Cyclonic Dissolved Gas Flotation (CDFU) vs. Conventional Dissolved Gas Flotation: Technical Innovation and Advantages

In oily wastewater treatment, cyclonic dissolved gas flotation (Cyclonic Dissolved Gas Flotation Unit, abbreviated as CDFU) is a new-generation flotation technology that comprehensively surpasses conventional dissolved gas flotation through multiple technology integration. This article analyzes in depth the technical differences between the two and the CDFU breakthrough advantages.

Innovation in Technical Principles

CDFU ingeniously integrates cyclonic centrifugal separation, ultra-fine bubble generation and dissolved gas flotation into a unique "triple synergy". Its core lies in a tangential inlet at a specific angle, which significantly increases swirl velocity and centrifugal acceleration to form a highly stable swirling flow field. This flow field strengthens the interaction between micro-bubbles and oil droplets and promotes their efficient coalescence toward the centre of the field, thereby improving flotation efficiency.

Conventional dissolved gas flotation relies on a single flotation principle, with bubble diameters typically 30-100 μm and only moderate uniformity, whereas CDFU generates bubbles as fine as 5-30 μm (median ≤20 μm); this ultra-fine bubble population offers larger specific surface area and stronger adsorption capacity.

Figure. Ultra-fine nano-bubble effect

Breakthrough in Structural Design

CDFU adopts an innovative dual flotation zone design: wastewater entering tangentially generates stronger centrifugal force and acceleration, favouring the aggregation of bubbles and oil droplets in the middle and improving flotation performance. This design offers higher space utilization and a more compact structure.

The conical bottom desanding design means that, under centrifugal force, particles are progressively thrown against the inner wall of the central cylinder and slide down into the conical zone, remaining in a swirling state and greatly reducing the likelihood of sand deposition. Conventional dissolved gas flotation is mostly an open reinforced concrete structure, whereas CDFU uses skid-mounted pressure vessel equipment, better suited to space-constrained operating environments.

Figure. A refinery wastewater treatment site — two-stage CDFU cyclonic dissolved gas flotation

Leap in Performance Parameters

On key performance indicators, CDFU shows significant advantages:

· Treatment efficiency: single-stage oil removal >90%, far exceeding the 60%-85% of conventional dissolved gas flotation; suspended solids removal >80%, 10-30 percentage points higher than conventional processes

· Treatment precision: stable removal of oil droplets smaller than 3 μm (removal >80%), whereas conventional processes can only handle particles >5 μm

· Retention time: under 5 minutes, only 1/8-1/3 of conventional dissolved gas flotation (15-40 minutes), greatly increasing treatment capacity

· Adaptability: stable performance across a flow fluctuation range of 10%-120%, coping with drastic changes in oilfield water quality

Advantages in Operation and Maintenance

CDFU uses a fully enclosed automatic control system, achieving truly intelligent management compared with the manual, open operation of conventional flotation. Its pressure-driven oil and sludge discharge requires no mechanical power, eliminating the frequent failures of conventional scraper systems.

Outstanding energy performance:

· Gas consumption is only 2%-3% of the influent volume, one-tenth of conventional processes

· System pressure drop ≤0.05 MPa, energy consumption reduced by 40%

· Oil discharge ratio 0.5%-2%, only one-fifth of conventional processes

More importantly, CDFU requires no chemicals throughout, the waste oil can be recovered, and the hazardous sludge caused by PAC/PAM addition in conventional processes is completely avoided, cutting sludge by 90% — truly green treatment.

Expansion of Application Scenarios

CDFU is particularly suited to difficult emulsified-oil wastewater (e.g. influent oil ≤5,000 mg/L) and shows unique value in harsh locations such as oilfields and offshore platforms. Field test data show that even with influent oil content as high as 3,464.35 mg/L, CDFU still achieved 94.98% removal, with effluent oil of only 173.83 mg/L.

Because of its large footprint and unstable efficiency, conventional dissolved gas flotation is mainly limited to onshore sites where space is not critical. In contrast, CDFU compact design (one-third the conventional footprint) and excellent shock resistance make it the first choice for offshore platforms and difficult industrial wastewater.

Technology Outlook

CDFU through innovations such as swirl field intensification and ultra-fine bubble generation, has moved flotation from "rough treatment" to "precision separation". Its purely physical separation perfectly matches current environmental requirements, while its intelligent operating mode responds to the O&M needs of the Industry 4.0 era. As oil and gas extraction moves toward deep water and unconventional resources, CDFU will become one of the core technologies for meeting complex water quality challenges.

Looking ahead, through combined application with catalytic ozonation (CDOF) and active filter media filtration (KFM), CDFU will play an even more critical role in zero-liquid-discharge systems, driving the entire water treatment industry toward higher efficiency, greener operation and greater intelligence.