THE DESALINATION OF SEA WATER REPRESENTS NOT ONLY A TECHNOLOGICAL CHALLENGE BUT ALSO A SOCIAL-ECONOMIC AND ENVIRONMENTAL CHALLENGE. TO EFFECTIVELY ADDRESS THIS TOPIC IT IS NECESSARY TO COMBINE SCIENTIFIC AND ENGINEERING ADVANCES WITH A DEEP UNDERSTANDING OF ECOLOGICAL DYNAMICS AND LONG-TERM HUMAN NEEDS
Desalination: lessons from history and current challenges
For millennia, humanity has faced the challenge of desalination of sea water to obtain both the sale is fresh drinking water.
However, this process is not without its limitations and sometimes the consequences can be drastic. A significant historical example concerns ancient times Mesopotamia during the period of Sumerian civilization (approximately 3500-2000 BC). Mesopotamian populations failed to effectively desalinate the water used for irrigation, which led to a buildup of salts in agricultural land. This phenomenon, known as soil salinization, caused a decline in soil fertility and contributed to the social and agricultural collapse of the region.
Second Sujay Kaushalhydrologist ofUniversity of Maryland a College Park, (USA), «It’s the oldest, most boring, but most serious question in the world.”.
This challenge has not only influenced civilizations historically, but continues to represent a critical difficulty in the modern era, where growing demand for freshwater and environmental concerns make the sustainable supply of desalinated seawater a paramount goal. Let’s try to understand better.
A global challenge
The issue of desalination is becoming increasingly urgent as salinity levels in freshwater are increasing for several reasons.
Rising sea levels are pushing salt into coastal groundwater, while excessive groundwater extraction in other areas is drawing deeper, saltier water into the aquifers.
Furthermore, human activities are significantly contributing to the contamination of surface waters with various types of salts.
De-icing road surfaces using sodium chloride (i.e. table salt) and other chemicals to prevent ice formation, or washing clothes which releases detergents rich in phosphates and chlorides into wastewater and fertilization of agricultural fields with fertilizers that contain various salts, are all factors that increase the salinity of the water.
Last October, Kaushal and colleagues reported a dramatic increase in salinity levels in major streams and rivers around the world; some water bodies today have much higher levels of salinity than a few decades ago and the phenomenon affects practically every continent.
The effects of salinity on health and the environment
Increasing salinity presents significant risks to human health, aquatic ecosystems and agriculture.
Impact on agriculture: the excessive presence of salts in the soil can reduce the ability of plants to absorb water, causing water stress and limiting crop growth. This leads to a decrease in agricultural yield and lower quality of products.
Impact on aquatic ecosystems: an increase in salinity can alter the composition of the species present, leading to a loss of biodiversity, compromising the general health of aquatic habitats.
Impact on human health: The salinity of drinking water is a public health concern. Even if theWorld Health Organization (WHO) established guidelines for safe levels of salinity in drinking water, these limits are still under debate.
Recent studies have linked high levels of sodium in drinking water to an increased risk of various diseases, including preeclampsiaa complication of pregnancy characterized by a sudden increase in blood pressure and damage to organs, often the kidneys.
Brines: a complementary challenge
Another related issue is the management of problematic waste arising from salamoie, i.e. aqueous solutions with a high concentration of salts, generated as a by-product in various industries. Oil and gas production, as well as desalination plants to produce drinking water, create large quantities of highly salty wastewater whose disposal is expensive and complex.
In California, the system Brine Line it transports brines over 100 kilometers to the sea, while elsewhere they are injected underground, albeit with controversy regarding potential seismic effects.
«We must find effective solutions to manage brine”points out Menachem Elimelechenvironmental engineer fromYale University in New Havennel Connecticut (USA).
Sustainable management of brines is key to minimizing environmental impact and ensuring that these processes and projects can operate effectively and sustainably in the long term.
This implies that operations can continue without causing irreversible damage to the environment, while keeping costs manageable and acceptable.
Innovative technologies for desalination and brine management
Research and innovation are working to improve both the production of drinking water and the management of residual brine. Advanced desalination technologies not only aim to provide more fresh water but also seek to convert brine, traditionally considered a problem, into an economic opportunity. Which?
Traditional evaporation of brine in ponds, while effective in hot, sunny climates, is slow and requires large spaces. A faster alternative is accelerated evaporation, which uses vapor heating and compression. However, this method is energy intensive and requires corrosion-resistant materials.
Recently, mining companies are targeting brines as resources lithium vital for battery and green technologies.
Methods such as nanofiltration and chromatography are being investigated to concentrate and recover lithium more efficiently and economically.
Furthermore, the use of electricity, new materials and solvents is opening up new possibilities for treating a wide range of chemicals found in these waste products.
However, Shihong Lin dell’Vanderbilt University of Nashville, Tennessee (USA), points out that there is no universal technology to address the diversity of brines: “It’s like a thousand different problems”.
Jason Ren from the Princeton University in New Jersey (USA) argues that the approach should shift towards valorization of salts extracts rather than just focusing on water production.