Indian Institute of Technology Guwahati (IIT Guwahati) researchers have developed an eco-friendly biological approach to treat textile wastewater containing toxic azo dyes.
The research provides a scientific foundation to develop biological treatment systems for textile wastewater containing azo dyes. The approach could offer an eco-friendly alternative or complementary treatment to conventional chemical and physicochemical methods.
Their research demonstrates the ability of a novel bacterium called ‘Brevundimonas sp. AJZ05’ to degrade 98.50% of Direct Blue-6 (DB-6), a widely used synthetic dye, while producing degradation products that were found to be non-toxic after bacterial treatment.
The research was supported by the Ministry of Education, Government of India, through the Prime Minister’s Research Fellowship (PMRF), with support from the Department of Chemical Engineering & Technology, IIT (BHU), Varanasi.
‘THREAT TO ACQUATIC SYSTEMS’
Textile wastewater can contain azo dyes that are difficult to remove because of their stable chemical structure. These dyes contain an azo bond (–N=N–), which contributes to their colour and chemical stability, making them resistant to conventional treatment processes. Untreated textile effluents can pose risks to aquatic ecosystems and may have implications for human health.
Conventional chemical and physicochemical treatment methods can also be energy-intensive and may generate secondary pollutants. Importantly, simply removing the visible colour from wastewater does not necessarily eliminate the underlying toxicity.
To address this challenge, the researchers isolated Brevundimonas sp. AJZ05 from a native textile effluent discharge site. The bacterium was found to produce azoreductase, an enzyme capable of attacking the azo bond that gives dyes their characteristic colour and stability.
Using a statistical multi-objective optimisation approach based on Response Surface Methodology, the researchers simultaneously optimised dye degradation and azoreductase production. Under the optimised conditions, the bacterium achieved 98.50% degradation of DB-6, along with 0.761 U/mL of azoreductase activity.
The findings were published in Environmental Geochemistry and Health (https://doi.org/10.1007/s10653-026-03332-3), a peer-reviewed, cross-disciplinary journal that publishes innovative research linking health and the environment. The paper was co-authored by Mr. Ajithkumar Veluchamy, Ms. Jothika Jeyabalan and Dr. Selvaraju Narayanasamy from IIT Guwahati and Dr. Ankur Verma from the Department of Chemical Engineering and Technology, IIT (BHU), Varanasi.
Elaborating on the research, Dr. Selvaraju Narayanasamy, Associate Professor, Biochemical and Environmental Engineering Laboratory, Department of Biosciences and Bioengineering, IIT Guwahati, said, “A key feature of the study is that we went beyond measuring colour removal. Our research team analysed the metabolites formed during the biodegradation process and assessed their toxicity. The degradation products were found to be non-toxic after bacterial treatment, indicating that the process can potentially transform the dye into safer compounds rather than only making contaminated water appear visually cleaner. Through this research, we have demonstrated a promising biological route towards safer and more sustainable wastewater treatment.”
Speaking about the current status of the research and the real-world applications, Dr. Selvaraju Narayanasamy added, “We are now working towards translating the laboratory-scale findings into a practical and scalable wastewater treatment technology. The next step involves immobilising Brevundimonas sp. AJZ05 in a suitable support matrix to improve its stability, operational performance and reusability. We plan to develop a continuous treatment system for azo-dye removal from textile wastewater, with the long-term goal of advancing the microbial platform towards industrial application.”
INDUSTRIAL WASTEWATER
Another significant finding is the bacterium’s tolerance to several metal ions, which could be advantageous because industrial wastewater often contains complex mixtures of contaminants. This characteristic may help the microbial system perform under conditions closer to those encountered in real industrial effluents.
Potential applications include:
- Textile wastewater treatment: Development of microbial treatment systems for wastewater containing persistent azo dyes such as DB-6.
- Safer wastewater remediation: Biological degradation of dyes into simpler, less-toxic products rather than only removing visible colour.
- Lower environmental impact: Potential reduction in dependence on chemical-intensive treatment processes and associated secondary pollutants.
- Treatment of other industrial dye effluents: The azoreductase-mediated degradation strategy could potentially be explored for other industrial wastewater streams containing synthetic azo dyes.
- Scalable biological treatment technologies: The bacterium could serve as a platform for developing continuous microbial treatment systems for industrial applications.
