A New Process Combining CDFU and KFM Technologies for Oilfield Produced Water Treatment

In the field of oilfield produced water treatment, SINOKLE Technology's CDFU (Cyclonic Dissolved Gas Flotation Unit) and the KFM (active filter media filter) can be integrated to form a highly efficient, purely physical new process. Targeting oilfield produced water with high oil content (50-1,500 ppm), high suspended solids (SS 50-500 mg/L) and complex water quality, it achieves full-process treatment from coarse separation to advanced purification, suitable for reinjection or discharge requirements.

New process flow

1. Primary treatment: CDFU cyclonic dissolved air flotation

Produced water mixed with dissolved-air water enters the CDFU unit, where cyclonic centrifugal force and ultrafine bubbles (D50 of about 25 um) rapidly collide with and adhere to oil droplets and suspended solids, forming floating scum that rises and is discharged. The treatment time is only 1-3 minutes, the single-stage oil removal efficiency is over 90%, emulsified oil removal exceeds 90%, and no chemicals are required.

2. Secondary treatment: KFM active filter media filtration

   CDFU The effluent (oil at or below 30 ppm, SS at or below 30 mg/L) enters the KFM filter, where the adsorption and filtration action of the silicate active filter media (negatively charged surface, molecular sieve structure) further removes residual oil and grease, suspended solids and fine particles. The graded media particle size design provides coarse filtration (Grade III) and fine filtration (Grade II); the effluent oil is at or below 6 ppm, SS at or below 2 mg/L, and the median particle size is at or below 1.5 um. The backwash cycle is 8-12 hours.

Fig. Oilfield produced water treatment process flow

3. Integrated system: skid-mounted design with fully automatic control (IoT + AI real-time monitoring); a single unit can treat more than 500 m3/h. After CDFU pre-deoiling, the produced water goes directly to the KFM, avoiding filter media clogging and improving overall stability.

This process draws on the experience of combining CDFUCDFU with walnut shell filters, but KFM, as an upgraded active filter media, provides higher filtration precision and durability, suitable for offshore platforms or onshore oilfields.

Advantages

- High efficiency: CDFU short residence time plus KFM high-precision filtration gives an overall COD removal rate of over 85%, far exceeding the 70-85% of conventional CFU or IGF (induced gas flotation). It adapts to high emulsified oil and high salinity, treating 3-8 times faster than conventional processes.

- Economy: purely physical with zero chemicals; the operating cost is as low as 0.375 CNY/ton, 35% lower than conventional processes; KFM filter media has a long service life (wear-resistant and contamination-resistant) and low maintenance cost.

- Environmental friendliness: no secondary pollution and no sludge production, compliant with the GB 8978-1996 standard; supports water reinjection, reduces fresh water consumption and promotes sustainable development.

- Compact and stable: occupies only 1/3 of the conventional footprint, operates fully enclosed, has strong shock resistance (adaptable to pH 3-10), and is suitable for space-constrained oilfield environments.

- Field application: for example, in a Changqing Oilfield case, a similar CDFUCDFU + KFM combination treated 20 m3/h of produced water; the effluent met the reinjection standard (oil at or below 10 ppm) with costs reduced by 20-30%.

Fig. Case site and inlet/outlet treatment results

This new process improves the efficiency of oilfield produced water treatment and promotes green oil and gas development, suitable for oilfields worldwide such as the Middle East or onshore projects in China.