Every time a washing machine spins, tiny plastic fibres are released from synthetic clothing. Most are invisible to the eye, but their impact is increasingly hard to ignore. Household laundry is now recognised as a major source of microplastics entering wastewater systems, where these particles can accumulate in sewage sludge and ultimately enter soils, waterways and food chains.
New research from the University of Bonn suggests an unexpected solution. By copying how fish filter plankton from water, scientists have developed a simple, self-cleaning filter that can remove more than 99 per cent of microplastic fibres from washing machine wastewater before it enters the sewer.
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Why washing machines are a major source of microplastics
Textile abrasion during washing releases large quantities of microplastic fibres, particularly from synthetic fabrics. Estimates suggest that wastewater from a single four-person household can generate up to 500 grams of microplastics each year.
Once released, these fibres travel through sewer networks to wastewater treatment plants. While many are captured in sewage sludge, that sludge is often reused as fertiliser. This creates a direct pathway for microplastics to move from households into agricultural soils and surrounding environments.
For water utilities, this represents a diffuse pollution problem that is difficult to address once fibres are already mixed into wastewater streams.
What existing microplastic filters struggle to achieve
A number of filtration systems have been proposed to remove microplastics from washing water. However, many face practical limitations. Fine meshes can clog quickly, while coarser filters allow fibres to pass through. Some designs rely on complex mechanical components, which increase costs and maintenance requirements.
“The filter systems available so far, however, have various disadvantages,” said Dr Leandra Hamann from the Institute for Organismic Biology at the University of Bonn. “Some of them quickly become clogged, others do not offer adequate filtration.”
The challenge has been finding a system that combines high capture efficiency with long-term operational stability.
How fish gills inspired a new filtration design
To solve this problem, the research team looked to fish that feed by filtering plankton from water, such as anchovies, sardines and mackerel. These species have evolved highly efficient filtration systems over hundreds of millions of years.
Instead of pushing water straight through a flat filter, fish use a funnel-shaped gill arch system. Water flows through the permeable walls of the funnel, while particles too large to pass through are retained and guided toward the gullet.
“We took a closer look at the construction of this system and used it as the model for developing a filter that can be used in washing machines,” said Dr Alexander Blanke, who led the research alongside Hamann.
Why the filter does not clog
A key advantage of the fish-inspired design is its ability to avoid blockages. The funnel shape creates a cross-flow effect. Rather than hitting the filter head-on, fibres roll along the mesh surface toward the outlet.
“Thanks to the funnel shape, it then rolls towards the gullet, where it is collected,” Blanke explained. “This prevents the filter from being blocked and effectively cleans the system.”
The researchers replicated this principle by varying the funnel’s mesh size and opening angle to find an optimal balance between capture efficiency and self-cleaning behaviour.
What the tests revealed about performance
Using a combination of laboratory experiments and computer simulations, the team identified a configuration that removed more than 99 per cent of microplastic fibres from washing machine wastewater.
Crucially, the filter maintained performance without clogging. The design does not rely on complex mechanics, making it potentially inexpensive to manufacture and robust in everyday use.
Captured microplastics are continuously transported to a collection outlet, where they can be suctioned away several times per minute. The fibres could then be compacted inside the machine, forming a small plastic pellet that users remove and dispose of with general waste after multiple washes.
Why this matters for water systems beyond households
While the filter is designed for washing machines, its implications extend further. Preventing microplastics from entering sewers reduces the load arriving at wastewater treatment plants, where removal options are limited and costly.
For Australian water utilities, source control is increasingly recognised as one of the most effective ways to manage emerging contaminants. Technologies that stop microplastics at the household level reduce downstream treatment complexity and environmental risk.
The research also reinforces the potential of bio-inspired engineering to address problems that conventional mechanical approaches struggle to solve.
From laboratory concept to real-world impact
The University of Bonn team, working with the Fraunhofer Institute for Environmental, Safety, and Energy Technology UMSICHT, has already filed a patent application in Germany, with European patenting underway. The researchers hope manufacturers will integrate the filter into future washing machine designs.
This would not eliminate microplastic pollution entirely, but it could significantly reduce one of its largest sources.
Analyses increasingly suggest that microplastics may pose serious health risks. They have already been detected in breast milk, placental tissue and even the human brain. Reducing emissions at the source could therefore deliver benefits well beyond cleaner wastewater.