Reactions of chlorine dioxide with nitrogen-containing pollutants in water treatment: Mechanism and product formation

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Chlorine dioxide (ClO2) is widely used in water treatment as disinfectant and oxidant for pollutant control. However, major aspects of its reaction mechanisms are yet unclear. Recently, it was reported that ClO2 may form free available chlorine as secondary oxidant which may affect, by-product- and transformation product formation as well as oxidation of pollutants. The present proposal deals with the reaction of ClO2 with N-containing pollutants which represent a large fraction of pollutants in the aquatic environment. The aim of the planned work is to understand the elementary steps of the reaction of ClO2 with model compounds for prediction of the behaviour of more complex pollutants in ClO2 based processes. Thereby, formation of secondary oxidants (e.g., free available chlorine) and inorganic chlorine species, reaction kinetics and transformation product formation as well as fundamental aspects such as the influence of oxygen will be investigated. Based on these investigations, reaction mechanisms will be established and used to predict the degradation efficiency and transformation product formation of complex model compounds. These predictions will be compared with experimental data on product formation from experiments with complex N-containing micropollutants in defined solutions and real water systems. The present proposal strives to improve the overall understanding of ClO2 reactions in water treatment, which will result in significant advances in the scientific field of water chemistry and water treatment. It will also be very useful to improve ClO2 based water treatment regarding predictions on degradation efficiency of pollutants and by- and transformation product formation of N-containing compounds.