Researchers in Indonesia have found an unusual solution to the problem of microplastic pollution - filtering it out of water using sound.

Microplastics find their way into rivers and oceans, causing problems for marine life and the environment. Filtering and removing the small particles from water has traditionally been a difficult task - but acoustic waves may provide a solution.

The new method uses speakers to generate bulk acoustic waves in order to force microplastic particles in water to separate from the liquid, allowing for the quick and easy removal of the particles.

Led by Dr Dhany Arifianto, the research team at the Sepuluh Nopember Institute of Technology in Surabaya used two speakers to generate acoustic waves through a sample of water laden with microplastic particles, which was circulated through a tube. As the tube splits into three channels, the microplastic particles are pressed towards the centre as the clean water flows towards the two outer channels.

Results showed that the technique made it possible to clean 150 litres of polluted water per hour. Its effectiveness largely depended on the type of water used and varied with the type of plastic it contained. They also found that acoustic frequency, speaker-to-pipe distance, and the density of the water affected efficiency.

The team acknowledge this is only a proof-of-concept and while the technology is promising when it comes to tackling the scourge of microplastics, more work needs to be done to ensure the acoustic waves do not negatively impact marine life.