The Surbiton Park compressor room

The challenge

Both treatment plants had several Roots-type positive displacement (PD) blowers, each around 100 kW. The new compressors were to provide all the duty air required, but the customer still wanted to retain the ability to use the PD blowers in the same manifold. The replacement work was difficult as the existing blower rooms were noisy. It was not possible to work safely, and the installation could not be done without shutting down the plant.

The solution

Most of the PD blowers were removed and replaced with Sulzer HST turbocompressor. The HST turbocompressors are equipped with active magnetic bearings, so they can withstand the pulsations generated by the PD blowers discharging into the same manifold. This is a key point of difference compared with air-bearing machines.

To remove the existing units without shutting down the plant, one of the new HST turbocompressors was temporarily installed in a shipping container outside the building, piped in and commissioned. This arrangement allowed unrestricted access to replace the existing units, which would have been impossible without the HST’s quiet, vibration-free operation and small footprint.

Customer benefit

  • The upgrade of the aeration blowers at Surbiton Park and Sunbury resulted in higher reliability and efficiency, with significant savings in both energy and maintenance. The customer experienced an 18% power saving immediately.
  • The compressor installation was part of a larger upgrade, and when that comes on-line, the duty point will move closer to the best efficiency point (BEP) further increasing the efficiency of the system.
  • The reliability of the system has increased significantly with no failures since 2011.
  • Health and Safety has improved as hearing protection is no longer required in the compressor rooms.
Product specification

Two units HST40-350 turbocompressor for Surbiton Park and two units HST40-400 for Sunbury

Surbiton Park:

  • Capacity: 18 mld
  • Process: Oxidation ditches

HST40-350-1-L turbocompressor

Capacity 14'000 Nm3/hr
Pressure 40-65 kPa
Motor power 350 kW


  • Capacity 8 mld
  • Process: Oxidation ditches 

HST40-400-1-L turbocompressor

Capacity 16'000 Nm3/hr
Pressure 40-65 kPa
Motor power 400 kW
  • HST™ turbocompressor
    The modern and silent HST™ turbocompressor features an advanced design with proven magnetic bearing technology and a high-speed motor driven through a built-in frequency converter.
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