The project was launched in September 2020 by the Audi Environmental Foundation and TU Berlin and initial field and lab tests have now demonstrated the efficiency of the URBANFILTER system which has already been deployed on the streets of Berlin.
Tyre and road wear particles are generated by all traffic and an estimated 110,000 metric tonnes of it ends up on the streets in the form of microplastics every year in Germany alone. From there, it is blown into the environment by the wind, or is washed by the rain as urban runoff through the sewers into the soil, rivers and ultimately the oceans.
The new filter concept for urban runoff traps the respective dirt particles as close as possible to the location where they are generated before rainwater can rinse them into the sewers. Tests in a laboratory at TU Berlin have shown that the filters work very effectively. Without clogging up, the filters permanently trapped street cleaning waste, cigarette filters, microplastics in the form of plastic granulates up to three mm in size, sweet wrappers, and lids of disposable coffee cups.
The sediment filters are divided into three zones – street, sewer, and drain – and consist of nine modules. Up to three modules can be combined to achieve the best result depending on the location. In the uppermost area (road), this might be a special runoff channel. Below this, in the sewer itself, larger solids are filtered out, for example, with the aid of an optimised leaf basket or what is known as a filter skirt. The lowest area (drain) is about fine filtration, for which a magnet module can be used.
This filtering out of ultra-fine particles is still presenting the research team of with challenges. “The system has already passed tests with ground tyre rubber between 20 to 1,000 micrometres (µm) in size in conditions of light to medium rainfall. Now we’re working on improving the filter performance when there is strong rainfall,” explains Daniel Venghaus, research associate in the Department of Urban Water Management at TU Berlin. “However, ground tyre rubber, which can be used for testing purposes, behaves differently to genuine tyre wear particles. Field tests on roads will provide further information.
The goal of the tests and of further development work is for the URBANFILTER to be in operation for up to a year without having to be maintained or cleaned.