In most of the developed world, clothes washing machines and toilets are supplied with clean drinking water. New solutions need to be tested and implemented to help relieve pressure on global water supplies and ensure that the next generation has access to drinking water.


Using rainwater in households for things like washing and flushing could cut global drinking water consumption by as much as 40 percent. In Aarhus, Denmark, a water treatment utility company, a real-estate developer, an engineering company and a water treatment plant manufacturer joined forces to implement a solution in a new part of the city.



In the new neighborhood of, Nye, which is a suburb of Aarhus where up to 10,000 new homes are planned to be built, rainwater will be used for toilet flushing and laundry.  To accomplish this, the area has taken a novel approach to rainwater capture and reuse. 

Rainwater is collected in an artificial lake and cleaned to a quality that is acceptable for clothes washing and toilet flushing at a treatment plant using:

  1. A pressure filter system 
  2. Ultrafiltration (as a membrane technology)
  3. Ultraviolet disinfection

Water will be sent to homes through a separate pipe system developed specifically for this purpose. The pipes are sized based on a calculation of the need for water for laundry and toilet flushing, and they are colored purple so that they are clearly different from the drinking water pipes.


The new approach to water conservation is expected to serve about 20,000 residents and will also prove the importance of thinking about water conservation and reuse in more nuanced and innovative ways. 


The solution is developed in a cooperation between Aarhus Vand, Tækker, COWI, and Silhorko-Eurowater.