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-------
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Lift statlon-A junction ol two or more sewer lines where the wastewater is lifted to a higher elevation by
a pump or hydraulic lift.
MODELS AVAILABLE TO ESTIMATE EMISSIONS PROM MUNICIPAL SEWERS
Six models were found that could be used to predict emissions from sewers:
• BACT/LAER-IWW/MRE (Manhole regression equation from the Industrial Wastewater-Best Available
Control Technology/Lowest Achievable Emission Rate document);1
BASTE (Bay Area Sewage Toxics Emissions)?
CHEMDAT7;*
CORAL+ (Collection Organic Release Algorithm);*
SIMS (Surface Impoundment Modeling System);4 and
WATERS.'
Of these six models, only two (BASTE and CORAL+) were not developed by the EPA; these models were also
the only models of the six listed above that were specifically created to address municipal wastewater
emissions. The EPA models were primarily created to address on-slte Industrial emissions and, In some cases,
used industrial data to develop the models. Although the authors of WATERS state that the model can be used
with either municipal or industrial sewers, only industrial sewer data were used to develop the model.
Vents in reach manholes and drop structures are the most frequently found sewer emissions points in
municipal sewers. In municipal sewer systems, most sewer components outside of the POTWs are enclosed,
but vented to the atmosphere. The sewer system components addressed by each model are noted in Table 1.
Components likely to be part of a municipal sewer system are also noted in Table 1. The EPA models, in
general, address sewer components that are more likely to be included In an industrial sewer system than in a
municipal sewer system. Only four models, BACT/LAER-IWW/MRE, BASTE, CORAL+, and WATERS, can be
used to estimate HAP emissions from municipal sewer components.
METHOD TO ESTIMATE HAP EMISSIONS FROM MUNICIPAL SEWERS
The goal for this study was to provide a method to estimate HAP emissions from municipal sewers that
state and local air pollution agencies can use to develop a sewer emissions inventory from available data. Of
course, the most accurate means of estimating HAP emissions from sewers would be to obtain air
measurement data on a continuous basis. Because of the extensive area over which sewers are located, this
approach would be highly impractical. Even the continuous measurement of wastewater concentration data,
the second best approach to providing sewer emissions estimates, would also be difficult to implement on a
large scale.
In the absence of measurement data, a method was developed that can be used to estimate sewer HAP
emissions from relatively available data and one of the sewer models discussed above. This method is
described and demonstrated for a large U. S. city.
Description of the Method
The method developed to estimate HAP emissions from sewers relies on three components:
• Sewer wastewater HAP concentration data;
• Sewer physical and operating data; and
• A model that relates the above two data components to emissions.
Since most regions donl regularly measure sewer concentrations, the Industrial wastewater discharge
data reported to EPA's Toxic Release Inventory System (TRIS), under the authority of the Superfund
Amendments Reauthorizatlon Act, were used to provide one estimate of HAP inputs to sewer wastewater.
Another source of data was influent POTW wastewater measurements performed for the National Pollution
Discharge Effluent System (NPDES).
• Developed by R. L. Corsi and available from the Bay Area Air Toxics (BAAT) group, c/o CH2MHill Inc
Oakland, CA 96404 ' "
b Developed by R. L. Corsi and available from Enviromega, Ltd., Hamilton, Ontario, Canada. L9J 1K3
2
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TRIS data are available in terms of annual chemical discharge (by total weight) into sewer wastewater,
on a per-tacillty basis. Unfortunately, TRIS data do not include residential and commercial waslewater inputs to
the sewer system, since these sources are not required to report to TRIS. Therefore, the use of TRIS data will
underestimate sewer HAP emissions for areas where residential and commercial wastewater are significant
contributors to the municipal sewer system. TRIS also does not Include six of the 189 HAPs; one of the six,
hexane, Is a commonly used chemical that may be a significant sewer input In some areas.
Influent POTW wastewater concentration data are required to be reported annually to the NPDGS for
111 priority pollutants as defined by the Clean Water Act. Frequently, data for other pollutants In the
wastewater are also provided by the methods used to test the priority pollutants. Of the 111 priority pollutants,
only 46 are HAPs; therefore, the HAP coverage of the NPDES data is expected to be low as compared to the
universe of 189 potential HAPs and the 183 HAPs reported to TRIS. Within the 46+ HAP coverage, the
NPDES data, however, are expected to be more representative of a municipal sewer system than TRIS data,
since measurements are taken from wastewater that Is composed of Industrial, commercial, and residential
sewer inputs. Although, since NPDES data are usually obtained from only one annual wastewater sample, the
data may or may not represent the annual average wastewater concentration entering a POTW. Nevertheless,
the NPDES data represent the HAP wastewater concentrations after sewer emissions occur, since the POTWs
are downstream of the sewer emission points. If NPDES data are used to predict sewer emissions, the
estimate may be much lower than if wastewater samples could be taken at the influent points in the sewer
system.
The CORAL+ model was chosen as the model to estimate HAP emissions from sewers, since this model
was developed from municipal sewer studies and provided emissions estimates for both reach manholes and
drops. Of the six available models listed earlier, CORAL+ is only capable of estimating emissions from a single
section of the sewer (a reach) and a single drop." In order to estimate sewer emissions for an entire region,
the CORAL+ model was first used to estimate emissions from a single reach manhole and drop, and then
scaled up to the municipal level with information on the number of reach manholes and drops in the city.
The following sewer physical and operating data were needed to use the CORAL+ model and to scale
up the individual reach and drop manhole emissions to the city level:
Total length of sewer pipeline;
Average wastewater velocity in reach;
Average reach diameter;
Average wastewater depth in a reach;
Average wastewater depth in a drop;
Average reach slope;
Reach ventilation rate or air/water volume ratio;
Approximate frequency of occurrence of reach and drop manholes, per length of sewer pipeline;
Average drop diameter; and
Vertical distance from surface to reach and drop.
These data were found to be available either from municipal sewer authorities or by estimating from literature
values.
Sewer HAP Emissions for a Large U. S. City
The method described above was used with both 1989 TRIS data and 1989 NPDES data for a U. S. city
(hereafter referred to as the "City") to estimate sewer HAP emissions. The City has a population of
approximately 5 million and covers 2,259 square kilometers (872 square miles).
TRIS Data-The 1989 TRIS data for the City are shown in the second column in Table 2.' There were
40 HAPs identified as discharges into the City sewer system. The total amount of each HAP discharged from
all facilities ranged from 0.02 to 766 megagrams (Mg) (0.03 to 842 tons), and the total amount of all HAPs
discharged equalled 2,543 Mg (2,797 tons). The concentration of each HAP in the City's sewer wastewater
was estimated by dividing the annual amount of each HAP discharge reported to TRIS summed for all facilities
in the City by the volume of waslewater processed by the municipal treatment system (per year). The
wastewater volume was assumed to be the sum of the annual influent wastewater volumes for all POTWs in
A "city" model is under development at this time.
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the City's sewer system (5.5 million cubic meters per day or 1,443 million gallons per day [MGD]).' The
calculated sewer wastewaler concentrations ol the 40 HAPs are shown In the third column ol Table 2. The
concentrations ranged from 0.014 to 381 mlcrograms per liter (ng/L), (or a total HAP concentration ol 1,260
MO/L tor the CHy's wastewater.
NPDES Data-HAP wastewater concentration data were obtained for the City from annual NPDES
reports ol Influent wastewater concentrations for all POTWs In the CKy In 1989.7 The City-wide HAP
wastewater concentrations were estimated from the average of the concentrations for each POTW weighted by
the wastowater volume treated at each facility. The estimated City-wide HAP wastewater concentrations are
shown In Table 3. There were 24 HAPs Identified In the Influent to the CHy POTWs. The weighted HAP
concentrations ranged from 0.01 to 381 micrograms per liter (ug/L) for a total HAP concentration of 1,056 ug/L
Table 3 also shows the wastewater concentrations calculated for these same HAPs from TRIS data
(trom Table 2). This comparison reveals that of the 24 HAPs measured In the City's POTW Influent wastewater
for NPDES, 14 were also found in the City's TRIS reports. The 10 HAPs missing from the TRIS reports are
likely to be (solely) components of the commercial and residential wastewater In the City. The NPDES-reported
wastewater concentration of these 10 HAPs. however, were only 4 percent of the total POTW wastewater
concentration for all 24 HAPs and, therefore, were not expected to be major contributors to the municipal sewer
emissions.
The data in Table 3 also show that the TRIS-calculated concentrations were greater than the NPDES
values for only 4 out of the 14 HAPs that were Identified In both NPDES and TRIS data for the City. For the
other 10 HAPs, the NPDES wastewater concentrations were greater than the TRIS wastewater concentrations,
by factors of 2 to 1.659. These 10 HAPs were believed to represent a major portion of the unaccounted-for
contribution to the sewers from commercial and residential wastewater. Note that some uncertainty is
associated with both the TRIS and NPDES data. This uncertainty may be as high as a factor of 10 on a plant-
by-plant basis.
Sewer Physical and Operating Data-Table 4 shows the sewer physical and operating values that were
used to estimate the City sewer emissions with the CORAL+ model. These values were estimated from
information obtained from the City's sewer engineers, assumptions about the sewer system, or calculations
made trom one or both of these sources. In many cases, an average value was used in the model if only a
range of values was available. The source or method of obtaining these data Is also shown in Table 4.
Model Estimates-Estimates of HAP emissions from the City sewers were obtained using the CORAL+
model, sewer physical and operating data, and the two sets of HAP input data described above. These
emissions are shown in Table 5.
Using the TRI3 data, the estimated total sewer HAP emissions were approximately 27 Mg per year (30
tons per year [tpy]) for the 40 HAPs identified in TRIS for the City. Reach emissions comprised 42 percent of
the total estimated emissions; drop emissions comprised 58 percent. Using the NPDES data, the estimated
total sewer HAP emissions were 278 Mg per year (306 tpy) for the 14 HAPs identified with NPDES sampling
(and also identified in TRIS data). Reach emissions comprised 52 percent of the total estimated emissions;
drop emissions comprised 48 percent.
Table 5 also shows that the 14 HAPs included in both TRIS and NPDES reports account for 98 percent
of the TRIS-reported HAPs, therefore the NPDES data were believed to have included the HAPs that
comprised the majority of the quantity of sewer influent pollutants. For this reason, and because the NPDES
data are a reflection of industrial, residential, and commercial wastewater discharges, the sewer HAP emissions
estimate from NPDES data was thought to be the more representative sewer HAP emissions estimate.
The total sewer HAP emissions calculated from NPDES data were 10 times the amount estimated for
the same HAPs with TRIS data. This factor, although large, implies an even larger true value, since the
NPDES data were taken from city wastewater after emissions from the sewer system occurred. If the sewer
system were a single point source, both the TRIS and NPDES estimates would enable the sewer system to
qualify as a major HAP emission source under Title III of the CAAA through both of the applicable criteria: one
HAP with an emission rate over 9 Mg per year (10 tpy) and combined HAP emission rates over 23 Mg per year
(25 tpy).
The total annual wastewater flow was estimated from the sum of the wastewater volumes treated per
day in the City POTWs, multiplied by 365 days per year.
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Sources of Uncertainty In the Sewers Emissions Estimate
There are three primary sources of uncertainty In this sewers emissions estimate:
• The sewer wastewater HAP concentration data;
• The scaling ot reach manhole and drop emissions to the City level; and
• The average values used as sewer physical and operating data.
The primary source ot uncertainty In the sewers emissions estimate Is thought to be the sewer HAP
concentration data; I.e., the extent to which the NPDES data underestimate sewer wastewater concentrations.
More work Is needed to determine the correlation ol NPDES wastewater measurements (POTW Influent) to
sewer influent wastewater concentrations or to obtain a better source ol sewer Influent data.
COMPARISON OF PREDICTED SEWER HAP EMISSIONS TO PREDICTED HAP EMISSIONS FROM
POTWS AND OTHER AREA SOURCES IN THE CITY
This portion of the paper compares the estimate of the City sewer emissions, obtained with the method
described above, to estimates of HAP emissions for other area sources In the City. In particular, estimates of
HAP emissions from POTWs were compared to the sewer estimates developed In this study In order to observe
the relative magnitude of emissions from each of these two components of a wastewater handling and
treatment system. Comparisons were also made to estimates of emissions from two common urban area
sources-graphic arts and dry cleaning-in the City. The methods used to obtain these estimates are also
described below.
Comparison to POTW Emissions Estimates
The City sewer emissions estimates developed in this paper were first compared to estimates of POTW
emissions, since the sewer system and POTW are both parts of the municipal sanitary system. In HAP
emissions inventories, the POTW is usually the only component of the municipal sanitary system that is
addressed.1 This comparison, then, will show whether the omission of sewer emissions neglects a significant
contributor of HAP emissions in a municipality.
Two estimates of HAP emissions from POTWs in the City were obtained using different methods. The
first estimate of HAP emissions from POTWs was obtained using an emission inventory approach,' where an
activity factor in terms of the amount of wastewater treated was multiplied by generic emission factors
developed for 15 HAPs in a number of wastewater treatment processes that were thought to be part of a typical
POTW. The generic emission factors were developed from test data from another U. S. city and were obtained
from EPA's Factor Information Retrieval System (FIRE) data base.1 Using this approach, the total estimated
HAP emissions from POTWs in the City were 94 Mg per year (103 tpy). The estimated emissions for the 15
HAPs are shown in Table 6. The weaknesses in the emissions inventory approach to estimating POTW
emissions were (1) the applicability of the typical POTW configuration to the City's POTW configuration, and (2)
the applicability of the 15 HAPs to the City's wastewater treatment system. The sewer emissions estimate from
NPDES, at 278 Mg per year (306 tpy), was three times the total POTW emissions estimated with this first
approach.
A second estimate of POTW emissions was obtained using a 20-percent volatilization factor with HAP
discharge data reported to TRIS.* The total HAP emissions from POTWs using this approach were estimated
to be 504 Mg per year (554 tpy). The sewer emissions estimate obtained with NPDES data* was over half of
the 504 Mg per year (554 tpy) POTW emissions estimate obtained with the 20-percent volatilization factor
approach. The two sewer and POTW emissions estimates are shown In Table 7. A simple volatilization
approach to estimating POTW emissions has many obvious drawbacks, such as the inability to account for the
different types of treatment processes used at POTWs and the degree of volatility of each HAP.
Since the NPDES estimate is a low estimate based on sewer wastewater effluent concentrations, the
true sewer emissions are likely to be equal to if not greater than POTW emissions, considering the POTW
emissions estimates obtained with these two methods.
•Described in an EPA report scheduled for publication early in 1995.
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Comparison to Graphic Arts and Dry Cleaning Area Source Emissions Estimates for the City
The City's sewer emissions estimates were also compared to air emissions estimated for graphic arts
and dry cleaning operations. This comparison was made to show the relative contribution of sewer emissions
as compared to other area sources that are typically found In the urban setting, An emission Inventory
approach* was also used to estimate HAP emissions from graphic arts and dry cleaning area sources In the
City. The graphic arts area sources emissions estimate was obtained using a per capita emission factor, with
the estimated City population being the activity factor. The total HAP emissions estimated for graphic arts area
sources In the City using this method were 1,522 Mg per year (1,674 tpy). For dry cleaning, a per employee
emission factor was multiplied by the estimated number of employees In area sources In the City to estimate
HAP emissions. Using this method, the total HAP emissions estimated for dry cleaning area sources In the City
were 3,101 Mg per year (3,411 tpy).
The HAP emissions estimated for graphic arts and dry cleaning area sources In the City using the
emission inventory approach, at 1,522 and 3,101 Mg per year (1,674 and 3,411 tpy), respectively, were greater
than both TRIS and NPDES sewer emissions estimates. Although the sewer emissions estimated with NPDES
data were only 9 and 18 percent of the emissions estimated for dry cleaning sources and graphic arts,
respectively, the sewers emissions estimate from NPDES is likely to underestimate the sewer emissions Impact.
Therefore, sewer emissions may be comparable to emissions from these other area sources, If true sewer
emissions were known. Table 7 shows the HAP emissions estimates from the City sewers, POTWs, and two
area source categories produced with the various emissions estimation methods.
COMPARISON OF CITY SEWER EMISSIONS TO DATA FOR OTHER CITIES
Estimates of sewer gas HAP concentrations in the City, obtained with CORAL+, were compared to
measurements of sewer gas HAP concentrations reported in the literature for other municipal sewer systems.
Table 8 shows the predicted City sewer gas concentrations for four HAPs (benzene, ethylbenzene. toluene, and
xylene) from the two sewer emissions data sources used in this study as compared to measurements of sewer
gas reported in the literature for reach manholes in California;9 Toronto, Canada;10-11 and London,
England.12 Note that data for no more than three of the four HAPs were reported in each literature source.
The measured gas concentration data ranged from 0.18 to 170 parts per million (ppm). The sewer gas
concentrations calculated with NPDES data were comparable in magnitude to some of the measured data, and
ranged from 1.4 to 5.1 ppm. This comparison supports the opinion presented here that the sewer HAP
emissions estimate obtained with NPDES data was a more realistic estimate of sewer emissions for the City
than the estimate obtained with TRIS data; also, that the NPDES data may also have underestimated the sewer
HAP emissions for the City, since the data from the literature were in general higher than the NPDES data.
However, the literature measurement data may have been obtained at points in the sewer system where high
concentrations of HAP emissions were likely to occur (I.e., near industrial discharges). The tower values for the
City would then reflect the results of averaging the data over the entire City sewer system.
CONCLUSIONS AND RECOMMENDATIONS
A method was developed to estimate sewer HAP emissions from readily available sewer physical and
operating data and one of the models available to predict sewer emissions. The method was used with POTW
influent wastewater concentration data from NPDES, with the CORAL+ model. Wastewater HAP concentration
data obtained from the NPDES reports were thought to be more representative of sewer conditions than TRIS
data, because the NPDES data were a reflection of industrial, residential, and commercial wastewater
discharges. The CORAL+ model was chosen because it is the only model that can be used to predict
emissions from reaches and drops, frequent emission points in municipal sewer systems.
The method developed here was used to estimate sewer emissions for a large U. S. city. The estimated
sewer HAP emissions for the city, at 278 Mg per year (306 tpy), were believed to be a low estimate, since
NPDES data are POTW influent and sewer effluent measurements. This sewer emissions estimate showed
that sewer HAP emissions are a significant component of the total urban HAP wastewater emissions (sewer
emissions plus POTW emissions), and are likely to be greater than POTW emissions. Sewer HAP emissions
may also be comparable to emissions from other area sources, such as dry cleaning and graphic arts. Since
the sewer emissions estimated here are more likely to be emitted from manholes near the sources' discharge
'Described in an EPA report scheduled to be published early in 1995.
6
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to the sewer and not spread evenly around the chy, there also Is potentially a significant threat to public health
from Individual emissions points throughout the sewer system.
REFERENCES
1. Telecon. Darcy Campbell, Radian Corporation, Research Triangle Park, North Carolina, with Julian
Jones, Air and Energy Engineering Research Laboratory, U. S. Environmental Protection Agency,
Research Triangle Park, North Carolina. April 1,1993. Evaluation of air toxics Inventories from selected
urban areas.
2. Elliott, J. and S. Watklns. Industrial Wastewater Volatile Organic Compound Emissions-Background
Information for BACT/LAER Determinations. EPA-450/3-90-004 (NTIS PB90-194754).
U. S. Environmental Protection Agency, Office of Air Quality Planning and Standards, Research Triangle
Park, North Carolina. January 1990.
3. Hazardous Waste Treatment, Storage, and Disposal Facilities (TSDF)-Alr Emissions Models
Documentation. EPA-450/3-87-026 (NTIS PB88-198619). U. S. Environmental Protection Agency,
Office of Air Quality Planning and Standards, Research Triangle Park, North Carolina. December 1987.
4. Watkins, S. Surface Impoundment Modeling System (SIMS) User's Manual. EPA-450/4-89-013a (NTIS
PB90-141227). U. S. Environmental Protection Agency, Office of Air Quality Planning and Standards,
Research Triangle Park, North Carolina. September 1989.
5. Personal Communication from F. Elaine Manning, Office of Air Quality Planning and Standards,
Emission Standards Division, to Julian W. Jones, Air and Energy Engineering Research Laboratory, on
estimation of air emissions from airflow in wastewater collection systems (WATERS Model). U. S.
Environmental Protection Agency, Research Triangle Park, North Carolina. November 30,1993.
6. Memorandum. Calvin Overcash, EC/R, Inc. Durham, North Carolina, to Eric Crump, Emission Standards
Division, U. S. Environmental Protection Agency, Office of Air Quality Planning and Standards, Research
Triangle Park, North Carolina. Summary of the Toxic Release Inventory System. January 28,1993.
7. Letter. Metropolitan Water Reclamation District of the City to Donna Lee Jones, Radian Corporation,
transmitting 1989 NPDES data for the City. July 14, 1994.
8. U.S. Environmental Protection Agency. Factor Information Retrieval (FIRE) System Database, Version
3.0. Office of Air Quality Planning and Standards, Research Triangle Park, North Carolina. March 1994.
9. Chang, D. P. Y., E. D. Schroeder, and R. L. Corel. Emissions of Volatile and Potentially Toxic Organics
from Sewage Treatment Plants and Collection Systems. CARS A5-127-32. California Air Resources
Board, Sacramento, California. 1987.
10. Quigley, C., P. Marios, and R. L. Corsi. VOC Emissions from a Municipal Sewer Interceptor. 86th Air
and Waste Management Association Annual Meeting. Denver, Colorado. 93-WA-72A.03. June 1993.
11. Whitmore, A., R. L. Corsi, J. Shepherd, and D. Thompson. Examining Gas-Liquid Mass Transfer of
Volatile and Semi-volatile Organic Compounds along Sewer Reaches. Proc. 85th Air and Waste
Management Association Annual Meeting. Kansas City, Missouri. 1992.
12. Reid, J. M. and M. McEvoy. Monitoring Sewer Atmospheres for Organic Vapors. J. Institute of Water
and Environmental Management. 1(2)161. 1987.
ACKNOWLEDGMENTS
The authors would like to thank Richard Corel and Jennifer Shepherd of the University of Texas-Austin
for their technical review of the paper.
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TABLE 1. SEWER COMPONENTS ADDRESSED BY THE MODELS
Model
BACT/LAER-IWW
BASTE
CHEMDAT7
CORAL+
SIMS
WATERS
Drops*
Manholes* Open Closed*
X
X X
XXX
X
Lift Stations
Open Closed*
X
X
X
X X
Boxes Open Closed
X X
X
X
X
Sumps
Open Closed
X
X
X
X X
Open
ConduRs
X
X
Likely component of a municipal sewer system.
00
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TABLE 2. SEWER WASTEWATER HAP CONCENTRATION DATA FOR THE CITY
ESTIMATED FROM TRIS REPORTS
Compound
Acrylamlde
Aniline
Benzene
Beniyt chloride
B)s(2-«thythexyt) phthalate
Cadmium compounds
Carbon dfeuffide
Chromium compounds
Cobalt compounds
Cresols
Cyanide compounds
Dibutyt phthalate
Dichlorome thane
Diethanolamine
Epchlorohydrin
Ethyl acrylate
Ethylbenzene
Ethytene glycol
Formaldehyde
Glycol ethers
Hydrogen chloride
Hydrogen fluoride
Hydroqulnone
Lead compounds
Manganese compounds
Methanol
4.4-methylenedianl[ine
Methyl ethyl ketone
Methyl Isobutyl ketone
Methyl methacrytate
Naphthalene
Nickel compounds
2-nitropropane
Phenol
Phosphorous
Propylene oxide
Toluene
1.1.1-trichloroethane
Vinyl acetate
Xytenes
TOTAL
TRIS 1080
Reported 8«w«r
Dltehargt,1
Mg(toni)
0.18(0.16)
277(304)
9.1(10)
0.12(0.13)
0.12 (0.132
0.35 (0.38)
12(13)
8.5 (0.3)
0.16 (0.18)
606(766)
3.7(4.1)
0.35 (0.30)
0.45 (0.50)
1.7(1.8)
0.12 (0.13)
0.12 (0.13)
1.1 (1.3)
21 (23)
14 (15)
83(02)
766 (842)
0.12(0.13)
0.43 (0.47)
1.8 (2.1)
5.2 (5.8)
147 (162)
0.12 (0.13)
0.23 (0.25)
0.12(0.13)
0.12(0.13)
0.38 (0.42)
4.7(5.1)
0.68 (0.75)
464(510)
0.12(0.13)
0.12(0.13)
6.2 (6.8)
8.6 (0.4)
0.02 (0.03)
7.9 (8.7)
2.543 (2.707)
Calouliled
WattoMtor
Concentration,*
MO/1-
0.07
137
4.5
0.06
0.06
0.17
5.0
4.2
0.08
346
1.0
0.18
0.23
0.82
0.06
0.06
0.57
10.4
7
44
381
0.06
0.21
0.04
2.6
73
0.06
0.11
0.06
0.06
0.19
2.3
0.34
231
0.06
0.06
3.1
4.3
0.014
3.9
1,260
• Reference 6.
b From annual TRIS data* divided by annual POTW volumes estimated from
daily POTW flowrates.
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TABLE 3. COMPARISON OF SEWER WASTEWATER HAP CONCENTRATIONS CALCULATED
FROM NPDES AND TRIS DATA FOR THE CITY
HAP
Aniline
Benzene
Bis(2-ethylhexyl)phtha'ate
Carbon disutflde
Chlorobenzene
Chloroform
Cresol
Dibenzofuian
Dibutylphthalate
Dichlorobenzene (1 ,4)
Dichtoromethane
Dimethylphthalate
Ethylbenzene
Isophorone
Methyl ethyl ketone
Naphthalene
Phenol
Polychlorinated biphenyls
PoJycyclto aromatic hydrocarbons
Styrene
Toluene
Trichlorobenzene (1 ,2,4)
Trichloroethane (1,1,1)
Xylenes
Calculated Wastewater
NPDES Data*
91
8
26
4
1
6
270
1
7
3
381
0.3
17
3
13
14
83
0.5
21
0.01
35
0.3
11
60
Concentration, jig/L
TRIS Data"
137
4.5
0.1
5.9
NP«
NP
346
NP
0.2
NP
0.2
NP
0.6
NP
0.1
0.2
231
NP
NP
NP
3.1
NP
4.3
3.9
Prom NPDES reports of measured POTW Influent wastewater concentrations, weighted by
individual POTW wastewater volume7.
From TRIS reports of discharges to sewer wastewater and total wastewater volume to the POTWs
in the city8.
Not present in TRIS reports.
10
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TABLE 4. CASE STUDY SEWER PHYSICAL AND OPERATING DATA FOR A LARGE U. S. CITY*
Parameter
Drop height
Drop diameter
Drop taiKvater depth
Number of drops
Number of reach manholes
Reach air/Water volume fraction
Reach diameter
Reach length
Reach manhole gas volume
Reach slope
Reach type
Reach ventilation rate
Roughness coefficient
VOC concentration in ambient air
Wastewater depth/height
4.6
15
1.8
6
0.91
3
2.000
4.000
0.015
2.3
7.5
183
600
15.6
551
0.1
closed
10
0.015
0
1.1
3.6
Data
meters
feet
meters
feet
meters
feet
dmensJontess
meters
feet
meters
feet
cubic meters
cubic feet
percent
turnovers per day
CTOD)
dmensionless
ppm
meters
feet
Source of Information
City-supplied data
City-supplied data
Assumed as 40 percent of reach height/diameter
City-supplied data
City-supplied data
Calculated from reach ventilation rate and wastewater Bowrato
City-supplied data
City-supplied data
Calculated from manhole diameter and reach height a* a cyfndar
Assumed, based on Rterature
Assumed, based on municipal scenario
Assumed, based on Itersture
Based on concrete pipes
Assumed, based on Rterature
Manning's formula (for turbulent flow of water in open channel) and hyofeufe
Wastewater flowrete
Wastewater temperature
243,381 cubic meters
per day
8.591.349 cubic feet per day
20 »C
parameters
Calculated from wastewater velocity provided: i
rf roach hafrU
Assumed, based on iterature
The dty contains approximately 5 million people and covers 2,259 square kilometers (872 square mfles).
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TABLE 5. ESTIMATE OF SEWER HAP EMISSIONS FROM THE CITY USING TRIS AND NPDES DATA
8«wtr Emlulont, Mg per ytar (ipy)
TRI80ATA
Compound
Cartoon dfculflde
1,1.1-tricNoRMttwrw
Xytwm
Benzene
Toluene
Methanol
Ethylbenzene
Cresols
Dkhtorome thane
Phosphorous
Methyl teobutyl ketone
Phenol
Aniline
Naphthalene
Methyl methacrylate
2-THtropropano
Methyl ethyl ketone
Propylene oxide
Benzyl chloride
Ethyl acrylate
Vinyl acetate
Formaldehyde
Epichlorohydrin
Hydrogen fluoride
Glycol ethers*
Dibutyl phthalate
Ethylene glycol
Bis(2-ethylhexyl) phlhalate
Hydroquinone
Acrylamide
Diethanolamine
4,4-melhylenedianiKne
Cadmium compounds
Chromium compounds
Cobalt compounds
Cyanide compounds
Hydrogen chloride
Lead compounds
Manganese compounds
Nickel compounds
TOTAL
Alt Data
10(11)
e.e (7.6)
3.2 (3.6)
3.2 (3.6)
2.4 (2.7)
0.44 (0.40)
0.37 (0.40)
0.10(0.11)
0.08 (0.00)
0.06 (0.07)
0.05 (0.06)
0.05 (0.06)
0.04 (0.05)
0.01 (0.02)
0.01 (0.02)
0.01 (0.01)
0.005 (0.005)
0.003 (0.004)
0.003 (0.003)
0.003 (0.003)
0.001 (0.001)
4E-04 (4E-04)
3E-04 (4E-04)
2E-04 (3E-04)
2E-03 (3E-03)
8E-06 (OE-06)
3E-06 (« s-06)
3E-06 (3E-06)
5E-08 (6E-08)
3E-09 (3E-09)
2E-10 (2E-10)
0
0
0
0
0
0
0
0
0
27(30)
NPDES
Matohtd
10(11)
6.1 (7.6)
3.2 (3.6)
3.2 (3.6)
2.4 (2.7)
0.37 (0.40)
0.10(0.11)
0.06 (0.00)
0.05 (0.06)
0.04 (0.05)
0.01 (0.02)
0.005 (0.005)
OE-06 (9E-06)
3E-06 (3E-06)
26(29)
NPDES
DATA
6.0 (7.8)
17(18)
61 (6fl)
6.7 (6.3)
28 (31)
14 (15)
0.07 (0.06)
154 (169)
0.02 (0.02)
0.03 (0.03)
1.1 (1.2)
0.51 (0.56)
4E-04 (4E-
04)
8E-04(1E-
03)
278(306)
Ethylene glycol was used to represent this group of compounds.
12
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TABLE 6. ESTIMATE OF HAP EMISSIONS FROM THE CITY'S POTWS
USING AN EMISSIONS INVENTORY APPROACH1
HAP
Benzene
Carbon tetrachtoride
Chloroform
Dlchtorobenzene
1,4-Dtoxane
Formaldehyde
Methytene chloride
Perchtoroethylene
Styrene
Toluene
1,1,1-Trichloroethane
Trichloroethylene
Vinyl chloride
Vinylidene chloride
Xylenes
Total
POTW
Emissions,
Mq per year (tpy)
3.2 (3.6))
21.9(24.1)
12.1 (13.3)
2.5 (2.7)
0.10(0.11)
2.5 (2.8)
10.1 (11.1)
7.9 (8.7)
1.2(1.4)
9.5(10.5)
5.6 (6.2)
5.8 (6.4)
1.3 (1.4)
2.6 (2.8)
7.3 (8.0)
94 (103)
Described in an EPA report scheduled to be published early in 1995.
13
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TABLE 7, COMPARISON OP CITY SEWER HAP EMISSIONS ESTIMATES
TO EMISSIONS ESTIMATES FOR OTHER AREA SOURCES IN THE CITY
Estimated
Method ol HAP Emissions,
Area Source Estimating Emission! Mq per year (tpy)
Sewers CQRAL+ with TRIS data 27 (30)
Sewers CORAU with NPOES data 278 (306)
POTWs Emissions Inventory approach* 04(103)
POTWs Simple volatilization factor approach1" 504 (554)
Graphic Arts Emissions inventory approach* 1,522 (1,674)
Dry Cleaning Emissions inventory approach* 3,101(3,411)
* Decribed in an EPA report scheduled to be published early in 1995.
k Reference 6.
14
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TABLE 8. COMPARISON OF THE CITY'S PREDICTED SEWER GAS HAP CONCENTRATIONS
TO MEASURED VALUES IN OTHER CITIES
Sewer Gas Concentration, ppm
City
Compound THIS NPDES
Benzene 027 2.0
Ethylbenzene 0.01 1.4
Toluene 0.19 3.2
Xylenes 0.01 5.1
California' London1' Toronto*
4.4-5.8 52
0.18-13
4.4-5.8 170 8-17
1.4
Tocortor
—
4
44
31
• In an industrialized municipal sewer system. References.
b In a municipal sewer with small quantities of industrial wastewater. Reference 12.
• In a municipal sewer system. Reference 10.
' In a large municipal sewer with industrial discharge. Reference 1 1 .
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