From 20,000 ppm Inlet Oil to Discharge Quality: CDFU Units Across Four Deployments

High-concentration oily wastewater is the stress test of any oil-water separation technology: the oil arrives in bulk, droplet sizes span orders of magnitude, and the feed refuses to stay constant. Developed by SINOKLE, the CDFU (Cyclonic Dissolved Gas Flotation Unit) was engineered for exactly this regime, and its record across refinery, oilfield and power generation duty shows how the design performs when the water is at its worst.

One unit, three separation mechanisms

CDFU technology merges centrifugal separation, dissolved gas flotation and ultra-fine bubble generation into a single integrated treatment unit. The three mechanisms are complementary rather than redundant. Centrifugal force flings free and dispersed oil out of the flow path first. Dissolved gas released as micro and nano bubbles then attaches to the finer droplets and suspended solids that centrifugation cannot capture, and the synergy of swirl plus bubbles removes oil and suspended solids efficiently in one pass.

The measurable consequences follow from the physics. Single-stage oil removal efficiency runs above 90%, and the minimum removable particle size extends down below 2 um - territory where gravity equipment and ordinary flotation simply stop working. Retention time is only 1-5 minutes, and the footprint comes to roughly 10% of what conventional dissolved air flotation requires for the same duty.

Designed to keep running

Reliability in oily service often fails at the internals: screens blind, plates foul, packing plugs. The CDFU carries no filter screens, coalescing plates or similar internals inside the vessel, so there is little to clog and long-term stable operation follows. Adaptability extends across hydraulic load swings, oil viscosity differences and oil specific gravity variation - the three variables that most often destabilize oily water systems in practice.

Refinery duty: Dushanzi and Cangzhou

Desalter wastewater is among the oiliest regular streams a refinery produces. At the PetroChina Dushanzi Petrochemical desalter wastewater treatment project, commissioned in 2019, a unit rated at 100 m3/h takes inlet oil of 2000 ppm or less and delivers effluent oil of 10 ppm or less. That single-stage performance across a two-orders-of-magnitude cut illustrates what combined centrifugal and bubble separation achieves on emulsified refinery feed.

At Sinopec Cangzhou Refining and Chemical, the desalter wastewater duty is heavier: capacity of 50 m3/h against inlet oil of 20,000 ppm or less, with average effluent oil of 50 ppm or less. Tenfold concentration differences between the two refineries, handled by the same technology, demonstrate the tolerance to feed variation that the design was built around.

Oilfield duty: Xinjiang and Congo

An oilfield project in Xinjiang, started in 2023, applies the unit to desalter and tank-farm black water at 150 m3/h. Inlet oil reaches 20,000 ppm or less, and effluent oil is held at 150 ppm or less - a level suitable for the downstream treatment stages that follow. Black water of this kind carries wax and viscous crude fractions that defeat standard equipment, making the result a useful reference for heavy-oil operations.

The most demanding duty to date is in Africa: the Congo (Brazzaville) Jiayu oilfield produced water and fracturing flowback deep treatment project, running since 2024 at 4,600 m3/d. The plant meets strict sea discharge standards, where limits are tighter than most onshore requirements and compliance failures carry visible consequences.

What the case spread proves about the design

Taken together, the four projects form a controlled experiment in tolerance. Feed oil concentrations differ by a factor of ten between Dushanzi and Cangzhou, yet both meet their targets with the same equipment family. Water sources range from refinery desalter drainage to tank-farm black water to produced water and fracturing flowback, each with distinct droplet distributions and solids profiles. Geographic and climatic spread runs from northwestern China to equatorial Africa, where shipping spares and site services are slower and reliability matters more. A technology only earns the adjective stable when it survives that spread, and the deployment list above is the practical evidence that the three-mechanism design holds its performance across all of it.

What operators gain beyond the effluent number

• Purely physical separation. No chemical dosing enters the process, and the recovered oil is of high enough quality to be reused directly.
• No secondary pollution. Oily sludge, classed as hazardous waste, is not generated, so disposal liability disappears at the source.
• Economic return. Oil recovery creates value and O&M costs stay low across the service life.
• Rapid deployment. The skid-mounted design supports fast installation and online implementation without prolonged plant shutdown.

Where the technology is heading

From petrochemical desalters to offshore-discharge oilfields and heavy-oil power generation, the applied record now covers the main high-concentration oily water scenarios industry faces. As discharge requirements tighten, the combination of compact footprint, chemical-free operation and tolerance to feed swings positions CDFU as practical infrastructure for the green transition of industrial sites - and as a reminder that the hardest streams often respond best to the right physics rather than more chemistry.