Turning wastewater into reusable water using reverse osmosis to further purify it is an idea quickly growing around the world. In some parts of California, namely Carmel and Orange County, it is already a reality. Wastewater is 99.9% water, yet we dispose of this valuable resource down drains, into rivers, and out to sea. Wastewater contains useful chemicals that can may also be recycled in the future.
The link below contains a video from Stanford professor, Craig Criddle describing how we can benefit from making our water a renewable natural resource.
Using Wastewater as a Resource: http://woods.stanford.edu/cgi-bin/focal.php?name=wastewater&focal_area=freshwater