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Issue no 30, 26 October - 01 November 2024

Harnessing Membrane Technology

CSMCRI's Response to India's Growing Water Demand

Water is essential to life. Its numerous uses, widespread availability, and excellent solvent properties make it impossible to imagine life without it. Over the past six decades, India's urban population has nearly tripled, significantly increasing the demand for clean drinking water. According to a report from the Indian Water Resources Ministry, India is home to 18% of the global population but has access to only 4% of the world's usable water resources. Another report predicts that by 2050, India will become a waterstressed country. Given this situation, advancing research and technology in water treatment is crucial.

The Central Salt & Marine Chemicals Research Institute (CSMCRI), a key laboratory under CSIR, is at the forefront of this effort. Based in Bhavnagar, Gujarat, CSMCRI has emerged as a leading research institute in India, specialising in the development of membrane technologies for water desalination and purification. Through its pioneering work in designing and manufacturing artificial membranes, the institute is playing a crucial role in addressing India's growing water needs.

Membrane Technologies for Water Desalination and Purification

Water scarcity affects not only the availability of drinking water but also agricultural water supplies, making it a global crisis, particularly in countries like India. In response, desalination has become a viable solution for addressing water shortages. Membrane-based technologies, such as Reverse Osmosis (RO), Nanofiltration (NF), Ultrafiltration (UF), and Electrodialysis (ED), play an essential role in the sustainable desalination and purification of water.

One of the key focusses of water desalination is brackish water, which has a higher salt content than freshwater but is less salty than seawater. Brackish water is often found in coastal areas, rivers, and estuaries, where freshwater and seawater mix. It is unsuitable for direct consumption or agriculture, making desalination critical for its use. CSIRCSMCRI has developed and commercialised an RO membrane technology specifically designed for brackish water desalination. The performance of these indigenously developed membranes is highly competitive, often surpassing that of commercially available alternatives. CSMCRI has successfully installed several brackish water RO (BWRO) plants in coastal states such as Gujarat and Tamil Nadu to provide purified water.

CSMRI's Pioneering Achievements in Membrane Technologies

CSMCRI has developed a range of membrane-based technologies using indigenous polymeric membranes for water desalination and purification, which have been commercialised and successfully tested in remote rural areas of India, providing safe drinking water. Additionally, these charged polymer electrolyte membranes have found diverse applications in energy devices such as fuel cells and storage batteries, further extending their technological impact.

The effectiveness of a membrane in desalination depends on its selectivity, which is determined by factors such as pore size or surface charge. Based on pore size, membranes are classified into microfiltration (MF), ultrafiltration (UF), nanofiltration (NF), and reverse osmosis (RO). Membranes can also be classified by their surface charge: cation exchange membranes (with acidic charge) and anion exchange membranes (with basic charge).

CSMCRI has developed indigenous polysulfone and PVDF based hollow fibre membrane technologies for water clarification and purification with potable water recovery of more than 98%. Such membranes offer a great avenue for the removal of pathogens (like bacteria/viruses) with minimal interventions of cleaning, better throughput, and at affordable cost, truly suitable for urban water settings.

A Thin Film Composite (TFC) RO Membrane-based two-stage RO system for seawater desalination has also been developed by CSMCRI. High water recovery, low capital, and operating costs are attractive features of this technology.

Mobile Water Desalination & Purification Van/Bus

CSMCRI has developed an advanced mobile desalination and water purification unit that incorporates RO, ED, and UF technologies, along with water testing equipment. Installed in a van or bus, this unit has been highly effective in delivering safe drinking water to people across India, providing on the go water purification wherever needed.

Key Features of CSMCRI's Mobile Desalination and Water Purification Van/Bus

·       The van/bus can purify up to 2,000 litres of brackish water and 500 litres of seawater per hour, depending on water turbidity.

·       It is equipped with indigenously developed water purification technologies capable of removing harmful contaminants, salts, and substances dangerous to human health, such as arsenic, fluoride, and nitrate, as well as suspended particles.

·       The purified water meets the World Health Organization (WHO) drinking water standards.

·       It uses the vehicle's engine to generate the electricity needed to operate the unit.

·       The unit is environmentally friendly and can be easily transported across various terrains and remote locations.

This innovation has been a game-changer in disaster management. During natural disasters, the van/bus quickly reaches affected areas, providing safe drinking water and offering much-needed relief to those in distress. As part of its commitment to national service, the van/bus has been deployed in several disaster-stricken regions, including Cyclone Aila in West Bengal and Karnataka floods (2009), North India floods in Uttarakhand (2013), Cyclone Phailin in Odisha (2013), the Latur drought in Maharashtra (2016), Kerala floods (2018), Cyclone Fani in Odisha (2019), floods in the Konkan region of Maharashtra (2021), and the severe flooding caused by Cyclone Tauktae in Gujarat (2021).

CSMCRI also provides technical training to local residents for the operation and maintenance of the van/bus, creating employment opportunities and empowering communities.

Electrodialysis (ED) Based Water Desalination/ Purification Unit

CSIR-CSMCRI has developed a domestic ED system capable of desalinating water and producing mineral-balanced, nutritious drinking water with an output of 15-20 litres per hour.

In remote areas where salt is produced, basic amenities like electricity and transportation are often lacking. The water in these regions, though abundant with salt, is not suitable for drinking. As a result, drinking water is sometimes transported from distant sources, which is insufficient to meet the needs. The technology developed by CSIR-CSMCRI converts salty water into clean, potable water. The ED system offers unique benefits, including easy integration with solar energy and control over Total Dissolved Solids (TDS) in the purified water. CSIR-CSMCRI has extensive expertise in solar energy and indigenous ion-exchange membranes, leading to the development of a solar-powered ED system for producing safe drinking water.

Thin Film Composite (TFC) Reverse Osmosis Membrane

CSIR-CSMCRI has developed indigenous second generation polyamide TFC membrane, and benchmarked the membrane/module with international membranes. A 10000 litre per hour output BWRO plant based on this technology has been installed at Central University of Punjab, Bathinda.

Rejuvenation of the End-of-life Seawater Reverse Osmosis Membrane Elements

With the increasing demand for RO membranes, there is a corresponding increase in the discarded RO membrane elements at end-of-life. RO membrane waste is a potentially hazardous polymer waste. CSIR-CSMCRI has developed a technology to reuse the membranes after their useful life is over. This process technology can convert the discarded RO membrane elements into usable membranes for various applications such as partial replacement for new membranes in the same application, brackish water reverse osmosis, waste water reuse, zero liquid discharge applications, etc.

RO Membrane Rejuvenation System

The innovations done in membrane-based technologies by CSMCRI have proven crucial for water desalination and purification, providing safe drinking water, especially in remote rural areas. These technologies are not only cost-effective but also environmentally friendly, addressing the urgent need for sustainable water solutions in India and globally. CSMCRI's work exemplifies the potential of scientific innovation to tackle pressing environmental challenges, ensuring a better future for communities facing water scarcity.

 

Interview

Dr. Kannan Srinivasan

Director, CSIR-CSMCRI, Bhavnagar

Q. What are the latest advancements in membrane technology for water desalination and purification at CSIR-CSMCRI?

A. At CSIR-CSMCRI, we are at the forefront of developing membranes for various applications, particularly in water desalination and purification. Our recent innovations include polymeric high-performance hollow fiber membranes that can effectively separate pathogens such as bacteria and larger viruses. These membranes represent the best system currently available for disinfecting water, ensuring the provision of safe drinking water at high throughput.

Q. How is CSMCRI contributing to the reduction of green hydrogen production costs through membrane technology, and what are the specific applications of these technologies in industrial wastewater treatment?

A. We have recently developed a new Polymer Electrolyte Membrane (PEM) that significantly lowers the production costs of green hydrogen. Our focus has been on creating various ion exchange membranes and their composites for multiple energy applications, including fuel cells, electrolyzers, and batteries. These advancements are aimed at providing accessible and affordable energy solutions, including green hydrogen. Additionally, the institute is actively working on eco-friendly membrane-based technologies to treat brackish water, seawater, and industrial saline wastewater. By integrating different membrane processes, we can enhance treatment efficiency and reduce energy consumption, making them suitable for a range of industrial applications.

Q. The Mobile Water Desalination and Purification Van developed by CSMCRI is gaining media attention these days; how do you characterise it as state-of-the-art technology?

A. The mobile unit utilises advanced membrane technology with indigenously developed thin-film composite and ultrafiltration membranes. These membranes are designed to efficiently treat turbid, flood-affected, and contaminated water, providing potable water on-site during natural disasters. Moreover, the van operates self-sufficiently, eliminating the need for an external power source, unlike many other mobile desalination units. It has the capacity to desalinate between 2,000 and 3,000 litres of brackish water per hour, ensuring a reliable supply of clean drinking water in emergencies such as cyclones, floods, and droughts.

(Contributed by: Science Media Communication Cell, CSIRNIScPR, New Delhi)