SA Water’s $4.7 million upgrade to the Bolivar Wastewater Treatment Plant’s anaerobic digesters has passed a major milestone, with a 115 tonne steel cover of one of the digesters craned off the structure by a 350 tonne crane – one of the largest crane lifts in the utility’s history. 

Anaerobic digesters are large, sealed concrete tanks that heat the solid organic waste from sewage – known as sludge – in an oxygen-free environment, to promote the natural bacterial metabolic processes that break it down, with Bolivar’s standing at 14m tall with a capacity of 8.5 million litres.

Port Augusta business, MAX Cranes, worked together with crews from SA Water and Fulton Hogan to carefully guide the 30m-diameter cover on top of a temporary support system during the hour lift, enabling the infrastructure’s safe refurbishment.

SA Water’s General Manager Sustainable Infrastructure, Amanda Lewry, said the successful crane lift was the culmination of 12 months of planning.

“Safety was at the forefront of this incredible feat and people might not be aware of the behind-the-scenes planning for the secure operation, which included compaction testing of the ground and an extensive bearing capacity assessment to help protect underground pipes,” Ms Lewry said. 

“Eight heavy-duty slings were attached to fixing points pre-welded to the cover, while counterweights were used to stabilise the crane as it lifted our cover off the digester and atop the support structure. 

“Our crews will now work on upgrading the cover during the next few months, including reinforcing the roof’s structure, installing a new insulation panelling system and cleaning the digester.”

Constructed in the 1960s, the upgrade of two of Bolivar’s six digesters will improve their performance by enhancing insulation to the covers – ensuring an optimal internal environment for the digestion process.

Ms Lewry said the metabolic processes inside the digesters release a source of renewable energy, biogas.

“Upgrading our digesters enhances their ability to hold waste at a constant 38 degrees and creates an optimal environment for bacteria inside to help prevent the escape of biogas, a product we can reuse,” Ms Lewry said. 

“Harnessing the power of biogas through our on-site gas engines creates a source of renewable energy for the treatment plant, which typically provides around 85 per cent of the Bolivar facility’s energy needs. 

“Biogas generation is an important part of our approach to energy management and by reducing and reusing waste, we are taking action as proactive environmental leaders to help enable a sustainable future.”

The renewable electricity generated through biogas at the Bolivar Wastewater Treatment Plant is enough to power around 4,000 houses a year.

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