While the Western world pretty much have an infinite access to fresh water, the situation is quite different in many countries, among them African countries. With nanotechnology, you could use a sheet of graphene to filter water from salt and other unwanted substances. This is possible due to the size of the rings in which the carbon atoms are arranged in graphene. Water molecules are small enough to pass through, salts and other molecules are not. This could have ENORMOUS implications for the health and well being of people living in Africa and other places where the access to fresh water is scarce.