Fish-Inspired Filter Removes 99% of Microplastics From Washing Machines, Study Finds
Microplastic Pollution From Laundry Wastewater
Wastewater discharged from washing machines is widely regarded as a major contributor to microplastic pollution—those minute plastic fragments believed to pose risks to both human and animal health. Scientists at the University of Bonn have now devised a filter to tackle this issue, drawing inspiration from the gill arches of fish.
In early trials the patent-pending device removed more than 99% of plastic fibers from washing machine effluent. The findings have been reported in npj Emerging Contaminants.
How Washing Machines Release Microplastics
A single washing machine in a household of four can generate up to 500 grams of microplastics each year, largely due to the abrasion of textiles. Domestic appliances are therefore among the leading contributors to these microscopic particles. At present, microplastics flow straight into the sewage sludge produced by wastewater treatment plants. Because this sludge is frequently used as fertilizer, the fibers eventually find their way onto agricultural land.
Limitations in Existing Filter Systems
As a result, many manufacturers are seeking effective ways to remove microplastics from laundry water before they escape into the environment. "However, the filter systems available to date have several drawbacks," notes Dr Leandra Hamann from the Institute for Organismic Biology at the University of Bonn. "Some clog rapidly, while others fail to provide sufficient filtration."
Researchers Turn to Nature for a Solution
Studying the Gill Arches of Fish
Looking inside the mouths of Fish
In search of a practical solution, the researcher—together with her doctoral supervisor, Dr Alexander Blanke, and their team—turned to the animal kingdom for inspiration. They focused on fish, long regarded as exceptional natural filtration experts, having refined their mechanisms over hundreds of millions of years.
Certain species, such as mackerel, sardines and anchovies, feed by filtering water. They swim with their mouths open, using their gill arch system to extract plankton. "We examined the anatomy of this system in detail and used it as the blueprint for a washing-machine filter," explains Blanke, who is part of the University of Bonn's Life & Health and Sustainable Futures research areas.
Natural Cross-Flow Filtration
Over their evolutionary history, these fish have developed a form of cross-flow filtration. Their gill arches form a funnel-like structure, widest at the mouth and narrowing towards the gullet. The sides of this funnel are created by branchial arches equipped with comb-shaped structures covered in small teeth, forming a natural mesh held taut by the arches.
"During feeding, water passes through the permeable walls of the funnel, where it is filtered before the cleaned, particle-free water is expelled through the gills," Blanke explains. "The plankton, however, is too large to pass through the natural sieve and is therefore trapped. Thanks to the funnel's shape, it rolls down toward the gullet, where it accumulates until the fish swallows—clearing and resetting the system."
High-Efficiency Microplastic Removal
The New Filter Achieves Over 99% Efficiency
This mechanism ensures the filter never clogs. Rather than striking the filter directly, particles roll along its surface towards the gullet. It is also remarkably efficient, removing almost all plankton from the water—two key qualities required in a microplastic filter. The team therefore recreated the gill arch system, adjusting both the mesh size of the sieve and the angle of the funnel aperture.
"We have identified a set of parameters that allows our filter to remove more than 99% of microplastics from the water without becoming clogged," Hamann explains. To reach this result, the team relied not only on laboratory tests but also on computer simulations. The nature-inspired design requires no complex mechanics, making it inexpensive to produce.
Disposal and Practical Use
The captured microplastics accumulate in the filter outlet, where they are extracted several times per minute. According to Hamann—who has since taken up a position at the University of Alberta in Edmonton —the material could then be compressed within the machine to eliminate excess water. The resulting plastic pellet would need to be removed every few dozen wash cycles and disposed of with normal household waste.
Patent, Adoption and Future Impact
Patent Application and Industry Prospects
The team from the University of Bonn, together with the Fraunhofer Institute for Environmental, Safety and Energy Technology UMSICHT, has already filed a patent application for the invention in Germany, with an EU-wide application now in progress.
A Potential Turning Point in Microplastic Pollution
The researchers hope manufacturers will take the design forward and incorporate the filter into future washing machine models. Doing so could significantly reduce the release of microplastics from textiles— a necessary step; given growing concerns about their impact on health. Studies have detected these particles in breast milk, the placenta and even in the brain.
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