June 2, 2022
The electrochemical oxidation process used for the breakdown of organic compounds has been gaining acceptance in the realm of Advanced Oxidation Processes (AOPs) since its introduction in the 1970’s. Electrochemical Advanced Oxidation Processes (eAOP’s) are implemented using electrodes which conduct a low voltage, high amperage electric charge. This generates mixed oxidants such as ozone, chlorine, and hydrogen peroxide synthesized from previous constituents found in the water or oxidation of water itself. This process, combined with direct electron transfer reactions on the electrode surface, has been found to break target contaminants down to their basic building blocks (mineralization). eAOPs have been tested for the destruction of nearly all organics as well as some inorganics like ammonia and cyanide, and new studies show that they can be used for mineralization/destruction of PFAS as well.
Electrochemical oxidation systems use variations in voltage, salinity, and electrode material to achieve different intensities of destruction. At low voltages (2-3V), disinfection of bacteria and microorganisms can occur. Steadily increasing the voltage leads to the disintegration of tougher compounds like ammonia, 1,4-Dioxane, pharmaceuticals and VOCs into simpler molecules like CO2, N2, and H2 In the case of PFAS, higher voltages (5–6V) generate free electrons. At the surface of the electrode, it is free electrons that break down the “forever chemicals” to free fluoride, small amounts of HF, and CO2.
Many researchers are validating PFAS destruction mechanisms to confirm defluorination ratios and understand the full mass balance. Those at University of Massachusetts Amherst, University of Michigan, and other institutions around the world have shown that it is possible to achieve non detectable levels of PFOA and PFOS in landfill leachate, AFFF and other concentrated waste streams with the technology.
The work of these institutions has led the way for a handful of private companies who are commercializing this technology for pilot- and full-scale applications. Significant confidence has been achieved to develop long term piloting at sites with PFAS contaminated waste streams. Leachates, waste brines, fire fighting foams, and other concentrated liquid waste streams have become ideal targets for pilot operations because of their high organics content, often high salinity, and need to address future regulations. eAOPs can offer permanent elimination of PFAS within these key waste streams to limit the long term expenditure of conventional treatment and disposal methods such as granular activated carbon or deep-well injection.