Indian Institute of Technology Madras (IIT Madras) has developed and deployed an advanced new technology for efficiently processing wastewater from the textile industry.

The discharge from these industries not only affects the aesthetic value and water clarity but also reduces photosynthetic activity and poses toxic risks to humans, aquatic organisms, and other life forms.

This project focuses on improving the techno-economic feasibility of Zero Liquid Discharge (ZLD) plants by developing an innovative electrochemical-based methodology.

To mitigate the environmental impacts, textile industries in India are mandated to implement ZLD systems, which aim to recover and reuse wastewater and salts. However, the conventional ZLD process is associated with high capital and operating costs, significant energy consumption, and a large carbon and area footprint.

The technology development was undertaken through comprehensive lab-scale studies using synthetic wastewater ranging from small volumes of 500 ml to larger volumes of 50 Litres for the Electrochemical Ozone oxidation system (ECOOP) for the removal of organic dyes.

Led by Prof. Indumathi M. Nambi of IIT Madras, this pilot project was implemented at Kunnakalpalayam Common Effluent Treatment Plant (CETP) in Tirupur district of Tamil Nadu during 2023. It showed a significant reduction in harmful compounds in ECOOP-treated samples compared to chlorinated samples from the CETP. The pilot system has successfully achieved 96% colour removal and 60% COD removal for dyebath effluent.

Based on the results obtained from the initial deployment, the research team scaled up the system to process 400 litres per day. These trials aim to optimise the system for real-world application.

The Advantages of this technology in comparison to existing technologies include

⮚ Segregation of dyebath effluent for colour removal which reduces 75% load on RO system

⮚ Reduction in capital infrastructure cost for RO and reject Evaporators and hence lower carbon foot print.

⮚ Chlorine free colour removal process which avoids formation of carcinogenic chlorinated compounds

Elaborating on this innovative and high-impact project, Prof. Indumathi M. Nambi, Environmental and Water Resources Engineering (EWRE) Division, Department of Civil Engineering, IIT Madras, said, “This innovative approach reduces the number of RO units required in the treatment plant, ultimately lowering the total treatment cost by 25% and cuts down the RO infrastructure cost by 75%. It efficiently removes colour and organic pollutants without the use of Chlorine which is reported to produce harmful byproducts. Our treatment system promotes cleaner water resources and supports healthier ecosystems, aligning with UN Sustainable Development Goals (SDGs) 6,12,13,14, 15 and 17 and advancing environmental responsibility in the textile industry.”

Prof. Indumathi M. Nambi added, “This approach combines an advanced oxidation process, known as the Electrochemical Ozone Oxidation process (ECOOP), with Capacitive Deionization (CDI) for efficient organic and salt removal. The ECOOP process effectively degrades dyes and other organic pollutants in textile wastewater, achieving organic mineralisation without producing sludge. CDI technology is used for salt removal, offering a lower energy expenditure compared to reverse osmosis (RO), particularly for effluents with lower TDS levels.”

Envisioning upcoming plans, Prof. Indumathi M. Nambi said, “Looking ahead, the future directions include optimising the pilot plant to enhance its efficiency, versatility, and adaptability to treat different wastewaters from multiple units. Additionally, we are working towards propagating the adoption of the Electrochemical Ozone Oxidation System by smaller dyeing industries which do not have RO systems.”

Shri T Christuraj, IAS, District Collector of Tirupur, inaugurated the Pilot Project at Kunnankalpalayam CETP on 1st December 2023 and it has been successfully running since then. More R&D efforts are undertaken by IITMadras team to reduce the costs and improve efficiency.

PROJECT BACKGROUND

In India, the textile industry contributes significantly to the Nation's economy, accounting for 5% of the GDP, 7% of industrial output by value, and 12% of export earnings. However, this revenue comes with a steep environmental cost, as the industry is responsible for 20% of global clean water pollution, particularly from dyeing and finishing processes. The wastewater from textile industries contains a variety of harmful chemicals, both biodegradable and non-biodegradable, including dyes, dispersants, heavy metals, acids, and alkalis.

Recognising that only 10% of effluent in a dyeing unit constitutes a dye bath with high TDS, while the remaining 90% consists of wash water with lower TDS levels, this IIT Madras project developed a tailored treatment strategy. The Researchers suggested treating dye bath effluent using the ECOOP system, followed by Reverse Osmosis (RO), while directing wash water to a conventional Biological Oxidation system, followed by CDI.

This collaborative project, supported by Indo-German Science and Technology Centre (IGSTC), has achieved significant milestones in advancing wastewater treatment technology. As part of the project, a two-day Ecotoxicology workshop was organized by IIT Madras during November 2023, in collaboration with SRM Institute. The workshop included lectures by leading experts such as Prof. Henner Hollert (Goethe University) and Dr. S. R. Marigoudar (NCCR, Chennai), among others, and provided hands-on training in ecotoxicology using zebrafish as specimens.

The active participation of researchers from IIT Madras, Germany, and industry scientists greatly contributed to the workshop's success. The in-person consortium meeting on November 30th, 2023, brought together researchers from IIT Madras, Goethe University, RWTH from Germany, and industry partners Eurofins and Tamilnadu Water Investment Company (TWIC) to discuss the project's progress, challenges, and future directions. This collaboration has fostered innovation and knowledge exchange, leading to the successful inauguration of the pilot plant.