United States
Environmental Protection
Agency
Industrial Environmental Resea
Laboratory
Research Triangle Park NC 27711
Research and Development
EPA-600/S7-81-003d Oct. 1981
Project Summary
Emissions Assessment of
Conventional Stationary
Combustion Systems:
Summary Report
C. C. Shih and A. M. Takata
Multimedia emissions from 39
source categories of conventional
stationary combustion systems are
characterized in this study. In the
assessment process, existing emis-
sions data were first examined to
determine the adequacy of the data
base. This was followed by the
conduct of a measurement program to
fill identified data gaps. Emissions
data obtained from the sampling and
analysis program were combined with
existing emissions data to provide
estimates of emission levels, and to
define the need for additional data.
The results of this study indicate
that conventional stationary combus-
tion systems contribute significantly
to the nationwide emissions burden.
Flue gas emissions of NOX. SOz, and
particulate matter from the 39 source
categories studied account for approx-
imately 86, 66, and 36 percent,
respectively, of the emissions of these
pollutants from all stationary sources.
Additionally, flue gas emissions of
sulfates and several trace elements
from coal- and oil-fired combustion
sources also require further attention.
POM compounds in flue gas emissions
are mostly naphthalene, phenanthrene,
and pyrene. However, dibenz(a.h)an-
thracene and possibly benzo(a)pyrene,
both active carcinogens, were detected
at a limited number of coal-fired sites.
Also, dibenz(a,h)anthracene, and
possibly benzo(a)pyrene and benzo
(g,h,i)perylene, another active carcin-
ogen, were detected at one coal- and
one wood-fired underfeed stoker
tested. The possible presence of
benzo(a)pyrene in significant amounts
was indicated in the emissions of two
other wood-fired boilers.
A second major source of air emis-
sions in steam electric plants is vapors
and drifts from cooling towers. Air
emissions of chlorine, magnesium,
phosphorus, and sulfates from me-
chanical draft cooling towers were
found to be comparable to flue gas
emissions of these pollutants from oil-
fired utility boilers.
Wastewater streams are generated
from several operations in steam
electric plants, and in industrial and
commercial/institutional facilities but
to a much lesser extent. Overall,
concentrations of iron, magnesium,
manganese, nickel, and phosphorus
are at levels that may be of environ-
mental concern. Average organic
levels ranged from 0.01 mg/l for ash
pond effluents to 6.0 mg/l for boiler
blowdown. Also, no POM was de-
tected in wastewater streams.
Data on coal fly ash and bottom ash
show that from 11 to 16 trace
elements are present at potentially
harmful levels. The only POMs de-
-------
tected, however, were naphthalene,
alkyl naphthalenes, and other relatively
nontoxic compounds.
This Project Summary was devel-
oped by EPA's Industrial Environmen-
tal Research Laboratory, Research
Triangle Park, NC, to announce key
findings of the research project that is
fully documented in a separate report
of the same title (see Project Report
ordering information at back).
Introduction
In response to the need for a compre-
hensive characterization of pollutants
from stationary conventional combus-
tion processes, EPA's Industrial Envi-
ronmental Research Laboratory at
Research Triangle Park (IERL-RTP) in
North Carolina established the Conven-
tional Combustion Environmental As-
sessment (CCEA) Program as the
primary vehicle for filling identified data
gaps. The component project under
which this study was performed is
known as the Emissions Assessment of
Conventional Combustion Systems
(EACCS) project, whose objectives are
the:
• Compilation and evaluation of all
available emissions data on pollu-
tants from selected stationary
conventional combustion proc-
esses.
• Acquisition of needed new emis-
sions data from field tests.
• Characterization of air emissions,
wastewater effluents, and solid
wastes generated by selected
stationary conventional combustion
processes, utilizing combined data
from existing sources and field
tests.
• Determination of additional data
needs, including specific areas of
data uncertainty.
The combustion source types assessed
were selected because of their relevance
to emissions and because they are
among the largest, potentially largest,
and most numerous (in use) of existing
combustion source types. As shown in
Table 1, 39 source types were selected
for study. Selected source types were
classified into five principal categories.
The results of emissionsassessmentfor
these five combustion source categories
are detailed in the following group/cat-
egory reports:
Volume I, Gas- and Oil-Fired Resi-
dential Heating Sources (EPA-600/7-
79-029b; NTIS PB 298494).
Volume II, Internal Combustion Sources
(EPA-600/7-79-029c; NTIS PB 296390).
Volume III, External Combustion
Sources for Electricity Generation
(EPA-600/7-81 -003a; NTIS PB 81-
145195).
Volume IV, Commercial/Institutional
Combustion Sources (EPA-600/7-
81 -003b; NTIS PB 81-145187).
Volume V, Industrial Combustion
Sources (EPA-600/7-81-003c; NTIS
PB 81-225559).
The highlights of these group/cate-
gory reports are documented in this
report summary.
Assessment Methodology
The assessment method employed in
the project involved a critical examina-
tion of existing emissions data, followed
by a measurement program to fill data
gaps based on a phased sampling and
analysis strategy. Data acquired as
result of the measurement program,
combination with the existing dai
were further evaluated. Data inadequ
cies identified at the completion of tl
project are discussed with respect tot!
need for additional study.
Specifically, the phased approach
environmental assessment providi
comprehensive emissions informatic
on all process waste streams in a co
effective manner. To achieve this goc
two distinct samplings and analyses ai
employed. Level I utilizes semiquantiti
tive (+ a factor of 3) techniques >
sample collection and laboratory ar
field analysis: 1) to provide preliminai
emissions data for waste streams ar
pollutants not adequately characterizei
2) to identify potential problem area1.
and 3) to prioritize waste streams an
pollutants in those streams for furthe
Table 1. Combustion Systems Considered in the Study
Combustion
Source
Type
External Combustion
Coal
Bituminous
Pulverized dry
Pulverized wet
Cyclone
All stokers
Anthracite
Pulverized dry
All stokers
Lignite
Pulverized dry
Cyclone
All stokers
Petroleum
Residual oil
Tangential firing
All other
Distillate oil
Tangential firing
All other
Gas
Tangential firing
All other
Wood
Stoker
Internal Combustion
Distillate Oil
Gas turbine
Reciprocating engine
Gas
Gas turbine
Reciprocating engine
Electricity
Generation
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
user
Industrial
X
X
X
X
X
X
X
X
X
X
X
oecfor
Commercial/
Institutional Residential
X
X
X
X
X X
X X
X
X
X
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more quantitative testing. Using the
information from Level I, available
resources can be directed toward Level
II testing which involves specific quanti-
tative analysis of components of those
streams that contain significant pollu-
tant levels. The data developed at Level
II are used to identify control technology
needs and to further define environ-
mental hazards associated with emis-
sions.
Existing Emissions Data Base
A major task in the project was the
identification of gaps and inadequacies
in the data base. Decisions as to the
adequacy of the data base were made
using criteria developed by considering
both the reliability and variability of the
data. Estimated environmental risks
associated with the emission of each
pollutant were also considered in
determining the need for, and extent of,
the sampling and analysis program.
Gas- and Oil-Fired Residential
Heating Sources
The sources of emissions data for
residential gas- and oil-fired systems
are limited to early data used to
generate EPA emission factors and
more recent data developed by EPA
contractors for criteria pollutants. For
gas-fired systems, the data base for
SO2, N0», total hydrocarbons, and CO
emissions is adequate. However, the
data base for paniculate and organic
emissions is inadequate. For oil-fired
systems, the emissions data base for
particulate, S02, NOX, HC, and CO is
adequate, but inadequate for SOs,
particulate sulfate, trace element, and
organic emissions.
Internal Combustion Sources
The evaluation of emissions data for
electricity generation and industrial
internal combustion sources indicates
that the emissions data base is adequate
for gas-fueled turbines and reciprocating
engines. For distillate-oil-fueled gas
turbines, the existing data base for NOX,
total hydrocarbons, CO, particulate,
S02, and SOs emissions is adequate.
However, the data base for trace
elements and specific organic emissions
is inadequate. For distillate-oil-fueled
reciprocating engines, the data base for
NOX, total hydrocarbons, CO, and S02
emissions is adequate. The data base
for particulates, S03, trace elements,
and specific organic emissions was
found to be inadequate.
External Combustion Sources
for Electricity Generation
For flue gas emissions, the status of
the data base can be summarized as
follows:
• The data base for criteria pollutants
is generally adequate.
• For SOs emissions, the data base is
adequate for bitummous-coal-fired
boilers, residual-oil-fired boilers,
and gas-fired boilers, and inade-
quate for lignite-fired boilers. For
emissions of primary sulfates, the
data base is adequate for pulverized
bituminous dry- and wet-bottom
boilers, residual-oil-fired boilers,
and gas-fired boilers, and inade-
quate for other combustion source
categories.
• For emissions of particulates by
size fraction and trace elements,
the data base is adequate for gas-
fired boilers and inadequate for all
other combustion source cate-
gories.
• For emissions of specific organics
and polycyclic organic matter
(POM), the data base is inadequate
for all combustion source cate-
gories.
Two other sources of air emissions of
environmental concern are cooling
tower emissions and emissions from
coal storage piles. The data bases
characterizing air emissions from these
two sources are inadequate.
For wastewater effluents from exter-
nal combustion sources for electricity
generation, the data base is adequate
for wastewater from water treatment
processes-, and inadequate for all other
streams.
The evaluation of emissions data for
solid wastes indicated the inadequacy
of the organic data base for coal fly ash
and bottom ash, and the inadequacy of
the inorganic and organic data bases for
FGD sludges. On the other hand, the
inorganic data base for coal ash is
considered to be adequate because of
the adequate characterization of the
inorganic content of coal. Similarly, the
data base for water treatment wastes is
considered to be adequate, because the
waste -constituents are inorganic and
can be estimated from the raw water
constituents and the treatment method
used.
Commercial/Institutional
Combustion Sources
Evaluation of emissions data indicates
that the data base for gas- and oil-fired
external combustion sources, although
limited, is adequate for NOX, total
hydrocarbons, CO, particulates, and
SOa. However, the data base for specific
organic emissions for these sources is
inadequate, and, for the oil-fired sources,
the data base for SOs and trace
elements is inadequate. Emissions data
from solid-fuel-fired sources are gener-
ally inadequate for all pollutants.
In the case of oil-fired internal
combustion sources, data are inade-
quate for SOa, trace element, and
specific organic emissions. Data for
gas-fired reciprocating engines are
adequate; however, one unit was tested
in this program to confirm data adequacy.
Industrial Combustion Sources
The status of the data base can be
summarized as follows:
• The data base for criteria pollutants
is adequate, except for emissions
from wood-fired combustion
sources.
• The data base for particulate
sulfate and sulf uric acid emissions
is adequate only for gas-fired
sources.
• The data base for specific organics
is inadequate for all industrial
source categories.
The Source Measurement
Program
Because of the deficiencies in the
emissions data base, source tests were
conducted at a selected number of sites
for each of the five principal combustion
source categories.
Gas- and Oil-Fired Residential
Heating Sources
Five gas- and five oil-fired residential
sources were initially selected for
testing. Upon review of the results
obtained from the testing of the 10 sites,
1 gas-fired and 2 oil-fired systems were
subsequently tested to study the effect
of cycle mode on organic emissions.
Level II analyses for SO2, S03, and
particulate sulfate were also conducted
at the two oil-fired sites.
Internal Combustion Sources
Eleven internal combustion sites
were selected for testing to better
characterize the emissions associated
with these sources. The sites tested
included one gas-fueled gas turbine,
five distillate-oil-fueled gas turbines,
and five distillate-oil-fueled recipro-
cating engines (diesel engines). A gas-
-------
fueled gas turbine site was included to
ensure that previously unidentified
pollutants are not being emitted in
environmentally unacceptable quanti-
ties.
Test results from the first phase were
evaluated to determine the need for and
type of additional sampling and analysis.
These evaluations led to the recommen-
dation of additional tests to determine
S03 and organic emissions from elec-
tricity-generation distillate-oil recipro-
cating engines. Level II tests were
subsequently conducted at three of the
diesel engine sites previously tested.
External Combustion Sources
for Electricity Generation
Forty-six sites were selected for
sampling and analysis of flue gas
emissions. These 46 sites include: 3
pulverized dry bottom, 7 pulverized wet
bottom, 6 cyclone, and 3 stoker bitumi-
nous-coal-fired boilers; 3 pulverized dry
bottom, 2 cyclone, and 2 spreader-
stoker lignite-fired boilers; 4tangentially
fired and 8 wall-fired boilers fueled with
residual oil; and 3 tangentially fired and
5 wall-fired boilers fueled with natural
gas.
At a selected number of these sites,
wastewater streams and solid wastes
were also sampled and analyzed.
Wastewater streams sampled and
analyzed included cooling tower blow-
down, once-through cooling water,
boiler blowdown, fly ash pond overflow,
bottom ash pond overflow, and combined
ash pond overflow. Intermittent waste-
water streams such as chemical clean-
ing wastes and coal pile runoff were not
sampled. Solid waste streams sampled
and analyzed included fly ash, bottom
ash, and FGD scrubber sludge.
In addition to the modified Level I
tests, comprehensive Level II tests were
also conducted for a bituminous-coal-
fired cyclone boiler, two bituminous-
coal-fired pulverized dry bottom boilers,
and an oil-fired boiler. All these coal-
fired boilers were equipped with flue
gas desulfurization (FGD) systems. The
oil-fired boiler tested used off-stoichio-
metric firing and flue gas recirculation
for NOx control.
Because direct measurements of
chemical constituents present in cooling
tower exhausts have not been made
(except for a limited number of trace
elements), six cooling towers were
selected for testing. Cooling tower
streams sampled and analyzed included
air emissions (as evaporation and drift)
and blowdown.
Commercial/Institutional
Combustion Sources
Twenty-two external combustion
systems were tested. These included:
five gas-fired, three distillate-oil-fired,
five residual-oil-fired, three anthracite
stokers, three bituminous stokers, two
bituminous pulverized dry units, and
one wood-fired stoker. Four oil-fired,
one gas-fired, and one dual-fired
internal combustion reciprocating en-
gines were also tested.
Industrial Combustion Sources
Twenty-two external combustion
systems were tested. These include: 10
gas-fired, 3 distillate oil-fired, and 5
residual-oil-fired boilers; 3 bituminous
pulverized wet bottom and 2 bituminous
pulverized dry bottom units; 3 bitumi-
nous stokers; and 5 wood-fired stokers.
Sampling and Analysis
Methodology
Level I Field Testing
The Source Assessment Sampling
System (SASS) train, developed by EPA,
was used to collect both vapor and pani-
culate emissions in quantities sufficient
for the wide range of analyses needed to
adequately characterize emissions from
external combustion sources. Briefly,
the SASS train consists of a conven-
tional heated probe, three cyclones, and
a filter in a heated oven which collect
four paniculate size fractions (>10/um,
3-10 //m, 1-3 fjm, <1 //m); a gas
conditioning system; an XAD-2 polymer
adsorbent trap to collect gaseous
organics and some inorganics; and
impingers to collect the remaining
gaseous inorganics and trace elements.
The train is run until at least 30 m3 of
gas has been collected.
In addition to using the SASS train for
stack gas sampling, other equipment
was used to collect components that
could not be analyzed from the train
samples. A gas chromatograph (GC)
with flame ionization detection was
used in the field to analyze hydrocar-
bons in the boiling point range of-160°
to 90°C (reported as d - C6) collected in
gas sampling bags. Additionally, these
samples were analyzed for CO, COz, Oz,
and S02 by GC using a thermal conduc-
tivity detector.
Water samples were generally taken
by either tap or dipper sampling. Tap
samples, obtained on contained liquids
in motion or static liquids in tanks or
drums, was generally applicable 1
cooling tower or boiler blowdown. Th
method involved fitting the valve (
stopcock used for sample removal wit
a length of precleaned Teflon tubin
long enough to reach the bottom of th
container. Dipper sampling, applicabl
to sampling ponds or open discharg
streams, was used to acquire ash pon
discharge samples. The method involve
a dipper with a flared bowl and attache
handle, long enough to reach discharg
areas. After sample recovery, wate
analyses using the Hach Kit were per
formed in the field to determine pi-
conductivity, total suspended solid
(TSS), hardness, alkalinity or acidity
ammonia nitrogen, cyanide, nitrat
nitrogen, phosphate, sulfite, and sulfate
For solids sampling, the fractiona
shovel grab samples procedure wa:
used unless the plant had an automatii
sampling system. The concept of frac
tional shoveling involves the acquisitioi
of a time-integrated grab sampl<
representative of overall process inpu
or output during a given run time period
A standard, square-edged, 12-in, (30.5
cm) wide shovel was used. For stream;
entering or exiting a process operation
a full cross-stream cut sample wa:
taken from the belt hourly. Each hourly
shovel sample was added to a pile tc
eventually form a run time penoc
composite. At the conclusion of the run
this pile was coned and quartered tc
form a final representative sample
weighing from 2.3 to 4.5 kg. When
plants were equipped with automatic
samplers to remove representative
cross sections of a stream while
automatically forming a homogeneous
composite, these were used in prefer-
ence to the shovel technique.
In addition to the above sampling
methods, air emissions from cooling
towers were sampled, using a modified
EPA Method 5 train without the filter
assembly.
Modified Level I Laboratory
Analysis
The basic Level I schematic, outlining
flow of samples and analysis plans for
paniculate and gaseous emissions, is
depicted in Figure 1. The corresponding
schematic for solid, slurry, and liquid
samples is presented in Figure 2. These
schematics provide a general idea of the
apportionment of samples for analysis.
For example, Figure 1 shows that the
probe-and-cyclone-rinses combination
will only be subjected to inorganic
4
-------
Probe and
Cyclone
Rinses
SASS Train Gas
Conditioner
Condensate
* Weigh
Individual
Catches
f// Inorganics
are Greater than
10%of Total Catch.
3-1
1-3/J*
Filter
SASS Train
Impingers
Extraction
Extraction
2nc
Organics
Extract
Inorganics
Inorganics
As. Sb. Hg
Inorganics
Organics
Physical Separation
into LC Fractions,
IR/LRMS
Elements (SSMS) and
Selected Anions
Elements and
Selected Anions
Elements (SSMS) and
Selected Anions
Physical Separation
into LC Fractions. IR/LRMS
Same as Above
Chemiluminescence
or Method 7
Elements (SSMS)
and Selected
Anions^
Physical
Separation
into LC Fractions,
'R/LRMS
Inorganic
(Grab)
Organic
Material >C6
Organic
Material Ci-C6
One-Site Gas
Chromatography
XAD-2
Absorber,
Module Rinse
On-Site Gas
Chromatography
Elements (SSMS) and
Selected Anions
Aliquot for Gas
Chromatographic
Analysis
Physical Separation
into LC Fractions,
IR/LRMS
Figure 1. Basic level 1 sampling flow and analytical plan for particulates and gases.
analysis if the dried sample exceeds 10
percent of the total cyclone-and-filter-
sample weight. Details of the sample
handling, transfer, and analysis proce-
dures are in the IERL-RTP Procedures
Manual: Level I Environmental Assess-
ment. EPA-600/2-76-160a* (NTIS PB
257850). A brief description of inorganic
and organic analyses performed and
deviations from the basic Level I
procedure follows.
•Although superseded by EPA-600/7-78-201
(NTIS PB 293795), the earlier procedures were
used in this study
Inorganic Analyses
Level I analysis was used for all
inorganic analyses. It was designed to
identify all elemental species in the
SASS train fractions and to provide
semiquantitative data on the elemental
distributions and total emission factors.
The primary tool for Level I inorganic
analysis is Spark Source Mass Spec-
trometry (SSMS). SSMS data were
supplemented with Atomic Absorption
Spectrometry (AAS) data for mercury,
arsenic, and antimony, and with specific
ion electrode determinations for chlo-
rides.
The following SASS train fractions
were analyzed for elemental composi-
tion: 1)the particulate filter, 2) the XAD-
2 sorbent, and 3) a composite sample
containing portions of the XAD-2
module condensate and HMOs rinse,
and the first impinger solution. Analy-
ses of the carbon, hydrogen, nitrogen,
oxygen, and trace element contents and
heating values of the fuel were also
performed for the coal- and oil-fired
sources.
Organic Analyses
Level I organic analyses provide data
on volatile (boiling point range of 90 to
300°C, corresponding to the boiling
points of C7 - Ci6 n-alkanesand reported
as C7 - Cie) and non-volatile organic
compounds (boiling point >300°C,
corresponding to the boiling points of
>C16 n-alkanes and reported as >Cie) to
supplement data for gaseous organics
(foiling point range of -160 to 90°C,
corresponding to the boiling points of Ci
- C6 n-alkanes and reported as Ci - Ce)
measured in the field. Organics in the
XAD-2 module condensate trap and
XAD-2 resin were recovered by methy-
lene chloride extraction. SASS train
components including the tubing were
carefully cleaned with methylene
chloride or methylene chloride/meth-
anol solvent to recover all organics
collected in the SASS train.
Because all samples are too dilute to
detect organic compounds by the
majority of instrumental techniques
employed, the first step in the analysis
was to concentrate the sample fractions
from 1000to10mlinaKuderna-Danish
apparatus in which rinse solvent is
-------
Leachable
Materials
Inorganics
Organics
Inorganics
Selected
Water
Tests
Organic
Extraction
or Direct
Analysis
Selected Anions
Physical Separation
into LC Fractions.
IR/LRMS
Suspended
So/ids
Elements (SSMSJ and
Physical Separation mtt
LC Fractions, IR/LRMS
Elements (SSMS) and
Selected A n/'ons
Elements (SSMS) and
Selected Anions
Physical Separation into
LC Fractions, IR/LRMS
Physical Separation into
LC Fractions, IR/LRMS
Aliquot for Gas
Chromatographic
Analysis
Figure 2. Basic level 1 sampling flow and analytical scheme for solids, slurries, and liquids.
evaporated while the organics of
interest are retained.* Kuderna-Danish
concentrates were then evaluated by
gas chromatography (GC), infrared
spectrometry (IR), liquid chromatography
(LC) and gravimetric analysis, low
resolution mass spectroscopy (LRMS),
and sequential gas chromatography/
mass spectrometry (GC/MS)f. The
extent of the organic analysis is deter-
mined by the stack gas concentrations
found for total organics (volatile and
non-volatile). If the total organics
indicate a stack gas concentration
below 500 Aig/m3, a liquid concentra-
tion below 0.1 mg/l, or a solid concen-
tration below 1 mg/kg, further analysis
"Kuderna-Danish is a glass apparatus for evaporat-
ing bulk amounts of solvents.
fine major modification in the Level I sampling and
analysis procedure was the addition of GC/MS
analysis for POM.
is not conducted. If the concentrations
are above these levels, a class fraction-
ation by liquid chromatography is
conducted followed by GC and IR
analyses. Additionally, if the concentra-
tions in a LC fraction are above these
levels, LRMS is conducted for that
particular LC fraction.
Level II Sampling and
Analysis
In addition to the modified Level I
tests. Level II tests were also conducted
at a number of sites. Level II sampling
and analysis techniques used for these
sites included:
• Continuous monitoring of NO,
emissions by chemiluminescent
instrumentation.
• Continuous monitoring of SOa
emissions by pulsed flourescent
analyzer.
Determination of sulfate emissions
by the Goksoyr-Ross Controlled
Condensation System.
Determination of particle size
distribution by Polarized Light
Microscopy (PLM) and MRI cas-
cade impactor.
Determination of trace element
concentrations by Atomic Absorp-
tion Spectroscopy (AAS) and In-
ductively Coupled Plasma Optical
Emission Spectroscopy (ICP).
Identification of inorganic com-
pounds from specific infrared band
correlations by Fourier Transform
IR (FTIR).
Identification of crystalline material
in solid samples by X-ray Diffrac-
tion (XRD).
' Determination of the surface and
subsurface sulfur concentrations
-------
and oxidation state of bulk samples
by Electron Spectroscopy for Chem-
ical Analysis (ESCA).
• Determination of the surface and
subsurface composition of bulk
samples by Secondary Ion Mass
Spectrometry (SIMS).
• Determination of elemental com-
position of single particles by
Scanning Electron Microscope
with Energy Dispersive X-ray
Fluorescence (SEM-EDX).
• Identification and quantification of
non-POM organic compounds by
GC/MS.
Conclusions
The results of the field measurement
rogram, along with supplementary
alues from the data base, were
valuated in terms of data adequacy and
y using the concept of severity factors.
wo types of severity factors, ambient
nd discharge, were used in data
valuation. For air emissions, the
mbient severity factor, defined as the
itio of the calculated maximum ground
ivel concentration of a pollutant
pecies to an ambient air quality level or
lazard factor, was used. The hazard
ictor for noncriteria pollutants is a
educed threshold limit value (TLV);
vhile for criteria pollutants, it is the
imbient air quality standard. The TLV is
educed by a factor of 300 (24/8 x 100)
o account for length of exposure and an
idded safety factor due to the higher
.usceptibility of the general population
>f exposure effects. An ambient severity
actor of greater than 0.05 indicates a
>otential problem requiring further
ittention. The "greater than 0.05"
;riterion reflects an uncertainty factor
}f 20 in the calculation of ambient
severity, because of potential errors
ntroduced in the application of the
dispersion model, and in Level I sampling
and analysis. For residential sources, a
modified ambient severity factor based
on multiple sources was used. Maxi-
mum ground level concentrations for
multiple sources were determined
using a dispersion model for an array of
1000 sources and a grid of houses 80 x
80 m.
For wastewater effluents and solid
wastes, discharge severities were used
in data evaluation. Discharge severity is
the ratio of discharge concentration to
the health-based water or solid Dis-
charge Multimedia Environmental Goal
(DMEG). A discharge severity greater
than 1.0 indicates a potential hazard
requiring further attention. The "greater
than 1.0" criterion, instead of the
"greater than 0.05" criterion for
ambient severity, was used because
calculation of discharge severities was
based on conservative DMEG values.
Also, the uncertainty in the calculated
values only involved potential sampling
and analysis errors. The error due to the
application of dispersion models was no
longer a component.
Flue Gas Emissions
The conventional stationary combus-
tion source categories investigated in
this study contribute significantly to the
nationwide emissions burden. As
shown in Table 2, flue gas emissions of
NOX, SOz, paniculate matter, CO, and
total hydrocarbons from the 39 source
categories studied account for approxi-
mately 86, 66, 36, 10, and 5 percent,
respectively, of the emissions of these
pollutants from all stationary sources.
From an environmental standpoint,
emissions of NOX, SOz, and particulate
matter are of particular concern.
Ambient severity factors for NOX emis-
sions far exceed 0.05 for internal
combustion sources, utility boilers,
industrial boilers, and coal-fired com-
mercial/institutional boilers. Addition-
ally, ambient severity factors for emis-
sions of SOz and particulate matter far
exceed 0.05 forallbituminous-coal-and
lignite-fired boilers. Emissions of SO2
are also considered to be environ-
mentally significant for all residual-oil-
fired boilers.
Emissions of total hydrocarbons are
considered to be a lesser problem.
Ambient severity factors for emissions
of total hydrocarbons exceed 0.05 only
for large bituminous-coal-, lignite-, and
residual-oil-fired utility boilers, indus-
trial and commercial/institutional coal-
fired and wood-fired stokers, and
distillate-oil and gas reciprocating
engines.
Emissions of CO are not an environ-
mental concern: their ambient severity
factors are all well below 0.05.
Aside from the criteria pollutants, flue
gas emissions of SOs (in the form of
sulfuric acid vapor and aerosol) from
several combustion source -categories
require further attention. These com-
bustion source categories include: oil-
fired residential sources, electricity
generation and industrial oil-fueled
internal combustion sources, bitumi-
nous-coal- and residual-oil-fired utility
boilers, bituminous-coal-f ired commer-
cial/institutional boilers, and bitumi-
nous-coal- and residual-oil-fired- in-
dustrial boilers. Ambient severity
factors for SOa emissions from these
sources range from 0.05 to 7.4. For
bituminous-coal- and lignite-fired boilers,
emissions of particulate sulfate are also
associated with ambient severity factors
in excess of 0.05 and merit special
concern.
Of the trace elements present in
bituminous coal, flue gas emissions of
aluminum, beryllium, calcium, chlorine,
cobalt, chromium, fluorine, iron, lead,
lithium, nickel, phosphorus, and silicon
Table 2. Contribution of Conventional Stationary Combustion Systems
to Nationwide Emissions Burden
Combustion
Category
Emission Contribution as Percentage of All
Stationary Sources
SOZ Particulates Hydrocarbons CO
Gas- and Oil-fired
Residential Heating
Sources
Internal Combustion
Sources
External Combustion
Sources for
Electricity Generation
Commercial/Institu-
tional Combustion
2.5 0.9
18 0.07
50 57
0.2
0.1
25
0.2
3.7.
0.6
0.5
2.7
4.3
Sources
Industrial External
Combustion Sources
TOTAL
5.0
10
86
3.0
5.7
66
1.7
9.0
36
0.3
0.4
5
0.5
1.7
10
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from most coal-fired boilers are of
environmental significance. For residual-
oil-fired boilers, flue gas emissions of
beryllium, chlorine, chromium, copper,
lead, magnesium, nickel, phosphorus,
and vanadium are of principal concern.
Elements with ambient severity factors
in excess of 0.05 also include chromium,
nickel, phosphorus, and vanadium from
distillate-oil-fired industrial boilers,
nickel from distillate-oil-fired commer-
cial/institutional boilers, barium, cal-
cium, potassium, and phosphorus from
wood-fired boilers, and copper, nickel,
and phosphorus from oil-fueled internal
combustion sources.
Analysis of organic emissions indi-
cated that the principal constituents of
flue gas are: saturated straight-chain
and branched hydrocarbons and substi-
tuted benzenes from oil-fueled internal
combustion sources; glycols, ethers,
ketones, and saturated and aliphatic
hydrocarbons from utility boilers; ali-
phatic and aromatic hydrocarbons,
esters, ketones, and carboxylic acids
from commercial/institutional sources;
and esters, ethers, glycols, and aliphatic
and aromatic hydrocarbons from indus-
trial boilers. The most prevalent consti-
tuents are generally associated with
DMEG values in the 10 to 1000 mg/m3
range. Ambient severity factors for
these organic compounds (excluding
POM) are all well below 0.05 and
probably not of concern with respect to
human health. ROMs emitted at the
highest concentrations in flue gas
streams include naphthalene, phen-
anthrene, pyrene, fluoranthene, and
chrysene from bituminous-coal-fired
sources. Dibenz(a,h)anthracene and
possibly benzo(a)pyrene and benzo
(g,h,i) perylene, all active carcinogens,
were detected at a limited number of
sites. POM emissions from wood-fired
boilers were found to be significantly
higher than those from coal-fired
boilers. Dibenz(a,h)anthracene and also
possibly benzo(a)pyrene and benzo(g,h,i)
perylene were detected at some of the
sites tested. The only POMs identified in
flue gas emissions from lignite-fired
sources were biphenyl and trimethyl
propenyl naphthalene. Carcinogenic
POMs were not detected. For residual-
oil-fired sources, POMs emitted at the
highest concentrations in flue gas
streams are naphthalene and biphenyl.
Again, carcinogenic POMs were not
detected. No POM was detected in flue
gas streams from gas-fired utility boiler
sites.
Air Emissions from
Cooling Towers
Two potential environmental problems
associated with the air emissions from
cooling towers have been identified.
First, air emissions of chlorine, magne-
sium, and phosphorus from mechanical
draft cooling towers with high drift rates
are comparable to flue gas emissions of
these elements from residual-oil-fired
utility boilers and are of environmental
significance. Second, sulfate emissions
from mechanical draft cooling towers
employing sulfuric acid as an additive,
and with design drift losses in the 0.1 to
0.2 percent range, are of the same
magnitude as sulfate emissions from
coal- and oil-fired utility boilers.
Wastewater Discharges
The major sources of wastewater
discharges from external combustion
sources for electricity generation are:
once-through cooling water, blowdown
from recirculating cooling systems,
wastes from water treatment processes,
chemical cleaning wastes, and coal pile
runoff. Discharges from once-through
cooling system amount to 7,780,000
I/sec and account for approximately
99.8 percent of the total wastewater
from conventional utility power plants.
Of the remaining sources, blowdown
from recirculating cooling systems is
the largest contributor to wastewater
discharge.
From an environmental standpoint,
the pollutants of most concern in
wastewater effluents from conventional
utility power plants are iron, magne-
sium, manganese, nickel, and phos-
phorus. The average organic levels in
the ash pond effluents sampled were
less than 0.1 mg/l. Average organic
levels in the cooling tower blowdown
and boiler blowdown sampled were 1 .5
and 6.0 mg/l, respectively. POMs were
not found above the detection limit of 2
Based on discharge severities, the
once-through cooling tower and ash
pond overflow streams appear to be of
less environmental significance than
the other wastewater streams from
conventional fossil-fueled steam elec-
tric plants. Total pollutant loading from
wastewater streams will, however,
depend on individual discharge flow
rates.
Industrial and commercial/institu-
tional boilers are smaller contributors to
wastewater discharges when compared
with electricity generation sources.
Further, characteristics of wastew
discharges from these sources woul
similar to those from electricity gen
tion sources.
Solid Wastes
Solid waste streams generatec
conventional utility power plants cor
primarily of coal ash and sludge f
FGD systems. In 1978, total
production was 63.6 Tg and total F
sludge production was 2.1 Tg (ash-fr
Ash production from industrial .
commercial/institutional sources \
proportionally less and FGD slu>
production from these sources \
negligible.
Leaching of trace elements from c
ash may result in environmental c
tamination. Concentrations of 11 to
trace elements in bituminous coal <
and lignite ash exceed their heal
based solid DMEG values. The polluta
of most concern are aluminum, arser
calcium, chromium, iron, mangane
nickel, potassium, and silicon.
Recommendations
Because of inadequacies in the dc
•base that characterizes emissions frc
conventional stationary combustii
systems, it is recommended that ad<
tional studies be conducted to provi<
the following key data needs.
Flue Gas Emissions
• There is a lack of emissions data f i
pulverized dry-bottom boilersfirir
Texas lignite. This is a serious dai
deficiency because approximate
16,000 MW of added generatin
capacity is planned for this sourc
category in the 1978-1985 perio<
• Size distribution data for flue ga
emissions of particulates ar
inadequate for bituminous-coa
lignite-, and residual-oil-firei
boilers.
• The date bases for particulat
sulfate emissions from bituminous
coal- and lignite-fired sources an
inadequate. Also, SOs emission;
data for lignite-fired sources art
presently unavailable.
• For bituminous-coal-fired boilers
equipped with wet scrubbers oi
mechanical precipitators, the data
bases characterizing flue gas
emissions of trace elements are
inadequate. Data for flue gas
emissions of trace elements from
lignite-fired boilers are generally
8
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not available. Analysis of the data
acquired in this program indicated
the need for additional characteri-
zation studies.
• Although current data indicated
that flue gas emissions of specific
organics (excluding POM) are
probably not of concern with
respect to human health, more
detailed Level II organic analysis
would be required to conclusively
determine the significance of
organic emissions.
• Emissions of POM from bitumi-
nous coal- and wood-fired sources
will require further characteriza-
tion, with special emphasis on the
positive identification and quantifi-
cation of carcinogenic compounds
such as dibenz(a,h)anthracene,
benzo(a)pyrene, and benzo(g,h,i)
perylene.
fVastewater Discharges
• The data bases characterizing cooling
tower blowdown, ash pond over-
flow, chemical cleaning wastes,
wet scrubber wastewater, and coal
pile runoff are inadequate. The
present study has been instru-
mental in applying Level I techni-
ques to identification of waste-
water constituents which pose
potential environmental problems.
Since potential problems were
detected by Level I techniques,
further studies using Level II
techniques will be required to
adequately characterize wastewater
effluents from utility boilers.
Solid Wastes
• The data base characterizing flue
gas emissions of POM from bitu-
minous-coal-fired sources is ade-
quate except for dibenz(a,h)an-
thracene and benzo(a)pyrene.
Emissions of these specific POMs
will require further characteriza-
tion.
C. C. Shih and A. M. Takata are with TRW Environmental Engineering Division,
One Space Park, Redondo Beach, CA 90278.
Michael C. Osborne is the EPA Project Officer (see below).
The complete report, entitled "Emissions Assessment of Conventional Station-
ary Combustion Systems: Summary Report, "(Order No PB 82-109 414; Cost:
$9.50, subject to change) will be available only from.
National Technical Information Service
5285 Port Royal Road
Springfield, VA 22161
Telephone: 703-487-4650
The EPA Project Officer can be contacted at:
Industrial Environmental Research Laboratory
U.S. Environmental Protection Agency
Research Triangle Park, NC 27711
U. S. GOVERNMENT PRINTING OFFICE: I98I/559-092/3347
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