Analysis of Oily Wastewater Pretreatment in Heavy-Oil Tank Farms at Thermal Power Plants
Oily wastewater from heavy-oil tank farms at thermal power plants has a complex composition, typically containing high concentrations of petroleum substances (up to 1,000 mg/L) and suspended solids, with high oil viscosity and a high degree of emulsification, making treatment difficult. If discharged directly or improperly treated, such wastewater severely pollutes the environment and also affects the stable operation of the plant's water circulation system.
The main treatment difficulties are: oil-water separation is hard, especially for emulsified oil; conventional processes adapt poorly to high-concentration oily wastewater and are easily upset by water-quality fluctuations; and the treatment process may generate large amounts of oily sludge and other secondary pollutants, increasing disposal costs.
Conventional Treatment Processes and Their Shortcomings
Thermal power plants once widely used oil separation tanks, flotation and chemical flocculation. Oil separation tanks can only separate floating oil and are of limited use for dispersed and emulsified oil; flotation can remove fine oil droplets but requires high equipment investment and energy; chemical flocculation needs chemical dosing and generates large amounts of floc, with high treatment costs and a tendency to cause secondary pollution. These methods generally suffer from long process flows, large footprints, weak shock resistance and unstable operation.
SINOKLE's New Process: CDFU and KFM Filter Synergy
To address these shortcomings, SINOKLE (Shenzhen) Technology Co., Ltd. introduced a new heavy-oil tank farm oily wastewater pretreatment process centred on CDFU (compact cyclonic dissolved gas flotation) together with KFM active filter media filters.
The process mainly comprises:
Primary oil-water separation in an oil separation tank.
The wastewater enters the CDFU unit, where cyclonic centrifugal separation, dissolved gas flotation and ultra-fine bubble technology efficiently break the emulsion and make oil droplets aggregate and float.
CDFU effluent then enters KFM active filter media filters for further removal of residual fine oil droplets and suspended solids.
Waste oil generated in the process is recovered, and off-gas is treated by a dedicated system.
Process flow diagram of wastewater treatment in a heavy-oil tank farm at a thermal power plant
Notable Advantages of the New Process
SINOKLE's CDFU+KFM combined process offers multiple advantages:
Highly efficient, stable and shock-resistant: purely physical separation with no chemicals, oil removal above 95%. The system withstands large fluctuations in water quality and quantity and operates stably and reliably.
Environmental and economic win-win: no chemical addition, no oily sludge (hazardous waste), avoiding secondary pollution. Recovered oil can be returned to the crude tank, creating economic benefit.
Compact, energy-saving and easy to maintain: integrated skid-mounted design with a footprint only 1/10 of conventional processes. High automation, few moving parts, simple operation and maintenance, and a short construction period.
Excellent effluent quality: after treatment, effluent petroleum substances and suspended solids both stably drop below 20 mg/L, better than conventional discharge standards, laying a good foundation for further advanced treatment or compliant discharge.
Oily wastewater treatment unit manufactured by SINOKLE for a heavy-oil power plant in Sierra Leone (two-stage CDFU+KFM active filter media filters)
In summary, the pretreatment process centred on CDFU and KFM filters provides an efficient, environmentally friendly and economical solution for oily wastewater treatment in heavy-oil tank farms at thermal power plants, with important promotional value and application prospects.
