• Defence Research & Development Organisation (DRDO) has successfully developed indigenous nanoporous multilayered polymeric membrane for high-pressure seawater desalination.

• Defence Materials Stores and Research & Development Establishment (DMSRDE), the Kanpur-based laboratory of DRDO, has developed the technology for desalination plant in the Indian Coast Guard ships, based on their operational requirement to address the serious challenge of stability when exposed to chloride ions in saline water. The development has been completed in a record time of eight months.

• DMSRDE, along with the Indian Coast Guard, successfully carried out initial technical trials in the existing desalination plant of Offshore Patrolling Vessel (OPV). 

• The initial safety and performance trials of the polymeric membranes were found to be fully satisfactory. The final operational clearance will be given by the Indian Coast Guard after 500 hours of operational testing.

• Presently, the unit is under testing and trials on OPV. 

• This membrane will be a boon for desalination of seawater in coastal areas after certain modifications. 

What is desalination?

• The scarcity of freshwater resources and the need for additional water supplies is already critical in many arid regions of the world and will be increasingly important in the future. Many arid areas simply do not have freshwater resources in the form of surface water such as rivers and lakes. • They may have only limited underground water resources, some that are becoming more brackish as extraction of water from the aquifers continues.

• The process of converting saline water into drinking quality water is called desalination.

• Solar desalination evaporation is used by nature to produce rain, which is the main source of freshwater on Earth.

• The main hurdle that must be overcome to turn seawater into freshwater is to remove the dissolved salt in seawater. That may seem as easy as just boiling some seawater in a pan, capturing the steam and condensing it back into water (distillation). 

• Desalination has been used for thousands of years. Greek sailors boiled water so that fresh water could evaporate away from the salt. Also, the Romans trapped salt with clay filters.

• Other methods are also available, but these technological processes must be done on a large scale to be useful to large populations. However, the current processes are expensive, energy-intensive, and involve large-scale facilities.

• Another way saline water is desalinised is by reverse osmosis procedure. In simplistic terms, water, containing dissolved salt molecules, is forced through a semi-permeable membrane (essentially a filter), in which the larger salt molecules do not get through the membrane holes but the smaller water molecules do. 

• Reverse osmosis is an effective means to desalinate saline water, but it is more expensive than other methods.

• Today, desalination plants are used to convert seawater to drinking water on ships and in many arid regions of the world, and to treat water in other areas that is fouled by natural and unnatural contaminants.

• There are about 15,000 desalination plants around the world. The most notable and biggest plants are in the United Arab Emirates, Saudi Arabia and Israel. Saudi Arabia has some of the largest desalination facilities in the world.

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