petoskey wwtp headworks improvements - … 4 - dennis benoit.pdf• replaced with “muffin...
TRANSCRIPT
7/11/2012
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Michigan Water Environment Association Annual Conference
June 26, 2012 Dennis J. Benoit, P.E., Hubbell, Roth & Clark, Inc.
Petoskey WWTP Headworks Improvements
Problem Statement: 40 Year Old WWTP
Headworks Badly in Need of Improvement
Original Design
Influent Flume for Flow Monitoring
Wastewater Grinding
• Originally Comminutor
• Replaced with “Muffin Monster” in 2002
Aerated Grit Channel
• Bucket Elevator with Horizontal
Auger Conveyor
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40 Year Old WWTP Headworks Badly in
Need of Improvement
Horizontal Auger
Wet Grit
Huge Odor Issues
Manual Transfer Of Grit Was
Very Labor intensive
Wet “Sloppy” Grit
Problems with Original Headworks
Grinding Never works Flawlessly!
Numerous Cases of Screened
Material “Reweaving”
Odors
Minimal Ventilation
Wet Grit
Grit Required Manual Handling from Auger to Dumpster
Waste Hauler Refused Acceptance Due to Free Liquid
• Rectified with Visquine-Lined Dumpster
• Hauling three 12 CY Dumpsters per week at one point
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Problems with Original Headworks
Corroded Equipment
Grit Chain Replaced on Numerous Occasions
Bucket Elevator Jams
Criteria for Headworks Revisions
Fine Screening
• ¼ inch opening size desired
• Washer/Compactor to Reduce Organics in Screenings
• Reuse Existing structure if Possible to Minimize New Land
Aerated Grit Removal
• Requested by Operators to “Freshen” Waste
Clean, Dry Grit
• Free of Organics
• Reduce Moisture to Minimize Disposal Costs
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Criteria for Headworks Revisions
(Continued)
Capture Odors and Treat
• Indoor Housing for Grit Dumpster For Weather
Protection and Odor Containment
• Carbon Contactor on Building Ventilation
• Energy Recovery Due to Significant Ventilation
Volumes
Air to Air Contactors Recover Energy
Criteria for Headworks Revisions
(Continued)
Foul Air Streams To Aeration Blowers
• Foul Air From Wastewater Channels
• Aerated Tank Off-gas Routed To Aeration Tanks
• This Required A Duct From Headworks Building To
Administration Building And Modified Air Filter Inlet Boxes
• An Existing Foul Air Duct From A Biosolids Holding Tank Was
Also Connected
• The Duct Included A Fresh Air Inlet Prior To Blowers For
Blending
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Project Highlights
Bid in July 2011
Estimated at $2.52M
Low Bid at $2.64M
Expectation Was Closer To $2.2m
• Value Engineering Reduced Project Cost To 2.27m
• Sloped Grit Tank Floor
Reduced Undermining Potential of Main Electrical Feed
Duct
• Lowered West Half of Building Two Feet
Made Channels More Accessible
• Deleted OC Unit, One Grit Pump, Aeration Blower, Other Items
Construction Start September 2011
Underground Construction
• Main Duct Bank Underpinning
• Utility Location Conflicts
• Relocations of…
Sludge Line
Biogas Line
Chlorine Solution Lines
Others
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Construction (Continued)
Plant Bypass
• Plan Detailed on Construction Drawings
• Modified by Contractor Based on Available Equipment
• Grit Removal using Precast Concrete Tank and Used
Grit Removal Equipment Including:
Pump
Cyclone
Grit Washer (Auger Type)
• Contractor Constructed Temporary Building to House
Equipment Throughout Winter
Bypass Infrastructure
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Dumpster Room Footings
and New Structure Floors
Building Walls and Interior Channel Floors
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Interior Building Finishes (Cont.)
Highlights of Project
Reuses Existing Channel Structure
In Place Bypass Saved Extensively
Fine Screening Reduces Downstream Maintenance
Screenings Washer Compactor Reduces Odor
Potential of Screenings
Clean Grit Washer Minimizes Grit Volume as Well as
Odor and Moisture Content
Extensive Savings on Grit Disposal Costs
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Highlights of Project (Continued)
Existing Aeration Blowers:
• Provide Rolling Air For Grit Tank
• Pull Foul Air From Channels and Tanks
• Control Valve Regulates Air Flow
Unique Approach to Odor Control
LED Light Fixtures Save Energy
Energy Recovery Ventilation System Saves
Energy
Lessons Learned
Fine Screening Operation
• Developing a mat on the screen is beneficial to screenings
removal.
• Putting the screenings into a Washer Compactor with Similar size
openings can be counterproductive.
Screenings Odors
• Probably the most significant source of odor in the room
Grit Removal
• Plant Effluent Water used for counter current washing.
• Produces very clean grit.
• Steep Auger used on washer produces very dry grit.
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Lessons Learned (Continued)
Aeration
• Air Use For Aerated Grit Is Minimal (Using About 50 CFM
Versus 110 CFM Manufacturer’s Recommendation)
• Control Valve Is Used To Regulate The Air Flow To Grit
Tank
• Routing Air Flow Supply To Aeration Blowers Can Keep
Influent Channels Under Negative Pressure.
Old and New Building
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Dumpster Area
Staff Acknowledgments
Sherrie Elliott - Public Works Supervisor
Steve Keel – Crew Leader
Mike Robbins - Director of Public Works
Dan Ralley – City Manager