Think.Link.Do. – our motto of the research field E+E – was also the focus of this evening, as moderator Prof. Dr.-Ing. Peter Pelz (Vice President for Sustainability and Digitalization and co-spokesperson for the E+E research field) emphasized, focusing on the courage for new ideas, constructive exchange and concrete solutions. In her welcoming address, TU President Tanja Brühl also made it clear: “We need bold innovations, we need exchange and understanding – and we need to take bold and collaborative action!” She emphasized that our social mission as a university is to research innovative and practicable solutions.

The evening began with two interesting keynote speeches, one dealing with pollutant inputs and emission sources of micropollutants in the water cycle and the other with the potential of the fourth purification stage in wastewater treatment plants. Firstly, Prof. Dr. Thomas Ternes from the Federal Institute of Hydrology clearly showed how pollutants – such as pharmaceutical residues, pesticides, industrial chemicals and microplastics – enter our waters via various sources. It was particularly alarming to learn that, in addition to treated wastewater from sewage treatment plants, uncontrolled combined sewer overflows and stormwater drains also play a major role. During heavy rainfall, not only treated wastewater but also unfiltered mixed water – for example with highly problematic tire abrasion, which has already led to fish kills in Canada – flows directly into the water cycle.

The second keynote speech, given by Professor Susanne Lackner (IWAR, TU Darmstadt), an expert in the field of water and environmental biotechnology, focused on the possibilities and limitations of the fourth treatment stage. Advanced technologies such as activated carbon filtration and ozonation were presented, which have the potential to reliably remove pollutants from wastewater. At the same time, it became clear that purification via wastewater treatment plants can only remove part of the trace substances and micropollutants, as around two thirds of the pollution load enters the water cycle unfiltered via discharge plants. The principle of prevention should therefore be the top priority – an approach that is to be conceptually implemented within the framework of the EU's Urban Wastewater Directive (EU-WWD) through extended producer responsibility.

One thing became clear from the presentations and the discussion: although the majority of trace substances can be removed from our water cycle, the concentrations of micropollutants have been increasing for decades and will continue to rise in the future, according to Prof. Dr. Thomas Ternes (BfG). Efficient solutions are therefore urgently needed. In addition, chemical pollutants often remain in the recycling cycle, which has a lasting impact on the quality of the materials. A central concern must therefore be the promotion of reuse and the circular economy, according to Dr. Ulrike Braun (UBA). Instead of constantly developing new material and packaging solutions that ultimately cause new problematic emissions, we should work on high-quality products that can be effectively degraded or removed – and fundamentally rethink our consumption. As one member of the audience aptly put it: We are all ultimately polluters when we use these products.

The evening provided a comprehensive insight into the many challenges and opportunities in dealing with trace substances in the water cycle. The discussion made it clear that, in addition to technical innovations, close cooperation between science, politics, industry and the public is also required in order to develop sustainable solutions. Future efforts and innovative concepts are necessary to protect our water resources for future generations.