The shiny, round stainless-steel tank is 3.5 meters high. Wastewater is fed into the top via a hose, and at the bottom, it emerges cleaned of microplastics through a funnel and is channeled into a basin.
Inside this bioreactor at the Petershausen treatment plant, the finest microplastic particles are removed from the wastewater in an unusual way. Professor Sabine Grüner-Lempart from the Weihenstephan-Triesdorf University of Applied Sciences developed the project with a team of bioengineers: “We now have a community of microorganisms inside—bacteria and fungi—that coexist well and thrive excellently under these conditions. These microorganisms are capable of breaking down microplastic particles.”
A sturdy ladder stands beside the large tank. Climbing up it, you can peer inside through several small windows. The view reveals small lava stones, over which the wastewater trickles in fine streams. These lava stones from the Vulkaneifel region play a central role, according to scientist Anna Lena Schuhmacher, who oversees the project: “A biofilm forms on the lava stones. The whole system is then trickled with wastewater. Any remaining microplastic particles in the water can settle into this biofilm, where the microorganisms then get the opportunity to break them down.” In Petershausen, the process leaves behind particles that look like oatmeal.
Researchers have found that every person ingests about 5 grams of microplastics per week—roughly the weight of a credit card. The exact effects of these substances on the human body are not yet fully known, but they are suspected to be harmful.
The pilot system was developed by a Bayreuth-based company for water and wastewater technology, in collaboration with the scientists from Freising. The project is funded by the German Federal Ministry for Economic Affairs and Climate Action.
A conventional wastewater treatment plant has three cleaning stages: mechanical, biological, and chemical. A new EU requirement will soon mandate a fourth stage for micro-pollutants. And this fourth stage is now being tested with the help of the Petershausen community. The municipality has had positive experiences collaborating with scientists in recent years, even saving significant money, as Mayor Marcel Fath (independent) explains: “As a small community, we benefit greatly. During our last renovation a few years ago, when we expanded the treatment plant, we were able to utilize a research project. Through its practical implementation, we saved millions of euros.”
The Petershausen treatment plant is well-suited for this pilot because it is representative of standard plants in Germany, designed for wastewater from 3,000 to 30,000 citizens. The scientists, company, and municipality are delighted that this new method is now being implemented and proven to work in a real-world setting. The partners hope the pilot system will soon become a market-ready fourth cleaning stage for wastewater treatment plants.
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