6
edits
Changes
Major additions, all sections; two illustrations added
SODIS (Solar Water Disinfection Process) uses sunlight to inactivate harmful microorganisms in water almost completely. Transparent plastic (PET) or glass bottles filled with contaminated, but clear, water are exposed to the sun for six hours in sunny weather or two days in cloudy weather. If a temperature of 50 degrees Celsius is reached, an exposure time of one hour is sufficient.
[[Image:Sodis.PNG|thumb|right|150px|Plastic bottles filled with contaminated water are placed in the sunlight ]] This technology was awarded a prize by [[SIMAVI]] and organisations such as SANDEC are promoting it in many developing countries.Solar disinfection is recommended by the World Health Oganization (WHO) as one viable option for drinking water treatment at household level.
{| border="1" cellpadding="5" cellspacing="0" align="center"
! style="background:#ffdead;" | Disadvantages
|-
| valign="top" | Very cheap.<br>Independent from energy sources other than sunlight.<br> Treated water is protected from re-contamination in the bottles.<br> The taste of treated water is fresh, not stale or otherwise altered.| valign="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> ==Disinfection mechanism== 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 320-400nm) 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.* Infrared radiation heats the water. If the water temperatures raises above 50°C, the disinfection process is three times faster. At a water temperature of about 30°C (86°F), a threshold solar radiation intensity of at least 500 W/m<sup>2</sup> (all spectral light) is required for about 5 hours for SODIS to be efficient. This dose contains energy of 555 Wh/m<sup>2</sup> in the range of UV-A and violet light, 350nm-450nm, corresponding to about 6 hours of mid-latitude (European) midday summer sunshine. At water temperatures higher than 45°C (113°F), synergetic effects of UV radiation and temperature further enhance the disinfection efficiency. == Guidelines for the application at household level == [[Image:Pictograms SODIS.jpg]] * Water from contaminated sources are filled into transparent water bottles. For oxygen saturation, bottles can be filled three quarters, then shaken for 20 seconds (with the cap on), then filled completely. Highly turbid water (turbidity higher than 30 NTU (Nephelometric Turbidity Unit) must be filtered prior to exposure to the sunlight.* Filled bottles are then exposed to the sun. Better temperature effects can be achieved if bottles are placed on a corrugated roof as compared to thatched roofs. * The treated water can be consumed. The risk of re-contamination can be minimized if water is stored in the bottles. The water should be consumed directly from the bottle or poured into clean drinking cups. Re-filling and storage in other containers increases the risk of contamination.<br> Suggested treatment schedule{| border="1" cellpadding="3" cellspacing="0"|-! width="50%" | Weather Conditions! | Minimum Treatment Duration|-| valign="top" |Sunny<br> 50% cloudy<br> 50-100% cloudy<br> continuous rainfall<br> | valign="top" |6 hours <br>6 hours<br>2 days<br>unsatisfactory performance, use rainwater harvesting<br>
|}
==Health impact, diarrhea reduction==
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%
==Worldwide application of SODIS==
Numbers: Used by more than 1,000,000 in Asia, Africa and Latin America.
[[Image:SODIS map for Akvo.5.jpg|Worldwide application of SODIS in projects coordinated by Eawag]]
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].
== Costs ==
Very low, re-use of plastic bottles. 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.
== Applying conditions ==
==Games (Dutch)==
==SODIS Manual==
Although SODIS is very easy to do, SODIS has a [http://www.sodis.ch/files/SODIS_pamphlet_e.pdf pamphlet] with more specific information.<br>A more extensive [http://http://www.sodis.ch/files/SODIS_Manual_english.pdf manual] is available [http://www.sodis.ch/Text2002/T-EducationMaterials.htm online] in different languages.
* Philippines [http://www.youtube.com/watch?v=FnjO-y8-Crw www.youtube.com/watch?v=FnjO-y8-Crw ]
* Sri Lanka short [http://www.youtube.com/watch?v=gwivMQkAcfg&feature=channel_page http://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 workshop 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_page]* Water Sch2ool [http://www.youtube.com/watch?v=jBsyH7aGUGg&feature=related http://www.youtube.com/watch?v=jBsyH7aGUGg&feature=related ]
== External links ==
*[http://www.sodis.ch SODIS Reference Center ]
* [http://www.simavi.org Simavi ]
