Mechanism of ozonation enhanced formation of haloacetaldehydes during subsequent chlorination

Yuqin Mao, Shengqi Qi, Erzhuo Zhao, Hongwei Yang, Yuefeng F. Xie

Research output: Contribution to journalArticle

Abstract

Haloacetaldehydes (HAs) are the third prevalent group of disinfection by-products of great health concern. A bench-scale study was performed to investigate the formation and speciation of HAs in raw and treated waters after chlorination and ozonation-chlorination. Pre-ozonation resulted in enhanced HA formation during subsequent chlorination, and the HA yields from ozonation-chlorination were 1.66 and 1.63 times higher than that from chlorination of raw and treated waters. The mechanism about the increase of HA formation during ozonation-chlorination was systematically investigated in this study. The results showed that acetaldehyde formed after ozonation was the dominant precursor for the enhanced HA formation during subsequent chlorination. Increase in pH and chlorine dose increased HA formation during acetaldehyde chlorination. Based on the kinetic studies on the HA formation during acetaldehyde chlorination and the HA stabilities with and without free chlorine, it was found that chlorine was incorporated into the α-hydrogen in acetaldehyde to form a sequence of mono-, di- and tri-chloroacetaldehyde. During this process, these three chlorinated acetaldehydes would also undergo base-catalyzed hydrolysis through decarburization and dehalogenation pathways. This study elucidated that acetaldehyde formed after ozonation resulted in the increase of HA formation during subsequent chlorination. This study also revealed the formation pathway of HA during chlorination of acetaldehyde, which would help to minimize HA formation at drinking water plants.

Original languageEnglish (US)
Article number124361
JournalChemosphere
Volume236
DOIs
StatePublished - Dec 2019

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Ozonization
Chlorination
Halogenation
chlorination
Acetaldehyde
acetaldehyde
Chlorine
chlorine
ozonation
Dehalogenation
Decarburization
Water
Disinfection
Potable water
Drinking Water
disinfection
Byproducts
Hydrogen
hydrolysis
Hydrolysis

All Science Journal Classification (ASJC) codes

  • Environmental Engineering
  • Environmental Chemistry
  • Chemistry(all)
  • Pollution
  • Health, Toxicology and Mutagenesis

Cite this

Mao, Yuqin ; Qi, Shengqi ; Zhao, Erzhuo ; Yang, Hongwei ; Xie, Yuefeng F. / Mechanism of ozonation enhanced formation of haloacetaldehydes during subsequent chlorination. In: Chemosphere. 2019 ; Vol. 236.
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abstract = "Haloacetaldehydes (HAs) are the third prevalent group of disinfection by-products of great health concern. A bench-scale study was performed to investigate the formation and speciation of HAs in raw and treated waters after chlorination and ozonation-chlorination. Pre-ozonation resulted in enhanced HA formation during subsequent chlorination, and the HA yields from ozonation-chlorination were 1.66 and 1.63 times higher than that from chlorination of raw and treated waters. The mechanism about the increase of HA formation during ozonation-chlorination was systematically investigated in this study. The results showed that acetaldehyde formed after ozonation was the dominant precursor for the enhanced HA formation during subsequent chlorination. Increase in pH and chlorine dose increased HA formation during acetaldehyde chlorination. Based on the kinetic studies on the HA formation during acetaldehyde chlorination and the HA stabilities with and without free chlorine, it was found that chlorine was incorporated into the α-hydrogen in acetaldehyde to form a sequence of mono-, di- and tri-chloroacetaldehyde. During this process, these three chlorinated acetaldehydes would also undergo base-catalyzed hydrolysis through decarburization and dehalogenation pathways. This study elucidated that acetaldehyde formed after ozonation resulted in the increase of HA formation during subsequent chlorination. This study also revealed the formation pathway of HA during chlorination of acetaldehyde, which would help to minimize HA formation at drinking water plants.",
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Mechanism of ozonation enhanced formation of haloacetaldehydes during subsequent chlorination. / Mao, Yuqin; Qi, Shengqi; Zhao, Erzhuo; Yang, Hongwei; Xie, Yuefeng F.

In: Chemosphere, Vol. 236, 124361, 12.2019.

Research output: Contribution to journalArticle

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AU - Qi, Shengqi

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