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. 45 mm – Filtration Rate: 3. 83 gpm/ft 2 (clean water) – Actual Rate: 2. 55 gpm/ft 2 (12 MGD)

Maintenance History • • 20 -year useful life (1986 - 2006) Repairs 2007 Repair Costs, $50, 000 $ 200, 000 $ 150, 000 2008 Repair Costs, $100, 000 $ 100, 000 2009 Repair Costs, $200, 000 $ 50, 000 $- 2007 2008 2009 • 155 component & subcomponent failures over 3 -year period • Cost Estimate to Rebuild: $1. 6 to $2. 4 million

Quest for Alternatives • • • 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 • 1 st Generation Cloth Media System – Outside/In, totally submerged, pile cloth

Site Visits • 2 nd Generation Cloth Media System – Inside/Out, partially submerged, woven cloth

Site Visits • 3 rd Generation Cloth Media System – Inside/Out, partially submerged, woven cloth

RFP and Selection Process • Proposals from one 1 st Generation, two 2 nd Generation, and one 3 rd 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 Existing Contractor on-site Project too BIG for Change Order MSD purchased the Equipment direct (~$1 M) Bid the Demolition of the Old Units and Installation of the Disc Filters (~$300 k) • 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

n o i t a l l a t s n I d e t e l p m Co

Disc Filter Features • • 4 units installed (3 -duty, 1 -standby) 18 discs per unit (809 ft 2) 28 filter panels per disc 3, 236 ft 2 total installed Filter Rate: up to 5. 15 gpm/ft 2 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)

Performance Results Filter Tested Water level at Filter Flow, effluent weir, MGD inches 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 • • CH 2 M Hill, design consultant SIEMENS, disc filter manufacturer PAE Construction, general contractor Lake Erie Electric, electrical subcontractor • TOTAL Project Cost: ~$1. 5 M

THANKS TO OWEA Time for Questions? ?