More than 70% of the Earth’s surface is covered by water – a feature so prominent that our planet appears blue when viewed from space, earning it the nickname ‘the Blue Planet.’ Such an abundance of water – most of it in liquid form – sets the Earth apart from other planets in the solar system. Not only is water the largest constituent of the human body, water is vital for all known forms of life.
Of all the water found on the surface of the Earth, however, only about 2.5% is fresh water, more than two thirds of which is present as ice in ice caps and glaciers. In other words, while water is plentiful on our planet, only a fraction of it is drinkable or relatively easy to make suitable for human consumption.
Rapid population growth, urbanization and global warming are among the main contributors to the ever-greater demand for drinking water. Hot and dry climate make the Middle East, parts of Africa, Australia and Asia the thirstiest regions in the world, but droughts across the planet and other factors have made shortage of water supply a truly global problem.
Mesfin M. Mekonnen and Arjen Y. Hoekstra of the University of Twente in the Netherlands have recently found that global water shortage is actually far worse than previously thought. According to their study published in the Science Advances journal, around 4 billion people, i.e., more than half of the world’s population, suffer from severe water scarcity for at least one month out of the year. Previous studies estimated this number to be considerably lower, between 1.7 and 3.1 billion.
Period: 1996–2005. ‘Blue water’ refers to fresh surface and groundwater, i.e., the water in freshwater lakes, rivers and aquifers.
Luckily, many of the worst-affected regions border seas and oceans, thus having immediate access to endless sources of water, or, more precisely, salt water. Salt water is of course not suitable for human consumption, but the minerals making it undrinkable can fortunately be removed. The process whereby salt water is turned into drinking water is called desalination. According to the International Desalination Association, nearly 16,000 desalination plants operated worldwide in June 2011, producing 66.5 million cubic meters of drinking water per day, enough to meet the needs of 300 million people, i.e., nearly 5% of the world’s population at the time. Not surprisingly, this number continues to grow, making desalination a fast-growing industry.
The high temperatures and high salinity in desalination plants produce extremely corrosive operating environments, necessitating the use of corrosion-resistant materials capable of withstanding the most severe conditions. Among the alloying elements importantly contributing to the corrosion resistance of stainless steel and, in turn, to the viability of desalination is molybdenum. To learn more about desalination in general and the specific molybdenum-alloyed stainless steels commonly used in desalination plants in particular, read the article “Preventing Desalination Plant Corrosion: The Role of Molybdenum” by Tim Outerridge, Secretary-General of the International Molybdenum Association (IMOA), published in the April issue of Stainless Steel World News.