Transformation and fate of dissolved organic nitrogen in drinking water supply system: A full scale case study from Yixing, China

Abstract The transformation of dissolved organic nitrogen (DON) in the drinking water treatment plants could be closely associated with nitrogenous disinfection by-product (N-DBP) formation. In this study, we have assessed the molecular transformation of DON and its impact on N-DBP formation in a full scale drinking water treatment plant. Based on the result of Fourier transform ion cyclotron resonance mass spectrometry (FT-ICR MS) analysis, DON compounds with low molecular weight ( 2 and CHON 3 according to the number of nitrogen atoms. Via the analytical window of van Krevelen diagrams, we found that the molecular structural features of CHON, CHON 2 and CHON 3 were not altered before the chlorination process. In detail, the CHON 2 and CHON 3 compositions were concentrated on the regions assigned to a lignin-structure while CHON compositions were also distributed in other compounds including proteins, carbohydrates and tannin. Furthermore, CHON formation was more difficult to be removed before the V-filter process. For N-DBP, chlorine-containing DON (Cl-DON) composition was likely to be removed through flocculation and sedimentation processes, whereas N -nitrosamine compounds were removed in V-filter and biological activated carbon filter processes. The health risks of aromatic structure N -nitrosamines due to the pre-chlorination of the raw water should be further studied.