Water shortages and poor water quality are considered as the major obstacles to achieving sustainable development and improvement in the quality of life. According to the United Nations, by 2030, water demand will exceed supply by 40%. The use of desalination technology is seen as the looming alternative to tackling water shortage in the coming years. Dr A N Brijesh Nair, Professor, VIT University, Vellore, gives a clear picture of the desalination technologies used in different parts of the world, including its small presence in India.
Here are some alarming facts – 97.5% of all water on Earth is saltwater, and, of the remaining 2.5%, over two-thirds are inaccessible ice and permanent snow cover, and, hence, water is acutely and unevenly distributed. The world’s water consumption rate is doubling every 20 years, outpacing by two times the rate of population growth. The availability of good quality water is on the decline, and water demand is on the rise. Worldwide availability of fresh water for industrial needs and human consumption is limited.
Various industrial and developmental activities in recent times have resulted in increasing the pollution level and deteriorating the water quality. Water shortages and unreliable water quality are considered as the major obstacles to achieving sustainable development and improvement in the quality of life. Large parts of the world are already experiencing either water stress or water scarcity.
According to the UN, by 2030, water demand will exceed supply by 40%, with up to two-thirds of the global population inhabiting areas that are officially defined as water-stressed. About 884 million people in the world today have no access to safe, potable drinking water. Now, what can be a technology that can be a solution for these alarming facts – the answer may be desalination.
Desalination involves the removal of salt and minerals from saline or brackish water by means of one or more processes to produce (potable) water fit for human consumption. Desalination is the term broadly used to describe the production of potable water from various sources of raw water.
The sources may include brackish water, river water, waste-water, pure water, and seawater. In this sense, desalination is the process of reducing the
concentration of dissolved solids in the water to below the WHO target for potable water.
Over the last few decades, desalination technologies have been used increasingly throughout the world to produce drinking water from brackish groundwater and seawater, to improve the quality of existing supplies of freshwater for drinking and industrial purposes, and to treat industrial and
municipal waste water prior to discharge or reuse. There are five basic techniques that can are mostly used to remove salt and other dissolved
solids from water: distillation, reverse osmosis (RO), electrodialysis (ED), ion exchange (IX), and freeze desalination. Distillation and freezing involve
removing pure water, in the form of water vapour or ice, from salty brine. RO and ED use membranes to separate dissolved salts and minerals from water. IX involves an exchange of dissolved mineral ions in the water for other, more desirable dissolved ions, as the water passes through chemical resins.
(Read the full article from the April Issue of Safety Messenger Magazine 2015)