5770
Paper No. 69 - 175
TRENDS IN AIR POLLUTION CONTROL REGULATIONS
by
Terry L. Stumph and Robert L. Duprey
Division of Control Agency Development
To be presented at the Annual Meeting of the Air Pollution
Control Association, New York, New York, June 22-26, 1969
U. S, DEPARTMENT OF HEALTH, EDUCATION, AND WELFARE
Public Health Service
Consumer Protection and Environmental Health Service
National Air Pollution Control Administration
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ABSTRACT
This paper analyzes recent trends in air-pollution-control
regulations adopted by state and local agencies. Many of the regu-
lations were evaluated by personnel of the Division of Control Agency
Development of the National Air Pollution Control Administration, and
written comments were sent to the agencies to assist them in develop-
ing sound regulations.
The emphasis of discussion is on concepts of control regulations
rather than on specific emission limits. Trends in control regula-
tions have been towards preventing air pollution through required
application of known control techniques. Outmoded concentration
emission standards are rapidly being replaced by those that limit
total mass-emission rate. Allowable emission rates usually vary
according to the size of the source.
Control of all visible emissions is being accepted as necessary
to any control program. Particulate matter from fuel-burning equip-
ment is being controlled to a high degree; emission standards for
sulfur oxides from fuel combustion are anticipated in the near future.
Incinerator emission standards are relatively undeveloped, due to the
lack of knowledge about the performance of high-efficiency dust
collectors on these sources. Control of many types of process indus-
tries presents a challenge in the design of equitable emission stan-
dards. The familiar process-weight-rate regulation is rapidly
becoming the standard for limiting particulate matter from this
source category. The potential-emission-rate concept shows promise
for certain source types and pollutants. Odor regulations have
mainly involved ambient air measurements using the human sense of
smel1.
KEY WORDS
Emission standard
Equivalent opacity
Process weight
Potential-emission rate
Odors
AGEFf"i
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INTRODUCTION
Conservation or degradation? Prevention or action based only
on proven adverse effects? Stringent emission control or use of
atmospheric dilution? These are the options confronting state and
local governments in developing air-pollution-control regulations.
The prospects of an increasing air pollution problem, growing public
demand for action, and the general failure of conciliation, persua-
sion, and voluntary control have resulted in the need for and
growing tendency toward government regulation.
Federal stimulatory program grants have accelerated the progress
of this activity at the state and local levels. In order to receive
maintenance-grant support, an agency must be able to prevent and
control air pollution from all sources under its jurisdiction.
Federal abatement actions under the Clean Air Act have also stimulated
state and local regulatory actions. With the advent of the requirements
of the Air Quality Act of 1967, further advances can be expected on
a regional basis in the designated air-quality-control regions.
What, then, are the trends in modern air-pollution-control regu-
lations? The consensus has clearly been in favor of air pollution
prevention, air resource conservation, and increasingly stringent
emission control regulations. Most emission control standards adopted
in recent years by state and local agencies have been based on maximum
application of modern control technology rather than on atmospheric
dispersion. Some reasons for this tendency include:
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1. Realization that future demands on atmospheric resources
are not easy to predict, which indicates the necessity for
a present policy of conservation.
2. Inability of most state and local agencies to develop
sophisticated air-resource-management programs.
3. Necessity for concentrating limited agency resources on
solving immediate pollution problems.
4. Need for regulations the emission limits of which are
readily known by source owners and agency personnel, espe-
cially for design of new collection systems.
5. Desire of most agency personnel for regulations that
can be readily and directly applied to the numerous sources
found in most urban areas, without extensive monitoring and
data collection.
6. Realization that emissions from multiple sources are
practically untraceable after discharge into a common air
envelope.
This paper attempts to analyze the particular control regulations
that have evolved from state and local agencies over the years. Specu-
lation about future trends will be limited to immediate extensions of
typical current regulations, without discussing the larger questions
and potential approaches associated with more sophisticated air-manage-
ment programs.
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CONCEPTS OF EMISSION STANDARDS
Early Concepts
Early emission standards limited the concentration of pollutants
in the effluent gas stream in such terms as pounds per thousand pounds,
grains per standard cubic foot, parts per million, and micrograms per
standard cubic meter. Concentrations based on pollutant mass per
unit gas volume vary with temperature and pressure so correction to
standard temperature and pressure is necessary, usually 60 F and
14.7 pounds per square inch absolute. To prevent circumvention of
standards by diluting pollutants with large quantities of air, con-
centration standards have to be standardized. This is usually accom-
plished by correcting flue-gas volumes to a percentage of the theoreti-
cal quantity of air required for complete cumbustion of fuel. Because
early emission standards were primarily intended for coal-burning
boiler plants, pollutant concentrations were corrected to 50 percent
excess air which, for most bituminous coals, results in a carbon
dioxide concentration of approximately 12 percent in the dry flue gas.
Unfortunately, emission standards of this type have the following
deficiencies:
1. Pollutant concentration, by itself, does not indicate
total pollutant discharge, because flue-gas volumes vary
considerably.
2. An emission standard specifying a single concentration
requires essentially the same degree of control for large
and small sources, whereas large sources emit more pollu-
tants and are usually capable of purchasing and operating
more efficient collectors.
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3. Standardization with respect to percent excess air is
meaningful only for pure combustion processes where no other
materials are contacted by the fuel or its combustion products.
The first emission standards were derived for coal-fired equipment,
but were occasionally applied to incinerators and industrial processes.
Emission limits applied to coal-fired equipment were not related to the
emission rates of incinerators and industrial processes, and standard-
ization for excess combustion air raised special problems for each.
Correction of incinerator effluents to 50 percent excess air is
not as simple as for coal combustion, because combustion of different
wastes with 50 percent excess air produces different quantities of
carbon dioxide. The specific quantity produced for each waste should
be known in order to make a valid correction to 50 percent excess air.
Because waste properties vary considerably, incinerator effluents are
usually corrected to 12 percent carbon dioxide in the dry flue gas,
without the contribution of auxiliary fuel. This value of 12 percent
carbon dioxide is not related to any specific waste but is simply a
convenient reference condition for allowable dilution. The correction
procedure is not affected by the selection of specific emission limits
for various types of waste. It can be affected, however, by the use
of wet collectors because water can absorb a significant quantity of
the carbon dioxide produced by incineration.
Despite these difficulties, pure combustion effluents can theoret-
ically be standardized for excess combustion air so that concentration
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standards can be applied. However, such standards are not applicable
to industrial operations that involve various combinations of combus-
tion, chemical, and physical processes. A cement plant discharges
large quantities of carbon dioxide from the thermal decomposition of
limestone. The charging of limestone into foundry cupolas also results
in discharge of carbon dioxide. Some drying operations use hot air
that has been heated indirectly and, thus, contains no gaseous com-
bustion products. For these and other industrial processes, deter-
mination of percent of excess combustion air becomes meaningless.
Resultant flue-gas volumes cannot be effectively standardized, and
circumvention of a concentration standard by dilution with outside air
cannot be detected or prevented.
Some operations, such as foundry cupolas, infiltrate large quan-
tities of air for cooling purposes, during certain portions of the
melting cycle. Mcllvaine^ gives data that illustrate how deceptive
pollutant concentrations can be. With minimum infiltration, pollutant
concentration was 0.19 grain per standard cubic foot. With greatly
increased infiltration, the concentration was reduced to 0.05 grain
per standard cubic foot with no reduction in mass-emission rate. There-
fore, low effluent concentrations do not necessarily indicate low
emission rates, especially for industrial processes that normally use
large quantities of dilution air (e.g., foundry cupolas and basic
oxygen furnaces).
Collection-efficiency standards are similar to concentration
standards in that they (1) do not directly limit total emissions, (2)
usually specify a single degree of control regardless of source size,
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and (3) are subject to circumvention. Regarding the last point,
collection efficiency is determined by measuring pollutant flow rate
both before and after the collector. The efficiency of many types of
collectors increases with the quantity of material passing through
them because of the attendant increase in particle size. Some methods
of increasing pollutant flow rate include recirculating collected solids
and entrainment of larger particles from the process by increasing gas-
flow rates. Although these practices often increase collection
efficiency, they are usually accompanied by increased emission rates.
New Concepts
The deficiencies associated with concentration and collection-
efficiency standards have led to development of more meaningful stan-
dards that restrict total emission rate in units such as in pounds per
hour. This type of standard eliminates the possibility of circumvention
and directly limits total pollutant discharge to the atmosphere. An-
other feature of newer standards is that sources with large potential
for pollution are being more strictly controlled because they (1)
usually contribute a greater pollution load to the atmosphere and (2)
can usually afford and maintain more expensive and efficient control
devices, due to economics of size. Parameters that reflect source size
are also approximate measures of pollution potential. Thus, emission
limits for fuel-burning equipment usually vary on the basis of total
heat input in millions of Btu per hour, whereas some incinerator stan-
dards are based on the total weight of refuse charged in pounds per hour.
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Industrial processes include many types of operations, making it more
difficult to select a single parameter to indicate pollution potential.
Many emission standards for industrial processes vary with process-
weight rate; others vary with potential-emission rate. Whenever an
emission standard applies to a specific industry, any convenient
measure of source size usually correlates with pollution potential.
There have been complaints about the difficulty of accurately
determining various size parameters, especially for operations that dd
not employ calibrated feeding devices. This difficulty, however, also
applies to the older concentration standards. To equitably apply a
concentration standard, the unit must be operated at its design capacity
during compliance testing. Otherwise, many operations might be able
to comply by operating at less than design capacity.
There has been inconsistency in the application of total mass-
emission-rate standards to multiple equipment units existing in a
plant. Some regulations apply to the total plant capacity; others
apply to individual units. The latter condition presents an oppor-
tunity to circumvent the intent of the regulation by constructing
several small units rather than a single large one. This temptation
should not exist. A source should have to meet a fixed emission limit
dependent only upon the total capacity of all "like" units (e.g.,
boilers, cement kilns, driers and recovery furnaces) in the plant.
VISIBLE EMISSION REGULATIONS
Since the introduction of the Ringelmann chart in 1890, the
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regulation of black smoke plumes caused by poor combustion has been
widely accepted. In 1947 the Health and Safety Code of California
was amended to include the "equivalent opacity concept," which
extended the Ringelmann chart for application to a visible plume of
any color, which obscures the view of an observer to the same degree
as black smoke. This concept has now spread to numerous jurisdic-
tions throughout the Nation including most of the major urban areas.
Its legality has been upheld in the courts.^
Equivalent opacity regulations are especially useful for main-
taining surveillance of a large number of source installations with-
out having to sample the source. Enforcement of the regulation
assures continuous maintenance and proper operation of equipment.
Despite its usefulness, a number of technical questions have arisen
concerning the validity of equivalent opacity. Foremost among these
is the question concerning the benefits to be gained by control of
non-black visible emissions.
The visibility of a plume is more a function of the size of en-
trained particulate matter than of the total weight. Particles in the
size range of 0.1 to 1.0 micron have the optimum effect in scattering
light. A high collection efficiency by weight of particulate matter
may still allow an offensive visible plume due to the remaining
presence of many submicron particles. Such particles remain suspended
in the atmosphere for long periods of time and, during inversions,
accumulate to cause severe visibility reduction and soiling of buildings
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and materials. These small particles are also inhaled by man and
can be retained in the lower respiratory tract. Visible plumes are
offensive from an aesthetic standpoint and, in some cases, are direct
hazards to ground and air transportation.
Because mass-emission standards are unrelated to particle size,
they are not always effective in eliminating visible plumes. The use
of standards involving visible emissions is the only practical means
for controlling submicron particles until measurement techniques and
emission standards that limit the number of discharged particles
according to size are developed.
A second technical question concerns the reproducibility of
reading equivalent opacity of plumes. Common objections are that
opacity varies with the position of the observer relative to the sun,
atmospheric lighting and background. These sources of error also apply
to observation of black plumes, but even the strongest opponents of
pollution control have accepted the desirability of controlling smoke
emissions. Observers can be taught to compensate for these variables
to a reasonable degree of accuracy. With smoke school training, an
observer is required to reproduce his reading of opacity usually within
10 percent of actual plume transmittance before he is certified. This
is believed to compare favorably with the accuracy of many other
sampling and analytical procedures routinely used in the field of air
pollution control.
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A third question concerns the method for complying with equiva-
lent opacity as compared to the usual method for complying with smoke
regulations. When smoke is the offending agent, control can be
achieved by improved combustion efficiency. When plume visibility
is due to the emission of fine fly ash from fuel combustion or to
fumes from metallurgical processes, control must then be achieved by
use of collection equipment. Collection of submicron particles
requires highly efficient devices such as baghouses, high-energy
scrubbers, and high-efficiency electrostatic precipitators. Collec-
tion sufficient for compliance with mass-emission-rate standards may
not be sufficient for compliance with equivalent opacity standards.
Mass concentration can be related to plume transmittance for
specific particle sizes and types, and plume thickness. Conner"
demonstrated a close correlation between plume transmittance and mass
concentration for oil particles by calculation and measurement. Other
relationships have been published for different types of particles and
sources.'>°
Equipment manufacturers make use of such existing data, however
limited, to design control equipment to opacity requirements. This
practice has, by necessity, depended primarily on the vendor's
experience with similar installations on specific source types rather
than on theoretical relationships. Correlation of particle size and
concentration data with plume visibility for additional sources is
needed to aid designers in eliminating offensively visible plumes.
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Many new industrial plants install equipment for purposes of
eliminating all visible plumes, even if not required to do so. Such
action constitutes good public relations, and plant managers realize
their chances of being singled out for complaints and source sampling
are greatly diminished if their plumes are invisible.
Until recently, most visible emission standards have been less
than number 2 Ringelmann or its equivalent opacity. The present
trend of new regulations is to require all incinerators and new sources
of all types to meet number 1 Ringelmann or its equivalent opacity. A
few areas require all sources to meet number 1 Ringelmann. Some areas
prohibit all visible discharges from automobiles except for short
periods of time. The trend appears to be toward prohibition of all
unnecessary visible emissions and, ultimately, toward elimination of
all visible emissions.
CONTROL OF PARTICIPATE EMISSIONS FROM FUEL-BURNING EQUIPMENT
No source of particulate matter has been more extensively regu-
lated than coal-fired heating and power plants. The reason is obvious:
coal is the major fuel used for generating heat and electric power in
most of the major urban areas. Coal contains considerable ash (from
10 to 20 percent), most of which is discharged as air contaminants
unless collection equipment is employed.
Until recent years, most particulate-matter emission standards
were based on a 1949 American Society of Mechanical Engineers (ASME)
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Model Code, which limits emissions to 0.85 pound of dust per thousand
pounds of flue gas, corrected to 50 percent excess air. The collec-
tion-efficiency requirements vary from about 50 to 85 percent,
depending on the type of equipment used to burn coal with 10 percent
ash and 13,000 Btu per pound. Even the largest power plants can meet
the standard using mechanical collectors.
ASME issued a new model in 1966 entitled "Recommended Guide for
the Control of Dust Emission -- Combustion for Indirect Heat Exchangers"
commonly known as ASME Standard APS-1. The new ASME model limits the
mass-emission rate of particulate matter rather than the in-stack
concentration used in the 1949 model. This new model requires a
varying degree of control dependent on plant size and stack height.
ASME Standard APS-1 has had only limited acceptance by state and local
air-pollution-control agencies perhaps due to the following limitations:
1. It is based on meteorological dispersion- equations appli-
cable only to single source emissions located on essentially
flat terrain. Maximum allowable ground-level concentrations
are based on the "critical wind speed" with no consideration
for inversion and possible fumigation conditions. Obviously,
these assumed conditions do not exist in urban areas nor in
areas where irregular terrain or adjacent buildings negate
the theoretical benefits of dispersion.
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2. Allowable mass-emission rate is dependent on the stack
height. Increased stack height can be used to meet the
standard in lieu of emission control, although there is no
minimum stack-height requirement.
3. The use of a taller stack does not reduce the total
quantity of pollutants discharged but merely disperses the
effluent over a wider area, perhaps degrading the air else-
where.
4. The control requirements of the standard are generally
lenient compared to other modern regulations and to the
degree of control now being applied to new fuel-burning
Q
installations. The standard can be restrictive for a
plant with a large number of short stacks. However, the
trend is to build large plants with a single tall stack,
principally for dispersing sulfur dioxide emissions. Any
unit burning pulverized coal with 10 percent ash and 13,000
Btu per pound can comply with the most stringent ASME
provision with a collection efficiency of only 87 percent
merely by erecting a tall stack. For example, a 500-
megawatt plant with a 700-foot stack can comply with an 87
percent efficient collector.
Most urban areas, many states, and the Federal government (Federal
facilities) use what is commonly known as the sliding scale concept to
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regulate particulate-matter emissions from fuel-burning equipment.
Figure 1 illustrates three of the more restrictive standards that are
currently in use. The first such standard was adopted by New York
City in 1964. It was based on the lowest line of an ASME proposed
model10 that was later replaced by ASME Standard APS-1.
It is common practice to compare collector performance using
collection efficiency rather than total pollutant-emission rate.
Keeping with this practice, collection-efficiency requirements for
each of the three standards are presented in Table 1 for various types
and sizes of equipment, based on coal with an average heat content of
13,000 Btu per pound and an ash content of 10 percent. The efficiency
requirements of a sliding scale standard increase with increasing size
of the installation and also with increasing emission potential of the
source. In view of the number of new source installations being
designed with control equipment having collection efficiencies greater
than 99 percent,9>H»12 ^^ seems clear that these standards are attain-
able with currently available control technology. There is some jus-
tification for more restrictive standards, at least for new installa-
tions, since the emission standards shown have not yet reached the
limits of technical feasibility and are, perhaps, unnecessarily lenient
for installations greater than 10,000 million Btu per hour. Plants
with even greater capacities are being designed.
CONTROL OF SULFUR OXIDE EMISSIONS FROM FUEL-BURNING EQUIPMENT
Combustion of high-sulfur coal and residual fuel oil is the prin-
cipal source of sulfur oxides in most areas of the Nation.13 Present
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atmospheric levels of sulfur oxides and potential increases in
emissions have led to considerable recent activity in adopting control
regulations. Use of low-sulfur fuels (natural or cleaned) and/or flue-
gas desulfurization are potential means of reducing sulfur oxide
emissions, other than elimination of the source.
The first attempt at regulation involved the 1937 St. Louis Law
that required washing of high-sulfur coals. Los Angeles County (which
uses no coal) has limited the sulfur content of liquid and gaseous
fuels since 1958. The stated aim of the Los Angeles County Air
Pollution Control District is to eliminate the use of fossil fuels in
power plants and to have an adequate supply of natural gas for other
fuel consumers. Since 1964, several cities and states, and the
Federal Government (Federal facilities in New York, Chicago, and
Philadelphia) have adopted regulations governing the sulfur content
of fuels. Regulations of maximum allowable sulfur content usually
carry an alternative provision whereby any fuel may be used if flue-
gas desulfurization can be shown to result in an equivalent or lower
rate of sulfur oxide emissions, as measured in pounds of sulfur oxides
per million Btu. The "emission standard" is obtained by direct conver-
sion from sulfur content of fuel and is based on air quality considera-
tions. An excellent discussion on the development of sulfur oxide
regulations has been published by High and Megonnell.^
Regulation of sulfur oxides from small multiple sources will
probably continue to be based on sulfur content of fuel, because this
is easily enforced by regulation of the importation, distribution and
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sale of high-sulfur fuels. Emission testing of numerous small sources
is not feasible. However, establishment of emission standards for
large industrial sources and steam-electric power plants is likely
and desirable when economical flue-gas desulfurization techniques
become available. The emission standards could be formulated so that
they require the maximum use of those techniques. They can also be
based on needed reduction in sulfur oxide emissions, recognizing that
this could require either more or less control than is technically
feasible. If more control is needed, other alternatives such as fuel
substitution would have to be considered. Emission standards for
sulfur oxides would logically be stated in the same units as those
shown in Figure 1 for particulate matter. The "size" of the installa-
tion to be regulated by use of emission standards could perhaps begin
at 1000 x 10 Btu per hour. The control-efficiency requirements of the
emission standard would logically increase with the size of the
installation, for the same reasons discussed in reference to particulate-
matter restrictions. A similar standard based on potential-emission
rate could be developed to reflect the same considerations as those
used in developing a standard based on plant size. Either method
should be suitable since potential-emission rate and installation size
are easily determined for fuel-burning installations.
PROCESS EQUIPMENT REGULATION
About 20 years ago, the Los Angeles County Air Pollution Control
District (LACAPCD) developed the so-called process-weight regulation,
which restricted total particulate-matter emission rates from
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industrial processes as a function of the process-weight rate.
Process weight is, generally, the total weight of all materials,
except gases, introduced into a process. This approach removed
dilution as a factor in meeting emission standards and assured
increasingly strict control of larger source operations.
The Los Angeles County process-weight regulation was derived
after a thorough study of the many metallurgical industries located
there. Well-controlled and well-operated plants served as the basis
for determining the degree of control that was technically and econ-
omically feasible. The application of this regulation also demon-
strated that many types of industries, regardless of the specific
nature of their products, can comply with the emission limits. The
maximum-allowable emission limit was set at 40 pounds per hour.
In 1959, the Bay Area Air Pollution Control District in San
Francisco (BAAPCD) developed still another process-weight regulation
based on well-controlled process industries found there. They
included some of the larger mineral-based operations not found in Los
Angeles County. Consequently, the Bay Area Regulation is comparable to
the Los Angeles County Regulation in the lower range, but allowable
emissions increase at a reduced rate above 40 pounds per hour with
increasing size of operation. This regulation is perhaps more
reasonable for a wider-range of source types than the Los Angeles
County Regulation and, therefore, has been more widely accepted.
Other control agencies have also developed process-weight regulations,
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but these regulations have had limited acceptance.
The LACAPCD and BAAPCD process-weight regulations are compared
graphically in Figure 2, which also shows a large number of actual
source operations that have complied with the Bay Area Regulation.
These sources are identified in Table 2. The first eleven sources
were ones used to construct the original Bay Area Regulation. -*
Figure 2 demonstrates that a wide variety of source types can comply
with this regulation, some with relative ease. Indeed, the standard
is not restrictive for some source types, such as asphalt plants.
Many additional industrial process operations could be shown on this
graph by plotting source-test data for other well-controlled plants.
Some sources, however, have difficulty in meeting the Bay Area Regula-
tion because of relatively difficult technical problems that can
result in economic hardship. Examples of these are wet-process
cement kilns and jobbing cupolas.
Control regulations for industrial gaseous emissions have in the
past been mainly limited to sulfur oxides. These regulations have
consisted of a mixture of emission standards and property-line con-
centration standards. Emission standards for sulfur dioxide are rela-
tively unrefined, consisting of specified effluent concentration based
on measured performance of well-designed and well-operated contact
sulfuric acid plants. The standard of 2,000 parts per million has
been enforced for over 20 years in Los Angeles for all sources. St.
Louis applied this standard to existing sources in 1966 and required
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new plants to limit sulfur dioxide emissions to 500 parts per million
based upon reported performance of European sulfuric acid plants using
the double-contact process. St Louis has emission standards estab-
lished for sulfur trioxide or sulfuric acid mist based upon studies
of sulfuric acid plants.
Sulfur oxide emission standards similar to those adopted in St.
Louis have been adopted by many other control agencies. They leave
much to be desired because they (1) originated from studies on a
single source category and hence have questionable applicability to
other major sources of sulfur oxides (e.g., smelters and petroleum
refineries) and (2) limit pollutant concentration rather than mass-
emission rate and, thus, are subject to circumvention by dilution.
The generalized process-weight regulation has been used i:or many
years. Its insensitivity to certain industries has recently led to
development of a few specialized process-weight regulations. West
Virginia adopted one specifically for asphalt plants which is slightly
more restrictive than the Bay Area Regulation. New York State adopted
a special standard for a certain category of existing ferrous foundries.
This standard is slightly less restrictive than the Bay Area Regulation
and is intended to give an economic break to the owners of these small,
non-continuous operations.
The States of Pennsylvania and New York have developed regulations,
the emission limits of which vary with the pollution potential of the
source. The Pennsylvania Regulation, shown in Figure 3, limits the
mass rate of emission in pounds per hour as a function of potential-emission
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rate, also in pounds per hour. The regulation contains several sets
of emission limits, applicable to different areas of the State. It
is designed to require greater collection efficiency for those opera-
tions that would otherwise discharge large quantities of pollutants.
This type of regulation appears readily adaptable to sources, the un-
controlled emission rates of which are easily determined. Many
operations that discharge sulfur oxides through the processing of
sulfur-bearing raw materials meet this condition. Sulfur oxide
emissions from primary smelters and sulfuric acid plants, among others,
could be restricted according to potential-emission rate, which, in
these cases, is a direct function of the total weight of sulfur fed
into the operations. The same is true for some industries that
process materials containing fluorides. Sulfur oxides and particu-
late matter from fuel-burning equipment also lend themselves to de-
termination of potential-emission rate.
The Pennsylvania Regulation presents some difficulty when applied
to the many industrial operations discharging particulate matter,
because the uncontrolled emission rates bear no direct relationship
to quantity of feed material but, rather, depend upon the amount of
material entrained in the exhaust gases during a particular operation.
Potential-emission rate, in these instances, would be determined by
sampling the uncontrolled effluent gases, and source compliance would
be determined by measuring collector efficiency. This requires twice
the normal amount of source sampling and presents some opportunity
for the source owner to manipulate the quantity of material entrained
in the effluent gases. There is also the problem of assuring that
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tests are run at normal conditions, probably requiring establishment
of normal process-weight rate or production rate. An alternative
approach would be to assign potential-emission rates to these problem
sources through use of pre-established emission factors. Because an
emission factor ideally represents the average measured emission rate
from a number of similar installations (e.g., basic oxygen furnaces),
the use of such factors is a logical and equitable substitute for
determining potential-emission rate for each individual source.
Allowable emissions according to the Bay Area Regulation and the
most stringent provision of Pennsylvania's potential-emission-rate
regulation are compared with actual emission rates measured on some
selected industrial sources. These data appear in Table 3. Poten-
tial-emission rates have been calculated, using published emission
factors. This comparison does not indicate the relative merits of
each type of regulation, but it does indicate the relative stringency
of the specific emission limits contained in each one. Based upon
these few examples, it appears that the Pennsylvania Regulation (Class
D) is comparable to the Bay Area Regulation for sources with small
pollution potential, but less restrictive for sources with large
potential-emission rates. The Bay Area Regulation appears to be quite
stringent for sources with a combination of large process-weight rate
and large emission factors (e.g., cement plants). It is noticeably
lenient for sources with small emission factors such as asphalt plants.
There is likely to be a continuing need for generalized regulations
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that apply to a variety of industrial sources. These might be based
either on process-weight rate or on potential-emission rate. The use
of one type rather than the other for an individual source might
depend upon the relative ease with which necessary measurements can
be made.
In areas containing a significant number of similar industry types,
there may be a need for tailored regulations that apply to a single
source category (e.g., foundry cupolas) and more nearly reflect attain-
able emission rates for that particular source. Generalized regula-
tions for process industries apply to many types of operations and
are usually inadequate for a certain few source types, being either
very lenient or very stringent. Tailored regulations for these parti-
cular sources might also be based either on process-weight or potential-
emission rate, depending upon the nature of the specific source
operation.
INCINERATOR REGULATIONS
The numerous small incinerators found in most urban areas cause
many localized nuisances through discharge of smoke, odors^ and fly
ash. If enough incinerators are present, the discharged pollutants
may constitute a significant portion of the total community emissions.
Control of incinerator emissions and elimination of nuisance complaints
has been accomplished by the use of incinerator design and emission
standards, and elimination of certain types of incinerators.
Control agencies have long recognized that incinerators must
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burn refuse as completely as possible to minimize pollutant discharge.
Well-designed, multiple-chamber incinerators are considered necessary
by most authorities to achieve satisfactory combustion. Therefore,
many agencies ban single-chamber incinerators and specify acceptable
designs for construction of multiple-chamber incinerators. The most
frequently used design standards are those adopted by the Los Angeles
County Air Pollution Control District and those recommended by the
Incinerator Institute of America. The LACAPCD standards are quite
rigid and are generally considered to produce a more efficient combus-
tion device. Because Incinerator-Institute-of-America standards are
more flexible and allow considerable variation in actual design, some
incinerators built in accordance with these standards may be inefficient
combustion devices. Although some designers resent being told how to
design incinerators, this is the only feasible method of controlling
the numerous domestic and commercial incinerators existing in most
major urban ai^eas. It would be impossible to sample each one in order
to determine compliance with emission standards. Large municipal and
industrial incinerators are more suitable to direct control through
source testing and enforcement of emission standards.
Emission standards specific for incinerators are relatively new
and are undergoing revision. Los Angeles County has for many years
enforced a concentration standard of 0.3 grain per standard dry
cubic foot, corrected to 12 percent carbon dioxide, without the con-
tribution of auxiliary fuel. This was a level felt to be attainable
-------
-24
with well-designed, multiple-chamber incinerators, without control
equipment. In 1966, the Federal Government applied this standard to
its incinerators smaller than 200 pounds per hour and required
larger units to meet a standard of 0.2 grain per standard dry cubic foot.
The latter value was found to be attainable ^ with installation of
certain low-efficiency wet collectors, operating at pressure drops of
about 0.5 inch of water. These particular standards have been adopted
by many other control agencies in the past few years. The State of
New Jersey requires that incinerators with capacities greater than
2000 pounds per hour meet a standard of 0.1 grain per standard dry
cubic foot, and smaller ones a standard of 0.2 grain per standard dry
cubic foot.
In 1967, New York City and New York State developed standards
that restrict mass-emission rate in pounds per hour as a function of
increasing,incinerator size, as determined by total weight-rate of
refuse charged in pounds per hour. This is more logical than con-
centration standards, which are somewhat difficult to standardize
for percent of carbon dioxide, if auxiliary fuel is used or if a wet
collector is employed. Furthermore, it is more meaningful to restrict
mass-emission rate than to restrict effluent concentration.
The standards for Federal Facilities (0.3 and 0.2 grain per
standard dry cubic foot) have been converted to equivalent mass-
emission rates on the basis of selected normal refuse. These converted
standards, the basis for conversion, and the New York City and New
York State regulations are shown in Figure 4. The dotted lines,
-------
-25
for Federal Facilities, represent constant emission concentrations and,
hence, require about the same degree of collection efficiency for all
incinerators with capacities above and below 200 pounds per hour,
respectively. Any line parallel to these lines (e.g., New York State's
existing units) also represents a single concentration and constant
collection efficiency for all sizes. This is less than ideal for
reasons already discussed. Larger units discharge more pollutants and
are better suited to installation of the more efficient collectors.
Lines B (New York State's new units) and C (New York City) have
decreasing slopes with increasing weight of refuse charged. These
two standards require increasingly greater control for large units.
The technical basis for constructing lines B and C is not known to the
authors, and so no evaluation can be made as to their current technical
feasibility. It is generally agreed, however, that most municipal-
type incinerators are presently under-controlled, considering the
current availability of high-efficiency collectors for particulate
matter. Perhaps these standards will require upgrading of collection
equipment on such incinerators. More will be known about technical
feasibility of lines B and C after tests have been made on those
municipal incinerators currently being equipped with electrostatic
precipitators and high-energy scrubbers. Once these tests are completed,
it should be possible to construct a new standard based on the best-
available control equipment.
Because of the large number of small incinerators existing in most
-------
-26
large cities, control of individual sources is expected to be accom-
plished primarily through application of incinerator design standards.
Emission standards shown on Figure 4 will serve mainly as a basis for
evaluating various incinerator designs. Incinerators with capacities
greater than 1000 pounds per hour should be few enough in number so
that compliance with the emission standards through source testing
can be required.
Even well-designed incinerators, especially the smaller ones,
can cause odors and other nuisance conditions if improperly operated.
For this reason, some agencies are considering the gradual elimination
of certain types and sizes of incinerators. The most efficient pro-
cedure for incinerating urban refuse would appear to be one whereby
refuse is collected and incinerated at central points in municipal-
type incinerators. In this manner, the most efficient collectors can
be installed, and proper operation can be assured by hiring and train-
ing full-time operators. These measures are not feasible for on-site
incineration as now practiced in many urban areas.
Because different waste materials have different emission factors,
it might be advantageous to apply different emission standards to
different types of incinerators. Junk automobile incinerators emit
little particulate matter in comparison to total weight charged,
therefore, the standards in Figure 4 might be too lenient. Other
unusual wastes might also require specific emission limits, if suit-
able application of control technology is to be assured.
-------
-27
ODOR REGULATIONS
Odors constitute the most perplexing and often the most objec-
tionable air pollution problems. They are caused by a variety of
substances, many of which are detectable at trace concentrations
below one part per billion. There are many cases in which odorous sub-
stances cannot be detected by normal chemical analysis, but are
detectable by the sense of smell. The human nose is, by necessity,
the present standard for determining odor intensity in the ambient
air and in source effluents.
It is no simple matter to trace an odor to its source, especially
if multiple odor sources are located in close proximity. Existing
odor control regulations consist of a variety of partially successful
measures, including:
1. Nuisance-type restrictions based on ambient air detection
of odors.
2. Process restrictions for certain known odor-producing
sources.
3. Control equipment requirements, for specific source
operations.
The three categories of regulations either specify techniques that
are likely to reduce odorous emissions or declare that such emissions
must not cause objectionable conditions. Most odor regulations are
directed at measurement of odors in the ambient air. After this is
done, there remains the problem of tracing the odor to its source and
then specifying adequate control techniques. This approach is somewhat
-------
-28
justified because human response to ambient odor must be the ultimate
criterion of acceptable odorous emissions.
Early ambient air standards for odors consisted of applying the
nuisance prohibition without attempting to evaluate,odor intensity.
Because this approach is entirely complainant oriented, control
officials felt the need for a tool by which odors can be evaluated
and abated before nuisance conditions develop. St. Louis adopted a
regulation that allows a panel of observers to evaluate odor intensity
of ambient air samples when such samples are diluted with specified
quantities of odor-free air. If odors can be detected after the
specified dilution has occurred, the odors are deemed objectionable.
What happens thereafter is not predictable because the offending odors
may originate from many sources, or may be untraceable. Such approaches
to odor control are both technically and legally difficult.
Another procedure for evaluating odor in the ambient air has
been proposed by Huey. ^ This technique makes use of a mechanical
dilution device, which simplifies the task of assigning numerical
strengths to detectable odors. He also suggests a regulation by which
a single observer, rather than a panel of observers, determines the
objectionability of ambient odors. Both this and the St. Louis
Regulation are concerned with evaluating ambient odors and differ only
in the mechanics of such determinations. Neither offers a method for
abating such odors at the source.
Odor control regulations, in the form of process restrictions
-------
-29
and control equipment specifications, have been applied to certain
known odor-producing operations. Los Angeles, St. Louis, and many
other agencies require that effluents from animal-matter reduction
be incinerated at a temperature of 1200°F for at least 0.3 second.
These are minimum design standards for an afterburner. Other process
restrictions and control requirements seek simply to prevent unneces-
sary discharge of odors. Examples of these are restrictions on
practices in the Kraft pulping industry and operation requirements
for animal feed-lots.
Los Angeles County Air Pollution Control District has developed
a quantitative odor-measurement technique, based on American Society
for Testing Materials Method D 1391-57, that can be applied at the
source. Odor concentration is expressed in odor units per standard
cubic foot of flue gas. An odor unit is the quantity of odorous sub-
stances that, when completely dispersed in 1 cubic foot of odor-free
air, produces a threshold odor response by 50 percent of an odor panel.
Determination of odor units requires dilution of a sample of odor-
bearing air with odor-free air to the threshold of detection by 50
percent of a panel of observers. Odor concentration, in odor units per
standard cubic foot of gas, can be determined for any source category,
either ahead of or following control devices. Odor emission rate can
be calculated as odor units per minute by multiplying the odor concen-
tration by the volumetric flow rate. Mi 11s19 has determined odor
emission rates for both controlled and uncontrolled industrial sources
-------
-30
in Los Angeles County. Although Los Angeles has not developed
emission standards based on odor units per minute, they have applied
the sampling procedure administratively in evaluating performance of
odor-control devices and in abating nuisances.
CONCLUSIONS
Recent trends in air-pollution-control regulations have been
toward conservation of air resources through required application of
maximum control technology. Older-style concentration emission stan-
dards are rapidly being replaced by ones that limit total mass-emission
rates on a schedule that requires increasing control with increasing
size of source. Control of all visible emissions is being accepted
as necessary to any control program. Particulate matter from fuel-
burning equipment can be and is being controlled to a high degree;
emission standards for sulfur oxides created by fuel combustion will
probably be established. Control of process industries represents a
real challenge in the design of equitable emission standards. The
process-weight-rate concept, developed on the Pacific Coast, is
rapidly becoming the standard for this varied category of sources.
The potential-emission-rate concept, developed more recently in the
East, shows real promise for certain source types. Incinerator
emission standards are relatively undeveloped, because of the present
scarcity of units equipped with efficient collectors. Odor regu-
lations have dealt mainly with ambient air measurements using the
sense of smell, although Los Angeles County has used a similar pro-
cedure for source sampling of odorous effluents. Some possible
-------
-31
developments in control regulations include:
1. Required elimination of all visible emissions.
2. Emission standards for sulfur oxides from fuel combustion
similar to ones now used for particulate matter.
3. Process-weight-rate and potential-emission-rate regula-
tions for specific industry types for both particulate and
gaseous pollutants.
4. Mass-emission-rate standards that require application
of modern fly-ash collectors to incinerators.
5. Emission standards that limit the mass rate of emission
of odors measureable by source sampling.
-------
-32
REFERENCES
1. Federal Register, Vol. 32, No. 104, May 30, 1967.
2. Mcllvaine, Robert W., "Air Pollution Equipment for Foundry Cupolas,"
Journal of the Air Pollution Control Association, Vol. 17, No. 8,
August 1967.
3. 62 Wash. 2d. 834 P 2d. 859(1963) cert. den. 377 U.S. 906,
84 S. Ct. 1166, 12 L. Ed. 2d. 177 (1964).
102 Cal. App. 2d. Supp. 925, 226 P 2d. 587 (1951).
137 Cal. App. 2d. Supp. 859, 291. 2d. 587 (1955) Cert.
den. 351 U. S. 990 76S. Ct. 1046, 100L. Ed. 1503 (1955).
4. "Air Quality Criteria for Particulate Matter," NAPCA Publication
No. A.P. 49. January 1969.
5. Rom, J.J. "Reading Visible Emission," Training Course Manual,
National Air Pollution Control Administration, Durham, North
Carolina, April 1968.
6. Conner, W. D. and Hodkinson, J. R. "Optical Properties and Visual
Effects of Smoke-Stack Plumes," NAPCA Publication No. AP-30, 1967.
7. Stern, A. C., Chapter 51, p. 706, Air Pollution Standards,
Air Pollution, Vol. Ill, 2nd Ed. Academic Press, New York, 1968.
8. Air Pollution Manual--Part II--Control Equipment, Chapter 2,
AIHA, Detroit, 1968.
9. Moore, W. W., "Reduction in Ambient Air Concentrations of Flyash--
Present and Future Prospects," Proceedings-Third National Conference
on Air Pollution, Washington, D. C. December 12-14, 1966.
-------
-33
10. Schueneman, J. J. "Air Pollution from Use of Fuel—current
status and future of particulate emission control," National
Engineer, March 1965.
11. Stern, A. C. "The Regulation of Air Pollution from Power Plants
in the United States," Presented at International Symposium on
Emission Regulations, Essen, Germany, March 1966.
12. Engelbrecht, H. L., "Electrostatic Precipitators in Thermal Power
Stations using Low Grade Coal," Presented at 28th Annual Meeting
of American Power Conference, Illinois Institute of Technology,
April 1966.
13. Control Techniques for Sulfur Oxide Air Pollutants, NAPCA Publica-
tion No. AP 52, January 1969.
14. High, M. and Megonnell, W., "Development of Regulations for Sulfur
Oxide Emissions," Presented at 61st Annual Meeting of Air Pollution
Control Association, Paper No. 68-40, June 1968.
15. Unpublished Report, "Restrictions on Particulate Emissions Based
on Process Weight," Bay Area Air Pollution Control District, 1959.
16. Duprey, Robert L., "Compilations of Air Pollutant Emission Factors,"
NAPCA Publication No. AP-42, 1968.
17. Sableski et al., "Development of Incineration Guidelines for
Federal Facilities," Presented at the annual meeting of the Air
Pollution Control Association, June 1968.
18. Huey, N. A., "Ambient Odor Evaluation," Paper presented at annual
meeting of the Air Pollution Control Association, June 1968.
19. Mills, J. L., et al., "Quantitative Odor Measurement," Journal
of the Air Pollution Control Association, September 1963.
-------
NEW YORK CITY, ST. LOUIS, et a
MARYLAND, MONTANA, KANSAS CITY, D. C.
0.05
102 103 104
EQUIPMENT CAPACITY RATING, 106 Btu/hr
Figure 1. Paniculate matter standards for fuel-burning equipment.
-------
ALLOWABLE EMISSION, Ib/hr
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POTENTIAL EMISSION RATE, Ib/hr
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Figure 3. Pennsylvania potential-emission-rate standard.
-------
A - NEW YORK STATE (EXISTING UNITS)
B - NEW YORK STATE (NEW UNITS)
C - NEW YORK CITY
D - FEDERAL FACILITIES (0.3 gr/scf) 1 35.3% CARBON
E - FEDERAL FACILITIES (0-2 gr/scf)
12% C02 (DRY), 70
0.1,
50 100
500 1,000 5,000 10,000
REFUSE CHARGED, Ib/hr
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Figure 4. Particulate matter standards for refuse-burning equipment.
-------
Table I. REQUIRED COLLECTION EFFICIENCIES FOR FUEL-BURNING INSTALLATIONS*1
Unit
Underfeed
Traveling
grate
Spreader
stoker
Cyclone
Pulverized
Size
10° Btu/hr
10
50
50
50R
100
100R
500
5,000
10,000
500
5,000
10,000
Required collection efficiency, %
W. Va.
70.8
80.2
92.3
95.0
93.3
95.7
88.5
90.1
90.1
96.4
96.9
96.9
Md. et al.
68.8
78.6
91.9
94.6
93.0
95.4
87.4
92.6
93.7
96.0
97.7
98.1
New York City et al.
68.8
76.0
90.9
94.0
92.0
94.8
84.3
89.5
90.6
95.2
96.8
97.1
a Basis: 10% ash and 13,000 Btu/lb; R: Reinjection.
-------
Table II. CONTROLLED PROCESSES ILLUSTRATED IN FIGURE 2
1. Coffee roaster
2. Electric steel furnace
3. Chemical drying and fertilizer operation
4. Battery plate smelting
5. Steel open-hearth furnace
6. Gray iron cupola
7. Lead smelting
8. Lead sintering
9. Asphalt batch plant
10. Thermofor catalytic cracker regenerator
11. Fluid catalytic cracker regenerator
12. Kraft recovery furnace
13. Blast furnace
14. Sintering (main strand)
15. EOF (no gas recovery)
16. Gray iron cupola
17. Fluid catalytic cracker regenerator
18. Dry-process cement kiln
19. Wet-process cement kiln
20. Secondary lead smelting
21. Secondary zinc sweating furnace
22. Secondary aluminum sweating furnace
23. Mineral wool curing oven
24. Mineral wool blowchamber
25. Barley grain cleaner
26. Frit smelter
-------
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