It’s most important to close the circle of water usage and reduce wasted water, this circular use of water has to include all waters and materials in the water, to effectively be more sustainable. This closing of the water loop must have the goal to reduce wastewater to almost zero. 

In the future the aim will be that these circular cities will be self-sustained in water usage and can grow without using more and more water.

New buildings have to be design with a circular water usage in mind. 

• Rain has to be captured and collect in cisterns
• Permeable concrete has to be used to collect rainwater for later use 
• Industries have to use water and their wastewater efficiently 

An example on how industries could use water more efficiently, they could use their warm wastewater as a heating source for the city. Another use for wastewater could also be, to use it as biomass, to produce energy or as fertiliser for the agriculture sector. [3,6,7,9]