How Dissolved Air Flotation Works: Micro-Bubble Generation
Micro-bubble physics, coagulation chemistry, and 25 years of engineering refinement — combined to consistently deliver 90–99% TSS removal.
What Is Dissolved Air Flotation?
Dissolved air flotation is a water clarification process. It uses millions of microscopic air bubbles to float contaminants to the surface of a clarification tank. These contaminants include suspended solids, fats, oils, and greases. They form a consolidated float layer, which is mechanically skimmed and removed.
The principle sounds simple. The engineering behind it is not. Bubble size, recycle ratio, contact time, coagulant chemistry, tank geometry, and skimmer design all matter. Together they decide whether a DAF system delivers the removal efficiency your discharge permit requires, or fails to meet it.
DAF Corp has spent 25 years perfecting every one of these variables. Our systems consistently achieve 90–99% TSS removal across food processing, dairy, municipal, oil and gas, and industrial applications — because we start with lab analysis of your actual wastewater before we design anything.
Request Lab AnalysisPerformance Specifications
- Flow Rate Range
- 5 – 11,000 GPM
- TSS Removal
- 90 – 99%
- Bubble Diameter
- 10 – 30 microns
- FOG Removal
- Up to 99%
- Hydraulic Loading
- Up to 4 GPM/ft²
- Recycle Ratio
- 10 – 30%
- Operating Pressure
- 60 – 90 PSI
- Materials
- 304 / 316 SS, Carbon Steel
Get Your Free Consultation
DAF Corporation works with food processors, municipalities, dairy operations, and industrial facilities to solve complex wastewater challenges. Our process begins with your water — not a catalog.
Book an AppointmentWhy Micro-Bubble Size Matters
The efficiency of a DAF system is directly determined by bubble size. Larger bubbles rise too fast to attach to fine particles. DAF Corp's pressurization and nozzle design produces bubbles in the 10–30 micron range — smaller than a human hair — creating the perfect buoyancy profile to lift even colloidal particles and emulsified oils that conventional clarifiers cannot capture.
Our proprietary recycle pressurization system dissolves air into a recycle stream at 60–90 PSI. When that stream is introduced into the flotation tank through precision release valves, the sudden pressure drop causes the dissolved air to form a cloud of billions of micro-bubbles per liter — a bubble density that maximizes particle-bubble contact across the full contact zone.
The DAF Process Explained
From influent wastewater to clarified effluent, a properly designed DAF system executes six distinct and interdependent treatment steps.
Influent Screening & Pre-Treatment
Raw wastewater first passes through a screen that removes large debris and protects downstream equipment. Depending on the application, equalization and pH adjustment may follow. These steps condition the wastewater for chemical treatment. Proper pre-treatment is foundational. Without it, coagulant chemistry cannot perform as designed.
Chemical Coagulation
Coagulant is dosed into the influent at a precisely controlled rate. We set that rate through laboratory jar testing. The coagulant destabilizes the electrostatic charge that keeps colloidal particles suspended. The particles can then begin forming larger aggregates. The right coagulant type and dosage is the single most important factor in DAF performance. That is why we never skip the lab analysis step.
Flocculation
The coagulated wastewater then enters a flocculation stage. Gentle, controlled mixing makes the destabilized particles collide and form larger, more buoyant floc. Mixing intensity and detention time are critical. Too aggressive, and the floc breaks apart. Too slow, and particles never reach the right size for bubble attachment. DAF Corp engineers size the flocculation zone for each application.
Micro-Bubble Injection & Contact Zone
Pressurized recycle water saturated with dissolved air is released through precision nozzles at the inlet of the flotation tank. The sudden pressure drop releases billions of 10–30 micron bubbles. These rise through the contact zone and attach to floc particles, making them buoyant. Contact zone geometry, recycle ratio, and bubble distribution determine how completely particles are captured before they reach the separation zone.
Flotation & Float Layer Formation
Bubble-particle aggregates rise to the surface of the flotation tank. There they form a consolidated float layer (sludge blanket) above the clarified water. A rotating flight system skims the float layer at a rate calibrated to your system's solids loading. This keeps the float layer dense and the clarified zone beneath it clean. Proper skimmer timing is critical to effluent quality.
Clarified Effluent Discharge
Clarified water exits through a submerged effluent launder at the outlet end of the tank. It is drawn from below the float layer to ensure the clearest possible effluent. The effluent can then proceed to polishing filtration, discharge, or water reuse, depending on your permit requirements. A portion is diverted back as recycle flow to the pressurization system. This completes the DAF cycle.
See How This Process Works for Your Facility
Every DAF system starts with a laboratory analysis of your specific wastewater. Send us a sample and we'll tell you exactly what your system needs — before you commit to anything.
DAF Technology Overview
Watch a complete walkthrough of dissolved air flotation technology — from influent to clarified effluent discharge.
Typical Removal Efficiency by Contaminant
Performance achieved with properly designed coagulant chemistry and optimized operating parameters. Results vary by wastewater composition — contact us for application-specific data.
| Contaminant Type | Industries Affected | Typical Removal | Best Case Removal |
|---|---|---|---|
| Total Suspended Solids (TSS) | All industries | 90–95% | 99% |
| Fats, Oils & Greases (FOG) | Food, dairy, meat, fish | 85–95% | 99% |
| Emulsified Oils | Oil & gas, metalworking | 80–92% | 97% |
| Biological Oxygen Demand (BOD) | Brewery, food, municipal | 40–70% | 80% |
| Algae | Municipal, aquaculture | 90–98% | 99% |
| Fibrous Solids | Paper & pulp, textile | 85–95% | 98% |
| Colloidal Particles | Industrial, municipal | 75–90% | 96% |
| Phosphorus (with chemical precipitation) | Municipal, food | 80–95% | 98% |
Frequently Asked Questions
Technical answers to the questions we hear most often from plant managers, engineers, and project owners evaluating dissolved air flotation.