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L Solar water disinfection is a type of portable water purification that uses solar energy to make biologically-contaminated (e.g. bacteria, viruses, protozoa and worms) water safe to drink. Water contaminated with non-biological agents such as toxic chemicals or heavy metals require additional steps to make the water safe to drink. There are three primary subsets of solar water disinfection: # Electric. Solar disinfection using the effects of electricity generated by photovoltaic panels (solar PV). # Heat. Solar thermal water disinfection. # UV. Solar ultraviolet water disinfection. Solar disinfection using the effects of electricity generated by photovoltaics typically uses an electric current to deliver electrolytic processes which disinfect water, for example by generating oxidative free radicals which kill pathogens by damaging their chemical structure. A second approach uses stored solar electricity from a battery, and operates at night or at low light levels to power an ultraviolet lamp to perform secondary solar ultraviolet water disinfection. Solar thermal water disinfection uses heat from the Sun to heat water to 70–100 °C for a short period of time. A number of approaches exist here. Solar heat collectors can have lenses in front of them, or use reflectors. They may also use varying levels of insulation or glazing. In addition, some solar thermal water disinfection processes are batch-based, while others (through-flow solar thermal disinfection) operate almost continuously while the Sun shines. Water heated to temperatures below 100 °C is generally referred to as Pasteurized water. High energy ultraviolet radiation from the Sun can also be used to kill pathogens in water. The SODIS method uses a combination of UV light and increased temperature (solar thermal) for disinfecting water using only sunlight and PET plastic bottles. SODIS is a free and effective method for decentralized water treatment, usually applied at the household level and is recommended by the World Health Organization as a viable method for household water treatment and safe storage.〔 SODIS is already applied in numerous developing countries. Educational pamphlets on the method are available in many languages,〔 each equivalent to the English-language version.〔 == Principle of SODIS == Exposure to sunlight has been shown to deactivate diarrhea-causing organisms in polluted drinking water. Three effects of solar radiation are believed to contribute to the inactivation of pathogenic organisms: * UV-A interferes directly with the metabolism and destroys cell structures of bacteria. * UV-A (wavelength 320–400 nm) reacts with oxygen dissolved in the water and produces highly reactive forms of oxygen (oxygen free radicals and hydrogen peroxides) that are believed to also damage pathogens. * Cumulative solar energy (including the infrared radiation component) heats the water. If the water temperatures rises above , the disinfection process is three times faster. At a water temperature of about , a threshold solar irradiance of at least 500 W/m2 (all spectral light) is required for about 5 hours for SODIS to be efficient. This dose contains energy of 555 Wh/m2 in the range of UV-A and violet light, 350–450 nm, corresponding to about 6 hours of mid-latitude (European) midday summer sunshine. At water temperatures higher than , synergistic effects of UV radiation and temperature further enhance the disinfection efficiency. 抄文引用元・出典: フリー百科事典『 ウィキペディア（Wikipedia）』 ■ウィキペディアで「Solar water disinfection」の詳細全文を読む スポンサード リンク
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