The Surface Aerator

Advantages of the BSK®‑Turbine

Excelling high efficiency

The special hydraulic of the BSK®‑Turbine makes it possible: up to 2,8 kg O2/kWh

Advantage: significant savings in operating costs (More than 60 % of the energy demand of a wastewater treatment plant is spent on the aeration of the biological stages.)

Exemplary good aeration and circulation

The special hydraulic design according to the “Francis-concept” allows not only an optimized aeration, but also the circulation rate is unique, even in deep tanks.

Made of stainless steel

No material in the waste water is better than stainless steel: No corrosion and almost unlimited lifetime. Free choice of alloy is possible (AISI 304L, 316L etc.)

Durable construction

(365 operating days per year and) maximum daily services require extremely robust components.

BSK® drives provide the answer: Service factors ≥ 2,8 and oversized bearing technology.

No loss of efficiency

Design-immanent, permanently constant power, high alpha (α) factor ≥ 0.9, no loss of efficiency in oxygen transfer efficiency compared to fine-bubble aeration.

No Pipes, no Blowers

No construction structures for compressed air units, no formation of condensation, no sludge deposits, minimal installation effort

Easy Maintenance

No maintenance components under water. The only maintenance is an oil change every 3–4 years (full synthetic oil). In case of repair: Easy disassembly without emptying the tanks.

Low Spray Height

Low spray height, practically no aerosol formation, splashguard covers can be omitted

Fields of application

  • Aeration and mixing of activated sludge in biological wastewater treatment (SB-reactors, traditional continuous systems)
  • Aerobic sludge stabilization
  • water treatment

Typical applications in the field of biological wastewater treatment:

  • Municipal wastewater treatment plants:
    • Wastewater treatment plants for municipalities and cities
    • Sewage treatment plants for hotels
    • Wastewater treatment plants for military camps
  • Industrial wastewater treatment plants for the food industry:
    • Dairies
    • Fish canneries
    • Potato processing industry
    • Slaughterhouses
  • Industrial wastewater treatment systems for the non-food sector:
    • Paper mills
    • Textile mills
    • Tobacco industry
    • Rendering plants, etc.

Construction details

General Layout of the BSK®‑Turbine surface aeration system

  • 1 Three-phase motor
  • 2 Flat gear unit
  • 3 Oil reservoir
  • 4 Baseplate for gear unit
  • 5 BSK®‑Turbine
  • 6 Drive shaft
  • 7 Fixed bridge or floating system

Components of the BSK®‑Turbine

  • 1 Connection flange
  • 2 Crown ring
  • 3 Conveyor blades
  • 4 Baffle

(All parts are made of stainless steel)


Versions / Sizes


11 different standard sizes available: diameters from 900 up to 3.000 mm (other dimensions can be created depending on the requirements)


Manufacturing is possible in various alloys of stainless steel:

  • stainless steel (AISI 304L)
  • stainless steel (AISI 316L)

Special steels are possible if necessary

Drive system

Motor power from 5,5 kW to 130 kW, Standard efficiency class: IE3, on request: IE4

High-performance gear in industrial quality with hollow shaft or flanged shaft

Direction of rotation

left- or right-handed available


Mounting on floating systems (changeable in height according to changing water levels e. g. in SB-reactors) or fixed installation on steel or concrete bridges (at constant level)

Oxygen input

up to 270 kgO2/h


  • 1960 based on proven “Francis”-design – testing program over several years
  • 1990 continuous improvement process – highly efficient hydraulic design
  • Based on the experience of the last 40 years, combined with the latest hydraulic models, a new generation (BSK®‑Turbine) was developed


More than 2,000 BSK®‑Turbines are in operation worldwide (including the references of our Swiss partner NORM A.M.C. AG), e.g.:

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