using rotating effluent filters to replace sand filters · • greasing of bearings of center inf....
TRANSCRIPT
Using Rotating Effluent Filters to Replace Sand Filters
Douglas Nelson, PE
Thomas Steinbach
Project Drivers
• Diminishing Hydraulic Capacity
• Decreased Reliability• Poor Solids Capture• Introduction of New
Technologies
Project Steps
• Study Options– Need for Replacement
– General Costs• Detailed Financial Analysis• Design• Construction
Options Considered
• Replace the Existing Filters in Kind• Construct Deep Bed Filters in a Different
Structure
• Construct Cloth Bed Traveling Bridge Filters• Construct Rotary Disc Media Filters
Options Considered‐Replace in Kind
• Known Entity• Flows Limited to
Existing Flows
• High Backwash Rates
Options Considered‐Deep Bed Filters
• Similar Technology
• Lower Flow/SF• NEEDS MORE HEAD
– Pumps
– $$$$
Options Considered‐Cloth Traveling Bridge Filters
• Similar Technology
• Greater Flux Rate• Could be Retrofitted
into Existing Space
Options Considered‐Rotary Disc Filters
• Proven New Technology• High Flux Rates• Same or More
Mechanicals as Other Systems
• Low Head Loss (No Pumps)
Non Monetary Elimination
Replacement
• Saw P rules coming‐High
Solids Pass‐through
• Needed Additional
Capacity/ Building Cost
Deep Bed Sand Filter
• High Construction Cost
• Need to Add More Pumping
• Higher O&M
Financial Analysis Cloth Filter Traveling Bridge 2005 Costs
Financial Analysis Disc Filter 2005 Costs
O&M Costs 2005 Costs
Cloth TB
Actual Costs
$2,188,754
$2,246,676
City of Oconomowoc
Wastewater Treatment Facility
Headworks
and Effluent Filter Upgrade
Inf. Screen 9.0
12.0
Tertiary
Filt. 9.0
12.0
2008 Inf. Screen and Tertiary
Filter upgrade & Expansion
Existing Tertiary Filters
Kruger disc filter
Present Operations
• Two filters at a time – six months
• Upon removal from service – bleach soak and drain
• One filter on each side of inf. channel.• Normal backwash cycle time = 6 minutes
Maintenance
• Greasing of bearings of center inf. tube – once every two weeks.
• Drive chain lubrication – once per year.• Reducer oil change – every three years.• Backwash filter cleaning – once every six months.
• Cleaning after use, one day.• Acid cleaning for mineral fouling. As needed.
• Spray nozzle cleaning – as needed.
0
50
100
150
200
250
300
‐1.0
1.0
3.0
5.0
7.0
9.0
11.0
13.0
2006 2007 2008 2009 2010
Backwash Volume ‐Gal/day x 1,000
Effluent SS ‐mg/l
Effluent SS, Backwash Volume, and Filter CapacityEffluent SS
Filter Capacity
Filter Backwash
Filter Installation
‐37% or 87,000 gal/day
Backwash Reduction
• 37% average reduction• 87,000 gallons / day• 350 equivalent residential units
Iron Fouling During Phosphorus Removal Testing
April – June 2011
Phosphorus Removal Testing
• Goal ‐
Reduce our effluent to 0.4 mg/l monthly average
• Ferrous Chloride fed to primary clarifier
• Chemical increase from 150 to 220 Gal/day
• In two months we noted increasing backwash frequency.
• First chemical fouling since startup
Summary
• Filters have reduced maintenance significantly.
• Reduced footprint while increasing capacity• Eliminated filter bypassing
• Increased operational flexibility• Reduced energy in filter building• Reduced filter fly headaches
Successful Project Wisdom
• Take the time to review current technology
• Visit sites • Talk to operators• Look at value over the long term – LIFE CYCLE
ANALYSIS –
including consumables
• Lock in prices early – before the project bid
We thank you for your attention !!!
Questions ???