Analysis of CDFU Cyclonic Dissolved Air Flotation Performance in Oily Wastewater Treatment
The main pollutants in oily wastewater include floating oil, emulsified oil, dissolved oil and suspended particulate matter. If discharged directly, they can easily cause water eutrophication, damage to the ecological chain and pipeline blockage. Traditional treatment technologies (such as gravity separation, standalone dissolved air flotation and biological treatment) have limitations including low oil removal efficiency (especially for emulsified and dissolved oil), weak resistance to shock loading and long treatment cycles.
CDFU (Cyclonic Dissolved Gas Flotation Unit) process, a dissolved air flotation technology based on swirl intensification, achieves efficient oil separation through the synergistic action of cyclonic shear and fine-bubble adsorption, providing an efficient solution for oily wastewater treatment.
1. Introduction to the Cyclonic Dissolved Air Flotation Unit
Pre-treated wastewater enters the cyclonic dissolved air flotation tank, where pressurised dissolved air generates fine bubbles 5-30 um in diameter. The centrifugal force produced by the cyclonic device intensifies the collision and adsorption between oil droplets and bubbles, forming gas-solid-liquid complexes with a density lower than water. Under the combined action of cyclonic shear and buoyancy, these complexes quickly rise to the surface and are scraped off, achieving efficient separation of oil from water.
2. CDFU Process Treatment Performance Analysis
(1) Oil removal performance
CDFU process achieves an overall oil removal rate of 90%-95%
(2) COD removal performance
CDFU process achieves a total COD removal rate of 30%-50%; by optimising the swirl intensity and dissolved-air parameters, the COD removal rate can be pushed even higher.
(3) Synergistic removal of suspended solids and other pollutants
SS removal exceeds 90%; at the same time, the CDFU process also removes characteristic pollutants such as petroleum hydrocarbons and volatile phenols effectively, demonstrating its broad-spectrum purification capability for complex oily wastewater.
3. Optimisation of Key Influencing Factors
(1) Cyclonic dissolved air flotation conditions
- By adjusting the dissolved-air pressure and dissolved-air time, the bubble diameter distribution can be changed; optimising the cyclonic rotation speed strengthens droplet collision and coalescence, giving higher bubble adsorption efficiency;
- Combining the process with chemical dosing (such as PAC flocculant) strengthens the binding efficiency between flocs and bubbles, further improving cyclonic flotation separation;
- Integrating an intelligent control system with online monitoring (such as oil content and COD sensors) allows real-time adjustment of process parameters.
CDFU applied in a refinery wastewater treatment case
4. Advantages Compared with Traditional Processes
Compared with conventional dissolved air flotation (70%-85% oil removal) and biological treatment (cycle > 24 h), the CDFU process offers the following advantages:
(1) High oil removal efficiency: the synergy of cyclonic shear and bubble adsorption achieves efficient separation of emulsified and floating oil, with oil removal of 90%-95%;
(2) Strong shock-load resistance: it tolerates influent oil content fluctuations of about 30% and maintains stable effluent quality;
(3) Short treatment cycle: only 1/5-1/10 that of conventional biological treatment;
5. Conclusion
In summary, the CDFU cyclonic dissolved air flotation process offers efficient, stable and low-cost advantages in oily wastewater treatment and can provide technical support for industrial wastewater discharge compliance.
