Sludge an easy feed for Lincoln’s new digester

An eight-metre-high waste-loving concrete anaerobic digester is now up and running at the Port Lincoln Wastewater Treatment Plant and teeming with microscopic bugs central to the biological process inside.

In the latest major milestone for SA Water’s $18 million upgrade, the digester is used during one of the final stages of the wastewater treatment process, helping to process sludge and transform it into a source of renewable energy called biogas.

An important component of commissioning involved feeding sludge from SA Water’s Bolivar Wastewater Treatment Plant to the digester, helping promote the growth of microbiological organisms that break down organic waste.

SA Water’s Senior Manager of Production and Treatment Lisa Hannant said the ‘seeding’ process was crucial to creating an optimal environment for the tiny bugs to thrive.

“The biological process inside the digester relies on active, healthy microorganisms breaking down the organic material in sludge, and we’ve bred a batch of busy bugs at our Port Lincoln treatment plant,” Lisa said.

“Once we tested all of the new electrical and mechanical equipment and removed all of the oxygen from inside the digester, the tank was filled with water and heated to 38 degrees before introducing ‘seed’ sludge from our Bolivar facility, along with thickened sludge from the Port Lincoln plant.

“This method establishes a strong population of bacteria and over time, generates enough biomass packed with the microbiological organisms that eat away at sludge and produce biogas during the process.

“Biogas is extracted from the digester and burnt to provide a source of heat to hold the waste inside at a constant temperature – creating an environment the bacteria love and they’ve acquired quite a taste for the city’s sewage, processing more than a million litres of sludge to date.

“Our upgrade champions sustainable waste management and resource recovery by reducing the plant’s carbon footprint and giving back to nature in the form of biosolids, which are removed from the digester and put to use on farmland as a nutrient-rich fertiliser.”

Over the past few months, SA Water together with lead contractor Guidera O’Connor have also completed construction of the facility’s new odour control system, dewatering plant, and general site drainage and road upgrades, and will now continue optimising the digester’s biological process.

“We’re rolling through the milestones and remain on track to complete the project by the end of the year, priming Port Lincoln’s treatment plant to support continued residential and industrial growth while delivering enhanced environmental performance,” Lisa said.

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