tailieunhanh - Ultraviolet Light in Water and Wastewater Sanitation - Chapter 3

Số lượng của các hệ thống nước uống dựa trên chiếu xạ tia cực tím (UV) để khử trùng nước, hiện nay, được ước tính là khoảng 3000-5000. Việc sử dụng kỹ thuật này có thể cao hơn nhiều về số lượng, bởi vì các ứng dụng này thường không hoàn toàn ghi nhận: • Point-of-sử dụng của hệ thống trên quy mô hộ gia đình, trại căn cứ • giải trí và cơ thể sức khỏe các ứng dụng • Các ứng dụng trong vùng nguy cơ như bệnh viện , vườn ươm, và trường học ở vùng sâu. | 3 Use of Ultraviolet Light for Disinfection of Drinking Water 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. Since late 1979 in the area of Berlin Germany the treated water has not been postchlorinated. 2002 by CRC Press LLC The question of maintaining an active residual in the water in the distribution system certainly remains a .