United States
Environmental Protection
Agency
Office of Research and
Development
Washington, DC 20460
EPA/625/4-91/030
December 1991
Technology Transfer
vvEPA Seminar Publication
Medical and Institutional
Waste Incineration:
Regulations, Management,
Technology, Emissions, and
Operations
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EPA/625/4-91/030
December 1991
Seminar Publication
Medical and Institutional Waste Incineration
Regulations, Management, Technology,
Emissions, and Operations
Center for Environmental Research Information
Office of Research and Development
U.S. Environmental Protection Agency
Cincinnati, OH 45268
Printed on Recycled Paper
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Disclaimer
This document has been reviewed in accordance with the U.S.
Environmental Protection Agency's peer and administrative
review policies and approved for publication. Mention of trade
names or commercial products does not constitute endorse-
ment or recommendation for use. ;
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Preface
Many medical waste incinerators in the United States are not
designed to adequately handle the complex waste streams
generated by modern medical facilities. Issues of concern to
both die public and medical facility owners/operators are:
What are the adverse health and environmental effects from
improper handling and disposal of generated wastes? What can
I do with waste generated at my facility? Do regulations exist
to protect the public?
The U. S. Environmental Protection Agency (EPA) was
aware of some of these concerns, and research was under-
way when Congress passed the Medical Waste Tracking Act
in the Summer of 1988. The purpose of that legislation was
to respond to public concern and to gather information in
limited geographic areas. Meanwhile, the public, regulators,
and facility owners/operators continued to ask: Is medical
waste being handled and disposed of properly? Is technol-
ogy available to answer these concerns? What must be con-
sidered when responding to these questions? Can correct
answers to these questions be found? To respond to some of
these concerns, EPA's Center for Environmental Research
Information decided to sponsor a series of seminars to
provide information on technologies that could be applied to
medical waste handling and disposal.
A series of five seminars was held, beginning in October,
1989, in Providence, Rhode Island, and concluding in
February, 1990, in Tallahassee, Florida. This document is a
summary of the material presented at these seminars.
Because the document was written based on notes from
the presentations, it presents information as it was
known in 1989. Thus the Medical Waste Tracking Act,
for example, is discussed in the present verb tense, even
though the demonstration program has been completed.
Additionally, some other information is no longer ap-
plicable, and may even be obsolete, in light of regulations
being developed at the federal level as a result of the
1990 Clean Air Act Amendments. Furthermore, existing
state regulations may provide more specific guidance
than that presented in this document. The document,
however, contains general principles that remain of inter-
est to those who are concerned with medical waste han-
dling and disposal.
til
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Contents
Page
Chapter 1 Introduction j. 1
1.1 Organization of the Report 1
1.2 Sources of Information L . 1
Chapter 2 Overview of Medical Waste Regulations and Guidelines 2
2.1 Historical Perspective . _ 2
2.2 Medical Waste Tracking Act of 1988 ; 2
2.2,1 Overview of the Act 2
2.2,2 Description of the Demonstration Program 3
2.3 Other Regulations and Guidelines Affecting the Management of Medical Waste 4
2.3.1 Federal Regulations and Guidelines 4
2.3,2 NIH Standard Operating Procedures I ........5
2.3.3 Joint Commission on Accreditation of Healthcare Organizations (JCAHO) Standards 5
2.3,4 State and Local Regulations |. 5
i
Chapter 3 Technical Overview of Medical Waste Management and Treatment 7
i
3.1 Technical and Administrative Considerations j, 7
3.1.1 Definitions and Sources of Medical Waste r 7
3.1.2 Waste Disposal Evaluations 8
3.1.3 Waste Minimization J. 8
3.1.4 Disposal Option Selection j. 8
3.2 Treatment and Disposal Options for Medical Waste.... 9
3.2.1 Biomedical Waste Options \ 9
3.2.2 Chemical/Hazardous Waste Options t 14
3.2.3 Radioactive Waste Options j, : 14
1
Chapter 4 Incineration of Medical Waste \ 15
4.1 Technical Aspects of Medical Waste Incineration r 15
4.1.1 Principles of Combustion j, .....; 15
4.1.2 Types of Incinerators : 16
4.1.3 Incinerator Operating Modes i, 17
4.1.4 Incinerator Design Parameters j. 17
4.1,5 Incineration Systems and Equipment !. 23
4.2 Incinerator Emissions and Air Pollution Control Equipment 27
4.2.1 Incinerator Emissions I '. 27
4.2,2 Regulatory Requirements for Emission Control , ,28
4.2.3 Emission Control Strategies I 28
4.2.4 Air Pollution Control Equipment i 28
4.2.5 Selection of Pollution Control Devices 33
4.3 Other Regulatory and Permitting Considerations '. 34
iv
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Page
Chapter 5 Designing and Implementing Waste Management Plans 35
5.1 Designing a Waste Management Plan 35
5.1.1 Waste Disposal Evaluations .....35
5.1.2 Incineration Option Selection 35
5.2 Selecting and Procuring an Incineration System 35
5.2.1 System Selection and/or Design Deficiencies 36
5.2.2 Fabrication and/or Installation Deficiencies..... ....: 37
5.2.3 Operation and/or Maintenance Deficiencies 37
5.2.4 Avoiding Incineration System Deficiencies 37
5.3 Training, Safety, and Operations : 38
5.3.1 Personal Safety 38
5.3.2 Equipment Safety Procedures 38
5.3.3 Fire Safety 38
5.3.4 Proper Operation and Maintenance (O&M) 38
Chapter 6 References.
40
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Figures
Number
3-1
3-2
3-3
4-1
4-2
4-^
4-4
4-5
4-6
4-7
4-8
4-9
4.tn
4-11
4-12
4.17
4-14
4-1'?
4-16
4-17
4-18
4-19
Gravity steam-autoclaving system
System for shredding with chemical disinfection
Major components of an incineration system
Control of temperature as a function of excess air
Tnlinp mn1tin1f*-rhflmlv*r incinerator with crate
A/fatnrpntnnnn^ntQ of a rnntrollfifl-air incinerator
Tn/*in/»rfltnr rsvnaritipc &
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Tables
Page
Number
3-1 Incinerator Institute of America Waste Generation Factors 9
3-2 Comparisons of Onsite Biomedical Waste Treatment Technologies , 10
3-3 Comparisons of Offsite Biomedical Waste Treatment and Disposal Methods 13
4-1 Incinerator Institute of America Waste Classifications 20
4-2 Waste Data Chart 21
4-3 Maximum Burning Rate of Various Waste Types 22
5-1 Waste Characterization Data Deficiencies Necessitating System Capacity Reductions 36
5-2 Incineration System Performance Problems ; 35
5-3 Recommended Incineration System Implementation Steps 38
VII
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Acknowledgments
The material presented in this seminar series was prepared
by Jacqueline Sales, HAZMED, and Lawrence G. Doucet,
P.E., Doucet & Mainka, P.C., to match their presentations.
Ms. Sales presented the bulk of the material contained iin
Chapter 2, while Mr. Doucet and John Bleckman, Doucetj&
Mainka, presented the remaining material. Karen Natsios
Rehmus, Eastern Research Group, Inc., was responsible for
logistical arrangements for the seminars and was on site!at
all locations to provide support. ;
Anne C. Jones, Eastern Research Group, Inc., prepared the
written manuscript from handout material available from the
seminars. Denis J. Lussier and Justice A. Manning, U.S.
EPA, Center for Environmental Research Information
(CERI), prepared most of the narrative slides.
James A. Eddinger, EPA, Office of Air Quality Planning
and Standards, and Kristina L. Meson, EPA, Office of Solid
Waste, are especially acknowledged for their peer review of
this document. Justice Manning, CERI, was the project of-
ficer for both the seminars and this publication.
viii
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Chapter 1
Introduction
Medical waste management is becoming an increasingly im-
portant issue as medical institutions face public fears and
perceptions, tightening legislation, and fewer disposal op-
dons. Many medical institutions are responding to these
problems by reevaluating their waste management practices,
particularly the treatment and disposal methods they are
now using. Because landfill space is vanishing and because
more states are requiring onsite treatment and disposal of
medical wastes, onsite incineration of medical waste is be-
coming an increasingly attractive waste management option.
To address this growing interest in medical waste incineration,
the U.S. Environmental Protection Agency (EPA) initiated a
series of seminars entitled Medical and Institutional Waste In-
cineration: Regulations, Management Technology, Emissions,
and Operations presented from October 1989 to February
1990 in 5 of the 10 EPA Regions. These seminars were
designed to assist those responsible for managing medical
waste in understanding the applicable regulations; developing
waste management plans; selecting appropriate waste manage-
ment options, including incineration; determining data collec-
tion needs; and managing the selection, procurement, and
operation of medical waste incinerators.
The information presented in the seminar series, including in-
formation on combustion theory, air pollution control equip-
ment, and operator training needs, is summarized in this
document Generally, it is organized to follow the sequence of
the major topics presented in the seminar series. Because only
that information presented at these seminars is summarized
here, this document is not a source of the most recent informa-
tion on these subjects. More recent information on these sub-
jects is available.1-213
1.1 Organization of the Report
This report is organized into four chapters, in addition to this
introduction and references. The existing federal, state, and
local regulations governing medical waste management, treat-
ment, and disposal are discussed in Chapter 2, which focuses
on the Medical Waste Tracking Act of 1988 as an example of
how medical waste may be regulated in the future. Pending
regulations and guidelines that affect the management of medi-
cal waste also are presented.
The administrative and technical issues that must be con-
sidered when options for medical waste treatment are inves-
tigated, including methods for waste minimization, are
summarized in Chapter 3. Principal technologies used to treat
and dispose of medical waste, including steam autoclaving,
shredding with chemical disinfection, and incineration, also
are summarized.
The basics of combustion theory, the major incineration tech-
nologies in use, emission control strategies, pollution control
equipment, and other equipment used in incineration systems
are summarized in Chapter 4. Also covered in this chapter are
the types of data critical to incinerator design, the operating
parameters that can affect incinerator efficiency and emissions,
and some of the basic regulatory and permitting requirements
for incinerators.
Additional considerations specific to developing a waste
management plan for medical waste incinerators are discussed
in Chapter 5. A method for ensuring that an institution's needs
will be met throughout the incinerator selection, procurement,
and acceptance phases is presented, and common pitfalls that
can occur during selection and procurement are identified. The
chapter is concluded with an outline of the information that
should be covered by operator training programs to ensure the
safe and proper operation of medical waste incinerators.
1.2 Sources of Information
Most of the report is drawn from the materials handed out at
the seminars, which were organized as a document entitled
Seminar—Medical and Institutional Waste Incineration:
Regulations, Management, Technology, Emissions, and
Operations.4 These materials are reprints of slides used at the
seminars as well as three papers written by Lawrence G.
Doucet5'6'7 Chapter 2 summarizes the presentation made by
Jacqueline Sales at the seminar series. Most of Chapter 3 is
based on Reference 5. Portions of Chapter 4 and most of Chap-
ter 5 are a summary of Reference 6. Other major sources of in-
formation concerning combustion theory, some descriptions of
incinerator equipment, and operator training needs were drawn
from Reference 8. The portion of Chapter 4 covering air
pollution control devices was summarized primarily from
Reference 9.
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Chapter 2
Overview of Medical Waste Regulations and Guidelines*
A broad spectrum of federal, state, and local regulations and
guidelines govern the management of medical wastes. TJhe
federal regulations and guidelines that affect the handling;of
medical waste are discussed in this chapter. Guidelines
developed by EPA and other entities are discussed, and a
selection of state and local regulations that might affect medi-
cal waste management and disposal planning are summarized.
Regulatory issues affecting medical waste incinerators are dis-
cussed in Chapter 4. [
2.1 Historical Perspective
For a number of years, various federal agencies and organiza-
tions, including the National Institutes of Health (NIH), the
Centers for Disease Control (CDC), and the Nuclear
Regulatory Commission (NRC), have regulated or issiied
guidelines for handling and treating medical wastes. Many
states and some local governments also regulate the manage-
ment of these wastes. In May 1986, EPA actively became fin-
volved in overseeing medical waste management by issuing its
Guide for Infectious Waste Management,"1 in which a number
of practices, including those for waste segregation, storage,
packaging, treatment, transport, and disposal, are recom-
mended, i
i
Despite guidelines and regulations, a number of incidents in-
volving the mismanagement of medical waste have occurred.
In the summer of 1988, improper handling and storage, of
medical waste became a heated public issue when beaches
along the east coast were closed after medical and other wastes
washed up along shore. Reports of syringes, needles, and other
medical waste found around dumpsters, gutters, and other
public areas added to the furor over improperly disposed^ of
medical waste. Furthermore, fear of AIDS and other com-
municable diseases has been increasing steadily. Although^no
evidence has been found linking mismanagement of medical
waste to any case of injury or infection in the general public,
Congress enacted The Medical Waste Tracking Act11 in the fall
of 1988 in response to these public concerns.
As a result of this increase in public and Congressional con-
cern and the growing volumes of medical waste generated,: in-
creasingly stringent regulations are likely to be promulgated.
To prepare for new requirements, those involved in ithe
management or treatment of medical waste should familiarize
themselves with all levels of regulations and guidelines in
*Ai noted in the preface, the seminar series was begun in late 1989. iThe
regulatory situation as it existed at that time is presented in this chapter, i
effect, proposed, or under consideration. The Medical Waste
Tracking Act with resulting regulations and other existing and
proposed federal regulations and guidelines that affect how
medical waste is managed are discussed in the sections below.
Selected state and local regulations and guidelines are
reviewed briefly, as well.
2.2 Medical Waste Tracking
Act of 1988
2.2.1 Overview of the Act
The Medical Waste Tracking Act (MWTA),11 a 2-year program
running from June 1989 to June 1991, most likely will have a
significant impact on how medical waste is handled and dis-
posed of in future years. The Act defines medical waste as
"...any solid waste which is generated in the diagnosis, treat-
ment, or immunization of human beings or animals, in re-
search pertaining thereto, or in the production or testing of
biologicals...." In enacting the law, Congress recognized that
medical waste requires special handling and disposal and that
experience gained from a pilot program would serve as a guide
to its proper management. Moreover, Congress anticipated that
a regionwide demonstration program would provide a realistic
test for determining the need for a national program to track
medical wastes.12
The MWTA amended the Resource Conservation and
Recovery Act (RCRA) by adding Subtitle J, which establishes
the demonstration tracking program for medical wastes as a
first step in minimizing irresponsible medical waste disposal.
Subtitle J is designed to ensure that medical waste is properly
packaged and separated from general refuse to protect
workers, the public, and the environment from possible risk.
The program also will set up a tracking system to identify and
increase the accountability of those who generate, transport,
and dispose of these wastes. Since much of this waste no
longer will be handled as ordinary refuse, EPA expects that
less medical waste will wash up on beaches and float on water-
ways in the participating states.12
Initially the Act specified New York, New Jersey, Connec-
ticut, and the seven states bordering the Great Lakes as par-
ticipants in the demonstration program.13 These states were
allowed to decline to join the program, and other states were
invited to petition into the program; New York, New Jersey,
Connecticut, Rhode Island, and Puerto Rico are those which
have elected to participate.
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EPA, in cooperation with the participating states, will review
and evaluate the demonstration program. As required by the
law, the Agency will report to Congress on program ac-
complishments, limitations, and any problems encountered
during the 2 years.1'2 This information is being used to design
guidelines for the nonparticipating states and to develop proper
environmental laws for future national application.14 ,
2.2.2 Description of the Demonstration Program
A description of the program is provided because it was part of
the seminar.4 EPA expects that many components have been
and will be incorporated into state regulatory programs, and
many also may become part of future EPA regulations.
2.2.2.1 Facilities and Wastes Covered by the MWTA
The EPA rule covers only medical waste generated in the par-
ticipating states by institutional and commercial sources such
as hospitals, medical clinics, drug treatment centers, clinical
and research laboratories, nursing homes, funeral homes,
veterinary practices, and military vessels at port. The rule
defines the following medical wastes as regulated medical
waste (RMW):15
• Cultures and stocks of infectious agents
• Human pathological wastes
• Human blood and blood products
• Sharp implements—used and unused
• Contaminated animal waste
• Isolation waste from patients with highly communicable
diseases
Waste excluded from coverage includes:
• Domestic sewage
• Hazardous waste
• Household waste
• Treated and destroyed waste
• Human remains to be cremated or interred
• Samples collected for enforcement purposes
2.2.2.2 Segregation, Packaging, and Handling of
Medical Waste
Before medical waste leaves the site where it is .produced, gen-
erators must take certain precautions to protect workers, hand-
lers, and die public from exposure to the material.15 First,
generators must separate it from general trash. Then, to ensure
that the waste is packed securely and will not leak, medical
waste must be packaged in rigid, leak-resistant containers.
Sharps, such as scalpels and needles with their residual fluids,
must be separated from other medical waste and packed into
puncture-resistant containers, and uncontained fluids must be
poured into tightly stoppered, break-resistant containers.
The regulation is designed to prevent packages from being
damaged during shipping and handling, thus preventing ac-
cidental contact with workers or the public. Therefore a rigid
outer container, or secondary packaging, generally is required
during shipping. Specific standards also apply to regulated
wastes that are stored during preparation for shipping and
disposal.
When secondary packages, such as bins, buckets, and boxes,
are reused, they must be cleaned thoroughly. Primary pack-
ages—inner containers—are not reusable and are handled as
medical wastes. Generators must label and mark packages
clearly, identifying the contents, the generator, and the
transporter.
If the generator treats or destroys waste onsite, records of
quantity must be maintained. If offsite waste is accepted by the
facility for destruction, the source of the waste, date received,
quantity of waste, and date destroyed must be recorded and
maintained. Those facilities with onsite incinerators further
must maintain incinerator operation logs and must submit two
reports to EPA summarizing information collected during the
first and third 6-month periods of the demonstration program.
2.2.2.3 Tracking Medical Waste
As medical waste moves through the disposal process, it must
be carefully tracked.15 When a generator finishes preparing a
package of medical waste bound for treatment or disposal at
another site, the generator fills out a tracking form, a copy of
which must .be retained for recordkeeping. Only those
transporters who have registered with EPA may carry this
waste from the generator to its final destination. In the case of
a generator of small quantities (less than 50 Ibs) of medical
waste, a log shows who is carrying the waste and where the
waste is going, and a tracking form is initiated by the
transporter. Transporters must comply with all handling re-
quirements as outlined for generators and also must maintain
records and file reports with EPA.
As the waste travels to its final disposal site, the tracking form
goes with it. Each transporter and owner or operator of a treat-
ment or disposal facility signs and keeps one copy of the track-
ing form. The generator receives the final copy, indicating the
waste was received at an authorized disposal facility. When a
generator fails to receive a copy of the completed tracking
form, an exception report must be filed with the state.
The operations at the disposal facility may be controlled by
other federal, state, and local laws and regulations. All
facilities disposing of regulated medical waste, however, must
manage the waste in accordance with the handling require-
ments outlined above, comply with all tracking form require-
ments, maintain all required records, and prepare and submit to
EPA reports (such as discrepancy reports) that detail any
discrepancies between a shipment and its accompanying
papers. These standards apply to all disposal facilities receiv-
ing RMW even if the facility is located in a nonparticipating
state.
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2.2.2.4 Enforcement >,
EPA has the authority to issue formal and informal enfonie-
ment actions if a facility is in violation of the regulations.15
Examples of serious violations include transporting RMW
without a tracking form, improper marking and labeling,
failure of the transporter to notify EPA of its intent to transport
RMW, and failure to file exception or discrepancy reports.
Criminal actions also may be filed, when appropriate.
1
2.3 Other Regulations and Guidelines
Affecting the Management of \
Medical Waste
Although the information gathered through the MWTA
demonstration program might be used to develop federal
regulations, a number of regulations that affect the manage-
ment of medical waste are in place or will be promulgated
shortly. State and local regulations tend to vary widely in thfeir
stringency, leading to a need for medical waste managers'to
understand many levels of regulations before designing thfeir
medical waste management programs. Because of the trend
towards more stringent regulation, existing guidelines could
become law, so these, too, should be reviewed before medical
waste management procedures are developed or modified and
before disposal facilities are designed or updated.
2.3.1 Federal Regulations and Guidelines
Most medical waste is considered a nonhazardous solid waste
(i.e., ordinary trash) under Subtitle D of RCRA and thus is not
subject to any special handling or disposal requirements unless
more stringent state or local regulations exist. Certain types, of
medical waste, however, are covered by Subtitle C of RCRA
(as hazardous waste)16 or by Nuclear Regulatory Commission
regulations.17 Additionally, some medical waste handling pro-
cedures will be regulated by the Occupational Safety and
Health Administration (OSHA) under the proposed Blood-
borne Pathogen Rule.18 i
2.3.1.1 RCRA Subtitle C \
RCRA Subtitle C regulates solid waste that is either listed1 in
the regulation as hazardous or that exhibits certain hazardous
characteristics: ignitability, corrosivity, reactivity, or toxicity
characteristic leachate procedure (TCLP) toxicity (the leachate
contains levels of certain metals that exceed specified con-
centrations).16 The only wastes listed in Subtitle C that may [be
generated by medical facilities, which would include
laboratory wastes and chemotherapy treatment wastes, are cer-
tain chemotherapy agents. Other wastes generated by medical
facilities may, however, exhibit hazardous characteristics- If
the waste could exhibit hazardous waste characteristics,; it
generally must be tested. If testing demonstrates that the waste
exhibits hazardous characteristics, the generator then mjust
comply with Subtitle C requirements. These requirements
specify waste packaging, storage, labeling, transport, and dis-
posal procedures. Subtitle C also requires a hazardous waste
manifest to accompany the waste from generation to final
disposal. \
Generators of less than 100 kilograms (220 pounds) of hazard-
ous waste per month are excluded from the hazardous waste
regulations if they dispose of the waste at a state-licensed or
permitted Subtitle D facility, such as a municipal solid waste
landfill, and if they meet all state requirements, which may be
more stringent than federal requirements. Generators of 100 to
1,000 kilograms per month of hazardous waste must comply
with all RCRA regulations but are exempt from certain report-
ing requirements. Generators of 1,000 kilograms or more per
month of hazardous waste must notify EPA and obtain a
federal ID number, prepare a manifest for offsite shipments of
hazardous waste; treat, store, and dispose of hazardous waste
in a federally permitted facility; arid meet reporting and
recordkeeping requirements.
2.3.1.2 NRC Regulations
Current NRC regulations address the disposal of low-level
radioactive waste.17 These regulations specify that animal car-
casses and liquid scintillation fluids containing less than 0.50
microcuries/gram of tritium or carbon-14 are "biomedically
exempt" and may be discarded without special procedures
under NRC regulations. Those containing more than 0.50
microcuries/gram of these substances or containing other
radiological components must be disposed of in accordance
with NRC regulations under 10 CFR Part 20.
Because some radiological components, or radionuclides, of
medical waste can decay in storage, the NRC allows waste
containing radiologicals with a half-life of 65 days or less (ex-
cept iridium) to be stored until a minimum of 10 half-lives
have passed. For example, a waste with a half-life of 6 days
must be held for at least 60 days, at which point it can be dis-
posed of as a nonradioactive waste if residual radioactivity is
measured at equal to or less than background levels. If the
waste is disposed of as a nonradioactive waste, all radiation
warning labels must be removed or obliterated before disposal.
Recordkeeping requirements also are specified for medical
wastes held in storage for disposal as nonradioactive waste. In-
formation such as storage dates, background levels, radioac-
tivity detection instruments used, nuclides disposed, date of
disposal, and a contact person must be maintained for 3
years.
2.3.1.3 Proposed OSHA Regulation for Health Care
Facilities
In May 1988, OSHA proposed a health standard regulation
covering the management of medical wastes to ensure the
protection of any workers who may be exposed to human
blood or body fluids in the course of their employment,,18 The
facilities to be covered include all health service facilities,
funeral services, and crematories.
The proposed regulation is intended, to protect health care
workers from occupational exposure to blood-borne diseases.
Personal protection during activities such as drawing blood,
housekeeping requirements, sanitation and waste disposal
procedures is addressed, and specifications for accident
4
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prevention are provided. A general duty clause is in effect and
is applied routinely even though the regulations are not final
yet. The general duty clause requires employers to vaccinate
at-risk employees for hepatitis B, identify and label con-
taminated linen, sterilize and disinfect reusable equipment, and
require employees to follow CDC's handwashing guidance19
and wear appropriate personal protective equipment.
2.3.1.4 EPA Guidelines
EPA recommends that each facility prepare an Infectious
Waste Management Plan addressing procedures such as
segregation, storage, transport, treatment, disposal, contingen-
cy planning, and training.10 Also provided in the EPA
guidelines are recommendations for procedures to follow, in-
cluding labeling of infectious waste, packaging types to use,
limiting access to storage areas, and transporting wastes in
leak-proof trucks or dumpsters. Preferred treatment methods
also are indicated. These preferred treatment methods include
incineration or steam autoclaving for most types of waste and
discharge of treated liquids and ground-up solids to the sewer
system; land disposal of treated solids and incinerator ash is
the recommended disposal method.
2.3.1.5 CDC Guidelines
CDC epidemiologically defines outbreaks of disease in the
health care environment and in the community and develops
strategies for prevention and control. It is not a regulatory
agency and therefore provides only recommendations for
managing one portion of medical waste—infectious waste.
CDC defines infectious waste as isolation wastes, micro-
biological cultures and stocks, blood and blood products,
pathological wastes, and sharps.19 CDC specifies secure pack-
aging and recommends incineration or decontamination of
wastes, although blood and body fluids may be discharged to
. the sewer system. More recently, CDC issued Recommenda-
tions for Prevention of Human Immunodeficiency Virus (HIV)
Transmission in Health Care Settings, or "Universal Precau-
tions."20 •. These recommendations state that all patients should
be considered potentially infected with HIV or other blood-
borne diseases, unless specifically diagnosed otherwise.
2.3.2 NIH Standard Operating Procedures
The NIH (as well as similar organizations and facilities) has
developed standard operating procedures for the management
and disposal of infectious waste.21 Infectious waste is defined
as waste contaminated with infectious agents and includes
items such as surgery and autopsy wastes, patient care wastes,
and other contaminated wastes. NIH specifies secure packag-
ing, special labeling, onsite incineration or steam autoclaving,
and disposal of treated waste and ash as general waste.
2.3.3 Joint Commission on Accreditation of
Healthcare Organizations (JCAHO)
Standards
The overall framework in which medical facilities must
operate is outlined by the Joint Commission on Accreditation
of Healthcare Organizations (JCAHO).22 In general, JCAHO
requires compliance with all applicable laws and regulations. It
also mandates that policies and procedures for identifying and
managing hazardous/infectious waste be instituted. JCAHO
also establishes standards for safety, patient care, staffing, and
training programs at health care organizations. Standard IC.2,
Infection Control, and Standard PL1.6, Hazardous Waste
Management, are specified in the JCAHO Accreditation
Manual for Hospitals (AMH).22 These standards address label-
ing of containers, space and equipment requirements, waste
stream segregation, and training for all employees who use or
are exposed to hazardous and infectious materials, emergency
response teams, and supervisory personnel. The training must
address regulatory requirements and must cover internal dis-
aster plans, emergency response plans, and contingency plans.
JCAHO also requires that a system must be instituted to safely
manage hazardous materials and wastes from points of entry to
final disposal. Additionally, committees must be established to
annually review the waste management plan and evaluate its
effectiveness.
2.3.4 State and Local Regulations
State and local regulations vary widely. The way in which
waste from medical facilities is defined by a state or locality
can profoundly affect the volume of waste that must be hand-
led as potentially infectious. State and local regulations also
can determine the available options for treatment and disposal.
About half the states and several major cities mandate that cer-
tain types of medical waste (i.e., that defined as potentially in-
fectious by the regulatory authority) be treated on site, restrict
its offsite transport, and/or prohibit it from being landfilled.7
Many additional states are planning similar requirements in the
next few years. These restrictions, combined with require-
ments or recommendations for incinerating infectious waste,
heavily encourage the use of onsite incineration as an infec-
tious waste treatment method. Approximately 30 states desig-
nate or define infectious waste for regulatory or policy-making
purposes, and at least 7 states include infectious wastes under
their hazardous waste regulations. Approximately 20 states7
are planning to either promulgate new infectious waste legisla-
tion or tighten existing infectious waste legislation or
guidelines very shortly.**
To see how infectious waste is regulated at the state level, it is
useful to summarize the existing or planned requirements of
the 10 states originally selected for the MWTA program.13 Of
these states, 6 (New York, New Jersey, Illinois, Minnesota,
Pennsylvania, and Wisconsin) had medical waste regulations
in place at the time the MWTA was promulgated and 4 (Con-
necticut, Indiana, Ohio, and Michigan) had no medical waste
regulations. All 10 states, however, were either amending or
developing medical waste regulations. Most of the states were
requiring or will require special packaging and labeling (New
York, New Jersey, Minnesota, Pennsylvania, Connecticut, and
Ohio) and nearly all were requiring or will require treatment of
at least some types of waste prior to disposal (only Michigan
**This information dates from 1988. A total of 45 states now have some form
of medical waste regulations, 14 states track waste using a chain-of-custody
system, and 42 states require treatment before disposal (Meson, Kristina, U.S.
EPA, Washington, DC, personal communication, November, 1991).
-------
has no plans for requiring treatment). Recordkeeping require-
ments were less universal, with only four states (New York,
New Jersey, Illinois, and Connecticut) requiring or proposing
to require recordkeeping by generators, transporters, and treat-
ment/disposal facilities. Half of the states (New York, New
Jersey, Illinois, Connecticut, and Ohio) did or will require
some type of tracking program. Permits for disposal facilities
were or will be required in all the MWTA states. Transport
permits were or will be required in New York, New Jersey,
Illinois, Connecticut, and Ohio. None of the MWTA states,
however, had existing requirements for permitting generators;
Ohio was planning to require generator permitting.
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Chapter 3
Technical Overview of Medical Waste Management and Treatment
Medical waste is a heterogenous mixture of many types of
wastes that can include general waste ("trash"), potentially
infectious waste, and pathological waste. Many facilities
dial-generate medical waste also generate hazardous waste,
radioactive waste, and other types of special waste. The
technical options available for treating and disposing of
medical wastes vary depending on the types and quantities
of waste generated by the facility. Thus, the first step in
choosing waste management options is to identify, or char-
acterize, and quantify wastes. Waste characterization and
quantification data then can be used to select the waste
management technology options most suited to the
institution's needs. The technical and administrative aspects
of characterizing wastes, minimizing waste generation rates,
and selecting treatment and disposal options are discussed
in Section 3.1. The technical options for treating and dispos-
ing of the types of waste generated at medical institutions
are described in Section 3.2. Further discussion of the ad-
ministrative aspects of designing a waste management plan
is presented in Chapter 5.
3.1 Technical and Administrative
Considerations
3.1.1 Definitions and Sources of Medical Waste
One of the first steps in managing medical waste is to deter-
mine the types and quantities of waste generated and whether
it should be classified as solid waste, potentially infectious
waste, hazardous waste, or radioactive waste. The regulatory
definitions for hazardous or radioactive wastes are clear;
however, definitions of medical waste that should be managed
and disposed of as potentially infectious vary depending on
which regulation or guideline is considered. Each type of
waste and its sources are discussed in the sections below.
3.1.1.1 Potentially Infectious Waste
A portion of the medical waste stream from most health care
and similar institutions is categorized or is regulated as being
potentially infectious. Other common terms for infectious
waste are biohazardous waste, biological waste, biomedical
waste, contaminated waste, pathogenic waste, pathological
waste, red-bag waste, and regulated medical waste (RMW).
Regardless of regulatory definition, however, a waste is infec-
tious when all of the following conditions' are met
simultaneously:4
• The presence of a virulent pathogen
• Sufficient concentration of that pathogen
• Presence of a host
• Portal of entry
• Host susceptibility
Because infectious waste often is defined in broader terms,
medical facilities must take into account the regulatory defini-
tions of infectious waste, interpret these definitions to their
particular situation, create internal policies and protocols for
its proper and safe management, and administer a proper waste
management program.
Definitions and designations for infectious waste vary widely
from state to state and in different federal regulations and
guidelines. Some of the various federal designations of infec-
tious waste include those by the CDC,19 the EPA Guide for In-
fectious Waste Management,10 the Medical Waste Tracking Act
of 1988,n and others. CDC defines infectious waste as any
waste from microbiology laboratories, pathological waste,
sharps, and blood or blood-product waste.19 More recently,
CDC recommended "universal precautions," which suggest
that all patients be considered potentially infected with AIDS
or other blood-borne diseases until otherwise diagnosed.20
EPA's Guide designations are more specific: isolation waste,
cultures and stocks of infectious agents, human blood and
blood products, pathological waste, contaminated sharps, and
contaminated animal carcasses, body parts, and bedding all are
considered infectious.10 "Optional infectious waste," which is
waste that may not pose a risk, also is listed in the Guide. EPA
leaves the decision of whether optional waste should be hand-
led as infectious to a responsible authorized person or commit-
tee at the individual facility. Among these optional wastes are
surgery and autopsy wastes, miscellaneous laboratory wastes,
dialysis unit wastes, and contaminated equipment. The Medi-
cal Waste Tracking Act defines regulated medical waste
(RMW) to include cultures and stocks of infectious agents,
human pathological wastes, human blood and blood products,
sharps, contaminated animal wastes, and isolation wastes.4
The definitions presented above encompass increasingly broad
infectious waste designations. The volume of medical waste
generated by institutions that would be defined as infectious by
older CDC designations19 is about 3 to 5 percent of the total
volume.5 The EPA Guide10 would categorize 7 to 15 percent of
medical waste as infectious,5 and CDC's universal precautions
definition of infectious waste20 would label 60 to 80 percent of
all medical waste as infectious.5 Depending on the hauler or
the disposal facility used for medical waste, the contractor
-------
might consider anywhere from none to all of the waste from a
medical facility infectious for the purposes of setting hauling
or disposal fees and handling procedures.5 Because infectious
wastes are defined in so many ways, because the general
public tends to perceive all medical waste as potentially infec-
tious, because offsite disposal contractors may define any
medical waste as potentially infectious, and because of the
recent CDC recommendations concerning "universal precau-
tions," many institutions may begin categorizing all patient-
contact wastes as potentially infectious and may choose [to
define infectious wastes in very broad terms.5 '
3.1.1.2 Chemical/Hazardous Waste
Hazardous wastes are defined in RCRA Subtitle C,16 and either
are listed or meet certain characteristics of ignitability, cor-
rosivity, reactivity, or TCLP toxicity (see Section 2.3.1.J1).
Many chemotherapy wastes may be defined by RCRA as haz-
ardous, and therefore are regulated by 40 CFR Parts 260-265.
If a container has less than 3 percent by weight of the original
amount or capacity of hazardous material remaining, it is con-
sidered empty and does not require disposal as a hazardous
waste (40 CFR 261.7). This exemption does not apply to seven
chemotherapy drugs listed by EPA as acutely toxic (40 CFR
261.33f). [
Sources of potentially hazardous chemical wastes include
clinical and research laboratories, patient-care activities, phar-
macies (spills and expired items), physicians' offices (outdated
items), physical plant departments, or buildings and grounds
departments (e.g., pesticides and solvents). j
3.1.1.3 Sources of Radioactive Waste
Low-level radioactive waste may be produced through a num-
ber of activities, including those associated with research
laboratories, clinical laboratory procedures, and nuclear
medicine procedures such as diagnostic and therapeutic ap-
plications. These wastes may take several forms. Low-level
radioactive solid waste may include animal carcasses, clinical
items, and other contaminated "dry" materials. Liquid radioac-
tive wastes include liquid scintillation fluids (LSC), biological
and chemical research chemicals, and wastes stemming from
the decontamination of radioactive spills.
3.1.2 Waste Disposal Evaluations
After the sources and general types of waste have been iden-
tified, detailed waste disposal evaluations should be per-
formed. These evaluations encompass a data collection phase
in which the type and volume of waste is characterized fully
and quantified. Improper characterization or quantification can
lead to the improper selection of treatment methods, and in the
case of incineration, may result in an underutilized incinerator
or in severe management or operational problems.5 As part of
the evaluation, existing waste management practices should be
reviewed to determine areas for change or improvement. !
i
In performing a waste characterization, the task can be made
easier by designing forms on which classes of waste, e.g., dry
and solid (such as paper, plastic, cloth, or laboratory animal
cage waste), pathological (such as carcasses and tissue, body
parts, or cadavers), or liquid (such as solvents and chemicals or
blood and body fluids), can be noted by type of waste. After all
waste types have been determined, the waste can be charac-
terized based on its composition and constituents, forms and
categories (e.g., highly compacted or high ash content), physi-
cal parameters (e.g., solid or liquid), and chemical parameters
(e.g., organics, inorganics).
Waste volumes can be quantified in several ways. One way
would be to use waste generation factors. As an example, in
1968, the Incinerator Institute of America (HA) published fac-
tors that show approximate waste generation rates at various
institutions and other facilities (see Table 3-1).23 A more ac-
curate means of estimating waste generation rates is to use of-
fsite hauling and disposal records, sucii as billing records, and
analyses of waste volumes and frequencies of disposal. Cal-
culations using this type of information, however, could lead
to gross inaccuracies if waste managers do not account for
variabilities in waste container fullness or in the compaction
densities of container contents. Records of truck-scale weigh-
ings, if available, may be useful. The most accurate method,
however, is to perform a waste survey and weighing program
over a period of perhaps 2 weeks.
Waste surveys can be performed in a number of different
ways.5 The survey can use waste collected from a disposal
area or from specific sources. Waste can be weighed or its
weight can be estimated. The waste can be quantified by bulk
volumes such as carts or by individual containers, such as
bags. Waste can be selected randomly or all waste can be
weighed or estimated. Waste types can be identified specifical-
ly or approximations can be used (see Section 4.1.3.1 for a
description of waste-type approximations). The extent of the
survey can encompass from one day to several weeks.
3.1.3 Waste Minimization
Following a waste characterization, the feasibility of minimiz-
ing waste generation should be evaluated. Three basic ap-
proaches to minimizing potentially infectious, hazardous, or
radiological waste can be taken: source reduction, in which
potential wastes are reused, recycled, or recovered; substitution,
in which items destined to become a part of the hazardous
waste stream are replaced with nonhazardous substitutes (or
eliminated from use); and segregation, in which all three types
of special-handling wastes (potentially infectious, hazardous,
or radiological wastes) are separated from the general waste
stream at the institution.
Segregation is one of the most practical and cost-effective
waste management policies an institution can implement.5 If
potentially infectious waste can be segregated from general
waste, substantial costs savings for waste treatment can be
realized.
Some waste minimization schemes also become a useful tool
when waste is treated or disposed. For example, emissions of
acid gases such as hydrogen chloride (HC1) from incinerators
can be minimized if poly vinyl chloride (PVC) plastics can be
substituted by nonchlorinated plastics. In this case, HC1
8
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Table 3-1. Incinerator Institute of America Waste Generation Factors
Classification
Industrial buildings
Commercial buildings
Residential
Schools
Institutions
Hotels, etc.
Miscellaneous
Building Types
Factories
Warehouses
Office buildings
Department Stores
Shopping centers
Supermarkets
Restaurants
Drug stores
Banks
Private homes
Apartment buildings
Grade schools
High schools
Universities
Hospitals
Nurses or interns homes
Homes for aged
Rest homes
Hotels— 1st class
Hotels — medium class
Motels
Trailer camps
Veterinary hospitals
Industrial plants
Municipalities
Quantities of Waste Produced
Survey must be made
2 Ibs per 1 00 sq ft per day
1 1b per 100 sq ft per day
4 Ibs per 100 sq ft per day
Study of plans or survey required
9 Ibs per 100 sq ft per day
2 Ibs per meal per day
5 Ibs per 100 sq ft per day
Study of plans or survey required
5 Ibs basic & 1 Ib per bedroom
4 Ibs per sleeping room per day
10 Ibs per room & 1/2 Ib per pupil per day
8 Ibs per room & 1/2 Ib per pupil per day
Survey required
15 Ibs per bed per day
3 Ibs per person per day
3 Ibs per person per day
3 Ibs per person per day
3 Ibs per room and 2 ibs per meal per day
1-1/2 Ibs per room & 1 Ib per meal per day
2 Ibs per room per day
6 to 10 Ibs per trailer per day
Study of plans or survey required
Source: Reference 23.
emissions might be controlled by substitution alone, obviating
the need for expensive emission control equipment. Other
types of wastes such as solvents can be segregated as part of an
overall waste segregation program. Containers of solvents,
when fed directly into incinerators, can cause severe operating
problems. These same solvents when segregated from other
waste and injected into an incinerator designed to burn sol-
vents as auxiliary fuel can be disposed of safely, as well as
more economically.
3.1.4 Disposal Option Selection
The next step in the administration of the waste management
process is to evaluate waste disposal options. First, technical
and economic evaluations should be undertaken. These evalua-
tions include investigating the sites and utilities that might be
available for the treatment or disposal of waste, calculating the
costs of all viable options for comparison purposes, and
reviewing regulatory and permitting requirements for each vi-
able option to determine additional costs or difficulties that
might be associated with the choices selected. Next, the plan-
ner can develop a matrix of alternatives that incorporates the
technical evaluations, schematics, and economic analyses,
leading to a group of appropriate options. Along with the dis-
posal options that could be considered, variables such as
degree of onsite or offsite treatment might be listed. For ex-
ample, all waste can be treated and disposed of offsite. Alter-
natively, selected types of wastes can be treated onsite, while
other types (such as hazardous waste) might be treated and dis-
posed of offsite. Finally, all wastes might be treated onsite.
Options also will include alternative technologies, combina-
tions of treatment technology choices, and add-on equipment.
Requirements for redundancy and backup systems should be
included, and any siting considerations should be noted.
When estimating costs, the planner should note not only capi-
tal costs and annual operating and maintenance costs, but also
should determine the annualized costs (for example, the capital
recovery costs) of owning and operating the equipment.
In selecting a waste management option, the planner should
consider the total economic picture, the contingencies and out-
ages that may arise, future scenarios and potential changes,
such as to regulations and standards, and noneconomic issues
such as siting feasibility and public opposition to one or more
treatment or disposal options.
3.2 Treatment and Disposal Options
for Potentially Infectious Waste
3.2.1 Biomedical Waste Options
Medical waste-generating facilities have a number of waste
management options from which to choose, depending on the
quantity and nature of the waste they generate, state and local
regulations or recommendations, and economic factors. These
options can be divided into onsite and offsite treatment and
disposal methods. Onsite treatment methods include various
types of disinfection and shredding techniques as well as in-
cineration. Incineration is the primary offsite treatment
-------
method, but several offsite disposal firms have recently in*
stalled steam autoclaves with shredders. Incinerator ash must
be disposed of by landfilling. Treated waste may be disposed
of by landfilling, incineration, or discharge of ground-up solids
to the sewer system. Treated liquids also can be discharged [to
the sewer system if approved by the local sewer authority.
Various alternative treatment technologies and options are dis-
cussed, along with the advantages and disadvantages of eajch
choice, in the following sections.
i
3.2.1.1 Qnslte Treatment Technologies \
Few treatment and disposal technologies are available for
managing the increasing volumes of medical waste generated
annually at many facilities. The principal technologies for
treating potentially infectious waste are steam autoclaving,
shredding with chemical disinfection, and incineration. Tjhe
advantages and disadvantages of each technology are sum-
marized in Table 3-2. Innovative and emerging technologies,
such as glass-slagging systems, high-temperature plasma sys-
tems, and systems combining shredding and radiation are not
yet commercially available? The principal technologies of
autoclaving, shredding with chemical disinfection, and in-
cineration are the focus of this section; however, a few emerg-
ing technologies are discussed briefly. The various types |of
incinerators and their operation are covered more fully in
Chapter 4. ;
Steam Autoclaving .
In autoclaving, steam is used to kill pathogenic microor-
ganisms in the waste. Autoclave types and designs generally
differ in their levels of steam contact efficiency and in the
volume of waste that can be processed within the shortest pos-
sible time. The contact efficiency of any autoclave system is a
direct function of steam penetration into the packages of waste
being treated by the system. Factors such as waste type and
density, packaging materials, and waste loading procedures
directly affect the extent of steam penetration and the exposure
times necessary for effective treatment. If sterilization is not
achieved within a reasonable time, inadequate steam penetra-
tion may be the cause.
Three basic types of autoclave systems are available: gravity
systems, prevacuum systems, and retort systems. Steam pres-
sure alone is used in gravity systems to evacuate air from the
autoclave chamber (see Figure 3-1). Prevacuum systems use
pumps to evacuate air from the autoclave chamber, and retort
systems are designed to operate at high steam pressures.
Gravity systems require more time to process waste than
prevacuum systems, which typically require more time than
retort systems. Gravity systems typically operate with steam at
15 psi and corresponding steam temperatures of 250°F. About
15 minutes of direct steam contact typically are required under
these conditions, but cycle times are usually 60 to 90 minutes
per load to allow for steam to penetrate fully into densely
packed wastes. More rapid and efficient steam penetration can
be achieved by prevacuum systems and by retort systems,
which use high-pressure steam to minimize cycle times.
A variation on these three basic systems is an autoclave system
that functions as a combined, integral prevacuum autoclave
and general waste compactor. After the autoclave cycle is
completed, treated biomedical waste is ejected automatically
into an integral trash compactor. The treated biomedical waste
Table 3-2. Comparisons of Onslte Biomedical Waste Treatment Technologies*
Principal Treatment
Technologies
Autoclaving
Shredding/chemical
disinfection
Incineration
Advantages
Low costs
Low space requirements
Ease of implementation
Simplicity of operation
Substantial volume reduction
Suitable for many wastes
Relative simplicity
Alters waste forms
Disposes of most waste types
Suitable for large volumes
Large weight and volume redi
Sterilization and detoxification
Heat recovery
Disadvantages
Limited capacity
Not suitable for all wastes
Waste handling system/bags
Odor control
Waste volume unchanged
Waste appearance and form unaltered
Relatively high costs
Manual waste handling
Limited capacity
Liquid effluent contaminants
Room noise and chemical disinfectant levels
Only one manufacturer
Level of treatment achieved
and forms Relatively high costs
High maintenance and repair requirements
ictions Stack emissions and concerns
Permitting difficulties
Public opposition
Source: References.
'There have been many recent developments in alternative treatment technologies since the seminar series was
presented. The final Report to Congress on Medical Waste Management in the United States, which should be published
in 1992, will have a discussion of new and emerging treatment technologies and their efficacy (Meson. Kristina, U.S. EPA.
Washington, DC, personal communication, November, JI991.)
10
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Saturated
Steam
Inlet
Pressure
Vessel
Trap Passes
Air-Steam
Mixtures
and Retains
Pure Steam
Air
Figure 3-1. Gravity steam-autodaving system.
Source: Reference 24.
and general trash then are compacted into a close-coupled,
roll-off container for of fsite disposal.
To ensure that autoclave systems are loaded, operated, and
maintained correctly, temperature monitoring and frequent
sterilization-efficiency testing must be performed; these proce-
dures are mandated in some states. The sterilization-efficiency
testing, known as biological challenging, involves introducing
heat-resistant spores into worst-case waste loads and measur-
ing the extent of spore inactivation or destruction.
The principal advantages of steam-autoclave systems are low
capital and operating costs, relatively small space requirements,
and ease of operation. The principal disadvantages include the
relatively limited processing capacity of these systems, their
need for special waste packaging and handling to ensure steam
penetration, and the need for odor control and drainage
management. Autoclaving is not recommended for carcasses
and body parts, wastes with high liquid content, and volatile
chemical waste such as chemotherapy waste. Also, autoclaving
does not change the appearance of the waste; biohazard sym-
bols on packaging, blood stains, needles, and syringes remain
identifiable.
Shredding with Chemical Disinfection
A system that uses chemical disinfectants in combination with
shredding has been developed recently.* A midwestern firm
developed a treatment system that shreds and treats waste with
sodium hypochlorite. Systems are available both for small
operations, such as laboratories, and for large operations, such
as hospitals. In the large-capacity system, which can handle up
to about 1,500 pounds per hour, waste is loaded onto a con-
veyor belt that lifts it into a high-torque, low-speed shredder
(see Figure 3-2). At the bottom of the shredder, the waste is
discharged into a hammermill, where it is granulated. During both
the shredding and granulating stages, the waste is sprayed with a
sodium hypochlorite solution. A perforated conveyor belt
separates the solids from the slurry. The liquids then are dis-
charged to the sewer, and the solids are retained for offsite dis-
posal. Airborne contamination is contained by drawing air from
the system and passing it through a series of prefilters and a
chlorine-resistant HEPA filter before being discharged to the
atmosphere.
*Several systems are now available. (Doucet, Lawrence G., Doucet & Mainka,
P.C., personal communication, November, 1991).
Chlorine Solution
Waste Conveyor
Waste
Figure 3-2. System for shredding with chemical disinfection.
Source: Reference 25.
11
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The principal advantages of this system are its relative simplicity
and its ability to substantially reduce waste volume (reportedlyjas
high as eight to one). All waste items are rendered unrecog-
nizable, making it suitable for treating all types of wastes except
pathological remains and large metal objects, which could
damage the hammermill. '
The principal disadvantages are the relatively high costs of the
system (as much as a medium-capacity incinerator); limited
throughput capacities; potential problems or concerns with slurry
contaminants, workplace disinfectant concentrations; noise levels;
and bioaerosol emissions. Furthermore, chemical disinfection sys-
tems do not provide sterilization, which may be a problem in the
states in which sterilization is required. Discharge permits might
be required for the slurry, and adherence to occupational
workplace standards might require special precautions. [
Incineration
Incineration is a process using controlled, high-temperature
combustion to destroy organics in waste materials. Modem in-
cinerators are designed to maximize combustion efficiencies
(see Figure 3-3). :
Three standard, or widely used, basic incineration technologies
are suitable for combusting medical waste:
• Multiple-chamber incinerators, which are constructed
with several chambers (two or three), generally operat-
ing under excess air conditions.
• Rotary-kiln incinerators, which feature cylindrical,
refractory-lined combustion chambers that rotate the
waste from the loading end to the discharge end, where it
is discharged as ash. |
• Controlled-air incinerators, which first burn wastes
under starved-air conditions in a primary chamber, then
burn the resulting combustion products and volatile
gases under excess-air conditions in a secondary
chamber.
These incinerators and the advantages and disadvantages
specific to each system for incinerating medical waste will be
discussed in detail in Chapter 4. In addition to these incinerator
types, various innovative incineration designs have been intro-
duced over the years, many of which have been either tech-
nologies transplanted from hazardous waste incinerator
applications or untried experimental concepts.
The onsite incineration of medical waste has many advantages.
Incineration sterilizes pathogenic wastes; provides volume and
mass reductions of up to 90 to 95 percent; converts offensive
waste, such as animal carcasses, to innocuous ash; can provide
waste-heat recovery; and in some cases, can be used simul-
taneously to dispose of hazardous chemicals and low-level
radioactive waste. Current and developing medical waste
legislation encourages the use of onsite incineration. As dis-
cussed in Chapter 2, many states restrict offsite management of
infectious waste, and some require or recommend incineration
as the preferred method for treating potentially infectious
waste. Furthermore, onsite incineration solves the problems of
locating suitable offsite treatment and disposal facilities, which
have become increasingly scarce arid expensive in recent
years.
The disadvantages of onsite incineration are increasingly strin-
gent regulatory restrictions and permitting difficulties,**
public opposition to incineration, and residue disposal restric-
tions that in some cases require incinerator ash to be handled
**EPA's Demonstration Program has shown a decrease in the number of on-
site incinerators because of difficulties meeting state air-quality requirements.
(Meson, Kristina, U.S. EPA, Washington, DC, personal communication,
November, 1991.)
To Atmosphere
" *
To Atmosphere
Stack
Air
PolluSion
Control
System
Ash
Figure 3-3, Major components of an incineration system.
Source: References.
12
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as special or hazardous waste. All of these disadvantages in-
crease the costs of onsite incineration and in many cases can
make the onsite incineration of medical waste prohibitively
expensive. Because onsite incineration is the overwhelming
choice for many facilities, medical waste managers need to
understand the basics of incinerator types, system com-
ponents, operations, regulatory requirements, and selection
and procurement considerations. These issues are discussed in
detail in Chapters 4 and 5.
Emerging Technologies
Two emerging technologies with potential application to medi-
cal wastes include irradiation and microwave treatment.* In ir-
radiation, ionizing radiation from a source such as Cobalt 60 or
an electron beam is used to destroy pathogens. The technique
is similar to that currently being used to sterilize medical sup-
plies, food, and other consumer products. Following treatment,
the wastes are typically ground, compacted, and shipped to a
landfill. In microwave treatment* wastes are ground and
shredded to improve system effectiveness and sprayed with
water. An auger moves the waste past a series of microwave
power packs that subject the waste to microwaves. The
microwaves destroy pathogens and heat the waste to 200°F.
Volatiles and water are driven off during the process.26
3.2.1.2 Off site Treatment and Disposal
Offsite treatment and disposal may be chosen when onsite
treatment is not available. Some of the advantages and disad-
vantages of offsite treatment and disposal are summarized in
Table 3-3.
Three options available as alternatives to onsite treatment are:
• Contract disposal—The facility pays a fee to an inde-
pendent, commercial firm to transport and dispose of infec-
tious waste at an offsite facility, typically an incinerator.
The waste may be hauled and incinerated at the
contractor's incinerator, or the contractor may haul the
waste to another contractor's incinerator or to an onsite
In its final report to Congress on Medical Waste Management in the United
States, EPA will present an evaluation of a number of new and emerging treat-
ment technologies and their efficacy (Meson, Kristina, U.S. EPA, Washington,
DC, personal communication, November, 1991).
incinerator at a hospital. Rates for these services are
usually set on a cost-per-pound or cost-per-box basis,
and packaging materials may be provided as part of the
service. Occasionally, contractors offer refrigerated
trucks for longer-term storage and transport.
• Disposal at another institution's incinerator—Some
hospitals with excess incineration capacity offer disposal
services to other institutions, either on a fee-for-service
or shared-cost basis.
• Disposal at a regional incineration facility—An inde-
pendent hospital group or association might own and
operate a regional facility, either at a member hospital
site or some other location. The facility may be
developed, administered, and financed by the association
itself or by a private developer.
The advantages of contracted offsite treatment and disposal in-
clude simplicity and short implementation time relative to
designing, building, and starting up an onsite system. Addi-
tionally, for the generator, siting and permitting problems are
avoided, capital investment needs are eliminated, and building
space and support services are not required. Regional or
shared-service facilities have additional advantages over onsite
treatment facilities—economies of scale can be realized, a
single permit covers the treatment of waste from all facilities
in the region, and centralized operation allows the resources of
several institutions to be pooled.
The major disadvantage of offsite treatment and disposal is
that reliable, reputable, and affordable contractors and
facilities may be difficult to find in certain areas of the
country. Most existing offsite incinerators are operating at
peak capacity, and adding capacity is not simple and may be
infeasible. Several states have moratoriums on new in-
cinerators or make the siting or permitting of new facilities
very difficult Additionally, most hospitals are reluctant to in-
cinerate waste from other hospitals, and regional incineration
facilities are limited in some geographic areas because of
siting and permitting problems.
A further disadvantage of contracted offsite transport and dis-
posal is the high annual cost. Onsite incineration systems often
realize payback periods of less than 2 years when compared
Table 3-3. Comparisons of Offsite Biomedical Waste Treatment and Disposal Methods
Principal Options
Advantages
Disadvantages
Offsite disposal
-Commercial facility
-Another institution's incinerator
-Regional facility
Minimal capital investment
Minimal onsite space requirements
Simplicity
Short implementation time
Onsite disposal permitting avoided
Locating reliable and reputable firms and facilities
Potential liabilities and concerns
High annual costs
Special packaging requirements
Manifesting and tracking
Regional or shared-service
incineration facility*
Favorable economics
Single permit
Centralized operations
Siting and permitting difficulties
Special packaging and transport requirements
Manifesting and tracking
"Hazardous" designation (some states)
*vs. individual onsite incinerators
Source: References.
13
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with offsite disposal costs. As an example, typical annualized
onsite incineration capital and operating costs average about
S0.05 to $0.20 per pound, whereas contracted offsite disposal
may cost from $0.30 to $2.00 per pound. The Medical Waste
Tracking Act11 and similar state legislation also add to the costs
of offsite disposal with the packaging, manifesting, and
transporting requirements of the regulations developed under
these laws. !
3.2.2 Chemical/Hazardous Waste Options
Several chemical waste management and disposal options are
available to hazardous waste generators, including minimiza-
tion, recycling^recovery, chemical treatment, physical treat-
ment, thermal treatment, and disposal. These options are
subject to the hazardous waste management regulations
specified in 40 CFR Parts 260-265. Procedures to minimize
hazardous waste generation include modifying the processes
that produce the waste by eliminating the use of the substance
or by using a nonhazardous substitute. Volume reductions
might be achievable, and reclaiming or recycling may be pos-
sible—the waste may be recovered directly, distilled and
recovered, or reclaimed through waste exchange.
3.2.3 Radioactive Waste Options
Four basic methods of treatment and disposal are avail-
able to low-level radioactive waste generators. The waste
may be concentrated and confined to allow the material to
decay in storage (see Section 2.3.L2). Alternatively, it
may be diluted and dispersed by discharging to the sewer
system, or volume reduction and dispersion cam be
achieved by incineration. The final option may be to
transport the waste to an offsite low-level radioactive
waste disposal facility. The management and disposal of
low-level radioactive waste are subject to the NRC
regulations under 10 CFR 20."
14
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Chapter 4
Incineration of Medical Waste
Onsite incineration is becoming a preferred method of medical
waste treatment for most institutions. Numerous difficulties
can arise, however, when incineration systems are not
designed for the types or volumes of wastes generated at each
site. To help waste management personnel at hospitals and
other institutions in the selection, procurement, and operation
of onsite incineration systems, the basic principles of combus-
tion and variations in operating parameters that may affect in-
cinerator performance are reviewed in this chapter. The
various types of incinerators are described, the general system
layout in typical incinerator types is indicated, and the ad-
vantages and disadvantages of each type are discussed. The
chapter continues with a discussion of incinerator air emissions
and types of air pollution control devices that can be used to
control emissions. Finally, a summary of incinerator permit-
ting and other regulatory issues is given.
This chapter is not intended to be a complete guide to the in-
cineration of medical waste. For more detailed information on
this subject, the reader is referred to EPA's 1990 handbook en-
titled Operation and Maintenance of Hospital Medical Waste
Incinerators.* Additional, more technical, information is avail-
able from references cited in this handbook, as well as from
consultants and vendors.
4.1 Technical Aspects of Medical
Waste Incineration
4.1.1 Principles of Combustion
Incineration is a combustion process in which waste is reduced
to ashes through a chemical reaction.8 This reaction involves
rapid oxidation of the organic substances in the waste and
auxiliary fuels, releasing energy and converting the organic
materials to an oxidized form. Four basic principles are in-
volved in the combustion process: the basic chemical reac-
tions, the combustion air requirements, the thermochemical
relations, and the volumetric air flow.
4.1.1.1 Chemical Reactions
During combustion, the carbon and hydrogen components of
the waste react with gaseous oxygen to produce carbon
dioxide, water, and heat Other, more complex reactions occur
as well, but the general basis for complete combustion can be
represented by this principle. Incomplete combustion results in
the production of carbon monoxide (CO) and compounds
known as products of incomplete combustion (PICs). PICs are
unturned hydrocarbons and reformed molecules, some of
which may be considered health threats if released to the at-
mosphere at sufficiently high concentrations or rates. The
presence of sulfur, nitrogen, chlorine, and metals in the waste
also contribute to air emissions problems during the combus-
tion process. The reactions of these waste constituents and
resulting emissions will be discussed in Section 4.2.1.
4.1.1.2 Combustion Air
The theoretical amount of oxygen required for complete com-
bustion is known as the stoichiometric or theoretical oxygen.
Specific stoichiometric oxygen requirements are determined
by the nature and quantity of the combustible material to be
burned. Combustion oxygen usually is obtained from atmos-
pheric air. The additional oxygen (or air) available for combus-
tion over and above the stoichiometric amount is called
"excess air." When the amount of oxygen (or air) is less than
the stoichiometric amount, it is called starved air or
substoichiometric air. Under starved-air conditions, incomplete
combustion occurs, which results in the production of CO and
PICs. The formation of these combustion products is charac-
terized by the release of smoky emissions containing unburned
hydrocarbons and volatiles.
Maximum combustion temperatures are achieved at stoich-
iometric conditions. If excess air is present, combustion
temperatures drop because energy is used to heat the combus-
tion air from ambient temperature to the combustion chamber
temperature. During starved-air combustion, combustion tempera-
ture also drops because complete combustion cannot occur. A
graph of temperature as a function of excess air percentages is
presented in Figure 4-1.
As excess air increases, several components of incinerator
emissions change. Oxygen levels increase, and carbon dioxide
concentrations decrease (although the total carbon dioxide
generated does not change, the dilution of carbon dioxide with
excess air produces a lower concentration). Thus oxygen and
carbon dioxide concentrations of incinerator emissions are use-
ful indicators of excess air levels and are used to monitor the
combustion process. Too much excess air results in lower
temperatures, consumption of more auxiliary fuel, more
entrainment of particulates, larger flue-gas volumes, greater
system horsepower needs, and less efficiency. Too little excess
air results in poor combustion and increased emissions.
15
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Temperature
Deficient Air j Excess Air
Percent Excess Air
Figure 4-1. Control of temperature as a function of excess air.
Source: Reference 27.
4.1.1.3 Thermochemlcal Relations
Thermochemical calculations are used to estimate heat release
and heat transfer associated with combustion. These calcula-
tions permit the amount of energy released by the combustion
process and its transfer to the environment to be determined.
The amount of heat released during the combustion process
can be calculated from the heating value of the waste and sup-
plemental or auxiliary fuels. This heat is released to the en-
vironment through incineration effluents and other pathways,
such as radiative heat losses.
4.1.1.4 Volumetric Gas Flows
Gas flows through a combustion system are a major con-
sideration in the design and operation of the system. The total
gas flow comprises combustion air, gaseous products of com-
bustion, and evaporated moisture in the waste. A primary gqal
of the design and operation of a medical waste incineration
system is the complete destruction of pathogens and the com-
plete combustion of organic materials. Achieving this goal re-
quires the waste to be exposed to high temperatures for' a
sufficient retention time. Hue-gas retention time is a function
of incinerator chamber volume and volumetric gas flow rate,
which in turn is dependent on the flue-gas temperature. Proper
incineration requires sufficient combustion air, as well as suffi-
cient combustion temperatures, sufficient time during whiph
combustion reactants are exposed to the high combustion
temperature, and sufficient mixing (turbulence), which ensures
good contact of the waste/fuel with the combustion air. These
latter factors typically are termed the three Ts of combustion:
time, temperature, and turbulence.4 '
4.1.2 Types of Incinerators
i
Three major incinerator types have been used to incinerate
medical waste: multiple-chamber incinerators, rotary-kiln in-
cinerators, and controlled-air incinerators. These three types of
incinerators are discussed below. A few innovative in-
cinerators have been used, but these systems vary widely !in
success and a description of these systems is beyond the scope
of this document.
4.1.2.1 Multiple-Chamber Incinerators
Multiple-chamber incinerators were developed during the 1950s
and until the mid-1960s were the type used almost exclusively by
hospitals and similar institutions. To control combustion and limit
emissions, these systems use settling chambers and are designed
to operate at very high excess-air levels. Air emissions are unac-
ceptably high with these systems, thus air pollution control
equipment must be installed. Additionally, many states require
performance and operating conditions that these systems can-
not meet without substantial upgrading and state-of-the-art
combustion control equipment.6
Few multiple-chamber incinerators are being built, but many
older systems remain. Unfortunately, many of these are
operated improperly, leading to emission problems. Further-
more, some were built with grates in their primary combustion
chamber. These grates allow uncombusted waste to fall into
the ash pit, exposing cleanout operators to unbumed infectious
waste and sharps.
Multiple-chamber incinerators are of two basic types: the in-
line design and the retort design (see Figures 4-2 and 4-3).
Combustion gases flow straight through inline incinerators,
turning vertically only. In the retort design, gases turn horizon-
tally as well as vertically. Retort multiple-chamber incinerators
are more compact, and they are more efficient than inline in-
cinerators at small capacities.
4.1.2.2 Rotary-Kiln Incinerators
Rotary-kiln incinerators feature cylindrical, refractory -lined
combustion chambers that rotate on a slightly inclined,
horizontal axis (see Figure 4-4). Waste is loaded at one end,
and the rotation of the incinerator moves the waste to the other
Charging Door' Ignition
withOverfire_Chamber,
Air Port
Secondary" Curtain Wall -i
gecond|?y
Combustion
Chamber
Grates
Cleanout Doors with' .
Underrate Air Port Location of
a Secondary / cleanout
Burner ' Doors Curtain
Mixing Wa|| port
Chamber
Figure 4-2. Inline multiple-chamber incinerator with grate.
Source: References.
16
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Primary Combustion Chamber
Charging Door
Flameport
Secondary Combustion
Chamber
Underhearth Port Out
Solid
Refractory
Hearth
Underhearth Chamber
Underhearth Port In
Secondary Mixing
Chamber
Figure 4-3. Retort-type multiple-chamber Incinerator.
Source: Reference 4.
end, where it is discharged as ash. To comply with air emis-
sions standards, rotary-kiln incinerators require air pollution
control equipment and secondary combustion chambers.
*
Rotary-kiln incinerators have been used widely for incinerat-
ing hazardous waste and have been promoted recently for
use with medical waste. The rotation promotes excellent
turbulence, produces a good-quality ash, and allows for
continuous-feed operations (i.e., the incinerator does not have
to be shut down to clean out ashes). To date, however, very
few rotary-kiln incinerators are in operation for medical waste
treatment. Their high capital and operating costs, which exceed
those for other incinerator technologies, hamper their more
widespread use. Repair and maintenance costs are particularly
high because the waste tumbles through the rotary chamber,
abrading the refractory lining. Another disadvantage is that
small-capacity rotary-kiln incinerators may require additional
waste processing before incineration. In such applications,
waste may need to be shredded before it enters the rotary
chamber. As the waste is shredded, usually with a mechanism
termed an auger feeder, waste spills from infectious-waste
bags onto the feed mechanism, leading to potential main-
tenance and clean-up hazards.
4.1.2.3 Controlled-Air Incinerators
Controlled-air incinerators use two or more separate combus-
tion chambers to burn waste (see Figure 4-5). The first cham-
ber operates under starved-air conditions to volatilize the
moisture in the waste, vaporize the volatile fraction of the
waste, and combust the fixed carbon in the waste. The com-
bustion gases are then passed into the secondary (or combus-
tion chamber) of the system where combustion air is regulated
to provide excess-air conditions and complete the combustion
of the volatiles and other hydrocarbons emitted from the
primary chamber. Good turbulence is provided to promote
mixing of the combustion gases and combustion air. The
gas/air mixture then is burned at high temperatures. Both
primary and secondary chambers usually are controlled auto-
matically to maintain optimum burning conditions with vary-
ing waste-loading rates, composition, and characteristics.
Controlled-air incinerators have several advantages over the
older, multiple-chamber incineration technology. The starved-
air condition of the primary chamber allows slow, quiet com-
bustion to occur, which minimizes entrainment of particulates
in the combustion gases and thus reduces paniculate emissions
to the atmosphere. The lower temperatures achieved in this
chamber help avoid the melting and fusion temperatures of
most metals, glass, and other noncombustibles, thus minimiz-
ing slagging and clinker formation. The high temperatures and
excess-air conditions of the second chamber help ensure com-
plete combustion of volatile gases, reducing hydrocarbon
emissions. Because of their low cost and relatively clean com-
bustion, controlled-air incinerators are extremely popular—
more than 95 percent of ail medical waste incinerators in-
stalled in the last 20 years are controlled-air incinerators.6
Their popularity is deserved because of their low cost and their
relatively clean combustion. Until the last 3 to 5 years, most
controlled-air systems did not require pollution control equip-
ment to meet air quality standards, but as states pass increas-
ingly stringent regulations, these systems possibly may need
additional emission controls.
4.1.3 Incinerator Operating Modes
Medical waste incinerators can be operated in three modes:
batch, intermittent-duty, and continuous-duty. Batch in-
cinerators bum a single batch load of waste, typically only
once per day. Waste is loaded manually, burned under auto-
matically controlled conditions, and automatically cooled; the
ashes then are removed manually. Intermittent-duty in-
cinerators, loaded continuously and frequently with small
•waste batches, operate less than 24 hours per day. A typical in-
termittent-duty operating cycle for a system with manual ash
removal includes a 15- to 30-minute period for cleanout of ash
from the previous day, a 15- to 60-minute period for preheat of
the incinerator, a 12- to 14-hour waste-loading period, a 2- to
4-hour burndown period, and a 5- to 8-hour cool-down period.
Continuous-duty incinerators are operated 24 hours per day
and use automatic charging systems to charge waste into the
unit in small, frequent batches. All continuous-duty in-
cinerators operate using a mechanism for automatically remov-
ing the ash from the incinerator.
4.1.4 Incinerator Design Parameters
All incinerators, regardless of type, must be designed with a
number of considerations in mind. The type and volume of
waste per unit time (or waste generation rate) are primary con-
siderations for determining required incineration capacity and
the design and sizing of the incinerator and its components.
The first steps in selecting and designing an incinerator include
characterizing the waste to be incinerated and determining the
amount of waste generated per unit time. These factors then
can be used to determine the size and rating of the primary and
secondary chambers and the total capacity of the system.
17
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1 Waste Incinerator
2 Auto-cycle feeding system:
feed hopper, pneumatic feeder, slide gates
3 Combustion air in
4 Refractory-lined, rotating cylinder
5 Tumble-burning action
6 Incombustible ash
7 Ash bin
8 Auto-control Burner Package:
programmed pilot burner
9 Self-compensating instrumentation controls
10 Wet-Scrubber Package:
stainless steel, corrosion-free wet scrubber;
gas quench
11 Exhaust fan and stack
12 Recycle water, flyash sludge collector
13 Support frame
14 Support frame
15 Afterburner chamber
16 Precooler
Rgura 4-4. Rotary-kiln incinerator.
Source: Reference 28.
18
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4.1.4.2 Incinerator Sizing and Rating
Stack
Secondary Chamber
Control Panel
Primary
Burner
Secondary Combustion
Air Blower
Mechanical
Charge System
Viewport
Secondary Burner
Viewport
•Ash Removal
Door
Primary Chamber
Primary Combustion
Air Burner Blower
Figure 4-5. Major components of a controlled-air incinerator.
Source: Reference 29.
4.1.4.1 Waste Characterization
Incinerators must be properly designed for the specific proper-
ties and characteristics of the waste to be processed. In-
cinerator designs typically are specific to facility needs or
applications and to waste types and characteristics, such as ash
content, moisture, and heating value. The general terminology
sometimes used when making purchase-order specifications,
such as "trash," "infectious waste," or "biological waste," does
not define waste types or specific characteristics adequately.
Using this terminology could lead to the installation of an un-
suitable incinerator. To mitigate problems that can arise when
waste is not characterized adequately, the Incinerator Institute
of America (IIA) developed a classification system to
categorize wastes into seven types.23 The definitions of Types 0
through 4 are presented in Table 4-1. Types 5 and 6 are not
associated with medical waste. These characterizations com-
monly are used to classify waste types approximately, and the
popularity of this classification is enhanced through its use by
most incinerator manufacturers, who rate their equipment in
terms of HA waste types.
Alternatively, and more appropriately, waste streams can be
sampled to determine their approximate composition, or com-
ponent breakdown, and then published data such as that
presented in Table 4-2 can be used to characterize the waste.
Laboratory analysis of the sampled waste to determine "exact"
heating values, moisture content, etc., is not recommended be-
cause of high cost and lack of significant benefit over other ac-
ceptable approximations.6
A key factor in specifying an incineration system for a par-
ticular application is the clear identification of the ranges of
waste properties and waste characteristics. Use of averages
could lead to inadequate incinerator capacity and could jeop-
ardize performance.
Primary Combustion Chamber
Primary combustion chambers generally are rated in terms of
burning capacity, that is, the pounds of a specific waste that
can be burned per hour. Incinerators usually have different
ratings depending on the type of waste burned. Different types
of waste have different heating values. Primary combustion
chambers are sized and designed according to two criteria:
heat-release rate and burning rate. The heat-release rate is cal-
culated by multiplying the burning capacity in pounds/hour by
the heating value of the waste in Btu/pound and dividing by
the volume of the chamber in cubic feet, that is:
^ = capacity x heating value = Btu/hr/cu ft
primary chamber volume
where:
HR = heat release rate
or
HR =
(Ib/hr of waste) x (Btu/lb of waste)
(cu ft of primary chamber volume)
An optimum heat-release value is typically in the range of
15,000 to 25,000 Btu per cubic foot.
To maintain the design heat-release rate, less waste can be
loaded as heating, values of the waste increase. Thus, less
Type 0 waste, which has a heating value of 8,500 Btu/lb, can
be burned per hour than Type 1 waste, which has a heating
value of 6,500 Btu/lb. As moisture content increases substan-
tially, however, the use of auxiliary fuel needed to vaporize and
superheat high-moisture-content wastes limits effective in-
cinerator capacity. Therefore, although Waste Types 3 (garbage)
and 4 (animal solids and organic wastes) have lower heating
values than Waste Types 0 and 1, incinerator capacity ratings are
reduced when these high-moisture-content wastes are incinerated
(see Figure 4-6).
Burning rate, the other criterion used for designing primary
chambers, basically establishes the size of the hearth area in
the primary chamber. The maximum recommended pounds of
waste that should be loaded per square foot of hearth area per
hour for each type of waste have been determined empirically
and are shown in Table 4-3.
Note that when incinerator systems are evaluated and rated,
burning rate is not the same as charging or loading rate:
Either term may be used by a manufacturer to rate a system.
Burning rate is the amount of waste that can be burned per
hour, whereas charging or loading rate is the amount of
waste that can be loaded per hour. Loading rates often ex-
ceed burning rates if the system operates less than 24 hours
per day.
Secondary Combustion Chamber
Secondary combustion chambers basically are sized and
designed using the three Ts (time, temperature, and tur-
bulence). These factors, which are used to effect complete
19
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Table 4-1. Incinerator Institute of America Waste Classifications
Classification of Wastes
Type
Description
Principal
Components
Approximate
Composition %
by Weight
Moisture
Content %
Incom-
bustible
Solids %
Btu Value/Lb
of Refuse as
Fired
Highly combustible waste,
paper, wood, cardboard
cartons, including up to 10%
treated papers, plastic or
rubber scraps; commercial
and industrial sources
I Trash 100%
10%
5%
8,500
1
2
3
4
Rubbish
Refuse
Garbage
Animal solids
and organic
wastes
Combustible waste, paper,
cartons, rags, wood scraps,
combustible floor sweepings;
domestic, commercial and
industrial sources
Rubbish and garbage;
residential sources
Animal and vegetable
wastes, restaurants, hotels,
markets; institutional,
commercial and club sources
Carcasses, organs, solid
organic wastes; hospital,
laboratory, abattoirs, animal
pounds and similar sources
Rubbish 80% 25%
Garbage 20%
Rubbish 50% 50%
Garbage 50%
Garbage 65% 70%
Rubbish 35%
100% animal 85%
and human tissue
10% 6,500
7% 4,300
5% 2,500
5% 1,000
Source: Reference 23.
combustion of the flue gases from the primary chamber, are in-
terdependent For example, a secondary chamber designed for
very high turbulence and short retention times often [can
achieve performance equal to that of a chamber designed for
less effective turbulence and longer retention times. Regulatory
requirements, however, often dictate retention times and com-
bustion temperatures. ;
Retention times are calculated by dividing the secondary
chamber volume by the volumetric flue-gas flow rate. The gas
flow rate, which can be calculated or measured, is a function
of waste type, combustion air quantities, and operating
temperatures. In practice, gas flow rates vary widely and
frequently. |
Of the three Ts, temperature is the easiest to control. Tempera-
ture control is achieved by modulating combustion air, 'the
amount of auxiliary fuel used, the rate at which waste is fed to
the incinerator, and the type or composition of the waste. The
amount of retention time is built into the size of the incinerator
and is fixed. Turbulence also is a function of incinerator design
and can be revised only slightly within limits. !
i
Turbulence is effected mechanically (for solids) and aero-
dynamically (for gases). Types of equipment that produce
mechanical turbulence include hand pokers, grates, rams,
rotary kilns, and pulse hearths. Aerodynamic turbulence is
achieved using such features as high-velocity air injection, baf-
fles and restrictions, directional changes, cyclonic flow, and
suspension firing. I
4.1.4.3 Capacity Determination
Three factors affect the selection of incineration system
capacity: waste generation rates; waste types, forms, and sizes;
and operating hours. The effect of waste type on heat-release
rates and thus on incinerator capacity has been discussed
above. The effects of waste generation rates, waste form and
size, and operating hours are discussed below.
Waste generation rates must be eslimated or calculated to
determine optimum capacity. When computing rates, waste
managers should consider not only averages, but peaks,
ranges, and fluctuation cycles as well. The most accurate
method of determining this information is to institute a 2-week
or longer weighing program. When waste generation is es-
timated using numbers and volume of containers hauled off-
site, the variations in waste density and the possibility of
partial loading of containers can lead to gross errors in waste
generation rates. When waste generation rates are grossly un-
derestimated, the selected incineration capacity may be too
small, which could result in system overloading and con-
comitant operational problems. When waste generation rates
are overestimated, the selected incinerator capacity may be too
large and reduced operating hours may be required, leading to
other types of problems, such as waste handling problems or
insufficient heat recovery to justify the costs of operating the
system.
Waste type and forms also affect incinerator capacity. Densely
packed material has an effective incinerability factor much less
20
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Table 4-2. Waste Data Chart*
Material
Type 0 Waste
Type 1 Waste
Type 2 Waste
Type 3 Waste
Type 4 Waste
Acetic acid
Animal fats
Benzene
Brown paper
Butyl sole composition
Carbon
Citrus rinds
Coated milk cartons
Coffee grounds
Com cobs
Corrugated paper
Cotton seed hulls
Ethyl alcohol
Hydrogen
Kerosene
Latex
Linoleum scrap <
Magazines
Methyl alcohol
Naphtha
Newspaper
Plastic coated paper
Polyethylene
Polyurethane (foamed)
Rags (linen or cotton)
Rags (silk or wool)
Rubber waste
Shoe leather
Tar or asphalt
Tar paper (1/3 tar-2/3 paper)
Toluene
Turpentine
1/3 wax-2/3 paper
Wax paraffin
Wood bark
Wood bark (fir)
Wood sawdust
Wood sawdust (pine)
BtuValue/Lb
as Fired
8.500
6,500
4,300
2,500
1,000
6,280
17,000
18,210
7,250
10,900
14,093
1,700
11,330
10,000
. 8,000
7,040
8,600
13,325
61,000
18,900
10,000
11,000
5,250
10,250
15,000
7,975
7,340
20,000
13.000
7,200
8400-8,900
9,000-11,000
7,240
17,000
11,000
18,440
17,000
11,500
18,621
8,000-9.000
9.500
7,800-8.500
9,600
Weight in
Lbs/Cu Ft
(Loose)
8-10
8-10
15-20
30-35
45-55
50-60
7
25
40
5
25-30
10-15
7
25-30
45
70-100
35-50
7
7
40-60
2
10-15
10-15
62-125
20
60
10-20
7-10
12-20
12-20
10-12
10-12
Weight in
Lbs/Cu Ft
65.8
55
138
49.3
0.0053
50
45
49.6
41.6
60
2
2
20-30
21
1
2
52
53.6
54-57
3
3
3
3
Content by Weight in %
Ash
5
10
7
5
5
0.5
0
0.5
1
30
0
0.75
1
2
3
5
2
0
0
0.5
0
20-30
22.5
0
0
1.5
2.6
0
0
2
5
0
7.5
0
1
0.5
0
3
0
10
10
10
10
Moisture
10
25
50
70
85
0
0
0
6
1
0
75
3.5
20
5
5
10
0
0
0
0
1
5
0
0
6
5
0
0
5
0
0
1
0
'This chart shows the various Btu values of materials commonly encountered in incinerator designs. The values given are ap-
proximate and may vary based on their exact characteristics or moisture content.
Source: Reference 23.
21
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2800
Auxiliary Heat
Controls
Capacity
Heat Release
Controls
Capacity
1
8
1
4
3
2
1
12000
Type 4 Type 3
•Generic models not related to any vendor. :
Figure 4-€. Incinerator capacities as a function of waste types.
Source: Reference 29.
Table 4-3. Maximum Burning Rate (Ibs/sq ft/hr) of Various Type Wastes
Heat Content
BTU/Pound
Capacity
(Ibs/hr)
100
200
300
400
500
600
700
800
900
1000
Logarithm
2.00
2.30
2.48
2.60
2.70
2.78
2.85
2.90
2.95
3.00
Type 1 Waste
Factor 13 I
26 j
30 :
32 !
34 !
35 !
36 |
37 [
38
38 i
39
Type 2 Waste
Factor 10
20
23
25
26
27
28
28
29
30
30
Type 3 Waste
Factor 8
16
' 18
20
21
22
22
23
23
24
24
Type 4 Waste
No Factor
10
12*
14*
15*
16*
17*
18*
18*
18*
18*
*Tho maximum burning rate in Ibs/sq ft/hr for Type 4 waste depends to a great extent on the size of the largest animal to be incinerated. 'There-
fore, whenever the largest animal to be incinerated exceeds 1/3 the hourly capacity of the incinerator, use a rating of 10 Ibs/sq ft/hr for the 'design
of the incinerator.
Maximum burning rate (BR), expressed in Ibs/sq ft/hr, for Type 1,2, and 3 waste is calculated using factors as noted in
the formula below:
BR s Factor for type waste x log of capacity/hr
where: Type 1 waste factor = 13
Type 2 waste factor =10 t
Type 3 waste factor = 8
For example, assuming Type 1 waste and an incinerator capacity of 100 Ibs/hr for this waste type, BR is
calculated as follows:
BR > 13 (factor for Type 1 waste) x Log 100 (jsapacity/hr) = 13 x 2 = 26 Ibs/sq ft/hr
Source: Reference 23.
22
-------
than that of loosely packed material of the same type. Also,
waste with high ash-formation tendencies may have lower
burning rates, and highly volatile wastes may require burning-
rate reductions to avoid smoking problems.
The physical size of individual waste items is also an impor-
tant factor in incinerator capacity selection. One rule of thumb
is that an average incinerator waste load should weigh ap-
proximately 10 percent of the rated, hourly capacity of the
system.
Finally, the capacity of the incinerator also depends on the
number of hours it will be operating. For example, controlled-
air incinerators with manual ash cleanout usually are limited to
a maximum of 12 to 14 hours of operation per day.
4.1.5 Incineration Systems and Equipment
Incinerators typically are only one of the many components re-
quired for a complete incineration system. Other components
include waste and ash handling equipment, burner and com-
bustion air-blower systems, flue-gas handling systems, con-
trols and instrumentation, and, in many installations, air
pollution control systems and waste-heat' recovery systems.
These systems are discussed in the sections below, except for air
pollution control systems, which are discussed in Section 4.2.
4.1.5.1 Waste Handling and Loading Equipment
Waste handling systems include equipment to collect and
transport waste, storage equipment, pretreatment equipment
(such as shredders), and incinerator loading equipment Not all
incinerators have loading equipment; small incinerators may
use manual loading. Several states, however, now require
mechanical loaders on all incinerators because of the numerous
advantages of these systems.
The primary advantage of mechanical waste loaders is that
heat, flames, and combustion products are prevented from es-
caping the incinerator, thus protecting personnel and prevent-
ing fires. Also, ambient air infiltration into the incinerator is
minimized by mechanical loaders. Air infiltration affects com-
bustion conditions and can lead to lower furnace temperatures,
smoking, increases in auxiliary fuel use, and accelerated
refractory deterioration. Mechanical loaders also facilitate
charging incinerators with small batches of waste at regulated
intervals, thus providing stabilized combustion conditions and
protecting against overcharging. ,
Most incinerators are equipped with a hopper/ram-type charg-
ing system (see Figure 4-7), in which waste is loaded into a
charging hopper, the hopper cover is closed, a primary cham-
ber fire-door opens, and a charging ram then pushes the waste
into the incinerator. The loading hopper of hopper/ram systems
is sized for volume on the basis of waste type, waste container
size, method of loading the hopper, and incinerator capacity.
Incorrect sizing of hoppers could lead to waste spilling or un-
dercharging or overcharging the incinerator. Most hopper/ram
assemblies are equipped with a water system to quench the
face of the charging ram after each loading cycle to prevent
burning waste from sticking to the ram and igniting new waste
Hydraulic Fire Vj
Door Actuator —LJ-
Fire
Door -\
Hopper Cover -
Waste
Charging
Hopper
Hydraulic
Ram
Actuator
Primary
Combustion
Chamber
Fire Door
Enclosure
'Charging Ram
Ram" Quench
Spray
Furnace
Opening
Figure 4-7. Hopper/ram mechanical waste-feed system.
Source: References.
as it is loaded into the hopper. Hoppers also may be equipped
with flame scanners and alarms, fire spray systems, or emer-
gency override switches that allow hopper contents to be
pushed immediately into the incinerator.
One rotary-kiln manufacturer uses an auger feeder
(see Figure 4-8). The feeder not only loads the incinerator but
shreds the waste to a size that can be accommodated by the in-
cinerator. As discussed, this type of loading or pretreatment
system typically is required on small-capacity rotary kilns
burning medical waste.
Various systems and equipment, including conveyors, cart
dumpers, and skid-steer tractors, are used to feed incinerator
loading systems mechanically. A cart-dumper is a device for
lifting and dumping waste carts into the hopper of loading sys-
tems. This type of system is used in many installations because
it reduces waste handling and eliminates the need for inter-
mediate storage containers and additional waste-handling
equipment.
4.1.5.2 Residue Removal and Handling System
Most small incinerators and many older incinerators must be
cleaned out manually. Manual cleaning is undesirable or unac-
ceptable for several reasons:
• Difficult labor requirements.
• Hazards to operating personnel from exposure to heat,
flaming materials, glowing ashes, etc., and aesthetic,
environmental, and fire safety problems when handling
hot ashes outside the incinerator.
• Daily cool-down and start-up cycles that consume
auxiliary fuel, reduce operating hours, and reduce life of
incinerator refractories.
• Possible regulatory restrictions.
23
-------
To Atmosphere
Rotating Primary
Oxidation Chamber
High Temp. Secondary
I Oxidation Chamber
Stack
Exhaust Fan
riflure4-«. Rotary kiln with auger feed.
Source: Referenced.
Large-capacity, multiple-chamber incinerators use mechanical
grates, or stokers, to facilitate ash removal. Rotary-kiln [ in-
cinerators use the rotation of the kiln to remove ashes. Auto-
matic ash removal from controlled-air incinerators, howeyer,
has been difficult to achieve. Early ash-removal systems!for
controlled-air incinerators were designed to use an opening
floor in the primary chamber to drop ashes into a container or
vehicle, but these systems had serious operating problems.
Other early controlled-air incinerator designs used rams to push
the ash out a discharge door, but these systems also had only
limited success.
The most successful ash-handling system on controlled-air in-
cinerators, found on almost all modern systems, uses the
charging ram of the hopper/ram loading system to push jash
through the chamber to the discharge chute for removal. Large
controlled-air incinerators use internal transfer rams to help
push ashes through the chamber, whereas smaller units might
use only the waste-charging ram to move the ash across [the
hearth. A continuous-duty controlled-air incinerator with ash
transfer rams is illustrated in Figure 4-9. When the ash reaches
the end of the hearth, it drops off the end of the hearth into a
discharge chute and into either an empty ash container or a
water pit where the ash is quenched. The ash is allowed to
drain and then is discharged into a collection container. An in-
novative method for ash removal on controlled-air incinerators
uses a "pulse hearth" to transfer ashes. With this system, the
entire floor of the chamber pulses, and as it does so, it causes
the ash to move across the floor to the discharge chute.
Two methods are used to remove ash from the incinerator after
it has been discharged from the primary chamber:
• A semiautomatic system using ash collection carts, which
are located within an air-sealed enclosure beneath the drop
chute. The collected ashes are sometimes sprayed with
water to quench them slightly and to suppress dust. Loaded
ash carts then are removed manually and replaced with
empty carts. Once the ashes are cooled, ash carts are
emptied into a larger container for offsite disposal or are
brought directly to the landfill.
• A fully automatic system using a. water quench trough and
ash conveyor. This system operates continuously, bringing
quenched ashes to a container or vehicle via the conveyor,
which may be a drag, or flight, conveyor, or a "backhoe" or
"scoop" design. The conveyor system must be properly
designed to withstand severe service.
24
-------
To Boiler
Secondary Chamber
11
Feed Ram
Ash Transfer Rams
Air Tube
Ash Discharge Ram'
Ash Chute
Fossil Fuel Burner
/ Primary Chamber
Ash Sump
I
Ash Quench
Figure 4-9. Incinerator with step hearths and automatic ash removal.
Source: Reference 4.
4.1.5.3 Waste-Heat Recovery
Waste-heat recovery often is used to reduce incinerator operat-
ing costs by providing useful energy in the form of steam or
hot water. Some waste-heat recovery systems are installed not
only because of favorable economics, but because of local
regulatory requirements. The costs of some waste-heat
recovery installations are justified when the facility receives a
Department of Energy matching grant Furthermore, a waste-
heat recovery system often is justified partially because it
provides a substantial reduction in air pollution control system
costs and requirements by lowering flue-gas temperatures.
Several types of waste-heat recovery boilers are used on in-
cinerators. Firetube boilers, both single and multipass, are used
most frequently because of their simplicity and low cost One
controlled-air incinerator manufacturer exclusively uses a single-
drum watertube-type boiler. Watertube boilers, however, typi-
cally are used only on large-capacity systems requiring high
steam pressures. Waterwall heat-recovery systems are con-
structed with radiant sections or watertubes in the primary
chamber of the incinerator, and these waterwall sections usual-
ly are installed in series with a convective-type waste-heat
boiler. This type of heat-recovery system is used on very-
large-capacity incinerators.
Other equipment may be part of the heat-recovery system.
Some facilities use supplemental fuel-fired boilers to generate
steam when the incinerator is not operating. Automatic soot-
blowing systems may be installed to increase online time and
recovery efficiencies.
Heat-recovery efficiencies realistically range from 50 to 60
percent, although claims have been made for higher efficien-
cies. The energy recovered is basically a function of the flue-
gas mass flow rate and inlet and outlet temperatures. Inlet
temperatures usually are limited to about 2^00°F, and outlet
temperatures are limited by the flue-gas dewpoint temperature
(usually about 300° to 350°F) to prevent condensation and cor-
rosion of heat-exchanger surfaces. Usually about 3 to 5 pounds
of steam can be recovered per pound of typical medical waste
burned, but the economics of the heat-recovery system depend
on the ability of the facility to use the recovered energy. If
only a portion of the steam can be used, heat recovery may not
be cost effective.
Waste-heat boilers (and air pollution control systems) must be
equipped with bypass systems to divert flue gases away from
the boiler, directly to a stack (see Figure 4-10). The diversion
systems may include a dump stack upstream of the boiler or a
bypass breaching connection between the incinerator and the
stack. Isolation dampers or stack lids are included on modern,
well-designed bypass systems. Without such dampers or lids,
hot flue gases can bypass the boiler, or ambient air can dilute
gases to the boiler. Isolation dampers thus substantially im-
prove heat-recovery efficiencies.
Some incinerator designs incorporate air-preheating systems.
These systems consist of jacketing around the primary or
secondary chamber through which combustion air is pulled.
The combustion air is heated by as much as several hundred
degrees, thus reducing auxiliary fuel usage by as much as 10 to
15 percent. The jacketing on some systems also helps reduce
or limit incinerator skin temperature to within regulatory
limits.
4.1.5.4 Other Incinerator Components and
Appurtenances
Other incinerator components and features that require proper
attention and design include incinerator burning surfaces;
Bypass
Shutotf
Valve
Incinerator
Waste Heat Damper
Boiler
Figure 4-10. Incinerator with waste-heat boiler bypass stack.
Source: Referenced.
25
-------
refractories and linings; auxiliary fuel equipment and burners;
flue-gas handling components, such as breechings and stacks;
and controls and instrumentation. Each of these is discussed
briefly below.
• Incinerator burning surface—The burning surface may
include hot or cold refractory hearths, fixed or moving
grates, or combinations of these surfaces. ;
• Refractories—Refractories are heat-resistant materials
that provide containment of the combustion process.
They also radiate heat back into the incinerator; support
the burning waste and ash; and protect personnel, the en-
vironment, and surrounding areas. Refractories may be
castables or preshaped bricks.
• Incinerator linings—Incinerator linings typically include
the refractory, an insulation layer, steel casings, and, in
some cases, an air jacketing or shrouding.
• Auxiliary fuel—Auxiliary fuel systems are used to ignite
the waste, preheat the incinerator chamber, maintain
high temperatures, and control bum-down. Ignition,
preheating, and the burning of low-energy waste are the
functions of these systems in the primary chamber. In the
secondary chamber, auxiliary fuel is used for preheating,
maintaining high temperatures, and providing a [hot
flame for improved burnout of organics. Burner controls
can range from fully manual to fully automatic. Modern
systems integrate burner and air-blower controls for im-
proved efficiencies. I
• Flue-gas handling—Flue-gas handling equipment in-
cludes high- or low-temperature breeching; main land
bypass stacks; dampers; and draft inducers, or induced-
draft fans.
• Stacks—Depending on operating temperature and flue-
gas conditions, stacks may be lined with high-tempfera-
ture refractory or constructed of fiberglass-reinforced
plastic for low-temperature operation if handling
saturated gases from wet scrubbers. They also may be
built with masonry or other special construction
materials. Stack heights are determined by the heights of
surrounding buildings or topography, building and Ifire
codes, draft requirements, entrapment avoidance, and/or
ambient air quality and dispersion modeling. Stack1 ac-
cessories may include an exit cone, spark arrester, itest
ports (with platform), ladder with safety cage, lightning
protection, aircraft warning lights, cleanout door, and
drain. !
• Incinerator draft controls—Incinerator draft may! be
natural, forced, induced, or balanced. Draft controls in-
clude barometric dampers, modulating dampers, Sand
variable-speed fans. •
i
• Combustion controls—Combustion controls provide
automatic integrated management and control of waste
charging operations, burner operatibns, combustion air
supply, and draft.
• Control and instrumentation (C&I) systems—These sys-
tems include mechanical/electrical systems or solid-state
programmable controller systems for centralized com-
bustion control, monitoring, and integrated operation of
all system components and equipment.
• Monitoring and recording equipment—Temperatures
typically are monitored in the primary and secondary
chambers, at the boiler inlet and outlet, and at the air pol-
lution control equipment inlet and outlet. Pressures
usually are monitored at the primary chamber as draft, in
the air pollution control equipment as pressure drop, and
in the combustion air manifolds. Typically, scrubber
water pressures also are monitored. Flows usually are
monitored for scrubber water and blowdown, auxiliary
fuel, and recovered steam. Scrubber pH is monitored, as
are many types of emissions (see Section 4.2). Devices
for continuously monitoring carbon monoxide, oxygen,
and sometimes hydrogen chloride are known as a con-
tinuous emissions monitoring system (CEMS).
4.1.6 Special Incineration Applications
Medical waste incinerators sometimes are used to incinerate
low-level radioactive waste or chemical waste, which may in-
clude hazardous waste. A number of special considerations
apply to incinerators in which these types of wastes are
burned.
Most chemical wastes burned in medical waste incinerators are
solvents burned as fuels with solid waste. A simple method for
incinerating these wastes is to inject them into the flame of an
auxiliary fuel burner using an atomizer nozzle. Larger in-
cinerators may use special, packaged burners designed to fire
solvents. These burners may handle solvents exclusively, or
may be able to handle fuel oils when solvents are unavailable.
Most solvent firing occurs in primary chambers to assist in
burning the waste and to utilize secondary chamber volumes
fully. Injectors and burners must be located so that solvents do
not impinge on furnace walls or on other burners to avoid poor
combustion or emission problems.
Alternatively, depending on incinerator capacity and design,
small amounts of chemicals sometimes can be loaded in bot-
tles or vials without affecting incinerator operations. When
large numbers of chemical containers are burned, however,
severe operating problems may ensue. These problems can in-
clude rapid, uncontrolled combustion, leading to smoking and
excessively high temperatures, and melting and slagging of
glass containers, which can damage refractory materials and
plug air-supply ports.
In addition to the firing system, a properly designed chemical-
waste handling system also must be used when chemical
wastes are incinerated. The system should include a receiving
26
-------
and unloading station, a storage tank, a pump set to feed the in-
jector or burner, appropriate spill containment (diking) and
protection, monitoring devices, and safety protection devices.
Most of this equipment should be located in a separate, fire-
rated room with special ventilation and explosion-proof
electrical fixtures.
Federal, state, and local regulations must be followed when
transporting, handling, storing, and burning chemical waste. If
the waste is designated as a hazardous waste under state or
federal regulations (see Section 2.3.1.1), the incinerator must
be permitted in accordance with RCRA requirements (Part B
permitting), trial burn tests (which are very costly) must be
run, and additional, costly, continuous monitoring and control
equipment is required. Part B permitting requirements include
development of waste sampling and analysis plans; security,
closure, and contingency plans; inspections; recordkeeping;
special personnel training; and liability coverage. Obtaining
permits could delay incinerator startup by as much as 12 to 18
months.6 Before an operating permit is issued, trial bums must
show 99.99 percent destruction and removal efficiency (DRE),
paniculate emissions of less than 0.08 grain/dscf at 7 percent
oxygen, and hydrogen chloride emissions of less than 4 Ib/hr,
or 99 percent removal.4 One exception to these requirements is
waste that is classified as hazardous only because of its "ig-
nitability," i.e., it has a flashpoint of less than 140°F. In-
cinerators burning these types of ignitable wastes are not likely
to be classified as hazardous waste incinerators, and thus may
avoid the hazardous waste incinerator permitting process. The
storage and handling of the ignitable waste, however, most
likely will require a facility to obtain a Part B permit as a treat-
ment, storage, and disposal (TSD) facility.
Incinerators burning low-level radioactive waste must have
emissions that meet dose levels specified by the national emis-
sion standards for hazardous air pollutants (NESHAPs)30 as
well as those mandated by NRC regulations in 10 CFR Part 20.
Some low-level radioactive wastes, however, are biomedically
exempt, i.e., they exhibit radioactivity below specified limits
and thus are not subject to NRC regulations. Mixed wastes,
such as liquid scintillation cocktails (LSC), which are radioac-
tive chemical solvents, must comply with both RCRA and
NRC regulations.
4.2 Incinerator Emissions and Air Pollution
Control Equipment
The types of incinerator emissions of concern and the emission
limits often imposed on medical incinerators are summarized
in this section. Strategies for controlling emissions are dis-
cussed, and the technology for achieving emissions control is
summarized.
4.2.1 Incinerator Emissions
Emissions from medical waste incinerators are generated from
either waste constituents, components of combustion air, or
byproducts of the combustion process itself. Pollutants of con-
cern include paniculate matter, toxic metals, toxic organics,
carbon monoxide, and acid gases (hydrogen chloride, sulfur
dioxide, and nitrous oxides). Each of these pollutant categories
is discussed below.
4.2.1.1 Paniculate Matter
Particulate matter is generated when noncombustible material
is suspended, when incomplete combustion of combustible
materials occurs, and when vaporous materials condense.
Suspension of paniculate matter can occur when combustion
air is added to the incinerator. If the amount of air entering the
primary combustion chamber is kept to the minimum neces-
sary, paniculate entrainment will be reduced. Proper control of
combustion will minimize particulate emissions from incom-
plete combustion. Vaporous materials condense on the surface
of fine particles when combustion temperatures are high
enough to vaporize some of the fuel constituents, which then
cool in the flue gas. Particulate material can consist of com-
bustibles or minerals. Combustible participates may be char
(large particles of carbonated materials such as paper that are
incompletely combusted) or smoke (fine particulates). Minerals
consist mostly of salts or silicates, which are not a health con-
cern but which contribute to particulate emissions.
4.2.1.2 Toxic Metals
Toxic metals appear in emissions as particulates. The con-
centration of metals emissions depends on the quantity of met-
als in the waste material. Some metals are emitted as metal
oxides in micron or submicron sizes. Other metals are volatil-
ized and deposit on small, difficult to control particles. Metals
that are thought to condense on other particles include arsenic,
cadmium, chromium, nickel, lead, and zinc. As many as 12 to
14 different metals have been identified by some regulatory
agencies as potential health risks when emitted from
incinerators.*
4.2.1.3 Toxic Organics
Toxic organics can be combusted completely to form carbon
dioxide and water; however, incomplete combustion can create
new organic species (products of incomplete combustion, or
PICs). Chlorine, derived from the incineration of PVC plastics,
can combine with organics to form toxic chlorinated organics,
such as dioxins and furans.
4.2.1.4 Carbon Monoxide
Carbon monoxide is a product of incomplete combustion and
is a good measure of incinerator efficiency. Many state agen-
cies require monitoring of carbon monoxide emissions to en-
sure proper operating conditions in the incinerator. Carbon
monoxide production is limited when oxygen concentrations,
mixing, and temperatures are adequate.
4.2.1.5 Acid Gases
Acid gases are created when nitrogen, sulfur, and chlorine are
released during combustion. The acid gas of most concern in
*Doucet, Lawrence G., Doucet & Mainka, P.C., personal communication,
November, 1991.
27
-------
medical waste incinerators is hydrogen chloride. Hydrogen
chloride is created when wastes containing chlorine, such as
PVC materials, are incinerated. Sulfur also may be found in
the waste stream, whereas nitrogen is a waste component and a
constituent of the combustion air.
4.2.2 Regulatory Requirements for Emission
Control
State regulations limiting emissions from medical waste in-
cinerators can include emission limits on all of the pollutants
of concern listed above. Many states have passed new, ami in-
creasingly stringent regulations for medical waste incinerators.
These regulations often include limits on specific pollutant
concentrations in stack gases, as well as limits on concentra-
tions of toxic metals and organics in the ambient air. Further-
more, under Sections 129 and lll(b) of the Clean Air Act of
1990, EPA is developing new source performance standards
(NSPS) to regulate the emissions of new medical incinerators.
The pollutants to be regulated are paniculate matter, |acid
gases, trace metals (lead, cadmium, and mercury), carbon
monoxide, and organics such as dioxins and furans. EPA ex-
pects to promulgate these regulations in 1992.31 !
Some regulatory agencies establish ambient air-quality limits.
To demonstrate compliance with such limits, air-quality
modeling of stack gas dispersion must be performed, often as
part of the permitting procedure. Stack testing is required to
demonstrate compliance with limits on stack gas emissions.
Ash residues also may need to be tested for constituents to
demonstrate compliance with regulations.
Best available control technology (BACT) for paniculate
emissions is not well defined and varies from state to state.
Some states define BACT for paniculate emissions as OlOlS
gr/dscf.6 State designation of BACT for hydrogen chloride
emissions typically is identified as a 90 percent reductioh in
hydrogen chloride by the air pollution control (APC) system or
a concentration of 30 parts per million in the stack gas. [Re-
quirements for small systems (e.g., those handling under [200
to 500 Ibs/hour) and for existing systems are usually less sfrin-
gent than those for larger or new systems.6 •
4.2.3 Emission Control Strategies
Emission control begins with controlling the waste feed
material. Heavy metals, chlorinated organics, and acid gas
emissions all can be reduced by eliminating the use of certain
materials at the institution, segregating wastes at the point of
origin, or removing problem materials before incineration. For
example, substituting polyethylene plastics for PVC can
reduce the amount of chlorine-containing wastes incinerated,
thereby reducing concentrations of chlorinated organics and
hydrogen chloride. Segregation or removal of noncombustible
dusts and powders (to reduce paniculate matter emissions), heavy
metals (such as wastes from dental clinics or laboratories), and
PVC plastics would reduce the emission of many problem pol-
lutants.
Combustion control also relates to emission control. Incjam-
plete or poor combustion produces excess paniculate matter,
PICs, and carbon monoxide. Because of the variability of
medical waste, incinerators must be operated flexibly, varying
operating conditions as waste constituents vary. In general,
combustion conditions improve with higher temperatures,
well-controlled excess-air rates, flue-gas mixing or turbulence,
and retention times. However, greater costs and (depending on
the waste-feed composition) increased emissions of nitrous
oxides and toxic metals can result from operating incinerators
at higher temperatures. Not all pollutants, however, can be
controlled by controlling incinerator operating parameters.
Hydrogen chloride and sulfur dioxide emissions are not af-
fected by operating conditions in the incinerator.
When feed material and combustion controls do not produce
emission levels compatible with regulatory requirements, air
pollution control systems must be installed. The types of air
pollution control equipment, how this equipment operates to
control emissions, and some of the advantages and disad-
vantages of each type of equipment are discussed in the fol-
lowing section.
4.2.4 Air Pollution Control Equipment
Many types of emission control equipment are available. Sys-
tems include wet and dry scrubbers, settling chambers,
mechanical cyclones, and electrostatic precipitators. Settling
chambers and mechanical cyclones do not meet new emission
standards; electrostatic precipitators are far too costly for most
medical waste incinerators, have problems with corrosion and
fouling, and can pass large particles through the system. To
date, only two basic types of systems have been used success-
fully on medical waste incinerators to meet the new stringent
state emission limits: wet and dry scrubbers.9
4.2.4.1 Wet Scrubbers
Wet scrubbers are the most common air pollution control
devices currently used on medical incinerators because of their
low cost and ease of operation. They can be used to remove
acid gases alone or acid gases and paiticulates.
Large liquid droplets are used to capture small particles in wet
scrubbers. The droplets collect particles either by a process
known as impaction or by diffusion. In impaction, large par-
ticles hit the liquid droplets, and the liquid with its captured
particulates then can be removed from the system. In diffusion,
very small particles are bumped by gas molecules, causing the
particles to move randomly in the exhaust stream. This random
movement, or diffusion, causes the particles to collide with
droplets, which then are removed from the system.
Acid gases are controlled by the absorption of the gaseous
pollutants in the liquid. Scrubbers that effectively remove acid
gases provide a large contact area between the gas and liquid
phases, provide good mixing of the two phases, and allow suf-
ficient contact time. In addition, a basic (high-pH) mixture is
added to the liquid to improve acid-gas removal.
Three types of wet scrubbers are commonly used: venturi
scrubbers, packed-bed scrubbers, and spray towers. Venturi
scrubbers primarily remove particulates and packed-bed
28
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scrubbers primarily remove acid gases. When these scrubbers
are used together, both types of emissions can be controlled
more effectively. Spray towers, which are used to control both
particulates and acid gases, cannot meet die newest state
regulations for particulates, so are used typically with venturi
scrubbers. Other types of scrubbers used more infrequently are
impingement tray, collision, ejector, and wet-ionizing scrub-
bers. Venturi scrubbers, packed-bed scrubbers, and spray
towers are discussed below.
Venturi Scrubbers
Venturi scrubbers (see Figure 4-11) are the wet scrubbers most
commonly installed on medical incinerators. A venturi scrub-
ber consists of equipment in which a liquid is sprayed
upstream from a vessel containing a converging and diverging
cross-sectional area (as illustrated in Figure 4-12). The nar-
rowest portion of the venturi is known as the throat. In this
area, the gas velocity and turbulence are at a maximum. The
liquid droplets are atomized by using either the shearing action
of the high gas velocity in the throat or spray nozzles that force
high-pressure liquid through small orifices.
Flue-Gas Inlet from Quench
Outlet
Inlet
Quench Section
Liquid Feeds
Venturi
Liquid Distributor
Packing
Packing Support
Wetted Elbow
Combination Cyclonic
Separator and Packed
Bed Absorber
Liquid Discharge
Particles
accelerate
Particles collide
with droplets
Particles
decelerate
Converging
Region
Droplets have
no axial velocity
Spray Nozzle
Diverging
Region
Figure 4-11. Venturi-scrubber system.
Source: Reference 32.
Droplets
accelerate
Flue-Gas Outlet to Separator Tower Section
Figure 4-12. The behavior of solid particles and liquid droplets in a
venturi-scrubber section. Source: Reference 33.
To attain a high collection efficiency, venturi scrubbers need to
achieve gas velocities between 10,000 and 40,000 feet per
minute in the throat The design gas velocity in the throat
depends on the required particulate removal efficiency and the
size distribution of the particulate matter. Removal efficiencies
decrease with particle size. Particulate collection efficiency,
however, is correlated more directly with pressure drop across
the venturi. Pressure drop, which is easily measured, influen-
ces the size of the induced draft fan required in the system,
which directly affects the electrical operating costs of the sys-
tem. Thus pressure drop, size of ID fan, and cost increase as
particulate collection efficiency requirements increase or par-
ticle size decreases.
Following the venturi section, the saturated flue gases and
droplets enter a separator, usually at the bottom of a cylindrical
tower, which cyclonically separates the droplets and captured.
particles using centrifugal force. The top of the tower typically
is equipped with a mist eliminator, a device that removes most
of the remaining entrained water droplets to prevent the emis-
sion of these droplets from the scrubber system.
29
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Packed-bed Scrubbers I
Venturi scrubbers often are operated with packed-bed scrub-
bers, which provide additional acid-gas removal. A schematic
for a venturi-scrubber system with a packed tower is shown in
Figure 4-13. In the most common type of packed-bed system,
the bed is vertical, and liquid (usually water with sodium
hydroxide added to neutralize the absorbed acid gases) is
sprayed from the top and flows downward across the bed (see
Figure 4-14). The effectiveness of the acid-gas absorption is a
function of the uniformity of gas velocity distribution, the sur-
face area of the packing material, and the amount and uniform
distribution of the scrubber solution. Packed-bed scrubbers are
equipped with mist eliminators to capture most of the small
particles created by the evaporation of the water droplets that
escape from the scrubber.
Spray Towers
Spray towers typically consist of a cylindrical steel vessel, con-
taining nozzles that spray the liquid scrubbing media into the
vessel (see Figure 4-15). Because very small droplets could be
carried out of the scrubber, droplet particles cannot be too
small, and exhaust-gas velocity must be kept low. For these
and other reasons, collection efficiency is low, and the syistem
Figure 4r14. Countercurrent Packed-Tower Scrubber.
Source: References.
By-Pass
Scrubber
Product
Discharge
. (Wet)
Figure 4-13. Schematic for a venturi-scrubber/packed-tower system.'
Source: References. i
30
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Liquid
Sprays
Figure 4-15. Countercurrent-flow spray tower.
Source: References.
is useful only for collecting larger particles. Because control-
led-air incinerators emit relatively fine particles, these systems
are unsuitable for use on these units. Spray towers are used,
however, on multiple-chamber incinerators, which emit large
quantities of relatively large particles.
4.2.4.2 Dry Scrubbers
Dry scrubbers generally consist of an acid-gas removal system,
in which a dry alkaline substance, such as lime, is injected
upstream from a paniculate removal device, usually a fabric
filter (baghouse). Because fabric filters do not remove acid
gases and because they can be corroded by these gases, they
always have been used with acid-gas removal systems. Two
major types of dry-scrubber/fabric-rfilter systems are used:
spray-dryer/fabric-filter and dry-injection/fabric-filter systems
(see Figures 4-16 and 4-17). The main difference between
these systems is the method of introducing the alkaline absorb-
ent. Spray dryers use a slurry of water and lime injected
through nozzles or rotary atomizers. The acid gases react with
the lime in the slurry, and the water then is evaporated by the
gas-stream heat until only the solid reaction particles are left
for collection at the baghouse. These systems are much more
expensive and complex than dry-injection systems and have
not been used on medical waste incinerators. In a dry-injection
system, the lime is injected directly into the gas stream to ab-
sorb acid gases. More lime is required than that for a spray
dryer, and the reaction is not as efficient. Thesb systems
are sufficiently effective, however, and their relatively
low cost compared to spray-dryer/baghouse systems makes
them popular. Figure 4-18 contains a schematic for a dry-
injection/fabric-filter system.
Combustion
Gases
Figure 4-16. Components of a spray-dryer absorber system (semiwet process).
Source: References.
31
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Feoder
Combustion
Gases from
Incinerator
Stack
Figure 4-17. Components of a dry-injection absorption system (dry process).
Source: References. !
Water
By-Pass
/
Incinerator
Rue Gas In
Fabric
Filter
(Baghouse)
Stack
I.D. Fan
Rgure 4-18. Schematic of a dry-injection/fabric-filter system.
Source: Reference 9.
32
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The baghouse portion of the dry-scrubber system is a collec-
tion of bags constructed from fabrics, such as nylon, wool, or
other material, hung inside a housing (see Figure 4-19). Bag
materials must be selected carefully to withstand high flue-gas
temperatures and other potentially adverse conditions. The
combustion gases are drawn into the housing and pass through
the bags, where the particles are retained on the fabric material
while the clean gases pass through and are exhausted through a
stack. The .collected particles and cake buildup typically are
removed from the bags by blasts of air, and the removed par-
ticles (or flyash) are stored in collection hoppers. Fabric filters
are classified by the type of mechanism used to remove par-
ticles from the bags: mechanical shaker, reverse air, and pulse
jet. Pulse-jet fabric filters are the only type used to date on
medical waste incinerators.
Operating temperature is a critical factor in fabric-filter perfor-
mance. If temperatures are too low, any remaining acid gas
will condense and corrode the housing or the bags; if tempera-
tures are too high, bags will degrade or even fail completely. A
temperature of about 350°F typically is maintained to avoid
both types of problems.
4.2.5 Selection of Pollution Control Devices
Data from several facilities appear to indicate that dry-scrubber
systems using dry alkaline injection can achieve lower
Clean Air Plenum.
Blow Pipe
To Clean-ouflet
-Air Outlet
and Exhauster
Housing
•'Tubular
Filter Bags
Dirty Air Pienum
Rotary Valve Air Lock
paniculate emission levels than venturi scrubbers.** Venturi
scrubbers, even those with mist eliminators and other special
equipment, only barely may achieve the highly stringent emis-
sion limitation requirements mandated by some states, but dry-
injection systems appear to be able to meet or exceed these
requirements*
Another factor in the choice of a system is the size of the
facility. Small facilities may be subject to less-stringent pollu-
tion removal requirements. For this and other reasons, venturi
scrubbers are the APC system of choice for smaller medical
waste incinerators; Initial capital costs are lower, and venturi
scrubbers are not as sensitive as fabric filters to cold-startup
conditions necessitated by the cycling of batch and intermit-
tent-duty incinerators. Furthermore, because of the sensitivity
of fabric filters to high temperatures, combustion gases must
be cooled by a heat-recovery system and another cooling sys-
tem before they reach the fabric filter. Because waste-heat
recovery often is not economical for small incinerators, this re-
quirement adds to the cost of operating a fabric-filter system.
Finally, start-up requirements for a baghouse system are more
stringent. Therefore, a sophisticated control system is required,
which is costly and generally not included in APC systems for
small facilities. Venturi scrubbers, on the other hand, have
proved themselves as appropriate systems on small medical
waste incinerators because of their ability to accept hot flue
gases directly and because they require no special startup con-
siderations. Additionally, many existing facilities are required
to add pollution control equipment, and venturi scrubbers re-
quire less space than dry-injection 3ystems. Thus venturi
scrubbers are easier to retrofit in most small facilities, where
space quite often is restricted.
Another consideration that can affect the choice of an APC
system is the cost of collecting flyash and liquid effluent dis-
posal. Wet scrubbers produce a liquid effluent that usually is
discharged directly to the sewer system, whereas baghouses
produce flyash, which may be classified as either a solid waste,
special-handling waste, or hazardous waste. In some cases,
scrubber effluent can contain concentrations of heavy metals
that potentially may exceed local sewer pretreatment standards
or federal regulations. Most facilities can mix this effluent with
other liquid discharges to dilute it. This procedure almost al-
ways reduces metal concentrations well below regulatory
limits. Other facilities may require special spray evaporators to
dry and concentrate the solids for disposal in a landfill, which
greatly increases costs. Alternatively, if flyash is categorized
as hazardous, disposal costs may be exorbitant Currently,
flyash seems to be classified as special handling waste, which
is more costly to dispose of than solid waste, but is less costly
than hazardous waste. A few medical incineration facilities
have combined baghouses and wet scrubbers. These systems
remove metals in the flyash, rather than in the scrubber water,
and the scrubber acts to remove additional acid gas and
Figure 4-19. Pulse-jet-type baghouse filter.
Source: Reference 34.
**Doucet, Lawrence G., Doucet & Mainka, P.C., personal communication,
November, 1991.
^Recent developments and add-on features for venturi scrubbers, however,
have enabled these systems to achieve paniculate removal efficiencies com-
parable to those for dry scrubbers. (Doucet, Lawrence G., Doucet & Mainka,
P.C., personal communication November, 1991.)
33
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participates. Combination systems are rarely required,
however, and usually are much more costly than either system
alone.
4.3 Other Regulatory and
Permitting Considerations
Incinerator equipment and operations other than APC equip-
ment and emissions also are regulated, and the specific state
requirements vary widely. Equipment such as mechanical
waste loaders, modulating burners, and enclosed ash-remjaval
systems may be required. Incinerator operating conditions such
as temperature and retention time usually are specified in
regulations or permit conditions, and types of monitoring and
recording activities can be required (e.g., loading rates,
primary and secondary chamber temperatures, opacity, [and
flue-gas constituents). Requirements for operator training
programs also may be included. I
Many states require that air-quality modeling and health :risk
assessments be performed as part of the permitting process for
medical waste incinerators. Air-quality modeling entails using
an EPA-approved air-quality model to estimate how the sjtack
emissions or plume affects pollutant concentrations at ambient
and sensitive receptors (e.g., nearby residents). Inputs to. the
model include flue-gas parameters, pollutant emission rates,
meteorological conditions, stack parameters, local terrain fea-
tures (such as tall buildings or hills), and atmospheric dispersion
parameters such as temperature gradients and wind-velocity
profiles. The model produces estimates of pollutant concentra-
tions, which must be compared to state and federal standards
for ambient air-quality concentrations to show compliance
with the regulations.
Where no state pollutant standards exist, the permittee may
be required to perform a health risk analysis to show jthat
the estimated pollutant concentrations will not increase
significantly the risk to public health. This analysis estimates
the incremental cancer risks potentially attributable to in-
cinerator emissions. The incremental cancer risk is the es-
timated excess probability of contracting cancer as the result of
constant 24-hour-per-day exposure to worst-case ambient pol-
lutant concentrations over a 70-year lifetime resulting from in-
cinerator operations. An incremental cancer risk of less than
one in a million is considered an acceptable risk by most
states.
The estimated maximum concentration of each pollutant of
concern is multiplied by the unit risk factor associated with
that pollutant to give the estimated incremental cancer risk.
These unit risk factors are based on carcinogenic potency
factors established by EPA's Office of Health and Environ-
mental Assessment, which are conservative estimates of the
carcinogenic risk. Because maximum lifetime exposures to
maximum concentrations are assumed, and because the car-
cinogenic potency factors are designed to include large safety
factors, the health risk assessment is a very conservative es-
timate of health risk.
Health risk assessments also may be required for noncar-
cinogenic pollutants, such as toxic metals and acid gases.
Toxic metals include mercury and lead, which have known
negative health effects. Acid gases, such as hydrogen chloride,
are not life threatening at typical emission levels but can affect
the quality of life and are potentially injurious.
Public hearings are usually a part of the permitting process.
These hearings are used to address public concerns such as
health risks as well as aesthetics and visibility, traffic levels,
and property values. The health risk assessment can become
a useful public relations tool; it can illustrate the compara-
tive risks associated with medical waste incinerators, which
in general pose incremental cancer risks of less than one in
a million.
34
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Chapters
Designing and Implementing Waste Management Plans
Waste management planning requires that the institution's
needs for waste disposal be determined, that the proper treat-
ment and disposal option for the facility's needs be selected
and procured, and that a program of employee training be es-
tablished to ensure safety and proper equipment operation.
These three areas of waste management planning are reviewed
in this chapter as they relate to the design and implementation
of a waste management plan emphasizing onsite incineration
as the chosen waste treatment option.
5.1 Designing a Waste Management Plan
Medical waste management is becoming an increasingly im-
portant issue to all types of institutions. Broadening legislation,
fears of AIDS and other blood-borne diseases, tightening
policies by institutions with public image concerns, and fears
of liability all contribute to the need for institutions to consider
carefully their existing waste management practices. Addition-
ally, increasing limitations on landfill space and other offsite
disposal options further require institutions to evaluate,
redesign, and/or develop an integrated waste management
program.
A waste management program should address four major con-
cerns: the safety and health of employees who must handle
potentially infectious waste; existing and proposed federal,
state and local regulations and accreditation requirements; off-
site liabilities and risks of exposing offsite populations to
infectious waste; and costs of treating and disposing of infec-
tious and other waste generated by the institution.4
In meeting these concerns, the waste management program
will be most effective if it is manageable and enforceable, al-
lows for some flexibility, ensures compliance with all regula-
tions and standards, ensures the health and safety of workers
and others, preserves environmental integrity, and promotes a
cost-effective solution to the institution's waste management
needs.
5.1.1 Waste Disposal Evaluations
The early steps of designing a waste management plan include
the waste disposal evaluations and the option selection
processes outlined in Chapter 3. These evaluations determine
waste types, sources, quantities, and other important
parameters needed to select the waste treatment and disposal
options that can meet the institution's needs.
If the incineration option is selected, additional waste charac-
terizations may be required. Heating values for the types of
waste to be incinerated must be determined. Heating values
can be calculated based on an assumed average IIA waste type
(see Section 4.1.4.2) or on individual waste components. In
some cases, laboratory analysis can be used. A proximate
analysis can be used to determine the weight percentage of
moisture, volatiles, fixed carbon, and noncombustibles in the
waste. An ultimate analysis can be undertaken to determine the
weight percentages of elemental constituents of carbon,
hydrogen, oxygen, nitrogen, chlorine, sulfur, metals, etc. The
physical form of the waste also must be considered; that is,
whether the waste is loosely or highly compacted and whether
large items, such as large animal carcasses, must be in-
cinerated (see Section 4.1.4.3). All these factors will affect sig-
nificantly the size of the incinerator needed at the institution,
as well as which emission controls may be most suitable.2 In-
correct characterization of the waste can lead to operating
problems and/or the need to reduce system capacities. Some of
the deficiencies of waste characterizations and their effect on
capacity are summarized in Table 5-1.
5.1.2 Incineration Option Selection
Various options that often need to be evaluated and selected
for an incineration system and design include parameters such
as operating period, ash removal, waste-heat recovery, monitoring
and recording, degree of automation, and redundancy. When
selecting incineration options or add-ons, the planner also may
want to consider whether it would be viable or cost-effective to
coincinerate flammable solvents, chemotherapy chemicals in bulk
or trace amounts, or low-level radioactive wastes with medical
wastes. Site-selection criteria also must be evaluated for an in-
cinerator. Such criteria include how large a space is available,
how accessible the location will be, what types of waste and
residue handling are most appropriate and can be accom-
modated, how flue gases will be handled, how to deal with
visibility and aesthetics, how acceptable the installation will be
to the surrounding inhabitants, and what types of operations
will be performed.
5.2 Selecting and Procuring an
Incineration System
Not all incinerators perform up to expectations. Incinerator
systems provide good performance only if their design and
35
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Table 5-1. Waste Characterization Data Deficiencies Necessitating System Capacity Reductions
Actual Waste Characterization
Deviations from Selected
"Design" Values
Typical Examples
Basic Reasons for Reduced Capacities*
Heating values (btu/lb)
excessive
Greater concentrations of paper and plastic
components (or less moisture) than those
originally identified and specified
Incinerator volumetric heat release rates
(Btu/Cu ft/hr) exceed design limits"
Moisture concentrations
excessive
Greater concentrations of high water-content
wastes, such as animal carcasses or food
scraps (garbage), than those originally
identified and specified
Increased auxiliary fuel firing rates and
additional time required for water evaporation
and superheating
Volatiles excessive
Greater concentrations of plastic (such as
polyethylene and polystyrene) or flammable
solvents than those originally identified and
specified
Rapid (nearly instantaneous) releases of
combustibles (volatiles) in large quantities along
with excessively high temperature surges
Densities excessive
Computer printout, compacted waste, books,
pamphlets, and blocks of paper
Difficulties in heat and flames penetrating and
burning through dense layers of waste
High ash-formation
tendencies
Animal bedding or cage wastes, wood chips,
shavings or sawdust
Ash layer formation on surface of waste pile
insulates bulk of waste from heat, flames, and
combustion air
*Failure to reduce capacities, or hourly waste loading rates, to accommodate indicated deviations would most likely result in other
more serious operational problems.
"Based on accepted, empirical values, primary chamber heat release rates should be in the range of 15,000 to
20,000 Btu/cu ft/hr.
Source: References.
operation satisfy specific user objectives such as burning
capacity, destruction, environmental integrity, and online
reliability. Performance problems can range from minor
nuisances to major disabilities, and corrective measures can
range from simple adjustments to major modifications and
even to total abandonment According to several estimates ap-
proximately 25 percent of all medical waste incineration!sys-
tems installed within the last 10 years do not operate properly
or do not satisfy user performance objectives.11 |
Several fundamental reasons or typical examples for poor in-
cinerator performance are outlined in Table 5-2. Typically, if
incinerator performance is poor, the incinerator contractor is
blamed for providing inferior equipment, but this is not always
the cause or the only cause of problems. In fact, incinej-ator
deficiencies or inadequacies usually are related to problems in
three areas: selection and/or design (before procurement),
fabrication and/or installation (during procurement), !and
operation and/or maintenance (after acceptance). Examples of
deficiencies in these three areas are discussed below. '
5.2.1 System Selection and/or Design •
Deficiencies '
When incinerator system and design decisions are made based
on incorrect or inadequate waste data or when specific, unique
facility requirements are not addressed, problems can ensue.
For example, if waste generation rates are underestimated, an
incineration system with inadequate capacity will be procured.
Table 5-2. Incineration System Performance Problems
Major Examples
Performance
Difficulties
Objectionable Out of compliance with air pollution control regulations.
stack Visible emissions
emissions Odors
Hydrochloric acid gas deposition and deterioration
Entrapment of stack emissions into building air intakes
Inadequate Cannot accept standard-size waste containers
capacity Low hourly charging rates
Low daily burning rates (throughput)
Poor burnout Low waste volume reduction
Recognizable waste items in ash residue
High ash residue carbon content (combustibles)
Excessive Frequent breakdowns and component failures
repairs High maintenance and repair costs
and downtime Low system reliability
Unacceptable High dusting conditions and fugitive emissions
working Excessive waste spillage
environment Excessive heat radiation and exposed hot surfaces
Blowback of smoke and combustion products from
the incinerator
System > Excessive auxiliary fuel usage
inefficiencies Low steam recovery rates
Excessive operating labor costs.
Source: References.
36
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Improper waste characterizations also can lead to operating
problems. When heating values, moisture content, volatility,
density, and physical form are specified improperly, objec-
tionable stack emissions, unacceptable ash quality, or other
problems could develop, requiring reductions in incinerator
capacity by as much as two-thirds.6
System design criteria and associated contract documents also
must be checked to ensure that they adequately satisfy the per-
formance objectives. For example, if incinerator furnace
volumes are not related to any specific criteria such as accept-
able heat-release rates or if waste loaders or ash removal sys-
tems are not suitable for the operating schedules or rigors of
operation expected, then the system design clearly is
inadequate.
5.2.2 Fabrication and/or Installation Deficiencies
The incinerator may be deficient because of inferior workman-
ship and/or materials used either in the fabrication or installa-
tion of the system. The qualifications of the incinerator
contractor relate to how serious these deficiencies could be.
Unqualified contractors may be unable to or uninterested in
providing a system that meets the specified criteria, either be-
cause of inexperience or disregard for criteria that differs from
their "standard way of doing business or furnishing equip-
ment" Even the most experienced and qualified contractors
deviate to some extent from design documents or criteria, be-
cause no "standard" or "universal" incineration systems exist,
and various substitutions may be proposed. These variations
must be evaluated carefully to determine whether they comply
with construction criteria and reflect proven design and ap-
plication. If these variations are not properly assessed, unfor-
tunate consequences could ensue.
The number and severity of fabrication and installation
deficiencies also relate directly to quality control during con-
struction. Contractor submittals should be reviewed before
equipment is delivered, site inspections should be made during
construction to detect possible deficiencies, and specific
operating and performance testing should be performed before
final acceptance. Some of the common reasons for fabrication
and installation deficiencies are: .
• An unqualified vendor (manufacturer).
• An unqualified installation contractor.
• Inadequate guidance from the manufacturer to the instal-
lation contractor.
• No clear lines of responsibility between the manufac-
turer and the installation contractor.
• Failure to review manufacturer's drawings, catalog cuts
and materials, and construction data to ensure com-
pliance with design documents.
• Inadequate quality control during and after construction.
• Failure to relate payment schedules to system perfor-
mance milestones.
• Failure to require final acceptance testing.
5.2.3 Operation and/or Maintenance Deficiencies
Successful performance of any incineration system ultimately
depends on the abilities, training, and dedication of the
operators. Unqualified, uncaring, poorly trained, and unsuper-
vised operators could impair system performance in the
shortest time. Incinerators operate under severe conditions and
require frequent adjustments and routine preventive main-
tenance to provide good performance. If regular adjustments
and maintenance are not included in planning and budgeting,
the incineration system will provide increasingly poor perfor-
mance and equipment deterioration will be accelerated.
Operating incineration equipment until it breaks down results
in extensive, costly repair work and substantially reduces
equipment reliability. The common operational and main-
tenance deficiencies that could affect incineration system per-
formance are summarized below.
• Unqualified operators.
• Negligent, irresponsible, or uncaring operators.
• Inadequate operator training programs.
• Failure to maintain recordkeeping or operating logs to
monitor and verify performance.
• Inadequate supervision.
• Failure to perform periodic inspections, adjustments, and
preventive maintenance.
• Using equipment that, requires repairs or maintenance
work.
5.2.4 Avoiding Incineration System Deficiencies
To procure a good incineration system, four basic principles
should be understood.
• Incineration technology is more of an art than a
science—no textbook formulas can guarantee a success-
ful system.
• There is no "universal" incinerator. Incinerators must be
selected, designed, and built to meet each facility's
specific needs.
• There is no "typical" application. Even similar types of
institutions have wide differences in waste types and
quantities, waste management practices, space availability,
etc.
• Incinerator manufacturers differ widely in capabilities
and qualifications.
Based on these principles, six steps for implementing a suc-
cessful incinerator project are outlined in Table 5-3. If these
steps are followed, incinerator deficiencies should be mini-
mized or eliminated, leading to an increased likelihood of a
successful incinerator system installation.6
5.3 Training, Safety, and Operations
A comprehensive training program for incinerator operators
is a key part-of any waste management plan for onsite
37
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Table 5-3. Recommended Incineration System Implementation Steps
Step One
Evaluations .
and
Selections
Collect and
consolidate waste,
facility, cost, and
regulatory data
Identify and
evaluate options
and alternatives
Select system and
components
Step Two
Design
(contract)
Documents
Define wastes to be
incinerated-avoid
generalities and
ambiguous terms
Specify
performance
requirements
Specify /u//work
scope
Specify minimum
design and
construction criteria
Step Three j
Contractor
Selection
Solicit bids from
prequalified
contractors
i
Evaluate bids on
quality and '
completeness-not
strictly least cost
Evaluate and
negotiate proposed
substitutions^ and
deviations t
t
Negotiate payment
terms I
Consider !
•performance
bonding
Step Four
Construction
and Equipment
Installation
Establish lines of
responsibility
Require shop
drawing approvals
Provide inspections
during construction
and installation
Step Five
Startup and
Final
Acceptance
Use "punch-out"
system for contract
compliance
Require
comprehensive
testing: system
operation,
compliance with
performance
requirements, and
emissions
Obtain operator
training
Step Six
After
Final
Acceptance
Employ qualified
and trained
operators
Maintain operator
supervision
Monitor and record
system operations
Provide regular
inspections and
adjustments
Implement
preventive
maintenance and
prompt repairs —
consider service
contracts
Source: Reference 6.
incineration. Operators must be properly trained to minimize
worker exposure to infectious waste, to minimize incinerator
emissions, and to promote safe operation of the incineirator.
The first step in developing a training program is to work with
safety and operating information provided by the manufac-
turers of the incineration and air pollution control systems. Ex-
isting safety procedures in place at the institution also should
be reviewed. Regulations and accreditation requirements such
as OSHA and JCAHO safety precaution and emergency
response plans should be included. The operator training
program should include all these types of information. The
goal of any incinerator operator training program should be to
promote personal safety, safe operation of the incinerator, fire
safety, and proper operation and maintenance of the in-
cinerator to minimize emissions and ensure good ash quality.
5.3.1 Personal Safety
Personal safety can be ensured by training all incinerator
operators to minimize handling of medical waste and to wear
proper personal protective equipment (PPE) during all phases
of waste handling and incinerator operation and maintenance
procedures. Training should include use of PPE (thick rubber
gloves, hard-soled rubber shoes, and safety glasses) as well as
procedures to maintain the integrity of medical waste con-
tainers. ;
i
5.3.2 Equipment Safety Procedures
In addition to procedures recommended by manufacturers,
employees must be trained to observe proper cautionary proce-
dures when feeding waste to the incinerator (e.g., containers of
flammable liquids or explosives should not be fed into the in-
cinerator), when opening the charging door or cleanout ports,
when working around any hot-surface area, and when under-
taking any maintenance that involves entering incinerator
chambers or other enclosed spaces (e.g., lockout procedures
and "buddy" system) to avoid starting up equipment while
operators are repairing it. Proper cautionary procedures also
should be followed around air pollution control devices to
avoid caustic burns from scrubber water treatment systems,
and accidents involving dust inhalation, explosions, oxygen
deficiency, exposure to heat stress, or exposure to toxic chemi-
cals when maintaining fabric filters.
5.3.3 Fire Safety
Fire safety is particularly important when working around in-
cinerators because of the high temperatures associated with the
combustion process. Operators should be trained to exercise
caution in three areas: waste storage, waste charging to the in-
cinerator, and ash removal. Waste should be stored away from
the incinerator and ash storage areas to prevent access block-
age and premature ignition of waste by stray sparks or burning
flyash. Waste charging is particularly hazardous, although
some equipment is installed with various types of safety equip-
ment to mitigate problems. These problems include burning
wastes sticking to charging rams, which then draw the waste
out of the incinerator, thereby setting fire to wastes in the
charging hopper. Ash handling is another critical area where
operators must be trained to avoid fires and burns. Ash may
contain hot spots, thus operators should wear all proper PPE
and be alert to burning embers during ash handling procedures.
5.3.4 Proper Operation and [maintenance (O&M)
In addition to training operators to operate and maintain all
equipment safely, the operators also must be taught proper
operation and maintenance of the incineration and air
pollution control equipment so as to minimize pollutant
38
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emissions from the incinerator. Most of the information
needed to teach proper operation and maintenance is obtained
from the manufacturers; general training includes how to inter-
pret monitoring and control instrumentation, how to adjust in-
cineration and air pollution control operations, diagnostic
procedures to be followed, and proper maintenance schedules
to be undertaken.*
Proper incinerator operation depends on maintaining proper
operating conditions that are commonly monitored. The
parameters that are frequently monitored include temperature, •
pressure, oxygen, carbon monoxide, opacity, and charge rate.
Carbon monoxide levels provide indications of whether com-
plete combustion is occurring. If carbon monoxide levels are
excessive, emissions of other, more objectionable pollutants
are likely. Measurements of temperature and oxygen often are
used by the incineration system automatically to adjust
combustion-air inputs and auxiliary fuel rate.
Proper APC system operation depends on several factors that
often are monitored as well: pressure and pressure drop, scrub-
ber liquid flow, scrubber liquid pH, and temperature. For ven-
turi scrubbers, pressure drop and scrubber liquid flow usually
are controlled automatically. Control of pH is necessary to
prevent damage to the scrubber, and temperature control is
necessary in fabric filters to prevent damage from condensed
acid gases or excessive heat.
Operators should be trained to diagnose various operating
problems that contribute to excessive incinerator emissions.
For example, excessive stack emissions from controlled-air in-
cinerators may be caused by the following problems:
*Since the completion of this seminar, EPA has published an O&M handbook
for medical hospital incinerators8 and has developed a basic operator training
course.29 The American Hospital Association also has developed a 4-day
course entitled Incinerator Operator Training for Medical Waste and Small
Volume Waste Combustors.
• Setpoint for the secondary burner temperature is not high
enough.
• Excessive negative draft in the primary chamber.
• Excessive infiltration air from the charging door.
• Excessive underfire ah- from the primary chamber;
• Operating at a primary-chamber temperature that is too
high.
• Overcharging.
• Problem wastes.
• Inadequate secondary combustion air.
Operators should know symptoms of poor operation, such as
the emission of black or white smoke, to pinpoint the exact ad-
justments that must be made for proper operation and emission
control. For example, black smoke from a controlled-air in-
cineration system indicates incomplete combustion. Adjust-
ments to ensure complete combustion must be made. White
smoke may indicate the presence of small aerosols in the ef-
fluent gas that can be caused by too much excess air either
entraining small particles or cooling the combustion gases
prematurely.
Knowledge of maintenance schedules for both incinerator and
APC equipment is critical to the proper maintenance and
operation of incinerators to avoid emission problems. In-
cinerators that are operated until they break down generally
perform poorly. Air pollution control equipment that is becom-
ing clogged with particulates or suffering from corrosion,
erosion, or scaling cannot operate as efficiently as properly
cleaned and maintained equipment. Effective preventive main-
tenance and replacement or repair of damaged equipment will
help ensure efficient, clean operation of medical waste
incineration systems.
39
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Chapter 6
References
When an NTIS number is cited in a reference, that reference is
available from: !
National Technical Information Service
5285 Port Royal Road
Springfield, VA 22161
(703)487-4650
i
1. U.S. EPA. Medical Waste Management in the United
States. First Interim Report to Congress. EPA/503rSW-
90-051A, Office of Solid Waste, Washington, DC, May,
1990. [
t
2. U.S. EPA. Medical Waste Management in the United
States. Second Interim Report to Congress. EPA/530-SW-
90-087A, Office of Solid Waste, Washington, DC,
December, 1990.
3. Government Accounting Office (GAO). Medical Waste
Regulation: Health and Environmental Risks Need T\o Be
Fully Assessed. GAO/RCED-90-86, Washington, \ DC,
March, 1990.
4. U.S. EPA. Seminar—Medical and Institutional Waste In-
cineration: Regulations, Management, Technology, Emis-
sions, and Operations. Center for Environmental
Research Information, CERI 89-247, Cincinnati, OH,
November, 1989. i
5. Doucet, L.G. Infectious Waste Treatment and Disposal
Alternatives. Presented at the Symposium on Infection
Control: Dilemmas and Practical Solutions, November 3-
4,1988, Philadelphia, PA. Sponsored by the Eastern t>en-
nsylvania Branch of the American Society | for
Microbiology, June 12, 1989. Paper included in Refer-
ence 4. '
6. Doucet, L.G. State-of-the-Art Hospital and Institutional
Waste Incineration: Selection, Procurement, and Opera-
tions. Presented at the 75th Annual Meeting of the As-
sociation of Physical Plant Administration of Universities
and Colleges, Washington, DC, July 24,1988. Revised,
updated, and issued as a Technical Document (No.
055872) through the American Society for Hospital En-
gineering, January 1986. Paper included in Reference^.
7. Doucet, L.G. Hospital/Infectious Waste Incineration
Dilemma and Resolutions. Presented at First National Sym-
posium on Incineration of Infectious Waste, Washington,
DC, May, 1988. Included as paper in Reference 4.
8. U.S. EPA. Handbook: Operation and Maintenance of
Hospital Medical Waste Incinerators. EPA/625/6-89-024,
Office of Air Quality Planning and Standards, Research
Triangle Park, NC, and Center for Environmental Re-
search Information, Cincinnati, OH, January, 1990.
9. Corbus, D. Medical Waste Incinerator Emissions and Air
Pollution Control. Prepared by Doucet and Madnka for
EPA's Center for Environmental Research Information,
Cincinnati, Ohio, December, 1990.
10. U.S. EPA. EPA Guide for Infectious Waste Management.
EPA/500-SW-86-014, NTIS PB86-199130, Office of
Solid Waste and Emergency Response, Washington, DC.
May, 1986.
11. Medical Waste Tracking Act of 1988. Public Law 100-
582. EPA/530-SW-89-008, Washington, DC, November 1,
1988.
12. U.S. EPA. Tracking Medical Wastes. EPA/530-SW-89-
020, Office of Solid Waste, Washington, DC, May, 1989.
13. U.S. EPA. Background Document, Resource Conserva-
tion and Recovery Act, Subtitle. J—Demonstration Medi-
cal Waste Tracking Program, Section 11003 Tracking of
Medical Waste, 40 CFR Part 259, Subparts E-J. Office of
Solid Waste, Washington, DC, 1988.
14. Lee, C. C. Environmental Engineering Dictionary.
Governmental Institute, Inc., 966 Hungerford Drive, No.
24, Rockville, MD 20850, 1989. As cited in Lee, Huf-
fman, and Nalesnik, Summary of Current Medical Waste
Management Knowledge. U.S. EPA, Office of Research
and Development, Risk Reduction Engineering
Laboratory, Cincinnati, OH, January, 1990.
15. U.S. EPA. Managing and Tracking Medical Wastes—A
Guide to the Federal Program for Generators. EPA/530-
SW-89-021, Solid Waste and Emergency Response,
Washington, DC, September, 1989.
40
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16. Code of Federal Regulations. 40 CFR Parts 260 to 265.
17. Code of Federal Regulations. 10 CFR Part 20.
18. Federal Register, Vol. 54, No. 102, pp. 22875-23192,
May 30,1989.
19. CDC. Guideline for Handwashing and Hospital Environ-
mental Control. NTIS PB85-923404,1985.
20. CDC. Recommendations for Prevention of Human Im-
munodeficiency Virus (HIV) Transmission in Health Care
Settings. Morbidity and Mortality Weekly Report, Vol.
36, August 21,1987.
21. National Institutes of Health (NIH). Internal Standard
Operating Procedures. NIH, Bethesda, MD, 1989.
22. Joint Commission on Accreditation of Health Care Or-
ganizations (JCAHO). JCAHO Accreditation Manual for
Hospitals. Volume 1—Standards. JCAHO, Oakbrook Ter-
race, IL, 1991.
23. Incinerator Institute of America (IIA). Incinerator Stand-
ards. IIA, New York, NY, 1968. As cited in Reference 6.
24. Block, S.S. Disinfection, Sterilization, and Preservation.
Lea and Febiger, Philadelphia, PA, 1977. As cited in Ref-
erence 6.
25. Medical SafeTec, Inc. Catalog. Indianapolis, IN, undated.
As cited in Reference 6.
26. Cross, F.L., Jr. Comparison of Disposal Techniques for
Infectious Waste. Infectious Disposal Conference,
Washington, DC. As cited in Lee, Huffman, and
Nalesnik, 1990. Summary of Current Medical Waste
Management Knowledge. U.S. EPA, Office of Research
and Development, Risk Reduction Engineering
Laboratory, Cincinnati, OH, January, 1990.
27. McRee, R. Operation and Maintenance of Controlled Air
Incinerators. Joy Energy Systems, Inc., Charlotte, NC,
undated. As cited in Reference 4.
28. C. E. Raymond, Inc., Chicago,. EL, undated. As cited in
Reference 4.
29. U.S. EPA. Hospital Incineration Operator Training
Course Manual EPA 450/3-89-004, NTIS PB 89-189880,
Research Triangle Park, NC, March, 1989.
30. Code of Federal Regulations. 40 CFR Part 61.
31. Maxwell, W.H. Development of New Source Perfor-
mance Standards for Medical Waste Incinerators.
Presented at the Medical Waste Management Workshop.
Sponsored by the Air and Waste Management Associa-
tion, American Industrial Hygiene Association and Mid-
west Research Institute, September 18-19, 1989, Overland
Park, KS. As cited in Lee, C. C., G. L. Huffman, and R.P.
Nalesnik, 1990. Summary of Current Medical Waste
Management Knowledge, U.S. EPA, Office of Research
and Development, Risk Reduction Engineering Laboratory,
Cincinnati, OH, January, 1990.
32. Anderson 2000, Inc. Catalog. Peachtree City, GA, un-
dated. As cited in Reference 4.
33. Energy and Environmental Research Corporation. State-
of-the-Art-Assessment of Medical Waste Thermal Treat-
ment. Energy and Environmental Research Corporation,
Irvine, CA, December, 1989. As cited in Reference 9.
34. U.S. EPA. Control Techniques for Paniculate Emissions
from Stationary Sources, Volume 1. EPA-450/3-81-
0005a, NTIS PB 83-127498, September, 1982. As cited in
Reference 4.
35. American Hospital Association (AHA). Incinerator
Operator/Training for Medical Waste and Small Volume
Waste Combusters. Prepared by Calvin R. Brunner and
Doucet and Mainka, P.C., for American Hospital
Association, American Society for Hospital Engineering,
American Society for Healthcare Environmental Services,
and Washington State Hospital Association. AHA, Deer-
field, EL, October-December, 1991.
41
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