BY MARIA BURKE
Engineers have designed a protective coating for concrete pipes that could significantly reduce the formation of ‘fatbergs’ in sewers.
Fat, oil, and grease (FOG) in wastewater can react with other constituents, forming insoluble solid deposits that stick to the inside of pipes and sewers, allowing ‘fatbergs’ to accumulate. This problem is made worse when FOG interacts with calcium released from the concrete. In the US alone, FOG is responsible for half of all sewer blockages costing $25bn to fix.
One solution is to coat the inside of sewer pipes with a protective layer to inhibit calcium leaching and so reduce the accumulation of FOG. Researchers from RMIT University in Melbourne, Australia, have designed a new polymeric hybrid material to act as a coating and one that can also repair damage to itself under normal operating conditions, thereby extending its lifespan.
They developed a Zn-polyurethane-centred hybrid material featuring three distinct healing bonds—polymeric dimethylglyoxime–urethane covalent bonds, Zn-coordination bonds and hydrogen bonds. These bonds make it mechanically very strong while enabling low-temperature healing. The novel material is stable up to 850°C and in water, they report.
The team coated concrete blocks with the material and tested them for 30 days under extreme conditions to mimic those found in sewers and to rapidly accelerate the process of fatberg formation. Results showed that the release of calcium from the coated concrete blocks was reduced by up to 80%, compared with uncoated concrete (Chemical Engineering Journal (DOI: 10.1016/j.cej.2024.156226). Additionally, the coating reduced build-up of FOG on concrete by 30%, compared with non-coated concrete. Scratching the surface triggered a self-healing process, meaning the coating could repair any damage to itself and extend its lifespan.
‘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 with the rough, uncoated concrete surface,’ says Biplob Pramanik, team leader. ‘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.’
It remains to be seen how reliable these laboratory tests are when put to work in an actual sewage system, says James Barker of Kingston University, UK, as these experiments were conducted in glassware at room temperature and for 30 days only. ‘The ability of the hybrid material to operate effectively at lower temperatures and when applied to cast iron pipes or brickwork tunnels over longer periods still remains to be seen.’
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