Every time we flush the toilet we turn 3 to 5 gallons of fresh drinking water into sewage. Yeah yuck… it’s not sustainable and requires enormous water and water treatment systems to maintain. The best solution I’ve run across is the sawdust toilet… a bucket + composting pile. You can read all about building and maintaining sawdust toilets at Joseph Jenkin’s website.
I also recently ran across a non-proit organization operating in Haiti that is turning a huge human waste problem into safe fetiliizer. The organization is called SOIL, Sustainable Organic Integrated Livelihoods. Also see them in this New York Times Video.