Treatment of Oily Wastewater from Power Plants
Oily wastewater from power plants mainly comes from oil depot drainage, floor washing water, oil pump house drainage and equipment leaks at heavy oil power stations. It is characterized by high oil content (50-500 mg/L), a high proportion of emulsified oil, large amounts of suspended solids (SS, 50-300 mg/L), high viscosity and large quality fluctuations. Without effective treatment it causes environmental pollution, equipment corrosion and resource waste. Conventional methods such as gravity settling or chemical flocculation suffer from low efficiency, secondary pollution and large footprints. CDFU (cyclonic dissolved gas flotation unit) and KFM (active filter media filter) technologies can be integrated into a purely physical process that offers an efficient and environmentally friendly solution.
Oily wastewater treatment system at a heavy oil power station in Sierra Leone
CDFU and KFM Technologies
CDFU Cyclonic dissolved gas flotation unit: integrates cyclonic centrifugal separation and dissolved gas flotation, using high-pressure dissolved gas to generate 5-30 μm ultra-fine bubbles that mix with the wastewater and, in the swirl field, rapidly collide with and attach to oil droplets and suspended solids, forming float that rises and is discharged. Treatment time is only 1-5 minutes, single-stage oil removal >90%, emulsified oil removal >90%, purely physical with no chemical addition.
KFM active filter media filter: uses modified silicate active filter media (negatively charged surface, molecular sieve structure) with a graded particle size design (stage III coarse filtration + stage II fine filtration) to deeply adsorb residual oil and fine particles. The media resists fouling and has a long service life; the backwash cycle is 8-12 hours, effluent oil ≤6 mg/L, SS ≤2 mg/L and median particle size ≤1.5 μm.
Combined Process Flow
For power plant oily wastewater treatment, CDFU +KFM can form a two-stage treatment process:
Stage 1 (CDFU) : the wastewater enters the two-stage CDFU, where the swirl field enhances bubble-oil droplet attachment and rapidly separates dispersed oil, emulsified oil and SS; effluent oil ≤30 mg/L and SS ≤30 mg/L, with no chemicals and less sludge.
Stage 2 (KFM): CDFU effluent enters the KFM filter, which further removes residual pollutants to ensure the effluent meets discharge or reuse standards (e.g. boiler make-up water).
System integration: skid-mounted design with fully automatic control (IoT + AI monitoring), flexible capacity (up to 500 m³/h per unit) and a footprint only one-fifth of conventional processes.
Process Advantages
High efficiency: CDFU short retention time plus KFM high-precision filtration delivers overall COD removal >85% and a treatment speed 3-8 times that of conventional methods, handling high-viscosity, highly emulsified wastewater.
Economy: a zero-chemical purely physical process with a cost as low as CNY 0.375 per ton, 35% lower operating cost; low maintenance with no wearing parts.
Environmental performance: no secondary pollution and no sludge, compliant with GB 8978-1996, supporting green and sustainable development.
Stability: tolerates water quality fluctuations (pH 3-10), fully enclosed operation with no odour leakage, suitable for complex operating conditions.
Compactness: modular skid-mounted, small footprint, easy installation, ideal for space-constrained power plants.
Application Case
At the 43.65 MW heavy oil power station project for the New Tonkolili iron ore mine in Sierra Leone, SINOKLE supplied a CDFU +KFM system treating 120 m³ of oily wastewater per day, supporting the plant in connecting its first unit to the grid in June 2025. The system overcame rainy-season and logistics challenges, ensuring clear effluent and compliant discharge while cutting operating costs by 40%. Similar technology also applies to oil depot drainage treatment at other heavy oil power plants.
This process drives power plant wastewater treatment toward higher efficiency and greener operation, and is applicable to heavy oil power station projects worldwide.
