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_C05.pdf

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 estab- lished in the United States than in Europe. A survey made for the U.S. 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. 5.1 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]) (O.J. 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