpart 0
Subpart P
Subpart S
Subpart U
Subpart Z
29 CFR Part 1926
Occupational Health and Environmental Controls
(Sections 1926.50 through 1926.57)
Personal Protection
(Sections 1926.100 through 1926.107)
Fire Protection
(Sections 1926.150 through 1926.155)
Signs and Signals
(Sections 1926.200 through 1926.203)
Ladders and Scaffolding
(Sections 1926.450 through 1926.452)
Mechanical Handling Equipment
(Sections 1926.600 through 1926.606)
Excavation and Trenching
(Sections 1926.650 through 1926.653)
Tunnels and Shafts
(Sections 1926.800 through 1926.804)
Blasting and Explosives
(Sections 1926.900 through 1926.914)
29 CFR Part 1910
Toxic and Hazardous Substances
(Sections 1910.1000 through 1910.1046)
7-4
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TABLE 7-2. POLICIES APPLICABLE TO REMEDIAL ACTIONS
EM 385-i-l, Safety and Health Requirements Manual.
29 CFR 1910, Parts 16, 94, 96, 106, 109, 111, 134, 151, Occupational Health
and Safety Standards.
Executive Order 12196, Section 1-201, Sec. (k), Occupational Health and
Safety Programs for Federal Employees.
29 CFR 1960.20 (1), Occupational Safety and Health for the Federal Employee.
EPA Occupational Health and Safety Manual, Chapter 7 (1).
EPA Training and Development Manual, Chapter 3, Par. 7 (b).
Occupational Health and Safety Act of 1971, PL 91-596, Sec. 6.
EPA Order on Respiratory Protection (Proposed).
49 CFR, Parts 100-177, Transportation of Hazardous Materials.
EPA Order 1000.18, Transportation of Hazardous Materials.
EPA Order 3100.1, Uniforms, Protective Clothing, and Protective Equipment.
7.3.2 Environment
Environmental concerns during the remedial action project are primarily
related to waste containment, to retention of the environment in its natural
state to the greatest extent possible, and to the enhancement of site appear-
ance in its final condition. Environmental protection as applied to the
remedial action as a whole generally includes consideration of, air, water,
and land resources. As specifically applied to the solidification/
stabilization processes, environmental considerations include the elimination
of the spread of contamination through minimization of organic vapor and/or
fugitive dust generation, decontamination of personnel and equipment, and
prevention and control of spills.
7.3.2.1 Organic Vapor and Dust Generation
Depending on the nature of the wastes found at a site and the
solidification/stabilization reagent selected, the possibility exists for a
release of volatile organic compounds which may have an adverse impact on
7-5
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public health. Objectives of the remedial action project must include mini-
mizing the release of organic vapors and monitoring onsite and offsite to
measure concentrations and types of vapors that may be released. The po-
tential for volatile organic vapor generation should be addressed during the
bench or pilot study phase (Section 5 of this Handbook) of the
solidification/ stabilization scenario selection process. Other than
elimination or minimization of the generation of organic vapors by a judi-
cious selection process, few technical options are available for control of
vapors. The general approach has been limited to the monitoring of organic
vapors. Both onsite and site-perimeter monitoring are recommended. Area-
type monitoring should be conducted on a periodic basis to determine whether
contaminants are migrating out of the contaminated area.
Migration of contaminants through transport of airborne particulates
(fugitive dust) could present a significant health and environmental hazard
during remedial action activities. Such hazards are particularly likely with
large-scale solidification/stabilization scenarios such as in-situ mixing and
area mixing. Fugitive dust that could cause a hazard or nuisance to others
must be eliminated.
The meteorological conditions at the site will strongly influence the
potential for this fugitive dust problems. Hot, dry, windy conditions pro-
duce the greatest potential for entrainment and transport of contaminants.
The solidification/stabilization reagent and application scenario, as well as
the waste being treated, will also affect the amount of fugitive dust
formation.
Techniques that can be used during the solidification/stabilization
process to mitigate airborne particulate transport include the following:
a. Minimizing the rehandling of waste materials.
b. Erecting portable wind screens.
c. Applying surface stabilizers or dust palliatives.
d. Using portable surface covers-on the work area during periods of
inactivity.
e. Constructing temporary enclosures around the solidification/
stabilization processing area.
7.3.2.2 Equipment and Personnel Decontamination
Although a maximum effort is made to prevent contamination of per-
sonnel and equipment, such contamination will inevitably occur as a result of
contact with the wastes being treated. Contamination may occur in a number
of ways, including the following:
7-6
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a.
b.
Contacting vapors, gases, mists, or particulates in the air.
Being splashed by materials while sampling, opening containers, or
conducting the solidification/stabilization process.
c. Walking through puddles of liquids or on contaminated materials.
d. Using contaminated instruments or equipment.
To prevent the spread of contaminants, methods for reducing contamina-
tion and decontamination procedures must be developed before the initiation
of site operations. Decontamination consists of physically removing the con-
taminants and/or changing their chemical nature to innocuous substances. The
nature and extent of the required decontamination process depends on a number
of factors, the most important of which is the type of contaminants being
solidified. This topic is treated further in Section 8, Cleanup and Closure.
7.3.2.3 Spill Control
Another important environmental concern is preventing the spread of
contamination through spills. A continuous effort should be made to prevent
any spillage of contaminated materials during the solidification/
stabilization process. A spill control program should as a minimum provide
all physical controls possible in areas where spills are likely to occur and
proceed in a deliberate and controlled fashion in handling all hazardous
materials. Activities presenting the highest probability of material spill-
age include the transfer of liquid or solid material to a staging area, han-
dling of deteriorated drums of liquid waste, and staging of liquid waste.
During solidification/stabilization operations, preventing spills is the re-
sponsibility of all workmen at the site.
7-7
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REFERENCES
Abdun-Nur, E. A. 1978. Techniques, Procedures, and Practices of Sampling of
Concrete and Concrete-Making Materials. In: Significance of Tests and Prop-
erties of Concrete and Concrete-Making Materials, ASTM Publ 169B, American
Society for Testing and Materials (ASTM), Philadelphia, Pennsylvania.
pp. 5-23.
Arni, H. T. 1978. Statistical Considerations"in Sampling and Testing. In:
Significance of Tests and Properties of Concrete and Concrete-Making Mate-
rials, ASTM Publ. 169B, American Society for Testing and Materials (ASTM),
Philadelphia, Pennsylvania, pp. 24-43.
Duvel, W. A., Jr., et al. 1978. State-of-the-Art of FGD Sludge Fixation.
Publication FP-671, Vol. 3, Electric Power Research Institute, Palo Alto,
California, not paginated.
U.S. Army. 1949. Handbook for Concrete and Cement, Vols. I and II.
U.S. Army Engineer Waterways Experiment Station, Vicksburg, Mississippi,
unpaginated, loose leaf.
7-8
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SECTION 8
CLEANUP AND CLOSURE
After completion of waste treatment and the final placement of the
stabilized and solidified waste, it will be necessary to ensure that all
equipment is adequately cleaned to prevent material from moving offsite and
that the plans for monitoring are implemented in a timely fashion. Programs
for decontaminating equipment are generally part of the safety planning
involved in the site activity. The postclosure monitoring program is devel-
oped as part of the master plan for site closure. Examples of cleanup and
closure activities" at actual remedial sites are found in EPA (1984).
8.1 Cleanup of Equipment
Stabilization and solidification require extensive mixing and materials
handling equipment. Decontamination of equipment may require high-pressure
washing systems and manual scraping. Most mixers are cleaned by putting
clean material in the mixer and cycling through several mixing operations.
Discarded equipment and cleaning water must be treated as a contaminated
waste and be disposed of in an EPA-approved manner. Where residual contami-
nation of equipment is suspected, a swabbing or rinsing procedure and chemi-
cal analysis of swabs and rinse water can be used to confirm the effective-
ness of the cleaning procedure.
8.2 Site Monitoring
A monitoring system is routinely established at any remedial action site
before, during, and after cleanup operations. This system ensures that no
adverse impact to air, surface water, or ground water occurs during the reme-
dial activities. These monitoring activities would normally continue after
site closure to evaluate the effects of remediation arid to act as an early
warning system for possible breakdown of liners or other containment struc-
tures (EPA 1985a).
If the remedial program involves leaving stabilized or solidified wastes
onsite, the monitoring should be designed to ensure that the treated wastes
do not become a new source of air or water pollution. The solidified wastes
are designed to provide the needed waste containment; therefore, placement of
8-1
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monitoring wells directly under or adjacent to the solidified waste should be
considered in developing the postclosure monitoring plan.
Even structural concrete can break down from exposure and weathering;
therefore, the possibility of solidified materials disintegrating or chemical
stabilization systems being defeated in natural weathering processes must be
considered in monitoring. For example, sulfate-rich ground water can cause
swelling and disintegration of Portland-cement/fly-ash-solidified waste, or
leaching by rainwater can remove buffering materials in a stabilized waste
and allow the pH to drop and metals to be taken into solution in contacting
water. If the breakdown of the treated waste is a possible problem, the
monitoring program should include the coring and retrieval of solidified
waste for leaching tests. Test holes in the wastes can also be filled with
clean water, and in-situ leaching rates can be determined.
8.3 Capping of Solidified Wastes
Most solidified wastes are not designed for constant exposure to
weathering. Freezing and thawing and wetting and drying can cause the mate-
rial to fragment badly (Bartos and Palermo 1977). A cap that is thick enough
to ensure that the solidified material maintains uniform moisture and is not
subjected to freezing is necessary to ensure that the waste does not deterio-
rate. The cap also should minimize the percolation of water into the waste.
Details on the design of closures are given in Brown and Associates
(1982) and Wyss et al. (1980). Selection of soils and vegetation for capping
landfills is discussed in detail in Lutton et al. (1979) and for solid haz-
ardous waste in Lutton (1982) and U.S. EPA (1985b).
A program for the periodic inspection and maintenance of the waste caps
is generally part of a remedial site master plan.
8-2
-------
REFERENCES
Bartos, M. J., Jr., and M. R. Palermo. 1977. Physical and Engineering Prop-
erties of Hazardous Industrial Wastes and Sludges. EPA-600/2-77-139, U.S.
Environmental Protection Agency, Cincinnati, Ohio. 89 pp.
Brown, K. W., and Associates. 1982. Inplace Closure of Hazardous Waste Sur-
face Impoundments. Draft Report, U.S. Environmental Protection Agency Con-
tract 68-03-2943. 92 pp.
Lutton, R. J., G. L. Regan, and L. W.
of Covers for Solid Waste Landfills.
Protection Agency, Cincinnati, Ohio.
Jones. 1979. Design and Construction
EPA 600/2-79-165, U.S. Environmental
274 pp.
Lutton, R. J. 1982. Evaluating Cover Systems for Solid and Hazardous Waste.
SW-872 (NTIS-PB81-181505). U.S. Environmental Protection Agency,
Washington, D.C.
U.S. EPA. 1984. Case Studies 1-23: Remedial Response at Hazardous Waste
Sites. EPA-540/2-84-0026, Office of Emergency and,Remedial Response,
U.S. Environmental Protection Agency, Washington, D.C. 637 pp.
U.S. EPA. 1985a. Remedial Action at Waste Disposal Sites (Revised).
EPA-625/6-85-006, U.S. Environmental Protection Agency, Cincinnati, Ohio.
497 pp.
U.S. EPA. 1985b.
EPA-540/2-85-002.
Covers for Uncontrolled Hazardous Waste Sites.
U.S. Environmental Protection Agency, Cincinnati, Ohio.
Wyss, A. W., et al. 1980. Closure of Hazardous Waste Surface Impoundments,
EPA-530/SW-873, U.S. Environmental Protection Agency, Cincinnati, Ohio.
100 pp.
8-3
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APPENDIX A
ACQUISITION AND COSTS OF REAGENTS
One of the items of concern which.is associated with all onsite
solidification/stabilization alternatives is the ability to obtain the neces-
sary process chemicals and transport them to the proposed project site at
reasonable cost. Onsite cost of the required chemicals is a major portion of
overall-project costs. The cost of chemicals associated with an onsite
solidification/stabilization project includes the purchase price from the
manufacturer, transportation cost from the point of manufacture to the point
of use, cost of onsite storage and handling of the chemicals, and the quan-
tity of chemicals required for a particular project.
A.I Purchase Price
The purchase price of chemicals is usually the most significant cost
associated with the total cost of chemicals for an onsite solidification/
stabilization project. Generally, prices are quoted as free on board
(f.o.b.) at the manufacturer's plant. The price for chemicals varies from
day to day and is a function of a variety of factors including the cost of
raw materials and manufacturing at a particular plant location, the current
demand for the product as reflected by general economic conditions, the
quantity of chemicals to be purchased, the nature of the shipment (e.g. bulk
versus bag for cement), and the reactivity of the material.
The major chemicals or materials used in the solidification/
stabilization of hazardous wastes are products associated with the construc-
tion industry. For this reason, the cost of these materials is strongly
related to construction activity. An example is the availability and cost of
Portland cement. Increased construction activity results in increased demand
which tends to drive prices up. Likewise, decreased construction activity
has the opposite effect. Note that this effect is also noticeable in the
secondary materials, i.e. cement-kiln dust and lime-kiln dust.
The results of an April 1983 survey of chemical costs for materials com-
monly used for solidification/stabilization are presented in Table A-l.
These costs represent telephone quotes for the materials f.o.b. at the points
of manufacture. A wide range of prices can be noted. This range represents
geographic differences in material costs. Also note that these prices are
probably depressed because of the recent slump in major construction activ-
ity. These prices are presented for comparison purposes only.
A-l
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TABLE A-l. TYPICAL COSTS OF CHEMICALS USED FOR STABILIZATION/
SOLIDIFICATION (APRIL 1983)
Chemical
Units
Cost Range
Portland cement
Portland cement
Quick lime (CaO)
Hydrated lime (Ca(OH)2)
Hydrated lime (Ca(OH)2)
Cement kiln dust
Waste quick lime
$/ton* (bulk)
$/ton (bag)
$/ton (bulk)
$/ton (bulk)
$/ton (bag)
$/ton
$/ton
$40
70
45
45
60
5
4
- $65
- 85
- 55
- 55
- 75
- 25
- 10
Fly ash
Gypsum
Sodium silicate
Concrete admixtures
$/ton
$/ton
$/pound
$/gallon
0
- 40
0 - 35
0.05 - 0.20
1.50 - 9.00
* Customary units are used because price quotations are made in these units.
All prices f.o.b. at point of manufacture.
A.2 Transportation Costs
The cost of transporting chemicals from the point of manufacture to the
point of use is generally the second most costly item associated with the
total onsite chemical cost for a solidification/stabilization project. In
those cases where waste materials (kiln dust) are used as the solidification/
stabilization agent, the cost of transportation may actually exceed the cost
of the material itself. The materials associated with solidification/
stabilization are commonly shipped by rail or truck. For application at
remedial action sites, truck haulage has the particular advantage of geogra-
phic flexibility, which limits consideration of rail transportation. There-
fore, for purposes of this discussion, the costs of chemical transportation
to the project site are based on haulage by trucks.
The cost of chemical transportation is primarily a function of the char-
acteristics of the material being handled (specific weight, liquid versus
solid, etc.), the quantity of material being transported, the nature of pack-
aging (bulk versus container), the distance over which the material is trans-
ported, and the type of carrier performing the transport services.
Because of the quantity of materials required at a typical remedial
action site, bulk transport is generally the method used for obtaining the
required chemicals. Truck types used for the movement of bulk materials are
essentially limited to two: dump trucks (open top with tarpaulin cover)
and/or tank-type trucks. Dump trucks are very commonplace and are used for
A-2
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hauling a variety of materials over relatively short distances. Tank-type
trucks are often used in the transport of lime and cement products. The
tank-type truck is fully enclosed and is loaded and unloaded pneumatically.
The time required to unload the tank-type truck is considerably longer than
the dump truck; however, the material is not exposed to the weather, which is
a definite advantage. Each type of truck is capable of transporting payloads
in the 40,000- to 50,000-pound (20,000- to 25,000-kg) range. The actual pay-
load capacity depends primarily on the specific weight of the material being
transported. The tank-type truck is the primary type of carrier employed for
the transportation of materials associated with onsite solidification/
stabilization projects.
Transportation rates are generally established as a tariff in the case
of common carriers, or they are negotiated between the carrier and the manu-
facturer in the case of contract carriers. For planning purposes, it is
easier to develop costs based on common carrier tariffs. Note, however, that
these tariffs can vary significantly within a region and certainly across the
Nation. The basis for a tariff may vary between carriers in such areas as
minimum load and distance traveled. At the planning stage, it is somewhat
difficult to compare tariffs directly. In any event, the chemical manufac-
turer or supplier generally arranges transportation to the site.
Figure A-l presents typical transportation costs of major chemicals
associated with solidification/stabilization technology. The costs presented
include the cost of transporting the material from the place of manufacture
to the project site. The manufacturer pays loading costs. In the case of
bulk shipments, the rate includes the cost of unloading. In the case where
packaged materials (lime or cement in bags) are transported, the person to
whom the materials are shipped is usually responsible for unloading services
(i.e. forklifts, etc.). Bag shipments are usually palletized for easy
off-loading.
The basic transportation cost will generally include a free time to
effect unloading. Typical free time ranges from 1-1/2 to 3 hr. Should un-
loading fail to be accomplished in this time frame, demurrage will be
charged. These demurrage rates are highly variable and are a function of the
demand for transportation services. Typical demurrage rates range from $20
to $50 per hour.
A.3 Onsite Chemical Handling
When compared with the purchase costs and transportation costs, the on-
site handling costs of solidification/stabilization chemicals are usually
minimal. Onsite handling costs incorporate those costs relating to the stor-
age and handling of the chemicals between the time of delivery and the mixing
of chemicals with the wastes being treated. The costs of onsite chemical
handling are a function of the method of materials delivery (containers or
bulk), the nature and quantity of materials being handled, the method of
storage, and the method used to mix the chemicals with the waste being
treated. Many of these factors are interrelated and difficult to define."
A-3
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0.30 i-
0.25
050
1
5 0.16
0.10
0.05
PORTLAND CEMENT- BULK
QUICK LIME - BULK
HYDRATED LIME - BAGS
50
100
150
200
HAUL DISTANCE, MILES
Figure A-l. Typical chemical transportation costs.
Total costs for onsite chemical handling are expected to range from
$0.10 per ton of chemical handled for automated conveyor or pneumatic systems
to as high as $0.50 per ton of added chemical for manual addition methods.
A.4 Quantity and Cost of Chemicals Required
The quantity of chemicals required on a specific remedial action project
is the driving force behind all other costs associated with the total onsite
chemical costs. The cost of chemicals can represent up to 95 percent of the
total cost of an onsite solidification/stabilization remedial action project.
The quantity of reagents required to ensure adequate performance of a partic-
ular process are usually determined through pilot- or laboratory-scale
studies. Reagent requirements can be determined on the basis of volume of
reagent per volume of waste, or weight of reagent to weight of waste. For
pilot or laboratory studies, it is often easy to determine requirements on a
weight/ weight basis. Results are usually expressed on a percentage basis
(i.e., 20 percent by weight Portland cement to be added).
In the field, it is often more convenient to measure the quantities of
wastes on a volume basis such as gallons or cubic yards to be treated. The
relationship between volume and weight is expressed as a specific weight,
usually in units such as pounds per cubic foot or pounds per cubic yard or
A-4
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metric equivalents. The specific weight for materials may vary depending on
the condition of the material (i.e., natural state, disturbed state, com-
pacted state, etc.). Specific weights for typical materials are presented in
Table A-2. Once the volume of waste material to be treated is determined
from field surveys, the total weight of material to be treated can be deter-
mined by multiplying the volume by the estimated (or measured) specific
weight.
Once the total weight of waste materials to be treated is determined,
the total quantity of reagents required can be determined using the results
of the pilot- or laboratory-scale studies. The weight of reagents required
is simply the reagent percent by weight obtained from the pilot or laboratory
study multiplied by the total weight of onsite material.
A-5
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TABLE A-2. SPECIFIC WEIGHTS FOR COMMON MATERIALS AT REMEDIAL
ACTION SITES
Material
Ashes, hard coal
Ashes, soft coal, ordinary
Ashes, soft coal w/ clinkers
Cement
Clay, natural bed
Clay, dry
Clay, wet
Clay with gravel, dry
Clay with gravel, wet
Earth, top soil
Earth, dry
Earth, moist
Earth, compacted
Earth, w/sand and gravel
Gypsum, fractured
Gypsum, crushed
Kaolin
Lime
Lime, slaked
Limestone, blasted
Limestone, loose, crushed
Mud, dry (close)
Mud, wet (moderately packed)
Peat, dry
Peat, wet
Sand, dry
* BCY ป Bank cubic yards, all
LCY E Loose cubic yards
Weight in bank Percent
(lb/BCY)* swell
700-1,000
1,080-1,215
1,000-1,515
2,970
3,400
3,100
3,500
2,800
3,100
2,350-2,550
2,450-2,600
2,700-3,000
3,000
3,100
5,300
4,700
2,800
4,200
2,160-2,970
2,970-3,510
800-1,300
1,600-1,800
2,450
(Continued)
specifications are
8
8
8
20
22
23
25
18
18
43
43
33
25
11
75
75
30
6,765
20
20
80
80
12
Swell Loose weight
factor (Ib/LCY)
/ 0.93
0.93
0.93
0.83
0.82
0.81
0.80
0.85
0.85
0.70
0.70
0.75
0.80
0.90
0.57
0.57
0.77
0.570.60
0.83
0.83
0.56
0.56
0.89
650-930
1,000-1,130
930-1,410
2,465
2,800
2,510
2,800
2,380
2,640
1,650-1,790
1,720-1,820
2,030-2,250
2,400
2,790
3,020
2,680
2,160
1,400
800-1,500
2,400-2,520
2,600-2,700
1,790-2,470
2,470-2,910
450-730
900-1,010
2,180
in customary units.
A-6
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TABLE A-2. (Concluded)
Material
Sand, dry, fine
Sand , damp
Sand, wet
Sand and gravel, dry
Sand and gravel, wet
Slag, sand
Slag, solid
Slag, crushed
Slag, furnace, granulated
Weight in bank
(Ib/BCY)
2,700
3,200
3,500
3,300
3,700
1,670
4,320-4,830
1,600
Percent
swell
12
12
14
12
11
12
33
12
Swell
factor
0.89
0.89
0.88
0.89
0.90
0.89
0.75
0.89
Loose weight
(Ib/LCY)
2,400
2,850
3,080
2,940
3,330
1,490
3,240-3,620
1,900
1,420
A-7
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APPENDIX B
TYPICAL STABILIZATION/SOLIDIFICATION EQUIPMENT
Many of the solidification/stabilization alternatives use similar
equipment and/or groups of equipment. The processing equipment used for the
solidification/stabilization of hazardous materials at remedial action sites
has generally been adapted from the materials processing and construction
industries. The equipment or groups of equipment used for the various treat-
ment programs identified in this study have been fabricated from readily
available, off-the-shelf equipment modules. The discussion that follows pro-
vides information on the technical attributes, available capacities, and
costs associated with each identified equipment module.
The equipment that has been adapted for use in solidification operations
is divided into four basic categories: chemical storage, materials handling,
materials mixing, and materials control. A variety of equipment modules are
available under each category. The more common types of equipment modules
identified during site visits of operating facilities conducted as a part of
this study are the primary focus of this discussion. No attempt has been
made to review all available equipment to optimize equipment sizes and mixes.
The cost information presented is based on the purchase cost or rental
cost of equipment modules. The costs presented have a July 1983 base year
and result from interviews with equipment manufacturers. Note, however, that
most of the identified equipment modules are readily available in the used or
rental equipment market at substantial cost savings. In addition, the type
of equipment generally utilized is designed for portability. As a result, it
can be moved from site to site with minimal loss of productive capacity.
Thus once it is purchased, the equipment could be amortized over several
projects at substantial savings when calculated on a basis of per-unit cost
of waste treated.
B.I Chemical Storage Facilities
Onsite facilities may be required for the storage of both dry and liquid
chemicals. The nature and size of required storage facilities are a function
of the solidification/stabilization process selected (the types of chemicals
required), the quantity of chemicals required, and the method of chemical
shipment (bulk or container). Chemical deliveries should be programmed to
minimize onsite storage requirements and ensure their continuous availability
at the site.
B-l
-------
The majority of remedial action projects are assumed to be large enough
to justify the bulk purchase of chemicals; however, some specialty chemicals
used in the various solidification/stabilization processes may be purchased
in smaller, containerized quantities. Therefore, consideration must be given
to the protection of both bulk and containerized chemicals during the plan-
ning phase.
B.I.I Dry Chemical Storage
On a volume or weight basis, the major dry chemicals used in a solidifi-
cation/stabilization process will normally be either Portland cement, quick
lime, hydrated lime, fly ash, gypsum, cement-kiln dust, or lime-kiln dust.
The. quality of these materials, measured by their reactivity, is subject to
severe degradation by exposure to moisture from precipitation or excessive
humidity. Storage can be provided in one of four ways: open storage, stor-
age with fabric or membrane covers, storage in a warehouse environment, or
closed bins and silos.
Open storage can be utilized for short periods of time during appro-
priate weather conditions for the less reactive dry reagents. Open storage
of the more reactive, dry reagents, such as Portland cement and quick lime,
would not be appropriate. For example, small amounts of the less reactive
dry reagents (e.g., weathered kiln dust) could be stored in the open pending
use in an in-situ mixing program without significant loss of reactivity.
Fugitive dust may be a severe problem when using this storage option in dry,
windy climates. Long-term open storage of dry reagents is not a recommended
option. A zero-cost, not including losses of material, may be given to the
open storage option.
Storage under a fabric or membrane cover is more appropriate than open
storage for low-reactivity materials such as kiln dust, fly ash, or gypsum.
Short-term storage in this manner should not result in significant deteriora-
tion in these materials. Fugitive dust, however, may still be a significant
problem when this method of storage is used. The cost of storage with fabric
or membrane covers is estimated to range between -$2.00 and $4.00 per square
foot of storage area provided. The majority of this cost is involved in the
cost of the fabric or membrane covering. This category of storage is not
appropriate for high-reactivity reagents such as quick lime, hydrated lime,
or Portland cement.
Covered storage in a warehouse environment provides an alternative for
onsite storage. Unheated warehouse storage can be provided for a cost rang-
ing between $8.00 and $10.00 per square foot. Fugitive dust control and
access to the materials may present problems. The high reactivity chemicals
still may suffer degradation from humidity effects.
Covered storage for the bulk solid materials associated with solidifica-
tion/stabilization processes is often provided in the form of metal storage
silos similar to those used for the storage of Portland cement. .Storage
capacities ranging from 1,000 to 5,000 cu ft are readily available. The
B-2
-------
estimated installed cost for these dry chemical storage silos is presented in
Figure B-l.
50
40
o
Q
u.
S30
Q
I
O
X
8 20
Q
I
10 -
BOL TED STEEL LIME SILO
_L
_L
_L
0 1 2 3 4 5 6
STORAGE CAPACITY, THOUSANDS OF CUBIC FEET
Figure B-l. Installed cost of dry chemical storage.
The required size for a storage silo is a function of the rate of chemi-
cal usage and the anticipated chemical delivery schedule. The minimum size
silo should be capable of holding at least the quantity of material in a bulk
tank truck (approximately 500 cu ft). Material suppliers should be consulted
to determine delivery schedules, minimum order quantities, and delivery
times.
B-3
-------
Containerized dry chemicals (generally bags or drums) can be stored in
open storage 'or covered storage. Some specialty chemicals may require pro-
tection from extreme cold or heat. Appropriate covered storage should be
provided for such materials. Heated warehouse space can be provided for
approximately $10.00 to $12.00 per square foot.
Rather than providing for the construction of onsite storage facilities,
it may be desirable to use the bulk transport trailer for onsite storage.
The cost for long-term use of the bulk transport trailers for such use is
subject to extreme variation. Business conditions may preclude the use of
this option because of the demand for bulk transportation services and resul-
tant high demurrage rates for bulk trailers. Materials transporters should
be consulted during the project planning phase.
B.I.2 Liquid Chemical Storage
Liquid reagents may be received in containers (generally drums) and in
bulk form. Containerized liquid reagents may be placed in open storage or
covered storage. Although less susceptible to degradation caused by moisture
(because of the nature of the shipping container), liquid reagents may be
more sensitive to temperature extremes. Changes in both degradation and
handling characteristics may result from exposure to temperature extremes.
Open and covered storage has been discussed under dry chemical storage above.
Similar storage facilities can be provided for liquid chemical storage.
Bulk liquid storage is provided in tanks. Typically, horizontal and/or
vertical tanks may be provided. Tanks may be equipped with heating coils to
ensure the maintenance of handling characteristics when exposed to low tem-
peratures. The estimated installed costs of various tank storage facilities
are presented in Figure B-2. As in the case of dry chemical storage, the
proper planning of chemical delivery schedules can be used to minimize onsite
storage requirements.
B.2 Materials Handling Equipment
One of the most important factors in the application of solidification/
stabilization technology to waste at a remedial action site is the form or
nature of the wastes to be processed. The forms that wastes may take
include:
a. Liquids from lagoons, settling ponds, drums, and the container.
b. Sludges from lagoons, settling ponds, and leaking drums or other
containers.
c. Contaminated soils caused by leaking containers or direct dumping
of liquids and sludges on the soil.
B-4
-------
16
14
o
Q
w
ง 8
U
Q
Ul
I
_L
_L
6 8
CAPACITY, THOUSANDS OF GAL
10
12
14
Figure B-2. Installed cost of liquid reagent storage
(FRP = fiber reinforced plastic).
d. Pasty solids from breached and/or intact containers.
e. Solids in drums or in other containers or from open contaminated
sites.
Materials handling equipment selected for a particular remedial action
project will depend on the forms of waste to be handled. Selection of
equipment for materials handling is a function of the physical characteris-
tics of the waste material being handled (percent solids, viscosity, etc.),
the packaging of the waste materials (drums, lagoons, open area, etc.), the
quantity of waste materials being handled, and the physical characteristics
of the solidified/stabilized wastes. It is desirable to transport liquids
and high-moisture-content sludges with pumps. Some low-moisture-content
sludges can be handled with special pumps. Low-moisture-content and/or
viscous sludges may be handled with earth-moving equipment such as clam-
shells, backhoes, and dump trucks. Contaminated soils are handled with
earth-moving equipment. Material conveying systems can also be utilized for
low-moisture-content sludges and contaminated soils. Care must be taken to
ensure compatibility between the material to be handled and the equipment
selected to do the handling.
B-5
-------
B.2.1 Pumps
Either centrifugal or diaphragm pumps may be used for the bulk transfer
of liquids and high-liquid-content sludges. Centrifugal pumps have the ad-
vantage of higher capacities, whereas diaphragm pumps are capable of handling
higher-solids-content materials, but generally have higher maintenance costs.
Centrifugal pumps used for handling materials to be solidified or stabilized
are generally referred to as self-priming, centrifugal trash pumps (Hicks
1971). Size ranges from 5 cm to 15 cm (2 in. to 6 in.) are commonly avail-
able with pumping capacities, based on pumping water, ranging between 95 and
5,100 ฃ/min at heads of up to 56 m. Capacity reductions may be significant
for high-solids-content materials. Both motor- and engine-driven pumps are
available on frame and trailer-mounted systems. A trailer-mounted, gasoline-
engine-driven pump is illustrated in Figure B-3.
Figure B-3. Trailer-mounted centrifugal
pump (Courtesy Gorman Rupp Company).
Self-priming trash pumps are generally limited to handling waste mate-
rials with a solids content less than 40 percent. Recent developments in
centrifugal pumping systems, incorporating chopper pumps and floating plat-
forms have produced systems capable of efficiently handling slurries con-
taining up to 60% solids. Commonly available sizes range from 7 cm to 15 cm
(3 in. to 6 in.) with pumping capacities, based on pumping water ranging
between 1,000 and 5,200 A/min at heads up to 44 m. As in the case with the
self-priming, centrifugal pumps, capacity reductions are significant when
pumping sludges with high solids content.- Since the pump impeller on the
floating system is in contact with the waste slurry, the floating system can
handle a higher-solids-content slurry. Figure B-4 illustrates a typical
floating pump system.
B-6
-------
Figure B-4. Typical floating centrifugal pump (Courtesy
Vaughan Pump Company).
Diaphragm pumps can be utilized on more viscous material with higher
solids content; however, capacities and head are generally limited, and
maintenance costs are higher. Commonly available diaphragm pump sizes range
from 40 to 570 ฃ/min at heads up to 8 m. Both electric and engine-driven
diaphragm pumps are available.
Figure B-5 presents the purchase costs for self-priming centrifugal
trash pumps, floating centrifugal pumps, and diaphragm pumps.
Waste materials that have been mixed with solidification/stabilization
reagents can also be transported with pumping systems. In addition to the
systems described above, concrete pumps have been used to transport treated
waste materials. Available capacities range from 40 to 120 cu yd/hr. Con-
crete pumps can handle very high solids content slurries; however, the high
cost of these systems has prohibited their wide-scale use. Figure B-6 pre-
sents the purchase cost of available units.
B.2.2 Construction Equipment
In those cases where waste material which is not amenable to pumping is
to be handled, reliance has been placed on the-use of conventional excavation
and earth-moving equipment. Typically, equipment used for the solidification/
stabilization of waste materials will include backhoes or all-purpose
B-7
-------
20 r-
16
O
Q
to
O
O
O
Q
-FLOATING SOLIDS
HANDLING PUMP
TRAILER MOUNTED
TRASH PUMP
DIAPHRAM PUMP
234567
PUMP SIZE, IN.
Figure B-5. Typical costs for pumping systems.
excavators, clamshells, or draglines; front-end loaders; and dump trucks.
Figure B-7 illustrates a backhoe-dump-truck operation for removal of contami-
nated soils. Other types of equipment including graders, dozers, compactors,
etc. may be used in the overall remedial action project; however, this dis-
cussion is limited to consideration of materials handling associated with the
solidification/stabilization process.
The required materials handling equipment is available in a wide range
of sizes. The selection of quantity, types, and size of equipment is pri-
marily a function of the quantity of materials to be handled and the working
area available.
Production rates for construction equipment used on remedial action
projects may vary significantly. Estimates of production rates are beyond
the scope of this study; however, a number of excellent references are
readily available to assist the project planner in preparing production and
cost estimates (Terex 1981; Caterpillar Tractor Co. 1981, 1982). In addi-
tion, direct consultation will often be provided by the equipment
manufacturer.
Estimation of the production rates expected on a particular job requires
careful preparation, a thorough knowledge of the material to be handled, and
a complete understanding of equipment capabilities. Factors to be considered
B-8
-------
120
c/j
5 100
o
Q
o
v>
O
I-
C/3
O
O
Q
HI
80
60
40
_L
20
40 60 80
CAPACITY, CU YD/HR
100
120
140
Figure B-6. Typical costs for trailer-mounted concrete pumps.
in preparation of the estimate include (1) cycle time of materials-moving
components; (2) job efficiency factors; (3) material weights, swell factors,
and handling characteristics; and (4) vehicle payloads.
The cycle time in construction activities is defined as the time for a
machine or group of machines to complete one cycle (i.e., load, haul, dump,
return, spot, and delay). Each of these components affects the total cycle
time and is controlled by a number of factors. Loading factors include:
size and type of loading equipment, nature of material being handled, capa-
city of hauling equipment, and skill of the operator. Haul factors include:
capability of hauling unit, hauling distance, haul road conditions, and
grades. Dumping, or unloading, factors include: destinations of material
(i.e. fill, stockpile, mixer, etc.), conditions of unloading area, maneuver-
ability of the hauling unit, and nature of the material. Return factors in-
clude: capability of the hauling unit, return distance, haul road condition,
and grades. Spot factors include maneuverability of the hauling unit, maneu-
ver area available, type of loading machine, and location of the loading
equipment. Delay factors include time spent waiting on the loading unit and
time spent waiting to unload.
B-9
-------
Figure B-7. Backhoe-dump-truck operation for removal of contami-
nated soils (Courtesy Albert H. Halff Associates).
Job efficiency factors are used to estimate the sustained or average
materials handling capability over a long period of time. Job efficiency is
influenced by such factors as operator skill, repair time, personnel delays,
and job layout (Caterpillar Tractor Co. 1982). Since many of these factors
are difficult to quantify, estimates of job efficiency are very complex.
Typical job efficiency factors are presented in Table B-l. Note that a 75%
efficiency (45 min/hr) is estimated for a job with good working conditions
and good management. Job efficiency factors as low as 25% may be anticipated
for some remedial action projects due to safety factors and nonoptimum work-
ing conditions.
Weight and handling characteristics of materials being moved are also
important factors in determining production rates. Materials handled with
construction equipment on typical remedial action projects are low-moisture-
content sludges with difficult handling characteristics. Specific weights of
the materials in-place are expected to vary between 700 and 1,400 kg/cu m.
The materials may also be subject to swelling and/or hardening in the loading
equipment.
Payloads for the loading and hauling equipment must be determined from
the manufacturer or his representative. Again, it must be noted that payload
data are developed based on earth and rock loading and hauling capabilities.
Few if any data are available on handling of the waste materials that are
candidates for solidification/stabilization.
B-10
-------
TABLE B-l. TYPICAL JOB EFFICIENCY FACTORS
Management condition
Job condition
Excellent
Good
Fair
Poor
Excellent
0.84
0.78
0.72
0.63
Good
0.81
0.75
0.69
0.61
Fair
0.76
0.75
0.69
0.61 ,;
Poor
0.70
0.65
0.60
0.52
Once production estimates have been developed, the onsite requirement
for each piece of construction equipment can be estimated. With this time
estimate, the job cost of each item of equipment can be estimated. Equipment
can be either purchased or rented. Of. course, purchased equipment can be
amortized over more than one project. For planning purposes, the normal pro-
cedure is to estimate costs based on equipment rental rates. Table B-2 pro-
vides information on the rental rates for various items of construction
equipment anticipated to be required on a typical remedial action project.
B.2.3 Conveyors
Belt conveyors, or stackers, can be used to transport materials with
.soil-like properties (i.e., contaminated soils or the solidified/stabilized
waste material). Belt conveyors are not suitable for the transport of
liquids, high-moisture-content sludges, or viscous materials. Portable con-
veying systems from 15 m to 70 m in length with 60-cm through 90-cm belt
widths are readily available. Capacities range from 300 to 700 tons/hr.
Estimated costs for an installed, portable conveyor system are presented in
Figure B-8. Figure B-9 illustrates a typical portable conveyor system.
B.2.4 Drum Handling
Waste to be solidified or stabilized is often stored in drums.
Efficient drum handling has been one of the most difficult problems in
materials handling associated with remedial action projects. Appropriate
procedures have been defined in the publication entitled "Drum Handling
Practices at Hazardous Waste Sites" (EPA 1982).
B-ll
-------
TABLE B-2. APPROXIMATE RENTAL RATES FOR CONSTRUCTION EQUIPMENT USED
FOR STABILIZATION/SOLIDIFICATION PROJECTS .
Equipment
Compactors - self-propelled
Vibratory plates
3 wheel steel (14 ton)*
Tandem (14 ton)
Rubber tired (11 ton)
Vibratory drum (10 ton)
Graders
14 ton
19 ton
25 ton
Front-end loaders
1 cu yd
2 cu yd
4 cy yd
5 cu yd
Crawler tractors
140 hp
300 hp
400 hp
Wheel tractors
180 hp
300 ht>
J\J\J 11^*
420 hp
Hydraulic pull shovel
1-1/2 cu yd
2**It vrf
(wU jr tl
3 cu yd
All purpose excavators
1/2 cu yd
3/4 cu yd
1-1/4 cu yd
Per Month
(176 hr)
$ 1,450.00
1,600.00
1,600.00
1,600.00
2,495.00
3,300.00
4,650.00
6,350.00
1,550.00
2,400.00
5,250.00
6,250.00
2,950.00
5,700.00
8,650.00
3,750.00
6,200.00
7,250.00
5,100.00
6,350.00
7,950.00
3,875.00
5,725.00
7,450.00
Per Week
(40 hr)
$ 485.00
535.00
535.00
535.00
800.00
1,100.00
1,550.00
2,100.00
525.00
825.00
1,750.00
2,100.00
1,000.00
1,900.00
2,900.00
1,250.00
2,050.00
2,400.00
1,700.00
2,100.00
2,650.00
1,275.00
1,900.00
2,500.00
Per Day
(8 hr)
$ 140.00
150.00
150.00
150.00
235.00
325.00
450.00
600.00
150.00
235.00
500.00
600.00
290.00
550.00
835.00
360.00
600.00
685.00
495.00
610.00
770.00
380.00
560.00
715.00
Approx.
Purchase
Price
$ 25,500.00
28,000.00
28,500.00
24,000.00
4,1,000.00
61,500.00
83,500.00
110,000.00
28*500.00
44,000.00
93,000.00
112,000.00
52,500.00
102,000.00
156,000.00
66,200.00
113,500.00
128,000.00
95,000.00
115,000.00
143,000.00
71,600.00
103,000.00
133,000.00
* Ratings are in customary units.
(Continued)
B-12
-------
TABLE B-2. (Concluded)
Equipment
Per Month
(176 hr)
Per Week
(40 hr)
Per Day
(8 hr)
Approx.
Purchase
Price
Mechanical shovels
2 cu yd
31/4 cu yd
41/4 cu yd
5-1/2 cu yd
Hydraulic crane
10 tons
15 tons
18 tons
35 tons
Mechanical crane-crawler
20 tons
30 tons
40 tons
50 tons
Truck crane
25 tons
50 tons
Water pumps
2-in. discharge
3-in. discharge
4-in. discharge
6-in. discharge
8-in. discharge
4,950.00
10,000.00
12,500.00
17,500.00
3,150.00
3,250.00
3,550.00
6,400.00
3,850.00
4,300.00
6,000.00
6,600.00
4,750.00
7,000.00
120.00
210.00
510.00
850.00
1,000.00
2,000.00
3,300.00
4,150.00
5,950.00
1,050.00
1,100.00
1,250.00
2,150.00
1,250.00
1,450.00
2,000.00
2,175.00
1,550.00
2,350.00
40.00
70.00
175.00
285.00
330.00
575.00
900.00
1,200.00
1,700.00
300.00
310.00
340.00
620.00
375.00
410.00
575.00
625.00
450.00
675.00
12.00
20.00
50.00
80.00
95.00
100,000.00
170,000.00
220,000.00
320,000.00
56,000.00
59,000.00
65,000.00
120,000.00
71,500.00
77,000.00
110,000.00
115,000.00
82,500.00
125,000.00
2,300.00
3,750.00
8,800.00
15,500.00
18,000.00
B-13
-------
50 r-
co
cc
40
8
u.
O
CO
Q
2
OT
O 30
H
te
8
O
20
g
700 TONS PER HOUR
480 TONS PER HOUR
300 TONS PER HOUR
_L
_L
10
40
50
60
70 80
LENGTH,FT
90
100
Figure B-8. Installed portable conveyor system costs.
"'"H-l
110
li!^
Figure B-9. Typical portable conveyor system (Courtesy
The Vince Hagen Company).
B-14
-------
B.3 Materials Mixing Equipment
Materials mixing equipment is used to blend reagents with the waste
materials to accomplish the solidification/stabilization reaction.
B.3.1 Construction Equipment
Backhoes, clamshells, and draglines have been applied to the in-situ
mixing of solidification/stabilization reagents with waste materials. Since
this is not a "normal" use for this equipment, little detailed information is
available concerning production rates and control of the mixing process
(i.e., is mixing adequate or do pockets of unreacted waste material remain?).
Backhoe mixing has been successfully applied at Resource Conservation and
Recovery Act (RCRA) disposal sites; however, this is usually done in rela-
tively small basins and the solidified/stabilized material is always re-
handled. Thus adequate mixing is usually ensured.
The high-speed rotary mixer (Figure B-10) has been used to mix
solidification/stabilization reagents with sludges and contaminated soils.
The procedure for using this equipment places alternating layers of waste and
treatment reagents. Data for application to the solidification/stabilization
of waste materials are not available; however, based on highway construction
experience, it is estimated that around 2,000 sq m (21,520 sq ft or about
1/2 acre) of surface per day could be mixed. Assuming a lift of 25 cm,
500 cu m/day of waste material could be mixed with the required reagents.
A variety of mixing and other types of materials handling equipment is
available from the concrete and roadway materials industry. Products that
can be readily adapted to the solidification/stabilization of hazardous
wastes include materials storage, batching, and mixing equipment., Mobile,
portable, and stationary equipment modules are readily available for all of
these functions. Modules can be purchased and assembled to meet site-
specific requirements. Equipment manufacturers provide consultative service
to address specific materials handling requirements.
A typical adaptation of concrete technology is the use of a base stabi-
lization plant for treating contaminated soils as illustrated in Figure B-ll.
Sizes for such plants range from 100 to 400 tons/hr and consist of materials
storage, batching, and mixing facilities. Materials mixing is generally
accomplished using a pug mill. The estimated cost of a base stabilization
plant is illustrated in Figure B-12.
Other applications from concrete mixing technology include the use of
concrete batch plants, central mixing facilities, and/or transit mixing
trucks. These can be used for both apportioning and mixing solidification/
stabilization reagents with the waste materials being treated. The costs of
both mobile and modular batching plants are illustrated in Figure B-13.
B-15
-------
f s 'a i,, i,,,* .n.e ;;;.; ; i,i,i,,,ii!,,,BLn.d.i!h .:..i;.i.:u.! ,:; ;;",,,,;cfi|i[!,|,,i!s:}E
' "" ' "*'
- ,-,
^gE-j.SSWiL^'** tL *K.T 7i!ปr '-^'' - ^
Figure B-10. Typical high-speed rotary mixer (Courtesy
Albert H. Halff Associates).
Figure B-ll. Typical base stabilization plant.
B-16
-------
240
(O
DC
O
Q 220
co
Q
1
O 200
I
co
O
O
Q
UJ 180
_j
<
co
160
'80
140
- BASE STABILIZATION
PLANT
ฑ
160
240
360
440
PLANT CAPACITY, TONS/HR
Figure B-12. Installed cost for base stabilization plant,
CO
DC
ง 120
CO
Q
O
I
I-
co
O
O
Q
HI
<
CO
100
80
60
MOBILE BATCHING
PLANT
STATIONARY BATCHING
PLANT
40 80 120 180
PLANT CAPACITY, CU YD/HR
Figure B-13. Installed cost for mobile and modular
concrete batching facility.
220
B-17
-------
Materials mixing can be accomplished by central mixing equipment (tilt-
ing mixers) or in transits-mix trucks. Tilting mixers are available in sizes
ranging from 6 to 12 cu yd per batch. The installed cost of a tilting mixer
is presented in Figure B-14.
160 r-
ta
a:
5 140
ง
1
0 120
0
w
100
80
50
100
150 200
BATCH CAPACITY, CU FT
250
300
350
Figure B-14. Installed cost for concrete tilting mixers.
Transit-mix trucks have been used to mix contaminated materials and
solidification/stabilization reagents. Typically, the materials are batched
in a mobile batch plant and mixed during transport to the final disposal
area. Transit-mix trucks are available in capacities ranging from 6 to
12 cu m.
Although the concept for using modified equipment from the concrete
industry has been developed, the equipment has not received widespread use
because of the relatively high cost compared with equipment used in the
scenarios developed in Sections 6.3 through 6.6 of this handbook. However,
the use of concrete industry equipment should be included in alternative
evaluations on a site-specific basis.
B.3.2 Process Mixing Equipment
A wide variety of process mixing equipment has been used, or is theoret-
ically available for use in the mixing of reagents with waste materials to be
solidified or stabilized. This equipment has been adapted from either the
food or chemical processing industry. Basic parameters, which include mixing
B-18
-------
characteristics, available sizes, and costs for the more significant mixer
types, are presented below. Additional information on the specific applica-
tion of each is provided in Section 6.
The scientific design of mixing equipment is complex and usually re-
quires detailed engineering study. Perry (1973) identifies properties of the
materials to be mixed that affect the selection of appropriate mixing equip-
ment: particle-size distribution; bulk density; true density; particle
shape; surface characteristics; friability; state of agglomeration; moisture
or liquid content of solids; density, viscosity, and surface tension; and
temperature characteristics. Little if any scientific design has been ap-
plied to mixing required for solidification/stabilization processes. Most
mixing equipment has been developed or modified by trial and error based on
field experience. One reason for this is the wide range of materials that
the typical system may be required, to handle. The major types of mixing
equipment for waste processing include the change-can mixer, ribbon blender,
muller mixer, rotor mixer, and propeller mixer. Detailed engineering has not
been performed to optimize the design of mixing equipment currently used for
solidification/stabilization of hazardous waste.
B.3.2.1 Change-Can Mixer
The change-can mixer is a vertical batch mixer in which the container is
separate from the frame of the machine. Capacities ranging from 0.5 ฃ to
1,100 H are available. The most common size used in the solidification of
hazardous wastes is the 200-ฃ drum. Figure B-15 illustrates a typical
change-can mixer.
The change-can mixer is ideally suited for use in drum solidification/
stabilization of wastes. The mixing head may be raised from the can (drum)
allowing the mixing blades to drain into the drum. If necessary, the blades
may be wiped down or cleaned by rotating .them in a solvent. When the can is
removed, cleaning the blades and support is a rather simple process.
Mixing of can contents is achieved in one of two ways. First, the
mixing unit assembly may rotate with a planetary motion so that the rotating
blades sweep the entire circumference of the can. Second, the can is mounted
on a rotating turntable so that all parts of the can will pass fixed scraper
blades on the agitation blades at a point of minimum clearance. The mixing
action is primarily in the horizontal, to and from the center of the can.
Vertical mixing results from the shape of the blades.
As mixing progresses, the flow characteristics usually change. In order
to achieve a minimum time cycle, variable speed or two-speed mixers are
desirable. A slow speed at the start of mixing will reduce dusting or
splashing.
The estimated costs for a change-can mixer installation are presented in
Figure B-16. ,
B-19
-------
Figure B-15. Typical change-
can mixer (Courtesy Charles
Ross & Son).
B.3.2.2 Ribbon Blender
A ribbon blender consists of a stationary shell and rotating horizontal
mixing elements (Figure B-17). To accommodate a wide variety of materials,
it is possible to modify such features as ribbon cross section, ribbon pitch,
the number of ribbons, and the clearance between ribbons and ribbons and
shell. The ribbon blender can be used for continuous or batch operations.
Installed costs for ribbon blenders of various sizes are presented in
Figure B-18.
B.3.2.3 Muller Mixer
The muller mixer consists of a stationary pan with rotating wheels and
plows (Figure B-19). The muller is typically used for batch operations; how-
ever, continuous-operation mullers are available. Installed cost for muller
mixing systems are presented in Figure B-20.
B.3.2.4 Rotor Mixers,
Rotor mixers consist of shafts with paddles or screws contained in a
stationary trough. These mixers may be equipped with single or twin shaft
B-20
-------
25 i
20
co
CC
o
Q
u.
O 15
CO
Q
CO
O
I-
00
8 10
Q
UJ
<
CO
0 5 10 15
BATCH CAPACITY, CU FT
Figure B-16. Installed cost for change-can mixers.
assemblies. Figure B-21 illustrates a twin-shaft rotor mixer. The installed
cost for a twin-shaft rotor mixer is presented in Figure B-22.
B.3.2.5 Propeller Mixer
The top-entering propeller mixer consists of a driver, shaft, and pro-
peller. This mixer is lightweight and highly portable, and it can be easily
changed from one drum to the next. This mixer works by changing the mixer
from drum to drum rather than by changing drums in the mixer. The mixer is
mounted on the drum with a clamp or special head frame. Typical cost of the
equipment is approximately $2,000.00. Figure B-23 illustrates a typical pro-
peller mixer.
B-21
-------
40 |-
30
u.
O
at
a
20
o
3
< 10
Figure B-17. "Typical ribbon blender
(Courtesy Beardsley & Piper).
20
40
60 80
BATCH CAPACITY, CU FT
100
120
Figure B-18. Installed cost for ribbon blenders,
140
B-22
-------
160
-------
50
VI
cc
3 40
g
u.
O
(a
O
O 30
fc
O
u
O
Ul
20
10
Figure B-21. Typical twin-shaft rotor mixer
(Courtesy Beardsley & Piper).
_L
_L
_L
1000
2000 3000 4000
DRY CAPACITY, CU FT/HOUR
5000
6000
Figure B-22. Installed cost for rotor mixers.
B-24
-------
Figure B-23. Typical top-entering
propeller mixer (Courtesy Mixing
Equipment).
\r
B.4 Materials Control Equipment
Solidification/stabilization processes require the addition of reagents
to waste materials in fixed, measured quantities, generally as determined from
pilot- or laboratory-scale studies. Adjustments are subsequently made as a
result of onsite experience with the particular waste being treated. The
control of materials, both the waste to be treated and the reagents to be
added, can be accomplished using methods based on either weight or volume.
In addition, either batch or continuous control systems are available. The
sophistication of the materials control technique selected for a particular
project can vary from simplistic systems incorporating manual feed to com-
plex, fully automated equipment.
Materials control (i.e., the proper proportioning of waste materials and
solidification/stabilization reagents) is one key to the proper performance
of the treated waste materials. Numerous materials control systems are
available off-the-shelf. The most common types of equipment used for mate-
rials control purposes are discussed below.
B.4.1 Waste Materials Control
Waste materials control can be accomplished by either volume- or weight-
based methods. The type of control system selected will depend on the
B-25
-------
materials handling equipment and the materials mixing equipment selected to
accomplish the solidification/stabilization process.
If the waste material is pumped and a continuous mixer is used, pump
curves can be consulted to determine the discharge under stated conditions.
Since manufacturers' pump curves are based on pumping clean water and the
typical remedial action project will handle sludges or high solids content
liquids, adjustment to the manufacturers' curves will be required. Calibra-
tion of pumps under field conditions may be required. For those systems
using pumps for waste material handling and batch-type mixing equipment, a
volumetric batching system can be employed. This system may consist of a
separate, level-controlled batch hopper, or the mixing vessel can simply be
filled to a predetermined level. Manual or automatic control can be used.
If the waste material is handled by construction equipment, material
control can be accomplished by volumetric measurement, or for granular mate-
rial, aggregate weigh batches from the concrete batch plant industry can be
used. Figure B-24 illustrates a weigh batcher being used to meter waste
materials. Volumetric measurements can be used in the same manner as for
pumped wastes; however, feeding the measuring or mixing equipment will be
more difficult. A less sophisticated method of measurement is merely to
count the number of truckloads of material and make an estimate of the volume
of waste material on each based on the known truck capacity.
Figure B-24. Weigh batcher system for waste materials
control (Courtesy Solid Tek).
B-26
-------
B.4.2 Solid Reagent Control
The control of solid reagents can be accomplished by either volumetric-
or weight-based methods. The type of equipment selected should be based on
the quantity of material to be fed to the waste and the solidification/
stabilization scenario selected.
The most common type of system for feeding dry solids is the screw
feeder (Figure B-25). The screw-type feeder is fairly rugged and well suited
for application in the field environment. The feed rate is controlled by
increasing or decreasing the speed of the screw. Assuming a constant bulk
density of material, the weight of material discharged from the screw feeder
can be accurately controlled. Screw feeders can be adapted for use with both
batch and continuous mixing systems.
MATERIALS STORAGE
MATERIALS FEED HOPPER
ROTATING SCREW
Figure B-25.
TO WASTE MATERIALS MIXER
Typical screw feeder.
Batch and continuous-feed systems based on measurement of weight are
also available. These systems, although somewhat more delicate than screw
feeder systems, provide for more accurate materials control. Batch weighing
systems suitable for use with batch mixing systems usually consist of a con-
tainment vessel or hopper mounted on a scale or load cell. The entire assem-
bly is usually mounted directly above the mixing unit. The material being
weighed is fed from a storage bin into the hopper. The flow of material is
controlled by signals from the load cell or scale. When the set point is
B-27
-------
reached, the flow of material is stopped and the batch is ready for addition
to the mixer. Weighing accuracies within ฑ0.25% are available from batch
weighing systems. Figure B-26 illustrates a typical weigh feeder system.
Figure B-26.
Rexnord).
Typical weigh feeder system (Courtesy
Continuous weighing involves a system that is sensitive to changes in
the weight of material on a continuous belt (Figure B-27). Typically, the
belt passes a weight-sensitive area (usually load cells) that measure and
total the weight of materials on the belt. A control signal is sent to a
gate controlling the flow of materials from a storage hopper to the belt.
Accuracies within ฑ1.0% are available from continuous weighing feeders.
B.4.3 Liquid Reagent Control
The control of liquid reagents is normally accomplished by volumetric
methods. Typically, liquid reagents will be proportioned with metering pumps
or flow-measuring systems sending a signal to a control valve. A popular
installation would include a turbine flow meter transmitter with output sig-
nal sent to digital or analog instruments for feed rate indication, totaling,
and flow control. Numerous other flow-measuring devices are also available,
including venturi meters, magnetic flow meters, orifice meters, etc. The
turbine flow meter seems, however, to offer greater sensitivity and control.
B-28
-------
63-9
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'ฃ3-3
-------
REFERENCES
Caterpillar Tractor Co. 1981. Handbook of Earthmoving. Caterpillar Tractor
Co., Peoria, Illinois.
Caterpillar Tractor Co. 1982. Caterpillar Performance Handbook. Caterpil-
lar Tractor Co., Peoria, Illinois.
Hicks, T. G., and T. W. Edwards. 1971. Pump Application Engineering.
McGraw-Hill Book Company, New York, New York.
Terex. 1981. Production and Cost Estimating of Material Movement with Earth-
moving Equipment. Terex Corporation, Hudson, Ohio.
Perry, R. H. 1973. Chemical Engineers' Handbook. McGraw-Hill Book Co.,
New York, New York.
U.S. EPA. 1985. Drum Handling Practices at Hazardous Waste Sites (Draft).
Municipal Environmental Research Laboratory, U.S. Environmental Protection
Agency, Cincinnati, Ohio.
B-30
-------
INDEX
Absorbent, 2-1, 2-3
Activated Alumina, 2-8
Activated Carbon, 2-8
Anhydrous Sodium Silicate, 6-7,
6-14, 6-26, 6-28, 6-35, A-2
Area Mixing Alternative, 6-31
Asphalt, 2-1, 2-16
Attapulgite, 2-12
Atterberg Limits, 3-1, 3-3
Bearing Capacity, 4-8
Bentonite, 2-6
Biodegradation, 4-2
Blender, Ribbon, 2-9, 2-12, 6-20,
B-20
Borate Salts, 2-16
Bottom Ash, 2-5
Bulk Density, 3-1, 3-3
CERCLA, 1-4
Calcite, 2-6
Capping of Solidified Wastes, 8-2
Celite, 2-3
Cellulosic Sorbents, 2-14
Chabazite, 2-6
Chelating Agents, 2-16
Chemical Binding, 2-5
Chemical Characterization, 3-4
Scavenging, 2-22
Storage Facilities, B-l
Chemsorption, 2-4
Clay, 2-2, 2-22
Cleanup of Equipment, 8-1
Closure, 8-1
Compatibility, 2-5, 4-7
Compressive Strength, 3-1, 3-4,
4-7, 7-2
Cone Index, 3-1, 3-3
Construction Equipment, B-7, B-.15
Conveyor Equipment, B-ll
Corrosivity, 1-3, 4-1
Cost Analysis and Comparison, 6-2,
6-36, A-2
Costs Alternative Reagents, 6-39
Area Mixing, 6-34
Equipment Leasing, B-l2, B-l3
In-Drum Mixing, 6-5
In-Situ Mixing, 6-12
Layering, 6-34
Labor, 6-3, 6-5, 6-7, 6-14,
6-26, 6-28, 6-35, 6-37
Mobile Plant Mixing, 6-25
Modular Mixing Plant 6-28, 6-29
INDEX-1
-------
Overhead and Profit, 6-5, 6-7,
6-14, 6-26, 6-28, 6-35, 6-37
Reagent Prices, A-l
Decontamination, 7-6
Delisting, 2-1
Density, 4-7
Dewatering, 2-23
Diadochy, 2-4
Diatomaceous Earth, 2-10
Drum Handling Equipment, B-ll
Drum-Over-Packs, 2-18
Dry Chemical Storage, B-2
Durability, 4-9, 4-10
Dust, 7-5
Elemental Sulfur, 2-16
Emulsifiers, 2-14
Environmental Concerns, 7-2
Expanded Mica, 2-3
Extraction Procedure (EP), 2-1,
4-1
Feldspar, 2-6
Filtering, 3-1
Fixation, Definition, 1-1
Flammability, 1-3, 4-1
Flowability, 3-2, 5-2
Floccing, 3-1
Fly ash, 1-2, 2-2, 2-5, 2-6,
5-2, B-2
6-8, Free Liquid, 2-2, 2-5, 4-2, 4-5,
4-10
Freeze-thaw Test, 4-3, 4-9
Fumes, 5-2
Classification, 2-2
Grain-Size Distribution, 3-1, 3-3
Ground Brick, 2-10
Ground Water, 4-2
Gypsum, 2-6, B-2
Heavy Metal Wastes and Sludges,
2-11, 2-16, 2-23
Hematite, 2-6
Heulondite, 2-6
Hydrated Silica Gel, 2-12
Ignitability, 1-3, 4-2, 4-5, 4-6,
4-10
Illite, 2-6, 2-7
In-Drum Mixing Alternative, 6-3
In-Situ Mixing Alternative, 6-10
Interference, 2-11
Ion Exchange Resins, 2-1, 2-22
Kaolinite, 2-6, 2-7
Kiln Dust, 2-2, 2-5, 2-6, 6-13,
B-2
Laumonite, 2-6
Layering, See Area Mixing
Alternative
Leachability, 1-3, 4-3, 4-10
Lime, 1-2, B-2 .
INDEX-2
-------
Lime-Fly Ash Pozzolan, 2-3
Liquid Chemical Storage, B-4
Macroencapsulation, 1-1, 2-3, 2-17
Microencapsulation, 1-1, 2-1, 2-4
2-15, 2-19
Mixer, Change-Can, 6-5, B-19
Construction Equipment, B-15
Muller, B-20 V
Propeller, 6-5, 6-6, B-21
Ribbon, See Blender, Ribbon
Rotor, 6-20, B-15, B-20
Mobile Plant Mixing Alternative,
6-18, 6-19, 6-21
Modular Plant Mixing Alternative,
6-23, 6-24, 6-27
Monofill, 1-1
Monolith, 1-1, 2-1
Mullite, 2-6
National Contingency Plan, 1-4
Native soil, 2-2
Neutralization, 2-1, 2-20
OSHA Regulations, 6-9, 7-3, 7-4
Oil Sludge, 2-5, 2-9, 2-11, 2-13
Oil and Grease, 2-11, 3-4
Onsite Chemical Handling, A-3 -
Organic Polymers, 2-1, 2-2
Organic Vapor and Dust
Generation, 7-5
Oxidation/Reduction, 2-22
pH, 2-20, 2-22 -. :
Particle-Size Distribution, 4-7 ;
Passivation, 2-4
Percent Moisturej 3-1
Permeability, 4-7, 4-9, 4-10
Personnel Protection Program, 7-3
Phenol, 2-23
Pilot Studies, 5-2, 5-3 -.-.>.
Polyethylene, 2-2, 2-16, 2-18 *'
Portland Cement, 2-2, 2-3, 2-10,
2-12, 2-13, B-2
Polypropylene, 2-16
Pozzolan, 2-2, 2-10, 2-12, 2-13
Pozzolan-Portland cement, 2-2,
2-3, 2-12, 2-13, 3-4
Pretreatment Techniques, 2-20
Pumpability, 3-2, 5-2
Pumps, B-6
Quality Control, 5-1, 6-30, 7-1
Resource Conservation and
Recovery Act, 1-4, 4-1, 6-17
Radioactive Waste, 2-1
Reactivity, 1-3, 4-1, 4-5, 4-6,
4-10
Redox Potential, 2-9
Reprecipitation, 2-4
Safety Concerns, 5-1, 6-9, 6-17,
6-29, 6-34, 7-3
Sampling of Treated Wastes, -7-1
Screw-Extruder, 2-17 - '-'.'
Screw Feeder, B-27
INDEX-3
-------
Self-Cementation, 2-2, 2-10
Settling, 3-1
Shear Strength, 3-4
Silica, 2-3, 2-22
Site Monitoring, 8-1
Smectite, 2-6
Soil-cement, 4-9
Solidification, Definition, 1-1
Solubilities, Metal Hydroxides,
2-21
Soluble Silicates, 2-3
Sorption, 2-3, 2-5
Specifications, 4-19
Spill Control, 7-7
Stability, Physical, 4-7
Biological, 4-8
Stabilization, Definition, 1-1
Stilbite, 2-6
Storage, B-2, B-3
Superfund, 1-4
Surfactants, 2-14
Suspended Solids, 3-1, 3-2
Testing of Treated Wastes, 7-2
Thermoplastic Microencapsulation,
2-3, 2-15, 2-19
Toluene, 2-16
Trafficability, 3-3
Transportation Costs, 6-1
Unconfined and Coiupressive
Strength, 3-1, 3-4, 4-7
Vermiculite, 2-6, 2-7
Waste Blending, 2-23
Wax, 2-16
Wet-dry Test, 4-3, 4-9
Xylene, 2-16
Zeolites, 2-1, 2-3, 2-6, 2-7, 2-14
INDEX-4
{I U.S. GOVERNMENT PRINTING OFFICEi 1986-646-116/40669
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Environmental Protection
Agency
Center for Environmental Research
Information
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