Fat, oil and grease (known as FOG) – notorious for solidifying inside pipes and concrete sewers – causes half of all sewer blockages in the United States and 40% in Australia. The cost of these blockages in terms of maintenance and rehabilitation is estimated at US $25 billion in the US and $100 million in Australia per year.

It is the mixture of fat, oil and grease with calcium and water in sewers that often leads to the formation of fatbergs, a solid mass of waste that forms in sewer systems when FOG combines with non-biodegradable solids. But the team’s zinc-enhanced polyurethane coating offers a promising sustainable solution by reducing the release of calcium from concrete blocks by up to 80% compared with uncoated concrete.

The study led by Dr Biplob Pramanik mimicked a sewer environment under extreme conditions that rapidly sped up the fatberg formation process over 30 days.

It showed the coating reduced build-up of FOG on concrete by 30% compared to non-coated concrete.

“The reduction of fat, oil and grease build-up can be attributed to the significantly reduced release of calcium from coated concrete, as well as less sticking of FOG on the coating surface compared to the rough, uncoated concrete surface,” said Pramanik, director of water, Effective Technologies and Tools (WETT) Research Centre at RMIT.

“Traditional coatings like magnesium hydroxide, widely used for over two decades, are effective in controlling sewer corrosion but can inadvertently contribute to FOG build-up by interacting with fatty acids.”

Dr Biplob Pramanik in his lab at RMIT University. Credit: Will Wright, RMIT University

The team’s invention is stable in water and withstands temperatures of up to 850 ℃. It is also self-healing at room temperature, meaning it can repair any damage to itself and extend its lifespan.

“We drew inspiration from the regenerative capabilities observed in nature, including human skin’s ability to heal itself,” Pramanik said.

Co-researcher Dr Sachin Yadav said the team examined the healing performance of the coatings by inflicting surface scratches with a blade.

“The creation of surface scratches on the self-healing polyurethane coating sample triggered the healing process,” Yadav said.

“After the healing period, we observed a noticeable improvement in the surface scratches.”

Dr Biplob Pramanik shows the difference between a concrete block coated with his team’s anti-fatberg invention compared to a block without any coating after undergoing an experiment that mimicked a sewer environment under extreme conditions to speed up the fatberg formation process. The white coloured blobs on the uncoated block are a mixture of fat, oil and grease (FOG). Credit: Will Wright, RMIT University

Next Steps

The team is developing an improved coating to achieve a greater reduction of FOG deposition in sewers by enhancing its self-healing capabilities and mechanical strength.

Pramanik is also the chief investigator for a recently announced ARC Linkage Project that will develop an advanced grease interceptor for restaurants and other food service establishments to remove small FOG particles more effectively than current technologies.

His team at RMIT is partnering with South East Water, VicWater, Water Research Australia, Barwon Region Water Corporation, Queensland Urban Utilities and water technology company ACO on the ARC Linkage Project.   

‘Novel hybrid coating material with triple distinct healing bond for fat oil and grease deposition control in the sewer system’ is published in the Chemical Engineering Journal (DOI: 10.1016/j.cej.2024.156226).

This story was originally published by RMIT University and can be viewed here.