PB88-185269
TECHNICAL GUIDANCE FOR CORRECTIVE
MEASURES: DETERMINING APPROPRIATE
TECHNOLOGY AND RESPONSE FOR AIR RELEASES
Alliance Technologies Corporation
Bedford/ MA
Mar 85
U.S. DEPARTMENT OF COMMERCE
National Technical Information Service
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GCA-TR-85-43-G
Prepared for
PB88-185269
U.S. ENVIRONMENTAL PROTECTION AGENCY
Office of Solid Waste
Land Disposal Branch
Washington, D.C. 20460
Contract No. 68-01-6871
Work Assignment No. 45
EPA Project Officer EPA Task Officer
Jon R. Perry Art Day
TECHNICAL GUIDANCE FOR
CORRECTIVE MEASURES-
DETERMINING APPROPRIATE
TECHNOLOGY AND RESPONSE
FOR AIR RELEASES
Draft Final Report
March 1985
Prepared by
Mark Arienti
Andrew Baldwin
Michael Kravett
CCA CORPORATION
GCA/TECHNOLOGY DIVISION
Bedford, Massachusetts 01730
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REPORT DOCUMENTATION
PAGE
1. REPORT NO.
EPA/530-SW-88-021
3. Recipient's Accession No.
- 185289ZAS
4. Title end Subtitle
Technical Guidance for Corrective Measures Determining
Appropriate Technology and Response for Air Releases
5. Report Oete
March 1985
7. Author(i)
Mark Arienti, etc.
8. Performing Organization Rept. No.
9. Performing Organisation Name and Address
GCA Corp.
GCA/Technology Division
Bedford, MA 01730
10. Project/Task/Work Unit No.
WA 45
11. Contract(C) or Grant(G) No.
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ABSTRACT
The reauthorization of the Resource Conservation and Recovery Act (RCRA)
requires that all treatment, storage, and disposal facilities (TSDFs) which
apply for a permit which release hazardous waste or constituents from any
solid waste management unit at the facility must remedy such release as a
condition for permit issuance. The purpose of the guidance document is to
assist EPA/State personnel in implementing the new corrective action
provisions by providing a central source of information on air emissions
control technologies and techniques for hazardous waste TSDFs. This document
provides RCRA permit writers with descriptions of waste management unit design
and operation practices which prevent or control vapor and particulate
releases from containerized waste storage, storage tanks, surface impoundments,
landfills, land treatment and waste piles. In addition, control technology
transfer from the industrial/commercial sector to the hazardous waste
management industry is discussed.
111
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CONTENTS
Figures. .« vi
Tables vii
1. Introduction 1-1
Background 1~1
Purpose of Document 1-2
Document Organization 1-3
Other Guidance Documents 1-3
2. Summary of Corrective Actions 2-1
Overview 2-1
Examples of Corrective Measures 2-1
Factors to Consider in Selecting Corrective
Measures. ....... 2-14
References 2-25
3. Control of Emissions from Containerized Waste 3-1
Introduction. ..... 3-1
Storage Modifications 3-5
Spillage Containment 3-11
Container Modification 3-22
Operating Practices 3-29
References 3-35
4. Control of Emissions from Storage Tanks 4-1
Introduction 4-1
Roofs 4-8
Covers 4-26
Insulation. 4-36
Vapor Control Systems 4-42
References 4-52
5. Control of Emissions from Surface Impoundments 5-1
Introduction 5-1
Covers. 5-2
Aerodynamic Modifications 5-13
Vapor Control Systems 5-18
Operating Practices 5-21
References 5-26
6. Landfills 6-1
Introduction 6-1
Soil Covers 6-2
Synthetic Covers 6-10
Foam Covers 6-15
Encapsulation/Solidification 6-17
IV
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CONTENTS (continued)
Gas Collection „ 6-20
Air-inflated Structures 6-24
References . 6-28
7. Control of Air Emissions from Land Treatment Facilities 7-1
Introduction 7-1
Changes in Operating Practices 7-1
Covers . 7-8
Air-inflated Structures 7-10
References 7-12
8. Control of Air Emissions from Waste Piles 8-1
Introduction 8-1
Stabilization 8-5
Windscreens 8-10
Covers 8-12
Gas Extraction 8-15
Changes in Operational Practices . 8-17
References 8-21
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FIGURES
Number Page
2-1 Flow chart for determining an appropriate corrective
action 2-2
3-1 Apparatus for encapsulating 208-liter (55-gal) drums
holding hazardous wastes 3-25
3-2 EPP overpack welding unit 3-26
3-3 Side view of the polyethylene fusion mold 3-27
4-1 Pan-type floating roof tank 4-12
4-2 Pontoon-type floating roof tank . . 4-12
4-3 Double-deck floating roof 4-15
4-4 Rim-mounted secondary seals on external floating roofs. . 4-17
4-5 Metallic Shoe Seal with shoe-mounted secondary seal . . . 4-19
4-6a. Interlocking configuration. . 4-29
4-6b. An uncovered cleaning tank emits large volumes of
corrosive acid steam. 4-29
4-c. A single layer of ALLPLAS balls floating on the surface
of the same temperature, virtually eliminates acid
emissions 4-29
4-7 Refrigerated vent condenser system 4-45
4-8 Activated-carbon adsorption system 4-47
4-9 Thermal oxidation unit 4-49
6-1 Two typical layered soil cover systems 6-6
6-2 Encapsulation process concept 6-19
6-3 Pipe and trench vents 6-22
vi
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TABLES
Number Pa§e
2-1 Primary Corrective Actions for Example Sources of Air
Emissions at TSDFs <• ° 2-3
2-2 Air Emission Control Technologies/TSDF—Matrix. . . . . . 2-11
2-3 Probable Corrective Actions as a Function of the Level of
Release 2-16
2-4 Cost and Reduction Efficiency of Air Emission Control
Technologies » 2-17
3-1 Advantages and Disadvantages of Containerized Waste
Emission Control Alternatives ...... 3-2
3-2 Rating of Efficiency of Current Response Techniques to
Control Evaporation . 3-16
3-3 Matrix of Foam Capabilities to Suppress or Otherwise
Minimize the Release of Toxic or Flammable Vapors from
Spilled Hazardous Chemicals as Listed 3-17
4-1 Advantages and Disadvantages of Storage Tank Emission
Control Alternatives 4-2
4-2 Cost of Building a Fixed-Roof Tank 4-22
4-3 Cost of Building an External Floating Roof Tank 4-23
4-4 Cost of Installing a Contact Single Seal Internal Floating
Roof 4-24
4-5 Cost of Installing a Noncontact Single Seal Internal
Floating Roof „ 4-25
4-6 Evaporation Reduction Achieved by Various Energy-
Reducing Methods 4-32
4-7 Number of Floating Spheres Required per unit Area and
Volume 4-34
vii
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TABLES (continued)
4-8 Costs of Various Types of Floating Spheres 4-35
4-9 Relative Effectiveness of Paints in Keeping Tanks from
Wanning in the Sun „ 4-38
4-10 Permeability and Moisture Absorption 4-40
4-11 Published Thermal Performance 4-41
5-1 Advantages and Disadvantages of Surface Impoundment
Control Alternatives 5-3
5-2 Synthetic Cover Characteristics . . 5-10
5-3 Evaporation Suppression by Shades ..... 5-17
6-1 Landfill Emission Technologies—Advantages and
Disadvantages 6-3
6-2 Unit Emissions Through 12-Inch Soil Covers for Soils of
Different Dry Porosity. 6-8
6-3 Chemical Resistance Chart (DuPont) 6-12
6-4 Permeation Rates for Organic Chemical Vapors Through
Synthetic Membranes 6-13
6-5 Estimated Unit Costs for Some Synthetic Membranes .... 6-14
6-6 Capital Costs for Air-inflated Structures 6-27
7-1 Land Treatment Emission Control Technologies—Advantages
and Disadvantages 7-2
7-2 Annual Emissions from a Theoretical 1 Acre Land
Treatment Area 7-6
8-1 Waste Pile Emission Control Technologies—Advantages and
Disadvantages 8-2
8-2 Cost and Relative Effectiveness of Some Chemical
Stabilization Agents 8-8
8-3 Approximate Storage Dome Costs 8-16
Vlll
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SECTION 1
INTRODUCTION
BACKGROUND
The 1984 amendments to the Resource Conservation and Recovery Act (RCRA)
provide the Agency with additional authorities for corrective action at
facilities seeking permits and for facilities with interim status under
Section 3005(e). The amendments for corrective action address:
• continuing releases at permitted facilities (Section 206);
• corrective action beyond facility boundaries (Section 207);
• financial responsibility for corrective action (Section 208); and
• interim status corrective action orders (Section 233).
The new authorization allows EPA to require corrective action in response to a
release of hazardous waste or constituents from any solid waste management
unit to the environment regardless of when the waste was managed. This
authority includes releases to all media, including air.
Currently, there are no regulatory requirements for monitoring ambient
air surrounding hazardous waste management facilities or emissions from such
facilities, or to submit such data with a permit application should the data
exist. Thus, the methods available for determining whether air releases are
occurring, or can potentially occur, from a hazardous waste management
facility are limited to the use of data submitted by the permit applicant.
The Office ot Air Quality Planning and Standards (OAQPS) has been given
the responsibility for developing regulations for area-source emissions from
hazardous waste treatment, storage, and disposal facilities (TSDFs). In this
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effort, OAQPS is currently evaluating the use of predictive models for
quantifying and assessing the health impact associated with TSDF air
releases. Due to the current state of development of these efforts and the
lack of a substantial base of field validation data, OAQPS has suggested that
guidance should be presented in such a way that it can be used as a "flagging
tool" for identifying those sites which are obvious contributors of air
releases. Once those sites are identified, some type of corrective action or
measure will be required to reduce the magnitude of, or eliminate the cause of
the air release. As such, the guidance provided in this document identifier
the corrective actions and technologies that may be utilized to control air
emissions at hazardous waste management facilities.
PURPOSE OF DOCUMENT
The purpose of the guidance presented in this document is to identify
corrective actions or specific technologies which will minimize or eliminate
the cause of atmospheric releases from hazardous waste TSDFs. Prior to
determining the appropriate methods that will minimize the atmospheric release
of hazardous waste constituents, the permit writer must first be aware of the
types of compounds and facility practices that can potentially lead to ambient
air releases. Supported by this background information (which is presented
in: "Technical Guidance for Corrective Measures - Identifying Air Releases")
the permit application can be reviewed to identify if these compounds and
practices of interest are in use at the waste management facility. If
identified, corrective measures can then be recommended or required to reduce
these air releases.
This document was developed for use as an index of technologies
applicable to controlling air emissions from TSDF operations. A large variety
of technologies have been described and their effectiveness regarding both
cost and reduction of emissions has been evaluated. Various technologies, or
combinations of technologies may be applicable to any specific situation. The
determination of the most appropriate technology and response will depend on
site-specific factors. Consequently, the information presented in this
document is general in nature, and the ultimate decision of the appropriate
corrective measure to recommend is left to the permit writer.
1-2
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DOCUMENT ORGANIZATION
Section 2 presents a summary of the corrective measures and technologies
for controlling air releases. Corrective measures for certain types of air
releases are listed, and technologies are categorized by the specific function
that they serve. In addition, a summary of data on cost effectiveness and
reduction efficiency is presented.
Sections 3 through 8 present, by facility type, information concerning
various methods for controlling air emissions at hazardous waste management
facilities. Control technologies for the three facility types which emit
primarily vapor phase releases (containers, storage tanks and surface
impoundments) are discussed in Sections 3, 4, and 5, while the facility types
which have the potential for emitting both vapor phase and particulate
emissions (landfills, land treatment, and waste piles) are discussed in
Sections 6, 7, and 8. For each of the control technologies which is
applicable to a facility type, information is presented to describe the
control technology, its particular application to the facility, the cost of the
control technology, and its effectiveness in reducing air emissions. Certain
control technologies may have multiple applications. In these cases, the
technology will be described in detail in the discussion of the first facility
type. Reference to the original discussions will be made for subsequent
applications.
OTHER GUIDANCE DOCUMENTS
Two additional technical guidance documents will be available for
determining the extent which corrective measures for air releases are
necessary. These documents published respectively in the spring and summer of
1985 are entitled:
Technical Guidance for Corrective Measures—Identifying Air
Releases; and
Technical Guidance for Corrective Measures—Assessing Emissions
Distribution and Impact.
1-3
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SECTION 2
SUMMARY OF CORRECTIVE ACTIONS
OVERVIEW
Facilities which propose unacceptable design and/or operating practices,
and those that fail to explicitly state these practices, are candidates for
corrective measures for reducing air releases. These measures are intended to
minimize or eliminate hazardous constituent emissions by correcting an
inadequate design or operating practice. The need for, and extensiveness of,
corrective measures must be determined on a site-specific basis.
Implementation of these measures must take into account the severity of the
problem, as well as the location of the nearest receptor. A flow chart
outlining the sequence to follow to determine the appropriate corrective
measure is presented in Figure 2-1. As is evident, it is first necessary to
answer several site specific questions before an effective response can be
selected.
EXAMPLES OF CORRECTIVE MEASURES
As shown in Table 2-1, several different corrective measures may be
applied to each type of air release. In addition, there may be several
specific technologies which can be used to carry out the corrective action.
Consequently, the recommendation of a corrective action to limit a particular
air release must be based upon the consideration of several alternatives.
After evaluating the advantages and disadvantages, the effectiveness, and the
cost of each technology, the optimal alternative can be selected.
Table 2-1 presents corrective actions for air emissions by the type of
facility at which the air release occurs. One of the most frequently
mentioned corrective actions is to cover open or exposed wastes. This type of
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None required
Determine the General
Characteristics of the
Required Corrective Action
Select a Specific Control
Technology and Response
Determine the need for
corrective actions from
PA/SI or Emission Assessment
Guidance
\t
Action Required
Consider the facility type:
(1) Container/drum storage
(2) Tank storage
(3) Surface impoundment
(4) Landfill
(5) Land treatment
(6) Waste pile
Consider the air emission
phase—particulate or vapor?
Is the emission related to:
(a) a design deficiency
(b) a poor operating practice.
If (a) is the design deficiency
related to:
A. Uncovered or uncontained waste
B. Unstabilized waste
C. Waste subject to wind
transport or evaporation
Di Vapors which are not collected
E. Collected vapors which are not
treated.
Determine the required control
efficiency or maximum acceptable
release rate.
X
Review Applicable Control
Methods in Sections 3-8
\
t
Compare cost of alternative
control methods (Table 2-4)
>
t
Compare reduction efficiency
of alternative methods
(Table 2-4)
A
t
Select appropriate air
emission control method
>
f
Recommend or implement
the corrective measure
\
t
Conduct testing to determine
the adequacy of the
corrective action
Figure 2-1. Flow chart for determining an appropriate corrective action.
2-2
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TABLE 2-1. PRIMARY CORRECTIVE ACTIONS FOR EXAMPLE SOURCES
OF AIR EMISSIONS AT TSDFs
Cause of emissions
Applicable corrective actions
DRUM STORAGE
Liquid leaking from containers
and volatilizing
Container storage without cover
or containment structure
Emissions due to environmental
factors such as wind, heat,
or sun
Splash loading
Spills
No vapor control during filling/
emptying or cleaning operations
STORAGE TANKS
Open top storage tank
Utilize spill drainage methods:
absorptive floor
- grid floor
- sloped floor
- collection trenches
Prevent serious leaks by implementing leak
detection and repair program.
Encapsulate container using:
- overpacks
- directly applied sprays
Cover container storage area with a
synthetic liner.
Contain storage area in a building or
air structure vented to a vapor control
system.
Use a lean-to-structure to shield
containers.
Use wind screens/barriers.
Utilize submerged or slow filling
instead of splash filling.
Improve drum handling methods:
- use drum grabbers
- decontaminate drums after emptying
Install collection and treatment system.
Cover tank with:
surfactant layer
- plastic spheres
- rafts
synthetic membrane
fixed roof
- floating roof (internal, external)
(continued)
2-3
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TABLE 2-1 (continued)
Cause of emissions
Applicable corrective actions
STORAGE TANKS (Cont'd)
Emissions due to insufficient
effectiveness of cover or
containment structure
Emissions due to environmental
factors such as sun or wind
Splash loading
No vapor control during filling/
emptying or cleaning operations
SURFACE IMPOUNDMENTS
Open top surface impoundment
Emissions due to environmental
factors such as sun and wind
Use alternate type of seal or add secondary
seal to floating roof.
Use conservation vent on fixed roof.
Use alternate synthetic liner material.
Use alternate tank design such as convert-
ing external floating roof to internal
floating roof.
Add vapor control system such as carbon
adsorption, condensation, or incineration
to fixed roof.
Add thermal insulation to tank walls or
cover.
Use reflective paint.
Employ wind barriers/screens.
Use submerged filling instead of splash
filling.
Install vapor collection and treatment
system.
Cover impoundment with:
synthetic membrane
floating spheres
rafts
- surfactant layer
air inflated structure vented to
vapor control system
Use screens/barriers around perimeter or
inside the impoundment.
Use shades.
(continued)
2-4
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TABLE 2-1 (continued)
Cause of emissions
Applicable corrective actions
SURFACE IMPOUNDMENTS (Cont'd)
Splash loading
Spills, overrun
Disposal by evaporation
LANDFILLS
Emission from operating face
of landfill
Emission through temporary
soil cover
Emission through permanent
cover
Employ submerged instead of surface
filling.
Increase the freeboard depth by:
- physically increasing height of
containment
- lowering waste level
Prohibit.
Place temporary wind screens around
working area.
Apply temporary cover material:
- synthetic liner
- foam
- soil
Enclose work area with air supported
structure and employ vapor control system.
Use wind screens in addition to soil cover.
Stabilize soil cover by:
- moisture control (watering)
- chemical additives
- physical additives
Decrease permeability of cover by:
using different cover material
vegetating soil cover
- moisture control (watering)
- adding chemical/physical stabilizers
(continued)
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TABLE 2-1 (continued)
Cause of emissions
Applicable corrective actions
LANDFILLS (Cont'd)
Emission through permanent
cover (cont'd)
Co-disposal of municipal
and hazardous waste
Emissions due to solidification
of liquids in situ
LAND TREATMENT
Pooling of liquids due to surface
application of wastes
Emissions caused by environmental
factors such as sun or wind
Open treatment area
Co-disposal of municipal and
hazardous waste
Spray Evaporation
WASTE PILES
Open waste piles
Add vapor collection and treatment system:
pipe vents with either forced or
unforced collection
trench vents (forced/unforced)
Prohibit.
Eliminate practice.
Enclose operating area and employ vapor
control system.
Use subsurface injections instead of
spraying or overland flow.
Decrease the application rate.
Dewater waste prior to application.
Cover waste with:
- soil and employ moisture control
synthetic covers
Use wind screens/barriers.
Enclose treatment area with air structure
and employ vapor control system.
Prohibit.
Prohibit.
Cover with flexible liner (tension
structure).
Enclose in rigid dome structure.
(continued)
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TABLE 2-1 (continued)
Cause of emissions
Applicable corrective actions
WASTE PILES (Cont'd)
Emissions due to environmental
factors such as wind or sun
Fugitive release due to
uncontrolled loading
Use wind screens.
Change pile orientation
Stabilize dust with:
- water application
- chemical additives
- vegetation
Reduce the slope of the pile.
Use alternate loading practices to lessen
particle generation:
- hinged boom conveyors
- telescopic shutes
- stone ladders
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nu-asuru is etEuctive by providing a barrier to tlie unrestricted volatilization
of hazardous waste constituents. The type and extent of the cover needed is
dependent on the waste characteristics and the type of facility at which the
cover will be used. Liquid wastes containing volatile organic compounds have
a high emission potential and require a more permanent and secure cover (e.g.,
floating roof) than a solid waste with few volatile components. For instance,
a waste pile may require only a portable synthetic cover to minimize both
vapor and particulate releases during its active life.
Changes in facility operating practices, namely those associated with the
emptying, filling, or cleaning of containers, and the loading or applying of
waste to landfills, wastepiles and land treatment facilities are another means
of providing corrective action. A common method of reducing emissions that
result from the filling of tanks, surface impoundments, or drums is to employ
submerged filling, as opposed to splash loading. Submerged filling minimizes
liquid surface turbulence, a factor which contributes to air releases.
Similarly, at land treatment facilities, use of subsurface injection in place
of spreading or pouring waste on the soil surface reduces the time and area of
waste contact with the atmosphere.
Treatment processes that are designed totally or in part, to provide for
the release of airborne contaminants as a way of reducing the solid or liquid
phases contaminant level should not be allowed. Practices such as disposal by
evaporation and co-disposal of hazardous and municipal wastes, in which
significant quantities of hazardous constituents may volatilize or evaporate
are two examples of such unacceptable practices. The purpose of these
practices is to promote evaporation and airborne release of the contaminants
and no change in the practice or add-on control equipment can change this
intent. Consequently, these practices should be prohibited.
Types of Corrective Actions
The two general types of corrective actions mentioned above and presented
in Table 2-1 are design or operational. Design measures are those that limit
the ambient emissions due to the intrinsic design of the waste management
hardware or the installation of air emission control devices. Operation
corrective actions minimize emissions by controlling the manner in which the
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waste is handled. Design practices can further be broken into groups based
upon the function that the specific design practice serves. These groups are:
• containment • gas collection
• insulation • vapor control
• stabilization
Containment—
The purpose of containment is to minimize the surface area of the waste
which is exposed to ambient air. This function is served by enclosing or
covering the facility or waste in some manner. The containment structure can
either be supported or be placed directly on top of the waste surface. For
example, a temporary cover may either be placed directly on the solid surface
of an active landfill or it may be supported above the waste. Supported and
unsupported structures are separated since supported containment generally
involves a much greater amount of construction or alteration than does
unsupported containment. For example, unsupported containment measures, such
as floating spheres and rafts, can simply be placed on a liquid surface of a
tank or impoundment, while a fixed roof or dome requires significant design
and construction to implement.
Insulation—
Methods of insulation serve to lessen the rate of air emissions by
specifically reducing the effects of wind and sun. Covers may also have this
effect, although they are primarily designed to enclose the waste and not
specifically to protect it from environmental factors. This type of
corrective action can generally be added on to the existing structure or
facility without changing the existing structure to a great degree.
Stabilization—
Stabilization is used to reduce particulate or volatile emissions from
the waste itself or to improve the performance of a cover material by making
the cover less permeable and/or more stable. Stabilization usually involves
the addition of a chemical, or other material, to the facility or its contents.
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Gas Collection—
The installation of gas collection systems at a TSDF may require that
extensive alterations be made if the system is added to an existing facility.
The effort required to retrofit an existing facility is dependent on the
facility type. For instance, the addition of a collection trench vent system
to a system will involve excavation, while the addition of a conservation vent
to a fixed roof will not require as extensive an effort. In any case, these
types of controls are more easily applied if incorporated into the original
design of the facility.
Vapor Control—
Vapor control or treatment is generally used in conjunction with some
type of containment structure and gas collection system. The cover serves to
channel the air pollutants to the collection device which then vents the
pollutant to a vapor control unit. The vapor control unit then serves either
to destroy the pollutant, as in fume incineration, or to merely remove it from
the gas phase as in adsorption or condensation. Vapor control systems act not
to prevent volatilization from occurring, but to treat the emissions once they
have occurred.
In Table 2-2, each of the types of air emission control methods discussed
above is listed, with the type of facility to which the control can be
applied. Certain technologies, such as the vapor control methods, apply to
all of the facility types, while others, such as subsurface injection, only
apply to one of the facility types. Only those controls which have a high
probability of application to the specific facility type are checked; those
controls which only have a very low potential of being applied have not been
checked.
In addition to the corrective actions listed in Table 2-2, there exist
several general classes of corrective actions which may be applicable on a
site specific basis. These measures include pretreatment of the waste,
consideration of alternate disposal options, and post-treatment.
Waste pretreatment refers to actions that reduce the air release
potential of the waste by removing the hazardous constituent of concern.
Examples of pretreatment include, but are not limited to:
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TABLE 2-2. AIR EMISSION CONTROL TECHNOLOGIES/TSDF—MATRIX
Surface Land
Drum storage Tank storage impoundment Landfills treatment Waste piles
CONTAINMENT
Supported
Air inflated structure X
Building X
Dome
Fixed roof
Floating roof
Unsupported
Clay/soil cover
Immiscible film
Inert gas blanket
Floating spheres
Floating rafts
Synthetic membrane
Foam
Drum encapsulation X
OPERATING PRACTICES
Subsurface injection
Submerged filling
Spill/leak control X
X
X
X
X
X
X
X
X
X
X
X
X X X X
X X
X
XXX
X
X
X
XXX
XXX
X
X
x x x x
(continued)
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TABLE 2-2 (continued)
I—»
NJ
Surface Land
Drum storage Tank storage impoundment Landfills treatment Waste piles
Increase freeboard depth
Less frequent filling/
emptying
Decrease application rate
Controlled loading
Moisture control
STABILIZATION
Wet dust suppression
Vegetation
Encapsulation
Chemical dust stabilization
INSULATION
Wind screens/Barriers
Shades
Thermal insulation
Painting
GAS COLLECTION
Pipe vents
Trench vents
Gas extraction
Conservation vents
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
(continued)
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TABLE 2-2 (continued)
VAPOR CONTROL
Adsorption
Fume incineration
Condensation
SPILL CONTROL
Foam
Water dilution
Adsorbents
Coolants
Drum storage
X
X
X
X
X
X
X
Tank storage
X
X
X
X
X
X
X
Surface
impoundment
X
X
X
X
X
X
X
Landfills
X
X
X
X
X
X
X
Land
treatment
X
X
X
X
X
X
X
Waste piles
X
X
X
X
X
X
X
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• Distillation • Wet oxidation
• Steam or air stripping • Chemical oxidation
• Adsorption • Biological oxidation
• Ozonation • Physical separation
These technologies are standard waste treatment technologies, which when
applied to a waste will reduce the hazardous constituents of concern.
The use of an alternate disposal option can be an appropriate corrective
action if the air release potential of the waste cannot be minimized using the
more conventional (and less expensive) techniques previously described. For
example, elimination of a waste containing volatile organic constituents by
incineration may be the most effective manner to reduce the emission potential
of the waste.
Post-treatment measures refer to those actions that are taken to insure
that the constituents emitted from the waste (gaseous or particulate) are
captured and effectively disposed so as not to result in an emission from the
facility. For instance, with regard to vapor collection systems on storage
tanks, captured organic vapors are condensed and returned to product storage
or disposed of in a manner that precludes their emission. Similarly, fugitive
particulate, once captured, must be handled and disposed so as to minimize the
potential for reentrainment.
Because pretreatment, alternate disposal, and post-treatment methods
involve action to the waste which would be conducted either previous or
subsequent to their management at the TSDF in question, they will not be
further addressed in this document. The permit writer need only be concerned
with recommending practices which could be implemented on site.
FACTORS TO CONSIDER IN SELECTING CORRECTIVE MEASURES
A major factor to consider when recommending a particular corrective
action is the severity of the emission. Some releases may require major or
emergency steps to be taken, while others will only require simple or minor
steps to be taken. Other factors to consider include the effectiveness of
2-14
-------
that ;iction in controlling ;i i r omissions, and the cost that is associated with
iinplonuMit ing the action. Tlics*? two tractors together can be combined to
evaluate the overall cost etfeetiveness of the corrective action. Each of
these factors is discussed below.
Severity of the Air Release—
The severity of an air release is based on the potential for endangering
human health and the environment. If it is determined that an unacceptable
risk is posed by some activity, then an immediate and possibly major
corrective action will be required. Conversely, if there is only a low
potential for toxic air emissions due to some poor design or operating
practice, the corrective action required may be less extensive in nature. As
seen in Table 2-3, the difference in the actions required for an emission of
minor or significant levels of concern is primarily based upon the level of
the air release. The difference between the actions required for an air
release of significant and major levels of concern, however, may necessitate
an entirely different sort of action, generally much more severe.
Cost —
The capital cost associated with each corrective action or technology
will depend on several factors. The major costs are those associated with
materials and equipment themselves, and those associated with the construction
or installation of the materials and equipment. The cost of some technologies
will be almost solely a function of the cost of materials, while the cost of
others will be predominantly installation costs. An example of the former is
the placement of floating spheres or rafts on the surface of an impoundment or
tank. An example of the latter is the covering of a surface impoundment or
other facility with an air supported structure. For example, if a surface
2
impoundment of 60,000 ft is to be covered by rafts, the cost will be
approximately $6,000. (Refer to Table 2-4). Conversely, the cost of
installing an air supported structure for this size impoundment will be
approximately $400,000. This difference in cost is primarily a result of the
difference in installation cost.
Other factors, however, must be considered in addition to the capital
cost of the corrective action. There are advantages and disadvantages of the
2-15
-------
TABLE 2-3. PROBABLE CORRECTIVE ACTIONS AS A FUNCTION OF THE LEVEL OF RELEASE
Minor
Level of release
Significant
Major
Cause:
Corrective Action: -
I
»—<
CTv
Toxic volatile or participate
wastes managed with poor
design and operating
conditions
Dust suppression
Cover drains and sumps
Install spill collection
system
Cover waste piles with liner
(small piles)
Cover landfill (small)
Submerged filling instead of
splash filling
Monitor
Fixed roof and vapor control
on open top tank (small
units).
Toxic volatiles and/or particulates
present in populated areas with no
controls
Highly toxic wastes managed
Dust suppression, capture and
collection
Vapor collection and disposal
Cover waste piles with liner (large
piles)
Fixed roof and vapor control on open
top tanks (large units)
Enclose drum storage area with vapor
collection and disposal
Cover landfill (large)
Unacceptable risk determined
due to activity; toxic vola-
tiles present and emitted
either by evaporation or
mobilization by CH^ or
C02
Prohibit disposal by evapor-
ation
Prohibit co-disposal of
hazardous wastes with
municipal wastes
-------
TABLE 2-4. COST AND REDUCTION EFFICIENCY OF AIR EMISSION CONTROL TECHNOLOGIES
Cost
Technology
Efficiency
(*)
Comments
Supported Containment
Air-inflated itructure
Building
Dome
External floating roof
tank
Contact internal floating
roof with primary seal
A00,000
+100,000
(t6-9/ft2 of floor space)
67,150
49,000-54,000
53,000-280,000
7,450-55,000
A. D. Little, 1984; total installed
cost of system over 425 x 150 ft lagoon.
High (>90Z) Including carbon adsorption vents.
A. D. Little, 1984; total installed unit
costs; does not include treatment system
costs.
80-99 SCS, 1983; for drum storage
(with treatment) with capacity of 33,120 ftj.
5-100 (parti
85-95 (vapor)
62-99b
95-100 (particulate) Vogel et al., 1983; installed cost for
waste pile storage dome with diameter of
61 ft, capacity 1150 tons.
88-99c
EPA, 1980; cost of whole tank 30-100 ft
diameter.
EPA, 1980; cost of roof, 15-90 ft diameter,
plus seal.
+ secondary seal
Noncontact internal
floating roof with
primary seal
Fixed roof
Unsupported Containment
Soil covers
15.68/ft circumference
6,000-40,000
34,000-354,000
109,000
11. 20-17. 20/yd3
40d EPA, 1980.
88-99c EPA, 1980; coat of roof and seal 15-90
diameter.
60 EPA 1980* cost of WLDBT sea 1
90b EPA, 1980; cost of whole tank 20-90 ft
diameter.
Vogel et al., 1983; 25 ft diameter
50,000 gallon tank.
50-100 EPA, 1982; costs range depending on
ft
whether clay or topsoil is used; includes
3ft £ /.-J 9
— /o/ yO*
hauling, spreading, compaction.
90 EPA, 1982; installed coat of various
materials from 20 mil PVC to Teflon-coated
fiberglass.
(continued)
-------
TABLE 2-4 (continued)
Technology
Unsupported Containment (Cont
Tension structure
Foam cover
Immiscible film
Floating spheres
Floating rafts
Inert gas blanket
M
1
. Drum encapsulation
Operating Practices
Subsurface injection
Controlled loading
Leak detection and repair
Drum handling equipment
Submerged filling
Cost
(*)"
'd)
4.30-6.50/ft2 of
surface area
0.11/ft2
4,350
0.03 cents/ ft2
4.65-8.69/ft2
0.05-0.13/ft2
0.11-0.33/gallon
capacity
65-90/drum
26-40/drum
100,000-160,000
5,500-8,700
10,500
30,000
200-3, 000/unit
300-600/unit
HA
Efficiency
U)
95-100 (particulate)
N/A
25-75
80-90
80-90
50-99
99
30-90
75
80
MA
HA
HA
Comments
Vogel et si., 1983; synthetic membrane
with auger feed system.
Vogel et al., 1983; cost of 2-inch layer
of urea-methane foam.
One-man application system.
Vogel et al., 1983; cost of hexadecanol
monolayer.
A. D. Little, 1984; costs depend on
sphere site.
A. D. Little, 1984.
Vogel et al., 1983; annual cost of
nitrogen blanket system; efficiency when
used with insulation and conservation
vent.
EPA, 1981; fiberglass-lined and welded
systems.
Directly applied system.
Vogel et al., 1983; subsurface injection
vehicle.
Tool bar filled to existing surface
application vehicle.
Bonn et al., 1978; telescopic chute uaed
for steel industry waste piles.
Stone ladder.
Cost of monitors, both portable and fixed.
Cost of drum grabbers.
Depends on construction requirements.
(continued)
-------
TABLE 2-4 (conntinued)
Cost
Technology ($)a
Operating Practices (Cont'd)
Decreased application rate NA
Increase free board depth NA
Change waste pile 0
orientation
Efficiency
(Z)
NA
11-80
NA
Low cost,
required
Comments
but increased area will
for same waste production
Costs are low depending on whether
surface is lowered or berm height
increased.
be
liquid
is
Vogel et al., 1983.
Improved cover practices
Stabilization
Wet dust suppression
Vegetation
Encapsulation/
solidification
Chemical dust
stabilization
Insulation
Wind barriers
Wind screen
Shades
MA
NA
90,000
1,550/acre
100-850 i/ton of waste
80-1,350/acre
0.04-0.23/ft2
14/lineal foot
0.07-0.18/ft2
90
A. D. Little, 198A; moisture control of
landfill covers.
50 (particulate) Efficiency based on Rosbury, 1985.
75 (particulate) Bohn et al., 1978; water spray system
used at steel industry waste piles.
NA
NA
R. S. Means, 1984; hydroseeding.
EPA, 1982; low cost for lime, high for
organic polymer.
80/100 (particulate) Drehmel et al., 1982; cost depends on
specific chemical used.
11-80 A. D. Little, 1984; cost for styrofoam
barriers 1-4 inches high in varying grid
patterns; based on surface impoundment
area.
0-30 (particulate) Vogel et al., 1983; cost based on 6 ft
high fence.
26-44
A. D. Little, 1984; black woven poly-
ethylene shade cloth.
(continued)
-------
TABLE 2-4 (continued)
Technology
Cost
<*)"
Efficiency
(Z)
Comments
Insulation (Cont'd)
I
NJ
o
Therul insulation
Reflective paint
Gas Collection
Pipe vents
Trench vents
0.05-0.76/in.-ft2
500-3, 000/tank
1,450/unit
330,000
50-99*
25
70-90
70-90
Gas extraction
Conservation vents
Vapor Control
Carbon adsorption
Fume incinerator
Condensation
17,000-40,000
0.01-0.09/per gallon
capacity
1,100-1,6007 tank
670-920/unit
7,500-11,000/tank
11,000-16,000/tank
70-90
50-90
85-97
85-99
85-95
Vogel et al., 1983; polyurethane coating;
efficiency when used with conservation
vent.
Petroleum storage facility estimate.
EPA, 1982; cost of 4-inch pipe vent, 30 ft
deep with forced ventilation.
EPA, 1982; total cost of 20 ft from vent,
4 ft wide, 1,500 ft long with a hypalon
liner; excavation is 80 percent of total
cost.
SCS, 1983; cost range for 2,000-100,000
ft^ waste pile and includes carbon
adsorption system.
Vogel et al., 1983.
Vogel et al., 1983; unit coat for large
system.
Calgon Corporation; cost for "barrel"
systjm.
Vogel et al., 1983; cost for 50,000 gallon
tank.
Vogel et al., 1983; cost for 50,000 gallon
tank.
(continued)
-------
TABLE 2-4 (continued)
Costs are all updated to March 1985.
As added to open tank (A. D. Little, 1984).
CAe added to open tank (EPA, 1980).
Increase in efficiency due to addition of secondary seal.
When used in conjunction with a conservation vent (Mitre, 1983).
References:
Arthur D. Little, Inc., EPA-450/3-8/017. November 1984.
Bohn, R.. et •!., EPA-600/2-78-050. March 1978.
Calgon Carbon Corporation, Sales Literature, March 1985.
Drehmel, D., et al. Relative Effectiveness of Chemical Additives and Windscreens for Fugitive Dust Control.
February 1982.
R. S. Means, Inc. Building Construction Cost Data. 1983.
SCS Engineers. Interim Report on Air Emissions. September 1983.
USEPA. EPA-450/3-80-034a. December 1980.
USEPA. EPA-600/2-81-138. July 1981.
USEPA. EPA-625/6-82-006. June 1982.
Vogel, G. A. and D. F. O'Sullivan. Air Emission Control Practices at Hazardous Waste Management
Facilities. June 1983.
-------
specific techno Logies which may negate any cost advantage? of ono technology
over the other. One of the major factors, of course, is the amount of air
emission reduction which can be achieved. Air emission reduction using
floating rafts has been estimated to be from 80 to 90 percent while the
reduction associated with using an air inflated structure can be greater than
90 percent. In some cases, the added reduction efficiency may justify the
added cost.
The cost data which is presented in Table 2-4 is based both on literature
and on current quotes provided by vendors. Literature cost estimates have
been updated to March 1985 using the Engineering News Record construction cost
index. Comments are used to explain exactly what the listed cost includes or
what it is based on. In addition, to obtain more detailed costs, one should
refer to the section in which the particular technology is discussed. These
cost data are intended to be approximate in nature, and actual costs will
depend on site specific factors. The costs indicated should provide the
permit writer a basis for a rough comparison of the cost of implementing
alternative corrective actions.
Effectiveness—
The percent reduction or control efficiency percentage attributed to a
certain technology is defined by the following relationship:
,...-.. uncontrolled emissions - controlled emissions n nn
Control efficiency = rr~J : : x 100
uncontrolled emissions
The controlled and uncontrolled emissions are usually expressed as a rate
and not as the total mass emissions. Reduction efficiencies for a variety
of control technologies are presented in Table 2-4. The purpose of a
corrective action can in some cases be to control volatile emissions, while in
other cases the action is implemented to control particulate emissions. It
should be noted that the technology efficiencies provided in Table 2-4 are for
vapor phase releases. However, certain technologies may be applicable for
both vapor and particulate control. In these cases, technology efficiencies
have been provided for both phases. In general, if a technique can mitigate
2-22
-------
vapor releases, it should be capable of controlling partLculate releases at
least as effectively.
The total control efficiency of corrective actions can be the result of
implementing several control schemes in series. For example, the control
efficiency of a gas collection system at a landfill will be a function of the
combined efficiencies of a trench vent, a cover material, and possibly a vapor
treatment system. If the collection system does not include an effective
cover material and lateral barriers, the vapors will not be collected in the
vent, and the control efficiency of the system will be correspondingly
decreased.
Another example of this involves the addition of a secondary seal to a
contact internal floating roof with a primary seal. In Table 2-4, the listed
efficiency of this action is 40 percent. This increase in control is over and
above the 88 to 99 percent efficiency attributed to the internal floating roof
with just a primary seal. In other words, if the primary control has an
emissions reduction efficiency of 88 percent, the installation of an add-on
secondary control with a 40 percent control efficiency will provide a combined
efficiency for the total system of 93 percent (0.88 + (0.12 x 0.40)).
Consequently, when evaluating the effectiveness of a corrective action, the
combined effects of several technologies may need to be considered.
Very few of the control efficiency estimates listed in Table 2-4 are
based on measurements carried out at actual TSDFs. Consequently, the level of
certainty of these estimates as applied to TSDFs is unknown. However, they
can be used as general indicators of reduction efficiency. Field testing of
the corrective actions will verify the correctness of these estimates. For
9
example, one recent study investigated the effectiveness of wind screens in
reducing particulate emissions from waste piles. The findings indicated that,
contrary to previous hypotheses, a reduction in wind speed does not
necessarily result in a commensurate reduction in particulate loss from the
pile. Consequently, reduction efficiencies which had been based on wind speed
have been lowered to the values presented in Table 2-4.
In general, reduction efficiencies attributable to supported containment
structures and vapor control systems are very high (>90 percent), while those
attributable to various other design and operational practices are variable
2-23
-------
and range from zero up to 99 percent. As mentioned previously, however, many
corrective actions which may not reduce emissions by more than 90 percent, may
still be worth implementing due to their low cost. These include operational
practices such as submerged filling, moisture control for landfill covers, and
unsupported containment designs such as placing floating spheres, rafts or
immiscible films on open surface impoundments and tanks.
2-24
-------
REFERENCES FOR SECTION 2
1. Vogel, G. A., and D. F. O'Sullivan. Air Emission Control Practices at
Hazardous Waste Management Facilities. MTR-83W89. Prepared for U.S.
Environmental Protection Agency, Office of Solid Waste. Contract
No. 68-01-6092. The MITRE Corporation. McLean, VA. June 1983.
2. Rosbury, K. D., and J. C. James. Control of Fugitive Dust Emissions at
Hazardous Waste Cleanup Sites. Draft Report sent to M. Arienti, GCA
Corporation. March 1985.
2-25
-------
SECTION 3
CONTROL OF EMISSIONS FROM CONTAINERIZED WASTE
INTRODUCTION
Hazardous waste material placed into containers can include both liquids
and solids. The material is put into containers either at the generator site
or at the TSDF. Containers used for this purpose may be either closed or
open-top, and loading may be done by either splash or submerged filling
techniques.
For the purpose of discussion, this section will focus upon waste
material held in steel 55-gallon drums. Releases from containerized wastes
occur primarily as a result of leakage or accidental spillage. Control
options available to facilities which handle, store, or dispose of
containerized wastes may be classified as follows:
• storage modifications;
• spillage containment;
• container modifications; and
• operating practices.
Table 3-1 provides an overview of the advantages and disadvatanges of
control alternatives described in this section. This section will develop and
describe technology options provided in Table 3-1 under each of these
classifications. Example systems will be cited, and relative effectiveness
(emission reduction- and cost-) will be presented for each.
3-1
-------
TABLE 3-1. ADVANTAGES AND DISADVANTAGES OF CONTAINERIZED WASTE EMISSION CONTROL ALTERNATIVES
Advantages
Disadvantages
Storage Modifications
• Can achieve high emission reduction efficiency.
• Insulates containers from external forces which
exacerbate emissions.
• Will not affect containers or waste materials.
• Various designs available, thus can be
applicable to any facility.
• Will not affect the operation of the facility.
• Better suited (than other options) for larger
facilities.
Spillage Containment
• Reduces emissions, and possibility of reemission
by isolating spilled substances from the
environment.
• Provides rapid mitigation of spill emissions.
• Well-suited to random spill incidents.
• Applicable to spills occurring both on land and
water.
• High implementation costs involved.
• Implementation is constrained by requirements
of location, layout, and manpower.
• Does not increase response time to spill or
leak.
• Maintenance costs will rise.
• May require handling of contaminated
materials.
• Emissions reductions achievable are not high.
• Facilities which handle many different types
of waste substances may need to implement
many different procedures, thus increasing
expense.
• Requires additional handling of hazardous or
volatile materials.
(continued)
-------
TABLE 3-1 (continued)
Advantages
Disadvantages
u>
I
U!
Spillage Containment (Cont'd)
• Technologies are readily transportable, thus are
applicable to any size facility.
• Manpower required, in general, are low.
• Materials needed, in general, are inexpen-
sive and can be obtained easily by a
facility.
• Application methods are relatively simple and
implementation of such procedures will be easy.
• Costs, overall, are expected to be low for such
procedures.
Container Modification
• Highly effective in reducing emissions from
containers—most effective of all technologies
described in this section—due to mitigation of
both spills and container breathing losses.
• Increases safety of container handling procedures.
• Permanent system—prevents further incidents.
• Applicable to prevention of both chemical and
mechanical stresses from both within the
container and externally.
• Requires disposition of contaminated
materials.
• Possible side effects (e.g., seepage of
chemicals into ground) may limit
applicability.
• A certain percentage of spills may not be
manageable at all due to volume or
location.
• Costs are subject to variations in materials
costs.
• Requires additional equipment, manpower, and
materials.
• Total costs to implement systems may be high.
• Costs may be particularly high for facilities
which would need to encapsulate a great many
drums.
• May require handling procedures to be altered.
• Drums would not be reusable.
(continued)
-------
TABLE 3-1 (continued)
Advantages
Disadvantages
Container Modification (Cont'd)
• Insulates container from thermal fluctuations
as well as mechanical shocks.
• Technology allows for transport to various points
around facility.
• Applicable to range of container sizes.
• Materials required are relatively easily obtainable.
Operating Practices
• Reduces leaks and spills, the major contributor
to containerized waste emissions.
• Does not change or affect containers or waste.
• Increases safety at facility.
• Applicable to any drum handling, disposal, or
storage facility.
• Very easy to implement procedures at an existing
facility.
• Accomplish emissions control quickly—either by
preventing emission from occurring or by rapid
response to spill or leak.
• Emission reductions achievable are low.
• May affect overall operation of facility
(input/output considerations, for example).
• May be less effective as number of drums
increase at a facility.
• May not be well suited to highly volatile
or toxic substances.
• Requires additional manpower and/or
equipment.
• Implementation may be limited by accessibility
of containe-s.
• Generally are low in total costs.
-------
STOKAGli MOD LFLCAT IONS
Introduction
Drum storage areas range in sophistication from simple, outside,
uncovered areas with no leakage or spillage containment, to fully enclosed
buildings which are evacuated and serviced by a vapor control system (e.g.,
carbon adsorption). Modifications to storage areas are classified as any
physical change in the area. This subsection will focus on three modification
options, which are as follows:
• Troughing/spill drainage;
• Wind deflection; and
• Building containment
All three of these options are used extensively at both TSDFs and industrial
processing plants.
Description
Because emissions from containers occur largely as a result of volatile
waste materials spilling or leaking from containers, all modifications are
intended either to reduce environmental factors such as wind and solar
irradiation, or more effectively manage spilled or leaked material so that
emissions can be limited. Emissions which occur due to container "breathing"
are expected to be mitigated by storage modifications, as well. In selecting
the modification option which is most applicable to a specific TSDF, the
following considerations must be made:
• Location of storage area. Whether the containers are stored outside
or inside, or where the storage area is in relation to other parts
of the TSDF.
• Available area. The storage area may be constrained in terms of
height, layout, and other space restrictions.
3-5
-------
Storage procedures. By virtue of which waste materials are being
stored, or how a facility is equipped to handle their waste
containers, the procedures by which the facility places containers
into and removes containers from storage.
Type of containers being stored. Whether containers are open-top or
enclosed.
Number of containers being stored. The number of containers to be
stored, and the frequency with which they are brought in and taken
out of storage.
The three modification options which are most applicable to TSDFs based upon
the above criteria, and which, therefore, are the most commonly employed
designs found in industry, are described below.
Troughing/Spill Drainage—
Troughs, grid floors, and other similar modifications serve to contain
emissions by channeling spilled (or leaked) materials away from the
containers, so that spills can be cleaned up more efficiently and
effectively. Most storage facilities should employ a drainage system of some
kind. Implementation of these systems is applicable to both outside and
inside storage areas. Examples of this type of modification include:
• perimeter trench or trench network;
• sloped floor;
• absorptive floor; and
• grid (screen) floor.
These systems may not be applicable to facilities which employ certain
storage procedures.
Trench System—A system of trenches can range in sophistication from a
simple moat around the perimeter, to a series of interconnected channels
within the storage area. The primary design features to be considered in
selecting the most appropriate trench system are trench depth and trench
3-6
-------
system layout. The trenches may, in addition, be Lined with a synthetic
membrane, or filled with absorptive material.
Sloped Floor—A sloped floor can be formed either by reconstructing an
existing floor, or installing a new floor. The primary design features to be
considered for this type of system are slope, permeability, and weight
handling requirement.
A sloped floor could also be coated in some way, e.g., a polyurethane
sealing compound, or could incorporate a trench system. The most common types
of sloped floor are those constructed of concrete. Concrete floors are
especially suitable for outside storage areas.
Absorptive Floor—An absorptive floor is a simple system in which an
absorbent material covers either the entire floor area or just under where the
containers will be placed. By placing drums directly on top of the absorbent,
leaks can be handled immediately, and clean-up procedures may be simplified
greatly. The primary design features to be considered in establishing such a
system are the type of absorbent material selected (must be chemically
compatible with waste materials), the depth of the absorbent layer, absorbent
layer layout (related to traffic patterns), contaminated absorbent handling
procedures, and layer regeneration. Such systems may also incorporate
synthetic membranes or other leachate handling systems.
Grid Floor—A grid, or screen floor is a simple system in which drums are
placed on a screen which is raised above the actual floor level. This type of
system allows spilled material to drop to the floor, thus separating the spill
from the drums. The primary design features to be considered in this type of
system are screen type (grid size, weight handling capacity, and screen
material), screen floor layout, distance between screen and floor, and waste
handling procedure. Screen floor systems might be expected to employ a layer
of absorbent material placed directly under the screen. The screens
themselves may be coated, to prolong their usable life.
3-7
-------
Wind Deflection—
Various systems designed to deflect the flow of wind away from
waste-containing drums are used. These controls are applicable only to
outside drum storage. Considerations involved in selecting the appropriate
system are:
• Type of barrier. Options include (and are not limited to) cyclone
fences, picket fences, corrugated steel walls, or cinder block walls.
• Height of barrier. The higher the barrier is, the more wind is
reduced. Higher barriers, however, must also be stronger
structurally.
• Materials of construction. Materials must be chosen with an
emphasis on low costs. The effect of chemical degradation must also
be considered.
• Storage area arrangement. By compartmentalizing, the effectiveness
of a barrier is increased. Compartmentalizing, however,
necessitates the use of more fencing, and makes the logistics of the
storage area more complex.
Examples of wind deflection systems include:
• simple perimeter system, and
• "compartmentalized" system.
Perimeter Wall—Perimeter walls are the most common type of wind
•a
deflector system. The primary design features to be considered in
establishing a perimeter wall system are the height of the wall and the type
of wall selected. The wall may be designed to vary in height according to
expected wind patterns.
Compartmentalized System—A compartmentalized system serves to bring the
nearest wall closer to each drum, thus increasing the effectiveness of the
wall. A wide variety of designs are available, ranging in sophistication from
randomly spaced sections to a "honeycomb" complex. The primary design
features to be considered in these systems are wall height and type, system
layout, and area access and egress. Such a system would allow a facility to
3-8
-------
segregate wastes, access tli<: area from different points, and install covers on
certain parts of the areas while leaving others uncovered.
Building Containment—
An enclosed structure will serve to contain emissions by providing a more
controlled environment for the drums and the waste material they contain. The
effects of wind, solar irradiation, and precipitation can be reduced
significantly if not eliminated completely. A building containment can be
more effective in reducing emissions than any other modification to an outside
storage area. A building containment can be equipped with various
appurtenances such as vapor control systems, or can be built with multiple
levels to provide more storage per area. Examples of building containment
designs which might be selected are:
• lean-tos; and
• free standing structures.
Building containments may be limited in applicability by various location or
area considerations.
Lean-tos—A lean-to is a simple structure, commonly built onto the side
of an existing structure. While in general a lean-to is constructed using
simple materials, these systems can range in sophistication from a simple roof
shade to a fully enclosed and insulated structure. The primary design
features to consider in selecting the most appropriate lean-to are storage
space needs, storage procedures, and construction materials.
Free-standing structures—A facility may choose any number of designs for
a free-standing structure. Among the many design features to be considered
are: available area, building layout (including decision to make multiple
levels), appurtenances (insulation, vapor control, etc.), and storage
procedures.
The relative ease or difficulty of implementing modifications to storage
facilities is dependent upon the unique constraints of each particular system
3-9
-------
and application. In general, installation of troughs or wind deflectors can
be accomplished with less cost and effort than construction of buildings.
This is due to the space and materials requirements involved, and also due to
the difficulties associated with construction at hazardous waste facilities.
Emission Reduction Effectiveness
Modification of the drum storage area is expected to yield moderately
high emission reductions. The availability of information on the efficiency,
however, is limited. No studies of such controls have been published in the
literature. Of the three modification categories described in this section,
building containment is expected to effect the highest reductions. A study of
air emissions done by SCS Engineers estimated that building containment can
achieve from 80 to 99 percent emission reduction. The effectiveness of a
wind barrier is directly proportional to its height (the effectiveness at any
point is dependent on the ratio of barrier height to the distance from the
base of the barrier to that point). One study estimated that windscreens at
waste piles can reduce wind erosion by an average of 80 percent.^
Co s t s
Modifications to the storage area are expected to vary in cost, depending
upon the design features selected. Costs are based upon construction labor
and materials, and operating materials requirements. There is no energy or
operating labor cost involved, and maintenance costs are assumed to be
relatively insignificant. Detailed information on the control systems
described in this section is not available. In general, troughing/spill
drainage modifications are expected to cost less than wind barriers, which in
turn are expected to cost less than building containments.
The costs of a spill drainage system was estimated by SCS in 1983 for a
system involving a concrete floor with curbs and gutters (a 1200 square foot
area of 6 in. thick sloped concrete pad with perimeter curbs and gutters).^
This system is estimated to cost $5,200 in current dollars (March 1985).
3-10
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The same study by SCS estimated that a fencing system consisting of a
6-foot high, 6 gauge galvanized industrial chain link fence with 2-inch line
posts and 10-foot 1-5/8 inch top soils and three strand barbed wire; two 15-ft
wide gates; and four 3-ft wide gates would cost $16,600 (in March 1985
dollars) for an area of 9000 ft2 (capable of holding 100 drums).
A building containment system was estimated by SCS for a structure of
33,120 cubic feet.^ In present value, the cost is estimated to be $68,000
for the building alone.
SPILLAGE CONTAINMENT
Introduction
Because the air release of hazardous constituents from containerized
wastes is largely attributable to leaks and spills of volatile hazardous
materials, those techniques established for containing, collecting, and
removing spilled material represent a significant area for emission control.
Spills of waste from containers generally occur during drum handling (moving)
operations, and to a lesser extent during drum loading operations. Leakage
from containers occurs primarily during storage and disposal. At present, the
various spill control techniques in use are limited in their applica-
>i
6
bility. The methods of controlling the vapor release of spills can be
generalized as belonging to one of the following categories:
• control by mechanical means;
• control by chemical means; and
• control by use of physical properties of the spilled substance,
Description
All spill control procedures incorporate the following elements:
• isolation of spilled substance;
• coverage of spilled substance;
3-11
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• absorption of spilled substance; and
• removal of spilled substance and contaminated materials.
The methods by which substances are absorbed and removed are standard
throughout the industry. This subsection will focus on procedures to isolate
and cover substances. In selecting a spill containment option, the following
considerations must be made in determining the applicability of the option.
• Type of material spilled. Chemical compatibility, volatility, or
physical properties of the spilled substance.
• Amount spilled. Whether a great deal of material must be contained
or only a small amount.
• Manpower and/or materials requirements. A facility needs to
consider the personnel or equipment capacity necessary.
• Spill location. Where a certain substance is spilled in relation to
other parts of a TSDF.
The three categories of spill containment options each include procedures
which satisfy much of the above criteria. The most commonly used procedures
are described below.
Control by Mechanical Means—
By placing a barrier between the hazardous material and the environment
(atmosphere), the release of volatile material can be hindered or
eliminated. Similar control technologies have been applied for control of
emissions from surface impoundments. A mechanical barrier is applicable to
most spills. Examples of this type of system are:
• tarpaulin or synthetic membrane; and
• foam cover.
A mechanical barrier may be limited in applicability due especially to
chemical compatibility or spill volume.
3-12
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Synthetic Membrane/Tarpaulin—A synthetic membrane or tarpaulin is
generally a simple sheet (blanket) which would be spread out over the spill.
These systems have been used extensively in industry. The primary design
features which must be considered in selecting the most appropriate membrane
cover are the size of the cover, resistance to chemicals, transportability to
spill location, and spreading technique. These covers may be treated with
special coatings. They may be packaged in certain ways (e.g., parachute
covers) which make for more facile usage. They may also be made from either
flexible or rigid materials.
Foam Cover—There are a wide variety of foams which have found
application for spill control, including protein foams, surfactant foams, and
alcohol-based foams. Foams are used extensively for application in
Q
fire-fighting and in control of natural gas spills. A foam blanket acts
both to isolate the spill from the atmosphere and sources of radiant energy,
and to either absorb the chemical or dilute the surface layer of the spill. A
foam cover can be used to control both landborne and aqueous spills of
volatile compounds. The primary design features to be considered in
selecting foam cover systems are the type of foam, the foam application
process required, and the handling of contaminated foara.
Control by Chemical Means—
By addition of selected chemicals to the spill, the physical or chemical
form of the spilled material may be altered, thus reducing the volatility of
the material. Chemical addition is applicable to many landborne spills,
but in most cases may not be used for aqueous spills. The two most common
methods employed are water dilution and chemical neutralization.
Water Dilution—Water may be applied to spilled materials in a variety of
ways, including as a spray or mist, or by simply flooding. Dilution with
water is the most common method employed for mitigation of spills. The
water acts as a diluent and/or a dispersant. The primary design features to
consider in selecting the water dilution system to be implemented are
availability of water supply, chemical compatibility of water with spilled
materials, water application procedure, and seepage control.
3-13
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Chemical Neutralization—Chemical neutralization agents are available in
H
various forms including foams, powders, and liquids. Neutralization is a
fairly common spill control procedure. It is applicable to most spills.
The primary considerations involved in selecting an appropriate neutralization
system are chemical compatibility, waste neutralizability (hazardous waste
materials tend not to be consistent in their properties, and thus a certain
"kind" of waste may not always be neutralized by a certain agent), application
procedure, and neutralization agent storage and handling procedures (the
agents themselves may be hazardous in nature).
Control by Use of Physical Properties—
By altering the conditions affecting the spill, it is possible to utilize
the physical properties of the spill to control vaporization. Among the
physical properties that might be taken advantage of are the sorptability, and
vaporization point temperature. The most commonly used control options of
this type are thus absorption and cooling.
Absorption—A wide variety of materials may be used as an absorbent,
including straw, charcoal, mulch, flour, or one of the many commercially
available sorbents. Absorption is, therefore, used extensively as a spill
containment alternative. The sorbents can be kept readily available. The
sorbents can be applied when needed either by hand or spray gun. Sorbents are
applicable to any spill situation. The primary design considerations to be
made in selecting an appropriate absorbent are type of materials spilled,
application method, and contaminated sorbent handling and disposal.
Cooling—Many different cryogenic materials are utilized to reduce the
temperature of a spill such that the volatility of the material is reduced,
including ice, dry ice, liquid CO^, and liquid nitrogen. Cooling has not
found wide application in spill control, although it is used in conjunction
with other procedures (cooling increases control effectiveness). Coolants are
generally applied by spraying over the spill. The primary considerations
involved in selecting a cooling system are coolant type and availability,
chemical compatibility, and coolant storage procedure.
3-14
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Spill control procedures are very simple to implement. Most do not
require complex application procedures or equipment. Relative to other
container emission control options, spillage containment are perhaps the
easiest to implement at a TSDF.
Emission Reduction Effectiveness
Spillage containment technology is considered to be a relatively
effective means of controlling emissions from spills of containerized waste.
As summarized in Table 3-2, ratings based upon field evaluation of control
technologies have been developed. Table 3-2 shows that certain technologies,
in particular foam covers and water dilution, are moderately to highly
effective in reduction of emissions.
Mechanical covers (synthetic membranes and foam covers) have been
assessed in a number of EPA documents. Synthetic membrane covers, which are
similar to the covers used for surface impoundment emission control described
in Section 5, have been estimated by MITRE to be up to 90 percent effective
9
for emission control from surface impoundments. The effectiveness of such
systems applied to spill control may be somewhat less, due to lower scale
application. In general, the effectiveness of synthetic membrane covers
relates to the vapor permeability of cover materials (see Table 4-2 in
Section 4) and the effectiveness of enclosure. Foam covers used for spill
control were assessed in detail by Gross and Hiltz. A summary of their
findings is presented in Table 3-3, and is detailed below:
1. High quality foams which have low drainage, i.e., retain their water
content, performed the best in mitigating the vapors during spill
control tests.
2. For nonpolar liquids, any high quality foam cover, regardless of its
chemical type, will provide some degree of mitigation of vapor
release.
3. Only alcohol foam was stable against hjighly polar low molecular
weight liquids such as acetone. Other types of foam rapidly
collapsed.
4. The vapors from polar spills may be mitigated with nonalcohol type
low expansion foams if the volume of foam is several times greater
than the volume of the spill. This reduction is mainly due to water
dilution rather than a foam cover.
3-15
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TABLE 3-2. RATING OF EFFICIENCY OF CURRENT RESPONSE TECHNIQUES TO CONTROL
EVAPORATION
Slight Moderate Highly
reduction reduction effective
Sumping and trenching
Wet Foaming
Deep soil burial
Sorbents (straw, mulch, etc.)
Water flooding
Dispersants (on thin water layers)
Source: Brown et al., 1981 (Ref. 6).
3-16
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TABLE 3-3. MATRIX OF FOAM CAPABILITIES TO SUPPRESS OR OTHERWISE MINIMIZE THE RELEASE OF
TOXIC OR FLAMMABLE VAPORS FROM SPILLED HAZARDOUS CHEMICALS AS LISTED
u>
I
i-octane
n-heptane
Cyclohexane
Hexane
Benzene
Toluene
Gasoline
Kerosene
Naphtha
Methanol
i-propanol
Butanol
Butyl Cellosolve
Acetone
Methyl Ethyl Ketone
Methyl 1-butyl ketone
Lacquer Thinner
Paint Thinner
Recommen-
dation
R
R
R
R
R
R
R
R
R
R
R
R
ND
R
ND
R
ND
ND
Surfacta
Low ex-
pansion
B+
B+
B+
B+
B+
B+
B+
B+
B+
E-
E-
E-
ND
fi-
ll
B+
U
U
,nt foams
High ex-
pansion
A+
A+
A+
A+
A+
A+
A+
A+
A+
E-
E-
E-
ND
E-
U
A+
ND
ND
Protein
B+
B+
B+
B+
-
-
B+
B+
B+
E-
E-
E-
U
fi-
ll
U
ND
ND
Fluoro-
protein
B+
B+
B+
B+
-
-
B+
B+
B+
E-
E-
E-
ND
E-
ND
ND
ND
ND
Alcohol
E-
E-
E-
E-
E-
E-
E-
E-
E-
A+
A+
A+
ND
A+
ND
ND
ND
ND
AFFFa
C+
C+
C+
C+
ND
ND
C+
C+
C+
E-
E-
E-
ND
E-
ND
ND
U
U
Mech.
U
U
U
U
ND
ND
U
C+
U
-
-
-
U
ND
ND
ND
ND
ND
(continued)
-------
TABLE 3-3 (continued)
Ul
I
OC
sici4
i-amyl Alcohol
Ethyl Acetate
Butyl Acetate
i-propyl Acetane
Methyl Acrylate
Methyl Methacrylate
so3
Acetic Acid
Caproic Acid
Methyl Bromide
Butyl Bromide
N,N '-dimethyl Formamide
Tetrachloroe thane
n-Octanol
Tetrahydronaph tha lene
LNG
Chlorine
Ammonia
Recommen-
dation
R
ND
ND
ND
ND
R
R
R
R
ND
ND
R
ND
R
R
R
R
R
R
Surf acts
Low ex-
pansion
C+
U
U
U
U
B+
B+
C+
A+
U
U
A+
U
B+
B+
B+
E-
B+
A+
mt foams
High ex-
pansion
C+
U
-
-
-
A+
A+
O
B+
ND
U
U
E-
A+
A+
A+
A+
A+
A+
Protein
C+
U
-
-
-
ND
ND
C+
ND
ND
ND
ND
ND
ND
B+
E-
F-
B-
B+
Fluoro-
protein
C+
ND
U
U
U
U
U
C+
ND
ND
ND
ND
ND
ND
+
ND
F-
B-
B+
Alcohol
ND
ND
ND
ND
ND
ND
ND
ND
ND
ND
ND
ND
ND
ND
-
ND
F-
ND
ND
AFFFS
F-
ND
ND
ND
ND
ND
ND
F-
ND
ND
ND
ND
ND
ND
ND
U
F-
E-
E-
Mech.
ND
ND
ND
ND
ND
ND
ND
ND
U
U
ND
ND
ND
ND
U
ND
ND
ND
ND
(continued)
-------
TABLE 3-3 (continued)
Identification of Symbols
aAFFF = Aqueous film forming foam
+ = Data available indicating vapor pollution control
- = Data available indicating no vapor pollution control
U = Limited data available - capability uncertain
R = Foam use recommended over spill
ND = Insufficient data
A = Best foam formulation
B = Next best foam formulation
C = Acceptable in some situations
E = Unsuitable foam formulation
F = Deleterious foam formulation
Source: Gross and Hiltz, 1982 (Reference 5).
-------
5. For liquids which are extremely water reactive, high expansion foam
provides the best control. This is due to the heats of reaction or
solution. The higher the expansion, the slower is the rate of water
addition to the reactive liquid.
6. Foams do not effectively mitigate the vapors for liquefied gases
which are heavier than air and not water reactive. The water
draining into the liquefied gas exaggerates the boil off rate. The
released vapors, being nonbuoyant, are not readily dispersed. There
are reports of foam being effective against butane, but the data
from the tests of this program are not in agreement.
7. For liquefied gases such as ethylene which are buoyant at ambient
temperatures, a high expansion foam blanket acts as a heat source.
The vapors rising through the foam increase in temperature and
dispersion of the released vapor is enhanced.
8. Laboratory tests can be conducted to predict the behavior of foams
under field conditions.
9o Environmental conditions such as wind and rain are more detrimental
to high expansion foams than to low expansion foams.
10. High expansion foams appear to mitigate a spill by containing the
vapors within the foam mass so a vapor-liquid equilibrium can be
maintained, thus reducing the driving force towards vaporization.
11. Low expansion foams appear to mitigate the vapor by forming a
barrier to prevent vaporization.
12. Foams are an inexpensive, effective method of initial vapor control
during an accidental spill, provided the correct foam made from a
quality agent is used.
13. The foam agent which produced the best results in terms of vapor
mitigation was the metal stearate-based alcohol type foam. This
foam agent was better than the newer forms of polar solvent foams.
The alcohol type foams were more difficult to apply, more was needed
to establish a desired thickness, and the foam cover is fairly
stiff. However, once the foam cover was established, it provided
good mitigation of vapors.
No data are available which quantifies the achievable reduction efficiency.
Control by chemical means were studied by Brown et al. Water dilution
and chemical neutralization were considered to be relatively effective,
however often produced unwanted hazardous side effects. Data which
quantify emission reduction effectiveness for these techniques are limited.
The effectiveness of a similar technique, application of surfactant on a
3-20
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2
surface impoundment, was estimated by MITRE at 25 to 75 percent. It is
expected that the control efficiency of these methods would fall within the
same range.
Control of spills by adsorption or cooling was considered by Brown et al.
to be only slightly to moderately effective. According to Brown, however,
Battelle considers control by cryogenic media to be an area of potential
development. Data which quantify emission reduction effectiveness by these
methods are also limited. Based upon the available information, these control
technologies are not expected to be as effective as either control by
mechanical or by chemical means.
Costs
The costs associated with various spillage control technologies are, in
general, expected to be relatively low. These costs will range widely,
however, as the complexity of the various systems is quite different from case
to case. Like emission reduction effectiveness data, cost data for these
systems are severely limited. The various costs are expected to be highly
dependent upon materials and labor, while operating and installation costs are
expected to be relatively low.
The costs of a synthetic membrane cover or foam cover system depend upon
the cover material chosen, and the installation method used. The synthetic
membrane or foam materials used are not unlike those in use for other similar
systems at TSDF processes. Costs for such materials are presented in
Section 6 on landfill emission control. They have been estimated to range
between $3 and $26/per square yard for synthetic membranes, and $2.25/per
9
square yard for temporary foams. Brown et al. estimated that a spill
containment foam system which could deliver approximately 15,000 gal/min of
aqueous-based foam would cost approximately $1,300 to implement at a
facility.6
The costs associated with implementing a water dilution or chemical
neutralization system are largely dependent upon the equipment costs
involved. The actual cost of chemical agents or water is assumed to be very
low in comparison. Brown et al. estimated that a water spray pump machine
3-21
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which can be used to apply a water mist blanket over a chemical spill would
cost less than $925 (March 1983 dollars).6 The costs associated with
storing neutralization agents or water to be used for this purpose have not
been evaluated.
The costs associated with using absorbents or coolants for spill
mitigation are similar to those for water dilution or chemical
neutralization. For solid absorbents, the costs would be based upon materials
costs only.
CONTAINER MODIFICATION
Introduction
Reduction of spillage and leaks from containers and, consequently,
significant reduction of emissions, may be effected by securing the containers
themselves. The containers are subject to a variety of stresses, both from
within and from outside, including corrosion, denting, and puncture.
Encapsulation systems are designed to insulate the containers from the outside
and also to contain corrosive materials inside should they leak from the
containers. There are two basic types of encapsulation systems, as follows:
• Overpack designs; and
• Directly-applied systems.
Encapsulation systems have only recently found application in industry. This
section will present alternatives based on information found chiefly through
laboratory test programs.
Description
The basic function of an encapsulation system is to completely enclose an
individual container. Emission of vapors resulting from both leakage and
breathing loss would essentially be eliminated. Drums placed in an
encapsulate would be insulated from mechanical and chemical stresses, and
3-22
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thermal fluctuations. Most encapsulates employ polymeric resins (e.g.,
polyethylene).9 Polymeric materials offer several advantages over steel or
other materials, including chemical compatibility, corrosion resistance,
weight, mechanical resilience, flexibility, strength, and low materials and
fabrication cost. Use of polymeric materials allows for fabrication to be
done onsite, and also allows the use of readily transportable equipment, thus
facilitating their use at a TSDF. In selecting the container modification
system most applicable to a specific TSDF, the following considerations must
be made in determining the applicability of the system:
• Type of material being handled. Chemical compatibility, density,
and volatility are all factors which must be considered.
• Type of containers being handled. Containers of a certain size or
material of construction may not be well handled by a certain
modification.
• Containerized waste fate. Encapsulation is most suited to unit
disposal.9 Whether the containers are to be disposed of,
shredded, or reused.
• Manpower requirements. Whether or not a facility will have the
manpower required for a certain container modification procedure.
• Availability of materials. Encapsulation requires the use of
certain special materials.
Overpack Systems —
An overpack is essentially a jar into which a container is placed. The
overpack is then covered and sealed, permanently. By sealing the container
into the impermeable overpack, emissions from waste are eliminated. Overpacks
are available commercially, and can be produced by any manufacturer of
Q
rotomolded plastics. They can be made in a variety of sizes, capable of
handling any size from small containers to 55-gallon drums. Overpacks are
commonly packed with sorbent material which fills the gap between the drum and
the overpack wall. The sorbent material will act to stabilize the drum
within the capsule, insulate the drum from both thermal fluctuations and
physical shocks, and absorb leaking waste. The key difference between
available overpack systems is in the method by which they are sealed. ^'^
The two designs described in the literature are as follows:
3-23
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• Single layer, friction welded;10 and
• Double layer, fiberglass-lined.9
Overpacks are the more applicable of the two types of encapsulation systems.
They are especially well suited to handling highly reactive or corrosive
wastes.
Single Layer, Friction Welded—Single layer type overpack systems are
generally formed from polyethylene, although polypropylene and polyvinyl
chloride types have been tested. The systems come in two pieces: the capsule
and the cover. To seal the capsule, friction welding has been proposed as the
most effective means of closure. (Other designs use mechanical closure or
adhesives.) A typical overpack welding system is shown in Figures 3-1
and 3-2. The system employs a welding device which may be made transportable
for use at a TSDF. The primary design considerations in implementing this
type of system are overpack materials (availability and compatibility),
manpower requirements, and type of containers being handled.
Double Layer, Fiberglass Lined—Double layer overpack systems also use
polyethylene, or polypropylene on the outside layer, and thus function
identically to single layer designs. The difference is that double layer
systems employ a fiberglass inner layer which is formed directly onto the
container, thus giving a seamless seal. The outer layer then adheres to the
fiberglass layer, eliminating the need to .seal the cover. Double layer
systems require two applicator systems: a spray gun applicator for the
fiberglass inner layer, and a fusion mold system, as shown in Figure 3-3, for
the polyethylene layer. The primary design features to be considered in
selecting a double layer system are the availability of materials, the
manpower requirements, the application procedure, whether or not to use
sorbents, and the transportability of equipment.
Directly-applied Systems—
Directly-applied systems involve spraying or brushing resin or other
material onto the surface of the container. Such systems have the advantage
3-24
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CYLINDER
PUMP
RECEPTACLE
55 gallon DRUM
Figure 3-1. Apparatus for encapsulating 208-liter (55-gal)
drums holding hazardous wastes.
Source: Lubowitz & Telles, 1981 (Reference 10).
3-25
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DRIVERTRAIN
LABELS
SLOTTED PLATTEN
RIBBED COVER
LOADING
PLATFORM
Figure 3-2. EPP overpack welding unit.
Source: Lubowitz & Telles, 1981 (Reference 10),
-------
UPPER HYDRAULIC
RAM
1 TON CAP
CLAM SHELL
HEATING JACKET
JACKET
HEATING COILS
INSULATION
LOADING
LEVEL
LOWER
HYDRAULIC
RAM
I TON CAP
YOKE 6" X 6" 1 BEAM
JACKET
SUPPORT
FLEXIBLE HYDRAULIC
AND HEATING LINES
TRUNNION BEARING AND
ROTATION MECHANISM
ROTATION
PIT
Figure 3-3. Side view of the polyethylene fusion mold,
Source: Lubowitz & Telles, 1981. Reference 9.
3-27
-------
of be Lnt; applicable Co any size or shape container, however do not insulate
the container as well as an overpack system. Such systems also have no
seams. A variety of materials are used in this application, including
fiberglass, polyethylene, and concrete. The primary considerations in
implementing a directly-applied encapsulation system are container materials,
chemical compatibility, manpower requirements, application procedure, and the
storage and handling of spray-on materials.
Encapsulation systems appear to be relatively easy to implement at a
TSDF. The requirements for operating an encapsulation system are the
encapsulation materials, application equipment (both of which must be
purchased) and trained operators.
Emission Reduction Effectiveness
The reduction efficiency of an overpack or directly-applied encapsulation
system has been described in several laboratory test reports. The systems
were found to be water-tight and performed better in strength tests than steel
overpack systems. The reduction efficiency was estimated to approach
100 percent with well insulated systems. Volatile organic compound (VOC)
emissions would be essentially eliminated unless extreme heat conditions were
encountered.
Costs
The costs involved in implementing this system include capital equipment,
material, and labor. The equipment includes conventional drum-handling
equipment, spray guns, or overpacking apparatus. Materials costs include
costs of resin and sorbent material. A total cost estimate of $65 to $90/drum
for overpack systems, and $26 to $40/drum for directly-applied systems has
been calculated based upon encapsulation of a 55-gallon steel drum as
described in this section.
3-28
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OPERATING PRACTICES
Introduction
Because container leakage and spillage play such a significant role in
emissions from containerized waste, operating practices are a potentially
significant area in which to effect emission reductions. Changes in operating
practices would be specifically intended to reduce mishandling or degradation
of the containers. This subsection will focus upon three changes in operating
practices, as follows:
• Improved drum equipment and/or procedures;
• Leak detection and repair programs; and
• Submerged loading.
Changes in operating practices are applicable to any TSDF.
Description
The purpose of improving operating practices is to insure that
mishandling of containers is prevented, factors which lead to the degradation
of containers (such as storage in a damp area) are reduced or eliminated, and
conditions which exacerbate the volatility of a waste are reduced. In
implementing changes in operating practices at a TSDF, the following
considerations must be taken into account:
• Manpower requirements. Whether or not a facility has the personnel
required to implement a certain change in operating practice.
• Storage procedures. The way containers are stored may determine the
applicability of a certain change in operating practice.
• Input/output. The turnover rate a facility maintains may determine
the applicability of a certain change in operating procedure.
The three changes to be reviewed in this subsection are quite common
practices at TSDFs and, as such, adhere to the above criteria.
3-29
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Improved Drum Handling—
By making improvements in the procedures used in the handling of
containers, either by purchase of better equipment or use of new procedurest
mishandling of drums can be reduced. Mishandling of drums is the primary
cause of spills and damage to containers (leading to leaks) at TSDFs. The
most common procedure now employed is to move drums, either two or four at a
time, by forklift. Spills or damage commonly occur when drums fall off of the
pallets when they are in transit, or when the forklift collides with another
object. Handling spills also occur during unloading of drums, and during drum
disposal operations. Three changes which are common are as follows:
• Drum "grabber" equipment;
• Slow pouring; and
• Drum decontamination.
Drum "Grabber" Equipment—Drum grabbers are specially made forklifts
designed for transport of 55-gallon drums. Drum grabbers are equipped with a
device which wraps around the drum, thus providing a secure hold. In some
designs, the drums are further protected by bumpers or screens so that damages
^
in the event of a collision can be reduced or eliminated. The primary
considerations involved in selecting drum grabber equipment are available
space requirements in the storage area, size of drums handled, and drum
turnover rate.
Slow pouring—Pouring of waste material from drums often is a major
source of spills. Through more careful procedures, these spills can be
reduced. Slow pouring may be accomplished either by implementing equipment
such as spouts, or simply by improved technique. The considerations to be
made in implementing this procedure are present pouring method (manual or
mechanical), waste viscosity, and drum type.
Drum Decontamination—After waste material has been poured from the
drums, they are either reused or disposed of. Residual waste often spills
3-30
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during handling of empty drums. These spills can be eliminated by
decontamination procedures. Decontamination involves scrubbing of the drum
walls, either manually, mechanically, or chemically. A variety of cleaning
solvents may be used for this application. Among the primary considerations
involved in this procedure are type of drums handled, cleaning solvents,
control of volatile emissions from cleaning materials and operations, and
disposal of waste materials.
Leak Detection and Repair (LDAR) Programs—
By instituting a program for continuously checking containers and
immediately repairing them if potential for leaking exists, a facility can
reduce the number of leaks that occur, increase the speed of response to those
that do occur and thus reduce emissions. Various monitoring techniques that
can be used in a leak detection program include individual component surveys,
unit area ("walkthrough") surveys, and fixed point monitoring systems.
Individual Component Survey—An individual component survey involves
checking each potential container leakage source for VOC leaks. This may be
accomplished by spraying a suspected leakage source with a soap solution and
observing bubble formation or measuring VOC concentration with a portable VOC
detector. In selecting an individual component survey LDAR program, the
primary considerations are the number of containers, manpower requirements,
personnel access to the containers and waste products.
Walk-through Survey—A walk-through survey involves checking each
container.for VOC leaks by measuring the VOC concentration close by. This is
accomplished with a portable VOC measurement device. This type of survey has
the advantage of being quicker and requiring less manpower, but is not as
thorough as an individual component survey. The primary considerations
involved in selecting a walk-through survey for LDAR are the number of
containers, prevailing weather (especially wind) conditions, access to
containers, and manpower requirements.
Fixed-Point Surveys—A fixed-point survey involves placing a continuous
monitor in various locations at the storage area. LDAR programs would then
3-31
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involve responding to an audio alarm system or monitoring the measurements on
a periodic basis. These programs can result in leaks being detected sooner.
Like walk-through surveys, however, they are not as thorough as individual
component surveys and, in addition, have higher equipment costs. The primary
considerations involved in selecting this option are the number of containers,
size of storage area, manpower requirements, weather conditions, and number of
units required. Of the three options, fixed-point surveys have found the most
widespread application to detection of hazardous or toxic emissions.
Submerged Loading—
Loading of containers is often done at a TSDF. Emissions from loading of
containers, like storage tanks, can be reduced by employing submerged
filling. For open containers, submerged filling would require a nozzle which
would be placed at the bottom of the drum. For enclosed containers, this may
require a pressure attachment to the bung hole. The primary considerations
involved in instituting submerged loading procedures are the type of drums
being filled, and the type of waste material.
Other Practices—
In addition to those described in detail above, there exist many other
changes that may be made in operating practices at a TSDF which may contribute
to reduction of emissions. These may include prohibiting drum stacking,
segregating wastes, and not allowing containerized wastes to be stored,
handled, or disposed of at all.
Implementation of the changes in operating practices at a TSDF are
dependent upon several factors, including new equipment, manpower, and
overall system complexity. Most of the changes described above are considered
to be extremely easy to implement.
Emission Reduction Effectiveness
Changes made in operating practices at a facility which handles
containerized hazardous wastes are expected to result in the reduction of air
emissions due to decreased mishandling, spills, and leaks. No detailed
3-32
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information has been published, however, which indicates the effectiveness of
such measures relative to add-on control systems. Based upon engineering
judgment, these measures are considered moderately effective, but not as
effective as many of the add-on control systems.
The effectiveness for better drum handling equipment is a direct function
of the reduction in accidents and mishandling of drums at a facility. A
survey of manufacturers of drum handling equipment revealed that such
equipment has been found to be responsible for reducing mishandling incidents
by 50 to 75 percent.12
The effectiveness of leak detection and repair programs may be measured
in terms of the percentage of previously undetected leaks which are detected
in the surveys. OAQPS reports that the effectiveness of various LDAR programs
13
is as follows:
• Individual component survey: 99. percent
• Walk-through survey: 50 percent
• Fixed-point survey: 33 percent.
The effectiveness of submerged loading has been studied extensively for
the filling and emptying of storage vessels. AP-42 reports that submerged
loading can result in emissions reductions of 66 percent.15
Costs
The costs involved in implementing operating practice changes at a TSDF
are expected to be relatively low, based upon limited information. These
costs are dependent upon the materials and/or equipment requirements, and
labor. Operating costs are generally expected to be low.
Improving drum handling equipment may involve costs associated with
purchasing drum grabber equipment or decontamination equipment and materials.
Decontamination procedures would also involve added materials handling and
disposition costs. Slow pouring would not involve any additional costs,
except those that may be incurred due to decreased rate of operation or added
manpower required. Drum grabber equipment was found to cost in the $300 to
3-33
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I rt
$6UO range.*, based upon conversations witli suppliers. Costs of
decontamination systems could not be determined based upon the available
information.
The costs involved in leak detection and repair programs essentially
involve just equipment and labor costs. Based on conversations with
suppliers, VOC monitoring equipment costs are estimated to be within the $200
to $1,000 range for portable units, and $500 to $3,000 for fixed
14
monitors. Labor costs would vary with the size of the facility.
The costs of submerged loading essentially involve just equipment costs.
No information detailing the cost of longer fill pipes, pressure nozzles, etc.
was found. It is estimated that such costs would be quite low.
3-34
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REFERENCES FOR SECTION 3
1. Engineering-Science. National Air Emissions from Tank and Container
Storage and Handling Operations at Hazardous Waste Treatment, Storage,
and Disposal Facilities. Prepared for U.S. Environmental Protection
Agency, Office of Air Quality Planning and Standards, Research Triangle
Park, NC. September 1984.
2. Vogel, G. A., and D. F. O'Sullivan. Air Emission Control Practices at
Hazardous Waste Management Facilities. Report No. MTR-83W89. Prepared
for U.S. Environmental Protection Agency, Office of Solid Waste, Contract
No. 68-01-6092. The MITRE Corporation, McLean, VA. June 1983.
3. Drehmel, D., B. Danel, and D. Corner. Relative Effectiveness of Chemical
Additives and Wind Screens for Fugitive Dust Control. Environmental
Progress 1(1) :16. February 1982.
4. SCS Engineers. Interim Report on Air Emissions. Prepared for U.S.
Environmental Protection Agency, Office of Solid Waste, Contract
No. 68-01-6621, SCS Engineers, Covington, KY. September 1983.
5. Gross, S. S., and R. H. Hiltz. Evaluation of Foams for Mitigating Air
Pollution from Hazardous Spills. EPA-600/2-82-029. U.S. Environmental
Protection Agency, Office of Research and Development, Cincinnati, OH.
Contract No. 68-03-2478. March 1982.
6. Brown, D., R. Craig, M. Edwards, N. Henderson, and T. J. Thomas.
Techniques for Handling Landborne Spills of Volatile Hazardous
Substances. EPA-600/2-81-207. U.S. Environmental Protection Agency,
Office of Research and Development, Cincinnati, OH. Contract
No. 68-02-1323. September 1981.
7. Greer, J. S., S. S. Gross. R. H. Hiltz, and M. J. McGoff. Modification
of Spill Factors Affecting Air Pollution. Vol. I - An Evaluation of
Cooling as a Vapor Mitigation Procedure for Spilled Volatile Chemicals.
EPA-600/2-81-214. U.S. Environmental Protection Agency, Office of
Research and Development, Cincinnati, OH. Contract No. 68-03-2648.
September 1981.
8. Greer, J. S., S. S. Gross, R. H. Hiltz, and M. J. McGoff. Modification
of Spill Factors Affecting Air Pollution. Vol. II - The Control of the
Vapor Hazard from Spills of Liquid Rocket Fuels. EPA-600/2-82-215. U.S.
Environmental Protection Agency, Office of Research and Development,
Cincinnati, OH. Contract No. 68-03-2648. September 1981.
3-35
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9. LubowLtz, H. R., an
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SECTION 4
CONTROL OF EMISSIONS FROM STORAGE TANKS
INTRODUCTION
There are two basic types of tanks found at TSDFs: open-top and
closed-top. The tanks in use range in capacity from 5000 to 1,500,000
gallons. Most are above ground, although some liquid wastes are stored in
submerged tanks. Hazardous materials are generally brought to a facility by
tank truck or rail car, and the tanks are loaded, generally via pipeline, by
either splash or submerged filling techniques.
Hazardous constituent releases from storage tanks can occur via two
mechanisms for closed-top tanks: working loss and breathing loss. Working
loss, which accounts for a more significant percentage of emissions, occurs
when liquid being put into a tank causes the displacement of an equal volume
of vapor. Breathing loss occurs when a volatile compound is vaporized and
released from tank due to temperature fluctuations affecting the tank. For
open-tanks, air releases of waste constituents are a function the diffusion
and mass transfer from the bulk material.
The control options available to a facility which stores volatile waste
material in tanks can be classified as follows:
• Roofs and associated control systems;
• Covers;
• Insulation; and
• Vapor control systems.
Table 4-1 provides an overview of advantages and disadvantages of control
alternatives described in this section. This section will describe technology
4-1
-------
TABLE 4-1. ADVANTAGES AND DISADVANTAGES OF STORAGE TANK EMISSION CONTROL ALTERNATIVES
Advantages
Disadvantages
i
to
ROOFS AND ASSOCIATED CONTROLS
Fixed Roofs:
• Highly effective in reducing emissions from open
tanks or external floating roof tanks.
• Provide a permanent rigid cover.
• Insulates constituents from solar irradiation,
rain, and wind.
• Very durable.
• Very low maintenance costs required.
• Easy to retrofit onto existing tanks (in
terms of design).
Floating Roofs (External and Internal):
• Very highly effective in reducing emissions
from tanks (higher than fixed roofs).
• Provides a permanent, rigid cover.
• Insulates constituents from solar irradiation
and wind and rain.
• Very high initial costs.
• Very heavy—may not be applicable to existing
tanks due to structural considerations.
• Requires venting due to internal pressure
considerations.
• May necessitate changing tank loading
procedure.
• Very expensive—particularly in terms of
maintenance (relative to fixed roofs).
• Heavy—may be limited by structural con-
siderations-
• Requires that inside design of tank contain
no support columns, or beams along side.
(continued)
-------
TABLE 4-1 (continued)
Advantages
Disadvantages
-P-
i
Floating Roofs (External and Internal) (Cont'd):
• Very durable.
• Easy to retrofit to existing tanks.
• Need not be vented.
• Not as heavy as fixed roofs.
• Less expensive initially than fixed roof.
Seals:
• Increase effectiveness of all. floating roofs.
• Simplistic designs, easily adaptable to existing
systems.
• Relatively inexpensive to install and maintain.
• Durable.
• Provide good thermal insulation, vapor
permeability.
• Relatively low costs, overall.
• Difficult to maintain.
• May warp or sink.
• Not as good insulator from external forces
(particularly heat) as fixed roofs.
• May require alteration of loading procedures.
• Application limited by design of primary
seal system, internal design of tank.
• May increase weight of roof.
• May not be applicable for use with all waste
substances (e.g., viscous materials).
• Weather conditions hinder effectiveness.
(continued)
-------
TABLE 4-1 (continued)
Advantages
Disadvantages
Vents:
• Necessary to reduce internal pressure
buildup inside enclosed tanks.
• Simple designs—easy to install on existing
vessels.
• Inexpensive to implement—only initial costs are
involved.
• Durable.
• Easy to maintain.
COVERS
• Highly effective in reducing emissions.
• Simple designs, easily adaptable to more
than one storage tank at a facility.
• Easy to implement.
• Applicable to varying size and shape
storage tanks.
• Provides a close-fitting cover, more flexible
than a roof.
• Increases working losses—not well suited for
highly volatile substances.
• By itself, not a control. Requires the use of
vapor control system.
• Less effective in reduction of emissions
than roofs.
• More permeable by vapors and gas.
• Less durable than roofs.
• Low strength characteristics.
• Poor weather resistance.
• Requires maintenance.
(continued)
-------
TABLE 4-1 (continued)
Advantages
Disadvantages
• Light weight—will not sink.
• Will not warp or corrode.
• Adaptable to changes in constituent type.
• Less costly than roofs, overall.
• Generally low operating costs.
• Removable.
INSULATION
• Reduces solar irradiation and wind on tanks
and tank constituents.
• Simplistic designs.
• Widespread usage in industry.
• Many available options to choose from.
• Highly adaptable to any storage tank.
• Can be used in conjunction with other
control technology.
• Requires little or no space.
Will transmit heat directly to liquid,
High maintenance and installed costs.
• Poor weather resistance.
• Applied directly to tank—effect may be
limited by design constraints.
• High maintenance costs.
• Emission reductions achievable are low.
(continued)
-------
TABLE 4-1 (continued)
Advantages
Disadvantages
INSULATION (Cont'd)
• Uses inexpensive materials.
• Low installed costs.
• Particularly attractive for open or external
floating roof tanks.
VAPOR CONTROL SYSTEMS
• Capable of achieving the highest emission
reduction efficiencies of the control options
described.
• Completely remove vapor from tanks.
• Equally effective in reducing working and
breathing losses.
• Best available technology for highly volatile
and/or toxic substances.
• Very safe to operate.
• Basic design of systems are simple—they are
easy to operate; and easy to design to fit
a tank.
• Most costly of all control options dis-
cussed for storage tanks.
• Highly complex systems to maintain.
• Manpower required.
• Materials required.
• Space required.
• Accessibility required.
• Requires enclosed tank.
• Requires equipment for the disposition
of vapor control process products.
(continued)
-------
TABLE 4-1 (continued)
Advantages Disadvantages
VAPOR CONTROL SYSTEMS (Cont'd)
• Can be applied to one or more than one tank • Subject to fire and explosion hazards.
vent systems at once.
• Can be subject to design capacity
• Can be a single-pass or multiple-pass system. limitations.
• Can selectively recover constituents. • Performance is affected by prevailing
weather conditions.
• Adaptable to a variety of wastes—can use even
if wastes stored changes.
• Can regenerate carbon beds for continuous use.
• Have found widespread usage at TSDFs.
-------
options provided in Table 4-1 under each of these classifications. Example
systems will be cited, and the relative emission reduction effectiveness and
cost of implementing these options to existing TSDFs will be examined.
ROOFS
Introduction
Storage tank roofs serve two basic purposes: (1) to keep tank
constituents contained; and (2) to shelter the constituents from external
forces such as solar irradiation, wind, and precipitation. Three basic roof
designs for storage tanks, include:
• Fixed roof;
• External floating roof; and
• Internal floating roof.
All three types have found widespread application at TSDFs.
Description
A storage tank roof is defined as any rigid, permanently affixed
mechanism for enclosing tank constituents from the environment. A roof is
primarily intended to keep tank constituents contained, while excluding
environmental factors from contact with these constituents. As a control
option, roofs are particularly attractive as they serve to limit working
losses. A variety of designs are available, including fixed roofs, roofs that
move as the liquid level of a tank changes, and roofs with and without vapor
seals and pressure vents. In addition, roofs may be made from a variety of
materials. In determining which design is most applicable to a particular
storage tank at a TSDF, the following factors should be considered.
4-8
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• Tank Design. The size, shape, structural reinforcement, and
structural strength of a storage tank.
• Type of material being stored. The volatility, viscosity, and
chemical nature of the materials being stored.
• Tank loading procedure. How the tank is loaded, when, and how often
the tank is loaded and emptied.
• Weather conditions. Sun, wind, and rain patterns of the local area.
The three basic roof designs have all found widespread usage at TSDFs. A
description of each roof design, how they may satisfy the above criteria for a
particular storage tank, and the considerations involved in formulating a
specific design is provided below.
Fixed Roof—
A fixed roof is defined as any rigid cover which is permanently affixed
to the top of a storage tank. A variety of fixed roof tanks are shown in
Reference 4. A fixed roof is the most common of the three roof designs.
There are three styles of fixed roofs: conical, domed, and flat. Conical
roofs are the most common of the three.
Fixed roofs may be constructed of steel, aluminum, or plastic. Choice of
materials is largely dependent upon the tank design. Fixed roofs may also be
equipped with various appurtenances, such as vents, sampling ports, and
manholes. Fixed roofs may be coated on the inside, insulated, raultilayered,
or painted a different color in an effort to reduce the effects of solar
irradiation of tank contents. The following considerations which are involved
in formulating a design for a fixed roof.
• Roof size and weight. Since storage tanks are constructed with thin
walls, the weight of a fixed roof may be limited by the structural
constraints of the tank.
• Roof reinforcement. The fixed roof may require columns, or bracings
in order to be applicable to a tank.
4-9
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• Root: venting. Due to the volatility of tank constituents, it may be
necessary to incorporate vents into the roof design to reduce
internal pressure buildup.
• Inflow/outflow pipe installation. Installation of a fixed roof
requires eliminating top loading procedures and installing inflow/
outflow pipes.
Fixed roofs are considered to be relatively effective in reducing
emissions from tanks, while remaining simple so that costs are not a major
factor. Analyses of reduction effectiveness and cost are presented later in
this section.
Pressure Tanks—A pressure tank is a special type of fixed roof tank
design. They are specifically designed to withstand relatively large internal
pressures. These types of tanks are the most commonly used for storage of
highly volatile and/or toxic materials. They are constructed in various
sizes and shapes, depending on the operating pressure range. Noded spheroid
and hemispheroid shapes are generally used for low pressure (117 to 207 kPa),
while horizontal cylinder and spheroid designs are generally used for
high-pressure tanks (up to 1827 kPa). Pressure tanks generally operate
3
with no emissions, as they are an enclosed system. Because of their
complex design and use of structural materials, such tanks tend to be much
more expensive. The primary considerations involved in selecting a pressure
tank design include the operating pressure range, loading and unloading
procedure, and tank maintenance considerations.
Flexible Diaphragm Tanks—Another specially modified type of fixed roof
tank incorporates a synthetic membrane, stretched over the top of the vapor
space. The membrane (also called "diaphragm" or "bladder") serves to limit
the emission of vapor due to working losses by expanding within the fixed roof
as the tank is filled. By expanding, the volume of vapor which is displaced
when the tanks is filled with liquid is not immediately pushed out of the
tank. The diaphragms are generally made from a synthetic rubber material or
polyvinyl chloride. The primary considerations involved in implementing a
flexible diaphragm system are the tank design (structural limitations),
compatibility of the diaphragm with the tank constituents, and diaphragm
venting.
4-10
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External Floating RooE Tanks—
A floating roof is defined as any rigid cover permanently incorporated
into the storage tank design which moves such that the volume of the tank
varies as the tank is filled and emptied. A floating roof operates by resting
directly upon the surface of the liquid. Storage tank working losses are
reduced because the floating roof imparts a slight pressure upon the liquid,
thus eliminating available vapor space. An external floating roof tank
utilizes such a roof as the sole means of enclosure. Floating roofs are
2
always equipped with a flexible vapor seal at the perimeter. In general,
they are constructed of aluminum or steel, although the use of plastic
materials has become increasingly common. There are several different types
of roof designs in use at TSDF storage tanks, the most common of which are:
• Pan roofs;
• Pontoon roofs; and
• Double-deck roofs.
Pan Roofs—Pan roofs have found widespread usage for approximately
50 years. A pan roof is the simplest floating roof design, involving a
simple flat cover resting directly upon the liquid surface as shown in
Figure 4-1. Emissions are controlled by such a design because the exposed
surface area of the liquid is virtually eliminated, and the weight of the roof
imparts a slight pressure which decreases volatility. Pan roofs almost always
are equipped with flexible perimeter seal system. There are basically two
types of pan roofs in use, including: (1) aluminum sandwich panel roofs with
a honeycomb aluminum core, and (2) flat steel pans. Pan roofs have found
widespread usage because of their simplicity and emission reduction
effectiveness.
There are several disadvantages associated with pan roofs, however,
including: (1) they require considerable support or trussing to prevent them
from buckling; (2) they are subject to warping or holes which can lead to
sinkage; (3) there are no effective drainage systems to release liquid
condensing on the top of the roof; and (4) in direct sunlight, heat is very
4-11
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A
Figure 4-1. Pan-Type Floating Roof Tank.
Source: API, 1973 (Reference 4).
Figure 4-2. Pontoon-type Floating Roof Tank.
Source: API, 1973 (Reference 4).
4-12
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readily transmitted through the metal plate to the tank contents, potentially
increasing the substances volatility. The primary design considerations
involved in selecting an applicable pan roof are the tank design (diameter and
weight capacity), roof thickness, seal system, and support structure.
Retrofit of a floating roof to an existing tank is a very common method
employed to effect emission control. A major limitation to retrofitting
floating roofs is the need for internal reinforcement (columns, bracings) of
an existing tank.
Pontoon Roofs—A pontoon roof, as shown in Figure 4-2, is similar to a
pan roof, except that it does not rest directly upon the liquid surface but
instead upon pontoons. This results in the creation of a vapor space between
the roof and the liquid surface, greatly increasing thermal insulation. Like
a pan roof, a pontoon roof will control working losses by limiting the
available vapor space and by imparting a slight pressure on the liquid.
Pontoon roofs are always equipped with a flexible perimeter seal.
Design variations for pontoon roofs include the following considerations.
• Shape of the roof. Flat, convex, and conical roof designs are
commonly used.
• Drainage system. Hinged or flexible connections may be used to
recycle vapor condensed on the top to the liquid space.
• Pontoon design and location. Pontoons of various size and shape are
in use (depending upon roof design), and may be located either at
the perimeter (most common) or the center, or both.
Pontoon roofs are considered to be most applicable to larger diameter
storage tanks. Design considerations involved in selecting the most
appropriate pontoon roof design are the tank design, the pontoon design
(including the compatibility of pontoon material with the tank constituents),
the roof design, the seal system, and the design of any roof support system
needed.
Double-deck Roofs—A double-deck roof is essentially a system which
incorporates design elements of both pontoon and pan roofs, as shown in
4-13
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Figure 4-3. The lower deck, like pan roof, rests directly upon the liquid
surface. Between decks is a series of compartments, set up so as to provide a
dead air insulator so that heat is not easily transmitted through the roof to
the liquid. The upper deck is equipped with drainage and seal systems. This
roof design will be buoyant and nonwarping, while providing less available
space for volatilization. The disadvantages of such a system are its weight,
high cost, and difficulty to retrofit to tanks. The primary considerations
involved in selecting a double-deck floating roof system are the tank design,
the roof mass, reinforcement or support system, seal system requirements, and
drainage system.
Internal Floating Roof Tanks—
A floating roof tank which is covered by a fixed roof is defined as an
internal floating roof tank. A tank equipped with this roof type incorporates
design elements of both fixed roof and floating roof tanks described earlier.
Internal floating roof tanks are the most effective in controlling emissions,
as the floating roof greatly reduces working losses, and the fixed roof
2
contains the breathing losses. The types of internal floating roofs used
in such tanks are of the same designs as in external floating roof tanks: pan
roofs, pontoon roofs, and double-deck roofs. The use of pan roofs in internal
floating roof tank, is widespread, as the provision for thermal insulation is
best of the three.
The use of internal floating roof tanks is more widespread at TSDFs than
external floating roof tanks, but not as widespread as fixed roof tanks.
Internal floating roof tanks are particularly applicable to higher volatility,
low molecular weight substances. Design considerations involved in selecting
an internal floating roof tank design are the tank diameter and structural
strength, tank venting requirements, floating roof drainage and seal system,
floating roof reinforcement, and maintenance considerations. Retrofit of an
internal floating roof to an existing fixed roof tank is generally impossible,
but installing a fixed roof on an existing external floating roof tank is the
most commonly performed retrofit control change.
4-14
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Figure 4-3. Double-Deck Floating Roof.
Source: American Petroleum Institute, 1973
(Reference 4).
4-15
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Seal Systems—
Most, if not all, floating roofs employ a vapor seal system. A floating
roof seal is designed to seal the gap between the perimeter of the floating
roof and the tank wall, such that vapors will not escape through the gap to
the atmosphere.3 The seal is attached to the roof, and slides against the
tank wall when the roof moves up and down (as the tanks is emptied or
filled). There are two classifications of seal systems: primary and
secondary. A secondary seal provides additional coverage to the primary
seal. There are differences between the types of vapor seals used on external
and internal floating roof tanks, as described below.
External Floating Roof Tank Seals—
There are basically three types of primary seals used on external
floating roof tanks: mechanical shoe seals, liquid filled seals, and
2
resilient foam-filled seals. These three comprise the majority of vapor
seal designs in use today.
2
Mechanical Shoe Seals— A mechanical, or metallic shoe seal is
characterized by a metallic sheet (the "shoe") held against the vertical tank
wall, as shown in Figure 4-4a. The shoe is connected by braces to the
floating roof and is held tightly against the wall by springs or weighted
levers.
o
Liquid-filled Seals—A liquid-filled seal consists of an envelope,
made either from fabric or flexible polymeric tubing, filled with liquid and
sheathed with a resilient fabric scuff band, as shown in Figure 4-4b. The
liquid is commonly a petroleum distillate or other liquid which will not
contaminate the stored product if the tube ruptures. Liquid seals are mounted
such that they rest directly upon the liquid surface, providing no vapor space
below the seal.
o
Resilient Foam-filled Seal—^A resilient foam-filled seal, as shown in
Figure 4-4c and d, is similar to a liquid-filled seal except a foam log
replaces the liquid. Such a system is mounted on or above the liquid surface,
as shown.
4-16
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RIM-MOUNTED
SECONDARY SEAL.
-TANK WALL
»RIM- MOUNTED
SECONDARY SEAL
FLOATING ROOF
SCUFF BAND
LIQUID-FILLED
TUBE
a. Shoe seal with rim-mounted
secondary seal.
b. Liquid-filled seal with rim-
mounted secondary seal.
-TANK WALL
-RIM-MOUNTED
SECONDARY SEAL
FLOATING ROOF,
SEAL FABRIC
RESILIENT FOAM
LOG
c. Resilient foam seal (vapor-mounted)
with rim-mounted secondary seal.
-TANK WALL
-RIM-MOUNTED
SECONDARY SEAL
FLOATING ROOF
SEAL FABRIC
RESILIENT FOAM
LOG
d. Resilient foam seal (liquid-
mounted) with rim-mounted
secondary seal.
Figure 4-4. Rim-mounted Secondary Seals on External Floating Roofs.
Source: Erikson, 1980 (Reference 3).
4-17
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Secondary seal systems employed on the external floating roof tanks are
quite important, as they provide weather protection to the seal. There are
two types of systems employed: . roof-mounted, or seal-mounted, as shown in
Figures 4-4 and 4-5.
The primary considerations involved in selecting an appropriate seal
system for an external floating roof tank are the type of material being
stored (compatibility with seal materials), size of gap between roof and wall,
tank design (interior reinforcements, tank wall imperfections, and tank weight
capacity), weather conditions, and floating roof design.
Internal Floating Roof Tank Seals—2
Internal floating flexible roofs typically incorporate one oZ two types
of flexible primary seals: resilient foam-filled seals, or wiper seals. The
foam-filled seals are the same as the type used for external floating roof
tanks. Wiper seals, which are the more common type, are simple systems in
which a flexible membrane is used to cover the gap between the roof and the
tank wall. These types of seals are usually vapor-mounted and are either
continuous (one piece extending around the perimeter), or shingled
(overlapping segments extended around the perimeter). Secondary seals are
less common for internal floating roof tanks. The considerations involved in
selecting an appropriate seal system for internal floating roof tanks are the
same as for external floating roof tanks, although weather consideration are
much less significant due to the fixed roof cover.
Vents—
All fixed roof tanks must be equipped with some type of venting system.
Tank vents serve as a protection against structural damage to the tank caused
by a buildup of vapor inside the vapor space, by releasing them to the
atmosphere. Vents may be installed in the roof or the tank walls (above the
maximum liquid level). Many types of vents are used, ranging in
sophistication from simple open vents to pressure-vacuum systems equipped with
flame and flash arrestors. The most common venting system used on tanks is a
conservation vent, which is described in detail below. In general, vents
4-18
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TANK WALL
SECONDARY SEAL
(WIPER TYPE)
Figure 4-5. Metallic Shoe Seal with Shoe-Mounted
Secondary Seal.
Source: Erikson, 1980 (Reference 3).
4-19
-------
are applicable to any tank with a fixed roof. The choice of a vent is
dependent upon tank design and the volatility of tank constituents.
Conservation Vents—
A conservation vent is defined as a system which is designed to release
vapors from a storage tank once the internal pressure reaches a predetermined
point. The set point is based upon the structural characteristics of the
tank. A conservation vent furthermore serves to prevent the inflow of air and
the formation of a vacuum inside the tank. There are three basic designs of
conservation vents: diaphragm, liquid-seal, and metal-to-metal.
Metal-to-metal seals have found the most widespread usage. The primary
considerations involved in selecting an appropriate conservation vent are the
volatility and flammability of the material, tank design, and vent location.
Emission Reduction Effectiveness
The general effectiveness of storage tank roofs in controlling emissions
is considered to be be high. The extent to which emissions from an existing
tank can be reduced depends upon the design chosen. A fixed roof is capable
of reducing emissions from open tanks or external floating roof tanks by
anywhere from 0 to 90 percent depending upon the volatility of the material
being stored, and the use of conservation venting or insulation. A floating
roof is capable of reducing emissions from open or fixed roof tanks by up to
99 percent depending upon the use of primary or secondary seals, venting, and
drainage. Installing secondary seals on a floating roof with an existing
primary seal may result in reductions between 60 to 90 percent depending on
the interior design constraints. Conservation vents have produced emission
reductions of up to 90 percent in fixed roof tanks.
Costs
The installation of a new tank, new roof, or associated system is
considered to be a highly expensive. The high costs involved are largely
based on capital costs (materials) and construction, and the associated design
work needed. The costs vary according to the size requirements, materials
used, and input and output considerations.
4-20
-------
Fixed roof tanks are the most widely varied design in terms of costs.
Simple fixed roof tanks of small dimensions are relatively inexpensive, while
high pressure tanks are the most expensive. Costs are dependent upon the
materials used, and the structural support considerations. Retrofitting a
fixed roof onto an existing tank is considered to be essentially as expensive
as constructing a new tank. Estimated costs (1980) for fixed roof tanks are
shown in Table 4-2.3 In March 1985 dollars, fixed roof tank costs range
from $36,000 to $281,000 for the size range indicated.
Floating roof tanks are somewhat more expensive to build than fixed roof
tanks, due to greater complexity involved in the roof design. Installation of
a floating roof on an existing tank, however, is much simpler and less
expensive than is the installation of a fixed roof due to their simpler design
and structural considerations. The costs of a floating roof are dependent
upon the design selected, materials, installation, and maintenance
requirements (more maintenance is required for floating roofs than for fixed
roofs). Table 4-3 presents construction costs for external floating roof
tanks. In March 1985 dollars, these costs range between $55,700 and
$295,000.
Estimated costs (1980) of installing an external floating roof with
primary seal for contact and noncontact designs are shown in Tables 4-4
and 4-5. In March 1985 dollars these costs range from $7,800 to $57,800
for contact roofs, and $6,300 to $41,800 for noncontact roofs.
The costs involved in installing a seal system on a floating roof are
dependent upon the design selected, materials, installation, and maintenance
requirements. MITRE estimated that the typical cost of retrofitting a
(secondary) seal system would range from $29 to $38 per linear foot of
circumference.
Conservation vents are the least expensive of the options described in
this section, due to their relative design simplicity and ease of
installation. MITRE estimated that a typical vent may cost between $540 to
$4,300 (in present day value) or approximately $0.01 to $0.09 per gallon of
capacity.
4-21
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TABLE 4-2. COST OF BUILDING A FIXED-ROOF TANK2
Diameter
(ft)
20
40
45
50
60
70
80
90
Height
(ft)
24
40
40
40
40
40
40
40
Installed cost3
26,000
63,000
73,000
89,000
113,000
139,000
168,000
202,000
aCosts in first quarter 1980 dollars.
Source: Erikson, 1980 (Reference 3).
4-22
-------
TABLE 4-3. COST OF BUILDING AN EXTERNAL FLOATING
ROOF TANK
Diameter
(ft)a
30
35
42.6
52
60
67
73.4
100
Height
(ft)
24
30
40
40
40
40
40
40
Installed costb
40,000
54,000
81,000
117,000
126,000
140,000
153,000
212,000
aCost of adding a secondary seal per foot
of circumference is $13.50.
bCosts in first quarter 1980 dollars.
Source: Erikson, 1980 (Reference 3).
4-23
-------
TABLE 4-4. COST OF INSTALLING A CONTACT SINGLE
SEAL INTERNAL FLOATING ROOF
Diameter
(ft)«
15
20
25
30
35
40
45
50
55
60
65
70
75
80
85
90
Installed cost
U)b
5,630
6,485
7,510
8,780
10,280
11,970
14,180
16,190
19,630
21,480
25,120
27,770
31,240
34,360
37,910
41,530
aCost of adding a secondary seal, per foot
of circumference is $11.85.
bCosts in first quarter 1980 dollars.
Source: Erikson, 1980 (Reference 3).
4-24
-------
TABLE 4-5. COST OF INSTALLING A NONCONTACT SINGLE
SEAL INTERNAL FLOATING ROOF
Diameter
(ft)a
15
20
25
30
35
40
45
50
55
60
65
70
75
80
85
90
Installed cost
($)b
4,500
6,000
7,300
9,300
10,000
12,000
13,300
14,700
16,500
17,400
19,700
21,500
23,500
25,200
27,800
30,000
alnstalled cost of adding a secondary wiper
seal per foot of circumference is $22.50.
^Costs in first quarter 1980 dollars.
Source: Erikson, 1980 (Reference 3).
4-25
-------
COVERS
Introduction
A cover is defined as any system which limits or prevents the
volatilization of material from a storage tank by acting as a barrier between
the volatile substances and the atmosphere. Covers, unlike roofs, are not
designed to be permanently affixed to a storage tank. Such systems,
therefore, are generally applied only to open or fixed roof tanks. A wide
variety of covers are available. Covers which have found application as
storage tank emission control devices include:
• Floating blankets;
• Floating spheres;
• Rafts;
• Surfactant layers; and
• Nitrogen blankets.
Use of covers for storage tanks is not as prevalent as that of roofs for
controlling emissions. This subsection will present examples of systems
which are in use or have been proposed for use at TSDFs.
Description
A cover serves to limit the emission of volatile substances from storage
tanks by acting as a barrier to volatilization, reducing volatility, and/or
insulating the substances from external forces such as heat, light, wind, and
precipitation, which serve to increase volatilization. All covers are applied
such that much of the liquid surface area is covered. Covers can either be
placed directly upon the liquid surface, on floats or pontoons just above the
liquid surface, or over the top of (open) tanks. The following considerations
must be made in determining the applicability of a cover system to a specific
storage tank at a TSDF.
4-26
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• Type of material to be stored. The chemical and physical properties
of the material to consider include, volatility, chemical
compatibility, and density.
• Design of storage tank. The diameter, weight capacity, inflow/
outflow pipe locations, and interior structural design (e.g., of
columns or bracings) of the tank.
• Storage procedures. The tank turnover rate (number of times emptied
and filled per year), tank usage, filling procedures, and tank level
preference are among the procedural factors.
• Weather conditions. Wind, sun, and precipitation patterns of the
local area.
• Manpower requirements. The availability of trained personnel for
maintenance or operating procedures.
All cover systems contain certain limitations which must be evaluated
against factors such as emission reduction efficiency, cost, and ease of
implementation. The cover systems introduced above have been demonstrated to
be the most applicable to storage tank emission control according to the above
criteria.
Floating Blankets—
Floating blanket covers perform similarly to pan-type floating roofs.
Resting directly upon the liquid surface, the flat covers apply pressure to
the liquid, thus eliminating vapor space and reducing breathing losses. As
the tank is filled and emptied, the cover rises and falls, thus reducing
working losses. Floating blankets are usually made from lightweight
synthetics, such as polyvinyl chloride. The blanket underside is constructed
of a large number of floats made from the same plastic material.^ The
blankets are commonly made so that only a very small gap will remain around
the periphery. Most floating blanket systems also employ a vertical skirt
around the edge to serve as a vapor seal over the annular area.-' Design
features to be considered in selecting the most appropriate floating blanket
design are the size and shape of the surface to be covered, the chemical
compatibility and vapor permeability of the synthetic material, the drainage
of liquid from the top of the cover, and the system weight.
4-27
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Floating blankets present certain advantages over a floating roof design.
They are lightweight, more flexible, will not sink, warp, or corrode, and are
removable. To date, these systems have found greater application in foreign
markets.
Floating Spheres—
Another way that lightweight plastic materials are used as a cover is in
the form of hollow plastic spheres. Floating spheres also perform similarly
to pontoon roofs, although they are far more fluid. Floating spheres will
cover approximately 90 percent of the available surface area, independent of
the sphere diameter. Because they are hollow, they will also act as dead air
insulators. Floating spheres are commonly made from either high molecular
weight polyethylene or polypropylene. Size ranges vary from microscopic to
6 inches in diameter. ' Common designs employ an antirotational collar so
that the spheres will interlock over the liquid surface and will not be
subject to natural or forced convection currents turning the wet sides of the
spheres to the air. (See Figure 4-6.)
Normally, only one layer of spheres is used to cover the liquid
surface. In certain cases, however (e.g., for highly toxic and/or volatile
substances), more than one layer is used. It has been demonstrated, that each
successive layer of spheres added is less effective, as the added weight
increasingly submerges the bottom layer. The considerations involved in
selecting the appropriate floating sphere cover are the diameter of the tank,
the size of the spheres, the number of layers, and the spheric material.
Floating spheres have several advantages over roofs or other cover systems.
They are more fluid and can, therefore, be used in any tank, they are good
insulators, will not sink, need no drainage system, and are removable.
Floating spheres have found a variety of applications including crude oil
waste storage, solvent storage, and at a European wastewater treatment
plant.
Rafts—
A raft is defined as any device which floats freely upon the liquid
surface. Rafts perform similarly to pan-type floating roofs. Rafts are
available in two designs, including foam blocks (the most common type) and
4-28
-------
I
ro
Figure 4-6a. Interlocking configuration.
Figure 4-6b. An uncovered cleaning tank emits
large volumes of corrosive acid
steam.
Figure 4-6c.
Source: Capricorn Chemicals.
A single layer of ALLPLAS balls
floating on the surface of the
same temperature, virtually
eliminates acid steam emission.
-------
membranes attached to a frame. An example of the foam block system is shown
Ln Reference 9.
A raft can be made from any kind of material. Styrofoanii polyethylene,
aluminum bonded to polyethyelne, butyl rubber, and floating concrete have all
O Q
been field tested. A raft can be made in any shape or thickness.
Several rafts may be used on one surface. They are easily installed and
maintained. Many rafts are coated with reflective material to decrease their
transmissivity of heat to the liquid.
The considerations involved in selecting an appropriate raft design are
the size and shape of the tank, chemical compatibility, raft insulating
capacity (related to thickness and color), number of rafts to be used, and the
drainage system. Rafts have the advantage of being lightweight, easy to
install and maintain, buoyant, nonwarping, and removable. Rafts have found
only limited application as a storage tank cover system, but have been used
extensively on surface impoundments.
Surfactant Layer—
A layer of liquid with which the volatile substances in storage are
immiscible may be applied as a cover. A floating liquid cover serves to limit
emissions in much the same way as other floating covers. As long as the layer
is maintained, volatiles can only be released if they diffuse through the
liquid barrier. The choice of a particular liquid for this application is
strongly dependent upon the materials being stored. Among those materials
cited in the literature were water (used in the storage of ethylene
dichloride) and lubricating oil (acrylonitrile wastewater). In such a
system, no vapor seals or drainage systems are needed.
The considerations involved in selecting a liquid cover system are
chemical compatibility, weather conditions, and layer regeneration method.
Use of a surfactant layer can be desirable due to the adaptability to any
shape or size tank, the completeness of coverage with no required
appurtenances, and the ease of implementation. The use of such a system,
however, has been quite limited.
Nitrogen Blanket—6
Nitrogen, or any other inert gas, may be maintained in the vapor space of
a tank as a cover system. Nitrogen blanketing works to control emissions by
4-30
-------
applying a slight positive pressure in the tank, thus inhibiting
volatilization. Like a surfactant layer, a nitrogen blanket acts as an
ultimately adaptable floating roof. Nitrogen blankets are mainly applicable
to fixed roof tanks. A small generating unit is required, to maintain the
blanket. Application of nitrogen is limited by the internal pressure
constraints in the tank.
The considerations involved in such a system are the design of the tank,
chemical compatibility, operation of nitrogen generators, and weather
conditions (particularly, temperature fluctuations). Nitrogen blankets are
especially applicable to highly reactive, highly volatile substances.
Overall, nitrogen blankets have the advantage of adaptability, completeness of
cover, inertness, and low equipment cost and maintenance.
Emission Reduction Effectiveness
In general, covers are expected to be a relatively effective means of
emission control. The effectiveness of such control systems has not be
studied in detail, due to constraints encountered in making emission tests on
tanks. The extent to which emissions from any tank may be reduced by a
specific cover system is highly dependent on the tank design (in particular,
the diameter and the structural characteristics), and the tank constituents.
In general, those cover systems which are the most flexible, limit
available liquid surface area the most, and are least subject to wind, and
other weather conditions will perform best. Thus, while floating spheres
might reduce emissions up to 90 percent, a floating surfactant layer, which
is subject to being dissipated by wind, might only reduce emissions by 25 to
75 percent. Nitrogen blanketing is estimated to be potentially the most
effective cover system, ranging from 50 to 99 percent reduction
efficiency. Rafts, similar in performance to floating spheres and blankets,
are estimated to range up to 90 percent in effectiveness.1 These estimates
are approximate. Other data accumulated by Cooley are presented in
Cl
Table 4-6. The basis of these estimates is the percentage of surface area
covered, and the vapor permeability of the covers. Covers are not expected to
4-31
-------
TABLE 4-6. EVAPORATION REDUCTION ACHIEVED BY VARIOUS ENERGY-REDUCING METHODS
Method
Area of water
surface covered,
as a percentage
Evaporation
reduction,
as a percentage
4>
OJ
1. Changing the water color:
Dye in water
Shallow, colored pans
2. Using wind barriers:
Baffles
3. Shading the water surface:
Plastic mesh
Blue polylaminated plastic
sheeting
4. Floating covers:
100
100
47
100
Evaporation from white pan compared with that from black pan.
Source: Cooley, 1983 (Reference 8).
6-9
35-50a
11
44
90
Perlite ore
Polystsyrene beads
Wax blocks
White spheres
White butyl sheets
Polystyrene sheets
Polystyrene rafts
Polystyrene wax
Foamed rubber
78
78
78
78
86
80
100
100
95
19
39
64
78
77
79
95
87
90
-------
perform as effectively as either vapor control systems or roofs, but are less
costly and easier to implement at an existing facility.
Costs
Cover systems are generally considered to be less expensive than roof
systems to implement at a storage tank facility. The costs of such systems
are strongly dependent upon the cost of materials and maintenance. Labor,
operation, and installation costs are considered to be relatively low.
Detailed cost estimates are highly dependent upon various design and materials
considerations (tank sizes, cover materials, etc.).
The cost of floating blanket covers is primarily dependent upon the
synthetic material selected. The estimated average cost of a synthetic cover
(as applied to a surface impoundment) is $1.48 to $3.26 per square foot.
(1985 dollars).
Floating spheres are available in a variety of sizes, and basically two
materials, polypropylene and polyethylene. The number of balls required for
coverage of a storage tank can be determined by geometry. Table 4-7, provides
some example requirements. Table 4-8 shows that the estimated average cost
for a cover of floating spheres ranges from $4.65 to $13.50 per square foot of
internal surface area.
Cost of raft system would be similar to floating sphere system, as both
only involve materials costs. A typical foam block raft system was estimated
at $130 to $210 for a medium size facility (25 ft diameter).1
The cost of a surfactant layer is dependent upon the surfactant chosen,
and application procedure. Cost is regarded as a primary factor in the choice
of a surfactant chemical for this application. MITRE estimated a cost of
0.09 cents per square foot (updated to 1985 dollars) for similar application
on a surface impoundment.
The cost of a nitrogen blanketing system is dependent upon nitrogen
consumption (dependent on tank capacity), and costs of nitrogen storage and
delivery equipment. The estimated annual installed cost of such a system is
$0.11 to $0.33 per gallon of tank capacity (Updated to 1985 dollars).^
4-33
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TABLE 4-7. NUMBER OF FLOATING SPHERES REQUIRED PER UNIT AREA AND VOLUME
Spheric size/
Quantity
Quant ity/m2
Quantity/ ft2
Quantity/m^
Quantity/ ft-*
20 mm
(3/4 in.)
2.500-3.000
230-280
165.000-167.000
4.670-4.730
38 mm
(1-1/2 in.)
750-800
75-85
24.500-25.000
690-710
45 mm
(1-3/4 in.)
500-575
45-55
14.500-15.000
410-425
150 mm
(6 in.)
45-50
4-5
350-400
10-11
Source: Capricorn Chemicals, 1985. (Reference 7K
4-34
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TABLE 4-8. COSTS OF VARIOUS TYPES OF FLOATING
SPHERES
Cost ($/ft2)
Polypropylene
Diameter 1-3/4 inches 4.65-6.55
Diameter 6 inches 7.50-8.69
High Density Polyethyelne
Diameter 1-3/4 inches 6.75-7.55
Source: A. D. Little, 1984 (Reference 1).
4-35
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INSULATION
Introduction
Any system or device which serves to reduce the effects of climatological
forces such as sunlight, ambient temperature fluctuation, wind, and
precipitation on storage tanks and tank constituents may be defined as a tank
insulation system. These forces serve to increase tank breathing losses by
increasing the volatility of constituents and/or by providing a transport
mechanism for emissions to enter the atmosphere. Insulation systems are
highly simplistic in design, and as a result, have found widespread
application. Mo«5t storage tanks are insulated in some way. The three
methods of tank insulation which have found the most widespread application
are:
• Thermal insulation;
• Reflective paint; and
• Wind barriers.
Description
Insulation systems form a barrier to the external forces described
above. Each of the insulation systems can be applied directly to the storage
tank, require little to no additional maintenance, and occupy very little
space. The following considerations must be made in selecting the
appropriate insulation system.
• Weather conditions. The affect of extreme heat, wind, or
precipitation on the insulation system.
• Storage tank design. The height, shape, and diameter of the tank
may.
• System design. The weight, height, and other complexities of the
insulation system.
4-36
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• Storage area. The area layout, and space for the insulation system.
Thermal Insulation^--
Thermal insulation systems may be applied to the sides and tops of
storage tanks. The insulation material serves to reduce the temperature
fluctuation of storage tank constituents, even when ambient conditions vary.
Various types of systems are employed, including both flexible and rigid
polymeric foam, and venniculite concrete. The most common materials in use
at TSDFs are spray-applied polyurethane foams and rigid polystyrene
12
foams. Design considerations involved in selecting a thermal insulation
material are the available surface area to be covered, tank wall material
(ease of applying insulation), weather conditions, insulation thickness, and
the total applied weight of the system.
Fresh Painted Tanks—
Fresh paint may also be applied to the sides and tops of storage tanks.
New paint will have the effect of reducing emissions by providing a better
more reflective outer surface. The two colors most commonly applied to
storage tanks are white and silver. A painted tank has been demonstrated
to emit less than an identical unpainted one (see Table 4-9). The factors
which are to be considered in selecting a new paint for storage tanks are the
chemical compatibility of paints with emitted materials, maintenance
requirements and, most importantly, sun conditions.
Wind Barriers—
Wind barriers are devices installed on or around storage tanks which
serve to reduce the flow of wind affecting a tank. Wind increases storage
tank emissions by three mechanisms, including: (1) increasing surface
turbulence inside a tank (particularly in the case of open tanks), leading to
greater volatilization of liquid; (2) sweeping vapor out of a storage tank as
wind flows over or through the tank vapor space; and (3) creating a pressure
differential leading to emissions via forced convection as wind flows over a
tank or tank vent. Barriers may be installed on a tank or around a tank.
The most common design is a barrier installed at the top of a tank, around the
4-37
-------
TABLE 4-9. RELATIVE EFFECTIVENESS OF PAINTS IN KEEPING TANKS
FROM WARMING IN THE SUN (NELSON, 1953).
Color
Relative effectiveness
as reflector or
rejector of heat (%)
Black
No paint
Red (bright)
Red (dark)
Green (dark)
Red
Aluminum (weathered)
Green (dark chrome)
Green
Blue
Gray
Blue (dark Prussian)
Yellow
Gray (light)
Aluminum
Tan
Aluminum (new)
Red iron oxide
Cream or pale blue
Green (light)
Gray (glossy)
Blue (light)
Pink (light)
Cream (light)
White
Tin plate
Mirror or sun shaded
0
10.0
17.2
21.3
21.3
27.6
35.5
40.4
40.8
45.5
47.0
49.5
56.6
57.0
59.2
64.5
67.0
69.5
72.8
78.5
81.0
85.0
86.5
88.5
90.0
97.5
100.0
Source: AP-40 (Reference 5).
4-38
-------
perimeter.14 Various types of barriers are used for this purpose, including
"cyclone" fences,; corrugated steel walls, and other, more complex designs.
Wind barriers are particularly applicable to open or external floating
roof tanks. They have not found widespread use at TSDFs for control of air
emissions from storage tanks, however. The considerations involved in
selecting a wind barrier system for storage tank control are the tank
structural requirements, prevailing wind conditions (direction, magnitude),
availability of space, and the height and design of the barrier.
Emission Reduction Effectiveness
Insulation systems are simple, and easy to install. However, the
effectiveness of such systems in reducing emissions, however, is relatively
low (compared to other add-on controls). This is primarily due to the fact
that they are chiefly designed to reduce breathing losses, which are generally
not as significant as working losses. Information on the effectiveness of
such controls is also limited.
Thermal insulation systems are generally quite effective in reducing, if
not eliminating, thermal fluctuations. The effectiveness of such systems is
dependent upon the thickness of the insulation layer, and amount of tank area
covered. Insulation effectiveness is also limited by the "gradual absorption
and permeation of moisture through the insulation. (See Table 4-10). The
thermal performance of several insulation materials is shown in Table 4-11.
MITRE estimated that the effectiveness of insulation in emission reduction
ranges from 50 to 99 percent."
The application of reflective paint is limited in its effectiveness as an
emission reduction technique. As shown previously in Table 4-9, effectiveness
varies widely with paint color. However, since the paint itself is a
relatively thin layer, heat energy will be transmitted to the tank. AP-40
reported that the emission reduction achieved, for example, by use of aluminum
paint (over black paint) was 25 percent based on data gathered by the American
Petroleum Institute.
Wind barriers have been used in many different ways (see Sections 5 and 8
in the document) at TSDFs. The effectiveness of such devices depends strongly
4-39
-------
TABLE 4-10. PERMEABILITY AND MOISTURE ABSORPTION
Insulation
material
FOAMGLAS®
Urethane
Polystyrene
Phenolic
Fiberglass
Mineral fiber
Calcium silicate
Expanded perlite
aPerm . Inch is the
permeability.
1 Po Tin . T«^.U — _
Permeability
Perm . Incha
0
1-3
0.5-4
6-7
75
150
NA
NA
accepted unit
1 Grain .
Absorption
% by Vol.
0.2b
1.6
0.7
10.0
65.0
70.0
75.0
16.0
of water vapor
Inch
Ft . Hr . Inch of Mercury
only moisture retained is that adhering to
surface cells after immersion.
Source: Pittsburgh Corning Corporation, 1985
(Reference 15).
4-40
-------
TABLE 4-11. PUBLISHED THERMAL PERFORMANCE
Thermal
Insulation
material
FOAMGLAS
Urethane
Polystyrene
Phenolic
Fiberglass
Mineral fiber
Calcium silicate
Expanded perlite
Maximum
use
temp.
(°F)
9003
200-225
175
250
450
1800
1200
1500
conductivity
Btu'In./
Hr . F . Ft2
-100
0.27
0.14
0.18
0.19
0.16
NA
NA
NA
+200
0.42
0.25
NA
0.26
0.30
0.35
0.42
0.47
limitation when used alone.
Source: Pittsburgh Corning Corporation, 1985,
(Reference 15).
4-41
-------
on prevalent wind patterns. While no direct measurements have been published
relative to the emission reduction effectiveness of wind barriers for storage
tanks, Runeha1 estimated that the reduction effectiveness would range from 22
to 50 percent. ^
The costs of insulation systems are generally regarded as being low,
relative to other add-on control systems. The costs generally involve only
materials and installation.
Thermal insulation costs vary widely depending on the materials used.
Costs are also dependent upon the thickness and percentage of surface area
covered. Based on estimates made by MITRE, the cost of thermal insulation
ranges from $0.65 to $0.76 per inch thickness per square foot of tank area,
plus an additional $1,00 to $1.25 per square foot for protective coating.
Painting costs are also widely variable. The costs depend on the type of
paint selected, application method, and labor costs. In general, painting is
regarded as a low-cost measure to effect control. A representative of Chevron
USA Inc. estimated that the average storage tank paint job costs between $500
and $3,000 per tank.14
Wind barrier costs are also regarded as being relatively low. These
costs depend upon the type of fence selected, height of fence, and
installation labor. An estimate of the cost of wind screens (as applied to
waste piles) is $2.00 to $2.50 per square foot of fence area (1982 dollars).^
VAPOR CONTROL SYSTEMS
Introduction
Vapor control systems control the emission of volatile substances from
storage tanks by evacuating vapors which form, and processing them physically
or chemically. Vapor control systems are the most complex and costly of
storage tank controls, but are the most effective at reducing emissions. Use
of vapor control on storage tanks is widespread, particularly in chemical
4-42
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processing. The three vapor control systems which are most commonly used
for storage tank emission control are:
• Vapor condensation;
• Carbon adsorption; and
• Fume incineration.
Description
The primary function of a vapor control system is to remove vapors which
form in a storage tank, by some physical or chemical process such that they
will not enter the environment. Such systems are equally effective at
controlling working or breathing losses, as any vapor which forms is evacuate
from the tank. All vapor control processes contain at least three steps:
(1) evacuation;
(2) vapor processing; and
(3) recycle or venting of products.
Use of vapor control requires that the storage tank be enclosed in some
manner. Thus, vapor control is applicable only to tanks equipped with fixed
roofs. Vapor control systems require the installation of ductwork, the
location of unit processing equipment in readily serviceable areas, and
equipment for disposing of products and materials. Vapor control has found
widespread application, particularly in the control of highly volatile and/or
toxic substances, due primarily to the high emission reduction efficiencies
that can be achieved. While the system designs may be relatively complex, the
unit processes are simple, utilizing physical or chemical properties such as
the vaporization point, adsorbability, or combustibility. The following
factors should be considered when determining the applicability of a
particular vapor control system to a certain storage tank or tanks.
4-43
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• Properties of the tank constituents including the volatility,
adsorbability on carbon or other substrates, and combustibility.
• Number of tanks to be serviced and the total capacity to be served
by the vapor control system.
• Manpower and materials requirements including maintenance, operating
labor, and materials required by the vapor control system.
• Availability of space which would affect the location of the vapor
processing unit, and attendant ductwork and systems.
The three most common vapor control systems, described in detail below,
have found widespread application.
Vapor Condensers—
Vapor condensation systems prevent emissions of volatile substances by
recondensing vapor which form in a storage tank. Condenser systems are the
most widely used form of vapor control for storage tanks. Condensers work
by extracting heat from the vapors either by contacting them with a coolant
(contact-type) or with a cooled surface (surface-type). Contact-type
condenser are not generally used for control of TSDF emissions, due to
chemical compatibility and waste handling considerations. The most common
type of condenser is the "shell and tube" type, as shown in Figure 4-7. In
this system, vapors are passed through a chamber which contains thin tubes.
Coolant is passed through the tubes, and cools the metal surfaces, which in
turn cool the vapors as they flow around the tubes. A variety of coolants are
used, depending upon the volatilization point of the vapors, including chilled
3
water, air, or freon.
Shell and tube condensers are commonly oriented horizontally, but some
designs orient them vertically. Coolant flow can either be countercurrent or
concurrent with vapor flow direction. It is common to install baffles in the
shell side of a condenser; or to design the condenser with more than one
chamber (pass), in order to increase the contact time between vapors and
tubes.
The considerations involved in selecting an appropriate condenser system
for control of storage tanks are the operating temperature range, coolant
type, number of condenser tubes, baffles or passes, refrigerant storage and
handling, and condensate and vapor recycle or handling. Condensers have
4-44
-------
COOLANT
INLET
VAPOR
OUTLET
VAPOR
INLET
COOLANT
OUTLET
INCOMING
VAPOR
, VENT
S_m
COOLANT
RETURN
COOLANT
SUPPLY
REFRIGERATION
UNIT
n
VENT
RECOVERED
TO STORAGE
RECOVERY
TANK
PUMP
Figure 4-7. Refrigerated Vent Condenser System.
Source: Erikson, 1986 (Reference 3).
4-45
-------
several advantages over other vapor control systems. They require less
maintenance, less materials and operating costs, they are considered to be
safer and less subject to process upset, and are more adaptable to different
types of vapors. A condenser can be used to selectively recover materials, if
desired. Condensers are generally less effective in reducing emissions,
however, and require additional facilities for coolant storage and handling
that other vapor control systems do not.
Carbon Adsorption—
Carbon adsorption systems prevent emissions of volatile substances by
removing vapors which form in a storage tank via adsorption onto carbon.
Carbon adsorption is not as widely used as vapor condensation for storage tank
control, but have found use at TSDFs both for controlling tank emissions and
emissions from other unit processes such as surface impoundments. Adsorption
devices utilize carbon's affinity for nonpolar organic compounds.
As shown in Figure 4-8, vapors are passed over beds of activated carbon.
The vapors adsorb onto the carbon, and exit the beds to either be recycled to
the adsorber or vented as clean air. Gradually, the adsorption capacity of
the carbon beds is reduced, until the beds become saturated with organic. At
that point, the beds are regenerated by passing steam through them. Multiple
carbon beds are often used, such that some beds may be used while others are
regenerated.
Adsorption system generally employ activated carbon, but recent
advancements in resin adsorption have begun to result in their increasing
usage for emission control. Adsorption systems range in complexity from
simple designs in which vapors are passed through drums filled with carbon, to
full scale systems employing multiple carbon beds as illustrated in
Figure 4-8. Adsorption can be carried out as a single-pass or multiple-pass
operations and carbon beds may be baffled to increase vapor residence time.
The most common system in use for storage tanks is the simple
"barrel"-type adsorbers^. These are used because it is considered safer to
control tanks individually than collectively (interconnected tank systems are
subject to increased risks of fire and explosion).
The considerations involved in selecting an appropriate carbon adsorption
system for control of storage tanks are the operating temperature range,
4-46
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LOW- PRESSURE
STEAM
PROCESS
BLOWER
VAPOR-LADEN
AIR STREAM
AMBIENT
AIR
CLEAN AIR
EXHAUST
ADSORBER I
i
J'
-1^
y
J.
ACTIVATED CARBON
JT
$ ADSORBER 2
ACTIVATED CARBON
\
^
-t
p
_f
-txl-
COOLING and
DRYING BLOWER
COOLING •
WATER
RECOVERED
SOLVENT
WASTE
WATER
Figure 4-8. Activated-Carbon Adsorption System.
Source: Erikson, 1980 (Reference 3).
4-47
-------
chemical compatibility and adsorbability of materials, number and sizing of
beds, regeneration and adsorbate handling systems, and carbon life span.
Carbon adsorbers have several advantages over other vapor control systems.
They can achieve higher emission reduction efficiencies, are relatively safe
and easy to operate, and are adaptable to different volatile organics. The
materials, energy, and maintenance costs are high for such systems, however,
and they also require additional facilities for steam regeneration.
Fume Incineration—
Fume incineration (thermal oxidation) systems prevent emission of
volatile substances by changing materials chemically via oxidation.
Incineration systems are not used as extensively as either vapor condensation
or carbon adsorption for control of storage tanks. They are most commonly
used in combination with a more significant process vent emission control
system. Incinerators work by utilizing a vapor's combustibility. As shown
in Figure 4-9, vapors are mixed with air, injected to a burner where a pilot
source ignites the air-vapor mixture, and a supplementary fuel burner
maintains flame temperature, and products are vented to the atmosphere.
Incineration systems may be either small units servicing one tank, or
large units serving an entire TSDF. There is little variation in the basic
design for incinerators. The considerations involved in implementing an
incinerator system for storage tank emission control are the vapor composition
and flow rate, combustion temperature, incinerator fuel, incinerator venting
control, and the number of tanks to be serviced.
The advantages of using fume incineration are the high efficiencies
achieved, the lack of attendant systems required, and the elimination of
volatile compounds (thus, no emissions will be caused by compounds which are
recovered). However, incineration requires high operating costs (due to
energy consumption and greater safety risks.
4-48
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OUTLET VAPOR
PILOT
BURNER
VAPOR
BURNER
I
STACK
MAIN BURNER
FUEL
S VAPOR SOURCE
AIR DAMPER
WATER SEAL
Figure 4-9. Thermal oxidation unit.
Source: Erikson, 1980 (Reference 3).
4-49
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Emission Reduction Effectiveness
Vapor control systems have found widespread application for control of
storage tank emissions, primarily because of the high reduction efficiencies
they can achieve. Vapor control systems are generally regarded as the most
effective means of controlling highly volatile substances. The percent
reductions achieved by an individual system is dependent upon design and
operating parameters, e.g., cooling temperature or tank exhaust flow rate.
Condensers are suitable for any volatile substance. Most condensers
utilize chilled water, at a temperature within the -5°C to 10°C range. The
effectiveness of a condenser is directly proportional to the surface area of
cooled tubes which contact the vapors to condense them. A typical condenser
system is estimated to reduce emissions by 85 to 95 percent.
Carbon adsorbers can be used for the control of volatile organic
compounds. When large-scale adsorber systems are utilized (controlling a
group of storage tanks), the system involves several units both in series and
in parallel. The effectiveness of carbon adsorption systems is directly
proportional to the length of time organic vapors are in contact with
activated carbon. The individual-type "barrel" systems, which are more
commonly used for the control of single storage tanks, are designed up with
two or more units in series. The effectiveness of carbon adsorption has been
estimated at a reduction efficiency range of 85 to 97 percent.
Fume incinerators can be used to control any combustible (oxidizable)
volatile substance. Generally the small systems winch are employed for the
control of an individual storage tank operate continuously. The effectiveness
of vent incinerators is dependent upon the combustibility of the exhaust gas.
Fume incinerators are estimated to be 85 to 99 percent efficient in reducing
6
emissions.
Costs
Vapor control systems are the most complete systems in use for control of
storage tank emissions and, as a result, are the most expensive. The costs
elements of such systems include design, construction, installation,
4-50
-------
material, storage, maintenance, energy, and labor. These costs depend
primarily upon the design of tanks, number of tanks to be serviced, type of
substances to be controlled, and materials handling considerations.
Condensers are more expensive than the small, individual storare tank
carbon adsorption or fume incineration units, and are much less expensive than
the larger carbon adsorption or vapor incineration systems. The cost of a
condenser is dependent on the vapor flow rate, and the heat transfer surface
area. Hall et al. estimated the costs of a variety of tank vent condensers to
be between $2,000 and $19,000 (in March 1985 dollars).17 The operating
costs, including power consumption, maintenance, and service were estimated at
approximately $10,000 annually.
Carbon adsorption systems used to control storage tank emissions vary
widely in cost between the large systems and the individual "barrel" type
units. In general, large systems, which can cost up to $300,000 (in March
9
1985 dollars) to install and operate, are not used to control TSDF storage
vessels. Individual units are totally self-contained systems which can be
easily installed as purchased. These systems have an expected lifetime of
6 months, depending upon the vapor exhaust flow rate. Many facilities use two
or more in series and/or parallel to handle the exhaust capacity. Such a
design scheme allows for continuous control if a particular unit needs to be
replaced. The cost of such units was reported by a supplier at $670 and $920
per unit, depending on model type selected (the more expensive unit is capable
of controlling hydrogen sulfide and acid gases). Activated carbon
suitable for adsorption of gas phase volatile compounds, may be purchased in
bulk for approximately $1.00 to $1.50 per pound.
Fume incinerators, similar to carbon adsorption systems, vary widely
between the large-scale systems and the individual tank units. The
large-scale systems may cost as much as $300,000 or more to install and
r\
operate (March 1985 dollars), but are not commonly used at TSDFs for
storage tank emission control. The cost of a small fume incinerator was
estimated by MITRE at $7,500 to $11,000 per tank (March 1985 dollars).6
Costs of such systems are highly dependent on vapor exhaust flow rate,
ignition fuel usage, and combustion temperature.
4-51
-------
REFERENCES FOR SECTION 4
1. Arthur D. Little, Inc. Evaluation of Emission Controls for Hazardous
Waste Treatment, Storage, and Disposal Facilities. EPA-450/3-84-017.
U.S. Environmental Protection Agency, Office of Air Quality Planning and
Standards, Research Triangle Park, NC. November 1984.
2. USEPA, Office of Air Quality Planning and Standards. Benzene Emissions
from Benzene Storage Tanks-Background Information for Proposed
Standards. EPA-450/3-80-034a. U.S. Environmental Protection Agency,
Office of Air Quality Planning and Standards, Research Triangle Park,
NC. December 1980.
3. Erikson, D.G. Storage and Handling, Report I in Organic Chemical
Manufacturing, Volume 3: Storage, Fugitive, and Secondary Sources.
EPA-450/3-80-025. U.S. Environmental Protection Agency, Office of Air
Quality Planning and Standards, December 1980.
4. API. Evaporation Loss in the Petroleum Industry - Cause and Control.
API Bulletin 2513. American Petroleum Institute, Washington, D.C. 1973.
5. USEPA, Office of Air Quality Planning and Standards. Air Pollution
Engineering Manual, Second Edition. AP-40. U.S. Environmental
Protection Agency, Office of Air Quality Planning and Standards, Research
Triangle Park, NC. 1973.
6. Vogel, G. A., and D. F. O'Sullivan. Air Emission Control Practices at
Hazardous Waste Management Facilities. MTR-83W89. Prepared for U.S.
Environmental Protection Agency, Office of Solid Waste, Contract
No. 68-01-6092, The MITRE Corporation, McLean, VA. June 1983.
7. Capricorn Chemicals Corporation, Secaucus, NJ. Sales Literature, 1985.
8. Cooley, K. R. Evaporation Reduction: Summary of Long-Term Tank
Studies. J. Irrigation and Drainage Engineering 1(109). March 1983.
9. Sandberg, H. W. PTFE-coated Foamed Glass Blocks Form a Floating Cover
that Prevents Acid Emissions. Chemical Processing. February 1982.
10. Key, J. A., and F. D. Hobbs. Ethylene Dichloride. Report I of Organic
Chemical Manufacturing, Volume 8: Selected Processes.
EPA-450/3-80-028c. U.S. Environmental Protection Agency, Office of Air
Quality Planning and Standards. October 1980.
4-52
-------
11. Cudahy, J. J., and R. L. Standifer. Secondary Emissions Report.
Report 3 of Organic Chemical Manufacturing, Volume 3: Storage, Fugitive,
and Secondary Sources. EPA-450/3-80-025. U.S. Environmental Protection
Agency, Office of Air Quality Planning and Standards. June 1980.
12. Bragg, R. W., W. R. Grace and Company, Construction Products Division,
Cambridge, MA. Communication with M. Kravett, GCA Corporation, March
1985.
13. Runchal, A. K. Hydrocarbon Vapor Emissions from Floating Roof Tanks and
the Role of Aerodynamic Modifications. J. Air Pollution Control
Association, 28(5) :498-501. May 1978.
14. Beck, D. C. Chevron USA Inc., Perth Amboy, NJ, Communication with M.
Kravett, GCA Corporation, March 1985.
15. Pittsburgh Corning Corporation, Pittsburgh, PA. Sales Literature, 1985.
16. Neulight, J. Calgon Carbon Corporation, Bridgewater, NJ. Communication
with M. Kravett, GCA Corporation, March 1985.
17. Hall, R. S., J. Mathey, and K. J. McNaughton. Estimating Costs of
Process Equipment. Chemical Engineering, April 5, 1982. pp. 83-116.
4-53
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SECTION 5
CONTROL OF EMISSIONS FROM SURFACE IMPOUNDMENTS
INTRODUCTION
A surface impoundment is defined as "a facility or part of a facility
which is a natural topographic depression, man-made excavation, or diked area
fortned primarily of earthen materials (although it may be lined with man-made
materials), which is designed to hold an accumulation of liquid wastes or
wastes containing free liquids, and which is not an injection well." There
are three basic types of surface impoundments: (1) totally excavated;
(2) filled; and (3) combination. Excavated surface impoundments are
constructed below grade-level; filled surface impoundments are built above
grade; and combination surface impoundments are partially below grade. Most
surface impoundments are combinations. Examples of surface impoundments are
holding ponds, settling ponds, aeration pits, and lagoons. In general,
surface impoundments are used for holding, storing, or treating large
quantities of waste.
Surface impoundments have been estimated to be the largest source of
o
emissions found at TSDFs. Emissions occur predominently as a result of
volatilization of substances from the surface. Particulate emissions may be
produced as a result of wind erosion of dry substances which have formed
around the impoundment perimeter. Gases may also be generated within a
surface impoundment as a result of a chemical reaction, e.g., methane
formation from decomposition of organics.
Emission control technologies applicable to surface impoundments may be
classified as systems which either minimize the exposed surface area or reduce
the affect of climatological forces such as wind, solar irradiation, or
precipitation. The control options which are in use at surface impoundments
may be categorized as follows:
5-1
-------
• Covers;
• Aerodynamic modifications;
• Vapor control systems; and
• Operating practices.
Table 5-1 provides an overview of the advantages and disadvantages of the
control options described in this section. Example systems will be cited, and
the relative emission reduction effectiveness and cost of implementing these
systems to existing TSDFs will be examined.
COVERS
Introduction
Covers placed over surface impoundments serve to limit emissions both by
minimizing the available surface area and by insulating the impoundment
constituents from wind and solar irradiation. Cover systems have been
reported as the most widely applied technique of controlling emissions from
surface impoundments. There are a variety of cover designs in use at
TSDFs, including:
• synthetic membrane covers;
• floating plastic spheres;
• rafts; and
• surfactant layers.
In general, cover systems are considered to be easy to install and
relatively effective in emission reduction. System costs are dependent upon
design and maintenance considerations. This section will present a detailed
deescription of each of the above technology options.
5-2
-------
TABLE 5-1. ADVANTAGES AND DISADVANTAGES OF SURFACE IMPOUNDMENT CONTROL ALTERNATIVES
Advantages
Disadvantages
COVERS:
Ul
I
Highly effective in reduction of surface
impoundment emissions.
Controls both working and breathing loss
emissions.
Increase facility safety via liquid
surface area minimization.
May be applicable to amy size or shape
impoundment.
May be made from chemically inert
materials and will not be reactive with
waste.
Nonrigid will not cause pressure buildup
Removable.
• Relatively low in installation and
operating costs.
AERODYNAMIC MODIFICATIONS:
• Reduces emissions by reducing the effect
of the wind creating turbulence on the
liquid surface and sweeping vapors away
from the impoundment to the atmosphere.
• Difficult to maintain.
• May have poor weather resistance.
• May not be chemically compatible if waste
constituents vary.
• High materials costs.
• Gas and vapor permeability characteristics may
be high.
• Direct-surface application may reduce thermal
insulation.
• Entrapped vapors may cause pressure buildup
and damage the cover system.
• Would require the addition of a vapor
collection system to control releases.
• Low emission reductions achievable.
• Low strength and durability characteristics.
• Has no effect on volatility impoundment
constituents.
(continued)
-------
TABLE 5-1 (continued)
Advantages
Disadvantages
Ul
.p-
AERODYNAMIC MODIFICATIONS: (Cont'd)
• Facilitates recondensation of vapors at a
surface impoundment.
• Simple designs, which can be adapted to
most impoundment sizes and shapes.
• Easy to implement at an existing facility.
• Little or no operating and maintenance
requirments.
• Low cost option.
• Increases overall safety of facility.
VAPOR CONTROL SYSTEMS:
• Capable of achieving the highest emission
reduction efficiencies of the control options
described herein.
• Completely remove vapor from cover system.
• Equally effective in reducing working and
breathing losses.
• May require alteration of facility operating
practices.
• Most costly of all control options.
• Highly complex systems to maintain.
• Manpower required.
• Materials required.
(continued)
-------
TABLE 5-1 (continued)
Advantages Disadvantages
VAPOR CONTROL SYSTEMS: (Cont'd)
• Best available technology for highly • Space required.
volatile and/or toxic substances.
• Accessibility required.
• Requires enclosed impoundment.
• Basic design of systems are simple—they
are easy to operate; and easy to design • Requires equipment for the disposition of
to fit a tank. vapor control process products.
• Can be applied to one or more than one • Subject to fire and explosion hazards.
impoundment.
• Can be subject to design capacity limitations.
• Can be a single-pass or multiple-pass
system. • Performance is affected by prevailing weather
weather conditions.
• Can selectively recover constituents.
• Adaptable to a variety of wastes—can be used
even if wastes stored changes.
• Can regenerate carbon beds for continuous use.
• Have found widespread usage at TSDFs.
OPERATING PRACTICES:
Increased Freeboard Depth
• Applicable to any surface impoundment • Emission reductions achievable are low.
design.
(continued)
-------
TABLE 5-1 (continued)
Advantages
Disadvantages
Ul
I
OPERATING PRACTICES: (Cont'd)
Increased Freeboard Depth
• Simple to implement at an existing facility,
• Only costs involved are in construction of
higher berms. No cost to lower level of
liquid. Very low costs overall.
Submerged Filling
• Reduces emissions due to decreased
turbulence of surface layer.
• Applicable to most impoundments.
• Particularly advantageous to impoundments
which form a dry layer on top.
• Low overall costs.
Less Frequent Drainage, Dredging, and Cleaning
• Very simple to implement.
• No costs involved (in fact, results in
cost savings).
• May affect overall operation of facility due to
lower impoundment capacity.
May be more applicable to smaller impoundment
due to expected emissions reduction effectiveness.
• Expense—may require construction and new
equipment (piping, pumps).
• Emission reduction efficiency is limited.
• Waste characteristics may limit applicability.
• Implementation may be difficult.
• May negatively affect the operation of the
impoundment.
• Emission reductions achievable are low.
(continued)
-------
TABLE 5-1 (continued)
Advantages
Disadvantages
Less Frequent Drainage, Dredging,
and Cleaning (Cont'd)
• May not be suited to all waste types, due to
residence time requirements.
• Many facilities already conduct these procedures
as infrequently as possible.
-------
Description
Covers serve to limit emissions from surface impoundments by acting as an
impermeable barrier. Waste constituents are thus held within an enclosed
system. Covers are applied in such a way as to cover all or as much as
possible of the available surface area. Cover systems may be placed directly
upon the liquid surface (contact), on floats at the surface, or over the
entire impoundment (noncontact). Covers may be made from a wide variety of
synthetic materials, including elastomeric sheet, rigid foam, flexible foam,
or liquid. In selecting an appropriate cover system, the following
considerations determine the applicability of the system to a specific
impoundment.:
• Type of waste impounded. The volatility, chemical reactiveness,
density, and chemical compatibility with liner and cover materials.
• Design of the impoundment. The diameter, shape, depth, berm design,
leachate collection mechanisms, and liner design.
• Inlet/outlet procedure. Whether the impoundment is filled and
emptied from the top or from submerged pipeline.
• Impoundment status. Whether the impoundment is currently active or
not, and the impoundment's primary function.
• Weather conditions. Wind, sun, and rain conditions which are
prevalent.
• Manpower and materials. Maintenance and materials required.
The four cover systems which have found the most widespread use are
described in detail below. Each system satisfies the above criteria to
varying degrees. In general, however, they are applicable to most surface
impoundments.
Synttietic Membrane Covers—
Covers made from flat sheets of synthetic material may be used to reduce
volatilization from surface impoundments. These systems are analogous to
floating blanket covers used to control storage tank emissions, which are
5-8
-------
described in Section 4. Synthetic membranes may be installed on surface
impoundments so that they rest directly upon the liquid surface, or above the
fy
liquid, supported by floats or frames. The cover may be constructed as one
continuous sheet, or as interlockable sections. A wide variety of synthetic
materials have been utilized as covers. Table 5-2 lists some of the more
common cover materials.
The covers may or may not be anchored around the perimeter of the
impoundment, they may be coated in some way, they may be exhausted to a vapor
control system (see detailed description of vapor control, presented later in
this subsection), and they may be colored to reflect sunlight. The primary
considerations involved in selecting an appropriate membrane cover design for
a surface impoundment are; chemical compatibility with waste constituents;
resistance to weather conditions; gas and vapor permeability; tensile and tear
strength; type of seams; anchoring technique;, and coloration.
One example of a cover system has been installed over an
(425 ft x 150 ft x 8 ft deep) aerated lagoon owned by Upjohn, Inc. in New
Haven, Connecticut. The air structure at Upjohn is a vinyl-coated, polyester
membrane coated with Teflon on the inside. It is harnessed to the foundation
around the impoundment by cables. Since installation, odor complaints have
been decreased significantly. This system is completely enclosed. Vapor
which forms underneath the cover is exhausted to carbon adsorbers by two 75-hp
aerators and 25 715-hp floating aerators. The carbon is regenerated by
steam.
A similar structure without a vapor recovery system was installed over
glauber salt storage ponds used by American Natural Gas in Beulah, N. Dakota,
to keep precipitation out. The air structure, which is movable from one pond
to another, covers approximately 2 acres and is made of vinyl-reinforced
material over a concrete foundation. Two air blowers are used to keep the
structure inflated. Another ground-mounted, air-supported structure was
installed in Livingston, LA in September 1984.
Floating Spheres—
A blanket of hollow plastic spheres may be used as a cover. These
systems perform very much like synthetic membranes. However, plastic spheres
are more fluid and are better thermal insulators. Gas and vapor permeability,
5-9
-------
TABLE 5-2. SYNTHETIC COVER CHARACTERISTICS
Ul
i—•
o
Synthetic material
Chlorosulfonated polyethylene
(Hypalon)
Polyethylene
Chlorinated polyethylene (CPE)
Polyvinyl chloride (PVC)
Polychloroprene (Neoprene)
Chlorinated polyethylene
CSPE
Epichlorohydrin rubber
(CO, ECO)
Ethylene propylene rubber
(EPDM)
Polyolef in
Chemical resistance
Inorganics — good
Organic s — poor
Good for organics
and inorganics
Inorganics and
alipha tics-good
Aromatic organics — poor
Inorganics — good
Organics — poor
Good for organics and
inorganics
Inorganics — good
Organics — poor
Good for organics
and inorganics
Inorganics — good
Organics — poor
Inorganics — good
Organics — poor
Gas
Weather permeability
resistance resistance Tear resistance
Excellent Good Poor
Poor Excellent Poor but better
with thick (125
mil) sheets
Excellent Good Cracks in cold
weather
Poor Good Good
Excellent Good Excellent
Good Good Poor
Excellent Good Good
Excellent Good Good
Excellent Good Good-but poor
in cold weather
Source: MITRE, 1983 (Reference 2).
-------
and weather resistance characteristics are not as attractive, however.
Similar systems are used to control storage tank emissions. The reader should
refer to Section 4 for further discussion.
Rafts—
A raft is defined as any device which floats freely upon the liquid
surface. Rafts perform similarly to floating plastic spheres. Rafts have
desirable gas and vapor permeability characteristics, may be designed to fit
any size and shape impoundment, and are easy to install. Rafts have been used
extensively to cover surface impoundments. Similar systems are used to
control storage tank emissions. The reader should refer to Section 4 for
further discussion.
Surfactant Layers—
A layer of liquid may also be used to cover a surface impoundment. In
general, the surfactant layer is applied as thin as possible. Surfactant
liquids generally employ long chain alcohols such as hexadecanol and
octadecanol. The primary factor affecting the effectiveness of a surfactant
layer cover is the maintenance of a continuous film on the liquid surface.
Similar systems have also been used to control emissions from storage tanks.
Refer to Section 4 for further details.
Surfactant layers have been used to cover settling basins at three
acrylonitrile manufacturing plants in Texas. The settling basins are
employed for suspended solids removal prior to deep-well injection of process
wastewater. A layer of high-molecular weight lubricating oil, maintained at a
thickness of approximately 0.1 m, is used to reduce the secondary VOC
emissions. The lubrication oil is periodically replaced to make up for losses
due to solubilization and evaporation.
Emission Reduction Effectiveness
Surface impoundment cover systems are attractive for control of air
emissions primarily due to the high emission control efficiencies which can be
attained. The emission control effectiveness is dependent upon the type of
compounds being held, the design (e.g., diameter, shape, depth) of the
5-11
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impoundment, and weather conditions.
The effectiveness of the four cover systems described in this subsection
is directly proportional to the amount of surface area covered. A synthetic
membrane is capable of covering the entire liquid surface area. Effectiveness
of synthetic membrane covers is generally limited by the vapor permeability of
the synthetic material and the perimeter seal. The efficiency of synthetic
2
membrane covers was estimated by MITRE at 90 pecent.
Rafts are capable of covering up to approximately 90 to 99 percent of
liquid surface area depending on the raft shape relative to the impoundment
shape. Effectiveness of rafts is also related to their thickness. Emission
reduction efficiency of rafts was estimated in one recent study at
90 percent.
Floating surfactant layers are capable of fully covering the liquid
surface area. The effectiveness of such cover systems is primarily related to
wind disruptions in the layers caused by wind. MITRE estimated that reduction
2
efficiencies of 25 to 75 percent were achievable by such systems.
Costs
The costs associated with a cover system on a surface impoundment are
highly dependent upon cover design, the purpose of the impoundment, and
operational considerations. The costs of covers include materials costs,
installation costs, operating costs, and maintenance costs. Due to the large
size of many surface impoundments, and the nature of the wastes they contain,
some cover materials and installation costs are considered to be particularly
high relative to other cover control options.
The costs associated with synthetic membrane covers are similar to those
involved in similar systems implemented at landfills, which are discussed in
detail in Section 6. Depending upon the synthetic material selected, the
installed costs of the liner may range between $3 and $26 per square yard of
impoundment area. The cost of an air supported synthetic membrane system
such as that at Upjohn was reported to cost over $500,000, while the
installation cost of the American Natural Gas system was a reported
$400,000.1
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The cost of a layer of plastic spheres is similar for surface
impoundments as that of the same technology applied to a storage tank. Refer
to Section 4 for further detail.
The cost of floating raft covers are largely dependent on design
considerations (e.g., raft thickness or coloration). Cost estimates for rafts
applied fo surface impoundments must consider the usable life span. Rafts
tend to become contaminated and must be occasionally replaced. The costs for
a typical raft system was reported by Arthur D. Little to range between $0.05
and $0.13 per square foot.
The costs of surfactant layers are potentially the lowest of any cover
system. Materials costs are dependent upon the market price of the liquid
used and, when these costs increase, other, cheaper liquids may be used.
Installation and operating costs should be very low, and maintenance costs can
be minimized by using the appropriate application procedure. The cost for
applying a layer of hexadecanol, for example, is approximately 0.09 cents per
A
square foot.
AERODYNAMIC MODIFICATIONS
Introduction
The role of aerodynamic modifications is to alter, deflect, or eliminate
the flow of wind across surface impoundments. Wind serves to cause or
increase emissions from surface impoundments by sweeping VOCs or particles
away from the surface impoundment to the environment. Aerodynamic
modifications are used extensively for control of surface impoundments. The
variety of designs currently in use may be classifed as either: barriers or
shades.
Wind barriers and shades are considered to be, in general, easy to
implement, and moderately effective at reducing emissions. Aerodynamic
modifications are an attractive control option due to low costs. This section
will present a detailed description of the above technology options.
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Description
Aerodynamic modifications reduce emissions from surface impoundments by
acting as a barrier or deflector to prevailing winds. Aerodynamic
modifications are constructed to maximize reduction of wind across the surface
impoundment. In general, the closer a barrier is to the impoundment, the more
effective it will be in reducing winds. The higher the wind barrier, the
larger its area of effectiveness. A wide variety of designs and materials of
construction are employed in aerodynamic modification systems. In selecting
the most effective aerodynamic modification system, the following
considerations influence the applicability of the modification.
• Impoundment constituents. The volatility, reactiveness, and
chemical compatibility (with barrier shades) of constituents.
• Design of the impoundment. The size, diameter, shape, depth, and
berm design.
• Weather conditions. The sun, precipitation, and particularly the
wind conditions.
• Maintenance and operating characteristics. The various maintenance
and operating procedures employed at the facility (including need to
access the impoundment).
Aerodynamic modifications have found widespread application for surface
impoundment emission control, both alone and in conjunction with other control
technologies. Barrier and shade systems, which are described in detail below,
vary in their applicability under the above criteria depending upon design and
operational constraints.
Wind Barriers—
A wind barrier is defined as any system which results in reduced wind
flow across a surface impoundment. Various designs have been used at surface
impoundments. These designs are similar to those which are used to control
emissions in drum storage areas.
There are two basic types of wind barrier designs, perimeter and
"compartmentalized." The barriers may be straight, or "zig-zag." Barriers
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may be oriented to face in one particular direction or may simply enclose the
entire facility. Among compartmentalized designs, the internal cells may be
uniform in size (e.g., the "honeycomb" design), or may be varied according to
the use of the surface impoundment, maintenance, and constituents. Three
examples of barrier designs, which have been tested in the field, and
described by Crow and Monges, are as follows:
• Open-picket baffles which consist of a picket-type snow fence
supported by floats. The floats can be adjusted for different
barrier heights, varying the ratio of the barrier spacing to the
barrier height (L/H).
• Closed wind barriers which consist of a picket fence with flexible
membrane linings fastened to the pickets.
• Styrofoam barriers consisting of Styrofoam strips joined to form a
grid over the impoundment surface. No floats are necessary.
The primary considerations involved in selecting the most appropriate
wind barrier design are the height of the barrier, compartmentalization,
barrier materials (strength needed for prevailing winds, and compatibility
with constituents), and impoundment access points.
Shades—
Shades are defined as systems which serve as wind-breakers and also
reduce solar irradiation over the surface of an impoundment. Unlike wind
barriers, therefore, shades serve to limit both the effects of wind and sun,
the two primary forces contributing to impoundment emissions. Various designs
of shades have been developed for impoundments. Most involve a polypropylene
mesh stretched over the surface of the impoundment. In general, field
testing has found that emission reduction effectiveness is proportional to
mesh size. Shades may be made of a variety of colors, to either reflect or
absorb radiant heat. They may also be coated with a chemical film to reduce
vapor permeability. The primary considerations involved in selecting the most
appropriate shade design are the mesh size, color, shade material (chemical
compatibility), resistance to weather conditions (e.g., ability to handle a
heavy snowfall), and shade anchoring. There are no application examples
currently available.
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Emission Reduction Effectiveness
The degree to which aerodynamic modifications are effective in reducing
emissions from surface impoundments has been studied through field testing.
The efficiencies that can be achieved are relatively moderate and, in some
cases, low. When used in conjunction with other systems, however, the
emission reductions that can be achieved are potentially attractive,
considering their ease of implementation and low cost.
The reduction of wind speed by a wind barrier is dependent upon its
height. The closer a wind barrier is to a certain point, the more effective
it is in reducing wind. Barriers which are close together, however, tend to
exacerbate emissions due to creation of a forced convection mechanism. That
is, wind flow over the barrier walls creates a pressure differential within
the enclosed cell, causing an upward flow of air which would increase
emissions. Testing on windbarriers has shown that efficiencies range from as
high as 80 percent to as low as 11 percent.
The effectiveness of a shade is dependent on the shade value (see
Table 5-3). Chemical films tend to increase the effectiveness of shades
due to decreasing vapor permeability. The efficiency of shade systems has
been estimated by ADL to be 44 percent for nonaerated and floating immiscible
layer impoundments.
Costs
Aerodynamic modifications are considered to be among the lower cost
control alternatives available for surface impoundments. The cost of such
systems primarily consists of construction costs. Operation and maintenance
costs are expected to be low under normal conditions. The costs of
installation are low relative to other control technologies, however, may vary
as the aerodynamic modification system complexity increases. Weather
conditions play a role in costs, as well. Damage due to extreme weather, such
as a blizzard or hurricane, may result in high replacement and repair costs.
The stronger the system is, the lower these costs may be. However, stronger
systems also tend to be more expensive. In general, the costs have been
estimated as follows:
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TABLE 5-3. EVAPORATION SUPPRESSION BY SHADES
Evaporation reduction
Material tested (percent)
Polypropylene Mesh 26
6 percent shade (natural)
Polypropylene Mesh 44
47 percent shade (black)
Source: ADL, 1984 (Reference 1).
5-17
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Barriers: $665/yr for styrofoam barriers formed in an 8 ft x 8 ft
grid over a surface impoundment of median size (0.46 acres).
Shades: $1663/yr for black woven polyethylene shades around a
surface impoundment of median size.
VAPOR CONTROL SYSTEMS
Introduction
Vapor control systems control the release of volatile substances from
surface impoundments by evacuating vapors which form and processing them
physically or chemically. Vapor control systems are the most complex and
costly of surface impoundment controls, but are the most effective at reducing
emissions. Use of vapor control at surface impoundments is widespread.
The three vapor control systems which are most commonly used for surface
impoundment emission control are:
• vapor condensation;
• Carbon adsorption; and
• Vapor incineration.
Of the three, carbon adsorption systems are probably the most frequently
used. The three systems will be described in detail below.
Description
The primary function of a vapor control system is to remove vapors which
form in a surface impoundment, and render them by physical or chemical process
such that they will not enter the environment. Such systems are equally
effective at controlling working or breathing losses, as any vapor which forms
is evacuated from the impoundment. All vapor control systems involve at least
three steps, as follows:
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(1) evacuation;
(2) vapor processing; and
(3) recycle or venting of products.
The use of vapor control technology requires that the surface impoundment
be enclosed. Therefore, only impoundments equipped with covers (see detailed
description presented earlier in this section) will be able to utilize vapor
control processes. Vapor control systems require the installation of
ductwork, the location of unit processing equipment in readily serviceable
areas, and equipment for the disposition of recovered products and materials.
Vapor control systems have found widespread application at TSDFs, particularly
in the control of highly volatile and/or toxic substances, due primarily to
the high emission reduction efficiencies these systems can achieve. A vapor
control system helps to alleviate a major drawback of surface impoundment
covers. Covers tend to entrap vapors to the point where internal pressure
builds up, and eventually causes damage to the system. Evacuation to vapor
control eliminates this, while preventing these substances from entering the
environment. The unit processes are themselves simple, utilizing the physical
or chemical properties of surface impoundment constituents, such as
vaporization point, adsorbability, or combustibility. In determining the
applicability of a particular vapor control system to certain surface
impoundment, the following factors should be considered.
• Properties of the surface impoundment constituents. The volatility,
adsorbility on carbon or other substrates, and combustibility of
waste constituents.
• Number of impoundments to be serviced. The total capacity to be
served by a vapor control system.
• Manpower and materials requirements. The maintenance, operating
labor, and materials required.
• Availability of space. The location of the vapor processing unit
and attendant ductwork.
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The three vapor control systems described below have found widespread
application both in the control of surface impoundments and storage tanks, due
not only to the high emission reduction efficiencies they can achieve, but
also their applicability under the above criteria.
Vapor Condensers—•
Vapor condensation systems prevent release of volatile substances by
recondensing the vapors which form in an impoundment. These systems are
identical to those used for control of storage tank emissions. Refer to
Section 4 for further discussion.
Carbon Adsorbers—
Carbon adsorption systems prevent the release of volatile substances by
adsorption of the volatile organic material onto activated carbon particles.
The systems used to control surface impoundment emissions are identical to
those used to control storage tank emissions. Refer to Section 4 for further
discussion.
Vapor Incinerators—
Vapor incineration systems, also called afterburners, control surface
impoundment emissions by oxidation (combustion) of volatile substances. The
systems in use for surface impoundment emission control are identical to those
used for storage tank emission control. Refer to Section 4 for further
discussion.
Emission Reduction Effectiveness
Vapor control systems are highly effective at reducing emissions from
surface impoundments. Efficiencies of these system were described in detail
in Section 4. Refer back for further discussion.
Costs
Vapor control systems are highly complex, including much engineering
design, materials, labor, operating costs, and maintenance. The control
5-20
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systems are, therefore, the most expensive of available control alternatives.
Costs for such systems were described in Section 4. Surface impoundments may
require additional installation and operating costs, d.ue to. their larger_size
requirement.
OPERATING PRACTICES
Introduction
The implementation of more effective operating practices at a surface
impoundment serves to reduce emissions by limiting the affect of
climatological forces (i.e., sunshine and wind) which contribute to
emissions. Operations during the active life involving temperature of
influent, dredging frequency, draining frequency, cleaning frequency, handling
of sediments and sludge from dredging and types of wastes accepted at a
facility could be designed to minimize emissions. Many different operating
practices have been instituted at TSDFs on the basis of reduced emission
generation. To exemplify the type of measures which might be instituted at a
surface impoundment, this subsection will focus upon three changes in
operating practice, as follows:
• Increased freeboard depth;
• Inflow/outflow drainage pipe relocation to effect submerged filling;
and
• Infrequent dredging, draining and cleaning.
While changes in operating practices are not considered to be more than
moderately effective in reducing emissions (relative to add-on controls), they
are often implemented at a TSDF on the basis of cost, ease of implementation,
and simplicity.
Description
Changes in opeating practice at a surface impoundment could involve those
which directly affect the waste material, the design of the surface
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impoundment, or external forces (such as sunshine, rain, and wind). These
changes may involve new equipment, manpower training, or management. The
following considerations should be made in determining the applicability of
operating practice changes for a surface impoundment.
• Type of materials. The physical or chemical characteristics of
impoundment constituents.
• Manpower requirements. Personnel and training requirements.
• Impoundment turnover. The rate at which a surface impoundment is
filled and emptied and the retention time of waste material.
The three examples presented in this section, which are described in detail
below, are commonly implemented at TSDFs due to their applicability under the
above criteria.
Increased Freeboard Depth—
The freeboard depth is the distance from the top of the berra to the
liquid surface. Increasing freeboard depth at a surface impoundment would
serve to reduce air emissions by reducing the effect of wind and surface
waveso This modification will decrease:
• volatilization;
• turbulence on the impoundment surface;
• spray formation; and
• erosion of dust and the dried surface of the impoundment.
There are two ways in which a facility can increase the freeboard depth
of an impoundment: (1) decreasing liquid level, and/or (2) increasing berm
height. Decreasing the liquid level of an impoundment would limit the
capacity of the facility. For surface impoundments which operate at steady
state (input rate = output rate, volume stays constant), a decrease in liquid
5-22
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level would also require changing (decreasing) the flow rate. Increasing the
height of the berm would require additional material and construction. The
draft RCRA Guideline Document (July 1982) suggest at least 60 cm (2 feet) of
freeboard to prevent overtopping. A way to increase freeboard is to minimize
runon into the impoundment by incorporating a runon control system.
The primary considerations involved in selecting an appropriate freeboard
depth for a surface impoundment are the capacity needed at the facility, the
surface impoundment size, the requirements involved in construction of higher
berms, and costs of berm material, labor, and more frequent draining of the
impoundment. Increasing freeboard depth is applicable to any surface
impoundment. Due to emission reduction effectiveness considerations,
increasing freeboard depth as the sole means of control may be more applicable
to small surface impoundments than to larger ones.
Inflow/Outflow Pipe Relocation—
By relocating the inflow and outflow pipes such that a surface
impoundment can be filled and emptied from submerged points, emissions will be
reduced due to reduced surface turbulence. Discharge of liquid on or above
the surface on the impoundment not only causes the surface to become more
turbulent but may also cause spray formation or degradation of any dry crust
which may have formed over the impoundment. In designing a submerged filling
system, it is advantageous to locate inflow pipes such that discharge occurs
into the liquid bulk and below the surface. Relocation of pipes may require
excavation for pipeline, new pipe, and new liner materials. The leachate
collection systems may also require modification. Among the considerations
involved in selecting a new inflow/outflow pipeline system are the size of
pipe required, flow rate, pressure effects on filling and emptying, waste
viscosity profile, excavation depth, and new materials requirements. New
designs of surface impoundments primarily employ submerged filling and
emptying. The frequency with which such systems are retrofit to existing
surface impoundments is not known.
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Less Frequent Dredging, Draining, and Cleaning—
By decreasing the frequency with which a surface impoundment is
disturbed, emissions would be reduced due to decreased turbulence. Three ways
in which this could be accomplished are through more infrequent dredging,
draining, or cleaning of the impoundment. Such measures would require less
labor and equipment, but might affect the impoundment process efficiency. The
primary considerations involved in implementing such measures are the effect
on the impoundment process (e.g., lowering the efficiency of settling), the
waste materials, and the size of the impoundment (the smaller the impoundment,
the less effective these measures would be). Such measures are quite
attractive on the basis of decreased operating costs and, therefore, have been
extensively used at TSDFs.
Emission Reduction Effectiveness
There is no in-depth analysis present in the available literature which
assesses the effectiveness of changes in operating practices in reducing
emissions from surface impoundments. On the basis of engineering judgment, it
is expected that such measures would be at most only moderately effective (in
terms of emission reduction percentage). Increasing freeboard depth, for
example, is analogous to construction of a perimeter wall of equal height. As
described previously, wind screens have been found to achieve efficiencies of
between 11 and 80 percent.
Costs
The costs involved in implementing changes in operating practice are
generally low, in relation to other control alternatives. Costs are the
primary factor in selecting such measures for TSDF surface impoundments.
The costs for increasing freeboard depth involve cost of berm materials,
labor, and/or costs of more frequent drainage or lower capacity. Such costs
are expected to be quite low, but are difficult to quantify. The more costly
of the two methods described earlier would be increasing berm height due to
materials costs.
5-24
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The costs for changing to submerged filling and emptying are potentially
the highest of the three operating changes described. Added costs would be
incurred during implementation of the system, including new equipment,
materials, construction labor, and maintenance labor. No information was
available which quantified the total costs involved in such a change in
operating practice.
5-25
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REFERENCES
1. Arthur D. Little, Inc. Evaluation of Emission Controls for Hazardous
Waste Treatment, Storage, and Disposal Facilities. EPA-450/3-84-017.
U.S. Environmental Protection Agency, Office of Air Quality Planning and
Standards, Research Triangle Park, N.C. November 1984.
2. Vogel, G. A., and D. F. O'Sullivan. Air Emission Control Practices at
Hazardous Waste Management Facilities. MTR-83W89. Prepared for U.S.
Environmental Protection Agency, Office of Solid Waste. Contract
No. 68-01-6092. The MITRE Corporation, McLean, VA. June 1983.
3o Breton, M., T. Nunno, P. Spawn, W. Farino, and R. Mclnnes. Assessment of
Air Emissions from Hazardous Waste Treatment Storage and Disposal
Facilities (TSDFs). Preliminary National Emissions Estimates. Prepared
for U.S. Environmental Protection Agency, Office of Solid Waste.
Contract No. 68-02-3168. GCA Corporation, Bedford, MA. August 1983.
4. Cudahy, J. J., and R. L. Standsifer. Secondary Emissions Report.
Report 3 of Organic Chemical Manufacturing. Volume 3: Storage,
Fugitive, and Secondary Sources. EPA-450/3-80-025. U.S. Environmental
Protection Agency, Office of Air Quality Planning and Standards, Research
Triangle Park, NC. June 1980.
5. USEPA, Office of Research and Development. Handbook for Remedial Action
at Waste Disposal Sites. EPA-626/6-82-006. U.S. Environmental
Protection Agency, Office of Research and Development, Cincinnati, OH.
June 1982.
6. SCS Engineers. Interim Report on Air Emissions. Prepared for U.S.
Environmental Protection Agency, Office of Solid Waste. Contract
No. 68-01-6621. SCS Engineers, Covington, KY. September 1983.
5-26
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SECTION 6
LANDFILLS
INTRODUCTION
A landfill is defined as a waste disposal facility where wastes are
placed in or on the land for custodial safekeeping. Solid or semisolid
wastes arrive in bulk or in containers, are placed in a landfill "cell" and
are covered over with a soil layer of from 6 to 12 inches. A landfill is
generally large in area, some extending several acres in size. Wastes in a
landfill are isolated from the environment in the soil, and are left to
degrade by chemical or biological process.
Atmospheric emissions from landfills can consist of both particulate
matter and volatile organic compounds (VOCs). Air emissions can occur as a
result of activities such as soil and waste handling, landfill maintenance,
vapor diffusion, and/or wind entrainraent. Diffusion may occur both vertically
and laterally from the landfill cell. Emissions may also result from the
leachate generated within a landfill and removed by a collection system.
There are two ways to control organic vapor emissions from landfills.
One method is to place a barrier on the landfill surface to minimize diffusion
into the atmosphere, thus, limiting the rate of volatilization. This type of
control includes the use of a soil, foam, synthetic membrane cover, or
encapsulation or solidification techniques. The other method is to collect
the vapors and vent them to a treatment system such as a carbon adsorber or
afterburner. This is the "ultimate" disposal method, because there is no
chance for future volatilization of the compounds. This type of control
includes gas collection.
6-1
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An overview of the advantages and disadvantages of the control options
described in this section is shown in Table 6-1. Also examined are the costs
and efficiencies obtainable relative to vapor emission reduction.
SOIL COVERS
Introduction
Soil covers serve to limit emissions by acting as a barrier to diffusion
and wind entrainment. Soil covers have experienced widespread use at
municipal landfills, primarily for minimizing odors, reducing particulate
emissions, and preventing rodent infestation. They have also been ussd to
prevent leaching of hazardous chemicals to ground water due to infiltrating
precipitation. A variety of soil covers have found usage as both a temporary
and permanent cover, utilizing a wide range of soil types. Soil covers are
considered to be relatively effective in preventing emissions and are very
cost-effective.
Description
Temporary soil covers are placed over landfilled wastes as soon as is
practical, usually at the end of each day. Soils suitable for use as
temporary covers can sometimes be found nearby the landfill site; otherwise,
they may have to be imported from offsite at added expense. Permanent soil
covers usually consist of higher density soils, such as clay, which are less
permeable to water percolation than are the soils usually used as temporary
covers.
Layered covers may also be constructed using different materials (see
Figure 6-1). These covers are placed over a landfill after all cells have
been filled and the landfill is being closed. They may also be used in
conjunction with a gas collection system. Often a layer of top-soil and
vegetation is placed over a permanent soil cover to protect it against drying
and physical damage.
The primary factor which controls the release of volatile organic
chemical (VOC) emissions through soil covers is the air-filled porosity of the
6-2
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TABLE 6-1. LANDFILL EMISSION TECHNOLOGIES—ADVANTAGES AND DISADVANTAGES
Advantages
Disadvantages
SOIL COVERS:
• High volatile emissions reductions possibly • Emissions may be significant depending on design,
depending on design operating practices operating practices, and soil types used.
and soil types used.
• Ultimate release of all volatile constituents
• Appropriate soils may be at or nearby landfill from landfill (unless gas collection used).
site.
• May crack or degrade due to natural processes
• Widely used technology. over time.
• Can be used as a temporary or permanent • Requires periodic maintenance (watering,
control measure. inspection, etc0)
• Properly designed permanent soil covers
serve dual purpose of minimizing infiltration
and reducing volatile emissions.
• Compatible with all waste types.
• Can be used in conjunction with other tech-
nologies (e.g., synthetic membrane covers,
gas collection).
• Standard construction equipment used in
implementation.
• Moderate costs.
SYNTHETIC MEMBRANE COVERS:
• Very effective when used in conjunction
with soil covers and/or gas collection.
• Virtually impermeable to infiltrating
precipitation.
• Available in many materials and thicknesses.
• Widely used technoloyg.
• Emissions may be significant over a large area if
not used in conjunction with other technologies.
• Certain cover materials not compatible with some
wastes.
• May be punctured or torn easily, limiting use
as a temporary cover.
• May crack or degrade due to natural processes
over time.
(continued)
-------
TABLE 6-1 (continued)
Advantages
Disadvantages
SYNTHETIC MEMBRANE COVERS: (Cont'd)
• Host materials are moderate in cost.
FOAM COVERS:
• May be used as a temporary cover.
• May be useful for fugitive dust control.
• Have been used at sanitary landfills in Europe.
• Have been shown to be somewhat effective in
mitigation of vapor release from spilled
organic chemicals.
• High performance materials may be very expen-
sive (e.g., Teflon).
• Requires periodic maintenance (inspection,
watering, etc.)
• Effectiveness questionable with respect to
reducing emissions from hazardous waste
landfills.
• Some foams are incompatible with certain wastes.
• Only effective as short-term control.
• Long time necessary to apply an effective cover.
• Application equipment and reagents costly.
ENCAPSULATION/SOLIDIFICATION:
• Classification and encapsulation may be very
effective.
• Solidification has been used effectively for
containment of radioactive wastes.
• High costs.
• Some solidification agents are not compatible
with organic wastes (e.g., thermoplastic
solidification).
• Encapsulation has not yet been developed on a
commercial scale.
• Solidification is not a proven technology for
vapor emission control.
• Not widely used technologies.
GAS COLLECTION:
• Expected to be very effective when used in
conjunction with • landfill cover system.
• Has been used for methane gas migration
control.
• Requires treatment system.
• Some methods high in cost (e.g., trench vents).
• Some gas barriers are not compatible with
certain vapors<.
(continued)
-------
TABLE 6-1 (continued)
Advantages Disadvantages
GAS COLLECTION: (Cont'd)
• A simple, inexpensive system may be effective • Some gas barriers may be be ineffective in the
over a large area (e.g., single pipe vent control of vapors.
with treatment).
• Can be constructed incrementally for use
uhile landfill is still active.
• Easy, proven construction techniques.
• Moderate cost for most methods.
AIR-INFLATED STRUCTURES:
• Expected to achieve high collection/removal • High costs.
efficiencies.
• Requires treatment system.
• Prevents infiltration as well as providing
emission control. • Structure may be somewhat permeable to vapors,
depending on materials used.
• Synthetic membrane of soil covers would not be
-------
Loam (for Vegetation)
Y//S7///////. Clay (Barr.cn
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Loam
(Barr.er)
Silt (Filter)
Sand (Buffer)
Figure 6-1. Two typical layered soil cover systems
(U.S. EPA, 1982) (Ref. 1)
6-6
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2 3
soil. • Decreasing the air-filled porosity decreases the effective
diffusivity of volatile materials through the soil. This can be achieved by
using a denser cover material or .by compacting existing materials. However,
the most effective method of reducing air-filled porosity is to increase the
moisture content of the soil. Maintaining the highest moisture content
possible consistent with good workability and structural integrity of the soil
will result in a significant decrease in emissions. This can be achieved by
spraying temporary covers from a spray truck or other device, or installing a
permanent sprinkler system after landfill closure. This will also prevent
drying and subsequent cracking of the cover.
Emission release rates are inversely proportional to cover thickness.
Hence, doubling the thickness of the soil layer will halve the release rate of
VOC's through the cover. In selecting an appropriate landfill soil cover, the
following considerations are important:
• type of soil used;
• thickness of soil layer;
• design of landfill cells; and
• landfill facility operating and maintenance practices.
Emission Reduction Efficiency
Soil covers are often used to control landfill emissions, due to the high
emission reductions they are capable of effecting. Measured emission rates of
hexachlorobenzene from an experimental landfill were reduced by 92 percent
with the addition of a 1-inch soil cover. A 40-inch soil layer was found
to reduce emissions by 99.8 percent.
In the study mentioned above it was also found that decreasing soil water
content by 2.3 percent increased hexachlorobenzene flux by 21.2 percent,
2 9
clearly an exponential relationship. A. D. Little calculated
theoretical emissions through 12-inch soil covers of different dry porosities
and different moisture contents as shown in Table 6-2. It can be seen that
increasing soil porosity increases the unit emission rate; increasing moisture
content reduces emissions to virtually zero in the case of low porosity
6-7
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TABLE 6-2. UNIT EMISSIONS THROUGH 12-INCH SOIL COVERS
FOR SOILS OF DIFFERENT DRY POROSITY3>b
Unit emission (ft/hr)
Dry porosity (bulk density)*^
% Waterc 0.3(118) 0.4(101)
0 0.056 0.083
5 0.016 0.039
10 0.0020 0.015
15 0.0000032 0.0036
20 - 0.00033
25 -
% Moisture at zero 15.8 24.7
porosity
3,, • Ib , Ib ^^
ft -hr ft
0.5(84)
0.111
0.069
0.039
0.020
0.0084
0.0027
37.1
0,6(67)
0.142
0.10
&.073
0.050
0.032
0.020
55.8
bDiffusivity in air = 0.28 ft2/hr; t = 1 ft.
cPercent of dry weight.
density (lb/ft^) in the parentheses, based on
particle density = 2.7.
Source: Arthur D. Little, Inc., 1984. (Reference 2).
6-8
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soils. It must be noted that these high levels of water content may not be
achievable in practice. It is evident, however, that significant emission
reductions are possible solely by increasing moisture content, probably on the
order of 75 to 99 percent, depending on the soil type.
n
Other laboratory tests indicate that changes in soil density on the
order of 10 to 15 percent may be achievable in the field using heavy
compacting machinery, depending on the type of soil. If the water content of
o
the soil is about 15 Ib/ft , this level of compacting can reduce effective
diffusivity from 50 to 100 percent, resulting in similar reductions in
emission rates.
Overall, it can be seen that both temporary and permanent soil covers are
effective at reducing VOC emissions from landfills, particularly if they are
maintained at a high moisture level.
Costs
The costs of soil cover systems used to control landfill emissions are
low relative to other control alternatives, making such systems highly
attractive. The costs of implementing such systems are largely dependent upon
installation and maintenance requirements.
The costs for hauling, spreading, and compaction of a clay cover are
about $11 per cubic yard of material. The costs for hauling, spreading,
and grading of top soil (sandy loam) are about $17 per cubic yard.
However, soils suitable for use as a temporary cover or for acting as a base
for vegetation are usually found near the landfill site. Clays are usually
not available nearby and hence must be trucked in from offsite.
The cost of hydroseeding grass over a landfill is about $1550 per acre of
4
land. Costs for irrigation systems or spray trucks have not been
estimated, but their use is expected to be very cost-effective with respect to
reducing air emissions. Other costs may be incurred for heavier earthmoving
equipment for added compaction ability, or additional labor required to
accommodate changes in operating procedures that reduce air emissions.
6-9
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SYNTHETIC COVERS
Introduction
Synthetic covers perform similarly to soil covers in controlling landfill
emissions. Placed on top of wastes, they serve to limit emissions by reducing
vapor diffusion and acting as a barrier to the wind, sun, and any
precipitation or runoff liquid. Synthetic covers have experienced widespread
use at both municipal and hazardous waste landfills, where their main function
has been the prevention of leachate generation. They are also effective in
reducing atmospheric emissions of volatiles from landfills, especially if used
in conjunction with a gas collection system and/or a soil cover. A wide
variety of synthetic materials have found usage in this application. Their
use with respect to emissions reduction will be discussed in this section.
Description
Synthetic membranes, commonly made of polymeric materials such as
Hypalon, Neoprene, and elasticized polyoLefin, can be used as temporary covers
over landfill cells until the daily soil cover has been put into place. This
practice will reduce atmospheric emissions to some degree. However, synthetic
membranes are prone to puncture or tearing by landfilling equipment or other
sharp objects, such as metal drums, and hence may have limited use as
temporary covers.
As was mentioned earlier, synthetic membranes may be very useful as a
permanent cover, especially if used in combination with a soil cover. A soil
cover will not only further reduce emissions, but will protect the synthetic
cover against drying and physical damage. Even when covered by soil, however,
the synthetic cover may be subject to cracking or rupture.
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It must be noted that certain organic vapors are incompatible with some
liners. Compatibility of some organic vapors with Hypalon and Neoprene
membranes is shown in Table 6-3. The primary considerations involved in
selecting an appropriate synthetic cover for landfill emission control are:
• synthetic material and its compatibility with waste constituents; and
• membrane thickness and durability with respect to landfill
operational and maintenance procedures.
Emission Reduction Effectiveness
Very little data exist on synthetic membrane permeability to volatile
organic chemical vapors. However, available data suggest that, although
synthetic membranes appear virtually impervious to water, they are somewhat
permeable to organic vapors. The permeability of a given polymeric membrane
to a given chemical depends on the solubility of chemical in the polymeric
membrane because, unlike soils, synthetic membranes are nonporous.
As can be seen from Table 6-4, which shows experimentally measured
permeation rates through polymeric membranes for various organic solvent
vapors, substantial variation occurs between compounds with different
properties as well as between liner materials. Even a high-performance
material such as Teflon does not appear to be effective against permeation of
volatile chlorinated organics such as chloroform.
Costs
The costs associated with implementing a synthetic cover system are
considered to be relatively low to moderate, depending upon the design of the
system selected. The costs are primarily a function of material costs. In
general, more favorable performance characteristics (e.g., low vapor
permeability, high tensile and tear strength), result in higher material costs.
Unit costs of some installed synthetic membranes are presented in
Table 6-5. These costs are only for the liner itself and do not include
maintenance and inspection costs, or costs for soil covers.
6-11
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TABLE 6-3. CHEMICAL RESISTANCE CHART (DUPONT)
Vapor type
Acetic acid (glacial)
Benzene
Butane
Butyraldehyde
Carbon tetrachloride
Cyclohexane
Dioctyl phthalate
Ethyl acetate
Ethyl alcohol
Formic acid
Gasoline
Hydrocyanic acid
Hydrogen sulfide
Kerosene
Methyl alcohol
Methylene chloride
Methyl ethyl ketone
Naphtha
Perch lor oethylene
Toluene
Trichloroethylene
Xylene
Hypalon3
X
C
A
X
C
C
C
C
A (158°F)
A
B
B
B
X
A (158°F)
C
C
B
X
C
C
C
Neoprene3
C
C
A
C
C
C
C
C
A (158°F)
A
B
A
A
B
A (158°F)
C (100°F)
C
C
C
C
C
C
aCured sheet.
A - Chemical has little or no effect.
B - Chemical has minor to moderate effect.
C - Chemical has severe effect.
X - No data - not likely to be compatible.
Unless otherwise noted, concentrations of aqueous
solutions are saturated.
All ratings are at room temperature, unless
specified.
Source: U.S. EPA, 1982. (Reference 1).
6-12
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TABLE 6-4. PERMEATION RATES FOR ORGANIC CHEMICAL VAPORS THROUGH SYNTHETIC MEMBRANES
o-
I
Membrane
Elasticized polyolefin
High-density polyethylene
Low-density polyethylene
Polybutylene
Teflon
Thickness
(mills)
22
30
30
27
4
Methanol
2.10
0.16
0.74
0.35
0.34
Vapor
Acetone
8.62
0.56
2.83
1.23
1.27
transmission 1
Cyclohexane
760
11.7
161
616
0.026
;§/m2/day]
Xylene
359
21.6
116
178
0.16
)
Chloroform
3230
54.8
570
2120
20.6
Source: Haxo et al., 1984. (Reference 5).
-------
TABLE 6-5. ESTIMATED UNIT COSTS FOR SOME SYNTHETIC MEMBRANES
Membrane Unit cost ($)
Hypalon (30-mil) 8.60/yd2
Neoprene 6.60/yd2
Ethylene propylene rubber 3.60 - 4.60/yd2
Butyl rubber 9.60 - 5.00/yd2
Teflon-coated fiberglass 26.50/yd2
Elasticized polyolefin 3.60 - 4.80/yd2
Chlorinated polyethylene 3.20 - 4.20/yd2
PVC membrane (20-30-rail) 3.20 - 4.20/yd2
Source: U.S. EPA, 1982 (Reference 1).
6-14
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Total cost estimate data are limited. In general, they are considered to
be somewhat greater than those for soil covers, but lower for most other
control measures.
FOAM COVERS
Introduction
Foam covers are a relatively new technology which can be used in much the
same manner as temporary soil covers. In terms of emission reduction, foam
covers perform identically to soil and synthetic cover systems described
previously. Foam covers have not been extensively utilized at hazardous waste
landfills, but they have been used in Europe for several years in sanitary
landfills as a substitute for a 6-inch soil cover. Use of foam covers in the
past, has served to minimize particulate and gaseous emissions, rodent
infestation, and disease-spreading organisms.
Description
Foam covers serve to limit emissions by acting as a barrier to vapor
diffusion and wind entrainment of wastes, and reducing the affect of solar
irradiation. In general, foams are used as a temporary cover system, applied
over waste materials at the end of each day.
Foams used as landfill covers are liquid-based materials. A wide variety
of foams may be applicable, depending on the waste characteristics and
landfill design. Foam systems used are either mixed on-site or are "ready
made" for immedite usage. Foams used to cover landfilled wastes are similar
to those used to control spills from containerized waste. For detailed
information on the materials, refer to Section 3.
Foam application is accomplished by either spraying or spreading material
over the waste. Foam systems may be applied by manual or mechanical devices.
Application equipment exists that can be operated by one worker. Larger
systems which can be attached to a tractor can cover an acre in 1-1/2 hours.
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Foam systems are a relatively new cover technology. The advantages to
such systems are their ease and speed of application, their ability to control
both particulate and VOC emissions, and their overall emission reduction
effectiveness. Foam systems are only applicable as a temporary system,
however, and thus necessitate daily costs. Foams may also be found to be
incompatible with certain types of waste.
The primary considerations involved in selecting and determining whether
a foam system is applicable for landfill coverage include:
• Type of foam. The chemical compatibilllty with waste materials,
mechanical (strength, durability) properties, and resistance to
prevailing weather conditions.
• Application procedure. The equipment, design, and personnel
required by a certain application procedure.
• Landfill status. Whether or not the landfill is active on a daily
basis, preparing for closure, or in the process of commencing
operations.
Emission Reduction Effectiveness
Foam covers are not a proven control technology for reducing VOC air
releases. As mentioned earlier, their primary use has been at sanitary
landfills. However, they may be effective at hazardous landfills as well. A
study on the effectiveness of various foams in the mitigation of air releases
from volatile chemical spills indicates that for nonpolar liquids, any high
quality foam cover, regardless of its chemical type, will provide some degree
Q
of mitigation of vapor release. Only alcohol foam was found to be stable
against highly polar low molecular weight liquids such as acetone. The best
foam agent in terms of vapor mitigation was the metal stearate-based alcohol
type foam. Actual efficiencies for vapor emission control were not available,
but it appears that most foams control vapors effectively for only 1 day or
less. Longer-term control may be achieved with respect to fugitive dust
releases.
6-16
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Costs
Costs of foam cover systems are, in general, moderate to high relative to
other comparable emission control alternatives. The costs are largely based
on materials, equipment, and operating expenses. The cost of chemical
reagents needed to generate a 2-inch layer of urea-methane complex foam is
approximately 11 cents per square foot. A one-man foam application system
costs about $4,350. The high capital cost for equipment and reagents, the
length of time required to apply the foam, and the temporary nature of foam
covers indicate that foam covers may not be the most cost-effective of
emission control options for vapor phase air release.
ENCAPSULATION/SOLIDIFICATION
Introduction
Encapsulation or solidification of wastes in a landfill serves to limit
emissions by changing the physical properties of the waste itself. This
process is considered to be effective for both vapor and particulate releases,
particularly in limiting the affect of external forces, such as wind, on waste
materials.
Solidification of wastes has been widely used, particularly in the
transport and disposal of radioactive wastes. Solidification has not,
however, been widely utilized at hazardous waste disposal sites, primarily
because of cost . Encapsulation techniques have only recently emerged from
development and testing stages, and no large commercial-scale encapsulation
facilities have yet been designed and operated. The application of these
technologies as vapor emission controls will be discussed in this section.
Description—
Waste solidification involves a number of techniques to seal wastes into
a hard, stable mass. The basic process involves combining waste material with
solidification agents. In theory, this would not only reduce the potential
for organics to be leached into ground water by infiltration, but would also
6-17
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limit Che evaporation of organics to the atmosphere. Six commonly used
methods of solidification are cement-based, lime-based thermoplastics, organic
polymers, self-cementation, and glassification. Absorbent materials can
also be used which reduce emissions by reducing the amount of exposed free
2
liquid. Mixing of solidification agents with waste should be carried out
in closed vessels or enclosures which are vented to a carbon adsorber or other
treatment system to minimize air releases to the atmosphere. Open mixing
2
should be avoided if possible.
Encapsulation is a process in which wastes are physically enclosed in a
synthetic encasement. TRW Systems Group has developed bench-scale processes
which are capable of encapsulating toxic and corrosive sludges and salts, as
well as containerized wastes. This system requires the use of polybutadiene
resin as an agglomeration agent and high-density polyethylene for an
encapsulation jacket. (See Figure 6-2). As was mentioned earlier, commercial
encapsulation facilities are not yet in operation at landfills. For a more
detailed discussion of encapsulation processes used to control emissions from
containerized waste, see Section 3.
The considerations which are involved in selecting an encapsulation or
waste solidification (e/ws) technology appropriate to a particular landfill
facility include:
• Waste characteristics. The volatility, density, corrosivity, and
diffusivity of waste materials to be encapsulated or solidified.
• Operational and equipment requirements. The need for specially
trained personnel, procedures, and equipment required by a certain
e/ws technology.
• Availability of materials. Whether or not the required materials
will be available, transportable, and interchangeable.
• Landfill status. Whether or not a landfill is active or inactive.
Emission Reduction Efficiency
No data are available in the literature on the fate of volatile organics
in solidified or encapsulated wastes. Some solidification agents are not
6-18
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-HIGH DENSITY
POLYETHYLENE
JACKET
WASTE/RESIN
AGGLOMERATE
PLATFORM
Figure 6-2. Encapsulation process concept.
(Source: U.S. EPA, 1982) (Ref. 1).
6-19
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compatible with organic wastes, and hence may not be applicable. These
include lime-based thermoplastics and self-cementing methods. The maximum
organic content of chemical wastes that can be solidified using cement is 2 to
3 percent because of process chemistry limitations. Organic polymers may
be biodegraded over time, losing their structural integrity and releasing
vapors to the atmosphere. Classification may be an effective solidification
method relative to emission reduction, but it has not yet been adequately
tested for this purpose.
Encapsulation is considered to have great potential in isolating many
types of waste from the environment, but also has not been adequately tested
on a large scale.
Costs
Cement costs range from $77 to $106 per ton at the mill.
Solidification costs will vary widely depending on the site and waste types.
Organic polymer solidification has been reported at $3.60 per gallon for
radioactive wastes. No specific cost information is available for
glassification, but it is expected to be very high because of its intensive
energy use, requirements for highly trained personnel, and sophisticated
machinery. Projected costs for encapsulation at a plant are $120 per ton of
waste. This estimate will vary depending on the nature of the waste and the
encapsulation materials used.
GAS COLLECTION
Introduction
Systems designed to collect gases which form at a landfill serve to limit
emissions by reducing the amount of volatile materials entering the
atmosphere. Gas collection systems are intended to divert vapors to control
systems such as a carbon adsorbers or afterburners. These technologies were
discussed previously for surface impoundments and storage tanks, and are
detailed in Section 4.
6-20
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Gas collection has been used primarily for controlling methane gas
generated in sanitary landfills, but lias also experienced some use for control
of volatile toxics as well.
In general, such technologies are considered to be highly effective. The
costs to implement such systems, however, may be high.
Description
In their simplest form, a gas collection system may consist of a single
pipe vent connected to a small fan, discharging to a treatment device. Since
the radius of influence of a single forced ventilation pipe has been found to
be as high as 200 to 300 feet, it is conceivable that a simple fan and vent
system could be used for landfills as large as 5 to 6 acres. Several
technologies are available for use in gas collection, including pipe vents,
trench vents, and gas barriers. These technologies are discussed below.
Pipe Vents—
Pipe vents consist of vertical or lateral perforated pipe installed in a
landfill either incrementally, as the landfill is still in operation, or as
part of landfill closure. They may be installed within or around the
landfill, and in combination with trench vents for lateral migration control.
The pipe vents are usually surrounded by a layer of coarse gravel or sand to
prevent clogging, as shown in Figure 6-3. Several pipe vents will connect to
an exhaust header which may, in turn, be one of several header branches
leading to a larger manifold blower. Each branch may have butterfly valves
for balancing and flowraeters for checking flow rate. Such complicated systems
are usually applicable only to landfills larger than 5 or 6 acres.
Trench Vents—
Trench vents are constructed by excavating a deep, narrow trench
surrounding a disposal site or spanning a section of the area perimeter. The
trench is backfilled with gravel, forming a path of least resistance through
which gases can pass. Trench vents are often used in conjunction with liners
to form an effective barrier against gas migration. To prevent organic vapor
emissions, the trenches are capped with clay or a synthetic membrane and
6-21
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NJ
To atmosphere
or treatment
To treatment
(a) Atmospheric
vent
Mushroom Top
Low permeability
soil
4-6" slotted
PVC pipe
Gravel
(b) Atmospheric
vent
"U" Top
(c) Forced
Ventilation
(d) Vertical pipe vents connected to forced
ventilation manifold system
Figure 6-3. Pipe and trench vents (U.S. EPA, 1982) (Ref. 1).
-------
fitted with collection pipes. These are connected to a negative pressure fan
which removes vapor from the landfill and directs them to a gas treatment
system such as an afterburner. Air can also be injected on one side of a
disposal area through a pipe or trench vent, and collected through a pipe or
trench vent on the other side. In some cases this may be the most effective
collection method. However, it is not desirable to exert net positive
pressure within a landfill, as seals may be ruptured, and vapors released.
Gas Barriers—
Barriers to gas or vapor migration can be employed in a number of ways at
waste disposal sites. Low permeability materials suitable for constructing
gas barriers include compacted clay, concrete slurry walls, gunite, and
synthetic liners. These barriers can be used to direct vapors or gases to
trench vents or prevent lateral migration outside of the landfill area.
Emission Reduction Effectiveness
The efficiency of gas collection and treatment systems depends primarily
on the collection system, because the treatment portion can usually achieve
2 Q
levels of efficiency exceeding 95 percent. One study has estimated that
landfill gas control efficiency is between 70 and 90 percent. Trench vents
attached to a negative pressure fan or blower by collection pipes offers the
most effective lateral control method if the trenches extend to ground water
or bedrock. Pipe vent systems may be somewhat less effective but may be less
o
expensive and useful at a greater depth. The use of gas barriers to
control lateral gas movement has not been tested. The discussion on synthetic
and clay liners, however, indicates that they will not be extremely effective
as they are somewhat permeable to some organic vapors. The integrity of
concrete slurry walls and gunite barriers may be difficult to achieve and
maintain.
6-23
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Costs
Costs associated with gas collection systems are considered to be high
relative to other control alternatives, due to the complexity of the systems
involved. The costs are based primarily on equipment costs and installation
costs. The cost of installed vent pipe range from $2.60 to $3.30 per inch
(diameter) per foot (depth) for small diameter pipes. This excludes casing
costs. Casing costs are $6.00 and $8.60 per foot for 4-inch and 6-inch
casings, respectively. In addition, the cost for a fan capable of producing
3 inches of static head and a flow rate of up to 3 cfm would be approximately
$800. Therefore, the total installed cost of a single forced ventilation pipe
vent, 4 inches in diameter and 30 ft deep would be approximately $1450. This
does not include treatment of the collected vapors.
The cost associated with trench vent installation includes the excavation
cost in addition to costs for the gravel fill, the lateral and rise pipe, and
liner material. Excavation accounts for 80 percent of the total cost. The
total installed cost of a trench vent 20 ft deep, 4 ft wide, and 500 ft long
o
(1500 yd ) using a hypalon liner would be approximately $330,000.1
AIR-INPLATED STRUCTURES
Introduction
• i i ^^^^— * *
An air-inflated structure is a system which completely covers a
landfill. Emissions are effectively reduced by such systems because they act
not only as a synthetic membrane cover, but as a gas collection system as well.
Air-inflated structures have been used to some degree for reducing
emissions from or keeping precipitation out of surface impoundments. The
principle behind air-inflated structures could be easily applied to
landfills. No information was found describing their use over landfills.
Description
An air-inflated structure consists of a large synthetic membrane, sealed
around the edges, and filled with air for support. Usually large fans or
b-24
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blowers introduce air into the structure, and the structure is vented to a
carbon adsorber, afterburner, or other gas treatment system. Thus, emissions
from a landfill would be collected and treated before they could reach the
atmosphere. Air locks for vehicle entrance and exit can be installed,
allowing emission-free entrance. Air-inflated structures could be used to
cover landfills ranging in size from a fraction of an acre to 5 or 6 acres.
Section 4 of this report provides a discussion of this vapor
collection/treatment system.
The use of air-inflated structures to cover landfills has not been
documented. This type of air emission control technology has, however, been
utilized to control emissions from surface impoundments. Two applications,
one at the UpJohn chemical company in New Haven, CT, and another at American
National Gas, in Beulah, ND, have been discussed previously in Section 5 of
this document.
The primary considerations involved in selecting and determining the
applicability of a suitable air-inflated structure design for a particular
landfill include:
• Synthetic membrane materials. The materials chemical compatibility
with waste materials, tensile and tear strength, and resistance to
weather conditions.
• Landfill design. The size, shape, and cell design of a particular
landfill.
• Landfill operational and maintenance characteristics. The frequency
of access and egress, usage patterns, and maintenance requirements
of a landfill.
• Support system. The costs, maintenance, location, and energy
requirements of the air support system.
Emission Reduction Effectiveness
The efficiency of an air-inflated structure is dependent primarily on the
vapor permeability of the membrane and the air-tightness of the structure.
Relatively impermeable, well-sealed structures vented to gas treatment systems
are generally 95 percent efficient, or more. As mentioned previously with
regard to synthetic covers, emissions through synthetic membranes may be
substantial. However, the use of a high-performance cover, such as the
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Teflon-lined membrane used at Che Upjohn facility will serve well to reduce
emissions.
Costs
The cost of the Upjohn structure was about $400,000, including
installation. In addition, carbon adsorbers, fans, and other expenses
totalled about $100,000. The American Natural Gas structure also cost
approximately $400,000, installed. Costs of this control option will vary
depending on the materials used and the size of the landfill. Estimated costs
for two sizes of air-inflated structures are presented in Table 6-6. The two
sizes represent the approximate range of landfill sizes over which an
air-inflated structure can be built. Based on these estimates, costs will
range from $6 to $9 per square foot of floor space.
Despite their high cost, air structures may be applicable in certain
situations. If an air-inflated structure were installed over a large
landfill, there would be no need for soil or synthetic covers or other gas
collection systems. Precipitation would be kept out, and volatiles would be
effectively collected and removed.
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TABLE 6-6. CAPITAL COSTS FOR AIR-INFLATED STRUCTURESa
17,000 ft2
260,000 ft2
Structure
Heating
Lighting
Vehicle air lock
Installation
Total
Annualized
(10%, 10 years)
70,000
24,500
15,000
15,000 - 24,000
25,500
150,000
24,000
985,000
175,000
Not estimated
Not estimated
390,000
1,600,000
250,000
Source: A. D. Little, 1984 (Reference 2).
aTreatment system costs not included.
6-27
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REFERENCES
1. USEPA, Office of Research and Development. Handbook for Remedial Action
at Waste Disposal Sites. EPA-625/6-82-006. U.S. Environmental
Protection Agency, Office of Research and Development, Cincinnati, OH.
June 1982.
2. Arthur D. Little, Inc. Evaluation of Emission Controls for Hazardous
Waste Treatment, Storage, and Disposal Facilities. EPA-450/3-84-017.
U.S. Environmental Protection Agency, Office of Air Quality Planning and
Standards, Research Triangle Park, NC. November 1984.
3. Farmer, W. J., M. S. Yang, J. Letey, and W. F. Spencer. Land Disposal of
Hexachlorobenzene Wastes. Controlling Vapor Movement in Soil.
EPA-600/2-80-119. U.S. Environmental Protection Agency, Office of
Research and Development, Cincinnati, OH. August 1980.
4. R. S. Means, Inc. Building Construction Cost Data. 42nd Edition. R.S.
Means, Inc. 1983.
5. Haxo, H., et al. Permeability of Polymeric Membrane Lining Materials.
Proceedings, International Conference on Geomembranes, Denver, CO. June
1984.
6. Vogel, G. A., and D. F. O'Sullivan. Air Emission Control Practices at
Hazardous Waste Management Facilities. MTR-83W89. Prepared for U.S.
Environmental Protection Agency, Office of Solid Waste. Contract
No. 68-01-6092. The MITRE Corporation, McLean, VA. June 1983.
7. Davanzo, T., U.S. Environmental Protection Agency Region I, Boston, MA.
Communication with A. Baldwin, GCA Corporation. March 1985.
8. Gross, S.S., and R. H. Hiltz. Evaluation of Foams for Mitigating Air
Pollution from Hazardous Spills. EPA-600/2-82-029. U.S. Environmental
Protection Agency, Office of Research and Development, Cincinnati, OH.
Contract No. 68-03-2478. March 1982.
9. SCS Engineers. Costs of Remedial Response Actions at Uncontrolled
Wastes Sites. Prepared for U.S. Environmental Protection Agency, Office
of Solid Waste. Contract No. 68-01-4885. SCS Engineers, Covington, KY.
April 1981.
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OTHER REFERENCES
Shrenfeld, J., and J. Bass. Handbook for Evaluating Remedial Action
Technology Plans. EPA-600/2-83-076. U.S. Environmental Protection
Agency. Office of Solid Waste, Washington, DC. August 1983.
Kinraan, R. N., and D. L. Nutini. Production, Migration, and Hazards
Associated with Toxic and Flammable Gases at Uncontrolled Hazardous
Waste Sites. Proceedings: Tenth Annual Research Symposium,
Ft. Mitchell, KY, April 3-5, 1984. EPA-600/9-84-007. U.S.
Environmental Protection Agency, Office of Research and Development,
Washington, DC.
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SECTION 7
CONTROL OF AIR EMISSIONS FROM
LAND TREATMENT FACILITIES
INTRODUCTION
Land treatment is a method of destroying wastes by applying them to a
plot of land and allowing soil microbes to biodegrade them. Because the waste
is often tilled to enhance biodegradation, significant volatilization of
organics may also occur. The technologies in this section describe methods
which reduce vapor emissions by.
• providing a barrier against free diffusion (covers);
• changing operating practices including subsurface injection,
decreasing application rate, and increasing soil moisture content;
and
• collecting and treating the vapors generated (air-inflated
structures).
Table 7-1 presents an overview of the advantages and disadvantages of the
land treatment facility control technologies described in this section. Costs
and efficiencies of these technologies will also be examined in detail.
CHANGES IN OPERATING PRACTICES
Introduction
Since volatilization of organic compounds in soil is greatly influenced
by such practices as tilling, changing certain operating practices can
significantly reduce emissions from land treatment areas. Changes in
7-1
-------
TABLE 7-1. LAND TREATMENT EMISSION CONTROL TECHNOLOGIES—ADVANTAGES AND DISADVANTAGES
Advantages
Disadvantages
OPERATIONAL PRACTICES
• Subsurface injection is expected to achieve
significant emission reductions for some
wastes.
• A subsurface injection tool bar can be
fitted onto an existing waste application
vehicle at nominal cost.
• Maintaining a high soil moisture content
will reduce emissions significantly.
• Reducing waste application rates may in-
crease biodegradation rates, resulting in
a decrease in emissions.
Subsurface injection may not be effective for
highly volatile compounds.
High initial cost for a complete subsurface
injection vehicle.
Increasing injection depth may decrease bio-
degradation rates, resulting in an increase
in emissions.
Reducing application rates may not be
economically justifiable, given the small
emissions reductions possible.
COVERS
May serve as effective temporary measures
to reduce emissions from land treatment
areas, especially if the wastes being
treated are highly volatile.
Soil covers increase the volume of material
present in the land treatment area, limiting
the volume of waste that may be applied.
Synthetic membranes can be easily torn or
punctured, limiting their effectiveness as
temporary covers.
Foam covers are not compatible with certain
wastes.
(continued)
-------
TABLE 7-1 (continued)
Advantages
Disadvantages
COVERS (continued):
AIR-INFLATED STRUCTURES
• Expected to achieve high collection/removal
efficiencies.
• May be necessary for land treatment areas
receiving highly volatile wastes or
located in densely populated areas.
• If adopted biodegradation rates could be
maximized without heed to odor generation
or volatilization.
• Have been constructed over surface
impoundments.
• Can cover areas as large as 5 to 6 acres.
• If a carbon adsorption system is used,
condensate from steam regeneration of the
carbon may be returned to the land treatment
area to be further biodegraded.
• Foam covers may be too expensive for
temporary use.
• Covers may decrease biodegradation rates,
resulting in an increase in emissions.
• High cost.
• Requires treatment system.
• May be somewhat permeable to vapors, depend-
ing on materials used.
• Have not been used over land treatment areas.
-------
operating practices involve both the purchase and installation of new
equipment or facilities, and/or the alteration of waste treatment and handling
methods employed at the facility. One change that can be made is to inject
wastes below the land surface, as opposed to applying them on the soil surface
and tilling them into the soil. Other changes include decreasing the waste
application rate and maintaining a high soil moisture content.
Description
Subsurface Injection—
Subsurface injection is a method of applying wastes below, as opposed to
on the land surface. This minimizes waste contact with the atmosphere,
resulting in reduced emission rates. Basic subsurface injection equipment
consists of a tool bar attached to the rear of a truck or tractor with two or
more chisels, similar to a chisel tooth plow, attached. Adjustable sweeps are
often mounted on or near the bottom of the chisels to open a wide but shallow
cavity underground. A tube connected to the waste source leads down the back
of the chisel, and, as the sweeps open a cavity, the waste is injected. With
proper adjustment and use, very little waste reaches the soil surface.
Using this method, waste is usually injected 4 to 8 inches below the land
surface. In other devices, waste is simultaneously injected below land
surface and mixed into the top 6 to 10 inches of soil. The initial injection
may be followed closely by a second pass with a cultivator to distribute waste
7
uniformly throughout the treatment area. In all cases, waste should be
injected to the maximum depth consistent with maintaining high biodegradation
rates. If biodegradation rates are decreased significantly by deep injection,
waste will remain in the soil for longer periods of time.
Subsurface injection was originally developed by the agricultural
industry and is commonly used for applying anhydrous ammonia and liquid
manures. Subsurface injection is recommended for any biodegradable wastes
with volatile and/or odorous constituents, such as wastes generated in the
petroleum and chemical manufacturing industries.
7-4
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Decreased Application Rate—
Emission rates are affected by the waste application rate per unit
area. In theory, waste should be applied at the maximum rate compatible
with the degradative capabilities of the land treatment soil/microbe system.
In practice, however, land treatment areas are generally overloaded with
waste, resulting in decreased biodegradation rates, and subsequently increased
emission rates due to increased residence time of wastes in the soil. Nominal
application rates range from about 22 to 66 metric tons per hectare.
Moisture Control—
As discussed earlier under the section on landfill soil covers (see
Section 6 for further details), effective diffusivity of organic vapors can be
increased dramatically with only small decreases in soil moisture content.
Maintaining soil moisture at the highest levels consistent with good
biodegradation rates and soil workability will serve to greatly reduce
2
emissions. This can be achieved by using spray trucks or by installation
of an irrigation system.
Emission Reduction Effectiveness
Table 7-2 shows theoretical annual losses from a 1-acre land treatment
i-\
area based on emission equations discussed by A. D. Little (1984).
Although the equations do not include the effects of biodegradation, the data
are useful for comparing surface application versus subsurface injection.
Actual emissions would probably be lower in both cases by varying amounts due
to biodegradation. The data indicate that for compounds of low volatility
(vapor concentrations below approximately 1000 ppm), subsurface injection
reduces emissions by more than 90 percent as compared to surface application
followed by plowing under. For higher volatility compounds, efficiency may be
less than 60 percent.
7-5
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TABLE 7-2. ANNUAL EMISSIONS FROM A THEORETICAL 1 ACRE LAND TREATMENT AREAa
Surface application
followed by tilling
Depth of injection
Depth of plow slice
0
4"
0
8"
Subsurface injection
4"
4"
8"
8"
Percent
4"
4"
reduction
8"
8"
Equilibrium Vapor Pressure
(ppm by volume)
1
5
10
50
100
10
50
100
500
,000
,000
,000
,000
,000
4.8
10.7
15.2
34
48
107
152
287b
287b
3.4
7.6
10.7
24
34
76
107
246
287b
0.1
0.2
0.4
2
4
20
40
200
287b
0.05
0.1
0.2
1
2
10
20
100
200
98%
98
97
94
92
81
74
<59
« 59
99%
99
98
96
94
87
81
59
<59
allnits are in metric tons per year; 287 metric tons of waste applied per year.
bComplete (100%) loss.
Source: A. D. Little, Inc., 1984. (Reference 2).
-------
The emissions reductions associated with reducing the application rate of
wastes will depend on factors such as soil type and waste types applied, but
overall will be relatively small as compared to reductions from using
subsurface injection.
Emissions reductions achievable by maintaining a high soil water content
have been described under the section on landfill soil covers (Section 6). In
general, a small increase in water content results in a substantial decrease
in emissions from soils due to the decrease in the soil's air-filled porosity.
Costs
The cost of a subsurface injection vehicle will range from $98,000 to
$158,000, depending on the vehicle's waste storage capacity, engine size, and
3
the addition of optional equipment. However, a subsurface injection tool
bar fitted onto an existing waste application vehicle costs between $5,400 and
$8,700.3
Decreasing the application rate may involve substantial costs, as more
land would be required to treat a given quantity of waste. If more land was
not available, costs would be incurred in the form of alternative offsite
treatment methods.
Maintaining a high soil moisture content may involve initial capital
costs for spray trucks or irrigation systems, but operating costs will be very
low.
Overall, it appears that both subsurface injection and maintaining a high
soil moisture content are very cost-effective methods for emission reduction.
Higher efficiencies can be obtained, particularly for highly volatile wastes,
or at land treatment areas in congested locations by installing systems such
as air-inflated structures with vapor collection/treatment devices. However,
costs can be substantially higher. (See Section 4 for a discussion of vapor
collection/treatment systems).
7-7
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COVERS
Introduction
Covers similar to those employed at landfill facilities (see Section 6)
may be used as a land treatment facility emission control device. A cover
acts as a physical barrier to both external forces such as wind, soil, and
vapor diffusion from the soil matrix. The various covers which may be used at
a land treatment facility are the same as those used at a landfill, namely:
• soil;
• synthetic membrane; and
• foam covers.
There is little evidence that covers have been used at land treatment.
However, covers are considered to be a potentially effective, relatively low
cost control option.
Description
Any material or system which can be applied over land treatment facility
which acts as a physical barrier to vapor diffusion, and to external forces
such as solar irradiation, wind, and precipitation is called a cover. Land
treatment covers are made from solid or semisolid (foam) materials, applied as
continuously as possible over the surface area. In general, application
procedures require a truck or tractor due to the size of the facility.
Depending on the system employed, land treatment covers are sprayed, sifted,
or spread over the soil/waste complex. Covers may be used as a temporary
emission control measure on active land treatment, but are perhaps more
applicable to inactive facilities. In general, the selection and
determination of the most appropriate cover system to be implemented at a
land-treatment facility must consider the following important factors:
• Design of land treatment facility. The size, shape, slope, and
vehicular negotiability of a land treatment facility.
7-8
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• Type of waste materials. The vapor diffusivity, chemical
compatibility with cover materials, biodegradation characteristics,
and application requirements of the waste materials.
• Design of cover systems. The application procedure, materials.
handling requirements, strength, weather resistance, durability, and
vapor permeability.
• Operating procedures. The personnel requirements, waste handling
methods, and activity of a particular facility.
Further detail on the three cover systems is provided in Section 6 of this
document on landfill emission control technologies.
Emission Reduction Effectiveness
The efficiency of covers in reducing emissions was discussed in detail in
the landfill section (Section 6). Synthetic membranes may be easily torn or
punctured in the field, and may be awkward to put into place. Foam covers may
not be effective for certain types of waste. Soil covers would increase the
volume of material in the land treatment area, limiting the volume of waste
that could be applied. In all cases, covers will provide a barrier to free
diffusion, but because they are not part of a collection and treatment system,
diffusion will continue at a reduced rate. Also, covers may affect the
biodegradation rate of wastes in the land treatment area by changing factors
such as oxygen content and/or temperature. Such changes may ultimately result
in greater emissions.
Costs
Costs for soil, synthetic, and foam covers have been discussed in the
landfill section of this report (Section 6). Overall, it appears that changes
in operating practices will be more cost-effective than covers. If, however,
the waste in question is of high volatility, and subsurface injection cannot
offer sufficient control, covers may be a viable option for temporary emission
control.
7-9
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AIR-INFLATED STRUCTURES
Introduction
The use of air-inflated structures at land treatment facilities has not
been documented in the literature. Such structures have been used for
reducing air emissions from surface impoundments, as discussed in Section 5.
It is conceivable that air-inflated structures would be equally, if not more
applicable to land treatment areas, due to the higher potential for
significant air releases.
Description
Air-inflated structures consist of a synthetic membrane structure
supported by air pressure and attached with cables or by other means to a
foundation. Fans force air into the structure which is then vented to a
treatment system to remove organic vapors. Used over a land treatment area,
biodegradation rates could be maximized without regard to volatilization from
the soil (e.g., by using surface application). Organic vapors emitted from
the soils would be captured by the structure and treated. If a carbon
adsorption system is used, condensate from steam regeneration of the carbon
may be returned to the land treatment area for further treatment. Air
structures can be constructed over land treatment operations ranging in size
o
from a fraction of an acre to 5 or 6 acres.
Emission Reduction Effectiveness
As mentioned in Section 6, the efficiency of air-inflated structures is
dependent on the permeability of the membrane and air-tightness of the
structure, as treatment technologies can effect greater than 95 percent
removal. Emissions through membranes can be significant over a large area.
However, since the vapor concentration within the structure is expected to be
lower than that under experimental conditions, it is expected that emissions
through the membrane will be minimal, hence, air-inflated structures are
7-10
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expected to achieve better emission reduction rates for higher volatility
compounds than subsurface injection. For low-volatility compounds, the
efficiency is expected.,tx> be about the same, or less.
Costs
Costs for air-inflated structures have been presented in the landfill
section (refer to Table 6-6 in Section 6). Air-inflated structures may be
more cost effective for land treatment areas than for landfills because of the
potential for greater emissions from land treatment. The use of air-inflated
structures is an option to be considered for land treatment areas in densely
populated zones and/or if highly volatile or odorous constituents are being
treated.
7-11
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REFERENCES
1. Brown, K. W., and L. Devel. Hazardous Waste Land Treatment. SW-874.
Second Edition. U.S. Environmental Protection Agency, Office of Research
and Development, Cincinnati, OH. February 1983.
2. Arthur D. Little, Inc. Evaluation of Emission Controls for Hazardous
Waste Treatment, Storage and Disposal Facilities. EPA-450/3-8-017. U.S.
Environmental Protection Agency, Office of Air Quality Planning and
Standards, Research Triangle Park, NC. November 1984.
3. Vogel, G. A., and D. F. 0'Sullivan. Air Emission Control Practices at
Hazardous Waste Management Facilities. MTR-83E89. Prepared for U.S.
Environmental Protection Agency, Office of Solid Waste. Contract
No. 68-01-6092. The MITRE Corporation, McLean, VA. June 1983.
7-12
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SECTION 8
CONTROL OF AIR EMISSIONS
FROM WASTE PILES
INTRODUCTION
Waste piles are a common method of storing solid wastes. Storage in a
waste pile is particularly applicable to fine-grained waste materials, such as
ash, sand, or contaminated sorbent. Some of the waste material kept in piles
at TSDFs may contain volatile organic compounds. Because of the physical
nature of these wastes, they may be subject to erosion by wind, resulting in
fugitive dust emissions, or volatilization of any organic materials present in
the wastes. A variety of methods are described in this section which control
fugitive dust emissions and/or vapor emissions from waste piles, including:
• enclosure (covers);
• stabilization (physical, chemical, vegetative, or wet dust
suppression);
• vapor collection and destruction (gas extraction);
• windscreens; and
• changes in operating practices.
Table 8-1 provides an overview of the advantages and disadvantages of waste
pile emissions control technologies described in this section. These methods
will also be examined in detail in terms of cost and emission reductions
effectiveness.
8-1
-------
TABLE 8-1. WASTE PILE EMISSION CONTROL TECHNOLOGIES—ADVANTAGES AND DISADVANTAGES
Advantages
Disadvantages
00
i
N>
STABILIZATION
• Chemical stabilization may be very effective
for extended periods of time.
• A wide variety of chemical stabilizers are
.available.
• Chemical stabilization is easy to implement.
• A vegetation/soil cover is adaptable to both
fugitive dust and organic vapor emissions.
• A wide variety of suitable plant species
are available for vegetative stabilization.
• Wet dust suppression can be used to minimize
dust emissions during material loading to the
waste pile as well as providing effective
short-term control.
• Some chemical stabilization agents are
expensive.
• Vegetative stabilization may require treatment
or soil covering of the waste pile before an
effective cover can be achieved.
• Vegetative stabilization will require some
period of time to establish an effective cover.
(Chemical stabilization may be used until the
plants develop).
• Wet dust suppression is effective only as a
temporary measure.
• Wet dust suppression may not be capable of
achieving high efficiencies.
• Actual efficiencies of physical and vegeta-
tive stabilization are unavailable.
• Stabilization is generally not an effective
control for vapor emissions.
(continued)
-------
TABLE 8-1 (continued)
Advantages
Disadvantages
00
I
WINDSCREENS
• Commercially available in many configura-
tions.
• Simple in design and construction.
• Reduces wind speed over pile surfaces.
COVERS
• Storage domes and synthetic membrane tension
structures reduce particulate emissions to
virtually zero.
• May be used as a gas collection system if
designed to be air-tight and vented to a
treatment system.
• Both may be used for active waste piles.
• Storage domes will retain their structural
integrity for a long period of time.
• Storage domes are a widely used technology
for material storage.
• Synthetic membranes are widely used at
landfills.
• Probably not effective in reducing emissions
of small, "respirable" particles.
• Installed costs are high.
• Tension structures may lose their structural
integrity due to natural processes.
• Requires treatment system if used for volatile
wastes.
(continued)
-------
TABLE 8-1 (continued)
Advantages
Disadvantages
do
I
GAS EXTRACTION
• May be effective in controlling organic
vapor emissions.
• Because the system is installed incremen-
tally, it can be operated while the waste
pile is still active.
• Can be used in combination with other
control technologies (e.g., tension
structures, chemical stabilization).
• Moderate cost.
OPERATIONAL PRACTICES
• Some changes cost little or nothing to
implement (e.g., increasing operator
awareness).
• Telescopic chutes may be very cost-
effective.
• Some controls have experienced usage in
the steel and crushed stone industries.
• Does not control fugitive dust emissions,,
• May not achieve high removal efficiencies if
used as sale control.
• Requires treatment system.
• Not a proven technology.
• No tests have been performed to determine
the efficiencies of these controls.
• Height-adjustable stackers and wind guards may
be very expensive.
• Changing slope, orientation, or surface area of
a waste pile are not proven control methods.
• These methods do not control organic vapor
emissions.
-------
STABILIZATION
Introduction
Stabilization is a means of decreasing fugitive dust (particulate)
emissions from waste piles by minimizing the effects of wind erosion on the
pile surface. Stabilization primarily affects particulate emissions, although
in some cases it may act to decrease the emission of volatile organic
chemicals as well. Stabilization techniques include dust suppression,
chemical stabilization, and vegetative stabilization. Stabilization
techniques have been used to control fugitive dust emissions from coal refuse
piles, mineral refuse piles, metallic tailings piles, and solid wastes which
are stored in piles. Stabilization, as a dust control method, has also been
used on unpaved roads, process materials handling, and agricultural dust sources
such as fields. In general, stabilization is considered to be easy to
implement at an existing facility, and capable of effecting moderately high
emission reduction. The costs involved in such systems range from being
inexpensive to very expensive, depending on the system selected and the
various constraints of the facility.
Description
Wet Dust Suppression—
Wet dust suppression involves the application of water or aqueous-based
wetting agents on the waste pile. This technique serves to limit fugitive
dust emissions by stabilizing dust particles in the pile via surface tension
effected by moisture, thus reducing entrainment of particles as wind blows
over the piles. Due to evaporation, wet dust suppression is a short-term
control. It is necessary in most cases to maintain the moisture content at a
certain level by frequent application of the wetting agent.
Water or wetting agents are usually applied by a spray truck or hose
every few hours, although a facility may alternatively choose to install a
permanent sprinkler system to service a pile or group of piles. A variety of
wetting agents have been used, depending largely on the type of waste
8-5
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materials being stored. The wetting agents serve to enhance particle wetting,
moisture spreading, and pile penetration, which can be key factors affecting
the effectiveness of wet dust suppression as an emission control.
Wet dust suppression has found widespread usage as an emission control
technique, largely due to the low cost and ease of implementing such systems.
It can also be used to control dust emissions during pile loading, and
material handling and transfer operations. The emission reduction
effectiveness of dust suppression, however, is considered to be low (relative
to other measures).
Chemical Stabilization—
Chemical stabilization is similar to wet dust suppression. This
technique utilizes chemical binding materials, which, upon drying, bind with
surface particles to form a protective crust. A wide variety of such chemical
suppressants are commercially available including such agents as Orzan GL-50
(lignosulfate). Coherex (oil byproduct), Liquidow (calcium chloride), and
1 2
SP-301 (synthetic polymer), to name a few. ' These agents may be more
effective on some wastes than on others.
Chemical stabilizers are usually applied in diluted form with spray
equipment in a manner similar to using wet dust suppression. The major
difference is that some chemical stabilizers may remain effective for periods
of 6 months or longer, as opposed to only a few hours for wet dust
3
suppression. Additionally, the emission reduction effectiveness of
chemical stabilization is much higher than that of wet dust suppression. The
cost of such agents, however, is also much higher.
Vegetative Stabilization—
Vegetative stabilization involves covering of a waste pile with a layer
of vegetation, such as grass. Vegetative stabilization is useful in the
stabilization of a variety of surfaces and can be used in conjunction with
other controls, such as chemical stabilization. A wide variety of plant
species have been found to be effective at stabilizing different waste pile
materials. The main factor in reducing dust emissions from waste piles is
achieving a uniform, high density plant cover. To that end, grasses such as
rye, bluegrass, sorghum, and bromegrass may be effective.
Usually some modification to the waste pile surface must be made before
effective stabilization can occur, such as the addition of topsoil,
8-6
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fertilization, pH modificatioa, and/or slope reduction. Vegetative
stabilization is restricted to inactive piles because of the time required to
achieve an effective cover. To minimize dust emissions while the cover is
developing, chemical stabilization agents may be applied.
Emission Reduction Efficiency
The available data on the control efficiency of wet dust suppression are
minimal. Reported efficiencies are 30 percent for highly disturbed storage
piles and 67 percent for nondisturbed storage piles, but these results are
very dependent on soil types, local climatic conditions, and frequency of
application.
A study on dust control measures for active hazardous waste site cleanup
indicates that water spraying of the working area of a front end loader and
duraptruck resulted in a control efficiency of 42 percent for particles less
than 30 micrometers in diameter, and 64 percent for particles smaller than
2.5 micrometers . Control efficiency for less than 3- micrometer particles
increased to 63 percent with the addition of Johnson-Marsh compound MR (a
surfactant). Watering proved to be effective for only a few hours.
As part of the same study, dust was sprayed as it was being dumped from
the front end loader into the dump truck. This method was determined to be
50 percent efficient for particles smaller than 30 micrometers, and 56 percent
for particles smaller than 2.5 micrometers.
Asa et al. found that some chemical stabilizers reduced asbestos
emissions from roads paved with surfacing material containing serpentinite by
80 to 90 percent. The study also found that stabilizers which formed a
solid, water-resistant surface coating which bound road aggregates together
retained better than 80 percent emission reduction after 6 months, despite
vehicular traffic. Drehmel et al. found that the stabilizers they tested in
the laboratory were generally 50 to 70 percent efficient.2 The relative
effectiveness of some of the chemicals they tested as represented by
entrainraent velocity are presented in Table 8-2. It can be seen that
8-7
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TABLE 8-2. COST AND RELATIVE EFFECTIVENESS OF SOME CHEMICAL
STABILIZATION AGENTS
re
Agent
Coherex
CPB-12
Lignosulfate
Oil and water
Pentron DC3
Polyco 2151
SP-301
Co s t at
icommended rateb
(^/hectare)
1160
874
1136
2360
1647
168
3020
Entrainment
At manufacturer's
recommended rate
55
35
61
61
44
48
55
velocity3
At a cost of
$750/hectareb
44
32
61
60
30
50
21
Source: Drehmel et al., 1982 (Reference 2).
aLowest wind velocity in mph to cause 10 gm/min reentrainment.
bFebruary 1982 dollars.
8-8
-------
lignosulfate and oil and water are probably the best dust control agents,
based on wind tunnel data using coal dust.
Rosbury et al. have reported that the chemical stabilizers they tested
were approximately 100 percent effective for 1 to 4 weeks, with declining
control efficiencies thereafter. Their results were based on actual field
measurements of particle emissions generated from exposed soil plots.
The control efficiency of vegetative stabilization will vary considerably
depending on the amount and type of cover on the pile. One report estimates a
control efficiency between 50 and 80 percent for tailings piles, based on
typical plant growth rates. The same report estimates a 93 percent
reduction in windblown emissions by using a combination of chemical and
vegetative stabilization. As mentioned earlier, the most important factor
in reducing emissions is to achieve complete, high density plant cover.
Efficiencies of 100 percent should be approached with careful construction of
soil cover and vegetation, which would be applicable to nonsoil wastes. Such
a cover system should also reduce organic vapor emissions substantially.
Contaminated soil may not support a dense vegetation cover depending on the
concentration and type of waste on it. In this case, the addition of a clean
topsoil cover may be necessary.
Costs—
Costs for various chemical stabilization agents tested by Drehmel et al.
are presented in Table 8-2. Also shown in Table 8-2 is a measure of relative
cost-effectiveness, and the entrainment velocity at an application cost of
$750/hectare (based on February 1982 dollars). It can be seen, for example,
that although SP-301 is effective at the manufacturer1s recommended
application rate, it is not effective when applied at a lower cost of $750 per
hectare. Lignosulfate, however, was equally effective at the recommended
application rate and the lower application cost of $750/hectare. Polyco 2151,
a synthetic copolymer manufactured by Borden, may be the most cost-effective
agent, being effective at a cost of only $168 per hectare (about $190/hectare
in March 1985 dollars).
Cost for wet dust suppression, physical stabilization, and vegetative
stabilization were unavailable. Costs for wet dust suppression and physical
8-9
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stabilization are expected to be low, labor generally being the largest cost
involved with implementation. Costs for vegetative stabilization may increase
substantially if significant pile surface modifications or treatment are
necessary in development of an effective cover.
WINDSCREENS
Introduction
Emissions from waste piles are impacted most significantly by the affects
of prevailing winds. Winds blowing over waste piles generate fugitive dust
emissions due to particle entrainment, and volatile organic compound emissions
(when waste pile material is contaminated with VOC) by forced convection.
Windscreens are devices used at waste piles to act as a physical barrier
to the wind. Windscreens have found widespread application at TSDF for waste
pile control. Many designs have been developed. The designs used are similar
to those described for the control of storage tanks (see Section 4), surface
impoundments (Section 5), and landfills (Section 6).
Windscreens are considered to be capable of achieving moderate emission
reductions. The costs of such systems are regarded as being relatively low,
depending on the physical constraints of the waste pile.
Description
Waste pile windscreens are very much like the wind barriers described in
previous sections (see above) for control of other TSDF processes. Typically,
a windscreen is a simple wall or fence, extending either completely around the
waste pile or placed in the direction of prevailing winds. The windscreens
are all setaiporous to wind, which is necessary because use of a solid wall
would create a turbulent layer opposite the "wind side" which would decrease
the wind reduction effectiveness.
A typical example of a waste pile windscreen is a "snow fence," i.e., a
picket fence to which a porous synthetic membrane is attached. In installing
a windscreen wind dispersal control of a waste pile, the following
considerations are most significant:
8-10
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• Height of windscreen. The barrier must be high enough to effect
emission reductions (the higher the barrier, the greater the area of
reduction effectiveness), but cannot be too high due to structural
and cost considerations.
• Windscreen material. The type,of material (system design) used may
depend on weather, chemical, and operational activities of the
facility.
• Operational considerations. The effect of a windscreen on the
normal operation of a waste pile facility may determine its
applicability.
• Orientation of windscreen. How the windscreen is set up relative to
the wind pile has a bearing or emission reduction effectiveness.
Constraints relative to orientation may therefore have an affect on
the applicability of a certain system.
Emission Reduction Effectiveness
Several laboratory and field tests have been conducted to determine the
effectiveness of windscreen control of waste piles. The results of the
studies have indicated that the efficiencies of such systems may be as high as
80 percent, and in general are expected to be moderately high. The general
results indicated, however, that the effectiveness of such systems is highly
dependent on particle size, and, in fact, below a certain particle size may be
ineffective. The studies also indicated that the effectiveness of waste pile
windscreens depends upon the height of the barrier, distance from the pile,
and orientation.
Soo et al. conducted wind tunnel tests to simulate the effectiveness wind
barriers in reducing wind velocity over storage piles. Preliminary results
indicated that a barrier simulating a snow fence one-third the pile height
with a wind porosity of 33 percent would reduce winds by 50 percent at a
distance of three pile-heights away.
Drehmel et al. conducted tests on wind barriers with porosities of 50 and
65 percent. Wind speeds were reduced by 65 percent and 40 to 70 percent,
respectively (depending on the location of the measurement).2 The study
also indicated that solid barriers provided no protection against wind
entrainraent at a storage pile due to increased turbulence.
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A study conducted by Rosbury et al. has indicated that windscreens are
only moderately effective on larger particles, and are ineffective on
wastepiles consisting of small particles. This study is considered to be
of great validity due to its reliance on actual emissions measurements rather
than modeling.
In general, windscreens are considered to be relatively effective, based
on their widespread application. They would not be expected to be as
effective as certain other measures, such as chemical suppression, but may be
used on the basis of other facility constraints.
Costs
The installed costs of windscreens are dependent on materials and
construction costs, only. No operating expenses are expected. A study by
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MITRE indicated a cost of from $2.00 to $2.70 per square foot of screen.
Another screen system, a 6-foot high polyester fence, was estimated to cost
$14 per linear foot. Windscreens are relatively attractive due to their
overall low cost, but the cost effectiveness of such systems is also
considered to be low.
COVERS
Introduction
Covers serve to limit emissions of both particulate matter and volatile
organic compounds by acting as a physical barrier to diffusion of vapors and
to climatological forces such as solar irradiation, wind, and precipitation.
Covers may be applied as a gas collection system, with vapors vented to a
treatment system (e.g., carbon adsorber, afterburner). There are two primary
cover designs in use at TSDFs, as follows:
• Storage domes; and
• Synthetic membranes (tension structures).
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Waste pile covers are essentially identical to similar systems used to
control emissions from surface impoundments (see Section 5), landfills
(Section 6), and land treatment facilities (Section 7). They have found
widespread application, due to the significant emission reductions they can
effect, their strength and versatility, and relative ease of implementation at
existing facilities. Costs of cover systems, however, are generally high.
Description
Waste pile covers are very similar to systems used to cover other TSDF
processes (refer to sections as indicated above, for further detail). Since
the control of particulate emissions is of much greater significance in waste
pile covers, foam, liquid, or gaseous systems are not applicable. The most
significant factors to consider in selecting and determining the applicability
of a waste pile cover system are:
• pile size and shape;
• operating procedures including waste input and output rates and
restrictions;
• waste material's chemical compatibility and vapor characteristics
(e.g., permeability of cover); and
• durability of cover including strength, tear resistance, weather
resistance, and chemical resistance.
Description
Storage Domes—
Storage domes are similar to the "beehives" used to store road salt. A
typical wooden dome structure is supported on a reinforced concrete foundation
wall, which may be 4 to 10 feet high. The waste rests on an asphalt pad about
4 inches thick. The domes may be filled to 85 percent of capacity using a
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front end loader. If the dome is designed to be air-tight, the enclosed
air may be vented to a treatment device to remove organic vapors which have
volatilized from wastes present in the dome. A dome structure will provide
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effective emission control while the waste pile is still active, and is
expected to have a long service life.
Synthetic Membrane Containment (Tension Structures)—
A synthetic membrane cover may be secured over a waste pile with tension
cables, having the same function as a storage dome. If the membrane is
constructed to form an air-tight seal around the foundation or asphalt pad,
the structure may be vented to a gas treatment system. Square waste piles are
more amenable to a membrane containment structure than are round piles,
because they are easier to secure. An auger feed system can be installed as
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part of the structure to allow waste loading and unloading. Tension
structures may degrade over time due to natural processes such as photo-
oxidation and drying, and thus, require regular inspection and maintenance.
Emission Reduction Effectiveness
Both storage domes and tension structures will reduce particulate
emissions significantly. Assuming that some material may escape during
loading into the dome or tension structures, achievable efficiencies should be
between 95 and 100 percent. The effectiveness of such systems in the control
of gaseous emissions will depend primarily on the ability of the dome or cover
to capture and contain the vapors, because gas treatment technologies can
exceed 95 percent removal efficiency. Collection efficiencies for domes are
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estimated to be about 92 percent. Achievable efficiencies including
treatment are probably in the range of 85 to 95 percent.
Emission control efficiencies for synthetic membrane containment will be
the same as those described for synthetic landfill covers (see Section 6).
Emissions through synthetic membranes from relatively undiluted organic wastes
may be substantial over large areas. However, if a forced-draft
collection system is employed, vapor concentrations within the structure will
remain low, minimizing emissions through the cover.
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Costs
The installed costs of several different sizes of storage domes are
presented in Table 8-3. These costs do not include expenditures for
installation of electric wiring, lighting, ventilation, equipment, or
treatment systems.
Installed costs of synthetic membrane tension structures range from $4.30
8
to $6.90 per square foot of pile surface area. This estimate includes
incorporation of the auger feed system mentioned earlier, but does not include
treatment cost estimates.
GAS EXTRACTION
Introduction
Gas extraction technology has not been used on waste piles to control
gaseous emissions, but it would be similar in construction to a landfill
leachate collection system. Gas extraction as applied to landfills was
proposed by SCS Engineers as a feasible technology which could be operated
while a waste pile was still active. It is not intended to control
fugitive dust emissions.
Description
A gas extraction system consists of a network of screened pipes installed
incrementally as each layer of waste is placed into the waste pile. The
network is attached to a negative pressure fan or blower which draws gases and
vapors from inside the waste pile and routes them to a treatment device such
as an afterburner or carbon adsorber. In this manner, gases generated within
the waste pile are withdrawn and treated before they can be emitted to the
atmosphere. Gas extraction can thus occur while waste is still being placed
into the pile, as well as after the pile is closed. This technology can be
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TABLE 8-3. APPROXIMATE STORAGE DOME COSTS
Dome diameter
(feet)
50
61
72
82
100
116
Capacity
(tons)
664
1158
1780
2629
4652
6663
Approximate cost
$ 49-50,000
$ 50-53,000
$ 61-64,000
$ 70-74,000
$ 85-89,000
$103-108,000
Source: Vogel et al., 1983. (Reference 8),
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used in combination with other control technologies such as storage domes or
synthetic membrane tension structures to minimize fugitive dust as well.
Emission Reduction Efficiency
The collection efficiency of a gas extraction system has been estimated
at between 70 and 90 percent, based on landfill gas control efficiency
estimates. As mentioned earlier, no particulate emission reductions will be
realized by installing a gas extraction system.
Costs
SCS has estimated that a gas extraction system with a carbon adsorption
unit will cost about $17,000 for a 2,000-cubic foot waste pile, and about
$40,000 for a 100,000-cubic foot waste pile.^ These estimates do not
include costs associated with construction of the waste pile itself, such as
pad construction, buildings, and fences.
Domes and membrane tension structures may be more cost-effective than gas
extraction systems because they offer control of fugitive dust as well as
gaseous emissions.
CHANGES IN OPERATIONAL PRACTICES
Introduction
Changes in operational practices may result in significant reductions in
emissions at little or no cost. This section will discuss the affect of
changing the way waste is added to the pile, and changing the slope,
orientation, and surface area of the pile. These changes will not have impact
on gaseous emissions, but rather on fugitive dust emissions from waste piles.
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Description
Changes in Waste Loading—
Reducing the fall distance of waste being dumped from front end loaders,
overhead conveyors, clamshell buckets, or other equipment used for the
formation and maintenance of waste piles will result in a decrease in fugitive
dust emissions due to a lessening of impact forces. In some cases, this only
requires increased awareness on the part of machine operators. In other
cases, use of equipment such as height-adjustable loading equipment may be
necessary. Such equipment allows for raising or lowering of the point of
transfer of the waste to the pile, resulting in a consistently short fall
distance.
Other methods for reducing dust emissions due to waste loading include
the use of rock or stone ladders, telescoping chutes, lowering wells, and
windguards. Rock or stone ladders let material fall short distances in a
step-like manner. By reversing the direction of travel on successive steps,
momentum received from the previous fall, and thus the amount of fugitive dust
generation, are reduced.
Telescoping chutes are enclosed, extendable tubes which carry material
from the discharge point to the waste pile. This minimizes exposure of the
waste to wind, and in so doing, minimizes dust emissions.
Lowering wells are perforated pipes projecting vertically out of the
waste pile through which waste is added to the pile. Material added to the
pile through the well flows out through the perforations, while dust generated
due to the impact of falling is largely retained inside the pipe.
Wind guards are placed around the discharge end of a stacker arm,
conveyor, telescoping chute, or other loading equipment to minimize wind
action on dusts generated by falling waste. As was mentioned in the section
on stabilization, water or water plus a wetting agent can be sprayed on the
material as it is being transferred to further reduce dust emissions.
Changes in Slope, Orientation, or Surface Area—
A mathematical analysis of waste pile shape has shown that minimum
surface area is exposed to the atmosphere when the angle of repose of the pile
is 55°. However, studies have shown that the slope and orientation of a
pile is more important than surface area with regard to control of fugitive
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dust emissions. Slope of the pile in the prevailing wind direction should be
less than 10 degrees, because measured up slope wind velocities accelerate
substantially for slopes greater than this. Particulate entrainment is not
necessarily proportional to wind speed, as discussed in the section on
windscreens. Fine particles may be entrained in significant quantities even
at low windspeeds.
Positioning the waste pile so that its length is perpendicular, as
opposed to parallel, to the prevailing wind direction, may also reduce dust
emissions.
Emission Reduction Effectiveness
Bohn et al. have estimated efficiencies for some of the controls
discussed above. All efficiencies depend on the operating practices in
effect before the changes were made.
Height adjustable equipment was estimated to achieve a 25 percent
reduction in fugitive dust emissions. Telescoping chutes were estimated to
reduce emissions over previous conditions by 75 percent. Stone ladders and
wind guards were estimated to achieve emission reductions of 80 percent and
50 percent, respectively. Stabilizing the material as it was transferred was
estimated to result in a 75 percent control efficiency.
Positioning the length of a pile perpendicular to the prevailing wind
direction can theoretically reduce dust emissions by 60 percent as compared to
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parallel positioning.
Costs
Costs have been estimated for the above-mentioned control techniques as
they are applied to iron and steel plants. Initial 1977 costs for the
controls are:
Control Initial cost
Height-adjustable stacker $150,000
Telescopic chutes $ 10,500
Stone ladders $ 30,000
Wind guards $ 15,000
Spray systems $ 90,000
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Equipment designed for smaller operations such as those encountered at
TSDFs is expected to cost less. Little or no cost should be associated with
changing the slope, orientation, or the adjusting fall distances through
increased awareness on the part of machine operators.
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REFERENCES
1. Carpenter, B. H., and G. E. Weant, III. Particulate Control for Fugitive
Dust. EPA-600/7-78-071. U.S. Environmental Protection Agency, Office of
Research and Development, Washington, D.C. April 1978.
2. Drehmel, D., B. Danel, and D. Corner. Relative Effectiveness of
Chemimcal Additives and Wind Screens for Fugitive Dust Control.
Environmental Progress 1(1): 16. February 1982.
3o Ase, P. K., R. Koch, and G. Yasmate. Chemical Stabilizers for the
Control of Fugitive Asbestos Emissions from Open Sources.
EPA-600/2-82-063. U.S. Environmental Protection Agency, Office of
Research and Development, Cincinnati, OH. April 1982.
4. Jutze, G., and K. Axetell. Investigation of Fugitive Dust, Volume I:
Sources, Emissions, and Control. EPA-450/3-74-036a. U.S. Environmental
Protection Agency, Office of Air Quality Planning and Standards, Research
Triangle Park, NC. May 1973.
5. Rosbury, K. D., and S. C. James. Control of Fugitive Dust Emissions at
Hazardous Waste Cleanup Sites. Draft Report sent to M. Arienti, GCA
Corporation. March 1985.
6. Soo, S. L., et al. Wind Velocity Distribution Over Storage Piles and Use
of. Barriers. Proceedings: Symposium on Iron and Steel Pollution
Abatement Technology for 1980 (Philadelphia, PA, 11/18-11/20/80).
EPA-600/9-81-017. U.S. Environmental Protection Agency. Office of
Research and Development, Washington, DC. March 1981.
7. Davanzo, T. U.S. Environmental Protection Agency, Region I, Boston, MA.
Communication with A. Baldwin, GCA Corporation, Bedford, MA. March 1985.
8. Vogel, G. A., and D. F. O'Sullivan. Air Emission Control Practices at
Hazardous Waste Management Facilities. MTR-83W89. Prepared for U.S.
Environmental Protection Agency, Office of Solid Waste. Contract No.
68-01-6092. The MITRE Corporation, McLean, VA. June 1983.
9. SCS Engineers and Putnam, Hayes, and Bartlett, Inc. Cost-Risk Analysis
of Air Emissions. Prepared for U.S. Environmental Protection Agency,
Office of Solid Waste. Contract No. 68-01-6621. SCS Engineers,
Covington, KY. March 1984.
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LO. tiaxo, H., et al. Permeability of Polymeric Membrane Lining Materials.
Proceedings: International Conference on Geomembranes, Denver, CO. June
1984.
11. Bohn, R., et al. Fugitive Emissions from Integrated Iron and Steel
Plants. EPA-600/2-78-050. U.S. Environmental Protection Agency, Office
of Air Quality Planning and Standards, Research Triangle Park, NC.
March 1978.
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