Using acoustic waves, small pieces of plastic can be effectively fished out of polluted water.
Microplastics are tiny, but a huge problem. Over the past decade, the amount of plastic lying around in the oceans has increased at an alarming rate. Meanwhile, good-natured scientists are looking for promising ways to make the ocean plastic-free again. And possibly sound waves can also help with that.
It should no longer be a secret that the ocean is littered with plastic waste. Scientists even predict that by 2050 the ocean will contain more plastic than fish. Microplastics are small (often microscopic) pieces of plastic that are no larger than 5 millimeters. They arise because they are intentionally produced in that size – and used in cosmetics, for example – but also when larger pieces of plastic are broken down into smaller and smaller pieces. This is done, for example, by UV rays from the sun or waves that cause the plastic waste to grind against stones, the seabed or other dirt. The pollutants eventually find their way into rivers and oceans. “Microplastics in the water pose a major threat, also to our own health,” says Dhany Arifianto in conversation with Scientias.nl. Yet it proves to be extremely difficult to filter these tiny plastic particles from both the fresh water we drink and from ocean water.
You may not realize it, but did you know that every time you do a load of laundry, countless microplastics are released? There’s little you can do about it: synthetic clothes are made up of millions of tiny, plastic microfibers that break down and are washed away in the washing machine. You can’t see any of this, the fibers are tiny (between 3 and 60 micrometers). Scientists once calculated that with one full washing machine, more than 700,000 microplastics are released. Incidentally, not so long ago, researchers developed a smart technique with which microplastics can be broken down with the help of electricity.
Nevertheless, researchers have now devised a promising way to fish microplastics from polluted water. For example, scientists are opening the hunt for microplastics with the help of sound waves.
The research team used two loudspeakers to generate sound waves. The force of these acoustic waves then separates the microplastics from the water by exerting pressure on a pipe with inflowing water. This tube splits into three channels, pushing the microplastics towards the center while the clean water flows to the two outer channels. “We had to search for the right frequency,” says Arifianto. “But after several adjustments, the microplastics were effectively pushed to the center of the pipe. Then we could easily filter them out of the water.”
The researchers tested three different types of microplastics. And while some types are easier to filter out of water than others, the method was found to be 56 percent efficient in freshwater and 58 percent efficient in seawater. “This efficiency is quite high,” explains Arifianto, although he emphasizes that these percentages were achieved in the laboratory, under controlled conditions. “We suspect that the efficiency will decrease somewhat when we apply our technique on the open sea or in rivers,” he continues. “This is partly because microplastics can then mix with other polluted substances.”
Although the researchers have shown that they may be able to capture microplastics using sound waves, they do have an important caveat. Acoustic waves that are within hearing range can be harmful to marine life. The researchers are currently studying this potential problem. “We’re examining the generated frequency and noise level to see if they could pose a potential hazard,” Arifianto says. “We may be able to manufacture a sound-absorbing material. We are still working on this and are working together with experts in the field of biomarine.”
Still, so early in the development phase, the findings are promising. “I mainly want to emphasize that our work is really still in its infancy,” says Arifianto. “We have only been working on this for a year now and are confident that the technology is a great way to clean up microplastics. It is easy to install and the operating costs are low.”
With his idea, the researcher hopes to make an important contribution to the capture of polluting microplastics that float in large numbers through both rivers and the oceans. “At the same time, we hope to convey an important message,” says Arifianto. “And it says we need to stop dumping plastic into the ocean. This will also benefit our own well-being.”
“Filtering microplastics trash from water with acoustic waves– Acoustical Society of America (via EurekAlert)
Interview with Dhany Arifianto
Image at the top of this article: Mary Theresa McLean via Pixabay