Bonacci Infrastructure delivered the structural design and construction phase services for the bioreactor and fine screen components of the Farley Waste Water Treatment Works Stage 3B upgrade.
The 10 ML bioreactor is a monolithic tank which combines two process trains, each including an anaerobic reactor, oxidation ditch, and dedicated secondary anoxic and aerobic zones. A common membrane bioreactor, consisting of six trains, flows into a common deaeration zone. Bonacci Infrastructure worked closely with the contractor and process designers to optimise the layout in order to improve structural performance and constructability, reduce material quantities, and to accelerate the construction program. The bioreactor is positioned over a decommissioned sludge lagoon and founded on a sloping rock profile which presented challenges in designing for large variations in ground stiffness and differential settlement.
Meticulous planning and design enabled the 1100 m3 post-tensioned bioreactor floor slab to be constructed in a single pour over a 16-hour period. The bioreactor walls were also successfully constructed without control joints which reduced maintenance costs and the risk of leaks often associated with conventional jointing systems. Precast elements were incorporated into the design where practical to reduce formwork and further accelerate the construction program. The bioreactor passed hydrostatic testing within the 7-day soak period which allowed early backfilling and practical completion.
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