College of Biology and Environmental Engineering, Zhejiang Shuren University, Hangzhou, 310015, China.
School of Environment, Tsinghua University, Beijing, 100084, China.
Chemosphere. 2019 Dec;236:124361. doi: 10.1016/j.chemosphere.2019.124361. Epub 2019 Jul 14.
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.
卤代乙二醛（HAs）是健康关注度较高的第三大消毒副产物。本研究采用中试规模，研究了氯化和臭氧化-氯化处理后原水和处理水中卤代乙二醛的形成和形态。预臭氧化会导致后续氯化过程中 HAs 的形成增加，而臭氧化-氯化的 HAs 生成量比原水和处理水的氯化生成量分别高 1.66 和 1.63 倍。本研究系统研究了臭氧化-氯化过程中 HAs 形成增加的机制。结果表明，臭氧化后形成的乙醛是后续氯化过程中 HAs 形成增加的主要前体。增加 pH 值和氯剂量会增加乙醛氯化过程中的 HAs 形成。基于乙醛氯化过程中 HAs 形成的动力学研究以及有和无游离氯时 HAs 的稳定性，发现氯会掺入乙醛的α-氢中，形成一系列一氯、二氯和三氯乙醛。在此过程中，这三种氯代乙醛也会通过脱羰和脱卤化途径通过碱催化水解。该研究阐明了臭氧化后形成的乙醛会导致后续氯化过程中 HAs 形成增加。本研究还揭示了乙醛氯化过程中 HAs 的形成途径，有助于在饮用水厂中尽量减少 HAs 的形成。
