Desalination, that is, the removal of the saline fraction from salt-containing water, can represent a valid solution against drought, provided that regulations are made stricter to safeguard the marine environment. This is the message put forward by the environmental association Marevivo, which brought together in Rome some of the leading experts in the field, in collaboration with the National Association of Minor Island Municipalities (Ancim) and Idroambiente srl. For some years now the subject has been widely debated in our country: we are periodically faced with difficulties in water supply, and yet, among the nations bordering the Mediterranean, none is surrounded by more water than ours.

The situation in the rest of the world

At a global level, the production of drinking water from the sea has exceeded 100 million cubic metres per day, involving primarily the Arab countries, Australia, the eastern coast of the United States and several realities not far from Italy. Such is the case of Israel, where 4 desalination plants guarantee 40 per cent of the national supply; or of the city of Barcelona, whose rainfall levels are comparable to those of some areas of our South: thanks to a hybrid system comprising 2 water treatment plants and 2 desalination plants, the Catalan capital manages to guarantee drinking water to 5 million residents and more than 8 million tourists per year. In Italy, by contrast, marine or brackish waters account for just 0.1 per cent of water supply sources: similar plants exist in Sicily, Sardinia and some of the minor islands, where they have replaced older supply systems such as the transport of drinking water by tanker ships.

The energy consumption of desalination

There are mainly two problems that have held back the development of this solution. The first concerns energy consumption, which is considerably higher than that of conventional drinking water production processes. On the one hand, technological improvements have reduced the incidence of kWh per cubic metre of water produced; on the other, there is an increasing tendency to supplement the electricity used to power the plants with energy produced on-site from renewable sources, such as solar and wind. The fact remains, however, that desalination is only economically and operationally sustainable in the presence of a water network with low losses — a condition that is far from common in Italy.

The environmental impact

There is also the question of returning to the sea the concentrated saline solutions that represent the "waste" of the treatment process. As lawyer Antonio Cavallo recalled during the conference, our country lacks adequate regulations on the environmental impact of these plants: "Legislative Decree 152/2006, which governs the matter of discharges, contains no specific provision on the subject; there is no obligation to carry out an environmental impact assessment; there is no indication of a cost-benefit analysis; and there is no express prohibition on discharging into the sea the chemical products derived from desalination processes."

The first studies conducted at Lipari and Ustica have confirmed that brine can cause problems, especially in enclosed or semi-enclosed basins. For Rosalba Giugni, president of Marevivo, "there is still much to be done in the scientific field to study the damage that such plants cause to the marine ecosystem. The data are still limited. Added to this is the regulatory shortfall, which must necessarily be addressed so that desalination can be our ally without impacting biodiversity."

For obvious reasons the subject is particularly felt in small islands, where access to drinking water is often difficult and dependent on weather conditions. "The issue," in the view of Gian Piera Usai of Ancim, "must be addressed according to a new holistic model and requires more strategic solutions in the context of the circular economy that is establishing itself."

Desalination yes, then — but the Rome conference sounds an initial alarm bell. Scientific investigation and regulatory updates are needed in order to prevent, or at least mitigate, the impacts of this technology on the sea as a resource.