Abstract
Iopamidol (an iodinated x-ray contrast media) and bromide are precursors in the formation of halogenated disinfection byproducts (DBPs). The interactions of these precursors are vital to elucidate the formation of halogenated DBPs during chloramination. This work investigated the formation of total organic halogen and select individual DBPs in two laboratory-chloraminated source waters (SWs) containing iopamidol and bromide. Experiments were carried out in batch reactors containing Barberton SW (BSW) and Cleveland SW (CSW), spiked with iopamidol (5 μM), bromide (15 μM), and 100 μM monochloramine. Total organic iodine concentrations were approximately equal regardless of SW since they are mostly unreacted iopamidol and iopamidol DBPs. Almost equal amount of total organic chlorine (3–4 nM) was produced in the SWs but higher quantities of total organic bromine were formed in BSW than CSW. Substantial quantities of regulated trihalomethanes (THMs) and haloacetic acids (HAAs) were formed in the SWs, along with appreciable concentrations of iodinated trihalomethanes (CHBrClI, CHCl2I, and CHBr2I). Low concentrations of iodo-HAAs were detected, especially at low pH. Overall, bromide concentrations appeared to suppress iodo-DBP formation during chloramination of iopamidol in the presence of natural organic matter. A good correlation (R2 = 0.801) between the yields of regulated DBPs and iodo-DBPs was observed.
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