|Demand of the question |
Introduction. Give a contextual Introduction.
Body. Discuss desalination technology. Limitations of desalination.
Conclusion. Way forward and solutions.
India facing a developing water crisis situation. Exploring technologies to harness fresh water is seen as one of the idea to deal with it, desalination being one of them. Desalination technology is not an esoteric idea, rather Chennai already uses desalinated water. However, it only has a limited application, given the operation costs.
What is desalination technology?
Desalination is a technology that convert salt water into freshwater using reverse osmosis (RO). Osmosis involves ‘a solvent (such as water) naturally moving from an area of low concentration, through a membrane, to an area of high concentration.
A reverse osmosis system applies an external pressure to reverse the natural flow of solvent and so seawater or brackish water is pressurised against one surface of the membrane, causing salt-depleted water to move across the membrane, releasing clean water from the low-pressure side’. In desalination a plant pumps in salty or brackish water, filters separate the salt from the water, and the salty water is returned to the sea. Fresh water is sent to households.
Limitations of desalination in harnessing potable water from the sea?
Energy intensive- Engineering such plants have to factor in various constraints, for instance, salt levels in the source water that is to be treated, the energy required for the treatment and disposing of the salt back into the sea. To remove the salt required, there has to be a source of electricity, either a power plant or a diesel or battery source. Estimates have put this at about 4 units of electricity per 1,000 litres of water.
- Hyper-salinity- Because RO plants convert seawater to fresh water, the major environmental challenge they pose is the deposition of brine (highly concentrated salt water) along the shores. Ever since the Chennai plants have started to function, fishermen have complained that the brine being deposited along the seashore is triggering changes along the coastline and reducing the availability of prawn, sardine and mackerel. Hyper salinity along the shore affects plankton, which is the main food for several of these fish species.
- Danger to sea life- Moreover, the high pressure motors needed to draw in the seawater end up sucking in small fish and life forms, thereby crushing and killing them, again a loss of marine resource.
- Wastage of land and freshwater- Another problem is that the construction of the RO plants required troves of groundwater. This was freshwater that was sucked out and has since been replaced by salt water, rendering it unfit for the residents around the desalination plants.
- Expensive- Desalination is cost intensive and water this produced is also costly. In light of India’s poor population, desalination may not work out. Investment is required to set up infrastructure, energy requirements and waste disposal.
- Waste Disposal– As with any process, desalination has by-products that must be taken care of. The process of desalination requires pre-treatment and cleaning chemicals, which are added to water before desalination to make the treatment more efficient and successful. These chemicals can be used for only a limited amount of time. Once they’ve lost their ability to clean the water, these chemicals are dumped, which becomes a major environmental concern. These chemicals often find their way back into the ocean, where they poison plant and animal life.
- Health Concerns- Desalination is not a perfected technology, and desalinated water can be harmful to human health as well. By-products of the chemicals used in desalination can get through into the “pure” water and endanger the people who drink it. Desalinated water can also be acidic to both pipes and digestive systems.
Excessive costs, energy consumption and the threat to fisheries and marine should make communities think twice about desalination as their solution. Conservation and recycling programs are usually much less expensive and less risky alternatives to building desalination plants. Companies today are helping homes and business make more efficient use of their water. By using water-efficient product choices—with no sacrifice to quality or product performance we can help conserve our most precious natural resource.