Art of Making Potable Water and the Craft of Desalination
Water is life. We live in a watery world. The ocean covers more than 70 percent of the surface of our planet. It is hard to imagine, but about 97 percent of the Earth’s water can be found in our ocean. Yet paradoxically we are stressed for safe potable water. Water is a universal solvent and dissolves salts making it unfit for our consumption. Sea water has 35000 parts per million of sodium chloride in it. Making sweet water from that is the challenge for science and technology.
Desalination has been used for thousands of years. Greek sailors used to boil water to evaporate fresh water away from the salt. Romans used clay filters to trap salt. Simply put, desalination is the process of removing salt and other impurities from seawater or brackish water to make it suitable for consumption and other applications. The two most prevalent methods of desalination are distillation and reverse osmosis.
Methods
Distillation involves heating seawater to create steam, which is then condensed back into liquid form, leaving the salts behind. India’s solar-rich landscape has encouraged innovative solar desalination techniques. The Sorek Desalination Plant in Israel serves as a prime example of distillation-based desalination, providing valuable lessons for India.
Reverse Osmosis (RO) employs a semi-permeable membrane that allows water molecules to pass through while blocking salt and other impurities. The Nemmeli Desalination Plant in Chennai, is a significant illustration of reverse osmosis technology, catering to the water needs of a water-stressed city.
India
There is a beautiful Indian myth that the swan can separate milk and water. Milk is mostly water with suspensions of fat and proteins and lactose. The gross composition of cow’s milk is 87.7% water, 4.9% lactose (carbohydrate), 3.4% fat, 3.3% protein, and 0.7% minerals. Scientific explanation is that, the Swan has got a sieve like structure, lamellae, in its mouth which separates water from mud. Which is why probably there is the belief that, swan can separate milk from water and drink just the pure milk!
Indian Canadian scientist, Srinivasa Sourirajan is regarded as the father of RO membranes along with American-Israeli scientist, Loeb. Their seminal work created the US$ 50 billion global membrane separation market to enrich the quality of worldwide life via providing clean water. Water, food and sanitation in their current status owe a lot to the transformative discoveries of Sourirajan. This is why Professor Menachem Elimelech asserted that “he should have received two Nobel Prizes- one for science and one for peace.
Sarabhai Dream
It was the visionary Indian Scientist, Dr. Vikram Sarabhai who conceived the concept of desalination as part of his dream project Nuclear Powered Agro industrial Complex. Uranium is the input for huge amounts of energy in the nuclear reactor. Reactors are located near seawater sources for cooling. He envisaged sea water desalination for agriculture and started research groups in Bhabha Atomic research Centre. Dr M.P.S.Ramani piloted these research endeavours and brought them to industrial scale operation. World class membrane research teams were nurtured here.
Success Story
Chennai, the capital city of Tamil Nadu, has been grappling with acute water scarcity due to erratic monsoons and depleting groundwater reserves. The Nemmeli Desalination Plant, established in 2010, produces 100 million liters of freshwater per day, alleviating the water crisis in the city to a considerable extent. However, challenges persist, including the high energy requirements of the desalination process and potential environmental impacts.
Gujarat with extensive coastlines, has harnessed solar power to drive desalination projects. The Solar Desalination Plant in Gandhinagar combines solar energy with the multi-effect distillation process to produce freshwater efficiently. This integration not only reduces the carbon footprint but also aligns with India’s commitment to renewable energy development
Challenges
Desalination processes are notorious for their high energy consumption. Breakthroughs in energy recovery devices, such as pressure exchangers, turbochargers, and isobaric chambers, are making strides in reducing energy demands. India’s desalination initiatives can benefit from adopting such innovations to make the process more sustainable.
Disposal of concentrated brine, a byproduct of desalination, can harm marine ecosystems. The Jal Shakti Ministry’s guidelines for brine disposal, incorporating dilution techniques and monitoring mechanisms, exemplify India’s efforts to balance technological advancements with environmental protection.
While desalination holds immense potential to address India’s water security challenges, a holistic approach is essential integrating sustainability into it. The Indian government’s emphasis on water conservation through campaigns like Jal Shakti Abhiyan is crucial to curbing wastage and enhancing the impact of desalination efforts.
In the relentless pursuit of SDG 6, desalination emerges as a pivotal tool to ensure water access for India’s burgeoning population. Through technological innovations and sustainable practices, the country can navigate its water security challenges while safeguarding its environment. By harnessing the power of the oceans and the brilliance of scientific advancement, India can lead the charge towards a water-secure future for all.
In the pursuit of sustainable water solutions, the future holds a promising ally in RO. This revolutionary technology is poised to redefine freshwater production, addressing the ever-growing global water scarcity crisis.
-Dr.A.P.Jayaraman
Chairman, NCSC
