Multivariate analysis of ozonation as a control for the formation of iodinated disinfection by-products from iopamidol oxidation

There is a global concern about iodinated contrast media because they may be an anthropogenic source of iodine, and thereby precursors of iodinated disinfection by-products during chlorine disinfection. These by-product compounds may exert higher toxicity than regulated-disinfection by-products (i.e., trihalomethanes and haloacetic acids). This represents a challenge for water utilities due to the unknown formation of these iodinated disinfection by-products. This work is two folded: on one hand, it researches the effects of ozone as pretreatment for iopamidol oxidation through a sequential treatment of low-pressure ultraviolet light followed by free chlorine, and in the other hand, it applies an algorithm of principal component analysis to obtain the multivariable of these sequential treatments. In this context, a formation iodinated disinfection by-products to iodide correlation models were developed under each treatment condition (i.e., UV-Cl₂, and O₃-UV-Cl₂). Additionally, five iodinated disinfection by-products were detected: dichloroidomethane, chlorodiiodomethane, iodoform, iodoacetonitrile and chloroiodoacetamide, corresponding to trihalomethanes, haloacetonitriles and haloacetamides respectively. Results showed that ozonation as a pre-treatment step (O₃-UV-Cl₂) reduced up to 53% by-products formation than UV-Cl₂. Using principal component analysis, it was found that iodinated disinfection by-products to iodide correlation models showed a better correlation for the ozonation pretreatment with a R² = 0.9122 along with a Pearson coefficient of r = 0.9551. Ozonation should be considered as a strategy to control the formation of these iodinated by-products for water reuse from waters enriched with anthropogenic iodine. Future experiments with different source waters should be addressed to explore the formation and control of unregulated iodinated disinfection by-products.