Denitrification Improvement Alternative Evaluation for Hilton ......Denitrification Improvement Alternative Evaluation for Hilton Head Public Service District using Extensive BNR Modeling

Denitrification Improvement Alternative Evaluation for Hilton Head Public Service District using Extensive BNR Modeling and Process Optimization

Don Lee, Ph.D., P.E.Senior Wastewater Process EngineerProject ManagerAECOMGreenville SC

OutlineIntroduction Wastewater Characterization and Capacity Assessment

Flows and loads characterizationsUnit process treatment capacity assessment

Denitrification Improvement Alternative Evaluation Alternative Development Evaluation with Extensive Modeling and OptimizationOpinions of Probable Construction Costs

Summary, Conclusions, and Q&A

OutlineIntroduction Wastewater Characterization and Capacity Assessment




Denitrification Improvement Alternative Evaluation for Hilton Head PSD

INTRODUCTIONHilton Head PSD Reclaimed Water Plant

6.4 MGD activated sludge plant

Golf course irrigation + surface water discharge

Currently treating 2.5 MGD average

EQ Basins

Influent PS

Aeration Basins

Clarifier

Clarifier

Clarifier


INTRODUCTION

Needs for denitrification No nitrate regulations under NPDES permit

Golf course irrigation – potential nitrate elevation in groundwater

Historical effluent nitrate with semi-Ludzack Ettinger and Post Anoxic

process mod: 15 - 25 mg/L

Other BNR benefits

– aeration energy savings, alkalinity recovery, bulking control

Project Goals Evaluate feasibility of denitrification (nitrate below 10 mg/L ) with

process optimizations (no capital improvement).

If not, propose minor capital improvements with process optimizations.

OutlineIntroductionWastewater Characterization and Capacity Assessment





WASTEWATER CHARACTERIZATIONS AND CAPACITY ASSESSMENT

Seasonal flows and loads variations General flows and loads trend: Summer high, Winter low

Seasonal loadings normalized by unit capacity

BOD and TSS: 200 mg/L avg, 250-300 mg/L max month

Mixed liquor temp: 27ºC Summer max, Winter low: 16ºC

Low BOD/N ratio 4:1 based on Jan – Feb 2016 sampling

May reflect out-of-town commuters and visitors

Target Capacity: 3 MGD (6.4 MGD permitted) • Eff nitrate goal: 8 mg/L

• Eff ammonia goal: 3 mg/L (5 mg/L limit)


WASTEWATER CHARACTERIZATIONS AND CAPACITY ASSESSMENT

UNIT PROCESS CAPACITY ASSESSMENT TO MEET TREATMENT GOALS

Unit Process/Structure

/EquipmentNo Descriptions

Each Size/Capacity

Total Size/Capacity

Total Size/Capacity Requirements Evaluation Criteria/Size and

Capacity RequirementSize

/CapacityUnit

Size /Capacity

UnitSize

/CapacityUnit

Aeration Basins 6 RectangularBasins

0.4 MG 2.4 MG 1.2 MG Provide 8-day SRT for completenitrification at 4,500 mg/L MLSSwith Maximum Month BOD andTSS loadings (BioWin prediction).

0.6 MG Provide 4-day SRT fordenitrification at 4,500 mg/L MLSSwith Maximum Month BOD andTSS loadings (BioWin prediction).

1.8 MG Provide total SRT of 12 days at4,500 mg/L MLSS with MaximumMonth BOD and TSS loadings(BioWin prediction).

EQ Basins 2 Rectangular Basins

0.561 MG 1.122 MG 0.6 MG Provide 4-day SRT fordenitrification at 4,500 mg/L MLSSwith Maximum Month BOD andTSS loadings (BioWin prediction).






DENITRIFICATION IMPROVEMENT ALTERNATIVE EVALUATION

Alternative Development

• Non-capital Improvement Alternatives (process optimization only)o Semi Ludzack Ettinger (LE) Process o Semi Post Anoxic Process

• Minor Capital Improvement Alternatives with Process Optimization o Aeration On-Off Cyclingo Modified Ludzack Ettinger (MLE) Process


NON-CAPITAL IMPROVEMENT ALTERNATIVE 1

Semi Ludzack-Ettinger (LE) Process

BOD Influent ANX Secondary Effluent

Sludge Holding Tank

Dewatered Cake

AER



Aeration on

EQ Basins

Influent PS

Clarifier

Clarifier

Clarifier

Aeration off

Semi Ludzack-Ettinger (LE) Process



Semi Ludzack Ettinger (LE) Process

0

5

10

15

20

25

4 5 6 7 8 9 10 11 12 13

Nitrate N at AAD Loadings

Nitrate N at MMAD Loadings

Ammonia N at AAD Loadings

Ammonia N at MMAD Loadings

Aerobic Solids Retention Time (days)

Nitr

ogen

(mg/

L )

Nitr

ogen

(mg/

L )

Nitrification Goal (Effluent Ammonia below 3 mg/L)

Denitrification Goal (Effluent Nitrate below 8 mg/L)

Process Optimization with BioWin default kinetic parameters (SND = 0.05 mg/L)

0

5

10

15

20

25

4 5 6 7 8 9 10 11 12 13






Nitr

ogen

(mg/

L )

Nitr

ogen

(mg/

L )



Process Optimization with adjusted SNDcoefficient (0.2 mg/L)



Semi Post-Anoxic Process

BOD Influent AER Secondary Effluent

Sludge Holding Tank

Dewatered Cake

ANX



Aeration on

Aeration off

Semi Post-Anoxic Process

EQ Basins

Influent PS

Clarifier

Clarifier

Clarifier



Semi Post-Anoxic Process (SND = 0.2 mg/L)

0

5

10

15

20

25

4 5 6 7 8 9 10 11 12 13






Nitr

ogen

(mg/

L )

Nitr

ogen

(mg/

L )




MINOR CAPITAL IMPROVEMENT ALTERNATIVE 1

Aeration On-Off Cycling

BOD Influent AER/ANX (AERATION ON-OFF CYCLING) Secondary Effluent

Sludge Holding Tank

Dewatered Cake

Aeration On

SRT allocation between oxic and anoxic conditions

Aeration Off

12:00 AM 01:00 AM 03:00 AM 04:00 AM 06:00 AM 07:00 AM

Aeration On

Aeration Off

Aeration On

Aeration Off

Additional BNR efficiency improvement using SND


MINOR CAPITAL IMPROVEMENT ALTERNATIVE 1Aeration On-Off Cycling

No structural improvement

New mechanical mixers in the aeration basins

New DO control system

Aeration On/OFF

EQ Basins

Influent PS

Clarifier

Clarifier

Clarifier


MINOR CAPITAL IMPROVEMENT ALTERNATIVE 1Aeration On-Off Cycling

= Unareaed Phase Length / Cycle Length

0

12

34

5

67

89

1011

1213

1415

16

0.25 0.3 0.35 0.4 0.45 0.5

Nitrate N (3 hr)

Ammonia N (3 hr)

Unaerated Phase Fraction = Unaerated Phase Length/Cycle Length

Optimum Range of Unaerated Phase Fraction

at 3 hr Cycle Length

Nitr

ogen

(mg/

L )

Aeration On

Aeration Off

Unaerated phase length ( 1 hour)

Cycle length ( 3 hour)12:00 AM 01:00 AM 03:00 AM 04:00 AM 06:00 AM 07:00 AM

Aeration On

Aeration Off

Aeration On

Aeration Off


MINOR CAPITAL IMPROVEMENT ALTERNATIVE 1Aeration On-Off Cycling (SND = 0.05 mg/L)

Efflu

ent N

itrat

e an

d Am

mon

ia

2-Dimension Optimization


MINOR CAPITAL IMPROVEMENT ALTERNATIVE 1Aeration On-Off Cycling (SND = 0.05 mg/L)

0

1

2

3

4

5

6

7

8

9

10

11

12

13

14

15

16

0.25 0.3 0.35 0.4 0.45 0.5

Nitrate N (1 hrcycle length)Nitrate N (2 hr)

Nitrate N (3 hr)

Ammonia N (1 hr)

Ammonia N (2 hr)

Ammonia N (3 hr)

Unaerated Phase Fraction (%)

Nitr

ogen

(mg/

L )

Optimum Range of Unaerated Phase Fraction (%)


Nitr

ogen

(mg/

L )



Maximum Month Loadings11 d SRTAverage Temp (20ºC)

= Unareaed Phase Length / Cycle Length

0

1

2

3

4

5

6

7

8

9

10

11

12

13

14

15

16

0.25 0.3 0.35 0.4 0.45 0.5


Nitrate N (3 hr)

Ammonia N (1 hr)

Ammonia N (2 hr)

Ammonia N (3 hr)


Nitr

ogen

(mg/

L )


at 3 hr Cycle Lengh


Nitr

ogen

(mg/

L ) Optimum Range of

Unaerated Phase Fraction (%) at 1 hr Cycle Lengh

Maximum Month Loadings16 d SRTAverage Temp (20ºC)

0

1

2

3

4

5

6

7

8

9

10

11

12

13

14

15

16

0.25 0.3 0.35 0.4 0.45 0.5


Nitrate N (3 hr)

Ammonia N (1 hr)

Ammonia N (2 hr)

Ammonia N (3 hr)


Nitr

ogen

(mg/

L )



Nitr

ogen

(mg/

L )



Annual Average Loadings16 d SRTWinter Minimum Temp (16ºC)

0123456789

101112131415161718

0.25 0.3 0.35 0.4 0.45 0.5


Nitrate N (3 hr)

Ammonia N (1 hr)

Ammonia N (2 hr)

Ammonia N (3 hr)


Nitr

ogen

(mg/

L )



Nitr

ogen

(mg/

L ) Optimum Range of

Unaerated Phase Fraction (%)at 1 hr Cycle Length

Maximum Month Loadings16 d SRTSummer Max Temp (28ºC)


MINOR CAPITAL IMPROVEMENT ALTERNATIVE 2Modified Ludzack-Ettinger (MLE) Modification

BOD Influent ANX Secondary Effluent

Sludge Holding Tank

Dewatered Cake

AER


MINOR CAPITAL IMPROVEMENT ALTERNATIVE 2-1MLE Modification (within oxic basins)

Minor structural improvement – Baffle walls within aeration basins New Internal Recirculation Pumping StationNew DO control system New mechanical mixing in anoxic basins

Aeration Basins

Anoxic Basins EQ Basins

Influent PS

Clarifier

Clarifier

Clarifier

IR Pumping


MINOR CAPITAL IMPROVEMENT ALTERNATIVE 2-2MLE Modification (with EQ basins)

New Internal Recirculation Pumping StationNew DO control system New mechanical mixing in anoxic basins

Aeration Basins Anoxic Basins

Influent PS

Clarifier

Clarifier

Clarifier

IR Pumping


MINOR CAPITAL IMPROVEMENT ALTERNATIVE ALT 2-2MLE Modification (SND = 0.05 mg/L)

0

5

10

15

20

25

4 5 6 7 8 9 10 11


Nitrate N at MMAAD Loadings




Nitr

ogen

(mg/

L )

Nitr

ogen

(mg/

L )



Various loadings6 – 10 day aerobic SRT400% internal recirculationAverage Temp (20ºC)

0

5

10

15

20

25

4 5 6 7 8 9 10 11


Nitrate N at MMAAD Loadings




Nitr

ogen

(mg/

L )

Nitr

ogen

(mg/

L )



Various loadings6 – 10 day aerobic SRT400% internal recirculationWinter min temp (16ºC)






Proposed ImprovementsALT 1 ALT 2-1 ALT 2-2


MLE ModificationMLE Modification (using EQ basins)

Submersible Mixers $ 189,000 $ 168,000 $ 120,000

Online Monitoring of ORP, Ammonia, and Nitrate $ 196,000 - - - -

Aeration Basins Structural Modification - - $ 72,000 - -

IR Pumping Station - - $ 789,000 $ 789,000

Yard Piping Upgrade - - $ 124,000 $ 154,000

Construction Subtotal $ 385,000 $ 1,153,000 $ 1,063,000 OPINIONS OF PROBABLE PROJECT COST (with makrups and contingencies)

$ 513,000 $ 1,534,000 $ 1,414,000

OPINIONS OF PROBABLE CONSTRUCTION COSTS

Proposed ImprovementsALT 1 ALT 2-1


MLE Modification (within oxic basins)

Submersible Mixers $ 189,000 $ 168,000

Online Monitoring of ORP, Ammonia, and Nitrate $ 196,000 - -

Aeration Basins Structural Modification - - $ 72,000

IR Pumping Station - - $ 789,000

Yard Piping Upgrade - - $ 124,000

Construction Subtotal $ 385,000 $ 1,153,000 OPINIONS OF PROBABLE PROJECT COST (with makrups and contingencies)

$ 513,000 $ 1,534,000

Proposed ImprovementsALT 1


Submersible Mixers $ 189,000

Online Monitoring of ORP, Ammonia, and Nitrate $ 196,000

Aeration Basins Structural Modification - -

IR Pumping Station - -

Yard Piping Upgrade - -

Construction Subtotal $ 385,000 OPINIONS OF PROBABLE PROJECT COST (with markups and contingencies)

$ 513,000






Summary

Denitrification improvements did not appear to be feasible with process optimization only – consistent with plant data.

Wastewater characteristics played key role in denitrification efficiency.

Denitrification improvements appeared to be feasible with minor capital improvements.

- Aeration on/off cycling: feasible with process optimization, less costs, more sensitive to operations

- MLE Modification: more costs, less sensitive to operations

Don Lee, Ph.D., P.E.Senior Wastewater Process Engineer/Project ManagerAECOM, Greenville SC

10 Patewood Dr Building 6 Suite 500Greenville SC [email protected]

Documents

Denitrification Improvement Alternative Evaluation for Hilton ......Denitrification Improvement Alternative Evaluation for Hilton Head Public Service District using Extensive BNR Modeling