Process For Household Application
- Colourless, transparent PET water or soda pop bottles (2 litre or smaller size) with few surface scratches are chosen for use. The labels are removed and the bottles are washed before the first use.
- Water from contaminated sources is filled into the bottles. To improve oxygen saturation, bottles can be filled three-quarters, shaken for 20 seconds (with the cap on), then filled completely and recapped. Very cloudy water with a turbidity higher than 30 NTU must be filtered prior to exposure to the sunlight.
- Filled bottles are then exposed to the sun. Bottles will heat faster and to higher temperatures if they are placed on a sloped sun-facing corrugated metal roof as compared to thatched roofs.
- The treated water can be consumed directly from the bottle or poured into clean drinking cups. The risk of re-contamination is minimized if the water is stored in the bottles. Refilling and storage in other containers increases the risk of contamination.
| Weather conditions | Minimum treatment duration |
|---|---|
| Sunny (less than 50% cloud cover) | 6 hours |
| Cloudy (50–100% cloudy, little to no rain) | 2 days |
| Continuous rainfall | Unsatisfactory performance, use rainwater harvesting |
The most favorable regions for application of the SODIS method are located between latitude 15°N and 35°N, and also 15°S and 35°S. These regions have high levels of solar radiation, with limited cloud cover and rainfall, and with over 90% of sunlight reaching the earth's surface as direct radiation. The second most favorable region lies between latitudes 15°N and 15°S. these regions have high levels of scattered radiation, with about 2500 hours of sunshine annually, due to high humidity and frequent cloud cover.
Local education in the use of SODIS is important to avoid confusion between PET and other bottle materials. Applying SODIS without proper assessment (or with false assessment) of existing hygienic practices & diarrhea incidence may not address other routes of infection. Community trainers must themselves be trained first.
Read more about this topic: SODIS
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