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Planning for the Future Battle Creek’s Approach to Upgrading its Secondary
Treatment Processes
Michigan Water Environment Association Annual Conference
June 21, 2016
Richard Beardslee, City of Battle Creek Nathan Cassity, Donohue & Associates
Outline and Acknowledgements
• Background
• Energy Evaluation
• Nutrient Evaluation
• Planned Upgrades
Outline
Battle Creek
• Marvin Krause
• Bryan Crawford
Donohue
• Mike Harvey
• Kendra Sveum
Acknowledgements
Battle Creek Background
Background: Battle Creek
Design capacity 27 mgd
Currently operating at 9 mgd
Flows have decreased over the years
Significant loadings from food processors and paper
Influent BOD
• 580 mg/L (2013-2014)
• 650 mg/L (2015)
Page 4 | November 12, 2015 MWEA
Background: Battle Creek
Page 5 | November 12, 2015 MWEA
Process Type: Single-Stage Activated Sludge with Nitrification
Background: Battle Creek
Background: Battle Creek, MI
• Project Drivers
– Energy conservation
– Aged facilities: Blowers cannot be repaired
– Aged facilities: Outdated aeration control
– Process Improvements: Nutrient deficiency issues
– Chemical Savings: Phosphorus control
Energy Evaluation
Energy Use
0%
10%
20%
30%
40%
50%
60%
Jan Feb Mar Apr May Jun Jul Aug Sep Oct Nov Dec
Pe
rce
nt
of
To
tal E
ne
rgy
Use
Estimated Average Blower Energy Use by Month
40-55% of total energy use with peak use in summer months
Energy Use
Aeration system is the “low-hanging fruit”
45%
4%
1%
50%
Percent of Plant Energy Use
Aeration
Settled Sewage Pumps
RAS Pumps
Other Misc. Loads
Multiple uses and equipment systems
Start with the “Low-Hanging Fruit” for Significant Reductions and Returns on Investment
Existing Blower Systems
(3) Multi-Stage Centrifugal Blowers Turndown: Manual Inlet Throttling Max Flow: 21,000 scfm Min Flow: 13,000 scfm Age: > 30 years, motor replaced recently
(4) Positive Displacement Blowers No Turndown Capability Flow: 7,000 scfm Age: > 40 years, parts not available
Existing Aeration Control
• All adjustments are manual
• Handheld DO profile each shift
• SCADA monitoring
– Blower airflow
– DO at end of basins
• Operator periodically adjusts blowers and butterfly valves
Blowers
Aeration Control
Aeration Energy Picture
Diffusers
Energy Evaluation Approach
Comprehensive Aeration System Study Approach
1. Provide the air more efficiently
a. More efficient blower system
2. Reduce the amount of air Provided
a. Improved automation and controls
b. Increased oxygen transfer efficiency
c. Biological nutrient removal
Provide Air More Efficiently
Blowers
Aeration Control
Aeration Energy Picture
Diffusers
Provide Air More Efficiently
High Efficiency Blowers Will Reduce Aeration Energy
Provide Air More Efficiently
Opportunity : Improve Blower Reliability, Operating Efficiency and Turndown
25% Reduction In Blower Energy Use Turndown to Lowest Operating Requirement
Replacement of Aging Equipment
Existing Blowers
0
10,000
20,000
30,000
40,000
50,000
60,000
70,000
0% 20% 40% 60% 80% 100%
Air
flo
w (
scfm
)
Percent of Time Equal or Less Than
Existing blower capacity
Turndown to 20th percentile requirements
Probability Distribution Curve
Propose Blower Upgrades
Improved Turndown
0
10,000
20,000
30,000
40,000
50,000
60,000
70,000
0% 20% 40% 60% 80% 100%
Air
flo
w (
scfm
)
Percent of Time Equal or Less Than
Remaining centrifugal blower capacity
New turbo blower capacity
New equipment sized to meet majority of demand
Greater Energy Efficiency Over Operating Range
Estimated Blower Savings
0
1,000,000
2,000,000
3,000,000
4,000,000
5,000,000
6,000,000
7,000,000
8,000,000
Current Blowers New Blowers
Esti
mat
ed
An
nu
al k
Wh
• 25% Reduction in Blower Energy Use • $121,000 in annual electricity cost savings • $139,000 incentive rebate from utility • 10-Year Payback (no control upgrades)
Anticipated Savings:
Reduce Amount of Air Provided
Diffuser Efficiency
SOTE Per Foot of Submergence Based on Air Flow and Basins in Service
4
5
6
7
10,000 15,000 20,000 25,000 30,000
Basins in Service
Air Flow (scfm)
1.90-2.00 2.00-2.10 2.10-2.20 2.20-2.30 2.30-2.40 2.40-2.50
As airflow per diffuser increases, oxygen transfer efficiency decreases
Estimated annual savings of $30,000 by placing a 5th basin in service
Air Required Versus Air Supplied
Goal is to save energy by more closely matching air supply to air requirements:
0
5,000
10,000
15,000
20,000
25,000
2012 2013 2014
Air
flo
w, S
CFM
Average Air Required
Observed Periods of Potential Over-Aeration -> Energy Reduction Opportunity
Estimated Annual Savings Potential: $100K
Improved Control Strategies
Several Options to Consider:
Basic Control
Capital Cost, Energy Savings
Intermediate Control Advanced Control
Control Alternative Aeration Reduction
Potential Achieved (%) Estimated Energy Savings (kWh/yr)
Estimated Cost Savings ($/yr)
Basic 40 569,000 $40,000
Intermediate 60 1,138,000 $80,000
Advanced 100 1,423,000 $100,000
Aeration Control Strategy
Airflow meter and control valve
DO Probe
• DO Control Loops
– Every pass
– Airflow meter + control valve
– Most-open-valve
• Blower Control
– Pressure and Airflow based
Aeration Control Strategy
Blowers
To Other Tanks/Passes
FIT
FIT
Blower Speed Adjusts to the Total
Flow Setpoint
DO
Each of 3 Passes in Every Aeration Tank
DO Control with Direct Blower Air Flow Control
Eliminating Pressure Setpoint Can Provide Additional Energy Savings
Combined Blower and Control Savings
Anticipated Savings:
0
1,000,000
2,000,000
3,000,000
4,000,000
5,000,000
6,000,000
7,000,000
8,000,000
Current System Improved System
Esti
mat
ed
An
nu
al k
Wh
Additional 1,420,000 kWh per year
45% Total Reduction in Aeration Energy Use
Total estimated savings of $220,000 annually
Nutrient Evaluation
• Phosphorus removal
– Ferric chloride used for chemical phosphorus removal
– Winter effluent limit 1 mg/L
– Summer TMDL limit of 0.5 mg/L
• Nutrient deficiency
– Nutrient addition required
• high food processor BOD loadings
– Nitrogen feed, urea: 25 tons annually
– Phosphorus feed, phosphoric acid: 823 tons annually
Battle Creek Nutrient Balance
High Calcium Quicklime, $98,758.40
Polymer (K275FLX), $208,845.00
Ferric Chloride, $119,400.00
Sodium Bisulfite, $25,976.00
Chlorine, $68,220.00
Phosphoric Acid, $88,007.50
UAN-28, $8,125.00
Bioxide, $50,055.00
Annual Total: $667,000
More than one third of current chemical use is related to nutrients
Annual Chemical Costs
• Nutrient Deficiency – BOD:N:P Ratio of 100:5:1 is Good Target
– Nutrient Addition
Page 30 | May 26, 2011
WWOA LMD
Battle Creek Primary Effluent
Date BOD TKN Tot-P
07/12/15 100 8.1 0.6
07/14/15 100 5.8 0.6
07/16/15 100 5.8 0.5
07/19/15 100 5.4 0.6
07/21/15 100 3.9 0.4
07/23/15 100 3.7 0.3
Battle Creek Nutrient Balance
• Nutrient Deficiency – BOD:N:P Ratio of 100:5:1 is Good Target
– Nutrient Addition – UAN-28 and Phosphoric Acid
Page 31 | May 26, 2011
WWOA LMD
Battle Creek PE including N + P Dosing
Date BOD TKN Tot-P
07/12/15 100 8.1 1.1
07/14/15 100 5.8 1.1
07/16/15 100 5.8 0.9
07/19/15 100 5.4 1.1
07/21/15 100 4.5 0.8
07/23/15 100 4.6 0.8
Battle Creek Nutrient Balance
• Nitrogen Deficiency
0.0
1.0
2.0
3.0
4.0
5.0
6.0
7.0
8.0
PE Pass 1 Pass 2 Pass 3
mgN
/L
Conceptual Profile – Excess Nitrogen
NH3-N NOX-N
Battle Creek Nutrient Balance
• Nutrient Deficiency – Battle Creek: 3 of 6 days showed similar numbers
0.00
0.50
1.00
1.50
2.00
2.50
Pass 1 Pass 2 Pass 3
mgN
/L
07/15/15 Nitrogen Profile
NH3-N NOX-N
Battle Creek Nutrient Balance
• Improve nutrient monitoring and control
– Effluent analyzers for ammonia, nitrate, and phosphorus
– Chemical feed based on maintaining minimum effluent concentrations
• Implement biological phosphorus removal
– Modify aeration basins to incorporate selectors
– Utilized BioWin modeling to estimate nutrient requirements and effluent P results
Battle Creek Nutrient Balance
Baffle Wall
Selector Mixer Diffuser
Modifications
Conceptual BPR Layout
Ammonia N
Nitrite + Nitrate
Soluble PO4-P
Chart
Primary Effluent Amended PE Pass 1 Zone 1 Pass 1 Zone 3 Pass 2 Zone 2 Pass 3 Zone 2 Effluent
CO
NC
. (m
g/L
)
11
10
9
8
7
6
5
4
3
2
1
0
6.8
10.9
10.0
0.10.4 0.5 0.5
0.0
1.4
0.0 0.0
1.9
4.9 4.9
1.61.8
3.1
0.6
0.1 0.2 0.2
(Selector)
P release in selector P uptake
Nutrient Profile Predicted in BioWin Model of Bio-P Configuration
Model Results – nutrient profiles
$0
$50,000
$100,000
$150,000
$200,000
$250,000
$300,000
Current Operation Improved Nitrogen Bio-P
Estimated Annual Spending
RAS Chlorine
Ferric Chloride
Phos. Acid
UAN-28
$34,000 Increase for Nitrogen Dosing
Net Savings: $178,000
$11,000 Savings on RAS Chlorination
+
Model Results – chemical cost savings
Summary of Planned Improvements
Summary of Planned Improvements
Improvement Estimated Construction
Estimated Annual Savings
Aeration Blowers $2.55M $121,000
Aeration Controls $1.54M $99,000
BPR Modifications $1.58M $110,000
Nutrient Feed Controls 0.365M $68,000
Total $6.04M $398,000
Planning for the Future Battle Creek’s Approach to Upgrading its Secondary
Treatment Processes
Michigan Water Environment Association Annual Conference
June 21, 2016
Richard Beardslee, City of Battle Creek Nathan Cassity, Donohue & Associates