Preoxidation Effectively Destroys <i>N</i>-Nitrosodimethylamine Precursors in Raw, Lime-Softened, and Recarbonated Surface Waters

Noe, Eric R.; Li, Jiaqi; Arnold, William A.; Hozalski, Raymond M.

doi:10.1089/ees.2023.0057

Cited by 6 publications

(4 citation statements)

References 42 publications

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“…The negative correlation between Region V (humic acid-like) and NDMA UFC indicates that humic acid-like substances are the primary competitors with NDMA precursors for chloramines. This is consistent with increased NDMA UFC after lime softening , because this process removes the high MW fractions of NOM (i.e., humic acids). The weak association between NDMA UFC concentrations and region III indicates that fulvic acid does not significantly affect NDMA formation.…”

Section: Discussionsupporting

confidence: 81%

Animal Feedlots and Domestic Wastewater Discharges are Likely Sources of N-Nitrosodimethylamine (NDMA) Precursors in Midwestern Watersheds

Li,

Arnold,

Hozalski

2024

Environ. Sci. Technol.

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N-nitrosodimethylamine (NDMA) precursor concentrations along four major rivers in Minnesota, USA were quantified and correlated with watershed land cover types, anthropogenic activity, and organic matter characteristics. River water samples (36 in total) were chloraminated under uniform formation conditions (UFC) before and after lime-softening treatment, and the resulting NDMA concentrations were quantified (NDMA UFC ). Regarding land cover, NDMA UFC in raw river water exhibited weak positive correlations with urban land (ρ = 0.33, p = 0.05) and cropland coverage (ρ = 0.35, p = 0.04). For anthropogenic activity, NDMA UFC in raw river water positively correlated with the number of feedlots (ρ = 0.57), total weight of animals (ρ = 0.68), and total number of domestic wastewater treatment plants (WWTPs; ρ = 0.63) with p < 0.01. NDMA UFC positively correlated with region IV fluorescence intensity from fluorescence excitation−emission spectra (ρ = 0.70, p < 0.01). Lime softening of river water typically increased NDMA UFC and preferentially removed organic matter that fluoresces in region V, suggesting that the organic matter in this region decreases NDMA UFC by competing for available chloramines. Overall, animal feedlots, along with domestic WWTPs, are predominant sources of NDMA precursors in the studied watersheds, while croplands and urban runoff are of lesser importance.

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Section: Discussionsupporting

confidence: 81%

Animal Feedlots and Domestic Wastewater Discharges are Likely Sources of N-Nitrosodimethylamine (NDMA) Precursors in Midwestern Watersheds

Li,

Arnold,

Hozalski

2024

Environ. Sci. Technol.

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“…66,67 Short contact with free chlorine potentially destroys some NDMA precursors, resulting in less NDMA formation after converting the residual chlorine to chloramines. 68,69 Thus, the UFC and FP tests represent moderate to worst-case scenarios, respectively, for NDMA formation, while free chlorine exposure followed by NH 3 addition would result in lower and likely more realistic NDMA concentrations. 32 The obvious trade-off with the free chlorine exposure strategy for preoxidizing NDMA precursors is the formation of halogenated DBPs including regulated compounds.…”

Section: ■ Resultsmentioning

confidence: 99%

“…One limitation of this study is that NDMA formation was measured by adding preformed chloramines via the UFC and FP tests. Many drinking water treatment plants in the United States use free chlorine as the primary disinfectant followed by the addition of NH 3 to convert the residual free chlorine to chloramines. , Short contact with free chlorine potentially destroys some NDMA precursors, resulting in less NDMA formation after converting the residual chlorine to chloramines. , Thus, the UFC and FP tests represent moderate to worst-case scenarios, respectively, for NDMA formation, while free chlorine exposure followed by NH 3 addition would result in lower and likely more realistic NDMA concentrations . The obvious trade-off with the free chlorine exposure strategy for preoxidizing NDMA precursors is the formation of halogenated DBPs including regulated compounds.…”

Section: Discussionmentioning

confidence: 99%

Spatiotemporal Variability in N-Nitrosodimethylamine Precursor Levels in a Watershed Impacted by Agricultural Activities and Municipal Wastewater Discharges and Effects of Lime Softening

Li,

Arnold,

Hozalski

2023

Environ. Sci. Technol.

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The Crow River, a tributary of the Mississippi River in Minnesota, U.S.A., that is impacted by agricultural activities and municipal wastewater discharges, was sampled approximately monthly at 12 locations over 18 months to investigate temporal and spatial variations in N-nitrosodimethylamine (NDMA) precursor levels. NDMA precursors were quantified primarily by measuring NDMA formed under the low chloramine dose uniform formation conditions protocol (NDMAUFC) and occasionally using the high dose formation potential protocol (NDMAFP). Raw water NDMAUFC concentrations (2.2 to 128 ng/L) exhibited substantial temporal variation but relatively little spatial variation. An increase in NDMAUFC was observed for 126 of 169 water samples after lime-softening treatment. A kinetic model indicates that under chloramine-limited UFC test conditions, the increase in NDMAUFC can be attributed to a decrease in competition between precursors and natural organic matter (NOM) for chloramines and reduced interactions of precursors with NOM. NDMAUFC concentrations correlated positively with dissolved nitrogen concentration (ρ = 0.44, p < 0.01) when excluding the spring snowmelt period and negatively correlated with dissolved organic carbon concentration (ρ = −0.47, p < 0.01). Overall, NDMA precursor levels were highly dynamic and strongly affected by lime-softening treatment.

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“…The similar R ct values in both contactors indicate the rapid degradation of ozone, likely due to the relatively high pH of the lime-softened and recarbonated water, resulting in similar hydroxyl radical exposures. This result is consistent with batch studies using SPRWS lime-softened and recarbonated water that showed that the amount of hydroxyl radical produced and the destruction of N -nitrosodimethylamine precursors were equivalent for ozone and AOP treatments . Relatedly, this rapid degradation of ozone and subsequent reactions of hydroxyl radical mean that extending the residence time of the contact chambers would have no effect on contaminant removal.…”

Section: Results and Discussionmentioning

confidence: 92%

Contaminant Removal in a Pilot Drinking Water Treatment Plant by Pre-oxidation Followed by Biological Activated Carbon Filtration: Spiking versus Ambient Studies

Berg,

Hozalski,

Kuo-Dahab

et al. 2023

ACS EST Water

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Advanced drinking water treatment including biological activated carbon (BAC) filtration, ozonation, and advanced oxidation processes (AOPs) can improve trace organic contaminant removal compared to conventional processes. Contaminant removals through a pilot-scale lime-softening drinking water treatment plant (pH > 8.5 after recarbonation) using BAC alone and parallel ozone and ozone/hydrogen peroxide (AOP) treatment units followed by BAC were compared. The BAC filters contained aged media (∼14 years) harvested from the full-scale facility. Taste and odor compounds, 1,4-dioxane, neonicotinoids, antibiotics, and other contaminants of emerging concern were spiked into the water ahead of the ozone contactors at concentrations ranging from 26 ng L–1 to 7.3 μg L–1. Removal by BAC filtration varied from 19 ± 11% for 1,4-dioxane to 77 ± 40% for geosmin. Ozone and hydroxyl radical exposures ranging over 0.49–1.27 × 10–2 M s and 0.19–4.67 × 10–10 M s, respectively, improved removal of all spiked contaminants compared to BAC filtration alone, especially for 1,4-dioxane (85 ± 16%). When evaluating contaminant removal at ambient concentrations, however, concentrations of many contaminants rebounded after ozone or AOP treatment due to desorption from the BAC media. Our findings suggest that contaminants may be released from aged BAC unless the material is replaced upon addition of ozone or AOPs to an existing treatment facility.

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Preoxidation Effectively Destroys N-Nitrosodimethylamine Precursors in Raw, Lime-Softened, and Recarbonated Surface Waters

Cited by 6 publications

References 42 publications

Animal Feedlots and Domestic Wastewater Discharges are Likely Sources of N-Nitrosodimethylamine (NDMA) Precursors in Midwestern Watersheds

Animal Feedlots and Domestic Wastewater Discharges are Likely Sources of N-Nitrosodimethylamine (NDMA) Precursors in Midwestern Watersheds

Spatiotemporal Variability in N-Nitrosodimethylamine Precursor Levels in a Watershed Impacted by Agricultural Activities and Municipal Wastewater Discharges and Effects of Lime Softening

Contaminant Removal in a Pilot Drinking Water Treatment Plant by Pre-oxidation Followed by Biological Activated Carbon Filtration: Spiking versus Ambient Studies

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