Yes, there have been standards for years already. It was proven in s US city some time ago when it faced a bad drought. Las Vegas is a 100% closed loop system.

Yes, there have been standards for years already. It was proven in s US city some time ago when it faced a bad drought. Las Vegas is a 100% closed loop system. All grey water is recycled back into Lake Mead fur reuse. Modern sewage treatment is a modern miracle.