Plenary Talk: Development of a Simple Electrochemical Advanced Oxidation Process for Potable Reuse

The production of hydroxyl radicals (*OH) by the UV photolysis of hydrogen peroxide (H₂O₂), an advanced oxidation process (AOP), is a key component of advanced treatment trains for the purification of municipal wastewater for potable reuse. However, due to the low absorption coefficient of H₂O₂ at 254 nm, the production of radicals is very inefficient, and only ~10% of the H₂O₂ is used despite the application of up to 1000 mJ/cm² UV fluence. This presentation describes the development of an electrochemical alternative pathway to *OH production. Previous electrochemical AOPs have focused on electro-Fenton processes, wherein Fe²⁺ provides an electron to H₂O₂ to produce *OH, and the resulting Fe³⁺ is converted back to Fe²⁺ at a cathode. This process is inefficient under the pH conditions of natural waters. Moreover, while it can function in batch reactors, the dissolved iron would be lost into the effluent of a flow-through reactor. We demonstrate the production of *OH by feeding electrons from the grid to H₂O₂ directly via a stainless steel cathode mesh. Potable reuse facilities typically must demonstrate 0.5-log removal of 1,4-dioxane to validate their AOP process. We demonstrate the achievement of this target with the electrochemical system over timescales relevant to full-scale treatment (i.e., minutes). We also demonstrate that this process requires lower H₂O₂ concentrations, and uses the H₂O₂ more efficiently.