Strategies for hydrogen peroxide dosing based on dissolved oxygen concentration for solar photo-Fenton treatment of complex wastewater

Hydrogen peroxide consumption is known to be one of the key parameters of the photo-Fenton process responsible for its high operating costs. The purpose of this study was to find out whether adding dissolved oxygen to the reaction medium in a continuous stream of pure oxygen or air with different H2O2 dosage strategies could improve the Dorfman mechanism, generating secondary oxidation species that could boost mineralization, and consequently, diminish H2O2 consumption. Experiments confirmed less efficient COD elimination. Additional DO slightly increased H2O2 consumption, as it initiated a series of reactions generating hydroxyl radical scavengers and H2O2 self-decomposition slowing down the reaction. At the same time, the study highlighted that automatic H2O2 dosing based on DO setpoints would be a highly attractive control option, however, more detailed studies on the initial amount of hydrogen peroxide and dosing rates must be undertaken.