There are elevated levels of phosphorus in the wastewater in Barntrup in North Rhine-Westphalia. In order to filter out the pollutants, the town is using an innovative process using fibre balls known as Fuzzy Filter® balls, which clean 95% of the wastewater.
Every year, 8,000 tonnes of medicines and 10 tonnes of microplastics enter Germany’s largest river, the Rhine. In order to reduce the pollution, there is an additional purification stage in many wastewater treatment plants. It filters out microplastics measuring between five micrometres and five millimetres and removes micro-pollutants such as pharmaceutical residues.
In a standard setting, an additional, large clarifier has to be used to filter out up to 80% of the pollutants. By comparison, wastewater treatment plants without this additional purification stage retain just 30% of the trace substances trapped.
The Westphalian town of Barntrup found this 80% level too low because the purified water can enter a drinking water catchment area via a river system. The town opted for the world’s first wastewater treatment plant using Fuzzy Filters®, which eliminate 95% of all trace substances while also cleaning the wastewater of microplastics and phosphorus. Another advantage is that no large clarifier is needed, just a small functional building.
Pure water thanks to activated carbon and Fuzzy Filter® balls
With both the standard process and the new technique, activated carbon is mixed into the water in the additional purification stage. Thanks to its porous and flaky structure, activated carbon has a huge inner surface. One teaspoon of powdered activated carbon has the same surface area, for example, as a football field. This area gives micro-pollutants and trace substances plenty of space to adhere to it.
With the Fuzzy Filter® solution, the contaminated water finally flows through the Fuzzy Filter® balls from top to bottom. These are made of synthetic fibres that are made into a ball around 33 millimetres in diameter with the aid of a clip. The balls remove the activated carbon with the micro-pollutants it has absorbed, along with the microplastics from the water and the filtered water then flows out of the system from the top.
Valves and slides are opened via Festo pneumatic swivel/linear drive units controlled by valve terminals, enabling the automatic inflow of wastewater containing micro-pollutants and the outflow of the purified water from the Fuzzy Filter® system.
Cleaning and reusing the Fuzzy Filter® balls
Both the Fuzzy Filter® balls and the activated carbon can be reused many times. They have to be cleaned using a backwash cycle. To do this, raw water flows into the filter, while an external bellows blows cleaning air into it. The filter balls are set dancing in the turbulent air flow so that dirt particles that have stuck to them are removed and are rinsed out of the filter. The filters are then returned to the aeration tank along with the activated carbon and used for another cleaning process because the activated carbon is only slightly contaminated with pollutants after the first cleaning process.
Festo pneumatic swivel/linear drive units are also used when cleaning the Fuzzy Filter® balls. They let the correct amount of cleaning air into the system and help to remove the sludge.