Due to their unique possibilities the relevance of pressure-driven membrane processes in the water technology field increases strongly. Their universal possible fields of application in seawater desalination and waste water treatment, as well as for process and drinking water production explain its enormous growth potential. This trend-setting technology has also become more and more important in Germany. Accordingly, the German WAG Wassergewinnungs- and aufbereitungsgesellschaft Nordeifel is currently building an extension of their existing water work (WW) at Roetgen/Aachen consisting of an ultrafiltration (UF) membrane plant with a capacity of 6,000 m3 h−1. Furthermore, a second UF stage with a capacity of 600 m3 h−1 for the treatment of the back-wash water of the first stage is being built.

The paper gives an overview of the planning process starting from first pilot plant experiments with small pilots to the ideal design of Germany's largest drinking water treatment plant by means of membrane technology. Further, it shows the benefit of efficient co-operation between a dedicated consumer, an internationally active research and consulting institute, and a well experienced planning agency.