V3I6P30

The Hydrogeological Implications and Management of Per- and Polyfluoroalkyl Substances (PFAS) in Aquifer Systems: A Critical Review

Bethel Emmanuel Nyejekwe^1*, Prof. G. J. Udom², Diepiriye Chenaboso Okujagu³

Abstract

This is a critical review of how Per- and Polyfluoroalkyl Substances (PFAS) also referred to as forever chemicals in colloquial terms, widely contradict groundwater resources around the world, with a particular focus on the complicated hydrogeological processes of contamination. The discussion confirms that the unprecedented retention of PFAS plumes is essentially the result of the unusual retention processes at the subsurface level. These mechanisms involve a process of matrix diffusion where mass storage in low-permeability areas has been demonstrated to contribute up to 82 per cent of the total contaminant load and a process of substantial air-water interface (AWI) partitioning in the unsaturated zone which stores an estimated 50 per cent to 75 per cent of the mobile mass. The resulting mass sequestration is a source of chronic back-diffusion and makes the traditional models of remediation non-existent. Existing technologies are also under review: whilst physical sequestration using state of the art Ion Exchange Resins (IXR) have high capacity mass concentration, true destructive sequestration, especially Electrochemical Oxidation (EO), is limited by the prohibitive energy usage, and the highly detrimental, reportedly documented liability of producing acutely toxic secondary byproducts, such as chlorate, many thousands of times above drinking water levels. The review ends with a call to action of the world to abandon reactive management of plumes to a compulsory requirement of upstream elimination of sources and the deployment of risk-managed hybrid treatment trains to traverse the radical difference between global regulatory standards.

Keywords:

Per- and polyfluoroalkyl substances (PFAS); groundwater remediation; matrix diffusion; air-water interface; electrochemical oxidation; aquifer management.