Effect Of Ultraviolet Disinfection On Drinking Water Microbial Inactivation And Biological Stability

As an important measure in water purification, chlorination, which had hitherto been routine of water disinfection is being doubted due to the disinfection by-products which have potential carcinogenic effects. It has been terribly exigent to improve the chlorination and to create new measures for water disinfection. As one of the green disinfection methods, Ultraviolet disinfection has gained more and more attention in recent years for its efficiency and environmental friendly. Because it has high efficiency and speed without chemic medicament, and the most important is, Ultraviolet disinfection will not produce the disinfection by-products. Thanks to its ability in killing bacteria, viruses, bacterial spores and oocysts of protozoa, UV disinfection has been used as an alternative to chlorine in drinking water for its many good advantages. Now there is a lack of basic research about UV disinfection, so the purpose of this study is to provide some theoretical basis for the domestic research and technological application about UV disinfection.In the study, E. coli and Huang pujiang water were selected. The effects of ultraviolet disinfection on water microbial inactivation and photoreactivation were studied. And the orthogonal tests were used to research the effects of UV-chlorine and UV-chloramine disinfection on microbial inactivation, photoreactivation and biological stability.E.coli's inactivation rate increases along with the ultraviolet dosage .But under the same dosage, High ultraviolet intensity excelleds the low ultraviolet intensity as to the E.coli's inactivation effect. When the ultraviolet intensity is 0.153 mw/cm~2, ultraviolet dosage is 60 mJ/cm~2, it may achieve 5 log to inactivation rate of E.coli's. In the study, under the irradiation of high ultraviolet, the E.coli's photoreactivation ability is obviously feebler than the low dose. Compared to the dosage 5 mJ/cm~2, 120 mJ/cm~2 is highly efficient, photoreactivation may reduce by at lest 1.51og; Therefore, when the ultraviolet dosage is certain, high ultraviolet intensity is propitious to control the E.coli's photoreactivation rate. In addition, high visible light intensity is able to accelerate the course of E.coli 's photoreactivation.The effect of the combined applications of UV irradiation and chlorine in inactivating E.coli was synergistic effect. The combination of UV irradiation and chloramine was synergistic effect either. And the UV-chlorine disinfection is better than UV-chloramine disinfection on the E.coli's inactivation. But considering the drinking water security, UV-chloramine disinfection is suggested because the possibility of chloramine produceing disinfection by-products is greatly lower than chlorine. The first factor of UV-chlorine and UV-chloramine disinfection on MAP is the same as HPC. Meanwhile because weenie change of MAP content would cause microorganism's multiplication possibly, it can not ignore the influence of MAP on the water biological stability when choosing synergistic disinfection methods.