Author(s)

Pirjo-Liisa Rantanen^1*, Minna M. Keinänen-Toivola², Merja Ahonen², Ilkka Mellin³, Duoying Zhang⁴, Tuula Laakso⁵, Riku Vahala¹

¹Department of Built Environment, School of Engineering, Aalto University, Espoo, Finland.
²Faculty of Technology, Satakunta University of Applied Sciences, Rauma, Finland.
³Department of Mathematics and Systems Analysis, School of Science, Aalto University, Espoo, Finland.
⁴School of Civil Engineering, Heilongjiang University, Harbin, China.
⁵Helsinki Regional Environmental Services Authority, Helsinki, Finland.

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.

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

Rantanen, P. , Keinänen-Toivola, M. , Ahonen, M. , Mellin, I. , Zhang, D. , Laakso, T. and Vahala, R. (2017) The Spatial Distribution of Nitrite Concentrations in a Large Drinking Water Distribution System in Finland. Journal of Water Resource and Protection, 9, 1026-1042. doi: 10.4236/jwarp.2017.98068.