SAF™ (Suspended Air® Flotation) by Heron Innovators uses an externally-generated bubble suspension with high air content. Each bubble is covered with a chemically active film which strongly attaches to the flocculated solids in the wastewater, achieving high rate and efficient flotation. DAF (Dissolved Air Flotation) uses high pressure to dissolve a small amount air in water with no chemically active agent, and depends on physical entrapment and a weak surface bond to float the flocculated solids.
SAF™ is re-writing the book on flotation technology, replacing DAF as the method of choice for removal of suspended solids from wastewater.
Here’s why:
1. SAF™ is smaller than DAF. Small equipment footprint is highly desirable, even necessary, in most applications. SAF™ flotation tanks are less than 20% as large as DAF tanks for the same treatment rate. This is because the SAF™ process operates at 10 times the hydraulic loading rate and 15 times the solids loading rate of DAF – 10 gpm per square foot hydraulic loading rate and 15 lb/hr per square foot solids flux. Two factors account for this:
- The volume fraction of air contained in the SAF™ air emulsion is 40%, 20 times the volume fraction of air in typical DAF recycle flow (see chart); and
- The chemically active film on the SAF™ air bubbles attaches much more strongly to flocculated wastewater particles than plain air bubbles.
2. SAF™ uses less power than DAF. Using a frothing agent in the process of generation of the Suspended Air® Emulsion radically reduces the power consumption per unit of air delivered to the flotation tank. One gpm of Suspended Air® Emulsion generated at approximately 20 psi contains as much air by weight as about 8.5 gpm of DAF recycle flow pressurized to 60 psi. Furthermore, because SAF™ flotation requires half (or less) as much air as DAF, a SAF™ can be just as effective as a DAF using only 2% of the power used by DAF for air generation.
3. SAF™ removes more solids than DAF. Each SAF™ bubble is a working bubble, with an electrically-charged film ready to attach and stick to oppositely-charged floc particles. SAF™ removes many more small size flocs than DAF could ever do.
4. SAF™ floated solids can be dewatered more easily than DAF solids. One of the most remarkable things about SAF™ flotation is the gelatin-like consistency of the floated solids. SAF™ floated solids, with firmly attached air bubbles entrained inside, appear “rubbery” as though high doses of polymer were added. This makes it possible to remove all free-draining water by simple gravity drainage on a Heron Innovators Model DWC slowly-moving thermoplastic chain belt.
5. SAF™ operation is more flexible than DAF. In virtually all industrial wastewater treatment applications, shutdowns of various durations are inevitable. SAF™ handles these with ease, but DAF always falters. Starting a SAF™ takes less than a minute of automatically timed “warmup” for the generator and NO operator attention is required. When a SAF™ stops, the floated solids all stay on top of the tank, ready to be scraped off during the next run period.
6. SAF™ is more cost-effective than DAF. In case after case, SAF™ installations have soundly trounced DAF in cost-effectiveness over the life cycle of the installation, with simple payback periods commonly 2 years or less.
SEE THE DIFFERENCE BETWEEN DAF AND SAF™ WHEN TREATING THE SAME WASTEWATER:
