[Influence of Chemical Pre-oxidation on Chloral Hydrate Formation of Threonine]

The influences of different chemical pre-oxidants, including sodium hypochlorite (NaClO), chlorine dioxide (ClO₂), permanganate (KMnO₄), hydrogen peroxide (H₂O₂), ozone (O₃) and ozone/hydrogen peroxide (O₃/H₂O₂), on chloral hydrate (CH) formation were studied for threonine that has the highest special chloral hydrate formation potential (SCHFP). Suitable pre-oxidants and corresponding optimal doses were determined to provide guidance for controlling chloral hydrate (CH) formation during drinking water treatment. The results indicated that the pre-oxidants that could decrease CH formation for one day incubation time (CH_1d) were H₂O₂, ClO₂, KMnO₄ and NaClO, and the corresponding suitable doses were 3, 0.5, 0.6 and 0.5 mg·L^-1, and the corresponding CH_1d removal rates were 61.54%, 47.63%, 29.77% and 10.94%, respectively. The pre-oxidants that could decrease CH formation potential (CHFP) were KMnO₄, NaClO, H₂O₂ and ClO₂, and the corresponding suitable doses were 0.6 mg·L^-1, 0.5 mg·L^-1, 3 mg·L^-1 and 0.5 mg·L^-1, and the corresponding CHFP removal rates were 41.01%, 33.38%, 8.36% and 2.40%, respectively. In addition, O₃ and O₃/H₂O₂ were not suitable for controlling CH in the conventional treatment process because they could increase CH_1d and CHFP.