Sustainable BNR Process Aeration Design and Optimization NYC DEP BEDC In-House Design
Presenter: Caitlin Hunt Co-Authors: Natalia Perez, Alexander Lopez, Patrick O’Connor
Jiren He
2
• Jamaica Bay Nitrogen Consent Order
• Brief Overview of Coney Island BNR Upgrade
• NYC WWTP Aeration System Benchmark
• BioWin Modeling
• Process Air Blowers and BNR Process Aeration Requirements
• Process Air Piping
• Diffuser Design
• DO Control
• Channel Mixing
• Questions
Agenda
Coney Island WWTP
3
Jamaica Bay Nitrogen Consent Judgment
Jamaica Bay
4
Jamaica Bay Nitrogen Consent Judgment
Jamaica WWTP
26th Ward WWTP
Coney Island WWTP
Rockaway WWTP
• Aggregate limit on the total pounds of nitrogen discharged into Jamaica Bay
• Coney Island BNR Upgrade • Cost-effective BNR upgrade • 36,400 lbs/day limit as of 08/2014
5
Coney Island BNR Upgrade
• Treats domestic and combined sewer wastewater
• 110 MGD dry weather flow
• 165 MGD flow through secondary treatment
• 220 MGD wet weather flow
• 4 aeration tanks with a total volume of 16.7 MG
• How do we accomplish Step Feed BNR?
o Increase SRT
o Aeration requirements expected to increase to meet nitrification requirements
o Create anoxic zones for denitrification
6
Coney Island BNR Upgrade
Anoxic and Oxic Zones
Anoxic/Swing Zone
Oxic Zone Baffle Wall
Pass A
Pass B
Pass C
RAS
MIXED LIQUOR
PRIMARY EFFLUENT
PRIMARY EFFLUENT
PRIMARY EFFLUENT
PRIMARY EFFLUENT
Pass D
7
NYC WWTP Aeration Benchmark
Data taken from historical plant monthly data from 1/2013 – 12/2013. *Rockaway data was taken from 11/2011 – 10/2012
15 MGD
214 MGD 27 MGD
56 MGD 78 MGD 28 MGD 93 MGD
88 MGD 28 MGD 112 MGD
0.00
0.20
0.40
0.60
0.80
1.00
1.20
1.40
1.60
1.80
2.00
Airf
low
/CB
O R
emov
ed
Airflow per Lbs of CBOD Removed At NYC WWTPs Airflow/Lbs CBOD Removed Ratio
8
BioWin Modeling
• BioWin was used as a process modeling tool to predict aeration requirements at different loadings and wastewater temperatures
• Model Calibration is important
• Used for aeration system design
o Optimize operations and equipment at future average conditions
o Predict treatment results
o Stress test BNR operation at maximum month conditions
9
• 4 Dresser-Roots two-stage centrifugal process air blowers rated at 23,800 SCFM at 8psi
• 3 duty and 1 standby
• Maximum Capacity of 71,400 SCFM at 8psi
• Originally manufactured in 1958 and refurbished in 1990s
Process Air Blowers
9
0 5,000
10,000 15,000 20,000 25,000 30,000 35,000 40,000 45,000
10/18/2012 10/18/2013 10/18/2014 En
ergy
(kW
h pe
r Day
) Date
Estimated Blower Energy Consumption (kWh/day)
10
Coney Island Aeration Requirements
0
10,000
20,000
30,000
40,000
50,000
60,000
70,000
Airf
low
(CFM
)
Date
Coney Island Airflow Historical Airflow (CFM) Es=mated BNR Airflow (CFM)
11
Blower Efficiency
0
1
2
3
4
5
6
7
8
9
10
0 5,000 10,000 15,000 20,000 25,000 30,000
Dis
char
ge P
ress
ure
(psi
g)
Airflow (SCFM)
Duty Point IGV = 20% IGV = 30% IGV = 50% IGV = 100%
BNR Opera=on Aera=on Range
Exis=ng Opera=on Aera=on Range
12
Temperature Effects on Blower
0
20,000
40,000
60,000
9:00 AM 3:00 PM 9:00 PM 3:00 AM 9:00 AM
Airf
low
(CFM
)
Time
Future BNR Aeration Requirements at Various Wastewater Temperatures 25°C 22°C
0
10
20
30
14
34
54
74
94
Dec Jan Feb Mar Apr May Jun Jul Aug Sep Oct Nov Dec Was
tew
ater
Tem
p. (°
C)
Am
bien
t Air
Tem
p. (°
F)
Month
Ambient Air and Wastewater Temperature at Coney Island WWTP
Max Ambient Air T Average Wastewater T
13
Temperature Effects on Blower
0
2
4
6
8
10
12
0 5,000 10,000 15,000 20,000 25,000 30,000 35,000
Dis
char
ge P
ress
ure
(psi
g)
Airflow (SCFM)
Duty Point 68°F 100% IGV 100F 100% IGV 0°F 100% IGV
14
Blower Turndown
20%
30%
40%
50%
60%
70%
80%
90%
100%
0 10,000 20,000 30,000 40,000 50,000 60,000 70,000 80,000
Gui
de V
ane
Posi
tion
(% O
pen)
Airflow (SCFM)
1 Blower 2 Blowers 3 Blowers
Coney Island Blower Capacity
Typical BNR Operating Range
Not having enough turndown uses excess energy and causes dangerous blower surge
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Process Air Piping
• Eliminate pipe leaks • Check control valve
sizing • Consider decentralized
blowers
16
Diffusers
• Type
o Coarse Bubble
o Ceramic Fine Bubble Disk
o Membrane Fine Bubble Disk
• Alpha and Fouling Factors
• Layout
• Design for average conditions
• Stress test at maximum conditions
• Prevent surge at minimum conditions
Coarse Bubble Tube Diffusers at Rockaway WWTP
Membrane Disk Diffuser Photo from Sanitaire Diffuser Product
Brochure
Ceramic Dome Diffusers at Coney Island WWTP
Ceramic Disk Diffusers at Coney Island WWTP
Photo from Sanitaire Diffuser Product Brochure
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Bowery Bay WWTP Before and After BNR
0
20,000
40,000
60,000
80,000
100,000
5/28/2005 10/10/2006 2/22/2008 7/6/2009 11/18/2010 4/1/2012 8/14/2013 12/27/2014
Airf
low
(CFM
)
Date
Bowery Bay Airflow (CFM) Airflow BNR Start Date Es=mated Construc=on Start Date
Coarse Bubble Diffuser
Fine Bubble Diffuser
Negative Net Aeration Requirements after a BNR upgrade. Diffuser efficiency is a key component for optimization.
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Diffuser Fouling
Pass A
• Earlier Passes have more biofilm accumulation and clogging
• Different αF factors throughout aeration tanks
• Diffuser fouling increases head losses
• Ceramic Diffusers are more likely to clog
19
Diffuser Design
A1
A2
B2 C2
A3 A4 A5
B3
B4 B5
C3
C4 C5 D3
D4 D5
D6
0
0.5
1
1.5
2
2.5
A1 -‐ Sw
ing
A2 -‐ Sw
ing
A3 -‐ Oxic
A4 -‐ Oxic
A5 -‐ Oxic
A6 -‐ An
oxic
B1 -‐ An
oxic
B2 -‐ Sw
ing
B3 -‐ Oxic
B4 -‐ Oxic
B5 -‐ Oxic
B6 -‐ An
oxic
C1 -‐ An
oxic
C2 -‐ Sw
ing
C3 -‐ Oxic
C4 -‐ Oxic
C5 -‐ Oxic
C6 -‐ An
oxic
D1 -‐ An
oxic
D2 -‐ An
oxic
D3 -‐ Oxic
D4 -‐ Oxic
D5 -‐ Oxic
D6 -‐ Oxic
Airf
low
per
Diff
user
(SC
FM)
Air Flux through Diffusers Minimum Air flux at 15° C Average Air Flux at 20° C
Design Minimum Diffuser Air flux
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DO Control
0
10,000
20,000
30,000
40,000
50,000
60,000
70,000
9:00
:00 AM
11:00:00
AM
1:00
:00 PM
3:00
:00 PM
5:00
:00 PM
7:00
:00 PM
9:00
:00 PM
11:00:00
PM
1:00
:00 AM
3:00
:00 AM
5:00
:00 AM
7:00
:00 AM
9:00
:00 AM
11:00:00
AM
Airf
low
(SC
FM)
Time
Coney Island Projected Future Average Airflow Requirements at 25°C
DO = 2.5mg/L DO = 2.0mg/L DO = 3.0mg/L
Changing the DO Setpoint by 1mg/L → 10,000 SCFM Increase
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Channel Mixing
• Most channels at NYC plants are mixed using coarse bubble diffusers and process air
• At Coney Island ~10% of process air is used for channel mixing
• Advantages of a separate channel mixing system:
o Increase capacity for process aeration
o Reduce denitrification problems
o Save energy
o Save $190,000 operating cost savings per year
o Operational flexibility
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Tank 1
Tank 3
Tank 2
Tank 4
Aeration Tanks Channel Air
Process Air
Aeration Tank Influent Channel
Aeration Tank Effluent Channel
Aeration Tank Influent Channel
Channel Air Connection
PST Influent Channel
Mixed Liquor Channel
AT Weir
Process Air Blowers
Channel Air Blowers
Existing Channel Aeration System
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Channel Aeration System Modifications
Tank 1
Tank 3
Tank 2
Tank 4
Aeration Tanks Existing Channel Air
Aeration Tank Influent Channel
Aeration Tank Effluent Channel
PST Influent Channel
Mixed Liquor Channel
AT Weir
New Channel Air pipe to AT Channels
New More Efficient Channel Air Blowers
Tie into Existing Diffusers and Drop Legs
New Channel Air
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Pulsed Air Channel Mixing
• Significant energy savings
o Remove coarse bubble diffusers
o Air supply not required to be continuous
• No moving or mechanical parts
• Low D.O. transfer
• Minimal life-cycle costs
• Channel mixing application has not been tested in NYC WWTPs
Photos from CCNY report: Evaluation of Anoxic Zone Miners at the Red Hook WPCP, 2007.
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Summary
• Benchmark Existing Performance
• Model Future Requirements
• Evaluate existing blowers at different loadings and temperatures
• Design diffuser grid to operate efficiently at average conditions
• Evaluate channel mixing alternatives
Questions?