These scientists are using sound waves to filter plastic fibres from washing machine wastewater

Every time we wash our clothes, tiny plastic fibres are released into the water. But while these microfibres are small, they’re amounting to a big problem.

About 60% of material made into clothing is plastic. And as many as 729,000 fibres could be released from a single 6 kg laundry load of synthetic materials, according to one report.

Multiply that by the number of washing machines in the world and it’s not hard to see why the simple act of cleaning our clothes is leading to a serious amount of ocean plastic pollution.

The sound of progress

Solutions include filtration systems that use mesh to trap microparticles. But currently they can’t capture everything.

So, rather than using ever-finer grades of mesh, scientists at Japan’s Shinshu University have suggested another approach: using what’s known as a bulk acoustic wave system.

Their system applies sound waves to wastewater before it leaves the machine, from either side of a central stream. This creates an acoustic wave in the centre, which traps microplastic fibres and other small particles.

The water containing the fibres is channelled in one direction, leaving the remaining wastewater to be expelled either side and dealt with via the regular pipes and plumbing.

The trapped fibres can then be isolated and extracted from the water via a process of evaporation before being safely disposed of.

A persistent problem

The extent of marine plastic pollution is well documented. The WWF says plastic is “choking our oceans”, and that around 700 marine species are threatened. One in two sea turtles has ingested plastic, it says, while 90% of sea birds have it in their stomachs.

Attempts to remove plastic from the ocean have included sea bins and booms.

Sea bins work better in confined areas with calmer water, such as marinas and bays or yacht clubs. They can capture around 20 kg of waste in a single day.

Larger operations, such as ocean-going booms, have the promise of collecting much larger amounts of waste. But they have a number of challenges to overcome, not least of which has been the problem of waste being washed over the side of the boom to once again pollute the ocean.

Positive results

So stopping plastics at their source, including plastic microfibres, will be key to helping clean up the oceans.

And, although not yet commercially available, tests on the Japanese scientists’ bulk acoustic wave system have yielded positive results. The researchers say it needs to be refined before it enters production, but in lab conditions, it captured 95% of PEP-T (polyethylene terephthalate) fibres, and 99% of Nylon 6 fibres.

Particles as small as just five micrometres can be caught, which is approximately the thickness of the silk from a spider’s web.