Seite - 62 - in Clean Water Using Solar and Wind - Outside the Power Grid

62 Clean Water Using Solar and Wind: Outside the Power Grid often the first step in water purification, Section 5.2. Desalination is a key technology to produce clean fresh water, Section 5.3. Disinfection, 5.4, is another important means of removing pathogens and protecting human health. 5.1 PRODUCING CLEAN WATER The required energy to clean water depends on the quality of the raw water supply. Often, available water sources in developing countries are contaminated and consequently there is a high demand on energy use by volume of water (such as kWh/m3) to treat the water to an acceptable quality. 5.1.1 Underground water resources Groundwater is the major source of water in many parts of the developing world and there is a serious problem in that in many places the water table is declining. As mentioned in Section 4.2, underground water has been pumped in an unsustainable way in many regions. There are two consequences: water sources are dwindling and the pumping energy to reach them is increasing. In many areas water that has been pumped from aquifers has been underground for thousands of years and is now being used far in excess of the rate at which the water is replenished. It may take generations or centuries to refill these aquifers via rainwater. Such a resource is non-renewable and this kind of practice can be called mining of groundwater. Irrigation will of course influence groundwater resources. Since the irrigation is mostly done in dry or arid areas there is a large risk that the groundwater levels will decrease, since the groundwater will not recover as quickly as it is consumed. 5.1.2 Saline water The need to use seawater as a source for fresh water has increased dramatically because of both population growth and climate change. Many dry regions have become drier. Using seawater as a source represents an important possibility in coastal areas. The salt concentration in seawater is typically 3.5% or 35,000 ppm (parts per million or mg/l). Many underground aquifers or other groundwater sources have brackish water that needs to be made drinkable by Downloaded from https://iwaponline.com/ebooks/book-pdf/520710/wio9781780409443.pdf by IWA Publishing user