wastewater treatment plant

Subjecting contaminated water to speaker system helps eliminate microplastics

A prototype speaker system has been shown to efficiently separate out microplastics from polluted water using acoustic waves.

Microplastics are released into the environment by cosmetics, clothing and industrial processes, or from larger plastic products as they break down naturally.

The pollutants eventually find their way into rivers and oceans, posing problems for marine life. Filtering and removing the small particles from water is a difficult task, but acoustic waves may provide a solution.

Researchers at the Sepuluh Nopember Institute of Technology in Surabaya, Indonesia, have developed a filtration prototype using two speakers to create acoustic waves.

The force produced by the waves separates the microplastics from the water by creating pressure on a tube of inflowing water. As the tube splits into three channels, the microplastic particles are pressed toward the centre with the clean water flowing toward the two outer channels.

The prototype device cleaned 150 litres per hour of polluted water and was tested with three different microplastics. Each was filtered with a different degree of efficiency, but all were above 56 per cent efficient in pure water and 58 per cent efficient in seawater.

Acoustic frequency, speaker-to-pipe distance and water density all affected the amount of force generated and therefore the efficiency.

However, the researchers did warn that acoustic waves could impact marine life if their frequency is in the audible range. The group is currently studying this potential issue.

“We believe further development is necessary to improve the cleaning rate, the efficiency, and particularly the safety of marine life,” said lead researcher Dhany Arifianto.

A study from October estimated that around 3,760 metric tons of micro and macroplastic debris are currently floating in the Mediterranean Sea.

One option to help deal with the problem is biodegradable plastics that will only cause a polluting effect on the environment for a limited time. But many options currently available lag behind fossil-based polymers in their required properties.

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