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 The Solar Car Book A complete kit for making a cool solar racecar. Everything is included: wheels, axles, motors, wires and a genuine one-volt solar cell. |
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Solar Water Disinfection & Pasteurisation Projects
See also:
Solar Chimney Solar Air Conditioning Solar Pond Salt Evaporation Pond Solar Furnace Solar Cooker Solar Still Solar Water Disinfection Solar Desalination Solar water disinfection, also known as solar water pasteurisation or SODIS, is a method of disinfecting water using only sunlight and plastic PET bottles.
PrincipleBy filling a polyethylene bottle with contaminated water and leaving it in bright sunlight, it is treated through three synergistic radiation mechanisms.
The combined effect of all three mechanisms is greater than the sum of the individual components. NotesSODIS efficiency depends on the physical condition of the plastic bottles, with scratches and other signs of wear reducing the efficiency of SODIS. Heavily scratched or old, blind bottles should be replaced. If the sunlight is less strong, due to overcast weather or a less sunny climate, a longer time in the sun is necessary. SODIS: Water Project Was lead By Dr Kevin McGuigan of The Royal College of Surgeons in Dublin. Professor Ronan Conroy part of the RCSI team worked with Dr T Michael Elmore-Meegan of ICROSS in Kenya pioneering the only clinical control trials of this innovation. Their work has led to the widespread use of SODIS internationally. An expanded research team has embarked on a multi country SODIS study including study areas in Zimbabwe, South Africa and Kenya. Suggested Treatment Schedule
CautionsIf the water bottles are not left in the sun for the proper length of time, the water may not be safe to drink and could cause illness. Some glass or PVC container materials may prevent ultraviolet light from reaching the water.[2] There is concern over whether plastic drinking containers can leach chemicals or toxic components into water, a process possibly accelerated by heat. The Swiss Federal Laboratories for Materials Testing and Research have examined the diffusion of adipates and phthalates (DEHA and DEHP) from new and reused PET-bottles in the water during solar exposure. The levels of concentrations found in the water after a solar exposure of 17 hours in 60°C water were far below WHO guidelines for drinking water and in the same magnitude as the concentrations of phthalate and adipate generally found in high quality tap water. Concerns about the general use of PET-bottles were also expressed after a report published by researchers from the University of Heidelberg on antimony being released from PET-bottles for soft drinks and mineral water stored over several months in supermarkets. The antimony concentrations found in the bottles however are orders of magnitude below WHO [1] and national guidelines for antimony concentrations in drinking water.[3][4][5] ApplicationsSODIS is valuable for treating water where fuel or cookers are unavailable or prohibitively expensive. Even where fuel is available, however, SODIS is a more economical and environmentally friendly option. In theory, the process could be used in disaster relief or refugee camps. However, supplying bottles may be more difficult than providing equivalent disinfecting tablets containing chlorine, bromine, or iodine. Additionally, in some circumstances, it may be difficult to guarantee that the water will be left in the sun for the necessary time. SODIS has been applied in several communities in Brazil, one of them being Prainha do Canto Verde north of Fortaleza. There, the villagers have been purifying their water with the SODIS method. It is quite successful, especially since the temperature during the day can go beyond the 40ºC (100ºF) and there is a limited amount of shade. See alsoReferences
External links
This article is licensed under the GNU Free Documentation License. It uses material from Wikipedia Encyclopedia article "Solar Water Disinfection" |
