Solar disinfection (sodis)

Updated - Monday 27 April 2009

I have heard that leaving contaminated water in a CLEAR plastic (PET) beveridge bottle for 24 hours in the tropical sun will render it safely drinkable. If this is true, would you please direct me to any research articles supporting this? I teach second and third year nursing students and am trying to make them aware of the concept of appropriate technology.

"Solar disinfection is an effective water treatment method [...], especially when no chemical disinfectants are available. Ultra-violet rays from the sun are used to inactivate pathogens present in water. This technique involves exposing water in clear plastic bottles to sunlight for a day, for example on the roof of a house. In emergencies, empty bottles can be used that are left over from an initial shipment of drinking water. Bottles need to be cleaned, filled to three quarters and shaken thoroughly 20 times, before being filled completely. The bottles are then exposed to sunlight for 6 hours (or for 2 days if the sun is obscured by clouds). The water should be consumed directly from the bottle or transferred in a clean glass for drinking. To be effective, solar disinfection must be applied to relatively clear water. For further information, see annex [...] and http://www.who.int/water_sanitation_health/dwq/wsh0207/en/."

Abstract taken from the International Network to Promote Household Water Treatment and Safe Storage (managed by WHO) - - to which they have just added a special fact sheet on emergencies

Contact e-mail: hhwater@who.int

Please note however that there are conflicting opinions on the use of sodis in emergency situations, looking at the criteria: relatively clear water, or the availability of clean bottles (if any).

Key web site

SODIS, Solar Water Disinfection, website by the Swiss Federal Institute for Environmental Science and Technology. Provides a number of online documents and manuals, news, project information, including case studies, and frequently asked questions on sodis.

Books and articles

Solar water disinfection: a guide for the application of SODIS
Meierhofer, R. and Wegelin, M. (2002).
A manual for project officers and technical field staff intending to implement SODIS projects. It contains technical information on the effects of SODIS, its advantages and limitations, detailed description of the application procedure, and important factors to be considered during SODIS application. The manual also contains information accumulated for more than a decade on training of promoters, training of SODIS users and on promotion of SODIS at national level. Available in English, Spanish, Uzbek, and Russian.