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SODIS - Safe drinking water in 6 hours
- 2. SOlar Water DISinfection SODIS is a simple, cost-effective, pointof-use method of treating water using UV rays from the sun In some studies, SODIS has reduced diarrheal disease by approximately 30% in children1 Image Source: http://news.bbc.co.uk/2/hi/science/nature/4048719.stm 1. Sobsey, Mark, et. al. “Point of Use Household Drinking Water Filtration: A Practical, Effective Solution for Providing Sustained Access to Safe Drinking Water in the Developing World“. Environmental Science & Technology. 2008, 42, 4261–4267. Web.
- 3. How SODIS Works: Overview PET (polyethylene terephthalate) bottles should be used Bottles are usually put on a tin roof, but can be anywhere in the sun 6 hours is the proper duration in direct sunlight; if sky is more than 50% clouded over, the bottles should stay in the sun for 2 days Source: http://www.sodis.ch/methode/anwendung/index_EN Fill ¾ of the way, shake for 20 seconds to oxygenate the water, finish filling the bottle Not effective on turbid water
- 4. How SODIS Works: Details Human pathogens are used to dark environments (human GI tract) and are highly susceptible to UV radiation UV radiation causes damage to bacterial DNA resulting in cell death UV radiation also produces highly reactive oxygen species in oxygenated water Works on bacteria (e.g., E. coli, V. cholerae); yeasts and molds; some viruses (e.g., rotavirus) Image Source: http://www.northsouth.ethz.ch/news/past_events/inaugurationnorthsouthcentre/posterexhibition/Sodis.pdf
- 5. Or More Technically Speaking… Image Source: http://www.elaguapotable.com/radiacion_ultravioleta.htm
- 6. Where SODIS can be Used Areas that get a lot of sunlight Does work in cool temperatures, but more effective at higher temps Areas with highest average solar radiation: near equator Most developing countries lie between the latitude lines where SODIS is most effective Best used on a tin roof; can be implemented in any village getting enough sun World Solar Radiation Image Source: http://www.matthewb.id.au/media/world_insolation_map.gif
- 7. Current Use An estimated 5 million people clean their water using the SODIS method SODIS projects are currently in 24 countries in Asia, Africa, and Latin America Selection based on number of people lacking safe drinking water Training sessions in homes, schools, health centers, and other institutions (depending on structural, political, and geographic circumstances) Image Source: http://www.sodis.ch/projekte/index_EN
- 8. Examples Peru Kenya SODIS In Foundation has been in Peru since 2003 working with a local NGO Objective to improve living conditions of 10,000 families in the Ancash region through a series of “healthy habits” the Kibera slum in Nairobi, local NGO is setting up water kiosks to educate others Source: http://www.sodis.ch/news/archiv/index_EN
- 9. Strengths Simple and safe method Acceptability by users because of simplicity No cost after obtaining plastic bottles Water still tastes fresh Bottles can be left on any surface If unopened, bottles can be stored indefinitely Weaknesses Need pretreatment of water with high turbidity Length of time Cannot use water that has been polluted with chemicals Can only use clear bottles Older/scratched bottles reduce effectiveness Bottles create waste Cannot treat in larger than 3 liter bottles
- 10. Sustainability Cheap and convenient Poor compliance, especially after cessation of surveillance/education (as low as 9%) May not perceive benefits because even when they drink SODIS-treated water they tend to supplement this with non-SODIS-treated water Discarded water bottles can be problematic Water bottles that are scratched or damaged do not work as well Image Source: http://blog.crisisaid.org/journal/2009/7/18/waterscarcity-an-issue-of-poverty.html
- 11. Scaling Up Primary challenge: educating to increase compliance Simple water treatment makes scaling up very achievable, if knowledge is disseminated Does not require commercial supply chain (given used PET bottles are available) SODIS Advocacy campaign Informing governments, NGOs, public authorities (teachers, nurses, etc.) Providing expert knowledge, training material, and practical support for the implementation of projects Image Source: http://www.sodis.ch/news/index_EN
- 12. References 1. CDC. “Household Water Treatment Options in Developing Countries: Solar Disinfection (SODIS)”. 2008. Web. 14 Oct 2011. 2. Meierhofer, R. and Wegelin, M. “Solar Water Disinfection: A Guide for the Application of SODIS”. SANDEC Report No 06/ 02, 2002. Web. 3. Sobsey, Mark, et. al. “Point of Use Household Drinking Water Filtration: A Practical, Effective Solution for Providing Sustained Access to Safe Drinking Water in the Developing World“. Environmental Science&Technology. 2008, 42, 4261–4267. Web. 4. SODIS. “SODIS Method” and “Projects”. SODIS: Safe Drinking Water for All, 2011. Web. 14 Oct. 2011.
Editor's Notes
- PET = “recyclable #1”, coke bottles, etc. so these are very common—don’t need to get bogged down by the chemical name…Test of water turbidity: if you place it on a newspaper, can you read a headline through it (from neck to bottom) filter firstCorrugated tin works well because there are synergistic effects of the UV and the raised temperature
- RAINY SEASON can be a problem: *rainwater harvesting suggested*
- -Selection based on number of people lacking safe drinking water-Collaboration with experiences and reliable partner organization (including: local/international NGOs, governmental development organizations, and the UN organization), who is responsible for the implementation in the field-Training in home, schools, health centers, and other institutions – selected based on the local structures, geographic circumstances, and political situation-Work several years in the project areas to achieve long-term application of SODIS-Sensitize governments for the SODIS methods in order to achieve a national dissemination-Guides and training materials (videos, flyers, posters, children’s books) in many languages
- PERU EXAMPLE: healthy habits include how to treat drinking water using SODIS, as well as solar showers, improved cooking stoves (to reduce consumption of firewood and improve indoor air quality).KENYA EXAMPLE: Women groups advise their neighbors on drinking water treatment and hygiene issues and sell products for treatment and hygiene. In the slums of Nyalenda and Manyatta in West Kenya, the project focus is mainly on training in schools.http://edition.cnn.com/video/?/video/world/2009/09/01/mckenzie.sun.water.cnn - Shows the application of the SODIS method in the Kibera slum in Nairobi, Kenya.
- Strengths:PET bottles have been proven safe, PVC should not be used.. Labels vary country to country. Set bottles on fire to find out, as PET burns quickly and smoke smells sweet, PVC does not burn easily, does not burn when away from flame, smoke smells bitter.SODIS method does not change the taste, the way boiling water or using chlorine does.Works quickest if bottles are on a reflective surface (like corrugated iron), but can be set on any surfaceStore in a cool, dark place. Dead bacteria cannot multiply again. The only things that may grow are algae – but that does not represent a health hazard.Weaknessesrecommend replacing old bottles and bottles that are no longer transparent after about 6 to 12 months of daily use
- A UNC study1 gives SODIS a poor sustainability ranking compared to other point-of-use treatments; while it is cost-effective and easy to use, compliance is very low and the overall quality of water consumed is also low, because people tend to drink both SODIS-treated water and water that was not SODIS-treated; only 9% adopted after a few months
- Very possible to scale up because of simple methods. However, need to spread the word and ensure sustainability.Make learning materials and publicity in many languages and cater to illiterate and children as well.Experiences have shown that SODIS is best promoted and disseminated by local institutions with experience in community health education. A long-term training approach and repeated contact with the community is needed to create awareness on the importance of treating drinking water and to establish corresponding changes in behavior.
- Developed in the 1980’s In 1991, the Swiss Federal Institute for Environmental Science and Technology began to investigate and implement SODIS to prevent diarrhea in developing countries