The water leaving your washing machine may soon be a lot more eco-friendly, thanks to the anchovy. A filter inspired by the tiny fish could remove microplastics from the outgoing water, keeping them from entering local waterways.
When most people think of microplastics, they likely picture waterborne plastic trash that disintegrates into minuscule fragments. And yes, that trash does constitute a lot of the problem.
However, the synthetic fibers shed by clothing as it's being washed also make up a significant source. Those fibers leave people's homes in the sewage lines and end up entering rivers, lakes and/or the ocean. As is the case with other microplastics, they then enter the food chain as they're consumed by fish and other organisms.
Researchers are still trying to understand how people's health may be affected by ingesting the microplastics in and of themselves. That said, harmful bacteria are often drawn to the plastics, living on or around them – and we definitely shouldn't be eating or drinking those microbes.
All of that brings us back to the anchovy, along with fish such as the sardine and mackerel.
They feed by swimming with their mouth open, allowing water to pass through a funnel-shaped arrangement of arches in their gills. Each of those "comb-like" arches is in turn covered with small teeth that allow water to pass through, but keep plankton from getting out.
That said, the plankton don't just get stuck against the teeth. Instead, the flow of the incoming water rolls the trapped plankton to the back of the funnel, where they collect in the fish's gullet until it swallows them.
Inspired by this clever system, Dr. Leandra Hamann, Dr. Alexander Blanke and colleagues at Germany's University of Bonn set out to replicate it in a device that could be integrated into a washing machine.
The resulting prototype mimics the gill arches via several arched support structures that can hold standard commercial filter meshes, and it's able to filter over 99% of microplastic fibers out of wash water without becoming clogged. Importantly, it is not mechanically complex, so it should be inexpensive to manufacture.
Several times a minute, the fibers that it has filtered from the water are suctioned away and stored. Further down the road, it is envisioned that the washing machine could press and dry those concentrated fibers into a compact pellet, which would then be disposed of along with the household garbage.
"I would say it is not far from entering commercial use. It needs optimization of the housing, the implementation of pressure sensors to automate the cleaning intervals, and a solution for the concentrate storage after it is extracted from the filter," Hamann tells us.
"It would also be necessary to test the filtration efficiency of other particle types that are common in washing machine effluents, like hair, cotton fibers, sand, dust etc. […] If a large filter company would take on those last experiments, and design and manufacturing challenges, it could be ready within one or two years."
A paper on the research was recently published in the journal npj Emerging Contaminants.
And no, this isn't the first fish-inspired microplastic-removing device we've seen. In 2022, University of Surrey chemistry undergrad Eleanor Mackintosh actually designed a filter-feeding robotic fish that could theoretically do the job.
Source: University of Bonn
