Effects of wavelength and water quality on photodegradation of N-Nitrosodimethylamine (NDMA) |
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Authors: | Hiroshi Sakai Tatsuro Takamatsu Koji Kosaka Naoyuki Kamiko Satoshi Takizawa |
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Institution: | a Dept. of Urban Engineering, The University of Tokyo, 7-3-1, Hongo, Bunkyo-ku, Tokyo 113-8656, Japan b Dept. of Water Supply Engineering, National Institute of Public Health, 2-3-6, Minami, Wako-city 351-0197, Japan c Dept. of Environment Systems Engineering, Ritsumeikan University, 1-1-1, Nojihigashi, Kusatsu-city, Shiga 525-8577, Japan |
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Abstract: | N-Nitrosodimethylamine (NDMA) is a potent carcinogen that yields a cancer risk of 10−6 at concentrations as low as 0.7 ng L−1. Tentative guideline values are set at 3 ng L−1 in California, USA; 9 ng L−1 in Ontario, Canada; 40 ng L−1 nationwide in Canada; and 100 ng L−1 by the World Health Organization. NDMA is a great concern in treating reclaimed water as well as drinking water. UV degradation can be considered effective degradation method. A 1-log reduction of NDMA is achieved by 1000 mJ cm−2 of a 254-nm low pressure (LP) mercury UV lamp. However, a higher degradation efficiency than that provided by LP lamps is desired in practical treatment. In this study, the effects of wavelength and water quality were investigated to achieve higher degradation efficiency. The effects of wavelength were examined by comparing three UV lamps: a 222-nm Kr Cl Excimer UV lamp, a 254-nm LP mercury UV lamp, and a 230- to 270-nm filtered medium pressure (FMP) mercury UV lamp. The 222-nm lamp and FMP lamp achieved 4 times and 2.8 times higher degradation efficiency, respectively, than the conventional 254-nm LP lamp. Effects on water quality were also simulated by using absorption spectrum data of nitrate solutions and process water from a drinking-water treatment plant. In the simulation, the 222-nm lamp was affected by UV-absorbing compounds in the water, whereas the FMP lamp showed more stable degradation efficiency. Appropriate use of these three types of lamps could enhance the efficiency of degradation of NDMA. |
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Keywords: | UV-absorbing compounds Nitrate Suwanee river natural organic matter Process water Drinking water treatment plant Quantum yield |
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