Research project makes Kassel's drinking water supply climate-proof

The drinking water supply in the city in northern Hesse has several drinking water sources and has proven to be reliable to date. One of the reasons for the current good situation is a heterogeneous raw water extraction area. It consists of two spring areas in the Habichtswald and Kaufunger Wald forests, several deep wells and a groundwater recharge at the Neue Mühle waterworks. However, climate change and extreme weather conditions such as prolonged periods of drought are leading to declining water resources, which are reflected, for example, in falling groundwater levels, lower spring discharges and lower water levels in the Fulda. For this reason, Städtische Werke Netz + Service is investigating several preventive measures in the area of water supply.

Researchers from the Department of Urban Water Management at the University of Kassel are now also contributing scientifically. In the "Flexillienz" research project, the university, Städtische Werke Netz + Service and other partners are investigating the permanent use of spring water from the Habichtswald forest, among other things. Project Leader Dr.-Ing. Philipp Otter points out that dry spells and heavy rainfall have also been recurring in Kassel since 2018 - both of which, like snowmelt, can contaminate spring water.

As part of "Flexilienz", a new type of "ultrafiltration system" is therefore to filter cloudy spring water from the Habichtswald. The technology is new, uses membranes with a smaller pore size than previous filter systems and requires no pumps and therefore no energy. This measure would make Kassel's drinking water supply even more resilient to climatic weather events.

At the same time, the researchers want to test new ways of producing hydrogen. "Hydrogen is the energy source of the future. But people rarely consider how much water is needed to produce it," explains Prof. Dr.-Ing. Tobias Morck, Head of the Department of Urban Water Management, and calculates: "To produce one kilo of hydrogen, you need 11 kilos of water. And that's not including the water for cooling, etc." The research consortium therefore wants to test how hydrogen can also be produced from filter backwash water, which cannot be used so far. To this end, an electrolyser will be combined with a special filter membrane at the Tränkeweg waterworks in Kassel-Niederzwehren.

And finally, the researchers want to investigate whether the pumping and storage systems of a water supplier can also serve as a kind of battery to temporarily store energy. Similar to a pumped storage plant, more drinking water could be pumped into the elevated tanks at times of high feed-in to the grid - i.e. when the sun is shining and the wind is blowing - in order to distribute it to consumers at times of low energy feed-in and high consumption. As critically low storage levels are also to be checked here, this investigation is initially being carried out as a simulation as part of "Flexilienz".

Andreas Kreher, Managing Director of Städtische Werke Nerz + Service, on the project: "We will put the entire water production on a broader basis if we use more spring water and more frequently. This would make the supply to Kassel and Vellmar as a whole noticeably more flexible. Our aim is therefore to permanently increase the so-called water supply. Greater availability of springs is very helpful here."

The project was launched in March 2025. In addition to Städtische Werke Netz + Service, the Fraunhofer IEE in Kassel, the Technologiezentrum Wasser TZW and the companies EnWaT GmbH and Oppermann GmbH - Ingenieurbüro are also involved. "Flexilienz" is being funded by the Federal Ministry of Education and Research with 2.6 million euros as part of the "Water Supply of the Future" funding measure; the University of Kassel is receiving 0.78 million euros of this. The results should be transferable to water suppliers throughout Germany and Europe.

Scientific contact person:

Dr.-Ing. Philipp Otter
University of Kassel
Department of Urban Water Management
Phone: +49 561 804-3021
Email: otter[at]uni-kassel[dot]de

Contact for the press:

Sebastian Mense
University of Kassel
Communication and Marketing
Phone: +49 561 804-1961
E-mail :presse@uni-kassel.de
http://www.uni-kassel.de www.uni-kassel.de