The fate and transformation of iodine species in UV irradiation and UV-based advanced oxidation processes. (1st November 2021)

• Record Type: Journal Article
• Authors: Ye, Tao; Zhang, Tian-Yang; Tian, Fu-Xiang; Xu, Bin
• Is Part Of: Water research. Volume 206(2021)
• Publication Date: 2021-11-01
• Subjects: Uv irradiation -- UV-based advanced oxidation processes (UV-AOPs) -- Iodinated disinfection byproducts (I-DBPs) -- Iodide -- Iodinated X-ray contrast media (ICM) -- Iodate; Water -- Pollution -- Research -- Periodicals; 363.7394
• DOI: 10.1016/j.watres.2021.117755
• Languages: English
• ISSNs: 0043-1354

Abstract

Highlights: Iodine species (e.g., I –, ICM, IO 3 − ) and their occurrence in water are reviewed. UV and UV-AOPs amend DOM and thus enhance I-DBP formation in post-disinfection. UV deiodinates and partly mineralizes ICM, releases I –, but less efficiently than UV-AOPs. UV and UV-AOPs can mineralize I-DBPs and liberate halides. UV can reduce IO 3 − to I –, leading to I-DBP formation in subsequent disinfection. Abstract: Iodinated disinfection byproducts (I-DBPs) formed in water treatment are of emerging concern due to their high toxicity and the tase-and-odor problems associated with iodinated trihalomethanes (I-THMs). Iodoacetic acid and dichloroiodomethane are currently regulated in Shenzhen, China and the Ministry of Health of the People's Republic of China has also been considering regulating I-DBPs. Iodide (I – ), organoiodine compounds (e.g., iodinated X-ray contrast media [ICM]), and iodate (IO3 – ) are the three common iodine sources in aquatic environment that lead to I-DBP formation. While UV irradiation effectively inactivate a wide range of microorganisms in water, it induces the transformation of these iodine sources, enabling the formation of I-DBPs. This review focuses on the fate and transformation of these iodine sources in UV-based water treatment (i.e., UV irradiation and UV-based advanced oxidation processes [UV-AOPs]) and the formation of I-DBPs in post-disinfection. I – released in UV-based treatments of ICM and can be oxidized in subsequent disinfection to hypoiodous acid (HOI), which reacts with natural organic matter (NOM) to produce I-DBPs. Both UV and UV-AOPs are not able to fully mineralize ICM and completely oxidize the released I – to (except UV/O3 ). Results reveal that UV and UV-AOPs are adequate for I-DBP degradation but require high UV doses. While the ideal I-DBP mitigation strategy awaits to be developed, understanding their sources and formation pathways aids in informed selections of water treatment processes, empowers water suppliers to meet drinking water standards, and minimizes consumers' exposure to I-DBPs. Graphic abstract: Image, graphical abstract