UV-source for germ-free water

In many sewage treatment plants, it is customary to sterilize microbes with ultraviolet rays. However, the cost of the process depends largely on the efficiency and service life of the lamps used. Now, an improved UV lamp could hold the key to increased efficiency.

Operators of municipal sewage treatment plants are increasingly tending to use UV radiation as a final stage to disinfect their effluent water. This is particularly done if there are bathing lakes or rivers downstream. The sterilization process has also proved to be an elegant solution in processing drinking water and water for swimming pools, as no chemicals are needed.

Ultraviolet radiation with a wavelength of around 254 nanometers causes such severe genetic damage to bacteria, fungi and viruses that if the dose is high enough, almost all germs lose their ability to proliferate. But the mercury-vapour lamps generally used for this purpose have a drawback: their performance gradually deteriorates and they only last for less than one year when in constant operation. With an efficiency ranging from 5 to 35%,  most of the electrical energy charged does no more than heating up the water.