What are the best Water Tech for Smart Cities

I'm looking for innovative solutions in water use, recycling, waste etc which could be adopted in developing a smart water city.

These innovations would be implemented into a new 2,000 smart homes. We are implementing in Garden Village/city in the North East of England for homes, retail and commercial buildings, including the urban environment and infrastructure. 

Which technologies do you suggest as most efficient, used and proven to be the best?