DEQ-CFW_00088122

WWTP Sludge Dryers Air Emissions Inventory Page 1 of 2
Supportin2 Documentation for WWTP Slud a Dryers (WTS-B and WTS-C
The Specific Conditions for the Impingement Type Wet Scrubber (ID No. WTCD-1) listed in
Item VII(1) of the site's Air Permit equipment list is discussed under Part 1 Section 2.1(F)(1) of
that permit. The Permit states that the scrubber is to control the "odorous emissions from the
wastewater treatment sludge dryers (Nos. WTC-B and WTS-C)."
Major categories of offensive odors from the drying of activated sludge could generally be
grouped into the following:
Odor Category
Common Chemical in
Odor Category
Odor Threshold of
Common Chemical
(Ppmv)
Amines
Methyl amine
0.021
Ammonia
Ammonia
1.5
Hydrogen sulfide
Hydrogen sulfide
0.13
Merca tans
Methyl merca tan
0.002
Organic sulfides
Dimethyl sulfide
0.001
Skatole
3-Methyl-1 H-indole
0.019
Based on the lack of odors coming from the discharge of the WWTP Sludge Dryer scrubber,
and the low odor threshold of the possible odorous compounds coming from the scrubber, it is
believed that only an insignificant amount of VOCs could be emitted from this source.
To quantify the worst -case scenario, it will be assumed that the scrubber is running
continuously for the entire year with the above compounds being vented at their odor threshold
concentration. This is an obvious overstatement of actual emissions since the WWTP Scrubber
normally operates with no detectable odors.
Conversion of concentration expressed as ppmv to mg/m3 is via the following equation:
mg _ ppmv x 12.187 x Molecular Weight
in (273.15 + Temperature) °C
For the purpose of this concentration conversion, it will be assumed that the actual scrubber
discharge temperature is a constant 27 °C. Therefore, the above equation reduces to:
m = 0.0406 x my x Molecular Wei t
in 3 ppmv t
For example, converting 0.021 ppmv of methyl amine (MW = 31) to mg/m3 follows:
0 grams mg
mole
0.0406 x 0.021 ppmv x 31 = 0.026 3
in
DEQ-CFW 00088122

WWTP Sludge Dryers Air Emissions Inventory Page 2 of 2
0 Conversion of concentration from ppmv to mg/m3
•
•
Compound
Molecular
Weight
(grams per mole
Odor Threshold
(ppmv)
Odor Threshold
(mg/m)
Methyl amine
31
0.021
0.026
Ammonia
17
1.5
1.035
Hydrogen sulfide
34
0.13
0.179
Methyl mercaptan
48
0.002
0.004
Dimethyl sulfide
62
0.001
0.048
3-Methyl-lH-indole
131
0.019
0.101
Scrubber (ID No. WTCD-3) design air flow rate is 23,850 cubic feet per minute.
This flow rate is converted to cubic meters per year by the following:
3 3 3
23,850 ft x 0.0283 inx 60 min x 8,760 - = 354,756,350 m
min ft 3 hr yr yr
Emissions Determination:
Multiplied by:
Multiplied by:
Equals:
Compound
Odor
Threshold
(mg/m3)
Scrubber
Flow Rate
(MI/yr)
Mass
Conversion
(lb/mg)
Emission
Rate
(lb/yr)
Methyl amine
0.026
354,756,350
2.2046 x 10-6
20.3
Ammonia(Note
1.035
354,756,350
2.2046 x 10-6
809.5
Hydrogen sulfide(Note
0.179
354,756,350
2.2046 x 10-6
140.0
Methyl mercaptan(Note
0.004
354,756,350
2.2046 x 10"6
3.1
Dimethyl sulfide(Note
0.048
354,756,350
2.2046 x 10-6
37.5
3-Methyl-lH-indole
0.101
354,756,350
2.2046 x 10-6
79.0
Note 1: These compounds are listed as HAPs and/or TAPS
VOC Emissions Determination:
Methyl amine
20.3 lb/yr
Methyl mercaptan
3.1 lb/yr
Dimethyl sulfide
37.5 lb/yr
3-Methyl-1 H-indole
79.0 lb/yr
Total VOC
139.9 lb/yr
Total VOC
0.07 TPY
DEQ-CFW 00088123