Without doubt, water is one of the most important resources worldwide. However, the manyfold use of water for irrigation, industrial processes and as drinking water leads to a severe reduction of the water quality. Due to its unique properties as solvent, it is far too often abused as mobile landfill or transport vehicle. Fortunately, used water passes purification processes on its way through the natural water cycle and can normally be reused. This natural water cycle, however, gets more and more frequently overcharged, and therefore the possibilities of reuse are limited by the water quality. It is technologically possible to reutilise used water directly, without undergoing the natural water cycle. However, this can only be done by understanding the underlying transport processes and the related biotic and abiotic conversion of substances. These are exactly the topics the members of the Chair cover in numerous projects which you can find on the following pages.