Effect of UV irradiation on iodinated trihalomethane formation during post-chloramination. (15th December 2018)

• Record Type: Journal Article
• Authors: Xia, Ying; Lin, Yi-Li; Xu, Bin; Hu, Chen-Yan; Gao, Ze-Chen; Tang, Yu-Lin; Chu, Wen-Hai; Cao, Tong-Cheng; Gao, Nai-Yun
• Is Part Of: Water research. Volume 147(2018)
• Page Start: 101
• Page End: 111
• Publication Date: 2018-12-15
• Subjects: Iodinated trihalomethanes (I-THMs) -- Ultraviolet (UV) irradiation -- Dissolved organic matter (DOM) -- Chloramination -- Fluorescence spectroscopy -- Iodine utilization factor (IUF); Water -- Pollution -- Research -- Periodicals; 363.7394
• DOI: 10.1016/j.watres.2018.09.045
• Languages: English
• ISSNs: 0043-1354

Abstract

Abstract: Ultraviolet (UV) irradiation has been widely used in drinking water treatment processes, but its influence on the formation of disinfection by-products (DBPs), especially the emerging iodinated trihalomethanes (I-THMs) during post-chloramination remains unclear. This study evaluated the impact of low pressure (LP) UV treatment on the formation of I-THMs during post-chloramination through two pathways. The first pathway is through the transition of DOM structure and composition during UV-chloramination, resulting significant increase of I-THM formation with increasing UV dosage in different dissolved organic matter (DOM)-containing water (49.7%–90.5% at 1160 mJ/cm 2 ). With the application of excitation emission matrix-parallel factor analysis (EEM-PARAFAC), we found that I-THM formation in UV-chloraminated water correlated well with two ratios of three PARAFAC humic-like components (C3/C2 and C1/C2, R 2 = 0.958–1.000), suggesting that the ratios of fluorescent components can be used as reliable indicators for I-THM formation. Moreover, the shift in these fluorescent components is crucial for I-THM formation during UV-chloramination. Another pathway for UV irradiation to affect I-THM formation during post-chloramination is through the transformation of iodine species. Large amounts of reactive iodine species (HOI/I2 and I3 − ) can be generated directly in the mixed iodine system by UV light, leading to the enhancement of iodine utilization factor (IUF) (up to 0.040) after post-chloramination. These results suggest that UV application to DOM-containing water may induce changes in organic precursors and iodine species so as to enhance I-THM formation during post-chloramination. Graphical abstract: Highlights: UV irradiation increased I-THM formation significantly during post-chloramination. The transition of DOM structure were elucidated using EEM-PARAFAC and GPC analyses. The ratios of three fluorescent components after UV-chloramination correlated well with I-THM formation. UV irradiation enhanced iodine utilization factor (IUF) remarkably during post-chloramination. Large amounts of reactive iodine species were generated directly in the mixed iodine system by UV irradiation.