Krasner, S.W., Mitch, W.A., McCurry, D.L., Hanigan, D., Westerhoff, P., Formation, Precursors, Control, and Occurrence of Nitrosamines in Drinking Water: A Review, Water Research (2013), doi: 10.1016/j.watres.2013.04.050.
This review summarizes major findings over the last decade related to nitrosamines in drinking water, with a particular focus on N-nitrosodimethylamine (NDMA), because it is among the most widely detected nitrosamines in drinking waters. The reaction of inorganic dichloramine with amine precursors is likely the dominant mechanism responsible for NDMA formation in drinking waters. Even when occurrence surveys found NDMA formation in chlorinated drinking waters, it is unclear whether chloramination resulted from ammonia in the the source waters. NDMA formation has been associated with the use of quaternary amine-based coagulants and anion exchange resins, and wastewater-impaired source waters. Specific NDMA precursors in wastewater-impacted source waters may include tertiary amine-containing pharmaceuticals or other quaternary amine-containing constituents of personal care products. Options for nitrosamine control include physical removal of precursors by activated carbon or precursor deactivation by application of oxidants, particularly ozone or chlorine, upstream of chloramination. Although NDMA has been the most prevalent nitrosamine detected in worldwide occurrence surveys, it may account for only ∼5% of all nitrosamines in chloraminated drinking waters. Other significant contributors to total nitrosamines are poorly characterized. However, high levels of certain low molecular weight nitrosamines have been detected in certain Chinese waters suspected to be impaired by industrial effluents. The review concludes by identifying research needs that should be addressed over the next decade.
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This is a very interesting study and begins to address the question: “If chlorine is added and nitrogenous DBPs are formed, are any formed due to reactions with the bacteria being killed?
Huang Huang, Qian-Yuan Wu, Xin Tang, Rui Jiang, Hong-Ying Hu. Formation of haloacetonitriles and haloacetamides during chlorination of pure culture bacteria. Chemosphere, Volume 92, Issue 4, July 2013, Pages 375–381.
The increasing reuse of organic nitrogen-rich wastewater raises concerns regarding the formation of nitrogenous disinfection by-products (N-DBPs), such as haloacetonitriles and haloacetamides. Previous research mainly focused on N-DBPs formation from dissolved organic matter in wastewater. In this study, dichloroacetonitrile (DCAN) and dichloroacetamide (DCAcAm) formation from particles in the secondary effluents of a domestic wastewater treatment plant during chlorination was assessed to account for 26–46% of the total formation. As part of particles in wastewater, bacterial cells enriched in organic nitrogen are considered a potential source for the formation of N-DBPs during chlorination. The formation of DCAN, DCAcAm and trichloroacetamide (TCAcAm) during the chlorination of a Gram-negative bacterium of Escherichia coli (E. coli) and a Gram-positive bacterium of Enterococcus faecalis (E. faecalis) were then evaluated. Compared with dissolved organic matter in the secondary effluent, bacterial cells formed more DCAN, DCAcAm and TCAcAm during chlorination. E. faecalis formed more DCAN, but less DCAcAm and TCAcAm than E. coli did under most chlorination conditions. Moreover, the effects of contact time, chlorine dose, pH value and ammonia nitrogen concentration on the N-DBPs formation from the two bacterial suspensions were investigated. Under the chlorination conditions in this study, DCAN formation from the bacterial suspensions initially increased and then decreased, while TCAcAm formation increased with increasing contact time and chlorine dose. DCAcAm formation from the bacterial suspensions increased with the prolonged contact time, and increased and then decreased with increasing chlorine dose. DCAN, DCAcAm and TCAcAm formation was favored under neutral pH condition, but was reduced with the addition of ammonia during the chlorination of the two bacterial suspensions.
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The Department of Justice has lost track of terrorists.
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