Metropolitan Sewer District of Greater Cincinnati Muddy ... Creek WWTP Aeration System Efficiency...
Transcript of Metropolitan Sewer District of Greater Cincinnati Muddy ... Creek WWTP Aeration System Efficiency...
Muddy Creek WWTP Aeration System Efficiency Upgrade
Metropolitan Sewer District of Greater Cincinnati
June 19 | 2013
Muddy Creek WWTP Aeration System Efficiency Upgrade Brian Mumy, P.E., Brown and Caldwell
Ryan Welsh, P.E., Metropolitan Sewer District of Greater Cincinnati
MSDGC Overview
• Serves the City of Cincinnati and most of Hamilton County
• 7 major treatment plants, 120 pump stations
• 3,000 miles of sanitary and combined sewers
• 184 mgd ADF combined
OWEA Annual Conference | June 19, 2013
Muddy Creek WWTP Overview
• Built in 1958
• 15 mgd Design ADF
• Discharges to Ohio River
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Muddy Creek WWTP Secondary Process
• Constructed in 1972
• Two tanks
• 220’x78’x15’ each
• 1.9 MG each
• Plug flow
• Three passes per tank
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•Aeration Demand: 6,400 - 13,400 scfm
•Blowers (4)
•Positive Displacement
•200 hp
•Rated at 4,650 scfm each
•Age: Installed in 1972
•Fine Bubble Diffusers
•Sanitaire Ceramic Disc
•Age: Installed in 2008
Prior to Upgrade
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• New Blowers with Automatic DO Control
• Contractors: Dugan & Meyers, Lake Erie Electric
• Design Engineers: Brown and Caldwell
• Designed in 2010
• Construction Started in Spring 2011
• Substantial Completion in Spring 2013
• Construction Cost: $7,703,000 *
* Construction contract includes new blowers, diffusers, and automatic DO control at Little Miami WWTP. Muddy Creek construction cost ≈ $2,500,000
Aeration Upgrade Project
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• Existing positive displacement blowers were 40 years old
• Decreasing reliability
• Increasing maintenance
• Increasing risk of failure
• Potential for energy savings
Project Motivation
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Source: Energy Conservation in Water and Wastewater Facilities,
Manual of Practice No. 32 (WEF, 2009)
Upgrade Evaluation
• Equipment Reliability
• Age of existing equipment
• Capital Costs
• Equipment
• Installation
• Operational Costs
• Maintenance
• Energy
OWEA Annual Conference | June 19, 2013
OWEA Annual Conference | June 19, 2013
Blower Technologies
• Positive Displacement
• Centrifugal – Single Stage
• Centrifugal – Multistage
• High Speed Turbo
High Speed Turbo Blowers
• Developed in the aerospace industry based on gas turbine engines
• Single stage centrifugal, direct drive
• High speed (15,000-60,000 rpm)
• Air foil bearing
• Blower, motor, VFD, and PLC in single enclosure
OWEA Annual Conference | June 19, 2013
OWEA Annual Conference | June 19, 2013
High Speed Turbo Blowers
Advantages
• High efficiency
• Package design, small footprint, low installation labor
• Lowest maintenance
• Low vibration – isolators not required
• Lowest noise
• Air plenum not required
OWEA Annual Conference | June 19, 2013
High Speed Turbo Blowers
Disadvantages
• Only for lower flow rates (8,000 to 15,000 scfm max flow per unit)
• VFDs require harmonic filters for protection
• New technology with limited installation base
Business Case Evaluation
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Final Alternatives Capital Cost Net Present
Value
1. Positive Displacement Blowers $3,865,000 $7,925,000
2. High Speed Turbo Blowers $2,937,000 $6,096,000
* Replace Blowers – MSDGC Useful Life of Capital Assets Report
* 30 Year Analysis, Electricity Cost $0.073 KW/HR
* MSDGC NPV analysis
High Speed Turbo Blowers Selected
• Lower Capital Cost
• Lower O&M Cost
• Lower Energy Cost
• Lower NPV
• Four High-Speed Turbo Blowers
• HP: 250
• Rated Capacity: 4,770 scfm
• Harmonic Filters
• Electrically Actuated
Butterfly Air Control
Valves
• Startup Date: February, 2012
Equipment Installed
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• Each Blower was provided as a package by the manufacturer
• A Master Control Panel (MCP) was also provided by the manufacturer to act as a pressure controller.
• New Dissolved Oxygen Meters
• New Air Flow Meters
Controls Installed
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• Luminescent technology
• No membranes or solutions
• Factory calibrated
Dissolved Oxygen Probes
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• Thermal Mass Flow technology
• Flow conditioner upstream
• Low pressure loss
Air Flow Meters
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Overview of Secondary Aeration
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AERATION TANK 1
PASS 1
PASS 2
PASS 3
PASS 1
PASS 2
PASS 3
AERATION TANK 2
BLOWERS
AIR MODULATING
VALVES
AIR FLOW
METERS
D.O. MEASUREMENT
Most Open Valve (MOV) Pressure Control
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M
PIT
MOV %
SETPOINT
AIR HEADER
PLC
PID
SPEED % - + -
DRIVE
PLC
MOV
LOGIC
PRESS
SP
AIR VALVE
POSITIONS
M
AIT
D.O.
SETPOINT
PLC
PID
% OPEN - + -
DISSOLVED OXYGEN
PLC
PID
FIT
- + -
FLOW
SETPOINT
FLOW
% OPEN TO MOV
CONTROLLER
PRESSURE
Blower Operation – Communications
OWEA Annual Conference | June 19, 2013
Aeration
Master PLC
Blower MCP Master Control
Panel
Blower 1
PLC
• 6 PLCs are inter-connected with Ethernet
• Each Blower PLC and the MCP have PanelView
touch-screens
Blower 2
PLC
Blower 3
PLC
Blower 4
PLC
Pressure Set-point
Blower Operation – MCP Pressure Controls
OWEA Annual Conference | June 19, 2013
• The MCP is programmed to
maintain header pressure
by adjusting the blower
speeds.
• MCP determines:
• Which blower is lead
• Time delays for
starting/stopping
• Which pressure
transmitter to use for
feedback
• Dead-bands
Blower Operation – Local Controls
OWEA Annual Conference | June 19, 2013
• Blower is normally controlled
from the MCP via Ethernet.
• It can be placed in Local
Control to manually
start/stop and adjust speed.
• Displays speed, pressure,
estimated flow, temperature,
etc.
• Indicates when filter
changes are required based
on pressure differential
Aeration System – HMI Controls
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Trending
Blower Details
Overview
Pop-Ups
Energy Savings - Estimated
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• Original Positive Displacement Blowers
• Estimated usage of 270 kW
• High Speed Turbo Blowers
• Estimated usage of 212 kW
• Estimated Energy Savings
• $3,000/mo
• $36,000/yr
• ≈ 20%
Actual Energy Savings – First Year
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$0
$5,000
$10,000
$15,000
$20,000
$25,000
Ae
rati
on
Bu
ild
ing M
on
thly
Po
we
r C
osts
Month
2009-2011
2012-2013
Average Energy
Savings:
≈ 40%
Actual Energy Savings – First Year
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• Average Annual Energy Cost 2009-2011
• $220,000
• Average Annual Energy Cost 2012
• $135,000
• Energy Savings
• $85,000/yr
• ≈ 40%
Lessons Learned
OWEA Annual Conference | June 19, 2013
• New Technology
• New manufacturers
• Purchase extended warranty
• Base bid manufacturer
• Performance Testing is Critical
• ASME Performance Test Codes
• PTC-10 – Compressors and Exhausters
• PTC-13 – Blowers – under development
Lessons Learned
OWEA Annual Conference | June 19, 2013
• Turndown
• Be weary of manufacturer claims
• Blower controls protect against surge – reduces operating range
• Muddy Creek HMI programming was modified to avoid LCP warnings and keep blow-off valves from opening
Lessons Learned
OWEA Annual Conference | June 19, 2013
• Programming System Controls is Critical
• Controls can contribute to energy savings as much as the blowers
• Startup adjustments will be necessary - flexibility in programming is required
• Muddy Creek HMI control was modified to maintain mixing airflow