UV紫外线杀菌器在水和废水处理中的应用英文原版研究论文_C03.pdf

3 Use of Ultraviolet Light for Disinfection of Drinking Water 3.1 INTRODUCTION The number of drinking water systems relying on ultraviolet (UV) irradiation for disinfection of the water, at present, is estimated to be about 3000 to 5000. The use of the technique is probably much higher in number, because these applications are often not completely recorded: • Point-of-use of the system on household scale, camp grounds • Recreational and body health applications • Applications in risk zones such as hospitals, nurseries, and schools in remote areas • Use in food processing industries such as breweries and soft drinks industries • Use on boats, ships, and railway trains Bactericidal effects of radiant energy from sunlight were first reported in 1877 [Downes and Blunt, 1877]. However, thanks to the absorption by atmospheric ozone, the part of UV from sunlight that reaches the surface of the earth is merely confined to wavelengths higher than 290 nm. The technical use of UV made progress by the discovery of the mercury vapor lamp by Hewitt [1901] and the drinking water of the city of Marseille in France was disinfected with UV light as early as 1910. The reliable operation and functioning of 5000 plants cannot be ignored in spite of some suspicions or objections that have been formulated (to be commented on in this chapter). Among them is the absence of active residual concentration in the treated water [Bott, 1983]. This point has pros and cons, but because no on-site storage of chemicals is required, the risk for the operators is eliminated and the safety measures and equipment for handling chemicals are not needed. In remote areas, transportation problems may be solved as well. Versions operated on the basis of solar photoelectric generators are developed now and are available