Guwahati: Researchers from IIT Guwahati have found a green way to clean toxic lead by developing a biological process that uses naturally occurring bacteria to extract lead from acidic industrial wastewater. Beyond battery recycling facilities, the developed process can be utilised for treating wastewater from mining, smelting and metallurgical industries, IIT Guwahati said on Wednesday.The major issue the world is currently facing is that wastewater generated during battery recycling is a major industrial source of lead pollution. The World Health Organization has also warned about the dangers of this metal. According to a World Health Organization report, exposure to lead can create a negative impact on cognitive development in children, damage the nervous system and cause long-term health problems.Prof. Pranab Kumar Ghosh, professor, Department of Civil Engineering at IIT Guwahati, along with his research scholar, Sreekanth Yadav Golla, have now utilised the capabilities of sulphate-reducing bacteria, a group of microorganisms that grow naturally in oxygen-free environments, in order to address the challenges that were being faced previously.Instead of using old chemical methods, this new system uses bacteria to do the job. What was conventionally done was time-consuming and produced a large amount of lead-containing sludge that needs to be disposed of separately, researchers said. They said that the amount of lead-containing sludge produced in this process was lower in comparison with the conventional methods.“Sulphate-reducing bacteria convert sulphate in wastewater into sulphide. This sulphide then reacts with lead dissolved in water to form lead sulphide, a solid mineral that can be easily removed. The process also reduces the acidity of the wastewater, creating better conditions for the bacteria to survive and improving overall treatment efficiency,” said Prof. Ghosh.The findings of the research were published in the prestigious Journal of Environmental Chemical Engineering recently.The researchers, however, noted that one challenge in using this biological treatment was the microorganisms’ ability to survive in high acidity and metal concentrations in wastewater. To counter this, the research team developed a process that gradually acclimatised the bacteria to increasingly extreme conditions. Using this approach, Ghosh said that the biological reactor removed lead from water and converted lead into solid, stable lead sulphide form. “This allowed the microorganisms to continue treating the wastewater effectively,” he added.Sreekanth Yadav Golla said that they examined the bio-sludge produced during the treatment process to determine its environmental safety. He said, “Most of the lead in the sludge was present in stable forms that do not easily move or dissolve.”As the next step, the research team is planning to work on enhancing economic viability by using low-cost carbon sources, minimising sulphide in the treated water and exploring potential metal recovery.
