International research to tackle contaminated groundwater

A Teesside University expert has been leading a global research project which is aiming to find new ways to clean contaminated groundwater.

Over two billion people globally rely on groundwater as their primary water source, despite the constant danger of contamination which can lead to serious illness.

Groundwater is an important natural resource created largely from rainfall. It gathers in pores, cracks and crevices underground and accumulates in permeable formations of sediments and rocks known as aquifers.

Industrial activity, such as chemical waste from metal processing plants or agriculture, can contaminate groundwater making it unsafe to consume. Contaminants such as chlorinated solvents can lead to kidney and liver damage, with some considered carcinogenic.

Teesside University academic Dr Tannaz Pak has been leading an international research team which examined new ways of cleaning contaminated groundwater resources.

The team, comprising a collaboration between Teesside University, the Brazilian Synchrotron Light Source, University of Parana in Brazil and the Polytechnic University of Turin in Italy, carried out research into a new technology which can reduce this contamination using a more sustainable process.

Their research has been published by scientific journal Proceedings of the National Academy of Sciences (PNAS), the official publication of the United States National Academy of Sciences. PNAS is one of the most prestigious and highly citied multidisciplinary research journals.

Dr Pak, Senior Lecturer in Petroleum Engineering, in the University’s School of Computing, Engineering & Digital Technologies, said: 'Water security is at risk due to unsustainable use, as well as industrial activities which have caused significant groundwater contamination since the beginning of the twentieth century.

'The team’s research is focused on the chlorinated solvents, which are among the most persistent aquifer contaminants. This global problem was created as a result of their wide industrial use in the past decades due to lack of understanding in the health risks associated with them.'

Dr Pak explained: 'This type of contamination is especially difficult to remove. Their release can last for decades and a small amount of these contaminants can render large volumes of water unsuitable for drinking. In addition to the contamination source, which contains free droplets of these contaminants, a wider contaminated zone is created, known as the plume, which contains water with contamination dissolved in it.

'Remediation technologies often treat the plume and not the source. They are therefore aimed at limiting the spreading of the contamination, rather than providing a final solution by eliminating the source. Conversely, a remediation technology able to treat and efficiently remove the contamination source, rather than only the dissolved plume, allows a faster and more efficient recovery of the site.'

The team studied the use of nanoremediation, a new technology in which reactive nanoparticles of iron are injected subsurface to react with the contaminant and degrade them in-situ.

Dr Pak said: 'Advanced technologies can target and degrade the contamination source without the need to remove the plume water. This eliminates the problem and lowers the remediation costs, such as energy use and water consumption, while also limiting disruption to the activities around the contaminated areas.'

The three-year study used state-of-the-art 4D (time-resolved 3D) imaging to capture the dynamics of nanoremediation at microscopic scale and inside the pores of a groundwater system, for the first time. The experiment was conducted at the x-ray computed micro-tomography beamline of the Brazilian synchrotron light source.

Dr Pak said: 'Our findings provide new insights into how the contaminant source is degraded as a result of the chemical reaction promoted by injection of nanoparticles.

'Our study shows that the two main mechanisms that drive the nanoremediation process at pore-scale, are firstly formation and flow of a gas phase during the in-situ chemical reaction, which displaces the contamination droplets previously trapped in the aquifer sediment, and secondly, direct degradation of the contaminant phase at its interface with nanoparticles.'

A series of 3D images were collected during the experiment, enabling the team to directly monitor the dynamics of the nanoremediation process at microscopic scale for the first time. The positive result indicated a reduction of the groundwater contamination.

Funding for the research project came from the FAPESP (The Sao Paulo Research Foundation) and UKRI (Global Challenges Research Fund, GCRF-QR).

---