Haloacetaldehydes (HALs) are the third prevalent group of disinfection by-products (DBPs) by weight in drinking water, and their cytotoxicity and genotoxicity are higher than regulated DBPs. In order to understand their formation mechanism during chlorination and ozonation-chlorination, this study examined the reaction kinetics of chloral hydrate (CH), dichloroacetaldehyde (DCA), chloroacetaldehyde (CA) and acetaldehyde by chlorine at different pH values and chlorine doses. The results showed that the reaction rate constants increased with pH and chlorine dose, except that the degradation of CH would not be affected by the presence of free chlorine. At the same pH and chlorine dose, the half-lives of CH, DCA, CA and acetaldehyde were in the order of CH > acetaldehyde ≫ DCA > CA. A kinetic model used to predict the formation of HALs and chloroform during chlorination of acetaldehyde was developed, and the predicted data fitted well with the measured data. As pre-ozonation could oxidize natural organic matter to acetaldehydes, the concentration of acetaldehyde formed after pre-ozonation was used to calculate the HAL yields during ozonation-chlorination by the kinetic model, which fitted the experimental results well. The kinetic model elucidated that the formation mechanism of HALs was a stepwise substitution process on the α-hydrogen of acetaldehyde during chlorination.

卤代乙醛 (HAL) 是饮用水中按重量计第三大类消毒副产物 (DBP)，其细胞毒性和遗传毒性高于规定的 DBP。为了了解它们在氯化和臭氧化-氯化过程中的形成机理，本研究检测了不同 pH 值和氯剂量下氯对水合氯醛 (CH)、二氯乙醛 (DCA)、氯乙醛 (CA) 和乙醛的反应动力学。结果表明，反应速率常数随着 pH 值和氯剂量的增加而增加，但 CH 的降解不受游离氯存在的影响。在相同的pH和氯剂量下，CH、DCA、CA和乙醛的半衰期顺序为CH>乙醛≫DCA>CA。建立了用于预测乙醛氯化过程中 HAL 和氯仿形成的动力学模型，预测数据与实测数据吻合良好。由于预臭氧化可以将天然有机物氧化成乙醛，因此利用预臭氧化后形成的乙醛浓度，通过动力学模型计算了臭氧化-氯化过程中的HAL产率，与实验结果吻合较好。动力学模型阐明了 HAL 的形成机制是一个逐步取代的过程。利用预臭氧化后形成的乙醛浓度，通过动力学模型计算了臭氧化-氯化过程中的HAL产率，与实验结果吻合较好。动力学模型阐明了 HAL 的形成机制是一个逐步取代的过程。利用预臭氧化后形成的乙醛浓度，通过动力学模型计算了臭氧化-氯化过程中的HAL产率，与实验结果吻合较好。动力学模型阐明了 HAL 的形成机制是一个逐步取代的过程。氯化过程中乙醛的α-氢。