tailieunhanh - Ultraviolet Light in Water and Wastewater Sanitation - Chapter 5

Ánh sáng tia cực tím (UV) là một giải pháp thay thế có giá trị để khử trùng nước thải được xử lý, bởi vì nó hình thức cấp không có hoặc rất thấp khử trùng sản phẩm. Trong số các tiêu cực của các phương pháp đã được coi là kích hoạt tiềm năng của các sinh vật sau khi tiếp xúc, có hay không liên quan đến che chắn của vật chất rắn lơ lửng. Hiện nay, không có quy tắc chung tồn tại (cao) liều tia cực tím cần thiết có thể thúc đẩy hình thành các. | 5 Use of Ultraviolet Light for Sanitation of Wastewater Ultraviolet UV light is a valuable alternative for disinfection of treated wastewater because it forms no or very low levels of disinfection by-products. Among the negatives of the method that have been considered is the potential reactivation of organisms after exposure whether or not in relation to shielding of organisms by suspended solids. At present no general rules exist for the necessary high UV doses that could promote formation of by-products. Pilot investigations are advisable for each particular case. The potential toxicity of the treated effluent must be evaluated. In contrast with drinking water treatment a wastewater method is better established in the United States than in Europe. A survey made for the . EPA 1986 found more than 600 utilities using UV for disinfection of secondary effluent with the period of experience more than 20 years Martin 1994 . This development still is in progress with the growing importance of the issue of disinfection by-products but 1200 stations were mentioned to be in operation in the United States and Canada in 1995 Blatchley and Xie 1995 . No clear report is available on the number of European applications in wastewater treatment. REGULATIONS AND GUIDELINES FOR DISINFECTION OF TREATED WASTEWATER Concerning wastewater reuse for the purpose of irrigation of crops the World Health Organization WHO recommends a maximum limit of 100 total coliforms per 100 mL in 80 of the samples collected at regular intervals. The Council Directive of the European Union concerning urban wastewater treatment 91 271 European Economic Community EEC . 25-05-1991 does not require specific disinfection of treated wastewater as it is discharged into the environment. The member stated or the local authorities can lay down specific requirements as a function of reuse of treated water recreation shellfish culture irrigation of crops. . The directive of the European council of December