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Iopamidol, one of the most commonly used and detected iodinated X-ray contrast media in water sources, is inert in the human body but reacts and degrades in the presence of aqueous chlorine to form highly cytotoxic/genotoxic disinfection by-products (DBPs). The objectives of this study were to investigate (1) the effect of iopamidol on the formation and speciation of DBPs in multiple source waters (SWs), (2) the formation of TOX/DBPs in SWs containing iopamidol, bromide, and chlorinated oxidants, (3) the impact of prechlorination time on TOX/DBP formation during chloramination of SWs containing iopamidol and (4) kinetic modeling of TOX, iodate, and DBP formation due to chlorination of iopamidol. SWs from Akron, Barberton, and Cleveland Water Treatment Plants containing iopamidol or iopamidol/bromide were dosed with chlorinated oxidant at pH 6.5-9.0 for 0-72 h.The study showed that the yields of either TTHMs or HAAs exhibited a strong correlation with humic, fulvic, and combined fulvic and humic fractions at pH 7.5. Similarly, the yields of TOCl/UTOCl exhibited strong correlation with SUVA254 at pH 7.5. Although iopamidol directly formed CHCl3, TCAA, and CHCl2I in chlorinated water; iopamidol exhibited minimal impact on DBP formation compared to NOM. In the presence of bromide and aqueous chlorine, iopamidol formed more DBPs. TOI loss was unaffected by the concentrations of bromide. TOCl and TOBr, respectively decreased and increased with increasing bromide concentration but was unaffected by iopamidol concentration. As bromide concentration increased the concentrations of fully brominated DBPs increased while fully chlorinated DBPs and CHCl2I decreased. CHBrClI increased with increasing bromide concentration in CSW. Also, iodo-DBPs increased with increasing iopamidol concentration.Generally, in the presence of bromide and iopamidol, lower amounts of DBPs including iodo-DBPs were formed in chloraminated SWs then chlorinated SWs. In SWs chlorinated before ammonia addition to form NH2Cl, significant amounts of iodo-DBPs were found during chloramination than prechlorination. However, CHCl3 and TCAA formation stopped after ammonia addition.The kinetic model adequately predicted TOI loss and, iodate, TOCl, and DBP formation. Since iopamidol impacted DBP formation, a limitation on the use of iopamidol in medical imaging facilities could reduce iopamidol concentrations in SWs.

The objectives of this study were to investigate the transformation of ICM as a function of pH (6.5 to 9.5) and time (up to either 72 or 168 hr) in the presence of chlorinated oxidants. Total organic iodide (TOI) loss was used as a surrogate for the ICM. Experiments were performed with and without natural organic matter (NOM). Degradation of TOI in the absence of NOM was carried out at low and high concentrations of iopamidol and aqueous chlorine. Also, the effect of NOM variation on iodate formation was investigated.The TOI degradation and iodate formation at low reactant and buffer concentrations were greatest at pH 7.5 and least at pH 9.5. TOI degradation followed observed first-order kinetics at all pH except pH 6.5, which exhibited bi-phasic degradation kinetics. Iodate formation did not follow either first or second order observed formation and was the predominant iodine-containing species after 24 hr. Furthermore, disinfection by-products (DBPs) formed at pH 6.5 – 8.5 were chloroform, trichloroacetic acid and chlorodiiodomethane. In the presence of monochloramine and in the absence of NOM, the loss of TOI was insignificant and no iodate formation was observed.At high concentrations of iopamidol and aqueous chlorine, TOI loss and iodate formation at pH 6.5 and 8.5 was rapid for the first 24 hr and ceased afterwards. The formation of total organic chloride (TOCl) was initially observed at 6 hr and 2 hr for pH 6.5 and 8.5 respectively. Also, chloroform, dichloroiodomethane, chlorodiiodomethane, dichloroacetic acid and trichloroacetic acid was observed. About 99% of the remaining TOI formed at each discrete time was contained in unidentified iopamidol transformation products.When TOI was monitored in the presence of NOM and aqueous chlorine, source waters from Akron, Barberton and Cleveland respectively recorded 68 to 74%, 62 to 72% and 68 to 77% loss of TOI. However, no iodate was formed in any of the source water experiments. No significant degradation of TOI was observed in the presence of NOM and monochloramine. Iodate was not formed in varying NOM concentrations in Barberton and Cleveland source waters.