&EPA
United States
Environmental Protection
Agency
Environmental
Regulations and
Technology
Control of Pathogens and
Vector Attraction in
Sewage Sludge
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EPA/625/R-92/013
Revised July 2003
Environmental Regulations and Technology
Control of Pathogens and Vector Attraction
in Sewage Sludge
(Including Domestic Septage)
Under 40 CFR Part 503
This guidance was prepared by
U.S. Environmental Protection Agency
Office of Research and Development
National Risk Management Research Laboratory
Center for Environmental Research Information
Cincinnati, OH 45268
Re
Pr
pa,... ..._
processed chlorine free.
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Notice
This report has been reviewed by the U.S. Environmental Protection Agency and approved
for publication. The process alternatives, trade names, or commercial products are only ex-
amples and are not endorsed or recommended by the U.S. Environmental Protection Agency.
Other alternatives may exist or may be developed.
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Foreword
The U.S. Environmental Protection Agency (EPA) is charged by Congress with protecting the
Nation's land, air, and water resources. Under a mandate of national environmental laws, the Agency
strives to formulate and implement actions leading to a compatible balance between human activities and
the ability of natural systems to support and nurture life. To meet this mandate, EPA's research program
is providing data and technical support for solving environmental problems today and building a science
knowledge necessary to manage our ecological resources wisely, understand how pollutants affect
our health, and prevent or reduce environmental risks in the future.
The National Risk Management Research Laboratory (NRMRL) is the Agency's center for
investigation of technological and management approaches for preventing and reducing risks from
pollution that threaten human health and the environment. The focus of the Laboratory's research
program is on methods and their cost-effectiveness for prevention and control of pollution to air, land,
water, and subsurface resources; protection of water quality in public water systems; remediation of
contaminated sites, sediments and ground water; prevention and control of indoor air pollution; and
restoration of ecosystems. NRMRL collaborates with both public and private sector partners to foster
technologies that reduce the cost of compliance and to anticipate emerging problems. NRMRL's
research provides solutions to environmental problems by: developing and promoting technologies that
protect and improve the environment; advancing scientific and engineering information to support
regulatory and policy decisions; and providing the technical support and information transfer to ensure
implementation of environmental regulations and strategies at the national, state, and community levels.
This publication has been produced as part of the Laboratory's strategic long-term research plan.
It is published and made available by EPA's Office of Research and Development to the user
community and to link researchers with their clients.
Hugh W. McKinnon, Director
National Risk Management Research Laboratory
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Contents
Chapter 1 Introduction 1
1.1 What is Sewage Sludge? 1
1.2 U.S. Regulation ofTreated Sewage Sludge (Biosolids) 4
1.3 Implementation Guidance 4
1.4 Definitions 5
1.5 Pathogen Equivalency Committee 6
1.6 What is in this Document? 6
Chapter 2 Sewage Sludge Pathogens 8
2.1 What are Pathogens? 8
2.2 Pathogens in Sewage Sludge 8
2.3 General Information on Pathogens 10
2.4 Protecting Public Health-The Part 503 11
2.5 Frequently Asked Questions 16
Chapters Overview of Part 503 Subpart D Requirements, Their Applicability, and
Related Requirements 20
3.1 Introduction 20
3.2 Pathogen Reduction Requirements 20
3.3 Vector Attraction Reduction (VAR) Requirements [503.33] 21
3.4 Applicability of the Requirements [503.15 and 503.25] 21
3.5 Frequency of Monitoring 22
3.6 Sampling Stockpiled orRemixed Biosolids 22
3.7 Recordkeeping Requirements [503.17 and 503.27] 23
3.8 Reporting Requirements for Sewage Sludge [503.18and 503.28] 23
3.9 Permits and Direct Enforceability [503.3] 25
Chapter 4 Class A Pathogen Requirements 26
4.1 Introduction 26
4.2 Vector Attraction Reduction to Occur With or After Class A Pathogen
Reduction [503.32(a)(2)] 26
4.3 Monitoring of Fecal Coliform or Salmonella sp. to Detect Growth of Bacterial Pathogens
[503.32(a)(3)-(8)] 27
4.4 Alternative 1: Thermally Treated Sewage Sludge [503.32(a)(3)] 28
4.5 Alternative 2: Sewage Sludge Treated in a High pH-High Temperature Process (Alkaline
Treatment) [503.32(a)(4)] 30
4.6 Alternative 3: Sewage Sludge Treated in Other Processes [503.32(a)(5)] 31
4.7 Alternative 4: Sewage Sludge Treated in Unknown Processes [503.32(a)(6)] 32
4.8 Alternative 5: Use of PFRP [503.32(a)(7)] 32
4.9 Alternative 6: Use of a Process Equivalent to PFRP [503.32(a)(8)] 33
4.10 Frequency of Testing 33
Chapter 5 Class B Pathogen Requirements and Requirements for Domestic Septage
Applied to Agricultural Land, a Forest, or a Reclamation Site 36
5.1 Introduction 36
5.2 Sewage Sludge Alternative 1: Monitoring of Fecal Coliform [503.32(b)(2)] 36
5.3 Sewage Sludge Alternative 2: Use of a Process to Significantly Reduce
Pathogens (PSRPs) [503.32(b)(3)] 37
5.4 Sewage Sludge Alternative 3: Use of Processes Equivalent to PSRP [503.32(b)(4)] 38
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5.5 Site Restrictions for Land Application of Biosolids [503.32(b)(5)] 38
5.6 Domestic Septage [503.32(c)] 41
Chapters Processes to Significantly Reduce Pathogens (PSRPs) 43
6.1 Introduction 43
6.2 Aerobic Digestion 43
6.3 Anaerobic Digestion 45
6.4 Air Drying 46
6.5 Composting 47
6.6 Lime Stabilization 48
6.7 Equivalent Processes 50
Chapter7 Processes to FurtherReduce Pathogens (PFRPs) 51
7.1 Introduction 51
7.2 Composting 51
7.3 Heat Drying 53
7.4 Heat Treatment 54
7.5 Thermophilic Aerobic Digestion 54
7.6 Beta Ray and Gamma Ray Radiation 55
7.7 Pasteurization 55
7.8 Equivalent Processes 56
Chapter 8 Requirements for Reducing Vector Attraction 58
8.1 Introduction 58
8.2 Option 1: Reduction in Volatile Solids Content [503.33(b)(1)] 58
8.3 Option 2: Additional Digestion of Anaerobically Digested Sewage Sludge [503.33(b)(2)]. 60
8.4 Option 3: Additional Digestion of Aerobically Digested Sewage Sludge [503.33(b)(3)] .... 60
8.5 Option 4: Specific Oxygen Uptake Rate (SOUR) for Aerobically Digested Sewage
Sludge [503.33(b)(4)] 60
8.6 Option 5: Aerobic Processes at Greater than 40°C [503.33(b)(5)] 61
8.7 Option 6: Addition of Alkali [503.33(b)(6)] 61
8.8 Option 7: Moisture Reduction of Sewage Sludge Containing No Unstabilized Solids
[503.33(b)(7)] 62
8.9 Option 8: Moisture Reduction of Sewage Sludge Containing Unstabilized
Solids [503.33(b)(8)] 62
8.10 Option 9: Injection [503.33(b)(9)] 62
8.11 Option 10: Incorporation of Sewage Sludge into the Soil [503.33(b)(10)] 63
8.12 Option 11: Covering Sewage Sludge [503.33(b)(11)] 63
8.13 Option 12: Raising the pH of Domestic Sludge [503.33(b)(12)] 63
8.14 Number of Samples and Timing 63
8.15 Vector Attraction Reduction Equivalency 63
Chapter 9 Sampling Procedures and Analytical Methods 65
9.1 Introduction 65
9.2 Laboratory Selection 65
9.3 Safety Precautions 65
9.4 Requirements for Sampling Equipment and Containers 66
9.5 Sampling Frequency and Number of Samples Collected 67
9.6 Sampling Free-Flowing Sewage Sludges 68
9.7 Sampling Thick Sewage Sludges 69
9.8 Sampling Dry Sewage Sludges 69
9.9 Control of Temperature, pH, and Oxygenation After Sample Collection
Samples for Microbial Tests 70
9.10 Sample Composting and Size Reduction 71
9.11 Packaging and Shipment 72
9.12 Documentation 73
9.13 Analytical Methods 73
VI
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9.14 Quality Assurance 74
Chapter 10 Meeting the Quantitative Requirements of the Regulation 76
10.1 Introduction 76
10.2 Process Conditions 76
10.3 Schedule and Duration of Monitoring Events 77
10.4 Comparison of Feed Sludge and Sludge Product Samples 79
10.5 The Effect of Sludge Processing Additives on Monitoring 79
10.6 Collecting Representative Samples 80
10.7 Regulatory Objectives and Number of Samples that Should be Tested 81
Chapter 11 Role of EPAs Pathogen Equivalency Committee in Providing Guidance Under
Part 503 90
11.1 Introduction 90
11.2 Overview of the PEC's Equivalency Recommendation Process 92
11.3 Basis for PEC Equivalency Recommendations 92
11.4 Guidance on Demonstrating Equivalency for PEC Recommendations 97
11.5 Guidance on Application for Equivalency Recommendations 98
11.6 Pathogen Equivalency Committee Recommendations 100
11.7 Current Issues 100
Chapter 12 References and Additional Resources 103
Appendices
A EPA Regional and State Biosolids Coordinators and Listing of EPA Pathogen
Equivalency Members 107
B SubpartD of the Part 503 Regulation 115
C Determination of Volatile Solids Reduction by Digestion 120
D Guidance on Three Vector Attraction Reduction Tests 127
E Determination of Residence Time for Anaerobic and Aerobic Digestion 133
F Sample Preparation for Fecal Coliform Tests and Salmonella sp. Analysis 137
G Kennerand Clark (1974) Analytical Method for Salmonella sp. Bacteria 141
H Method forthe Recovery and Assay of Total Culturable Viruses from Sludge 150
I Test Method for Detecting, Enumerating, and Determining the Viability of
AscarisOva in Sludge 166
J The Biosolids Composting Process 173
VII
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Acknowledgments
This guidance document was produced by the U.S. Environmental Protection Agency (EPA) Pathogen
Equivalency Committee (PEC) whose members include Robert Bastian, Bob Brobst, John Cicmanec, G.
Shay Fout, Hugh McKinnon, Mark Meckes, Frank Schaefer, Stephen Schaub, and James E. (Jim) Smith, Jr.
The contributions of Jim Smith, who was instrumental in the administration, organization, and direction of
this project; and of Bob Brobst, Mark Meckes, and Robert Bastian along with Greg B. Kester of the State of
Wisconsin, who provided significant comments and guidance, are especially appreciated. Eliot Epstein and
Nerissa Wu of E&A Environmental Consultants, Inc. in Canton, Massachusetts, prepared the document with
information and comments from the PEC and from EPA and State sludge coordinators and private contribu-
tors including Joseph B. Farrell, a consultant, and Robert Reimers of Tulane University. The assistance of
reviewers including John Colletti, Madolyn Dominy, Lauren Fondahl, Alia Roufaeal, and John Walker of
EPA; Jeffrey G. Faust of Bio Gro; Joe Pearce of the State of North Carolina; Bob Southworth, a consultant;
and all other contributors, too numerous to name, is very much appreciated.
The following individuals assisted by updating guidance for analytical procedures: Appendix F: Sample
Preparation for Fecal Coliform Tests and Salmonella sp. Analysis - Mark Meckes; Appendix H: Method for
the Recovery and Assay of Enteroviruses from Sewage Sludge - Shay Fout; Appendix I: Analytical Method
for Viable Helminth Ova - Frank Schaefer; Appendix J: Composting: Basic Concepts Related to Pathogens
and Vector Attraction - Eliot Epstein of E&A Environmental Consultants and Bob Brobst of EPA's Region 8
Office in Denver, CO.
VIII
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Chapter 1
Introduction
1.1 What is Sewage Sludge?
Sewage sludge - the residue generated during treatment
of domestic sewage (Figure 1-1)- is often used as an or-
ganic soil conditioner and partial fertilizer in the United States
and many other countries. It is applied to agricultural land
(pastures and cropland), disturbed areas (mined lands, con-
struction sites, etc.), plant nurseries, forests, recreational
areas (parks, golf courses, etc.), cemeteries, highway and
airport runway medians, and home lawns and gardens (see
photographs, pages 2 and 3). Certain treatment works (POTWs)
own or have access to land dedicated solely to disposal of
sewage sludge, a practice referred to as surface disposal.
The U.S. Environmental Protection Agency (EPA), the pri-
mary federal agency responsible for sewage sludge man-
agement, encourages the beneficial use of sewage sludge
through land application (Figure 1-2), after it has been ap-
propriately treated for its intended use. In 1995 it was found
that 54% of sewage sludge generated in the United States
was land applied (Bastian, 1997).
Sewage sludge has beneficial plant nutrients and soil
conditioning properties; however, it may also contain patho-
genic bacteria, viruses, protozoa, parasites, and other m i -
Domestic
Sewage
Generation
croorganisms that can cause disease. Land application and
surface disposal of untreated sewage sludge create a po-
tential for human exposure to these organisms through
direct and indirect contact. To protect public health from
these organisms and from the pollutants that some sew-
age sludge contains, many countries now regulate the use
and disposal of sewage sludge.
"Sewage Sludge" vs. "Biosolids"
Throughout the wastewater and sewage sludge indus-
try, the term "sewage sludge" has largely been replaced
by the term "biosolids." "Biosolids" specifically refers to
sewage sludge that has undergone treatment and meets
federal and state standards for beneficial use. The distinc-
tion between untreated sewage sludge and biosolids that
have undergone processing and analysis will be made
throughout this document.
What is Beneficial Use?
For the purposes of this document, land application is
considered to be beneficial use. The document specifically
deals with land application and the issues related to the
pathogen and vector attraction reduction requirements for
Sewage Sludge
Treatment
Digestion
Drying
Composting
Lime Stabilization
Heat Treatment
Etc.
Treated
Sewage I
Sludge f
.(Biosolids)1
Disposal
Industrial
Wastewater
Generation
Incineration
Surface Disposal
Land Application
Agricultural Land
Strip-mined Land
Forests
Plant Nurseries
Cemeteries
Parks, Gardens
Lawns and Home
Gardens
Figure 1-1. Generation, treatment, use, and disposal of sewage sludge.
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Highway median strip in Illinois after land application of dried sludges.
(Photo courtesy of Metropolitan Water Reclamation District of Greater Chicago)
Flower beds amended with sludge compost at the Betty Ford
Alpine Gardens, Vail, CO.
Injection of liquid sludge into sod.
Oat field showing sludge-treated (right) and untreated (left) areas.
(Photo courtesy of City of Tulsa, Oklahoma)
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Reclaimed mine spoil land. Kennecott Copper near Salt Lake
City, Utah.
Corn grown on sludge-treated soil (right) and untreated soil (left).
Mine spoil land sludge treatment. Note lush vegetative cover on
reclaimed soil which will support grazing. (Photo courtesy of City of
Tulsa, Oklahoma)
Cross-section of popular trees showing how sludge application
increases tree growth. Both cross sections are 8 years old; the
larger is aprox. 8 inches in diameter.
(Photo courtesy of Mike VanHam, British Columbia, Canada)
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The U.S. Environmental Protection Agency (EPA)
will actively promote those municipal sludge man-
agement practices that provide fpr the beneficial use
of sewage sludge while maintaining or improving en-
vironmental quality and protecting human health. To
implement this policy, EPA will continue to issue regu-
lations that protect public health and other environ-
mental values. The Agency will require states to es-
tablish and maintain programs to ensure that local
governments utilize sewage sludge management
techniques that are consistent with federal and state
regulations and guidelines. Local communities will
remain responsible for choosing among alternative
programs; for planning, constructing, and operating
facilities to meet their needs; and for ensuring the
continuing availability of adequate and acceptable
disposal or use capacity.
Figure 1-2. EPA policy on sewage sludge management.
Source: EPA, 1984.
land applied biosolids. For more information on the patho-
gen and vector attraction reduction requirements for the
surface disposal of biosolids, please refer to Section 503.25
of the regulation.
1.2 U.S. Regulation of Treated Sewage
Sludge (Biosolids)
In the United States, the use and disposal of treated
sewage sludge (biosolids), including domestic septage, are
regulated under 40 CFR Part 5031 This regulation, pro-
mulgated on February 19, 1993, was issued under the
authority of the Clean Water Act (CWA) as amended in
1977 and the 1976 Resource Conservation and Recovery
Act (RCRA). For most sewage sludge2, the new regulation
replaces 40 CFR 257, the original regulation governing
the use and disposal of sewage sludge, which has been in
effect since 1979.
The EPA policy shown below was developed in response
to specific language in the CWA and RCRA federal policy
statements in order to facilitate and encourage the benefi-
cial reuse of sewage sludge (U.S. EPA, 1984).
Protection of Public Health and the
Environment
Subpart D of the Part 503 regulation protects public
health and the environment through requirements designed
to reduce the potential for contact with the disease-bear-
ing microorganisms (pathogens) in sewage sludge applied
to the land or placed on a surface disposal site. These
requirements are divided into:
1 Because domestic septage is a form of sewage sludge, any use of the term "sew-
age sludge" in this document includes domestic septage.
2 Sewage sludge generated at an industrial facility during the treatment of domestic
sewage commingled with industrial wastewater in an industrial wastewater treat-
ment facility is still covered under 40 CFR Part 257 if the sewage sludge is applied to
the land.
Requirements designed to control and reduce patho-
gens in treated sewage sludge (biosolids)
Requirements designed to reduce the ability of the
treated sewage sludge (biosolids) to attract vectors
(insects and other living organisms that can transport
biosolids pathogens away from the land application or
surface disposal site)
Subpart D includes both performance and technology
based requirements. It is designed to provide a more flex-
ible approach than the approach in the Part 257, which
required sewage sludge to be treated by specific listed or
approved treatment technologies. Under Part 503, treat-
ment works may continue to use the same processes they
used under Part 257, but they now also have the freedom
to modify conditions and combine processes with each
other, as long as the applicable Part 503 requirements are
met.
Environmental Effects of Pathogens in
Sewage Sludge
Because of concern over the effect of pathogens from
biosolids on animal health (certain human pathogens can
cross species lines and infect animals, particularly warm
blooded animals) the 503 regulations require that sewage
sludge undergo pathogen treatment prior to land applica-
tion. For sewage sludge subject to Class B pathogen treat-
ment site restrictions are also required. While relatively
little research has been conducted on specific inter-spe-
cies crossover to wildlife, more information is available for
grazing animals which are more likely to have a greater
exposure to biosolids than wildlife. Available information
on the impact of biosolids pathogens on grazing animals
suggests that the Part 503 Subpart D requirements for
pathogen control (which include restrictions on grazing)
protect grazing animals (EPA, 1992). References regard-
ing the impact of biosolids application on both wild and
domestic animals are included at the end of this chapter.
1.3 Implementation Guidance
This document is not regulatory in nature. A complete
copy of Subpart D of the Part 503 Regulation appears in
Appendix B. This document is only intended to serve as
a guide to pathogen and vector attraction reduction for
anyone who is involved with the treatment of sewage sludge
for land application. This includes:
Owners and operators of domestic sewage treatment
works
Developers or marketers of sewage sludge treatment
processes
Groups that distribute and market biosolids products
Individuals involved in applying biosolids to land
Regional, state, and local government officials respon-
sible for implementing and enforcing the Part 503 Sub-
part D regulation
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Consultants to these groups
Anyone interested in understanding the federal require-
ments concerning pathogens in sewage sludge
This guide was previously released in 1993. The updates
and amendments to this document are a product of com-
ments and suggestions from the regulatory and sewage
sludge management community. This edition of the docu-
ment includes clarification of many of the sampling and
monitoring issues and reflects the increased understand-
ing of analytical issues. There are additional operational
guidelines and examples of how a variety of facilities have
complied with the Part 503 requirements. Some of the
notable additions to this edition include:
Clarification of Class A processes
More specific guidelines for the operation of composting
facilities
More information on site restrictions including permit
conditions which may apply to specific crops
Recommendation for the use of the Kenner and Clark
methodology for Salmonella sp. bacteria analysis
Guidelines for retesting biosolids products that have
been stored or remixed
More information on public health and pathogens
More information on sampling and monitoring proto-
cols
Updates on the Pathogen Equivalency Committee and
approved processes
Other publications related to pathogen or vector attrac-
tion issues include the "Technical Support Document for
Reduction of Pathogens and Vector Attraction in Sewage
Sludge" (U.S. EPA, 1992) and "Part 503 Implementation
Guidance" (U.S. EPA, 1995). Although the federal regula-
tion under 40 CFR Part 503 includes restrictions for pollut-
ant concentrations and application rates, this document is
intended to clarify pathogen and vector related require-
ments and does not discuss pollutant limits.
This document does not discuss the general require-
ments and management practices which must be followed
for land application of all biosolids except in the case of
"exceptional quality" biosolids which have met certain pol-
lutant limits and pathogen and vector attraction reduction
requirements. In addition to meeting the regulation set forth
in this document, bulk biosolids application must be con-
ducted in accordance with agronomic rates, and biosolids
appliers must ensure that applied biosolids are not applied
within 10 meters of any water body, do not enter surface
waters or wetlands without the approval of the appropriate
permitting authority, and do not adversely affect endan-
gered or threatened species or their habitats.
It should be noted that the Part 503 regulation and the
sampling and monitoring requirements outlined in the regu-
lation were developed as minimum requirements. EPA
supports the beneficial use of treated sewage sludge
(biosolids) and encourages facility operators and genera-
tors of biosolids products to develop sampling and moni-
toring plans that go beyond the minimum regulatory re-
quirements as needed to ensure consistent product qual-
ity.
For most states, the authority for implementing the Part
503 regulation currently remains with the Regional EPA
offices. A guide to EPA offices and relevant contacts can
be found in Appendix A.
1.4 Definitions
The sections of this document that discuss specific regu-
latory requirements utilize the same terminology used
throughout the Part 503 regulation in order to maintain
consistency between the regulation and this guidance
document. However, in some parts of this document, par-
ticularly in sections which discuss operational parameters
and other issues related to biosolids management, terms
which are not formally defined by the regulations are used.
The following glossary has been provided in order to pre-
vent confusion about the intent and jurisdiction of the Part
503 regulation.
Applier - The applier is the individual or party who land
applies treated sewage sludge (biosolids). This may in-
clude farmers, municipalities, and private enterprises that
land apply or their contractors.
Biosolids - Sewage sludge that has been treated and
meets state and federal standards for land application.
Control - Some of the regulatory requirements make a
distinction based on whether the biosolids preparer (see
below) has "control" over the material. A preparer loses
control over material when it is sold or given away. Until
that point, the material is still within the control of the
preparer even if the treatment process has ended and the
material is in storage on or off-site.
Detectable Limits - Minimum concentration at which
an analyte can be measured. The detectable limit for any
given analyte varies depending on the lab methodology
used and the volume of material analyzed. As such, de-
tectable limits may fluctuate. Throughout this document,
the term "detectable limit" refers to the limits as they are
defined in the allowable lab methodologies outlined in the
Appendices.
Exceptional Quality (EQ) Biosolids - The term "EQ" is
not used in the Part 503 regulation, but it has become a
useful description for regulators and biosolids preparers
when referring to biosolids that meet the pollutant concen-
tration limits of Table 3 of Section 503.13, Class A patho-
gen reduction, and one of the first eight treatment pro-
cesses for meeting vector attraction reduction standards.
Biosolids that fall into this category are not subject to the
Part 503 general requirements and management practices
for land application.
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Preparer - The person(s) who generate biosolids from
the treatment of domestic sewage in a treatment works or
change the quality of the sewage sludge received from
the generator. This includes facilities that derive a material
from sewage sludge prior to land application of the mate-
rial which could include wastewater treatment facilities,
composting or other sewage sludge processing operations,
and soil blenders who handle non-EQ biosolids materials.
A soil blender who takes EQ biosolids and mixes them
with other (non-sewage sludge) materials for land applica-
tion is not a preparer. However, a soil blender that takes
non-EQ biosolids and mixes it with other materials for land
application is a preparer.
Product - This may include materials such as
composted, heat-dried, lime stabilized, alkaline stabilized,
or otherwise processed biosolids which have met the re-
quirements of the Part 503. The term "product" is some-
times used in this document in discussions regarding ma-
terial distribution. The term "sludge derived material" is used
in the Part 503 to refer to these materials.
Sewage Sludge - The solid, semi-solid, or liquid resi-
due generated during the treatment of municipal sewage
in a treatment works. The term "biosolids" refers to sew-
age sludge which has undergone treatment and meets
state and federal requirements for land application. The
distinction between untreated sewage sludge and treated
biosolids is made throughout this document.
1.5 Pathogen Equivalency Committee
The Pathogen Equivalency Committee (PEC) is made
up of U.S. EPA experts who review pathogen and vector
attraction reduction issues and make recommendations
to the appropriate permitting authority. The primary role of
the PEC is to review proposals for Processes to Signifi-
cantly Reduce Pathogens (PSRP) and Processes to Fur-
ther Reduce Pathogens (PFRP) equivalency determina-
tions and to offer guidance on the issues associated with
pathogen and vector attraction reduction.
More information on the PEC and the process of apply-
ing for equivalency is presented in Chapter 11.
1.6 What is in this Document?
Chapter 2 of this document provides basic information
about pathogens and describes why pathogen control is
required to protect public health and the environment, and
Chapters 3 through 5 discuss the current federal require-
ments under Subpart D of Part 503. Chapters 6 and 7 re-
view the different PFRP and PSRP processes, and Chap-
ter 8 discusses vector attraction reduction issues. Chap-
ters 9 and 10 summarize sampling and analysis protocols
used to meet the quantitative requirements of Part 503.
Chapter 11 outlines the process for applying for equiva-
lency and discusses the kind of support EPA's Pathogen
Equivalency Committee can provide to permitting authori-
ties. Chapter 12 lists general references and additional
resources related to biosolids use; specific references re-
lated to particular topics are also included at the end of
each chapter.
The Appendices provide additional information on:
Determination of volatile solids and residence time for
digestion
Sample preparation and analytical methods for meet-
ing the Part 503 pathogen reduction requirements
Tests for demonstrating vector attraction reduction
Additional references on pathogen research and tech-
nical background to regulations
Appendix A lists EPA and state sewage sludge coordi-
nators, and Appendix B contains Subpart D of the Part
503 regulation.
References and Additional Resources
Alberici, T.M., W.E. Sopper, G.L. Storm, and R.H. Yahner.
1989. Trace metals in soil, vegetation, and voles from
mine land treated with sewage sludge. Journal of En-
vironmental Quality 18:115-120.
Anderson, T.J. and G.W. Barrett. 1982. Effects of dried
sewage sludge on meadow vole (Microtus
pennsylvanicus) populations in two grassland commu-
nities. Journal of Applied Ecology 19:759-772.
Bastian, R.K. 1997. The biosolids (sludge) treatment, ben-
eficial use, and disposal situation in the USA. Euro-
pean Water Pollution Control Journal, Vol 7, No. 2,
62-79.
Danron, B.L, H.R. Wilson, M.F. Hall, W.L Johnson,
0. Osuna, R.L. Suber, and G.T. Edds. 1982. Effects of
feeding dried municipal sludge to broiler type chicks
and laying hens. Polut. Sci. 61:1073-1081.
Hegstrom, L.J. and S.D. West. Heavy metal accumulation
in small mammals following sewage sludge applica-
tion to forests. Journal of Environmental Quality 18:345.
Keinholz, E.W. 1980. Effects of toxic chemicals present in
sewage sludge on animal health. P 153-171 in Sludge
- Health risks of land application. Ann Arbor Science
Publishers.
Keinholz, E.W., G.M. Ward, D.E. Johnson, J. Baxter, G.
Braude, and G. Stern. 1979. Metropolitan Denver
sludge fed to feedlot steers. J. Anim. Sci. 48:735-741.
National Research Council. 1996. Use of reclaimed water
and sludge in food crop production. Washington, D.C.
U.S. EPA/USDA/FDA. 1981. Land Application of Munici-
pal Sewage Sludge for the Production of Fruits and
Vegetables: A Statement of Federal Policy and Guid-
ance. SW-905. U.S. EPA, Office of Solid Waste, Wash-
ington, D.C. 21 pp.
U.S. EPA. 1984. EPA policy on municipal sludge manage-
ment. Federal Register, 49(114):24358-24359. June
12, 1984.
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U.S. EPA. 1991. Interagency Policy on beneficial use of 136618. Springfield, VA: National Technical Infor-
municipal sewage sludge on federal land. Federal mation Service.
Register, 56(138):33186-33188. July 19, 1991.
U.S. EPA. 1995. Part 503 implementation guidance. EPA/
U.S. EPA. 1992. Technical support document fpr Part 833/R-95/001. Washington, D.C.
503 pathogen and vector attraction reduction re-
quirements in sewage sludge. NTIS No.: PB89- WEF/U.S. EPA. 1997. Biosolids: A short explanation and dis-
cussion. In Biosolids Fact Sheet Project.
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Chapter 2
Sewage Sludge Pathogens
2.1 What are Pathogens?
A pathogen is an organism or substance capable of caus-
ing disease. The Part 503 regulation only discusses patho-
genic organisms, and throughout this document, "patho-
gen" refers only to living organisms, except where speci-
fied. Pathogens infect humans through several different
pathways including ingestion, inhalation, and dermal con-
tact. The infective dose, or the number of a pathogenic
organism to which a human must be exposed to become
infected, varies depending on the organism and on the
health status of the exposed individual.
Pathogens that propagate in the enteric or urinary sys-
tems of humans and are discharged in feces or urine pose
the greatest risk to public health with regard to the use and
disposal of sewage sludge. Pathogens are also found in
the urinary and enteric systems of other animals and may
propagate in non-enteric settings. However, because this
document is concerned with the regulation of sewage
sludge, this chapter focuses on the pathogens most com-
monly found in the human enteric system.
2.2 Pathogens in Sewage Sludge
What pathogens can be found in sewage
sludge?
The four major types of human pathogenic (disease-
causing) organisms (bacteria, viruses, protozoa, and hel-
minths) all may be present in domestic sewage. The ac-
tual species and quantity of pathogens present in the do-
mestic sewage from a particular municipality (and the sew-
age sludge produced when treating the domestic sewage)
depend on the health status of the local community and
may vary substantially at different times. The level of patho-
gens present in treated sewage sludge (biosolids) also
depends on the reductions achieved by the wastewater
and sewage sludge treatment processes.
The pathogens in domestic sewage are primarily asso-
ciated with insoluble solids. Primary wastewater treatment
processes concentrate these solids into sewage sludge,
so untreated or raw primary sewage sludges have higher
quantities of pathogens than the incoming wastewater.
Biological wastewater treatment processes such as la-
goons, trickling filters, and activated sludge treatment may
substantially reduce the number of pathogens in the waste-
water (EPA, 1989). These processes may also reduce the
number of pathogens in sewage sludge by creating ad-
verse conditions for pathogen survival.
Nevertheless, the resulting biological sewage sludges
may still contain sufficient levels of pathogens to pose a
public health and environmental concern. Part 503 Regu-
lation thus requires sewage sludge to be treated by a Class
A pathogen treatment process or a Class B process with
site restrictions. These requirements prevent disease trans-
mission. Table 2-1 lists some principal pathogens of
concern that may be present in wastewater and sewage
sludge. These organisms and other pathogens can cause
infection or disease if humans and animals are exposed to
sufficient levels of the organisms or pathogens. The lev-
els, called infectious doses, vary for each pathogen and
each host.
As mentioned in Chapter 1, one concern is the potential
effect of some human pathogens on animals. Enteric vi-
ruses can cross species lines, and animal life, particularly
warm blooded animals, can be affected if they are exposed
to some of the pathogens found in sewage sludge. Do-
mestic animals are protected by site restrictions which limit
grazing on sludge amended land.
How could exposure to these pathogens
occur?
If improperly treated sewage sludge was illegally applied
to land or placed on a surface disposal site, humans and
animals could be exposed to pathogens directly by com-
ing into contact with the sewage sludge, or indirectly by
consuming drinking water or food contaminated by sew-
age sludge pathogens. Insects, birds, rodents, and even
farm workers could contribute to these exposure routes by
transporting sewage sludge and sewage sludge pathogens
away from the site. Potential routes of exposure include:
Direct Contact
. Touching the sewage sludge.
. Walking through an area - such as a field, forest, or
reclamation area - shortly after sewage sludge appli-
cation.
. Handling soil from fields where sewage sludge has
been applied.
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Table 2-1. Principal Pathogens of Concern in Domestic Sewage and
Sewage Sludge
Organism
Disease/Symptoms
Bacteria
Salmonella sp.
Shigellasp.
Yersiniasp.
Vibrio cholerae
Campylobacter jejuni
Escherichia co/i
(pathogenic strains)
Enteric Viruses
Hepatitis A virus
Norwalk and
Norwalk-like viruses
Rotaviruses
Enteroviruses
Polioviruses
Coxsackieviruses
Echoviruses
Reovirus
Astroviruses
Caliciviruses
Protozoa
Cryptosporidium
Entamoeba histolytica
Giardia lamblia
Balantidium co/i
Toxoplasma gondii
Helminth Worms
Ascaris lumbricoides
Ascaris suum
Trichuris trichiura
Toxocara canis
Taenia saginafa
Taenia solium
Necator americanus
Hymenolepis nana
Salmonellosis (food poisoning),
typhoid fever
Bacillary dysentery
Acute gastroenteritis (including
diarrhea, abdominal pain)
Cholera
Gastroenteritis
Gastroenteritis
Infectious hepatitis
Epidemic gastroenteritis with severe
diarrhea
Acute gastroenteritis with severe
diarrhea
Poliomyelitis
Meningitis, pneumonia, hepatitis,
fever, cold-like symptoms, etc.
Meningitis, paralysis, encephalitis,
fever, cold-like symptoms, diarrhea, etc.
Respiratory infections, gastroenteritis
Epidemic gastroenteritis
Epidemic gastroenteritis
Gastroenteritis
Acute enteritis
Giardiasis (including diarrhea, abdomi-
nal cramps, weight loss)
Diarrhea and dysentery
Toxoplasmosis
Digestive and nutritional disturbances,
abdominal pain, vomiting, restlessness
May produce symptoms such as
coughing, chest pain, and fever
Abdominal pain, diarrhea, anemia,
weight loss
Fever, abdominal discomfort, muscle
aches, neurological symptoms
Nervousness, insomnia, anorexia,
abdominal pain, digestive disturbances
Nervousness, insomnia, anorexia,
abdominal pain, digestive disturbances
Hookworm disease
Taeniasis
Source: Kowal (1985) and EPA (1989).
Inhaling microbes that become airborne (via aerosols,
dust, etc.) during sewage sludge spreading or by strong
winds, plowing, or cultivating the soil after application.
Indirect Contact
Consumption of pathogen-contaminated crops grown
on sewage sludge-amended soil or of other food prod-
ucts that have been contaminated by contact with these
crops or field workers, etc.
Consumption of pathogen-contaminated milk or other
food products from animals contaminated by grazing
in pastures or fed crops grown on sewage sludge-
amended fields.
Ingestion of drinking water or recreational waters con-
taminated by runoff from nearby land application sites
or by organisms from sewage sludge migrating into
ground-water aquifers.
Consumption of inadequately cooked or uncooked
pathogen-contaminated fish from water contaminated
by runoff from a nearby sewage sludge application site.
Contact with sewage sludge or pathogens transported
away from the land application or surface disposal site
by rodents, insects, or other vectors, including graz-
ing animals or pets.
The purpose of the Part 503 regulation is to place barri-
ers in the pathway of exposure either by reducing the num-
ber of pathogens in the treated sewage sludge (biosolids)
to below detectable limits, in the case.of Class A treat-
ment, or, in the case of Class B treatment, by preventing
direct or indirect contact with any pathogens possibly
present in the biosolids.
Each potential pathway has been studied to determine
how the potential for public health risk can be alleviated.
The references listed at the end of this chapter include
some of the technical writings which summarize the re-
search on which the Part 503 regulation is based.
For example, the potential for public health impacts via
inhalation of airborne pathogens was examined. Patho-
gens may become airborne via the spray of liquid biosolids
from a splash plate or high-pressure hose, or in fine par-
ticulate dissemination as dewatered biosolids are applied
or incorporated. While high-pressure spray applications
may result in some aerosolization of pathogens, this type
of equipment is generally used on large, remote sites such
as forests, where the impact on the public is minimal. Fine
particulates created by the application of dewatered
biosolids or the incorporation of biosolids into soil may
cause very localized fine particulate/dusty conditions, but
particles in dewatered biosolids are too large to travel far,
and the fine particulates do not spread beyond the imme-
diate area. The activity of applying and incorporating
biosolids may create dusty conditions. However, the
biosolids are moist materials and do not add to the dusty
conditions, and by the time biosolids have dried sufficiently
to create fine particulates, the pathogens have been re-
duced (Yeager and Ward, 1981)
The study of each pathway and the potential for public
health risk resulted in site restrictions that are protective of
public health and the environment and that must be fol-
lowed when Class B biosolids are land applied. While the
site restrictions provided in the Part 503 rule are sufficient
to protect the public from health impacts, workers exposed
to Class B biosolids might benefit from several additional
precautions. For example, dust masks should be worn for
the spreading of dry materials, and workers should wash
-------
their hands carefully after working with sewage sludge or
biosolids. Other recommended practices for workers han-
dling biosolids or sewage sludge include:
Wash hands before eating, drinking, smoking or using
the restroom.
Use gloves when touching biosolids or sewage sludge
or surfaces exposed to biosolids or sewage sludge.
Remove excess sewage sludge or biosolids from
shoes prior to entering an enclosed vehicle.
Keep wounds covered with clean, dry bandages.
If contact with biosolids or sewage sludge occurs, wash
contact area thoroughly with soap and water.
Table 2-2 shows the various pathways of exposure and
how the process requirements and site restrictions of the
Part 503 regulation protect public health for each path-
way.
2.3 General Information on Pathogens
The EPA has attempted, through this and other docu-
ments, to provide the public with a broad understanding of
the risk assessment and scientific basis of the Part 503
regulation. The regulation is based on the results of exten-
sive research and experience with land application of
treated sewage sludge (biosolids). However, as for all regu-
lations, proper interpretation and implementation of the
regulation are the most important aspects of protecting
public health and the environment.
Biosolids preparers should have a basic knowledge of
microbiology so that they can:
Understand the goals of the Part 503 regulation and
what is expected to meet the requirements
Address questions regarding pathogens and the pro-
tection of public health and the environment
Design appropriate testing/sampling programs to meet
the Part 503 requirements
Make informed decisions about laboratory and ana-
lytical methodology selection
This section outlines some of the generic issues of patho-
gen testing and quantification. References related to these
issues are listed at the end of this chapter as well as in
Chapter 12. Other chapters discuss sampling and sample
preservation as well as meeting the Part 503 requirements
in more detail.
Survivability of Pathogens
Wastewater generally contains significantly high concen-
trations of pathogens which may enter the wastewater sys-
tem from industries, hospitals, and infected individuals. The
wastewater treatment process tends to remove pathogens
from the treated wastewater, thereby concentrating the
Table 2-2. Pathways of Exposure and Applicable Site Restrictions
(Class B Biosolids Only)
Pathways
Part 503 Required Site Restriction
Handling soil from fields where
sewage sludge has been applied
Handling soil or food from home
gardens where sewage sludge
has been applied
Inhaling dust**
Walking through fields where
sewage sludge has been
applied*
Consumption of crops from fields
on which sewage sludge has
been applied
Consumption of milk or animal
products from animals grazed on
fields where sewage sludge has
been applied
Ingestion of water contaminated
by runoff from fields where
sewage sludge has been applied
Ingestion of inadequately cooked
fish from water contaminated by
runoff from fields where sewage
sludge has been applied
Contact with vectors which have
been in contact with sewage
sludge
No public access* to application
sites until at least 1 year after
Class B biosolids application.
Class B biosolids may not be
applied on home gardens.
No public access to application
sites until at least 1 year after
Class B biosolids application.
No public access to fields until at
least 1 year after Class B biosolids
application.
Site restrictions which prevent the
harvesting of crops until environ-
mental attenuation has taken
place.
No animal grazing for 30 days after
Class B biosolids have been
applied.
Class B biosolids may not be
applied within 10 meters of any
waters in order to prevent runoff.
from biosolids amended land from
affecting surface water.
Class B biosolids may not be
applied within 10 meters of any
waters in order to prevent runoff
from biosolids amended land from
affecting surface water.
All land applied biosolids must
meet one of the Vector Attraction
Reduction options (see Chapter 8).
'Public access restrictions do not apply to farm workers. If there is low
probability of public exposure to an application site, the public access
restrictions apply for only 30 days. However, application sites which
are likely to be accessed by the public, such as ballfields, are subject
to 1 year public access restrictions.
''Agricultural land is private property and not considered to have a
high potential for public access. Nonetheless, public access restrictions
still are applied.
pathogens in the sewage sludge. Like any other living or-
ganisms, pathogens thrive only under certain conditions.
Outside of these set conditions, survivability decreases.
Each pathogen species has different tolerance to different
conditions; pathogen reduction requirements are therefore
based on the need to reduce all pathogenic populations.
Some of the factors which influence the survival of patho-
gens include pH, temperature, competition from other mi-
croorganisms, sunlight, contact with host organisms, proper
nutrients, and moisture level.
The various Class A and Class B pathogen reduction
processes as well as the site restrictions for the land appli-
10
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cation of Class B biosolids are based on research regard-
ing the survivability of pathogens under specific treatment
conditions. Table 2-3 shows a comparison of the survival
of bacteria, viruses, and parasites in different sewage
sludge treatments. Table 2-4 shows the survival time of
various pathogens on soil or plant surfaces after land ap-
plication of biosolids.
Identification of Pathogens
Some of the pathogens of concern that appear in do-
mestic sewage and sewage sludge are shown in the pho-
tographs on pages 12 and 13. These include ascarids (As-
caris lumbricoides and Toxacara), whipworms (Trichuris
sp.), tapeworms (Hymenolepis sp. and Taenia sp.), amoeba
(Entamoeba coif), and giardia (Giardia lamblia). As shown
in these photographs, several color staining procedures
are needed to identify the organisms and the different struc-
tures within the organisms. The photograph of Giardia
lamblia depicts specimens stained with Lugol's iodine so-
lution, showing two nuclei, a median body, and axonemes
in each. In addition, scientists use a blue filter when pho-
tographing the pathogenic organisms through a micro-
scope. This filter is necessary to show the natural color of
the organisms.
What Units are Used to Measure
Pathogens?
Density of microorganisms in Part 503 is defined as num-
ber of microorganisms per unit mass of total solids (dry
Table 2-3. Summary of the Effects of Sewage Sludge Treatment on
Pathogens (Log Reductions Shown*)
PSRP Treatment
Bacteria Viruses
Parasites (protozoa and
helminths)
Anaerobic Digestion
Aerobic Digestion
Composting (PSRP)
Air Drying
Lime Stabilization
0.5-4.0
0.5-4.0
2.0-4.0
0.5-4.0
0.5-4.0
0.5-2.0
0.5-2.0
2.0-4.0
0.5-4.0
4.0
0.5
0.5
2.0-4.0
0.5-4.0
0.5
*A 1-log reduction (10-fold) is equal to a 90% reduction. Class B
processes are based on a 2-log reduction.
Table 2-4. Survival Times of Pathogens in Soil and on Plant Surfaces3
Pathogen
Bacteria
Viruses
Protozoan cystsd
Helminth ova
Soil
Absolute
Maximum3
1 year
1 yearc
10 days
7 years
Plants
Common
Maximum
2 months
3 months
2 days
2 years
Absolute
Maximum13
6 months
2 months
5 days
5 months
Common
Maximum
1 month
1 month
2 days
1 month
For survival rates, see Sorber and Moore (1986).
b Absolute maximum survival times are possible under unusual
conditions such as consistently low temperatures or highly sheltered
conditions (e.g., helminth ova below the soil in fallow fields) (Kowal,
1985).
cSolisey and Shields, 1987.
d Little, if any, data are available on the survival times of Giardia cysts
and Cryptosporidium oocysts.
Source: Kowal, 1985.
weight). Ordinarily, microorganism densities are determined
as number per 100 milliliters of wastewater or sewage
sludge. While the use of units of volume is sensible for
wastewater, it is less sensible for sewage sludge. Many
microorganisms in sewage sludge are associated with the
solid phase. When sewage sludge is diluted, thickened, or
filtered, the number of microorganisms per unit volume
changes markedly, whereas the number per unit mass of
solids remains almost constant. This argues for reporting
their densities as the number present per unit mass of sol-
ids, which requires that sewage sludge solids content al-
ways be determined when measuring microorganism den-
sities.
A second reason for reporting densities per unit mass of
total solids is that biosolids application to the land is typi-
cally measured and controlled in units of mass of dry sol-
ids per unit area of land. If pathogen densities are mea-
sured as numbers per unit mass of total solids, the rate of
pathogen application to the land is directly proportional to
the mass of dry biosolids applied.
Different Methods for Counting
Microorganisms
The methods and units used to count microorganisms
vary depending on the type of microorganism. Viable hel-
minth ova are observed and counted as individuals (num-
bers) under a microscope. Viruses are usually counted in
plaque-forming units (PFU). Each PFU represents an in-
fection zone where a single infectious virus has invaded
and infected a layer of animal cells. For bacteria, the count
is in colony-forming units (CFU) or most probable number
(MPN). CFU is a count of colonies on an agar plate or filter
disk. Because a colony might have originated from a clump
of bacteria instead of an individual, the count is not neces-
sarily a count of separate individuals. MPN is a statistical
estimate of numbers in a sample. The sample is diluted at
least once into tubes containing nutrient medium. The tubes
are maintained under conditions favorable for bacterial
growth. The original bacterial density in the sample is esti-
mated based on the number of tubes that show growth
and the level of dilution in those tubes.
Part 503 Density Limits
Under Part 503, the density limits for the pathogens are
expressed as numbers of PFUs, CFUs, or MPNs per 4
grams dry weight sewage sludge. This terminology came
about because most of the tests started with 100 ml of
sewage sludge which typically contained 4 grams of sew-
age sludge solids. Also, expressing the limits on a "per
gram" basis would have required the use of fractions (i.e.,
0.25/g or 0.75/g). Density limits for fecal coliforms, the in-
dicator organisms, however, are given on a "per gram" basis
because these organisms are much more numerous than
pathogens.
2.4 Protecting Public Health - The Part 503
The Part 503 regulation protects public health by limit-
ing the potential for public exposure to pathogens. This is
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Ascaris lumbricoides (or var. suum) eggs, 66 um, from anaerobically
digested sludge. Two-cell stage. (Photos on this page courtesy of Fox et
al., 1981)
Toxocara sp. egg, 90 pm from raw sewage.
Ascaris lumbricoides (or var. suum) eggs, 65 um, from anaerobically
digested sludge.
Trichuris sp. egg, 60 um from anaerobically digested sludge.
12
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Taenia sp. ovum. (Photo courtesy of Fox et al., 1981)
Giardia lamblia cysts. (Photo courtesy of Frank Schaefer, U.S. EPA,
National Risk Management Research Laboratory, Cincinnati, Ohio)
Hymenolepis (tapeworm) ova. (Photo courtesy of Fox et al., 1981)
Preparing compost for pathogen analysis. (Photo courtesy of U.S.
Department of Agriculture, Beltsville, Maryland)
Entamoeba colicysts, 15 \nn from anaerobically digested sludge.
(Photo courtesy of Fox et al., 1981)
13
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accomplished through treatment of the sewage sludge or
through a combination of sewage sludge treatment and
restrictions on the land application site that prevent expo-
sure to the pathogens in the biosolids and allow time for
the environment to reduce the pathogens to below detect-
able levels. The Part 503 vector attraction reduction re-
quirements also help reduce the spread of pathogens by
birds, insects, and other disease carriers (i.e. vectors) by
requiring that all sewage sludge that is to be land applied
undergo vector attraction reduction.
The Part 503 regulation also establishes the analytical
protocol for pathogen analysis. More information on the
quantification of pathogens and how pathogen reduction
is measured is included in Chapter 10 and in the Appendi-
ces.
Reducing the Number of Pathogens
Pathogen reduction can be achieved by treating sew-
age sludge prior to use or disposal and through environ-
mental attenuation. Many sewage sludge treatment pro-
cesses are available that use a variety of approaches to
reduce pathogens and alter the sewage sludge so that it
becomes a less effective medium for microbial growth and
vector attraction (Table 2-5). Processes vary significantly
in their effectiveness. For example, some processes (e.g.
lime stabilization) may effectively reduce bacteria and vi-
ruses but have little or no effect on helminth eggs. The
effectiveness of a particular process can also vary depend-
ing on the conditions under which it is operated. For ex-
ample, the length of time and the temperature to which
sewage sludge is heated is critical to the effectiveness of
heat-based treatment processes.
Part 503 lists sewage sludge treatment technologies that
are judged to produce biosolids with pathogens sufficiently
reduced to protect public health and the environment. The
regulation also allows the use of any other technologies
that produce biosolids with adequately reduced pathogens
as demonstrated through microbiological monitoring. The
Part 503 establishes two classifications of biosolids based
on the level of pathogen reduction the biosolids have un-
dergone. Class A biosolids are treated to the point at which
pathogens are no longer detectable. For Class B biosolids,
a combination of treatment and site restrictions are de-
signed to protect public health and the environment.
Monitoring Indicator Species
Sewage sludge may contain numerous species of patho-
genic organisms, and analyzing for each species is not
practical. The microbiological requirements of the Part 503
are therefore based on the use of an indicator organism
for the possible presence of pathological bacteria and both
the representative and the hardiest of known species for
viruses and helminths to represent the larger set of patho-
genic organisms. The indicator and representative organ-
Table 2-5. General Approaches to Controlling Pathogens and Vector Attraction in Sewage Sludge
Approach Effectiveness
Process Example'
Application of high temperatures (temperatures
may be generated by chemical, biological, or
physical processes).
Application of radiation
Application of chemical disinfectants
Reduction of the sewage sludge's volatile
organic content (the microbial food source).
Removal of moisture from the sludge
Depends on time and temperature. Sufficient
temperatures maintained for sufficiently long
time periods can reduce bacteria, viruses,
protozoan cysts, and helminth ova to below
detectable levels. Helminth ova are the most
resistant to high temperatures.
Depends on dose. Sufficient doses can reduce
bacteria, viruses, protozoan cysts, and
helminth ova to below detectable levels.
Viruses are most resistant to radiation.
Substantially reduces bacteria and viruses
and vector attraction. Probably reduces
protozoan cysts. Does not effectively reduce
helminth ova unless combined with heat.
Reduces bacteria. Reduces vector attraction.
Reduces viruses and bacteria. Reduces
vector attraction as long as the sewage sludge
remains dry. Probably effective in destroying
protozoan cysts. Does not effectively reduce
helminth ova unless combined with other
processes such as high temperature.
Composting (using biological processes to
generate heat). Heat drying and heat treat-
ment (use physical processes to generate
heat, e.g., hot gases, heat exchangers).
Pasteurization (physical heat, e.g., hot gases,
heat exchangers).
Aerobic digestion (biological heat)b
Anaerobic digestion (physical heat)b
Gamma and high-energy electron beam
radiation.
Lime stabilization
Aerobic digestion
Anaerobic digestion
Composting13
Air or heat drying
aSee Chapters 6 and 7 for a description of these processes. Many processes use more than one approach to reduce pathogens.
bEffectiveness depends on design and operating conditions.
14
-------
isms are ones that have been found to respond to treat-
ment processes and environmental conditions in a man-
ner similar to other organisms. Monitoring the levels of
these organisms, therefore, provides information about the
survival of the larger group.
For example, for helminth ova, tests are employed to
determine their presence and viability. The only helminth
ova viability that can be determined is that of Ascaris sp.
Ascaris is the hardiest of known helminths; thus, if condi-
tions are such that it cannot survive, it is not possible for
other helminth species (Toxacara, Trichuris, and Hyme-
nolepis) to survive.
For viruses, a test is available that simultaneously moni-
tors for several enterovirus species (a subset of enteric
viruses - see Table 2-1), which are presumed to be good
representatives for other types of enteric viruses.
Salmonella sp. are bacteria of great concern as well as
good representatives of reduction of other bacterial patho-
gens because they are typically present in higher densi-
ties than are other bacterial pathogens and are at least as
hardy.
Fecal coliforms are enteric bacteria that are used as in-
dicators of the likelihood of the presence of bacterial patho-
gens. Although fecal coliforms themselves are usually not
harmful to humans, their presence indicates the presence
of fecal waste which may contain pathogens. These bac-
teria are commonly used as indicators of the potential pres-
ence of pathogens in sewage sludges. They are abundant
in human feces and therefore are always present in un-
treated sewage sludges. They are easily and inexpensively
measured, and their densities decline in about the same
proportion as enteric bacterial pathogens when exposed
to the adverse conditions of sludge processing (EPA, 1992).
In the case of Class B biosolids, the microbiological limit
for meeting Alternative 1 is 2 million MPN fecal coliforms
per gram dry weight. Because untreated sewage sludge
generally contains up to 100 million MPN fecal coliforms
per gram dry weight, this limit assumes an approximate 2-
log reduction in the fecal coliform population. Studies of
anaerobic or aerobic digestion of sludges have shown that
the corresponding reduction in the pathogen population
will be significant and sufficient so that environmental at-
tenuation can reduce pathogen levels to below detection
limit within the time period of site restrictions (Farrell et
al.1985; Martin et al. 1990).
For some processes, fecal coliforms may be an overly
conservative indicator. Because bacteria may proliferate
outside of a host, reintroduction of fecal coliforms into
treated biosolids may result in their growth. Concentra-
tions may exceed the Class A fecal coliform limit even
though pathogens are not present. In these cases, because
fecal coliforms themselves are not a concern, testing di-
rectly for Salmonella sp. as an indicator of pathogen sur-
vival is permissible. Another issue with fecal coliforms is
that the tests for these bacteria may overestimate the num-
ber of coliforms from human species. This is of particular
concern when additives such as wood chips or other bulk-
ing agents have been added to biosolids (Meckes, 1995).
In this case also, it is advisable to test directly for Salmo-
nella sp.
It must however be noted that high counts of fecal
coliforms may also indicate that a process is not being
operated correctly. While a preparer may meet the regula-
tory requirements by testing for and meeting the regula-
tory limits for Salmonella sp., it is recommended that the
pathogen reduction process be reviewed to determine at
what point fecal coliforms are potentially not being reduced
or are being reintroduced into treated biosolids, and en-
sure that process requirements are being fulfilled.
Regrowth of Bacteria
One of the primary concerns for biosolids preparers is
regrowth of pathogenic bacteria. Some bacteria are unique
among sewage sludge pathogens in their ability to multi-
ply outside of a host. The processes outlined in the Part
503 regulation and in this document have been demon-
strated to reduce pathogens, but even very small popula-
tions of certain bacteria can rapidly proliferate under the
right conditions, for example, in sewage sludges in which
the competitive bacterial populations have been essen-
tially eliminated through treatment (see Section 4.3). Vi-
ruses, helminths, and protozoa cannot regrow outside their
specific host organism(s). Once reduced by treatment, their
populations do not increase. The Part 503 regulation con-
tains specific requirements designed to ensure that re-
growth of bacteria has not occurred prior to use or dis-
posal.
Preventing Exposure
Exposure to pathogens in Class B biosolids is limited by
restricting situations in which the public may inadvertently
come into contact with biosolids and by limiting access to
biosolids by vectors which may carry pathogens from the
sewage sludge.
S/te Restrictions
In the case of land application of Class B biosolids, site
restrictions are sometimes required in order to protect pub-
lic health and the environment. The potential pathways of
exposure to Class B biosolids or to pathogens which may
exist in Class B biosolids, are listed in Table 2.2 along with
a description of how site restrictions impose barriers to
exposure pathways. Site restrictions, discussed in detail
in Chapter 5, place limits on crop harvesting, animal graz-
ing, and public access on land where Class B biosolids
have been applied.
The goal of site restrictions is to limit site activities such
as harvesting and grazing until pathogens have been re-
duced by environmental conditions such as heat, sunlight,
desiccation, and competition from other microorganisms.
Table 2-3 summarizes the survival rates of four types of
pathogenic organisms on soil and on plants. As shown,
15
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helminths have the longest survival time; consequently,
the duration of some of the site restrictions is based on
helminth survival potential.
Vector Attraction Reduction
Insects, birds, rodents, and domestic animals may trans-
port sewage sludge and pathogens from sewage sludge
to humans. Vectors are attracted to sewage sludge as a
food source, and the reduction of the attraction of vectors
to sewage sludge to prevent the spread of pathogens is a
focus of the Part 503 regulation. Vector attraction reduc-
tion can be accomplished in two ways: by treating the sew-
age sludge to the point at which vectors will no longer be
attracted to the sewage sludge and by placing a barrier
between the sewage sludge and vectors. The technologi-
cal and management options for vector attraction reduc-
tion are discussed in Chapter 8.
2.5 Frequently Asked Questions
Because land application of biosolids has increased dra-
matically in the past several years, and because of some
well publicized incidents of pathogen contamination (not
necessarily related to biosolids), there have been many
questions about the level to which public health is pro-
tected. Although it is not possible for every issue to be
considered, the following section includes some of the
questions which are most frequently asked. In addition,
references are included at the end of this chapter and in
Chapter 12.
Can biosolids carry the pathogen that
causes mad cow disease?
It has been found that Bovine Spongiform Encephalopa-
thy (BSE), or Mad Cow disease, is caused by a prion pro-
tein, or the resistant beta form of protein. The pathway for
transmission is through the ingestion of tissue from infected
animals. There has been no evidence that the BSE prion
protein is shed in feces or urine. There have been no known
cases of BSE in the United States, and the Food and Drug
Administration (FDA) has taken various measures to pre-
vent spread of the disease to or within the United States.
For example, the primary route for infection, the use of
animal carcasses in animal feed, is banned in this country.
These measures have been effective, and BSE has not
become a public health concern in the U.S. with regard to
ingestion of beef or other exposure routes. Thus there
should be no risk of BSE exposure from biosolids. (Tan, et
al. 1999)
Is there any risk of HIV infection from
biosolids?
The HIV virus is contracted through contact with blood
or other body fluids of an infected individual. Feces and
urine do not carry the HIV virus, but contaminated fluids
may be discharged in minor amounts to the sewerage sys-
tem. The conditions in the wastewater system are not fa-
vorable for the virus's survival. Separation from the host
environment, dilution with water, chemicals from house-
hold and industrial sewer discharges, and the length of
time from discharge to treatment all impede the survival of
the virus (WEF/U.S. EPA Fact Sheet, 1997). HIV is sel-
dom detected in wastewater, and the additional treatment
that wastewater goes through, producing an effluent and
sewage sludge which undergoes treatment to become
Class A or B biosolids, makes it virtually impossible that
biosolids would contain the HIV virus. (Lue-Hing, et al.
1999)
Wastewater treatment workers may come into contact
with contaminated objects (bandages, condoms, etc.), but
common sense hygiene practices already in place at waste-
water treatment plants including the use of protective cloth-
ing and gloves greatly reduce the potential for exposure.
The U.S. Department of Health and Human Services stated
in 1990 that". . .these workers (wastewater treatment work-
ers) have no increased potential of becoming infected by
blood borne infectious agents. Therefore, medical waste
discarded to the sanitary sewer is not likely to present any
additional public health effects to the wastewater workers
or to the general public." (Johnson, et al. 1994)
What is a bioaerosol?
Bioaerosols are airborne water droplets containing mi-
croorganisms. These may include pathogenic microorgan-
isms. Bioaerosols are a potential public health concern with
regard to Class B biosolids because if pathogens are con-
tained in the biosolids, they may become airborne and in-
fect workers or the public through direct inhalation or
through contact after settling on clothing or tools. It has
been found that aerosolization of protozoa and helminths
is unlikely, but bacteria or bacterial components (endot-
oxin) and viruses may become airborne and disperse from
an application source depending on local meteorological
and topographical conditions. However, Class B biosolids
are rarely applied dry enough to become airborne; apply-
ing wet biosolids, particularly when the biosolids are incor-
porated or injected into the land, makes it highly unlikely
that bioaerosols will be dispersed from land application.
The public access restrictions for land-applied Class B
biosolids are based on the various pathways by which
pathogens may impact public health. Site restrictions are
adequate for the protection of public health, but site work-
ers who are present during the application of Class B
biosolids should follow standard hygiene precautions such
as washing their hands after contacting biosolids and wear-
ing dust masks if applying extremely dry material. More
information on aerosolization of pathogens from land ap-
plication can be found in the references following this chap-
ter.
What is Aspergillus fumigatus?
Aspergillus fumigatus is a pathogenic fungus which is
found in decaying organic matter such as sewage sludge,
leaves, or wood. Because the fungus is heat resistant, and
because sewage sludge composting facilities often use
wood chips as a bulking agent, A. fumigatus has been as-
sociated with composting. Inhalation of A fumigatus spores
16
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may result in allergenic effects including irritation of the
mucous membranes and asthma. However, A. fumigatus
is a secondary, or opportunistic pathogen, and infection
from A. fumigatus ("Aspergillosis") is limited to debilitated
or immuno-compromised individuals. Studies of the health
status of compost facility workers, the population most likely
to be exposed to Aspergillus fumigatus, have not shown
any negative health impacts (Millner, et al. 1994).
A. fumigatus is a ubiquitous fungus and has been found
in homes, gardens, and offices at considerable levels.
Numerous studies have been conducted to determine the
level of the fungus in the areas surrounding active com-
post sites and compare this level to background concen-
trations of Aspergillus fumigatus. In general, it has been
found that concentrations of A. fumigatus drop to back-
ground levels within 500-1000 feet of site activity. A.
fumigatus is not covered in the Part 503.
There have been several incidents in which fruit has been
contaminated with pathogens. Was this due to the land
application of biosolids?
No. Pathogens such as Salmonella sp. and pathogenic
strains of £. coli are typically associated with animal prod-
ucts (meat and eggs), but outbreaks have been known to
occur as a result of vegetable or fruit contamination from
the use of animal manures. Some of the well-publicized
incidents include cases in which the consumption of fresh
apple juice and cider resulted in widespread illness and
the death of a child (Center for Disease Control, 1996).
One case was found to be due to contamination from E.
coli found in bovine feces, and the other was due to
Cryptosporidium sp., also suspected to be from contact
with animal manure. Other cases have involved the con-
tamination of berries, melons, and alfalfa sprouts.
The Part 503 regulation applies only to the land applica-
tion of biosolids. Education of field workers, regulation of
working conditions, both domestically and abroad, and the
use of animal manure products are beyond the scope of
this document.
What is the Fate of Giardia and
Cryptosporidium During Sewage Sludge
Treatment?
Giardia lamblia and Cryptosporidium parvurn are proto-
zoan parasites that can infect the digestive tract of hu-
mans and other warm blooded animals. Semi-aquatic
mammals can serve as hosts, transmitting the disease to
humans who consume contaminated water. Domestic
mammals (particularly ruminants) can serve as infective
hosts and contaminate a drinking water supply. It is cur-
rently believed that at least 7% of the diarrheal cases in
the United States are caused by Cryptosporidium sp.
West (1991) notes that human protozoan parasites such
as Cryptosporidium sp. and Giardia sp. possess several
traits which facilitate waterborne transmission. They can
(1) be excreted in feces in large numbers during illness;
(2) persist through conventional sewage treatment; (3)
survive in an environmentally robust form or demonstrate
resilience to inactivation while in aquatic environments; (4)
be resistant to commonly used disinfectants in the treat-
ment of drinking water; and (5) require low numbers to
elicit infection in susceptible hosts consuming or exposed
to contaminated water.
Stadterman et al. (1995) reported on an anaerobic di-
gestion study which spiked Cryptosporidium sp. oocysts
into the digester and then periodically removed samples
to determine the die-off. They found that conventional
anaerobic digestion produces about a 2-log removal or a
better log reduction on this protozoan than it does on bac-
teria and viruses, but it does not reduce densities to the
low values needed for Class A for this pathogen. The re-
ported survival of some protozoa after anaerobic diges-
tion at 35°C is a cause for concern.
Jenkins et al. (1998) reported that ammonia inactivates
these oocysts, depending on the concentration. High pH
processes that increase the free ammonia concentration
can inactivate these oocysts (although pH by itself does
little).
A conservative conclusion from the limited research per-
formed is that Class B processes can only be expected to
reduce protozoan pathogens by about a factor often. The
restrictions written into the regulation (access control, grow-
ing only certain crops, restrictions on root crops, etc.) are
necessary to prevent exposure to these pathogens. The
Class A processes reduce protozoa to below detectable
limits.
References and Additional Resources
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of pathogen destruction during storage of dewatered
biosolids. Water Environment Research, Vol. 67,
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Ault, Steven K. and Michael Schott. 1993. Aspergillus, as-
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Technical Bulletin No. 1. California Integrated Waste
Management Board.
Beuchat, Larry and J.H. Ryu. 1997. Produce handling and
processing practices. Emerging Infectious Diseases,
Centers for Disease Control and Prevention. Vol 3, No.
4.
Casson, L.W., et al. 1992. HIV survivability in water. Water
Environmental Research, Vol 64:213-215.
Engineering News Record, August 13, 1987. No AIDS
threat in sewage. Issue 47.
Farzadegan, Homayoon. 1991. Proceedings of a Sympo-
sium: Survival of HIV in environmental waters. Balti-
more, MD. National Science Foundation and the Johns
Hopkins University.
17
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Farrell, J.B., G. Stern, and A.D. Venosa. 1985. Microbial de-
structions achieved by full-scale anaerobic digestion.
Paper presented at Municipal Wastewater Sludge Dis-
infection Workshop, Kansas City, MO. Water Pollution
Control Federation, October 1985.
Feldman, Kathleen. 1995. Sampling for airborne contami-
nants. BioCycle, August 1995 (84-86).
Cover, Nancy. 1993. "HIV in wastewater not a recognized
threat, other pathogens can be." National Small Flows
Clearinghouse Newsletter. July 1993.
Gupta, Phalguni. 1991. HIV survivability in wastewater. Pro-
ceedings of a Symposium: Survival of HIV in Environ-
mental Waters. Baltimore, MD. National Science Foun-
dation and the Johns Hopkins University.
Haines, John. 1995. Aspergillus in compost: Straw man or
fatal flaw? BioCycle, April 1995 (32-35).
Harding, H.J., R.E. Thomas, D.E. Johnson, and C.A. Sorber.
1981. Aerosols generated by liquid sludge application
to land. Report No. EPA/600/1-81/028. Washington, DC:
U.S. EPA, Office of Research and Development.
Haug, Roger T. 1993. The practical handbook of compost
engineering. Lewis Publishers.
Hay, Johnathan C. 1996. Pathogen destruction and biosolids
composting. BioCycle, Vol. 37, No. 6:67-76.
Jenkins, M.B., D.D. Bowman, and W.C. Ghiorse. 1998. In-
activation of Cryptosporidium pan/urn oocysts by am-
monia. Appl. Envir. Microbiol. 64, No. 2:784-788.
Johns Hopkins School of Hygiene and Public Health. 1991.
HIV transmission in the environment: What are the risks
to the public's health? Public Health News.
Johnson, R.W., E.R. Blatchley, III, and D.R. Mason. 1994.
HIV and the blood borne pathogen regulation: Implica-
tions for the wastewater industry. Water Environment
Research, Vol. 66:684-691.
Kindzierski, W.B., R.E. Roberts, and N.J. Low. 1993. Health
effects associated with wastewater treatment, disposal,
and reuse. Water Environment Research, Vol. 65:599-
606.
Kowal, N.E. 1985. Health effects of land application of mu-
nicipal sludge. Pub. No.: EPA/600/1-85/015. Research
Triangle Park, NC: U.S. EPA Health Effects Research
Laboratory.
Kowal, N.E. 1994. Pathogen risk assessment: Status and
potential application in the development of Round II regu-
lations. Proceedings of the June 19-20,1994 Speciality
Conference. The Management of Water and Wastewa-
ter Solids for the 21st Century: A Global Perspective.
Water Environment Federation. Alexandria, VA.
Lue-Hing, Cecil, Leonard Casson, and Prakasam Tata. 1999.
HIV in wastewater: present survivability and risk to waste-
water treatment plant workers. Water Environment Fed-
eration monograph. Alexandria, VA.
Martin, J.H., Jr., H.F. Bastian, and G. Stern. 1990 Reduction
of enteric microorganisms during aerobic sludge diges-
tion. Wat. Res. 24(11): 1377-1385.
Meckes, Mark, E.W. Rice, C.H. Johnson, and S. Rock. 1995.
Assessment of the Bacteriological Quality of Compost
from a Yard Waste Processing Facility. Science and
Utilization. Vol. 3, No. 3:6-13.
Millner, P.O., S.A. Olenchock, E. Epstein, R. Rylander, J.
Haines, J. Walker, B.L. Ooi, E. Home, and M. Maritato.
1994. Bioaerosols associated with composting facilities.
Compost Science and Utilization. 2(4):6-57.
Moore, B.E. 1993. Survival of human immunodeficiency vi-
rus (HIV), HIV-infected lymphocytes, and poliovirus in
water. Applied and Environmental Microbiology. Vol. 59:
1437-1443.
Morbidity and Mortality Weekly Report. 1996. Outbreak of
E. coli 0157:H7 infections associated with drinking un-
pasteurized commercial apple juice. Centers for Disease
Control and Prevention. Vol. 45, No. 44.
Obeng, L. 1985. Health aspects of water supply and sanita-
tion. In Information and Training for Low-Cost Water
Supply and Sanitation. Ed D. Trattles. World Bank. Wash-
ington, D.C.
Pell, Alice. 1997. Manure and microbes: Public and animal
health problem? Journal of Dairy Science 80:2673-2681.
Ponugoti, Prabhaker R, Mohamed F. Dahab, and Rao Surampalli.
1997. Effects of different biosolids treatment systems
on pathogen and pathogen indicator reduction. Water
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Chapter 3
Overview of Part 503 Subpart D Requirements,
Their Applicability, and Related Requirements
3.1 Introduction
The Subpart D (pathogen and vector attraction reduc-
tion) requirements of the 40 CFR Part 503 regulation ap-
ply to sewage sludge (both bulk sewage sludge and sew-
age sludge that is sold or given away in a bag or other
container for application to the land) and domestic septage
applied to the land or placed on a surface disposal site.
The regulated community includes persons who generate
or prepare sewage sludge for application to the land, as
well as those who apply it to the land. Included is anyone
who:
Generates treated sewage sludge (biosolids) that is
land applied or placed on a surface disposal site
Derives a material from treated sewage sludge (biosolids)
Applies biosolids to the land
Owns or operates a surface disposal site
Sewage sludge cannot be applied to land or placed on a
surface disposal site unless it has met, among other things,
the two basic types of requirements in Subpart D:
Requirements to ensure reduction of pathogens.
Requirements to reduce the potential of the sewage
sludge to attract vectors (rodents, birds, insects, and
other organisms that can transport pathogens).
These two types of requirements are separated in Part
503 (they were combined in an earlier regulation, Part
257), which allows flexibility in how they are achieved. Com-
pliance with the two types of requirements must be dem-
onstrated separately. Therefore, demonstration that a re-
quirement for reduced vector attraction has been met does
not imply that a pathogen reduction requirement also has
been met, and vice versa.
This chapter provides an overview of the Subpart D re-
quirements, their applicability, and the requirements related
to frequency of monitoring and recordkeeping. Where rel-
evant, the titles of the sections in this chapter include the
number of the Subpart D requirement discussed in the
section. Chapters 4 through 8 provide detailed information
on the pathogen and vector attraction reduction require-
ments.
Some of the pathogen and vector attraction reduction
alternatives are suitable only for biosolids which have been
processed by particular methods, such as by aerobic or
anaerobic digestion or composting. Chapters 4 and 5 con-
tain examples of how some facilities have met Part 503
requirements using appropriate pathogen and vector at-
traction reduction protocols, and Chapter 8 discusses each
vector attraction option in detail.
3.2 Pathogen Reduction Requirements
Sewage Sludge [503.32(a) and (b)]
The pathogen reduction requirements for sewage sludge
are divided into two categories: Class A and Class B. These
requirements use a combination of technological and mi-
crobiological requirements to ensure reduction of patho-
gens.
The implicit goal of the Class A requirements is to re-
duce the pathogens in sewage sludge (including enteric
viruses, pathogenic bacteria, and viable helminth ova) to
below detectable levels, as defined in the 1992 regulation.
The implicit goal of the Class B requirements is to re-
duce pathogens in sewage sludge to levels that are un-
likely to pose a threat to public health and the environment
under the specific use conditions. For Class B biosolids
that are applied to land, site use restrictions are imposed
to minimize the potential for human or animal exposure to
Class B biosolids for a period of time following land appli-
cation and until environmental factors (e.g. sunlight, des-
iccation) have further reduced pathogens. Both Class A
treatment of the sewage sludge which reduces pathogens
to below detectable levels and the combination of Class B
sewage sludge treatment and use restrictions on the land
application site protect public health and the environment.
"Exceptional quality" (EQ) biosolids are biosolids which
have met the Part 503 pollutant concentration limits (Table
3 of Section 503.13) as well as Class A pathogen reduc-
tion requirements and one of the first eight vector attrac-
tion reduction options listed in 503.33(b)(1) through (b)(8).
EQ biosolids may be land applied without site restrictions.
20
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Application of Class B biosolids must be conducted in
compliance with site restrictions. Because it is not pos-
sible for regulators to follow the land application of biosolids
applied on lawns and home gardens, Class B biosolids
cannot be sold or given away in bags or other containers
or applied on lawns and home gardens.
The testing requirements outlined throughout this docu-
ment are minimum standards for compliance with the Part
503 rule. It should be pointed out that biosolids are prop-
erly distributed under the most recent test results. How-
ever, facilities which distribute biosolids between sampling
events may wish to enhance their sampling programs to
better ensure compliance with pathogen reduction require-
ments and to enhance public confidence in biosolids qual-
ity. More frequent testing should also enable the biosolids
generators and preparers to better detect any changes in
operations that might affect compliance and slow more
rapid correction in any adverse changes. It should be noted
that when additional determinations are made, even though
they are in excess of Part 503 regulatory requirements, all
these analytical results and records must be retained in
the generator's, preparer's or land applier's files or reported
to the regulatory authority depending on the classification
of the operation or the regulatory authority's wishes.
Domestic Septage [503.32(c)J
As stated in Chapter 1, domestic septage is a form of
sewage sludge. The requirements for domestic septage
vary depending on how it is used or disposed. Domestic
septage applied to a public contact site, lawn, or home
garden must meet the same requirements as treated sew-
age sludge (biosolids) applied to these types of land (Class
A requirements). Separate, less-complicated requirements
for pathogen reduction apply to domestic septage applied
to agricultural land, forests, or reclamation sites. These
requirements include site restrictions to reduce the poten-
tial for human exposure to domestic septage and to allow
for pH adjustment or environmental attenuation with site
restrictions only on harvesting crops. No pathogen require-
ments apply if domestic septage is placed on a surface
disposal site.
3.3 Vector Attraction Reduction (VAR)
Requirements [503.33]
Subpart D provides 12 options to demonstrate vector
attraction reduction. These are referred to in this docu-
ment as Options 1 through 12. Table 8-2 summarizes these
options, and Chapter 8 provides more detailed informa-
tion on the options.
Reduction through Treatment
Options 1 through 8 apply to sewage sludge that has
been treated in some way to reduce vector attraction (e.g.,
aerobic or anaerobic digestion, composting, alkali addi-
tion, drying). These options consist of either operating
conditions or tests to demonstrate that vector attraction
has been reduced in the treated sewage sludge. Option
12 is a requirement to demonstrate reduced vector attrac-
tion in domestic septage through elevated pH. This option
applies only to domestic septage.
Reduction through Barriers
Options 9 through 11 are "barrier" methods. These op-
tions require the use of soil as a physical barrier (i.e., by
injection, incorporation, or as cover) to prevent vectors from
coming in contact with the land applied biosolids. They
include injection of biosolids below the land surface, incor-
poration of biosolids into the soil, and placement of a cover
over the biosolids. Options 9 through 11 apply to both
biosolids and domestic septage. Option 11 may only be
used at surface disposal sites.
Timing of Pathogen and Vector Attraction
Reduction
In the case of Class A biosolids, pathogen reduction must
take place before or at the same time as vector attraction
reduction unless VAR Option 6, 7, or 8 is used. More in-
formation is provided in Section 4.2.
3.4 Applicability of the Requirements
[503.15 and 503.25]
The applicability of the pathogen and vector attraction
reduction requirements is covered in 503.15 and 503.25.
Tables 3-1 to 3-3 summarize the applicability of the Sub-
part D requirements to sewage sludge and domestic
septage.
Table 3-1. Subpart D Requirements for the Land Application of Bulk
Biosolids1
Applied to Agricultural
Land, a Forest, a Public
Contact Site2, or a
Reclamation Site3
Applied to a Lawn or
Home Garden
Pathogen
Requirements
Vector Attraction
Reduction
Requirements
Class A or Class B
with site restrictions
Options 1-105
Class A4
Options 1-85>6
1 Bulk biosolids are biosolids that are not sold or given away in a bag or
other container for application to the land.
2 Public contact site is land with a high potential for contact by the
public, e.g., public parks, ball fields, cemeteries, plant nurseries, turf
farms, and golf courses.
3 Reclamation site is drastically distrubed land (e.g., strip mine,
construction site) that is reclaimed using biosolids.
4The regulation does not permit use of biosolids meeting Class B
requirements on lawns or home gardens, because it would not be
feasible under these circumstances to impose the site restrictions that
are an integral part of the Class B requirements.
See Chapter 8 for a description of these options.
6The two vector attraction reduction requirements that cannot be met
when bulk biosolids are applied to a lawn or a home garden are
injection of the bulk biosolids below the land surface and incorporation
of bulk biosolids into the soil. Implementation of these requirements for
bulk biosolids applied to a lawn or a home garden would be difficult, if
not impossible.
21
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Table 3-2 Subpart D Requirements for Biosolids Sold or Given Away
in a Bag or Other Container for Application to the Land
Land Application
Pathogen Requirements Class A1
Vector Attraction Reduction Options 1-82
Requirements
1 Class B biosolids cannot be sold or given away for use on home
gardens or lawns because it is not feasible to impose the Class B site
restrictions for these uses.
20nly the treatment-related options for vector attraction reduction apply
to biosolids that are sold or given away in bags or other containers for
application to the land, because of the barrier options, which are
implemented at the site of application, would be impossible. See
Chapter 8 for a description of these options.
Table 3-3. Subpart D Requirements for Domestic Septage Applied to
Agricultural Land, a Forest, or a Reclamation Site1 or
Placed on a Surface Disposal Site
Application to Agricultural
Land, a Forest, or a
Reclamation Site2
Surface Disposal
Pathogen Reduction Class B site restrictions No pathogen
Requirements
Vector Attraction
Reduction
Requirements
only or a pH adjustment
(pH> 12 for 30 minutes)
plus restrictions concerning
crop harvesting
Options 9, 10,124
requirements
Options 9-124
1For application to all other types of land, domestic septage must meet
the same requirements as other forms of sewage sludge (see Tables 3-1
and 3-2).
Reclamation site is drastically disturbed land (e.g., strip mine, construc-
tion site) that is reclaimed using biosolids.
3There is no pathogen requirement for domestic septage placed on a
surface disposal site because site restrictions for grazing of animals,
public access, and crop growing are already imposed by the Part 503,
Subpart C management practices to reduce exposure to pollutants in
domestic septage placed on a surface disposal site.
^See Chapter 8 for a description of these options.
Table 3-4. Frequency of Monitoring for Land Application and Surface
Disposal
Amount of Biosolids1 (metric tons
dry solids per 365-day period)
Minimum Frequency
Greater than zero but less than 2902
Equal to or greater than 290 but less
than1,5002
Equal to or greater than 1,500 but
Iessthan15,0002
Equal to or greater than 15,0002
Once per year
Once per quarter (four times
per year)
Once per 60 days (six times
per year)
Once per month (12 times per
year)
1 Either the amount of bulk biosolids applied to the land, or the amount
of sewage sludge received by a person who prepares biosolids that are
sold or given away in a bag or other container for application to the
land (dry weight basis), or the amount of biosolids (excluding domestic
septage) placed on a surface disposal site.
2290 metric tons = 320 tons (approximately 0.9 tons/day for a year).
1,500 metric tons = 1,653 tons (approximately 4.5 tons/day for a year).
15,000 metric tons = 16,534 tons (approximately 45 tons/day for a
year).
3.5 Frequency of Monitoring
Sewage Sludge [503.16(a) and 503.26(a)]
The Class A and Class B pathogen requirements and
the vector attraction reduction Options 1 through 8 (the
treatment related methods) all involve some form of moni-
toring. The minimum frequency of monitoring for these re-
quirements is given in Part 503.16(a) for land application
and Part 503.26(a) for surface disposal. The frequency
depends on the amount of biosolids used or disposed an-
nually (see Table 3-4). The larger the amount used or dis-
posed, the more frequently monitoring is required.
In addition to monitoring frequency, a sampling plan
should address the minimum number of samples per sam-
pling event that are necessary to adequately represent
biosolids quality. Both of these issues are addressed in
Chapter 9.
As stated throughout this document, the monitoring re-
quirements set forth in the Part 503 and this document are
the minimum requirements. Persons or facilities that gen-
erate and distribute biosolids are encouraged to go be-
yond the minimum required programs as necessary.
Domestic Septage [503.16(b) and 503.26(b)]
One of the requirements that can be used for demon-
strating both pathogen reduction and vector attraction re-
duction in domestic septage is to elevate pH to 12 for 30
minutes (see Sections 5.6 and 8.13). When this require-
ment is to be met, each container of domestic septage
(e.g., each tank truckload) applied to the land or placed on
a surface disposal site must be monitored for pH over 30
minutes.
3.6 Sampling Stockpiled or Remixed
Biosolids
In many cases there are several steps of preparation
before biosolids are actually used or distributed. For ex-
ample, some products such as composted biosolids may
be prepared and then mixed with other materials to create
a soil blend. Other biosolids products may be prepared
and then stored either on site or at a field until the material
can be applied. In some cases, resampling and/or re-es-
tablishment of the biosolids quality may be necessary.
Whether or not biosolids must undergo additional sam-
pling or processing depends on the classification of the
biosolids and on whether the biosolids remain in the con-
trol of the preparer or if they have been distributed or sold.
EQ Biosolids
If the biosolids are classified as exceptional quality (EQ)
(see Section 3.2), they may be distributed for land appli-
cation without site restriction. EQ is an industry term rather
than a regulatory term. Land application of EQ biosolids is
not regulated by the Part 503 once the biosolids leave the
control of the biosolids preparer. Therefore, soil blenders
or other (non-preparer) users who take EQ biosolids may
store the biosolids or mix the EQ biosolids with other (non-
sewage sludge) materials without resampling the product.
22
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Conversely, if EQ biosolids remain within the control of the
preparer, they are still considered biosolids and are still cov-
ered by the Part 503. Like all Class A products, they must
undergo microbiological testing at the last possible point
before being distributed. In addition, if the preparer mixes
the EQ biosolids or otherwise changes the quality of the
biosolids, the new biosolids product must again comply with
pathogen reduction, vector attraction reduction, and micro-
biological requirements.
Non-EQ Class A Biosolids
Class A biosolids are not necessarily classified as EQ
biosolids; if pollutant levels exceed the Table 3 limits or if
one of the first eight vector attraction options has not been
met, the Class A biosolids are not considered EQ. All Class
A biosolids must undergo microbiological testing just before
they are distributed, so testing for fecal coliforms or Salmo-
nella sp. must take place after storage. In addition, if the
preparer mixes the Class A biosolids with other materials or
otherwise changes the quality of the biosolids, the new
biosolids product must comply with pathogen reduction, vec-
tor attraction reduction, and microbiological requirements.
Non-EQ Class A biosolids must also be monitored after
they are distributed. For example, if a Class Acompost which
does not meet one of the EQ pollutant limits is sold to a
vendor who mixes the compost with soil, the soil blender
becomes a biosolids preparer, and must therefore comply
with all Part 503 regulations. The new biosolids product must
comply with pathogen reduction, vector attraction reduction,
and microbiological requirements.
Class B Biosolids
Class B biosolids can meet pathogen reduction require-
ments at any point; there is no requirement that Class B
biosolids be tested just before distribution. Therefore,
biosolids which have met the Class B pathogen reduction
requirements can be stored on site without retesting. How-
ever, if the Class B biosolids are mixed with other materials
or the quality of the biosolids are otherwise altered, the new
biosolids product must meet pathogen reduction and vector
attraction reduction requirements.
The same is true for Class B biosolids that are distributed
and no longer under the control of the preparer. Stored Class
B biosolids do not have to be retested for pathogen reduc-
tion, unless the quality of the biosolids is somehow altered
through mixing or further processing.
3.7 Recordkeeping Requirements [503.17
and 503.27]
Recordkeeping requirements are covered in Part 503.17
for land application and Part 503.27 for surface disposal.
Records are required for both biosolids and domestic
septage that are used or disposed. All records must be
retained for 5 years except when the cumulative pollutant
loading rates (CPLRs)in Subpart B (Land Application) of
the Part 503 are usedi. If CPLRs are used, records of pol-
1 Cumulative pollutant loading rates are not related to pathogen control and there-
fore are not covered in this document.
lutant loading at each site must be kept indefinitely. All
records must be retained and made available to the regu-
latory authority upon request (see Section 3.8).
Land Application
Records must be kept to ensure that the biosolids meet
the applicable pollutant limits, management practices2, one
of the pathogen requirements, one of the vector attraction
reduction requirements and, where applicable, the site re-
strictions associated with land application of Class B
biosolids. When biosolids are applied to land, the person
preparing the biosolids for land application and the person
applying bulk biosolids must keep records3'4. The person
applying biosolids that were sold or given away does not
have to keep records.Table 3-5 summarizes the record-
keeping requirements for land application.
Surface Disposal
When biosolids are placed on a surface disposal site,
the person preparing the biosolids and the owner/operator
of the surface disposal site must keep records. In the case
of domestic septage applied to agricultural land, forest, or
a reclamation site or placed on a surface disposal site, the
person applying the domestic septage and the owner/op-
erator of the surface disposal site may be subject to patho-
gen record keeping requirements, depending on which
vector attraction reduction option is met. Table 3-6 sum-
marizes the pathogen-related recordkeeping requirements
for surface disposal.
Certification Statement
In every case, recordkeeping involves signing a certifi-
cation statement that the requirement has been met. Parts
503.17 and 503.27 of the regulation contain the required
certification language.
3.8 Reporting Requirements for Sewage
Sludge [503.18 and 503.28]
Reporting requirements for sewage sludge are found in
Part 503.18 for land application and Part 503.28 for sur-
face disposal. These requirements apply to Class I sludge
management facilities5 and to publicly owned treatment
2Pollutant limits and management practices are not related to the pathogen re-
quirements and therefore are not covered in this document.
3Person as defined under Part 503.9 may be an individual, association, partner-
ship, corporation, municipality, state or federal agency, or an agent or employee of
a state or federal agency.
4When biosolids are prepared by one person, and another person who places it in
a bag or other container for sale or give-away for application to the land changes
the quality of that biosolids, both persons must keep the records required of preparers
(see Table 3-5 and Section 3.6).
5 A Class I sewage sludge management facility is any publicly owned treatment
works (POTW) required to have an approved pretreatment program under 40 CFR
403.8(a) [including any POTW located in a state that has assumed local program
responsibilities under 40 CFR 403.1 (e)] and any treatment works treating domestic
sewage classified as a Class I sludge management facility by EPA or the state
sludge management program because of the potential for its sewage sludge use or
disposal practices to adversely affect public health and the environment.
23
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Table 3-5. Summary of Pathogen and Vector Attraction Reduction Recordkeeping Requirements for Land Application of Biosolids1
Description of
How Class A
Pathogen
Requirement
Was Met
Description of
How Class B
Pathogen
Requirement
Was Met
Description of
How the Class B
Site Restrictions
Were Met at Each
Site Where Sewage
Sludge Was Applied
Description of
How Pathogen
Requirement for
Domestic Septage
Applied to
Agricultural Land,
a Forest, or a
Reclamation Site
Was Met
Description of
How Vector
Attraction
Requirement
Was Met
Certification
Statement
that the
Requirement
Was Met
Biosolids - Pathogen
Requirements
Person preparing Class A
bulk biosolids
Person preparing Class A
biosolids for sale or give
away in a bag or other
container
Person preparing Class B
biosolids
Person applying Class B
biosolids
Biosolids - Vector-Attraction
Reduction Requirements
Person preparing biosolids
that meet one of the
treatment-related vector
attraction reduction
requirements (Options 1-8)
Person applying biosolids if a
barrier-related option
(Options 9-11) is used to
meet the vector attraction
reduction requirement
Domestic Septage
Person applying domestic
septage to agricultural
land, a forest, or a
reclamation site
1Other recordkeeping requirements, not covered in this document; apply to pollutant limits and management practices.
Table 3-6. Summary of Pathogen and Vector Attraction Reduction Recordkeeping Requirements for Surface Disposal of Biosolids1
Required Records
Description of How Class A
or B Pathogen Requirement
was Met
Description of How Vector
Attraction Requirement
was Met
Certification Statement that
the Requirement was
Met
Biosolids - Pathogen Requirements
Person preparing the biosolids V
Sewage Sludge - Vector Attraction Reduction Requirements
Person preparing biosolids that meet
one of the treatment-related vector
attraction reduction requirements
(Options 1-8)
Owner/operator of the surface
disposal site if a barrier-related
option (Options 9-11) is used to meet
the vector attraction reduction
requirement
continued
24
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Table 3-6. (Continued)
Required Records
Description of How Class A
or B Pathogen Requirement
was Met
Description of How Vector
Attraction Requirement
was Met
Certification Statement that
the Requirement was
Met
Domestic Septage
Person who places domestic
septage on the surface
disposal site if the domestic
septage meets Option 12 for
vector attraction reduction
Owner/operator of the surface
disposal site if a barrier-related
option (Options 9-11) is used
to meet the vector attraction
reduction requirement
10therrecordkeeping requirements, not covered in this document, apply to pollutant limits and management practices.
works either with a design flow rate equal to or greater
than 1 million gallons per day or that serve 10,000 or more
people, or if specifically required by the permitting author-
ity. Reports must be submitted to the regulatory authority
(see Tables 3-5 and 3-6) and/or as the owner/operators of
surface disposal sites (see Table 3-6) on February 19 of
each year. There are no reporting requirements associ-
ated with the use or disposal of domestic septage, but
records must be kept and made available to the regulatory
authority upon request.
3.9 Permits and Direct Enforceability
[503.3]
Permits
Under Part 503.3(a), the requirements in Part 503 may
be implemented through (1) NPDES permits issued to treat-
ment works treating domestic sewage by EPA permits is-
sued by states with an EPA-approved sludge management
program, and (2) by permits issued under Subtitle C of the
Solid Waste Disposal Act; Part C of the Safe Drinking Water
Act; the Marine Protection, Research, and Sanctuaries Act
of 1972; or the Clean Air Act. Treatment works treating
domestic sewage should submit a permit application6 to
the approved state program, or, if there is no such pro-
gram, to the EPA Regional Sludge Coordinator (see Ap-
pendix A).
Direct Enforceability
Under Part 503.3(b), the requirements of Part 503 auto-
matically apply and are directly enforceable even when no
federal permit has been issued for the use or disposal of
biosolids.
6 See 40 CFR Parts 122/123, and 501; 54 FR 18716/May 2,1989; and 58 FR 9404/
February 19,1993, for regulations establishing permit requirements and proce-
dures, as well as requirements for states wishing to implement approved sewage
sludge management programs as either part of their NPDES programs or under
separate authority.
25
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Chapter 4
Class A Pathogen Requirements
4.1 Introduction
This chapter principally discusses the Class A pathogen
requirements in Subpart D of the 40 CFR Part 503 regula-
tion. Biosolids that are sold or given away in a bag or other
container for application to land must meet these require-
ments (see Section 3.4). Bulk biosolids applied to a lawn
or home garden also must meet these requirements. Bulk
biosolids applied to other types of land must meet these
requirements if site restrictions are not met (see Chapter 5
for guidance on Class B biosolids). Some discussion is,
however, presented of vector attraction reduction.
There are six alternative methods for demonstrating
Class A pathogen reduction. Two of these alternatives pro-
vide continuity with 40 CFR Part 257 by allowing use of
Processes to Further Reduce Pathogens (PFRPs) and
equivalent technologies (see Sections 4.8 and 4.9). Any
one of these six alternatives may be met for the sewage
sludge to be Class A with respect to pathogens. The im-
plicit objective of all these requirements is to reduce patho-
gen densities to below detectable limits which are:
Salmonella sp.
Enteric viruses1
Viable helminth ova
less than 3 MPN per 4 grams
total solids biosolids (dry weight
basis)
less than 1 PFU per 4 grams
total solids biosolids (dry weight
basis)
less than 1 viable helminth ova/
4 gram total solids biosolids (dry
weight basis)
One of the vector attraction reduction requirements (see
Chapter 8) also must be met when biosolids are applied to
the land or placed on a surface disposal site. To meet the
Part 503 regulatory requirements, pathogen reduction must
be met before vector attraction reduction or at the same
time vector attraction reduction is achieved.
For the following sections, the title of each section pro-
vides the number of the Subpart D requirement discussed
1 Enteric viruses are monitored using a method that detects several enterovirus
species-a subset of enteric viruses. This method is presumed to be a good indica-
tor of enteric viruses. Since the objective of the Part 503 regulation is to reduce all
enteric viruses to less than 1 PFU per 4 grams total solids sewage sludge, this
document refers to "enteric viruses" when discussing this requirement, although, in
reality, the detection method enumerates only enteroviruses.
in the section. The exact regulatory language can be found
in Appendix B, which is a reproduction of Subpart D. Chap-
ters 9 and 10 provide guidance on the sampling and analy-
sis needed to meet the Class A microbiological monitoring
requirements.
4.2 Vector Attraction Reduction to Occur
With or After Class A Pathogen
Reduction [503.32(a)(2)]
Although vector attraction reduction and pathogen re-
duction are separate requirements, they are often related
steps of a process. Chapter 8 discusses the vector attrac-
tion reduction options in greater detail.
The order of Class A pathogen reduction in relation to
the reduction of vector attraction is important when certain
vector attraction reduction options are used. Part
503.32(a)(2) requires that Class A pathogen reduction be
accomplished before or at the same time as vector attrac-
tion reduction, except for vector attraction reduction by al-
kali addition [503.33(b)(6)] or drying [503.33(b)(7) and (8)]
(see Chapter 8).
This requirement is necessary to prevent the growth of
bacterial pathogens after sewage sludge is treated. Con-
tamination of biosolids with a bacterial pathogen after one
of the Class A pathogen reduction alternatives has been
conducted may allow extensive bacterial growth unless:
a) an inhibitory chemical is present, b) the biosolids are
too dry to allow bacterial growth, c) little food remains for
the microorganisms to consume, or d) an abundant popu-
lation of non-pathogenic bacteria is present. Vegetative
cells of non-pathogenic bacteria repress the growth of
pathogenic bacteria by "competitive inhibition" which is in
substantial part due to competition for nutrients. It should
be noted that vector attraction reduction by alkali addition
[503.3(b)(6)] or drying [503.3(b)(7)] and (8) is based on
the characteristic of the biosolids (pH or total solids) re-
maining elevated. Should the pH drop or the biosolids ab-
sorb moisture, the biosolids may be more hospitable to
microorganisms, and pathogenic bacteria, if introduced,
may grow. Therefore it is recommended that biosolids
treated with these methods be stored appropriately.
Biological treatment processes like anaerobic digestion,
aerobic digestion, and composting produce changes in the
26
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sewage sludge so that it satisfies one of the vector attrac-
tion reduction requirements [503.3(b)(1) through (5)]. They
repress bacterial growth by minimizing the food supply and
providing competition for the remaining food from non-
pathogenic organisms. The pathogen reduction alterna-
tive must precede the vector attraction reduction process;
otherwise, the large number of non-pathogenic bacterial
cells would be killed and growth of pathogenic bacteria
could occur. Certain pathogen reduction processes such
as composting accomplish vector attraction reduction by a
biological process simultaneously with thermal reduction
of pathogens. A non-pathogenic bacterial community sur-
vives which adequately suppresses growth of pathogenic
bacteria.
In the case of Class B biosolids, a population of non-
pathogenic bacteria is retained and inhibits the growth of
pathogenic bacteria through competition, and site restric-
tions are imposed with their land application to reduce the
risk of exposure to pathogens. Therefore, bacterial growth
is not a concern for Class B biosolids, and vector attrac-
tion reduction and pathogen reduction for compliance with
the Part 503 Rule requirements may be met in any order.
4.3 Monitoring of Fecal Coliform or
Salmonella sp. to Detect Growth of
Bacterial Pathogens [503.32(a)(3)-(8)]
The goal of Class A processes is to reduce the level of
pathogens to below detectable levels and below the level
at which they are infectious. The Class A processes have
been shown to sufficiently reduce pathogen levels in
biosolids, and studies to date have not found that the growth
of pathogenic bacteria may occur in materials after pro-
cesses take place or during storage. Favorable conditions
for the growth of pathogenic bacteria would be: adequate
moisture, absence of an inhibitory chemical, and inad-
equate reduction of nutritive value of the sewage sludges.
Because Class A biosolids may be used without site re-
strictions, all Class A material must be tested to show that
the microbiological requirements are met at the time when
it is ready to be used or disposed. In addition to meeting
process requirements, Class A biosolids must meet one of
the following requirements:
Either the density of fecal coliforms in the sewage
sludge be less than 1,000 MPN2 per gram total solids
(dry weight basis).
Or the density of Sa/mone//a sp. bacteria in the sew-
age be less than 3 MPN per 4 grams of total solids
(dry weight basis).
Although the Part 503 regulation does not specify the
number of samples that should be taken to show compli-
ance with Class A density requirements, sampling programs
should provide adequate representation of the biosolids
generated. Chapter 9 provides guidance for calculating the
number of samples that should be taken per sampling
event. Unlike Class B biosolids, compliance with Class A
requirements is not based on an average value. Each
sample analyzed must comply with the numerical re-
quirements.
The microbiological requirement must be met either:
At the time of use or disposal3, or
At the time the biosolids are prepared for sale or give
away in a bag or other container for land application,
or
At the time the biosolids or material derived from the
biosolids is prepared to meet the requirements in
503.10(b), 503. 10(c), 503.10(e), or 503.10(f)4.
If a facility stores material before it is distributed for use
or disposal, microbiological testing should take place after
storage.
In each case, the timing represents the last practical
monitoring point before the biosolids are applied to the land
or placed on a surface disposal site. Biosolids that are sold
or given away cannot be monitored just prior to actual use
or disposal; instead monitoring is required as it is prepared
for sale or give away. Biosolids that meet the 503.10(b, c,
d, or e) requirements are considered "Exceptional Quality"
and are therefore not subject to further control (see Sec-
tion 1.4). For this reason, the microbiological requirements
must be met at the time the biosolids are prepared to meet
the 503.10 requirements, which in most cases is the last
time the biosolids are under the control of a biosolids
preparer.
As discussed in Chapter 9, the timing of pathogen sam-
pling is also a function of laboratory turnaround time. Ob-
taining results for fecal coliform and Salmonella sp. analy-
sis may take several days if tests are performed in-house,
but commercial labs may require more time to process and
report results. It is not unusual for laboratories to have a
turnaround time of 2 weeks, even for simple tests such as
fecal coliform. If this is the case, this time should be fac-
tored into the sampling program so that results can be
obtained before biosolids are distributed for use or dis-
posal.
Monitoring Fecal Coliforms or Salmonella
sp.
Fecal coliforms are used in the Part 503 as an indicator
organism, meaning that they were selected to be moni-
tored because reduction in fecal coliforms correlates to
reduction in Sa/mone//a sp. and other organisms. The re-
2The membrane filter method is not allowed for Class A because, at the low fecal
coliform densities expected, the filter would have too high a loading of sewage
sludge solids to permit a reliable count of the number of fecal coliform colonies.
3Minus the time needed to test the biosolids and obtain the test results prior to use
or disposal (see Chapter 10).
4The 503.10(b)(c)(e) and (f) requirements are not discussed in this document.
27
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quirements were based on experimental work by Yanko
(1987) and correlations developed from Yanko's data by
Farrell (1993) which show that this level of fecal coliforms
correlate with a very low level of Salmonella sp. detection
in composted sewage sludge (EPA, 1992).
Anecdotal reports suggest that some composting facili-
ties may have difficulty meeting this requirement even when
Salmonella sp. are not detected. This might be expected
under several circumstances. For example, very severe
thermal treatment of sewage sludge during composting can
totally eliminate Salmonella sp. yet leave residual fecal
coliforms. If the sewage sludge has been poorly composted
and thus is a good food source, fecal coliforms may grow
after the compost cools down from thermophilic tempera-
tures. Because the Salmonella sp. are absent, they can-
not grow. An even more probable circumstance could oc-
cur if the sewage sludge is treated with lime before
composting. Lime effectively destroys Salmonella sp. in
sewage sludge and leaves surviving fecal coliforms (Farrell
et al., 1974). Under conditions favorable for growth, the
fecal coliforms can regrow to levels higher than 1,000 MPN
per gram. Research has shown that detection of Salmo-
nella sp. is much rarer in composted sewage sludge that
has been lime treated and composted than detection of
fecal coliforms. Fecal coliform densities maybe high there-
fore compared to pathogen densities in such cases and
maybe overly conservative. For this reason, all of the Part
503 Class A alternatives allow the direct measurement of
Salmonella sp. or fecal coliform analysis, but do not re-
quire both.
4.4 Alternative 1: Thermally Treated
Sewage Sludge [503.32(a)(3)]
This alternative may be used when the pathogen reduc-
tion process uses specific time-temperature regimes to
reduce pathogens. Under these circumstances, time-con-
suming and expensive tests for the presence of specific
pathogens can be avoided. It is only necessary to demon-
strate that:
Either fecal coliform densities are below 1,000 MPN
per gram of total solids (dry weight basis), or Salmo-
nella sp. bacteria are below detection limits (3 MPN
per 4 grams total solids [dry weight basis]) at the time
the sewage sludge is used or disposed, at the time
the sewage sludge is prepared for sale or given away
in a bag or other container for land application, or at
the time the sewage sludge or material derived from
the sewage sludge is prepared to meet the require-
ments in 503.10(b), 503.10(0), 503.10(e), or 503.10(1).
And the required time-temperature regimes are met.
Time-Temperature Requirement
Four different time-temperature regimes are given in
Alternative 1. Each regime is based on the percent solids
of the sewage sludge and on operating parameters of the
treatment process. Experimental evidence (EPA, 1992)
demonstrates that these four time-temperature regimes
reduce the pathogenic organisms to below detectable lev-
els.
The four time-temperature regimes are summarized in
Table 4-1. They involve two different time-temperature
equations. The equation used in Regimes A through C re-
sults in requirements that are more stringent than the re-
quirement obtained using the equation in Regime D. For
any given time, the temperature calculated for the Regime
D equation will be 3 Celsius degrees (5.4 Fahrenheit de-
grees) lower than the temperature calculated for the Re-
gimes A through C equation.
The time-temperature relationships described for Alter-
native 1 are based on extensive research conducted to
correlate the reduction of various pathogens in sewage
sludge to varying degrees of thermal treatment. The re-
sulting time-temperature relationship which is the basis for
Alternative 1 is shown in Figure 4-1. These requirements
are similar to the FDA requirements for treatment of egg-
nog, a food product with flow characteristics similar to those
of liquid sewage sludge. The Regimes A through D differ
depending on the characteristics of sewage sludge treated
and the type of process used because of the varying effi-
ciency of heat transfer under different conditions.
It is important to note that it is mandatory for all sew-
age sludge particles to meet the time-temperature re-
gime. Therefore, testing of temperatures throughout the
sewage sludge mass and agitating the material to ensure
uniformity would be appropriate. For processes such as
thermophilic digestion, it is important that the digester de-
sign not allow for short circuiting of untreated sewage
sludge. One approach that has been used to overcome
this problem has been to draw off treated sewage sludge
and charge feed intermittently with a sufficient time period
between draw-down and feeding to meet the time-tem-
perature requirement of Alternative 1. Another option would
be to carry out the process in two or more vessels in se-
ries so as to prevent bypassing.
These time-temperature regimes are not intended to be
used for composting (the time-temperature regime for
composting is covered in Alternative 5: Processes to Fur-
ther Reduce Pathogens).
A more conservative equation is required for sewage
sludges with 7% or more solids (i.e., those covered by
Regimes A and B) because these sewage sludges form
an internal structure that inhibits the mixing that contrib-
utes to uniform distribution of temperature. The more strin-
gent equation is also used in Regime C (even though this
regime applies to sewage sludges with less than 7% sol-
ids) because insufficient information is available to apply
the less stringent equation for times less than 30 minutes.
The time-temperature requirements apply to every par-
ticle of sewage sludge processed. Time at the desired tem-
perature is readily determined for batch or plug flow op-
erations, or even laminar flow in pipes. Time of contact
also can be calculated for a number of completely mixed
28
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Table 4-1. The Four Time-Temperature Regimes for Alternative 1 (Thermally Treated Sewage Sludge) [503.32(a)(3)]
Regime Part 503 Section Applies to
Required Time-
Temperature1
503.32(a)(3)(ii)(A)
Sewage sludge with at least
7% solids (except those covered
by Regime B)
D=131,700,000/1001400t
t>50°C (122°F)2
D>0.0139 (i.e., 20 minutes)3
503.32(a)(3)(ii)(B)
Sewage sludge with at least
7% solids that are small particles
heated by contact with either warmed
gases or an immiscible liquid4
D = 131,700,000/10°1400t
t>50°C(122°F)2
D>1.74X10-4 (i.e., 15
seconds)5
503.32(a)(3)(ii)(C)
Sewage sludge with less than
7% solids treated in processes with
less than 30 minutes contact time
D= 131,700,000/1001400t
1.74X 10-4 (i.e.,15
seconds) 50°C (122°F)2
D>0.021(i.e. 30 minutes)7
1D = time in days; t = temperature (°CV
2The restriction to temperatures of at least 50°C (122°F) is imposed because information on the time-temperature relationship at lower temperatures
is uncertain.
3A minimum time at 20 minutes is required to ensure that the sewage sludge has been uniformly heated.
"Two examples of sewage sludge to which this requirement applies are:
Sewage sludge cake that is mixed with previously dried solids to make the entire mass a mixture of separate particles, and is then dried by
contact with a hot gas stream in a rotary drier.
Sewage sludge dried in a multiple-effect evaporator system in which the system sludge particles are suspended in a hot oil that is heated by
indirect heat transfer with condensing steam.
5Time-at-temperature of as little as 15 seconds is allowed because, for this type of sewage sludge, heat transfer between particles and the healing
fluid is excellent. Note that the temperature is the temperature achieved by the sewage sludge particles, not the temperature of the carrier medium.
6Time-at-temperature of as little as 15 seconds is allowed because heat transfer and uniformity of temperature is excellent in thiswage
sludge. The maximum time of 30 minutes is specified because a less stringent regime (D) applies when time-at-temperature is 30 minutes or more.
7Time-at-temperature of at least 30 minutes is required because information on the effectiveness of this time-temperature regime for reducing
pathogens at temperatures of less than 30 minutes is uncertain.
100
90
80
O
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reactors in series (Schafer, et al, 1994). However, there
are concerns that flow-through systems may permit some
sludge to pass through without adequate treatment. It is
recommended that facilities wishing to use this alternative
for a flow-through system conduct tracer studies to dem-
onstrate that sewage sludge is treated at the required tem-
perature for sufficient time.
Vector Attraction Reduction
Thermally treated sewage sludge must be treated by an
additional vector attraction reduction process since ther-
mal treatment does not necessarily break down the vola-
tile solids in sewage sludge. Vector attraction reduction
can be met by further processing the sewage sludge with
pH adjustment or heat drying (Options 6 and 7), or by
meeting one of the other options (Options 8-11). Options
1 through 5 would not be applicable to thermally treated
sludge unless the sludge was subject to biological diges-
tion after or during thermal treatment.
Example of Meeting Class A Pathogen
and Vector Attraction Reduction
Requirements
Type of Facility
Testing
Vector Attraction
Reduction
Use or Disposal
Thermophilic Anaerobic Digester
Class A
Digested sewage sludge is retained
for at least 5 days at 50°C (Regime
D). Sewage sludge is agitated regu-
larly to ensure thorough mixing, and
temperatures are monitored con-
tinually in a batch mode of opera-
tion.
Sewage sludge is sampled 6 times
each year for pollutants and fecal
conforms. Compliance with vector
attraction reduction is also moni-
tored.
VAR is met by reducing volatile sol-
ids by over 38 percent. Five
samples of input and output sew-
age sludge from each batch are
analyzed for volatile solids content
over a period of two weeks.
The Class A biosolids are land ap-
plied.
Microbiological Requirement
Microbiological monitoring for either fecal coliforms or
Salmonella sp. is required to ensure that growth of bacte-
rial pathogens has not occurred.
4.5 Alternative 2: Sewage Sludge Treated in
a High pH-High Temperature Process
(Alkaline Treatment) [503.32(a)(4)]
This alternative describes conditions of a high tempera-
ture-high pH process that has proven effective in reducing
pathogens to below detectable levels. The process condi-
tions required by the Part 503 regulation are:
Elevating pH to greater than 12 and maintaining the
pH for more than 72 hours.
Maintaining the temperature above 52°C (126°F)
throughout the sewage sludge for at least 12 hours
during the period that the pH is greater than 12.
Air drying to over 50% solids after the 72-hour period
of elevated pH.
The hostile conditions of high pH, high temperature, and
reduced moisture for prolonged time periods allow a vari-
ance to a less stringent time-temperature regime than for
the thermal requirements under Alternative 1. The pH of
the sewage sludge is measured at 25°C (77°F) or an ap-
propriate correction is applied (see Section 10.7).
Example of Meeting Class A Pathogen and
Vector Attraction Reduction
Type of Process Alkaline Treatment
Class
Pathogen Reduction Alkaline material is used to bring
sewage sludge pH to 12 for 72
hours during which time tempera-
tures are above 52°C for 72 hours.
Sewage sludge is agitated during
the heat pulse phase to maintain
even distribution, and tempera-
ture and pH are measured at
multiple points within the sewage
sludge, the sewage sludge is
then moved to piles and main-
tained until moisture is reduced to
50 percent.
Piles are tested quarterly for pol-
utants and Salmonella sp.
Samples are taken from stock-
piled material, and material is not
distributed for use or disposal until
test results are received
VAR Option 6,pH adjustment; pH
is to remain elevated until
use/disposal.
During winter months (Nov-
March), biosolids remain on site.
In the spring, biosolids are re-
tested for pathogens before be-
ing distributed.
Testing
Vector Attraction
Reduction
Use or Disposal
Operational Issues
Because the elevated pH and temperature regimes must
be met by the entire sewage sludge mass, operational pro-
tocols which include monitoring pH and temperature at
various points in a batch and agitating the sewage sludge
during operations to ensure consistent temperature and
pH are appropriate.
30
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Vector Attraction Reduction
The pH requirement of vector attraction reduction Op-
tion 6 is met when Alternative 2 is met. Compliance with
Alternative 2 exceeds the pH requirements of Option 6.
Microbiological Requirements
As with all the Class A alternatives, microbiological moni-
toring for fecal coliforms or Salmonella sp. is required (see
Section 4.3) to ensure that pathogens have been reduced
and growth of pathogenic bacteria has not occurred.
4.6 Alternative 3: Sewage Sludge Treated in
Other Processes [503.32(a)(5)]
This alternative applies to sewage sludge treated by pro-
cesses that do not meet the process conditions required
by Alternatives 1 and 2. This requirement relies on com-
prehensive monitoring of bacteria, enteric viruses and vi-
able helminth ova to demonstrate adequate reduction of
pathogens:
Either the density of fecal coliforms in the sewage
sludge must be less than 1000 MPN per gram of total
solids (dry weight basis), or the Salmonella sp. bacte-
ria in sewage sludge must be less than 3 MPN per 4
grams of total solids (dry weight basis) at the time the
sewage is used or disposed, at the time the sewage
sludge is prepared for sale or given away in a bag or
other container for land application, or at the time the
sewage sludge or material derived from the sewage
sludge is prepared to meet the requirements in
503.10(b), 503.10(0), 503.10(e), or 503.10(f).
The density of enteric viruses in the sewage sludge
after pathogen treatment must be less than 1 PFU per
4 grams of total solids (dry weight basis).
The density of viable helminth ova in the sewage
sludge after pathogen treatment must be less than 1
per 4 grams of total solids (dry weight basis).
Testing for enteric viruses and viable helminth ova can
be complicated by the fact that they are sometimes not
present in the untreated sewage sludge. In this case, an
absence of the organisms in the treated sewage sludge
does not demonstrate that the process can reduce them
to below detectable limits. For this reason, Alternative 3
requires that the feed sewage sludge be analyzed for en-
teric viruses and viable helminth ova. If these organisms
are not detected in the feed sewage sludge, the sewage
sludge is presumed to be acceptable as a Class A mate-
rial until the next monitoring episode. Monitoring is contin-
ued until enteric viruses and/or viable helminth ova are
detected in the feed sewage sludge (i.e., the density of
enteric viruses is greater than or equal to 1 PFU per 4
grams total solids (dry weight basis) and/or the density of
viable helminth ova is greater than or equal to 1 per 4 grams
total solids (dry weight basis). At this point, the treated
sewage sludge is analyzed to see if these organisms sur-
vived treatment. If enteric viruses densities are below de-
tection limits, the sewage sludge meets Class A require-
ments for enteric viruses, and will continue to do so as
long as the treatment process is operated under the same
conditions that successfully reduced the enteric virus den-
sities. If the viable helminth ova densities are below detec-
tion limits, the process meets the Class A requirements for
enteric viruses and will continue to do so as long as the
treatment process is operated under the same conditions
that successfully reduced the viable helminth ova densi-
ties. Thus, it is essential to monitor and document operat-
ing conditions until adequate enteric virus and helminth
ova reduction has been successfully demonstrated.
Samples of untreated and treated sewage sludge must
correspond (see Section 7.4).
Enteric Virus and Viable Helminth Ova
Testing
Tests for enteric viruses and viable helminth ova take
substantial time: 4 weeks to determine whether helminth
ova are viable, and 2 weeks or longer for enteric viruses.
The treatment works operator does not know whether the
feed sewage sludge has enteric viruses or helminth ova
until at least 2 to 4 weeks after the first samples for testing
feed densities are taken. This works with rapid processes
but long-term process systems need to have temporally
related samples. In such cases, it may be feasible to ob-
tain results within the processing time constraints. For en-
teric viruses, the sewage sludge should be stored frozen,
unless the sample can be processed within 24 hours, in
which case the samples may be stored at 4°C (39°F). For
viable helminth ova, the sewage sludge should be stored
at 4°C (39°F) (see Section 9.6).
Finding a laboratory that performs viable helminth ova
and virus testing has been difficult for some sewage sludge
preparers. Chapter 9 has more information on how to se-
lect a laboratory. State and Regional EPA sludge coordi-
nators should also be contacted for information on quali-
fied labs in the region.
Since this option relies on testing, rather than process
and testing, to protect public health additional testings
should be completed. At a minimum, a detailed sampling
plan should be submitted to the permitting authority for
review.
Vector Attraction Reduction
For both Alternatives 3 and 4, meeting vector attraction
reduction depends on the process by which pathogen re-
duction is met. For example, sewage sludge subject to long-
term storage may meet vector attraction reduction through
volatile solids reduction (Options 1 - 3). Sewage sludges
may also undergo additional processing or be applied fol-
lowing the requirements in Options 8-11.
Microbiological Requirements
As with all the Class A alternatives, microbiological moni-
toring for fecal coliforms or Salmonella sp. is required (see
Section 4.3) to ensure that pathogens have been reduced
and growth of pathogenic bacteria has not occurred.
31
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4.7 Alternative 4: Sewage Sludge Treated in
Unknown Processes [503.32(a)(6)]
The sewage sludge must meet the following limits at the
time the biosolids (or material derived from sludge) are
used or disposed, at the time the sewage sludge is pre-
pared for sale or given away in a bag or other container for
land application, or at the time the sewage sludge or ma-
terial derived from the sewage sludge is prepared to meet
the requirements in 503.10(b), 503.10(c), 503.10(e), or
503.10(f):
The density of enteric viruses in the sewage sludge
must be less than 1 PFU per 4 grams of total solids
(dry weight basis).
The density of viable helminth ova in the sewage
sludge must be less than 1 per 4 grams of total solids
(dry weight basis).
In addition, as for all Class A biosolids, the sewage sludge
must meet fecal coliform or Salmonella sp. limits. As with
Alternative 3, Alternative 4 depends on a successful sam-
pling program that provides accurate representation of the
sewage sludge's microbial quality (see Chapter 9).
Example Of Meeting Class A Pathogen Vector
Attraction Reduction
Type of Facility
Class
Pathogen Reduction
Testing
Vector Attraction
Reduction
Distribution
Unknown Process
A
Sewage sludge is digested and
retained in a lagoon up to 2
years. Sewage sludge is then
moved to a stockpiling area where
it may stay for up to 2 years.
Before sewage sludge is distrib-
uted, each pile, representing ap-
proximately 1 year of sewage
sludge production, is tested for
Salmonella sp., viable helminth
ova, and enteric viruses. Since
quarterly testing is mandated,
based on the amount of sewage
sludge which is used or disposed,
four samples per pile are submitted
VAR is demonstrated by showing
a 38 percent reduction in volatile
solids. Records of incoming ma-
terial and volume, bulk density,
and percent volatile solids of out-
going material are used to calcu-
late the reduction.
Biosolids are distributed for land
application and agricultural land.
Examples of situations where Alternative 4 may be used:
. Sewage sludge treatment process is unknown.
. The sewage sludge was produced with the process
operating at conditions less stringent than the operat-
ing conditions at which the sewage sludge could qualify
as Class A under other alternatives.
Enteric Virus and Viable Helminth Ova
Testing
Tests for enteric viruses and viable helminth ova take
substantial time: 4 weeks to determine whether helminth
ova are viable, and 2 weeks or longer for enteric viruses.
The treatment works operator does not know whether the
feed sewage sludge has enteric viruses or helminth ova
until at least 2 to 4 weeks after the first samples for testing
feed densities are taken. This option works with rapid pro-
cesses but long-term process systems need to have tem-
porally related samples. In such cases, it may be feasible
to obtain results within the processing time constraints.
For enteric viruses, the sewage sludge should be stored
frozen, unless the sample can be processed within 24
hours, in which case the samples may be stored at 4°C
(39°F). For viable helminth ova, the sewage sludge should
be stored at 4°C (39°F) (see Section 9.6).
Finding a laboratory that performs viable helminth ova
and virus testing has been difficult for some sewage sludge
preparers. Chapter 9 has more information on how to se-
lect a laboratory. State and Regional EPA sludge coordi-
nators should also be contacted for information on quali-
fied labs in the region.
Since this option relies on testing, rather than process
and testing, to protect public health additional testings
should be completed. At a minimum, a detailed sampling
plan should be submitted to the permitting authority for
review.
Vector Attraction Reduction
For both Alternatives 3 and 4, meeting vector attraction
reduction depends on the process by which pathogen re-
duction is met. For example, sewage sludge subject to long-
term storage may meet vector attraction reduction through
volatile solids reduction (Options 1-3). Sewage sludges
may also undergo additional processing or be applied fol-
lowing the requirement in Options 8-11.
4.8 Alternative 5: Use of PFRP [503.32(a)(7)]
Alternative 5 provides continuity with the 40 CFR Part
257 regulation. This alternative states that sewage sludge
is considered to be Class A if:
It has been treated in one of the Processes to Further
Reduce Pathogens (PFRPs) listed in Appendix B of
the regulation, and
Either the density of fecal coliforms in the sewage
sludge is less than 1,000 MPN per gram total solids
(dry weight basis), or the density of Salmonella sp.
bacteria in the sewage sludge is less than 3 MPN per
4 grams total solids (dry weight basis) at the time the
sewage sludge is used or disposed, at the time the
sewage sludge is prepared for sale or give away in a
bag or other container for land application, or at the
32
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time the sewage sludge or material derived from the
sewage sludge is prepared to meet the requirements
in 503.10(b), 503.10(0), 503.10(e), or503.10(f).
To meet this requirement, the sewage sludge treatment
processes must be operated according to the conditions
listed in Appendix B of the regulation.
The Appendix B list of PFRPs is reproduced in Table 4-
2. This list is very similar to the PFRP technologies listed
in 40 CFR Part 257, with two major differences:
All requirements related to vector attraction reduction
have been removed.
All the "add-on" processes listed in Part 257 are now
full-fledged PFRPs.
Under this Alternative, treatment processes classified as
PFRP under 40 CFR Part 257 can continue to be oper-
ated; however, microbiological monitoring must now be
performed to ensure that the pathogen density levels are
below detection limits and to ensure that growth of Salmo-
nella sp. bacteria does not occur between treatment and
use or disposal.
For all PFRP processes, the goal of temperature moni-
toring should be to represent all areas of a batch or pile
and to ensure that temperature profiles from multiple points
in the process all meet mandated temperatures. In some
instances it may be possible to monitor representative ar-
eas of a batch or pile or a reasonable worst case area to
ensure compliance. Chapter 7 contains more guidelines
about the operation of PFRP processes.
4.9 Alternative 6: Use of a Process
Equivalent to PFRP [503.32(a)(8)]
The 40 CFR Part 257 regulation allowed any treatment
process to be determined equivalent to a PFRP. Under
Alternative 6, sewage sludge is considered to be a Class A
sewage sludge if:
It is treated by any process equivalent to a PFRP, and
Either the density of fecal coliforms in the sewage
sludge is less than 1,000 MPN per gram total solids
(dry weight basis), or the density of Salmonella sp.
bacteria in the sewage sludge is less than 3 MPN per
4 grams total solids (dry weight basis) at the time the
sewage sludge is used or disposed, at the time the
sewage sludge is prepared for sale or give away in a
bag or other container for land application, or at the
time the sewage sludge or material derived from the
sewage sludge is prepared to meet the requirements
in 503.10(b), 503.10(c), 503.10(e), or 503.10(f).
Facilities that meet Alternative 6 for pathogen reduction
must still meet vector attraction reduction requirements.
Processes Already Recommended as
Equivalent
Processes recommended to be equivalent to PFRP are
shown in Table 11.2. Products of all equivalent processes
must still meet the Class A fecal coliform or Salmonella sp.
requirements.
Who Determines Equivalency?
Part 503 gives the permitting authority responsibility for
determining equivalency under Alternative 6. The EPA's
Pathogen Equivalency Committee (PEC) is available as a
resource to provide guidance and recommendations on
equivalency determinations to both the permitting author-
ity and the regulated community (see Chapter 11).
4.10 Frequency of Testing
The Part 503 regulation sets forth minimum sampling
and monitoring requirements. Table 3-4 in Chapter 3 de-
Table 4-2. Processes to Further Reduce Pathogens (PFRPs) Listed in Appendix B of 40 CFR Part 5031
Composting
Heat Drying
Heat Treatment
Thermophilic Aerobic Digestion
Beta Ray Irradiation
Gamma Ray Irradiation
Pasteurization
Using either the within-vessel composting method or the static aerated pile composting method, the
temperature of sewage sludge is maintained at55°C (13TF) or higher for 3 consecutive days.
Using the windrow composting method, the temperature of the sewage sludge is maintained at 55°C
(131°F) or higher for 15 consecutive days or longer. During the period when the compost is maintained at
55°C (131°F) or higher, there shall be a minimum of five turnings of the windrow.
Sewage sludge is dried by direct or indirect contact with hot gases to reduce the moisture content of the
sewage sludge to 10% or lower. Either the temperature of the sewage sludge particles exceeds 80°C
(176°F) or the wet bulb temperature of the gas in contact with the sewage sludge as the sewage sludge
leaves the dryer exceeds 80°C (176°F).
Liquid sewage sludge is heated to a temperature of 180°C (356°F) or higher for 30 minutes.
Liquid sewage sludge is agitated with air or oxygen to maintain aerobic conditions and the mean cell
residence time (i.e., the solids retention time) of the sewage sludge is 10 days at 55°C (131°F) to 60°C
(140°F).
Sewage sludge is irradiated with beta rays from an electron accelerator at dosages of at least 1.0 megarad
at room temperature (ca. 20°C [68°F]).
Sewage sludge is irradiated with gamma rays from certain isotopes, such as Cobalt 60 and Cesium 137, at
dosages of at least 1.0 megarad at room temperature (ca. 20°C [68°F]).
The temperature of the sewage sludge is maintained at 70°C (158°F) or higher for 30 minutes or longer.
1Chapter 7 provides a detailed description of these technologies.
33
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scribes the minimum frequency at which the
sewage sludge must be sampled and analyzed for patho-
gens or vector attraction reduction in order to meet regula-
tory requirements. In addition to meeting these minimal
requirements, the EPA recommends that sewage sludge
generators and preparers also consider the potential pub-
lic health impact pathways and possible liability issues
when designing a sampling program. In some cases, it
may be appropriate to sample more frequently than the
required minimum.
Classification of biosolids as Class A or Class B is based
on the most recent test results available. For example, if a
facility produces a Class A compost, and sampling is per-
formed once each quarter, the compost produced after
each test result verifying Class A is returned is also as-
sumed to be Class A, assuming that the same process
continues to be followed. If a test result indicates that com-
post is not achieving Class A, all compost subsequently
generated would be classified as Class B (assuming it
meets Class B requirements). The Class B classification
would remain until a test result confirming Class A quality
is returned.
This raises several issues. Land application of Class B
biosolids without site restrictions is a violation of the 503
regulation. In addition, if material is mistakenly classified
as EQ biosolids and land applied without restriction to the
public, the biosolids preparer may be inadvertently creat-
ing a public health risk as well as opening the facility to
liability. The key issues to consider are:
At what point between the two sampling events does
the material change from Class A to C/ass B? This de-
pends on the particular situation. The Class B test result
may be an exception - the result of cross contamination
or faulty sampling or monitoring for one pile. On the other
hand, the test result could be indicative of an operation
which is not adequately reducing pathogens. The piles
which were actually sampled may have been used or dis-
tributed under the classification of the previous lab results
while lab results were pending (it generally takes 2 weeks
to get lab results back). Because distribution of this mate-
rial as Class A would constitute a violation of the Part 503
regulation, it is recommended that material generated dur-
ing and subsequent to a sampling event remain on site
until lab results are available.
What can you do if you suspect Class B biosolids
have been distributed as Class A biosolids? The first
question to answer is: has this material created a public
health risk. The material should be resampled to deter-
mine if it is indeed Class B and not Class A. The Part 503
requires that Class A biosolids meet either the fecal coliform
or the Salmonella sp. requirements (except for Alterna-
tives 3 and 4). If the material is out of compliance for fecal
coliforms, it should immediately be tested for Salmonella
sp. (and vice versa). In addition, the validity of the test
results should be checked by contacting the lab and re-
viewing the data.
Material distribution should then be tracked to determine
where material has been used. Businesses and individu-
als to whom material has been distributed should be noti-
fied and informed of the potential quality issue. If material
is stockpiled at distribution points such as at a soil blender
or landscaper, the material should be retested for patho-
gen levels, and distribution be curtailed until the process
is reviewed and acceptable results are achieved. The fa-
cility may even consider recalling the biosolids from the
users.
If material has already been distributed to public access
areas, including homes, gardens, parks, or other public
areas, the biosolids preparer may consider testing the soil.
If the testing indicates problems, corrective actions may
be necessary.
How can a situation like this be avoided? There are
several sampling practices that a facility should follow in
order to avoid a situation like this.
First, sampling should take place close enough to the
time of distribution so that results accurately reflect mate-
rial quality.
If possible, material sampled and subsequently produced
material should not be distributed until the results are avail-
able; there is usually a 2-week waiting period for lab re-
sults for fecal coliform or Salmonella sp. analysis.
More frequent sampling can help pinpoint when opera-
tional conditions change. This may allow more rapid cor-
rection of operations.
Stockpile biosolids in discrete batches and take multiple
samples per sampling event. This will allow better identifi-
cation of which piles may be out of compliance and will
allow for the distribution of material that is identified as
Class A.
References and Additional Resources
Barker, T.A. 1970. Pasteurization and sterilization of slud-
ges. Proc. Biochem, August, p 44-45.
Farrell, J.B., J.E. Smith, Jr., S.W. Hathaway, and R.B. Dean.
1974. Lime stabilization of primary sludges. J. WPCF
46(1): 113-122.
Farrell, J.B. 1993. Fecal pathogen control during composting.
p 282-300 in "Science & Engineering of Composting:
Design, Environmental, Microbiological, and Utilization
Aspects." edit. H.A.J. Hoitink and H.M. Keenerg.
Feachem, R-G., D.J. Bradley, H. Garelick, and D.D. Mara.
1983. "Sanitation and Disease: Health Aspects of Ex-
creta and Wastewater Management." Pub. for World
Bank by J. Wiley and Sons, NY.
Foess, Gerald W. and Ronald B. Sieger. 1993. Pathogen/
vector attraction reduction requirements of the sludge
rules. Water/Engineering & Management, June, p 25.
IRGRD (International Research Group on Refuse Disposal)
1968. Information Bulletin No. 21-31. August 1964 -
December 1967. p 3230 - 3340. Reprinted by US Dept.
HEW, Bureau of Solid Waste Management (1969).
34
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Lee, K.M., C.A. Brunner, J.B. Farrell, and A.E. Eralp. 1989.
Destruction of enteric bacteria and viruses during two-
phase digestion. J. WPCF 61 (8): 1422-1429.
Martin, J.H., Jr., H.E. Bostian, and G. Stern. 1990. Reduc-
tion of enteric microorganisms during aerobic sludge
digestion. Wat. Res. 24(11):1377-1385.
Schafer, P.L., J.B. Farrell, W.R. Uhte, and B. Rabinowitz.
1994. Pre-pasteurization, European and North Ameri-
can assessment and experience, p 10-39 to 10-50 in
"The Management of Water and Wastewater Solids
for the 21st Century: A Global Perspective." Confer-
ence Proceedings, June 19-22, 1992. Water Environ-
ment Federation.
U.S. Dept. of Health and Human Services. 1989. Grade A
Pasteurized Milk Ordinance, 1989 Revision, Public
Health Service/Food and Drug Administration Publi-
cation No. 229.
U.S. EPA. 1992. Technical support document for Part 503
pathogen and vector attraction reduction requirements
in sewage sludge. NTIS No: PB93-110609. Springfield,
VA: National Technical Information Service.
Yanko, W.A. 1987. Occurrence of pathogens in distribu-
tion and marketing municipal sludges. Report No.: EPA/
600/1-87/014. (NTIS: PB88-154273/AS.) Springfield,
VA: National Technical Information Service.
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Chapter 5
Class B Pathogen Requirements and Requirements for Domestic Septage
Applied to Agricultural Land, a Forest, or a Reclamation Site
5.1 Introduction
Class B pathogen requirements can be met in three dif-
ferent ways. The implicit objective of all three alternatives
is to ensure that pathogenic bacteria and enteric viruses
are reduced in density, as demonstrated by a fecal coliform
density in the treated sewage sludge (biosolids) of 2 mil-
lion MPN or CPU per gram total solids biosolids (dry weight
basis)1. Viable helminth ova are not necessarily reduced
in Class B biosolids.
Unlike Class A biosolids, which are essentially patho-
gen free, Class B biosolids may contain some pathogens.
Site restrictions that restrict crop harvesting, animal graz-
ing, and public access for a certain period of time are re-
quired. This allows environmental factors to further reduce
pathogens. Where appropriate, these restrictions are de-
signed to ensure sufficient reduction in viable helminth ova,
one of the hardiest of pathogens, since these pathogens
may not have been reduced during sewage sludge treat-
ment.
The Class B requirements apply to bulk biosolids that
are land applied to such areas as agricultural land, for-
ests, public contact sites, or reclamation sites. Biosolids
that are placed on a surface disposal site also must meet
the Class B pathogen requirements, unless the active
biosolids unit on which the biosolids are placed is covered
at the end of each operating day (see Table 3-1). Because
the use of Class B biosolids must be closely monitored,
Class B biosolids cannot be given away or sold in bags or
other containers.
Domestic septage applied to agricultural land, forest, or
a reclamation site must meet all of the Class B site restric-
tions under 503.32(b)(5) unless the domestic septage has
met specific pH requirements (see Section 5.6).
1 Farrell et al. (1985) have shown that if a processed sewage sludge is processed
by aerobic or anaerobic digestion it has a fecal coliform density of 2 million MPN or
CPU per gram, enteric viruses and bacteria are significantly reduced. A comparison
of suspended solids densities in entering wastewater to suspended solids densities
in treated sewage sludge shows that this density of fecal coliform in treated sew-
age sludge represents a 100-fold (Z-log) reduction in fecal coliform density, and is
expected to correlate with an approximately 1.5 log (approximately 32-fold) reduc-
tion in Salmonella sp. density and an approximately 1.3 log (20-fold) reduction in
the density of enteric viruses.
Class B biosolids and domestic septage also must meet
one of the vector attraction reduction requirements (see
Chapter 8). Note that the choice of vector attraction op-
tions may affect the duration of site restrictions in some
cases. Specifically, if Option 9 or 10 (injection or incorpo-
ration) is used to reduce vector attraction, the restriction
on harvesting for food crops grown below the soil surface
(potatoes, carrots, etc.) is increased from 20 months to 38
months.
Sections 5.2 to 5.4 discuss the three alternative Class B
pathogen requirements for sewage sludge. Section 5.5
discusses the site restrictions for land applied Class B
biosolids, and Section 5.6 presents the requirements for
domestic septage applied to agricultural land, forests, or
reclamation sites, me title of each section provides the
number of the Subpart D requirement discussed in the
section. A copy of Subpart D can be found in Appendix B.
Chapters 9 and 10 provide guidance on the sampling and
analysis necessary to meet the Class B microbiological
requirements.
5.2 Sewage Sludge Alternative 1:
Monitoring of Fecal Coliform
[503.32(b)(2)]
Alternative 1 requires that seven samples of treated sew-
age sludge (biosolids) be collected and that the geometric
mean fecal coliform density of these samples be less than
2 million CPU or MPN per gram of biosolids (dry weight
basis). This approach uses fecal coliform density as an
indicator of the average density of bacterial and viral patho-
gens. Over the long term, fecal cojiform density is expected
to correlate with bacterial and viral pathogen density in
biosolids treated by biological treatment processes (EPA,
1992).
Use of at least seven samples is expected to reduce the
standard error to a reasonable value. The standard devia-
tion can be a useful predictive tool. A relatively high stan-
dard deviation for the fecal coliform density indicates a wide
range in the densities of the individual samples. This may
be due to sampling variability or variability in the labora-
tory analysis, or it may indicate that the treatment process
is not consistent in its reduction of pathogens. A high stan-
dard deviation can therefore alert the preparer that the
sampling, analysis, and treatment processes should be
reviewed.
36
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Each of the multiple samples taken for fecal coliform
analysis should be taken at the same point in the process
so that treatment of each sample has been equal. Samples
must be handled correctly and analyzed within 24 hours in
order to minimize the effect of the holding time of the sample
on the microbial population.
Laboratory sampling should follow Standard Methods
as outlined in the Appendix of this document. Standard
QA/QC practices, including duplicates to verify laboratory
Calculating the Geometric Mean for Class B Alternative 1
Take seven samples over a 2-week period.
Analyze samples for fecal coliform using the membrane
filter or MPN dilution method.
Take the log (Base 10) of each result.
Take the average (arithmetic) of the logs.
Take the anti-log of the arithmetic average. This is the
geometric mean of the results.
Example: The results of analysis of seven samples of sew-
age sludge are shown below. The second column of the
table shows the log of each result.
Sample 1
Sample
Sample
Sample 4
Sample 5
Sample 6
Sample 7
Average (Arithmetic)
Antilog (geometric mean)
Log standard deviation
Fecal Coliform
(MPN/dry gram
sewage sludge)
6.4 x106
4.8 x104
6.0x105
5.7x105
5.8x105
4.4x106
6.2 x 107
1.5
Log
6.81
4.68
5.78
5.76
5.76
6.64
7.80
6.18
x 106
1.00*
Note that this sewage sludge would meet Class B fecal
coliform requirements even though several of the analysis
results exceed the 2.0 x 106/dry gram limit.
*Duplicate analyses on the same sample would give a
much lower standard deviation. Variability is inflated by dif-
ferences in feed and product over a 2-week sampling pe-
riod.
protocols should be followed. Generally a log standard
deviation between duplicate samples under 0.3 is accept-
able for lab analyses.
Process parameters including retention time and tem-
perature should be examined in order to verify that the
process is running as specified. Monitoring equipment
should be calibrated regularly.
The seven samples should be taken over a 2-week pe-
riod in order to represent the performance of the facility
under a range of conditions. For small facilities that are
required to sample infrequently, sampling should be per-
formed under worst case conditions, for example, during
the winter when the climatic conditions are the most ad-
verse.
It has been found that for Class B compliance, the
MPN dilution method for fecal coliform analysis is more
appropriate than the membrane filtration test. This is
because colloidal and suspended solids may interfere with
media transport through the membrane filter. Furthermore,
concentration of toxic or inhibitory substances at the filter
surface may affect results. It is therefore recommended
that the membrane filter procedure be used only after dem-
onstrating comparability between the membrane filter test
and the MPN method for a given sewage sludge.
Example of Meeting Class B Pathogen
Vector Attraction Reduction Requirements
Type of Facility
Class
Pathogen Reduction
Testing
Vector Attraction
Reduction
Use or Disposal
Extended Aeration
B
Quarterly testing for pollutants
and for fecal coliform to determine
if Class B Alternative 1 require-
ments are met.
The SOUR test is used to
demonstrate compliance with
VAR Option 4
The Class B biosolids are
delivered to farmers along with
information regarding analysis
and site restrictions
5.3 Sewage Sludge Alternative 2: Use of a
Process to Significantly Reduce
Pathogens (PSRPs) [503.32(b)(3)]
The PSRP Class B alternative provides continuity with
the 40 CFR Part 257 regulation. Under this Alternative,
treated sewage sludge (biosolids) is considered to be Class
B if it is treated in one of the "Processes to Significantly
Reduce Pathogens" (PSRPs) listed in Appendix B of Part
503. The biological PSRP processes are sewage sludge
treatment processes that have been demonstrated to re-
sult in a 2-log reduction in fecal coliform density. See Chap-
ter 7.
The PSRPs in the Part 503 are reproduced in Table 5-1
and described in detail in Chapter 6. They are similar to
the PSRPs listed in the Part 257 regulation, except that all
conditions related to reduction of vector attraction have
been removed. Under this alternative, sewage sludge
treated by processes that are PSRPs under 40 CFR Part
257 are Class B with respect to pathogens. Unlike the com-
parable Class A requirement (see Section 4.8), this Class
B alternative does not require microbiological monitoring.
37
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However, monitoring of process requirements such as time,
temperature, and pH is required.
Table 5-1. Processes to Significantly Reduce Pathogens (PSRPs)
Listed in Appendix B of 40 CFR Part 503
1. Aerobic Digestion Sewage sludge is agitated with air or
oxygen to maintain aerobic conditions for a
specific mean cell residence time (i.e.,
solids retention time) at a specific
temperature. Values for the mean cell
residence time and temperature shall be
between 40 days at 20°C (68° F) and 60
daysat15°C (59°F).
2. Air Drying Sewage sludge is dried on sand beds or
on paved or unpaved basins. The sewage
sludge dries for a minimum of 3 months.
During 2 of the 3 months, the ambient
average daily temperature is above 0°C
(32°F).
3. Anaerobic Digestion Sewage sludge is treated in the absence of
air for a specific mean cell residence time
(i.e., solids retention time) at a specific
temperature. Values for the mean cell
residence time and temperature shall be
between 15 days at 35°C to 55°C (131°F)
and 60 days at 20°C (68°F).
4. Composting Using either the within-vessel, static
aerated pile, or windrow composting
methods, the temperature of the sewage
sludge is raised to 40°C (104°F) or higher
and remains at 40°C (104°F) or higher for
5 days. For 4 hours during the 5 day
period, the temperature in the compost pile
exceeds 55°C (131 °F).
5. Lime Stabilization Sufficient lime is added to the sewage
sludge to raise the pH of the sewage
sludge to 12 for >2 hours of contact.
5.4 Sewage Sludge Alternative 3: Use of
Processes Equivalent to PSRP
[503.32(b)(4)]
The Part 257 regulation allowed the sewage sludge to
be treated by a process determined to be equivalent to a
PSRP. Under Class B Alternative 3, sewage sludge treated
by any process determined to be equivalent to a PSRP is
considered to be Class B biosolids. A list of processes that
have been recommended as equivalent to PSRP are
shown in Table 11.1.
Part 503 gives the regulatory authority responsibility for
determining equivalency. The Pathogen Equivalency Com-
mittee is available as a resource to provide guidance and
recommendations on equivalency determinations to the
regulatory authorities (see Chapter 11).
5.5 Site Restrictions for Land Application of
Biosolids [503.32(b)(5)]
Potential exposure to pathogens in Class B biosolids
via food crops is a function of three factors: first there must
be pathogens in the biosolids; second, the application of
Class B biosolids to food crops must transfer the patho-
gens to the harvested crop, and third, the crop must be
ingested before it is processed to reduce the pathogens.
Elimination of one of these steps eliminates the pathway
by which public health may be affected. The use of Class
A biosolids protects public health by reducing pathogens
in sewage sludge to below detectable levels. Biosolids that
meet the Class B requirements may contain reduced but
still significant densities of pathogenic bacteria, viruses,
protozoans, and viable helminth ova. Thus, site restrictions
are to allow time for further reduction in the pathogen popu-
lation. Harvest restrictions are imposed in order to reduce
the possibility that food will be harvested and ingested
before pathogens which may be present on the food have
died off. Harvest restrictions vary, depending on the type
of crop, because the amount of contact a crop will have
with biosolids or pathogens in biosolids varies.
The site restrictions are primarily based in the survival
rates of viable helminth ova, one of the hardiest of patho-
gens that may be present on sewage sludge. The survival
of pathogens, including the helminth ova, depends on ex-
posure to the environment. Some of the factors that affect
pathogen survival include pH, temperature, moisture, cat-
ions, sunlight, presence of soil microflora, and organic
material content. On the soil surface, helminth ova has
been found to die off within 4 months, but survival is longer
if pathogens are within the soil. Helminth ova have been
found to survive in soil for several years (Smith, 1997;
Kowal 1985). Site restrictions take this into account by
making a distinction between biosolids that are applied to
the land surface, biosolids that are incorporated into the
soil after at least 4 months on the soil surface, and biosolids
that are incorporated into the soil within 4 months of being
applied.
Site restrictions also take the potential pathways of ex-
posure into account. For example, crops that do not con-
tact the soil, such as oat or wheat, may be exposed to
biosolids, but pathogens on crop surfaces have been found
to be reduced very quickly (30 days) due to exposure to
sunlight, desiccation, and other environmental factors.
Crops that touch the soil, such as melons or cucumbers,
may also come into contact with biosolids particles, but
pathogens in this scenario are also subject to the harsh
effects of sunlight and rain and will die off quickly. Crops
grown in soil such as potatoes are surrounded by biosolids
amended soil, and pathogen die-off is much slower below
the soil surface.
These pathways should be considered when determin-
ing which site restriction is appropriate for a given situa-
tion. The actual farming and harvesting practices as well
as the intended use of the food crop should also be con-
sidered. For example, oranges are generally considered a
food crop that does not touch the ground. However, some
oranges grow very low to the ground and may come into
contact with soil. If the oranges that have fallen to the
ground or grew touching the ground are harvested for di-
rect consumption without processing, the 14-month har-
vest restriction for crops that touch the soil should be fol-
lowed. Orange crops which do not touch the ground at all
would not fall under the 14-month harvest restriction; har-
vest would be restricted for 30 days under 503.32(b)(5)(iv)
38
-------
which covers food crops that do not have harvested parts
in contact with the soil. For similar situations, the potential
for public health impacts must be considered. Harvest prac-
tices such as the use of fallen fruit or washing or process-
ing crops should be written into permits so that restrictions
and limits are completely clear. Figure 5-1 illustrates the
steps of exposure that should be considered when mak-
ing a decision about harvest and site restrictions. In addi-
tion, several examples of permit conditions are included.
The site restrictions for land applied Class B biosolids are
summarized below. The regulatory language is given in
italics. Note that the restrictions apply only to the harvest-
ing of food crops, but not to the planting or cultivation of
crops.
Food Crops with Harvested Parts That
Touch the Sewage Sludge/Soil Mixture
503.32(b)(5)(i): Food crops with harvested parts that
touch the sewage sludge/soil mixture and are totally above
the land surface shall not be harvested for 14 months after
application of sewage sludge.
This time frame is sufficient to enable environmental
conditions such as sunlight, temperature, and desiccation
to further reduce pathogens on the land surface. Note that
the restriction applies only to harvesting. Food crops can
be planted at any time before or after biosolids applica-
tion, as long as they are not harvested within 14 months
Does sewage sludge comply with Class B
requirements?
Yes
No
Must be diverted from land application.
Does sewage sludge comply with Class A
requirements?
No
Yes
Sludge can be land-applied without site
restrictions.
Is the sewage sludge applied to a food crop?
Yes
No
Site restrictions for sod farms grazing
animals, or public access should be
followed.
Does the food crop touch the ground or will
fruit that falls on the ground be harvested?
No
Harvest may not take place until 30 days
after application.
Yes
Is it possible that harvested food will be
eaten raw or handled by the public?
Yes
Is the edible part of the crop grown below
the surface of the land?
Yes
Does the sewage sludge remain on the
surface of the land for more than 4 months
after application?
No
Harvest may not take place until 38 months
after application.
No
No
Yes
Permitting authority may use discretion to
reduce waiting period from 14 months to 30
days, depending on the application.
Harvest may not take place until 14
after application.
months
Harvest may not take place until 20
after application.
months
Figure 5-1. Decision tree for harvesting and site restrictions.
39
-------
after sludge application. Examples of food crops grown on
or above the soil surface with harvested parts that typi-
cally touch the sewage sludge/soil mixture include lettuce,
cabbage, melons, strawberries, and herbs. Land applica-
tion should be scheduled so that crop harvests are not lost
due to harvest restrictions.
Food Crops with Harvested Parts Below the
Land Surface
503.32(b)(5)(ii): Food crops with harvested parts below
the surface of the land shall not be harvested for 20 months
after application of sewage sludge when the sewage sludge
remains on the land surface for 4 months or longer prior to
incorporation into the soil.
Pathogens on the soil surface will be exposed to envi-
ronmental stresses which greatly reduce their populations.
Helminth ova have been found to die off after 4 months on
the soil surface (Kowal, 1994). Therefore, a distinction is
made between biosolids left on the soil surface for 4 months
and biosolids which are disced or plowed into soil more
quickly.
For a September 1999 harvest, biosolids could be ap-
plied to the soil surface up to the end of December 1997,
plowed or disced into the soil in April 1998, and the crop
planted in order to allow it to be harvested in September
1999. Examples of crops with harvested parts below the
Examples of Site Restrictions for Questionable
Food Crop Situations
Tree Nut Crops - Nuts which are washed hulled, and de-
hydrated before being distributed for public consumption
must follow the 30-day restriction. Nuts which are harvested
from the ground and sold in their shell without processing
are subject to the 14-month restriction.
Sugar Beets - Sugar beets aren't expected to be eaten
raw. If the beets are transported off site and considerable
biosolids amended soil is carried off with them, the restric-
tions apply. If biosolids are left on the soil surface for 4
months or longer before being incorporated, the 20-month
restriction applies. If biosolids are incorporated within 4
months of application, the 38-month restriction applies.
Tomatoes (and peppers) - Fruit often comes in contact with
the ground. Tomatoes are sold both to processors and to
farm stands. Tomatoes may be eaten raw by the public
without further processing. The 14-month restriction ap-
plies.
land surface are potatoes, radishes, beets, onions and
carrots.
503.32(b)(5)(iii): Food crops with harvested parts below
the surface of the land shall not be harvested for 38 months
after application of sewage sludge when the sewage sludge
remains on the land surface for less than 4 months prior to
incorporation into the soil.
Exposure of the surface of root crops such as potatoes
and carrots to viable helminth ova is a principal concern
under these circumstances. Four months is considered the
minimum time for environmental conditions to reduce vi-
able helminth ova in biosolids on the land surface. Class B
biosolids incorporated into the soil surface less than 4
months after application may contain significant numbers
of viable helminth ova. Once incorporated into the soil, die-
off of these organisms proceeds much more slowly; there-
fore, a substantially longer waiting period is required to
protect public health. Thirty-eight months after biosolids
application is usually sufficient to reduce helminth ova to
below detectable levels.
Food Crops, Feed Crops, and Fiber Crops
503.32(b)(5)(iv): Food crops, feed crops, and fiber crops
shall not be harvested for 30 days after application of sew-
age sludge.
This restriction covers food crops that are not covered
by 503.32(b)(l-iii). This would include crops with harvested
parts that do not typically touch the biosolids/soil mixture
and which are not collected from the ground after they have
fallen from trees or plants. The restriction also applies to
all feed and fiber crops. These crops may be exposed to
pathogens when biosolids are applied to the land. Har-
vesting of these crops could result in the transport of
biosolids pathogens from the growing site to the outside
environment. After 30 days, however, any pathogens in
biosolids that may have adhered to the crop during appli-
cation will likely have been reduced to non-detectable lev-
els. Hay, corn, soybeans, or cotton are examples of a crop
covered by this restriction.
Animal Grazing
503.32(b) (5) (v): Animals shall not be allowed to graze
on the land for 30 days after application of sewage sludge.
Biosolids can adhere to animals that walk on biosolids
amended land and thereby be brought into potential con-
tact with humans who come in contact with the animals
(for example, horses and milking cows allowed to graze
on a biosolids amended pasture). Thirty days is sufficient
to substantially reduce the pathogens in surface applied
biosolids, thereby significantly reducing the risk of human
and animal contamination.
Turf Harvesting
503.32(b)(5)(vi): Turf grown on land where sewage
sludge is applied shall not be harvested for 7 year after
application of the sewage sludge when the harvested turf
is placed on either land with a high potential for public ex-
posure or a lawn, unless otherwise specified by the per-
mitting authority.
The 1-year waiting period is designed to significantly
reduce pathogens in the soil so that subsequent contact
40
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of the turf layer will not pose a risk to public health and
animals. A permitting authority may reduce this time pe-
riod in cases in which the turf is not used on areas with
high potential for public access.
Public Access
503.32(b)(5)(vii): Public access to land with a high po-
tential for public exposure shall be restricted for 1 year
after application of the sewage sludge.
As with the turf requirement above, a 1-year waiting pe-
riod is necessary to protect public health and the environ-
ment in a potential high-exposure situation. A baseball dia-
mond, playground, public park, or a soccer field are ex-
amples of land with a high potential for public exposure.
The land gets heavy use and contact with the soil is sub-
stantial (children or ball players fall on it and dust is raised
which is inhaled and ingested).
503,32(b)(5)(viii): Public access to land with a low po-
tential for public exposure shall be restricted for 30 days
after application of the sewage sludge,
A farm field used to grow corn or soybeans is an ex-
ample of land with low potential for public exposure. Even
farm workers and family members walk about very little on
such fields. Public access restrictions do not apply to farm
workers, but workers should be aware of the public health
implications of land application and the land application
schedule, and should follow good hygiene practice during
the 30-day period. For example, workers should be in-
structed to wash their hands after handling soil or crops
that come into contact with soil. Protective clothing and
footwear are recommended for workers who work on fields
that have recently been applied with Class B biosolids.
More safety recommendations for workers handling
biosolids are included in Section 2.2.
5.6 Domestic Septage [503.32(c)]
Under Part 503.32(c), pathogen reduction in domestic
septage applied to agricultural land, forest, or reclamation
sites2 may be reduced in one of two ways:
Either all the Class B site restrictions under
503.32(b)(5) -see Section 5.5-must be met,
Or the pH of the domestic septage must be raised to
12 or higher by alkali addition and maintained at pH
12 or higher for 30 minutes without adding more al-
kali, and the site restrictions on crop harvesting in
503.32(b)(5)(l-iv) must be met (see Section 5.5). The
Part 503 regulation uses the term alkali in the broad
sense to mean any substance that causes an increase
inpH.
Vector attraction reduction can be met with Option 9,
10, or 13. Domestic septage can be incorporated or in-
jected into the soil to prevent vector attraction, or the pH of
the domestic septage can be adjusted as outlined in Op-
tion 12 (see Section 8). pH adjustment can fulfill both patho-
gen and vector attraction reduction.
The pH requirement applies to every container of do-
mestic septage applied to the land, which means that the
pH of each container must be monitored. The first alterna-
tive reduces exposure to pathogens in land applied do-
mestic septage while environmental factors attenuate
pathogens. The second alternative relies on alkali treat-
ment to reduce pathogens and contains the added safe-
guard of restricting crop harvesting, which prevents expo-
sure to crops grown on domestic septage amended soils.
References and Additional Resources
Farrell, J.B., G. Stern, and A.D. Venosa. 1985. Microbial
destructions achieved by full-scale anaerobic diges-
tion. Workshop on Control of Sludge Pathogens, Se-
ries IV. Alexandria, VA: Water Pollution Control Fed-
eration.
Farrell, J.B., B.V. Salotto, and A.D. Venosa. 1990. Reduc-
tion in bacterial densities of wastewater solids by three
secondary treatment processes. Res. Jour. WPCF
62(2):177-184.
Gerba, C.P., C. Wallis, and J.L. Melmick. 1975. Fate of
wastewater bacteria and viruses in soil. J. Irrig. Drain
Div. Am. Soc. Civ. Engineers.101:157-174.
Kowal, N.E. 1985. Health effects of land application of
municipal sludge. Pub. No.: EPA/600/1-85/015. Re-
search Triangle Park, NC: U.S. EPA Health Effects
Research Laboratory.
Kowal, N.E. 1994. Pathogen risk assessment: Status and
potential application in the development of Round II
regulations. Proceedings of the June 19-20,1994 Spe-
ciality Conference. The Management of Water and
Wastewater Solids for the 21st Century: A Global Per-
spective. Water Environment Federation. Alexandria,
VA.
Moore, B.E., D.E. Camann, G.A. Turk, and C.A. Sorber.
1988. Microbial characterization of municipal waste-
water at a spray irrigation site: The Lubbock infection
surveillance study. J. Water Pollut. Control Fed. 60(7):
1222-1230.
Smith, J.E., Jr. 1988. Fate of pathogens during the sew-
age sludge treatment process and after land applica-
tion. In Proceedings of the January 21-22, 1998 Cali-
fornia Plant and Soil Conference: Agricultural chal-
lenges in an urbanizing state, Sacramento, CA.
Sobsey, M.D. and P.A. Shields. 1987. Survival and trans-
port of viruses in soils: Model studies. Pp. 155-177 in
V.C. Rao and J.L. Melnick, eds. Human viruses in sedi-
ments, sludges, and soils. Boca Raton, FL. CRC Press.
Sorber, C.A. and B.E. Moore. 1986. Survival and trans-
port of pathogens in sludge-amended soil, a critical
literature review. Report No.: EPA/600/2-87/028. Cin-
cinnati, OH. Office of Research and Development.
" Class B sewage sludge requirements apply to domestic septage applied to all other
types of land. No pathogen-related requirements apply to domestic septage placed
on a surface disposal site.
41
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Storey, G.W. and R.A. Phillips. 1985. The survival of para- U.S. EPA. 1992. Technical support document for Part 503
site eggs throughout the soil profile. Parasitology. pathogen and vector attraction reduction requirements
91:585-590. in sewage sludge. NTIS No.:PB93-110609. Springfield,
VA. National Technical Information Service.
42
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Chapter 6
Processes to Significantly Reduce Pathogens (PSRPs)
6.1 Introduction
Processes to Significantly Reduce Pathogens (PSRPs)
are listed in Appendix B of Part 503. There are five PSRPs:
aerobic and anaerobic digestion, air drying, composting,
and lime stabilization. Under Part 503.32(b)(3), sewage
sludge meeting the requirements of these processes is
considered to be Class B with respect to pathogens (see
Section 5.3). When operated under the conditions speci-
fied in Appendix B, PSRPs reduce fecal coliform densities
to less than 2 million CPU or MPN per gram of total solids
(dry weight basis) and reduce Salmonella sp. and enteric
virus densities in sewage sludge by approximately a fac-
tor of 10 (Farrell, et al., 1985).
This level of pathogen reduction is required, as a mini-
mum, by the Part 503 regulation if the sewage sludge is
applied to agricultural land, a public contact site, a forest,
or a reclamation site or placed on a surface disposal site1.
Because Class B biosolids may contain some pathogens,
land application of Class B biosolids is allowed only if crop
harvesting, animal grazing, and public access are limited
for specific periods of time following application of Class B
biosolids so that pathogens can be further reduced by en-
vironmental factors (see Section 5.5).
The PSRPs listed in Part 503 are essentially identical to
the PSRPs that were listed under the 40 CFR Part 257
regulation, except that all requirements related solely to
reduction of vector attraction have been removed. Vector
attraction reduction is now covered under separate require-
ments (see Chapter 8) that include some of the require-
ments that were part of the PSRP requirements under Part
257, as well as some new options for demonstrating vec-
tor attraction reduction. These new options provide greater
flexibility to the regulated community in meeting the vector
attraction reduction requirements.
Although theoretically two or more PSRP processes,
each of which fails to meet its specified requirements, could
be combined and effectively reduce pathogens (i.e. partial
treatment in digestion followed by partial treatment by air
drying) it cannot be assumed that the pathogen reduction
contribution of each of the operations will result in the 2-
log reduction in fecal coliform necessary to define the com-
bination as a PSRP. Therefore, to comply with Class B
pathogen requirements, one of the PSRP processes must
be conducted as outlined in this chapter, or fecal coliform
testing must be conducted in compliance with Class B Al-
ternative 1. The biosolids preparer also has the option of
applying for PSRP equivalency for the combination of pro-
cesses. Achieving PSRP equivalency enables the preparer
to stop monitoring for fecal coliform density.
This chapter provides detailed descriptions of the PSRPs
listed in Appendix B. Since the conditions for the PSRPs,
particularly aerobic and anaerobic digestion, are designed
to meet pathogen reduction requirements, they are not
necessarily the same conditions as those traditionally rec-
ommended by environmental engineering texts and manu-
als.
6.2 Aerobic Digestion
In aerobic digestion, sewage sludge is biochemically
oxidized by bacteria in an open or enclosed vessel (see
photo). To supply these aerobic microorganisms with
enough oxygen, either the sewage sludge must be agi-
tated by a mixer, or air must be forcibly injected (Figure 6-
1). Under proper operating conditions, the volatile solids
in sewage sludge are converted to carbon dioxide, water,
and nitrate nitrogen.
Aerobic systems operate in either batch or continuous
mode. In batch mode, the tank is filled with untreated sew-
age sludge and aerated for 2 to 3 weeks or longer, de-
pending on the type of sewage sludge, ambient tempera-
ture, and average oxygen levels. Following aeration, the
stabilized solids are allowed to settle and are then sepa-
rated from the clarified supernatant. The process is begun
again by inoculating a new batch of untreated sewage
sludge with some of the solids from the previous batch to
supply the necessary biological decomposers. In continu-
ous mode, untreated sewage sludge is fed into the digester
once a day or more frequently; thickened, clarified solids
are removed at the same rate.
The PSRP description in Part 503 for aerobic digestion
is:
1 Unless the active biosolids surface disposal unit is covered at the end of each
operating day, in which case no pathogen requirement applies.
Sewage sludge is agitated with air or oxygen to main-
tain aerobic conditions for a specific mean cell resi-
43
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Digester in Vancouver, Washington.
Raw
Sludge
Aerodigester
Settling
Tank
Oxidized
Overflow
to Treatment Works
Return Sludge
to Aerodigester
Stabilized
Sludge
to Disposal
Figure 6-1. Aerobic digestion.
44
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dence time at a specific temperature. Values for the
mean cell residence time and temperature shall be
between 40 days at 20°C (68°F) and 60 days at 15°C
(59°F).
For temperatures between 15°C (59°F) and 20°C (68°F)
use the relationship between time and temperature pro-
vided below to determine the required mean cell residence
time.
Time @T°C = 1.08(20-1)
40 d
The regulation does not differentiate between batch, in-
termittently fed, and continuous operation, so any method
is acceptable. The mean cell residence time is considered
the residence time of the sewage sludge solids. The ap-
propriate method for calculating residence time depends
on the type of digester operation used (see Appendix E).
Continuous-Mode, No Supernatant Removal For con-
tinuous-mode digesters where no supernatant is removed,
nominal residence times may be calculated by dividing liq-
uid volume in the digester by the average daily flow rate in
or out of the digester.
Continuous-Mode, Supernatant Removal In systems
where the supernatant is removed from the digester and
recycled, the output volume of sewage sludge can be much
less than the input volume of sewage sludge. For these
systems, the flow rate of the sewage sludge out of the
digester is used to calculate residence times.
Continuous-Mode Feeding, Batch Removal of Sew-
age Sludge For some aerobic systems, the digester is
initially filled above the diffusers with treated effluent, and
sewage sludge is wasted daily into the digester. Periodi-
cally, aeration is stopped to allow solids to settle and su-
pernatant to be removed. As the supernatant is drawn off,
the solids content in the digester gradually increases. The
process is complete when either settling or supernatant
removal is inadequate to provide space for the daily sew-
age sludge wasting requirement, or sufficient time for di-
gestion has been provided. The batch of digested sewage
sludge is then removed and the process begun again. If
the daily mass of sewage sludge solids introduced has
been constant, nominal residence time is one-half the to-
tal time from initial charge to final withdrawal of the digested
sewage sludge.
Batch or Staged Reactor Mode A batch reactor or two
or more completely-mixed reactors in series are more ef-
fective in reducing pathogens than is a single well-mixed
reactor at the same overall residence time. The residence
time required for this type of system to meet pathogen re-
duction goals may be 30% lower than the residence time
required in the PSRP definition for aerobic digestion (see
Appendix E). However, since lower residence times would
not comply with PSRP conditions required for aerobic di-
gestion in the regulation, approval of the process as a PSRP
by the permitting authority would be required.
Other Digesters are frequently operated in unique ways
that do not fall into the categories above. Appendix E pro-
vides information that should be helpful in developing a
calculation procedure for these cases. Aerobic digestion
carried out according to the Part 503 requirements typi-
cally reduces bacterial organisms by 2-log and viral patho-
gens by 1-log. Helminth ova are reduced to varying de-
grees, depending on the hardiness of the individual spe-
cies. Aerobic digestion typically reduces the volatile solids
content (the microbes' food source) of the sewage sludge
by 40% to 50%, depending on the conditions maintained
in the system.
Vector Attraction Reduction
Vector attraction reduction for aerobically digested sew-
age sludges is demonstrated either when the percent vola-
tile solids reduction during sewage sludge treatment equals
or exceeds 38%, or when the specific oxygen uptake rate
(SOUR) at 20°C (68°F) is less than or equal to 1.5 mg of
oxygen per hour per gram of total solids, or when addi-
tional volatile solids reduction during bench-scale aerobic
batch digestion for 30 additional days at 20°C (68°F) is
less than 15% (see Chapter 8).
Thermophilic aerobic systems (operating at higher tem-
peratures) capable of producing Class A biosolids are de-
scribed in Section 7.5.
6.3 Anaerobic Digestion
Anaerobic digestion is a biological process that uses
bacteria that function in an oxygen-free environment to
convert volatile solids into carbon dioxide, methane, and
ammonia. These reactions take place in an enclosed tank
(see Figure 6-2) that may or may not be heated. Because
the biological activity consumes most of the volatile solids
needed for further bacterial growth, microbial activity in
the treated sewage sludge is limited. Currently, anaerobic
digestion is one of the most widely used treatments for
sewage sludge treatment, especially in treatment works
with average wastewater flow rates greater than 19,000
cubic meters/day (5 million gallons per day).
Most anaerobic digestion systems are classified as ei-
ther standard-rate or high-rate systems. Standard-rate
systems take place in a simple storage tank with sewage
sludge added intermittently. The only agitation that occurs
comes from the natural mixing caused by sewage sludge
gases rising to the surface. Standard-rate operation can
be carried out at ambient temperature, though heat is some-
times added to speed the biological activity.
High-rate systems use a combination of active mixing
and carefully controlled, elevated temperature to increase
the rate of volatile solids destruction. These systems some-
times use pre-thickened sewage sludge introduced at a
uniform rate to maintain constant conditions in the reactor.
Operating conditions in high-rate systems foster more effi-
cient sewage sludge digestion.
The PSRP description in Part 503 for anaerobic diges-
tion is:
45
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Raw
Sludge
Supernatant
First Stage
(completely mixed)
Second Stage
(stratified)
Figure 6-2. Two-stage anaerobic digestion (high rate).
Sewage sludge is treated in the absence of air for a
specific mean cell residence time at a specified tem-
perature. Values for the mean cell residence time and
temperature shall be between 15 days at 35°C to 55°C
(95°F to 131°F) and 60 days at 20°C (68°F).
Straight-line interpolation to calculate mean cell resi-
dence time is allowable when the temperature falls be-
tween 35°C and 20°Q
Section 6.2 provides information on calculating residence
times. Anaerobic digestion that meets the required resi-
dence times and temperatures typically reduces bacterial
and viral pathogens by 90% or more. Viable helminth ova
are not substantially reduced under mesophilic conditions
(32°C to 38°C [90°F to 100°F]) and may not be completely
reduced at temperatures between 38°C (100T) and 50°C
(122°F).
Anaerobic systems reduce volatile solids by 35% to 60%,
depending on the nature of the sewage sludge and the
system's operating conditions. Sewage sludges produced
by systems that meet the operating conditions specified
under Part 503 will typically have volatile solids reduced
by at least 38%, which satisfies vector attraction reduction
requirements. Alternatively, vector attraction reduction can
be demonstrated by Option 2 of the vector attraction re-
duction requirements, which requires that additional vola-
tile solids loss during bench-scale anaerobic batch diges-
tion of the sewage sludge for 40 additional days at 30°C to
37°C (86°F to 99°F) be less than 17% (see Section 8.3).
The SOUR test is an aerobic test and cannot be used for
anaerobically digested sewage sludge.
6.4 Air Drying
Air drying allows partially digested sewage sludge to dry
naturally in the open air (see photo). Wet sewage sludge
is usually applied to a depth of approximately 23 cm (9
inches) onto sand drying beds, or even deeper on paved
or unpaved basins. The sewage sludge is left to drain and
dry by evaporation. Sand beds have an underlying drain-
age system; some type of mechanical mixing or turning is
frequently added to paved or unpaved basins. The effec-
tiveness of the air drying process depends very much on
the local climate: drying occurs faster and more completely
in warm, dry weather, and slower and less completely in
cold, wet weather. During the drying/storage period in the
bed, the sewage sludge is undergoing physical, chemical,
and biological changes. These include biological decom-
position of organic material, ammonia production, and des-
iccation.
Sludge drying operation. (Photo credit: East Bay Municipal Utility
District)
46
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The PSRP description in Part 503 for air drying is:
Sewage sludge is dried on sand beds or on paved or
unpaved basins. The sewage sludge dries for a mini-
mum of 3 months. During 2 of the 3 months, the ambi-
ent average daily temperature is above 0°C (32°F).
Although not required by the Part 503, it is advisable to
ensure that the sewage sludge drying beds are exposed
to the atmosphere (i.e., not covered with snow) during the
2 months that the daily temperature is above 0°C (32°F).
Also, the sewage sludge should be at least partially di-
gested before air drying. Under these conditions, air dry-
ing will reduce the density of pathogenic viruses by 1-log
and bacteria by approximately 2-log. Viable helminth ova
also are reduced, except for some hardy species that re-
main substantially unaffected.
Vector Attraction Reduction
Frequently sand-bed drying follows an aerobic or anaero-
bic digestion process that does not meet the specified pro-
cess requirements and does not produce 38% volatile sol-
ids destruction. However, it may be that the volatile solids
reduction produced by the sequential steps of digestion
and drying will meet the vector attraction reduction require-
ment of 38% volatile solids reduction. If this is the case,
vector attraction reduction requirements are satisfied.
Example of
Vector Attraction
Type of Facility
Class
Pathogen Reduction
Testing
Vector Attraction
Reduction
Use or Disposal
Meeting PSRP and
Reduction Requirements
Air Drying
B
Partially digested sewage
sludge is thickened and
spread in drying beds. Filling
of beds starts in June, and the
beds accommodate sewage
sludge generated over 1 full
year. Beds are then emptied
the following September so
that all sewage sludge is re-
tained over an entire summer
(>0°C ambient temperatures).
Sewage sludge is tested for
pollutants 2 weeks before
material is removed and dis-
tributed.
Biosolids are land applied
and plowed immediately into
the soil.
Biosolids are delivered to lo-
cal farmers. Farmers are
given information on site re-
strictions, and must follow
harvest, grazing, and public
access restrictions.
Vector Attraction Reduction
Air-dried sewage sludge typically is treated by aerobic
or anaerobic digestion before it is placed on drying beds.
Usually, the easiest vector attraction reduction requirement
to meet is a demonstration of 38% reduction in volatile
solids (Option 1, See Section 8.2), including the reduction
that occurs during its residence on the drying beds.
In dry climates, vector attraction reduction can be
achieved by moisture reduction (see Option 7 in Section
8.8, and Option 8 in Section 8.9).
6.5 Composting
Composting involves the aerobic decomposition of or-
ganic material using controlled temperature, moisture, and
oxygen levels. Several different composting methods are
currently in use in the United States. The three most com-
mon are windrow, aerated static pile, and within-vessel
composting. These are described below.
Composting can yield either Class A or Class B biosolids,
depending on the time and temperature variables involved
in the operation.
All composting methods rely on the same basic pro-
cesses. Bulking agents such as wood chips, bark, saw-
dust, straw, rice hulls, or even-finished compost are added
to the sewage sludge to absorb moisture, increase poros-
ity, and add a source of carbon. This mixture is stored (in
windrows, static piles, or enclosed tanks) for a period of
intensive decomposition, during which temperatures can
rise well above 55°C (131°F). Depending on ambient tem-
peratures and the process chosen, the time required to
reduce pathogens and produce Class B biosolids can range
from 3 to 4 weeks. Aeration and/or frequent mixing or turn-
ing are needed to supply oxygen and remove excess heat.
Following this active stage, bulking agents may or may
not be screened from the completed compost for recycling
(see photo), and the composted biosolids are "cured" for
an additional period.
Windrow composting involves stacking the sewage
sludge/bulking agent mixture into long piles, or windrows,
generally 1.5 to 2.7 meters high (5 to 9 feet) and 2.7 to 6.1
meters wide (9 to 20 feet). These rows are regularly turned
or mixed with a turning machine or front-end loader to fluff
up the material and increase porosity which allows better
convective oxygen flow into the material. Turning also
breaks up compacted material and reduces the moisture
content of the composting media (see photo, next page).
Active windrows are typically placed in the open air, ex-
cept in areas with heavy rainfall. In colder climates, winter
weather can significantly increase the amount of time
needed to attain temperatures needed for pathogen re-
duction.
Aerated static pile composting uses forced-air rather than
mechanical mixing (see Figure 6-3) to both supply suffi-
cient oxygen for decomposition and carry off moisture. The
sewage sludge/bulking agent mixture is placed on top of
47
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Composted sludge is screened to remove the bulking agent prior
to land application
Compost mixing equipment turns over a windrow of compost for
solar drying prior to screening [Photo credit: East Bay Municipal
Utility District)
either (1) a fixed underlying forced aeration system, or (2)
a system of perforated piping laid on the composting pad
surface and topped with a bed of bulking agent. The entire
pile is covered with a layer of cured compost for insulation
and odor control. Pumps are used to blow air into the com-
post pile or suck air through it. The latter provides greater
odor control because the compost air can be easily col-
lected and then filtered or scrubbed.
Within-vessel composting systems vary greatly in de-
sign, but they share two basic techniques: the process
takes place in a reactor vessel where the operating condi-
tions can be carefully controlled (see photo page 49), and
active aeration meets the system's high oxygen demand.
Agitated bed systems (one type of within-vessel
composting) depend on continuous or periodic mixing
within the vessel, followed by a curing period.
Pathogen reduction during composting depends on time
and temperature variables (see photo page 49). Part 503
provides the following definition of PSRP requirement for
pathogen reduction during composting:
Using either the within-vessel, static aerated pile, or
windrow composting methods, the temperature of the
sewage sludge is raised to 4CTC (104°F) or higher and
remains at 4ffC (104°F) or higher for 5 days. For 4
hours during the 5-day period, the temperature in the
compost pile exceeds 55°C (131°F).
These conditions, achieved using either within-vessel,
aerated static pile, or windrow methods, reduce bacterial
pathogens by 2-log and viral pathogens by 1-log.
A process time of only 5 days is not long enough to fully
break down the volatile solids in sewage sludge, so the
composted sewage sludge produced under these condi-
tions will not be able to meet any of the requirements for
reduced vector attraction. In addition, sewage sludge that
has been composted for only 5 days may still be odorous.
Breakdown of volatile solids may require 14 to 21 days for
within-vessel; 21 or more days for aerated static pile; and
30 or more days for windrow composting. Many treatment
works allow the finished sewage sludge compost to fur-
ther mature or cure for at least several weeks following
active composting during which time pile turning or active
aeration may continue.
Composting is most often used to meet Class A require-
ments. More guidance for composting operations and how
to meet Class A time and temperature requirements is pro-
vided in Chapter 7.
Vector Attraction Reduction
Vector attraction reduction must be conducted in accor-
dance with Option 5, or compost must be incorporated into
soil when land applied. This option requires aerobic treat-
ment (i.e., composting) of the sewage sludge for at least
14 days at over 40^ (104°F) with an average tempera-
ture of over 45°C (113°F).
6.6 Lime Stabilization
The lime stabilization process is relatively straightforward:
lime - either hydrated lime, Ca(OH)2; quicklime, CaO; or
lime containing kiln dust or fly ash - is added to sewage
sludge in sufficient quantities to raise the pH above 12 for
2 hours or more after contact, as specified in the Part 503
PSRP description for lime stabilization:
Sufficient lime is added to the sewage sludge to raise
the pH of the sewage sludge to 12 after 2 hours of
contact.
For the Class B lime stabilization process, the alkaline
material must be a form of lime. Use of other alkaline ma-
48
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Taulman Weiss in-vessel composting facility in Portland, Oregon.
Compost operator measures compost pile temperature as part of
process monitoring. (Photo credit: East Bay Municipal Utility District,
Oakland, California)
Air
Air
Composted
Sludge
Bulking Agent/
Sludge'Mixture
Porous Base:
Wood Chips or
Compost
Figure 6-3. Static aerated pile composting.
terials must first be demonstrated to be equivalent to a
PSRP. Elevation of pH to 12 for 2 hours is expected to
reduce bacterial and viral density effectively.
Lime may be introduced to liquid sewage sludge in a
mixing tank or combined with dewatered sewage sludge,
providing the mixing is complete and the sewage sludge
cake is moist enough to allow aqueous contact between
the sewage sludge and lime.
Mixing must be sufficient to ensure that the entire mass
of sewage sludge comes into contact with the lime and
Filter Pile of
Composted Sludge
undergoes the increase in pH and to ensure that samples
are representative of the overall mixture (see Chapter 9).
pH should be measured at several locations to ensure that
the pH is raised throughout the sewage sludge.
A variety of lime stabilization processes are currently in
use. The effectiveness of any lime stabilization process
for controlling pathogens depends on maintaining the pH
at levels that reduce microorganisms in the sewage sludge.
Field experience has shown that the application of lime
stablized material after the pH has dropped below 10.5
may, in some cases, create odor problems. Therefore it is
49
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recommended that biosolids application take place while
the pH remains elevated. If this is not possible, and odor
problems develop, alternate management practices in the
field include injection or incorporation or top dressing the
applied biosolids with additional lime. Alternate manage-
ment practices if the biosolids have not yet left the waste-
water treatment plant may include adding additional lime
to maintain the elevated pH or additional treatment through
drying or composting. Lime stabilization can reduce bac-
terial and viral pathogens by 99% or more. Such alkaline
conditions have little effect on hardy species of helminth
ova, however.
Vector Attraction Reduction
For lime-treated sewage sludge, vector attraction reduc-
tion is best demonstrated by Option 6 of the vector attrac-
tion reduction requirements. This option requires that the
sewage sludge pH remain at 12 or higher for at least 2
hours, and then at 11.5 or more for an additional 22 hours
(see Section 8.7).
Lime stabilization does not reduce volatile solids. Field
experience has shown that the application of lime stabi-
lized material after the pH has dropped below 10.5 may
create odor problems. Therefore it is recommended that
land application of biosolids take place as soon as pos-
sible after vector attraction reduction is completed and while
pH remains elevated.
6.7 Equivalent Processes
Table 11.1 in Chapter 11 lists some of the processes
that the EPA's Pathogen Equivalency Committee has rec-
ommended as being equivalent to PSRP under Part 257.
Information on the PEC and how to apply for equivalency
are discussed in Chapter 11.
References and Other Resources
Berg, G. and D. Berman. 1980. Destruction by anaero-
bic mesophilic and thermophijic digestion of vi-
ruses ana indicator bacteria indigenous to do-
mestic sludges. Appl. Envir. Microbiol. 39(2):361-
368.
Farrell, J.B., G. Stern, and A.D. Venosa. 1990. Mi-
crobial destructions achieved by full-scale
anaerobic digestion. Paper presented at Munici-
pal Wastewater Sludge Disinfection Workshop.
Kansas City, MO. Water Pollution Control Fed-
eration, October 1995.
U.S. EPA. 1992. Technical support document for re-
duction of pathogens and vector attraction in sew-
age sludge. EPA/822/R-93/004.
50
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Chapter 7
Processes to Further Reduce Pathogens (PFRPs)
7.1 Introduction
Processes to Further Reduce Pathogens (PFRPs) are
listed in Appendix B of the Part 503. There are seven
PFRPs: composting, heat drying, heat treatment, thermo-
philic aerobic digestion, beta ray irradiation, gamma ray
irradiation, and pasteurizafon. When these processes are
operated under the conditions specified in Appendix B,
pathogenic bacteria, enteric viruses, and viable helminth
ova are reduced to below detectable levels. The PFRPs
listed in Part 503 are essentially identical to the PFRPs
listed under the 40 CFR Part 257 regulation, except that
all requirements related solely to reduction of vector at-
traction have been removed.
This chapter provides detailed descriptions of the seven
PFRPs listed in Part 503. Because the purpose of these
processes is to produce Class A biosolids, the pathogen
reduction process must be conducted concurrent to or prior
to the vector attraction reduction process (see Section 4.2).
Under Part 503.32(a)(7), sewage sludge treated in these
processes is considered to be Class A with respect to hel-
minth ova, enteric viruses, and pathogenic bacteria. In
addition, Class A biosolids must be monitored for fecal
coliform or Salmonella sp. bacteria at the time of use on
disposal, at the time the biosolids are prepared for sale or
give away in a bag or other container for land application,
or at the time the biosolids are prepared to meet the re-
quirements for "exceptional quafity" sludge (see Chapter
2) in 503.10(b), 503.10(c), 503.10(e), or 503.10(f) to en-
sure that growth of bacteria has not occurred (see Section
4.3). Guidelines regarding the frequency of pathogen sam-
pling and sampling protocols are included in Chapter 9.
7.2 Composting
Composting is the controlled, aerobic decomposition of
organic matter which produces a humus-like material. Sew-
age sludge which is to be composted is generally mixed
with a bulking agent such as wood chips which increases
porosity in the sewage sludge, allowing air to more easily
pass through the composting material and maintain aero-
bic conditions. There are three commonly used methods
of composting: windrow, static aerated pile, and within-
vessel.
To be considered a PFRP under Part 503, the composting
operation must meet certain operating conditions:
Using either the within-vessel composting method or
the static aerated pile composting method, the tem-
perature of the sewage sludge is maintained at 55°C
(13TF) or higher for 3 consecutive days.
Using the windrow composting method, the tempera-
ture of the sewage sludge is maintained at 55°C (131°F)
or higher for 15 consecutive days or longer. During
the period when the compost is maintained at 55°C
(131°F) or higher, there shall be a minimum of five turn-
ings of the windrow.
For aerated static pile and in-vessel composting pro-
cesses, temperatures should be taken at multiple points
at a range of depths throughout the composting medium.
Points which are likely to be slightly cooler than the center
of the pile, such as the toes of piles, also should be moni-
tored. Because the entire mass of sewage sludge must
attain the required temperatures for the required duration,
the temperature profiles from every monitoring point, not
just the average of the points, should reflect PFRP condi-
tions.
It has been found that points within 0.3 m (1 foot) of the
surface of aerated static piles may be unable to reach PFRP
temperatures, and for this reason, it is recommended that
a 0.3 m (1 foot) or greater layer of insulating material be
placed over all surfaces of the pile. Finished compost is
often used for insulation. It must be noted that because
the insulation will most likely be mixed into the composted
material during post-processing or curing, compost used
as an insulation material must be a Class A material so as
not to reintroduce pathogens into the composting sewage
sludge.
For windrow composting, the operational requirements
are based on the same time-temperature relationship as
aerated static pile and in-vessel composting. The material
in the core of the windrow attains at least 55°C and must
remain at that temperature for 3 consecutive days. Wind-
row turning moves new material from the surface of the
windrow into the core so that this material may also un-
dergo pathogen reduction. After five turnings, all material
in the windrow must have spent 3 days at the core of the
pile. The time-temperature regime takes place over a pe-
riod of at least 15 consecutive days during which time the
temperature in the core of the windrow is at least 55°C.
See Appendix J for additional guidance.
51
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Pathogen reduction is a function of three parameters:
Ensuring that all sewage sludge is mixed into the core
of the pile at some point during active composting
Ensuring that all sewage sludge particles spend 3 con-
secutive days in the core during which time the tem-
peratures are at 55°C
Preventing growth of pathogenic bacteria in composted
material
The first issue, ensuring that all material is mixed into
the core of the pile, depends on the configuration of the
windrows and the turning methodology. Pile size and shape
as well as material characteristics determine how much of
the pile is in the "hot zone" at any given time. Additional
turning and maintenance of temperatures after the man-
dated 15 days are recommended, depending on the wind-
row configuration. For example, the Los Angeles County
Sanitation District found that as many as 12-15 turnings
were necessary to reduce pathogens in windrow
composted sewage sludge (Personal Communication,
Ross Caballero, Los Angeles County Sanitation District,
1998).
Second, it is important that once that material is in the
pile core it be subject to the full time-temperature regime
necessary to reduce pathogens. Therefore, the turning
schedule and the recovery of the core zone to 55°C are
important factors. If pile turning is not evenly distributed
throughout the 15-day period, some material may not spend
adequate time in the core of the pile. Additionally, pile tem-
peratures generally drop off immediately after turning; if
temperatures in the pile core do not quickly recover to 55°C
(within 24 hours), the necessary pathogen reduction pe-
riod of 3 days will not be achieved.
Because of the operational variability, pathogen reduc-
tion in windrow composting has been found to be less pre-
dictable than pathogen reduction in aerated static pile or
in-vessel composting. In order to improve pathogen re-
duction, the following operational guidelines are recom-
mended.
Windrow turning should take place after the pile core
has met pathogen reduction temperatures for 3 con-
secutive days. Windrow turnings should be evenly
spaced within the 15 days so that all material remains
in the core zone for 3 consecutive days; allowing addi-
tional time as needed for the core temperature to come
up to 55°C.
Pathogen reduction temperatures (55°C) must be met
for 15 consecutive days at the pile core.
Temperatures should be taken at approximately the
same time each day in order to demonstrate that 55°C
has been reached in the pile core within 24 hours after
pile turning.
Testing frequency should be increased; a large sew-
age sludge windrow composting operation recom-
mends testing each windrow for Salmonella sp. be-
fore piles are distributed (Personal Communication,
Ross Caballero, Los Angeles County Sanitation Dis-
trict, 1998). Samples are taken after turning is com-
pleted, and piles which do not comply with Class A
requirements are retained on site for further
composting.
Vector Attraction Reduction (VAR)
The options for demonstrating vector attraction reduc-
tion for both PFRP and PSRP composting are the same.
Option 5 is the most appropriate for composting opera-
tions. This option requires aerobic treatment (e.g.
composting) of the sewage sludge for at least 14 consecu-
tive days at over 40°C (104°F) with an average tempera-
ture of over 45°C (113°F). This is usually easily attained
by sewage sludge composting.
The PFRP and VAR requirements can be met concur-
rently in composting. For within-vessel or aerated static
pile composting, the temperature profile should show PFRP
temperatures at each of the temperature monitoring points
for 3 consecutive days, followed by a minimum of 11 more
days during which time the average temperature of the
pile complies with VAR requirements. For windrow piles,
the compliance with PFRP temperatures will also fulfill VAR
requirements.
PFRP temperatures should be met before or at the same
time that VAR requirements are fulfilled in order to reduce
the potential for pathogen regrowth. However, continued
curing of the composting material will most likely further
prevent the growth of pathogenic bacteria from taking place.
Like all microbiological processes, composting can only
take place with sufficient moisture (45-60%). Excessive
aeration of composting piles or arid ambient condition may
dry composting piles to the point at which microbial activ-
ity slows or stops. The cessation of microbial activity re-
sults in lowered pile temperatures which can easily be mis-
taken for the end-point of composting. Although composting
may appear to have ended, and compost may even meet
vector attraction reduction via Option 7, overly dried com-
post can cause both odor problems and vector attraction if
moisture is reintroduced into the material and microbial
activity resumes. It is therefore recommended that the
composting process be maintained at moisture levels be-
tween 45-60% (40-55% total solids) (Epstein, 1997).
Microbiological Requirements
If the conditions specified by the Part 503 regulation are
met, all pathogenic viruses, bacteria, and parasites will be
reduced to below detectable levels. However, it may be
difficult to meet the Class A microbiological requirement
for fecal coliforms even when Salmonella sp. bacteria are
not present. Biological sewage sludge treatment processes
involving high temperatures, such as composting, can re-
duce Salmonella sp. to below detectable levels while leav-
ing some surviving fecal coliforms. If sufficient nutrients
remain in the sewage sludge, bacteria can later grow to
52
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significant numbers. It may be preferable, therefore, to test
composted sewage sludge directly for Salmonella sp.,
rather than using fecal coliforms as an indicator of patho-
gen control.
Although not mandated by the Part 503 regulation, com-
post is usually maintained on site for longer than the re-
quired PFRP and VAR duration. In order to produce a high-
quality, marketable product, it has been found that a cur-
ing period, or the period during which the volatile solids in
the sewage sludge continue to decompose, odor potential
decreases, and temperatures decrease into the mesophilic
(40-45°C) range, is necessary. Depending on the feed-
stock and the particular process, the curing period may
last an additional 30 - 50 days after regulatory require-
ments are met.
In general, compost is not considered marketable until
the piles are no longer self-heating. It is important to note
that compost piles that are cooled by excessive aeration
or that do not self-heat because the material is too dry to
support microbial activity may not actually be fully decom-
posed.
It has been found that further reduction of organic mate-
rial takes place during the curing phase of composting
(Epstein, 1997). Therefore microbiological testing should
take place at the end of the curing process when compost
is prepared for sale or distribution. Compost which is stored
on site for extended periods of time until it can be sold or
distributed must be tested for compliance with microbio-
logical limits when it is to be used or disposed.
7.3 Heat Drying
Heat drying is used to reduce both pathogens and the
water content of sewage sludge. The Part 503 PFRP de-
scription of heat drying is:
Sewage sludge is dried by direct or indirect contact
with hot gases to reduce the moisture content to 10%
or lower. Either the temperature of the sewage sludge
particles exceeds 80°C (176°F) or the wet bulb tem-
perature of the gas in contact with the sewage sludge
as it leaves the dryer exceeds 80°C (176°F).
Properly conducted heat drying will reduce pathogenic
viruses, bacteria, and helminth ova to below detectable
levels. Four processes are commonly used for heat drying
sewage sludge: flash dryers, spray dryers, rotary dryers,
and steam dryers. Flash dryers used to be the most com-
mon heat drying process installed at treatment works, but
current practice favors rotary dryers. These processes are
briefly described below. More detailed descriptions are
provided in EPA's Process Design Manual (EPA, 1979).
Flash Dryers
Flash dryers pulverize sewage sludge in the presence
of hot gases. The process is based on exposing fine sew-
age sludge particles to turbulent hot gases long enough to
attain at least 90% solids content.
Spray Dryers
A spray dryer typically uses centrifugal force to atomize
liquid sewage sludge into a spray that is directed into a
drying chamber. The drying chamber contains hot gases
that rapidly dry the sewage sludge mist. Some spray dry-
ing systems use a nozzle to atomize sewage sludge.
Rotary Dryers
Rotary dryers function as horizontal cylindrical kilns. The
drum rotates and may have plows or louvers that mechani-
cally mix the sewage sludge as the drum turns. There are
many different rotary kiln designs, utilizing either direct
heating or indirect heating systems. Direct heating designs
maintain contact between the sewage sludge and the hot
gases. Indirect heating separates the two with steel shells.
Steam Dryers
Indirect steam dryers utilize steam to heat the surface of
the dryers which will come into contact with the sewage
sludge. The heat transfer surface may consist of discs or
paddles, which rotate to increase their contact with the
sewage sludge.
Vector Attraction Reduction
No further processing is required because the PFRP
requirements for heat drying also meet the requirements
of Option 8 for vector attraction reduction (the percent sol-
ids must be at least 90% before mixing the sewage sludge
with other materials). This fulfills the requirement of
Option 7 if the sewage sludge being dried contains no
unstabilized solids.
Drying of sewage sludge to 90% solids deters the at-
traction of vectors, however, unstabilized dried biosolids
which are rewet may become odorous and attract vectors.
Therefore, it is recommended that materials be used or
disposed while the level of solids remains high and that
dried material be stored and maintained under dry condi-
tions.
Some operators have found that maintaining stored
material at solids levels above 95% helps to deter reheat-
ing because microbiological activity is halted. However,
storage of materials approaching 90% total solids can lead
to spontaneous combustion with subsequent fires and risk
of explosion. While there is little likelihood of an explosion
occurring with storage of materials like pellets, precaution-
ary measures such as maintaining proper oxygen levels
and minimizing dust levels in storage silos and monitoring
temperatures in material can reduce the risk of fires.
Microbiological Requirements
Heat dried biosolids must be tested for fecal coliform or
Salmonella sp. at the last point before being used or dis-
posed. For example, biosolids should be tested immedi-
ately before they are bagged or before they leave the site
for bulk distribution. If material is stored for a long period
of time, it should be re-tested, even if previous testing has
53
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shown the biosolids to have met the Part 503 regulation.
This is particularly important if material has been rewetted.
7.4 Heat Treatment
Heat treatment processes are used to disinfect sewage
sludge and reduce pathogens to below detectable levefs.
The processes involve heating sewage sludge under pres-
sure for a short period of time. The sewage sludge be-
comes sterilized and bacterial slime layers are solubilized,
making it easier to dewater the remaining sewage sludge
solids. The Part 503 PFRP description for heat treatment
is:
Liquid sewage sludge is heated to a temperature of
180°C (356°F) or higher for 30 minutes.
Two processes have principally been used for heat treat-
ing sludge in preparation for dewatering: the Porteous and
the Zimpro process. In the Porteous process the sewage
sludge is preheated and then injected into a reactor ves-
sel. Steam is also injected into the vessel under pressure.
The sewage sludge is retained in the vessel for approxi-
mately 30 minutes after which it is discharged to a decant
tank. The resulting sewage sludge can generally be con-
centrated and dewatered to hign solids concentrations.
Further dewatering may be desirable to facilitate sewage
sludge handling.
The Zimpro process is similar to the Porteous process.
However, air is injected into the sewage sludge before it
enters the reactor and the vessel is then heated by steam
to reach the required temperature. Temperatures and pres-
sures are approximately the same for the two processes.
Vector Attraction Reduction
Heat treatment in most cases must be followed by vec-
tor attraction reduction. Vector attraction reduction Options
6 to 11 (pH adjustment, heat drying, or injection, incorpo-
ration, or daily cover) may be used (see Chapter 8). Op-
tions 1 through 5 would not typically be applicable to heat
treated sludge unless the sludge was digested or other-
wise stabilized during or after heat treatment (e.g. through
the use of wet air oxidation during heat treatment).
Microbiological Requirements
When operated according to the Part 503 requirements,
the process effectively reduces pathogenic viruses, bac-
teria, and viable helminth ova to below detectable levels.
Sewage sludge must be properly stored after processing
because organic matter has not been reduced, and there-
fore, growth of bacteria can occur.
Heat treated sewage sludge must be tested for fecal
coliform or Salmonella sp. at the time of use or disposal or
as it is prepared for sale or distribution. If heat treated
biosolids are subsequently composted or otherwise treated,
pathogen testing should take place after that processing
is complete.
7.5 Thermophilic Aerobic Digestion
Thermophilic aerobic digestion is a refinement of the
conventional aerobic digestion processes discussed in
Section 6.2. In this process, feed sewage sludge is gener-
ally pre-thickened and an efficient aerator is used. In some
modifications, oxygen is used instead of air. Because there
is less sewage sludge volume and less air to carry away
heat, the heat released from biological oxidation warms
the sewage sludqe in the diqester to as hiqh as 60°C
(140°F).
Because of the increased temperatures, this process
achieves higher rates of organic solids reduction than are
achieved by conventional aerobic digestion which oper-
ates at ambient air temperature. The biodegradable vola-
tile solids content of the sewage sludge can be reduced
by up to 70% in a relatively short time. The digested sew-
age sludge is effectively pasteurized due to the high tem-
peratures. Pathogenic viruses, bacteria, viable helminth
ova and other parasites are reduced to below detectable
limits if the process is carried out at temperatures exceed-
ing 55°C (131°F).
This process can either be accomplished using auxiliary
heating of the digestion tanks or through special designs
that allow the energy naturally released by the microbial
digestion process to heat the sewage sludge. The Part
503 PFRP description of thermophilic aerobic digestion is:
Liquid sewage sludge is agitated with air or oxygen to
maintain aerobic conditions and the mean cell resi-
dence time of the sewage sludge is 10 consecutive
days at 55°C to 60°C (131 °F to 140°F).
The thermophilic process requires significantly lower
residence times (i.e., solids retention time) than conven-
tional aerobic processes designed to qualify as a PSRP,
which must operate 40 to 60 days at 20°C to 15°C (68°F
to 59°F), respectively. Residence time is normally deter-
mined by dividing the volume of sewage sludge in the ves-
sel by the volumetric flow rate. Facility operation should
minimize the potential for bypassing by withdrawing treated
sewage sludge before feeding, and feeding no more than
once a day.
In the years following the publication of the Part 503 regu-
lation, advances in thermophilic digestion have been made.
It should be noted, however, that complete-mix reactors
with continuous feeding may not be adequate to meet Class
A pathogen reduction because of the potential for bypass-
ing or short-circuiting of untreated sewage sludge.
Vector Attraction Reduction
Vector attraction reduction must be demonstrated. Al-
though all options, except Options 2, 4, and 12 are pos-
sible, Options 1 and 3 which involve the demonstration of
volatile solids loss are the most suitable. (Option 2 is ap-
propriate only for anaerobically digested sludge, and Op-
tion 4 is not possible because it is not yet known how to
translate SOUR measurements obtained at high tempera-
tures to 20°C [68°F].)
Thermophilically aerobically digested biosolids must be
tested for fecal coliform or Salmonella sp. at the time of
54
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use or disposal or as it is prepared for sale or distribution.
If digested biosolids are subsequently composted or oth-
erwise treated, pathogen testing for either fecal coliform
or Salmonella sp. should take place after processing is
complete.
7.6 Beta Ray and Gamma Ray Radiation
Radiation can be used to disinfect sewage sludge. Ra-
diation destroys certain organisms by altering the colloidal
nature of the cell contents (protoplasm). Gamma rays and
beta rays are the two potential energy sources for use in
sewage sludge disinfection. Gamma rays are high-energy
photons produced by certain radioactive elements. Beta
rays are electrons accelerated in velocity by electrical po-
tentials in the vicinity of 1 millions volts. Both types of ra-
diation destroy pathogens that they penetrate if the doses
are adequate. The Part 503 PFRP descriptions for irradia-
tion systems are:
Beta Ray Irradiation
Sewage sludge is irradiated with beta rays from an
accelerator at dosages of at least 1.0 megarad at room
temperature (ca. 20°C [68°F]).
Gamma Ray Irradiation
Sewage sludge is irradiated with gamma rays from
certain isotopes, such as Cobalt 60 and Cesium 137
[at dosages of at least 1.0 megarad] at room tempera-
ture (ca. 20°C [68°F]).
The effectiveness of beta radiation in reducing patho-
gens depends on the radiation dose, which is measured in
rads. A dose of 1 megarad or more will reduce pathogenic
viruses, bacteria, and helminths to below detectable lev-
els. Lower doses may successfully reduce bacteria and
helminth ova but not viruses. Since organic matter has not
been destroyed with processing, sewage sludge must be prop-
erly stored after processing to prevent contamination.
Although the two types of radiation function similarly to
inactivate pathogens, there are important differences.
Gamma rays can penetrate substantial thicknesses of sew-
age sludge and can therefore be introduced to sewage
sludge by either piping liquid sewage sludge into a vessel
that surrounds the radiation source (Figure 7-1) or by car-
rying composted or dried sewage sludge by hopper con-
veyor to the radiation source. Beta rays have limited pen-
etration ability and therefore are introduced by passing a
thin layer of sewage sludge under the radiation source
(Figure 7-2).
Vector Attraction Reduction
Radiation treatment must be followed by vector attrac-
tion reduction. The appropriate options for demonstrating
vector attraction reduction are the same as for heat treat-
ment (see Section 7.4), namely Options 6 to 11. Options
1-5 are not applicable unless the sewage sludge is subse-
quently digested.
Microbiological Requirements
Irradiated sewage sludge must be tested for fecal coliform
or Salmonella sp. at the time of use or disposal or as it is
prepared for sale or distribution.
7.7 Pasteurization
Pasteurization involves heating sewage sludge to above
a predetermined temperature for a minimum time period.
For pasteurization, the Part 503 PFRP description is:
The temperature of the sewage sludge is maintained
at 70°C (158°F) or higher for 30 minutes or longer.
Sludge
Inlet
Vent
Sludge
Outlet
Figure 7-1. Schematic representation of cobalt-60 (gamma ray)
irradiation facility at Geiselbullach, Germany. Source:
EPA. 1979.
Input
(untreated or
Digested Sludge)
Electron
Beam
Constant
Head Tank
Underflow
Weir
Inclined
Feed Ramp
Electron Beam
Scanner
High Energy
Disinfection
Zone
Sludge
leceiving
Tank
Output
(Disinfected
Sludge)
Figure 7-2. Beta ray scanner and sludge spreader. Source: EPA,1979.
55
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Pasteurization reduces bacteria, enteric viruses, and vi-
able helminth ova to below detectable values. Sewage
sludge can be heated by heat exchangers or by steam
injection. Although sewage sludge pasteurization is uncom-
mon in the United States, it is widely used in Europe. The
steam injection method is preferred because it is more ef-
fective at maintaining even temperatures throughout the
sewage sludge batch being processed. Sewage sludge is
pasteurized in batches to prevent recontamination that
might occur in a continuous process. Sewage sludge must
be properly stored after processing because the organic
matter has not been stabilized and therefore odors and
growth of pathogenic bacteria can occur if sewage sludge
is re-inoculated.
In theory, quicklime can be used to meet the require-
ments for pasteurization of sewage sludge. The water in
the sludge slakes the lime, forming calcium hydroxide, and
generates heat. However, it is difficult to ensure that the
entire mass of sewage sludge comes into contact with the
lime and achieves the required 70°C for 30 minutes. This
is particularly true for dewatered sewage sludges. Pro-
cesses must be designed to 1) maximize contact between
the lime and the sewage sludge, 2) ensure that adequate
moisture is present, 3) ensure that heat loss is minimal,
and 4) if necessary, provide an auxiliary heat source. Pas-
teurization cannot be accomplished in open piles.
In addition, in order for pasteurization to be conducted
properly, facility operators must be trained with regard to
1) the proper steps to be taken to ensure complete hydra-
tion of the alkaline reagent used, 2) the evaluation of the
slaking rate of the lime-based alkaline material required
for their particular process, specifying the reactivity rate
required, 3) the proper measurement of pH, 4) an aware-
ness of the effect of ammonia gassing off and how this
affects the lime dose, and 5) the necessity for maintaining
sufficient moisture in the sewage sludge/alkaline mixture
during the mixing process to ensure the complete hydra-
tion of the quicklime and migration of hydroxyl ions through-
out the sewage sludge mass. This is to ensure that the
entire sewage sludge mass is disinfected.
EPA-sponsored studies showed that pasteurization of
liquid sewage sludge at 70°C (158°F) for 30 minutes inac-
tivates parasite ova and cysts and reduces the population
of measurable viruses and pathogenic bacteria to below
detectable levels (U.S. EPA, 1979). This process is based
on the pasteurization of milk which must be heated to at
least 63°C (145°F) for at least 30 minutes.
Vector Attraction Reduction
Pasteurization must be followed by a vector attraction
reduction process unless the vector attraction reduction
conditions of Option 6 (pH adjustment) have been met.
The options appropriate for demonstrating vector attrac-
tion reduction are the same as those for heat treatment
(see Section 10.4), namely Options 6 to 11. Options 1 to 5
are not applicable unless the sludge is subsequently di-
gested.
Microbiological Requirements
Pasteurized sludge must be tested for fecal coliform or
Salmonella sp. at the time of use or disposal or as it is
prepared for sale or distribution. In Europe, serious prob-
lems with regrowth of Salmonella sp. have occurred, so
pasteurization is rarely used now as a terminal treatment
process. Pre-pasteurization followed by mesophilic diges-
tion has replaced the use of pasteurization after digestion
in many European communities.
7.8 Equivalent Processes
Under Class A Alternative 6, sewage sludge treated in
processes that are determined to be equivalent to PFRP
are considered to be Class A with respect to pathogens
(assuming the treated sewage sludges also meet the Class
A microbiological requirement). Table 11-2 in Chapter 11
lists some of the processes that were found, based on the
recommendation of EPA's Pathogen Equivalency Commit-
tee, to be equivalent to PFRP under Part 257. Chapter 11
discusses how the PEC makes a recommendation of
equivalency.
References and Additional Resources
Caballero, Ross. 1984. Experience at a windrow
composting facility: LA County site technology trans-
fer. US EPA, Municipal Environmental Research
Laboratory Cincinnati, Ohio.
Composting Council. 1994. Compost facility operating
guide: A reference guide for composting facility and
process management. Alexandria, Virginia.
Epstein, Eliot. 1997. The science of composting. Technomic
Publishing Company.
Farrell, J.B. 1992. Fecal pathogen control during
composting. Presented at International Composting
Research Symposium, Columbus, Ohio.
Haug, Roger T. 1993. The practical handbook of compost
engineering. Lewis Publishers.
lacaboni, M.D., J.R. Livingston, and TJ. LeBrun. 1984.
Windrow and static pile composting of municipal sew-
age sludges. Report No.: EPA/600/2-84/122 (NTIS
PB84-215748).
U.S. EPA. 1979. Process design manual for sludge treat-
ment and disposal. Report No.: EPA/625/1-79/001.
Cincinnati, OH: Water Engineering Research Labora-
tory and Center for Environmental Research Informa-
tion.
USDA/U.S. EPA. 1980. Manual for composting sewage
sludge by the Beltsville aerated-pile method. Report
No.: EPA/600/8-80/022.
WEF/ASCE. 1998. WEF Manual of Practice No. 8, Design
of Municipal Wastewater Treatment Plants. Pub. WEF
(Alexandria, VA) and ASCE (New York, NY).
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Yankp, W.A. 1987. Occurrence of pathogens in distribu-
tion and marketing municipal sludges. Report No.: EPA/
600/1-87/014. (NTIS PB88-154273/AS.) Springfield,
VA: National Technical Information Service.
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Chapter 8
Requirements for Reducing Vector Attraction
8.1 Introduction
The pathogens in sewage sludge pose a disease risk
only if there are routes by which the pathogens are brought
into contact with humans or animals. A principal route for
transport of pathogens is vector transmission. Vectors are
any living organism capable of transmitting a pathogen
from one organism to another either mechanically (by sim-
ply transporting the pathogen) or biologically by playing a
specific role in the life cycle of the pathogen. Vectors for
sewage sludge pathogens would most likely include in-
sects, rodents, and birds.
Suitable methods for measuring vector attraction directly
are not available. Vector attraction reduction is accom-
plished by employing one of the following:
Biological processes which breakdown volatile solids,
reducing the available food nutrients for microbial ac-
tivities and odor producing potential
Chemical or physical conditions which stop microbial
activity
Physical barriers between vectors and volatile solids
in the sewage sludge
At the present time there is no vector attraction equiva-
lency committee that evaluates other options for vector
attraction reduction. The creation of one is being consid-
ered. The specific options outlined in the Part 503 regula-
tion are currently the only available means for demonstrat-
ing vector attraction reduction.
The term "stability" is often used to describe sewage
sludge. Although it is associated with vector attraction re-
duction, stability is not regulated by the Part 503 Rule. With
regard to sewage sludge, stability is generally defined as
the point at which food for rapid microbial activity is no
longer available. Sewage sludge which is stable will gen-
erally meet vector attraction reduction (VAR) requirements.
The converse is not necessarily true; meeting VAR require-
ments does not ensure sewage sludge stability. Because
stability is also related to odor generation and the contin-
ued degradation of sewage sludge, it is often considered
an important parameter when producing biosolids for sale
or distribution. Table 8-1 lists some of the common meth-
ods for measuring stability.
Table 8-1. Stability Assessment
Process
Monitoring Methods
Composting
Heat Drying
Alkaline Stabilization
Aerobic Digestion
Anaerobic Digestion
C02 respiration,
Moisture content
uptake
pH; pH change with storage; moisture;
ammonia evolution; temperature
SOUR; volatile solids reduction, additional
volatile solids reduction
Gas production; volatile solids reduction,
additional volatile solids reduction
More information on stability can be found in the WERF
publication, "Defining Biosolids Stability: A Basis for Public
and Regulatory Acceptance" (1997).
The Part 503 regulation contains 12 options, described
below and summarized in Table 8-2, for demonstrating a
reduction in vector attraction of sewage sludge. These re-
quirements are designed to either reduce the attractive-
ness of sewage sludge to vectors (Options 1 through 8
and Option 12) or prevent the vectors from coming in con-
tact with the sewage sludge (Options 9 through 11).
Guidance on when and where to sample sewage sludge
to meet these requirements is provided in Chapter 10.
As mentioned in Chapter 3, meeting the vector attrac-
tion reduction requirements must be demonstrated sepa-
rately from meeting the pathogen reduction requirements.
Therefore, demonstration of vector attraction reduction
(e.g., through reduction of volatile solids by 38% as de-
scribed below) does not demonstrate achievement of
pathogen reduction. It should be noted that for Class A
biosolids, vector attraction reduction must be met after or
concurrent with pathogen reduction to prevent growth of
pathogenic bacteria.
8.2 Option 1: Reduction in Volatile Solids
Content [503.33(b)(1)]
This option is intended for use with biological treatment
systems only. Under Option 1, reduction of vector attrac-
tion is achieved if the mass of volatile solids in the sewage
sludge is reduced by at least 38%. This is the percentage
58
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Table 8-2. Vector Attraction Reduction Options
Requirement What is Required?
Most Appropriate For:
Option 1
503.33(b)(1)
At least 38% reduction in volatile solids during
sewage sludge treatment
Sewage sludge processed by:
Anaerobic biological treatment
Aerobic biological treatment
Option 2
503.33(b)(2)
Less than 17% additional volatile solids loss during
bench-scale anaerobic batch digestion of the sewage
sludge for 40 additional days at 30°C to 37°C
(86°F to 99°F)
Only for anaerobically digested sewage sludge that
cannot meet the requirements of Option 1
Option 3
503.33(b)(3)
Option 4
503.33(b)(4)
Less than 15% additional volatile solids reduction during
bench-scale aerobic batch digestion for 30 additional days
at20°C (68°F)
SOUR at 20°C (68°F) is <1.5 mg oxygen/hr/g total
sewage sludge solids
Only for aerobically digested liquid sewage sludge with
2% or less solids that cannot meet the requirements of
Option 1 e.g., sewage sludges treated in extended
aeration plants. Sludges with 2% solids must be
diluted
Liquid sewage sludges from aerobic processes run at
temperatures between 10 to 30 °C. (should not be used
for composted sewage sludges)
Option 5
503.33(b)(5)
Option 6
503.33(b)(6)
Option 7
503.33(b)(7)
Option 8
503.33(b)(8)
Option 9
503.33(b)(9)
Aerobic treatment of the sewage sludge for at least 14
days at over 40°C (104°F) with an average temperature
ofover45°C(113°F)
Addition of sufficient alkali to raise the pH to at least 12
at 25°C (77°F) and maintain a pH >12 for 2 hours and a
pH>11.5 for 22 more hours
Percent solids > 75% prior to mixing with other materials
Percent solids >90% prior to mixing with other materials
Sewage sludge is injected into soil so that no significant
amount of sewage sludge is present on the land surface
1 hour after injection, except Class A sewage sludge
which must be injected within 8 hours after the pathogen
reduction process
Composted sewage sludge (Options 3 and 4 are likely
to be easier to meet for sewage sludges from other
aerobic processes)
Alkali-treated sewage sludge (alkaline materials include
lime, fly ash, kiln dust, and wood ash)
Sewage sludges treated by an aerobic or anaerobic
process (i.e., sewage sludges that do not contain
unstabilized solids generated in primary wastewater
treatment)
Sewage sludges that contain unstabilized solids
generated in primary wastewater treatment (e.g., heat-
dried sewage sludges)
Sewage sludge applied to the land or placed on a
surface disposal site. Domestic septage applied to
agricultural land, a forest, or a reclamation site, or
placed on a surface disposal site
Option 10 Sewage sludge is incorporated into the soil within 6 hours
503.33(b)(10) after application to land or placement on a surface disposal
site, except Class A sewage sludge which must be applied
to or placed on the land surface within 8 hours after the
pathogen reduction process
Option 11 Sewage sludge placed on a surface disposal site must be
503.33(b)(11) covered with soil or other material at the end of each
operating day
Option 12 pH of domestic septage must be raised to >12 at 25°C
503.33(b)(12) (77°F) by alkali addition and maintained > 12 for 30
minutes without adding more alkali
Sewage sludge applied to the land or placed on a
surface disposal site. Domestic septage applied to
agricultural land, forest, or a reclamation site, or placed
on a surface disposal site
Sewage sludge or domestic septage placed on a
surface disposal site
Domestic septage applied to agricultural land, a forest,
or a reclamation site or placed on a surface disposal
site
of volatile solids reduction that can generally be attained
by the "good practice" recommended conditions for
anaerobic digestion of 15 days residence time at 35°C
[95°F] in a completely mixed high-rate digester. The per-
cent volatile solids reduction can include any additional
volatile solids reduction that occurs before the biosolids
leave the treatment works, such as might occur when the
sewage sludge is processed on drying beds or in lagoons.
The starting point for measuring volatile solids in sew-
age sludge is at the point at which sewage sludge enters a
sewage sludge treatment process. This can be problem-
59
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atic for facilities in which wastewater is treated in systems
like oxidation ditches or by extended aeration. Sewage
sludges generated in these processes are already sub-
stantially reduced in volatile solids content by their long
exposure to oxidizing conditions in the process. If sewage
sludge removed from these processes is further treated
by anaerobic or aerobic digestion to meet VAR require-
ments, it is unlikely that the 38% reduction required to meet
Option 1 can be met. In these cases, use of Options 2,3,
or 4 is more appropriate.
The end point where volatile solids are measured to cal-
culate volatile solids losses can be at any point in the pro-
cess. Because volatile solids continue to degrade through-
out sewage sludge treatment, it is recommended that
samples be taken at the end point of treatment.
Volatile solids reduction is calculated by a volatile solids
balance around the digester or by the Van Kleeck formula
(Fisher, 1984). Guidance on methods of calculation is pro-
vided in Appendix C.
Volatile solids reduction is typically achieved by anaero-
bic or aerobic digestion. These processes degrade most
of the biodegradable material to lower activity forms. Any
biodegradable material that remains characteristically de-
grades so slowly that vectors are not drawn to it.
8.3 Option 2: Additional Digestion of
Anaerobically Digested Sewage Sludge
[503.33(b)(2)I
Under this option, an anaerobically digested sewage
sludge is considered to have achieved satisfactory vector
attraction reduction if it loses less than 17% additional vola-
tile solids when it is anaerobically batch-digested in the
laboratory in a bench-scale unit at 30°C to 37°C (86°F to
99°F) for an additional 40 days. Procedures for this test
are presented in Appendix D. As noted in Appendix D, the
material balance method for calculating additional volatile
solids reduction will likely show greater reductions than
the Van Kleeck method.
Frequently, return activated sludges have been recycled
through the biological wastewater treatment section of a
treatment works or have resided for long periods of time in
the wastewater collection system. During this time they
undergo substantial biological degradation. If they are sub-
sequently treated by anaerobic digestion for a period of
time, they are adequately reduced in vector attraction, but
because they entered the digester with volatile solids al-
ready partially reduced, the volatile solids reduction after
treatment is frequently less than 38%. The additional di-
gestion test is used to demonstrate that these sewage slud-
ges are indeed satisfactorily reduced in vector attraction.
It is not necessary to demonstrate that Option 1 cannot
be met before using Option 2 or 3 to comply with VAR
requirements.
This additional anaerobic digestion test may have utility
beyond use for sewage sludge from the classical anaero-
bic digestion process. The regulation states that the test
can be used for a previously anaerobically digested sew-
age sludge. One possible application is for sewage sludge
that is to be removed from a wastewater lagoon. Such
sewage sludge may have been stored in such a lagoon for
many years, during which time it has undergone anaero-
bic digestion and lost most of its volatile solids. It is only
recognized by the regulations as a sewage sludge when it
is removed from the lagoon. If it were to be further pro-
cessed by anaerobic digestion, the likelihood of achieving
38% volatile solids reduction is very low. The additional
anaerobic digestion test which requires a long period of
batch digestion at temperatures between 30°C and 37°C
would seem to be an appropriate test to determine whether
such a sewage sludge has the potential to attract vectors.
8.4 Option 3: Additional Digestion of
Aerobically Digested Sewage Sludge
[503.33(b)(3)]
Under this option, an aerobically digested sewage sludge
with 2% or less solids is considered to have achieved sat-
isfactory vector attraction reduction if it loses less than 15%
additional volatile solids when it is aerobically batch-di-
gested in the laboratory in a bench-scale unit at 20°C (68°F)
for an additional 30 days. Procedures for this test and the
method for calculating additional volatile solids destruc-
tion are presented in Appendix D. The test can be run on
sewage sludges up to 2% solids and does not require a
temperature correction for sewage sludges not initially di-
gested at 20°C (68°F). Liquid sludges with greater than
2% solids can be diluted to 2% solids with unchlorinated
effluent, and the test can then be run on the diluted sludge.
This option should not be used for non-liquid sewage sludge
such as dewatered cake or compost.
This option is appropriate for aerobically digested sew-
age sludges that cannot meet the 38% volatile solids re-
duction required by Option 1. These include sewage slud-
ges from extended aeration and oxidation ditch processes,
where the nominal residence time of sewage sludge leav-
ing the wastewater treatment processes section generally
exceeds 20 days. In these cases, the sewage sludge may
already have been substantially reduced in biological
degradability prior to aerobic digestion.
As was suggested for the additional anaerobic digestion
test, the additional aerobic digestion test may have appli-
cation to sewage sludges that have been aerobically treated
by other means than classical aerobic digestion.
8.5 Option 4: Specific Oxygen Uptake Rate
(SOUR) for Aerobically Digested
Sewage Sludge [503.33(b)(4)]
For an aerobically digested sewage sludge with a total
solids content equal to or less than 2% which has been
processed at a temperature between 10°- 30°C, reduc-
tion in vector attraction can also be demonstrated using
the SOUR test. The SOUR of the sewage sludge to be
used or disposed must be less than or equal to 1.5 mg of
60
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oxygen per hour per gram of total sewage sludge solids
(dry weight basis) at 20°C (68°F).i This test is based on
the fact that if the aerobically treated sewage sludge con-
sumes very little oxygen, its value as a food source for
vectors is very low and therefore vectors are unlikely to be
attracted to it. Frequently aerobically digested sewage slud-
ges are circulated through the aerobic biological waste-
water treatment process for as long as 30 days. In these
cases, the sewage sludge entering the aerobic digester is
already partially digested, which makes it difficult to dem-
onstrate the 38% reduction required by Option 1.
The oxygen uptake rate depends on the conditions of
the test and, to some degree, on the nature of the original
sewage sludge before aerobic treatment. The SOUR test
should not be used on sewage sludge products such as
heat or air dried sludge or compost. Because of the reduc-
tion of microbial populations that occur in these processes,
the SOUR results are not accurate and should not be used.
SOUR testing on sewage sludges with a total solids con-
tent below 0.5% may give inaccurately high results. Farrell,
et al. (1996) cite the work of several investigators indicat-
ing such an effect. Farrell, et al. (1996) also note that stor-
age for up to two hours did not cause a significant change
in the SOUR measurement. It is therefore suggested that
a dilute sewage sludge could be thickened to a solids con-
tent less than 2% solids and then tested, provided that the
thickening period is not in excess of two hours.
The SOUR test requires a poorly defined temperature
correction at temperatures differing substantially from 20°C
(68°F). SOUR cannot be applied to sewage sludges di-
gested outside the 10-30°C range (50-86°F). The actual
temperature of the sewage sludge tested cannot be ad-
justed because temperature changes can cause short-term
instability in the oxygen uptake rate (Benedict, et al. (1973);
Farrell, et al. [1996]), and this would invalidate the results
of the test. Guidance on performing the SOUR test and on
sewage sludge-dependent factors are provided in Appen-
dix D.
It should be noted that the limit on the use of the SOUR
test for sewage sludges at different solids and tempera-
ture levels is due to the lack of research and data on differ-
ent sewage sludges. EPA encourages the collection of
SOUR data for different sewage sludges so that at some
point, Option 4 may be expanded to include more sewage
sludge materials.
1 SOUR is defined in Part 503 as the mass of oxygen consumed per unit time per
unit mass of total solids (dry weight basis) in the sewage sludge. SOUR is usually
based on total suspended volatile solids rather than total solids because it is as-
sumed that it is the volatile matter in the sewage sludge that is being oxidized. The
SOUR definition in Part 503 is based on the total solids primarily to reduce the
number of different determinations needed and for consistency with application
rates, which are measured in total solids per unit area. Generally, the range in the
ratio of volatile solids to total solids in aerobically digested sewage sludges is not
large. The SOUR based on total solids will merely be slightly lower than if it had
been based on volatile suspended solids to indicate the same endpoint.
8.6 Option 5: Aerobic Processes at Greater
Than 40°C [503.33(b)(5)]
The sewage sludge must be aerobically treated for 14
days or longer during which time the temperature must be
over 40°C (104°F) and the average temperature higher than
45°C (113°F). This option applies primarily, but not exclu-
sively, to composted sewage sludge. These processed
sewage sludges generally contain substantial amounts of
partially decomposed organic bulking agents, in addition
to sewage sludge. This option must be used for composted
sewage sludge; other options are either not appropriate or
have not adequately been investigated for use with com-
post.
The Part 503 regulation does not specifically mention or
limit this option to composting. This option can be applied
to sewage sludge from other aerobic processes such as
aerobic digestion as long as temperature requirements can
be met and the sewage sludge is maintained in an aerobic
state for the treatment period, but other methods such as
Options 3 and 4 are likely to be easier to meet for these
sewage sludges.
If composting is used to comply with Class A pathogen
requirements, the VAR time-temperature regime must be
met along with or after compliance with the pathogen re-
duction time-temperature regime.
8.7 Option 6: Addition of Alkali
[503.33(b)(6)]
Sewage sludge is considered to have undergone ad-
equate vector attraction reduction if sufficient alkali is added
to:
Raise the pH to at least 12
Maintain a pH of at least 12 without addition of more
alkali for 2 hours
Maintain a pH of at least 11.5 without addition of more
alkali for an additional 22 hours
pH should be measured in a slurry at 25°C. For more
information on making a slurry, see Section 10.7. Either
sewage sludge samples may be taken and heated or
cooled to 25°C or results can be adjusted based on the
ambient temperature where pH is measured and the fol-
lowing calculation:
Correction Factor = 0.03 pH unitsX (Tmeas-25°C)
1.0°C
Actual pH = Measured pH +/- the Correction Factor
T = Temperature measured
Example of Using the pH Correction Factor
If the measured pH is 12.304 at 30°C, the actual pH can
be calculated as follows:
Correction Factor = 0.03 x (30-25) = +0.15
Actual pH = 12.304+ 0.15 = 12.454
61
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It should be noted that temperature compensation de-
vices on pH meters correct only for variations in the con-
ductance of pH probes, and not for the variability in solu-
tion concentration. Therefore, the temperature correction
noted above should be applied to pH measurements, even
if a pH meter with temperature settings is used.
As noted in Section 5.6, the term "alkali" means a sub-
stance that causes an increase in pH. Raising sewage
sludge pH through alkali addition reduces vector attrac-
tion by reducing or stopping biological activity. However,
this reduction in biological activity is not permanent. If the
pH drops, surviving bacteria become biologically active and
the sewage sludge will again putrefy and potentially at-
tract vectors. The more soluble the alkali, the less likely it
is that there will be an excess present when a pH of 12 is
reached. Consequently, the subsequent drop in pH with
time will be more rapid than if a less soluble alkali is used.
The conditions required under this option are designed
to ensure that the sewage sludge can be stored for at least
several days at the treatment works, transported, and ap-
plied to soil without the pH falling to the point where bio-
logical activity results in vector attraction. The requirement
of raising the pH to 12 increases the probability that the
material will be used before pH drops to a level at which
putrefaction can occur. The requirements for pH adjust-
ment of domestic septage are less stringent because it is
unlikely that septage haulers will hold domestic septage
for long periods of time.
Raising the pH to 12 and maintaining this pH for two
hours and a pH of 11.5 for an additional 22 hours ensures
that the pH will stay at adequately high levels to prevent
putrefaction before disposal in all but unusual cases. In
any event, it is prudent in a timely manner to apply sludge
in a thin layer or incorporate it into the soil for the preven-
tion of odors and vector attraction.
More information on alkali addition and measurement of
pH are included in Chapter 10.
8.8 Option 7: Moisture Reduction of
Sewage Sludge Containing No
Unstabilized Solids [503.33(b)(7)]
Under this option, vector attraction is considered to be
reduced if the sewage sludge does not contain unstabilized
solids generated during primary wastewater treatment and
if the solids content of the sewage sludge is at least 75%
before the sewage sludge is mixed with other materials.
Thus, the reduction must be achieved by removing water,
not by adding inert materials.
It is important that the sewage sludge not contain
unstabilized solids because the partially degraded food
scraps likely to be present in such a sewage sludge could
attract birds, some mammals, and possibly insects, even
if the solids content of the sewage sludge exceeds 75%.
The way dried sewage sludge is handled or stored be-
fore use or disposal can create or prevent vector attrac-
tion. If dried sewage sludge is exposed to high humidity,
the outer surface of the sewage sludge could equilibrate
to a lower solids content and attract vectors. Proper man-
agement should be conducted to prevent this from hap-
pening.
8.9 Option 8: Moisture Reduction of
Sewage Sludge Containing Unstabilized
Solids [503.33(b)(8)]
Vector attraction of any sewage sludge is considered to
be reduced if the solids content of the sewage sludge is
increased to 90% or greater. This extreme desiccation
deters vectors in all but the most unusual situations. As
noted for Option 7, the solids increase should be achieved
by removal of water and not by dilution with inert solids.
Drying to this extent severely limits biological activity and
strips off or decomposes the volatile compounds that at-
tract vectors.
Because sewage sludge meeting vector attraction re-
duction with this option may contain unstabilized solids,
material that absorbs moisture or is rewet may putrefy and
attract vectors. Proper storage and use of this material
should be considered in order to prevent potential patho-
gen growth and vector attraction.
8.10 Option 9: Injection [503.33(b)(9)]
Vector attraction reduction can be achieved by injecting
the sewage sludge below the ground. Under this option,
no significant amount of the sewage sludge can be present
on the land surface within 1 hour after injection, and, if the
sewage sludge is Class A with respect to pathogens, it
must be injected within 8 hours after discharge from the
pathogen-reduction process.
Injection of sewage sludge beneath the soil places a
barrier of earth between the sewage sludge and vectors.
The soil quickly removes water from the sewage sludge,
which reduces the mobility and odor of the sewage sludge.
Odor is usually present at the site during the injection pro-
cess, but it quickly dissipates when injection is complete.
The special restriction requiring injection within 8 hours
for Class A sewage sludge is needed because these sew-
age sludges are likely devoid of actively growing bacteria
and are thus an ideal medium for growth of pathogenic
bacteria (see Section 4.3). If pathogenic bacteria are
present (survivors or introduced by contamination), their
numbers increase slowly for the first 8 hours after treat-
ment, but after this period, their numbers can rapidly in-
crease. This kind of explosive growth is not likely to hap-
pen with Class B sludge because high densities of non-
pathogenic bacteria are present which suppresses the
growth of pathogenic bacteria. In addition, the use of Class
B biosolids requires site restrictions which reduce the risk
of public exposure to pathogens. Consequently, this spe-
cial requirement is not needed for Class B biosolids
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8.11 Option 10: Incorporation of Sewage
Sludge into the Soil [503.33(b)(10)]
Under this option, sewage sludge applied to the land
surface or placed on a surface disposal site must be incor-
porated into the soil within 6 hours after application to or
placement on the land. If the sewage sludge is Class A
with respect to pathogens, the time between processing
and incorporation after application or placement must not
exceed 8 hours -- the same as for injection under Option
9.
When applied at agronomic rates, the loading of sew-
age sludge solids typically is about 1/100th or less of the
mass of soil in the plow layer (approximately the top six
inches of soil). If mixing is reasonably good, the dilution of
sewage sludge in the soil surface is equivalent to that
achieved with soil injection. Odor will be present and vec-
tors will be attracted temporarily, as the sewage sludge
dewaters on the soil surface. This attraction diminishes
and is virtually eliminated when the sewage sludge is mixed
with the soil. The mixing method applies to liquid sewage
sludges, dewatered sewage sludge cake, and even to dry
sewage sludges that have not already met the vector at-
traction reduction requirements of the regulation by one of
the other options.
The 6 hours allowed to complete the mixing of sewage
sludge into the soil should be adequate to allow for proper
incorporation. As a practical matter, it may be wise to com-
plete the incorporation in a much shorter time. Clay soils
tend to become unmanageably slippery and muddy if the
liquid sewage sludge is allowed to soak into the first inch
or two of topsoil.
8.12 Option 11: Covering Sewage Sludge
[503.33(b)(11)]
Under this option, sewage sludge placed on a surface
disposal site must be covered with soil or other material at
the end of each operating day. Daily covering reduces vec-
tor attraction by creating a physical barrier between the
sewage sludge and vectors, while environmental factors
work to reduce pathogens.
8.13 Option 12: Raising the pH of
Domestic Septage [503.33(b)(12)]
This option applies only to domestic septage applied to
agricultural land, forest, a reclamation site, or surface dis-
posal site. Vector attraction is reduced if the pH is raised
to at least 12 through alkali addition and maintained at 12
or higher for 30 minutes without adding more alkali. (These
conditions also accomplish pathogen reduction for domes-
tic septage-see Section 5.6.) When this option is used,
every container (truckload) must be monitored to demon-
strate that it meets the requirement. As noted in Section
5.6, "alkali" refers to a substance that causes an increase
in pH.
This vector attraction reduction requirement is slightly
less stringent than the alkali addition requirement for sew-
age sludge. The method is geared to the practicalities of
the use or disposal of domestic septage, which is typically
treated by lime addition in the domestic septage hauling
truck. The treated septage is typically applied to the land
shortly after lime addition. During the very short time inter-
val, the pH is unlikely to fall to a level at which vector at-
traction could occur.
If domestic septage is not applied soon after pH adjust-
ment, it is recommended that pH be retested, and addi-
tional alkali be added to the domestic septage to raise the
pH to 12 if necessary. Alternatively, if pH has dropped and
the domestic septage begins to putrefy, it is advisable to
cover or incorporate the domestic septage in order to pre-
vent vector attraction.
8.14 Number of Samples and Timing
Unlike pathogenic bacteria, volatile solids cannot regen-
erate once they are destroyed, so samples can be taken
at any point along the process. However, since volatile
solids are destroyed throughout treatment, it is recom-
mended that samples be taken at the end of processing.
Facilities which use Option 2 or 3 to demonstrate vector
attraction reduction must schedule sampling to leave ample
time to complete the laboratory tests before sewage sludge
is used or disposed. A suggested procedure would be to
take several samples at evenly spaced time intervals dur-
ing the period between the required monitoring dates and
calculate running averages comprised of at least four vola-
tile solids results. This has the advantage of not basing
the judgement that the process is performing adequately
(or inadequately) on one or two measurements that could
be erroneous because of experimental error or a poorly
chosen sample inadvertently taken during a brief process
upset. It also provides an important quality control mea-
sure for process operations. Since the Part 503 regulations
do not specify a sampling program, it is recommended that
sewage sludge preparers consult with the regulatory au-
thority with regard to sampling schedules.
8.15 Vector Attraction Reduction
Equivalency
Many of the vector attraction reduction tests are time
consuming and inconvenient, particularly for small treat-
ment plants that do not have a laboratory. Efforts to define
new, simpler methods for measuring vector attraction are
on-going.
Since it is infeasible to measure the actual attraction of
vectors, given the large number of variables, methodology
development must continue to focus on the cause of vec-
tor attraction, namely the availability of a food source (vola-
tile solids) or odor. The tests to measure the attractants
may vary depending on the technology by which the sew-
age sludge is processed.
Some of the parameters which might be used to mea-
sure vector attraction may include gas production or mea-
sures of microbial activity. For example, several methods
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which measure carbon dioxide evolution or reheating po-
tential are currently in use to measure compost stability,
but these methods must be examined more closely to de-
termine if they can be applied to other forms of sewage
sludge and if results can be adequately correlated to vec-
tor attraction.
The responsibility to eventually develop additional vec-
tor attraction reduction test protocols lies with the scien-
tific community and the sewage sludge industry. Since there
is currently no standard procedure for considering VAR
equivalency, new methods must be submitted to the EPA
for consideration and potential inclusion in the next rule-
making effort.
References and Additional Resources
Benedict, A.M. and D.A. Carlson. 1973. Temperature ac-
climation in aerobic bio-oxidation systems. Jour.
WPCF: 45(1): 10-24. January.
Farrell, Joseph B., Vinayak Bhide, and James E. Smith, Jr.
1996. Development of EPA's new methods to quantify
vector attraction of wastewater sludges. Water Envi-
ronment Research, Volume 68, Number 3.
Fisher, WJ. 1984. Calculation of volatile solids destruc-
tion during sludge digestion. Pp 514-528 in Bruce, A.,
ed Sewage sludge stabilization and disinfection. Pub-
lished for Water Research Center. Chichester, England:
E.Harwood, Ltd.
Smith, J.E., Jr. and J.B. Farrell. Vector attraction reduc-
tion issues associated with the Part 503 Regulations
and Supplemental Guidance, Proceedings of the Wa-
ter Environment Federation's Conference, "Interna-
tional Management of Water and Wastewater Solids
for the 21st Century: A Global perspective, June 19-
22, 1994, Washington, DC, pp 1311-1330.
Switzenbaurm, Michael S., L.H. Moss, E. Epstein, A.B.
Pincince, J.F. Donovan. 1997. Defining biosolids sta-
bility: a basis for public and regulatory acceptance.
Water Environment Research Foundation.
WEF/ASCE. 1998. WEF Manual of Practice No. 8, Design
of Municipal Wastewater Treatment Plants. Pub. WEF
(Alexandria, VA) and ASCE (New York, NY).
WERF. 1997. Defining biosolids stability: A basis for public
and regulatory acceptance. Pub. WERF. Alexandria,
VA.
U.S. EPA. 1992. Technical support document for reduction
of pathogens and vector attraction in sewage sludge.
EPA/822/R-93/004. EPA, Washington, DC.
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Chapter 9
Sampling Procedures and Analytical Methods
9.1 Introduction
Many of the Part 503 Subpart D pathogen and vector
attraction reduction requirements call for monitoring and
analysis of the sewage sludge to ensure that microbiologi-
cal quality and vector attraction reduction meet specified
requirements (see Chapters 4 to 6 for a description of the
requirements).The purpose of this chapter is to describe
procedures for obtaining representative samples and en-
suring their quality and integrity. It also summarizes the
analytical methods required under Part 503, and directs
the reader to other sections of this document that describe
some of those methods.
Sampling personnel will also benefit from reading ex-
panded presentations on the subject. "Standard Methods"
(APHA, 1992), "Principles of Environmental Sampling"
(Keith, 1988), "Samplers and Sampling Procedures for
Hazardous Waste Streams" (EPA, 1980), "Sludge Sam-
pling and Analysis Guidance Document" (EPA, 1993) and
ASTM Standard E 300-86, "Standard Practice for Sam-
pling Industrial Chemicals" (ASTM, 1992a) are highly rec-
ommended. The latter publication provides an in-depth
description of available sampling devices and procedures.
When referring to other publications, it is important to
note that most guidance on specific sampling techniques
is directed toward chemical analysis. Procedures described
may be inappropriate for microbiological sampling because
they expose the samples to possible contamination, or may
be appropriate only after some modification to reduce the
risk of microbial contamination during sampling.
9.2 Laboratory Selection
A very important, but often overlooked component of
pathogen and vector attraction monitoring is selecting an
appropriate analytical laboratory. The analysis of sewage
sludge or biosolids for indicator and pathogenic organisms
is more complex than water analysis. Solid samples such
as biosolids are prepared differently than water samples
and also typically contain a much higher background mi-
crobial population than water contains. Biosolids products
such as compost can be very heterogeneous, requiring
special sample preparation procedures. It is therefore im-
portant to use a laboratory that has developed an exper-
tise through the routine analysis of biosolids products.
Regional and state sludge coordinators should be con-
tacted for assistance in selecting a qualified laboratory.
To ensure that a laboratory has adequate experience
with biosolids analyses, the following information should
be obtained and reviewed.
For how long has the laboratory been analyzing
biosolids for the specified parameters?
Approximately how many biosolids samples does the
laboratory analyze per week or month?
For how many wastewater treatment facilities is the
laboratory conducting the specified analyses?
A list of references.
Does the laboratory have a separate and distinct mi-
crobiology lab?
Does the laboratory have microbiologists on staff?
Request and review their resumes.
Who will actually perform the analyses?
Is the laboratory familiar with the analytical procedures
including sample preparation, holding times, and QA/
QC protocols?
A laboratory tour and reference check are also recom-
mended. A good laboratory should be responsive, provid-
ing requested technical information in a timely manner. It
is the biosolids generator's responsibility to provide accu-
rate analytical results. Consequently, the selection of an
appropriate laboratory is an important component of de-
veloping a biosolids monitoring plan.
9.3 Safety Precautions
Sewage sludges that are being sampled should be pre-
sumed to contain pathogenic organisms, and should be
handled appropriately. Both the sampler and the person
carrying out the microbiological analysis must take appro-
priate precautions. Safety precautions that should be taken
when sampling and when analyzing the samples are dis-
cussed in Standard Methods (APHA, 1992) in Sections
1060A and 1090C.
Individuals performing sampling (usually employees of
wastewater treatment works) should receive training in the
microbiological hazards of sewage sludge and in safety
65
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precautions to take when sampling. Laboratory personnel
should be aware that the outside of every sample con-
tainer is probably contaminated with microorganisms, some
of which may be pathogens. Personal hygiene and labo-
ratory cleanliness are also extremely important. Several
safety practices that should be standard procedures dur-
ing sample collection and analysis are:
Gloves should be worn when handling or sampling
untreated sewage sludge or treated biosolids.
Personnel taking the samples should clean sample
containers, gloves, and hands before delivering the
samples to others.
Hands should be washed frequently and always be-
fore eating, smoking, and other activities that involve
hand-to-mouth contact.
Photocell-activated or foot-activated hand washing
stations are desirable to reduced spreading of con-
tamination to others.
Employees should train themselves to avoid touching
their lips or eyes.
Mouth pipetting should be forbidden.
Smoking should not be allowed inside the lab.
Employees involved in sample collection (or any other
activity where they are exposed to wastewater or sewage
sludges) should review their immunization history. At a
minimum, employees should be immunized against teta-
nus. However, employees should consider immunization
for other diseases, particularly hepatitis A and B. Employ-
ees should also consider having a blood sample analyzed
to determine if they still have active antibodies for the vari-
ous immunizations they received as children.
Personnel analyzing sewage sludge or biosolids samples
should receive training in awareness and safety concern-
ing biohazards. Because microbiological laboratories have
safety programs, this subject is not covered in depth here.
A facility's sampling plan should include a section on mi-
crobiological hazards and appropriate safety practices or,
alternatively, refer the reader to another document where
this information is presented.
9.4 Requirements for Sampling Equipment
and Containers
Containers
Sampling containers may be of glass or plastic that does
not contain a plasticizer (Teflon, polypropylene, and poly-
ethylene are acceptable). Plastic bags are especially use-
ful for thick sewage sludges and free-flowing solids. Pre-
sterilized bags are available. Stainless steel containers are
acceptable, but steel or zinc coated steel vessels are not
appropriate. In addition to providing guidance on appropri-
ate containers for specific analyses, private analytical labo-
ratories will typically provide sample containers at no cost.
Sampling containers used for microbiological analyses
should be sterile. Sampling tools that come in contact with
the actual sample should be constructed of stainless steel,
which is easily cleaned, and sterilized. Tools made of wood,
which is difficult to sterilize because of porosity, should not
be used.
Equipment
The sampling equipment used is primarily dependent
on the type of material being sampled. For relatively high
solids content biosolids, a hand trowel or scoop may be
adequate, whereas, collecting stratified samples from a
lagoon requires more sophisticated and specialized equip-
ment. Automated sampling equipment, as commonly used
for wastewater, should not be used. Such equipment can
cause solids separation during sampling and is difficult to
clean, resulting in cross contamination. Sampling equip-
ment should be constructed of non-corrosive materials,
such as stainless steel, Teflon, or glass, that can be thor-
oughly cleaned. Sampling equipment should be dedicated
for this task and should not be used for other applications.
Equipment should be cleaned well with detergent and a
nylon scrub brush after each use and stored inside in a
dedicated location. The types of sampling equipment and
their applications are presented in Table 9-1. The use of
this equipment is discussed in greater detail in Sections
9.6 and 9.7.
Sterilization
The containers and tools used for sampling must be ster-
ilized if the biosolids product is to be analyzed for Class A
microbiological parameters. Alternatively, pre-sterilized,
disposable scoops, and other sampling devices can be
purchased, alleviating the need to sterilize sampling equip-
ment. Conservative microbiological practice also requires
sterilization of containers and sampling tools used for col-
lecting samples to be tested for meeting the Class B re-
quirements. Sample containers and equipment should be
scrupulously cleaned prior to actual sample collection. Af-
ter the samples are collected, the sampling equipment
should be cleaned well with soap and water and put away
until the next sampling event. Equipment should be dedi-
cated to sampling and not used for other activities. Only
equipment that touches the actual sample must be steril-
ized. Equipment such as shovels or heavy equipment used
to access a sludge pile interior does not need to be steril-
ized, but should be clean, as long as another sterile sample
collection device (such as a hand trowel) is used to ac-
cess and collect the actual sample. Sterilization is not re-
quired when collecting samples of sewage sludge to be
used in vector attraction reduction tests, but all equipment
must be clean.
Either steam or a sterilizing solution such as sodium
hypochlorite (household bleach) should be used for steril-
izing equipment. If bleach is used, equipment must be
rinsed thoroughly in order to prevent residual bleach from
having an effect on the microbial population in the sample.
Equipment should be thoroughly washed with water, soap,
and a brush prior to sterilization. If an autoclave or large
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Table 9-1. Equipment Used for Collecting Sewage Sludge Samples
Equipment
Application
Composite Liquid Waste
Sampler (Coliwasa)
Weighted Bottle
Dipper
Sampling Thief
Trier
Auger
Scoops and Shovels
The Coliwasa is a device employed to sample free-flowing sewage sludges contained in drums, shallow tanks, pits,
and similar containers. It is especially useful for sampling wastes that consist of several immiscible liquid phases.
The Coliwasa consists of a glass, plastic, or metal tube equipped with an end closure that can be opened and closed
while the tube is submerged in the material to be sampled.
This sampling device consists of a glass or plastic bottle, sinker, stopper, and a line that is used to lower, raise, and
open the bottle. The weighted bottle is used for sampling free flowing sewage sludges and is particularly useful for
obtaining samples at different depths in a lagoon. A weighted bottle with line is built to the specifications in ASTM
Method D270 and E300.
The dipper consists of a glass or plastic beaker clamped to the end of a two- or three-piece telescoping aluminum or
fiberglass pole that serves as the handle. A dipper is used for obtaining samples of free flowing sewage sludges that
are difficult to access. Dippers are not available commercially and must be fabricated.
A thief consists of two slotted concentric tubes, usually made of stainless steel or brass. The outer tube has a conical
pointed tip that permits the sampler to penetrate the material being sampled. The inner tube is rotated to open and
close the sampler. A thief is used to sample high solids content materials such as composted and heat dried biosolids
for which particle diameter is less than one-third the width of the slots. Thief samplers are available from laboratory
supply companies.
A trier consists of a tube cut in half lengthwise with a sharpened tip that allows the sampler to cut into sticky materials
such as dewatered cake and lime stabilized biosolids. A trier samples moist or sticky solids with a particle diameter
less than one-half the diameter of the trier. Triers 61 to 100 cm long and 1.27 to 2.54 cm in diameter are available
from laboratory supply companies
An auger consists of sharpened spiral blades attached to a hard metal central shaft. An auger can be used to obtain
samples through a cross section of a biosolids stockpile. Augers are available at hardware and laboratory supply
stores.
Scoops are used to collect samples from sewage sludge or biosolids stockpiles, shallow containers, and conveyor
belts. Stainless steel or disposable plastic scoops are available at laboratory supply houses. Due to the difficulty of
sterilizing shovels and other large sampling equipment, this type of equipment should only be used for accessing the
center of stockpiles and should not be used for collecting the actual sample.
pressure cooker is available, enclose the sampling tool in
a kraft paper bag and place the bag in the autoclave. A
minimum period of 30 minutes at a temperature of 12TC
is required for sterilization. The kraft paper bag keeps the
sampling device from becoming contaminated in the field.
A steam cleaner can also be used to sterilize sampling
equipment. Place the equipment in a heat resistant plastic
bucket and direct steam onto the equipment for a mini-
mum of 10 minutes. When done, place the sterilized equip-
ment in a kraft paper bag.
Many facilities do not have an autoclave or steam clean-
ing equipment and will need to use a sterilizing solution to
sterilize equipment. A 10% household bleach solution (1
part bleach, 9 parts water) is readily available and works
well. However, bleach is corrosive and may also affect the
microbial population of a sample and does need to be ad-
equately removed from the equipment prior to sample col-
lection. Make up the 10% solution in a clean plastic bucket.
Immerse each piece of clean equipment in the solution for
a minimum contact time of a minute. Rinse the equipment
in another bucket containing sterile or boiled water. Let
the equipment air dry for a few minutes or dry with sterile
paper or cloth towels. After drying, place the equipment in
a paper bag. Sterile plastic bags obtained from a scientific
equipment supplier can also be used for short-term sterile
equipment storage.
9.5 Sampling Frequency and Number of
Samples Collected
The primary objective of biosolids monitoring is to as-
sure that all of the biosolids produced meet the regula-
tory requirements related to land application. It is obviously
not feasible to sample and analyze every load of biosolids
leaving a facility, nor is it necessary. However, a sampling
plan does need to adequately account for the variability of
the biosolids. This entails collecting samples at an adequate
frequency and analyzing a sufficient number of samples.
The minimum sampling frequency and number of samples
to be analyzed are shown in 40 CFR Part 503. As shown
in Table 3-4, the sample collection frequency is determined
by the amount of biosolids used or disposed.
The number of samples which must be analyzed for com-
pliance with Class A microbiological parameters is not
specified, however, it is strongly recommended that mul-
tiple samples per sampling event be analyzed for biosolids.
The number of samples taken must be sufficient to ad-
equately represent biosolids quality. It must be noted that
for Class A biosolids, analytical results are not averaged:
every sample analyzed must meet the Class A require-
ments.: "Either the density of fecal coliform in the sewage
sludge must be less than 1,000 MPN per gram of total
solids (dry weight basis), or the density of Salmonella sp.
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bacteria in sewage sludge must be less than 3 MPN per 4
grams of total solids (dry weight basis)."
To meet Class B Alternative 1 requirements, seven
samples must be taken and the geometric mean of results
must meet the 2.0 x 106 MPN fecal coliform per dry gram
limit (see Chapter 5). It is recommended that the samples
be taken over a two-week period in order to adequately
represent variability in the sewage sludge.
The actual sampling and analysis protocol is typically
developed by the facility and reported to the regulatory
authority, which can require a more stringent sampling and
analysis protocol than that stipulated in the Part 503 regu-
lation. In some cases, the regulatory authority may initially
require a more stringent monitoring schedule which may
be relaxed once product consistency is established. The
biosolids preparer should carefully consider the treatment
process, analytical variability, end-use, and other factors
when determining the frequency and number of samples
to be analyzed. Collecting samples more frequently or
analyzing more samples will help to ensure the product
meets the regulatory criteria and that pathogen and vector
attraction reduction goals have been met. More informa-
tion on this subject is available in Chapter 10.
It is recommended that additional sampling be conducted
for heterogeneous biosolids products. A single grab sample
may adequately represent the sewage sludge in a digester
that is being mixed, but might not adequately represent
several hundred yards of compost product stored in sev-
eral stockpiles. Likewise, a facility that conducts a single
annual analysis should consider more frequent monitor-
ing, particularly if the analytical results from the annual
analysis are near the regulatory limit. It is a facility's re-
sponsibility and in the facility's best interest to develop a
monitoring plan that assures product quality.
9.6 Sampling Free-Flowing Sewage
Sludges
Sewage sludges below about 7% solids behave, at worst,
like moderately viscous liquids such as an SAE 20 lubri-
cating oil. They flow freely under small pressure gradients,
and flow readily into a sample bottle. They are heteroge-
neous, and concentration gradients develop upon stand-
ing. Generally settling is slow and is overcome by good
mixing.
Liquid sewage sludges may be flowing in pipes, under-
going processing, or stored in concrete or metal tanks, in
tank cars or tank trucks, or in lagoons. This section de-
scribes procedures for sampling from these various situa-
tions, except for lagoons, which are discussed in Section
9.7.
Filling Containers
Liquid sewage sludge samples are usually transferred
into wide mouth bottles or flexible plastic containers. Sew-
age sludges can generate gases, and pressure may build
up in the container. Consequently, the bottle or container
is generally not filled. If the sewage sludge is to be used
for the oxygen uptake test, the sample bottle should not
be more than half full, to provide some oxygen for respira-
tion of the microorganisms in the sewage sludge. Con-
versely, if the sewage sludge is to be used for the addi-
tional anaerobic digestion test for vector attraction reduc-
tion, it is important that it not be exposed to oxygen more
than momentarily. Consequently, sample bottles must be
completely filled to the top. Bottles should have closures
that can pop off, or else be made of flexible plastic that
can both stretch and assume a spherical shape to relieve
any internal pressure that develops.
The containers used to collect the samples can be
widemouth bottles that can be capped, or pails. If a pail is
used and only part of its contents will be taken as a sample,
the sample should be transferred to a bottle at the sam-
pling location. Preferably, the transfer should be made by
use of a ladle rather than by pouring, since some settling
can occur in the pail, particularly with primary or mixed
sewage sludges of solids contents below about 3%.
Collecting Liquid Sewage Sludge Samples
If liquid sewage sludges are to be sampled, it is most
desirable to sample them as they are being transferred
from one vessel to another. Preferably this is done down-
stream of a pump that serves to mix the sewage sludge
thoroughly. Ideally, the sample is taken through a probe
facing upstream in the center of the discharge pipe and is
withdrawn at the velocity of the liquid at the center-line of
the pipe. This approach generally is not possible with sew-
age sludge, because fibrous deposits can build up on the
probe and plug up the pipeline.
Sampling through a side tap off the main discharge pipe
is adequate only if the flow is turbulent and the sample
point is over ten pipe diameters downstream from the pipe
inlet (e.g., for a 3-inch [7.6-cm] pipe, 30 inches [76 cm]
downstream) or the tap is downstream from a pump. For
any kind of a slurry, the fluid at the wall contains fewer
particles than the bulk of the fluid in the pipe. The sample
should be withdrawn fast enough so that it minimizes the
amount of thinned-out fluid from the outside pipe wall that
enters the sample.
If the sewage sludge discharges into the open as it is
transferred from one vessel to another, it can be sampled
by passing a sample container through the discharge. The
container should be large enough to catch the whole dis-
charge during the sampling interval, rather than, for ex-
ample, just sampling the center or the edge of the dis-
charge. The sample container could be a pail or a beaker
at the end of an extension arm. Sample volume should be
about three times what is needed for the analyses planned.
The collection of a representative sample often requires
the use of time compositing procedures. For example, if a
digester is being sampled during a withdrawal that takes
about 15 minutes, a sample can be taken during the first,
second, and third 5-minute period. The three separate
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samples should be brought back to the laboratory and
composited into a single sample. If the sample is being
analyzed for bacteria, viruses, or vector attraction reduc-
tion, the composite should be prepared within an hour of
collecting the first individual grab sample. A longer time
period might allow microbiological changes to occur in the
first sample taken. Composite sampling over 24 hours is
possible for viable helminth ova analysis, provided that the
ova in the sample are not exposed to chemical or thermal
stress such as temperatures above 40°C (KMT) or cer-
tain chemicals such as ammonia, hydroxides, and oxidants.
Sampling Sewage Sludge in Tanks
The purpose of the sampling is to determine the proper-
ties of the entire mass of the sewage sludge, rather than,
for example, to find out if there is a gradient in the property
at various points in the tank. This requires that the tank be
well-mixed, otherwise many subsamples must be taken
throughout the tank and composited. Large tanks, even if
they are well-mixed, have the potential for developing gra-
dients in composition. An enclosed tank such as an anaero-
bic digester must be sampled through pipelines entering
the digester. A minimum of three taps on a side wall of the
enclosed tank is recommended. The sample tap pipe
should project several feet into the tank. Precautions must
be taken to minimize contamination from sample collec-
tion lines. When a sample is taken, enough material must
be withdrawn to thoroughly flush the line before the sample
is collected. This helps flush any contaminants in the
sample line and assure that a representative sample is
collected from the tank. The sample line should be back-
flushed with water after the sample is withdrawn to clean
out residual sewage sludge and prevent microbial growth.
Sampling should be conducted when the tank is being
agitated. An open tank such as an aerobic digester can be
sampled by drawing a vacuum on a vacuum-filtering flask
connected to a rigid tube lowered to the desired level in
the tank. A weighted sampling bottle may also be used to
sample the liquid at the desired depth in the tank (see ASTM
E30086, Par. 21, in ASTM [1992a]).
9.7 Sampling Thick Sewage Sludges
If sewage sludges are above 7% solids, they take on
"plastic" flow properties; that is, they require a finite shear
stress to cause flow. This effect increases as the solids
content increases. Solids may thicken in lagoons to 15%
solids. At these concentrations, they will not flow easily
and require a substantial hydrostatic head before they will
flow into a sample bottle.
Sampling of sewage sludge stored in lagoons may be
very difficult, depending on the objectives of sampling and
the nature of the sewage sludge in the lagoon. The thick-
ened sewage sludge solids are generally nonuniformly dis-
tributed in all three dimensions. It is desirable first to map
the distribution of depth with length and width to deter-
mine where the sampling should be concentrated. A length-
width grid should be established that takes the
nonuniformity of the solids deposit into account. ASTM
E300-86, Figure 19 (ASTM, 1992a), shows a grid for sam-
pling a uniform deposit in a railroad car.
The layer of water over the sewage sludge complicates
the use of many types of tube samplers because the over-
lying water should not be included in the sample. A thief
sampler (ASTM, 1992a) that samples only the sewage
sludge layer may be useful. Weighted bottle samplers
(ASTM, 1992a) that can be opened at a given depth can
be used to collect samples at a desired depth. Samples at
three depths can be taken and composited. Most likely the
sewage sludge will be as much as twice as high in solids
content at the bottom of the sewage sludge layer as at the
top. Compositing of equal volumes of samples from top,
middle, and bottom produces an excellent mass-average
sample and adjusts for this difference in solids content.
Generally there is no point in determining the gradient with
depth for microbiological and VAR parameters, because
there is no practical way of separately removing layers of
sewage sludge from a lagoon. Determining whether there
are gradients with length and width makes more sense
because, if desired, sewage sludge could be removed se-
lectively from part of a lagoon, leaving behind the unac-
ceptable material.
Sewage sludges from dewatering equipment such as
belt filter presses and centrifuges can have a solids con-
tent up to 35% and even higher following some condition-
ing methods. High solids content sewage sludges are easy
to sample if they are on moving conveyors, as described
in Section 9.5. However, if the sewage sludge is stored in
piles, obtaining a representative sample requires more
planning and a greater overall effort. As a result of the dif-
ferent environment between the pile surface and interior a
gradient will develop over time in the sewage sludge stor-
age pile. The sampling methodology used needs to ad-
dress this potential gradient between the pile surface and
interior. Sampling devices such as augers (a deeply
threaded screw) are used on high solids cakes (ASTM,
1992a) to collect a cross sectional sample. The auger is
"turned into the pile and then pulled straight out. The sample
is removed from the auger with a spatula or other suitable
device." Alternatively, a shovel can be used to collect
subsamples for compositing from the pile interior. The pile
should be sampled in proportion to its mass; more samples
are taken where the pile is deeper.
9.8 Sampling Dry Sewage Sludges
For purposes of this discussion, "dry" sewage sludges
contain as much as 60% water. They include heat dried
and composted sewage sludges, and sewage sludges from
dewatering processes, such as pressure filtration, that pro-
duce a cake which is usually handled by breaking it up into
pieces. Some centrifuge cakes are dry enough that they
are comprised of small pieces that remain discrete when
piled.
Dry sewage sludges are best sampled when they are
being transferred, usually on conveyors. Preferably mate-
rial across the entire width of the conveyor is collected for
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a short period of time. Several of these across-width
samples are collected and combined into a time-compos-
ite sample. If the entire width of the conveyor cannot be
sampled, the sample is collected from various points
across the breadth of the conveyor, and a space and time-
composited sample is collected.
Collecting a representative sample from a stockpile
containing a dried sewage sludge product poses a greater
challenge than collecting the sample from a conveyor. The
settling and classification of the material and the different
environments between the pile edge and interior must be
considered. When a material comprised of discrete par-
ticles is formed into a pile, classification occurs. If the par-
ticles are homogeneous in size and composition, a repre-
sentative sample can be easily obtained (assuming the
sample is collected within 24 hours of pile construction).
However if the particles are of a different size or composi-
tion, an unequal distribution of the particles may result
during settling. For example, a composted sewage sludge
may be heterogeneous, with respect to particle composi-
tion, even when oversized bulking agents have been re-
moved. It is important that the edges and interior of such
piles are properly weighted as part of the sample collec-
tion procedure. A sampling grid that prevents bias, such
as that presented in ASTM E300-86, Item 31.4 (ASTM,
1992a), should be used.
The heterogeneous nature and presence of large par-
ticles in some composted sewage sludges cause another
problem in sampling. For example, most augers and sam-
pling thiefs will be ineffective in getting a representative
sample from the interior of a pile containing large wood
chips and fine composted sewage sludge. There may be
no substitute for digging with a shovel to get to the desired
location.
Stockpile sampling is also made more difficult by the
constant evolution of the characteristics of stored mate-
rial. Immediately after a sewage sludge stockpile is con-
structed, physical, chemical, and biological changes be-
gin to occur within and on the surface of the stockpile.
Within a period as short as 24 hours, the characteristics of
the surface and outer part of the pile can differ substan-
tially from that of the pile interior. The outer part of a pile
tends to remain at or near ambient temperature, loses
moisture through evaporation, and volatilizes some com-
pounds such as ammonia. In contrast, pile interiors retain
heat (achieving temperatures that can be 40°C greater than
the pile surface), but lose little moisture or chemical com-
pounds through evaporation and volatilization. As a result,
the level of microbial growth and activity within the pile
and on the pile surface will also differ. The potential for
growth of fecal coliform bacteria in mesophilic regions of
the pile is of particular concern. If a sewage sludge stock-
pile is more than one day old, the sample should be col-
lected from a pile cross section. This is especially impor-
tant when there is a large temperature gradient between
the pile surface and interior.
9.9 Control of Temperature, pH, and
Oxygenation After Sample Collection
Samples for Microbial Tests
Table 9-2 summarizes the maximum holding times and
temperatures for sewage sludge samples taken for micro-
bial analyses. All samples should be cooled to appropriate
temperatures immediately after they are collected to mini-
mize changes in indicator organism and pathogen popula-
tions. For example, enteric viral and bacterial densities are
noticeably reduced by even 1 hour of exposure to tem-
peratures of 35°C (95° F) or greater. The requirement for
cooling limits the practical size of the sample collection
container. A gallon sample bottle takes much longer to cool
than a quart bottle. Use of bottles no larger than a quart is
recommended for most samples, particularly if the sew-
age sludge being sampled is from a process operated at
above ambient temperature. Granular solids and thick sew-
age sludges take a long time to cool, so use of containers
smaller than one quart is advised. For rapid cooling, place
the sample container in a slurry of water and ice. Placing
the sample container in a cpoler containing bagged ice or
"blue ice" is effective in maintaining low temperatures but
several hours can elapse before this kind of cooling re-
duces sample temperature to below 10°C (50°F) (Kent and
Payne, 1988). The same is true if warm samples are placed
in a refrigerator. The presence or absence of oxygen is not
a serious concern for the microbiological tests if the
samples are promptly cooled.
Table 9-2. Analytical Methods Required Under Part 503
Analysis
Enteric Viruses
Fecal Coliform
Salmonella sp.
Bacteria
Viable Helminth
Ova
Specific Oxygen
Uptake Rate
(SOUR)
Total, Fixed, and
Volatile Solids
Percent Volatile
Solids Reduction
Methodology
American Society for
Testing and Materials
Method D 4994-89
(ASTM,1992b)i
Standard Methods
Part 9221 E or Part
9222D(APHA, 1992)2
Standard Methods
Part 9260D
(APHA.1 992)2 or
Kenner and Clark
(1974) (see
Appendix G of this
document)
Yanko (1987) (see
Appendix I of this
document)
Standard Methods
Part 27108
(APHA.1992)
Standard Methods
Part 2540G
(APHA.,1992)
Appendlix C of this
document
Maximum Holding
Time3/Temperature
-18°C(0°F); up to 2
weeks
4°C (39.2°F) (do not
freeze); 24 hours
4°C (39.2°F) (do not
freeze); 24 hours
4°C (39.2°F) (do not
freeze); 1 month
20°C (sewage sludge
must be digested in the
10-30°C range); 2 hours
NA
NA
1 Appendix H of this document presents a detailed discussion of this
method.
2 Method SM-9221 E, the MPN procedure, is required for analysis of
Class A biosolids and recommended for Class B biosolids. Method SM-
9221 D, the membrane filtration procedure is also allowable for Class B
biosolids. See Appendix F of this document for recommended sample
preparation procedures and a discussion of the reporting of results.
3Time between sampling and actual analysis, including shipping time.
70
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Standard Methods (APHA, 1992) states that if analysis
for bacterial species (fecal coliform and Salmonella sp.)
will commence within 1 hour after sample collection,
no temperature adjustment is required. If analysis will
commence between 1 and 6 hours after collection,the
sample should be immediately cooled to at least 10°C.
If analysis will commence between 6 and 24 hours after
collection the sample should be immediately cooled to 4°C.
The sample should never be frozen and analysis must
commence within 24 hours of collection.
Proper planning and coordination with the courier ser-
vice and analytical laboratory are essential if bacterial
analyses are to be conducted within 24 hours of sample
collection. The laboratory needs to be notified several days
in advance so they can be prepared to initiate the analysis
within several hours of receiving the sample. If they are
not notified, the laboratory may not be adequately prepared
and another day may lapse before the samples are ana-
lyzed. Actual sample collection should be conducted in the
afternoon, within a few hours of the sample courier's ar-
rival. If the samples are collected in the morning, a greater
than 24-hour period may pass before the laboratory actu-
ally begins the analysis.
Follow-up with the laboratory is important to determine
the actual sample holding time and temperature of the
sample when it was received. This information can be used
to improve the overall sample collection and transfer pro-
cedure. Feedback received from the lab regarding sample
condition and holding times may also provide an explana-
tion for erroneous or unexpected test results.
The requirement for prompt chilling of samples is appro-
priate for viruses as well as bacteria. There are far fewer
laboratories capable of carrying out virus tests than can
conduct bacterial analyses, so time between sample col-
lection and analysis can routinely exceed 24 hours. Fortu-
nately, viruses are not harmed by freezing. Typically, virol-
ogy laboratories store samples at -70°C (-94°F) before
analysis. Samples can be frozen in a -18°C (0°F) freezer
and stored for up to 2 weeks without harm. Samples should
be frozen, packed in dry ice, and shipped overnight to the
analytical laboratory.
Viable helminth ova are only slightly affected by tem-
peratures below 35°C (95°F), provided chemicals such as
lime, chlorine, or ammonia are not utilized in the treatment
process. Nevertheless, chilling to 4°C (39.2°F) is advised.
If the samples are held at this temperature, a period of a
month can elapse between sampling and analysis. Freez-
ing should be avoided because the effect of freezing on
helminth ova is not well understood.
Vector Attraction Reduction Tests
For the vector attraction reduction tests that measure
oxygen uptake, or additional anaerobic or aerobic diges-
tion (see Appendix D), the samples must be kept at the
temperature at which they were collected. This sometimes
can be done just by collecting a large sample in a large
container. Covering the sample with an insulating blanket
or placing it in an insulated box provides adequate protec-
tion against temperature change in most cases. Desired
temperature can be maintained in the box by adding a "hot
water bottle" or a bag of blue ice.
Depending on whether the sewage sludge is from
an aerobic process or anaerobic digestion, the presence
or lack of oxygen will determine which vector attraction
reduction test is appropriate and therefore how the sample
should be handled. For aerobic sewage sludges, a lack of
oxygen will interfere with the metabolic rate of the aerobic
microorganisms in the sample. Similarly, presence of oxy-
gen will seriously affect or even kill the anaerobic organ-
isms that convert organic matter to gases in anaerobic di-
gestion. With samples taken for SOUR analysis, it has been
the experience of some investigators that if the test is not
run almost immediately after collection (within about 15
minutes), that erroneous results are obtained. The addi-
tional aerobic digestion test is more "forgiving" (because it
is a long-term test and shocked bacteria can revive); up to
4 hours of shortage of oxygen can be tolerated. For the
additional anaerobic digestion test, the sample containers
should be filled to exclude air. In any subsequent opera-
tions where there is a freeboard in the sample or testing
vessel, that space should be filled with an inert gas such
as nitrogen.
No pH adjustment is to be made for any of the vector
attraction reduction tests. For those vector attraction pro-
cesses that utilize lime, the only requirement is to mea-
sure pH after the time periods indicated in the vector at-
traction reduction option (see Section 8.7).
9.10 Sample Compositing and Size
Reduction
The amount of sample collected in the field generally far
exceeds the amount needed for analysis. The field sample
must therefore be reduced to a manageable size for the
analyst to handle. As for all sample handling, sample size
reduction is more difficult for microbial samples than for
samples taken for vector attraction reduction tests because
of the potential for microbial contamination. The labora-
tory may be better equipped to perform subsampling than
samplers in the field.
Microbial Tests
Freely flowing liquid samples can be adequately mixed
in the sample bottles by shaking the bottles. There must
be room in the bottle for adequate mixing. Compositing of
smaller samples is accomplished by pouring them into a
larger bottle with adequate freeboard and mixing it by shak-
ing or stirring it thoroughly with a sterile paddle. Pouring
off a portion of the contents of a large container into a
smaller bottle is not an acceptable procedure because the
top layer of any slurry always contains fewer solids than
do lower layers. Sampling with a pipette with a wide bore
is an acceptable alternative, provided the bore of the pi-
pette does not restrict the entry of solid particles. The
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sample should be drawn into the pipette slowly and the tip
moved through the sample to minimize selective collec-
tion of liquid over solid particles.
Sample size reduction for thick sewage sludges is diffi-
cult, because they cannot be mixed by shaking. Stirring
with a mechanical mixer or a paddle is often inadequate
(recall how long it takes to mix a can of paint). A satisfac-
tory approach is to hand mix a composite of subsamples,
and then take a large number of small grabs from the
composited sample to form the smaller sample for the ana-
lyst.
Dry solids samples can generally be mixed adequately
by shaking if there is sufficient head space in the sample
container, but the individual particles are frequently large
and must be reduced in size to get a representative sample.
If the particles are large and a number of subsamples must
be combined into a large composite, it may be necessary
to reduce the particle size before they are composited.
This can be done in a sterile covered chopper, blender, or
grinder. The individual subsamples are then combined and
mixed by shaking, rotating, and tumbling. A smaller com-
posite is then prepared by combining a number of grabs
from all parts of the combined sample. Many facilities do
not have adequate equipment needed to perform this size
reduction procedure. However, most analytical laborato-
ries have this capability and will typically perform this pro-
cedure at a nominal cost. Coordination with the analytical
laboratory regarding subsampling is an important part of
the sampling and analysis procedure that should not be
ignored. Some other sample size reduction methods, such
as "coning and quartering" (ASTM, 1992a) may be use
only if aseptic handling practices are observed. It should
be noted that particle size reduction is not appropriate if
the large pieces in the sample are not sewage sludge but
are other materials which have been added to the sewage
sludge for processing purposes. For the purpose of micro-
bial or volatile solids reduction testing, additives such as
wood chips should be removed from the sample before
size reduction or sample preparation (see Section 10.5). It
is recommended in these cases that a one-quarter inch
mesh sieve be used for this purpose.
Vector Attraction Reduction Tests
The lack of a need to prevent microbial contamination
makes compositing and size reduction easier for vector
attraction reduction tests than for the microbial tests. How-
ever, there is a need to keep the aerobic samples aerobic
and to prevent the anaerobic samples from coming into
contact with air. Subsamples for the anaerobic tests can
be collected into individual bottles at the sampling loca-
tion. As noted above, these sample bottles should be filled
completely and capped. A brief exposure to air will not
cause a problem, but any prolonged exposure, such as
might occur when several subsamples are being blended
together and reduced in size for a representative compos-
ite sample, must be avoided. One acceptable sample size
reduction procedure is to flush a large sterile bottle with
nitrogen, then pour in the subsamples and blend them to-
gether with nitrogen still bleeding into the vessel. Alterna-
tively, the nitrogen-filled vessel could be flushed with more
nitrogen after the admission of the subsamples, capped,
and then shaken thoroughly to accomplish the blending.
Analytical laboratories generally can perform this size re-
duction procedure.
9.11 Packaging and Shipment
Proper packaging and shipment are important to ensure
that the samples arrive in good condition (proper tempera-
ture, no spillage) within the specified time frame.
Sealing and Labeling Sample Containers
Sample containers should be securely taped to avoid
contamination, and sealed (e.g., with gummed paper) so it
is impossible to open the container without breaking the
seal. Sealing ensures that sample integrity is preserved
until the sample is opened in the laboratory. A permanent
label should be affixed to each sample container. At a mini-
mum the following information should be provided on each
sample container:
Type of analysis to be performed (e.g., Salmonella sp.,
fecal coliform bacteria, enteric virus, or viable helm-
inth ova)
Sample identification code (if used) or a brief descrip-
tion of the sample (that distinguishes it from other
samples) if no sample code system is used
Sample number (if more than one sample was col-
lected at the same point on the same day)
Other information may include:
Facility name, address and telephone number
Date and time the sample was taken
Facility contact person
This information should also be included on an enclosed
chain of custody form.
Shipment Container
A soundly constructed and insulated shipment box is
essential to provide the proper environment for the pre-
serving sample at the required temperature and to ensure
the sample arrives intact. Small plastic cased coolers are
ideal for sample shipping. It is recommended that the out-
side of the shipment container be labeled with the follow-
ing information:
The complete address of the receiving laboratory (in-
cluding the name of the person responsible for receiv-
ing the samples and the telephone number)
Appropriate shipping label that conforms to the
courier's standards
Number of samples included (i.e. "This cooler contains
10 samples")
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The words "Fragile" and "This End Up"
To maintain a low temperature in the shipment box, a
blue-ice type of coolant in a sealed bag should be included
in the box. If the blue ice has been stored in a 0°F (-18°C)
freezer (e.g., a typical household freezer), the coolant
should be "tempered" to warm it up to the melting point of
ice (0°C [32°F]) before it is placed around the sample. Ad-
ditional packing material (bubble wrap, Styrofoam peanuts,
balled-up newspaper) should be placed in the shipping
container to fill in empty space to prevent sample contain-
ers from moving and potentially breaking or spilling during
shipping. It is also recommended that the courier be con-
tacted in order to determine if there are any special re-
quirements for the shipping of this type of sample.
Adherence to Holding and Shipment Times
Adherence to sample preservation and holding time lim-
its described in Section 9.6 is critical. Samples that are not
processed within the specified time and under the proper
conditions can yield erroneous results, especially with the
less stable microorganisms (i.e., bacteria). Make sure the
analytical laboratory reports the date and time when the
samples arrived, and total holding time (period from when
the sample was collected to the initiation of analysis). This
information will be valuable for improving future sample
events and maintaining quality control.
9.12 Documentation
Sampling Plan
It is recommended that all procedures used in sample
collection, preparation, and shipment be described in a
sampling plan. At a minimum, a sampling plan should pro-
vide the following information:
Sample collection locations
Volume of sample to be collected
Sample compositing procedures
Days and times of collection
Required equipment
Instructions for labeling samples and ensuring chain
of custody
A list of contact persons and telephone numbers in
case unexpected difficulties arise during sampling
If a formal sampling plan is not available, a field log that
includes instructions and a sample collection form may be
used (EPA, 1980).
Sampling Log
All information pertinent to a sampling event should be
recorded in a bound log book, preferably with consecu-
tively numbered pages. At a minimum, the following infor-
mation should be recorded in the log book.
Purpose of sampling event
Date and time of sample collection
Location where samples were collected
Grab or composite sample (for composite samples,
the location, number, and volume of subsamples
should be included)
Name of the person collecting the sample(s)
Type of sewage sludge
Number and volume of the sample taken
Description of sampling point
Date and time samples were shipped
Chain of Custody
To establish the documentation necessary to trace
sample possession from the time of collection, it is recom-
mended that a chain-of-custody record be filled out and
accompany every sample. This record is particularly im-
portant if the sample is to be introduced as evidence in
litigation. Suggested information for the chain-of-custody
record includes, at a minimum:
Collector's name
Signature of collector
Date and time of collection
Place and address of collection
Requested preprocessing (subsampling, compositing,
particle size reduction)
Requested analyses
Sample code number for each sample (if used)
Signatures of the persons involved in the chain of pos-
session
A good rule of thumb is to record sufficient information
so that the sampling situation can be reconstructed with-
out reliance on the collector's memory. Chain-of-custody
forms can be obtained from the laboratory and should be
used even if the laboratory is on-site and part of the treat-
ment facility.
9.13 Analytical Methods
Part 503.8(b) of the Part 503 regulation specifies meth-
ods that must be used when analyzing for enteric viruses;
fecal coliform; Salmonella sp.; viable helminth ova; spe-
cific oxygen uptake rate; and total, fixed, and volatile sol-
ids. Table 9-2 lists the required methods. Complete refer-
ences for these methods can be found in Chapter 12, and
recommended sample preparation and analytical methods
can be found in the appendix as listed below.
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Calculating volatile solids reduction Appendix C
Conducting additional digestion and Appendix D
specific oxygen uptake rate (SOUR)
tests
Determination of residence time in Appendix E
digesters
Sample preparation - fecal Appendix F
coliform and Salmonella sp. analysis
Analytical method Salmonella sp. Appendix G
Analytical method enteroviruses Appendix H
in sewage sludge
Analytical method - viable Appendix I
helminth ova
As of the time of publication of this document, the allow-
able analytical methodologies are as listed above. How-
ever, in the case of fecal coliform analysis for Class B-
Alternative 1, it is recommended that the MPN method be
used instead of the membrane filter test (the MPN method
is required for Class A fecal coliform analysis), and that
the Kenner and Clark methodology be used for Salmo-
nella sp. analysis.
9.14 Quality Assurance
Quality assurance involves establishing a sampling plan
and implementing quality control measures and procedures
for ensuring that the results of analytical and test mea-
surements are correct. A complete presentation of this
subject is beyond the scope of this manual. A concise treat-
ment of quality assurance is found in Standard Methods
(APHA, 1992) and is strongly recommended. Parts 1000
to 1090 of Standard Methods are relevant to the entire
sampling and analysis effort. Part 1020 discusses quality
assurance, quality control, and quality assessment. Stan-
dard Methods (Part 1020B) states that "a good quality con-
trol program consists of at least seven elements: certifica-
tion of operator competence, recovery of known additions,
analysis of externally supplied standards, analysis of re-
agent blanks, calibration with standards, analysis of dupli-
cates, and maintenance of control charts." For most of the
tests to be carried out to meet the pathogen and vector
attraction reduction requirements of the Part 503 regula-
tion, these elements cannot be met completely, but they
should be kept in mind as a goal.
Microbial Tests
For the microbiological tests, quality assurance is needed
to verify precision and accuracy. Quality assurance for
microbiological methods is discussed in Part 9020 of Stan-
dard Methods. The quality control approach suggested is
recommended for the microbiological tests required by the
Part 503 regulation. In Part 9020B-4, Analytical Quality
Control Procedures, it is suggested that precision be ini-
tially established by running a number of duplicates, and
that thereafter duplicates (5% of total samples) be run to
determine whether precision is being maintained.
Spiking and recovery tests are an important part of quality
assurance. Yanko (1987) has found that spiking is useful
for the viable helminth ova test, but that testing recovery
effectiveness on unspiked sewage sludge is more useful
for quality assurance for bacterial or viral tests. With either
method, the density of the measured pathogens should
be at levels that are relevant to the Part 503 regulation.
For example, for viable helminth ova, samples should be
spiked to density levels of approximately 100 per gram.
Recovery of bacteria and viruses should be conducted on
primary sewage sludges that typically contain viruses at
low but consistent levels (such as primary sewage slud-
ges from large cities).
For both commercial and in-house laboratories, quality
assurance procedures should be incorporated into the
analytical method and assessed routinely. Communication
with the analytical personnel is an important part of devel-
oping a good sampling and analysis protocol. The sewage
sludge preparer should review quality assurance data along
with analysis results to ensure that laboratory performance
is acceptable.
Vector Attraction Reduction Tests
It is not possible to test for accuracy for any of the vector
attraction reduction tests, because standard sewage slud-
ges with consistent qualities do not exist. Standard Meth-
ods gives guidance on precision and bias. However, for
some of the vector attraction reduction options, this infor-
mation was not available or was approximate. Section 10.7
provides guidance on the number of samples to take. The
procedures for three of the vector attraction options devel-
oped for the Part 503 regulation (additional anaerobic and
aerobic digestion and the specific oxygen uptake rate test),
which are presented in Appendix D, have internal quality
control procedures that include replication. Since the tests
are newly proposed, the data are insufficient to judge
whether agreement between replicates is adequate. This
kind of information will be communicated as experience
with these options accumulates.
References and Additional Resources
APHA. 1992. Standard methods for the examination of
water and wastewater. 18th ed. Washington, DC: Ameri-
can Public Health Association.
ASTM. 1992a. Annual book of ASTM standards. Philadel-
phia, PA: American Society for Testing and Materials.
ASTM. 1992b. Standard practice for sampling industrial
chemicals. Philadelphia, PA: American Society for Test-
ing and Materials.
Kent, R.T. and K.E. Payne. 1988. Sampling groundwater
monitoring wells: Special quality assurance and qual-
ity control considerations, p 231-246 in Keith, L.H. Prin-
ciples of Environmental Sampling. American Chemi-
cal Society.
Kieth, L.H., ed. 1988. Principles of environmental sampling.
American Chemical Society.
U.S. EPA. 1980. Samplers and sampling procedures for
hazardous waste streams. Report No.: EPA/600/2-80/018.
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Cincinnati, OH: Municipal Environmental Re- U.S. EPA. 1999. Biosolids Management Handbook. U.S.
search Laboratory. EPA Region VIII, P-W-P, 999 18* street, Denver, CO
80202-2466.
U.S. EPA. 1993. POTW sludge sampling and analysis
guidance document. EPA/833/B-89/100. Office of Yanko, W.A. 1987. Occurrence of pathogens in distribu-
Water. tion and marketing municipal sludges. Report No.: EPA/
600/1-87/014. (NTIS PB88-154273/AS.) Springfield,
U.S. EPA. 1993. Sewage sludge sampling techniques VA: National Technical Information Service.
(video).
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Chapter 10
Meeting the Quantitative Requirements of the Regulation
10.1 Introduction
The Part 503 regulation contains operational standards
for pathogen and vector attraction reduction. It provides
only minimal guidance on the amount of information that
must be obtained during a monitoring event to prove that
a standard has been met or to demonstrate that process
conditions have been maintained. This document provides
more detailed information for regulators and facilities on
how to adequately satisfy the regulatory requirements.
Some frequently asked questions and answers are also
included at the end of this chapter.
In general, it has been found that the daily, weekly, and
seasonal fluctuations that occur in wastewater treatment
works and sludge quality make it difficult to adequately
represent sludge quality with minimum sampling. It is there-
fore recommended that multiple samples be taken for any
sampling event and that samples be taken over a mini-
mum 2-week period in order to best represent the perfor-
mance of a sludge treatment process. Although extensive-
sampling is time consuming and facility operators are of-
ten under pressure to reduce costs, it is strongly recom-
mended that multiple samples be included in a sampling
plan so that the variable quality of sludge can fully be un-
derstood.
There are many types of wastewater treatment plants
and sludge management practices. This document ad-
dresses some of the many operational variables and pro-
vides some examples of how to demonstrate compliance
with the regulations. The final decision about what to moni-
tor and how frequently to monitor it lies with the permitting
authority who may impose permit conditions based on spe-
cific parameters including the type of sludge produced, its
intended usage, and/or the history of the facility.
10.2 Process Conditions
Sufficient information must be collected about sludge
processing conditions and made available to the permit-
ting authority and any other interested parties to enable a
qualified reviewer to determine if the Part 503 requirements
have been met. How this information is collected and how
much information is needed depend on the process. The
following example illustrates the type of information and
the level of detail that may be included in a permit applica-
tion. Consider the case of a treatment works that meets
the pathogen reduction requirement for a Class B sludge
by using anaerobic digestion conducted at the PSRP con-
ditions of 35°C (95°F) with a 15-day residence time. To
meet the pathogen reduction requirement, the monitoring
results must demonstrate that the 35°C (95°F) tempera-
ture and 15-day residence time are maintained whenever
the process is being used. The example below illustrates
some of the factors to be considered in assuring compli-
ance with the regulation. In addition, a contingency plan in
case the conditions are not met, and product usage should
be specified.
Example
Facility Clarksdale Wastewater Treatment
Facility Anaerobic Digestion
Size: 300 dry metric tons per year
Class: B
Sewage sludge is treated in two digesters, operated in
parallel, fed by constant displacement progressive cavity
pumps. The facility complies with PSRP requirements by
maintaining sludge at a temperature at or above 35°C for
a minimum of 15 consecutive days.
Temperature During the first six months of opera-
tion under this permit, the permittee shall perform tem-
perature scans throughout the volume of the digester
to establish the location of the zone at which tempera-
ture is at a minimum. Scans will be conducted under
the expected range of operating conditions. Once the
location of the zone is established, the permittee will
continuously measure digester temperature in the zone
of minimum temperature. Temperatures will be re-
corded continuously or at intervals of eight hours. The
temperature measuring device will be calibrated on a
monthly basis.
Retention Time The permittee shall calculate the
working volume of the digester to determine residence
time. The permittee shall provide evidence that the
digester has been cleaned within the last two years,
or alternatively, determine the levels of grit and scum
accumulation. Residence time must be at least 15
days. Flow rate and residence time will be measured
and calculated each year.
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Vector Attraction Reduction - The facility will comply
with vector attraction reduction via management prac-
tices. After digestion, the sludge will be dewatered and
transported to farm land where it will be land applied
and disked immediately (within six hours) into the soil
(see below). Sludge will not be stored at application
sites.
Reporting- The data collected throughout the year
will be summarized and submitted to the permitting
authority annually. Reports will include temperature and
residence time records as well as records of all appli-
cation sites and sludge application rates.
Contingency Plan -If the facility fails to meet the 35°
C/15-day requirement, it has several options. The fa-
cility can try to meet the Class B time/temperature re-
quirement with lower temperatures and longer resi-
dence times as determined by a linear interpolation
between 35°C (95°F) and 15 days and 20°C (68°F)
and 60 days. If the facility does not have the flexibility
to maintain sludge in the digester for longer than 15
days, it can meet Class B requirements by sampling
the sludge for fecal coliform and demonstrating that
the sludge contains less than 2 million CPU or MPN
per gram of sludge on a dry weight basis. Alternatively,
the facility can dispose of the sludge by means other
than land application. In the case that the facility can-
not meet the time/temperature requirements, the per-
mitting authority must be contacted so that a sampling
plan which adequately represents sludge quality and
demonstrates Class B pathogen reduction can be de-
signed. If the facility decides to divert the sludge from
land application, it must notify the regulatory agency
of its plans.
Product Use - The sludge will be land applied in ac-
cordance with all Part 503 restrictions. The facility will
distribute the Class B sludge to local fruit farmers. The
facility will notify applicators of sludge quality and rel-
evant site restrictions. Crop harvesting will be restricted
in accordance with Part 503 site restrictions. In the
case of application to fruit trees, the farmer will wait a
minimum of 30 days after application to harvest the
fruit. If fruit that has fallen off the trees or otherwise
touched the ground will also be harvested, the farmer
will wait 14 months after sludge application to harvest
the fruit. If there is any question about the waiting
period or if the facility wishes to distribute sludge to
farmers of crops which touch the ground, the facility
should notify the regulator. Site restrictions for crops
which touch the soil or which grow below the soil sur-
face are subject to longer waiting periods.
The number and the level of detail of a permit's condi-
tions vary depending on the type of process. Facilities that
handle sludge or septage from more than one source
should be subject to more frequent testing until they can
demonstrate that the product consistently meets quality
standards. The permitting authority must determine at what
point the facility has adequately demonstrated consistency
and can reduce the level of sampling.
For example, consider a treatment facility that collects
liquid sewage sludge and septage from several different
sources. Although all of the sludge collected undergoes
standard treatment for Class B pathogen reduction, the
quality of the sludge generated may vary depending on
the particular feedstock received. Initially, the permitting
authority may require this facility to monitor every batch of
sludge in order to demonstrate that it consistently produces
sludge in compliance with regulatory and permit require-
ments. Eventually, if enough data is available showing that
the treated sewage sludge is rarely off specification, the
sampling frequency could be reduced.
For other processes, such as static pile composting, a
sampling plan might specify that one of several piles con-
structed in a day could be monitored, probably with sev-
eral thermocouples at different elevations and locations in
the pile, to demonstrate conformance for the whole day's
production.
At times, processes do not conform to process condi-
tions. In such cases, the operator should keep records
showing that the treated sludge produced was either re-
cycled to be processed again or diverted in some manner
for use or disposal consistent with its quality (e.g., disposal
in a landfill with daily cover or, if the sludge meets the Class
B requirements, application as a Class B [rather than as a
Class A] biosolids).
10.3 Schedule and Duration of Monitoring
Events
For purposes of this discussion:
A sampling event is defined as the period during which
samples are collected. Samples may include several
independently analyzed subsamples taken during the
sampling event.
A monitoring event includes the sampling period and
the period to analyze the samples and provide the re-
sults needed to determine compliance.
Monitoring events are intended to reflect the typical usual
performance of the treatment works. Conditions should be
as stable as possible before the monitoring event. Day-to-
day variations in feed rate and quality are inevitable in sew-
age sludge treatment, and the processes are designed to
perform satisfactorily despite these variations. However,
major process changes should be avoided before moni-
toring events, because long periods of time -as much as 3
months if anaerobic digestion is part of the process train-
are required before steady state operation is reestablished.
Monitoring for Microbiological Quality
To meet the Part 503 pathogen reduction requirements,
sewage sludges may have to be monitored to determine
densities of fecal coliforms, Salmonella sp., enteric viruses,
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and/or viable helminth ova. Monitoring for these microor-
ganisms presents special problems, primarily caused by
the length of time it takes to obtain microbiological test
results. This is a function of the time it takes to deliver the
samples to a laboratory, have the tests conducted, and
obtain the results. Microbiological analyses require a sub-
stantially longer period than conventional physical and
chemical analyses. The approximate time to complete spe-
cific microbiological analyses is summarized as follows.
Fecal coliform (MPN), 4 days
Salmonella sp. (MPN) 5 to 7 days
Enteric viruses, 14 days
Viable helminth ova, 28 days
Variations in the microbiological quality of the treated
sludge and intrinsic variation in the analytical methods are
generally large enough that a single measurement of a
microbiological parameter is inadequate to determine
whether a process meets or fails to meet a requirement.
The Pathogen Equivalency Committee recommends that
the monitoring event include at least seven samples taken
over a period of approximately 2 weeks (see Section 10.7).
Based on the reliability of the treatment process and his-
toric test results, there may be times when a reduction in
this monitoring recommendation is justified.
Thus, the time required for a monitoring event could
range from 3 to 7 weeks. During this time, the quality of
the treated sewage sludge generated is unknown. As dis-
cussed in Section 4.10, classification of sludge as Class A
or B is based on the most recent test results available.
Therefore, material can continue to be distributed under
its classification as Class A or B until more recent analyti-
cal results are available. However, it is recommended that
material generated during the monitoring event be retained
on site until results from the monitoring event are avail-
able. This will prevent misclassified sludge from being er-
roneously distributed.
For example, consider a facility producing a Class A
sludge that is sampled for Salmonella sp. analysis every
quarter. All historic data has shown the facility to be in com-
pliance with Class A standards including the most recent
set of lab analyses from the January monitoring event.
Under these results, materials are distributed as Class A
products even throughout April when a subsequent moni-
toring event takes place. This is acceptable because ma-
terial is still classified under the most recent available lab
result. However, suppose the April results show non-com-
pliance with Class A standards. Despite the fact that the
preparer complied with regulations, it is possible that some
Class B material was inadvertently distributed for Class A
use.
In order to avoid this situation, it is recommended that
the sludge processed during the monitoring event either
be stored until it is demonstrated that the processed sludge
meets the quality requirements for use as a Class A or B
sludge, or - if the sludge is being monitored for Class A
requirements - used or disposed as a Class B sludge (pro-
vided it meets the Class B requirements). This may take
up to 3 weeks in the case of fecal coliform or Salmonella
sp. analysis and much longer if sludge is being analyzed
for helminth ova or viruses. Contingencies for this type of
situation should be discussed with the regulatory authority
and included in permit conditions and operational plans. (For
more discussion on the timing of sampling and distribu-
tion, see Section 4.10.)
Monitoring for Vector Attraction Reduction
Not all the vector attraction reduction options listed in
the regulation (see Chapter 8) require lab testing. Four of
the methods (treatment of sewage sludge in an aerobic
process for 14 days or longer, injection below the surface
of the land, incorporation of sludge into the land, and place-
ment of sludge on a surface disposal site and covering it
at the end of each day) are technology descriptions. These
technologies have to be maintained throughout the year in
the manner described in the regulation. Examples of the
kind of information needed to demonstrate adequate per-
formance are provided in Section 10.2.
The remaining vector attraction reduction options are
based on laboratory testing for volatile solids reduction,
moisture content, or oxygen uptake reduction. Some of
the options can only be used with certain sludge processes.
For example, the oxygen uptake rate test is only appropri-
ate for a sludge from any aerobic digestion or wastewater
treatment process. Other options, such as the 38 percent
reduction in volatile solids, can be applied to a variety of
biological sludge treatment processes. In any case, the
technology aspect of the option, or the process by which
vector attraction reduction is being attained, must be docu-
mented in the manner described in Section 10.2. Monitor-
ing for vector attraction reduction should be performed at
a minimum according to the required monitoring sched-
ule.
Some tests for vector attraction reduction can be con-
ducted within a few hours while others can take more than
a month. For the tests that can be conducted within a few
hours, the sampling event must be more than a few hours
to account for the variability in the material tested and the
performance of the vector attraction reduction process as
affected by the changes in feedstock.
It is suggested in Section 8.14 that facilities maintain a
sampling program that involves sampling at evenly spaced
time intervals throughout an established monitoring period.
The on-going samples can be used to calculate running
averages of volatile solids reduction which are more rep-
resentative than single samples or an attempt to correlate
feed sludge and sludge product. As is the case for the mi-
crobiological tests, these vector attraction reduction tests
should be conducted over approximately 2 weeks to mini-
mize the expected effect of these variations. The 2-week
period can be the same 2-week period during which the
microbiological parameters are being determined.
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The longer VAR tests present a similar problem as moni-
toring for microbiological quality. Some of the tests - such
as the additional digestion tests - take more than a month
to complete. Unless the treatment works has several sets
of duplicate testing equipment, it will be impossible to run
these tests on enough samples during a 2-week sampling
period to assess the variability in the performance of the
treatment process. Storing samples taken during this pe-
riod until the equipment becomes available is not an op-
tion, because samples cannot be stored for more than a
limited time period (see Section 9.6.) In such circum-
stances, the preparer may wish to run the vector attraction
reduction tests more frequently than required in order to
demonstrate on-going compliance with the requirements.
More frequent testing will indicate if the facility is perform-
ing consistently and will reduce the need for multiple
samples during the sampling period.
The preparer may wish to conduct composite sampling
which combines samples taken within a 24-hour period to
better represent sludge quality. (See Section 10.6). Since
some of the bench scale tests may be affected by long-
term storage of samples, compositing should be limited to
a 24-hour period. If composting is done, the composite
should be held at 5°C during compositing, and the assay
must begin immediately upon completion of the compos-
ite.
Preparers should discuss specific facility parameters with
the permitting authority to design a sampling program that
is appropriate.
10.4 Comparison of Feed Sludge and
Sludge Product Samples
The enteric virus and viable helminth ova analytical re-
quirements to demonstrate that an existing or new sludge
treatment process is equivalent to a PFRP one and some
of the vector attraction reduction methods (e.g., percent
volatile solids reduction) involve taking input and output
samples that correspond (i.e., they are "before process-
ing" and "after processing" samples of the same batch of
sludge). The comparison of input and output samples al-
lows for the determination of whether enteric viruses and
helminth ova levels are being reduced to adequate levels
and/or percent volatile solids reduction.
Obtaining samples that correspond can be difficult for
sewage sludge treatment processes, such as anaerobic
digestion, that characteristically treat sludge in fully mixed
reactors with long residence times. For example, as men-
tioned in Section 10.3, it can take up to 3 months for an
anaerobic digester to achieve steady state operation after
some substantive change in feed sludge or process con-
dition is made. Samples taken only after the process has
reached steady state operation are considered as corre-
sponding.
Many of the treatment processes that might be consid-
ered for demonstrating equivalency to PFRP are either
batch or plug flow processes. In theory it is relatively simple
to obtain corresponding samples - it is only necessary to
calculate the time for the input material to pass through
the system and sample the downstream sludge at that time.
Achieving accurate correspondence in practice, however,
is seldom easy. Consider, for example, the difficulty of ob-
taining good correspondence of feed and treated sludge
for a composting operation in which the feed sewage sludge
is to be compared to composted sludge that has been
stored for 3 months.
Taking multiple samples and appropriately compositing
the samples of feed and treated sludge averages out the
composition of these sewage sludges and reduces the
correspondence problem. It is the regulatory authority's
task to determine how many samples should be taken and
how much data is necessary to demonstrate reduction of
microorganisms in corresponding samples. As indicated
in Section 10.6, limitations on the periods of time over which
microbiological samples can be collected limit the utility of
compositing.
10.5 The Effect of Sludge Processing
Additives on Monitoring
Many sewage sludge dewatering and stabilization pro-
cesses introduce other substances into the sludge. With
the exception of large bulky additives such as wood chips,
there is no need to modify sampling and analytical proce-
dures. As discussed below, additives such as wood chips
can complicate sample preparation and analysis and are
best removed prior to analysis.
Polymers, lime, ferric chloride, paper pulp, and recycled
sludge ash are frequently used to aid in dewatering. Disin-
fection by alkaline treatment requires the addition of lime
or other alkaline materials to increase the temperature of
the sewage sludge cake to disinfecting temperature. These
materials also reduce the microbial densities by dilution
and increased solids content. However, the change in mi-
crobial density caused by dilution may not be substantial.
For example, an increase in mass of 20% would result in a
reduction in the log density of a microbiological parameter
of only 0.079.
The exposure risk to human health is directly related to
the mass of treated sludge. So the achievement of patho-
gen reduction requirements and safe end-use is dictated
by the population of pathogenic organisms in the final prod-
uct. This is the approach taken by the Part 503 regulation,
which requires that the treated sludge, regardless of the
mass of other materials added, meet the standards for
Class A or Class B sludge.
For some sludges, particularly those treated by
composting (these usually will be Class A biosolids), the
amount of additive can be considerable. Nevertheless, the
regulation requires that the biosolids meet the standard,
which means that no correction need be made for dilution.
The issues of sampling and analytical procedures for
employment are different when considering wood chips or
other materials which are often added to sludge as a bulk-
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ing agent for composting. Compost product may be given
away or sold as a screened or unscreened product, and
although regulations require that the treated sludge, as it
is applied, meets 503 standards, in the case of wood chips
and other large particle size bulking materials, it is appro-
priate to remove large pieces before analysis takes place.
Large additives are removed in order to improve the
accuracy of the microbial measurements. The wood chips
are so big (typically 4 cm x 4 cm x 1 cm) that a very large
sample would have to be taken and blended to get a rep-
resentative subsample. Sample reliability is reduced when
the sample consists of a mix of sludge solids and fibrous
wood-chip residue from blending. Another reason for re-
moving the wood chips prior to microbial analysis is that
the exposure of users to the compost is related to the fine
particle content and not to large, physically distinct wood
chips. For example, a user who handles the compost gets
his or her hands covered with compost particles. Similarly,
the user might breathe in a dust of compost particles. In
both cases, it is the "fines" of the compost, not the wood
chips that the user is exposed to.
In order to ensure that wood chips are not included in
the lab's subsample, the facility should remove wood chips
after sampling, being careful not to contaminate, with a
sterilized sieve. The size of the sieve needed depends on
the dimensions of the wood chips, but the same sieve size
should be used for each sampling event. Alternatively, the
laboratory should be asked to remove wood chips from
samples before subsampling or analyses are conducted.
Again, the sieve size should be established so that a stan-
dard size is used.
10.6 Collecting Representative Samples
Sludge quality varies depending on the inputs to the
wastewater system. In addition, the process is subject to
ambient conditions which vary daily as well as seasonally.
The goal of a sampling program is to adequately repre-
sent the quality of sludge. Therefore, both the frequency
of sampling and the number of samples taken in any one
sampling event must be considered carefully. This section
discusses the issue of variability and how sampling fre-
quency and composite sampling can improve the quality
of data collected. A sampling plan is recommended for all
sampling events to assure representative samples.
Random Variability
Virtually all sewage sludge treatment processes will ex-
perience a certain amount of short-term random or cyclic
variation in the feed sludge and in process performance.
Evaluation of average performance over a 2-week time
period is suggested as a reasonable approach to account
for these variations. Cyclic variation can be minimized by
sampling on randomly selected days and time-of-day in a
given week. In the case of Class B fecal coliform analysis
ONLY variability is minimized by taking the geometric mean
of analytical results. In the case of Class A, all samples
must meet the fecal coliform or Salmonella sp. numerical
limit.
Seasonal Variability
For some sewage sludge treatment processes, perfor-
mance is poorer during certain parts of the year due to
seasonal variations in such factors as temperature, sun-
shine, and precipitation. For example, aerobic digestion
and some composting operations can be adversely affected
by low ambient temperature. In such cases, it is critical
that process performance be evaluated during the time of
year when poorest performance is expected. If a treatment
works is evaluated four or more times a year at intervals of
2 or 3 months, there is no problem, because all seasons of
the year will be covered. For small treatment works that
are evaluated only once or twice a year, it is important to
monitor in the time of year where performance is expected
to be poorest, to avoid approving a process that is not per-
forming adequately for much of the year. It may also be
beneficial to initially conduct sampling more frequently than
the required minimum, perhaps on a quarterly basis, in
order to determine the range of sludge quality. Process
criteria of PSRPs and PFRPs should be discussed by the
facility with the regulatory authority, and specific require-
ments should be included in permit conditions.
Composite Sampling
Composite sampling, or the combination of several grab
samples to better represent a large quantity of sludge, is
frequently practiced in wastewater treatment. Composites
may consist of grab samples taken over time (typically for
continuous flow processes) or from random locations in a
vessel or pile (typically for batch processes). Since the
purpose of composite sampling is to provide representa-
tion of a large quantity of sludge, the number and distribu-
tion of grab samples, the locations from where they are
taken, and the process of combining grab samples to cre-
ate a composite sample are important to consider.
The following is an example of a sampling procedure for
compositing a continuous flow process. A small stream of
wastewater or sludge is drawn off at rate proportional to
the flow of the main stream being sampled and collected
as a single sample. Typically, times of collection are for
one shift (8 hours) or one day (24 hours). In this case, the
accumulated sample represents a volume-average sample
over the period of time the sample is drawn. The sample is
chilled during the period it is being collected to prevent
chemical/microbiological change until it can be brought
back to the laboratory for analysis.
Composite sampling from stockpiled solid material in-
volves taking multiple grab samples from a range of loca-
tions in the stockpile. Samples should be taken from dif-
ferent interior sections of the pile which may represent
material produced in different time periods. Grab samples
should all be of the same size so that the composite is an
equal representation of all of the grab samples. The grab
samples should be mixed thoroughly and a subsample
pulled from the mixture.
Composite sampling is useful for any type of sampling,
but the protocol must be modified when microbial analy-
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ses are intended. Samples must be taken over a shorter
period of time so that microbial populations do not undergo
significant changes during the sampling event. For ex-
ample, a composite time-average sample can be obtained
by combining a series of small samples taken once every
5 minutes for a period of an hour. A composite sample for
bacterial and viral testing could be taken over an hour or
less under most circumstances without compromising the
results. Composite sampling over 24 hours, or even longer
if special precautions are taken, is possible for viable hel-
minth ova provided the ova in the sample are not exposed
to thermal or chemical stress (e.g., temperatures above
40°C [104°F] or the addition of certain chemicals such as
ammonia, hydroxides, and oxidants). In addition to limit-
ing the sampling period, sterile equipment must be used
when taking grab samples or compositing the samples for
microbiological analysis in order to prevent introducing
pathogenic bacteria.
Composite sampling may be possible for samples to be
used in some of the procedures to determine whether vec-
tor attraction reduction is adequate. It may not be appro-
priate for those procedures that depend on bacterial respi-
ration (i.e., aerobic or anaerobic digestion). This subject is
discussed in Appendix D which presents procedures for
three methods to demonstrate reduced vector attraction.
10.7 Regulatory Objectives and Number of
Samples that Should be Tested
Overall, it is recommended that numerous samples be
taken over a period of 2 weeks in order to represent the
average characteristics of a sludge stream. Unfortunately,
sampling for microbial and vector attraction reduction pa-
rameters is more complicated than sampling for heavy
metals because of the time limits and contamination is-
sues involved. In addition, the results of microbial testing
must be handled differently. The following is a review of
the primary sampling and monitoring issues that relate to
particular pathogen and vector attraction reduction param-
eters.
Class B: Monitoring for Fecal Coliform
Densities
Part 503 requires that seven samples be taken to dem-
onstrate compliance with the fecal coliform levels required
of Class B biosolids. Under the Class B requirements seven
samples also means seven analyses. Seven samples were
judged adequate to account for the short-term fluctuations
in treated sludge quality and allow determination of aver-
age performance. Variance of fecal coliform determinations
is known to be high, but analysis (presented below) showed
that if seven samples are averaged, the error band about
the mean value is sufficiently compressed that treatment
works with adequately treated sludge would not have diffi-
culty meeting the standard. If the mean value does not
meet the standard, the material is not a Class B biosolids
and must be disposed of otherwise until the standard is
met.
The regulation requires that the geometric mean fecal
coliform density of the seven samples be less than 2 mil-
lion CPU or MPN per gram of total solids sewage sludge
(dry weight basis). If a treatment works were producing a
treated sewage sludge with a true mean density of exactly
2 million fecal coliform per gram, measured values of the
fecal coliform density would cluster around 2 million per
gram, but half would be below and half would be above it.
Half the time, the treatment works would appear not to be
meeting the requirement. The true mean density must be
below 2 million per gram to be confident that the experi-
mentally determined average will be below 2 million per
gram. Just how much below depends on the standard er-
ror of the average.
Use of at least seven samples is expected to reduce the
standard error to a reasonable value. In tests on extended
aeration sludges, Farrell et al. (1990) obtained a standard
deviation of the logarithm of the fecal coliform density (s)
of 0.3 using the membrane filter method. This included the
variability in the analysis as well as variability over time
(approximately a year). Standard error for the average of
seven measurements (S.E.= s/(n1/2))is 0.11. Using the
normal probability distribution, the true mean must be be-
low 1.30 million if the geometric mean of seven measure-
ments is to be below 2 million 95% of the time (see Table
10-1 for details of this calculation). If the standard devia-
tion were higher, the true mean would have to be even
lower to be reasonably confident that the geometric mean
would be below 2 million per gram. Thus, efforts should be
made to reduce variability. Steps that can be taken are:
Reduce the standard error by increasing the number
of measurements used to determine the geometric
mean.
Reduce process variability.
Improve sampling and analytical techniques.
What action to take to reduce the geometric mean de-
pends on the process. For anaerobic or aerobic digestion,
some suggested steps are to increase temperature, in-
crease residence time, use a draw-and-fill feeding proce-
dure rather than fill-and-draw or continuous feeding, and
increase the time between withdrawal and feeding. After
an attempt at improvement, the evaluation should be re-
peated. If the process continues to fail, more substantial
changes to the process may be appropriate.
Class A: Monitoring for Fecal Coliform or
Salmonella sp. Densities
Part 503 requires that, to qualify as a Class A sludge,
sewage sludge must be monitored for fecal coliform or
Salmonella sp. and have a density of less than 1,000 MPN
fecal coliform per gram of total solids sewage sludge (dry
weight basis) or Salmonella sp. densities below detection
limits (3 MPN/4 g). The regulation does not specify the
number of samples that have to be taken during a moni-
toring event. One sample is not enough to properly repre-
sent the sewage sludge. It is recommended that multiple
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Table 10-1. True Geometric Mean Needed If Standard Fecal Coliform Density of 2 Million CPU Per Gram is to be Rarely Exceeded
Assumptions
The fecal coliform densities of the sewage sludge are log normally distributed. (The arithmetic mean of the logarithms of the fecal coliform
densities is the mean of the distribution. The geometric mean is the antilog of the arithmetic mean of the log values.)
The goal is to ensure that the measured mean value does not exceed the density requirement more than once in 20 monitoring events.
The standard deviation of the log density is 0.30.
Calculation
To predict the expected frequency of a measurement using the normal probability distribution, the variable x is converted to the standard measure
(u- see below) and its probability of occurrence is obtained from tabulated values of the probability distribution. In this case, the reverse is carried
out. A certain probability of occurrence is desired and the value of the standard measure is read from the tables. From the normal distribution table
(single-sided), u is 1.645 when P = 0.05 (one in 20),
Where:
and:
Where:
P =
u =
u =
y =
X =
n =
s =
the proportion of the area under the curve to the right of u relative to the whole area under the curve.
the standard measure
(x-u)/Sx (Equation 1)
true log mean
log mean of the measurements
Sx = s/n1'2
number of measurements that are averaged
standard deviation of a single measurement of log mean density
The logarithm of the fecal coliform density requirement (2 million CFU/g) is x (x= 6.301). This is the number that should not be exceeded more
than once in 20 monitoring episodes. Substituting into Equation 1 and calculating u,
1.645 = (6.301-u)/(0.3/71'2)
u = 6.114
Antilog 6.114 = 1.3 million CFU/g.
samples (>7) be taken over a period of two weeks in order
to adequately represent sludge quality. Based on the reli-
ability of the treatment process and historic test results,
there may be time when a reduction in this monitoring
recommendation is justified. In the case of Class A, ana-
lytical results from multiple samples are not averaged to-
gether; instead, all results must be in compliance with
Class A limits.
The measured fecal coliform density provides an esti-
mate of the likelihood of Salmonella sp. detection and, if
detected, the expected density. Yanko (1987) obtained a
good correlation between fecal coliform density and Sal-
monella sp. detections in his extensive investigation of
composts derived from sewage sludge. The fraction de-
tected is less than 10% when fecal coliform density is less
than 1,000 MPN/g. Yanko also obtained a good correla-
tion between fecal coliform density and Salmonella sp.
density for those samples for which Salmonella sp. were
detected. That correlation predicts that, for fecal coliform
densities less than 1,000 MPN/g,Salmonella sp. densities
will be less than 1.0 MPN/g. Thus, at fecal coliform densi-
ties 4,000 MPN/g, Salmonella sp. detections will be in-
frequent and, if detected, densities are expected to be
below 1 MPN/g.
The Part 503 allows the monitoring of either fecal coliform
or Salmonella sp. in order to demonstrate compliance with
Class A microbiological requirements. The Salmonella sp.
determination is somewhat similar to the fecal coliform test,
but it is much more expensive and requires a high experi-
ence level. In all likelihood, the Salmonella sp. tests would
have to be carried out by a contract laboratory.
The standard deviation for Class A sludges will most likely
be lower than for Class B. This is due to the fact that we
have many more organisms present in Class B sludges
which are not equally distributed within the biosolids. There-
fore you have greater variability and hence a higher S.D.
What action to take to further reduce pathogens in case
the fecal coliform requirement is not met depends on the
process. In general, verification of retention times and tem-
peratures as well as elimination of cross-contamination
between feed and treated sludge or opportunities for re-
introduction of pathogens into treated sludge are recom-
mended. For aerated deep-pile composting, thicker insu-
lating layers on the pile and longer maturing times are sug-
gested.
Class A: Monitoring for and Demonstration
of Enteric Virus and Viable Helminth Ova
Reduction
The accuracy of monitoring results demonstrating the
absence of enteric viruses and helminth ova is influenced
by the variability in the influent to the treatment works and
the inherent error in the experimental method. Information
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on method error for both enteric viruses and helminth ova
is available only on standard deviations calculated from
duplicate samples. Goyal et al. (1984) report that, in their
comparison of methods for determining enteroviruses, the
log standard deviation for the virus determination in sew-
age sludge was 0.26 (47 degrees of freedom). A review of
the work of Reimers et al. (1989) indicates that, in the range
of 5 to 100 viable Ascaris ova per 10 grams sewage sludge
solids, standard deviation was about half the number of
viable ova. This is equivalent to a log density of 0.3, which
is about the same as for fecal coliform. Thus, there is no
unusually high variability in the basic test methods that
would require an increased number of samples to mini-
mize this effect.
Deciding how many samples to take for enteric viruses
and viable helminth ova is more difficult than for fecal
coliform and Salmonella sp. because enteric viruses and
viable helminth ova often may not be present in untreated
sludge. For this reason, the interpretation of the density
determinations for these organisms in treated sludge de-
pends on the quality of the feed sludge. If no enteric vi-
ruses or viable helminth ova are detected in the feed sludge,
then the absence of these organisms in corresponding
samples of treated sludge does not indicate in any way
whether the process is or is not capable of reducing these
organisms to below detectable limits. The ability of a pro-
cess to reduce these organisms to below detectable limits
is indicated when analysis shows that these organisms
were present in the feed sludge and were not present in
corresponding samples of treated sludge. One important
questions is: What fraction of the total pairs of correspond-
ing samples must show positive in the feed sludge and
negative in the treated sfudge to provide convincing evi-
dence that the process consistently reduces enteric viruses
and viable helminth ova to below detectable levels? This
is a difficult question to answer.
Because viable helminth ova are relatively stable micro-
organisms, compositing is suggested as a way to obtain
meaningful representative samples and analytical results.
If precautions are taken, such as cooling the sample
promptly to close to 0°C (32°F) and destroying or neutral-
izing any added chemicals such as strong bases that were
added as part of the pathogen-reducing process, compos-
ites can be collected over a 2-week period. Correspond-
ing composites of feed and treated sludge can be com-
pared, with a much lower likelihood of not finding viable
helminth ova in the feed sewage sludge. Because the ana-
lytical method itself has a high variance (see above), a
minimum of four duplicates of the composite should be
tested.
For enteric viruses, the same approach may be used as
suggested above for viable helminth ova. Precautions are
taken to cool the sample and destroy or neutralize any
chemicals added in the pathogen-reducing process.
Samples are collected on separate days and are promptly
frozen at 0°F (-18°C), or -94°F (-70°C) if samples will be
stored for more than 2 weeks. When the samples are to
be analyzed, the individual samples are thawed and
composited, and viral densities determined.
The density of both viable helminth ova and enteric vi-
ruses in processed sludge must be based on the results of
several measurements. Most of these measurements are
expected to show below detectable densities. If any one
sample is above 1 PFU (for viruses) or 1 viable helminth
ovum (for helminths) per 4 grams, the process does not
meet the Part 503 operational standard.
Vector Attraction Reduction Tests
Reduction in Volatile Solids
One way to demonstrate reduction in volatile solids re-
quires measurement of volatile solids of the sewage sludge
before and after sludge treatment. The sampling point for
the "after treatment" measurement can be immediately
leaving the processing unit or at the point of use or dis-
posal, provided there has been no significant dilution down-
stream with inert solids.
Farrell et al. (1996) have determined the standard de-
viation of the percent volatile solids (%VS) determination
for separate samples withdrawn from pilot-scale digesters
to be 0.65% (total solids content ranged from 2% to 5%).
Conventional statistical procedures (see Davies and Gold-
smith, 1972) were used to calculate the standard error of
the percent volatile solids reduction (%VSR), which is cal-
culated from the %VS of the untreated and treated sludge.
The standard error of the %VSR when calculated by the
Van Kleeck equation (see Appendix D) is 2.0% in the range
of interest (38% VSR). The 95% confidence limits of the
%VSR are ±4%, which is excessive. If the %VSR is the
average of seven determinations, the confidence interval
is reduced to ±1.5%, which is a more acceptable value.
The most difficult problem with the %VSR determina-
tion, as discussed above in Section 10.4, is getting corre-
spondence of the influent sludge with the effluent sludge.
If there has been a significant change in an inlet concen-
tration or flow rate, achieving correspondence can require
several months of monitoring inlet and outlet volatile sol-
ids concentrations. If conditions have been steady and feed
compositions have been fluctuating about an average value
for a long period, data taken over a 2-week period would
be adequate to establish steady state performance.1 This
implies that data have been collected beforehand that dem-
onstrate that sewage sludge composition has reached
steady state for a long period before the 2-week sampling
period. It appears that regular collection of data for some
months before the sampling period is unavoidable to dem-
onstrate steady state performance before the testing pe-
riod. Fortunately, the total and volatile solids determina-
tions are not costly, and they provide valuable operating
information as well.
Total and volatile solids content of a sample do not
change significantly over the course of a day, particularly if
1Note that, unlike the plug flow case, there should be no displacement in time be-
tween comparisons of input and output for fully mixed reactors. Only when there
has been a significant change is it necessary to wait a long time before the com-
parisons can be made.
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the sludge is cooled. Time composites collected over a
course of a day can be used for these determinations.
Seven or more determinations are recommended to re-
duce the error band around the mean to minimize the
chance that a process that actually has a greater volatile
solids reduction than 38% might show an average that is
below this value.
Additional Digestion Tests
The essential measurement in the additional digestion
tests for aerobic and anaerobic sludges (see Sections 8.3
and 8.4) is the percent volatile solids content (%VS) from
which the percent volatile solids reduction is calculated
(%VSR). Using the standard deviation of 0.65% determined
by Farrell et al. (see above), the standard error of the %VSR
when calculated by the Van Kleeck equation (see Appen-
dix D) is 2.5% in the range of interest (15% VSR). The
95% confidence limits of the %VSR are ± 5%. The tests
(see Appendix D) require substantial internal replication
which shrinks these confidence limits. Samples should also
be taken to account for the variability in the process. The
2-week sampling period suggested for the Class A disin-
fection microbiological tests may be excessively restric-
tive if several samples are to be evaluated. The equip-
ment needed for the test is not expensive but the units
take up substantial bench space. It is unlikely that a treat-
ment works will want to have more than two sets of test
equipment. Since the tests take 30 to 40 days, it is not
possible to run more than one set of tests (two in a set)
within a monitoring event. It is suggested that these tests
be routinely carried out during the year and the results be
considered applicable to the monitoring period. It is esti-
mated on a best judgment basis that five tests are needed
to account for variability in the feed sludge and in the treat-
ment process itself.
Specific Oxygen Uptake Rate Test
The Oxygen uptake measuring part of the specific oxy-
gen uptake rate test (SOUR, see Appendix D) can be com-
pleted in the laboratory or field in a few minutes, so there
is no difficulty in completing the test during a monitoring
event. The test requires the SOUR determination to be
made on two subsamples of a given sample. Farrell et al.
(1996) found that, in the target SOUR value of 1.5 mg 02/
hr/g, sludge solids replicates agreed within about ± 0.1 mg
02/hr/g. Since the test is easy to run, it is suggested that
seven tests within the 2-week sampling event will ad-
equately define the SOUR. Labs performing this test should
demonstrate that they too can achieve this level of preci-
sion for replicates (±0.1 mg 02/hr/g). Arithmetic average
of the tests should be computed and compared against
the Part 503 SOUR value.
Raising the pH to 12
There are two options in the regulation that reduce vec-
tor attraction by pH adjustment. In the first, sludge is raised
in pH by alkali addition so that pH is >12 for 2 hours after
alkali addition and, without further alkali addition, remains
at pH >11.5 for an additional 22 hours (see Section 8.7).
The second method is for domestic septage. The pH is
raised to pH >12 by alkali addition and, without further ad-
dition of alkali, remains at >12 for 30 minutes (see Section
8.13). As noted in Section 5.6, the term alkali is used in the
broad sense to mean any substance that increases pH.
The pH requirement in the regulation was established
using data obtained at room temperature (Counts and
Shuckrow, 1975; Ronner and Oliver, 1987), which is pre-
sumed to have been 25°C (77°F). Consequently, pH should
be measured at 25°C (77°F) or measured at the existing
temperature and converted to 25°C (77°F) by use of a tem-
perature-versus-pH conversion table determined experi-
mentally for a treated sludge that meets the pH require-
ments. The correction is not trivial for alkaline solutions; it
is about -0.03 pH unitsfC (-0.017 pH units/°F)for aqueous
calcium hydroxide with a pH of about 12, and should not
be ignored. Note that temperature-compensated pH meters
only adjust instrument parameters and do not compen-
sate for the effect of temperature on the pH of the solution.
pH Adjustment and Septage
Each container of domestic septage being treated with
alkali addition must be monitored. The pH is monitored
just after alkali addition and a half hour or more after alkali
addition. Bonner and Oliver (1987) suggest that alkali (they
used slaked lime) be added to the septic tank or to the
septic tank truck while domestic septage is being pumped
from a septic tank into the tank truck. If slaked lime is used,
a dose of 0.35 Ib per 10 gallons (4.2 g per liter) is sufficient
to raise the pH to 12 for a typical domestic septage of about
1% solids content. The agitation from the high velocity in-
coming stream of septage distributes the lime and mixes it
with the domestic septage. The pH is measured when the
truck loading is complete. The truck then moves to the use
or disposal site. Agitation generated by the motion of the
truck may help in mixing and distributing the lime how-
ever, supplemental mixing in the tank may be needed. The
pH is again measured at the use or disposal site. The sec-
ond pH measurement should be at least a half hour after
the addition of lime. The sample may be obtained through
the top entry of the tank truck, using, for example, a stain-
less steel cup welded to a long handle to collect the sample.
The pH is most conveniently measured with alkaline pH
paper in the pH range of 11 to 13. The pH paper can age
and become contaminated. It is best to use strips from two
separate containers. If they do not agree, compare with a
third batch and reject the one that disagrees with the oth-
ers. Accuracy of these measurements is within ± 0.1 pH
unit. If the pH is below 12, either initially or after 30 min-
utes, more lime should be added and mixed in. After an
additional waiting period of at least 30 minutes, the pH
must again be measured to ensure that it is greater than
12.
pH Adjustment and Sewage Sludges
For addition of alkali to sewage sludges, the pH require-
ment is part of both the PSRP process description (see
Section 5.3) and the requirement of a vector attraction
option (see Section 8.7). Monitoring is required from 1 to
12 times a year (see Table 3-4 in Chapter 3), and the pro-
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cess must meet the prescribed operating conditions
throughout the year.
Alkali is sometimes added to liquid sludge and some-
times to dewatered sludge. The pH requirements as stated
in the regulation apply in the same way for both liquid and
dewatered sludge. For the first measurement of pH in liq-
uid sludge 2 hours after addition of alkali, it is assumed
that the alkali and the sludge have been mixed together
for a sufficient time to reach equilibrium (not considering
the gradual changes that occur over substantial periods of
time). Consequently, the pH measurement can be made
directly in the liquid sludge. The pH measurement is made
preferably with a pH meter equipped with a temperature
compensation adjustment and a low-sodium glass elec-
trode for use at pH values over 10. The pH electrode is
inserted directly in the sludge for the reading. The second
measurement is made 24 hours after addition of alkali. If
the sludge is still in the liquid state, the pH measurement
is made in the same fashion. However, if the process in-
cludes a dewatering step immediately following the alkali
addition and the sludge is now a dewatered cake, the cake
must be made into a slurry for the pH measurement. Ac-
ceptable procedures for preparing the sample and mea-
suring pH are given by EPA (1986). The procedure requires
adding 20 ml_ of distilled water (containing 0.01 M CaCy
to 10 g of sludge cake, mixing occasionally for half an hour,
waiting for the sample to clarify if necessary, and then
measuring pH. The important step is the mixing step that
allows the alkali-treated dewatered sludge to come into
equilibrium with the added water.
Number of Samples
The accuracy of pH meters and of pH paper is within ±
0.1 pH unit. More than one sample is necessary if the do-
mestic septage or sludge is not well mixed. If the lime has
been added gradually over the period in which septage is
being pumped into a tank truck is considered adequate and
a single measurement taken at the top of the tank truck is
sufficient. If alkali has been added to liquid sludge in a
tank at a treatment plant, tests are easily run to establish
how much mixing is required to produce a uniform pH in
the sludge. If this adequate mixing time is used, a single
sample withdrawn from the tank for pH measurement is
sufficient.
If alkali is added to sludge cake, more sampling is sug-
gested. Typically, alkali (usually lime) is added to sludge
cake in a continuous process. The sludge from the dewa-
tering process discharges continuously to a mixer, from
which it discharges to a pile or to a storage bin. Lime is
metered into the mixer in proportion to the sludge flow rate.
The flow rate and compositions of the sewage sludge can
vary with time. To demonstrate compliance on a given day,
several time-composite samples each covering about 5
minutes should be collected, and the pH measured. This
procedure should be repeated several times during the
course of a 2-week sampling event.
For sludge cake, the composites collected
for pH measurement must be reduced in size for the pH
measurement. The alkaline-treated sludge may be dis-
charged from the mixing devices in the form of irregular
balls that can be up to 5 to 7.6 cm (2 or 3 inches) in diam-
eter. It is important that the biosolids to which the environ-
ment will be exposed have been treated to reduce patho-
gens and vector attraction to the desired level. If the dis-
charged biosolids are ball shaped and the alkali has not
penetrated the entire ball, one or both of these goals is not
met for the material inside the ball. The entire ball should
be at the proper pH. It is suggested that the composite be
thoroughly mixed and that a subsample be taken for analy-
sis from the mixed composite. An even more conservative
approach is to sample only the interior of the balls.
Percent Solids Greater Than or Equal to
75% and 90%
The monitoring requirement for these vector attraction
options (see Sections 8.8 and 8.9) is simply measurement
or total solids. This measurement is described in Standard
Methods (APHA [1992], Standard Method 2540 G). Standard
Methods states that duplicates should agree within ± 0.5% of their
average. For 75% solids, this would be ± 3.8%. For a con-
tinuous process, a time-composite sample can be taken
over the course of a day, and duplicate analyses carried
out on this composite. This is possible because biological
activity essentially ceases at high solids content, and de-
composition will not occur. Approximately seven such com-
posites over the course of a 2-week sampling period would
provide adequate sampling.
Some drying processes such as drying sludge on sand
drying beds are batch processes. In such cases, it may be
desirable to ascertain that the sludge meets the vector at-
traction reduction requirements before removing the sludge
from the drying area. This can be done by taking two sepa-
rate space-composites from the dried sludge, analyzing
each of them in duplicate, and removing the sludge only if
it meets the required solids content.
Frequently Asked Questions
How many samples should be submitted for each
monitoring event for Class A pathogen tests? How
many grab samples should be taken for each com-
posite?
The 503 regulations do not specify a minimum number
of samples per sampling event for Class A sludge, but it is
strongly recommended that enough samples be taken to
adequately represent the mass of material which is to be
distributed. A minimum of seven samples, as required for
Class B fecal coliform testing is recommended, but the
number of samples, and the number of grab samples which
each composite should represent, depends on the size of
the facility and the volume of sludge product that is distrib-
uted. A sampling plan should be developed and submitted
to the permitting authority for review.
Are you out of compliance for Class A if you take more
than one sample, and one result is over the limit?
85
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Yes, In order to meet Class A standards, all material must
meet pathogen standards. Although Class B pathogen stan-
dards are based on a geometric mean of analytical re-
sults, geometric (or arithmetic) means are not acceptable
for compliance with Class A standards. Therefore, if sev-
eral samples are submitted for analysis during one moni-
toring event, and one sample is found to be out of compli-
ance with Class A pathogen standards, the entire batch
must be considered Class B (assuming it meets Class B
standards).
For batch processes, one way to prevent one 'out of
compliance' sample from affecting the classification of a
large volume of finished product is to maintain smaller sepa-
rate storage piles and to sample from segregated areas.
For example, finished compost could be separated into
piles based on when composting was completed. If one
result shows non-compliance with the Class A standards,
but other samples are within the Class A limits, it would be
relatively simple to separate put the non-compliance ma-
terial and reprocess it or distribute it as Class B material.
Continuous flow operations can reduce the probability
that one outlying result will cause their process to fail
by taking multiple samples over a 24-hour period and
compositing the samples. The composite sample can then
be analyzed in duplicate to provide more data.
Averaging lab results is allowable as a means to elimi-
nate laboratory variability; however, all data must be reported
to the permitting authority for review. For example, if a lab
runs duplicate fecal coliform analyses on one sample, the
results from these analyses can be averaged together for
one result. This is not intended to allow facilities to rerun
analyses on out-of-compliance samples in the hope of low-
ering average results.
Pathogen testing on our Class A sludge product has
shown that we consistently reduce Salmonella sp. to
below detectable limits, but fecal coliform levels are
sometimes over 1000 MPN per gram. Should we be
concerned about this? Should we be concerned if the
fecal coliform level in our Class A material is occa-
sionally as high as 990 MPN/gram?
According to the regulations, neither situation is a prob-
lem. You are required to comply with either the Salmonella
sp. or the fecal coliform standards, not both. However, the
level of fecal coliform in the product may indicate that there
is incomplete pathogen destruction or some regrowth in
your product, in which case you should examine your patho-
gen and vector attraction reduction processes to ensure
fnat you are complying fully with the requirements and are
not contaminating the product. The high fecal coliform
counts may also be due to the presence of other, non-
fecal coliforms in the sludge. These coliforms, which share
some characteristics with fecal coliforms, may be detected
in fecal coliform testing. They are particularly likely to ap-
pear in compost samples since they tend to be found in
woody materials.
In addition, certain processes have been found to leave
a residual population of fecal coliform which can repopu-
late the sludge. It is possible that testing would find fecal
coliform over the Class A limits even when the pathogenic
bacteria for which fecal coliform are intended to serve as
indicators have been reduced below detectable levels.
Composting and lime treatment are two of these processes.
It is therefore recommended that if properly operated Class
A facilities yield high populations of fecal coliform in fin-
ished solids that Salmonella sp. be used as the indicator
organism for these types of facilities.
Can we distribute finished material before getting
pathogen test results back? If yes, what do you do if
results later show that material was not Class A?
This issue is covered extensively in Section 4.10. Sludge
classification is based on the most recent available lab data,
and therefore, material generated during a sampling pe-
riod can be distributed before results from that sampling
period are available (based on the results of the previous
sampling event). However, it is recommended that materi-
als generated during the sampling period be held on site
until results are available in order to prevent a situation in
which material is erroneously classified and distributed as
Class A.
If composting piles are monitored for temperatures
at three different points, do all three points have to
meet PFRP at the same time?
All particles of sludge must undergo the PFRP time and
temperature regime. For aerated static pile and in-vessel
composting, the entire pile must meet the temperature re-
quirements concurrently. If one point is found to be below
the 55°C level during the temperature monitoring period,
the entire pile is considered to be out of compliance, and
the three consecutive day PFRP period must start over
again. However, if temperatures are taken in distinct piles
or cells of an in-vessel system, each section can meet the
PFRP requirements separately.
Our facility often stockpiles composted sewage
sludge over the winter. In the spring, we may have as
much as four months' production of compost on site.
How should sampling be conducted?
After material is stored on site, it must be resampled in
order to determine if regrowth of pathogens has taken
place. The number of samples should correspond to the
time period that the stockpile represents and the mandated
frequency of sampling based on the facility's size. For ex-
ample, if a facility is required to sample sludge every month,
and there are four months' worth of compost on site, a
minimum of four samples (therefore, 4 times 7 or 28 analy-
sis) from appropriate sections of the stockpile must be
submitted. Ideally, material will be stored in segregated
piles so that each month's production of compost can be
sampled separately.
This applies to other long-term sludge storage such as
lagoons. The number of samples taken from lagoons
should be based on the time period that the lagoon(s) repre-
86
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sent and the frequency of sampling that a facility is obli-
gated to follow because of the rate of sludge generation.
What should we do if our process changes or ex-
pands?
Permits are granted based on particular operational pa-
rameters. Therefore, any projected changes in the opera-
tion or expanded flow should be discussed with the per-
mitting authority before changes are made, even if you do
not have a permit.
Can we be permitted for operation only during cer-
tain months?
If your operation will only meet pathogen or vector at-
traction reduction standards during part of the year, your
permit can contain conditions which allow distribution only
during these times. Permits can also be written to take
ambient conditions into account; for example, some "low-
impact" composting facilities are required to retain mate-
rial over two summers. It may also be practical to limit stor-
age and utilization of particular types of sludges to some
seasons.
Can we combine two PSRP processes that individually
do not meet the specified process requirements to pro-
duce a Class B product? Can time in extended aeration be
added to digester time?
The only way to evaluate the effectiveness of pathogen
reduction through a combination of two or more PSRP pro-
cesses is by testing the sludge for fecal coliform density. If
sufficient pathogen reduction can be demonstrated con-
sistently, the preparer also may consider applying for a
PSRP equivalency for the combined processes in order to
eliminate the need for fecal coliform testing.
In general, extended aeration cannot be considered a
PSRP or part of a PSRP because raw sewage is continu-
ally being added to the aerator and blending with the mixed
liquor. Specific cases in which extended aeration is not
subject to short-circuiting and is thought to contribute sig-
nificantly to the pathogen reduction process should be
evaluated by testing the resulting sludge for fecal coliform
density and by the SOUR test or extended aerobic diges-
tion one for addressing VAR requirements.
If I produce an "exceptional quality" (EQ) product
and mix the product with topsoil before distribution,
does the mix have to be tested for 503 compliance?
Regulations regarding "exceptional quality" material, or
material which complies with the highest levels of patho-
gen and vector attraction reduction as well as heavy met-
als limits, are based on when the sludge preparer loses
control of the material. If the EQ material is still within your
control (i.e. on-site or owned by the preparer) when it is
mixed, the new product must undergo pathogen and vec-
tor attraction reduction processes and be analyzed for Part
503 parameters including pathogens, vector attraction re-
duction, and heavy metals. This may be problematic for
some facilities since a mix of stable compost and soil, for
example, is unlikely to meet/undergo PFRP time and tem-
perature requirements. You may have to test the mix for
helminth ova and enteric viruses in order to demonstrate
compliance with Class A pathogen reduction. If, however,
the EQ material has left your control (i.e. is sold to a soil
blender), the material falls out of the jurisdiction of the Part
503, and any subsequent blending of the material with other
products is not covered by these regulations. Non-EQ
materials are always subject to the Part 503, and storage
or mixing of non-EQ materials with soil, yard waste, or other
additives must be followed with re-testing and re-classifi-
cation. The party responsible for the sludge mixing is con-
sidered a sludge preparer and is therefore subject to all
Part 503 requirements.
Our sludge product meets vector attraction reduc-
tion requirements because the level of total solids in
the material is greater than 75 percent. If stored mate-
rial becomes wet because of rainfall, is the material
still in compliance with the requirements?
The vector attraction reduction requirement stipulates
that the material be processed to greater than 75 percent
(or 90 percent when unstabilized solids are present) total
solids. If dried sewage sludge (biosolids) is stored at your
facility and becomes wet, it still meets the vector attraction
reduction criteria as long as the facility has testing docu-
mentation that the biosolids were processed to >75 or 90
percent solids prior to the time the material became wet. It
is a gpod management practice however to prevent dried
biosolids from getting wet while it is being stored at the
facility.
In the case of vector attraction reduction Option 6, it is
required that the pH of the sludge be raised to >12 for 2
hours and >11.5 for 22 hours. It is not required that the
sludge be maintained at the elevated pH once the mate-
rial has fulfilled the vector attraction reduction requirement.
However, it is important to note that the sludge which ap-
pears to be stable under the elevated conditions may be-
come odorous and attract vectors if the pH declines. It is
recommended that sludge be utilized before the pH drops
below 10.5 in order to prevent odors or vector attraction
which may result in a public nuisance.
Can Alternative 1 be used to demonstrate pathogen
reduction for composting if the compost piles do not
attain 55° C for 3 consecutive days?
Alternative 1 is based on similar time/temperature rela-
tionships as the composting process. Regime A
(D=131,700,000/100-1400t in which t>50°C and D>0.0139
days) can apply to composting. The table below shows
some points on the time/temperature curve that would com-
ply with the regime.
Time (Days)
Temperature (°C)
0.02 (30 min)
0.04 (1 hour)
0.08 (2 hours)
1
2
3
70
68
66
58
56
55
87
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As shown, it is theoretically possible that a compost pile
could comply with Alternative 1 by reaching very high tem-
peratures for a short period of time. Alternative 1 is based
on the assumption that all particles of sludge are at-
taining these temperatures uniformly. This may be diffi-
cult in a compost pile unless the compost pile is completely
enclosed and well insulted. In addition, excessive tempera-
tures in a composting process may result in anaerobic
conditions and subsequent odors.
Our facility is planning to expand next year, and we
would like to implement a new process for pathogen
reduction. We will submit our request for equivalency
to the PEC this year, but, given the current turn around
time for applications, do not expect to have equiva-
lency granted for 2 more years. What should we do in
the interim?
Depending on the class of sludge you are hoping to pro-
duce, you have two options. If you are producing a Class
B sludge, you should continue to do fecal coliform testing
in order to demonstrate compliance with the Class B limit
of 2 million CPU or MPN per dry gram of sludge. If you are
producing a Class A sludge, you could follow Alternative 4
and test the sludge product for helminth ova and enteric
viruses as well as either fecal coliform or Salmonella sp.
In either case, an application for equivalency will require
data demonstrating pathogen reduction, so this data will
be useful in that respect.
You may also wish, in the case of Class A sludge, to test
the feed sludge for enteric virus and helminth ova. Adequate
demonstration that the process reduces these pathogens
on a consistent basis may Qualify the process as a PFRP
equivalent one (Class A, Alternative 6). You should con-
sult with the permitting authority to determine an accept-
able sampling protocol. Demonstration of helminth ova and
virus reduction is difficult, particularly if the density of these
pathogens in the influent is low or sporadic. The sampling
program must demonstrate that actual reduction is taking
place, not just that the pathogen density in the treated
sludge is low. Once pathogen reduction has been suffi-
ciently demonstrated, testing for enteric viruses and helm-
inth ova are no longer necessary as long as the process is
conducted in compliance with specified conditions for PFRP
equivalency.
Our facility distributes Class B lime stabilized sludge
to farmers who use the sludge on a variety of crops. Is
it our responsibility to keep track of how this sludge is
used?
You are required to provide the farmers with all sludge
quality data as well as regulatory information which will
allow them to comply with the appropriate site restrictions.
The applicator, and/or the POTW, is then responsible for follow-
ing the correct site and harvest restrictions. However, given
that any problems with land application will most likely af-
fect the public perception of sludge reuse and this may in
turn affect your facility, it is recommended that you work
closely with farmers to ensure that the regulations are be-
ing followed. In addition, the permitting authority may
choose to include conditions related to site and harvest
restrictions in your permit.
Is there any limit of how long Class B sludge can be
stored before it is used?
Part 503 Rule defines storage as "the placement of sew-
age sludge: on land on which the sewage sludge remains
for two years or less." It does not include placement of
sewage sludge on the land for treatment. After two years
the storage site is considered a final disposal one. The
permitting authority may include storage conditions in your
permit which mandates usage of the material while it still
retains certain characteristics (moisture content) or within
a certain time period. It is recommended that storage of
Class B material be limited to 30 days and be conducted
under similar site restrictions as usage of Class B mate-
rial. For example, public contact and access to the stor-
age site should be restricted.
If the vector attraction reduction requirements have
been fulfilled under Option 6, is there any need for the
sludge to remain at an elevated pH?
In the case of vector attraction reduction Option 6, it is
required that the pH of the sludge be raised to >12 for 2
hours and >11.5 for 22 hours. It is not required that the
sludge be maintained at the elevated pH once the mate-
rial has fulfilled the vector attraction reduction requirement.
However, it is important to note that sludge that appears to
be stable under the elevated conditions may become odor-
ous and attract vectors if the pH declines. It is recom-
mended that sludge be utilized before the pH drops below
10.5 in order to prevent odors or vector attraction that may
result in a public nuisance.
References and Additional Resources
Counts, C.A. and A.J. Shuckrow. 1975. Lime stabilized
sludge: its stability and effect on agricultural land. Rept.
EPA/670/2-75/012, pub. U.S. EPA.
Davies, 01. and P.L. Goldsmith, ad. 1972. Statistical meth-
ods in research and production. Essex, England:
Longman Group Ltd.
Farrell, J.B., B.V. Salotto, and A.D. Venosa. 1990. Reduc-
tion in bacterial densities of wastewater solids by three
secondary treatment processes. Res. J. WPCF 62(2):
177-184.
Farrell, J.B., V. Bhide, and J.E. Smith. 1996. Development
of EPA's new methods to quantify vector attraction re-
duction of wastewater sludges. Water Environment Re-
search, Vol. 68, No. 3.
Goyal, S.M., S.A. Schaub, F.M. Wellings, D. Berman, J.S.
Glass, C.J. Hurst, D.A. Brashear, C.A. Sorber, B.E.
Moore, G. Bitton, P.M. Gibbs, and S.R. Farrah. 1984.
Round robin investigation of methods for recovering
human enteric viruses from sludge. Applied & Environ.
Microbiology 48:531-538.
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Kowal, N.E. 1994. Pathogen risk assessment: Status and
potential application in the development of Round II regu-
lations. Proceedings of the June 19-20, 1994 Speciality
Conference. The Management of Water and Waste-
water Solids for the 21st Century: A Global Perspec-
tive. Water Environment Federation. Alexandria, VA.
Reimers, R.S., M.D. Little, T.G. Akers, W.D. Henriques,
R.C. Badeaux, D.B. McDonnell, and K.K. Mbela. 1989.
Persistence of pathogens in lagoon-stored sludge.
Rept. No. EPA/600/2-89/015 (NTIS No. PB89-190359/
AS). Cincinnati, OH: U.S. EPA Risk Reduction Engi-
neering Laboratory.
Ronner, A.B. and D.O. Cliver. 1987. Disinfection of viruses
in septic tank and holding tank waste by calcium hy-
droxide (Lime). Unpublished report, Small Scale Waste
Management Project. Madison, Wl: University of Wis-
consin.
U.S. EPA. 1986. Test methods for evaluating solid waste:
method 9045A, soil and waste pH, Revision 1, Nov.
1990. Washington, D.C.: Office of Solid Waste and
Emergency Response, U.S. EPA. (avail. U.S. Supt. of
Documents).
Weaver, R.W., J.S. Angle , and P.S. Bottomley. 1994. Meth-
ods of Soil Analysis. Part 2. Microbiological and Bio-
chemical properties. Madison, Wl. Soil Science Soci-
ety of America.
Yanko, W.A. 1987. Occurrence of pathogens in distribu-
tion and marketing municipal sludges. Report No.: EPA/
600/1-87/014. (NTIS PB88-154273/AS.) Springfield,
VA: National Technical Information Service.
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Chapter 11
Role of EPA's Pathogen Equivalency Committee in
Providing Guidance Under Part 503
11.1 Introduction
One way to meet the pathogen reduction requirements
of the Part 503 is to treat sewage sludge in a process
"equivalent to" the PFRP or PSRP processes listed in Ap-
pendix B of the Part 503 regulation (see Tables 4-2 and 5-
1 for a list of these processes):
Under Class A Alternative 6, sewage sludge that is
treated in a process equivalent to PFRP and meets
the Class A microbiological requirement (see Section
4.3) is considered to be a Class A biosolids with re-
spect to pathogens (see Section 4.9).
Under Class B Alternative 3, sewage sludge treated
by a process equivalent to PSRP is considered to be
a Class B biosolids with respect to pathogens (see
Section 5.4).
These alternatives provide continuity with the Part 257
regulation, which required that sewage sludge be treated
by a PSRP, PFRP, or equivalent process prior to use or
disposal. There is one major difference between Part 257
and Part 503 with respect to equivalency. Under Part 257,
a process had to be found equivalent in terms of both patho-
?en reduction and vector attraction reduction. Under Part
03, equivalency pertains only to pathogen reduction.
However, like all Class A and B biosolids, sewage sludges
treated by equivalent processes must also meet a sepa-
rate vector attraction reduction requirement (see Chapter
8).
What Constitutes Equivalency?
To be equivalent, a treatment process must be able to
consistently reduce pathogens to levels comparable to the
reduction achieved by the listed PSRPs or PFRPs. (These
levels, described in Section 11.3, are the same levels re-
quired of all Class A and B biosolids.) The process contin-
ues to be equivalent as long as it is operated under the
same conditions (e.g., time, temperature, pH) that produced
the required reductions. Equivalency may be site-specific;
equivalency applies only to that particular operation run at
that location under the specified conditions, and cannot
be assumed for the same process performed at a different
location, or for any modification of the process. Processes
that are able to consistently produce the required patho-
gen reductions under the variety of conditions that may be
encountered at different locations across the country may
qualify for a recommendation of national equivalency (a
recommendation that the process will be equivalent wher-
ever it is operated in the United States).
Who Determines Equivalency?
The permitting authority is responsible for determining
equivalency under Part 503. The permitting authority and
facilities are encouraged to seek guidance from EPA's
Pathogen Equivalency Committee (PEC) in making equiva-
lency determinations. The PEC makes both site-specific
and national equivalency recommendations.
What Are the Benefits of Equivalency?
A determination of equivalency can be beneficial to a
facility, because it reduces the microbiological monitoring
burden in exchange for greater monitoring of process pa-
rameters. For example a facility meeting Class A require-
ments by sampling for enteric viruses and viable helminth
ova in compliance with Alternative 4 may be able to elimi-
nate this monitoring burden if they are able to demonstrate
that their treatment process adequately reduces these
pathogens on a consistent basis1. Similarly, a facility meet-
ing Class B Alternative 1 requirements by analyzing sew-
age sludge for fecal coliform may be able to eliminate the
need for testing if the process is shown to reduce patho-
gens to the same extent as all PSRP processes. Equiva-
lency is also beneficial to facilities which may have low
cost, low technology systems capable of reducing patho-
gen populations. Options such as long-term storage, air
drying, or low technology composting have been consid-
ered by the PEC.
Because equivalency status allows a facility to eliminate
or reduce microbiological sampling, it is imperative that
the treatment processes deemed equivalent undergo rig-
orous review to ensure that the Part 503 requirements are
met. Obtaining a recommendation of equivalency neces-
sitates a thorough examination of the process and an ex-
1A determination of PFRP equivalency will not reduce the monitoring required for
Salmonella sp. or fecal coliform because all Class A biosolids, even biosolids pro-
duced by equivalent processes, must be monitored for Salmonella sp. or fecal
coliform (see Section 4.3).
90
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tensive sampling and monitoring program. The time needed
to review an application is contingent on the completeness
of the initial application. Sewage sludge preparers wishing
to apply for equivalency should review this chapter care-
fully and discuss the issue with the regulatory authority in
order to determine if equivalency is appropriate for their
situation.
Figure 11-1 indicates when application for equivalency
may be appropriate.
Recommendation of National Equivalency
The PEC can also recommend that a process be con-
sidered equivalent on a national level if the PEC finds that
the process consistently produces the required pathogen
reductions under the variety of conditions that may be en-
countered at different locations across the country. A rec-
ommendation of national equivalency can be useful for
treatment processes that will be marketed, sold, or used
at different locations in the United States. Such a recom-
No
Is your process capable of
consistently reducing enteric viruses
and viable helminth ova to below
detectable levels?
Is your process capable of consistently
reducing the density of fecal coliforms
to below 2 million CPU or MPN per
gram total sewage sludge solids?
No
Your process is
unlikely to be
equivalent to
PSRP
Are you a developer of a sewage
sludge treatment process that has
been or will be marketed and sold in
different areas of the United States?
recommendation
of national
equivalency is
unnecessary
Yes
Is your process covered under Class A
Alternative 1, 2 or 5?
Site-specific
PSRP
equivalency may
be useful
Site-specific
PFRP
equivalency may |
be useful (see
section 11.3)
Yes
Equivalency is
unnecessary
Are you a developer of a sewage
sludge treatment process that has
been or will be marketed and sold in
different areas of the United States?
Yes
Is the effectiveness of your process
independent of the variety of climatic
and other conditipns that may be
encountered in different locations in
the United States?
Yes
A recommendation of national PSRP
equivalency may be useful
Your process is
unlikely to be
recommended
as equivalent on
a national level
Is the effectiveness of your process
independent of the variety of climatic
and other conditipns that may be
encountered in different locations in
the United States?
A recommendation of national PFRP
equivalency may be useful
Figure 11-1. When is application for PFRP or PSRP equivalency appropriate?
91
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mendation may be useful in getting PFRP or PSRP equiva-
lency determinations from different permitting authorities
across the country.
Role of the Pathogen Equivalency
Committee
The U.S. Environmental Protection Agency created the
Pathogen Equivalency Committee (PEC) in 1985 to make
recommendations to EPA management on applications for
PSRP and PFRP equivalency under Part 257 (Whittington
and Johnson, 1985). The PEC consists of approximately
ten members with expertise in bacteriology, virology, para-
sitology, environmental engineering, medical and veteri-
nary sciences, statistics, and sewage sludge regulations.
It includes representatives from EPA's Research and De-
velopment Office, the Office of Water, and the regional of-
fices. The 1993 memorandum included at the end of this
chapter describes the role of the PEC.
Guidance and Technical Assistance on
Equivalency Determinations
The PEC continues to review and make recommenda-
tions to EPA management on applications for equivalency
under Part 503. Its members also provide guidance to ap-
plicants on the data necessary to determine equivalency,
and to permitting authorities and members of the regu-
lated community on issues (e.g., sampling and analysis)
related to meeting the Subpart D (pathogen and vector
attraction reduction) requirements of Part 503. It is not
necessary to consult the PEC with regard to sampling and
monitoring programs if a protocol is already approved un-
der one of the Class A alternatives. Figure 11-2 elaborates
on the role of the PEC under Part 503.
What's in This Chapter?
This chapter explains how the PEC makes equivalency
recommendations and describes how to apply for PEC
guidance. The guidance in this chapter may also prove
useful for permitting authorities in establishing the infor-
mation they will need to make equivalency determinations.
11.2 Overview of the PEC's Equivalency
Recommendation Process
The first point of contact for any equivalency determina-
tion, recommendation, or other guidance is usually the
permitting authority. This is the regional EPA office or the
State in cases in which responsibility for the Part 503 pro-
gram has been delegated to the state. Appendix A pro-
vides a list of EPA Regional and state Contacts. If PEC
involvement is appropriate, the permitting authority will
coordinate contact with the PEC.
The PEC considers each equivalency application on a
case-by-case basis. Applicants submit information on sew-
age sludge characteristics, process characteristics, climate,
and other factors that may affect pathogen reduction or
process efficiency as described in Section 11.5. The com-
mittee evaluates this information in light of current knowl-
edge concerning sewage sludge treatment and pathogen
reduction, and recommends one of five decisions about
the process or process sequence:
It is equivalent to PFRP.
It is not equivalent to PFRP.
It is equivalent to PSRP.
It is not equivalent to PSRP.
Additional data or other information are needed.
Site-specific equivalency is relevant for many applica-
tions; to receive a recommendation for national equiva-
lency, the applicant must demonstrate that the process will
produce the desired reductions in pathogens under the
variety of conditions that may be encountered at different
locations across the country. Processes affected by local
climatic conditions or that use materials that may vary sig-
nificantly from one part of the country to another are un-
likely to be recommended as equivalent on a national ba-
sis unless specific material specifications and process pro-
cedure requirements can be identified.
If the PEC recommends that a process is equivalent to a
PSRP or PFRP, the operating parameters and any other
conditions critical to adequate pathogen reduction are
specified in the recommendation. The equivalency recom-
mendation applies only when the process is operated un-
der the specified conditions.
If the PEC finds that it cannot recommend equivalency,
the committee provides an explanation for this finding. If
additional data are needed, the committee describes what
those data are and works with the permitting authority and
the applicant, if necessary, to ensure that the appropriate
data are gathered in an acceptable manner. The commit-
tee then reviews the revised application when the addi-
tional data are submitted.
11.3 Basis for PEC Equivalency
Recommendations
As mentioned in Section 11.1, to be determined equiva-
lent, a treatment process must consistently and reliably
reduce pathogens in sewage sludge to the same levels
achievable by the listed PSRPs or PFRPs. The applicant
must identify the process operating parameters (e.g., time,
temperature, pH) that result in these reductions.
PFRP Equivalency
To be equivalent to a PFRP, a treatment process must
be able to consistently reduce sewage sludge pathogens
to below detectable limits. For purposes of equivalency,
the PEC is concerned only with the ability of a process to
demonstrate that enteric viruses and viable helminth ova
have been reduced to below detectable limits. This is be-
cause Part 503 requires ongoing monitoring of all Class A
biosolids for fecal coliform or Salmonella sp. (see Section
92
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UNITED STATES ENVIRONMENTAL PROTECTION AGENCY
WASHINGTON. D.C. 20460
JUN 15 1993
OFFICE OF
WATER
MEMORANDUM
SUBJECT:
FROM:
The Role of the Pathogen Equivalency Committee Under
the Part 503 Standards for the Use or Disposal of
Sewage Sludge
TO:
PURPOSE
Michael B. Cook, Directd
Office of Wastewater Enforce
James A. Hanlon, Acting Director
Office of Science & Technology
Water Division Directors
Regions I - X
ce
This memorandum explains the role of the Pathogen
Equivalency Committee (PEC) in providing technical assistance and
recommendations regarding pathogen reduction equivalency in
implementing the Part 503 Standards for the Use or Disposal of
Sewage. The PEC is an Agency resource available to assist your
permit writers and regulated authorities. This information
should be sent to your Regi9nal Sludge Coordinators, Municipal
Construction Managers, Permits and Enforcement Coordinators, and
Solid Waste Offices, State Sludge Management Agencies and others
concerned with sewage sludge management.
BACKGROUND
The PEC Under Part 257
The Criteria for Classification of Solid Waste Facilities
and Practices (44 FR 53438, September 13, 1979), in 40 CFR Part
257 required that sewage sludge disposed on the land be treated
by either a Process to Significantly Reduce Pathogens (PSRP) or a
Process to Further Reduce Pathogens (PFRP). A list of PSRPs and
PFRPs were included in Appendix II to Part 257.
In 1985, the PEC was formed to provide technical assistance
and recommendations on whether sewage sludge treatment processes
not included in Appendix II to Part 257 were equivalent to PSRP
or PFRP. Under Part 257, the PEC provided technical assistance
to both the permitting authority and to members of the regulated
Figure 11-2. Role of the PEC under Part 503.
93
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A series of options are provided in the Part 503 regulation
for meeting the specific requirements for the two classes of
pathogen reduction. One of the Class A alternatives is to treat
the sewage sludge by a process equivalent to a PFRP and one of
the Class B alternatives is to treat the sewage sludge by a
process equivalent to a PSRP. The permitting authority must
decide whether a process is equivalent to a PFRP or a PSRP, which
is the same approach used under Part 257.
TEE PEC UNDER 503
Part 503 provides specific criteria and procedures for
evaluating bacterial indicators (Fecal coliforms and Salmonella
sp.), enteric virus and viable helminth ova as well as vector
attraction reduction. The PEC will continue to support the
permitting authority and members of the regulated community under
the new Part 503 regulation in evaluating equivalency situations
and providing technical assistance in matters such as sampling
and analysis. Specifically the PEC:
will continue to provide technical assistance to the
permitting authority and regulated community, including
recommendations to the permitting authority about
process equivalency. The PEC also will make both site-
specific and national (i.e., a process that is
equivalent anywhere in the United States where it is
installed and operated) recommendations on process
equivalency .
will submit recommendations on process equivalency to
the Director, Health and Ecological Criteria Division,
Office of Science and Technology, who will review those
recommendations and then notify the applicant and
appropriate permitting authorities of our
recommendation.
Ford site-specific recommendations, requests for PEC review
or assistance should be made through the appropriate Federal
permitting authority (e.g., the State sludge regulatory authority
for delegated programs or the EPA Regional Sludge Coordinator for
non-delegated programs). For national recommendations, requests
for PEC review or assistance can also be made through the
Director, Health and Ecological Criteria Division (4304T),
Office of Science & Technology, 1200 Pennsylvania Avenue,
Washington, DC 20460 or directly to the PEC Chairman. The
current PEC Chairman is: Dr. James E.\\ Smith, Jr., U.S. EPA,
NRMRL, (National Risk Management Research Laboratory) 26 W Martin
Luther King Dr., Cincinnati, OH 45268 (Tele: 513/569-7355).
Additional information and guidance to supplement the
pathogen reduction requirements of Part 503 and the procedures to
use to reach the PEC and the assistance provided by the PEC is
provided in "Control of Pathogens and Vector Attraction in Sewage
Figure 11-2. Role of the PEC under Part 503 (continued).
94
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community. The PEC membership has included representatives from
the Office of Research & Development (ORD), Office of Wastewater
Enforcement & Compliance (OWEC), and the Office of Science &
Technology (OST) with extensive experience in microbiology,
sludge process engineering, statistics and regulatory issues.
The PEC recommendations regarding the equivalency of processes
were forwarded to the Office of Science and Technology, which
notified applicants about the PEG'S recommendations. Final
decisions on equivalency were made by the permitting authority.
The Part 503 Sewage Sludge Standards
The 40 CFR Part 503 Standards for the Use or Disposal of
Sewage Sludge were published in the Federal Register on
February 19,1993(58EB 9248) under the authority of section 405
of the Clean Water Act, as amended. Part 503 establishes
requirements for sewage sludge applied to the land, placed on a
surface disposal site, or fired in a sewage sludge incinerator.
Along with the 40 CFR Part 258 Municipal Solid Waste (MSW)
Landfill Regulation (56 ER 50978, October 9, 1991), which
established requirements for materials placed in MSW landfills,
the Part 503 requirements for land application of sewage sludge
and placement of sewage sludge on a surface disposal site,
replaces the requirements for those practices, including the
requirement to treat the sewage sludge in either a PSRP or a
PFRP, in Part 257.
The Part 503 regulation addresses disease-causing organisms
(i.e., pathogens) in sewage sludge by establishing requirements
for sewage sludge to be classified either as Class A or Class B
with respect to pathogens as an operational standard. Class A
requirements are met by treating the sewage sludge to reduce
pathogens to below detectable limits, while the Class B
requirements rely on a combination of treatment and site
restrictions to reduce pathogens. The site restrictions prevent
exposure to the pathogens and rely on Natural Environmental
processes to reduce the pathogens in the sewage sludge to below
detectable levels. In addition to pathogen reduction, a vector
attraction reduction requirement has to be met when sewage sludge
is applied to the land or placed on a surface disposal site.
Vector attraction reduction requirements are imposed under
Part 503 to reduce the potential for spreading of infectious
disease agents by vectors (i.e., flies, rodents, and birds). A
series of alternative methods for meeting the vector attraction
reduction requirement are provided in the rule.
All sewage sludges that are to be sold or given away in a
bag or other container for land application, or applied to lawns
or home gardens must meet Class A pathogen control and vector
attraction reduction requirements. All sewage sludge intended
for land application must meet at least the Class B pathogen
control and vector attraction reduction requirements. Surface
disposal of sewage sludge reguires that Class A or Class B
requirements, along with one of the vector attraction reduction
practices, be met unless the sewage sludge is covered with soil
or other material daily.
Figure 11-2. Role of the PEC under Part 503 (continued).
95
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Sludge" (EPA 625/R-92/013), which will-be updated from time to
time by the PEC. This document is an update of the 1989 document
"Control of Pathogens in Municipal Wastewatsr Sludge"
(EPA/625/10-89/006), and is available from CERI.
if there are any questions about this memorandum, please
contact Bob Bastian from OWM at 202/564-0635 or Dr. Smith from
NRMRL at 513-569-7355..
Figure 11-2. Role of the PEC under Part 503 (continued).
96
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4.3) to ensure that Salmonella sp. are reduced to below
detectable limits (i.e., to less than 3 MPN per 4 grams total
solids sewage sludge [dry weight basis]) and that growth
of pathogenic bacteria has not occurred. Thus, to demon-
strate PFRP equivalency, the treatment process must be
able to consistently show that enteric viruses and viable
helminth ova are below the detectable limits, shown be-
low:
There are two ways these reductions can be demon-
strated:
Direct monitoring of treated and untreated sewage
sludge for enteric viruses and viable helminth ova
Comparison of the operating conditions of the process
with the operating conditions of one of the listed
PFRPs.
The process comparison approach to demonstrating
equivalency is discussed in Section 11.4.
PSRP Equivalency
To be equivalent to PSRPs, a process must consistently
reduce the density of pathogenic viruses and bacteria (num-
ber per gram of biosolids (dry weight basis)) in mixed sludge
from a conventional plant by equal to or greater than 1 log
(base 10). Data indicate tnat, for conventional biological
and chemical treatment processes (e.g.,digestion and lime
treatment) a reduction of 1 log (base 10) in pathogenic
virus and bacteria density correlates with a reduction of 1
to 2 logs (base 10) in the density of indicator organisms
(Farrell et al., 1985, Farrah et al., 1986). On this basis a 2-
log (base 10) reduction in fecal indicator density is accepted
as satisfying the requirement to reduce pathogen density
by 1 log (base 10) for these types of processes (EPA,
1989c). Specifically, the applicant must demonstrate a 2-
log (base 10) reduction (number per gram of biosolids (dry
weight basis)) in fecal coliforms.
There is substantial data to indicate that sludge produced
by conventional wastewater treatment and anaerobic di-
gestion at 35°C for more than 15 days contains fecal
coliforms at average log (base 10) densities (number per
gram of biosolids (dry weight basis)) of less than 6.0
(Farrell, 1988). Thus, for processes or combinations of
processes that do not depart radically from conventional
treatment (gravity thickening, anaerobic or aerobic biologi-
cal treatment, dewatering, air drying and storage of liquid
or sludge cake), or for any process where there is a dem-
onstrated correlation between pathogenic bacteria and vi-
rus reduction and indicator organisms reduction, the PEC
accepts an average log (base 10) density (no./g. TSS) of
fecal coliforms and fecal streptococci of less than 6.0 in
the treated sludge as indicating adequate viral and bacte-
rial pathogen reduction. (The average log density is the
log of the geometric mean of the samples taken. Calcula-
tions of average log density should be based on data from
approximately nine sludge samples to account for the natu-
ral variability and the variability of the microbiological tests.)
The data submitted must be scientifically sound in order
to ensure that the process can reliably produce the re-
quired reductions under all the different types of condi-
tions that the process may operate. For example, for pro-
cesses that may be affected by daily and seasonal varia-
tions in the weather, four or more sets of samples taken at
different times of the year and during different precipita-
tion conditions (including worst-case conditions) will be
needed to make this demonstration.
For national equivalency recommendations, the demon-
stration must show that the process can reliably produce
the desired reductions under the variety of climatic and
other conditions that may be encountered at different lo-
cations in the United States.
11.4 Guidance on Demonstrating
Equivalency for PEC
Recommendations
Many of the applicants seeking equivalency do not re-
ceive a recommendation from the PEC. The most com-
mon reason for this is incomplete applications or insuffi-
cient microbiological data. The review process can be both
lengthy and expensive, but it can be expedited and simpli-
fied if the applicant is aware of the type of data that will be
required for the review and submits a complete plan for
demonstrating equivalency in a timely fashion.
As described below, equivalency can be demonstrated
in one of two ways:
By comparing operating conditions to existing PFRPs
or PSRPs.
By providing performance and microbiological data.
Comparison to Operating Conditions for
Existing PSRPs or PFRPs
If a process is similar to a PSRP or PFRP described in
the Part 503 regulation (see Tables 4-2 and 5-1), it may be
possible to demonstrate equivalency by providing perfor-
mance data showing that the process consistently meets
or exceeds the conditions specified in the regulation. For
example, a process that consistently produces a pH of 12
after 2 hours of contact (the PSRP condition required in
Part 503 for lime stabilization) but uses a substance other
than lime to raise pH could possibly qualify as a PSRP
equivalent. In such cases, microbiological data may not
be necessary to demonstrate equivalency.
Process-Specific Performance Data and
Microbiologic Data
In all other cases, both performance data and microbio-
logical data (listed below) are needed to demonstrate pro-
cess equivalency:
A description of the various parameters (e.g., sewage
sludge characteristics, process operating parameters,
climatic factors) that influence the microbiological char-
97
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acteristics of the treated sewage sludge (see Section
11.5 for more detail on relevant parameters).
Sampling and analytical data to demonstrate that the
process has reduced microbes to the required levels
(see Section 11.3 for a description of levels).
Discussion of the ability of the treatment process to
consistently operate within the parameters necessary
to achieve the appropriate reductions.
Sampling and Analytical Methods
Sewage sludge should be sampled using accepted,
state-of-the-art techniques for sampling and analyzed us-
ing the methods required by Part 503 (see Chapter 9).
The sampling program should demonstrate the quality of
the sewage sludge that will be produced under a range of
conditions. Therefore, sampling events should include a
sufficient number of samples to adequately represent prod-
uct quality, and sampling events should be designed to
reflect how the operation might be affected by changes in
conditions including climatic and sewage sludge quality
variability.
Data Quality
The quality of the data provided is an important factor in
EPA's equivalency recommendation. The following steps
can help ensure data quality:
Use of accepted, state-of-the-art sampling techniques
(see Chapter 9).
Obtaining samples that are representative of the ex-
pected variation in sewage sludge quality.
Developing and following quality assurance procedures
for sampling.
Using an independent, experienced laboratory to per-
form the analysis.
Since processes differ widely in their nature, effects, and
processing sequences, the experimental plan to demon-
strate that the process meets the requirements for PSRP
or PFRP equivalency should be tailored to the process.
The permitting authority will evaluate the study design, the
accuracy of the data, and the adequacy of the results for
supporting the conclusions of the study.
Can Pilot-Scale Data Be Submitted?
Operation of the process at a full-scale facility is desir-
able. However, if a pilot-scale operation truly simulates full-
scale operation, testing on this reduced scale is possible.
The permitting authority and the PEC should be contacted
to discuss this possibility before testing is initiated. In such
cases, it is important to indicate that the data were ob-
tained from a pilot-scale operation, and to discuss why and
to what extent this simulates full-scale operation. Any data
available from existing full-scale operations would be use-
ful.
The conditions of the pilot-scale operation should be at
least as severe as those of a full-scale operation. The ar-
rangement of process steps, degree of mixing, nature of
the flow, vessel sizing, proportion of chemicals used, etc.
are all part of the requirement. Any substantial degree of
departure in the process parameters of the full-scale op-
eration that might reduce trie severity of the procedure will
invalidate any PEC equivalency recommendations and
permitting authority equivalency determinations and will
require a retest under the new condition.
11.5 Guidance on Application for
Equivalency Recommendations
The following outline and instructions are provided as
guidance for preparing applications for equivalency rec-
ommendations by EPA's Pathogen Equivalency Commit-
tee.
Summary Fact Sheet
The application should include a brief fact sheet that
summarizes key information about the process. Any im-
portant additional facts should also be included.
Introduction
The full name of the treatment works and the treatment
process should be provided. The application should indi-
cate whether it is for recommendation of:
PSRP or PFRP equivalency.
Site-specific or national equivalency.
Process Description
The type of sewage sludge used in the process should
be described, as well as other materials used in the pro-
cess. Specifications for these materials should be provided
as appropriate. Any terms used should be defined.
The process should be broken down into key steps and
graphically displayed in a quantified flow diagram of the
wastewater and sewage sludge treatment processes. De-
tails of the wastewater treatment process should be pro-
vided and the applicaton should precisely define which
steps constitute the beginning and end of sewage sludge
treatment.2 The earliest point at which sewage sludge
treatment can be defined as beginning is the point at which
the sewage sludge is collected from the wastewater treat-
ment process. Sufficient information should be provided
for a mass balance calculation (i.e., actual or relative volu-
metric flows and solids concentration in and out of all
streams, additive rates for bulking agents or other addi-
tives). A description of process parameters should be pro-
vided for each step of the process, giving typical ranges
and mean values where appropriate. The specific process
parameters that should be discussed will depend on the
type of process and should include any of the following
that affect pathogen reduction or process reliability:
Sewage Sludge Characteristics
Total and volatile solids content of sewage sludge be-
fore and after treatment
When defining which steps constitute the "treatment process," bear
in mind that all steps included as part of a process equivalent to PSRP
or PFRP must be continually operating according to the specifications
and conditions that are critical to pathogen reduction.
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Proportion and type of additives (diluents) in sewage
sludge
Chemical characteristics (as they affect pathogen sur-
vival/destruction, e.g., pH)
Type(s) of sewage sludge (unstabilized vs. stabilized,
primary vs. secondary, etc.)
Wastewater treatment process performance data (as
they affect sewage sludge type, sewage sludge age,
etc.)
Quantity of treated sewage sludge
Sewage sludge age
Sewage sludge detention time
Process Characteristics
Scale of the system (e.g., reactor size, flow rate)
Sewage sludge feed process (e.g., batch vs. continu-
ous)
Organic loading rate (e.g., kg volatile solids/cubic
meter/day)
Operating temperature(s) (including maximum, mini-
mum, and mean temperatures)
Operating pressure(s) if greater than ambient
Type of chemical additives and their loading rate
Mixing
Aerobic vs. anaerobic
Duration/frequency of aeration
Dissolved oxygen level maintained
Residence/detention time
Depth of sewage sludge
Mixing procedures
Duration and type of storage (e.g., aerated vs.
nonaerated)
Climate
Ambient seasonal temperature range
Precipitation
Humidity
The application should include a description of how the
process parameters are monitored including information
on monitoring equipment. Process uniformity and reliabil-
ity should also be addressed. Actual monitoring data should
be provided whenever appropriate.
Description of Treated Sewage Sludge
The type of treated sewage sludge (biosolids) should be
described, as well as the sewage sludge monitoring pro-
gram for pathogens (if there is one). How and when are
samples taken? For what parameters are the samples
analyzed? What protocols are used for analysis? What are
the results? How long has this program been in opera-
tion?
Sampling Technique(s)
The PEC will evaluate the representativeness of the
samples and the adequacy of the sampling techniques.
For a recommendation of national PFRP equivalency,
samples of untreated and treated sewage sludge are usu-
ally needed (see Sections 11.3, 4.6, and 10.4). The sam-
pling points should correspond to the beginning and end
of the treatment process as defined previously under Pro-
cess Description above. Chapters 9 and 10 provide guid-
ance on sampling. Samples should be representative of
the sewage sludge in terms of location of collection within
the sewage sludge pile or batch. The samples taken should
include samples from treatment under the least favorable
operating conditions that are likely to occur (e.g., winter-
time). Information should be provided on:
Where the samples were collected from within the sew-
age sludge mass. (If samples were taken from a pile,
include a schematic of the pile and indicate where the
subsamples were taken.)
Date and time the samples were collected. Discuss
how this timing relates to important process param-
eters (e.g., turning over, beginning of drying).
Sampling method used.
How any composite samples were compiled.
Total solids of each sample.
Ambient temperature at time of sampling.
Temperature of sample at time of sampling.
Sample handling, preservation, packaging, and trans-
portation procedures.
The amount of time that elapsed between sampling
and analysis.
Analytical Methods
Identify the analytical techniques used and the
laboratory(ies) performing the analysis.
Analytical Results
The analytical results should be summarized, preferably
in tabular form. A discussion of the results and a summary
of major conclusions should be provided. Where appropri-
ate, the results should be graphically displayed. Copies of
original data should be provided in an appendix.
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Quality Assurance
The application should describe how the quality of the
analytical data has been ensured. Subjects appropriate to
address are: why the samples are representative; the qual-
ity assurance program; the qualifications of the in-house
or contract laboratory used; and the rationale for selecting
the sampling technique.
Rationale for Why Process Should Be
Determined Equivalent
Finally, the application should describe why, in the
applicant's opinion, the process qualifies for PSRP or PFRP
equivalency. For example, it may be appropriate to de-
scribe or review particular aspects of the process that con-
tribute to pathogen reduction, and why the process is ex-
pected to operate consistently. Complete references should
be provided for any data cited. Applications for a recom-
mendation of national equivalency should discuss why the
process effectiveness is expected to be independent of
the location of operation.
Appendices
A copy of the complete laboratory report(s) for any sam-
pling and analytical data should be attached as an appen-
dix. Any important supporting literature references should
also be included as appendices.
11.6 Pathogen Equivalency Committee
Recommendations
Tables 11.1 and 11.2 list processes that the PEC has
recommended for use nationally as equivalent to PSRP or
PFRP, respectively. Space in the tables limits the detail
given for each of the processes. As such individuals hav-
ing an interest in any of the processes are encouraged to
contact either the PEC or the applicant for greater detail
on how the process must be operated to be PSRP or PFRP,
respectively.
Table 11-1. Processes Recommended as Equivalent to PSRP
Applicant Process Process Description
N-Viro Energy
Systems, Ltd.,
Toledo, Ohio
Synox Corp.,
Jacksonville, FL
Alkaline Addition
to achieve Lime
Stabilization
OxyOzonation
Use of cement kiln dust and
lime kiln dust (instead of lime)
to treat sludge by raising the
pH. Sufficient lime or kiln dust
is added to sludge to produce
a pH of 12 for at least 12
hours of contact
Batch process where sludge
is acidified to pH 3.0 by
sulfuric acid; exposed to 1 Ib.
Ozone/1000 gallons of treated
sludge under 60 psig
pressure for 60 minutes;
depressurized; mixed with
100 mg/l of sodium nitrite and
held for > 2 hours; and stored
at < pH 3.5. Limitations
imposed were for total solids
to be < 4%; temperature must
be>20°C; and total solids
must be < 6.2% before nitrite
addition.
11.7 Current Issues
The PEC is continuing to develop methodologies and
protocols for the monitoring of pathogen and vector attrac-
tion reduction. Current issues include:
Establishment of a vector attraction reduction equiva-
lency process
Conducting round robin laboratory testing for patho-
gens in sewage sludge and biosolids
In addition, the PEC continues to recommend interpre-
tations of the Part 503 with regard to the sampling and
monitoring requirements set forth in this document.
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Table 11-2. Processes Recommended as Equivalent to PFRP
Applicant Process
Process Description
CBI Walker, Inc.,
Aurora, Illinois
ATP Two Stage Sludge
Stabilization Process
Fuchs Gas und
Wassertechnik, Gmbh,
Mayen, Germany
Autothermal Thermophilic
Aerobic Digestion
International Process
Systems, Inc.,
Glastonbury,
Connecticut
K-F Environmental
Technologies, Inc.,
Pompton Plains, NJ
Type of Composting
Process
Sludge Drying
Sludge is introduced intermittently into a vessel, amounting to 5 to 20% of
its volume, where it is heated by both external heat exchange and by the
bio-oxidation which results from vigorously mixing air with the sludge
(pasteurized) and has a nominal residence time of 18 to 24 hours. Time
between feedings of unprocessed sludge can range from 1.2 (@ ~ 65°C) to
4.5 (@ > 60°C) hours. Exiting sludge is heat exchanged with incoming
unprocessed sludge. Thus the sludge is cooled before it enters a
mesophilic digester. Time and temperature in the first vessel are
critical and controlled by the equation below for sludges of < 7%
solids, times > 30 minutes, and temperatures >50°C. Operations
of the reaction vessel during the time-temperature period must be
either plug flow or batch mode.
D = 50,070,00071 o°1400t where D = time required in days; t =
temperature in °C
ATAD is a two-stage, autothermal aerobic digestion process. The stages
are of equal volume. Treated sludge amounting to 1/3 the volume of a
stage is removed every 24 hours from the second stage as product. An
equal amount then is taken from the first stage and fed to the second stage.
Similarly, an equal amount of untreated sludge is then fed to the first stage.
In the 24-hour period between feedings, the sludge in both stages is
vigorously agitated and contacted with air. Bio-oxidation takes place and
the heat produced increases the temperature. Sludge temperature in
the reactors averages between 56 and 57°C for >a 16-hour period, while
the overall hydraulic residence time is 6 days.
40 CFR 503.32(a)(7) states that when the within-vessel composting
method is employed, the sludge is to be maintained at operating conditions
of 55 °C or greater for three days, for the product to be PFRP. IPS Process'
operation is to further be controlled so that the composting mass passes
through a zone in the reactor in which the temperature of the compost is at
least 55°C throughout the entire zone, and the time of contact in this zone is
at least three days.
Sludge is heated to a minimum temperature of 100°C and indirectly dried
to below 10% moisture using oil as a heat transfer medium. The final
discharge product has exceeded a temperature of 80°C and is granular dry
pellet that can be land applied, incinerated or landfilled. In addition the
following conditions must be met: Dewatered sludge cake is dried by direct
or indirect contact with hot gases, and moisture content is reduced to 10%
or lower. Sludge particles reach temperatures well in excess of 80°C or the
wet bulb temperature of the gas stream in contact with the sludge at the
point where it leaves the dryer is in excess of 80°C.
Lyonnaise des Eaux,
Le Pecz-Sur-Seine, France
Two-Phase Thermo-Meso
Feed Sequencing Anaerobic
Digestion*
ATW, Inc.
Santa Barbara,
CA
Alkaline Stabilization
Sewage sludge is treated in the absence of air in an acidogenic thermophilic
reactor and a mesophilic methanogenic reactor connected in series. The
mean cell residence time shall be at least 2.1 days (± 0.05 d) in the
acidogenic thermophilic reactor followed by 10.5 days (± 0.3 d) in the
mesophilic methanogenic reactor. Feeding of each digester shall be
intermittent and occurring 4 times per day every 6 hours. The mesophilic
methanogenic reactor shall be fed in priority from the acidogenic
thermophilic reactor. Between two consecutive feedings temperature inside
the acidogenic thermophilic reactor should be between 49°C and 55°C with
55°C maintained during at least 3 hours. Temperature inside the mesophilic
methanogenic reactor shall be constant and at least 37°C.
Manchak process uses quicklime to simultaneously stabilize and pasteurize
biosolids. Quicklime, or a combination of quicklime and flyash, is mixed with
dewatered biosolids at a predetermined rate in a confined space. An instant
exothermic reaction is created in the product wherein the pH is raised in
excess of 12 after two hours of contact, in addition, the temperature is
raised in excess of 70°C for > 30 minutes.
(continued)
101
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Table 11-2. Continued.
Applicant
Process
Process Description
N-Viro Energy Systems, Ltd.,
Toledo, OH
Advanced Alkaline stabilization
with subsequent accelerated
drying
Synox Corp.,
Jacksonville, FL
OxyOzonation
Ultraclear,
Marlboro, NJ
Microbiological Conditioning
and Drying Process (MVCD)
Alternative 1: Fine alkaline materials (cement kiln dust, lime kiln dust,
quicklime fines, pulverized lime, or hydrated lime) are uniformly mixed by
mechanical or aeration mixing into liquid or dewatered sludge to raise the
pH to >12 for 7 days. If the resulting sludge is liquid, it is dewatered. The
stabilized sludge cake is then air dried (while pH remains >12 for >7 days)
for >30 days and until the cake is > 65% solids. A solids concentration of >
60% is achieved before the pH drops below 12. The mean temperature of
the air surrounding the pile is > 5°C (41°F) for the first 7 days.
Alternative 2: Fine alkaline materials (cement kiln dust, lime kiln dust,
quicklime fines, pulverized lime, or hydrated lime) are uniformly mixed by
mechanical or aeration mixing into liquid or dewater sludge to raise the pH
to > 12 for >72 hours. If the resulting sludge is liquid, it is dewatered. The
sludge cake is then heated, while the pH > 12, using exothermic reactions
or other thermal processes to achieve temperatures of > 52°C (126°F)
throughout the sludge for > 12 hours. The stabilized sludge is then air dried
(while pH > 12 for > 3 days) to > 50% solids.
Operation occurs in a batch mode and under the following conditions:
sludge temperature of > 20°C; sludge solids of < 6% TSS; pH during
ozonation of 2.5 - 3.1 and during nitrite contact of 2.6 - 3.5; sludge ORP
after ozonation of > 100 mV; nitrite dose of > 670 mg (NCy/l sludge or 16
g (N02)/kg sludge solids, whichever is greater is to be mixed into the
ozonated sludge. Ozonation takes place in a pressure vessel operating at
60 psig.
In this process, sludge cake passes through several aerobic-biological type
stages (Composting is an example) where different temperatures are
maintained for varying times. Stage 1 occurs at 35°C for 7-9 hours; stage 2
occurs at 35-45°C for 8-10 hours; stage 3 occurs at 45-65°C for 7-10 hours;
and the last stage is pasteurization at 70-80°C for 7-10 hours. In addition
one of two conditions described below must be met:
Condition 1: Dewatered sludge cake is dried by direct or indirect contact
with hot gases, and moisture content is reduced to 10% or lower. Sludge
particles reach temperatures we//in excess of80°C or the wet bulb
temperature of the gas stream in contact with the sludge at the point where
it leaves the dryer is in excess of 80°C. OR
Condition 2: A) Using the within-vessel, static aerated pile, or windrow
composting methods, the sludge is maintained at minimum operating
conditions of 40°C for 5 days. For 4 hours during the period the temperature
exceeds 55°C; {Note: another PS RP-type process should be substituted for
that of composting}; and B) Sludge is maintained for at least 30 minutes at a
minimum temperature of70°C.
'Currently a site specific recommendation. Undergoing further study for national equivalency.
References and Additional Resources
Farrah, S.R., G. Bitton, and S.G. Zan. 1986. Inactiva-
tion of enteric pathogens during aerobic digestion
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047. Water Engineering Research Laboratory, Cin-
cinnati, OH. NTIS Publication No. PB86-183084/AS.
National Technical Information Service. Springfield.
Virginia.
Farrell, J.B., G. Stern, and A.D. Venosa. 1985. Micro-
bial destructions achieved by full-scale anaerobic
digestion. Workshop on control of sludge pathogens.
Series IV. Water Pollution Control Federation. Alex-
andria, Virginia.
Smith, James E. Jr. and J.B. Farrell. 1996. Current and future
disinfection - Federal perspectives. Presented at Water
Environment Federal 69th Annual Conference and Exposi-
tion.
Whittington, W.A. and E. Johnson. 1985. Application of 40 CFR
Part 257 regulations to pathogen reduction preceding land
application of sewage sludge or septic tank pumpings.
Memorandum to EPA Water Division Directors. U.S. EPA
Office of Municipal Pollution Control, November 6.
102
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Chapter 12
References and Additional Resources
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Ault, S.K. and M. Schott. 1993. Aspergillus, Aspergillosis, and
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Benedict, A.M. and D.A. Calrson. 1973. Temperature accli-
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Berg G. and D. Berman. 1980. Destruction by anaerobic
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Bonner, A.B. and D.O. Cliver. 1987. Disinfection of viruses in
septic tank and holding tank waste by calcium hydrox-
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Casson, L.W., C.A. Sorber, R.H. Palmer, A. Enrico, and P.
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Farrell, J.B., V. Bhide, and J.E. Smith Jr. 1996. Develop-
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(Photos in Chapter 2 reproduced with permission of the
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106
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A
of
Thelma Hamilton Murphy
U.S. EPA Region!
Office of Ecco-System Protection
Boston, MA 02203
(617)918-1615(phone)
(617)918-1505{fax)
MURPHY.THELMA@EPAMAIL.EPA.GOV
Alia Roufaeal
U.S. EPA Region I!
Div. of Enforcement and Compliance Assist.
290 Broadway- 20th Floor
New York, NY 10007-1866
(212)637-3864
(212)637-3953
ROUFAEAL.ALIA@EPAMAIL.EPA.GOV
AnnCarkhuff
U.S. EPA Region III
Water Protection Div.
841 Chestnut Street
Philadelphia, PA 19107
(215) 566 5735 (phone)
(215) 566 2301 (fax)
CARKHUFF.ANN@EPAMAIL.EPA.GOV
Madolyn S. Dominy
Region 4 Biosolids Coordinator
U.S. Environmental Protection Agency
61 Forsyth Street, SW
Atlanta, GA 30303
ph. (404)562-9305
fax (404)562-8692
dominy.madolyn@epa.gov
JohnCoIIetti
U.S. EPA Region V (WN-16J)
Water Division
77 West Jackson Blvd.
Chicago, IL 60604-3590
(312) 886-6106 (phone)
(312) 886-7804 (fax)
COLLETTI.JOHN@EPAMAIL.EPA.GOV
Stephanie Kordzi (6WQ-PO)
U.S. EPA Region VI
Water Quality Management Division
1445 ROSS Avenue #1200
Dallas, TX 75202-2733
(214) 665-7520 (phone)
(214)665-2191 (phone)
KORDZI.STEPHANIE@EPA.GOV
John Dunn
U.S. EPA Region VII
Waste Management Division
726 Minnesota Ave.
Kansas City, KS 66101
(913) 551-7594 (phone)
(913) 551-7765 (fax)
DUNN.JOHN@EPAMAIL.EPA.GOV
Bob Brobst
Biosolids Program manager (P2-W-P)
U.S. EPA Region VIII
999 18th Street, Suite 500
Denver, CO 80202-2466
(303)312-6129(phone)
(303) 312-7084 (fax)
BROBST.BOB@EPA.GOV
Lauren Fondahl
U.S. EPA Region IX(WTR-7)
Biosolids Coordinator
Office of Clean Water Act Compliance
75 Hawthorne Street
San Francisco, CA 94105-3901
(415) 744-1909 (phone)
(415) 744.1235 (fax)
FONDAHL.LAUREN@EPAMAIL.EPA.GOV
Dick Hetherington
U.S. EPA Region X
Permits Unit (OW-130)
1200 Sixth Avenue
Seattle, WA 98101
(206) 553-1941 (phone)
(206) 553-1280 (fax)
HETHERINGTON.DICK@EPAMAlL.EPA.GOV
107
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State Sludge Coordinators
Region I
Connecticut
Bob Norwood/Warren Herzig
CTDEP
Water Compliance Unit
79 Elm Street
Hartford, CT 06106-1632
(860) 424-3746 (phone)
(860) 424-4067 (fax)
ROBERT.NORWOOD@PO.STATE.CT.US
Maine
David Wright
Maine DEP
Sludge Residuals Unit
State House, Station 17
Augusta, ME 04333
(207) 287-2651 (phone)
(207) 287-7826 (fax)
DAVID.W.WRIGHT@STATE.ME.US
Massachusetts
Larry Polese
MA DEP
50 Route 20
Millbury, MA01527
(508) 752-8648 (phone)
(508) 755-9253 (fax)
LARRY.POLESE@STATE.MA.US
New Hampshire
Michael Rainey
Sludge & Septage Management
NHDES
6 Hazen Drive
Concord, NH 03301
(603) 271-2818 (phone)
(603) 271-7894 (fax)
M_RAINEY@DES.STATE.NH.US
Rhode Island
Warren Towne, P.E.
Supervising Sanitary Engineer
Rl DEM, Office of Water Resources
235 Promenade St.
Providence, Rl 02908
(401) 222-6820 (phone)
(401) 222-6177 (fax)
Vermont
Cathy Jamieson
VTDept. of Environmental Conservation
103 S. Main St., Sewing Bldg.
Waterbury,VT 05676
(802) 241-3831 (phone)
(802) 241-2596 (fax)
CATHYJ@DEC.ANR.STATE.VT.US
Region 2
New Jersey
Mary Jo M. Aiello, Chief
Bureau of Pretreatmentand Residuals
Watershed Permitting Element, DWQ
NJDEP
P.O. Box 029
Trenton, NJ 08625-0029
(609) 633-3823 (phone)
(609) 984-7938 (fax)
MAIELLO@DEP.STATE.NJ.US
New York
Sally J. Rowland, Ph.D., PE
NY Dept. of Environmental Conservation
Division of Solid and Hazardous Materials
50 Wolf Road, Room 212
Albany, NY 12233-7253
(518) 457-3966 (phone)
(518) 457-1283 (fax)
SJROWLAN@GW.DEC.STATE.NY.US
Puerto Rico
Robert Allada
Water Quality Area
Environmental Quality Board
PO Box 11488
Santurce,PR00916
(787) 767-8073 (phone)
Virgin Islands
Leonardo. Reed, Jr.
Environmental Protection Division
Department of Planning & Natural Resources
396-1 Foster Plaza
St. Thomas, VI 00802
(340) 777-4577 (phone)
108
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Region 3
Delaware
Steve Rohm
DEDNREC
P.O. Box 1401
89 Kings Highway
Dover, DE19903
(302) 739-5731 (phone)
(302) 739-3491 (fax)
SROHM@DNREC.STATE.DE.US
District of Columbia
Jeruselem Bekele
Water Quality Control Branch
Department of Health
2100 MLK Jr. Avenue SE #203
Washington, DC 20020
(202)645-6617
Maryland
HussainAlhija, Chief
Design & Certification Division
Maryland Department of the Environment
2500 Broening Highway
Baltimore, MA 21224
(410)631-3375
(410)631-3842
Martha Hynson
MD Dept. of the Environment
2500 Broening Hwy
Baltimore, MD 21224
(410)631-3375 (phone)
(410)631-3321 (fax)
Pennsylvania
DeniseUzupis
Bureau of Water Quality Protection
P.O. Box8774
RCSUB 11th Floor
Harrisburg, PA 17105-8774
(717) 787 7381 (phone)
(717) 772-5156 (fax)
duzupis@state.pa.us
Virginia
CalM. (C.M.) Sawyer
VA Dept. of Health
Division of Wastewater Engineering
Box2448
Richmond, VA 23218
(804) 786-1755 (phone)
(804) 371-2891 (fax)
CSAWYER@VDH.STATE.VA.US
Lily Choi
VADEQ
P.O. 60x11143
Richmond, VA23230-1143
(804) 698-4054 (phone)
(804) 698-4032 (fax)
YCHOI@DEQ.STATE.VA.US
West Virginia
Clifford 6rowning
WVDEP
Office of Water Resources
1201 Greenbrier Street
Charleston, WV25311
(304) 558-4086 (phone)
(304) 558-5903 (fax)
Region 4
Alabama
L. Cliff Evans
Municipal 6ranch, Water Division
AL Dept. of Environmental Management
P.O. 60x301463
Montgomery, AL 36130-1463
(334) 271-7816 (phone)
(334) 279-3051 (fax)
LCE@ADEM.STATE.ALUS
Florida
Maurice 6arker
Domestic Wastewater, Section MS #3540
Florida Department of Environmental Protection
Twin Towers Office 6ldg, 2600 6lair Stone Road
Tallahassee, FL 32399-2400
(850) 922-4295 (phone)
(850) 921-6385 (fax)
8ARKER_M@DEP.STATE.FLUS
Georgia
Sam Shepard/Nancy Prock
Municipal Permitting Program- Environmental
Protection Division
GADNR
4244 International Pkwy, Suite 110
Atlanta, GA 30354
(404) 656-4708 (phone)
(404) 362-2680 (phone)
(404) 362-2691 (fax)
NANCY_PROCK@MAILDNR.STATE.GA.US
109
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Kentucky
Mark Grim/Bob Bickner
Solid Waste Branch, Division of Waste Manage-
ment
KY Department of Natural Resources and Environ-
mental Protection
Frankfort Office Park
14ReillyRoad
Frankfort, KY40601
(502) 564-6716 (phone)
(502) 564-4049 (fax)
CRIM@NRDEP.NR.STATE.KY.US
BICKNER@NRDEP.NR.STATE.KY.US
Art Curtis
Facilities Construction Branch, Division of Water
Kentucky Department of Natural Resources and
Environmental Protection Cabinet
Frankfort Office Park, 14 Reilly Road
Frankfort, KY 40601
(502) 564-4310 (phone)
(502) 564-4245 (fax)
CURTIS@NRDEP.NR.STATE.KY.US
Mississippi
Glenn Odom, P.E.
MSDEQ
Office of Pollution Control
P.O. Box10385
Jackson, MS 39289-0385
(601)961-5159 (phone)
(601) 961-5376 (fax)
GLENN_ODEM@DEQ.STATE.MS.US
North Carolina
Dennis Ramsey
Division of Water Quality
NC Department of Environment and Natural
Resources
P.O. Box29535
512 N.Salisbury Street
Raleigh, NC 27626-0535
(919) 733-5083 ext. 528 (phone)
(919) 733-0719 (fax)
DENNIS_RAMSEY@H20.ENR.STATE.NC.US
Kim H. Colson
Division of Water Quality
NC Department of Environment and Natural
Resources
P.O. 60x29535
512 N.Salisbury Street
Raleigh, NC 27626-0535
(919) 733-5083 (phone)
(919) 733-0719 (fax)
KIM COLSON@H2O.ENR.STATE.NC.US
South Carolina
Michael Montebello
Domestic Wastewater Division
SC Dept. of Health & Environment
2600 Bull Street
Columbia, SC 29201
(803) 734-5226 (phone)
(803) 734-5216 (fax)
MONTEBMJ@COLUM632.DHEC.STATE.SC.US
Tennessee
John McClurkan/RogerLemaster
Div. of Water Pollution Control
TNDEC
401 Church Street, Sixth Floor Annex
Nashville, TN 37243-1534
(615) 532-0625 (phone)
(615) 532-0603 (fax)
JMCCLURKAN@MAILSTATE.TN.US
Region 5
Illinois
S. Alan Keller
ILEPA
DWPC, Permits Section
P.O. 60x19276
1021 N. Grand Avenue, East
Springfield, IL62794-9276
(217) 782-0610 (phone)
(217) 782-9891 (fax)
EPA1185@EPA.STATE.ILUS
Indiana
Dennis Lasiter, Chief
Land Use Section
IN DEM
P.O. 60x6015
1 DON. Senate Avenue
Indianapolis, IN 46206-6015
(317) 232-8732 (phone)
(317) 232-3403 (fax)
DLASITER@DEM.STATE.IN.US
Michigan
6ob 6abcock
Chief, Pretreatmentand 6iosolids Unit
MIDEQ
Surface WQ Div., Permits Section
Knapp's Office Center, Second Floor
300 S. Washington Square
P.O. 60x30273
Lansing, Ml 48909-7773
(517) 373 8566 (phone)
(517) 373 2040 (fax)
6A6COCKR@STATE.MI.US
110
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Grace Scott
(517) 335-4107 (phone)
SCOTTG@STATE.MI.US
Minnesota
JorjaDuFresne
WQ Div., Point Source Section
MN Pollution Control Agency
520 Lafayette Road
St. Paul, MN 55155-4194
(612) 296-9292 (phone)
(612) 297-8683 (fax)
JORJA.DUFRESNE@PCA.STATE.MN.US
Ohio
Brad Gallant
Division of Surface Water
Ohio EPA
P.O. Box 1049
1800 Watermark Drive
Columbus, OH 43216-0149
(614) 644-2001 (phone)
(614) 644-2329 (fax)
BRAD@GALLANT@EPA.STATE.OHIO.US
Annette De Havilland
Division of Solid & Infectious Waste Mgmt.
Ohio EPA
P.O. Box1049
Columbus, OH 43216-1049
(614) 644-2621 (phone)
(614) 728-5315 (fax)
ANNETTE.DEHAVILLAND@EPA.STATE.OH.US
Wisconsin
GregKester(WT/2)
WIDNR
Bureau of Watershed Mgmt., Point Source
Section
101 South Webster Street
Madison, Wl 53707
(608) 267 7611 (phone)
(608) 267 7664 (fax)
KESTEG@DNR.STATE.WI.US
Region 6
Arkansas
Keith Brown, P.E.
Manager, State Permits Branch
Water Division
AR Department of Pollution Control and Ecology
P.O. Box8913
Little Rock, AR 72219
(501) 682-0648 (phone)
(501) 682-0910 (fax)
BROWNK@ADEQ.STATE.AR.US
Jamal Solaimanian, Ph.D
AR Department of Pollution Control and Ecology
P.O. Box8913
Little Rock, AR 72219-8913
(501) 682-0648 (phone)
(501) 682-0910 (fax)
JAMAL@ADEQ.STATE.AR.US
Louisiana
J. Kilren Vidrine
Water Pollution Control Division
Louisiana Department of Environmental Quality
P.O. 60x82215
6aton Rouge, LA 70884-2215
(504) 765-0534 (phone)
(504) 765-0635 (fax)
KILRENV@DEQ.STATE.LA.US
Hoa Van Nguyen
Solid Waste Division
Louisiana Department of Environmental Quality
P.O. 60x82178
6aton Rouge, LA 70884-2178
(504) 765-0249 (phone)
(504) 765-0299 (fax)
HOAVAN_N@DEQ.STATE.LA.US
Yolunda Righteous
Solid Waste Division
LADEQ
P.O. 60x82178
6aton Rouge, LA 70884-2178
(504) 765-0249 (phone)
YOLUNDAR@DEQ.STATE.LA.US
NewMexico
Jim Davis
NMED Surface Water Quality 6ureau
NM Environment Department
P.O. 60x26110
Santa Fe, NM 87502
Oklahoma
Danny Hodges
WaterQuality Division
OK Dept. of Environmental Quality
1000 NE Tenth Street
Oklahoma City, OK 73117-1299
(405) 271-5205 (phone)
(405) 271-7339 (fax)
DANNY.HODGES@DEQMAILSTATE.OK.US
111
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Texas
Paul Curtis
TX Natural Resource Conservation Commission
P.O. Box 13087
Austin, TX 78711-3087
(512) 239-4580 (phone)
(512) 239-4750 (fax)
PCURTIS@TNRCD.STATE.TX.
Region 7
Iowa
Billy Chen
IA Dept. of Water, Air & Waste Mgmt.
Henry A. Wallace Building
900 East Grand
DesMoines, IA50319
(515) 281-4305 (phone)
(515) 281-8895 (fax)
Kansas
Mark Gerard
Kansas Dept. of Health & Environment
Forbes Field Building 283
Topeka,KS 66620-0001
(785) 296-5520 (phone)
(785) 296-5509 (fax)
Missouri
Ken Arnold
MODNR
P.O. Box 176
205 Jefferson Street
Jefferson City, MO 65102
(573) 751-6825 (phone)
(573) 526-5797 (fax)
Nebraska
Rudy Fiedler
Permits and Compliance
NEDEQ
Suite 400 The Atrium
1200 N. Street, P.O. Box 98922
Lincoln, NE 68509-8922
(402)471-4239
(402)471-2909
DEQ118@MAILDEQ.STATE.NE.US
Region 8
Colorado
Lori Tucker
Water Quality Control Division
CO Dept. of Public Health & Environment
4300 Cherry Creek Drive South
Denver, CO 80246-1530
(303) 692-3613 (phone)
(303) 782-0390 (fax)
LORI.TUCKER@STATE.CO.US
Montana
Paul LeVigne
MT Dept of Environmental Quality
Technical & Financial Assistance Bureau
Metcalf Building
Helena, MT 59620
(406) 444-6697 (phone)
(406) 444 6836 (fax)
PLAVIGNE@MT.GOV
North Dakota
Gary Bracht
Environmental Health Section
Division of Water Quality
ND Dept. of Health
1200 Missouri Ave.
P.O. Box5520
Bismarck, ND 58505-5520
(701) 221-5210 (phone)
(701)328-5200 (fax)
CCMAILGBRACHT@RANCH.STATE.ND.US
South Dakota
Eric Meintsma
SD Dept. of Environment and Natural Resources
Joe Foss Building
523 East Capital
Pierre, SD 57501-3181
(605) 773-3351 (phone)
(605) 773 5286 (fax)
ERICM@DENR.STATE.SD.US
Utah
Mark Schmitz
UTDEQ
Division of Water Quality
28814 1460 Street West
Salt Lake City, UT 84114-4870
(801) 538-6097 (phone)
(801) 538-6016 (fax)
MSCHMITZ@DEQ.STATE.UT.US
Wyoming
Larry Robinson
WYDEQ
HerschlerBldg., 4th Floor West
122 W. 25th Street
Cheyenne, WY 82002
(307) 777-7075 (phone)
(307) 777-5973 (fax)
LROBIN@MISSC.STATE.WY.US
112
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Region 9
Arizona
Nicole Heffington
AZDEQ
3033 N. Central
Phoenix, AZ 85012
(602) 207-4158 (phone)
(602) 207-2383 (fax)
HEFFINGTON.NICOLE@EV.STATE.AZ.US
JillGalaway
AZDEQ
3033 N. Central
Phoenix, AZ 85012
(602) 207-4125 (phone)
(602) 207-2383 (fax)
GALAWAY.JILL@EV.STATE.AZ.US
California
Todd Thompson, P.E.
Division of Water Quality
State Water Resources Control Board
PO Box 944213
Sacramento, CA 94244-2130
(916) 657-0577 (phone)
(916) 657-2388 (fax)
THOMT@DWQ.SWRCB.CA.GOV
Michael Wochnick
CA Integrated Waste Mgmt. Board
Remediation, Closure, and Technical Services
Branch
8800 Cal Centre Drive
Sacramento, CA 95826
(916) 255-1302 (phone)
MWOCHNIC@CIWMB.CA.GOV
Bill Orr
CA Integrated Waste Mgmt. Board
8800 Cal Centre Drive
Sacramento, CA 95826
BORR@MRT.CIWMB.CA.GOV
Hawaii
Dennis Tulang/Gayle Takasaki, Engineer
Wastewater Branch
HI Dept. of Health
P.O. Box3378
Honolulu, HI 96813
(808) 586-4294 (phone)
(808) 586-4370 (fax)
GTAKASAKI@EHA.HEALTH.STATE.HI.US
Nevada
BillCoughlin
NVDEP
333 West Nye Lane
Carson City, NV 89706-0866
(702) 687-4670 ext. 3153 (phone)
(702) 687-5856 (fax)
Region 10
Alaska
Kris McCumby
Solid Waste Program
AK Dept. of Environmental Conservation
610 University Avenue
Fairbanks, AK 99709-3643
(907) 451-2134 (phone)
(907) 451-2187 (fax)
KMCCUMBY@ENVIRCON.STATE.AK.US
Idaho
RickHuddleston
DEQ Construction & Permits Bureau
IDDHW
1410 North Hilton
Boise, ID 83706-1253
(208) 373-0501 or (208) 373-0502 (phone)
(208) 373-0576 (fax)
RHUDDLES@DEQ..STATE.ID.US
Oregon
MarkCullington,Biosolids Coordinator
DEQ Water Quality Division, Land Application &
Licensing
Oregon Department of Environmental Quality
811 S.W. Sixth Avenue
Portland, OR 97204
PHONE: 503/229-6442; 229-5411; FAX:
503-229-5408
NET:cullington.mark@deq.state.or.us
Washington
Kyle Dorsey
Biosolids Coordinator
Washington State Department of Ecology
PO Box47600
Olympia, WA 98504-7600
(360) 407-6107 (phone)
(360) 407-7157 or-6102 (fax)
KDOR461 @ECY.WA.GOV
113
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USEPA - 2003
Robert K. Bastian, Senior Environmental Scientist
U.S. EPA (Biologist)
Office of Wastewater Management (4204M)
Ariel Rios BIdg. Rm.7220B ICC BIdg.
1200 Pennsylvania Ave., NW
Washington, DC 20460
Tele:
Fax: 202-501-2397
e-mail: Bastian.Robert@epa.gov
Robert B. Brobst, PE
Environmental Engineer
Biosolids Program Manager
USEPA-Region 8 (P2-W-P)
999 18th Street, Suite 500
Denver, CO 80202-2466
303-312-6129
Brobst.Bob@epa.gov
Don Brown
Environmental Engineer
USEPA-NRMRL
26 West Martin Luther King Drive
Cincinnati, OH 45268
513-569-7630
Brown.DonaId@epa.gov
Dr. John Cicmanec (MS-G75)
Veterinarian
USEPA-NRMRL-TTSD
26 W Martin Luther King Drive
Cincinnati, OH 45268
513-569-7481
Cicmanec.John@epa.gov
Dr. G.ShayFout(MS-320)
Viro legist
USEPA-NERL
26 W Martin Luther King Drive
Cincinnati, OH 45268
513-569-7387
Fout.Shay@epa.gov
Dr. Hugh Mainzer
Environmental Health Services Branch
Emergency & Environmental Health Services Division
CDC, National Center for Environmental Health
4770 Highway, NE
Mailstop F-29
Atlanta, GA 30341-3724
770-488-3138
hmm2@cdc.gov
Mark Meckes (MS-489)
Microbiologist
USEPA-NRMRL
26 W Martin Luther King Drive
Cincinnati, OH 45268
513-569-7348
Meckes.Mark@epa.gov
Dr. Frank W. Schaefer, 111
Parasitologist
USEPA-NERL
26 W Martin Luther King Drive
Cincinnati, OH 45268
513-569-7222
Schaefer.Frank@epa.gov
Dr. Stephen A. Schaub (4304T)
Virologist
USEPA-OST-HECD-HRAB
Ariel Rios Building
1200 Pennsylvania Avenue, N. W.
Washington, DC 20460
202-566-1126
Schaub.Stephen@EPA.GOV
Dr. Jim Smith (MS-G77)
Chair & Senior Environmental Engineer
USEPA-NRMRL-TTSD
26 W Martin Luther King Drive
Cincinnati, OH 45268
513-569-7355
Smith.James@epa.gov
114
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Appendix B
Subpart D of the Part 503 Regulation
[Code of Federal Regulations]
[Title 40, Volume 21, Parts 425 to 699]
[Revised as of July 1,1998]
From the U.S. Government Printing Office via GPO Access
[CITE: 40CFR503.30]
TITLE 40 - PROTECTION
ENVIRONMENT
OF
CHAPTER I - ENVIRONMENTAL
PROTECTION AGENCY (Continued)
PART 503 - STANDARDS FOR THE USE OR
DISPOSAL OF SEWAGE SLUDGE-Table of
Contents
Subpart D-Pathogens and Vector
Attraction Reduction
Sec. 503.30 Scope.
(a) This subpart contains the requirements for a sewage
sludge to be classified either Class A or Class B with re-
spect to pathogens.
(b) This subpart contains the site restrictions for land on
which a Class B sewage sludge is applied.
(c) This subpart contains the pathogen requirements for
domestic septage applied to agricultural land, forest, or a
reclamation site.
(d) This subpart contains alternative vector attraction
reduction requirements for sewage sludge that is applied
to the land or placed on a surface disposal site.
Sec. 503.31 Special definitions.
(a) Aerobic digestion is the biochemical decomposition
of organic matter in sewage sludge into carbon dioxide
and water by microorganisms in the presence of air.
(b) Anaerobic digestion is the biochemical decomposi-
tion of organic matter in sewage sludge into methane gas
and carbon dioxide by microorganisms in the absence of
air.
(c) Density of microorganisms is the number of microor-
ganisms per unit mass of total solids (dry weight) in the
sewage sludge.
(d) Land with a high potential for public exposure is land
that the public uses frequently. This includes, but is not
limited to, a public contact site and a reclamation site lo-
cated in a populated area (e.g., a construction site located
in a city).
(e) Land with a low potential for public exposure is land
that the public uses infrequently. This includes, but is not
limited to, agricultural land, forest, and a reclamation site
located in an unpopulated area (e.g., a strip mine located
in a rural area).
(f) Pathogenic organisms are disease-causing organ-
isms. These include, but are not limited to, certain bacte-
ria, protozoa, viruses, and viable helminth ova.
(g) pH means the logarithm of the reciprocal of the hy-
drogen ion concentration.
(h) Specific oxygen uptake rate (SOUR) is the mass of
oxygen consumed per unit time per unit mass of total sol-
ids (dry weight basis) in the sewage sludge.
(i) Total solids are the materials in sewage sludge that
remain as residue when the sewage sludge is dried at 103
to 105 degrees Celsius.
(j) Unstabilized solids are organic materials in sewage
sludge that have not been treated in either an aerobic or
anaerobic treatment process.
(k) Vector attraction is the characteristic of sewage sludge
that attracts rodents, flies, mqsquitos, or other organisms
capable of transporting infectious agents.
(I) Volatile solids is the amount of the total solids in sew-
age sludge lost when the sewage sludge is combusted at
550 degrees Celsius in the presence of excess air.
115
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Sec. 503.32 Pathogens.
(a) Sewage sludge-Class A. (1) The requirement in Sec.
503.32(a)(2) and the requirements in either Sec.
503.32(a)(3), (a) (4), (a) (5), (a) (6) (a)(7) or (a) (8) shall be
met for a sewage sludge to be classified Class A with re-
spect to pathogens.
(2) The Class A pathogen requirements in Sec. 503.32
(a)(3) through (a)(8) shall be met either prior to meeting or
at the same time the vector attraction reduction require-
ments in Sec. 503.33, except the vector attraction reduc-
tion requirements in Sec. 503.33 (b)(6) through (b)(8), are
met.
(3) Class A-Alternative 1. (i) Either the density of fecal
coliform in the sewage sludge shall be less than 1000 Most
Probable Number per gram of total solids (dry weight ba-
sis), or the density of Salmonella sp. bacteria in the sew-
age sludge shall be less than three Most Probable Num-
ber per four grams of total solids (dry weight basis) at the
time the sewage sludge is used or disposed; at the time
the sewage sludge is prepared for sale or give away in a
bag or other container for application to the land; or at the
time the sewage sludge or material derived from sewage
sludge is prepared to meet the requirements in Sec. 503.10
(ii) The temperature of the sewage sludge that is used
or disposed shall be maintained at a specific value for a
period of time.
(A) When the percent solids of the sewage sludge is
seven percent or higher, the temperature of the sewage
sludge shall be 50 degrees Celsius or higher; the time
period shall be 20 minutes or longer; and the temperature
and time period shall be determined using equation (2),
except when small particles of sewage sludge are heated
by either warmed gases or an immiscible liquid.
sludge is 50 degrees Celsius or higher; and the time pe-
riod is 30 minutes or longer, the temperature and time pe-
riod shall be determined using equation (3).
D =
131,700,000
Eq. (2)
0.14001
Where,
D=time in days.
t=temperature in degrees Celsius.
(B) When the percent solids of the sewage sludge is
seven percent or higher and small particles of sewage
sludge are heated by either warmed gases or an immis-
cible liquid, the temperature of the sewage sludge shall be
50 degrees Celsius or higher; the time period shall be 15
seconds or longer; and the temperature and time period
shall be determined using equation (2).
(C) When the percent solids of the sewage sludge is
less than seven percent and the time period is at least 15
seconds, but less than 30 minutes, the temperature and
time period shall be determined using equation (2).
(D) When the percent solids of the sewage sludge is
less than seven percent; the temperature of the sewage
D =
50,070,000
100.1400t
Eq.3
Where,
D=time in days.
t=temperature in degrees Celsius.
(4) Class A - Alternative 2. (i) Either the density of fecal
coliform in the sewage sludge shall be less than 1000 Most
Probable Number per gram of total solids (dry weight ba-
sis), or the density of Salmonella sp. bacteria in the sew-
age sludge shall be less than three Most Probable Num-
ber per four grams of total solids (dry weight basis) at the
time the sewage sludge is used or disposed; at the time
the sewage sludge is prepared for sale or give away in a
bag or other container for application to the land; or at the
time the sewage sludge or material derived from sewage
sludge is prepared to meet the requirements in Sec. 503.10
(b), (c), (e), or (f).
(ii)(A) The pH of the sewage sludge that is used or dis-
posed shall be raised to above 12 and shall remain above
12 for 72 hours.
(B) The temperature of the sewage sludge shall be above
52 degrees Celsius for 12 hours or longer during the pe-
riod that the pH of the sewage sludge is above 12.
(C) At the end of the 72 hour period during which the pH
of the sewage sludge is above 12, the sewage sludge shall
be air dried to achieve a percent solids in the sewage sludge
greater than 50 percent.
(5) Class A - Alternative 3. (i) Either the density of fecal
coliform in the sewage sludge shall be less than 1000 Most
Probable Number per gram of total solids (dry weight ba-
sis), or the density of Salmonella sp. bacteria in sewage
sludge shall be less than three Most Probable Number per
four grams of total solids (dry weight basis) at the time the
sewage sludge is used or disposed; at the time the sew-
age sludge is prepared for sale or give away in a bag or
other container for application to the land; or at the time
the sewage sludge or material derived from sewage sludge
is prepared to meet the requirements in Sec. 503.10 (b),
(c),(e),or(f).
(ii)(A) The sewage sludge shall be analyzed prior to
pathogen treatment to determine whether the sewage
sludge contains enteric viruses.
(B) When the density of enteric viruses in the sewage
sludge prior to pathogen treatment is less than one Plaque-
forming Unit per four grams of total solids (dry weight ba-
sis), the sewage sludge is Class A with respect to enteric
viruses until the next monitoring episode for the sewage
sludge.
(C) When the density of enteric viruses in the sewage
sludge prior to pathogen treatment is equal to or greater
116
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than one Plaque-forming Unit per four grams of total sol-
ids (dry weight basis), the sewage sludge is Class A with
respect to enteric viruses when the density of enteric vi-
ruses in the sewage sludge after pathogen treatment is
less than one Plaque-forming Unit per four grams of total
solids (dry weight basis) and when the values or ranges of
values for the operating parameters for the pathogen treat-
ment process that produces the sewage sludge that meets
the enteric virus density requirement are documented.
(D) After the enteric virus reduction in paragraph
(a)(5)(ii)(C) of this section is demonstrated for the patho-
gen treatment process, the sewage sludge continues to
be Class A with respect to enteric viruses when the values
for the pathogen treatment process operating parameters
are consistent with the values or ranges of values docu-
mented in paragraph (a)(5)(ii)(C)of this section.
(iii)(A) The sewage sludge shall be analyzed prior to
pathogen treatment to determine whether the sewage
sludge contains viable helminth ova.
(B) When the density of viable helminth ova in the sew-
age sludge prior to pathogen treatment is less than one
per four grams of total solids (dry weight basis), the sew-
age sludge is Class A with respect to viable helminth ova
until the next monitoring episode for the sewage sludge.
(C) When the density of viable helminth ova in the sew-
age sludge prior to pathogen treatment is equal to or greater
than one per four grams of total solids (dry weight basis),
the sewage sludge is Class A with respect to viable helm-
inth ova when the density of viable helminth ova in the
sewage sludge after pathogen treatment is less than one
per four grams of total solids (dry weight basis) and when
the values or ranges of values for the operating param-
eters for the pathogen treatment process that produces
the sewage sludge that meets the viable helminth ova den-
sity requirement are documented.
(D) After the viable helminth ova reduction in paragraph
(a)(5)(iii)(C) of this section is demonstrated for the patho-
gen treatment process, the sewage sludge continues to
be Class A with respect to viable helminth ova when the
values for the pathogen treatment process operating pa-
rameters are consistent with the values or ranges or val-
ues documented in paragraph (a)(5)(iii)(C) of this section.
(6) Class A - Alternative 4. (i) Either the density of fecal
coliform in the sewage sludge shall be less than 1000 Most
Probable Number per gram of total solids (dry weight ba-
sis), or the density of Salmonella sp. bacteria in the sew-
age sludge shall be less than three Most Probable Num-
ber per four grams of total solids (dry weight basis) at the
time the sewage sludge is used or disposed; at the time
the sewage sludge is prepared for sale or give away in a
bag or other container for application to the land; or at the
time the sewage sludge or material derived from sewage
sludge is prepared to meet the requirements in Sec. 503.10
(b), (c), (e), or (f).
(ii) The density of enteric viruses in the sewage sludge
shall be less than one Plaque-forming Unit per four grams
of total solids (dry weight basis) at the time the sewage
sludge is used or disposed; at the time the sewage sludge
is prepared for sale or give away in a bag or other con-
tainer for application to the land; or at the time the sewage
sludge or material derived from sewage sludge is prepared
to meet the requirements in Sec. 503.10 (b), (c), (e), or (f),
unless otherwise specified by the permitting authority.
(iii) The density of viable helminth ova in the sewage
sludge shall be less than one per four grams of total solids
(dry weight basis) at the time the sewage sludge is used
or disposed; at the time the sewage sludge is prepared for
sale or give away in a bag or other container for applica-
tion to the land; or at the time the sewage sludge or mate-
rial derived from sewage sludge is prepared to meet the
requirements in Sec. 503.10 (b), (c), (e), or (f), unless oth-
erwise specified by the permitting authority.
(7) Class A - Alternative 5. (i) Either the density of fecal
coliform in the sewage sludge shall be less than 1000 Most
Probable Number per gram of total solids (dry weight ba-
sis), or the density of Salmonella sp. bacteria in the sew-
age sludge shall be less than three Most Probable Num-
ber per four grams of total solids (dry weight basis) at the
time the sewage sludge is used or disposed; at the time
the sewage sludge is prepared for sale or given away in a
bag or other container for application to the land; or at the
time the sewage sludge or material derived from sewage
sludge is prepared to meet the requirements in Sec.
503.10 (b), (c), (e), or (0.
(ii) Sewage sludge that is used or disposed shall be
treated in one of the Processes to Further Reduce Patho-
gens described in Appendix B of this part.
(8) Class A - Alternative 6. (i) Either the density of fecal
coliform in the sewage sludge shall be less than 1000 Most
Probable Number per gram of total solids (dry weight ba-
sis), or the density of Salmonella, sp. bacteria in the sew-
age sludge shall be less than three Most Probable Num-
ber per four grams of total solids (dry weight basis) at the
time the sewage sludge is used or disposed; at the time
the sewage sludge is prepared for sale or given away in a
bag or other container for application to the land; or at the
time the sewage sludge or material derived from sewage
sludge is prepared to meet the requirements in Sec.
503.10 (b), (c), (e), or (f).
(ii) Sewage sludge that is used or disposed shall be
treated in a process that is equivalent to a Process to Fur-
ther Reduce Pathogens, as determined by the permitting
authority.
(b) Sewage sludge-Class B. (1)(i) The requirements in
either Sec. 503.32(b)(2), (b)(3), or (b)(4) shall be met for
a sewage sludge to be classified Class B with respect to
pathogens.
(ii) The site restrictions in Sec. 503.32(b)(5) shall be met
when sewage sludge that meets the Class B pathogen
requirements in Sec. 503.32(b)(2), (b)(3), or (b)(4) is ap-
plied to the land.
117
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(2) Class B - Alternative 1. (i) Seven samples of the sew-
age sludge shall be collected at the time the sewage sludge
is used or disposed.
(ii) The geometric mean of the density of fecal coliform
in the samples collected in paragraph (b)(2)(i) of this
section shall be less than either 2,000,000 Most Probable
Number per gram of total solids (dry weight basis) or
2,000,000 Colony Forming Units per gram of total solids
(dry weight basis).
(3) Class B - Alternative 2. Sewage sludge that is used
or disposed shall be treated in one of the Processes to
Significantly Reduce Pathogens described in Appendix B
of this part.
(4) Class B - Alternative 3. Sewage sludge that is used
or disposed shall be treated in a process that is equivalent
to a Process to Significantly Reduce Pathogens, as deter-
mined by the permitting authority.
(5) Site restrictions, (i) Food crops with harvested parts
that touch the sewage sludge/soil mixture and are totally
above the land surface shall not be harvested for 14 months
after application of sewage sludge.
(ii) Food crops with harvested parts below the surface of
the land shall not be harvested for 20 months after appli-
cation of sewage sludge when the sewage sludge remains
on the land surface for four months or longer prior to incor-
poration into the soil.
(iii) Food crops with harvested parts below the surface
of the land shall not be harvested for 38 months after ap-
plication of sewage sludge when the sewage sludge re-
mains on the land surface for less than four months prior
to incorporation into the soil.
(iv) Food crops, feed crops, and fiber crops shall not be
harvested for 30 days after application of sewage sludge.
(v) Animals shall not be allowed to graze on the land for
30 days after application of sewage sludge.
(vi) Turf grown on land where sewage sludge is applied
shall not be harvested for one year after application of the
sewage sludge when the harvested turf is placed on either
land with a high potential for public exposure or a lawn,
unless otherwise specified by the permitting authority.
(vii) Public access to land with a high potential for public
exposure shall be restricted for one year after application
of sewage sludge.
(viii) Public access to land with a low potential for public
exposure shall be restricted for 30 days after application
of sewage sludge.
(c) Domestic septage. (1) The site restrictions in Sec.
503.32 (b)(5) shall be met when domestic septage is ap-
plied to agricultural land, forest, or a reclamation site; or
(2) The pH of domestic septage applied to agricultural land,
forest, or a reclamation site shall be raised to 12 or higher
by alkali addition and, without the addition of more alkali,
shall remain at 12 or higher for 30 minutes and the site
restrictions in Sec. 503.32 (b)(5)(i) through (b)(5)(iv) shall
be met.
Sec. 503.33 Vector attraction reduction.
(a)(1) One of the vector attraction reduction requirements
in Sec. 503.33 (b)(1) through (b)(10) shall be met when
bulk sewage sludge is applied to agricultural land, forest,
a public contact site, or a reclamation site.
(2) One of the vector attraction reduction requirements
in Sec. 503.33 (b)(1) through (b)(8) shall be met when bulk
sewage sludge is applied to a lawn or a home garden.
(3) One of the vector attraction reduction requirements
in Sec. 503.33 (b)(1) through (b)(8) shall be met when sew-
age sludge is sold or given away in a bag or other con-
tainer for application to the land.
(4) One of the vector attraction reduction requirements
in Sec. 503.33 (b)(1) through (b)(11) shall be met when
sewage sludge (other than domestic septage) is placed
on an active sewage sludge unit.
(5) One of the vector attraction reduction requirements
in Sec. 503.33 (b)(9), (b)(10), or (b)(12) shall be met when
domestic septage is applied to agricultural land, forest, or
a reclamation site and one of the vector attraction reduc-
tion requirements in Sec. 503.33 (b)(9) through (b)(12) shall
be met when domestic septage is placed on an active sew-
age sludge unit.
(b)(1) The mass of volatile solids in the sewage sludge
shall be reduced by a minimum of 38 percent (see calcu-
lation procedures in "Environmental Regulations and Tech-
nology - Control of Pathogens and Vector Attraction in
Sewage Sludge," EPA/625/R-92/013,1992, U.S. Environ-
mental Protection Agency, Cincinnati, Ohio 45268).
(2) When the 38 percent volatile solids reduction require-
ment in Sec. 503.33 (b)(1) cannot be met for an anaerobi-
cally digested sewage sludge, vector attraction reduction
can be demonstrated by digesting a portion of the previ-
ously digested sewage sludge anaerobically in the labora-
tory in a bench-scale unit for 40 additional days at a tem-
perature between 30 and 37 degrees Celsius. When at
the end of the 40 days, the volatile solids in the sewage
sludge at the beginning of that period is reduced by less
than 17 percent, vector attraction reduction is achieved.
(3) When the 38 percent volatile solids reduction require-
ment in Sec. 503.33 (b)(1) cannot be met for an aerobi-
cally digested sewage sludge, vector attraction reduction
can be demonstrated by digesting a portion of the previ-
ously digested sewage sludge that has a percent solids of
two percent or less aerobicaliy in the laboratory in a bench-
scale unit for 30 additional days at 20 degrees Celsius.
When at the end of the 30 days, the volatile solids in the
sewage sludge at the beginning of that period is reduced
118
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by less than 15 percent, vector attraction reduction is
achieved.
(4) The specific oxygen uptake rate (SOUR) for sewage
sludge treated in an aerobic process shall be equal to or
less than 1.5 milligrams of oxygen per hour per gram of
total solids (dry weight basis) at a temperature of 20 de-
grees Celsius.
(5) Sewage sludge shall be treated in an aerobic pro-
cess for 14 days or longer. During that time, the tempera-
ture of the sewage sludge shall be higher than 40 degrees
Celsius and the average temperature of the sewage sludge
shall be higher than 45 degrees Celsius.
(6) The pH of sewage sludge shall be raised to 12 or
higher by alkali addition and, without the addition of more
alkali, shall remain at 12 or higher for two hours and then
at 11.5 or higher for an additional 22 hours.
(7) The percent solids of sewage sludge that does not
contain unstabilized solids generated in a primary waste-
water treatment process shall be equal to or greater than
75 percent based on the moisture content and total solids
prior to mixing with other materials.
(8) The percent solids of sewage sludge that contains
unstabilized solids generated in a primary wastewater treat-
ment process shall be equal to or greater than 90 percent
based on the moisture content and total solids prior to mix-
ing with other materials.
(i) Sewage sludge shall be injected below the surface
of the land.
(ii) No significant amount of the sewage sludge shall be
present on the land surface within one hour after the sew-
age sludge is injected.
(iii) When the sewage sludge that is injected below the
surface of the land is Class A with respect to pathogens,
the sewage sludge shall be injected below the land sur-
face within eight hours after being discharged from the
pathogen treatment process.
(10) (i) Sewage sludge applied to the land surface or
placed on a surface disposal site shall be incorporated into
the soil within six hours after application to or placement
on the land.
(ii) When sewage sludge that is incorporated into the
soil is Class A with respect to pathogens, the sewage sludge
shall be applied to or placed on the land within eight hours
after being discharged from the pathogen treatment pro-
cess.
(11) Sewage sludge placed on an active sewage sludge
unit shall be covered with soil or other material at the end
of each operating day.
(12) The pH of domestic septage shall be raised to 12 or
higher by alkali addition and, without the addition of more
alkali, shall remain at 12 or higher for 30 minutes.
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Appendix C
Determination of Volatile Solids Reduction by Digestion
Introduction
Under 40 CFR Part 503, the ability of sewage sludge to
attract vectors must be reduced when sewage sludge is
applied to the land or placed on a surface disposal site.
One way to reduce vector attraction is to reduce the vola-
tile solids in the sewage sludge by 38% or more (see Sec-
tion 8.2 of this document). Typically, volatile solids reduc-
tion is accomplished by anaerobic or aerobic digestion.
Volatile solids reduction also occurs under other circum-
stances, such as when sewage sludge is stored in an
anaerobic lagoon or is dried on sand beds. To give credit
for this extra loss in volatile solids, the regulation allows
the untreated sewage sludge to be compared with the
treated sewage sludge that leaves the treatment works,
which should account for all of the volatile solids reduction
that could possibly occur. For most processing sequences,
the processing steps downstream from the digester, such
as short-term storage or dewatering, have no influence on
volatile solids content. Consequently, the appropriate com-
parison is between the sewage sludge entering the digester
and the sewage sludge leaving the digester. The remain-
der of the discussion is limited to this circumstance, ex-
cept for the final section of this appendix, which compares
incoming sewage sludge with the sewage sludge leaving
the treatment works.
The Part 503 regulation does not specify a method for
calculating volatile solids reduction. Fischer (1984) ob-
served that the United Kingdom has a similar requirement
for volatile solids reduction for digestion (40%), but also
failed to prescribe a method for calculating volatile solids
reduction. Fischer has provided a comprehensive discus-
sion of the ways that volatile solids reduction may be cal-
culated and their limitations. He presents the following
equations for determining volatile solids reduction:
Full mass balance equation
Approximate mass balance equation
"Constant ash" equation
Van Kleeck equation
The full mass balance equation is the least restricted
approach but requires more information than is currently
collected at a wastewater treatment plant. The approxi-
mate mass balance equation assumes steady state con-
ditions. The "constant ash" equation requires the assump-
tion of steady state conditions as well as the assumption
that the ash input rate equals the ash output rate. The Van
Kleeck equation, which is the equation generally suggested
in publications originating in the United States (WPCF,
1968), is equivalent to the constant ash equation. Fischer
calculates volatile solids reduction using a number of ex-
amples of considerable complexity and illustrates that dif-
ferent methods frequently yield different results.
Fischer's paper is extremely thorough and is highly rec-
ommended for someone trying to develop a deep under-
standing of potential complexities in calculating volatile
solids reduction. However, it was not written as a guid-
ance document for field staff faced with the need to calcu-
late volatile solids reduction. The nomenclature is precise
but so detailed that it makes comprehension difficult. In
addition, two important troublesome situations that com-
plicate the calculation of volatile solids reduction - grit depo-
sition in digesters and decantate removal - are not explic-
itly discussed. Consequently, this presentation has been
prepared to present guidance that describes the major pit-
falls likely to be encountered in calculating percent volatile
solids reduction.
It is important to note that the calculation of volatile sol-
ids reduction is only as accurate as the measurement of
volatile solids content in the sewage sludge. The principal
cause of error is poor sampling. Samples should be repre-
sentative, covering the entire charging and withdrawal
periods. Averages should cover extended periods of time
during which changes in process conditions are minimal.
For some treatment, it is expected that periodic checks of
volatile solids reduction will produce results so erratic that
no confidence can be placed in them. In this case, ad-
equacy of stabilization can be verified by the method de-
scribed under Options 2 and 3 in Chapter 8 -periodically
batch digest anaerobically digested sewage sludge for 40
additional days at 30°C (86°F) to 37°C (99°F), or aero-
bically digested sewage sludge for 30 additional days at
20°C (68°F). If the additional VS reduction is less than
17% for the anaerobically digested sewage sludge or less
than 15% for the aerobically digested sewage sludge, the
sewage sludge is sufficiently stable (see Sections 8.3 and
8.4).
120
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Equations for FVSR
The equations for fractional volatile solids reduction
(FVSR) that will be discussed below are the same as those
developed by Fischer (1984), except for omission of his
constant ash equation. This equation gives identical re-
sults to the Van Kleeck equation so it is not shown. Fischer's
nomenclature has been avoided or replaced with simpler
terms. The material balance approaches are called meth-
ods rather than equations. The material balances are drawn
to fit the circumstances. There is no need to formalize the
method with a rigid set of equations.
In the derivations and calculations that follow, both VS
(total volatile solids content of the sewage sludge or
decantate on a dry solids basis) and FVSR are expressed
throughout as fractions to avoid the frequent confusion that
occurs when these terms are expressed as percentages.
"Decantate" is used in place of the more commonly used
"supernatant" to avoid the use of "s" in subscripts. Simi-
larly, "bottoms" is used in place of "sludge" to avoid use of
"s" in subscripts.
Method Full Mass Balance
The full mass balance method must be used when steady
conditions do not prevail over the time period chosen for
the calculation. The chosen time period must be substan-
tial, at least twice the nominal residence time in the di-
gester (nominal residence time equals average volume of
sludge in the digester divided by the average volumetric
flow rate. Note: when there is decantate withdrawal, vol-
ume of sewage sludge withdrawn should be used to cal-
culate the average volumetric flow rate). The reason for
the long time period is to reduce the influence of short-
term fluctuations in sewage sludge flow rates or composi-
tions. If input compositions have been relatively constant
for a long period of time, then the time period can be short-
ened.
An example where the full mass balance method would
be needed is where an aerobic digester is operated as
follows:
Started with the digester 1/4 full (time zero)
Raw sewage sludge is fed to the digester daily until
the digester is full
Supernatant is periodically decanted and raw sewage
sludge is charged into the digester until settling will
not occur to accommodate daily feeding (hopefully after
enough days have passed for adequate digestion)
Draw down the digester to about 1/4 full (final time),
discharging the sewage sludge to sand beds
The full mass balance is written as follows:
Sum of total volatile solids inputs in feed streams during
the entire digestion period = sum of volatile solids outputs
in withdrawals of decantate and bottoms + loss of volatile
solids + accumulation of volatile solids in the digester. (1)
Loss of volatile solids is calculated from Equation 1.
FVSR is calculated by Equation 2:
FVSR = loss in volatile solids
sum of volatile solids inputs (2)
The accumulation of volatile solids in the digester is the
final volume in the digester after the drawdown times final
volatile solids concentration less the initial volume at time
zero times the initial volatile solids concentration.
To properly determine FVSR by the full mass balance
method requires determination of all feed and withdrawal
volumes, initial and final volumes in the digester, and vola-
tile solids concentrations in all streams. In some cases,
which will be presented later, simplifications are possible.
Approximate Mass Balance Method
If volumetric inputs and outputs are relatively constant
on a daily basis, and there is no substantial accumulation
of volatile solids in the digester over the time period of the
test, an approximate mass balance (AMB) may be used.
The basic relationship is stated simply:
volatile solids input rate = volatile solids output rate + rate
of loss of volatile solids. (3)
The FVSR is given by Equation 2.
No Decantate, No Grit Accumulation (Problem 1)
Calculation of FVSR is illustrated for Problem 1 in Table
C-1, which represents a simple situation with no decantate
removal and no grit accumulation. An approximate mass
balance is applied to the digester operated under constant
flow conditions. Because no decantate is removed, the
volumetric flow rate of sewage sludge leaving the digester
equals the flow rate of sewage sludge entering the digester.
Applying Equations 3 and 2,
FYf = BYb + loss
Loss = 100(50-30) = 2000
FVSR = Loss
FY,
FVSR = 2000 = 0.40
(100) (50)
(4)
(5)
(6)
(7)
Nomenclature is given in Table C-1. Note that the calcu-
lation did not require use of the fixed solids concentra-
tions.
The calculation is so simple that one wonders why it is
so seldom used. One possible reason is that the input and
output volatile solids concentrations (Yf and Yb ) typically
will show greater coefficients of variation (standard) devia-
tion divided by arithmetic average) than the fractional vola-
tile solids (VS is the fraction of the sewage sludge solids
121
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Table C-1. Quantitative Information for Example Problems
1,2,3
Problem Statement Number
Parameter
Symbol
Units
Nominal Residence Time
Time period for averages
Feed Sludge
Volumetric flow rate
Volatile solids concentration
Fixed solids concentration
Fractional volatile solids
Mass flow rate of solids
Digested Sludge (Bottoms)
Volumetric flow rate
Volatile solids concentration
Fixed solids concentration
Fractional volatile solids
Mass flow rate of solids
Decantate
Volumetric flow rate
Volatile solids concentration
Fixed solids concentration
Fractional volatile solids
Mass flow rate of solids
6
F
Yf
Xf
vsf
Mf
B
Yb
xb
vsb
Mb
D
Yd
xd
VSd
Md
d
d
rrWd
kg/m3
kg/m3
kg/kg
kg/d
m3/d
kg/m3
kg/m3
kq/kq
kgV
rrWd
kg/m3
kg/m3
kg/kg
kg/d
20
60
100
50
17
0.746
6700
100
30
17
0.638
4700
0
20
60
100
50
17
0.746
6700
100
41.42
15
0.667
4500
0
20
60
100
50
17
0.746
6700
41.42
23.50
0.638
12.76
7.24
0.638
20
60
100
50
17
0.746
6700
49.57
41.42
23.50
0.638
50.43
12.76
7.24
0.638
Conditions are steady state; all daily flows are constant. Volatile solids are not accumulating in the digester, although grit may be settling out in the
digester.
Numerical values are given at 3 or 4 significant figures. This is unrealistic considering the expected accuracy in measuring solids concentrations
and sludge volumes. The purpose of extra significant figures is to allow more understandable comparisons to be made of the different calculation
methods.
3AII volatile solids concentrations are based on total solids, not merely on suspended solids.
that is volatile-note the difference between VS and Y). If
this is the case, the volatile solids reduction calculated by
the approximate mass balance method from several sets
of YfYbdata will show larger deviations than if it were cal-
culated by the Van Kleeck equation using VSf -VS^ data.
Grit deposition can be a serious problem in both aerobic
and anaerobic digestion. The biological processes that
occur in digestion dissolve or destroy the substances sus-
pending the grit, and it tends to settle. If agitation is inad-
equate to keep the grit particles in suspension, they will
accumulate in the digester. The approximate mass bal-
ance can be used to estimate accumulation of fixed sol-
ids.
For Problem 1, the balance yields the following:
FXf = BXb + fixed solids loss (8)
(100)(17) = (100)(17) + Fixed Solids Loss
Fixed Solids Loss = 0
(9)
(10)
The material balance compares fixed solids in output
with input. If some fixed solids are missing, this loss term
will be a positive number. Because digestion does not con-
sume fixed solids, it is assumed that the fixed solids are
accumulating in the digester. As Equation 10 shows, the
fixed solids loss equals zero. Note that for this case, where
input and output sewage sludge flow rates are equal, the
fixed solids concentrations are equal when there is no grit
accumulation.
Grit Deposition (Problem 2)
The calculation of fixed solids is repeated for Problem 2.
Conditions in Problem 2 have been selected to show grit
accumulation. Parameters are the same as in Problem 1
except for the fixed solids concentration (Xb) and param-
eters related to it. Fixed solids concentration in the sew-
age sludge is lower than in Problem 1. Consequently, VS
is higher and the mass flow rate of solids leaving is lower
than in Problem 1. A mass balance on fixed solids (input
rate = output rate + rate of loss of fixed solids) is presented
in Equations 11-13.
FXf = BXb + Fixed Solids Loss
(11)
Fixed Solids Loss = FXf- BXb (12)
Fixed Solids Loss = (100)(7) - (100)(15) = 200 kg/d (13)
The material balance, which only looks at inputs and
outputs, informs us that 200 kg/d of fixed solids have not
appeared in the outputs as expected. Because fixed sol-
ids are not destroyed, it can be concluded that they are
accumulating in the bottom of the digester. The calcula-
tion of FVSR for Problem 2 is exactly the same as for Prob-
lem 1 (see Equations 4 through 7) and yields the same
result. The approximate mass balance method gives the
122
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correct answer for the FVSR despite the accumulation of
solids in the digester. As will be seen later, this is not the
case when the Van Kleeck equation is used.
Decantate Withdrawal, No Grit Accumulation (Problem 3)
In Problem 3, decantate is withdrawn daily. Volatile and
fixed solids concentrations are known for all streams but
the volumetric flow rates are not known for decantate and
bottoms. It is impossible to calculate FVSR without know-
ing the relative volumes of these streams. However, they
are determined easily by taking a total volume balance
and a fixed solids balance, provided it can be assumed
that loss of fixed solids (i.e., accumulation in the digester)
is zero.
Selecting a basis for F of 100 m3/d
Volume balance: 100 = B + D
Fixed solids balance: 100 Xf + BXb +
(14)
(15)
Because the three Xs are known, B and D can be found.
Substituting 100-D for B and the values for the Xs from
Problem 3 and solving for D and B,
(100)(17) = (100 - D)(23.50) + (D)(7.24)
D = 40.0m3/d, B = 60.0m3/d
(16)
(17)
The FVSR can now be calculated by drawing a volatile
solids balance:
FYf = BYb + DYd + loss
FVSR= loss = FYf-BYb-DYd
FY f FYf
(18)
(19)
FVSR = (100) (50)- (60) (41.42) -(40)(12.76) = 0 40
(100) (50) (2°)
Unless information is available on actual volumes of
decantate and sewage sludge (bottoms), it is not possible
to determine whether grit is accumulating in the digester.
If it is accumulating, the calculated FVSR will be in error.
When the calculations shown in Equations 18 through
20 are made, it is assumed that the volatile solids that are
missing from the output streams are consumed by biologi-
cal reactions that convert them to carbon dioxide and meth-
ane. Accumulation is assumed to be negligible. Volatile
solids are less likely to accumulate than fixed solids, but it
can happen. In poorly mixed digesters, the scum layer that
collects at the surface is an accumulation of volatile sol-
ids. FVSR calculated by Equations 18 through 20 will be
overestimated if the volatile solids accumulation rate is
substantial.
Decantate Withdrawal and Grit Accumulation (Problem 4)
In Problem 4, there is suspected grit accumulation. The
quantity of B and D can no longer be calculated by Equa-
tions 14 and 15 because Equation 15 is no longer correct.
The values of B and D must be measured. All parameters
in Problem 4 are the same as in Problem 3 except that
measured values for B and D are introduced into Problem
4. Values of B and D calculated assuming no grit accumu-
lation (Problem 3-see previous discussion), and measured
quantities are compared below:
D
Calculated
60
40
Measured
49.57
50.43
The differences in the values of B and D are not large
but they make a substantial change in the numerical value
of FVSR. The FVSR for Problem 4 is calculated below:
FVSR = (100)(50) - (49.57)(41.42) - (50.43)(12.76)
(100)(50)
= 0.461
(21)
If it had been assumed that there was no grit accumula-
tion, FVSR would equal 0.40 (see Problem 3). It is pos-
sible to determine the amount of grit accumulation that has
caused this change. A material balance on fixed solids is
drawn:
FXf = BXb + DXd + Fixed Solids Loss
(22)
The fractional fixed solids loss due to grit accumulation
is found by rearranging this equation:
Fixed Solids Loss = FXf - BXb- Dxj
FXf FXf (23)
Substituting in the parameter values for Problem 4,
Fixed Solids Loss = (100)(17) - (49.57)(23.50) - (50.43)(7.24)
FXf
(100)(17)
= 0.100
(24)
If this fixed solids loss of 10 percent had not been ac-
counted for, the calculated FVSR would have been 13%
lower than the correct value of 0.461. Note that if grit accu-
mulation occurs and it is ignored, calculated FVSR will be
lower than the actual value.
The Van Kleeck Equation
Van Kleeck first presented his equation without deriva-
tion in a footnote for a review paper on sewage sludge
treatment processing in 1945 (Van Kleeck, 1945). The
equation is easily derived from total solids and volatile sol-
ids mass balances around the digestion system. Consider
a digester operated under steady state conditions with
decantate and bottom sewage sludge removal. A total sol-
ids mass balance and a volatile solids mass balance are:
Mf = Mb + Md + (loss of total solids)
(25)
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Mf VSf = Mb VSb + Md VSd + (loss of volatile solids)
(26)
where
Mf, Mb, andMd are the mass of solids in the feed, bot-
toms, and decantate streams.
The masses must be mass of solids rather than total
mass of liquid and solid because VS is an unusual type of
concentration unit-it is "mass of volatile solids per unit mass
of total solids."
It is now assumed that fixed solids are not destroyed
and there is no grit deposition in the digester. The losses
in Equations 25 and 26 then comprise only volatile solids
so the losses are equal. It is also assumed that the VS of
the decantate and of the bottoms are the same. This means
that the bottoms may have a much higher solids content
than the decantate but the proportion of volatile solids to
fixed solids is the same for both streams. Assuming then
that VSt, equals VS^, and making this substitution in the
defining equation for FVSR (Equation 2),
FVSR= Loss of vol. solids = -|. (Mb + Md) VSb
Mf x VSf Mf x VSf (27)
From Equation 25, recalling that we have assumed that
loss of total solids equals loss of volatile solids,
Mb + Md + Mf - loss of vol. solids (28)
Substituting for Mb + Md into Equation 27,
FVSR = 1 - (Mf"loss °fv0'- solids) VSb (29)
Mf VSf
Simplifying further,
1-(1/VSf-FVSR)'VSb (30)
Solving for FVSR,
FVSR= VSf-VSb
VSf-(VSf VSb)
(31)
This is the form of the Van Kleek equation found in WPCF
Manual of Practice No. 16 (WPCF, 1968). Van Kleeck
(1945) presented the equation in the following equivalent
form:
FVSR= 1 -VSbx(1-VSf)
VSfx(1-VSb)
(32)
Approximate Mass
Balance (AMB)
Van Kleeck (VK)
1
0.40
0.40
2
0.40
0.318
3
0.40
0.40
0.461
0.40
Problem 1: No decantate and no grit accumulation. Both
methods give correct answer.
Problem 2: No decantate but grit accumulation. VK is
invalid and incorrect.
Problem 3: Decantate but no grit accumulation. AMB
method is valid. VK method is valid only if VSb equals VSd-
Problem 4: Decantate and grit accumulation. AMB
method valid only if B and D are measured. VK method is
invalid.
The Van Kleeck equation is seen to have serious short-
comings when applied to certain practical problems. The
AMB method can be completely reliable, whereas the Van
Kleeck method is useless under some circumstances.
Average Values
The concentrations and VS values used in the equa-
tions will all be averages. For the material balance meth-
ods, the averages should be weighted averages accord-
ing to the mass of solids in the stream in question. The
example below shows how to average the volatile solids
concentration for four consecutive sewage sludge addi-
tions
Addition Volume Total Solids VS
Concentration
1
2
3
4
12 m3
8m3
13 m3
10 m3
72 kg/m3
50 kg/m3
60 kg/m3
55 kg/m3
0.75
0.82
0.80
0.77
Weighted by Mass
(33)
VSav =
12x72x0.75 + 8x50x0.82
+ 13 x 60 x 0.80 + 10x55x0.77
12 x 72 + 8x 50+ 13 x 60 + 10 x 55
= 0.795
(34)
Weighted by Volume
vs av = 12 x 0.75 + 8 x 0.82 +13 x 0.80 + 10 x 0.77
12+8+13+10
= 0.783
(35)
Arithmetic Average
The Van Kleeck equation is applied below to Problems 1
through 4 in Table C-1 and compared to the approximate
mass balance equation results:
vs gv = 0.75 + 0.82 + 0.80 + 0.77 = 0.785
4 (36)
In this example the arithmetic average was nearly as
close as the volume-weighted average to the mass-
weighted average, which is the correct value.
Which Equation to Use?
Full Mass Balance Method
The full mass balance method allows calculation of vola-
tile solids reduction for all approaches to digestion, even
124
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processes in which the final volume in the digester does
not equal the initial volume and where daily flows are not
steady. A serious drawback to this method is the need for
volatile solids concentration and the volumes of all streams
added to or withdrawn from the digester, as well as initial
and final volumes and concentrations in the digester. This
can be a daunting task, particularly for the small treatment
works that is most likely to run digesters in other than steady
flow modes. For treatment works of this kind, an "equiva-
lent" method that shows that the sewage sludge has un-
dergone the proper volatile solids reduction is likely to be
a better approach than trying to demonstrate 38% volatile
solids reduction. An aerobic sewage sludge has received
treatment equivalent to a 38% volatile solids reduction if
the specific oxygen uptake rate is below a specified maxi-
mum. Anaerobically digested sewage sludge has received
treatment equivalent to a 38% volatile solids reduction if
volatile solids reduction after batch digestion of the sew-
age sludge for 40 days is less than a specified maximum
(EPA, 1992).
Approximate Mass Balance Method
The approximate mass balance method assumes that
daily flows are steady and reasonably uniform in composi-
tion, and that digester volume and composition do not vary
substantially from day to day. Results of calculations and
an appreciation of underlying assumptions show that the
method is accurate for all cases, including withdrawal of
decantate and deposition of grit, provided that in addition
to composition of all streams the quantities of decantate
and bottoms (the digested sewage sludge) are known. If
the quantities of decantate and bottoms are not known,
the accumulation of grit cannot be determined. If accumu-
lation of grit is substantial and FVSR is calculated assum-
ing it to be negligible, FVSR will be lower than the true
value. The result is conservative and could be used to show
that minimum volatile solids reductions are being achieved.
Van Kleeck Method
The Van Kleeck equation has underlying assumptions
that should be made clear wherever the equation is pre-
sented. The equation is never valid when there is grit ac-
cumulation because it assumes the fixed solids input equals
fixed solids output. Fortunately, it produces a conservative
result in this case. Unlike the AMB method it does not pro-
vide a convenient way to check for accumulation of grit. It
can be used when decantate is withdrawn, provided VS^
equals VS^. Just how significant the difference between
these VS values can be before an appreciable error in
FVSR occurs is unknown, although it could be determined
by making up a series of problems with increasing differ-
ences between the VS values, calculating FVSR using the
AMB method and a Van Kleeck equation, and comparing
the results.
The shortcomings of the Van Kleeck equation are sub-
stantial, but the equation has one strong point: The VS of
the various sewage sludge and decantate streams are likely
to show much lower coefficients of variation (standard de-
viation divided by arithmetic average) than volatile solids
and fixed solids concentrations. Reviews of data are needed
to determine how seriously the variation in concentrations
affect the confidence interval of FVSR calculated by both
methods. A hybrid approach may turn out to be advanta-
geous. The AMB method could be used first to determine
if grit accumulation is occurring. If grit is not accumulating,
the Van Kleeck equation could be used. If decantate is
withdrawn, the Van Kleeck equation is appropriate, par-
ticularly if the decantate is low in total solids. If not, and if
VSd differs substantially from VSb, it could yield an incor-
rect answer.
Volatile Solids Loss Across All Sewage
Sludge Treatment Processes
For cases when appreciable volatile solids reduction can
occur downstream from the digester (for example, as would
occur in air drying or lagoon storage), it is appropriate to
calculate the volatile solids loss from the point at which
the sewage sludge enters the digester to the point at which
the sewage sludge leaves the treatment works. Under
these circumstances, it is virtually never possible to use
the approximate mass balance approach, because flow
rates are not uniform. The full mass balance could be used
in principle, but practical difficulties such as measuring the
mass of the output sewage sludge (total mass, not just
mass of solids) that relates to a given mass of entering
sewage sludge make this also a practical impossibility.
Generally then, the only option is to use the Van Kleeck
equation, because only the percent volatile solids content
of the entering and exiting sewage sludge is needed to
make this calculation. As noted earlier, this equation will
be inappropriate if there has been a selective loss of high
volatility solids (e.g., bacteria) or low volatility solids (e.g.,
grit) in any of the sludge processing steps.
To make a good comparison, there should be good cor-
respondence between the incoming sewage sludge and
the treated sewage sludge to which it is being compared
(see Section 10.4). For example, when sewage sludge is
digested for 20 days, then dried on a sand bed for 3 months,
and then removed, the treated sludge should be compared
with the sludge fed to the digester in the preceding 3 or 4
months. If no selective loss of volatile or nonvolatile solids
has occurred, the Van Kleeck equation (see Equation 31)
can be used to calculate volatile solids reduction.
References
EPA. 1992. Technical Support Document for Part 503
Pathogen and Vector Attraction Reduction Require-
ments in Sewage Sludge. Office of Water, U.S. EPA,
Washington, DC. NTIS No PB93-110609. Natl. Techni-
cal Information Service, Springfield, VA.
Fischer, WJ. 1984. Calculation of volatile solids during
sludge digestion. In: Bruce, A., ed. Sewage Sludge
Stabilization and Disinfection, pp. 499-529. Water
Research Centre, E. Norwood Ltd., Chichester, En-
gland.
125
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Van Kleeck, L.W. 1945. Sewage Works J., Operation of Water Pollution Control Federation. 1968. Manual of Prac-
Sludge Drying and Gas Utilization Units. 17(6): 1240- tice No. 16, Anaerobic Sludge Digestion. Washington,
1255. DC.
126
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Appendix D
Guidance on Three Vector Attraction Reduction Tests
This appendix provides guidance for the vector attrac-
tion reduction Options 2,3, and 4 to demonstrate reduced
vector attraction (see Chapter 8 for a description of these
requirements).
1. Additional Digestion Test for
Anaerobically Digested Sewage Sludge
Background
The additional digestion test for anaerobically digested
sewage sludge is based on research by Jeris et al. (1985).
Farrell and Bhide (1993) explain in more detail the origin
of the time and volatile solids reduction requirements of
the test.
Jeris et al. (1985) measured changes in many param-
eters including volatile solids content while carrying out
additional digestion of anaerobically digested sludge from
several treatment works for long periods. Samples were
removed from the digesters weekly for analysis. Because
substantial amount of sample was needed for all of these
tests, they used continuously mixed digesters of 18 liters
capacity. The equipment and procedures of Jeris et al.,
although not complex, appear to be more elaborate than
needed for a control test. EPA staff (Farrell and Bhide, 1993)
have experimented with simplified tests and the procedure
recommended is based on their work.
Recommended Procedure
The essentials of the test are as follows:
Remove, from the plant-scale digester, a representa-
tive sample of the sewage sludge to be evaluated to
determine additional volatile solids destruction. Keep
the sample protected from oxygen and maintain it at
the temperature of the digester. Commence the test
within 6 hours after taking the sample.
Flush fifteen 100-mL volumetric flasks with nitrogen,
and add approximately 50 ml of the sludge to be tested
into each flask. Frequently mix the test sludge during
this operation to assure that its composition remains
uniform. Select five flasks at random, and determine
total solids content and volatile solids content, using
the entire 50 ml for the determination. Seal each of
the remaining flasks with a stopper with a single glass
tube through it to allow generated gases to escape.
Connect the glass tubing from each flask through a
flexible connection to a manifold. To allow generated
gases to escape and prevent entry of air, connect the
manifold to a watersealed bubbler by means of a ver-
tical glass tube. The tube should be at least 30-cm
long with enough water in the bubbler so that an in-
crease in atmospheric pressure will not cause backflow
of air or water into the manifold. Maintain the flasks
containing the sludge at constant temperature either
by inserting them in a water bath (the sludge level in
the flasks must be below the water level in the bath) or
by placing the entire apparatus in a constant tempera-
ture room or box. The temperature of the additional
digestion test should be the average temperature of
the plant digester, which should be in the range of 30°C
to 40°C (86°F to 104°F). Temperature should be con-
trolled within + 0.15°C (0.27°F).
Each flask should be swirled every day to assure ad-
equate mixing, using care not to displace sludge up
into the neck of the flask. Observe the water seal for
the first few days of operation. There should be evi-
dence that gas is being produced and passing through
the bubbler.
After 20 days, withdraw five flasks at random. Deter-
mine total and volatile solids content using the entire
sample for the determination. Swirl the flask vigorously
before pouring out its contents to minimize the hold up
of thickened sludge on the walls and to assure that
any material left adhering to the flask walls will have
the same average composition as the material with-
drawn. Use a consistent procedure. If holdup on walls
appears excessive, a minimal amount of distilled wa-
ter may be used to wash solids off the walls. Total re-
moval is not necessary, but any solids left on the walls
should be approximately of the same composition as
the material removed.
After 40 days, remove the remaining five flasks. De-
termine total and volatile solids content using the en-
tire sample from each flask for the determination. Use
the same precautions as in the preceding step to re-
move virtually all of the sludge, leaving only material
with the same approximate composition as the mate-
rial removed.
127
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Total and volatile solids contents are determined using
the procedures of Method 2540 G of Standard Methods
(APHA, 1992).
Mean values and standard deviations of the total solids
content, the volatile solids content, and the percent vola-
tile solids are calculated. Volatile solids reductions that
result from the additional digestion periods of 20 and 40
days are calculated from the mean values by the Van
Kleeck equation and by a material balance (refer to Ap-
pendix C for a general description of these calculations).
The results obtained at 20 days give an early indication
that the test is proceeding satisfactorily and will help sub-
stantiate the 40-day result.
Alternative approaches are possible. The treatment
works may already have versatile bench-scale digesters
available. This equipment could be used for the test, pro-
vided accuracy and reproducibility can be demonstrated.
The approach described above was developed because
Farrell and Bhide (1993) in their preliminary work experi-
enced much difficulty in withdrawing representative
samples from large digesters even when care was taken
to stir the digesters thoroughly before sampling. If an al-
ternative experimental setup is used, it is still advisable to
carry out multiple tests for the volatile solids content in
order to reduce the standard error of this measurement,
because error in the volatile solids content measurement
is inflated by the nature of the equation used to calculate
the volatile solids reduction.
Variability in flow rates and nature of the sludge will re-
sult in variability in performance of the plant-scale digest-
ers. It is advisable to run the additional digestion test rou-
tinely so that sufficient data are available to indicate aver-
age performance. The arithmetic mean of successive tests
(a minimum of three is suggested) should show an addi-
tional volatile solids reduction of < 17%.
Calculation Details
Appendix C, Determination of Volatile Solids Reduction
by Digestion, describes calculation methods to use for di-
gesters that are continuously fed or are fed at least once a
day. Although the additional anaerobic digestion test is a
batch digestion, the material balance calculations approach
is the same. Masses of starting streams (input streams)
are set equal to masses of ending streams (output streams).
The test requires that the fixed volatile solids reduction
(FVSR) be calculated both by the Van Kleeck equation
and the material balance method. The Van Kleeck equa-
tion calculations can be made in the manner described in
Appendix C.
The calculation of the volatile solids reduction (and the
fixed fractional solids reduction [FFSR]) by the mass bal-
ance method shown below has been refined by subtract-
ing out the mass of gas lost from the mass of sludge at the
end of the digestion step. For continuous digestion, this
loss of mass usually is ignored, because the amount is
small in relation to the total digesting mass, and mass be-
fore and after digestion are assumed to be the same. Con-
sidering the inherent difficulty in matching mass and com-
position entering to mass and composition leaving for a
continuous process, this is a reasonable procedure. For
batch digestion, the excellent correspondence between
starting material and final digested sludge provides much
greater accuracy in the mass balance calculation, so in-
clusion of this lost mass is worthwhile.
In the equations presented below, concentrations of fixed
and volatile solids are mass fractions- mass of solids per
unit mass of sludge (mass of sludge includes both the sol-
ids and the water in the sludge)- and are indicated by, the
symbols lowercase y and x. This is different from the us-
age in Appendix C where concentrations are given in mass
per unit volume, and are indicated by the symbols upper-
case y and x. This change has been made because masses
can be determined more accurately than volumes in small-
scale tests.
In the material balance calculation, it is assumed that as
the sludge digests, volatile solids and fixed solids are con-
verted to gases that escape or to volatile compounds that
distill 9ff when the sludge is dried. Any production or con-
sumption of water by the biochemical reactions in diges-
tion is assumed to be negligible. The data collected (vola-
tile solids and fixed solids concentrations of feed and di-
gested sludge) allow mass balances to be drawn on vola-
tile solids, fixed solids, and water. As noted, it is assumed
that there is no change in water mass - all water in the feed
is present in the digested sludge. Fractional reductions in
volatile solids and fixed solids can be calculated from these
mass balances for the period of digestion. Details of the
calculation of these relationships are given by Farrell and
Bhide (1993). The final form or the equations for fractional
volatile solids reduction (mass balance [m.b.] method) and
fractional fixed solids reduction (m.b. method) are given
below:
FVSR(m.b.)=
yf(1-xb-yb)
rr^Df ^
FFSR(m.b.)=
where:
y = mass fraction of volatile solids in the liquid sludge
x = mass fraction of fixed solids in the liquid sludge
f = indicates feed sludge at start of the test
b = indicates "bottoms" sludge at end of the test
If the fixed solids loss is zero, these two equations are
reduced to Equation 2 below:
FvsR(m.b.) = (yf-yb)/yf(i-yb)
(2)
If the fixed solids loss is not zero but is substantially
smaller than the volatile solids reduction, Equation 2 gives
surprisingly accurate results. For five sludges batch-di-
gested by Farrell and Bhide (1993), the fixed solids reduc-
128
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tions were about one-third of the volatile solids reductions.
When the FVSR(m.b.) calculated by Equation 1a averaged
15%, the FVSR(m.b.) calculated by Equation 2 averaged
14.93%, which is a trivial difference.
The disappearance of fixed solids unfortunately has a
relatively large effect on the calculation of FVSR by the
Van Kleeck equation. The result is lower than it should be.
For five sludges that were batch-digested by Farrell and
Bhide (1993), the FVSR calculated by the Van Kleeck
method averaged 15%, whereas the FVSR (m.b.) calcu-
lated by Equation 1a or 2 averaged about 20%. When the
desired endpoint is an FVSR below 17%, this is a sub-
stantial discrepancy.
The additional digestion test was developed for use with
the Van Kleeck equation, and the 17% requirement is based
on results calculated with this equation. In the future, use
of the more accurate mass balance equation may be re-
quired, with the requirement adjusted upward by an ap-
propriate amount. This cannot be done until more data with
different sludge become available.
2. Specific Oxygen Uptake Rate
Background
The specific oxygen uptake rate of a sewage sludge is
an accepted method for indicating the biological activity of
an activated sewage sludge mixed liquor or an aerobically
digesting sludge. The procedure required by the Part 503
regulation for this test is presented in Standard Methods
(APHA, 1992) as Method 2710 B, Oxygen-Consumption Rate.
The use of the specific oxygen uptake rate (SOUR) has
been recommended by Eikum and Paulsrud (1977) as a reli-
able method for indicating sludge stability provided tem-
perature effects are taken into consideration. For primary
sewage sludges aerobically digested at 18°C (64°F), sludge
was adequately stabilized (i.e., it did not putrefy and cause
offensive odors) when the SOUR was less than 1.2 mg
02/hr/g VSS (volatile suspended solids). The authors in-
vestigated several alternative methods for indicating sta-
bility of aerobically digested sludges and recommended
the SOUR test as the one with the most advantages and
the least disadvantages.
Ahlberg and Boyko (1972) also recommend the SOUR
as an index of stability. They found that, for aerobic digest-
ers operated at temperatures above 10°C (SOT), SOUR
fell to about 2.0 mg 02/hr/gVSS after a total sludge age of
60 days and to 1.0 mg 02/hr/g VSS after about 120 days
sludge age. These authors state that a SOUR of less than
1.0 mg 02/hr/g VSS at temperatures above 10°C (SOT)
indicates a stable sludge.
The results obtained by these authors indicate that long
digestion times-more than double the residence time for
most aerobic digesters in use today-are needed to elimi-
nate odor generation from aerobically digested sludges.
Since the industry is not being deluged with complaints
about odor from aerobic digesters, it appears that a higher
SOUR standard can be chosen than they suggest without
causing problems from odor (and vector attraction).
The results of long-term batch aerobic digestion tests
by Jeris et al. (1985) provide information that is helpful in
setting a SOUR requirement that is reasonably attainable
and still protective. Farrell and Bhide (1993) reviewed the
data these authors obtained with four sewage sludges from
aerobic treatment processes and concluded that a stan-
dard of 1.5 mg 02/hr/g TS at 20°C (68T) would discrimi-
nate between adequately stabilized and poorly stabilized
sludges. The "adequately digested" sludges were not to-
tally trouble-free, i.e., it was possible under adverse con-
ditions to develop odorous conditions. In all cases where
the sludge was deemed to be adequate, minor adjustment
in plant operating conditions created an acceptable sludge.
The SOUR requirement is based on total solids rather
than volatile suspended solids. This usage is preferred for
consistency with the rest of the Part 503 regulation where
all loadings are expressed on a total solids basis. The use
of total solids concentration in the SOUR calculation is ra-
tional since the entire sludge solids and not just the vola-
tile solids degrade and may exert some oxygen demand.
Making an adjustment for the difference caused by basing
the requirement on TS instead of VSS, the standard is
about 1.8 times higher than Eikum and Paulsrud's recom-
mended value and 2.1 times higher than Ahlberg and
Boykos' recommendation.
Unlike anaerobic digestion, which is typically conducted
at 35°C (95T), aerobic digestion is carried out without any
deliberate temperature control. The temperature of the di-
gesting sludge will be close to ambient temperature, which
can range from 5°C to 30°C (41 °F to 86°F). In this tem-
perature range, SOUR increases with increasing tempera-
ture. Consequently, if a requirement for SOUR is selected,
there must be some way to convert SOUR test results to a
standard temperature. Conceivably, the problem could be
avoided if the sludge were simply heated or cooled to the
standard temperature before running the SOUR test. Un-
fortunately, this is not possible, because temperature
changes in digested sludge cause short-term instabilities
in oxygen uptake rate (Benedict and Carlson [1973], Farrell
and Bhide [1993]).
Eikum and Paulsrud (1977) recommend that the follow-
ing equation be used to adjust the SOUR determined at
one temperature to the SOUR for another temperature:
(SOUR)T1/(SOUR)T2 = 6(T1'T2)
(3)
where:
(SOUR)n = specific oxygen uptake rate at T-|
(SOUR)T2 = specific oxygen uptake rate atT2
9 = the Streeter-Phelps temperature sensitivity
coefficient
129
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These authors calculated the temperature sensitivity
coefficient using their data on the effect of temperature on
the rate of reduction in volatile suspended solids with time
during aerobic digestion. This is an approximate approach,
because there is no certainty that there is a one-to-one
relationship between oxygen uptake rate and rate of vola-
tile solids disappearance. Another problem is that the
coeffficient depends on the makeup of each individual
sludge. For example, Koers and Mavinic (1977) found the
value of 9 to be less than 1.072 at temperatures above
15°C (59°F) for aerobic digestion of waste activated slud-
ges, whereas Eikum and Paulsrud (1977) determined 0 to
equal 1.112 for primary sludges. Grady and Lim (1980)
reviewed the data of several investigators and recom-
mended that 9 = 1.05 be used for digestion of waste-acti-
vated sludges when more specific information is not avail-
able. Based on a review of the available information and
their own work, Farrell and Bhide (1993) recommend that
Eikum and Paulsruds' temperature correction procedure
be utilized, using a temperature sensitivity coefficient in
the range of 1.05 to 1.07.
Recommended Procedure for Temperature
Correction
A SOUR of 1.5 mg 02/hr/g total solids at 20°C (68°F)
was selected to indicate that an aerobically digested sludge
has been adequately reduced in vector attraction.
The SOUR of the sludge is to be measured at the tem-
perature at which the aerobic digestion is occurring in the
treatment works and corrected to 20°C (68°F) by the fol-
lowing equation:
= SOURTx9(2°-T)
(4)
where
9 = 1.05 above 20°C (68°F)
1.07 below 20°C (68°F)
This correction may be applied only if the temperature
of the sludge is between 10°C and 30°C (50° F and 86° F).
The restriction to the indicated temperature range is re-
quired to limit the possible error in the SOUR caused by
selecting an improper temperature coefficient. Farrell and
Bhide's (1993) results indicate that the suggested values
for 9 will give a conservative value for SOUR when trans-
lated from the actual temperature to 20°C (68°F).
The experimental equipment and procedures for the
SOUR test are those described in Part 2710 B, Oxygen
Consumption Rate, of Standard Methods (APHA, 1992).
The method allows the use of a probe with an oxygen-
sensitive electrode or a respirometer. The method advises
that manufacturer's directions be followed if a respirom-
eter is used. No further reference to respirometric meth-
ods will be made here. A timing device is needed as well
as a 300-mL biological oxygen demand (BOD) bottle. A
magnetic mixer with stirring bar is also required.
The procedure of Standard Method 2710 B should be
followed with one exception. The total solids concentra-
tion instead of the volatile suspended solids concentration
is used in the calculation of the SOUR. Total solids con-
centration is determined by Standard Method 2540 G.
Method 2710 B cautions that if the suspended solids con-
tent of the sludge is greater than 0.5%, additional stirring
besides that provided by the stirring bar be considered.
Experiments by Farrell and Bhide (1993) were carried out
with sludges up to 2% in solids content without difficulty if
the SOUR was lower than about 3.0 mg 02/g/h. It is pos-
sible to verify that mixing is adequate by running repeat
measurements at several stirrer bar speeds. If stirring is
adequate, oxygen uptake will be independent of stirrer
speed.
The inert mineral solids in the wastewater in which the
sludge particles are suspended do not exert an oxygen
demand and probably should not be part of the total solids
in the SOUR determination. Ordinarily, they are such a
small part of the total solids that they can be ignored. If the
ratio of inert dissolved mineral solids in the treated waste-
water to the total solids in the sludge being tested is greater
than 0.15, a correction should be made to the total solids
concentration. Inert dissolved mineral solids in the treated
wastewater effluent is determined by the method of Part
2540 B of Standard Methods (APHA, 1992). This quantity
is subtracted from the total solids of the sludge to deter-
mine the total solids to be used in the SOUR calculation.
The collection of the sample and the time between
sample collection and measurement of the SOUR are im-
portant. The sample should be a composite of grab samples
taken within a period of a few minutes duration. The sample
should be transported to the laboratory expeditiously and
kept under aeration if the SOUR test cannot be run imme-
diately. The sludge should be kept at the temperature of
the digester from which it was drawn and aerated thor-
oughly before it is poured into the BOD bottle for the test.
If the temperature differs from 20°C (68° F) by more than
±10°C (±18°F), the temperature correction may be inap-
propriate and the result should not be used to prove that
the sewage sludge meets the SOUR requirement.
Variability in flow rates and nature of the sludge will re-
sult in variability in performance of the plant-scale digest-
ers. It is advisable to run the SOUR test routinely so that
sufficient data are available to indicate average perfor-
mance. The arithmetic mean of successive tests-a mini-
mum of seven over 2 or 3 weeks is suggested-should give
a SOUR of < 1.5 mg O^/hr/g total solids.
3. Additional Digestion Test for
Aerobically Digested Sewage Sludge
Background
Part 503 lists several options that can be used to dem-
onstrate reduction of vector attraction in sewage sludge.
These options include reduction of volatile solids by 38%
and demonstration of the SOUR value discussed above
(see also Chapter 8). These options are feasible for many,
but not all, digested sludges. For example, sludges from
extended aeration treatment works that are aerobically di-
130
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gested usually cannot meet this requirement because they
already are partially reduced in volatile solids content by
their exposure to long aeration times in the wastewater
treatment process.
The specific oxygen uptake test can be utilized to evalu-
ate aerobic sludges that do not meet the 38% volatile sol-
ids reduction requirement. Unfortunately, this test has a
number of limitations. It cannot be applied if the sludges
have been digested at temperatures lower than 10°C (50°F)
or higher than 30°C (86° F). It has not been evaluated un-
der all possible conditions of use, such as for sludges of
more than 2% solids.
A straightforward approach for aerobically treated slud-
ges that cannot meet either of the above criteria is to de-
termine to what extent they can be digested further. If they
show very little capacity for further digestion, they will have
a low potential for additional biodegradation and odor gen-
eration that attracts vectors. Such a test necessarily takes
many days to complete, because time must be provided
to get measurable biodegradation. Under most circum-
stances, this is not a serious drawback. If a digester must
be evaluated every 4 months to see if the sewage sludge
meets vector attraction reduction requirements, it will be
necessary to start a regular assessment program. A record
can be produced showing compliance. The sludge currently
being produced cannot be evaluated quickly but it will be
possible to show compliance over a period of time.
The additional digestion test for aerobically digested slud-
ges in Part 503 is based on research by Jeris et al. (1985),
and has been discussed by Farrell et al. (EPA, 1992). Farrell
and Bhide (1993) explain in more detail the origin of the
time and volatile solids reduction requirements of the test.
Jeris et al. (1985) demonstrated that several parameters--
volatile solids reduction, COD, BOD, and SOUR-declined
smoothly and approached asymptotic values with time as
sludge was aerobically digested. Any one of these param-
eters potentially could be used as an index of vector at-
traction reduction for aerobic sludges. SOUR has been
adopted (see above) for this purpose. Farrell and Bhide
(1993) have shown that the additional volatile solids re-
duction that occurs when sludge is batch digested aerobi-
cally for 30 days correlates equally as well as SOUR with
the degree of vector attraction reduction of the sludge. They
recommend that a sewage sludge be accepted as suitably
reduced in vector attraction when it shows less than 15%
additional volatile solids reduction after 30 days additional
batch digestion at 20°C (68°F). For three out of four slud-
ges investigated by Jeris et al. (1985), the relationship
between SOUR and additional volatile solids reduction
showed that the SOUR was approximately equal to 1.5
mg 02/hr/g (the Part 503 requirement for SOUR) when
additional volatile solids reduction was 15%. The two re-
quirements thus agree well with one another.
Recommended Procedure
There is considerable flexibility in selecting the size of
the digesters used for the additional aerobic digestion test.
Farrell and Bhide (1993) used a 20-liter fish tank. A tank of
rectangular cross-section is suggested because sidewalls
are easily accessible and are easily scraped clean of ad-
hering solids. The tank should have a loose-fitting cover
that allows air to escape. It is preferable to vent exhaust
gas to a hood to avoid exposure to aerosols. Oil and par-
ticle-free air is supplied to the bottom of the digester through
porous stones at a rate sufficient to thoroughly mix the
sewage sludge. This will supply adequate oxygen to the
sludge, but the oxygen level in the digesting sludge should
be checked with a dissolved oxygen meter to be sure that
the supply of oxygen is adequate. Oxygen level should be
at least 2 mg/L. Mechanical mixers also were used to keep
down foam and improve mixing.
If the total solids content of the sewage sludge is greater
than 2%, the sludge must be diluted to 2% solids with sec-
ondary effluent at the start of the test. The requirement
stems from the results of Reynolds (1973) and Malina
(1966) which demonstrate that rate of volatile solids re-
duction decreases as the feed solitis concentration in-
creases. Thus, for example, a sludge with a 2% solids con-
tent that showed more than 15% volatile solids reduction
when digested for 30 days might show a lower volatile
solids reduction and would pass the test if it were at 4%.
This dilution may cause a temporary change in rate of vola-
tile solids reduction. However, the long duration of the test
should provide adequate time for recovery and demon-
stration of the appropriate reduction in volatile solids con-
tent.
When sampling the sludge, care should be taken to keep
the sludge aerobic and avoid unnecessary temperature
shocks. The sludge is digested at 20°C (68°F) even if the
digester was at some other temperature. It is expected
that the bacterial population will suffer a temporary shock
if there is a substantial temperature change, but the test is
of sufficient duration to overcome this effect and show a
normal volatile solids reduction. Even if the bacteria are
shocked and do not recover completely, the test simulates
what would happen to the sludge in the environment. If it
passes the test, it is highly unlikely that the sludge will at-
tract vectors when used or disposed to the environment.
For example, if a sludge digested at 35°C (95°F) has not
been adequately reduced in volatile solids and is shocked
into biological inactivity for 30 days when its temperature
is lowered to 20°C (68°F), it will be shocked in the same
way if it is applied to the soil at ambient temperature. Con-
sequently, it is unlikely to attract vectors.
The digester is charged with about 12 liters of the sew-
age sludge to be additionally digested, and aeration is com-
menced. The constant flow of air to the aerobic digestion
test unit will cause a substantial loss of water from the
digester. Water loss should be made up every day with
distilled water.
Solids that adhere to the walls above and below the water line
should be scraped off and dispersed back into the sludge
daily. The temperature of the digesting sludge should be
approximately 20°C (68°F). If the temperature of the labora-
131
-------
tory is maintained at about 22°C (72°F), evaporation of
water from the digester will cool the sludge to about 20°C
(68°F).
Sewage sludge is sampled every week for five succes-
sive weeks. Before sampling, makeup water is added (this
will generally require that air is temporarily shut off to allow
the water level to be established), and sludge is scraped
off the walls and redistributed into the digester. The sludge
in the digester is thoroughly mixed with a paddle before
sampling, making sure to mix the bottom sludge with the
top. The sample is comprised of several grab samples
collected with a ladle while the digester is being mixed.
The entire sampling procedure is duplicated to collect a
second sample.
Total and volatile solids contents of both samples are
determined preferably by Standard Method 2540 G (APHA,
1992). Percent volatile solids is calculated from total and
volatile solids content. Standard Methods (APHA, 1992)
states that duplicates should agree within 5% of their av-
erage. If agreement is substantially poorer than this, the
sampling and analysis should be repeated.
Calculation Details
Fraction volatile solids reduction is calculated by the Van
Kleeck formula (see Appendix C) and by a mass balance
method. The mass balance (m.b.) equations become very
simple, because final mass of sludge is made very nearly
equal to initial mass of sludge by adjusting the volume by
adding water. These equations for fractional volatile solids
reduction (FVSR) and fractional fixed solids reduction
(FFSR) are:
FVSR(m.b.)=
FFSR(m.b.) =
where:
/ Xf
(5a)
(5b)
y and x = mass fraction of volatile and fixed solids, re-
spectively (see previous section
on "Calculation details" for explanation of
"mass fraction")
f and b = subscripts indicating initial and final sludges
This calculation assumes that initial and final sludge
densities are the same. Very little error is introduced by
this assumption.
The calculation of the fractional fixed solids reduction is
not a requirement of the test, but it will provide useful infor-
mation.
The test was developed from information based on the
reduction in volatile solids content calculated by the Van
Kleeck equation. As noted in the section on the additional
anaerobic digestion test, for batch processes the material
balance procedure for calculating volatile solids reduction
is superior to the Van Kleeck approach. It is expected that
the volatile solids reduction by the mass balance method
will show a higher volatile solids reduction than the calcu-
lation made by using the Van Kleeck equation.
4. References
Ahlberg, N.R. and B.I. Boyko. 1972. Evaluation and de-
sign of aerobic digesters. Jour. WPCF 44(4):634-643.
Benedict, A.M. and D.A. Carlson. 1973. Temperature ac-
climation in aerobic big-oxidation systems. Jour. WPCF
45(1): 10-24.
Eikum, A., and B. Paulsrud. 1977. Methods for measuring
the degree of stability of aerobically stabilized slud-
ges. Wat. Res. 11:763-770
EPA. 1992. Technical support document for Part 503 patho-
gen and vector attraction reduction requirements in
sewage sludge. NTIS No.: PB93-110609. Springfield,
VA: National Technical Information Service.
Farrell, J.B., V. Bhide, and Smith, J. E. Jr. 1996.
Development of methods EPA's new methods to
quantifying vector attraction of wastewater sludges,
Water Envir. Res.,68,3,286-294
APHA (American Public Health Association). 1992. Stan-
dard methods for the examination of water and waste-
water. Greenberg, A.E., L.S. Clesceri, and A.D. Eaton
(eds.). APHA, AWWA, and WEF, Washington, DC.
Grady, C.P.L., Jr. and H.C. Lim. 1980. Biological waste-
water treatment: theory and applications. Marcel
Dekker, New York.
Jeris, J.S., D. Ciarcia, E. Chen, and M. Mena. 1985. De-
termining the stability of treated municipal sludge. EPA
Rept. No. 600/2-85/001 (NTIS No. PB 85-1471891
AS). U.S. Environmental Protection Agency, Cincin-
nati, Ohio.
Koers, D.A. and D.V. Mavinic. 1977. Aerobic digestion of
waste-activated sludge at low temperatures. Jour.
WPCF 49(3):460-468.
Malina, Jr., J.F. 1966. Discussion, pp. 157-160, in paper
by D. Kehr, "Aerobic sludge stabilization in sewage
treatment plants." Advances in Water Pollution Re-
search, Vol. 2, pp 143-163. Water Pollution Control
Federation, Washington, DC.
Reynolds, T.D. 1973. Aerobic digestion of thickened waste-
activated sludge. Part 1, pp. 12-37, in Proc. 28th
Industr, Waste Conf., Purdue University.
132
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Appendix E
Determination of Residence Time for Anaerobic and Aerobic Digestion
Introduction
The PSRP and PFRP specifications in 40 CFR 257 for
anaerobic and aerobic digestion not only specify tempera-
tures but also require minimum mean cell residence times
of the sludge in the digesters. The mean cell residence
time is the time that the sludge particles are retained in the
digestion vessel under the conditions of the digestion. The
calculation of residence time is ordinarily simple but it can
become complicated under certain circumstances. This
appendix describes how to make this calculation for most
of the commonly encountered modes for operating digest-
ers.
Approach
The discussion has to be divided into two parts: resi-
dence time for batch operation and for plug flow, and resi-
dence time for fully mixed digesters. For batch operation,
residence time is obvious-it is the duration of the reaction.
For plug flow, the liquid-solid mixture that is sludge passes
through the reactor with no backward or forward mixing.
The time it takes the sludge to pass through the reactor is
the residence time. It is normally calculated by the follow-
ing equation:
6 = V/q (1)
where
6 = plug flow solids residence time
V = volume of the liquid in the reactor
q = volume of the liquid leaving the reactor
Normally the volume of liquid leaving the reactor will
equal the volume entering. Conceivably, volume leaving
could be smaller (e.g., because of evaporation losses) and
residence time would be longer than expected if 6 were
based on inlet flow. Ordinarily, either inlet or outlet flow
rate can be used.
For a fully mixed reactor, the individual particles of the
sludge are retained for different time periods-some par-
ticles escape very soon after entry whereas others circu-
late in the reactor for long periods before escaping. The
average time in the reactor is given by the relationship:
where
8s = an increment of sludge solids that leaves the reactor
6 = time period this increment has been in the reactor
6n= nominal average solids residence time
When the flow rates of sludge into and out of the com-
pletely mixed vessel are constant, it can be demonstrated
that this equation reduces to:
e
t>n =
qcq
(3)
On =
Z(8s x 6)
E(5s)
(2)
where
V = reactor volume
q = flow rate leaving
Cv = concentration of solids in the reactor
Cq = concentration of solids in exiting sewage sludge
It is important to appreciate that q is the flow rate leaving
the reactor. Some operators periodically shut down reac-
tor agitation, allow a supernatant layer to form, decant the
supernatant, and resume operation. Under these condi-
tions, the flow rate entering the reactor is higher than the
flow rate of sludge leaving.
Note that in Equation 3, VCV is the mass of solids in the
system and qC is the mass of solids leaving. Ordinarily Cv
equals Cq and these terms could be canceled. They are
left in the equation because they show the essential form
of the residence time equation:
Q mass of solids in the digester
mass flow rate of solids leaving (4)
Using this form, residence time for the important operat-
ing mode in which sludge leaving the digester is thickened
and returned to the digester can be calculated.
In many aerobic digestion installations, digested sludge
is thickened with part of the total volume returned to in-
crease residence time and part removed as product. The
calculation follows Equation 4 and is identical with the SRT
(solids retention time) calculation used in activated sludge
process calculations. The focus here is on the solids in the
digester and the solids that ultimately leave the system.
Applying Equation 4 for residence time then leads to Equa-
tion 5:
133
-------
en = vcv
pcp
(5)
where
p = flow rate of processed sludge leaving the system
Cp = solids concentration in the processed sludge
The subscript p indicates the final product leaving the
system, not the underflow from the thickener. This approach
ignores any additional residence time in the thickener since
this time is relatively short and not at proper digestion con-
ditions.
Sample Calculations
In the following paragraphs, the equations and principles
presented above are used to demonstrate the calculation
of residence time for several commonly used digester op-
erating modes:
Case 1
Complete-mix reactor
Constant feed and withdrawal at least once a day
No substantial increase or decrease in volume in the
reactor (V)
One or more feed streams and a single product stream
(q)
The residence time desired is the nominal residence time.
Use Equation 3 as shown below:
9n= VCV = V
qcq q
The concentration terms in Equation 4 cancel out be-
cause Cv equals Cq.
Case 2a
Complete-mix reactor
Sludge is introduced in daily batches of volume (Vj)
and solids concentration (Cj)
Vessel contains a "heel" of liquid sludge (Vf) at the
beginning of the digestion step
When final volume (Vf) is reached, sludge is discharged
until Vh remains and the process starts again
Some aerobic digesters are run in this fashion. This prob-
lem is a special case involving a batch reaction. Exactly
how long each day's feeding remains in the reactor is
known, but an average residence time must be calculated
as shown in Equation 2:
j x time that batch i remains in the reactor
n =
Let Vh = 30 m3 (volume of "heel")
Vd= 130 m3 (total digester volume)
Vj = each day 10 m3 is fed to the reactor at the begin-
ning of the day
Cj =12 kg/m3
Vf is reached in 10 days. Sludge is discharged at the
end of Day 10.
Then 9n =(10-12-10+10-12-9 +...+10-12-1)
(10-12 + 10-12 + ... 10-12)
9n = 10-12-55 = 5.5 days
10-12-10
Notice that the volume of the digester or of the "heel" did
not enter the calculation.
Case 2b
Same as Case 2a except:
The solids content of the feed varies substantially from
day to day
Decantate is periodically removed so more sludge can
be added to the digester
The following problem illustrates the calculation:
Let Vh = 30m3, and Vd = 130m3
Day vi (m3)
Solids Content (kg/rtf)
Decantate (m3)
1
2
3
4
5
6
7
8
9
10
11
12
10
10
10
10
10
10
10
10
10
10
10
10
10
15
20
15
15
10
20
25
15
10
15
20
0
0
0
0
0
0
0
0
10
0
10
0
The following problem illustrates the calculation:
9n = (10-10-12+10-15-11+10-20-10+...
...+10-10-3+10-15-2+10-20-1)
(10-10+10-15+10-20+...
+10-10+10-15+10-20
9n =11,950/1,900 = 6.29d
The volume of "heel" and sludge feedings equaled 150
m3, exceeding the volume of the digester. This was made
possible by decanting 20 m3.
Case 3
Same as Case 2 except that after the digester is filled it
is run in batch mode with no feed or withdrawals for sev-
eral days.
A conservative 9n can be calculated by simply adding
the number of extra days of operation to the 6n calculated
134
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for Case 2. The same applies to any other cases followed
by batch mode operation.
Case 4
Complete-mix reactor
Constant feed and withdrawal at least once a day
No substantial increase or decrease of volume in the
reactor
One or more feed streams, one decantate stream re-
turned to the treatment works, one product stream;
the decantate is removed from the digester so the
sludge in the digester is higher in solids than the feed
This mode of operation is frequently used in both anaero-
bic and aerobic digestion in small treatment works.
Equation 3 is used to calculate the residence time:
LetV=100m3
qf = 10 m3/d (feed stream)
Cf = 40 kg solids/m3
q = 5 m3/d (existing sludge stream)
Cv = 60 kg solids/m3
9n = 100x60 = 20d
5x60
Case 5
Complete-mix reactor
Constant feed and withdrawal at least once a day
Volume in digester reasonably constant
One or more feed streams, one product stream that is
thickened, some sludge is recycled, and some is drawn
off as product
This mode of operation is sometimes used in aerobic
digesters. Equation 5 is used to calculate residence time.
Let V = 100 m3
Feed flow rate = 10 m3/d
Feed solids content = 10 kg/m3
Flow rate from the digester = 12 m3/d
Solids content of sludge from the digester = 13.3 kg/m3
Flow rate of sludge from the thickener = 4 m3/d
Solids content of sludge from the thickener = 40 kg/m3
Flow rate of sludge returned to the digester = 2 m3/d
Flow rate of product sludge = 2 m3/d
en = 100x13.3 = 16.6d
2x40
The denominator is the product of the flow rate leaving
the system (2 m3/d) and the concentration of sludge leav-
ing the thickener (40 kg/m3). Notice that flow rate of sludge
leaving the digester did not enter into the calculation.
Comments on Batch and Staged Operation
Sludge can be aerobically digested using a variety of
process configurations (including continuously fed single-
or multiple-stage completely mixed reactors), or it can be
digested in a batch mode (batch operation may produce
less volatile solids reduction for a primary sludge than the
other options because there are lower numbers of aerobic
microorganisms in it). Single-stage completely mixed re-
actors with continuous feed and withdrawal are the least
effective of these options for bacterial and viral destruc-
tion, because organisms that have been exposed to the
adverse condition of the digester for only a short time can
leak through to the product sludge.
Probably the most practical alternative to use of a single
completely mixed reactor for aerobic digestion is staged
operation, such as use of two or more completely mixed
digesters in series. The amount of slightly processed sludge
passing from inlet to outlet would be greatly reduced com-
pared to single-stage operation. If the kinetics of the reduc-
tion in pathogen densities are known, it is possible to esti-
mate how much improvement can be made by staged op-
eration.
Farrah et al. (1986) have shown that the declines in den-
sities of enteric bacteria and viruses follow first-order ki-
netics. If first-order kinetics are assumed to be correct, it
can be shown that a one-log reduction of organisms is
achieved in half as much time in a two-stage reactor (equal
volume in each stage) as in a one-stage reactor. Direct
experimental verification of this prediction has not been
carried out, but Lee et al. (1989) have qualitatively verified
the effect.
It is reasonable to give credit for an improved operating
mode. Since not all factors involved in the decay of micro-
organisms densities are known, some factor of safety
should be introduced. It is recommended then that for
staged operation using two stages of approximately equal
volume, the time required be reduced to 70% of the time
required for single-stage aerobic digestion in a continu-
ously mixed reactor. This allows a 30% reduction in time
instead of the 50% estimated from theoretical consider-
ations. The same reduction is recommended for batch
operation or for more than two stages in series. Thus, the
time required would be reduced from 40 days at 20°C (68°F)
to 28 days at 20°C (68°F), and from 60 days at 15°C (59°F)
to 42 days at 15°C (59°F). These reduced times are also
more than sufficient to achieve adequate vector attraction
reduction.
If the plant operators desire, they may dispense with the
PSRP time-temperature requirements of aerobic digestion
but instead demonstrate experimentally that microbial lev-
els in the product from their sludge digester are satisfacto-
rily reduced. Under the current regulations, fecal coliform
densities must be less than or equal to 2,000,000 CFU or
MPN per gram total solids. Once this performance is dem-
onstrated, the process would have to be operated between
monitoring episodes at time-temperature conditions at least
as severe as those used during their tests.
135
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References N.TIS Publication No. PB86-183084/AS. National Tech-
nical Information Service, Springfield, Virginia.
Farrah. S.R., G. Bitton, and S.G. Zan. 1986. Inactivation
of enteric pathogens during aerobic digestion of waste- Lee, K.M., C.A. Brunner, J.B. Farrell, and A.E. Eralp. 1989.
water sludge. EPA Pub. No. EPA/600/2-86/047. Wa- Destruction of enteric bacteria and viruses during two-
ter Engineering Research Laboratory, Cincinnati, OH. phase digestion. Journal WPCF 61(6):1421-1429.
136
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Appendix F
Sample Preparation for Fecal Coliform Tests and Salmonella sp. Analysis
1. Sample Preparation for Fecal Coliform
Tests
1.1 Class B Alternative 1
To demonstrate that a given domestic sludge sample
meets Class B Pathogen requirements under alternative
1, the density of fecal coliform from at least seven samples
of treated sewage sludge must be determined and the
geometric mean of the fecal coliform density must not ex-
ceed 2 million Colony Forming Units (CPU) or Most Prob-
able Number (MPN) per gram of total solids (dry weight
basis). The splids content of treated domestic sludge can
be highly variable. Therefore, an aliquot of each sample
must be dried and the solids content determined in accor-
dance with procedure 2540 G. of the 18th edition of Stan-
dard Methods for the Examination of Water and Wastewa-
ter (SM).
Sludge samples to be analyzed in accordance with SM
9221 E. Fecal Coliform MPN Procedure and 9222 D. Fe-
cal Coliform Membrane Filter Procedure may require dilu-
tion prior to analysis. An ideal sample volume will yield
results which accurately estimate the fecal coliform den-
sity of the sludge. Detection of fecal coliform in undiluted
samples could easily exceed the detection limits of these
procedures. Therefore, it is recommended that the follow-
ing procedures be used (experienced analysts may sub-
stitute other dilution schemes as appropriate).
For Liquid Samples:
1. Use a sterile graduated cylinder to transfer 30.0 ml
of well mixed sample to a sterile blender jar. Use
270 ml of sterile buffered dilution water (see Sec-
tion 9050C) to rinse any remaining sample from the
cylinder into the blender. Cover and blend for two
minutes on high speed. 1.0 ml of this mixture is 0.1
ml_ of the original sample or 1.0X10"1.
2. Use a sterile pipette to transfer 11.0 ml_ of the
blended sample mixture to 99 ml of sterile buffered
dilution in a sterile screw cap bottle and mix by vig-
orously shaking the bottle a minimum of 25 times.
This is dilution "A." 1.0 ml of this mixture is 0.010
ml_ of the original sample or 1.0X10"2.
3. Use a sterile pipette to transfer 1.0 ml of dilution
"A" to a second screw cap bottle containing 99 ml
of sterile buffered dilution water, and mix as before.
This is dilution "B." 1.0 ml of this mixture is 0.00010
ml of the original sample or 1.0X104.
4. Use a sterile pipette to transfer 1.0 ml of dilution
"B" to a sterile screw cap bottle containing 99 ml of
sterile buffered dilution water, and mix as before.
This is dilution "C." Go to step 5 for MPN analysis
(preferred) or 7 for MF analysis.
5. For MPN analysis, follow procedure 9221 E. in SM.
Four series of 5 tubes will be used for the analysis.
Inoculate the first series of 5 tubes each with 10.0
ml of dilution "B." This is a 0.0010 m L of the original
sample. The second series of tubes should be in-
oculated with 1.0 ml of dilution "B" (0.00010). The
third series of tubes should receive 10.0 ml of
"C" (0.000010). Inoculate a fourth series of 5 tubes
each with 1.0 ml of dilution "C" (0.0000010). Con-
tinue the procedure as described in SM.
6. Refer to Table 9221 .IV. in SM to estimate the MPN
index/100 ml. Only three of the four series of five
tubes will be used for estimating the MPN. Choose
the highest dilution that gives positive results in all
five tubes, and the next two higher dilutions for your
estimate. Compute the MPN/g according to the fol-
lowing equation:
MPN Fecal Coliform/g =
10 x MPN Index/100 ml
largest volume x % dry solids
Examples:
In the examples given below, the dilutions used to de-
termine the MPN are underlined. The number in the nu-
merator represents positive tubes; that in the denomina-
tor, the total number of tubes planted; the combination of
positives simply represents the total number of positive
tubes per dilution.
Example
a
b
c
0.0010
ml
5/5
5/5
0/5
0.00010
ml
5/5
3/5
1/5
0.000010
ml
3/5
1/5
0/5
0.0000010
ml
0/5
0/5
0/5
Combination
of positives
5-3-0
5-3-1
0-1-0
137
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For each example we will assume that the total solids
content is 4.0%.
For example a:
The MPN index/100 ml from Table 9221.4 is 80. There-
fore:
.._,... 10x80
MPN/g =
0.00010x4.0
= 2.0x106
For example b:
The MPN index/100 mLfrom Table 9221.4 is 110. There-
fore:
10x110
MPN/g =
0.0010x4.0
= 2.8 x 105
For example c:
The MPN index/100 ml from Table 9221.4 is 2. There-
fore:
10x2
MPN/g = =5.0x103
0.0010x4.0
5. Alternately the membrane filter procedure may be
used to determine fecal coliform density. This
method should only be used if comparability with
the MPN procedure has been established for the
specific sample medium. Three individual filtrations
should be conducted in accordance with SM 9222
D. using 10.0 ml of dilution "C," and 1.0 ml and
10.0 ml of dilution "B." These represent 0.000010,
0.00010, and 0.0010 ml of the original sample. In-
cubate samples, and count colonies as directed.
Experienced analysts are encouraged to modify this
dilution scheme (e.g. half log dilutions) in order to
obtain filters which yield between 20 and 60 CFU.
6. Compute the density of CFU from membrane filters
which yield counts within the desired range of 20 to
60 fecal coliform colonies:
coliform colonies/g =
For Solid Samples:
coliform colonies counted x 100
ml sample x % dry solids
1. In a sterile dish weigh out 30.0 grams of well mixed
sample. Whenever possible, the sample tested
should contain all materials which will be included
in the sludge. For example, if wood chips are part of
a sludge compost, some mixing or grinding means
may be needed to achieve homogeneity before test-
ing. One exception would be large pieces of wood
which are not easily ground and may be discarded
before blending. Transfer the sample to a sterile
blender. Use 270 m L of sterile buffered dilution wa-
ter to rinse any remaining sample into the blender.
Cover and blend on high speed for two minutes. One
milliliter of this sample contains 0.10 g of the origi-
nal sample.
2. Use a sterile pipette to transfer 11.0 ml of the
blender contents to a screw cap bottle containing
99 ml_ of sterile buffered dilution water and shake
vigorously a minimum of 25 times. One milliliter of
this sample contains 0.010 g of the original sample.
This is dilution "A."
3. Follow the procedures for "Liquid Samples" starting
at Step 3.
Examples:
Seven samples of a treated sludge were obtained prior
to land spreading. The solids concentration of each sample
was determined according to SM. These were found to
be:
Sample No.
1
2
3
4
5
6
7
Solids Concentration
3.8
4.3
4.0
4.2
4.1
3.7
3.9
The samples were liquid with some solids. Therefore the
procedure for liquid sample preparation was used. Fur-
thermore, the membrane filter technique was used to de-
termine if the fecal coliform concentration of the sludge
would meet the criteria for Class B alternative 1. Samples
were prepared in accordance with the procedure outlined
above. This yielded 21 individual membrane filters (MF)
plus controls. The results from these tests are shown in
Table 1
Table 1. Number of Fecal Coliform Colonies on MF Plates
Sample No.
1
2
3
4
5
6
7
0.000010
mL Filtration
0
2
0
0
0
0
0
0.00010
mL Filtration
1
18
8
5
1
1
1
0.0010
mL Filtration
23
TNTC
65
58
17
39
20
The coliform density is calculated using only those MF
plates which have between 20 and 60 blue colonies when-
ever possible. However, there may be occasions when the
total number of colonies on a plate will be above or below
the ideal range. If the colonies are not discrete and appear
to be growing together results should be reported as "too
numerous to count" (TNTC). If no filter has a coliform count
falling in the ideal range (20 - 60), total the coliform counts
on all countable filters and report as coliform colonies/g.
For sample number 2 the fecal coliform density is:
138
-------
coliform colonies/g =
(2+18)x100
(0.000010 +0.00010) x 4.3
= 4 2 x 106 For Lic|uic' Samples:
Sample number 3 has two filters which have colony
counts outside the ideal range also. In this case both count-
able plates should be used to calculate the coliform den-
sity/g. For sample number 3, the fecal coliform density is:
coliform colonies/g =
(8 + 65) x 100
(0.00010 + 0.0010)x 4.0
= 1.6x106
Except for sample number 5, all of the remaining samples
have at least one membrane filter within the ideal range.
For these samples, use the number of colonies formed on
that filter to calculate the coliform density. For sample num-
ber 1, the fecal coliform density is:
... ... 23x100
coliform colonies/g =
0.0010x3.8
= 6.0x 105
Coliform densities of all the samples were calculated and
converted to Iog10 values to compute a geometric mean.
These calculated values are presented in Table 2.
Table 2. Coliform Density of Sludge Samples
Sample No.
1
2
3
4
5
6
7
Coliform Density
6.0 x105
4.2x106
1.6x106
1.4x105
4.0x105
1.0 x106
5.1x105
l°9io
5.78
6.63
6.22
6.14
5.60
6.02
5.71
The geometric mean for the seven samples is determined
by averaging the log 10 values of the coliform density and
taking the antilog of that value.
(5.78 + 6.63 + 6.22 + 6.14 + 5.60 + 6.02 + 5.71)/7 = 6.01
The antilog of 6.01 = 1.03 x 106
Therefore, the geometric mean fecal coliform density is
below 2 million and the sludge meets Class B Pathogen
requirements under alternative 1.
1.2 Class A Alternative 1
Part 503 requires that, to qualify as a Class A sludge,
treated sewage sludge must be monitored for fecal coliform
(or Salmonella sp. and have a density of less than 1,000
MPN fecal coliform per gram of total solids (dry weight
basis). The regulation does not specify total number of
samples. However, it is suggested that a sampling event
extend over two weeks and that at least seven samples
be collected and analyzed. The membrane filter procedure
may not be used for this determination. This is because
the high concentration of solids in such sludges may plug
the filter or, render the filter uncountable. The total solids
content for each sample must be determined in accordance
with procedure 2540 G. of SM.
Follow procedure 9221 E. in SM. Inoculate at least
four series of five tubes using ten fold serial dilu-
tions. Prepare the sample as described for "Class
B Alternative 1, Liquid Samples," except inoculate
each of the first series of tubes with 10.0 m L of the
blender contents (the concentration of the enrich-
ment broth must be adjusted to compensate for the
volume of added sample). This is equivalent to add-
ing 1.0 ml_ of sludge to the first series of tubes. In-
oculate the remaining tubes and complete the analy-
sis in accordance with SM.
2. Calculate the MPN as directed in Step 4 above.
For Solid Samples:
1. Follow procedure 9221 E. in SM. Inoculate at least
four series of five tubes using ten fold serial dilu-
tions. Prepare the sample as described for "Class
B Alternative 1, Solid Samples," except inoculate
each of the first series of tubes with 10.0 ml of the
blender contents (the concentration of the enrich-
ment broth must be adjusted to compensate for the
volume of added sample). This is equivalent to add-
ing 1.0 g of sludge (wet wieght) to the first series of
tubes. Inoculate the remaining tubes and complete
the analysis in accordance with SM.
2. Calculate the MPN as directed in step 4 above.
2. Sample Preparation for Salmonella sp.
Analysis
Salmonella sp. quantification may be used to demon-
strate that a sludge meets Class A criteria, instead of ana-
lyzing for fecal coliforms. Sludges with Salmonella sp. den-
sities below 3 MPN/4 g total solids (dry weight basis) meet
Class A criteria. The analytical method described in Ap-
pendix F of this document describes the procedure used
to identify Salmonella sp. in a water sample. Similarly, the
procedures for analysis of Salmonella sp. in SM (Section
9260 D) do not address procedures for sludges, the sample
preparation step described here should be used, and the
total solids content of each sample must be determined
according to method 2540 G in SM.
For Liquid Samples:
1. Follow the same procedure used for liquid sample
preparation for fecal coliform analysis described un-
der "Class A Alternative 1." However, the enrichment
medium used for this analysis should be dulcitol se-
lenite broth (DSE) as described in Appendix G of
this document or dulcitol selenite or tetrathionate
broth as described in SM. Only three series of five
tubes should be used for this MPN procedure. Use
a sterile open tip pipette to transfer 10.0 mL of well
mixed sample to each tube in the first series. These
tubes should contain 10.0 mL of double strength
enrichment broth. Each tube in the second series
should contain 10.0 mL of double strength enrich-
ment broth. These tubes should each receive 10.0
139
-------
ml of the blended mixture. The final series of tubes
should contain 10.0 ml of single strength enrich-
ment broth. These tubes should each receive 1.0
ml of the blended mixture. Complete the MPN pro-
cedure as described in Appendix G or SM as ap-
propriate.
2. Refer to Table 9221.IV. in SM to estimate the MPN
index/100 ml. Calculate the MPN/4 g according to
the following equation:
Salmonella sp. MPN/4 g = MPN Index/100 mL x 4
% dry solids
For example:
If one tube in the first series was identified as being posi-
tive for Salmonella sp. and no other tubes were found to
be positive, from Table 9221. IV one finds that a 1-0-0 com-
bination of positives has an MPN index/100 ml of 2. If the
percent of dry solids for the sample was 4.0, then:
Salmonella sp. MPN/4g
2x4
4.0 = 2
= 2
For Solid Samples:
1. Follow the procedure for solid sample preparation
for fecal coliform analysis described under Class A
Alternative 1 above. However, the enrichment me-
dium used for this analysis should be dulcitol selen-
ite broth (DSE) as described in Appendix G or dulci-
tol selenite or tetrathionate broth as described in
SM, and only three series of five tubes should be
used for this MPN procedure. Use aseptic technique
to weigh out and transfer 10.0 g of well mixed sample
to each screw cap tube in the first series, shake
vigorously to mix. These tubes should contain 10.0
ml of double strength enrichment broth. Likewise,
each tube in the second series should contain 10.0
ml of double strength enrichment broth. These tubes
should receive 10.0 ml of the blended mixture. The
final series of tubes should contain 10.0 ml of single
strength enrichment broth. These tubes should re-
ceive 1.0 ml of the blended mixture. Alternately,
because the calculated detection limit is dependent
upon the total solids content of the sample, samples
with total solids contents >28% can be blended as
described above and the blender contents can be
used for inoculating the initial series of tubes. When
this option is chosen, the final series of tubes will
contain 0.1 ml of the blender contents. Complete
the MPN procedure as described in Appendix G or
SM as appropriate.
2. Refer to Table 9221 .IV. in SM to estimate the MPN
index/100 ml. Calculate the MPN/4 g according to
the following equation:
Sa/mone//a sp. MPN/4g = MPN Index/1 OOmLx 4
% dry solids
140
-------
Appendix G
Kenner and Clark (1974) Analytical Method for Salmonella sp. Bacteria*
Detection and enumeration of Salmonella
and Pseudomonas aeruginosa
BERNARD A. KENNER AND HAROLD P. CLARK
THE FEDERAL WATER POLLUTION CON-
TROL AMENDMENTS of 1972 1 4 may
well require the quantification and enu-
meration of pathogens such as Salmonella
species in all classes of waters. The re-
quirements are described by Shedroff.5
One of the continuing programs of the
Environmental Protection Agency (EPA)
is a research project concerned with the
development of practical laboratory meth-
ods for the isolation, quantification, and
enumeration of pathogens from polluted
waters. This paper reports a monitoring
method developed for the simultaneous
isolation and enumeration of Salmonella
species and Pseudomonas aeruginosa from
potable waters, reuse waters, treatment
plant effluents, receiving waters, and
sludges.
The method described herein, and de-
veloped by Kenner,6 is practical because
readily available bacteriological media,
chemicals, and equipment are all that are
required to obtain the desired results.
These results are the establishment of the
absence or presence of Salmonella species
(pathogenic hazardous bacteria) and/or
Pseudomonas aeruginosa (potential patho-
gens) that affect persons who are in a
debilitated condition and are very com-
mon as infectious agents in hospitals be-
cause of their resistance to antibiotic
therapy.7 9 Potable waters have also been
shown to contain Ps. aeruginosa^ The
sources of these potential pathogens are
human and animal feces and waste-
waters.11'12
When the monitoring method was used,
it was found that 100 percent of municipal
wastewaters and treatment plant sludges
contained both of these potential patho-
gens. Ps. aeruginosa has been found in
potable water supplies of large and small
municipalities where insufficient residual
chlorine is evident. Also important is the
fact that these organisms may be found in
the absence of fecal coliforms, whereas
negative indicator tests may give a false
sense of security. It is believed by the
authors that these organisms may be better
indicators than fecal coliforms of pollu-
tion in potable, direct reuse, bathing, and
recreational waters.
MATERIALS AND METHODS
The monitoring method uses a multiple
tube (MPN) procedure in which dulcitol
selenite broth (DSE) 13 is used for primary
enrichment medium, and is modified by
the use of sodium acid selenite (BBL).
The formula is proteose peptone (Bacto),
0.4 percent; yeast extract (Bacto), 0.15
percent; dulcitol, 0.4 percent; BBL, 0.5
percent; NazHPCM, 0.125 percent; and
KH2PO4, 0.125 percent in distilled water.
The constituents are dissolved in a sterile
flask, covered with foil, and heated to
88°C in a water bath to obtain a clear
sterile medium that does not require ad-
justment of pH. Productivity for Salmo-
nella species is enhanced by the addition
of an 18-hr, 37°C culture of Salmonella
paratyphi A (10 percent by volume) in
single-strength DSE broth, killed by heating
to 88°C.
Concentration of bacteria from large
volumes of water is necessary when pota-
ble, direct reuse, receiving waters, and
treatment effluents are being monitored.
-Vol. 46, No. 9, September 1974 2163
141
-------
KENNER AND CLARK
TABLE I.-Retentive Characteristics of SeveralGlass Fiber Filter Papers*
Compared with Membrane Filters
Filter
Total Bacteria f
Filtered
Number
Filter
Percentage
Retention
Millipore (MF) HAWG 047 HA 0.45 |0,
grid, 47 mm, Millipore Filter Corp.
984H Ultra Glass Fiber Filter, 47 mm,
Reeve Angel Corp.
GF/F Glass Paper Whatman, 147 mm,
Reeve Angel Corp.
GF/D Glass Paper Whatman,* 47 mm>
Reeve Angel Corp.
934AH Glass Fiber Filter, 47 mm,
Reeve Angel Corp.
GF/A Glass Paper Whatman, 47 mm,
Reeve Angel Corp.
white,
1,376
1,229
2,698
2,622
1,049
1,066
0
25
6
2,166
198
680
100
98
99.8
17.4
81
36
* The 984H Ultra Glass Fiber Filter is flexible when wet, readily allows filtration of large volumes of water,
can readily be bent double with forceps, and, when placed into primary enrichment broth, disintegrates when
tube is shaken and releases entrapped bacteria.
f Enteric bacteria. E. coli, 0.5 X 1-3 |a
{ A new paper filter GF/F has better retentive properties than the 984H, and has same properties (tested
Oct. 1973).
Concentration is attained by filtration
through glass fiber filters* in a membrane
filter apparatus. After the desired volume
of water is filtered through the ultra filter,
tube in the first row of the setup into 10
ml of double-strength DSE is made, 1 ml
of sample in 9 ml of single-strength DSE
in the second row, and so on. The MPN
the flexible filter is folded double with table in "Standard Methods" 14 is used to
sterile forceps and inserted into a suitable
volume of single-strength DSE medium
contained in a test tube located in the
first row of the multiple tube setup. The
tube should then be shaken to cause
filter to disintegrate (Table I and Figure
1). To obtain MPN results per one 1 or
per 10 1, 100 ml or 1,000 ml of sample,
respectively, are filtered for each tube of
DSE medium in the first row of the five-
tube MPN setup. Additional dilutions are
made by transferring material from tubes
in the first row to tubes farther back in
the setup.
Obtaining results on a per 1-gal (3.8-1)
basis requires filtration of 380 ml, and on
a per 10-gal (38-1) basis requires filtration
of 3,600 ml for each tube in the first row.
Where concentration of bacteria is not
usually required, as in municipal waste-
waters, sludges, or primary effluents, the
regular transfer of 1 0 ml of sample to each
* Reeve Angel 984H ultra glass fiber filter, 47
mm Reeve Angel & Co., Inc., Clifton, N. J.
Mention of trade names does not constitute en-
dorsement or recommendation by EPA.
read directly the results per volume of
sample.
Incubation temperature of 40° ± 0.2°C
for 1 and 2 days is critical to obtain opti-
mum recovery of Salmonella sp. and
Pseudomonas aeruginosa when DSE broth
is used for primary enrichment. After
primary incubation at 40°C surface loop-
fuls (scum) (7 mm platinum or nichrome
wire loop) are removed from each multi-
ple-tube culture and streaked on each of
two sections of a divided plate of Xylose
lysine desoxychqlate agar (XLD) 15 in order
to isolate colonial growth. The numbered
plates are inverted and incubated at 37°C
for a period not to exceed 24 hr.
Commercial dehydrated XLD agars (BBL
and Difco) are satisfactory if they are re-
constituted in distilled water in sterile
foil-covered flasks and heated to 88° or
92°C, respectively. The agar is then
cooled to 55° to 60°C and distributed in
sterile petri dishes. This laboratory pre-
fers 10-ml portions in each section of a
divided sterile disposable plastic dish
(Figure 1).
2164 Journal WPCF
142
-------
PATHOGEN DETECTION
Sterile
polypropylene
container
Filter funnel
for 47-mm 984 H
filer pad
2 Gallon
sample
of waler
vacuum
flask
After filtration filter-pad is
folded double with forceps
4
5 1000ml pad inserted into 20ml
1xDSE broth for each of 5-tubes
_in 1st row
I 2ml to
8ml 1xDSE in
_2nd row
1 ml Irom
2nd row to
9ml ixDSE /
3rd row etc
N Completed MPN Incubated at 40C for
1- and 2- days-Secondary medium streaked for
Isolated colonies from surface MPN tubes with
7 mm Nichrome 22 gauge loop
6
XLD Agar plate invert plates incubate 37C 20-24 hrs
Loosen cap & incubate
-_ 6-20 hrs
W toe
Chloroform
extract
I blue
1000A
King A
Tech Agar
Loosen caps
Pick Black centered If
* colonies to KIA ,
slants 1000 A. [Red or
_i < no-change
i Lslanl
'H2S
Black
Yellow
Acid
Bull
Pink colonies
rarely
Salmonella sp
'Streak and Slab butt
Blue Green
Ps. aeruginosa
Slide Serology
Salmonella "0". poly A-l
or Salmonella "H" poly a-z \ Negativex
Incubate Slants at 35-
Pick flat erose edge 37C 18-20 hr.
grayish alkaline colonies
to Tech Agar streak & stab
Urease
' Test
. typical slant
^r Salmonella sp
Purify on XLD Plate
for isolated pure strains
FIGURE I.~Procedure for isolation of pathogens.
Positive incubated XLD plate cultures
contain typical clear, pink-edged, black-
centered Salmonella colonies, and flat,
mucoid, grayish alkaline, pink erose-edged
Ps. aeruginosa. The Salmonella colonies
are picked to Kligler iron agar (KIA) or
Triple sugar iron agar slants for typical
appearance, purification, and identity tests.
Ps. aeruginosa colonies are picked to King
A agar slants (Tech agar BBL) for obtain-
ing the bluegreen pyocyanin confirmation
at 40°C (Figure 1).
Typically, Salmonella sp. slant cultures
(streaked and stabbed), incubated over-
-Vol. 46, No. 9, September 1974 2165
143
-------
KENNER AND CLARK
TABLE IL-Advantage of Ultra-filter 984H Use in Monitoring Suspected
Waters for Salmonella species
Type of Sample
Stormwater runoff
Stormwater runoff
Activated sludge effluent
Municipal wastewater
Municipal wastewater
Activated sludge effluent
Mississippi River water,
mile 403.1
Municipal wastewater
Salmonella
(no/100 ml)
4.5
<3.0
<3.0
6.2
<3.0
<3.0
43
3.0
Serotypes Found
(no./100ml)
S. bareilly7
none
none
Arizona3
none
none
S. ohio10
S. cholerasuis
var. kunzendorf2
Salmonella
(no/gal)
210
7.3
3.6
1,500
110
28
>11,000
21
Serotypes Found
(no./gal)
S. kottbus10
S. t>areilly"
S. Java4
S. muenchen2
S. group G4
Arizona4
S. anatum2
S. newporf
S. san diego7
S. worthington2
S. anatum3
S. derby1
S. newporf
S. Uockley7
S. newporf
S. ohio19
S. derby2
S. mdeagridis6
S. cholerasuis
var. kunzendorf5
S. navport6
night at 37°C, give an unchanged or alka-
line red-appearing slant; the butt is black-
ened by ri~2S, is acid-yellow, and has gas
bubbles, except for rare species. Typical-
appearing slant cultures are purified by
transferring them to XLD agar plates for
the development of isolated colonies. The
flat or umbonated-appearing colonies with
large black centers and clear pink edges
then are picked to KIA slants (streaked and
stabbed), incubated at 37°C, and urease
tested before the identification procedure
(Figure 1). Urease-negative tubes are re-
tained for presumptive serological tests
and serotype identification.
Typical Tech agar slant cultures for Ps.
aeruginosa that are incubated at 40°C
overnight turn a bluegreen color from
pyocyanin, a pigment produced only by
this species. A reddish-blue color is caused
by the additional presence of pyorubin.
The blue pigment is extractable in chloro-
form and is light blue in color after a few
hours at room temperature. No further
tests are necessary. The count is read di-
rectly from the MPN table.
2166 Journal WPCF
JUSTIFICATION FOR PROCEDURES
Choice of primary enrichment medium
and secondary isolation agar. Most of the
enrichment media described in contem-
porary literature were designed for the
isolation of pathogens from clinical speci-
mens from ill persons or from samples of
suspected foods, and they work quite well
for those types of samples. When they
are used, however, for the isolation of
pathogens from polluted waters and other
types of environmental samples, such as
soils, they do not prove adequate. En-
richment media that were tested and found
wanting in regard to detection and selec-
tivity were tetrathionate broth (Tl), with
and without brilliant green at 41.5°C;
selenite cystine broth at 37°C; selenite
F broth at 37°C; selenite brilliant green,
with and without sulfa, at 37° and 41.5°C;
and Gram-negative broth (GN) at 40°C and
41.5°C.
None of the media named worked well
at 37°C for the isolation of Salmonella sp.,
and isolation from wastewaters only oc-
144
-------
PATHOGEN DETECTION
TABLE III.-Percentage of Colony Picks from DSE-XLD Combination Positive
for Salmonella species
Liquid Samples
Municipal wastewater
Stockyard wastewater
Rivers
Mississippi
Ohio
Storm water runoffs
Activated sludge biological
effluent
Trickling filter effluent
Package plant effluent
Package plant sludge
Chlorinated primary outfall
Creek 1 mile (1.6 km) below
package plant outfall
Home cisterns
Dupont R-O
Feed
Reject
Product-negative
Raw primary sludge
Primary activated sludge
Anaerobic digester sludge
Anaerobic digester sludge
(28 days)
Activated secondary sludge
Total
No.
15
1
8
I
20
7
6
2
2
2
2
1
1
4
1
3
1
6
84
Total Picks
from XLD
315
36
110
18
386
103
83
41
17
37
17
20
16
80
15
78
9
189
1,570
No.
Positive
250
36
84
14
306
78
55
37
13
16
10
14
8
66
13
65
3
155
1,223
No.
Negative
65
0
26
4
80
25
28
40
4
21
7
6
8
14
2
13
6
34
347
Percentage
Positive
79
100
76
78
79
76
66
90
76
43
59
70
50
83
87
83
33
82
average 78
Range of
Salmonella
count^lOO ml
3.0-1,500
2,100
1.5->300
0.2-1.5
0.1-1,100
0.35-140
1.8-620
43-240
3-43
4.5-12
0.26-1.1
4.3
0.91
13-700
23
79-170
2
11->11,000
curred by chance and was purely qualita-
tive. Of the above-named media used in
preliminary tests, selenite brilliant green
sulfa broth (SBGS) at 41.5°C gave the
best isolation of Salmonella sp. from waste-
waters (with and without the addition of
S. typhimuriumin known numbers). Of
thirteen wastewater samples tested in SBGS
at 41.5°C, six contained Salmonella or 46
percent were positive. With DSE broth at
40°C, 28 of 28, or 100 percent of waste-
water samples, gave positive results.
Studies were not continued on SBGS me-
dium when it was noted that some lots of
commercially available SBGS seemed to be
selective for Salmonella sp. while others
were not. The medium was then pre-
1 R
pared according to the original formula
with six different lots of brilliant green
(certified), only one of which was selec-
tive. The use of brilliant green agar as
a selective medium is subject to the same
variability, according to Read and Reyes.17
The main reasons for rejection of TT,
with and without brilliant green, and for
selenite broth's using brilliant green agar
and XLD agar as secondary media are not
only fewer isolations of Salmonella sp., but
also the poor selectivity of these combina-
tions when they are used for monitoring
polluted waters. These combinations' poor
selectivity at 41.5°Cis apparent in the
results of Dutka and Bell,*8 where the TT
broth-XLD combination yielded 26 percent
confirmation of colonial picks, and selenite
broth-BGA and selenite broth-XLD gave 55
and 56 percent confirmations, respectively.
The authors had similar results. The GN-
XLD combination was poorest for water
samples at 40° and 41.5°C yielding less
than 10 percent isolations from waste-
waters.
Effect of incubation temperature on iso-
lation of Salmonella sp. In a study of
26 wastewater samples that was conducted
with the DSE multiple tube setups at three
-Vol. 46, No. 9, September 1974 2167
145
-------
KENNER AND CLARK
TABLE rV.-Serotypes of Salmonella Found in
Polluted Waters
; Vo of
Serotjpe strains
1 lyphiitmrium* 375
2 derby 287
3 cubana 223
4 Chester 203
5 nwport 1 188
6 kottbus , 158
7 blocklry : 157
8 infautis 141
9 entiriMis 128
10 aiiafHin 127
11 htidtlbrrg 111)
12 manhaltaii '17
13 paratyplii B 91
14 i(II> i 42
22 {£nIOff£tt>'f i 41
23 orioii ' 41
24 stnftinbrrf 39
25 jchwarsengrund t 37
26<«i»fioii 33
27 cholerasuis 30
28 ftiiizn ; 29
29 cholfraittis var.
kunzcndorf 29
Other fcrotyiws:
30 albauy 20
314«>i/lra : 10
32 braendfrttp -, 13
JJ brancastcr 1
34 brtdfiiry 8
35 California i
3d dry pool ' 14
37 fricilcimu 4
38 tire 25
40 /iui/d . 2
41 karlfivJ 2
42 hatantt . 16
43 iitJiitna > 10
44>,mi 15
45 jiiriiiiid 13
46hlcfc.«!i-U 17
47 Uitnita 26
48 mtlfimriilis ! 18
49 musiiiit i 14
50 ntwiiiKlm i
51 ntwltlii.ls ; K
52 fn)ru'ic/l : 14
53 ii/iiii 19
54 prriiim 2
55 retitliiiR 26
56 /u6r:[uui 15
57 saiiil /inn! 21
59 jiw>*&ury 9
60 JuA-joiiy 16
61 l.iiiifj),,- 12
62 lyplii-sias var.
voldiin-ei! '
63 i{-
-------
PATHOGEN DETECTION
TABLE V.-Percentage of Various Types of Water Samples Positive for Salmonella species
Type of Sample
Number of
Samples
Number
Positive
Number
Negative
Percentage
Positives
Municipal wastewaters 28
Municipalprimary effluents
(chlorinated) 9
Activated sludge effluents (clarified) 40
Activated sludge effluents
Before chlorination 5
After chlorination, 1.4-2.0 mg/1
residual, 5 min contact 8
Trickling filter effluents 26
Package plant effluents 15
Creek 1 mile (1.6 km) below package
plant 3
Ohio River above Cincinnati public
landing 20
Wabash River 4
Mississippi River 4
Streams collective 31
Stormwater runoff after heavy rain 6
Farm wells 4
Home cisterns suburban 5
Septic tank sludges 6
Totals 183
28
5
29
0
15
7
4
11
114
13
3}
4
3
3
69
56.0
72.5
80.0
0.0
57.7
46.7
100.0
45.0
75.0
75.0
58.0
50.0
0.0
40.0
50.0
* Municipal intake.
f Positive by per-gallon technique.
{ Negative by per-100 ml technique.
concentrate the bacteria in a 10-gal (38-1)
sample or a 100-gal (380-1) sample of
potable or reuse water to obtain results,
and still not require even more expensive
filtration or centrifugation equipment. It
also seems unrealistic to test only extremely
small samples of the water being examined,
because they may not be representative.
Table IV contains a list of Salmonella
serotypes isolated from polluted waters and
ranked according to the frequency of sero-
type isolations. It will be noted that all
of the serotypes except S. typhi were iso-
lated from environmental samples by the
monitoring method, and that only 6 of the
65 serotypes reported were not reported
as occurring in humans in the U. S. over
the period from 1965 to 1971.
Table V summarizes the percentage of
various types of water samples positive
for Salmonella sp. Of interest is the fact
that 100 percent of the municipal waste-
waters tested contain Salmonella sp., that
56 percent of chlorinated primary effluents
tested contain the pathogens, and that 100
percent of chlorinated secondary effluents
are negative for pathogens. There are
more studies scheduled for testing of sec-
ondary and tertiary effluents to obtain
minimal chlorine residuals. Calabro et
al.20 reported that more than 50 attempts
at isolating Salmonella sp. from septic tank
samples using SBGS-BGSA combinations were
unsuccessful.
Table VI summarizes the isolation of
Ps. aeruginosa from potable water supply,
that is, wells, cisterns, and small municipal
water supply. It should be noted that
fecal coliforms were not detected in most
of these samples. Fecal streptococci counts
were higher than fecal coliform counts
where both tests were used. Ps. aeruginosa
were present in all but three of the tests,
and Salmonella sp. were isolated from
two different cistern samples.
It is of importance to the user of patho-
gen tests that the test be quantitative. In
initial studies on the DSE-XLD combination,
it was important to know if the enrichment
broth would support the growth of a wide
-Vol. 46, No. 9, September 1974 2169
147
-------
KENNER AND CLARK
TABLE Vl.-Isolation of Pseudomonas aeruginosa from Potable Water Supply
Type of Sample
Well 8/16/71
Well 8/25/71
Well 3/27/72
Well 3/27/72
(chlorinated)
Well 8/23/72
Well 10/ 4/72
Suburban cisterns
87 4/72
107 9/72*
III 6/72*
117 6/72
11/26/72
Municipal supplies
Population served 54,700
3/17/71
6/21/71
7/19/71
6/19/72
107 9/72
57 8/72
Population served 14,000
57 8/72
10/24/72
Population served < 10,000
11/27/72
Ps. aeruginosa
Isolation
+
+
+
+
+
+
+
+
+
+
+
+
+
+
0
0
+
0
Indicators/100 ml
Total
Coliforms
4
22
Fecal
Coliforms
<1
0.25
<2
180
15
<2
<2
3
<1
<1
0.26
<1
<1
-------
PATHOGEN DETECTION
of large volumes of high quality waters,
wherein the absence of indicator bacteria
(that is, total coliforms, fecal coliforms,
and fecal streptococci), may give a false
sense of security because of the low
volumes of water usually tested. Justifica-
tion for each step of the procedural method
is presented.
ACKNOWLEDGMENTS
Credits. The technical assistance of
Pauline C. Haley in performing the neces-
sary serology for identifying many of the
Salmonella serotypes reported is gratefully
acknowledged.
Authors. Bernard A. Kenner is super-
visory research microbiologist, and Harold
P. Clark is biological technician, Waste
Identification and Analysis Activity of the
Advanced Waste Treatment Research Lab-
oratory, Natonal Environmental Research
Center, U. S. Environmental Protection
Agency, Cincinnati, Ohio.
REFERENCES
1. Federal Water Pollution Control Amendments,
PL 92-500, 86 Stat. 816, 33 U. S. Code
Sec. 1151 et seq. (1972).
2. FWPCA, Section 504 as amended (1972).
3. FWPCA, Section 307 (a) (1972).
4. FWPCA, Section 311 (1972).
5. Quality Assurance Division, Office of Research
and Monitoring, U. S. EPA, "Proc. 1 st
Microbiology Seminar on Standardization
of Methods." EPA-R4-73-022 (Mar. 1973).
6. Kenner, B. A., et al., "Simultaneous Quantita-
tion of Salmonella species and Pseudomonas
aeruginosa. I. Polluted Waters. II. Persist-
ence of Pathogens in Sludge Treated Soils.
III. Analysis of Waste Treatment Sludges
for Salmonella species as a Surveillance
Tool." U. S. EPA, National Environ-
mental Research Center, Cincinnati, Ohio
(Sept. 1971).
7. Moody, M. R., et al., "Pseudomonas aeruginosa
in a Center for Cancer Research. I. Dis-
tribution of Intraspecies Types from
Human and Environmental Sources." Jour.
Inf Diseases, 125. 95 (1972).
8. Edmonds, P., et al., "Epidemiology of Pseudo-
monas aeruginosa in a Burns Hospital. Sur-
veillance by a Combined Typing System."
Appl. Microbiol, 24, 219 (1972).
9. "New Hospital Controls Urged to Stem
Pseudomonas Rise." din. Lab. forum
(Eli Lilly), 2, 1 (May-June 1970).
10. Reitler, R., and Seligmann, R., "Pseudo-
monas aeruginosa inDrinking Water."
]our. Appl. Bacterial, 20, 145 (1957).
11. Ringen, L. M., and Drake, C. H., "A Study
of the Incidence of Pseudomonas aeruginosa
from Various Natural Sources." Jour.
Bacterial, 64, 841 (1952).
12. Drake, C. H., "Evaluation of Culture Media
for the Isolation and Enumeration of
Pseudomonas aeruginosa." Health Lab.
Set,, 3, 10 (1966).
13. Raj. H., "Enrichment Medium for Selection
of Salmonella from Fish Homogenate."
Appl. Microbiol., 14, 12 (1966).
14. "Standard Methods for the Examination of
Water and Wastewater." 13th Ed., Amer.
Pub. Health Assn., New York, N. Y. (1971).
15. Taylor, W. L, "Isolation of Shigellae. I.
Xylose Lysine Agars; New Media for Iso-
lation of Enteric Pathogens." Tech. Bull.
Reg. Med. Technol., 35, 161 (1965).
16. Osborne, W. W., and Stokes, J. L., "A Modi-
fied Selenite Brilliant-Green Medium for
the Isolation of Salmonella from Egg Prod-
ucts." Appl Microbiol, 3, 295 (1955).
17. Read, R. B., Jr., and Reyes, A. L., "Variation
in Plating Efficiency of Salmonellae on
Eight Lots of Brilliant Green Agar." Appl
Microbiol, 16, 746 (1968).
18. Dutka, B. J., and Bell, J. B., "Isolation of
Salmonellae from Moderately Polluted
Waters." Jour. Water Poll. Control Fed.,
45, 316 (1973).
19. Martin, W. J., and Ewing, W. H., "Prevalence
of Serotypes of Salmonella." Appl. Micro-
biol., 17, 111 (1969).
20. Calabro, J. F., el al." "Recovery of Gram Nega-
tive Bacteria with Hektoen Agar." Jour.
Water Poll. Control Fed., 44, 491 (1972).
-Vol. 46, No. 9, September 1974 2171
149
-------
Appendix H
Method for the Recovery and Assay of Total Culturable Viruses from Sludge
1. Introduction
1.1. Scope
This chapter describes the method that must be
followed to produce Class A sludge when virus monitoring
under 40 CFR Part 503 is required. The method is designed
to demonstrate that sludges meet the requirement that
human enteric viruses (i.e., viruses that are transmitted via
the fecal-oral route) are less than one plaque-forming unit
(PFU) per 4 g of total dry solids.
1.2. Significance
More than 100 different species of pathogenic human
enteric viruses maybe present in raw sludge. The presence
of these viruses can cause hepatitis, gastroenteritis and
numerous other diseases. Hepatitis A virus and noroviruses
are the primary human viral pathogens of concern, but
standard methods for their isolation and detection have not
been developed. The method1 detailed in this chapter
detects total culturable viruses, which primarily include the
human enteroviruses (e.g., polioviruses, coxsackieviruses,
echoviruses) and reoviruses.
1.3. Safety
The sludges to be monitored may contain pathogenic
human enteric viruses. Laboratories performing virus analy-
ses are responsible for establishing an adequate safety plan
and must decontaminate and dispose of wastes according
to their safety plan and all applicable regulations. Aseptic
techniques and sterile materials and apparatus must be
used throughout the method.
2. Sample Collection
For each batch of sludge that must be tested for
viruses, prepare a composite sample by collecting ten
representative samples of 100 mL each (1,000 mL total)
from different locations of a sludge pile or at different times
from batch or continuous flow processes. Combine and mix
thoroughly all representative samples for a composite.
Batch samples that cannot be assayed within 24 hours of
collection must be frozen at -70°C; otherwise, they should
be held at 4°C until processed. If representative samples
must be frozen before they can be combined, then thaw,
combine and mix them thoroughly just prior to assay. Then
remove a 50 mL portion from each composite sample for
solids determination as described in section 3. The remain-
ing portion is held at 4°C while the solids determination is
being performed or frozen for later processing if the assay
cannot be initiated within 8 hours.
Freeze/thawing biosolids may result in some virus
loss.
3. Determination of Total Dry Solids2
3.1. Weigh a dry weighing pan that has been held in a
desiccator and is at a constant weight. Place the 50 mL
sludge portion for solids determination into the pan and
weigh again.
3.2. Place the pan and its contents into an oven main-
tained at 103-105°C for at least one hour.
3.3. Cool the sample to room temperature in a desiccator
and weigh again.
3.4. Repeat the drying (1 h each), cooling and weighing
steps until the loss in weight is no more than 4% of the
previous weight.
3.5. Calculate the fraction of total dry solids (T) using the
formula:
T =
(A-C)
(B-C)
where A is the weight of the sample and dish after drying, B
is the weight of the sample and dish before drying, and C is
the weight of the dish. Record the fraction of dry solids (T)
as a decimal (e.g., 0.04).
4. Total Culturable Virus Recovery from
Sludge
4.1. Introduction
Total culturable viruses in sludge will primarily be
associated with solids. Although the fraction of virus
associated with the liquid portion will usually be small, this
fraction may vary considerably with different sludge types.
To correct for this variation, samples will first be treated to
'Method D4994-89, AS1M(1992)
2Modified from EPA/600/4-84/013(R7), September 1989 Revision (section 3). This
and other cited EPA publications may be requested from the Biohazard Assessment
Research Branch, National Exposure Research Laboratory, U.S. Environmental Pro-
tection Agency, Cincinnati, Ohio, USA 45268.
150
-------
bind free virus to solids. Virus is then eluted from the solids
and concentrated prior to assay.
4.2. Conditioning of Suspended Solids
Conditioning of sludge binds unadsorbed total cultura-
ble viruses present in the liquid matrix to the sludge solids.
Each analyzed composite sample (from the portion re-
maining after solids determination) must have an initial total
dry solids content of at least 16 g. This amount is needed
for positive controls and for storage of a portion of the
sample at-70°C as a backup in case of procedural mistakes
or sample cytotoxicity.
4.2.1 Preparation
(a) Apparatus and Materials
(a.1) Refrigerated centrifuge capable of attaining 10,000
*g and screw-capped centrifuge bottles with 100 to 1000 ml_
capacity.
Each bottle must be rated for the relevant centrifugal
force.
(a.2) A pH meter with an accuracy of at least 0.1 pH unit,
equipped with a combination-type electrode.
(a.3) Magnetic stirrer and stir bars.
(b) Media and Reagents
Analytical Reagent or ACS grade chemicals (unless
specified otherwise) and deionized, distilled water (dH2O)
should be used to prepare all reagents. All water used must
have a resistance of greater than 0.5 megohms-cm, but
water with a resistance of 18 megohms-cm is preferred.
(b.1) Hydrochloric acid (HCI) 1 and 5 M.
Mix 10 or 50 mL of concentrated HCI with 90 or 50mL
ofdH2O, respectively.
(b.2) Aluminum chloride (AICI3 6H2O) 0.05 M.
Dissolve 12.07 g of aluminum chloride in a final
ne o
minutes.
volume of 1000 mL of dH2O. Autoclave at 121 °C for 15
(b.3) Sodium hydroxide (NaOH) 1 and 5 M.
Dissolve 4 or 20 g of sodium hydroxide in a final
volume of 100 mL ofdH2O, respectively.
(b.4) Beef extract (Difco Product No. 0115-17-3 or
equivalent).
Prepare buffered 10% beef extract by dissolving 10 g
beef extract, 1.34 g Na2HPO4 7H2O and 0.12 g citric acid
in 100mL of dH2O. The pH should be about 7.0. Dissolve
by stirring on a magnetic stirrer. Autoclave for 15 minutes
at121°C.
Do not use paste beef extract (Difco Laboratories
Product No. 0126) for virus elution. This beef extract tends
to elute cytotoxic materials from sludges.
(b.5) HOCI 0.1%
Add 19 mL of household bleach (Clorox, The Clorox
Co., or equivalent) to 981 mL ofdH2O and adjust the pH of
the solution to 6-7 with 1 M HCI.
(b.6) Thiosulfate 2% and 0.02%
Prepare a stock solution of 2% thiosulfate by dissolv-
ing 20 g of thiosulfate in a total of 1 liter of dH20. Sterilize
the solution by autoclaving at 121°C for 15 minutes.
Prepare a working solution of 0.02% thiosulfate just prior to
use by mixing 1 mL of 2% thiosulfate with 99 mL of sterile
dH2O.
4.2.2 Conditioning Procedure
Figure 1 gives a flow diagram for the procedure to
condition suspended solids.
(a) Calculate the amount of sample to condition.
Use a graduated cylinder to measure the volume. If
the volumes needed are not multiples of 100 mL (100, 200,
300 mL, etc.), add sterile water to bring the volume to the
next multiple of 100 mL. Each sample should then be
aliquoted into 100 mL portions before proceeding. Samples
must be mixed vigorously just before aliquoting because
solids begin to settle out as soon as the mixing stops. Each
aliquot should be placed into a 250 mL beaker containing a
stir bar.
CAUTION: Always avoid the formation of aerosols by
slowly pouring samples down the sides of vessels.
(a.1) Calculate the amount needed to measure the
endogenous total culturable virus in a composite sludge
sample using the formula:
Xts =
12
Y
where Xts equals the milliliters of sample required to obtain
12 g of total solids and T equals the fraction of total dry sol-
ids (from section 3).3
(a.2) Calculate the amount needed for a recovery control
for each sludge composite from the formula:
4
Xpc = -
where Xpc equals the milliliters of sample required to obtain
4 g of total solids.
Add 400 plaque forming units (PFU) of a Sabin
poliovirus stock to the recovery control sample. Use a virus
stock that has been filtered through a 0.2 pm filter (see
Section 4.3.1) prior to assay to remove clumped virus
particles.
(a.3) Place 30 mLof 10% buffered beef extract and 70 mL
of dH2O into a 250 mL beaker with stir bar to serve as a
negative process control.
(a.4) Freeze any remaining composite sample at -70°C for
backup purposes.
3This formula is based upon the assumption that the density of the liquid in sludge is
1 g/mL. If the fraction of total dry solids is too low (e.g., less than 0.02), then the
volume of sludge collected must be increased.
151
-------
SUSPENDED SOLIDS (PER 100 ml_)
I Mix suspension on magnetic stirrer.
A. Add 1 mL of 0.05 M AICI3.
SALTED SOLIDS SUSPENSION
Continue mixing suspension.
I Adjust pH of salted suspension to 3.5 ±0.1
I with 5 M HCI.
» Mix vigorously for 30 minutes.
pH-ADJUSTED SOLIDS SUSPENSION
Centrifuge salted, pH-adjusted suspension
I at 2,500 xg for 15 minutes at 4°C.
»ly Discard supernatant.
Retain solids.
SOLIDS
Figure 1. Flow diagram of method for conditioning suspended
solids
(b) Perform the following steps on each 100 mL aliquot
from steps 4.2.2a.1 to 4.2.2a.3.
(b. 1) Place the beaker on a magnetic stirrer, cover loosely
with aluminum foil, and stir at a speed sufficient to develop
vortex. Add 1 mL of 0.05 M AICI3 to the mixing aliquot.
The final concentration of AICI3 in each aliquot is
approximately 0.0005 M.
(b.2) Place a combination-type pH electrode into the
mixing aliquot. Adjust the pH of the aliquot to 3.5 ± 0.1 with
5 M HCI. Continue mixing for 30 minutes.
The pH meter must be standardized at pH 7 and 4.
When solids adhere to an electrode, clean it by moving up
and down gently in the mixing aliquot.
After adjusting the pH of each sample, rinse the
electrode with dH2O and sterilize it with 0.1% HOCI for five
minutes. Neutralize the HOCI by submerging the electrode
in sterile 0.02% thiosulfate for one to five minutes.
The pH of the aliquot should be checked at frequent
intervals. If the pH drifts up, readjust it to 3.5 ±0.1 with 5 M
HCI. If the pH drifts down, readjust it with 5 M NaOH. Use
1 M acid or base for small adjustments. Do not allow the pH
to drop below 3.4.
(b.3) Pour the conditioned aliquot into a centrifuge bottle
and centrifuge at 2,500 xgfor 15 minutes at 4°C.
To prevent the transfer of the stir bar into the centri-
fuge bottle when decanting the aliquot, hold another stir bar
or magnet against the bottom of the beaker. Solids that
adhere to the stir bar in the beaker may be removed by
manipulation with a pipette. It may be necessary to pour the
aliquot back and forth several times from the centrifuge
bottle to the beaker to obtain all the solids in the bottle. If a
large enough centrifuge bottle is available, the test sample
aliquots may be combined into a single bottle at this step.
If there is more than one recovery control aliquot, they may
also be combined into another centrifuge bottle.
(b.4) Decant the supernatant into a beaker and discard.
Replace the cap onto the centrifuge bottle. Elute the solids
by following the procedure described in section 4.3.
4.3. Elution of Viruses from Solids
4.3.1 Apparatus and Materials
In this and following sections only apparatus and
materials which have not been described in previous
sections are listed.
(a) Membrane filter apparatus for sterilization 47 mm
diameter Swinnex filter holder and 60 mL slip-tip syringe
(Millipore Corp. Product No. SXOO 047 00 and Becton
Dickinson Product No. 1627 or equivalent).
(b) Discfilters, 47 mm diameter3.0, 0.45, and0.2|jm
pore size filters (Mentec America, Filterite Div., Duo- Fine
series, Product No. 8025-030, 8025-034 and 8025-037 or
equivalent). Filters may be cut to the proper diameter from
sheet filters.
Disassemble a Swinnex filter holder. Place the filter
with a 0.2 urn pore size on the support screen of the filter
holder and stack the remaining filters on top in order of
increasing pore size. Reassemble and tighten filter holder.
Wrap filter stack in foil and sterilize by autoclaving at 121 °C
for 15 min.
Filters stacked in tandem as described tend to clog
more slowly when turbid material is filtered through them.
Prepare several filter stacks.
4.3.2 Elution Procedure
A flow diagram of the virus elution procedure is given
in Figure 2.
(a) Place a stir bar and 100 mL of buffered 10% beef
extract into the centrifuge bottle containing the solids (from
section 4.2.2b.4).
If the test and control samples are divided into more
than one centrifuge bottles, the solids should be combined
at this step.
Place the centrifuge bottle on a magnetic stirrer, and
stir at a speed sufficient to develop a vortex for 30 min at
room temperature.
To minimize foaming (which may inactivate viruses),
do not mix faster than necessary to develop vortex.
(b) Remove the stir bar from each bottle with a long
sterile forceps or a magnet retriever and centrifuge the
solids-eluate mixture at 10,000 xg for 30 minutes at 4°C.
Decant supernatant fluid (eluate) into a beaker and discard
the solids.
Determine if the centrifuge bottle is appropriate for the
centrifugal force that will be applied.
152
-------
SOLIDS
Add 100 mL of buffered 10% beef extract,
I adjust to pH 7.0 ±0.1 if necessary.
w Mix resuspended solids on magnetic stirrer for
30 minutes to elute viruses.
RESUSPENDED SOLIDS
Centrifuge resuspended solids for 30 minutes
I at 4°C using a centrifugal force of 10,000 *g
»l* Discard solids.
Retain eluate (supernatant).
ELUATE
Filter eluate through 47 mm Filterite filter
I stack of 3.0, 0.45 and 0.2 |_im pore sizes
I with the 0.2 |_im pore size on support screen
W/ of filter and remaining filters on top in
order of increasing pore size.
FILTERED ELUATE
Figure 2. Flow diagram of method for elution of virus from solids.
Centrifugation at 10,000 *g is normally required to
clarify the sludge samples sufficiently to force the resulting
supernatant through the filter stacks.
(c) Place a filter holder that contains filter stacks (from
section 4.3.1b) onto a 250 mL Erlenmeyer receiving flask.
Load 50 mL syringes with the supernatants from step 4.3.2c.
Place the tip of the syringe into the filter holder and force the
supernatant through the filter stacks into 250 mL receiving
flasks.
Prior to use, pass 15 mL of 3% beef extract through
each filter holder to minimize non-specific adsorption of
viruses. Prepare 3% beef extract by mixing 4.5 mL of 10%
beef extract and 10.5 mL of dH2O. Take care not to break
off the tip of the syringe and to minimize pressure on the
receiving flask because such pressure may crack or topple
the flask. If the filter stack begins to clog badly, empty the
loaded syringe into the beaker containing unfiltered eluate,
fill the syringe with air, and inject air into filter stack to force
residual eluate from the filters. Continue the filtration proce-
dure with another filter holder and filter stack. Discard con-
taminated filter holders and filter stacks. This procedure
may be repeated as often as necessary to filter the entire
volume of supernatant. Disassemble each filter holder and
examine the bottom 0.2 /jm filters to be certain they have
not ruptured. If a bottom filter has ruptured, repeat the step
with new filter holders and filter stacks.
Proceed immediately to section 4.4.
4.4. Organic Flocculation
This organic flocculation concentration procedure
(Katzenelson et al., 1976) is used to reduce the number of
cell cultures needed for assays by concentrating total cul-
turable viruses in the eluate. The step significantly reduces
costs associated with labor and materials.
Floe formation capacity of the beef extract reagent
must be pretested. Because some beef extract lots may not
produce sufficient floe, each new lot must be pretested to
determine virus recovery. This maybe performed by spiking
100 mL of dH2O with a known amount of poliovirus in the
presence of a 47 mm nitrocellulose filter. This sample
should be conditioned using section 4.2 above to bind virus
to the filter. Virus should then be eluted from the filter using
the procedure in section 4.3, and concentrated and assayed
using the following procedures. Any lot of beef extract not
giving a overall recovery of at least 50% should not be used.
4.4.1 Media and Reagents
In this and following sections only media and reagents
which have not been described in previous sections are
listed.
(a) Sodium phosphate, dibasic (Na2HPO4 7H2O)
0.15 M.
Dissolve 40.2 g of sodium phosphate in a final volume
of 1000 mL Autoclave at 121°C for 15 minutes.
4.4.2 Virus Concentration Procedure
A flow diagram for the virus concentration procedure
is given in Figure 3.
(a) Pour the filtered eluates from the test sample,
recovery control and negative process control from section
4.3.2d into graduated cylinders, and record their volumes.
Transfer the samples into separate 600 mL beakers and
cover them loosely with aluminum foil.
(b) For every 3 mL of beef extract eluate, add 7 mL of
dH2O to the 600 mL beakers. Add stir bars to each beaker.
The concentration of beef extract is now 3%. This
dilution is necessary because 10% beef extract often does
not process well by the organic flocculation concentration
procedure.
(c) Record the total volume of the diluted eluates. Place
the beakers onto a magnetic stirrer, cover loosely with
aluminum foil, and stir at a speed sufficient to develop
vortex.
To minimize foaming (which may inactivate viruses),
do not mix faster than necessary to develop vortex.
(d) For each diluted, filtered beef extract, insert a sterile
combination-type pH electrode and then add 1 M HCI slowly
until the pH of the extract reaches 3.5 ±0.1. Continue to stir
for 30 minutes at room temperature.
The pH meter must be standardized at pH 4 and 7.
Sterilize the electrode by treating it with 0.1% HOCI for five
minutes. Neutralize the HOCI by treating the electrode with
0.02% sterile thiosulfate for one to five minutes.
153
-------
FILTERED ELUATE
Add sufficient volume of dH2O to filtered eluate
I to reduce concentration of beef xtract from
»L 10% to 3%. Record total volume of the
V diluted beef extract.
DILUTED, FILTERED ELUATE
Mix diluted eluate on a magnetic stirrer.
I Adjust the pH of the eluate to 3.5 ±0.1 with
I M HCI. A precipitate (floe) will form.
» Continue mixing for 30 minutes.
FLOCCULATED ELUATE
Centrifuge flocculated eluate at 2,500 xg for
15 minutes at 4°C.
I Discard supernatant.
^|r Retain floe.
FLOC FROM ELUATE
Add 0.15 M Na2HPO4 to floe, using 1/20th of
the recorded volume of the diluted 3% beef
I extract.
I Mix suspended floe on magnetic stirrer until
^ floe dissolves.
Adjust to a pH of 7.0 to 7.5.
DISSOLVED FLOC
See section 5 for virus assay procedure.
ASSAY DISSOLVED FLOC FOR VIRUSES
Figure 3. Flow diagram of method for concentration of viruses
from beef extract eluate.
A precipitate will form. If the pH is accidentally re-
duced below 3.4, add 1 M NaOH until it reaches 3.5 ± 0.1.
Avoid reducing the pH below 3.4 because some inactivation
of virus may occur.
(e) Pour the contents of each beaker into 1,000 mL
centrifuge bottles. Centrifuge the precipitated beef extract
suspensions at 2,500 *g for 15 minutes at 4°C. Pour off
and discard the supernatants.
To prevent the transfer of the stir bar into a centrifuge
bottle, hold another stir bar or magnet against bottom of the
beaker when decanting contents.
(f) Place stir bars into the centrifuge bottles that con-
tains the precipitates. To each, add a volume of 0.15 M
Na2HPO4 7H2O equal to exactly 1/20 of the volume record-
ed in step 4.4.2c. If the precipitate from a sample is in more
than one bottle, divide the 1/20th volume equally among the
centrifuge bottles containing that sample. Place the bottles
onto a magnetic stirrer, and stir slowly until the precipitates
have dissolved completely.
Support the bottles as necessary to prevent toppling.
Avoid foaming which may inactivate or aerosolize viruses.
The precipitates may be partially dissipated with sterile spa-
tulas before or during the stirring procedure.
(g) Measure the pH of the dissolved precipitates.
If the pH is above or below 7.0-7.5, adjust to that
range with either 1 M HCI or 1 M NaOH.
(h) Freeze exactly one half of the dissolved precipitate
test sample (but not the positive and negative controls) at -
70°C. This sample will be held as a backup to use should
the sample prove to be cytotoxic. Record the remaining test
sample volume (this volume represents 6 g of total dry
solids). Refrigerate the remaining samples immediately at
4°C until assayed in accordance with the instructions given
in section 5 below.
If the virus assay cannot be undertaken within 24
hours, store the remaining samples at -70°C.
5. Assay for Plaque-forming Viruses4
5.1. Introduction
This section outlines procedures for the detection of
viruses in sludge by use of the plaque assay system. The
system uses an agar medium to localize virus growth follow-
ing attachment of infectious virus particles to a cell mono-
layer. Localized lesions of dead cells (plaques) developing
some days after viral infection are visualized with the vital
stain, neutral red, which stains only live cells. The number
of circular unstained plaques are counted and reported as
plaque forming units, whose number is proportional to the
amount of infectious virus particles inoculated.
The detection methodology presented in this section
is geared towards laboratories with a small-scale virus as-
say requirement. Where the quantities of cell cultures,
media and reagents set forth in the section are not sufficient
for processing the test sample concentrates, the prescribed
measures may be increased proportionally to meet the
demands of more expansive test regimes.
5.2. Plaque Assay Procedure
5.2.1 Apparatus and materials.
(a) Waterbath set at 50 ± 1 °C.
Used for maintaining the agar temperature (see
section 5.2.2J).
5.2.2 Media and Reagents.
(a) ELAH 0.65% lactalbumin hydrolysate in Earle's
base.
Dissolve 6.5 g of tissue culture, highly soluble grade
lactalbumin hydrolysate (Gibco BRL Product No. 11800 or
4ModifiedfromEPA/600/4-84/013(Rll), March 1988 Revision
154
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equivalent) in 1 L of Earle's base (Gibco BRL Product No.
14015 or equivalent) prewarmed to 50-60°C. Sterilize ELAH
through a 0.22 /jm filter stack and store for up to two months
at 4°C.
(b) Wash mediumAdd 1 ml_ of penicillin-streptomycin
stock (see section 6.4.2e.1 for preparation of antibiotic
stocks), 0.5 ml_ of tetracycline stock and 0.2 ml_ of fungi-
zone stock per liter to ELAH immediately before washing of
cells.
(c) HEPES 1 M (Sigma Chemical Product No.
H-3375 or equivalent).
Prepare 50 mL of a 1 M solution by dissolving 11.92g
of HEPES in a final volume of 50 mL dH2O. Sterilize by
autoclaving at 121 °C for 15 min.
(d) Sodium bicarbonate (NaHCO3) 7.5% solution.
Prepare 50 mL of a 7.5% solution by dissolving 3.75
g of sodium bicarbonate in a final volume of 50 mL dH2O.
Sterilize by filtration through a 0.22 /jm filter.
(e) Magnesium chloride (MgCI2 6H20) 1.0% solution.
Prepare 50 mL of a 1.0% solution by dissolving 0.5g
of magnesium chloride in a final volume of 50 mL dH2O.
Sterilize by autoclaving at 121°C for 15 min.
(f) Neutral red solution 0.333%, 100 mL volume
(GIBCO BRL Product No. 630-5330 or equivalent).
Procure one 100 mL bottle.
Some neutral red solutions are cytotoxic. All new solu-
tions should be tested prior to their use for assaying sludge
samples. Testing may be performed by assaying a stock of
poliovirus with known titer using this plaque assay proce-
dure.
(g) Bacto skim milk (Difco Laboratories Product No.
0032-01 or equivalent).
Prepare 100mL of 10% skim milk in accordance with
directions given by manufacturer.
(h) Preparation of Medium 199.
The procedure described is for preparation of 500m L
of Medium 199 (GIBCO BRL Product No. 400-1100 or equi-
valent) at a 2X concentration. This procedure will prepare
sufficient medium for at least My 6 oz glass bottles or eighty
25 cm2 plastic flasks.
(h.1) Place a three inch stir bar into a one liter flask. Add
the contents of a 1 liter packet of Medium 199 into the flask.
Add 355 mL of dH2O. Rinse medium packet with three
washes of 20 mL each of dH2O and add the washes to the
flask.
Note that the amount ofdH2O is 5% less than desired
final volume of medium.
(h.2) Mix on a magnetic stirrer until the medium is com-
pletely dissolved. Filterthe reagent under pressure through
a filter stack (see section 6.2.6).
Tesf each lot of medium to confirm sterility before the
lot is used (see section 6.5). Each batch may be stored for
two months at 4°C.
(i) Preparation of overlay medium for plaque assay.
The procedure described is for preparation of 100 mL
of overlay medium and will prepare sufficient media for at
least ten 6 oz glass bottles or twenty 25 oz plastic flasks
when mixed with the agar prepared in section 5.2.2J.
(i. 1) Add 79 mL of Medium 199 (2X concentration) and 4 mL
of serum to a 250 mL flask.
(i.2) Add the following to the flask in the order listed, with
swirling after each addition: 6 mLof7.5% NaHCO3, 2 mLof
1 % MgCI2, 3 mL of 0.333% neutral red solution, 4 mL of 1 M
HEPES, 0.2 mLof penicillin-streptomycin stock (see section
6.4.2e for a description of antibiotic stocks), 0.1 mL of
tetracycline stock, and 0.04 mL of fungizone stock.
(i.3) Place flask with overlay medium in waterbath set at 36
± 1°C.
G)
Preparation of overlay agar for plaque assay.
(j.1) Add 3 g of agar (Sigma Chemical Product No. A-9915
or equivalent) and 100 mL of dH2O to a 250 mL flask. Melt
by sterilizing the agar solution in an autoclave at 121 °C for
15 min.
(j.2) Cool the agar to 50°C in waterbath set at 50 ± 1°C.
(k) Preparation of agar overlay medium.
(k.1) Add 2 mL of 10% skim milk to overlay medium pre-
pared in section 5.2.2L
(k.2) Mix equal portions of overlay medium and agar by
adding the medium to the agar flask.
To prevent solidification of the liquified agar, limit the
portion of agar overlay medium mixed to that volume which
can be dispensed in 10 min.
5.2.3 Procedure for Inoculating Test Samples.
Section 6.6 provides the procedures for the prepara-
tion of cell cultures used for the virus assay in this section.
BGM cell cultures used for virus assay are generally
found to be at their most sensitive level between the third
and sixth days after initiation. Those older than seven days
or which are not 100% confluent should not be used.
(a) Decant and discard the growth medium from pre-
viously prepared cell culture test vessels.
To prevent splatter, a gauze-covered beaker may be
used to collect spent medium.
The medium is changed from one to four hours before
cultures are to be inoculated and carefully decanted so as
not to disturb the cell monolayer.
(b) Replace discarded medium with an equal volume of
wash medium (from section 5.2.2b) on the day the cultures
are to be inoculated.
155
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Table 1. Guide for Virus Inoculation, Suspended Cell Concentration and
Overlay Volume of Agar Medium
Volume of Volume of Agar
Virus Inoculum Overlay Medium Total Number of
Vessel Type
1 oz glass
bottle1
25 cm2 plastic
flask
6 oz glass bottle
75 cm2 plastic
flask
(mL)
0.1
0.1-0.5
0.5-1.0
1.0-2.0
(mL)
5
10
20
30
Cells
1 x 107
2 x 107
4x 107
6x 107
Size is given in oz only when it is commercially designated in that unit.
To reduce shock to cells, prewarm the wash medium
to 36.5 ± 1 °C before placing it onto the cell monolayer.
To prevent disturbing cells with the force of the liquid
against the cell monolayer, add the wash medium to the
side of cell culture test vessel opposite the cell monolayer.
(c) Identify cell culture test vessels by coding them with
an indelible marker. Return the cell culture test vessels to
a 36.5 ± 1°C incubator and hold at that temperature until the
cell monolayers are to be inoculated.
(d) Decant and discard the wash medium from cell cul-
ture test vessels.
Do not disturb the cell monolayer.
(e) Inoculate BGM cultures with the test sample and
positive and negative process control samples from section
4.4.2h. Divide each sample onto a sufficient number of BGM
cultures to ensure that the inoculum volume is no greater
than 1 mL for each 40 cm2 of surface area. Use Table 1 as
a guide for inoculation size.
Avoid touching either the cannula or the pipetting de-
vice to the inside rim of the cell culture test vessels to avert
the possibility of transporting contaminants to the remaining
culture vessels.
If the samples are frozen, thaw them rapidly by placing
them in warm water. Samples should be shaken during the
thawing process and removed from the warm water as soon
as the last ice crystals have dissolved.
(e. 1) Inoculate BGM cultures with the entire negative pro-
cess control sample using an inoculum volume per vessel
that is appropriate for the vessel size used.
(e.2) Inoculate two BGM cultures with an appropriate vol-
ume of 0.15 M Na2HPO4 7H2O preadjusted to pH 7.0-7.5
and seeded with 20-40 PFU of poliovirus. These cultures
will serve as a culture sensitivity control.
(e.3) Remove a volume of the test sample concentrate
exactly equal to 1/6th (i.e., 1 g of total dry solids) of the vol-
ume recorded in section 4.4.2h. Seed this subsample with
20-40 PFU of poliovirus. Inoculate the subsample onto one
or more BGM cultures using a inoculum volume per vessel
that is appropriate for the vessel size used. These cultures
will serve as controls for cytotoxicity (see section 5.2.5b).
(e.4) Inoculate BGM cultures with the entire recovery con-
trol sample using an inoculum volume per vessel that is
appropriate for the vessel size used.
(e.5) Record the volume of the remaining 5/6th portion of
the test sample. This remaining portion represents a total
dry solids content of 5 g. Inoculate the entire remaining por-
tion (even if diluted to reduce cytotoxicity) onto BGM
cultures using an inoculum volume per vessel that is appro-
priate for the vessel size used. Inoculation of the entire
volume is necessary to demonstrate a virus density level of
less than 1 PFU per 4 g total dry solids.
(f) Rock the inoculated cell culture test vessels gently
to achieve uniform distribution of inoculum over the surface
of the cell monolayers. Place the cell culture test vessels on
a level stationary surface at room temperature (22-25°C) so
that the inoculum will remain distributed evenly over the cell
monolayer.
(g) Incubate the inoculated cell cultures at roomtemper-
ature for 80 min to permit viruses to adsorb onto and infect
cells and then proceed immediately to section 5.2.4.
It may be necessary to rock the vessels every 15-20
min during the 80 min incubation to prevent cell death in the
middle of the vessels from dehydration.
5.2.4 Procedure for Overlaying Inoculated Cul-
tures with Agar.
If there is a likelihood that a test sample will be toxic to
cell cultures, the cell monolayer should be treated in accor-
dance with the method described in section 5.2.5b.
(a) To each cell culture test vessel, add the volume of
warm (42-46°C) agar overlay medium appropriate for the
cell surface area of the vessels used (see Table 1).
The preparation of the overlay agar and the agar over-
lay medium must be made far enough in advance so that
they will be at the right temperature for mixing at the end of
the 80 min inoculation period.
To prevent disturbing cells with the force of the liquid
against the cell monolayer, add the agar overlay medium to
the side of the cell culture test vessel opposite the cell
monolayer.
(b) Place cell culture testvessels, monolayer side down,
on a level stationary surface at room temperature (22-25°C)
so that the agar will remain evenly distributed as it solidifies.
Cover the vessels with a sheet of aluminum foil, a tightly
woven cloth, or some other suitable coverto reduce the light
intensity during solidification and incubation. Neutral red
can damage or kill tissue culture cells by light-induced
crosslinking of nucleic acids.
Care must be taken to ensure that all caps on bottles
and flasks are tight; otherwise, the gas seal will not be com-
plete and an erroneous virus assay will result.
Agar will fully solidify within 30 min.
156
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(c) After 30 min, invert the cell culture test vessels and
incubate them covered in the dark at 36.5 ± 1°C.
5.2.5 Plaque Counting Technique.
(a) Count, mark and record plaques in cell culture test
vessels on days one, two, three, four after adding the agar
overlay medium. Plaques should be counted quickly using
a lightbox (Baxter Product No. B5080-1 or equivalent) in a
darkened room. Most plaques should appear within 1 week.
Depending on the virus density and virus types
present in the inoculated sample, rescheduling of virus
counts at plus or minus one day may be necessary. Virus
titers are calculated from the total plaque count. Note that
not all plaques will be caused by viruses.
(b) Determine if samples are cytotoxic by macroscopic
examination of the appearance of the cell culture monolayer
(compare negative, positive and recovery controls from
section 5.2.3e with seeded and unseeded test samples)
after one to four days of incubation at 36.5 ± 1°C. Samples
show cytotoxicity if cell death is observed on test and
recovery control samples prior to its development on
positive controls. Cytotoxicity should be suspected when
the agar color is more subdued, generally yellow to yel-
low-brown. This change in color results in a mottled or
blotchy appearance instead of the evenly diffused "reddish"
color observed in "healthy" cell monolayers. Cytotoxicity
may also cause viral plaques to be reduced in number or to
be difficult to distinguish from the surrounding monolayer.
To determine if this type of cytotoxicity is occurring, compare
the two types of positive controls (section 5.2.3e). If
samples are cytotoxic, do not proceed to the next steps.
Re-assay a small amount of the remaining sample using
1:2, 1:4 and 1:8 dilutions. Then re-assay the remaining
sample as specified in section 5.2.3 using the dilution which
removes cytotoxicity and the specified number of flasks
times the reciprocal of the dilution.
A small amount of sample maybe tested for cytotoxici-
ty prior to a full assay.
(c) Examine cell culture test vessels as in step 5.2.5a on
days six, eight, twelve and sixteen.
If no new plaques appear at 16 days, proceed with
step 5.2.6; otherwise continue to count, mark and record
plaques every two days until no new plaques appear be-
tween counts and then proceed with step 5.2.6.
Inoculated cultures should always be compared to un-
inoculated control cultures so that the deterioration of the
cell monolayers is not recorded as plaques. If experience
shows that cultures start to deteriorate prior to 16 days, a
second layer of agar can be added after 7 days as de-
scribed in section 5.2.4.
If negative process controls develop plaques or if pos-
itive controls fail to develop plaques, stop all assays until the
source of the problem is corrected.
Samples giving plaque counts that are greater than 2
plaques per cm2 should be diluted and replated.
5.2.6 Virus Plaque Confirmation Procedure
The presence of virus in plaques must be confirmed
for all plaques obtained from sludge samples. Where more
than ten plaques are observed, it is allowable to confirm at
least ten well-separated plaques per sample or 10% of the
plaques in a sample, whichever is greater. Flasks may be
discarded after samples are taken for plaque confirmation.
(a) Apparatus, Materials and Reagents
(a.1) Pasteur pipettes, disposable, cotton plugged 229
mm (9 inches) tube length and rubber bulb 1 ml_ capa-
city.
Flame each pipette gently about 2 cm from end of the
tip until the tip bends to an approximate angle of 45°. Place
the pipettes into a 4 liter beaker covered with aluminum foil
and sterilize by autoclaving or by dry heat.
(a.2) 16 x 150 mm cell culture tubes containing BGM
cells.
See section 6.6 for the preparation of cell culture
tubes.
(a.3) Tissue culture roller apparatus 1/5 rpm speed
(New Brunswick Scientific Product No. TC-1 or equivalent)
with culture tube drum for use with roller apparatus (New
Brunswick Scientific Product No. ATC-TT16 or equivalent).
(a.4) Freezer vial, screw-capped (with rubber insert) or
cryogenic vial 0.5-1 dram capacity.
(b) Procedure for obtaining viruses from plaque.
In addition to plaques from sludge samples, perform
the procedure on at least three negative regions of negative
process control flasks and at least three plaques from pos-
itive control flasks.
(b.1) Place a rubber bulb onto the upper end of a cotton-
plugged Pasteur pipette and then remove the screw-cap or
stopper from a plaque bottle.
(b.2) Squeeze the rubber bulb on the Pasteur pipette to
expel the air and penetrate the agar directly over the edge
of a plaque with the tip of the pipette. Gently force the tip of
the pipette through the agar to the surface of the vessel, and
scrape some of the cells from the edge of the plaque.
Repeatedly scratch the surface and use gentle suction
to insure that virus-cell-agar plug enters the pipette.
(b.3) Remove the pipette from the plaque bottle and tightly
replace the cap or stopper.
(c) Procedure for inoculating cell cultures with agar
plugs from negative control samples and from plaques.
(c.1) Prepare plaque conformation maintenance medium
by adding 5 ml_ of serum and 5 ml_ of dH2O per 90 ml_ of
wash medium (section 5.2.2b) on day samples are to be
tested.
(c.2) Pour the spent medium from cell culture tubes and
discard the medium. Replace the discarded medium with 2
157
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ml_ of the plaque conformation maintenance medium. Label
the tubes with sample and plaque isolation identification
information.
To prevent splatter, a gauze-covered beaker may be
used to collect spent medium.
To reduce shock to cells, warm the maintenance medi-
um to 36.5 ± 1 °C before placing on cell monolayer.
To prevent disturbing cells with the force of the liquid
against the cell monolayer, add the maintenance medium to
the side of cell culture test tube opposite the cell monolayer.
Note that cells will be only on the bottom inner surface of the
culture tube relative to their position during incubation.
(c.3) Remove the cap from a cell culture tube and place
the tip of a Pasteur pipette containing the agar plug from
section 5.2.6b.3 into the maintenance medium in the cell
culture tube. Force the agar plug from the Pasteur pipette
by gently squeezing the rubber bulb. Withdraw and discard
the pipette, and replace and tighten down the screw-cap on
the culture tube.
Tilt cell culture tube as necessary to facilitate the pro-
cedure and to avoid scratching the cell sheet with the
pipette.
Squeeze bulb repeatedly to wash contents of pipette
into the maintenance medium.
(c.4) Place the cell culture tubes in the drum used with the
tissue culture roller apparatus. Incubate the cell cultures at
36.5 ± 1°C while rotating at a speed of 1/5 rpm. Examine
the cells daily microscopically for 1 week for evidence of
cytopathic effects (CPE).
CPE may be identified as cell disintegration or as
changes in cell morphology. Rounding-up of infected cells
is a typical effect seen with enteric virus infections. How-
ever, uninfected cells round up during mitosis and a sample
should not be considered positive unless there are signifi-
cant clusters of rounded-up cells over and beyond what is
observed in the uninfected controls. If there is any doubt
about the presence of CPE or if CPE appears late (i.e., on
day 6 or 7), the conformation process should be repeated by
transferring 0.2 mL of the medium in the culture tube to a
freshly prepared tube.
Incubation ofBGM cells in roller apparatus for periods
greater than 1 week is not recommended as cells under
these conditions tend to die-off if held longer.
If tubes receiving agar plugs from negative controls
develop CPE or tubes receiving agar plugs from positive
controls fail to develop CPE, stop all assays until the source
of the failure is identified and corrected.
Tubes developing CPE may be stored in a -70°C
freezer for additional optional tests (e.g., the Lim Benyesh-
Melnick identification procedure.5
(c.5) Determine the fraction of confirmed plaques (C) for
each sludge sample tested. Calculate "C" by dividing the
number of tubes inoculated with agar plugs from plaques
that developed CPE by the total number of tubes inoculated
(i.e., if CPE was obtained from 17 of 20 plaques, C = 0.85).
5.2.7 Calculation of virus titer.
If more than one composite sample was assayed,
average the titer of all composite samples and report the
average titer and the standard deviation for each lot of
sludge tested.
(a) If the entire remaining portion of a test sample was
inoculated onto BGM cultures as described in section
5.2.3e.5, calculate the virus titer (V) in PFU per 4 g of total
dry solids according to the formula:
VU O.S=x=Px=C
where P is the total number of plaques in all test vessels for
that sample and C equals the fraction of confirmed plaques.
(b) If the sample was diluted due to high virus levels
(e.g., when the virus density of the input to a process is be-
ing determined; see section 5.2.5c), calculate the virus titer
(V) in PFU per 4 g total dry solids with the formula:
P
V O.&x x=D x S x C D
in
where P is the total number of plaques in all test vessels for
dilution series, I is the volume (in mL) of the dilution inocu-
lated, D is reciprocal of the dilution made on the inoculum
before plating, S is the volume of the remaining portion of
the test sample (as recorded in section 5.2.3e.5) and C is
the fraction of confirmed plaques.
5.2.8 Calculate the percent of virus recovery (R) using the
formula: p
where P is the total number of plaques on all test vessels
inoculated with the recovery control.
6. Cell Culture Preparation and
Maintenance6
6.1. Introduction
This section outlines procedures and media for cultur-
ing the Buffalo Green monkey (BGM) kidney cell line and is
intended for the individual who is experienced in cell culture
preparation. BGM cells are a continuous cell line derived
from African Green monkey kidney cells. The characteris-
tics of this line were described by Barron et al. (1970). Use
of BGM cells for recovering viruses from environmental
samples was described by Dahling et al. (1974). The media
and methods recommended are the results of the BGM cell
line optimization studies by Dahling and Wright (1 986). The
BGM cell line can be obtained by qualified laboratories from
the Biohazard Assessment Research Branch, National
Exposure Research Laboratory, U. S. Environmental Protec-
tion Agency, Cincinnati, Ohio, USA 45268. Although BGM
!For more information see EPA/600/4-84/013(R12), May 1988 Revision
'Modified from EPA/600/4-84/013(R9), January 1987 Revision
158
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ce//s will not detect all enteric viruses that maybe present in
sludges, the use of this cell line alone is sufficient to meet
the requirements of 40 CFR Part 503.
6.2. Apparatus and Materials
6.2.1 Glassware, Pyrex (Corning Product No. 1395 or
equivalent).
Storage vessels must be equipped with airtight clo-
sures.
6.2.2 Autoclavable inner-braided tubing with metal
quick-connect connectors or with screw clamps for
connecting tubing to equipment to be used under
pressure.
Quick-connect connectors can be used only after
equipment has been properly adapted.
6.2.3 Positive pressure air, nitrogen or 5% CO2
source equipped with pressure gauge.
Pressure sources from laboratory air lines and pumps
must be equipped with an oil filter. The source must not
deliver more pressure to the pressure vessel than is recom-
mended by manufacturer.
6.2.4 Dispensing pressure vessel 5 or 20 liter
capacity (Millipore Corp. Product No. XX67 OOP 05
and XX67 OOP 20 or equivalent).
6.2.5 Disc filter holders 142 mm or 293 mm diame-
ter (Millipore Corp. Product No. YY30 142 36 and
YY30 293 16 or equivalent).
Use only pressure type filter holders.
6.2.6 Sterilizing filter stacks 0.22 |jm pore size
(Millipore Corp. Product No. GSWP 142 50 and
GSWP 293 25 or equivalent). Fiberglass prefilters
(Millipore Corp. Product No. AP15 142 50 or AP15
293 25 and AP20 142 50 or AP20 293 25 or equiva-
lent).
Stack AP20 and AP15 prefilters and 0.22 fjm mem-
brane filter into a disc filter holder with AP20 prefilter on top
and 0.22 /jm membrane filter on bottom.
Always disassemble the filter stack after use to check
the integrity of the 0.22 /jm filter. Refilter any media filtered
with a damaged stack.
6.2.7 Positively-charged cartridge filter 10 inch
(Zeta plus TSM, Cuno Product No. 45134-01-600P or
equivalent). Holder for cartridge filter with adaptorfor
10 inch cartridge (Millipore Corp. Product No. YY16
012 00 or equivalent).
6.2.8 Culture capsule filter (Gelman Sciences Prod-
uct No. 12140 or equivalent).
6.2.9 Cell culture vessels Pyrex, soda or flint glass
or plastic bottles and flasks or roller bottles (e.g.,
Brockway Product No. 1076-09A, 1925-02, Corning
Product No. 25100-25, 25110-75, 25120-150, 25150-
1750 or equivalent).
Vessels must be made from clear glass or plastic to
allow observation of the cultures and be equipped with
airtight closures. Plastic vessels must be treated by the
manufacturer to allow cells to adhere properly.
6.2.10 Screw caps, black with rubber liners (Brock-
way Product No. 24-414 for 6 oz bottles7 or equiva-
lent).
Caps for larger culture bottles usually supplied with
bottles.
6.2.11 Roller apparatus (Bellco Product No. 7730 or
equivalent).
6.2.12 Incubator capable of maintaining the temper-
ature of cell cultures at 36.5 ± 1 °C.
6.2.13 Waterbath, equipped with circulating device
to assure even heating at 36.5 ± 1°C.
6.2.14 Light microscope, with conventional light
source, equipped with lenses to provide 40X, 100X,
and 400X total magnification.
6.2.15 Inverted light microscope equipped with lens-
es to provide 40X, 100X, and 400Xtotal magnification.
6.2.16 Cornwall syringe pipettors, 2, 5 and 10 ml
sizes (Curtin Matheson Scientific Product No. 221-
861, 221-879, and 221-887 or equivalent).
6.2.17 Brewer-type pipetting machine (Curtin Mathe-
son Scientific Product No. 138-107 or equivalent).
6.2.18 Phase contrast counting chamber (hemocy-
tometer) (Curtin Matheson Scientific Product No.
158-501 or equivalent).
6.2.19 Conical centrifuge tubes, sizes 50 ml and
250 ml.
6.2.20 Rack fortissue culture tubes (Bellco Product
No. 2028 or equivalent).
6.2.21 Bottles, aspirator-type with tubing outlet, size
2,000 ml.
Bottles for use with pipetting machine.
6.2.22 Storage vials, size 2 ml.
Vials must withstand temperatures to -70°C.
6.3. Media and Reagents
6.3.1 Sterile fetal calf, gammagobulin-free newborn
calf or iron-supplemented calf serum, certified free of
7Size is given in oz only when it is commercially designated in that unit.
159
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viruses, bacteriophage and mycoplasma (GIBCO BRL
or equivalent).
Tesf each lot of serum for cell growth and toxicity
before purchasing. Serum should be stored at -20°C for
long-term storage. Upon thawing, each bottle should be
heat-inactivated at 56°C for 30 min and stored at 4°C for
short term use.
6.3.2 Trypsin, 1:250 powder (Difco Laboratories
Product No. 0152-15-9 or equivalent) ortrypsin, 1:300
powder (BBL Microbiology Systems Product No.
12098 or equivalent).
6.3.3 Sodium (tetra) ethylenediamine tetraacetate
powder (EDTA), technical grade, (Fisher Scientific
Product No. S657-500 or equivalent).
6.3.4 Thioglycollate medium (Difco Laboratories
Product No. 0257-01-9 or equivalent).
6.3.5 Fungizone (amphotericin B, Sigma Chemical
Product No. A-9528 orequivalent), Penicillin G (Sigma
Chemical Product No. P-3032 orequivalent), dihydro-
streptomycin sulfate (ICN Biomedicals Product No.
100556 orequivalent), and tetracycline (ICN Biomed-
icals Product No. 103011 orequivalent).
Use antibiotics of at least tissue culture grade.
6.3.6 Eagle's minimum essential medium (MEM) with
Hanks' salts and L-glutamine, without sodium bicar-
bonate (GIBCO BRL Product No. 410-1200 or equiva-
lent).
6.3.7 Leibovitz's L-15 medium with L-glutamine
(GIBCO BRL Product No. 430-1300 orequivalent).
6.3.8 Trypan blue (Sigma Chemical Product No. T-
6146 orequivalent).
Note: This chemical is on the EPA list of proven or
suspected carcinogens.
6.3.9 Dimethyl sulfoxide (DMSO; Sigma Chemical
Product No. D-2650 or equivalent).
6.3.10 Mycoplasma testing kit (Irvine Scientific Prod-
uct No. T500-000 or equivalent).
6.4. Preparation of Cell Culture Media
6.4.1 General Principles
(a) Equipment care Carefully wash and sterilize
equipment used for preparing media before each use.
(b) Disinfection of work area Thoroughly disinfect sur-
faces on which the medium preparation equipment is to be
placed. Many commercial disinfectants do not adequately
kill total culturable viruses. To ensure thorough disinfection,
disinfect all surfaces and spills with either a solution of 0.5%
(5 g per liter) iodine in 70% ethanol or 0.1% HOCI.
(c) Aseptic technique Use aseptic technique when
preparing and handling media or medium components.
(d) Dispensing filter-sterilized media To avoid post-
filtration contamination, dispense filter-sterilized media into
storage containers through clear glass filling bells in a micro-
biological laminar flow hood. If a hood is unavailable, use
an area restricted solely to cell culture manipulations.
(e) Coding media Assign a lot numberto and keep a
record of each batch of medium or medium components
prepared. Place the lot number, the date of preparation, the
expiration date, and the initials of the person preparing the
medium on each bottle.
(f) Sterility test Test each lot of medium and medium
components to confirm sterility as described in section 6.5
before the lot is used for cell culture.
(g) Storage of media and medium components Store
media and medium components in clear airtight containers
at 4°C or -20°C as appropriate.
(h) Sterilization of NaHCO3-containing solutions Ster-
ilize media and other solutions that contain NaHCO3 by
positive pressure filtration.
Negative pressure filtration of such solutions increases
the pH and reduces the buffering capacity.
6.4.2 Media Preparation Recipes
(a) Sources of cell culture media Commercially
prepared liquid cell culture media and medium components
are available from several sources. Cell culture media can
also be purchased in powder form that requires only dissolu-
tion in dH2O and sterilization. Media from commercial
sources are quality-controlled. The conditions specified by
the supplier for storage and expiration dates should be
strictly observed. However, media can also be prepared in
the laboratory directly from chemicals. Such preparations
are labor intensive, but allow quality control of the process
at the level of the preparing laboratory.
(b) Procedure for the preparation of EDTA-trypsin.
The procedure described is for the preparation of 10
liters of EDTA-trypsin reagent. It is used to dislodge cells
attached to the surface of culture bottles and flasks. This
reagent, when stored at4°C, retains its working strength for
at least four months. The amount of reagent prepared
should be based on projected usage over a four-month
period.
(b.1) Add 30 g oftrypsin (1:250) or 25 g oftrypsin (1:300)
and two liters of dH2O to a six liter flask containing a three
inch stir bar. Place the flask onto a magnetic stirrer and mix
the trypsin solution rapidly for a minimum of one hour.
Trypsin remains cloudy.
(b.2) Add four liters of dH2O and a three-inch stir bar into
20 liter clear plastic carboy. Place the carboy onto a mag-
netic stirrer and stir at a speed sufficient to develop a vortex
while adding the following chemicals: 80 g NaCI, 12.5 g
160
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EDTA, 50 g dextrose, 11.5 g Na2HPO4 7H2O, 2.0 g KCI,
and 2.0 g KH2PO4.
Each chemical does not have to be completely dis-
solved before adding the next one.
(b.3) Add four more liters of dH2O to carboy.
Continue mixing until all chemicals are completely dis-
solved.
(b.4) Add the two liters oftrypsin fromstep6.4.2b.1 to the
prepared solution in step 6.4.2b.3 and mix for a minimum of
one hour. Adjust the pH of the EDTA-trypsin reagent to 7.5
-7.7.
(b.5) Filter reagent under pressure through a disc filter
stack and store the filtered reagent in tightly stoppered or
capped containers at 4°C.
The cartridge prefilter (section 6.2.7) can be used in
line with the culture capsule sterilizing filter (section 6.2.8)
as an alternative to a filter stack (section 6.2.6).
(c) Procedure forthe preparation of MEM/L-15 medium.
The procedure described is for preparation of 10 liters
of MEM/L-15 medium.
(c. 1) Place a three inch stir bar and four liters of dH2O into
20 liter carboy.
(c.2) Place the carboy onto a magnetic stirrer. Stir at a
speed sufficient to develop a vortex and then add the con-
tents of a five liter packet of L-15 medium to the carboy.
Rinse the medium packet with three washes of 200 ml_ each
of dH2O and add the rinses to the carboy.
(c.3) Mix until the medium is evenly dispersed.
L-15 medium may appear cloudy as it need not be
totally dissolved before proceeding to step 6.4.2c.4.
(c.4) Add three liters of dH2O to the carboy and the con-
tents of a five liter packet of MEM medium to the carboy.
Rinse the MEM medium packet with three washes of 200
ml_ each of dH2O and add the rinses to the carboy. Add 800
ml_ of dH2O and 7.5 g of NaHCO3 and continue mixing for
an additional 60 min.
(c.5) Transfer the MEM/L-15 medium to a pressure can
and filter under positive pressure through a 0.22 |_im steriliz-
ing filter. Collect the medium in volumes appropriate forthe
culturing of BGM cells (e.g., 900 ml_ in a 1 liter bottle) and
store in tightly stoppered or capped containers at 4°C.
Medium may be stored for periods of up to two
months.
(d) Procedure for preparation of trypan blue solution.
The procedure described is for the preparation of 100
mL of trypan blue solution. It is used in the direct determina-
tion of the viable cell counts of the BGM stock cultures. As
trypan blue is on the EPA suspect carcinogen list, particular
care should be taken in its preparation and use so as to
avoid skin contact or inhalation. The wearing of rubber
gloves during preparation and use is recommended.
(d.1) Add 0.5g of trypan blue to 100 ml_ofdH2Oin a 250
mL flask. Swirl the flask until the trypan blue is completely
dissolved.
(d.2) Sterilize the solution by autoclaving at 121 °C for 15
minutes and store in a screw-capped container at room tem-
perature.
(e) Procedure for preparation of stock antibiotic solu-
tions.
If not purchased in sterile form, stock antibiotic solu-
tions must be filter-sterilized by the use of 0.22 /jm mem-
brane filters. It is important that the recommended antibiotic
levels not be exceeded when planting cells as the cultures
are particularly sensitive to excessive concentrations at this
stage.
Antibiotic stock solutions should be placed in screw-
capped containers and stored at -20°C until needed. Once
thawed, they may be refrozen; however, repeated freezing
and thawing of these stock solutions should be avoided by
distributing them in quantities that are sufficient to support
a week's cell culture work.
(e.1) Preparation of penicillin-streptomycin stock solution.
The procedure described is for preparation often 10
mL aliquots of penicillin-streptomycin stock solution at
concentrations of 1,000,000 units of penicillin andl, 000,000
fjg of streptomycin per 10mL unit. The antibiotic concentra-
tions listed in step 6.4.2e.1.1 may not correspond to the
concentrations obtained from other lots or from a different
source.
(e.1.1) Add appropriate amounts of penicillin G and dihydro-
streptomycin sulfate to a 250 mL flask containing 100 mL of
dH2O. Mix the contents of the flasks on magnetic stirrer un-
til the antibiotics are dissolved.
For penicillin supplied at 1435 units permg, add 7gof
the antibiotic.
For streptomycin supplied at 740 mg per g, add 14 g
of the antibiotic.
(e.1.2) Sterilize the antibiotics by filtration through 0.22 |jm
membrane filters and dispense in 10 mL volumes into
screw-capped containers.
(e.2) Preparation of tetracycline stock solution. Add 1.25
g of tetracycline hydrochloride powder and 3.75 g of ascor-
bic acid to a 125 mL flask containing 50 mL of dH2O. Mix
the contents of the flask on a magnetic stirrer until the antibi-
otic is dissolved. Sterilize the antibiotic by filtration through
a 0.22 |jm membrane filter and dispense in 5 mL volumes
into screw-capped containers.
(e.3) Preparation of amphotericin B (fungizone) stock
solution. Add 0.125 g of amphotericin B to a 50 mL flask
containing 25 mL of ddH2O. Mix the contents of the flask on
a magnetic stirrer until the antibiotic is dissolved. Sterilize
the antibiotic by filtration through 0.22 |jm membrane filter
and dispense 2.5 mL volumes into screw-capped contain-
ers.
161
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6.5. Procedure for Verifying Sterility of
Liquids
There are many techniques available for verifying the
sterility of liquids such as cell culture media and medium
components. The two techniques described below are
standard in many laboratories. The capabilities of these
techniques are limited to the detection of microorganisms
that grow unaided on the test medium utilized. Viruses,
mycoplasma, and microorganisms that possess fastidious
growth requirements or that require living host systems will
not be detected. Nonetheless, with the exception of a few
special contamination problems, the test procedures and
microbiological media listed below should prove adequate.
Do not add antibiotics to media or medium components until
after sterility of the antibiotics, media and medium compo-
nents has been demonstrated. BGM cell lines should be
monitored every six months for mycoplasma contamination
according to test kit instructions. Cells that are contami-
nated should be discarded.
6.5.1 Procedure for Verifying Sterility of Small Volumes of
Liquids. Inoculate 5 ml_ of the material to be tested for
sterility into 5 ml_ of thioglycollate broth. Shake the mixture
and incubate at 36.5 ± 1°C. Examine the inoculated broth
daily for seven days to determine whether growth of contam-
inating organisms has occurred.
Vessels that contain thioglycollate medium must be
tightly sealed before and after medium is inoculated.
6.5.2 Visual Evaluation of Media for Microbial Contami-
nants. Incubate media at 36.5 ± 1°C for at least one week
prior to use. Visually examine and discard any media that
lose clarity.
A clouded condition that develops in the media
indicates the occurrence of contaminating organisms.
6.6. Procedures for Preparation and
Passage of BGM Cell Cultures
A laminar flow biological safety cabinet should be used
to process cell cultures. If a biological safety cabinet is not
available, cell cultures should be prepared in controlled
facilities used for no other purposes. Viruses or other
microorganisms must not be transported, handled, or stored
in cell culture transfer facilities.
6.6.1 Vessels and Media for Cell Growth
(a) The BGM cell line grows readily on the inside sur-
faces of glass or specially treated, tissue culture grade plas-
tic vessels. 16 to 32 oz (or equivalent growth area) flat-sid-
ed, glass bottles, 75 or 150 cm2 plastic cell culture flasks,
and 690 cm2 glass or 850 cm2 plastic roller bottles are
usually used for the maintenance of stock cultures. Flat-sid-
ed bottles and flasks that contain cells in a stationary
position are incubated with the flat side (cell monolayer side)
down. If available, roller bottles and roller apparatus units
are preferable to flat-sided bottles and flasks because roller
cultures require less medium than flat-sided bottles per unit
of cell monolayer surface. Roller apparatus rotation speed
should be adjusted to one-half revolution per minute to
ensure that cells are constantly bathed in growth medium.
(b) Growth and maintenance media should be prepared
on the day they will be needed. Prepare growth medium by
supplementing MEM/L-15 medium with 10% serum and anti-
biotics (100 ml_ of serum, 1 ml_ of penicillin-streptomycin
stock, 0.5 ml_ oftetracycline stock and 0.2 ml_ of fungizone
stock per 900 ml_ of MEM/L-15). Prepare maintenance
medium by supplementing MEM/L-15 with antibiotics and
2% or 5% serum (20 or 50 mL of serum, antibiotics as
above for growth medium and 70 or 50 mLof dH2O, respec-
tively).
6.6.2 General Procedure for Cell Passage
Pass stock BGM cell cultures at approximately seven
day intervals using growth medium.
(a) Pour spent medium from cell culture vessels, and
discard the medium.
To prevent splatter, a gauze-covered beaker may be
used to collect spent medium.
Before discarding, autoclave all media that have been
in contact with cells or that contain serum.
(b) Add to the cell cultures a volume of warm EDTA-
trypsin reagent equal to 40% of the volume of medium
replaced.
See Table 2 for the amount of reagents required for
commonly used vessel types.
To reduce shock to cells, warm the EDTA-trypsin
reagent to 36.5 ± 1°C before placing it on cell monolayers.
Dispense the EDTA-trypsin reagent directly onto the cell
monolayer.
(c) Allow the EDTA-trypsin reagent to remain in contact
with the cells at either room temperature or at 36.5 ± 1°C
until cell monolayer can be shaken loose from inner surface
of cell culture vessel (about five min).
If necessary, a sterile rubber policeman (or scraper)
may be used to physically remove the cell sheet from the
bottle. However, this procedure should be used only as a
last resort because of the risk of cell culture contamination
inherent in such manipulations. The EDTA-trypsin reagent
should remain in contact with the cells no longer than neces-
sary as prolonged contact can alter or damage the cells.
(d) Pour the suspended cells into centrifuge tubes or
bottles.
To facilitate collection and resuspension of cell pellets,
use tubes or bottles with conical bottoms. Centrifuge tubes
and bottles used for this purpose must be able to withstand
the g-force applied.
(e) Centrifuge cell suspension at 1,000 xgfor 10 min to
pellet cells. Pour off and discard the supernatant.
Do not exceed this speed as cells maybe damaged or
destroyed.
162
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TABLE 2. Guide for Preparation of BGM Stock Cultures
Vessel Type P,0,'1?^
XH Volume (mL)
16 oz glass flat
bottles3
32 oz glass flat
bottles
75 cm2 plastic
flat flask
150 cm2 plastic
flat flask
690 cm2 glass
roller bottle
850 cm2 plastic
roller bottle
10
20
12
24
40
50
Media Volume
(mL)2
25
50
30
60
100
120
Total No. Cells to
Plate per Vessel
2.5
5.0
3.0
6.0
7.0
8.0
x 106
x 106
x 106
x 106
x 107
x 107
'The volume required to remove cells from vessels.
2Serum requirements: growth medium contains 10% serum; maintenance medium
contains 2-5% serum. Antibiotic requirements: penicillin-streptomycin stock solution,
1.0 mL/ liter; tetracycline stock solution, 0.5 mL/liter; fungizone stock solution, 0.2
ml/liter.
3Size is given in oz only when it is commercially designated in that unit.
(f) Suspend the pelleted cells in growth medium (see
section 6.6.1b) and perform a viable count on the cell
suspension according to procedures in section 6.7.
Resuspend pelleted cells in sufficient volumes of medi-
um to allow thorough mixing of the cells (to reduce sampling
error) and to minimize the significance of the loss of the 0.5
mL of cell suspension required for the cell counting proce-
dure. The quantity of medium used for resuspending
pelleted cells varies from 50 to several hundred mL, de-
pending upon the volume of the individual laboratory's need
for cell cultures.
(g) Dilute the cell suspension to the appropriate cell
concentration with growth medium and dispense into cell
culture vessels with either a Cornwall-type syringe or Brew-
er-type pipetting machine dispenser.
Calculate the dilution factor requirement using the cell
count established in section 6.7 and the cell and volume
parameters given in Table 2 for stock cultures and in Table
3 for virus assay cultures.
As a general rule, the BGM cell line can be split at a
1:3 ratio. However, a more suitable inoculum is obtained if
low passages of the line (passages 100-150) are split at a
1:2 ratio and higher passages (generally above passage
250) are split at a 1:4 ratio. To plant two hundred 25 cm2
cell culture flasks weekly from a low-level passage of the
line would require the preparation of six roller bottles (sur-
face area 690 cm2 each): two to prepare the six roller bottles
and four to prepare the 25 cm2 flasks.
(h) Except during handling operations, maintain BGM
cells at 36.5 ± 1°C in airtight cell culture vessels.
6.6.3 Procedure for Changing Medium on Cultured Cells
Cell monolayers normally become 95 to 100% confluent
three to four days after seeding with an appropriate number
of cells, and growth medium becomes acidic. Growth
medium on confluent stock cultures should then be replaced
with maintenance medium containing 2% serum. Mainte-
nance medium with 5% serum should be used when
monolayers are not yet 95% to 100% confluent but the
medium in which they are immersed has become acidic.
The volume of maintenance medium should equal the
volume of discarded growth medium.
6.7. Procedure for Performing Viable Cell
Counts
With experience a fairly accurate cell concentration
can be made based on the volume of packed cells. How-
ever, viable cell counts should be performed periodically as
a quality control measure.
6.7.1 Add 0.5 mL of cell suspension (or diluted cell sus-
pension) to 0.5 mL of 0.5% trypan blue solution in a test
tube.
To obtain an accurate cell count, the optimal total
number of cells per hemocytometer section should be be-
tween 20 and 50. This range is equivalent to between 6.0
x 105 and 1.5 * 106 cells per mL of cell suspension. Thus,
a dilution of 1:10 (0.5 mL of cells in 4.5 mL of growth
medium) is usually required for an accurate count of a cell
suspension.
6.7.2 Disperse cells by repeated pipetting.
Avoid introducing air bubbles into the suspension, be-
cause air bubbles may interfere with subsequent filling of the
hemocytometer chambers.
6.7.3 With a capillary pipette, carefully fill a hemocyto-
meter chamber on one side of a slip-covered hemo-
cytometer slide. Rest the slide on a flat surface for about
one min to allow the trypan blue to penetrate the cell
membranes of nonviable cells.
Do not under or over fill the chambers.
6.7.4 Under 100Xtotal magnification, countthe cells in the
four large corner sections and the center section of the
hemocytometer chamber.
Include in the count cells lying on the lines marking the
top and left margins of the sections, and ignore cells on the
lines marking the bottom and right margins. Trypan blue is
excluded by living cells. Therefore, to quantify viable cells,
count only cells that are clear in color. Do not count cells
that are blue.
Table 3. Guide for Preparation of Virus Assay Cell Cultures
Volume of Medium Final Cell Count per
(mL)1 Bottle
Vessel Type
1 oz glass bottle2
25 cm2 plastic flask
6 oz glass bottle
75 cm2 plastic flask
16 mm x 150 mm
tubes
4
10
15
30
2
9.0 x 105
3.5 x 106
5.6 x 106
1.0 x 107
4.0 x 10"
'Serum requirements: growth medium contains 10% serum; maintenance medium
contains 2-5% serum. Antibiotic requirements: penicillin-streptomycin stock solution,
1.0 mL/liter; tetracycline stock solution, 0.5 mL/liter; fungizone stock solution, 0.2
mL/liter.
2Size is given in oz only when it is commercially designated in that unit.
163
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6.7.5 Calculate the average number of viable cells in each
ml_ of cell suspension by totaling the number of viable cells
counted in the five sections, multiplying this sum by 4000,
and where necessary, multiplying the resulting product by
the reciprocal of the dilution.
6.8. Procedure for Preservation ofBGM Cell
Line
An adequate supply ofBGM cells must be available to
replace working cultures that are used only periodically or
become contaminated or lose virus sensitivity. Cells have
been held at -70°C for more than 15 years with a minimum
loss in cell viability.
6.8.1 Preparation of Cells for Storage
The procedure described is for the preparation of 100
cell culture vials. Cell concentration per mL must be at least
1 x 106.
Base the actual number of vials to be prepared on
usage of the line and the anticipated time interval require-
ment between cell culture start-up and full culture produc-
tion.
(a) Prepare cell storage medium by adding 10 mL of
DMSO to 90 mL of growth medium (see section 6.6.1b).
Sterilize cell storage medium by passage through an 0.22
|jm sterilizing filter.
Collect sterilized medium in 250 mL flask containing a
stir bar.
(b) Harvest BGM cells from cell culture vessels as
directed in section 6.6.2. Count the cells according to the
procedure in section 6.7 and resuspend them in the cell
storage medium at a concentration of 1 x 106 cells per mL.
(c) Place the flask containing suspended cells on a
magnetic stirrer and slowly mix for 30 min. Dispense 1 mL
volumes of cell suspension into 2 mL vials.
6.8.2 Procedure for Freezing Cells
The freezing procedure requires slow cooling of the
cells with the optimum rate of-1 °C per min. A slow cooling
rate can be achieved using the following method or by using
the recently available freezing containers (e.g., Nalge
Company Product No. 5100-0001 or equivalent) as recom-
mended by the manufacturers.
(a) Place the vials in a rack and place the rack in refrig-
erator at 4°C for 30 min, in a -20°C freezer for 30 min, and
then in a -70°C freezer overnight. The transfers should be
made as rapidly as possible.
To allow for more uniform cooling, wells adjoining each
vial should remain empty.
(b) Rapidly transfer vials into boxes or other containers
for long-term storage.
To prevent substantial loss of cells during storage,
temperature of cells should be kept constant after-70°C has
been achieved.
6.8.3 Procedure for Thawing Cells
Cells must be thawed rapidly to decrease loss in cell
viability.
(a) Place vials containing frozen cells into a 36°C water
bath and agitate vigorously by hand until all ice has melted.
Sterilize the outside surface of the vials with 0.5% iodine in
70% ethanol.
(b) Add BGM cells to either 6 oz tissue culture bottles or
25 cm2 tissue culture flasks containing an appropriate
volume of growth medium (see Table 3). Use two vials of
cells for 6 oz bottles and one vial for 25 cm2 flasks.
(c) Incubate BGM cells at 36.5 ± 1°C. After 18 to 24 h
replace the growth medium with fresh growth medium and
then continue the incubation for an additional five days.
Pass and maintain the new cultures as directed in section
6.6.
7. Bibliography and Suggested Reading
ASTM. 1998. Standard Methods for the Examination of
Water and Wastewater (L.S. Clesceri, A.E. Greenberg
and A.D. Eaton, ed), 20th Edition. United Book Press,
Baltimore, MD.
Barren, A.L., C. Olshevsky, and M.M. Cohen. 1970. Charac-
teristics of the BGM line of cells from African green
monkey kidney. Archiv. Gesam. Virusforsch. 32: 389-392.
Berg, G., D. Berman, and R.S. Safferman. 1982. A Method
for concentrating viruses recovered from sewage sludges.
Can. J. Microbiol. 28:553-556.
Berg, G., R.S. Safferman, D.R. Dahling, D. Berman, and
C.J. Hurst. 1984. USEPAManualof MethodsforVirology.
U.S. Environmental Protection Agency Publication No.
EPA/600/4-84-013, Cincinnati, OH.
Berman, D., G. Berg, and R.S. Safferman. 1981. A method
for recovering viruses from sludges. J. Virol. Methods. 3:
283-291.
Brashear, D.A., and R.L Ward. 1982. Comparison of
methods for recovering indigenous viruses from raw
wastewater sludge. Appl. Environ. Microbiol. 43:MIS-
MIS.
Dahling, D.R., and B.A. Wright. 1986. Optimization of the
BGM cell line culture and viral assay procedures for
monitoring viruses in the environment. Appl. Environ.
Microbiol. 51:790-812.
Dahling, D.R., G. Berg, and D. Berman. 1974. BGM, a
continuous cell line more sensitive than primary rhesus
and African green kidney cells forthe recovery of viruses
from water. Health Lab. Sci. 11:275-282.
Dahling, D. R., G. Sullivan, R. W. Freyberg and R. S.
Safferman. 1989. Factors affecting virus plaque confirma-
tion procedures. J. Virol. Meth. 24:111-122.
164
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Dahling, D. R., R. S. Safferman, and B. A. Wright. 1984.
Results of a survey of BGM cell culture practices. Envi-
ron. Internal 10:309-313.
Dulbecco, R. 1952. Production of plaques in monolayer
tissue cultures by single particles of an animal virus. Proc.
Natl. Acad. Sci. U.S.A. 38:747-752.
Eagle, H. 1959. Amino acid metabolism in mammalian cell
cultures. Science. 130:432-437.
Hay, R. J. 1985. ATCC Quality Control Methods for Cell
Lines. American Type Culture Collection, Rockville, MD.
Hurst, C. J. 1987. Recovering viruses from sewage sludges
and from solids in water, pp. 25-51. In G. Berg (ed),
Methods for Recovering Viruses from the Environment.
CRC Press, Boca Raton, FL.
Katzenelson, E., B. Fattal, and T. Hostovesky. 1976.
Organic flocculation: an efficient second-step concentra-
tion method forthe detection of viruses in tap water. Appl.
Environ. Microbiol. 32:638-639.
Lennette, E. H. and N. J. Schmidt (ed.). 1979. Diagnostic
Procedures for Viral, Rickettsial and Chlamydial Infec-
tions, 5th ed. American Public Health Association, Inc.,
Washington, D.C.
Safferman, R. S., M. E. Rohrand T. Goyke. 1988. Assess-
ment of recovery efficiency of beef extract reagents for
concentrating viruses from municipal wastewater sludge
solids by the organic flocculation procedure. Appl. Envi-
ron. Microbiol. 54:309-316.
Stetler, R. E., M. E. Morris and R. S. Safferman. 1992.
Processing procedures for recovering enteric viruses from
wastewater sludges. J. Virol. Meth. 40:67-76.
Ward, R. L, and C. S. Ashley. 1976. Inactivation of polio-
virus in digested sludge. Appl. Environ. Microbiol.
31:921-930.
165
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Appendix I
Test Method for Detecting, Enumerating, and
Determining the Viability of Ascaris Ova in Sludge
1.0 Scope
1.1 This test method describes the detection, enu-
meration, and determination of viability of Ascaris ova
in water, wastewater, sludge, and compost. These patho-
genic intestinal helminths occur in domestic animals and
humans. The environment may become contaminated
through direct deposit of human or animal feces or
through sewage and wastewater discharges to receiv-
ing waters. Ingestion of water containing infective /As-
caris ova may cause disease.
1.2 This test method is for wastewater, sludge, and
compost. It is the user's responsibility to ensure the va-
lidity of this test method for untested matrices.
1.3 This standard does not purport to address all
of the safety problems, if any, associated with its use. It
is the responsibility of the user of this standard to es-
tablish appropriate safety and health practices and de-
termine the applicability of regulatory limitations prior
to use. For specific hazard statements, see section 9.
2.0 Referenced Documents
2.1 ASTM Standards:
° D 1129 Terminology Relating to Water1
0 D 1193 Specification for Reagent Water2
0 D 2777 Practice for Determination of Precision
and Bias of Applicable Methods of committee
D-19on Water3
3.0 Terminology
(Definitions and Descriptions of Terms must be ap-
proved by the Definitions Advisor.)
3.1 Definitions - For definitions of terms used in
this test method, refer to Terminology D 1129.
3.2
dard:
Descriptions of Terms Specific to This Stan-
3.2.1 The normal nematode life cycle consists of
the egg, 4 larval stages and an adult. The larvae are
similar in appearance to the adults; that is, they are typi-
cally worm-like in appearance.
3.2.2 Molting (ecdysis) of the outer layer (cuticle)
takes place after each larval stage. Molting consists of
2 distinct processes, the deposition of the new cuticle
and the shedding of the old one or exsheathment. The
cuticle appears to be produced continuously, even
throughout adult life.
3.2.3 A molted cuticle that still encapsulates a larva
is called a sheath.
3.2.4 Ascarid egg shells are commonly comprised
of layers. The outer tanned, bumpy layer is referred to
as the mammillated layer and is useful in identifying
Ascaris eggs. The mammillated layer is sometimes
absent. Eggs that do not possess the mammillated layer
are referred to as decorticated eggs.
3.2.5 A potentially infective Ascaris egg contains a
third stage larva4 encased in the sheaths of the first
and second larval stages.
4.0 Summary of Test Method
4.1 This method is used to concentrate pathogenic
Ascaris ova from wastewater, sludge, and compost.
Samples are processed by blending with buffered wa-
ter containing a surfactant. The blend is screened to
remove large particulates. The solids in the screened
portion are allowed to settle out and the supernatant is
decanted. The sediment is subjected to density gradi-
ent centrifugation using magnesium sulfate (specific
gravity 1.20). This flotation procedure yields a layer likely
1Annual Book of ASTM Standards, Vol 11.01.
2Annual Book of ASTM Standards, Vol 11.01.
3Annual Book of ASTM Standards, Vol 11.01.
4P.L. Geenen, J. Bresciani, J. Boes, A. Pedersen, L. Eriksen,
H.P. Fagerholm, and P. Nansen (1999)The morphogenesis
of Ascaris suum to the infective third-stage larvae within
the egg, J. Parasitology 85(4):616-622.
166
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to contain Ascaris and some other parasitic ova, if
present, in the sample. Small particulates are removed
by a second screening on a small mesh size screen.5
The resulting concentrate is incubated at 26EC until
control Ascaris eggs are fully embryonated. The con-
centrate is then microscopically examined for the cat-
egories of Ascaris ova on a Sedgwick-Rafter counting
chamber.
5.0
5.1 This test method is useful for providing a quan-
titative indication of the level of Ascaris ova contamina-
tion of wastewater, sludge, and compost.
5.2 This test method will not identify the species of
Ascaris detected nor the host of origin.
5.3 This method may be useful in evaluating the
effectiveness of treatment.
6.0
6.1 Freezing of samples will interfere with the buoy-
ant density of Ascaris ova and decrease the recovery
of ova.
7.0
7.1 A good light microscope equipped with
brightfield, and preferably with phase contrast and/or
differential contrast optics including objectives ranging
in power from 10X to 45X.
7.2 Sedgwick-Rafter cell.
7.3 Pyrex beakers, 2 L. Coat with organosilane.
7.4 Erlenmeyer flask, 500 ml. Coat with
organosilane.
7.4 A centrifuge that can sustain forces of at least
660 X G with the rotors listed below.
7.4.1 A swinging bucket rotorto hold 100or250 ml
centrifuge glass or plastic conical bottles.
7.4.2 A swinging bucket rotorto hold 15 ml conical
or plastic centrifuge tubes.
7.5 Tylersieves.
7.5.1 20 or 50 mesh.
7.5.2 400 mesh, stainless steel, 5 inch in diameter.
7.5.3 A large plastic funnel to support the sieve.
Coat with organosilane.
7.6 Teflon spatula.
7.7 Incubator set at 26EC.
7.8 Large test tube rack to accommodate 100 or
250 ml centrifuge bottles.
7.9 Small test tube rack to accommodate 15 ml
conical centrifuge tubes.
7.10 Centrifuge bottles, 100 or 250 ml. Coat with
organosilane.
7.11 Conical centrifuge tubes, 15 ml. Coat with
organosilane.
7.12 Pasteur pipettes. Coat with organosilane.
7.13 Vacuum aspiration apparatus.
7.13.1 Vacuum source.
7.13.2 Vacuum flask, 2 L or larger.
7.13.3 Stopperto fit vacuum flask, fitted with a
or metal tubing as a connector for 1/4 inch tygon tub-
ing.
7.14 Spray bottles (16 floz.) (2).
7.14.1 Label one "Water".
7.14.2 Label one "1%7X".
8.0
8.1 Purity of Reagents Reagent grade chemi-
cals shall be used in all tests. Unless otherwise indi-
cated, it is intended that all reagents shall conform to
the specifications of the Committee on Analytical Re-
agents of the American Chemical Society6. Other
may be used, provided it is first ascertained that
the reagent is of sufficiently high purity to permit its use
without lessening the accuracy of the determination.
5This method is based on a protocol published by Bowman,
D.D., M.D. Little, and R.S. Reimers (2003) Precision and
accuracy of an assay for detecting Ascaris eggs in various
biosolid matrices. Water Research 37(9):2063-2072.
6Reagent Chemicals. American Chemical Specifications.
American Chemical Society, Washington, D.C. For sugges-
tions on testing of Reagents not listed by the American
Chemical Society, see Analar Standards for Laboratory
Chemicals, BHD Ltd., Poole, Dorset, U.K. and the United
States Pharmacopeia and National Formulary, U.S. Phar-
maceutical Convention, Inc. (USPC).
167
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8.2 Purity of WaterUnless otherwise indicated,
references to water shall be understood to mean re-
agent water conforming to Specification D 1193, Type I.
8.3 Preparation of Reagents Prepare reagents
in accordance with Practice E200.
8.3.1 Phosphate-buffered water (1 L = 34.0 g
KH2PO4, pH adjusted to 7.2 ± 0.5 with 1 N NaOH).
1 % (v/v) 7X ("ICN" laboratory detergent) (1 L
= 999 ml phosphate-buffered water, 1 ml 7X "ICN",
Adjust pH to 7.2 ± 0.1 with 1N NaOH).
8.3.3 Magnesium sulfate, sp. gr. 1.20. (1 L = 215.2
g MgSO4, check specific gravity with a hydrometer; ad-
just as necessary to reach 1.20).
8.3.4 Organosilane. For coating glassware. Coat
all glassware according to manufacturer's instructions.
8.3.5 Fresh Ascaris ova for positive control, puri-
fied from Ascaris infected pig fecal material.
9.0 Precautions
9.1 When handling Ascaris ova and biosolids, per-
sonal protective measures must be employed to pre-
vent infection. Prevention of infection in humans is a
matter of good personal hygiene. Wear a laboratory
coat at all times in the laboratory. In addition, latex or
nitrile gloves and protection safety should
always be worn in the laboratory. Mouth pipetting is
strictly forbidden. Contaminated pipettes are never laid
down on the bench top but are immediately placed in a
pipette discard container which has disinfectant in it.
Contaminated equipment is separated as it is used into
containers for disposable materials and containers for
re-cycling. After these containers which are always
autoclave pans, are full, they are autoclaved for 30 min-
utes at 121 EC and 15 pounds/in2. Contaminated glass-
ware is never washed until after it has been autoclaved.
Eating, drinking, and smoking in the laboratory is not
permitted. Likewise, refrigerators are not to be used
for storing lunches or other items for human consump-
tion. If infective Ascarisova are ingested they may cause
disease.
10.0
10.1 Collect 1 liter of compost, wastewater, or
sludge in accordance with Practice D 1066, Specifica-
tion D 1192, and Practices D 3370, as applicable.
10.2 Place the sample containers) on wet ice or
around chemical ice and ship back to the laboratory for
analysis within 24 hours of collection.
10.3 Store the samples in the laboratory refriger-
ated at 2 to SEC. Do not freeze the samples during
transport or storage.
11.0 Preparation of Apparatus
11.1 Test the centrifuge with a tachometer to make
sure the revolution's per minute correlate with the speed
gauge.
11.2 Calibrate the incubator temperature with a
NIST traceable thermometer.
11.3 Microscope.
11.3.1 Clean the microscope optics.
11.3.2 Adjust the condenser on the microscope, so
Kohler illumination is established.
12.0
12.1 The percentage moisture of the sample is de-
termined by analyzing a separate portion of the sample,
so the final calculation of ova per gram dry weight can
be determined. The concentration of ova in liquid sludge
samples may be expressed as ova per unit volume.
12.2 Initial preparation:
12.2.1 Dry or thick samples: Weigh about 300 g
(estimated dry weight) and place in about 500 ml water
in a beaker and let soak overnight at 4 -1 DEC. Transfer
to blender and blend at high for one minute. Divide
sample into four beakers.
12.2.2 Liquid samples: Measure 1,000 ml or more
(estimated to contain at least 50 g dry solids) of liquid
sample. Place one half of sample in blender. Add about
200 mL water. Blend at high speed for one minute trans-
fer to a beaker. Repeat for other half of sample.
12.3 Pour the homogenized sample into a 1000
mL tall form beaker and using a wash bottle, thoroughly
rinse blender container into beaker. Add 1 % 7X to reach
900 ml final volume.
12.4 Allow sample to settle four hours or overnight
at 4 -1 DEC. Stir occasionally with a wooden applicator,
as needed to ensure that material floating on the sur-
face settles. Additional 1 % 7X may be added, and the
mixture stirred if necessary.
12.5 After settling, vacuum aspirate supernatant
to just above the layer of solids. Transfer sediment to
blender and add water to 500 ml, blend again for one
minute at high speed.
12.6 Transfer to beaker, rinsing blender and add
1% 7Xto reach 900 ml. Allow to for two hours at
4 - 10EC, vacuum aspirate supernatant to just above
the layer of solids.
168
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12.7 Add 300 ml 1% 7X and stir for five minutes
on a magnetic stirrer.
12.8 Strain homogenized sample through a 20 or
50 mesh sieve placed in a funnel over a tall beaker.
Wash sample through sieve with a spray of 1 % 7X from
a spray bottle.
12.9 Add 1%7X to 900 ml final volume and allow
to settle for two hours at 4 -1 DEC.
12.10 Vacuum aspirate supernatant to just above
layer of solids. Mix sediment and distribute equally to
50 ml graduated conical centrifuge tubes. Thoroughly
wash any sediment from beaker into tubes using water
from a wash bottle. Bring volume in tubes up to 50 ml
with water.
12.11 Centrifuge for 10 minutes at 1000 X G.
Vacuum aspirate supernatant from each tube down to
just above the level of sediment. (The packed sediment
in each tube should not exceed 5 ml. If it exceeds this
volume, add water and distribute the sediment evenly
among additional tubes, repeat centrifugation, and
vacuum aspirate supernatant.)
12.12 Add 10 to 15 ml of MgSO4 solution (spe-
cific gravity 1.20) to each tube and mix for 15 to 20 sec-
onds on a vortex mixer. (Use capped tubes to avoid
splashing of mixture from the tube.)
12.13 Add additional MgSO4 solution (specific
gravity 1.20) to each tube to bring volume to 50 ml.
Centrifuge for five to ten minutes at 800 to 1000 X g.
DO NOT USE BRAKE.
12.14 Allow the centrifuge to coast to a stop with-
out the brake. Pourthetop25to35 ml of supernatant
from each tube through a 400 mesh sieve supported in
a funnel over a tall beaker.
12.15 Using a water spray bottle, wash excessive
flotation fluid and fine particles through sieve.
12.16 Rinse sediment collected on the sieve into
a 100 ml beaker by directing the stream of water from
the wash bottle onto the upper surface of the sieve.
12.17 After thoroughly washing the sediment from
the sieve, transferthe suspension to the required num-
ber of 15 ml centrifuge tubes, taking care to rinse the
beaker into the tubes. Usually one beaker makes one
tube.
12.18 Centrifuge the tubes forthree minutes at 800
X G, then discard the supernatant.
12.19 If more than one tube has been usedforthe
sample, transfer the sediment to a single tube, fill with
water, and repeat centrifugation.
12.20 Aspirate the supernatant above the solids.
12.21 Resuspend the solids in 4 ml 0.1 N H2SO4
and pour into a 20-mL polyethylene scintillation vial or
equivalent with loose caps.
12.22 Before incubating the vials, mark the liquid
level in each vial with a felt tip pen. Incubate the vials,
along with control vials containing Ascaris ova mixed
with4ml_0.1 N H2SO4, at 26EC forthree to four weeks.
Everyday or so, check the liquid level in each vial. Add
reagent grade water up to the initial liquid level line as
needed to compensate for evaporation. After 18 days,
suspend, by inversion and sample small aliquots of the
control cultures once every 2 - 3 days. When the ma-
jority of the control Ascaris ova are fully embryonated,
samples are ready to be examined.
12.23 Examine the concentrates microscopically
using a Sedgwick-Rafter cell to enumerate the detected
ova. Classify the ova as either unembryonated, em-
bryonated to the first, second, or third larval stage. In
some embryonated Ascaris ova the larva may be ob-
served to move. See Figure 1 for examples of various
Ascaris egg categories.
13.0 Calculation
13.1 Calculate % total solids using the % mois-
ture result:
% Total solids = 100% - % moisture
13.2 Calculate catagories of ova/g dry weight in
the following manner:
Ova/g dry wt = (NO) x (CV) x (FV)
(SP) x (TS)
Where:
NO = no. ova
CV = chamber volume(= 1 ml)
FV = final volume in ml
SP = sample processed in ml org
TS = % total solids
14.0 Report
14.1 Report the results as the total number of As-
caris ova, number of unembryonated Ascaris ova, num-
ber of 1st, 2nd, or 3rd stage larva; reported as number
of Ascaris ova and number of various larval Ascaris ova
perg dry weight.
15.0 Keywords
Ascaris, ova, embryonation, viability assay, helminth.
169
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Notice
The PEC was consulted in a recent (1998-1999) pi-
lot study by Lyonnaise des Eaux concerning the use of
a microscope in making helminth ova counts for differ-
ent types of sludge. Solids and debris present in the
sludge being viewed with the microscope were found to
impair ones ability to count. Dilution of raw sludge and
digested sludge, however, with phosphate-buffered
water priorto analyzing them significantly improved the
numberof ova that could be counted. Raw sludges were
diluted by a factor of 20 and digested sludges by a fac-
tor of 5. QA/QC procedures were followed to validate
this procedure. The PEC should be consulted for more
details.
[revised May 15,2003]
170
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Figure A1.1. Ascaris ovum: potentially non-fertile,
note bumpy mammilated outer layer.
Figure A1.2. Ascaris ovum: fertile, note the bumpy
outer mammilated layer.
Figure A1.3. Ascaris ovum: decorticated, unembryonated.
Note the outer mammilated layer is gone
Figure A1.4. Ascaris ovum: decorticated and embryonated.
171
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Figure A1.5. Ascaris ovum: decorticated, embryonated.
Figure A1.6. Ascaris ovum with second stage larva;
note the first stage larval sheath at the anterior end of
the worm
172
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Appendix J
The Biosolids Composting Process
Introduction
Composting is the biological decomposition of organic
matter under controlled aerobic conditions. The objectives
of composting are to reduce pathogens to below detect-
able levels, degrade volatile solids, and produce a usable
product. Pathogen reduction is a function of time and tem-
perature. Composted biosolids is one way to meet 40 CFR
Part 503 pathogen (and vector attraction) reduction require-
ments. Composted biosolids can meet either a "Process
to Significantly Reduce Pathogens" (PSRP/Class B) or a
"Process to Further Reduce Pathogens" (PFRP/Class A)
standard, depending upon the operating conditions main-
tained at the facility. Process and operational consider-
ations must be taken into account when a facility desires
to meet the pathogen and vector attraction requirements
of 40 CFR 503. The 40 CFR Part 503 regulations require
composted biosolids applied to the land to meet specific
pollutant limits, site restrictions, management practices,
and pathogen and vector attraction reduction processes,
depending upon whether they: 1) are applied to agricul-
tural land, forest, a public contact site, or a reclamation
site; 2) are sold or given away in a bag or other container;
or 3) are applied to a lawn or home garden. Discussions
provided here are presented in summary form; it is recom-
mended that the facility seek additional details in develop-
ing a compost operation.
Composting Process Description
The addition of a bulking agent to sewage sludge pro-
vides optimum conditions for the composting process,
which usually lasts 3 to 4 weeks. A bulking agent acts as a
source of carbon for the biological process, increases po-
rosity, and reduces the moisture level. The composting
process has several phases, including the active phase,
the curing phase, and the drying phase.
Active phase. During the active or stabilization phase,
the sewage sludge/bulking agent mix is aerated and the
sewage sludge is decomposed due to accelerated biologi-
cal activity. The biological process involved in composting
can raise the temperature up to 60°C or more. At these
high temperatures, all of the disease-causing pathogens
are destroyed. Windrow systems must meet this condition
by achieving 55°C for a minimum of 15 consecutive days
during which time the windrow is turned five times. The
critical requirement is that the material in the core of the
compost pile be maintained at the required temperatures
(55°C) for the required time (3 days). Therefore, the first
phase typically lasts 21 days. Aeration is accomplished in
one of two ways: 1) by mechanically turning the mixture
so that the sewage sludge is exposed to oxygen in the air;
or 2) by using blowers to either force or pull air through the
mixture.
Curing phase. After the active phase, the resulting ma-
terial is cured for an additional 30 days to 180 days. At this
time, additional decomposition, stabilization, pathogen
destruction, and degassing takes place. Composting is
considered complete when the temperature of the com-
post returns to ambient levels. Depending upon the extent
of biodegradation during the active phase and the ultimate
application of the finished product, the curing phase may
not be carried out as a separate process.
Drying phase. After curing, some operations add another
step called the drying phase which can vary from days to
months. This stage is necessary if the material is to be
screened to either recover the unused bulking agent for
recycling or for an additional finished product. If the prod-
uct is to be marketable, the final compost should be 50%
to 60% solids.
There are two main process configurations for the
composting process:
Unconfined composting. This process is conducted in
long piles (windrows) or in static piles. Operations using
unconfined composting methods may provide oxygen to
the compost by turning the piles by hand or machine or by
using air blowers which may be operated in either a posi-
tive (blowing) or negative (suction) mode. For windrows
without blower aeration, it is typical to turn the windrow
two or three times a week, using a front-end loader. Prop-
erly operating aerated static piles do not require turning.
Confined (in-vessel) composting. This process is car-
ried out within an enclosed container, which minimizes
odors and process time by providing better control over
the process variables. Although in-vessel composting has
been effective for small operations, typically these opera-
tions are proprietary and therefore will not be described
any further in this fact sheet.
173
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Operational Considerations
The key process variables for successful composting are
the moisture content and carbon to nitrogen (C:N) ratio of
the biosolids/bulking agent mixture, and temperature and
aeration of the compost pile. Other process parameters
such as volatile solids content, pH, mixing and the materi-
als used in the compost also affect the process.
Bioso/ids/Bu/king Agent Mixture Moisture Content. Mois-
ture control is an important factor for effective composting.
Water content must be controlled for effective stabiliza-
tion, pathogen inactivation, odor control and finished com-
post quality (Benedict, 1988). The optimum moisture con-
tent of the mix is between 40% and 60%. At less than 40%
water, the material is too fluid, has reduced porosity and
has the potential for producing septic conditions and odors;
above 60% solids, the lack of moisture may slow down the
rate of decomposition. Since typical dewatered sewage
sludge or biosolids are often in the range of 15% to 20%
solids for vacuum filtered sewage sludge or biosolids and
20% to 35% solids for belt press or filter pressed sewage
sludge or biosolids, the addition of drier materials (bulking
agents) is usually essential.
Biosolids/Bulking Agent Mixture Carbon to Nitrogen Ra-
tio. Microorganisms need carbon for growth and nitrogen
for protein synthesis. For efficient composting, the carbon
to nitrogen (C:N) ratio of the biosolids/bulking agent mix-
ture should be in the range of 25:1 to 35:1
Oxygen levels. For optimum aerobic biological activity,
air within the pile should have oxygen levels of between
5% and 15%. Lower levels of oxygen will create odors and
reduce the efficiency of the composting. Excessive aera-
tion will cool the pile, slow the composting process, and
will not provide the desired pathogen and vector attraction
reduction.
Conventional windrows obtain necessary oxygen through
the natural draft and ventilation induced from the hot, moist
air produced during active composting and from the peri-
odic windrow turning. Where blowers are used for aera-
tion, it is typical to provide at least one blower per pile.
Biosolids/Bulking Agent Mixture Volatile Solids Con tent.
The volatile solids content of the biosolids/bulking agent
mix should be greater than 50% for successful composting
(EPA, 1985). This parameter is an indicator of the energy
available for biological activity and therefore compostability.
Bioso/ids/Bu/king Agent Mixture pH. The pH of the
biosolids/bulking agent mix should be in the range of 6 to
9 for efficient composting (EPA, 1985). Higher pH mixtures
may result if lime stabilized biosolids are used. They can
be composted; however, it may take longer for the
composting process to achieve the temperatures needed
to reduce pathogens.
Biosolids and Bulking Agent Mixing. Uniform mixing is
necessary in order to assure that moisture concentration
is constant through the pile and that air can flow throughout.
Type of Biosolids. The type of biosolids used
may have an effect on the composting process.
Composting can be accomplished with unstabilized
biosolids, as well as anaerobically and aerobically digested
biosolids. Raw sludge has a greater potential to cause
odors because they have more energy available and will,
therefore, degrade more readily. This may cause the com-
post pile to achieve higher temperatures faster unless suf-
ficient oxygen is provided and may also cause odors (EPA,
1985).
Material for Bulking Agents. Materials such as wood
chips, sawdust and recycled compost are usually added
as "bulking agents" or "amendments" to the compost mix-
ture to provide an additional source of carbon and to con-
trol the moisture content of the mixture. Other common
bulking agents used by facilities around the country include
wood waste, leaves, brush, manure, grass, straw, and
paper (Goldstein, 1994). Because of their cost, wood chips
are often screened out from the matured compost, for re-
use. Although sawdust is frequently used for in-vessel
composting, coarser materials such as wood chips, wood
shavings, and ground-up wood are often preferred because
they permit better air penetration and are easier to remove.
Recycled compost is often used as a bulking agent in wind-
rows, especially if bulking agents must be purchased. How-
ever, its use is limited because the porosity decreases as
the recycle ages (EPA, 1989). The amount of biosolids
and bulking agent which must be combined to make a suc-
cessful compost is based on a mass balance process con-
sidering the moisture contents, C:N ratio, and volatile sol-
ids content.
Compost Pile Size. In general, assuming adequate aera-
tion, the larger the pile the better. A larger pile has less
surface area per cubic yard of contents and therefore re-
tains more of the heat that is generated and is less influ-
enced by ambient conditions. In addition, less cover and
base material (recycled compost, wood chips, etc.) is
needed as well as the overall land requirements for the
compost operation. Larger piles tend to retain moisture
longer. The surface area to volume ratio has an effect on
the temperature of the pile. Assuming other factors are
constant (e.g., moisture, composition, aeration), larger piles
(with their lower surface area to volume ratio), retain more
heat than smaller piles. Ambient temperatures have a sig-
nificant impact on composting operations (Benedict, 1988).
A typical aerated static pile for a large operation would
be triangularly shaped in cross section about 3 meters(m)
high by 4.5 to 7.5 m wide (15 to 25 feet) at the base by 12
to 15 m long (39 to 50 feet) (Haug, 1980). One survey
study indicates that extended aerated static pile (where
piles are formed on the side of older piles) heights were
typically 12 to 13 feet high. Minimum depths of base and
cover materials (recycled compost, wood chips, etc.) were
12 and 18 inches, respectively (Benedict, 1988).
In windrow composting, the compost mix is stacked in
long parallel rows. In cross section, windrows may range
from rectangular to trapezoidal to triangular, depending
174
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upon the material and the turning equipment. Atypical trap-
ezoidal windrow might be 1.2 m (4 feet) high by 4.0 m (13
feet) at its base and 1.0 m (3 feet) across the top (Haug,
1980).
Monitoring and Sampling of the Compost
Pile
Unless the entire composting mass is subject to the
pathogen reduction temperatures, organisms may survive
and repopulate the mass once the piles or windrows are
cooled. Therefore it is crucial that temperatures be attained
throughout the entire pile. For aerated static piles or in-
vessel systems using static procedures such as tunnels or
silos, temperature monitoring should represent points
throughout the pile, including areas which typically are the
coolest. In aerated static piles this is usually the toes of
the pile (Figure 1). Temperatures should be taken at many
locations and at various depths to be assured that the core
of the pile maintains the required temperature. Records of
the temperature, date, and time should be maintained and
reviewed on an ongoing basis. Microbial analysis should
at a minimum be taken in a matter to represent the entire
compost pile. Operational parameters such as moisture,
oxygen as well as the others should be monitored at a
frequency necessary to assure that the compost opera-
tion is operating within acceptable ranges.
For composting, vector attraction reduction (VAR) is
achieved through the degradation of volatile solids. The
extent to which the volatile solids are degraded is often
referred to as compost stability. Stabilization requires suf-
ficient time for the putrescible organic compounds and for
other potential food sources for vectors to decompose.
Under this vector attraction reduction option, the Part 503
requires that biosolids be maintained under aerobic condi-
tions for at least 14 days, during which time temperatures
are over 40°C(104°F), and the average temperature is
over 45°C (113°F) (503.33(b)(5). These criteria are based
on studies which have shown that most of the highly pu-
trescible compounds are decomposed during the first 14
days of composting and that significant stability is achieved
at mesophilic (<45°C ) temperatures.
Recommendations for Specific
Technologies
Aerated static pile - Aerated static piles should be cov-
ered with an insulation layer of sufficient thickness to en-
sure that temperatures throughout the pile, including the
pile surface, reach 55°C. It is recommended that the insu-
lation layer be at least 1 foot thick. Screened compost is a
more effective insulation than unscreened compost or wood
chips. Screened compost also provides more odor control
than the other two materials.
Air flow rate and the configuration of an aeration system
are other factors which affect temperature. Air flow must
be sufficient to supply oxygen to the pile, but excessive
aeration removes heat and moisture from the composting
material. The configuration of an aeration system is also
important. Aeration piping too close to pile edges may re-
sult in uneven temperatures in the pile and excessive cool-
ing at the pile toes. If holes in the perforated piping are too
large or not distributed properly, portions of the pile may
receive too much air and be too cool as a result.
Windrows - Compliance with the pathogen reduction
requirements for windrows depends on proper windrow size
and configuration. If windrows are too small, the high sur-
face area to volume ratio will result in excessive heat loss
from the pile sides. Turning must ensure that all material
A 1 foot thick insulation layer is recommended to ensure that the
entire pile reaches pathogen reduction temperatures.
Blower
Pile toes are usually the coolest part of an aerated static pile.
Figure 1a. Aerated static pile.
175
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Pile Core
z
\
/ \
Material turned into the pile core reaches pathogen reduction temperatures.
Operations must ensure that all material is turned into the core at some point
during composting and that core temperatures rise to 55 degrees after turning.
Figure 1b. Windrow.
in a windrow be introduced into the pile core and raised to
pathogen reduction temperatures. This is most easily
achieved with a windrow turning machine.
In-Vessel systems- It is difficult to provide guidance for
these systems as there are numerous types with varying
configurations. Two key factors that apply to all in-vessel
systems are aeration and available carbon. As with aer-
ated static piles, the air flow configuration and rate can
affect the distribution of aeration to different parts of a
composting mass and the temperature profile of a pile.
Many in-vessel systems use sawdust as an amendment.
This may not provide sufficient energy if the volatile solids
in the biosolids are low.
Requirements for Class A/Class B Compost
For class A biosolids, aerated static pile, conventional
windrow and in-vessel composting methods must meet the
PFRP requirements, including the following temperature/
time requirements:
Aerated static piles and in-vessel systems must be
maintained at a minimum operating temperature of
55°C (131°F) for at least 3 days; and
Windrow piles must be maintained at a minimum op-
erating temperature of 55°C (131°F) for 15 days or
longer. The piles must be turned five times during this
period.
For class B biosolids, aerated static pile, conventional
windrow and in-vessel composting methods must meet the
PSRP requirements, including the following temperature/
time requirements:
The compost pile must be maintained at a minimum of
40°C for at least five days; and
During the five-day period, the temperature must rise
above 55°C for at least four hours to ensure pathogen
destruction. This is usually done near the end of the
active composting phase in order to prevent inactivat-
ing the organic destroying bacteria.
To meet 40 CFR Part 503 vector attraction reduction
requirements using the "aerobic process" alternative,
composting operations must ensure that the process lasts
for 14 days or longer at a temperature greater than 40°C.
In addition, the average temperature must be higher than
45 °C.
Additional References
Benedict, Arthur et al., Composting Municipal Sludge: A
Technology Evaluation, Pollution Technology Review
No. 152, Noyes Data Corporation, Park Ridge, New
Jersey, 1988.
BioCycle, Managing Sludge by Composting, JG Press Inc.,
Emmaus,PA, 1984.
Goldstein, N. et al., "1994 Biocycle Biosolids Survey."
Biocycle: Journal of Composting and Recycling, De-
cember 1994.
Haug, Roger T., Compost Engineering, Principles and Prac-
tice, Ann Arbor Science Publishers, Ann Arbor, Michi-
gan, 1980.
Information Transfer Inc., 1977 National Conference on
Composting of Municipal Residues and Sludges, Au-
gust 23-25,1977, Information Transfer, Inc., Rockville,
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