The Spatial Distribution of Nitrite Concentrations in a Large Drinking Water Distribution System in Finland

Pirjo-Liisa Rantanen, Minna M. Keinänen-Toivola, Merja Ahonen, Ilkka Mellin, Duoying Zhang, Tuula Laakso, Riku Vahala

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Nitrite in drinking water is a potential health hazard and monitoring its concentrations in distributed water is of paramount importance. When monochloramine is used in secondary disinfection in drinking water distribution systems (DWDSs), nitrite is often formed by nitrification in the biofilm on the inner surface of distribution pipes. This article attempts to identify areas with a risk of increased nitrite concentrations as well as the main reasons leading to nitrite occurrence in a large urban DWDS in Finland using spatial inspection of obligatory monitoring data. Nitrification was found to occur throughout the study area, though nitrite was not increased everywhere. Instead, nitrite was increased close to the water treatment plants (WTPs) and was connected to fresh drinking water than stagnant drinking water. Temperature effects on nitrite concentrations were surprisingly insignificant, even though it is well known that nitrification reactions are affected by temperature. The temperature dependence of ammonium and total residual chlorine was more significant than the dependence of nitrite. The findings of this study emphasize the need to monitor nitrite concentrations close to WTPs.
Original languageEnglish
Pages (from-to)1026-1042
Issue number8
Publication statusPublished - 2017
MoE publication typeA1 Journal article-refereed


  • Ammonium
  • Disinfection with Monochloramine
  • Distribution System
  • Drinking Water
  • DWDS
  • Maximum Water Age
  • Nitrification
  • Nitrite Concentrations
  • Residual Total Chlorine
  • Spatial Inspection
  • Temperature


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