To evaluate the application prospect of UV/dichloroisocyanurate (UV/DCCNa) technology in the treatment of water containing diethyl phthalate (DEP), the degradation kinetics and transformation products of DEP in UV/DCCNa and UV/sodium hypochlorite (UV/NaClO) processes were studied comparatively. The results showed that the UV/DCCNa process was more beneficial for DEP degradation efficiency. According to quenching experiments, OH radical, Cl radical, and ClO tadical were all involved in the two systems. Although there were differences in the identified products of the two systems, the formation pathways were basically the same, being hydroxylation, hydrolysis, chlorination, nitrosation, and coupling. In addition, DEP could also be degraded effectively at a low initial concentration (0.4 µM) in both systems, in which disinfection byproduct yields met the drinking water disinfection standard. Subsequently, a series of influencing factors were investigated for the UV/DCCNa system. The degradation efficiency and rate did not increase significantly when the concentration of HOCl exceeded 120.0 µM, and the degradation rate reached the fastest when pH = 5.0. NH4+, Ca2+, NO3−, and HCO3− had a remarkable impact on DEP degradation. Compared to the PAE-only system, the removal of short-chain PAEs decreased in the five PAEs mixed system, which was probably caused by the generation of short-chain PAEs during the reaction and the competitive reaction of reactive free radicals (i.e., OH radical, ClO radical, and Cl radical) occurred between the five PAEs. This study provided insight into the advantages and disadvantages of UV/DCCNa and UV/NaClO processes, which can provide a theoretical basis for selecting the disinfection process in water treatment.

Assessment of the UV/DCCNa oxidation process for the degradation of diethyl phthalate (DEP) in the aqueous system compared with the UV/NaClO process: Implications for water treatment

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