Compact electron accelerator for treating PFAS-contaminated water

So-called forever chemicals or PFAS compounds are a growing environmental problem. An innovative approach to treating PFAS-contaminated water and soil now comes from accelerator physics: high-energy electrons can break down PFAS molecules into harmless components through a process called radiolysis. A recent study published in PLOS One shows that an accelerator developed at HZB, based on a SRF photoinjector, can provide the necessary electron beam.

PFAS compounds can now be detected in many places in our environment. These synthetic chemicals accumulate in water and soil, from where they enter the food chain. Due to their extremely stable carbon-fluorine bonds, they are hardly degraded by natural processes. Some PFAS are considered harmful to health. For instance, the area around the former Tegel Airport is heavily contaminated with PFAS, which entered the soil and groundwater as a result of previous firefighting exercises.

High energy electrons against PFAS

Accelerator physics now offers a new approach to tackling this problem: high-energy electrons can break down PFAS molecules into harmless components through a process called radiolysis. In a feasibility study, a team led by Prof. Dr. Thorsten Kamps has shown that an accelerator developed at HZB based on an SRF photoinjector can deliver the electron beam required for this purpose. This electron beam must have a specific energy and high average power. An SRF photoinjector is a new accelerator concept using a superconducting radio-frequency cavity with high frequency electromagnetic fields to accelerate electrons. Since the acceleration field can be always on, one can generate high average beam power, as required by electron beam water treatment.

‘The SHF photoinjector concept is highly flexible and perfectly suited for the further development of accelerator-based PFAS water treatment. This allows us to find out which beam parameters optimise the chemical yield for specific PFAS compounds,’ says Tasha Spohr, lead author of the study.

Competitive alternative for PFAS treatment

In the case study, the team compared the filter system currently used for PFAS removal at the former TXL airport with the proposed accelerator concept. ‘In terms of operating costs, we could be competitive with conventional technology within the next years,’ says Kamps. ‘We have demonstrated that accelerator physics is not only a tool for exciting basic research, but can also deliver new technologies to address urgent societal issues.’

Compact accelerator in a box

The vision for this technology is a compact electron accelerator that fits into a container. This could be used at contamination hotspots – such as the former Berlin Tegel Airport – at potentially lower costs and with less effort than conventional remediation technology using filter systems. Although development work is still needed before practical implementation, the study shows that the SRF photoinjector is a suitable platform for systematically optimising the benefits, efficiency and costs of such systems.

Note: The study was funded as part of the HGF Hi-Acts Initiative.