In the area of UV disinfecting, besides temperature, the transparency of the medium for the wavelength 254nm is of great importance. The greater the amount of energy which is lost through absorption, the less energy remains to kill microbes.

Basically salts containing iron and organic contents absorb the largest amount of ultraviolet energy. The degree of turbidity/ opacity (wavelengths above 400nm) permit nearly no conclusions to be made. This has been proven in various tests. In addition the absorption level increases with the depth of the water to the distance from the ray source.