Abstract

N-nitrosodimethylamine (NDMA) is a chloramine disinfection by-product, and its formation in drinking waters can increase due to the addition of cationic polydiallyldimethylammonium chloride (polyDADMAC). PolyDADMAC is a cationic polymer added as a coagulant or coagulant aid to enhance turbidity removal during sedimentation and filtration. This paper answers two central questions to understanding the nature of the NDMA precursors in polyDADMAC. First, what is the reactivity of different molecular weight (MW) fractions of polyDADMAC with chloramines? NDMA formation potential (NDMAFP) and kinetic experiments with chloramines were conducted for non-fractionated (raw) and size-excluded fractions (<3K, 3–10K, and >10K Da.) of polyDADMAC. The lower MW fraction (<3K Da.) of polyDADMAC solutions was responsible for forming 64 ± 6% of the NDMA, despite containing only 8.7 and 9.8% of the carbon or nitrogen present in the bulk polymer. The chloramine demand kinetics of the lowest MW fraction were also >2× faster than the higher MW fractions. Therefore, in a water treatment application the lower MW polyDADMAC likely contributes to most of the NDMA attributed to the use of polyDADMAC. The second question was: can 1H and 13C nuclear magnetic resonance spectroscopy (NMR) be used to characterize the molecular structures in polyDADMAC that react with chloramines? A peak for 1H NMR dimethylamine (DMA), a known low MW NDMA precursor, was found in a commercial polyDADMAC solution and decreased upon chloramination. The estimated DMA alone could not account for the observed NDMAFP, indicating the presence of other low MW precursors. Diffusion order spectroscopy (DOSY) NMR also showed multiple lower MW organics in polyDADMAC that change upon chloramination, including a 1.5× decrease in MW, suggesting chloramines cleave C–C or C–N bonds. These reactions may produce intermediates responsible for NDMA formation. Polymer manufacturers could use NMR to synthesize polyDADMAC with less DMA and other low MW compounds that produce NDMA upon chloramination.

Original languageEnglish (US)
Pages (from-to)466-472
Number of pages7
JournalWater Research
Volume150
DOIs
StatePublished - Mar 1 2019

Fingerprint

formation water
Water treatment
water treatment
Molecular weight
chloride
Nuclear magnetic resonance spectroscopy
spectroscopy
nuclear magnetic resonance
polymer
Disinfection
Turbidity
Polymers
Sedimentation
Potable water
Molecular structure
Byproducts
disinfection
turbidity
aid
Spectroscopy

Keywords

  • Chloramination
  • N-nitrosodimethylamine
  • Nuclear magnetic resonance
  • polyDADMAC
  • Size fractionation

ASJC Scopus subject areas

  • Ecological Modeling
  • Water Science and Technology
  • Waste Management and Disposal
  • Pollution

Cite this

Lower molecular weight fractions of PolyDADMAC coagulants disproportionately contribute to N-nitrosodimethylamine formation during water treatment. / An, Dong; Chen, Yanan; Gu, Bin; Westerhoff, Paul; Hanigan, David; Herckes, Pierre; Fischer, Natalia; Donovan, Samantha; Croue, Jean Philippe; Atkinson, Ariel.

In: Water Research, Vol. 150, 01.03.2019, p. 466-472.

Research output: Contribution to journalArticle

An, Dong ; Chen, Yanan ; Gu, Bin ; Westerhoff, Paul ; Hanigan, David ; Herckes, Pierre ; Fischer, Natalia ; Donovan, Samantha ; Croue, Jean Philippe ; Atkinson, Ariel. / Lower molecular weight fractions of PolyDADMAC coagulants disproportionately contribute to N-nitrosodimethylamine formation during water treatment. In: Water Research. 2019 ; Vol. 150. pp. 466-472.
@article{80131833db844e338c8182b668fb9e72,
title = "Lower molecular weight fractions of PolyDADMAC coagulants disproportionately contribute to N-nitrosodimethylamine formation during water treatment",
abstract = "N-nitrosodimethylamine (NDMA) is a chloramine disinfection by-product, and its formation in drinking waters can increase due to the addition of cationic polydiallyldimethylammonium chloride (polyDADMAC). PolyDADMAC is a cationic polymer added as a coagulant or coagulant aid to enhance turbidity removal during sedimentation and filtration. This paper answers two central questions to understanding the nature of the NDMA precursors in polyDADMAC. First, what is the reactivity of different molecular weight (MW) fractions of polyDADMAC with chloramines? NDMA formation potential (NDMAFP) and kinetic experiments with chloramines were conducted for non-fractionated (raw) and size-excluded fractions (<3K, 3–10K, and >10K Da.) of polyDADMAC. The lower MW fraction (<3K Da.) of polyDADMAC solutions was responsible for forming 64 ± 6{\%} of the NDMA, despite containing only 8.7 and 9.8{\%} of the carbon or nitrogen present in the bulk polymer. The chloramine demand kinetics of the lowest MW fraction were also >2× faster than the higher MW fractions. Therefore, in a water treatment application the lower MW polyDADMAC likely contributes to most of the NDMA attributed to the use of polyDADMAC. The second question was: can 1H and 13C nuclear magnetic resonance spectroscopy (NMR) be used to characterize the molecular structures in polyDADMAC that react with chloramines? A peak for 1H NMR dimethylamine (DMA), a known low MW NDMA precursor, was found in a commercial polyDADMAC solution and decreased upon chloramination. The estimated DMA alone could not account for the observed NDMAFP, indicating the presence of other low MW precursors. Diffusion order spectroscopy (DOSY) NMR also showed multiple lower MW organics in polyDADMAC that change upon chloramination, including a 1.5× decrease in MW, suggesting chloramines cleave C–C or C–N bonds. These reactions may produce intermediates responsible for NDMA formation. Polymer manufacturers could use NMR to synthesize polyDADMAC with less DMA and other low MW compounds that produce NDMA upon chloramination.",
keywords = "Chloramination, N-nitrosodimethylamine, Nuclear magnetic resonance, polyDADMAC, Size fractionation",
author = "Dong An and Yanan Chen and Bin Gu and Paul Westerhoff and David Hanigan and Pierre Herckes and Natalia Fischer and Samantha Donovan and Croue, {Jean Philippe} and Ariel Atkinson",
year = "2019",
month = "3",
day = "1",
doi = "10.1016/j.watres.2018.12.002",
language = "English (US)",
volume = "150",
pages = "466--472",
journal = "Water Research",
issn = "0043-1354",
publisher = "Elsevier Limited",

}

TY - JOUR

T1 - Lower molecular weight fractions of PolyDADMAC coagulants disproportionately contribute to N-nitrosodimethylamine formation during water treatment

AU - An, Dong

AU - Chen, Yanan

AU - Gu, Bin

AU - Westerhoff, Paul

AU - Hanigan, David

AU - Herckes, Pierre

AU - Fischer, Natalia

AU - Donovan, Samantha

AU - Croue, Jean Philippe

AU - Atkinson, Ariel

PY - 2019/3/1

Y1 - 2019/3/1

N2 - N-nitrosodimethylamine (NDMA) is a chloramine disinfection by-product, and its formation in drinking waters can increase due to the addition of cationic polydiallyldimethylammonium chloride (polyDADMAC). PolyDADMAC is a cationic polymer added as a coagulant or coagulant aid to enhance turbidity removal during sedimentation and filtration. This paper answers two central questions to understanding the nature of the NDMA precursors in polyDADMAC. First, what is the reactivity of different molecular weight (MW) fractions of polyDADMAC with chloramines? NDMA formation potential (NDMAFP) and kinetic experiments with chloramines were conducted for non-fractionated (raw) and size-excluded fractions (<3K, 3–10K, and >10K Da.) of polyDADMAC. The lower MW fraction (<3K Da.) of polyDADMAC solutions was responsible for forming 64 ± 6% of the NDMA, despite containing only 8.7 and 9.8% of the carbon or nitrogen present in the bulk polymer. The chloramine demand kinetics of the lowest MW fraction were also >2× faster than the higher MW fractions. Therefore, in a water treatment application the lower MW polyDADMAC likely contributes to most of the NDMA attributed to the use of polyDADMAC. The second question was: can 1H and 13C nuclear magnetic resonance spectroscopy (NMR) be used to characterize the molecular structures in polyDADMAC that react with chloramines? A peak for 1H NMR dimethylamine (DMA), a known low MW NDMA precursor, was found in a commercial polyDADMAC solution and decreased upon chloramination. The estimated DMA alone could not account for the observed NDMAFP, indicating the presence of other low MW precursors. Diffusion order spectroscopy (DOSY) NMR also showed multiple lower MW organics in polyDADMAC that change upon chloramination, including a 1.5× decrease in MW, suggesting chloramines cleave C–C or C–N bonds. These reactions may produce intermediates responsible for NDMA formation. Polymer manufacturers could use NMR to synthesize polyDADMAC with less DMA and other low MW compounds that produce NDMA upon chloramination.

AB - N-nitrosodimethylamine (NDMA) is a chloramine disinfection by-product, and its formation in drinking waters can increase due to the addition of cationic polydiallyldimethylammonium chloride (polyDADMAC). PolyDADMAC is a cationic polymer added as a coagulant or coagulant aid to enhance turbidity removal during sedimentation and filtration. This paper answers two central questions to understanding the nature of the NDMA precursors in polyDADMAC. First, what is the reactivity of different molecular weight (MW) fractions of polyDADMAC with chloramines? NDMA formation potential (NDMAFP) and kinetic experiments with chloramines were conducted for non-fractionated (raw) and size-excluded fractions (<3K, 3–10K, and >10K Da.) of polyDADMAC. The lower MW fraction (<3K Da.) of polyDADMAC solutions was responsible for forming 64 ± 6% of the NDMA, despite containing only 8.7 and 9.8% of the carbon or nitrogen present in the bulk polymer. The chloramine demand kinetics of the lowest MW fraction were also >2× faster than the higher MW fractions. Therefore, in a water treatment application the lower MW polyDADMAC likely contributes to most of the NDMA attributed to the use of polyDADMAC. The second question was: can 1H and 13C nuclear magnetic resonance spectroscopy (NMR) be used to characterize the molecular structures in polyDADMAC that react with chloramines? A peak for 1H NMR dimethylamine (DMA), a known low MW NDMA precursor, was found in a commercial polyDADMAC solution and decreased upon chloramination. The estimated DMA alone could not account for the observed NDMAFP, indicating the presence of other low MW precursors. Diffusion order spectroscopy (DOSY) NMR also showed multiple lower MW organics in polyDADMAC that change upon chloramination, including a 1.5× decrease in MW, suggesting chloramines cleave C–C or C–N bonds. These reactions may produce intermediates responsible for NDMA formation. Polymer manufacturers could use NMR to synthesize polyDADMAC with less DMA and other low MW compounds that produce NDMA upon chloramination.

KW - Chloramination

KW - N-nitrosodimethylamine

KW - Nuclear magnetic resonance

KW - polyDADMAC

KW - Size fractionation

UR - http://www.scopus.com/inward/record.url?scp=85058508116&partnerID=8YFLogxK

UR - http://www.scopus.com/inward/citedby.url?scp=85058508116&partnerID=8YFLogxK

U2 - 10.1016/j.watres.2018.12.002

DO - 10.1016/j.watres.2018.12.002

M3 - Article

VL - 150

SP - 466

EP - 472

JO - Water Research

JF - Water Research

SN - 0043-1354

ER -