To counter climate change, we must rethink the way we design and experience our cities: public health, the environment, urban planning and innovation must converge in a single “One Health” approach, as defined by the World Health Organisation, that involves public bodies, academia and businesses.

In this vision, one of the crucial challenges is the water emergency: extreme events, once very rare, now occur almost every year; sudden floods are alternating with long periods of drought; aquifers are threatened by emerging pollutants; and the water system is under pressure as never before.

“In building resilient and smart cities, we must no longer limit ourselves to enduring water, but we must learn to manage it, reuse it and return it as a precious asset to the community,” explains Michele Falcone, general manager of Gruppo CAP. The company manages the integrated water service for the metropolitan city of Milan and is also active in the waste treatment, bioenergy, green energy and circular economy sectors, through a system of shareholdings, business networks and joint ventures.

From water that flows out to water that stays

Up until a few decades ago, water services were managed by local councils, which tended to channel rainwater away from their own areas, transporting it through increasingly larger pipes to neighbouring municipalities or waterways. “A seemingly simple but short-sighted solution: each municipality focused on solving the issue in their own area, regardless of the problem upstream or the consequences downstream,” notes Falcone. Today, the perspective has changed. “There is a coordinated vision that views water basins as interconnected systems. Milan and its metropolitan area, therefore, think of themselves as a single system, in which what happens in the north has effects in the south, and vice versa.”

In the Milan metropolitan area, covering an overall surface area of approximately 1,500 km², there are almost 7,000 km of sewers and nearly twice as many smaller networks, such as canals and agricultural ditches, often, however, neglected: “They need to be reactivated and integrated into a system capable of retaining water, absorbing it and releasing it gradually: currently, only 11% of rainwater is recovered. Furthermore, Milan floats on one of the largest aquifers in Europe, so it has a duty and an opportunity to transform this abundance of water into a sustainable model. There is still a long way to go, but the change has already begun.”

Towards the “sponge city” design

The concept of the sponge city has been widespread internationally for about ten years now. It is a strategy of adaptation, not resistance, to climate change: “The principle is simple and revolutionary at the same time: the land must act like a sponge, capable of absorbing water during heavy rainfall and releasing it gradually without causing damage when the pressure drops.”

This is why we are taking action with nature-based solutions, from which everyone is asked to draw inspiration, whether it be for the construction of homes, commercial buildings, open spaces or roads: permeable surfaces instead of asphalt, flower beds, drainage car parks, green roofs and walls, urban forests and alternative rainwater management systems. These solutions not only prevent damage, but also reduce heat islands, restore ecosystems and improve quality of life.

One example of this is the Città metropolitana spugna (Metropolitan Sponge City) project by Gruppo CAP and the Milan Municipality, funded with €50 million from the PNRR (National Recovery and Resilience Plan): the initiative involves 90 urban drainage projects in 32 municipalities to reduce flooding, combat soil erosion and increase urban resilience.

In Varedo, meanwhile, the shutdown of an old wastewater treatment plant has made way for a new 60,000 m² river park, redeveloping a degraded area and returning it to the citizens. In Morimondo, instead, lies a sewage treatment plant that is a perfect combination of innovative technologies and environmental awareness, engineered by CAP and inspired by the principle of phytoremediation: a natural water treatment system that mimics the self-purification process found in aquatic environments, while also creating a habitat for biodiversity.

The organisation is also tackling another widespread problem, that of water wastage: in Italy, on average, over a third of water (42.24%) does not reach its destination, while in Lombardy the level stands at around 30%, falling to 19% in the metropolitan area of Milan managed by the Gruppo CAP. “This is well below the national average, but still high,” continues Falcone. In this instance, with a specific allocation of 42 million from the PNRR, CAP is renovating 18 km of pipes in 133 municipalities and implementing state-of-the-art digital technologies for real-time monitoring and predictive fault analysis, thus reducing leaks and improving the quality of the water supply service.

Quantity and quality: the dual water challenge

Besides the challenge of managing water in terms of quantity, there is also the issue of the quality of this invaluable resource: thanks to analytical technologies, it is today possible to detect infinitesimal concentrations of micropollutants, such as pharmaceutical and cosmetic residues and pesticides. “To ensure the absolute safety of drinking water, European regulations require very strict standards, following the precautionary principle: in practice, to give an example, if a substance is harmful to human health at a concentration of 1,000, the alert threshold is set at 10.”

Operators are therefore focused on the constant improvement of treatment and filtering technologies, with a steady commitment to investment, mainly covered by the tax paid by citizens, thus placing an additional burden on the community. “However, it is important that these increasing costs are also borne by those responsible for most of the emerging pollutants, according to the polluter pays principle,” reflects Falcone. He cites the case of “aquifers polluted by LM6, a pesticide precipitate widespread in the 1980s, whose remediation costs are borne solely by public operators, while the contribution from agriculture and industry is zero.”

In this regard, the EU is discussing Directive 2024/3019, which introduced the extended producer responsibility (EPR) system for the pharmaceutical and cosmetics sectors. This requires companies to take economic responsibility for various aspects of the process, including quaternary wastewater treatment and micro-pollutant monitoring systems.

The issue of costs is crucial: in Italy, the average water tariff is around €1.30/m³, compared to €5-6/m³ in Denmark. This difference may seem positive, but it actually reflects the difficulty of financing adequate investments in water infrastructure, characterised by very long payback periods, in order to keep pace with the climate crisis and European directives.

Circular economy and energy sustainability

Another fundamental principle to be applied to the water cycle is that of circularity: “Purification plants should not be seen merely as treatment facilities, but as hubs of the circular economy,” explains Falcone. The Gruppo CAP manages 40 such plants across the region, aiming to reach 200,000 tonnes of liquid and agri-food waste treated for conversion into resources by 2028. “High-quality sludge from water purification can be transformed into agricultural fertiliser without first being classified as waste. Lower-quality sludge can still be used to generate energy.”

According to a general calculation for 2022, by exploiting all the plants already operating in Lombardy for the treatment of wet waste (FORSU) and sludge, it would be possible to obtain 70 million cubic metres of biomethane, enough to power 200,000 cars for 11,000 km per year each.

An important prospect on the road to improving Italy's energy mix, looking ahead to the goals of the energy transition, but also to the obstacles posed by the current international situation. Among the Gruppo CAP's plants of excellence are the one in Robecco sul Naviglio, which increased its capacity to receive liquid and agri-food waste by almost six times, from 4,800 to 27,000 tonnes, thanks to a €150,000 investment in the installation of new turbines ; and Rozzano, which will treat over 100,000 tonnes of non-hazardous liquid waste per year, transforming sludge into energy thanks to anaerobic biodigesters.

These water treatment processes are highly energy-intensive: Gruppo CAP, like all European operators, has set the goal of energy neutrality by 2045. “Today, we cover part of our needs thanks to photovoltaic and agrivoltaic systems located close to existing treatment plants, so that we have zero-kilometre green energy, with the aim of reaching 35% by 2030,” explains Falcone.

The European strategy for water resilience 

Finally, at the regulatory level, the benchmark for this evolution is the European Water Resilience Strategy, approved by the European Commission in June 2025. It aims to restore and protect the water cycle, ensuring clean water at affordable prices for all and creating a sustainable, resilient, smart and competitive water economy.

According to Falcone, there are two fundamental aspects: “Firstly, sponge cities are highlighted as one of the main tools for addressing the challenges associated with sustainable water management, especially in a context of climate change, more frequent extreme weather events, and increasing urbanisation. Secondly, the importance of building a truly circular water economy is emphasised. Regulations must be introduced that require the use of a certain percentage of recycled materials and recognise the economic value of recovered resources, such as purified water and substances obtained from water treatment processes. Only then will the circular economy cease to be a slogan and become a reality; otherwise, these products will not find a market outlet.”

Cover: Milan, photo Envato