Water dew collection ?

I remember watching a documentary on tv that shows how water can be collected if you are outside camping.The idea was to trap/collect water dew in the early morning of the day,using a plastic bag placed on a hole digged on the ground.A process called CONDENSATION if I not mistaken.

What if in future,every housing has this water dew collection at the top of the building,then filtered to go through every household.The water can be either used for flushing or cleaning.Either way if the water can be filtered for safe drinking

Just an idea how to collect & recycle water.Possible?