How CDFU Plus KFM Handles Oily Wastewater at Heavy Oil Power Stations

A heavy oil power station is an energy supply facility first and a wastewater generator second, but the second role is unavoidable. Tank farm drainage, floor washing water, equipment maintenance drainage and the occasional spill all end up in the same sump, and the resulting stream is heavy on oil and grease, heavy on emulsified oil in particular, variable in composition and full of suspended solids, colloids, dissolved organics and trace heavy metals.

Why conventional separation struggles here

Oil separation plus coagulating sedimentation is a reasonable train for light oil on a steady feed. Against heavy oil and emulsified oil it is neither stable nor efficient, and the effluent rarely meets tightening discharge limits or reuse requirements. The plant then carries environmental exposure while wasting water it could reuse.

A two-stage answer built around two unit operations

The SINOKLE environmental technology team responded with an integrated route that pairs CDFU cyclonic dissolved-air flotation with KFM active filter media filtration, covering pretreatment and advanced purification in one train. The logic is sequential: take the bulk load out fast, then polish what remains.

Stage one: CDFU cyclonic dissolved-air flotation

CDFU is one of the SINOKLE core patented technologies and combines cyclone separation with dissolved-air flotation. Four things happen in order. The influent first enters the cyclone section, where a strong centrifugal field throws out most of the free oil and the denser suspended solids, cutting the load on the flotation section. The pre-separated water then enters the dissolved-air section, where a high-efficiency air system generates dense, uniform micro-nano bubbles. After chemical conditioning such as demulsification and coagulation, those bubbles collide with and attach to fine oil droplets, emulsified oil and colloidal matter, forming bubble-particle complexes. Buoyancy lifts the complexes to the surface as a stable scum layer that a scraper removes on a cycle.

The separation efficiency is well above that of conventional air flotation, and the gain is largest exactly where it is needed: breaking and removing hard-to-treat emulsified oil. The unit is compact, has a small footprint, runs at a high degree of automation, and tolerates shock loads, which suits a power station whose water quality and volume swing widely. After this stage, most floating oil, dispersed oil and emulsified oil is gone and both effluent oil content and suspended solids are sharply reduced.

Stage two: KFM active filter media

To reach a higher standard, whether for reuse as circulating cooling water make-up and plant landscaping or for the strictest discharge limits, a KFM active filter media filter follows as the polishing unit. The media is a composite that has undergone special process modification, and it brings several surface characteristics at once.

• Fine physical interception. The bed formed by the media particles traps the trace fine suspended solids and colloidal matter left in the CDFU effluent.
• Adsorption. Abundant pore structures and active sites take up dissolved organics, some heavy metal ions and residual trace oil, pushing removal rates for COD, BOD and specific pollutants higher.
• Hydrophilic and oleophobic behaviour. The modified surface passes water and repels oil, so the bed is not easily blinded by oil contamination; service life extends and backwash regeneration stays effective.
• Simple upkeep. Automated control triggers backwashing on pressure difference or on a time cycle, which keeps maintenance and management straightforward.

The effluent leaves clear and transparent, and key indicators such as petroleum-based substances, suspended solids and COD stabilise at or beyond the Grade I standard of the Integrated Wastewater Discharge Standard (GB 8978-1996) or the applicable reuse water standards.

What the operating data show

The combined process has been applied in several new-build and retrofit projects for oily wastewater at heavy oil power stations. Overall removal reaches more than 99.5% for petroleum-based substances and more than 98% for suspended solids, with effluent petroleum-based concentration holding below 3 mg/L and at times below 1 mg/L. Energy consumption is low because the system is highly integrated, and chemical dosage is modest because flotation does the heavy lifting. KFM media last far longer than ordinary filter media between replacements.

The economic case is straightforward. Treated water is reused where the plant needs it, which saves fresh water and lowers operating cost. Compliance risk disappears rather than being managed, which matters more than the line item suggests when a station sits inside an air-quality control zone and every discharge is watched.

Where the train fits best

This configuration suits sites with heavy oil, stable emulsification and fluctuating load: heavy oil power stations obviously, but also tank farms and maintenance workshops with similar drainage. It is less compelling where the oil is light and free, because a simpler separator already meets the limit and the second stage adds cost without adding compliance. Matching the train to the oil state is the whole design decision; everything else is sizing, and sizing done well is what separates a plant that runs quietly from one that is always chasing a new bottleneck.