Turning city drains into the first line of defence against microplastics

Every time it rains in the city, invisible traces of tyre wear, road dust and microplastics are washed into the drains and further out into lakes, streams and coastal waters, where they are almost impossible to remove. With a modular filter system installed directly in manholes, BAIONYX and partners aim to capture microplastics at the source, before they ever reach the aquatic environment.

Road traffic sends microplastics straight into the water environment

Microplastics from tyre and road wear are one of the largest, yet often overlooked, sources of plastic pollution. As stormwater runs off road surfaces and into drains and combined sewer overflows, these particles are carried along and discharged into rivers, lakes and coastal areas, where they accumulate in sediments and food chains. Existing treatment solutions are rarely designed to tackle this pollution at source – especially not in stormwater discharges. At the same time, very different loading patterns (from quiet residential streets to heavily trafficked arteries) mean that a single, one-size-fits-all solution is unlikely to perform well everywhere.

Modular filters directly in the urban drainage system

BAIONYX has developed a modular filter solution that can be installed in existing manholes to capture microplastics and other particles directly in the drainage system. In this project, the technology will be further developed through testing of different filter mesh types and combinations – for example coarse and fine filters placed in sequential manholes and adapted to local loading conditions. The Danish Technological Institute contributes with method selection, test design and experience-based advice, while Frederiksberg Municipality and Utility provide test sites and operational experience from previous BAIONYX pilots. The aim is to identify filter configurations that are technically robust, easy to operate and scalable to many different cities.

From pilot filters to a standard solution for cities

The project is intended to move the solution from prototype to a documented, pre-commercial filter system with concrete performance data on the reduction of microplastics and suspended solids under different conditions. In the short term, the ambition is to deliver knowledge that gives municipalities and utilities the confidence to move ahead with full-scale tests and first roll-outs – and to sign agreements with additional Danish pilot cities. In the longer term, the vision is that modular microplastic filters become a standard element in stormwater and drainage projects in Nordic and European cities, so that urban road runoff is no longer one of the major “hidden highways” for plastic pollution into nature.