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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
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
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
Denitrification Improvement Alternative Evaluation for Hilton Head PSD
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
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
Denitrification Improvement Alternative Evaluation for Hilton Head PSD
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)
Denitrification Improvement Alternative Evaluation for Hilton Head PSD
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).
OutlineIntroductionWastewater 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
Denitrification Improvement Alternative Evaluation for Hilton Head PSD
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
Denitrification Improvement Alternative Evaluation for Hilton Head PSD
NON-CAPITAL IMPROVEMENT ALTERNATIVE 1
Semi Ludzack-Ettinger (LE) Process
BOD Influent ANX Secondary Effluent
Sludge Holding Tank
Dewatered Cake
AER
Denitrification Improvement Alternative Evaluation for Hilton Head PSD
NON-CAPITAL IMPROVEMENT ALTERNATIVE 1
Aeration on
EQ Basins
Influent PS
Clarifier
Clarifier
Clarifier
Aeration off
Semi Ludzack-Ettinger (LE) Process
Denitrification Improvement Alternative Evaluation for Hilton Head PSD
NON-CAPITAL IMPROVEMENT ALTERNATIVE 1
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
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 adjusted SNDcoefficient (0.2 mg/L)
Denitrification Improvement Alternative Evaluation for Hilton Head PSD
NON-CAPITAL IMPROVEMENT ALTERNATIVE 2
Semi Post-Anoxic Process
BOD Influent AER Secondary Effluent
Sludge Holding Tank
Dewatered Cake
ANX
Denitrification Improvement Alternative Evaluation for Hilton Head PSD
NON-CAPITAL IMPROVEMENT ALTERNATIVE 2
Aeration on
Aeration off
Semi Post-Anoxic Process
EQ Basins
Influent PS
Clarifier
Clarifier
Clarifier
Denitrification Improvement Alternative Evaluation for Hilton Head PSD
NON-CAPITAL IMPROVEMENT ALTERNATIVE 2
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
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)
Denitrification Improvement Alternative Evaluation for Hilton Head PSD
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
Denitrification Improvement Alternative Evaluation for Hilton Head PSD
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
Denitrification Improvement Alternative Evaluation for Hilton Head PSD
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
Denitrification Improvement Alternative Evaluation for Hilton Head PSD
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
Denitrification Improvement Alternative Evaluation for Hilton Head PSD
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 (%)
at 3 hr Cycle Length
Nitr
ogen
(mg/
L )
Optimum Range of Unaerated Phase Fraction (%)
at 1 hr Cycle Length
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 (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 (%)
at 3 hr Cycle Lengh
Unaerated Phase Fraction (%)
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 (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 (%)
at 3 hr Cycle Length
Nitr
ogen
(mg/
L )
Optimum Range of Unaerated Phase Fraction (%)
at 1 hr Cycle Length
Annual Average Loadings16 d SRTWinter Minimum Temp (16ºC)
0123456789
101112131415161718
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 (%)
at 3 hr Cycle Length
Nitr
ogen
(mg/
L ) Optimum Range of
Unaerated Phase Fraction (%)at 1 hr Cycle Length
Maximum Month Loadings16 d SRTSummer Max Temp (28ºC)
Denitrification Improvement Alternative Evaluation for Hilton Head PSD
MINOR CAPITAL IMPROVEMENT ALTERNATIVE 2Modified Ludzack-Ettinger (MLE) Modification
BOD Influent ANX Secondary Effluent
Sludge Holding Tank
Dewatered Cake
AER
Denitrification Improvement Alternative Evaluation for Hilton Head PSD
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
Denitrification Improvement Alternative Evaluation for Hilton Head PSD
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
Denitrification Improvement Alternative Evaluation for Hilton Head PSD
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 AAD Loadings
Nitrate N at MMAAD 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)
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 AAD Loadings
Nitrate N at MMAAD 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)
Various loadings6 – 10 day aerobic SRT400% internal recirculationWinter min temp (16ºC)
OutlineIntroductionWastewater 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
Denitrification Improvement Alternative Evaluation for Hilton Head PSD
Proposed ImprovementsALT 1 ALT 2-1 ALT 2-2
Aeration On-Off Cycling
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
Aeration On-Off Cycling
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
Aeration On-Off Cycling
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
OutlineIntroductionWastewater 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
Denitrification Improvement Alternative Evaluation for Hilton Head PSD
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]