FILE
UNITED STATES ENVIRONMENTAL PROTECTION AGENCY
WASHINGTON. D.C. 204SQ
'December 15, 1989 EPA-SAB-EC-tO-004
Honorable William K. Reilly
Administrator
U.S* Environmental Protection Agency
401 M street, S»W,
Washington, D.C. 20460
OSW's Proposed Controls for
Hazardous Waste Incinerators
Products of
Dear Mr. Reilly:
The Science Advisory Board's Products of Incomplete Combustion
Subcommittee has reviewed the feroposed Controls for. Hazardous Waste
Incinerators^Products of Incomplete Co.mb_us_tion fPICs) for the
Office of Solid Waste. The Office of Solid Wast® seeks to propose
and promulgate rules which amend existing standards fo? boilers and
industrial furnaces burning hazardous wastes fuels and for all
hazardous waste incinerators. The Science Advisory Board was asked
to address three questions:
l. Whether limiting carbon monoxide (CO) and total
hydrocarbons {THC) is a reasonable approach to control
emissions of PICs, given the current data base and
statutory time constraints?
2. What is the feasibility of monitoring THC to determine
to the aggregate emission rate of organic compounds?
3. Whether the proposed approach to assess the health
risk from THC emissions is reasonable given the
current data base and statutory time constraints?
To address these questions, the Subcommittee reviewed the
documentation provided on PICs controls and held open meetings
December 14 and IS, 1988, and January 26 and 27, 1989, in
Washington, D.C. A final publicly announced meeting vas held
September 15, 1989 by conference call.
The Subcommittee also addressed; atmospheric dispersion
simulation, selection of CO and THC concentration limits, selection
of averaging methods and periods, alternate control approaches and
research iieerk .
The proposal for controls was made even though OSW has not
established that emission of PICs from hazardous waste incinerators
currently pose a substantial risk. EPA's risk assessments indicate
that emission of jPICs at currently measured level* are not likely
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to produce significant human health effects. However, since the
current DR1 standard applies only to designated POHCs, a 4-nines
(99.i9%) DUE does not preclude the possibility that emission of
PICS could present significant human health risk
The Subcommittee findings and recommendations are found in the
attached report. The Subcommittee would like to emphasize that,
while the concept of using CO and/or THC concentrations to control
incinerator operations is reasonable, their use to reduce the risk
posed by the emission of PICs is based on policy rather than on
science, because of limited data. In addition, there is a
technical obstacle to the implementation of this concept if co
alone is controlled. When CO is high, THC (a surrogate for PICs)
may be high or low? this lack of correlation at high concentrations
of CO limits the usefulness of CO alone as an operational control
for emission of PICs. Thus at high CO 'concentrations, a better
measure of PICs is THC.
Due to the limitations of the emissions data and the large
degree of uncertainty introduced by the various assumptions
employed in the risk assessment methodology, the Subcommittee
considers the methodology only sufficient to provide a risk-based
check on the proposed THC emissions limit used when CO
concentrations are high. Further, the Agency's evaluation of the
emissions limit provides some evidence of adequate safety,
However, the risk assessment is not sufficient for site-specific
applications.
The SAB would like to compliment the Office of Solid Waste
staff and that of the Atmospheric Research and Exposure Assessment
Laboratory for their active and helpful participation in. our review
of the PICs issues.
The Science Advisory Board is pleased to have been invited to
review this important issue and looks forward to a written response
from EPA on the implementation of the Board's recommendations.
Sincerely,
Raymond CTtbehr, Chairman
Executive Committee and
chairman, Products of
Incomplete Combustion
Subcommittee, Science
/loft ftrfrtung,
Vic* Chairman, Products of
Incomplete Combustion
Subcommittee
cc: D. Barnes, J. Berlow, D. Bussard, J. cannon, J. Denit,
S. Garg, R..Hoi 1 away, D. Hlustick, S. Lowrance
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REPORT OF THE
PRODUCTS OF INCOMPLETE COMBUSTION SUBCOMMITTEE
SCIENCE ADVISORY BOARD
U.S. ENVIRONMENTAL PROTECTION AGENCY
REVIEW OF THE
OFFICE OF SOLID WASTE
PROPOSED CONTROLS FOR HAZARDOUS WASTE INCINERATORS:
PRODUCTS OP INCOMPLETE COMBUSTION
October 24, Ifif
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ABSTRACT
*
The Products of Incomplete Combustion (Pics) Subcommittee of
the EPA's Science Advisory Board reviewed the Office of Solid
Waste's (OSW) proposal to control emissions of PICS from haiardous
waste incinerators by instituting process controls based on Co and
THC emission concentrations. Because compounds known to cause
adverse human health effects have been detected at very low
concentrations in FXCs, it is prudent to take precautionary
measures to control PICs. However, the linkages between emission
concentration, exposure, and effects {health and environmental)
were not documented.
The proposal for controls was made even though QSW has not
established that emission of PICs from hazardous waste incinerators
currently pose a substantial risk. EPA's risk assessments indicate
that emission of PICs at currently measured levels are not likely
to produce significant human health effects. However, since the
current ORE standard applies only to designated PQHCs, a 4-nines
(99,99%) ORE does not preclude the possibility that emission of
PICS could present significant human health risk.
The concept of using CO and/or THC as guidance for incinerator
operational control is reasonable. The concentration limits for
CO and THC, the averaging methods, and the averaging periods EPA
.chose were selected on the basis of informed judgments using the
best available data.
Continuous emissions monitoring for THC with a cold system
appears to be practical for routine operations. Because
incinerators may emit more PICs when upset from changes in waste
quantity or composition that can result from abrupt waste feed
shutoff, a poorly implemented, automatic shutdown strategy has the
potential to create more pollution than it stops.
The Subcommittee found the data base characterizing PICs in
emissions would not allow a correlation to be established with CO
or THC levels for various combustion devices and/or conditions.
The sparseness of data introduces large uncertainties into EPA's
risk assessment. This uncertainty limits the usefulness of one
approach proposed by OSW to control THC emissions—using site-
specific quantitative risk assessment to establish acceptable THC
emission rates* Despite the limitation* of the risk assessment
methodology, however, the Subcommittee considers the methodology
sufficient to provide a risk-based check on an alternative proposal
by OSW—limiting THC concentrations to levels representative of
good operating practice.
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NOTICE
This report has been written as part of the activities of
the Science Advisory Board, a public advisory froup providing
extramural scientific information and advice to the Administrator
and cither officials of the Environmental Protection Agency, The
Board is structured to provide a balanced expert assessment of
scientific matters related to problems facing the Agency. This
report has not been reviewed for approval by the Agency? hence,
the contents of this report do not necessarily represent the views
and policies of the Environmental Protection Agency or of other
Federal Agencies. Any mention of trade names or commercial
products do not constitute endorsement or recommendation for use.
ii
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U.S. ENVIRONMENTAL PROTECTION AGENCY
SCIENCE ADVISORY BOARD
Products of Incomplete Combustion (PlCs) Subcommittee
Chairman
Or. Raymond c, Loehr
H* M. Alharthy, Centennial Chair in civil Engineering
8.614 EOJ Hall
University of Texas
Austin, TX 7S712
Vice-chairman
Dr. Rolf Hartung
Professor of Environmental Toxicology
School of Public Health
University of Michigan
3125 Fernwood Avenue
Ann Arbor, Michigan 48108
Members
Dr. Walter F, Dabberdt
Senior Manager and Scientist
National Center for Atmospheric Research
Atmospheric Technology Division
Post Office Box 3000
Boulder, CO 80307-3000
Dr. Richard Denison
Senior Scientist
Environmental Defense Fund
isis p street, M.W.
Washington, D.c. 20036
Dr. Judith Harris
vice President
Arthur 0* Little, Inc.
15W-315 Acorn ParJc
Cambridge, MA 02140
Dr. Robert J. Huggett
Professor of Marine Science
Virginia Institute of Marine Science
College of William and Mary
Gloucester Point, VA 23062
iil
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Dr. Kun-ehieh Lee
Engineering Scientist
union Carbide Corporation
Post office BOX 8361
South Charleston, wv 25303
Dr, Morton Lippmann
Institute of Environmental Medicine
Hew York University
Lanza Laboratory
Long Meadow Road
Tuxedo, New vork 10987
Mr, Charles 0, Velzy
Velzy/Weston
355 Main Street
Armonk, New York 10SQ4
Dr. Adel Sarofim
Department of Chemical Engineering
Massachusetts Institute of Technology
Cambridge, MA 02139
Executive
Dr. K. Jack Kooyoomjian
Science Advisory Board
U.S. Environmental Protection Agency
401 M Street, S,W. - A1Q1F
Washington, D.C. 20460
SJ^aff Secretary
Mrs. Marie Miller
Science Advisory Board
U.S. Environmental Protection Agency
401 M Street, S.W. - A101P
Washington, D.C. 20460
Deputy Director^ .Science Advisory Board
Mrs, Kathleen W, Conway
O.S, Invironmentml Protection Agency
401. It Str«*t, S.W. - A101F
Washington, D.C. 20460
Science Advisory Board
Dr. Donald G. Barnes
U.S. Environmental Protection Agency
401 If Street, S.W. - A101F
Washington, D.C. 20460
IV
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TABLE OF CONTENTS
1. EXECUTIVE SUMMARY ,...........,...,„".. 1
2. BACKGROUND ....................... 4
2.1 Process ,,...„,. ... 4
2,2 The Charge for the Pica Subcommittee , 5
2.3 Regulations ....... , g
2.4 Technical ....... ....... 7
2.4.1 Chemistry ..,.„,. 7
2.4.2 Incinerators 7
2.4.3 . Measurements ............ 8
2.4.4 Risk Reduction, Upsets, and
Emissions .*...,«.,.... 10
2.4.5 Pics in Perspective 10
3. RESPONSE TO THE FIRST QUESTION . 14
3.1 Comments on the General Concept . . » 14
3.2 The Critical Linkage Between EPA's Proposed Two-Tier
Approach and the capability for Continuous or
Frequent THC Monitoring . . ...,»» 15
3.3 current Available Data Correlating CO and organic
Emissions ..................... is
3.3.1 Investigations of Potential
Correlation of CO with Specific
PlCs; .,....,....,».. 16
3.3.2 Investigations of Potential
Correlation of CO with DRE at Low CO
Levels s 17
3.3.3 Investigation of Potential
Correlation of CO and THC ..... 17
3.4 Summary i?
4. RESPONSE TO THE SECOND QUESTION . ....... 18
4.1 Availability of "Total Hydrocarbon" Monitor .... is
4.2 Availability of a Sampling System 19
4.3 Ruggedness (Operability and Maintainability) of THC-
CEM Systems .................... 20
4,4 Documentation of THC-CEM System Feasibility ...» 21
4.5 Summary * 22
5. RESPONSE TO THE THIRD QUESTION 23
5.1 A Brief Description of EPA's Risk Assessment and Two
Regulatory Approaches .......... 23
5.2 Discussion of Assumptions Used in Risk Assessment . 25
5.3 Evaluation of the Risk Assessment 28
543.1 Is the Use of the Risk Assessment
Methodology Reasonable and
Appropriate as A Risk-Based Check on
the Proposed Technology-THC Limit
(20 ppm)? ............. 23
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5.3.2 Is the Ose of the Risk Assessment
Methodology in Site-Specific
Assessments Reasonable and
Appropriate to Support Facility
Operation at CO Levels in Excess of
100 ppm? . . . , , * . « 29
5.4 Summary . . ,.........„...„ 29
6. VIEWS OH OTHER TECHNICAL ISSUES ............. 30
6*1 Risk Assessment and Exposure Modeling
Considerations .................. 30
6.1.1 Atmospheric Dispersion Simulation . 30
6.1.2 Recommendations .......... 31
6.2 Selection of CO and THC Levels 32
6.3 choice'of Averaging Method ............ 36
6.4 Alternative Approaches ......... 37
6*4.1 Alternative Measures of
Performance ............ 37
€.4.2 Alternative Actions ,....,.. 38
6.5 Research Needs .................. 38
7. CONCLUSIONS AND RECOMMENDATIONS ............. 41
7.1 Conclusions .................... 41
7.2 Recommendations .................. 44
APPENDIX A—Discussion of Averaging
APPENDIX B—Letter from R. Denision
APPENDIX C—Comments from P. Deisler
APPENDIX D—Glossary of Terms
APPENDIX E —References
vi
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List of Ficnirss and Tables
Figure A - Benzene (a PIC) Concentration Versus Those of
CO (bottom scale) and THC (top scale).*...*.... 12
Figure B - Vinyl chloride Concentration versus Those of CO
(bottom scale) and THC (top scale)..,,,.. ,. 13
Figure C - Methyl Chloride Concentration Versus Those of CO
(bottom scale) and THC (top scale)......,»,,.,.. 12
Figure D In-Situ CO Monitoring Data and Rolling Hour
Average Data Uneorrected for Moisture and Oxygen
at A Multipurpose Rotary Kiln Incinerator
(Plant A) ................. ,. 35
Figure A-l Ditto ,,»», „ ...» A-3
Figure A-2 Extractive co Monitoring Data Uncorrected for
oxygen at a Multipurpose Rotary Kiln Incinerator
(Plant B) ...... A-4
Figure A-3 Extractive CO Monitoring Data Corrected for
Oxygen with Four Rolling Average scenarios, for
A Multipurpose Rotary Kiln incinerator (Plant C) A-s
Figure A-4 Extractive CO Monitoring Data Uncorrected for
Oxygen at a Multipurpose Multiple-Chamber
Incinerator (Plant D)...................... A-7
Figure A-5 instantaneous CO Monitoring Data Corrected for
Oxygen at a Multipurpose Rotary Kiln Incinerator
(Plant C) ,.,, .A-IO
Figure A-6 Four Rolling Average Scenarios for co Monitoring
Data Shown in Figure p-a (Plant C) -A-ll
Table I The Number of Appendix VIII Compounds Used to
Calculate the THC Unit Risk Value and the Basis
for Their Assumed Concentrations..................24
Table II Incinerator CO/THC/Oata from Research Tests....... 3 3
Table A-I Relationship Between the Ratio of Geometric
Average (GA) and Arithmetic Average (AA) and the
Standard Derivation(s) at Three Observed CO
Hourly AA Levels Shown in Figure F...............A-9
vii
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1. EXECUTIVE SUMMARY
At the request of the Office of Solid Waste (QSW) , the Science
Advisory Board's products of Incomplete Combustion (PIC)
Subcommittee reviewed the approach OSW proposed in June 1988 for
the control emission of PICs. The Subcommittee was charged to
address the following three questions:
1, Whether limiting carbon monoxide (CO) and total
hydrocarbons (THC) is a reasonable approach to control
emission of PICs, given the current data base and
statutory tine constraints,
2. What is the feasibility of monitoring THC to determine
the aggregate emission rate of organic compounds?
3. Whether the proposed approach to assess the health risk
from THC emissions is reasonable given the current data
base and statutory time constraints?
The Subcommittee also addressed; atmospheric dispersion
simulation, selection of CO and THC concentration limits, selection
of averaging method and period, alternate control approaches, and
research needs.
The Subcommittee's task was to review the documents provided,
to provide advice on the technical and scientific adequacy of the
indicated approaches, and to suggest how to improve the approaches.
The task was not to provide on-going continuing oversight of the
EPA effort as it may have evolved since the Subcommittee meetings.
Agency staff were present at the Subcommittee meetings,
participated in the discussions and heard the comments of the
Subcommittee members. In addition, Agency staff were provided with
drafts of this report as it was being prepared. This report has
been compiled from information obtained and discussions held at
the Subcommittee meetings (including the publicly announced
conference call meeting of September 15), from written comments
submitted by the subcommittee members and from comments supplied
from the members mm they reviewed earlier drafts of this report.
The data base on PICs is sparse particularly for full-scale
incinerator*. (Notes In this report the terms "PICs11 and "THC11
refer to emissions of residual organic compounds and include toxic
compounds Stteh as chlorinated dioxins and benzene as well as non-
chronically toxic compounds such as ethane and methane.) Those
emissions which have been characterized have shown that individual
PICs are present over a wide range of concentrations. Likewise,
the potential toxieities of the PICs differ over a wide spectrum
of concentrations. Under good combustion conditions, the
concentrations of individual measured PICs have been found to be
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relatively low in relation to the known toxic concentrations, the
correlation of CO, THC, or other parameters with combustion
efficiency and PICs emission concentration is weak for some
conditions and for some combustion devices. The relationship
between THC and emission of PICs below levels of public health
concern for hazardous waste incinerators indicates that at low CO
concentrations (less than 100 ppm) THC emissions are low (less
than 20 ppm). At higher CO concentrations, THC may or may not be
high.
Compounds known to cause adverse health effects are among the
PICs detected in the ppb and ppt range in actual incinerator
emissions. One risk assessment, based on measured emission levels
and employing conservative assumptions, suggests that PICs do not
pose a significant health risk.(2,7) This risk assessment,
however, considered only organic compounds in the emissions that
were actually identified and quantified (for example, these ranged
from 1% to €0% of the total organic emissions at a specific site),
and was limited to the direct inhalation route. Environmental
risks and human health risks resulting from indirect routes of
exposure have not been assessed.
Plant upsets can increase emission of PICs. Therefore, any
proposed controls should minimize unnecessary waste feed shutoffs
which may result in upsets; otherwise, the controls may cause more
pollution than they prevent, osw's approach can result in
automatic shutdowns and plants may be upset by sudden changes in
the amount or composition of waste or auxiliary fuel burned,
Parameters used for control must relate to actual emission of PICs
and be practical as well if they are to be of use. oxygen
monitoring, frequent periodic testing for THC and other factors
discussed in the report may be additional guides for operational
controls. The appropriate control parameter and level may vary by
class of combustion device.
Because the available database on CO and organic emissions
shows CO does not correlate well with THC at high CO
concentrations, reliance on controlling CO alone would have serious
limitations.
While EPA1* risk assessment approach in this case follows
previously accepted methodologies, the Subcommittee believes that
it lacks both the precision and accuracy needed to be useful in a
site-specific regulatory context. Given the assumptions and
uncertainties, it im the judgment of the Subcommittee that it is
not possible to calculate total THC risks reliably and that at
present th* method is not suitable for setting site-specific limits
based upon THC levels alone*
Due to the limitations of the emissions data and the large
degree of uncertainty introduced by th« various assumptions
employed in the risk assessment methodology, the Subcommittee
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considers the methodology only sufficient to provide a risk-based
check on the proposed THC emissions limit. Further, the Agency's
evaluation of tile emissions limit provides some evidence of
adequate safety. The concept of using CO and/or THC to control
PICs is reasonable.
The Subcommittee addressed research needs. Since only a small
fraction of the total number of compounds produced during upset
conditions can be monitored, there is a need to relate the simple
measures of emissions produced by a CO, THC, or other detection
surrogates to risk. Emission of PICs from incinerators are a
potential problem that forms part of the broader problem of organic
emissions from combustors. Comparative emissions and risk
assessments of different combustion categories would be desirable
in order to assign priorities for risk reduction measures.
Overall, the Subcommittee believes that the general concept
of using CO and THC for the purpose of ensuring that PIC emissions
are below levels of public health concern is reasonable. The
Subcommittee, however, is concerned about the averaging method, the
averaging period, and the concentrations chosen for the CO and THC
standard. The Subcommittee understands that these parameters and
values were chosen primarily based on informed judgments using the
best available data. However, the supporting documentation does
not convincingly demonstrate that a CO concentration of loo ppm is
better than 50 ppm or 150 ppm, nor that a one-hour rolling average
is better than an eight-hour rolling average for CO.
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2. BACKGRGUHD
2.i process
In a memo dated June 28, 1988, Mr. Joseph Cam, Director of
the Waste Management Division of th* Office of Solid Waste (OSW),
requested a meeting with Dr. Donald Barnes, then Acting Director
of the Science Advisory Board, to discuss how and when SAB could
review osw's proposed approach to control the potential for
emissions of products of incomplete combustion (PICs) that occur
during the incineration of hazardous wastes.(57) The memo also
described the basic approach of OSW in the control of potential
PICs. The memo acknowledged that "the approach is based on a
number of assumptions and a relatively thin data base* However,
we know of no viable alternative. SAB comments on improvements to
this approach or alternative approaches to control Pic emissions
would be helpful." Accompanying the memo was a draft of the
proposed rule and supporting background documents for SAB staff
review.
Following initial consideration of the matter, the SAB
Executive Committee approved formation of a "PICs Investigative
Group11 to focus the review and to select reviewers, once the charge
was clear. The PICs Investigative Group was composed of SAB
Executive Committee members, Dr. Raymond Loehr, Dr. Rolf Hartung,
and Dr. Richard Griesemer. Background materials were provided in
July 1988. A teleconference August 30, 1988 sharpened the scope
and focus of the review.
This activity produced a charge (Section 2.2) setting forth
the questions to be addressed by the PICs Subcommittee. The SAB
and OSW agreed this review need not address metals, residues, or
specific organic emissions such as dioxin because of extensive SAB
reviews of single chemical risk assessments and prior reviews of
incineration issues. Participants identified the expertise needed
to address these questions including: engineering,
instrumentation, risk assessment, and human health. The Pics
investigative Group also established a preliminary schedule.
The SAB PICs Subcommittee held its first meeting December 15-
16, 1988, drafted a report, and held a second meeting January 26-
17, 1989, at which the report was extensively revised. Both
meetings were held in Washington and were open to the public. An
additional publicly announced meeting was held by conference call
on September 15, 1989. All revisions made to the report prior to
its submittal to the Executive Committee wer* made by mail and
telephone. The Executive Committee recommended improvements and
considered the report at a public meeting July 17-11, 1989, in
Washington and approved it at a public meeting October 23-24, 1989,
also in Washington.
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The Subcommittee's task was to review the documents ,
to provide advice on the technical and scientific adequacy of the
indicated approaches, and to suggest how to improve the approaches,
The task was not to provide on-going continuing oversight of the
EPA effort as it nay have evolved since the Subcommittee meetings*
Agency staff were present at the Subcommittee meetings,
participated in the discussions and heard the comments of the
Subcommittee members. In addition, Agency staff were provided with
drafts of this report as it was being prepared. This report has
been compiled from information obtained and discussions held at
the Subcommittee meetings (including the publicly announced
conference call meeting of September 15), from written comments
submitted by the Subcommittee members and from comments supplied
from the members as they reviewed earlier drafts o£ this report.
2.2 The charge for the Pies Subcommittee
OSW has developed a regulatory program to control emission of
PICs based on limiting CO and THC concentrations in stack emissions
of incinerators, boilers, and industrial furnaces. In establishing
concentration limits on CO and THC that would ensure emission of
PICs did not pose a significant health risk, OSW developed a risk
.assessment methodology to conservatively estimate the inhalation
risk posed by THC.
OSW requested that the PICs Subcommittee provide comments on
the technical merits of the proposed approach to control emission
of PICs, Specifically, OSW requested comments om
o Whether limiting CO and THC is a reasonable approach to
control emission of PICs, given the current data base and
statutory time constraints?
o what is the feasibility of monitoring THC to determine
the aggregate emission rate of organic compounds?
o Whether the proposed approach to assess the health risk
from THC emissions is reasonable, given the current data
base and statutory time constraints?
2.3 Regulations
Hazardous waste incinerators have been subject to controls
under the Resource Conservation and Recovery Act (RCRA) since 1981.
The- existing regulations control emissions of organic compounds by
requiring a 99.§9% Destruction and Removal Efficiency (ORE) for
Principal Organic Hazardous Constituents (POHC) in the waste feed.
while these standards do not directly control emissions of Products
of Incomplete Combustion (PIC), the quality of operation needed to
achieve a 99.99% ORE also generally results in low emission of
PICs.
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Trial burn data have shown, however, that hazardous waste
incinerators can operate at CO levels indicative of combustion
upset conditions and still achieve 99.99% ORE. Under these high
CO conditions, the EPA is concerned that Pics could -be present at
concentrations that pose unacceptable health risks. Therefore, the
Office of Solid Waste (OSW) proposes to amend the existing
regulations to control emission of PICs from hazardous waste
incineration using the same limits on carbon monoxide (CO) and
total hydrocarbons (THC) that are being proposed for control of
PICs from boilers and industrial furnaces (1 - 5)^
The OSW staff believes that requiring incinerators to operate
at high combustion efficiency will Minimize the potential health
risk posed by emission of PICs. Stack gas CO is a conventional
indicator of combustion efficiency and' a sensitive indicator of
poor efficiency under most combustion conditions. THC is a
surrogate for PICs. When THC is high, CO is always high. However,
when CO is high, THC may or may not be high. THC is currently
measured as part of routine operations at a number of incinerators
and is a better indicator of poor efficiency than CO when CO is
high. Therefore, PICs and thereby the toxic fraction of PICs could
be controlled by ensuring that hasardous waste incinerators operate
at high combustion efficiency through limits on stack gas
concentrations of CO and/or THC.
Studies characterizing Pica formed during the incineration of
hazardous waste largely represent good combustion conditions where
CO and THC are low. While a large fraction (that is, from 40 to
99%) of the hydrocarbon emissions at any particular facility have
not been identified, and health data do not exist for nany of the
compounds that have been identified, many identified hydrocarbons
are known to cause adverse human health effects.(4) EPA's risk
assessments indicate that while emission of PICs at the currently
measured levels are not likely to cause significant human health
problems, the current 4-nines (99.99%) DSS standard could
theoretically allow PICs emission levels which could present
significant human health risks,(2,3,4) These observations are
consistent with the findings of the SAB in its "Report on the
Incineration of Liquid Hazardous Wastes."(7) Given the uncertainty
about the health risk emission of PICs posed, and the strong public
concerns about risks from incineration, OSW believes it is prudent
to institute additional regulatory requirements controls to
minimize the potential for health risks from possible elevated
concentrations of PICs.
The proposal for controls was made even though osw has not
established that emission of PICs from hazardous waste incinerators
currently pose a substantial risk. SPA's risk assessments indicate
that emission of PICs at currently measured levels are not likely
to produce significant human health effects. However, since the
current ORE standard applies only to designated POHCs, a 4-nines
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(99.99%) ORE does not preclude the possibility that emission of
PICS could present significant human health risk.
2.4 Technical
2*4.1 Chemistry
Combustion is a chemical process. In the incineration of
hazardous wastes, waste and air are combined with heat to 'produce
major products, by-products, and unburned wastes. The major
products for incineration are simple molecules such as water,
carbon dioxide, and hydrochloric acid; these simple molecules make
up approximately 99.99% of the emissions. Organic components in
the emissions are generally referred to as "Products of Incomplete
Combustion (PICs)" which include various hydrocarbons (THC)
including chlorinated hydrocarbons, Metals present in the waste
are not destroyed by incineration and will be found in the
emissions and in the residue of incineration.
The incineration of wastes proceeds by means of a series of
complex parallel and sequential processes, including the heating
and volatilization of the waste, mixing of the vapor feed or
volatile products with the oxidant, and the chemical reaction of
the gaseous species. The oxidation reactions may involve several
hundred elementary reactions, but with very few exceptions, carbon
monoxide (CO) is an intermediate product between the carbon in the
waste being incinerated and the most oxidized form of carbon, which
is carbon dioxide (CO2),
On a weight basis, the majority of the PlCs are CO and
methane. (34) The others are trace amounts of the various partially
oxidized organics, polynuclear aromatic hydrocarbons, and
soot.(34,44)
2.4.2 Incinerators
If an incinerator is properly designed and operated to provide
adequate time, temperature and turbulence, the dominant factor
which impacts on the PICs emission level is the excess air or
combustion chamber oxygen level. When there is adequate oxygen
supply in a properly designed combustion chamber or chambers! and
adequate air/fuel mixing, the emission of PICs is extremely ""low,
The concentration* of PICs increase when the oxygen content is
close to the atoichiometric requirement. when less than the
stoichiometric amount of oxygen exists in the combustion chamber,
PICs increase even more.(27)
Very high destruction efficiencies can be attained in the high
temperature oxidizing environment of an incinerator. However, the
destruction of the organic hazardous compounds in a waste does not
guarantee the absence of by-products formed from the waste during
combustion. High concentrations of such products of incomplete
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combustion (PICs) usually are a consequence of a perturbation in
the incinerator operation resulting from rapid transients in feed
rate or composition, failure to adequately atomize a liquid fuel,
excursions in operating temperature, instances where the
combustible mixture fraction is outside the range of good operating
practice, or inadequate mixing between the combustibles and
oxidant. Modern incinerators are equipped with a large combustion
chamber or secondary combustion chamber to minimize the impact of
these perturbations. Waste feed management and- sound process
control systems further reduce or compensate for any adverse
impact. The amount and composition of Pies will depend in a
complex and unpredictable way on the nature of the perturbation.
Current data have indicated that the state-of-art incinerators
can be operated extremely efficiently. Under good combustion
conditions, the combustion efficiency (conversion to C02) is
typically higher than 99.9%. The destruction efficiency of the
parent compounds are typically around f§.999%.
A study of combustion test data obtained from various types
of incinerators, boilers, and process furnaces reveals that under
normal operating conditions, about 80% of the principal organic
hazardous constituents (POHC) and the major compounds in PICs (with
the exception of methane) are found in the flue gas at
concentrations between 0,1 and 20 ppbv.(io» 11, 12, 13, 14, 15, 22,
50, and 51) This relatively narrow concentration range was
observed even though the data were obtained from tests on
facilities of many different designs, operating at different
conditions, burning different types of wastes with different POHC
compounds selected, and operated by different personnel. This
indicates that there is a wide range of designs and operating
conditions which achieve good combustion performance. However, the
compounds that were analyzed in the gaseous emissions were often
limited in number and types,
The flue gas POHC and PiCs levels in state-of-the-art
incinerators, if operated properly, may be limited by reaction and
reactor kinetics, or by som« other typ* of limitation due to
quenching effects. Studies conducted on several new/innovative
incineration technologies indicate that their performance may be
no better than existing incinerators.(11)
2.4.3 Measurements
Emission of PICs composed of thousands of different compounds,
some of which ar* present in very minute quantities and cannot be
detected and quantified without very elaborate and expensive
sampling and analytical (S&A) techniques. Such S&A work is not
feasible in trial bums for permitting purposes and can only be
done in research tests. Very few research tests have been
conducted to date which attempted to identify and quantify all the
PICs in a typical emission sample. Such tests were unsuccessful
8
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because sampling and analysis techniques are not available to
identify or quantify many of the potential compounds emitted, nor
are toxieity data available for all the compounds.(2)
In view of the large number of possible compounds that can be
produced and their presence at concentrations approaching their
practical detection limits, it is at present impractical to design
a monitoring scheme to identify and quantify the individual toxic
compounds in incinerator stack emissions. What is needed is A
robust, continuous monitor to measure a compound or class of
compounds, the concentration of which correlates with those of the
toxic PICs.
Carbon monoxide, being an intermediate in the combustion
process and one for which continuous detectors are available, is
a candidate for such monitoring. The rate of oxidation of carbon
monoxide is slow relative to that of most organic compounds and,
as a consequence, perturbations in combustion conditions, will
usually result in an increase in carbon monoxide concentration well
before tftat of other Pies.(13) CO is expected to persist beyond
the completion of combustion of other combustion intermediates.
Total hydrocarbons (THC) provides an alternative measure of PICs,
because the concentration of THC may better correlate with the
large number of PICs which are hydrocarbons.
The results of several studies on the use of CO and THC as
surrogates for PICs are summarized in a document made available to
the Subcommittee»{3) Figure A from that document (which can also
be found on page 12 of this report) plots the concentration of
benzene as a function of the CO concentration and the total
hydrocarbon concentration for data obtained at several sites.
Benzene was the only compound for which some general correlation
could be found within the data obtained from different facilities.
Whenever the benzene concentration is high, the CO or THC is also
high; however, there are a significant number of measurements in
which the CO or THC concentration is high but the benzene level is
low* These data indicate that the use of CO and THC as a surrogate
for benzene will protect against high levels of benzene, but may
also give false positives, i.e., high readings when the
concentrations of benzene is low. The potential for false
positives is also seen in Figures B and C taken from the same
reference (and which can be found on page 12 of this report)«
Figures B and C plot vinyl chloride and methyl chloride data from
one test facility against the carbon monoxide and THC
concentrations. Since the data came from a single test facility,
there wad no impact of design parameters on the results,Benzene,
vinyl chloride, and methyl chloride are individual PICs. while the
concentrations of these PICs did correlate with CO and THC, the
concentrations of other PICs did not. The high concentration of CO
or THC may instead reflect high concentrations of other PICs.
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2*4.4 Risk Reduction, Upsets, and Emissions
Risks are involved in all human activities. Risks are also
involved with any waste treatment and disposal operations,
including waste minimization efforts,
In the case of PICs, risk may be associated with exposure to
PICs. Controlling the concentration of PICs in emissions is one
approach to reducing the risks PICs may present. Incinerators
monitor CO as an indicator of combustion efficiency. CO may be
high for a variety of reasons. For example, some incinerators may
have high CO (but low emission of PICs) because of the type of
waste burned,- generally, this situation is identified in the test
burn and requires no additional action to reduce risk* CO may be
high for very short periods because of small perturbations in the
flame zone? typically those perturbations last seconds to minutes
and may actually be over before they are detected. In such cases,
corrective action to reduce emission of PICs is virtually
impossible and very likely unnecessary. Longer lasting high CO
concentrations do call for corrective action and a variety of these
are possible (such as readjusting combustion air, increasing
turbulence, or decreasing the rate at which waste is fed) , In some
cases, corrective action requires shutting down the incinerator to
fix the problem. These temporary elevations in CO concentration
are often called upsets,
High concentrations of PICs may be associated with major
upsets in incinerator operations. Sudden significant changes in
feed rate or composition can cause such upsets. While it may seem
counter-intuitive, very strict controls could, by leading to more
frequent shutdowns, actually increase emission of PICs rather than
decrease them. A good control system will minimize both false
positives (shutting down when the incinerator is operating
correctly) and false negatives (operating the incinerator when it
is running inefficiently).
2.4.S PICs in Perspective
The emission of PICs is a consequence of any combustion
process. (44,45,46,47,48,49, and 50) Emissions from hazardous waste
incinerators contribute a relatively small fraction of the total
combustion emissions released into the environment each year.
However, with PICs the concerns are effects on the local
environment, not the aggregate national emissions, and the local
impacts may vary considerably.
Present analytical methods do not allow scientists to identify
and measure all compounds in incinerator emissions—or in many
other materials. The best studies characterizing PICs have
accounted for about 60% of the mass, some studies have accounted
for as little as 1% of the mass.(4)
10
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The available data show that a well designed and operated
incinerator does not emit Pies in substantially greater quantities
than fossil fuel combustion processes.
11
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FIGURE A - Benzene (a PIC) Concentration Versus Those of CO
(Bottom Scale) and THC (Top Scale)
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FIGURE C - Methyl Chloride Concentration Versus Those of CO
(Bottom Scale) and THC (Top Scale)
13
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3, RESPONSE TO THE FIRST QUESTION
The first question the PICs Subcommittee considered was
"Whether limiting carbon monoxide (CO) and total hydrocarbon
emissions (THC) is a reasonable approach to control emission of
PICs, given the current data base and statutory time constraints?"
3.1 Comments on the General Concept
Both the laboratory and field test data, and both the
non-flame and flame test data have indicated that CO is a good
conservative indicator of combustion performance,
(3,4,6,10,13,24,25) Combustion of CO reguires very high ignition
energy. CO is the dominant combustion by-product. Combustion of
other organics requires much lower ignition energy and the
reactions proceed more quickly. While poor combustion conditions
are always indicated by high CO levels, a high CO level may not
indicate poor combustion conditions.
THC level, as measured by a flame ionization detector (FID)
with a heated sampling line, is a measure of carbon-hydrogen based
volatile and semi-volatile organics. While there are indications
that a FID detector may be inappropriate for chlorine based
compounds such as carbon tetrachloride, test data indicated that
this is not important for regulatory control purposes. Carbon
tetrachloride is very difficult to oxidize by itself and has to be
burned with large amounts of carbon-hydrogen based high heating
value fuel or wastes. Most EPA sponsored combustion tests and
industry sponsored trial burn tests used carbon tetrachloride as
a POHC.
Abundant test data indicate that CO and associated carbon
based PICs are the dominant compounds in the flue gas. If both CO
and PICs are low, the carbon tetrachloride level also is low.
Hence, the available test data indicates that CO and/or THC
concentration may be a good indicator of the emission level of PICs
in stack flue gas even when carbon tetrachloride is burned.
Some test data indicate that under certain conditions the flue
gas THC level may be higher than th* CO level. At other
conditions, the flue gas soot level is higher than the co and the
THC level. Further evaluation of those teat conditions (31, 32)
indicated that when the THC level was higher than the CO level,
there was no excess oxygen in the combustion region and the system
was in a reducing environment.
Under extreme reducing or pyrolyzing conditions where less
than the stoichiometrlc amount of oxygen is available and the
temperature is high, most organics will be thermally cracked into
soot. Under this condition, the THC reading may be close to zero
because the carbon is in the soot. However, the observed CO level
14
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will be in the percent range and much higher than the 100 ppm range
which is of interest for regulatory compliance purposes*
Therefore, reducing conditions will be identified by the CO
compliance concentration or low excess oxygen concentrations and
not by a high THC concentration.
3.2 The Critical Linkage Between EPA's Proposed Two-Tier Approach
and the Capability for Continuous or Frequent THC Monitoring
In its September 1988 guidelines, EPA originally proposed a
two-tiered approach to applying limits on CO in the stack exhaust
gas as a surrogate for emission of pics. (3) Under Tier 1, CO
emissions would be limited to 100 ppm (corrected to 7 percent
oxygen, based on an hourly rolling average)i compliance with this
limit would be demonstrated initially during the trial burn and
thereafter through continuous emissions monitoring for CO, EPA's
rationale for this approach is based on data demonstrating that at
co levels below 100 ppm, PICs appear to generally pose acceptably
low risk.
EPA's Tier II approach was developed for facilities which,
despite operating at higher CO levels, may nevertheless produce
PICs at acceptably low levels. (3) If CO levels are found to exceed
100 ppm during the trial burn, the highest hourly CO average would
serve as the co limit in the permit, and operation would be
permitted up to this level if total hydrocarbon (THC) emissions
measured during the trial burn are sufficiently low. EPA's
rationale for this approach is that, when CO levels are above 100
ppm, there is virtually no correlation between CO and emission of
PICs? that is, when CO is high, emission of FlCs may be high or
low. Under Tier II, therefore, THC levels (which serve as a
surrogate for emission of PICs) would need to be measured to
determine whether they are acceptably low. EPA has proposed that
measured THC emissions levels would be required to either »eet
specified screening limits or be demonstrated on a site-specific
basis not to pose an unacceptable risk. The agency is considering
modifying this proposal by placing an upper limit of 20 ppmv on THC
emissions,
While this general approach appears to be a reasonable one,
given the available data, it contains one serious deficiency that
must be addressed. As proposed, THC emissions would be measured
only during the trial burn. If found acceptable, operation at
permitted CO levels (above 100 ppm) would be presumed to produce
THC emissions on a routine basis that are not greater than those
measured during the trial burn; no verification would be required.
Yet the entire basis of Tier II is the lack of any correlation
between CO and THC when CO exceeds 100 ppm. Thus, THC levels
measured during the trial burn cannot be assumed to be
representative of routine THC emissions.
15
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EPA indicates that it is considering requiring continuous
emissions monitoring (CEM) of TEC, because of the limitations of
CO as a surrogate for THC. Significant questions haves been raised,
however, regarding the current feasibility and reliability of CEM
capability for THC, CEM is necessary for the viability of the
entire Tier II approach. At the very least, frequent (weekly or
on some other time frame determined by appropriate testing) routine
stack testing for THC must be conducted as an alternative to CEM,
to provide a basis for assessing both compliance with THC limits
and the correlation (if any) between CO levels and THC emissions,
waste feed characteristics, and operating conditions,
3.3 Current Available Data Correlating CO and Organic Emissions
In the past few years, EPA has spent extensive effort in
studying the emission of products of incomplete combustion from
hazardous wastes. In most of those studies, EPA has only attempted
to analyze and quantify Appendix VIII toxic compounds. In only one
study, has EPA tried to identify and quantify all compounds found
in incinerator emissions. (19)
As discussed in Section 2.4.3, the Subcommittee agrees that
due to the large number of possible compounds and their typical
presence in the stack flue gas at concentrations approaching their
practical detection limits, it is difficult to identify and
quantify all the Pies. However, due to public concern over
emission of PICs, the Subcommittee considers the available data on
Pics is still sparse and more study should be conducted. The
ultra-low level of PICs and the similarity to those emitted from
other combustion devices (22,44,45,46,47,48,49,50), however,
suggest that this is not an important or unique problem associated
with hazardous waste incinerators.
Below is a brief summary of the data presented by SPA to date,
trying to find correlations among CO, specific PICs, ORE and THC,
Specific relationships normally can be found for data obtained at
the same facility where most of the parameters which have impact
on combustion performance are fixed. However, only general
correlation can be found for data obtained at different facilities
where many parameters were changed in the data collection process.
3.3.1 Investigations of Potential Correlation of CO with
Specific PICs:
a. One study of four full-scale incinerators found that
three of four PICs (benzene, toluene, carbon
tetrachloride) were low (on the order of 0.1 ng/L) when
co was below 100 ppm; a fourth (trichloroethylene),
however, did not show this correlation with CO*(22)
16
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b. Another study of a pilot-scale facility examined il PICSJ
while the two most abundant Pies showed a good
correlation with CO, the other nine did not.(40)
3.3,2 Investigations of Potential Correlation of CO with DUE
at Low CO Levels:
a. One study of a bench-scale facility revealed little
effect on DRE at CO levels ranging between 15 and 522
ppm.(42)
b. Another study of a pilot-scale facility found that DEE
was fairly constant at Co levels up to 220 ppm. (41)
3.3.3 Investigation of Potential correlation of CO and THC:'
a. Data from 9 full-scale incinerators of various designs
at many operating conditions and burning various types
of wastes demonstrated that when CO levels were below
100 ppm, THC levels were almost always below 20 ppmv.
Higher CO levels were usually associated with higher THC
emissions,(33)
b. Data from 11 industrial boilers of various designs and
at different operating conditions, co-firing hazardous
waste indicate a similar correlation, with the exception
of one firetube boiler burning natural gas,(43,51)
c. Data from 10 cement kilns co-firing hazardous waste
indicate the same correlationi however, at CO levels
higher than 100 ppm, no clear trend was seen because
both high and low THC emissions were observed.(43)
3.4 summary
In the subcommittee's view, the available data correlating
CO with THC emissions at low CO levels are sufficient to support
the Agency's concent; of limiting CO as a means of ensuring high
combustion efficiency and reducing total organic emissions. The
data do nojt, however, provide a sufficient basis for assessing
emission levels for specific PICs. The data also do not
convincingly support EPA's choice of a limit as low as 100 ppmv for
CO.
17
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4. RESPONSE TO THE SECOND QUESTION
The second question asked of the FICs Subcommittee was, "What
is the feasibility of monitoring THC to determine the aggregate
emission rate of organic compounds?"
The feasibility of continuously monitoring THC to determine
the aggregate emission rate of organic compounds can be subdivided
into several parts:
a. Is there an available detection system that is
responsive to "total hydrocarbons"?
b. Is there an available sampling system that can
reproducibly deliver to the detection system a sample
of stack gas that is representative of the actual stack
gases?
c. Are the detection and sampling systems sufficiently
rugged for use in a continuous monitoring mode during
routine or trial burn hazardous waste combustion
operations?
d. Has the feasibility of the overall THC system been
sufficiently well documented to serve as a basis for
regulation?
Each of these issues is discussed separately below.
4.1 Availability of a "Total Hydrocarbon" Monitor
Accurate determination of the "aggregate emission rate of
organic compounds" requires a detection system whose response
depends on, and only onf the mass of organic material present in
the stack gas. The Flame lonization Detector (FID) represents a
commercially available detector that comes close to meeting this
criterion, in that it is responsive to most classes of organic
chemicals, including those likely to be most abundant as PICs in
hazardous waste combustor emissions, at sub-ppm (v/v)
concentrations in air,
However, the magnitude of the FID response depends both on
the concentration and the composition of the organic material
present. A report presented to the Committee notes that "The
response (relative to methane taken as 1.0) varies from 0 for
formaldehyde and formic acid to 0.4 for methylanine (CH3NH3) and
0.76 for dichloromethane
-------
(methane, etc.), some of the methane could have been unburned fuel
rather than a product from the waste since auxiliary fuel is, in
some cases, burned at the time of sample collection. Since
compounds such as methane have high FID response factors, they will
tend to dominate the magnitude of the total hydrocarbon analyzer
signal. A 10- or 100-fold increase in the concentration of a low
response factor but highly toxic, organic compound might go
undetected against the background signal of high response factor
nontoxic hydrocarbons. Many different mixtures of chlorinated and
nc-nchlorinated organics could give rise to exactly the same total
FID response.
The Office of Solid Waste addressed the response factor issue
by developing a "weighted average response factor" based on a
hypothetical worst case composition of PJCs in incinerator
emissions.(38) However, in actual hazardous waste combustion
processes, the composition of the organic species will not
necessarily approximate this hypothetical distribution and the
actual average response factor will differ. Further, the
composition of organics in the stack gas, and thus the average
response factor, will vary. Thus, even for a single incinerator
burning a single waste, it will not be possible to deduce whether
a change in the FID signal represents a change in the emission rate
or a change in composition,
Despite these caveats, the Subcommittee thinks it probable
that the average response factor of the organic species present in
relatively high concentration in the stack gas will be sufficiently
constant that the FID response could provide a useful approximation
or estimate of the level of PICs. Such an estimate could serve as
an indicator of good combustion control (but not as the basis for
a health risk estimate),
4.2 Availability of a Sampling System
The FID monitor responds only to organic compounds that reach
the detector in the vapor phase. In order to achieve an estimate
of the aggregate emission rate of organic compounds, it is
necessary to use a sampling system that delivers, at a minimum, a
constant fraction of the total organics present in the original
flue gas to the detector.
The Office of Solid Waste asked the Subcommittee to address
the question of using a "hot" (1S06F) versus "cold" (ambient
temperature) transfer line to deliver the stack gas sample to the
FID. A 150°F transfer line may not eliminate sorption problems,
although the hot line should allow a broader range of compounds to
reach the detector. The proposed regulations assume that a
constant fraction (25%) of the THC (the "missing carbon") will be
lost due to absorption effects.(38) No evidence was presented to
the Committee to document that the "missing carbon11 percentage will
be constant. in fact, data were presented which show "missing
19
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carbon" percentages ranging from 2% to 71.1%.(4) It was not
possible to determine whether the variability wag due to differing
degrees of absorption/condensation in the sampling system or to
differences in the composition of orgmnics present or both.
With a cold transfer line, most lower volatility, higher
molecular weight organics will condense out of the vapor phase.
Cold sampling systems typically include a conctensate trap to
collect these non-volatile organics, along with water. The
relatively volatile compounds will reach the detector and the
variability in their concentration should be mainly a function of
stack gas composition, rather than sampling train problems. This
may be advantageous relative to using hydrocarbons as a measure of
good combustion, but not for risk estimates because the risk
assessment relies on the accuracy of mass emission rate of toe
pollutant. Using a method which measures only a portion of the THC
is acceptable in view of EPA's proposed technology based 20 ppm THC
limit, although it is desirable to measure the total THC or at
least a relatively constant fraction of the total. However, the
reliability and operability of the system in all modes of operation
is also important so that a comparative picture of the emissions
is available on a continuous basis. Heated THC systems, although
potentially detecting a greater fraction of the THC, have been
observed to experience problems attributable to plugging of sample
extraction lines due to heavy particulate loading and/or condensed
organics. Unheated fie systems have a longer history of use and
have a much higher availability. A recent survey of continuous
THC monitoring systems reported that 6 facilities have been
continuously monitoring THCs using "cold11 or "conditioned" systems
for periods ranging from 1 to 7 years and did not have any
significant loss of availability due to breakdowns or malfunctions.
Moreover, the Subcommittee has learned that continuous THC monitors
are required by regulations in Germany and Switzerland and the
facilities reported no major problems with routine (daily)
maintenance.(58) The Subcommittee believes that "cold" or
"conditioned" monitoring systems for hazardous waste incinerators
are available at this time.
Under upset conditions, the presence of high-surface-area
particulate matter (soot) in the stack could act as condensation
nuclei or absorption sites, thus reducing the quantity of organic
material reaching the FID. However, excessive levels of soot would
be likely to be accompanied by other indications of upset
conditions, such as high CO readings and/or low excess oxygen
readings (see Section 3,1),
4,3 Kuggedness (Operability and Maintainability) of THC-CEM
Systems
The feasibility of monitoring hydrocarbons using heated
systems in hazardous waste incinerator stack emissions on a
continuous basis during routine operations was not documented.
20
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While such systems (like the leckman 402 and Ratfisch 455) have
been available for a long time and used in trial burn test or
research tests, their continuous usage for any extended period of
time (such as a month) could not be documented either in the
U.S.and Europe. In fact, the Subcommittee heard anecdotal evidence
that the "hot" THC system(s) can present reliability difficulties
even under trial burn conditions.
Commercially available "total hydrocarbon analyzers" using
sample conditioning lines and a cold FID system are considerably
more rugged than typical laboratory instruments such as gas
chromatographs. However, the FID-based monitors are still subject
to corrosion and plugging under conditions that may exist in
hazardous waste incinerator gaseous emissions. Use of the FID as
a continuous monitoring system may require considerable (probably
daily) maintenance under the direction of a reasonably experienced
chemist or chemical technician.
The "hot" sampling line may also retire periodic (frequent)
maintenance or cleaning to prevent build-up of condensable organics
and losses of THC over time. This could require the installation
of two parallel sampling lines - one in service and the other being
washed/baked-out at any given tine. Another alternative might be
frequent replacement of a short section of transfer line close to
the stack.
The Subcommittee is convinced that successful implementation
of a continuous THC monitoring system will require rigorous
attention to Quality Assurance/Quality control (QA/QC) protocols,
as well as requiring the careful training of skilled operators.
A single gaseous organic, such as propane, is conventionally
used to calibrate continuous hydrocarbon monitors. This may also
be appropriate for hazardous waste combustion purposes. However,
two caveats need to be made, it is critically important that the
calibration standard(s) be introduced at or immediately behind the
probej this will be the only way to approximate the kinds of
absorption losses that have been postulated. Also, some checks of
the monitoring system should be made using calibration gases
containing less-volatile organics (perhaps naphthalene, or tri~ or
tetrachlorofoenzene). Preferably, these compounds would be
introduced into the stack gas stream by the method of standard
additions? this could provide a check on the constancy of the
"response factor" and also on absorptive losses.
4.4 Documentation of THC-CEM System Feasibility
While there are limited data available on the accuracy and
precision of continuous THC measurements over time periods of days
to weeks, QSW did not provide documentation of the operability and
maintainability of the FID detector and sampling system by facility
personnel under routine operations until late in the subcommittee's
21
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review process. As discussed above, the OSW recently submitted to
the Subcommittee a survey of continuous THC monitoring systems that
indicates that^"cold" or "conditioned gas" systems can be operated
continuously without unusual operation or maintenance problems. (58)
Although the Subcommittee has not reviewed the report in detail,
it appears to document the feasibility of continuous cold THC
monitoring.
Notwithstanding the field experience with continuous THC
monitoring, there is a need to investigate and document the
magnitude of effects such as rate of condensation, build-up of
non-volatile organics, flue gas moisture effects, and effects of
partieulate matter on the medium- to long-term performance of the
system. The selection of appropriate calibration compounds and
determination of precision and accuracy data over various time
periods and concentrations is also a subject for further
investigation. There is evidence indicating that a cold THC
analyzer with a flue gas pre-conditioning system can function
reasonably reliably. The reliability is improved due to the fact
that those components which cause corrosion and plugging problems
have been removed, but, at the same time, these chemicals have been
removed from the system and have not been detected.
4.5 Summary
The feasibility of using a heated line to continuously
monitor total hydrocarbons (THC) has not been documented. However,
recent survey data appear to show that unheated THC monitors using
sample conditioning systems (refrigerated condensate traps) are
feasible and already in operation at several facilities in the
United states and Europe.
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5. RESPONSE TO THE THIRD QUESTION
The third question asked of the PICs Subcommittee was,
"Whether the proposed approach to assess the health risk from THC
emissions is reasonable given the current data base and statutory
time constraints?11
5,1 A Brief Description of EPA's Risk Assessment and Two
Regulatory Approaches
To support its proposal to limit THC emissions as a means of
reducing the potential risks posed by PICs, EPA developed a means
of estimating the human carconogenic risk posed by inhalation of
THC at a given level. Specifically, the EPA derived a unit cancer
risk value for a mixture of compounds assumed by 1PA to represent
THC (elsewhere in this section this mixture will be refered to as
"estimated THC11.) using a set of assumptions to predict the array
of specific PICs actually present in THC.
EPA's starting point for deriving the unit risk value is its
historical data base on emissions of individual compounds from
hazardous waste incinerators, boilers, and industrial furnaces.
Several hundred toxic compounds which have been found in wastes are
listed in Appendix VIII of the Code of Federal Regulations (CPR
261). For each Appendix VIII compound identified in the emissions
data base, EPA assumed that it is present in THC at its 95th
percentile concentration, as a "reasonable worst-case value" {EPA's
wording),(4) However, as Appendix B shows, this assumption may not
be conservative in this particular instance. For each Appendix
viii compound that has not been detected in emissions and is
therefore not in the data base, but for which adequate health
effects data are available to establish a risk-specific dose, EPA
assumed it is present in THC at a nominal detection limit of o.l
ng/L.
The list was further expanded by including methane and ethane
emissions from fossil fuel combustion and formaldehyde
concentrations from municipal waste incinerators also at- their 95th
percentile concentration. In recognition of the fact that even, the
most complete analyses of incinerator emissions have failed to
account for all of the emissions, the list of compounds was further
expanded by 'including all compounds that have been quantitatively
assessed by the Cancer Assessment Group (CAG) of the Agency*
Table I indicates the number of Appendix VIII compounds (out
of a total of more than 350 and not all are organic compounds) used
to calculate the THC unit risk value and the basis for their
assumed concentrations.
23
-------
Table I: The Number of Appendix VIII Compounds Used to
Calculate the THC Unit Risk Value and the Basis for
Their Assumed Concentrations
No. of App. VIII Compounds Detected in
Emissions (including formaldehyde) 25
No. of App. VIII Compounds Assumed at
0.1 ng/L 45
Total No. of App. VIII Compounds Used to
Calculate the THC Unit Risk Value 70
24
-------
Approximately 70% of the identified emissions (on a weight
basis) from these facilities are associated with known systemic
toxicants,* 30% of the identified emissions are associated with
Known carcinogens,(37) All of the individual systemic toxicants
occurred at concentrations that were calculated to be lower than
the Reference Air Concentration (RAC). The reference air
concentration (RAC) is an estimate (accurate within an order of
magnitude) of the concentration to which humans could be exposed
for a lifetime without suffering adverse effects. EPA assumed that
the individual non-carcinogenic compounds in the mixture did riot
act additively and that consequently, because the exposures to
systemic toxicants were estimated at sub-threshold concentrations,
EPA reasoned that exposure to the mixture would not generate health
concerns for systemic toxicity,
EPA then applied compound-specific unit cancer risk factors
to each concentration value to obtain a risk level for each
compound. A unit risk factor is the upper bound estimate of the
excess lifetime cancer risk associated with a lifetime of exposure
to one unit of concentration (usually one milligram per cubic
meter) . A unit risk value of zero was assumed for all
non-carcinogens (e.g., methane). Finally, these risk levels were
summed to produce a weighted 95th percentile unit risk value for
estimated THC. This unit risk factor was then used to calculate
the risk associated with inhalation of estimated THC emissions at
particular levels using a variety of additional assumptions
regarding dispersion and point of exposure.
5.2 Discussion of Assumptions Used in Risk Assessment
The estimation of potential risks associated with various
levels of total hydrocarbon (THC) emissions involves many
assumptions. In addition, the many assumptions required to derive
the unit risk factor and to calculate risks arising from exposure
to estimated THC render the methodology even more unreliable for
the purposes of site-specific regulation. These assumptions
are commonly used in EPA risk assessments and while the
Subcommittee did not consider it within its charge to challenge the
assumptions. Additional comments relating "to the general issue of
risk assessment and which are relevant in part to this particular
instance, are found in Appendix C.
Below are listed some of the assumptions with commentary from
the Subcommittee and Executive Committee. Some of these
assumptions are clearly conservative, while others are not. Some
of the conservative assumptions are the following;
a. Compounds that have been determined by EPA to be
carcinogenic in any context, but which have not been
identified in the emissions data bas«, are nevertheless
assumed to occur in emissions at their approximate
25
-------
detection limits. A nore realistic risk assessment
should omit from consideration those compounds which are
highly unlikely to be present in incinerator emissions,,
for example diethylsilbesterol.
b. Individual risks are calculated at upper plausible
limits to risk. A different approach is described in
Appendix C.
c. Although not measured in the studies of hazardous waste
incinerator emissions contained in the data base, it is
assumed that formaldehyde is emitted at a level
corresponding to the 95th percentile of the available
data from municipal waste combustors.
d. The receptor is a Maximum Exposed Individual (Mil) who
is postulated to reside continually at the site of
maximum annual average calculated ground level
concentration for a full 70 years.
e. The estimated THCs are assumed to reach a postulated
receptor (the MEI) after dilution in ambient air, based
on the use of conservative dispersion coefficients for
reasonable worst-case facilities,
ft Individual unit risk(s) are added, assuming that
carcinogenic risks are additive. Appendix c shows how
the addition of upper 95% bounds of risk for individual
compounds leads to a higher percentile bound for the
combined risk.
The following assumptions in the risk assessment are either
neutral or insufficient data exist to determine whether their
effect would be conservative or non-conservatives
a. Although SPA uses 95th-pereentile emission levels in
calculating risk from emission of PICs, this risk is not
significantly conservative compared with one calculated
using "median11 levels. Factors leading to this result
are: the high degree of skewness of emission level
distributions, the assignment of 0.1 nanograns/liter to
some supposed PICs (especially diethylstilbesterol with
its high contribution to risk at the "median" levels)
at both levels and the zero risk contribution of ci and
C2.
b, Synergistic or antagonistic effects among carcinogens
or between carcinogens mnel non-carcinogens are not
considered.
c. Only Appendix VIII compounds for which adequate health
effects data exist are considered in calculating the
26
-------
unit risk factor for estimated; THC. Because this unit
risk value is applied to the entire mass of estimated
THC, the aggregate of all other compounds present in the
emissions is assumed to pose the same risk. Data
indicate that non-Appendix VIII compounds are present
in estimated THC in at least the same order of
magnitude as Appendix Vlll compounds? semi-volatile
compounds not in Appendix VIII are a particularly high
fraction of the total.(4) These compounds may pose
lesser or greater risk than those included in
calculating the unit risk value.
d. It is assumed that a single THC unit risk value, based
on a hypothetical reasonable worst-case composition, can
be applied to all incinerators.
e. In calculating RACs for compounds lacking direct
inhalation data, oral RfDs are used, assuming a
conversion factor of 1 between the two routes of
exposure.
f. Exposure to the same carcinogenic compounds contributed
by other sources (combustion or otherwise) is not
considered in assessing overall risk.
Finally, certain assumptions are clearly non-conservative:
a. The emissions data base is derived in large part from
facilities operating under good combustion conditions
(e.g., research tests), which is likely to
underestimate, to an unknown degree, the emissions that
occur during routine operations? the nature and
magnitude of emissions under the range of conditions
which may be experienced during the lifetime of a
facility's operation is poorly understood. A more
realistic assessment would not be restricted to good
operating conditions. Continuous CO monitoring records
could be inspected to estimate the amount of time spent
in excursions.
b. Direct inhalation of carcinogenic PICs is the only route
of exposure considered; indirect exposure through other
routes (e.g., the food chain) are not included, although
available data indicate that such routes may produce
exposures that may be much greater than direct
inhalation, particularly for environmentally persistent
compounds.(39)
c. Reliance on RfDs, which are based on risks to the
general population, may not adequately protect sensitive
members of the population. RfDs include a factor of ten
for the extrapolation from animal studies to human
27
-------
health effects and another factor of ten because of the
variability of sensitivity in human populations? in many
cases this appears to be adequate, but not in all
cases.(2,52,53)
d. No consideration is given to environmental effects due
to a lack of sufficient information. These effects may
occur at levels of exposure lower than those affecting
human populations.(2)
In the THC risk assessment process, conservative assumptions
are used to compensate for many sources of uncertainty arid areas
of insufficient information. However, the toxicity of the total
estimated THC mixture cannot be assessed, in part because of the
great likelihood of the emission of unknown compounds. In addition,
humans can also suffer adverse effects from pollutants to which
they are indirectly exposed (through the food chain or by breathing
resuspended dusts which contain contaminants, etc.)- other living
creatures may also be affected by pollutants. To the extent that
the risk assessment excludes these effects, it is not conservative.
5.3 Evaluation of the Risk Assessment
EPA, has proposed two different regulatory applications of
its risk assessment methodology {including use of the THC unit risk
value). The first application involves its use as a risk-based
check on the Agency's proposed technology-based THC emissions limit
of 20 ppm, (5) The second application involves its use in
site-specific risk assessments conducted to support facility
operation at CO flue gas concentrations in excess of 100 ppmv.(3)
These two applications are discussed separately below, since the
Subcommittee reached different conclusions regarding the adequacy
of the two approaches.
5.3.1 Is the Use of the Risk Assessment Methodology Reasonable
and Appropriate as A Risk-'Based Check on the Proposed
Technology-THC Limit (20 ppm}?
EPA has proposed to limit THC emissions to 20 ppm, based
primarily on consideration of the actual THC levels achieved by
units operating under good combustion conditions that is, based on
good operating practice. In further evaluating the choice of this
value, EPA employed the THC unit risk value described above (as
well as other assumptions regarding dispersion of and exposure to
THC emissions) to provide a risk-based check on the technology-
based limit of 20 ppm, in order to determine whether such a limit
will be generally protective of human health and the .environment.
Despite the limitations of the emissions data and the large
degree of uncertainty introduced by various assumptions employed
in the risk assessment Methodology, the Subcommittee considers that
the methodology is sufficient to provide a risk-based check on the
23
-------
proposed THC emissions limit, and that the Agency's evaluation of
the emissions limit provides evidence of adequate safety.
Therefore, considering the results of the THC risk assessment
calculations presented, measured THC emissions of 20 ppmv are
likely to present actual carcinogenic risks below the suggested
limit of 1 in 100,000 in the majority of cases. However, given the
assumptions and uncertainties discussed above, the Subcommittee
concludes that (a) it is not possible to calculate reliable total
THC risks—to both human health and the environment and (b) at
present, the method is not suitable for setting specific limits
based upon THC levels alone.
5,3.2 Is the Use of the Risk Assessment Methodology in Site-
Specific Assessments Reasonable and Appropriate to
Support Facility Operation at CO Levels in Excess of 100
ppm?
While EPA's risk assessment approach follows previously
accepted methodologies, because of the data limitations, the
Subcommittee believes that the risk assessment lacks both the
precision and accuracy needed to be useful in a site-specific
regulatory context. For site-specific applications SPA would need
to replace the assumptions currently used with hard data. Such data
would have to include at least: wind direction, the nature of the
waste mixture, and the specific concentrations of individual
compounds found in the emissions. The Subcommittee is not
recommending a large data gathering effort to QSW, but only
recognizing that the data requirements for site-specific
applications are very high.
THC is used as a surrogate for PICs and for those compounds
in the PICs which may cause cancer. Since THC does not correlate
well with CO when the concentration of CO is higher than loo ppmv,
reliance on these data, however necessary* introduces considerable
uncertainty into risk estimations. The Subcommittee therefore
considers the Agency's risk assessment methodology, which would
rely on THC concentrations obtained during trial burn tests only,
to be inadequate for site-specific applications, as proposed under
the original Tier II. (3) The revision made by requesting continuous
THC monitoring using a cold system should be satisfactory. (37)
5.4 Summary
The Subcommittee considers EPA's risk assessment adequate to
provide a risk-based check on the proposed THC emissions limit of
20 ppm. However, because high levels of CO do not necessarily mean
THC is high, the risk assessment methodology is inadequate for
site-specific applications, as proposed under the initial Tier II
approach.(3)
29
-------
6, VIEWS ON OTHER TECHNICAL ISSUES
6.1 Risk Assessment and Exposure Modeling Considerations
6,1.1 Atmospheric Dispersion Simulation
6*1.1,1 Introduction
The approach to dispersion modeling employed in the
evaluation of exposure and the risk assessment associated with
hazardous waste incinerators is reasonable and appropriate,
especially in view of the relatively small uncertainty in these
estimates when compared with uncertainties associated with other
components of the risk assessment, such as emission estimates and
risk factors. There are a few areas where the procedures are in
need of some "tightening"1' or clarification, and in one or two
areas, minor revision. These include: so-called dispersion
coefficients; sensitivity analyses? representative meteorological
data; and low stack-height considerations.
6.1.1.2 Dispersion Coefficients
The dispersion modeling discussion refers to the use of
•dispersion coefficients' whereas, in fact, a more appropriate term
would be "dilution factor." The coefficient or factor referenced
is the modeled atmospheric concentration (C) normalized by the
stack mass emission rate (Q)I i.e., C/Q, This ratio is a factor
that denotes the effluent dilution, normalized by the rate.
Convention considers dispersion factors to characterize the rate
(temporal or spatial) at which the atmospheric motions cause a
volume of some additive to spread. The two concepts are quite
distinct and use of "dispersion coefficients' as originally drafted
is inappropriate and misleading.
6.1.1.3 Sensitivity Analyses
Applicants and regulators would be helped by sensitivity
analyses of the relative impact of stack height and ambient
meteorology on dilution factors. Selecting worst-case dilution
factors from multiple-year applications of a dispersion model
eliminates most of the site-specific meteorological variability and
emphasizes the importance of effective stack height. This emphasis
nay be appropriate because stack height is an applicant-controlled
variable, whereas meteorology can only be controlled by relocating
the plant. Given these considerations, the type of sensitivity
analysis suggested would be beneficial*
30
-------
6.1.1.4 Representative Meteorological Data
EPA's "Information Requirements" section also addresses
representative meteorological site data, and indicates virtually
any data should be used if representative site-specific data are
not available,(4) This is a significant weakness of the
requirements section. In the absence of representative data, other
data should only be allowed on an interim basis if such data meet
identified acceptance criteria? such criteria need to be included
in the document.
6.1.1.5 Low Stack-Height Considerations
The preamble to the hazardous waste incinerator regulation
presents many tables that illustrate feed rate screening limits foe-
various compounds in both complex and non-complex terrain* These
tables illustrate effective staclc heights that vary from 4 m to 120
m. Inclusion of the smaller stack-height values in the tables
suggests that these are acceptable values. However, as a general
practice, small stacJc heights are to be discouraged! specific
guidance can only be given in combination with information on
aerodynamic roughness (z°) of the local environment and the
height and fetch of nearby tall buildings. Such information should
also be required specifically under the data needs enumerated in
Part Four; Section VI "Information Requirements,"(4)
Sites where potentially adverse ambient concentrations may
be found are apt to be associated with plants whose effective staclc
heights are small relative to the height of nearby buildings or
where the fetch to nearby buildings is small (or both). In such
casest mathematical dispersion modeling may not be the preferred
simulation methodology, and fluid modeling in a boundary-layer wind
tunnel may be desirable. The draft regulations do not address this
issue and should be amended to reflect a selected preference for
fluid modeling in certain situations. The Agency already has in
place guidelines for good engineering practices in the application
of fluid modeling, and these should be referenced and cited as an
acceptable (or preferred) alternative to mathematical
modeling.(1,2,8.9)
6.1,2 Recommendations
a. Replace so-called 'dispersion coefficients' in the
context presently used with the term »dilution factor1
and clarify related ambiguities.
b.' Present a sensitivity analysis that illustrates the
relative impact on dilution factors of: stack height and
ambient meteorology.
c. Develop guidelines for acceptable representative
meteorological site data.
31
-------
d. Identify and support the role of fluid modeling for
site-specific assessments involving low stacks and/or
tall buildings.
6.2 Selection of CO and TEC Levels !
EPA's proposed strategy for reducing the risk from emission
of Pics is to stop all hazardous waste feeds when the allowed co
limit is exceeded. The incinerator operator is encouraged to set
an alarm level at a lower level at which corrective action would
be initiated with the aim of avoiding waste feed cutoff. Such an
alarm level will reduce frequent transient startups and shutdowns
which could become the source of increased emission of PICs. The
proposed CO and THC regulatory limits should be set at
concentrations that provide enough margins above the background
levels to provide the incinerator operator sufficient leeway to
take corrective action. The CO and THC regulatory limits are for
measurements corrected to 7 percent oxygen. In cases in which
oxygen is added after the combustion chamber, incinerators
operating at higher flue gas oxygen levels will have lower actual
or "uncorrected" CO and THC concentration readings because of
dilution* Those incinerators which operate at high oxygen levels
normally are burning high BTU waste and require extra air as a heat
sink. Flame temperatures will be high. Some carbon monoxide may
come from dissociation of carbon dioxide as discussed below and the
carbon monoxide level may be relatively high. THC will be lower
due to better air/fuel mixing. In this case, excess air is not a
dilution air, but combustion air. OSW has taken this into account
by proposing a CO waiver if THC is less than 20 pp«u
The Subcommittee was provided with data (summarized in Table
II) from research tests on nine industrial hazardous waste
incinerators* (4) These show that six of the units meet the
proposed standards for CO and THC'by a wide margin.
The results of tests on such incinerators are not. necessarily
representative of those on other combustion devices. Two examples
where the CO and THC concentrations may not be related to the
efficiency of combustion were brought up during the Subcommittee' s
deliberations. Cement kilns involve the countercuirrent flow of
limestone and the combustion products. In calcining limestones
with a high organic content, CO and THC may be produced during the
heat up of the limestone and will yield high exit concentrations
unrelated to the efficiency of the combustion process.
32
-------
u
u
SHE 10
Hltche)!
DuPont
1W1
DM
RUN HO.
I
t
3
Average
1
1
1
Average
1
2
3
4
Average
1
2
3
4
Average
62
{PERCENT)
9.4
10.5
9.9
9.t
9.2
9.6
10.3
9.1
12.4
13.0
13.2
15,6
13.6
10.1
11. 1
11.5
11.2
11.0
AVERAGE CO
MS MEASURED)
1.4
1.0
< 1
1.4
666
422
624
§n
4.3
o.t
1.2
0.6
1.8
1
NA
I
10
4.0
mm OR*)*
(PP. n 021
i.?
2.4
1.2
1.8
?9Q
518
816
708
7.0
1.6
2.2
1.6
3.1
1.3
M
1.5
14
S.6
AVERAGE T1C7J
(AS MEASURED}
< 1
< I
0.6
0.9
75.9
47.6
sea
60.5
2.5
1.9
1.?
o.a
1,7
2.5
2.3
2.1
2.9
2.5
mjRfp
IriifiSf
1.2
1.3
O.J
1.1
90.1
58. 5
76.0
74. fl
4.1
3.3
3,1
2.1
3.1
3.3
3.2
3.0
4.2
3.4
iilfiHfir J*KM61I~iuirs~
(ppn DRV §71021
CO 111C
6.1 1.3
4.1 1.4
16,3 2.3
1,364.4 Ififi.l
1.BS4.4 105.4
1.W5.J 112.9
107.9 4.?
24.2 3.?
4.1 3.9
5.2 5.4
-
110,5 11.6
11.2
3.7 14.7
1, 02fi.fi 230.0
_
Sources: HRI "Perforaance Eviluatliui of Full-Scale Hazardous HaUe Inclneralors. Voliwe 2. loci nerd tors
Perfaraince Resulti.» fPA-600/2-84-iail). PB85-129S18, Hov. 1984.
Nil "Tot*I Mass EBlssloni Iron a llaiirdous Uaste Incinerator," HRI Project No. B671-L(1>. Hdy
* All THC dii« are Measured propane wlttt liie exception of DOM Site where T11C was measured as nethnne,
Healed CMtraction syste« and healed TtlC nonllor was used. Ihe THC data for Hits Site MAS converted to
propane using the following equal ton;
1HC (propanej * iHC («elhaii*|/3 |to account for the f fO response factor)
TABLE 11- Incinerator CO/THC Data from Research Tests
-------
u
SITE 10
Flint B
Boss
Up John
Z*p«ta
A. Cyanaald
RIM Ml.
1
2
3
4
5
Average
1
I
3
Average
1
2
3
Average
1 i
2
3
4
Avenge
t
2
3
4
5
Average
02
(KMXMT)
11. B
10.3
10.7
14,3
10.1
U.4
10.4
lO.fl
10.7
10.6
8.1
a. 3
0.4
0.3
e.2
12.0
ti.a
11.9
11.0
10.3
12.4
—
12.7
13.0
12.1
AVERAGE CO
TATttfASUREfif
14.8
< 1.0
6.9
7.2
4,100
866
4.8
9.1
4.7
6.?
10. S
11.2
9.9
10.5
1.275
22.2
7.S
a. a
328.4
6.7
19.3
.
i3.a
14.3
13.5
P|M urn*
(pp. It 021
22,5
1,3
9.4
15,0
5.523
1.114
6.3
12.5
6.4
8.4
11.4
12.3
mo
11.6
1.394
34.5
11.4
13.5
363. i
6.8
31.4
-
23.3
2i,0
22.1
AVERAGE HIC I
7AS MEASURED1
< 1
< I
< 1
< 1
341
69
< 1
0.9
1.0
1.0
8.9
6.0
3.9
6.3
71.0
1.9
< 1
< I
18,7
< 1
< 1
-
< 1
< I
1.0
jMjJWJ*
Wlffiff
1.5
1.3
1.4
2.1
43a
89
1.3
1.2
1.4
1.3
9.6
£.6
4.3
6.9
77.7
3.0
1.5
1.5
20.9
1.1
1.6
-
1.7
i.a
1.6
tflClI$T RECORDED VALUES
« HftV tl*Q2)
co me
34.2 KS
1.3 1.3
14.5 2.6
17.6 2.3
6.935.a 671.7
-
9.8 1.3
21.3 3.2
u.a 3.1
-
7.3 7.9
7.6 6.Q
6.7 4.1
-
1,717.2 235.2
612.9 63.6
13.4 1.5
28.2 4.5
-
40.2 , 2.1
60.7 4.2
-
43.0 1. 7
45.0 1.9
-
TABLE II- Incinerator CO/THC Data from Research Tests (Continued)
-------
a.
1
U.I
1
>
s
Q.
5 <
~ H
Q
O
S
i
O
S
a
o
ei
a
920 ppmv a i?i-SO =^55=3
O 710 ppfflv -^=t==i;_yrd —glf
^HsferJ ^"-"L-VA:
I
I
8
6PM
2PM
TIME OF TOE DAY
FIGURE D - in-situ CO Monitoring Data and Rolling Hour Average Data
Uncorrected for Moisture and Oxygen at a Multipurpose Rotary
Kiln incinerator (Plant A)
35
-------
Another situation that may lead to high CO concentrations
that are not representative of poor combustion is that in which the
products of combustion are rapidly cooled* CO is produced in
combustion chambers operated at high temperatures by the
dissociation of C02. When the combustion products are rapidly
quenched, the high CO concentrations inevitably present in a well-
operated high temperature combustor will persist. This source of
CO will not correlate with emission of PlCs, but THC will be less
than 20 ppm if combustion is efficient.
The Subcommittee suggests that the facilities be encouraged
to set an alarm level which helps an individual facility improve
its operations. Alarm levels for CO and THC should be designed to
provide enough margin above background concentrations but below
shutoff values to provide the incinerator operator sufficient
leeway to take corrective measures. The; individual operator can
best determine how much lead time is needed to take corrective
measures. For liquid injection incinerators, the lead time could
be very short, while for rotary kiln incinerators, it could be very
long. Further the Subcommittee does not think it is appropriate
to, in effect, raise the CO limit by providing for a phase down
period. The intention is to reduce the number of automatic waste
feed cutoffs which could potentially increase emission of PICs due
to frequent shutdowns and restarts.
6,3 Choice of Averaging Method
The Subcommittee believes that there is a need to justify the
particular selection of the proposed averaging technique. Although
OSW proposes use of a one-hour rolling arithmetic average, OSW
presented no statistical analysis of CO monitoring data from well-
operated incinerators to evaluate the impact of the proposed
regulation on incinerators operating under realistic conditions.
The Subcommittee has obtained access to data from four plants
which are discussed in some detail in Appendix A in order to
elaborate on the issues that need to be addressed when selecting
an averaging method.
The Subcommittee believes that the selection of levels of CO
and THC and averaging procedures in the short terra will involve a
certain element of judgment, it could be argued that an arithmetic
mean is preferable for the following reasons. The geometric mean
is substantially lower (by a factor of three) than the arithmetic
mean with CO and THC levels are relatively steady. The SAS does
not believe that these lower values should be considered for
conformance with the limits because: (l) CO and THC are indicators
of combustion efficiency, a parameter which is based on an
instantaneous measure of CO? (2) EPA is allowing for inevitable
spikes in the CO/THC levels that occur even when facilities are
well designed and operated by allowing the CO/THC levels to be
averaged; (3) the flexibility provided by the arithmetic average
36
-------
is sufficient to enable the vast majority of incinerators to
routinely meet the recommended Tier I CO limit; and (4) for
facilities that cannot easily meet the lOOppmv CO limit, EPA is
providing a waiver that would allow higher CO levies provided that
the THC levels do not exceed an hourly rolling average of 20 ppmv,
a THC level that the vast majority (perhaps all) of the well
designed and well operated incinerators meet. It should, therefore,
be recognized that the values may need to be revised in the future
as new information becomes available.
6.4 Alternative Approaches
EPA's proposed approach to controlling emission of PICs is
to stop all hazardous waste feeds when the allowed CO concentration
is exceeded, without considering whether the shutdown will actually
increase emission of PICs. Three major conditions may result in
high emission of PICs at properly designed incinerators. These
conditions are inadequate oxygen or too much fuel, too high
instantaneous thermal load for batch feed, and too low a
temperature in the incinerator. Parameters other than CO and THC
concentrations can be used for making control decisions and actions
other than automatic shutdown can be used to control emission of
PICs.
6.4.1 Alternative Measures of Performance
while CO monitoring data provide a very good indicator for
combustion performance, CO alone may not be appropriate for
combustion control. Oxygen monitoring should be considered for
all hazardous waste incinerator operations because oxygen
monitoring provides much better guidance to the operator when the
fuel feed rate is getting too high or the air supply rate is
getting too low.
For incinerators with batch feed, there is a special CO spike
problem. As long as there is some oxygen available (1-3%), little
emission of PICS occurs. However, if oxygen is completely
depleted, high emission of PICs is possible.
Besides oxygen control, possible alternates include
combustion chamber temperature or the rate of change of combustion
chamber temperature. A high temperature or high rate of increase
usually indicates that the waste feed rate is getting too high.
A lov temperature or fast decrease in temperature usually indicates
that the waste feed is getting too low or the waste feed does not
have enough heating value.
while these alternative measures of performance are useful
to operators and such monitoring could be retired, because of the
complexity of incinerator operations, particular concentrations,
temperatures, or rates of change should not be made permit
conditions.
37
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6.4.2 Alternative Actions
Once an "upset" condition has been identified, it is
desirable to correct the situation without causing increased
emission of Pics. With an automatic shutdown strategy/ the change
in fuel property or quality (from hazardous waste to supplementary
fuel), the change in fuel quantity, and the restart of hazardous
waste feeds all have the potential to upset operations and increase
emission of PICs.
Therefore, the Subcommittee proposes use of a corrective
action approach as the first response to high CO and THC followed
by a facility before considering an automatic waste feed shutoff.
For example, a staged reduction in waste feed or other operational
controls (such as readjusting combustion air or increasing
turbulence) seem more appropriate in reducing emission of PICs than
a shutdown. It is probably not possible to specify corrective
action (or "alarm") concentrations except on a facility specific
basis, while the practice of corrective action could be required
based on generally applicable criteria, the concentrations are best
developed at the facility.
For example, high CO spikes due to momentary depletion of
oxygen can occur for certain types of waste material. From trial
burn tests and past operating experience, the operator should have
a pretty good idea on the limitation of batch feed size. However,
flame combustion of solid waste is an extremely complex process and
there is always the possibility that a certain material performs
differently in the combustion chamber. Those CO spikes can be
identified from the oxygen monitoring data. Since there is a time
lag between the waste feed and the time that the CO analyzer
recorded a super-high CO spike, or the oxygen analyzer recorded a
zero oxygen period, the automatic cutoff of all waste feeds will
not solve the problem but may create more problems. If the CO
spike causes the hourly rolling CO level to approach the
permitted level, a 20% (or other appropriate number), cutback of
waste feeds as discussed previously may avoid an exeeedence and
the problems that an automatic waste shutoff can cause without
further upsetting the operation.
6.5 Research Needs
One long-term research need, which hazardous waste
incineration has in common with other combustion systems, is for
the development of continuous fast-response monitors. Additional
research questions arei (a) how to develop reliable continuous
monitors, (b) how to convert measurements made by the monitors to
indicators of risk, and (c) how to correct operations of a unit
when emissions approach unacceptable levels.
38
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Short-term continuous monitoring research needs to include
better definition of the limits of existing monitors for CO, o?
and "total hydrocarbons." In addition, considerable research is
needed on: (a) developing flue gas conditioning systems for THC
monitors that would preclude the plugging up of sample extraction
lines and also provide a reasonably accurate measure of mass
emission rates, and (b) on developing procedures for quality
control and quality assurance (QC/QA) of monitors during extended
operations.
Longer-term research should be undertaken to evaluate or
develop alternate monitoring methods for initial use as research
tools, and eventually for more routine monitoring or audit
purposes. A number of promising techniques already exist, but have
had little or no practical application to combustion sources. A
few examples of devices with high potential for application are
Fourier Transform infrared spectroscopy (FT1R), photoionization
detectors, molecular beam mass spectroscopy, laser spectroscopy of
several kinds including absorption, fluorescence, laser activated
infrared spectroscopy and Raman spectroscopy.
FTIR has the potential to monitor approximately twenty-two
flue gas components simultaneously including carbon monoxide,
water, hydrochloric acid, and sulfur dioxide many individual
organic compounds, and a measure of "total organics." A laser
fluorescence monitor for PAHs has been demonstrated in research.
with some additional modification and further testing, development,
and simplification of these systems might then be ready for use in
industrial application.
The current cost of some of these devices is relatively high,
but this could be reduced dramatically with further research. The
potential returns on such research are very high. A continuing
program to evaluate the most promising monitoring techniques and
to adapt them for application to a variety of combustion sources
would strengthen the ability to control pollution from these
sources.
since only a small fraction of the total number of compounds
produced during upset conditions can be monitored, there is a need
to relate the simple measures of emissions produced by a CO, THC,
or other detection surrogates to risk. Emission of Pies from
incinerators are a potential problem that forms part of the broader
problem of organic emissions from combustors. comparative
emissions and risk, assessments of different combustion categories
would be desirable in order to assign priorities for risk reduction
measures.
The presence of spikes of CO during operation of rotary kilns
raises the question on the best averaging method for emissions.
There is insufficient data on whether any PICs are emitted with the
episodic co emissions and if these emissions are at levels of
39
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concern, A lack of correlation of PICs with CO during the spiKes
would favor a geometric averaging, but more data are needed to
provide an evaluation of the problem*
The current incinerator permitting process is costly and time
consuming. A better understanding of the relationship of operating
parameters to emissions is needed in order to judiciously select
the parameters to control and to establish their limits. A goal
should be to use continuous monitors such as oxygen and temperature
to provide an early warning of equipment malfunction to provide the
operator with time to take corrective actions.
40
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7. CONCLUSIONS AND RECOMMENDATIONS
7.1 Conclusions
The Products of Incomplete Combustion (FICs) subcommittee of
the EPA'S Science Advisory Board reviewed the office of solid
Waste's (OSW) proposal to control emissions of PICs from hazardous
waste incinerators by instituting process controls based on CO and
THC emission concentrations. Because compounds known to cause
adverse human health effects have been detected at very low
concentrations in Pies, it is prudent to take precautionary
measures to control PlCs. However, the linkages between emission
concentration, exposure, and effects (health and environmental)
were not documented.
The proposal for controls was made even though OSW has not
established that emission of PICs from hazardous waste incinerators
currently pose a substantial risk. EPA's risk assessments indicate
that emission of PICs at currently measured levels are not likely
to produce significant human health effects. However, since the
current DRl standard applies only to designated POHCs, a 4-nines
(99,99%) DRl does not preclude the possibility that emission of
PICS could present significant human health risk,
overall, the concept of using CO and THC for the purpose of
regulating PICs is reasonable. However, EPA has not convincingly
documented the superiority of the selected averaging period, the
concentrations chosen for the CO and THC standard, and has not
evaluated emissions problems associated with unnecessary automatic
shutdowns, other values or approaches may be better. Individual
conclusions, referenced to the relevant sections' of this report
appear below.
1. PICs, including compounds known to have adverse effects on
human health, have been detected at concentrations in the
ppbv and pptv range in the emissions of hazardous waste
incinerators, boilers, industrial furnaces and other
combustion sources. (Section 5,1)
2. Carbon monoxide (CO) is a good, but conservative indicator
of combustion performance. Poor combustion conditions are
always indicated by high Co levels. A high CO concentration
may not indicate poor combustion conditions* (Section 3.1)
3, CO does not correlate with THC when CO exceeds 100 ppm. In
addition, THC concentrations measured during the trial burn
cannot be assumed to be representative of routine THC
emissions even if CO concentration remains unchanged.
(Section 3.2)
41
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4. Even frequent routine stack testing for THC may not be
adequate to provide a basis for assessing compliance with THC
limits. (Section 3.2)
5, continuous emissions Monitoring (CEM) of THC is desirable
because of the limitations of CO as a surrogate for THC,
(Section 3.2 and 4.3)
6. While there are data relating CO and THC emissions at low co
concentrations sufficient to support the concept of limiting
CO to ensure high combustion efficiency and reduced total
organic emissions, the existing data base is not sufficient
for assessing emission concentrations for potential PICs,
(Section 3.4)
7. Although the commercially available flame ionization detector
(FID) responds to those classes of organic chemicals most
abundant as PICs in hazardous waste combustion emissions, the
magnitude of the FID response varies with the composition of
the organic material present. While the FID response could
provide an approximation of the PICs concentration good
enough to serve as an indicator of good combustion control,
it is not appropriate as the basis for a health risk
estimate. (Section 4.1)
8. In principle, a hot transfer line is better than a cold one.
However, the iso°c transfer line proposed by EPA has not been
validated for reliability and maintenance problems.
Anecdotal evidence was presented that THC systems can present
reliability difficulties even during trial burns.
(Section 4.2)
9. A recent survey was presented to indicate hydrocarbons in
hazardous waste emissions are being monitored on a continuous
basis during routine operations in several facilities for
periods ranging from l to 7 years using unheated FID systems.
A cold THC system may be more practical to serve as a
combustion performance indicator. A hot THC system would
detect a larger fraction of the THC if operability and
maintenance problems could be overcome. (Section 4*3 and 4.4)
10. Use of a "cold" or "conditioned gas" FID as a continuous THC
monitor will, however, require routine maintenance and
rigorous attention to QA/QC protocols, and the careful
training of skilled operators. (Section 4.3}
11. Despite the limitations of the data and the uncertainties
introduced by the assumptions, the risk assessment
methodology is sufficient to provide a risk-based check on
the proposed THC emissions limit. (Section 5.3.1}
42
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12, Although the toxicity of the total THC mixture cannot be
assessed, the measured THC emissions of 20 ppmv are likely
to present carcinogenic risles below the suggested limit of
1 in 100,000 in most cases. Thus, EPA'a evaluation of the
emissions limit provides evidence of adequate safety.
13. The approach to dispersion modeling employed by the Office
of Solid Waste in the evaluation of exposure and the risk
assessment associated with hazardous waste incinerators is
reasonable and appropriate. (Section 6*1*1)
14. Sensitivity analyses of the relative impact of stack height
and ambient meteorology on dilution factors would be helpful
to applicants and regulators. (Section 6.1.1*3)
15. In cases where stack heights are low relative to the height
of nearby buildings or where the fetch to nearby buildings
is small, fluid modeling in a boundary-layer wind tunnel may
be preferable to mathematical dispersion modelling. (Section
6.1.1.5)
16. While CO monitoring data provide a good indicator of
combustion performance, CO alone may not be sufficient for
combustion control purposes. Oxygen monitoring data provides
better guidance to the operator* (Section 6.2)
17. Other controls, related to change in temperature, can be used
as alternatives to oxygen control. (Section 6.2)
18. Sudden changes in fuel feeds can cause upsets to incinerator
operation. Such upsets may produce increased emissions of
PICs, (Section 6.2)
19. The most likely cause for continuous high CO concentrations
in a large-scale incinerator with multiple feeds is that the
total waste feed is too high; the same is generally true for
small liquid injection type incinerators, low incinerator
operating temperature may also cause high co. (Section 6.2)
20. Unnecessary shutdown of the waste feed to incinerators may
be counterproductive to control of PICs in some cases and
should be discouraged. Alternate approaches, including
taking corrective measures to avoid an automatic wastefeed
cutoff or phased shutdown, may be more effective* Facility
operators should be encouraged to set an alarm level to alert
of impending waste feed cutoffs and take remedial measures
to avoid them.
21. A major research need which hazardous waste incineration
shares with other combustion systems, is for the development
of continuous fast-response monitors that could be used for
feedback control. (Section 6.3)
43
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22. combustion devices differ and the differences between
devices, such as those between cement kilns and hazardous
waste incinerators, need to be accounted for in developing
a strategy for controlling PICs. (Section 3,3.3)
23. The risk assessment methodology should not be applied to
specific sites as proposed under Tier II by using THC data
obtained during trial burn tests only because of the lack of
assurance that THC will remain low during routine operations
if carbon Monoxide alone is continuously monitored. Routine
monitoring of THC is necessary. {Section 5.2)
7.2 Recommendations
l. EPA should conduct more studies to better define whether or
not a problem exists with the emission of PICs, the source(s)
of the problem if it exists, and how to minimize the problem.
2. To assure that THC remains low even when CO is high, the Tier
II approach should require GEM of THC* This is necessary
because CO concentration does not correlate with THC
concentrations when CO exceeds 100 pp». Therefore,even if
a CO limit is set and monitored for,the THC concentrations
measured during the trial burn cannot be assumed to be
representative of routine THC emissions. (Section 3.2)
3. EPA should develop and validate a heated sampling system.
Until such a line is validated, the continued use of a cold
transfer line may be appropriate because the cold transfer
line has been shown to operate successfully under the
temperature and operating conditions expected. {Section 4*2)
4. EPA should investigate and document the magnitude of effects
such as rate of condensation, build-up of non-volatile
organics, flue gas moisture effects, and effects of
particulate matter on the medium- to long-term performance
of the monitoring system. The selection of appropriate
calibration compounds and determination of precision and
accuracy data over various time periods and concentrations
is also a subject for further investigation* (Section 4.4)
5, EPA should revise its discussion of dispersion modeling to
employ standard terminology. (Section 6,1.1.2)
6. EPA should include sensitivity analyses in the supporting
documentation for the regulation. (Section 6,1.1.3)
7. EPA should expand on the data needs enumerated in Part Four
of its document to include more information on terrain.(4)
(section 6.1.1.3)
44
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8. Fluid modeling in a boundary-layer wind tunnel should be
considered where staclc heights are small relative to the
height of nearby buildings or where the fetch to nearby
buildings is small. In such cases, mathematical dispersion
modeling may not be the preferred simulation methodology,
(Section 6.1.1.5)
9. An oxygen concentration limit should not be used as a permit
condition although it provides useful guidance to operators
for decisions on corrective actions. Controls related to
temperature may be considered as alternatives to provide
information for corrective action, (Section 6,2.1)
10, A corrective action system should be considered as a first
response to CQ/THC concentrations that approach permit limits
in order to avoid unnecessary automatic waste cutoffs because
sudden changes in fuel feeds may create major upsets in
incinerator operations which may lead to the release of more
PICs to the environment than are associated with a CO spilce.
Nonetheless, an automatic waste shutoff should be triggered
when CO and THC levels reach the permit limit.(Section 6.2)
11, EPA should conduct research on how to develop reliable THC
continuous monitors, how to convert measurements made by the
monitors to indications of risk, and how to correct
operations of a unit when emissions approach unacceptable
levels. (Section 6,3)
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APPENDIX A
A Discussion of Averaging as it Applies to Emissions Data Controls
One problem results from occasional momentary high CO spikes
which may give one-hour rolling average CO values above the current
proposed CO standard. If the CO remains higher than normal for a
prolonged period of time, it is likely that there is a combustion
problem and the waste feeds should be shutoff to inspect the
problem. The current proposed standards adequately address this
concern. However, since CO is a conservative indicator for
combustion performance, CO spikes will be observed during the
normal incinerator operation. Any disturbance in the flame zone
may produce a CO spike which can be large or small. The CO spike
data will form a skewed (lognormal) distribution with most of the
data being very low (around 20-30 ppmv), but some of the spike
values will be very large (higher than 1,000 ppmv). Depending on
the cause, those spikes may last from only a few seconds to one or
two minutes in the combustion chamber, but will show up as a wider
peak at an extractive CO monitor due to the baffling and damping
effect of the air pollution control equipment, the sampling line,
and the flue gas sample conditioning system.
There are many reasons for the generation of such spikes.
The major ones aret
(a) the combined effect of a particular batch feed has too
high a volatilization rate and too high heat content;
(to) purging clean a plugged feed line;
(c) loss of feed in one of the burners due to line plugging
or failure in the flame management system and the
associated safety shutdowni
(d) switching feeds and the associated shutoff and startup,•
and
(e) waste feed rate change due to control response or
mechanical response.
The CO spikes generated are lognormally distributed. Based
on some preliminary discussion with rotary kiln operators, the
Subcommittee offers the following as a typical scenario. A 5,000
ppav CO spike may occur once every few months. A 2,000 pprav CO
spike may occur a few times per week. A 500 ppmv CO spike may
occur a few times per day. There will be times when CO spikes
occur more or less frequently.
The impact of those CO spikes on the rolling hour average is
shown in Figure A-l for an in-situ mounted CO analyzer {Plant A).
A-l
-------
Figure A-2 shows similar monitoring data for an extractive CO
analyzer at a different facility (Plant 1)» As can be seen, those
rare high CO spikes will cause incinerator operation to be shut
down if the CO standard is not set properly. Such CO spikes cannot
be entirely avoided, due to random statistical variation as the
result of complexities of a multiple-purpose rotary kiln operation
and high sensitivity of CO as a combustion performance indicator.
During Plant A's RCRA trial burn compliance test, it was shown that
as long as the flue gas oxygen level is higher than 1%, the CO
spikes did not cause deterioration in destruction performance.
In Figure A-2, each temperature peak represents a batch feed.
As can be seen, the majority of the batch feeds did not cause a
high CO spike problem. Since the solids volatilization and the
associated combustion phenomena are very complex, and due to the
fact that CO is a very sensitive indicator, certain batch feeds
will generate high CO spikes. The same situation applies to burner
switchover,* it may or may not generate high CO spikes.
During Plant B's RCRA trial burn compliance test, the batch
feed rates were accelerated to produce as many high CO spikes as
possible (over ten spikes higher than 2,000 ppmv uncorrected were
produced). During the trial burn test, flue gas organics level was
continuously monitored with a MS/MS (two Mass Spectroscopies in
series for better compound speciation) mounted in a mobile van.
There was no deterioration in destruction performance during those
high CO spikes observed. However, there is insufficient data on
other compounds to be confident that no other PICs were present.
Figure A-3 shows a two-hour period, extractive CO monitoring
data (adjusted from 13% to 7% oxygen) at a third plant (Plant C).
Four methods to calculate the rolling average data were used and
will be discussed. Figures A-4 and A-5 extended the data to a ten-
hour period to show the long-terra trend.
Figure A-4 shows extractive CO monitoring data (uncorrected)
at a multiple-chamber incinerator with multiple feeds (Plant 0).
During one of Plant D's RCRA trial burn compliance tests, pint
bottles of four different materials (solid, slurry, and two
liquids) were burned. Forty pint bottles (ten of each material)
were burned in controlled order (one bottle followed with another
of different content) during each vosf sampling period. Figure A-
6 shows data for three VOST sampling periods under the same
operating conditions. The resulting measurements were different
even though the content and operating conditions were the same.
The highest CO spike observed was the result of emergency shutdown,
since the facility was operated under a permit which allows a CO
spike no higher than 150 ppm. The test results differed because
each bottle had been subjected to a different flame condition and
broke in a different manner. However, test data indicated no
deterioration in destruction performance.
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A-3
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The Subcommittee recommends that EPA evaluate the impact of
those occasional CO spikes which would occur in real-world
incinerator operation. The Subcommittee also recommends that EPA.
evaluate the use of geometric average (GA) as an alternative to the
arithmetic average (AA) . It the intent of the regulation is to
regulate the total amount of CO discharged at an incinerator, an
arithmetic mean is more appropriate and will account for the total
amount of GO discharged. Since the Subcommittee understands the
intent of the regulation is to use CO as a surrogate combustion
performance indicator, then a geometric mean may be more
appropriate, because the CO data are lognorraally distributed.
The relationship between the GA and AA can be expressed by
the following equation: z
AA*1 +• S*
where "S" is the standard deviation of the data points used to
calculate AA and GA. Table K-l shows the ratio of GA to AA and
its relationship with standard deviation, S, at three CO hourly
rolling average levels observed in Figure A-3. The three levels
were: AA at 32 ppmv between 0 to 20 minutes, AA at 112 ppmv
between 20 to 50 minutes, and AA at 185 pptav between 60 and 80
minutes .
During normal CO variation between 10 to 60 ppmv (as shown
between 0 to 20 minutes in Figure F) the AA was 32 ppmv, the
standard deviation(s) was about 10 ppmv, and the GA was 31 ppmv,
which was almost the same as AA (GA/AA =0,96), If the standard
deviation increased to 20 ppmv, the CO spikes would have to vary,
repeatedly, between approximately 10 to 100 ppmv. Even so, the
ratio of GA/AA would be 0.87.
Between 20 to 50 minutes, the observed AA was 112 ppmv and
GA was 39 ppmv, which was 35% of AA. This means the standard
deviation of the data points had to be 300 ppmv. As shown in
Figure F, the increase in AA was caused by only two large CO
spiJces, if the operation was seriously faulty, there would be
repeated CO spikes and the standard deviation would be narrower.
For example, if the CO spikes had varied repeatedly between 50 and
250 ppmv, the standard deviation would be about 50 ppmv. The
observed GA would then be approximately 102 ppmv, which is 91% of
the observed AA,
A-5
-------
200
ARITHMETIC (M) GEOMETRIC (GA) AVERAGES
\
INSTANTANEOUS CO
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140
TIME (MINUTES)
FIGURE A-3 Extractive CO Monitoring Data Corrected for Gxyfjen with
Four Roll-inq Averaqe Scenarios, for a Multipurpose
Rotary Kiln Incinerator (Plant C)
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Between 60 to 80 minutes, the observed AA was 185 ppmv and
<3A was 44 ppmv, which was 24% of the AA. This means the standard
deviation of the data points had to be 750 ppmv. As shown in
Figure A-3, the increase in AA was caused by the two additional
large CO spikes. If the operation was seriously faulty, there
would also be repeated, CO spikes. For example, if the CO spikes
had varied repeatedly between 30 to 500 ppmv, the standard
deviation would be about 200 ppmv. The observed GA would then be
approximately 125 ppmv which is 68% of the observed AA. The
difference between GA and AA will be less if the standard deviation
is smaller.
As shown in the above discussion, the geometric average
removes the effect of a few very large values which will occur
occasionally in incinerator operation. However, the difference
between the geometric average and arithmetic average will be small,
if the combustion conditions is seriously faulty as indicated by
repeated CO spikes or continuous high CO levels.
EPA should also evaluate the averaging time, which will have
major impacts as well. Figures A-5 and A-6 illustrated the impact
of averaging time (one hour and three hours were used) to the
arithmetic average and to the geometric average for operation at
Plant C.
In Figure A-5, continuous CO values are plotted for a period
of 600 minutes (10 hours). For the entire period, 97.3% of all
values (adjusted to 7% oxygen) were less than 200 ppmv and 96.5%
were less than 100 ppmv.
The one-hour and three-hour rolling geometric averages (l hr
GA, 3 hr GA) and arithmetic averages (1 hr AA, 3 hr AA) are plotted
for the same 600 minute period in Figure A-6. During periods of
relatively constant operation, the CO is more normally distributed
and the AA and GA approach each other. Examples are shown at times
0-130, 200-240, and 340-400 minutes. Although the instantaneous
CO value exceeded 100 ppmv less than 3.5% of the time, the one-hour
AA appears to exceed 100 ppmv about 25% of the time. The
arithmetic average, therefore, exaggerates relatively short events.
In summary, a good control strategy should not only address
the limit, and averaging times, but also the frequency of both
false positives (shutting down when the incinerator is operating
correctly) and false negatives (operating the incinerator when it
is running inefficiently) , A problem is that too many false
positives nay result In higher overall emissions. As was discussed
earlier, the CO level is a conservative indicator of combustion
performance, so modifying the standard to reduce false positives
might not increase the false negatives.
A-8
-------
AA =• 32 ppmv AA - 112 SOtnv AA *= 135 somv
_S_ GA/AA S_ GA/AA S
5 .99
10 .95
15 .91
20 .35
30 .73
50 .34 50 .91
100 .74
ISO .59
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250 ,40
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100 .38
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200 .68
250 ,60
300 .S3
500 .35
700 .26
750 .24
800 .23
TABLE A-l Relationship Between the Ratio of Geometric Average (GA)
and Arithmetic Average (AA) and the standard Deviation (S) at
Three Observed CO Hourly AA Levels Shown in Figure F.
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A-9
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incinerator {Plaru C),
-------
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OT f*
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OH
w p
^S
B?b
gS
c &
<<
*w< «rf*
a Q
0
TIME (MINUTES)
FIGURE A 6 Four rolling average scenarios for CO monitoring daia shown in Figure 3A (Plant C).
-------
ENVIRONMENTAL DEFENSE FUND
1616 P Street, NW
Washington, DC 20036
<202) 387.3500
July U, 1989
National Headquarterr
257 Park Avenue South
New York, NY JOOlO
(212) 505-2100
1405 Arapahoe Avenue
Boulder. CO 80302
(303)440-4901
5655 College Avenue
Oakland, CA 94618
(415)658-8001
1108 East Main Street
Richmond, VA 23219
(804) 780-1297
12S East Hargftt Street
Raleigh, NC 27601
(919)821-7793
Kathleen White Conway
Deputy Director, SAB
1418 South Monroe Street
Arlington, VA 22204
Dear Kathleen:
As I mentioned co you on the photic earlier today, I
have looked in some detail at Che derivation of the THC UTIXC
risk value used by EFA in its risk assessment for assessing
the risk of PIC emissions froa hazardous waste incinerators.
One of the assumptions used in the risk assessment
that has been considered by both EPA and che PIC
Subcommittee to be very conservative is ch« use of
95eh-percentile emission levels for individual FIG
compounds, I have examined this assumption more closely
after noticing that EPA also used 5Sth*p*rcentile values for
non-carcinogenic Cl and C2 hydrocarbons. Se* Table 18 of
the "Background Information Cod-menC for Che Development of
Regulations for PIC Emissions from Hazardous Waste
Incinerators."
The raw Cl and C2 hydrocarbon emission data used by
EPA were actually measured in fossil fuel burning devicts,
and are listed in Attachment 1. As you can see, the 95th
pereeneile values used by EPA (17575 ng/L for Cl and 34200
ng/L for C2) are heavily influenced by the single high
values measured in the wood boiler,-test #1,
To test the actual conservatism of EPA's use of the
95th peteentile values, I calculated the THC unit risk value
that would be predicted using median (rather than f5ch
petcentile) emission values for both individual carcinogenic
PICs and Cl and C2 hydrocarbons. While my calculation did
not include all of the carcinogenic compounds EPA included
(see Table 14 of che Background Information Document), it
included all of the compounds chat contributed significantly
to the calculated risk, the Bass of PIC emissions, or both.
The compounds I Included account far 96% of the total THC
risk and 98% of the total THC moss in EtA's calculation,
My analysis Is shown in Attachment 2. It shows thac
us* of asdlan values predicts a THC unit risk value thac is
almost 90% of that predicted using the 95th percentile
emission values.
-------
July 14, 19S9
Page 2
In short, and perhaps contrary to intuition, IPA's assunption is not at
a.11 conservative. Thin is because ElA's use «f 9Sth pereentila values for Cl
and C2 hydrocarbons (which do not contribute at all to risk) downwardly skevs
the weight fractions, and therefore the weighted unit risks, of the individual
carcinogenic PIC compounds.
Given that this factor was assumed by tha PIC' Sttbcouaiitte« to very
significantly contribute to the overall conservatism of EfA'a risk assessment,
we may need to re* evaluate the language pertaining to this issue in our
report,
Flease feel free to call ne if you have questions on this natter.
Sincerely,
Richard A. Denison, Fh.D»
Senior Scientist
Attachaents
cc; SAB FIC Subcommittee
Jack Kooyoomjian
Bob Hollowmy
-------
All I i \
t~TH^Ji*^<2M^l L
\ \. ^frW \* ~" %„ i^»
d AND Ct GQHCENTRAT1QNS BASED OH OATA IH TABLE I
Case no.
from Taoli 2 Ft«d type Test
2 Wood 1
2
3 iasiHne
Low NOX
4
5 Caal/watir 1
2
• 6 Caal/wtter/on 1
2
8 Caal Dry bottom
Wet bottom
Cyclont
Stoker.
Lignltt Dry bottom
Cyclone
Stoker
Rtsldual oil Tanfintlally find
Wall fired
Natural gas Wall find
10*
("9/U
18,500
2,500
0
0
200
3,500
3,000
0
0
3f33Q
3,330
610
970
2,570
6,440
1,780
1,450
5,910
330
929
(ng/U)
36,OCO
5,000
3,600
2,500
0
10,500
5,800
900
0
0
630
270
5,770
310
SCO
330
260
520
330
0
1 Data froo "Total Mass Emissions from a Hazardous waste Incinerator,"
Final Report, HR1 Project Ho* 8671-1(1).
B-2
-------
Recalculating risk using median instead ot 95th pereentile emission values
£The eoapovnds listed below account far 96% of the risk, 9i% of the total
mass, and 90% of the non-C^/C-, mass chac were calculated using the 95th
pereentile emission values.]
Weight
Median
Benzene
Carbon Tetrachloride
Chloroform
Chlo ronethane
1,2-Dichloroethane
1,1-Dichloroethylene
DiethylsCilbestrol
Formaldehyde
Hexachlorobenzane
2,3,7,8-HxCDD
Kethylene Chlatide
2,3,7,8-PeCDD
2,3,7,8-TCDF
2,3,7,8-TCDD
Other TCDDa
1,1,2,2 -Te trachloroe than*
Tetraehloroethylen*
1,1,2-Trichloro*ehane
Tr ichla ro
-------
Benzene
Carbon Tetrachlori.de
Chloroform
Chloromeehsne
t.2-Diehloraethana
1,1-Dichloroethylene
Formaldehyde
Hexachlotobenzene
2,3,7,8-HxCDD
Hethylene Chloride
2,3,7,8-FeCDD
2,3,7,8-TCDF
2»3f7.8-TCDD
Ochet TCDDs
1,1,2,2*Tecraehloroetham
Tecrachloroecfaylene
1,1,2-Triehloroathane
Tzrichloroathylwne
2,4,6-Trichlorophenol
Vinyl Chloride
Cl Hydrocarbons
C2 Hydrocarbons
Hightail
0
0
0
0
s
Median
48
5.1
31
474.6
4.8
2.6
398.5
2.3
.0000425
21
.0000053
.0000190
, 0000425
0.00029
5.7
7,3
15
6.2
8.3
1.7
1615
575
1,
1.
9.
1,
I,
8.
Weight
Fxa
49e-02
SSe-03
62*-03
47e-0l
49e-Q3
Q7t»G4
7.
1.
2.
3.
2,
3,
tJhit
Risk
10«-06
50e-05
30e-05
30* -06
60e-05
30e-04
1.24e-01 l,30e*Q5
7.
1.
6.
.14* -04
.32e-OS
,52*-03
1.64«-09
5.
1,
9
1
,90*-09
.32e-08
.QQ«-08
,77e-03
2,27e-03
4
*
2
5
5
1
.66«.03
,92*-Q3
,58e-03
.28e*04
,01e-01
.7S«-01
5.
2,
4,
2.
5.
OOe-06
OOe-«-00
20e-06
, 5Qa+01
,00»*00
S.QOe+01
S,
,00c-01
S.fO«-05
4.
1
1
5
5
.80*-07
.60«-05
.30*-Q6
. 60«-06
.00* -06
.«
__
1.
2.
2.
4.
3.
2.
1.
3.
2.
2.
4
2
6
4
1
i
7
2
1
2
Unit
Risk
06*-07
37*-08
21*-07
86e-07
87*-08
66«-07
6U-06
,S7«-09
,S4«-08
.74* -08
.1U-08
,95«-08
.SOe-07
. 50«.Q3
.04«-07
.09* -09
,45* -08
.50a-09
,44«-08
.64e-09
--
--
%
of
Total
Risk
2.
0.
5.
12.
1.
7.
42.
0,
0
0
80
63
85
86
02
04
.53
.09
.70
.72
1-09
0
17
1
2
0
1
0
0
0
.78
,45
.19
.76
.01
.97
.07
.38
.07
--
TOTAL
3222.1
1.000
3,7S*-Q6
100
-------
Benzene
Carbon TecrachXoride
Chloroform
Chloromethane
1,2-DichloroeChane
1,1-Dichloroethylene
Hexachlorobenzene
2,3,7,8-HxCDD
Methylene Chloride
2,3,7,8-PeCDD
2,3,7,8-TCDF
2,3,7,8-fCDD
Other TGDDs
1,1,2,2-Tetraehloroethane
Tetrschloroethylen*
1-, 1,2-Triehloroe than*
Triehloreethylenc
2,4,6-TrlchloEophenol
Vinyl Chlorid*
Cl Hydrocarbons
C2 Hydrocarbons
0.
0.
0.
0.
1
Median
48
5.1
31
474,6
4.8
2.6
2,3
0000425
21
0000053
0000190
0000425
0,00029
5.7
7,3
15
6.2
8,3
1.7
1615
575
1
1
1
1
1
9
8
1
7
1
6
1
1
2
2
5
2
2
6
5
2
Weight
Fxn
.70**Q2
.aie-03
.10* -02
.68*-Ql
.70* -03
.2U-Q4
.15* -04
.Sla-QS
.44«-03
.384-09
.73*-09
,51* -08
,03*-07
.02e-03
.59*-03
.31*-Q3
.20*-03
.94* -03
.02* -04
-72«-01
.04* -01
7
Unit
Risk
.10e-06
l.SOe-OS
2
3
2
3
5
2
4
2
5
5
5
5
4
1
I
5
.30e-05
,30*-0i
,60e*05
.30* -04
.OOe-06
.OOe-t-00
.20*-06
, 5Q*+Q1
, 00*+OQ
, OOe^-01
.OOc-01
.fOe-05
.80* -07
,iQ*-05
Weighted
Unit
Risk
1.
2.
2,
5.
4.
3.
4,
3,
3,
4.
3.
7,
5.
1.
1.
a,
21*-07
716-08
53«-07
55e-Q?
42e-08
Q4e-Q?
07e-09
Ole-08
12e-08
69e-08
3£«-Q8
53e-07
14e-08
Wa-07
24e-09
,50* -08
.30e-06 2.85e-Q9
. 60«'06 l,65e-08
5.00*-0fi
--
--.
3,
.Qle-Q§
--
.,
i of
Total
Risk
4,
1.
10,
22.
1.
12,
0.
1.
1.
1.
1,
30,
2.
4.
0,
3.
0.
0,
0
87
09
18
37
78
25
16
21
26
85
36
35
,07
80
,05
,43
,12
.66
.12
--
TOTAL
2823.6
l.OQQ
100
-------
APPENDIX C
Conunents from Paul Diesler of the Executive Committee
1. If you have the upper 95% bounds of risk PA and P8 at
concentrations (or doses, exposures) CA and Cg, this means that
there is only one chance in twenty that the risks will,
individually, equal or exceed the upper 95% bounds. If A and B
occur together at CA and CB, the sura of the risks, PAB^PA+PB is
not at the 95% upper bound, but, rather at a higher percentile.
In this case, if A and B act independently, the joint percentile
is 1-(1/20) (V2Q)=1~Q.0025=0.9975; or 99.75%. (If A and 1, and
therefore PA and P8, are correlated in some way, constrained, etc,..
the calculation is less simple but the result is the same
qualitatively, if instead of A and B one has A,B,e,D, etc.. the
percentile becomes still greater, fhis is the situation when
adding up the risks of many PICS in hazardous waste incinerator
emissions,
2. To obtain an upper bound risk for a mixture of &,B,C, etc.
at the 95% percentile (and so to be comparable to other risks at
the same level of confidence) just calculate the expectations of
mean risks, __ __ _ _
p= pA + p8 + pc
at CA, Cf, Cc, etc...; the mean for the mixture is then
P - PA + P^ + P! + etc.
(at the low levels of risk involved, and assuming independence—no
synergism, antagonism). Similarly the variance of the risk for the
mixture can be obtained from the sum of the variances of the
individual risks, from which the standard deviation (the square
root of the variance) can be obtained. Given the mean and standard
deviation of the mixture's risk, the upper 95% bond of risk for the
mixture can be estimated—putting the estimate of the upper bound
of risk for a mixture on the same basis as other such risk
estimates. (Notei The regression or curve fitting method with
which the upper 95% percentile risks are calculated should also
estimate, if asked, the mean risks expected.)
-------
3* Partial ReconstructJOJOL. of the 95th Percentile^Calculations
ca.se_I.L If all PICs were, in fact, combustion, products
Sm = sum of median concentrations of carcinogenic PICs
S9S =• sum of 95th percentile concentrations of carcinogenic
CB = sum of median concentrations of Cl and C2
c?s = sum of 95th percentile concentrations of ci and C2
rm = unit risk of the carcinogenic PICs in the median case
r9S = unit risk of the carcinogenic PICs in the 95th
percentile case
Now:
s.13 x 10*
B. rw = - 9.23 X 10"
c* rH = 0.88 r,5
where rm and r9S are the weighted unit risks in the median
and 95th percentile cases, respectively.
From A, e, and Cs
f\ QQ
Vr * OO
Now:
C,, * 1,615 + 575 - 2,190
SB 4- CB - 3,222.2
Therefore, S,,, = 1,032.2
Also CM = 17,575 + 34,200 = 51,775
C-2
-------
The Cl and C2 emissions are highly skewed to the right
(C95 » cm) . Suppose the other Pics are skewed and that
S95 = 103^ (where m>l) .
could they be highly skewed?
suppose the other (other than Cl and C2) PICs distributions
are similarly shaped,* then _ _
rn * r95 as a limit*
Then : _ _
*m • *m ' «*• + 51'775
0.88* ---- ---- ---- • --------- • --- •
a*. 3222.2
and, with Sm - 1032.2, m * 29
or, therefore, the other PICs are highly skewed.*... too . in
Case I enough so that relative to the skewness of Cl and C2 , Sm is
only 88% of S95.
If all the above is true (check the distributions) , this
result has nothing to do with the zero risk of Cl and C2 but only
with the relative skewness of the distributions of Cl, C2, and the
carcinogenic PICs,
_ _ (Note: for various r^/rm > 1, m is still large unless
r95/rm is unbelieveably large) — Must check skewness of
carcinogenic PICs (that is, actual ratio of
Case II; Allow for effect on r95/r_of diethvlstilbesterol
10=
At the median case, DBS contributes more than 1/2 of total
risk; same is true of rm since Cl and C2 contribute no risk.
Therefore at the 95th percentile case DBS contributes very little
to the average iw because its concentration (O.l nanogran/liter)
does not change but that of the non-Gl/C2 PICs rises. Thus, DES
has the effect of decreasing average r^/r,, compared to what it
would be if OSS concentrations behaved naturally, skewness of the
non-Cl/C2 PICs still needs to be great to compensate here.
C-3
-------
Glossary of Tenas
APPENDIX D
AA - ARITHMETIC AVERAGE
ADI - ALLOWABLE DAILY INTAKE
C - MODELED ATMOSPHERIC CONCENTRATION
CE - COMBUSTION EFFICIENCY
CEM - CONTINUOUS EMISSIONS MONITORING/CONTINUOUS EMISSIONS
MONITOR
CEMS - CONTINUOUS EMISSION MONITORING SYSTEM
CO - CARSON MONOXIDE
C0_ - CARBON DIOXIDE
v£
ORE - DESTRUCTION REMOVAL EFFICIENCY
EPA * ENVIRONMENTAL PROTECTION AGENCY
FID - FLAME IONIZATION DETECTOR
FTIR - FOURIER TRANSFORM INFRARED SPECTROSCOPY
GA - GEOMETRIC AVERAGE
GOP - GOOD OPERATING PRACTICE
MEI - MAXIMUM EXPOSED INDIVIDUAL
MWI - MUNICIPAL WASTE INCINERATION
02 - OXYGEN
ORD - OFFICE OF RESEARCH AND DEVELOPMENT AT SPA
OSW - OFFICE OF SOLID WASTE AT EPA
PAH - FOLYCYCLIC AND/OR POLYNUCLEAR AROMATIC HYDROCARBONS
PCDD * POLYCHLORINATED DIBEN2Q-P-DIOXIN
PCDF - POLYCHLORINATED DIBENZOFURAN
PCP - PSNTACHLOROPHENOL
PIC - PRODUCTS OF INCOMPLETE COMBUSTION
PICS - PRODUCTS OF INCOMPLETE COMBUSTION SUBCOMMITTEE OF THE
EXECUTIVE COMMITTEE OF THE SAB
PNA - POLYCYCLIC AND/OR POLYNUCLEAR AROMATICS
POHC - PRINCIPAL ORGANIC HAZARDOUS CONSTITUENTS
POM - POLYCYCLIC AND/OR POLYNUCLEAR ORGANIC MATTER
PPM - PARTS-PER-MILLION (BY VOLUME OFTEN IMPLIED)
PPBV - PARTS-PER-BILLION BY VOLUME
PPTV - PARTS-PER-TRILLION BY VOLUME
Q - STACK MASS EMISSION RATE
QC/QA - QUALITY CONTROL AND QUALITY ASSURANCE
RAC - REFERENCE AIR CONCENTRATION
RCRA - RESOURCE CONSERVATION AND RECOVERY ACT
RfD - REFERENCE DOSE
S - STANDARD DEVIATION
SAB - SCIENCE ADVISORY BOARD
TCDD - 2,3,7,8, - TSTRACHLORODIBlNEO-P-DIOXIN
THC - TOTAL HYDROCARBONS
TSDF - HAZARDOUS WASTE TREATMENT, STORAGE AND DISPOSAL FACILITY
VOC - VOLATILE ORGANIC COMPOUND
VOST - VOLATILE ORGANICS SAMPLING TRAIN
Z. - AERODYNAMIC ROUGHNESS
-------
APPENDIX E
References
1. EPA Memorandum dated November 16, 1988 from Bob Holloway to
Jack Kooyoomjian entitled "SAB Review of PIC Controls for
Hazardous Waste Incinerators."
2. Draft Preamble for Hazardous Waste Incinerator Regulation
(40 CFR, Parts 260, 261, 264 and 270), dated June 14, 1988.
3. Guidance on Carbon Monoxide Controls for Hazardous waste
Incinerators, Midwest Research institute Draft Final Report
to EPA, dated September 9, 1988,(Supereeeded by reference
#37)
4. Background Information Document for the Development of
Regulations for PIC Emissions from Hazardous Waste
Incinerators, Midwest Research Institute Draft Final Report
to SPA, dated July 1989.
5. Briefing for SAB Entitled, "Proposed Controls for Hazardous
Waste Incinerators: Products of Incomplete Combustion
(PICs)," dated December 15-16, 19S8.
6. LaFord, R.K,, J.L. Kramlich, and W.R, Seeker, "Evaluation of
Continuous Performance Monitoring Techniques for Hazardous
Waste Incinerators," APCA Journal. 33. (6); 658? June 1985.
7. Report to the Administrator on the Incineration of Liquid
Hazardous Wastes — Environmental Effects, Transport and Fate
Committee — USEPA Science Advisory Board, April 1985.
8. U.S.E.P.A. (1981a): Guidelines for fluid modeling of
atmospheric diffusion. EPA-600/8-81-009, Office of Air
Quality Planning and Standards, Research Triangle Park, North
Carolina 27711.
9. U.S.E.P.A. (1981b); Guideline for use of fluid modeling to
determine good engineering practice stack height.
EPA-45Q/4-81-003, Office of Air Quality Planning and
Standards, Research Triangle Park, North Carolina 27711,
10. Kun-chieh Lee, "Research Areas for Improved Incineration
Systen Performance/1 Journal^of the Air Pollution Control
Association (JAPCA), Vol. 38, No. 12, December 1988,
pp. 1542-1SSQ.
11. "Hazardous Waste Incineration, A Resource Document," The
American Society of Mechanical Engineers, Co-sponsored by
Air Pollution Control Association, American institute of
Chemical Engineers, and U.S. Environmental Protection Agency,
January 1988,
12. E.T. Oppelt, "Incineration of hazardous waste, A critical
review," JAPCA 371558(1987).
-------
13. J.D. Kramlich, et al*f Laboratory Scale Flame-Mode Hazardous
Thermal Destruction Research," Energy and Environmental
Research Corporation, EPA-600-/2-84-086, NTIS PB-84-184902,
April 1984.
14. A. Trenholm, "Performance Evaluation of Full-scale Hazardous
Incineration,!" EPA, P1-85-1295QQO, 1984 VolS. 1-5.
15. "Handbook, Permit Writer's Guide to Test Burn Data, Hazardous
Waste Incineration/1 EPA 625/6-86/012, September 1986.
16. W. Tsang, W, Shauto, "Chemical Processes in the Incineration
of Hazardous Materials,11 National Bureau of Standards, in
J.H. Exner, ed., Detoxification of Hazardous Waste. Ann Arbor
Science, pp. 41-60(1982).
17. K.C. Lee, et al.r "Revised Model for the Prediction of the
Time-Temperature Requirements for Thermal Destruction of
Dilute Organic Vapors and Its Usage for Predicting Compound
Destructibility," Paper presented at the 75th Annual meeting
of the Air Pollution Control Association, New Orleans, LA,
June 1982.
18. W.M, Shaub, W. Tsang, "Dioxin formation in incinerators,"
Environmental Science Technology I7j721 (1983).
19, "Total Mass Emissions From a Hazardous Waste Incinerator,"
Midwest Research Institute report to EPA-QRD, NTIS PB
87-228508, August 1987.
20. D.S. Duvall, W.S. Rubey,"Laboratory Evaluation of High
Temperature Destruction of Polychlorinated liphenyls and
Related Compounds," university of Dayton Research Institute,
EPA-600/2-77-228, NTIS PB-269139, December 1977.
21. B. Dellinger, et al., "Determination of the Thermal
Decomposition Properties of 20 Selected Hazardous Organic
Compounds, M University of Dayton Research Institute,
EPA-600/2-84-138, NTIS PB 84-232487, August 1984.
22. A. Trenholm and C.C. Lee, "Analysis of PIC and Total Mass
Emissions From an Incinerator,11 Proceedings of the 12th
Annual EPA Research Symposium on Land Disposal, Remedial
Action, Incineration, and Treatment of Hazardous Waste,
Cincinnati, Ohio, April 21-23, 1986, EPA 600/9-86-022, August
1986.
23, "Non-steady State Testing of Industrial Boilers Burning
Hazardous waste,I1* EPA/600-9-86-022, Accurex, 12th Annual
EPA Research Symposium, April 1986.
24. D. Bose, s,M. Senkan, "On the combustion of chlorinated
hydrocarbons I.—Trichlorethylent," combustion Science
Technology 35sl (1984).
-------
2S, w* D, Chang, S.B* Karra, 3, K. Senkan, "Molecular beam mass
spectroscopic study of trichlorethylejie flames,11
gnvironmentaj. Science and Technology 20S1243 (1986).
26. W.D. Chang, S.B. Karra, s.M. Senkan, "A detailed mechanism
for the high temperature oxidation of G^HCLj," Combustion
gcienge. Technology 49:107 (1986),
27. B. Bellinger, g£ al. , "pie Formation Under Pyrolytic and
starved Air Conditions ," EPA/6QO/S2-86-QG6, July 1986,
28. K.C. Lee, "Incineration of hazardous waste, critical review
discussion paper," JAPCA 37:1011 (1987).
29. B.N. Ames, at al • f "Ranking Possible Carcinogenic Hazards,"
Science 236:271 (1987).
29-a. B.N. Ames, "Dietary Carcinogens and Anticarcinogens , " science
221:1256(1983).
30. 0. Zimmerman et a\. t "Anthropogenic Emissions Data for the
1985 NAPAP Inventory, "Final Report by Alliance Technologies
Corp to EPA's Air and Energy Engineering Research Laboratory,
RTF, North Carolina, USEPA, ORD (This study was conducted in
cooperation with the National Acid Precipitation Assessment
Program, IPA Contract No. 6S-02-4274, Work Assignments 26 and
28), September 1988.
31. W.P. Linak, et; al. f "On the occurrence of transient puffs in
a rotary kiln incinerator simulator, I. prototype solid
plastic wastes f" JAPCA 37: 54(1987).
32. W.P. Linak et al. r "On the occurrence of transient puffs in
a rotary kiln incinerator simulator, II. contained liquid
wastes on sorbent," JAPCA 37:934 (1987).
33, Trenholm, A.f P, Gorman and G* Jungclaus, MRI, "Performance
Evaluation of Full-Scale Hazardous Waste Incinerators.
Volume 2. Incinerators Performance Results,"
EPA-600/2-84-1811S, PS85-129518, November 1984.
34. MRI, "Total Mass Emissions from a Hazardous Waste
Incinerator," MRI Project No. 8671-L(1), May 1987. (Same as
119)
35. H.M. Freeman, editor, Standard Handbook of Hazardous Waste
Treatment and Disposal, McGraw-Hill Book Company, 1989. (See
especially Section 8.5 Cement Kilns, by John P. Chadboume,
Ph.D).
36. Sylvia 1C. Lowrence, Director, EPA Office of Solid Waste,
Memorandum to Hazardous Waste Division Director, Regions l-x,
entitled "Use of Omnibus Authority to Control Emissions of
Metals, HCL and PICs from Hazardous Waste Incinerator,11
February 27, 1989.
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37. u.s.s.p.A. (April 1989). Guidance on P£C Controls for
Hazardous Waste Incinerator, Volume 5 of the Hazardous Waste
Incineration Guidance Series, Office of Solid Waste,
Washington, D.C. (Draft Final Report),
38. Castaltini et al., "Guidance on the Control of Products of
Incomplete Combustion (PlCs) from Hazardous Waste
incinerator," December 1988.(Superceeded by reference #37)
39* Minnesota Pollution Control Agency, Supplemental Health Risk
Assessment Technical Work Paper, Volume I: Folychlorinated
Dioxins/Polychlorinated Furons, Winina County Rescue Recovery
Facility, May 1988.
40. Chang, D,, and M. Sorbo, "Evaluation of a Pilot-Scale
circulating Bed Combustor as a Potential Hazardous Waste
Incinerator," presented at the Incineration and Treatment of
Hazardous Waste 12th Annual Symposium, Cincinnati, Ohio,
March 1987.
41. Waterland, L.R., "Pilot-Scale Investigation of Surrogate
Means of Determining POHC Destruction, ** Final Report for the
Chemical Manufacturers Association, Acurex Corporation,
Mountain view, California, July 1983.
42. EPA, Engineering Assessment Report on Hazardous Waste
Cofiring in Industrial Boiler, Volume I, EPA 600/2-4-1772,
PB85-187838/AS.
43, Hlustick, D. Memo dated October 10, 1988, to s. Garg
entitled "Summary of Total Hydrocarbon Measurements in Cement
Kilns," found in EPA Background Document on Boiler and
Industrial Furnaces.
44, Edwards, J.B., Combustion: The Formation and Emission of
Trace Species, Ann Arbor Science, Ann Arbor, MX, 1977.
45. Harris, J., J. Perwak, and S. Coons, "An Exposure and Risk
Assessment for Benzo(a)Pyrene and Other Polycyclic Aromatic
Hydrocarbons," A.D. Little, Inc., EPA contract Ho, 68-01*
6160, 1982.
46. Kites, R.JU, "Sources and Fates of Atmospheric Polycyclic
Aromatic Hydrocarbons,11 Indiana University, Atmospheric
Aerosol, pp. 187-195, ACS Symposium Series 167, American
Chemical Society, Washington, D.C., 1981*
47. Jackson, 8., L. Scinto, and C. Shih, "Emissions of Reactive
Volatile Organic Compounds from Utility Boilers," TRW, Inc.,
EPA-600/7-80-11, NTIS PB80-200343, May 1980.
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48. Junk, G.A., and C.S. Ford, "A Review of organic Emissions
From Selected Combustion Processes," Antes Laboratory, Iowa
State University, Chemosphere, vol. 9, No. 4, pp. 137-230,
1980*
49. Lao, R.C., R.S. Thomas, M- Lanoy, and S.tt. Lee,
"Investigation of PAH and Polychlorinated Organic Pollutant
Emissions from Wood Combustion Sources," Environment Canada,
Po-lynuclear Aromatic Hydrocarbons: Formation, Metabolism and
Measurement, Proceedings of the seventh International
Symposium,, pp. 745-755, Battelle Press, Columbus, 1983.
50. National Research Council, Polycyelie Aromatic Hydrocarbons:
Evaluation of Sources and Effects, "Chapter 1: Polycyclic
aromatic hydrocarbons from mobile sources and their
atmospheric concentrations," Chapter 2; "Polycyclic aromatic
hydrocarbons from natural and stationary sources and their
atmospheric concentration," EPA Contract No. 68-01-4655, NTIS
PB34-15523 3, National Academy Press, Washington, D.C., 1983.
51. Background information Document for the Development of
Regulations to Control the Burning of Hazardous Wastes in
Boilers and Industrial Furnaces, 3 vols., for USEPA, Office
of Solid Waste, by Engineering Science, Inc., January 1987*
52. Dour son, M.L, and J.F. Stava, "Regulatory History and
Experimental Support of Uncertainty (Safety) Factors,"
Regulatory Toxicology and Pharmacology 2, 224-283 (1983).
53. Calabrese, E.J., "Uncertainty Factors and Interindividual
Variation," Regulatory Toxicology and Pharmacology £, 190-
196 (1985).
54. Lee, Eun-Chieh, "Incineration of Hazardous Waste: Critical
Review Discussion Papers," Journal of the Air Pollution
control Association, Vol. 37, No. §f pp. 1011-1017,
1987.(Same as 28)
55* Lee, Kun-Chieh, "Research Areas for Improved Incineration
System Performance,11 Journal of the Air Pollution control
Federation, Vol. 38, No. 12, pp. 1541-1550, December
1988.(Same a« 110)
56. staley, L.J*, M.K. Richards, 6.L. Huffman, R.A. Olexsey, and
B. Dellinger, "Relationship Between CO, POHC, and PIC
Emissions from a simulated Hazardous Waste Incinerator,1*
Journal of the Air Pollution Control Association, Vol. 39,
NO. 39, pp. 321-327, 1989.
57. Carra, Joseph of USEPA*s Waste Management Division,
Memorandum requesting review by the SAB, June 28, 1988.
58. THC Monitor Survey, MRI. Draft Final Report June 20, 1989.
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