UniSA finds that sludge in sewer pipes helps beat acid attack

University of South Australia (UniSA) researchers have demonstrated a new corrosive-resistant material containing sludge from water treatment, which the university has said is over 50 per cent stronger than traditional cement-based pipes “and resistant to acid-induced degradation.”

According to a statement from UniSA on Thursday, concrete is common in sewage pipes – due to its strength and affordability – but is vulnerable to acid and microbial corrosion. This requires ongoing repairs and maintenance costing the nation approximately $70 billion each year.

A new study in the Journal of Building Engineering (linked) looks at alkali-activated materials (AAMs) and their potential in sewage infrastructure worldwide.

Samples with 20 per cent to 40 per cent of alum-based water treatment sludge (AWTS) retained over 50 per cent higher compressive strength versus 100 per cent ground granulated blast furnace slag (GGBS), which is used in cement making. Samples also limited penetration by sulphur-oxidising bacteria and slowed acid-reduced degradation.

Civil engineering PhD candidate Weiwei Duan said the work also addressed the issue of disposing of sludge, which normally went into landfill sites, where it could be environmentally harmful. Weiwei’s work earned him the 2025 Australian Water Association Student Water Prize last month..

Research lead Professor Yan Zhuge said findings suggest partial replacement of blast furnace slag with 20 – 40 per cent water treatment sludge was a promising solution.

“This has the potential to extend the service life of sewage pipes, reduce maintenance costs, and promote the reuse of water treatment byproducts, thus contributing to the circular economy,” said Zhuge.

“The construction industry is one of the world’s biggest greenhouse gas emitters, so if we can cut down on the need for cement, we will be helping to lower carbon emissions.”

Picture: credit UniSA