How SAF Works
SAF floated this from vegetable processing
wastewater - solids are 21% by weight.
Two Model F200 SAF Generators
Model CF125 Flotation Tank - part of skid-
mounted system at Kendall-Jackson
Santa Rosa, CA.
If you have an application for flotation... Have a look at Suspended Air Flotation (SAF) by Heron Innovators.
Bubbles rise...but solids suspended in water generally dont. In flotation treatment, the trick is to make the suspended solids ride the bubbles to the surface where they can be skimmed off, leaving clarified water underneath to be discharged. The trick is mostly in the bubbles.
There are bubbles...
All of these methods have some things in common:
- made by chopping large bubbles into fine bubbles with a spinning impeller (Induced Air Flotation or IAF)
- made by dissolving air in water under pressure, then releasing the pressure so the air comes out of solution as fine bubbles (Dissolved Air Flotation or DAF)
- made by inducing a vacuum near a spinning impeller, causing cavitation and releasing a string of fine bubbles
- made by a variety of other methods.
- The solids are only weakly attached to the bubbles, if they are attached at all. Success depends on being able to physically entrap the bubbles within solid masses. Many bubbles never see a solid to float and are wasted.
- The bubble generating machinery is power-hungry, runs at high speed with close mechanical tolerances, and is costly to buy and especially costly to repair.
- Each square foot of flotation area is limited to a maximum of 2 - 3 gallons per minute of wastewater, and 1 - 2 pounds per hour of suspended solids (dry weight). Failure is assured if these limits are exceeded.
...and then there are BUBBLES! Suspended Air® Emulsion, 40% air by volume in micron-size bubbles with a chemically active film, takes flotation treatment a quantum leap beyond anything available on the market today. These bubbles know all the tricks.
Every SAF bubble is a working bubble. Each coated suspended bubble binds electrostatically with polymer molecules of opposite charge on the flocculated solids, forming a much stronger bond than is possible with a plain air bubble. Much less air is necessary to float solids with SAF. Experience with many wastewaters has shown that with SAF, an air-to-solids percentage (weight to weight) of 0.5% is sufficient for treatment for solids concentrations up to 2,000 mg/L, compared with a minimum requirement of 2% for competing technologies, rising to as much as 15% for applications with suspended solids concentrations 2,000 mg/L and higher. This translates directly into a better and better footprint advantage for SAF for applications with higher and higher solids concentrations.
One of the most remarkable things about SAF flotation is the gelatin-like consistency of the floated solids. Typically, solids floated by other technologies are sloppy and require additional high doses of polymer to be dewatered further. In contrast, SAF floated solids, with air bubbles firmly attached inside, appear rubbery as though high doses of polymer were added, and dewater easily by simple gravity drainage. These solids will not sink during periods when the flotation process is not operating, allowing the process to re-start automatically. See video for comparison.
SAF is versatile and cost-effective. Suspended Air® Emulsion generators operate at a modest 20 - 25 psi pressure. A DAF pressurizes the recycle flow to 60 - 80 psi. Suspended Air® Emulsion generators use standard, easily maintained components such as low-speed gear pumps. Others use specialized, high speed pumps which are expensive to rebuild. The SAF process runs automatically, saving operating labor.
Although SAF requires an additional chemical, it is a nontoxic, easily-metered liquid product costing less than $0.03 per thousand gallons treated. The chemical cost is typically less than the cost of additional power to run competing systems.
SAF can rescue an overloaded flotation process, saving capital dollars and installation time. Complete SAF systems cost less than competing systems, and fit in much less space.
Our bubbles welcome your wastewater! For each candidate application type, Heron Innovators engineers perform bench scale treatability and flotation testing to establish the correct chemical treatment program and select the frothing agent to be used to produce the Suspended Air® Emulsion. The results of bench scale testing are immediately applicable to the full scale process. There is no scale-up problem because the flocculation and flotation processes all operate on a micro physical scale much smaller than the bench testing units. See video for bench scale flotation test demonstration using ferric hydroxide precipitate.