Egg Shaped Digesters

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Project: Egg Shaped Digesters
Client: Thiess Contractors Pty Ltd

The Egg Shaped Digesters (ESDs), the first of their type to be constructed in Australia, provide a modern and efficient treatment of sewage sludge at the Woodman Point Waste Water Treatment Plant near Perth, Western Australia. The egg shape provides for an efficient circulation of the effluent by eliminating dead areas that are common in conventional, cylindrical tanks.

Features:

  • The ESDs have a capacity of 8,000m3 each, are approximately 38m high from the foundation to the top of the digester and have a maximum diameter of 23m.
  • The lower 12.5m of the digester is founded below ground level in profiled natural limestone, thus avoiding the need for a ring beam and piling.
  • The complex egg shape required detailed analysis to identify the optimum post-tensioning cable arrangement.
  • Specialised, adjustable formwork was required to form the egg shape.

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