• Four months of test operation on Frederiksberg in Copenhagen show a significantly higher retention of microparticles across the entire 6-500 µm spectrum - with particularly strong performance from 63 µm and upwards - despite the test period seeing only light to moderate rainfall and a total of 121 mm.

• Laboratory tests confirm that up to 97% of TSS can be retained - a potential now being translated into practice.

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Copenhagen, 28 November 2025 - After approximately four months of test operation on Frederiksberg Allé in Copenhagen, the results for BAIONYX’s particle filter - with a special focus on microplastics from tyre wear - are highly positive. A customised version of the filter, designed specifically for Danish gully dimensions, was installed in roadside drains on a busy stretch with an average of 7,700 vehicles per day. Compared to standard gullies, the filter captured more than twice as many solids and microplastics in the sediment trap.
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The filter primarily retained particles in the 6-500 µm range, with a marked increase in efficiency from 63 µm and above. For comparison, common everyday particles fall within this size spectrum: flour (<180 µm), human hair (80-120 µm), sugar (400 µm), and espresso powder (300-400 µm). The results demonstrate that the filter solution can be a valuable addition to urban drainage systems - particularly in areas where road runoff is not connected to a wastewater treatment plant.
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The Copenhagen test is the fourth real-world trial, following previous field tests conducted by the Audi Environmental Foundation in collaboration with Technische Universität (TU) Berlin. Earlier trials were carried out on the heavily trafficked Clayallee in Berlin, on ADAC’s wet-handling tracks, and on a curved through-road in Klein Schöppenstedt near Braunschweig in Lower Saxony - all showing similarly strong results.
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The filter’s effectiveness has also been documented at laboratory scale under controlled and reproducible conditions at TU Berlin’s test facility, where the particle filter retained up to 97% of Total Suspended Solids (TSS). The real-world tests additionally confirm the system’s long-term durability and ease of maintenance.

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The filter solution used in Copenhagen was developed in cooperation between filter manufacturer GKD and the Danish startup BAIONYX.
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“We are very pleased with the results from Frederiksberg, which confirm the effectiveness of the solution - even under conditions with only light to moderate rainfall and a total of 121 mm during the test period. This means the results are conservative and can be expected to be even more pronounced during heavy rain and cloudbursts, where a standard gully quickly loses grip and washes particles straight through,” says Søren Dandanell, Nordic Lead for BAIONYX’s filter solution.

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Rüdiger Recknagel, Managing Director of the Audi Environmental Foundation, adds:
“Microplastics are now found everywhere in the environment, and we know today that these particles are also present in the human body. It is therefore essential to filter out as many microplastic particles as possible before they enter natural ecosystems or the human body. We are very pleased with the positive test results.”

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