| Drinking water risk issue has been an international research hotspot. At present people are facing many new drinking water risks, nitrosamine pollution is one of these new risks. Previously, the focus of nitrosamines mainly concentrated in food, daily consumer goods as well as air pollution, and other fields. Since N-nitrosodimethylamine (NDMA) had been detected up to 400000 ng·L-1 in drinking water wells near to California rocket engine test site, it triggered the concerns of nitrosamines in drinking water. Since then, NDMA, N-nitrosopyrrolidine (NPyr), and N-nitrosopiperidine (NPip) had been also detected in the chlorination and chloramination of drinking water and sewage. Nitrosamines has become a new concern of drinking water disinfection by-products (DBPs) after the halogenated DBPs. Nitrosamines is stable, and is not likely to bioaccumulate, biodegrade, adsorb to particulate matter, or volatilize difficult. Conventional water treatments can not deal with removal of nitrosamines effectively. In order to improve drinking water quality, it is essential to develop effective treatment methods for nitrosamines removal, and reducing the possibility of their regeneration.In this paper, UV direct photolysis of nitrosamines, such as NDMA, N-Nitrosodiethylamine (NDEA), NPyr and NPip in aqueous was investigated. The objectives were not only to assess the removal efficiency of nitrosamines photodegradation by UV irradiation, but also to identify the products of each nitrosamine photodegradation, and deduce the degradation pathways especially. Then, the more effectual and thorough treatment for nitrosamines removal from water can be find out on the basis of these results.Firstly, the analysis method of nitrosamines in water was set up. Nitrosamines were analyzed by reverse phase high performance liquid chromatogram (HPLC) with UV detection. The method can not only detert the nitrosamines quickly, but also has good linear relationship, precision and accuracy. The relative standard deviation of the method was less than 2%, and the recovery with standard addition was 85.2%～108%.Taken the alkylation nitrosamines NDMA and NDEA as straight-chain nitrosamines representatives, the law of straight-chain nitrosamines degradation by UV irradiation was studied. The result showed that UV irradiation was an effective method for NDMA and NDEA removal from water. Compared with the NDMA, the longer straight-chain structure of NDEA makes it easy for UV degradation. Solution pH had great effects on NDMA and NDEA photodegradation by UV irradiation. Degradation of NDMA and NDEA by UV can generate their precursors, nitrite and nitrate. The mechanisms of NDMA and NDEA degradation by UV were basically the same, which were both considered as a result of N-N bond fission due to UV irradiation.Taken the NPyr and NPip as ring nitrosamines representatives, the law of ring nitrosamines degradation by UV irradiation was studied. The result showed that UV irradiation was an effective method for NPyr and NPip removal from water. Compared with the NPyr, NPip was easy for UV degradation. Solution pH did not affect the NPyr degradation by UV. However, solution pH had different effect on NPip photodegradation by UV irradiation. The mechanisms of NPyr and NPip degradation by UV were both considered as a result of N-N bond fission due to UV irradiation.As the major degradation products of nitrosamines, aliphatic amines, nitrite and nitrate are also the important precursors for nitrosamines. Once the appropriate conditions, aliphatic amines were likely to regenerate nitrosamines again. In order to eliminate NDMA contamination completely, and minish the possibility of NDMA regeneration at the same time, control of DMA formation became the key problem. In this paper, degradation of NDMA and NDEA by advanced oxidation technology UV-O3 were carried out. The results showed that, UV-O3 not only could degrade NDMA and NDEA effectively, accelerate the degradation rate, but also could control the formation of DMA, DEA and NO2- effectively, reduce the the possibility of regeneration. Hydroxyl radicals grnerated in UV-O3 system due to the introduction of ozone, which resulted in increasing the rate of NDMA and NDEA degradation. In UV-O3 process, not only UV irradiation takes part in the degradation of nitrosamines, but also the hydroxyl radicals were involved in the degradation of pollutants. Therefore, UV-O3 advanced oxidation technology was more capacity to the degradation of organic matter.Finally, the control of NDMA regeneration by UV-O3 advanced oxidation technology was investigated. The results showed that UV-O3 could degrade NDMA effectively, and control the formation of the DMA, resulting in reducing or avoiding the possibility of NDMA regeneration. As UV, ozone and the hydroxyl radicals in UV-O3 process, the mechanism of controlling on DMA formation became very complicated. On one hand, after being produced from NDMA, DMA was degraded by ozone or hydroxyl radicals. On the other hand, the mechanism of NDMA degradation was changed by introducing ozone into UV process. Reaction of NDMA and hydroxyl radical produced MA resulted in reducing the yields of DMA.
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