As the water crisis becomes severe in Indian cities, alternative methods of water treatment have taken centre stage. The desalination of abundant seawater has emerged as a viable solution in recent years, gaining attention for municipal as well as industrial treated water use. To facilitate this treatment, state governments and private players are collaborating to leverage the extensive coastline by setting up new and decentralised desalination plants. Many institutes and organisations are conducting extensive research to develop indigenous technologies and increase the efficiency of seawater treatment. As the sector expands, there is also a focus on the utilisation of solar energy and management of brine.
Application of indigenous and advanced technologies
Various Indian research organisations are harnessing the potential of indigenous technologies to treat seawater. They are exploring alternative techniques that can be implemented in ongoing and upcoming desalination projects. These techniques also include sustainable solutions, such as the use of by products like heating scrap tyres. This process was developed by the Department of Chemical Engineering of BITS Pilani, Goa, in November 2023. Under this process, a modified carbon black derivative is produced from the advanced heating of tyres. This solid derivate can be used to fabricate membranes for desalination. The technique has also received a grant of Rs 270 million from the Council of Scientific and Industrial Research (CSIR), Government of India, to validate the concept before its large-scale implementation.
Meanwhile, the Bhabha Atomic Research Centre has developed indigenous desalination technologies applied in the desalination plant at the Odisha Sand Complex in Ganjam, Odisha. This plant, with a capacity of 5 million litres per day (mld), was inaugurated on March 4, 2024.
Similarly, the Central Salt and Marine Chemicals Research Institute of CSIR has been dedicated to developing membrane-based technologies. Its thin-film composite membranes have been incorporated in the installation of several large-scale desalination plants. These plants, which are based on reverse osmosis, produce potable water.
The Nemmeli water desalination plant in Tamil Nadu, inaugurated on February 24, 2024, is also a pioneer in the use of advanced technologies. With a capacity of 150 mld, the plant uses lamella clarifiers that are designed to remove total suspended solids (TSS) particles up to 300 parts per million. Further, the plant uses 120 disc filters (DFs) and 30 skids of automatic DFs to remove particles above 100 microns. Ultra-filters with a pore size of 0.05 microns have also been deployed to filter out almost all TSS, viruses and bacteria. Moreover, five dual media filters that remove TSS have been used.
Increased use of solar energy
Desalination plants have a high carbon footprint that releases approximately 7 tonnes of carbon dioxide for the desalination of 1,000 cubic metres of seawater. In an effort to mitigate this impact, solar energy is increasingly being utilised for treating seawater in various cities. New methods to harness this renewable source of energy are being developed. For instance, researchers from various universities in Chennai have designed a solar-powered distillation system to reduce the salinity of the city’s groundwater. The gradual intrusion of seawater has elevated the salinity levels of water along the east coast. This system utilises a solar panel to heat water through a solar panel, distills it, removes the salts and condenses the vapours to form purer water.
In another development, a technology based on the use of solar power is being promoted by the Indian Institute of Technology Guwahati. In October 2023, it developed a novel heat transfer fluid based on nanofluids that can efficiently transfer heat generated using solar power to desalination systems. In this, the nanoparticles are suspended in a deep eutectic solvent, which is a safe and environmentally friendly solvent. Typically, these fluids are imported by India, increasing the capital cost of the project. This initiative will help in optimising the project cost.
Furthermore, the upcoming desalination plants, such as the Manori desalination plant in Mumbai, Maharashtra, rely on this clean source. With a capacity of 200 mld, the plant was approved by the Maharashtra Coastal Zone Management Authority on November 2, 2023. It is planned to be operated completely on solar energy by the Brihanmumbai Municipal Corporation upon its likely completion by 2027. There is also an additional provision of increasing its capacity to 400 mld in the future.
Projects under PPPs and intergovernmental collaborations
Several large-scale projects are being undertaken by the government in partnership with private players. One such example is the largest desalination plant in Southeast Asia with a capacity of 400 mld at Perur in Tamil Nadu. The Tamil Nadu government laid its foundation stone on August 21, 2023, and excavation work to build the intake sump and treated water storage system has already started. The project is being executed by key sector players, including VA Tech Wabag Limited and Metito Overseas in a joint venture. They are implementing the plant on a design-build-operate basis in the public-private partnership (PPP) mode, along with operations and maintenance for 20 years. The work is expected to be completed by December 2026 at a cost of around Rs 44 billion. Other upcoming plants in PPP mode include plants in Mandvi, Dwarka, Mundra and Ghogha in Gujarat. Meanwhile, the Indian government is collaborating with other countries to build new desalination plants. For instance, a desalination project is announced to be established in the Lakshadweep islands in partnership with the Government of Israel. Their alliance is expected to drive other innovations in the sector.
Better management of brine disposal
As the use of the desalination process increases in water treatment, the safe discharge of brine (rejected water) has also become a matter of concern. Its direct disposal into the sea damages aquatic life and water resource quality due to high salinity and temperature. Therefore, government bodies like the National Institute of Ocean Technology (NIOT), under the Ministry of Earth Sciences, are prioritising this issue.
The NIOT has recommended an erosion management plan to address this concern for the Perur desalination plant. As a result, the plant’s brine outfall system is equipped with diffusers to reduce brine release and disperse the high salt concentration to a larger area. Low temperature thermal distillation technology (LTTD) is also being deployed at the plant to reduce brine release, addressing this challenge. LTTD will be utilised in upcoming small-scale plants in Lakshadweep. These plants with a capacity of 0.15 mld each will be set up at Amini, Androth, Chetlet, Kadmat, Kalpeni and Kiltan.
Meanwhile, zero liquid discharge (ZLD) is gaining traction in the sector. It effectively closes the water loop with no eventual discharge of brine. It is gaining traction in several industries such as textiles, pharmaceuticals, food and beverages, chemicals and petrochemicals, and paper and pulp. In a recent development, The Energy and Resources Institute has introduced an advanced oxidation technology, TADOX®, to ensure ZLD in treating textile effluent at a common effluent treatment plant (CETP) in the Rooma Industrial Area, Kanpur, Uttar Pradesh. It has completed the first phase of this pilot CETP project with the National Mission for Clean Ganga, which treats 20,000 litres of effluent daily. Besides, many companies in the sector, such as A.T.E. HUBER Envirotech Private Limited, have successfully implemented related projects across different industry verticals. Their solutions have low life cycle costs and can be easily deployed.
Future insights
The desalination sector is steadily advancing with significant potential to expand its footprint in the industrial segment. More than 370 mld of capacity is expected to be added by 2025 with a tentative investment of around Rs 40 billion as per India Infrastructure Research. This capacity is expected to be established in key coastal states/UTs — Tamil Nadu, Andhra Pradesh, Gujarat, Maharashtra, Odisha, Karnataka and the Lakshadweep islands. Ports and oil refineries will monetise this growth with new projects.
In line with this, the New Mangalore Port Authority and Mangalore Refinery and Petrochemicals Limited have signed an MoU for the development of a desalination plant at Mangalore port in Karnataka. It aims to meet the rising demand for treated water at the port at an estimated cost of Rs 15 billion. In addition, the use of ocean wave energy to power desalination plants is expected to receive attention from the government. The Deep Ocean Mission under the Ministry of Earth Sciences will promote high capacity offshore ocean thermal energy conversion.
Shubhangi Goswami
