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Microplastics (微塑料) pollute drinking water. Data now suggest all of us have microplastics in our bodies. Some plastics are harmful.

Menake Piyasena, a professor at the New Mexico Institute of Mining and Technology, and his team worked on a new process. In the past, Piyasena used ultrasound (超声波) to separate microbes and other cells from water. He recalls thinking: “What if we can use the same method to concentrate on microplastics?”

The researchers send polluted water down a tube. The tube’s water flows past a transducer, which turns electrical energy into sound energy. It makes ultrasound waves that travel from one side of the tube to the other. When they hit microplastics, these waves exert（施加）a force on the plastic bits.

What happens next depends on the size of those plastic bits. Ones less than about 180micrometers across will move to the center of the flow. Larger ones will interact with each other and create an additional force. This sends those larger ones toward the other end of flowing water.

The ultrasound treatment removed about four in every five plastic bits from the water. It took about 90 minutes to clean one liter. It cost only about 10 cents to do that. “We think our approach will be cost-effective and simple,” Piyasena says.

“Microplastics are a problem worldwide,” says a research chemist Souhail Al-Abed, who works for the US Environmental Protection Agency. In his opinion, this tech is not yet ready to be rolled out for widespread use. “I’d like to express praise for Piyasena’s team that are conducting this research,” Al-Abed adds. “Research does not have all the answers on day 1 or day 2 or day 100. But continuing work by these researchers may find a good solution for the future.”