[[Image:Sodis_icon.png |right]]__NOTOC__
SODIS (Solar Water Disinfection Process) uses sunlight to inactivate harmful microorganisms in water almost completely. Transparent plastic (PET) or glass bottles filled with contaminated{{Potential_Treatment_Capacity_table| highly=- Bacteria<br>- Viruses<br> - Protozoa<br>- Helminths<br>| somewhat= | not= - Turbidity<br>- Chemicals<br>- Taste, but clearodour, 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. colour| process=Disinfection<br> Safe Storage| watcrit=Turbidity < 30 NTU}}
[[Image:Sodis.PNG|thumb|right|150px|Plastic bottles filled with contaminated water are placed in the sunlight ]]
This technology ==What is SODIS?==SODIS is a household water treatment method which uses solar energy to destroy pathogens. 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. The idea of solar water disinfection (SODIS) was awarded presented by Professor Aftim Acra for the first time in a prize booklet published by [[SIMAVI]] 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 organisations such as SANDEC are promoting it in many developing countriesto 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. Other forms of batch treating and continuous treatment of water with sunlight are under development by various organizations.
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==Disinfection mechanism==
==How Does It Remove Contamination?==Exposure to sunlight has been shown to deactivate diarrhea-causing organisms in polluted drinking water. Three EAWAG/SANDEC (2002) describes the three effects of solar radiation which are believed to contribute to the inactivation of pathogenic organisms:
* Ultraviolet-A (UV-A interferes directly with the metabolism ) radiation causes damage to DNA and destroys cell structures of bacteriakills living cells.
* 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 waterand causes pasteurization when the temperature is raised to 70-75 degrees Celsius. 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)Many pathogens are not able to resist increased temperatures, a threshold solar nor do they have any protection mechanisms against UV 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 WhEAWAG/m<sup>2</sup> in the range of UV-A and violet light, 350nm-450nmSANDEC, corresponding to about 6 hours of mid-latitude (European2002) midday summer sunshine.
At More pathogens are destroyed when they are exposed to both high temperature and UV-A light at the same time. A synergy of these two effects occurs for water temperatures higher than 45°C above 50 degrees Celsius (113°FWegelin et al, 1994), synergetic effects of UV radiation and temperature further enhance the disinfection efficiency.
== Guidelines for SODIS is more efficient in water with high levels of oxygen. Sunlight produces highly reactive forms of oxygen in the application at household level ==water. These reactive molecules also react with cell structures and kill pathogens (Kehoe et al, 2001).
==Operation==
[[Image:Pictograms SODIS.jpg]]
* Water Transparent water bottles are filled with water from contaminated sources are filled into transparent water bottles. For To increase the oxygen saturationdissolved in the water, 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 The treatment efficiency can be achieved improved if the plastic bottles are placed on sunlight reflecting surfaces, such as corrugated aluminum or zinc roofs. This can increase the water temperature by about 5°C. Place the bottles horizontally on a corrugated roof or rack in the sun for the following times: * 6 hours in sunny weather * 6 hours for up to 50% cloudy weather<br>* 2 consecutive days for 50-100% cloudy weather<br> * Do not use SODIS during days of continuous rainfall, use rainwater harvesting instead. The efficiency of SODIS is dependent on the amount of sunlight available. The bottles must NOT be placed so that they are in shade for part of the day. The most favourable geographical regions for SODIS are located between latitudes 15oN and 35oN (as compared well as 15oS and 35oS). The majority of developing countries are located between latitudes 35oN and 35oS (EAWAG/SANDEC, 2002). If the water bottles are not exposed to thatched roofssunlight for the proper length of time, the water may not be safe to drink and could cause illness. * The treated After treatment, the 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 contaminationrecontamination. Non-pathogenic organisms, such as algae, may grow in the conditions created in a SODIS bottle (EAWAG/SANDEC, 2002). ==Treatment efficiency=={{Treatment_Efficiency|extra_field=-|lab:bacteria=99.9 – 99.99% |lab:viruses=90 - 99.9% |lab:protozoa=90 - 99.9% <ref name=temp50>Depends on reaching a water temperature of 50 degrees.<br/ref> |lab:helminths= <ref name=temp50/>|lab:turbidity=0|lab:chemicals=0 |lab:extra=|field:bacteria=91.3-99.4% |field:viruses=not available|field:protozoa=not available|field:helminths=not available|field:turbidity=0|field:chemicals=0|field:extra=-}} ==Operating criteria==*'''Flow rate:''' 1-2 liters/bottle, per 6-48 hours*'''Batch volume:''' 1-2 litres/bottle *'''Daily water supply:''' Dependant on the weather and number of bottles The following issues should be considered for SODIS operation: * '''Bottle material:''' Some glass or PVC materials may prevent ultraviolet light from reaching the water. Commercially available bottles made of PET (Polyethylene terephthalate), such as the plastic bottles in which soft drink beverages are sold, are recommended. The handling is much more convenient in the case of PET bottles. Polycarbonate blocks all UVA and UVB rays, and therefore should not be used. Glass also blocks UV rays and therefore would be ineffective. * '''Aging of plastic bottles:''' SODIS efficiency depends on the physical condition of the plastic bottles, with scratches and other signs of wear reducing the efficiency of SODIS. Heavily scratched or old, blind bottles should be replaced. * '''Shape of Containers:''' the intensity of the UV radiation decreases rapidly with increasing water depth. Bottles used for SODIS should not exceed 10 cm in water depth. 1-2 litre volume PET bottles do not exceed this depth when they are horizontally placed in the sunlight (EAWAG/SANDEC, 2002). PET soft drink bottles are often easily available and thus most practical for the SODIS application. * '''Oxygen''': Sunlight produces highly reactive forms of oxygen (oxygen free radicals and hydrogen peroxides) in the water. These reactive molecules contribute in the destruction process of the microorganisms. Under normal conditions (rivers, creeks, wells, ponds, tap) water contains sufficient oxygen (more than 3 mg oxygen per litre) and does not have to be aerated before the application of SODIS.
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* For turbidity levels greater than 30 NTU, use rainwater harvesting<br>|}the water should first be filtered through a cloth or sedimented (Sommer et al, 1997).
==Health impact, diarrhea reductionRobustness==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. The system is not useful for treating large volumes of water, several are bottles needed for a large family. Bottles will melt and deform if the temperature reaches 65°C. Users are unable to determine when sufficient disinfection has taken place. Users need to organize a rotation system to ensure they always have treated water and know which bottles have been treated.
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%
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 Estimated lifespan==Bottles become scratched or aged by sunlight and must be replaced periodically.
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$0.63 per person.==Manufacturing requirements==
== Applying conditions ===Materials and facilities=====* 1 or 2 litre clear plastic bottles (2 sets of 2 bottles per person, one set of bottles must be filled and placed on the roof each day, while the water in the other set is consumed)* Accessible surface that receives full sunlight (e.g. roof, rack).
If the water bottles are not exposed to sunlight for the proper length of time, the water may not ==Maintenance requirements==Bottles and caps should be safe to drink and could cause illness. If the intensity of sunlight is reduced, i.e. due to overcast weather, cleaned on a longer exposure time is necessaryregular basis.
The following issues should also be considered:==Cost=={{Treatment_Cost|CapCost=US$ 0-5 (* '''Bottle material:''' Some glass or PVC materials may prevent ultraviolet light from reaching the water. Commercially available bottles made of PET (Polyethylene terephthalate) are recommended|OpCost=US$ 0|ReplCost=US$ 2-5/year|5yCost=US$ 10-25|litreCost= US$ 0. The handling is much more convenient in the case of PET bottles003-0. Polycarbonate blocks all UVA and UVB rays008}}Note: Program, transportation and therefore should education costs are not be usedincluded. Glass also blocks UV rays and therefore would (*) PET bottles may be ineffectivefree or cost less than US$0.50
* '''Aging The cost of SODIS are very low, re-use of plastic bottlesis common. According to a comparative [http:''' SODIS efficiency depends //www.iwaponline.com/jwh/005/jwh0050599.htm study] on the physical condition cost-effectiveness of the plastic bottlesdifferent household water treatment systems, with scratches and other signs of wear reducing the efficiency of SODIS. Heavily scratched or old, blind bottles should be replaced. * '''Shape of Containers:''' is the intensity of the UV radiation decreases rapidly least expensive method with increasing water depth. At a water depth of 10cm and moderate turbidity an annual mean cost of 26 NTU, UV-A radiation is reduced to 50%US$0. PET soft drink bottles are often easily available and thus most practical for the SODIS application63 per person.
* '''Oxygen''': Sunlight produces highly reactive forms ==Safety==There has been some concern over the question whether plastic drinking containers can release chemicals or toxic components into water, a process possibly accelerated by heat. The Swiss Federal Laboratories for Materials Testing and Research have examined the diffusion of oxygen adipates and phthalates (oxygen free radicals DEHA and hydrogen peroxidesDEHP) from new and reused PET-bottles in the waterduring solar exposure. These reactive molecules contribute The levels of concentrations found in the destruction process water after a solar exposure of the microorganisms. Under normal conditions 17 hours in 60°C water were far below World Health Organization (rivers, creeks, wells, ponds, tapWHO) guidelines for drinking water contains sufficient oxygen (more than 3 mg Oxygen per litre) and does not have to be aerated before in the same magnitude as the application concentrations of SODISphthalate and adipate generally found in high quality tap water.
* '''Leaching of bottle material:''' There has been some concern over the question whether plastic drinking containers can release chemicals or toxic components into water, a process possibly accelerated by heat. The Swiss Federal Laboratories for Materials Testing and Research have examined the diffusion of adipates and phthalates (DEHA and DEHP) from new and reused PET-bottles in the water during solar exposure. The levels of concentrations found in the water after a solar exposure of 17 hours in 60°C water were far below World Health Organization (WHO) guidelines for drinking water and in the same magnitude as the concentrations of phthalate and adipate generally found in high quality tap water.<br /> Concerns about the general use of PET-bottles were also expressed after a report published by researchers from the University of Heidelberg on antimony being released from PET-bottles for soft drinks and mineral water stored over several months in supermarkets. However, the antimony concentrations found in the bottles are orders of magnitude below WHO [http://www.who.int/water_sanitation_health/dwq/chemicals/antimonysum.pdf] and national guidelines for antimony concentrations in drinking water. Furthermore, SODIS water is not stored over such extended periods in the bottles.
==Games (Dutch)==
*[http://www.legacy.laika.nl/games/game.php?id=petfles Game Solar Disinfection]
==Manuals==* [http://www.legacysodis.ch/files/SODIS_pamphlet_e.pdf pamphlet] A brochure with information on Sodis.<br>* A more extensive [http://http://www.sodis.laikach/files/SODIS_Manual_english.nlpdf manual] is available [http:/games/gamewww.php?id=petfles Game Solar Disinfectionsodis.ch/Text2002/T-EducationMaterials.htm online] ==SODIS Manual==in different languages.
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.
== Movies ==
==Movies==
* 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]
* Water Sch2ool [http://www.youtube.com/watch?v=jBsyH7aGUGg&feature=related http://www.youtube.com/watch?v=jBsyH7aGUGg&feature=related]
== External links ==
==External links==*[http://www.sodis.ch SODIS Reference Center EAWAG (The Swiss Federal Institute of Aquatic Science and Technology) and SANDEC (EAWAG's Department of Water and Sanitation in Developing Countries)]*[http://www.cawst.org CAWST (Centre for Affordable Water and Sanitation Technology)] * [http://www.simavienpho.org Simavi /drinking_water_quality.htm Drinking water quality information from Environment and Public Health Organization (ENPHO)]*[http://web.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/options-sodis.pdf Centers for Disease Control and Prevention] ==Footnotes==<references/> ==References==* EAWAG/SANDEC (2002). 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, K., Fleischmann, T., Pesaro, F. and A. Metzler (1994). 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, M., Bucheli, T., Haefliger, O., Zenobi, R., McGuigan, K., Kelly, M., Ibrahim, P. and M. Larroque. (2000) Does sunlight change the material and content of polyethylene terephthalate (PET) bottles? IWA Publishing, Journal of Water Supply: Research and Technology, Aqua No. 1.