Department of Civil and Environmental Engineering, Imperial College London, London, UK; Wetsus, European Centre of Excellence for Sustainable Water Technology, Leeuwarden, The Netherlands.
WLN, Glimmen, The Netherlands.
Water Res. 2016 Dec 1;106:312-319. doi: 10.1016/j.watres.2016.10.001. Epub 2016 Oct 3.
The role of natural organic matter (NOM) on nitrite formation from nitrate photolysis by low pressure ultraviolet lamp (LP-UV) photolysis and LP-UV/HO treatment was investigated. Nitrate levels up to the WHO guideline maximum of 50 mg NO/L were used in tests. The presence of 4 mg/L Suwannee River natural organic matter (NOM) led to increased nitrite yields compared to NOM-free controls. This was caused partly by NOM scavenging of OH radicals, preserving the produced NO as well as the ONOO that leads to NO formation, but also via the production of radical species (O, O- and OH) by the photolysis of NOM. In addition, solvated electrons formed by NOM photolysis may reduce nitrate directly to nitrite. For comparison, Nordic Lake NOM, representative of aquatic NOM, as well as Pony Lake NOM, which had a greater nitrogen content (6.51% w/w) than the other two types of NOM, were investigated, yielding similar nitrite levels as Suwannee River NOM. The results suggest that neither the type nor the nitrogen content of the NOM have an effect on the nitrite yields obtained over the range of UV/HO doses applied (UV fluences of 500-2100 mJ/cm and hydrogen peroxide doses of 10, 25, and 50 mg/L). The findings indicate that for UV fluences above 1500 mJ/cm the resulting nitrite concentration can exceed the 0.1 mg/L EU regulatory limit for nitrite, suggesting that nitrite formation by LP-UV advanced oxidation of nitrate-rich waters is important to consider.
研究了天然有机物 (NOM) 在低压紫外灯 (LP-UV) 光解和 LP-UV/HO 处理下由硝酸盐光解生成亚硝酸盐的作用。测试中使用了高达世界卫生组织指南最大值 50 mg NO/L 的硝酸盐水平。与无 NOM 对照相比，存在 4 mg/L 的苏湾河天然有机物 (NOM) 导致亚硝酸盐产率增加。这部分是由于 NOM 清除了 OH 自由基，保留了产生的 NO 和导致 NO 形成的 ONOO，但也通过 NOM 光解产生了自由基（O、O- 和 OH）。此外，NOM 光解形成的溶剂化电子可能将硝酸盐直接还原为亚硝酸盐。为了进行比较，研究了代表水生 NOM 的北欧湖 NOM 以及比其他两种 NOM 具有更高氮含量（6.51%w/w）的 Pony Lake NOM，它们产生的亚硝酸盐水平与苏湾河 NOM 相似。结果表明，在应用的 UV/HO 剂量范围内（UV 通量为 500-2100 mJ/cm 和过氧化氢剂量为 10、25 和 50 mg/L），NOM 的类型和氮含量都不会影响亚硝酸盐产率。研究结果表明，对于高于 1500 mJ/cm 的 UV 通量，产生的亚硝酸盐浓度可能超过欧盟对亚硝酸盐的 0.1 mg/L 监管限值，这表明富含硝酸盐的水的 LP-UV 高级氧化产生的亚硝酸盐形成值得考虑。
