Researchers at the University of South Australia have been using a water treatment byproduct as an additive to concrete sewer pipes
A research team at the University of South Australia (UniSA) has been investigating the use of sludge from water treatment as an additive to concrete for use in wastewater pipes.
The idea was to develop an eco-friendly alternative solution to traditional cement sewer pipes that are prone to cracking and corroding.
By combining sludge from water treatment and blast-furnace slag, UniSA engineers have demonstrated that a new, corrosive-resistant material is more than 50 per cent stronger than cement and resistant to acid-induced degradation.
Concrete is widely used for making sewage pipes due to its availability, affordability and structural strength, but it is highly susceptible to acid and microbial corrosion in sewers, requiring ongoing repairs and maintenance that cost Australian taxpayers close to $70 billion each year.
A new study published in the Journal of Building Engineering evaluates the effectiveness of the alkali-activated materials and demonstrates why they could revolutionise sewage infrastructure worldwide.
Samples containing 20 per cent to 40 per cent of alum-based water treatment sludge retained over 50 per cent higher compressive strength compared to 100 per cent ground granulated blast furnace slag, which is used in the production of cement.
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The new material also limited the penetration of sulphur-oxidizing bacteria and slowed acid-reduced degradation.
UniSA civil engineering PhD candidate Weiwei Duan, whose research is based on this project, says there is another major benefit: finding a cost-effective and environmental use for water treatment residue.
“Sludge is usually disposed of in landfill sites, which not only reduces available land for other uses, but also harms the environment, creating CO₂ emissions from transporting the waste,” Weiwei says.
Principal supervisor and lead researcher on the project, Professor Yan Zhuge, says the findings suggest that partially replacing the blast furnace slag with 20–40 per cent of water treatment sludge makes them “promising candidates” for use in sewers.
“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,” Zhuge says.
“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.”