Removal of PFAS from groundwater and wastewater by electrosorption/desorption on modified activated carbons and electrochemical degradation “PFAStrea”

Motivation

The increasing contamination of groundwater, drinking water and wastewater with short-chain and highly mobile per- and polyfluorinated alkyl substances (PFAS) poses considerable technical and economic challenges for water suppliers, industry and authorities. In particular, short-chain compounds such as PFBA or TFA elude efficient removal due to their high water solubility, persistence and low sorption tendency compared to conventional activated carbon filters. At the same time, national and European regulations, in particular the amended Drinking Water Ordinance (TrinkwV 2023) significantly tighten the limit values for the sum of selected PFAS. This creates an immediate pressure to act for operators of water extraction and treatment plants. Currently available processes are either energy-intensive, generate problematic by-products or are not sufficiently effective for short-chain PFAS. Thermal regeneration processes lead to high energy consumption and material losses, while electrochemical oxidation processes are promising, but can promote the formation of toxic halogen oxoanions such as perchlorate, chlorate or bromate. A holistic, modular approach combining sorption, targeted concentration, electrochemical mineralization and downstream biological elimination of potential by-products has not yet been established. Against this background, there is an urgent need for a scalable, energy-efficient and economically viable process that is particularly accessible to small and medium-sized enterprises (SMEs). The development of a modular system for the needs-based removal and mineralization of PFAS not only addresses regulatory requirements, but also makes a significant contribution to precautionary water protection and sustainable resource use. The motivation of the project thus lies in closing a technological gap between regulatory requirements and practical feasibility.

Objectives

The aim of the project is to develop and validate a modular process for the efficient removal and complete mineralization of PFAS from groundwater, drinking water and process water. To this end, three independently scalable modules are to be designed, optimized and combined in a demonstrator system. In the first module, electrosorption on specifically modified granulated activated carbons (GAC) is developed and optimized. Chemical, thermal or electrochemical modification of the carbon surfaces is intended to increase the electrical conductivity and significantly improve the binding capacity, especially for short-chain PFAS. The reversible polarization of the activated carbon is intended to enable targeted desorption and thus regenerability, reducing material consumption and operating costs. The second module covers the electrochemical treatment of the generated desorbates using boron-doped diamond electrodes (BDD). The goal is to fully mineralize the concentrated PFAS while minimizing the formation of undesirable by-products. For this purpose, process parameters such as current density, flow rate, electrolyte composition and pH value are systematically examined and optimized to ensure high energy efficiency and process stability. The third module addresses the possible formation of halogen oxoanions by a downstream microbiological treatment stage. Denitrifying microorganisms are intended to reduce perchlorate, chlorate and bromate to non-critical anions under controlled conditions. The aim is to ensure a pollutant-free overall treatment without additional chemical reagents. The overarching goal is to demonstrate an integrated, flexibly deployable overall system that can be adapted to the load situation. In addition to technical feasibility, energy requirements, regeneration cycles, material resistance and economic efficiency are to be evaluated. In the long term, the method is to be designed in such a way that it can be used both stationary in waterworks and mobile in temporary cases of pollution. With the successful completion of the project, a transferable, sustainable and economically scalable concept will be available that enables water utilities and industrial companies to safely comply with current and future limit values for PFAS while meeting ecological and economic requirements.