SODIS

Solar water disinfection, often abbreviated as SODIS, is a simple, low-cost method for treating drinking water at the household level. It utilizes the sun's ultraviolet (UV) radiation and heat to kill or inactivate pathogenic microorganisms present in water, making it safe for consumption. The process involves filling transparent plastic bottles, typically made from PET (polyethylene terephthalate), with water and exposing them to direct sunlight for a period of at least six hours on a clear day, or two consecutive days if the weather is cloudy.

The effectiveness of SODIS relies on two primary mechanisms. Firstly, the UV-A radiation from the sun causes damage to the DNA of pathogens, hindering their ability to reproduce and leading to their inactivation. Secondly, the solar heat generated within the bottles increases the water temperature. Temperatures above 50°C (122°F) significantly enhance the disinfection process by denaturing essential proteins and enzymes within microorganisms. For optimal results, a temperature of around 65°C (149°F) is ideal.

SODIS is particularly effective against a wide range of waterborne pathogens, including bacteria like E. coli and cholera, viruses, and protozoa such as Giardia and Cryptosporidium. It is a recommended method by organizations like the World Health Organization (WHO) and is widely practiced in regions where access to safe drinking water is limited. The method requires minimal resources, primarily relying on readily available clear plastic bottles and sunlight, making it an accessible and sustainable solution for improving water quality and reducing the incidence of waterborne diseases.