The cheapest and most efficient method to disinfect water

The solar water disinfection SODIS is a method of disinfecting water using sunlight and appropriate clear plastic bottles. This means that it kills microorganisms harmful to human health. Ultraviolet radiation from the sun disinfects it.

SODIS is a method inexpensive and efficient for water treatment decentralized, generally applied for home use and is recommended by the World Health Organization as a viable method for home water treatment and safe storage. It is already applied in many developing countries.

Solar radiation has three ranges of wavelengths: visible light, ultraviolet (UV) radiation, and infrared radiation. From the near UV light spectrum, we are concerned about UV-A, which reaches the earth’s surface because it has a detrimental effect on many microorganisms that live in water and are sensitive to this light because they do not cannot adapt to these conditions. life because its habitat is our dark digestive system. On the other hand, these microorganisms are sensitive to heat (infrared radiation) and with the time of exposure to the sun, these can be eliminated when the water reaches a certain temperature. Therefore, the combination of these two factors effectively eliminates many pathogens such as diarrhea or cholera bacteria.

SODIS It is a solar water disinfection method. Studies have certified that sunlight has enough ultraviolet radiation to inactivate bacteria that may be found in water and therefore can be used as a method of home water purification.

SODIS solar disinfection

Application procedure.

The method consists of leaving a bottle of water for a few hours in the sun. All transparent bottles up to a volume of 5 liters are used to manufacture SODIS. Returnable bottles are less effective than non-returnable (disposable) bottles, but both types of bottles work well.

  1. Wash the bottle well with detergent.
  2. Fill 3/4 of the bottle with water.
  3. Shake the bottle for 20 seconds. (This is done to aerate the water and increase oxygen levels, which helps eliminate pathogens)
  4. Fill the bottle completely and close the cap.
  5. Place the bottle on a sheet or in an easily accessible location where it can get good sun exposure.
  6. Leave the bottle exposed to the sun from morning to evening (minimum 6 hours with good radiation and two days in cloudy weather).
  7. After this time, you can drink water.

The efficiency of the process depends on the microorganism. A large number of investigations (with solar radiation and artificial light) have shown that all the pathogens studied to date are sensitive to the SODIS process, but to varying degrees.

The most sensitive organisms are bacteria, such as Salmonella, Vibrio Cholerae, and fecal coliforms. Within 6 hours, very high concentrations of these pathogens can be completely inactivated (more than 1 million microorganisms per 100 ml).

Viruses are more resistant. However, SODIS has been shown to effectively kill rotavirus (over 99.9%).

Protozoa are also more resistant than bacteria to SODIS treatment. However, studies of infectivity have shown that organisms that survive the process lose their ability to cause disease.


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The solar disinfection method SODIS is an efficient method of treating water where fuel or stoves are unavailable or at prohibitive cost. Even where fuel is available, SODIS is a cheaper and less aggressive option for the environment. Application of SODIS is limited if there are not enough bottles available, or if the water is very cloudy.


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What types of bottles can be used?

In practice, glass bottles or any type of plastic bottle can be used (there are two types of plastic bottles, those made from polyutyrene terephthalate (PET) and those from polyvinyl chloride (PVC), but the best results are They are obtained with PET type bottles, due to their durability, shape, transparency and ease of transport.This type of bottle is recognizable because they do not have the bluish glow of PVC type bottles and also burn more quickly.