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Pushing sludge: flushing waste out of wastewater treatment processes

University of Melbourne School of Engineering PhD student Sam Skinner said better sludge disposal could significantly reduce the cost of wastewater treatment.

Mr Skinner’s research, published in a special edition of the journal Water Research, focuses on how to reduce the vast quantities of sludge that are left once what’s flushed down the toilet or washed down the kitchen sink has been treated.

“Wastewater treatment is arguably the greatest achievement of the industrial revolution and it means 5 million people can live in Melbourne without major health and sanitation issues,” Mr Skinner said.

“But the end product of wastewater treatment is sludge and getting rid of this sludge is the major cost of wastewater treatment. We keep creating more and more of it but we have no way of getting rid of it. So it sits there and is stockpiled in ‘sludge mountains’.”

According to the United Nations, more than 663 million people around the world do not have a safe water supply close to home. The UN also says 80 per cent of the wastewater from homes, cities, industry and agriculture flows straight back to nature without being treated or reused.

It is this link between a lack of access to water and a lack of wastewater treatment options that drives Mr Skinner’s research.

His research showed that what is done in the treatment process can significantly affect how much sludge is left to dispose of.

“My research accurately models the sludge filtration process to compare different sludge types and to optimise filtration at wastewater treatment plants,” he said.

“We showed that sludge filtration is significantly improved by destroying the organic component of the sludge – that is the bacteria and the sticky substances that they produce.”

“Stockpiling of sludge is a huge environmental issue facing modern society and these findings can help reduce the amount of sludge that goes into huge mountains of the stuff.”

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