Technical Bulletin 128
Basic Aeration Design
Calculations
by:
Environmental Dynamics
Dyna
s International
Published: 1/2017
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1
Design
Calculations
Technical Bulletin 128–BasicBasic
Aerationration
Design
Calculations
Revisedevised
September
9,
2013
September
9, 2013
Copyright © Environmental Dynamics International 2017 – All Rights Reserved
© Environmental Dynamics International
TECHNICAL BULLETIN 128 – BASIC AERATION DESIGN
CALCULATIONS
requirements are
areusually
usuallydeveloped
developed
evelopedfrom
frombasic
basic
process
design
data
developed
devel to
edeach
at each
Aeration requirements
process
design
data
applicable
site. We
Air have
requirements
most co
monly developed
follows: below.
site.
providedare
common
air calculations
in the as
examples
Example Number 1
Known data:
•
•
•
•
Population: 3,000
Typical
domestic
1. Population
of 3wastewater
0 persons
2.
Typical
domesti
wastewater
Allow 0.2 lb BOD/person per day (0.0972 kg/person)
BOD
per day
(0.0972 kg/person)
Allow 2 lb O2/lb
BODerson
(2 kg/kg)
to accommodate
some nitrification when NH3
/lb BOD
B D (2 kg/kg) to accommodate some nitrification when
wh NH
(ammonia) concentration is not known.
(ammonia) not g en.
Oxygen Calculations
Estimated field O2 requirement for extended aeration:
e nded
• /day =O2/day
= 3000 persons
* 0.2 lb BOD/person * 2 lb O2/lb BOD = 1,200 lb O2/day
3000 persons
(0. lb BOD/
(544.32kg/day)
•
.68 kg* O
O2 required = /hr
50 (lb O2/hr
22.68 kg O2/hr = field or process conditions = AOR
Oxygen Transfer SOTE= 1 % at 10 ft Diffuser Submergence (typical) = SOTE
•
Oxygen Transfer SOTE = 18% at 10 ft Diffuser Submergence (typical) = SOTE
(5.5% per meter and 3.05 diffuser submergen
(5.5% per meter and 3.05m diffuser submergence)
Note: SOTE increases as air/diffuser is reduced.
•
Assumed AOR/SOR* = 0.45 (typical correction for clean water efficiency to field
Assumed AOR/SOR* = 0.45
0.4 (typical correction of clean water efficiency to field
efficiency). This value is calculated from site elevation, process, DO level in the
efficiency) This value calc ted from site elevation, process, DO level in tank,
tank, and
temperature,
temperature,
density and density of diffusers.
•
SOR = 50 lb/hr/0.45 = 111.72 lb/hr (50.68 kg O2/hr)
SOR = 50 lb/hr/0.45 = 111 2 lb/hr (50.68 kg O
(0.18) * 0.18
9
•
Air = 111.72/1.044
= 595 SCFM (942 Nm3/hr)
Note: SCFM = Standard Cubic Foot of Air per Minute. 1 SCFM of air equals 1.584
SCFM equals Sta ard Cubic Foot or Air per Minute
or approximately
1.7 Sm3/hr.
1 scfm ofNm3/hr
air equals
1.584 m
*Note: For process calculations of AOR/SOR, see EDI’s computerized Design Brief procedures or
For process
of AOR/SOR
R/SOR see EDI’s
computerized
Designupon
Brief request
procedures
proc dures
Integrated
Diffusedcalculations
System Analysis
Procedures.
Calculations
are available
fromor
EDI.
Integrated Diffused System Analys Procedures. Calculations
available upon requ st from EDI.
2
Basic ration Design Calculations
Technical Bulletin 128–Basic Aeration Design Calculations
evised September 9, 2013
Revised September 9, 2013
Copyright © Environmental
Dynamics
International
2017 – All Rights Reserved
© Environmental
Dynamics
International
Example Number 2
Known data:
5 mgd (18
onventional activated
1m
•
Municipal waste
Conventional
activated sludge
30–mg/l
(A
onia)
•
requir ents
Flow – 5 mgd (18,931 m3/day)
•
BOD – 250 mg/l
•
•
per kilogram o
OD)
c. % SOTE
SOT = 18% @ 10 ft diffuser submergence (clean water efficiency)
fficiency)
(5.5% p r meter and 3.05 m submergence)
NH3 (ammonia) – 30 mg/l
d. Assumed AOR/SOR
A /SOR = 0.45 (typical correction of clean water eff
efficiency
iency
to field effi ency)
Process O2 requirements
c bonaceous
5 mgd (8.34) 250 mg/l (1.2 lb/lb
o
1.2 lb O2/lb carbonaceous BOD (1.2 kg O2/kg of BOD)
/hr OR (236.5 kg O
o
4.6 lb O2/lb NH3 (4.6 kg O2/kg of ammonia)
o
% SOTE = 18% @ 10 ft diffuser submergence (clean water efficiency)
7. SOR = 521.25/0.45 = 58.4 lb O
(5.5% per meter and 3.05 m submergence)
8. Air for Carbonaceous
158.4/1.044 (0.18) = 6165 scfm (9765
o
Assumed AOR/SOR = 0.45 (typical correction for clean water efficiency to
for ammonia = 5 m (8.34) 30 mg/l (4.6 lb/lb) = AOR
field efficiency)
a OR = 5754.6 lb/day (2610.3 kg O
b OR =
/day = 532.9 lb/hr (241 2 kg O
Oxygen Calculations
10. Air for ammonia = 532 lb/hr/1.044 (0.18) = 2836 scfm (4492 Nm
Process or field O2 for carbonaceous BOD:
Total air = Carbonaceous
Carbonac us + Nitrogenous = 6165 scfm + 2836 scfm = 960
9601
•
5 mgd * 8.34 * 250 mg/l * 1.2 lb O2/lb BOD = 521.25 lb O2/hr AOR (236.5 kg O2/hr)
•
SCFM equals Sta ar
SOR = 521.25/0.45 = 1,158.4 lb O2/hr (525.4 kg O2/hr)
1 scfm of air equals 1.584 m
•
Air for Carbonaceous = 1,158.4/1.044 * 0.18 = 6,165 SCFM (9,765 Nm3/hr)
•
O2 for ammonia = 5 mgd * 8.34 * 30 mg/l * 4.6 lb O2/lb NH3 = AOR
o
AOR = 5,754.6 lb/day (2,610.3 kg O2/day)
o
SOR = 5,754.6/0.45 = 12,788 lb O2/day = 532.9 lb/hr (241.72 kg O2/hr)
The calculation of air volumes allows
ows confirmation of design including blower sselections.
ctions. For
•Integrated
Air Diffused
for ammonia
= 532.9
lb/hr/1.044
* 0.18and
= 2,836
SCFM (4,492
Nm3/hr)
Aeration
Syst
ms Analysis
optimization,
a more
rigorous valuation is
•
Total air = Carbonaceous + Nitrogenous = 6,165 SCFM + 2,836 SCFM = 9,601
SCFM (16,562 Nm3/day)
Note: SCFM = Standard Cubic Foot of Air per Minute. 1 SCFM of air equals 1.584 Nm3/hr
or approximately 1.7 Sm3/hr.
Calculating air volumes allows confirmation of design and blower selections. For Integrated Diffused
Aeration Systems analysis and optimization, EDI conducts a more rigorous evaluation.
3
Basic ration Design Calculations
Technical Bulletin 128–Basic Aeration
Design
Calculations
evised
September
9, 2013
Revised September 9, 2013
Environmental
Dynamics
Internationa
Copyright © ©
Environmental
Dynamics
International
2017 – All Rights Reserved