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Biocontrol Sci. 2018;23(3):139-143. doi: 10.4265/bio.23.139.

Behavior of Nitrate-Nitrogen and Nitrite-Nitrogen in Drinking Water.

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Division of Biomedical Engineering, Research Institute, National Defense Medical College.
Department of Oral and Maxillofacial Surgery, National Defense Medical College.
Division of Environmental Medicine, Research Institute, National Defense Medical College.


Nitrate-nitrogen (NO3-N) and nitrite-nitrogen (NO2-N) are constituents of the nitrogen cycle. NO3-N is toxic to humans, primarily due to its reduction to NO2-N. In Japan, NO3-N and NO2-N levels in tap water must not exceed 10 mg/L and only NO2-N alone not 0.04 mg/L, respectively. In this study, we verified the effect of microorganisms and ultraviolet (UV) to increase of NO2-N in water. First, all tested drinking-waters including tap water and commercial mineral water in PET bottles had < 2 mg/L NO3-N and undetectable levels (< 0.01 mg/L) of NO2-N. However, we found that NO2-N was generated in tap water left to stand at room temperature for several days, leading to increases in CF and TC counts and reduction of NO3-N. We also demonstrated that direct UV and sunlight irradiation of NO3-N-containing drinking water generated NO2-N in 1-2 h, with NO2-N reaching > 0.04 mg/mL by 4-6 h. On the other hand, NO3-N and NO2-N were undetectable in commercially purified water.


Disinfectant; Microbicidal activity; Nitrate; Nitrite; Stability

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