Decreased natural organic matter in water distribution decreases nitrite formation in non-disinfected conditions, via enhanced nitrite oxidation Rantanen, Pirjo Liisa Nitrite Nitrification Natural organic matter Water distribution systems Non-disinfected conditions Nitrite in drinking water is a potentially harmful substance for humans, and controlling nitrite formation in drinking water distribution systems (DWDSs) is highly important. The effect of natural organic matter (NOM) on the formation of nitrite in simulated distribution systems was studied. The objective was to inspect how a reduced NOM concentration affected nitrite development via nitrification, separated from the effects of disinfection. We observed that nitrite formation was noticeably sensitive to the changes in the NOM concentrations. Nitrite declined with reduced NOM (TOC 1.0 mg L-1) but increased with the normal NOM concentration of tap water (TOC 1.6 mg L-1). Ammonium oxidation was not altered by the reduced NOM, however, nitrite oxidation was enhanced significantly according to the pseudo-first order reaction rate model interpretation. The enhanced nitrite oxidation was observed with both ammonium and nitrite as the initial nitrogen source. The theoretical maximum nitrite concentrations were higher with the normal concentration of NOM than with reduced NOM. The results suggest that the role of nitrite oxidation may be quite important in nitrite formation in DWDSs and worth further studies. As a practical result, our study supported enhanced NOM removal in non-disinfected DWDSs. 2021-02-12T12:14:32Z 2021-02-12T12:14:32Z 2020-09-30 info:eu-repo/semantics/article Rantanen, P. L., Keinänen-Toivola, M. M., Ahonen, M., González-Martínez, A., Mellin, I., & Vahala, R. (2020). Decreased natural organic matter in water distribution decreases nitrite formation in non-disinfected conditions, via enhanced nitrite oxidation. Water research X, 9, 100069. [https://doi.org/10.1016/j.wroa.2020.100069] http://hdl.handle.net/10481/66513 10.1016/j.wroa.2020.100069 eng http://creativecommons.org/licenses/by/3.0/es/ info:eu-repo/semantics/openAccess Atribución 3.0 España Elsevier