Transcript Replacing Old Sand Filters with Modern Disc Filters

Replacing Old Sand Filters with
Modern Disc Filters
MSD of Greater Cincinnati
Sycamore Creek TP
By
Tom Kutcher, P.E.
Assistant Superintendent – WWT Division
Sand Filters Installed - 1986
• Part of Settlement with Zimpro
• Installed to filter Plant and Secondary
Bypasses prior to disinfection
• Features:
– (8) cells 12’ x 34’, 10” of media
– Mono-media sand, effective size 0.45mm
– Filtration Rate: 3.83 gpm/ft2 (clean water)
– Actual Rate: 2.55 gpm/ft2 (12 MGD)
Maintenance History
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20-year useful life (1986 - 2006)
2007 Repair Costs, $50,000 $200,000
2008 Repair Costs, $100,000 $150,000
$100,000
2009 Repair Costs, $200,000 $50,000
Repairs
$-
200720082009
• 155 component & subcomponent failures over
3-year period
• Cost Estimate to Rebuild: $1.6 to $2.4 million
Quest for Alternatives
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Rebuild the same (~$2 million)
Replace with travelling bridge filters
Replace with cloth media filters
– Pile cloth media
– Woven cloth media
• Plant Hydraulic Considerations
• Ease of Construction/Retrofit
• Ease of Operation & Maintenance
Site Visits
• 1st Generation Cloth Media System
– Outside/In, totally submerged, pile cloth
Site Visits
• 2nd Generation Cloth Media System
– Inside/Out, partially submerged, woven cloth
Site Visits
• 3rd Generation Cloth Media System
– Inside/Out, partially submerged, woven cloth
RFP and Selection Process
• Proposals from one 1st Generation, two 2nd
Generation, and one 3rd Generation System
• Independent evaluations by Engineer and
Plant O&M staff
• Selected top two systems and received formal
quotations.
• Looked at Life Cycle Costs and Capital Costs to
Install
• Quote “N+1” units (Duty/Standby)
Evaluation
• Non-Numeric
– Experience – 10 pts
– Performance at Existing Installations – 10 pts
– Ease of O&M at Existing Installations – 10 pts
• Numeric
– Manufacture’s Price – 40 pts
– Life Cycle Costs – 30 pts
Alternative Delivery
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Existing Contractor on-site
Project too BIG for Change Order
MSD purchased the Equipment direct (~$1M)
Bid the Demolition of the Old Units and
Installation of the Disc Filters (~$300k)
• Engineer assisted MSD with the Direct Purchase
and Bid Documents for the Construction
Time Line
• Sand Filters failed: September, 2009
• Goal: New Filters on-line by May 1, 2011
– Summer NPDES Permit Season
• Contract Awarded: October 28, 2010
• Units Ready for Testing: March 30, 2011
– 5 months!!
• Biggest Challenge: City Purchasing and getting
units delivered in timely fashion.
Demolition of Existing Cells
• Only 4 out of 8 cells needed to be retrofitted
• MSD had removed sand media
Demolition
Demolition
Demolition
Retrofit Cells for Discs
Effluent Pipe
Retrofit
Cells for
Discs
Effluent Pipe
Retrofit
Cells for
Discs
Equipment
Pad
Retrofit
Cells for
Discs
Equipment
Pad
Retrofit Cells for Discs
Weir
Wall
Retrofit Cells for Discs
Tank
Drain
Install Disc Filters
Retrofit Cells for Discs
Electrical and
Control Panels
Retrofit Cells for Discs
• Walkway Grating
and Handrail
Disc Filter Features
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4 units installed (3-duty, 1-standby)
18 discs per unit (809 ft2)
28 filter panels per disc
3,236 ft2 total installed
Filter Rate: up to 5.15 gpm/ft2
Backwash Rate: 196 gpm at 109 psi
Backwash Cycle: 90 seconds at 1 rpm
Disc Drive: 1.5 Hp, BW Pump: 25 Hp
Performance Testing
• 12-hr Functional Performance Test
– (all 4 units)
• 12-hr Peak Hydraulic Test
– (Two units, 6 MGD/unit)
• 12-hr Process Performance Test
– (Two units, 3 MGD/unit)
– (One unit, 6 MGD/unit)
– (One unit, 6 MGD/unit)
Performance Results
Filter Tested
Water level at
effluent weir,
inches
Filter
Flow,
MGD
Influent
Turbidity,
NTU
Effluent
Turbidity,
NTU
Turbidity
Removal %
Influent
TSS, mg/l
Effluent
TSS, mg/l
TSS
Removal %
GOAL: Effluent TSS < 5 mg/L
4
4.26
5.38
1.94
1.23
36.48
3.94
2.08
47.22
3
3.97
4.89
1.69
1.05
37.44
3.19
2.20
31.28
1
4.28
5.40
3.66
1.31
64.15
7.24
2.36
67.38
2*
4.33
5.57
19.67
1.65
91.61
30.97
2.97
90.40
* On Filter 2, there were (2) hourly influent readings > 30 mg/L (72 mg/L and
232 mg/L), but both effluent TSS were still < 5 mg/L.
Effluent TSS
20
Filter Operations Started
April 4, 2011
TSS, mg/L
15
10
5
0
01-Jan-11
01-Feb-11
01-Mar-11
01-Apr-11
01-May-11
Thanks to our Partners
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CH2M Hill, design consultant
SIEMENS, disc filter manufacturer
PAE Construction, general contractor
Lake Erie Electric, electrical subcontractor
• TOTAL Project Cost: ~$1.5M
THANKS TO OWEA
Time for Questions??