The role of natural organic matter in nitrite formation by LP-UV/H 2 O 2 treatment of nitrate-rich water

The role of natural organic matter (NOM) on nitrite formation from nitrate photolysis by low pressure ultraviolet lamp (LP-UV) photolysis and LP-UV/H O 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...

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Bibliographic Details
Published in:Water research (Oxford) 2016-12, Vol.106, p.312
Main Authors: Semitsoglou-Tsiapou, Sofia, Mous, Astrid, Templeton, Michael R, Graham, Nigel J D, Hernández Leal, Lucía, Kruithof, Joop C
Format: Article
Language:English
Subjects:
Hydrogen Peroxide
Nitrates
Nitrites
Oxidation-Reduction
Ultraviolet Rays
Water
Water Purification
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Summary:The role of natural organic matter (NOM) on nitrite formation from nitrate photolysis by low pressure ultraviolet lamp (LP-UV) photolysis and LP-UV/H O 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/H O 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.
ISSN:1879-2448