Formation of iodinated trihalomethanes during breakpoint chlorination of iodide-containing water

Zhi Liu; Yi-Li Lin; Bin Xu; Chen-Yan Hu; An-Qi Wang; Ze-Chen Gao; Sheng-Ji Xia; Nai-Yun Gao

doi:10.1016/j.jhazmat.2018.04.009

Formation of iodinated trihalomethanes during breakpoint chlorination of iodide-containing water

J Hazard Mater. 2018 Jul 5:353:505-513. doi: 10.1016/j.jhazmat.2018.04.009. Epub 2018 Apr 10.

Authors

Zhi Liu¹, Yi-Li Lin², Bin Xu³, Chen-Yan Hu⁴, An-Qi Wang⁵, Ze-Chen Gao⁵, Sheng-Ji Xia⁵, Nai-Yun Gao⁵

Affiliations

¹ State Key Laboratory of Pollution Control and Resource Reuse, Key Laboratory of Yangtze Water Environment, Ministry of Education, College of Environmental Science and Engineering, Tongji University, Shanghai 200092, PR China; Shanghai Institute of Pollution Control and Ecological Security, Shanghai 200092, PR China.
² Department of Safety, Health and Environmental Engineering, National Kaohsiung University of Science and Technology, Kaohsiung 824, Taiwan, ROC.
³ State Key Laboratory of Pollution Control and Resource Reuse, Key Laboratory of Yangtze Water Environment, Ministry of Education, College of Environmental Science and Engineering, Tongji University, Shanghai 200092, PR China; Shanghai Institute of Pollution Control and Ecological Security, Shanghai 200092, PR China. Electronic address: tjwenwu@tongji.edu.cn.
⁴ College of Environmental and Chemical Engineering, Shanghai University of Electric Power, Shanghai 200090, PR China.
⁵ State Key Laboratory of Pollution Control and Resource Reuse, Key Laboratory of Yangtze Water Environment, Ministry of Education, College of Environmental Science and Engineering, Tongji University, Shanghai 200092, PR China.

PMID: 29709870
DOI: 10.1016/j.jhazmat.2018.04.009

Abstract

This study investigated the formation of toxic iodinated trihalomethanes (I-THMs) during breakpoint chlorination of iodide-containing water. Impact factors including I^- concentration, natural organic matter (NOM) concentration and type, pH as well as Br^-/I^- molar ratio were systematically investigated. Moreover, the incorporation of I^- into I-THM formation was also calculated. The results showed that I-THM formation varied in different zones of the breakpoint curves. I-THMs increased with increasing chlorine dosage to breakpoint value and then dropped significantly beyond it. Iodoform (CHI₃) and chlorodiiodomethane (CHClI₂) were the major I-THMs in the pre-breakpoint zone, while dichloroiodomethane (CHCl₂I) was the dominant one in the post-breakpoint zone. The formation of I-THMs increased remarkably with I^- and dissolved organic carbon (DOC) concentrations. More bromine-containing species were formed as Br^-/I^- molar ratio increased from 0.5 to 5. In addition, the major I-THM compound shifted from CHCl₂I to the more toxic CHClBrI. As pH increased from 6.0 to 8.0, I-THM formation kept increasing in the pre-breakpoint zone and the speciation of I-THMs changed alongside the breakpoint curves. The incorporation of I^- during breakpoint chlorination was highly dependent on chlorine, I^-, and NOM concentrations, NOM type, solution pH and Br^-/I^- molar ratio.

Keywords: Breakpoint chlorination; Disinfection by-products (DBPs); Iodinated trihalomethanes (I-THMs); Monochloramine; Residual oxidant.

Publication types

Research Support, Non-U.S. Gov't