Brominated trihalomethane formation in halogenation of humic acid in the coexistence of hypochlorite and hypobromite ions

• Published in: Water research (Oxford) Vol. 33; no. 2; pp. 477 - 483
• Main Authors: Ichihashi, Keiko, Teranishi, Kiyoshi, Ichimura, Akio
• Format: Journal Article
• Language: English
• Published: Oxford Elsevier Ltd 01.02.1999; Elsevier Science
• Subjects: Applied sciences; brominated trihalomethane; Drinking water and swimming-pool water. Desalination; Exact sciences and technology; humic acid; hypobromite; hypochlorite; Pollution; redox reaction; Water treatment and pollution; hypobromite; humic acid; hypochlorite; brominated trihalomethane; redox reaction; Sodium Hypochlorites; Drinking water treatment; Chlorination; Reaction product; Reaction mechanism; Trihalomethane; Sodium Hypobromites; Disinfection; Experimental study; Humic acid; Halogen Organic compounds
• ISSN: 0043-1354; 1879-2448
• DOI: 10.1016/S0043-1354(98)00227-9

Brominated trihalomethanes (Br-THMs) such as CHCl 2Br, CHClBr 2, and CHBr 3 are produced by the reaction of hypobromite with humic acid in the presence of hypochlorite. In the presence of excess NaOCl, addition of NaOBr enhanced the formation of Br-THMs but reduced the formation of CHCl 3. The product distribution of THMs was affected by the ratio of [NaOBr]/[NaOCl] and was independent of pH and reaction time. In the presence of excess NaOBr, the yield of CHBr 3 only increased linearly with the NaOCl concentration added. However, the other three THMs were hardly produced even though NaOCl concentration was increased up to 0.5 of the [NaOCl]/[NaOBr] molar ratio. Our results suggest that in the process of THM formation, hypochlorite ion reacts effectively with humic acid in the oxidation reaction and hypobromous acid plays a predominant role in the electrophilic substitution when both of hypohalites are present.