United States
Environmental Protection
Agency
Solid Waste
and Emergency Response
(5306W)
EPA530-R-99-009
September 1999
www.epa.gov
Biosolids Generation,
Use, and Disposal in
The United States
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> Printed on paper that contains at least 30 percent postconsumer fiber.
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Biosolids Generation, Use, and Disposal
in the United States
U.S. Environmental Protection Agency
Municipal and Industrial Solid Waste Division
Office of Solid Waste
EPA530-R-99-009
September 1999
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Contents
Executive Summary
Section One
1.1
1.2
Introduction
How This Report Can Be Used
Sources of Information
4
5
5
Section Two
2.1
2.2
2.3
Background
Wastewater Treatment
Biosolids Treatment
2.2.1 Stabilization Processes
2.2.2 Dewatering
Biosolids Use and Disposal Practices
2.3.1 Land Application and Other Beneficial Use Options for Biosolids
2.3.2 Incineration of Biosolids
2.3.3 Surface Disposal and Landfilling
Section Three Generation, Use, and Disposal of Biosolids in 1998
3.1 Generation of Biosolids in 1998
3.2 Biosolids Management Practices in 1998
3.2.1 Beneficial Use of Biosolids in 1998
3.2.2 Disposal of Biosolids in 1998
3.2.3 Amount of Biosolids Managed by MSW Facilities in 1998
Section Four
4.1
4.2
Trends and Projections for Biosolids Generation,
Use, and Disposal
Generation
Use and Disposal
4.2.1 Use Trends
4.2.2 Disposal Trends
4.2.3 Use and Disposal Projections
7
8
10
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25
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31
31
34
35
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Contents
Section Five Beneficial Use of Biosolids
5.1 Overview of Beneficial Use
5.2 Potential Barriers to Increased Beneficial Use
5.2.1 Public Acceptance
5.2.2 Liability Concerns
5.2.3 Costs
5.2.4 Crop Considerations
5.3 Examples of Beneficial Use
5.3.1 King County, Washington
5.3.2 Los Angeles County, California, Sanitation Districts
5.3.3 City of Austin, Texas
5.3.4 Columbus, Ohio
5.3.5 Charlottesville, Virginia
References
Appendix Biosolids Generation, Use, and Disposal Methodology
38
38
39
39
43
44
47
47
47
49
50
51
52
54
57
and Results
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List of Tables
Section Two
2-1 Types of Wastewater Treatment and Resulting Types of Biosolids
2-2 Benefits of Using Compost
2-3 Stabilization Technologies and Associated Use or Disposal Methods
Section Three
3-1 Estimates of Biosolids Generation for Use or Disposal (1998)
3-2 Estimates of Biosolids Use and Disposal
Section Four
4-1 Projections of Biosolids Generation for Use or Disposal in 2000,
2005, and 2010
4-2 Projections of Use and Disposal in 2000, 2005, and 2010
4-3 Projections of Biosolids Use and Disposal in 2000, 2005,
and 2010 (million U.S. dry tons)
Section Five
5-1 Biosolids Composting Costs (1997 data from 100 composting facilities)
Appendix
A-1 Estimate of Biosolids Generation Factor
A-2 Estimate of Biosolids Generated by POTWs in 1996 and 1998
A-3 Adjustment for Biosolids Generation From Privately and Federally
Owned Treatment Works
A-4 Biosolids Use and Disposal Based on WEF Survey Data (million U.S. dry tons)
A-5 Comparison of WEF (1997) and BioCycle (1998) Data on Use
and Disposal Practices
A-6 Estimates of Biosolids Use and Disposal With Adjustments for
Biosolids Receiving Advanced Treatment (million U.S. dry tons)
A-7 Trend Analysis of Flow (1984 to 1996)
A-8 Wastewater Flow Projections for POTWs and Privately and
Federally Owned Treatment Works in 2000, 2005, and 2010
A-9 Projected Percentages of Biosolids Use and Disposal in 2000, 2005, and 2010
A-10 Projected Quantities of Biosolids Use and Disposal in 2000, 2005,
2010 (million U.S. dry tons)
9
14
16
25
27
30
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37
45
63
63
64
66
67
69
71
72
73
73
IV
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List of Figures
Executive Summary
ES-1 Estimates of Biosolids Use and Disposal (1998) 3
Section Three
3-1 Estimates of Biosolids Use and Disposal (1998) 27
Section Four
4-1 Projections of Biosolids Generation for Use and Disposal in 31
2000, 2005, and 2010
4-2 Projections of Use and Disposal for 2000, 2005, and 2010 36
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Executive Summary
The purpose of this report is to broaden the U.S. Environmental Protection
Agency's (EPA) series of solid waste studies by quantifying the amount of
biosolids managed by municipal solid waste (MSW) facilities. Biosolids are
the byproduct of municipal wastewater treatment and also are known as sewage
sludge. This report focuses on biosolids generated by publicly owned treatment
works (POTWs) and the subsequent management practices used by POTWs for
treating and then recycling or disposing of biosolids. The quantity of biosolids
processed by POTWs and the treatment methods they select are likely to affect
MSW decision-makers regarding their involvement in biosolids management.
EPA hopes to support MSW operators and state and local solid waste decision-
makers in developing coordinated biosolids management programs with local
POTWs and other generators to encourage the cost-effective, beneficial use of
biosolids. In beneficial use, biosolids are used for their soil-conditioning and
nutrient-containing properties. This report also examines the advantages to
MSW operators of using biosolids in composting operations for land application
and sale to the public. The key areas discussed in this report regarding the
beneficial use or the disposal of biosolids, particularly at MSW facilities, are
detailed below:
The use or disposal of biosolids
— The use or disposal of biosolids begins with wastewater treatment. The type
and level of wastewater treatment has an effect on the type, quantity, and
quality of biosolids generated. Pretreatment of wastewater by industry can
improve biosolids quality considerably.
— Biosolids treatment is inherent in the proper use of wastewater solids.
Various stabilization processes control odor, pathogens (e.g., disease-caus-
ing bacteria and viruses), biodegradable toxins (e.g., hydrocarbons), and
vectors (e.g., rodents and flies) and can bind heavy metals. Composting is a
highly effective way of stabilizing and reducing pathogens in biosolids,
resulting in a valuable soil conditioning product that often has many useful
properties (e.g., slower and steadier nutrient availability unmatched by
conventional chemical fertilizers). Dewatering is necessary for landfilling and
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Executive Summary
incineration of biosolids and can be a critical step in preparing biosolids for
composting.
Biosolids management practices primarily involve land application, which can
include the use of compost or other highly treated biosolids and other benefi-
cial uses (e.g., landfill cover). Other biosolids management options include
landfilling and other forms of surface disposal and incineration.
Quantities of biosolids generated, used, and disposed of between
1998 and 2010
— This report estimates that approximately 6.9 million tons of biosolids were
generated in 1998, of which about 60 percent were used beneficially (e.g.,
land applied, composted, used as landfill cover) and 40 percent disposed of
(i.e., discarded with no attempt to recover nutrients or other valuable proper-
ties). This report further estimates that at least 20 percent of biosolids were
managed by MSW facilities through either landfilling (17 percent) or as landfill
cover (3 percent). An estimated additional 6 percent were managed by MSW
facilities in composting programs. "MSW facility" defined here includes any
commercial, noncommercial, or municipal entity that composts organic MSW
(e.g., yard trimmings) with biosolids. Thus, about a quarter of all biosolids
have been managed by MSW facilities, mostly by MSW landfill operators
(see Figure ES-1).
— We expect that the use of biosolids will increase in the future due to the ben-
efits from recycling, cost considerations, and public perception issues associ-
ated with disposal. In 2000, we estimate that 7.1 million tons of biosolids will
be generated for use or disposal, growing to 7.6 million tons in 2005 and to
8.2 million tons in 2010. We anticipate that the percentage of biosolids used
(rather than disposed of) will grow from 63 percent in 2000 to 66 percent in
2005 and to 70 percent in 2010. A trend away from disposal and toward use
would result in a decline in biosolids disposed of in MSW landfills and an
increase in the use of biosolids as landfill cover and in composting programs
at MSW facilities. In 2000, we estimate that at least 14 percent of biosolids
will be landfilled and 3 percent used as landfill cover. An estimated additional
6 percent might be used in composting programs, for a total of at least
17 percent to a possible 23 percent of all biosolids managed by MSW facili-
ties. We expect that changes will occur in 2005 due to increasing reuse of
biosolids and a corresponding decrease in landfilling, primarily because of
cost and siting considerations. An estimated 13 percent will be landfilled,
3 percent will be used as landfill cover, and 6.5 percent will be composted at
MSW facilities, for a total of at least 16 percent to possibly 22 percent of
biosolids being managed by MSW facilities by 2005. In 2010, we estimate
that 10 percent might be landfilled, 3 percent used as landfill cover, and pos-
sibly 7 percent used in composting programs, for a total of at least
13 percent to possibly 20 percent of biosolids managed by MSW facilities
(as defined above).
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Executive Summary
Concerns about beneficial use and ways to address them
— The beneficial use of biosolids is hindered by public opposition in some areas
of the country. The public acceptance issues involve concerns about pollu-
tants in the biosolids, risk of disease, and nuisance issues such as odors.
When properly treated and managed in accordance with existing regulations
and standards, biosolids are safe for the environment and human health.
Furthermore, over time, as industrial pretreatment of wastewater has
advanced, the quality of biosolids has continued to improve. Public accept-
ance concerns can be effectively addressed through a combination of
approaches, including careful assessment of public attitudes, modifications to
biosolids management programs, aggressive outreach and education, and
strong marketing of biosolids products. These approaches are successfully
employed by a number of biosolids managers (as presented in the case stud-
ies in Section 5.3), resulting in highly effective programs that emphasize cost-
effective beneficial use of biosolids. In addition, a new Environmental
Management System for biosolids management is being developed, with the
support of Congress, by the National Biosolids Partnership program.
Voluntary membership in the National Biosolids Partnership program includes
the public, generators, land appliers, farmers, academics, federal, state, and
local governments, and other interested parties.
Figure ES-1
Estimates of Biosolids Use and Disposal (1998)
COMBINED
BENEFICIAL USE
4.1 MDT (60%)
Land Application"
2.8 MDT (41%)
COMBINED
DISPOSAL
2.8 MDT (40%)
Other Disposal
0.1 MDT(1%)
Incineration
1.5 MDT (22%)
irtace Disposal/Landfill
1.2 MDT (17%)
Advanced Treatment
0.8MDT(12%)
Other Beneficial Use
0.5 MDT (7%)
MDT (1998) = millions of dry tons
Source: See Appendix A.3.
Without further processing or stabilization such as composting.
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Section One
Introduction
Biosolids (historically known as sewage sludge) are the solid organic mat-
ter produced from private or community wastewater treatment processes
that can be beneficially used, especially as a soil amendment. The
amount of biosolids generated and the use or disposal of biosolids, as dis-
cussed in this report, are of interest to municipal solid waste (MSW) facility
operators and others (e.g., farmers, foresters, land reclaimers, landscapers) for
several reasons, including:
• Disposal of biosolids commonly occurs in MSW landfills
• Ash from biosolids incineration might be disposed of in MSW landfills
• Biosolids can be composted (recycled) with other organic MSW materials
• Biosolids can be used as a soil amendment and fertilizer
• Biosolids can be used as daily cover or part of a final landfill cover
This report discusses the amount of biosolids generated in the United States
and their subsequent use or disposal. Section Two summarizes the various
treatment, use, and disposal practices for biosolids and includes brief refer-
ences to regulatory requirements influencing these practices. Section Three pro-
vides actual estimates of the amount of biosolids generated, recovered, and
disposed of in the United States. Section Four discusses current and possible
future trends in the generation, use, and disposal of biosolids through 2010.
Section Five discusses beneficial uses of biosolids, addresses concerns about
beneficial use, and presents several case studies that illustrate a variety of suc-
cessful biosolids management programs. The Appendix provides the full
methodology and detailed results of the data analyses summarized in Sections
Three and Four.
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Introduction Section One
1.1 How This Report Can Be Used
This report contains information on biosolids treatment and management that
may be useful to MSW managers who are considering the impact of biosolids
on their operations, as well as for other varied users of biosolids. MSW man-
agers can use the generation, use, and disposal figures in this report, for exam-
ple, to gain a better perspective of the various management options available
for biosolids and what the current trends are in the use and disposal of
biosolids. MSW managers can also use this report to explore what trends may
affect future biosolids management practices over the next 15 years, including
the potential markets for composted biosolids. This report also may help clarify
the relationship between MSW facility operators and POTW operators and
encourage them to work cooperatively. By showing how solid wastes, such as
yard trimmings, and biosolids can be managed together in a composting opera-
tion, for example, this report might help various municipal groups, such as solid
waste and wastewater treatment departments, deal more efficiently and cooper-
atively with recycling and waste handling issues. Federal, state, and local solid
waste decision-makers can use this report to help determine the amounts of
biosolids potentially available for beneficial use projects and facilitate planning
for future use and disposal operations.
The data estimates made in this report target the quantities of biosolids that are
likely to be generated by POTWs whose management practices ultimately affect
the quality of resulting biosolids and, therefore, MSW facilities' management
options. For that reason, this report does not include information on domestic
septage that is not treated at POTWs. Domestic septage is the liquid or solid
material removed from septic tanks, cesspools, portable toilets, Type III marine
sanitary devices, or similar systems. This report also does not quantify the
amount of biosolids incinerator ash generated and disposed of, although up to
22 percent of total biosolids generated in 1998 were incinerated. Biosolids incin-
eration as a disposal practice, however, is discussed in this report.
1.2 Sources of Information
To estimate biosolids generation, use, and disposal and to prepare this report, a
number of information sources were used. The 1988 National Sewage Sludge
Survey (NSSS) surveyed 479 POTWs in 1988 and provided a statistically valid
estimate of the amounts of biosolids used or disposed of by POTWs using sec-
ondary or tertiary treatment in that year (U.S. EPA, 1993a). EPA's Needs Survey
(1986 through 1996 data) also was used in this report and assesses the number
of wastewater treatment facilities in operation, their existing and projected
wastewater flow, and the number of people they serve. In addition, the results of
the following recent studies and surveys were used: a 1995 inventory conducted
by the Water Environment Federation (WEF) and the Association of Metropo-
litan Sewerage Agencies (AMSA) on biosolids generation, beneficial use, and
disposal (WEF, 1997); a 1996 survey of state regulators (Bastian, 1997); and
1991, 1997, and 1998 surveys of state regulators (BioCycle, 1991, 1997, and
1998). In the near future, however, data on biosolids quality and management
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Introduction Section One
will be more readily available through EPA's Biosolids Data Management
System, which is a data program that allows for electronic reporting (and access
of data) among treatment facilities, states, and EPA.
These sources and the information used are discussed in more detail in the
Appendix. Additional sources of information are cited as referenced; full citations
can be found in the references section at the end of this report.
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Section Two
Background
The Clean Water Act requires that communities treat their wastewater to
return this resource safely to the environment. When wastewater is treat-
ed, the process produces a semisolid, nutrient-rich byproduct known as
biosolids. When treated and processed properly, biosolids can be recycled and
applied to crop land to improve soil quality and productivity because of the nutri-
ents and organic matter that they contain. Historically called sewage sludge,
biosolids is the term now used to emphasize the beneficial nature of this recy-
clable material.
Biosolids often contain approximately 93 to 99 percent water, as well as solids
and dissolved substances present in the wastewater or added during waste-
water or biosolids treatment processes. The quantity of municipal biosolids pro-
duced annually in the United States has increased dramatically since 1972, from
roughly 4.6 million dry tons in 1972 (Bastian, 1997) to 6.9 million dry tons in
1998. This is a 50 percent increase from 1972, when the Clean Water Act first
imposed minimum treatment requirements for municipal wastewater, and is
greater than the 29 percent increase in U.S. population from 1972 to 1998
(Council of Economic Advisors, 1999).
Treatment works treat both wastewater as well as the resulting biosolids, often
using different technologies designed specifically for each treatment process.
This section, therefore, divides the discussion of treatment into wastewater
treatment and biosolids treatment. The influence of wastewater treatment on
biosolids generation is addressed first, followed by a discussion of biosolids
treatment. The different types of biosolids use and disposal practices are then
discussed, including practices that might involve MSW facilities. Additionally, the
regulatory requirements found in The Standards for the Use or Disposal of
Sewage Sludge (Title 40 of the Code of Federal Regulations [CFR], Part 503),
which was published in the Federal Register in 1993, are discussed and will be
referred to in this document as "the Part 503 Biosolids Rule" or "Part 503." This
rule establishes the regulations limiting the pollutants and pathogens in
biosolids. Also discussed are the municipal solid waste landfill regulations, pub-
lished in 1991 under Title 40 CFR Part 258, as they apply to the disposal of
biosolids in MSW landfills. Discussion of landfill regulations in this document will
be referred to as "the Part 258 Landfill Rule."
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Background Section Two
2.1 Wastewater Treatment
Domestic, commercial, and industrial wastewater are collected through an
extensive network of sewers and transported to wastewater treatment plants
(usually POTWs).1 Prior to the release of wastewater into the municipal sewer
network, most industrial plants must pretreat their wastewater to remove certain
contaminants (including metals, such as copper, lead, cadmium, and chromium,
and other pollutants such as chlorinated hydrocarbons). Over the past 20 years,
industrial pretreatment and pollution prevention programs have substantially
reduced levels of metals and other pollutants going into POTWs, resulting in
noticeable improvements in biosolids quality (Walker, 1998). At the POTW,
before it is discharged into the environment, wastewater undergoes preliminary,
primary, secondary, and, in some cases, tertiary treatment (see Table 2-1). The
quantity and characteristics of the biosolids generated at a POTW depend on
the composition of the wastewater, the type of wastewater treatment used, and
the type of subsequent treatment applied to the biosolids. Even within an indi-
vidual plant, the characteristics of the biosolids produced can change annually,
seasonally, or even daily because of variations in the incoming wastewater com-
position and variations in treatment processes.
Generally, higher degrees of wastewater treatment can increase the total vol-
ume of biosolids generated. Higher levels of treatment also can increase the
concentrations of contaminants in biosolids, because many of the constituents
removed from the wastewater end up in the biosolids. Furthermore, wastewater
processes that involve the addition of chemicals to precipitate the solids (such
as ferric chloride, alum, lime, or polymers) can result in increased concentra-
tions of these chemicals in the biosolids. Other, indirect effects also can occur,
such as when alum (as aluminum hydroxide) adsorbs phosphorus or causes
trace metals (e.g., cadmium) to precipitate out of the wastewater and into the
biosolids. Industrial pretreatment regulations for wastewater, required by federal
and state agencies, as well as pollution prevention programs can reduce levels
of metals and other pollutants in the wastewater treated at POTWs and in the
subsequent biosolids produced. Thus, the type of wastewater treatment or pre-
treatment used affects the characteristics of biosolids, which in turn can affect
the types of biosolids treatment chosen. The marked improvements in biosolids
quality resulting from pretreatment and pollution prevention programs, for exam-
ple, can encourage POTWs to process their solids further, such as by compost-
ing them. When biosolids achieve the low levels of pollutants that make the
widest distribution of biosolids products possible, processes such as composting
become more attractive.
Although the focus of this report is on biosolids generated by POTWs, quantities of biosolids gen-
erated by privately and federally owned treatment works are included in estimates presented in
Sections Three and Four. Operations at these treatment works, although smaller than those at
many POTWs, are similar to POTWs.
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Background
Section Two
Table 2-1
Types of Wastewater Treatment and Resulting Types of Biosolids
Wastewater Treatment Level
Types of Biosolids Produced
Screening and Grit Removal
Wastewater screening removes
coarse solids that can interfere with
mechanical equipment. Grit
removal separates heavy,
inorganic, sandlike solids that
would settle in channels and
interfere with treatment processes.
Screenings and grit are handled as
a solid waste and nearly always
landfilled. This material is excluded
from the definition of biosolids and
from the 40 CFR Part 503
regulation governing the use or
disposal of biosolids.
Primary Wastewater Treatment
Usually involves gravity
sedimentation of screened,
degritted wastewater to remove
suspended solids prior to
secondary treatment.
Biosolids produced by primary
wastewater treatment usually
contain 3 to 7 percent solids;
generally their water content can be
easily reduced by thickening or
dewatering.
Secondary Wastewater Treatment
Generally relies on a biological
treatment process (e.g., suspended
growth or fixed growth systems), in
which microorganisms are used to
reduce biochemical oxygen
demand and remove suspended
solids. Secondary treatment is the
minimum treatment level required
for POTWs under the Clean
Water Act.
Biosolids produced by secondary
wastewater treatment usually have
a low solids content (0.5 to
2 percent) and are more difficult to
thicken and dewater than primary
biosolids.
Tertiary (Advanced) Wastewater Treatment
Used at POTWs that require higher
effluent quality than that produced
with secondary treatment. Common
types of tertiary treatment include
biological and chemical
precipitation and processes to
remove nitrogen and phosphorus.
Lime, polymers, iron, or aluminum
salts used in tertiary wastewater
treatment produce biosolids
with varying water-absorbing
characteristics. Also, high-level lime
precipitation produces alkaline
biosolids.
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Background Section Two
2.2 Biosolids Treatment
Most biosolids undergo additional treatment on site before they are used or dis-
posed of to meet regulatory requirements that protect public health and the
environment, facilitate handling, and reduce costs. Biosolids characteristics can
determine a municipality's choice of use or disposal methods. Only biosolids
that meet certain regulatory requirements for pathogens, vector attraction reduc-
tion, and metal content (discussed in Section 2.3.1), for example, can be land
applied or used as compost. Even those biosolids that are disposed of rather
than land applied must meet regulatory requirements (see Sections 2.3.2 and
2.3.3). Also, with regard to handling and cost, the water content of biosolids can
affect many aspects of biosolids management, such as transportation and the
size of treatment and use or disposal operations. Some biosolids treatment
processes reduce the volume or mass of the biosolids (such as biosolids diges-
tion processes), while others increase biosolids mass (for example, when lime is
added to control pathogens.) The two most common types of biosolids treat-
ment processes are stabilization and dewatering.2
Stabilization refers to a number of processes that reduce pathogen levels, odor,
and volatile solids content. Biosolids must be stabilized to some extent before
most types of use or disposal. Major methods of stabilization include alkali
(lime) stabilization, anaerobic digestion (digestion of organics by microorgan-
isms in the absence of oxygen), aerobic digestion (digestion of organics by
microorganisms in the presence of oxygen), composting, and/or heat drying
(described in more detail in Section 2.2.1).
Dewatering removes excess water from biosolids and generally must be per-
formed before biosolids are composted, landfilled, dried (e.g., pelletized or heat
dried), or incinerated. A number of dewatering processes can be used, including
air drying, vacuum filters, plate-and-frame filters, centrifuges, and belt filter
presses (discussed in Section 2.2.2).
2.2.1 Stabilization Processes
Alkaline Stabilization
The improved structural characteristics of stabilized biosolids (compared to
dewatered biosolids cake without lime stabilization) generally reduce pathogens
and odors, allow for more efficient handling operations, and provide a source of
lime to help neutralize acid soils. While lime is most commonly used, other alka-
line materials, such as cement kiln dust, lime kiln dust, Portland cement, and fly
ash, have also been used for biosolids stabilization.
Most of the information discussed in Sections 2.2.1 and 2.2.2 has been taken from the
Regulatory Impact Analysis of the Part 503 Regulations (U.S. EPA, 1993a), Process Design
Manual on Land Application of Sewage Sludge (U.S. EPA, 1995a), A Plain English Guide to the
Part 503 Biosolids Rule (U.S. EPA, 1994a), and Use and Disposal of Municipal Wastewater
Sludge (U.S. EPA, 1984).
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Background Section Two
Historically, alkaline stabilization has been implemented using either quicklime
(CaO) or hydrated lime (CA[OH]2), which is added to either liquid biosolids
before dewatering or dewatered biosolids in a contained mechanical mixer.
Traditional lime stabilization processes are capable of producing biosolids
meeting the minimum pathogen and vector attraction reduction requirements
found in the 40 CFR Part 503 rules governing land application of biosolids; suffi-
cient lime is added so that the pH of the biosolids/lime mixture is raised to 12.0
or above for a period of 2 hours. The elevated pH helps to reduce biological
action and odors.
In recent years, a number of advanced alkaline stabilization technologies have
emerged, some of which use other chemical additives to replace the lime (in
part or fully). Many of the newer technologies use similar biosolids handling and
mixing equipment as traditional lime stabilization (although some use special
equipment), but the precise chemical formulas of the stabilization additives
and/or the processing steps used are generally proprietary. Thus, many of these
technologies are available only to POTWs as procurements from private firms.
The most common modifications used in these newer technologies include the
addition of other chemicals, a higher chemical dose, and/or supplemental
drying, which: 1) increase solids content and granularity; 2) reduce mobility of
heavy metals; 3) increase the agricultural lime value; 4) achieve a higher degree
of pathogen reduction, including the production of a biosolids product with
pathogens below detectable levels; and/or 5) achieve long-term stability of the
product to allow for storage with minimum potential for odor production or
regrowth of pathogens. Potential markets for advanced alkaline-stabilized
biosolids products include agricultural, slope stabilization, structural fill, and
MSW landfill cover operations.
Anaerobic Digestion
Anaerobic digestion involves biologically stabilizing biosolids in a closed tank to
reduce the organic content, mass, odor (and the potential to generate odor),
and pathogen content of biosolids. In this process, microorganisms consume a
part of the organic portion of the biosolids. Anaerobic bacteria that thrive in the
oxygen-free environment convert organic solids to carbon dioxide, methane
(which can be recovered and used for energy), and ammonia. Anaerobic
digestion is one of the most widely used biosolids stabilization practices,
especially in larger treatment works, partly because of its methane recovery
potential. Anaerobic digestion is typically operated at about 35° C (95° F), but
also can be operated at higher temperatures (greater than 55° C [131° F]) to
further reduce solids and pathogen content of the stabilized biosolids.
Aerobic Digestion
Aerobic digestion involves biologically stabilizing biosolids in an open or closed
vessel or lagoon using aerobic bacteria to convert the organic solids content to
carbon dioxide, water, and nitrogen. Pathogens and odors (and the potential to
generate odors) are reduced in the process. Aerobic digestion is commonly
used by smaller POTWs and often is accomplished using wastewater treatment
11
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Background Section Two
lagoons containing aeration equipment. The high-temperature operation
(i.e., higher than 55° C [131° F]) of aerobic digestion is becoming more popular
because it can produce biosolids with lower pathogen levels and higher
solids content.
Composting
Composting is the decomposition of organic matter by microorganisms in an
environment that controls the size and porosity of the pile, thereby facilitating an
increase in temperature (typically to about 55° to 60° C [131° to 140° F]) to
destroy most pathogens. The moisture and oxygen levels of this process are
also controlled to reduce the potential for processing odors. During the process,
biosolids are degraded to a humus-like material with excellent soil conditioning
properties at a pH range of 6.5 to 8, which is conducive to growing healthy
plants and reducing the mobility of metals. Composting involves mixing dewa-
tered biosolids with a bulking agent (such as wood chips, municipal yard
trimmings, bark, rice hulls, straw, or previously composted material) and
allowing the biosolids mixture to decompose aerobically (in the presence of
oxygen) for a period of time. The biosolids mass is initially increased due to the
addition of the bulking agent. The bulking agent is used to lower the moisture
content of the biosolids mixture, increase porosity, and add a source of carbon.
Depending on the method used, the biosolids compost can be ready in about
3 to 4 weeks of active composting followed by about one month of less-active
composting (curing).
Three different composting processes are typically used: windrow composting,
aerated static piles, and in-vessel composting. In windrow composting, the
biosolids and bulking agent mixture are formed into long, open-air piles. The
piles are turned frequently to introduce oxygen into the pile, ensure that ade-
quate moisture is present throughout the pile, and ensure that all parts of the
pile are subjected to temperatures of 55° C (131° F) for destruction of patho-
gens. Aerated static piles (or windrows) are rectangular piles supplied with
oxygen via blowers connected to perforated pipes or grates running under the
piles. In-vessel composting takes place in a completely enclosed container
where temperature and oxygen levels can be closely monitored and controlled.
In-vessel composting also helps contain process and building air so that it can
be captured and treated for odors.
Various odor control measures, such as frequent turnings, are used in conjunc-
tion with most composting operations (see Section Five). Frequent turnings help
reduce odor-producing anaerobic pockets in the composting biosolids by intro-
ducing oxygen and remixing pile ingredients. This approach, however, might not
work well for large operations near residential areas because the turnings them-
selves (while adding more oxygen to the process) generate more odors initially.
In these cases, timing the turnings to occur when conditions are ideal (such as
when climate conditions are most advantageous) is used to minimize odors as
well as collecting and scrubbing the off-gasses chemically or biologically
(through packed towers, mist towers, or constructed biofilters).
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Background Section Two
Biosolids composting might interest MSW facility operators because biosolids
can be composted in combination with various organic components of MSW
such as yard trimmings (e.g., leaves, grass clippings, brush), paper, and
chipped wood debris. The benefits of composting (see Table 2-2) include divert-
ing these resources from landfills while producing a high-quality soil amend-
ment. If biosolids are included as part of the compost, the processing and
product are subject to the 40 CFR Part 503 Biosolids Rule. Furthermore, if the
finished compost product meets 40 CFR Part 503 Biosolids Rule Class A speci-
fications for the highest level of pathogen and vector control (as described in
Section 2.3.1) and specific metals limits, the compost product can be widely
used, like any other fertilizer or soil-conditioning product. MSW operators who
compost can simply meet these Part 503 Biosolids Rule requirements for Class
A pathogen status and vector attraction reduction by using good management
practices, careful documentation, and high-quality biosolids (that meet the
pollutant concentration limits in Table 3, Section 503.13). Important end uses for
biosolids compost include landscaping projects, nursery operations, and appli-
cations to parks, lawns, and home gardens. Additionally, biosolid compost is
often used for soil blending, landfill cover, application to golf courses, mine
reclamation, degradation of toxics, pollution prevention, erosion control, and
wetlands restoration. It also is used for agricultural purposes, such as applica-
tion to citrus crops (BioCycle, 1997 and U.S. EPA, 1997a). Composts made
from biosolids can also be tailored to remediate contaminated soils (U.S. EPA,
1997a; U.S. EPA1998a).
Although biosolids compost has less total nitrogen than most other forms of
treated biosolids (due to processing and dewatering, dilution of nutrients by
bulking material, and loss of ammonia during the composting process), this
nitrogen is released more slowly and, thus, is available to plants over a longer
period of time, which is more consistent with plant uptake needs. Biosolids com-
post also is an excellent soil conditioner, and the slow release of nitrogen in
compost reduces leaching of nitrogen into the water table—a common problem
with other types of soil conditioners and conventional fertilizers. Also, by promot-
ing a healthy soil microflora, compost can help prevent plant diseases. For more
information on the composting process, see Section Five, as well as the
sources Composting of Yard Trimmings and Municipal Solid Waste (U.S. EPA,
1993b), Compost—New Applications for an Age-Old Technology (U.S. EPA,
1997a), and An Analysis of Composting as an Environmental Remediation
Technology (U.S. EPA, 1998a). A number of communities have highly success-
ful, cost-effective composting programs. In 1997, 198 biosolids composting facil-
ities were in operation in the United States (BioCycle, 1998). Some of these
programs are profiled in Section Five.
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Background
Section Two
Table 2-2
Benefits of Using Compost
Benefit
Soil Enhancement
Plant Growth
Pollution Prevention
Description
Compost aerates the soil and
improves the soil's water-holding
capacity and structure by adding
organic materials.
Compost provides a slowly released,
long-term source of nutrients,
promotes faster root development,
and can reduce plant disease by
promoting beneficial microorganisms
that reduce plant parasites.
The soil and plant improvements
that composting provides can
result in reduced use of fertilizers
and pesticides.
When compost is used,
fertilizers, metals, organic
chemicals, and pesticides are
less able to migrate to and
contaminate ground water and
surface water.
Compost also can help prevent
soil erosion by increasing water
infiltration.
Composting instead of landfilling
reduces methane gas formation
in landfills, which can contribute
to global warming if not
appropriately captured and
utilized.
Source: Adapted from Garland, et al., 1995.
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Background Section Two
Heat Drying and Palletizing
Heat drying involves using active or passive dryers to remove water from
biosolids (solar drying is used in some locations). It is used to destroy
pathogens and eliminate most of the water content, which greatly reduces the
volume of biosolids. Heat-dried biosolids from secondary treatment processes
generally do not have objectionable odors, especially when stored dry, whereas
heat-dried primary biosolids can have objectionable odors even when stored
dry. Several highly successful products are prepared using this process
(e.g., Milorganite®, produced and sold by the city of Milwaukee since the 1920s)
(U.S. EPA, 1995a). Heat drying has the advantage of conserving nitrogen but
does require fuel for processing. In some cases, the heat-dried biosolids are
formed into pellets. These products are very dry and, therefore, can save
significantly on transportation costs over compost or other forms of biosolids
with higher moisture contents. Thus, heat drying and pelletizing might be
processes of choice for urban communities where distances to agricultural land
can be substantial. Boston, Massachusetts, and New York City, for example,
pelletize and transport their biosolids out of state.
2.2.2 Dewatering
Dewatering decreases biosolids volume by reducing the water content of
biosolids and increasing the solids concentration. Dewatering often is a neces-
sary process before treatment or use, such as before composting, heat drying,
or biosolids preparation for land application, although liquid biosolids can be
land applied using common or specialized application methods (see Section
2.3.1). Dewatering also is necessary for biosolids destined for incineration to
prevent damage to boilers and decrease the energy required for biosolids
combustion. Additionally, landfilled biosolids are required to be dewatered
because disposal of liquids in landfills is prohibited. Dewatering makes handling
of the biosolids easier by converting liquid biosolids to a damp cake and
reduces transportation costs, although cost savings should be weighed against
the cost of dewatering. Dewatering might be undesirable for land application of
biosolids in regions where water itself is a valuable agricultural resource.
Prior to dewatering, biosolids are usually conditioned and thickened. In
conditioning, chemicals, such as ferric chloride, lime, or polymers, are added to
facilitate the separation of solids by aggregating small particles into larger
masses or "floes." In thickening, part of the water bound to biosolids particles is
removed to concentrate the solid materials. Gravity thickening is a common
practice (Walker, 1998).
Typical dewatering methods include air drying and mechanical systems.
Air drying involves placing biosolids on a sand bed and allowing them to dry
through evaporation and drainage. This process can produce a solids content in
primary biosolids of as high as 45 to 90 percent. Air drying systems are relative-
ly simple in terms of operation but require large land areas and relatively long
periods of time and, therefore, tend to be used by small POTWs that generate
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Background
Section Two
small amounts of biosolids. Larger POTWs rely on mechanical dewatering sys-
tems such as vacuum filters, plate-and-frame filter presses, centrifuges, and belt
filter presses. Vacuum filters, which typically achieve 12- to 22-percent solids
content, involve rotating a drum submerged in a vat of biosolids and applying a
vacuum from within the drum, drawing water into the drum, and leaving the
solids or "filter cake" on the outer drum filter medium. The dewatered biosolids
are scraped off the filter. This form of dewatering is now being replaced by belt
filter presses, centrifuges, and, in some cases, plate-and-frame presses.
Centrifuges spin biosolids in a horizontal, cylindrical vessel at high speeds, with
the solids concentrating on the outside of the vessel. These solids are then
scraped off. Centrifuging can result in a 25- to 35-percent solids content. Belt fil-
ter presses can achieve 20- to 32-percent solids content. They work by exerting
pressure on biosolids placed between two filter belts, which are passed through
a series of rollers. The pressure forces water out of the biosolids, and the dried
biosolids cake is retained on the filter belt. Plate-and-frame presses are the
most expensive system to operate and can produce 35- to 45-percent solids
content. They work by squeezing the biosolids between two porous plates or
diaphragms. The pressure forces water out of the biosolids, and the dried
biosolids cake is retained on the plates.
Table 2-3 presents some of the common stabilization technologies and the use
or disposal method typically associated with each process.
Table 2-3
Stabilization Technologies and Associated Use or Disposal Methods
Treatment Process
Aerobic or Anaerobic Treatment
(Digestion)
Alkaline Treatment
Composting
Heat-Drying/Pelletizing
Use or Disposal Method
Produces biosolids used as a soil
amendment and organic fertilizer on
pasture and row crops, forests, and
reclamation sites; additional
treatment, such as dewatering, also
can be performed (see note below).
Produces biosolids useful for land
application and for use as daily
landfill cover.
Produces highly organic, soil-like
biosolids with conditioning properties
for horticultural, nursery, and
landscape uses.
Produces biosolids for fertilizers
generally used at a lower rate
because of higher cost and higher
nitrogen content.
Note: Two or more processes are often used for treating biosolids (e.g., anaerobic digestion with
dewatering and composting).
Source: Adapted from U.S. EPA, 1997b.
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Background Section Two
2.3 Biosolids Use and Disposal Practices
The most common destinations for biosolids include various types of land
application sites (after the biosolids have been treated to meet regulatory
requirements), landfills, and incinerators.
2.3.1 Land Application and Other Beneficial Use Options for
Biosolids
Land application involves the spreading of biosolids on the soil surface or
incorporating or injecting biosolids into the soil. Land application has been prac-
ticed for decades and continues to be the most common method for using
biosolids. Biosolids serve as a soil enrichment and can supplement or replace
commercial fertilizers. Nutrients (e.g., nitrogen and phosphorus), micronutrients
including essential trace metals (e.g., copper, zinc, molybdenum, boron, calci-
um, iron, magnesium, and manganese), and organic matter in the biosolids are
beneficial for crop production, gardening, forestry, turf growth, landscaping, or
other vegetation.
Biosolids generally have lower nutrient contents than commercial fertilizers.
Biosolids typically contain 3.2 percent nitrogen, 2.3 percent phosphorus, and
0.3 percent potassium, while commercial fertilizers might contain 5 to 10 percent
nitrogen, 10 percent phosphorus, and 5 to 10 percent potassium (Metcalf &
Eddy, 1991). Nevertheless, the use of biosolids conditions the soil and reduces
or eliminates the need for commercial fertilizers, thereby reducing the impacts of
high levels of excess nutrients entering the environment. Furthermore, although
biosolids contain metals, so do fertilizers, although data on metals in fertilizers
are not comprehensive. States are only now starting to look at regulating metals
levels in fertilizers, whereas metals in biosolids have been regulated for years.
See Box 1 for a discussion of regulations affecting the land application and
other beneficial uses of biosolids.
Biosolids treatment before land application can involve digestion, composting,
alkaline treatment, heat treatment, or other methods. Biosolids are treated to dif-
ferent levels, depending on the end use. In many cases, land application of
biosolids is less expensive than disposal methods (Federal Register, Vol. 54,
No. 23, pp. 5476-5902, February 6, 1989). Biosolids composting adds cost, but
the resulting compost has a wide variety of uses, and a composting program
has the potential to reduce municipal funding normally spent on purchasing soil
amendments and/or provide a high-quality compost to many other users.
Furthermore, composting offers ease of storage and ease of application
because of its semidry product, less odors, and more flexibility in land applica-
tion due to its high quality.
Some of the uses for biosolids and biosolids composts include their application
to various types of land including agricultural lands, forests, mine reclamation
sites and other drastically disturbed lands, parks, and golf courses. Composted
and treated biosolids are used frequently by landscapers and nurseries and by
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Background
Section Two
Box 1: Regulations Affecting Beneficial Use of Biosolids
Biosolids must meet the requirements specified in the 40 CFR Part 503
Biosolids Rule, "The Standards for the Use or Disposal of Sewage Sludge"
before they can be beneficially used. The Part 503 Biosolids Rule land
application requirements ensure that any biosolids that are land applied
contain pathogens and metals that are below specified levels to protect the
health of humans, animals, and plants. Part 503 also requires that the
biosolids are applied at an "agronomic rate," which is the biosolids applica-
tion rate designed to provide the amount of nitrogen needed by the crop or
vegetation and to minimize the amount of nitrogen in the biosolids that
passes below the root zone of the crop to the ground water. In addition,
Part 503 requires that vector (e.g., flies and rodents) attraction be reduced
and includes specific management practices, monitoring frequencies, and
recordkeeping and reporting requirements.
More specifically, the Part 503 Biosolids Rule sets metals limits in land
applied biosolids for nine metals. Four sets of limits are provided: the ceil-
ing limits for land application, more stringent high-quality pollutant concen-
tration limits, the cumulative loading limits, and the annual limits for bagged
products not meeting the high quality pollutant concentration limits.
Biosolids that meet pollutant concentration limits can be applied to sites
without tracking cumulative loading limits, as long as the rate does not
exceed the agronomic rate. Biosolids that meet the ceiling limits but not the
pollutant concentration limits can only be applied until the amount of metals
on the site have accumulated up to the cumulative limits.
The Part 503 Biosolids Rule divides biosolids into "Class A" and "Class B"
biosolids in terms of pathogen levels. It also imposes a vector attraction
reduction requirement, providing specific alternatives for meeting the
requirement. Whether biosolids are Class A or Class B can affect MSW
facility operators in several ways. Class A biosolids must undergo treat-
ment that reduces pathogens (including pathogenic bacteria, enteric virus-
es and viable helminth ova) in the biosolids below detectable levels. Once
these goals are achieved, Class A biosolids can be land applied without
any pathogen-related restrictions at the site. Class A biosolids (but not
Class B) can be used as bagged biosolids marketed to the public. Some of
the treatment processes described earlier, such as composting, heat dry-
ing, and high-temperature aerobic digestion, can meet the Part 503
Biosolids Rule Class A pathogen reduction requirements if they are con-
ducted to meet operating conditions also specified in the rule. Biosolids
having the least further restrictions on beneficial use are those meeting the
Class A pathogen and vector attraction reduction requirements, and the
high-quality pollutant concentration limits for metals. Once these require-
ments are met, the biosolids can be used with no more restrictions than
any other fertilizer or soil amendment product.
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Background
Section Two
Class B biosolids ensure that pathogens in biosolids have been reduced to
levels that are protective of public health and the environment under the
specific use conditions. Site restrictions apply to Class B biosolids, which
minimize the potential for human and animal contact with the biosolids until
environmental factors have reduced pathogens to very low levels. Class B
biosolids cannot be sold or given away in a bag or other container for land
application at public contact sites, lawns, and home gardens. Class B
biosolids can be used in bulk at appropriate types of land application sites,
such as agricultural lands, forests, and reclamation sites, if the biosolids
meet the limits on metals, vector attraction reduction, and other manage-
ment requirements of Part 503. Biosolids can be used as MSW landfill
cover, as long as they meet regulatory requirements in 40 CFR Part 258,
which governs MSW landfills (the Part 503 Biosolids Rule does not cover
biosolids that are disposed of in MSW landfills but states that biosolids dis-
posal in MSW landfills must meet the Part 258 Landfill Rule requirements).
See 40 CFR Part 503 for specific requirements, including which biosolids
treatment processes are approved for Class A and B biosolids, and the
Part 258 Landfill Rule for specific MSW landfill requirements. Section 2.3.3
discusses the Part 258 MSW landfill requirements specific to biosolids
disposal in more detail.
homeowners for lawns and home gardens. Agricultural land application of
biosolids has worked well for many communities. Application of biosolids to for-
est lands, which currently involves a relatively small percentage of biosolids, can
help shorten pulp wood and lumber production cycles by accelerating tree
growth (U.S. EPA, 1994c). At reclamation sites, biosolids help revegetate barren
land and control soil erosion; relatively large amounts of biosolids are used to
achieve these goals at reclamation sites. A growing market is the use of
biosolids in manufactured soils, which can be used for erosion control, roadway
construction, and parks (U.S. EPA, 1998a). Composted and heat dried or pel-
letized biosolids used on public lands, lawns, and home gardens are often sold
or given away in bags or bulk quantities; these forms are usually of excellent
quality (with very low levels of metals and pathogens below detection levels),
are easy to store and handle, and are usually in high demand.
The value of crop or other vegetation improvements from using marketed
biosolids products (such as bagged or other containerized biosolids) has been
estimated at between $35 to $50 per dry ton more than the value generated by
other potting media (U.S. EPA, 1995a). In some areas, such as King County,
Washington, a high demand for composted biosolids products exists. Some
communities, such as Austin, Texas, give away some of their composted
biosolids (although a nominal cost is strongly recommended to support regional
compost markets). Biosolids also have valuable properties that many commer-
cial fertilizers cannot duplicate (e.g., the slow release of nutrients providing long-
term nourishment to plants). A number of communities, such as Milwaukee with
its well-known Milorganite® brand biosolids product (heat dried, not composted),
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Background Section Two
have successfully marketed brand-name biosolids fertilizers or soil conditioning
products. Although ventures in developing composted or further processed
biosolids products involve additional costs for communities over direct land
application, the sale of these products can generate revenue that offsets some
of the costs. Also, communities with existing composting operations, such as for
yard trimmings, may easily incorporate biosolids into their operation using yard
trimmings as a bulking agent. Combining these materials to produce a biosolids
compost could avoid additional costs, since a composting operation is already in
place. Federal and state regulations regarding biosolids composting, however,
must be taken into consideration.
Liquid or dewatered biosolids can be applied by surface spreading or, in the
case of liquid biosolids, by subsurface injection. Surface application methods
include spreading by farm manure spreaders, tank trucks, or special applicator
vehicles. After being applied to the surface and allowed to dry partially, biosolids
are commonly incorporated into the soil by plowing, discing, or other methods.
Liquid biosolids may be malodorous but can be injected below the soil surface
by tank trucks with injection shanks to minimize odors. At forest sites and recla-
mation sites, spray irrigation of liquid biosolids and special flinging of dewatered
biosolids are common.
2.3.2 Incineration of Biosolids
Incineration of biosolids involves firing biosolids at high temperatures in a com-
bustor or combustion device. The volatile organic materials in the biosolids are
burned in the presence of oxygen. Incineration reduces biosolids to a residue
primarily consisting of ash, which is approximately 20 percent of the original vol-
ume. The incineration process destroys virtually all of the volatile solids and
pathogens and degrades most toxic organic chemicals, although compounds
such as dioxin may be formed, and products of incomplete combustion must be
controlled. Metals are not degraded and are concentrated in the ash and in the
paniculate matter that is contained in the exhaust gases generated by the
process. Air pollution control devices, such as high-pressure scrubbers, are
required to protect air quality. See Box 2 for information on the regulations
affecting biosolids incineration. Nonhazardous biosolids incinerator ash can be
disposed of in a MSW landfill as allowed by 40 CFR Part 258 Landfill Rule. The
ash also can be used in aggregate (e.g., concrete) production, as a fluxing
agent in ore processing, or for other purposes such as an athletic field amend-
ment (see Section Five).
The types of incinerators most commonly used are multiple-hearth and fluidized-
bed furnaces. Fluidized-bed furnaces, however, are known to have fewer prob-
lems with emissions than multiple-hearth units because of their more advanced
technology resulting in more uniform combustion of biosolids. Common types of
air pollution control devices include wet scrubbers, dry and wet electrostatic pre-
cipitators, fabric filters (all of which control particulates), and afterburners (which
can control releases of partially burned organics). Some municipalities opt for
biosolids incineration when land is scarce or unsuitable for land application.
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Background
Section Two
Box 2: Regulations Affecting the Incineration of Biosolids
Several regulatory considerations apply to facilities that incinerate
biosolids. The 40 CFR Part 503 Biosolids Rule includes pollutant limits for
metals in emissions that effectively become site-specific limits on metals in
biosolids that are incinerated; limits on total hydrocarbons or carbon
monoxide in emissions; general requirements and management practices;
frequency of monitoring requirements; and recordkeeping and reporting
requirements. If biosolids incinerator ash is applied to land other than in a
MSW landfill, regulations in 40 CFR Part 257 must be followed. Any incin-
erated waste that meets the definition of a hazardous waste must meet
regulations in 40 CFR Parts 261 through 268 for hazardous wastes.
Additionally, if biosolids and MSW are cofired and MSW accounts for less
than 30 percent of the mixture, the mixture is considered auxiliary fuel and
must meet Part 503 requirements for incineration. If the percentage of
MSW in a biosolids/MSW mixture is greater than 30 percent, then the mix-
ture is not regulated as an auxiliary fuel under the Part 503 Biosolids Rule
but rather is regulated as MSW under 40 CFR Parts 60 and 61. The equip-
ment used in incinerators that cofire biosolids with other wastes generally
must be specially designed for this purpose (e.g., include flash dryers and
separate burners) to handle the moisture content and odor potential of
biosolids successfully. In the near future, incinerators also will be subjected
to regulation under provisions of the Clear Air Act that are more stringent
and are based on what is technically achievable.
In some cases, municipalities use incinerators as standby units on an
as-needed basis for use when other biosolids management options cannot
be implemented.
The type of biosolids incinerated affects incineration efficiency. Due to their high-
er volatile solids content (i.e., heat content), for example, biosolids from primary
wastewater treatment processes (see Table 2-1) are more suitable for incinera-
tion than those that have undergone secondary treatment or above. Biosolids
from secondary wastewater treatment processes are more difficult to incinerate
because of their lower volatile solids content and the higher water content.
Biosolids dewatering is required prior to incineration. Biosolids incinerator ash
can be recovered and used in aggregate or can be used for other products such
as an athletic field amendment (see case studies in Section Five).
Only a few facilities in the United States currently cofire biosolids with MSW
(communication with Steven Levy, U.S. EPA, October, 1997). This practice
is so rarely used that, for the purposes of this report, we assume all incineration
of biosolids discussed in Sections Three and Four to take place in biosolids-
only incinerators.
Although biosolids incinerators require auxiliary fuel, many facilities that inciner-
ate biosolids include energy recovery as part of the process (communication
with Bob Bastian, U.S. EPA, October, 1997). Most of these facilities use the
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Background Section Two
energy generated within the facility for the incineration process itself (some facil-
ities have claimed to be autothermal, or self-sufficient in producing and using
their own energy) or for energy for other facility processes. A few facilities have
in the past sold at least part of the energy they produced from the incineration
process. In many cases, air quality requirements determine incinerator operation
to some extent because the requirements are temperature-based (i.e., an after-
burner to raise the temperature of exit gases might be needed to destroy
unburned hydrocarbons) and often cannot be met economically unless energy
recovery is included in the process. Numerous facilities that incinerated
biosolids have closed over the past decade because other biosolids manage-
ment options became more publicly acceptable or less expensive, even when
the facilities recovered energy.
To the extent that biosolids are successfully being used for energy recovery and
to the extent that energy recovery might be considered a beneficial use, the
quantities of biosolids that are estimated in this report to be beneficially used
might be somewhat understated. Defining incineration as a disposal method,
however, is consistent with the Part 503 Biosolids Rule, which categorizes
biosolids incineration as a disposal method, since that is the primary purpose of
incinerating biosolids.
2.3.3 Surface Disposal and Landfilling
Most biosolids that are disposed of in or on land are landfilled with MSW. This
report combines most discussions of surface disposal (as covered by the Part
503 Biosolids Rule for biosolids-only disposal in or on land) and landfilling
(defined here as disposal of biosolids in MSW landfills, which is covered by the
Part 258 Landfill Rule rather than by Part 503). See Box 3 for information on the
regulations affecting surface disposal on land and landfilling of biosolids in
MSW landfills.
Surface disposal is defined by the Part 503 Biosolids Rule as biosolids placed
on an area of land where only biosolids are placed for final disposal. It does not
include biosolids that are placed on land for either storage (generally less than 2
years) or treatment (e.g., lagoon treatment for pathogen reduction). It involves
landfilling of biosolids in monofills (biosolids-only landfills), disposal in perma-
nent piles or lagoons used for disposal (rather than treatment or temporary stor-
age), and dedicated surface disposal practices. The difference between surface
disposal and land application primarily involves the application rate. If biosolids
are spread on land at greater than the agronomic rate, then the ability of the
cover crop to retain nitrogen might be exceeded, and the excess nitrogen could
migrate through the soil and contaminate ground water. Any time the application
rate exceeds the agronomic rate (except as permitted by the permitting authority
for reclamation sites), EPA considers the practice to be surface disposal, and
the site must comply with all of the management practices outlined for surface
disposal in the Part 503 Biosolids Rule, including ground-water monitoring. If,
however, the applier reduces the application rate or changes the cover crop
from a low-nitrogen-demand crop to a high-nitrogen-demand crop, and the
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Background Section Two
practice meets Part 503 requirements for land application (assuming the land
application criteria for metals concentrations and pathogens and vectors are
met; see Box 1), then the practice is considered land application.
At the time the National Sewage Sludge Survey was conducted, biosolids from
most POTWs practicing surface disposal were determined to be able to meet
the Part 503 pollutant concentration criteria for land application, and, in many
cases, the biosolids were being applied at rates that could be considered agro-
nomic rates (U.S. EPA, 1993a). Therefore, the practice of spreading biosolids
on land for disposal purposes was nearly eliminated by the Part 503 Biosolids
Rule because: 1) the cost of meeting surface disposal management require-
ments (including ground-water monitoring) is usually much higher than that for
meeting land application requirements and 2) most operations could be easily
adapted to meet the Part 503 definitions of land application.
The vast majority of biosolids currently reported as either surface disposed or
landfilled are likely to be disposed of in MSW landfills.3 The small amounts of
biosolids reported as surface disposed or landfilled that are not disposed of in
MSW landfills are likely primarily disposed of in biosolids-only monofills
(i.e., landfills dedicated to accepting only biosolids). Monofilling, possibly the
most common surface disposal technique covered by the Part 503 Biosolids
Rule, typically is undertaken using a series of unlined trenches dug into the
ground, into which dewatered biosolids (meeting concentration limits imposed
by Part 503 for unlined surface disposal units) are placed and then covered with
soil. Other techniques less commonly used include fill mounds, area fill layers,
and diked containment.
This conjecture is further substantiated by communication with Bob Bastian, U.S. EPA, May, 1997
and by information in BioCycle (1998), which indicates that among the 34 surveyed states that
provided adequate data, less than 2 percent of biosolids are reported to be surface disposed in
biosolids-only monofills.
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Background
Section Two
Box 3: Regulations Affecting the Surface
Disposal and Landfilling of Biosolids
The Part 503 Biosolids Rule regulates the surface disposal of biosolids
other than landfilling of biosolids with MSW in an MSW landfill, which is
required to meet the Part 258 Landfill Rule. According to Design, Operation
and Closure of Municipal Solid Waste Landfills (U.S. EPA, 1994b), all
biosolids disposed in MSW landfills must pass the paint-filter liquids test
(dewatering biosolids to about 20 percent solids or more will generally
meet this goal). Furthermore, the biosolids cannot contain more than 50
parts per billion of polychlorinated biphenyls (PCBs) (40 CFR Part 761)
and must not meet the definition of hazardous wastes under the Resource
Conservation and Recovery Act (RCRA) (that is, they must not meet the
definition of hazardous waste as defined by RCRA or the Toxicity
Characteristic Leachate Procedure test).
Biosolids used as MSW landfill cover should be dewatered to achieve soil-
like characteristics. The Part 258 Landfill Rule requires that the daily MSW
landfill cover consist of 6 inches of earthen material (or alternative materi-
als or thickness approved by the state) and that the solid waste be covered
at the end of each day or more frequently as needed to control disease
vectors, fires, odors, blowing litter, and scavenging. Biosolids can be used
as part of a final MSW landfill cover, which must meet the Part 258 Landfill
Rule cover criteria for permeability, infiltration, and erosion control.
For surface disposal in biosolids-only facilities, Part 503 requires that the
site meet certain locational restrictions similar to the site restrictions in the
Part 258 Landfill Rule. Provisions for closure and postclosure care must be
made, and a plan for leachate collection (if the unit is lined), methane mon-
itoring, and public access restrictions must be developed. If the surface
disposal unit is unlined, the biosolids must meet concentration limits on
arsenic, chromium, and nickel. Also, the surface disposal unit must meet
management requirements similar to those for MSW landfills. These man-
agement practices include requirements for runoff collection, leachate col-
lection and disposal (if the unit is lined), vector control, methane
monitoring, and ground-water monitoring or certification, and restrictions on
public access, growing of crops, and grazing of animals. See the Part 503
Biosolids Rule and U.S. EPA, 1994a for more details.
24
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Section Three
Generation, Use, and Disposal of
Biosolids in 1998
3.1 Generation of Biosolids in 1998
This report uses the National Sewage Sludge Survey (NSSS) estimate of
the quantity of biosolids used or disposed of in 1988 and data on waste-
water flow between 1988 and 1996 from the Needs Surveys conducted
during those years to estimate the quantity of biosolids generated in 1998. This
estimate was made on the basis of increased wastewater flow since 1988 and
on the assumption that biosolids generation per gallon of wastewater has
remained approximately the same from 1988 to 1998. (See the Appendix for a
detailed discussion of the methodology used in this report, the sources used,
the assumptions made to derive this estimate, and a presentation of intermedi-
ate results.) On the basis of this approach, we estimate that 6.9 million dry tons
of biosolids were generated in 1998. Table 3-1 presents a breakdown of this
estimate to show the quantities of biosolids estimated to have been generated
by primary-only treatment POTWs or secondary-or-above treatment POTWs
and by privately or federally owned treatment works.
Table 3-1
Estimates of Biosolids Generation for Use or Disposal (1998)
Treatment Group
Primary-Only Treatment POTWs
Secondary-or-Above Treatment POTWs
Privately and Federally Owned Treatment Works
Total
1998 Biosolids
Generation (million
U.S. dry tons)
0.5
6.3
0.1
6.9
Source: See Appendix A.2.2.
25
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Generation, Use, and Disposal of Biosolids in 1998 Section Three
3.2 Biosolids Management Practices in 1998
This report primarily used the 1997 Water Environment Federation (WEF) report
results (with some modifications; see the Appendix) to divide biosolids manage-
ment practices into use and disposal categories (see Section 1.2). Categories of
management practices considered beneficial use include land application, com-
posting and other approaches to further processing, and other beneficial use.
Composting and further processing and stabilization is a special category partly
created out of WEF survey responses indicating "treatment" or other related
management practices including responses such as fertilizer, lawns and gar-
dens, potted growing media, soil amendments, composting, or pelletizing.
Generally, biosolids receiving further processing (also referred to as "advanced
treatment" in this report) are considered likely to have met Class A pathogen
and vector reduction requirements (see Box 1 in Section Two). We consider the
ultimate end use of these biosolids to be primarily land application. We included
survey responses indicating landfill cover or aggregate in the "other beneficial
use" category. The Part 503 Biosolids Rule does not regulate landfill cover if it is
being placed on MSW landfills; however, we consider landfill cover to be a ben-
eficial use for the purposes of this report. Therefore, the amount of biosolids
used for landfill cover or as aggregate is accounted for within the total amount
of biosolids beneficially used and not within the disposal totals.
Disposal, for the purposes of this document, as discussed in Section Two,
includes surface disposal, landfilling, and incineration. Additionally, in this report,
we have defined an "other" category, which includes WEF survey responses of
any unidentified processes. We have placed quantities included in this very
small category within the disposal totals.
3.2.1 Beneficial Use of Biosolids in 1998
Table 3-2 and Figure 3-1 present a breakdown of the various biosolids manage-
ment options, which are categorized as either a beneficial use option or a dis-
posal option. As the table shows, 60 percent of all biosolids generated in 1998
were land applied, received advanced treatment and then land applied, or were
otherwise beneficially used. This category of "other beneficial use," which
accounts for 7 percent of all biosolids generated, intends to capture and include
as beneficial use the fraction of biosolids that might be used as alternative daily
landfill cover, as part of a final landfill cover, or as aggregate.4 We assume for
the purposes of this report that the land application category is generally associ-
ated with Class B biosolids and the advanced treatment category is associated
with Class A biosolids. Out of a total of 6.9 million dry tons, we estimate that 2.8
million dry tons have been land applied after being treated to a Class B
pathogen status. We estimate an additional 0.8 million dry tons to have been
beneficially used after further treatment, such as composting, advanced alkaline
"This total differs from the estimate, made by Bastian in 1997, that only 54 percent of all biosolids
generated were beneficially used. The difference is due to the inclusion in this report of an "other
beneficial use" category (i.e., landfill cover and aggregate) accounting for 7 percent of the total
amount contributing to the beneficial use total of 60 percent.
26
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Generation, Use, and Disposal of Biosolids in 1998
Section Three
stabilization, or heat treatment, and that 0.5 million dry tons have been benefi-
cially used in another manner for a total of 4.1 million dry tons. See the
Appendix for how we estimated these quantities.
Table 3-2
Estimates of Biosolids Use and Disposal
Estimate
(millions)
1998 Dry
Tons
Percent of
Total
Beneficial Use
Land
Application"
2.8
41%
Advanced
Treatment"
0.8
12%
Other
Beneficial
Use
0.5
7%
Total
4.1
60%
Disposal
Surface
Disposal/
Landfill
1.2
17%
Inciner-
ation
1.5
22%
Other
0.1
1%
Total
2.8
40%
Total
6.9
1 00%
Note: Numbers may not add up properly due to rounding.
Source: See Appendix A.3.
"Without further processing or stabilization such as composting.
"Such as composting.
Figure 3-1
Estimates of Biosolids Use and Disposal (1998)
COMBINED
BENEFICIAL USE
4.1 MDT (60%)
Land Application9
2.8 MDT (41%)
COMBINED
DISPOSAL
2.8 MDT (40%)
Other Disposal
0.1 MDT(1%)
Incineration
1.5 MDT (22%)
Surface Disposal/Landfill
1.2 MDT (17%)
Advanced Treatment
0.8MDT(12%)
Other Beneficial Use
0.5 MDT (7%)
MDT (1998) = millions of dry tons
Source: See Appendix A.3.
"Without further processing or stabilization such as composting.
27
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Generation, Use, and Disposal of Biosolids in 1998 Section Three
3.2.2 Disposal of Biosolids in 1998
Table 3-2 also presents a breakdown of the disposal categories. We estimated
that 17 percent of all biosolids were surface disposed or landfilled, 22 percent
were incinerated, and 1 percent were disposed of in some unidentified manner.
Thus, 40 percent (2.8 million dry tons) of all biosolids generated in 1998 were
disposed of primarily in landfills (1.2 million dry tons) or incinerated (1.5 million
dry tons).5
3.2.3 Amount of Biosolids Managed by MSW Facilities in 1998
Out of the total 6.9 million dry tons of biosolids generated in 1998, we estimate
that a total of 1.2 million dry tons were disposed of at MSW landfills, and 0.2
million tons of treated biosolids were handled at MSW facilities as landfill cover
(daily or final). Additionally, MSW facilities6 might have composted biosolids
either on or off a landfill site. The total amount of biosolids that might have been
composted by MSW facilities is not known at this time, but we estimate the total
amount to have been 0.4 million dry tons based on the assumptions listed
below. Thus, we estimate that possibly 1.4 to 1.8 million dry tons, or 20 to 26
percent of biosolids generated in 1998, might have been managed by MSW
facilities after processing by POTWs. As noted, these estimates depend on the
following assumptions:
•All surface-disposed or landfilled biosolids are disposed of in MSW landfills.
This assumption is reasonable given the small amount of biosolids believed
to be disposed of in monofills, piles, or surface disposal sites (see Section
Two).7
• No biosolids are coincinerated with solid waste. This is a reasonable
assumption because coincineration is not a common practice.8
• We assume that the advanced treatment category is split such that half is
managed at MSW facilities (landfill, commercial, noncommercial, or municipal
operations, as defined above). MSW facilities are assumed to include any
composting facilities that handle both organic MSW (e.g., yard trimmings)
and biosolids. The actual percentage of the advanced treatment category
(composted) biosolids managed by MSW facilities is not known at this time,
and further research is recommended.
5The quantity of biosolids incinerated might be overstated, but supporting information is inade-
quate to adjust the data; see discussion in the Appendix.
6An MSW facility is defined for the purposes of this report to include: 1) any facility, such as an
MSW landfill, that handles MSW; 2) any commercial or noncommercial operation that composts
biosolids and organic MSW suitable for composting (e.g., yard trimmings); and 3) municipal oper-
ations not associated with MSW landfills, such as parks departments, public works departments,
or POTWs, that manage composting programs using both organic MSW and biosolids.
'Also based on communication with Bob Bastian, U.S. EPA, May, 1997.
"Based on communication with Steven Levy, U.S. EPA, October 1997, and Bob Bastian, U.S.
EPA, October 1997.
28
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Section Four
Trends and Projections for
Biosolids Generation, Use, and
Disposal
A variety of factors have influenced biosolids generation and use over the
years. Advancements in wastewater and biosolids treatment technologies,
including wastewater pretreatment, pollution prevention programs, and
population growth, have resulted in increased volumes of higher quality
biosolids (Stehouwer and Wolf, 1998). Increases in biosolids amounts and
improvements in quality are only part of the story, however. Federal and state
regulations and guidance, in particular the Part 503 Biosolids Rule, have
encouraged recycling and use of biosolids rather than disposal.9 Additionally, a
number of factors have contributed to increased biosolids use (see Section
Five). These factors include outreach and marketing efforts, high costs for dis-
posal of biosolids in some locations, bans on disposal of biosolids in landfills
(such as in New Jersey), landfill capacity concerns, closures of landfills following
implementation of landfill regulations, bans of yard trimmings in landfills, and
continuing research into the safe beneficial use of biosolids. In some areas of
the country, however, biosolids use has temporarily decreased. In these areas,
landfill costs are relatively low because of the presence of very large landfills
(megafills). This situation is causing some beneficial use operations to begin
landfilling their biosolids. It is not yet clear, however, whether this factor will
affect the overall trend away from disposal of biosolids. This section presents a
summary of these and other factors affecting current trends in biosolids man-
agement and includes specific projections for biosolids generation, use, and dis-
posal through 2010.
4.1 Generation
The U.S. population and the population served by municipal sewers have
increased dramatically over the past 20 years. These increases have
Three federal beneficial use policies have had an important influence. See U.S. EPA, FDA, and
USDA 1981; Federal Register, Vol. 49, No. 114, pp. 24358-59, July 12, 1984; and Federal
Register, Vol. 50, No. 138, pp. 33186-88, July 10, 1991.
29
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Trends and Projections for Biosolids Generation, Use, and Disposal
Section Four
contributed to an increase in the volume of biosolids produced since 1972
(nearly a 50 percent increase; see Section Two). As population levels continue
to increase, we expect the generation of biosolids to increase (Bastian, 1997).
Moreover, during the past 20 years, POTWs increasingly have been treating
wastewater at more advanced levels. By 1988, over 75 percent of the U.S. pop-
ulation was served by POTWs providing secondary wastewater treatment as
mandated by the Clean Water Act. By 1996, this figure had increased to over 90
percent (U.S. EPA Needs Surveys, 1988 to 1996). Also, some secondary waste-
water treatment methods can produce additional amounts of biosolids over that
generated by primary treatment alone. The total amount of biosolids produced
annually has increased at a somewhat greater rate than the increased U.S. pop-
ulation being served by sewers (see Appendix calculations and projections).
These increases in quantity have been accompanied by improved environmen-
tal quality of biosolids due to the greater prevalence of pretreatment and pollu-
tion prevention programs undertaken by industrial wastewater generators. The
physical quality of biosolids also has improved because of advanced mechani-
cal dewatering equipment, automated process control systems, aeration sys-
tems, and odor control systems. New technologies such as these have allowed
for lower water content, less odor, and easier handling of biosolids.
The trends in wastewater flow increases during 1986 to 1996 show an average
of a 4 percent per year decrease in wastewater flow at POTWs using only pri-
mary treatment, while wastewater flow at POTWs using secondary or higher lev-
els of treatment has increased about 2 percent per year (see the Appendix).
Assuming that these trends will continue into the future, and using the same
methodology used to estimate 1998 biosolids generation, the expected biosolids
generation amounts in 2000, 2005, and 2010 are shown in Table 4-1 and Figure
4-1 (see the Appendix for methodology). Future biosolids production is expected
to increase from 6.9 million dry tons in 1998 to 7.1 million dry tons in 2000, 7.6
million dry tons in 2005, and 8.2 million dry tons in 2010. This represents a 19
percent increase from 1998 to 2010. These increases are largely due to antici-
pated increases in population served and, to a lesser extent, the increase in
POTWs using secondary treatment and the subsequent slight increases in
quantities of biosolids produced.
Table 4-1
Projections of Biosolids Generation for Use
or Disposal in 2000, 2005, and 2010
Year
1998
2000
2005
2010
Total (million
U.S. dry tons)
6.9
7.1
7.6
8.2
Source: See Appendix A.5.
30
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Trends and Projections for Biosolids Generation, Use, and Disposal
Section Four
Figure 4-1
Projections of Biosolids Generation for Use
or Disposal in 2000, 2005, and 2010
10r
8
c
CD O
§ >> 6
CD -o
(f) r-
.204
CO = ^
0
8.2
7.6
7.1
2000
2005
Year
2010
Source: See Appendix A.5.
4.2 Use and Disposal
The following sections discuss general trends in use and disposal that are
expected to continue into the future.
4.2.1 Use Trends
Just as the generation of biosolids has increased over the past 20 years, so has
the use of biosolids. There are three major reasons for this increase. First, regu-
latory influences on both the federal and state levels have encouraged the ben-
eficial use of biosolids, either directly through guidance and federal policies on
beneficial use or indirectly because of stringent and higher-cost requirements for
disposal practices (e.g., incineration and landfilling). Second, better biosolids
research and technology also have helped alleviate public concern regarding
the human health and environmental impacts of biosolids. Third, outreach, edu-
cation, and marketing efforts have been improving public perceptions in some
31
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Trends and Projections for Biosolids Generation, Use, and Disposal Section Four
areas of the United States about the beneficial use of biosolids, although public
acceptance problems persist in other areas. The potential for a growing positive
acceptance of beneficial use of biosolids could lead to increasing biosolids
recovery in the future.
Regulatory influences on biosolids use include the indirect effects from the
Clean Water Acts of 1977 and 1986 and the more direct effects of the Part 503
Biosolids Rule. The Clean Water Act mandated more active federal involvement
in biosolids management, which previously had been handled primarily at a
state level. Effluent restrictions were set by the National Pollutant Discharge
Elimination System (NPDES) program for industrial facilities discharging to
POTWs. As a result, POTW influent and the resulting biosolids now have lower
levels of contaminants. Biosolids quality has dramatically improved since the
1970s. Regulations promulgated in response to the 1988 Ocean Dumping Ban
Act and the Clean Water Act (i.e., Part 503) prohibited ocean dumping of
biosolids and imposed comprehensive controls on biosolids use and disposal
practices.
More importantly, Part 503, codified in 1993, clearly defines biosolids quality
requirements for use or disposal and has become a useful tool for biosolids
managers in marketing efforts (U.S. EPA, 1994a). The Part 503 Biosolids Rule
helps biosolids managers identify "exceptional quality biosolids" (i.e., biosolids
that meet the most stringent metals limits and Class A pathogen and vector con-
trol requirements—see Box 1 in Section Two). Exceptional quality biosolids are
subject only to the same regulations as any other fertilizer product; thus, the rule
provides a useful public relations tool that has opened the door for greater use
of biosolids as fertilizer and soil conditioner and has also expanded potential
markets for products such as compost made from biosolids. The Part 503 rule
has encouraged POTWs to treat biosolids to a higher quality level and provide
for the least constraints on use. Furthermore, for disposal methods, Part 503
requires relatively expensive pollution control equipment and/or management
practices, such as ground-water monitoring, further encouraging biosolids recy-
cling and use options rather than disposal.
The increase in biosolids use associated with the implementation of the Part
503 Biosolids Rule is measurable according to a study performed by BioCycle
magazine. This study notes that 37 states have regulations in place that are the
same or more stringent than Part 503 (BioCycle, 1997). Thirty-four states regu-
late exceptional quality biosolids in the same way they do fertilizers. Both of
these regulatory conditions provide incentives for biosolids recovery and reuse.
Thirty states have increased the beneficial use of biosolids, and many communi-
ty programs have encouraged biosolids use. Composting programs on the com-
munity level, such as in Portland, Oregon; Palm Beach County, Florida; and
Hampton, New Hampshire, have lowered the cost of composting biosolids
(Snow, 1995) by combining biosolids with yard trimmings in their composting
operations. Additionally, composting facilities often charge a tipping fee to
receive yard trimmings, which offsets processing costs.
During the development of the Part 503 Biosolids Rule, EPA extensively
researched the risks of beneficially using biosolids and determined that risks
32
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Trends and Projections for Biosolids Generation, Use, and Disposal Section Four
from properly managed biosolids are negligible (U.S. EPA, 1992a). This
research has allowed EPA to set standards that are protective of human health
and the environment. An independent report by the National Research Council
in 1996 titled Use of Reclaimed Water and Sludge in Food Crop Production con-
cluded that established numerical limits (in the Part 503 rule) on concentrations
of pollutants added to cropland by biosolids are adequate to ensure the safety
of crops produced for human consumption (National Research Council, 1996).
These findings also tend to encourage beneficial use.
Another factor influencing biosolids recycling is public perception, which plays
an important role in biosolids marketability. With the evolution of regulatory stan-
dards for biosolids, marketing and promotion of biosolids or products made from
biosolids have been made possible. Although public education on the attributes
of beneficial use has increased public acceptance, increased public awareness
also has the tendency to generate skepticism about the risks of biosolids use,
public health, and the environment. Public opposition to biosolids use, whether
legitimate or unfounded, can arise from any change to the status quo.
The ability to market biosolids products will be determined by the public's per-
ception of the safety and value of biosolids recovery. In an effort to improve pub-
lic acceptance on a national scale and to increase the beneficial use of
biosolids, the National Biosolids Partnership has been established and, with the
support of Congress, will be working with stakeholders to develop an
Environmental Management System (EMS) for Biosolids. The National Biosolids
Partnership consists of representatives from the Water Environment Federation,
the Association of Metropolitan Sewerage Agencies, EPA, states, the U.S.
Department of Agriculture, and other stakeholders. The EMS is a voluntary pro-
gram designed to help ensure the responsible management of biosolids from
generation of solid wastewater treatment residuals through the further treatment,
transport, storage, and use of the resulting biosolids. Successful EMS develop-
ment and ultimate implementation depends in great part on the participants and
the development process. Those stakeholders involved in this process include
the public; generators; land appliers; farmers; academics; federal, state, and
local governments; and other interested parties. At a minimum, entities who
pledge to follow the EMS code must be in compliance with all applicable rules
as well as managing nutrients and controlling nuisances such as odors, noise,
and traffic. It is envisioned that the EMS will have:
• A code of good practices that defines broad goals to guide the operation of
biosolids management programs at all facilities and for all projects that adopt
an EMS.
• A manual of good practice that describes the full range of practices available
to facilities and projects that choose to implement an EMS. Each project or
facility will select from the manual those specific practices that are appropri-
ate to its situation.
• A set of procedures that can be used by all entities who pledge to meet the
code in designing and implementing their own EMS.
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Trends and Projections for Biosolids Generation, Use, and Disposal Section Four
• An ongoing program of one or more forms of independent third-party verifica-
tion and advisory input to insure continuing effective implementation based
on the code.
•Atraining program to help entities understand what meaningful participation
in the EMS will be.
For more information regarding public acceptance, Section Five of this report
presents a number of issues concerning biosolids use that can negatively affect
public perceptions (e.g., human health risks). Section Five also addresses how
these issues can be dealt with effectively with a careful and well planned
biosolids management program. In addition, several case studies are presented
that highlight successful beneficial use/composting programs.
4.2.2 Disposal Trends
Disposal of biosolids is expected to decrease because of regulatory influences,
voluntary improvements in biosolids quality, and the resulting increase in
biosolids use. Regulatory influences include the increased restrictions on incin-
eration, surface disposal, and landfilling in the Part 503 Biosolids Rule, the Part
258 Landfill Rule, and various state requirements, which also have driven up the
costs of these disposal methods (U.S. EPA, 1993a). In some municipalities,
however, decreases in landfill costs are causing shifts toward increased landfill-
ing and reductions in biosolids recycling. This trend is evident primarily among
municipalities using landfills with excess capacity. The long-term effects of this
factor on biosolids beneficial use is not yet known at this early stage.
As incineration becomes more costly, disposal of biosolids through this method
is expected to decrease. Incineration is a costly means of disposal and is prima-
rily used in large urban areas (proposed Part 503 rule, Federal Register, Vol.
54, No. 23, February 6, 1989, pp. 5476-5902; U.S. EPA, 1993a). Public concern
about the environmental and health impacts of incineration has made this dis-
posal option even more costly and difficult to undertake. Public resistance to
incineration is so great that no new incinerators have been built in recent years,
and expansions or upgrades to existing incinerators are difficult to get approved
(Bastian, 1997).
Any increased costs of biosolids disposal also are expected to promote benefi-
cial use. MSW landfills built to meet the Part 258 Landfill Rule requirements
incorporate liners, gas control, leachate control, and plans and funding for moni-
toring and long-term care after closure, which makes them more expensive than
landfills built prior to issuance of the Part 258 Landfill Rule (Regulatory Impact
Analysis (RIA) for 40 CFR Part 258 [U.S. EPA, 1991]). The national average tip-
ping fee is expected to rise from $35 per ton (prior to the Part 258 Landfill Rule
implementation in 1997 dollars) to $38 per ton (U.S. EPA, 1998b). Other analy-
ses, however, have shown no increase in tipping fees in 1998, and according to
these analyses, a very slight downward trend is expected to hold for the next
few years (Glenn, 1998). Where local increases in tipping fees are occurring,
however, communities will be encouraged to consider diverting high-volume,
34
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Trends and Projections for Biosolids Generation, Use, and Disposal
Section Four
readily compostable organic residues from their landfills. Tipping fees around
the country range anywhere from $15 per ton (Texas) to over $100 per ton (New
Jersey) (U.S. EPA, 1999).
4.2.3 Use and Disposal Projections
Based on the above discussion of expected trends in biosolids use and dispos-
al, Table 4-2 provides projections on the percentages of biosolids that will be
used or disposed of in 2000, 2005, and 2010. The use and disposal of biosolids
were estimated in dry tons for those years (see Table 4-3) in an effort to charac-
terize trends in biosolids use and disposal methods more accurately. As shown
in Table 4-2, beneficial use of biosolids is expected to increase from 60 percent
in 1998 to 63 percent in 2000, 66 percent in 2005, and 70 percent in 2010.
Thus, by 2010, we estimate that disposal might only account for about 30 per-
cent of all biosolids generated.
Table 4-2
Projections of Use and Disposal
in 2000, 2005, and 2010
Year
1998
2000
2005
2010
Beneficial Use
Land
Application
41%
43%
45%
48%
Advanced
Treatment
12%
12.5%
13%
13.5%
Other
Beneficial
Use
7%
7.5%
8%
8.5%
Total
60%
63%
66%
70%
Disposal
Surface
Disposal/
Landfill
17%
14%
13%
10%
Incineration
22%
22%
20%
19%
Other
1%
1%
1%
1%
Total
40%
37%
34%
30%
Source: See Appendix A.5.
Table 4-3 and Figure 4-2 below show estimated quantities of biosolids, in mil-
lions of U.S. dry tons, projected to be used or disposed of based on the percent-
ages in Table 4-2 and the quantities of biosolids projected to be generated. The
amount of biosolids estimated to be used beneficially is expected to increase to
4.5, 5.0, and 5.7 million dry tons in 2000, 2005, and 2010, respectively, with 2.6,
2.6, and 2.5 million dry tons, respectively, being disposed of. A positive trend in
the beneficial use of biosolids is expected to continue in the future, while the
trend toward disposal decreases slightly.
35
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Trends and Projections for Biosolids Generation, Use, and Disposal
Section Four
Figure 4-2
Projections of Use and Disposal for 2000, 2005, and 2010
BENEFICIAL USE
100
90
80
70
60
LU
O 50
DC
LU
D_
40
30
20
10
1996 2000 2005 2010
YEAR
DISPOSAL
Surface Disposal/Landfill
Incineration
1996 2000 2005
YEAR
2010
Source: See Appendix A.5.
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Trends and Projections for Biosolids Generation, Use, and Disposal
Section Four
Table 4-3
Projections of Biosolids Use and Disposal in
2000, 2005, and 2010 (million U.S. dry tons)
Year
2000
2005
2010
Beneficial Use
Land
Application
3.1
3.4
3.9
Advanced
Treatment
0.9
1.0
1.1
Other
Beneficial
Use
0.5
0.6
0.7
Total
4.5
5.0
5.7
Disposal
Surface
Disposal/
Landfill
1.0
1.0
0.8
Inciner-
ation
1.6
1.5
1.5
Other
0.1
0.1
0.1
Total
2.6
2.6
2.5
Total
7.1
7.6
8.2
Note: Numbers may not add up properly due to rounding.
Source: See Appendix A.5.
The amount of biosolids going to MSW facilities, as defined in Section Three,10
in the years 2000, 2005, and 2010 reach 1.6, 1.7, and 1.6 million dry tons,11
respectively, with declines in landfilled biosolids being offset by increases in use
of biosolids for landfill cover and in composting.
Therefore, MSW facilities are likely to be handling about 1.6 million dry tons of
the 7.1 million dry tons generated in 2000 (23 percent), 1.7 million dry tons of
the 7.6 million dry tons generated in 2005 (22 percent), and only about 1.6 mil-
lion dry tons of the 8.2 million dry tons generated in 2010 (20 percent). These
figures include amounts of biosolids disposed of in MSW landfills, used for land-
fill cover, or composted for sale or given away to farmers, contractors, or the
general public.
10An MSW facility is defined for the purposes of this report to include: 1) any facility, such as an
MSW landfill, that handles MSW, 2) any commercial or noncommercial operation that composts
biosolids and organic MSW suitable for composting (such as yard trimmings), and 3) municipal
operations not associated with MSW landfills, such as parks departments, public works depart-
ments, or POTWs, that manage composting programs using both organic MSW and biosolids.
"The quantity of biosolids handled by MSW facilities is estimated to rise slightly by 2005 because
the upward trend in beneficial use offsets declines in disposal, but at varying rates over the years.
The categories of biosolids considered to be managed by MSW facilities include the surface dis-
posal and landfill category and half of the advanced treatment category. See Appendix for more
details of these calculations.
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Section Five
Beneficial Use of Biosolids
5.1 Overview of Beneficial Use
The beneficial qualities of biosolids as a soil enhancement are generally
recognized. When added to soil, biosolids contribute nutrients and
improve soil properties. Depending on agricultural needs, these benefits
can be even greater with composted biosolids, which enhance the physical,
chemical, and biological properties of soil. Noncomposted biosolids have a high
nutrient availability and decompose and mineralize quickly and easily in soils.
This rapid decomposition of land-applied biosolids can provide large amounts of
nitrogen and phosphorous for immediate use by crops. Composted biosolids, on
the other hand, retain highly stable organic materials that decompose at a slow
rate, therefore releasing nutrients at a slower and steadier rate than noncom-
posted biosolids (USDA, 1998). Composted biosolids thus provide a long-term
source of slow-release nutrients.
Biosolids compost helps ensure pH stability; improves soil water-holding capaci-
ty, aeration, and structural stability; increases resistance to water and wind ero-
sion; and improves root penetration. By promoting beneficial microorganisms,
compost reduces attack by parasites, promotes faster root development, con-
tributes to higher yields of agricultural crops, and reduces reliance on pesticides,
herbicides, and fungicides. Furthermore, compost's ability to improve the water-
holding capacity of soil and fix nitrogen into a form that can be used by plants
reduces the potential for nonpoint-source pollution, such as that associated with
applications of commercial fertilizers. Compost also contributes to water conser-
vation by reducing water loss from percolation, evaporation, and runoff. In addi-
tion, compost can be used to bioremediate many toxic contaminants in soil
(Garland, etal., 1995; U.S. EPA, 1997a; U.S. EPA, 1998a).
According to the Organic Materials Management Strategies report (U.S. EPA,
1998b), the Composting Council estimated the potential demand for compost to
be over 1 billion cubic yards per year (based on 1992 data). The report
describes nine markets for compost: agriculture, silviculture (forests), sod pro-
duction, residential retail, nurseries, delivered topsoil, landscaping, landfill cover,
and surface mine reclamation. In practice, biosolids compost is more commonly
used by nurseries, landscapers, and soil blenders rather than for agricultural
purposes. Nevertheless, in its analysis, the Composting Council concluded that
the demand for compost in agriculture and silviculture alone could exceed
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Beneficial Use of Biosolids Section Five
current and potential supplies. While cost is a constraint with regard to process-
ing, transportation, and bulk application equipment, the primary constraint to
increased use of compost by these markets is the generation of odors during
production.
Compost is just one form of biosolids that can be beneficially used, however.
The combined potential of using either composted or noncomposted biosolids is
great. By addressing the environmental and public health issues related to
biosolids, the Part 503 Biosolids Rule also has greatly encouraged land applica-
tion of many other types of biosolids, including advanced alkaline stabilized,
heat-treated, and pelletized biosolids, as well as less highly processed liquid
biosolids and biosolids cake. While there is a trend toward the beneficial use of
biosolids, this trend is sometimes constrained, principally by lack of public
acceptance, as described below.
5.2 Potential Barriers to Increased Beneficial Use
Several factors limit the potential for expanding the beneficial use of biosolids.
These factors include limited public acceptance especially with regard to odors,
liability concerns of landowners, certain cost factors, and the type of crop grown.
This section discusses these barriers as well as ways that these barriers might
be overcome, such as through increasing public outreach efforts and ensuring
the availability of diverse biosolids products for a variety of uses (e.g., both
advanced treatment [such as composted] biosolids as well as less highly
processed Class B biosolids products [to which site restrictions and use restric-
tions apply]).
5.2.1 Public Acceptance
Some public resistance to the beneficial use of biosolids persists based primari-
ly on concerns about potential health, environmental, or nuisance impacts. The
public's perceptions of biosolids treatment and application can affect whether a
facility is built, where it is sited, and how it is operated. Although public percep-
tion is often not based on science and can be irrespective of the degree of risk
to human health or the environment, it can present a significant deterrent to
increased beneficial use. Understanding what the public concerns are can allow
biosolids managers to address these concerns as part of their biosolids man-
agement program. Overcoming public resistance to the beneficial use of
biosolids involves a combination of sensitivity to public perception issues, a
framework within which the concerns can be addressed, and a willingness to
address these issues through management practices and technologies, effective
outreach programs, and active marketing of biosolids products.
The public's concerns can be addressed and alleviated in part by increasing
their understanding of how advancements in biosolids technologies and regula-
tions governing the use and disposal of biosolids have resulted in high-quality
products that are safe and suitable for use. One very effective approach toward
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Beneficial Use of Biosolids Section Five
accomplishing public education is to assemble a biosolids "team" that includes
representatives from all key community stakeholders including university or
other scientists, water quality professionals, public health officials, agricultural
groups and farmers, the environmental community, regulatory officials, and the
media. Although some in the environmental community may oppose biosolids
use, obtaining the involvement of an environmental group can result in a more
successful effort. For example, consider the experience of existing groups that
have addressed public concerns about biosolids, including the Information
Sharing Group in New Jersey and New York, whose efforts included researching
the use of biosolids in an ecologically sensitive area, and the Northwest
Biosolids Management Association (NBMA), in which a member conservation
organization, the Mountains to Sound Greenway Trust, conducts a highly suc-
cessful public education campaign (Walker, 1998) (see the case study on King
County, Washington, in Section 5.3 for more information on the NBMA).
In addition to implementing a good public education campaign, it appears that
going beyond the requirements of the Part 503 Biosolids Rule (such as conduct-
ing additional site monitoring or using Class A biosolids), which is occurring in a
number of locations, can increase the public's acceptance of biosolids use. It is
important to note that a number of biosolids projects are currently being placed
on hold until states and counties develop their own more stringent rules or ordi-
nances for biosolids use.
Public concern also persists regarding the perceived lack of oversight of
biosolids regulations. Successful oversight can be provided in part by incorpo-
rating an operation fee into a biosolids management program that is designated
specifically for third-party inspectors who ensure compliance with the regula-
tions. Also, the biosolids community is now working to develop an
Environmental Management System (EMS) for biosolids that will encourage
good management and community practices that go beyond basic compliance
with the applicable federal, state, and local rules and will include third-party
oversight. The EMS concept for biosolids helps generators, processors (e.g.,
composters), and others focus on critical control points. For example, a critical
control point for odor is at the POTW, and proper management would involve
analyzing how the biosolids are conditioned, thickened, dewatered, and stabi-
lized at the POTW. In addition, conducting demonstration projects that illustrate
good biosolids management and the benefits and safety of using biosolids may
also improve public acceptance of biosolids use (Walker, 1998).
Odors
The potential for offensive odors can be a significant obstacle, if not the greatest
obstacle, to increasing the beneficial use of biosolids. Not only do the odors
themselves cause a public concern, but odors also trigger fears that 'foul-
smelling' residues from municipalities and industry must be toxic and harmful. In
some parts of the country, where rapid suburbanization of former farmland has
occurred, biosolids application might no longer be used on the remaining farm-
land because proximity to residential areas makes actual or potential odor con-
cerns unacceptable to the new neighbors. In other areas, treatment and good
management practices can control most odor problems keeping them to a
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Beneficial Use of Biosolids Section Five
minimum; however, occasionally even the best run operations may emit offen-
sive odors. In these instances, there are a number of odor-control methods,
from biofilters to neutralizing solutions, that can help. The composting process
may generally be able to reduce biosolids odors, although the composting
process itself could generate offensive odors if not managed properly.
Considerable information is available on abating or controlling odors generated
from composting or other biosolids use operations, and new methods are being
developed. Odors can be controlled by treating malodorous biosolids with lime
prior to shipping to an application site, minimizing anaerobic conditions, maxi-
mizing the ability of microbes to break down substances, injecting biosolids into
the soil rather than spreading them on the land surface, and collecting, treating,
and dispersing any odors that are formed (USDA, 1997; Walker, 1998).
Mitigating odor problems is another opportunity for the successful implementa-
tion of an EMS where generators, processors, and recyclers of biosolids prod-
ucts will decrease the generation of odors in addition to minimizing other
nuisances impacting public acceptance and perceived oversight. Thus, odor
problems can be prevented or mitigated with technology, advanced planning,
and/or good management practices.
Environmental and Health Concerns
Environmental and health concerns are often the major issues that biosolids
managers must address. The public's concerns about biosolids often focus on
infectious diseases, bioaerosols, water quality, and the introduction of pollutants
into the environment. A large number of disease-causing bacteria, viruses, and
parasites, including Salmonella and Shigella, are found in untreated wastewater
and biosolids. To the extent that people are unaware of how thoroughly
biosolids are treated to control pathogens, public concern over exposure to
pathogens can impede beneficial use projects. Increasing the public's aware-
ness of the regulatory requirements of the Part 503 Biosolids Rule for pathogen
reduction can help mitigate this concern. Box 4 summarizes the two levels of
pathogen reduction, other requirements, and typical uses of Class A and Class
B biosolids. These requirements include treatment of the biosolids (e.g., through
heat drying, composting, or other methods) to reduce pathogens to below
detectable levels and reduce odor and vector attraction (Class A); in some
cases, site restrictions are required that allow further pathogen destruction and
reduce potential public exposure (Class B).
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Beneficial Use of Biosolids
Section Five
Box 4: Biosolids Classifications
The Part 503 Biosolids Rule classifies biosolids on their level of pathogen
reduction.
Class A Biosolids undergo advanced treatment to reduce pathogen levels
to below detectable levels. Heat drying, composting, and high-temperature
aerobic digestion (described in Section 2.2) are treatment processes that
typically achieve Class A pathogen reduction requirements. Class A
biosolids, often sold in bags, can be beneficially used without pathogen-
related restrictions at the site. If they also meet vector reduction require-
ments and Part 503 concentration limits for metals, Class A biosolids can
be used as freely and for the same purposes as any other fertilizer or soil
amendment product.
Class B Biosolids are treated to reduce pathogens to levels protective of
human health and the environment, but not to undetectable levels. Thus,
Class B biosolids require crop harvesting and site restrictions, which mini-
mize the potential for human and animal contact until natural attenuation of
pathogens has occurred. Class B biosolids cannot be sold or given away
for use on sites such as lawns and home gardens, but can be used in bulk
on agricultural and forest lands, reclamation sites, and other controlled
sites, as long as all Part 503 vector, pollutant, and management practice
requirements also are met.
Concerns also have been raised about the possible health effects associated
with inhalation of airborne dust ("bioaerosols") originating from composting facili-
ties. According to research published in Compost Science & Utilization (Millner,
et al., 1994), bioaerosols (e.g., Aspergillus fumigatus) from composting do not
impose any unique endangerment to the health and welfare of the general pub-
lic. The report acknowledges, however, that further research into the occupa-
tional hazards of workers at composting sites is needed. Use of proper worker
protection (e.g., dust masks or respirators) at composting sites during screening
would reduce such risks considerably.
The Part 503 Biosolids Rule also provides numerous safeguards for protecting
water quality (for example, when Class B biosolids are applied in bulk, Part 503
states that they cannot be applied less than 10 meters from any surface
waters). Nevertheless, public concerns remain about the potential for biosolids
to pollute water resources. As explained in EPAs technical support documents
for Part 503 for land application and pathogen control (U.S. EPA, 1992a; U.S.
EPA, 1992b), the potential for contaminants in land-applied biosolids, such as
heavy metals, volatile and semivolatile organic compounds, pesticides, nutri-
ents, PCBs, and pathogens, to reach surface water and ground water was
extensively evaluated, and limits for metals were established that ensure protec-
tion of surface waters. (EPAs risk assessment showed that of all potential tox-
ins, only metals were potentially present in biosolids at levels that might be of
environmental concern.)
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Beneficial Use of Biosolids Section Five
The limits set for metals in the Part 503 Biosolids Rule ensure that risks of con-
taminants entering surface or ground water will be minimal. Additionally, even at
these minimal levels set for metals, composting binds the existing metals in the
biosolids and prevents them from migrating to water resources, being absorbed
by plants, or becoming bioavailable to humans (U.S. EPA, 1997a). Furthermore,
under most circumstances, biosolids must be land applied only at rates that
meet the nitrogen needs of a crop and minimize leaching of nitrogen to ground
water, thus protecting ground water from possible nitrate contamination. Also,
many states go beyond the Part 503 requirements in terms of management
practices and setback requirements, and a few states have more stringent metal
limits than those set in Part 503. Increasing public awareness about the low risk
of contamination of ground water or surface water by nutrients, pathogens, or
chemicals in biosolids and composted biosolids is an important component of a
biosolids beneficial use program.
Public concerns also persist regarding the presence of pollutants and pathogens
in biosolids that might find their way to humans through plant uptake, direct con-
tact, and animal ingestion. Although considerable independent research exists
to demonstrate that the risks to humans are negligible, the public might perceive
higher risks due to the origin of biosolids and past management practices
(USDA, 1997). The Part 503 Biosolids Rule was designed specifically to protect
human health and the environment from these types of risks. EPA's technical
support document for the rule presents the data, assumptions, and methodolo-
gies EPA used to set limits on pollutants in land applied biosolids (U.S. EPA,
1992a). The Agency investigated 14 pathways of exposure including plant and
animal uptake of metals with subsequent ingestion by humans and direct inges-
tion of biosolids by children. The limits set in Part 503 are protective of human
health and the environment under all likely ways that plants, animals, or humans
can be exposed to pollutants in biosolids.
Informative outreach programs that deal directly with health and environmental
issues and that present the ways in which the Part 503 Biosolids Rule and state
pollutant limits and management practices minimize these risks can help to
increase public acceptance, as demonstrated by the example programs high-
lighted in Section 5.3. A useful document for reference on the protection provid-
ed by the Part 503 rule is EPA's Guide to the Biosolids Risk Assessments for
the EPA Part 503 Rule (U.S. EPA, 1995b).
5.2.2 Liability Concerns
Property owners, lending institutions, and others involved in biosolids land appli-
cation have expressed concerns about liability under laws such as the
Comprehensive Environmental Response, Compensation, and Liability Act
(CERCLA) of 1980 and nuisance lawsuits. Adherence to the requirements of the
Part 503 Biosolids Rule, however, addresses these concerns. Persons who land
apply and beneficially use biosolids in accordance with Part 503 are not subject
to CERCLA liability or other federal enforcement actions (Walker and Albee,
1994). The pollutant limits and management practices required in the Part 503
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Beneficial Use of Biosolids Section Five
rule for land application of biosolids ensure that land-applied biosolids are non-
hazardous. Also, the records maintained as part of meeting the Part 503
Biosolids Rule requirements provide evidence that the biosolids placed on a site
are nonhazardous.
5.2.3 Costs
The Part 503 Biosolids Rule regulates numerous biosolids management options,
but communities must decide which options are most appropriate and cost-
effective given their circumstances. Data developed for the proposed Part 503
rule (Federal Register, Vol. 54, No. 23, pp. 5476-5902, February 6, 1989) indi-
cated that the least expensive management options were surface disposal and
crop application. (Surface disposal has become significantly less prevalent
because of the additional costs imposed by the Part 503 Biosolids Rule; crop
application, prior to the promulgation of either the municipal solid waste landfill
regulations or Part 503, was roughly equal to an assumed average cost for
landfilling [including transportation].) Land application costs (due to suburbaniza-
tion and possible increases in hauling distances to agricultural land in some
areas) may have increased in the intervening years. Monofilling of biosolids was
roughly 20 percent more expensive than either surface disposal or land applica-
tion on average and most likely is still more expensive following the implementa-
tion of Part 503. Furthermore, landfilling, since the municipal solid waste landfill
regulations came into effect, has generally increased in cost disproportionately
in comparison to these other methods, although landfill costs in some areas are
very inexpensive due to the construction of increasingly large landfills, some-
times called "megafills."
Cost information for different types of composting processes, researched by
BioCycle magazine is shown in Table 5-1, including capital and operating and
maintenance costs for different types of composting methods. The wide varia-
tions in costs are due to vast differences in size from the smallest to largest
facilities. Small facilities will generally incur the smallest capital costs, but can
incur relatively higher operation and maintenance costs on a per-ton basis. A
high cost per ton is typical of facilities that compost only a few tons per year.
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Beneficial Use of Biosolids
Section Five
Table 5-1
Biosolids Composting Costs"
(1997 data from 100 composting facilities)
Type of Composting
Method
Aerated Static Pile
In-Vessel
Windrow
Aerated Windrow
Static Pile
Capital Costs"
$36,000 - $20 million
$850,000 - $33 million
$50,000 - $8 million
$450,000°
not reported
Operation and
Maintenance Costs
$12-$500/dryton
$1 8.24 -$540/dry ton
$2.15 -$245/dry ton
$50 - $325/ton
$25 -$165/ton
Source: Goldstein and Block, 1997.
aDoes not reflect revenue generated from the sale of composted products.
"Costs reported by operations are estimates in many cases. The wide range reflects management
differences at sites, as well as what each facility factors into the operating costs.
°0nly one facility reported a capital cost.
Based on the research, distribution and marketing of biosolids products (e.g.,
composting operations) was, on average, more than three times the cost of the
least expensive options, although this does not take into account revenue from
the sale of the compost, which will offset some of these costs (100 composting
facilities reported revenues of from $1 to $35 per cubic yard, according to
Goldstein and Block, 1997). Also, with reductions in nearby agricultural land in
some areas and the fact that many users of compost provide their own trans-
portation, the difference in cost between composted biosolids and land applica-
tion of less highly processed biosolids is likely to be decreasing. Furthermore,
there are considerable economies of scale involved in composting, and some
communities might find that composting operations using both biosolids and
organic MSW materials, especially yard trimmings, might become more eco-
nomical on a cost-per-ton basis than disposing of either waste individually.
Incineration and land reclamation were, prior to 1989 and most likely still are,
the most expensive options on a unit cost basis. The cost of land reclamation as
presented in the Federal Register, however, includes the cost of the reclamation
process itself. If one compares the cost of reclamation with biosolids to the cost
of reclamation without biosolids (that is, using soils purchased or obtained from
other locations), the cost of reclamation using biosolids could be relatively much
lower, and might even represent a cost savings. In land reclamation, it is the
expense of landshaping using costly earth-moving equipment, and not the
biosolids use, that drives costs. Also, three times the amount of biosolids can be
applied for land reclamation as for land spreading at the agronomic rate for crop
growth. Furthermore, the costs of land reclamation reported in the Federal
Register also do not take into consideration the difference between the costs of
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unused, unproductive land and reclaimed productive land through enrichment by
biosolids or composted biosolids.
Although land application of biosolids is one of the least-cost management
options, the cost to municipalities or farmers of applying biosolids, monitoring,
recordkeeping, and meeting the management practices of federal, state, and
local regulatory agencies can impede biosolids use. Although biosolids are valu-
able to farmers as a soil amendment, and some or all of these costs can be
incurred by the contractor or POTW, the availability of low-cost commercial fertil-
izers may limit farmers' willingness to pay for biosolids (National Research
Council, 1996). In some municipalities, however, such as Seattle, Washington,
and Madison, Wisconsin, users pay for their biosolids. In others, POTW man-
agers can promote biosolids use by setting up demonstration projects using
biosolids, assisting in the recordkeeping tasks, and covering the cost of applying
the biosolids. In several localities, marketing of biosolids for beneficial use is not
a problem at all; in Madison, Wisconsin, for example, as well as other areas, the
demand for biosolids as a soil amendment exceeds the local supply (see
Section 5.3).
In comparison, composting is considerably more expensive than land applica-
tion, based on EPA's Regulatory Impact Analysis (RIA) for the proposed Part
503 Biosolids Rule (U.S. EPA, 1989), although, as discussed above, the cost
differential may be shrinking in some areas. The cost of composting operations
can affect whether this particular beneficial use option is chosen, but the desir-
ability of the composted product and the potential market for a sellable product
that is proven to be safe can offset some of this cost. In Columbus, Ohio, for
example, the city's compost product, which is sold to the general public as a soil
amendment, has been so successful that on various occasions demand has far
exceeded supply. The case studies presented in Section 5.3 illustrate the
demand for biosolids and the process that can be used to market composted
and other types of biosolids.
Transportation of biosolids is also a substantial cost category for POTWs, and
these costs can have the most significant effect on the total costs of land appli-
cation. Furthermore, the distance to land application sites is increasing as avail-
able land closer to the point of generation becomes more developed (thus
requiring biosolids to be hauled farther). Reducing biosolids volume through
thickening, dewatering, conditioning, and drying can reduce these costs.
Preparation and long-distance shipping of pelletized biosolids, for example, gen-
erally can be less expensive than for nonpelletized biosolids because the
reduced water weight results in lower transport costs (communication with
Massachusetts Water Resources Authority, February, 1998). Transportation
costs also can be greatly reduced by finding local markets for biosolids
compost.
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5.2.4 Crop Considerations
In a number of locations, fiber crops are being replaced with food crops. When
Class B biosolids are applied to land where food crops are raised, waiting peri-
ods before harvesting are imposed, which can reduce the usefulness of Class B
biosolids. Municipalities applying biosolids in these areas might need to have
their treatment plants change their treatment process to produce Class A
biosolids (i.e., nondetectable pathogen levels), which require no waiting period
before crop harvest, to encourage farmers to continue to use biosolids; transport
biosolids farther to land apply; or landfill biosolids instead of land apply them.
These trends highlight a need for municipalities to: 1) continue identifying new
locations suitable for land application of Class B biosolids or 2) consider adding
Class A treatment processes.
5.3 Examples of Beneficial Use
The following five examples illustrate how some communities have successfully
addressed the management and beneficial use of biosolids, often in cooperation
with municipal solid waste operations. Each of the programs stresses the impor-
tance of education and outreach to obtain public acceptance. The programs
also rely on a variety of disposal and use options, which ensures that biosolids
will be properly managed even in the event that any one option is no longer
viable. Some of the case studies were summarized from applications submitted
to EPA's Office of Water for its annual Biosolids Beneficial Use Awards Program
for Operating Projects, Technology Development, Research, and Public
Acceptance. These summaries were updated in 1998 with information provided
by key operating personnel in the municipalities.
5.3.1 King County, Washington
King County operates a highly successful biosolids management program that
results in the beneficial use of all biosolids produced at the West Point
Treatment Plant in Seattle and the East Division Treatment Plant in Renton. In
1996, these two wastewater treatment plants, with secondary treatment capabili-
ties, processed a combined 100,000 wet tons (20,000 dry tons) of biosolids,
which were eventually digested anaerobically, dewatered using a centrifuge or a
belt-filter press, and land applied. In 1995, one of the biosolids products origi-
nating from these two plants, a Class B biosolids cake, was used for agricultural
land fertilizer and forest applications (such as reclaiming and regreening scars
left from logging roads). A portion of the biosolids is composted by a private
contractor and marketed under the name GroCo® as a general compost for a
variety of applications including those in Seattle parks.
King County receives revenues from its biosolids cake product provided to farm-
ers and forest owners at $15 to $25 per acre and $35 to $60 per acre, respec-
tively. These prices reflect what each buyer would pay for equivalent chemical
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fertilizers. In fact, land application of King County's biosolids cake product,
accounting for 90 percent of the county's biosolids, has proven to be so effec-
tive as a soil fertilizer or amendment that current demand significantly exceeds
the supply. The county also receives $5 per dry ton from the contractor who
composts and markets the other 10 percent of the county's biosolids. In 1995,
King County received over $100,000 in revenues from selling biosolids, which
helps offset the cost of hauling biosolids from the treatment plant to the contrac-
tor. King County also pays to have the biosolids land applied. These hauling and
application costs are less expensive than disposal in a landfill.
In the early 1980s, the King County biosolids management program suffered a
series of setbacks due to organized public resistance to land purchases for
long-term biosolids cake application projects. As a result of the public's resist-
ance, most land application projects receiving treated biosolids were halted. The
King County Council then required that the staff of the Biosolids Management
Program be accountable to the council and the public regarding the issuance of
permits and informing the public of projects. Augmenting this shift in accounta-
bility from private contractors to the county staff was the formation of the
Northwest Biosolids Management Association (NBMA), an association of 150
municipal biosolids agencies and private firms that work together to share man-
agement strategies and initiate research and public education programs.
Together, these developments helped improve public acceptance and provided
information to regulatory agencies, elected officials, and the public.
The current success of King County's biosolids management program is mainly
due to the county's extensive outreach and education efforts through NBMA, the
program's excellent performance record (i.e., no contamination events or regula-
tory compliance issues), and the development of an efficient and reliable
biosolids and biosolids compost market.
Public trust and interest has been solidified through the Mountains to Sound
Greenway Biosolids Forestry Program, a comprehensive effort to restore and
protect logged-over mountain slopes and road scars in the I-90 corridor of
Washington State by the Washington Department of Natural Resources,
Weyerhaeuser Company, University of Washington, King County, and the
Mountains to Sound Greenway Trust. The Weyerhaeuser Company will increase
its use of King County biosolids from 2,000 dry tons to 5,000 dry tons per year
to stimulate accelerated vegetative growth in this region. The Greenway Trust, a
respected conservation organization, promotes the use of biosolids, conducts
public education on biosolids recycling and environmental sustainability, and
manages the compost land application program. This project represents a new
way of doing business for wastewater treatment utilities, offers a creative way to
reduce ratepayer costs, and helps the public realize the value of the services
and products created by wastewater treatment.
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5.3.2 Los Angeles County, California, Sanitation Districts
Use of biosolids in Los Angeles County began in 1928 with a contract between
a fertilizer supply company and the Joint Water Pollution Control Plant (JWPCP)
in Carson, California, to distribute dewatered, digested biosolids cake from the
plant. Since that time, the County Sanitation Districts of Los Angeles County
(CSDLAC) system, which operates the JWPCP, has grown to seven POTWs
linked by a common sewer system serving 5 million people in Los Angeles
County and treating 500 million gallons per day (MGD) of wastewater.
Residual solids from six upstream treatment plants with a combined flow of 170
MGD are returned to the sewer system for centralized processing at the
JWPCP, where an additional 330 MGD of wastewater are also treated. All solids
are anaerobically digested at 35° C (96° F) for 20 days and dewatered using
scroll centrifuges to 26 percent total solids. CSDLAC has adopted a strict pre-
treatment program that helps ensure all biosolids meet the Part 503 require-
ments for quality. In 1997, the JWPCP generated 119,000 dry tons of Class B
biosolids that meet the Part 503 Biosolids Rule high-quality pollutant concentra-
tion limits.
JWPCP operation and maintenance costs in 1997 were approximately $50 mil-
lion. These costs would have been considerably higher if not for various cost
saving measures implemented on site, such as using digester gas to produce
steam for heating, fuel pump engines, and generate electrical power. These
measures allowed JWPCP to be energy self-sufficient and save nearly $5 mil-
lion in 1997. Another cost saving measure has been to enhance the dewatering
performance of the centrifuges, resulting in a major reduction in cake production
and a savings of several million dollars.
Because of the tremendous volume served by JWPCP, the county developed
various ways to manage biosolids in the last several years. This diversity
ensures that no one contractor, locality, or management practice is relied on so
heavily that its absence in the program would threaten the CSDLAC's ability to
handle its biosolids. The program currently consists of four different manage-
ment practices in five counties at seven independent sites that are located up to
200 miles from JWPCP. The four biosolids management practices include: land
application, which accounts for 76 percent of the system's biosolids; injection
into a cement kiln, which accounts for another 12 percent of the biosolids and
helps reduce the levels of nitrogen oxide (NOX) air emissions from the cement
making process; composting, which has been moved off site to two privately
operated facilities; and landfilling, which accounts for approximately 12 percent
of the system's biosolids. CSDLAC is in an advantageous position because it
owns and operates a sanitary landfill. The landfill adds flexibility to the entire
biosolids system by providing disposal capacity when conditions might be
unsuitable for land application.
Diversity thrives on a continuous evaluation of new alternatives. The CSDLAC
has a long history of biosolids processing research and development. An exam-
ple is the construction of a demonstration (2 dry tons per day) in-vessel com-
posting unit combined with a CSDLAC-patented air pollution control system that
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Beneficial Use of Biosolids Section Five
produces virtually no odors or pollutant emissions. CSDLAC also plays an active
role in local and statewide organizations that promote biosolids use and guide
the development of new regulations that address the public's needs while
encouraging beneficial use.
5.3.3 City of Austin, Texas
The City of Austin Water and Wastewater Utility has operated a successful
biosolids recycling program since 1986. Austin's biosolids recycling program
receives approximately 500,000 gallons, or 50 dry tons, of biosolids daily from
the city's three wastewater treatment plants. The biosolids are mixed in a flow
equalization basin and thickened to 6 to 8 percent solids content before being
anaerobically digested. After anaerobic digestion, the biosolids are dried in a
mechanical dewatering unit or directed to one of five, 5-acre, open-air concrete
drying basins and dried to a solids concentration of 15 to 25 percent.
About 55 percent of the dried biosolids are mixed with bulking agents (including
yard and tree trimmings), windrow composted, and sold as Dillo Dirt® to the gen-
eral public through registered vendors. This compost product is used as a soil
conditioner for residential lawns and flower gardens and complies with Part 503
Biosolids Rule requirements for Class A pathogen and vector attraction reduc-
tion. Approximately 20,000 cubic yards of Dillo Dirt® are produced annually, with
95 percent sold for $7 per cubic yard to registered vendors including landscap-
ers, nurseries, and garden centers. The remaining 5 percent is given away to
other city departments and local nonprofit organizations. Due to the success of
marketing efforts, the demand for Dillo Dirt® often exceeds the supply.
The remaining 45 percent of dewatered biosolids cake meets Part 503 require-
ments for Class B pathogen and vector attraction reduction and is land applied
to a farm where hay and pecans are grown.
The Austin program enjoys strong public acceptance resulting from public edu-
cation and outreach efforts, tours, positive media coverage, and strict adher-
ence to permit requirements. The city has demonstrated the benefits of
biosolids-based soil amendments in various local projects. Also, in a jointeffort
with the Texas Department of Transportation, the city has demonstrated the
benefits of using compost to increase vegetation along Texas highway
roadsides.
The annual operating budget for the Hornsby Bend Biosolids Management
Plant, the city's centralized biosolids treatment and use facility serving a popula-
tion of 550,000, is approximately $3 million. Revenues generated through the
sale of Dillo Dirt® and the land application of dried biosolids exceeds $150,000
annually. In addition, all of the city's yard and tree trimmings are recycled by the
program, resulting in approximately $500,000 in avoided landfill disposal costs
per year.
Austin's biosolids recycling program has prospered through many challenges,
including the lack of usable equipment and bulking agents for compost and the
50
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Beneficial Use of Biosolids Section Five
lack of space for a compost pad. A unique and successful partnership between
the multiple city departments, including solid waste services, electric utility,
parks and recreation, and water and wastewater, has allowed the program to
expand by sharing costs for additional equipment and personnel.
5.3.4 Columbus, Ohio
Several years ago, when federal funding for new incinerators was unavailable,
EPA encouraged the city of Columbus to establish a biosolids beneficial use
program. In response, the Columbus Department of Public Utilities established a
biosolids recycling program through three city-owned facilities: Columbus
Compost Facility, Southerly Wastewater Treatment Plant, and the Jackson Pike
Wastewater Treatment Plant.
The Jackson Pike facility handled 78 MGD of wastewater and produced approxi-
mately 15,400 dry tons of biosolids in 1997. Biosolids are stabilized in an anaer-
obic digester on site with a 58 percent volatile solids reduction. A portion of the
biosolids from the Jackson Pike Plant, locally distributed as Bio-Rich®, is applied
to agricultural areas using a subsurface injection process. The remainder of the
biosolids is incinerated. Biosolids produced by the Jackson Pike Plant are cate-
gorized as Class B biosolids products under Part 503.
In 1997, the Southerly facility treated 82 MGD of wastewater and produced
28,400 dry tons of biosolids, of which 3.8 percent was stabilized using alkaline
treatment on site, 30.5 percent was composted, 8 percent was landfilled, and
the remainder was incinerated during production of "Flume Sand." A product of
incineration, Flume Sand is a fine red sand that absorbs water more readily,
costs less, and is less abrasive than natural sand. It is used throughout the
Columbus area as an athletic-field amendment. Sales and distribution of Flume
Sand were suspended in June 1997 once the pilot project came to an end,
because the city failed to acquire state approval to finalize the program due to a
lack of state environmental standards. The city is currently preparing a plan for
distribution of Flume Sand that will be submitted to the state for approval.
A portion of the biosolids is diverted from the dewatering centrifuges to lime sta-
bilization, then land applied by subsurface injection at 6 percent total solids. The
remaining biosolids and raw primary biosolids are blended and dewatered to 20
percent total solids for composting or 24 percent total solids for incineration. In
the composting operation, the dewatered biosolids cake is composted using
aerated static piles. It is then placed in windrows to cure for 60 days, producing
a Class A product according to the Part 503 Biosolids Rule. The compost is sold
in bulk and bags as Corn-Til® to the general public for use as a soil amendment.
From 1994 to 1997, the city of Columbus averaged 9,800 dry tons of Corn-Til®
sales per year.
The city's biosolids management program has proved to be cost-effective and
adaptable. From 1994 through 1996, Flume Sand use resulted in $92,000 per
year in avoided landfill disposal costs and generated $18,190 per year in rev-
enues. During that same period, Corn-Til® also generated $263,250 per year in
51
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Beneficial Use of Biosolids Section Five
additional revenues. Corn-Til® has been so successful that on various occasions
the product has been sold out.
The city's biosolids recycling program is well accepted throughout the communi-
ty, and there is high demand for all the biosolids products. This situation is pri-
marily due to the various marketing programs, education, and outreach efforts of
the city's Department of Public Utilities. Educational programs have focused on
the environmental and neighbor-friendly aspects of the various biosolids prod-
ucts. The program, however, initially had to overcome some obstacles.
Problems with excessive biosolids stockpiling on farmland, low market demand
for biosolids products, odor, and poor public perception (stemming from poten-
tial contamination events brought about by runoff) were encountered. These
problems were solved by diverting a large portion of the biosolids to land appli-
cation without centrifuge dewatering. The biosolids, at 6 percent solids, were
lime stabilized and land applied by injection, which reduced odors (when com-
pared to surface-applied cake biosolids), reduced concerns about runoff, and
eliminated field stockpile problems. Diverting a large portion of biosolids from
the dewatering process also helped improve the performance of the centrifuges
and, indirectly, the incinerator, as a result of the higher solids content of the final
dewatered cake. Furthermore, by increasing the total solids content of the
biosolids, the centrifuges also reduced compost material handling costs.
5.3.5 Charlottesville, Virginia
The Rivanna Water and Sewer Authority oversees the operation of the Moores
Creek Advanced Wastewater Treatment Plant in Charlottesville, Virginia, which
is located approximately 120 miles southwest of Washington, DC. The plant
began operating in 1981 and today serves a population of 75,000 (26,000 con-
nections) from the city of Charlottesville and portions of surrounding Albemarle
County. The plant treats 11 MGD of wastewater and has a design capacity of 15
MGD. The plant is equipped with primary, secondary, and tertiary treatment sys-
tems, which produce a total of approximately 7,500 cubic yards of dewatered
biosolids per year on average. Wanting to be on the cutting edge of wastewater
management, the city of Charlottesville began to look into ways it could use its
biosolids beneficially while saving landfill disposal costs. As a result, the Moores
plant began composting its biosolids in 1984. Today, the facility produces and
sells 5,700 cubic yards of compost annually for use as a soil amendment. The
remaining 1,500 cubic yards (25 percent) of biosolids is land-applied or used as
landfill cover. The plant hopes to begin composting 100 percent of its biosolids
in the future.
Once filtered from wastewater, the solids are anaerobically digested. Methane
gas, approximately 95,000 cubic feet per day produced by the digestion
process, is used to operate gas engines that run the blowers providing air for
the aeration basins used in the secondary and tertiary treatment stages. Water
heated using waste heat from these engines also helps heat the digesters and
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Beneficial Use of Biosolids Section Five
some of the buildings at the plant. After digestion, the solids are dewatered in a
diaphragm filter press (plate-and-frame filter press), which removes about
65 percent of the water. From there, the biosolids are ready for use in the com-
posting process.
The biosolids are transported to an adjoining compost area on the plant premis-
es. Biosolids from the wastewater treatment plant are mixed with wood chips at
a ratio of three parts wood chips to one part biosolids. The facility annually uses
4,000 cubic yards of wood chips that come from chipped pallets purchased from
a pallet company located in Richmond, Virginia, for $5 per cubic yard ($18 to
$22 per ton). The biosolids/wood chip mixture is placed on a bed of fresh wood
chips covering an asphalt pad in a series of static piles protected from the
weather. The compost temperature is monitored and maintained between 55° C
and 77° C (131° F and 170° F) for 5 days. The temperature probes are then
removed and the piles are left to compost for an additional 10 days, for a total of
15 days to complete the active composting process. The compost is then cured
for 1 month and is tested for salmonella and metals on a quarterly basis.
The Moores Creek plant's compost is made available for sale once a month to
the public, selling for $12 per cubic yard in bulk and $15 per cubic yard for small
purchases. Some compost is also manually bagged and sold for $3.50 per
40-pound bag. It is sold to individuals, nurseries, farmers, and local park and
recreation departments for use on lawns, flowers, house plants, trees, shrubs,
and vegetables.
53
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References
Bastian, R., 1997. "The Biosolids (Sludge) Treatment, Beneficial Use, and
Disposal Situation in the USA." European Water Pollution Control
Journal. Vol. 7, No. 2, pp. 62-79. March.
BioCycle, 1991. "Sludge Management Practices in the U.S." March.
BioCycle, 1997. "Biosolids Management Practices in the U.S." May.
BioCycle, 1998. "Biosolids Management Update." January.
Council of Economic Advisors, 1999. Economic Report of the President: 1999.
U.S. Government Printing Office, Washington, DC.
Garland, G., Grist, T, and R. Green, 1995. "The Compost Story: From Soil
Enrichment to Pollution Remediation. BioCycle. October.
Glenn, Jim, 1998. "State of Garbage." BioCycle. April.
Goldstein, N. and D. Block, 1997. "Biosolids Composting Holds its Own."
BioCycle. December.
Metcalf & Eddy, 1991. Wastewater Engineering. 3rd ed. New York: McGraw Hill
Publishing.
Millner, P.D, S.A. Olenchock, E. Epstein, R. Rylander, J. Haines, MD, J. Walker,
B.L. Ooi, E. Home, and M. Maritato, 1994. "Bioaerosols Associated
with Composting Facilities," Compost Science & Utilization. Autumn.
National Research Council, 1996. Use of Reclaimed Water and Sludge in Food
Crop Production. National Academy Press, Washington, DC.
Snow, Darlene, 1995. "Getting Down to Earth with Trash and Sludge." MSW
Management. January/February.
Stehouwer, R. and A. Wolf, 1998. Pennsylvania Sewage Sludge Quality Survey:
1978-1998. Pennsylvania State University.
USDA, 1997. Interagency Agreement between the U.S. EPA and USDA
Agricultural Research Service with Respect to Beneficial
Management of Municipal Biosolids and Other Municipal and
Agricultural Organic and Inorganic Recyclable Products.
54
-------
References
USDA, 1998. Agricultural Uses of Municipal, Animal, and Industrial Byproducts.
Agricultural Research Service: Conservation Research Report
Number 44. January.
U.S. EPA, FDA, and USDA, 1981. Land Application of Municipal Sewage
Sludge for the Production of Fruits and Vegetables: A Statement of
Federal Policy and Guidance.
U.S. EPA, 1984. Environmental Regulations and Technology. Use and Disposal
of Municipal Wastewater Sludge. EPA625-10-84-003. September.
U.S. EPA, 1989. Regulatory Impact Analysis of the Proposed 40 CFR Part 503
Rule. PB89-136634. February.
U.S. EPA, 1991. Regulatory Impact Analysis for Final Criteria for Municipal Solid
Waste Landfills. PB92-100847. September.
U.S. EPA, 1992a. Technical Support Document for the Land Application of
Sewage Sludge. PB93-110583. November.
U.S. EPA, 1992b. Technical Support Document for Pathogens and Vector
Attraction Reduction in Sewage Sludge. PB93-110609. November.
U.S. EPA, 1993a. Regulatory Impact Analysis of the Part 503 Sewage Sludge
Regulation. PB93-110625. February.
U.S. EPA, 1993b. Composting of Yard Trimmings and Municipal Solid Waste.
Office of Solid Waste and Emergency Response. November.
U.S. EPA, 1994a. A Plain English Guide to the EPA Part 503 Biosolids Rule.
EPA832-R-93-003. September.
U.S. EPA, 1994b. Seminar Publication: Design, Operation, and Closure of
Municipal Solid Waste Landfills. EPA625-R-94-008. September.
U.S. EPA, 1994c. Biosolids Recycling: Beneficial Technology for a Better
Environment. EPA832-R-94-009. June.
U.S. EPA, 1995a. Process Design Manual: Land Application of Sewage Sludge
and Domestic Septage. EPA625-R-95-001. September.
U.S. EPA, 1995b. A Guide to the Biosolids Risk Assessments for the EPA Part
503 Rule. Office of Wastewater Management. EPA832-B-93-005.
September.
U.S. EPA. Needs Survey, Report to Congress, 1984, 1986, 1988, 1992, 1996.
Assessment of Needed Publicly Owned Wastewater Treatment
Facilities in the United States. Office of Municipal Pollution Control.
U.S. EPA, 1997a. Compost—New Applications for an Age-Old Technology.
Office of Solid Waste and Emergency Response. EPA530-F-97-047.
October.
55
-------
References
U.S. EPA, 1997b. Biosolids Management, Use and Disposal. Office of Water.
U.S. EPA, 1998a. An Analysis of Composting as an Environmental Remediation
Technology. EPA530-R-98-008. April.
U.S. EPA, 1998b. Organic Materials Management Strategies. Office of Solid
Waste and Emergency Response. EPA530-R-97-003. May.
U.S. EPA, 1999. Cutting the Wastestream in Half: Community Record Setters
Show How. Institute for Local Self-Reliance. Unpublished document.
Walker, J., 1998. "Biosolids Management, Use and Disposal." In: Encyclopedia
of Environmental Analysis and Remediation." Robert A. Meyers, ed.
John Wiley & Sons, Inc.
Walker, J. M. and R. N. Albee, 1994. Yes, But What About the Liability? EPA
and Farm Credit Bank Find Fertile Ground for Dealing with Land
Application Liability Issues. In "Water Connection." Newsletter of the
New England Interstate Water Pollution Control Commission. Vol 11,
2:10-11, Fall.
Water Environment Federation (WEF), 1997. National Outlook: State Beneficial
Use of Biosolids Activities. June.
56
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Appendix
Biosolids Generation,
Use, and Disposal
Methodology and Results
A.I Introduction
Biosolids generation, use, and disposal estimates made in this report in
Section Three and projections of generation, use, and disposal in Section
Four are based on a number of information sources. Estimates of
biosolids generation were based primarily on the 1988 National Sewage Sludge
Survey (NSSS) and the 1984 through 1996 Needs Surveys, as discussed in
detail in Section A.2 and A.4 of this appendix. Several other sources of informa-
tion on generation rates and use and disposal methods were also investigated,
such as the Water Environment Federation's (WEF) 1997 report and Robert
Bastian's 1997 paper, which provide data estimates on biosolids generation,
use, and disposal in 1995 and 1996, respectively. 0/oCyc/e(1991, 1997, and
1998) also provides information on generation and use and disposal methods.
The biosolids generation estimates from the WEF report or Bastian (1997) were
considered, but this report also made additional estimates as described in this
appendix to verify the results of these other studies. This appendix discusses
the major data sources used for estimating generation, use, and disposal of
biosolids; the strengths and weaknesses of the data sources; and the method-
ologies and results of this analysis.
In 1988, EPA conducted the NSSS, a survey of a random sample of 479 pub-
licly owned treatment works (POTWs) to support the development of the Part
503 Biosolids Rule. The survey produced a statistically valid estimate of the
amounts of biosolids used or disposed of by POTWs using at least secondary
wastewater treatment processes. At that time, the number of POTWs using at
least secondary wastewater treatment totaled approximately 11,400. The survey
was stratified on the basis of POTW size (amount of wastewater processed
daily) and principal use or disposal method. The survey also collected data on
pollutant concentrations in biosolids, from which EPA could determine whether
biosolids would meet the criteria being developed under the Part 503 Biosolids
57
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Methodology and Results Appendix
Rule. At the time, EPA considered the NSSS estimate of the amount of biosolids
used or disposed of as the most accurate estimate to date. The NSSS, howev-
er, is no longer current and also does not provide estimates of biosolids genera-
tion by POTWs using primary wastewater treatment processes12 or by privately
or federally owned treatment works. Most importantly, the NSSS cannot provide
an estimate of current practices because the survey was undertaken before the
Part 503 Biosolids Rule was finalized. The Part 503 rule has had an impact on
POTWs' choices of use or disposal methods, since it generally was written to
encourage POTWs to choose beneficial use rather than disposal if the biosolids
were of sufficiently high quality (U.S. EPA, 1993a).
The WEF (1997) report, which was conducted in cooperation with the
Association of Metropolitan Sewer Agencies (AMSA) using an EPA grant, is an
inventory of biosolids generation, beneficial use, and disposal practices for
1995. WEF surveyed 162 AMSA members and received 117 responses. Twenty-
five states and federal regulators also responded to the survey. Additionally, the
report presented information on biosolids beneficial use practices, appropriate
regulations, and attitudes. Although the information in this report is current and
represents half the wastewater flow in this country, the survey primarily captured
data from AMSA members, which tend to be the largest POTWs. The POTWs
associated with the other half of the flow might not operate like the POTWs rep-
resented by the WEF data, although the addition of data from other sources
might have helped reduce the large-POTW bias in the data. Despite possible
drawbacks, the WEF data does provide breakdowns of biosolids quantities by
use and disposal methods that can easily be adapted to the categories of use
and disposal methods used in this report.
Data from Bastian (1997) are current for 1996. That paper, published in
European Water Pollution Control (March 1997) presented results of a survey of
state regulators who were asked for 1996 data on total biosolids production and
the percentage of biosolids used or disposed of by land application, surface dis-
posal, incineration, and other means. The paper also describes changes in
biosolids management and treatment and discusses obstacles to biosolids man-
agement, such as public acceptance and liability issues. Unless the state is
authorized as the permitting authority, however, it might not have detailed
records of biosolids generation, use, and disposal that would best support a
national estimate. Furthermore, some states do not have easy access to permit
information (i.e., in database form) from which viable aggregate data might be
drawn. Finally, much of the more detailed data are kept primarily at the POTW
level (particularly among the smaller POTWs, which are not required to report
any of their recordkeeping data to the states unless specifically requested or
unless their biosolids quality triggers specific reporting requirements). Therefore,
although some states have excellent data from which to compile state estimates
of biosolids generation, use, and disposal, other states may only be able to esti-
mate roughly the amounts of biosolids generated, used, or disposed of.
Additionally, the WEF report further refines the breakdown of use and disposal
12For purposes of this appendix, the term primary processes means those considered less than
secondary and the term secondary processes means those considered at least secondary.
58
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Methodology and Results Appendix
categories, originally presented in Bastian (1997), in a way that is effective for
the purposes of this report.
Researchers at BioCycle, a journal that covers recycling and management of
biosolids and other organic wastes, surveyed state regulators regarding
biosolids generation and management in 1989, 1996, and 1998. The surveys
provide a state-by-state breakdown of management practices according to land
application, composting, lime stabilization, heat drying or pelletizing, landfilling,
incineration, or surface disposal. The journal also conducts an annual survey of
biosolids composting operations. Again, because these are state data, the infor-
mation can vary from sketchy to excellent, depending on the level of data collec-
tion and management at the state level. As discussed below, the most recent
survey (1997 data) provides data on both total quantities of biosolids generated
(in dry tons) and use and disposal practices for 34 states (BioCycle, 1998).
Because only 34 states with adequate data for the purposes of this report are
represented in the data, any conclusions drawn from these data may be some-
what limited.
All these sources of information on generation, use, and disposal of biosolids
have their relative strengths and weaknesses. Ultimately, the choice was made
to estimate biosolids generation using the NSSS to provide one more data point
for consideration in addition to analyzing data from the 1997 WEF report and
Bastian (1997) and to use the 1997 WEF report for the distribution of use and
disposal methods. The BioCycle (1998) data and the NSSS were also used as
additional support for the estimates of use and disposal methods. As the results
show later in this appendix, the biosolids generation estimates from the WEF
(1997) report, Bastian (1997), and this report are remarkably similar. We esti-
mate that 6.7 million U.S. dry tons of biosolids were generated for use or dis-
posal in 1996 (both 1996 and 1998 estimates are made in this report). Our
estimate falls between the 1995 WEF estimate of 6.4 million dry tons and the
1996 Bastian (1997) estimate of 6.9 million U.S. dry tons. This estimate is used
in this report for biosolids generated by POTWs practicing secondary or above
wastewater treatment (the major source of biosolids in this country), along with
additional information from other sources about primary treatment biosolids and
those generated by privately and federally owned facilities (U.S. EPA, 1993a).
This report uses the 1997 WEF study primarily as the basis for determining use
and disposal practices in 1998, because the combined data from POTWs and
states are likely to be more accurate than data strictly from the states alone.
The WEF data were also chosen because of how the use and disposal cate-
gories are broken out.
A.2 Estimate of Biosolids Generation in 1998
This section describes our estimate of the quantities of biosolids generated in
1996 and then further estimates the quantities generated in 1998. These esti-
mates are primarily based on the 1988 NSSS (results of which are reported in
the Regulatory Impact Analysis (RIA) for the Part 503 Biosolids Rule [U.S. EPA,
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Methodology and Results Appendix
1993a]) and the 1988 through 1996 Needs Surveys.13 The NSSS does not
address biosolids generation at POTWs using only primary treatment processes
or biosolids generation at privately or federally owned treatment works, there-
fore, additional information was incorporated from the RIA and the Needs
Surveys to estimate these quantities. To determine quantities of biosolids gener-
ated by POTWs using primary treatment processes, this report used an esti-
mate of primary biosolids generation from the RIA (U.S. EPA, 1993a), which
also was based on the 1988 Needs Survey. For POTWs using at least second-
ary treatment processes, this report used the NSSS and the Needs Surveys.
We estimated privately and federally owned treatment works biosolids quantities
using information developed in the RIA (U.S. EPA, 1993a). This stratification
also was necessary to account for differences in biosolids generation rates at
POTWs using either primary or secondary treatment processes, because pri-
mary processes can generate different amounts of biosolids per gallon of waste-
water processed than secondary processes. The following discussion shows the
development of an estimate of biosolids generation at POTWs, then follows with
the development of an estimate of biosolids generation at privately and federally
owned treatment works.
A.2.1 Estimate of 1998 Biosolids Generation at POTWs
Methodology
This report begins with an estimate of 1996 biosolids generation because 1996
is the most recent year for which data on total U.S. wastewater flow is available.
The 1998 estimate is based on a projection from this 1996 base year.
The key assumption in this report for first estimating 1996 biosolids generation
at POTWs is that once biosolids quantities are split between primary and sec-
ondary processes, the quantity of biosolids generated per gallon of wastewater
treated at POTWs would not be substantially different in 1996 than it was in
1988.14Two Biosolids Generation Factors (BGFs), therefore, were created for
estimating biosolids quantities resulting from each process, one for primary
treatment and one for secondary and above. Each of the BGFs (BGFprimary and
BGFsecondary) is equal to the biosolids estimated to be generated by each treat-
13The 1984 and 1986 Needs Surveys also are used to identify trends in wastewater flow over time
later in this appendix.
"Tertiary processes create additional biosolids per gallon of wastewater treated than either pri-
mary or secondary processes, and to the extent that wastewater going to tertiary treatment
processes has increased since 1988, this approach could slightly underestimate biosolids genera-
tion rates. This underestimation was not corrected because summary data for the NSSS did not
distinguish between biosolids generated in secondary treatment processes and those generated
in tertiary treatment processes. The amount of wastewater going to tertiary treatment is, however,
relatively small compared to that going to secondary treatment. Furthermore, biosolids generation
might be slightly overstated (particularly for projections made later in this section) because de-
watering processes are changing from ferric and lime processes to polymer processes, which
reduce the volume of biosolids generated. Also, with bans on phosphates in detergents, fewer
chemicals are needed for removing phosphates from wastewater, leading to further reductions in
biosolids volume.
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Methodology and Results Appendix
ment group in 1988 divided by the 1988 annual flow of wastewater treated by
each treatment group. The formula below illustrates an example of this
calculation:
Biosolids Generated in 1988 Primary Processes (U.S. dry tons) _ BGF ...
- primary (1)
Total 1988 Annual Primary Wastewater Flow (MGD)
For this calculation, estimates of primary and secondary biosolids generation in
1988 were obtained from the RIA supporting the Part 503 Biosolids Rule (U.S.
EPA, 1993a). For POTWs using secondary processes, the estimates of
biosolids disposal and use from the 1988 NSSS (as reported in U.S. EPA,
1993a) were used to represent the amount of biosolids generated from second-
ary and above treatment operations.15 The 1988 NSSS data were not used to
estimate primary treatment process biosolids because the survey did not gather
data on biosolids generated exclusively from primary processes. To identify
quantities of biosolids generated from primary processes in 1988, the estimate
of primary biosolids amounts that was developed in the RIA (U.S. EPA, 1993a)
was used. This estimate was based on information obtained from the 1988
Needs Survey and engineering estimates.
Annual wastewater flow numbers associated with primary and secondary treat-
ment were then obtained. The amount of 1988 annual flow for each treatment
group (both primary and secondary) was taken directly from the 1988 Needs
Survey. The 1996 Needs Survey data did not distinguish the flow rate by level of
wastewater treatment process, however. We assumed that the flow for each
treatment group was proportionate to the total population served for each treat-
ment level reported in 1996.16 For example:
Population Served by Primary Treatment _ Percent of Total Flow Attributable /2)
Total Population Served to Primary Treatment
and
Population Served by Secondary Treatment _ Percent of Total Flow Attributable /3\
Total Population Served to Secondary Treatment
15Biosolids can be generated in one year and used or disposed of in another year. It is assumed
that the NSSS estimate of use or disposal in 1988 is roughly equivalent to generation, since some
biosolids that were used or disposed of in 1988 were generated in previous years, whereas some
biosolids that were generated in 1988 were not used or disposed of until later years. Although the
NSSS did ask for data on generation, this information did not appear to be presented in any sum-
mary document reviewed. NSSS data on biosolids generation might have been of limited accura-
cy, since respondents with treatment lagoons who did not dispose of biosolids in 1988 would have
needed to estimate generation rates.
16ln making this calculation, the 1996 Needs Survey treatment levels were collapsed into two
groups, primary treatment and secondary treatment. The primary treatment group is the same as
the "less than secondary treatment" category, and the at-least-secondary treatment category
includes the "secondary," "tertiary," and "no discharge" categories.
61
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Methodology and Results Appendix
The percentages of population served for each treatment group in 1996 were
applied to the total 1996 flow to estimate the flow attributable to POTWs in each
treatment category. The applicable BGFs were then multiplied by the estimated
1996 flow for each treatment group (primary and secondary). For example:
BGF Primary x Total 1996 Annual Flow _ Biosolids Generated in 1996 from /^\
for Primary Treatment (MGD) Primary Flow (U.S. dry tons)
and
BGF Secondary x Total 1996 Annual Flow _ Biosolids Generated in 1996 from /g\
for Secondary Treatment (MGD) Secondary Flow (U.S. dry tons)
These results provided an estimate of the quantity of biosolids generated in
1996 for both the primary and the secondary treatment groups, the sum of
which gave the total biosolids (in U.S. dry tons) generated by POTWs in 1996.
The estimate for 1996 was extrapolated to 1998 on the basis of an analysis pre-
sented in Section A.4. As Section A.4 discusses, primary treatment wastewater
has been declining on average about 4 percent per year, and secondary and
above treatment wastewater has been increasing on average about 2 percent
per year. These increases and decreases are incorporated into projections of
wastewater flow in those two treatment categories to derive estimates of
biosolids generation in 1998.
Results17
As shown in Table A-1, we estimate (using Equation 1) that the BGFprimary is
203. The BGFsecondary is 206.18 We also estimate that, in 1996, primary flow
was 2,900 MGD and secondary flow was 29,200 MGD using Equations 2 and 3
(see Table A-2). These flow numbers and the BGFs calculated in Table A-1 are
"Throughout the tables in this appendix, totals might not appear to compute exactly because of
rounding.
18Both factors fall within the expected ranges of biosolids generation from wastewater treatment
processes, although generally one might expect the difference between BGFprimary and
BGFsecondary t° De somewhat greater because of the ability of secondary processes to remove
additional pollutants from wastewater. There are several reasons for this result, however. The pri-
mary reason is that many POTWs with secondary wastewater treatment also treat their biosolids
in biosolids treatment processes such as digesters that can dramatically reduce (by up to 90 per-
cent in some cases) the volume of biosolids initially generated in the wastewater treatment
process. Thus, the BGFsecondary factor is associated with the ultimate, not the initial, biosolids vol-
ume generated. Biosolids generated by POTWs that use only primary treatment are much less
likely to be treated in costly biosolids treatment processes that result in large volume reductions.
Another major reason is that BGFprimary and BGFsecondary might not be directly comparable num-
bers. That is, BGFsecondary, rather than being a true estimate of a generation rate, reflects a way
to relate two very different databases (Needs Survey and NSSS), which have very different data
collection methods and sampling approaches, and use them to approximate an increase in
biosolids amounts over time. BGFprimary, on the other hand, relies on engineering estimates and
reflects an engineering-based estimate of a generation rate. Furthermore, the volumes of
biosolids reported in the NSSS reflect the huge variation in the generation of biosolids by second-
ary wastewater treatment processes. Primary wastewater treatment processes generate biosolids
within in a much narrower range of rates.
62
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Methodology and Results
Appendix
used in Table A-2 to calculate the estimate of biosolids generated by POTWs in
1998 using Equation 4 and the projections discussed above. As shown in Table
A-2, we estimate that 0.5 million dry tons of biosolids were generated by
POTWs using primary treatment processes in 1998 and 6.3 million dry tons of
biosolids were generated by POTWs using secondary and above treatment
processes in 1998, for a total of 6.8 million dry tons of biosolids.
Table A-1
Estimate of Biosolids Generation Factor
Treatment Category
Primary
Secondary
1988 Biosolids
Generation (million
U.S. dry tons)
0.875
5.018
1988
Wastewater Flow
(MGD)
4,300
24,400
Biosolids
Generation Factor
(U.S. dry tons/MGD)
203
206
Source: U.S. EPA, 1993a; 1988 Needs Survey (U.S. EPA, 1988).
Table A-2
Estimate of Biosolids Generated by POTWs in 1996 and 1998
Treatment
Group
Primary
Secondary
Total
Population
Served
17,177,500
172,533,400
189,710,900
% of Total
Population
Served
9.05%
90.95%
100.00%
1996
Estimate of
Flow by
POTW Type
(MGD)
2,910
29,300
32,200
1998
Estimate of
Flow by
POTW Type
(MGD)
2,700
30,400
33,100
BGF (U.S.
dry tons/
MGD)
203
206
—
1996
Estimated
Biosolids
Generated
by POTWs
(million U.S.
dry tons)
0.6
6.0
6.6
1998
Estimated
Biosolids
Generated
by POTWs
(million U.S.
dry tons)
0.5
6.3
6.8
Source: 1996 Needs Survey (U.S. EPA, 1996).
A.2.2 Estimate of Biosolids Generation in 1998 from Privately and
Federally Owned Treatment Works
Methodology
The NSSS also did not collect data from privately or federally owned treatment
works, therefore, an estimate of flow from privately and federally owned treat-
ment works presented in the Part 503 RIA (U.S. EPA, 1993a) was used. This
source indicates that flow from these types of treatment works averaged
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Methodology and Results
Appendix
0.09 MGD in 1991 and that about 5,080 treatment works of this type were
known to exist in that year. Thus, 460 MGD of wastewater were estimated to be
processed by privately and federally owned treatment works in 1991. We then
determined that this flow was 1.5 percent of the flow from POTWs in 1992,
according to the 1992 Needs Survey. Also, we assumed that privately and fed-
erally owned treatment works operate like POTWs, with the same proportion of
wastewater going to primary and secondary treatment processes and with the
same BGFs. Therefore, the amount of biosolids estimated for POTWs in 1996
and 1998 was increased by 1.5 percent to account for biosolids generation in
1996 and 1998 by this group of treatment works.
Results
As Table A-3 shows, increasing the 1998 estimates of biosolids generated by
POTWs by 1.5 percent produces a 1998 biosolids generation estimate of 6.9
million U.S. dry tons, with about 0.1 million dry tons attributable to privately and
federally owned treatment works, or about 0.2 million U.S. dry tons more than
that estimated for 1996.
Table A-3
Adjustment for Biosolids Generation From Privately
and Federally Owned Treatment Works
Treatment
Group
Primary
Secondary
Total
1996 Estimate of
Biosolids
Generated by
POTWs (million
U.S. dry tons)
0.6
6.0
6.6
1998 Estimate of
Biosolids
Generated by
POTWs (million
U.S. dry tons)
0.5
6.3
6.8
Factor for
Privately and
Federally Owned
Treatment
Works
1 .5%
1 .5%
1 .5%
Total 1996
Estimate of
Biosolids
Generated by All
Treatments
Works (million
U.S. dry tons)
0.6
6.1
6.7
Total 1998
Estimate of
Biosolids
Generated by All
Treatments
Works (million
U.S. dry tons)
0.6
6.4
6.9a
"Note: Numbers may not add up properly due to rounding.
Source: Table A-2 and U.S. EPA (1993a).
A.2.3 Total Estimate of Biosolids Generation in 1998
Using these above approaches, we estimate that a total of 6.9 million dry tons
were generated in 1998 (see Table A-3). Note that the 1996 estimate is about
6.7 million dry tons, which falls between the two previous estimates of total 1995
and 1996 biosolids production; WEF (1997) estimated 6.4 million dry tons for
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Methodology and Results Appendix
1995, while Bastian (1997) estimated 6.9 million dry tons for 1996. Thus, all
these recent estimates tend to support each other.19
A.3 Estimates of Biosolids Use and Disposal in 1998
Methodology
To estimate the amount of biosolids going to various use or disposal methods,
the WEF (1997) survey data were used and applied toward this report's esti-
mate of 1998 biosolids generation total of 6.9 million dry tons (see Section
A.2.3). The WEF study was chosen over other data sources to calculate per-
centages of biosolids going to various use or disposal methods primarily
because it provides fairly current 1995 data and also is broken down into vari-
ous use and disposal categories in such a way as to provide data that are rele-
vant to this report. It also is the most complete source of current data on use
and disposal practices because it combines state data with POTW data. This
combination of data is useful because some states do not have complete
records of biosolids generation, use, and disposal. The data presented in WEF's
report also are arranged in categories that correspond most appropriately to the
categories of most interest, allowing biosolids management practices to be
divided into the use and disposal categories discussed in Sections Two and
Three of this report.20
WEF divided biosolids management into four categories: land application, sur-
face disposal, incineration, and other. The "other" category included biosolids
used for landfill cover, landfill, composting, and other further stabilized or
enhanced products. The percentages presented in the WEF report were further
adjusted by incorporating the narrative portion of WEF's survey responses to
characterize use and disposal methods more precisely for this report. Specific-
ally, since WEF requested and received detailed responses associated with the
"other" category on a state basis, it was possible to distribute these responses
to the "other" category into the use and disposal categories of interest. There-
fore, these responses were distributed into the following categories: surface dis-
posal and landfilling (including landfill, codisposal, and lagoons), incineration
19Although the WEF (1997) estimate is for 1995, the difference between the 1996 estimate made
in this report and WEF's estimate is about 0.1 million dry tons (using generation trends developed
later in this appendix to compare across years).
20A drawback to this approach is that WEF's sample of POTWs was composed primarily of larger
facilities, as discussed earlier. Smaller POTWs tend to have different use and disposal patterns
than larger POTWs. Therefore, using data based on samples of large POTWs could tend to over-
state some percentages and understate other percentages of biosolids going to various use and
disposal methods. Incineration, for example, is more often practiced by larger POTWs, and small-
er POTWs are often located in rural areas where landfill space is still available and land applica-
tion has been in use for many years. Larger POTWs are often located in urban areas where
dwindling landfill space and public perception have prompted some POTWs to institute land appli-
cation as a method of biosolids management, despite the transport distances involved. Thus, a
survey favoring larger POTWs might slightly overstate incineration and might also slightly over-
state shifts from landfilling to land application since 1988. WEF, however, has supplemented its
POTW data with data from state agencies, lessening the potential for bias.
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Methodology and Results
Appendix
(including incineration and combustion stabilization processes), advanced treat-
ment (including fertilizer, compost, lawn and garden, potted growing media,
lime-stabilized fertilizer, soil amendment, and pelletizing), other beneficial use
(including landfill cover and aggregate), and other (all other unidentified
processes). This adjustment resulted in a total list of six categories for EPA's
needs, including the beneficial use categories of land application, advanced
treatment, and other beneficial use as well as the disposal categories of surface
disposal and landfilling, incineration, and other (i.e., unidentified processes).
Percentages of biosolids use and disposal for the adjusted categories were
applied to the total amount of biosolids generated in 1998, providing an estimate
of the dry tons of biosolids going to each use and disposal method (see Table
A-4). According to these estimates, 60 percent of biosolids generated in 1998
were beneficially used. Broken down further, 53 percent of biosolids generated
in 1998 were land applied or received advanced treatment, such as composting,
and were land applied. An additional 7 percent were otherwise beneficially used
(3 percent were used as landfill cover and 4 percent were used as aggregate).21
Table A-4 presents this breakdown of use and disposal methods based on the
WEF data. BioCycle (1998) also notes a national trend toward beneficial use of
biosolids, with 34 states indicating overall that 61 percent of their biosolids are
beneficially used.
Table A-4
Biosolids Use and Disposal Based on WEF Survey Data (million U.S. dry tons)
Year
1998
Percent of
Total
Beneficial Use
Land
Application
3.6
52%
Advanced
Treatment
0.07
1%
Other
Beneficial
Use
0.5
7%
Total
4.1
60%
Disposal
Surface
Disposal/
Landfill
1.2
17%
Inciner-
ation
1.5
22%
Other
0.07
1%
Total
2.8
40%
Total
6.9
1 00%
Source: WEF (1997) and estimates of the distribution of "other" use or disposal method responses in the WEF survey (see
text).
The 52 percent of biosolids going to land application without advanced treat-
ment probably includes some biosolids that did, in fact, receive advanced
treatment (defined here as heat treated, lime stabilized, composted, pelletized,
or otherwise generally meeting Class A pathogen and vector control
21The beneficial use category might be somewhat understated since this report does not distin-
guish between incineration for disposal and incineration where energy recovery or ash use is
practiced, as discussed in Section Two.
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Methodology and Results
Appendix
requirements—see Section Two), since the WEF survey did not specifically ask
respondents to identify amounts of biosolids that received advanced treatment.
Thus, we adjusted this figure further, using BioCycle (1998) data on composted
biosolids, to account more accurately for the amount of biosolids that received
advanced treatment before land application.
In BioCycle (1998), a total of 34 states provided adequate data for the purposes
of this analysis. Data were excluded from some states, such as Louisiana, that
reported biosolids volumes in wet tons or that provided breakdowns but no total
quantities or total quantities with no breakdowns. Several caveats associated
with these data must be noted, however. First, BioCycle's data collection effort
for biosolids receiving advanced treatment is likely to be the most extensive of
all current efforts, since this journal specifically tried to capture data on
advanced treatment from the states. Not all states, however, provided sufficient
data to clearly break out composted biosolids from biosolids that are normally
land applied without advanced treatment because a large portion of advanced
treatment biosolids are ultimately land applied.
Second, these data can be used for extrapolation only with the assumption that
the "missing" states are not significantly different from the ones that did provide
data (an assumption that might not be true). Finally, the data are only as good
as the states' records. Some states have accurate recordkeeping, while others,
as mentioned in the article, are still in the process of developing accurate
recordkeeping. Nevertheless, state data are likely to become more accurate
over time.
BioCycle columns "land application," "composting," "lime stabilization," and "heat
treatment/pelletizing" were grouped into a beneficial use category and the "land-
fill," "surface disposal," "incineration," and "other" columns were grouped into a
disposal category. A total of 61 percent of the biosolids fall into the beneficial
use category and 39 percent fall into the disposal category (compared to the
WEF data that indicate that 60 percent could be considered beneficial use and
40 percent disposal, using similar assumptions about classifications). Table A-5
shows how these two sets of data overlap in the area of advanced treatment
and other beneficial use.
Table A-5
Comparison of WEF (1997) and BioCycle (1998)
Data on Use and Disposal Practices
Data
Source
WEF
BioCycle
Land
Application
52%
47%
Advanced
Treatment
1%
Other
Beneficial
Use
7%
1 4%a
Surface
Disposal/
Landfill
17%
19%
Incineration
22%
20%
Other
1%
1%
Sources: WEF (1997); BioCycle (1998).
a6.8 percent is composted, 2.7 percent is lime stabilized, and 4.8 percent is heat dried/pelletized.
67
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Methodology and Results Appendix
According to BioCycle's data, about 14 percent of the total biosolids appear to
receive advanced treatment. As discussed earlier, it is clear from footnotes in
the tables, as well as caveats in the text, that the land application category in
the BioCycle data includes some biosolids that were lime treated or received
advanced treatment. Thus, the quantity of biosolids listed in BioCycle data treat-
ment categories are underestimated. Even so, these quantities of biosolids that
received advanced treatment, according to BioCycle, are still larger than the
estimates based solely on WEF data. Using this assumption, we estimate that
of the 14 percent of the biosolids that BioCycle presents as receiving advanced
treatment, 7 percent received advanced treatment and were later land applied
while an additional 7 percent received advanced treatment and were beneficially
used (as landfill cover and aggregate).
Even the 0/oCyc/e-based estimate might understate the amount of biosolids that
receive advanced treatment, therefore, one more approach was used to esti-
mate this figure. According to the NSSS, in 1988 an estimated 1,519,700 U.S.
dry tons of biosolids were land applied, of which 329,900 U.S. dry tons were
composted, sold, or otherwise likely to have been applied to public contact sites.
Biosolids that were composted, sold, or applied to public contact sites (which
implies advanced treatment),22 therefore, constituted 22 percent of all land-
applied biosolids in 1988 (U.S. EPA, 1993a). This percentage of biosolids going
to land application may actually belong in the advanced treatment category.
Thus, we estimate that 12 percent (12 percent is 22 percent of the 53 percent of
biosolids that are land applied or receive advanced treatment) of all biosolids
generated in 1998 might have been treated and land applied.23 The percentages
presented in Table A-4 were then adjusted to reflect this assumption, as dis-
cussed below.
Results
Based on the adjustments to WEF data, out of the total 6.9 million dry tons, 2.8
million dry tons are estimated to have been land applied without any special
treatment, such as composting or pelletizing, 0.8 million dry tons are estimated
to have been land applied after special treatment, and 0.5 million dry tons are
estimated to have been beneficially used in some other manner (i.e., as landfill
cover or aggregate), for a total of 4.0 million dry tons estimated to have been
beneficially used. It also is estimated that 1.2 million dry tons were surface dis-
posed, 1.5 million dry tons were incinerated, and 0.1 million dry tons were
disposed of in another manner.
22Given the public access restrictions outlined in the Part 503 Biosolids Rule associated with
applying biosolids to public contact sites that have not been further treated (for example, by com-
posting), it is assumed that most biosolids currently applied to public contact sites are likely to
have received advanced treatment.
23This estimate might still understate the quantity of biosolids treated, since any trend toward
advanced treatment of biosolids is not captured using this approach. It is believed, however, that
12 percent receiving advanced treatment and land applied might be a better estimate than 7 per-
cent receiving advanced treatment and then land applied.
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Methodology and Results
Appendix
Table A-6
Estimates of Biosolids Use and Disposal With Adjustments for Biosolids
Receiving Advanced Treatment (million U.S. dry tons)
Year
1998
Percent of
Total
Beneficial Use
Land
Application
2.8
41%
Advanced
Treatment
0.8
12%
Other
Beneficial
Use
0.5
7%
Total
4.1
60%
Disposal
Surface
Disposal/
Landfill
1.2
17%
Inciner-
ation
1.5
22%
Other
0.01
1%
Total
2.8
40%
Total
6.9
1 00%
Source: Table A-5 with adjustments for advanced treatment.
The amount of biosolids likely to be going to municipal solid waste facilities can
be estimated after some assumptions are made. First, we assumed that all sur-
face-disposed biosolids are disposed of in municipal solid waste landfills.24 This
assumption is reasonable given the small amount of biosolids believed to be
disposed of in biosolids monofills, piles, and lagoons or applied to land strictly
for disposal (see discussion in Section Two of this report), and given the results
of the BioCycle (1998) survey, which indicate less than 2 percent of biosolids
are surface-disposed among the 34 states with adequate data. Second, for the
purpose of this report, it is assumed that no incinerated biosolids are coinciner-
ated with solid waste, although this might occur in rare instances.25 The
advanced treatment category is the only category that is likely to be split
between municipal solid waste facilities and others, where municipal solid waste
facilities are defined as commercial, noncommercial, or municipal entities that
compost municipal solid waste (including yard trimmings) with biosolids. It is
estimated that, based on the percentage of biosolids estimated to be used as
landfill cover as reported in the WEF (1997) report (3 percent), 0.2 million dry
tons of biosolids were used as landfill cover (landfill cover was included in the
"other beneficial use" category). At a minimum, 1.4 million dry tons, or 20 per-
cent of total biosolids generated in 1998, are likely to have been managed at
municipal solid waste facilities through landfilling or use as a landfill cover.
Some additional amount of biosolids might be composted at municipal solid
waste facilities (as defined above) for land application, but this quantity is not
known. Numbers presented in Section Three include an assumption that half of
the advanced treatment category biosolids (0.4 million of the 0.8 million dry tons
shown in Table A-6) might be composted at municipal solid waste facilities or at
24Based on communication with Bob Bastian, U.S. EPA, May 1997.
25Based on communication with Bob Bastian, U.S. EPA, October 1997, and with Steven Levy,
U.S. EPA, October 1997.
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Methodology and Results Appendix
facilities that manage both biosolids and municipal solid waste, including yard
trimmings. Adding the 0.4 million dry tons to the 1.4 million dry tons estimated
above to be handled by municipal solid waste or composting facilities brings the
total to 1.8 million dry tons or 26 percent of the amount of biosolids estimated to
be generated in 1998.
A.4 Projections of Biosolids Generation in 2000, 2005, and 2010
Methodology
This report based projections of biosolids generation for 2000, 2005, and 2010
on trends in wastewater flow rates, which were obtained from available Needs
Surveys from the years 1984 to 1996. The amount of flow for each treatment
method (primary or secondary treatment) was not available in the Needs
Surveys for most years. We, therefore, estimated the flow for each treatment
group using the population served for each treatment level as a percentage of
the total population served. This calculation is similar to calculations discussed
in Section A.2 to determine the Biosolids Generation Factor for each treatment
method for a given year's flow.
In each year of the Needs Survey for which data on total flow and population
were available (1988, 1992, and 1996), the percentage of those served by pri-
mary treatment or secondary treatment to the total population served by all
POTWs was calculated.26 These percentages then were applied to the total flow
to estimate the flow attributable to POTWs in each treatment category, as was
done earlier for estimating 1996 flow. The trend in flow across the years for
which data were available was calculated, and the trend factors were applied to
1996 flows to calculate the flows in 2000, 2005, and 2010 using the estimate of
percent change per year and the number of intermediate years.
The BGF for each treatment level was multiplied by flow to estimate the dry tons
of biosolids generated, as discussed in Section A.2, for developing the initial
estimate of 1996 biosolids generation.
Flow Projection (MGD) x BGF = Biosolids Generation (U.S. dry tons) (6)
This calculation was repeated for each of the years 2000, 2005, and 2010 and
for each treatment level.
Results
Table A-7 presents the calculations of trends. Given the overall increase in flow
due to steady increases in the population served, flow from POTWs using only
primary treatment was estimated to be decreasing at an annual rate of about 4
percent, while flow from POTWs using at least secondary treatment methods
26Again, secondary treatment for this discussion includes secondary, tertiary, and no discharge
categories.
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Methodology and Results
Appendix
was estimated to be increasing at an annual rate of about 2 percent. With these
rates of change, flow was projected for 2000, 2005, and 2010 (see Table A-8).27
Based on the above methodology, we estimate that the percentage of total
biosolids production attributable to POTWs using primary treatment levels will
fall from 8 percent in 1998 (see Table A-3) to 4 percent in 2010. Concurrently,
we estimate that total biosolids production will increase by 19 percent from 1998
to 2010. By 2010, a total of 8.2 million dry tons of biosolids are expected to be
used or disposed of annually (see Table A-8).
Table A-7
Trend Analysis of Flow (1984 to 1996)
Year
1984
1986
1988
1990
1992
1994
1996
Trend
(1 -year)
Total Flow
(MGD)
27,095
27,692
28,736
29,113"
29,490
30,833a
32,175
—
Primary as
% of Total
Population
15%
12%
9%
—
Secondary
as % of
Total
Population
85%
88%
91%
—
Primary
Flow
4,320
3,545
2,913
—
Secondary
Flow
24,416
25,945
32,175
—
Trend
Primary
—
-0.18
-0.13
-0.04
Secondary
—
+0.03
+0.10
+0.02
Total
—
+0.02
+0.04
+0.01
+0.01
+0.05
+0.04
+0.015
Note: Blanks indicate years with missing data.
Source: 1984-1998 Needs Surveys.
Computed as the midpoint between years when data were unavailable.
270ver total flow, some variation in the trend was seen over time, with the mid-1980s associated
with greater flow increases than the early to late 1990s. After the early 1990s, however, increases
picked up again. This is consistent with the accelerating and delaying of wastewater treatment
projects that might have occurred. These variations could have been driven by several factors. In
the mid-1980s, POTWs were aware that the Construction Grants Program was being eliminated
and, thus, might have accelerated some building programs into those years. The Construction
Grants Program, which was being phased out in the late 1980s, received its last appropriation in
the fiscal year 1990. In the late 1980s and early 1990s, the acceleration of the mid-1980s could
have led to a slowdown in wastewater programs, (since many would have been completed), while
other POTWs, which had delayed their projects, further delayed them as they investigated new
sources of funding. With the onset of the recession in the early 1990s, further delays were likely.
Finally, by the mid-1990s, the improving economic conditions and the accumulation of construc-
tion programs that could no longer be delayed might have led to the greater increases in flow
seen in these years. Taking these factors into account, it is believed that smoothing these trends
by averaging them over the years of data available is appropriate.
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Methodology and Results
Appendix
Table A-8
Wastewater Flow Projections for POTWs and Privately
and Federally Owned Treatment Works in
2000, 2005, and 2010
Treatment
Group
Primary
Secondary
Total
Wastewater Flow (MGD)
2000
2,430
32,280
34,710
2005
2,000
35,085
37,085
2010
1,640
38,130
39,780
Biosolids
Generation
Factor
203
206
—
Biosolids Generated
(million U.S. dry tons)
2000
0.5
6.6
7.1
2005
0.4
7.2
7.6
2010
0.3
7.9
8.2
Source: Tables A-2 and A-7. Includes 1.5 percent additional flow to account for privately and federally owned treatment works
under the assumption that these treatment works will follow the same trends as POTWs.
A.5 Use and Disposal of Biosolids in 2000, 2005, and 2010
Methodology
The percentages of biosolids going to the various use and disposal methods
were estimated on the basis of expected future trends in factors affecting
biosolids use and disposal. As discussed in Section Four, we expect factors
favoring the increased recovery of biosolids, including the regulatory environ-
ment, technological development, and public acceptance, to contribute to a con-
tinuing increase in the beneficial use of biosolids. Concurrently, we anticipate
the amount of biosolids going to surface disposal and incineration to decrease,
partially due to the rising costs of incineration and, in some locations, landfilling.
Amounts incinerated are not expected to decrease rapidly, since this category
has grown since 1988.28 Some small decline in incineration is expected, howev-
er, given public concerns about environmental impacts of incineration. (See
Section Four for a more detailed discussion of trends.) We then determined the
quantities of biosolids going to each use or disposal method on the basis of the
projected quantities of biosolids generated in 2000, 2005, and 2010 and the per-
centage assigned to each method. To account for trends and the projections of
biosolids generation for 2000, 2005, and 2010, we first developed percentage
estimates for those years (see Table A-9) and then applied these percentages
against our previously estimated flow data (Table A-8).
28A total of 16.1 percent of biosolids were estimated to have been incinerated in 1988 while 22
percent were estimated to have been incinerated in 1995 (WEF, 1997); note, however, that the
WEF (1997) data might somewhat overstate amounts incinerated, as discussed earlier in Section
A.3. This conjecture might be supported by BioCycle (1998). The data presented in this source
indicate that 20 percent of biosolids generated (in the 34 states with sufficient data) were
incinerated.
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Methodology and Results
Appendix
Results
As Table A-10 shows, we expect beneficial use of biosolids to increase from 60
percent in 1998 to 63 percent in 2000, 66 percent in 2050, and 70 percent in
2010. Thus, by 2010, disposal might only account for about 30 percent of all
biosolids generated.
Table A-9
Projected Percentages of Biosolids Use and Disposal
in 2000, 2005, and 2010
Year
1998
2000
2005
2010
Beneficial Use
Land
Application
41%
43%
45%
48%
Advanced
Treatment
12%
12.5%
13%
13.5%
Other
Beneficial
Use
7%
7.5%
8%
8.5%
Total
60%
63%
66%
70%
Disposal
Surface
Disposal/
Landfill
17%
14%
13%
10%
Incineration
22%
22%
20%
19%
Other
1%
1%
1%
1%
Total
40%
37%
34%
30%
Source: EPA estimates.
Table A-10
Projected Quantities of Biosolids Use and Disposal
in 2000, 2005, and 2010 (million U.S. dry tons)
Year
2000
2005
2010
Beneficial Use
Land
Application
3.1
3.4
3.9
Treatment/
Land
Application
0.9
1.0
1.1
Other
Beneficial
Use
0.5
0.6
0.7
Total
4.5
5.0
5.7
Disposal
Surface
Disposal/
Landfill
1.0
1.0
0.8
Inciner-
ation
1.6
1.5
1.5
Other
0.1
0.1
0.1
Total
2.6
2.6
2.5
Total
7.1
7.6
8.2
Source: Tables A-9 and A-10.
Based on this assessment of likely trends, we estimate the amount of biosolids
to be beneficially used to increase to 4.4, 5.0, and 5.7 million dry tons in 2000,
2005, and 2010, respectively, with 2.6, 2.6, and 2.5 million dry tons, respective-
ly, being disposed of. Compared to current breakdowns between use and dis-
posal methods, a positive trend in the use of biosolids continues in the future,
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Methodology and Results Appendix
but the trend in disposal becomes slightly negative. The amount of biosolids
going to municipal solid waste facilities is projected to be 1.2, 1.2, and 1.0 mil-
lion dry tons (not including composted biosolids managed by municipal solid
waste facilities, as defined earlier, that are not used as landfill cover) in 2000,
2005, and 2010, respectively.29 Declines in landfilled biosolids are offset slightly
by small increases in use of biosolids for landfill cover, but not enough to
change the overall decline rate at municipal solid waste facilities. Municipal solid
waste facilities, therefore, are likely to be handling at a minimum 17 percent of
the 7.1 million dry tons generated in 2000, 16 percent of the 7.6 million dry tons
generated in 2005, and 12 percent of the 8.2 million dry tons generated in 2010.
As discussed in Section Four, some portion of the amount estimated to receive
advanced treatment might be prepared by municipal solid waste facilities. As
much as half (approximately 0.5 million dry tons of the 0.9, 1.0, and 1.1 million
dry tons shown in Table A-10) might be handled by these facilities. When these
amounts are added to the above estimates, municipal solid waste facilities might
manage 1.6 million dry tons of the 7.1 million dry tons generated in 2000 (23
percent), 1.7 million dry tons of the 7.6 million dry tons generated in 2005 (22
percent), and 1.6 million dry tons of the 8.2 million dry tons generated in 2010
(20 percent). These figures include amounts of biosolids disposed of in munici-
pal solid waste landfills, used for landfill cover, or composted for sale or distribu-
tion to farmers, contractors, or the general public.
29Using the same assumption as above about the relative ratios of landfill cover to aggregate in
the other beneficial use category.
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