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Sound waves could capture microplastics from laundry wastewater

When washed, our clothes shed tiny microfibers that drain into wastewater—and eventually into the ocean. A new device might break that cycle.
December 19, 2019

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By 2050 there could be more plastic in the oceans than fish, according to the World Economic Forum. Most of the plastic waste in the oceans is made of microscopic pieces. And a major source of microplastics are synthetic fabrics that shed tiny fibers every time we do laundry.

New research shows a simple, effective way to collect plastic microfibers and microbeads from water using sound waves. The technique, reported in the journal Sensors and Actuators B: Chemical, could help to capture microplastics from laundry drains, keeping them from polluting our waterways and oceans.

Microplaltics wind up in water bodies in two ways. Larger pieces of plastic can degrade and break down to form these tiny particles. The other source is wastewater entering the oceans, since water treatment plants have no way to filter out these microplastics.

Laundry is big culprit behind microplastics pollution in wastewater. More and more our clothes are made of synthetic fibers like acrylic, nylon and polyethylene, all of which are types of plastic. When washed, they shed tiny microfibers that drain into wastewater. Plus, laundry detergents also contain tiny plastic microbeads, a recent study found.

Besides floating around in oceans for decades, microplastics also end up eaten by corals, plankton and fish, winding all the way up the food chain into human stomachs. The long-term effects of this plastic exposure is unknown.

The new plastic-corralling system designed by researchers at Shinshu University in Japan uses a piezoelectric device—a device that converts electricity into mechanical vibrations—to apply vibrating sound waves to a thin channel of wastewater containing plastic microbeads and microfibers.

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The waves are focused on the center of the channel, which makes the plastic particles amass in the center. Just downstream from the piezoelectric device, the channel splits into three. The plastics go down the center to be collected, while clean water goes down the two sides. In lab tests, the system captured 95 percent of polyethylene fibers and 99 percent of Nylon fibers.

One downside is that the process is slow, but if the researchers could find a way to make it faster, a device like this could be integrated in washing machine drains to filter out microplastics.

Source: Yoshitake Akiyama et al. Acoustic focusing of microplastics in microchannels: A promising continuous collection approach. Sensors and Actuators B: Chemical, 2019.


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