The Fraunhofer IGB has been testing this new concept for water management in a development area belonging to Knittlingen, a town near Pforzheim, since 2006. The project, entitled DEUS 21, is funded by the German Federal Ministry of Education and Research (BMBF). A vacuum plant was put into operation at the end of 2005. It is a reliable system for collecting wastewater from the houses on the new estate and passing it on for purification. The pilot plant was set up initially to cater for only a small number of inhabitants living on the development area at that time. From 2006 onwards, it operated from the so-called water house in order to gather the exact data needed for the technical plant. By 2008, the plant had been optimized technically to purify the wastewater of the meantime number of inhabitants viz. 175. It can easily be expanded to cope with the expected population of the development area. While the anaerobic wastewater technique was being developed, technologies for recovering phosphor and nitrogen from the plant’s effluent were tested and then incorporated as technical units in the water house’s process line.
Rainwater is collected in separate tanks and stored in underground cisterns for subsequent treatment in the water house. The aim is to purify rainwater until it reaches drinking water quality and then deliver it to the inhabitants of the estate through a separate network in order to save large quantities of drinking water. Treated rainwater can be used for flushing toilets, watering gardens, operating washing machines and dish washers and use in sinks and showers. The first stage involved testing the collected rainwater over a longer period of time and trying out various process techniques for treating water. Meanwhile the inhabitants are supplied with communal drinking water from Knittlingen's central system.