It was demonstrated both in the laboratory and in the field that the method kills germs effectively.
Bacteria are highly sensitive to UV-A radiation (wavelength 320-400nm) and are quickly killed by sunlight. The viruses are slightly more resistant, but are also killed within the recommended 6 hours. Parasites are less sensitive to sunlight. While giardia cysts are rendered inactive within 6 hours, cryptosporidia cysts must be exposed to direct sunlight for at least 10 hours before they are neutralised. Amoebas do not die until the water temperature has been warmer than 50°C for over an hour.
How UV-A kills germs
Research into the question of why the germs die is not yet complete. At the moment, scientists think that the bacteria die because the process by which they respire is damaged by UV-A radiation. This damage is evidently so severe that the bacteria can no longer repair it.
Water temperature affects disinfection
A warmer water temperature speeds up the process. However, bacteria, viruses, giardia and cryptosporidia are killed by UV-A radiation even when water is cooler.
Overview of the most common germs
The following table shows a summary of the most important research results. It should be noted that many germs can no longer be detected in very low concentrations. In these cases, it is not possible to provide scientific proof of a 100% reduction.
Research results in the areas of Microbiology, Health, Training strategies, PET bottles | more >>