Researchers at IIT Guwahati have developed a biological treatment process that uses naturally occurring bacteria to remove lead from acidic industrial wastewater, offering an alternative to conventional chemical treatment methods.
The research was carried out by Professor Pranab Kumar Ghosh of the Department of Civil Engineering and research scholar Sreekanth Yadav Golla. The findings have been published in the Journal of Environmental Chemical Engineering.
According to the researchers, wastewater generated during battery recycling is a major source of lead pollution. Exposure to lead can adversely affect cognitive development in children, damage the nervous system and cause long-term health problems, according to a World Health Organization report.
Conventional treatment methods for lead-contaminated wastewater rely on chemical processes that are time-consuming and generate large quantities of lead-containing sludge requiring separate disposal.
To address these challenges, the IIT Guwahati team utilised sulphate-reducing bacteria, microorganisms that naturally grow in oxygen-free environments. The bacteria convert sulphate present in wastewater into sulphide, which reacts with dissolved lead to form lead sulphide, a solid mineral that can be removed from water.
Explaining the process, Prof. Pranab Kumar Ghosh said, “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.”
One of the challenges faced by the researchers was ensuring the survival of microorganisms in highly acidic wastewater containing elevated metal concentrations. To overcome this, the team developed a method to gradually acclimatise the bacteria to increasingly extreme conditions.
According to the institute, the biological reactor successfully removed lead from wastewater and converted it into stable lead sulphide, enabling continued treatment of the wastewater. The process also generated less lead-containing sludge compared to conventional methods.
Discussing the bio-sludge produced during treatment, Sreekanth Yadav Golla said, “We examined the bio-sludge produced during the treatment process to determine its environmental safety. Most of the lead in the sludge was present in stable forms that do not easily move or dissolve.”
The researchers said leaching tests showed only very small amounts of lead were released from the sludge, with concentrations remaining below regulatory limits.
They added that the process could also be applied to wastewater treatment in mining, smelting and metallurgical industries.
Future research will focus on improving economic viability, reducing sulphide in treated water and exploring metal recovery possibilities.
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IIT Guwahati unveils bio-process to purify acidic industrial wastewater
