Thermal Power Plant Oily Water: Two-Stage CDFU plus KFM Filtration in a Sierra Leone Case

A thermal power station is an energy conversion plant, and the water side of that conversion is easy to overlook until it becomes a compliance issue. Daily operation produces a steady trickle of oily wastewater from four directions: wash water from fuel oil tank farms, flushing water from oil pump and pipeline leakage, oily drainage from the coal handling system, and water from transformers and auxiliary areas.

Each stream looks manageable on its own. Collected together they form a wastewater whose composition is complex and highly variable, and whose oil content, though usually only a few hundred mg/L, is enough to place a serious shock load on the downstream treatment plant when it is handled badly. The consequences are the usual trio: unstable operation, non-compliant effluent, and an operating cost that climbs as the plant tries to compensate with chemistry.

Why the Settling Tank Route Runs Out of Room

Most thermal power plants treat this water with an oil separation tank followed by gravity settling. The approach is cheap to specify and easy to understand, and it has two structural weaknesses. It needs long retention times, which means a large footprint in a plant where land is already allocated. And it performs very poorly on fine oil droplets and emulsified oil, which is precisely the fraction that dominates after a pump seal has been leaking for a month.

To stay compliant, plants then dose large amounts of chemicals to aid demulsification. That raises operating cost and generates large quantities of oily sludge classified as hazardous waste, which converts a water problem into a waste problem with a manifest attached. The tank also has to be cleaned periodically by hand, which is the kind of maintenance task that gets deferred until it becomes an incident.

A Purely Physical Train: Two-Stage CDFU plus KFM

The SINOKLE solution for thermal power plants is built around a core process of two-stage CDFU followed by KFM filters. The first stage does the bulk oil removal; the second stage polishes what the first stage leaves behind. No chemical is added anywhere in the chain, so the sludge problem never arises.

The CDFU system is the compact swirl dissolved air flotation unit that carries much of the company patented technology. It combines swirl centrifugation, dissolved air flotation and ultrafine bubble technology to achieve purely physical oil removal, with single-stage oil removal efficiency above 90%. The recovered crude oil is of high quality and can be returned to the fuel system rather than disposed of as waste — an outcome that changes the economics of the whole installation.

Separation is fast and the equipment is compact. The footprint is only 1/5 of conventional flotation processes, which matters in a power plant where the available space is usually a gap between existing structures rather than a greenfield plot. Operation is fully automatic in a closed loop under PLC control, pressurised and sealed with no hazardous gas release, and simple enough that a shift team can run it without a dedicated operator.

Shock resistance is the characteristic that plant managers notice first. Power plant wastewater quality moves sharply with fuel type, tank cleaning cycles and rainfall, and a process that tolerates those swings keeps delivering compliant effluent instead of a monthly average that hides three bad weeks.

The KFM Filter as the Last Line

The KFM active media filter uses silicate-based media modified by atomic deposition technology. Its super-hydrophilic nanostructure and filtration mechanism remove trace oil and suspended solids that survived flotation, and the result is effluent that is clear and transparent rather than merely within a numeric limit. That distinction matters where the receiving body is visible or where the water is reused internally.

The Sierra Leone Heavy Oil Plant

The strongest evidence for the train comes from outside China. At a heavy oil power plant in Sierra Leone, Africa, the wastewater treatment project runs a two-stage CDFU plus KFM filter process, purely physical, at a treatment scale of 120 m3/d.

The operating result is the part worth reading twice. With zero chemical addition, influent oil content of 200 mg/L was reduced to below 5 mg/L, and influent suspended solids fell from 972 mg/L to 4.6mg/L. Those are not marginal improvements on a limit; they are a different class of water. The project was commissioned in June 2025 and has since brought the plant wastewater back within limits while recovering large amounts of usable crude oil.

What the Configuration Buys Beyond Compliance

Three things. First, the recovered oil has value, so the treatment cost is partly offset by product rather than being a pure expense. Second, there is no chemical store, no dosing skid and no hazardous sludge to ship, which simplifies both the safety case and the waste register. Third, the automation layer means the unit runs unattended, which is the only way a small wastewater system survives in a plant whose staffing is built around the turbine hall.

The same configuration covers heavy oil and light oil tank farm wastewater, coal washing wastewater and transformer wastewater. The differences between those streams are handled by adjusting the flotation stage and the filter media rather than by changing the process concept, which is why the reference list has been able to grow across plant types without a redesign each time.