Comparison of UV-induced AOPs (UV/Cl(2), UV/NH(2)Cl, UV/ClO(2) and UV/H(2)O(2)) in the degradation of iopamidol: Kinetics, energy requirements and DBPs-related toxicity in sequential disinfection processes

The UV-induced advanced oxidation processes (AOPs, including UV/Cl(2), UV/NH(2)Cl, UV/ClO(2) and UV/H(2)O(2)) degradation kinetics and energy requirements of iopamidol as well as DBPs-related toxicity in sequential disinfection were compared in this study. The photodegradation of iopamidol in these processes can be well described by pseudo-first-order model and the removal efficiency ranked in descending order of UV/Cl(2) > UV/H(2)O(2) > UV/NH(2)Cl > UV/ClO(2) > UV. The synergistic effects could be attributed to diverse radical species generated in each system. Influencing factors of oxidant dosage, UV intensity, solution pH and water matrixes (Cl(−), NH(4)(+) and nature organic matter) were evaluated in detail. Higher oxidant dosages and greater UV intensities led to bigger pseudo-first-order rate constants (K(obs)) in these processes, but the pH behaviors exhibited quite differently. The presence of Cl(−), NH(4)(+) and nature organic matter posed different effects on the degradation rate. The parameter of electrical energy per order (EE/O) was adopted to evaluate the energy requirements of the tested systems and it followed the trend of UV/ClO(2) > UV > UV/NH(2)Cl > UV/H(2)O(2) > UV/Cl(2). Pretreatment of iopamidol by UV/Cl(2) and UV/NH(2)Cl clearly enhanced the production of classical disinfection by-products (DBPs) and iodo-trihalomethanes (I-THMs) during subsequent oxidation while UV/ClO(2) and UV/H(2)O(2) exhibited almost elimination effect. From the perspective of weighted water toxicity, the risk ranking was UV/NH(2)Cl > UV/Cl(2) > UV > UV/H(2)O(2) > UV/ClO(2). Among the discussed UV-driven AOPs, UV/Cl(2) was proved to be the most cost-effective one for iopamidol removal while UV/ClO(2) displayed overwhelming advantages in regulating the water toxicity associated with DBPs, especially I-THMs. The present results could provide some insights into the application of UV-activated AOPs technologies in tradeoffs between cost-effectiveness assessment and DBPs-related toxicity control of the disinfected waters containing iopamidol.