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{{Wikipedia}} | {{Wikipedia}} | ||
[[Drinking water]] can be [[water disinfection|disinfected]] using the heat and (usually) the [[UV]] light of the sun. It is a very simple and [[low cost]] way of disinfecting small volumes of water. | |||
Radiation in the spectrum of UV-A (wavelength 320-400nm) and increased water temperature. Both factors cause damage to the DNA of the pathogens. The effects are also synergistic - the DNA being more prone to UV damage if the temperature is very high. If the water temperatures raises above 50°C, the disinfection process is three times faster, and much better results are obtained from | |||
Certain pathogens such as [[giardia]],{{wp sup|giardia]] however, are not easily killed by UV. For these, the heat is more important,{{fact}} and other steps such as [[filtration|filtering]] might also be considered. | |||
== SODIS - solar water disinfecting with soda bottles and sunlight == | == SODIS - solar water disinfecting with soda bottles and sunlight == | ||
Solar water disinfection, or {{WP|SODIS}}, is a method to disinfect water using sunlight and PET bottles. | Solar water disinfection, or {{WP|SODIS}}, is a method to disinfect water using sunlight and PET bottles. | ||
Effectiveness can be increased by placing on a dark or reflective surface, or by painting half the bottle black, such that when laying down the clear half is facing the sky. | |||
==Using reflectors== | ==Using reflectors== | ||
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This uses simple cardboard based reflectors and a black jug. Heat is considered by the authors to be the more reliable mechanism for disinfection. | This uses simple cardboard based reflectors and a black jug. Heat is considered by the authors to be the more reliable mechanism for disinfection. | ||
==History== | ==History== | ||
Revision as of 18:38, 14 November 2007
Drinking water can be disinfected using the heat and (usually) the UV light of the sun. It is a very simple and low cost way of disinfecting small volumes of water.
Radiation in the spectrum of UV-A (wavelength 320-400nm) and increased water temperature. Both factors cause damage to the DNA of the pathogens. The effects are also synergistic - the DNA being more prone to UV damage if the temperature is very high. If the water temperatures raises above 50°C, the disinfection process is three times faster, and much better results are obtained from
Certain pathogens such as giardia,{{wp sup|giardia]] however, are not easily killed by UV. For these, the heat is more important,[verification needed] and other steps such as filtering might also be considered.
SODIS - solar water disinfecting with soda bottles and sunlight
Solar water disinfection, or W, is a method to disinfect water using sunlight and PET bottles.
Effectiveness can be increased by placing on a dark or reflective surface, or by painting half the bottle black, such that when laying down the clear half is facing the sky.
Using reflectors
Enhancement of Solar Water Pasteurization with Reflectors, Negar Safapourdagger and Robert H. Metcalf, 1998, Department of Biological Sciences, California State University Sacramento, Sacramento, California.
This uses simple cardboard based reflectors and a black jug. Heat is considered by the authors to be the more reliable mechanism for disinfection.
History
Prof Aftim Acra of Lebanon researched this technique beginning in 1979. See Cleaning water with sunshine, Robert Bourgoing, IDRC Reports, April 1989. (or the original format with image, in PDF.) See also An Interview with Aftim Acra, Professor Emeritus of Environmental Sciences, Winter 2004.
External links
- Scientific Publications on Solar Water Disinfection at the SODIS website. Links to PDF format articles.
- Water testing & Pasteurization in Africa - A guide to water testing without access to a laboratory, and how to pasteurize contaminated water using sunshine and a simple solar cooker. Images with captions, by Bob Metcalf.
Project links
- The Contacts page on the SODIS website has many case examples in PDF form.
- Bintaro Baru in South Jakarta: Yayasan Emmanuel Water Program[1] - SODIS program described at Country Water Action: Indonesia Simple Science Solves Slum Water Problem (Asian Development Bank site, from Asiawaterwire.net, August 2007)