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Improving Efficiency of DewateringAlternatives to Conventional Dewatering
Technologies
Robert Gillette, PE, BCEESteve Swanback, PE
Rebecca Overacre, PE
2009 PNCWA Webinar Recent Developments In
Biosolids Management Processes
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Outline
1. Screw press technologya. Performance survey resultsb. Pilot testing resultsc. Lifecycle cost evaluation (Class A and Class B)d. Design considerations
2. Rotary fan press technologya. Performance survey resultsb. Pilot testing resultsc. Lifecycle cost evaluation (Class A and Class B)d. Design considerations
3. Overview of R&D Technologies
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Screw Press Technology
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Screw Press Manufacturers
• Huber (inclined)
• FKC (horizontal)
Screw Press General Description
Dewatering by Volume Reduction
Screw Press Expanded View
Screw Press Expanded ViewClass A Option
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Flow Schematic
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Tallahassee, FL, FKC InstallationTallahassee, FL, FKC Installation
FKC Screw Press
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FKC Screw Press
Petaluma, CA, FKC InstallationPetaluma, CA, FKC Installation
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Huber Press
Magna, UT, Huber InstallationMagna, UT, Huber Installation
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Huber Press
Maine, Huber InstallationMaine, Huber Installation
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Performance Survey
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Survey of 22 Full Scale Installations –The Cake Solids Concentration Depends on Type of Sludge
Type of Sludge Screw Press Cake (% solids)FKC 15 – 20
FKC (with steam and lime) 20 – 45Huber 12 – 20FKC 21 – 28
WAS
Huber 22 – 25Raw Huber 18 – 40
PS+WASFKC > 18
Huber 19 – 24Aerobically Digested
Anaerobically Digested
FKC 17 – 25Anaerobically Digested Huber 13 – 16
Raw
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Survey of 22 Full Scale Installations –The Median Cleaning Schedule is Once Per Week
Manual Cleaning Schedule(times per month)
0
5
10
15
20
25
30
1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22Facility Number
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Case Study –St Petersburg, FL
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Pilot Results - Projected Full Performance – St. Petersburg
Manufacturers Recommendations
Screw PressBelt Press CentrifugeClass B Class A
Minimum Cake Solids Concentration (% solids)
18 21 16 33
Maximum Polymer Dosage (lb/DT)
19 25 30 33
Minimum Solids Capture (%)
95 95 90 90
Parameter
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“Relative” Cost Comparison
BFP Centrifuge Screw Press
Capital Cost $ $$$ $$
Building Modifications $ $$ $$
Odor Control $$$ $ $
Power $ $$$ $
Maintenance $$ $$ $
Chemical $$ $$$ $$
Hauling $$ $ $$
Disposal $$ $ $$
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Performance Comparison
Will Vary Depending on Conditions!!!Will Vary Depending on Conditions!!!
BFP Centrifuge Screw Press
% Solids Produced ++ +++ +
Filtrate/Centrate Quality ++ ++ +
Reliability ++ ++ +++
Operator Attention Required + ++ +++
Ease of startup and shutdown ++ + ++
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Design Considerations
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Design Considerations
• Lead time (from Japan or Germany): prepurchase?
• Custom design – varying dimensions until shop drawing
• Performance guarantee and penalty for non-compliance
• Basis of design– Loading & capacity: pilot test– Run time, unattended operation
• Effect of rising steel costs – units all SST
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Design Considerations, Continued
• Need headroom if RST on mezzanine• Monorail/overhead crane• Building considerations – footprint
requirement – or outside• Provision for Class A in future• Cake conveyance options affects layout
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Design Parameters
• Range of Capacity: Up to 8.5 DT/day– At “nominal” speed
• RST output (% Solids): around 4%• Screw Press output (% Solids): 15 – 28%• Polymer consumption: 20 – 40 lb/DT• Detention time: approximately 4 hours• Motor speed: as low as 0.3 rpm• Motor HP – largest unit is 7.5 HP
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Rotary Press Technology
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Rotary Press Manufacturers
Fournier
Prime Solutions
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Rotary Press Schematic
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Process Cutaway
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Design Parameters
• Range of Capacity: 7-250 gpm• Cake % Solids: 12 – 28%• Detention time: N/A• Motor speed: as low as 1-3 rpm• Motor HP: 5-20 HP
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Fournier Rotary Press
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• Size Compared to Other Technologies
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Multiple Channels on Single Drive
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Fournier Rotary Press Pilot Test
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Prime Solutions Rotary Fan Press
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Performance Survey
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Survey Results
Facility EquipmentFacility
Size (mgd)
Solids Type Incoming % TS
Discharge % TS
Raiford, FL Prison WWTP
Rotary fan press 1.1 Extended aeration
1.6-2.5 19-22
Front Royal, VAMunicipal WWTP
Rotary fan press 3.3 Thermophilic Anaerobic Digestion
3.5 25
Fairfield, CAMunicipal WWTP
Rotary fan press 15.5 Conventional Anaerobic Digestion
2 17
Lafayette, TNMunicipal WWTP
Rotary press 0.5 Conventional Anaerobic Digestion
1.0-1.5 25
Portland, MEMunicipal WWTP
Rotary press 19.8 Thickened PS/WAS
3-6 19-25
Hampton, NHMunicipal WWTP
Rotary press 2.5 Septage/PS/WAS
6-8 26-28
Murfreesboro, TNMunicipal WWTP
Rotary press 15 PS/WAS 0.8-1 12-14
Scarborough, MEMunicipal WWTP
Rotary press 1.4 Thickened PS/WAS
3 28
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Rotary Dewatering Features
• Low speed, low vibration, low shear• Uses less energy than centrifuges or BFPs• Modular• Small footprint• Minimal start-up and shutdown time• Minimal moving parts• Odors contained
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R&D Technologies
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EKG Technologies
• Electrokinetic Geosynthetics (EKG) Technology– Theory – Electro-osmotic principle
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Uses of EKG Technology
• Ashbrook Product– Anaerobically/Aerobically Digested
Sludge• Fresno• England
– Alternative to conventional dewatering
• Siemen’s Product– Secondary dewatering process– Alternative to sludge drying
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Siemen’s ELODE Technology
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Siemen’s ELODE Technology
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Siemen’s ELODE Technology
