Chloramination of nitrogenous contaminants (pharmaceuticals and pesticides): NDMA and halogenated DBPs formation

Julien Le Roux (1) , Hervé Gallard (2) , Jean-Philippe Croué (2)

1 LEESU - Laboratoire Eau Environnement et Systèmes Urbains
2 LCME - Laboratoire de chimie et microbiologie de l'eau [Poitiers]

Disinfection with chloramines is often used to reduce the production of regulated disinfection by-products (DBPs) such as trihalomethanes (THMs) and haloacetic acids (HAAs). However, chloramination can lead to the formation of N-nitrosamines, including N-nitrosodimethylamine (NDMA), a probable human carcinogen. Previous research used dimethylamine (DMA) as a model precursor of NDMA, but certain widely used tertiary dimethylamines (e.g. the pharmaceutical ranitidine) show much higher conversion rates to NDMA than DMA. This study investigates the NDMA formation potential of several tertiary amines including pharmaceuticals and herbicides. The reactivity of these molecules with monochloramine (NH2Cl) is studied through the formation of NDMA, and other halogenated DBPs such as haloacetonitriles (HANs) and AOX (Adsorbable Organic Halides). Several compounds investigated formed NDMA in greater amounts than DMA, revealing the importance of structural characteristics of tertiary amines for NDMA formation. Among these compounds, the pharmaceutical ranitidine showed the highest molar conversion to NDMA. The pH and dissolved oxygen content of the solution were found to play a major role for the formation of NDMA from ranitidine. NDMA was formed in higher amounts at pH around pH 8 and a lower concentration of dissolved oxygen dramatically decreased NDMA yields. These findings seem to indicate that dichloramine (NHCl2) is not involved into the formation of NDMA from ranitidine. Dissolved oxygen was also found to influence the formation of other oxygen-containing DBPs (i.e. trichloronitromethane and haloketones), which shows that dissolved oxygen could be incorporated into those DBPs. The results of this study identify several anthropic precursors of NDMA, indicating that chloramination of waters impacted by these tertiary amines could lead to the formation of important amounts of NDMA and other non-regulated DBPs of potential health concern (e.g. dichloroacetonitrile or trichloronitromethane). This could be of particular importance for the chloramination of wastewater effluents, especially during water reuse processes.

Mots clés: NDMA; Nitrosamine; Chloramination; Disinfection By-products; Ranitidine

Domaines: Chimie

Julien Le Roux, Hervé Gallard, Jean-Philippe Croué. Chloramination of nitrogenous contaminants (pharmaceuticals and pesticides): NDMA and halogenated DBPs formation. Water Research, 2011, 45 (10), http://www.sciencedirect.com/science/article/pii/S0043135411001461. ⟨10.1016/j.watres.2011.03.035⟩. ⟨hal-01201554⟩