The "Bubble Magic" of Wastewater Treatment: Demystifying Dissolved Gas Flotation Technology

In industrial wastewater treatment, and especially in the treatment of oily wastewater, there is an efficient and remarkable physical purification technology --dissolved air flotation (DAF). If a sedimentation tank purifies water by making solids "sink down", then flotation achieves the separation of clear water from turbidity by making them "float up".

This article takes a deep look at the working principle of flotation technology, and how SINOKLE uses its innovativeCDFUcyclonic dissolved gas flotation technologyto take this process to its limit.

1. What Is Flotation Technology?

Flotation technology involves introducing large numbers of highly dispersedmicro-bubblesinto the water to be treated, so that they act as carriers and adhere to suspended particles in the water (such as oil droplets or flocs). These bubble-laden particles form flocs with an overall density lower than water, and under buoyancy they rise to the surface to form scum, thereby achieving solid-liquid and liquid-liquid separation.

The flotation process generally involves three core stages:

1. Bubble generation: a specific device creates large numbers of micron-scale bubbles.

2. Adhesion between bubbles and suspended matter: this is the most critical step of flotation, in which bubbles effectively collide and "stick" to pollutants in the water.

3. Separation and rising: the flocs carry the pollutants up to the liquid surface, where they form scum that is then skimmed off.

2. The Secret of Adhesion: Why Do Particles "Fall in Love" with Bubbles?

Bubbles can capture pollutants mainly thanks to the physics ofwettabilityandinterfacial energy.

• Hydrophobic substances: substances that "dislike water", such as oil droplets (contact angle $\theta > 90^\circ$), are more likely to adhere to bubbles; after adhesion, the total interfacial energy of the system decreases and the structure becomes more stable.

• Characteristics of micro-nano bubbles: research by SINOKLE shows that micro-nano bubble surfaces are rich in negative charge (high zeta potential), and that when they burst they generate instantaneous local high temperature and pressure, releasing strongly oxidizing hydroxyl radicals ($\cdot$OH); this not only aids physical separation but also helps degrade organic pollutants in the water.

3. Size Determines Efficiency: Are Smaller Bubbles Always Better?

In the flotation process,the higher the bubble concentration and the smaller the bubble size, the higher the removal efficiency.

• Collision probability: reducing bubble size significantly increases the bubble concentration per unit volume, thereby greatly increasing the probability of collision between bubbles and oil droplets.

• Demulsification capability: smaller bubbles have stronger surface tension and can more easily tear open the oil film, achieving "physical demulsification", which is crucial for treating highly emulsified wastewater.

SINOKLE's CDFUtechnology produces bubbles only5-30 micronsin diameter (with excellent uniformity), far smaller than the 100-500 micron bubbles produced by conventional flotation.

4. SINOKLE's Breakthrough Technology:CDFUCyclonic Dissolved Gas Flotation

Conventional dissolved gas flotation often suffers from long residence times (15-40 minutes), a large footprint and the need to dose large amounts of chemical agents. Through its independently developed patented product --CDFU(Cyclonic Dissolved gas Flotation Unit)SINOKLE creatively combinescyclonic centrifugal separationanddissolved gas flotationinto one.

CDFU's unique working process:

1. Efficient gas dissolution: a specially structured multi-stage impeller dissolved gas pump produces micro- and nano-scale bubbles through high-pressure, high-speed shearing.

2. Strong cyclonic collision: after the wastewater is mixed with the dissolved gas water, it enters thetangentiallycyclone separation zone along the tank wall. Under the powerful centrifugal force, the water flow accelerates in its rotation, greatly increasing the probability of collision between bubbles and oil droplets.

3. Ultra-fast separation: under the cyclonic action, flocs carrying oil droplets rapidly gather toward the center and rise, while heavy suspended solids (such as sand) are flung toward the wall and discharged downward.

5. CDFUThe "Dimensionality Reduction Strike" Against Conventional Technology

Compared with conventional processes, SINOKLE's dissolved gas flotation technology offers clear advantages:

• Purely physical demulsification: no chemicals are needed, or only a minimal amount, eliminating the generation of oily sludge (hazardous waste).

• Extremely compact: treatment residence time is only1-5 minutes(1/8-1/3 of conventional processes), and the footprint is only10%-20%

• High efficiency: single-stage oil removal efficiency exceeds90%, and the oil content of the effluent can be reduced to below 10 mg/L or even lower.

Conclusion

Dissolved gas flotation technology is evolving from conventional "passive flotation" toward efficient, intelligent and green "cyclonic active separation". Through precise control of micro-nano bubbles and the cyclonic field, SINOKLE not only solves the challenge of oily wastewater treatment but also, throughcomplete recovery of waste oil, achieves a win-win of environmental protection and economic benefit. This science hidden deep within "bubbles" is contributing technological strength to clean waters and green mountains around the world.