DEQ-CFW_00086172

9 2008 Air Emissions Inventory Supporting Documentation
•
Emission Source ID No.: WTS-A
Emission Source Description: Central Wastewater Treatment Plant
Process and Emission Description:
The Wastewater Treatment Plant (WWTP) consists of the biological treatment of process and
sanitary wastewater utilizing extended aeration. The WWTP is comprised of an open
equalization basin and open -top tanks and clarifiers. The basin is mixed using floating
mixers and the tanks are aerated primarily with diffused air.
Emissions from the WWTP result from the volatilization of solubilized compounds which are
air stripped via the aeration of the wastewater. The extent of the volatilization is a function of
the specific compound's solubility in water and its vapor pressure, typically expressed as the
compound's Henrys Law Constant. Also, the volatilization of an organic compound is
dependent on its rate of biodegradability. For example, methanol which is a Hazardous Air
Pollutant (HAP), is highly biodegradable, and as such its biodegradation rate is much faster
than its volatilazation rate, thereby limiting the air emissions of methanol from the WWTP.
Basis and Assumptions:
The emissions of methanol and dimethylformamide from the WWTP were determined using
the EPA WATER8 model. This modeling takes into account the specific operational units of
the WWTP to predict the ultimate fate of specific compounds. Two major compounds that
are treated in the WWTP are ethylene glycol and butyraldehyde. The Henry's Law Constant
for ethylene glycol is 6.0 x 10e-08 atm-m3/mole which is very similar to the Henry's Law
Constant for dimethylformamide of 7.4 x 10e-08 atm-m3/mole. Not surprisingly, ethylene
glycol and dimethylformamide are both exempt from the wastewater control requirements of
40 CFR 63 Subpart G as both are excluded from Table 9 of that subpart.
Because of the above, it will be assumed that the WWTP unit operation's emission factors for
ethylene glycol are the same as those for dimethylformamide. However, the biodegradation
rate of ethylene glycol will be assumed to be the same as that of methanol, since the technical
literature found in the Handbook of Environmental Data on Organic Chemicals indicates that
for an acclimated system, ethylene glycol is biodegraded at twice the rate of methanol. To be
conservative, the slower methanol rate will be used.
DEQ-CFW 00086172

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The Henry's Law Constant for butyraldehyde is 1.15 x 10e-04 atm-m3/mole which is higher
than the Henry's Law Constant for methanol of 4.55 x 10e-06 atm-m3/mole, meaning the
quantity that is air stripped from the wastewater would be expected to be higher than that for
methanol. According to the Handbook of Environmental Data on Organic Chemicals,
butyraldehyde is biodegraded at the same rate of methanol in an acclimated system.
Because of the above, it will be assumed that the WWTP unit operation's emission factors for
butyraldehyde are twice as those for methanol. To be conservative, the biodegradation rate of
butyraldehyde will be assumed to be the same as that of the slower dimethylformamide rate.
Information Inputs and Source of Inputs:
Information Inputs
Source of Inputs
Estimated quantity of compounds entering
the WWTP for the year
SARA 313 Report and other Air Emission
Inventory inputs
Fugitive Emissions Determination:
All air emissions from the Wastewater Treatment Plant are fugitive. Estimates of the
emission for individual components are given in the following pages.
DEQ-CFW 00086173

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2008 Emissions from Wastewater Treatment Plant (WTS-A)
BA
DMF
EtGly
McOH
To WWTP from Butacite (lb)
106,800
13,902
7,126
129,300
To WWTP from Nafion (lb)
-
-
-
49,283
To WWTP from PMDF (lb)
-
-
-
-
To WWTP from SentryGlas (lb)
-
-
-
To WWTP from Other Sources (lb)
-
-
-
-
Total to WWTP (lb)
106,800
13,902
7,1261
178,583
Quantity entering EQB (lb)
106,800
13,902
7,126
178,583
Percent of compound volatilized
23.42%
0.29%
0.29%
11.71 %
Quantity volatilized from EQB (lb)
25,013
40
21
20,912
Quantity leaving EQB (lb)
81,787
13,862
7,105
157,671
Quantity entering Predigester (lb)
81,787
13,862
7,105
157,671
Percent of compound volatilized
8.30%
0.10%
0.10%
4.15%
Quantity volatilized from Predigester (lb)
6,788
14
7
6,543
Quantity leaving Predigester (lb)
74,999
13,848
7,098
151,128
Quantity entering Aeration Tank (lb)
74,999
13,848
7,098
151,128
Percent of compound volatilized
0.16%
0.002%
0.002%
0.08%
Quantity volatilized from Aeration Tank (lb)
120
0
0
121
Percent of compound biodegraded
94.40%
94.40%
99.74%
99.7406
Quantity biodegraded in Aeration Tank (lb)
70,799
13,072
7,080
150,735
Quantity leaving to Cape Fear River (lb)
4,080
775
18
272
Butacite Quantity to Cape Fear River (lb)
4,080
775.19252
18
197
Nafion Quantity to Cape Fear River (lb)
-
-
-
75
PMDF Quantity to Cape Fear River (lb)
SentryGlas Quantity to Cape Fear River (lb)
Nafion Quantity to Cape Fear River (lb)
Total Quantity to Cape Fear River (lb)
4,080
775
18
272
Butacite Fraction Volatilized to Air (lb)
31,921
54
28
19,966
Nafion Fraction Volatilized to Air (lb)
-
-
-
7,610
PMDF Fraction Volatilized to Air (lb)
-
-
-
-
SentryGlas Fraction Volatilized to Air (lb)
-
-
-
-
Nafion Fraction Volatilized to Air (lb)
-
-
-
-
Total Volatilized to Air (lb)
1 31,921
1 541
28
1 27,576
* Source of Reduction Factors: EPA WATER8 computer model
BA = Butyraldehyde
DMF = Dimethylformamide
EtGly = Ethylene Glycol
McOH = Methanol
DEQ-CFW 00086174

9 2008 Air Emissions Summary
WTS-A Central Wastewater Treatment Plant
A. VOC Compound Summary
Compound
CAS Chemical Name
CAS No.
Emission
(lb.)
BA
Butyraldehyde
123-72-8
31,921
DMF
Dimethylformamide
68-12-2
54
EtGly
Ethylene Glycol
107-21-1
28
McOH
Methanol
67-56-1
27,576
Total VOC Emissions (Ib.)
59,580
Total VOC Emissions (tons)
29.8
B. Hazardous Air Pollutant Summary
Compound
CAS Chemical Name
CAS No.
Emission
(lbs)
DMF
Dimethylformamide
68-12-2
54
EtGly
Ethylene Glycol
107-21-1
28
McOH
Methanol
67-56-1
27,576
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DEQ-CFW 00086175