United States
Environmental Protection
Agency
Office of
Research and Development
Washington, DC 20460
EPA/600/8-91/031
April 1991
Methodology for
Assessing Environmental
Releases of and
Exposure to Municipal
Solid Waste
Combustor Residuals
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EPA/600/8-91/031
April 1991
Final
METHODOLOGY FOR ASSESSING ENVIRONMENTAL RELEASES OF
AND EXPOSURE TO MUNICIPAL SOLID
WASTE COMBUSTOR RESIDUALS
Exposure Assessment Group
Office of Health and Environmental Assessment
U.S. Environmental Protection Agency
Washington, DC 20460
Printed on Recycled Paper
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DISCLAIMER
This document has been reviewed in accordance with U.S. Environmental Protection Agency
policy and approved for publication. Mention of trade names or commercial products does not constitute
endorsement or recommendation for use.
11
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CONTENTS
-•.-:'-. "-. - '••.•;- • - •••••. •• . . •. • •••'-•• ' •.•-•'. '" • •• .'-^ *.-;•••.'. •"..•- ••;•.''•.•,••'.: •. .-'PageNo.
Tables ..... >... ..,. .................,,-.... -;-., •_•;.-: •,%,•;-••—. • -,-.- -^.•'•^•:--••:,•>•• •,^^^:-'^'- v •..-•
Figures • • • v|
Foreword • • • '• --^'•'•r-'• ^ ..... • • - • • vii<
Preface y111
Authors and Reviewers ix
1. INTRODUCTION 1-1
2. MUNICIPAL WASTE COMBUSTION IN THE UNITED STATES 2-1
2.1. Municipal Solid Waste Residuals 2-1
2.2. Municipal Waste Combustion Facilities 2-3
2.2.1. Mass Burn Incinerators 2-3
2.2.2. Refuse Derived Fuel Incinerators 2-3
2.2.3. Air Pollution Control Devices 2-4
2.3. Distribution and Capacity of MWC Facilities in the United States 2-6
3. CHARACTERIZATION OF MUNICIPAL WASTE COMBUSTION ASH 3-1
3.1. Factors Affecting the Chemical Composition and
Concentration of Residuals 3-1
3.2. Quality of Reported Data on MWC Constituent Concentrations 3-2
3.3. Chemical Characteristics of Bottom Ash and Fly Ash 3-21
3.3.1. Inorganic Constituents 3-21
3.3.2. Organic Constituents 3-21
3.3.3. Intra- and Inter-Facility Variability 3-22
3.4. Leachate Characteristics 3-23
3.4.1. Inorganic Constituents in Leachate 3-24
3.4.2. Organic Constituents in Leachate 3-28
3.5. Physical Parameters of MWC Ash 3-29
3.5.1. Particle Morphology and Mineralogy 3-29
3.5.2. Particle Size Distribution 3-30
3.5.3. Particle Sizes and Chemical Composition 3-30
3.5.4. Engineering Characteristics 3-30
3.6. Summary and Conclusions 3-33
iii
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CONTENTS (continued)
Page No.
4. MUNICIPAL WASTE COMBUSTION RESIDUAL MANAGEMENT ............. 4,1
4.1. Intraplant Collection and Transport of Residuals 4^1
4.2. Potential Sources of Release During Transport and
Disposal Activities ".'. '....'.".'....... 4-2
4.3. Uses of Residuals 4-8
4.3.1. Stabilization of MWC Ash '.: ..,,...;.., 4-10
5. EXPOSURE PATHWAYS '.."...:.'.':...;.'.'..'..''..:,...."....;..'.;;;;. 51
5.1. Mechanisms of Release: Fugitive Emissions ........................... 5-1
5.1.1. Conveying Residues to On-Site Storage 5-2
5.1.2. On-Site Storage r .. 5-2
5.1.3. Loading and Unloading of Trucks . .............. . ............. 5-2
5.1.4. Transportation to Landfill .'.....',.'..'. ^....'/ 5-3
5.1.5. Spreading and Compacting at Disposal Sites 5-3
5.1.6. Wind Erosion ."....:,...... ..... 5-5
5.1.7. Vehicular Traffic in the Vicinity of Storage and
Disposal Areas 5.7
5.1.8. Application of AP-42 Emission Factor Equations .................. 5-8
5.2. Mechanisms of Release: Leachate and Runoff 5-11
5.3. Mechanisms of Release: Drainage of Moist Ash ........................ 5-12
5.4. Estimating Environmental Concentrations ...I.... .1............ 5-13
5.5. Mechanisms of Release: Intermedia Transport 5-14
6. EXPOSURE PATHWAY AND EXPOSED POPULATION ANALYSES ..... . . :;'.'! 6-1
7. DEMONSTRATION OF METHODOLOGY ..:.:... . . . . . . . . , . ... .;. . , '. . 7-1
7.1. Quantification of Release Rates of MWC Residuals 7-1
7.2. Comparison of the Example Scenario to a Field
Study of Fugitive Ash Emissions . , . . 7-54
7.3. Exposure Pathways ... ........... . ..". . . 7.54
7.4. Integration of Source Terms into an Exposure/Risk Assessment ............... 7-55
8. REFERENCES '. . "*. . . . . . '.', .".,'.'.".'. '. ''.I 8-1
IV
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TABLES
; ' '•'• Page No.
2-1. RDF Classification . ....... ........... 2-5
3-1. Ranges of Concentrations of Some Inorganic Constituents of Fly,
Bottom, and Combined Ash from Municipal Waste Combustors 3-4
3-2. Ranges of Concentrations of Some Organic Constituents of Fly
and Bottom Ash from Municipal Waste Incinerators 3-5
3-3. Ranges of Concentrations of PCDDs, PCDFs, and PCBs
in Municipal Waste Combustor Ash 3-6
3-4. Ranges of Extract Concentrations of Some Inorganic
Constituents from Municipal Waste Combustor Fly Ash , 3-7
3-5. Ranges of Extract Concentrations of Some Inorganic
Constituents of Bottom Ash from Municipal Waste Combustors 3-8
3-6. Ranges of Extract Concentrations of Some Inorganic Constituents
of Combined Fly and Bottom Ash from Municipal Waste Combustors ........... 3-9
3-7. Ranges of Extract Concentrations of Some Organic Constituents
of Fly Ash from Municipal Waste Incinerators 3-10
3-8. Ranges of Extract Concentrations of Some Organic Constituents
of Bottom Ash from Municipal Waste Incinerators ................ v .v 3-11
3-9. Ranges of Extract Concentrations of Some Organic Constituents
of Combined Fly and Bottom Ash from Municipal Waste Incinerators 3-12
3-10. Ranges of Extract Concentrations of PCDDs, PCDFs, and PCBs
from Fly and Combined Ash from Municipal Waste Incinerators , 3-13
3-11. Summary of Literature Database Quality . .,.,,,..,............. 3-14
3-12. Summary of Conditions for EP, TCLP, and SW-924 Leaching Methods ....... . . . 3-25
3-13. Concentration of 13 Inorganic Constituents in Ash, Laboratory
Extracts, and Field Leachates from Five Municipal Waste Combustor
Facilities and Their Associated Land Disposal Sites ........... 3-26
5-1. Considerations for Application of AP-42 Emission Factor Equations 5-10
7-1. Summary of Source Terms for Example Illustration 7-56
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FIGURES
• • - ..•"-...•':.•... ;'.. Page No.
2-1. Flow Diagram of MSW Incineration , .. 2-2
2-2. Total Municipal Waste Combustor Facilities by State . ..;'.'. •.'. . •"-• 2-7
3-1. Grain Size Distribution of Mixed Ash ."'. '.". . .'.'.' 3-31
3-2. Particle Size Distribution of Fly Ash .......,„.., ,3-32
4-1. Source Analysis for MWC Residuals Release ......... .;......; . .. . . ;.•..-.• 4-3
4-2. Runoff Containment Measures Used by MWC Operators ........ .. . .. . . ... .. 4-5
4-3. Fugitive Dust Containment Measures Used by MWC Operators .............. ... 4-6
4-4. Precautions to Control Fugitive Dust Emissions During Transportation . . .... .. : .. 4-7-
4-5. Ash Disposal Options Frequency of Use .......................'. V".'"'.". ."". . 4-9
5-1. Atmospheric Fate Analysis for MWC Ash Exposure ....,.,, 5-15
5-2, Surface Water Fate Analysis for MWC Ash Exposure .. .. ....... . .. . ;.... . ; . -'5-16
5-3. Soils Fate Analysis for MWC Ash Exposure ..................!.... 5-17
5-4. Groundwater Fate Analysis for MWC Ash Exposure 5-18
6-1. Exposed Populations - Identification of Relevant Exposure Routes . . ...,.:.. . . . : 6-4
7-1. Source Analysis for MWC Residuals Release - Step 1 ........'.. 7-3
7-2. Source Analysis for MWC Residuals Release - Step 2 7-5
7-3. Source Analysis for MWC Residuals Release - Step 3 7-8
7-4. Source Analysis for MWC Residuals Release - Step 4 7-21
7-5. Source Analysis for MWC Residuals Release - Step 5 7-25
7-6. Source Analysis for MWC Residuals Release - Step 6 7-33
7-7. Source Analysis for MWC Residuals Release - Step 7 7-41
7-8. Source Analysis for MWC Residuals Release - Step 8 7-49
VI
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The Exposure Assessment Group (BAG) of EPA's Office of Health and Environmental Assessment
(OHEA) has three main functions: (1) to conduct exposure assessments, (2) to review assessments and
related documents, and (3) to develop guidelines for Agency exposure assessments. The activities under
each of these functions are supported by and respond to the needs of the various EPA program offices.
In relation to the third function, EAG sponsors projects aimed at developing or refining techniques used
in exposure assessments.
The purpose, of this document is to provide users with a methodology to assess the potential exposure
to municipal solid waste (MSW) residuals, commonly known as ash. This document is designed to
complement another OHEA document titled, Methodology for Assessing Health Risks Associated with
Indirect Exposure to Combustor Emissions (EPA, 1990b). The risk commonly associated with MSW
combustors has been from direct exposure to, combustor emissions. These two OHEA-documents now
allow for a more complete evaluation of risk from release of contaminants of MSW combustion. This
document accomplishes the following: (1) summarizes existing information on MSW combustor design,
types, and location of MSW facilities nationally; beneficial uses of ash; characteristics of ash; and
contaminant concentrations of ash, (2). summarizes the management of MSW. ash to identify points of
environmental release from generation to disposal in a landfill,, (3) provides methodologies to quantify
these releases, and (4) directs the reader to other documents, particularly the companion document noted
above, which detail fate and transport models, and exposure and risk algorithms.' The document closes
with an example of the methodologies -applied Jo an organic contaminant, TCDD, :and an inorganic
contaminant, cadmium, both common in MSW combustor residuals. L
- Michael A. Callahan
Director
Exposure" Assessment Group
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PREFACE
The Exposure Assessment Group (BAG) of the Office of Health and Environmental Assessment
(OHEA) has prepared this document under the Research to Improve Health Research Assessment (RIHR A)
program, Topic II: Integrated Exposure Assessment.
The purpose of this document is to provide users with a methodology to assess the potential exposure
to municipal solid waste (MSW) residuals. MSW residuals, or ash, can be released to the environment
from the point they are generated within the municipal waste combustor (MWC) facility to when they are
disposed of in a landfill. This document identifies all such points of potential release and provides
methods to quantify these releases. A comprehensive example is provided to demonstrate this
methodology on an organic and an inorganic contaminant common in MSW ash.
This document does not describe or demonstrate methodologies to estimate the further transport of
ash releases from the point of release to the point of the exposed individual, nor does it describe
methodologies to quantify exposure and risk. However, it does provide overview guidance on these issues,
and directs the user to appropriate materials.
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AUTHORS AND REVIEWERS
The Exposure Assessment Group (BAG) within EPA's Office of Health and Environmental
Assessment was responsible for the preparation of this document. The document was: prepared .by
Technical Resources, Inc. under EPA Contract No. 68-02-4199, Work Assignment No. 21. BAG task
managers included John Segna, Russell Kinerson, and Matthew Lorber. They provided overall direction
and coordination as well as technical assistance and guidance. ;
AUTHORS
Abe Mittehnan, Project Manager ,; , ;
Isaac Diwan . r , ,
Joseph Greenblott
Ron Brown
Lou Cofone . , . .
Risk Assessment and Regulatory Toxicology Group
Technical Resources, Inc.
Rockville, MD
Matthew Lorber
Exposure Assessment Group
Office of Health and Environmental Assessment
Office of Research and Development
US EPA, Washington, DC
Among the authors, Abe Mittelman served as Project Manager for this effort and directed project
activities. Isaac Diwan was principal author of Sections 4 through 7. Joseph Greenblott contributed
Sections 2 and 3. Ron Brown consolidated the document and reconciled inconsistencies. Lou Cofone
assisted with graphics design.
Matthew Lorber made changes to the text as a result of reviewers comments and otherwise. In
particular, he made significant additions to Sections 5 and 7, including a more thorough discussion of AP-
42 emission factor equations, the addition of two mechanisms of ash release (vehicular resuspension and
drainage of moist ash), and the refinement and correction of all release estimates made in Section 7.
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REVIEWERS -. i v
The following individuals within EPA reviewed an earlier draft of this document and provided
valuable comments: ' ; . ; ,,-?. • . v
Carlton Wiles ...-.•
Charles I. Mashni .,
Risk Reduction Engineering Laboratory
Cincinnati, OH
Doreen Sterling
Office of Solid Waste • .,=
Washington, DC ,
Randall Bruins
Environmental Criteria and Assessment Office
Office of Health and Environmental Assessment
Cincinnati, OH
The following individuals outside of EPA also-reviewed this document -and provided helpful
comments and'suggestions: •••,•-•:•••• .^ •-, t.-. '••...•..'. ,•..-....,., . .-,- .,
Peter Pohlot
Ogden Projects, Inc.
Fairfield, NJ
Richard Denison
Environmental Defense Fund
Washington, DC •
ACKNOWLEDGEMENTS
Of the reviewers noted above, the authors are particularly grateful for the line-by-line scrutiny, text
additions, and suggestions made by Doreen Sterling and Richard Denison: The authors also wish to thank
Christine Chang for word processing and proofreading assistance. , . '
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1. INTRODUCTION
Incineration of municipal solid waste (MSW) is increasingly being used as a means of reducing
the volume of waste that must ultimately be disposed in a landfill. However, the residuals that are
generated by the combustion of such wastes must still be managed in some manner. In the past, risk
assessments of MSW incineration have been concerned with human health and environmental impacts
resulting from stack emissions. This document focuses on another fundamental issue, that of exposure
to municipal waste combustion (MWQ residuals.
The objective of this document is to develop guidance for assessing exposure to MWC residuals
or their chemical constituents that is consistent with methods that are already in use within the U.S.
Environmental Protection Agency (EPA). Existing guidance includes methods for selection and use of
media-specific fate and transport models, and methods for performing multi-media pathway-specific
exposure assessments. To avoid redundancy with existing documents, this methodology will direct
assessors to the appropriate EPA source materials and focus on issues germane to the assessment of risk
posed by exposure to MWC residuals.
: Another goal of this document is to complement the Methodology for Assessing Health Risks
Associated with Indirect Exposure to Combustor Emissions (EPA, 1990b). Therefore, this document not
only provides guidance in defining and quantifying the sources of environmental release of MWC
residuals, but also directs the user to the appropriate sections of the previous document that addressed
MWC risk assessment methodology for completion of the assessment and evaluation of health risks.
The Methodology for Assessing Environmental Releases of and Exposure to Municipal Solid Waste
Combustor Residuals is organized as follows. Section 2. is an overview of the incineration process. It
describes some common facility types and the use of MWC in the United States. Section 3. reviews the
subject of chemical and physical characterization of MWC residuals. It represents a summary of the state-
of-the-science and recently completed efforts at characterizing ashes and leachates. Section 4. describes
the MWC residuals management process and identifies potential sources of release during and following
such management activities. This chapter enables the assessor to determine where releases are likely to
ocpur during the residuals management process. Methods for determining the extent of these
environmental releases are presented in Section 5. Section 6. refers the assessor to appropriate existing
documents necessary to complete the exposure assessment process. Finally, Section 7. provides a
demonstration of the methodology described in this document. An integral part of this demonstration is
the step-by-step reiteration of the source analysis process. The output of an analysis of the type
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demonstrated in Section 7. are release rates appropriate for use in subsequent fate and transfer assessment.
It should be emphasized that a number of uncertainties remain with regard to MWC residuals
exposure/risk assessment. These are described in detail within the text and summarized in Section 7.
Predictive methodologies for MWC residuals exposure/risk assessment are in their developmental infancy.
Insufficient information exists, for example, to predict pollutant specific concentrations based on facility
type or source composition. Limited information is available concerning the environmental impact if
residuals are managed in a way other than disposal in a landfill. Subsequently, this document focuses Only
on that management option. Additionally, many of the predictive equations described in this document
have not been adequately field tested. Such uncertainties should be considered when conducting an
exposure/risk assessment for MWC residuals.
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2. MUNICIPAL WASTE COMBUSTION IN THE UNITED STATES
The'goal of municipal solid waste (MSW) incineration is to reduce the volume arid mass of
material that ultimately needs to be disposed. During the process of incineration, the combustible portion
of the solid waste is converted into gases and heat. The heat is often used for steam arid electricity
generation/while the gases are released to the atmosphere. The noncombustible or uricdmbusted fractions
of the waste remain for disposal. These wastes are known as combustion residues or residuals. This
section will describe the process of residual production, the types of facilities most often used, and the
geographic distribution of these facilities across the United States.
2.1. MUNICIPAL SOLID WASTE RESIDUALS
The flow of materials within a typical municipal waste incineration facility is shown in Figure 2-1.
The materials flowing out of a MSW incinerator are ashes, quench water, and gases. The ashes can be
divided into two main categories: bottom ash and fly ash. Bottom ash consists of slags and cinders
remaining in the combustion chamber after burning. These are generally noncombustible materials and
materials with boiling points greater than the combustion temperature. The bottom ash is usually removed
from the combustion chamber by a conveyor and then passed through a quench system to wet and cool
the ash. Fly ash includes those particulates and fine particles that are collected from the stack and
pollution control devices. The small particles that make up fly ash are noncombustible materials and may
be carried by the combustion gases. Some of the products of incomplete combustion may be captured in
the pollution control devices and some noncombustible materials with boiling points lower than the
combustion temperature may also be entrained as volatilized vapors along with the combustion gases. As
the combustion gases cool, these volatile constituents may condense and precipitate onto small particles
in the stack, the stack itself, and pollution control devices within the stack.
The different effluents that result from MSW incineration may be managed in a number of ways.
Bottom and fly ash may be mixed together or managed separately. Quench water may be completely or
partially recycled within the facility, or discharged as effluent. The bottom and fly ashes make up the
bulk of municipal waste combustion residuals, and their proper management represents a principal concern.
The physical and chemical characteristics of these residuals will be discussed in detail in Section 3.
2-1
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2.2. MUNICIPAL WASTE COMBUSTION FACILITIES
A number of different incinerator types are currently in operation in the United States. Common
features of all combustion facilities include a mechanism to feed the MSW fuel, a combustion chamber,
a heat (energy) recovery system, a poUution/emission control system, and mechanisms to collect and
remove ash. Incineration facilities may be classified by the fuel type and combustor design (e.g., mass
burn, processed refuse derived fuel, modular, starved air, dedicated stoker, co-firing, etc.), or by pollution
control system (e.g., electrostatic precipitator, baghouse, scrubbers, sorbant injection). Each combination
of fuel type, design, and pollution control system may potentially result in significant differences in the
quantity and composition of the residual produced, and in consequent variations in exposure to specific
constituents. Unfortunately, there exists a lack of research to statistically compare such characteristics by
facility design.
2,2.1. Mass Burn Incinerators
Mass burn incinerators make up almost 90% of MWC facilities in operation in the United States
(EPA, 1989a). A mass bum incinerator is so termed because it incinerates unprocessed municipal waste.
The central component of a mass burn incinerator is the furnace. Newer units employ a waterwall furnace,
while a refractory wall furnace is common in older designs. The furnace enclosure is positioned over the
combustor grate. Older mass burn units introduce waste into the bum chamber using a gravity chute,
while newer models use hydraulic rams. A number of grate designs are used in mass bum incinerators.
All grates use one or a combination of forms of fuel agitation to produce uniform burning and to
maximize the combustion of the waste. The grates are agitated in reciprocating, oscillary, or rotary
motion. As the grates agitate, the waste is moved from the drying portion of the grate to the burn portion
and finally toward the burnout grate for removal from the furnace. In mass bum units, combustion air
is introduced below the grate and above the fire. The combustor air may be introduced in excess or it
may be controlled (starved air combustors) to regulate the combustion temperatures and to ensure complete
combustion. The noncombustible portion of the waste and the unburned carbon fall off the grate as
bottom ash or are carried up by the flue gases as fly ash, Bottom ash usually drops off into a water filled
bath for quenching. Fly ash is collected by the air pollution control devices present in the stack.
2.2.2. Refuse Derived Fuel Incinerators
Refuse derived fuel (RDF) combustion uses MSW that has been processed to some degree. RDF
incinerators are less commonly used than mass burn incinerators in the United States (EPA, 1989a). RDF
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has been classified according to the amount of processing it has undergone (Table 2-1). The advantages
of using RDF rather than unprocessed MSW lie in its greater uniformity in composition and greater
efficiency as a fuel. RDF combustors are generally able to achieve better combustion control than units
using heterogenous wastes as fuels. In dedicated stoker boilers, fuel is injected into the furnace by air
swept spouts. Traveling grates drop the bed ash into hoppers as they move towards rne front of the boiler.
Several levels of overfire air nozzles induce turbulence and provide the necessary mixing of partially
combusted flue gas as it exits the grate bed.
Highly processed RDF (e.g., RDF 3, 4, or 5) is the least often used fuel for MWC facilities.
However, when it is used, it is often co-fired with another fuel, such as coal, wood, or sewage sludge.
Co-firing may be done in a spreader-stoker furnace or a utility steam generator. Fluff RDF (RDF-3) may
be pneumatically injected into the furnace or stoker units.
2.23. Air Pollution Control Devices
Both mass bum and RDF incinerators use air pollution control devices in their stacks to capture
fly ash as it is transported upward by the flue gases. Air pollution control devices used on MWC facilities
include electrostatic precipitators (ESP), fabric filters, and scrubbers.
Electrostatic Precipitators
Electrostatic precipitators are efficient at removing paniculate matter that is entrained with the
gases. ESPs have been used alone, linked in series, or used with other pollution control devices such as
scrubbers. ESPs function by inducing an electrical charge to the dust particles in the gas stream. The
presence of an electric field in the gas space between the high voltage discharge electrodes and the
collection plate propels the charge paniculate matter towards Hie collection plate. The last step in the
process involves the removal of the dust from the collection electrodes. A rapping device periodically hits
the collection plates, and the dust is collected into a hopper. The fly ash is then conveyed to storage or
disposal points.
Fabric Filters
In a fabric filter, dust particles impact onto a fabric as the gas is filtered and passes through the
cloth and dust cake. The fabric used is typically woven or felt. The dust cake that forms on the filter
plays a key role in improving the overall efficiency of the filter. The dust cake is periodically removed
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Table 2-1. RDF Classification
RDF-1
RDF-2
RDF-3
RDF-4
RDF-5
RDF-6
RDF-7
MSW with minimal processing to remove bulky wastes.
Coarsely processed MSW, with or without ferrous metal separation such that
95% (by weight) passes through a 6 inch square mesh.
Shredded MSW with glass, metals and other inorganic materials removed.
95% by weight of the material passes through a 2 inch square mesh.
Powdered combustible fraction of MSW, such that 95% by weight of
material passes through a 10-mesh screen.
the
Combustible waste fraction compressed into pellets.
Combustible waste fraction processed into a liquid.
Combustible waste fraction processed into a gaseous fuel.
Source: Hickman, 1983
from the filter surface by shaking, reverse air cleaning, or blow-back of compressed air. Fabric filters are
not usually used alone on MSW incinerators, but are normally downstream of lime injection scrubbers.
Scrubbers
Scrubbers come in three forms: wet, dry, and wet-dry. Wet scrubbers operate on the principle of
intimate contact between a gas stream and a liquid that may contain absorbents or reagents for removal
of acid gases. The main disadvantage of wet scrubbers is the generation of liquid waste effluent and a
wet plume from the stack. Newer scrubbers are either of the dry or wet-dry configuration. In dry
scrubbers, a powdered dry sorbent is typically injected into the gas stream. Intimate mixing of the sorbent
with the gas occurs, then the dry gases are directed into a paniculate removal device such as a fabric filter
or an ESP. A dry scrubber may be preceded by a heat exchange or water-spray system to cool the gases.
A wet-dry scrubber is also called a spray dryer or semi-dry scrubber. This kind of scrubber uses a liquid
sorbent stream sprayed into the gas stream. The amount of liquid is controlled so all the liquid evaporates
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into a gas stream, thereby yielding a dry fly ash product. These particulates are then removed by passing
the gas stream through a baghouse or ESP.
2.3. DISTRIBUTION AND CAPACITY OF MWC FACILITIES IN THE UNITED STATES
Approximately 140 to 155 MWC facilities were in operation in the United States in 1988 (EPA,
1989a; Ujihara and Gough, 1989). These facilities have an estimated total installed capacity of 78,700
tons per day (Ujihara and Gough, 1989). Currently, 14% of the municipal solid waste stream is
incinerated. The greatest number of these facilities can be found in three states: New Hampshire, New
York, and Virginia. These states each had more than 9 incinerators in operation in 1988 (Figure 2-2).
The total number of incinerators in the United States has been projected to increase to 227 by 1992 (Levy,
1989).
The results of a survey conducted by the U.S. EPA Office of Solid Waste (EPA, 1989a) indicate
that over 90% of the MWC facilities in the United States use some form of mass burn combustor. Most
facilities operate 7-days-a-week, 24-hours-a-day. The average amount of municipal solid waste combusted
in an MWC facility in the United States is about 9,355 tons per month on an annual basis, with facilities
receiving 8% more waste in the summer than in the winter months. The typical mix of waste combusted
is approximately 68% residential, 23% commercial and 9% industrial.
Municipal waste combustors in the United States produce about 2.8 to 5.5 million tons of ash per
year, with fly ash comprising from 5-15% of the total. The total amount of ash produced could potentially
increase 2 to 5 times, depending on how many new facilities are constructed (OTA, 1989).
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3. CHARACTERIZATION OF MUNICIPAL WASTE COMBUSTION ASH
Fly ash, bottom ash, and quench water make up the major waste streams exiting a MWC facility.
Possible exposures to the chemicals contained in these ashes, and to the leachates that are generated
following disposal, account for the major health and environmental risks posed by these residuals. An
understanding of the chemical and physical characteristics of municipal incinerator residuals is therefore
the first step in defining the potential exposures and risks. Information regarding the chemical and
physical characteristics of MWC ashes and leachates can be found in:
• EPA, 1987a; 1988a. Characterization of Municipal Waste Combustor Ashes and Leachates from
Municipal Solid Waste Landfills, and Co-Disposal Sites. Volumes I to VII
and Addendum. Prepared by NUS Corporation for the EPA Office of
Solid Waste (OSW).
« EPA, 1990a. Characterization of Municipal Waste Combustion Ash, Ash Extracts, and
Leachates. Coalition on Resource Recovery and the Environment
(CORRE) and the EPA Office of Solid Waste and Emergency Response
(OSWER).
This section provides a general overview of the current information on ash and leachate character-
ization. The assessor is directed to the above documents for more detailed information.
3.1. FACTORS AFFECTING THE CHEMICAL COMPOSITION AND CONCENTRATION OF
RESIDUALS
The concentrations of constituents found in the ashes, and their concentration in ash leachates, may
be affected by a number of factors, including:
• Sources of municipal solid waste: A 1988 industry survey (EPA, 1989a) found that the
average MWC facility incinerates waste from a combination of sources. At a typical facility, the primary
waste stream is from residential sources (68.3%); however commercial sources contribute 23.1%.
Industrial wastes contributed the smallest percentage to the MWC facility's waste stream (< 9%).
Differences in ash characteristics might be explained in part by the proportion of the total combustible
waste originating from each source.
• Operating conditions: Differences in operating conditions and combustion practices might also
explain differences in ash characteristics. Fly ash from similar incinerators located in different countries
(Norway and Canada) has been shown to contain different concentrations of organic contaminants,
including polychlorinated dibenzo-p-dioxins (PCDDs), polycyclic aromatic hydrocarbons (PAHs),
polychlorinated biphenyls (PCBs), and polychlorinated dibenzofurans (PCDFs) (Viau et al., 1984).
3-1
-------
• Incinerator and pollution control equipment characteristics: As described in Section 2 0
the Specific incinerator design can greatly affect the quality of the residuals that are produced. Residuals
vary with incinerator operating parameters and efficiency, and are dictated by the bum temperature, mixing
of air with combustion gases, grate design, turbulence, and fuel characteristics. Residuals, especially fly
ash, can also vary with the pollution control equipment used. The use of catalysts or adsorbents, such as
lime, can also significantly affect the particle size distribution and the leachability of different components
of the ash. ,
• Type of residual (e.g., quench water, fly ash, bottom ash, and combined ash): The exposure
and risk characteristics of MWC residuals differ with residue type. The majority of MWC residuals are
managed as combined bottom and fly ash. Approximately 72% of the MWC (disposal) facilities receive
combined ash. The remaining 28% of disposal facilities receive only bottom ash or only fly; ash (EPA,
1988c). The differences in the organic and inorganic chemical makeup of fly ash and bottom ash are
further discussed in Sections 3.3. and 3.4. ,, •
• Pretreatment of MSW: Pretreatment of the MSW stream may affect the composition and
physical characteristics of the residuals. A survey of industry practice (EPA, 1989a) found that '61.1%
of the facilities removed some combustible materials and 86.4% removed some non-combustibles from
the waste prior to incineration. The wastes that are removed from the waste stream may be diverted to
recycling facilities. Removal of metallic waste and batteries may decrease the levels of cadmium, mercury,
lead, and other metals from the ash.
3.2. QUALITY OF REPORTED DATA ON MWC CONSTITUENT CONCENTRATIONS
The ranges of concentrations of ash constituents that have been reported by various authors are often
seen to vary by several orders of magnitude. This variation has been attributed to differences in sampling,
analytical, and quality assurance/quality control protocols (Clement et al., 1984). For example, Van der
Sloot et al. (1989) compared the composition of bottom ash and fly ash from an incinerator in the
Netherlands with values reported in the literature for incinerators in Canada, Denmark, and other Dutch
incinerators. Although there appeared to be general agreement between the elemental composition of ash
from facilities in different countries, there was a wide range of variation in the results previously reported
in the literature when compared to the authors' recently acquired data. The authors suggest that these
differences in the magnitude of data variability between older and recent data may be the result of
improved sampling and analytical techniques and due to more efficient, pretreatment of waste in the recent
Studies. Since many of the analytical techniques used to analyze MWC ash have not been standardized,
it is not unusual to find differences in the data originating from different researchers. In addition, many
researchers report data from leaching studies as compositional data, when, in fact, the techniques are
designed to predict only the concentrations of ash constituents in landfill leachates.
Given the variability of the data reported in the literature, the prediction of potential concentrations
3-2
-------
of chemical constituents of ash based on the factors described above is not generally possible. Ideally,
it would be advantageous to be able to predict the concentrations of constituents in ash from those factors
which effect ash composition, so that knowledge of facility type and location, combustion parameters, and
fuel source would be sufficient to enable prediction of the concentrations of constituents,of concern in ash.
Methods for determining these relationships have been documented (Hasselriis, 1989). However, the state-
of-the-science is such that predictions of this kind are not yet possible. There are two major causes for
this limitation: the extreme heterogeneity of ash and deficiencies in the literature database.
Many factors affect ash composition; the result is that ash is a very heterogeneous substance (Ujihara
and Gough, 1989). Therefore, the acquisition of a representative sample of ash is a very difficult task.
Although EPA has recommended the use of standard sampling and Quality Assurance/Quality Control
(QA/QC) protocols for MWC residuals (EPA, 1990a), the literature contains little or no consistency in the
way ash^samples arecollected, handled, or prepared for analysis.
The heterogeneous nature of ash is reflected in the broad ranges of concentrations for constituents
in ash that are reported in the literature. For example, Mika and Feder (1985) took 9,6 samples of bottom
ash from a mass burn incinerator over a single 48-hour period. Using the EPA Extraction Procedure, they
found the concentration range for lead to be from 0.08-15.08 mg/L, and for cadmium to be from below
detection limits to 1.59 mg/L. A second series of 48 samples taken over another 48-hour period showed
concentrations of lead to be from 0.04 to 33.42 mg/L, and cadmium to be from 0.01 to 0.53 mg/L. This
variability is typical of that found in the literature. Tables 3-1 to 3-10 summarize the available data on
the composition of ash from MSW combustors. The wide range of values reported in these tables for ash
constituents underscores the heterogeneity of MWC ash. ;
The second major reason for the inability to predict ash constituent concentrations for facility
parameters is the lack of a sufficiently strong database. Table 3-11 was compiled to provide a brief
overview of the kind of research that has been conducted on MWC ash, and the quality and usefulness
of the data that has been published. This literature was reviewed with the goal of developing a
representative data set of ash constituent concentrations that could be used in developing general
parameters for exposure assessments. However, it was quickly discovered that data from the literature are
often of little help in establishing the interactive effects of the various factors affecting composition
because of incomplete data on MSW fuel characteristics, MWC facility design and operating parameters,
representativeness of ash samples, and accuracy/precision of analytical methods employed.
3-3
-------
Table 3-1. Ranges of Concentrations of Some Inorganic Constituents of Fly, Bottom, and Combined Ash
from Municipal Waste Combustors (concentration in ug/g or ppm)
Chemical
Aluminum
Antimony
Arsenic
Barium
Beryllium
Boron
Bromine
Cadmium
Calcium
Carbon
Cesium
Chlorine
Chromium
Cobalt
Copper
Huorine
Iron
Lead
Lithium
Magnesium
Manganese
Mercury
Molybdenum
Nickel
Nitrogen
Phosphorus
Potassium
Selenium
Silicon
Silver
Sodium
Strontium
Sulfur
Thorium
Tin
Titanium
Vanadium
Zinc
ND s not detected
NR st not reported
Hy Ash
5,300-176,000
4.4-760
1-750
80-9,000
ND-<4
5-5,654
21-250
0.3-2,100
3,000-290,000
17,000-74,000
2,100-12,000
1,160-253,000
110-13,000
2.3-5,000
69-3,100
1,500-3,100
900-87,000
6-26,600
7.9-34
2,000-40,000
65-8,500
ND-40
9.2-700
9.9-1,966
ND
1,000-12,000
4,300-74,800
0.48-16
1,783-320,000
ND-77,500
477-80,000
98-1,100
4,000-40,000
NR
<100-12,500
<50-42,000
22-298
120-152,000
at the detection limit
Combined Ash
5,000-60,000
20-<260
2.9-
-------
Table 3-2. Ranges of Concentrations of Some Organic Constituents of Fly and Bottom Ash from
Municipal Waste Incinerators (concentration in ng/g or ppb)
Constituent
Fly Ash
Bottom Ash
Acenaphthene
Acenaphthylene
Anthanthrene
Anthracene
Benzanthrene
Benzo(k)flupranthene
Benzo(a)pyrene
Benzo(g,h,i)perylene
Biphenyl
Bis(2-ethylhexyl)phthalate
Butyl benzyl phthalate
Chlorobenzenes
Chlorophenols
Chrysene
l,l-Dichloro-3-phenylpropane
Di-n-butyl phthalate
Diethyl phthalate
Fluoranthene
Fluorene
M. cyclopentaindene*
Naphthalene
Normal alkanes
Thio-PAHs"
Triptycene
Phenanthrene
3-Methyl phenanthrene
Pyrene
NR
ND-3,500
NR
1-500
ND-300
ND-470
ND-400
ND-190
2-1,300
852,100
ND
80-4,220
50.1-9,630
ND-690
80.2
ND
6,300
ND-6,500
ND-115
60
270-9,300
3,647-50,000
50-75
NR
21-7,600
NR
ND-5,400
28
37-390
305
53
NR
ND-180
ND-5
ND
NR
NR
180
17
ND
ND-37
NR
360-1500
105.2
4.5-230
ND-150
NR
570-580
NR
NR
85.0
500-540
2.5
31.3-220
ND = not detected at the detection limit
NR = not reported
1 Methyldiphenylhexahydrocyclopentaindene
b Alkyl-substituted dibenzothiophene = 50 ng/g
2,5-Bis(p-Chlorophenyl)l,4-diithin = 75 ng/g
Sources: EPA, 1987a; EPA, 1988a; EPA, 1990a; Clement et al., 1984; Viau et al., 1984; Northeim et al., 1989;
Hrudey et al., 1974; Giordano, et al., 1983; Lisk, 1988; Belevi and Baccini, 1989; Van der Sloot et al., 1989;
DiPietro et al., 1989; Kullberg and Fallman, 1989; Austin and Newland, 1985; Kuehl et al., 1985; Kuehl et al., 1986;
Kuehl et al., 1987; Buser et al., 1978; Tanaka and Takeshita, 1987.
3-5
-------
Table 3-3. Ranges of Concentrations of PCDDs, PCDFs, and PCBs in Municipal Waste Combustor Ash
(concentration in ng/g or ppb) , , ,
Constituent
MCDD
DCDD
T3CDD
T4CDD
PCDD
H6CDD
H7CDD
OCDD
2,3,7,8-TCDD
Total PCDD
MCDF
DCDF
T3CDF
T4CDF
PCDF
H6CDF
HrCDF
OCDF
2,3,7,8-TCDF
Total PCDF
Mono CB
DiCB
TriCB
TctraCB
Pcnta CB
Hcxa CB
Hepta CB
OctaCB
Nona CB
Dcca CB
Total PCB
Fly Ash
2.0
0.4-200
1.1-82
ND-250
ND-722
ND-5,565
ND-3,030
ND-3,152
ND-330
5-10,883
41
ND-90
0.7-550
ND-410
ND-1800
Tr-2,353
Tr-887
ND-398
0.05-5.4
3.73-2,396
0.29-9.5
0.13-9.9
ND-110
0.5-140
0.87-225
0.45-65
ND-0.1
ND-1.2
ND
ND
ND-360
Combined Ash
ND
ND-120
- ND-33
0.14-14
0.07-50
0.07-78
0.07-120
0.07-89
0.02-0.78
6.2-350
1.1
. ND-42
ND-14 ;
. 2,3-9
1.6-37
- 1.2-35
, . . 0.62-36
0.18-8.4
0,41-12
6.14-153.9
ND •
0.126-1.35
0.35-14.3
16.5
ND
ND-39
,ND
,ND
•ND
ND
ND-32.15
Bottom Ash
NR :,;.. : ,
NR
NR • •. . ,
<0.04-410
ND-800
ND-1,000
ND-290 ..
ND-55
<0.04-6.7
ND-2,800
NR
NR
NR
10.1-350
0.07-430
ND-920
ND-210
. ND-11
ND-13
ND-1,600
ND-1.3
ND-5.5
ND-80
ND-47
ND-48
• NR ..-;
NR •••...
NR • \ '
NR
NR
ND-180
ND = not detected at the detection limit
NR = not reported
Tr = 0.01
-------
Table 3-4. Ranges of Extract Concentrations of Some Inorganic Constituents from Municipal Waste
Combustor Fly Ash (concentration in mg/L or ppm)
Chemical
Aluminum
Arsenic
Antimony
Barium
Beryllium
Boron
Cadmium
Calcium
Chlorine
Chromium
Cobalt
Copper
Iron
Lead
Lithium
Magnesium
Manganese
Mercury
Molybedenum
Nickel
Potassium
Selenium
Silver
Sodium
Strontium
Sulfate
Tin
Titanium
Vanadium
Yttrium
Zinc
TDS
• SW-924"
0.09-0.805
ND-0.14
0.080
0.19-1.68
ND-0.01
ND-2,100
ND-33
646-4,620
133-18,500
0.0025-176
ND-0.12
0.0025-1,240
0.0025-12
ND-150,000
0.27-0.38
0.03-37.6
0.0005-0.052
0.00002-0.02
0.22-0.34
ND-420
19-2,530
0.0025-0.108
0.02-0.05
16-971
2.6-17.7
80-10,400
0.09
0.05
0.004-0.02
0.05
0.0015-2,000
484-10,900
TCLPb
0.09-16.0
ND-0.111
0.154
<0.1-1.86
ND-0.01
1.36-7.3
0.015-120
1,250-5,390
NR
0.0025-0.544
0.03-0.14
0.0025-14.70
0.0025-190
0.025-65
0.25-0.55
0.04-171
0.01-14.7
<0.0002-0.004
J).10-0.31
0.0075-2.48
574-2,780
0.002-0.1
<0.01-0.08
474-2,500
3.4-17.30
NR
0.09
0.05
0.02-0.464
0.05
0.151-885
NR
EP°
0.159-18.8
0.002-0.23
NR
<0.02-22.8
0.001-0.005
0.7-8
<0.005-120
1,150-5,810
NR
0.0025-<0.20
0.025-0.114
0.033-10.6
0.0025-38
0.019-65.0
0.261-0.455
0.093-149
0.005-61
ND-0.007
0.10-0.229
0.09-11
616-2,170
0.003-0.62
0.001-0.57
506-821
3.5-16
NR
0.09
0.05
0.015
0.05
3.36-768
NR
TDS = total disolved solids
ND = not detected at the detection limit
NR = not report
* Monofilled Water Extraction Procedure
b Toxicity Characteristic Leaching Procedure
0 Extraction Procedure
Sources: EPA, 1987a; EPA, 1988a; EPA, 1990a; Clement et al., 1984; Viau et al., 1984; Northeim et al., 1989;
Hrudey et al., 1974; Giordano et al., 1983; Lisle, 1988; Belevi and Baccini, 1989; Van der Sloot et aL, 1989; DiPietro
et al., 1989; Kullberg and Fallman, 1989; Austin and Newland, 1985; Kuehl et al., 1985; Kuehl et al., 1986; Kiiehl
et al., 1987; Buser et ah, 1978; Tanaka and Takeshita, 1987.
3-7
-------
Table 3-5.
Ranges of Extract Concentrations of Some Inorganic Constituents of Bottom Ash. from
Municipal Waste Combustors (concentration in mg/L or ppm)
Constituent
SW-924'
TCLPb
EP°
Arsenic
Barium
Cadmium
Chromium
Cobalt
Copper
Lead
Mercury
Nickel
Selenium
Silver
Zinc
. MR
MR .
0.001-0.05
<0.01
<0.02
0.04
0.01-1
ND
<0.05
MR
MR
0.1-5
<0.02
<0.5-0.74
<0.01-0.034
<0.05
.MR
NR '
0.067-6.4
<0.0002
NR
«0.02
.<0.01
NR ;
<0.007-0.13 ,--,.••-,*
<0.02-<0.20
<0.005-1.1
0.011^<0.2
:NR ; ,. •.-,,..
NR .,. ; , • . ••
-------
Table 3-6. Ranges of Extract Concentrations of Some Inorganic Constituents of Combined Fly and
Bottom Ash from Municipal Waste Combustors (concentration in mg/L or ppm)
Parameter
Aluminum
Arsenic
Barium
Beryllium
Boron
Cadmium
Calcium
Chlorides
Chromium
Cobalt
Copper
Iron
Lead
Lithium
Magnesium
Manganese
Mercury
Molybedenum
Nickel
Potassium
Selenium
Silver
Sodium
Strontium
Sulfate
Tin
Titanium
Vanadium
Yttrium
Zinc
SW-924'
0.17-29.4
<0.001-0.54
0.15-2.83
ND-0.01
ND-0.95
ND-0.03
122-536
209-960
0.0025-<0.05
0.01-0.03
0.0025-0.19
ND-0.09
0.021-2.98
0.01-0.05
ND-0.19
ND-0.03
ND-0.1
0.07-0.1
0.0075-0.09
85.2-120
0.002-0.07
ND-0.05
68.3-85.3
0.58-3.19
156-571
0.02-0.09
0.01-0.05
0.02-0.03
0.01-0.05
0.0015-0.96
TCLP"
0.01-0.05
0.005-0.10
-------
Table 3-7.
Ranges of Extract Concentrations of Some Organic Constituents of Fly Ash from Municipal
Waste Incinerators (concentration in ng/g or ppb)
Constituent
SW-924"
TCLPb
EP=
Chlorobenzenes
Chlorophcnols
Dimethyl Propdiol
Naphthalene
Mclhoxy Ethanol
Methyl Naphthalene
Mcthyoxy Ethane
ND
ND-675
ND
ND
ND
ND
ND
NR
NR
ND
ND
ND-10
ND
ND-10
NR
NR
ND
ND
ND
ND
ND
NR = not reported
* Monofillcd Waste Extraction Procedure
6 Toxicity Characteristic Leaching Procedure
• Extraction Procedure . ,
Sources: EPA, 1987a; EPA, 1988a; EPA, 1990a; Clement et al., 1984; Viau et al, 1984; Northeim et al., 1989;
Hrudcy et al., 1974; Giordano et al., 1983; Lisk, 1988; Belevi and Baccini, 1989; Van der Sloot et al., 1989; DiPietro
ctal., 1989; Kullberg and Fallman, 1989; Austin and Newland, 1985; Kuehl et al., 1985; Kuehl et al., 1986; Kuehl
et al., 1987; Buser et al., 1978; Tanaka and Takeshita, 1987.
3-10
-------
Table 3-8. Ranges of Extract Concentrations of Some Organic Constituents of Bottom Ash from
Municipal Waste Incinerators (concentration in ng/g or ppb)
Constituent
SW-924"
TCLPb
EF
Benzoic Acid
Bis oxy Ethanold
Cycloocta Decone"
Dimethyl Propdiolf
Ethoxy Ethanol8
E. Dim Dioxaneh
M. Furan Dione1
Methyl Naphthalene
Methyoxy Ethane*
Naphthalene
Oleyl Alcoholk
Phenol
ND-46
ND
ND-150
ND
ND
ND
ND-6
ND
ND-10
ND
ND
ND-28
ND
ND
ND
NDND
ND
ND
ND
NDND
ND-22
ND
ND
ND
ND
ND
ND
ND
ND
ND
ND-12
ND
ND
ND
' Monofilled Waste Extraction Procedure
b Toxicity Characteristic Leaching Procedure
c Extraction Procedure
d 2,2-[l,2-Ethanediyllbis(oxy)bis-ethanol (CAS 112-27-6)
e 1,4,7,10,13,16-Hexaoxacyclooctadecane (CAS 17455-13-8
f 2,2-Dimethyl-l,3-propanediol (CAS 126-30-7)
8 2-[2-(Ethenyloxy)ethoxy]-ethanol (CAS 929-37-3)
h 5-Ethyl-2,2-dimethyl-l,3-dioxane (CAS 25796-26-3)
1 3,4-Dimethyl-2-5-furandione (CAS 766-39-2)
> l-Methoxy-2-(methoxy methoxy)ethane (CAS 74498-88-7)
k (2)-9-Octadecen-l-Ol (CAS 143-28-2)
Sources: EPA, 1987a; EPA, 1988a; EPA, 1990a; Clement et al., 1984; Viau et al., 1984; Northeim et al., 1989;
Hrudey et al., 1974; Giordano et al., 1983; Lisk, 1988; Belevi and Baccini, 1989; Van der Sloot et al., 1989; DiPietro
et al., 1989; Kullberg and Fallman, 1989; Austin and Newland, 1985; Kuehl et al., 1985; Kuehl et al., 1986; Kuehl
et al., 1987; Buser et al., 1978; Tanaka and Takeshita, 1987.
3-1.1
-------
Table 3-9. Ranges of Extract Concentrations of Some Organic Constituents of Combined Fly and Bottom
Ash from Municipal Waste Incinerators (concentration in ng/g or ppb)
Constituent
SW-924"
TCLPb
EF
Bis oxy Ethanold
Cycloocta Decone8
Dimethyl Propdiolf
E. Dim Dioxane*
Ethoxy Ethanolh
M. Furan Dione1
Methoxy Ethanol
Methyl Naphthalene
Methyoxy Ethane'
Naphthalene
Oleyl Alcohol*
Phenol
ND-96
ND-1,200
ND-160
ND-510
ND-390
ND
ND
ND-80
ND
ND
ND-88
ND-33
ND
ND
ND-140
ND
ND
ND
ND
ND
ND
ND
ND
ND
ND
ND
ND-190
ND
ND
ND
ND
ND-18
ND
ND-8
ND-18
ND
ND = not detected at detection limit
CAS = Chemical Abstract Services
* Monofillcd Waste Extraction Procedure
b Toxicity Characteristic Leaching Procedure
c Extraction Procedure
d2,2-[l,2-Ethancdiyllbis(oxy)bis-ethanol (CAS 112-27-6)
e 1,4,7,10,13,16-Hexaoxycyclooctadecane (CAS 17455-13-8)
r 2,2-Dimethyl-l,3-propanediol (CAS 126-30-7)
* 2-[2-(Ethcnyloxy)ethoxy]-ethanol (CAS 929-37-3)
N 5-Ethyl-2,2-dimethyl-l,3-dioxane (CAS 25796-26-3)
1 3,4-Dimcthyl-2-5-furandione (CAS 766-39-2)
J l-Methoxy-2-(methoxy methoxy)ethane (CAS 74498-88-7)
k (2)-9-Octadecen-l-ol (CAS 143-28-2)
Sources: EPA, 1987a; EPA, 1988a; EPA, 1990a; Clement et'al., 1984; Viau et al., 1984; Northeim et al., 1989;
Hrudey et al., 1974; Giordano et al., 1983; Lisk, 1988; Belevi and Baccini, 1989; Van der Sloot et al., 1989; DiPietro
Ct al., 1989; Kullberg and Fallman, 1989; Austin and Newland, 1985; Kuehl et al., 1985; Kuehl et al., 1986; Kuehl
ct al., 1987; Buser et al., 1978; Tanaka and Takeshita, 1987.
3-12
-------
Table 3-10. Ranges of Extract Concentrations of PCDDs, PCDFs, and PCBs from Fly and Combined Ash
from Municipal Waste Incinerators (concentration in ng/L or ppt)
Constituent
Fly Ash
SW-924'
Fly Ash
TCLPb
Combined Ash
TCLP"
TCDD *
PCDD
HCDD
H7CDD
OCDD
2,3,7,8-TCDD
Total PCDD
TCDF
PCDF
HCDF
H7CDF
OCDF
2,3,7,8-TCDF
Total PCDF
Total PCB
NR
NR
MR
NR
NR
NR
ND
NR
NR
NR
NR
NR
NR
ND
ND
<0.056-<0.094
<0.040-<0.056
<0.019-<0.027
<0.038-0.11
<0.078-0.11
<0.056-<0.094
ND-0.188
<0.048-<0.120
<0.016-<0.026
<0.013-<0.020
<0.020-<0.063
<0.015-<0.089
<0.048-<0.012
ND-0.1S2
<0.038-
<0.023-
<0.015-
<0.028-
<0.035-
<0.038-
ND-<0
•<0.023
•<0.067
•<0.044
<0.120
<0.091
•<0.230
.091
<0.031-<0.200
<0.013-<0.042
<0.008-<0.025
<0.013-<0.043
<0.060-<0.054
<0.031-<0.200
ND-0.054
ND = not detected at detection limits
NR = not reported
* Monofilled Waste Extraction Procedure
b Toxicity Characteristic Leaching Procedure
Sources: EPA, 1987a; EPA, 1988a; EPA, 1990a; Clement et al., 1984; Viau et al., 1984; Northeim et al., 1989;
Hrudey et al., 1974; Giordano et al., 1983; Lisk, 1988; Belevi and Baccini, 1989; Van der Sloot et al., 1989; DiPietro
et al., 1989; Kullberg and Fallman, 1989; Austin and Newland, 1985; Kuehl et al., 1985; Kuehl et al., 1986; Kuehl
et al., 1987; Buser et al., 1978; Tanaka and Takeshita, 1987.
3-13
-------
Table 3-11. Summary of Literature Database Quality
Reference*
Giordano ct al.
(1983)
Bclcvi and Baccini
(1989)
Chcsncr (1990)
DiPictro ct at.
(1989)
Eighmy ci al. (1990)
EPA (1990a)
Bagclii and
Sopcich (1989)
Holland ct al. (1989)
Research Goal
Study mobility.
plant availability,
and attenuation of
Pb and Cd from
ash
Analyze bottom
ash from combus-
tor in Switzerland
with respect to
long-term leaching
Characterize and
compare ash with
natural aggregate
material
Evaluate effects of
pH and redox
potential on metal
leaching
Study factors af-
fecting heavy me-
tal leachabililty
Enhance the data-
base on MWC ash
characteristics.
laboratory extracts
of ash, and leach-
ates from ash dis-
posal facilities
Characterize ash
Compare physical
and leaching pro-
perties of stabil-
ized ash
MSW Fuelb
Not reported
Not reported
Not reported
Not reported
Not reported
Not reported
Not reported
Table taken
from 1988 refer-
ence that is not
listed in refer-
ence section of
paper
Facility0
Reported only
that ash received
from 8 facilities
in U.S. and
Canada
Not reported
Reported
Reported in
detail
Reported
Reported in
detail for 5 dif-
ferent facilities
Reported
Reported
Sampling0
Not reported
Sample prepara-
tion reported; ash
sampling protocol
and number of
samples not re-
ported
Referenced
Sample prepara-
tion reported;
sampling protocol
not reported
Sampling method
and sample types
reported, number
of samples not
reported
Reported
Sampling protocol,
number of sam-
ples, and sample
preparation re-
ported
Ash sampling
location, duration,
and sample pre-
paration reported;
ash sampling pro-
tocol and number
of samples not
reported
Analysis
Methodology re-
ported or refer-
enced; some
tests done in
triplicate;
« QA/QC unclear
Extraction pro-
cedure reported;
analytical pro-
cedure and
QA/QC not re-
ported
Methodology
and QA/QC re-
ported or ref-
erenced
Methodology
and QA/QC re-
ported
Methodology re-
ported; QA/QC
not reported
Methodology
and QA/QC re-
ported or ref-
erenced
Methodology re-
ported or refer-
enced; QA/QC
not reported
Methodology
and QA/QC re-
ported or refer-
enced
3-14
-------
Table 3.11. Summary of Literature Database Quality (continued)
Referencea"
Kullberg and Fallman
(1989)
Mintott (1989)
Mohamad et al. (1988)
Northeim et al. (1989)
Sawell and
Constable (1989)
Van der Sloot et al.
(1989)
Clement et al. (1988)
Bleifuss et al. (1988)
Research Goal
Investigate physical,
chemical, and techni-
cal properties of flue
gas cleaning residues
from Swedish
facilities
Describe operating
principles and envi-
ronmental parameters
of fluidized bed
combustors
Characterize coal-
RDF fly .ash
Evaluate laboratory
leaching tests
Evaluate ash streams
from a RDF and a
modular facility in
Canada
Examine metal leac-
hing behavior of ash
from combustor in
The Netherlands
Determine if com-
bustion conditions
could affect forma-
tion of PCDDs and
PCDFs
Evaluate EP toxicity
and ASTM water
leach tests for fly
ash
MSW Fuel"
Not reported
Not reported
Reported
Not reported
Not reported
Not reported
Highly industrial-
ized area
Not reported
Facility0
Not reported
Reported
Name and location
of facility only
reported
Not reported
Reported or refer-
enced
Facility name,
location, capacity,
and ash handling
reported; operating
parameters not
reported
Reported
Name and location
of combustor only
reported
Sampling*1
Not reported
Not reported
Sampling protocol,
number of samples,
and sample prepara-
tion reported
Sample preparation
reported; 2 ash sam-
pling protocol refer-
enced analysis
Sampling protocol,
number of samples,
and sample prepara-
tion reported
Ash sample prepara-
tion reported; ash
sampling protocol
and number of sam-
ples not reported
Reported
Composite test lots
of ash from 3 facili-
ties prepared and dis-
tributed to partici-
pating laboratories;
, sample preparation
reported
Analysis"
Methodology re-
ported or refer-
enced; QA/QC not
reported
Analyses con-
ducted by EPA-
certified laborat-
ory; methodology
and QA/QC not
reported
Methodology and
QA/QC reported
Methodology and
QA/QC reported
Methodology re-
ported or refer-
enced; QA/QC not
reported
Methodology re-
ported or refer-
enced; some pro-
cedures performed
in duplicate,
QA/QC for others
not reported
Methodology and
QA/QC reported
Methodology ref-
erenced; QA/QC
varied between
laboratories
3-15
-------
Table 3-11. Summary of Literature Database Quality (continued)
Reference*
Research Goal MSW Fuel" Facility*"
Sampling"
Analysis'
EPA (1988i)
Kamada ct al. (1988)
Phcrson (1988)
Schwind et al. (1988)
Sovocool ct al.
(1988)
EPA (1987a)
Frauds and White
(1987)
Karasek and
Dickson (1987)
Karasek ct al. (1987)
Characterize MWC
ash and Icachates
from disposal
facilities; summar-
izes data reported in
literature
Measure amount of
PCDDs in flue gas
and ash from 7 Japa-
nese incinerators
Study ability of
solidification to
fixate Pb in ash
Analyze fly ash for
PB/CDDs and
PB/CDFs
Isolate and identify
brominated organics
in fly ash
Characterize ash and
leachate
Study leaching of
toxic metals
Study of dioxin
formation from pre-
cursors in incinera-
tors from Canada
and Japan
Study leaching of
organics from Ca-
nadian fly ash
Not reported
Not reported
Not reported
Not reported
Not reported
Not reported
Not reported
Not reported
Not reported
Not reported
Reported in detail
Not reported
Not reported
Not reported
Reported
Location of facil-
ities only reported
Location and com-
bustor type only
reported
Location only
reported
Not reported
Reported in detail
One 55-gal drum of
mixed ash, sampling
protocol not reported
Single ash sample
used for analysis;
sampling protocol
not reported; sample
preparation reported
Sampling protocol
and number of sam-
ples not reported;
sample handling and
preparation reported
Reported or refer-
enced
Referenced
Sampling protocol
and sample number
not reported; sample
preparation reported
Single sample from
ESP
Not reported
Reported in detail
Methodology and
QA/QC reported
Methodology and
some QA/QC re-
ported
Methodology and
some QA/QC
referenced or re-
ported
Methodology and
QA/QC reported
or referenced
Methodology re-
ported or refere-
nced
Methodology and
QA/QC reported
Methodology and
QA/QC reported
3-16
-------
Table 3-11. Summary of Literature Database Quality (continued)
Reference*
Research Goal
MSWFuelb
Facility0
Sampling"
Analysis'
Kuehl et al. (1987)
Tanaka and
Takeshita (1987)
Carsch et al. (1986)
Kuehl et al. (1986)
Tong and Karasek
(1986)
Austin and Newlsnd
(1985)
Kuehl et al. (1985)
Mika and Feder (1985)
Morselli et al.
(1985)
Determine isomer
dependent bioavaila-
bility of PCDDs and
PCDFs in fly ash to
freshwater fish
Summary of research
projects and liter-
ature on TCDDs and
PCDDs in fly ash
Study leaching be-
havior of organics in
fly ash from inciner-
ator in Germany
(FRG)
Study bioavailability
of PCDD/ PCDFs
from fly ash
Compare PCDD and
PCDF isomer distri-
bution pattern and
concentrations from
fly ash from differ-
ent countries
Study leaching of Cd
and Mn from comb-
ustor in The Nether-
lands
Determine bioava-
ilability of TCDD
from fly ash to
freshwater fish ,
Provide information
on the nature of resi-
due in the environ-
ment
Study effect of dif-
ferent technologies
and working condi-
tions on toxic orga-
nics in fly ash
Not reported
Not reported
Not reported
Not reported
Not reported
Not reported
Not reported
Not reported
Reported in fair
detail
Location of com-
bustor only repor-
ted
Combustor type
only repotted
Not reported
Not reported
Location of com-
bustors only re-
ported
Briefly repotted
Regional location
of combustor only
reported
Facility location,
operating condi-
tions, APC, ash
handling and trea-
tment reported
Reported in detail
Sampling protocol
and number of sam-
ples not reported;
sample handling and
preparation reported
Sampling protocol
and number of -sam-
ples not reported;
sample preparation
reported
Samples taken from
2 incinerator!!; sam-
pling protocol and
number of samples
not reported
Not reported
Sampling protocol
number of samples
not reported; sample
handling preparation
reported or refer-
enced
Single sample taken;
sample preparation
reported
Sampling protocol
not reported; sample
handling and prepa-
ration reported
Ash sampling prot-
ocol not reported;
2 samplings under
same conditions,
details not reported
Methodology and
QA/QC reported
or referenced
Methodology
briefly reported;
QA/QC not re-
ported
Methodology and
QA/QC reported
or referenced
Not reported
Methodology and
some QA/QC re-
ported or refer-
enced
Methodology and
QA/QC reported
Methodology and
QA/QC reported
or referenced
Methodology and
some QA/QC
reported
Reported in detail
3-17
-------
Table 3-11. Summary or Literature Database Quality (continued)
Reference*
Wakimoto and
Talsukawa (1985)
Clement ct el.
(1984)
Rghci and Eiccman
(1984)
Tong ct al.
(1984)
Viau et al.
(1984)
Ballschinitcr ct al.
(1983)
Eiceman and
Vandivcr (1983)
Karasck ct al.
(1983)
Research Goal
Determine pres-
ence of PCDDs
and PCDFs in fly
ash from 9
Japanese incinera-
tors
Compare analyti-
cal methods for
analysis of organ-
ics in fly ash from
Canada
Characterize ad-
sorption and
chlorination reac-
tions of DD and
1-MCDD on fly
ash
Demonstrate use
of HPLC in quan-
tifying PCDDs in
fly ash
Evaluate source of
hazardous organic
compounds in fly
ash from Canada
and Norway
Compare proced-
ures used to anal-
yze PCDDs and
PCDFs in fly ash
Measure adsorp-
tion of PAHs on
fly ash
Study operating
conditions of in-
cinerator to mini-
mize dioxin for-
mation
MSW Fuel"
Not reported
Not reported
Not reported
Not reported
Not reported
Not reported
Not reported
Analyzed for
PVC content
only
Facility"
Location of in-
cinerator and
type of APC
device briefly
reported
Not reported
Not reported
Briefly reported
Location of
facility only re-
ported
Not reported
Location of
facility only
reported
Reported
Sampling*1
Not reported
Sampling protocol
not reported; 3
grab samples, and
sample handling
and treatment re-
ported
Referenced
One grab sample
from each of two
facilities and some
sample handling
reported; sampling
protocol not re-
ported
Not reported
Not reported
Sampling protocol
and number of
samples not re-
ported; sample
handling and pre-
paration reported
Reported
Analysis'
Methodology
and some
QA/QC reported
or referenced
Methodology
and QA/QC
reported or ref-
erenced
Referenced
Methodology
and some
QA/QC reported
or referenced
Methodology
and QA/QC
reported or ref-
erenced '
Methodology re-
ported or refer-
enced; QA/QC
not reported
Methodology
and QA/QC
reported or ref-
erenced
Methodology
and QA/QC
reported
3-18
-------
Table 3-11. Summary of Literature Database Quality (continued)
Reference"
Clement and
Karasek (1982)
Karasek et al.
(1982)
Olie et al.
(1982)
Buser et al. (1978)
Research Goal MSW Fuel"
Facility"1
Sampling*1
Hrudey et al. (1974)
Measure concen-
tration of PCDDs
on different size
fractions of fly ash
Analyze concen-
tration of organic
compounds on
different size frac-
tions of fly ash
Evaluate PCDDs
and PCDFs in fly
ash from the
Netherlands
Analyze PCDFs in
fly ash
Analyze constitu-
ents of ash
Not reported
Reported
Not reported
Reported
Not reported
Not reported
Not reported
Country location
only reported
Not reported
Not reported
Sampling protocol
not reported; nu-
mber of samples
and sample pre-
paration reported
Reported in detail
Not reported
Sampling protocol
and number of
samples not
reported; sample
preparation refer-
enced
Sample handling
and preparation
only reported
Analysis'
Cavallaro et al.
(1982)
Study PCDDs and Not reported
PCDFs in inciner-
ator effluents
Not reported Sampling protocol
and sample pre-
paration refer-
enced; number of
samples not re-
ported
Methodology
and some
QA/QC reported
or referenced
Methodology
and some
QA/QC reported
or referenced
Reported in
detail
Methodology
and QA/QC
reported or ref-
erenced
Methodology
and some
QA/QC reported
or referenced
Methodology
and some
QA/QC reported
or referenced
References are arranged by year of publication in reverse chronological order and alphabetized within years.
"Reported" or "referenced" in this column indicates that a characterization of the MSW combusted was conducted.
"Reported" in this column indicates that a description of the facility and combustion parameters was included in the
referenced report.
This column indicates whether a description of where, when, and how many ash samples were acquired from the
MWC facility prior to any analysis. In general, sample handling and preparation includes only those physical
processes used to make the ash amendable to analysis (e.g., storage, grinding, or screening).
"Reported" or "referenced" in this column indicates that a description of methodology or QA/QC procedures was
included in the report. "Not reported" does not necessarily indicate that proper methodology or QA/QC was not used,
only that there is no mention of it in the text. Methodology includes experimental and control procedures (e.g.,
extraction, dilution, and column leaching tests) and analytical procedures (e.g., GC/MS and AA Spectroscopy).
QA/QC includes replicate testing, instrument calibration, standards, controls, discriptive statistics, etc.
3-19
-------
As shown in Table 3-11, virtually no studies have been undertaken that attempt to relate the source
and composition of MSW fuel, incinerator type, location, operating parameters, and pollution control
devices to ash composition. Much of the research on ash was performed for purposes other than providing
representative data on ash composition. In most studies, no attempt was made to collect ash that is
representative of the facility, or to determine intra-facility variability. Often, research was performed on
single grab samples of ash provided to the researcher by facility operators or third parties. Thus, although
most studies pay adequate attention to analytical QA/QC, few studies document sampling and sample
handling protocols, or even the number of samples taken. Our intent is not to criticize the researchers or
the research, since obtaining representative samples was usually not necessary to address their specific
research objectives, but to point out the difficulty in using these data for an exposure/risk assessment for
MWC residuals.
The use of a number of different procedures to characterize MWC ash can be found in the literature.
There has been considerable confusion over the basis and the roles of some of these tests, in particular
the TCLP (Toxicity Characteristic Leaching Procedure) and EP (Extraction Procedure). The TCLP (which
recently replaced the EP) is used for identifying those wastes which may present a risk to human health
and the environment when improperly managed. Wastes that fail this test are hazardous wastes under
RCRA. In developing this test, EPA chose a reasonable worst case mismanagement scenario in order to
ensure that wastes would be adequately controlled, regardless of the manner in which they are actually
managed. The results of these tests were never intended to be compared with actual field leachates.
A number of other tests, such as the Monofilled Extraction Procedure (SW-924), have been
developed to estimate the presence of leachable constituents in wastes under different disposal scenarios.
Although these procedures may be useful for predicting the leachability of a waste under a particular
disposal scenario, they carry no regulatory weight.
Nevertheless, these extraction procedures continue to be used to characterize ash in many studies.
Although a comprehensive research, development, and demonstration program has been proposed by EPA
to redress the deficiencies in the ash database (EPA, in preparation), it will still require several years and
a great deal of resources before confident predictions of ash composition can be made from existing data,
without actually sampling ash from individual facilities. For all of these reasons, values reported in this
section should be viewed with extreme caution and only in the context of a demonstration of the ranges
of constituent concentration reported in the literature.
3-20
-------
3.3. CHEMICAL CHARACTERISTICS OF BOTTOM AND FLY ASH
As discussed in Section 3.2, and shown in Tables 3-1 to 3-3, the ranges of concentrations of the ash
constituents that have been reported by various authors are often seen to vary by several orders of
magnitude. This section describes in more detail the inorganic and organic constituents that have been
reported in bottom and fly ash from MWC facilities, and further underscores the reported intra- and inter-
facility variability in the chemical makeup of MWC ash.
3.3.1. Inorganic Constituents
High concentrations of heavy metals and other inorganic constituents have been reported to be
present in MWC residues (Healy et al, 1979; EPA, 1987a; EPA,1988a). The concentration ranges of
some inorganic constituents in bottom, fly, and combined ash from municipal solid waste incinerators are
shown in Table 3-1. Higher concentrations of inorganic chemicals have generally been found in fly ash
than in bottom ash. For example, fly ash usually has greater mass values of cadmium and lead than
bottom ash. However, bottom ash has generally been found to have greater total mass values for silicon,
aluminum, calcium, iron, copper, and zinc.
The partitioning of inorganic constituents between bottom and fly ash may be due to the deposition
of metal oxides, hydroxides, or salts on fly ash particles by means of the volatilization-condensation
reaction mechanism. This reaction is controlled by the individual vapor pressures and boiling points of
the various metals. However, the reported partitioning of a number of elements cannot be explained by
this reaction alone. In some cases, the concentration of these chemicals (copper, iron, lead, chromium,
cadmium, tin, strontium, cobalt, barium, and phosphorus) has been reported to be higher in bottom ash
than in fly ash. Many of these constituents volatilize under combustion conditions, and therefore could
become oxides on particle surfaces. Some metals, such as cadmium, apparently concentrate on the surface
of fly ash particles, while others, such as manganese, appear to occur as a matrix component of fly ash
particles (Austin and Newland, 1985).
3.3.2. Organic Constituents
The ranges of concentrations reported in the literature of some organic constituents present in
municipal waste combustor ash are shown in Table 3-2. Polycyclic aromatic hydrocarbons (PAHs),
phthalates, chlorobenzenes, and chlorophenols are the most prevalent types of organic compounds found
in municipal waste combustor ashes. The concentrations of organic constituents are generally greater in
fly ash than in bottom ash, while the concentrations of organic constituents in combined ash have
3-21
-------
intermediate values. The various data sets also indicate an absence of volatile organic compounds.
Volatile compounds would not be expected in materials that are combusted at temperatures that are much
higher than their boiling points, such as those temperatures present in municipal waste combustors. Also,
they would tend to be lost during extraction and analysis procedures.
Like the inorganic constituents, the concentration ranges of organic constituents vary over several
orders of magnitude in MWC ash. This may be due to the variability in combustion quality, difficulties
in obtaining representative samples, and some of the same factors effecting inorganic constituent
concentrations.
PCDDs, PCDFs, and PCBs, and their homologs, have been detected and quantified in MWC ash
(EPA, 1987a; 1988a; Lisk, 1988; Kuehl et al., 1985, 1986, and 1987; Tanaka and Takeshita, 1987;
Clement et al., 1984; Viau et al., 1984; Buser et al., 1978). Table 3-3 shows the reported concentration
ranges of PCDDs, PCDFs and PCBs in fly, bottom, and combined ash. These compounds are usually
found in greater concentrations among the smaller particle sizes, such as found in fly ash. This differential
partitioning may be explained by the fact that smaller sized particles have larger surface areas relative to
weight and therefore have a greater area for sorption per mass unit.
The variation in reported concentrations of PCDDs, PCDFs and PCBs is relatively greater than the
variation in concentration of other organic compounds or inorganic compounds found in ash. This
variability may be due to sampling location within the incinerator, operating conditions, and the incinerator
or air pollution control system configurations and designs.
3.33. Intra- and Inter-Facility Variability
The concentration of residual components may vary in relation to the operating parameters of an
incineration facility, and in relation to the variability of the feedstock. Since MSW is a heterogeneous
product, a lack of homogeneity in the composition of the residuals produced is to be expected. A
comparative analysis of the inorganic and organic constituents of the residues produced from four
municipal waste combustpr facilities has been conducted (EPA 1987a; EPA,1988a). The four incineration
facilities were all continuous feed, mass bum incinerators having different grate designs (one rotary, one
traveling grate, and two with reciprocating grates), and ranging in operation dates from 1972 to 1986. The
study examined the composition of residuals sampled over different shifts, days, and incinerator units.
The results of one study indicated a wide variability in contaminant concentrations within the same facility
over the different days, shifts, and units. These results implied that a slight change in feed material or
operating parameters would significantly affect the composition of the residuals. Furthermore, intra-
3-22
-------
facility comparisons found that the variability of contaminant concentrations between facilities was so large
that the standard deviation of the sample means exceeded the average concentration of each contaminant
(EPA, 1988a). In addition, results indicated a substantially higher variability within and between facilities
for bottom ash alone and for combined ash, than the variability found in fly ash samples from different
facilities.
3.4. LEACHATE CHARACTERISTICS
The direct contamination of groundwater, surface water, and soil by leachates from MWC residuals
represents a potential route of exposure to the compounds that are found in ash. Leachate characteristics
may also determine the extent of contaminant migration in environmental media. Two approaches have
been taken to determine the composition of MWC residuals leachates: (1) the generation of simulated
leaphates, and (2) the study of field-generated leachates.
Although each approach has certain limitations, laboratory leachability simulation studies have been
used to understand the potential leachability of organic and inorganic constituents in MWC ash. These
extraction procedures were devised to simulate natural leaching conditions in the absence of actual field
leaehate data. The tests were designed to be conservative, i.e., they maximize the potential for leaching
to occur, since the data generated from these tests are used for designing landfills and leaehate treatment
facilities, or to designate a waste as hazardous or not. Because a number of such leaching procedures
exists, the data generated from these leaehate tests have been criticized for the variabilities in experimental
conditions, and for their inability to predict long-term leaching behavior at all disposal sites and for all
types of residues (Van der Sloot et al., 1989; Northeim et al., 1989; Francis and White, 1987; Belevi and
Baccini, 1989; EPA, 1989a; Kellermeyer and Ziemer, 1989; Ujihara and Gough, 1989). Furthermore, the
characterization data available on ash extracts are more limited than data on ash itself, and relate mostly
to the inorganic constituents rather than the organic content of ash extracts.
Of the commonly used laboratory leaching methods, two have regulatory significance for the U.S.
EPA: the Extraction Procedure (EP) and the Toxicity Characteristic Leaching Procedure (TCLP). The
TCLP replaced the EP in 1989 as the test used by EPA to determine if a waste exhibits hazardous
characteristics, and should therefore be handled under hazardous waste regulations. The Monofilled Waste
Extraction Procedure (also called the Deionized Water Extraction test method, and referred to as SW-924)
has been used to estimate the presence of potentially leachable constituents in a solid waste, and to
measure the concentration of these constituents in extracts. Simulated Acid Rain extraction is another
commonly used test procedure that is a more aggressive variant of SW-924. However, SW-924 and the
3-23
-------
Simulated Acid Rain extraction procedure are not appropriate for regulatory pruposes. The conditions for
the EP, TCLP, and SW-924 are summarized in Table 3-12.
The EP and TCLP tests were designed to identify wastes which may present a risk if mismanaged.
The design of these tests is based on a scenario of co-disposal with MSW in an unlined sanitary landfill.
EPA (1987a; 1988a) found that leachates produced under simulated laboratory conditions showed greater
concentrations of lead and cadmium than actual leachates collected in the field. This is not unexpected
given the design of these tests. However, it should be noted that these studies relied on the collection of
a small number of leachates over a relatively short period of time. Therefore, sampling conditions may
not adequately reflect the long-term teachability of these elements. As well, the EP Tox and TCLP tests
have underestimated the presence of other elements, as seen in Table 3-13 for arsenic, barium, manganese,
selenium, chloride, and sulfate.
3.4.1. Inorganic Constituents in Leachate
Several authors have investigated the factors that affect concentration of inorganic constituents in
leachate. Ontiveros (1988) found that extract concentrations of cadmium were dependent on pH, while
extraction concentrations of lead were enhanced by the addition of anions. Van der Sloot and colleagues
(1989) also observed a relationship between pH and teachability for several metals. These findings
underscore the need for a study of the long-term pH changes in disposal or construction sites that contain
combustor residues. Under oxidizing conditions, Van der Sloot et al. (1989) observed minimum leaching
of metals within the pH range of 8-10, but found large increases in metal leachability when the pH was
decreased to 6 or 5. In addition, increasing the pH to above 10 increased the potential for leaching of lead,
zinc, and copper. Under reducing conditions, however, metals were thought to be effectively retained as
sulfides. DiPietro et al. (1989) also examined the effects of pH and redox potential on leachability of
metals from combined bottom and fly ash. Lower pH levels increased the concentrations of metals, except
for sodium and aluminum, in laboratory leachates. This finding has been attributed to a greater adsorption
and precipitation of metals at moderate pH. Sodium concentrations were found to increase slightly at
higher pH levels, possibly as a result of ion-exchange. Aluminum concentrations were higher at pH levels
of 10 and 4 than at pH 7, reflecting aluminum's amphiprotic nature (the pH minimum of aluminum
hydroxides is generally around pH 6).
'3-24
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Table 3-12. Summary of Conditions for EP, TCLP, and SW-924 Leaching Methods
Conditions
Liquid:Solid Ratio
Extraction Medium
pH Control
Extraction Time
Agitation Method
Temperature Control
Particle Size
Number of Extractions
EF
20:1
0.5 N acetic acid
5
24 hours
Tumbler
20 - 40° C
<9.5 mm
1
TCLP"
20:1
0.01 N acetate buffer
5 or 3
18 hours
Tumbler at 30+2 rpm
22 +3° C
<9.5 mm
1
SW-924"
10:1 per extraction
Distilled/deionized
water
None
18 hours per
extraction
Tumbler
25+l°C
<9.5 mm
4, sequentially
* EP = Extraction Procedures (40 CFR 261,Appendix II), 1980
b TCLP =
Toxicity Characteristic Leaching Procedure (Revised 40 CFR 261, Appendix II), 1986
c SW-924 = MonofiUed Waste Extraction Procedure (A Procedure for Estimating Monofilled Solid Waste
Leachate Composition. Technical Document SW-924. 2nd edition).
Source: EPA, 1987a.
3-25
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Table 3-13.
Concentration of 13 Inorganic Constituents in Ash, Laboratory Extracts, and Field
Leachates from Five Municipal Waste Combustor Facilities and Their Associated
Land Disposal Sites"
Chemical"
Arsenic
Barium
Cadmium
Chromium
Copper
Lead
Manganese
Mercury
Selenium
Silver
Zinc
Chloride
Sulfate
CO2
10.3
298.0
92.9
3.4
160.0
92.5
1068.8
8.0
2.5
2.6
17705.9
666.6
628.8
Ash Extract by Six Methods (ug/L)b
SW924 EPTox TCLP1 TCLP2 SAR
11.0
599.2
2.5
5.4
123.2
571.6
3.3
0.3
2.5
2.0
257.5
695.9
267.9
10.4
221.0
633.3
35.9
1211.8
6621.1
2917.4
15.6
2.5
2.0
48768.2
711.3
852.1 ..
8.5
491.7
344.2
3.1
116.3
1869.7
1476.3
0.4
2.5
2.0
21150.3
744.3
644.1
14.5
373.2
611.9
150.6
300.9
8188.0
3438.4
0.3
2.5
2.0
58835.9
716.9
845.3
8.5
695.0
2.3
4.2
127.7
584.2
1.5
0.3
3.9
2.0
241.7
1030.2
544.6
Leachate
Pg/L
79.5
1404.3
2.0
74
3 8
21.5
4217.5
0.1
56
20
103.5
7571.4
1391.1
Extract values reported in this table are mean concentrations from five samples of ash extract from five
facilities, i.e., 25 samples. Leachate mean was from 16 samples: 7 from one land disposal site, 3 from
one site, and 2 each from 3 sites. When not detected, the value assumed to determine mean
concentration was 1/2 the limit of detection. Data from EPA, 1990a, statistical analysis in MRI, 1990b.
b CO2: CO2 saturated deionized water
SW 924:MonofiUed Waste Extraction Procedure
EP Tox: Extraction Procedure (EP) toxicity method
TCLP1: Toxicity Characteristic Leaching Procedure (TCLP) method #1
TCLP2: TCLP method #2
SAR: Simulated Acid Rain
0 Limit of Detections for ash extraction and leachates, ug/L:
Arsenic:
Chromium:
Manganese:
Silver:
Sulfate:
17
4
2
4
0.5
Barium: 1
Copper: 4
Mercury: 0.2
Zinc: 2
Cadmium: 4
Lead: 32
Selenium: 5
Chloride: 0.5
Source: EPA, 1990a; MRI, 1990b.
3-26
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Redox potentials dramatically affect the soluble metal concentrations of zinc, copper, nickel, iron,
and lead (DiPietro et al., 1989). These metals are known to precipitate as insoluble metal sulfides under
reducing conditions. DiPietro et al. (1989) noted that changes in redox potentials may affect metal
solubility by directly changing redox sensitive metal oxidation states to more soluble/insoluble species,
by changing the extent of redox sensitive metal surfaces available for adsorption, and by changing the
degree of co-precipitation, precipitation, and complexation with other redox sensitive cations and anions.
In general, iron concentrations in laboratory leachate experiments were found to be greatest at low pH and
low redox potentials. The solubilities for zinc, copper, nickel, and aluminum were greatest at low pH and
high redox potentials.
A study by Kullberg and Fallman (1989) indicates that differences in the flue gas cleaning processes
can produce fly ash having different metal and salt leaching properties. Fly ash produced from four flue
gas cleaning processes in Swedish incinerator facilities had little variation in inorganic concentrations.
However, the flue gas cleaning process greatly affected the variation in leaching of inorganic constituents,
especially chloride, lead, and cadmium. Greater leaching was observed in residues produced from semi-
dry processes that use lime slurry scrubbers than from fabric filter processes or washing tower condensing
processes.
The leachability of metals has been found to be less affected by particle sizes than would be
expected to result from differential surface areas (Van der Sloot et al., 1989). Leaching test differences
between crushed and untreated bottom ash have been found to vary by only 12-50%. This indicates that
metal leaching may be dictated more by the ash matrix, and less by exposed surface area (Van der Sloot
et al., 1989).
The ranges of concentrations reported in the literature of some inorganic constituents determined by
SW-924, TCLP, and EP in fly ash, bottom ash, and combined bottom and fly ash extracts are shown in
Tables 3-4, 3-5, and 3-6. As can be seen, there are wide variations in reported concentrations, within and
between laboratory procedures.
There are also differences between laboratory procedures and field leachates in some limited
comparison sampling that has been done. Table 3-13 compares the concentration of 13 inorganic
constituents in combined ash, ash extracts by 6 methods, and in leachate collected from land disposal sites.
This study was conducted by EPA and CORRE on 5 MWC facilities and their associated land disposal
sites (EPA, 1990a). Five ash samples were taken from each facility and measured for the 13 constituents;
all six extraction methods were also run on each of the five samples. Two leachate samples were taken
from 3 of the associated land disposal sites; 3 and 7 samples were taken from the remaining 2 disposal
3-27
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sites. Further details of this study can be found in EPA (1990a). The statistical evaluation and the
summary provided in Table 3-13 was conducted by MRI (1990b). Although the sample sizes were small,
particularly for the field leachates, some observations can be made. Generally higher field leachates were
noted for arsenic, barium, manganese, selenium, and chloride, while the laboratory extraction procedures
generally had higher concentrations for copper, lead, and zinc. Four of 6 laboratory procedures had
substantially higher results for cadmium as compared to the field leachates, while only 1 of 6 laboratory
results differed substantially for chromium. Without statistical rigor, reasonable agreement between
laboratory results and field leachates were noted for other results (statistical correlation analysis performed
in MRI, 1990b). Concentration of these inorganic compounds were provided on Table 3-13 for
comparison.
3.4.2. Organic Constituents in Leachate
A range of the concentrations of some organic constituents from extracts of fly ash and bottom ash
are shown in Table 3-7 to 3-10. Few data exist on the concentrations of organic constituents in fly ash
and bottom ash extracts from laboratory leaching tests. The concentrations of most organic constituents
analyzed in fly ash and bottom ash extracts are generally below detection limits or at trace levels. The
concentration of chlorophenols in fly ash determined by SW-924 were detected only in incinerators not
equipped with fabric filter dust collectors. Trace concentrations of several organic constituents were found
in bottom ash extracts using the SW-924 method (e.g., benzoic acid, cyclooctadecane, dimethyl furandione,
methyoxy ethane, and phenol). As shown in Table 3-8, methoxy ethane was the only organic constituent
found in bottom ash extracts using the TCLP or EP methods, and its concentration was only slightly above
the detection limits.
Results of laboratory leaching studies for combined bottom and fly ash are shown in Table 3-9. As
with the fly ash and bottom ash databases, this information is also extremely limited. Only dimethyl
propdiol was detected in combined ash extracts using the TCLP method. Several organic constituents
were detected at various concentrations in combined ash extracts using the SW-924 method.
Limited information exists on concentrations of PCDDs, PCDFs, and PCBs in fly ash extracts from
simulated leaching tests (Table 3-10). No PCDDs, PCDFs, or PCBs have been found above the detection
limit by the SW-924 method. Individual homolog concentrations of PCDDs, PCDFs, or PCBs were never
found to exceed 0.12 ng/L (parts per trillion) in fly extracts determined by TCLP. Total PCDDs did not
exceed 0.188 ng/L and total PCDFs did not exceed 0.152 ng/L in fly ash extracts determined by the TCLP
method. No data were found for concentrations of these compounds in laboratory leaching test extracts
3-28
-------
for bottom ash.... The concentrations of PCDDs, PCDFs, and PCBs in combined bottom and fly ash extracts
using the TCLP method are similar to those for fly ash extracts.
3.5. PHYSICAL PARAMETERS OF MWC ASH
The physical characteristics of MWC residuals represent anjmportant consideration in analyzing their
potential for environmental transport and human exposure. A source analysis must necessarily include
a description;* the physical characteristics of the released substances'. This information is used to develop
a better understanding of the environmental transport and fate characteristics of the containment and its
exposure potential.
.3.5.1. Particle Morphology and Mineralogy
As described below, the chemical and physical properties of the ash (e.g., particle morphology and
mineralogy) from MWC facilities will largely determine the extent to which ash constituents will be
released via leaching, . . -
Ontiveros (1988) reported that the morphology of fly ash did not vary significantly between samples
from different incinerators. Eighmy et al. (1990) examined the particle morphology and mineralogy of
MWC ashes using scanning electron microscopy. In general, municipal waste incinerator residues were
described as amorphous non-descript and mineralogically diverse. Ettringite or calcium silicate hydrate
crystal morphologies were also not observed in bottom or combined ash, indicating that solidification of
these ashes may be CaCO3- or Ca(OH)2-based pozzolan-like cementation. A pozzolon is a siliceous
material which reacts to the presence of moisture and alkali and alkaline earths to yield a cementitious
product. However, Ontiveros (1988) reported crystals heavily dispersed on fly ash particle surfaces.
The "core" principal elements found in ash particles are aluminum, calcium, iron, sulfur, and silicon.
In addition, calcium and iron, aluminosilicates are observed to form the major solid phase of fly ash,
bottom ash, and combined fly and bottom ash with scrubber residue (Ontiveros, 1988; Eighmy et
al., 1990). A number of other minerals have been identified in ash, including NaAlBr4, FeCr2O4, and
CaC03 in bottom ash; CaSO4 and. CuFe2S3 in fly ash; and Ca^O* CaSO3, CaHPO4, CaCl2, and Ca^O?
in scrubber residue. Lead and cadmium are found as PbSO4 and CdSiO3, respectively, in bottom ash;
CdSO4 in fly ash; and Pb5(PO^)3Cl in scrubber residue. A number of other sulfate minerals, as well as
chlorides and oxides are found in residues (Ontiveros, 1988; Eighmy et al., 1990).
3-29
-------
3.5.2. Particle Size Distribution
Hy ash is made up of much finer particles than bottom ash. As shown in Figure 3-1, the grain size
distribution of mixed ash has been determined by Forrester (1988). A particle size analysis for fly ash
at one site was performed as part of the Red Wing RDF Ash Disposal Site Risk Assessment (Northern
States Power Company, 1987). Only particles less than 50 pm diameter were considered to have wind
erosion/rugitive emission potential. Less than 6.7% of mixed ash consists of such particles. The particle
size distribution for this potentially fugitive ash fraction is shown in Figure 3-2.
3.53. Particle Sizes and Chemical Composition
The constituent elements of ash exhibit a differential sorption on to different sized particles. For
example, more than 75% of the mass of the following elements was found on small particles (<2um) from
the incinerators (Greenberg et al., 1978): Na, Cs, Cl, Br, Cu, Zn, As, Ag, Cd, In, Sn, Sb, W, Pb, while
the following elements had a predominant large particle distribution: Ca, Al, Ti, Sc, La, and Vanadium.
Constituent elements such as Cr, Mn, Fe, Co and Se had mixed size distributions.
According to the EPA (1986a), data on the distribution of organic compounds adsorbed on different
sized particles of ash is lacking.
3.5.4. Engineering Characteristics
The aggregate characteristics of ash are important in determining its potential use as a substitute in
construction and in landfill liner and cover systems. These characteristics are also important in
determining potential exposure routes and contaminant release. Various beneficial uses of ash are
described in Section 4.
Chesner (1990) reported interim results of physical and engineering tests of the non-ferrous portion
of combined ash from three facilities. Ash from these facilities was described as having a "well graded"
grain size distribution. This characteristic make the ash potentially frost-susceptible, and thus unusable
for an unbound aggregate base, sub-base, or select fill material.
The moisture content of ash is greatly affected by the ash quenching and draining methods that are
employed at a facility. The moisture content from the three facilities studied by Chesner (1990) ranged
from 29.6-48.0% of total weight. This range is much too high for direct use of ash in many construction
material applications. However, a decrease in moisture content has been reported after the ash had been
Stored over one month, resulting a more attractive material for reuse (EPA, 1988a).
3-30
-------
Figure 3-1
Grain Size Distribution of Mixed Ash
12.7%
10,2%
Percentage
(Dry Weight Basis)
Particle Diameter
> 2 mm
2-1 mm
1000-500 urn
500-250 urn
250-125 um
25^63 um
6 3 um
Source: Forrester, 1988
3-31
-------
Figure 3-2
Particle Size Distribution of Fly Ash
50.0%
12.0%
11.0%
16.0%
Percentage (dry wt. basis)
Source: Northern States Power Company, 1987
Particle
Diameter(um)
4.0%
.0%
0-10
10-15
15-20
20-30
30-40
40-50
3-32
-------
Gravimetric tests indicate that combined ash is more absorptive than natural aggregate materials, with
values ranging from approximately 3.5-7.0% for coarse fraction material to 4.7-14.8% for fine fraction
material. The frost-susceptibility of construction material incorporating ash is therefore potentially greater
as a result of this property. The "less than two inch" ash fraction is a lightweight material when compared
to natural material
Engineering tests of the durability of construction materials that incorporate ash show that such
materials may be only marginally durable as compared to materials that use natural aggregates. Chesner
(1990) concluded that the potential use of ash may be limited to such applications as an aggregate
substitute in asphaltic concrete, portland cement concrete, stabilized base, granular base, sub-base, and fill
applications.
3.6. SUMMARY AND CONCLUSIONS
Several constituents of ash are known to be important environmental pollutants, including certain
heavy metals and organic contaminants. However, data on the presence and concentration of these
constituents underscores the great variability that exists in the characteristics of the ash between facilities
and residue types. This makes development of an exposure assessment for MWC residuals difficult, since
input parameters such as concentrations and quantities of inorganic and organic constituents, and their
leachability and physical properties, are numerous and variable both within and between sites. The
differences in operating parameters and location of facilities clearly contribute to the observed variability
in ash characteristics. In addition, much of the data reported in the literature is of little statistical use
because of poor or unreported quality control/quality assurance, or because of insufficient information on
the MSW fuel type, facility design, and facility operating parameters. Therefore, field research should be
undertaken to develop information relating facility design and MSW fuel characteristics with ash
characteristics. Such information would greatly support exposure assessments by clearly identifying and
quantifying ash characteristics.
3-33
-------
-------
4. MUNICIPAL WASTE COMBUSTION RESIDUAL MANAGEMENT
The analysis of the sources of potential release of MWC residuals into the environment is an
essential first step in performing an exposure assessment of this material. This analysis begins with an
understanding of the material flow from an incineration facility to the final disposal or reuse site. The
following discussion provides an overview of common industry practices in the management of MWC
residuals.
4.1. INTRAPLANT COLLECTION AND TRANSPORT OF RESIDUALS
The ash conveying systems in use at MSW incinerators were analyzed as part of a review of MWC
systems operations and maintenance (EPA, 1987b). Bottom ash collected on or under the furnace is
generally conveyed to a quench pit by a hopper. The residue hopper is normally discharged through a
watertight gate valve into trucks or containers for storage or shipment to disposal sites.
Heavy fly ash may be collected in the mixing chamber, a vessel that holds volatile furnace gases at
the proper temperature for a long enough period for complete combustion to occur. Cooling towers and
air pollution control equipment also act as fly ash collection points. Conveyor systems may be employed
to transport the collected ash from each of these collection points. Hy ash may also be combined with
the bottom ash in the mechanical conveyor system prior to entering the quench pit, conveyed to a separate
quench and combined with bottom ash after removal from the quench pit, or managed separately and not
quenched.
The quench pit is a water-filled pit into which the ash falls after it exits the furnace. The quench
serves to cool and wet the ash to reduce fugitive dust emissions. Ash dumped into the quench pit is
normally removed by a drag conveyor submerged in the pit. This conveyor is constructed to permit
drainage of water back into the pit and conveys wet ash (bottom, fly, or mixed) either to holding hoppers
or directly into trucks.
Quench water is usually collected by draining basins or overflow tanks. In some facilities, quench
water may be completely recycled within the system. In others, the quench water may be released as an
effluent. Quench effluents usually require some form of treatment before being discharged, often to a
publicly owned treatment facility.
4-1
-------
4.2. POTENTIAL SOURCES OF RELEASE DURING TRANSPORT AND DISPOSAL
ACTIVITIES
Disposal of MWC residual in a landfill is by far the most common fate for such wastes. (Other
fates, including commercial uses of MWC ash, are outlined in Section 4.3.). The sources of potential
environmental release of residuals during disposal activities include:
• Vaporization and fugitive emissions within the incinerator conveyor system during quenching
and movement of ash to the storage/transport containers,
• Contaminated water releases from spray and quench water,
• Fugitive emissions, ground contamination, and runoff when the ash is dropped into the
transport/storage containers or dumped into temporary storage piles or pits,
• Fugitive emissions or excess moisture drainage during truck loading and travel,
• Fugitive emissions due to deposition of ash on roadways and haul routes near storage and
disposal points and subsequent vehicular traffic over these roadways and routes
• Fugitive emissions during unloading and spreading operations at the disposal site, and
• Fugitive emissions, runoff, and leachate generation at the disposal site.
These processes are represented in the source analysis schematic presented as Figure 4-1.
A particularly good source of information on operating practices common in the MWC industry, with
respect to the transport and disposal of ash, is the survey conducted by the EPA Office of Solid Waste
(OSW) in 1989 (EPA, 1989a; hereafter referred to as the OSW survey). EPA received responses from
121 of the 139 facilities surveyed, or a response rate of 87%. All of the statistics quoted in this report
arc based upon properly completed or "valid" responses. The number of valid responses varied by
question. Some questions, such as "name of the facility" had a very high rate of valid response. Other
questions, such as "amount of liquid residue generated" had very low valid response rates. Through this
survey, EPA received information on:
• the design and operating practices of facilities used to incinerate MSW,
• the types of waste received by these facilities,
• the establishment of any recycling activities at these facilities, and
4-2
-------
Figure 4-1
Source Analysis for MWC Residuals Release
8305.207/91052.5
^v
ssionsV^ Y ^
nthe • >- . *
,/
Physical and
characterization
fr-
Release rates to
air
^^^JL*.
asedj^-* ^
Efficacy of
control measures
>
Physical and
characterization
fr
Release rates to
soil/water
Release rates to air, soil,
surface water, groundwater
Physical and
chemical
characterization
Is ash stored
at the MWC
site?
Are fugitives
controlled?
Efficiency of
control measures
Physical and
chemical
characterization
Are fugitives
controlled?
Efficiency of
control measures
Physical and
chemical
characterization
Do trucks
use dust control
measures?
Is ash
transported to
a disposal
Ite?
Is the ash
moist or
dry?
Efficiency of control
measures
Do trucks
restrict free
drainage
restricting free drainage
Is ash
spread and
compacted?
Physical and
chemical
characterization
Load size, exposed
surface area
Does the cap
control wind erosion,
surface runoff,
leachl
Release rates to air
soil, surface water,
groundwater
Is ash
exposed at the
isposal site
Efficiency of control
Are
vehicular
resuspension
emissions
controlle
hicular
traffic occur
the vicinity of the
Physical and
chemical
characterization
Conclude Assessment
4-3
-------
• how MWC residues are generated, handled, transported, stored, and disposed of at these
facilities.
The data obtained in this survey are necessary to evaluate the MWC waste management techniques
currently employed in the United States, and subsequently to assess the potential for individuals in the
population to become exposed to the toxic constituents of MWC residuals.
Because of the high response rate in this survey (87%), the results are assumed to be fairly
representative of the operating practices of MSW incinerator facilities in the U.S. As a result, the OSW
survey is able to accurately represent the potential sources of release of MWC residuals during transport
and disposal. Therefore, the following discussion of potential sources of release of MWC residuals is
based largely on the results of the OSW survey.
With regard to disposal practices, the OSW survey reported that 46.2% of the responding MWC
operators stored ash on-site prior to disposal. This stored ash consisted of combined ash (66% of the
cases), only fly ash (7%), only bottom ash (20%) and separate fly and bottom ash storage areas (7%).
The average capacity of the storage area of the respondents to the survey was found to 876 tons, while
the average quantity of ash stored was 380 tons.
Storage areas can act as sources of release of residues to the environment. These release mechanisms
may be through runoff, leaching, or fugitive dust emissions. The OSW survey found that various
contaminant control measures were used by MWC operators (Figures 4-2 and 4-3).
Ash is exclusively transported by truck from the incinerator/storage facility to the disposal site.
Distance between the incinerator and respective disposal site were found in the OSW survey to range from
0 to 700 miles, with a mean distance of 32 miles, and a median distance of 8 miles.
Fugitive dust emissions can occur during transport of the residues to the disposal site. The majority
(92%) of respondents to the OSW survey reported that precautions were taken at their facility to avoid
fugitive dust releases during transportation. The relative use of various means to control fugitive dust
emissions that may occur during transportation is shown in Figure 4-4.
Another means of limiting fugitive dust emissions, and possibly reducing leachates, is to treat the
ash prior to disposal. The OSW survey found that only 10.2% of MWC operators treat the ash prior to
disposal. This treatment can include neutralization or stabilization.
Fugitive dust emissions may also occur at a landfill during dumping and. smoothing operations. No
information was identified in the literature regarding precautions used to prevent or limit fugitive
emissions at disposal sites.
4-4
-------
Figure 4-2
Runoff Containment Measures
Used by MWC Operators
20.2%
2.0%
8.1%
3.0%
9.1%
Containment Measures
15.2%
13.1%
8.1%
12.1%
Percent Sample
Sanitary Sewer
Drainage and/or
Recirculation
Sewer & Drainage
Ash in Pit
Gravity Settling
Wastewater Treatment
Storage Tank
None
Other
Unknown
Source: EPA,1989a
4-5
-------
Figure 4-3
Fugitive Dust Containment Measures
Used by MWC Operators
12.6%
39.1%
5.7%
Sample Percentages
17.2%
Containment Measures
Ash Wetted/Condition
Wetted Conveyors
Recircylato/Capture
None
Other
Unknown
Source: EPA, 1989a
4-6
-------
Figure 4-4
Precautions to Control Fugitive Dust Emissions
During Transportation
37.7%
28.1%
25.4%
Sample Percentages
7.9%
0.9%
Ash Wetting
Truck Covering
-------
The majority of ash is disposed of in municipal solid waste landfills where it may be segregated
from other wastes or mixed with other trash. The frequency of use of the various sites is shown in Figure
4-5.
Protective liners may be used at onsite or offsite disposal facilities to prevent leachate migration.
In the OSW survey, the MWC facilities were asked to provide information, to the extent possible, on the
types of protective liners used at the land disposal site accepting their ash, on-site or off-site. This
question had a low response rate of 42%. Of those responding, 96.1% used protective liners, the majority
of which (54.9%) were clay liners. The balance of respondents used facilities with composite or synthetic
liners (13.7% each), both clay and composite (2.0%), did not specify liner type (11.8%), or did not use
liners (3.9%). A related question on this survey was on the use of a leachate collection system. This
question also had a low response rate of 30%. Of those responding, 68% did employ a leachate collection
system.
An EPA Office of Research and Development (ORD) laboratory conducted a follow-up survey to
the OSW survey on the very same disposal facilities. In their case, however, they queried the land
disposal facility in contrast to the MWC facility. Of 72 facilities they queried, including both off-site and
on-site facilities, 40.3% used no liner material. Other respondents indicated: 38.9% used natural clay
liners, 11.1% used synthetic liners, and 9.8% used a combination of liners. Asking also about leachate
collection, they found that 50% of the facilities employed a leachate collection system and 34.7% of all
facilities treated their leachates (EPA, 1988c).
If improperly managed, this leachate could also be a point of contaminant release into the
environment. Management options include sewage or on-site treatment, placing back on top of the
landfill, and spray irrigation onto large land areas to promote evaporation.
The data summarized in this section, which were obtained in the OSW survey conducted in 1989,
not only provide an overview of MWC operating practices common in the U.S., but also allow the
exposure assessor to identify likely sources by which MWC residuals can be released into the
environment.
4.3. USES OF RESIDUALS
Although disposal is presently the favored method of MWC ash management in the United States,
increased landfilling costs and the potential for beneficial re-use may encourage alternatives in the treat-
ment and use of MWC residuals. Previous documents have reviewed such potential treatments and
beneficial uses of combustion residues (EPA, 1988a). It is not clear that potential re-use mitigates
4-8
-------
Figure 4-5
Ash Disposal Options
Frequency of Use
55.5%
2.6%
12.8%
17.1%
Percent Use
Disposal Options
MSW Landfill
Industrial Landfill
On-Site Ash Monofili
Off-Site Ash Monofili
Surface Impoundments
On-Site Stockpile
Other
Source: EPA,1989a
4-9
-------
environmental contamination. A discussion of environmental considerations can be found in Denison
(1988). MWC ash has been used for several purposes (EPA, 1988a), including:
• construction fill material for minor roads, turning and parking areas,
• landfill cover,
• aggregate for highway construction,
• glassy frit after fusion of ashes via glassification or vitrification,
• soil enhancer for grass, ornamental plants, and non-edible foliage,
• substitute for gravel and cobble stones,
• substitute for artificial reefs,
• reclaim abandoned land,
• sub-base material, and
• building blocks for furnaces.
Municipal waste combustion bottom ash has been used as road construction material in the past.
In the early 1970s, several streets in Harrisburg, PA, were constructed using ash from the local waste-to-
energy combustor (Strauss, 1989). A demonstration project using incinerator residue as a substitute for
road construction aggregate has been conducted by the Massachusetts Department of Environmental
Management since 1982 (EPA, 1988a). Bottom ash was used to fill the road bed.
4.3.1. Stabilization of MWC Ash
Research has been conducted to determine the effectiveness of stabilization in reducing the potential
for hazardous constituents to leach from MWC ash. Stabilization/solidification techniques that have been
used to process hazardous solid waste may be amenable for treating MWC ash. These processes include
thermoplastic, encapsulation, glassification (vitrification), and cement- and lime-based fixation.
The effectiveness of cement- and lime-based fixation agents to retard the release of metals from
MWC ash matrices depends on both the physical and chemical properties of the binding mechanism and
on the environmental conditions (Holland et al., 1989). For example, Kullberg and Fallman (1989)
reported that lower concentrations of lead were found in leachate from semi-dry fly ash residue stabilized
by mixing with water, cement, bentonite, sodium metalilicate, or vermiculite, than in leachate from
unstabilized fly ash. However, other research (Holland et al., 1989) has shown that combined ash
amended with cement was not successful in stabilizing aluminum, lead, and, to a lesser extent, nickel.
4-10
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Similarly, Holland et al. (1989) has reported that combined fly and bottom ash amended with lime failed
to immobilize manganese and zinc. All other metals that were tested for in this research were effectively
stabilized by these two treatments.
In an effort to gather additional data on innovative ash stabilization technologies, EPA's ORD initiated
a project to investigate the effectiveness of solidification/stabilization and other technologies in eliminating
or reducing the release of toxic constituents from MWC ash and its leachate. A technical Advisory Panel,
consisting of members from the private sector, environmental advocacy groups, incineration vendors,
academia, and state, federal, and foreign regulatory agencies, assisted EPA in developing the program,
evaluating proposals, and selecting vendors. The results of this study are expected to be available in the
spring of 1991.
4-11
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5. EXPOSURE PATHWAYS
The analysis of exposure pathways addresses the transport of MWC residuals and their constituents
from the source of release to their point of exposure with the affected individuals or populations. This
analysis is concerned with the qualitative and quantitative examination of the releases which affect the
environmental fate and transport of residuals and their constituents and which ultimately influence
exposure point concentrations. The initiation of an exposure pathway analysis begins with the
identification of the relevant environmental transport media. This step is followed by a quantitative
estimation of exposure point concentrations of the residuals and residual components using appropriate
environmental fate and transport models. The components of an exposure pathway analysis are:
« a qualitative and quantitative description of the scenarios and mechanisms of release of the
residuals to the environment, including a description of the environmental transport media
responsible for the transport of ash, and of the mechanisms of contaminant transfer from one
medium to another, and
• a description of the points of potential receptor contact with contaminated media (exposure
points), and the relative contribution of exposure routes at exposure points.
The release of MWC ash residuals to the environment can occur through fugitive dust emissions and
leaching of ash components, to eventual transport to soil, groundwater and surface water bodies. This
chapter focuses on these two mechanisms of release of MWC residuals and their components. The
exposure points and relative exposures are described in Section 6.0.
5.1. MECHANISMS OF RELEASE: FUGITIVE EMISSIONS
Municipal waste combution residues can be emitted into the air at a number of points along the route
from the incinerator to the landfill/disposal site. In addition, residues can be released into the air after they
have been disposed in a landfill. These fugitive emissions may occur through normal handling of MWC
residuals through activities such as:
• conveying residues to storage piles,
• on-site storage,
• conveying and loading residues at the incinerator site,
• release along roadways while trucks are traveling to the disposal sites,
• unloading the trucks,
5-1
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• spreading and smoothing operations at the landfill,
• wind erosion of the exposed ash surface at the landfill, and
• vehicular traffic in the vicinity of storage and disposal sites.
Methods to estimate the release of MWC residuals into the environment at these points is discussed below.
Most of the methodologies are commonly known as "AP-42" emission factors. These have been
developed by EPA's Office of Air Quality Planning and Standards (EPA, 1985a; EPA, 1988d), and are
empirical equations. They are commonly used to estimate fugitive dust emissions, including applications
described below for ash management (MRI, 1990a; EPA, 1988e; Kellermeyer and Zeimer, 1989).
5.1.1. Conveying Residues to On-Site Storage
The emission of particulates during conveying operations from the MWC to the on-site storage site
offers one possible pathway of release. Whenever the MWC facility uses a quenching system for both
fly and bottom ash, air emissions would be expected to be limited. The high moisture content of the ash
exiting a quenching system causes fine particles to adhere to the surfaces of larger particles with a
resulting dust suppression effect. As mentioned in Section 3., over 50% of facilities use wetting or
conditioning steps to limit paniculate emissions during conveying operations.
If the moisture content is very low, the processes of loading and unloading, and transporting to the
storage pile, can result in fugitive emissions. The loading and unloading emissions may be quantified
in a manner described in Section 5.1.3.; emission from trucks is described in section 5.1.4.
5.1.2. On-Site Storage
The amount of fugitive ash released during on-site storage prior to final disposal can be estimated
in a manner described in Section 5.1.6., on wind erosion.
5.1.3. Loading and Unloading of Trucks
Loading and unloading operations at MWC and disposal sites may result in the release of fugitive
dust. The emission factor equation is developed to provide emission factors for kilograms of paniculate
emitted per megagram (metric ton) of soil loaded and unloaded (EPA, 1988d):
\-1.4
where:
Elu
k
Elu = k(0.0016)(U/2.2)L3(M/2)
emission factor for loading and unloading(kg fugitive dust/Mg ash)
particle size multiplier (dimensionless)
5-2
(5-1)
-------
U = wind speed (m/s)
M = material moisture content (%)
5.1.4. Transportation to Landfill
Fugitive emissions from trucks carrying ash can be minimized by wetting the ash or the use of truck
covers. Since no emission factors have yet been developed for estimating emissions from open trucks,
EPA (1988e) used the following approach:
1. Estimate daily number of truck loads transported
2.
3.
4.
Estimate surface area of ash in each truckload capacity
Estimate emission of ash per time travel period (minute) by multiplying the surface area by the
emission factor
Estimate the total participate emission rate by multiplying the value of the particle emission rate
by the travel time and by the number of daily loads.
The emission factor was one earlier developed for emissions from aggregate piles. (EPA, 1985a; a more
refined methodology for emissions from aggregate piles is described below):
where:
s
P
.5)[(365-P)/235](f/15)
(5-2)
emission factor 1 for wind erosion from stationary piles (kg/day/hectare)
silt content (%)
number of days with >0.25 mm precipitation per year (use 365 if ash is wet prior to
transport)
percentage of time that the obstructed wind speed exceeds 5.4 m/s (assumed to be 100%
when truck travels faster than 12 mph)
As this equation was developed for stationary piles rather than moving trucks, it is likely to be a
source of uncertainty. Still, transport of ash of very low moisture content without proper truck covering
(i.e., poor management practices) is likely to result in quantifiable fugitive emissions. Such a release
should be considered in some manner, and equation 5-2 might give a reasonable first approximation.
The application of this equation to a situation where the ash is properly wetted prior to transport
would show that no fugitive emissions of dust are expected to occur (e.g., P=365, E=0).
5.1.5. Spreading and Compacting at Disposal Sites
Fugitive dust emissions from spreading and compacting ash at disposal sites have been estimated
in more than one way, although the different ways found in the literature to estimate emissions from these
5-3
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processes are all based on AP-42 emission factor equations. The differences in the approaches were due
to assumptions as to which processes the spreading and compacting of ash was most analagous to, and
used the AP-42 factor developed for that process. MRI (1990a) used an AP-42 emission factor developed
for dozer moving of overburden in western surface coal mines. This is given in EPA (1988d) as:
Eb = 0.34(s)1'7(M)
\1.4
(5-3)
where:
Eb = emission factor for bulldozing of overburden (kg/hr)
s = silt content of overburden (%)
M = moisture content of overburden (%)
Kellermeyer and Ziemer (1989) assumed that the spreading and compaction of ash was analagous to
vehicular transport on unpaved surfaces, and used the emission factor for that process (EPA, 1988d):
(5-4)
Eup = k[1.7(s/12)(Vs/48)(W/2.7)°-7(nw/4)as(365-P)/365)]
where:
Eup = emission factor for unpaved surfaces (kg/VKt - vehicle kilometer traveled)
k = particle size multiplier (dimensionless)
s = silt content (%)
Vs = mean vehicle speed (km/hr)
W = mean vehicle weight (kg)
nw = mean number of wheels
P = number of days with at least 0.254 mm (0.01 inch) precipitation per year.
In applying this equation, Kellermeyer and Ziemer (1989) made the following assumptions:
• vehicle wt = 19 tons
• vehicle velocity = 2 mi/hr
• fraction of time on exposed ash surface = 65% of an 8 hr day
• number of wheels = 2 (tracked vehicle).
EPA (1988e) seperated the processes of spreading and compacting. For compacting, they assumed the
process of vehicular transport over unpaved surfaces. For spreading, they assumed that the process was
analagous to agricultural tillage. That emission factor equation is (EPA, 1985a):
Eat = k(5.38)(s)'
,0.6
(5-5)
where:
5-4
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Eat = emission factor for agricultural tillage (kg/ha)
k = particle size multiplier (dimensionless)
- s = silt content (%).
The best approach to take is somewhat arbitrary, although some site-specific considerations might
lead to a rational selection. Visual inspection of the process can indicate whether fugitive emissions are
occurring at all; spreading and compacting of very moist ash may lead to no fugitive emissions. If
portions of the disposal area are uncovered for long periods of time such that the ash can dry out, then
any traffic associated with spreading and compacting over these areas can mimic vehicular traffic over
unpaved surfaces. One rational approach might be to iteratively use combinations-of all three equations
presented above, so that potential emissions from spreading and compacting can be bounded by a
sensitivity analysis approach. Another consideration is that, since equations 5-4 and 5-5 were not
developed as a function of the moisture content of the ash, a wetness coefficient might be introduced to
provide a more realistic estimate of emissions. Alternatively, if the ash is often, but not always, moist
when spreading and compacting traffic occurs, the value of P in equation 5-4 can be set to a number near
365.
5.1.6. Wind Erosion
Equation 5-2, used above for estimating emissions from trucks, was developed for fugitive emissions
from stationary piles (EPA, 1985a). This AP-42 emission factor was replaced by a more sophisticated
emission factor (EPA, 1988d):
Ew = •
(5-6)
1=1
where:
Ew2 =
k
N =
P, =
emission factor 2 for wind erosion from stationary piles, g/m2
particle size multiplier (dimensionless)
number of disturbances per year
erosion potential corresponding to the observed (or probable) fastest mile of wind for the
ith period between disturbances, g/m2
EPA (1988d) further presents equations to estimate P; as a function of wind speed, friction velocity, and
threshold friction velocity. Means to estimate these variables are non-trivial, and it is only applicable on
a site-specific and event basis. Further details are supplied in EPA (1988d).
Another method of estimating fugitive dust emissions was developed in EPA (1985c) based on
Gillette's (1981) field measurements of highly credible soils. Application of this method to ash piles or
5-5
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uncovered portions of disposal sites assumes that the exposed surface is uncrusted and consists of finely
divided particles. Under these conditions, an essentially "unlimited reservoir" of ash exists. This may not
be an appropriate assumption in all circumstances. For example, fly ash which has been through a lime
scrubber is thought to take on a pozzolonic nature which may reduce wind erosion (a pozzolon is a
siliceous material which reacts to the presence of moisture and alkali and alkaline earths to yield a
cementitious product). Also, and like some of the emission factors above, there is no moisture term in
this approach.
The flux of dust particles from an unlimited reservoir is given as (EPA, 1985c): ,
where:
E
V
Um
Ut
F(x)
E = 0.036 (l-V)(Um/Ut)3F(x)
total wind erosion flux of particles <10 um (g/m2 hr)
fraction of vegetation cover
mean wind speed (m/s)
threshold wind speed (m/s)
a dimensionless ratio function.
(5-7)
EPA (1985c) provides details allowing for the application of this equation under a variety of
circumstances. The following is offered as guidance specific to ash applications:
E: As developed in EPA (1985c), this approach is most appropriate for particles of grain size less than
10 um (for more discussion on grain size, see section 5.1.8 below).
V: A value of 0.0 is appropriate for uncovered portions of storage piles of disposal sites.
Um: Table 4-1 in EPA (1985d) gives mean annual wind speeds for key cities around -the United States.
Values range from 2.7 to 6.3 m/s.
Ut: The threshold wind velocity is the wind velocity seven meters above the ground surface that is
needed to initiate erosion. Determining Ut according to the methodology in EPA (1985c) is a multi-step
procedure:
Step 1. Determine wind erosion threshold friction velocity. This is a function of the aggregate
size distribution of the credible material. Figure 3-2 implies an average grain size of 1.3 mm for
combined ash. Figure 3-4 in EPA (1985c) shows that a grain size of 1.3 mm translates to a
threshold friction velocity of 72 cm/sec.
Step 2. Determine the roughness height. Figure 3-6 in EPA (1985c) graphically shows the
roughness height for the range of possible conditions. Included in this range are a roughness height
of 0.1 cm for natural snow, 1.0 cm for a plowed field, 4.0 cm for a wheat field, an up to 1000 cm
for high rise buildings (30+ floors). For ash surfaces, 1.0 cm is suggested.
5-6
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Step 3. Determine the ratio of wind speed at 7 m to friction velocity. Figure 4-1 in EPA
(1985c) gives this as a function of roughness height. For a height of 1.0 cm, this ratio is 18.
Step 4. Solve for ut. This is simply the product of the ratio given in step 3 and the friction
velocity: 18 x 72 cm/sec = 13 m/s.
F(x): The value of x is given as 0.886(Ut/Um). Assuming a mean annual wind velocity of 5.0 m/s, x
is solved as 2.3. Figure 4-3 in EPA (1985c) gives F(x) as a function of x, up to a value of x of 2.0. For
values of x greater than 2.0, F(x) is approximated as: 0.18(8x3 + 12x)exp(-x2). With x = 2.3, F(x) is 0.11.
Whether ash dries out sufficiently for wind erosion is dependent on many factors. The amount of
time ash is exposed to wind and the wind speeds necessary to "initiate" wind erosion are critical issues,
which were addressed in the Red Wing Ash disposal risk assessment (Northern States Power Company,
1987). In situ drying tests showed an average daily drying rate of 1.2% for exposed ash. The wind
speeds required to initiate erosion were determined to vary with the moisture content of the ash. A 10-
minute exposure to winds with an average speed of 17 mph can initiate wind erosion at 1% moisture
content, while winds in excess of 22-24 mph are needed to initiate erosion of ash containing 9-19%
moisture.
5.1.7. Vehicular Traffic in the Vicinity of Storage and Disposal Areas
Ash residues can build up on roadways that are near storage areas for ash within combustor facilities
as well as on haul routes in landfills where ash is disposed. Such build-ups can result from the tire track-
but of trucks hauling ash away or just after dumping it, from the dripping of excess moisture from haul
trucks through "weep holes" or cracks in truck beds, from wind erosion of storage piles or uncovered
disposal areas, and so on. Vehicular traffic on these roadways, which can be paved or unpaved, can stir
up and resuspend dust and this dust represents a source of release of ash contaminants into the air.
This point of release of MWC residuals is distinct from all others described here in that it is
"indirect"—the release is not directly from the ash piles that reside in containment, transport, or disposal
points. Still, the quantities released into air and subject to downwind transport can be significant because
of the potential for heavy vehicular traffic on these roadways other than trucks transporting ash. Common
practices to contain dust along haul routes, particularly necessary for visibility on unpaved routes that are
common in landfills, include vacuuming, wetting, sweeping, and chemical dust suppression. At some
MWC facilities, storage areas for ash piles are partially housed, with an opening for trucks to load and
transport ash. These housed areas provide protection against wind erosion and transport of fugitive
emissions. Containment measures at disposal areas/such as compacting or wetting, also reduce the
transport of fugitive ash onto nearby roadways. One key difficulty in estimating the quantity of
contaminant release through this indirect pathway is in estimating the length of roadway in the vicinity
5-7
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of the storage and disposal areas that is impacted. A second difficulty is estimating the concentration of
contaminant on impacted dust. It would be less than that of the ash because it mixes with clean dust, and
also because of dust containment on roadways and sanitary practices near ash containment areas.
Sampling of dust along roadways is the best way to resolve these difficulties. Such sampling was done
in MRI (1990a).
The emission factor equations for vehicular traffic on unpaved roads was given above in equation 5-4.
For paved roads, the emission factor is given in EPA (1988e) as:
where:
Ep = k(sL/12)-;
(5-8)
Ep = emission factor from paved surfaces (kg/VKt) (vehicle kilometer traveled)
k = particle size multiplier (dimensionless)
sL = mass of silt-sized material per unit of paved road material (g/m2)
An application of these equations to estimate emission from paved and unpaved roads impacted by ash
management and disposal, within MWC facilities and at disposal sites, used the following values for these
parameters (sL and s values derived from sample collection at 6 MWC and associated disposal sites)
(MRI, 1990a):
• mass of silt-sized material, sL, combustor site: 0.38-17 g/m2 (median = 2.5, n = 12)
• mass of silt-sized material, s, disposal site: 0.19-10.0 g/m2 (n=2)
• silt content, unpaved road: 6.7-20.1 % (n=2)
• vehicle velocity = 8-30 km/hr
• vehicle weight =14-40 Mg
• number of wheels = 6-14
Application of these equations further requires estimates of the number of vehicle kilometers traveled.
Two considerations are relevent for this estimate: the number of vehicles which traverse over a specific
length of roadway assumed to contain fugitive dust, and this specified length. Both issues were examined
in depth in MRI (1990a).
5.1.8. Application of AP-42 Emission Factor Equations
Site-specific considerations are critical for application of these equations.. These include not only
parameter values (silt content, moisture content, etc.) for the equations, but also additional reductions in
estimated emissions because of control practices associated with ash management. The AP-42 emission
5-8
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factor equations were developed with no controls in place. At MWC facilities and disposal sites, control
measures are taken to reduce fugitive emissions. These were summarized in Section 4. Estimations using
the emission factors must be reduced assuming some efficiency of control measures. This "control
efficiency" reduction is demonstrated in Section 7.
Three additional considerations are relevent for application of the AP-42 emission factor equations.
These considerations are summarized on Table 5-1 and discussed below.
One is the qualitative rating of A through E, with A being the best. They are subjective and reflect
the quality and amount of data available in the development of the equations. The developers indicate
that they should be considered as an indicator of the accuracy and precision of a given factor when used
to estimate emissions from a large number of sources, and perhaps could be used to infer error bounds
around estimates (EPA, 1985a).
The second consideration is the range of parameter values for which application of the equations is
considered appropriate. These were derived from the specific values of the parameters from the sites
studied for development of the equations. The ratings described above are only relevent for parameter
values within these ranges. Application of the equations for parameter values outside the specified range
would have a high uncertainty. The guidance given in EPA (1985a, 1988d) is to recommend they not be
used, or, in some cases, reduce the rating by a letter.
The final consideration is the appropriate selection of the dimensionless particle size multiplier, k.
This multiplier is defined according to particle size: calculated emissions are relevent for all particles that
size and less. An important consideration in the development of the k values is that the fugitive emission
process is only expected to generate emissions of particles that are as high as the highest k presented. For
example, agriculture tillage k values are as given for "total suspended particulates", while paved road k
are only defined for particle sizes less than 15 um. From an exposure standpoint, selection of k values
among the ones available can vary according to the intent of the exercise. If the objective is only to
evaluate the risk due to inhalation of "inhalable fraction" size particles, then k values corresponding to
particle sizes of 10 urn or less are appropriate. Emission estimations made with this strategy are
commonly referred to as "PM-10" (paniculate matter - 10 urn) emissions. If instead the objective is to
model total emissions, perhaps to then incorporate these emissions into air models for downwind
deposition onto soil, biota, or surface water, the highest k value presented would be appropriate.
Equation 5-7 is not an AP-42 factor equation; the only qualifier given in its development is that is
appropriate for 10 um size particles and less.
5-9
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Table 5-1. Considerations for Application of AP-42 Emission Factor Equations"
Equation/Description
Rating15
Parameter limits0
Particle Size
Multiplier4
Equation 5-1
Loading and Unloading
Equation 5-2
Truck transport6
C,D
M: .25-4.8
U: 0.6-6.7
None given
<30pm
<15um
<10pm
<5pm
<2.5 pm
TSP
0.74
0.48
0.35
0.20
0.11
jsquauon o-o
Dozer overburden
Equation 5-4
Unpaved roads
Equation 5-5
Agricultural tillage
Equation 5-8
Paved roads
JB s:
M:
A s:
Vs:
W:
nw:
A or Bf s:
3.8-15.1
2.2-16.8
4.3-20
21-64
2.7-142
4-13
1.7-88
A sL: 2-240
MVWg: 6-42
<15 pm
<10pm
<2.5 pm
<30 pm
<15 pm
<10pm
<5 pm
<2.5 pm
TSP
<30pm
<15 pm
<10pm
<5 pm
<2.5 pm
<15 pm
<10 pm
<3.5 pm
0.45
0.34
0.05
0.80
0.50
0.36
0.20
0.095
1.0
0.33
0.25
0.21
0.15
0.10
0.28
0.22
0.081
* Equations 5-6 and 5-7 are not included in this table; equation 5-6 is a complex event-oriented wind
erosion AP-42 equation - refer to EPA (1988d) for more details; equation 5-7 is not an AP-42 equation
A - best rating, E - worst rating; See Section 5.1.8. for discussion of ratings
" See appropriate sections of Section 5.1. for definition of and units of variables.
The particle size multiplier, k, is unitless; see Section 5.1.8. for discussion of k; TSP = total suspended
particulates.
e Equation 5-2 was developed for erosion from open piles and not truck transport; see Section 5.1.4. for
discussion.
f Rating is A if used to estimate total paniculate emissions, and B if used for a specific particle size.
8 MVW = mean vehicle weight, Mg (metric tons); although equation 5-8 does not have vehicle weight
in it, this was identified in EPA (1988d) as the range of vehicle weights for which the equation was
developed, and for the which the A rating is retained.
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5.2. MECHANISMS OF RELEASE: LEACHATE AND RUNOFF
The production of leachates and runoff of contaminated water at an ash disposal facility, or from
reused ash, represents the second source of release of MWC ash components into the environment.
Leachates and runoff can contaminate surrounding soils, surface waters, or groundwater, and eventually
represent a pathway of exposure to humans.
Leachates from an ash landfill or storage site can potentially enter the ground water following loss
of liner integrity. The total leachate generation from an ash landfill can be calculated as:
where:
L = 0.01 Q [Fw(Aw) + FcCA,)]
(5-9)
L =
Q =
Fw =
A —
"w ~-
•p
Ac =
leachate volume (m3/yr)
potential percolation (cm/yr)
fraction of potential percolation, Q, which results from precipitation falling on the working
(exposed) portion of the landfill
working landfill area (m2)
fraction of potential percolation, Q, which results from precipitation falling on the covered
portion of the landfill
covered landfill area (m2).
Fw and Fc have been conservatively estimated by Kellermeyer and Ziemer (1989) as being 1.0 (100% of
the potential percolation for the uncovered portion of a landfill) and 0.15 (15% of the potential percolation
for a covered landfill). Kellermeyer and Ziemer (1989) also conservatively assumed that Q (potential
percolation) was equal to annual precipitation.
While more detailed models of percolation are available (e.g., Lu et al., 1985), a screening level
estimate can be obtained by applying a water balance equation (EPA, 1985b):
where:
Q
I
P
E
Q = P + I - E
(5-10)
annual percolation (cm)
annual irrigation (cm)
annual precipitation (cm)
annual evapotranspiration (cm).
This model relies on estimates of evapotranspiration and precipitation. In their document that
describes screening techniques for determining the presence of pollutants in groundwater or surface water,
5-11
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the EPA Environmental Research Laboratory-Athens (EPA, 1985b) presents a map of the United States
with gradients of mean annual potential evapotranspiration minus precipitation.
Equation 5-8 neglects surface runoff, and/or conservatively assumes it is zero. For uncovered
portions of landfills, surface runoff can transport contaminants in exposed ash to surface water bodies.
Methods to estimate site-specific and event-oriented surface runoff are described in EPA (1985c).
Alternately, regional estimates of annual surface runoff can be obtained in the Water Atlas of the United
States (Geraghty et al., 1973). Annual totals of runoff need to be converted to volume of runoff water:
RV = 0.01 R Aw
(5-11)
where:
RV
R
runoff volume (mVyr)
annual runoff (cm/yr)
working (exposed) landfill area (m2).
5.3. MECHANISMS OF RELEASE: DRAINAGE OF MOIST ASH
Drainage can occur in the management of very moist ash. The moisture content of ash at the MWC
load-in point, the point of temporary storage after quenching where it is loaded onto trucks, was measured
at between 8 and 42%, with a median of about 25% (7 samples from 6 MWC study sites; MRI, 1990a).
Such high moisture contents can lead to drainage loss prior to loading, spillage when loading onto trucks,
leakage from trucks, and so on. For example, one facility (studied in MRI, 1990a) discharged ash directly
from the quench tank into dump trucks. Weep holes in the trucks were opened during loading to allow
drainage of excess water, which was collected and recirculated to quench tanks. While this particular
management minimizes environmental release, mismanagement or poor containment in trucks carrying
very moist ash can result in leakage along the truck's route.
Leakage of water along a truck's route can be estimated as follows:
where:
El
MC,
MQ
TT
TD
C
E,
El = 10(MQ - MC0)OT/rD)C(l-Et/100)
amount of leakage during a truck haul, L
moisture content of ash at truck loading, % by volume
moisture content of ash below which free drainage will not occur, % by volume
truck travel time, hr
total time to drain from Mq to MC0, hr
truck capacity, m3
efficiency of truck at restricting free drainage, %
(5-12)
5-12
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Such an approach to estimating leakage from trucks has never been attempted, and hence should be used
with caution.
The grain size distribution of ash as shown in Figure 3-2 implies an average grain size of 1.3 mm.
This grain size, would be classified as a "coarse sand" according to USDA soil classifications (Brady,
1984). Drainage from this type of soil is very rapid, in a matter of hours, and the higher moisture contents
that were noted at the load-in in MRI (1990a), as high as 42%, are unlikely to be representative of
.moisture contents of ash when transport to a disposal site occurs, even when the ash is moist enough so
that this mechanism of release should be considered. At the site studied by MRI (1990a), where ash was
directly discharged from the quench tank into the trucks, this mechanism of release might be considered,
but even there the truck filling and drainage from the weep holes took between 12 and 16 hours. Another
consideration is that very moist ash is very difficult to handle. It is probably not unreasonable that an MQ
of 20-30% is the highest that should be considered for this mechanism of release.
The comparison of ash grain size to that of a coarse sand provides a means to estimate MC0. The
"field capacity" of coarse sand, or moisture content at and below which free drainage is restricted, is in
the neighborhood of 5% (Brady, 1984). This is a reasonable value for MC0. The assignment of a time
to drain from MQ to MC0, TD, can be thought of as the time it would take to drain if the truck weep
holes were open, and no resistence, other than the truck bed, were offered to free drainage. The truck bed
or any impermeable surface offers resistence, however. This resistence can be understood by visualizing
the drainage that would occur if very moist ash (or very moist soil) were suspended in air by a fine wire
mesh. Selection of TD is speculative, but a value of 24 hours might not be unreasonable.
Totally open weep holes in transit implies an % of 0%, whereas an airtight truck would have 100%
efficiency. A truck reasonably airtight, but through which dripping can occur, might have an 80 or 90%
efficiency, whereas a truck with cracks allowing more than dripping might have an efficiency less than
50%.
5.4. ESTIMATING ENVIRONMENTAL CONCENTRATIONS
The preceding discussion has focused on methods used to estimate the volume of leachate or runoff
water, or the mass of fugitive ash emissions. It should be recognized that the mass release of the
contaminant of concern is a simple product of the volume of leachate or runoff, or mass of ash, containing
the contaminant and the concentration of the contaminant in the matrix of concern. The best way to
ascertain this concentration is through actual sampling of ash or leachate water as part of a site-specific
assessment. If this is not possible, however, simple assumptions must be made. It can be assumed, for
example, that the concentration of the contaminant in the leachate or runoff water is equal to
concentrations from laboratory leachate testing. Much information also exists concerning the
5-13
-------
concentrations of contaminants on ash (Section 3). It can be further assumed, as a first approximation,
that the concentration of contaminants in ash or leachate water is not affected by degradation processes.
However, it should be recognized that these assumptions are likely to result in conservative estimates of
the concentration of most contaminants in ash or leachate water. Likewise, the ultimate fate of the
contaminant includes chemical and physical transformations, dilution, and other processes reducing the
concentrations estimated at the point of release.
5.5. MECHANISMS OF RELEASE: INTERMEDIA TRANSPORT
Intermedia transfers refer to the ability of some substances to transfer from one environmental
medium to another. Some common intermedia transfer processes have already been discussed. For
example, fugitive dust generation from ash waste piles transfers dust from the ground to the air. Leachate
generation and surface runoff may result in transfers of ash constituents from the soil to surface water or
groundwater. An additional mechanism by which intermedia transfer can occur is through the uptake by
biota of ash contaminants in air, water, soil, or other biota through direct contact, ingestion, or inhalation
pathways. These processes are demonstrated in greater detail in Figures 5-1 to 5-4.
Intermedia transfer mechanisms are an important factor to consider when estimating media specific
contaminant concentrations. The intermedia transport parameters that may be of concern when performing
an exposure assessment for MWC residuals include:
resuspension of dust into the atmosphere;
• dust deposition into aquatic receptors, on soil, or on plants;
• leaching of contaminants from the soil or disposal site to groundwater, or transport to
surface water bodies; and
• uptake of ash components by flora, aquatic biota, wildlife, or livestock followed by
bioaccumulation or bioconcentration.
As noted in the above list, particularly in the last bullet, an endpoint of concern is "biota" that can
be ingested by humans. This endpoint is also noted in Figures 5-1 to 5-4 in the branches titled, "Go-to
biota fate/food chain analysis". Most multi-media exposure assessments estimate contaminant
concentrations in biota as a simple product of two factors: the concentration of the contaminant in the
media in contact with the biota and an empirical factor such as a "bioconcentration factor." Alternately,
there are complex food chain models (e.g., for fish), deposition models, and plant uptake models.
Methodologies for estimating biota concentrations appropriate for the screening level approach of this
document are given in EPA (1990b).
5-14
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8905.207/91052.3
Figure 5-1 Atmospheric Fate Analysis for MWC Ash Exposure
Select appropriate atmospheric
dispersion and deposition
model (Chapter 6)
Implement atmospheric
dispersion and deposition
model
Do
contaminants
reach surface
waterbodies?
Do
contaminants reach
soil?
Do contaminants
reach agricultural/hunting/
fishing areas?
Go to exposed
population assessment
Probable data requirements:
Direction and distance of .particulate
movement. Wind currents, speed,
particle size distribution.
J
f Go to surface water fate analysis
Go to soil fate analysis
J
YGo to biota fate/food chain analysis J
5-15
-------
8905.207/91052.1
Figure 5-2 Surface Water Fate Analysis for MWC Ash Exposure
Select appropriate
surface water fate
and transport model
(Chapter 6)
Implement surface water fate
and transport model
N
Is the contaminant
volatile?
Is the
contaminated water
used to irrigate, livestock, or
does it support commercial^
sport fisheries?
Probable data needs:
contaminant input rates,
hydrogeology of water
body, contaminant sorption
and dissipation parameters
Go to atmospheric fate analysis
Go to biota fate/food chain analysis
c
Go to exposed
population assessment
5-16
-------
8905.207/91052.2
Figure 5-3 Soils Fate Analysis for MWC Ash Exposure
Determine concentration
of ash and ash components
in soil
c
Go to exposed
population assessment
Does the
contaminated soil support
edible species?
Are
contaminants volatile
or sorbed to fine
articulates
Do contaminants
reach groundwater?
(GO to biota fate/food chain analysi^
C Go to atmospheric fate analysis
Y f Go to ground water
"" analysis
Go to surface water
fate analysis
J
5-17
-------
8905.207/91052.4
Figure 5-4 Groundwater Fate Analysis for MWC Ash Exposure
Select appropriate ground
water fate and transport model
(Chapter 6)
Implement ground water
fate and transport models
Do
contaminants reach"
surface water body via
ground water
recharge?
Is groundwater
used for
livestock or
irrigation?
Probable data needs:
contaminant input rates, aquifer
characteristics, contaminant
sorptive and dissipation parameters
Go to surface water
fate analysis
Go to biota fate/food chain analysis J
to exposed population assessment)
5-18
-------
6. EXPOSURE PATHWAY AND EXPOSED POPULATION ANALYSES
An exposure pathway and exposed population analysis consists of a quantitative and qualitative
description of exposure points, the routes of exposure at each point, and the population facing exposure
from each route. This analysis is generally implemented following the determination and description of
the potential releases of contaminants to the various environmental media.
The potential for fugitive releases of ash dust into the air can occur as a result of loading and
unloading activities, vehicular resuspensionnear storage, handling, and disposal areas, transport, spreading
and compaction, and wind erosion at a landfill. As fugitive ash enters the atmosphere, its concentration
is diluted by meteorological mixing processes. In addition, some constituents can react physically or
chemically with other airborne pollutants. Finally, the ash can be deposited on the ground by fallout or
rainout.
A number of computer models are available to: EPA for simulating the atmospheric dispersion of
MWC residues. The models vary in sophistication and in their ability to incorporate simulations of certain
processes important to determining the atmospheric fate of ash. The models recommended by EPA are
evaluated and described in two documents:
• EPA, 1988b. Air Dispersion Modeling as Applied to Hazardous Waste Incinerator
Evaluations, An Introduction for the Permit Writer. OSW, Waste Treatment
Branch
• EPA, 1986b. Guidelines on Air Quality Models. (EPA-450l2r-78-207R).
Releases of ash constituent chemicals into groundwater can follow the disposal of ash in a landfill,
deposition of ash on a land surface, or reuse of ash in concrete or road material. Leachates of ash
chemicals from MWC monofills or co-disposal facilities can enter the environment if there is no liner,
following catastrophic liner failure, or through a liner leakage extending over a long period of time.
Mismanagement of leachate collected from a landmi can potentially impact soil or-ground water.
Leachates can reach the groundwater or contaminate the soil following deposition of fugitive ash on the
ground, a process that might occur along a transport corridor, or in the vicinity of storage or uncovered
(or partially covered) disposal areas.
Leachates reaching groundwater can be diluted by mixing processes. Metals in leachates may
adsorb to sediment, or speciate into forms that exhibit differing transport or lexicological properties.
Organic compounds existing in the ash leachate are also prone to adsorption onto the soil matrix of the
aquifer, and to undergo transformation or degradation into different compounds.
6-1
-------
There exists an abundance of models for simulating groundwater contaminant transport. Selection
criteria and a summary of these models is available in:
• EPA, 1988f. Selection Criteria for Mathematical Models Used in Exposure Assessments:
Ground-Water Models. (EPA/600/8-88/075).
Surface water bodies may be contaminated by MWC ash foUowing direct deposition of fugitive
dust into a body of water, surface runoff of ash constituents (e.g., leachate), mismanagement of quench
water or collected leachate water, or influx of contaminated groundwater. As ash constituent chemicals
enter a surface water body, their concentration may be diluted by mixing processes. Furthermore, ash
particulates and constituents may be influenced by various physical, chemical, and biological processes
that take place in the particular water-body. Exposure to ash-contaminated surface waters is of concern
if the water is used recreationaUy or for household water supplies, or supports fish that are consumed.
When surface bodies of water are contaminated by ash, it may be necessary to apply an
appropriate aquatic fate and transport model in order to estimate exposure point concentrations. A number
of models are available for this purpose. Selection criteria and descriptions of surface water contaminant
transportation models can be found in:
• EPA, 1987c. Selection Criteria for Mathematical Models Used in Exposure Assessments:
Surface Water Models. (EPA/600/8-87/042).
In all of the possible situations that result in the contamination of environmental media by MWC
ash and residuals, three significant direct contributions to exposure exist. These are:
• inhalation of air contaminated by dust particles,
skin absorption through contact with contaminated soil or contaminated water while
swimming or bathing, and
ingestion of contaminated soil (as dust or garden soil, e.g.) or water, or ingestion of food
which is contaminated directly or indirectly through contact with ash components deposited
from contaminated air or water.
The analysis of exposed populations requires that environmental contamination data be linked with
population data. A quantitative analysis of exposed populations consists of an identification, enumeration,
and characterization of exposed populations. The goal of this analysis is to determine the likelihood of
human contact with the ash or ash constituents through one of the pathways outlined above. The decision
network for performing an exposed population analysis is illustrated in Figure 6-1.
6-2
-------
Guidance for performing an exposed population analysis and calculating exposure through each possible
exposure pathways is provided in a number of EPA documents:
• EPA, 1989b. Risk Assessment Guidance for Superfund. Human Health Evaluation Manual, Part A.
(9285.701A)
• EPA, 1988g. Superfund Exposure Assessment Manual. (EPA/540/1-88/001)
• EPA, 1990c. Interim Guidance for Dermal Exposure Assessment
• EPA, 1989c. Exposure Factors Handbook (EPA/600/8-89/043).
6-3
-------
8905.207/91052.6
Figure 6-1 Exposed Populations - Identification of Relevant Exposure Routes
Are persons
exposed by
inhalation?
Can contaminants
migrate to air?
Consider inhalation
exposure
Are contaminated
waters fished
commercially or
recreationally?
Can contaminants
migrate to surface
water?
Consider ingestion
exposure of fish
Is the waterbody
used recreationally?
Are contaminated
waters used as a
source of domestic
water?
Consider exposures
via dermal contact,
ingestion, and inhalation
while swimming
Consider exposure
by ingestion, dermal
contact and inhalation
while bathing
Consider exposure
by ingestion, dermal
contact and inhalation
while bathing.
Is groundwater
used as a source
of domestic
water?
Can contaminants
migrate to
ground vva'.of?
Are
contaminated
sites residential or
otherwise accessible
to the public'
Consider exposure by
contact and inhalation
and accidental or
intentional ingestion
Can
contaminants
migrate into
soils?
Are
food crops
raised on
contaminated
soils?
Consider ingestion
exposure
Can
contaminant
otherwise migrate
edicts biota? (particle
deposition, contaminated
irrigation water,
e.g.)
Consider ingestion
exposure
6-4
-------
7. DEMONSTRATION OF METHODOLOGY
The purpose of this section is to demonstrate the methodology described in this document. This
demonstration occurs in the context of a comprehensive example where all mechanisms of release are
described and key parameters quantified. The example uses two contaminants, cadium and 2,3,7,8-
tetrachlorodibenzo-p-dioxin (TCDD), to illustrate the methodologies. The selection of these two was made
in order to demonstrate the methodology on an organic and an inorganic contaminant found in ash. Also,
the related OHEA document, Methodology for Assessing Health Risks Associated with Indirect Exposure
to Combustor Emissions, used the same approach by demonstrating its methodology on cadmium and a
different organic compound, benzo(a)pyrene.
7.1. QUANTIFICATION OF RELEASE RATES OF MWC RESIDUALS
The first step in a comprehensive exposure/risk assessment is the quantification of rates at which
MWC residuals are released into environmental receptor media (air, soil, water). Knowledge of the
concentration of specific chemical contaminants in these ash releases enables the exposure assessor to
estimate release rates for these contaminants. Once deposited in the environmental media, the exposure
assessor then needs to consider further fate and transport of ash contaminants until they reach a point
where populations are exposed: in the air they breathe, water they drink, food (or soil) they ingest, and
so on.
It is important to understand that the example presented in this section is not meant to be an
exposure assessment itself, or the beginnings of an exposure assessment. It is presented for the purpose
of demonstration only. Assumptions and parameter values are justified where possible, otherwise they are
assigned "in the absence of better information." Users of this methodology are encouraged to base their
exposure assessments on data from specific sites they are evaluating, including any analysis of ash or
leachate samples to estimate site-specific contaminant concentrations.
That being said, it is also fair to say that the key scenario definitions, amount of ash generated and
contaminant concentrations, are high in comparison to industry averages. On the other hand, assumptions
and parameters in the equations estimating release rates were determined from real and reasonable sources
when possible. For example, "control efficiencies," or the parameters reducing maximum possible
emissions because of control practices associated with a release, were high if information indicated that
control practices were common. Key assumptions for this framework include:
• Ash generation: The hypothetical facility produces 1.82 x 108 kg, or 200,000 tons, ash per year.
This is less than the maximum noted in the OSW survey of 287,000 tons (EPA, 1989a), but greater than
7-1
-------
the 95th percentile tonnage generated of 137,679 tons/year (as statistically evaluated from the OSW survey
in MM, 1990a).
• Cadmium and TCDD concentrations: The concentration of cadmium and TCDD in fugitive
ash emissions is assumed to be equal to the upper-bound reported concentrations of Cd, 100 pg/g, and
TCDD, 7.8 x 10~* pg/g, in combined bottom and fly ash. The concentration in water releases is assumed
to be equal to the EP-Tox limit for Cd, 1000 pg/L, and the upper-bound reported concentration for TCDD,
2.3 x 104 pg/L, in extract from combined ash using the TCLP.
• General framework: Ash is temporarily stored at the MWC facility before it is trucked to an
industrial solid waste (ISW) landfill located 32 miles from the facility. Transport in 20 truckloads per day
is required to dispose of the ash, and this transport occurs 260 days/year (landfills are not open 365 days
per year, although ash is generated 365 days/yr). The assumption of disposal in an industrial solid waste
landfill is made for two reasons: it justifies the somewhat long trip of 32 miles (an ash monofill is likely
to be much closer to the MWC facility; travel distances have been noted as high as 700 miles (EPA,
1989a)), and the size of an ISW landfill is typically larger than an ash monofill. This impacts one key
point of release: resuspension of contaminated dust along the haul route in the vicinity of ash disposal.
Length of an ISW landfill haul route and the daily vehicle transactions are both higher for an ISW in
comparison to an ash monofill (MRI, 1990a). The total area in the landfill which contains ash is 8.25
hectares, although ash is only being disposed of on 0.25 ha at any time. The area not worked on is
assumed to be capped, which eliminates wind erosion and surface runoff, and reduces leachate losses.
When estimating fugitive ash emissions into air, the conservative assumption of 0.25% ash moisture
content is made. In estimating the potential loss in leaking from the trucks in transit, the conservative
estimate of 20% moisture content is made.
All other assumptions are detailed in their appropriate context.
The source analysis decision process for MWC residuals was described in Figure 4-1, and is repeated
in this chapter (Figures 7-1 through 7-8) to facilitate discussion of the example. Portions of this figure
are repeated as the example progresses through the decision framework. It is noted that at the beginning
of each "step", and at places within steps, a possible "No emissions will occur..." decision sends the
assessor to the next step. The methodology described in this document does not address how to determine
whether or not an emission is likely to occur. As pointed out in parts of this example, however, quite
often visual inspection of the specific site being assessed under normal conditions of operation can be
informative as to whether an emission will occur or not.
7-2
-------
8905.207/91052.73
Figure 7-1
Source Analysis for MWC Residuals Release - Step 1
v' \.
Physical and
characterization
Release rates to
.;,*-" •:••
Go to Step 2
7-3
-------
STEP 1: DO FUGITIVE EMISSIONS OCCUR WITHIN THE MWC FACILITY?
RATIONALE
Anywhere ash moves within a MWC facility, such as along hoppers and conveyors, the possibility exists
for emissions of small particulates. Dust films, on surfaces are an indication that such emissions are
occurring. Without complete combustion, volatile organics or metals, such as mercury, can also be
emitted into the air. This document has not provided guidance on quantifying potential releases within
a MWC facility. However, such releases can result in exposures to MWC workers.
NO, FUGITIVE EMISSIONS DO NOT OCCUR WITHIN THE MWC FACILITY.
Go to Step 2.
YES, FUGITIVE EMISSIONS OCCUR WITHIN THE MWC FACILITY.
The following data must be obtained:
* Physical and chemical characterization of residuals at the point of escape,
• Release rates and frequency.
Fugitive emissions of vapors or particulates wiU not only introduce these contaminants into the air, but
may also result in deposition of the compounds on surfaces. It is generally not necessary to use fate and
transport models in this step, since the releases occur at the exposure point within the facility; however,
it is necessary to identify relevant exposure routes (see Figure 6-1) and to quantify exposures.
Go to Step 2.
7-4
-------
8905.207/91052.70
Step 1
Step 2
Figure 7-2
Source Analysis for MWC Residuals Release - Step 2
Go to Step 3
Physical and
chemical
characterization
Roloaso ratos to
air
n5r^~>.^ Y ^
Ma*d3^--^ "*:
g
^—
Efficacy of
control measures
•
Physical and
characterization
Release rates to
soil/water
7-5
-------
STEP 2: IS QUENCH WATER RELEASED?
RATIONALE
A quench water system used in a MWC serves two purposes. It provides a seal to the furnace, and
quickly cools and wets the bottom (and/or mixed ash) prior to its transfer to a conveying system and then
to be either temporarily stored or transported to a disposal area. The wetting of ash tends to suppress
fugitive dust emissions. Sudden quenching also tends to alter the physical characteristics of ash: it tends
to break up large masses into smaller particles. With the subsequent increase in surface area, there is the
greater potential for desorption of contaminants from ash particles, and hence a greater potential for
leaching of various chemicals. Quench water can be treated on-site, recycled, or otherwise managed so
as not to be released to the environment. Mismanagement can result in environmental release.
NO, QUENCH WATER IS NOT RELEASED.
Go to StepS.
YES, QUENCH WATER IS RELEASED.
Step 2a: Determine the following:
• Physical and chemical characteristics of the quench water..
• Release rates and frequencies.
The mean volume of quench water generated by a facility is 3.64 xlO7 gallons per year (1.37 x 108
liters/year) (EPA, 1989a). Information is generally unavailable regarding the disposal methods for quench
water. However, one might assume that facilities that collect and/or treat leachates will also handle
quench water in a similar way. In the EPA (1988c) survey, it was found that 77.8% of the operators
implemented some means of runoff collection and treatment, while no such measures were identified in
22.2 % of the cases.
7-6
-------
l»r
*' Volume 0£ is IB place inch lhai: not aS qufeiidi w^r gesemted; is telexed to the
. Based on tlie sarvejr results noted above/it wai assumed, ttiat 25% of that
generated gets released: to tM'eimroament. - ''^ / -
The volume of quench water =1.37 x 108 L/yr x 0.25 =3.43 x K? L/yr;
Mass loadlnil 'to the environment of coiitantfutant in fhe^euarjo ft-om the release of
untreated quench water: ' ,
The coricetttration of the example cotitamiftantts ia the qaeacfe ^ateris asstiuied 'to be e<|ual to
the EP-Tox Haiti ft» Cd
3.43
L
water
1$ x JtO*
Since the environmental release of quench water-can occur into groundwater, soil, and'surface water, the
exposure assessor should choose appropriate environmental fate and transport models (Figures 5-2-'and 5-3)
and identify relevant exposure routes (Figure 6-1).
Go to Step3. ,. . .....,<•.
7-7
-------
8905.207/91052.70
Step 1
Step 2
Slap 3
Figure 7-3
Source Analysis for MWC Residuals Release - Step 3
Don
"fugitive emlufci
occur wkhln thi
MWC
l> quo
Is «sh stored
at the MWC
•he?
istonrv y
^x*^
^
Physical and
characterization
Release rules to
air
asedj^*1"-"*'
Efficacy of
control measures
Physical and
characterization
Releoui rules to .
soil/Water
Are fugitives
controlled?
Efficiency of
control measured
Physical and
chemical
characterization
Roleaso rate* to air, soil,
surface woKir. greundwater
Go to Step 4
7-8
-------
STEP 3: IS THE ASH STORED AT THE MWC SITE?
RATIONALE
Some facilities store ash on-site prior to transport to a disposal facility. These storage areas can act as
sources of runoff and of fugitive emissions.
NO, ASH IS NOT STORED AT THE MWC SITE.
Go to Step 4.
YES, ASH IS STORED AT THE MWC SITE.
On-site storage occurs at approximately 46% of MWC facilities (EPA, 1989a). An average of 380 tons
(3.5 x 10s kg) are stored at each such site.
Step 3a: Are fugitive emission control measures used at the ash storage site?
NO, FUGITIVE EMISSION CONTROL MEASURES ARE NOT USED.
Assume a control efficiency of 0%.
Go to Step 3a(i).
YES, FUGITIVE EMISSION CONTROL MEASURE ARE USED.
The OSW survey (EPA, 1989a) revealed that 77% of MWC operators that store ash on site also use dust
containment measures. The effectiveness of such measures varies. Some measures, such as wetting, may
be highly effective in suppressing fugitive dust emissions; others, such as use of recirculation/capture
systems, may be somewhat less effective. Of the operators using dust containment measures, 51.7% wet
the ash or use a combination of wetting and covered conveyors (EPA, 1989a).
'. • '7-9
-------
The efficiency of fugitive dust controls must be used when calculating release rates from the storage site.
This can be done by calculating a control efficiency index:
• * t ' ' •" '' •' ' • ; ' ~- - '- • • •. , - '.-, . - - " ,V ,
• If wetting is used all the time, and the amount of wetting is judged sufficient to suppress fugitive
emissions, assume a control efficiency of 100%. ,
* By way of example, and in the absence of other information, a-control efficiency of 40% is assumed.
Control efficiency = 0.40; [100(1-0.40) = 60 % release]
Goto3a(i). ,; .
Step 3a(i): Determine the following: •.' ,, . A ,,,
• Physical and chemical characteristics of the ash.
Possible changes in the physical and chemical character of ashes depend on the exact conditions
and duration of storage. Storage can lead to a reduction ija the moisture content of the ash, to
the formation of a surface crust, and to the cementation p£ particles into larger masses. All these
changes may affect the fugitivity and credibility of ash particles.
• Release rates and frequency.
Wind generated releases of ash from a storage site can be calculated using equation 5-7:
E = 0.036 (l-V)(Um/Ut)3F(x)
where:
E
V
Urn
Ut
F(x)
total flux of particles <10 urn (g/m2 hr)
fraction of vegetation coyer .,- ; .. •,
mean wind speed (m/s)
threshold wind speed (m/s)
a dimensionless ratio function.
The following assumptions and default values are used in this example scenario to estimate wind-generated
release rates of ash from a storage site.
7-10
-------
Assumptions for the scenario} r ,„, / " . -----^
Application of eojaation 5.7 was describelin ssctfojnu5J*6., including recommendations for
parameter valuer Those parameter values wiB. lie- used in trns'example, and they are:
----- \" ''^7 - *" ';»'" /r ,-, % ,^ - - -
" ------
Vi No vegetative cover* or V
Urn: A mean annual wind speed; of 5*0 mfc was usedl in the Discussion in section 5.L6,
' -, " -v/-'" ;/™v « / -> v " ^w ' v--- -
Ut: This was solved for as lS.Otn/s - s ^;
The unit emission Wived for by Ration 5,7 is units, of g/io55 hr,^ To cortvert to.an^armtial basis,
thefonowingassimpfionsareihader\ * "//' - . " ^ - " ^
* •• •• -^ %'•-
•.-.-. • % . •. , ::..:'
Exposed Area: Trie exposed surface area^for an *sh stoiage site at a MWC facility must be
determined on a site-specific basis. This illustration will use a conservative assumption of an ,
area- equal to 0.25 hectare; or 2500 m*. ' - -
""' " '"'
•.-., . ,
Hows; For fhii example, it will ^assumed that the ash is stored prior to loading onto trucks
- for transport to the landfill. It will be assumed that tie storage area is covered during non-
worMng hours. Since' transport occurs during 260 woik-days/yr> the number of hours per year
equals: 260 wd/yrx & hr/wd =2080 hrk ^,- %,v \ -' ;r5 "\^
Using these assumptions, one can calculate the wind generated release of ash from a storage site (E) as
follows:
E = 0.036 (l-V)(Um/Ut)3F(x)
E = 0.036 (5/13)3(0.11)
E = 2.25 x 1O4 g/m2-hr
For an area of 2500 m2 and for 2060 hours/yr, the annual emission equals: 2.25 x IO4 x 2500 x 2060 =
1158 g/yr
7-11
-------
Step 3a(ii): Apply the control efficiency factor
Determine net fugitive releases in the presence of controlling factors (E^ using the following equation:
Enet = E [l-(control efficiency/100)]
The control efficiency index in our scenario is assumed to be 0.6. Note that the storage area was assumed
to be covered during non-working hours. Therefore, this efficiency can be interpreted as the efficiency
of other measures not captured in the estimation, for example, wetting of ash in storage areas. The net
fugitive release of ash from the storage site is:
1158 g/yr x 0.6 = 695 g/yr , -.v
Mass loadings to the environment of ea<$! confeminantjn the scenario from^the release of
fugitive ash emissions at $e storage site: - "- > \, ; \ - '-' \ -'^' -^--.; \ *
•> ^ ^ s ^ % ^ ^ S ^ ' ' ^ ^ "* •• ' '
The concenttation of the*exam^le%ntam'jnah^ In this scetmr|o is assumed to b$ equal to 'the'
upper-bound reported cdncerAratiQns.bf 'OltlOD pg/g) and TCI>D' (7,8 V lO4 ug/g) Jn ^cbmbined' '
bottom and fly ash (s^eTabI^s;^rl^nAoSV"tnA\*^ ^rf/« »«li™L^KP ^ ^«4 i._. >sa \ i •. ,, v-.
Cd: : 695 g fugitive
TCDD: 695 g fugitive M ^Se^/year x 7J x^ JJg .TCDWg ash a ,5 M tCOt*
released/year^ ! •-- - ...-"-< ^*.... - - **
Go /o S/ep 36.
Step 3b: Are Leachate or Runoff Control Measures Used?
YES, LEACHATE OR RUNOFF CONTROL MEASURES ARE USED.
7-12
-------
Runoff containment measures are used by approximately 75% of MWC operators that store ash on the
premises (EPA, 1989a). These measures include drainage and release to sanitary sewers, wastewater
treatment, or storage.
The efficiency of the control measures must be included in any calculation of leachate or runoff release
into the environment. This can be accomplished by using a control efficiency factor.
• If runoff and/or leachate containment measures are used, and if it is reasonable to assume that the
measures; are effective, assume a control efficiency of 100%. -
Go to Step 3ft . : '
If it is not possible to determine if effective containment measures are used, some efficiency must be
assumed. For the sake of this example, it will be assumed that the containment efficiency equals the
frequency of use of leachate control measures, i.e. 75%.
Go to Step<3b(i). "
NO, LEACHATE 0R RUNOFF CONTROL MEASURES ARE NOT USED.
Assume a control efficiency of 0%.
Go to Step 3b(i).
Step 3b(i): Determine the following:
• Physical and chemical characteristics of the runoff or leachate.
• Leachate generation rate.
The rate of leachate or runoff water must be estimated; doing so requires an assessment of the leaching
and/or runoff potential of the soil within the storage area. If the storage area is in an area that contains
generally sandy soils, than excess water can be assumed to,percolate; if otherwise the soil is a clay soil
with poor drainage, much of the excess water will run off the storage area. For this example, it is
7-13
-------
assumed that the soil has good drainage, and therefore, equation 5-10 will be used to estimate the amount
of percolation: ,
where:
Q
I
P
E
= annual percolation (cm)
= annual irrigation (cm)
= annual precipitation (cm)
= annual evapotranspiration (cm)
Assumption for the scenario: s--^ N^M-^ *.- ,~V~ •-•---" \ " ..... ,, ,,
• •• ; ,.>?t **>s^ ^; :- - : - ; s" - ',t
•X 3 ^s s S5 i JJ. -.•• "• •"•• """ -. vX •> i •.** ~"
Irrigation: Irrigation will not be considered *tb exist: at the landfill'site, therefore I will be set at
O1* *' -X% •* v!* \ ,, ^ i. •» ^ v y.f "'',;; f . J
. -•• ^ •.,•• - -••••; s ••••••%•. v K*'" '••.5 •• <
•. '^V •)• iv.\ --\ » \v • •. M,,~,,,,, - y- ' •> ' '••••••' ••
s •
, -. ^
Precipitation w&'Bvwtiiaxjj^ gradients of
mean annual potential evapotranspiraaor^mirius'precipitatton. These values range from +70
inches in the desert regions of the scJuja^etfto s50? inches in fiie Pacific Northwest, A value
similar to those found on^the msrCoas^wiFbVosed: i,e< -2»0 mches » -50,8 om
The total leachate generated from the storage area can then be calculated from equation 5-9:
where:
L
Q
Fw
**Vf
Fc
L = 0.01 Q [Fw(Aw) + Fc(Ac)]
leachate volume (m3/yr)
potential percolation (cm/yr) '
fraction of potential percolation, Q, which results from precipitation falling on the working
(exposed) portion of the landfill
working landfill area (m2)
fraction of potential percolation, Q, which results from precipitation falling on the covered
portion of the landfill
covered landfill area (m2).
7-14
-------
Assumption for the scenario^,, ... ; , ^ -,•.•- "";,,"'
Percolation: The value for mean anmial potential evapotransplration. minus palpitation, from
equation 5 JO, will te used;'50<8 on/year. v s ~* * , ' ' „ -
•- %""" "" v "* % •" v sv* " *" ^
Exposed Area* In this s&iple example, the storage area is «Uh& entirely covered or entirely ^
bare Themfbi«, as a sarmgafc for exposed aieat we can multiply the total area toy fiie fraction
of time it fe exposed, or 2500 x <2QoW{365 x 24)), or 588 ra* , \ ^ - ^ ^ -
' C«ver0d Landfill Area; IMs 1§ then equal to the tafei atea aain^s the, sui*ogaU above for
exposed area: 2500 -588 * 1912 m2. r,l, ^ " ~- \; % ,
Working Area Per^Iation; Similar to KeBeTOeyer and 2iemer, 198^, the conservative
^assumptiofi of 1.0 i$ assumed., , , ,„ -,"" ~i , i """ - "
- -/' " ' *"* - , , ^ " v- ^ - , : <
Exposed Area Percolation: The cover cannot be assumed to be 100% effective, or Fc =vQ<&
Some leakage ihrough a canvas tarpaulin, if that were used as a cover, or Sideways .water ;,
Intrusion is to be expected.. Similar to Kellermeyerand 2iemer, 1989, a value of 0.15 is
assumed for Fc ,,,-•.-•- r ^ %'^ ,-- , ^ \"V,,"-vs'- ",-~ -- 5"^-\,,-
Calculation of leachate generation:
L = 0.01 Q [FwCAJ + FcCA,)]
L = 0.01 (50.8 cm/yr)[ 1.0(588 m2) + 0.15(1912 m2)]
L = 444 m3 per year or 4.44 x 10s liters/year.
Step 3b(ii): Apply the containment control efficiency factor to the release rate to determine net
The assumption was earlier made that the containment is 75% efficient. Therefore, 25% is assumed to
be available for release. The net volume of leachate produced at this site (L^), can be calculated by:
Lnct = 0.25 (L) = 0.25 x 4.44 x 10s liters/year = 1.11 x 10s liters/year.
7-15
-------
Mass loadings into the environment of contaminants in the scgn^rio'from teaehate release
at the storage site: " , < -^;^*";, „ >\ .'"s£^* *"""'"* "*', "•" ;,\^
The concentration of the example contaminants in the leachafcls assumed to be"equal to< the EP-
Tox limit for Cd (1000 ug/L) and the upper-bound reported concentration 'fat TC0D irt extract
from combined ash using the TCLP (2,3 je Itr4 pgyl,). " * ' ' '-T",, -',_ /% _
Cd: l.ll x 10* L of leachate;released/year x 1000 ug/L^olIeaehate = L1I xKb» ]
TCDD: til x 10s L of leachate released/yea* x 2,3 x 104 pg fCDt)/t ofleachate *
The environmental release of this leachate is into the soil or groundwater, which can migrate to surface
water. The exposure assessor should choose the appropriate environmental fate and transport models
(Figures 5-2 and 5-3), and identify relevant exposure routes (Figure 6-1)
Go to Step 3c.
Step 3c: Are emissions from vehicular resuspension controlled?
YES, CONTROL MEASURES TO SUPPRESS VEHICULAR RESUSPENSION ARE USED.
Measures to remove or contain ash residues which have been deposited on roadways near storage areas
include vacuuming, sweeping, wetting, and chemical dust suppression. Use of any of these measures will
provide some protection against vehicular resuspension of contaminated dust particles from roadways.
In many facilities, storage areas are located near quench pits and within partially enclosed housing, with
openings to allow for trucks to load and transport the ash. This housing, in combination with dust
containment measures, is likely to provide the optimum protection.
The efficiency of dust containment or suppression measures must be included in any calculation of dust
resuspension by vehicular traffic on roadways near storage piles. This can be accomplished by using a
control efficiency factor.
7-16
-------
It should be noted that, even when storage does not occur at an MWC facility, roadways near where ash
exits the quench tank and in fact, anywhere along the route of the trucks carrying ash to a disposal site,
can become contaminated with ash residues. For this example, dust resuspension by vehicular traffic over
roadways is calculated near storage areas, and near disposal areas because this is likely where the release
will be highest and of most concern, if it does occur.
• If containment and/or suppression measures are used, and these can be evaluated as fully effective,
assume a control efficiency of 100%.
Go to Step 4.
If it is not possible to evaluate the effectiveness of dust resuspension or containment measures, then some
estimate of containment efficiency must be assumed. In the absence of specific information on efficiency
of different measures, a control efficiency of 25% will be used in this example.
Go to step 3c(i).
NO, DUST CONTAINMENT OR SUPPRESSION MEASURES WHICH WOULD REDUCE
VEHICULAR RESUSPENSION ARE NOT USED.
• Assume a control efficiency of 0%.
Go to Step 3c(i).
7-17
-------
Step 3c(i): Determine the following:
• Length of impacted roadway.
• Vehicle passes per day.
The length of impacted roadway times the vehicles passes per day equals the vehicle kilometers
travelled per day.
• Proportion of impacted roadway that is paved.
Significantly more dust would be suspended if the roadway were unpaved. Unpaved roadways in
MWC facilities are uncommon (MRI, 1990a) and are not assumed here.
The rate of dust resuspension due to vehicular traffic on paved roads near storage piles can be determined
by applying equation 5-8 (EPA, 1985a):
where:
Ep
sL
Ep = 220(sL/12)':
emission factor from paved surfaces (kg/VKt) (vehicle kilometer traveled)
mass of silt-sized material per unit of paved road material (g/m2)
Assumptions for the scenario: -,,,"'-'
Length of impacted roadway: MRI Cl§90a} evaluated six MWC facilities for this mechanism
of ash release. The haul roads for these facilities, ranged in length from 100 to 400 meters, with
an average of 238 meters., They determined that 25% of the haul length was commonlylravelled
by trucks transporting ash arid other veniclesV" What Is likely to be equally, if not more,
important than commonly traveled roadway^ is the length of roadway in the vicinity of Storage
pile that is Impacted by fugitive emissions^from the pilef Lacking specific information.^'the$ame
25% of roadway, or 60 meters; wjlfbe assumed for the length of impacted roadway.
Vehicles per days MRI (1990a> determined, witfi actual counts of ysWeS passes in ihefr W
facilities and other experience, that between 100 and 1000 vehicle palses per day occur over haul
routes at MWC facilities, with the higher estimate for large capacity facilities. Since the facility
in this example is a large capacity facility, the upper estimate of 1000 vehicle passes per day is
assumed. . ",,_,,.,,' -- x , ,- - ; ,.,, *- -/ ; ;„,,„
Silt loading: MRI (1990a) took 17 samples of roadway dust at their six'faciMes. The median
SL, 2.5 g/m2, is assumed for this example.'" '- s """ - -
7-18
-------
Using these assumptions, one can calculate the unit resuspension of dust due to vehicular traffic as
follows:
Ep = 220(sL/12)'3
Ep = 220(2.5/12)'3
Ep = 137.42 kg/VKt
Step 3c(ii): Apply the control efficiency factor
Determine net dust resuspension in the presence of controlling factors (Enet) using the following equation:
Enet = Ep[l-(control efficiency/100)]
Since the control efficiency in this example is assumed to be 25%, the net dust resuspension per vehicle
kilometer traveled is: 137.42 x 0.75 = 103.07 kg/VKt. The total annual dust resuspension is:
103.07 kg/VKt x 1000 g/kg x (.06 x 1000) VKtfd x 365 d/yr = 2.26 x 109 g.
7-19
-------
v^ •'•• • - '
Mass loadings to the environment of ;^el "eoiif aiidn|nt in the &~' <'"'•:'' '* vs C*-^; 5} ^ ' 'vvy«^
As noted in Chapter 5, $*&($$$ f^oA && ?^laway pa«ic«i8ie$ wSl'be 1?$$ ffiatt the ^ " ^
concentration on ash Itself oecau&e of miking with clean dast pa«lele$t ^ MR1 (l^Oa) took
samples of ash as well as roadway particuIafes^M &eir sis sites and meastired to'tfifor cadmium
(and other metals), but not TODE^ concentrations, The ratio of concentratlops (dw$f *
concentratiott/ash concentration) %$$& between 0,ranil^ but, the sjediw mib> was 0^5, '<
This ratio will be applied ^^^^J^^3p^ (In die absence of
Cd
cone/ash cone = 6.l7x
Go to Step 4.
7-20
-------
890S.a07/91052.7d
Step 1
Figure 7-4
Source Analysis for MWC Residuals Release - Step 4
isstons^ Y ^
£>x^ • • •• •
Physical and
characterization
,
Release rates to
air •
TCh*'^^^ Y, ^
QSHtft^^ ™
" -. '• ' '
^
Efficacy of
control measures .
Physical and
characterization
— . ^
Release rates to ,
soil/water
Releasa ratos to air, soil,
surface water, groundwater
Go to Step 5
7-21
-------
STEP 4: IS THE ASH DROPPED INTO TRUCKS?
RATIONALE
According to the OSW survey (EPA, 1989a), ash is transported in the U.S. solely by trucks from MSW
incinerators to disposal sites. Ash may be loaded directed onto trucks at the MWC facility using a
conveyor dropping ash into a truck, or equipment may be employed to move the ash from on-site storage
sites to the trucks. .,,-..'
NO, ASH IS NOT DROPPED INTO TRUCKS.
Go to Step 5.
YES, ASH IS DROPPED INTO TRUCKS.
Step 4a: Are fugitive emissions controlled?
Fugitive emissions may be controlled by wetting the ash or by enclosing the conveyor and hopper system.
Purposefully wetting the ash for control of emissions may not be necessary if the trucks are loaded very
shortly after exiting the quench tank. In that case, the ash is likely to wet enough so that fugitive
emissions into air are unlikely. Alternately, wetting may be performed intentionaUy prior to transporting
ash, if ash has been stored on-site. . ,.. .,
YES, FUGITIVE EMISSIONS ARE CONTROLLED.
• If ash is sufficiently wetted prior to dropping into truck, assume 100% control of fugitive emissions
Go to Step 5.
7-22
-------
• If control measures other than wetting are used, or if ash is incompletely wetted, assume a lower level
of .control. Lacking, such data, this scenario Will use a level equal to 75% control.
NO, FUGITIVE EMISSIONS ARE NOT CONTROLLED.
Go to Step 4a(i).
Step 4a(i): Determine the following:
• Physical and chemical characteristics of the residuals
• Release rates and frequency.
Fugitive release rates can be estimated using equation 5-1:
where:
Elu
k
U
M
Elu = k(0.0016)(U/2.2)1'3(M/2)-1-'
emission factor for loading and unloading(kg fugitive dust/Mg ash)
particle size multiplier (dimensionless)
wind speed (m/s)
material moisture content (%)
Assumptions for the scenario: ;
Particle size multiplier, total emissions w&t be estimated. Therefore, the maximum k value, ^
for parUde diameters <30 um, 0,74A wiir be
Wind speeds The application of this equation Is limited to situations wheref the wind speeds
range between 0.6-&7 m/s, In step 1, {he wind speed was assumed to be 5X> m& for calculation
of wind erosion. That same wind speed vM be used here* : \\
Moisture Content. The^appfieaticsn of this equation is limited to materials with a moisture
content ranges between 0,25-4.8%. The example scenario win use a conservative estimate of
0.25 %, ^ ^~ '
7-23
-------
Using these assumptions, the fugitive release rates for ash loaded onto trucks is:
Elu = k(0.0016)(U/2.2)K3(M/2)-1'4
Elu = .74(0.0016)(5/2.2)1'3(.25/2)-1-4
Elu = 6.32 x Iff2 kg/Mg ash dropped.
If fugitive emission control measures are applied, then E^ is calculated by:
= Elu(l- [control efficiency/100])
6.32 x Iff2 kg/Mg (0.25) = 1.6 x 10'2 kg/Mg load.
Finally, total annual emissions from loading prior to transport equals:
1.6 x Iff2 kg/Mg x 1.82 x 10s Mg/yr = 2.91 x 103 kg/yr, or 2.91 x 106 g/yr
Mass loadings to the environment of each contaminant In the scenario from^the'release of
fugitive ash emissions from loading ash onto trucks at the storage site:
The concentration of the example contaminants in this scenario iVassumed to be apa! to'trie
upper-bound reported concentrations o'f Cd (100 jig/g) and TCDDK7.8 'x 10"* jiig/gj in combiiied
bottom and fly ash (see Tables 3,1 and 3.3!). "N ,,,'--
Cd: 2,91 x 10* g fugitive ash released/yr x 100 ug Cd/g ash flH x 10* pg C<
released/yr* ^ . ^ ^ir*,f.,.^. , ^ ...,„,,,„ --^ ^*'^,-.* ,, s,v
- , „ , .. ..
TCDD: 2.91 x tO6 g ftigidve kh reteased/yr x 7.8 x itf jig TCWg ash * 237 'jTl
* ss ss :ss : :
TCDD refeased/yr. .
Since environmental release occurs into air and onto soil and surface water, the exposure assessor should
choose appropriate environmental fate and transport models (Figures 5-2 and 5-3), and identify relevant
exposure routes (Figure 6-1).
Go to Step 5.
7-24
-------
Figure 7-5
Source Analysis for MWC Residuals Release - Step 5
8905.207/91052.79
Step 1
Step 2
Step 3
ugWv» •misslonKv Y _ Physical and ^
Uft/£ jr characterization
^
**\$ quencn*"^*^ Y Efficacy of ^ chemical ^
.water reloasedZ^* *~ contlDl measures characterization
Release rates to
air
Release
soll/w
T.
atesto
ater
Release rates to air, soil,
surface water, groundwater
Physical and
chemical
characterization
Go to Step 6
7-25
-------
STEP 5: IS ASH TRANSPORTED TO A DISPOSAL SITE ?
RATIONALE
Based on the results of the OSW survey (EPA, 1989a), it is assumed that ash is transported exclusively
by trucks from the MWC facility to the various disposal sites. Distances for such transport can be as long
as 700 miles. Two types of releases can occur, depending on whether the ash is very moist or very dry.
Fugitive dust emissions can occur during transport if the ash is dry, and leaking of excess moistiire can
occur if the ash is very moist. Both possibilities are examined in this section, although obviously both
possibilities cannot exist simultaneously. "
NO, ASH IS NOT TRANSPORTED TO A DISPOSAL SITE.
Go to Step 6. , .
YES, ASH IS TRANSPORTED TO A DISPOSAL SITE.
Step 5a: Are either of the two possible releases of concern: high moisture content such that
leakage from the trucks is possible, or low moisture content such that fugitive emissions are
possible?
As indicated in Section 5., wind erosion, which was the surrogate process used to estimate fugitive
emissions from trucks in transit, is a function of both moisture content arid wind speed. At higher wind
speeds, which can be expected for trucks, wind erosion can occur at higher ash moisture content. It might
be surmised that wetting alone will not provide 100% protection for wind erosion, and the 'key for
determining whether fugitive emissions from trucks is likely is in the use and effectiveness of truck
coverings. The possibility that leakage from trucks will 'occur is best ascertained by visual inspection just
before the truck begins transporting the ash.
With certainty, neither fugitive emissions or truck leakage will occur in transport of ash to a
disposal site.
7-26
-------
Go to Step 6.
Fugitive emissions should be considered.
Go to Step 5a.
Truck leakage should be considered.
Go to Step 5b.
Step 5a: Do trucks use dust control measures?
The majority of MWC operators (92%) responding to the OSW survey (EPA, 1989a) reported precautions
to avoid fugitive dust releases during transportation. These precautions include covering the truck and/or
wetting the ash.
NO, TRUCKS DO NOT USE DUST CONTROL MEASURES.
Go to Step 5a(i).
YES, TRUCKS USE DUST CONTROL MEASURES.
Although trucks use dust control measures, these measures may not be totally effective. Therefore, one
should first estimate the efficiency of the control measures. If ash is covered or wetted, and it can be
evaluated that such measures are fully effective, then assume 100% control efficiency. If no such data
are available, then something must be assumed. Given that the frequency of use of such measures was
high according to the OSW survey, 92%, it seems reasonable to also assume a high efficiency in the
absence of information. In this example, a 90% efficiency will be used.
Go to Step 5a(i). ,
7-27
-------
Step 5a(i): Determine the foUowing:
* Physical and chemical characteristics of the residuals
• Release rates and frequency.
Assuming some release of ash does occur during transport, the release rates can be calculated using
equation 5-2:
Ewx = 1.9 (s/1.5) [(365-P)/235](f/15)
where:
Ewt = total suspended paniculate emission factor (kg/day/hectare)
s = silt content (%)
P = number of days per year with more than 0.25 mm of rain
f = percent of time that wind speed is greater than 5.4 m/s (assumed to be 100 when the truck
travels at a velocity > 12 mph)
Assumptions for the scenario* ~ _ "«^s, N ^ l-^v_ - — i,,.-, '^^^•^^^^^^'^'^T^
Silt content: A number of studies have provided values for thTsilt content of; mixed MWC ash*
These values range from 6.7%^(Forrester, T,<%8> to 18.2% (Wells et aij 1988). Based onlae
scenarios developed fay Wells et & (J.988^ a conservative estimate of i9% $t eonteoi; is used, *
Precipitation: EPA (I988d) presents Vriia^ of the United States showinglhe number of days
with more than 0.25 mm (0.01 mcty o! rain.- Regional values range irom; I - -'',-* -*-""
150 to 170 days for the Northeast -""4" v V ' ' I „ ~' f' """"
110 to 120 da^s for thes South. East ^x ' - , -,', »^ -, ,\
70to 110 days for the Mdand South West ," ,^^, I,,""'"- •' /v"
40 to 30 days for tlie'^otithew. "West Coast """ " '-^
90 to 150 days for iheNoBieWWest Coast/ " '',' ^ ,!,//!'^'
«^ - "I •• ^ •• ••' * ? " " 'v''"'^ v\''^s '
A value of 121 days will be applied.to thV example scenario (i.&<, 365/3). $ipc<| most of the
MWC facilities in the U.S. are fa tfie Northeasj:, Southeast, and Pacific Nortto£s& this seems to
be a reasonable estimate for otur scenario. ^ •"• x~- X-. \ v % "• *" *" **
Wind speeds: The trucks will be assumed to travel faster than 12 mph for the complete distance
from the MWC facility to the disposal site. 1, \ " • ' - '"'" • • " •
Using these assumptions, the release rate of ash during transit can be calculated by:
7-28
-------
j = 1.9 (s/1.5)[(365-P)/235](f/15)
j = 1.9 (19/1.5)[(365-121)/235](100/15)
j = 166.6 kg/day/ha.
Then, apply the emission control factor estimated for this scenario (1 - 0.9 = 0.1) to the emission rate to
obtain the net emission rate
Enet = EWj x 0.1 = 166.5 kg/day/ha x 0.1 = 16.7 kg/day/ha.
This is equivalent to an hourly emission rate of .07 g/hr/m2.
Assumption tar the scenario
-.-.-. >JJ«rt -. _^
» The approximate (futatipn <>f a £rip & 2 hours, assuming a jnean distance ol 32 miles (51,2
km) atid,M average track;velocity of 25 km/ht, ^||^,—,
N \%®. ^ ^y;, ,- , 5--,;, v
s ~ The hypbtitetlcal^acaity pro|tac€!s L82 x 108 kg of a^f rjet year (200^000 tons/year, 5 x^S?- - ^
*• icW/tavV and n^s^ds trt dlsiirtse of^thexsanie-volusie ihai is produ<2^\, *" v " -^'
Kg/day), and needs to
, » The average densltf of mixe^ ash can vary Mm 55 tov80 Ib/ft a (Wells et^ 19^88) or 893 to
* 1301) kg/m3* A,value of^894 kg/m3 will b& «sed for t(e scenario^;; "K ^ ^" - ;
The ^verage;vblutr|e of a truck ttansportln^ suf,4G si3; with a sprface area of 40 ma: Witti flus
trucjfc can,,ha«! S5760kgof ^a^i per '
V s » ".. -.-.•.•. «vj ' " ' ~ ••••'' *'••
• In the example facility^ hauling occurs 260 day&per yearL Therefor it is ti0ces$ary to load.
20 truckloads orash per day «L82 x 10s fcg/yr)/<260d/yrx 35760 kg/load}). \:
Using these assumptions and the estimated hourly ash emission rate, the total emission of ash for such a
trip is: , >
07 g/hr/m2 x 40 m2/truck x 2 hr/trip x 20 trip/day x 260 workday/yr = 2.91 x 10* g/yr.
7-29
-------
Mass loadings to the environment of each contarninant in the scenario from tRi$ release o|,
fugitive ash emissions from trucks enroute to the disposal '
• • X''
The concentration of the example contaminants minis sc^narjQJs assumed to be equal to tie
upper-bouod reported concentrations olCd (10Q ug/g) *id TC£>E> <7,8 x W* ug/g) k combined
bottom and fly ash (see Tables 3-\
-------
Assuming some truck leakage does occur during transport, the release rates can be calculated using
equation 5-10:
El = 10(MC, - MC0)(TT/TD)C(1-E/100)
where:
El = amount of leakage during a truck haul, L
MQ = moisture content of ash at truck loading, % by volume
MC0 = moisture content of ash below which free drainage will not occur, % by volume
TT - truck travel time, hr
TD = total time to drain from MQ to MC0, hr
C = truck capacity, m3
Et = efficiency of truck at restricting free drainage, %
Assumption for the scenario; - ^ ,
Moisture content at transport: As discussed In Chapter 5, the^molsture content of ash shortly
after exiting the quench tank, can be very high, over 40%, however, transport would, most IwMy
not begin with moisture contents this high; some drainage will be allowed to occur through weep
holes, or drainage occurs during storage. For this example, 20% moisture content .will be
assumed* " " """"' ,% ' „
Moisture content when no Drainage will occurs Also as discussed in Section 5, a value of 5%
reasonable for-tihis parameter. """"""" , „ - - - -
-, ..... ,'V"*~ v v «
Truck travel time; As noted earlier, the assumed travel time Is 2 hours;
, , ,T^^ -
Total time to drainage: A value of 24 hours was suggested in Chapter 5.
Truck capacity: The track capacity for this example is 40 nr\
Truck efficiency: Since the weep holes will be closed, it will be assumed that the truck is 75% v
efficient in restricting free drainage^
Using these assumptions, the amount of water leakage that would occur per trip to the disposal site is:
El = 10CMC, - MC0)(TT/TD)C(1-E/100)
El = 10(20 - 5)(2/24)40( 1-75/100)
El= 125 L
7-31
-------
Using this value, and multiplying by 20 trips/day and 260 days/year, leads to an annual release of 6.5 x
Mass loadings to the environment of each contaminant in the scenario from the leakage
from trucks during transport to disposal
«» « TO « *, 1 s ••••••. •.-.•.•.
The concentration of the example coMamtaants in the leakage is assumed to be equal i» the EP™'
Tox limit for Cd (1000 pg/L) and upper-bound reported concentration for TCDD in extract from
combined ash using the TCUP; &3 x
"
Cd: 6,5 x 10s L of leakagc^year x 1000 pg Cd/L of leakage » 6.5 x 10& ug/year
ssN ,, ••••^ •.-.
TCDD: 6.5 x 1C5 L of leakage/year x &3 x 104 pg tCDW^ W leakage * 149,5 ig
The environmental release of the leakage occurs along the travel route, and can end up in storm sewers,
road shoulders, otherwise transported by other cars via sorption to their tires, and so on. Determining the
ultimate fate of such leakage needs to site-specific, and would likely involve some creativity on the part
of the exposure assessor.
Go to Step 6.
7-32
-------
8905.207/91052.7)
Step 1
Step 2
Step 3
Step 4
Step 6
Figure 7-6
Source Analysis for MWC Residuals Release - Step 6
>w
sslon^v Y
;/
Physical and
chemical
characterization
Release rates to
air
^ST--^ Y
ased^**"*"" "
.4
EHIcacy of
control measures
Physical and
characterization
»
Release rates to
sollAwater
Release rates to air, soil,
surface water, groundwater
Physical and
chemical
characterization
Efficiency of
restricting free drainage
Load size, exposed
surface area
Physical and
chemical
characterization
Release rates to
air
Go to Step 7
7-33
-------
STEP 6: IS THE ASH SPREAD AT THE DISPOSAL SITE AND DOES VEHICULAR
TRAFFIC OCCUR OVER PREVIOUSLY SPREAD ASH?
RATIONALE
At a landfill, dumping and spreading activities, and vehicular traffic over previously spread ash (e.g.,
during compaction), can result in fugitive emissions. The frequency of use of these operations has not
been documented.
NO, THE ASH IN NOT SPREAD.
Go to Step 7.
YES, THE ASH IS SPREAD.
Go to Step 6a.
Step 6a: Emissions from Unloading.
Fugitive release rates can be estimated using equation 5-1:
\-lA
where:
Elu
k
U
M
Elu = k(0.0016)(U/2.2)L3(M/2)
emission factor for loading and unloading (kg fugitive dust/Mg ash)
particle size multiplier (dimensionless)
wind speed (m/s)
material moisture content (%)
7-34
-------
Assumptions for the scenario;
Particle size multiplier. Total emissions will be estimated. Therefore* the maximum fc value ,
provided in EPA (1988d), for particle diameters < 30 pu, win be used; fc = 0 J4, - ^
Wind speed. The application of this equation is limited to situation where thes wind speeds
range between 0,6-6.7 m/s. In step 1, the wind speed was assamed to be 5.0 ta/s for calculatipn
of wind erosion* That same wind speedl will be used here, -•,,, "" - •
Moisture Content. ..The application of this equation Is limited to materials wltii a moisture
content ranges between-0.25-4.8%. The example scenario wilTuse a conservative estimate of
0.25 %k ^ , , ». „
Using these assumptions, the fugitive release rates for ash loaded onto trucks is:
Elu = k(0.0016)(U/2.2)1'3(M/2)-1'4
Elu = .74(0.0016X5/2.2)ll3(.25/2)-M ' ' ;' " ( ' '
Elu = 6.32 x 10'2 kg/Mg ash unloaded.
Next, determine net emissions if wetting or other fugitive controls are used. For this example, it will be
assumed that the ash is unloaded at the landfill site with no control measures to reducefugitive emissions:
6.32 x la2 kg/MG ash unloaded x 1.82 x 10s MG ash unloaded/yr x 1000 g/kg = 1.15 x 107 g/year.
Mass loadings to the environment of each contaminant in the scenario from the release of
fugitive ash emissions from unloading operations at the disposal site:
The concentration of the example contaminants la this scenario is assumed to be equal to the0
; upper-bound reported concentrations of Cd (100 pg/g>and TCDD 0,8 * 10^ ug/g} w combined
bottom and fly ash' (see Tables 3-1 and 3-3^ ^,, ^ ,, r -s
Cd; L15 x 10T g fugitive ash released/year x 100 jig Cd/g ash =\J5 x 10* «g Cd
released/year _ " '' „ ' ^ -\ , "
TCDDi 1.15 x 10T g fugitive ash released/year x 7.8 x W* us TCD0/S ash = B,97 x 10s ug %
TCDD released/year, " ' ;~* -- ^ ' ^
7-35
-------
Go to Step 6b or 6c as necessary.
Step 6b: If the ash is spread after unloading, determine the emissions from spreading operations.
The emission rate for fugitive dust released from spreading operations can be calculated by using equation
5-5: . - ' •.-..- ......
,0.6
where:
Eat
k
s
Eat = k(5.38)(s)'
emission factor for agricultural tillage (kg/ha)
particle size multiplier (dimensionless)
silt content (%)
Assumptions for the scenariof „„,,,," ;-,,,,
Particle size multipUer. Total emissions will be estimated. Therefore, the raaBmim Rvalue
provided in EPA (I988d), for particle diameters < 30 ur*^ will be used: k «? 0.3&
Silt content: A number of workers Mvg provided values for the silt content of mixed MWC
ash. These values range &om6J% ^Forrester, 1988)40 i%$%; (V^ells et al, 39&£)< Based oa
the scenarios developed by.Wel3Sssetsat.tl988), a
-------
» Spreader velocity is 12 tevtor (3.2 x 10 rm/1if). ^N
* Spreader width is 5 nt* , : '* % ~ _ \1
,F Spreader woifcs for 8 hr per aay.
Since ash is spread at a rate of:
(lha/104 m2)(3.2 x 103 m/hr)(5 m)= 1.6 ha/hr,
then the emission factor, in units of kg/hr, can be calculated by:
Eat (kg/hr) = (Eat kg/ha)(spreading rate)
Eat (kg/hr) = 10.4 kg/ha x 1.6 ha/hr
Eat =16.6 kg/hr.
Therefore, assuming an 8 hour workday, the total emissions are:
16.6 kg/hr x 8 hours/day x 260 workdays/yr x 1000 g/kg = 3.45 x 107 g/year
This value likely overestimates of the emissions, since the formula does not consider the moisture content
of the ash that is being spread. This would be less true for this example, however, since the ash is
assumed to have a very low moisture content of 0.25 %.
7-37
-------
Mass loadings to the ^h$iMtie&at each eoiiafolki&t Ift th^,«;eiiai-io,firoit< t«f relive of
fugitive ash emissions fr0M spreading the ash at:the disposal sltet
: .*c * x%« \«V"-s "Xs;"4 », J^:x^v\ :"^^--v v^ \lxx^\^ ' -' , ",,
The concentration or the example eontammants m ^^ksenano'is^ssuinlci'tp be equal 1» the upper-
bound reported coiiteetJtt'atiori^oi'.OiJ (100 jjgYg) " —
and fly ash (see Tables 3-1 "*^^*
Cd: MS K
TCDD
x
i: $.45 x 10? g^gltftC^^Me^&a^ear f 7,S x KTt.pg TCDD/g ash. » 2.69 x 10* }
TCDD released/ye^r; vf|V{ , ""- Jr^-\xv-v ' ^s " " a , , ',-, '" ' ".,. '
- -^c ^^ :-^~3§8x -- . -;l" '*;""•', " -' ",»"
Step 6c: If vehicles traverse over spread ash, as in compacting activities, determine the
emissions that result from vehicular traffic over the spread ash.
The magnitude of fugitive emissions occurring during vehicular traffic over previously spread ash (e.g.,
compacting activities) can be estimated using equation 5-4:
Eup=k[1.7(s/12)(Vs/48)(W/2.7)a7(nw/4)as((365-P)/365)]
where:
Eup
k
s
Vs
W
nw
P
emission factor for unpaved roads (kg/VKt) (vehicle kilometer traveled)
= particle size multiplier (dimensionless)
= silt content (%)
= mean vehicle speed (km/hr)
= mean vehicle weight (Mg)
= mean number of wheels •
= number of days with at least 0.254 mm (0.01 inch) precipitation per year.
In the absence of actual data, the following assumptions and default values will be used in our scenario.
7-38
-------
Assumptions for the scenario; ^ ^ 5_ „,„.",,, s, ,>,"., ,' % ";,,""••'"' N
Particle size multiplier: 'Totai emissions will'be caicuiated.^ "Therefore, the matxraium 1: value! "
for particles diameters < 30loa, will sbe used:,k = J9$G> / - -7 ^ , , s " ; s vx , x
- v , - - " , , ~ '- -^ - -- . -"1 ^ ^N^-4\X
-------
The concentration; of fi»r example^cp^ta^lnanlsirihls scenario & |ssuined 10 fae equal to the
upper-bound ^ported c6fl,e^ntmtjoiir^| Cd^ipO jigfe) an4tCt>|>l7>8 x I&4 jig/g) a*
bottom ^nd fly ash {sebTabl^^l!tttd" 3,31 -^^ ^ ; *;; r ^ '
Cd: 2.08 x 108 g'fugiiive asMeaseWyear K 100 pg Cd/g ash « 2,06 x JO10 p&Cd
..;. released/year , %St» x ,^ - -t—-- J —«
^\k^Ss ^ X **- ^ " , -
TVTTyrv O nfi v "If^ «• •fiift?f3\V^;^ro'5t^-ti*»lAaoii/?/t?A!aV'v *7 S v liTf' ni^'T^r^r^Tl/W' £- A I.U JLlg
TCDD
Since environmental release may occur into air, soil, and surface water, the exposure assessor should
choose appropriate environmental fate and transport models (Figures 5-2 and 5-3) and identify relevant
exposure routes (Figure 6-1).
Go to Step 7.
7-40
-------
Figure 7-7
Source Analysis for MWC Residuals Release - Step 7
S905.207/91052.7fl
Step 1
Step 2
Step 3
Step 4
\
te,lon>vY
I/
Physical and
characterization
Release rates to
air
asedj^>~~~*'
-4
Efficacy of
control measures
Physical and
characterization
Release rates to
soil/water
Release rates to air, soil,
surface water, groundwater
Go to Step 8
7-41
-------
STEP 7: IS ASH EXPOSED AT THE DISPOSAL SITE ?
RATIONALE
It might be reasonable to assume that an inactive, capped landfill is no longer susceptible to natural
processes of release of ash and ash contaminants. These processes include wind erosion, surface runoff,
and leaching. In this example, it is assumed that 0.25 ha of a total of 8.25 ha is active, and susceptible
to these processes. Further, it will be assumed that the capped portion; 8 ha, is not fully protective of
water which could leach to ground water carrying ash contaminants.
NO, ASH IS NOT EXPOSED AT THE DISPOSAL SITE.
Go to Step 8.
YES, ASH IS EXPOSED AT THE DISPOSAL SITE.
Step 7a: Determine the following:
• Physical and chemical characteristics of the residuals.
• Release rates and frequency.
Two types of releases will be estimated from the working, or uncapped, portion of the landfill. One is
wind erosion resulting in fugitive emissions, and'the other is surface runoff. A third type of release,
leachate, is estimated for both capped and uncapped portions of the landfill.
Go to Step 7b, 7c, or 7d, as necessary. ,
Step 7b. Estimate fugitive emissions from wind erosion from uncapped portion of landfill.
7-42
-------
Wind generated releases of ash from uncovered portions of a landfill site can be calculated using equation
5-7:
where:
E
V
Um
Ut
F(x)
E = 0.036 (l-V)(Um/Ut)3F(x)
total wind erosion flux of particles <10 urn (g/m2 hr)
.fraction of vegetation cover
mean wind speed (m/s)
threshold wind speed (m/s)
a dimensionless ratio function.
The following assumptions and default values are used in this example scenario to estimate wind-generated
release rates of ash.
Assumptions forttie scenario:
Application of equation 5-7 was described: m Section 5J.-&, including le
parameter valses< , Those parameter values ^wj&jbe ,used jn fhjls example* and,they are:
,-Vt No vegetative coveE o£¥ « 01) ^s - \%%T
•. V, V. mm*. •.:•.: : ::
: :: ::: •.mvnvnvnxvn •.'•'• •. % ™««™ •• ^ •"••. ^ < •• •• v, ^-* v ^ %O
: A raiean^anniial wind speed of 5,0 ra/s was used in the discussion, jn Section 5- "^ ,"
The uftit emission solved for by-equattoa 5-7 is units of j/nr hr. To eoaveitto an annual basis,
fhe fbllowtog assumptions are made: ,
v , -. -. 7. •• v. v. %•
Exposed Area: The exposed surface area for a disposal site must b^s defermineil on a "site- J
specific basis. This example, wllf assume that me area m which asEis: spreiad on at any given "
time Is equal to storage area "at the MWC facility, or Gt25 nectare, or 2500 tri\ - - _;
Houfsr For this example; ft wiS be assumed thattbe 4ispO&$ area Is covered during noft-
working hours. Since disposal occurs'affritigs 260 i*ork-days/yr;1he humber of hours per year
equate: 260 wd/yrxShrewd-2080tors. " - ^"^
Control Efficiencyf^It will be assumed there are r*o Controls to reduce wind erosion during
working hoots, " - ', \, .. « ,^ -
7-43
-------
Using these assumptions, one can calculate the wind generated release of ash from a disposal site (E) as
follows:
E * 0.036 (l-V)(Um/Ut)3F(x)
E = 0.036 (5/13)3(0.11)
E = 2.25 x 104 g/m2-hr
For an area of 2500 m2 and for 2060 hours/yr, the annual emission equals: 2.25 x 10"4 x 2500 x 2060 =
1158 g/yr \ /'
Mass loadings to tfte 6nyiron^mlB|^^l^hi^iniiiani jjgjft* ^ir%rio front; tlife reteass of
windblown fugitive ash emissions " " ' - - " :
"
,
YS " s 1 v> .. Xs' ^ ' 0 a •• "' , < > •. ! * %
\s »^*%«; ^ J-f<5 > < ^- v: \"J '•< '-^v 's^< s •"<. v ••n-l ^ •. ^v ^
The concentration of the^example Contaminants m Iftis scenario is assumed to t» e<3ual. to Hie
upper-bound repotted cos|ceiftttattoas of pd'X'lOa p|/gyand TCI>£> <7,8 x 10^* /ln coaibio
upper-bound repotted cos|ceiftttattoas of pd'X'lOa p|/gyand TCI>£> <7,8 x 10^* Fg/g)ln
bottom and fly ash. se.£ Tuples 3-1
Cd:
1 158 g
sh. £se.£ Tuples 3-1 4ftd^-3) ; ^-- „- r > .^ ',,/-•
"v *"•••.'•.- " ^ ' •• % 'f,-- \ "-..':. % ' v ' "" ,","„'' ' '
\ -" -? "s '-'-"5, - "!' " J' ",^^v'% ' "
lugitlvejsli released/year x 100 pg Cd/g'ash = 1.16 x 10s jig C^$ released/year
s X -v ,. *• -.""s "* *'*''' ** f •. "* \X-^-, ** "••»••% j-""
'S\'.'' ^•.N^&X ,>*""$ !Vv<»,V,,'' ' '"i vv.'.v., ,„„,. Z : ^ ^..^"'^ "'•-''f-"J^ $••#:•'....••....•• "
fugitive ash released/year x 7.13 * JO* jig TCDI>/ ash « .9 u TCt»3d
TCDD: 1158 g fugitive ash releas^dyyear x 7V8 KW4
released/year,
Note that this wind erosion emission is distinct from the emissions estimated for unloading, spreading and
compacting. Since the environmental release of ash may occur into air, soil, and surface water, the
exposure assessor should choose appropriate environmental fate and transport models (Figures 5-2 and 5-3)
and identify relevant exposure routes (Figure 6-1).
Step 7c. Estimate surface runoff from uncapped portion of landfill.
The volume of runoff water can be estimated using equation 5-11:
RV = .01 R Aw
7-44
-------
where:
RV
R
Aw
runoff volume (m3/yr)
annual runoff (cm/yr)
working (exposed) landfill area (m2).
Assumptions for the scenario: , _5 ,„„. * - -
-. -. % V. •.;. „•<. -^ % \ < \ ^ % "- ^ ^ % v v •- ~ •- ^ v. -..£. ^ •, v. -^ v, v.
Exposed landfill areas The working area ol&25 ha, or^OOra2, is susceptible to runoff; _
"'•'••• - •• "t v % ' •.
Annual riinoff: EP& C19$S«CTdeS(5ribes methods to estimate runoff and also includes r
(Figure I&9} wWch^cbntains Iscflines of mean annual tow ciop ainoff for ate eastern part of the
United States^ --Jfo iisoJSnes for ann»ial row crop runoff for the soil M^biest in nteoff pDjenttJEtt ^ %
j(jswil type "ID'*) ane iiiost appropri^e for this «pplicaliott, ev^R jjiough the a«h and the soil beneath
It may have fobd drainage and be less susceptible ia runoff, Htfs is beeau^s a lafldM is mote ,
priately "fallow" lather than -row crop" and that runoff, for fallow conditions jpe&fly exceed
for row crop conditions* - From. &at figure^ annual runoff for a *b" soil' on fee eastern , %
ai'd range front 5 to 1? inches* " A -valw of 34 inches/yeat, or S.8 cm/yr,Hs assumed Jfqr thig.
efample. ,-•.•., „' \r " r" % 5"\ ^, x - , ss ,
The runoff volume for this example then equals:
RV = .01 (28) (2500) . .
RV = 700 m3/yr, or 7 x 10s L/yr
Mass loadings to the enwonrnent of contaminant in the scenario from Etiraoff release at the
disposal site: , -,
The concentration of the example contaminants In theleachate is assumed to be equal to the EP-
- ^ Tox litnlt for Cd (1(KK) pg/L) andf upper-boond reported concentra^on for TCDD in, extract from
- the *FCLP (2,3 ^ s% '
« — s * --
Cd: 7 x 10s L of leachate released/^ear x 1000 |ig"cSi/L of teachate - 7 x 10* ug Cd ,
released/year ,, , " ,™^ , - - """
TCDE); 7 n 10* L of leachate released/year x 2,3 x 104 jig TCDD/L of ieachate ^ I6l jig ^
-- - TCDB released/year. - -T " - .. , _ , "- ,- _- >* __
«? j , -
7-45
-------
STEP 7d: Estimate leaching from capped and uncapped portions of landfill.
The use of landfill liners is important in determining the possibility of groundwater contamination. In the
ORD/EMSL study survey (EPA, 1988c) it was reported that liners were used by 60% of 72 respondents.
Unfortunately, no data have been developed regarding liner failure rates in ash landfills. However, three
different leachate loss scenarios have been used in an evaluation of leachate release from an MWC ash
landfill (Kellermeyer and Ziemer, 1989). This illustration scenario will be applied to liner failure resulting
in loss of 100%, 10% and 1% of the total leachate.
The rate of percolation can be determined by applying equation 5-10. (EPA, 1985c):
where:
Q =
I =
P =
E =
annual percolation (cm)
annual irrigation (cm)
annual precipitation (cm)
annual evapotranspirau'on (cm).
Assumptions for the scenario:: ; \ x \ -
Irrigation; Irrigation will not be considered to exist at the landfill site, therefore! will be set at
0.
Precipitation and Evapotranspiration; EPA (1985c) presents a map showing gradients of "
mean annual potential evapotranspiratiop minus precipitation.These values range from +70 inches
in the desert regions of the Sputhwsst to - 50 ifl fhejfaeific Northwest A value simifo^to those
found on the East Coast will be used: -20 Inches ^-50.8 crft. ""'" ? °
The total leachate generation can be calculated from equation 5-9:
L = .01 Q [Fw(Aw) + Fc(Ac)]
7-46
-------
where:
L = leachate volume (m3/yr)
Q = potential percolation (cm/yr)
Fw = fraction of potential percolation, Q, which results from precipitation falling on the working
(exposed) portion of the landfill
Aw = working landfill area (m2) ^
Fc = fraction of potential percolation, Q, which results from precipitation falling on the covered
portion of the landfill
Ac = covered landfill area (m2). '
Percolation: Tie value determined usmg eqaaJioB
be used: m8 on/year ^
ea and covered landfill ar*a; The expokd 'tawlftfrftfe* witt be estimated #> be _
approximately the same as the area of fiie tai-site st&rage facffi^ Le,, 0.25 ha <2500 m X By
be 8 1 ha (80.00D m )* ' , „,„
of 1.0 is assumed.
As s - s
Covered 4rea Feeotation: ^
"
Kelermeyer and 23eaier,
sSsssss^w v -.-.
assumpttori of OJ
Using these assumptions, and equation 5-9, the total leachate rate can be calculated by:
L = .01 Q [Fw(AJ +
L = .01 (50.8) [1.0(2,500) + 0.15(80,000)]
L = 7.37 x 103 nrYyear, or 7.37 x 106 L/year.
Applying the liner failure rates gives:
At 100% failure: 7.37 x 106 L/year
At 10 % failure: 7.37 x 10s L/year
At \% failure: 7.37 x 104 L/year
7-47
-------
s s % v f^vwwyf *•>, c ;TTI,IV, ,v...,.,.,.,. ,.
s s •, -. s •& vwS»vv •w*-"' fs ; ^^^ st t t f f
Mass loadings into the environment of cohtetninant; liIhe scenario from I<&c¥ate1retea$fc of
the disposal site with varying degrees of Jiner failure;
- s ~* *r > - ,'-,', -•, '. •• -— - - --
*$*v v «--v^w*« , ,\... „ , < •• "'
The concentration of the example Contaminants in.jJ3esJeachateJs^siiine(i to be' equal to tiie EP« ""
Tox limit for Cd (1000 p^/L) and upper-bound'wport^ cwowwffii'tor.lxSt^ ii* extract torn
combined ash using the TCLP (2,3 xiq^M^X^ ' """!,- ^ ; ,- \, ;,4^- ^
"\s ' ' ^ "" -^-'-- x- - '' '' '"'' ,,'/,, > ;,; -
Cd: 100% failure: 7<3^x 10s L of leachate/yr x 1000 »g Cd/L of leachate = 7,37 x 10s
pg/year ' ^>^T/!r ^ ^ "•' _„ - >r*
10% failure: 7,37x 10»^ear^ ':""\.
1% failure; 7.37 )f Hf pgfrear ^ -: \- . \
^ " •
^ t *• •- •.•.•. f y.y.y. ;>. v, ^ •• % vv
TCDD: 100% failure: 7,37 x itf t of leachate/yr x 7,8 xlcr* {ig TCE>D/t of leachate '» $,7, x'
iQ*iear "":- - -""" ""•-? • - '. '" "
failure: L7 x lO1 yg/year
l%failure: 17jig/year „, ,;
Since the environmental release of the leachate occurs into the groundwater or soil, and subsequently to
surface water, the exposure assessor should choose appropriate environmental fate and transport models
(Figures 5-2 and 5-3) and identify relevant exposure routes (Figure 6-1).
Go to Step 8.
7-48
-------
8905.207/91052.7H
Figure 7-8
Source Analysis for MWC Residuals Release - Step 8
Step 1
Step 2
Step 3
Step 4
Step 5
Step 6
Step 7
Step 8
islonsS^Y ^_
nlhe ^ --.... ^
IS
_^
Physical and
characterization
Release ratos to
air
lich ^^ Y ^
aasedj^* ^
g
.4
EHioaoy of
control measures
^
Physical and
characterization
fr
Release rates to
soll^water
stored^s,^ Y
MWC ^ »
8? >^
N
.*
^'Are fugitives^^x^
^x^^^ controlled? ^^
i&Y
Efficiency of
control measures
N ^
t
Physical and
chemica)
characterization
Release rates to air, soil,
surface water, groundwater
'
exposed at the
disposal sfte£
Physical and
chemical
characterization
Release rates to
air
Physical and
chemical
characterization
>h\^ Y
and >-!-».
•*&6T.S^
£
Load size, exposed
surface area
Physical and
chemical
characterization
— *
Release rates to
air
Does the caj>
'control wind erosion?*
surface runoff,^
Jeachlng
Physical and
chemical
characterization
fc-
Release rates to air,
soil, surface water,
groundwater
\
N
YY"^
Efficiency of control 1
measures |
Does
vehicular
traffic occur In
the vicinity of the
disposal
she?
7-49
-------
STEP 8: DOES VEHICULAR TRAFFIC OCCUR IN THE VICINITY OF DISPOSAL
RATIONALE
Often, haul routes in landfills are unpaved, which can lead to significant resuspension of dust due to
vehicular traffic. Such traffic includes the trucks hauling ash and other vehicles. Roadside particulates
can become contaminated because of fugitive emissions from the disposal site, drainage from trucks,
vehicle track-out from spreading and compacting vehicles, and so on.
NO, VEHICULAR TRAFFIC DOES NOT OCCUR IN THE VICINITY OF DISPOSAL SITES.
Conclude Assessment
YES, VEHICULAR TRAFFIC OCCURS IN THE VICINITY OF DISPOSAL SITES
Step 8a: Are vehicular resuspension emissions controlled?
The principal measures to remove or contain ash residues which have been deposited on haul routes within
disposal facilities are wetting and chemical dust suppression. Use of these can become critical for driver
visibility if the haul route is unpaved, which it most often is within a landfill.
• If containment and/or suppression measures are used, and these can be evaluated as fully effective,
assume a control efficiency of 100%.
Conclude assessment.
If it is not possible to evaluate the effectiveness of dust resuspension or containment measures, then some
estimate of containment efficiency must be assumed. In the absence of specific information on efficiency
of different measures, a containment measure of 90% will be used in this example.
7-50
-------
Go to step 8(i).
NO, DUST CONTAINMENT OR SUPPRESSION MEASURES WHICH WOULD REDUCE
VEHICULAR RESUSPENSION ARE NOT USED.
• Assume a containment efficiency of 0%.
Go to Step8(i).
Step 8(i): Determine the following:
• Length of impacted haul route.
• Vehicle passes per day.
The length of impacted roadway times the vehicles passes per day equals the vehicles travelled
per day.
• Proportion of impacted roadway that is unpaved.
Significantly more dust would be suspended if the roadway were unpaved. Unpaved roadways
are not uncommon in MSW landfills, particularly in the active portions of the landfill. Unpaved
roadways are assumed for this example.
The magnitude of fugitive emissions occurring during vehicular traffic over unpaved roadways can be
estimated using equation 5-4:
Eup = k[1.7(s/12)(Vs/48)(W/2.7)°-7(nw/4)a5((365-P)/365)]
where;
Eup = emission factor for unpaved roads (kg/VKt) (vehicle kilometer traveled)
k = particle size multiplier (dimensionless)
s = silt content (%)
Vs = mean vehicle speed (km/hr)
W = mean vehicle weight (Mg)
nw = mean number of wheels
P = number of days with at least 0.254 mm (0.01 inch) precipitation per year.
In the absence of actual data, the following assumptions and default values will be used in our scenario.
7-51
-------
assumed,
Assumptions for the s^ario;^^ 7 ^^ /^ %"V?
Particle size multiplier: Total emissions^wlE be estimated^ Therefore, the it vine for Itie - ''
largest sized particles, those w&htfamefati; <3f& jm, vM^s used: fe"= (J^Gf. " "" ','..
Silt Contents MRI (1990a> took tWO,sample&Norll«ripaved haul routes in two landfill^ and
obtained silt contents of 6.7 arid 2ai^r«tlie mean bl%se twoxVaMes* i3.4f, Will be ass»
Vehicle Speed: M3RI (1990a) assumed a vehicle speed of ^4 tovhr {15 mph) iui9t'%*'
of dust resuspension. This will besomed in fti$ example.' \ '"
Vehicle Weight: A range of vehicle wejgmssfor ;vel2cles\disposing'raaterials1ii'lSW landfills
was given as.14-40 x I03 kg fo MRT (1^90a), the midpoint of m iange,'27 x '10* kg wSl be
assumed here.. _ \^-%l '"-""^/"-;--- ' ff/%\ --'L , - "*-> -';-
Number of Wheels: A range for the numbey of wheels was given as 6-14 to. MRI O^0a> The
midpoint of this range, 10, wiTbe assumed heref ^ * ,,;;,, --''' r - * ,v
Precipitation: As in previous step£ca Vaiuejrfm .days win be applied to^ the examrfte
scenario. "•.,"'••.•••. ? , t'tt£}" ----''.. *;-&'" .,^>
z^ ^ f s •• •• j v %j,^ f^: ^The mediamL;haul rpmte Jengtto from 46 ISW landfills was-
407 m (1320 ft). Like the assessment otresaspended dust in tbst vicinity of storage ai^as, it wil
be assumed that 25% of tfite length, or 102 m; is impacted by the ash disposaT " ^ %
s "*
' ^-. o s ^*** Vw '"••
Vehicle Passes per Day: In this same surveyVMRI determined that the median uumter of daily
vehicle transactions, excluding ash haulers, was 26. s However; not all 26 vehicles will pass over
the same impacted roadway/since different portions of the landfill po«ld be activi As'Sumihg ' '
half of them pass over the impaaed roadway, or i3 .trucks, tftjs transia^es to 26 passeC This is
added to the 20 ash haulers per day, or 40 passes; for a total of 66 vehicle passes per daylbr -
Ms example. ^^ >: ^ ; ,.5 v^4i;!\l-,, .,,;>>^A
•.V . . *» "!''"'. - -~, ------- W.' ". ,K *i .^f'XSK"'",^ *' '!,!!,•. '„.
Using these assumptions, and equation 5-4, a value for the release of ash due to vehicular traffic and
resulting resuspension of contaminated dust operations can be estimated:
Eup = k[1.7(s/12)(Vs/48)(W/2.7)°-7(nw/4)as((365-P)/365)]
Eup = 0.80[1.7(13.4/12)(24/48)(2.7 x 104/2.7)°-7(10/4)°-s((365-121)/365)]
Eup = 506.4 kg/km travelled.
7-52
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Step 3c(ii): Apply the control efficiency factor
Determine net dust resuspension in the presence of controlling factors (Enet) using the following equation:
Enet = Eup[l -(control efficiency/100)]
Since the control efficiency in this example is assumed to be 90%, the net dust resuspension per vehicle
kilometer traveled is: 506.4 x 0.10 = 51 kg/km.
The total annual dust resuspension considers the 102 m, or .1 km, assumed for impacted haul route, the
260 days/year, and 66 vehicle passes per day: 51 kg/km x 1000 g/kg x (.1 x 66) km/d x 260 d/yr = 8.75
x 107 g/yr
loadings to the environment of each contaminant in the scenario From the ,
resuspension of contaminated ^articulates in foe vicinity of storage sites:
As noted in. Section 5,, Uie^cojBcentratiQii on roadway particulars will be less than the
concentration on ash itself because of mixing with clean dust particles, etev MSI £L$90) took' -
samples of combined as|* as well as haul route '^articulates in four of tfielr six sites and measured
both for cadmturn '(and other metals), but not TCEirX concentrations. "Hie ratio of concentrations
was wide, between. 0<01 and 0,45, but the mean ratio was 0,24. This ratio will be applied to,
both ea&nium and TCPt> (in the absence of better data for TCDD).
flie concentration of the exaraple'contaminants in this scenario Is assumed to be equal to the
apper-bound reported concentrations of Cd JlOQ ug/g) and TCDD (7.8 x 10^ pg/g) in combined%
bottom and fly asn (see Tables M and 3-3),
Cd: 8.75 x I07 g stit-sized dust issuspended/fr x 100 jig Cd/g ash x 0,24 dust cone/ash
cone = 2,1 x^lO* pg Cd released/year*
TCDD: &.75,x 107 g Mt-^ited dust re$«spended/yr x 7,8 x 10"* u^ TCDtt/g ash x 0,24 dust
, , cone/ash vcone ~ 1.64 x 104 jig TCDD released/yr. , ' ,
Conclude Assessment
7-53
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7.2. COMPARISON OF THE EXAMPLE SCENARIO TO A FIELD STUDY OF FUGITIVE ASH
EMISSIONS
A study was conducted to estimate the amount of fugitive dust generated at the ash monofill located
adjacent to the Ogden Haverhill Associates (OHA) Resource Recovery Facility in Haverhiil, Massachusetts
(Hahn et al., 1990). However, in addition to simply using predictive equations and default values, field
monitoring data and site-specific meteorological information were obtained at the OHA landfill, - It was
used to examine the ability of two AP-42 emission equations of the type presented in Section 5. and 7.
of this document to predict ash emissions at the site. One was an early version of the emission from batch
drop operations (EPA, 1985a) that has been since updated to be of the form presented as equation 5-1,
and the other was equation 5-4 to estimate emissions from unpaved roads used in this application to
estimate emissions from spreading.
The authors of the OHA study report that fugitive ash emissions measured in the field for unloading
and spreading operations were significantly less than those predicted by the use of these equations when
actual data on moisture content of the ash, wind speed and quantity of ash dumped were used in place of
conservative default values. However, the actual moisture content in this study was 25%., This is
significantly higher than the 0.25-0.70% range for moisture content recommended in EPA (1985a) for use
with the "batch drop" equation. Also, equation 5-4 does not have a moisture content term, but the related
term (365-P)/365 (where P is the number days where rainfall exceeds 0.01 mm) certainly implies that high
moisture content reduces emissions; it also implies that this equation is most appropriately applied on an
average basis, rather than an event basis. ,
The example in this section did assume a conservative moisture content of 0.25%. Noting this twp-
order-of-magnitude difference between the example moisture content and the measured moisture content
at Haverhill, it is likely that predicted annual fugitive ash emissions in the example presented in Section
7.1. of this document are higher than those that can be found at many actual facilities. However, the
purpose of this example is not to provide a relative indication of the amount of ash emissions that result
under average operating conditions, nor is it necessarily intended to provide default values for the input
parameters of the equations listed in Section 5., but rather to take the exposure assessor through a step-by-
step process for estimating the release of MWC ash into the environment. As described below, subsequent
steps are required to quantify the health risk posed by exposure to MWC residuals.
7.3. EXPOSURE PATHWAYS
The analysis of exposure pathways addresses the transport of MWC residuals and their constituents
from the source of release to their point of exposure with the affected individuals or populations. The
7-54
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initiation of an exposure pathway analysis begins with the identification of the relevant environmental
transport media. The decision network for such identification was described in Figures 5-1 through 5-4.
An exposure pathway analysis further requires that the exposure point concentrations of the
chemicals in question be known or estimated. They are often estimated using fate and transport models
which take the contaminant from the point of entry into a media until it reaches an exposed individual.
Before using fate and transport models, one must first convert emission rates to a chemical-specific basis,
as described in Section 5.3. Section 6. described the source documents for selection of appropriate fate
and transport models.
7.4. INTEGRATION OF SOURCE TERMS INTO AN EXPOSURE/RISK ASSESSMENT
The release rates of the MWC residuals and mass loadings of two environmental pollutants, cadmium
and TCDD, were estimated in this example scenario under a defined set of conditions. The source terms
for this example illustration are summarized in Table 7-1. These release rates and mass loadings can lie
used in an exposure assessment by following the procedures outlined documents identified in earlier
sections of this report. In addition, the source terms can be used as input parameter in the equations in
the Methodology for Assessing Health Risks Associated with Indirect Exposure to Combusior Emissions
(EPA, 1990b). This methodology provides risk assessors with the guidance necessary to estimate health
risks following indirect human exposures to contaminants in soil, vegetation, and water bodies.
Furthermore, the methodology guides the assessor to determine exposure through the various pathways,
and to a final risk determination. Although the methodology does not address the inhalation pathway,
guidance for determining human exposure by that route can be obtained in a number of publications such
as:
EPA (1989b). Risk Assessment Guidelines for Superfund.
EPA (1988g). Superfund Exposure Assessment Manual.
7-55
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Table 7-1. Summary of Source Terms for Example Illustration
Step
1
2
3
3a
3b
3c
4
5
5a
5b
6
6a
6b
6c
7
7a
7b
7c
8
Description
Vaporization
Quench release
Ash storage
fugitive emissions
Icachate release
vehicular resuspension
Truck loading
Ash transport
fugitive emissions
truck leakage
Landfill operations
unloading
spreading
compacting
Landfill releases
wind erosion
run off
percolation
100% liner failure
10% liner failure
1% liner failure
Vehicular resuspension
Residual Release
Rate
n/a
3.43 x 107 L/year
695 g/year
1.11 x 10s L/year
2.26x 109 g/year
2.91 x 106 g/year
2.91 x 104 g/year
6.5 x 10s L/year
1.15 x 107 g/year
3.45 x 107 g/year
2.08 x 10s g/year
1158 g/year
7x10*
7.37 x 10s L/year
7.37 x 10s L/year
7.37 x 104 L/year
8.75 x 107 g/year
Cadmium
Release Rate
(pg/yr)
n/a
3.43 x 1010
6.95 x 10*
1.11 x 108
7.91 x 1010
2.91 x 108
2.91 x 10s
6.5 x 108
1.15 x 109
3.45 x 109
2.08 x 1010
1.16 x 10s
7x 108
7.37 x 109
7.37 x 108
7.37 x 107
2.1 x 109
TCDD
Release Rate
(pg/yr)
n/a
7.88 x 103
0.5
25.5
6.17 x 10s
2.27 x 103
22.7
149.5
8.97 x 103
2.69 x 104
1.62 x 105
0.9
161
1.7 x 103
1.7 x 102
17
1.64 x 10*
Receiving Medium
air, surface deposition
surface water,
groundwater, soil
air, soil, surface water
groundwater, surface
water, soil
air, soil, surface H2O
air, surface water, soil
air, surface water, soil
soil
air, surface water, soil
air, surface water, soil
air, surface water, soil
air, surface water, soil
soil, surface water
soil, groundwater, surface
water
groundwater, surface water
groundwater, surface water
air, soil, surface water
7-56
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*U,S. GOVERNMENT PRINTING OFFICE: *9 *» .sm. IB 7/1(5006
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