Department of Environmental Engineering and Earth Sciences, Clemson University, Anderson, South Carolina 29625, United States.
Environ Sci Technol. 2011 Dec 15;45(24):10429-37. doi: 10.1021/es202745t. Epub 2011 Nov 29.
An increasing number of utilities in the United States have been switching from chlorination to chloramination practices to comply with the more stringent trihalomethane (THM) and haloacetic acid (HAA) regulations. This has important implications for disinfection byproduct (DBP) formation because the reactions of chlorine and monochloramine (NH(2)Cl) with natural organic matter (NOM) are not the same. In this study, iodinated trihalomethane (I-THM) formation from preformed NH(2)Cl and prechlorination (at two chlorine doses and contact times) followed by ammonia addition was compared. A representative bromide/iodide ratio of 10:1 was selected and four bromide/iodide levels (ambient, 50/5 or 100/10, 200/20, and 800/80 [μg/L/μg/L]) were evaluated. The results showed that I-THM formation was generally lower for prechlorination as compared to preformed NH(2)Cl due to the oxidation of iodide to iodate by chlorine. However, while prechlorination minimized iodoform (CHI(3)) formation, prechlorination sometimes formed more I-THMs as compared to preformed NH(2)Cl due to a large increase in the formation of brominated I-THM species, which were formed at much smaller amounts from preformed NH(2)Cl. I-THM concentrations and speciation for the two chloramination scenarios (i.e., preformed NH(2)Cl vs prechlorination followed by ammonia) depended on chlorine dose, contact time, bromide/iodide concentration, and NOM characteristics of the source water (SUVA(254)).
越来越多的美国公用事业公司已经从氯化改为氯胺消毒，以遵守更严格的三卤甲烷（THM）和卤乙酸（HAA）法规。这对消毒副产物（DBP）的形成有重要影响，因为氯气和一氯胺（NH2Cl）与天然有机物（NOM）的反应并不相同。在这项研究中，比较了预生成的 NH2Cl 和预氯化（两种氯剂量和接触时间）后加氨形成的碘代三卤甲烷（I-THM）。选择了一个代表性的溴/碘比为 10:1，并评估了四个溴/碘水平（环境、50/5 或 100/10、200/20 和 800/80[μg/L/μg/L]）。结果表明，由于氯将碘化物氧化为碘酸盐，预氯化与预生成的 NH2Cl 相比，I-THM 的形成通常较低。然而，虽然预氯化最大限度地减少了碘仿（CHI3）的形成，但由于溴代 I-THM 物种的形成大量增加，预氯化有时比预生成的 NH2Cl 形成更多的 I-THM，而溴代 I-THM 物种则是由预生成的 NH2Cl 形成的量要小得多。两种氯胺化方案（即预生成的 NH2Cl 与预氯化后加氨）的 I-THM 浓度和形态取决于氯剂量、接触时间、溴/碘浓度以及水源的 NOM 特性（SUVA254）。
