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A New Pretreatment Technology
A New Pretreatment Technology Case Study:
Suspended Air® Flotation
Simmons Foods in Siloam Springs, Arkansas
Andy Brashear, Area Environmental Manager, Simmons Foods
- SAF® = Suspended Air® Floatation
- Uses froth made from an anionic surfactant, water, and air instead of
air bubbles for flotation. - One gallon of froth = 0.8 ml soap =
- 0.6 gal water and 0.4 gal (0.05ft3) air.
- Bubbles have an anionic charge so are attracted to the floc.
- Increases flotation rate so units can float 20-40 lbs (spec’ed at 30lbs)
of solids per square foot per hour (lbs/hr/ft2). - Decreases the size of the unit vs. DAF; no lamella style plates
- Less Maintenance
- More Highly Dewatered Skimmed Solids
- Better Results – Water Clarity
What is SAF®?
- Installed two new units in Siloam Springs*One primary
- One Secondary
- Installed one new unit in Van Buren
- Primary treatment.
- Converted two existing DAF units to SAFs in Southwest City.
- One primary
- One Secondary
Simmons has gone SAF®
New SAF® Units for Siloam Springs.
Siloam Springs SAF® Effluent
- ClearFloater Model CF250
- 35ft2 Float Cell – rated for 700 gpm @ 3000Mg/L TSS
- 350 gpm – current actual flow
- From Secondary SAF
- Influent flow contained 3000 mg/L MLSS.
Froth Generator
Model F-200 Froth Generator Shown
Froth Flow Meter & Froth
Froth Generation Summary
- Tote of Anionic Surfactant.
- Froth Generator.
- Surfactant metering pump.
- Water line.
- Froth pump.
- Holding tank.
- Flow meter.
- Flow control valve.
- Floc Mixer – Active Mixing Chamber.
DAF to SAF Conversion:
Froth Generator & Floc Mixer
Floc Mixer – replaces previous connection from floc tube to DAF inlet flange
Secondary SAF®
-
Secondary DAF
-
216 ft2 of surface area.
-
At 1.8 MGD before SAF conversion it could handle 1500 mg/L influent suspended solids.
-
It now handles 3500 mg/L with no carry over Average effluent TSS = 15 mg/L.
-
Specified Maximum Flow @ Current Loading ~3500 gpm
Secondary SAF® Effluent
Secondary DAF to SAF® Cost Comparison
Secondary DAF |
| 60 HP Recirculation Pump $31,367/yr @ $0.08/KWHR |
| N/A |
| Coagulant Consumption: $350,000/yr |
| Cationic Polymer Consumption: 120Lbs/Day; $87,600/yr |
| Total O&M Costs/yr: $468,967 |
SAF® Conversion |
| Equivalent – 10HP; $5,230/yr @ $0.08/KWHR |
| Frothing Agent Consumption @ 25 GPM Output; (1)-tote/6wks; $38,780/yr |
| Coagulant Consumption: $140,000 |
| Cationic Polymer Consumption: 60Lbs/Day; $43,800/yr |
| Total O&M Costs/yr: $227,810 |
| Net Savings/yr: $241,157 |
*Difficult to quantify savings associated with directly reclaiming water vs requiring additional treatment
Primary DAF to SAF® Conversion
-
Converted Primary DAF.
-
It was maxed out at 1250 gpm and 2000 – 2500 mg/L influent solids.
-
It now treats an additional 700 gpm.
-
Specified to treat a maximum 2400 gpm.
-
Cost effective way to increase capacity.
Primary DAF to SAF® Cost Comparison
Primary DAF |
|
40 HP Recirculation Pump $20,920/yr @ $0.08/KWHR |
| N/A |
|
Organic Coagulant Consumption: 700Lbs/Day; $130,000/yr |
|
Cationic Polymer Consumption: 120Lbs/Day; $87,600/yr |
|
Anionic Polymer Consumption: 110Lbs/Day; $50,000/yr |
|
Total O&M Costs/yr: $288,540 |
SAF® Conversion |
| Equivalent – 10HP; $5,230/yr @ $0.08/KWHR |
| Frothing Agent Consumption @ 25 GPM Output; (1)-tote/6wks; $38,780/yr |
| Organic Coagulant Consumption: 350Lbs/Day; $65,000/yr |
| Cationic Polymer Consumption: 120Lbs/Day; $87,600/yr |
| Anionic Polymer Consumption: 0-Lbs/Day; $0.00/yr |
| Total O&M Costs/yr: $196,610 |
| Net Savings/yr: $91,930 |
Conclusions
-
SAF is mechanically simpler than a DAF:
-
Removes recirculation pump, header, compressor, and air lines.
(No more air lines plugging in header which would also cause packing to blow out on recirc pump.) -
No requirement for lamella style plates
-
Less maintenance
-
It’s operator friendly.
-
It’s 6 times more efficient than a DAF (20-40 lbs/hr/ft2 vs. 5 lbs/hr/ft2).
-
You can adjust the froth flow (i.e. floatation air) to the loading.
-
Feed less chemical (less polymer mixing).
-
Better results
-
Thicker Solids
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