Protecting water: from aquifers to space

Water, our most vital resource, is under pressure today: there are many factors that threaten its availability, not only in terms of quantity but also of quality. Politecnico di Torino is tackling these challenges with an interdisciplinary approach and advanced technologies that look beyond Earth: ranging from innovative systems for managing the deepest aquifers to methods for purifying water extracted from the lunar surface.

Rajandrea Sethi, coordinator of the interdepartmental Clean Water Centre (CWC) at PoliTO and professor of Sanitary and Environmental Engineering, helps us to frame the issue: “Water is life, in the most literal sense: it is the solvent in which all biological reactions take place; it is an essential component of every organism; and it is also the agent through which civilisations have developed. The United Nations recognised it as a fundamental human right in 2010, yet today more than two billion people worldwide do not have access to safe drinking water, and around three and a half billion lack adequate sanitation facilities.”

Such an essential yet fragile resource. Water security is now under threat from a range of factors that intersect and influence one another: “Climate change is altering rainfall patterns and intensifying droughts and floods; population and economic growth are driving up demand; pollution is degrading the quality of available resources; whilst the food and energy industries consume enormous quantities of it. The problem is not distant from us: in 2022, 34 per cent of the European Union’s territory experienced a water crisis. And these are not future scenarios: this is already the present.”

To tackle these challenges, PoliTO draws on multi- and interdisciplinary expertise. Sethi goes on to explain: “A vital issue that underpins our research is the link between water and energy – a key area of study at our interdepartmental centre, which involves a wide range of expertise. Not only does producing clean water require energy: desalination, in particular, is a very energy-intensive process. Energy production itself very often requires water: at PoliTO, we address the entire chain of water treatment processes, from start to finish, from the management of deep aquifers right through to new systems for purifying and reusing water in space.”

Elio Chiavazzo, professor of Industrial Technical Physics at the “Galileo Ferraris” Department of Energy (DENERG) – one of the departments affiliated with the centre – confirms this, as he coordinates the SMALL infrastructure: “Water and energy issues are closely linked: it is no coincidence that scientific literature refers to the ‘water-energy nexus’, and a substantial part of our research is devoted to identifying practices that optimise both aspects, particularly through systems based on the utilisation of waste energy, focusing on sustainability.”

Costantino Manes, professor of Hydraulics at the Department of Environmental, Land and Infrastructure Engineering (DIATI), and member of the CWC, points out that research is proceeding along two parallel yet interlinked tracks: “On the one hand, there is the need to purify water resources from even invisible threats and emerging contaminants; on the other, there is the imperative to protect infrastructure and ecosystems from hydraulic stresses, which are becoming increasingly unpredictable due to climate change.”

Sethi continues: “A significant part of our work is aimed at improving water quality, and is therefore focused on the issue of pollutants, in particular emerging contaminants, whose dangers emerged relatively recently.”

These include pharmaceutical compounds, pesticides, microplastics and microfibres, and above all, the notorious PFAS – pollutants that include carcinogens and endocrine disruptors, characterised by extreme persistence and found in a vast array of everyday products, from waterproof jackets to non-stick frying pans. At the end of their life cycle, these substances can be released into the environment and reach groundwater. As Sethi explains: “The research aims to understand the environmental and health impacts of these contaminants, to study the processes by which they accumulate in living organisms, to develop technologies for their removal and degradation, and to ensure water safety.”

However, this is just one of the many fields of research: the Clean Water Centre – and, more broadly, the water-related research carried out at PoliTO – represents an entire scientific ecosystem that brings together departments and expertise in chemical, materials, environmental, energy, hydraulic and electronic engineering, as well as the basic sciences, to develop innovative technologies to ensure sufficient quantities of high-quality water.

Here are some of the most important areas of research at the CWC, as highlighted by Sethi.

• Removal of pollutants. Research is focusing on advanced membrane processes – one of the CWC’s main areas of expertise – which consist of systems for filtering water to remove pollutants in an environmentally sound and energy-efficient manner. Another focus is on advanced oxidation processes, which are particularly effective against pollutants that are difficult to remove using other methods.
• Fluid dynamics. The research aims to understand the physics underlying the behaviour of water in natural and industrial systems. On the one hand, it studies natural environments, such as rivers and seas, in order to protect infrastructure and coastal areas from extreme events. On the other hand, it focuses on the design of industrial plants, including those dedicated to the removal of pollutants.
• Monitoring devices. Researchers are studying and designing systems that can monitor various water parameters, including pollution levels. These systems can monitor water quality directly within aquifers, in real-time, and at depths of up to 200 meters. They utilize advanced techniques such as Raman spectroscopy to achieve this.
• Study of aquifers. The research focuses on two main aspects. The first concerns the treatment of contaminated groundwater, using innovative techniques that can be applied directly within the aquifer, including through the use of nanomaterials. The second concerns the controlled recharge of aquifers, that is, the injection of water into the subsoil to increase available reserves and improve water quality, especially when water systems are under greater stress.
• Low-enthalpy geothermal systems. This technology harnesses the relatively stable temperature of the subsoil and groundwater, which can be used as a heat source or heat sink. Using heat pumps, even small temperature differences compared with the outside environment can be utilised to heat or cool buildings extremely efficiently. The performance of these systems depends on the characteristics of the subsoil and, in particular, on the presence and movement of groundwater, which can contribute to heat exchange and increase the system’s efficiency.

A significant proportion of the Earth’s water resources does not flow on the surface: around 10 million cubic kilometres of fresh water is found underground, stored in aquifers. These aquifers feed wells and springs, and enable agricultural irrigation in many regions of the world. Contaminating them – with industrial solvents, heavy metals or PFAS – means jeopardising resources that take decades or centuries to replenish.

The most common treatment approach involves extracting the water to treat it on the surface: a costly, slow, and often ineffective approach for the most stubborn contaminants. DELTANOVA, a spin-off from Politecnico di Torino, founded in 2020 by Carlo Bianco, a researcher at DIATI, Rajandrea Sethi and Tiziana Tosco, a lecturer in Sanitary and Environmental Engineering at DIATI, employs an alternative method: nanoremediation, i.e. in-situ remediation by injecting reactive nanomaterials directly into the subsoil, right where they are needed.

As Carlo Bianco explains, nanomaterials – such as nanoscale zero-valent iron, but also more innovative materials currently under investigation – are injected into the subsoil via purpose-built wells: “Thanks to their small size, nanomaterials move more easily through the pores of the subsoil, where they encounter contaminants and rapidly degrade them. Size matters: iron itself, when reduced from millimetre-scale particles to nanoscale particles, increases its reactivity by several orders of magnitude. The reason is simple: a nanometre-scale particle exposes an immensely larger surface area to the contaminant than the same mass of granular material, significantly reducing the degradation time.”

Some of these technologies are already available on the market: zero-valent iron nanoparticles for the removal of carcinogenic chlorinated solvents (such as trichloroethylene) have been applied by us at contaminated sites in Italy, the United States and Australia. The patent portfolio of the research group includes six registered patents. Other technologies are being transferred from the laboratory to the field, as we seek pilot sites in which to test more innovative approaches: a delicate endeavour aimed at protecting a vital resource for humanity.

Water is not merely a resource that needs treatment, but a vital element of natural systems, and a potential risk factor for humans and the built environment.

PoliTO’s Hydraulics and Fluid Mechanics Laboratory, headed by Costantino Manes, professor of Hydraulics at DIATI, focuses on what we might call the other aspect of water science: not treatment, but the study of the motion of water and its interaction with the physical and biological world, with all its many – and sometimes surprising – applications.

Safer river bridges in a changing climate

Climate change is increasing the frequency and intensity of river floods, endangering strategic infrastructure such as bridges. As Manes explains: “Bridges, designed for past hydrological conditions, are now subjected to new and greater stresses. The most critical phenomenon is scouring, that is, the erosion of the riverbed around piers and abutments caused by the force of the current during floods. The turbulent vortices that form around the piers remove sediment and carve out holes that weaken the foundations, representing one of the main causes of river bridge collapse. Our group develops physically based models – not purely empirical ones – to predict the depth of scouring as a function of flood characteristics, sediment, and pier geometry. These are essential tools for designing safer bridges and for assessing the hydraulic risk to existing infrastructure in a changing climate.”

Plants protecting the coast: the SHIEELD project

The dangers posed by water do not come solely from rivers. Coasts are exposed to erosion and coastal flooding, phenomena that are intensifying as sea levels rise and extreme weather events become more frequent. The SHIEELD project, developed with researcher Davide Vettori thanks to a Marie Skłodowska Curie EU grant, has studied the role of seagrass beds (such as Posidonia oceanica, which is very common in Italian waters) in dissipating wave energy and thus protecting coastlines from erosion.

The critical issue is that seagrasses are flexible structures, and their mechanical behaviour under the action of waves and currents is difficult to describe. Manes explains: “To study this, we had to be creative, building plastic models with similar properties to seagrasses. This enabled us to run loads of controlled experiments in the lab, identifying the physical processes that govern the dissipation of wave energy and developing predictive models. One of the resulting papers was published in PNAS (Proceedings of the National Academy of Sciences), and was highlighted by Science as a significant contribution.”

Industrial and biomedical hydraulics

The Bubbles for Life project exploits the phenomenon of cavitation: the formation and subsequent violent collapse, within liquids, of vapour bubbles generated by sudden changes in pressure. Manes explains: “We are studying how to exploit this phenomenon to mechanically break down bacteria and thus disinfect water, without the use of chemical additives.” Other applications include the lysis of microalgae to extract compounds useful to the pharmaceutical and cosmetics industries.

But hydraulics even applies to the biomedical field. Manes is the inventor of a stent for urological applications, designed to prevent fouling and occlusion by optimising the geometry of the drainage holes, solely using hydrodynamic methods. The stent has already been tested on dozens of patients in the United Kingdom.

Studying how fish swim to protect them

Perhaps the most unexpected application concerns fish. River fragmentation, that is, the disruption of the continuity of watercourses caused by dams and weirs, is one of the main factors behind the decline of river ecosystems, which are among the most endangered in the world in terms of biodiversity. These barriers prevent fish from moving around for breeding and feeding purposes. Manes explains: “The engineering solution is fish ladders: lateral passages that allow fish to bypass the barriers. To design them, however, we need a clear understanding of what fish can do in terms of their motor abilities. The study, funded by the European RIBES project, has made it possible to quantify fish’s ability to swim against the current by testing the animals under controlled hydrodynamic conditions in a specially designed channel. The results will enable fish ladders to be designed more accurately and with less uncertainty.” This approach integrates hydraulics and biology to translate research into a practical solution for environmental protection.