Oxley Creek Wastewater Treatment Plant –
Digester Maintenance

Bonacci Infrastructure developed a comprehensive lift design to enable the extraction of four floating roof structures which formed part of the digesters at the Oxley Creek Wastewater Treatment Plant.

The floating roof structures were in poor condition as a result of internal hydrogen sulphide attack. Rigorous design was required to ensure that lifting points had sufficient capacity in their in-situ condition, and that the structure was capable of distributing its weight between the lifting points.

In addition to the temporary works, Bonacci Infrastructure provided condition assessments and strengthening designs for each of the four digester roof structures to permit the required extension to their in-service life.

Carbon fibre reinforced polymer (CFRP) was used to strengthen the
concrete capping beams at the top of each digester tank which otherwise became overloaded when the dome roof structures reached their highest position under design wind conditions.