What is SODIS?
SODIS, Solar water disinfection is a simple method to improve the quality of drinking water by using sunlight to inactivate pathogens causing diarrhea. During the exposure, the sun destroys the pathogens. If the water temperature rises above 50°C, the disinfection process only requires one hour solar exposure.
Note: Boiling is the best. Use SODIS only when boiling is difficult.
How to apply SODIS?
- A bottle of volume 1-2 litres is to be used. ( A. Preferably made of plastic material (preferably Polyethylene terepthalate or PET), B. Glass bottles take more time to increase the water temperature, are heavy, expensive, breakable.)
- Bottles can be painted black on one side and the transparent surface exposed to sun.
- At least 2 bottles for each member of the family must be exposed to sun while there are other 2 ready for consumption. Hence each family member would ideally need about 4 bottles.
- Use clear transparent bottles only, not green or brown plastic bottles.
- Bottle of volume of 1-2 litres is the best. Don’t use bottles that are too big.
- Lay bottles horizontally, not upright.
- The black painted side of the bottle needs to be on the bottom, not on top.
- Consume the treated water directly from the bottle using a clean glass or a cup. Avoid transferring the water into different containers.
- Fill the bottle completely before exposing to the sun. Partially filled bottles are not as effective.
- Close the bottle tightly to avoid water leakage.
- Wash the bottles properly, by using filtered water before filling them with water and exposing them to sunlight.
- Expose the bottle fully to sunlight, from early in the morning to evening. Even partial shade can reduce effectiveness.
- Never place the bottles on inflammable materials like cloth, straw. This can lead to fire.
- Don'’t use old, scratched blind bottles, as much as possible.(Replace such bottles after one year of SODIS application.)
Limitations of SODIS
- SODIS does not change the chemical water quality
- SODIS requires relatively clear water
- SODIS is not as effective in cloudy weather. (Exposure time: A. 2 consecutive day under 100% cloudy sky, During days of continuous rainfall, B. SODIS does not perform satisfactorily.)
- Not as effective as boiling. Use only when boiling is infeasible.
- SODIS processed water is not advisable for babies less than 18 months.
- It is also not advisable for those with chronic gastrointestinal illness, severely ill children and adults, severely malnourished children or adults.
- Not as effective against virus and parasites.
