India has an extensive network of rivers and receives around 4,000 cubic kilometers of rain in a year. Despite this abundance, India regularly experiences a water crisis, which is affecting the economy, people’s wellbeing, and the ecological state of the country.
Advances in seawater desalination in India have sparked interest in this technology as a potential solution to the freshwater shortage in India. With saline seawater comprising over 97% of the earth’s surface water, can seawater desalination be the answer to India’s water supply issues?
What is Seawater Desalination?
Seawater desalination is simply the removal of salts and other minerals from seawater and filtering the dirt. Currently, there are two general methods for seawater desalination. One is a thermal process called ‘seawater distillation’, which involves heating seawater so that freshwater can vaporize, get condensed, and then collected. Another popular method of seawater desalination involves the use of reverse osmosis membranes. This process is called reverse osmosis, where pressure is applied through an electricity-driven process that forces the separation of salt molecules from seawater. Water is passed through a semi-permeable membrane, the pressure applied causes smaller water molecules to pass through while leaving behind large salt molecules.
Most seawater desalination factories around the world rely on fossil fuel for energy. But as renewable energy technology becomes smarter and cheaper, there is a good chance we will see more such plants running on wind, sunlight, or hydropower in the near future.
Various companies are already operating dozens of plants around the world relying merely on solar energy. Currently, the price they offer per unit is higher than fossil fuel-based plants and their efficiency is lower. But if the world leaders are serious about reaching the goals of the Paris climate agreement – subsidizing renewable desalination factories must be on their to-do list.
Seawater Desalination: Benefits and Challenges
The biggest advantage of seawater desalination is its independence from rainfall. It is drought-proof, so it is especially helpful for arid areas that seasonally experiencing spells of drought. They can rely on seawater desalination for freshwater supply all-year-round. This technology is widely used in regions like the Middle East, where freshwater resources are meager or unavailable. Desalination can also be utilized as a steady source of irrigation water in regions where a steady supply of water is difficult, thereby also providing improved food security.
One of the major constraints for adopting seawater desalination is the high cost of energy, requiring large investments, operation, and plenty of maintenance. Currently, this technology is more expensive to build and operate than harnessing freshwater from rivers or groundwater. The most important environmental issue in seawater desalination is the disposal of the brine residue that contains high concentrations of salt, minerals, and other pretreatment chemicals.
When not disposed of properly, brine thrown back into the sea could reduce the level of dissolved oxygen and be detrimental to marine wildlife. Furthermore, salts could sink to the bottom and accumulate in the seabed, causing toxicity for marine life. If injected through a well, brine could contaminate a nearby aquifer.
Another significant issue in seawater desalination is the removal of essential minerals such as iodine from the water. A study by Israeli scientists showed that desalinated seawater removes vital minerals for humans like calcium, magnesium, fluoride, and iodine. The study linked a possible correlation between iodine deficiency in adults and exposure to desalinated drinking water.
Similarly, desalination removes salts that are harmful to crops, it also removes essential nutrients like magnesium, calcium, and sulfates that are important for agricultural productivity. On the other hand, since irrigation water standards are less stringent than drinking water standards, desalinated water blended with treated water from other sources could bring down the cost of water desalination.
Seawater Desalination in India: Appealing or Appalling?
Seawater desalination had been used for years in arid areas across the world such as the Middle East, the Mediterranean, the Caribbean Islands, South Africa, and Australia. Scarcity of alternative, cheaper sources of water makes desalination a viable option for these areas. The lower cost of fossil fuels in Middle Eastern countries significantly brings down the cost of desalinating seawater.
In India, or elsewhere, seawater desalination will make sense when production plants are situated near coastal areas. Equally important factors are the site’s elevation (higher elevation will translate to higher cost of pumping), feedwater characteristics (higher salinity has higher costs), and the consumer’s capacity and willingness to pay for water.
High population density and increased water stress indices in cases like Kolkata and Chennai justify the need for seawater desalination. Chennai, in fact, hosts the largest desalination plant in the country, the Minjur Desalination Plant. The plant generates 36.5 million cubic meters of water per year, servicing 2.5 million residents in Chennai. Another desalination plant located in Nemmeli, Chennai, supplies fresh water at the same capacity. Being able to ease a quarter of the city’s water requirement with just the two plants, the state government plans to replicate more desalination plants in the city.
However, desalination operations don’t come without disadvantages. Complaints by locals were reported regarding the erosion of the coastline, dwindling prawn and fish catch, and saltwater intrusion in nearby groundwater sources.
How to Solve Water Scarcity in India?
Considering the case of the desalination plant in Chennai, one may conclude that additional desalination plants can greatly alleviate India’s water needs. But are we sure that the benefits are worth the associated environmental damage and energy demand?
Compared with freshwater-starved countries whose only viable choice is desalinated water, India has several available freshwater resources that are not being utilized to the fullest. Technology, policy control, and most importantly, an open mindset can lead to a lot of opportunities for efficiently harnessing what’s already available.
Seawater desalination offers a potential solution to water shortage in India. However, before looking at solutions for increasing water supply, we need to consider reducing water consumption, improving water use efficiency, prevention of water pollution, implementation of administrative controls, and empowering people to conserve natural resources.
Author byline – Omri Barmats aims to help people make “greener” choices in their shopping cart. The Lessen is his online platform for recommending eco-friendly alternatives to everyday products, and for talking about green consumerism in general.