centrifuge or screw press? to incinerate or not to ... · the city of lynnwood • population over...
TRANSCRIPT
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The City of Lynnwood
Centrifuge or Screw Press?
To Incinerate or not to Incinerate
a Best Practice Review
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Agenda
• The City of Lynnwood
• Lynnwood Wastewater
Treatment
• Evaluation Process
• O&M Cost Comparison
• Summary & Questions
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The City of Lynnwood
• Population over 35,000
• Fourth largest City in Snohomish County and twenty-
ninth largest in Washington State.
• The city is a mix of urban, suburban, small city,
crossroads, and bedroom community
• 16 miles north of Seattle – the city covers 7.8 square
miles
• Scriber Lake, Hall Lake and Swamp Creek all run
through Lynnwood
• Central Washington University and Edmonds
Community College have locations in Lynnwood
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Lynnwood Wastewater Treatment
• Lynnwood provides sewer service to approximately 35,000 people
with:
• 104 miles of sewer mains
• 6 lift stations
• 1 Wastewater Treatment Plant (WWTP)
• The Lynnwood WWTP treats sewage for 90% of Lynnwood plus a
portion of Edmonds north of Olympic View Drive
• The facility has a rated capacity of 7.4 MGD and an average flow
of 5 MGD.
• Peak flow has reached 20 MGD during severe storm weather
• The 36” diameter outfall into Browns Bay goes out approximately
1000 feet and is 120 feet deep
• 8,000-10,000 pounds of dried solids are incinerated daily
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Lynnwood WWTP Biosolids
Handling Challenges
Dewatering
• The existing Centrifuges at end of life and
require significant capital investment
• High risk of failure and cost of sludge
hauling
• Funds allocated in CIP for new centrifuges
• High O&M costs, maintenance burden
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Lynnwood WWTP Biosolids
Handling Challenges
Incineration
• New EPA air quality regulations for
wastewater incineration
• Annual emissions testing
• High risk of failure and cost of sludge
hauling
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Dewatering Evaluation Process
• Why screw press?
• Tour facilities with existing installations
• Define performance requirements
• Sludge sampling, signed performance guarantees
• Evaluation matrix to determine manufacturer
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Lynnwood Wastewater Treatment
Evaluation Process
• Project team selected 3 screw press manufacturers
• Project team developed performance specification
• Each manufacturer signed the performance spec
• An evaluation matrix was developed by project team in
order of City priorities and drivers
• The manufacturers were scored and the equipment was
selected
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Screw Press Matrix
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Centrifuge vs Screw Press
O&M Cost Comparisons
**Ongoing dryer evaluation
O&M Costs Centrifuge Screw Press
O&M 26,000$ 1,000$
Energy Use 11,000$ 1,140$
Total Annual O&M Costs 37,000$ 2,140$
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Incineration vs. Drying
• Incineration – challenges
• Risk of increasing EPA restrictions
• Sludge hauling
• 24/7 operation
• O&M Costs
• Rock formation
• Drying Benefits
• Fits limited WWTP real estate
• Reduced Sludge Hauling Risk
• Natural gas vs. diesel fuel
• Reduced O&M costs
• Marketable waste product
**Ongoing dryer evaluation
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Incineration vs. Drying
O&M Cost Comparisons
**Ongoing dryer evaluation
O&M Costs Incinerator Dryer
Ash/Sludge Hauling 50,000$ 70,000$
Staff Overtime Cost 6,000$
Sand Replacement & Downtime Cost 4,000$
Emissions Testing (annual) 40,000$
Annual Incinerator Down Time & Associated
Hauling Costs 235,000$
Dryer Annual Maintenance 5,000$
Total Annual O&M Costs 335,000$ 75,000$
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Project Goals – Phase 1
Replace Centrifuge with Screw Press• Limit City’s risk
• Stretch CIP funding
• Replace end of life equipment, energy savings
• Increase system reliability
• Reduce annual energy consumption and O&M costs/labor
• Reduce project management burden on City staff
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Energy Savings Performance Contracting
• City gets what they want
• Reduced burden on City staff
• Guaranteed maximum price
• Maximize grant/incentive dollars
• Leverage CIP funding to optimize cash flow
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Laying the foundation of partnership
• Lynnwood selected Trane because Trane partnered with the
City to make it the City’s project
• Design Build Construction
• Lynnwood involved throughout design to shape the project
through equipment/consultant selection and driving
solutions
• Guaranteed Maximum Cost and Guaranteed Minimum
Savings (known max budget before project starts)
• City maintains control over the project
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Questions?