Although 72% of the earth surface is covered by water, less than 1% of the world’s fresh water is directly accessible for human uses. Given humans’ water consumption patterns and the world population growth rate, these fresh water reserves have been shrinking all over the world at an alarming rate. There are currently more than 800 million people facing water scarcity and the United Nations project that approximately 2 to 7 billion people will be left without water by 2050; moreover, in the next 20 years, the average global supply of water per person will drop by one-third (see United Nations, 2003 and 2006).