Conventional DAF vs. CDFU Cyclonic Dissolved Gas Flotation: A Parameter Comparison
Flotation is a mainstay process for oily wastewater treatment, yet the gap between one "flotation" system and another can be enormous. Conventional dissolved air flotation (DAF) has been in service for decades but carries many pain points: long retention time, large footprint, high chemical consumption, and unstable oil-removal efficiency. The CDFU (Cyclonic Dissolved Gas Flotation Unit) independently developed by SINOKLE offers a different answer through patented technology. Rather than vague narrative, here is a direct comparison.
Product Overview
The CDFU (Cyclonic Dissolved Gas Flotation Unit) cyclonic dissolved air flotation device is a new-generation, high-efficiency, compact, sealed, and pressurized flotation system built on SINOKLE's patented technology and first of its kind in China. It organically combines cyclonic centrifugal separation, micro-bubble generation, and dissolved air flotation to achieve fast, efficient separation of waste oil, emulsified oil, and suspended solids.
Core working principle: micro-bubbles (5–30 µm) mix with the wastewater and enter a cyclonic flow; centrifugal force drives the bubbles and oil droplets toward the center, where they coalesce into scum and are discharged with nitrogen from the oil outlet, while cleaned water exits from the bottom outlet.
Head-to-Head: Conventional DAF vs. CDFU
| Aspect | Conventional DAF | CDFU |
|---|---|---|
| Retention time | 15–40 min | < 5 min (only 1/8 to 1/3 of conventional) |
| Single-stage oil removal | 60%–85% | > 90% |
| Single-stage suspended-solids removal | 50%–70% | > 80% |
| Removable particle size | > 5 µm | < 3 µm (clear advantage for fine particles and emulsified oil) |
| Bubble quality | 5–100 µm, average uniformity | 5–30 µm, good uniformity |
| Operation & sludge discharge | Manual, open operation, mechanical scraper | Automatic, enclosed, pressure-driven oil/sludge discharge, no mechanical power, no on-site oil-gas leakage |
| Structure & footprint | Reinforced-concrete, civil works, long lead time | Pressure-vessel skid, factory-prefabricated, only 1/3 the footprint |
| Energy & chemical use | — | Energy only 10% of conventional IGF; gas 1%–3% of throughput; low chemical/sludge; handles 10%–120% flow variation |
Validated by Cases
Oil-depot draw-off water: CDFU + KHC coalescing oil remover, a purely physical process with fully enclosed operation and off-gas to the oil-gas recovery system, recovers high-quality light oil for direct reuse; widely used in tank farms of CNPC, Sinopec, and China Power.
WWTP flotation upgrade: Two-stage CDFU scheme — first stage purely physical demulsification with oil recovery and no hazardous waste; second stage only a small dose of PAC; effluent oil and suspended solids both ≤ 20 mg/L.
Oily fire-fighting wastewater: CDFU + MACT combination, oil removal ≥ 90%, withstands 10%–120% flow fluctuation, providing skid-mounted rapid emergency treatment.
Fracturing flowback fluid: CDOF gel-breaking and viscosity reduction + CDFU high-efficiency oil/solids removal + fine filtration; skid equipment can be vehicle-mounted for on-site operation; filtered water meets reuse standards.
Pharmaceutical wastewater: Front-end CDFU with 5–20 µm ultra-fine bubbles achieves SS removal > 95% and extends catalyst life by > 30%; a pilot at a large Inner Mongolia pharmaceutical group succeeded.
Conclusion
Behind the comparison lies a divergence of two technological routes: conventional flotation seeks balance in "big tanks + long retention", while CDFU re-engineers efficiency with cyclonic flow and micro-bubbles. For new projects, skid-mounting means faster construction; for retrofits, it means a smaller footprint; for operators, it means lower chemical use and easier maintenance. This comparison is worth keeping.
