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TRANSCRIPT
From Rags to Riches lift station ragging solutions
Presented by:Craig B Anderson, P.E., Principal Engineer
Murray, Smith & Associates, Inc.
PACIFIC NORTHWEST CLEAN WATER ASSOCIATION2010 CONFERENCEOctober 24-27, 2010
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Presentation Overview
Background– New household products– Collection system impacts
Case Study (Glenwood Lift Station)– History– Options Evaluated– Solution Effectiveness– Return on Investment
Other Mitigation Options Conclusion
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BackgroundNonwoven technologies developed in 1940s and 1950s
Limited commercial products until 1990s
New product development and rapid growth starting in 1990s
2010 slow down (saturation)
Flushable/”Green”solutions VF
D US
E
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Background
Life at home made easier, but at a cost….
– Increased sewer back-ups (service lines)
– Increased Sewer Rates (O&M)
– Lift stations
– WWTP
– Collection System
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Glenwood Lift Station (Boise)
Problem StatementFacility built in 1976 (good condition)
Critical Facility/Location
High and increasing levels of pump maintenance
Gravity service potential in <10 years
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Glenwood Lift Station (Boise)
Glenwood Lift Station
West Boise WWTP
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Glenwood Lift Station (Boise)
75 ft
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Glenwood Lift Station (Boise)
OPTIONS EVALUATED
• Do Nothing• Operational Changes• Impeller Retrofit (Delta Impeller)• Grinder• Pump Replacement
• Grinder Pump
• Helical Impeller
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Glenwood Lift Station (Boise)
OPTION REFINEMENT
• Do Nothing• Operational Changes• Impeller Retrofit• Grinder• Pump Replacement
• Grinder Pump
• Helical Impeller
(80 man-days a year)
(no effect)
(low cost, but capacity decrease)
(City decision to not evaluate)
(moderate initial cost & City experience)
(initial option – collection system concern)
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Glenwood Lift Station (Boise)
OPTION EVALUATION
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Glenwood Lift Station (Boise)
OPTION EVALUATION
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Glenwood Lift Station (Boise)
SOLUTION EFFECTIVENESS
• Installed in early 2007• No ragging/problems since installed
• 2 year simple payback (45% ROI)
• PW break even at only 24% O&M reduction
• PW break even with replacement every 2 ½ years
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Other Options
Rag Removal– Regular Pump Maintenance (Do nothing)
– Public Education
– Screening
– Grinder
– Product (rag) development
Lift Station Modification– Operation (VFD low flow point & pump sequencing)
– Modified Pump Types (grinder and helical)
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Public EducationTheory of removing rags from waste stream by education
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Public Education
Success based on customer ownership of problem
• Local lift station
• Increasing sewer rates
If no ownership, then education can result in……
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Operation
VFD Setting
• Increase minimum flow point
Pump Cycling
• Return to on/off control
• Make sure motors protected
Combination
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OperationPump Cycling
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Modified Pump/Impeller TypesGrinder Pumps
• Standard for some City’s in Southern Idaho
• Higher HP
• Can be favorable with downstream re-ragging
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Modified Pump/Impeller TypesHelical Impellers
• Passes rags (no breakdown)
• Comparable HP
• Specify hardened impeller and volute
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Conclusions
Lift station ragging conclusions: Do Nothing costs can be significant
Multiple solutions (facility specific)
Evaluate City Standards for flow-paced facilities
Acknowlegements• City of Boise/CH2M HILL
• City of Nampa/Pharmer Engineering
• Pump Suppliers (Vaughan, Wemco & Hayward Gordon)
Questions/Discussions