Trade-offs in disinfection byproduct formation associated with precursor preoxidation for control of N-nitrosodimethylamine formation
| Autor: | Amisha D. Shah, William A. Mitch, Urs von Gunten, Chih Fen Tiffany Lee, Stuart W. Krasner |
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| Rok vydání: | 2012 |
| Předmět: |
Chlorine dioxide
Chloramine Ozone Ultraviolet Rays Drinking Water chemistry.chemical_element Oxides General Chemistry Dimethylnitrosamine Disinfection chemistry.chemical_compound chemistry N-Nitrosodimethylamine Environmental chemistry polycyclic compounds Chlorine Water Pollution Chemical Environmental Chemistry PolyDADMAC Water treatment Chlorine Compounds Chloramination |
| Zdroj: | Environmental sciencetechnology. 46(9) |
| ISSN: | 1520-5851 |
| Popis: | Chloramines in drinking water may form N-nitrosodimethylamine (NDMA). Various primary disinfectants can deactivate NDMA precursors prior to chloramination. However, they promote the formation of other byproducts. This study compared the reduction in NDMA formation due to chlorine, ozone, chlorine dioxide, and UV over oxidant exposures relevant to Giardia control coupled with postchloramination under conditions relevant to drinking water practice. Ten waters impacted by treated wastewater, poly(diallyldimethylammonium chloride) (polyDADMAC) polymer, or anion exchange resin were examined. Ozone reduced NDMA formation by 50% at exposures as low as 0.4 mg×min/L. A similar reduction in NDMA formation by chlorination required ∼60 mg×min/L exposure. However, for some waters, chlorination actually increased NDMA formation at lower exposures. Chlorine dioxide typically had limited efficacy regarding NDMA precursor destruction; moreover, it increased NDMA formation in some cases. UV decreased NDMA formation by ∼30% at fluences500 mJ/cm(2), levels relevant to advanced oxidation. For the selected pretreatment oxidant exposures, concentrations of regulated trihalomethanes, haloacetic acids, bromate, and chlorite typically remained below current regulatory levels. Chloropicrin and trichloroacetaldehyde formation were increased by preozonation or medium pressure UV followed by postchloramination. Among preoxidants, ozone achieved the greatest reduction in NDMA formation at the lowest oxidant exposure associated with each disinfectant. Accordingly, preozonation may inhibit NDMA formation with minimal risk of promotion of other byproducts. Bromide500 μg/L generally increased NDMA formation during chloramination. Higher temperatures increased NDMA precursor destruction by preoxidants but also increased NDMA formation during postchloramination. The net effect of these opposing trends on NDMA formation was water-specific. |
| Databáze: | OpenAIRE |
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