Page - 67 - in Clean Water Using Solar and Wind - Outside the Power Grid

Water treatment 67 exhaustion of conventional energy resources, it is a very attractive and promising prospect to use renewable energy to produce clean water. This is particularly true in the case of solar energy since regions with great water shortages tend to be those with higher solar radiation. The water supply source for desalination is not always seawater, as shown in Table 5.2. Brackish groundwater is common in many water- scarce regions in the world. Table 5.2 Potable water sources (globally) for desalination. Desalination From Percentage Seawater 59 Brackish water 21 River water 9 Pure water for industrial applications 5 Used water for reuse <5 Source: Wikipedia. In many parts of the developing world there is plenty of both brackish water and solar energy. The use of solar energy to supply power for local desalination of brackish water is an interesting option where potable water is scarce. 5.3.2 Distillation – thermal methods By heating up the water it is possible to separate the salt and dissolved minerals from the water in seawater or brackish water. This is called distillation. The basic principle of distillation is simply to heat up the water, let it evaporate and then condense it, producing fresh water. This principle has been used in warm and dry countries over the centuries by using sunlight. In ancient times sailors at sea obtained drinking water from primitive distillation systems. Inventors like Leonardo da Vinci and Thomas Jefferson experimented with seawater desalination. Aristotle, as early as the fourth century BC, described a method to evaporate impure water and then condense it to obtain potable water (Kalogirou, 2005). Downloaded from https://iwaponline.com/ebooks/book-pdf/520710/wio9781780409443.pdf by IWA Publishing user