In the futuristic city they will recycle their water.
It will be pretty much a closed loop.
Likely in this case the water from sewage wll be cleaned to brown water standards and then sent to green houses or vertical growing centers to grow food and then it will be cleaned again for drinking
The technology to do it is already available. Its not widely used because of the ick factor.
Yeah, the RATs will be all over it. They're into urine and scatology. They wouldn't even want the purifying technology.
As I recall, the Gates Foundation funded that technology. I remember seeing a video of Bill Gates himself drinking water that was recycled from sewage. Tons of tests were performed and the water produced by the system was cleaning, bacteria -free, and without adverse smell or taste.
If you don’t think about it, the ick factor goes away.