Seite - 90 - in Clean Water Using Solar and Wind - Outside the Power Grid

90 Clean Water Using Solar and Wind: Outside the Power Grid capacity even if the product quality is unfailing. Thus, membrane fouling and cleaning are of major importance. A good overview of membrane technology in used water treatment is found in Leslie and Bradford-Hartke (2013). 7.2.5 Disinfection Disinfection has been described in Chapter 5.4. The aim of any type of sanitation system must be to inactivate or reduce potentially pathogenic organisms. Since a decentralised system often aims at water reuse, for example when greywater is used for personal hygiene, it becomes crucial to reduce the pathogens. As mentioned in Chapter 7.1, there are international guidelines for hygiene in water (WHO, 2006). Stenström (2013) has described major issues in reducing pathogens in water. Storage of urine has been mentioned as an effective way of reducing pathogens. In faecal excreta, on the other hand, a much longer time is needed to reduce the risk of pathogens. The hygienisation depends on the storage time, pH and temperature. The storage time is usually more than a year. Thus, anaerobic treatment is advantageous, both to produce energy and to reduce the pathogens. 7.3 ENERGY ASPECTS The main operations of used water operations that depend on electric energy are: • Pumping; • Aeration; • Disinfection. Energy for pumping has been discussed in Chapter 4. Three aspects are essential: the required flow rate, the elevation of the water and the timing of the pumping. The various types of used water may be stored in tanks and can be brought into the tanks mostly by gravity. The timing of when the tanks are to be emptied is not critical, which is helpful when electricity generation is intermittent. For activated sludge plants the typical energy use in Sweden, Germany and Switzerland is of the order 15–45 kWh/person/year, where small plants have the higher specific-energy demand. Aeration Downloaded from https://iwaponline.com/ebooks/book-pdf/520710/wio9781780409443.pdf by IWA Publishing user