Question

Can water actually be cleaned by putting it in a glass bottle and leaving it in the sun?

Answer 1

Leaving water in a glass bottle in the sun can help to improve its quality, but it may not necessarily make it completely clean or safe to drink, especially if the water is heavily contaminated. This process is known as solar water disinfection (SODIS).

SODIS takes advantage of the sun's ultraviolet (UV) rays and the heat from sunlight to kill or inactivate harmful microorganisms like bacteria, viruses, and parasites present in the water. The process works as follows:

1. Filling the bottle: Fill a clear glass or PET (polyethylene terephthalate) bottle with water from a relatively clean and safe source. It is essential to remove any visible debris or particles before using SODIS.

2. Exposing to sunlight: Place the filled bottle in direct sunlight for 6 hours on a clear day or 2 consecutive days if the weather is cloudy. The UV radiation and heat from the sun will work to disinfect the water by killing many harmful microorganisms.

It is important to note a few limitations of SODIS:

1. Effectiveness against different contaminants: SODIS is most effective against bacteria and viruses, but it may not effectively remove chemical pollutants or heavy metals from the water.

2. Turbid water: If the water is very turbid or cloudy, the UV rays may not penetrate deeply enough to disinfect all the microorganisms, reducing the effectiveness of the method.

3. Time and weather dependency: SODIS requires a relatively long exposure time to sunlight, which may not be practical in all situations or climates.

4. Bottles and cleanliness: The bottles used for SODIS must be clean and not scratched, as scratches can provide hiding places for microorganisms, potentially reducing the effectiveness of disinfection.

While SODIS can be a low-cost and simple method to improve water quality in certain situations, it is essential to recognize its limitations. In areas with severe water contamination or where waterborne diseases are prevalent, additional water treatment methods, such as boiling, filtration, or chemical disinfection, may be necessary to ensure the water is safe for consumption.