reference book "Ökologisches bauen"

Chapter Water:

The importance of water as basis on which life depends has been mentioned previously. Water will be the main problem in future. The actual handling with water and wastewater results in high water consumption, considerable quantities of waster water and the overuse of natural water resources. Pure drinking water is used for flushing away sanitary sewage. Large amounts of substances are needlessly water-diluted and are pipelined to central sewage treatment plants. By cost-intensive treatment, this wastewater will be purified and conveyed into waters.
The protection of the water cycle with all valuable substances is the guiding objective. This correlates with the chapter urban space, because the quality and design of open space is closely connected with water. Measures concerning building include conserving rainwater in urban space, decentralised wastewater treatment, water saving and water recycling