Two UK students have received the prestigious Stockholm Junior Water Prize 2024 for their work on PFAS pollution reduction from surface water in the Thames basin.

Per and polyfluoroalkyl substances (PFAS) pollution is a growing concern worldwide, including in the catchment of the River Thames, which flows through London.

PFAS are a group of synthetic chemicals that have been used in consumer products since the 1950s. They are known as 'forever chemicals' because they do not break down easily in the environment and can persist for a long time - ending up in bodies of water and sometimes in drinking water if not properly treated.

In researching a solution, Christopher Whitfield and Wenqi (Jonathan) Zhao from Eton College, a boarding school in Windsor, have developed software called PFASolve, which detects and predicts PFAS concentrations of surface water at a given location, with 95% accuracy. Users enter their location into the software and PFASolve uses a machine-learning, geospatial neural network to estimate the concentration of PFAS using several parameters.

With those predictions, the students designed and tested a point-of-use filtration device made from granular activated carbon that can be installed on domestic taps, and observed a 93% reduction in PFAS concentration, bringing it below the globally recognised health limits of 4 nanograms per litre. They optimised the design to allow a 10mm depth of activated carbon to be used for up to two-and-a-half months, with minimal impact on flow rate and introducing no impurities into the water.

Their proposed solution is helping to advance the reduction of the impacts of PFAS pollution while presenting a potential solution that could be accessible to all.

Zhao said, ”We are very proud to have won this prize. We are scientists, united by the prospect of clean water, especially when seeing how that's threatened by the emergence of PFAS chemicals. We seek to combine our passions in natural sciences and computer science for the cause."

Through the development of PFASolve, Whitfield and Zhao have been able to connect and deepen conversations about PFAS with local governments, water charities and environmental organisations to raise awareness of the problem and solutions.

They were presented with their prize during an award ceremony at World Water Week by HRH Crown Princess Victoria of Sweden, the Prize’s Official Patron.

The Diploma of Excellence was awarded to Shanni Valeria Mora Fajardo and Rosa Mendoza Sosa from Mexico for their work on developing a home filtration system to facilitate the reuse of inked wastewater in domestic vegetable cultivation. The People’s Choice Award was awarded to Manoel José Nunes Neto from Brazil for a project which develops a low-cost autonomous aquatic rover vehicle to measure physical-chemical parameters in freshwater ecosystems to identify environmental impacts.

The Stockholm Junior Water Prize is an international competition where students between the ages of 15 and 20 present solutions to major water challenges and has been organised every year at the SIWI World Water Week since 1997. It is hosted by the Stockholm Water Foundation, with Xylem as a founding partner.

Austin Alexander, vice president of sustainability and social impact at Xylem said, “Innovation is paving the way to a more water-secure world, and the next generation is accelerating progress. The Stockholm Junior Water Prize competitors are an inspiring example of the ingenuity and passion young innovators bring to the table.

"On behalf of Xylem, I’d like to congratulate all those who took part in this year’s competition."