In-Depth Breakdown: How Two-Stage CDFU Cyclonic Dissolved Air Flotation + KFM Active Media Filtration Stably Reduces Oil Content in Oil-Depot Draw-Off Water Below 10 mg/L
The draw-off water from heavy-fuel-oil storage tanks at power plants is a typical "hard nut" in industrial wastewater: it carries high oil and suspended-solids content, suffers from severe emulsification, looks black, and its treated effluent oil must be stably held below 10 mg/L. No single treatment method can cope. SINOKLE's process of "two-stage CDFU cyclonic dissolved air flotation + KFM active media filter" provides a systematic solution through a combination of "physical demulsification + deep filtration". This article breaks it down from three dimensions: water-quality characteristics, equipment mechanism, and process division of labor.
1. Know the opponent first: why is oil-depot draw-off water difficult?
The difficulty of oil-depot draw-off water concentrates on three features:
High oil content: oil exists mixed as floating oil, dispersed oil and emulsified oil. Gravity settling only removes floating oil and is essentially ineffective against dispersed and emulsified oil.
Severe emulsification: oil and water form a stable emulsion; oil droplets are wrapped in an interfacial film, so conventional demulsification hardly works. This is the core contradiction of "difficult-to-treat draw-off water".
High suspended solids, black water: large amounts of tank-bottom sediment and impurities mix in, increasing the treatment load and making sensory indicators hard to meet.
The industry control target for oil-depot draw-off water is effluent oil below 10 mg/L. Going from "black oil" to "clear water" requires a process that can truly tear apart the emulsion.
2. Core weapon: CDFU, the "three-in-one" of pure physical demulsification
CDFU (Cyclonic Dissolved Gas Flotation Unit) is a proprietary patented technology independently developed by SINOKLE, a new-generation, highly efficient, compact, enclosed and pressurized flotation technology with internationally advanced levels and pioneered domestically. Its design essence lies in organically combining three technologies:
Cyclonic centrifugal separation: creates a cyclonic centrifugal force field inside the enclosed chamber, using the oil-water density difference to strengthen oil-droplet coalescence and accelerate separation.
Micro-fine bubble generation: produces large numbers of tiny bubbles that act like countless small "grippers" adhering to oil-droplet surfaces, greatly improving the rise efficiency of oil droplets.
Dissolved air flotation: dissolves and releases air in an enclosed pressurized environment, releasing bubbles uniformly and efficiently to achieve rapid separation of oil, water and suspended solids.
Working in synergy, these three achieve efficient and rapid separation of foul oil, emulsified oil and suspended solids — and the entire process is pure physical demulsification, adding no chemicals at all. This is the fundamental difference from the traditional chemical-dosing flotation route.
3. Two-stage design: the wisdom of gradient division of labor
The "two-stage CDFU" in this process is not a simple series connection, but a gradient division of labor:
First-stage CDFU: bears the main treatment load, rapidly removes large amounts of floating oil and coarse suspended solids, reducing the burden on subsequent fine treatment.
Second-stage CDFU: performs fine separation of emulsified and finely dispersed oil, handing the hardest-to-break "bone" to specialized treatment.
The two stages work in synergy to ensure efficient treatment of "high-oil, high-suspended-solids, high-emulsification" water while avoiding the performance fluctuation caused by overload of a single unit. The separated foul oil enters a collection tank — because the whole process is pure physical separation, the oil is not contaminated by chemicals, giving high-quality recovered oil with real reuse value.
4. Last line of defense: the "bottom-line" logic of the KFM active media filter
After the two-stage CDFU, residual trace oil droplets and fine suspended solids are subject to the final deep filtration by the KFM active media filter. The deep interception capability of the active media locks the effluent oil content firmly below 10 mg/L. The KFM is periodically backwashed during operation; the backwash water enters the sludge tank for centralized treatment, ensuring the filter maintains high efficiency over the long term — this "periodic backwash" detail is precisely the safeguard mechanism for long-term stable compliance.
5. Comparison with the conventional route
| Comparison dimension | Simple oil separation / chemical DAF | Two-stage CDFU + KFM active media |
|---|---|---|
| Demulsification mechanism | Chemical dosing demulsification, or separator unable to break emulsified oil | Cyclonic + microbubble + DAF physical demulsification |
| Process design | Single-stage treatment, load-sensitive | Two-stage gradient separation + deep-filtration backup |
| Effluent compliance | Large fluctuation, unstable | Stable ≤ 10 mg/L |
| Chemical dependence | Continuous dosing, secondary pollution | Pure physical, zero chemicals |
| Oil recovery | Mixed with chemicals, hard to recover | High quality, reusable |
| Operation & maintenance | Complex chemical management | Enclosed pressurized, closed-loop backwash |
6. Summary
The two-stage CDFU is responsible for "physical demulsification + gradient separation", and the KFM for "deep filtration + backwash regeneration". The two chains interlock to stably control the effluent oil of oil-depot draw-off water below 10 mg/L. Pure physical, zero chemicals, stable compliance, and recoverable oil — this process provides a systematic solution for the treatment of heavy-fuel-oil storage-tank draw-off water that combines technical reliability, operational economy and resource-recovery value.
