WSP* has achieved a significant breakthrough in the development of an innovative electro-oxidation technology.
The technology solves a particularly challenging and urgent problem in wastewater and groundwater treatment: the destruction of per-and poly-fluoroalkyl substances, or PFAS. These compounds have been widely used for more than 50 years in several industrial and household products, and their presence in the environment is now widespread.
Based on the needs we are seeing in various sectors, finding a solution for destruction of PFAS was paramount. So, the PFAS team set out to find a sustainable, cost-effective, commercially available, modular and scalable technology that could be easily applied at various types of sites and water.
Electro-oxidation – an efficient way to destroy PFAS in effluent streams
We focused on electro-oxidation technology using a unique kind of long-lasting boron-doped diamond (BDD) electrodes. In this technology, the PFAS-laden water passes by an array of electrodes, a positively charged anode, and a negatively charged cathode, and similar to the firm’s other pioneering work on electrocoagulation.
In BDD electrodes, the anode generates the oxidation process and forms oxidizing radicals and electrons, that, through a complex chemical process, break down the PFAS molecules into shorter molecules and eventually carbon dioxide for organics molecules and fluorides. The cathode produces primarily hydrogen gas and provides reduction reactions. Electro-oxidation can be viewed as a chemical combustion of compounds in water.
The first electro-oxidation tests focused on two types of PFAS – known as PFOS and PFOA – that are some of the most persistent and recalcitrant, and are regulated by health authorities worldwide. The large-scale test removed 100 percent of PFOS and 100 percent of PFOA to meet the Health Canada and the U.S. Environmental Protection Agency guidelines for drinking water for these two substances.
As expected, based on the PFAS EO team experience, the process has been found to generate some by-products – including hypochlorite and perchlorate. However, by optimizing the process, the team was able to significantly reduce these problematic constituents, including reducing the formation of perchlorate by more than 99 percent.
Since fluoride is one of the building blocks of all PFAS molecules, some fluoride will be produced by the electro-oxidation process as the final breakdown product of these molecules. The team focused on making sure that the effluent from the process has fluoride levels that are within applicable regulatory standards.
All of the treatability tests have been done out of our treatability center in Montreal. The water analysis for PFAS has been carried out by state-of-the-art analytical laboratories in the Civil Engineering department at Montreal’s McGill University, which has supported the project with its PFAS analytical expertise since inception in 2019.