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

15

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

17

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.

18

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

20

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

21

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

23

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?