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.