__NOTOC__<small-title />[[Image:Sodis_icon.png|right|80px]][[Image:Sodis.PNG|thumb|right|250px200px|Plastic bottles filled with contaminated water are placed in the sunlight . Photo: [http://www.sodis.ch/index_EN SODIS.]]]
Solar disinfection is a simple water treatment method using solar radiation (UV-A light and temperature) to destroy pathogenic bacteria and viruses present in the water. It can be used to disinfect small quantities of water with low turbidity. Most commonly, contaminated water is filled into transparent plastic bottles and exposed to full sunlight. The pathogens are destroyed during the exposure to the sun. Users determine the length of exposure based on the weather conditions.
Other forms of batch treating and continuous treatment of water with sunlight are under development by various organizations.
====How it works====
Exposure to sunlight has been shown to deactivate diarrhea-causing organisms in polluted drinking water. EAWAG/SANDEC (2002) describes the three effects of solar radiation which are believed to contribute to the inactivation of pathogenic organisms:
SODIS is more efficient in water with high levels of oxygen. Sunlight produces highly reactive forms of oxygen in the water. These reactive molecules also react with cell structures and kill pathogens (Kehoe et al, 2001).
The SODIS method (and other methods of household water treatment) can very effectively remove pathogenic contamination from drinking water. However, infectious diseases are also transmitted through other pathways such as direct person-to-person contact, food, or unhygienic living conditions. Lack of sanitation and hygiene practices exacerbate the problem. [http://www.sodis.ch/Text2002/T-Research.htm Studies] on the reduction of diarrhea among SODIS users show reduction values of 30-80%.
====History====
The fact that sunlight can kill micro-organisms has been known for centuries and has been scientifically established.
The idea of solar water disinfection (SODIS) was presented by Professor Aftim Acra for the first time in a booklet published by UNICEF in 1984. SODIS has been promoted worldwide since 1991 when an interdisciplinary research team at EAWAG/SANDEC began laboratory and field tests to assess the potential of SODIS and to develop an effective, sustainable and low cost water treatment method. Solar disinfection is recommended by the World Health Oganization (WHO) as one viable option for drinking water treatment at household level.
===Suitable conditions ===
Basically the SODIS is suitable for batches of 1-2 litres per bottle. The system is not useful for treating large volumes of water, several are bottles needed for a large family.
* For turbidity levels greater than 30 NTU, the water should first be filtered through a cloth or sedimented (Sommer et al, 1997).
{{procontable | proborder="1" cellpadding="5" cellspacing="0" align="center"|-! width="50%" style="background:#efefef;" | Advantages! style="background:#f0f8ff;" | Disadvantages|-| valign="top" | - Very cheap, no capital costs except plastic bottle, no consumables required. <br>
- Independent from energy sources other than sunlight. <br>
- Treated water is protected from re-contamination in the bottles.<br>
- Convenient for storage and transportation. <br>
- SODIS has shown to significantly reduce diarrhoea
| convalign= "top" | - Cannot be used on days with continuous rainfall.<br>
- Cannot be used to treat very turbid water (>30 NTU).<br>
- Bottles need to be replaced every 4-6 months.<br>
- Needs to be cooled before consumption <br>
- Does not remove suspended partices of dissolved compounds<br>
}|}
The bottle can be used as a safe storage container. Requires suitable climate and weather conditions: the most favourable location is between latitudes 15° and 35° north/south; next most favourable location is between latitudes 15° north/south and the equator. PET bottles are abundant in urban areas, but may not be available in rural areas.
===Construction, operations and maintenance===
====Operation====
Bottles become scratched or aged by sunlight and must be replaced periodically.
===Costs===
{{Treatment_Cost
|CapCost=US$ 0-5 (*)
The cost of SODIS are very low, re-use of plastic bottles is common. According to a comparative [http://www.iwaponline.com/jwh/005/jwh0050599.htm study] on the cost-effectiveness of different household water treatment systems, SODIS is the least expensive method with an annual mean cost of US$0.63 per person.
===Field experiences===
Used by more than 1,000,000 in Asia, Africa and Latin America.
The Swiss Federal Institute of Aquatic Science and Technology (Eawag), through the Department of Water and Sanitation in Developing Countries (Sandec), coordinates SODIS promotion projects in 33 countries including Bhutan, Bolivia, Burkina Faso, Cambodia, Cameroon, DR Congo, Ecuador, El Salvador, Ethiopia, Ghana, Guatemala, Guinea, Honduras, India, Indonesia, Kenya, Laos, Malawi, Mozambique, Nepal, Nicaragua, Pakistan, Perú, Philippines, Senegal, Sierra Leone, Sri Lanka, Togo, Uganda, Uzbekistan, Vietnam, Zambia, and Zimbabwe. Contact addresses and case studies of the projects coordinated by the Swiss Federal Institute of Aquatic Science and Technology (Eawag) are available at [http://www.sodis.ch/ sodis.ch].
==Reference manuals=Manuals, videos, and links=== ====Video==== {|border="1" cellspacing="0" |-|[http://www.youtube.com/watch?v=_k-SeaRj_QY Alternative design of a SODIS container]|[http://www.youtube.com/watch?v=DSBz8f87ohQ&feature=channel_page Bolivia]|[http://www.youtube.com/watch?v=5fAvX6sZXTM Kenya 1]|[http://www.youtube.com/watch?v=jBsyH7aGUGg&feature=related Kenya 2]* A Dutch Game|[http: //www.youtube.com/watch?v=5s9fZ1Fi0nM&feature=channel_page Nepal pt.1]|[http://www.legacyyoutube.com/watch?v=8KKanLz36bs&feature=channel_page Nepal pt.2]|-|[http://www.laikayoutube.nlcom/watch?v=g5o2tJ8gb0Q&feature=channel_page Nepal short]|[http:/games/gamewww.youtube.phpcom/watch?idv=kh47lXnqzyI&feature=petfles Game Solar Disinfectionchannel_page Pakistan]* |[http://www.sodisyoutube.chcom/watch?v=FnjO-y8-Crw Philippines]|[http://fileswww.youtube.com/SODIS_pamphlet_ewatch?v=CXkgyaIreuc&feature=related Sierra Leone Sodis pt.pdf pamphlet1] A brochure with information on |[http://www.youtube.com/watch?v=nJiV0qKm1T8&feature=related Sierra Leone Sodispt.2]|[http://www.youtube.com/watch?v=3A7I5S8k_ro South India]|-|[http://www.youtube.com/watch?v=gwivMQkAcfg&feature=channel_page Sri Lanka short]|[http://www.<br>youtube.com/watch?v=RN_c22teWME&feature=channel_page Sri Lanka Tsunami]* A more extensive |[http://www.youtube.com/watch?v=LwJ9p5UHwhc&feature=channel_page Sri Lanka pt.1]|[http://www.sodisyoutube.com/watch?v=5RXkT_7fdpQ&feature=channel Sri Lanka pt.ch2]|[http:/files/SODIS_Manual_englishwww.youtube.pdf manualcom/watch?v=jBsyH7aGUGg&feature=related Water ScH2Ool] is available |} ====Links==== * [http://www.sodis.ch/Text2002methode/anwendung/ausbildungsmaterial/index_EN SODIS Training Material]. SODIS (short for Solar Water Disinfection) is an initiative of Eawag, the Swiss Federal Institute of Aquatic Sciences and Technology. * [http://T-EducationMaterialsenpho.htm onlineorg/ Drinking water quality information] from Environment and Public Health Organization (ENPHO). ENPHO at present runs a government accredited laboratory for environmental monitoring and analysis and is actively involved in different languagespromoting eco-friendly technologies such as SODIS, Ecosan toilets and waste water treatment through reed bed systems. * [http://web.mit.edu/watsan/tech_hwts_chemical_kanchanarsenicfilter.html Kanchan Arsenic filter information from Massachusetts Institute of Technology (MIT)]
* Philippines [http://www.youtubecdc.comgov/watch?v=FnjO-y8-Crw www.youtube.comsafewater/publications_pages/watch?v=FnjO-y8options-Crw ]* Sri Lanka short [http://wwwsodis.youtube.com/watch?v=gwivMQkAcfg&feature=channel_page httppdf Household Water Treatment Options in Developing Countries://www.youtube.com/watch?v=gwivMQkAcfg&feature=channel_page]* Sri Lanka pt.1 [http://www.youtube.com/watch?v=LwJ9p5UHwhc&feature=channel_page http://www.youtube.com/watch?v=LwJ9p5UHwhc&feature=channel_page]* Sri Lanka pt.2 [http://www.youtube.com/watch?v=5RXkT_7fdpQ&feature=channel http://www.youtube.com/watch?v=5RXkT_7fdpQ&feature=channel]* Sri Lanka Tsunami [http://www.youtube.com/watch?v=RN_c22teWME&feature=channel_page http://www.youtube.com/watch?v=RN_c22teWME&feature=channel_page]* Nepal pt.1 [http://www.youtube.com/watch?v=5s9fZ1Fi0nM&feature=channel_page http://www.youtube.com/watch?v=5s9fZ1Fi0nM&feature=channel_page]* Nepal pt.2 [http://www.youtube.com/watch?v=8KKanLz36bs&feature=channel_page http://www.youtube.com/watch?v=8KKanLz36bs&feature=channel_page]* Nepal short [http://www.youtube.com/watch?v=g5o2tJ8gb0Q&feature=channel_page http://www.youtube.com/watch?v=g5o2tJ8gb0Q&feature=channel_page]* Pakistan [http://www.youtube.com/watch?v=kh47lXnqzyI&feature=channel_page * South India [http://www.youtube.com/watch?v=3A7I5S8k_ro http://www.youtube.com/watch?v=3A7I5S8k_ro]* Kenya 1 [http://www.youtube.com/watch?v=5fAvX6sZXTM http://www.youtube.com/watch?v=5fAvX6sZXTM]* Kenya 2 [http://www.youtube.com/watch?v=jBsyH7aGUGg&feature=related http://www.youtube.com/watch?v=jBsyH7aGUGg&feature=related]* Sierra Leone Sodis pt.1 [http://www.youtube.com/watch?v=CXkgyaIreuc&feature=related http://www.youtube.com/watch?v=CXkgyaIreuc&feature=related]* Sierra Leone Sodis pt.2 [http://www.youtube.com/watch?v=nJiV0qKm1T8&feature=related www.youtube.com/watch?v=nJiV0qKm1T8&feature=related ]* Bolivia [http://www.youtube.com/watch?v=DSBz8f87ohQ&feature=channel_page http://www.youtube.com/watch?v=DSBz8f87ohQ&feature=channel_pageCDC Solar Disinfection (SODIS)]* Water Sch2ool [http://www.youtubeCenters for Disease Control and Prevention.com/watch?v=jBsyH7aGUGg&feature=related http://wwwJanuary 2008.youtube.com/watch?v=jBsyH7aGUGg&feature=related]* Alternative design of a SODIS container [http://www.youtube.com/watch?v=_k-SeaRj_QY]
*[http://www.sodissolvatten.ch EAWAG (The Swiss Federal Institute of Aquatic Science and Technology) and SANDEC (EAWAG's Department of Water and Sanitation in Developing Countries)]*[http:se//www.cawst.org CAWST (Centre for Affordable Water and Sanitation Technology)Solvatten]*[http://www- a commercial product using SODIS principles.enphoSolvatten is a household water treatment unit.org/drinking_water_quality.htm Drinking water quality information from Environment The portable 11 liter container is a patented and Public Health Organization (ENPHO)]*[http://webscientifically proven Swedish invention.mit.edu/watsan/tech_hwts_chemical_kanchanarsenicfilter.html Kanchan Arsenic filter information from Massachusetts Institute of Technology (MIT)]*[http://www.cdc.gov/safewater/publications_pages/optionsPut Solvatten in a sunny place, give it 2-sodis.pdf Centers for Disease Control 6 hours and Prevention]*[http://wwwthe water will be drinkable.solvattenAn indicator shows when it is safe to drink.se/ Solvatten - can also be used as a commercial product using SODIS principles]solar water heater, providing hot water for cooking and hygiene.
==Footnotes=References===
<references/>
===Acknowledgements===
This article is based on a factsheet from [http://www.cawst.org/ Centre for Affordable Water and Sanitation Technology (CAWST)], which is gratefully acknowledged.
* EAWAG/SANDEC (2002). [http://www.sodis.ch/methode/anwendung/ausbildungsmaterial/dokumente_material/manual_e.pdf Solar Water Disinfection: A Guide for the Application of SODIS]. SANDEC Report No 06/02.
* Saladin, M. (2002). SODIS in Nepal – Technical Aspects. EAWAG/SANDEC and ENPHO.
* Wegelin, M., Canonica, S., Mechsner, Ket al., Fleischmann, T., Pesaro, F. and A. Metzler (1994). [http://www.washdoc.info/docsearch/title/107952 Solar Water Disinfection: Scope of the Process and Analysis of Radiation Experiments], J Water SRT, Aqua Vol. 43, No. 4, pp 154-169.* Wegelin, M., Canonica, S., Alder, A., Marazuela, D, Suter, Met al., Bucheli, T(2000) [http://www., Haefliger, Oenvironmental-expert., Zenobi, Rcom/Files%5C5302%5Carticles%5C5905%5Ca2., McGuigan, K., Kelly, M., Ibrahim, P. and M. Larroque. (2000) pdf Does sunlight change the material and content of polyethylene terephthalate (PET) bottles? ] or ([http://www.washdoc.info/docsearch/title/152914 alternative link]). IWA Publishing, Journal of Water Supply: Research and Technology, Aqua No. 1.