The Seasonality of Nitrite Concentrations in a Chloraminated Drinking Water Distribution System

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

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We studied the seasonal variation of nitrite exposure in a drinking water distribution system (DWDS) with monochloramine disinfection in the Helsinki Metropolitan Area. In Finland, tap water is the main source of drinking water, and thus the nitrite in tap water increases nitrite exposure. Our data included both the obligatory monitoring and a sampling campaign data from a sampling campaign. Seasonality was evaluated by comparing a nitrite time series to temperature and by calculating the seasonal indices of the nitrite time series. The main drivers of nitrite seasonality were the temperature and the water age. We observed that with low water ages (median: 6.7 h) the highest nitrite exposure occurred during the summer months, and with higher water ages (median: 31 h) during the winter months. With the highest water age (190 h), nitrite concentrations were the lowest. At a low temperature, the high nitrite concentrations in the winter were caused by the decelerated ammonium oxidation. The dominant reaction at low water ages was ammonium oxidation into nitrite and, at high water ages, it was nitrite oxidation into nitrate. These results help to direct monitoring appropriately to gain exact knowledge of nitrite exposure. Also, possible future process changes and additional disinfection measures can be designed appropriately to minimize extra nitrite exposure.
Original languageEnglish
Article number1756
Number of pages17
JournalInternational Journal of Environmental Research and Public Health
Issue number8
Publication statusPublished - 15 Aug 2018
MoE publication typeA1 Journal article-refereed


  • nitrite
  • disinfection by-product
  • drinking water distribution systems
  • seasonality


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